WO2007071724A1

WO2007071724A1 - Led illumination means

Info

Publication number: WO2007071724A1
Application number: PCT/EP2006/070002
Authority: WO
Inventors: Hugues Lefevre
Original assignee: Agc Flat Glass Europe Sa
Priority date: 2005-12-20
Filing date: 2006-12-20
Publication date: 2007-06-28
Also published as: EA012477B1; EA200801569A1; EP1965976A1

Abstract

The present invention relates to illumination means in which the light output generator elements are light-emitting diodes. The diode illumination means according to the invention includes a laminated assembly consisting of at least one organic or inorganic glass sheet combined with at least one thermoplastic sheet incorporating the diodes. The individual power features of each diode, the operating conditions thereof and the diode distribution over the surface of the sheets are such that the generated light output is of at least 300 lm.

Description

Light emitting diode

The present invention relates to lighting using light emitting diodes (LEDs).

The use of diodes as light sources is still limited because of the particularities of implementation of these elements. Individually LEDs provide only a relatively low luminous flux. In general, the very limited spectrum of LEDs is also a factor that does not allow a satisfactory color rendering especially compared to that of incandescent lamps.

However, we know how to produce LEDs, or associations of LEDs, which can find a light whose spectrum is wide enough to provide a lighting giving a good color rendition.

In all cases lighting with LED requires to gather a large number of units to achieve light powers that correspond to those obtained by means of incandescent or discharge lamps, said fluorescence.

Despite the constraints mentioned above, the use of LEDs for lighting has a number of interesting features. Among these, the lifetime of LEDs is particularly remarkable compared to that of incandescent lamps. Another feature is the fact that LEDs dissipate little heat which allows them to be used in conditions that make incandescent lamps inconvenient. A Another very popular characteristic is the luminous efficiency, that is the quantity of light produced by energy consumed. However, the use of diodes as a light source still offers many other advantages in terms of convenience of implementation, in particular because of their very small dimensions, which allows their implantation in locations that prohibit or make it difficult to install light bulbs. incandescence or discharge.

Incandescent lamps, because of the energy dissipated in heat, have a relatively low luminous efficiency which is between 12 and 20 lm / W. Fluorescence lamps have a much higher efficiency which is between 50 and 80 lm / W. The corresponding characteristic of the LEDs is in permanent progress. It is located with current LEDs between 15 and 60 lm / W and should reach and quickly exceed the level of fluorescent lamps. The estimate of the order of 80 to 100 lm / W at 5 years is presented as the most likely.

These luminous efficiency values are those corresponding to the diode itself with the protective envelope. The quality of the latter is an element that can alter the efficiency due to insufficient light transmission. In the recent past the envelopes used led to a rapid decrease in efficiency due to opacification that could reduce light transmission by 30% or more after only a few hundred hours of operation. Envelopes including ceramics developed recently can prevent this loss of efficiency.

To achieve lighting of sufficient power for uses traditionally conducted by means of incandescent or fluorescent lamps, given the low power of each diode, it is necessary to associate them in number in a same together. Among the means gathering these diodes, the most satisfactory consist of panels comprising at least one sheet of transparent material. In these panels the diodes are arranged in an arrangement that takes into account both technical and aesthetic features.

In all cases the diodes are normally disposed behind the sheet of transparent material which protects them by avoiding exposing them to mechanical hazards related to traditional modes of use. The lighting means are in particular subject to regular cleaning. In the absence of this protective sheet the diodes themselves or their fasteners and connections could be damaged.

In order to constitute conveniently usable lighting assemblies, it has been proposed in particular to arrange the diodes in a laminated assembly of the type consisting of at least two sheets of transparent materials, including a sheet of mineral or organic glass, and a thermoplastic sheet. in which the diodes are incorporated. These sets also include a diode supply circuit most often in the form of one or more conductive layers disposed on the faces of the sheets constituting the laminated assembly. In this type of laminated assembly, the most usual consists of an assembly comprising two rigid sheets associated with one or more thermoplastic sheets.

