US20150077982A1 - Led module, lighting device, and lamp - Google Patents
Led module, lighting device, and lamp Download PDFInfo
- Publication number
- US20150077982A1 US20150077982A1 US14/387,312 US201314387312A US2015077982A1 US 20150077982 A1 US20150077982 A1 US 20150077982A1 US 201314387312 A US201314387312 A US 201314387312A US 2015077982 A1 US2015077982 A1 US 2015077982A1
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- Prior art keywords
- light
- led module
- led
- led chip
- submount
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
- F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
- F21K9/20—Light sources comprising attachment means
- F21K9/27—Retrofit light sources for lighting devices with two fittings for each light source, e.g. for substitution of fluorescent tubes
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Definitions
- the present invention relates to an LED module, a lighting device, and a lamp.
- the light emission apparatus 100 includes a submount substrate 120 having a nitride-based ceramic substrate 121 , an Au layer 124 provided on a surface of the nitride based ceramic substrate 121 , an oxide layer 123 interposed between the nitride based ceramic substrate 121 and the Au layer 124 , and an LED light-emitting element 126 mounted on the submount substrate 120 via a solder layer 125 .
- the oxide layer 123 includes a metal oxide as a main component.
- the submount substrate 120 has a reflecting layer 122 composed of at least one of Ag and Al that is formed on the surface of the nitride-based ceramic substrate 121 so as not to overlap the Au layer 124 .
- Patent Document 1 discloses that, for the purpose of extracting light efficiently from the LED light-emitting element 126 , it is preferable to use the nitride-based ceramic substrate 121 of aluminum nitride having high reflectance.
- the chip-type light-emitting element includes an insulating substrate 201 , an LED chip 206 that is mounted on a surface of the insulating substrate 201 , and a package 207 which covers the LED chip 206 and surroundings thereof.
- Patent Document 2 discloses that blue light propagating toward the back face of the substrate of the LED chip 206 can be reflected by the insulating substrate 201 that is a white insulating substrate composed of ceramics such as alumina and aluminum nitride.
- the light emission apparatus includes: a light-emitting element housing package having a substrate 304 and a reflecting member 302 ; and a light-emitting element 306 constituted by an LED chip mounted on a mounting portion 304 a of the substrate 304 .
- Patent Document 3 discloses that the substrate 304 and the reflecting member 302 are preferably composed of white ceramics. Also, Patent Document 3 discloses a lighting apparatus including the above-mentioned light emission apparatus as a light source.
- part of the light emitted from a light-emitting layer of the light-emitting element 306 propagates toward the substrate 304 through the light-emitting element 306 , and is reflected by the substrate 304 . It is speculated that light outcoupling efficiency decreases due to absorption, multiple reflection, and the like of the light in the light-emitting element 306 .
- the present invention has been made in view of the above-described insufficiencies, and an object of the present invention is to provide an LED module, a lighting device, and a lamp each having improved light outcoupling efficiency.
- An LED module in accordance with the present invention includes: an opaque substrate on which a wiring circuit is provided; a submount bonded to a surface of the opaque substrate with a first bond; an LED chip bonded with a second bond to a face on an opposite side of the submount from the opaque substrate; and wires electrically connecting the LED chip to the wiring circuit.
- Each of the first bond and the second bond allows light emitted from the LED chip to pass therethrough, and the submount is a light-transmissive member.
- the submount preferably has light diffusing properties.
- the submount preferably has a planar size larger than a planar size of the LED chip.
- the surface of the opaque substrate preferably has light diffusing properties.
- the surface of the opaque substrate preferably has specular reflective properties.
- the opaque substrate preferably functions as a heat sink.
- At least one of the first bond and the second bond preferably contains a first fluorescent material which is excited by the light emitted from the LED chip to emit light having a different color from the light emitted from the LED chip.
- This LED module preferably includes a color conversion portion made of a transparent material containing a second fluorescent material which is excited by the light emitted from the LED chip to emit light having a different color from the light emitted from the LED chip, the color conversion portion covering sides of the LED chip and an opposite surface of the LED chip from the first bond.
- the color conversion portion preferably contains a light diffusion material.
- This LED module preferably includes a resin portion which is situated over the face of the submount and serves as an outer cover through which light passes last, the resin portion being made of a transparent resin which contains a light diffusion material.
- the submount is preferably constituted by a plurality of light-transmissive layers which are stacked in a thickness direction of the submount and have different optical properties so that a light-transmissive layer of the plurality of light-transmissive layers which is farther from the LED chip is higher in reflectance in a wavelength range of the light emitted from the LED chip.
- each of the plurality of light-transmissive layers is a ceramic layer.
- a lighting device in accordance with the present invention includes a device main body; and the LED module which is held on the device main body.
- a lamp in accordance with the present invention includes a light source that is the LED module.
- the LED module in accordance with the present invention includes: the first bond and the second bond each allowing the light emitted from the LED chip to pass therethrough; and the submount being the light-transmissive member, and therefore can have improved light outcoupling efficiency.
- the lighting device in accordance with the present invention can have improved light outcoupling efficiency.
- the lamp in accordance with the present invention can have improved light outcoupling efficiency.
- FIG. I is a schematic cross-section of an LED module of Embodiment 1;
- FIG. 2 is a schematic explanatory diagram of a propagating path of light in the LED module of Embodiment 1;
- FIG. 3 is a schematic explanatory diagram of a propagating path of light in the LED module of Embodiment 1;
- FIG. 4 is a schematic explanatory diagram of a propagating path of light in the LED module of Embodiment 1;
- FIG. 5 is a schematic explanatory diagram of a propagating path of light in the LED module of Embodiment 1;
- FIG. 6 is a schematic cross-section illustrating the first modification of the LED module of Embodiment 1;
- FIG. 7 is a main portion schematic cross-section of the second modification of the LED module of Embodiment 1;
- FIG. 8 is a main portion schematic cross-section of the third modification of the LED module of Embodiment 1;
- FIG. 9 is a main portion schematic cross-section of an exemplary configuration of the fourth modification of the LED module of Embodiment 1;
- FIG. 10 is a main portion schematic cross-section of the fifth modification of the LED module of Embodiment 1;
- FIG. 11 is a main portion schematic cross-section of the sixth modification of the LED module of Embodiment 1;
- FIG. 12 is a main portion schematic cross-section of the seventh modification of the LED module of Embodiment 1;
- FIG. 13 is an explanatory diagram of dimensional parameters of a submount and an LED chip of the seventh modification of the LED module of Embodiment 1;
- FIG. 14A is a schematic perspective view illustrating another exemplary configuration of the submount of the seventh modification of the LED module of Embodiment 1;
- FIG. 14B is an explanatory diagram of dimensional parameters of the exemplary configuration of the submount of the seventh modification of the LED module of Embodiment 1;
- FIG. 15A is a schematic perspective view illustrating another exemplary configuration of the submount of the seventh modification of the LED module of Embodiment 1;
- FIG. 15B is an explanatory diagram of dimensional parameters of the exemplary configuration of the submount of the seventh modification of the LED module of Embodiment 1;
- FIG. 16 is a schematic cross-section illustrating the submount and the LED chip of the seventh modification of the LED module of Embodiment 1;
- FIG. 17 is a main portion schematic cross-section of the eighth modification of the LED module of Embodiment 1;
- FIG. 18 is a main portion schematic cross-section of the ninth modification of the LED module of Embodiment 1;
- FIG. 19 is a main portion schematic cross-section of the tenth modification of the LED module of Embodiment 1;
- FIG. 20 is a schematic cross-section of an LED module of Embodiment 2.
- FIG. 21 is a perspective view of a submount of the LED module of Embodiment 2;
- FIG. 22 is a schematic explanatory diagram of a propagating path of light in the LED module of Embodiment 2;
- FIG. 23 is an explanatory diagram of the relation between a particle diameter and reflectance of an alumina particle
- FIG. 24 is an explanatory diagram of a simulation result of the relation between a thickness of a submount and light outcoupling efficiency in an LED module of a comparative example
- FIG. 25 is an explanatory diagram of a simulation result of the relation between a planar size of the submount and a light outputting amount of the LED module of the comparative example;
- FIG. 26 is an explanatory diagram of an experimental result of the relation between a thickness of the submount and light outcoupling efficiency
- FIG. 27 is a reflectance-wavelength characteristic diagram of a submount and an alumina substrate in Example 1 of Embodiment 2;
- FIG. 28 is an explanatory diagram of an experimental result of the relation between a particle diameter of an alumina particle in a first ceramic layer and efficiency and color difference;
- FIG. 29 is a schematic explanatory diagram of the submount in the LED module of Embodiment 2;
- FIG. 30 is an explanatory diagram of the relation between a glass compounding ratio of the submount in the LED module of Embodiment 2 and integrated intensity of an integrating sphere;
- FIG. 31 is a reflectance-wavelength characteristic diagram of the submount and an alumina substrate in Example 2 of Embodiment 2;
- FIG. 32 is a schematic cross-section illustrating the first modification of the LED module of Embodiment 2;
- FIG. 33 is an inferred mechanism diagram for illustrating the principle relating to improvement of light outcoupling efficiency in the first modification of the LED module of Embodiment 2;
- FIGS. 34A to 34C are inferred mechanism diagrams for illustrating the principle relating to improvement of light outcoupling efficiency in the first modification of the LED module of Embodiment 2;
- FIG. 35 is a schematic perspective view of the second modification of the LED module of Embodiment 2 with a partial cutaway thereof;
- FIG. 36 is a schematic perspective view of the third modification of the LED module of Embodiment 2, which is partially exploded;
- FIG. 37 is a main portion schematic cross-section of the fourth modification of the LED module of Embodiment 2;
- FIG. 38A is a schematic cross-section of an LED module of Embodiment 3.
- FIG. 38B is a schematic cross-section taken along X-X in FIG. 38A ;
- FIG. 38C is a schematic cross-section taken along Y-Y in FIG. 38A ;
- FIG. 39 is a schematic perspective view of the modification of the LED module of Embodiment 3 with a partial cutaway thereof;
- FIG. 40 is a schematic cross-section of the modification of the LED module of Embodiment 3.
- FIG. 41A is a schematic perspective view of a lighting device of Embodiment 3, which is partially exploded;
- FIG. 41B is a main portion enlarged view in FIG. 41A ;
- FIG. 42A is a schematic perspective view of a straight-tube LED lamp of Embodiment 3, which is partially exploded;
- FIG. 42B is a main portion enlarged view in FIG. 42A ;
- FIG. 43 is a schematic perspective view of another lighting device of Embodiment 3.
- FIG. 44 is a schematic perspective view of the lighting device of Embodiment 3, which is partially exploded;
- FIG. 45 is a cross section of a light emission apparatus of a conventional example.
- FIG. 46 is a perspective explanatory diagram of a chip-type light-emitting element of another conventional example.
- FIG. 47 is a cross section of a configuration of yet another conventional example.
- the LED module 1 includes: an opaque substrate 2 on which patterned conductors (patterned wiring circuit) 8 serving as a wiring circuit is provided; a submount 4 bonded to a surface 2 sa of the opaque substrate 2 with a first bond 3 ; an LED chip 6 bonded with a second bond 5 to a face 4 sa on an opposite side of the submount 4 from the opaque substrate 2 ; and wires 7 electrically connecting the LED chip 6 to the patterned conductors 8 , respectively.
- patterned conductors (patterned wiring circuit) 8 serving as a wiring circuit is provided
- a submount 4 bonded to a surface 2 sa of the opaque substrate 2 with a first bond 3
- an LED chip 6 bonded with a second bond 5 to a face 4 sa on an opposite side of the submount 4 from the opaque substrate 2
- wires 7 electrically connecting the LED chip 6 to the patterned conductors 8 , respectively.
- the first bond 3 and the second bond 5 allows light emitted from the LED chip 6 to pass therethrough, and the submount 4 is a light-transmissive member.
- the light-transmissive member propagates incident light to the outside through refraction or internal diffusion (scattering).
- the LED module 1 part of the light emitted from a light-emitting layer (not shown) in the LED chip 6 passes through the LED chip 6 and the second bond 5 , and thereafter is diffused inside the submount 4 . Consequently, the light that has passed through the LED chip 6 and the second bond 5 is less likely to be totally reflected, and more likely to emerge from the submount 4 through either side faces 4 sc or the face 4 sa . Therefore, in the LED module 1 , light outcoupling efficiency can be improved and a total light flux amount can be increased.
- the LED chip 6 includes a first electrode (not shown) serving as an anode electrode and a second electrode (not shown) serving as a cathode electrode both on a face of the LED chip 6 in the thickness direction.
- the LED chip 6 includes, as shown in FIG. 2 , a substrate 61 and an LED structure portion 60 on a main surface of the substrate 61 .
- the LED structure portion 60 includes an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer.
- the stacking order of the n-type semiconductor layer, the light-emitting layer, and the p-type semiconductor layer is the n-type semiconductor layer, the light-emitting layer, and the p-type semiconductor layer from the substrate 61 .
- the stacking order is not limited thereto, however, and the stacking order may be the p-type semiconductor layer, the light-emitting layer, and the n-type semiconductor layer from the substrate 61 .
- the LED chip 6 more preferably has a structure in which a buffer layer is provided between the LED structure portion 60 and the substrate 61 .
- the light-emitting layer preferably has a single quantum well structure or a multiple quantum well structure, but is not limited thereto.
- the LED chip 6 may have a doublehetero structure configured by the n-type semiconductor layer, the light-emitting layer, and the p-type semiconductor layer. Note that, the structure of the LED chip 6 is not particularly limited.
- the LED module 1 may be an LED chip which includes a reflector such as a Bragg reflector.
- the LED chip 6 may be a GaN-based blue LED chip which emits blue light, for example.
- the LED chip 6 includes a sapphire substrate serving as the substrate 61 .
- the substrate 61 of the LED chip 6 is not limited to the sapphire substrate, and the substrate 61 may be a transparent substrate with respect to light that is emitted from the light-emitting layer.
- the chip size of the LED chip 6 is not particularly limited.
- the LED chip 6 may have a chip size of 0.3 mm sq. (0.3 mm by 0.3 mm), 0.45 mm sq. (0.45 mm by 0.45 mm), 1 mm sq. (1 mm by 1 mm), or the like.
- the planar shape of the LED chip 6 is not limited to a square shape, and, for example, may be a rectangular shape. When the planar shape of the LED chip 6 is a rectangular shape, the chip size of the LED chip 6 may be 0.5 mm by 0.24 mm or the like.
- the material and the emission color of the light-emitting layer is not particularly limited. That is, the LED chip 6 is not limited to a blue LED chip, and may be a violet LED chip, an ultraviolet LED chip, a red LED chip, a green LED chip, or the like.
- the second bond 5 which bonds the LED chip 6 to the submount 4 may be formed of a transparent material such as a silicone resin, an epoxy resin, and a hybrid material composed of a silicone resin and an epoxy resin.
- the light-transmissive member which is the submount 4 is light-transmissive so as to transmit light in an ultraviolet wavelength region and a visible wavelength region. As shown schematically by arrows in FIG. 2 , the light-transmissive member transmits and diffuses light that is emitted from the light-emitting layer of the LED structure portion 60 of the LED chip 6 .
- the light-transmissive member which is the submount 4 may be formed of light-transmissive ceramics (such as alumina and barium sulfate), for example. Properties of the light-transmissive ceramics such as transmittance, reflectance, refractive index, and thermal conductivity can be adjusted by the type and concentration of a binder, an additive substance, or the like.
- the LED chip 6 is bonded to a center of the face 4 sa of the submount 4 with the second bond 5 .
- the submount 4 preferably has light diffusing properties. Accordingly, in the LED module 1 , as shown schematically by arrows in FIG. 3 , light emitted from the light-emitting layer of the LED structure portion 60 of the LED chip 6 toward a further face of the LED chip 6 in the thickness direction is diffused inside the submount 4 . Therefore, in the LED module 1 , it is possible to prevent light emitted toward the submount 4 from the LED chip 6 from returning to the LED chip 6 and therefore light can be more easily extracted from the face 4 sa and the side faces 4 sc of the submount 4 . The light outcoupling efficiency of the LED module 1 can thereby be improved. Note that, in FIG. 3 .
- broken-line arrows schematically show propagating directions of rays of light that are diffused inside the submount 4 .
- a solid-line arrow schematically shows a propagating direction of a ray of light which emerges from the submount 4 through the side face 4 sc.
- the submount 4 has a rectangular shape in a planar view, but the shape thereof is not limited thereto, and may be a round shape, a polygonal shape other than a rectangle, or the like.
- the planar size of the submount 4 is set to be larger than the planar size of the LED chip 6 . Accordingly, light outcoupling efficiency of the LED module 1 can be improved.
- the submount 4 preferably has a stress alleviation function of alleviating stress which acts on the LED chip 6 caused by the difference between the linear expansion coefficients of the LED chip 6 and the opaque substrate 2 .
- the stress alleviation function is provided by designing the submount 4 to have a linear expansion coefficient close to that of the LED chip 6 . Accordingly, in the LED module 1 , it is possible to alleviate the stress which acts on the LED chip 6 caused by the difference between the linear expansion coefficients of the LED chip 6 and the opaque substrate 2 .
- the submount 4 preferably has a heat conduction function of conducting heat which is generated in the LED chip 6 toward the opaque substrate 2 . Also, the submount 4 preferably has a heat conduction function of conducting heat which is generated in the LED chip 6 to a region which is larger than the chip size of the LED chip 6 . Accordingly, in the LED module 1 , heat generated in the LED chip 6 can be efficiently dissipated via the submount 4 and the opaque substrate 2 .
- the first bond 3 for bonding the submount 4 to the opaque substrate 2 may be made of a transparent material such as a silicone resin, an epoxy resin, and a hybrid material composed of a silicone resin and an epoxy resin, for example.
- the first bond 3 may be made of a conductive paste (such as silver paste and gold paste) or a resin containing a filler (such as titania and zinc oxide) or the like.
- a gas barrier layer composed of an adhesive having high gas barrier properties or the like.
- the mask layer may be used as the first bond 3 .
- the opaque substrate 2 is ideally an opaque medium (non-transparent body) which does not transmit light in a visible wavelength region, and is an non-transparent substrate which does not transmit light in the visible wavelength region.
- the transmittance of the opaque substrate 2 with respect to light in a visible wavelength region is preferably 0% to 10%, more preferably 0 to 5%, and still more preferably 0 to 1%.
- the opaque substrate 2 ideally does not absorb light in the visible wavelength region, and the absorptance thereof with respect to light in the visible wavelength region is preferably 0% to 10%, more preferably 0 to 5%, and still more preferably 0 to 1%.
- the transmittance and the absorptance are measured using an integrating sphere.
- the opaque substrate 2 may be made of aluminum, an aluminum alloy, silver, copper, phosphor bronze. a copper alloy (such as alloy 42), a nickel alloy, or the like.
- the opaque substrate 2 may be constituted by a base material formed of the above-described material and a reflection layer (not shown) provided on a surface of the base material, the reflection layer having higher reflectance than the base material with respect to light that is emitted from the LED chip 6 . That is, the opaque substrate 2 may include the reflection layer as a surface treatment layer.
- the reflection layer may be formed of an Ag film, a stack of an Ni film, a Pd film, and an Au film, a stack of an Ni film and an Au film, a stack of an Ag film, a Pd film, and an Au—Ag alloy film, or the like.
- the reflection layer formed of a metal material preferably includes a plating layer or the like.
- the reflection layer formed of a metal material is preferably formed by a plating method.
- the reflection layer may be formed of, for example, a white mask layer.
- the white mask for the mask layer may be composed of a resin (such as silicone resin) that contains a white pigment such as barium sulfate (BaSO 4 ) and titanium dioxide (TiO 2 ).
- the white mask may be made of ASA COLOR (registered trademark) RESIST INK available from Asahi Rubber Inc., which is a white mask material made of silicone, or the like.
- the white mask layer may be formed by coating, for example.
- the opaque substrate 2 may be a highly reflective substrate including: an aluminum plate serving as the base material; an aluminum film on a surface of the aluminum plate; and a reflection enhancing film on the aluminum film.
- the aluminum film has higher purity than the aluminum plate, and the reflection enhancing film is constituted by two kinds of dielectric films having different refractive indices.
- the two kinds of dielectric films are preferably an SiO 2 film and a TiO 2 film, for example.
- the LED module 1 can have reflectance of 95% or more with respect to visible light, due to using the highly reflective substrate as the opaque substrate 2 .
- the highly reflective substrate may be MIRO2 or MIRO (registered trademark) available from Alanod, for example.
- the aforementioned aluminum plate may be an aluminum plate having a surface which has been subjected to an anodic oxidation treatment.
- the opaque substrate 2 may be an insulating substrate formed of a material including a resin and a filler to increase reflectance.
- This insulating substrate may be made of unsaturated polyester and titania as the resin and the filler, respectively, for example.
- the resin of the insulating substrate is not limited to unsaturated polyester, and may be vinylester or the like.
- the filler is not limited to titania and may be magnesium oxide, boron nitride, or aluminum hydroxide, for example.
- the opaque substrate 2 may be a resin substrate composed of a white resin, or a ceramic substrate having a reflection layer formed of a white resin.
- the patterned conductors 8 (hereinafter also referred to as “patterned circuit”) serving as a wiring circuit to supply power to the LED chip 6 is provided.
- the electrodes (first electrode and second electrode) of the LED chip 6 are electrically connected to the patterned conductors 8 via wires 7 individually.
- the wire 7 may be a gold wire, an aluminum wire, or the like, for example.
- the patterned conductors 8 may be made of, for example, copper, phosphor bronze, a copper alloy (such as 42 alloy), a nickel alloy, aluminum, an aluminum alloy, or the like.
- the patterned conductors 8 may be formed of a lead frame, a metal foil, a metal film, or the like.
- an insulation layer may be provided between the opaque substrate 2 and the patterned conductors 8 .
- the opaque substrate 2 and the patterned conductors 8 constitute a mounting substrate, and the LED chip 6 is mounted on the mounting substrate with the submount 4 being interposed therebetween.
- the planar shape of the opaque substrate 2 is a rectangular shape, but the planar shape is not limited thereto, and may be a round shape, an elliptical shape, a triangular shape, a polygonal shape other than a rectangle, or the like.
- the number of LED chips 6 that are arranged on the surface 2 sa of the opaque substrate 2 is not limited to one, and may be two or more.
- the LED module 1 may be configured such that the planar shape of the opaque substrate 2 is an elongated shape, and a plurality of LED chips 6 are arranged along a longitudinal direction of the opaque substrate 2 , for example.
- the patterned circuit 8 may be configured to be connected to the plurality of LED chips 6 in series, in parallel, or in series-parallel.
- the LED module 1 may have a circuit configuration in which a plurality of LED chips 6 are connected in series, may have a circuit configuration in which a plurality of LED chips 6 are connected in parallel, or may have a circuit configuration in which a plurality of LED chips 6 are connected in series-parallel.
- the surface 2 sa of the opaque substrate 2 preferably has light diffusing properties or specular reflective properties.
- the LED module 1 When the surface 2 sa of the opaque substrate 2 has light diffusing properties, in the LED module 1 , it is possible to diffusely reflect light which is emitted from the light-emitting layer of the LED structure portion 60 in the LED chip 6 and then passes through the second bond 5 , the submount 4 , and the first bond 3 , by the surface 2 sa of the opaque substrate 2 , as shown schematically by arrows in FIG. 4 . As a result, light returning to the LED chip 6 can be reduced.
- the broken-line arrows schematically show propagating directions of rays of light which strike the face 4 sa of the submount 4 and are diffusely reflected by the surface 2 sa of the opaque substrate 2 .
- the solid-line arrow schematically shows a propagating direction of a ray of light which enters the submount 4 through the face 4 sa and then emerges from the submount 4 through the side face 4 sc.
- the LED module 1 When the surface 2 sa of the opaque substrate 2 has specular reflective properties, in the LED module 1 , it is possible to specularly reflect light which is emitted from the LED chip 6 , then passes the second bond 5 , the submount 4 , and the first bond 3 , and thereafter obliquely enter the surface 2 sa of the opaque substrate 2 as shown schematically by an arrow in FIG. 5 . As a result, light outcoupling efficiency of the side faces 4 sc of the submount 4 can be improved.
- the right arrow schematically shows a propagating direction of a ray of light that strikes the face 4 sa of the submount 4 and is specularly reflected by the surface 2 sa of the opaque substrate 2 .
- the left arrow schematically shows a propagating direction of a ray of light that enters the submount 4 through the face 4 sa and then emerges from the submount 4 through the side face 4 sc.
- the LED module 1 includes the opaque substrate 2 having the surface 2 sa with light diffusing properties or specular reflective properties, light outcoupling efficiency thereof can be further improved.
- the opaque substrate 2 preferably serves as a heat sink.
- the opaque substrate 2 when the opaque substrate 2 is made of metal having high thermal conductivity such as aluminum and copper, the opaque substrate 2 can function as a heat sink. Accordingly, in the LED module 1 , heat generated in the LED chip 6 can be more efficiently dissipated, and as a result light output can be increased.
- the heat dissipation property of the LED module 1 can be improved without increasing the number of parts, when the LED module 1 has a configuration in which a plurality of fins 22 protruding from a further surface 2 sb are integrally provided on the further surface 2 sb of the opaque substrate 2 like the first modification shown in FIG. 6 .
- the opaque substrate 2 in which the plurality of fins 22 are integrally provided can be formed by aluminum die-casting or the like.
- the LED module 1 of the second modification differs from the LED module 1 of Embodiment 1 in that each of the first bond 3 and the second bond 5 is composed of a transparent material and a first fluorescent material.
- the first fluorescent material is a fluorescent material that is excited by the light emitted from the LED chip 6 to emit light having a different color from a color of the emitted light of the LED chip 6 .
- the LED module 1 of the second modification differs from the LED module 1 of Embodiment 1 in that the first bond 3 and the second bond 5 contain the fluorescent material that is excited by the light emitted from the LED chip 6 to emit light having a different color from a color of the emitted light of the LED chip 6 .
- the fluorescent material functions as a wavelength conversion material that converts the light emitted from the LED chip 6 to light with a longer wavelength than that of the light from the LED chip 6 . Accordingly, it is possible, using the LED module 1 , to obtain mixed-color light constituted by light that is emitted from the LED chip 6 and light emitted from the fluorescent material.
- the LED module 1 can emit white light. That is, in the LED module 1 , blue light that is emitted from the LED chip 6 and light that is emitted from the yellow fluorescent material can pass through the LED chip 6 and the submount 4 , and as a result white light can be obtained.
- FIG. 7 schematically illustrates propagating paths of light which are emitted from the LED chip 6 and of light produced as a result of wavelength conversion by the fluorescent material in the second bond 5 .
- the fluorescent material serving as the wavelength conversion material is not limited to the yellow fluorescent material, and may include, for example, a set of a yellow fluorescent material and a red fluorescent material, or a set of a red fluorescent material and a green fluorescent material. Also, the fluorescent material serving as the wavelength conversion material is not limited to one kind of yellow fluorescent material, and may include two kinds of yellow fluorescent materials having different emission peak wavelengths. The color rendering property of the LED module 1 can be improved by use of a plurality of fluorescent materials as the wavelength conversion material.
- the LED module 1 at least one of the first bond 3 and the second bond 5 may contain the second fluorescent material which is excited by light emitted from LED chip 6 to emit light having a different color from the emitted light of the LED chip 6 . Accordingly, the LED module 1 can produce mixed-color light constituted by light emitted from the LED chip 6 and light emitted from the fluorescent material.
- the fluorescent material in the first bond 3 and the fluorescent material in the second bond 5 may emit light rays having different wavelengths from each other.
- the fluorescent material in the second bond 5 that is closer to the LED chip 6 may be a fluorescent material that emits light having a relatively long wavelength (such as red fluorescent material) among two kinds of fluorescent materials
- the fluorescent material in the first bond 3 that is farther from the LED chip 6 may be a fluorescent material that emits light having a relatively short wavelength (green fluorescent material). Accordingly, in the LED module 1 , it is possible to suppress secondary absorption of light converted by the fluorescent material in the second bond 5 , by the fluorescent material in the first bond 3 .
- the LED module 1 includes a combination of the red fluorescent material and the green fluorescent material as the combination of the two kinds of fluorescent materials.
- the green fluorescent material is a fluorescent material having poor temperature characteristics (a fluorescent material in which temperature quenching occurs frequently) compared with the red fluorescent material, the green fluorescent material can be arranged close to the opaque substrate 2 which functions as a heat sink, and therefore, temperature increase of the green fluorescent material can be suppressed, and as a result, the temperature quenching of the green fluorescent material can be suppressed.
- the LED module 1 may include a fluorescent material to emit light having a relatively short wavelength (green fluorescent material) as the fluorescent material in the second bond 5 that is close to the LED chip 6 , and a fluorescent material to emit light having a relatively long wavelength (red fluorescent material) as the fluorescent material in the first bond 3 that is distant from the LED chip 6 , for example, among two kinds of fluorescent materials. Accordingly, in the LED module 1 , it is possible to suppress secondary absorption of light which has been converted by the fluorescent material in the first bond 3 , by the fluorescent material in the second bond 5 .
- the opaque substrate 2 preferably functions as a heat sink, similarly to the LED module 1 of Embodiment 1.
- the LED module 1 of the third modification differs from the LED module 1 of Embodiment 1 in including a color conversion portion 10 made of a transparent material containing a second fluorescent material.
- the second fluorescent material is a fluorescent material that is excited by the light emitted from the LED chip 6 to emit light having a different color from a color of the emitted light of the LED chip 6 .
- constituent elements similar to those in Embodiment 1 are provided with the same reference numerals, and redundant description thereof will be omitted.
- FIG. 8 illustrations of the wires 7 and the patterned wiring circuit 8 shown in FIG. 1 are omitted.
- the color conversion portion 10 is provided to cover side faces of the LED chip 6 and an opposite surface of the LED chip 6 from the second bond 5 . Accordingly, in the LED module 1 , color unevenness can be suppressed.
- the transparent material for the color conversion portion 10 may be, for example, a silicone resin, an epoxy resin, an acrylic resin, glass, or an organic/inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer (nm) level or molecular level.
