JP5708721B2 - Organic electroluminescence device, organic EL display device, and organic EL lighting - Google Patents

Description

The present invention relates to a composition for an organic electroluminescent element used for forming a light emitting layer of an organic electroluminescent element by a wet film forming method.
The present invention also relates to an organic thin film and an organic electroluminescent element using the composition for organic electroluminescent elements, and an organic EL display device and organic EL illumination using the organic electroluminescent element.

  In recent years, organic electroluminescence (organic EL) elements have been actively developed as a technology for manufacturing light-emitting devices such as displays and lighting, and put into practical use mainly for small to medium-sized display applications. Has begun.

  An organic electroluminescent element obtains light emission by injecting positive and negative charges (carriers) into an organic layer between electrodes and recombining the carriers.

  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. However, this vacuum deposition method is difficult to uniformly deposit on a large-area substrate, and is not suitable for manufacturing a large-area organic EL panel such as a large display or a large-area surface-emitting illumination. In addition, there is a problem that the utilization efficiency of the organic material as the vapor deposition source is low and the manufacturing cost is likely to be high.

  On the other hand, as a means for manufacturing such a large area organic EL panel, a method for manufacturing an organic EL panel by a wet film forming method represented by a spin coating method, an ink jet method, a dip coating method, various printing methods, etc. is proposed. Has been.

  However, an organic electroluminescent device having a light emitting layer formed by a wet film forming method has a problem that its lifetime is shorter than that of an organic electroluminescent device having a light emitting layer formed by a conventional vacuum deposition method.

  In order to solve such problems, for example, in Patent Document 1 to Patent Document 3, the ionization potential of the charge transporting material contained in the light emitting layer and the ionization potential of the hole transporting layer material adjacent to the light emitting layer are disclosed. Organic electroluminescence obtained by paying attention to the relationship between the ionization potential of the charge transporting material contained in the light emitting layer and the material involved in light emission (hereinafter sometimes referred to as light emitting material) An attempt is made to achieve high efficiency and long life of the device.

  However, the techniques of these patent documents are directed to organic electroluminescent elements that form organic thin film layers by conventional vacuum deposition techniques, and these techniques are applied to organic thin films by a wet film formation method that the present inventors are examining. When trying to apply to organic electroluminescent devices that form layers, there may be cases where certain high efficiency or long life is achieved, but it is not always possible to achieve high efficiency and long life of the device. It was.

JP 2007-311759 A JP 2006-128636 A Japanese Patent No. 3949214

  An object of the present invention is to provide an organic electroluminescent device having a high efficiency and a long lifetime in an organic electroluminescent device having a light emitting layer formed by a wet film forming method.

In order to solve the above problems, the present inventor has not yet known physical property values specific to each material used when preparing a composition for forming a light emitting layer of an organic electroluminescent device by a wet film forming method. In order to improve the luminous efficiency and lifetime of organic electroluminescent devices that have a light-emitting layer formed by a wet film-forming method, there are some laws that have not been found, and it is necessary to find out these unexplained physical properties, and intensive studies It was.
As a result, among the multiple components mixed in the composition to form the light emitting layer, a material added to transport holes injected from the anode side (hereinafter referred to as “hole transporting material”) And the difference between the ionization potentials of the light emitting materials that emit light via hole-electron recombination and the content ratio of the light emitting material to the total solid content in the composition The present inventors have found that the organic electroluminescence device finally obtained exhibits a certain correlation with the luminous efficiency and lifetime.

  As a result of further studies based on this discovery, the present inventor has found that the amount of holes injected / transported into the light-emitting layer can be increased by using a wet film-forming composition that satisfies a specific condition. It is possible to precisely control the time during which the holes move from the charge transporting material to the light emitting material and stay on the light emitting material as a result, and as a result, the excited light emitting material generated inside the light emitting layer ( It is possible to improve the luminous efficiency without deactivating the excitons), and at the same time, by suppressing the decomposition of the material due to the charge accumulated in the luminescent layer (ie, long-term generation of radical state molecules) As a result, the inventors have found that it is possible to extend the life of the device, and have completed the present invention.

That is, the gist of the present invention is an organic electroluminescent device having a luminescent layer between an anode and a cathode, wherein the luminescent layer contains two or more organic electroluminescent device materials and a solvent. And at least one of the organic electroluminescent element materials is a luminescent material, and at least one is a hole transporting material, and the organic electroluminescent element composition satisfying the following formula (1) When there are two or more organic electroluminescent element materials corresponding to the hole transporting material in the composition for organic electroluminescent elements, the absolute value of the ionization potential is small among these two or more hole transporting materials. When the material satisfies the following formula (1) and there are two or more types of light emitting materials in the composition for organic electroluminescent elements, each light emitting material satisfies the following formula (1)). A thin film Adjacent to a layer having a hole transporting layer is a layer hole transport layer is formed by a wet film formation method, the hole transport layer material, the weight-average molecular weight of 1000 or more, 1,000,000 fragrance It is a group tertiary amine compound, and the hole transport layer has a structure represented by the following formula (U1) or (U2) and is a layer formed by using a structure conversion type compound by heat The organic electroluminescent element.

0 ≦ {Ip (H) −Ip (D)} / C (D) ≦ 10 (1)
(In formula (1), Ip (H), Ip (D) and C (D) are defined as follows.
Ip (H): absolute value of ionization potential of hole transporting material contained in the composition Ip (D): absolute value of ionization potential of light-emitting material contained in the composition C (D): The content weight ratio of the luminescent material with respect to the total solid content in the composition)

(In the formula (U1), ring A ⁰ represents an aromatic hydrocarbon ring to which a thermally dissociable soluble group is bonded. The aromatic hydrocarbon ring may have a substituent. A ring may be formed directly or via a divalent linking group.
S ¹ , S ² and R ^{1 to} R ⁶ are each independently a hydrogen atom, a hydroxyl group, an alkyl group which may have a substituent, an aromatic hydrocarbon ring group which may have a substituent, An aromatic heterocyclic group which may have a substituent, an aralkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy which may have a substituent A group, an acyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an acyloxy group which may have a substituent, It represents an arylamino group which may have a substituent, a heteroarylamino group which may have a substituent, or an acylamino group which may have a substituent.
In formula (U2), ring B ⁰ represents an aromatic hydrocarbon ring to which a thermally dissociable soluble group is bonded. The aromatic hydrocarbon ring may have a substituent. Further, the substituents may form a ring directly or via a divalent linking group.
S ^{11 to} S ¹⁴ and R ^{11 to} R ¹⁶ are each independently the same as those shown as S ¹ , S ² , and R ^{1 to} R ⁶ . )

  Another gist of the present invention resides in an organic EL display device and an organic EL illumination characterized by using such an organic electroluminescent element.

  If it is the composition for organic electroluminescent elements of this invention, the quantity of the hole inject | poured and transported in a light emitting layer, this hole will move from a charge transport material to a light emitting material, and will stay on a light emitting material as it is. Thus, a light-emitting layer capable of precisely controlling the time to be formed can be formed.

