JP5157399B2 - Organic electroluminescent element material, organic electroluminescent element composition, organic electroluminescent element, and organic EL display - Google Patents

Description

  The present invention relates to materials for organic electroluminescent elements.

In recent years, organic electroluminescent elements using organic thin films have been developed. An organic electroluminescent element usually has each layer such as a light emitting layer between an anode and a cathode, and each layer is usually formed by a vapor deposition film forming method or a wet film forming method. Among these, the wet film forming method is suitable for large-area applications such as a large full-color panel.
For example, Patent Document 1 describes a light-emitting ink composition for an organic EL device that is used in a wet film forming method and contains an anthracene derivative represented by the following formula.

International Publication No. 2006/070712 Pamphlet

By the way, among organic electroluminescent elements, a blue light emitting element has not yet been satisfactory from the viewpoints of efficiency, life, and heat resistance. In the case of the wet film forming method, it is necessary to prepare a solution in which the material for forming each layer of the organic electroluminescent element is dissolved in a predetermined solvent.
However, some conventional materials do not satisfy the required physical properties of the wet film-forming method such as low solubility in solvents and poor heat resistance. Furthermore, since the hole injection / transport property of the host is poor, it may not be practical for wet film formation.

  The present invention has been made in view of the above problems. That is, an object of the present invention is a material useful for an organic layer of an organic electroluminescent device. When an organic layer is formed by a wet film-forming method, it has excellent solubility in a predetermined solvent, high efficiency, and long life. It is an object to provide a material for an organic electroluminescent element from which a simple organic electroluminescent element can be obtained.

  Thus, according to the present invention, there is provided a material for an organic electroluminescent device, which is a condensed polycyclic hydrocarbon derivative having a diphenylamino group, and comprising a compound having a structure represented by the following formula (1): Is done.

Here, in Formula (1), Ar ¹ represents an aromatic condensed polycyclic hydrocarbon group selected from the group consisting of a chrycenyl group, a phenanthrenyl group, a pyrenyl group, and a benzophenanthrenyl group.
However, when Ar ¹ is a chrycenyl group, the diphenylamino group to which ring A ¹ and ring B ¹ are bonded is bonded to positions 1 and 4 of the chrysenyl group.
Cy ¹ represents a cycloalkyl group. Ring A ¹ represents a benzene ring which may have a substituent other than Cy ¹ . Ring B ¹ represents a benzene ring which may have a substituent. n represents an integer of 1 or more.

Further, the solubility of the condensed polycyclic hydrocarbon derivative in toluene is preferably 1% by weight or more.
Furthermore, the organic electroluminescent element material to which the present invention is applied is preferably used for wet film formation.

  Next, according to the present invention, there is provided a composition for an organic electroluminescent device used for forming an organic electroluminescent device, the organic electroluminescent device material comprising the above-mentioned condensed polycyclic hydrocarbon derivative having a diphenylamino group. And a predetermined solvent are provided. The composition for organic electroluminescent elements is provided.

According to the present invention, there is also provided an organic electroluminescent device comprising an anode, a cathode, and an organic layer provided between the anode and the cathode, wherein the organic layer has the above-described condensed polyphenyl group having a diphenylamino group. An organic electroluminescent device comprising an organic electroluminescent device material comprising a cyclic hydrocarbon derivative is provided.
Here, the organic layer of the organic electroluminescent element is preferably a light emitting layer.
Moreover, it is preferable that the organic layer of an organic electroluminescent element is formed by the wet film-forming method using the composition containing an organic electroluminescent element material and a predetermined solvent.

  Furthermore, according to the present invention, there is provided an organic EL display having a transparent support substrate and an organic electroluminescent element laminated on the transparent support substrate, wherein the organic electroluminescent element has the above-described condensed polycyclic ring having a diphenylamino group. An organic EL display characterized by being an organic electroluminescent element containing an organic electroluminescent element material comprising a hydrocarbon derivative is provided.

  The organic electroluminescent element material of the present invention is highly soluble in a solvent, suitable for an organic layer of an organic electroluminescent element formed by a wet film-forming method, and has a high efficiency and a long lifetime. Is obtained.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

  The material for an organic electroluminescence device to which the present embodiment is applied is composed of a condensed polycyclic hydrocarbon derivative having a condensed polycyclic hydrocarbon skeleton as a basic structure and having a diphenylamino group bonded thereto.

  Furthermore, examples of the condensed polycyclic hydrocarbon derivative having a diphenylamino group constituting the material for an organic electroluminescent element to which the exemplary embodiment is applied include compounds having a structure represented by the following formula (1).

Here, in Formula (1), Ar ¹ represents an aromatic condensed polycyclic hydrocarbon group selected from the group consisting of a chrycenyl group, a phenanthrenyl group, a pyrenyl group, and a benzophenanthrenyl group. Cy ¹ represents a cycloalkyl group. Ring A ¹ represents a benzene ring which may have a substituent other than Cy ¹ . Ring B ¹ represents a benzene ring which may have a substituent. n represents an integer of 1 or more.

