JP2010239008A - Organic electroluminescent element, organic el display, and organic el illumination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic elecrtroluminescent element low in drive voltage, high in luminous efficiency and long in a driving life in the organic electroluminescent element including a light emitting layer formed by a wet film-deposition method and containing a low molecular weight compound and an organic layer formed adjacent to a cathode side of the light emitting layer and constituted of a compound containing no metal atoms. <P>SOLUTION: In the organic electroluminescent element including an anode, the light emitting layer, the first organic layer disposed adjacent to the light emitting layer, and the cathode in this order, wherein the light emitting layer is a layer containing a compound containing an aryl amine compound and an anthracene ring, the first organic layer is a layer constituted of the compound containing no metal atoms. and the light emitting layer is a layer formed by a wet film-deposition method, the organic electroluminescent element satisfies a relation (3) of 0.8≤ n<SP>H</SP>/n<SP>E</SP>≤1.6 (wherein, n<SP>H</SP>denotes the refractive index of the first organic layer and n<SP>E</SP>denotes the refractive index of the light emitting layer). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent element, and an organic EL display and an organic EL illumination including the organic electroluminescent element.

In recent years, organic electroluminescent elements have been actively developed as light emitting devices such as displays and lighting. This organic electroluminescent element injects positive and negative charges into an organic thin film between electrodes and takes out an excited state generated by recombination as light.
Organic electroluminescent devices that are currently in practical use are generally produced using a technique in which a relatively low molecular weight compound is heated under high vacuum conditions and vapor-deposited on an upper substrate. This method is used for small and medium-sized displays that have been put to practical use. Further, by adjusting the film thickness of the organic compound layer between the electrodes, it is possible to select the optical path length suitable for the emission wavelength, and it is possible to optimize the emission of each color of RGB. However, this vacuum evaporation method is difficult to uniformly deposit on a large area substrate and is not suitable for manufacturing a large display. Moreover, the utilization efficiency of the organic material which is a vapor deposition source is low, and there also exists a problem that manufacturing cost is high because the frequency | count of coating with a mask increases.

  On the other hand, as a means for producing these large-area organic EL panels, a method for producing an organic EL panel by a wet film formation method typified by a spin coating method, an ink jet method, a dip coating method, various printing methods and the like has been proposed. Yes. These methods are said to be advantageous in terms of cost as compared with the vacuum evaporation method, but various performances required for an organic electroluminescent display such as low voltage driving, high efficiency, and long life are difficult in single layer wet film formation. Therefore, multilayer lamination by wet film formation is very important in aiming at high performance of the coating type organic electroluminescence device. Patent Document 1 discloses multi-layer lamination by coating, but an element having high driving stability has not been obtained, and there are still many problems in practical use. Patent Document 2 discloses a device in which a light-emitting layer is wet-formed using an anthracene compound and a chrysene compound, and Alq3 is formed as an electron transport layer by vapor deposition. However, both current efficiency and driving life are improved. There is a need.

JP 2004-19935 A JP 2008-166629 A

  The present invention relates to an organic electroluminescent device having a light emitting layer containing a low molecular weight compound formed by a wet film forming method and an organic layer made of a compound not containing a metal atom adjacent to the cathode side of the light emitting layer. Another object of the present invention is to provide an organic electroluminescence device having a low driving voltage, high luminous efficiency, and long driving life.

As a result of intensive studies by the present inventors, the inventors have found that the above problems can be solved by defining the refractive index of the light emitting layer and the organic layer adjacent to the cathode side of the light emitting layer, and have reached the present invention.
That is, the present invention includes an anode, a light emitting layer, a first organic layer provided adjacent to the light emitting layer, and a cathode in this order, and the light emitting layer includes a compound represented by the following formula (1), and It is a layer containing a compound represented by the following formula (2), the first organic layer is a layer made of a compound not containing a metal atom, and the light emitting layer is a layer formed by a wet film forming method. In the organic electroluminescent element, the organic electroluminescent element, organic EL display, and organic EL illumination satisfy the following formula (3).

(In formula (1), Ar ^{1 to} Ar ⁴ each independently represents an aromatic hydrocarbon group which may have a substituent.)

(In formula (2), Ar ^{5 to} Ar ⁶ each independently represents an aromatic hydrocarbon group which may have a substituent.)

0.8 ≦ n ^H / n ^E ≦ 1.6 (3)

(In the formula, n ^H represents the refractive index of the first organic layer, and n ^E represents the refractive index of the light emitting layer.)

  According to the present invention, in an organic electroluminescent device having a light-emitting layer containing a chrysenediamine derivative and an anthracene derivative formed by a wet film formation method, the driving voltage of the organic electroluminescent device is low, the current efficiency is high, In addition, the drive life is long.

It is sectional drawing which shows typically an example of the structure of the organic electroluminescent element of this invention.

Embodiments of the organic electroluminescent element, organic EL display, organic EL lighting, and organic EL signal device of the present invention will be described in detail. The description of the constituent elements described below is an example of the embodiment of the present invention (representative example). The present invention is not specified in these contents unless it exceeds the gist.
The organic electroluminescent element of the present invention includes an anode, a light emitting layer, a first organic layer provided adjacent to the light emitting layer, and a cathode in this order, and the light emitting layer is represented by the following formula (1). A layer containing a compound and a compound represented by the following formula (2), wherein the first organic layer is a layer made of a compound not containing a metal atom, and the light emitting layer is formed by a wet film-forming method. In the organic electroluminescence device which is a layer, the organic electroluminescence device satisfies the following formula (3).

(In formula (1), Ar ^{1 to} Ar ⁴ each independently represents an aromatic hydrocarbon group which may have a substituent.)

(In formula (2), Ar ^{5 to} Ar ⁶ each independently represents an aromatic hydrocarbon group which may have a substituent.)

0.8 ≦ n ^H / n ^E ≦ 1.6 (3)

(In the formula, n ^H represents the refractive index of the first organic layer, and n ^E represents the refractive index of the light emitting layer.)
Hereinafter, although the structural requirements of the present invention will be described, the present invention is not limited to these.

[Light emitting layer]
In the present invention, a layer that is excited by recombination of holes injected from the anode and electrons injected from the cathode between the electrodes to which an electric field is applied (anode and cathode) and becomes a main light emitting source. It is.
Hereinafter, although the structural requirement of a light emitting layer is demonstrated, this invention is not limited to these.

[Compound represented by Formula (1)]
The light emitting layer in this invention is a layer containing the compound represented by following formula (1).

(In formula (1), Ar ^{1 to} Ar ⁴ each independently represents an aromatic hydrocarbon group which may have a substituent.)
Ar ^{1 to} Ar ⁴ each independently represents an aromatic hydrocarbon group which may have a substituent. Examples of the aromatic hydrocarbon group represented by Ar ^{1 to} Ar ⁴ include a benzene ring such as a benzene ring, a naphthalene ring, a phenanthrene ring, an anthracene ring, a pyrene ring, a chrysene ring, a naphthacene ring, and a benzophenanthrene ring. A group derived from a condensed ring formed by condensing ˜5. In particular, a phenyl group is preferable for obtaining blue light emission.

As the substituent that the aromatic hydrocarbon group in Ar ^{1 to} Ar ⁴ may have, an alkyl group, an alkenyl group, an alkoxy group, an aromatic hydrocarbon group, an aromatic heterocyclic group, and the like are preferable. Alkyl groups of oily substituents are preferred.
Further, the molecular weight of the substituent is usually 400 or less, preferably about 250 or less.
When Ar ^{1 to} Ar ⁴ have a substituent, the substitution position is preferably para-position or meta-position, particularly preferably para-position, with respect to the substitution position of the nitrogen atom.

Although the preferable specific example of a compound represented by Formula (1) below is shown, this invention is not limited to these.
<Specific Example of Compound Represented by Formula (1)>

  The molecular weight of the compound represented by the formula (1) is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, Usually, it is 100 or more, preferably 200 or more, more preferably 300 or more, and still more preferably 400 or more. If the molecular weight of the arylamine compound is too small, the heat resistance is remarkably reduced, gas is generated, the film quality is deteriorated when the film is formed, or the morphology of the organic electroluminescent device is changed due to migration, etc. Or may come. On the other hand, if the molecular weight of the arylamine compound is too large, purification of the arylamine compound tends to be difficult, or it may take time to dissolve the arylamine compound in a solvent.