- the fluorescent material for the color conversion portion 10 functions as a wavelength conversion material that converts light emitted from the LED chip 6 to light having longer wavelength than the light emitted from the LED chip 6 . Accordingly, the LED module 1 can emit mixed-color light constituted by light emitted from the LED chip 6 and light emitted from the fluorescent material.
- the LED module 1 can provide white light. That is, blue light that is emitted from the LED chip 6 and light that is emitted from the yellow fluorescent material can pass through the LED chip 6 and the submount 4 , and as a result the LED module 1 can emit white light.
- the fluorescent material serving as the wavelength conversion material is not limited to the yellow fluorescent material, and may include, for example, a set of a yellow fluorescent material and a red fluorescent material, or a set of a red fluorescent material and a green fluorescent material. Also, the fluorescent material serving as the wavelength conversion material is not limited to one kind of yellow fluorescent material, and may include two kinds of yellow fluorescent materials having different emission peak wavelengths. The color rendering property of the LED module 1 can be improved by use of a plurality of fluorescent materials as the wavelength conversion material.
- the color conversion portion 10 is in the form of a layer.
- the color conversion portion 10 can be formed by a method such as molding and screen-printing.
- the color conversion portion 10 is formed into a layer-form so as to be thin, and therefore it is possible to reduce an amount of light which is to be converted to heat by the fluorescent material in the color conversion portion 10 .
- the color conversion portion 10 has a thin layer shape.
- the shape of the color conversion portion 10 is not limited to this, and may be hemisphere, semiellipse, semicylinder, or the like.
- the LED module 1 may be configured such that the color conversion portion 10 contains a light diffusion material.
- the light diffusion material is preferably composed of particles and dispersed in the color conversion portion 10 .
- the material of the light diffusion material may be an inorganic material such as aluminum oxide, silica, titanium oxide, and Au, an organic material such as a fluorine based resin, an organic and inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer level or molecular level, or the like.
- the larger the difference between the refractive indices of the light diffusion material and the transparent material of the light conversion portion 10 the smaller the required light diffusion material content to obtain an effect to suppress color unevenness to a similar level.
- the LED chip 6 is a blue LED chip and the color conversion portion 10 contains a plurality of fluorescent materials (green fluorescent material and red fluorescent material) and the light diffusion material. Furthermore, it is possible to further improve the color rendering property of the LED module 1 by that the LED chip 6 is an ultraviolet LED chip and the color conversion portion 10 contains a plurality of kinds of fluorescent materials (blue fluorescent material, green fluorescent material, and red fluorescent material) and the light diffusion material.
- the LED module 1 may be configured such that at least one of the first bond 3 and the second bond 5 contains a first fluorescent material, in addition to the color conversion portion 10 .
- the first fluorescent material is a fluorescent material which is excited by light emitted from the LED chip 6 to emit light having a different color from the emitted light of the LED chip 6 .
- the LED module 1 may be configured such that the color conversion portion 10 is provided so as to cover not only the LED chip 6 but also periphery of the submount 4 (in the example in FIG. 9 , the periphery of the face 4 sa and the side faces 4 sc ), like the fourth modification shown in FIG. 9 , for example.
- FIG. 9 illustrations of the wires 7 and the patterned conductors 8 shown in FIG. 1 are omitted.
- a fluorescent material in the color conversion portion 10 provided around the submount 4 is preferably a fluorescent material to emit light having a relatively short wavelength compared with the fluorescent material in the second bond 5 . Accordingly, in the LED module 1 , it is possible to suppress re-absorption in the color conversion portion 10 provided around the submount 4 .
- the opaque substrate 2 preferably functions as a heat sink.
- the LED module 1 of the fifth modification differs from the LED module 1 of the third modification in including a resin portion 11 on the face 4 sa of the submount 4 .
- the resin portion 11 preferably serves as an outer cover through which light passes last (in other words, an outer cover for extracting light). Note that, constituent elements similar to those in the third modification are provided with the same reference numerals, and redundant description thereof will be omitted. Also, in FIG. 10 , illustrations of the wires 7 and the patterned conductors 8 shown in FIG. 1 are omitted.
- the resin portion 11 is preferably formed of a transparent resin containing a light diffusion material.
- the transparent resin is a silicone resin.
- the transparent resin is not limited to the silicone resin, and may be an epoxy resin, an acrylic resin, or the like.
- the material of the light diffusion material may be an inorganic material such as aluminum oxide, silica, titanium oxide, and Au, an organic material such as a fluorine based resin, or an organic and inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer level or molecular level, or the like.
- the resin portion 11 has a hemispherical shape, but the shape is thereof not limited to the hemispherical shape, and may be a hemispherical shape or a hemicylindrical shape.
- the LED module 1 of the fifth modification includes the resin portion 11 , and therefore the reliability can be improved. Also, the LED module 1 may be configured such that the resin portion 11 contains the light diffusion material, as described above. Accordingly, in the LED module 1 , color unevenness can be further suppressed. Also, when the color conversion portion 10 contains a plurality of kinds of fluorescent materials and the resin portion 11 contains a light diffusion material, the color rendering property of the LED module 1 can be further improved.
- the opaque substrate 2 of the LED module 1 of the fifth modification preferably functions as a heat sink.
- the LED module 1 of the sixth modification differs from the LED module 1 of the second modification in including a resin portion 11 on the face 4 sa of the submount 4 .
- the resin portion 11 serves as an outer cover through which light is extracted. Note that, constituent elements similar to those in the second modification are provided with the same reference numerals, and redundant description thereof will be omitted. Also, in FIG. 11 , illustrations of the wires 7 and the patterned conductors 8 shown in FIG. 1 are omitted.
- the resin portion 11 is preferably formed of a transparent resin containing a light diffusion material.
- the transparent resin is a silicone resin.
- the transparent resin is not limited to the silicone resin, and may be an epoxy resin, an acrylic resin, or the like.
- the material of the light diffusion material may be an inorganic material such as aluminum oxide, silica, titanium oxide, and Au, an organic material such as a fluorine based resin, or an organic and inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer level or molecular level, or the like.
- the resin portion 11 has a hemispherical shape, but the shape of the resin portion 11 is not limited to the hemispherical shape, and may be a hemiellipse spherical shape or a hemicylidrical shape.
- the LED module 1 of the sixth modification has improved reliability due to the resin portion 11 .
- the LED module 1 may be configured such that the resin portion 11 contains the light diffusion material, as described above. Accordingly, in the LED module 1 , color unevenness can be suppressed. Also, when the LED module 1 is configured such that at least one of the first bond 3 and the second bond 5 contains a plurality of kinds of fluorescent materials (first fluorescent materials) and the resin portion 11 contains the light diffusion material, the color rendering property can be further improved.
- the opaque substrate 2 of the LED module 1 of the sixth modification preferably functions as a heat sink.
- the LED module 1 of the seventh modification differs from the LED module 1 of Embodiment 1 in including the color conversion portion 10 containing a transparent material and a first fluorescent material.
- the second fluorescent material is a fluorescent material that is excited by the light emitted from the LED chip 6 to emit light having a different color from the emitted light of the LED chip 6 .
- constituent elements similar to those in Embodiment 1 are provided with the same reference numerals, and redundant description thereof will be omitted.
- illustrations of the wires 7 and the patterned conductors 8 shown in FIG. 1 are omitted.
- the transparent material for the color conversion portion 10 may be, for example, a silicone resin, an epoxy resin, an acrylic resin, glass, or an organic/inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer (nm) level or molecular level.
- the fluorescent material for the color conversion portion 10 functions as a wavelength conversion material that converts light emitted from the LED chip 6 to light having longer wavelength than the light emitted from the LED chip 6 . Accordingly, the LED module 1 can emit mixed-color light constituted by light emitted from the LED chip 6 and light emitted from the fluorescent material.
- the LED module 1 can provide white light. That is, blue light that is emitted from the LED chip 6 and light that is emitted from the yellow fluorescent material can pass through the LED chip 6 and the submount 4 , and as a result the LED module 1 can emit white light.
- the fluorescent material serving as the wavelength conversion material is not limited to the yellow fluorescent material, and may include, for example, a set of a yellow fluorescent material and a red fluorescent material, or a set of a red fluorescent material and a green fluorescent material. Also, the fluorescent material serving as the wavelength conversion material is not limited to one kind of yellow fluorescent material, and may include two kinds of yellow fluorescent materials having different emission peak wavelengths. The color rendering property of the LED module 1 can be improved by use of a plurality of fluorescent materials as the wavelength conversion material.
- the color conversion portion 10 has a hemispherical shape and is formed on the surface 2 sa of the opaque substrate 2 so as to cover the first bond 3 , the submount 4 , the second bond 5 , and the LED chip 6 .
- the LED module 1 of the seventh modification some of rays of the light produced in a light-emitting layer (not shown) in the LED chip 6 and then passing through the LED chip 6 and the second bond 5 are diffused in the submount 4 . Consequently, the light passing through the LED chip 6 and the second bond 5 is less likely to be totally reflected, and more likely to be extracted from the submount 4 through any one of the side faces 4 sc and the face 4 sa . Therefore, in the LED module 1 , light outcoupling efficiency can be improved and a total light flux amount can be increased.
- the LED module 1 by providing the surface 2 sa of the opaque substrate 2 with diffuse reflective properties or specular reflective properties, light emitted toward the opaque substrate 2 from the color conversion portion 10 is likely to be reflected by the opaque substrate 2 , and thus light outcoupling efficiency can be improved. In this case, in the LED module 1 , some of rays of light that are reflected by the opaque substrate 2 and travel toward the color conversion portion 10 enter the color conversion portion 10 again, and consequently, the conversion rate at the color conversion portion 10 can be increased.
- the inventors performed simulation in terms of values of dimensional parameters of the submount 4 , which are effective to improve the light outcoupling efficiency of the LED module 1 .
- the inventors obtained knowledge that the dimensional parameters preferably satisfy conditions defined by Equations (1), (2), and (3) described later.
- the simulation is a geometric optical simulation by Monte Carlo ray tracing.
- dimensional parameters of the LED chip 6 and the submount 4 are defined as shown in FIG. 13 .
- a dimensional parameter of the color conversion portion 10 is defined as shown in FIG. 12 .
- a planar shape of the LED chip 6 is assumed to be rectangular, and a lengthwise dimension of a side along the left and right direction of FIG. 12 is denoted by Wc [mm], a lengthwise dimension of a side along the direction perpendicular to the sheet of FIG. 12 is denoted by Lc [min], and the thickness dimension is denote by Hc [mm].
- a planar shape of the submount 4 is assumed to be rectangular, and a lengthwise dimension of a side along the left and right direction in FIG. 12 is denoted by Ws [mm], a lengthwise dimension of a side along the direction perpendicular to the sheet of FIG. 12 is denoted by Ls [mm], and the thickness dimension is denoted by Hs [mm].
- the radius is denoted by R [mm].
- the LED chip 6 is assumed to include the substrate 61 made of sapphire having a refractive index of 1.77 and the LED structure portion 60 made from GaN having a refractive index of 2.5.
- the light-emitting layer is assumed to isotropically emit light rays with the same intensity along all directions from all the points of the light-emitting layer.
- the first bond 3 and the second bond 5 are assumed to be made of silicon resin with a refractive index of 1.41.
- the structure of the submount 4 is assumed to be a structural model where spherical particles compounded in a base material composed of ceramics and having different refractive index from that of the particles, and the refractive index of the base member is supposed to be 1.77, the refractive index of the particles is supposed to be 1.0, and a filling rate of the particles is supposed to be 16.5%.
- Equations (1), (2), and (3) are as follows.
- the planar shape of the submount 4 is not limited to a rectangular shape, and may be a polygonal shape other than the rectangle or a round shape, for example.
- the above-described dimensional parameters Ws and Ls each denote a dimension between two opposite sides of the regular hexagon as shown in FIG. 14 . Then, when the requirements defined by the above-mentioned Equations (1), (2), and (3) are satisfied, it is possible to improve the light-outcoupling efficiency of the LED module 1 .
- simulation conditions are an example, and are not particularly limited.
- chamfers 41 may be formed between the face 4 sa and the side faces 4 sc at a periphery of the face 4 sa .
- the chamfer 41 is a C chamfer with a chamfering angle of 45°, but the chamfer is not limited thereto and may be an R chamfer.
- the color conversion portion 10 has a hemispherical shape, but the shape thereof is not limited thereto, and may be a hemiellipse spherical shape or a hemicylindrical shape.
- the opaque substrate 2 of the LED module 1 of the seventh modification preferably functions as a heat sink.
- an encapsulating portion composed of a transparent resin having the same shape as the color conversion portion 10 may be provided.
- the LED module 1 of the eighth modification differs from the LED module 1 of the seventh modification in terms of the shape of the color conversion portion 10 . Note that, constituent elements similar to those in the seventh modification are provided with the same reference numerals, and redundant description thereof will be omitted. Also, in FIG. 17 , illustrations of the wires 7 and the patterned conductors 8 shown in FIG. 1 are omitted.
- the color conversion portion 10 in the LED module 1 of the eighth modification has a bombshell shape.
- the color conversion portion 10 having the bombshell shape has a hemispherical portion at the front end (the end that is distant from the opaque substrate 2 ) and a columnar portion at the back end (the end that is close to the opaque substrate 2 ).
- the inventors performed simulation in terms of values of dimensional parameters of the submount 4 , which are effective to improve the light outcoupling efficiency of the LED module 1 .
- the inventors obtained knowledge that the dimensional parameters preferably satisfy conditions defined by Equations (4), (5), and (6) described later.
- the simulation conditions for this simulation are substantially the same as the simulation conditions described in the seventh modification, but are different therefrom in the following points.
- a dimensional parameter of the color conversion portion 10 is defined as shown in FIG. 17 . That is, with regard to the dimensional parameter of the color conversion portion 10 , a radius of the hemispherical portion is denoted by R [mm]. Besides, with regard to the dimensional parameters of the submount 4 , a dimension from the face 4 sa of the submount 4 to the center of the hemispherical portion of the color conversion portion 10 is denoted by Hs′ [mm].
- Equations (4), (5), and (6) are as follows.
- the planar shape of the submount 4 is not limited to a rectangular shape, and may be a polygonal shape other than the rectangle or a round shape, for example.
- the opaque substrate 2 of the LED module 1 of the eighth modification preferably functions as a heat sink.
- the LED module 1 of the ninth modification differs from the LED module 1 of the seventh modification in that the color conversion portion 10 is formed to have a semispherical shape on the face 4 sa of the submount 4 .
- constituent elements similar to those in the seventh modification are provided with the same reference numerals, and redundant description thereof will be omitted.
- illustrations of the wires 7 and the patterned conductors 8 shown in FIG. 1 are omitted.
- the inventors performed simulation in terms of values of dimensional parameters of the submount 4 , which are effective to improve the light outcoupling efficiency of the LED module 1 .
- the inventors obtained knowledge that the dimensional parameters preferably satisfy conditions defined by Equations (7), (8), and (9) described later.
- the simulation conditions for this simulation are basically the same as the simulation conditions described in the seventh modification.
- the LED module 1 of the ninth modification is different from the LED module 1 of the seventh modification in that, in the ninth modification, the center of the color conversion portion 10 with a hemispherical shape is present on the face 4 sa of the submount 4 while, in the seventh modification, the center of the color conversion portion 10 with a semispherical shape is situated on the surface 2 sa of the opaque substrate 2 .
- Equations (7), (8), and (9) are as follows.
- the planar shape of the submount 4 is not limited to a rectangular shape, and may be a polygonal shape other than the rectangle or a round shape, for example.
- the opaque substrate 2 of the LED module 1 of the ninth modification preferably functions as a heat sink.
- the basic configuration of the LED module 1 of the tenth modification is substantially the same as that of the LED module 1 of the ninth modification shown in FIG. 18 , but differs therefrom in that the opaque substrate 2 (refer to FIG. 18 ) is constituted by a device main body of a lighting device (unshown) and the device main body and the submount 4 are bonded with the first bond 3 (refer to FIG. 18 ).
- the opaque substrate 2 (refer to FIG. 18 ) is constituted by a device main body of a lighting device (unshown) and the device main body and the submount 4 are bonded with the first bond 3 (refer to FIG. 18 ).
- constituent elements similar to those of the LED module 1 of the ninth modification are provided with the same reference numerals, and redundant description thereof will be omitted.
- FIG. 19 illustrations of the wires 7 and the patterned conductors 8 shown in FIG. 1 are omitted.
- the inventors performed simulation in terms of values of dimensional parameters of the submount 4 , which are effective to improve the light outcoupling efficiency of the LED module 1 .
- the inventors obtained knowledge that the dimensional parameters preferably satisfy conditions defined by Equations (10), (11), and (12) described later.
- the simulation conditions for this simulation are substantially the same as the simulation conditions described in the ninth modification.
- Equations (10), (11), and (12) are as follows.
- the planar shape of the submount 4 is not limited to a rectangular shape, and may be a polygonal shape other than the rectangle or a round shape, for example.
- the opaque substrate 2 of the LED module 1 of the tenth modification preferably functions as a heat sink.
- each of the LED modules 1 of Embodiment 1 and the first modification to the ninth modification can be used as light sources of various lighting apparatuses.
- the lighting apparatus which includes the LED module 1 may be, for example, a lighting device including a light source that is the LED module 1 and is provided on a device main body.
- the lighting device may include the device main body and the LED module 1 that is held on the device main body. In the lighting device including the LED module 1 , light outcoupling efficiency can be improved.
- the lighting apparatus which includes the LED module 1 may be, for another example, a straight-tube LED lamp which is a type of a lamp.
- the lamp may include a light source that is the LED module 1 .
- light outcoupling efficiency can be improved.
- straight-tube LED lamp “straight-tube LED lamp system with L-type pin cap GX16t-5 (for general illumination)” (JEL 801:2010) is standardized by Japan Electric Lamp Manufacturers Association, for example.
- Such a straight-tube LED lamp may include: a tube main body having a straight-tube shape and made of a light-transmissive material (such as milky white glass and a milky white resin); and a first cap and a second cap which are respectively provided at an end and the other end of the tube main body in the longitudinal direction.
- the LED module 1 is accommodated in the tube main body.
- the opaque substrate 2 has an elongated shape, and a plurality of LED chips 6 are aligned along the longitudinal direction of the opaque substrate 2 .
- the LED module 1 of the present embodiment differs from the LED module 1 of the seventh modification of Embodiment 1 in that the submount 4 is constituted by two layers of ceramic layers 4 a and 4 b which are stacked in the thickness direction. Note that, constituent elements similar to those in the seventh modification of Embodiment 1 are provided with the same reference numerals, and redundant description thereof will be omitted.
- the ceramic layers 4 a and 4 b have different optical properties from each other, and the ceramic layer 4 a , which is farther from the LED chip 6 , is higher in reflectance with respect to light emitted from the LED chip 6 .
- the optical properties refer to reflectance, transmittance, absorptance, or the like.
- the submount 4 is required to be constituted by at least two ceramic layers stacked in the thickness direction, and have such a property that optical characteristics of the ceramic layers are different from each other, and the further the ceramic layer is from the LED chip 6 , the higher the reflectance thereof is with respect to the light emitted from the LED chip 6 .
- the LED module 1 Accordingly, in the LED module 1 , light emitted from the light-emitting layer of the LED structure portion 60 of the LED chip 6 toward the further face of the LED chip 6 in the thickness direction is more likely to be reflected at the interface between the ceramic layer 4 b and the ceramic layer 4 a as shown schematically by arrows in FIG. 22 . Therefore, in the LED module 1 , it is possible to prevent light which is emitted from the LED chip 6 toward the submount 4 from returning to the LED chip 6 and to prevent the light from entering, the surface 2 sa of the opaque substrate 2 . As a result, light can be more easily extracted from the face 4 sa and the side faces 4 sc of the submount 4 .
- the LED module 1 Consequently, in the LED module 1 , light outcoupling efficiency can be improved. Moreover, it is possible to reduce the influence of reflectance of the opaque substrate 2 , and to increase the degree of freedom in terms of the materials of the opaque substrate 2 .
- the opaque substrate 2 when the opaque substrate 2 includes an organic-based substrate or a metal plate and a mask layer composed of a white mask thereon, the reflectance of the opaque substrate 2 is prone to decrease with time. Accordingly, there is a concern that the light outcoupling efficiency may decrease with time greatly.
- the uppermost ceramic layer 4 b that is the closest to the LED chip 6 may be referred to as a first ceramic layer 4 b
- the lowermost ceramic layer 4 a that is the farthest from the LED chip 6 may be referred to as a second ceramic layer 4 a , for convenience of description.
- the first ceramic layer 4 b may be made of alumina (Al 2 O 3 ), for example.
- the first ceramic layer 4 b may be an alumina substrate, for example.
- the particle diameter of alumina particles of the alumina substrate is preferably in a range between 1 ⁇ m to 30 ⁇ m.
- the larger the particle diameter of the alumina particles the smaller the reflectance of the first ceramic layer 4 b .
- the smaller the particle diameter of the alumina particles the larger the scattering effect of the first ceramic layer 4 b . In short, reducing the reflectance and increasing the scattering effect are in a trade-off relationship.
- the aforementioned particle diameter is determined by a number-size distribution curve.
- the number-size distribution curve is obtained by measuring a particle size distribution by an imaging method.
- the particle diameter is determined by a particle size (two-axis average diameter) and the number of particles determined by image processing of a SEM image obtained by scanning electron microscope (SEM) observation.
- SEM scanning electron microscope
- the particle diameter value at the integrated value of 50% is referred to as a median diameter (d 50 ), and the aforementioned particle diameter refers to the median diameter.
- FIG. 23 shows a theoretical relation between the particle diameter and the reflectance of a spherical alumina particle in the alumina substrate.
- the relation of the first ceramic layer 4 b between the median diameter (d 50 ) and the measured value of reflectance is approximately the same as the theoretical value shown in FIG. 23 .
- the reflectance is measured using a spectrophotometer and an integrating sphere.
- the second ceramic layer 4 a may be made of, for example, a composite material that contains SiO 2 , Al 2 O 3 , a material having a higher refractive index than Al 2 O 3 (such as ZrO 2 and TiO 2 ), CaO, and BaO as components.
- the particle diameter of Al 2 O 3 particles is preferably in a range between 0.1 ⁇ m to 1 ⁇ m.
- the optical properties (such as reflectance, transmittance, and absorptance) of the second ceramic layer 4 a can be adjusted by adjusting components, composition, particle diameter, thickness, or the like of the composite material.
- the first ceramic layer 4 b should be made of a material having the particle diameter larger than that for the second ceramic layer 4 a.
- the inventors selected, as a comparative example of the LED module 1 of the present embodiment, an LED module including the submount 4 configured by a single layer of alumina substrate. Then, the inventors performed a simulation regarding light outcoupling efficiency of the comparative example of the LED module with a parameter which is the dimension of the submount 4 of the LED module of the comparative example.
- FIG. 24 shows an example of the results.
- the simulation is a geometric optical simulation by Monte Carlo ray tracing. Note that, in the simulation, the reflectance of the surface 2 sa of the opaque substrate 2 and the absorptance of the opaque substrate 2 are assumed to be 95% and 5%, respectively. Also, in the simulation, the chip size of the LED chip 6 is assumed to be 0.5 mm by 0.24 mm.
- the horizontal axis represents a thickness of the submount 4
- the vertical axis represents light outcoupling efficiency.
- a curve denoted by “B1” in the diagram shows a case where the planar size of the submount 4 is 1 mm sq. (1 mm by 1 mm)
- a curve denoted by “B2” in the diagram shows a case where the planar size of the submount 4 is 2 mm sq. (2 mm by 2 mm). From FIG. 24 , it is inferred that, when the thickness of the submount 4 is 2 mm or less, the light outcoupling efficiency decreases due to light absorption by the opaque substrate 2 , regardless of the planar size of the submount 4 .
- FIG. 24 teaches that, when the thickness of the submount 4 is 2 mm or less, the light outcoupling efficiency is higher with a decrease in the planar size of the submount 4 .
- FIG. 25 shows an example of the results.
- This simulation is a geometric optical simulation by Monte Carlo ray tracing. Note that, in the simulation, the reflectance of the surface 2 sa of the opaque substrate 2 and the absorptance of the opaque substrate 2 are assumed to be 95% and 5%, respectively. Also, in the simulation, the chip size of the LED chip 6 is assumed to be 0.5 mm by 0.24 mm. Also, in the simulation, only a Fresnel loss is assumed to occur at the side faces of the LED chip 6 .
- Reference sign “I1” in FIG. 25 denotes a ratio of the outputted light amount directly from the LED chip 6 .
- Reference sign “I2” in FIG. 25 denotes a ratio of the outputted light amount from an exposed surface (exposed portion of the face 4 sa of the submount 4 ) of the submount 4 at the side of the LED chip 6 .
- Reference sign 13 ′′ in FIG. 25 denotes a ratio of the outputted light amount from the side faces 4 sc of the submount 4 .
- the inventors investigated a relation between the thickness of the submount 4 and the light flux emitted by the LED module 1 with respect to various opaque substrates 2 in condition that a planar size of the submount is 2 mm sq. (2 mm by 2 mm).
- the light flux is measured by an integrating sphere.
- the inventors obtained an experimental result shown in FIG. 26 .
- the LED chip 6 adopted was a blue LED chip in which the substrate was a sapphire substrate and the emission peak wavelength from the light-emitting layer was 460 nm.
- the chip size of the LED chip 6 was 0.5 mm by 0.24 mm.
- the color conversion portion 10 was composed of a silicone resin containing a yellow fluorescent material.
- the white circles ( ⁇ ) in line C1 in FIG. 26 denote measured values of light flux with respect to an LED module of Reference Model 1 .
- the submount 4 was an alumina substrate, and the opaque substrate 2 was a silver substrate having reflectance of 98% with respect to light with a wavelength of 460 nm.
- the white triangles ( ⁇ ) in line C2 in FIG. 26 designate measured values of light flux with respect to an LED module of Reference Model 2 .
- the submount 4 was an alumina substrate, and the opaque substrate 2 was a substrate including a copper substrate and a reflection layer composed of a white mask having reflectance of 92% with respect to light with a wavelength of 460 nm on a surface of the copper substrate.
- the white rhombuses ( ⁇ ) in line C3 in FIG. 26 designate measured values of light flux with respect to an LED module of Reference Model 3 .
- the submount 4 was an alumina substrate, and the opaque substrate 2 was an aluminum substrate having reflectance of 95% with respect to light with a wavelength of 460 nm.
- the light outcoupling efficiency of the LED module 1 of the present embodiment can be improved by increasing the thickness of the submount 4 . Also, in the LED module 1 of the present embodiment, it is speculated that the light outcoupling efficiency can be improved by using a silver substrate as the opaque substrate 2 similarly to Reference Model 1 .
- the submount 4 is thinner.
- the light outcoupling efficiency and the heat dissipation property are in a trade-off relationship.
- the inventors fabricated an LED module having a reference structure in which the submount 4 was not provided and a high purity alumina substrate was used as the opaque substrate 2 , and performed an experiment of measuring a light flux emitted by the LED module having the reference structure.
- the black square ( ⁇ ) in FIG. 26 designates measured values of light flux with respect to the LED module having the reference structure.
- the inventors obtained an experimental result that, the LED module of aforementioned Reference Model 1 is required to include the submount 4 having the thickness of 0.4 mm or more to emit greater light flux than the LED module having the reference structure.
- the inventors considered that it is preferable to adjust the thickness of the submount 4 to an approximate range of 0.4 mm to 0.5 mm, in view of the light outcoupling efficiency and the heat dissipation property.
- the thickness of the alumina substrate is 1 mm
- the particle diameter of particles constituting the alumina substrate is 1 ⁇ m.
- the reflectance of the alumina substrate is 91%.
- the opaque substrate 2 includes a base material (cupper substrate) made of cupper and a reflection layer composed of the white mask layer provided on a surface of the base material, and the submount 4 is the light-transmissive member having a configuration in which the second ceramic layer 4 a and the first ceramic layer 4 b are stacked in the thickness direction.
- Example 1 The inventors performed an experiment of measuring light flux emitted by Example 1 of the LED module 1 of the present embodiment.
- the submount 4 had the thickness of 0.5 mm
- the second ceramic layer 4 a had the thickness Hsa (refer to FIG. 21 ) of 0.1 mm and the reflectance of 96% to light with a wavelength of 450 nm
- the first ceramic layer 4 b had the thickness Hsb (refer to FIG. 21 ) of 0.4 mm and the reflectance of 80% to light with a wavelength of 450 nm.
- the black circle ( ⁇ ) in FIG. 26 designates a measured value of light flux with respect to Example 1.
- FIG. 26 teaches that the LED module 1 of Example 1 emits a greater light flux than the LED module having the reference structure. Also, from FIG. 26 , it is speculated that the LED module 1 of Example 1 emits a greater light flux than those of Reference Models 1 , 2 , and 3 in which the submount 4 has the thickness of 0.5 mm.
- reflectance-wavelength characteristics of the submount 4 in Example 1 are as shown by a curve denoted by reference sign A1 in FIG. 27
- reflectance-wavelength characteristics of a single layer alumina substrate with a thickness of 0.4 mm are as shown by a curve denoted by reference sign A2 in FIG. 27
- the alumina substrate has the same specification as those of the alumina substrates in Reference Models 1 , 2 , and 3 .
- the reflectance-wavelength characteristics shown in FIG. 27 were measured using a spectrophotometer and an integrating sphere.
- the inventors performed an experiment to measure light flux and chromaticity of light emitted from the LED module 1 .
- the measurement was made for each of the different particle diameters (median diameter) of the alumina particle in the first ceramic layer 4 b .
- the LED chip 6 was a blue LED chip in which the substrate was a sapphire substrate and the emission peak wavelength from the light-emitting layer was 460 nm.
- the chip size of the LED chip 6 was 0.5 mm by 0.24 mm.
- the thickness and the planar size of the submount 4 were 0.49 mm and 2 mm sq. (2 mm by 2 mm), respectively.
- the chromaticity is a psychophysical property of color that is determined by chromaticity coordinates in an xy chromaticity diagram of a CIE color system.
- the chromaticity was measured in a direction in which the radiation angle of light emitted from the LED module 1 is 0° (light axis direction), and in a direction in which the radiation angle is 60° (direction in which the angle relative to the light axis is 60°).