In the formula (1), the aromatic condensed polycyclic hydrocarbon group represented by Ar ¹ may have a substituent other than n diphenylamino groups. Specific examples of such a substituent include a methyl group, an ethyl group, an n-propyl group, a 2-propyl group, an n-butyl group, an isobutyl group, and a tert-butyl group having 1 to 8 carbon atoms. Linear or branched alkyl group; alkenyl group having 1 to 8 carbon atoms such as vinyl group, allyl group and 1-butenyl group; alkynyl group having 1 to 8 carbon atoms such as ethynyl group and propargyl group; benzyl group and the like An aralkyl group having 1 to 8 carbon atoms; an amino group having one or more alkyl groups having 1 to 8 carbon atoms in a substituent such as a methylamino group, a dimethylamino group, a diethylamino group, or a dibenzylamino group; Group, diphenylamino group, arylyl group such as ditolylamino group; heteroarylamino group such as pyridylamino group, thienylamino group, dithienylamino group Acetylamino group, an acylamino group such as benzoylamino group; methoxy group, an ethoxy group, an alkoxy group having 1 to 8 carbon atoms such as butoxy group;

Aryloxy groups having aromatic hydrocarbon groups and heterocyclic groups such as phenyloxy group, 1-naphthyloxy group, 2-naphthyloxy group, pyridyloxy group, thienyloxy group; formyl group, acetyl group, benzoyl group, etc. An acyl group having 1 to 8 carbon atoms; an alkoxycarbonyl group having 2 to 13 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group; an aryloxycarbonyl group having 2 to 13 carbon atoms such as an acetoxy group;

An alkylthio group having 1 to 8 carbon atoms such as a methylthio group and an ethylthio group; an arylthio group having 1 to 8 carbon atoms such as a phenylthio group and a 1-naphthylthio group; a sulfonyl group such as a mesyl group and a tosyl group; Silyl groups such as phenylsilyl groups; Boryl groups such as dimesitylboryl groups; Phosphino groups such as diphenylphosphino groups;

Aromatic hydrocarbon groups derived from benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, etc .; furan ring, benzofuran ring, thiophene ring Benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, Thienofuran ring, benzisoxazole ring, benzisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoki Phosphorus ring, perimidine ring, a quinazoline ring, a quinazolinone ring, azulene ring and an aromatic heterocyclic group derived.

These substituents may further have a substituent. Furthermore, examples of the substituent that may be included include an aromatic hydrocarbon group and an aromatic heterocyclic group in addition to the alkyl group and diarylamino group described above.
As the aromatic hydrocarbon group, for example, an aromatic hydrocarbon derived from a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, etc. Groups.

The aromatic heterocyclic group includes a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, a carbazole ring, a pyrroloimidazole ring, and a pyrrolopyrazole ring. , Pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzisoxazole ring, benzisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, Aromatic heterocyclic groups derived from quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring and the like can be mentioned.
These substituents may further have a substituent. Further, examples of the substituent that may be included include the above-described alkyl group, diarylamino group, aromatic hydrocarbon group, and aromatic heterocyclic group.
Furthermore, a carboxy group, a cyano group, a hydroxyl group, a thiol group, etc. are mentioned.

Here, in the formula (1), when the aromatic condensed polycyclic hydrocarbon group represented by Ar ¹ is a chrysenyl group, the diphenylamino group to which the ring A ¹ and the ring B ¹ are bonded is the 1-position of the chrysenyl group And binds to the 4 position.
In the formula (1), the compound in which the aromatic condensed polycyclic hydrocarbon group represented by Ar ¹ is a chrysenyl group preferably has a structure represented by the following formula (2).

Here, in Formula (2), Cy is synonymous with Cy ¹ in Formula (1). Two Cy in the formula (2) may be the same or different. In Formula (2), the benzene ring bonded to the amino group and the chrysenyl group bonded to the amino group may further have a substituent.

Moreover, when Ar < ¹ > is a phenanthrenyl group, a pyrenyl group, or a benzophenanthrenyl group, it is preferably represented by the following formulas (3) to (6), respectively.

In formula (3), Cy is synonymous with Cy ¹ in formula (1), and two Cy in formula (3) may be the same or different. In Formula (3), the benzene ring bonded to the amino group and the phenanthrenyl group bonded to the amino group may further have a substituent.

In formula (4), Cy is synonymous with Cy ¹ in formula (1), and two Cy in formula (4) may be the same or different. In formula (4), the benzene ring bonded to the amino group and the pyrenyl group bonded to the amino group may further have a substituent.

In formula (5), Cy is synonymous with Cy ¹ in formula (1). In Formula (5), the benzene ring bonded to the amino group and the pyrenyl group bonded to the amino group may further have a substituent.

In formula (6), Cy is synonymous with Cy ¹ in formula (1), and two Cy in formula (6) may be the same or different. In Formula (6), the benzene ring bonded to the amino group and the benzophenanthrenyl group bonded to the amino group may further have a substituent.

In formula (1), Cy ¹ represents a cycloalkyl group. Examples of the cycloalkyl group include a cyclopentyl group and a cyclohexyl group. Among these, a cyclohexyl group is preferable.

In the formula (1), ring A ¹ represents a benzene ring which may have a substituent other than Cy ¹ . Examples of such a substituent include those exemplified as the substituent that Ar ¹ may have other than n diphenylamino groups, as described above.

In the formula (1), ring B ¹ represents a benzene ring which may have a substituent. Examples of such a substituent include those exemplified as the substituent that Ar ¹ may have other than n diphenylamino groups, as described above.

  In the formula (1), n represents an integer of 1 or more. However, it is usually 4 or less, preferably 3 or less, and most preferably 2.

  In the present embodiment, the molecular weight of the organic electroluminescent element material comprising a condensed polycyclic hydrocarbon derivative having a diphenylamino group is usually 400 or more, preferably 500 or more. However, it is usually 2,000 or less, preferably 1,000 or less.

Next, specific examples of materials for organic electroluminescent elements to which the present exemplary embodiment is applied will be shown.
In the condensed polycyclic hydrocarbon derivative having a phenanthrenyl group represented by the following chemical formula (EqI) as a mother nucleus, among the substituents R ₁ to R ₁₀ , the substituent R ₉ and the substituent R ₁₀ are diphenylamino groups. Table 1 shows compounds 1 to 6 as specific examples.

Here, in Table 1, -H represents a hydrogen atom.
Further, BM1 to BM6 which are diphenylamino groups are as follows.

