JP2008130754A - Organic electroluminescent device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent device having an excellent electroluminescent characteristics and running durability. <P>SOLUTION: The organic electroluminescent device has at least a light emission layer and an electron injection promotion layer adjacent on the negative pole side of the light emission layer between a pair of electrodes. The light emission layer contains an electroluminescent material, while the electron injection promotion layer contains an electron transport material expressed by a general expression (A-1). The electron injection promotion layer has a thickness of 3 nm or less, and the electron transport material expressed by the general expression (A-1) has an electron affinity larger than that of the electroluminescent material. In the general expression (A-1), Z<SP>A1</SP>represents a group of atoms necessary for forming a nitrogen-contained heterocycle, L<SP>A1</SP>represents a linking group, and n<SP>A1</SP>is an integer of 2 or above. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent element (hereinafter also referred to as “organic EL element”, “light emitting element”, or “EL element”) that can emit light by converting electric energy into light.

Today, research and development on various display elements are active. Among them, organic electroluminescence (EL) elements are attracting attention as promising display elements because they can emit light with high luminance at a low voltage.
The organic electroluminescent element is composed of a light emitting layer or a counter electrode sandwiching a plurality of organic layers including a light emitting layer, and electrons injected from the cathode and holes injected from the anode are recombined in the light emitting layer, One that uses light emission from the generated exciton, or one that uses light emission from the exciton of another molecule generated by energy transfer from the exciton.
There has been disclosed a technique for improving the efficiency and extending the life by providing an electron transfer control layer that suppresses the flow of electrons to the light emitting layer (see, for example, Patent Document 1).
In addition, a technique for preventing the leakage of holes and improving the light emission efficiency by providing a hole blocking layer is disclosed (for example, see Patent Documents 2 and 3).
However, none of the above organic electroluminescent elements has sufficient luminous efficiency and durability, and improvement in characteristics is required.
JP 2004-273163 A JP 2000-243571 A Japanese Unexamined Patent Publication No. 2000-3790

  An object of the present invention is to provide an organic electroluminescence device having good light emission characteristics and driving durability.

In view of the above circumstances, the present inventors have conducted extensive research and found that the above problems can be solved, thereby completing the present invention.
That is, the present invention is achieved by the following means.

<1> An organic electroluminescent element having at least a light emitting layer and an electron injection promoting layer adjacent to the cathode side of the light emitting layer between a pair of electrodes, the light emitting layer containing a light emitting material, and the electrons The injection promoting layer contains an electron transport material represented by the following general formula (A-1), and the film thickness of the electron injection promoting layer is 3 nm or less, and is represented by the general formula (A-1). An organic electroluminescent device characterized in that the electron affinity of the electron transport material is equal to or higher than the electron affinity of the light emitting material.

(In General Formula (A-1), Z ^A1 represents an atomic group necessary for forming a nitrogen-containing heterocycle. L ^A1 represents a linking group. N ^A1 represents an integer of 2 or more.)

<2> The light emitting layer contains a host material, and the electron affinity of the electron transport material represented by the general formula (A-1) is equal to or higher than the electron affinity of the host material <1 The organic electroluminescent element of>.

<3> The organic electroluminescent element as described in <1> or <2> above, wherein the light emitting material is a phosphorescent material.
<4> The above <1> to <3>, wherein an electron affinity of the electron transport material represented by the general formula (A-1) contained in the electron injection promoting layer is 2.7 eV or more. Organic electroluminescent element as described in any one of these.

<5> The organic electroluminescence device according to any one of <1> to <4>, wherein the electron injection promoting layer has a thickness of 0.1 to 2 nm.
<6> The <1> to <1>, wherein the electron transport material represented by the general formula (A-1) contained in the electron injection promoting layer is a material containing three or more nitrogen atoms. The organic electroluminescent element as described in any one of <5>.

<7> The organic electroluminescent element according to any one of <2> to <6>, wherein the host material has a carbazole group.
<8> Any one of the above <1> to <7>, wherein an electron transport layer containing a compound represented by the following general formula (C) is provided adjacent to the cathode side of the electron injection promoting layer. The organic electroluminescent element according to item.

(In the formula, at least one of R _{1 to} R ₆ represents a substituent, and the rest represents a hydrogen atom. M represents aluminum, gallium, or indium. Y may have a substituent. Represents an aromatic group or a silyl group.)

  According to the present invention, there is provided an organic electroluminescent device having good light emission characteristics and driving durability.

[Organic electroluminescence device]
Hereinafter, the organic electroluminescent element of the present invention (hereinafter sometimes referred to as “organic EL element” as appropriate) will be described in detail.
The organic electroluminescent device of the present invention is an organic electroluminescent device having at least a light emitting layer and an electron injection promoting layer adjacent to the cathode side of the light emitting layer between a pair of electrodes, and the light emitting layer contains a light emitting material. And the electron injection promoting layer contains an electron transport material represented by the following general formula (A-1), the film thickness of the electron injection promoting layer is 3 nm or less, and the general formula (A The electron affinity of the electron transport material represented by -1) is greater than or equal to the electron affinity of the light emitting material.
Since the organic electroluminescent element of the present invention has the above-described configuration, it is possible to improve luminous efficiency and at the same time have an effect of excellent driving durability.

It is presumed that the light-emitting element of the present invention has an excellent effect in driving durability and light-emitting characteristics (light-emitting efficiency) by the following mechanism.
In the electron injection promoting layer of the present invention, the electron transport material represented by the general formula (A-1) contained improves the carrier balance in the light emitting layer by improving the injection of electrons into the light emitting layer, and emits light. Has the ability to improve efficiency. Electron injection is promoted by setting the electron affinity of the electron transport material represented by the general formula (A-1) contained to be equal to or higher than the electron affinity of the light emitting material, thereby improving the light emission efficiency. However, when the electron injection promoting layer is thickened, holes are injected into the electron transport material represented by the general formula (A-1) to be contained and are easily decomposed. In general, when a thick layer made of an electron transport material is formed adjacent to the light emitting layer, it functions as a hole blocking layer, and light emission efficiency can be improved by preventing leakage of holes from the light emitting layer. However, since the holes are easily injected into the electron transport material contained therein, the element has low durability. This is because electron transport materials generally have poor resistance to hole injection.
In the present invention, by setting the film thickness of the electron injection promoting layer to 3 nm or less, the electron transport material is prevented from being decomposed and the element durability is improved. Strictly speaking, the electron injection promoting layer is not in a film state but in an island shape, so that holes are hardly injected into the electron transport material. That is, it is considered that when the island-shaped structure is used, holes leaking from the light-emitting layer do not enter the electron injection promoting layer and pass to the next adjacent layer, thereby preventing deterioration of the electron transport material.
In addition, the film thickness in this invention points out an average film thickness. A single film having a film thickness of about 50 to 200 nm of each material is formed, and the film thickness is measured by means such as a step meter or an optical film thickness system. Set the thickness.
In the present invention, a particularly large effect can be obtained by applying a phosphorescent material as the light emitting material. A phosphorescent light-emitting element is an important technique for achieving high efficiency because it can in principle have a luminous efficiency four times that of a fluorescent light-emitting element. In the phosphorescent light emitting device, exciton lifetime is long, and thus a shift in carrier balance in the light emitting layer greatly affects the light emission efficiency. However, according to the present invention, this carrier balance can be improved.