In practice, when the lighting is directed on one side of the laminated assembly, which is the case in particular of lighting placed on a ceiling or a wall of a room, the supply circuit is preferably located. behind the diodes in relation to the face from which the light emanates. In this case the circuit can be opaque. Where appropriate the use of substantially transparent conductive layers makes it possible to arrange the diodes behind these conductive layers.

The realization of lighting means must still satisfy various conditions. The luminous flux must be sufficiently concentrated and powerful in particular to limit the dimensions of these means. On the other hand, the nature of the constituents of the laminates and the incorporation of the diodes in materials of a thermoplastic nature must take into account the dissipation of the heat generated by the diodes. This condition is all the more delicate as the dimensions of the diodes being very reduced the heat that their operation produces, is punctually very concentrated. In addition, since the diodes are incorporated in a weakly conductive medium, that of a thermoplastic sheet, the evacuation of heat is made more difficult.

The optical characteristics of the materials used in these laminates also partly determine the transmission efficiency of the light flux generated by the diodes. It is necessary to adapt accordingly the mode of incorporation of the diodes in these lighting means.

The invention proposes lighting means which take into account these different requirements and others which will appear later in this description.

The lighting means according to the invention comprises a laminated assembly formed of at least one sheet of an organic or inorganic glass associated with at least one thermoplastic sheet in which the diodes are incorporated. For this lighting means, the choice of the light-emitting diodes, in particular their power, their operating conditions, and moreover their distribution in the laminated assembly, are such that the luminous flux generated is from less300 Im, preferably at least 500 Im, and most preferably is greater than 1000 Im.

In order to obtain these luminous fluxes, the lighting means according to the invention gather on a surface of restricted dimensions a large number of diodes. The conditions for obtaining can also be directly related to the power of these lighting means. Thus the luminous flux reported on the surface of these means is at least 500 Im per square meter of surface of this lighting means. This power is chosen on the one hand to provide illumination means of dimensions compatible with the most common uses and on the other hand to take into account what can be achieved by means of the characteristics of the commercially available diodes.

This choice is also the result of a compromise between very dense diode distributions such that the generated luminous flux is as high as possible, and the need to maintain the assembly under temperature conditions compatible with the behavior of the constituent materials of FIG. on the one hand and the best light efficiency of the diodes on the other hand. In particular, as a function of the quality of the diodes used and the materials constituting the laminated assemblies, the power can amount to at least 1000 lm / m ² , and preferably to 2500 lm / m ² and more.

For laminated assemblies the temperature rise is a factor that limits the point power of each diode. The resorption of the heat generated by the operation of the diodes is relatively modest in the materials traditionally used in the manufacture of these sets. These include glass sheets which are known to be poor conductors of heat, it is it is also the polymeric materials constituting the interlayer sheets in which the diodes are housed.

In the assemblies according to the invention, use is advantageously made of the usual interlayer materials, such as polyacetals, in particular polyvinyl butyrals (PVB), ethylene vinyl acetate (EVA) or any analogous material used in particular in conventional manner in laminated glazings. . With these thermoplastic materials, the temperature near the diodes should preferably not exceed 80 ^° C. It is advantageously less than 60 ^° C.

It is all the more necessary to keep the temperature as low as possible as the luminous efficiency of each diode decreases when the temperature rises. In other words, the higher the temperature, the higher the amount of energy consumed in the form of heat. This difference is extremely sensitive, so the luminous efficiency of the diodes can be reduced by more than 30% when the temperature of the diode goes from 50 ⁰ C to 80 ⁰ C.

Given the various characteristics of diodes currently commercially available, including the luminous efficiency, but also the dimensions of these diodes which partially condition the heat exchange with the surrounding environment, namely the polymer sheet in which the diodes are housed it is advantageous to limit the operating power of each diode. In practice, it is preferable to ensure that the power dissipated by each diode does not exceed 2 W, and preferably not 1.5 W. Most often the operating power of each diode is maintained at less than 1 W and preferably at less than 0.5 W.

