JP2008147399A - Organic electroluminescence element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescence element having no pixel defects and ensuring high luminous efficiency regardless of a low voltage, and a long lifetime. <P>SOLUTION: In the organic electroluminescence element, a hole injection layer and/or a hole-transporting layer contain a metal complex compound in a specific structure in an organic electroluminescence element, where an organic thin-film layer having at least a luminous layer and the hole injection layer and/or the hole-transporting layer is clamped between negative and positive electrodes. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence device, and more particularly to an organic electroluminescence device having no pixel defects and high luminous efficiency while having a low voltage.

An organic electroluminescence (EL) element is a self-luminous element utilizing the principle that a fluorescent substance emits light by recombination energy of holes injected from an anode and electrons injected from a cathode by applying an electric field. .
As light-emitting materials for organic EL elements, chelate complexes such as tris (8-quinolinolato) aluminum complex, luminescent materials such as coumarin derivatives, tetraphenylbutadiene derivatives, distyrylarylene derivatives, oxadiazole derivatives and the like are known. Has been reported that light emission in the visible region from blue to red can be obtained, and realization of a color display element is expected (see, for example, Patent Documents 1 to 3).
In recent years, it has also been proposed to use an organic phosphorescent material in addition to a light emitting material for the light emitting layer of an organic EL element (see, for example, Non-Patent Documents 1 and 2).
Thus, high luminous efficiency is achieved by utilizing the singlet state and triplet state of the excited state of the organic phosphorescent material in the light emitting layer of the organic EL element. When electrons and holes are recombined in an organic EL device, it is considered that singlet excitons and triplet excitons are generated at a ratio of 1: 3 due to the difference in spin multiplicity. If a light-emitting material is used, it can be considered that the light emission efficiency is 3 to 4 times that of an element using only fluorescence.
In such an organic EL element, an anode, a hole transport layer, an organic light emitting layer, an electron transport layer (a hole blocking layer) are sequentially arranged so that a triplet excited state or a triplet exciton is not quenched. A structure in which layers are stacked such as an electron injection layer and a cathode has been used, and a host compound and a phosphorescent compound have been used for an organic light emitting layer (see, for example, Patent Documents 4 to 5). In these patent documents, 4,4-N, N dicarbazole biphenyl has been used as a host compound, but since this compound has a glass transition temperature of 110 ° C. or lower and is too symmetric, it is crystallized. In addition, when the heat resistance test of the element is performed, there is a problem that a short circuit or a pixel defect occurs. As phosphorescent complexes, Patent Documents 6 to 8 disclose azole complexes.
It was also found that during the deposition, crystal growth occurs in places where foreign matters or electrode protrusions exist, and defects are generated from the initial state before the heat resistance test. A carbazole derivative having a three-fold symmetry is also used as a host. However, since the symmetry is good, it is inevitable that when vapor deposition is performed, crystal growth occurs in places where foreign matters or electrode protrusions exist, and defects are generated from the initial state before the heat resistance test.

JP-A-8-239655 JP 7-138561 A JP-A-3-200809 US Pat. No. 6,097,147 International Publication WO01 / 41512 International Publication WO2004 / 085450 Special table 2006-523231 US Publication No. 2006/232194 D.F.O'Brien and M.A.Baldo et al "Improved energy transferin electrophosphorescent devices" Applied Physics letters Vol. 74 No.3, pp442-444, January 18, 1999 M.A.Baldo et al "Very high-efficiencygreen organic light-emitting devices based on electrophosphorescence" Applied Physics letters Vol.75 No.1, pp4-6, July 5, 1999

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an organic EL element that has no pixel defects, has high luminance and luminous efficiency, and has a long lifetime.

As a result of intensive research to achieve the above object, the present inventors have used the following specific metal complex compounds for the hole injection layer and / or the hole transport layer of the organic EL element. The present inventors have found that the above problems can be solved and have completed the present invention.
That is, the present invention relates to an organic EL device in which an organic thin film layer having at least a light emitting layer and a hole injection layer and / or a hole transport layer is sandwiched between a cathode and an anode. The organic EL element in which a hole transport layer contains the metal complex compound represented by the following general formula (a) is provided.