- a spectral distribution in each of the radiation angles was obtained by a spectrophotometer, and the chromaticity in the CIE color system was calculated from each of the spectral distribution.
- the experimental results are summarized in FIG. 28 .
- the horizontal axis in FIG. 28 indicates a particle diameter.
- the left vertical axis in FIG. 28 indicates efficiency calculated by a light flux and input power supplied to the LED module 1 .
- the right vertical axis in FIG. 28 indicates a color difference.
- the color difference is defined as the value of x (hereinafter referred to as “x 1 ”) in the direction in which the radiation angle is 60° in the chromaticity coordinates, when a value of x (hereinafter referred to as “x 0 ”) in the direction in which the radiation angle is 0° in the chromaticity coordinates is set as a reference. That is, the color difference in the right vertical axis in FIG.
- the black rhombuses ( ⁇ ) in FIG. 28 designate measured values of the efficiency of the LED module 1 .
- the black squares ( ⁇ ) in FIG. 28 designate measured values of the color difference of the LED module 1 .
- the white rhombus ( ⁇ ) in FIG. 28 designates a measured value of the efficiency of the aforementioned LED module having the reference structure.
- the white square ( ⁇ ) in FIG. 28 designates a measured value of the color difference of the aforementioned LED module having the reference structure. Note that, since the LED module having the reference structure does not include the submount 4 , the particle diameter in the horizontal axis in FIG. 28 shows a particle diameter of particles in the alumina substrate.
- the allowable range of the color difference in the LED module 1 is preferably in a range between ⁇ 0.0015 to 0.0015, for example, from a viewpoint of suppressing color unevenness and a viewpoint of realizing a color difference similar to the color difference of the LED module having the reference structure or less.
- FIG. 28 teaches that the LED module 1 has higher efficiency than the LED module having the reference structure. Also, from FIG. 28 , it is inferred that the efficiency of the LED module 1 can be increased compared with that of the LED module having the reference structure by setting the particle diameter in a range between 1 ⁇ m to 4 ⁇ m, while suppressing the color difference from exceeding the allowable range (in other words, becoming larger than the color difference of the LED module having the reference structure).
- the first ceramic layer 4 b is a first dense layer composed of ceramics sintered at a high temperature in an approximate range of 1500° C. to 1600° C.
- the first ceramic layer 4 b has good rigidity compared with the second ceramic layer 4 a , since ceramic particles are bound strongly to each other by the high temperature sintering.
- the good rigidity indicates that a flexural strength is relatively high.
- alumina is preferable as a material of the first ceramic layer 4 b .
- the second ceramic layer 4 a is composed of ceramics sintered at 1000° C. or less (850° C. to 1000° C., for example) which is a relatively low temperature compared with the sintering temperature of the first ceramic layer 4 b .
- the ceramics constituting the second ceramic layer 4 a may be a second dense layer which contains a ceramic filler (ceramic microparticles) and a glass component, or a porous layer containing a ceramic filler (ceramic microparticles) and a glass component, for example.
- the second dense layer is composed of dense ceramics in which ceramic fillers are bound each other by sintering and glass components are arranged around the ceramic fillers as a matrix.
- the ceramic filler mainly performs a function of reflecting light.
- the second dense layer may be made of borosilicate glass, glass ceramics which contains lead borosilicate glass and alumina, a material in which a ceramic filler is mixed to glass ceramics which contains soda-lime glass and alumina, or the like.
- the glass content of the glass ceramics is preferably set in a range of around 35 to 60 wt %.
- the ceramics content of the glass ceramics is preferably set in a range of around 40 to 60 wt %.
- the zinc component of the lead borosilicate glass can be substituted for titanium oxide or tantalum oxide to increase refractive index of the glass ceramics.
- the ceramic filler is preferably made of a material having higher refractive index than glass ceramics, and may be, for example, tantalum pentoxide, niobium pentoxide, titanium oxide, barium oxide, barium sulfate, magnesium oxide, calcium oxide, strontium oxide, zinc oxide, zirconium oxide, or silicate oxide (zircon).
- second ceramic layer 4 a is constituted by a porous layer (hereinafter, “second ceramic layer 4 a ” is also referred to as “porous layer 4 a ”)
- a first glass layer 40 aa is interposed between a porous layer 4 a having a plurality of pores 40 c and the first ceramic layer 4 b
- a second glass layer 40 ab is formed on an opposite side of the porous layer 4 a from the first ceramic layer 4 b , as shown in the schematic diagram in FIG. 15 .
- the porosity of the porous layer 4 a is set to be around 40%, but is not limited thereto.
- the first glass layer 40 aa and the second glass layer 40 ab are transparent layers composed of a glass component and transmit visible light.
- the thicknesses of the first glass layer 40 aa and the second glass layer 40 ab may be set to around 10 ⁇ m, for example, but are not limited thereto.
- Around half of the glass component of each of the first glass layer 40 aa and the second glass layer 40 ab is composed of SiO 2 , but the glass component is not limited thereto.
- the first glass layer 40 aa is provided so as to be interposed between the porous layer 4 a and the first ceramic layer 4 b , and is closely-attached to the surface of the porous layer 4 a and to the surface of the first ceramic layer 4 b by sintering at the time of manufacture.
- the second glass layer 40 ab is provided on the opposite face of the porous layer 4 a from the first ceramic layer 4 b , and protects the porous layer 4 a . Accordingly, pores 40 c that exist on the opposite surface of the porous layer 4 a from the first ceramic layer 4 b is enclosed by the second glass layer 40 ab.
- the porous layer 4 a contains a ceramic filler (ceramic particulate) and a glass component.
- the ceramic fillers are combined to form clusters by sintering so as to form a porous structure.
- the glass component serves as a binder for the ceramic filler.
- the ceramic filler and the plurality of pores mainly perform a function of reflecting light. Note that, the porous layer 4 a can be formed in accordance with a manufacturing process of a package disclosed in paragraphs [0023]-[0026] and in FIG. 4 in WO2012/039442 A1.
- the reflectance of the porous layer 4 a can be changed by, for example, changing a weight ratio between the glass component and the ceramic component (such as alumina and zirconia). That is, the reflectance of the porous layer 4 a can be changed by changing the glass compounding ratio.
- the horizontal axis indicates a glass compounding ratio
- the vertical axis indicates an integrated intensity measured with an integrating sphere. In measurement with the integrating sphere, intensities of reflected light with wavelengths between 380 to 780 nm are integrated.
- FIG. 30 teaches that the reflectance can be increased with a decrease in the glass compounding ratio.
- the first ceramic layer 4 b is formed by sintering alumina at 1600° C.
- the porous layer 4 a is formed by sintering materials at 850° C., the materials being compounded such that the weight ratio of the glass component to the ceramic component is 20:80.
- the glass component is borosilicate glass with a median diameter of around 3 ⁇ m
- the alumina is a compound of alumina with a median diameter of around 0.5 ⁇ m and alumina with a median diameter of around 2 ⁇ m
- the zirconia has a median diameter of around 0.2 ⁇ m.
- Example 2 the first ceramic layer 4 b has the thickness of 0.38 mm, and the porous layer 4 a has the thickness of 0.10 mm.
- the reflectance-wavelength characteristics of the submount 4 in Example 2 is indicated by a curve designated by “A3” in FIG. 31 and the reflectance-wavelength characteristics of the single layer alumina substrate with a thickness of 0.38 mm is as shown by a curve designated by “A4” in FIG. 31 .
- the weight ratio of the glass component to the ceramic component in the porous layer 4 a and the particle diameters (median diameters) of the respective materials are not particularly limited.
- the porous layer 4 a has a graded composition in which the density of the glass component gradually decreases from the both sides thereof to the inside in the thickness direction, since the glass components of the first glass layer 40 aa and the second glass layer 40 ab infiltrate at the time of manufacture.
- the submount 4 is constituted by the two ceramic layers 4 a and 4 b , and optical properties of these two ceramic layers 4 a and 4 b differ from each other, and the ceramic layer 4 a which is further from the LED chip 6 has a higher reflectance with respect to light emitted from the LED chip 6 than the ceramic layer 4 b that is closer to the LED chip 6 . Accordingly, light outcoupling efficiency of the LED module 1 of the present embodiment can be improved compared with that of a LED module including the submount 4 which is constituted by a single layer alumina substrate.
- the LED module 1 of the present embodiment it is possible to reduce an amount of light reflected from the face 4 sa of the submount 4 , and as a result, absorption loss in the LED chip 6 can be reduced. Furthermore, in the LED module 1 of the present embodiment, absorptance of light (approximately 0%) of the submount 4 can be smaller than the absorptance of light (around 2 to 8%, for example) of the opaque substrate 2 , and parts of light incident on the face 4 sa of the submount 4 can be scattered in the ceramic layer 4 b and can be reflected at the interface between the ceramic layer 4 b and the ceramic layer 4 a .
- the LED module 1 it is possible to reduce an amount of light which passes through the submount 4 and arrives at the surface 2 sa of the opaque substrate 2 and absorption loss at the opaque substrate 2 . As a result, light outcoupling efficiency can be improved.
- the first ceramic layer 4 b has relatively higher light transmittance
- the second ceramic layer 4 a has relatively higher light scattering rate, out of the first ceramic layer 4 b and the second ceramic layer 4 a . Accordingly, it is inferred that, in the LED module 1 , light can be diffused in the second ceramic layer 4 a that is farther from the LED chip 6 , and an amount of light that is diffused before arriving at the opaque substrate 2 increases compared with a LED module having only the first ceramic layer 4 b . Also, it is speculated that, in the LED module 1 , the possibility that light reflected by the opaque substrate 2 directly below the submount 4 is diffused without returning to the LED chip 6 can be increased.
- the LED module 1 when the submount 4 is constituted by only the second ceramic layer 4 a , the possibility that light is scattered in the vicinity of the LED chip 6 and then returns to the LED chip 6 may be increased, unfortunately, because the possibility that light emitted from the LED chip 6 toward the submount 4 is scattered in a vicinity of the LED chip 6 may be increased. Consequently, it is speculated that, in the LED module 1 , it is possible to reduce an amount of light returning to the LED chip 6 , compared with a LED module including the submount 4 constituted by only the second ceramic layer 4 a . Moreover, in the LED module 1 , it is possible to reduce the thickness of the submount 4 required to obtain the same reflectance, compared with the submount 4 constituted by only the first ceramic layer 4 b.
- the color conversion portion 10 is formed on the submount 4 and has a hemispherical shape so as to cover the LED chip 6 and a portion of each of the wires 7 . Therefore, the LED module 1 whose configuration is shown in FIG. 20 preferably includes an encapsulating portion (not shown) which covers the exposed portion of each of the wires 7 and the color conversion portion 10 .
- the encapsulating portion is preferably made of a transparent material.
- the transparent material of the encapsulating portion may be, for example, a silicone resin, an epoxy resin, an acrylic resin, glass, or an organic and inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer level or molecular level.
- the transparent material of the encapsulating portion is preferably a material having a linear expansion coefficient which is close to that of the transparent material of the color conversion portion 10 , and is more preferably a material having a linear expansion coefficient that is the same as that of the transparent material of the color conversion portion 10 . Accordingly, in the LED module 1 , it is possible to suppress the concentration of stress on each of the wires 7 in a vicinity of the interface between the encapsulating portion and the color conversion portion 10 due to the difference between the linear expansion coefficients of the encapsulating portion and the color conversion portion 10 . Consequently, in the LED module 1 , disconnection of wires 7 can be suppressed.
- the encapsulating portion is preferably formed in a hemispherical shape, but the shape thereof is not limited thereto, and may be a semiellipse spherical shape or a semicircular columnar shape.
- the color conversion portion 10 may be formed in a hemispherical shape which covers the LED chip 6 , the wires 7 , and the submount 4 , similarly to that of the LED module 1 of the first modification of shown in FIG. 32 .
- the reason why the light outcoupling efficiency of the LED module 1 is improved will be described with reference to the inferred mechanism diagrams in FIGS. 33 , 34 A, 34 B, and 34 C. Note that the first modification is in the scope of the present invention, even if the inferred mechanism is different from the mechanism described below.
- FIGS. 33 , 34 A, 34 B, and 34 C schematically illustrate propagating paths of rays of light which are emitted from the light-emitting layer of the LED structure portion 60 in the LED chip 6 .
- Solid-line arrows in FIGS. 33 , 34 A, and 34 B schematically illustrate propagating paths of rays of light which are emitted from the light-emitting layer and are reflected by the face 4 sa of the submount 4 .
- Broken-line arrows in FIGS. 33 , 34 A, 34 B, and 34 C schematically illustrate propagating paths of rays of light which are emitted from the light-emitting layer of the LED structure portion 60 and enter the submount 4 .
- reflection and refraction occur in the second ceramic layer 4 a at the interface between the pore and the grain boundary phase caused by a difference between the refractive indices of the pore and the grain boundary phase.
- the inventors inferred that, with respect to a ceramic plate, when the plate thickness is the same, the larger the particle diameter of the ceramic particles in the plate, the smaller the reflectance and the larger the transmittance, since the larger the particle diameter of the ceramic particles, the smaller the number of interfaces, and the probability that light passes through the interface between the ceramic particles and the grain boundary phase is reduced when light propagates a unit length.
- the inventors inferred that light outcoupling efficiency of the LED module 1 can be improved by causing light emitted from the LED chip 6 to pass through the first ceramic layer 4 b as much as possible, and causing the light to be reflected in the second ceramic layer 4 a as much as possible. Therefore, it is preferable that, in the submount 4 , the first ceramic layer 4 b includes ceramic particles having a greater particle diameter than the second ceramic layer 4 a while the second ceramic layer 4 a includes ceramic particles having a smaller particle diameter than the first ceramic layer 4 b and further include pores.
- the opaque substrate 2 may have an elongated shape, and a plurality of LED chips 6 may be arranged along the longitudinal direction of the opaque substrate 2 .
- the wires 7 may extend along a direction perpendicular to the arrangement direction of the LED chips 6
- the color conversion portions 10 may have a hemispherical shape to cover the respective LED chips 6 and portions of the respective wires 7 on the submount 4 , similarly to a LED module of the second modification shown in FIG. 35 , for example.
- the patterned conductors 8 in FIG. 20 are omitted.
- the wires 7 may extend along the arrangement direction of the LED chips 6 , and the color conversion portions 10 may haves a convex shape to cover the submount 4 , the respective LED chip 6 , and the respective wires 7 , similarly to a LED module of the third modification shown in FIG. 36 , for example.
- the patterned conductors 8 in FIG. 20 are omitted.
- the wires 7 may extend along the arrangement direction of the LED chips 6 , and the color conversion portions 10 may haves a convex shape to cover most part of the submount 4 , the respective LED chip 6 , and the respective wires 7 , similarly to a LED module of the fourth modification shown in FIG. 37 , for example.
- the patterned conductors 8 in FIG. 20 are omitted.
- the plurality of ceramic layers (first ceramic layer 4 b and second ceramic layer 4 a ) of the submount 4 are light-transmissive layers having different optical properties.
- the submount 4 is constituted by the plurality of light-transmissive layers stacked in the thickness direction, and is required to have such a property that optical properties of the plurality of light-transmissive layers differ from each other, and a light-transmissive layer of the plurality of light-transmissive layers which is farther from the LED chip 6 is higher in reflectance in a wavelength range of the light emitted from the LED chip 6 .
- the uppermost light-transmissive layer which is the closest to the LED chip 6 may be referred to as a first light-transmissive layer
- the lowermost light-transmissive layer which is farther from the LED chip 6 may be referred to as a second light-transmissive layer.
- the first light-transmissive layer is preferably composed of a material that has high transmittance with respect to light emitted from the LED chip 6 , and has a refractive index close to the refractive index of the LED chip 6 .
- the refractive index of the first light-transmissive layer being close to the refractive index of the LED chip 6 means that the difference between the refractive index of the first light-transmissive layer and the refractive index of the substrate 61 in the LED chip 6 is 0.1 or less, and is more preferably 0.
- the first light-transmissive layer is preferably composed of a material having a high thermal resistance.
- the material of the first light-transmissive layer is not limited to ceramics, and may be glass, SiC, GaN, GaP, sapphire, an epoxy resin, a silicone resin, unsaturated polyester, or the like.
- the material of the ceramics is not limited to Al 2 O 3 , and may be another metal oxide (such as magnesia, zirconia, and titania), a metal nitride (such as aluminum nitride), or the like.
- ceramics is more preferable than a single crystal from a viewpoint of causing light emitted from the LED chip 6 to be forward-scattered.
- the light-transmissive ceramics may be LUMICERA (registered trademark) available from Murata Manufacturing Co., Ltd., HICERAM (product name) available from NGK Insulators, Ltd., or the like.
- LUMICERA(registered trademark) has a Ba(Mg,Ta)O 3 -based complex perovskite structure as the main crystal phase.
- HICERAM is a light-transmissive alumina ceramic.
- the first light-transmissive layer made of ceramic preferably include particles having the particle diameter of around 1 ⁇ m to 5 ⁇ m.
- the first light-transmissive layer may be a single crystal in which voids, a modified portion having a different refractive index, or the like is formed.
- the voids, the modified portion, or the like may be formed by irradiating, with a laser beam from a femto-second laser, a scheduled formation region of the voids, the modified portion, or the like in the single crystal.
- the wavelength and the irradiation conditions of the laser beam from the femto-second laser may vary appropriately according to the material of the single crystal, the forming target (void or modified portion), the size of the forming target, or the like.
- the first light-transmissive layer may be made of a base resin (such as epoxy resin, silicone resin, and unsaturated polyester) (hereinafter, referred to as “first base resin”) which contains a filler (hereinafter, referred to as “first filler”) having a refractive index different from the base resin. It is more preferable that a difference between the refractive indices of the first filler and the first base resin is small.
- the first filler preferably has higher thermal conductivity.
- the first light-transmissive layer preferably has a high density of the first filler, from a viewpoint of increasing thermal conductivity.
- the shape of the first filler is preferably a sphere, from a viewpoint of suppressing total reflection of incident light.
- the first light-transmissive layer may be configured such that a first filler having a relatively large particle diameter is present in a region of the first light-transmissive layer close to the LED chip 6 in the thickness direction, and a first filler having a relatively small particle diameter is present in a region thereof distant from the LED chip 6 .
- the first light-transmissive layer may include a plurality of stacked layers having the first fillers with different particle diameters.
- a fine asperity structure portion is preferably formed around the mounting region of the LED chip 6 so as to suppress total reflection of light which is emitted from the LED chip 6 toward the submount 4 and is reflected by or refracted in the submount 4 .
- the asperity structure portion may be formed by roughening the surface of the first light-transmissive layer by sandblast processing or the like.
- the surface roughness of the asperity structure portion is preferably such that an arithmetic average roughness Ra specified in JIS B 0601-2001 (ISO 4287-1997) is around 0.05 ⁇ m.
- the submount 4 may have a configuration in which a resin layer having a smaller refractive index than the first light-transmissive layer is formed on the surface of the first light-transmissive layer close to the LED chip 6 around the mounting region of the LED chip 6 .
- the material of the resin layer may be a silicone resin, an epoxy resin, or the like.
- the material of the resin layer may be a resin containing a fluorescent material.
- the second light-transmissive layer is more preferably configured such that light emitted from the LED chip 6 is diffusely reflected, than configured such that the light is specularly reflected.
- the material of the second light-transmissive layer is not limited to ceramics, and may be glass, SiC, GaN, GaP, sapphire, an epoxy resin, a silicone resin, unsaturated polyester, or the like.
- the material of the ceramics is not limited to Al 2 O 3 , and may be another metal oxide (such as magnesia, zirconia, and titania), a metal nitride (such as aluminum nitride), or the like.
- the second light-transmissive layer made of ceramics preferably includes particles having the particle diameter of 1 ⁇ m or less, and more preferably include particles having the particle diameter of around 0.1 ⁇ m to 0.3 ⁇ m. Also, the second light-transmissive layer may be the aforementioned porous layer 4 a . In a case where the first light-transmissive layer was the first ceramic layer 4 b composed of alumina having purity of 99.5%, the bulk density of the first light-transmissive layer was 3.8 to 3.95 g/cm 3 .
- the bulk density of the first light-transmissive layer was 3.7 to 3.8 g/cm 3 .
- the bulk density of the second light-transmissive layer was 3.7 to 3.8 g/cm 3 .
- the aforementioned bulk density is a value estimated by image processing a SEM image observed and obtained by an SEM.
- the second light-transmissive layer may be of a single crystal in which voids, a modified portion having a different refractive index, or the like is formed.
- the voids, the modified portion, or the like may be formed by irradiating, with a laser beam from a femto-second laser, a scheduled formation region of the voids, the modified portion, or the like in the single crystal.
- the wavelength and the irradiation conditions of the laser beam from the femto-second laser may vary appropriately according to the material of the single crystal, the forming target (void or modified portion), the size of the forming target, or the like.
- the second light-transmissive layer may be made of a base resin (such as epoxy resin, silicone resin, unsaturated polyester, and a fluorine resin) (hereinafter, referred to as “second base resin”) which contains a filler (hereinafter, referred to as “second filler”) having a refractive index different from the base resin.
- second base resin such as epoxy resin, silicone resin, unsaturated polyester, and a fluorine resin
- second filler hereinafter, referred to as “second filler” having a refractive index different from the base resin.
- the second light-transmissive layer may be configured such that a second filler having a relatively large particle diameter is present in a region of the second light-transmissive layer close to the LED chip 6 in the thickness direction, and a second filler having a relatively small particle diameter is present in a region thereof distant from the LED chip 6 .
- the material of the second filler is preferably, for example, a white inorganic material, and may be a metal oxide such as TiO 2 and ZnO.
- the particle diameter of the second filler is preferably in a range between around 0.1 ⁇ m to 0.3 ⁇ m, for example.
- the filling rate of the second filler is preferably in a range of around 50 to 75 wt %, for example.
- the silicone resin for the second base resin may be methyl silicone, phenyl silicone, or the like. In a case where the second filler is in a form of solid particle, it is preferable that there is a great difference between the refractive indices of the second filler and the second base resin.
- a material containing the second base resin and the second filler in the second base resin may be KER-3200-T1 available from Shin-Etsu Chemical Co., Ltd. or the like.
- the second filler may be a core-shell particle, hollow particle, or the like.
- the refractive index of the core of the core-shell particle can be arbitrarily selected, but is preferably smaller than the refractive index of the second base resin. It is preferable that the hollow particle has a smaller refractive index than the second base resin, and that inside of the hollow particle is gas (such as air and inert gas) or vacuum.
- the second light-transmissive layer may be a light diffusion sheet.
- the light diffusion sheet may be a white polyethylene terephthalate sheet having a plurality of bubbles, or the like.
- the submount 4 may be formed by, in a case of both the first light-transmissive layer and the second light-transmissive layer being made of ceramics, stacking ceramic green sheets to be the first light-transmissive layer and the second light-transmissive layer individually and sintering the stacked sheets. Note that, in the submount 4 , provided that the second light-transmissive layer includes bubbles, the first light-transmissive layer may include bubbles. In such a case, it is preferable that the first light-transmissive layer is smaller in the number of bubbles and higher in the bulk density than the second light-transmissive layer.
- the first light-transmissive layer and the second light-transmissive layer are preferably composed of a material that has a high resistance to light and heat, which are emitted from the LED chip 6 and the fluorescent material.
- the LED module 1 may include a reflection layer over the further face 4 sb of the submount 4 to reflect light from the LED chip 6 or the like.
- the reflection layer may be made of silver, aluminum, a silver aluminum alloy, silver alloys other than the silver aluminum alloy, an aluminum alloy, or the like.
- the reflection layer may be constituted by a thin film, a metal foil, a solder mask (solder), or the like.
- the reflection layer may be provided on the submount 4 , or may be provided on the opaque substrate 2 .
- An LED module 1 of the present embodiment differs from the LED module 1 of Embodiment 2 in that, as shown in FIGS. 38A , 38 B, and 38 C, an opaque substrate 2 has an elongated shape and a plurality of LED chips 6 are included. Note that, constituent elements similar to those in Embodiment 2 are provided with the same reference numerals, and redundant description thereof will be omitted.
- the plurality of LED chips 6 are aligned in a prescribed direction (in the horizontal direction in FIG. 38B ) on a surface 2 sa of the opaque substrate 2 .
- the LED chips 6 aligned in the prescribed direction and wires 7 that are connected to the respective LED chips 6 are covered by a color conversion portion 10 having a band shape.
- the color conversion portion 10 has recessed portions 10 b to suppress total reflection of light emitted from the LED chips 6 between adjacent LED chips 6 to each other in the prescribed direction.
- a patterned conductors (patterned wiring circuit) 8 serving as a wiring circuit includes a first patterned wiring (first pattern) 8 a to which a first electrode of the LED chip 6 is to be connected and a second patterned wiring (second pattern) 8 b to which the second electrode of the LED chip 6 is to be connected.
- the first patterned wiring 8 a and the second patterned wiring 8 b each have a planar shape of a comb shape, and are arrayed so as to interdigitate in the lateral direction of the opaque substrate 2 .
- a first shaft 8 aa of the first patterned wiring 8 a faces a second shaft 8 ba of the second patterned wiring 8 b .
- first comb teeth 8 ab of the first patterned wiring 8 a and second comb teeth 8 bb of the second patterned wiring 8 b are arranged alternately in in the longitudinal direction of the opaque substrate 2 and separated by a space.
- the plurality of (nine in an example shown in the diagram) LED chips 6 are arranged in the longitudinal direction (in the aforementioned prescribed direction) of the opaque substrate 2 and are connected in parallel.
- power can be supplied to a parallel circuit in which the plurality of LED chips 6 are connected in parallel.
- power can be supplied to all the LED chips 6 by applying voltage between the first patterned wiring 8 a and the second patterned wiring 8 b .
- adjacent LED modules 1 may be electrically connected by conductive members, wires for feed wiring (not shown), connectors (not shown), or the like.
- one power supply unit can supply power to the plurality of LED modules 1 so that all the LED chips 6 of the respective LED modules 1 can emit light.
- the patterned conductors 8 are preferably provided with a surface treatment layer (not shown).
- the surface treatment layer is preferably made of a metal material having higher oxidation-resistance and corrosion-resistance than the material of the patterned conductors 8 .
- the surface treatment layer is preferably a nickel film, a stack of a nickel film and a gold film, a stack of a nickel film, a palladium film, and a gold film, a stack of a nickel film and a palladium film, or the like, for example.
- the surface treatment layer is more preferably a stack of a nickel film and a palladium film, from the viewpoint of cost reduction.
- the surface treatment layer may be formed by plating.
- the color conversion portion 10 is made of a resin containing a fluorescent material, for example.
- the color conversion portion 10 is preferably made of the resin in which the fluorescent material is dispersed.
- the resin of the color conversion portion 10 is not particularly limited, as long as it transmits light emitted from the LED chip 6 as well as light emitted from the fluorescent material.
- the resin of the color conversion portion 10 may be a silicone resin, an epoxy resin, an acrylic resin, an urethane resin, an oxetane resin, a polycarbonate resin, or the like.
- the silicone resin is preferable from a viewpoint of thermal resistance and weather resistance, and gel-like silicone is more preferable from a viewpoint of suppressing breaking of the wires 7 due to a thermal stress caused by temperature cycling.
- the fluorescent material functions as a wavelength conversion material to convert light emitted from the LED chip 6 into light having a longer wavelength than the light emitted from the LED chip 6 . Accordingly, the LED module 1 can provide mixed-color light constituted by the light emitted from the LED chip 6 and light emitted from the fluorescent material.
- the color conversion portion 10 has a function serving as a wavelength conversion portion to convert light emitted from the LED chip 6 into light having a longer wavelength than the light emitted from the LED chip 6 .
- the color conversion portion 10 has a function serving as an encapsulating portion for encapsulating each LED chip 6 and each wire 7 .
- the LED module 1 can emit white light. That is, in the LED module 1 , blue light emitted from the LED chip 6 and light emitted from the yellow fluorescent material can be emitted outside through the surface of the color conversion portion 10 , and as a result, white light can be obtained.
- the fluorescent material serving as the wavelength conversion material is not limited to the yellow fluorescent material, and may include, for example, a set of a yellow fluorescent material and a red fluorescent material, or a set of a red fluorescent material and a green fluorescent material. Also, the fluorescent material serving as the wavelength conversion material is not limited to one kind of yellow fluorescent material, and may include two kinds of yellow fluorescent materials having different emission peak wavelengths.
- the color rendering property of LED module 1 can be improved by use of a plurality of fluorescent materials as the wavelength conversion material.
- the color conversion portion 10 has, as described above, recessed portions 10 b to suppress total reflection of light emitted from each of the LED chips 6 between the LED chips 6 which are adjacent to each other in the prescribed direction. Accordingly. in the LED module 1 , it is possible to suppress total reflection of light which is emitted from the LED chip 6 and then strikes an interface between the color conversion portion 10 and air. Consequently, in the LED module 1 , it is possible to reduce an amount of light which is confined due to total reflection, compared with the LED module including the color conversion portion 10 having a hemicylindrical shape, and therefore light outcoupling efficiency can be improved. In short, in the LED module 1 , a total reflection loss can be reduced, and light outcoupling efficiency can be improved.
- the color conversion portion 10 is formed so as to have a cross section including a step which corresponds to a step between the face of the LED chip 6 and the surface 2 sa of the opaque substrate 2 . Consequently, the color conversion portion 10 has a cross section along a direction orthogonal to the arrangement direction of the LED chips 6 , and a cross section along the arrangement direction of the LED chips 6 , the former is a convex shape while the latter has recesses and convexes. In short, in the LED module 1 , the color conversion portion 10 with a band shape has a recess and convex structure to improve the light outcoupling efficiency.
- the period of the recess and convex structure is the same as the array pitch of the LED chips 6 .
- the period of the recess and convex structure is the array pitch of the convex portions 10 a which cover respective LED chips 6 .
- the surface shape of the color conversion portion 10 may be designed such that the angle between a light ray from the LED chip 6 and a normal line on the surface of the color conversion portion 10 at a point where the light ray from the LED chip 6 crosses the surface thereof is smaller than the critical angle.
- each of the convex portions 10 a of the color conversion portion 10 is preferably designed to have the surface shape such that, in substantially all the areas of the surface of the convex portion 10 a of the color conversion portion 10 , the incident angle (light incident angle) of the light ray from the LED chip 6 is smaller than the critical angle.
