WO2011030882A1

WO2011030882A1 - Color filter and light-emitting display element

Info

Publication number: WO2011030882A1
Application number: PCT/JP2010/065681
Authority: WO
Inventors: Yosuke Takeuchi; Seiji Yamashita
Original assignee: Fujifilm Corporation
Priority date: 2009-09-14
Filing date: 2010-09-06
Publication date: 2011-03-17
Also published as: JP2011059611A; JP5473506B2

Abstract

A color filter for use in a light-emitting display element which emits at least white light, the color filter including a circularly polarizing layer, wherein the circularly polarizing layer is formed only in an optical path of the white light.

Description

DESCRIPTION

Title of Invention

COLOR FILTER AND LIGHT-EMITTING DISPLAY ELEMENT Technical Field

The present invention relates to a color filter for use in a light-emitting display element which emits white Ught, and a light-emitting display element containing the color filter.

Background Art

Light-emitting display elements such as organic EL elements display full-color images employing, for example, a so-called RGB method. In this RGB method, white Ught for white color display is synthesized after color lights emitted from light-emitting layers corresponding to R pixels, G pixels and B pixels are divided once through color filters. Thus, some of light emitted from the light-emitting layers is dampened by the color filters, which requires more electricity for maintaining the brightness of white light. In order to solve this problem, PTL 1 discloses a method in which full-color images are displayed using four pixels of R, G, B and W (white). In this method, unlike the above RGB method, white light is obtained with no use of a color filter; i.e., white light is directly emitted from light-emitting layers that emit white Ught. Therefore, white Ught can be emitted without being dampened by the color filter.

However, in the light-emitting display element emitting white light, external Ught enters the element through the optical path of white light, is reflected inside the element, and then is emitted again to the outside through the optical path of white light. As a result, display performances are adversely affected to cause problematic phenomena such as glare of outside views, and a decrease in contrast.

In order to solve this problem, PTL 2 discloses an organic EL element including a film substrate having an organic EL film laminated on one surface of the film substrate and a linearly polarizing plate provided on the other surface of the film substrate, wherein the film substrate serves also as a 1/4 wavelength plate. With this structure, the number of layers through which light passes to be emitted outside of the element becomes smaller than in conventional structures. Thus, light scattering at the interfaces between the layers is reduced to shield reflected light more reliably.

However, in this structure, the linearly polarizing plate and the 1/4 wavelength plate are provided not only in the optical path of white light but also in the optical paths of red, blue and green lights. Since the linearly polarizing plate is provided in the optical paths of red, blue and green lights, light transmittance is decreased to about 50% due to the presence of the linearly polarizing plate, problematically decreasing light use efficiency of the element.

Citation List

Patent Literature

PTLl: Japanese Patent Application Laid-Open (JP-A) No. 2003-178875 PTL2: JP-A No. 2001-076865

Summary of Invention Technical Problem

The present invention aims to provide a color filter which prevents a decrease in light use efficiency and a decrease in contrast caused as a result of reflection of external light, and a light-emitting display element containing the color filter.

Solution to Problem

The present inventors conducted extensive studies to achieve the above objects, and have found that the above problems can be solved by forming a circularly polarizing layer only in the optical path through which white light passes. The present invention has been completed on the basis of the finding.

< 1 > A color filter for use in a light-emitting display element which emits at least white light, the color filter including:

a circularly polarizing layer,

wherein the circularly polarizing layer is formed only in an optical path of the white light.

< 2 > The color filter according to < 1 > above, wherein the circularly polarizing layer comprises a polarizing layer and a 1/4 wavelength layer.

< 3 > The color filter according to one of < 1 > and < 2 > above, wherein the color filter includes a support, and the support is a transparent support.

< 4 > The color filter according to < 3 > above, wherein the support is the 1/4 wavelength layer.

< 5 > A light-emitting display element including^

the color filter according to any one of < 1 > to < 4 > above, and a light-emitting layer which emits at least white light. < 6 > The light-emitting display element according to < 5 > above, wherein the light-emitting display element has an optical resonator structure.

< 7 > The light-emitting display element according to one of < 5 > and < 6 > above, wherein the light-emitting layer comprises at least one

phosphorescent light-emitting material.

Advantageous Effects of Invention

The present invention can provide a color filter which prevents a decrease in light use efficiency and a decrease in contrast caused as a result of reflection of external light, and a hght- emitting display element containing the color filter. These can solve the problems pertinent in the art and achieve the above objects.

Brief Description of Drawings

Fig. 1 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 2 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 3 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 4 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 5 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 6 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 7 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 8 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 9 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 10 is a cross-sectional view of one embodiment of a color filter of the present invention.

Fig. 11 is a cross- sectional view of one embodiment of a color filter of the present invention.

Fig. 12 is a cross-sectional view of one embodiment of a light-emitting display element of the present invention.

Fig. 13 is a cross-sectional view of one embodiment of a light-emitting display element of the present invention.