Wherein M is a metal having an atomic weight greater than 40, (CN) is a substituted or unsubstituted cyclometalated ligand, and (CN) is at least one bonded to the metal. Different from other ligands.
R _{8 to} R ₁₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkylaryl group, CN, CF ₃ , CO ₂ R, C (O) R, NR ₂ , NO ₂ , OR (where R is a substituent) or a halogen atom, and two optional adjacent substitution positions together, independently fused A 4- to 7-membered cyclic group is formed, and the cyclic group is a cycloalkyl group, a cycloheteroalkyl group, an aryl group or a heteroaryl group, and the 4- to 7-membered cyclic group may be substituted. .
m is an integer of 1 or more, n is an integer of 1 or more, and m + n is the maximum number of ligands that can bind to the metal. )

  The organic EL device of the present invention has no pixel defects and high luminous efficiency while being low voltage.

  The organic EL device of the present invention is an organic EL device in which an organic thin film layer having at least a light emitting layer and a hole injection layer and / or a hole transport layer is sandwiched between a cathode and an anode. The layer and / or hole transport layer contains at least one selected from metal complex compounds represented by the following general formula (a) as a hole injection material (or hole transport material).

In the general formula (a), M is a metal having an atomic weight greater than 40, and Ir, Pt, Pd, Rh, Re, Ru, Os, Tl, Pb, Bi, In, Sn, Sb, Te, Au, and Ag. Ir and Pt are preferable, and Ir is more preferable.
In the general formula (a), (CN) is a substituted or unsubstituted cyclometalated ligand, and (CN) is different from at least one other ligand bonded to the metal.
(CN) represents a photoactive ligand, which is “photoactive”. This is because it is considered that it directly contributes to the photoactive characteristics of the luminescent material. Whether a ligand is photoactive depends on the specific compound in which the ligand is present. For example, each ppy ligand of Ir (ppy) ₃ (tris (2-phenylpyridine) iridium) is considered photoactive. However, in the compound (ppy) ₂ IrX, two ppy ligands are coordinated to Ir, and the X ligand is coordinated to the Ir. In particular, the X ligand is ppy coordinated. A ppy ligand may not be photoactive if it has a lower triplet energy than the child. Preferred (CN) ligands include 2- (p-tolyl) pyridine, 2-phenylpyridine, 2- (4 ′, 6′-difluorophenyl) pyridine, 2- (4 ′, 6′-difluoro Phenyl) -4-methoxypyridine, 2- (4 ′, 6′-difluorophenyl) -4- (N, N-dimethylamino) pyridine, 2-phenylpyridine and 2- (2′-thienyl) pyridine. . Other examples of photoactive ligands are disclosed in Brown et al. US patent application Ser. No. 10 / 289,915, which is incorporated herein in its entirety.

In the general formula (a), R _{8 to} R ₁₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, substituted or unsubstituted An alkylaryl group, CN, CF ₃ , CO ₂ R, C (O) R, NR ₂ , NO ₂ , OR (where R is a substituent) or a halogen atom, and two optional adjacent substitution positions together Independently forming a condensed 4- to 7-membered cyclic group, and the cyclic group is a cycloalkyl group, a cycloheteroalkyl group, an aryl group, or a heteroaryl group, and the 4- to 7-membered cyclic group May be substituted.

Examples of the halogen atom include fluorine, chlorine, bromine, and iodine.
The alkyl group includes linear and branched alkyl groups. Preferred alkyl groups are those containing 1 to 15 carbon atoms, including methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl and the like. In addition, the alkyl group is one or more substituents selected from a halogen atom, CN, CO ₂ R, C (O) R, NR ₂ , cyclic amino, NO ₂ , and OR (R is a substituent). It may be replaced.
The cycloalkyl group includes a cyclic alkyl group. Preferred cycloalkyl groups are those containing 3 to 7 carbon atoms and include cyclopropyl, cyclopentyl, cyclohexyl, and the like. In addition, the cycloalkyl group is one or more substituents selected from a halogen atom, CN, CO ₂ R, C (O) R, NR ₂ , cyclic amino, NO ₂ , and OR (R is a substituent). It may be replaced with.
The alkenyl group includes both linear and branched alkenyl groups. Preferred alkenyl groups are those containing 2 to 15 carbon atoms. In addition, an alkenyl group is one or more substituents selected from a halogen atom, CN, CO ₂ R, C (O) R, NR ₂ , cyclic amino, NO ₂ , and OR (R is a substituent). It may be replaced.