The nominal power of the diodes used may be substantially greater than that of their use. It is possible for example to use diodes at half or less of their power nominal. By operating the diodes at a reduced power, their "wear" is slowed down but, above all, their heating is limited. For this reason one can be led to use diodes of 5 W or more. The choice of high nominal powers determines the cost and the volume of the diodes. It is therefore necessary to choose the best compromise between the nominal power and that of operation. As a rule, the operating power will not be less than a quarter and preferably one third of the nominal power. This operating power is also preferably at most 4/5 of the nominal power and preferably at most ³ A of this power.

The heating of the lighting means according to the invention arises not only from the diodes but also from the supply circuit thereof. When the lighting means in the form of panels offer only a transparent face to the light emitted by all the diodes it is possible to design power circuits in which the joule dissipation is very modest. Metal conductive circuits can indeed offer a very low resistance. When, on the other hand, the power supply is interposed in the path of the light emitted, and this power supply circuit must remain practically invisible, this is the case of transparent luminous panels, the supply is obtained traditionally either by means of very thin metal son taken in the laminate, or even using conductive layers of very small thicknesses to not obstruct the light transmission. These layers, which are well known in the field of laminated glazings, in particular heated glazings, have significant resistances, and all the more so because their thickness is smaller. Furthermore, the Joule effect is all the more marked locally because the contact of the conductive layer with the conductors feeding each diode is less extensive, and that Accordingly, near these conductors the electric current concentrates on a restricted surface of the layer resulting in a relative increase in resistance.

To minimize the joule effect it is advantageous to supply the diodes under the highest possible voltage compatible with a convenient use. In domestic applications in particular, it will not exceed a voltage of more than 30Ov. The operating voltage of each LED generally does not exceed 50 volts, and most often is less than 25 volts. The arrangement of the LEDs in series makes it possible to increase the supply voltages very sensitively. The number of LEDs placed in series also determines the reliability of the entire series. If a diode is faulty the whole series is affected. To limit this risk of alteration of the lighting means, one solution is for example to double each diode in parallel.

In all cases, the nature and the configuration of the circuit as well as the supply voltage are chosen so that the Joule effect energy dissipation due to the supply circuit is as low as possible and advantageously is not greater than 50% of the total energy, and preferably not more than 30%.

In the case of the invention, when thin layers constitute the power supply network of the diodes, these layers advantageously offer the lowest resistance compatible with the highest possible light transmission. Under the usual optically acceptable conditions, the light transmission of the layers is advantageously more than 90%.

For applied voltages suitable for diode-powered assemblies, the thin layers used preferably a resistance that is not greater than 30 Ω / [], and preferably not greater than 20 Ω / Q.

When the means can offer only one transparent face, the other side is advantageously made of a good heat conducting material to facilitate the evacuation thereof.

The face in question is advantageously formed of a metal sheet, and in this case is an element of the laminated assembly. In this case it goes without saying that in order to minimize the energy losses of the supply circuit, the latter is constituted so as to reduce the resistance as much as possible. As the transparency is no longer imposed on the face comprising the metal foil, the feed is advantageously made by means of conducting wires.

If the heat formed due to the materials entering the structure of the lighting means according to the invention can not be eliminated in a particularly convenient manner, efforts are made to minimize this heat and for this purpose the diodes with the best light efficiency are used. In practice, given the availabilities, it is advantageous to use diodes whose luminous efficiency is not less than 20 μm / W and preferably greater than 30 μm / W. In the measure of their commercial availability, diodes whose efficiency is equal to or greater than 40 lm / W are preferred.

When optimizing the luminous efficiency generated by the diodes, it must also be endeavored to ensure that the structure of the lighting means, and therefore that of the laminated implemented best transmits the luminous flux created. In particular, it is necessary to ensure that the luminous flux is practically available in its entirety for lighting. Part of this flow due to the reflections that can develop inside the laminate, can be trapped in this laminate. To prevent this part of the flow from being significant endeavors to limit the angle of emission with respect to the normal at the interface between the organic or inorganic glass sheet and the surrounding atmosphere.