  For this reason, according to the composition for organic electroluminescent elements of the present invention, in an organic electroluminescent element having an organic layer such as a luminescent layer formed by a wet film forming method, The residence time can be appropriately controlled, and as a result, an organic electroluminescent device having high efficiency and long life can be provided. Moreover, a high quality organic EL display apparatus and organic EL illumination can be provided using such an organic electroluminescent element.

It is typical sectional drawing which showed an example of the organic electroluminescent element of this invention.

  Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. It is not specified in the contents.

[Composition for organic electroluminescence device]
The composition for organic electroluminescent elements of the present invention is a composition for organic electroluminescent elements containing two or more organic electroluminescent element materials and a solvent, and at least one of the organic electroluminescent element materials is A light emitting material, at least one kind, is a hole transporting material and satisfies the following formula (1).
0 ≦ {Ip (H) −Ip (D)} / C (D) ≦ 10 (1)

In formula (1), Ip (H), Ip (D) and C (D) are defined as follows.
Ip (H) represents the absolute value of the ionization potential of the hole transporting material contained in the composition.
Ip (D) represents the absolute value of the ionization potential of the luminescent material contained in the composition.
C (D) represents the content weight ratio of the light emitting material to the total solid content in the composition.

Here, the ionization potential is any electrochemical or optical measurement method (for example, AC-1, AC-2, AC-3 manufactured by Riken Keiki, PCR-101 manufactured by OPTEL, etc.) for organic electroluminescent element materials. It is a value measured directly by, and preferably measured by PCR-101.
The “content weight ratio” is a weight ratio of the content when the total solid content in the composition is 1, for example, the total solid content in the composition is the light emitting material. (100% of the total solid content is the luminescent material), the content weight ratio is 1, and when 10 wt% of the total solid content in the composition is the luminescent material, the content weight ratio is 0.1. That is, when the weight ratio of the total solid content and the light emitting material in the composition for organic electroluminescent elements of the present invention is expressed as total solid content: light emitting material = a: b, C (D) = b / a It is.

{Organic electroluminescent material}
First, the organic electroluminescent element material contained in the composition for organic electroluminescent elements of this invention is demonstrated.
The organic electroluminescent element material in the present invention is a material contained in a layer between the anode and the cathode of the organic electroluminescent element. Examples of the organic electroluminescent element material include charge transport materials such as a hole transport material and an electron transport material, light emitting materials, and electron accepting compounds.

  The content of the organic electroluminescent element material in the composition for organic electroluminescent elements of the present invention is usually 0.0001 wt% or more, preferably 0.001 wt% or more, more preferably 0.1 wt% or more, and usually 90 wt%. Hereinafter, it is preferably 70 wt% or less, more preferably 50 wt% or less. If this content is less than the above lower limit, the film thickness of the thin film formed by the wet film formation method becomes thin, and when it is used as an element, it may cause black spots or short circuits. If this content is higher than the above upper limit, the film thickness of the thin film formed by the wet film forming method becomes thick, and when it is used as an element, the driving voltage is likely to increase or film non-uniformity (coating unevenness) is likely to occur. And uneven brightness may occur.

The molecular weight of the organic electroluminescent element material in the present invention 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 The range 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 organic electroluminescent element material is too small, the glass transition temperature, melting point, decomposition temperature, etc. are likely to be low, and the heat resistance of the organic electroluminescent element material and the organic thin film to be formed is significantly reduced. In some cases, the film quality is deteriorated due to the migration of the element, the impurity concentration is increased due to the thermal decomposition of the material, and the element performance is deteriorated.
On the other hand, if the molecular weight is too large, the solubility of the organic electroluminescent device material in the solvent may be too small depending on the structure of the organic electroluminescent device material and the type of solvent used for preparing the composition (ink). Purification in the manufacturing process may be difficult. In addition, there is a problem that a portion where a thin film is not formed during film formation or a film thickness of the formed organic thin film becomes too thin, which may cause black spots or short-circuiting when used as an element. .

<Light emitting material>
Of the two or more organic electroluminescent element materials contained in the composition for organic electroluminescent elements of the present invention, at least one is a luminescent material, and the composition for organic electroluminescent elements of the present invention is usually organic. Used to form a light emitting layer of an electroluminescent element.

  A luminescent material is a material that has a fluorescence quantum yield of 30% or more in a dilute solution at room temperature in an inert gas atmosphere, and is manufactured using it in comparison with a fluorescence spectrum in a dilute solution. A part or all of the EL spectrum obtained when the organic electroluminescence device is energized is defined as a material attributed to the light emission of the material.

  The light emitting material is not limited as long as it is usually used as a light emitting material of an organic electroluminescent element. For example, a fluorescent material or a phosphorescent material may be used, but a phosphorescent material is preferable from the viewpoint of internal quantum efficiency. In addition, a fluorescent material may be used for the blue light emitting material, and a phosphorescent light emitting material may be used for the green light emitting material and the red light emitting material.

  As the light emitting material, for the purpose of improving the solubility in a solvent, a material in which the symmetry or rigidity of the molecule is reduced or a lipophilic substituent such as an alkyl group is introduced is used. preferable.

  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 dye) that emits blue light include naphthalene, chrysene, perylene, pyrene, anthracene, coumarin, p-bis (2-phenylethenyl) benzene, and derivatives thereof. Of these, anthracene, chrysene, pyrene, and derivatives thereof are preferable.

Examples of the fluorescent light-emitting material (green fluorescent dye) that gives green light emission include aluminum complexes such as quinacridone, coumarin, Al (C ₉ H ₆ NO) _3, and derivatives thereof.

  Examples of the fluorescent material that gives yellow light (yellow fluorescent dye) include rubrene, perimidone and derivatives thereof.

  Examples of fluorescent light-emitting materials (red fluorescent dyes) that emit red light include DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyrene) -4H-pyran) -based compounds, benzopyran, and rhodamine. , Xanthenes such as benzothioxanthene and azabenzothioxanthene, and derivatives thereof.

  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. A Werner complex or an organometallic complex containing a metal as a central 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. Among these, iridium or platinum is more preferable.

  As the ligand of the complex, a ligand in which a (hetero) aryl group such as a (hetero) arylpyridine ligand or a (hetero) arylpyrazole ligand and a pyridine, pyrazole, phenanthroline, or the like is connected is preferable. 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 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 it is 200 or more, More preferably, it is 300 or more, More preferably, it is the range of 400 or more. If the molecular weight of the luminescent material is too small, the heat resistance will be significantly reduced, gas generation will be caused, the film quality will be reduced when the film is formed, or the morphology of the organic electroluminescent element will be changed due to migration, etc. Sometimes come. On the other hand, if the molecular weight of the luminescent material is too large, it tends to be difficult to purify the organic compound of the luminescent material, or it may take time to dissolve in the solvent.

  In addition, only 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.