- each of the convex portions 10 a which covers a corresponding LED chip 6 is preferably formed in a hemispherical shape.
- Each convex portion 10 a is designed such that the light axis of the convex portion 10 a is aligned with the light axis of the LED chip 6 covered with the convex portion 10 a in the thickness direction of the opaque substrate 2 . Accordingly, in the LED module 1 , it is possible to suppress not only the total reflection at the surface (interface between the color conversion portion 10 and air) of the color conversion portion 10 but also color unevenness.
- the color unevenness is a state in which chromaticity varies depending on an irradiation direction of light. In the LED module 1 , the color unevenness can be suppressed to such an extent the color unevenness cannot be perceived visually.
- each convex portion 10 a of the color conversion portion 10 is not limited to hemisphere, and may be a semielliptical shape, for example. Note that, each convex portion 10 a may have a shape, a cuboid shape, or the like.
- the opaque substrate 2 is prepared. Thereafter, the LED chips 6 are die-bonded on the surface 2 sa of the opaque substrate 2 with a die bonding apparatus or the like. Thereafter, the first electrode and the second electrode of each of the LED chips 6 are connected to the patterned wiring circuit 8 via the respective wires 7 with a wire bonding apparatus, or the like. Thereafter, the color conversion portion 10 is formed using a dispenser system or the like.
- a material of the color conversion portion 10 is applied by discharging the material from a nozzle while a dispenser head is moved in the arrangement direction of the LED chips 6 , for example.
- the material is discharged and applied while the dispenser head is moved, for example.
- an application amount is varied by varying the moving speed of the dispenser head while the distance between the nozzle and the surface 2 sa of the opaque substrate 2 directly under the nozzle is varied by moving the dispenser head up and down. More specifically, the moving speed of the dispenser head is relatively varied in applying the material between in a region to form the convex portion 10 a of the color conversion portion 10 and in a region to form a portion of the color conversion portion 10 between adjacent convex portions 10 a .
- the moving speed of the dispenser head is slow in the former region, and the moving speed thereof is fast in the latter region. Moreover, the dispenser head is moved up and down depending on the surface shape of the color conversion portion 10 . Accordingly, by the method of forming the color conversion portion 10 with the dispenser system, it is possible to form, with the material, the application shape in accordance with the surface shape of the color conversion portion 10 .
- the application shape may be set in view of contraction in curing the material.
- the dispenser system preferably includes: a movement mechanism constituted by a robot for moving the dispenser head; a sensor unit for measuring heights of the surface 2 sa of the opaque substrate 2 and the nozzle from a table; and a controller for controlling the movement mechanism and a discharge amount of the material from the nozzle.
- the controller can be realized, for example, by loading an appropriate program to a microcomputer.
- the dispenser system can be adapted to various types of products different in the array pitch of the LED chips 6 , the number of the LED chips 6 , the width of the color conversion portion 10 , or the like, by changing the program loaded to the controller appropriately.
- the surface shape of the color conversion portion 10 can be controlled by adjusting viscosity or the like of the material, for example.
- the curvature of the surface (convex face) in each of the convex portions 10 a can be designed with viscosity and surface tension of the material, a height of the wire 7 , or the like. Larger curvature can be realized by increasing the viscosity and the surface tension of the material, or by increasing the height of the wire 7 .
- a smaller width (band width) of the color conversion portion 10 having the band shape can be realized by increasing the viscosity and the surface tension of the material.
- the viscosity of the material is preferably set to be in a range of around 100 to 2000 mPa ⁇ s. Note that, the value of the viscosity may be measured under a room temperature using a cone and plate rotational viscometer, for example.
- the dispenser system may include a heater to heat an un-cured material so as to adjust viscosity to a desirable value. Accordingly, in the dispenser system, reproducibility of the application shape of the material can be improved, and reproducibility of the surface shape of the color conversion portion 10 can be improved.
- a plurality of LED chips 6 are arranged on the surface 2 sa of the opaque substrate 2 in a prescribed direction (hereinafter, referred to as “first direction”) at equal intervals.
- the patterned conductors 8 serving as a wiring circuit includes the first patterned wiring 8 a and the second patterned wiring 8 b which are each formed into a comb shape and interdigitate.
- the first patterned wiring 8 a is electrically connected to the first electrode of each of the LED chip 6 via the wire 7 (hereinafter, referred to as “first wire 7 a ”).
- the second patterned wiring 8 b is electrically connected to the second electrode of each of the LED chip 6 via the wire 7 (hereinafter, referred to as “second wire 7 b ”).
- the first patterned wiring 8 a includes a first shaft 8 aa formed along the first direction and a plurality of first comb teeth 8 ab which are formed along a second direction orthogonal to the first direction.
- the second patterned wiring 8 b includes a second shaft 8 ba which is formed along the first direction and a plurality of second comb teeth 8 bb which are formed along the second direction.
- the plurality of first comb teeth 8 ab of the first patterned wiring 8 a are constituted by first comb teeth 8 ab ( 8 ab 1 ) having a relatively large tooth width and first comb teeth 8 ab ( 8 ab 2 ) having a relatively small tooth width.
- first comb teeth 8 ab 1 and the narrow first comb teeth 8 ab 2 are arranged alternately in the first direction.
- the plurality of second comb teeth 8 bb of the second patterned wiring 8 b are constituted by second comb teeth 8 bb ( 8 bb 1 ) having a relatively large tooth width and second comb teeth 8 bb ( 8 bb 2 ) having a relatively small tooth width.
- the wide second comb teeth 8 bb 1 and the narrow second comb teeth 8 bb 2 are arranged alternately in the first direction.
- the patterned conductors 8 includes the wide first comb teeth 8 ab 1 , the narrow second comb teeth 8 bb 2 , the narrow first comb teeth 8 ab 2 , and the comb teeth 8 bb 1 which are arranged cyclically in the first direction.
- the opaque substrate 2 is provided with the patterned wiring circuit 8 on a surface of a base substrate 2 a having an electrical insulation property. and a mask layer 2 b which covers the patterned wiring circuit 8 over the surface of the base substrate 2 a .
- the mask layer 2 b is formed over the surface of the base substrate 2 a so as to also cover portions in which the patterned wiring circuit 8 is not formed.
- the material of the mask layer 2 b may be a white mask made of a resin (such as silicone resin) which contains a white pigment such as barium sulfate (BaSO 4 ) and titanium dioxide (TiO 2 ).
- the white mask may be a white mask material “ASA COLOR(registered trademark) RESIST INK” made of silicone produced by Asahi Rubber Inc., or the like.
- the mask layer 2 b has a plurality of openings 2 ba for exposing first pads on the first comb teeth 8 ab to which the respective first wires 7 a are connected and a plurality of openings 2 bb for exposing second pads on the second comb teeth 8 bb to which the respective second wires 7 b are connected.
- the mask layer 2 b has the openings 2 ba and the openings 2 bb which are formed alternately in the first direction.
- the plurality of openings 2 ba and the plurality of openings 2 bb are formed so as to be aligned on a line.
- the openings 2 ba for exposing the first pads on the wide first comb teeth 8 ab 1 are located at a distant side from the respective adjacent narrow second comb teeth 8 bb 2 with respect to the respective center lines of the wide first comb teeth 8 ab 1 in the first direction.
- the submounts 4 and the LED chips 6 are arranged vertically above regions on the wide first comb teeth 8 ab 1 that are close to the respective narrow second comb teeth 8 bb 2 with respect to the respective center lines thereof.
- the openings 2 ba for exposing the first pads on the narrow first comb teeth 8 ab 2 are located on the respective center lines of the narrow first comb teeth 8 ab 2 .
- the openings 2 bb for exposing the second pads on the wide second comb teeth 8 bb 1 are located at a distant side from the respective adjacent narrow first comb teeth 8 ab 2 with respect to the respective center lines of the wide second comb teeth 8 bb 1 in the first direction.
- the submounts 4 and the LED chips 6 are arranged vertically above regions on the wide second comb teeth 8 bb 1 that are close to the respective narrow first comb teeth 8 ab 2 with respect to the respective center lines thereof.
- the openings 2 bb for exposing the second pads on the narrow second comb teeth 8 bb 2 are located on the respective center lines of the narrow second comb teeth 8 bb 2 .
- Each LED chip 6 is located between, in a planar view, the first pad to which the first electrode is connected via the first wire 7 a and the second pad to which the second electrode is connected via the second wire 7 b .
- the plurality of LED chips 6 , the plurality of first pads, and the plurality of second pads are formed so as to be aligned on a line in a planar view.
- the color conversion portion 10 is formed in a band shape to cover the plurality of LED chips 6 , the plurality of first wires 7 a , and the plurality of second wires 7 b .
- the cross section of the color conversion portion 10 along a direction orthogonal to the first direction is a hemispherical shape.
- the color conversion portion 10 may have a similar shape to that of Embodiment 3.
- the patterned conductors 8 is present on the opaque substrate 2 to overlap respective vertical projection regions of the LED chips 6 .
- heat generated in the LED chips 6 and the color conversion portions 10 in lighting can thereby be conducted to a wide area via the patterned conductors 8 . That is, in the LED module 1 of the modification, a heat dissipation property can be improved, and light output can be increased.
- the directions of the LED chips 6 can be made the same. handling of the LED chips 6 in bonding process of the LED chips 6 on the respective submounts 4 on the opaque substrate 2 can be facilitated, and manufacturing can be facilitated.
- the LED modules 1 of Embodiments 2 and 3 and the LED module 1 of the modification of Embodiment 3 can be used as a light source for a variety of lighting apparatuses, similar to the LED modules 1 of Embodiment 1 and the first modification to the eleventh modification of Embodiment 1.
- a lighting apparatus which includes the LED module 1 include: a lighting device having a light source which is the LED module 1 and provided on a device main body; and a lamp (such as a straight-tube LED lamp and a bulb type lamp), but the lighting apparatus is not limited thereto and may be other lighting apparatuses.
- a lighting device 50 including the LED module 1 of Embodiment 3 as a light source will be described with reference to FIGS. 41A and 41B .
- the lighting device 50 is an LED lighting device and includes a device main body 51 and an LED module 1 serving as a light source held by the device main body 51 .
- the device main body 51 is formed in an elongated shape (rectangle plate shape, here) and is larger than the LED module 1 in a planar size.
- the LED module 1 is provided on a surface 51 b of the device main body 51 in the thickness direction.
- the LED module 1 and the device main body 51 are arranged such that the longitudinal direction of the LED module 1 is aligned with the longitudinal direction of the device main body 51 .
- the lighting device 50 includes a cover 52 for covering the LED module 1 provided on the surface 51 b of the device main body 51 .
- the cover 52 transmits light which is emitted from the LED module 1 .
- the lighting device 50 includes a lighting unit 53 which supplies direct current electric power to the LED module 1 for lighting (allowing light emission) each of the LED chips 2 .
- the lighting unit 53 and the LED module 1 are electrically connected via wires 54 e.g., lead wires.
- a recess 51 a is formed to house the lighting unit 53 .
- the recess 51 a is formed along the longitudinal direction of the device main body 51 .
- the device main body 51 has a through hole (not shown) to which the wire 54 is to be inserted. The through hole penetrates a thin portion between the surface 51 b and the inner bottom face of the recess 51 a.
- connection portion between the patterned conductors 8 and the wire 54 may be a connection portion composed of a conductive bonding material such as solder, a connection portion constituted by a male connector and a female connector, or the like.
- the LED module 1 can be lighted with direct current electric power supplied from the lighting unit 53 .
- the lighting unit 53 may receive power from an alternating current power supply such as a commercial power supply, or receive electric power from a direct current power supply such as a solar cell and a storage battery.
- the light source in the lighting device 50 is not limited to the LED module 1 of Embodiment 3, but may be any of LED modules 1 of Embodiment 1, the first modification to the ninth modification of Embodiment 1, Embodiment 2, and the first modification to the fourth modification of Embodiment 2.
- the device main body 51 is preferably made of a material having high thermal conductivity, and is more preferably made of a material having higher thermal conductivity than the opaque substrate 2 .
- the device main body 51 is preferably made of a metal having high thermal conductivity such as aluminum and copper.
- the LED module 1 may be fixed to the device main body 51 by: a method using a fixture such as a screw; or bonding the device main body 51 to the LED module 1 by providing therebetween an epoxy resin layer which is a thermoset sheet adhesive.
- the sheet adhesive may be a sheet adhesive made of a stack of a plastic film (PET film) and a B stage epoxy resin layer (thermoset resin).
- the B stage epoxy resin layer contains a filling material composed of a filler such as silica and alumina and has a property in which viscosity becomes small and fluidity becomes large when heated.
- Such a sheet adhesive may be an adhesive sheet TSA available from Toray Industries, Inc. or the like.
- the filler may be an electrical insulation material having high thermal conductivity than an epoxy resin which is a thermoset resin.
- the thickness of the aforementioned epoxy resin layer is set to be 100 ⁇ m, but this value is an example, and the thickness is not limited thereto, and may be set in a range of around 50 ⁇ m to 150 ⁇ m as appropriate.
- the thermal conductivity of the aforementioned epoxy resin layer is preferably larger than 4 W/m ⁇ K.
- the epoxy resin layer which is a sheet adhesive described above has high thermal conductivity, high fluidity when heated, and high adhesiveness to a surface having asperity, along with having an electrical insulation property. Consequently, in the lighting device 50 , it is possible to suppress generation of gaps between the aforementioned insulation layer of the epoxy resin layer and the LED module 1 and between the insulation layer and the device main body 51 , and as a result it is possible to improve adhesion reliability and to suppress an increase of a thermal resistance and occurrence of variation due to lack of adhesion.
- the insulation layer has an electrical insulation property and thermal conductivity, and has a function of connecting the LED module 1 and the device main body 51 thermally.
- the lighting device 50 it is possible to lower a thermal resistance between each LED chip 6 and the device main body 51 and reduce a variation of thermal resistances, compared with a lighting device where a heat dissipation sheet (heat conduction sheet) of a rubber sheet type or a silicone gel type such as Sarcon(registered trademark) is interposed between the LED module 1 and the device main body 51 . Accordingly, in the lighting device 50 , since the heat dissipation property is improved and therefore an increase in junction temperature of each of the LED chips 6 can be suppressed. Hence, input power can be increased and light output can be increased.
- a heat dissipation sheet heat conduction sheet
- a silicone gel type such as Sarcon(registered trademark)
- the thickness of the aforementioned epoxy resin layer is set to be 100 ⁇ m, but this value is an example, and the thickness is not limited thereto, and may be set in a range of around 50 ⁇ m to 150 ⁇ m as appropriate.
- the thermal conductivity of the aforementioned epoxy resin layer is preferably larger than 4 W/m ⁇ K.
- the cover 52 may be made of an acrylic resin, a polycarbonate resin, a silicone resin, glass, or the like.
- the cover 52 has a lens portion (not shown) which is formed integrally therewith and controls a directional distribution of light emitted from the LED module 1 . Cost can be reduced compared with a configuration in which a lens which has been separately prepared from the cover 52 is attached to the cover 52 .
- the lighting device 50 described above includes the LED module 1 serving as the light source, and therefore cost thereof can be reduced and light output thereof can be increased.
- the lighting device 50 includes the device main body 51 made of metal, and therefore the heat dissipation property thereof can be improved.
- a straight-tube LED lamp 80 including a light source that is the LED module 1 of Embodiment 3 will be described with reference to FIGS. 42A and 42B .
- the straight-tube LED lamp 80 includes: a tube main body 81 having a straight-tube shape (cylindrical shape) formed of a light-transmissive material; and a first cap 82 and a second cap 83 that are respectively provided at an end portion and the other end portion of the tube main body 81 in the longitudinal direction.
- the LED module 1 of Embodiment 3 is housed in the tube main body 81 .
- the LED module 1 is not limited to the LED module 1 of Embodiment 3, but may be any of LED modules 1 of Embodiment 1, the first modification to the ninth modification of Embodiment 1, Embodiment 2, the first modification to fourth modification of Embodiment 2, and the modification of Embodiment 3.
- “straight-tube LED lamp system with L-type pin cap GX16t-5 (for general illumination)” JEL 801:2010
- JEL 801:2010 is standardized by Japan Electric Lamp Manufacturers Association, for example.
- the tube main body 81 may be made of transparent glass, milky white glass, a transparent resin, a milky white resin, or the like.
- the first cap 82 has two power supply terminals 84 and 84 (hereinafter referred to as “first lamp pins”) which are electrically connected to the LED module 1 . These two first lamp pins 84 and 84 are configured to be electrically connected to two power supply contacts respectively of a lamp socket for a power supply which is held in the device main body of a lighting device (not shown).
- the second cap 83 has one grounding terminal 85 (hereinafter referred to as “second lamp pin”) for grounding.
- This one second lamp pin 85 is configured to be electrically connected to a grounding contact of a lamp socket for grounding which is held in the device main body.
- Each of the first lamp pins 84 is formed in an L-shape. and is constituted by a pin main body 84 a which protrudes along the longitudinal direction of the tube main body 81 and a key portion 84 b which extends along the radial direction of the tube main body 81 from the tip of the pin main body 84 a .
- the two key portions 84 b extend in directions so as to be farther from each other. Note that each of the first lamp pins 84 is formed by bending a long metal plate.
- the second lamp pin 85 protrudes from an end face (cap reference face) of the second cap 83 in the opposite direction to the tube main body 81 .
- the second lamp pin 85 is formed in a T-shape.
- the straight-tube LED lamp 80 is preferably configured so as to meet the standard of “straight-tube LED lamp system with L-type pin cap GX16t-5 (for general illumination)” (JEL 801:2010) which is standardized by Japan Electric Lamp Manufacturers Association, or the like.
- the straight-tube LED lamp 80 as described above includes the aforementioned LED module 1 in the tube main body 81 , and therefore cost thereof can be reduced and light output thereof can be increased.
- a lamp which includes the LED module 1 is not limited to the aforementioned straight-tube LED lamp, and may be a straight-tube LED lamp including the LED module 1 and a lighting unit to switch on the LED module 1 both in the tube main body. Note that power is supplied to the lighting unit from an external power supply via lamp pins.
- the LED module 1 of Embodiment 3 includes the opaque substrate 2 having an elongated shape and a plurality of the LED chips 6 , but the shape of the opaque substrate 2 and the number of LED chips 6 and arrangement of the LED chips 6 can be changed as appropriate depending on the type or the like of the lighting device to which the LED module 1 is applied.
- the lighting device 70 is an LED lighting device which can be used as a downlight, and includes a device main body 71 and a light source that is the LED module 1 and is held by the device main body 71 .
- the lighting device 70 includes a case 78 which has a rectangular box shape and accommodates a lighting unit to operate the LED module 1 .
- the lighting unit and the LED module 1 are electrically connected by wires (unshown) or the like.
- the device main body 71 is formed in a disk shape, and the LED module 1 is present on a face of the device main body 71 .
- the lighting device 70 includes a plurality of fins 71 ab which protrude from a further face of the device main body 71 .
- the device main body 71 and the fins 71 ab are formed integrally.
- an opaque substrate 2 has a rectangular shape, a plurality of (not shown) LED chips are arranged in a two-dimensional array on a surface 2 sa of the opaque substrate 2 , and a color conversion portion 10 covers all these plurality of LED chips. Note that. this LED chip may be the same as the LED chip 6 in Embodiment 3.
- the lighting device 70 includes a first reflector 73 to reflect light which is emitted laterally from the LED module 1 , a cover 72 , and a second reflector 74 to control a directional distribution of light which is outputted from the cover 72 .
- a first reflector 73 to reflect light which is emitted laterally from the LED module 1
- a cover 72 to control a directional distribution of light which is outputted from the cover 72 .
- an outer cover to house the LED module 1 , the first reflector 73 and the cover 72 is constituted by the device main body 71 and the second reflector 74 .
- the device main body 71 has two projecting base portions 71 a , which face each other on the face thereof.
- a plate shaped fixing member 75 to fix the LED module 1 is attached to the two projecting base portions 71 a .
- the fixing member 75 is formed of a metal plate, and is fixed to each of the projecting base portions 71 a by a screw 77 .
- the first reflector 73 is fixed to the device main body 71 .
- the LED module 1 may be sandwiched between the first reflector 73 and the fixing member 75 .
- the first reflector 73 is formed of a white synthetic resin.
- the fixing member 75 has an opening 75 a for exposing part of the opaque substrate 2 of the LED module 1 .
- the lighting device 70 includes a thermal conduction portion 76 interposed between the opaque substrate 2 and the device main body 71 .
- the thermal conduction portion 76 has a function of conducting heat from the opaque substrate 2 to the device main body 71 .
- the thermal conduction portion 76 is formed of a heat-conductive grease, but is not limited thereto, and may be formed of a heat-conductive sheet.
- the heat-conductive sheet may be a silicone gel sheet having electrical insulation and thermal conductivity.
- the silicone gel sheet used as the heat-conductive sheet is preferably soft. This king of silicone gel sheet may be Sarcon(registered trademark) or the like.
- the material of the heat-conductive sheet is not limited to silicone gel, and may be elastomer, for example, so long as the material has electrical insulation and thermal conductivity.
- heat generated in the LED module 1 can be efficiently conducted to the device main body 71 via the thermal conduction portion 76 . Consequently, in the lighting device 70 , heat generated in the LED module 1 can be efficiently released from the device main body 71 and the fins 71 ab.
- the device main body 71 and the fins 71 ab are preferably formed of a material having high thermal conductivity, and more preferably made of a material having higher thermal conductivity than the opaque substrate 2 .
- the device main body 71 and the fins 71 ab are preferably formed of a metal having high thermal conductivity such as aluminum and copper.
- the cover 72 may be made of an acrylic resin, a polycarbonate resin, a silicone resin, glass, or the like.
- the cover 72 may has a lens portion (not shown) for controlling a directional distribution of light emitted from the LED module 1 .
- the cover 72 and the lens portion may be formed integrally.
- the second reflector 74 may be made of aluminum, stainless steel, a resin, ceramic, or the like.
- the lighting device 70 described above includes a light source that is the aforementioned LED module 1 , and therefore cost can be reduced and light output can be increased. Besides, the lighting device 70 may have a configuration in which the device main body 71 also serves as the opaque substrate 2 of the LED module 1 .
Abstract
An LED module includes: an opaque substrate on which a wiring circuit is provided; a submount bonded to a surface of the opaque substrate with a first bond; an LED chip bonded with a second bond to an opposite side of the submount from the opaque substrate; and wires electrically connecting the LED chip to patterned wiring circuit. In the LED module, the first bond and the second bond each allow light emitted from the LED chip to pass therethrough. The submount is a light-transmissive member. A lighting device includes a device main body and the LED module. The lamp includes the LED module.
Description
- The present invention relates to an LED module, a lighting device, and a lamp.
- Heretofore, a
light emission apparatus 100 having a configuration shown inFIG. 45 has been proposed (JP 2008-91831A: Patent Document 1). Thelight emission apparatus 100 includes asubmount substrate 120 having a nitride-basedceramic substrate 121, anAu layer 124 provided on a surface of the nitride basedceramic substrate 121, anoxide layer 123 interposed between the nitride basedceramic substrate 121 and theAu layer 124, and an LED light-emitting element 126 mounted on thesubmount substrate 120 via asolder layer 125. Theoxide layer 123 includes a metal oxide as a main component. Thesubmount substrate 120 has a reflectinglayer 122 composed of at least one of Ag and Al that is formed on the surface of the nitride-basedceramic substrate 121 so as not to overlap theAu layer 124. -
Patent Document 1 discloses that, for the purpose of extracting light efficiently from the LED light-emittingelement 126, it is preferable to use the nitride-basedceramic substrate 121 of aluminum nitride having high reflectance. - Also, heretofore, a chip-type light-emitting element having a configuration shown in
FIG. 46 has been proposed (JP 11-112025A: Patent Document 2). The chip-type light-emitting element includes aninsulating substrate 201, anLED chip 206 that is mounted on a surface of theinsulating substrate 201, and apackage 207 which covers theLED chip 206 and surroundings thereof. -
Patent Document 2 discloses that blue light propagating toward the back face of the substrate of theLED chip 206 can be reflected by theinsulating substrate 201 that is a white insulating substrate composed of ceramics such as alumina and aluminum nitride. - Also, heretofore, as shown in
FIG. 47 , a configuration has been proposed in which a light emission apparatus is mounted on an external circuit substrate 301 (JP 2006-237557A: Patent Document 3). The light emission apparatus includes: a light-emitting element housing package having asubstrate 304 and a reflectingmember 302; and a light-emittingelement 306 constituted by an LED chip mounted on amounting portion 304 a of thesubstrate 304. -
Patent Document 3 discloses that thesubstrate 304 and the reflectingmember 302 are preferably composed of white ceramics. Also,Patent Document 3 discloses a lighting apparatus including the above-mentioned light emission apparatus as a light source. - In the
light emission apparatus 100 having the configuration shown inFIG. 45 , it is speculated that part of light emitted from a light-emitting layer of the LED light-emittingelement 126 propagates toward the nitride-basedceramic substrate 121 through the LED light-emittingelement 126 and is reflected by thesolder layer 125. However, in thelight emission apparatus 100, it is speculated that light outcoupling efficiency decreases due to absorption, multiple reflection and the like of the light reflected by thesolder layer 125 in the LED light-emitting element 126. - In the chip-type light-emitting element having the configuration shown in
FIG. 46 , blue light that propagates toward the back face of the substrate of theLED chip 206 is reflected by theinsulating substrate 201. It is speculated that light outcoupling efficiency decreases due to absorption, multiple reflection and the like of the light in theLED chip 206. - In the configuration shown in
FIG. 47 , part of the light emitted from a light-emitting layer of the light-emittingelement 306 propagates toward thesubstrate 304 through the light-emittingelement 306, and is reflected by thesubstrate 304. It is speculated that light outcoupling efficiency decreases due to absorption, multiple reflection, and the like of the light in the light-emittingelement 306. - The present invention has been made in view of the above-described insufficiencies, and an object of the present invention is to provide an LED module, a lighting device, and a lamp each having improved light outcoupling efficiency.
- An LED module in accordance with the present invention includes: an opaque substrate on which a wiring circuit is provided; a submount bonded to a surface of the opaque substrate with a first bond; an LED chip bonded with a second bond to a face on an opposite side of the submount from the opaque substrate; and wires electrically connecting the LED chip to the wiring circuit. Each of the first bond and the second bond allows light emitted from the LED chip to pass therethrough, and the submount is a light-transmissive member.
- In this LED module, the submount preferably has light diffusing properties.
- In this LED module, the submount preferably has a planar size larger than a planar size of the LED chip.
- In this LED module, the surface of the opaque substrate preferably has light diffusing properties.
- In this LED module, the surface of the opaque substrate preferably has specular reflective properties.
- In this LED module, the opaque substrate preferably functions as a heat sink.
- In this LED module, at least one of the first bond and the second bond preferably contains a first fluorescent material which is excited by the light emitted from the LED chip to emit light having a different color from the light emitted from the LED chip.
- This LED module preferably includes a color conversion portion made of a transparent material containing a second fluorescent material which is excited by the light emitted from the LED chip to emit light having a different color from the light emitted from the LED chip, the color conversion portion covering sides of the LED chip and an opposite surface of the LED chip from the first bond.
- In this LED module, the color conversion portion preferably contains a light diffusion material.
- This LED module preferably includes a resin portion which is situated over the face of the submount and serves as an outer cover through which light passes last, the resin portion being made of a transparent resin which contains a light diffusion material.
- In this LED module, the submount is preferably constituted by a plurality of light-transmissive layers which are stacked in a thickness direction of the submount and have different optical properties so that a light-transmissive layer of the plurality of light-transmissive layers which is farther from the LED chip is higher in reflectance in a wavelength range of the light emitted from the LED chip.
- In this LED module, each of the plurality of light-transmissive layers is a ceramic layer.
- A lighting device in accordance with the present invention includes a device main body; and the LED module which is held on the device main body.
- A lamp in accordance with the present invention includes a light source that is the LED module.
- The LED module in accordance with the present invention includes: the first bond and the second bond each allowing the light emitted from the LED chip to pass therethrough; and the submount being the light-transmissive member, and therefore can have improved light outcoupling efficiency.
- The lighting device in accordance with the present invention can have improved light outcoupling efficiency.
- The lamp in accordance with the present invention can have improved light outcoupling efficiency.
