WO2011030620A1

WO2011030620A1 - Organic el device optical member and organic el device

Info

Publication number: WO2011030620A1
Application number: PCT/JP2010/062133
Authority: WO
Inventors: Jun Kodama
Original assignee: Fujifilm Corporation
Priority date: 2009-09-09
Filing date: 2010-07-13
Publication date: 2011-03-17
Also published as: JP2011060549A

Abstract

An organic EL device optical member used in an organic EL device containing a light-emitting layer, the organic EL device optical member including a reflective layer which reflects light emitted from the light-emitting layer, a light-extraction layer which extracts the light emitted from the light-emitting layer, and an optical path length adjusting layer disposed between the reflective layer and the light-extraction layer

Description

DESCRIPTION

Title of Invention

ORGANIC EL DEVICE OPTICAL MEMBER AND ORGANIC EL DEVICE Technical Field

The present invention relates to an optical member for use in an organic EL device (organic EL device optical member) and an organic EL device.

Background Art

Organic electroluminescence (EL) devices have high-speed response, wide viewing angle, high resolution, wide color reproducibihty, high energy conversion efficiency and high contrast ratio, as compared with conventional thin display devices such as liquid crystal displays. In addition, the EL devices can be enlarged easier than such conventional thin display devices. Thus, extensive studies and development have been conducted on them, and some can be seen on the market.

Such organic EL devices generally have a multi-layered structure composed of a light-emitting layer made of an organic light-emitting material or the like, a pair of electrodes disposed so as to sandwich the light-emitting layer, and optional other layers such as a reflective layer (which adjusts light emitted from the light-emitting layer so as to emit in one direction) and a seal layer (which prevents degradation of the light-emitting material due to oxygen). When light emitted from the light-emitting layer is allowed to emit from the light-emitted surface through the above multi-layered structure, nonnegligeble light reflection occurs between the layers due to the difference in their refractive indices. Thus, in order for the light (emitted from the light-emitting layer) to efficiently emit through these several layers from the light-emitted surface, the direction in which the light from the light-emitting material travels must be effectively controlled, considering the reflectances at the refraction interfaces between the layers so as to prevent light reflection from occurring at the refraction interfaces. Some patent literatures disclose techniques of controlling the direction in which the light emitted from the light-emitting material travels, by providing a layer having the function of extracting light (scattering light) such as a layer having a diffraction grating, a layer containing fine particles, a layer composed of a high-refractive index layer and a low-refractive-index layer (see PTLs 1 and 2).

PTL 1 discloses a display device composed of a rear electrode, a front electrode, an active layer disposed therebetween including a Ught-emitting layer, a reflective layer (which reflects light emitted from the light-emitting layer) and a light-extraction layer (which is disposed so as to come into contact with the reflective layer). Here, the light-extraction layer extracts light propagating in a direction parallel to the main place of the active layer. PTL 2 discloses an organic Ught-emitting diode display device composed of an organic material layer made of a Ught-emitting material, a reflective electrode having reflectivity (which is disposed so as to come into contact with the organic material layer) and a light-extraction film of a high-refractive -index layer and a low-refractive index.

Although these devices hve a layer having the function of extracting light (scattering light) in order for the Ught emitted from the light-emitting material to efficiently emit from the Ught-emitted surface, their light-extraction efficiency is not stiU satisfactorily high. Praticulalry in organic EL devices having a light resonance structure (microcavity (MC) structure), by which the light emitted from the light-emitting element is repeatedly reflected between the Ught-emitting element and the reflective layer to cause multiplex interference, color purity is improved, but light-extraction efficiency must be further improved.

Also, the MC structure poses problems in image reproducibility depending on the viewing angle. For example, the brightness decreases or the color purity changes depending on the viewing angle, which are peculiar phenomena caused by multiplex interference in the MC structure.

Citation List

Patent Literature

PTL l: Japanese Patent Application Laid Open (JP-A) No. 2008-515129

PTL 2: U.S. Patent Application Publication No. 2009/0015142

Summary of Invention

Technical Problem

The present invention solves the above existing problems pertinent in the art. Specifically, an object of the present invention is to provide an organic EL device optical member capable of further improving light-extraction efficiency and reducing the viewing angle dependency peculiar to multiplex interference, and an organic EL device using the same.

Another object of the present invention is to provide an organic EL device optical member capable of being optimally designed in structure in individual pixels, and an organic EL device using the same.

Solution to Problem

The present inventors conducted extensive studies to solve the above objects, and have found that the objects can be achieved by providing an optical path length adjusting layer between a reflective layer and a bight-extraction layer.

The present invention has been completed on the basis of this finding.

The present invention is based on the finding obtained by the present inventors. Means for solving the above problems are as follows.

< 1 > An organic EL device optical member used in an organic EL device containing a light-emitting layer, the organic EL device optical member including- a reflective layer which reflects light emitted from the light-emitting layer, a light-extraction layer which extracts the light emitted from the light-emitting layer, and

an optical path length adjusting layer disposed between the reflective layer and the light-extraction layer.

The organic EL device optical member has the optical path length adjusting layer between the reflective layer and the light-extraction layer, and thus, achieves higher light-emission efficiency.

< 2 > The organic EL device optical member according to < 1 > above, wherein the thickness of the optical path length adjusting layer is varied in individual pixels.

< 3 > The organic EL device optical member according to one of < 1 > and < 2 > above, further including an electrode located in a light-emitting direction from the light-extraction layer.

< 4 > The organic EL device optical member according to any one of < 1 > to < 3 > above, further including a substrate such that the reflective layer is located between the substrate and the light- extraction layer.

< 5 > An organic EL device including:

the organic EL device optical member according to any one of < 1 > to < 4 > above.

< 6 > The organic EL device according to < 5 > above, further including a first substrate, a pair of electrodes, and a light-emitting layer disposed between the electrodes,

wherein the hght-emitting layer is located in the light-emitting direction of the organic EL device from the light-extraction layer.

< 7 > The organic EL device according to one of < 5 > and < 6 > above, wherein the thickness of the optical path length adjusting layer is varied in individual pixels.

< 8 > The organic EL device according to any one of < 5 > to < 7 > above, further including a second substrate such that the reflective layer is located between the second substrate and the light-extraction layer.

< 9 > The organic EL device according to < 8 > above, wherein the second substrate is a barrier film substrate.

< 10 > The organic EL device according to any one of < 5 > to < 9 > above, further including a low-refractive-index layer located in the light-emitting direction from the light-emitting layer.

< 11 > The organic EL device according to any one of < 5 > to < 10 > above, wherein the organic EL device is of top-emission type.

< 12 > The organic EL device according to any one of < 5 > to < 10 > above, wherein the organic EL device is of bottom-emission type.

< 13 > The organic EL device optical member according to any one of < 1

> to < 4 > above, wherein the optical path length adjusting layer is disposed so as to be in contact with the reflective layer and the light-extraction layer.

< 14 > The organic EL device optical member according to any one of < 1

> to < 4 > and < 13 > above, further including a high-refractive -index smooth layer between the light-extraction layer and the electrode.

< 15 > The organic EL device optical member according to < 14 > above, wherein the high-refractive-index smooth layer is disposed so as to be in contact with the light-extraction layer and the electrode.

< 16 > The organic EL device according to any one of < 5 > to < 12 > above, wherein the optical path length adjusting layer is disposed so as to be in contact with the reflective layer and the light-extraction layer.

< 17 > The organic EL device according to any one of < 5 > to < 12 > and < 16 > above, further including a high-refractive -index smooth layer between the light-extraction layer and the electrode.

< 18 > The organic EL device according to < 17 > above, wherein the high-refractive-index smooth layer is disposed so as to be in contact with the light-extraction layer and the electrode.

< 19 > The organic EL device according to any one of < 10 > to < 12 > and < 16 > to < 18 > above, wherein the low-refractive -index layer is a hollow layer.

< 20 > The organic EL device according to any one of < 10 > to < 12 > and < 16 > to < 18 > above, wherein the lowrefractive-index layer is a layer filled with material.

Advantageous Effects of Invention

The present invention can provide an organic EL device optical member capable of further improving light-extraction efficiency and reducing the viewing angle dependency peculiar to multiplex interference, and an organic EL device using the same. These can solve the above-described problems pertinent in the art and achieve the above objects. Brief Description of Drawings

Fig. 1 is a schematic cross-sectional view of one exemplary organic EL device optical member of the present invention.

Fig. 2 is a schematic cross-sectional view of another exemplary organic EL device optical member of the present invention.

Fig. 3 is a schematic cross- sectional view of a top -emission type organic EL device which is one exemplary organic EL device of the present invention.

Fig. 4 is a schematic cross-sectional view of a bottom-emission type organic EL device which is another exemplary organic EL device of the present invention.

Description of Embodiments

Next, detail description will be given with respect to an organic EL device optical member of the present invention and an organic EL device having the organic EL device optical member.

(Organic EL device optical member)

An organic EL device optical member of the present invention is used in the belowdescribed organic EL device having a light-emitting layer. The organic EL device optical member includes a reflective layer (which reflects light emitted from the light-emitting layer), a light-extraction layer (which extracts light emitted from the light-emitting layer) and an optical path length adjusting layer disposed between the reflective layer and the light-extraction layer; and, if necessary, further includes other layers. Figs. 1 and 2 schematically illustrate cross-sections of the organic EL device optical members. Fig. 1 schematically illustrates an example of the organic EL device optical member of the present invention. Fig. 2 schematically illustrates another example of the organic EL device optical member of the present invention. Notably, in Figs. 1 and 2, the layers shown by dotted lines and dotted arrows are not contained in these organic EL device optical members, but these are described for easy understanding.

As illustrated in Fig. 1, the organic EL device optical member of the present invention may be used in a so-called top-emission type organic EL device. The organic EL device optical member includes a reflective layer 16 (which reflects light emitted from a light-emitting layer 102 described below), a

light-extraction layer 14 (which is provided in the light-emitting direction of the organic EL device from the reflective layer 16) and an optical path length adjusting layer 12 disposed between the reflective layer 16 and the

light-extraction layer 14. If necessary, the organic EL device optical member of the present invention may further include an electrode 22, a high-refractive -index smooth layer 24, a substrate 26 and a gas barrier layer 28 described below.

As illustrated in Fig. 2, the organic EL device optical member of the present invention may be used in a so-called bottom-emission type organic EL device. Similar to the organic EL device optical member of Fig. 1, the organic EL device optical member includes a reflective layer 16 (which reflects light emitted from a light-emitting layer 102 described below), a light-extraction layer 14 (which is provided in the light-emitting direction of the organic EL device from the reflective layer 16) and an optical path length adjusting layer 12 disposed between the reflective layer 16 and the light-extraction layer 14. If necessary, the organic EL device optical member of the present invention may further include a joining layer 25 and a barrier film substrate 106 described below.

In addition to the reflective layer, light-extraction layer and optical path length adjusting layer, the organic EL device optical member of the present invention may further include other layers for use, as required.