The alkynyl group includes both straight-chain and branched alkynyl groups. Preferred alkynyl groups are those containing 2 to 15 carbon atoms. In addition, the alkynyl group may be substituted with one or more substituents selected from a halogen atom, CN, CO ₂ R, C (O) R, NR ₂ , cyclic amino, NO ₂ , and OR. .
The alkylaryl group includes an alkyl group having an aromatic group as a substituent. In addition, the alkylaryl group is aryl substituted with one or more substituents selected from halogen atoms, CN, CO ₂ R, C (O) R, NR ₂ , cyclic amino, NO ₂ , and OR. May be.
The cycloheteroalkyl group includes a non-aromatic cyclic group. Preferred cycloheteroalkyl groups are those containing 3 to 7 ring atoms containing at least one heteroatom, cyclic amines such as morpholino groups, piperidino groups, pyrrolidino groups, and the like, and tetrahydrofuran, tetrahydro Includes cyclic ethers such as pyran and the like.
The aryl group includes a monocyclic group and a polycyclic group. A polycyclic ring is one in which two carbons are shared by two adjacent rings (they are fused) and at least one ring is aromatic, for example, the other ring is cyclo An alkyl group, a cycloalkenyl group, an aryl group, a heterocyclic ring, and a heteroaromatic group.
The heteroaryl group is a monocyclic heteroaromatic group that may contain 1 to 3 heteroatoms, such as pyrrole, furan, thiophene, imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine, and pyrimidine. Can be mentioned. A heteroaryl group includes a polycyclic heteroaromatic group having two or more rings in which two atoms are shared in two adjacent rings (the rings are fused), wherein at least one The ring is heteroaryl, for example, the other ring can be cycloalkyl, cycloalkenyl, aryl, heterocycle, and / or heteroaromatic.
The substituents for R _{8 to} R ₁₄ are each independently a halogen atom, hydroxyl group, amino group, nitro group, cyano group, alkyl group, alkenyl group, cycloalkyl group, alkoxy group, aromatic hydrocarbon group, aromatic Group heterocyclic group, aralkyl group, aryloxy group, alkoxycarbonyl group, fluorinated alkyl group, fluorinated aryl group or carboxyl group.
In the general formula (a), m is an integer of 1 or more, and n is an integer of 1 or more, preferably 2. m + n is the maximum number of ligands that can bind to the metal.
Each ligand for M is an organometallic (sex).

Specific structures of the general formula (a) include the following structures.

X is a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkylaryl group, CN, CF ₃ , CO ₂ R, C (O) R, NR ₂ , NO ₂ , OR (where R is a substituent) or a halogen atom, and two optionally substituted positions adjacent to each other are independently fused 4- to 7-membered cyclic groups And the cyclic group is a cycloalkyl group, a cycloheteroalkyl group, an aryl group or a heteroaryl group, and the 4- to 7-membered cyclic group may be substituted. Specific examples and substituents of these groups are the same as those for R _{8 to} R ₁₄ .

Specific examples of the compound represented by formula (a) in the present invention are shown below, but are not limited to these exemplified compounds.

Hereinafter, the element structure of the organic EL element of the present invention will be described.
The organic EL device of the present invention is a device in which a multilayer organic thin film layer having at least a light emitting layer and a hole injection layer and / or a hole transport layer is sandwiched between a cathode and an anode as described above. is there. The light emitting layer contains a light emitting material, and may further contain a hole injecting material or an electron injecting material in order to transport holes injected from the anode or electrons injected from the cathode to the light emitting material. Moreover, it is preferable that a luminescent material has extremely high fluorescence quantum efficiency, high hole transport ability, and electron transport ability, and forms a uniform thin film. Multi-layer type organic EL devices include (anode / hole injection layer (and hole transport layer) / light emitting layer / cathode), (anode / hole injection layer (and hole transport layer) / light emitting layer / electron injection). There are those laminated in a multilayer structure such as (layer / cathode).