The content of the luminescent material contained in the composition for organic electroluminescent elements of the present invention is preferably 0.000001 wt% or more, more preferably 0.0001 wt% or more, particularly preferably 0.01 wt% or more, and 25 wt% or less. Preferably, 15 wt% or less is more preferable, and 15 wt% or less is particularly preferable.
When the content of the light emitting material in the composition for organic electroluminescent elements is less than this lower limit, a portion where a thin film is not formed during film formation occurs due to insufficient solid content in the composition for organic electroluminescent elements, Or the problem that the film thickness of the formed thin film becomes too thin may occur, and it may not be possible to obtain the desired function sufficiently, such as generation of black spots or short circuit in the finally obtained device. is there. In addition, the relative value of the concentration with respect to the charge transporting material usually contained in the composition for organic electroluminescent elements is lowered, the charge or energy transfer from the charge transporting material becomes insufficient, and the consumption due to the increase in reactive current. There may be a color shift due to a decrease in power or light emission from the charge transporting material itself.
On the other hand, if the content of the luminescent material in the composition for organic electroluminescent elements exceeds this upper limit, the film thickness of the thin film obtained at the time of film formation becomes too thick, and the driving voltage of the element rises. In some cases, the desired function cannot be sufficiently obtained, such as uneven coating) which easily causes luminance unevenness on the light emitting surface of the element. In addition, quenching phenomenon due to increased interaction between light emitting material molecules, generally called concentration quenching, aggregation of the light emitting material during drying, and increase in driving voltage due to the light emitting material acting as a trap for charges injected into the light emitting layer In some cases, the durability of the device may be reduced.
When there are a plurality of light emitting materials contained in the composition for organic electroluminescent elements of the present invention, the content represents the total amount.

<Charge transport material>
In the organic electroluminescence device, the light emitting material preferably emits light upon receiving electric charge or energy from a charge transporting host material. Therefore, in addition to the light emitting material, the organic electroluminescent element material contained in the composition for organic electroluminescent elements of the present invention is preferably a charge transporting material such as used as the host material. Examples of the charge transport material include a hole transport compound (hole transport material) and an electron transport compound (electron transport material).

  Here, examples of the charge transport material include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, thiophene compounds, benzylphenyl compounds, fluorene compounds, hydrazone compounds, silazane compounds, and silanamine compounds. Phosphamine compounds, quinacridone compounds, triphenylene compounds, carbazole compounds, pyrene compounds, anthracene compounds, phenanthroline compounds, quinoline compounds, pyridine compounds, triazine compounds, oxadiazole compounds, imidazole compounds Etc.

  More specifically, two or more condensed aromatic rings containing two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl Aromatic amine compounds having a starburst structure such as aromatic amine compounds substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine Compound (Journal of Luminescence, 1997, Vol. 72-74, pp. 985), an aromatic amine compound composed of a tetramer of triphenylamine (Chemical Communications, 1996, pp. 2175), 2, 2 ′ , 7,7'-tetrakis- (diphenylamino) -9,9'-spirobifluorene Orenic compounds (Synthetic Metals, 1997, Vol. 91, pp. 209), 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND), 2,5-bis (6 '-(2', 2 "-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), bathophenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10 -Phenanthroline (BCP, bathocuproine), 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 4,4'-bis (9 -Carbazole) -biphenyl (CBP) and the like.

The molecular weight of the charge transporting material in the present invention 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 charge transporting material is too small, the glass transition temperature, melting point, decomposition temperature, etc. are likely to be lowered as in the case of the luminescent material, and the heat resistance of the organic electroluminescent element material and the obtained organic thin film is significantly reduced. However, the film performance may be reduced due to recrystallization, molecular migration, or the like, and the impurity concentration may be increased due to thermal decomposition of the material.
On the other hand, if the molecular weight of the charge transporting material is too large, the solubility of the material in the solvent becomes too small depending on the structure of the organic electroluminescent element material and the type of the solvent used for preparing the composition. This makes it difficult to increase the impurity concentration, resulting in a decrease in the luminous efficiency and durability of the organic electroluminescence device, or a portion where no thin film is formed during wet film formation, resulting in a thin film thickness. In some cases, the desired function cannot be sufficiently obtained, such as generation of black spots or short-circuiting of the finally obtained device.

  In addition, any 1 type may be used for the charge transport material mentioned above, and it may use 2 or more types together by arbitrary combinations and ratios.

  The content of the charge transporting material contained in the composition for organic electroluminescent elements of the present invention is preferably 0.000001 wt% or more, more preferably 0.0001 wt% or more, and still more preferably 0.01 wt% or more. Moreover, 50 wt% or less is preferable, 30 wt% or less is more preferable, and 15 wt% or less is still more preferable. If the content of the charge transporting material in the composition for organic electroluminescent elements is below this lower limit, the driving voltage is increased due to a decrease in the charge transporting ability in the thin film formed by the wet film forming method, or the luminous efficiency. May cause a decrease in In addition, the solid content in the composition for organic electroluminescent elements is insufficient, resulting in a problem that a thin film is not formed at the time of coating film formation, or the formed thin film is too thin. This is not preferable because a desired function may not be sufficiently obtained, such as generation of a black spot or a short circuit in the finally obtained device. On the other hand, if the content of the charge transport material exceeds this upper limit, the thickness of the thin film obtained at the time of film formation becomes too thick, the drive voltage of the device rises, coating unevenness is likely to occur, and the brightness of the light emitting surface of the device Since the desired function may not be sufficiently obtained such as causing unevenness, it is not preferable.

  Further, the ratio of the content of the light emitting material to the content of the charge transporting material in the composition for organic electroluminescent elements is preferably 0.01 wt% or more, more preferably 0.1 wt% or more, and further preferably 1 wt% or more. preferable. Moreover, 50 wt% or less is preferable, 30 wt% or less is more preferable, and 10 wt% or less is still more preferable. If the ratio of the content of the light-emitting material to the content of the charge-transporting material in the composition for organic electroluminescent elements is below this lower limit, the transfer of charge or energy from the charge-transporting material becomes insufficient, and the reactive current is reduced. A decrease in power consumption due to the increase or a color shift due to light emission from the charge transporting material itself occurs. On the other hand, if this ratio exceeds the above upper limit, quenching phenomenon due to an increase in interaction between light emitting material molecules, generally called concentration quenching, aggregation of the light emitting material during drying, trapping of charges injected into the light emitting layer. As a result, the driving voltage increases and the durability of the element decreases.

{solvent}
The composition for organic electroluminescent elements of the present invention contains a solvent. Here, the solvent in the present invention is a liquid in an atmosphere of 20 ° C. and 1 atm, and can dissolve the light emitting material and the charge transporting material contained in the composition for organic electroluminescent elements of the present invention. A compound.

  The solvent is not particularly limited as long as it is a commercially available polar or nonpolar solvent. Among them, a substituted or unsubstituted aromatic such as benzene, toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene, and dichlorobenzene. Aromatic hydrocarbon solvents, aromatic ether solvents such as anisole, benzoic acid ester, diphenyl ether, aromatic ester solvents, linear or cyclic alkane solvents such as hexane, heptane, cyclohexane, and carboxylic acid ester solvents such as ethyl acetate Solvents, carbonyl-containing solvents such as acetone and cyclohexanone, water, alcohols, cyclic ethers and the like are preferable, and aromatic hydrocarbon solvents are more preferable. Among them, benzene, toluene, mesitylene and cyclohexylbenzene are preferable.