In the condensed polycyclic hydrocarbon derivative having a chrysenyl group represented by the following chemical formula (EqII) as a mother nucleus, among the substituents R ₁₁ to R ₂₂ , the substituent R ₁₁ and the substituent R ₁₄ are diphenylamino groups. Table 2 shows compounds 7 to 14 as specific examples. In Table 2, ET represents an ethyl group.

In the condensed polycyclic hydrocarbon derivative having a benzophenanthrenyl group represented by the following chemical formula (EqIII) as a parent nucleus, among the substituent R ₃₁ to the substituent R ₄₂ , the substituent R ₃₅ and the substituent R ₃₈ are diphenyl. Table 3 shows compounds 15 to 22 as specific examples in the case of an amino group.

In the condensed polycyclic hydrocarbon derivative represented by the chemical formula (EqIII) described above, as specific examples of the substituent R ₃₁ to the substituent R ₄₂ , the substituent R ₃₁ and the substituent R ₃₄ are diphenylamino groups, The compounds 23 to 30 are shown in Table 4.

In the condensed polycyclic hydrocarbon derivative having a pyrenyl group represented by the following chemical formula (EqIV) as a parent nucleus, the substituent R ₅₁ and the substituent R ₅₆ among the substituents R ₅₁ to R ₆₀ are diphenylamino groups. Table 5 shows compounds 31 to 36 as specific examples.

In the condensed polycyclic hydrocarbon derivative represented by the chemical formula (EqIV) described above, compounds 37 to 42 are given as specific examples of the substituent R ₅₁ being a diphenylamino group among the substituents R ₅₁ to R _60. Is shown in Table 6.

(Composition for organic electroluminescence device)
In the present embodiment, a composition for an organic electroluminescent element containing the above-described organic electroluminescent element material and a predetermined solvent is prepared, and this is formed by a wet film forming method to form an organic electroluminescent element. It is preferable to form a layer. Here, the solvent is a volatile liquid component that is used to form a layer containing a material for an organic electroluminescent element to which the present embodiment is applied by a wet film forming method.
In this case, in the organic electroluminescent element composition, the solubility of the organic electroluminescent element material in toluene is preferably 1% by weight or more, more preferably 1.5% by weight or more, and particularly preferably 2% by weight or more. . If the solubility is excessively small, the quality of the formed thin film tends to deteriorate and become non-uniform when an organic layer is formed by a wet film formation method. In addition, the selection of various solvents may be limited.

The organic electroluminescent element material to which this exemplary embodiment is applied may be used for the light emitting layer of the organic electroluminescent element, or for the hole transport layer or the electron transport layer. For example, when forming a light emitting layer, an organic electroluminescent element material may be used independently or may be used with other charge transport materials. Furthermore, the organic electroluminescent element material of the present embodiment may be used as a host material or a dopant material.
In any case, when each layer of the organic electroluminescent element is formed by a wet film forming method, in addition to the material for the organic electroluminescent element of the present invention, a material necessary for each layer is added to the composition for the organic electroluminescent element. Furthermore, it is preferable to contain.

(solvent)
Here, the solvent is not particularly limited as long as it dissolves the above-described organic electroluminescent element material satisfactorily. Specifically, alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, and tetralin; chlorobenzene, dichlorobenzene, trichlorobenzene, and the like Halogenated aromatic hydrocarbons; 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2, Aromatic ethers such as 4-dimethylanisole and diphenyl ether; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; cyclohexanone, Alicyclic ketones such as Looctanone and Fencon; Alicyclic alcohols such as cyclohexanol and cyclooctanol; Aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol; Ethylene glycol dimethyl ether and ethylene And aliphatic ethers such as glycol diethyl ether and propylene glycol-1-monomethyl ether acetate (PGMEA). Among these, alkanes and aromatic hydrocarbons are preferable. One of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.

(Boiling point of solvent)
The boiling point of the solvent used in this embodiment is usually 100 ° C. or higher, preferably 150 ° C. or higher, more preferably 200 ° C. or higher. If the boiling point of the solvent is excessively low, the solvent may evaporate from the composition for organic electroluminescent elements when forming a film by a wet film forming method, and film forming stability may be reduced.
In order to obtain a more uniform film, it is preferable that the solvent evaporates from the liquid film immediately after the film formation at an appropriate rate. For this reason, the boiling point of the solvent is usually 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher, and usually 270 ° C. or lower, preferably 250 ° C. or lower, more preferably 230 ° C. or lower.

(amount to use)
The amount of the solvent used is preferably 10 parts by weight or more, more preferably 50 parts by weight or more, particularly preferably 80 parts by weight or more, and preferably 99.95 parts by weight with respect to 100 parts by weight of the organic electroluminescent element material. Part or less, more preferably 99.9 parts by weight or less, and particularly preferably 99.8 parts by weight or less. When the amount of the solvent used is excessively small, the viscosity of the composition for organic electroluminescent elements becomes too high, and the film forming workability may be lowered. On the other hand, when the amount of the solvent used is excessively large, the thickness of the film after film formation tends to decrease, and film formation tends to be difficult.

(Other ingredients)
It is preferable that the composition for organic electroluminescent elements of the present embodiment further contains materials necessary for each layer in addition to the materials for organic electroluminescent elements described above. Examples of such other components include charge transport materials.
As such a charge transport material, a compound in which an aromatic ring is condensed on a central skeleton, preferably 3 or more, more preferably 4 or more, and preferably 7 or less, more preferably 6 or less is preferable. Examples of the central skeleton include chrysene, naphthacene, anthracene, phenanthrene, pyrene, coronene, fluoranthene, and benzophenanthrene.