[Compound represented by Formula (2)]
The organic electroluminescent element of this invention contains the compound represented by Formula (2) in a light emitting layer.

(In Formula (2), Ar ⁵ and Ar ⁶ are each independently an aromatic hydrocarbon group which may have a substituent)
Ar ⁵ and Ar ⁶ each independently represents an aromatic hydrocarbon group which may have a substituent. Examples of the aromatic hydrocarbon group of Ar ⁵ and Ar ⁶ include benzene ring, naphthalene ring, phenanthrene ring, anthracene ring, pyrene ring, chrysene ring, naphthacene ring, benzophenanthrene ring, benzene ring, or benzene ring 2 A group derived from a condensed ring formed by condensing ˜5.

  Among these, a compound represented by the following formula (2 ′) is preferable from the viewpoint of excellent redox stability and an appropriate energy gap.

(In Formula (2 ′), Ar ⁷ and Ar ⁸ each independently represent an aromatic hydrocarbon group which may have a substituent.)
Ar ⁷ and Ar ⁸ each independently represent an aromatic hydrocarbon group which may have a substituent. Examples of the aromatic hydrocarbon group of Ar ⁵ and Ar ⁶ include benzene ring, naphthalene ring, phenanthrene ring, anthracene ring, pyrene ring, chrysene ring, naphthacene ring, benzophenanthrene ring, benzene ring, or benzene ring 2 A group derived from a condensed ring formed by condensing ˜5.

  The molecular weight of the anthracene compound is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, and usually 100 or more, preferably 200. The range is more preferably 300 or more, and still more preferably 400 or more. If the molecular weight of the anthracene compound is too small, the heat resistance may be significantly reduced, gas may be generated, the film quality may be deteriorated when the film is formed, or the morphology of the organic electroluminescent element may be changed due to migration or the like. Sometimes come. On the other hand, if the molecular weight of the anthracene compound is too large, it tends to be difficult to purify the anthracene compound, or it may take time to dissolve in the solvent.

Although the preferable example of an anthracene compound is shown below, this invention is not limited to these.
<Specific examples of anthracene compounds>

[Others that may be contained]
The organic electroluminescent element of the present invention contains, in the light emitting layer, the compound represented by the formula (1) and the compound represented by the formula (2). However, as long as the effects of the present invention are not impaired, A luminescent material, a charge transport material, and an electron transport material may be contained.
(Luminescent material)
Hereinafter, examples of the fluorescent light emitting material among the light emitting materials will be described, but the fluorescent light emitting material is not limited to the following examples.

Examples of the fluorescent light-emitting material (blue fluorescent light-emitting material) that emits blue light include naphthalene, perylene, pyrene, anthracene, coumarin, p-bis (2-phenylethenyl) benzene, and derivatives thereof.
Examples of the fluorescent light emitting material that gives green light emission (green fluorescent light emitting material) include quinacridone derivatives, coumarin derivatives, aluminum complexes such as Al (C ₉ H ₆ NO) _3, and the like.

Examples of the fluorescent light-emitting material that gives yellow light (yellow fluorescent light-emitting material) include rubrene and perimidone derivatives.
Examples of fluorescent light-emitting materials that give red light (red fluorescent light-emitting materials) include DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) compounds, benzopyran derivatives, rhodamine derivatives. Benzothioxanthene derivatives, azabenzothioxanthene and the like.

As the phosphorescent material, for example, a long-period type periodic table (hereinafter referred to as a long-period type periodic table when referred to as “periodic table” unless otherwise specified) is selected from the seventh to eleventh groups. And an organometallic complex containing a metal.
Preferred examples of the metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

The ligand of the complex is preferably a ligand in which a (hetero) aryl group such as a (hetero) arylpyridine ligand or (hetero) arylpyrazole ligand is linked to pyridine, pyrazole, phenanthroline, etc. A pyridine ligand and a phenylpyrazole ligand are preferable. Here, (hetero) aryl represents an aryl group or a heteroaryl group.

  Specific examples of the phosphorescent material include tris (2-phenylpyridine) iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum, tris (2- Phenylpyridine) osmium, tris (2-phenylpyridine) rhenium, octaethyl platinum porphyrin, octaphenyl platinum porphyrin, octaethyl palladium porphyrin, octaphenyl palladium porphyrin, and the like.

The molecular weight of the compound used as the light emitting material is the same as that described in the above section [Arylamine compound]. Moreover, a preferable aspect is also the same.
In addition, any 1 type may be used for the luminescent material mentioned above, and 2 or more types may be used together by arbitrary combinations and a ratio.
[Charge transport material]
The charge transport material in the present invention is a compound having charge transport properties such as hole transport properties and electron transport properties.

In the present invention, only one type of charge transport material may be used, or two or more types may be used in any combination and ratio.
In the light emitting layer, it is preferable to use a light emitting low molecular weight compound as a dopant material and a charge transport material as a host material.
The charge transport material may be a compound that has been conventionally used in a light emitting layer of an organic electroluminescent device, and particularly a compound that is used as a host material of the light emitting layer.

  Specific examples of charge transport materials include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds in which tertiary amines are linked by a fluorene group, hydrazone compounds Compounds, silazane compounds, silanamine compounds, phosphamine compounds, quinacridone compounds, anthracene compounds, pyrene compounds, carbazole compounds, pyridine compounds, phenanthroline compounds, oxadiazole compounds, silole compounds, etc. It is done.

For example, two or more condensed aromatic rings including two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl are substituted with nitrogen atoms. Aromatic amine compounds having a starburst structure (J. Lumin, etc.) such as aromatic diamines (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine, etc. , 72-74, 985, 1997), an aromatic amine compound comprising a tetramer of triphenylamine (Chem. Commun., 2175, 1996), 2, 2 ′, 7, 7 ′. -Fluorene compounds such as tetrakis- (diphenylamino) -9,9'-spirobifluorene (Synth. Metals, 91, 209, 1997), 4,4'-N, N'- Carbazole compounds such as carbazole biphenyl, 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 2,5-bis (1- Oxadiazole compounds such as naphthyl) -1,3,4-oxadiazole (BND), 2,5-bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl-3 , 4-diphenylsilol (PyPySPyPy) and other silole compounds, bathophenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproin) and other phenanthroline compounds It is done.

(Method for forming light emitting layer)
The light emitting layer in the present invention is formed by a wet film forming method.
In order to form by the wet film-forming method, a composition further containing a solvent is used for the arylamine compound and, if necessary, other light-emitting materials or charge transport materials.
The solvent contained in the composition for forming the light emitting layer (hereinafter sometimes referred to as “the composition for forming the light emitting layer”) is a solvent in which the light emitting low molecular weight compound and the charge transporting material are well dissolved. There is no particular limitation.

The solubility of the solvent is usually 0.01% by weight or more, preferably 0.05% by weight or more, and more preferably 0.1% by weight of the light-emitting low molecular weight compound and the charge transport material at normal temperature and normal pressure, respectively. % Or more is preferable.
Although the specific example of a solvent is given to the following, as long as the effect of this invention is not impaired, it is not limited to these.

  For example, alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, and tetralin; halogenated fragrances such as chlorobenzene, dichlorobenzene, and trichlorobenzene Group hydrocarbons: 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethyl Aromatic ethers such as anisole and diphenyl ether; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; Alicyclic ketones such as Sanone, Cyclooctanone and Fencon; Alicyclic alcohols such as cyclohexanol and cyclooctanol; Aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol; Ethylene And aliphatic ethers such as glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA).

Of these, alkanes and aromatic hydrocarbons are preferable. One of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.
In order to obtain a more uniform film, it is preferable that the solvent evaporates from the liquid film immediately after the film formation at an appropriate rate. For this reason, the boiling point of the solvent is usually 80 ° C or higher, preferably 100 ° C or higher, more preferably 120 ° C or higher, and usually 270 ° C or lower, preferably 250 ° C or lower, more preferably 230 ° C or lower.

  The amount of the solvent used is arbitrary as long as the effects of the present invention are not significantly impaired, but is preferably 10 parts by weight or more, more preferably 50 parts by weight or more, particularly preferably 100 parts by weight of the composition for forming a light emitting layer. Is 80 parts by weight or more, preferably 99.95 parts by weight or less, more preferably 99.9 parts by weight or less, and particularly preferably 99.8 parts by weight or less. When the content is lower than the lower limit, the viscosity becomes too high, and the film forming workability may be lowered. On the other hand, when the value exceeds the upper limit, the film thickness obtained by removing the solvent after film formation cannot be obtained, so that film formation tends to be difficult. In addition, when mixing and using 2 or more types of solvents as a composition for light emitting layer formation, it is made for the sum total of these solvents to satisfy | fill this range.