  In the composition for organic electroluminescent elements of the present invention, one type of solvent may be contained, or may be contained in a combination of two or more types of solvents, but usually one or more types, preferably Are preferably contained in combinations of 2 or more, usually 10 or less, preferably 8 or less, more preferably 6 or less.

  In addition, when two or more solvents are used as a mixture, the mixing ratio is not limited at all, but the solvent having the largest mixing ratio is usually 1 wt% or more, preferably 5 wt% in all the solvents. Or more, more preferably 10 wt% or more, and usually 100 wt% or less, preferably 90 wt% or less, more preferably 80 wt% or less, and the solvent having the smallest mixing ratio is usually 0.0001 wt% or more in all the solvents, preferably The mixing ratio is preferably 0.001 wt% or more, more preferably 0.01 wt% or more, and usually 50 wt% or less.

{Other ingredients}
The composition for an organic electroluminescent device of the present invention is a coating improver such as a leveling agent, an antifoaming agent, a thickener, a charge transporting aid such as an electron accepting compound or an electron donating compound, a binder resin, etc. May be contained. The content of these other components in the composition for organic electroluminescence devices does not significantly inhibit the charge transfer of the formed thin film, does not inhibit the light emission of the luminescent material, does not deteriorate the film quality of the thin film, etc. From the viewpoint, it is usually 50 wt% or less.

{Solvent concentration / Solid concentration}
When the composition for organic electroluminescent elements of the present invention is used as a composition for forming a light emitting layer for forming a light emitting layer of the organic electroluminescent element of the present invention described later, the solvent in the composition for organic electroluminescent elements is used. Although content is arbitrary unless the effect of this invention is impaired remarkably, it is usually 50 wt% or more and usually 99.9999 wt% or less. In addition, when mixing and using 2 or more types of solvents as a solvent, it is made for the sum total of these solvents to satisfy | fill this range.
Further, the total solid content concentration of the light emitting material, the charge transporting material, etc. is usually 0.01 wt% or more and usually 70 wt% or less. If this concentration is too high, film thickness unevenness of the formed thin film may occur, and if it is too low, defects may occur in the formed thin film.

{Formula (1)}
Next, Formula (1) which is the characteristic of this invention is demonstrated.
0 ≦ {Ip (H) −Ip (D)} / C (D) ≦ 10 (1)
In formula (1), Ip (H), Ip (D) and C (D) are defined as follows.

Ip (H) represents the absolute value of the ionization potential of the hole transporting material contained in the composition.
Ip (D) represents the absolute value of the ionization potential of the luminescent material contained in the composition.
C (D) represents the content weight ratio of the luminescent material to the total solid content in the composition.

  The preferable range of C (D) is usually 0.0001 or more, preferably 0.01 or more, more preferably 0.05 or more, and usually 0.9 or less, preferably 0.7 or less, more preferably 0. .5 or less. When this value exceeds the above upper limit, the interaction between the light emitting materials becomes strong, and a significant decrease in light emission efficiency generally called concentration quenching is caused, which is not preferable. On the other hand, if this value is less than the above lower limit, the transfer of charge or energy from the charge transporting material to the light emitting material becomes insufficient, which is not preferable because the light emitting efficiency and the lifetime are reduced.

  When {Ip (H) -Ip (D)} / C (D) in formula (1) is less than 0, the ionization potential of the light emitting material becomes deeper than the ionization potential of the hole transporting material, and holes are formed on the dopant. The light emission efficiency may decrease because it becomes difficult to transfer, and if it exceeds 10, the light emitting material acts as a deep hole trap, causing the radical cations to stay for a long time, resulting in a lifetime due to decomposition of the material, etc. May cause decline. {Ip (H) -Ip (D)} / C (D) is preferably 0.01 or more, more preferably 0.1 or more, preferably 9.95 or less, more preferably 9.90 or less.

  Generally, those used as hole transporting materials have an ionization potential of −5.0 to −6.0 eV, and those used as light emitting materials have an ionization potential of about −4.5 to −5.8 eV. Therefore, in the present invention, a combination of a hole transporting material and a light emitting material having an appropriate ionization potential difference is selected from these materials according to the content ratio of the light emitting material, and the formula (1) Adjust the value to be 0-10.

When there are two or more organic electroluminescent element materials corresponding to the hole transporting material in the composition for organic electroluminescent elements, the absolute value of the ionization potential is small among these two or more hole transporting materials. The material satisfies the above formula (1).
The hole transporting material in the composition for organic electroluminescence elements differs depending on the use of the composition for organic electroluminescence elements (use of a thin film formed using the same), but the above-described charge transportability. Among the materials, those exemplified as the hole transporting compound contained in the hole injection layer described later can be mentioned.
Moreover, when two or more types of luminescent materials are in the composition for organic electroluminescent elements, each luminescent material shall satisfy | fill said Formula (1).

[Organic thin film]
The organic thin film of the present invention is preferably formed by a wet film formation method using the above-described composition for organic electroluminescent elements of the present invention, and is usually between the cathode and the anode of the organic electroluminescent element. Used as a layer.
Here, the wet film forming method is as described later.

  The film thickness of the organic thin film of the present invention is appropriately determined according to the application. For example, in the case of a light emitting layer of an organic electroluminescent element, as described later, usually 3 nm or more, preferably 5 nm or more, usually 200 nm or less, preferably 100 nm or less.

[Organic electroluminescence device]
The organic electroluminescent element of the present invention has a luminescent layer between an anode and a cathode, and this luminescent layer is preferably formed by a wet film-forming method using the above-described composition for organic electroluminescent elements of the present invention. It is characterized by comprising the organic thin film of the present invention.

  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 composition for an organic electroluminescent element of the present invention used as a film-forming composition in the wet film-forming method is met.

Below, the layer structure of the organic electroluminescent element of this invention, its general formation method, etc. are demonstrated with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent element 10 of 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.

{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, 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.

  The anode 2 is usually 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 method for forming the hole injection layer 3 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 injection layer 3 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable. In particular, a layer formed by a wet film-forming method, which contains a hole transporting compound and an electron accepting compound, which will be described in detail below, is preferable.

  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 the hole injection layer 3 is formed by a wet film formation method, a material for forming the hole injection layer 3 is usually mixed with an appropriate solvent (a solvent for hole injection layer) to form a film-forming composition ( The composition for forming a hole injection layer) is prepared, and this composition for forming the hole injection layer is applied onto 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 depositing and drying.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as constituent materials of the hole injection layer.

  The hole transporting compound may be a high molecular compound or a low molecular compound as long as it is a compound having a hole transporting property that is usually used in a hole injection layer of an organic electroluminescence device. .

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 compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzidine compounds, benzylphenyl compounds, and tertiary amines linked by fluorene groups. Compounds, hydrazone compounds, silazane compounds, silanamin compounds, phosphamine compounds, quinacridone compounds, low molecular or high molecular materials that are arbitrarily combined with these, and the like.
In addition, as the hole transporting compound, it is also preferable to use a crosslinkable compound exemplified below as a compound used for the hole transporting layer or a structure conversion compound by heat.