The electron affinity in the present invention is defined by calculating the band gap from the long wave end of the absorption spectrum of the single layer film, obtaining the electron affinity from the value of ionization potential (Ip) measured separately from this, and defining this value.
The ionization potential is defined by a value measured at room temperature and in the atmosphere using an ultraviolet photoelectron analyzer AC-1 (Riken Keiki Co., Ltd.). The measurement principle of AC-1 is described in Chiyaya Adachi et al., “Organic thin film work function data collection” issued by CMC Publishing Co., Ltd. 2004.
For materials whose ionization potential exceeds 6.2 eV, USP (vacuum ultraviolet photoelectron spectroscopy) is used because of the problem of measurement range.

Next, the structure in the organic electroluminescent element of this invention is demonstrated.
The light emitting device of the present invention has a pair of a cathode and an anode, and is composed of at least a light emitting layer between both electrodes and an electron injection promoting layer adjacent to the cathode side of the light emitting layer. The cathode and the anode are preferably formed on a substrate. Further, another organic compound layer may be provided between the light emitting layer and the anode and between the electron injection promoting layer and the cathode. In view of the properties of the light emitting element, at least one of the anode and the cathode is preferably transparent. Usually, the anode is transparent.
As an aspect of the lamination of the organic electroluminescent element in the present invention, an aspect in which the hole transport layer, the light emitting layer, and the electron injection promoting layer are laminated in this order from the anode side is preferable. Furthermore, you may have a charge block layer etc. between the positive hole transport layer and the light emitting layer.
In the present invention, each of the layers including a light emitting layer between a pair of electrodes is collectively referred to as an “organic compound layer”.
Next, the elements constituting the present invention will be described in detail.

<Board>
The substrate that can be used in the present invention is preferably a substrate that does not scatter or attenuate light emitted from the light emitting layer. Specific examples thereof include zirconia stabilized yttrium (YSZ), inorganic materials such as glass, polyesters such as polyethylene terephthalate, polybutylene phthalate, and polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, polyarylate, polyimide, and polycycloolefin. , Organic materials such as norbornene resin and poly (chlorotrifluoroethylene).

For example, when glass is used as the substrate, it is preferable to use non-alkali glass as the material in order to reduce ions eluted from the glass. Moreover, when using soda-lime glass, it is preferable to use what gave barrier coatings, such as a silica. In the case of an organic material, it is preferable that it is excellent in heat resistance, dimensional stability, solvent resistance, electrical insulation, and workability.
There is no restriction | limiting in particular about the shape of a board | substrate, a structure, a magnitude | size, It can select suitably according to the use, purpose, etc. of a light emitting element. In general, the shape of the substrate is preferably a plate shape. The structure of the substrate may be a single layer structure, a laminated structure, may be formed of a single member, or may be formed of two or more members.
The substrate may be colorless and transparent or colored and transparent, but is preferably colorless and transparent in that it does not scatter or attenuate light emitted from the light emitting layer.
The substrate can be provided with a moisture permeation preventing layer (gas barrier layer) on the front surface or the back surface.
As a material for the moisture permeation preventive layer (gas barrier layer), inorganic materials such as silicon nitride and silicon oxide are preferably used. The moisture permeation preventing layer (gas barrier layer) can be formed by, for example, a high frequency sputtering method.
When a thermoplastic substrate is used, a hard coat layer, an undercoat layer, or the like may be further provided as necessary.

<Anode>
The anode usually has a function as an electrode for supplying holes to the organic compound layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the light-emitting element. Thus, it can be appropriately selected from known electrode materials. As described above, the anode is usually provided as a transparent anode.

  As a material of the anode, for example, a metal, an alloy, a metal oxide, a conductive compound, or a mixture thereof can be suitably cited, and a material having a work function of 4.0 eV or more is preferable. Specific examples of the anode material include conductive metals such as tin oxide (ATO, FTO) doped with antimony or fluorine, tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), etc. Metals such as oxides, gold, silver, chromium, nickel, and mixtures or laminates of these metals and conductive metal oxides, inorganic conductive materials such as copper iodide and copper sulfide, polyaniline, polythiophene, polypyrrole, etc. Organic conductive materials, and a laminate of these and ITO. Among these, conductive metal oxides are preferable, and ITO is particularly preferable from the viewpoints of productivity, high conductivity, transparency, and the like.

The anode is composed of, for example, a wet method such as a printing method and a coating method, a physical method such as a vacuum deposition method, a sputtering method, and an ion plating method, and a chemical method such as a CVD and a plasma CVD method. It can be formed on the substrate according to a method appropriately selected in consideration of suitability with the material to be processed. For example, when ITO is selected as the anode material, the anode can be formed according to a direct current or high frequency sputtering method, a vacuum deposition method, an ion plating method, or the like.
In the organic electroluminescent element of the present invention, the formation position of the anode is not particularly limited and can be appropriately selected according to the use and purpose of the light emitting element, but it is preferably formed on the substrate. In this case, the anode may be formed on the entire one surface of the substrate, or may be formed on a part thereof.
The patterning for forming the anode may be performed by chemical etching such as photolithography, or may be performed by physical etching such as laser, or vacuum deposition or sputtering with a mask overlapped. It may be performed by a lift-off method or a printing method.
The thickness of the anode can be appropriately selected depending on the material constituting the anode and cannot be generally defined, but is usually about 10 nm to 50 μm, and preferably 50 nm to 20 μm.