Moreover, the composition for light emitting layer formation in this invention may contain various additives, such as a leveling agent and an antifoamer, for the purpose of improving film forming property.
After application of the composition for forming a light emitting layer, the obtained coating film is dried, and the light emitting layer is removed by removing the solvent for the light emitting layer. The method of the wet film formation method is not limited as long as the effects of the present invention are not significantly impaired, for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, Examples thereof include a capillary coating method, an inkjet method, a screen printing method, a gravure printing method, and a wet method such as a flexographic printing method.

Among these, the spin coating method and the ink jet method are preferable.
The thickness of the light emitting layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. If the light emitting layer is too thin, defects may occur in the film, and if it is too thick, the driving voltage may increase.

[First organic layer]
The first organic layer in the present invention is a layer that is provided adjacent to the cathode side of the light emitting layer and is made of a compound that does not contain a metal atom.
The low molecular weight compound not containing a metal atom is a compound that does not contain an atom classified as a metal element or a metalloid element in the compound in the periodic table.

  The molecular weight of the low molecular weight compound not containing metal is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, and usually 100 The range is preferably 200 or more, more preferably 300 or more, and still more preferably 400 or more. If the molecular weight of the low molecular weight compound that does not contain metal is too small, the heat resistance will be significantly reduced, gas generation will occur, the film quality will deteriorate when the film is formed, or organic electroluminescence due to migration, etc. In some cases, the morphology of the element may be changed. On the other hand, if the molecular weight of the compound is too large, purification of the compound becomes difficult.

Specific examples of low molecular weight compounds not containing metal, which are preferable in terms of excellent mobility and high durability, are shown below, but the present invention is not limited to these.
<Specific examples of low molecular weight compounds not containing metal>

(Film formation method)
Although the formation method of the 1st organic layer in this invention does not have a restriction | limiting in particular unless the effect of this invention is impaired, It forms with a vacuum evaporation method.
When the first organic layer is formed by vacuum deposition, one or more of the constituent materials of the first organic layer (the aforementioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum vessel. Put in crucibles installed (in case of using two or more materials, put them in each crucible), evacuate the inside of the vacuum vessel to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then heat the crucible (two types When using the above materials, heat each crucible) and evaporate by controlling the amount of evaporation (when using two or more materials, evaporate by independently controlling the amount of evaporation) and face the crucible Then, the hole injection layer 3 is formed on the anode 2 of the substrate placed on the substrate. In addition, when using 2 or more types of materials, those mixtures can be put into a crucible, and it can heat and evaporate, and the 1st organic layer 3 can also be formed.

The degree of vacuum at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) or more, usually 9.0 × 10 ⁻⁶ Torr. (12.0 × 10 ⁻⁴ Pa) or less. The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 Å / second or more and usually 5.0 Å / second or less. Although the substrate temperature at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, it is preferably 10 ° C. or higher, and preferably 50 ° C. or lower.

(Second organic layer)
The organic electroluminescent element of the present invention preferably has a second organic layer between the anode and the first organic layer. The second organic layer is a layer containing a hole transporting compound, and preferably further contains an electron accepting compound.
(Hole transporting compound)
The material for forming the hole injection / transport layer (hole injection / transport material) is preferably a material having a high hole transport capability and capable of efficiently transporting the injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities that become traps are not easily generated during manufacturing or use.

When used in contact with the light emitting layer, it is particularly preferable not to quench the light emitted from the light emitting layer or reduce the efficiency by forming an exciplex with the light emitting layer.
Furthermore, in order to improve the number of electron spins per mg, a hole injection / transport material that is easily oxidized by one electron is preferable. From this viewpoint, a compound having an ionization potential of 4.5 eV to 6.0 eV is preferable.

  Examples of such hole injection / transport materials include arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, siloles. Derivatives, oligothiophene derivatives, condensed polycyclic aromatic derivatives, metal complexes and the like.

  Also, for example, polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ether sulfone derivatives containing tetraphenylbenzidine, polyarylene vinylene derivatives, polysiloxane derivatives, polythiophenes Derivatives, poly (p-phenylene vinylene) derivatives, and the like. These may be any of an alternating copolymer, a random copolymer, a block polymer, or a graft copolymer. Further, it may be a polymer having a branched main chain and three or more terminal portions, or a so-called dendrimer.

Of these, polyarylamine derivatives and polyarylene derivatives are preferred.
The polyarylamine derivative is preferably a polymer compound containing a repeating unit represented by the following formula (II). In particular, it is preferably a polymer compound composed of a repeating unit represented by the following formula (II). In this case, Ar ^a or Ar ^b may be different in each repeating unit.

(In formula (II), Ar ^a and Ar ^b each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.)
Examples of the aromatic hydrocarbon group which may have a substituent include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, and an acenaphthene. Examples include a group derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a fluoranthene ring, a fluorene ring, and a group in which these rings are linked by a direct bond.

Examples of the aromatic heterocyclic group which may have a substituent include a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, and a carbazole ring. , Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine Ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc. ring Are those groups group and the rings of from 2-4 fused ring is linked by a direct bond or two or more rings.

Solubility, from the viewpoint of heat resistance, Ar ^a and Ar ^b independently represents a benzene ring, a naphthalene ring, anthracene ring, phenanthrene ring, triphenylene ring, pyrene ring, thiophene ring, pyridine ring, from the group consisting of fluorene ring A group derived from a selected ring or a group formed by linking two or more benzene rings (for example, a biphenyl group, a biphenylene group, a terphenyl group, or a terphenylene group) is preferable.

Among these, a group derived from a benzene ring (phenyl group), a group formed by connecting two benzene rings (biphenyl group), and a group derived from a fluorene ring (fluorenyl group) are preferable.
Examples of the substituent that the aromatic hydrocarbon group and aromatic heterocyclic group in Ar ^a and Ar ^b may have include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, and a dialkyl. Examples thereof include an amino group, a diarylamino group, an acyl group, a halogen atom, a haloalkyl group, an alkylthio group, an arylthio group, a silyl group, a siloxy group, a cyano group, an aromatic hydrocarbon ring group, and an aromatic heterocyclic group.

As the polyarylene derivative, an arylene group such as an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent exemplified as Ar ^a or Ar ^b in the formula (II) is used as ^a repeating unit. The high molecular compound which has is mentioned.
As the polyarylene derivative, a polymer compound having a repeating unit consisting of the following formula (III-1) and / or the following formula (III-2) is preferable.

(In formula (III-1), R ^a , R ^b , R ^c and R ^d are each independently an alkyl group, an alkoxy group, a phenylalkyl group, a phenylalkoxy group, a phenyl group, a phenoxy group, an alkylphenyl group, Represents an alkoxyphenyl group, an alkylcarbonyl group, an alkoxycarbonyl group, or a carboxy group, and t and s each independently represent an integer of 0 to 3. When t or s is 2 or more, they are contained in one molecule. A plurality of R ^a or R ^b may be the same or different, and adjacent R ^a or R ^b may form a ring.)

(In formula (III-2), R ^e and R ^f are each independently the same as R ^a , R ^b , R ^c or R ^d in formula (III-1). Independently represents an integer of 0 to 3. When r or u is 2 or more, a plurality of R ^e and R ^f contained in one molecule may be the same or different, and adjacent R ^e or A ring may be formed by R ^f, and X represents an atom or a group of atoms constituting a 5-membered ring or a 6-membered ring.)
Examples of X, -O -, - BR - , - NR -, - SiR 2 -, - PR -, - SR -, - it is or they are formed by bonding group - CR _2. R represents a hydrogen atom or an arbitrary organic group.

  The polyarylene derivative has a repeating unit represented by the following formula (III-3) in addition to the repeating unit represented by the following formula (III-1) and / or the following formula (III-2). Is preferred.

(In formula (III-3), Ar ^{c to} Ar ^j each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and v and w each represent Independently represents 0 or 1.)
Specific examples of Ar ^{c to} Ar ^j are the same as Ar ^a and Ar ^b in the formula (II).
Specific examples of the above formulas (III-1) to (III-3) and specific examples of polyarylene derivatives include those described in JP-A-2008-98619.