In the present invention, the "light-emitting direction" is a direction in which light emitted from the light-emitting layer is finally emitted through the intended light-emitting surface toward the outside of the organic EL device. In the case of the organic EL device optical member used in the top-emission type organic EL device illustrated in FIG. 1, the light-emitting direction is, as indicated by the arrow, a direction in which light travels from the light-emitting layer 102 so as to be distanced from the substrate 26 (i.e., the direction in parallel with the figure and toward the top). In the case of the organic EL device optical member used in the bottom-emission type organic EL device illustrated in FIG. 2, the light-emitting direction is, as indicated by the arrow, a direction in which light travels toward an unillustrated substrate from the light-emitting layer 102 (i.e., the direction in parallel with the figure and toward the bottom).

< Reflective layer >

In the present invention, the reflective layer is not particularly limited, so long as it reflects light emitted from the belowe described light-emitting layer, and may be appropriately selected depending on the purpose of the present invention. The shape, structure and size of the reflective layer may be

determined depending on the purpose of the present invention. The thickness of the reflective layer may be appropriately determined depending on the purpose of the present invention, and may be 10 nm to 1,000 nm.

The position at which the reflective layer is to be disposed may be appropriately determined depending on the structure of an organic EL device into which the organic EL device optical member is to be mounted. When the organic EL device optical member is used in a top -emission type organic EL device having a TFT substrate, the reflective layer may be disposed between the channel side of the substrate and the below-described light-emitting layer. When the organic EL device optical member is used in a bottom-emission type organic EL device having a TFT substrate, the reflective layer may be disposed between the gate side of the substrate and the below-described light-emitting layer.

The material for the reflective layer is not particularly limited, so long as it reflects light emitted from the light-emitting layer. For example, the material may be that having a reflectance of 70% or higher with respect to the light emitted from the light-emitting layer. Examples of the material for the reflective layer include metals (e.g., Al, Ag, Mg, Mo, Au and W) and alloys thereof (e.g., Ag-Mg and Al-Mo).

< Light-extraction layer >

In the present invention, the light-extraction layer is not particularly limited, so long as it positively changes the direction of light emitted from the below-described light-emitting layer, so that the light is extracted toward the outside of the organic EL device. The shape of the light-extraction layer may be appropriately determined depending on the purpose of the present invention.

For example, the light-extraction layer may be a light-extraction layer having fine concave and convex portions in a surface thereof, a light-extraction layer containing fine particles dispersed therein, and a light-extraction layer in which a structure (e.g., a prism or lens) is provided. The thickness of the light-extraction layer may be appropriately determined depending on the purpose of the present invention, and may be 10 nm to 5,000 nm.

The position at which the light-extraction layer is to be disposed may be appropriately determined depending on the structure of an organic EL device into which the organic EL device optical member is to be mounted, so long as the light-extraction layer is disposed between the reflective layer and the

light-emitting layer. For example, the light-extraction layer may be disposed between the below-described electrodes so as to sandwich desired layers (e.g., the below-described high-refractive -index smooth layer). Further, the

light-extraction layer may be disposed so as not to be in contact with the reflective layer, from the viewpoint of controlling the light -extraction efficency and image quality described below.

The particles contained in the light-extraction layer are not particlarly limited, so long as they positively changes the direction of light emitted from the below-described light-emitting layer, so that the light is extracted toward the outside of a panel. Examples thereof include high-refractive-index particles such as Zr0₂ and Ti0₂.

In the case of the light-extraction layer containing particles for achieving light-extraction effect, the amount of the particles contained in the

light-extraction layer is not particularly limited, so long as incident light to the light-extraction layer is scattered to a predetermined extent. The amount of the particles is preferably 1% by mass to 50% by mass, more preferably 5% by mass to

20% by mass, particularly preferably 6% by mass to 10% by mass, to the mass of the light-extraction layer. When the amount of the particles is less than 1% by mass, desired effects may not be obtained. Whereas when the amount of the particles exceeds 50% by mass, the light-extraction layer may not transmitt light.

When the amount of the particles falls within the above particularly preferable range, light is advantageously extracted.

Notably, in the present invention, the description "light emitted from the light-emitting layer is extracted with the light-extraction layer" means that the optical path of incident light to the light-extraction layer (hereinafter, this light and incident light to other layers are collectively referred to as "incident light") is changed so that the incident light finally emits from the light-emitted surface of the organic EL device. The optical path of the incident light is changed by, for example, appropriately scattering the incident light to the light-extraction layer, diffracting the incident light, and allowing the incident light to pass through several layers with different refractive indices to appropriately refract or scatter the incident light. In particular, a light-extraction structure is preferably provided at a position close to the light-emitting source, from the viewpoints of improving light-extraction efficiency and reducing image failures (e.g., bleeding). < Optical path length adjusting layer >

In the present invention, the optical path length adjusting layer is not particularly limited, so long as it can adjust the distance over which the incident light travels therein. Examples of the optical path length adjusting layer include those adjusting the optical path length from a reflective layer to a transparent or semi-transparent electrode to an integral multiple of λ/2, where λ denotes a wavelength of light emitted from the light-emitting layer. The shape, structure, size, etc. of the optical path length adjusting layer are not particularly limited, so long as the optical path length adjusting layer has the above-described function. The thickness of the optical path length adjusting layer may be 10 nm to 1,000 nm. The thickness thereof may be the same or different among pixels. In particular, the thickness of the optical path length adjusting layer is preferably different, since an optimal structure can be designed in each pixel.

The position at which the optical path length adjusting layer is to be disposed is not particularly limited, so long as it is disposed between the reflective layer and the light-extraction layer. For example, the optical path length adjusting layer is disposed so as to come into contact with the reflective layer and the light-extraction layer.

The material for the optical path length adjusting layer is not particulary limited, so long as it dose not considerably affect the wavelength and the light intensity of the incident light. Examples thereof include a variety of optically transparent inorganic or organic materials. Specific examples thereof include transparent resins such as polyacrylates, methyl polymethacrylates and polyimides.

< Electrode >

In the present invention, the electrode is not particulary limited, so long as it can apply an electrical field to the light-emitting layer. The electrode may be appropriately an anode or cathode, or transparent or semi-transparent in consideration of its position in the organic EL device optical member or organic EL device. For example, the electrode located in the Ught-emitting direction from the light-emitting layer of the organic EL device may be transparent.

« Anode »

In general, the anode may be any material, so long as it has the function of serving as an electrode that supplies holes to the organic compound layers constituting the light-emitting layer. The shape, structure, size, etc. thereof are not particularly limited and may be appropriately selected from known electrode materials depending on the application/purpose of the organic EL device. As described above, the anode is generally provided as a transparent anode.

Preferred examples of the materials for the anode include metals, alloys, metal oxides, conductive compounds and mixtures thereof. Specific examples include conductive metal oxides such as tin oxides doped with, for example, antimony and fluorine (ATO and FTO); tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO) and indium zinc oxide (IZO); metals such as gold, silver, chromium and nickel; mixtures or laminates of these metals and the conductive metal oxides; inorganic conductive materials such as copper iodide and copper sulfide; organic conductive materials such as polyaniline, polythiophene and polypyrrolei and laminates of these materials and ITO. Among them, conductive metal oxides are preferred. In particular, ITO is preferred from the viewpoints of productivity, high conductivity, transparency, etc.

The anode may be formed on the substrate by a method which is appropriately selected from wet methods such as printing methods and coating methods; physical methods such as vacuum deposition methods, sputtering methods and ion plating method; and chemical methods such as CVD and plasma CVD methods, in consideration of suitability for the material for the anode. For example, when ITO is used as a material for the anode, the anode may be formed in accordance with a DC or high-frequency sputtering method, a vacuum deposition method, or an ion plating method.

In the present invention, a position at which the anode is to be disposed is not particularly limited, so long as the anode is provided so as to come into contact with the light-emitting layer. The position may be appropriately determined depending on the application/purpose of the organic EL device. The anode may be entirely or partially formed on one surface of the light-emitting layer.

Patterning for forming the anode may be performed by a chemical etching method such as photolithography; a physical etching method such as etching by laser,^" a method of vacuum deposition or sputtering using a mask; a lift-off method; or a printing method.

The thickness of the anode may be appropriately selected depending on the material for the anode and is, therefore, not definitely determined. It is generally about 10 nm to about 50 μηι, preferably 50 nm to 20 μιη.

The resistance of the anode is preferably 10³ Ω/spuare or less, more preferably 10² Ω/spuare or less. When the anode is transparent, it may be colorless or colored. For extracting luminescence from the transparent anode side, it is preferred that the anode has a light transmittance of 60% or higher, more preferably 70% or higher.

Concerning transparent anodes, there is a detail description in "TOUMEI DOUDEN-MAKU NO SHINTENKAI (Novel Developments in Transparent Electrode Films)" edited by Yutaka Sawada, published by C.M.C. in 1999, the contents of which can be applied to the present invention. When a plastic substrate having a low heat resistance is used, it is preferred that ITO or IZO is used to form a transparent anode at a low temperature of 150°C or lower.

« Cathode »

In general, the cathode may be any material so long as it has the function of serving as an electrode which injects electrons into the organic compound layers constituting the above light-emitting layer. The shape, structure, size, etc.

thereof are not particularly limited and may be appropriately selected from known electrode materials depending on the application/purpose of the organic EL device.

Examples of the materials for the cathode include metals, alloys, metal oxides, conductive compounds and mixtures thereof. Specific examples thereof include alkali metals (e.g., Li, Na, K and Cs), alkaline earth metals (e.g., Mg and Ca), gold, silver, lead, aluminum, sodium-potassium alloys, lithium -aluminum alloys, magnesium-silver alloys and rare earth metals (e.g., indium and

ytterbium). These may be used individually, but it is preferred that two or more of them are used in combination from the viewpoint of satisfying both stability and electron-injection property.

Among them, as the materials for forming the cathode, alkali metals or alkaline earth metals are preferred in terms of excellent electron-injection property, and materials containing aluminum as a major component are preferred in terms of excellent storage stability. The term "material containing aluminum as a major component" refers to a material composed of aluminum alone; alloys containing aluminum and 0.01% by mass to 10% by mass of an alkali or alkaline earth metaL" or the mixtures thereof (e.g., lithium-aluminum alloys and

magnesium-aluminum alloys).

The materials for the cathode are described in detail in JP-A Nos.

02-15595 and 05-121172. The materials described in these literatures can be used in the present invention.

The method for forming the cathode is not particularly limited, and the cathode may be formed by a known method. For example, the cathode may be formed by a method which is appropriately selected from wet methods such as printing methods and coating methods; physical methods such as vacuum deposition methods, sputtering methods and ion plating methods; and chemical methods such as CVD and plasma CVD methods, in consideration of suitability for the material for the cathode. For example, when a metal (or metals) is (are) selected as a material (or materials) for the cathode, one or more of them may be applied simultaneously or sequentially by a sputtering method.