Description of Embodiments

(Color filter)

A color filter of the present invention includes a circularly polarizing layer formed only in the optical path of white light emitted from a

light-emitting display element; and, if necessary, includes other members.

The shape of the color filter may be appropriately determined depending on the structure of the belowdescribred light-emitting display element. For example, the color filter may be a film or layer.

The structure of the color filter is not particularly limited, so long as a circularly polarizing layer is formed, as described above, only in the optical path of white light emitted from a light-emitting display element, and may be appropriately determined depending on the intended purpose. Exemplary structures of the color filter will be described with reference to the drawings.

Each of Figs. 1 to 6 is a cross-sectional view of one embodiment of the color filter of the present invention. A color filter 1 includes a circularly polarizing layer 16 composed, for example, of a 1/4 wavelength layer 14 and a polarizing layer 12. The color filter 1 also includes a filter layer 18 which transmits light having a desired wavelength among lights emitted from the light-emitting display element. Notably, in Figs. 1 to 6, each arrow indicates a direction in which light is emitted from the light-emitting display element.

The circularly polarizing layer 16 may have any structure so long as it is formed in the optical path through which white light travels in the color filter. For example, as illustrated in Figs. 1 and 3, the 1/4 wavelength layer 14 may be formed on the entire surface of the filter layer 18, and the polarizing layer 12 may be formed on a part of the filter layer 18, the part being present above the light-emitted surface of a white filter portion 18w through which white light passes. Also, as in the circularly polarizing layer 16 illustrated in Fig. 2, the 1/4 wavelength layer 14 may be formed on a support 22, and the polarizing layer 12 may be formed on a part of the 1/4 wavelength layer 14, the part being present above the light-emitted surface of the white filter portion 18w (through which white light passes) in the filter layer 18. Furthermore, as in the circularly polarizing layer 16 illustrated in Fig. 6, the 1/4 wavelength layer 14 may be formed at the light-emitting display element side of the color filter, and the polarizing layer 12 may be formed at the side opposite to the light-emitting display element side (i.e., the upper surface of the filter layer 18 in Fig. 6).

In addition, as in the circularly polarizing layer 16 illustrated in Figs. 4 and 5, the 1/4 wavelength layer 14 may be formed only on the light-emitted surface of the white filter portion 18w (through which white light passes) in the filter layer 18, and the polarizing layer 12 may be formed on the 1/4 wavelength layer 14. Further, as illustrated in Fig. 5, the circularly polarizing layer 16 may be formed on a support 22 on the light-emitted surface of the white filter portion 18w (through which white light passes) in the filter layer 18. Also, as in the circularly polarizing layer 16 illustrated in Figs. 6 and 7 to 11, the polarizing layer 12 and the 1/4 wavelength layer 14 may be placed so as to sandwich the filter layer 18.

< Circularly polarizing layer >

In the present invention, the circularly polarizing layer is not

particularly limited, so long as it transmits light having entered the color filter from outside (hereinafter the light may be referred to as "external light") and, after the transmitted light is reflected on a reflective plate and enters again the color filter, prevents the thus-reflected light from being emitted outside of the color filter, and may be appropriately selected depending on the intended purpose. For example, the circularly polarizing layer may have a 1/4 wavelength layer and a polarizing layer which transmits a linearly polarized light only. With this structure, among external light entering the color filter, some linearly polarized light vibrating in a predetermined direction (i.e., in such a vibration direction that be allowed to transmit the polarizing layer) transmits the polarizing layer. After that, the linearly polarized light passes through the 1/4 wavelength layer to become a circularly polarized light after the slow axis of the linearly polarized light shifts by 1/4 of the wavelength (i.e., by 90°) with respect to the fast axis thereof. The circularly polarized light is reflected on a reflective member in the light-emitting display element (e.g., an electrode disposed on the light-emitting layer in the element) and then, becomes a circularly polarized light whose rotating direction has been reversed and which travels in the opposite direction to the direction in which the linearly polarized light enters the 1/4 wavelength layer. The circularly polarized bight whose rotating direction has been reversed enters again the 1/4 wavelength layer to become a linearly polarized light whose polarization direction is different by 90° from the initial linearly polarized light. The linearly polarized light whose polarization direction has shifted by 90° cannot transmit the above polarizing layer. As a result, the external light having entered the color filter is not emitted from the color filter, preventing reflection of the external light.

- Polarizing layer -

The polarizing layer is not particularly limited, so long as it may be a layer which changes bight vibrating in any direction (e.g., natural light) to a linearly polarized light, and may be appropriately selected depending on the intended purpose. Preferred examples of the polarizing layer include iodine-based polarizing plates, dye-based polarizing plates containing a dichroic material, and polyene-based polarizing plates. Among these polarizing plates, iodine-based polarizing plates and dye-based polarizing plates can be generally produced by stretching a polyvinyl alcohol film and adsorbing iodine or the dichroic material on the film. In this case, the polarization axis of the polarizing layer is perpendicular to the stretching direction of the film.