  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. When two or more hole transporting compounds are contained, the combination thereof is arbitrary, but one or more of aromatic tertiary amine polymer compounds and one of other hole transporting compounds or Two or more types are preferably used in combination.

  Among the above 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. Y represents a linking group selected from the following linking group group. Moreover, among Ar ^{1 to} Ar ⁵ , two groups bonded to the same N atom may be bonded to each other to form a ring.

（上記各式中、Ａｒ^６〜Ａｒ^１６は、それぞれ独立して、置換基を有していてもよい芳香族炭化水素基または置換基を有していてもよい芳香族複素環基を表す。Ｒ^２１およびＲ^２２は、それぞれ独立して、水素原子または任意の置換基を表す。）］

(In said each formula, Ar < ⁶ > -Ar < ¹⁶ > represents each independently the aromatic hydrocarbon group which may have a substituent, or the aromatic heterocyclic group which may have a substituent. R ²¹ and R ²² each independently represent a hydrogen atom or an arbitrary substituent.

As the aromatic hydrocarbon group and the 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 this 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 ²¹ and R ²² 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 above formula (I) include those described in WO2005 / 089024.

  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 wt% or more in terms of film thickness uniformity, preferably It is 0.1 wt% or more, more preferably 0.5 wt% or more, and usually 70 wt% or less, preferably 60 wt% or less, more preferably 50 wt% 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 well as a hole-transporting 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 (WO2005 / 089024); iron chloride (Only one of them may be used, or two or more may be used in any combination and ratio.) (Japanese Patent Laid-Open No. 11-251067), high-valent inorganic compounds such as ammonium peroxodisulfate A cyano compound such as tetracyanoethylene; an aromatic boron compound such as tris (pendafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365); a fullerene derivative; iodine 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 2 or more types may be used together by arbitrary combinations and ratios, but the hole injection property from an anode and the hole transport property to a cathode side are good. From the viewpoint of ensuring, the content in the hole injection layer is preferably 80 wt% or less.

(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 a hole injection layer, the composition is formed on a layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by a wet film formation method, and dried. The hole injection layer 3 can be formed.

  The temperature in the film forming step is preferably 10 ° C. or higher, and preferably 50 ° C. or lower, in order to prevent film loss due to the formation of crystals in the composition.

  Although the relative humidity in a film-forming process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally and 80% or less normally.

  After the film formation, 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 the hole injection layer and sufficient insolubilization of the thin film does not occur, but preferably 10 seconds or longer, usually 180 minutes. It is as follows. 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 a vacuum deposition method, one or more of the constituent materials of the hole injection layer 3 (the aforementioned hole transporting compound, electron accepting compound, etc.) are contained in a vacuum container. (If two or more materials are used, put them in each crucible), evacuate the vacuum vessel to about 10 ⁻⁴ Pa with an appropriate vacuum pump, and then heat the crucible (2 When using more than one kind of material, heat each crucible) and evaporate by controlling the amount of evaporation (when using more than two kinds of materials, evaporate by controlling the amount of evaporation independently) A hole injection layer 3 is formed on the anode 2 of the substrate placed face to face. 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.

The degree of vacuum at the time of vapor deposition is not limited as long as the effects of the present invention are not significantly impaired, but 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 organic electroluminescent element of the present invention preferably has a hole transport layer 4.

  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.

  In particular, in the organic electroluminescent device of the present invention in which the luminescent layer is formed using the composition for organic electroluminescent device of the present invention, the hole injection barrier between the hole injection layer and the luminescent layer is relaxed. In addition, it has a hole transport layer from the viewpoint of reducing driving voltage, suppressing deterioration of materials due to accumulation of holes at the layer interface, and improving luminous efficiency by improving efficiency of hole injection into the light emitting layer. This hole transport layer is formed by a wet film formation method from the viewpoint of uniformly covering the hole injection layer, and further washing away or covering the projections derived from the anode and fine foreign matters such as particles. It is preferred that

  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. However, the organic electroluminescent element 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.

  Such a 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, 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., 72) such as aromatic diamines (Japanese Patent Laid-Open No. 5-234811), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine -74, 985, 1997), an aromatic amine compound consisting of a tetramer of triphenylamine (Chem. Commun., 2175, 1996), 2,2 ', 7,7'-tetrakis- ( Spiro compounds such as diphenylamino) -9,9′-spirobifluorene (Synth. Metals, 91, 209, 1997), 4,4′-N, N′-dica Examples thereof include carbazole derivatives such as vazole biphenyl, and polyarylene ether sulfone (Polym. Adv. Tech.) Containing, for example, polyvinyl carbazole, polyvinyl triphenylamine (JP-A-7-53953) and tetraphenylbenzidine. 7, Vol. 33, 1996).

  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.

  When the hole transport layer is formed by vacuum deposition, the film forming conditions are the same as those for 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 be a layer formed by crosslinking a crosslinkable compound. Here, the crosslinkable compound is a compound having a crosslinking group, and forms a polymer by crosslinking. 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.

  Examples of the crosslinking group of the crosslinking compound include cyclic ethers such as oxetane and epoxy; unsaturated double bonds such as vinyl group, trifluorovinyl group, styryl group, acrylic group, methacryloyl and cinnamoyl; benzocyclobutane and the like. It is done.

  The number of crosslinkable groups possessed by the crosslinkable compound, that is, the monomer, oligomer or polymer having a crosslinkable group is not particularly limited, but is generally less than 2.0, preferably 0.8 or less, more preferably 0 per unit charge transport unit. A number that is .5 or less is preferred. This is to adjust the relative dielectric constant of the hole transport layer forming material to a suitable range. Moreover, when the number of crosslinking groups is too large, reactive active species are generated, which may adversely affect other materials. Here, when the material forming the crosslinkable polymer is a monomer body, the unit charge transport unit is a monomer body itself, and indicates a skeleton (main skeleton) excluding a crosslinking group. Even when other types of monomers are mixed, the main skeleton of each monomer is shown. When the material forming the crosslinkable polymer is an oligomer or polymer, in the case of repeating a structure in which conjugation is broken organically, the repeated structure is defined as a unit charge transport unit. In the case of a structure in which conjugation is widely connected, a minimum repeating structure exhibiting charge transporting property or a monomer structure is shown. Examples include polycyclic aromatics such as naphthalene, anthracene, phenanthrene, tetracene, chrysene, pyrene, perylene, fluorene, triphenylene, carbazole, triarylamine, tetraarylbenzidine, 1,4-bis (diarylamino) benzene, and the like. It is done.

  Furthermore, as the crosslinkable compound, it is preferable to use a hole transporting compound having a crosslinkable group. Examples of the hole transporting compound in this case 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; Examples include phenylamine 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 particular, the crosslinkable compound is preferably a crosslinkable compound having a group represented by the following formula from the viewpoints of a high reaction rate, a low reaction temperature, and a small number of side reactions.