Patterning for forming the cathode may be performed by a chemical etching method such as photolithography,^" a physical etching method such as etching by laser," a method of vacuum deposition or sputtering using a mask; a lift-off method,^" or a printing method.

In the present inventio, a position at which the cathode is to be disposed is not particularly limited, so long as the cathode can apply an electric field to the light-emitting layer. The cathode may be entirely or partially formed on the light-emitting layer.

Furthermore, a dielectric layer having a thickness of 0.1 nm to 5 nm and being made, for example, of fluorides and oxides of an alkali or alkaline earth metal may be inserted between the cathode and the organic compound layer.

The dielectric layer may be considered to be a kind of electron-injection layer.

The dielectric layer may be formed by, for example, a vacuum deposition method, a sputtering method and an ion plating method. The thickness of the cathode may be appropriately selected depending on the material for the cathode and is, therefore, not definitely determined. It is generally about 10 nm to about 5 μιη, and preferably 50 nm to 1 μιη.

Moreover, the cathode may be transparent, semi-transparent or opaque. The transparent cathode may be formed as follows. Specifically, a 1 nm- to 10 nm-thick thin film is formed from a material for the cathode, and a transparent conductive material (e.g., ITO and IZO) is laminated on the thus-formed film. < Substrate >

The organic EL device optical member of the present invention may include a substrate (which usually transmitts light and supports the entire panel) for the purpose of preventing water from permeating the organic EL device from outside. No particular limitation is imposed on the substrate, so long as it can prevent water permeation as described above. The shape, structure, size, etc. thereof may be appropriately determined. In general, the substrate preferably has a plate-like shape. The structure of the substrate may be single -layered or multi-layered. Also, the substrate is composed of a single member or two or more members. The substrate may be colorless or colored transparent. Preferably, the substrate is colorless transparent, since such colorless transparent substrate does not diffuse or damp light emitted from the organic light-emitting layer.

The position at which the substrate is to be disposed is not particularly limited, so long as the substrate does not adversely affect the characteristics of light emitted from the light-emitting layer. In particular, the substrate is preferably disposed such that the reflective layer is located between the substrate and the light-extraction layer, since the characteristics of light emitted from the light-emitting layer are not adversely affected, and the organic EL device is sufficiently sealed.

The material for the substrate is not particularly limited and may be appropriately selected depending on the intended purpose. Specific examples thereof include inorganic materials such as yttria-stabilized zirconia (YSZ) and glass; and organic materials such as polyesters (e.g., polyethylene terephthalate, polybutylene phthalate and polyethylene naphthalate), polystyrene,

polycarbonate, polyether sulfone, polyarylate, polyimide, polycycloolefin, norbornene resins and poly(chlorotrifluoroethylene).

For example, when the substrate is made of glass, the glass is preferably alkali-free glass in order to reduce ions eluted from it. Also, when soda-lime glass is used for the material of the substrate, a barrier coat of silica, etc., is preferably provided on the substrate (e.g., barrier-film substrates). The organic materials are preferably used since they are excellent in heat resistance, dimensional stability, solvent resistance, electrical insulation and processability.

When a thermoplastic substrate is used, a hard coat layer, an under coat layer and other layers may be additionally provided as necessary.

< Other layers >

« High-refractive-index smooth layer »

In the present invention, the high-refractive-index smooth layer is not particularly limited, so long as it does not advesely affect as a result of absorption of light. The shape of the high-refractive-index smooth layer is not particulary limited, so long as its surface in contact with the light-extraction layer (e.g., a scattering particle layer) has a smoothness Ra of 100 nm or lower. The surface preferably has a smoothness of 1 nm to 50 nm, more preferably 10 nm or lower, particularly preferably 5 nm or lower. When the smoothness is higher than 100 nm, a short circuit may occur. In contrast, when the smoothness falls within the above particularly preferable range, the reliability advantageously increases (i.e., the occurrence of defects in multi-pixel panels decreases). For example, the smoothness may be measured with a surface roughness meter, or through observation under a laser microscope or an atomic force microscope (AFM). The structure, size, etc. of the high-refractive-index smooth layer are not particulalry limited, so long as the above-described requirements are met. The high-refractive index smooth layer preferably has a refractive index of 1.7 or higher. Notably, in the present invention, the "(high) refractive index" of the high-refractive index smooth layer has the same meaning as the refractive index of the light-emitting layer contained in the organic EL device.

The position at which the high-refractive -index smooth layer is to be disposed is not particulalry limited, so long as the high-refractive-index smooth layer is disposed in the vicinity of the insulative layer or the seal layer. For example, the high-refractive-index smooth layer may be disposed between the electrode and the light-extraction layer.

The material for the high-refractive-index smooth layer is not particularly limited, so long as the above-described requirements are met. Examples thereof include high-refractive-index resins such as acrylic resins containing

high-refractive -index micr op articles (e.g., ZrO2 and Ti02) dispersed therein.

« Gas barrier layer »

In the present invention, a gas barrier layer may be provided for the purpose of preventing air, water and other foreign matter from permeating. The shape, structure, size, etc. of the gas barrier layer may be appropriately

determined depending on the intended purpose of the present invention. The position at which the gas barrier layer is to be disposed is not particularly limited, so long as the characteristincs of the other layers are not adversely affected as a result of permeation of air, moisture, etc., and may be appropriately determined depending on the intended purpose. Preferably, the gas barrier layer is made of inorganic compounds (e.g., silicon nitride and silicon oxide), or is a laminate of an inorganic compound and an organic compound. The gas barrier layer may be formed on the substrate with, for example, a high-frequency sputtering method.

< Method for forming layers of organic EL device optical member >

In the organic EL device optical member of the present invention, a method for forming the layers thereof is not particularly limited unless specifically specified. The layers may be formed with a known method in the art. For example, the method may be appropriately selected from, for example, dry film-forming methods (e.g., a vapor deposition method and a spurttering method), a transfer method, a printing method, a coating method, an inkjet method and a spray method.

(Organic EL device)

An organic EL device of the present invention includes the

above-described organic EL device optical member of the present invention.

Specifically, the organic EL device includes a substrate, a light-emitting layer disposed between a pair of electrodes, a reflective layer, a light -extraction layer, and an optical path length adjusting layer disposed between the reflective layer and the light-extraction layer, and if necessary, further includes other layers. Here, the reflective layer reflects light emitted from the light-emitting layer, and the light- extraction layer extracts light from the light-emitting layer. Figs. 3 and 4 schematiclly illustrate such layer structures. Fig. 3 is a schematic view of a top -emission type organic EL device as one example of the organic EL device of the present invention. Fig. 4 is a schematic view of a bottom-emission type organic EL device as another example of the organic EL device of the present invention. In Figs. 3 and 4, the layers corresponding to the organic EL device optical member of the present invention have the same reference numerals as the organic EL device optical member, and the arrows indicate the light-emitting direction.

As illustrated in Fig. 3, a top-emission type organic EL device 100 of the present invention has a first substrate 26 (made of, for example, glass), a light-emitting layer 102 (which is disposed between a pair of electrodes 22 and

122), a reflective layer 16 (which reflects light emitted from the light-emitting layer 102, a light -extraction layer 14 (which extracts light from the light-emitting layer 102), an optical path length adjusting layer 12 (which is disposed between the reflective layer 16 and the light-extraction layer 14) and if necessary, further includes other layers such as a high-refractive-index smooth layer 24, a gas barrier layer 28, a lowrefractive-index layer 104, a barrier film substrate 106 (a second substrate), a protective layer 124 and a reflection preventing layer 126.

As illustrated in Fig. 4, a bottom-emission type organic EL device 100 of the present invention has a barrier film substrate 106 (which has been

barrier-coated), a light-emitting layer 102 (which is disposed between a pair of electrodes 22 and 122), a reflective layer 16 (which reflects light from the light-emitting layer 102), a light-extraction layer 14 (which extracts light from the light-emitting layer 102) and an optical path length adjusting layer 12 (which is disposed between the reflective layer 16 and the light-extraction layer 14) and, if necessary, further includes other layers such as a joining layer 25, a substrate 26, a gas barrier layer 28, a lowrefractive-index layer 104, a protective layer 124 and a reflection preventing layer 126.

In the organic EL device of the present invention, the shape, structure, size, material, etc. of the reflective layer, light-extraction layer and optical path length adjusting layer may be the same as described in the organic EL device optical member of the present invention. Thus, description will next be given with respect to other layers contained in the organic EL device of the present invention.

« Light-emitting layer »

In the present invention, the light-emitting layer is not particulalry limited, so long as it can emit light upon application of an electrical field, and may be appropriately selected depending on the intended purpose.

The light-emitting layer may be made of, for example, organic or inorganic light-emitting materials. In particular, organic light-emitting materials are preferably used from the viewpoints of exhibiting high light-emission efficiency, providing a larger device, and exhibiting high color purity. Next, description will be given with respect to the organic compound layer containing the light-emitting layer made of the organic light-emitting material.

< Organic compound layer >

As a lamination pattern of the organic compound layer, preferably, a hole -transport layer, an organic light-emitting layer and an electron transport layer are laminated in this order from the anode side. Moreover, a hole -injection layer is provided between the hole-transport layer and the cathode, and/or an electron-transportable intermediate layer is provided between the organic light-emitting layer and the electron transport layer. Also, a hole-transportable intermediate layer may be provided between the organic Ught-emitting layer and the hole -transport layer. Similarly, an electron-injection layer may be provided between the cathode and the electron-transport layer. Notably, each layer may be composed of a plurality of secondary layers.

The organic Ught-emitting layer corresponds to the light-emitting layer, and the anode, the cathode and the other layers than the organic light-emitting layer correspond to the above other layers.

The layers constituting the organic compound layer can be suitably formed by any of a dry film-forming method (e.g., a vapor deposition method and a sputtering method), a transfer method, a printing method, a coating method, an ink-jet method and a spray method.

The organic EL device of the present invention includes at least one organic compound layer including an organic light-emitting layer. Examples of the other organic compound layers than the organic light-emitting layer include a hole-transport layer, an electron transport layer, a hole blocking layer, an electron blocking layer, a hole injection layer and an electron injection layer.

In the organic EL device of the present invention, the layers constituting the organic compound layer can be suitably formed by any of a dry film-forming method (e.g., a vapor deposition method and a sputtering method), a wet film-forming method, a transfer method, a printing method and an ink-jet method.

« Organic light-emitting layer »

The organic light-emitting layer is a layer having the functions of receiving holes from the anode, the hole injection layer, or the hole -transport layer, and receiving electrons from the cathode, the electron-injection layer, or the electron transport layer, and providing a field for recombination of the holes with the electrons for light emission, when an electric field is applied.

The light-emitting layer may be composed only of a light-emitting material, or may be a layer formed form a mixture of a host material and a light-emitting dopant. The light-emitting dopant may be a fluorescent or phosphorescent light-emitting material, and may contain two or more species. The host material is preferably a charge -transporting material. The host material may contain one or more species, and, for example, is a mixture of a hole -transporting host material and an electron-transporting host material.

