JP2002170676A - Luminescent element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a luminescent element, and its manufacturing method, which, excellent in luminous efficiency, brightness, and durability, can be made in a larger screen, and so can be effectively utilized for a surface light source such as full-color display, backlight, illumination light source or the like, and a light source array or the like such as a printer. SOLUTION: The luminescent element has on a substrate a luminescent laminated layer with a transparent electrode, one or more organic compound layers including a luminescent layer and a back electrode laminated, of which, the luminescent layer is an element containing a phosphorescent compound, and at least one of the organic compound layers is one filmed by a wet-process film-forming method under atmosphere with oxygen concentration of 100 ppm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device which is excellent in light emission luminance and light emission efficiency and can be manufactured at low cost, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Organic light-emitting elements using organic substances are expected to be used as solid-state light-emitting inexpensive large-area full-color display elements and writing light source arrays, and active research and development have been advanced in recent years. . In general, an organic light-emitting device includes an organic compound layer including a light-emitting layer and a pair of counter electrodes sandwiching the organic compound layer. When a voltage is applied to such an organic light emitting device, electrons are injected from the cathode into the organic compound layer, and holes are injected from the anode. The electrons and holes are recombined in the light emitting layer, and light is emitted by emitting energy as light when the energy level returns from the conduction band to the valence band.

The conventional organic light emitting device has a problem that the driving voltage is high and the light emission luminance and light emission efficiency are low. In recent years, various techniques for solving this problem have been reported. For example, an organic light-emitting device having an organic thin film formed by vapor deposition of an organic compound is known (Applied Physics Letters, 51, 913, 1987). ). This organic light-emitting device has a laminated two-layer structure of an electron transporting layer made of an electron transporting material and a hole transporting layer made of a hole transporting material, and exhibits significantly improved emission characteristics as compared with a single-layered device. A low molecular weight amine compound is used as the hole transport material, and an 8-quinolinol aluminum complex (Al
q) is used, and the emission color is green. Many organic light-emitting devices having vapor-deposited organic thin films have been reported thereafter (Macromolecular Symposium, Vol. 125, p. 1,
However, such an organic light-emitting device has a very low luminous efficiency as compared with an inorganic LED device and a fluorescent tube, which is a serious problem in practical use.

[0004] Most of the conventional organic light-emitting devices utilize fluorescence emitted from singlet excitons of an organic light-emitting material. In a simple quantum chemistry mechanism, the ratio of a singlet exciton capable of obtaining fluorescence emission to a triplet exciton capable of obtaining phosphorescence emission in an exciton state is 1: 3. That is,
As long as fluorescent light is used, only 25% of the excitons can be effectively used, and the light emitting efficiency of the fluorescent light emitting device is low. Under such circumstances, a phosphorescent device using an iridium phenylpyridine complex has recently been reported (Applied Physics Letter, Vol. 75, pp. 4, 1999, Japanese Journal of Applied Physics, Vol. 38, L1502, 1
999 years). These phosphorescent devices exhibit luminous efficiencies that are 2-3 times higher than those of conventional fluorescent luminous devices, but their luminous efficiencies are lower than the theoretical luminous efficiency limit, and the luminous efficiency is further improved for practical use. Is required.

On the other hand, in forming an organic compound layer of an organic light emitting device, various methods such as a vapor deposition method, a sputtering method, a CVD method, a PVD method, and a coating method using a solvent can be used. In view of simplification of the manufacturing process, reduction of manufacturing cost, improvement of workability, application to flexible large-area elements such as backlights and illumination light sources, wet film forming methods such as coating methods are advantageous. . In the above-mentioned known phosphorescent device, since an organic compound layer made of a low molecular compound is formed by a dry method such as a vapor deposition method, deterioration of the device due to crystallization of the low molecular compound is inevitable, and High cost,
There is a serious problem of poor manufacturing efficiency. Some organic light-emitting devices in which a polymer compound is formed by a wet film-forming method have already been reported, and as the polymer compound, polyparaphenylene vinylene that emits green light (Nature, vol.
39, 1990), poly (3-alkylthiophene) exhibiting red-orange emission (Japanese Journal of Applied Physics, 30, L1938, 1991), polyalkylfluorene exhibiting blue emission (Japanese Journal of Applied Physics, Volume 30, L1941
P. 1991). Also, JP-A-2-2-2231
No. 88 reports a method of dispersing a low molecular compound in a binder resin and forming a film by wet coating. However, all of these wet film-forming devices use singlet excitons, and the fundamental problem of low luminous efficiency remains.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface light source such as a full color display, a backlight, and an illumination light source because of its excellent light emission luminance and light emission efficiency, low manufacturing cost and large area. It is an object of the present invention to provide a light emitting element which can be effectively used for a light source array of a printer or the like, and a method of manufacturing the same.