Furthermore, as other charge transport materials, for example, a condensed aromatic ring compound substituted with an arylamino group and / or a styryl derivative substituted with an arylamino group, a condensed aromatic ring represented by the formula (III) described later Compounds and the like.
As the condensed aromatic ring compound substituted with an arylamino group, compounds represented by the formulas (6) to (11) in International Publication No. 2006/070712 are preferable. In addition, as an aryl group having 5 to 40 nuclear carbon atoms in the formula (11), benzophenanthryl is also preferable in addition to the examples described in International Publication No. 2006/070712.

As the charge transport material, a condensed aromatic ring compound represented by the following formula (III) is also preferable.
Ar ¹⁰ -R (III)
Here, in the formula (III), Ar ¹⁰ is a substituted or unsubstituted aryl group having 5 to 40 nuclear carbon atoms. This aryl group preferably has a structure in which aromatic ring nuclei are condensed to 3 or more, more preferably 4 or more, preferably 7 or less, more preferably 6 or less. Specific examples of Ar ¹⁰ include, for example, chrysenyl group, naphthacenyl group, anthryl group, phenanthryl group, pyrenyl group, coronyl group, fluoranthenyl group, benzophenanthryl group, acenaphthofluoranthenyl group, fluorenyl group, and the like. Can be mentioned.
In the formula (III), R is selected from a hydrogen atom, an alicyclic hydrocarbon group, or a group exemplified as a substituent for the aryl group of the formula (11) in WO 2006/070712. As the alicyclic hydrocarbon group, for example, an alicyclic hydrocarbon group having 5 to 8 carbon atoms is preferable, and specific examples include a cyclohexyl group and a cyclopentyl group. Further, among the groups exemplified as the substituent of the aryl group of the formula (11) in the pamphlet of International Publication No. 2006/070712, an alkyl group is preferable, and a tertiary carbon atom or a quaternary carbon atom is particularly preferable. An alkyl group is preferable, and an alkyl group having 4 to 15 carbon atoms is particularly preferable.

  The other charge transport material may be a host material or a dopant material. The content of the other charge transporting material in the light emitting layer is preferably 0.1% to 98% by weight and further 0.3% by weight in total with the organic electroluminescent element material of the present embodiment. It is preferable to contain -97weight%.

  The composition for organic electroluminescent elements of the present embodiment may further contain other compounds in addition to the above-described compounds as necessary. For example, you may contain the other solvent different from said solvent. Examples of such solvents include amides such as N, N-dimethylformamide and N, N-dimethylacetamide; dimethyl sulfoxide and the like. One of these may be used alone, or two or more may be used in any combination and ratio. Moreover, you may contain various additives, such as a leveling agent and an antifoamer, for the purpose of the improvement of film formability.

(Organic electroluminescence device)
Next, an organic electroluminescent element will be described.
The organic electroluminescence device to which the present embodiment is applied is an organic electroluminescence device having an anode and a cathode, and further comprising an organic layer provided between the anode and the cathode, , Containing the material for an organic electroluminescent element described above. Here, examples of the organic layer include a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, and a cathode buffer layer.
FIG. 1 is a schematic cross-sectional view showing a preferred structural example of an organic electroluminescent element 10 to which the exemplary embodiment is applied. As shown in FIG. 1, the organic electroluminescent element 10 includes an anode 2, a hole injection layer 3, a hole transport layer 4, a light emitting layer 5, a hole blocking layer 6, an electron transport layer 7, a cathode on a substrate 1. A buffer layer 8 and a cathode 9 are stacked in this order. Of these layers, except for the light emitting layer 5, the hole injection layer 3, the hole transport layer 4, the hole blocking layer 6, the electron transport layer 7 and the cathode buffer layer 8 are laminated as necessary. Such a layer may not be laminated.
Moreover, the organic electroluminescent element 10 to which this Embodiment is applied is not limited to the structure shown in FIG. 1 unless the effect of this invention is impaired remarkably, Arbitrary shapes, arrangement | positioning, etc. can be employ | adopted. For example, each layer may be laminated on the substrate 1 in the reverse order of the organic electroluminescent element 10 described above, that is, from the cathode side.
In addition, in the organic electroluminescent element 10 to which this Embodiment is applied, it is preferable that the organic layer containing the organic electroluminescent element material or the organic electroluminescent element composition described above is the luminescent layer 5. Hereinafter, each layer will be described in detail.

(Substrate 1)
The substrate 1 serving as a support for the organic electroluminescent element 10 can be formed using a known material, and the type of the material is not particularly limited. Examples of the material of the substrate 1 include orientation materials such as quartz, glass plates, metal plates, and metal foils; and organic materials such as plastic films, sheets, and plates. In particular, a glass plate and a plastic plate are preferable. As the plastic plate, a transparent plate made of a synthetic resin such as polyester, polymethacrylate, polycarbonate, polysulfone or the like is preferable. One of these may be used alone, or two or more may be used in any combination and ratio.
When a synthetic resin plate is used as the substrate 1, it is desirable to pay attention to the gas barrier property of the synthetic resin plate. If the gas barrier property of the substrate 1 is excessively low, the organic electroluminescent element 10 tends to deteriorate due to the outside air that has passed through the substrate 1. For this reason, it is preferable to provide a silicon oxide film or the like on at least one surface of the substrate 1.

The thickness of the substrate 1 is not particularly limited, but is usually 0.01 mm or more, preferably 0.1 mm or more, more preferably 0.2 mm or more, and usually 5 cm or less, preferably 2 cm or less, more preferably 1 cm or less. .
In addition, the board | substrate 1 may be the structure which consists of a single layer, and may have the structure by which the several layer was laminated | stacked. In the latter case, the plurality of layers may be layers made of the same material or layers made of different materials.

(Anode 2)
The anode 2 formed on the substrate 1 plays a role of hole injection into an adjacent layer in the opposite direction to the substrate 1.
The material of the anode 2 is not particularly limited as long as it has conductivity. For example, metals such as aluminum, gold, silver, nickel, palladium and platinum; metal oxides such as oxides of indium and / or tin; halogenated metals such as copper iodide; carbon black; poly (3-methylthiophene) Conductive polymers such as polypyrrole and polyaniline are preferred. One of these may be used alone, or two or more may be used in any combination and ratio.