Conventionally, diodes are offered with a reflective element in the form of a cup whose concave face is turned towards the diode. This construction not only makes it possible to reflect the flux towards one side only of the lighting means, but also the flux is reduced to a beam whose opening can thus be limited. This opening is advantageously such that the incidence of the luminous flux at the interface of the glass sheet with the outside is not greater than 60 degrees of angle, preferably this incidence is kept below 45 degrees of angle and even better at less than

30 degrees.

The invention is described below in detail with reference to drawing plates in which:

FIGS. 1a and 1b show in a cavalier perspective a laminated lighting assembly by means of diodes according to the invention;

FIG. 2a illustrates in perspective the path of the light flux coming from a diode in a laminate of the type presented in FIG. 1;

Figure 2b shows in section and in an enlarged manner the flow of the luminous flux presented in 2a;

Figure 3 is a graph illustrating a typical distribution of light intensity as a function of the direction of light flux with respect to the transmission axis. Figure la la presents partially "exploded" the constituent elements of lighting means according to the invention. This form comprises a transparent sheet 1 which is for example a glass sheet which can be transparent or translucent if it is desired a diffuse light effect. A sheet of thermoplastic material 2 transparent as the glass sheet itself is disposed between the sheet 1 and a series of diodes 3 which will be incorporated during assembly in the thermoplastic sheet 2.

In the form shown, the diodes 3 are uniformly distributed over a supply circuit constituted for example by a thin conductive layer deposited on a second rigid sheet 5.

In an alternative form, the diodes and the conductive layer or the conductive wires feeding the diodes are disposed on a flexible sheet which replaces the sheet 5. The flexible sheet carrying the supply circuit is for example a PET sheet.

The layer supplying the diodes is divided for example by ablation along lines 4 separating conductive strips. The diodes are connected to two contiguous strips each connected to a terminal of the power supply.

In the form shown the diodes are in parallel in rows of 6, and in series by 9. The diodes are relatively little distant from each other so as to develop a relatively large luminance intensity despite what each offers only a relatively low power typically of the order of 0.5 W or a little more. In the example presented, 54 diodes are collected under dimensions of dimensions, for example 20 × 30 cm.

Still for the example envisaged, the assembly of the constituent elements is represented in Ib. The laminated considered brings together the two sheets 1 and 5 through the intermediate sheet 2. The diodes are introduced into the interlayer sheet during a typical operation of forming laminated glazing. For this, the sheets are subjected to pressure, after having been brought to a softening temperature of the interlayer thermoplastic sheet 2.

In the assembly made, the connectors supplying the conductive strips are not shown. These connectors may be applied at the time of assembly or after it to the two conductive strips at the ends.

In an embodiment obtained by combining two sheets of glass 3mm thick, a 0.76mm PVB interlayer sheet and a set of 54 LEDs sold under the trade name of Nishia Riguel white light, a luminous flux of 500 Im order equivalent to the flux of a 40 W incandescent lamp. The flux per unit area is thus about 8000 lm / m ² .

A set of the same nature formed of a panel of 50x50 cm, gathering 225 LEDs distributed in a regular way, develops a luminous flux of the order of 2000 Im corresponding to the flux of an incandescent lamp of more than 150 W.

Of course, the dimensions and the number of LEDs can be increased according to the desired flux, provided that the density conditions of the LEDs remain compatible with a local temperature rise meeting the indicated conditions.

The conductive circuit consists of a thin layer of tin oxide doped with antimony, deposited on the sheet 5. Its resistance is of the order of 15 Ω / Q. In this configuration, the highest temperature near the diode is of the order of 50 ⁰ C.

The question of the effectiveness of the lighting means according to the invention as a function of its optical configuration is illustrated in the following figures. In these figures, light is assumed directed entirely through the sheet 1. This is the case, for example, of a luminaire disposed on an opaque wall. In this case the diodes are advantageously chosen with a reflector turned towards the sheet 1.

The radiation from the diode 3 incorporated in the interlayer sheet 2 passes through it and the transparent sheet 1.

According to the incidence of radiation with respect to the normal to the face of the sheet 1 facing outwards and the index of refraction of the sheet 1, the rays are diffracted or reflected.

Figure 2b illustrates this feature for the case for example of a glass sheet 1 in contact with the surrounding air.