[0007]

As a result of intensive studies in view of the above problems, the present inventor has found that a phosphorescent device using triplet excitons is different from a fluorescent light emitting device using singlet excitons in oxygen emission. We found that the quenching phenomenon was caused by oxygen, which is easily affected, and that a phosphorescent light-emitting element with excellent luminescence characteristics can be obtained by forming an organic compound layer by a wet film forming method in an atmosphere having a low oxygen concentration. Discover
The present invention has been made.

That is, the light emitting device of the present invention comprises a substrate, a transparent electrode, one or more organic compound layers including a light emitting layer, and a back electrode, wherein the light emitting layer contains a phosphorescent compound. At least one of the organic compound layers has an oxygen concentration of 10
It is a layer formed by a wet film formation method in an atmosphere of 0 ppm or less. The light emitting device of the present invention has excellent light emission luminance and light emission efficiency, and can be manufactured at low cost.
Further, since the area can be increased, it can be effectively used for a full-color display, a surface light source such as a backlight and an illumination light source, and a light source array such as a printer.

Further, the manufacturing method of the present invention is a method of manufacturing the light emitting device of the present invention, wherein at least one of the organic compound layers is formed by a wet film forming method in an atmosphere having an oxygen concentration of 100 ppm or less. It is characterized by the following.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The light emitting device of the present invention is formed by laminating a transparent electrode, one or more organic compound layers and a back electrode on a substrate. The organic compound layer includes a light emitting layer, and the light emitting layer contains a phosphorescent compound. If necessary, an organic compound layer other than the light-emitting layer, a protective layer, and the like may be provided. The light emitting device of the present invention can be manufactured by the manufacturing method of the present invention including a wet film forming method. In the production method of the present invention, at least one of the organic compound layers is formed by a wet film formation method in an atmosphere having an oxygen concentration of 100 ppm or less.

The structure of the light emitting device of the present invention comprises a transparent electrode / light emitting layer / back electrode, a transparent electrode / light emitting layer / electron transport layer / back electrode, a transparent electrode / hole transport layer / light emitting layer / electron on a substrate. Transport layer / Back electrode, Transparent electrode / Hole transport layer / Emitting layer / Back electrode, Transparent electrode / Emitting layer / Electron transport layer / Electron injection layer / Back electrode, Transparent electrode / Hole injection layer / Hole transport layer / Emitting layer /
A configuration in which an electron transport layer / an electron injection layer / a back electrode and the like are laminated in this order, a configuration in which these are reversed, and the like may be used. The light emitting layer contains a phosphorescent compound, and light is normally extracted from the transparent electrode. Specific examples of the compound used for each layer are described in, for example, “OLED Display” (Techno Times), a separate volume of “Monthly Display”, October 1998.

The formation position of the organic compound layer is not particularly limited and can be appropriately selected depending on the use and purpose of the light emitting device. However, the organic compound layer is preferably formed on a transparent electrode or a back electrode. At this time, the organic compound layer may be formed on the entire surface or a part of the transparent electrode or the back electrode. The shape of the organic compound layer,
The size and thickness can also be appropriately selected according to the purpose.

The organic compound layer may be formed by a dry film forming method or a wet film forming method. However, when the wet film forming method is used, the area of the organic compound layer can be easily increased, and high luminance and luminous efficiency can be obtained. A light-emitting element having an excellent quality can be efficiently obtained at low cost, which is preferable. As a dry film forming method, a vapor deposition method, a sputtering method, etc. can be used, and as a wet film forming method, a dipping method, a spin coating method, a dip coating method, a casting method, a die coating method,
Roll coating, bar coating, gravure coating and the like can be used. These film forming methods can be appropriately selected according to the material of the organic compound layer. When the film is formed by a wet film forming method, the film may be dried after forming the film. Drying is performed by selecting conditions such as temperature and pressure so as not to damage the coating layer.