The resistance value of the anode is preferably 10 ³ Ω / □ or less, and more preferably 10 ² Ω / □ or less. When the anode is transparent, it may be colorless and transparent or colored and transparent. In order to take out light emission from the transparent anode side, the transmittance is preferably 60% or more, and more preferably 70% or more.
The transparent anode is detailed in Yutaka Sawada's “New Development of Transparent Conductive Film” published by CMC (1999), and the matters described here can be applied to the present invention. In the case of using a plastic substrate having low heat resistance, a transparent anode formed using ITO or IZO at a low temperature of 150 ° C. or lower is preferable.

<Cathode>
The cathode usually has a function as an electrode for injecting electrons into the organic compound layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the light-emitting element. , Can be appropriately selected from known electrode materials.
Examples of the material constituting the cathode include metals, alloys, metal oxides, electrically conductive compounds, and mixtures thereof, and those having a work function of 4.5 eV or less are preferable. Specific examples include alkali metals (eg, Li, Na, K, Cs, etc.), alkaline earth metals (eg, Mg, Ca, etc.), gold, silver, lead, aluminum, sodium-potassium alloys, lithium-aluminum alloys, magnesium. -Rare earth metals such as silver alloys, indium, ytterbium, and the like. These may be used alone, but two or more can be suitably used in combination from the viewpoint of achieving both stability and electron injection.
Among these, as a material constituting the cathode, an alkali metal or an alkaline earth metal is preferable from the viewpoint of electron injecting property, and a material mainly composed of aluminum is preferable from the viewpoint of excellent storage stability.
The material mainly composed of aluminum is aluminum alone, an alloy of aluminum and 0.01 to 10% by mass of alkali metal or alkaline earth metal, or a mixture thereof (for example, lithium-aluminum alloy, magnesium-aluminum alloy, etc.) Say.
The cathode materials are described in detail in JP-A-2-15595 and JP-A-5-121172, and the materials described in these publications can also be applied in the present invention.

There is no restriction | limiting in particular about the formation method of a cathode, According to a well-known method, it can carry out. For example, the cathode described above is configured from a wet method such as a printing method or a coating method, a physical method such as a vacuum deposition method, a sputtering method, or an ion plating method, or a chemical method such as CVD or plasma CVD method. It can be formed according to a method appropriately selected in consideration of suitability with the material. For example, when a metal or the like is selected as the cathode material, one or more of them can be simultaneously or sequentially performed according to a sputtering method or the like.
Patterning when forming the cathode may be performed by chemical etching such as photolithography, physical etching by laser, or the like, or by vacuum deposition or sputtering with the mask overlaid. It may be performed by a lift-off method or a printing method.
In the present invention, the cathode formation position is not particularly limited, and may be formed on the entire organic compound layer or a part thereof.
Further, a dielectric layer made of an alkali metal or alkaline earth metal fluoride or oxide may be inserted between the cathode and the organic compound layer with a thickness of 0.1 to 5 nm. This dielectric layer can also be regarded as a kind of electron injection layer. The dielectric layer can be formed by, for example, a vacuum deposition method, a sputtering method, an ion plating method, or the like.

The thickness of the cathode can be appropriately selected depending on the material constituting the cathode and cannot be generally defined, but is usually about 10 nm to 5 μm, and preferably 50 nm to 1 μm.
Further, the cathode may be transparent or opaque. The transparent cathode can be formed by depositing a thin cathode material to a thickness of 1 to 10 nm and further laminating a transparent conductive material such as ITO or IZO.

<Organic compound layer>
The organic electroluminescent element of the present invention has the light emitting layer and an electron injection promoting layer adjacent to the cathode side of the light emitting layer, but may include other layers as described above.
Examples of the other layers include a hole transport layer, an electron transport layer, a charge blocking layer, a hole injection layer, and an electron injection layer.
Details of these layers will be described later.

-Formation of organic compound layer-
Each layer constituting the organic compound layer in the organic electroluminescent element of the present invention can be suitably formed by any of a dry film forming method such as a vapor deposition method and a sputtering method, a transfer method, and a printing method.

-Light emitting layer-
The light-emitting layer receives holes from the anode, the hole injection layer, or the hole transport layer when an electric field is applied, receives electrons from the cathode, the electron injection layer, or the electron transport layer, and recombines holes and electrons. It is a layer which has the function to provide and to emit light.
The light emitting layer in the present invention contains a light emitting material, but preferably contains a host material and the light emitting material as a dopant, and the light emitting material is more preferably a phosphorescent light emitting material.
The host material is not particularly limited, but is preferably a charge transport material.
The light emitting layer may be a single layer or two or more layers.
The phosphorescent material contained in the light emitting layer is generally a complex containing a transition metal atom or a lanthanoid atom.
Although it does not specifically limit as a transition metal atom, Preferably, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, and platinum are mentioned, More preferably, they are rhenium, iridium, and platinum.
Examples of lanthanoid atoms include lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Among these lanthanoid atoms, neodymium, europium, and gadolinium are preferable.
Examples of the ligand of the complex include G.I. Wilkinson et al., Comprehensive Coordination Chemistry, Pergamon Press, 1987, H.C. Examples include ligands described in Yersin's "Photochemistry and Photophysics of Coordination Compounds" published by Springer-Verlag 1987, Akio Yamamoto "Organic Metal Chemistry-Fundamentals and Applications-" .

Specific ligands are preferably halogen ligands (preferably chlorine ligands), nitrogen-containing heterocyclic ligands (eg, phenylpyridine, benzoquinoline, quinolinol, bipyridyl, phenanthroline, etc.), diketones Ligand (for example, acetylacetone), carboxylic acid ligand (for example, acetic acid ligand), carbon monoxide ligand, isonitrile ligand, cyano ligand, more preferably nitrogen-containing Heterocyclic ligand. The complex may have one transition metal atom in the compound, or may be a so-called binuclear complex having two or more. Different metal atoms may be contained at the same time.
The phosphorescent material is preferably contained in the light emitting layer in an amount of 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass.

Examples of the host material that can be contained in the light emitting layer in the present invention include those having a carbazole skeleton, those having a diarylamine skeleton, those having a pyridine skeleton, those having a pyrazine skeleton, those having a triazine skeleton And those having an arylsilane skeleton, and the like. Although not particularly limited, those having a carbazole skeleton are preferred.
The T _{1 of the} host material (the energy level of the lowest multiplet excited state) is preferably greater than the T ₁ level of the dopant material. Note that by co-evaporating the host material and the dopant material, a light-emitting layer in which the dopant material is doped into the host material can be suitably formed.

Although the thickness of a light emitting layer is not specifically limited, Usually, it is preferable that they are 1 nm-500 nm, it is more preferable that they are 5 nm-200 nm, and it is still more preferable that they are 10 nm-100 nm.
The host material is preferably contained in the light emitting layer in an amount of 50 to 99.9% by mass, and more preferably 70 to 99.9% by mass.