The index of the glass of the order of 1.5, makes the diode rays that are inclined (alfa) more than about 60 degrees of angle from the normal at the glass / air interface are reflected inwards and by successive reflections do not participate in the luminous flux useful for lighting.

The distribution of the luminous flux as a function of the direction relative to the normal to the glass sheet follows a curve of the type shown in FIG.

Claims

1. Light-emitting diode illumination means comprising a laminated assembly formed of at least one sheet of an organic or inorganic glass associated with at least one thermoplastic sheet in which the diodes are incorporated, the individual power characteristics of each diode, their operating conditions, and the distribution of the diodes on the surface of the sheets being such that the luminous flux generated is at least 300 μm.

2. Lighting means according to claim 1 wherein the light flux generated is at least 500 μm.

3. Light-emitting diode illumination means comprising a laminated assembly of a sheet of an organic or inorganic glass associated with at least one thermoplastic sheet in which the diodes are incorporated, the individual power characteristics of each diode, their operating conditions. operation, and the distribution of the diodes on the surface of the sheets being such that its power is at least 500 Im per square meter of surface of this lighting means.

4. Lighting means according to claim 3 whose power is at least 1000 Im per square meter of surface of this lighting means.

5. Lighting means according to claim 3 whose power is at least 2500 Im per square meter of surface of this lighting means.

6. Lighting means according to one of the preceding claims wherein the individual power characteristics of each diode, the distribution of the diodes and the general configuration of the laminate are such that punctual continuous operation does not generate for each diode a temperature local exceeding 80 ⁰ C.

7. Lighting means according to claim 6 wherein the individual power characteristics of each diode, the distribution of the diodes and the general configuration of the laminate are such that punctually the operation does not generate for each diode a local temperature exceeding 60 ^° C. vs.

8. Lighting means according to one of the preceding claims wherein the diodes are not used at an individual power greater than 2W.

9. Lighting means according to claim 8 wherein the diodes are not used at an individual power greater than 1.5 W.

10. Lighting means according to claim 8 wherein the diodes are not used at an individual power greater than 0.5 W.

11. Lighting means according to one of the preceding claims comprising a laminated assembly with two sheets of organic or mineral glass on either side of a (or) sheet (s) interlayer (s) thermoplastic (s) in which the diodes are incorporated, the power supply of the diodes being made via an electrical circuit consisting of a substantially transparent conductive thin layer, the resistance of which is such that the joule effect energy dissipation in the layer is less than 50% of the energy consumed.

12. Lighting means according to one of the preceding claims comprising a laminated assembly with two sheets of organic or mineral glass on either side of a (or) sheet (s) interlayer (s) thermoplastic (s) in which the diodes are incorporated, the power supply of the diodes being made via an electrical circuit consisting of a substantially transparent conductive thin layer, whose resistance is at most 30 Ω / D.

13. Lighting means according to claim 12 wherein the power supply of the diodes is performed via an electrical circuit consisting of a substantially transparent conductive thin layer, whose resistance is at most 20 Ω / D. .

14. Lighting means according to one of claims 11 to 13 wherein the power supply of the diodes is performed via an electrical circuit consisting of a substantially transparent conductive thin layer whose light transmission is not less than 90%.

15. Lighting means according to one of the preceding claims wherein the light beam emitted by the diodes is directed so that its incidence with the normal at the interface of the glass sheet with the atmosphere is not greater than 60 degrees of angle.

16. Lighting means according to claim 15 wherein the light beam emitted by the diodes is directed in such a way. that its incidence with the normal at the interface of the glass sheet with the atmosphere is not greater than 45 degrees of angle.

17. Lighting means according to one of the preceding claims wherein the laminated assembly comprises in addition to the glass sheet and the interlayer sheet in which the diodes are incorporated, a high thermal conduction sheet including a metal foil.

18. Lighting means according to one of the preceding claims wherein the diodes used have a luminous efficiency of not less than 20 lm / W.

19. Lighting means according to claim 17 wherein the diodes used have a luminous efficiency of not less than 30 lm / W.