In the present invention, at least one of the organic compound layers is formed by a wet film forming method in an atmosphere having an oxygen concentration of 100 ppm or less. That is, the step of applying a coating solution in the wet film forming method and the step of drying the applied coating solution are performed in an atmosphere having an oxygen concentration of 100 ppm or less. When the coating liquid is applied in air, the heat of vaporization generated when the solvent is vaporized lowers the substrate temperature, and a gas such as oxygen is adsorbed on the applied organic compound layer. As a result, the phosphorescent compound is strongly affected by oxygen, and the light emission luminance and light emission efficiency of the device are reduced. In the present invention, by performing the film-forming step in an atmosphere having an oxygen concentration of 100 ppm or less, the amount of oxygen gas adsorbed in the organic compound layer can be reduced, and the performance of the phosphorescent compound can be maximally used. Light emission luminance, light emission efficiency, and durability can be improved.

The above-mentioned coating solution usually comprises a material for an organic compound layer and a solvent for dissolving or dispersing the same. The solvent is not particularly limited, and may be selected according to the material used for the organic compound layer. Specific examples of the solvent include halogen-based solvents (chloroform, carbon tetrachloride, dichloromethane, 1,2-
Dichloroethane, chlorobenzene, etc., ketone solvents (acetone, methyl ethyl ketone, diethyl ketone, n-
Propyl methyl ketone, cyclohexanone, etc.), aromatic solvents (benzene, toluene, xylene, etc.), ester solvents (ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, Examples thereof include diethyl carbonate), ether solvents (such as tetrahydrofuran and dioxane), amide solvents (such as dimethylformamide and dimethylacetamide), dimethyl sulfoxide, and water. The amount of the solid content relative to the solvent in the coating solution is not particularly limited, and the viscosity of the coating solution can be arbitrarily selected according to the film forming method.

The method for obtaining an atmosphere having an oxygen concentration of 100 ppm or less is not particularly limited. For example, it is preferable to form a film under an atmosphere of an inert gas such as nitrogen or argon having an oxygen concentration of 100 ppm or less.

In order to improve the light emission luminance and the light emission efficiency of the light emitting device, the oxygen concentration in the atmosphere at the time of applying the coating solution is preferably 100 ppm or less, more preferably 50 ppm.
The content is particularly preferably 30 ppm or less. Also in the drying step after coating, the oxygen concentration is preferably 100 ppm or less, more preferably 50 ppm or less, particularly preferably 30 ppm or less.

The light emitting device of the present invention emits light when a DC voltage (which may include an AC component) or a DC current of about 2 to 40 V is applied between the transparent electrode and the back electrode. When driving the light emitting device of the present invention,
2-148687, 6-301355, 5-29080, 7-134558
No. 8-234685, No. 8-241047, U.S. Pat.
And the driving methods described in Japanese Patent No. 6023308 and Japanese Patent No. 2784615 can be used. Hereinafter, each element constituting the light emitting device of the present invention will be described in detail, but the present invention is not limited thereto.

(A) Substrate The substrate used in the present invention includes inorganic materials such as zirconia-stabilized yttrium (YSZ) and glass; polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polystyrene; polycarbonate; Ether sulfone, polyarylate,
It may be composed of polymer materials such as allyl diglycol carbonate, polyimide, polycycloolefin, norbornene resin, poly (chlorotrifluoroethylene), Teflon (registered trademark), and polytetrafluoroethylene-polyethylene copolymer. . The substrate may be formed of a single material or may be formed of two or more materials. Among them,
In order to form a flexible light-emitting element, a polymer material is preferable, and polyester, polycarbonate, which have excellent heat resistance, dimensional stability, solvent resistance, electric insulation and workability, and low air permeability and low moisture absorption, Polyether sulfone, poly (chlorotrifluoroethylene), Teflon,
A polymer material containing a fluorine atom, such as a polytetrafluoroethylene-polyethylene copolymer, is more preferable.

The shape, structure, size and the like of the substrate can be appropriately selected according to the use and purpose of the light emitting device. The shape is generally plate-like. The structure may be a single layer structure or a laminated structure. The substrate may be colorless and transparent or colored and transparent, but is preferably colorless and transparent in that light emitted from the light emitting layer is not scattered or attenuated.

A moisture permeation preventing layer (gas barrier layer) may be provided on the surface of the substrate on the electrode side, the surface on the side opposite to the electrode, or both. It is preferable to use an inorganic substance such as silicon nitride or silicon oxide as a material constituting the moisture permeation preventing layer. The moisture permeation preventing layer can be formed by a high frequency sputtering method or the like. Also,
The substrate may be provided with a hard coat layer or an undercoat layer as needed.