-Electron injection promotion layer-
The electron injection promoting layer is a layer having a function of promoting electron injection from the cathode side to the light emitting layer. In the present invention, an electron injection promoting layer is provided as an organic compound layer adjacent to the light emitting layer on the cathode side.
The electron affinity of the electron transport material represented by the general formula (A-1) contained in the electron injection promoting layer needs to be equal to or higher than the electron affinity of the light emitting material, and efficiently injects electrons into the light emitting layer. In view of the above, when the light emitting layer contains a host material, the electron affinity of the electron transport material represented by the general formula (A-1) is preferably equal to or higher than the electron affinity of the host material.
In particular, the electron affinity of the electron transport material represented by the general formula (A-1) is preferably 2.7 eV or more, more preferably 2.7 eV or more and 4.1 eV or less, and 2.9 eV or more and 3. 9 eV or less is more preferable, and 3.2 eV or more and 3.9 eV or less is particularly preferable.
The thickness of the electron injection promoting layer is essentially 3 nm or less, more preferably 0.1 to 2 nm, still more preferably 0.1 nm to 1 nm, and particularly preferably 0.2 to 0.8 nm.

The electron transport material represented by the general formula (A-1) is preferably a material containing three or more nitrogen atoms.
Examples of the electron transport material include azoles (for example, oxazole, oxadiazole, imidazole, triazole, thiazole, thiadiazole, and derivatives thereof (including condensates)), azines (for example, And pyridine, pyrimidine, triazine, and derivatives thereof (including condensates), and organic silanes (eg, silole, aryl-substituted silane, and derivatives thereof (including condensates)). ), Fluorine-substituted aromatic hydrocarbon rings, metal complexes of 8-quinolinol, metal phthalocyanine, various metal complexes represented by metal complexes having benzoxazole or benzothiazole as a ligand, and derivatives thereof. .

  The electron transport material represented by the general formula (A-1) used in the present invention is preferably an azole compound or an azine compound.

  Next, the compound represented by the general formula (A-1) will be described.

In General Formula (A-1), Z ^A1 represents an atomic group necessary for forming a nitrogen-containing heterocycle. L ^A1 represents a linking group. n ^A1 represents an integer of 2 or more.

L ^A1 in the general formula (A-1) represents a linking group. The linking group represented by L ^A1 is preferably a linking group formed of a carbon atom, a silicon atom, a nitrogen atom, a phosphorus atom, a sulfur atom, an oxygen atom, a boron atom, a germanium atom, etc. in addition to a single bond. More preferably a single bond, a carbon atom, a silicon atom, a boron atom, an oxygen atom, a sulfur atom, a germanium atom, an aromatic hydrocarbon ring or an aromatic heterocycle, and still more preferably a carbon atom, a silicon atom or an aromatic ring. A hydrocarbon ring, an aromatic heterocycle, more preferably a divalent or higher aromatic hydrocarbon ring, a divalent or higher aromatic heterocycle, or a carbon atom, more preferably a divalent or higher aromatic carbon ring. A hydrogen ring or a divalent or higher aromatic heterocycle, particularly preferably 1,3,5-benzenetriyl group, 1,2,5,6-benzenetetrayl group, 1,2,3,4,5 , 6-Benze Hexayl group, 2,2′-dimethyl-4,4′-biphenylene group, 2,4,6-pyridinetriyl group, 2,3,4,5,6-pyridinepentyl group, 2,4,6- A pyrimidine triyl group, a 2,4,6-triazine triyl group, and a 2,3,4,5-thiophenetetrayl group. Specific examples of the linking group represented by L ^A1 include the following.

L ^A1 may have a substituent, and examples of the substituent include an alkyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms; For example, methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (preferably having 2 to 30 carbon atoms) Preferably it is C2-C20, Most preferably, it is C2-C10, for example, vinyl, allyl, 2-butenyl, 3-pentenyl etc.), an alkynyl group (preferably C2-C30, more) Preferably it is C2-C20, Most preferably, it is C2-C10, for example, a propargyl, 3-pentynyl, etc. are mentioned. ), An aryl group (preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyl, p-methylphenyl, naphthyl, and anthranyl). An amino group (preferably having 0 to 30 carbon atoms, more preferably 0 to 20 carbon atoms, particularly preferably 0 to 10 carbon atoms, such as amino, methylamino, dimethylamino, diethylamino, dibenzylamino, diphenylamino, Ditolylamino, etc.),

An alkoxy group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 10 carbon atoms, such as methoxy, ethoxy, butoxy, 2-ethylhexyloxy, etc.), An aryloxy group (preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyloxy, 1-naphthyloxy, 2-naphthyloxy and the like. ), A heterocyclic oxy group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy and the like.) An acyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably carbon number) -12, for example, acetyl, benzoyl, formyl, pivaloyl, etc.), an alkoxycarbonyl group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 12 carbon atoms). For example, methoxycarbonyl, ethoxycarbonyl, etc.)

An aryloxycarbonyl group (preferably having a carbon number of 7 to 30, more preferably a carbon number of 7 to 20, particularly preferably a carbon number of 7 to 12, such as phenyloxycarbonyl), an acyloxy group (preferably carbon 2 to 30, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, such as acetoxy and benzoyloxy), acylamino group (preferably 2 to 30 carbon atoms, more preferably Has 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include acetylamino, benzoylamino and the like, and an alkoxycarbonylamino group (preferably 2 to 30 carbon atoms, more preferably 2 carbon atoms). -20, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonylamino An aryloxycarbonylamino group (preferably having 7 to 30 carbon atoms, more preferably 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonylamino). A sulfonylamino group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include methanesulfonylamino and benzenesulfonylamino).

