WO2014122937A1

WO2014122937A1 - Organic electroluminescence element

Info

Publication number: WO2014122937A1
Application number: PCT/JP2014/000651
Authority: WO
Inventors: 江美子神戸; 中村　雅人; 由美子水木; 舟橋　正和
Original assignee: ソニー株式会社; 出光興産株式会社
Priority date: 2013-02-08
Filing date: 2014-02-07
Publication date: 2014-08-14
Also published as: JPWO2014122937A1; TW201446744A

Abstract

An organic electroluminescence element having, in the following order, an anode, a light-emitting layer, an electron injection layer, and a cathode, the electron injection layer and the light-emitting layer being adjacent, the electron injection layer containing a π-electron-deficient compound and an electron-donating material. The light-emitting layer contains at least a first host material, a second host material, and a phosphorescent light-emitting dopant material.

Description

Organic electroluminescence device

The present invention relates to an organic electroluminescence element.

In recent years, in organic electroluminescence (EL) devices, research on phosphorescent materials has been actively conducted in order to achieve high luminous efficiency.
Phosphorescence emission is expected to have a high efficiency of up to about 4 times that of fluorescence emission. However, phosphorescence emission requires more energy than fluorescence emission in the process of excitation, and the emission tends to be unstable, so that sufficient emission efficiency cannot be obtained, and the device has a problem of shortening the lifetime. .

In order to stabilize the host material constituting the light emitting layer, it has been proposed to use a mixture of two types of host materials (Patent Document 1).
In addition, a host material including an electron transporting group and a hole transporting group has been proposed (Patent Document 2).
In order to smoothly transfer energy from the host to the phosphorescent dopant in the light emitting layer, a method in which two types of phosphorescent dopants are mixed with the host has been proposed (Patent Document 3).
In each of the organic EL elements of Patent Documents 1 to 3, a hole blocking layer and an electron transport layer are laminated adjacent to the light emitting layer.

Japanese Patent No. 4850521 Patent 4208766 Patent 4039023

The technique for stabilizing the light-emitting layer disclosed in the above document is insufficient for obtaining stable light emission. Specifically, the charge balance in the light emitting layer is poor, and excitons approach the electron transport layer side. As a result, in order to prevent the absorption of excitons by the electron transport layer, a hole blocking layer having a large energy gap is required adjacent to the light emitting layer. However, since the hole blocking layer has a large energy gap, it is difficult to inject charges and has a low charge transport capability. Therefore, the light emission efficiency was lowered due to an increase in driving voltage and a shortage of charge injected into the light emitting layer.
Moreover, the hole injection into the hole blocking layer is likely to cause deterioration of the blocking layer itself, which causes a shortened life of phosphorescence.
Furthermore, the increase in the number of stacked organic layers causes problems in device thickness design, and also increases the manufacturing cost.
An object of the present invention is to simply provide a phosphorescent light-emitting element having high luminous efficiency, low driving voltage, and long life.

As a result of intensive studies to solve the above-described problems, the present inventors have used two or more kinds of predetermined host materials for the light emitting layer and laminated a layer containing an electron donating material adjacent to the light emitting layer. The inventors have found that a device having a high light emission efficiency and a low driving voltage and having a long lifetime can be formed, and the present invention has been completed.

According to the present invention, the following organic EL elements are provided.
1. Having an anode, a light emitting layer, an electron injection layer, and a cathode in this order;
The electron injection layer and the light emitting layer are adjacent to each other;
The electron injection layer includes a π electron deficient compound and an electron donating material. The light emitting layer includes at least a first host material, a second host material, and a phosphorescent dopant material. .
2. 2. The organic electroluminescence device according to 1, wherein the first host material and the second host material are selected from materials represented by any of the following formulas (1) to (3).

[In Formula (1),
Z ¹ represents a ring structure represented by the following formula (1-1) or (1-2) condensed at a. Z ² represents a ring structure represented by the following formula (1-1) or (1-2) condensed at b. However, at least one of Z ¹ and Z ² is represented by the following formula (1-1).
M ¹ is a substituted or unsubstituted nitrogen-containing heteroaromatic ring having 5 to 30 ring-forming atoms,
L ¹ represents a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted divalent heterocyclic group having 5 to 30 ring atoms, and a ring forming carbon number. It represents a 5-30 cycloalkylene group or a group in which these are linked.
k represents 1 or 2. ]

[In the above formula (1-1),
c represents condensation in a or b in the formula (1).
In the above (1-2), any one of d, e and f represents condensation in a or b in the general formula (1).
In the above formulas (1-1) and (1-2),
X ¹¹ represents a sulfur atom, an oxygen atom, N—R ¹⁹ , or C (R ²⁰ ) (R ²¹ ).
R ¹¹ to R ²¹ each independently represents a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted ring atom number of 5 to 30 heterocyclic groups, substituted or unsubstituted alkyl groups having 1 to 30 carbon atoms, substituted or unsubstituted alkenyl groups having 2 to 30 carbon atoms, substituted or unsubstituted alkynyl groups having 2 to 30 carbon atoms, substituted or An unsubstituted silyl group, a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 ring carbon atoms Represents a group.
Adjacent R ¹¹ to R ²¹ may be bonded to each other to form a ring. ]

[In Formula (2),
Z ¹¹ represents a ring structure represented by the formula (1-1) or (1-2) condensed at a. Z ²¹ represents a ring structure represented by the formula (1-1) or (1-2) condensed at b. However, at least one of Z ¹¹ and Z ²¹ is represented by the formula (1-1).
M ¹¹ is a substituted or unsubstituted nitrogen-containing heteroaromatic ring having 5 to 30 ring atoms.
k ¹ represents 1 or 2. ]

[In Formula (3),
A ¹ and A ² each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms.
A ³ represents a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a substituted or unsubstituted divalent heterocyclic group having 5 to 30 ring atoms.
m represents an integer of 0 to 3.
X ¹ to X ⁸ and Y ¹ to Y ⁸ each independently represent N or CR ^a .
R ^a is independently a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, a substituted or unsubstituted group. It represents a substituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted silyl group, a halogen atom or a cyano group. When ^a plurality of R ^a are present, the plurality of R ^a may be the same or different.
One of X ⁵ to X ⁸ and one of Y ¹ to Y ⁴ are bonded via A ³ .
Further, the formula (3) satisfies at least one of the following (i) to (v).
(I) At least one of A ¹ and A ² is an aromatic hydrocarbon group having 6 to 30 ring carbon atoms substituted with a cyano group, or a heterocycle having 5 to 30 ring atoms substituted with a cyano group. It is a cyclic group.
(Ii) At least one of X ¹ to X ⁴ and Y ⁵ to Y ⁸ is CR ^a , and at least one of R ^a in X ¹ to X ⁴ and Y ⁵ to Y ⁸ is substituted with a cyano group It is an aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a heterocyclic group having 5 to 30 ring atoms substituted with a cyano group.
(Iii) m is an integer of 1 to 3, and at least one of A ³ is substituted with a divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms substituted with a cyano group, or a cyano group And a divalent heterocyclic group having 5 to 30 ring atoms.
(Iv) At least one of X ⁵ to X ⁸ and Y ¹ to Y ⁴ is CR ^a , and at least one of R ^a in X ⁵ to X ⁸ and Y ¹ to Y ⁸ is substituted with a cyano group It is an aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a heterocyclic group having 5 to 30 ring atoms substituted with a cyano group.
(V) At least one of X ¹ to X ⁸ and Y ¹ to Y ⁸ is C-CN. ]
3. 3. The organic electroluminescence device according to 2, wherein the first host material is a material represented by the formula (1), and the second host material is a material represented by the formula (3).
4). 3. The organic electroluminescence device according to 2, wherein the first host material is a material represented by the formula (2), and the second host material is a material represented by the formula (3).
5. 3. The organic electroluminescence device according to 2, wherein the first host material is a material represented by the formula (1), and the second host material is a material represented by the formula (2).
6). 6. The organic electroluminescence device according to any one of 1 to 5, wherein the π electron deficient compound is selected from compounds represented by the following formulas (I) to (III).

[Wherein, R ^1a to R ^7a , R ^1b to R ^7b , and R ^1c to R ^6c each independently represent a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 60 ring carbon atoms, substituted or unsubstituted. Pyridyl group, substituted or unsubstituted quinolyl group, substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, substituted or unsubstituted cycloalkyl group having 3 to 50 carbon atoms, substituted or unsubstituted 7 to 7 carbon atoms 50 aralkyl groups, substituted or unsubstituted alkoxy groups having 1 to 50 carbon atoms, substituted or unsubstituted aryloxy groups having 6 to 50 ring carbon atoms, substituted or unsubstituted arylthio groups having 6 to 50 ring carbon atoms A substituted or unsubstituted alkoxycarbonyl group having 2 to 50 carbon atoms, an amino group substituted with a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, halo Emissions atom, a cyano group, a nitro group, a hydroxyl group or a carboxyl ^group, R ^1a ~ ^{R 7a,} of R 1b ^{~ R 7b} or ^R 1c ^{~ R 6c,} are bonded to each other to form a ring in which adjacent Also good.
L ^1a and L ^1b are each a single bond or a linking group.
Ar ^1a , Ar ^1b , Ar ^1c and Ar ^2c are each a substituted or unsubstituted aromatic group having 6 to 60 carbon atoms.
n is 1 to 4, and when n is 2 or more, the groups having a phenanthroline skeleton in parentheses may be the same or different. ]
7). Any one of 1 to 6, wherein the electron donating material is at least one selected from a simple substance of an alkali metal, a simple substance of an alkaline earth metal, a simple substance of a rare earth metal, a rare earth metal compound, and a rare earth metal complex. The organic electroluminescent element of description.
8). 8. The organic electroluminescence device according to any one of 1 to 7, wherein the content of the first host material with respect to the total of the first host material and the second host material is 30 to 95% by mass.
9. 8. The organic electroluminescence device according to any one of 1 to 7, wherein the content of the first host material is 50 to 95% by mass with respect to the total of the first host material and the second host material.
10. 10. The organic electroluminescence device according to any one of 1 to 9, wherein the content of the electron donating material in the electron injection layer is 20% by mass or less.
11. 11. The organic electroluminescence device according to any one of 1 to 10, wherein the phosphorescent dopant material is an orthometalated complex of a metal atom selected from iridium (Ir), osmium (Os), and platinum (Pt).
12 12. The organic electroluminescence device according to any one of 1 to 11, having only the electron injection layer between the light emitting layer and the cathode.

According to the present invention, by laminating layers containing an electron donating material adjacent to each other, it is possible to provide an organic EL device with high luminous efficiency, low driving voltage, and long life.

It is a figure which shows the layer structure of one Embodiment of the organic EL element of this invention. It is a figure which shows the layer structure of other embodiment of the organic EL element of this invention.