Further, a material which does not emit light nor transport any charge may be contained in the organic light-emitting layer.

The organic light-emitting layer may be a single layer or two or more layers. When it is two or more layers, the layers may emit lights of different colors.

The above light-emitting dopant may be, for example, a phosphorescent light-emitting material (phosphorescent light-emitting dopant) and a fluorescent light-emitting material (fluorescent light-emitting dopant).

The organic light-emitting layer may contain two or more different light-emitting dopants for improving color purity and/or expanding the

wavelength region of light emitted therefrom. From the viewpoint of drive durability, it is preferred that the light-emitting dopant is those satisfying the following relation(s) with respect to the above-described host compound: i.e., 1.2 eV > difference in ionization potential (Δΐρ) > 0.2 eV and/or 1.2 eV > difference in electron affinity (AEa) > 0.2 eV.

The fluorescent light-emitting material is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include complexes containing a transition metal atom or a lanthanoid atom.

The transition metal atom is not particularly limited and may be selected depending on the purpose. Preferred are ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium gold, silver, copper and platinum. More preferred are rhenium, iridium and platinum. Particularly preferred are iridium and platinum.

The lanthanoid atom is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, with

neodymium, europium and gadolinium being preferred.

Examples of ligands in the complex include those described in, for example, "Comprehensive Coordination Chemistry" authored by G. Wilkinson et al., published by Pergamon Press Company in 1987; "Photochemistry and

Photophysics of Coordination Compounds" authored by H. Yersin, published by Springer- Verlag Company in 1987; and "YUHKI KINZOKU KAGAKU— KISO TO OUYOU— (Metalorganic Chemistry— Fundamental and Application— )" authored by Akio Yamamoto, published by Shokabo Publishing Co., Ltd. in 1982.

Preferred examples of the ligands include halogen ligands (preferably, chlorine ligand), aromatic carbon ring ligands (preferably 5 to 30 carbon atoms, more preferably 6 to 30 carbon atoms, still more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as cyclopentadienyl anion, benzene anion and naphthyl anion); nitrogen- containing hetero cyclic ligands (preferably 5 to 30 atoms, more preferably 6 to 30 carbon atoms, still more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenyl pyridine, benzoquinoline, quinolinol, bipyridyl and

phenanthrorine), diketone ligands (e.g., acetyl acetone), carboxylic acid ligands (preferably 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, still more preferably 2 to 16 carbon atoms, such as acetic acid ligand), alcoholate ligands (preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 6 to 20 carbon atoms, such as phenolate ligand), silyloxy ligands (preferably 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, still more preferably 3 to 20 carbon atoms, such as trimethyl silyloxy ligand, dimethyl tert-butyl silyloxy ligand and triphenyl silyloxy ligand), carbon monoxide ligand, isonitrile ligand, cyano ligand, phosphorus ligand (preferably 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, still more preferably 3 to 20 carbon atoms, particularly preferably, 6 to 20 carbon atoms, such as triphenyl phosphine ligand), thiolate ligands (preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, still more preferably 6 to 20 carbon atoms, such as phenyl thiolate ligand) and phosphine oxide ligands (preferably 3 to 30 carbon atoms, more preferably 8 to 30 carbon atoms, particularly preferably 18 to 30 carbon atoms, such as triphenyl phosphine oxide ligand), with

nitrogen-containing hetero cyclic ligand being more preferred.

The above-described complexes may be a complex containing one transition metal atom in the compound, or a so-called polynuclear complex containing two or more transition metal atoms. In the latter case, the complexes may contain different metal atoms at the same time.

Among them, specific examples of the light-emitting dopants include phosphorescence luminescent compounds described in Patent Literatures such as

US6303238B1, US6097147, WO00/57676, WO00/70655, WO01/08230,

WO01/39234A2, WO01/41512A1, WO02/02714A2, WO02/15645A1, WO02/44189A1, WO05/19373A2, JP-A Nos. 2001 247859, 2002-302671,

2002-117978, 2003 133074, 2002-235076, 2003-123982 and 2002-170684,

EP1211257, JP-A Nos. 2002-226495, 2002-234894, 2001-247859, 2001-298470, 2002-173674, 2002-203678, 2002-203679, 2004 357791, 2006-256999, 2007-19462, 2007-84635 and 2007-96259. Among them, Ir complexes, Pt complexes, Cu complexes, Re complexes, W complexes, Rh complexes, Ru complexes, Pd complexes, Os complexes, Eu complexes, Tb complexes, Gd complexes, Dy complexes and Ce complexes are preferred, with Ir complexes, Pt complexes and Re complexes being more preferred. Among them, Ir complexes, Pt complexes, and Re complexes each containing at least one coordination mode of metal-carbon bonds, metal-nitrogen bonds, metal-oxygen bonds and metal-sulfur bonds are still more preferred. Furthermore, Ir complexes, Pt complexes, and Re complexes each containing a tri-dentate or higher poly-dentate ligand are particularly preferred from the viewpoints of, for example, light-emission efficiency, drive durability and color purity.

The fluorescence luminescent dopant is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include benzoxazole, benzoimidazole, benzothiazole, styrylbenzene, polyphenyl,

diphenylbutadiene, tetraphenylbutadiene, naphthalimide, coumarin, pyran, perinone, oxadiazole, aldazine, pyralidine, cyclopentadiene, bis-styrylanthracene, quinacridone, pyrrolopyridine, thiadiazolopyridine, cyclopentadiene, styrylamine, aromatic dimethylidene compounds, condensed polyaromatic compounds (e.g., anthracene, phenanthroline, pyrene, perylene, rubrene and pentacene), various metal complexes (e.g., metal complexes of 8-quinolynol, pyromethene complexes and rare-earth complexes), polymer compounds (e.g., polythiophene,

polyphenylene and polyp he nylenevinylene), organic silanes and derivatives thereof.

Specific examples of the luminescent dopants include the following



D-1 8

D-27 D-28

30

The light-emitting dopant is contained in the light-emitting layer in an amount of 0.1% by mass to 50% by mass with respect to the total amount of the compounds generally forming the light-emitting layer. From the viewpoints of drive durability and external light-emission efficiency, it is preferably contained in an amount of 1% by mass to 50% by mass, more preferably 2% by mass to 40% by mass.

Although the thickness of the light-emitting layer is not particularly limited, in general, it is preferably 2 nm to 500 nm preferred. From the viewpoint of external light-emission efficiency, it is more preferably 3 nm to 200 nm, particularly preferably 5 nm to 100 nm.

The host material may be hole transporting host materials excellent in hole transporting property (which may be referred to as a "hole transporting host") or electron transporting host compounds excellent in electron transporting property (which may be referred to as an "electron transporting host").

Examples of the hole transporting host materials contained in the organic light-emitting layer include pyrrole, indole, carbazole, azaindole, azacarbazole, triazole, oxazole, oxadiazole, pyrazole, imidazole, thiophene, polyarylalkane, pyrazolone, pyrazolone, phenylenediamine, arylamine, amino-substituted chalcone, styrylanthracene, fluorenone, hydrazone, stilbene, silazane, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidine compounds, porphyrin compounds, polysilane compounds, poly(N-vinylcarbazole), aniline copolymers, conductive high-molecular- weight oligomers (e.g., thiophene oligomers and polythiophenes), organic silanes, carbon films and derivatives thereof.

Among them, indole derivatives, carbazole derivatives, aromatic tertiary amine compounds and thiophene derivatives are preferred. Also, compounds each containing a carbazole group in the molecule are more preferred. Further, compounds each containing a t-butyl-substituted carbazole group are particularly preferred.

The electron transporting host to be used in the organic light-emitting layer preferably has an electron affinity Ea of 2.5 eV to 3.5 eV, more preferably 2.6 eV to 3.4 eV, particularly preferably 2.8 eV to 3.3 eV, from the viewpoints of improvement in durability and decrease in drive voltage. Also, it preferably has an ionization potential Ip of 5.7 eV to 7.5 eV, more preferably 5.8 eV to 7.0 eV, particularly preferably 5.9 eV to 6.5 eV, from the viewpoints of improvement in durability and decrease in drive voltage.

Examples of the electron transporting host include pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole, oxazole, oxadiazole, fluorenone,

anthraquinone dime thane, anthrone, diphenylquinone, thiopyrandioxide, carbodiimide, fiuorenylidenemethane, distyrylpyradine, fluorine -substituted aromatic compounds, heterocyclic tetracarboxylic anhydrides (e.g., naphthalene and perylene), phthalocyanine, derivatives thereof (which may form a condensed ring with another ring) and various metal complexes such as metal complexes of 8-quinolynol derivatives, metal phthalocyanine, and metal complexes having benzoxazole or benzothiazole as a ligand.

Preferred electron transporting hosts are metal complexes, azole derivatives (e.g., benzimidazole derivatives and imidazopyridine derivatives) and azine derivatives (e.g., pyridine derivatives, pyrimidine derivatives and triazine derivatives). Among them, metal complexes are preferred in terms of durability. As the metal complexes (A), preferred are those containing a ligand which has at least one nitrogen atom, oxygen atom, or sulfur atom and which is coordinated with the metal.

The metal ion contained in the metal complex is not particularly limited and may be appropriately selected depending on the purpose. It is preferably a beryllium ion, a magnesium ion, an aluminum ion, a gallium ion, a zinc ion, an indium ion, a tin ion, a platinum ion or a palladium ion; more preferably is a beryllium ion, an aluminum ion, a gallium ion, a zinc ion, a platinum ion or a palladium ion; particularly preferably is an aluminum ion, a zinc ion or a palladium ion.

Although there are a variety of known ligands to be contained in the metal complexes, examples thereof include those described in, for example, "Photochemistry and Photophysics of Coordination Compounds" authored by H. Yersin, published by Springer- Verlag Company in 1987; and "YUHKI KINZOKU KAGAKU— KISO TO OUYOU— (Metalorganic Chemistry— Fundamental and Application— )" authored by Akio Yamamoto, published by Shokabo Publishing Co., Ltd. in 1982.

The ligand is preferably nitrogen-containing heterocyclic ligands

(preferably having 1 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 3 to 15 carbon atoms). It may be a unidentate ligand or a bi- or higher-dentate ligand. Preferred are bi- to hexa-dentate ligands, and mixed ligands of bi- to hexa-dentate ligands with a unidentate ligand.

Examples of the ligand include azine ligands (e.g., pyridine ligands, bipyridyl ligands and terpyridine ligands); hydroxyphenylazole ligands (e.g., hydroxyphenylbenzoimidazole ligands, hydroxyphenylbenzoxazole ligands, hydroxyphenylimidazole ligands and hydroxyphenylimidazopyridine ligands); alkoxy ligands (those having preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 10 carbon atoms, such as methoxy, ethoxy, butoxy and 2-ethylhexyloxy); and aryloxy ligands (those having preferably 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenyloxy, 1-naphthyloxy, 2-naphthyloxy, 2,4,6-trimethylphenyloxy and 4-biphenyloxy).