When the hole injecting / transporting material is a polymer compound, the polymer compound containing a fluorene ring in the repeating unit is preferable from the viewpoint of improving the charge transporting ability.
A compound having an insolubilizing group in the skeleton of the hole injecting / transporting material (hereinafter sometimes referred to as “insolubilizing compound”) is preferable from the viewpoint that the insolubility of the film in an organic solvent can be improved.
A compound having an insolubilizing group (hereinafter, sometimes referred to as “insolubilizing compound”) is preferable because it can be easily laminated.

[Insolubilized group]
The insolubilizing group is a group that reacts by irradiation with heat and / or active energy rays, and is a group having an effect of lowering solubility in an organic solvent or water after the reaction than before the reaction.
In the present invention, the insolubilizing group is preferably a dissociating group or a crosslinkable group.
(Dissociable group)
The hole injecting / transporting material in the present invention preferably has a dissociating group as an insolubilizing group in terms of excellent charge transporting ability after insolubilization (after dissociation reaction).

  Here, the dissociating group refers to a group that dissociates from a bonded aromatic hydrocarbon ring at 70 ° C. or more and is soluble in a solvent. Here, being soluble in a solvent means that the compound is dissolved in toluene at 0.1% by weight or more at room temperature in a state before reacting by irradiation with heat and / or active energy rays. The solubility in toluene is preferably 0.5% by weight or more, more preferably 1% by weight or more.

Such a dissociating group is preferably a group that thermally dissociates without forming a polar group on the aromatic hydrocarbon ring side, and more preferably a group that dissociates thermally by a reverse Diels-Alder reaction.
Furthermore, it is preferably a group that thermally dissociates at 100 ° C. or higher, and preferably a group that thermally dissociates at 300 ° C. or lower.

Specific examples of the dissociating group are as follows, but the present invention is not limited thereto.
A specific example in the case where the dissociating group is a divalent group is as shown in <Divalent dissociating group group A> below.
<Divalent dissociation group A>

A specific example in the case where the dissociating group is a monovalent group is as shown in <Monovalent dissociating group B> below.
<Monovalent dissociation group B>

(Crosslinkable group)
In addition, the hole transport material in the present invention has a crosslinkable group as an insolubilizing group, and is soluble in a solvent before and after a reaction (insolubilizing reaction) caused by irradiation with heat and / or active energy rays. It is preferable in that a large difference can be generated.
Here, the crosslinkable group refers to a group that reacts with the same or different groups of other molecules located nearby by irradiation with heat and / or active energy rays to form a new chemical bond.

Examples of the crosslinkable group include groups shown in the crosslinkable group group T in that it is easily insolubilized.
[Crosslinkable group T]

(In formula, R < ¹ > -R < ⁵ > represents a hydrogen atom or an alkyl group each independently. Ar < ³¹ > may have the aromatic hydrocarbon group or substituent which may have a substituent. Represents an aromatic heterocyclic group.)
Groups that are insolubilized by cationic polymerization, such as cyclic ether groups such as epoxy groups and oxetane groups, and vinyl ether groups are preferred because they are highly reactive and easily insolubilized. Among these, an oxetane group is particularly preferable from the viewpoint that the rate of cationic polymerization can be easily controlled, and a vinyl ether group is preferable from the viewpoint that a hydroxyl group that may cause deterioration of the device during the cationic polymerization is hardly generated.

A group that undergoes a cycloaddition reaction, such as an arylvinylcarbonyl group such as a cinnamoyl group, or a group derived from a benzocyclobutene ring, is preferred from the viewpoint of further improving electrochemical stability.
Among the crosslinkable groups, a group derived from a benzocyclobutene ring is particularly preferable in that the structure after insolubilization is particularly stable.
The crosslinkable group may be directly bonded to the aromatic hydrocarbon group or aromatic heterocyclic group in the molecule, but may be bonded via a divalent group. As the divalent group, a group selected from an —O— group, a —C (═O) — group, or an (optionally substituted) —CH ₂ — group may be selected from 1 to 30 in any order. It is preferable to bind to an aromatic hydrocarbon group or an aromatic heterocyclic group via a divalent group formed by connecting them individually.

(Electron-accepting compound)
The second organic layer preferably contains an electron accepting compound, and therefore the second organic layer forming composition preferably also contains an electron accepting compound. As the electron-accepting compound, a compound having an oxidizing power and an ability to accept one electron from the above-described hole-transporting compound is preferable. Specifically, a compound having an electron affinity of 4 eV or more is preferable, and a compound of 5 eV or more is more preferable.

Examples of the electron-accepting compound include a triaryl boron compound, a metal halide, a Lewis acid, an organic acid, an onium salt, a salt of an arylamine and a metal halide, and a salt of an arylamine and a Lewis acid. 1 type, or 2 or more types of compounds etc. chosen from are mentioned. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate or triphenylsulfonium tetrafluoroborate (WO 2005/089024) High-valent inorganic compounds such as iron (III) chloride (Japanese Patent Laid-Open No. 11-251067) and ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris (pendafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365) Aromatic boron compounds; fullerene derivatives; iodine and the like. In addition, only 1 type may be used for an electron-accepting compound, and 2 or more types may be used together by arbitrary combinations and arbitrary ratios.

Since these electron-accepting compounds oxidize the hole-transporting compound, the conductivity of the second organic layer can be improved.
The content of the electron-accepting compound with respect to the hole-transporting compound is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is usually 100 mol% or less, preferably 40 mol% or less.

(solvent)
At least one of the solvents contained in the second composition for forming an organic layer is preferably a solvent that can dissolve the material of the second organic layer.
Moreover, the boiling point of a solvent is 110 degreeC or more normally, Preferably it is 140 degreeC or more, More preferably, it is 200 degreeC or more, and is 400 degrees C or less normally, Preferably it is 300 degrees C or less. If the boiling point of the solvent is too low, the drying rate of the formed film is high and the film quality may deteriorate. Moreover, if the boiling point of the solvent is too high, the temperature of the drying process increases, which may adversely affect other layers 2 and the substrate 1 (for example, a glass substrate).

  Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents and the like. Specifically, examples of the ether solvent include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3- And aromatic ethers such as dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, and 2,4-dimethylanisole. Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate. Further, examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-iropropylbiphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Etc. Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, and the like. In addition, dimethyl sulfoxide and the like can also be used as a solvent.

Among the solvents described above, a solvent having a high ability to dissolve the material of the second organic layer (dissolution ability) or a high affinity with the material is preferable. This is because the concentration of the second organic layer forming composition can be arbitrarily set to prepare a composition having a concentration excellent in the efficiency of the film forming process.
In addition, 1 type may be used for a solvent and it may use 2 or more types together by arbitrary combinations and arbitrary ratios.

(Other materials)
The second composition for forming an organic layer may further contain other components in addition to the hole transporting compound and the electron accepting compound as long as the effects of the present invention are not significantly impaired. Examples of other components include various light emitting materials, electron transporting compounds, binder resins, and coating property improving agents. In addition, 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and arbitrary ratios.

(Film formation method)
The second organic layer can be formed using a known technique, but is preferably formed by a wet film forming method using the second organic layer forming composition in terms of excellent film uniformity. .
After preparing the composition for forming the second organic layer, the composition is applied onto a layer (usually an anode) corresponding to the lower layer of the second organic layer by a wet film-forming method, and dried. Two organic layers are formed.

The temperature in the coating step is preferably 10 ° C. or higher, and preferably 50 ° C. or lower, in order to prevent film defects due to the formation of crystals in the composition.
Although the relative humidity in an application | coating process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally, and usually 80% or less.
After coating, the film of the composition for forming a hole injection layer is usually dried by heating or the like. Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  The heating temperature in the heating step is preferably heated at a temperature equal to or higher than the boiling point of the solvent used in the composition for forming a hole injection layer as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more types of solvents used in the hole injection layer, at least one type is preferably heated at a temperature equal to or higher than the boiling point of the solvent. In consideration of an increase in the boiling point of the solvent, the heating step is preferably performed at 120 ° C. or higher, preferably 410 ° C. or lower.

  In the heating step, the heating time is not limited as long as the heating temperature is not lower than the boiling point of the solvent of the composition for forming a hole injection layer and sufficient insolubilization of the coating film does not occur. Is less than a minute. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.

  Further, when an insolubilizing compound is used as a material for forming the second organic layer, for example, heating or light is used to cause insolubilization reaction after coating and improve insolubility in the solvent. Irradiation of active energy. These heating and active energy irradiation may be carried out independently or in any combination of a plurality of means. When performing in combination, the order of implementation is not particularly limited. It is also possible to combine heating and active energy irradiation.