Sulfamoyl group (preferably having 0 to 30 carbon atoms, more preferably 0 to 20 carbon atoms, and particularly preferably 0 to 12 carbon atoms, such as sulfamoyl, methylsmethylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl ), A carbamoyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl, etc. An alkylthio group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms such as methylthio and ethylthio), an arylthio group. (Preferably 6 to 30 carbon atoms, more preferably 6 to 6 carbon atoms. 0, particularly preferably 6 to 12 carbon atoms, such as phenylthio, etc.), a heterocyclic thio group (preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 carbon atom). For example, pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio, etc.), a sulfonyl group (preferably having 1 to 30 carbon atoms, more preferably carbon 1 to 20, particularly preferably 1 to 12 carbon atoms, such as mesyl and tosyl), sulfinyl group (preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably Having 1 to 12 carbon atoms, such as methanesulfinyl, benzenesulfinyl, etc.),

Ureido group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include ureido, methylureido, phenylureido), phosphoric acid amide group (Preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 12 carbon atoms, such as diethyl phosphoric acid amide and phenyl phosphoric acid amide), hydroxy group, mercapto Group, halogen atom (eg fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, heterocyclic group (preferably It has 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms. Examples of the hetero atom include a nitrogen atom and an oxygen atom. A sulfur atom, specifically, imidazolyl, pyridyl, quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, carbazolyl group, azepinyl group, etc.), silyl group (preferably 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, for example, trimethylsilyl, triphenylsilyl, etc.), silyloxy group (preferably 3 to 40 carbon atoms, More preferably, it has 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, and examples thereof include trimethylsilyloxy, triphenylsilyloxy and the like.

  These substituents may be further substituted. The substituent is preferably an alkyl group, an aryl group, a heterocyclic group, a halogen atom or a silyl group, more preferably an alkyl group, an aryl group, a heterocyclic group or a halogen atom, still more preferably an alkyl group or an aryl group. An aromatic heterocyclic group or a fluorine atom.

In General Formula (A-1), Z ^A1 represents an atomic group necessary to form a nitrogen-containing heterocycle, and even if the nitrogen-containing heterocycle containing Z ^A1 is a single ring, two or more rings are condensed. It may be a condensed ring. The nitrogen-containing heterocycle containing Z ^A1 is preferably a 5- to 8-membered nitrogen-containing heterocycle, more preferably a 5- to 7-membered nitrogen-containing heterocycle, and even more preferably a 5- or 6-membered nitrogen-containing aromatic. And particularly preferably a 5-membered aromatic heterocycle. A plurality of nitrogen-containing heterocycles containing Z ^A1 connected to L ^A1 may be the same or different.

Specific examples of the nitrogen-containing hetero ring containing Z ^A1, for example a pyrrole ring, indole ring, an oxazole ring, oxadiazole ring, thiazole ring, Chiazaizoru ring, azaindole ring, a carbazole ring, a carboline ring (norharman ring), imidazole Ring, benzimidazole ring, imidazopyridine ring, purine ring, pyrazole ring, indazole ring, azaindazole ring, triazole ring, tetrazole ring, azepine ring, iminostilbene ring (dibenzoazepine ring), tribenzoazepine ring, phenothiazine ring A oxadiazole ring, a triazole ring, an imidazole ring, a benzimidazole ring, and an imidazopyridine ring, and more preferably a benzimidazole ring and an imidazopyridine ring.
Z ^A1 may further form a condensed ring with another ring, if possible, and may have a substituent. As the substituent for Z ^A1 , for example, those exemplified as the substituent for L ^A1 in formula (A-1) can be applied, and the preferred range is also the same.
n ^A1 represents an integer of 2 or more, preferably 2 to 8, more preferably 2 to 6.

The compound in the present invention, the general formula (A-1) may be a low molecular compound, and an oligomer compound or a polymer compound (weight average molecular weight (polystyrene conversion) is preferably 1000 to 5000000, more preferably 2000 to 1000000. Further, it may be 3000 to 100,000, but the compound in the present invention is preferably a low molecular compound.
Specific examples of the general formula (A-1) in the present invention are listed below, but the present invention is not limited to these compounds.

The electron transport material represented by the general formula (A-1) used for the electron injection promoting layer in the present invention may be used alone or in combination.
One of the preferred modes of the electron injection promoting layer in the present invention is that it is composed only of the electron transport material represented by the general formula (A-1), but it can also contain another material. It is.
In the electron injection promoting layer, the electron transport material represented by the general formula (A-1) is preferably contained in an amount of 50 to 99.9% by mass, and more preferably 70 to 99.9% by mass. 80 to 99.9% by mass is more preferable, and 100% by mass is most preferable.

-Hole injection layer, hole transport layer-
The hole injection layer and the hole transport layer are layers having a function of receiving holes from the anode or the anode side and transporting them to the cathode side. By providing a hole transport layer on the anode side of the light emitting layer, hole transport can be promoted. Moreover, it is possible to promote the injection of holes from the anode by providing a hole injection layer further on the anode side than the hole transport layer.

  Specifically, the hole injection layer and the hole transport layer are carbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamines. Derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidin compounds, porphyrin compounds, organosilane derivatives, carbon , Etc. are preferable.

The thicknesses of the hole injection layer and the hole transport layer are each preferably 50 nm or less from the viewpoint of lowering the driving voltage.
The thickness of the hole transport layer is preferably 5 to 50 nm, and more preferably 10 to 40 m. In addition, the thickness of the hole injection layer is preferably 0.5 to 50 nm, and more preferably 1 to 40 nm.
The hole injection layer and the hole transport layer may have a single-layer structure composed of one or more of the materials described above, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions. .

  An electron-accepting dopant can be contained in the hole injection layer or the hole transport layer of the organic EL device of the present invention. As the electron-accepting dopant introduced into the hole-injecting layer or the hole-transporting layer, an inorganic compound or an organic compound can be used as long as it has an electron-accepting property and oxidizes an organic compound.

  Specifically, examples of the inorganic compound include metal halides such as ferric chloride, aluminum chloride, gallium chloride, indium chloride, and antimony pentachloride, and metal oxides such as vanadium pentoxide and molybdenum trioxide.

In the case of an organic compound, a compound having a nitro group, halogen, cyano group, trifluoromethyl group or the like as a substituent, a quinone compound, an acid anhydride compound, fullerene, or the like can be preferably used.
In addition, JP-A-6-212153, JP-A-11-111463, JP-A-11-251067, JP-A-2000-196140, JP-A-2000-286054, JP-A-2000-315580, JP-A-2001-102175, JP-A-2001-2001. -160493, JP2002-252085, JP2002-56985, JP2003-157981, JP2003-217862, JP2003-229278, JP2004-342614, JP2005-72012, JP20051666667 The compounds described in JP-A-2005-209643 and the like can be preferably used.

  These electron-accepting dopants may be used alone or in combination of two or more. Although the usage-amount of an electron-accepting dopant changes with kinds of material, it is preferable that it is 0.01 mass%-50 mass% with respect to hole transport layer material, and it is 0.05 mass%-20 mass%. It is further more preferable and it is especially preferable that it is 0.1 mass%-10 mass%.