- 1/4 wavelength layer - The 1/4 wavelength layer is not particularly limited, so long as it can adjust a difference in optical path between ordinary rays and extraordinary rays to 1/4 of the wavelength of an incident light, and may be appropriately selected depending on the intended purpose. The 1/4 wavelength layer may be made of a material having birefringence anisotropy such as a uniaxially stretched polymer film.

< Filter layer >

The color filter of the present invention includes a filter layer 18 which transmits light having a desired wavelength among lights emitted from the light-emitting display element. The shape of the filter layer 18 may be appropriately selected depending on the shape of the color filter. The structure of the filter layer 18 may be appropriately selected depending on the intended purpose, so long as the filter layer can transmit white Ught emitted from the light-emitting display element and emit light having a desired wavelength among lights emitted from the light-emitting display element. The filter layer may have a white filter portion 18w which transmits white light emitted from the light-emitting display element. The filter layer 18 may additionally have a blue filter portion 18b, a green filter portion 18g and a red filter portion 18r which respectively transmit blue Ught, green light and red light among lights emitted from the light-emitting display element.

< Other members >

« Support »

The color filter of the present invention may have a support for the purpose of increasing the strength of the color filter. The support is not particularly limited, so long as it does not adversely affect the optical characteristics of the color filter. The support may be, for example, a transparent support which is optically inactive. Also, the support may be those having the functions of the above-described 1/4 wavelength layer, in order for the support to change a linearly polarized light to a circularly polarized light. Use of such a support can simplify the structure of the color filter.

The material for the support is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include inorganic materials such as glass and metal oxides; and organic materials excellent in resistance to an organic solvent, such as polyesters (e.g., polyethylene terephthalates and polyethylene naphthalates), polyolefins (e.g., polyethylenes and polyp ropylenes), polyamides, polyethers, polystyrenes, polyesteramides, polycarbonates, polyphenylene sulfides, polyether esters, polyvinyl chlorides, polyacrylic acid esters, polymethacrylic acid esters, polyether ketones and polyethylene fluorides. The thickness of the support is not particularly limited, so long as the support has a commonly used thickness, and may be appropriately determined depending on the intended purpose. For example, the thickness thereof is preferably 10 μπι to 1 cm.

- Production method of color filter -

A method for producing the color filter is not particularly limited, so long as the method can produce a color filter having the above -described structure, and may be appropriately selected depending on the intended purpose. In one employable method, as illustrated in Figs. 1 and 2, the 1/4 wavelength layer 14 is laminated on the filter layer 18 on the support 22 or laminated on the support 22 on the filter layer 18, which is composed of the white filter portion 18w, the red filter portion 18r, the green filter portion 18g and the blue filter portion 18b, and then the polarizing layer 12 is properly laminated only in the optical path through which white light travels. In another employable method, as illustrated in Fig. 3, the 1/4 wavelength layer 14 is laminated on the filter layer 18, and then the polarizing layer 12 is properly laminated only in the optical path through which white light travels. In still another employable method, as illustrated in Figs. 4 and 5, the 1/4 wavelength layer 14 and the polarizing layer 12 are laminated on the filter layer 18 on the support 22 or the support 22 on the filter layer 18 so that these layers are fomed only in the optical path through which white light travels. In yet another employable method, the support 22, the 1/4 wavelength layer 14 and the filter layer 18 are laminated, and then the polarizing layer 12 is fomed only in the optical path through which white light travels.

The proper method for laminating the polarizing layer 12 and/or the 1/4 wavelength layer 14 is not particularly limited, so long as the above-described layer structure can be obtained, and may be appropriately selected depending on the intended purpose. In one employable method, the polarizing layer 12 and/or the 1/4 wavelength layer 14 is cut so as to have such a slit shape that is disposed in the optical path of white light emitted from the light-emitting display element, and then the patterned layer is disposed in the optical path of white light emitted from the light-emitting display element. In another employable method, the polarizing layer 12 and/or the 1/4 wavelength layer 14 is patterned so as to have such a shape that is disposed in the optical path of white light emitted from the light-emitting display element, and then the cut layer is disposed in the optical path of white light. In still another employable method, the polarizing layer 12 and/or the 1/4 wavelength layer 14 is disposed by an imprint method through patterning using a wire grid. In yet another employable method, an orientation layer is disposed at a position where the polarizing layer 12 and/or the 1/4 wavelength layer 14 is to be formed, and a dichroic dye or other materials for the polarizing layer 12 and/or the 1/4 wavelength layer 14 is applied to the orientation layer by, for example, an inkjet method. In even another employable method, a photo- orientable orientation film is provided at a position corresponding to the white filter portion 18w of the filter layer 18, followed by photo-orientating, and liquid crystal materials are directly injected and oriented so as to have properties of the polarizing layer 12 and/or the 1/4 wavelength layer 14.