The organic EL device of the present invention has an anode, a light emitting layer, an electron injection layer, and a cathode in this order.
FIG. 1 shows an element configuration of an embodiment of an organic light emitting element according to the present invention.
The organic EL element 1 has a configuration in which an anode 10, a hole injection layer 20, a hole transport layer 30, a light emitting layer 40, an electron injection layer 50, and a cathode 60 are laminated in this order.
In the present invention, the electron injection layer 50 and the light emitting layer 40 are adjacent to each other. Moreover, the electron injection layer 50 and the light emitting layer 40 each contain the following structural component.
The electron injection layer includes a π electron deficient compound and an electron donating material.
The light emitting layer includes at least a first host material, a second host material, and a phosphorescent dopant material.

In the present invention, by using the electron injecting layer and the light emitting layer, the charge balance in the light emitting layer is improved, so that the light emission efficiency is improved. Further, since the light emitting layer becomes stable, the life is improved.
In addition, between the light emitting layer and the cathode (intermediate electrode in the case of a stack type organic EL device), in conventional devices, it is generally formed by laminating two or more electron transport layers, hole blocking layers, and the like. However, since the present invention is excellent in charge balance, high luminous efficiency can be obtained even when only one electron injection layer is formed.
Hereinafter, the electron injection layer and the light emitting layer, which are the features of the present invention, will be described.

1. Electron Injection Layer The electron injection layer of the present invention includes a π electron deficient compound and an electron donating material.
Examples of the π electron deficient compound include compounds capable of coordinating with metal atoms. Specific examples include phenanthroline compounds, benzimidazole compounds, quinolinol, and the like.

As the phenanthroline-based compound, compounds represented by the following formulas (I) to (III) are preferable. Of these, compounds represented by the following formula (I) or (II) are preferred.

In the above formulas (I) to (III), R ^1a to R ^7a , R ^1b to R ^7b , and R ^1c to R ^6c are each independently a hydrogen atom, a substituted or unsubstituted ring-forming carbon number of 6 to 60 Aryl group, substituted or unsubstituted pyridyl group, substituted or unsubstituted quinolyl group, substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, substituted or unsubstituted cycloalkyl group having 3 to 50 carbon atoms, substituted Or an unsubstituted aralkyl group having 7 to 50 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 50 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 50 carbon atoms, a substituted or unsubstituted ring Substituted with an arylthio group having 6 to 50 carbon atoms, a substituted or unsubstituted alkoxycarbonyl group having 2 to 50 carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms Amino group, a halogen atom, a cyano group, a nitro group, a hydroxyl group or a carboxyl group.
Of R ^1a to R ^7a , R ^1b to R ^7b , or R ^1c to R ^6c , adjacent ones may be bonded to each other to form a ring. Examples of the ring include a benzene ring, a naphthalene ring, a pyrazine ring, a pyridine ring, and a furan ring.
L ^1a and L ^1b are each a single bond or a linking group. Examples of the linking group include a substituted or unsubstituted aromatic group having 6 to 20 ring carbon atoms, a substituted or unsubstituted alkylene chain having 1 to 8 carbon atoms, and a substituted or unsubstituted heterocyclic ring. Specifically, a substituted or unsubstituted benzene ring, a substituted or unsubstituted naphthalene ring, a substituted or unsubstituted methylene chain, or a substituted or unsubstituted pyridine ring is preferable.
Ar ^1a , Ar ^1b , Ar ^1c and Ar ^2c are each a substituted or unsubstituted aromatic group having 6 to 60 carbon atoms.
n is 1 to 4, and when n is 2 or more, the groups having a phenanthroline skeleton in parentheses may be the same or different.

As the compound represented by the formula (I) or (II), a compound represented by the following formula (Ia), (Ib), (II-a) or (II-b) is preferable.

By having a group having a phenanthroline skeleton and a group having an anthracene skeleton, it is possible to achieve both a function as an electron acceptor and a transport ability as an electron transport layer. Furthermore, deposition stability and film formability are improved.

In the formulas (Ia), (Ib), (II-a) and (II-b), R ^1a to R ^7a , R ^1b to R ^7b , L ^1a and L ^1b are each represented by the formula (I) And the same group as R ^1a to R ^7a , R ^1b to R ^7b , L ^1a and L ^1b in (II).
R ^11a to R ^20a and R ^11b to R ^20b are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 60 ring carbon atoms, a substituted or unsubstituted pyridyl group, a substituted or unsubstituted quinolyl. Group, substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, substituted or unsubstituted cycloalkyl group having 3 to 50 carbon atoms, substituted or unsubstituted aralkyl group having 7 to 50 ring carbon atoms, substituted or unsubstituted Substituted alkoxy group having 1 to 50 carbon atoms, substituted or unsubstituted aryloxy group having 6 to 50 ring carbon atoms, substituted or unsubstituted arylthio group having 5 to 50 ring carbon atoms, substituted or unsubstituted carbon An alkoxycarbonyl group having 2 to 50 amino acids, an amino group substituted with a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, a halogen atom, Anomoto, a nitro group, a hydroxyl group or a carboxyl group.
Of R ^11a to R ^20a or R ^11b to R ^20b , adjacent ones may be bonded to each other to form a ring. Examples of the ring include a benzene ring, a naphthalene ring, a pyrazine ring, a pyridine ring, and a furan ring.

Hereinafter, examples of each group such as the above-described formula (I) will be described.
In the present specification, the aryl group includes a monocyclic aromatic hydrocarbon ring group and a condensed aromatic hydrocarbon ring group in which a plurality of hydrocarbon rings are condensed, and the heteroaryl group is a monocyclic heteroaromatic group. And a hetero-fused aromatic ring group in which a plurality of heteroaromatic rings are condensed, and a hetero-fused aromatic ring group in which an aromatic hydrocarbon ring and a heteroaromatic ring are condensed.
Ring-forming carbon (nuclear carbon) means a carbon atom constituting an aromatic ring, and ring-forming atom (nuclear atom) constitutes a heterocyclic ring (including a saturated ring, an unsaturated ring and an aromatic heterocyclic ring). Means carbon and heteroatoms.
The “carbon number ab” in the expression “substituted or unsubstituted X group having carbon number ab” represents the number of carbons when the X group is unsubstituted, and the X group is substituted. The carbon number of the substituent in the case where it is present is not included.
In the present invention, the hydrogen atom includes isotopes having different numbers of neutrons, that is, light hydrogen (protium), deuterium (triuterium), and tritium.

The aryl group having 6 to 60 ring carbon atoms preferably has 6 to 30 carbon atoms, particularly preferably 6 to 20 carbon atoms. For example, phenyl, fluorenyl, naphthyl, anthryl, phenanthryl, chrysenyl, pyrenyl, triphenylenyl, fluorane And tenenyl.
Examples of the aromatic group represented by Ar ^1a , Ar ^1b , Ar ^1c and Ar ^2c include the above-described aryl group and a monovalent or divalent or higher group derived by removing a hydrogen atom from the aryl group.
R ^1a to R ^7a and R ^1b to R ^{7b in the} formulas (I) and (II) are preferably hydrogen, phenyl, or naphthyl.

As the alkyl group having 1 to 50 carbon atoms, there is a linear or branched alkyl group. Preferably it has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, and examples thereof include methyl, ethyl, propyl, butyl, pentyl, hexyl and the like.

Examples of the cycloalkyl group having 3 to 50 ring carbon atoms include cyclopentyl and cyclohexyl.

The aralkyl group having 7 to 50 carbon atoms is represented by —Y—Z. Examples of Y include alkylene examples corresponding to the above alkyl groups, and examples of Z include the above aryl groups. It is done. The aryl part of the aralkyl group preferably has 6 to 30 carbon atoms. The alkyl moiety preferably has 1 to 10 carbon atoms, particularly preferably 1 to 6 carbon atoms. For example, benzyl group, phenylethyl group, 2-phenylpropan-2-yl group.

An alkoxy group having 1 to 50 carbon atoms is represented as —OY, and examples of Y include the above alkyl groups. The alkoxy group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms, and examples thereof include methoxy, ethoxy, propoxy, butoxy and the like.

An aryloxy group having 6 to 50 ring carbon atoms is represented by —OY, and examples of Y include the above aryl groups. The number of carbon atoms is preferably 6 to 20, more preferably 6 to 16, and particularly preferably 6 to 12, and examples thereof include phenyloxy and 2-naphthyloxy.

An arylthio group having 6 to 50 ring carbon atoms is represented by —SY, and examples of Y include the above aryl groups. Preferably it has 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenylthio.

The alkoxycarbonyl group having 2 to 50 carbon atoms preferably has 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, and particularly preferably 2 to 12 carbon atoms, and examples thereof include methoxycarbonyl and ethoxycarbonyl.

Examples of the amino group substituted with a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms include diarylamino, alkylarylamino, and arylamino. Examples of the alkyl group and aryl group bonded to the nitrogen atom include the above-described aryl group and alkyl group. Preferably it has 6 to 20 carbon atoms, more preferably 6 to 12 carbon atoms, particularly preferably 6 carbon atoms, and examples thereof include diphenylamino and the like.

Examples of the halogen atom include a fluorine atom, a chlorine atom and a bromine atom, preferably a fluorine atom.

Substituents for the above groups are each independently a linear or branched alkyl group having 1 to 20 carbon atoms, a linear or branched alkenyl group having 2 to 20 carbon atoms, or a ring-forming carbon number of 3 A cycloalkyl group having 20 to 20 carbon atoms, a trialkylsilyl group having an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 24 ring carbon atoms or a silyl group having an alkyl group, an alkyl group having 1 to 20 carbon atoms, and a ring An alkylarylsilyl group having an aryl group having 6 to 24 carbon atoms, an aryl group having 6 to 24 ring carbon atoms, a heteroaryl group having 5 to 24 ring atoms, an alkoxy group having 1 to 20 carbon atoms, a halogen atom Or it is a cyano group. Specific examples include the aryl group, alkyl group, cycloalkyl group, heteroaryl group, alkoxy group, halogen atom, and cyano group. Furthermore, these groups may have a similar substituent.
Examples of the alkenyl group include a substituent having an unsaturated bond in the molecule of the alkyl group described above.
Examples of the silyl group having an aryl group include a triarylsilyl group, an alkylarylsilyl group, and a trialkylsilyl group.
Examples of suitable substituents include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, cyclohexyl, phenyl, 1-naphthyl, 2-naphthyl, trimethylsilyl, triphenylsilyl.
Specific examples of the compounds represented by formulas (I) to (III) are shown below.

For the synthesis of the compounds represented by formulas (I) and (II), reference can be made to WO2007 / 018004, WO2006 / 64484, and WO2006 / 021982.

Examples of the benzimidazole compound include benzimidazole derivatives represented by the following formula (IV).