For the organic thin film layer, a known host material, light emitting material, doping material, hole injection material or electron injection material can be used and combined. The organic EL element has a multilayer structure, so that it is possible to prevent a decrease in luminance and lifetime due to quenching, and it is used in combination with other doping materials that improve light emission luminance and light emission efficiency or contribute to phosphorescence emission. Thus, the conventional light emission luminance and light emission efficiency can be improved.
In addition, the hole injection layer, the light emitting layer, and the electron injection layer in the organic EL device of the present invention may be formed of two or more layers. In that case, in the case of the hole injection layer, the layer that injects holes from the electrode is referred to as a hole injection layer, and the layer that receives holes from the hole injection layer and transports holes to the light emitting layer is referred to as a hole transport layer. Similarly, in the case of an electron injection layer, a layer that injects electrons from an electrode is referred to as an electron injection layer, and a layer that receives electrons from the electron injection layer and transports electrons to a light emitting layer is referred to as an electron transport layer. Each of these layers is selected and used depending on factors such as the energy level of the material, heat resistance, adhesion with the organic thin film layer or the metal electrode.

  Examples of the light-emitting material or host material that can be used in the light-emitting layer include anthracene, naphthalene, phenanthrene, pyrene, tetracene, coronene, chrysene, fluorescein, perylene, phthaloperylene, naphthaloperylene, perinone, phthaloperinone, naphthaloperinone, metaphenylene compound, benzofuran derivative, benzofuran. Thiophene derivative, arylsilane compound, pyridine ring-containing compound, pyrimidine ring-containing compound, triazine ring-containing compound, triphenylene compound, quinoxaline compound, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, aldazine, bisbenzoxazoline, bisstyryl, Pyrazine, cyclopentadiene, quinoline metal complex, aminoquinoline metal complex, benzoquinoline metal complex, imine Examples include, but are not limited to, diphenylethylene, vinylanthracene, diaminoanthracene, diaminocarbazole, pyran, thiopyran, polymethine, merocyanine, imidazole chelating oxinoid compounds, quinacridone, rubrene, stilbene derivatives, and fluorescent dyes. . In addition, as the light emitting material, a phosphorescent organometallic complex is preferable in that the external quantum efficiency of the device can be further improved. As the metal atom of the organometallic complex, ruthenium, rhodium, palladium, silver, rhenium, osmium, Examples include those containing iridium, platinum, gold, copper, and the like.

As the luminescent material or the host material, compounds represented by the following general formula (1) described in International Publication WO 04/074399 and the following general formulas (2) to (3) described in International Publication WO 03/080760 are preferable.

(In the formula, Cz is a carbazolyl group, an arylcarbazolyl group having 18 to 60 carbon atoms, an azacarbazolyl group, an arylazacarbazolyl group having 18 to 60 carbon atoms, an acridinyl group, a phenoxazinyl group, or a dibenzoazepinyl group. Ar ¹ and Ar ² are each independently a substituted or unsubstituted aryl group having 6 to 60 carbon atoms or a substituted or unsubstituted heterocyclic group having 3 to 60 carbon atoms. ³ is an aromatic hydrocarbon group having 6 to 60 carbon atoms or a substituted or unsubstituted heterocyclic group having 3 to 60 carbon atoms, Ar ⁴ is a substituted or unsubstituted benzene residue, substituted or unsubstituted A thiophene residue, a substituted or unsubstituted triazole residue, a substituted or unsubstituted fluorene residue, or a substituted or unsubstituted spirobifluorene residue That.
a is an integer of 0 to 1, b is an integer of 0 to 4, c is an integer of 1 to 3, and when Cz and Ar ⁴ are plural, they may be the same as or different from each other.
However, when a = 0 and c = 1, Ar ³ and Ar ⁴ are benzene residues, and Ar ² is a phenylcarbazolyl group or a carbazolyl group. When a = 1, b = 0 and c = 1, the case where Ar ³ is a benzene residue and Ar ¹ and Ar ² are phenylcarbazolyl groups is excluded. Further, when b = 0 and c = 1, the case where Ar ³ is a benzene residue and Ar ¹ , Ar ² and Cz are a carbazolyl group or a phenylcarbazolyl group is excluded. )

(Cz-) _n A (2)
Cz (−A) _m (3)
[In the formula, Cz represents a substituted or unsubstituted arylcarbazolyl group or carbazolylalkylene group, or a substituted or unsubstituted arylazacarbazolyl group, and A represents the following general formula (A). Group. n and m are integers of 1 to 3, respectively.
(M) p- (L) q- (M ') r (A)
(M and M ′ are each independently a nitrogen-containing heteroaromatic ring having 2 to 40 carbon atoms that forms a substituted or unsubstituted ring, and may be the same or different. L is a single bond or a substituted ring. Alternatively, it is an unsubstituted aryl group or arylene group having 6 to 30 carbon atoms, a substituted or unsubstituted cycloalkylene group having 5 to 30 carbon atoms, or a substituted or unsubstituted heteroaromatic ring having 2 to 30 carbon atoms. p is 0 to 2, q is 1 to 2, and r is an integer of 0 to 2. However, p + r is 1 or more.)]
In the general formulas (1) to (3) and (a), the signs of Cz, n, m, and M overlap, but each formula is independent.