(Light-emitting display element)

A light-emitting display element of the present invention includes the color filter of the present invention and a light-emitting layer which emits at least white light; and, if necessary, includes other members.

Each of Figs. 12 and 13 is a cross-sectional view of one embodiment of the light-emitting display element of the present invention. A nght-emitting display element 100 includes the above-described color filter 1 of the present invention, and a light-emitting layer 106 emitting at least white light and disposed between a pair of electrodes (a cathode 102 and an anode 104).

Notably, in Figs. 12 and 13, each arrow indicates a direction in which light is emitted from the light-emitting layer 106. In Figs. 12 and 13, the space between the color filter 1 and a substrate 114 or the cathode 102 means that a layer structure in the space is not particularly limited and, if necessary, appropriate members may be disposed in the space.

The light-emitting display element of the present invention may have an optical resonator structure (light resonance structure) in which light emitted from the light-emitting layer is optically resonated as a result of repetitive reflection/interference. The optical resonator structure is not particularly limited, so long as light emitted from the light-emitting layer can be repeatedly reflected/interfered, and may be appropriately selected depending on the intended purpose. For example, in the Ught-emitting display element 100 illustrated in Figs. 12 and 13, a semi-transparent cathode 102, a light-emitting layer 106 and a reflective layer 112 are provided between the color filter 1 and a flattening layer 116 so that the semi-transparent cathode, the light-emitting layer and the reflective layer are disposed in this order from the side of the color filter 1, to thereby form a light resonance structure between the cathode 102 and the reflective layer 112. With this structure, the color intensity is increased by virtue of multiplex interference. Thus, provision of this structure enables the light-emitting display element to exhibit high light intensity.

Notably, in the light-emitting display element 100 illustrated in Figs. 12 and 13, reference numeral 114 denotes a substrate such as a glass substrate, reference numeral 108 denotes an optical path length adjusting layer which adjusts the optical path length in each pixel, reference numeral 110 denotes an insulative layer which electrically insulates each pixel, and reference numeral 118 denotes a TFT.

< Light-emitting layer >

The light-emitting layer is not particularly limited, so long as it emits white light when an electrical field is applied, and may be appropriately selected depending on the intended purpose. The structure of the

light-emitting layer is not particularly limited, so long as the light-emitting layer emits white light. The light-emitting layer may have layers all of which emit white light. Alternatively, the light-emitting layer may have layers emitting white light as well as layers emitting blue light, green light and/or red light. Notably, the light-emitting display device illustrated in Fig. 12 contains a single light-emitting layer, but the present invention encompasses

light-emitting display devices containing layers emitting white, blue, green and red lights disposed along the light-emitted sureface of the light-emitting layer.

The relationship in position between the light-emitting layer and the color filter is not particularly Umited, so long as the circularly polarizing layer is disposed only in the optical path of white light emitted from the light-emitting layer, and may be appropriately determined depending on the intended purpose. When all the light-emitting layers emit white light, the circularly polarizing layer 16 of the color filter 1 may be disposed above the light-emitting layer, since white light is emitted from the entire light-emitted surface of the light-emitting layers. In the case where the layer emitting white light as well as the layer(s) emitting blue light, green light and/or red light are provided along the light-emitted surface of the light-emitting layer, the circularly polarizing layer may be formed in the optical path of white light emitted from the light-emitting layer.

The material for the light-emitting layer may be an organic

light-emitting material or an inorganic light-emitting material. In particular, an organic light-emitting material is preferred, since various hues can be selected and required drive voltage is low. Next, description will be given with respect to an organic compound layer having a light-emitting layer made of an 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 light-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 light-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 light-emitting display element 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 light-emitting display element 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 hght-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 intended 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 intended 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 intended 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, International Publication Nos. WO00/57676, WO00/70655, WO01/08230, WO01/39234A2, WO01/41512A1, WO02/02714A2, WO02/15645A1, WO02/44189A1 and 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, Ught-emission efficiency, drive durability and color purity.

The fluorescence luminescent dopant is not particularly limited and may be appropriately selected depending on the intended 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-quinolinol, pyromethene complexes and rare-earth complexes), polymer compounds (e.g., polythiophene, polyphenylene and polyphenylenevinylene), organic silanes and derivatives thereof.

Specific examples of the luminescent dopants include the following compounds, which should be construed as limiting the present invention thereto.

21

D-27 D-28

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 hght-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.

The thickness of the light-emitting layer is not particularly limited and may be appropriately determined depending on the intended purpose. It is preferably 2 nm to 500 nm. 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, pyrazoline, 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.