(B) Transparent electrode Usually, the transparent electrode has a function as an anode for supplying holes to the organic compound layer, but it can also function as a cathode. In this case, the back electrode functions as an anode. Less than,
The case where the transparent electrode is used as the anode will be described.

The shape, structure, size and the like of the transparent electrode are not particularly limited, and can be appropriately selected depending on the use and purpose of the light emitting device. As a material for forming the transparent electrode, a metal, an alloy, a metal oxide, an electrically conductive compound, a mixture thereof, or the like can be used, and preferably, the work function is 4 eV.
The above materials are used. Specific examples include tin oxide (ATO) doped with antimony, tin oxide (FTO) doped with fluorine, and semiconductive metal oxides (tin oxide, zinc oxide,
Indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), etc.), metals (gold, silver, chromium, nickel, etc.), mixtures or laminates of these metals and conductive metal oxides, inorganic conductive materials (Copper iodide, copper sulfide, etc.),
Organic conductive materials (polyaniline, polythiophene, polypyrrole, etc.) and laminates thereof with ITO are listed.

The transparent electrode is formed on a substrate by a wet method such as a printing method or a coating method, a physical method such as a vacuum deposition method, a sputtering method, an ion plating method, or a chemical method such as a CVD method or a plasma CVD method. can do. The formation method may be appropriately selected in consideration of suitability for the transparent electrode material. For example, when ITO is used as the material of the transparent electrode, a direct current or high frequency sputtering method, a vacuum deposition method, an ion plating method, or the like may be used. When an organic conductive material is used as the material of the transparent electrode, a wet film forming method may be used.

The patterning of the transparent electrode can be performed by chemical etching using photolithography or the like, physical etching using a laser or the like. Alternatively, patterning may be performed by vacuum evaporation using a mask, sputtering, a lift-off method, a printing method, or the like.

The position for forming the transparent electrode may be appropriately selected according to the use and purpose of the light emitting device, but is preferably formed on a substrate. At this time, the transparent electrode may be formed on the entire surface of the substrate or only on a part thereof.

The thickness of the transparent electrode may be appropriately selected according to its material, but is usually 10 nm to 50 μm, preferably 5 nm.
0 nm to 20 μm. The transparent electrode preferably has a resistance value of 10 ³ Ω / □ or less, more preferably 10 ² Ω / □ or less. The transparent electrode may be colorless and transparent or colored and transparent. In order to extract light emission from the transparent electrode side, the transmittance is preferably 60% or more, more preferably 70% or more. The transmittance can be measured according to a known method using a spectrophotometer.

Further, electrodes described in detail in "New Development of Transparent Conductive Film" (edited by Yutaka Sawada, published by CMC, 1999) can also be applied to the present invention. In particular, when a plastic substrate having low heat resistance is used, it is preferable to use ITO or IZO as a transparent electrode material and form a film at a low temperature of 150 ° C. or lower.

(C) Back Electrode Normally, the back electrode has a function as a cathode for injecting electrons into the organic compound layer, but can also function as an anode. In this case, the transparent electrode functions as a cathode. Hereinafter, a case where the back electrode is a cathode will be described.

The shape, structure, size and the like of the back electrode are not particularly limited, and can be appropriately selected according to the use and purpose of the light emitting device. As a material for forming the back electrode, a metal, an alloy, a metal oxide, an electrically conductive compound, a mixture thereof, or the like can be used.
Use the material below V. Specific examples include alkali metals (Li, Na, K, Cs, etc.) and alkaline earth metals (Mg, Ca
Etc.), gold, silver, lead, aluminum, sodium-potassium alloy, lithium-aluminum alloy, magnesium-
Silver alloy, indium, rare earth metal (ytterbium, etc.)
And the like. These may be used alone, but it is preferable to use two or more of them in order to achieve both stability and electron injection properties. Among these materials, alkali metals and alkaline earth metals are preferable from the viewpoint of electron injecting property, and materials mainly composed of aluminum are preferable from the viewpoint of storage stability. Here, the material mainly composed of aluminum refers to aluminum alone, an alloy or a mixture of aluminum and 0.01 to 10% by mass of an alkali metal or an alkaline earth metal (such as a lithium-aluminum alloy and a magnesium-aluminum alloy). As the material of the back electrode,
Those described in detail in JP-A-2-15595 and JP-A-5-121172 can also be used.