Specific preferred examples of the light emitting material or the host material used in the present invention are shown below, but are not limited to these exemplified compounds.

The hole injection material has the ability to transport holes, has a hole injection effect from the anode, an excellent hole injection effect for the light emitting layer or the light emitting material, and excitons generated in the light emitting layer. A compound that prevents movement to the electron injection layer or the electron injection material and has an excellent thin film forming ability is preferable.
In the present invention, a known hole injection material may be used in addition to the metal complex compound of the general formula (a). Specifically, phthalocyanine derivatives, naphthalocyanine derivatives, porphyrin derivatives, oxazoles, oxalates, and the like. Diazole, triazole, imidazole, imidazolone, imidazolethione, pyrazoline, pyrazolone, tetrahydroimidazole, oxazole, oxadiazole, hydrazone, acylhydrazone, polyarylalkane, stilbene, butadiene, starburst amine, triarylamine, benzidine type tri Phenylamine, styrylamine-type triphenylamine, diamine-type triphenylamine, hexaazatriphenylene compounds, and their derivatives, and polyvinylcarbazole, polysilane, Although and polymer materials such as conductive polymers, but are not limited thereto.

Among these hole injection materials, more effective hole injection materials are aromatic tertiary amine derivatives or phthalocyanine derivatives. Specific examples of the aromatic tertiary amine derivative include triphenylamine, tolylamine, tolyldiphenylamine, N, N′-diphenyl-N, N ′-(3-methylphenyl) -1,1′-biphenyl-4, 4′-diamine, 4,4 ′, 4 ″ -tri (N-carbazolyl) triphenylamine, N, N, N ′, N ′-(4-methylphenyl) -1,1′-phenyl-4, 4′-diamine, N, N, N ′, N ′-(4-methylphenyl) -1,1′-biphenyl-4,4′-diamine, N, N′-diphenyl-N, N′-dinaphthyl- 1,1′-biphenyl-4,4′-diamine, N, N ′-(methylphenyl) -N, N ′-(4-n-butylphenyl) -phenanthrene-9,10-diamine, N, N— Bis (4-di-4-tolylaminophenyl) -4-phenyl-cyclohex Sun or the like, or oligomers or polymers having these aromatic tertiary amine skeletons, but are not limited thereto. Specific examples of phthalocyanine (Pc) derivatives are H ₂ Pc, CuPc, CoPc, NiPc, ZnPc, PdPc, FePc, MnPc, ClAlPc, ClGaPc, ClInPc, ClSnPc, Cl ₂ SiPc, (HO) AlPc, (HO) GaPc, Although it is a phthalocyanine derivative and a naphthalocyanine derivative such as VOPc, TiOPc, MoOPc, and GaPc-O-GaPc, it is not limited thereto.

As an electron injection material, it has the ability to transport electrons, has an electron injection effect from the cathode, and an excellent electron injection effect for the light emitting layer or light emitting material. The compound which prevents the movement to and is excellent in thin film forming ability is preferable. Specifically, fluorenone, anthraquinodimethane, diphenoquinone, thiopyran dioxide, oxazole, oxadiazole, triazole, imidazole, triphenylene, polyphenylene, perylenetetracarboxylic acid, quinoxaline, fluorenylidenemethane, anthraquinodimethane, Anthrone and the like and derivatives thereof may be mentioned, but are not limited thereto.
Among these electron injection materials, more effective electron injection materials are metal complex compounds or nitrogen-containing five-membered ring derivatives. Specific examples of the metal complex compound include 8-hydroxyquinolinate lithium, bis (8-hydroxyquinolinato) zinc, bis (8-hydroxyquinolinato) copper, bis (8-hydroxyquinolinato) manganese, tris ( 8-hydroxyquinolinato) aluminum, tris (2-methyl-8-hydroxyquinolinato) aluminum, tris (8-hydroxyquinolinato) gallium, bis (10-hydroxybenzo [h] quinolinato) beryllium, bis ( 10-hydroxybenzo [h] quinolinato) zinc, bis (2-methyl-8-quinolinato) chlorogallium, bis (2-methyl-8-quinolinato) (o-cresolate) gallium, bis (2-methyl-8-quinolinato) ) (1-Naphtholate) aluminum, bis (2-methyl-8-) Norinato) (2-naphtholato) gallium and the like, but not limited thereto.