Specific examples of the electron transporting host include pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole, oxazole, oxadiazole, fluorenone, anthraquinonedime thane, anthrone, diphenylquinone,

thiopyrandioxide, carbodiimide, fluorenylidenemethane, 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-quinolinol 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 intended purpose. For example, it is preferably a beryUium 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 OZTTOi 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 trie thoxy siloxy group and a

triisopropylsiloxy group); aromatic hydrocarbon anion ligands (those having 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 low-molecular-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 light-emitting display element. 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, nvdinitrobenzene, o-dinitrobenzene, 1,4-naphthoquinone, 2,3-dichloronaphthoquinone,

1,3-dinitronaphthalene, 1,5-dinitronaphthalene, 9, 10-anthraquinone,

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 tetrafluorotetracyanoquinodime thane.

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

lowmolecular-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 light-emitting display element 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 hght-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 FeCl₃), 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 and may be appropriately selected depending on the intended purpose. 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 CaF^ 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.

- Electrode -

The electrode is not particularly limited, so long as it can apply an electrical field to the light-emitting layer. Depending on the position in the light-emitting display element, the electrode may be appropriately selected from a transparent anode, a transparent cathode, a semi-transparent anode, a semi-transparent cathode, a light-transmissive anode, a light-transmissive cathode, a light-intransmissive anode and a light-intransmissive cathode. For example, a transparent electrode may be used as an electrode located in the light-emitting direction from the light-emitting layer of the light-emitting display element.

- 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 light-emitting display element. 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 polypyrrole; 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 light-emitting display element. 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 μπι, preferably 50 nm to 20 μπι.

The resistance of the anode is preferably 10³ Ω/square or less, more preferably 10² Ω/square 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 hght transmittance of 60% or higher, more preferably 70% or higher.

Concerning transparent anodes, there is a detail description in

" TOUMEI DOUDEN-MAKU NO SHINTENKA1 (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 light-emitting display element.

The material for the cathode is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof 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., Uthium -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 suitabiUty 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 Umited, 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 alkaU or alkaUne 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 μπι, and preferably 50 nm to 1 μπι.

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. < Reflective layer >

In the present invention, the reflective layer is not particularly limited, so long as it reflects light emitted from the light-emitting layer, and may be appropriately selected depending on the intended purpose. The shape, structure and size of the reflective layer may be determined depending on the intended purpose. The thickness of the reflective layer is preferably 300 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 the light-emitting display element. When the below-described substrate is provided, the reflective layer may be disposed between the substrate and the light-emitting layer.

The material for the reflective layer is not particularly limited, so long as it can reflect light emitted from the light-emitting layer. Examples of the material employable include those having a reflectance of 70% or higher with respect to the emitted light. Specific examples of the material for the reflective layer include metals such as Al, Ag and Ni.

< Substrate >

The light-emitting display element of the present invention may contain a substrate for the purposes of ensuring the strength of the light-emitting display element and protecting the light-emitting display element from hazardous materials derived from the environment. The shape, structure, size, etc. of the substrate may be appropriately determined, so long as the above purposes can be achieved. 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 and may be appropriately determined depending on the intended purpose. Preferably, the substrate is disposed at the outermost position of the light-emitting display element from the viewpoint of shielding hazardous materials derived from the environment.

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-stabihzed 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 members >

The light-emitting display element of the present invention may appropriately contain other members known in the art depending on the intended purpose. Examples of the other members include a light-extraction layer which emits light emitted from the light-emitting layer toward the outside of the light-emitting display element, an optical path length-adjusting layer which adjusts the optical path length of light emitted from the light-emitting layer, a gas barrier layer which prevents permeation of air and moisture to the light-emitting display element, a protective layer which protects the members of the light-emitting display element from physical/chemical external forces, and an anti-reflecting layer which prevents reflection of light outside and/or inside of the light-emitting display element.

Examples The present invention will next be described in detail by way of

Examples and Comparative Examples given below, but should not be construed as being limited to Examples.

(Example 1)

< Fabrication of RGBW color filters >

Black color resist CK-8400 (product of FUJIFILM Electronics Materials Co., Ltd.) was applied by a spin coater onto a glass substrate for fabricating a color filter so as to have a thickness (after drying) of 1.0 μπι, followed by drying at 120°C for 2 min, to thereby form a uniform black coating film.

Next, using an exposing device, the resultant coating film was irradiated through a 100 μπι-thick mask with light having a wavelength of 365 nm at an exposure dose of 300 mJ/cm². After irradiation, the exposed film was developed with a developer of 10% CD-I (product of FUJIFILM Electronics Materials Co., Ltd.) at 26°C for 90 sec. Subsequently, the developed film was rinsed with running water for 20 sec, dried with an air knife, and thermally treated at 220°C for 60 min, to thereby form a black matrix pattern (image).

Next, the following three color curable compositions were dispersed with a sand mill for one day. Notably, the green color dispersion liquid may be referred to as dispersion liquid (A-l), the red color dispersion liquid as dispersion liquid (A-2), and the blue color dispersion liquid as dispersion liquid (A-3).