In the formula, A ₁₄ has a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a polycyclic aromatic hydrocarbon group condensed with 3 to 40 aromatic rings, substituted or unsubstituted, An unsubstituted hydrocarbon group having 6 to 60 carbon atoms or a nitrogen-containing heterocyclic group.
Specific examples of the halogen atom and the alkyl group having 1 to 20 carbon atoms are the same as those in the above formula (I).

A polycyclic aromatic hydrocarbon group having 3 to 40 aromatic rings condensed therein and a polycyclic aromatic hydrocarbon group having 6 to 60 carbon atoms and a condensed polycyclic ring having 3 to 40 aromatic rings condensed Examples of the aromatic hydrocarbon group include anthracene, naphthacene, pentacene, pyrene and chrysene. Examples of the hydrocarbon group having 6 to 60 carbon atoms include an alkyl group, a cycloalkyl group, and an aryl group. In addition, these specific examples are the same as that of Formula (I) mentioned above. As the hydrocarbon group, an aryl group is preferable, and among them, a phenyl group, a naphthyl group, a biphenyl group, a terphenyl group, a fluorenyl group, and the like are preferable. These may have a substituent.
Examples of the nitrogen-containing heterocyclic group include a pyridine ring and triazine.

B is a single bond or a substituted or unsubstituted aromatic ring group. As the aromatic ring group, a phenylene group and an anthracenylene group are preferable.
R ₃₁ and R ₃₂ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 60 carbon atoms, substituted or unsubstituted An unsubstituted nitrogen-containing heterocyclic group, or a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms. Specific examples of the groups are the above-mentioned formula (I), is the same as A _14.
Specific examples of the compound represented by the formula (IV) are shown below.

As the quinolinol, 8-hydroxyquinoline is preferable.

Examples of the electron donating material include an electron donating metal simple substance, a metal compound, and a metal complex. Specifically, alkali metals, alkali metal compounds, organometallic complexes containing alkali metals, alkaline earth metals, alkaline earth metal compounds, organometallic complexes containing alkaline earth metals, rare earth metals, rare earth metal compounds, and rare earth metals Of the organometallic complexes containing, a layer containing at least one is preferable. Among these, it is preferable to contain at least one of an alkali metal, an alkaline earth metal, a rare earth metal, a rare earth metal compound, and a rare earth metal complex.

Examples of the alkali metal include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and the like, and those having a work function of 2.9 eV or less are particularly preferable. Of these, Li, K, Rb, and Cs are preferable, Li, Rb, and Cs are more preferable, and Li is most preferable.
Examples of the alkaline earth metal include calcium (Ca), magnesium (Mg) strontium (Sr), barium (Ba) and the like, and those having a work function of 2.9 eV or less are particularly preferable.
Examples of the rare earth metal include scandium (Sc), yttrium (Y), cerium (Ce), terbium (Tb), ytterbium (Yb) and the like, and those having a work function of 2.9 eV or less are particularly preferable.
Among the above metals, preferred metals are particularly high in reducing ability, and by adding a relatively small amount to the electron injection region, it is possible to improve the light emission luminance and extend the life of the organic EL element.

Examples of the alkali metal compound include lithium oxide (Li ₂ O), cesium oxide (Cs ₂ O), alkali oxides such as potassium oxide (K ₂ O), lithium fluoride (LiF), sodium fluoride (NaF), fluorine. Examples thereof include alkali halides such as cesium fluoride (CsF) and potassium fluoride (KF), and lithium fluoride (LiF), lithium oxide (Li ₂ O), and sodium fluoride (NaF) are preferable.
Examples of the alkaline earth metal compound include barium oxide (BaO), strontium oxide (SrO), calcium oxide (CaO), and barium strontium oxide (Ba _x Sr _1-x O) (0 <x <1), Examples thereof include barium calcium oxide (Ba _x Ca _1-x O) (0 <x <1), and BaO, SrO, and CaO are preferable.
The rare earth metal compound, ytterbium fluoride _(YbF 3), scandium fluoride _(ScF 3), scandium oxide _(ScO 3), yttrium oxide _(Y _{2 O} 3), cerium oxide _(Ce _{2 O} 3), gadolinium fluoride _(GdF 3), include such terbium fluoride (TbF ₃₎ _{_{is, YbF 3, ScF 3, TbF}} 3 are preferable.

The organometallic complex is not particularly limited as long as it contains at least one of an alkali metal ion, an alkaline earth metal ion, and a rare earth metal ion as a metal ion as described above. The ligands include quinolinol, benzoquinolinol, acridinol, phenanthridinol, hydroxyphenyl oxazole, hydroxyphenyl thiazole, hydroxydiaryl thiadiazole, hydroxydiaryl thiadiazole, hydroxyphenylpyridine, hydroxyphenylbenzimidazole, hydroxybenzotriazole, Hydroxyfulborane, bipyridyl, phenanthroline, phthalocyanine, porphyrin, cyclopentadiene, β-diketones, azomethines, and derivatives thereof are preferred, but are not limited thereto.

As the addition form of the metal, compound and complex, it is preferable to form a layer or island in the interface region. As a forming method, while vapor-depositing at least one of the above metal, compound and complex by resistance heating vapor deposition, an organic material which is a light emitting material or an electron injection material for forming an interface region is simultaneously deposited, and the above metal, A method of dispersing at least one of the compound and the complex is preferable. The dispersion concentration is usually organic matter (π electron deficient compound): metal, compound and complex = 1000: 1 to 1: 1000, preferably 100: 1 to 1: 1, in terms of film thickness ratio.

When forming at least one of the metal, the compound and the complex in a layered form, after forming the light emitting material or the electron injecting material which is an organic layer at the interface in a layered form, at least one of the metal, the compound and the complex is singly used. Vapor deposition is performed by resistance heating vapor deposition, and the layer is preferably formed with a thickness of 0.1 nm to 15 nm.

When forming at least one of the metal, compound, and complex in an island shape, after forming a light emitting material or an electron injection material, which is an organic layer at the interface, in an island shape, at least one of the metal, the compound, and the complex is formed. Vapor deposition is performed by a resistance heating vapor deposition method alone, and is preferably formed with an island thickness of 0.05 nm to 1 nm.

In the organic EL device of the present invention, the ratio of at least one of the main component and the metal, compound and complex is a film thickness ratio of main component: electron donating dopant and / or organometallic complex = 100: The ratio is preferably 1: 1 to 1: 1, and more preferably 50: 1 to 4: 1.

The thickness of the electron injection layer is preferably from 0.1 nm to 100 nm, particularly preferably from 1 nm to 50 nm.

2. Light-emitting layer The light-emitting layer is an organic layer having a light-emitting function, and is formed of one layer or a plurality of layers. Among these layers, one layer includes the first host material, the second host material, and the phosphorescent dopant material as described above. contains.
The first host material and the second host material are different compounds and have different electron mobility. In the present application, the higher host mobility is the first host material.
The content of the first host material with respect to the total of the first host material and the second host material is preferably 30 to 95% by mass, and particularly preferably 50 to 95% by mass. Within this range, it becomes easy to achieve charge balance, low driving voltage, and easy formation of a long-life element.

The first host material and the second host material are preferably materials represented by any of the following formulas (1) to (3), for example.

[In the above formula (1-1),
c represents condensation in a or b in the formula (1).
In the above (1-2), any one of d, e and f represents condensation in a or b in the general formula (1).
In the above formulas (1-1) and (1-2),
X ¹¹ represents a sulfur atom, an oxygen atom, N—R ¹⁹ , or C (R ²⁰ ) (R ²¹ ).
R ¹¹ to R ²¹ each independently represents a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted ring formation. A heterocyclic group having 5 to 30 atoms, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms A group, a substituted or unsubstituted silyl group, a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted ring forming carbon number Represents 6 to 30 aryloxy groups;
Adjacent R ¹¹ to R ²¹ may be bonded to each other to form a ring. ]

In formula (2), Z ¹¹ , Z ²¹ , M ¹¹ , and k ¹ each represent the same group as Z ¹ , Z ² , M ¹ , and k in formula (1). The compound of the formula (2) represents a compound in which L ¹ of the formula (1) is a single bond.

[In Formula (3),
A ¹ and A ² each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms.
A ³ represents a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a substituted or unsubstituted divalent heterocyclic group having 5 to 30 ring atoms.
m represents an integer of 0 to 3.
X ¹ to X ⁸ and Y ¹ to Y ⁸ each independently represent N or CR ^a .
R ^a is independently a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, a substituted or unsubstituted group. It represents a substituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted silyl group, a halogen atom or a cyano group. When ^a plurality of R ^a are present, the plurality of R ^a may be the same or different.
One of X ⁵ to X ⁸ and one of Y ¹ to Y ⁴ are bonded via A ³ .
Further, the formula (3) satisfies at least one of the following (i) to (v).
(I) At least one of A ¹ and A ² is an aromatic hydrocarbon group having 6 to 30 ring carbon atoms substituted with a cyano group, or a heterocycle having 5 to 30 ring atoms substituted with a cyano group. It is a cyclic group.
(Ii) At least one of X ¹ to X ⁴ and Y ⁵ to Y ⁸ is CR ^a , and at least one of R ^a in X ¹ to X ⁴ and Y ⁵ to Y ⁸ is substituted with a cyano group It is an aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a heterocyclic group having 5 to 30 ring atoms substituted with a cyano group.
(Iii) m is an integer of 1 to 3, and at least one of A ³ is substituted with a divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms substituted with a cyano group, or a cyano group And a divalent heterocyclic group having 5 to 30 ring atoms.
(Iv) At least one of X ⁵ to X ⁸ and Y ¹ to Y ⁴ is CR ^a , and at least one of R ^a in X ⁵ to X ⁸ and Y ¹ to Y ⁸ is substituted with a cyano group It is an aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a heterocyclic group having 5 to 30 ring atoms substituted with a cyano group.
(V) At least one of X ¹ to X ⁸ and Y ¹ to Y ⁸ is C-CN. ]
In the formula (3), an aromatic hydrocarbon group having 6 to 30 ring carbon atoms substituted with a cyano group and a heterocyclic group having 5 to 30 ring atoms substituted with a cyano group are further represented by cyano You may have substituents other than group.
The m is preferably 0 to 2, more preferably 0 or 1. When m is 0, one of X ⁵ to X ⁸ and one of Y ¹ to Y ⁴ are bonded through a single bond.

In the present invention, when the first host material is a material represented by the above formula (1) and the second host material is a material represented by the formula (3), the first host material is represented by the formula (2). And the second host material is a material represented by formula (3), and the first host material is a material represented by formula (1), and the second host material Is preferably a material represented by the formula (2).