The back electrode can be formed by a wet method such as a printing method or a coating method, a physical method such as a vacuum evaporation method, a sputtering method, an ion plating method, or a chemical method such as a CVD method or a plasma CVD method. . The formation method may be appropriately selected in consideration of suitability with the back electrode material.
For example, when two or more kinds of metals or the like are used as the material of the back electrode, the materials can be formed by sputtering the materials simultaneously or sequentially.

Patterning of the back electrode can be performed by chemical etching using photolithography or the like, physical etching using a laser or the like, or the like. Alternatively, patterning may be performed by vacuum evaporation using a mask, sputtering, a lift-off method, a printing method, or the like.

The formation position of the back electrode may be appropriately selected according to the use and purpose of the light emitting device, but is preferably formed on the organic compound layer. At this time, the back electrode may be formed on the entire surface of the organic compound layer or only on a part thereof. Further, a dielectric layer made of an alkali metal or alkaline earth metal fluoride is provided between the back electrode and the organic compound layer by 0.1.
It may be installed with a thickness of ５5 nm. The dielectric layer can be formed by a vacuum deposition method, a sputtering method, an ion plating method, or the like.

The thickness of the back electrode may be appropriately selected depending on its material, but is usually 10 nm to 5 μm, preferably 5 nm.
0 nm to 1 μm. The back electrode may be transparent or opaque. The transparent back electrode is composed of one layer of the material described above.
It can be formed by forming a thin film having a thickness of about 10 nm and further laminating a transparent conductive material such as ITO or IZO.

(D) Light Emitting Layer In the light emitting device of the present invention, the light emitting layer contains a phosphorescent compound. The phosphorescent compound used in the present invention is not particularly limited as long as it can emit light from triplet excitons. As the phosphorescent compound, an orthometalated complex or a porphyrin complex is preferably used, and an orthometalated complex is more preferably used. Among porphyrin complexes, porphyrin platinum complexes are preferred. The phosphorescent compounds may be used alone or in combination of two or more.

The orthometalated complex referred to in the present invention is described in "Basic and applied organometallic chemistry" by Akio Yamamoto, p.150 and p.232.
Page, Shokabosha (1982), Photochemistr by H. Yersin
y and Photophysics of Coordination Compounds, '' 71
-77 and 135-146, Springer-Verlag (1987)
Etc. are generic names of the compound groups described in the above. The ligand forming the orthometalated complex is not particularly limited, but may be a 2-phenylpyridine derivative, a 7,8-benzoquinoline derivative,
It is preferably a (2-thienyl) pyridine derivative, a 2- (1-naphthyl) pyridine derivative or a 2-phenylquinoline derivative. These derivatives may have a substituent. Further, other ligands may be included in addition to the ligands essential for forming these ortho-metalated complexes. As the central metal forming the orthometalated complex, any transition metal can be used, and in the present invention, rhodium, platinum, gold, iridium, ruthenium, palladium and the like can be preferably used. Of these, iridium is particularly preferred. The organic compound layer containing such an ortho-metalated complex is excellent in light emission luminance and light emission efficiency. Specific examples of the orthometalated complex are also described in Japanese Patent Application No. 2000-254171, paragraphs 0152 to 0180.

The orthometalated complex used in the present invention is In
org. Chem., 30, 1685, 1991; Inorg. Chem., 27, 346.
4, 1988, Inorg. Chem., 33, 545, 1994, Inorg. Chim.
Acta, 181, 245, 1991; J. Organomet. Chem., 335, 2
93, 1987, J. Am. Chem. Soc., 107, 1431, 1985 and the like.

The content of the phosphorescent compound in the light emitting layer is not particularly limited, but is, for example, 0.1 to 70% by mass,
It is preferably 0% by mass. When the content of the phosphorescent compound is less than 0.1% by mass or more than 70% by mass, the effect may not be sufficiently exhibited.

In the present invention, the light emitting layer may contain a host compound, a hole transporting material, an electron transporting material, an electrically inactive polymer binder, and the like, if necessary.