Although the method for forming the anode 2 is not limited, a sputtering method, a vacuum deposition method, or the like is usually used. Further, when the anode 2 is formed using metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, etc., these are used as an appropriate binder. The anode 2 can be formed by dispersing it in a resin solution and applying it onto the substrate 1.
Furthermore, when a conductive polymer is used as a material, 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 ( For example, Appl.Phys.Lett., 60, 2711, 1992).

  As shown in FIG. 1, the anode 2 has a single layer structure, but may have a laminated structure in which a plurality of layers are laminated as desired. In the latter case, the plurality of layers may be layers made of the same material or layers made of different materials. Furthermore, the anode 2 may be formed integrally with the substrate 1 described above, and the anode 2 may also serve as the substrate 1.

The thickness of the anode 2 is appropriately selected depending on the transparency required for the anode 2. When the anode 2 is required to be transparent, 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 usually 1000 nm or less, preferably 500 nm or less. When the thickness of the anode 2 is excessively thin, the electric resistance tends to increase. Moreover, when it is too thick, there exists a tendency for transparency to fall. In addition, when the anode 2 may be opaque, the thickness of the anode 2 is arbitrary.
Further, in order to remove impurities adhering to the anode 2 and adjust the ionization potential to improve the hole injection property, the surface of the anode 2 is subjected to ultraviolet (UV) treatment, ozone treatment, oxygen plasma, argon plasma, etc. It is preferable to perform plasma treatment.

(Hole injection layer 3)
The hole injection layer 3 formed on the anode 2 serves to transport holes to a layer adjacent to the anode side of the anode 2. In the present embodiment, the organic electroluminescent element 10 may have a configuration in which the hole injection layer 3 is omitted.
The hole injection layer 3 preferably contains a hole transporting compound, and more preferably contains a hole transporting compound and an electron accepting compound. Furthermore, the hole injection layer 3 preferably contains a cation radical compound, and particularly preferably contains a cation radical compound and a hole transporting compound. Moreover, the positive hole injection layer 3 may also contain binder resin and a coating property improving agent as needed. The binder resin is preferably one that does not easily act as a charge trap.
The hole injection layer 3 may be formed by first depositing only an electron-accepting compound on the anode 2 by a wet film-forming method, and directly applying and stacking a charge transport material composition thereon. Is possible. In this case, a part of the charge transport material composition interacts with the electron-accepting compound, so that a layer excellent in hole injecting property is formed.

(Hole transporting compound)
As the hole transporting compound, a compound having an ionization potential of 4.5 eV to 6.0 eV is preferable. However, when the wet film-forming method is used, it is preferable that the solubility in the solvent to be used is higher.
Examples of the hole transporting compound include aromatic amine compounds, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, and the like. Of these, aromatic amine compounds are preferred from the viewpoints of amorphousness and visible light transmittance.

The type of the aromatic amine compound is not particularly limited, and may be a low molecular compound or a high molecular compound. From the viewpoint of the surface smoothing effect, the weight average molecular weight is 1,000 or more, 1,000,000. A polymer compound having a molecular weight of 000 or less (a polymerizable hydrocarbon compound in which repeating units are continuous) is preferable. Of the aromatic amine compounds, 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.
Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (i).

(In the above formula (i), Ar ^a1 and Ar ^a2 each independently represent an aromatic hydrocarbon group which may have a substituent, or an aromatic heterocyclic group which may have a substituent. Ar ^{a3 to} Ar ^a5 each independently represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent. Z ^a represents ^a linking group selected from the following group of linking groups, and among Ar ^{a1 to} Ar ^a5 , two groups bonded to the same N atom are bonded to each other to form a ring. You may do it.)

(In the above linking groups, Ar ^{a6 to} Ar ^a16 are each independently derived from an aromatic hydrocarbon ring which may have a substituent, or an aromatic heterocyclic ring which may have a substituent. Each represents a monovalent or divalent group, each of R ^a1 and R ^a2 independently represents a hydrogen atom or an optional substituent.

As Ar ^{a1 to} Ar ^a16 , any monovalent or divalent group derived from any aromatic hydrocarbon ring or aromatic heterocyclic ring is applicable. These groups may be the same or different from each other. Further, these groups may further have an arbitrary substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less.
Ar ^a1 and Ar ^a2 are preferably monovalent groups derived from a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene ring, or a pyridine ring from the viewpoints of solubility, heat resistance, and hole injection / transport properties of the polymer compound. More preferred are a phenyl group and a naphthyl group.
Ar ^{a3 to} Ar ^a5 are preferably divalent groups derived from a benzene ring, a naphthalene ring, an anthracene ring, or a phenanthrene ring from the viewpoint of heat resistance and hole injection / transport properties including redox potential. A group, a biphenylene group, and a naphthylene group are more preferable.

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (i) include compounds described in International Publication No. 2005/089024 pamphlet.
The hole transporting compound used as the material for the hole injection layer 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 aromatic tertiary amine polymer compounds and one or two other hole transporting compounds are used. It is preferable to use the above together.

(Electron-accepting compound)
As the electron-accepting compound, a compound having an oxidizing power and an ability to accept one electron from the above-described hole-transporting compound is preferable. Specifically, a compound with an electron affinity of 4 eV or more is preferable, and a compound with a compound of 5 eV or more is more preferable.
Examples of the electron-accepting compound include, for example, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate; iron (III) chloride (Japanese Patent Laid-Open No. 11-251067) Publication), high-valence inorganic compounds such as ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene; aromatic boron compounds such as tris (pentafluorophenyl) borane (JP-A-2003-31365); fullerene derivatives, iodine Etc.
Of the above-mentioned compounds, an onium salt substituted with an organic group, a high-valence inorganic compound, and the like are preferable because they have strong oxidizing power. In addition, an onium salt substituted with an organic group, a cyano compound, an aromatic boron compound, or the like is preferable because it is soluble in various solvents and can be applied to wet coating.