In the material represented by the above formula (1), the nitrogen atom of the carbazole derivative skeleton responsible for injecting and transporting holes and the nitrogen-containing heteroaromatic ring skeleton responsible for injecting and transporting electrons are linked via a linking group (L ¹ ). Therefore, the hole injection transport skeleton and the electron injection transport skeleton have little influence on each other, and therefore, it is considered that the charge injection transport effect related to charge transfer is most excellent.
In the material represented by the above formula (2), the nitrogen atom of the carbazole derivative skeleton responsible for injecting and transporting holes and the nitrogen-containing heteroaromatic ring skeleton responsible for injecting and transporting electrons are directly bonded. Since the hole injecting and transporting skeleton and the electron injecting and transporting skeleton have some influence on each other, the charge injecting and transporting effect tends to be somewhat lower than that of the material represented by the above formula (1).
Since the material represented by the above formula (3) has a cyano group, the electron trapping property tends to be improved and the electron mobility tends to be low.

Therefore, the materials represented by the above formulas (1) to (3) tend to have the highest electron mobility in the material of formula (1) and the lowest in the material of formula (3). In the case of the above combination, it becomes easy to balance holes and electrons, and it becomes easy to balance charges in a single layer in the light emitting layer, and it is possible to realize a high-efficiency, long-life, low-voltage element.

Among the above formulas (1), those represented by the following formula (1a) are preferable.

[In Formula (1a),
Z ¹ represents a ring structure represented by the general formula (1-1) or (1-2) condensed in a. Z ² represents a ring structure represented by the general formula (1-1) or (1-2) condensed at b. However, at least one of Z ^{1 and} Z ² is represented by the general formula (1-1).
L ¹ has the same meaning as ^{L 1} in Formula (1).
X ¹² to X ¹⁴ are each independently a nitrogen atom, CH, or a carbon atom bonded to R ³¹ or L ^1, and at least one of X ¹² to X ¹⁴ is a nitrogen atom.
Y ¹¹ to Y ¹³ each independently represent CH or a carbon atom bonded to R ³¹ or L ¹ .
Each of R ³¹ independently represents a halogen atom, a cyano group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, A substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms, a substituted or unsubstituted silyl group, A substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 ring carbon atoms.
If R ³¹ there are a plurality, a plurality of R ³¹ may be the same or different from each other and, R ³¹ may be bonded to each other to form a ring adjacent.
k represents 1 or 2, and n represents an integer of 0 to 4.
C in the formula (1-1) is condensed in a or b in the general formula (1a);
Any one of d, e and f in the general formula (1-2) is condensed in a or b in the general formula (1a). ]

Here, examples of the compound in which the general formulas (1-1) and (2-2) are condensed in a and b in the above formula (1a) include those represented by the following general formula.

The compound represented by the above formula (1) is more preferably represented by the following formula (1b), and particularly preferably represented by the following formula (1c).

Expression (1b) middle L ¹ has the same meaning as ^{L 1} in Formula (1).
X ¹² to X ¹⁴ are each independently a nitrogen atom, CH, or a carbon atom bonded to R ³¹ or L ^1, and at least one of X ¹² to X ¹⁴ is a nitrogen atom.
Y ¹¹ to Y ¹³ each independently represent CH or a carbon atom bonded to R ³¹ or L ¹ .
Each of R ³¹ independently represents a halogen atom, a cyano group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, A substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms, a substituted or unsubstituted silyl group, A substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 ring carbon atoms.
If R ³¹ there are a plurality, a plurality of R ³¹ may be the same or different from each other and, R ³¹ may be bonded to each other to form a ring adjacent.
n represents an integer of 0 to 4.
R ⁴¹ to R ⁴⁸ are each independently a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted ring formation. A heterocyclic group having 5 to 30 atoms, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms A group, a substituted or unsubstituted silyl group, a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted ring forming carbon number Represents 6 to 30 aryloxy groups;
Adjacent R ⁴¹ to R ⁴⁸ may be bonded to each other to form a ring. ]

[In Formula (1c),
L ¹ has the same meaning as ^{L 1} in Formula (1).
X ¹² to X ¹⁴ are each independently a nitrogen atom, CH, or a carbon atom bonded to R ³¹ or L ^1, and at least one of X ¹² to X ¹⁴ is a nitrogen atom.
Y ¹¹ to Y ¹³ each independently represent CH or a carbon atom bonded to R ³¹ or L ¹ .
Each of R ³¹ independently represents a halogen atom, a cyano group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, A substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms, a substituted or unsubstituted silyl group, A substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 ring carbon atoms.
Further, adjacent R ³¹ may be bonded to each other to form a ring.
n represents an integer of 0 to 4.
L ² and L ³ are each independently a single bond, a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted 2 to 5 ring atom having 2 to 30 ring atoms. A valent heterocyclic group, a cycloalkylene group having 5 to 30 ring carbon atoms, or a group in which these are connected is represented.
R ⁵¹ to R ⁵⁴ each independently represent a halogen atom, a cyano group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms. A cyclic group, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms, a substituted or unsubstituted group A silyl group, a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 ring carbon atoms Represents.
If R ⁵¹ there are a plurality, a plurality of R ⁵¹ may be the same or different, and, R ⁵¹ may be bonded to each other to form a ring adjacent.
If R ⁵² there are a plurality, a plurality of R ⁵² may be the same or different, and, R ⁵² may be bonded to each other to form a ring adjacent.
If R ⁵³ there are a plurality, a plurality of R ⁵³ may be the same or different, and, R ⁵³ may be bonded to each other to form a ring adjacent.
If R ⁵⁴ there are a plurality, the plurality of R ⁵⁴ may be the same or different from each other and, R ⁵⁴ may be bonded to each other to form a ring adjacent.
M ² represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms.
p and s each independently represent an integer of 0 to 4, and q and r each independently represents an integer of 0 to 3. ]

Hereinafter, examples of groups such as the above-described formula (1) will be described.
In the above formulas (1) and (2), examples of the nitrogen-containing heteroaromatic ring represented by M ¹ or M ¹¹ include pyridine, pyrimidine, pyrazine, triazine, aziridine, azaindolizine, indolizine, imidazole, indole, Examples thereof include isoindole, indazole, purine, pteridine, β-carboline, naphthyridine, quinoxaline, terpyridine, bipyridine, acridine, phenanthroline, phenazine, and imidazopyridine, and pyridine, pyrimidine, and triazine are particularly preferable.

In the formulas (1), (1a), (1b), (1c), (1-1) and (1-2), R ¹¹ to R ²¹ , R ³¹ , R ⁴¹ to R ⁴⁸ and R ⁵¹ to R Examples of the halogen atom represented by ⁵⁴ include fluorine, chlorine, bromine, iodine and the like, and fluorine is preferred.

Examples of the aromatic hydrocarbon group having 6 to 30 ring carbon atoms include a non-condensed aromatic hydrocarbon group and a condensed aromatic hydrocarbon group, and more specifically, phenyl group, naphthyl group, phenanthryl group, biphenyl. Group, terphenyl group, quarterphenyl group, fluoranthenyl group, triphenylenyl group, phenanthrenyl group, fluorenyl group, spirofluorenyl group, 9,9-diphenylfluorenyl group, 9,9'-spirobi [9H-fluorene ] -2-yl group, 9,9-dimethylfluorenyl group, benzo [c] phenanthrenyl group, benzo [a] triphenylenyl group, naphtho [1,2-c] phenanthrenyl group, naphtho [1,2-a] And triphenylenyl group, dibenzo [a, c] triphenylenyl group, benzo [b] fluoranthenyl group, and the like. Group, naphthyl group, biphenyl group, terphenyl group, phenanthryl group, triphenylenyl group, fluorenyl group, spirobifluorenyl group, fluoranthenyl group are preferable, phenyl group, 1-naphthyl group, 2-naphthyl group, biphenyl- 2-yl group, biphenyl-3-yl group, biphenyl-4-yl group, phenanthren-9-yl group, phenanthren-3-yl group, phenanthren-2-yl group, triphenylene-2-yl group, 9,9 -Dimethylfluoren-2-yl group and fluoranthen-3-yl group are more preferable.

Examples of the heterocyclic group having 5 to 30 ring atoms include a non-condensed heterocyclic group and a condensed heterocyclic group, and more specifically, a pyrrole ring, an isoindole ring, a benzofuran ring, an isobenzofuran ring, and a dibenzothiophene. Ring, isoquinoline ring, quinoxaline ring, phenanthridine ring, phenanthroline ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, indole ring, quinoline ring, acridine ring, pyrrolidine ring, dioxane ring, piperidine ring, morpho Phosphorus ring, piperazine ring, carbazole ring, furan ring, thiophene ring, oxazole ring, oxadiazole ring, benzoxazole ring, thiazole ring, thiadiazole ring, benzothiazole ring, triazole ring, imidazole ring, benzimidazole ring, pyran ring, Dibenzofuran Benzo [c] dibenzofuran ring and groups formed from these derivatives, and the like, and dibenzofuran ring, carbazole ring, dibenzothiophene ring and groups formed from these derivatives are preferred, dibenzofuran-2-yl group, dibenzofuran A -4-yl group, a 9-phenylcarbazol-3-yl group, a 9-phenylcarbazol-2-yl group, a dibenzothiophen-2-yl group, and a dibenzothiophen-4-yl group are more preferable.

Examples of the alkyl group having 1 to 30 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, Examples include n-hexadecyl group, n-heptadecyl group, n-octadecyl group, neopentyl group, 1-methylpentyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group, adamantyl group, and the like. , Ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butyl group, cyclopent Group, a cyclohexyl group is preferred.

Examples of the alkenyl group having 2 to 30 carbon atoms and the alkynyl group having 2 to 30 carbon atoms include the above-described alkyl groups having a double bond or a triple bond.

Examples of substituted or unsubstituted silyl groups include trimethylsilyl group, triethylsilyl group, tributylsilyl group, dimethylethylsilyl group, t-butyldimethylsilyl group, vinyldimethylsilyl group, propyldimethylsilyl group, dimethylisopropylsilyl group, Examples include dimethylpropylsilyl group, dimethylbutylsilyl group, dimethyltertiarybutylsilyl group, diethylisopropylsilyl group, phenyldimethylsilyl group, diphenylmethylsilyl group, diphenyltertiarybutylsilyl group, and triphenylsilyl group. , Triethylsilyl group, t-butyldimethylsilyl group, vinyldimethylsilyl group, and propyldimethylsilyl group are preferable.