  When insolubilization is caused by heating, there is no particular limitation on the heating conditions as insolubilization proceeds, but the heating temperature is usually 120 ° C or higher, preferably 150 ° C or higher, and usually 400 ° C or lower, preferably 300 ° C or lower. Next, the layer formed using the composition for organic electroluminescent elements of the present invention is heated. If the temperature is too low, the insolubilization may not proceed, and if the temperature is too high, the element may be deteriorated.

The heating time is usually 1 minute or longer, preferably 5 minutes or longer, and is usually 24 hours or shorter, preferably 3 hours or shorter. If the time is too short, the insolubilization may not proceed sufficiently, and if it is too long, the cost may increase.
Although it does not specifically limit as a heating means, Means, such as mounting the laminated body which has the formed layer, for example on a hotplate, or heating in oven, is used.

As specific heating conditions, for example, conditions such as heating on a hot plate at 120 ° C. or more for 1 minute or more can be used.
In addition, when insolubilization is caused by irradiation with active energy such as light, the irradiation conditions are not particularly limited as long as insolubilization proceeds.
As the irradiation method of active energy, when irradiating light, for example, a method of directly using an ultraviolet / visible / infrared light source such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a halogen lamp, an infrared lamp; And a method of irradiating using a mask aligner having a built-in light source, a conveyor-type light irradiator, and the like. Moreover, when performing active energy irradiation other than light, the method etc. which irradiate using the apparatus (what is called a microwave oven) which irradiates the microwave generated with the magnetron, etc. are mentioned, for example.

As the irradiation time, it is preferable to set conditions necessary for lowering the solubility of the film, usually 0.1 seconds or more, preferably 1 minute or more, and usually 10 hours or less, preferably 1 hour or less. To do. If the time is too short, the insolubilization may not proceed sufficiently, and if it is too long, the cost may increase.
In order to reduce the amount of moisture contained in the organic layer obtained after implementation and / or the amount of moisture adsorbed on the surface, the heating and active energy irradiation described above are performed in an atmosphere that does not contain moisture, such as a nitrogen gas atmosphere. Preferably it is done. For the same purpose, when combined with heating and / or active energy irradiation, it is particularly preferable to perform at least the step immediately before the formation of the organic light emitting layer in an atmosphere containing no moisture such as a nitrogen gas atmosphere.

The film thickness of the second organic layer formed as described above is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less. If the film thickness is too thin, the hole injection ability may be insufficient, and if it is too thick, the resistance may be increased.
The second organic layer may be composed of a single layer, or may be composed of a plurality of layers. In the latter case, the plurality of layers may be layers made of the same material or layers made of different materials.

<About refractive index>
The organic electroluminescent element of the present invention is obtained by the method described in the section [Method of measuring refractive index] below, and n ^H / n ^E (n ^H : refractive index of the first organic layer, n ^E : refraction of the light emitting layer). Ratio) is usually 0.8 or more, preferably 0.9 or more, more preferably 1.0 or more, and usually 1.6 or less, preferably 1.5 or less, more preferably 1.4 or less.

Within the above range, electron injection from the first organic layer to the light-emitting layer becomes good, so that more excited states are generated in the light-emitting layer, the efficiency is high, and the first organic layer escapes. Therefore, an element having a long driving life can be obtained.
[Measurement method of refractive index]
The refractive index can be measured using various methods. Using a spectroscopic ellipsometer (manufactured by JA Woollam), for example, a phase difference delta and an amplitude ratio psi are set to wavelengths at incident angles of 70 °, 75 °, and 80 ° with respect to a sample in which a compound is formed on a substrate. Measured as a function of (250 nm to 1320 nm). For a wavelength region where there is no optical absorption by the formed compound, fitting assuming a Cauchy dispersion relationship is performed, and the refractive index and film thickness are calculated so as to best fit the measured delta and psi.

<Reason for obtaining the effect of the present invention>
Since the organic electroluminescent element of the present invention has a refractive index in the above range, the electron injecting property from the first organic layer to the light emitting layer is good.
Therefore, more excited states can be obtained in the light emitting layer, and the number of holes that pass through the light emitting layer and reach the first organic layer is reduced, resulting in good driving life, driving voltage, and luminous efficiency. It is.

<Organic electroluminescent device>
Below, the layer structure of the organic electroluminescent element manufactured by the method of the present invention, its general formation method and the like will be described with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent device according to the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 Represents a light-emitting layer, 6 represents a hole blocking layer, 7 represents an electron transport layer, 8 represents an electron injection layer, and 9 represents a cathode.

In the case of the element shown in FIG. 1, the hole blocking layer corresponds to the first organic layer, and the hole injection layer corresponds to the second organic layer. In the case where there is no hole blocking layer, the electron transport layer corresponds to the first organic layer.
Each layer described below is formed by selecting a material that satisfies the above-described conditions as the conditions of the second organic layer, the light emitting layer, and the first organic layer, to which these correspond.
In the present invention, the wet film forming method includes, for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, capillary coating method, ink jet method, screen printing. This method is a wet film formation method such as a method, a gravure printing method, or a flexographic printing method. Among these film forming methods, a spin coating method, a spray coating method, and an ink jet method are preferable. This is because the liquid property specific to the coating composition used for the organic electroluminescent element is matched.

(substrate)
The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, polysulfone or the like is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

(anode)
The anode 2 serves to inject holes into the layer on the light emitting layer side.
This anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium, or platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or It is composed of a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline.

  In general, the anode 2 is often formed by a sputtering method, a vacuum deposition method, or the like. In addition, when forming the anode 2 using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, an appropriate binder resin solution It is also possible to form the anode 2 by dispersing it and applying it onto the substrate 1. Furthermore, in the case of a conductive polymer, a thin film can be directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett. 60, 2711, 1992).

The anode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.
The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and the anode 2 may be the same as the substrate 1. Furthermore, it is also possible to laminate different conductive materials on the anode 2 described above.

For the purpose of removing impurities adhering to the anode 2 and adjusting the ionization potential to improve the hole injection property, the surface of the anode 2 is treated with ultraviolet (UV) / ozone, or with oxygen plasma or argon plasma. It is preferable to do.
(Hole injection layer)
The hole injection layer 3 is a layer that transports holes from the anode 2 to the light emitting layer 5, and is usually formed on the anode 2.

The material and method for forming the hole injection layer are preferably formed by the material and method described in the above section [First organic layer], but may be formed by other materials and methods.
An example of forming with other materials and methods will be described below.
When the hole injection layer 3 is formed by other materials and methods, the formation method may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but from the viewpoint of reducing dark spots, the hole injection layer 3 3 is preferably formed by a wet film formation method.

The thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.
<Formation of hole injection layer by wet film formation method>
When forming the hole injection layer 3 by wet film formation, the material for forming the hole injection layer 3 is usually mixed with an appropriate solvent (hole injection layer solvent) to form a film-forming composition (positive A composition for forming a hole injection layer), and applying the composition for forming a hole injection layer on a layer (usually an anode) corresponding to the lower layer of the hole injection layer 3 by an appropriate technique. The hole injection layer 3 is formed by coating and drying.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as a constituent material of the hole injection layer.
As long as the hole transporting compound is a compound having a hole transporting property, which is usually used in a hole injection layer of an organic electroluminescence device, a monomer or the like may be a polymer compound or the like. Although it may be a low molecular weight compound, it is preferably a high molecular weight compound.

  The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3. Examples of hole transporting compounds include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which tertiary amines are linked by a fluorene group, hydrazone derivatives, silazane derivatives, silanamines Derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon and the like.

In the present invention, the derivative includes, for example, an aromatic amine derivative and includes an aromatic amine itself and a compound having an aromatic amine as a main skeleton. It may be a mer.
The hole transporting compound used as the material for the hole injection layer 3 may contain any one of these compounds alone, or may contain two or more. In the case of containing two or more kinds of hole transporting compounds, the combination is arbitrary, but one or more kinds of aromatic tertiary amine polymer compounds and one or two kinds of other hole transporting compounds. It is preferable to use the above in combination.

Among the above-mentioned examples, an aromatic amine compound is preferable from the viewpoint of amorphousness and visible light transmittance, and an aromatic tertiary amine compound is particularly preferable. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.
The type of the aromatic tertiary amine compound is not particularly limited, but from the viewpoint of uniform light emission due to the surface smoothing effect, a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (a polymerizable compound in which repeating units are linked) is further included. preferable. Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (I).