Specific examples of an onium salt substituted with an organic group, a cyano compound, and an aromatic boron compound suitable as an electron-accepting compound include those described in International Publication No. 2005/089024. The example is similar. Examples thereof include compounds represented by the following structural formula. However, it is not limited to these.
In addition, a potential receptive compound may be used individually by 1 type, and may use 2 or more types by arbitrary combinations and a ratio.

(Cation radical compound)
As the cation radical compound, an ionic compound composed of a cation radical which is a chemical species obtained by removing one electron from a hole transporting compound and a counter anion is preferable. However, when the cation radical is derived from a hole transporting polymer compound, the cation radical has a structure in which one electron is removed from the repeating unit of the polymer compound.
The cation radical is preferably a chemical species obtained by removing one electron from the aforementioned compound as a hole transporting compound. A chemical species obtained by removing one electron from a compound preferable as a hole transporting compound is preferable in terms of amorphousness, visible light transmittance, heat resistance, solubility, and the like.

  Here, the cation radical compound can be generated by mixing the hole transporting compound and the electron accepting compound. That is, by mixing the hole transporting compound and the electron accepting compound, electron transfer occurs from the hole transporting compound to the electron accepting compound, and the cation radical and the counter anion of the hole transporting compound A cation ion compound consisting of

Cationic radical compounds derived from polymer compounds such as PEDOT / PSS (Adv. Mater., 2000, 12, 481) and emeraldine hydrochloride (J. Phys. Chem., 1990, 94, 7716) It is also produced by oxidative polymerization (dehydrogenation polymerization).
The oxidative polymerization referred to here is a method in which a monomer is chemically or electrochemically oxidized using peroxodisulfate or the like in an acidic solution. In the case of this oxidative polymerization (dehydrogenation polymerization), the monomer is polymerized by oxidation, and a cation radical that is removed from the polymer repeating unit by using an anion derived from an acidic solution as a counter anion is removed. Generate.

(Method for producing hole injection layer 3)
As a method of forming the hole injection layer 3 on the anode 2, a conventionally known method can be adopted and is not particularly limited. For example, a wet film forming method or a vacuum deposition method can be used.
When the hole injection layer 3 is formed by a wet film formation method, first, one or more predetermined amounts of each of the above-described materials (hole transporting compound, electron accepting compound, cation radical compound) are necessary. Thus, a coating solution is prepared by dissolving it in a solvent together with a binder resin and a coating property improving agent which do not easily act as traps for electric charges. Next, the hole injection layer 3 is formed by applying a coating solution on the anode 2 by a wet film formation method such as spin coating, spray coating, dip coating, die coating, flexographic printing, screen printing, and ink jet method, and drying. .

As a solvent used when forming the hole injection layer 3 by the wet film forming method, any solvent can be used as long as it can dissolve the above-described materials (hole transporting compound, electron accepting compound, cation radical compound). The type is not particularly limited. In addition, it does not include a deactivating substance or a substance that generates a deactivating substance that may deactivate each material (hole transporting compound, electron accepting compound, cation radical compound) used for the hole injection layer 3. It is preferable. Specific examples of such solvents are preferably ether solvents or ester solvents.
The concentration of the solvent in the coating solution is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, and usually 99.999% by weight or less, preferably 99.99% by weight. Hereinafter, it is more preferably 99.9% by weight or less. In addition, when mixing 2 or more types of solvents, the total of these solvents should just satisfy this range.

When the hole injection layer 3 is formed by the vacuum deposition method, first, one or more of the aforementioned materials (hole transporting compound, electron accepting compound, cation radical compound) are placed in a vacuum container. The crucible is put into each crucible (in the case where two or more kinds of materials are used, put in each crucible), and then the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with an appropriate vacuum pump. After that, the crucible is heated (each crucible is heated when two or more materials are used), and the evaporation amount is controlled to evaporate (when two or more materials are used, the evaporation amount is independently controlled and evaporated). And the hole injection layer 3 can be formed on the anode 2 of the substrate 1 placed facing the crucible. When two or more kinds of materials are used, a mixture of them can be put in a crucible, heated and evaporated to be used for forming the hole injection layer 3.

The thickness of the hole injection layer 3 formed as described above is usually in the range of 5 nm or more, preferably 10 nm or more, and usually 1,000 nm or less, preferably 500 nm or less. If the thickness of the hole injection layer 3 is excessively thin, the hole injection property may be insufficient. Moreover, when the thickness is excessively large, the resistance may be increased.
Note that the hole injection layer 3 may be configured by a single layer, or may be configured by stacking a plurality of layers. In the latter case, the plurality of layers may be layers made of the same material or layers made of different materials.

(Hole transport layer 4)
The hole transport layer 4 is formed on the hole injection layer 3 when the hole injection layer 3 is provided, and on the anode 2 when the hole injection layer 3 is not provided. can do. By providing the hole transport layer 4, holes can be transported to the light emitting layer 5 and injected efficiently.
The organic electroluminescent element 10 in the present embodiment may have a configuration in which the hole transport layer 4 is omitted.

A material (hole transport material) that can be used for the hole transport layer 4 is preferably a material that has high hole transportability and can efficiently transport 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, since the hole transport layer 4 is in contact with the light emitting layer 5, light emission from the light emitting layer 5 is not quenched, and further, exciplexes are not formed with the light emitting layer 5 to reduce efficiency. Is preferred.