Examples of the alkoxy group having 1 to 30 carbon atoms include groups in which the alkyl moiety is the alkyl group.
Specific examples of the aralkyl group having 7 to 30 carbon atoms include benzyl group, 2-phenylpropan-2-yl group, 1-phenylethyl group, 2-phenylethyl group, 1-phenylisopropyl group and 2-phenylisopropyl group. Phenyl-t-butyl group, α-naphthylmethyl group, 1-α-naphthylethyl group, 2-α-naphthylethyl group, 1-α-naphthylisopropyl group, 2-α-naphthylisopropyl group, β-naphthylmethyl Group, 1-β-naphthylethyl group, 2-β-naphthylethyl group, 1-β-naphthylisopropyl group, 2-β-naphthylisopropyl group, 1-pyrrolylmethyl group, 2- (1-pyrrolyl) ethyl group, p -Methylbenzyl group, m-methylbenzyl group, o-methylbenzyl group, p-chlorobenzyl group, m-chlorobenzyl group, o-chlorobenzyl P-bromobenzyl group, m-bromobenzyl group, o-bromobenzyl group, p-iodobenzyl group, m-iodobenzyl group, o-iodobenzyl group, p-hydroxybenzyl group, m-hydroxybenzyl group, o -Hydroxybenzyl group, p-aminobenzyl group, m-aminobenzyl group, o-aminobenzyl group, p-nitrobenzyl group, m-nitrobenzyl group, o-nitrobenzyl group, p-cyanobenzyl group, m-cyano Examples include benzyl group, o-cyanobenzyl group, 1-hydroxy-2-phenylisopropyl group, 1-chloro-2-phenylisopropyl group and the like.

Examples of the aryloxy group having 6 to 30 ring carbon atoms include groups in which the aryl moiety is the aromatic hydrocarbon group.

A divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms represented by L ¹ to L ³ in formulas (1), (1a), (1b) and (1c); Examples of the divalent heterocyclic group 30 include groups corresponding to the divalent groups described above for the aromatic hydrocarbon group and heterocyclic group.

As the optional substituents in the above-mentioned formulas and the formula (3) described later, which may be “substituted or unsubstituted” and “may have a substituent”, a halogen atom (fluorine, chlorine, bromine, iodine) ), A cyano group, an alkyl group having 1 to 20 (preferably 1 to 6) carbon atoms, a cycloalkyl group having 3 to 20 (preferably 5 to 12) carbon atoms, and 1 to 20 carbon atoms (preferably 1 to 5). An alkoxy group, a haloalkyl group having 1 to 20 carbon atoms (preferably 1 to 5), a haloalkoxy group having 1 to 20 carbon atoms (preferably 1 to 5), and a 1 to 10 carbon atoms (preferably 1 to 5 carbon atoms). An alkylsilyl group, an aromatic hydrocarbon group having 6 to 30 (preferably 6 to 18) ring-forming carbon atoms, an aryloxy group having 6 to 30 (preferably 6 to 18) ring-forming carbon atoms, 6 to 30 carbon atoms ( Preferably 6-18) arylsilyl groups 7 to 30 carbon atoms (preferably 7-20) aralkyl group, and ring atoms 5 to 30 (preferably 5 to 18) and the heteroaryl group.
Specific examples of the alkyl group having 1 to 20 carbon atoms used as the optional substituent include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t -Butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n -Tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, neopentyl group, 1-methylpentyl group and the like.
Specific examples of the cycloalkyl group having 3 to 20 carbon atoms used as the optional substituent include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group, adamantyl group and the like.
Specific examples of the alkoxy group having 1 to 20 carbon atoms used as the optional substituent include groups in which the alkyl moiety is the alkyl group.
Specific examples of the haloalkyl group having 1 to 20 carbon atoms used as the optional substituent include groups in which part or all of the hydrogen atoms of the alkyl group are substituted with halogen atoms.
Specific examples of the haloalkoxy group having 1 to 20 carbon atoms used as the optional substituent include groups in which part or all of the above-described alkoxy groups are substituted with halogen atoms.
Specific examples of the alkylsilyl group having 1 to 10 carbon atoms used as the optional substituent include trimethylsilyl group, triethylsilyl group, tributylsilyl group, dimethylethylsilyl group, t-butyldimethylsilyl group, vinyldimethylsilyl group. Propyldimethylsilyl group, dimethylisopropylsilyl group, dimethylpropylsilyl group, dimethylbutylsilyl group, dimethyltertiarybutylsilyl group, diethylisopropylsilyl group and the like.

Specific examples of the aromatic hydrocarbon group having 6 to 30 ring carbon atoms used as the optional substituent include the same aromatic hydrocarbon groups as those described above for R ^{11 and the} like.
Specific examples of the aryloxy group having 6 to 30 ring carbon atoms used as the optional substituent include groups in which the aryl moiety is the aromatic hydrocarbon group.
Specific examples of the arylsilyl group having 6 to 30 carbon atoms used as the optional substituent include a phenyldimethylsilyl group, a diphenylmethylsilyl group, a diphenyl tertiary butylsilyl group, and a triphenylsilyl group.
Specific examples of the aralkyl group having 7 to 30 carbon atoms used as the optional substituent include the aralkyl groups represented by R ^{11 and the} like.
Specific examples of the heteroaryl group having 5 to 30 ring atoms used as the optional substituent include the same heterocyclic groups as those described above for R ^{11 and the} like.

The optional substituent is preferably a fluorine atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 30 ring carbon atoms, or a heteroaryl group having 5 to 30 ring atoms. , Fluorine atom, phenyl group, naphthyl group, biphenyl group, terphenyl group, phenanthryl group, triphenylenyl group, fluorenyl group, spirobifluorenyl group, fluoranthenyl group, dibenzofuran ring, carbazole ring, dibenzothiophene ring and these A group formed from a derivative, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butyl group, cyclopentyl group, and cyclohexyl group are more preferable.
The above arbitrary substituents may further have a substituent, and specific examples thereof are the same as the above arbitrary substituents.

The material represented by the above formula (2) is preferably a material obtained by changing L ¹ in the above formulas (1a) to (1c) to a single bond.
Examples of the compound represented by the formula (1) or (2) include the following. In addition, in the following structural formulas, a bond having no chemical formula (CN, benzene ring, or the like) at its end represents a methyl group.

In the above formula (3), the aromatic hydrocarbon group having 6 to 30 ring carbon atoms represented by A ¹ , A ² and R ^a is an aromatic hydrocarbon group represented by R ¹¹ or the like in the above formula (1). The same group is mentioned.
Examples of the divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms represented by A ³ include groups obtained by divalent groups described above for the aromatic hydrocarbon group having 6 to 30 ring carbon atoms. It is done.

Examples of the heterocyclic group having 5 to 30 ring atoms represented by A ¹ , A ² and R ^a include the same groups as the heterocyclic groups represented by R ^{11 and the} like in the above formula (1).
Examples of the divalent heterocyclic group having 5 to 30 ring atoms represented by A ³ include groups obtained by divalent groups mentioned above for the heterocyclic group having 5 to 30 ring atoms.

Alkyl group of the R ^a having 1 to 30 carbon atoms indicated by a substituted or unsubstituted silyl group, examples of the halogen atom, respectively, include the same groups as R ¹¹ or the like shown in the formula (1) described above It is done.

R ^a is preferably a hydrogen atom or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms.

In the material represented by the above formula (3), groups represented by the following formulas (a) and (b) are linked via — (A ³ ) _m —, and the bonding position is the above described X ⁵ to Any one of X ⁸ and any one of Y ¹ to Y ⁴ . Specifically, X ^6- (A ³ ) _m -Y ³ , X ^6- (A ³ ) _m -Y ² , X ^6- (A ³ ) _m -Y ⁴ , X ^6- (A ³ ) _m- ^{^{^{_{Y 1, X 7 - (A}}}} 3) m -Y 3, X 5 - (A 3) m -Y 3, X 8 - (A 3) m -Y 3, X 7 - (A 3) m -Y 2 ^{^{_{^{, X 7 - (A 3)}}}} m -Y 4, X 7 - (A 3) m -Y 1, X 5 - (A 3) m -Y 2, X 8 - (A 3) m -Y 2, X ^{^{_{^{8 - (A 3) m -Y}}}} 4, X 8 - (A 3) m -Y 1, X 5 - (A 3) m -Y 1, X 5 - (A 3) m -Y 4 and the like.

In the material represented by the above formula (3), the groups represented by the above formulas (a) and (b) are represented by X ^6- (A ³ ) _m -Y ³ , X ^6- (A ³ ) _m -Y. ^{^{^{_{2, X 7 - (a 3}}}} ) is preferably attached at either the binding position of m -Y ^3. That is, a compound represented by any one of the following formulas (3a), (3b), and (3c) is more preferable.

(In the formulas (3a) to (3c), X ¹ to X ⁸ , Y ¹ to Y ⁸ , A ¹ to A ³ and m are X ¹ to X ⁸ and Y in the formula (3), respectively. ¹ to Y ⁸ , A ¹ to A ³ and m are the same, and the formulas (3a) to (3c) satisfy at least one of the conditions (i) to (v) in the formula (3). Fulfill.)

The material represented by the above formula (3) satisfies at least one of the above (i) to (v). That is, a cyano group is introduced into a biscarbazole derivative to which groups represented by the above formulas (a) and (b) are linked.
This material has improved hole resistance due to introduction of an electron injection / transport cyano group. Therefore, the organic EL device of the present invention containing a material having a cyano group has an effect of extending the lifetime as compared with a conventional organic EL device using a host material having no cyano group.

A ³ in the formula (3) is a single bond, a substituted or unsubstituted divalent monocyclic hydrocarbon group having 6 ring-forming carbon atoms, or a substituted or unsubstituted bivalent monocyclic ring having 6 ring atoms. It preferably represents a heterocyclic group.

In the above formulas (3), (3a), (3b) and (3c), m is 0 and one of X ⁵ to X ⁸ and one of Y ¹ to Y ⁴ are bonded via a single bond. Or A ³ is preferably a substituted or unsubstituted monocyclic hydrocarbon group having 6 ring atoms or a substituted or unsubstituted monocyclic heterocyclic group having 6 ring atoms.

The material of the formula (3) preferably satisfies at least one of the following (i) and the following (ii).
(I) an aromatic hydrocarbon group having 6 to 30 ring carbon atoms in which at least one of A ¹ and A ² is substituted with a cyano group, or a complex having 5 to 30 ring atoms substituted with a cyano group; It is a cyclic group.
^(Ii) at least one of X 1 ~ ^{X 4} and ^Y 5 ~ ^{Y 8} is CR ^{^a,} at least one of ^{R a} in the X 1 ~ ^{X 4} and ^Y 5 ~ ^{Y 8} is substituted with a cyano group ring It is an aromatic hydrocarbon group having 6 to 30 carbon atoms or a heterocyclic group having 5 to 30 ring atoms substituted with a cyano group.
That is, the material of the formula (3) preferably corresponds to any of the following (1) to (3).
(1) The above (i) is satisfied, and the above (ii) to (v) are not satisfied.
(2) The above (ii) is satisfied, and the above (i) and (iii) to (v) are not satisfied.
(3) Both the above (i) and (ii) are satisfied, and the above (iii) to (v) are not satisfied.