[Green color: Dispersion liquid (A-l)]

Benzy methacrylate/methacrylic acid copolymer: 80 parts by mass

(weight average molecular weight- 30,000, acid value^'- 120 mgKOH/g)

Propylene glycol monomethyl ether acetate: 500 parts by mass Copper phthalocyanine pigment: 33 parts by mass

C. I. Pigment Yellow 185: 67 parts by mass

[Red color: Dispersion liquid (A-2)]

Benzy methacrylate/methacrylic acid copolymer: 80 parts by mass

(weight average molecular weight: 30,000, acid value: 120 mgKOH/g)

Propylene glycol monomethyl ether acetate: 500 parts by mass

C. I. Pigment Red 254: 50 parts by mass

C. I. Pigment Red PR177: 50 parts by mass

[Blue color: Dispersion liquid (A- 3)]

Benzy methacrylate/methacrylic acid copolymer: 80 parts by mass

(weight average molecular weight: 30,000, acid value: 120 mgKOH/g)

Propylene glycol monomethyl ether acetate: 500 parts by mass

C. I. Pigment Blue 15:6: 95 parts by mass

C. I. Pigment Violet 23: 5 parts by mass

Next, the following components were added to 60 parts by mass of each of the above color curable compositions (i.e., dispersion liquids (A-l), (A-2) and (A- 3)), to thereby obtain compositions of every color.

Dipentaerythritol hexaacrylate (DPHA): 80 parts by mass

4-[o-Bromo-p-N,N-di(ethoxycarbonyl)aminophenyl]2,

6- di(trichloromethyl)^_S-triazine: 5 parts by mass

7- [{4-Chloro-6'(diethylamino)-S-triazin-2-yl}amino] -3-phenylcoumalin: 2 parts by mass

Hydroquinone monomethyl ether: 0.01 parts by mass

Propylene glycol monomethyl ether acetate: 500 parts by mass

The above-prepared compositions for each color were homogeneously mixed and then filtrated with a filter having a pore size of 5 μιη, to thereby obtain three color curable compositions of the present invention. Of these, the green curable composition was applied by a spin coater onto the glass substrate, on which the black matrix had been formed, so as to have a thickness (after drying) of 1.0 μπι, followed by drying at 120°C for 2 min, to thereby form a uniform green coating film.

Next, using an exposing device, the resultant coating film was irradiated through a 100 μπι-thick mask with light having a wavelength of 365 nm at an exposure dose of 300 mJ/cm². After irradiation, the exposed film was developed with a developer of 10% CD-I (product of FUJIFILM Electronics Materials Co., Ltd.) at 26°C for 60 sec. Subsequently, the developed film was rinsed with running water for 20 sec, dried with an air knife, and thermally treated at 220°C for 60 min, to thereby form a patterned green image (green pixels). In the same manner as in the green curable composition, each of the red curable composition and the blue curable composition was applied to the same glass substrate, to thereby sequentially form a patterned red image (red pixels) and a patterned blue image (blue pixels).

Subsequently, a polarizing plate (TS polarizing film: 43781-K, product of Edmont Optics Japan) was cut so as to have a size of a white pixel in the formed patterned image. The cut polarizing plate was attached to the white pixel with a UV-ray curable adhesive (XNR5516HV, product of Nagase-Chiba Co.).

Furthermore, a phase difference film (a 1/4λ phase difference film:

27344K, product of Edmont Optics Japan) was attached to the entire back surface of the glass substrate with a UV-ray curable adhesive (XNR5516HV, product of Nagase-Chiba Co.) so that an angle of 45° was formed between the transmission axis of the polarizing plate and the slow axis of the phase difference film, to thereby fabricate color filter 1 of the present invention.

< Fabrication of EL element >

An indium tin oxide (ITO) transparent conductive film (thickness: 150 nm) (product of GEOMATEC Corporaiton) on a glass substrate having TFTs was patterned through photolithography and hydrochloric acid etching, to thereby form an anode.

The thus-patterned ITO substrate was washed through ultrasonication in acetone, washed with pure water, and washed through ultrasonication in isopropyl alcohol. The washed substrate was dried by nitrogen blow, and finally washed through UV-ozone washing. The thus-treated substrated was placed in a vacuum vapor-deposition apparatus, and then, the vacuum vapor-deposition apparatus was evacuated.

Subsequently, 4,4'-bis[N-(l-naphthyl)-N-phenylamino]biphenyl (a-NPD) was heated in the vacuum vapor-deposition apparatus so as to be

vapor-deposited at a deposition rate of 0.2 nm/sec, to thereby form a 40 nnvthick hole transport layer.

Subsequently, the following host material, blue light-emitting material, green light-emitting material and red light-emitting material (i.e., the materials for forming a light -emitting layer) were heated and co-deposited simultaneously on the formed hole transport layer for forming light-emitting layers.