The above-mentioned host compound is a compound that causes energy transfer from its excited state to the phosphorescent compound, thereby causing the phosphorescent compound to emit light. Specific examples thereof include carbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, and styryl anthracene derivatives , Fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, porphyrin compounds, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyrandioxide Derivatives, carbodiimide derivatives, fluorenylidenemethane derivatives, distyrylpyrazine derivatives, and naphthaleneperylene Carboxylic acid anhydrides, phthalocyanine derivatives, 8-quinolinol derivative metal complexes, metal phthalocyanine, metal complexes having benzoxazole or benzothiazole as a ligand, polysilane compounds, poly (N-
(Vinyl carbazole) derivatives, aniline copolymers, thiophene oligomers, conductive polymers such as polythiophene,
Examples thereof include a polythiophene derivative, a polyphenylene derivative, a polyphenylenevinylene derivative, and a polyfluorene derivative. The host compound may be used alone or in combination of two or more.

The hole transporting material is not particularly limited as long as it has any of a function of injecting holes from the anode, a function of transporting holes, and a function of blocking electrons injected from the cathode. Alternatively, it may be a low molecular material or a high molecular material. Specific examples thereof include 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 derivative, hydrazone derivative, stilbene derivative, silazane derivative, aromatic tertiary amine compound, styrylamine compound, aromatic dimethylidene compound, porphyrin compound, polysilane compound, poly (N-vinylcarbazole) derivative, aniline copolymer, thiophene Examples thereof include oligomers, conductive polymers such as polythiophene, polythiophene derivatives, polyphenylene derivatives, polyphenylenevinylene derivatives, and polyfluorene derivatives. These may be used alone or in combination of two or more.

The electron transporting material is not particularly limited as long as it has any of a function of injecting electrons from a cathode, a function of transporting electrons, and a function of blocking holes injected from an anode. For example, triazole derivatives, oxazole derivatives, oxadiazole derivatives, fluorenone derivatives, anthraquinodimethane derivatives, anthrone derivatives,
Diphenylquinone derivatives, thiopyrandioxide derivatives, carbodiimide derivatives, fluorenylidenemethane derivatives, distyrylpyrazine derivatives, heterocyclic tetracarboxylic anhydrides such as naphthaleneperylene, phthalocyanine derivatives, metal complexes of 8-quinolinol derivatives, metallophthalocyanines, Metal complexes having benzoxazole or benzothiazole as ligands, aniline copolymers, thiophene oligomers, conductive polymers such as polythiophene, polythiophene derivatives, polyphenylene derivatives, polyphenylenevinylene derivatives, polyfluorene derivatives, etc. can be used. .

As the polymer binder, polyvinyl chloride, polycarbonate, polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon resin, ketone resin, phenoxy resin,
Polyamide, ethyl cellulose, vinyl acetate, ABS resin, polyurethane, melamine resin, unsaturated polyester, alkyd resin, epoxy resin, silicone resin, polyvinyl butyral, polyvinyl acetal and the like can be used. The light emitting layer containing the polymer binder can be easily applied to a large area by a wet film forming method.

The thickness of the light emitting layer is preferably from 10 to 200 nm, more preferably from 20 to 80 nm. 200nm thickness
If it exceeds, the driving voltage may increase, and if it is less than 10 nm, the light emitting element may be short-circuited.

(E) Electron Transport Layer The light emitting device of the present invention may have an electron transport layer made of the above-described electron transport material, if necessary. The electron transport layer may contain the polymer binder described above. The thickness of the electron transport layer is preferably from 10 to 200 nm, more preferably from 20 to 80 nm. When the thickness exceeds 200 nm, the driving voltage may increase, and when the thickness is less than 10 nm, the light emitting element may short-circuit.

(F) Hole Transport Layer The light emitting device of the present invention may have a hole transport layer made of the above-described hole transport material, if necessary. The hole transport layer may contain the polymer binder described above. The thickness of the hole transport layer is preferably from 10 to 200 nm, more preferably from 20 to 80 nm. When the thickness exceeds 200 nm, the driving voltage may increase, and when the thickness is less than 10 nm, the light emitting element may short-circuit.

(G) Others The light emitting device of the present invention is disclosed in JP-A-7-85974 and JP-A-7-192866.
, No. 8-22891, No. 10-275682, No. 10-106746 and the like. The protective layer is formed on the uppermost surface of the light emitting device. Here, the uppermost surface refers to the outer surface of the back electrode when the base material, the transparent electrode, the organic compound layer and the back electrode are laminated in this order, and the base material, the back electrode, the organic compound layer and the transparent electrode in this order. When laminating, it refers to the outer surface of the transparent electrode. The shape, size, thickness and the like of the protective layer are not particularly limited. The material forming the protective layer is not particularly limited as long as it has a function of preventing the light emitting element such as moisture or oxygen from deteriorating or permeating into the element. Silicon, germanium oxide, germanium dioxide and the like can be used.