The lifetime of the organic EL device of the present invention having a light emitting layer containing a material satisfying at least one of the above (i) and (ii) and a material represented by formula (1) or formula (2) is long. In addition to the above effects, the luminous efficiency of the organic EL element is improved.

When the material of the formula (3) satisfies the condition (i), at least one of the A ¹ and the A ² is a phenyl group substituted with a cyano group, a naphthyl group substituted with a cyano group, a cyano group Phenanthryl group substituted with cyano group, dibenzofuranyl group substituted with cyano group, dibenzothiophenyl group substituted with cyano group, biphenyl group substituted with cyano group, terphenyl group substituted with cyano group, cyano group 9,9-diphenylfluorenyl group substituted with 1,9,9′-spirobi [9H-fluoren] -2-yl group substituted with cyano group, 9,9′-dimethylfluoride substituted with cyano group It is preferably an olenyl group or a triphenylenyl group substituted with a cyano group, a 3′-cyanobiphenyl-2-yl group, a 3′-cyanobiphenyl-3-yl group, or a 3′-cyano group. Biphenyl-4-yl group, 4′-cyanobiphenyl-3-yl group, 4′-cyanobiphenyl-4-yl group, 4′-cyanobiphenyl-2-yl group, 6-cyanonaphthalen-2-yl group, 4-cyanonaphthalen-1-yl group, 7-cyanonaphthalen-2-yl group, 8-cyanodibenzofuran-2-yl group, 6-cyanodibenzofuran-4-yl group, 8-cyanodibenzothiophen-2-yl group 6-cyanodibenzothiophen-4-yl group, 7-cyano-9-phenylcarbazol-2-yl group, 6-cyano-9-phenylcarbazol-3-yl group, 7-cyano-9,9-dimethylfluorene A -2-yl group and a 7-cyanotriphenylene-2-yl group are more preferable.
The material of formula (3) is, A ¹ is substituted with a cyano group, it is preferred that A ² is not substituted with a cyano group. Furthermore, in this case, it is more preferable that the material of the formula (3) does not satisfy the condition (ii).

When the material of the formula (3) satisfies the condition (ii), at least one of X ¹ to X ⁴ and Y ⁵ to Y ⁸ is CR ^a , and X ¹ to X ⁴ and Y ⁵ to At least one of R ^a in Y ⁸ is a phenyl group substituted with a cyano group, a naphthyl group substituted with a cyano group, a phenanthryl group substituted with a cyano group, a dibenzofuranyl group substituted with a cyano group, a cyano group Dibenzothiophenyl group substituted with a group, biphenyl group substituted with a cyano group, terphenyl group substituted with a cyano group, 9,9-diphenylfluorenyl group substituted with a cyano group, substituted with a cyano group And 9,9′-spirobi [9H-fluoren] -2-yl group, 9,9′-dimethylfluorenyl group substituted with cyano group, or triphenylenyl group substituted with cyano group. More preferably, 3'-cyanobiphenyl-2-yl group, 3'-cyanobiphenyl-3-yl group, 3'-cyanobiphenyl-4-yl group, 4'-cyanobiphenyl-3-yl group, 4'- Cyanobiphenyl-4-yl group, 4′-cyanobiphenyl-2-yl group, 6-cyanonaphthalen-2-yl group, 4-cyanonaphthalen-1-yl group, 7-cyanonaphthalen-2-yl group, 8 -Cyanodibenzofuran-2-yl group, 6-cyanodibenzofuran-4-yl group, 8-cyanodibenzothiophen-2-yl group, 6-cyanodibenzothiophen-4-yl group, 7-cyano-9-phenylcarbazole- 2-yl group, 6-cyano-9-phenylcarbazol-3-yl group, 7-cyano-9,9-dimethylfluoren-2-yl group, 7-cyanotriphenylene-2-yl group A further preferred.
Furthermore, when the material of Formula (3) satisfies the condition (ii), it is more preferable that the condition (i) is not satisfied.

In the formulas (3) and (3a) to (3c), the A ¹ and the A ² are preferably different from each other. Among them, it is more preferable that the group which is A ¹ is substituted with a cyano group and the group which is A ² is not substituted with a cyano group. That is, the material of the formula (3) preferably has an asymmetric structure. By such a structure, the material of the formula (3) has good crystallinity and non-crystallinity. Therefore, since the organic EL element using the material of the formula (3) has excellent film quality, for example, high performance can be achieved in organic EL characteristics such as current efficiency.

The method for producing the material of the formula (3) is not particularly limited, and may be produced by a known method. For example, tetrahedron 40 (1984) 1435 to 1456 for carbazole derivatives and aromatic halogenated compounds. Or a coupling reaction using a palladium catalyst described in Journal of American Chemical Society 123 (2001) 7727-7729.

Although the specific example of the material of Formula (3) is described below, the compound of this invention is not limited to the following compound.

The phosphorescent dopant material (phosphorescent dopant) is a compound that can emit light from the triplet excited state, and is not particularly limited as long as it emits light from the triplet excited state, but Ir, Pt, Os, Au, Cu, Re and An organometallic complex containing at least one metal selected from Ru and a ligand is preferable. The ligand preferably has an ortho metal bond. A metal complex containing a metal atom selected from Ir, Os and Pt is preferred in that the phosphorescent quantum yield is high and the external quantum efficiency of the light emitting device can be further improved, and an iridium complex, an osmium complex, or a platinum complex. Are more preferable, iridium complexes and platinum complexes are more preferable, and orthometalated iridium complexes are particularly preferable.

The content of the phosphorescent dopant in the light emitting layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, it is preferably 0.1 to 70% by mass, more preferably 1 to 30% by mass. If the phosphorescent dopant content is 0.1% by mass or more, sufficient light emission can be obtained, and if it is 70% by mass or less, concentration quenching can be avoided.

Specific examples of preferred organometallic complexes as phosphorescent dopants are shown below.

A phosphorescent dopant material may be used independently and may use 2 or more types together.
The emission wavelength of the phosphorescent dopant material contained in the light emitting layer is not particularly limited, but at least one of the phosphorescent dopant materials contained in the light emitting layer preferably has a peak emission wavelength of 490 nm to 700 nm. More preferably, it is 650 nm or less.

The phosphorescent host is a compound having a function of efficiently emitting the phosphorescent dopant by efficiently confining the triplet energy of the phosphorescent dopant in the light emitting layer. In the organic EL device of the present invention, compounds other than the first host material and the second host material can be appropriately selected as a phosphorescent host according to the purpose.
The first host material, the second host material, and other compounds may be used in combination as a phosphorescent host material in the same light emitting layer. When there are a plurality of light emitting layers, one of the light emitting layers The first host material and the second host material may be used as the phosphorescent host material, and a compound other than the first host material or the second host material may be used as the phosphorescent host material of another light emitting layer. The first host material and the second host material can also be used for organic layers other than the light emitting layer.

Specific examples of compounds other than the first host material and the second host material and suitable as a phosphorescent host 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 derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds , Porphyrin compounds, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimide derivatives, fluoresceins Represented by metal complexes of redenemethane derivatives, distyrylpyrazine derivatives, heterocyclic tetracarboxylic anhydrides such as naphthaleneperylene, phthalocyanine derivatives, 8-quinolinol derivatives, metal phthalocyanines, metal complexes with benzoxazole and benzothiazole ligands. Various metal complexes such as polysilane compounds, poly (N-vinylcarbazole) derivatives, aniline copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, polythiophene derivatives, polyphenylene derivatives, polyphenylene vinylene derivatives, polyfluorene derivatives, etc. Examples thereof include polymer compounds. Phosphorescent hosts other than the first host material and the second host material may be used alone or in combination of two or more. Specific examples include the following compounds.

When the light emitting layer is composed of a plurality of layers and the doping system is employed in addition to the above light emitting layer containing the first host material and the second host material, the light emitting layer includes a host material and a dopant material. At this time, the host material mainly has a function of encouraging recombination of electrons and holes and confining excitons in the light emitting layer, and the dopant material efficiently emits excitons obtained by recombination. It has a function.
In the case of a phosphorescent element, the host material mainly has a function of confining excitons generated by the dopant in the light emitting layer.

The above light emitting layer may adopt a double dopant in which each dopant emits light by adding two or more kinds of dopant materials having a high quantum yield. Specifically, a mode in which yellow emission is realized by co-evaporating a host, a red dopant, and a green dopant to make the light emitting layer common is used.

The above light-emitting layer is a laminate in which a plurality of light-emitting layers are stacked, so that electrons and holes are accumulated at the light-emitting layer interface, and the recombination region is concentrated at the light-emitting layer interface to improve quantum efficiency. Can do.
The ease of injecting holes into the light emitting layer may be different from the ease of injecting electrons, and the hole transport ability and electron transport ability expressed by the mobility of holes and electrons in the light emitting layer may be different. May be different.

A light emitting layer can be formed by well-known methods, such as a vapor deposition method, a spin coat method, LB method, for example. The light emitting layer can also be formed by thinning a solution obtained by dissolving a binder such as a resin and a material compound in a solvent by a spin coating method or the like.
The light emitting layer is preferably a molecular deposited film. The molecular deposited film is a thin film formed by deposition from a material compound in a gas phase state or a film formed by solidifying from a material compound in a solution state or a liquid phase state. The thin film (molecular accumulation film) formed by the LB method can be classified by the difference in the aggregation structure and the higher-order structure, and the functional difference resulting therefrom.

The thickness of the light emitting layer is preferably 5 to 50 nm, more preferably 7 to 50 nm, and still more preferably 10 to 50 nm. When the thickness is 5 nm or more, it is easy to form a light emitting layer, and when the thickness is 50 nm or less, an increase in driving voltage can be avoided.

The organic EL device of the present invention only needs to have a structure in which the electron injection layer and the light emitting layer described above are adjacent to each other. Any member known in the art can be used as appropriate.
Hereinafter, examples of the constituent members will be briefly described.

(substrate)
The organic EL element of the present invention is produced on a translucent substrate. The light-transmitting substrate is a substrate that supports the organic EL element, and is preferably a smooth substrate having a light transmittance in the visible region of 400 nm to 700 nm of 50% or more. Specifically, a glass plate, a polymer plate, etc. are mentioned. Examples of the glass plate include those using soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, quartz and the like as raw materials. Examples of the polymer plate include those using polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, polysulfone and the like as raw materials.

(anode)
The anode of the organic EL element plays a role of injecting holes into the hole transport layer or the light emitting layer, and it is effective to use a material having a work function of 4.5 eV or more. Specific examples of the anode material include indium tin oxide alloy (ITO), tin oxide (NESA), indium zinc oxide, gold, silver, platinum, copper, and the like. The anode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. When light emitted from the light emitting layer is extracted from the anode, it is preferable that the transmittance of light in the visible region of the anode is greater than 10%. The sheet resistance of the anode is preferably several hundred Ω / □ or less. The film thickness of the anode depends on the material, but is usually selected in the range of 10 nm to 1 μm, preferably 10 nm to 200 nm.