  In addition, the hole transport layer according to the present invention is formed by using a heat-converted compound having a structure represented by the following formula (U1) or (U2), and the reaction speed and reaction temperature. Is preferable from the standpoint of low low side reactions and side reactions.

(In the formula (U1), ring A ⁰ represents an aromatic hydrocarbon ring to which a thermally dissociable soluble group is bonded. The aromatic hydrocarbon ring may have a substituent. A ring may be formed directly or via a divalent linking group.
S ¹ , S ² and R ^{1 to} R ⁶ are each independently a hydrogen atom, a hydroxyl group, an alkyl group which may have a substituent, an aromatic hydrocarbon ring group which may have a substituent, An aromatic heterocyclic group which may have a substituent, an aralkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy which may have a substituent A group, an acyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an acyloxy group which may have a substituent, It represents an arylamino group which may have a substituent, a heteroarylamino group which may have a substituent, or an acylamino group which may have a substituent.
In formula (U2), ring B ⁰ represents an aromatic hydrocarbon ring to which a thermally dissociable soluble group is bonded. The aromatic hydrocarbon ring may have a substituent. Further, the substituents may form a ring directly or via a divalent linking group.
S ^{11 to} S ¹⁴ and R ^{11 to} R ¹⁶ are each independently the same as those shown as S ¹ , S ² , and R ^{1 to} R ⁶ . )

  The molecular weight of the crosslinkable compound is usually 5000 or less, preferably 2500 or less, preferably 300 or more, more preferably 500 or more.

  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 a wet film formation method. Then, the crosslinkable compound is crosslinked.

  This composition for hole transport layer formation may contain the additive which accelerates | stimulates a crosslinking reaction other than a crosslinkable compound. Examples of additives that accelerate 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. One of these may be used alone, or two or more may be used in any combination and ratio.

  Further, the composition for forming a hole transport layer may further contain a coating property improver such as a leveling agent and an antifoaming agent, an electron accepting compound, a binder resin, and the like.

  In this composition for forming a hole transport layer, the crosslinkable compound is usually 0.01 wt% or more, preferably 0.05 wt% or more, more preferably 0.1 wt% or more, usually 50 wt% or less, preferably 20 wt% or less, More preferably, it contains 10 wt% 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 electromagnetic energy such as light. Are polymerized by crosslinking.

  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, and examples thereof include heat drying and reduced pressure drying. The heating temperature condition in the case of heat drying is usually 120 ° C. or higher, preferably 400 ° C. or lower.

  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, a means such as heating on a hot plate at 120 ° C. or more for 1 minute or more can be employed.

  In the case of irradiation with electromagnetic 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 the above-mentioned light source is incorporated. Examples include a mask aligner and a method of irradiation using a conveyor type light irradiation device. In electromagnetic 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.

  Heating and irradiation of electromagnetic energy such as light may be performed individually 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.

<Light emitting layer material>
The light emitting layer 5 contains at least a material having a light emitting property (light emitting material) as a constituent material thereof, and preferably a compound having a hole transporting property (hole transporting material) or an electron transport. A charge transporting material such as a compound (electron transporting material) having the following properties: A light emitting material may be used as a dopant material, and a hole transporting material, an electron transporting material, or the like may be used as a host material. There is no particular limitation on the light-emitting material, and a material that emits light at a desired light emission wavelength and has favorable light emission efficiency may be used. Furthermore, the light emitting layer 5 may contain other components as long as the effects of the present invention are not significantly impaired. In addition, when forming the light emitting layer 5 with a wet film-forming method, it is preferable to use a low molecular weight material in any case.

  In the organic electroluminescent element of the present invention, the light emitting layer 5 is preferably the organic thin film of the present invention formed by a wet film forming method using the above-described composition for an organic electroluminescent element of the present invention. Therefore, specific examples of the light emitting material and the charge transporting material included in the light emitting layer 5 according to the present invention include specific examples of the light emitting material and the charge transporting material included in the above-described composition for an organic electroluminescence device of the present invention. These may be the same as those exemplified above, and each of these may be used alone, or two or more may be used in any combination and ratio.

  In order to form the light emitting layer 5 using the composition for organic electroluminescent elements of the present invention, the obtained thin film is dried and the solvent is removed after the organic electroluminescent element composition is wet-formed. Here, the method of the wet film forming method is not limited as long as the effects of the present invention are not significantly impaired, and any of the above-described methods can be used. A specific method of the wet film formation is the same as the method described in the formation of the hole injection layer 3.

  The thickness of the light-emitting layer 5 thus formed is arbitrary as long as the effects of the present invention are not significantly impaired, but are usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. It is. If the thickness of the light emitting layer 5 is too thin, defects may occur in the film, and if it is too thick, the driving voltage may increase.

  Further, the content ratio of the light emitting material in the light emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.05 wt% or more and usually 35 wt% or less. If the amount of the light emitting material is too small, uneven light emission may occur. If the amount is too large, the light emission efficiency may be reduced. In addition, when using together 2 or more types of luminescent material, it is made for the total content of these to be contained in the said range.

  Further, when the light emitting layer 5 contains an electron transporting material, the content ratio of the electron transporting material in the light emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.1 wt% or more, usually 65 wt%. % Or less. If the amount of the electron transporting material in the light emitting layer is too small, it may be easily affected by a short circuit, and if it is too large, the film thickness may be uneven. In addition, when using together 2 or more types of electron transport materials in a light emitting layer, it is made for the total content of these to be contained in the said range.

  When the light emitting layer 5 contains a hole transporting material, the ratio of the hole transporting material in the light emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.1 wt% or more, usually 65 wt% or less. If the hole transporting material in the light emitting layer is too small, it may be easily affected by a short circuit, and if it is too large, film thickness unevenness may occur. In addition, when using together 2 or more types of hole transportable materials in a light emitting layer, it is made for the total content of these to be contained in the said range.

{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. Examples of the material of the hole blocking layer 6 satisfying such conditions include, for example, bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum. Mixed ligand complexes such as, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives, etc. Of styryl compounds (JP-A-11-242996), triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole 7-41759), phenanthroline derivatives such as bathocuproine (JP-A-10-79297), and the like. It is. Further, a compound having at least one pyridine ring substituted at positions 2, 4, and 6 described in International Publication No. 2005-022962 is also preferable as a material for the hole blocking layer 6.

  In addition, the material of the hole-blocking layer 6 may use only 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  There is no restriction | limiting in the formation method of the hole-blocking layer 6, A wet film-forming method, a vapor deposition method, and another method are employable.

  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 transport 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 are transported efficiently with high electron mobility. 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, A wet film-forming method, a vapor deposition method, and another method are employable.

  The 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, and the like, it is possible to improve electron injection / transport properties and achieve both excellent film quality. Therefore, it is 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, A wet film-forming method, a vapor deposition method, and another method are employable.

{cathode}
The cathode 9 plays a role of injecting electrons into a layer (such as the electron injection layer 8 or the light emitting layer 5) on the light emitting layer 5 side.

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

Examples of the layer that may be included in addition to the layers described above 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 produced by a wet film formation method using the composition for organic electroluminescence elements of the present invention, 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 (described in 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 electronic blockage | prevention layer, A wet film-forming method, a vapor deposition method, and another method are employable.