The nitrogen-containing five-membered derivative is preferably an oxazole, thiazole, oxadiazole, thiadiazole or triazole derivative. Specifically, 2,5-bis (1-phenyl) -1,3,4-oxazole, dimethyl POPOP, 2,5-bis (1-phenyl) -1,3,4-thiazole, 2,5- Bis (1-phenyl) -1,3,4-oxadiazole, 2- (4′-tert-butylphenyl) -5- (4 ″ -biphenyl) 1,3,4-oxadiazole, 2,5 -Bis (1-naphthyl) -1,3,4-oxadiazole, 1,4-bis [2- (5-phenyloxadiazolyl)] benzene, 1,4-bis [2- (5-phenyloxa) Diazolyl) -4-tert-butylbenzene], 2- (4′-tert-butylphenyl) -5- (4 ″ -biphenyl) -1,3,4-thiadiazole, 2,5-bis (1-naphthyl) ) -1,3,4-thiadiazole, 1,4-bis [2- (5-fur Nilthiadiazolyl)] benzene, 2- (4′-tert-butylphenyl) -5- (4 ″ -biphenyl) -1,3,4-triazole, 2,5-bis (1-naphthyl) -1, Examples include, but are not limited to, 3,4-triazole and 1,4-bis [2- (5-phenyltriazolyl)] benzene.
Further, the charge injection property can be improved by adding an electron accepting material to the hole injecting material and an electron donating material to the electron injecting material.

  As the conductive material used for the anode of the organic EL device of the present invention, a material having a work function larger than 4 eV is suitable, and carbon, aluminum, vanadium, iron, cobalt, nickel, tungsten, silver, gold, platinum Palladium, etc. and their alloys, metal oxides such as tin oxide and indium oxide used for ITO substrates and NESA substrates, and organic conductive resins such as polythiophene and polypyrrole are used. As the conductive material used for the cathode, those having a work function smaller than 4 eV are suitable, and magnesium, calcium, tin, lead, titanium, yttrium, lithium, ruthenium, manganese, aluminum, and alloys thereof are used. However, it is not limited to these. Examples of alloys include magnesium / silver, magnesium / indium, lithium / aluminum, and the like, but are not limited thereto. The ratio of the alloy is controlled by the temperature of the vapor deposition source, the atmosphere, the degree of vacuum, etc., and is selected to an appropriate ratio. If necessary, the anode and the cathode may be formed of two or more layers.

The organic EL device of the present invention may have an inorganic compound layer between at least one electrode and the organic thin film layer. Preferred inorganic compounds used in the inorganic compound layer include alkali metal oxides, alkaline earth oxides, rare earth oxides, alkali metal halides, alkaline earth halides, rare earth halides, SiO _x , AlO _x , SiN. _{X, SiON, AlON, GeO X} , LiO X, LiON, TiO X, TiON, TaO X, TaON, TaN X, C and various oxides, nitrides, and oxide nitrides. In particular, as the component of the layer in contact with the anode, SiO _x , AlO _x , SiN _x , SiON, AlON, GeO _x , and C are preferable to form a stable injection interface layer. In particular, LiF, MgF ₂ , CaF ₂ , MgF ₂ , and NaF are preferred as the components of the layer in contact with the cathode.

In order for the organic EL device of the present invention to emit light efficiently, it is desirable that at least one surface be sufficiently transparent in the light emission wavelength region of the device. The substrate is also preferably transparent.
The transparent electrode is set using the above-described conductive material so as to ensure a predetermined translucency by a method such as vapor deposition or sputtering. The electrode on the light emitting surface preferably has a light transmittance of 10% or more. The substrate is not limited as long as it has mechanical and thermal strength and is transparent, and examples thereof include a glass substrate and a transparent resin film. Transparent resin films include polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polypropylene, polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketone. , Polysulfone, polyethersulfone, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinyl fluoride, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, Polyvinylidene fluoride, polyester, polycarbonate, polyurethane, polyimide, polyetherimide, polyimide, polypropylene, etc. It is.
The organic EL device of the present invention can be provided with a protective layer on the surface of the device, or the entire device can be protected with silicon oil, resin, or the like in order to improve stability against temperature, humidity, atmosphere, and the like.