-Electron injection layer, electron transport layer-
The electron injection layer and the electron transport layer are layers having a function of receiving electrons from the cathode or the cathode side and transporting them to the anode side. By providing an electron transport layer on the cathode side of the light emitting layer, electron transport can be promoted. In addition, by providing an electron injection layer further on the cathode side than the electron transport layer, injection of electrons from the cathode can be promoted.

  Specifically, the electron injection layer and the electron transport layer are triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, fluorenone derivatives, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, Carbodiimide derivatives, fluorenylidenemethane derivatives, distyrylpyrazine derivatives, aromatic tetracarboxylic anhydrides such as naphthalene and perylene, phthalocyanine derivatives, metal complexes of 8-quinolinol derivatives, metal phthalocyanines, benzoxazoles and benzothiazoles as ligands It is preferably a layer containing various metal complexes typified by metal complexes, organosilane derivatives, and the like.

The thicknesses of the electron injection layer and the electron transport layer are each preferably 50 nm or less from the viewpoint of lowering the driving voltage.
The thicknesses of the electron transport layer and the electron transport layer are preferably 5 to 50 nm, and more preferably 10 to 50 nm.
The electron injection layer and the electron transport layer may have a single layer structure including one or more of the materials described above, or may have a multilayer structure including a plurality of layers having the same composition or different compositions.
An electron transport layer containing a compound represented by the following general formula (C) is preferably provided adjacent to the cathode side of the electron injection promoting layer.

In general formula (C), at least one of R _{1 to} R ₆ represents a substituent, and the rest represents a hydrogen atom. M represents aluminum, gallium or indium. Y represents an aromatic group or silyl group which may have a substituent.

  The silyl group represented by Y is preferably an alkylsilyl group (preferably an alkylsilyl group having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, such as trimethylsilyl, Dimethyl-tert-butylsilyl, etc.), an arylsilyl group (preferably an arylsilyl group having preferably 18 to 60 carbon atoms, more preferably 18 to 50 carbon atoms, and particularly preferably 18 to 40 carbon atoms. Phenylsilyl, diphenyl-1-naphthylsilyl, diphenyl-2-naphthylsilyl, etc.), alkylarylsilyl groups (preferably having 15 to 60 carbon atoms, more preferably 15 to 50 carbon atoms, particularly preferably carbon numbers). 15 to 40 alkylarylsilyl groups such as dimethylphenylsilyl Diphenylmethylsilyl, diphenyl-1-naphthylsilyl, diphenyl-2-naphthylsilyl, etc.), aromatic heterocyclic substituted silyl groups (preferably having 3 to 60 carbon atoms, more preferably 3 to 50 carbon atoms, Particularly preferred are aromatic heterocyclic substituted silyl groups having 3 to 40 carbon atoms, such as tripyridylsilyl, diphenylpyridylsilyl, etc.), more preferred are arylsilyl groups, and even more preferred are carbons. The number of 18 to 60 is particularly preferably a triphenylsilyl group even if it has a substituent.

  The aromatic group represented by Y may be either an aromatic hydrocarbon group or an aromatic heterocyclic group. The aromatic hydrocarbon group represented by Y preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and particularly preferably 6 to 12 carbon atoms. For example, phenyl, 4-methyl-phenyl, 4- And cyano-phenyl, 1-naphthyl, 2-naphthyl, 1-anthranyl, 1-phenanthryl, 1-pyrenyl and the like.

  The aromatic heterocyclic group represented by Y is preferably an aromatic heterocyclic group having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 12 carbon atoms. For example, a nitrogen atom, an oxygen atom, a sulfur atom, etc. are mentioned. Specific examples of the aromatic heterocyclic group represented by Y include imidazolyl, pyridyl, quinolyl, quinoxalyl, furyl, thienyl, pyrazolyl, benzoxazolyl, benzimidazolyl, benzthiazolyl, carbazolyl group, azepinyl group and the like.

  The silyl group and aromatic group represented by Y may have a substituent, and examples of the substituent include an alkyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably carbon atoms. Examples thereof include methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl and the like, and an alkenyl group (preferably. 2-30 carbon atoms, more preferably 2-20 carbon atoms, particularly preferably 2-10 carbon atoms, such as vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), alkynyl groups (preferably 2-30 carbon atoms, more preferably 2-20 carbon atoms, particularly preferably 2-10 carbon atoms, such as propargyl, 3-pentynyl Etc., and the like.),

An aryl group (preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyl, p-methylphenyl, naphthyl, anthranyl and the like), amino. Group (preferably having 0 to 30 carbon atoms, more preferably 0 to 20 carbon atoms, particularly preferably 0 to 10 carbon atoms, such as amino, methylamino, dimethylamino, diethylamino, dibenzylamino, diphenylamino, ditolylamino, etc. An alkoxy group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms, such as methoxy, ethoxy, butoxy, 2-ethylhexyloxy, etc. An aryloxy group (preferably having 6 to 30 carbon atoms, more preferably carbon 6 to 20, particularly preferably 6 to 12 carbon atoms, such as phenyloxy, 1-naphthyloxy, 2-naphthyloxy, and the like, and heterocyclic oxy groups (preferably having 1 to 30 carbon atoms, more preferably ) Has 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy, and the like.

An acyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as acetyl, benzoyl, formyl, pivaloyl, etc.), an alkoxycarbonyl group ( Preferably it has 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 12 carbon atoms, and examples thereof include methoxycarbonyl, ethoxycarbonyl and the like, and an aryloxycarbonyl group (preferably having a carbon number). 7 to 30, more preferably 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonyl, and acyloxy groups (preferably 2 to 30 carbon atoms, more preferably carbon atoms). 2 to 20, particularly preferably 2 to 10 carbon atoms, for example, acetoxy, benzoyloxy An acylamino group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include acetylamino and benzoylamino). ,

An alkoxycarbonylamino group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonylamino), aryloxycarbonylamino group ( Preferably it has 7 to 30 carbon atoms, more preferably 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms, and examples thereof include phenyloxycarbonylamino, etc., and a sulfonylamino group (preferably 1 to 1 carbon atoms). 30, More preferably, it is C1-C20, Most preferably, it is C1-C12, for example, methanesulfonylamino, benzenesulfonylamino, etc.), a sulfamoyl group (preferably C0-30, more preferably) Has 0 to 20 carbon atoms, particularly preferably 0 to 12 carbon atoms. Amoiru, methylsulfamoyl, dimethylsulfamoyl, and the like phenylsulfamoyl.),

A carbamoyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl and the like), alkylthio. A group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylthio and ethylthio), an arylthio group (preferably having 6 to 6 carbon atoms). 30, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenylthio, and the like, and a heterocyclic thio group (preferably 1 to 30 carbon atoms, more preferably 1 carbon atom). -20, particularly preferably 1 to 12 carbon atoms, such as pyridylthio, 2-benzimidazolyl Oh, 2-benzoxazolyl thio, and 2-benzthiazolylthio the like.),

A sulfonyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as mesyl and tosyl), a sulfinyl group (preferably having 1 carbon atom). To 30, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfinyl, benzenesulfinyl, etc.), ureido groups (preferably 1 to 30 carbon atoms, more preferably C1-C20, Most preferably, it is C1-C12, for example, a ureido, methylureido, phenylureido etc. are mentioned), phosphoric acid amide groups (preferably C1-C30, more preferably carbon number) 1 to 20, particularly preferably 1 to 12 carbon atoms, such as diethyl phosphoric acid amide and phenyl phosphoric acid amide That.), Hydroxy group, a mercapto group, a halogen atom (e.g. fluorine atom, chlorine atom, bromine atom, iodine atom),

Cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, As, for example, nitrogen atom, oxygen atom, sulfur atom, specifically imidazolyl, pyridyl, quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, carbazolyl group, azepinyl group, etc. ), A silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, and examples thereof include trimethylsilyl and triphenylsilyl), silyloxy group (Preferably 3 to 40 carbon atoms, more preferably 3 to 3 carbon atoms. , Particularly preferably 3 to 24 carbon atoms, for example trimethylsilyloxy, etc. triphenylsilyl oxy and the like.) And the like. These substituents may be further substituted. Moreover, you may connect with substituents and may form a ring.

  Y is preferably an aromatic group, more preferably an aromatic hydrocarbon group, and still more preferably a phenyl group or naphthyl group which may have a substituent.

  Specific examples of the general formula (C) in the present invention are listed below, but the present invention is not limited to these compounds.

The electron injection layer or the electron transport layer of the organic EL device of the present invention can contain an electron donating dopant. The electron donating dopant introduced into the electron injecting layer or the electron transporting layer only needs to have an electron donating property and a property of reducing an organic compound, such as an alkali metal such as Li or an alkaline earth metal such as Mg. Transition metals including rare earth metals and reducing organic compounds are preferably used. As the metal, a metal having a work function of 4.2 eV or less can be preferably used. Specifically, Li, Na, K, Be, Mg, Ca, Sr, Ba, Y, Cs, La, Sm, Gd , And Yb. Examples of the reducing organic compound include nitrogen-containing compounds, sulfur-containing compounds, and phosphorus-containing compounds.
In addition, materials described in JP-A-6-212153, JP-A-2000-196140, JP-A-2003-68468, JP-A-2003-229278, JP-A-2004-342614, and the like can be used.

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

<Protective layer>
In the present invention, the entire organic EL element may be protected by a protective layer.
As a material contained in the protective layer, any material may be used as long as it has a function of preventing materials that promote device deterioration such as moisture and oxygen from entering the device.
Specific examples thereof include metals such as In, Sn, Pb, Au, Cu, Ag, Al, Ti, and Ni, MgO, SiO, SiO ₂ , Al ₂ O ₃ , GeO, NiO, CaO, BaO, and Fe ₂ O. ₃ , metal oxides such as Y ₂ O ₃ , TiO ₂ , metal nitrides such as SiN _x , SiN _x O _y , metal fluorides such as MgF ₂ , LiF, AlF ₃ , CaF ₂ , polyethylene, polypropylene, polymethyl Monomer mixture containing methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene, tetrafluoroethylene and at least one comonomer Copolymer obtained by copolymerization, cyclic in the copolymer main chain Examples thereof include a fluorine-containing copolymer having a structure, a water-absorbing substance having a water absorption of 1% or more, and a moisture-proof substance having a water absorption of 0.1% or less.

  The method for forming the protective layer is not particularly limited, and for example, vacuum deposition, sputtering, reactive sputtering, MBE (molecular beam epitaxy), cluster ion beam, ion plating, plasma polymerization (high frequency) Excited ion plating method), plasma CVD method, laser CVD method, thermal CVD method, gas source CVD method, coating method, printing method, transfer method can be applied.

<Sealing>
Furthermore, the organic electroluminescent element of this invention may seal the whole element using a sealing container.
Further, a moisture absorbent or an inert liquid may be sealed in a space between the sealing container and the light emitting element. Although it does not specifically limit as a moisture absorber, For example, barium oxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calcium sulfate, magnesium sulfate, phosphorus pentoxide, calcium chloride, magnesium chloride, copper chloride Cesium fluoride, niobium fluoride, calcium bromide, vanadium bromide, molecular sieve, zeolite, magnesium oxide and the like. The inert liquid is not particularly limited, and examples thereof include fluorinated solvents such as paraffins, liquid paraffins, perfluoroalkanes, perfluoroamines, perfluoroethers, chlorinated solvents, and silicone oils. It is done.

  The organic electroluminescence device of the present invention emits light by applying a direct current (which may include an alternating current component as necessary) voltage (usually 2 to 15 volts) or a direct current between the anode and the cathode. Obtainable.

The driving method of the organic electroluminescence device of the present invention is described in JP-A-2-148687, JP-A-6-301355, JP-A-5-29080, JP-A-7-134558, JP-A-8-234658, and JP-A-8-2441047. The driving method described in each publication, Japanese Patent No. 2784615, US Pat. Nos. 5,828,429, 6023308, and the like can be applied.
The driving durability of the organic electroluminescent element in the present invention can be measured by the luminance half time at a specific luminance. For example, using a source measure unit 2400 manufactured by KEITHLEY, a direct current voltage is applied to the organic EL element to emit light, and a continuous driving test is performed under the condition of an initial luminance of 2000 cd / m ² , and the luminance becomes 1000 cd / m ² . The brightness half-life time can be determined by comparing the brightness half-life time with a conventional light emitting device. This numerical value was used in the present invention.
In addition, the luminous efficiency as the luminous characteristic was measured as the luminance-current-voltage characteristic simultaneously with the measurement of the driving durability, and was defined as the luminous efficiency (cd / A) in the present invention.