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 ). Inserting an ultrathin insulating film (0.1 to 5 nm) formed by the above method is also an effective method for improving the efficiency of the device (Applied Physics Letters, 1997, Vol. 70, pp. 152; (Kaihei 10-74586; IEEE Transactions on Electron Devices, 1997, 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 of FIG. 1, the other components on the substrate 1 are the cathode 9, the electron injection layer 8, the electron transport layer 7, the hole blocking layer 6, the light emitting layer 5, the hole transport layer 4, the positive layer. 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.

In addition, 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) (in the case where the anode is ITO and the cathode is Al, these two layers), for example, a charge made of vanadium pentoxide (V ₂ O ₅ ) 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 device]
The organic EL display device of the present invention uses the above-described organic electroluminescent element of the present invention. There is no restriction | limiting in particular about the model and structure of the organic electroluminescent display apparatus of this invention, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.
For example, the organic EL display device of the present invention can be obtained by the method described in “Organic EL display” (Ohm, published on Aug. 20, 2004, Shizushi Tokito, Chiba Adachi, Hideyuki Murata). Can be formed.

[Organic EL lighting]
The organic EL illumination of the present invention uses the above-described organic electroluminescent element of the present invention. There is no restriction | limiting in particular about the model and structure of the organic EL illumination of this invention, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.

  Examples The present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of the following examples unless it exceeds the gist.

[Example 1]
The organic electroluminescent element shown in FIG. 1 was manufactured.
An indium tin oxide (ITO) transparent conductive film formed on a glass substrate with a thickness of 150 nm (sputtered film, sheet resistance of 15Ω) is patterned into a 2 mm wide stripe by ordinary photolithography technology. Anode 2 was formed. The substrate 1 on which the anode 2 was formed was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning and the like.

A hole injection layer 3 was formed on the substrate after the treatment as follows.
As a hole transporting compound used for the hole injection layer, an aromatic amine polymer compound PB-1 having a repeating structure shown below (weight average molecular weight: 29400, number average molecular weight: 12600), electron accepting having a structure shown below A composition for forming a hole injection layer containing the active compound PI-1 and ethyl benzoate as a solvent was prepared. In the composition for forming a hole injection layer, the total concentration of the aromatic amine polymer compound PB-1 and the electron accepting compound PI-1 is 2 wt%, and the aromatic amine polymer compound PB-1 and The weight ratio of the electron-accepting compound PI-1 was (aromatic amine polymer compound PB-1) :( electron-accepting compound PI-1) = 10: 4.

The composition for forming a hole injection layer was spin-coated on the substrate after the above treatment at a spinner rotation speed of 1500 rpm and a spinner rotation time of 30 seconds. Thereafter, heat drying was performed at 260 ° C. for 180 minutes.
The thin film of the uniform hole injection layer 3 with a film thickness of 30 nm was formed by the above operation.

Next, a hole transport layer 4 was formed on the formed hole injection layer 3 as follows.
As a crosslinkable compound, a composition for forming a hole transport layer containing polymer compound HT-1 having a repeating structure shown below (weight average molecular weight: 17000, number average molecular weight: 9000) and cyclohexylbenzene as a solvent was prepared. The concentration of the polymer compound HT-1 in the composition for forming a hole transport layer was 1.4 wt%.

The composition for forming a hole transport layer was spin-coated on the hole injection layer 3 at a spinner rotation speed of 1500 rpm and a spinner rotation time of 30 seconds. Thereafter, the polymer compound HT-1 was cured by heating at 230 ° C. for 60 minutes to cause a crosslinking reaction.
By the above operation, a uniform thin film of the hole transport layer 4 having a film thickness of 20 nm was formed.

Next, the light emitting layer 5 was formed on the formed hole transport layer 4 as follows.
For the formation of the light emitting layer 5, the composition for organic electroluminescent elements of the present invention was used. That is, first, as a light-emitting material (dopant material), compound D-1 having the structure shown below, compounds H-1 and H-2 having structures shown below as two types of hole transporting materials (host materials), and solvents A composition for an organic electroluminescent device containing cyclohexylbenzene was prepared.

  The total concentration of Compound D-1, Compound H-1, and Compound H-2 in the composition for organic electroluminescent elements was 5.0 wt%. The weight ratio of Compound D-1, Compound H-1 and Compound H-2 was (Compound D-1) :( Compound H-1) :( Compound H-2) = 1: 10: 10. .

  The ionization potential of the compound H-1 of the hole transporting material in the composition for organic electroluminescence device is −5.8 eV, the absolute value Ip (H) is 5.8, and the ionization potential of the compound H-2 is − The absolute value Ip (H) was 6.0 eV at 6.0 eV. Therefore, the value of compound H-1 is adopted as Ip (H) in formula (1). Further, the ionization potential of the light-emitting material compound D-1 was −5.4 eV and the absolute value Ip (D) was 5.4. C (D) was 0.048, and {Ip (H) -Ip (D)} / C (D) in the formula (1) was 8.33.

The composition for organic electroluminescence device was spin-coated on the hole transport layer 4 at a spinner rotation speed of 1000 rpm and a spinner rotation time of 30 seconds. Then, it heated and dried at 130 degreeC for 60 minutes.
The thin film of the uniform light emitting layer 5 with a film thickness of 50 nm was formed by the above operation.

  Next, a compound HB-1 shown below was formed as a hole blocking layer 6 on the formed light emitting layer 5 by a vacuum deposition method so as to have a film thickness of 10 nm.

  Next, a compound ET-1 shown below was formed as an electron transport layer 7 on the formed hole blocking layer 6 so as to have a film thickness of 30 nm by a vacuum deposition method.

  Next, on the formed electron transport layer 7, the anode 2 is formed by vacuum deposition so that the electron injection layer 8 has a thickness of 0.5 nm of lithium fluoride (LiF) and the cathode 9 has a thickness of 80 nm. In a stripe shape with a width of 2 mm perpendicular to each other.

  As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained.

It was confirmed that green light emission with an EL peak wavelength of 512 nm was obtained from this device.
Using this element, a constant current drive test was performed at room temperature under an initial luminance of 4000 cd / m ^2. As a result, the time required to reduce the front luminance by half (luminance half-life) was 500 hours and a long lifetime. The current efficiency at a front luminance of 1000 cd / m ² was a high value of 26.5 cd / A.
The results are shown in Table 1.

[Comparative Example 1]
The compound H-1 is not used as the hole transporting material contained in the composition for organic electroluminescent elements used when forming the light emitting layer 5, and the light emitting material (compound D-1) and the hole transporting material ( An organic electroluminescent element was produced in the same manner as in Example 1 except that the weight ratio of Compound H-2) was (Compound D-1) :( Compound H-2) = 1: 20.

  The absolute value Ip (H) of the compound H-2 ionization potential of the hole transporting material is 6.0. The value of {Ip (H) -Ip (D)} / C (D) calculated for the composition for organic electroluminescence device was 12.50.