(In formula (I), Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Represents a linking group selected from the group of linking groups, and among Ar ^{1 to} Ar ⁵ , two groups bonded to the same N atom may be bonded to each other to form a ring.

(In said each formula, Ar < ⁶ > -Ar < ¹⁶ > represents the aromatic heterocyclic group which may have a substituent or the aromatic hydrocarbon group which may have a substituent each independently. R ¹ and R ² each independently represents a hydrogen atom or an arbitrary substituent.))
As the aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ , a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene from the viewpoint of the solubility, heat resistance, hole injection / transport property of the polymer compound A group derived from a ring or a pyridine ring is preferred, and a group derived from a benzene ring or a naphthalene ring is more preferred.

The aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ may further have a substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less. As the substituent, an alkyl group, an alkenyl group, an alkoxy group, an aromatic hydrocarbon group, an aromatic heterocyclic group and the like are preferable.
When R ¹ and R ² are optional substituents, examples of the substituent include alkyl groups, alkenyl groups, alkoxy groups, silyl groups, siloxy groups, aromatic hydrocarbon groups, aromatic heterocyclic groups, and the like. .

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (I) include those described in International Publication No. 2005/089024.
In addition, as a hole transporting compound, a conductive polymer (PEDOT / PSS) obtained by polymerizing 3,4-ethylenedioxythiophene (3,4-ethylenedioxythiophene), a polythiophene derivative, in high molecular weight polystyrene sulfonic acid. Is also preferred. Moreover, the end of this polymer may be capped with methacrylate or the like.

  The concentration of the hole transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably in terms of film thickness uniformity. Is 0.1% by weight or more, more preferably 0.5% by weight or more, and usually 70% by weight or less, preferably 60% by weight or less, more preferably 50% by weight or less. If this concentration is too high, film thickness unevenness may occur, and if it is too low, defects may occur in the formed hole injection layer.

(Electron-accepting compound)
The composition for forming a hole injection layer preferably contains an electron accepting compound as a constituent material of the hole injection layer.
The electron-accepting compound is preferably a compound having an oxidizing power and the ability to accept one electron from the above-described hole transporting compound, specifically, a compound having an electron affinity of 4 eV or more is preferable, and 5 eV or more. The compound which is the compound of these is further more preferable.

Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples thereof include one or more compounds selected from the group. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate, triphenylsulfonium tetrafluoroborate (International Publication No. WO 2005/089024); High-valent inorganic compounds such as iron (III) chloride (Japanese Patent Laid-Open No. 11-251067), ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene; Aromatic boron compounds such as); fullerene derivatives; iodine; sulfonate ions such as polystyrene sulfonate ions, alkylbenzene sulfonate ions, camphor sulfonate ions, and the like.

These electron accepting compounds can improve the conductivity of the hole injection layer by oxidizing the hole transporting compound.
The content of the electron-accepting compound in the hole-injecting layer or the composition for forming a hole-injecting layer with respect to the hole-transporting compound is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is usually 100 mol% or less, preferably 40 mol% or less.

(Other components)
As a material for the hole injection layer, other components may be further contained in addition to the above-described hole transporting compound and electron accepting compound as long as the effects of the present invention are not significantly impaired. Examples of other components include various light emitting materials, electron transporting compounds, binder resins, and coating property improving agents. In addition, only 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and ratios.

(solvent)
At least one of the solvents of the composition for forming a hole injection layer used in the wet film formation method is preferably a compound that can dissolve the constituent material of the hole injection layer. The boiling point of this solvent is usually 110 ° C. or higher, preferably 140 ° C. or higher, particularly 200 ° C. or higher, usually 400 ° C. or lower, and preferably 300 ° C. or lower. If the boiling point of the solvent is too low, the drying speed is too high and the film quality may be deteriorated. Further, if the boiling point of the solvent is too high, it is necessary to increase the temperature of the drying step, which may adversely affect other layers and the substrate.

Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and the like.
Examples of ether solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole , Phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, aromatic ethers such as 2,4-dimethylanisole, and the like.

Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate.
Examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-isopropylpropylphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Can be mentioned.
Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, and the like.

In addition, dimethyl sulfoxide and the like can also be used.
These solvent may use only 1 type and may use 2 or more types by arbitrary combinations and a ratio.
(Film formation method)
After preparing the composition for forming the hole injection layer, this composition is applied onto the layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by wet film formation, and dried by drying. The injection layer 3 is formed.

The temperature in the coating step is preferably 10 ° C. or higher, and preferably 50 ° C. or lower, in order to prevent film defects due to the formation of crystals in the composition.
Although the relative humidity in an application | coating process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally, and usually 80% or less.
After coating, the film of the composition for forming a hole injection layer is usually dried by heating or the like. Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  The heating temperature in the heating step is preferably heated at a temperature equal to or higher than the boiling point of the solvent used in the composition for forming a hole injection layer as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more types of solvents used in the hole injection layer, at least one type is preferably heated at a temperature equal to or higher than the boiling point of the solvent. In consideration of an increase in the boiling point of the solvent, the heating step is preferably performed at 120 ° C. or higher, preferably 410 ° C. or lower.

  In the heating step, the heating time is not limited as long as the heating temperature is not lower than the boiling point of the solvent of the composition for forming a hole injection layer and sufficient insolubilization of the coating film does not occur. Is less than a minute. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.

<Formation of hole injection layer by vacuum deposition>
When the hole injection layer 3 is formed by vacuum deposition, one or more of the constituent materials of the hole injection layer 3 (the aforementioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum vessel. Put in crucibles installed (in case of using two or more materials, put them in each crucible), evacuate the inside of the vacuum vessel to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then heat the crucible (two types When using the above materials, heat each crucible) and control the evaporation amount to evaporate (when using two or more materials, control each evaporation amount independently) and face the crucible Then, the hole injection layer 3 is formed on the anode 2 of the substrate placed on the substrate. In addition, when using 2 or more types of materials, the hole injection layer 3 can also be formed by putting those mixtures into a crucible, heating and evaporating.

Vacuum degree during vapor deposition is not limited unless significantly impairing the effects of the present invention is usually ^{0.1 × 10 -6 Torr (0.13 ×} 10 -4 Pa) or more, usually 9.0 × ¹⁰ -6 Torr (
12.0 × 10 ⁻⁴ Pa) or less. The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 Å / second or more and usually 5.0 Å / second or less. The film forming temperature at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 10 ° C. or higher, preferably 50 ° C. or lower.

[Hole transport layer]
The method for forming the hole transport layer 4 according to the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but the hole transport layer 4 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.
The hole transport layer 4 can be formed on the hole injection layer 3 when there is a hole injection layer and on the anode 2 when there is no hole injection layer 3. The organic electroluminescent device of the present invention may have a configuration in which the hole transport layer is omitted.

  The material for forming the hole transport layer 4 is preferably a material having high hole transportability and capable of efficiently transporting injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities that become traps are not easily generated during manufacturing or use. In many cases, it is preferable not to quench the light emitted from the light emitting layer 5 or to form an exciplex with the light emitting layer 5 to reduce the efficiency because it is in contact with the light emitting layer 5.

  The material for the hole transport layer 4 may be any material conventionally used as a constituent material for the hole transport layer. For example, the hole transport property used for the hole injection layer 3 described above. What was illustrated as a compound is mentioned. In addition, arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, silole derivatives, oligothiophene derivatives, condensed polycyclic aromatics Group derivatives, metal complexes and the like.

  Also, for example, polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ether sulfone derivatives containing tetraphenylbenzidine, polyarylene vinylene derivatives, polysiloxane derivatives, polythiophenes Derivatives, poly (p-phenylene vinylene) derivatives, and the like. These may be any of an alternating copolymer, a random polymer, a block polymer, or a graft copolymer. Further, it may be a polymer having a branched main chain and three or more terminal portions, or a so-called dendrimer.

Of these, polyarylamine derivatives and polyarylene derivatives are preferred.
The polyarylamine derivative is preferably a polymer containing a repeating unit represented by the following formula (II). In particular, the polymer is preferably composed of a repeating unit represented by the following formula (II). In this case, Ar ^a or Ar ^b may be different in each repeating unit.