  The organic EL element of the present invention can be suitably used for display elements, displays, backlights, electrophotography, illumination light sources, recording light sources, exposure light sources, reading light sources, signs, signboards, interiors, optical communications, and the like.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.
[Comparative Example 1]
Using an ITO target having an In ₂ O ₃ content of 95% by mass on a 0.5 mm thick, 2.5 cm square glass substrate, DC magnetron sputtering (conditions: substrate temperature 100 ° C., oxygen pressure 1 × 10 ⁻³ Pa), an ITO thin film (thickness 0.2 μm) was formed as a transparent anode. The surface resistance of the ITO thin film was 10Ω / □.
Next, the substrate on which the transparent anode was formed was placed in a cleaning container and subjected to IPA cleaning, and then UV-ozone treatment was performed for 30 minutes. On this transparent anode, copper phthalocyanine (CuPC) was provided with a 10 nm hole injection layer at a rate of 0.5 nm / second by vacuum deposition.
On top of that, α-NPD ((N, N′-di-α-naphthyl-N, N′-diphenyl) -benzidine) is formed by a vacuum deposition method at a rate of 0.5 nm / sec. Was provided. On top of this, CBP as a host material in the light emitting layer and Ir (ppy) ₃ as a phosphorescent light emitting material in the light emitting layer were co-deposited at a ratio of 100/5 by a vacuum evaporation method to obtain a 30 nm light emitting layer.
On the light-emitting layer, BAlq was deposited at a rate of 0.5 nm / second by a vacuum deposition method, and 10 nm was deposited thereon, and Alq ₃ was deposited at a rate of 0.2 nm / second by a vacuum deposition method. An electron injection layer was provided.
Further, a patterned mask (a mask having a light emission area of 2 mm × 2 mm) was placed on this layer, and lithium fluoride was deposited by 1 nm by a vacuum deposition method. Further, aluminum was deposited thereon by a vacuum deposition method to provide a 0.1 μm cathode.
The obtained light-emitting laminate is put in a glove box substituted with nitrogen gas, and sealed with a stainless steel sealing can provided with a desiccant and an ultraviolet curable adhesive (XNR5516HV, manufactured by Chiba Nagase). Thus, a comparative light emitting element was obtained.
The operations from the deposition of copper phthalocyanine to the sealing were performed in a vacuum or nitrogen atmosphere, and the device was fabricated without exposure to the atmosphere.

[Evaluation]
Each electron affinity (Ea) in the electron transport material of the electron injection promoting layer, the light emitting material of the light emitting layer, and the host material is calculated by calculating the band gap from the long wave end of the absorption spectrum of the single layer film (single layer). The electron affinity (Ea) was calculated from the ionization potential (Ip) value measured by the UV photoelectron analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.). The results are shown in Table 1 below.

Moreover, drive durability and luminous efficiency were measured by the following method using the light emitting element obtained by the above.
-Driving durability test-
The light emitting element was subjected to a continuous driving test under the condition of a current density of 10 mA / cm ² , and the time when the luminance was reduced by half was defined as the luminance half time T (1/2).
-Luminous efficiency-
A voltage was applied to the light emitting element, the luminance-current-voltage characteristic of this element was measured, and the light emission efficiency (cd / A) was calculated.

[Comparative Example 2]
In Comparative Example 1, the same procedure as in Comparative Example 1 was performed, except that the following compound a was deposited as an electron injection promoting layer between the light emitting layer and the electron transport layer by 10 nm at a rate of 0.05 nm / second by a vacuum deposition method. A comparative light-emitting element was obtained and subjected to the same evaluation test. The results are shown in Table 1.

[Comparative Example 3]
In the electron injection promoting layer of Comparative Example 2, a light emitting device was obtained in the same manner as in Comparative Example 2 except that α-NPD was deposited by 1 nm at a rate of 0.05 nm / second by vacuum deposition instead of Compound a, A similar evaluation test was conducted. The results are shown in Table 1 below.

[Example 1]
A light emitting device was obtained in the same manner as in Comparative Example 2 except that in the electron injection promoting layer of Comparative Example 2, the following compound b was formed by a vacuum evaporation method at a rate of 0.05 nm / second to a thickness of 0.5 nm. The same evaluation test was conducted. The results are shown in Table 1.

As is clear from Table 1, the luminance half time was significantly reduced in Comparative Example 2 compared to Comparative Example 1, although the luminous efficiency was improved. In Comparative Example 3, the luminance half time was significantly reduced as compared with Comparative Example 1. Even when the electron injection promoting layer is formed, the luminance half-life and the luminous efficiency are lowered unless the film thickness and the electron affinity of the contained electron transport material are within the scope of the present invention.
On the other hand, as is clear from the examples, it can be seen that a light-emitting element having good luminous efficiency and luminance half-time can be obtained by setting the film thickness and electron affinity within the scope of the present invention.

Claims (8)

An organic electroluminescent device having at least a light emitting layer and an electron injection promoting layer adjacent to the cathode side of the light emitting layer between a pair of electrodes, the light emitting layer containing a light emitting material, and the electron injection promoting layer Contains an electron transport material represented by the following general formula (A-1), and the thickness of the electron injection promoting layer is 3 nm or less, and the electron transport represented by the general formula (A-1) An organic electroluminescent device, wherein the material has an electron affinity greater than or equal to that of the light emitting material.

(In General Formula (A-1), Z ^A1 represents an atomic group necessary for forming a nitrogen-containing heterocycle. L ^A1 represents a linking group. N ^A1 represents an integer of 2 or more.) The light emitting layer contains a host material, and the electron affinity of the electron transport material represented by the general formula (A-1) is greater than or equal to the electron affinity of the host material. Organic electroluminescent device. The organic electroluminescent element according to claim 1, wherein the light emitting material is a phosphorescent light emitting material. The electron affinity of the electron transport material represented by the general formula (A-1) contained in the electron injection promoting layer is 2.7 eV or more, according to any one of claims 1 to 3. The organic electroluminescent element as described. The organic electroluminescence device according to any one of claims 1 to 4, wherein the electron injection promoting layer has a thickness of 0.1 to 2 nm. The electron transport material represented by the general formula (A-1) contained in the electron injection promoting layer is a material containing three or more nitrogen atoms. The organic electroluminescent element according to one item. The organic electroluminescent element according to claim 2, wherein the host material has a carbazole group. The organic electric field according to claim 1, wherein an electron transport layer containing a compound represented by the following general formula (C) is provided adjacent to the cathode side of the electron injection promoting layer. Light emitting element.

(In the formula, at least one of R _{1 to} R ₆ represents a substituent, and the rest represents a hydrogen atom. M represents aluminum, gallium, or indium. Y may have a substituent. Represents an aromatic group or a silyl group.)