Further examples include heteroaryloxy ligands (those having preferably

1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, examples of which include pyridyloxy, pyrazyloxy, pyrimidyloxy and quinolyloxy); alkylthio ligands (those having preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to

12 carbon atoms, examples of which include methylthio and ethylthio); arylthio ligands (those having preferably 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, examples of which include phenylthio)," heteroarylthio ligands (those having preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, examples of which include pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio and 2-benzothiazolylthio); siloxy ligands (those having preferably 1 to 30 carbon atoms, more preferably 3 to 25 carbon atoms,

particularly preferably 6 to 20 carbon atoms, examples of which include a triphenylsiloxy group, a triethoxysiloxy group and a triisopropylsiloxy group); aromatic hydrocarbon anion ligands (those havin preferably 6 to 30 carbon atoms, more preferably 6 to 25 carbon atoms, particularly preferably 6 to 20 carbon atoms, examples of which include a phenyl anion, a naphthyl anion and an anthranyl anion); aromatic heterocyclic anion ligands (those having preferably 1 to 30 carbon atoms, more preferably 2 to 25 carbon atoms, and particularly preferably 2 to 20 carbon atoms, examples of which include a pyrrole anion, a pyrazole anion, a triazole anion, an oxazole anion, a benzoxazole anion, a thiazole anion, a benzothiazole anion, a thiophene anion and a benzothiophene anion); and indolenine anion ligands. Among them, nitrogen-containing heterocyclic ligands, aryloxy ligands, heteroaryloxy groups, siloxy ligands, etc. are preferred, and nitrogen-containing heterocyclic ligands, aryloxy ligands, siloxy ligands, aromatic hydrocarbon anion ligands, aromatic heterocyclic anion ligands, etc. are more preferred.

Examples of the metal complex electron transporting host include compounds described in, for example, JP-A Nos. 2002-235076, 2004-214179, 2004-221062, 2004-221065, 2004-221068 and 2004-327313.

In the light-emitting layer, it is preferred that the lowest triplet excitation energy (Tl) of the host material is higher than Tl of the phosphorescence light-emitting material, from the viewpoints of color purity, light-emission efficiency and drive durability. Although the amount of the host compound added is not particularly limited, it is preferably 15% by mass to 95% by mass with respect to the total amount of the compounds forming the light-emitting layer, in terms of light emitting efficiency and drive voltage.

« Hole-injection layer and hole -transport layer »

The hole -injection layer and hole -transport layer are layers having the function of receiving holes from the anode or from the anode side and transporting the holes to the cathode side. Materials to be incorporated into the hole-injection layer or the hole -transport layer may be a lowmolecular-weight compound or a high-molecular-weight compound.

Specifically, these layers preferably contain, for example, pyrrole

derivatives, carbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidine compounds, phthalocyanine compounds, porphyrin compounds, thiophene derivatives, organosilane derivatives and carbon.

Also, an electron- accepting dopant may be incorporated into the

hole-injection layer or the hole-transport layer of the organic EL device. The electron-accepting dopant may be, for example, an inorganic or organic compound, so long as it has electron accepting property and the function of oxidizing an organic compound.

Specific examples of the inorganic compound include metal halides (e.g., ferric chloride, aluminum chloride, gallium chloride, indium chloride and antimony pentachloride) and metal oxides (e.g., vanadium pentaoxide and molybdenum trioxide). As the organic compounds, those having a substituent such as a nitro group, a halogen, a cyano group and a trifluoromethyl group; quinone compounds; acid anhydride compounds; and fullerenes may be preferably used.

In addition, there can be preferably used compounds described in, for example, JP-A Nos. 06 212153, 11-111463, 11-251067, 2000-196140, 2000 286054, 2000-315580, 2001-102175, 2001-160493, 2002 252085, 2002 56985, 2003-157981, 2003-217862, 2003-229278, 2004 342614, 2005-72012, 2005-166637 and

2005-209643.

Among them, preferred are hexacyanobutadiene, hexacyanobenzene, tetracyanoethylene, tetracyanoquinodimethane,

tetrafluorotetracyanoquinodimethane, p fluoranil, p chloranil, p-bromanil, p-benzoquinone, 2,6-dichlorobenzoquinone, 2,5-dichlorobenzoquinone,

1,2,4,5-tetracyanobenzene, 1,4-dicyanotetrafluorobenzene,

2,3 dichloro-5,6-dicyanobenzoquinone, p-dinitrobenzene, m-dinitrobenzene, o-dinitrobenzene, 1,4-naphthoquinone, 2,3-dichloronaphthoquinone,

1,3- dinitronaphthalene , 1,5- dinitronaphthalene , 9,10- anthr aquinone ,

1,3,6,8-tetranitrocarbazole, 2,4,7-trinitro-9-fluorenone, 2,3,5,6-tetracyanopyridine and fullerene C60. More preferred are hexacyanobutadiene, hexacyanobenzene, tetracyanoethylene, tetracyanoquinodimethane,

tetrafluorotetracyanoquinodimethane, p-fluoranil, p-chloranil, p-bromanil,

2,6-dichlorobenzoquinone, 2,5-dichlorobenzoquinone, 2,3-dichloronaphthoquinone,

1.2.4.5- tetracyanobenzene, 2,3 dichloro-5,6-dicyanobenzoquinone and

2.3.5.6- tetracyanopyridine. Particularly preferred is

tetrafluorotetracyanoquinodimethane.

These electron-accepting dopants may be used alone or in combination.

Although the amount of the electron- accepting dopant used depends on the type of material, the dopant is preferably used in an amount of 0.01% by mass to 50% by mass, more preferably 0.05% by mass to 20% by mass, particularly preferably 0.1% by mass to 10% by mass, with respect to the material of the hole-transport layer.

The thicknesses of the hole-injection layer and the hole-transport layer are each preferably 500 nm or less in terms of reducing drive voltage.

The thickness of the hole-transport layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, still more preferably 10 nm to 100 nm. The thickness of the hole-injection layer is preferably 0.1 nm to 200 nm, more preferably 0.5 nm to 100 nm, still more preferably 1 nm to 100 nm.

Each of the hole -injection layer and the hole -transport layer may have a single -layered structure made of one or more of the above-mentioned materials, or a multi-layered structure made of a plurality of layers which are identical or different in composition.

« Electron-injection layer and electron-transport layer »

The electron-injection layer and the electron-transport layer are layers having the functions of receiving electrons from the cathode or the cathode side and transporting the electrons to the anode side. The electron-injection materials or electron-transport materials for these layers may be

low-molecular-weight or high-molecular-weight compounds.

Specific examples thereof include pyridine derivatives, quinoline

derivatives, pyrimidine derivatives, pyrazine derivatives, phthalazine derivatives, phenanthoroline derivatives, triazine derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, fluorenone derivatives, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, carbodiimide derivatives,

fluorenylidenemethane derivatives, distyrylpyradine derivatives, aryl

tetracarboxylic anhydrides such as perylene and naphthalene, phthalocyanine derivatives, metal complexes (e.g., metal complexes of 8-quinolinol derivatives, metal phthalocyanine, and metal complexes containing benzoxazole or benzothiazole as the ligand) and organic silane derivatives (e.g., silole).

The electron-injection layer or the electron-transport layer in the organic EL device of the present invention may contain an electron donating dopant. The electron donating dopant to be introduced in the electron-injection layer or the electron-transport layer may be any material, so long as it has an

electron- donating property and a property for reducing an organic compound. Preferred examples thereof include alkali metals (e.g., Li), alkaline earth metals (e.g., Mg), transition metals including rare-earth metals, and reducing organic compounds. Among the metals, those having a work function of 4.2 eV or less are particularly preferably used. Examples thereof include Li, Na, K, Be, Mg, Ca, Sr, Ba, Y, Cs, La, Sm, Gd and Yb. Also, examples of the reducing organic compounds include nitrogen-containing compounds, sulfur-containing compounds and phosphorus-containing compounds.

In addition, there may be used materials described in, for example, JP-A Nos. 06-212153, 2000 196140, 2003 68468, 2003-229278 and 2004-342614.

These electron donating dopants may be used alone or in combination. The amount of the electron donating dopant used depends on the type of the material, but it is preferably 0.1% by mass to 99% by mass, more preferably 1.0% by mass to 80% by mass, particularly preferably 2.0% by mass to 70% by mass, with respect to the amount of the material of the electron transport layer.

The thicknesses of the electron-injection layer and the electron-transport layer are each preferably 500 nm or less in terms of reducing drive voltage.

The thickness of the electron-transport layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, particularly preferably 10 nm to 100 nm. The thickness of the electron-injection layer is preferably 0.1 nm to 200 nm, more preferably 0.2 nm to 100 nm, particularly preferably 0.5 nm to 50 nm.

Each of the electron-injection layer and the electron-transport layer may have a single -layered structure made of one or more of the above-mentioned materials, or a multi-layered structure made of a plurality of layers which are identical or different in composition.

« Hole blocking layer »

The hole blocking layer is a layer having the function of preventing the holes, which have been transported from the anode side to the light-emitting layer, from passing toward the cathode side, and may be provided as an organic compound layer adjacent to the Ught-emitting layer on the cathode side.

Examples of the compound forming the hole blocking layer include aluminum complexes (e.g., BAlq), triazole derivatives and phenanthroline derivatives (e.g., BCP).

The thickness of the hole blocking layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, particularly preferably 10 nm to 100 nm.

The hole blocking layer may have a single-layered structure made of one or more of the above-mentioned materials, or a multi-layered structure made of a plurality of layers which are identical or different in composition.

« Electron blocking layer »

An electron blocking layer is a layer having the function of preventing the electrons, which have been transported from the cathode side to the light-emitting layer, from passing toward the anode side, and may be provided as an organic compound layer adjacent to the light-emitting layer on the anode side in the present invention.

Examples of the compound forming the electron blocking layer include those listed as a hole-transport material.

The thickness of the electron blocking layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, particularly preferably 10 nm to 100 nm.

The electron blocking layer may have a single-layered structure made of one or more of the above-mentioned materials, or a multi-layered structure made of a plurality of layers which are identical or different in composition. In order to improve the light-emission efficiency, the light-emitting layer may have such a configuration that charge generation layers are provided between a plurality of light-emitting layers.

The charge generation layer is a layer having the functions of generating charges (i.e., holes and electrons) when an electrical field is applied, and of injecting the generated charges into the adjacent layers.

The material for the charge generation layer is not particularly limited, so long as it has the above-described functions. The charge generation layer may be made of a single compound or a plurality of compounds.

Specifically, the material may be those having conductivity, those having semi-conductivity (e.g., doped organic layers) and those having electrical insulating property. Examples thereof include the materials described in JP-A Nos. 11-329748, 2003-272860 and 2004-39617.

Specific examples thereof include transparent conductive materials (e.g., ITO and IZO (indium zinc oxide)), fullerenes (e.g., C60), conductive organic compounds (e.g., oligothiophene, metal phthalocyanine, metal-free

phthalocyanine, metal porphyrins and non-metal porphyrins), metal materials (e.g., Ca, Ag, Al, Mg-Ag alloys, Al-Li alloys and Mg-Li alloys), hole conducting materials, electron conducting materials and mixtures thereof.