- FIG. I is a schematic cross-section of an LED module of
Embodiment 1; -
FIG. 2 is a schematic explanatory diagram of a propagating path of light in the LED module ofEmbodiment 1; -
FIG. 3 is a schematic explanatory diagram of a propagating path of light in the LED module ofEmbodiment 1; -
FIG. 4 is a schematic explanatory diagram of a propagating path of light in the LED module ofEmbodiment 1; -
FIG. 5 is a schematic explanatory diagram of a propagating path of light in the LED module ofEmbodiment 1; -
FIG. 6 is a schematic cross-section illustrating the first modification of the LED module ofEmbodiment 1; -
FIG. 7 is a main portion schematic cross-section of the second modification of the LED module ofEmbodiment 1; -
FIG. 8 is a main portion schematic cross-section of the third modification of the LED module ofEmbodiment 1; -
FIG. 9 is a main portion schematic cross-section of an exemplary configuration of the fourth modification of the LED module ofEmbodiment 1; -
FIG. 10 is a main portion schematic cross-section of the fifth modification of the LED module ofEmbodiment 1; -
FIG. 11 is a main portion schematic cross-section of the sixth modification of the LED module ofEmbodiment 1; -
FIG. 12 is a main portion schematic cross-section of the seventh modification of the LED module ofEmbodiment 1; -
FIG. 13 is an explanatory diagram of dimensional parameters of a submount and an LED chip of the seventh modification of the LED module ofEmbodiment 1; -
FIG. 14A is a schematic perspective view illustrating another exemplary configuration of the submount of the seventh modification of the LED module ofEmbodiment 1; -
FIG. 14B is an explanatory diagram of dimensional parameters of the exemplary configuration of the submount of the seventh modification of the LED module ofEmbodiment 1; -
FIG. 15A is a schematic perspective view illustrating another exemplary configuration of the submount of the seventh modification of the LED module ofEmbodiment 1; -
FIG. 15B is an explanatory diagram of dimensional parameters of the exemplary configuration of the submount of the seventh modification of the LED module ofEmbodiment 1; -
FIG. 16 is a schematic cross-section illustrating the submount and the LED chip of the seventh modification of the LED module ofEmbodiment 1; -
FIG. 17 is a main portion schematic cross-section of the eighth modification of the LED module ofEmbodiment 1; -
FIG. 18 is a main portion schematic cross-section of the ninth modification of the LED module ofEmbodiment 1; -
FIG. 19 is a main portion schematic cross-section of the tenth modification of the LED module ofEmbodiment 1; -
FIG. 20 is a schematic cross-section of an LED module ofEmbodiment 2; -
FIG. 21 is a perspective view of a submount of the LED module ofEmbodiment 2; -
FIG. 22 is a schematic explanatory diagram of a propagating path of light in the LED module ofEmbodiment 2; -
FIG. 23 is an explanatory diagram of the relation between a particle diameter and reflectance of an alumina particle; -
FIG. 24 is an explanatory diagram of a simulation result of the relation between a thickness of a submount and light outcoupling efficiency in an LED module of a comparative example; -
FIG. 25 is an explanatory diagram of a simulation result of the relation between a planar size of the submount and a light outputting amount of the LED module of the comparative example; -
FIG. 26 is an explanatory diagram of an experimental result of the relation between a thickness of the submount and light outcoupling efficiency; -
FIG. 27 is a reflectance-wavelength characteristic diagram of a submount and an alumina substrate in Example 1 ofEmbodiment 2; -
FIG. 28 is an explanatory diagram of an experimental result of the relation between a particle diameter of an alumina particle in a first ceramic layer and efficiency and color difference; -
FIG. 29 is a schematic explanatory diagram of the submount in the LED module ofEmbodiment 2; -
FIG. 30 is an explanatory diagram of the relation between a glass compounding ratio of the submount in the LED module ofEmbodiment 2 and integrated intensity of an integrating sphere; -
FIG. 31 is a reflectance-wavelength characteristic diagram of the submount and an alumina substrate in Example 2 ofEmbodiment 2; -
FIG. 32 is a schematic cross-section illustrating the first modification of the LED module ofEmbodiment 2; -
FIG. 33 is an inferred mechanism diagram for illustrating the principle relating to improvement of light outcoupling efficiency in the first modification of the LED module ofEmbodiment 2; -
FIGS. 34A to 34C are inferred mechanism diagrams for illustrating the principle relating to improvement of light outcoupling efficiency in the first modification of the LED module ofEmbodiment 2; -
FIG. 35 is a schematic perspective view of the second modification of the LED module ofEmbodiment 2 with a partial cutaway thereof; -
FIG. 36 is a schematic perspective view of the third modification of the LED module ofEmbodiment 2, which is partially exploded; -
FIG. 37 is a main portion schematic cross-section of the fourth modification of the LED module ofEmbodiment 2; -
FIG. 38A is a schematic cross-section of an LED module ofEmbodiment 3; -
FIG. 38B is a schematic cross-section taken along X-X inFIG. 38A ; -
FIG. 38C is a schematic cross-section taken along Y-Y inFIG. 38A ; -
FIG. 39 is a schematic perspective view of the modification of the LED module ofEmbodiment 3 with a partial cutaway thereof; -
FIG. 40 is a schematic cross-section of the modification of the LED module ofEmbodiment 3; -
FIG. 41A is a schematic perspective view of a lighting device ofEmbodiment 3, which is partially exploded; -
FIG. 41B is a main portion enlarged view inFIG. 41A ; -
FIG. 42A is a schematic perspective view of a straight-tube LED lamp ofEmbodiment 3, which is partially exploded; -
FIG. 42B is a main portion enlarged view inFIG. 42A ; -
FIG. 43 is a schematic perspective view of another lighting device ofEmbodiment 3; -
FIG. 44 is a schematic perspective view of the lighting device ofEmbodiment 3, which is partially exploded; -
FIG. 45 is a cross section of a light emission apparatus of a conventional example; -
FIG. 46 is a perspective explanatory diagram of a chip-type light-emitting element of another conventional example; and -
FIG. 47 is a cross section of a configuration of yet another conventional example. - Hereinafter, an
LED module 1 of the present embodiment will be described with reference toFIGS. 1 to 5 . - The
LED module 1 includes: anopaque substrate 2 on which patterned conductors (patterned wiring circuit) 8 serving as a wiring circuit is provided; asubmount 4 bonded to asurface 2 sa of theopaque substrate 2 with afirst bond 3; anLED chip 6 bonded with asecond bond 5 to aface 4 sa on an opposite side of thesubmount 4 from theopaque substrate 2; andwires 7 electrically connecting theLED chip 6 to the patternedconductors 8, respectively. - In the
LED module 1, thefirst bond 3 and thesecond bond 5 allows light emitted from theLED chip 6 to pass therethrough, and thesubmount 4 is a light-transmissive member. The light-transmissive member propagates incident light to the outside through refraction or internal diffusion (scattering). - Accordingly, in the
LED module 1, part of the light emitted from a light-emitting layer (not shown) in theLED chip 6 passes through theLED chip 6 and thesecond bond 5, and thereafter is diffused inside thesubmount 4. Consequently, the light that has passed through theLED chip 6 and thesecond bond 5 is less likely to be totally reflected, and more likely to emerge from thesubmount 4 through either side faces 4 sc or theface 4 sa. Therefore, in theLED module 1, light outcoupling efficiency can be improved and a total light flux amount can be increased. - Hereinafter, each constituent element of the
LED module 1 will be described in detail. - The
LED chip 6 includes a first electrode (not shown) serving as an anode electrode and a second electrode (not shown) serving as a cathode electrode both on a face of theLED chip 6 in the thickness direction. - The
LED chip 6 includes, as shown inFIG. 2 , asubstrate 61 and anLED structure portion 60 on a main surface of thesubstrate 61. TheLED structure portion 60 includes an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer. The stacking order of the n-type semiconductor layer, the light-emitting layer, and the p-type semiconductor layer is the n-type semiconductor layer, the light-emitting layer, and the p-type semiconductor layer from thesubstrate 61. The stacking order is not limited thereto, however, and the stacking order may be the p-type semiconductor layer, the light-emitting layer, and the n-type semiconductor layer from thesubstrate 61. TheLED chip 6 more preferably has a structure in which a buffer layer is provided between theLED structure portion 60 and thesubstrate 61. The light-emitting layer preferably has a single quantum well structure or a multiple quantum well structure, but is not limited thereto. For example, theLED chip 6 may have a doublehetero structure configured by the n-type semiconductor layer, the light-emitting layer, and the p-type semiconductor layer. Note that, the structure of theLED chip 6 is not particularly limited. TheLED module 1 may be an LED chip which includes a reflector such as a Bragg reflector. - The
LED chip 6 may be a GaN-based blue LED chip which emits blue light, for example. In this case, theLED chip 6 includes a sapphire substrate serving as thesubstrate 61. Note that, thesubstrate 61 of theLED chip 6 is not limited to the sapphire substrate, and thesubstrate 61 may be a transparent substrate with respect to light that is emitted from the light-emitting layer. - The chip size of the
LED chip 6 is not particularly limited. TheLED chip 6 may have a chip size of 0.3 mm sq. (0.3 mm by 0.3 mm), 0.45 mm sq. (0.45 mm by 0.45 mm), 1 mm sq. (1 mm by 1 mm), or the like. Also, the planar shape of theLED chip 6 is not limited to a square shape, and, for example, may be a rectangular shape. When the planar shape of theLED chip 6 is a rectangular shape, the chip size of theLED chip 6 may be 0.5 mm by 0.24 mm or the like. - In the
LED chip 6, the material and the emission color of the light-emitting layer is not particularly limited. That is, theLED chip 6 is not limited to a blue LED chip, and may be a violet LED chip, an ultraviolet LED chip, a red LED chip, a green LED chip, or the like. - The
second bond 5 which bonds theLED chip 6 to thesubmount 4 may be formed of a transparent material such as a silicone resin, an epoxy resin, and a hybrid material composed of a silicone resin and an epoxy resin. - The light-transmissive member which is the
submount 4 is light-transmissive so as to transmit light in an ultraviolet wavelength region and a visible wavelength region. As shown schematically by arrows inFIG. 2 , the light-transmissive member transmits and diffuses light that is emitted from the light-emitting layer of theLED structure portion 60 of theLED chip 6. The light-transmissive member which is thesubmount 4 may be formed of light-transmissive ceramics (such as alumina and barium sulfate), for example. Properties of the light-transmissive ceramics such as transmittance, reflectance, refractive index, and thermal conductivity can be adjusted by the type and concentration of a binder, an additive substance, or the like. In theLED module 1, theLED chip 6 is bonded to a center of theface 4 sa of thesubmount 4 with thesecond bond 5. - The
submount 4 preferably has light diffusing properties. Accordingly, in theLED module 1, as shown schematically by arrows inFIG. 3 , light emitted from the light-emitting layer of theLED structure portion 60 of theLED chip 6 toward a further face of theLED chip 6 in the thickness direction is diffused inside thesubmount 4. Therefore, in theLED module 1, it is possible to prevent light emitted toward thesubmount 4 from theLED chip 6 from returning to theLED chip 6 and therefore light can be more easily extracted from theface 4 sa and the side faces 4 sc of thesubmount 4. The light outcoupling efficiency of theLED module 1 can thereby be improved. Note that, inFIG. 3 . broken-line arrows schematically show propagating directions of rays of light that are diffused inside thesubmount 4. Also, inFIG. 3 , a solid-line arrow schematically shows a propagating direction of a ray of light which emerges from thesubmount 4 through theside face 4 sc. - The
submount 4 has a rectangular shape in a planar view, but the shape thereof is not limited thereto, and may be a round shape, a polygonal shape other than a rectangle, or the like. The planar size of thesubmount 4 is set to be larger than the planar size of theLED chip 6. Accordingly, light outcoupling efficiency of theLED module 1 can be improved. - The
submount 4 preferably has a stress alleviation function of alleviating stress which acts on theLED chip 6 caused by the difference between the linear expansion coefficients of theLED chip 6 and theopaque substrate 2. The stress alleviation function is provided by designing thesubmount 4 to have a linear expansion coefficient close to that of theLED chip 6. Accordingly, in theLED module 1, it is possible to alleviate the stress which acts on theLED chip 6 caused by the difference between the linear expansion coefficients of theLED chip 6 and theopaque substrate 2. - The
submount 4 preferably has a heat conduction function of conducting heat which is generated in theLED chip 6 toward theopaque substrate 2. Also, thesubmount 4 preferably has a heat conduction function of conducting heat which is generated in theLED chip 6 to a region which is larger than the chip size of theLED chip 6. Accordingly, in theLED module 1, heat generated in theLED chip 6 can be efficiently dissipated via thesubmount 4 and theopaque substrate 2. - The
first bond 3 for bonding thesubmount 4 to theopaque substrate 2 may be made of a transparent material such as a silicone resin, an epoxy resin, and a hybrid material composed of a silicone resin and an epoxy resin, for example. Alternatively, thefirst bond 3 may be made of a conductive paste (such as silver paste and gold paste) or a resin containing a filler (such as titania and zinc oxide) or the like. When thefirst bond 3 is made of the silver paste, it is preferable to surround thefirst bond 3 by a gas barrier layer composed of an adhesive having high gas barrier properties or the like. When theopaque substrate 2 is provided with a mask layer at thesurface 2 sa, the mask layer may be used as thefirst bond 3. - The
opaque substrate 2 is ideally an opaque medium (non-transparent body) which does not transmit light in a visible wavelength region, and is an non-transparent substrate which does not transmit light in the visible wavelength region. The transmittance of theopaque substrate 2 with respect to light in a visible wavelength region is preferably 0% to 10%, more preferably 0 to 5%, and still more preferably 0 to 1%. Also, theopaque substrate 2 ideally does not absorb light in the visible wavelength region, and the absorptance thereof with respect to light in the visible wavelength region is preferably 0% to 10%, more preferably 0 to 5%, and still more preferably 0 to 1%. The transmittance and the absorptance are measured using an integrating sphere. - The
opaque substrate 2 may be made of aluminum, an aluminum alloy, silver, copper, phosphor bronze. a copper alloy (such as alloy 42), a nickel alloy, or the like. - The
opaque substrate 2 may be constituted by a base material formed of the above-described material and a reflection layer (not shown) provided on a surface of the base material, the reflection layer having higher reflectance than the base material with respect to light that is emitted from theLED chip 6. That is, theopaque substrate 2 may include the reflection layer as a surface treatment layer. The reflection layer may be formed of an Ag film, a stack of an Ni film, a Pd film, and an Au film, a stack of an Ni film and an Au film, a stack of an Ag film, a Pd film, and an Au—Ag alloy film, or the like. The reflection layer formed of a metal material preferably includes a plating layer or the like. In short, the reflection layer formed of a metal material is preferably formed by a plating method. Also, the reflection layer may be formed of, for example, a white mask layer. The white mask for the mask layer may be composed of a resin (such as silicone resin) that contains a white pigment such as barium sulfate (BaSO4) and titanium dioxide (TiO2). The white mask may be made of ASA COLOR (registered trademark) RESIST INK available from Asahi Rubber Inc., which is a white mask material made of silicone, or the like. The white mask layer may be formed by coating, for example. - The
opaque substrate 2 may be a highly reflective substrate including: an aluminum plate serving as the base material; an aluminum film on a surface of the aluminum plate; and a reflection enhancing film on the aluminum film. The aluminum film has higher purity than the aluminum plate, and the reflection enhancing film is constituted by two kinds of dielectric films having different refractive indices. Here, the two kinds of dielectric films are preferably an SiO2 film and a TiO2 film, for example. TheLED module 1 can have reflectance of 95% or more with respect to visible light, due to using the highly reflective substrate as theopaque substrate 2. The highly reflective substrate may be MIRO2 or MIRO (registered trademark) available from Alanod, for example. The aforementioned aluminum plate may be an aluminum plate having a surface which has been subjected to an anodic oxidation treatment. - Alternatively, the
opaque substrate 2 may be an insulating substrate formed of a material including a resin and a filler to increase reflectance. This insulating substrate may be made of unsaturated polyester and titania as the resin and the filler, respectively, for example. The resin of the insulating substrate is not limited to unsaturated polyester, and may be vinylester or the like. Also, the filler is not limited to titania and may be magnesium oxide, boron nitride, or aluminum hydroxide, for example. Theopaque substrate 2 may be a resin substrate composed of a white resin, or a ceramic substrate having a reflection layer formed of a white resin. - On the
surface 2 sa of theopaque substrate 2, the patterned conductors 8 (hereinafter also referred to as “patterned circuit”) serving as a wiring circuit to supply power to theLED chip 6 is provided. The electrodes (first electrode and second electrode) of theLED chip 6 are electrically connected to the patternedconductors 8 viawires 7 individually. Thewire 7 may be a gold wire, an aluminum wire, or the like, for example. The patternedconductors 8 may be made of, for example, copper, phosphor bronze, a copper alloy (such as 42 alloy), a nickel alloy, aluminum, an aluminum alloy, or the like. The patternedconductors 8 may be formed of a lead frame, a metal foil, a metal film, or the like. When theopaque substrate 2 has electrical conductivity, an insulation layer may be provided between theopaque substrate 2 and thepatterned conductors 8. Note that, in theLED module 1 of the present embodiment, theopaque substrate 2 and thepatterned conductors 8 constitute a mounting substrate, and theLED chip 6 is mounted on the mounting substrate with thesubmount 4 being interposed therebetween. - The planar shape of the
opaque substrate 2 is a rectangular shape, but the planar shape is not limited thereto, and may be a round shape, an elliptical shape, a triangular shape, a polygonal shape other than a rectangle, or the like. - The number of
LED chips 6 that are arranged on thesurface 2 sa of theopaque substrate 2 is not limited to one, and may be two or more. TheLED module 1 may be configured such that the planar shape of theopaque substrate 2 is an elongated shape, and a plurality ofLED chips 6 are arranged along a longitudinal direction of theopaque substrate 2, for example. In this case, the patternedcircuit 8 may be configured to be connected to the plurality ofLED chips 6 in series, in parallel, or in series-parallel. In short, theLED module 1 may have a circuit configuration in which a plurality ofLED chips 6 are connected in series, may have a circuit configuration in which a plurality ofLED chips 6 are connected in parallel, or may have a circuit configuration in which a plurality ofLED chips 6 are connected in series-parallel. - In the
LED module 1, thesurface 2 sa of theopaque substrate 2 preferably has light diffusing properties or specular reflective properties. - When the
surface 2 sa of theopaque substrate 2 has light diffusing properties, in theLED module 1, it is possible to diffusely reflect light which is emitted from the light-emitting layer of theLED structure portion 60 in theLED chip 6 and then passes through thesecond bond 5, thesubmount 4, and thefirst bond 3, by thesurface 2 sa of theopaque substrate 2, as shown schematically by arrows inFIG. 4 . As a result, light returning to theLED chip 6 can be reduced. Note that, inFIG. 4 , the broken-line arrows schematically show propagating directions of rays of light which strike theface 4 sa of thesubmount 4 and are diffusely reflected by thesurface 2 sa of theopaque substrate 2. Also, inFIG. 4 , the solid-line arrow schematically shows a propagating direction of a ray of light which enters thesubmount 4 through theface 4 sa and then emerges from thesubmount 4 through theside face 4 sc. - When the
surface 2 sa of theopaque substrate 2 has specular reflective properties, in theLED module 1, it is possible to specularly reflect light which is emitted from theLED chip 6, then passes thesecond bond 5, thesubmount 4, and thefirst bond 3, and thereafter obliquely enter thesurface 2 sa of theopaque substrate 2 as shown schematically by an arrow inFIG. 5 . As a result, light outcoupling efficiency of the side faces 4 sc of thesubmount 4 can be improved. Note that, inFIG. 5 , the right arrow schematically shows a propagating direction of a ray of light that strikes theface 4 sa of thesubmount 4 and is specularly reflected by thesurface 2 sa of theopaque substrate 2. Also, inFIG. 5 , the left arrow schematically shows a propagating direction of a ray of light that enters thesubmount 4 through theface 4 sa and then emerges from thesubmount 4 through theside face 4 sc. - When the
LED module 1 includes theopaque substrate 2 having thesurface 2 sa with light diffusing properties or specular reflective properties, light outcoupling efficiency thereof can be further improved. - In the
LED module 1, theopaque substrate 2 preferably serves as a heat sink. In theLED module 1, when theopaque substrate 2 is made of metal having high thermal conductivity such as aluminum and copper, theopaque substrate 2 can function as a heat sink. Accordingly, in theLED module 1, heat generated in theLED chip 6 can be more efficiently dissipated, and as a result light output can be increased. The heat dissipation property of theLED module 1 can be improved without increasing the number of parts, when theLED module 1 has a configuration in which a plurality offins 22 protruding from afurther surface 2 sb are integrally provided on thefurther surface 2 sb of theopaque substrate 2 like the first modification shown inFIG. 6 . Theopaque substrate 2 in which the plurality offins 22 are integrally provided can be formed by aluminum die-casting or the like. - Hereinafter, the second modification of the
LED module 1 of the present embodiment will be described with reference toFIG. 7 . - The
LED module 1 of the second modification differs from theLED module 1 ofEmbodiment 1 in that each of thefirst bond 3 and thesecond bond 5 is composed of a transparent material and a first fluorescent material. The first fluorescent material is a fluorescent material that is excited by the light emitted from theLED chip 6 to emit light having a different color from a color of the emitted light of theLED chip 6. In short, theLED module 1 of the second modification differs from theLED module 1 ofEmbodiment 1 in that thefirst bond 3 and thesecond bond 5 contain the fluorescent material that is excited by the light emitted from theLED chip 6 to emit light having a different color from a color of the emitted light of theLED chip 6. Note that, constituent elements similar to those inEmbodiment 1 are provided with the same reference numerals, and redundant description thereof will be omitted. Also, inFIG. 7 . illustrations of thewires 7 and thepatterned conductors 8 shown inFIG. 1 are omitted. - The fluorescent material functions as a wavelength conversion material that converts the light emitted from the
LED chip 6 to light with a longer wavelength than that of the light from theLED chip 6. Accordingly, it is possible, using theLED module 1, to obtain mixed-color light constituted by light that is emitted from theLED chip 6 and light emitted from the fluorescent material. - When including a blue LED chip as the
LED chip 6 and a yellow fluorescent material as the fluorescent material of the wavelength conversion material for example, theLED module 1 can emit white light. That is, in theLED module 1, blue light that is emitted from theLED chip 6 and light that is emitted from the yellow fluorescent material can pass through theLED chip 6 and thesubmount 4, and as a result white light can be obtained. Note that,FIG. 7 schematically illustrates propagating paths of light which are emitted from theLED chip 6 and of light produced as a result of wavelength conversion by the fluorescent material in thesecond bond 5. - The fluorescent material serving as the wavelength conversion material is not limited to the yellow fluorescent material, and may include, for example, a set of a yellow fluorescent material and a red fluorescent material, or a set of a red fluorescent material and a green fluorescent material. Also, the fluorescent material serving as the wavelength conversion material is not limited to one kind of yellow fluorescent material, and may include two kinds of yellow fluorescent materials having different emission peak wavelengths. The color rendering property of the
LED module 1 can be improved by use of a plurality of fluorescent materials as the wavelength conversion material. - In the
LED module 1, at least one of thefirst bond 3 and thesecond bond 5 may contain the second fluorescent material which is excited by light emitted fromLED chip 6 to emit light having a different color from the emitted light of theLED chip 6. Accordingly, theLED module 1 can produce mixed-color light constituted by light emitted from theLED chip 6 and light emitted from the fluorescent material. - In the
LED module 1, when both thefirst bond 3 and thesecond bond 5 contain the fluorescent materials, the fluorescent material in thefirst bond 3 and the fluorescent material in thesecond bond 5 may emit light rays having different wavelengths from each other. - In this case, the fluorescent material in the
second bond 5 that is closer to theLED chip 6 may be a fluorescent material that emits light having a relatively long wavelength (such as red fluorescent material) among two kinds of fluorescent materials, and the fluorescent material in thefirst bond 3 that is farther from theLED chip 6, may be a fluorescent material that emits light having a relatively short wavelength (green fluorescent material). Accordingly, in theLED module 1, it is possible to suppress secondary absorption of light converted by the fluorescent material in thesecond bond 5, by the fluorescent material in thefirst bond 3. TheLED module 1 includes a combination of the red fluorescent material and the green fluorescent material as the combination of the two kinds of fluorescent materials. Even when the green fluorescent material is a fluorescent material having poor temperature characteristics (a fluorescent material in which temperature quenching occurs frequently) compared with the red fluorescent material, the green fluorescent material can be arranged close to theopaque substrate 2 which functions as a heat sink, and therefore, temperature increase of the green fluorescent material can be suppressed, and as a result, the temperature quenching of the green fluorescent material can be suppressed. - Furthermore, the
LED module 1 may include a fluorescent material to emit light having a relatively short wavelength (green fluorescent material) as the fluorescent material in thesecond bond 5 that is close to theLED chip 6, and a fluorescent material to emit light having a relatively long wavelength (red fluorescent material) as the fluorescent material in thefirst bond 3 that is distant from theLED chip 6, for example, among two kinds of fluorescent materials. Accordingly, in theLED module 1, it is possible to suppress secondary absorption of light which has been converted by the fluorescent material in thefirst bond 3, by the fluorescent material in thesecond bond 5. - Note that, in the
LED module 1 of the second modification, theopaque substrate 2 preferably functions as a heat sink, similarly to theLED module 1 ofEmbodiment 1. - Hereinafter, the third modification of the
LED module 1 of the present embodiment will be described with reference toFIG. 8 . - The
LED module 1 of the third modification differs from theLED module 1 ofEmbodiment 1 in including acolor conversion portion 10 made of a transparent material containing a second fluorescent material. The second fluorescent material is a fluorescent material that is excited by the light emitted from theLED chip 6 to emit light having a different color from a color of the emitted light of theLED chip 6. Note that, constituent elements similar to those inEmbodiment 1 are provided with the same reference numerals, and redundant description thereof will be omitted. Also, inFIG. 8 , illustrations of thewires 7 and the patternedwiring circuit 8 shown inFIG. 1 are omitted. - The
color conversion portion 10 is provided to cover side faces of theLED chip 6 and an opposite surface of theLED chip 6 from thesecond bond 5. Accordingly, in theLED module 1, color unevenness can be suppressed. - The transparent material for the
color conversion portion 10 may be, for example, a silicone resin, an epoxy resin, an acrylic resin, glass, or an organic/inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer (nm) level or molecular level. - The fluorescent material for the
color conversion portion 10 functions as a wavelength conversion material that converts light emitted from theLED chip 6 to light having longer wavelength than the light emitted from theLED chip 6. Accordingly, theLED module 1 can emit mixed-color light constituted by light emitted from theLED chip 6 and light emitted from the fluorescent material. - For example, when the
LED chip 6 is a blue LED chip and the fluorescent material of the wavelength conversion material is a yellow fluorescent material, theLED module 1 can provide white light. That is, blue light that is emitted from theLED chip 6 and light that is emitted from the yellow fluorescent material can pass through theLED chip 6 and thesubmount 4, and as a result theLED module 1 can emit white light. - The fluorescent material serving as the wavelength conversion material is not limited to the yellow fluorescent material, and may include, for example, a set of a yellow fluorescent material and a red fluorescent material, or a set of a red fluorescent material and a green fluorescent material. Also, the fluorescent material serving as the wavelength conversion material is not limited to one kind of yellow fluorescent material, and may include two kinds of yellow fluorescent materials having different emission peak wavelengths. The color rendering property of the
LED module 1 can be improved by use of a plurality of fluorescent materials as the wavelength conversion material. - In the
LED module 1 of the present embodiment, thecolor conversion portion 10 is in the form of a layer. Thecolor conversion portion 10 can be formed by a method such as molding and screen-printing. In theLED module 1, thecolor conversion portion 10 is formed into a layer-form so as to be thin, and therefore it is possible to reduce an amount of light which is to be converted to heat by the fluorescent material in thecolor conversion portion 10. Thecolor conversion portion 10 has a thin layer shape. However, the shape of thecolor conversion portion 10 is not limited to this, and may be hemisphere, semiellipse, semicylinder, or the like. - The
LED module 1 may be configured such that thecolor conversion portion 10 contains a light diffusion material. The light diffusion material is preferably composed of particles and dispersed in thecolor conversion portion 10. In theLED module 1, due to thecolor conversion portion 10 containing the light diffusion material, color unevenness can be further suppressed. The material of the light diffusion material may be an inorganic material such as aluminum oxide, silica, titanium oxide, and Au, an organic material such as a fluorine based resin, an organic and inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer level or molecular level, or the like. In theLED module 1, the larger the difference between the refractive indices of the light diffusion material and the transparent material of thelight conversion portion 10, the smaller the required light diffusion material content to obtain an effect to suppress color unevenness to a similar level. - It is possible to further improve the color rendering property of the
LED module 1 by that theLED chip 6 is a blue LED chip and thecolor conversion portion 10 contains a plurality of fluorescent materials (green fluorescent material and red fluorescent material) and the light diffusion material. Furthermore, it is possible to further improve the color rendering property of theLED module 1 by that theLED chip 6 is an ultraviolet LED chip and thecolor conversion portion 10 contains a plurality of kinds of fluorescent materials (blue fluorescent material, green fluorescent material, and red fluorescent material) and the light diffusion material. - The
LED module 1 may be configured such that at least one of thefirst bond 3 and thesecond bond 5 contains a first fluorescent material, in addition to thecolor conversion portion 10. The first fluorescent material is a fluorescent material which is excited by light emitted from theLED chip 6 to emit light having a different color from the emitted light of theLED chip 6. TheLED module 1 may be configured such that thecolor conversion portion 10 is provided so as to cover not only theLED chip 6 but also periphery of the submount 4 (in the example inFIG. 9 , the periphery of theface 4 sa and the side faces 4 sc), like the fourth modification shown inFIG. 9 , for example. InFIG. 9 , illustrations of thewires 7 and thepatterned conductors 8 shown inFIG. 1 are omitted. - In a case of the fourth modification, a fluorescent material in the
color conversion portion 10 provided around thesubmount 4 is preferably a fluorescent material to emit light having a relatively short wavelength compared with the fluorescent material in thesecond bond 5. Accordingly, in theLED module 1, it is possible to suppress re-absorption in thecolor conversion portion 10 provided around thesubmount 4. - Note that, in each of the
LED modules 1 of the third modification and the fourth modification, as with theLED module 1 ofEmbodiment 1, theopaque substrate 2 preferably functions as a heat sink. - Hereinafter, the fifth modification of the
LED module 1 of the present embodiment will be described with reference toFIG. 10 . - The
LED module 1 of the fifth modification differs from theLED module 1 of the third modification in including aresin portion 11 on theface 4 sa of thesubmount 4. Theresin portion 11 preferably serves as an outer cover through which light passes last (in other words, an outer cover for extracting light). Note that, constituent elements similar to those in the third modification are provided with the same reference numerals, and redundant description thereof will be omitted. Also, inFIG. 10 , illustrations of thewires 7 and thepatterned conductors 8 shown inFIG. 1 are omitted. - The
resin portion 11 is preferably formed of a transparent resin containing a light diffusion material. The transparent resin is a silicone resin. The transparent resin is not limited to the silicone resin, and may be an epoxy resin, an acrylic resin, or the like. The material of the light diffusion material may be an inorganic material such as aluminum oxide, silica, titanium oxide, and Au, an organic material such as a fluorine based resin, or an organic and inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer level or molecular level, or the like. - The
resin portion 11 has a hemispherical shape, but the shape is thereof not limited to the hemispherical shape, and may be a hemispherical shape or a hemicylindrical shape. - The
LED module 1 of the fifth modification includes theresin portion 11, and therefore the reliability can be improved. Also, theLED module 1 may be configured such that theresin portion 11 contains the light diffusion material, as described above. Accordingly, in theLED module 1, color unevenness can be further suppressed. Also, when thecolor conversion portion 10 contains a plurality of kinds of fluorescent materials and theresin portion 11 contains a light diffusion material, the color rendering property of theLED module 1 can be further improved. - Note that, as with the
LED module 1 of theEmbodiment 1, theopaque substrate 2 of theLED module 1 of the fifth modification preferably functions as a heat sink. - Hereinafter, the sixth modification of the
LED module 1 of the present embodiment will be described with reference toFIG. 11 . - The
LED module 1 of the sixth modification differs from theLED module 1 of the second modification in including aresin portion 11 on theface 4 sa of thesubmount 4. Theresin portion 11 serves as an outer cover through which light is extracted. Note that, constituent elements similar to those in the second modification are provided with the same reference numerals, and redundant description thereof will be omitted. Also, inFIG. 11 , illustrations of thewires 7 and thepatterned conductors 8 shown inFIG. 1 are omitted. - The
resin portion 11 is preferably formed of a transparent resin containing a light diffusion material. The transparent resin is a silicone resin. However, the transparent resin is not limited to the silicone resin, and may be an epoxy resin, an acrylic resin, or the like. The material of the light diffusion material may be an inorganic material such as aluminum oxide, silica, titanium oxide, and Au, an organic material such as a fluorine based resin, or an organic and inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer level or molecular level, or the like. - The
resin portion 11 has a hemispherical shape, but the shape of theresin portion 11 is not limited to the hemispherical shape, and may be a hemiellipse spherical shape or a hemicylidrical shape. - The
LED module 1 of the sixth modification has improved reliability due to theresin portion 11. Furthermore, theLED module 1 may be configured such that theresin portion 11 contains the light diffusion material, as described above. Accordingly, in theLED module 1, color unevenness can be suppressed. Also, when theLED module 1 is configured such that at least one of thefirst bond 3 and thesecond bond 5 contains a plurality of kinds of fluorescent materials (first fluorescent materials) and theresin portion 11 contains the light diffusion material, the color rendering property can be further improved. - Note that, as with the
LED module 1 ofEmbodiment 1, theopaque substrate 2 of theLED module 1 of the sixth modification preferably functions as a heat sink. - Hereinafter, the seventh modification of the
LED module 1 of the present embodiment will be described with reference toFIGS. 12 to 16 . - The
LED module 1 of the seventh modification differs from theLED module 1 ofEmbodiment 1 in including thecolor conversion portion 10 containing a transparent material and a first fluorescent material. The second fluorescent material is a fluorescent material that is excited by the light emitted from theLED chip 6 to emit light having a different color from the emitted light of theLED chip 6. Note that, constituent elements similar to those inEmbodiment 1 are provided with the same reference numerals, and redundant description thereof will be omitted. Also, inFIG. 12 , illustrations of thewires 7 and thepatterned conductors 8 shown inFIG. 1 are omitted. - The transparent material for the
color conversion portion 10 may be, for example, a silicone resin, an epoxy resin, an acrylic resin, glass, or an organic/inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer (nm) level or molecular level. The fluorescent material for thecolor conversion portion 10 functions as a wavelength conversion material that converts light emitted from theLED chip 6 to light having longer wavelength than the light emitted from theLED chip 6. Accordingly, theLED module 1 can emit mixed-color light constituted by light emitted from theLED chip 6 and light emitted from the fluorescent material. - For example, when the
LED chip 6 is a blue LED chip and the fluorescent material of the wavelength conversion material is a yellow fluorescent material, theLED module 1 can provide white light. That is, blue light that is emitted from theLED chip 6 and light that is emitted from the yellow fluorescent material can pass through theLED chip 6 and thesubmount 4, and as a result theLED module 1 can emit white light. - The fluorescent material serving as the wavelength conversion material is not limited to the yellow fluorescent material, and may include, for example, a set of a yellow fluorescent material and a red fluorescent material, or a set of a red fluorescent material and a green fluorescent material. Also, the fluorescent material serving as the wavelength conversion material is not limited to one kind of yellow fluorescent material, and may include two kinds of yellow fluorescent materials having different emission peak wavelengths. The color rendering property of the
LED module 1 can be improved by use of a plurality of fluorescent materials as the wavelength conversion material. - The
color conversion portion 10 has a hemispherical shape and is formed on thesurface 2 sa of theopaque substrate 2 so as to cover thefirst bond 3, thesubmount 4, thesecond bond 5, and theLED chip 6. - In the
LED module 1 of the seventh modification, some of rays of the light produced in a light-emitting layer (not shown) in theLED chip 6 and then passing through theLED chip 6 and thesecond bond 5 are diffused in thesubmount 4. Consequently, the light passing through theLED chip 6 and thesecond bond 5 is less likely to be totally reflected, and more likely to be extracted from thesubmount 4 through any one of the side faces 4 sc and theface 4 sa. Therefore, in theLED module 1, light outcoupling efficiency can be improved and a total light flux amount can be increased. Moreover, in theLED module 1, by providing thesurface 2 sa of theopaque substrate 2 with diffuse reflective properties or specular reflective properties, light emitted toward theopaque substrate 2 from thecolor conversion portion 10 is likely to be reflected by theopaque substrate 2, and thus light outcoupling efficiency can be improved. In this case, in theLED module 1, some of rays of light that are reflected by theopaque substrate 2 and travel toward thecolor conversion portion 10 enter thecolor conversion portion 10 again, and consequently, the conversion rate at thecolor conversion portion 10 can be increased. - Incidentally, the inventors performed simulation in terms of values of dimensional parameters of the
submount 4, which are effective to improve the light outcoupling efficiency of theLED module 1. As a result, the inventors obtained knowledge that the dimensional parameters preferably satisfy conditions defined by Equations (1), (2), and (3) described later. The simulation is a geometric optical simulation by Monte Carlo ray tracing. - For this simulation, dimensional parameters of the
LED chip 6 and thesubmount 4 are defined as shown inFIG. 13 . and a dimensional parameter of thecolor conversion portion 10 is defined as shown inFIG. 12 . - With regard to the dimensional parameters of the
LED chip 6, a planar shape of theLED chip 6 is assumed to be rectangular, and a lengthwise dimension of a side along the left and right direction ofFIG. 12 is denoted by Wc [mm], a lengthwise dimension of a side along the direction perpendicular to the sheet ofFIG. 12 is denoted by Lc [min], and the thickness dimension is denote by Hc [mm]. - With regard to the dimensional parameters of the
submount 4, a planar shape of thesubmount 4 is assumed to be rectangular, and a lengthwise dimension of a side along the left and right direction inFIG. 12 is denoted by Ws [mm], a lengthwise dimension of a side along the direction perpendicular to the sheet ofFIG. 12 is denoted by Ls [mm], and the thickness dimension is denoted by Hs [mm]. - With regard to the dimensional parameter of the
color conversion portion 10, the radius is denoted by R [mm]. - In the simulation, the
LED chip 6 is assumed to include thesubstrate 61 made of sapphire having a refractive index of 1.77 and theLED structure portion 60 made from GaN having a refractive index of 2.5. Besides, the light-emitting layer is assumed to isotropically emit light rays with the same intensity along all directions from all the points of the light-emitting layer. Thefirst bond 3 and thesecond bond 5 are assumed to be made of silicon resin with a refractive index of 1.41. Besides, regarding physical properties of thesubmount 4, the structure of thesubmount 4 is assumed to be a structural model where spherical particles compounded in a base material composed of ceramics and having different refractive index from that of the particles, and the refractive index of the base member is supposed to be 1.77, the refractive index of the particles is supposed to be 1.0, and a filling rate of the particles is supposed to be 16.5%. - The above-mentioned Equations (1), (2), and (3) are as follows.