Host materials:

4,4'-N,N'-Dicarbazole-biphenyl (CBP)

Blur light-emitting materials : Iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2]picolinate (Firpic)

Green light-emitting material:

Tris(2-phenylpyridine)iridium (Ir(ppy)3)

Red light-emitting material:

Dopant A given below

Notably, in the co- deposition, the deposition rate of CBP was adjusted to be 0.2 nm/sec. Also, the amount of Firpic was adjusted to be 1.5% by mass, Ir(ppy)3 0.5% by mass and Dopant A 0.5% by mass. The light-emitting layer laminated on the hole transport layer was 30 nm.

Furthermore, aluminum(III) bis(2-methyl-8-quinolinato)-4-phenyl phenolate (BAlq) was deposited on the light-emitting layer at a deposition rate of 0.1 nm sec, to thereby form an electron transport layer having a thickness of 30 nm.

Thereafter, lithium fluoride (LiF) was deposited on the electron transport layer at a deposition rate of 0.1 nm/sec, to thereby form an electron injection layer having a thickness of 1 nm. In addition, aluminum was deposited on the electron injection layer at a deposition rate of 0.5 nm/sec, to thereby form a cathode having a thickness of 150 nm.

Also, an aluminum lead wire was connected to the anode and the cathode. Notably, during vapor deposition, the layer thickness was monitored with a crystal oscillation-type deposition controller so as to obtain a desired layer thickness.

Without being exposed to air, the obtained laminate was placed in a glove box which had been purged with nitrogen gas. Separately, in the glove box, a water absorber (product of SAES Getters Co.) was attached to a glass sealing cover having concave portions in the inner wall. The laminate was sealed by this sealing cover with a UV-ray curable adhesive (XNR5516HV, product of Nagase-Chiba Co.).

Through the above procedure, an organic EL element of Example 1 was fabricated.

The above-fabricated color filter and the EL element were joined with each other with a UV-ray curable adhesive (XNR5516HV, product of

Nagase-Chiba Co.) so that the color filter was disposed at the side where light emitted from the EL element was emitted to the outside, to thereby fabricate light-emitting display element 1 of the present invention.

(Example 2)

A phase difference film (a 1/4λ phase difference film: 27344K, product of Edmont Optics Japan) was attached with a UV-ray curable adhesive

(XNR5516HV, product of Nagase-Chiba Co.) to the entire surface of RGBW pixels of an organic EL which had been formed in the same manner as in Example 1. After that, a polarizing plate (TS polarizing film: 43781-K, product of Edmont Optics Japan) was cut so as to have a size of a white pixel in the patterned RGBW pixel image. The cut polarizing plate was attached to the white pixel with a UV-ray curable adhesive (XNR5516HV, product of

Nagase-Chiba Co.) so that an angle of 45° was formed between the transmission axis of the polarizing plate and the slow axis of the phase difference film. The other treatments were performed similar to Example 1, to thereby fabricate color filter 2 and light-emitting display element 2 of the present invention. (Comparative Example 1)

The procedure of Example 1 was repeated, except that no polarizing plate was formed, to thereby fabricate comparative color filter 1 and

comparative light-emitting display element 1.

(Comparative Example 2)

The procedure of Example 1 was repeated, except that the polarizing plate was attached to the entirety of a patterned image instead of to the white pixels, to thereby fabricate comparative color filter 2 and comparative light-emitting display element 2.

(Comparative Example 3)

The procedure of Example 1 was repeated, except that no color filter was provided, to thereby fabricate comparative light-emitting display element 3.

(Example 3)

< Fabrication of EL element >

(l) Through vacuum film formation, a 100 nm-thick aluminum (Al) layer (serving as a light-reflective layer) patterned correspondingly to R, G, B and W subpixels was formed on a glass substrate having TFTs. (2) Through ion plating, SiON was laminated on the light-reflective layer of the R, G, B, and W subpixels (i.e., 120 nm in R subpixel, 70 nm in G subpixel, 30 nm in B subpixel, and 2,200 nm in W subpixel), to thereby form optical path length-adjusting layers of a transparent insulative material.

(3) Transparent electrodes (ITO, thickness : 60 nm) were formed through patterning in the optical path length-adjusting layers of the subpixels. Each transparent electrode was conductively connected to the electrode of each TFT through a contact hole provided in the optical path length-adjusting layer and the reflective layer.

(4) Light-emitting portions were covered with a metal cover, and light non-emitting portions were covered with an insulative layer.

(5) Through vacuum vapor deposition, a light-emitting layer (white color light-emitting electrical field) and a semi-transmissive reflective electrode were formed as follows on the transparent electrodes of the R, G, B and W subpixels. < Light-emitting layer >

A 40 nm-thick hole-injection layer was formed by co-depositing

4,4',4"-tris(2-naphthylphenylamino)triphenylamine (which is abbreviated as "2-TNATA") and F4-TCNQ (tetrafluorotetracyanoquinodimethane) so that the amount of F4-TCNQ was 1.0% by mass with respect to 2-TNATA.

Subsequently, crNPD was laminated to form a 10 nm-thick hole transport layer.