Examples of the hole conducting materials include hole transport organic materials (e.g., 2-TNATA and NPD) doped with an oxidant having an

electron- attracting property (e.g., F4-TCNQ, TCNQ and FeCle), P-type conductive polymers and P-type semiconductors. Examples of the electron conducting materials include electron transport organic materials doped with a metal or metal compound having a work function lower than 4.0 eV, N-type conductive polymers and N-type semiconductors. Exmaples of the N-type semiconductors include N-type Si, N-type CdS and N-type ZnS. Examples of the P-type semiconductors include P-type Si, P-type CdTe and P-type CuO. Also, the charge generation layer may be made of electrical insulating materials such as V2O5.

The charge generation layer may have a single -layered or multi-layered structure. Examples of the multi-layered structure the charge generation layer has include a structure in which a conductive material (e.g., transparent conductive materials and metal materials) is laminated on a hole or electron transport material, and a structure in which the above-listed hole conducting material is laminated on the above -listed electron conducting material.

In general, the thickness and material of the charge generation layer is preferably determined so that the transmittance thereof with respect to visible light is 50% or higher. The thickness thereof is not particulalry limited and may be appropriately determined depending on the intended purpose. The thickness is preferably 0.5 nm to 200 nm, more preferably 1 nm to 100 nm, still more preferably 3 nm to 50 nm, particularly preferably 5 nm to 30 nm.

The forming method for the charge generation layer is not particularly limited. The above-described forming methods for the organic compound layer may be employed.

The charge generation layer is formed between two or more layers of the above light-emitting layer. The charge generation layer may contain, at the anode or cathode side, a material having the function of injecting charges into the adjacent layers. In order to increase injectability of electrons into the adjacent layers at the anode side, electron injection compounds (e.g., BaO, SrO, L12O, LiCl, LiF, MgF2, MgO and CaF2) may be deposited on the charge generation layer at the anode side.

In addition to the above-listed materials, the material for charge generation layer may be selected from those described in JP-A No. 2003-45676, and U.S. Pat. Nos. 6337492, 6107734 and 6872472.

< Low-refractive-index layer > In the organic EL device of the present invention, the low-refractive-index layer is not particularly limited, so long as the refractive index thereof is different from that of the substrate. The refractive index of the lowrefractive-index layer is not particularly Umited, so long as the surface in contact with the substrate or sealing plate has a refractive index of 1.4 or lower. This refractive index is preferably 1.0 to 1.4, more preferably 1.0 to 1.3, particularly preferasbly 1.2 or lower. When the refractive index is less than 1.4, the light-emission efficiency may increase. Whereas when the refractive index exceeds 1.4, the light-emission efficiency may decrease. When the refractive index falls within the above particularly preferable range, optically advantageous effects can be obtained. In the present invention, the refractive index is measured with, for example, an elipsometer. The structure, size, etc. of the low-refractive-index layer are not particularly limited, so long as the above-described requirements can be met. The lowrefractive-index layer may have hollow layers containing, for example, air in consideration of pressurization. Alternatively, from the viewpoint of increasing the strength of the panel, the lowrefractive-index layer may be a solid layer made of the belowexemplified materials. In particular, the

lowrefractive-index layer is preferably a transparent layer having a low

refractive index from the viewpoints of improving the light-emission efficiency and forming high-quality images (without coloring).

The position at which the low-refractive-index layer is to be disposed is not particularly limited, so long as the lowrefractive-index layer is disposed at any position in the light-emitting direction from the reflective layer. Preferably, the lowrefractive-index layer is disposed directly below the substrate from the viewpoint of exhibiting advantageous optical characteristics. When the lowrefractive-index layer is disposed in this manner, gas-barrier property and sealing property can be maintained.

The material for the lowrefractive-index layer is not particularly limited, so long as it meets the above requirements. Examples thereof include aerogel and fluorine-containing resins.

< Other layers >

« Joining layer »

In the organic EL device of the present invention, a joining layer may be provided to join the layers with each other. The shape, structure, size, etc. of the joining layer may be appropriately determined depending on the purpose of the present invention. Examples of the joining layer include those having a high refractive index and those having adhesion property. Here, the "high refractive index" refers to a refractive index higher than that of glass. The material for the joining layer is not particularly limited. Preferred examples thereof include those having transparency and low-light-absorbability. Specific examples include acrylic and epoxy adhesives containing high-refractive -index

microparticles (e.g., ZrO2 and T1O2) dispersed therein.

The position at which the joining layer is to be disposed is not particularly limited, so long as the joining layer can join the layers with each other.

Preferably, the light-extraction layer is disposed on or attached to other layers via the joining layer(s).

« Protective layer »

In the organic EL device of the present invention, a protective layer may be provided for the purpose of ensuring the functions of the organic EL device by, for example, preventing degradation due to water, oxygen, etc.

The position at which the protective layer is to be disposed is not particularly limited, so long as the above purpose can be achieved. For example, the protective layer is disposed so that the device is protected from moisture present outside thereof. Preferably, from the viewpoint of protecting the device from moisture, the protective layer is disposed in the vicinity of the electrode and/or the light-emitting layer. In particular, the protective layer is preferably disposed so as to be in contact with the electrode.

The material contained in the protective layer may be those having the function of preventing moisuture, oxygen, etc. (which accelerate degradation of the organic compound layer containing the light-emitting layer) from entering the organic compound layer. Specific examples thereof include metals (e.g., In, Sn, Pb, Au, Cu, Ag, Al, Ti and Ni), metal oxides (e.g., MgO, SiO, Si0₂, A1₂0₃, GeO, NiO, CaO, BaO, Fe₂0₃, Y2O3 and Ti0₂), metal nitrides (e.g., SiN_x and SiN_xO_y), metal fluorides (e.g., MgF₂, LiF, AIF3 and CaF^, polyethylenes, polypropylenes, polymethyl methacrylates, polyimides, polyureas, polytetrafluoroethylenes, polychlorotrifluoroethylenes, polydichlorofluoroethylenes, copolymers of chlorotrifluoroethylenes and dichlorofluoroethylenes, copolymers produced through compolymerization of a monomer mixture containing tetrafluoroethylene and at least one comonomer, fluorine -containing copolymers containing a ring structure in the copolymerization main chain, water-absorbing materials each having a water absorption rate of 1% or more, and moisture permeation

preventive substances each having a water absorption rate of 0.1% or less.

The method for forming the protective layer is not particularly limited. Examples thereof include a vacuum deposition method, a sputtering method, a reactive sputtering method, an MBE (molecular beam epitaxial) method, a cluster ion beam method, an ion plating method, a plasma polymerization method

(high-frequency excitation ion plating method), a plasma CVD method, a laser CVD method, a thermal CVD method, a gas source CVD method, a coating method, a printing method and a transfer method.

Also, the protective layer may contain a moisture absorbent or an inert liquid. The moisture absorbent is not particularly limited and may be

appropriately selected depending on the intended purpose. Specific examples thereof include barium oxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calcium sulfate, magnesium sulfate, phosphorus pentaoxide, calcium chloride, magnesium chloride, copper chloride, cesium fluoride, niobium fluoride, calcium bromide, vanadium bromide, molecular sieve, zeolite and magnesium oxide. Also, the inert liquid is not particularly limited and may be appropriately selected depending on the intended purpose. Specific examples thereof include paraffins; liquid paraffins; fluorine -containing solvents such as perfluoroalkanes, perfluoroamines and perfluoroethers; chlorinated solvents; and silicone oils.

The protective layer may contain a resin for preventing the device from being exposed to air to prevent degradation of its performance due to oxygen and moisture. The resin is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include acrylic resins, epoxy resins, fluorine -containing resins, silicone resins, rubber resins and ester resins. Among them, epoxy resins are preferred from the viewpoint of preventing water permeation. Among the epoxy resins, thermosetting epoxy resins and photo-curable epoxy resins are preferred.

The forming method for the protective layer containing the resin is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a method by coating a solution/dispersion liquid containing the resin in addition to the above-listed material for the protective layer, a method by press-bonding or hot press-bonding a resin sheet, and a method by polymerizing under dry conditions (e.g., vapor deposition and sputtering).

The protective layer containing the resin preferably has a thickness of 1 μπι to 1 mm, more preferably 5 μηι to 100 μιη, particularly preferably 10 μηι to 50 μιη. When the thickness of the protective layer is smaller than 1 μπι, the inorganic film may be damaged upon attachment of the second substrate.

Whereas when the thickness of the protective layer is larger than 1 mm, the thickness of the organic EL device itself becomes large, resulting in that the thin organic EL device cannot be obtained in some cases.

« Reflection preventing layer »

In the organic EL device of the present invention, the reflection preventing layer is not particularly limited, so long as incident light to the reflection preventing layer can be prevented from being reflected therein. The shape, structure and size of the reflection preventing layer may be appropriately determined.

In the organic EL device of the present invention, the position at which the reflection preventing layer is to be disposed may be appropriately determined depending on the purpose of the present invention. For example, the reflection preventing layer is disposed on the uppermost surface at the light-emitted side of the organic EL device, and is disposed inside the substrate or the sealing film at the light-emitted side. In particular, the reflection preventing layer is preferably disposed on the uppermost surface at the light-emitted side of the organic EL device from the viewpoint of reflecting external light most efficiently.

For example, the reflection preventing layer may be made of a material which absorbs external light. The material for the reflection preventing layer is not particulary limited, so long as it meets the above requirements, and may be appropriately determined depending on the intended purpose.

< Method for forming layers of organic EL device >

In the organic EL device of the present invention, a method for forming the layers thereof is not particularly limited unless specifically specified. The layers may be formed with a known method in the art. For example, the method may be appropriately selected from, for example, dry film-forming methods (e.g., a vapor deposition method and a spurttering method), a transfer method, a printing method, a coating method, an inkjet method and a spray method.

< Driving >

The organic EL device can emit light when a DC voltage (which, if necessary, contains AC components) (generally 2 volts to 15 volts) or a DC is applied to between the anode and the cathode.

For the driving method of the organic EL layer, applicable are those described in, for example, JP-A Nos. 02-148687, 06-301355, 05-29080, 07-134558, 08-234685 and 08-241047, Japanese Patent No. 2784615, and U.S. Pat. Nos. 5828429 and 6023308.

< Microcavity structure >

The organic EL device of the present invention may have a so-called light resonance structure (microcavity structure) in which light is reflected/interferred between the reflective layer and the transprent or semi-transparent electrode via the transpresnt electrode and the light-emitting layer including the organic compound layer. For example, the light resonance structure may be formed by a semi-transparent electrode (i.e., one reflective plate) and a reflective layer (i.e., the other reflective plate) so that light is repeatedly reflected/resonated between these reflective plates. The light resonance structure increases color intensity by virtue of multiplex interference, and thus, provision of the light resonance structure enables the organic EL device to exhibit high light intensity.