-
2R>Ws>Wc+0.4 (1) -
2R>Ls>Lc+0.4 (2) -
Hs<(0.54/0.75)R−Hc (3) - The planar shape of the
submount 4 is not limited to a rectangular shape, and may be a polygonal shape other than the rectangle or a round shape, for example. In a case where thesubmount 4 is a regular hexagon, the above-described dimensional parameters Ws and Ls each denote a dimension between two opposite sides of the regular hexagon as shown inFIG. 14 . Then, when the requirements defined by the above-mentioned Equations (1), (2), and (3) are satisfied, it is possible to improve the light-outcoupling efficiency of theLED module 1. - Note that, the above-described simulation conditions are an example, and are not particularly limited.
- In the
submount 4, as shown inFIG. 16 , chamfers 41 may be formed between theface 4 sa and the side faces 4 sc at a periphery of theface 4 sa. Thechamfer 41 is a C chamfer with a chamfering angle of 45°, but the chamfer is not limited thereto and may be an R chamfer. - The
color conversion portion 10 has a hemispherical shape, but the shape thereof is not limited thereto, and may be a hemiellipse spherical shape or a hemicylindrical shape. - Note that, as with the
LED module 1 ofEmbodiment 1, theopaque substrate 2 of theLED module 1 of the seventh modification preferably functions as a heat sink. Also, in theLED module 1 of the seventh modification, instead of thecolor conversion portion 10, an encapsulating portion composed of a transparent resin having the same shape as thecolor conversion portion 10 may be provided. - Hereinafter, the eighth modification of the
LED module 1 of the present embodiment will be described with reference toFIG. 17 . - The
LED module 1 of the eighth modification differs from theLED module 1 of the seventh modification in terms of the shape of thecolor conversion portion 10. Note that, constituent elements similar to those in the seventh modification are provided with the same reference numerals, and redundant description thereof will be omitted. Also, inFIG. 17 , illustrations of thewires 7 and thepatterned conductors 8 shown inFIG. 1 are omitted. - The
color conversion portion 10 in theLED module 1 of the eighth modification has a bombshell shape. Thecolor conversion portion 10 having the bombshell shape has a hemispherical portion at the front end (the end that is distant from the opaque substrate 2) and a columnar portion at the back end (the end that is close to the opaque substrate 2). - Incidentally, the inventors performed simulation in terms of values of dimensional parameters of the
submount 4, which are effective to improve the light outcoupling efficiency of theLED module 1. As a result, the inventors obtained knowledge that the dimensional parameters preferably satisfy conditions defined by Equations (4), (5), and (6) described later. The simulation conditions for this simulation are substantially the same as the simulation conditions described in the seventh modification, but are different therefrom in the following points. - In the
LED module 1 of the eighth modification, a dimensional parameter of thecolor conversion portion 10 is defined as shown inFIG. 17 . That is, with regard to the dimensional parameter of thecolor conversion portion 10, a radius of the hemispherical portion is denoted by R [mm]. Besides, with regard to the dimensional parameters of thesubmount 4, a dimension from theface 4 sa of thesubmount 4 to the center of the hemispherical portion of thecolor conversion portion 10 is denoted by Hs′ [mm]. - The above-mentioned Equations (4), (5), and (6) are as follows.
-
2R>Ws>Wc+0.4 (4) -
2R>Ls>Lc+0.4 (5) -
Hs′<(0.54/0.75)R−Hc (6) - The planar shape of the
submount 4 is not limited to a rectangular shape, and may be a polygonal shape other than the rectangle or a round shape, for example. - Note that, as with the
LED module 1 ofEmbodiment 1, theopaque substrate 2 of theLED module 1 of the eighth modification preferably functions as a heat sink. - Hereinafter, the ninth modification of the
LED module 1 of the present embodiment will be described with reference toFIG. 18 . - The
LED module 1 of the ninth modification differs from theLED module 1 of the seventh modification in that thecolor conversion portion 10 is formed to have a semispherical shape on theface 4 sa of thesubmount 4. Note that, constituent elements similar to those in the seventh modification are provided with the same reference numerals, and redundant description thereof will be omitted. Also, inFIG. 18 , illustrations of thewires 7 and thepatterned conductors 8 shown inFIG. 1 are omitted. - Incidentally, the inventors performed simulation in terms of values of dimensional parameters of the
submount 4, which are effective to improve the light outcoupling efficiency of theLED module 1. As a result, the inventors obtained knowledge that the dimensional parameters preferably satisfy conditions defined by Equations (7), (8), and (9) described later. The simulation conditions for this simulation are basically the same as the simulation conditions described in the seventh modification. Note that, theLED module 1 of the ninth modification is different from theLED module 1 of the seventh modification in that, in the ninth modification, the center of thecolor conversion portion 10 with a hemispherical shape is present on theface 4 sa of thesubmount 4 while, in the seventh modification, the center of thecolor conversion portion 10 with a semispherical shape is situated on thesurface 2 sa of theopaque substrate 2. - The above-mentioned Equations (7), (8), and (9) are as follows.
-
Ws>2R>Wc+0.4 (7) -
Ls>2R>Lc+0.4 (8) -
Hs<(0.44/0.75)R−He (9) - The planar shape of the
submount 4 is not limited to a rectangular shape, and may be a polygonal shape other than the rectangle or a round shape, for example. - Note that, as with the
LED module 1 ofEmbodiment 1, theopaque substrate 2 of theLED module 1 of the ninth modification preferably functions as a heat sink. - Hereinafter, the tenth modification of the
LED module 1 of the present embodiment will be described with reference toFIG. 19 . - The basic configuration of the
LED module 1 of the tenth modification is substantially the same as that of theLED module 1 of the ninth modification shown inFIG. 18 , but differs therefrom in that the opaque substrate 2 (refer toFIG. 18 ) is constituted by a device main body of a lighting device (unshown) and the device main body and thesubmount 4 are bonded with the first bond 3 (refer toFIG. 18 ). Note that, constituent elements similar to those of theLED module 1 of the ninth modification are provided with the same reference numerals, and redundant description thereof will be omitted. Also, inFIG. 19 , illustrations of thewires 7 and thepatterned conductors 8 shown inFIG. 1 are omitted. - Incidentally, the inventors performed simulation in terms of values of dimensional parameters of the
submount 4, which are effective to improve the light outcoupling efficiency of theLED module 1. As a result, the inventors obtained knowledge that the dimensional parameters preferably satisfy conditions defined by Equations (10), (11), and (12) described later. The simulation conditions for this simulation are substantially the same as the simulation conditions described in the ninth modification. - The above-mentioned Equations (10), (11), and (12) are as follows.
-
Ws>2R>Wc+0.4 (10) -
Ls>2R>Lc+0.4 (11) -
Hs<(0.44/0.75)R−He (12) - The planar shape of the
submount 4 is not limited to a rectangular shape, and may be a polygonal shape other than the rectangle or a round shape, for example. - Note that, as with the
LED module 1 of Embodiment, theopaque substrate 2 of theLED module 1 of the tenth modification preferably functions as a heat sink. - Incidentally, not only the
LED module 1 of the tenth modification, but each of theLED modules 1 ofEmbodiment 1 and the first modification to the ninth modification can be used as light sources of various lighting apparatuses. - The lighting apparatus which includes the
LED module 1 may be, for example, a lighting device including a light source that is theLED module 1 and is provided on a device main body. The lighting device may include the device main body and theLED module 1 that is held on the device main body. In the lighting device including theLED module 1, light outcoupling efficiency can be improved. - The lighting apparatus which includes the
LED module 1 may be, for another example, a straight-tube LED lamp which is a type of a lamp. The lamp may include a light source that is theLED module 1. In the lamp including a light source that is theLED module 1, light outcoupling efficiency can be improved. Note that, in terms of the straight-tube LED lamp, “straight-tube LED lamp system with L-type pin cap GX16t-5 (for general illumination)” (JEL 801:2010) is standardized by Japan Electric Lamp Manufacturers Association, for example. - Such a straight-tube LED lamp may include: a tube main body having a straight-tube shape and made of a light-transmissive material (such as milky white glass and a milky white resin); and a first cap and a second cap which are respectively provided at an end and the other end of the tube main body in the longitudinal direction. The
LED module 1 is accommodated in the tube main body. Theopaque substrate 2 has an elongated shape, and a plurality ofLED chips 6 are aligned along the longitudinal direction of theopaque substrate 2. - Hereinafter, an
LED module 1 of the present embodiment will be described with reference toFIGS. 20 to 22 . - The
LED module 1 of the present embodiment differs from theLED module 1 of the seventh modification ofEmbodiment 1 in that thesubmount 4 is constituted by two layers ofceramic layers Embodiment 1 are provided with the same reference numerals, and redundant description thereof will be omitted. - In the
submount 4, theceramic layers ceramic layer 4 a, which is farther from theLED chip 6, is higher in reflectance with respect to light emitted from theLED chip 6. In this regard, the optical properties refer to reflectance, transmittance, absorptance, or the like. Thesubmount 4 is required to be constituted by at least two ceramic layers stacked in the thickness direction, and have such a property that optical characteristics of the ceramic layers are different from each other, and the further the ceramic layer is from theLED chip 6, the higher the reflectance thereof is with respect to the light emitted from theLED chip 6. - Accordingly, in the
LED module 1, light emitted from the light-emitting layer of theLED structure portion 60 of theLED chip 6 toward the further face of theLED chip 6 in the thickness direction is more likely to be reflected at the interface between theceramic layer 4 b and theceramic layer 4 a as shown schematically by arrows inFIG. 22 . Therefore, in theLED module 1, it is possible to prevent light which is emitted from theLED chip 6 toward thesubmount 4 from returning to theLED chip 6 and to prevent the light from entering, thesurface 2 sa of theopaque substrate 2. As a result, light can be more easily extracted from theface 4 sa and the side faces 4 sc of thesubmount 4. Consequently, in theLED module 1, light outcoupling efficiency can be improved. Moreover, it is possible to reduce the influence of reflectance of theopaque substrate 2, and to increase the degree of freedom in terms of the materials of theopaque substrate 2. For example, in theLED module 1 of the seventh modification ofEmbodiment 1, when theopaque substrate 2 includes an organic-based substrate or a metal plate and a mask layer composed of a white mask thereon, the reflectance of theopaque substrate 2 is prone to decrease with time. Accordingly, there is a concern that the light outcoupling efficiency may decrease with time greatly. In contrast, in theLED module 1 ofEmbodiment 1, it is possible to reduce influences of the reflectance of theopaque substrate 2 on the light outcoupling efficiency, and therefore suppress deterioration with time in the light outcoupling efficiency. - With regard to the
submount 4, the uppermostceramic layer 4 b that is the closest to theLED chip 6 may be referred to as a firstceramic layer 4 b, and the lowermostceramic layer 4 a that is the farthest from theLED chip 6 may be referred to as a secondceramic layer 4 a, for convenience of description. - The first
ceramic layer 4 b may be made of alumina (Al2O3), for example. The firstceramic layer 4 b may be an alumina substrate, for example. When the firstceramic layer 4 b is the alumina substrate, the particle diameter of alumina particles of the alumina substrate is preferably in a range between 1 μm to 30 μm. The larger the particle diameter of the alumina particles, the smaller the reflectance of the firstceramic layer 4 b. The smaller the particle diameter of the alumina particles, the larger the scattering effect of the firstceramic layer 4 b. In short, reducing the reflectance and increasing the scattering effect are in a trade-off relationship. - The aforementioned particle diameter is determined by a number-size distribution curve. Here, the number-size distribution curve is obtained by measuring a particle size distribution by an imaging method. Specifically, the particle diameter is determined by a particle size (two-axis average diameter) and the number of particles determined by image processing of a SEM image obtained by scanning electron microscope (SEM) observation. In the number-size distribution curve. the particle diameter value at the integrated value of 50% is referred to as a median diameter (d50), and the aforementioned particle diameter refers to the median diameter.
- Note that,
FIG. 23 shows a theoretical relation between the particle diameter and the reflectance of a spherical alumina particle in the alumina substrate. The smaller the particle diameter, the higher the reflectance. The relation of the firstceramic layer 4 b between the median diameter (d50) and the measured value of reflectance is approximately the same as the theoretical value shown inFIG. 23 . The reflectance is measured using a spectrophotometer and an integrating sphere. - The second
ceramic layer 4 a may be made of, for example, a composite material that contains SiO2, Al2O3, a material having a higher refractive index than Al2O3 (such as ZrO2 and TiO2), CaO, and BaO as components. In the secondceramic layer 4 a, the particle diameter of Al2O3 particles is preferably in a range between 0.1 μm to 1 μm. The optical properties (such as reflectance, transmittance, and absorptance) of the secondceramic layer 4 a can be adjusted by adjusting components, composition, particle diameter, thickness, or the like of the composite material. In thesubmount 4, when the firstceramic layer 4 b and the secondceramic layer 4 a are made of the same kind of material, the firstceramic layer 4 b should be made of a material having the particle diameter larger than that for the secondceramic layer 4 a. - Incidentally, the inventors selected, as a comparative example of the
LED module 1 of the present embodiment, an LED module including thesubmount 4 configured by a single layer of alumina substrate. Then, the inventors performed a simulation regarding light outcoupling efficiency of the comparative example of the LED module with a parameter which is the dimension of thesubmount 4 of the LED module of the comparative example.FIG. 24 shows an example of the results. The simulation is a geometric optical simulation by Monte Carlo ray tracing. Note that, in the simulation, the reflectance of thesurface 2 sa of theopaque substrate 2 and the absorptance of theopaque substrate 2 are assumed to be 95% and 5%, respectively. Also, in the simulation, the chip size of theLED chip 6 is assumed to be 0.5 mm by 0.24 mm. - In
FIG. 24 , the horizontal axis represents a thickness of thesubmount 4, and the vertical axis represents light outcoupling efficiency. A curve denoted by “B1” in the diagram shows a case where the planar size of thesubmount 4 is 1 mm sq. (1 mm by 1 mm), and a curve denoted by “B2” in the diagram shows a case where the planar size of thesubmount 4 is 2 mm sq. (2 mm by 2 mm). FromFIG. 24 , it is inferred that, when the thickness of thesubmount 4 is 2 mm or less, the light outcoupling efficiency decreases due to light absorption by theopaque substrate 2, regardless of the planar size of thesubmount 4. - Also,
FIG. 24 teaches that, when the thickness of thesubmount 4 is 2 mm or less, the light outcoupling efficiency is higher with a decrease in the planar size of thesubmount 4. - Besides, the inventors simulated a ratio between light emission amounts from the faces of the LED module, regarding the LED modules of the comparative examples each including the
submount 4 constituted by the alumina substrate only. The submounts had the same thickness of 0.4 mm, and the planar sizes of 1 mm sq. and 2 mm sq., respectively.FIG. 25 shows an example of the results. This simulation is a geometric optical simulation by Monte Carlo ray tracing. Note that, in the simulation, the reflectance of thesurface 2 sa of theopaque substrate 2 and the absorptance of theopaque substrate 2 are assumed to be 95% and 5%, respectively. Also, in the simulation, the chip size of theLED chip 6 is assumed to be 0.5 mm by 0.24 mm. Also, in the simulation, only a Fresnel loss is assumed to occur at the side faces of theLED chip 6. - Reference sign “I1” in
FIG. 25 denotes a ratio of the outputted light amount directly from theLED chip 6. Reference sign “I2” inFIG. 25 denotes a ratio of the outputted light amount from an exposed surface (exposed portion of theface 4 sa of the submount 4) of thesubmount 4 at the side of theLED chip 6.Reference sign 13″ inFIG. 25 denotes a ratio of the outputted light amount from the side faces 4 sc of thesubmount 4. - From the results in
FIGS. 24 and 25 , the inventors obtained knowledge that the smaller the planar size of thesubmount 4, the higher the ratio of the outputted light amount from the side faces 4 sc of thesubmount 4, and as a result the light outcoupling efficiency can be improved. - Moreover, the inventors investigated a relation between the thickness of the
submount 4 and the light flux emitted by theLED module 1 with respect to variousopaque substrates 2 in condition that a planar size of the submount is 2 mm sq. (2 mm by 2 mm). The light flux is measured by an integrating sphere. As the result, the inventors obtained an experimental result shown inFIG. 26 . In the experiment, as theLED chip 6, adopted was a blue LED chip in which the substrate was a sapphire substrate and the emission peak wavelength from the light-emitting layer was 460 nm. The chip size of theLED chip 6 was 0.5 mm by 0.24 mm. Thecolor conversion portion 10 was composed of a silicone resin containing a yellow fluorescent material. The white circles (◯) in line C1 inFIG. 26 denote measured values of light flux with respect to an LED module ofReference Model 1. In the LED module ofReference Model 1, thesubmount 4 was an alumina substrate, and theopaque substrate 2 was a silver substrate having reflectance of 98% with respect to light with a wavelength of 460 nm. The white triangles (Δ) in line C2 inFIG. 26 designate measured values of light flux with respect to an LED module ofReference Model 2. In the LED module ofReference Model 2, thesubmount 4 was an alumina substrate, and theopaque substrate 2 was a substrate including a copper substrate and a reflection layer composed of a white mask having reflectance of 92% with respect to light with a wavelength of 460 nm on a surface of the copper substrate. The white rhombuses (⋄) in line C3 inFIG. 26 designate measured values of light flux with respect to an LED module ofReference Model 3. In the LED module ofReference Model 3, thesubmount 4 was an alumina substrate, and theopaque substrate 2 was an aluminum substrate having reflectance of 95% with respect to light with a wavelength of 460 nm. - From values denoted by reference signs C1, C2, and C3 in
FIG. 26 , it is inferred that the light outcoupling efficiency of theLED module 1 of the present embodiment can be improved by increasing the thickness of thesubmount 4. Also, in theLED module 1 of the present embodiment, it is speculated that the light outcoupling efficiency can be improved by using a silver substrate as theopaque substrate 2 similarly toReference Model 1. - On the other hand, from a viewpoint of efficiently dissipating heat generated in the
LED chip 6 to the further surface of the opaque substrate 2 (that is, from a viewpoint of improving the heat dissipation property), it is preferable that thesubmount 4 is thinner. In short, the light outcoupling efficiency and the heat dissipation property are in a trade-off relationship. - Moreover, the inventors fabricated an LED module having a reference structure in which the
submount 4 was not provided and a high purity alumina substrate was used as theopaque substrate 2, and performed an experiment of measuring a light flux emitted by the LED module having the reference structure. The black square (▪) inFIG. 26 designates measured values of light flux with respect to the LED module having the reference structure. The inventors obtained an experimental result that, the LED module ofaforementioned Reference Model 1 is required to include thesubmount 4 having the thickness of 0.4 mm or more to emit greater light flux than the LED module having the reference structure. Therefore, the inventors considered that it is preferable to adjust the thickness of thesubmount 4 to an approximate range of 0.4 mm to 0.5 mm, in view of the light outcoupling efficiency and the heat dissipation property. Note that, with regard to the alumina substrate used in the LED module having the reference structure, the thickness of the alumina substrate is 1 mm, the particle diameter of particles constituting the alumina substrate is 1 μm. and the reflectance of the alumina substrate is 91%. - In the LED module of
Reference Model 1 in which the silver substrate was used as theopaque substrate 2, there is concern that the reflectance may decrease due to sulfurization of the silver substrate. In the LED module ofReference Model 2 in which the reflection layer composed of the white mask is used, there is concern that the reflectance may decrease due to thermal degradation of the white mask. - Accordingly, in the
LED module 1 of the present embodiment, theopaque substrate 2 includes a base material (cupper substrate) made of cupper and a reflection layer composed of the white mask layer provided on a surface of the base material, and thesubmount 4 is the light-transmissive member having a configuration in which the secondceramic layer 4 a and the firstceramic layer 4 b are stacked in the thickness direction. - The inventors performed an experiment of measuring light flux emitted by Example 1 of the
LED module 1 of the present embodiment. In Example 1, thesubmount 4 had the thickness of 0.5 mm, the secondceramic layer 4 a had the thickness Hsa (refer toFIG. 21 ) of 0.1 mm and the reflectance of 96% to light with a wavelength of 450 nm, and the firstceramic layer 4 b had the thickness Hsb (refer toFIG. 21 ) of 0.4 mm and the reflectance of 80% to light with a wavelength of 450 nm. The black circle () inFIG. 26 designates a measured value of light flux with respect to Example 1.FIG. 26 teaches that theLED module 1 of Example 1 emits a greater light flux than the LED module having the reference structure. Also, fromFIG. 26 , it is speculated that theLED module 1 of Example 1 emits a greater light flux than those ofReference Models submount 4 has the thickness of 0.5 mm. - Note that, reflectance-wavelength characteristics of the
submount 4 in Example 1 are as shown by a curve denoted by reference sign A1 inFIG. 27 , and reflectance-wavelength characteristics of a single layer alumina substrate with a thickness of 0.4 mm are as shown by a curve denoted by reference sign A2 inFIG. 27 . Note that the alumina substrate has the same specification as those of the alumina substrates inReference Models FIG. 27 were measured using a spectrophotometer and an integrating sphere. - Moreover, the inventors performed an experiment to measure light flux and chromaticity of light emitted from the
LED module 1. In the experiment, the measurement was made for each of the different particle diameters (median diameter) of the alumina particle in the firstceramic layer 4 b. In the experiment, theLED chip 6 was a blue LED chip in which the substrate was a sapphire substrate and the emission peak wavelength from the light-emitting layer was 460 nm. The chip size of theLED chip 6 was 0.5 mm by 0.24 mm. The thickness and the planar size of thesubmount 4 were 0.49 mm and 2 mm sq. (2 mm by 2 mm), respectively. - The chromaticity is a psychophysical property of color that is determined by chromaticity coordinates in an xy chromaticity diagram of a CIE color system. The chromaticity was measured in a direction in which the radiation angle of light emitted from the
LED module 1 is 0° (light axis direction), and in a direction in which the radiation angle is 60° (direction in which the angle relative to the light axis is 60°). In the measurement of the chromaticity, a spectral distribution in each of the radiation angles was obtained by a spectrophotometer, and the chromaticity in the CIE color system was calculated from each of the spectral distribution. - The experimental results are summarized in
FIG. 28 . The horizontal axis inFIG. 28 indicates a particle diameter. The left vertical axis inFIG. 28 indicates efficiency calculated by a light flux and input power supplied to theLED module 1. The right vertical axis inFIG. 28 indicates a color difference. The color difference is defined as the value of x (hereinafter referred to as “x1”) in the direction in which the radiation angle is 60° in the chromaticity coordinates, when a value of x (hereinafter referred to as “x0”) in the direction in which the radiation angle is 0° in the chromaticity coordinates is set as a reference. That is, the color difference in the right vertical axis inFIG. 28 is a value of (x1-x0). When the value of (x1-x0) is positive, it means that the larger the absolute value thereof, the larger the shift of the chromaticity to the yellowish-white side. When the value of (x1-x0) is negative, it means that the larger the absolute value thereof, the larger the shift of the chromaticity to the blue-white side. Note that the design value of the chromaticity in theLED module 1 is (0.33, 0.33). That is, the design value of x in the chromaticity coordinates is 0.33. The design value of the chromaticity is an example, and is not limited thereto. - The black rhombuses (♦) in
FIG. 28 designate measured values of the efficiency of theLED module 1. The black squares (▪) inFIG. 28 designate measured values of the color difference of theLED module 1. The white rhombus (⋄) inFIG. 28 designates a measured value of the efficiency of the aforementioned LED module having the reference structure. The white square (□) inFIG. 28 designates a measured value of the color difference of the aforementioned LED module having the reference structure. Note that, since the LED module having the reference structure does not include thesubmount 4, the particle diameter in the horizontal axis inFIG. 28 shows a particle diameter of particles in the alumina substrate. - The allowable range of the color difference in the
LED module 1 is preferably in a range between −0.0015 to 0.0015, for example, from a viewpoint of suppressing color unevenness and a viewpoint of realizing a color difference similar to the color difference of the LED module having the reference structure or less. -
FIG. 28 teaches that theLED module 1 has higher efficiency than the LED module having the reference structure. Also, fromFIG. 28 , it is inferred that the efficiency of theLED module 1 can be increased compared with that of the LED module having the reference structure by setting the particle diameter in a range between 1 μm to 4 μm, while suppressing the color difference from exceeding the allowable range (in other words, becoming larger than the color difference of the LED module having the reference structure). - The first
ceramic layer 4 b is a first dense layer composed of ceramics sintered at a high temperature in an approximate range of 1500° C. to 1600° C. The firstceramic layer 4 b has good rigidity compared with the secondceramic layer 4 a, since ceramic particles are bound strongly to each other by the high temperature sintering. Here, the good rigidity indicates that a flexural strength is relatively high. As a material of the firstceramic layer 4 b, alumina is preferable. - The second
ceramic layer 4 a is composed of ceramics sintered at 1000° C. or less (850° C. to 1000° C., for example) which is a relatively low temperature compared with the sintering temperature of the firstceramic layer 4 b. The ceramics constituting the secondceramic layer 4 a may be a second dense layer which contains a ceramic filler (ceramic microparticles) and a glass component, or a porous layer containing a ceramic filler (ceramic microparticles) and a glass component, for example. - The second dense layer is composed of dense ceramics in which ceramic fillers are bound each other by sintering and glass components are arranged around the ceramic fillers as a matrix. In the second dense layer, the ceramic filler mainly performs a function of reflecting light. The second dense layer may be made of borosilicate glass, glass ceramics which contains lead borosilicate glass and alumina, a material in which a ceramic filler is mixed to glass ceramics which contains soda-lime glass and alumina, or the like. The glass content of the glass ceramics is preferably set in a range of around 35 to 60 wt %. The ceramics content of the glass ceramics is preferably set in a range of around 40 to 60 wt %. Note that, in the second dense layer, the zinc component of the lead borosilicate glass can be substituted for titanium oxide or tantalum oxide to increase refractive index of the glass ceramics. The ceramic filler is preferably made of a material having higher refractive index than glass ceramics, and may be, for example, tantalum pentoxide, niobium pentoxide, titanium oxide, barium oxide, barium sulfate, magnesium oxide, calcium oxide, strontium oxide, zinc oxide, zirconium oxide, or silicate oxide (zircon).