  Examples of such a hole transport material include 4,4′-bis [N- (1-naphthyl) -N-phenyl in addition to the hole transport compound used for the hole injection layer 3 described above. Aromatic diamines containing two or more tertiary amines and having two or more condensed aromatic rings substituted with nitrogen atoms, as represented by amino] biphenyl (Japanese Patent Laid-Open No. 5-234681); 4,4 ′ , 4 ″ -tris (1-naphthylphenylamino) triphenylamine and other aromatic amine compounds having a starburst structure (J. Lumin., 72-74, 985, 1997); Aromatic amine compound consisting of a monomer (Chem. Commun., 2175, 1996): 2,2 ′, 7,7′-tetrakis- (diphenylamino) -9,9′-spirobifluorene Spiro compounds (Synth.Metals, 91 vol, 209 pp., 1997); 4,4'-N, such as a carbazole derivative such as N'- dicarbazole biphenyl.

Furthermore, after forming a thin film by a film forming method to be described later, it is also possible to use a polymer that is polymerized by heating, irradiation with electromagnetic waves such as light or magnetism, or a polymer in which any plural compounds are polymerized in advance.
Examples of such a polymerizing compound include triarylamine derivatives and fluorene derivatives having a crosslinking group.
Examples of the polymer include polyvinyl carbazole, polyvinyl triphenylamine (Japanese Patent Laid-Open No. 7-53953); polyarylene ether sulfone (Polym. Adv. Tech., Vol. 7, 33) containing tetraphenylbenzidine. Page, 1996). One of these may be used alone, or two or more may be used in any combination and ratio.

The hole transport layer 4 is formed by, for example, a normal coating method such as a spray method, a printing method, a spin coating method, a dip coating method, or a die coating method, or a wet film forming method such as various printing methods such as an ink jet method or a screen printing method. It can be formed by a dry film forming method such as a vacuum evaporation method.
In the case of the coating method, one or more of the hole transport materials is mixed with an additive such as a polymerization initiator, a binder resin that does not trap holes, or a coating property improver, if necessary. The solution is dissolved to prepare a coating solution, which is coated on the anode 2 or the hole injection layer 3 by a method such as spin coating, and dried to form the hole transport layer 4.
Examples of the binder resin include polycarbonate, polyarylate, and polyester. When the amount of the binder resin added is excessively large, the hole mobility tends to be lowered. Therefore, the content in the hole transport layer 4 is usually preferably 50% by weight or less.

In the case of the vacuum evaporation method, for example, the hole transport material is put in a crucible installed in a vacuum vessel, the inside of the vacuum vessel is decompressed with an appropriate vacuum pump, and then the crucible is heated to form a hole transport material. The hole transport layer 4 can be formed on the anode 2 or the hole injection layer 3 placed opposite to the crucible.
The thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and is usually 300 nm or less, preferably 100 nm or less. In order to uniformly form the hole transport layer 4 having such a small thickness, generally, a spin coating method or a vacuum deposition method is often used.

(Light emitting layer 5)
When the hole transport layer 4 is provided, the light emitting layer 5 is formed on the hole transport layer 4. When the hole transport layer 4 is not provided and the hole injection layer 3 is provided, the hole injection layer 3 is provided. When the hole transport layer 4 and the hole injection layer 3 are not provided on the layer 3, they are formed on the anode 2.
The light emitting layer 5 may be a layer independent of the hole injection layer 3 and the hole transport layer 4 described above and the hole blocking layer 6 and the electron transport layer 7 described later. In addition, another organic layer such as the hole transport layer 4 or the electron transport layer 7 may serve as the light emitting layer 5 without forming the independent light emitting layer 5.

The light-emitting layer 5 includes holes injected directly from the anode 2 or through the hole injection layer 3 and the hole transport layer 4 between the electrodes to which an electric field is applied, and directly from the cathode 9 or the cathode buffer layer 8. And excited by recombination with electrons injected through the electron transport layer 7, the hole blocking layer 6, etc., and becomes a main light emitting source.
In the present embodiment, the light emitting layer 5 is preferably formed using the organic electroluminescent element material or organic electroluminescent element composition used in the present embodiment.

  The method for forming the light emitting layer 5 includes a conventionally known method and is not particularly limited. For example, the light emitting layer 5 is formed on the anode 2 by a wet film forming method or a vacuum deposition method. However, when manufacturing the organic electroluminescent element 10 having a large area, a wet film forming method is preferable. When forming the light emitting layer 5 by the wet film-forming method and the vacuum evaporation method, the same operation as the case of forming the hole injection layer 3 described above can be performed.

In addition to the light emitting layer 5, when the hole injection layer 3 and the hole transport layer 4 and further organic layers such as a hole blocking layer 6 and an electron transport layer 7 described later are included, the light emitting layer 5 and other organic layers are combined. The total film thickness is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more, 1,000 nm or less, preferably 500 nm or less, more preferably 300 nm or less.
In general, in an organic electroluminescent device, when compared with the same material, the thinner the film thickness between the electrodes, the larger the effective electric field and the greater the injected current, resulting in a lower drive voltage. Therefore, the total film thickness of the organic layers provided between the electrodes should be thin. However, if the total film thickness is excessively thin, a protrusion caused by the electrode such as ITO causes a short circuit or excitation near the adjacent layer interface. Quenching or the like due to child diffusion occurs. Therefore, the total thickness of the organic layer needs to have a certain thickness.

In addition, when the conductivity of other organic layers provided in addition to the light emitting layer 5 is high, the amount of charge injected into the light emitting layer 5 increases. For example, by increasing the thickness of the hole injection layer 3 and reducing the thickness of the light emitting layer 4, the driving voltage can be lowered while maintaining a certain thickness as the total thickness of the plurality of organic layers. It is. In this case, the thickness of the light emitting layer 5 is usually 10 nm or more, preferably 20 nm or more, and usually 300 nm or less, preferably 200 nm or less.
In addition, when the organic electroluminescent element 10 of this Embodiment has only the light emitting layer 5 between both electrodes of the anode 2 and the cathode 9, as a film thickness of the light emitting layer 5, it is 30 nm or more normally, Preferably it is 50 nm or more. Also, it is usually 500 nm or less, preferably 300 nm or less.