With reference to the drawings, description will be given to the process from light generation to light emission. Notably, although the organic EL device illustrated in Fig. 3 (i.e., a top-emission type) is different from that illustrated in Fig. 4 (i.e., a bottom-emission type), the process from light generation to light emission is almost the same in these organic EL devices. Thus, the process from light generation to light emission will be described referring only to the

top-emission type organic EL device of Fig. 3.

In the top -emission type organic EL device of Fig. 3, when an electrical field is applied to electrodes 22 and 122, a light-emitting material in a

light-emitting layer 102 (organic compound layer) emits light, which then travels from the light-emitting layer 102 in all directions. Some of the light traveling from the light-emitting layer 102 toward the light-emitting direction of the organic EL device 100 is reflected on the electrode 122, and some is not reflected on the electrode 122 and travels toward the light-emitting direction.

The light reflected on the electrode 122 travels through several layers in an opposite direction to the light-emitting direction of the organic EL device, and finally, most of the light is reflected on the reflective layer 16. The light reflected on the reflective layer 16 follows almost the same process as the light emitted from the light-emitting material of the light-emitting layer 102 follows. Notably, the light reflected on the electrode 122 is reflected/interfered in the above microcavity structure.

Meanwhile, the light having not been reflected on the electrode 122 and having traveled in the light-emitting direction of the organic EL device, and the light having been reflected on the reflective layer 16, and having traveled through several layers and the electrode 122 toward the light-emitting direction of the organic EL device further travel through several layers. Finally, the Ught travels toward air through the light-emitted surface of a reflection preventing layer 126, and is observed in air. In this manner, the light derived from the light-emitting material in the organic EL device of the present invention is observed.

The organic EL device of the present invention may be a fuU color-type display device. As a method for making the organic EL device of the present invention to be a fuU color-type display device, there are known, for example, as described in "Monthly Display," September 2000, pp. 33 to 37, a tricolor light emission method by arranging, on a substrate, layers emitting Ughts

corresponding to three primary colors (blue color (B), green color (G) and red color

(R)),^' a white color method by separating white Ught emitted from a layer for white color emission into three primary colors through a color filter." and a color conversion method by converting a blue light emitted from an organic EL device for blue Ught emission into red color (R) and green color (G) through a fluorescent dye layer.

Further, by combining a plurality of layers emitting lights of different colors which are obtained by the above-described methods, plane-type light sources emitting lights of desired colors can be obtained. For example, there are exemplified white Ught-emitting sources obtained by combining blue and yellow light emitting elements, and white light-emitting sources obtained by combining blue, green and red light Ught-emitting elements.

Examples

Next, the present invention will be described in detal by way of Examples and Comparative Examples. However, the present invention is not construed as being limited to Examples.

(Example 1)

As described below, top-emission type organic EL device 1 of the present invention was fabricated so as to have the layer structure shown in Table 1 and

Fig. 3. In Table 1, the symbol "T" described in the row "Light-emitting direction" means that the organic EL devices obtained in Examples of Table 1 are so-called top-emission type organic EL devices. Also, the Ught-emitting direction corresponds to a top-to-bottom direction of the layer structure in Table 1.

Further, "scattering particles," "fine concave and convex portions," "hoUow," and

"filled with material" indicate respectively a Ught-extraction layer containing scattering particles, a Ught-extraction layer having fine concave and convex portions, a hollow lowrefractive-index layer and a lowrefractive-index layer filled with material. The symbol "-" means that the corresponding layers are not provided. Notably, the substrate disposed at the farthest position from the light-emitted surface of the organic EL device is a glass (film) substrate provided with TFTs capable of driving individual pixels in the case of the top-emission type organic EL device, or is a sealing film (glass) substrate in the case of the bottom-emission type organic EL device.

< Method for forming gas barrier layer >

A gas barrier layer of SiN was formed with the following method.

Specifically, through CVD, silane gas and nitrogen gas were reacted with each other in RF plasma (13.56 MHz) to form an SiN film on the substrate, whereby a 50-nm thick gas barrier layer was formed.

< Method for forming reflective layer >

Next, Al was vapor-deposited on the above formed gas barrier layer through sputtering, whereby a 200-nm thick reflective layer was formed.

< Method for forming optical path length adjusting layer >

A photocurable, transparent acrylic resin (product of TORAY

INDUSTRIES, INC.) was spin coated on the above formed reflective layer, and then, was exposed to UV rays through a mask produced so as to mask intended portions. The unnecessary portions other than the cured resin portions were removed, to thereby form an optical path length adjusting layer having a thickness of 10 nm to 200 nm.

< Method for producing light-extraction layer containing scattering particles >

A light-extraction layer composition containing the following scattering particles was prepared.

Photocurable acrylic resin (product of TORAY INDUSTRIES, INC.): 99% by volume to 80% by volume

ZrO₂ (product of FURUCHI Co.): l% by volume to 20% by volume (particle diameter: l μηι to 5 μπι)

The above-prepared light-extraction layer composition was spin coated on the optical path length adjusting layer, followed by curing through UV irradiation, to thereby form a 2,000-nm thick light-extraction layer containing scattering particles.

< Method for forming high-refractive -index smooth layer > A high-refractive -index smooth layer composition containing the following components was prepared.

Thermosetting acrylic resin (product of TORAY INDUSTRIES, INC.): 70 parts by mass

ZrO₂ (product of FURUCHI Co.): 30% by mass (particle diameter: 10 nm to 100 nm)

The thus-prepared high-refractive -index smooth layer composition was spin coated on the light-extraction layer, followed by curing under heating at 120°C for 2 hours, to thereby form a 2,000-nm thick high-refractive -index smooth layer.

< Method for producing transparent electrode >

Through sputtering using ITO (product of FURUCHI Co.) as a target material (sputtering apparatus used: product of ULVAC, Inc.), a 150-nm thick transparent electrode was formed (laminated) on the above high-refractive -index smooth layer.

< Method for forming organic compound layer containing light-emitting layer >

A hole injection layer composition and a hole transport layer composition each having the folowing components were prepared.

2-TNATA (BANDO CHEMICAL INDUSTRIES, LTD.)

NPD (Nippon Steel Chemical Co., Ltd.)

Also, a light-emitting layer/ electron transport layer composition having the following component was prepared.

Alq3 (Nippon Steel Chemical Co., Ltd.)

Next, the hole injection layer composition and the hole transport layer composition were vapor-deposited in vaccum on the transparent electrode, to thereby form a 200-nm thick hole injection layer and a 50-nm thick hole transport layer.

Thereafter, the light-emitting layer/electron transport layer composition (Alq3) was vapor-deposited in vaccum on the hole transport layer, to thereby form a 100-nm thick hght-emitting layer.

Thereafter, an electron injection layer composition (LiF (product of FURUCHI Co.)) was vapor-deposited in vaccum on the light-emitting layer, to thereby form a 0.5-nm thick electron transport layer.

Through the above procedure, an organic compound layer containing the light-emitting layer (consisting of the 200-nm thick hole transport layer, the 100-nm thick light-emitting layer/electron transport layer and the 0.5-nm thick electron injection layer) was formed.

< Method for forming semi-transparent electrode >

A semi-transparent electrode composition having the following

components was prepared.

Ag (product of FURUCHI Co.)

ITO (product of FURUCHI Co.)

Next, the semi-transparent electrode composition was deposited through sputtering on the organic compound layer, to thereby form a semi-transparent electrode consisting of a 5-nm thick Ag layer and a 100-nm thick ITO layer.

< Merthod for forming protective layer >

A protective layer composition having the following components was prepared.

SiO₂ (target) (product of FURUCHI Co.)

N₂ gas (product of NIPPON SANSO Co.)

Next, the protective layer composition was deposited with a reactive sputtering method on the semi-transparent electrode for forming an SiON film, to thereby form a 150-nm thick protective layer.

< Method for forming hollow low-refractive-index layer >

A hollow lowrefractive-index layer was formed with the below-described method. Specifically, a sealing glass member having a hollow counterbore was bonded with a photo- or heat-curable adhesive onto the protective layer on the substrate as fabricated above, whereby a low-refractive-index layer was formed. The hollow counterbore of the sealing glass member is filled with air (refractive index n = l).

< Method for forming sealing film/substrate >

In this Example, the sealing glass member of the hollow

low-refractive-index layer serves also as a sealing substrate. When a sealing film was used for sealing, a barrier film having a barrier property was attached to the substrate (on which the EL layers had been formed) with a heat-curable adhesive via a spacer (height: 100 μπι) through thermal curing at 80°C for 1 hour. The barrier film was formed by coating both surfaces of a PEN film (thickness^ 100 μπι) with SiON through sputtering or CVD. The barrier film may also be a laminate of SiON/acrylic resin.

< Method for forming reflection preventing layer >

An AR coat (laminate of thin films of, for example, Cr, Ag, Au and Ni) was laminated through sputtering on the sealing film/substrate, to thereby form a 50-nm thick reflection preventing layer.

Through the above procedure, organic EL device 1 of Example 1 was obtained.

(Example 2)

The procedure of Example 1 was repeated, except that a light-extraction layer having fine concave and convex portions was formed as described below instead of the light-extraction layer containing scattering particles, to thereby fabricate organic EL device 2 having the layer structure as shown in Table 1 and Fig. 3.

< Method for forming light -extraction layer having fine concave and convex portions >

Through nanoimprinting, a light-extraction layer containing a heat-curable acrylic resin was deposited in the form of fine concave and convex portions on the optical path length adjusting layer formed similar to Example 1, followed by curing, to thereby form a light-extraction layer. The convex portions in the fine concave/convex portions were found to be densely arranged and have a columnar shape (height: 100 nm, diameter^ 100 nm and interval: 300 nm).

(Example 3)

The procedure of Example 1 was repeated, except that a

lowrefractive-index layer filled with material was formed as described below instead of the hollow lowrefractive-index layer, to thereby fabricate organic EL device 3 having the layer structure as shown in Table 1 and Fig. 3.

< Method for forming lowrefractive-index layer filled with material >

A composition containing the following component (for forming a lowrefractive-index layer filled with material) was prepared.

Fluorine -containing resin (polyhexafluoroisopropyl acrylate) (product of Sigma-Aldrich Co.)

Next, this lowrefractive-index layer composition was laminated with a spin coat method on the protective layer, followed by thermal curing, to thereby form 2,000-nm thick lowrefractive-index layer filled with material.

(Example 4)

The procedure of Example 3 was repeated, except that the light-extraction layer having fine concave and convex portions was formed as described above instead of the light-extraction layer containing scattering particles, to thereby fabricate organic EL device 4 having the layer structure as shown in Table 1 and Fig. 3.

(Example 5)

The procedure of Example 1 was repeated, except that the

lowrefractive-index layer was not formed, to thereby fabricate organic EL device

5 having the layer structure as shown in Table 1 and Fig. 3. (Example 6)

The procedure of Example 2 was repeated, except that the

low refractive-index layer was not formed, to thereby fabricate organic EL device 6 having the layer structure as shown in Table 1 and Fig. 3.