Each layer of the organic EL device of the present invention can be formed by applying any one of dry deposition methods such as vacuum deposition, sputtering, plasma and ion plating, and wet deposition methods such as spin coating, dipping and flow coating. Can do. The thickness of each layer is not particularly limited, but must be set to an appropriate thickness. If the film thickness is too thick, a large applied voltage is required to obtain a constant light output, resulting in poor luminous efficiency. If the film thickness is too thin, pinholes and the like are generated, and sufficient light emission luminance cannot be obtained even when an electric field is applied. The normal film thickness is suitably in the range of 5 nm to 10 μm, but more preferably in the range of 10 nm to 0.2 μm.
In the case of the wet film forming method, the material for forming each layer is dissolved or dispersed in an appropriate solvent such as ethanol, chloroform, tetrahydrofuran, dioxane or the like to form a thin film, and any solvent may be used. In any layer, an appropriate resin or additive may be used for improving the film formability and preventing pinholes in the film. Usable resins include polystyrene, polycarbonate, polyarylate, polyester, polyamide, polyurethane, polysulfone, polymethyl methacrylate, polymethyl acrylate, cellulose and other insulating resins and copolymers thereof, poly-N-vinyl. Examples thereof include photoconductive resins such as carbazole and polysilane, and conductive resins such as polythiophene and polypyrrole. Examples of the additive include an antioxidant, an ultraviolet absorber, and a plasticizer.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.
Example 1 (Production of organic EL device)
A glass substrate with an ITO transparent electrode having a thickness of 25 mm × 75 mm × 1.1 mm (manufactured by Geomatic Co., Ltd.) was subjected to ultrasonic cleaning in isopropyl alcohol for 5 minutes and then UV ozone cleaning for 30 minutes. The glass substrate with a transparent electrode line after washing is mounted on a substrate holder of a vacuum deposition apparatus, and the complex (with a film thickness of 10 nm is first covered on the surface where the transparent electrode line is formed so as to cover the transparent electrode. C19) was deposited. This film functions as a hole injection layer. Further, following the formation of the hole injection layer, the following material HTM (see the following structural formula) having a film thickness of 85 nm was formed. The HTM film functions as a hole transport layer. Further, following the formation of the hole transport layer, the compound (11) as a host compound and the complex F (facial body) as a dopant were co-deposited by resistance heating on the film at a thickness of 30 nm. The concentration of complex F was 7.5 wt%. This host compound: (11) film functions as a light emitting layer. Then, following the formation of the light emitting layer, the following material ETM1 was formed to a thickness of 25 nm, and further, the following material ETM2 was formed to a thickness of 5 nm on the ETM1. The ETM1 layer and the ETM2 layer function as an electron transport layer and an electron injection layer. Thereafter, LiF was used as an electron injecting electrode (cathode), and a film thickness of 1 nm / min was formed to a thickness of 0.1 nm. Metal Al was vapor-deposited on the LiF layer, and a metal cathode was formed to a thickness of 150 nm to form an organic EL element.
(Emission performance evaluation of organic EL elements)
The organic EL device produced as described above was caused to emit light by direct current drive (current density J = 1 mA / cm ² ), the luminance (L) was measured, and the luminous efficiency (lm / W) was obtained. It is shown in 1.

Examples 2-3
An organic EL device was produced in the same manner as in Example 1 except that (C1) and (C4) were used instead of the complex (C19). About each obtained organic EL element, luminous efficiency was measured like Example 1, and a result is shown in Table 1.
Example 4
In Example 1, an organic EL device was produced in the same manner except that the compound (7) was used instead of the compound (11) as a host compound. About the obtained organic EL element, luminous efficiency was measured like Example 1, and a result is shown in Table 1.

Comparative Example 1
An organic EL device was produced in the same manner as in Example 1 except that complexP was used as the complex instead of the complex (C19). About the obtained organic EL element, luminous efficiency was measured like Example 1, and a result is shown in Table 1.

Comparative Example 2
An organic EL device was produced in the same manner as in Example 1 except that the following CBP was used instead of the host compound (11) and complexP was used instead of the complex (C19). About the obtained organic EL element, luminous efficiency was measured like Example 1, and a result is shown in Table 1.