The method for forming the protective layer is not particularly limited, and includes, for example, a vacuum deposition method, a sputtering method, a reactive sputtering method, a molecular sen epitaxy method, a cluster ion beam method, an ion plating method, a plasma polymerization method, a plasma CVD method, Laser CVD, thermal CVD, coating, etc. can be applied.

It is preferable that the light emitting element is provided with a sealing layer for preventing intrusion of moisture or oxygen. As a material for forming the sealing layer, a copolymer of tetrafluoroethylene and at least one comonomer, a fluorinated copolymer having a cyclic structure in the copolymer main chain, polyethylene, polypropylene, polymethyl methacrylate, polyimide, Polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, chlorotrifluoroethylene or copolymer of dichlorodifluoroethylene with other comonomers, water absorption 1%
The above water-absorbing substances, moisture-proof substances having a water absorption of 0.1% or less, metals (In, Sn, Pb, Au, Cu, Ag, Al, Tl, Ni, etc.), metal oxides (MgO, SiO, SiO ₂ , Al ₂ O ₃ , GeO, NiO, CaO, BaO, F
e ₂ O ₃ , Y ₂ O ₃ , TiO ₂ etc.), metal fluorides (MgF ₂ , LiF, AlF
₃ , CaF ₂ etc.), liquid fluorinated carbon (perfluoroalkane, perfluoroamine, perfluoroether etc.),
What disperse | distributed the adsorbent of moisture and oxygen in this liquid fluorinated carbon etc. can be used.

In order to block moisture and oxygen from outside,
The light-emitting element is preferably sealed with a sealing plate, a sealing container, or the like using a sealing agent. Materials used for the sealing plate, the sealing container, and the like include glass, stainless steel, metal (aluminum, etc.),
Plastics (poly (chlorotrifluoroethylene), polyester, polycarbonate, etc.), ceramics and the like can be used. As the sealant, an ultraviolet curable resin, a thermosetting resin, a two-component curable resin, or the like can be used.

Further, in the present invention, a water absorbent or an inert liquid may be inserted into the space between the sealing container and the light emitting element. The water absorbent is not particularly limited, and specific examples thereof include barium oxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calcium sulfate, magnesium sulfate, phosphorus pentoxide, calcium chloride, magnesium chloride, copper chloride, and cesium fluoride. , Niobium fluoride, calcium bromide, vanadium bromide, molecular sieve, zeolite, magnesium oxide and the like. As the inert liquid, paraffins, liquid paraffins, fluorine solvents (perfluoroalkane, perfluoroamine, perfluoroether, etc.), chlorine solvents, silicone oils and the like can be used.

[0052]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 A glass plate having a thickness of 0.2 mm was cut into 2.5 cm square to prepare a substrate, which was introduced into a vacuum chamber. On this substrate, a DC magnetron sputtering (condition: substrate temperature of 100 ° C., using an ITO target having a SnO ₂ content of 10% by mass).
An ITO transparent electrode was formed at an oxygen pressure of 1 × 10 ⁻³ Pa).
The thickness of the transparent electrode is 0.2 μm and its surface resistance is 10Ω / □
Met.

The substrate on which the transparent electrode is formed is placed in a cleaning container.
After IPA cleaning, UV-ozone treatment was performed for 30 minutes. Then, on this transparent electrode, poly (ethylenedioxythiophene)
・ Polystyrene sulfonic acid aqueous dispersion (manufactured by BAYER, Baytr
on P: solid content 1.3%), and vacuum-dried at 150 ° C for 2 hours to form a 100-nm-thick hole injection layer.

Next, polyvinyl carbazole (Mw = 6300)
0, manufactured by Aldrich, hole transporting material and host material), tris (2-phenylpyridine) iridium complex (phosphorescent material), and 2- (4-biphenylyl) -5- (4-t-butylphenyl) -1 4,3,4-oxadiazole (PBD, electron transport material)
It was dissolved in dichloroethane at a mass ratio of 0: 1: 12 to prepare a coating solution.