(In formula (II), Ar ^a and Ar ^b each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.)
Examples of the aromatic hydrocarbon group which may have a substituent include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, and an acenaphthene. Examples include a group derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a fluoranthene ring, a fluorene ring, and a group in which these rings are linked by a direct bond.

  Examples of the aromatic heterocyclic group which may have a substituent include a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, and a carbazole ring. , Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine Ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc. ring Are those groups group and the rings of from 2-4 fused ring is linked by a direct bond or two or more rings.

In view of solubility and heat resistance, Ar ^a and Ar ^b are each independently selected from the group consisting of a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, triphenylene ring, pyrene ring, thiophene ring, pyridine ring, and fluorene ring. A group derived from a selected ring or a group formed by connecting two or more benzene rings (for example, a biphenyl group (biphenylene group) or a terphenyl group (terphenylene group)) is preferable.

Among these, a group derived from a benzene ring (phenyl group), a group formed by connecting two benzene rings (biphenyl group), and a group derived from a fluorene ring (fluorenyl group) are preferable.
Examples of the substituent that the aromatic hydrocarbon group and aromatic heterocyclic group in Ar ^a and Ar ^b may have include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, and a dialkyl. Examples thereof include an amino group, a diarylamino group, an acyl group, a halogen atom, a haloalkyl group, an alkylthio group, an arylthio group, a silyl group, a siloxy group, a cyano group, an aromatic hydrocarbon ring group, and an aromatic heterocyclic group.

As the polyarylene derivative, an arylene group such as an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent exemplified as Ar ^a or Ar ^b in the formula (II) is used as ^a repeating unit. The polymer which has is mentioned.
As a polyarylene derivative, the polymer which has a repeating unit which consists of following formula (III-1) and / or following formula (III-2) is preferable.

(In formula (III-1), R ^a , R ^b , R ^c and R ^d are each independently an alkyl group, an alkoxy group, a phenylalkyl group, a phenylalkoxy group, a phenyl group, a phenoxy group, an alkylphenyl group, Represents an alkoxyphenyl group, an alkylcarbonyl group, an alkoxycarbonyl group, or a carboxy group, and t and s each independently represent an integer of 0 to 3. When t or s is 2 or more, they are contained in one molecule. A plurality of R ^a or R ^b may be the same or different, and adjacent R ^a or R ^b may form a ring.)

(In formula (III-2), R ^e and R ^f are each independently the same as R ^a , R ^b , R ^c or R ^d in formula (III-1). Independently represents an integer of 0 to 3. When r or u is 2 or more, a plurality of R ^e and R ^f contained in one molecule may be the same or different, and adjacent R ^e or R ^f may form a ring, and X represents an atom or a group of atoms constituting a 5-membered ring or a 6-membered ring.)
Examples of X, -O -, - BR - , - NR -, - SiR 2 -, - PR -, - SR -, - it is or they are formed by bonding group - CR _2. R represents a hydrogen atom or an arbitrary organic group. The organic group in the present invention is a group containing at least one carbon atom.

  Moreover, as a polyarylene derivative, in addition to the repeating unit which consists of said Formula (III-1) and / or said Formula (III-2), it further has a repeating unit represented by following formula (III-3). Is preferred.

(In formula (III-3), Ar ^{c to} Ar ^j each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and v and w each represent Independently represents 0 or 1.)
Specific examples of Ar ^{c to} Ar ^j are the same as Ar ^a and Ar ^b in the formula (II).
Specific examples of the above formulas (III-1) to (III-3) and specific examples of polyarylene derivatives include those described in JP-A-2008-98619.

In the case of forming the hole transport layer 4 by a wet film formation method, a composition for forming a hole transport layer is prepared in the same manner as the formation of the hole injection layer 3 and then heated and dried after the wet film formation. .
The composition for forming a hole transport layer contains a solvent in addition to the above hole transport compound. The solvent used is the same as that used for the composition for forming a hole injection layer. The film forming conditions, heat drying conditions, and the like are the same as in the case of forming the hole injection layer 3.

In the case where the hole transport layer is formed by the vacuum deposition method, the film forming conditions are the same as those in the case of forming the hole injection layer 3.
The hole transport layer 4 may contain various light emitting materials, electron transport compounds, binder resins, coating property improving agents, and the like in addition to the hole transport compound.
The hole transport layer 4 may also be a layer formed by crosslinking a crosslinkable compound. The crosslinkable compound is a compound having a crosslinkable group, and forms a network polymer compound by crosslinking.

Examples of this crosslinkable group include groups derived from cyclic ethers such as oxetane and epoxy; groups derived from unsaturated double bonds such as vinyl, trifluorovinyl, styryl, acrylic, methacryloyl and cinnamoyl; benzo Examples include groups derived from cyclobutene.
The crosslinkable compound may be any of a monomer, an oligomer, and a polymer. The crosslinkable compound may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.

  As the crosslinkable compound, a hole transporting compound having a crosslinkable group is preferably used. Examples of the hole transporting compound include those exemplified above, and those having a crosslinkable group bonded to the main chain or side chain with respect to these hole transporting compounds. In particular, the crosslinkable group is preferably bonded to the main chain via a linking group such as an alkylene group. In particular, the hole transporting compound is preferably a polymer containing a repeating unit having a crosslinkable group, and the above formula (II) and formulas (III-1) to (III-3) can be used as a crosslinkable group. Is preferably a polymer having a repeating unit bonded directly or via a linking group.

  As the crosslinkable compound, a hole transporting compound having a crosslinkable group is preferably used. Examples of hole transporting compounds include nitrogen-containing aromatic compound derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives, phthalocyanine derivatives, porphyrin derivatives; triphenylamine derivatives Silole derivatives; oligothiophene derivatives, condensed polycyclic aromatic derivatives, metal complexes and the like. Among them, nitrogen-containing aromatic derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives; triphenylamine derivatives, silole derivatives, condensed polycyclic aromatic derivatives, metal complexes, etc. Particularly preferred are triphenylamine derivatives.

In order to form a hole transport layer 4 by crosslinking a crosslinkable compound, a composition for forming a hole transport layer in which a crosslinkable compound is dissolved or dispersed in a solvent is usually prepared and deposited by wet film formation. To crosslink.
The composition for forming a hole transport layer may contain an additive for promoting a crosslinking reaction in addition to the crosslinking compound. Examples of additives that promote the crosslinking reaction include polymerization initiators and polymerization accelerators such as alkylphenone compounds, acylphosphine oxide compounds, metallocene compounds, oxime ester compounds, azo compounds, onium salts; condensed polycyclic hydrocarbons, And photosensitizers such as porphyrin compounds and diaryl ketone compounds.

Further, it may contain a coating property improving agent such as a leveling agent and an antifoaming agent; an electron accepting compound; a binder resin;
In the composition for forming a hole transport layer, the crosslinkable compound is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, usually 50% by weight or less, preferably 20%. It is contained by weight% or less, more preferably 10% by weight or less.

After forming a composition for forming a hole transport layer containing a crosslinkable compound at such a concentration on the lower layer (usually the hole injection layer 3), the composition is crosslinked by heating and / or irradiation with active energy such as light. Are crosslinked to form a network polymer compound.
Conditions such as temperature and humidity during film formation are the same as those during the wet film formation of the hole injection layer 3.
The heating method after film formation is not particularly limited. As heating temperature conditions, it is 120 degreeC or more normally, Preferably it is 400 degrees C or less.

The heating time is usually 1 minute or longer, preferably 24 hours or shorter. The heating means is not particularly limited, and means such as placing a laminated body having a deposited layer on a hot plate or heating in an oven is used. For example, conditions such as heating on a hot plate at 120 ° C. or more for 1 minute or more can be used.
In the case of irradiation with active energy such as light, a method of irradiating directly using an ultraviolet / visible / infrared light source such as an ultra high pressure mercury lamp, a high pressure mercury lamp, a halogen lamp or an infrared lamp, or

Includes a mask aligner having a built-in light source, a method of irradiating using a conveyor type light irradiation device, and the like. In active energy irradiation other than light, for example, there is a method of irradiation using a device that irradiates a microwave generated by a magnetron, a so-called microwave oven. As the irradiation time, it is preferable to set conditions necessary for reducing the solubility of the film, but irradiation is usually performed for 0.1 seconds or longer, preferably 10 hours or shorter.