From this element, it was confirmed that green light emission with an EL peak wavelength of 513 nm was obtained.
As a result of performing a constant current drive driving test at room temperature under an initial luminance of 4000 cd / m ² using this element, the time required for the front luminance to be halved (luminance half-life) is as extremely short as 42 hours. The current efficiency at a front luminance of 1000 cd / m ² was also as low as 19.3 cd / A.
The results are shown in Table 1.

[Example 2]
The weight ratio of the light emitting material (Compound D-1) and the hole transporting material (Compound H-1 and Compound H-2) contained in the composition for organic electroluminescent elements used when forming the light emitting layer 5 is determined. (Compound D-1) :( Compound H-1) :( Compound H-2) = 1: 15: An organic electroluminescent device was produced in the same manner as in Example 1, except that the ratio was 1: 15: 5.

  The value of {Ip (H) −Ip (D)} / C (D) calculated for the composition for an organic electroluminescence device was 8.33 as in Example 1.

It was confirmed that green light emission with an EL peak wavelength of 512 nm was obtained from this device.
Using this element, a constant current drive test was performed at room temperature under an initial luminance of 4000 cd / m ^2. As a result, the time required to reduce the front luminance by half (luminance half-life) was 497 hours, and the front luminance was 1000 cd / m. The current efficiency at m ² is 33.1 cd / A, which is long and high in the same manner as in Example 1. The lifetime and efficiency of the obtained organic electroluminescent element are the hole transport materials H-1 and H−. Regardless of the composition ratio of 2, it was found to depend on the value of {Ip (H) -Ip (D)} / C (D) of the present invention.
The results are shown in Table 1.

[Example 3]
The weight ratio of the light emitting material (Compound D-1) and the hole transporting material (Compound H-1 and Compound H-2) contained in the composition for organic electroluminescent elements used when forming the light emitting layer 5 is determined. , (Compound D-1): (Compound H-1): (Compound H-2) = 1: 5: 15 An organic electroluminescent device was produced in the same manner as in Example 1, except that the ratio was 1: 5: 15.

  The value of {Ip (H) −Ip (D)} / C (D) calculated for the composition for an organic electroluminescence device was 8.33 as in Example 1.

It was confirmed that green light emission with an EL peak wavelength of 512 nm was obtained from this device.
As a result of conducting a constant current drive driving test at room temperature under an initial luminance of 4000 cd / m ² using this element, the time required to reduce the front luminance by half (luminance half-life) was 504 hours, and the front luminance was 1000 cd / m. The current efficiency at m ² is 30.6 cd / A, which is long and high in the same manner as in Example 1. The lifetime and efficiency of the organic electroluminescent element obtained are the hole transport materials H-1 and H− Regardless of the composition ratio of 2, it was found to depend on the value of {Ip (H) -Ip (D)} / C (D) of the present invention.
These results are shown in Table 1.

[Example 4]
An organic electroluminescent element was produced in the same manner as in Example 1 except that the following polymer compound HT-2 was used instead of the polymer compound HT-1 used in forming the hole transport layer 4. did.

  The value of {Ip (H) −Ip (D)} / C (D) calculated for the composition for an organic electroluminescence device was 8.33 as in Example 1.

It was confirmed that green light emission having an EL peak wavelength of 511 nm was obtained from this device.
Using this element, a constant current drive test was performed at room temperature under an initial luminance of 4000 cd / m ^2. As a result, the time required to reduce the front luminance by half (luminance half-life) was 507 hours, and the front luminance was 1000 cd / m. The current efficiency at m ² is 31.8 cd / A, which is long and high in the same manner as in Example 1. The lifetime and efficiency of the organic electroluminescent device obtained are the hole transporting materials H-1 and H- Regardless of the composition ratio of 2, it was found to depend on the value of {Ip (H) -Ip (D)} / C (D) of the present invention.

These results are shown in Table 1.
Table 1 shows the types of compounds used and the absolute value of the ionization potential and the value of the formula (1): {Ip (H) -Ip (D)} / C (D).

  From the above results, it can be seen that a long-life and high-efficiency organic electroluminescence device can be realized using the composition for organic electroluminescence device of the present invention.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection 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)

In an organic electroluminescent device having a light emitting layer between an anode and a cathode, the light emitting layer comprises:
A composition for an organic electroluminescent device comprising two or more organic electroluminescent device materials and a solvent,
Among the organic electroluminescent element materials, at least one is a luminescent material, at least one is a hole transporting material, and the composition for organic electroluminescent elements satisfying the following formula (1) (however, the organic electroluminescent element) In the composition for use, when there are two or more organic electroluminescent element materials corresponding to the hole transporting material, a material having a small absolute value of ionization potential among these two or more hole transporting materials is represented by the following formula: When the organic electroluminescent device composition satisfies (1) and there are two or more luminescent materials, each luminescent material satisfies the following formula (1)):
A hole transport layer adjacent to the light emitting layer, the hole transport layer is a layer formed by a wet film formation method;
The hole transport layer material is an aromatic tertiary amine compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less,
The organic electroluminescent device, wherein the hole transport layer is a layer formed by using a heat-converted compound having a structure represented by the following formula (U1) or (U2).
0 ≦ {Ip (H) −Ip (D)} / C (D) ≦ 10 (1)
(In formula (1), Ip (H), Ip (D) and C (D) are defined as follows.
Ip (H): absolute value of ionization potential of hole transporting material contained in the composition Ip (D): absolute value of ionization potential of light-emitting material contained in the composition C (D) : The content weight ratio of the light-emitting material to the total solid content in the composition)

(In the formula (U1), ring A ⁰ represents an aromatic hydrocarbon ring to which a thermally dissociable soluble group is bonded. The aromatic hydrocarbon ring may have a substituent. A ring may be formed directly or via a divalent linking group.
S ¹ , S ² and R ^{1 to} R ⁶ are each independently a hydrogen atom, a hydroxyl group, an alkyl group which may have a substituent, an aromatic hydrocarbon ring group which may have a substituent, An aromatic heterocyclic group which may have a substituent, an aralkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy which may have a substituent A group, an acyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an acyloxy group which may have a substituent, It represents an arylamino group which may have a substituent, a heteroarylamino group which may have a substituent, or an acylamino group which may have a substituent.
In formula (U2), ring B ⁰ represents an aromatic hydrocarbon ring to which a thermally dissociable soluble group is bonded. The aromatic hydrocarbon ring may have a substituent. Further, the substituents may form a ring directly or via a divalent linking group.
S ^{11 to} S ¹⁴ and R ^{11 to} R ¹⁶ are each independently the same as those shown as S ¹ , S ² , and R ^{1 to} R ⁶ . )   2. The organic electroluminescent device according to claim 1, wherein the luminescent material is a compound having a molecular weight of 10,000 or less.   A layer containing a hole-transporting compound and an electron-accepting compound, which has a hole-injecting layer between the anode and the light-emitting layer, and the hole-injecting layer is formed by a wet film-forming method The organic electroluminescent element according to claim 1 or 2, wherein   An organic EL display device using the organic electroluminescent element according to claim 1.   An organic EL illumination comprising the organic electroluminescence device according to claim 1.

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