- When the second
ceramic layer 4 a is constituted by a porous layer (hereinafter, “secondceramic layer 4 a” is also referred to as “porous layer 4 a”), it is preferable that afirst glass layer 40 aa is interposed between aporous layer 4 a having a plurality ofpores 40 c and the firstceramic layer 4 b, and asecond glass layer 40 ab is formed on an opposite side of theporous layer 4 a from the firstceramic layer 4 b, as shown in the schematic diagram inFIG. 15 . The porosity of theporous layer 4 a is set to be around 40%, but is not limited thereto. Thefirst glass layer 40 aa and thesecond glass layer 40 ab are transparent layers composed of a glass component and transmit visible light. The thicknesses of thefirst glass layer 40 aa and thesecond glass layer 40 ab may be set to around 10 μm, for example, but are not limited thereto. Around half of the glass component of each of thefirst glass layer 40 aa and thesecond glass layer 40 ab is composed of SiO2, but the glass component is not limited thereto. - The
first glass layer 40 aa is provided so as to be interposed between theporous layer 4 a and the firstceramic layer 4 b, and is closely-attached to the surface of theporous layer 4 a and to the surface of the firstceramic layer 4 b by sintering at the time of manufacture. - The
second glass layer 40 ab is provided on the opposite face of theporous layer 4 a from the firstceramic layer 4 b, and protects theporous layer 4 a. Accordingly, pores 40 c that exist on the opposite surface of theporous layer 4 a from the firstceramic layer 4 b is enclosed by thesecond glass layer 40 ab. - The
porous layer 4 a contains a ceramic filler (ceramic particulate) and a glass component. In theporous layer 4 a. the ceramic fillers are combined to form clusters by sintering so as to form a porous structure. The glass component serves as a binder for the ceramic filler. In theporous layer 4 a, the ceramic filler and the plurality of pores mainly perform a function of reflecting light. Note that, theporous layer 4 a can be formed in accordance with a manufacturing process of a package disclosed in paragraphs [0023]-[0026] and inFIG. 4 in WO2012/039442 A1. - The reflectance of the
porous layer 4 a can be changed by, for example, changing a weight ratio between the glass component and the ceramic component (such as alumina and zirconia). That is, the reflectance of theporous layer 4 a can be changed by changing the glass compounding ratio. InFIG. 30 , the horizontal axis indicates a glass compounding ratio, and the vertical axis indicates an integrated intensity measured with an integrating sphere. In measurement with the integrating sphere, intensities of reflected light with wavelengths between 380 to 780 nm are integrated.FIG. 30 teaches that the reflectance can be increased with a decrease in the glass compounding ratio. - Accordingly, in Example 2, the first
ceramic layer 4 b is formed by sintering alumina at 1600° C., and theporous layer 4 a is formed by sintering materials at 850° C., the materials being compounded such that the weight ratio of the glass component to the ceramic component is 20:80. In Example 2, the glass component is borosilicate glass with a median diameter of around 3 μm, and the alumina is a compound of alumina with a median diameter of around 0.5 μm and alumina with a median diameter of around 2 μm, and the zirconia has a median diameter of around 0.2 μm. In Example 2, the firstceramic layer 4 b has the thickness of 0.38 mm, and theporous layer 4 a has the thickness of 0.10 mm. The reflectance-wavelength characteristics of thesubmount 4 in Example 2 is indicated by a curve designated by “A3” inFIG. 31 and the reflectance-wavelength characteristics of the single layer alumina substrate with a thickness of 0.38 mm is as shown by a curve designated by “A4” inFIG. 31 . Note that, the weight ratio of the glass component to the ceramic component in theporous layer 4 a and the particle diameters (median diameters) of the respective materials are not particularly limited. - The
porous layer 4 a has a graded composition in which the density of the glass component gradually decreases from the both sides thereof to the inside in the thickness direction, since the glass components of thefirst glass layer 40 aa and thesecond glass layer 40 ab infiltrate at the time of manufacture. - Specifically, as the result of observing a cross-section along the thickness direction of the
porous layer 4 a with a thickness of around 100 μm with a microscope, it was found out that in regions from respective faces of theporous layer 4 a to the depth of around 20 μm in the thickness direction, glass dense layers exist in which glass occupies 70% or more of the area per unit area. In contrast to this, in the internal region deeper than 20 μm from respective faces of theporous layer 4 a in the thickness direction, glass occupies around 20% of the area per unit area, and a non-dense layer exists in which the glass and the ceramic filler are mixed at a certain ratio. - In the
LED module 1 of the present embodiment, thesubmount 4 is constituted by the twoceramic layers ceramic layers ceramic layer 4 a which is further from theLED chip 6 has a higher reflectance with respect to light emitted from theLED chip 6 than theceramic layer 4 b that is closer to theLED chip 6. Accordingly, light outcoupling efficiency of theLED module 1 of the present embodiment can be improved compared with that of a LED module including thesubmount 4 which is constituted by a single layer alumina substrate. In theLED module 1 of the present embodiment, it is possible to reduce an amount of light reflected from theface 4 sa of thesubmount 4, and as a result, absorption loss in theLED chip 6 can be reduced. Furthermore, in theLED module 1 of the present embodiment, absorptance of light (approximately 0%) of thesubmount 4 can be smaller than the absorptance of light (around 2 to 8%, for example) of theopaque substrate 2, and parts of light incident on theface 4 sa of thesubmount 4 can be scattered in theceramic layer 4 b and can be reflected at the interface between theceramic layer 4 b and theceramic layer 4 a. Consequently, in theLED module 1, it is possible to reduce an amount of light which passes through thesubmount 4 and arrives at thesurface 2 sa of theopaque substrate 2 and absorption loss at theopaque substrate 2. As a result, light outcoupling efficiency can be improved. - Incidentally, in the
LED module 1 of the present embodiment, the firstceramic layer 4 b has relatively higher light transmittance, and the secondceramic layer 4 a has relatively higher light scattering rate, out of the firstceramic layer 4 b and the secondceramic layer 4 a. Accordingly, it is inferred that, in theLED module 1, light can be diffused in the secondceramic layer 4 a that is farther from theLED chip 6, and an amount of light that is diffused before arriving at theopaque substrate 2 increases compared with a LED module having only the firstceramic layer 4 b. Also, it is speculated that, in theLED module 1, the possibility that light reflected by theopaque substrate 2 directly below thesubmount 4 is diffused without returning to theLED chip 6 can be increased. In contrast, it is speculated that, in theLED module 1, when thesubmount 4 is constituted by only the secondceramic layer 4 a, the possibility that light is scattered in the vicinity of theLED chip 6 and then returns to theLED chip 6 may be increased, unfortunately, because the possibility that light emitted from theLED chip 6 toward thesubmount 4 is scattered in a vicinity of theLED chip 6 may be increased. Consequently, it is speculated that, in theLED module 1, it is possible to reduce an amount of light returning to theLED chip 6, compared with a LED module including thesubmount 4 constituted by only the secondceramic layer 4 a. Moreover, in theLED module 1, it is possible to reduce the thickness of thesubmount 4 required to obtain the same reflectance, compared with thesubmount 4 constituted by only the firstceramic layer 4 b. - As shown in
FIG. 20 , thecolor conversion portion 10 is formed on thesubmount 4 and has a hemispherical shape so as to cover theLED chip 6 and a portion of each of thewires 7. Therefore, theLED module 1 whose configuration is shown inFIG. 20 preferably includes an encapsulating portion (not shown) which covers the exposed portion of each of thewires 7 and thecolor conversion portion 10. The encapsulating portion is preferably made of a transparent material. The transparent material of the encapsulating portion may be, for example, a silicone resin, an epoxy resin, an acrylic resin, glass, or an organic and inorganic hybrid material in which an organic component and an inorganic component are mixed and/or combined at a nanometer level or molecular level. The transparent material of the encapsulating portion is preferably a material having a linear expansion coefficient which is close to that of the transparent material of thecolor conversion portion 10, and is more preferably a material having a linear expansion coefficient that is the same as that of the transparent material of thecolor conversion portion 10. Accordingly, in theLED module 1, it is possible to suppress the concentration of stress on each of thewires 7 in a vicinity of the interface between the encapsulating portion and thecolor conversion portion 10 due to the difference between the linear expansion coefficients of the encapsulating portion and thecolor conversion portion 10. Consequently, in theLED module 1, disconnection ofwires 7 can be suppressed. Furthermore, in theLED module 1, it is possible to suppress the occurrence of cracks in the encapsulating portion or in thecolor conversion portion 10 due to the difference between the linear expansion coefficients of the encapsulating portion and thecolor conversion portion 10. The encapsulating portion is preferably formed in a hemispherical shape, but the shape thereof is not limited thereto, and may be a semiellipse spherical shape or a semicircular columnar shape. - The
color conversion portion 10 may be formed in a hemispherical shape which covers theLED chip 6, thewires 7, and thesubmount 4, similarly to that of theLED module 1 of the first modification of shown inFIG. 32 . - With regard to the first modification shown in
FIG. 32 , the reason why the light outcoupling efficiency of theLED module 1 is improved will be described with reference to the inferred mechanism diagrams inFIGS. 33 , 34A, 34B, and 34C. Note that the first modification is in the scope of the present invention, even if the inferred mechanism is different from the mechanism described below. - Arrows shown in
FIGS. 33 , 34A, 34B, and 34C schematically illustrate propagating paths of rays of light which are emitted from the light-emitting layer of theLED structure portion 60 in theLED chip 6. Solid-line arrows inFIGS. 33 , 34A, and 34B schematically illustrate propagating paths of rays of light which are emitted from the light-emitting layer and are reflected by theface 4 sa of thesubmount 4. Broken-line arrows inFIGS. 33 , 34A, 34B, and 34C schematically illustrate propagating paths of rays of light which are emitted from the light-emitting layer of theLED structure portion 60 and enter thesubmount 4. - The inventors inferred that, as shown in
FIGS. 33 , 34A, and 34B, reflection and refraction occur in the firstceramic layer 4 b at the interface between the ceramic particles and the grain boundary phase (glass component is the main component therein) caused by a difference between the refractive indices of the ceramic particle and the grain boundary phase. Also, the inventors inferred that, as shown inFIGS. 33 and 34C , reflection and refraction occur in the secondceramic layer 4 a at the interface between the ceramic particle and the pore and the grain boundary phase (glass component is the main component) caused by a difference between the refractive indices of the ceramic particle and the pore and the grain boundary phase. Also, the inventors inferred that, as shown inFIGS. 33 and 34C , reflection and refraction occur in the secondceramic layer 4 a at the interface between the pore and the grain boundary phase caused by a difference between the refractive indices of the pore and the grain boundary phase. Also, the inventors inferred that, with respect to a ceramic plate, when the plate thickness is the same, the larger the particle diameter of the ceramic particles in the plate, the smaller the reflectance and the larger the transmittance, since the larger the particle diameter of the ceramic particles, the smaller the number of interfaces, and the probability that light passes through the interface between the ceramic particles and the grain boundary phase is reduced when light propagates a unit length. - The inventors inferred that light outcoupling efficiency of the
LED module 1 can be improved by causing light emitted from theLED chip 6 to pass through the firstceramic layer 4 b as much as possible, and causing the light to be reflected in the secondceramic layer 4 a as much as possible. Therefore, it is preferable that, in thesubmount 4, the firstceramic layer 4 b includes ceramic particles having a greater particle diameter than the secondceramic layer 4 a while the secondceramic layer 4 a includes ceramic particles having a smaller particle diameter than the firstceramic layer 4 b and further include pores. - In the
LED module 1, theopaque substrate 2 may have an elongated shape, and a plurality ofLED chips 6 may be arranged along the longitudinal direction of theopaque substrate 2. In this case, in theLED module 1, thewires 7 may extend along a direction perpendicular to the arrangement direction of theLED chips 6, and thecolor conversion portions 10 may have a hemispherical shape to cover therespective LED chips 6 and portions of therespective wires 7 on thesubmount 4, similarly to a LED module of the second modification shown inFIG. 35 , for example. Note that, inFIG. 35 , the patternedconductors 8 inFIG. 20 are omitted. - Alternatively, in the
LED module 1, thewires 7 may extend along the arrangement direction of theLED chips 6, and thecolor conversion portions 10 may haves a convex shape to cover thesubmount 4, therespective LED chip 6, and therespective wires 7, similarly to a LED module of the third modification shown inFIG. 36 , for example. Note that, inFIG. 36 , the patternedconductors 8 inFIG. 20 are omitted. - Alternatively, in the
LED module 1, thewires 7 may extend along the arrangement direction of theLED chips 6, and thecolor conversion portions 10 may haves a convex shape to cover most part of thesubmount 4, therespective LED chip 6, and therespective wires 7, similarly to a LED module of the fourth modification shown inFIG. 37 , for example. Note that, inFIG. 34 , the patternedconductors 8 inFIG. 20 are omitted. - In the
LED module 1 shown inFIG. 37 , opposite ends of thesubmount 4 in a perpendicular direction to the arrangement direction of theLED chips 6 are not covered with thecolor conversion portion 10 and are exposed. - In the
LED module 1 of the present embodiment, the plurality of ceramic layers (firstceramic layer 4 b and secondceramic layer 4 a) of thesubmount 4 are light-transmissive layers having different optical properties. - The
submount 4 is constituted by the plurality of light-transmissive layers stacked in the thickness direction, and is required to have such a property that optical properties of the plurality of light-transmissive layers differ from each other, and a light-transmissive layer of the plurality of light-transmissive layers which is farther from theLED chip 6 is higher in reflectance in a wavelength range of the light emitted from theLED chip 6. Hereinafter, the uppermost light-transmissive layer which is the closest to theLED chip 6 may be referred to as a first light-transmissive layer, and the lowermost light-transmissive layer which is farther from theLED chip 6 may be referred to as a second light-transmissive layer. - The first light-transmissive layer is preferably composed of a material that has high transmittance with respect to light emitted from the
LED chip 6, and has a refractive index close to the refractive index of theLED chip 6. The refractive index of the first light-transmissive layer being close to the refractive index of theLED chip 6 means that the difference between the refractive index of the first light-transmissive layer and the refractive index of thesubstrate 61 in theLED chip 6 is 0.1 or less, and is more preferably 0. The first light-transmissive layer is preferably composed of a material having a high thermal resistance. - The material of the first light-transmissive layer is not limited to ceramics, and may be glass, SiC, GaN, GaP, sapphire, an epoxy resin, a silicone resin, unsaturated polyester, or the like. The material of the ceramics is not limited to Al2O3, and may be another metal oxide (such as magnesia, zirconia, and titania), a metal nitride (such as aluminum nitride), or the like. As the material of the first light-transmissive layer, ceramics is more preferable than a single crystal from a viewpoint of causing light emitted from the
LED chip 6 to be forward-scattered. - The light-transmissive ceramics may be LUMICERA (registered trademark) available from Murata Manufacturing Co., Ltd., HICERAM (product name) available from NGK Insulators, Ltd., or the like. LUMICERA(registered trademark) has a Ba(Mg,Ta)O3-based complex perovskite structure as the main crystal phase. HICERAM is a light-transmissive alumina ceramic.
- The first light-transmissive layer made of ceramic preferably include particles having the particle diameter of around 1 μm to 5 μm.
- The first light-transmissive layer may be a single crystal in which voids, a modified portion having a different refractive index, or the like is formed. The voids, the modified portion, or the like may be formed by irradiating, with a laser beam from a femto-second laser, a scheduled formation region of the voids, the modified portion, or the like in the single crystal. The wavelength and the irradiation conditions of the laser beam from the femto-second laser may vary appropriately according to the material of the single crystal, the forming target (void or modified portion), the size of the forming target, or the like. The first light-transmissive layer may be made of a base resin (such as epoxy resin, silicone resin, and unsaturated polyester) (hereinafter, referred to as “first base resin”) which contains a filler (hereinafter, referred to as “first filler”) having a refractive index different from the base resin. It is more preferable that a difference between the refractive indices of the first filler and the first base resin is small. The first filler preferably has higher thermal conductivity. The first light-transmissive layer preferably has a high density of the first filler, from a viewpoint of increasing thermal conductivity. The shape of the first filler is preferably a sphere, from a viewpoint of suppressing total reflection of incident light. The larger the particle diameter of the first filler, the smaller the reflectivity and the refractivity thereof. The first light-transmissive layer may be configured such that a first filler having a relatively large particle diameter is present in a region of the first light-transmissive layer close to the
LED chip 6 in the thickness direction, and a first filler having a relatively small particle diameter is present in a region thereof distant from theLED chip 6. In this case, the first light-transmissive layer may include a plurality of stacked layers having the first fillers with different particle diameters. - On the surface of the first light-transmissive layer close to the LED chip 6 (the
face 4 sa of the submount 4), a fine asperity structure portion is preferably formed around the mounting region of theLED chip 6 so as to suppress total reflection of light which is emitted from theLED chip 6 toward thesubmount 4 and is reflected by or refracted in thesubmount 4. The asperity structure portion may be formed by roughening the surface of the first light-transmissive layer by sandblast processing or the like. The surface roughness of the asperity structure portion is preferably such that an arithmetic average roughness Ra specified in JIS B 0601-2001 (ISO 4287-1997) is around 0.05 μm. - The
submount 4 may have a configuration in which a resin layer having a smaller refractive index than the first light-transmissive layer is formed on the surface of the first light-transmissive layer close to theLED chip 6 around the mounting region of theLED chip 6. The material of the resin layer may be a silicone resin, an epoxy resin, or the like. The material of the resin layer may be a resin containing a fluorescent material. - The second light-transmissive layer is more preferably configured such that light emitted from the
LED chip 6 is diffusely reflected, than configured such that the light is specularly reflected. - The material of the second light-transmissive layer is not limited to ceramics, and may be glass, SiC, GaN, GaP, sapphire, an epoxy resin, a silicone resin, unsaturated polyester, or the like. The material of the ceramics is not limited to Al2O3, and may be another metal oxide (such as magnesia, zirconia, and titania), a metal nitride (such as aluminum nitride), or the like.
- The second light-transmissive layer made of ceramics preferably includes particles having the particle diameter of 1 μm or less, and more preferably include particles having the particle diameter of around 0.1 μm to 0.3 μm. Also, the second light-transmissive layer may be the aforementioned
porous layer 4 a. In a case where the first light-transmissive layer was the firstceramic layer 4 b composed of alumina having purity of 99.5%, the bulk density of the first light-transmissive layer was 3.8 to 3.95 g/cm3. In a case where the first light-transmissive layer was the firstceramic layer 4 b composed of alumina having purity of 96%, the bulk density of the first light-transmissive layer was 3.7 to 3.8 g/cm3. In contrast, in a case where the second light-transmissive layer was theporous layer 4 a, the bulk density of the second light-transmissive layer was 3.7 to 3.8 g/cm3. Note that, the aforementioned bulk density is a value estimated by image processing a SEM image observed and obtained by an SEM. - The second light-transmissive layer may be of a single crystal in which voids, a modified portion having a different refractive index, or the like is formed. The voids, the modified portion, or the like may be formed by irradiating, with a laser beam from a femto-second laser, a scheduled formation region of the voids, the modified portion, or the like in the single crystal. The wavelength and the irradiation conditions of the laser beam from the femto-second laser may vary appropriately according to the material of the single crystal, the forming target (void or modified portion), the size of the forming target, or the like. The second light-transmissive layer may be made of a base resin (such as epoxy resin, silicone resin, unsaturated polyester, and a fluorine resin) (hereinafter, referred to as “second base resin”) which contains a filler (hereinafter, referred to as “second filler”) having a refractive index different from the base resin. The second light-transmissive layer may be configured such that a second filler having a relatively large particle diameter is present in a region of the second light-transmissive layer close to the
LED chip 6 in the thickness direction, and a second filler having a relatively small particle diameter is present in a region thereof distant from theLED chip 6. The material of the second filler is preferably, for example, a white inorganic material, and may be a metal oxide such as TiO2 and ZnO. The particle diameter of the second filler is preferably in a range between around 0.1 μm to 0.3 μm, for example. The filling rate of the second filler is preferably in a range of around 50 to 75 wt %, for example. The silicone resin for the second base resin may be methyl silicone, phenyl silicone, or the like. In a case where the second filler is in a form of solid particle, it is preferable that there is a great difference between the refractive indices of the second filler and the second base resin. A material containing the second base resin and the second filler in the second base resin may be KER-3200-T1 available from Shin-Etsu Chemical Co., Ltd. or the like. - The second filler may be a core-shell particle, hollow particle, or the like. The refractive index of the core of the core-shell particle can be arbitrarily selected, but is preferably smaller than the refractive index of the second base resin. It is preferable that the hollow particle has a smaller refractive index than the second base resin, and that inside of the hollow particle is gas (such as air and inert gas) or vacuum.
- The second light-transmissive layer may be a light diffusion sheet. The light diffusion sheet may be a white polyethylene terephthalate sheet having a plurality of bubbles, or the like.