  As described in detail above, the organic EL device of the present invention has no pixel defects and has high luminous efficiency while being at a low voltage. This organic EL element can be used in, for example, electrophotographic photoreceptors, flat light emitters such as wall-mounted television flat panel displays, light sources such as copiers, printers, liquid crystal display backlights or instruments, display boards, indicator lights, accessories, etc. Preferably used.

Claims (4)

In an organic electroluminescence device in which an organic thin film layer having at least a light emitting layer and a hole injection layer and / or a hole transport layer is sandwiched between a cathode and an anode, the hole injection layer and / or the hole transport The organic electroluminescent element in which a layer contains the metal complex compound represented by the following general formula (a).

Wherein M is a metal having an atomic weight greater than 40, (CN) is a substituted or unsubstituted cyclometalated ligand, and (CN) is at least one bonded to the metal. Different from other ligands.
R _{8 to} R ₁₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkylaryl group, CN, CF ₃ , CO ₂ R, C (O) R, NR ₂ , NO ₂ , OR (where R is a substituent) or a halogen atom, and two optional adjacent substitution positions together, independently fused A 4- to 7-membered cyclic group is formed, and the cyclic group is a cycloalkyl group, a cycloheteroalkyl group, an aryl group or a heteroaryl group, and the 4- to 7-membered cyclic group may be substituted. .
m is an integer of 1 or more, n is an integer of 1 or more, and m + n is the maximum number of ligands that can bind to the metal. )   The organic electroluminescence device according to claim 1, wherein M in the general formula (a) is iridium (Ir). The organic electroluminescent element of Claim 1 in which the said light emitting layer contains the compound represented by following General formula (1).

(In the formula, Cz is a carbazolyl group, an arylcarbazolyl group having 18 to 60 carbon atoms, an azacarbazolyl group, an arylazacarbazolyl group having 18 to 60 carbon atoms, an acridinyl group, a phenoxazinyl group, or a dibenzoazepinyl group. Ar ¹ and Ar ² are each independently a substituted or unsubstituted aryl group having 6 to 60 carbon atoms or a substituted or unsubstituted heterocyclic group having 3 to 60 carbon atoms. ³ is an aromatic hydrocarbon group having 6 to 60 carbon atoms or a substituted or unsubstituted heterocyclic group having 3 to 60 carbon atoms, Ar ⁴ is a substituted or unsubstituted benzene residue, substituted or unsubstituted A thiophene residue, a substituted or unsubstituted triazole residue, a substituted or unsubstituted fluorene residue, or a substituted or unsubstituted spirobifluorene residue That.
a is an integer of 0 to 1, b is an integer of 0 to 4, c is an integer of 1 to 3, and when Cz and Ar ⁴ are plural, they may be the same as or different from each other.
However, when a = 0 and c = 1, Ar ³ and Ar ⁴ are benzene residues, and Ar ² is a phenylcarbazolyl group or a carbazolyl group. When a = 1, b = 0 and c = 1, the case where Ar ³ is a benzene residue and Ar ¹ and Ar ² are phenylcarbazolyl groups is excluded. Further, when b = 0 and c = 1, the case where Ar ³ is a benzene residue and Ar ¹ , Ar ² and Cz are a carbazolyl group or a phenylcarbazolyl group is excluded. ) The organic electroluminescent element of Claim 1 in which the said light emitting layer contains the compound represented by following General formula (2) and / or (3).
(Cz-) _n A (2)
Cz (−A) _m (3)
[In the formula, Cz represents a substituted or unsubstituted arylcarbazolyl group or carbazolylalkylene group, or a substituted or unsubstituted arylazacarbazolyl group, and A represents the following general formula (A). Group. n and m are integers of 1 to 3, respectively.
(M) p- (L) q- (M ') r (A)
(M and M ′ are each independently a nitrogen-containing heteroaromatic ring having 2 to 40 carbon atoms that forms a substituted or unsubstituted ring, and may be the same or different. L is a single bond or a substituted ring. Alternatively, it is an unsubstituted aryl group or arylene group having 6 to 30 carbon atoms, a substituted or unsubstituted cycloalkylene group having 5 to 30 carbon atoms, or a substituted or unsubstituted heteroaromatic ring having 2 to 30 carbon atoms. p is 0 to 2, q is 1 to 2, and r is an integer of 0 to 2. However, p + r is 1 or more.)]