The obtained coating solution was treated with an oxygen concentration of 30 ppm and a dew point of -8.
It was placed in a glove box replaced with nitrogen gas at 0 ° C., and was applied on the hole injection layer using a spin coater.
Subsequently, apply the applied coating solution in a glove box at 100 ° C.
For 2 hours to form a light emitting layer having a thickness of 100 nm. Further, a patterned mask (a mask having a light emitting area of 5 mm × 5 mm) is provided on the light emitting layer, and a magnesium / silver alloy (magnesium: silver = 10: 1 (molar ratio)) is vapor-deposited at 0.25 μm in a vapor deposition apparatus. Then, 0.3 μm of silver was deposited to form a back electrode. An aluminum lead wire was connected from the transparent electrode and the back electrode to form a laminated structure. This laminated structure was sealed in a glass sealing container with an ultraviolet-curable adhesive (XNR5493, manufactured by Chise Nagase) to produce a light emitting device of Example 1.

Example 2 The above glove box was placed in an atmosphere having an oxygen concentration of 30 ppm and a dew point of -80 ° C.
A light emitting device of Example 2 was prepared in the same manner as in Example 1 except that the nitrogen gas was replaced with an argon gas having an oxygen concentration of 70 ppm and a dew point of -80 ° C.

Example 3 2,2 ', 2''-(1,3,5-benzenetriyl) tris
[3- (2-methylphenyl) -3H-imidazo [4,5-b] pyridine]
Example 1 except that was deposited at a rate of 1 nm / sec to provide an electron transport layer having a thickness of 0.024 μm, and a back electrode was provided thereon.
Similarly to the above, a light emitting device of Example 3 was produced.

COMPARATIVE EXAMPLE 1 The above glove box was subjected to an oxygen concentration of 30 ppm and a dew point of -80 ° C.
In the same manner as in Example 1 except that the nitrogen gas was replaced with a nitrogen gas having an oxygen concentration of 200 ppm and a dew point of −80 ° C.
A light emitting device of Comparative Example 1 was produced.

Comparative Example 2 The coating and drying of the above coating solution were performed at an oxygen concentration of 30 ppm and a dew point of -8.
A light-emitting device of Comparative Example 2 was produced in the same manner as in Example 1 except that the light-emitting device was performed in the air, instead of in a glove box replaced with nitrogen gas at 0 ° C.

Evaluation of Emission Luminance and Emission Efficiency Using a source measure unit 2400 manufactured by Toyo Technica, a DC voltage was applied to each of the light emitting elements obtained as described above to emit light, and the luminance was measured. Maximum brightness of each light emitting element
L _max, the voltage V _max when the maximum luminance L _max is obtained, the luminance 20
Luminous efficiency η ₂₀₀ when emitted at 0 cd / m ² , luminance 2000 cd /
Luminous efficiency η ₂₀₀₀ when emitted at m ² (external quantum efficiency)
Are also shown in Table 1.

[0062]

[Table 1]

From Table 1, it can be seen that the light emitting device of Comparative Example 1 in which the wet film formation was performed in a nitrogen atmosphere having a high oxygen concentration and the light emitting device of Comparative Example 2 in which the wet film formation was performed in air were compared with those of the light emitting device of Comparative Example 1. It can be seen that the light-emitting elements of Examples 1 to 3 of the invention show excellent light emission luminance and light emission efficiency.

[0064]

As described above in detail, the light-emitting device of the present invention, which effectively utilizes triplet excitons, has excellent light-emitting luminance and light-emitting efficiency, is low in manufacturing cost, and can have a large area. It can be effectively used for full-color displays, backlights, surface light sources such as illumination light sources, and light source arrays such as printers.

Claims (2)

[Claims] 1. A light emitting device having one or more organic compound layers including a substrate, a transparent electrode, and a light emitting layer and a back electrode, wherein the light emitting layer contains a phosphorescent compound, and at least one of the organic compound layers is A light-emitting element, which is a layer formed by a wet film-forming method in an atmosphere having an oxygen concentration of 100 ppm or less. 2. A method for producing a light-emitting device having one or more organic compound layers including a substrate, a transparent electrode, and a light-emitting layer and a back electrode, wherein the light-emitting layer contains a phosphorescent compound and the organic compound layer At least one layer with an oxygen concentration of 10
A method for manufacturing a light-emitting element, comprising forming a film by a wet film-forming method in an atmosphere of 0 ppm or less.