- The
submount 4 may be formed by, in a case of both the first light-transmissive layer and the second light-transmissive layer being made of ceramics, stacking ceramic green sheets to be the first light-transmissive layer and the second light-transmissive layer individually and sintering the stacked sheets. Note that, in thesubmount 4, provided that the second light-transmissive layer includes bubbles, the first light-transmissive layer may include bubbles. In such a case, it is preferable that the first light-transmissive layer is smaller in the number of bubbles and higher in the bulk density than the second light-transmissive layer. - The first light-transmissive layer and the second light-transmissive layer are preferably composed of a material that has a high resistance to light and heat, which are emitted from the
LED chip 6 and the fluorescent material. - The
LED module 1 may include a reflection layer over thefurther face 4 sb of thesubmount 4 to reflect light from theLED chip 6 or the like. The reflection layer may be made of silver, aluminum, a silver aluminum alloy, silver alloys other than the silver aluminum alloy, an aluminum alloy, or the like. The reflection layer may be constituted by a thin film, a metal foil, a solder mask (solder), or the like. The reflection layer may be provided on thesubmount 4, or may be provided on theopaque substrate 2. - An
LED module 1 of the present embodiment differs from theLED module 1 ofEmbodiment 2 in that, as shown inFIGS. 38A , 38B, and 38C, anopaque substrate 2 has an elongated shape and a plurality ofLED chips 6 are included. Note that, constituent elements similar to those inEmbodiment 2 are provided with the same reference numerals, and redundant description thereof will be omitted. - In the
LED module 1, the plurality ofLED chips 6 are aligned in a prescribed direction (in the horizontal direction inFIG. 38B ) on asurface 2 sa of theopaque substrate 2. In theLED module 1, theLED chips 6 aligned in the prescribed direction andwires 7 that are connected to therespective LED chips 6 are covered by acolor conversion portion 10 having a band shape. Thecolor conversion portion 10 has recessedportions 10 b to suppress total reflection of light emitted from theLED chips 6 betweenadjacent LED chips 6 to each other in the prescribed direction. - A patterned conductors (patterned wiring circuit) 8 serving as a wiring circuit includes a first patterned wiring (first pattern) 8 a to which a first electrode of the
LED chip 6 is to be connected and a second patterned wiring (second pattern) 8 b to which the second electrode of theLED chip 6 is to be connected. - The first
patterned wiring 8 a and the secondpatterned wiring 8 b each have a planar shape of a comb shape, and are arrayed so as to interdigitate in the lateral direction of theopaque substrate 2. In this regard, in the patternedconductors 8, afirst shaft 8 aa of the firstpatterned wiring 8 a faces asecond shaft 8 ba of the secondpatterned wiring 8 b. In thepatterned conductors 8,first comb teeth 8 ab of the firstpatterned wiring 8 a andsecond comb teeth 8 bb of the secondpatterned wiring 8 b are arranged alternately in in the longitudinal direction of theopaque substrate 2 and separated by a space. - In the
LED module 1, the plurality of (nine in an example shown in the diagram)LED chips 6 are arranged in the longitudinal direction (in the aforementioned prescribed direction) of theopaque substrate 2 and are connected in parallel. In theLED module 1, power can be supplied to a parallel circuit in which the plurality ofLED chips 6 are connected in parallel. In short, in theLED module 1, power can be supplied to all theLED chips 6 by applying voltage between the firstpatterned wiring 8 a and the secondpatterned wiring 8 b. When a plurality of theLED modules 1 are arranged,adjacent LED modules 1 may be electrically connected by conductive members, wires for feed wiring (not shown), connectors (not shown), or the like. In this case, one power supply unit can supply power to the plurality ofLED modules 1 so that all theLED chips 6 of therespective LED modules 1 can emit light. - The patterned
conductors 8 are preferably provided with a surface treatment layer (not shown). The surface treatment layer is preferably made of a metal material having higher oxidation-resistance and corrosion-resistance than the material of the patternedconductors 8. When the patternedconductors 8 are made of copper, the surface treatment layer is preferably a nickel film, a stack of a nickel film and a gold film, a stack of a nickel film, a palladium film, and a gold film, a stack of a nickel film and a palladium film, or the like, for example. Here, the surface treatment layer is more preferably a stack of a nickel film and a palladium film, from the viewpoint of cost reduction. Note that the surface treatment layer may be formed by plating. - The
color conversion portion 10 is made of a resin containing a fluorescent material, for example. Thecolor conversion portion 10 is preferably made of the resin in which the fluorescent material is dispersed. The resin of thecolor conversion portion 10 is not particularly limited, as long as it transmits light emitted from theLED chip 6 as well as light emitted from the fluorescent material. - The resin of the
color conversion portion 10 may be a silicone resin, an epoxy resin, an acrylic resin, an urethane resin, an oxetane resin, a polycarbonate resin, or the like. As the resin, the silicone resin is preferable from a viewpoint of thermal resistance and weather resistance, and gel-like silicone is more preferable from a viewpoint of suppressing breaking of thewires 7 due to a thermal stress caused by temperature cycling. - The fluorescent material functions as a wavelength conversion material to convert light emitted from the
LED chip 6 into light having a longer wavelength than the light emitted from theLED chip 6. Accordingly, theLED module 1 can provide mixed-color light constituted by the light emitted from theLED chip 6 and light emitted from the fluorescent material. In short, thecolor conversion portion 10 has a function serving as a wavelength conversion portion to convert light emitted from theLED chip 6 into light having a longer wavelength than the light emitted from theLED chip 6. Besides, thecolor conversion portion 10 has a function serving as an encapsulating portion for encapsulating eachLED chip 6 and eachwire 7. - When including a blue LED chip as the
LED chip 6 and a yellow fluorescent material as the fluorescent material being the wavelength conversion material, for example, theLED module 1 can emit white light. That is, in theLED module 1, blue light emitted from theLED chip 6 and light emitted from the yellow fluorescent material can be emitted outside through the surface of thecolor conversion portion 10, and as a result, white light can be obtained. - The fluorescent material serving as the wavelength conversion material is not limited to the yellow fluorescent material, and may include, for example, a set of a yellow fluorescent material and a red fluorescent material, or a set of a red fluorescent material and a green fluorescent material. Also, the fluorescent material serving as the wavelength conversion material is not limited to one kind of yellow fluorescent material, and may include two kinds of yellow fluorescent materials having different emission peak wavelengths. The color rendering property of
LED module 1 can be improved by use of a plurality of fluorescent materials as the wavelength conversion material. - The
color conversion portion 10 has, as described above, recessedportions 10 b to suppress total reflection of light emitted from each of theLED chips 6 between theLED chips 6 which are adjacent to each other in the prescribed direction. Accordingly. in theLED module 1, it is possible to suppress total reflection of light which is emitted from theLED chip 6 and then strikes an interface between thecolor conversion portion 10 and air. Consequently, in theLED module 1, it is possible to reduce an amount of light which is confined due to total reflection, compared with the LED module including thecolor conversion portion 10 having a hemicylindrical shape, and therefore light outcoupling efficiency can be improved. In short, in theLED module 1, a total reflection loss can be reduced, and light outcoupling efficiency can be improved. - The
color conversion portion 10 is formed so as to have a cross section including a step which corresponds to a step between the face of theLED chip 6 and thesurface 2 sa of theopaque substrate 2. Consequently, thecolor conversion portion 10 has a cross section along a direction orthogonal to the arrangement direction of theLED chips 6, and a cross section along the arrangement direction of theLED chips 6, the former is a convex shape while the latter has recesses and convexes. In short, in theLED module 1, thecolor conversion portion 10 with a band shape has a recess and convex structure to improve the light outcoupling efficiency. - The period of the recess and convex structure is the same as the array pitch of the
LED chips 6. The period of the recess and convex structure is the array pitch of theconvex portions 10 a which coverrespective LED chips 6. - The surface shape of the
color conversion portion 10 may be designed such that the angle between a light ray from theLED chip 6 and a normal line on the surface of thecolor conversion portion 10 at a point where the light ray from theLED chip 6 crosses the surface thereof is smaller than the critical angle. Here, in theLED module 1, each of theconvex portions 10 a of thecolor conversion portion 10 is preferably designed to have the surface shape such that, in substantially all the areas of the surface of theconvex portion 10 a of thecolor conversion portion 10, the incident angle (light incident angle) of the light ray from theLED chip 6 is smaller than the critical angle. - For this reason, in the
color conversion portion 10, each of theconvex portions 10 a which covers acorresponding LED chip 6 is preferably formed in a hemispherical shape. Eachconvex portion 10 a is designed such that the light axis of theconvex portion 10 a is aligned with the light axis of theLED chip 6 covered with theconvex portion 10 a in the thickness direction of theopaque substrate 2. Accordingly, in theLED module 1, it is possible to suppress not only the total reflection at the surface (interface between thecolor conversion portion 10 and air) of thecolor conversion portion 10 but also color unevenness. The color unevenness is a state in which chromaticity varies depending on an irradiation direction of light. In theLED module 1, the color unevenness can be suppressed to such an extent the color unevenness cannot be perceived visually. - In the
LED module 1, it is possible to substantially equalize light path lengths of light rays from theLED chip 6 to the surface of theconvex portion 10 a regardless the emission direction of light from theLED chip 6. As a result, color unevenness can be further suppressed. The shape of eachconvex portion 10 a of thecolor conversion portion 10 is not limited to hemisphere, and may be a semielliptical shape, for example. Note that, eachconvex portion 10 a may have a shape, a cuboid shape, or the like. - For manufacturing the
LED module 1, first, theopaque substrate 2 is prepared. Thereafter, theLED chips 6 are die-bonded on thesurface 2 sa of theopaque substrate 2 with a die bonding apparatus or the like. Thereafter, the first electrode and the second electrode of each of theLED chips 6 are connected to the patternedwiring circuit 8 via therespective wires 7 with a wire bonding apparatus, or the like. Thereafter, thecolor conversion portion 10 is formed using a dispenser system or the like. - In a case where the
color conversion portion 10 is formed with a dispenser system, a material of thecolor conversion portion 10 is applied by discharging the material from a nozzle while a dispenser head is moved in the arrangement direction of theLED chips 6, for example. - In order to apply the material of the
color conversion portion 10 with the dispenser system so as to form an application shape corresponding to the surface shape of thecolor conversion portion 10, the material is discharged and applied while the dispenser head is moved, for example. Specifically, an application amount is varied by varying the moving speed of the dispenser head while the distance between the nozzle and thesurface 2 sa of theopaque substrate 2 directly under the nozzle is varied by moving the dispenser head up and down. More specifically, the moving speed of the dispenser head is relatively varied in applying the material between in a region to form theconvex portion 10 a of thecolor conversion portion 10 and in a region to form a portion of thecolor conversion portion 10 between adjacentconvex portions 10 a. The moving speed of the dispenser head is slow in the former region, and the moving speed thereof is fast in the latter region. Moreover, the dispenser head is moved up and down depending on the surface shape of thecolor conversion portion 10. Accordingly, by the method of forming thecolor conversion portion 10 with the dispenser system, it is possible to form, with the material, the application shape in accordance with the surface shape of thecolor conversion portion 10. The application shape may be set in view of contraction in curing the material. - The dispenser system preferably includes: a movement mechanism constituted by a robot for moving the dispenser head; a sensor unit for measuring heights of the
surface 2 sa of theopaque substrate 2 and the nozzle from a table; and a controller for controlling the movement mechanism and a discharge amount of the material from the nozzle. The controller can be realized, for example, by loading an appropriate program to a microcomputer. The dispenser system can be adapted to various types of products different in the array pitch of theLED chips 6, the number of theLED chips 6, the width of thecolor conversion portion 10, or the like, by changing the program loaded to the controller appropriately. - The surface shape of the
color conversion portion 10 can be controlled by adjusting viscosity or the like of the material, for example. The curvature of the surface (convex face) in each of theconvex portions 10 a can be designed with viscosity and surface tension of the material, a height of thewire 7, or the like. Larger curvature can be realized by increasing the viscosity and the surface tension of the material, or by increasing the height of thewire 7. A smaller width (band width) of thecolor conversion portion 10 having the band shape can be realized by increasing the viscosity and the surface tension of the material. The viscosity of the material is preferably set to be in a range of around 100 to 2000 mPa·s. Note that, the value of the viscosity may be measured under a room temperature using a cone and plate rotational viscometer, for example. - The dispenser system may include a heater to heat an un-cured material so as to adjust viscosity to a desirable value. Accordingly, in the dispenser system, reproducibility of the application shape of the material can be improved, and reproducibility of the surface shape of the
color conversion portion 10 can be improved. - Hereinafter, a modification of the
LED module 1 of the present embodiment will be described with reference toFIGS. 39 and 40 . Note that, constituent elements similar to those inEmbodiment 3 are provided with the same reference numerals, and redundant description thereof will be omitted appropriately. - In an
LED module 1 of the modification, a plurality ofLED chips 6 are arranged on thesurface 2 sa of theopaque substrate 2 in a prescribed direction (hereinafter, referred to as “first direction”) at equal intervals. - The patterned
conductors 8 serving as a wiring circuit includes the firstpatterned wiring 8 a and the secondpatterned wiring 8 b which are each formed into a comb shape and interdigitate. The firstpatterned wiring 8 a is electrically connected to the first electrode of each of theLED chip 6 via the wire 7 (hereinafter, referred to as “first wire 7 a”). The secondpatterned wiring 8 b is electrically connected to the second electrode of each of theLED chip 6 via the wire 7 (hereinafter, referred to as “second wire 7 b”). - The first
patterned wiring 8 a includes afirst shaft 8 aa formed along the first direction and a plurality offirst comb teeth 8 ab which are formed along a second direction orthogonal to the first direction. - The second
patterned wiring 8 b includes asecond shaft 8 ba which is formed along the first direction and a plurality ofsecond comb teeth 8 bb which are formed along the second direction. - The plurality of
first comb teeth 8 ab of the firstpatterned wiring 8 a are constituted byfirst comb teeth 8 ab (8 ab 1) having a relatively large tooth width andfirst comb teeth 8 ab (8 ab 2) having a relatively small tooth width. In the firstpatterned wiring 8 a, the widefirst comb teeth 8 ab 1 and the narrowfirst comb teeth 8 ab 2 are arranged alternately in the first direction. - The plurality of
second comb teeth 8 bb of the secondpatterned wiring 8 b are constituted bysecond comb teeth 8 bb (8 bb 1) having a relatively large tooth width andsecond comb teeth 8 bb (8 bb 2) having a relatively small tooth width. In thesecond conductor 8 b, the widesecond comb teeth 8 bb 1 and the narrowsecond comb teeth 8 bb 2 are arranged alternately in the first direction. - The patterned
conductors 8 includes the widefirst comb teeth 8 ab 1, the narrowsecond comb teeth 8 bb 2, the narrowfirst comb teeth 8 ab 2, and thecomb teeth 8 bb 1 which are arranged cyclically in the first direction. - The
opaque substrate 2 is provided with the patternedwiring circuit 8 on a surface of abase substrate 2 a having an electrical insulation property. and amask layer 2 b which covers the patternedwiring circuit 8 over the surface of thebase substrate 2 a. Themask layer 2 b is formed over the surface of thebase substrate 2 a so as to also cover portions in which the patternedwiring circuit 8 is not formed. The material of themask layer 2 b may be a white mask made of a resin (such as silicone resin) which contains a white pigment such as barium sulfate (BaSO4) and titanium dioxide (TiO2). The white mask may be a white mask material “ASA COLOR(registered trademark) RESIST INK” made of silicone produced by Asahi Rubber Inc., or the like. - The
mask layer 2 b has a plurality ofopenings 2 ba for exposing first pads on thefirst comb teeth 8 ab to which the respectivefirst wires 7 a are connected and a plurality ofopenings 2 bb for exposing second pads on thesecond comb teeth 8 bb to which the respectivesecond wires 7 b are connected. In short, themask layer 2 b has theopenings 2 ba and theopenings 2 bb which are formed alternately in the first direction. In themask layer 2 b, the plurality ofopenings 2 ba and the plurality ofopenings 2 bb are formed so as to be aligned on a line. - The
openings 2 ba for exposing the first pads on the widefirst comb teeth 8 ab 1 are located at a distant side from the respective adjacent narrowsecond comb teeth 8 bb 2 with respect to the respective center lines of the widefirst comb teeth 8 ab 1 in the first direction. In theLED module 1, thesubmounts 4 and theLED chips 6 are arranged vertically above regions on the widefirst comb teeth 8 ab 1 that are close to the respective narrowsecond comb teeth 8 bb 2 with respect to the respective center lines thereof. - The
openings 2 ba for exposing the first pads on the narrowfirst comb teeth 8 ab 2 are located on the respective center lines of the narrowfirst comb teeth 8 ab 2. - The
openings 2 bb for exposing the second pads on the widesecond comb teeth 8 bb 1 are located at a distant side from the respective adjacent narrowfirst comb teeth 8 ab 2 with respect to the respective center lines of the widesecond comb teeth 8 bb 1 in the first direction. In theLED module 1, thesubmounts 4 and theLED chips 6 are arranged vertically above regions on the widesecond comb teeth 8 bb 1 that are close to the respective narrowfirst comb teeth 8 ab 2 with respect to the respective center lines thereof. - The
openings 2 bb for exposing the second pads on the narrowsecond comb teeth 8 bb 2 are located on the respective center lines of the narrowsecond comb teeth 8 bb 2. - Each
LED chip 6 is located between, in a planar view, the first pad to which the first electrode is connected via thefirst wire 7 a and the second pad to which the second electrode is connected via thesecond wire 7 b. In short, in theLED module 1, the plurality ofLED chips 6, the plurality of first pads, and the plurality of second pads are formed so as to be aligned on a line in a planar view. - The
color conversion portion 10 is formed in a band shape to cover the plurality ofLED chips 6, the plurality offirst wires 7 a, and the plurality ofsecond wires 7 b. The cross section of thecolor conversion portion 10 along a direction orthogonal to the first direction is a hemispherical shape. Thecolor conversion portion 10 may have a similar shape to that ofEmbodiment 3. - In the
LED module 1 of the modification, the patternedconductors 8 is present on theopaque substrate 2 to overlap respective vertical projection regions of theLED chips 6. In theLED module 1 of the modification, heat generated in theLED chips 6 and thecolor conversion portions 10 in lighting can thereby be conducted to a wide area via the patternedconductors 8. That is, in theLED module 1 of the modification, a heat dissipation property can be improved, and light output can be increased. In theLED module 1 of the modification, since the directions of theLED chips 6 can be made the same. handling of theLED chips 6 in bonding process of theLED chips 6 on therespective submounts 4 on theopaque substrate 2 can be facilitated, and manufacturing can be facilitated. - Incidentally, the
LED modules 1 ofEmbodiments LED module 1 of the modification ofEmbodiment 3 can be used as a light source for a variety of lighting apparatuses, similar to theLED modules 1 ofEmbodiment 1 and the first modification to the eleventh modification ofEmbodiment 1. Preferable examples of a lighting apparatus which includes theLED module 1 include: a lighting device having a light source which is theLED module 1 and provided on a device main body; and a lamp (such as a straight-tube LED lamp and a bulb type lamp), but the lighting apparatus is not limited thereto and may be other lighting apparatuses. - Hereinafter, a
lighting device 50 including theLED module 1 ofEmbodiment 3 as a light source will be described with reference toFIGS. 41A and 41B . - The
lighting device 50 is an LED lighting device and includes a devicemain body 51 and anLED module 1 serving as a light source held by the devicemain body 51. - The device
main body 51 is formed in an elongated shape (rectangle plate shape, here) and is larger than theLED module 1 in a planar size. In thelighting device 50, theLED module 1 is provided on asurface 51 b of the devicemain body 51 in the thickness direction. In thelighting device 50, theLED module 1 and the devicemain body 51 are arranged such that the longitudinal direction of theLED module 1 is aligned with the longitudinal direction of the devicemain body 51. Thelighting device 50 includes acover 52 for covering theLED module 1 provided on thesurface 51 b of the devicemain body 51. Thecover 52 transmits light which is emitted from theLED module 1. - The
lighting device 50 includes alighting unit 53 which supplies direct current electric power to theLED module 1 for lighting (allowing light emission) each of theLED chips 2. In thelighting device 50, thelighting unit 53 and theLED module 1 are electrically connected viawires 54 e.g., lead wires. - In the
lighting device 50, at thefurther surface 51 c of the devicemain body 51 in the thickness direction, arecess 51 a is formed to house thelighting unit 53. Therecess 51 a is formed along the longitudinal direction of the devicemain body 51. Also, the devicemain body 51 has a through hole (not shown) to which thewire 54 is to be inserted. The through hole penetrates a thin portion between thesurface 51 b and the inner bottom face of therecess 51 a. - In the
LED module 1, thewires 54 can be connected to exposed portions of the patternedconductors 8. A connection portion between thepatterned conductors 8 and thewire 54 may be a connection portion composed of a conductive bonding material such as solder, a connection portion constituted by a male connector and a female connector, or the like. - In the
lighting device 50, theLED module 1 can be lighted with direct current electric power supplied from thelighting unit 53. Note that, thelighting unit 53 may receive power from an alternating current power supply such as a commercial power supply, or receive electric power from a direct current power supply such as a solar cell and a storage battery. - The light source in the
lighting device 50 is not limited to theLED module 1 ofEmbodiment 3, but may be any ofLED modules 1 ofEmbodiment 1, the first modification to the ninth modification ofEmbodiment 1,Embodiment 2, and the first modification to the fourth modification ofEmbodiment 2. - The device
main body 51 is preferably made of a material having high thermal conductivity, and is more preferably made of a material having higher thermal conductivity than theopaque substrate 2. Here, the devicemain body 51 is preferably made of a metal having high thermal conductivity such as aluminum and copper. - The
LED module 1 may be fixed to the devicemain body 51 by: a method using a fixture such as a screw; or bonding the devicemain body 51 to theLED module 1 by providing therebetween an epoxy resin layer which is a thermoset sheet adhesive. The sheet adhesive may be a sheet adhesive made of a stack of a plastic film (PET film) and a B stage epoxy resin layer (thermoset resin). The B stage epoxy resin layer contains a filling material composed of a filler such as silica and alumina and has a property in which viscosity becomes small and fluidity becomes large when heated. Such a sheet adhesive may be an adhesive sheet TSA available from Toray Industries, Inc. or the like. The filler may be an electrical insulation material having high thermal conductivity than an epoxy resin which is a thermoset resin. The thickness of the aforementioned epoxy resin layer is set to be 100 μm, but this value is an example, and the thickness is not limited thereto, and may be set in a range of around 50 μm to 150 μm as appropriate. The thermal conductivity of the aforementioned epoxy resin layer is preferably larger than 4 W/m·K. - The epoxy resin layer which is a sheet adhesive described above has high thermal conductivity, high fluidity when heated, and high adhesiveness to a surface having asperity, along with having an electrical insulation property. Consequently, in the
lighting device 50, it is possible to suppress generation of gaps between the aforementioned insulation layer of the epoxy resin layer and theLED module 1 and between the insulation layer and the devicemain body 51, and as a result it is possible to improve adhesion reliability and to suppress an increase of a thermal resistance and occurrence of variation due to lack of adhesion. The insulation layer has an electrical insulation property and thermal conductivity, and has a function of connecting theLED module 1 and the devicemain body 51 thermally. - Thus, in the
lighting device 50, it is possible to lower a thermal resistance between eachLED chip 6 and the devicemain body 51 and reduce a variation of thermal resistances, compared with a lighting device where a heat dissipation sheet (heat conduction sheet) of a rubber sheet type or a silicone gel type such as Sarcon(registered trademark) is interposed between theLED module 1 and the devicemain body 51. Accordingly, in thelighting device 50, since the heat dissipation property is improved and therefore an increase in junction temperature of each of theLED chips 6 can be suppressed. Hence, input power can be increased and light output can be increased. The thickness of the aforementioned epoxy resin layer is set to be 100 μm, but this value is an example, and the thickness is not limited thereto, and may be set in a range of around 50 μm to 150 μm as appropriate. The thermal conductivity of the aforementioned epoxy resin layer is preferably larger than 4 W/m·K. - The
cover 52 may be made of an acrylic resin, a polycarbonate resin, a silicone resin, glass, or the like. - The
cover 52 has a lens portion (not shown) which is formed integrally therewith and controls a directional distribution of light emitted from theLED module 1. Cost can be reduced compared with a configuration in which a lens which has been separately prepared from thecover 52 is attached to thecover 52. - The
lighting device 50 described above includes theLED module 1 serving as the light source, and therefore cost thereof can be reduced and light output thereof can be increased. - The
lighting device 50 includes the devicemain body 51 made of metal, and therefore the heat dissipation property thereof can be improved. - Hereinafter, a straight-
tube LED lamp 80 including a light source that is theLED module 1 ofEmbodiment 3 will be described with reference toFIGS. 42A and 42B . - The straight-
tube LED lamp 80 includes: a tubemain body 81 having a straight-tube shape (cylindrical shape) formed of a light-transmissive material; and afirst cap 82 and asecond cap 83 that are respectively provided at an end portion and the other end portion of the tubemain body 81 in the longitudinal direction. TheLED module 1 ofEmbodiment 3 is housed in the tubemain body 81. TheLED module 1 is not limited to theLED module 1 ofEmbodiment 3, but may be any ofLED modules 1 ofEmbodiment 1, the first modification to the ninth modification ofEmbodiment 1,Embodiment 2, the first modification to fourth modification ofEmbodiment 2, and the modification ofEmbodiment 3. Note that, in terms of a general straight-tube LED lamp, “straight-tube LED lamp system with L-type pin cap GX16t-5 (for general illumination)” (JEL 801:2010) is standardized by Japan Electric Lamp Manufacturers Association, for example. - The tube
main body 81 may be made of transparent glass, milky white glass, a transparent resin, a milky white resin, or the like. - The
first cap 82 has twopower supply terminals 84 and 84 (hereinafter referred to as “first lamp pins”) which are electrically connected to theLED module 1. These two first lamp pins 84 and 84 are configured to be electrically connected to two power supply contacts respectively of a lamp socket for a power supply which is held in the device main body of a lighting device (not shown). - The
second cap 83 has one grounding terminal 85 (hereinafter referred to as “second lamp pin”) for grounding. This onesecond lamp pin 85 is configured to be electrically connected to a grounding contact of a lamp socket for grounding which is held in the device main body. - Each of the first lamp pins 84 is formed in an L-shape. and is constituted by a pin
main body 84 a which protrudes along the longitudinal direction of the tubemain body 81 and akey portion 84 b which extends along the radial direction of the tubemain body 81 from the tip of the pinmain body 84 a. The twokey portions 84 b extend in directions so as to be farther from each other. Note that each of the first lamp pins 84 is formed by bending a long metal plate. - The
second lamp pin 85 protrudes from an end face (cap reference face) of thesecond cap 83 in the opposite direction to the tubemain body 81. Thesecond lamp pin 85 is formed in a T-shape. Note that the straight-tube LED lamp 80 is preferably configured so as to meet the standard of “straight-tube LED lamp system with L-type pin cap GX16t-5 (for general illumination)” (JEL 801:2010) which is standardized by Japan Electric Lamp Manufacturers Association, or the like. - The straight-
tube LED lamp 80 as described above includes theaforementioned LED module 1 in the tubemain body 81, and therefore cost thereof can be reduced and light output thereof can be increased. - A lamp which includes the
LED module 1 is not limited to the aforementioned straight-tube LED lamp, and may be a straight-tube LED lamp including theLED module 1 and a lighting unit to switch on theLED module 1 both in the tube main body. Note that power is supplied to the lighting unit from an external power supply via lamp pins. - The
LED module 1 ofEmbodiment 3 includes theopaque substrate 2 having an elongated shape and a plurality of theLED chips 6, but the shape of theopaque substrate 2 and the number ofLED chips 6 and arrangement of theLED chips 6 can be changed as appropriate depending on the type or the like of the lighting device to which theLED module 1 is applied. - Hereinafter, an embodiment of another
lighting device 70 including theLED module 1 will be described with reference toFIGS. 41 and 42 . - The
lighting device 70 is an LED lighting device which can be used as a downlight, and includes a devicemain body 71 and a light source that is theLED module 1 and is held by the devicemain body 71. Besides, thelighting device 70 includes acase 78 which has a rectangular box shape and accommodates a lighting unit to operate theLED module 1. The lighting unit and theLED module 1 are electrically connected by wires (unshown) or the like. - In the
lighting device 70, the devicemain body 71 is formed in a disk shape, and theLED module 1 is present on a face of the devicemain body 71. Thelighting device 70 includes a plurality offins 71 ab which protrude from a further face of the devicemain body 71. The devicemain body 71 and thefins 71 ab are formed integrally. - In the
LED module 1, anopaque substrate 2 has a rectangular shape, a plurality of (not shown) LED chips are arranged in a two-dimensional array on asurface 2 sa of theopaque substrate 2, and acolor conversion portion 10 covers all these plurality of LED chips. Note that. this LED chip may be the same as theLED chip 6 inEmbodiment 3. - Moreover, the
lighting device 70 includes afirst reflector 73 to reflect light which is emitted laterally from theLED module 1, acover 72, and asecond reflector 74 to control a directional distribution of light which is outputted from thecover 72. Note that, in thelighting device 70, an outer cover to house theLED module 1, thefirst reflector 73 and thecover 72 is constituted by the devicemain body 71 and thesecond reflector 74. - The device
main body 71 has two projectingbase portions 71 a, which face each other on the face thereof. In thelighting device 70, a plate shaped fixingmember 75 to fix theLED module 1 is attached to the two projectingbase portions 71 a. The fixingmember 75 is formed of a metal plate, and is fixed to each of the projectingbase portions 71 a by ascrew 77. Thefirst reflector 73 is fixed to the devicemain body 71. TheLED module 1 may be sandwiched between thefirst reflector 73 and the fixingmember 75. Thefirst reflector 73 is formed of a white synthetic resin. - The fixing
member 75 has anopening 75 a for exposing part of theopaque substrate 2 of theLED module 1. Thelighting device 70 includes athermal conduction portion 76 interposed between theopaque substrate 2 and the devicemain body 71. Thethermal conduction portion 76 has a function of conducting heat from theopaque substrate 2 to the devicemain body 71. Thethermal conduction portion 76 is formed of a heat-conductive grease, but is not limited thereto, and may be formed of a heat-conductive sheet. - The heat-conductive sheet may be a silicone gel sheet having electrical insulation and thermal conductivity. The silicone gel sheet used as the heat-conductive sheet is preferably soft. This king of silicone gel sheet may be Sarcon(registered trademark) or the like.
- The material of the heat-conductive sheet is not limited to silicone gel, and may be elastomer, for example, so long as the material has electrical insulation and thermal conductivity.
- In the
lighting device 70, heat generated in theLED module 1 can be efficiently conducted to the devicemain body 71 via thethermal conduction portion 76. Consequently, in thelighting device 70, heat generated in theLED module 1 can be efficiently released from the devicemain body 71 and thefins 71 ab. - The device
main body 71 and thefins 71 ab are preferably formed of a material having high thermal conductivity, and more preferably made of a material having higher thermal conductivity than theopaque substrate 2. Here, the devicemain body 71 and thefins 71 ab are preferably formed of a metal having high thermal conductivity such as aluminum and copper. - The
cover 72 may be made of an acrylic resin, a polycarbonate resin, a silicone resin, glass, or the like. - The
cover 72 may has a lens portion (not shown) for controlling a directional distribution of light emitted from theLED module 1. Thecover 72 and the lens portion may be formed integrally. - The
second reflector 74 may be made of aluminum, stainless steel, a resin, ceramic, or the like. - The
lighting device 70 described above includes a light source that is theaforementioned LED module 1, and therefore cost can be reduced and light output can be increased. Besides, thelighting device 70 may have a configuration in which the devicemain body 71 also serves as theopaque substrate 2 of theLED module 1.
Claims (15)
1-14. (canceled)
15. An LED module comprising:
an opaque substrate on which a wiring circuit is provided;
a submount bonded to a surface of the opaque substrate with a first bond;
an LED chip bonded with a second bond to an opposite side of the submount from the opaque substrate; and
wires electrically connecting the LED chip to the wiring circuit,
the first bond and the second bond each allowing light emitted from the LED chip to pass therethrough,
the submount being a light-transmissive member,
the LED chip including:
a LED structure portion including a n-type semiconductor layer, a light-emitting layer, a p-type semiconductor layer; and
a substrate being transparent to light emitted from the light-emitting layer,
the LED structure portion provided on a main surface of the substrate,
the substrate being situated closer to the light-transmissive member than the LED structure portion,
the light-transmissive member having a planar size greater than a planar size of the LED chip, and
the transparent member allowing parts of the light emitted from the light-emitting layer of the LED chip towards the transparent member to be diffused in the light-transmissive member and emerge from the light-transmissive member through the face and/or side faces.
16. The LED module according to claim 15 , wherein:
the submount has light diffusing properties.
17. The LED module according to claim 15 , wherein
the submount has a planar size larger than a planar size of the LED chip.
18. The LED module according to claim 15 , wherein
the surface of the opaque substrate has light diffusing properties.
19. The LED module according to claim 15 , wherein
the surface of the opaque substrate has specular reflective properties.
20. The LED module according to claim 15 , wherein
the opaque substrate functions as a heat sink.
21. The LED module according to claim 15 , wherein
at least one of the first bond and the second bond contains a first fluorescent material which is excited by the light emitted from the LED chip to emit light having a different color from the light emitted from the chip.
22. The LED module according to claim 21 , further comprising:
a color conversion portion made of a transparent material containing a second fluorescent material which is excited by the light emitted from the LED chip to emit light having a different color from the light emitted from the LED chip,
the color conversion portion covering sides of the LED chip and an opposite surface of the LED chip from the second bond.
23. The LED module according to claim 22 , wherein
the color conversion portion contains a light diffusion material.
24. The LED module according to claim 21 , further comprising a resin portion which is situated over the face of the submount and serves as an outer cover through which light passes last,
the resin portion being made of a transparent resin which contains a light diffusion material.
25. The LED module according to claim 15 , wherein
the submount is constituted by a plurality of light-transmissive layers which are stacked in a thickness direction of the submount and have different optical properties so that a light-transmissive layer of the plurality of light-transmissive layers which is farther from the LED chip is higher in reflectance in a wavelength range of the light emitted from the LED chip.
26. The LED module according to claim 25 , wherein
each of the plurality of light-transmissive layers is a ceramic layer.
27. A lighting device comprising:
a device main body; and
the LED module according to claim 15 which is held on the device main body.
28. A lamp comprising:
a tube main body; and
a light source that is the LED module according to claim 15 .
Applications Claiming Priority (7)
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JP2012242686 | 2012-11-02 | ||
JP2012-242686 | 2012-11-02 | ||
PCT/JP2013/003301 WO2013179624A1 (en) | 2012-05-31 | 2013-05-24 | Led module, lighting device, and lamp |
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US14/387,703 Expired - Fee Related US9685594B2 (en) | 2012-05-31 | 2013-05-24 | LED module and method of preparing the LED module, lighting device |
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US14/387,703 Expired - Fee Related US9685594B2 (en) | 2012-05-31 | 2013-05-24 | LED module and method of preparing the LED module, lighting device |
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EP (2) | EP2819185B1 (en) |
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WO (2) | WO2013179625A1 (en) |
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Also Published As
Publication number | Publication date |
---|---|
EP2822045A1 (en) | 2015-01-07 |
CN104205371B (en) | 2017-03-01 |
EP2819185A4 (en) | 2015-03-18 |
EP2819185B1 (en) | 2018-01-03 |
WO2013179625A1 (en) | 2013-12-05 |
JP5861115B2 (en) | 2016-02-16 |
US9685594B2 (en) | 2017-06-20 |
EP2819185A1 (en) | 2014-12-31 |
CN104205372B (en) | 2018-03-02 |
EP2822045B1 (en) | 2018-04-11 |
EP2822045A4 (en) | 2015-03-18 |
US20150137149A1 (en) | 2015-05-21 |
CN104205371A (en) | 2014-12-10 |
JPWO2013179625A1 (en) | 2016-01-18 |
CN104205372A (en) | 2014-12-10 |
JPWO2013179624A1 (en) | 2016-01-18 |
WO2013179624A1 (en) | 2013-12-05 |
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