Table 1

(Example 7)

As a bottom-emission type organic EL device, organic EL device 7 was formed as described below so as to have the layer structure as shown in Table 2 and Fig. 4. In Table 2, the symbol "B" described in the row "Light-emitting direction" means that the organic EL devices obtained in Examples of Table 2 are so-called bottom-emission type organic EL devices. Also, the light-emitting direction corresponds to a top -to-bottom direction of the layer structure in Table 2. The other indications have the same meanings as in Table 1.

Specifically, similar to Example 1, a low-refractive-index layer, a gas barrier layer, a transparent electrode, an organic layer, a second electrode and a sealing protective layer were formed on a substrate for use in a bottom-emission type organic EL device. Then, a member consisiting of a sealing film substrate, a reflective layer, an optical path length adjusting layer and a light-extraction layer was bonded to the resultant product via a joining layer.

In the formation of this member, the reflective layer, the optical path length adjusting layer and the light-extraction layer were formed on the sealing film/substrate in the same manner as in Example 1. Thereafter, the joining layer was formed on the obtained product as described below.

< Method for forming joining layer >

A joining layer composition having the following components was prepared.

UV ray and heat-curable adhesive : 70 parts by mass (modified epoxy resin) (product of Nagase ChemteX Corporation)

Zr02 particles (particle diameter : 50 nm to 100 nm) (product of FURUCHI Co.): 30% by mass

Next, the joining layer composition having a refractive index (n = 1.7) was laminated on the light-extraction layer with a pressure lamination method, followed by irradiating with UV light for temporal adhesion, to thereby form a 2,000-nm thick joining layer.

The thus-formed joining layer was attached to the TFT substrate on which a low-refractive-index layer, a gas barrier layer, a transparent electrode, an organic compound layer, a second electrode and a sealing/protective layer had been formed similar to Example 1, followed by heating (curing) at 80°C for 1 hour.

Thereafter, in the same manner as in Example 1, a reflection preventing layer was formed on the formed organic EL substrate.

Through the above procedure, organic EL device 7 of Example 7 was obtained.

(Example 8)

The procedure of Example 7 was repeated, except that a light-extraction layer having concave and convex portions was formed as described above instead of the light-extraction layer containing scattering particles, to thereby form organic EL device 8 having the layer structure shown in Table 2 and Fig. 4.

(Example 9)

The procedure of Example 7 was repeated, except that a

lowrefractive-index layer filled with material was formed as described above instead of the hollow low-refractive -index layer, to thereby form organic EL device 9 shown in Table 2 and Fig. 4.

(Example 10)

The procedure of Example 9 was repeated, except that a light-extraction layer having concave and convex portions was formed as described above instead of the light-extraction layer containing scattering particles, to thereby form organic EL device 10 having the layer structure shown in Table 2 and Fig. 4.

(Example 11)

The procedure of Example 7 was repeated, except that the

low-refractive-index layer was not formed, to thereby form organic EL device 11 having the layer structure shown in Table 2 and Fig. 4. (Example 12)

The procedure of Example 8 was repeated, except that the

lowrefractive-index layer was not formed, to thereby form organic EL device 12 having the layer structure shown in Table 2 and Fig. 4.

Table 2

(Comparative Example l)

As a top -emission type organic EL device, comparative organic EL device 1 was formed as described below so as to have the layer structure as shown in Table 3. In Table 3, the symbol "T" described in the row "Light-emitting direction" means that the organic EL devices obtained in Comparative Examples of Table 3 are so-called top-emission type organic EL devices. Also, the light-emitting direction corresponds to a top-to-bottom direction of the layer structure in Table 3. The other indications have the same meanings as in Table 1.

The procedure of Example 1 was repeated, except that the optical path length adjusting layer and the light-extraction layer were not formed, to thereby form comparative organic EL device 1.

(Comparative Example 2)

The procedure of Example 1 was repeated, except that the optical path length adjusting layer and the lowrefractive-index layer were not formed, to thereby form comparative organic EL device 2 having the layer structure shown in Table 3.

(Comparative Example 3)

The procedure of Example 2 was repeated, except that the optical path length adjusting layer and the lowrefractive-index layer were not formed, to thereby form comparative organic EL device 3 having the layer structure shown in Table 3.

(Comparative Example 4)

The procedure of Example 1 was repeated, except that the optical path length adjusting layer was not formed and that a transparent electrode was formed on the organic compound layer instead of the semi-transparent electrode, to thereby form comparative organic EL device 4 having the layer structure shown in Table 3.

(Comparative Example 5) The procedure of Comparative Example 4 was repeated, except that a light-extraction layer having concave and convex portions was formed as described above instead of the light- extraction layer containing scattering particles, to thereby form comparative organic EL device 5 having the layer structrure shown in Table 3.

(Comparative Example 6)

The procedure of Comparative Example 4 was repeated, except that the low-refractive -index layer filled with material was formed instead of the hollow low-refractive-index layer, to thereby form comparative organic EL device 6 having the layer structure shown in Table 3.

(Comparative Example 7)

The procedure of Comparative Example 6 was repeated, except that a light-extraction layer having concave and convex portions was formed instead of the light -extraction layer containing scattering particles, to thereby form comparative organic EL device 7 having the layer structure shown in Table 3.

Table 3

(Comparative Example 8)

As a bottom-emission type organic EL device, comparative organic EL device 8 was formed as described below so as to have the layer structure as shown in Table 4. In Table 4, the symbol "B" described in the row "Light-emitting direction" means that the organic EL devices obtained in Comparative Examples of Table 4 are so-called bottom-emission type organic EL devices. Also, the light-emitting direction corresponds to a top -to-bottom direction of the layer structure in Table 4. The symbol "-" means that the corresponding layers are not provided. The other indications have the same meanings as in Table 1.

The procedure of Example 7 was repeated, except that the optical path length adjusting layer and the light-extraction layer were not formed and that a transparent electrode was formed instead of the semi-transparent electrode, to thereby form comparative organic EL device 8.

(Comparative Example 9)

The procedure of Example 7 was repeated, except that the optical path length adjusting layer was not formed and that a transparent electrode was formed instead of the semi-transparent electrode, to thereby form comparative organic EL device 9 having the layer structure shown in Table 4.

(Comparative Example 10)

The procedure of Comparative Example 9 was repeated, except that a light-extraction layer having concave and convex portions was formed as described above instead of the light-extraction layer containing scattering particles, to thereby form comparative organic EL device 10 having the layer structure shown in Table 4.

(Comparative Example 11)

The procedure of Comparative Example 9 was repeated, except that a low-refractive -index layer filled with material was formed instead of the hollow low-refractive-index layer, to thereby form comparative organic EL device 11 having the layer structure shown in Table 4.

(Comparative Example 12)

The procedure of Comparative Example 11 was repeated, except that a light-extraction layer having concave and convex portions was formed as described above instead of the light-extraction layer containing scattering particles, to thereby form comparative organic EL device 12 having the layer structure shown in Table 4.

Table 4

< Evaluation method >

« Evaluation regarding viewing angle »

(1) Brightness at 45°

Each of the above -obtained devices was measured with a radiation brightness meter (CS-1000, product of Konica Minolta Co.) for front brightness (cd/m²) (angle 0°) and oblique brightness (angle 45° (up/down or right/left) with respect to the front) at the light-emitted surface. Then, the ratio of the oblique brightness (angle 45°) to the front brightness (angle 0°) was calculated.

(2) Difference in chromaticity

Using the above radiation brightness meter, chromaticities viewed from the front (0°) and at 45° were measured, and the difference therebetween (AU'V) was calculated.

«< Overall evaluation regarding viewing angle »>

The results obtained in (l) and (2) above were evaluated on the basis of the following criteria.

- (l) Viewing angle 45° -

A: The ratio of the oblique brightness (angle 45°) to the front brightness (angle 0°) was 60% or higher

B^" The ratio of the oblique brightness (angle 45°) to the front brightness (angle 0°) was lower than 60%

- (2) Difference in chromaticity - A-- AU'V was 0.02 or lower

B: AU'V was higer than 0.02

- Overall evaluation -

A: Evaluations in both (l) and (2) were A

B- Evaluation in either (l) or (2) was B

C: Evaluations in both (l) and (2) were B

« Light-extraction effect » Each of the obtained devices was measured with a radiation brightness meter (CS-1000, product of Konica Minolta Co.) for front brightness (cd/m²) at the light-emitted surface. Similarly, the device containing no light-extraction structure was measured for front brightness. Then, the ratio of the former front brightness to the latter front brightness (regarded as 1.0) was calculated.

Table 5

Table 6

Industrial Applicability

The organic EL device optical member of the present invention can be suitably used in display devices based on organic electroluminescence (EL).

The organic EL device of the present invention realizes high-definition, full-color display, and thus, can be suitably used in a variety of applicaiotns such as cell phone displays, personal digital assistants (PDAs), computer displays, vehicle's information displays, TV monitors and common lights.

Reference Signs List

10: Organic EL device optical member

12: Optical path length adjusting layer

14: Light -extraction layer

16: Reflective layer

22: Electrode

24: High-refractive-index smooth layer

25: Joining layer 26: Substrate

28: Gas barrier layer

100: Organic EL device

102: Light-emitting layer 104: Low-refractive-index layer 106'· Barrier film substrate 122: Electrode

124: Protective layer

126: Reflection preventing layer

Claims

1. An organic EL device optical member used in an organic EL device containing a light-emitting layer, the organic EL device optical member

comprising:

a reflective layer which reflects light emitted from the light-emitting layer, a light-extraction layer which extracts the light emitted from the light-emitting layer, and

2. The organic EL device optical member according to claim 1, further comprising an electrode located in a light-emitting direction from the

light-extraction layer.

3. The organic EL device optical member according to one of claims 1 and 2, further comprising a substrate such that the reflective layer is located between the substrate and the light-extraction layer.

4. An organic EL device comprising^

the organic EL device optical member according to any one of claims 1 to 3.

5. The organic EL device according to claim 4, further comprising a first substrate, a pair of electrodes, and a light -emitting layer disposed between the electrodes,

wherien the light-emitting layer is located in the light-emitting direction of the organic EL device from the light-extraction layer.

6. The organic EL device according to one of claims 4 and 5, wherein the thickness of the optical path length adjusting layer is varied in individual pixels.

7. The organic EL device according to any one of claims 4 to 6, further comprising a second substrate such that the reflective layer is located between the second substrate and the light-extraction layer.

8. The organic EL device according to claim 7, wherein the second substrate is a barrier film substrate.

9. The organic EL device according to any one of claims 4 to 8, further comprising a lowrefractive-index layer located in the light-emitting direction from the light-emitting layer.

10. The organic EL device according to any one of claims 4 to 9, wherein the organic EL device is of top-emission type.

11. The organic EL device according to any one of claims 4 to 9, wherein the organic EL device is of bottom-emission type.