(cathode)
The cathode plays a role of injecting electrons into the electron injection layer, the electron transport layer or the light emitting layer, and is preferably formed of a material having a small work function. The cathode material is not particularly limited, and specifically, indium, aluminum, magnesium, magnesium-indium alloy, magnesium-aluminum alloy, aluminum-lithium alloy, aluminum-scandium-lithium alloy, magnesium-silver alloy and the like can be used. Similarly to the anode, the cathode can be produced by forming a thin film by a method such as vapor deposition or sputtering. Moreover, you may take out light emission from the cathode side as needed.

(Hole transport zone)
Examples of the layer in the hole transport zone (region between the anode and the light emitting layer) include a hole transport layer and a hole injection layer. The hole transport layer is a layer that assists hole injection into the light emitting layer and transports it to the light emitting region, and has a high hole mobility and a small ionization energy of usually 5.5 eV or less. Such a hole transport layer is preferably a material that transports holes to the light-emitting layer with a lower electric field strength, and further has a hole mobility of at least 10 when an electric field of 10 ⁴ to 10 ⁶ V / cm is applied. ^-4 cm ² / V · sec is preferred.

Specific examples of the material for the hole transport layer include, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives. , Styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, polysilanes, aniline copolymers, conductive polymer oligomers (particularly thiophene oligomers), and the like.

For the hole injection layer or the hole transport layer (including the hole injection transport layer), an aromatic amine compound, for example, an aromatic amine derivative represented by the following formula (4) is preferably used.

In the formula (4), Ar ³¹ to Ar ³⁴ are each an aromatic hydrocarbon group having 6 to 50 ring carbon atoms (which may have a substituent), or a condensed aromatic group having 6 to 50 ring carbon atoms. Group hydrocarbon group (which may have a substituent), an aromatic heterocyclic group having 2 to 40 ring carbon atoms (which may have a substituent) 40 condensed aromatic heterocyclic groups (which may have a substituent), a group obtained by bonding these aromatic hydrocarbon groups and these aromatic heterocyclic groups, these aromatic hydrocarbon groups and these A group in which a fused aromatic heterocyclic group is bonded, a group in which the condensed aromatic hydrocarbon group and the aromatic heterocyclic group are bonded, or a condensed aromatic hydrocarbon group and the condensed aromatic heterocyclic group; Represents a group to which is bonded.
L represents a single bond or a group similar to Ar ³¹ to Ar ³⁴ .

Moreover, the aromatic amine of following formula (5) is also used suitably for formation of a positive hole injection layer or a positive hole transport layer.

In the formula (5), the definitions of Ar ³¹ to Ar ³³ are the same as the definitions of Ar ³¹ to Ar ^{34 in} the formula (4).

The hole injection layer is a layer provided to further assist hole injection. The material for the hole injection layer may be the organic EL material of the present invention alone, or may be used in combination with other materials. As other materials, the same materials as the hole transport layer can be used. In addition, a porphyrin compound, an aromatic tertiary amine compound, and a styrylamine compound can also be used. Further, HAT or F4TCNQ used in the P layer of the charge generation layer, or a compound represented by the formula (4) can also be used.

Also usable are conductive thiophene oligomers, conductive oligomers such as arylamine oligomers disclosed in JP-A-8-193191, conductive dendrimers such as arylamine dendrimers, and the like.
In addition to aromatic dimethylidin compounds, inorganic compounds such as p-type Si and p-type SiC can also be used as the material for the hole injection layer.

The hole injection layer or the hole transport layer can be formed, for example, by thinning the above-described compound by a known method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method. The thickness of the hole injection layer or hole transport layer is not particularly limited, but is usually 1 nm to 5 μm.

(Electronic transport band)
Examples of the layer in the electron transport zone (the region between the cathode and the electron injection layer) include an electron transport layer.
The electron transport layer is a layer that helps injection of electrons into the light emitting layer and transports it to the light emitting region, and has a high electron mobility.
The electron transport layer is appropriately selected with a film thickness of several nm to several μm, but when the film thickness is particularly large, the electron mobility is at least 10 when an electric field of 10 ⁴ to 10 ⁶ V / cm is applied in order to avoid an increase in voltage. It is preferably ⁻⁵ cm ² / Vs or higher.
As a material used for the electron transport layer, 8-hydroxyquinoline or a metal complex of its derivative or a nitrogen-containing heterocyclic derivative is preferable.
As a specific example of the above-mentioned metal complex of 8-hydroxyquinoline or a derivative thereof, a metal chelate oxinoid compound containing a chelate of oxine (generally 8-quinolinol or 8-hydroxyquinoline) such as tris (8-quinolinol) aluminum is injected. It can be used as a material.
As the nitrogen-containing heterocyclic derivative, for example, oxazole, thiazole, oxadiazole, thiadiazole, triazole, pyridine, pyrimidine, triazine, phenanthroline, benzimidazole, imidazopyridine and the like are preferable, and among them, benzimidazole derivative, phenanthroline derivative, imidazopyridine derivative Is preferred.

In one embodiment of the present invention, a layer made of an insulator or a semiconductor may be provided between the cathode and the electron transport layer. As a result, current leakage can be effectively prevented and the electron injection property can be improved.

As the insulator, it is preferable to use at least one metal compound selected from the group consisting of alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides and alkaline earth metal halides. If this layer is composed of these alkali metal chalcogenides or the like, it is preferable in that the electron injection property can be further improved.

Specifically, preferable alkali metal chalcogenides include, for example, Li ₂ O, LiO, Na ₂ S, Na ₂ Se, and NaO, and preferable alkaline earth metal chalcogenides include, for example, CaO, BaO, SrO, and BeO. , BaS, and CaSe. Further, preferable alkali metal halides include, for example, LiF, NaF, KF, CsF, LiCl, KCl, and NaCl. Examples of preferable alkaline earth metal halides include fluorides such as CaF ₂ , BaF ₂ , SrF ₂ , MgF ₂ and BeF ₂ , and halides other than fluorides.

Examples of the semiconductor include oxide, nitride, or oxynitride containing at least one element of Ba, Ca, Sr, Yb, Al, Ga, In, Li, Na, Cd, Mg, Si, Ta, Sb, and Zn. Or a combination of two or more.
The inorganic compound constituting this layer is preferably a microcrystalline or amorphous insulating thin film.
Examples of such inorganic compounds include the alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides described above.

In the organic EL device of the present invention, high luminous efficiency can be obtained without forming the above-described electron transport layer or the like in the electron transport region.

The organic EL device of the present invention can be produced by a known method. Specifically, the anode and the cathode can be formed by a method such as vapor deposition or sputtering. Each organic thin film layer such as a light-emitting layer can be formed by a method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method.

The organic EL element of the present invention is not limited to the configuration shown in FIG. For example, since the hole transport layer and the hole injection layer are arbitrary layers, they can be omitted, and an electron transport layer or the like can be provided between the electron injection layer and the cathode.

The configuration of the organic EL element of the present invention is not limited to the above-described embodiment, and other known configurations can be adopted. For example, it can also be used for an organic EL element (MPE element) having a configuration in which a plurality of light emitting units each composed of an organic layer having at least a light emitting layer are disposed between an anode and a cathode via a charge generation layer. In this case, at least one of the plurality of light emitting units only needs to have a structure in which the electron injection layer and the light emitting layer of the present invention are adjacent to each other.

FIG. 2 is a schematic cross-sectional view of another embodiment of the organic EL device of the present invention.
The organic EL element 2 of this embodiment includes an anode 20, a first light emitting unit 71, a charge generation layer 72, a second light emitting unit 73, and a light transmissive cathode 60 on a substrate 10 in this order.
Each of the two light emitting units has a single layer or a stacked structure having at least a light emitting layer. For example, the light emitting unit preferably has a multilayer structure in which a hole transport layer, a light emitting layer, and an electron injection layer are stacked from the anode side. In the present invention, at least one of the two light emitting units has a structure in which the electron injection layer and the light emitting layer of the present invention are adjacent to each other.

Regarding the constituent members of the MPE element such as the charge generation layer, JP2003-45676, JP2003-272860, JP11-329748, JP2006-24791, JP2004-39617, JP2006-73484, Reference can be made to Japanese Patent Publication No. 2006-173550.

The organic EL element 2 has the same configuration as the organic EL element 1 shown in FIG. 1 except that two light emitting units are formed. In other words, the organic EL element 1 has an element configuration having one light emitting unit including the hole injection layer 20, the hole transport layer 30, the light emitting layer 40, and the electron injection layer 50.
In the present embodiment, for example, an organic EL element that emits white light can be obtained by changing the light emission color of each light emitting unit, that is, by changing the material of the light emitting layer.

The organic EL element of the present invention may be a top emission type or a bottom emission type.

In Examples and Comparative Examples, organic EL devices were produced using the following compounds.

Example 1
ITO was formed to a thickness of 240 nm as an anode on a substrate made of a 30 mm × 30 mm glass plate. Next, a cell for an organic EL element in which a region other than the light emitting region of 2 mm × 2 mm was masked with an insulating film by SiO ₂ vapor deposition was produced.
On the anode, as a hole injection layer, hexanitrile azatriphenylene (the following formula (HAT)) was formed to a thickness of 10 nm by vapor deposition.
Subsequently, as the hole transport layer 1, compound HT-1 was formed to a thickness of 180 nm by vapor deposition. On top of this, as a hole transport layer 2, compound HT-2 was formed to a thickness of 20 nm by vapor deposition.
Next, compounds H1-1, H2-1, and Ir (PPy) ₃ were co-evaporated on the hole transport layer 2 to form a light-emitting layer having a thickness of 30 nm. In the light emitting layer, the ratio (mass ratio) of the host material was 1: 1. The dopant content was 10% (mass ratio).
Subsequently to the light emitting layer, Li and compound E-1 were binary evaporated to form an E-1: Li film (Li 2% (mass ratio)) of 30 nm to form an electron injection layer. On the electron injection layer, metal Al was deposited to a thickness of 80 nm to form a cathode, and an organic EL device was produced.
The produced organic EL device was measured for voltage (V) and luminance (cd / m ² ) at a current density of 10 mAcm ⁻² , and luminance half-life when driven at 40 mA / cm ² .
Table 1 shows the host material used in the light emitting layer, the layer structure from the light emitting layer to the cathode, and the evaluation results.

Examples 2-5
An organic EL device was prepared and evaluated in the same manner as in Example 1 except that the compounds used in the host material and the electron injection layer of the light emitting layer were changed as shown in Table 1. The results are shown in Table 1.