The irradiation of active energy such as heating and light may be performed alone or in combination. When combined, the order of implementation is not particularly limited.
The film thickness of the hole transport layer 4 thus formed is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 100 nm or less.
{Light emitting layer}
When the hole injection layer 3 or the hole transport layer 4 is provided, the light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is a layer that is excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 between electrodes to which an electric field is applied, and becomes a main light emitting source.

The material and method for forming the light emitting layer can be formed by the material and method described in the above section [Light emitting layer]. The preferred embodiment is also the same.
{Hole blocking layer}
A hole blocking layer 6 may be provided between the light emitting layer 5 and an electron injection layer 8 described later. The hole blocking layer 6 is a layer laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

The hole blocking layer 6 has a role of blocking holes moving from the anode 2 from reaching the cathode 9 and a role of efficiently transporting electrons injected from the cathode 9 toward the light emitting layer 5. Have

The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high.

As the material and method for forming the hole blocking layer, the material and method described in the above section [First organic layer] can be used. Moreover, a preferable aspect is also the same.
The thickness of the hole blocking layer 6 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.

{Electron transport layer}
An electron transport layer 7 may be provided between the light emitting layer 5 and an electron injection layer 8 described later.
The electron transport layer 7 is provided for the purpose of further improving the light emission efficiency of the device, and efficiently transports electrons injected from the cathode 9 between the electrodes to which an electric field is applied in the direction of the light emitting layer 5. Formed from a compound capable of

  As an electron transporting compound used for the electron transport layer 7, usually, the electron injection efficiency from the cathode 9 or the electron injection layer 8 is high, and the injected electrons having high electron mobility are efficiently transported. The compound which can be used is used. Examples of the compound satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives , Distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds ( JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide , N-type zinc sulfide, n-type zinc Such as emissions of zinc, and the like.

In addition, the material of the electron carrying layer 7 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of the electron carrying layer 7. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
In the case of an element configuration in which the hole blocking layer is omitted, the electron transport layer may be the first organic layer. In this case, the material and method for forming the electron transport layer can be formed by the material and method described in the above section [First organic layer]. Moreover, a preferable aspect is also the same.

The film thickness of the electron transport layer 7 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.
{Electron injection layer}
The electron injection layer 8 plays a role of efficiently injecting electrons injected from the cathode 9 into the light emitting layer 5. In order to perform electron injection efficiently, the material for forming the electron injection layer 8 is preferably a metal having a low work function. Examples include alkali metals such as sodium and cesium, alkaline earth metals such as barium and calcium, and the film thickness is preferably from 0.1 nm to 5 nm.

  Furthermore, an organic electron transport compound represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.), it is possible to improve the electron injection / transport properties and achieve excellent film quality. preferable. In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

In addition, the material of the electron injection layer 8 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of the electron injection layer 8. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
{cathode}
The cathode 9 plays a role of injecting electrons into a layer on the light emitting layer 5 side (such as the electron injection layer 8 or the light emitting layer 5).

As the material of the cathode 9, the material used for the anode 2 can be used. However, for efficient electron injection, a metal having a low work function is preferable. For example, tin, magnesium

A suitable metal such as silicon, indium, calcium, aluminum, silver, or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.

In addition, the material of the cathode 9 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The film thickness of the cathode 9 is usually the same as that of the anode 2.
Further, for the purpose of protecting the cathode 9 made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere because the stability of the device is increased. For this purpose, for example, metals such as aluminum, silver, copper, nickel, chromium, gold and platinum are used. In addition, these materials may be used only by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

{Other layers}
The organic electroluminescent element according to the present invention may have another configuration without departing from the gist thereof. For example, as long as the performance is not impaired, an arbitrary layer may be provided between the anode 2 and the cathode 9 in addition to the layers described above, and an arbitrary layer may be omitted. .

<Electron blocking layer>
Examples of the layer that may be included include an electron blocking layer.
The electron blocking layer is provided between the hole injection layer 3 or the hole transport layer 4 and the light emitting layer 5 and prevents electrons moving from the light emitting layer 5 from reaching the hole injection layer 3. Thus, the probability of recombination of holes and electrons in the light emitting layer 5 is increased, the excitons generated are confined in the light emitting layer 5, and the holes injected from the hole injection layer 3 are efficiently collected. There is a role to transport in the direction of. In particular, when a phosphorescent material or a blue light emitting material is used as the light emitting material, it is effective to provide an electron blocking layer.

  The characteristics required for the electron blocking layer include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). Furthermore, in the present invention, when the light emitting layer 5 is formed as an organic layer according to the present invention by a wet film formation method, the electron blocking layer is also required to be compatible with the wet film formation. Examples of the material used for such an electron blocking layer include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (International Publication No. 2004/084260).

In addition, the material of an electron blocking layer may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of an electron blocking layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.

Further, at the interface between the cathode 9 and the light emitting layer 5 or the electron transport layer 7, for example, lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ). It is also an effective method to improve the efficiency of the element by inserting an ultrathin insulating film (0.1 to 5 nm) formed by the method (Applied Physics Letters, 1997, Vol. 70, pp. 152; Kaihei 10-74586; I
EEE Transactions on Electron Devices, 1
997, Vol. 44, pp. 1245; SID 04 Digest, pp. 154 etc.).

Moreover, in the layer structure demonstrated above, it is also possible to laminate | stack components other than a board | substrate in reverse order. For example, in the case of the layer configuration in FIG. The hole injection layer 3 and the anode 2 may be provided in this order.
Furthermore, it is also possible to constitute the organic electroluminescent element according to the present invention by laminating components other than the substrate between two substrates, at least one of which is transparent.

Further, a structure in which a plurality of components (light emitting units) other than the substrate are stacked in a plurality of layers (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, instead of the interface layer between the steps (between the light emitting units) (when the anode is ITO and the cathode is Al, these two layers), for example, a charge made of vanadium pentoxide (V ₂ O ₅ ) or the like. When a generation layer (Carrier Generation Layer: CGL) is provided, a barrier between steps is reduced, which is more preferable from the viewpoint of light emission efficiency and driving voltage.

Furthermore, the organic electroluminescent device according to the present invention may be configured as a single organic electroluminescent device, or may be applied to a configuration in which a plurality of organic electroluminescent devices are arranged in an array. You may apply to the structure by which the cathode is arrange | positioned at XY matrix form.
Each layer described above may contain components other than those described as materials unless the effects of the present invention are significantly impaired.

<Organic EL display and organic EL lighting>
The organic electroluminescent element of the present invention is used for organic EL displays and organic EL lighting. The organic EL display and the organic EL lighting obtained by the present invention are described in, for example, “Organic EL Display” (Ohm Co., Ltd., issued on August 20, 2004, Shizushi Tokito, Chiba Adachi, Hideyuki Murata). The organic EL display and the organic EL illumination can be formed by such a method.

  The present invention relates to various fields in which organic electroluminescent elements are used, for example, light sources (for example, light sources of copiers, flat panel displays (for example, for OA computers and wall-mounted televisions) and surface light emitters). It can be suitably used in the fields of liquid crystal displays and backlights of instruments), display panels, indicator lamps and the like.

1 Substrate
2 Anode
3 First organic layer
4 hole transport layer
5 Light emitting layer
6 Hole blocking layer
7 Electron transport layer
8 Electron injection layer
9 Cathode

Claims (5)

An anode, a light emitting layer, a first organic layer provided adjacent to the light emitting layer, and a cathode in this order;
The light emitting layer is a layer containing a compound represented by the following formula (1) and a compound represented by the following formula (2),
The first organic layer is a layer made of a compound not containing a metal atom,
In the organic electroluminescence device, the light emitting layer is a layer formed by a wet film formation method.
An organic electroluminescent element characterized by satisfying the following formula (3).

(In formula (1), Ar ^{1 to} Ar ⁴ each independently represents an aromatic hydrocarbon group which may have a substituent.)

(In formula (2), Ar ^{5 to} Ar ⁶ each independently represents an aromatic hydrocarbon group which may have a substituent.)

0.8 ≦ n ^H / n ^E ≦ 1.6 (3)

(In the formula, n ^H represents the refractive index of the first organic layer, and n ^E represents the refractive index of the light emitting layer.)   The organic electroluminescent element according to claim 1, further comprising a second organic layer formed by a wet film forming method between the light emitting layer and the anode.   The organic electroluminescent element according to claim 2, wherein the second organic layer is a layer containing an electron accepting compound.   An organic EL display comprising the organic electroluminescent element according to claim 1.   An organic EL illumination comprising the organic electroluminescent element according to claim 1.

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