In addition, a 30 nm-thick light-emitting layer was formed on the hole transport layer by co-depositing l,3-bis(carbazol-9-yl)benzene (which is abbreviated as "mCP"), light-emitting material A (15% by mass to mCP), light-emitting material B (0.13% by mass to mCP) and light-emitting material C (0.13% by mass to mCP).

Next, BAlq was laminated on the light -emitting layer to form a 40 nnrthick electron transport layer.

Furthermore, LiF was deposited so as to have a thickness of 0.5 nm, and Al was deposited so as to have a thickness of 1.5 nm, whereby an electron injection layer was formed.

Light-emitting Light-emitting Light-emitting material A material B material C

< Semi-transmissive reflective electrode >

A metal electrode of the light-emitting layer (Ag, thickness^ 20 nm) was formed through vacuum film formation.

Without being exposed to air, the obtained laminate was placed in a glove box which had been purged with nitrogen gas. Subsequently, the laminate was sealed by a glass sealing cover having concave portions in the inner wall with a UV-ray curable adhesive (XNR5516HV, product of

Nagase-Chiba Co.). Through the above procedure, EL element 3 was fabricated.

Furthermore, color filter 1 obtained in Example 1 and EL element 3 were joined with each other with a UV-ray curable adhesive (XNR5516HV, product of Nagase-Chiba Co.) so that the color filter was disposed at the side where light emitted from the EL element was emitted to the outside, to thereby fabricate light-emitting display element 3 of the present invention. (Comparative Example 4)

The procedure of Example 3 was repeated, except that no polarizing plate was formed, to thereby fabricate comparative color filter 4 and

comparative light-emitting display element 4.

(Comparative Example 5)

The procedure of Example 3 was repeated, except that the polarizing plate was attached to the entirety of a patterned image instead of to the white pixels, to thereby fabricate comparative color filter 5 and comparative light-emitting display element 5.

(Comparative Example 6)

The procedure of Example 3 was repeated, except that no color filter was provided, to thereby fabricate comparative light-emitting display element 6.

< Evaluation >

Each of the above-obtained light-emitting display elements was measured with a luminance meter (SR-3, product of Top Com. Co.) for white luminance and black luminance. The luminance meter was placed 1 m apart from the light-emitting display element and at the same height as the center of the light-emitting display element in the vertical direction. Also, the luminance meter was placed at an oblique angle of 5° in the horizontal direction with respect to the center of the light-emitting display element. At a position where the luminance meter was placed, the vertical luminance was adjusted to 1,000 lux with a fluorescent light.

In this state, a luminance measured without applying current to the light-emitting display element was used as the black luminance, and a luminance measured when the light-emitting display element was lit (operated) was used as the white luminance. The thus-obtained white luminance of each EL element was used to calculate a relative value to the white luminance in Comparative Example 3 or Comparative Example 6 (regarded as 100). Also, the above-obtained black luminance and white luminance were used to calculate the ratio of white luminance to black luminance. The results are shown in Table 1.

Since the circularly polarizing layer (circularly polarizing plate) was provided in the optical light path of white light from the hght-emitting layer, reflection of external light was reduced while the white luminance (i.e., light emission of the hght-emitting display element) was being maintained. As a result, a decrease in contrast (white luminance/black luminance) was

prevented, and thus, a clear display image could be observed even in the presence of external light.

Table 1

Table 2

Industrial Applicability

The color filter of the present invention can be suitably used in a light-emitting display element which emits white light. The light-emitting display element containing the color filter realizes high- definition, full-color display, and thus, can be suitably used in a variety of applications such as cell phone displays, personal digital assistants (PDAs), computer displays, vehicle's information displays, TV monitors and common lights.

Reference Signs List

l: Color filter

12: Polarizing layer

14: 1/4 wavelength layer

16: Circularly polarizing layer

18: Filter layer

18w: White filter portion

18r: Red filter portion

18g: Green filter poriton

18b: Blue filter portion

22: Support

100: Light-emitting display element 102: Cathode

104: Anode

106: Light-emitting layer

108: Oprtical path length adjusting layer

110: Insulative layer

112: Reflective layer

114: Substrate

116: Flattening layer

118: TFT

Claims

1. A color filter for use in a light-emitting display element which emits at least white light, the color filter comprising:

a circularly polarizing layer,

2. The color filter according to claim 1, wherein the circularly polarizing layer comprises a polarizing layer and a 1/4 wavelength layer.

3. The color filter according to one of claims 1 and 2, wherein the color filter comprises a support, and the support is a transparent support.

4. The color filter according to claim 3, wherein the support is the 1/4 wavelength layer.

5. A light-emitting display element comprising:

the color filter according to any one of claims 1 to 4, and

a light-emitting layer which emits at least white light.

6. The light-emitting display element according to claim 5, wherein the light-emitting display element has an optical resonator structure.

7. The light-emitting display element according to one of claims 5 and 6, wherein the light-emitting layer comprises at least one phosphorescent light-emitting material.