Comparative Example 1
The process was the same as in Example 1 until the formation of the light emitting layer.
Following the light emitting layer, an Alq3 layer was formed to a thickness of 30 nm, and LiF was formed to a thickness of 0.5 nm. Thereafter, a cathode was formed in the same manner as in Example 1 to produce an organic EL device. The results evaluated in the same manner as in Examples are shown in Table 1.

Comparative Example 2
The process was the same as in Example 1 until the formation of the light emitting layer.
Subsequent to the light emitting layer, a BAlq layer having a thickness of 20 nm was formed as a hole blocking layer. Subsequently, an Alq3 layer was formed to 10 nm, and LiF was formed to a thickness of 0.5 nm. Thereafter, a cathode was formed in the same manner as in Example 1 to produce an organic EL device. The results evaluated in the same manner as in Examples are shown in Table 1.

Comparative Example 3
An organic EL device was prepared and evaluated in the same manner as in Example 1 except that only CBP was used as the host material. The results are shown in Table 1.

Comparative Example 4
An organic EL device was prepared and evaluated in the same manner as in Comparative Example 2 except that only CBP was used as the host material. The results are shown in Table 1.

Comparative Example 5
The procedure was the same as in Example 1 except that only CBP was used as the host material until formation of the light emitting layer.
Thereafter, a BAlq layer having a thickness of 10 nm was formed as a hole blocking layer. Subsequently, an Alq3 layer was formed to 10 nm, and a mixed layer of E-1 and Li (Li: 2%) was formed to a thickness of 10 nm as an electron injection layer. Thereafter, a cathode was formed in the same manner as in Example 1 to produce an organic EL device. The results evaluated in the same manner as in Examples are shown in Table 1.

Comparative Example 6
The procedure was the same as in Example 1 except that only CBP was used as the host material until formation of the light emitting layer.
Thereafter, a layer made of only E-1 was formed as an electron injection layer with a thickness of 30 nm. Furthermore, LiF was formed with a thickness of 0.5 nm. Thereafter, a cathode was formed in the same manner as in Example 1 to produce an organic EL device. The results evaluated in the same manner as in Examples are shown in Table 1.

Comparative Example 7
An organic EL device was prepared and evaluated in the same manner as in Example 1 except that H2-1 was not used as the host material but only H1-1 was used. The results are shown in Table 1.

In Examples 1 to 5 of the present invention, devices with high efficiency, low voltage and long life were obtained. On the other hand, in Comparative Examples 1 and 2, since the electron injection layer is not adjacent to the light emitting layer, a high voltage and a short life occurred due to insufficient electron injection into the light emitting layer.
In Comparative Example 3, since the electron injection layer is adjacent to the light emitting layer, the voltage is lower than that in Comparative Example 4, but the efficiency of the light emitting layer is shortened and the life is shortened due to the poor charge balance of the light emitting layer. . In Comparative Examples 4 and 5, the hole blocking material prevented the exciton loss and compensated for the efficiency, but the use of the hole blocking material having a low charge transporting capability resulted in a high voltage.
In Comparative Example 6, since the electron transport layer is adjacent to the light emitting layer, the voltage is slightly higher than that in Comparative Example 5. However, the charge balance of the light emitting layer is poor, resulting in lower efficiency and shorter life. did.
In Comparative Example 7, since the light emitting layer host was not mixed, the charge balance was insufficient, so that the lifetime was shortened.

The organic EL device of the present invention can be used for a flat light emitter such as a flat panel display of a wall-mounted television, a copying machine, a printer, a light source such as a backlight of a liquid crystal display or instruments, a display board, a marker lamp, and the like.

Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will appreciate that these exemplary embodiments and / or embodiments are substantially without departing from the novel teachings and advantages of the present invention. It is easy to make many changes to the embodiment. Accordingly, many of these modifications are within the scope of the present invention.
All the contents of the Japanese application specification that is the basis of the priority of Paris in this application are incorporated herein.

Claims

Having an anode, a light emitting layer, an electron injection layer, and a cathode in this order;
The electron injection layer and the light emitting layer are adjacent to each other;
The electron injection layer includes a π electron deficient compound and an electron donating material. The light emitting layer includes at least a first host material, a second host material, and a phosphorescent dopant material. .
2. The organic electroluminescence device according to claim 1, wherein the first host material and the second host material are selected from materials represented by any of the following formulas (1) to (3).

[In Formula (1),
Z 1 represents a ring structure represented by the following formula (1-1) or (1-2) condensed at a. Z 2 represents a ring structure represented by the following formula (1-1) or (1-2) condensed at b. However, at least one of Z 1 and Z 2 is represented by the following formula (1-1).
M 1 is a substituted or unsubstituted nitrogen-containing heteroaromatic ring having 5 to 30 ring-forming atoms,
L 1 represents a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted divalent heterocyclic group having 5 to 30 ring atoms, and a ring forming carbon number. It represents a 5-30 cycloalkylene group or a group in which these are linked.
k represents 1 or 2. ]

[In the above formula (1-1),
c represents condensation in a or b in the formula (1).
In the above (1-2), any one of d, e and f represents condensation in a or b in the general formula (1).
In the above formulas (1-1) and (1-2),
X 11 represents a sulfur atom, an oxygen atom, N—R 19 , or C (R 20 ) (R 21 ).
R 11 to R 21 each independently represents a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted ring atom number of 5 to 30 heterocyclic groups, substituted or unsubstituted alkyl groups having 1 to 30 carbon atoms, substituted or unsubstituted alkenyl groups having 2 to 30 carbon atoms, substituted or unsubstituted alkynyl groups having 2 to 30 carbon atoms, substituted or An unsubstituted silyl group, a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, or a substituted or unsubstituted aryloxy group having 6 to 30 ring carbon atoms Represents a group.
Adjacent R 11 to R 21 may be bonded to each other to form a ring. ]

[In Formula (2),
Z 11 represents a ring structure represented by the formula (1-1) or (1-2) condensed at a. Z 21 represents a ring structure represented by the formula (1-1) or (1-2) condensed at b. However, at least one of Z 11 and Z 21 is represented by the formula (1-1).
M 11 is a substituted or unsubstituted nitrogen-containing heteroaromatic ring having 5 to 30 ring atoms.
k 1 represents 1 or 2. ]

[In Formula (3),
A 1 and A 2 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms.
A 3 represents a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a substituted or unsubstituted divalent heterocyclic group having 5 to 30 ring atoms.
m represents an integer of 0 to 3.
X 1 to X 8 and Y 1 to Y 8 each independently represent N or CR a .
R a is independently a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, a substituted or unsubstituted group. It represents a substituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted silyl group, a halogen atom or a cyano group. When a plurality of R a are present, the plurality of R a may be the same or different.
One of X 5 to X 8 and one of Y 1 to Y 4 are bonded via A 3 .
Further, the formula (3) satisfies at least one of the following (i) to (v).
(I) At least one of A 1 and A 2 is an aromatic hydrocarbon group having 6 to 30 ring carbon atoms substituted with a cyano group, or a heterocycle having 5 to 30 ring atoms substituted with a cyano group. It is a cyclic group.
(Ii) At least one of X 1 to X 4 and Y 5 to Y 8 is CR a , and at least one of R a in X 1 to X 4 and Y 5 to Y 8 is substituted with a cyano group It is an aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a heterocyclic group having 5 to 30 ring atoms substituted with a cyano group.
(Iii) m is an integer of 1 to 3, and at least one of A 3 is substituted with a divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms substituted with a cyano group, or a cyano group And a divalent heterocyclic group having 5 to 30 ring atoms.
(Iv) At least one of X 5 to X 8 and Y 1 to Y 4 is CR a , and at least one of R a in X 5 to X 8 and Y 1 to Y 8 is substituted with a cyano group It is an aromatic hydrocarbon group having 6 to 30 ring carbon atoms or a heterocyclic group having 5 to 30 ring atoms substituted with a cyano group.
(V) At least one of X 1 to X 8 and Y 1 to Y 8 is C-CN. ]
The organic electroluminescence device according to claim 2, wherein the first host material is a material represented by the formula (1), and the second host material is a material represented by the formula (3).
The organic electroluminescent element according to claim 2, wherein the first host material is a material represented by the formula (2), and the second host material is a material represented by the formula (3).
The organic electroluminescence device according to claim 2, wherein the first host material is a material represented by the formula (1), and the second host material is a material represented by the formula (2).
6. The organic electroluminescent device according to claim 1, wherein the π electron deficient compound is selected from compounds represented by the following formulas (I) to (III).

[Wherein, R 1a to R 7a , R 1b to R 7b , and R 1c to R 6c each independently represent a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 60 ring carbon atoms, substituted or unsubstituted. Pyridyl group, substituted or unsubstituted quinolyl group, substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, substituted or unsubstituted cycloalkyl group having 3 to 50 carbon atoms, substituted or unsubstituted 7 to 7 carbon atoms 50 aralkyl groups, substituted or unsubstituted alkoxy groups having 1 to 50 carbon atoms, substituted or unsubstituted aryloxy groups having 6 to 50 ring carbon atoms, substituted or unsubstituted arylthio groups having 6 to 50 ring carbon atoms A substituted or unsubstituted alkoxycarbonyl group having 2 to 50 carbon atoms, an amino group substituted with a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, halo Emissions atom, a cyano group, a nitro group, a hydroxyl group or a carboxyl group, R 1a ~ R 7a, of R 1b ~ R 7b or R 1c ~ R 6c, are bonded to each other to form a ring in which adjacent Also good.
L 1a and L 1b are each a single bond or a linking group.
Ar 1a , Ar 1b , Ar 1c and Ar 2c are each a substituted or unsubstituted aromatic group having 6 to 60 carbon atoms.
n is 1 to 4, and when n is 2 or more, the groups having a phenanthroline skeleton in parentheses may be the same or different. ]
The electron-donating material is at least one selected from an alkali metal simple substance, an alkaline earth metal simple substance, a rare earth metal simple substance, a rare earth metal compound, and a rare earth metal complex. An organic electroluminescence device according to any one of the above.
The organic electroluminescence device according to any one of claims 1 to 7, wherein a content ratio of the first host material with respect to a total of the first host material and the second host material is 30 to 95% by mass.
The organic electroluminescence device according to any one of claims 1 to 7, wherein a content ratio of the first host material with respect to a total of the first host material and the second host material is 50 to 95% by mass.
10. The organic electroluminescence device according to claim 1, wherein the content of the electron donating material in the electron injection layer is 20% by mass or less.
The organic electroluminescence device according to any one of claims 1 to 10, wherein the phosphorescent dopant material is an orthometalated complex of a metal atom selected from iridium (Ir), osmium (Os), and platinum (Pt). .
12. The organic electroluminescence device according to claim 1, wherein only the electron injection layer is provided between the light emitting layer and the cathode.