(Hole blocking layer 6)
The hole blocking layer 6 can be formed on the light emitting layer 5. As a material for forming the hole blocking layer 6, the holes injected from the anode 2 can be blocked from reaching the cathode 9, and the electrons injected from the cathode 9 can be efficiently transported to the light emitting layer 5. Injectable compounds are desirable.
In the present embodiment, the organic electroluminescent element 10 may have a configuration in which the hole blocking layer 6 is omitted.

  A material that can be used for the hole blocking layer 6 preferably has a high electron mobility and a low hole mobility. Further, the energy gap (difference between HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital)) is large, and the energy of excitons generated in the light emitting layer 5 is positive. It is preferable not to move to the material for forming the hole blocking layer 6, to form an exciplex with the light emitting layer 5, and not to reduce the efficiency.

  Examples of a material for forming the hole blocking layer 6 satisfying such conditions include bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato). ) Mixed ligand complexes such as aluminum; metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes; distyrylbiphenyl Styryl compounds such as derivatives (Japanese Patent Laid-Open No. 11-242996); triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole ( JP-A-7-41759); Phenanthroline derivatives such as bathocuproine (JP-A-10-79297); , 4,6-position, and the like compounds having at least one pyridine ring substituted (WO 2005/022962 pamphlet). One of these may be used alone, or two or more may be used in any combination and ratio.

  The film thickness of the hole blocking layer 6 is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less. The hole blocking layer 6 can be formed by the same method as each layer from the hole injection layer 3 to the light emitting layer 5, and a wet film-forming method, a vacuum evaporation method, etc. can be used.

(Electron transport layer 7)
The electron transport layer 7 is formed on the hole blocking layer 6 when the hole blocking layer 6 is provided, and on the light emitting layer 5 when the hole blocking layer 6 is not provided.
The electron transport layer 7 is preferably formed of a compound (electron transport compound) that can efficiently transport electrons injected from the cathode 6 in the direction of the light emitting layer 5 between electrodes to which an electric field is applied. In the present embodiment, the organic electroluminescent element 10 may have a configuration in which the electron transport layer 7 is omitted.

The electron transporting compound that forms the electron transport layer 7 is a compound that has high electron injection efficiency from the cathode 9 or the cathode buffer layer 8 and has high electron mobility and can efficiently transport the injected electrons. Preferably there is.
Examples of the electron transporting compound that satisfies such conditions include metal complexes such as 8-hydroxyquinoline aluminum complex (Japanese Patent Laid-Open No. 59-194393); metal complexes of 10-hydroxybenzo [h] quinoline; oxadiazole Derivatives, distyrylbiphenyl derivatives, silole derivatives, 3- or 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds (special (Kaihei 6-207169), phenanthroline derivatives (JP-A-5-331459), 2-t-butyl-9,10-N, N′-dicyanoanthracenediimine, n-type hydrogenated amorphous silicon carbide, Examples include n-type zinc sulfide and n-type zinc selenide. One of these may be used alone, or two or more may be used in any combination and ratio.

  The film thickness of the electron transport layer 7 is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less. The electron transport layer 7 can be formed by the same method as each layer from the hole injection layer 3 to the hole blocking layer 6, and can be formed by, for example, a wet film formation method or a vacuum evaporation method. Of these, vacuum deposition is preferred.

(Cathode buffer layer 8)
The cathode buffer layer 8 is formed on the electron transport layer 7 when the electron transport layer 7 is provided, and on the hole block layer 6 when the hole blocking layer 6 is provided without the electron transport layer 7. When the transport layer 7 and the hole blocking layer 6 are not provided, they are formed on the light emitting layer 5.
The cathode buffer layer 8 has a role of efficiently injecting electrons injected from the cathode 9 into an adjacent organic layer. In the present embodiment, the organic electroluminescent element 10 may have a configuration in which the cathode buffer layer 8 is omitted.

As a material that can be used for the cathode buffer layer 8, it is preferable to use a metal having a low work function. This is because electrons are efficiently injected into the organic layer.
Specifically, for example, alkali metals such as sodium and cesium; alkaline earth metals such as barium and calcium are used. _{Further, LiF, MgF 2, Li 2} O, may also be used a metal salt such as _Cs 2 CO ₃ (Appl.Phys.Lett, 70 vol, 152 pp., 1997;. Hei 10-74586 JP; IEEE Trans. Electron. Devices, 44, 1245, 1997; SID 04 Digest, 154). One of these may be used alone, or two or more may be used in any combination and ratio.

The film thickness of the cathode buffer layer 8 is usually 0.01 nm or more, preferably 0.1 nm or more, and usually 10 nm or less, more preferably 5 nm or less.
The cathode buffer layer 8 can be formed by the same method as each of the layers from the hole injection layer 3 to the electron transport layer 7 described above. For example, a wet film forming method or a vacuum evaporation method can be employed. In the case of the vacuum evaporation method, for example, an evaporation source is put in a crucible or a metal boat installed in the vacuum vessel, and the inside of the vacuum vessel is depressurized by an appropriate vacuum pump. Thereafter, the crucible or metal boat is heated and evaporated to form the cathode buffer layer 8 on the substrate placed facing the crucible or metal boat.

  In the case of depositing an alkali metal, for example, an alkali metal dispenser in which nichrome is filled with an alkali metal chromate and a reducing agent can be used. By heating the dispenser in a vacuum container, the alkali metal chromate is reduced and the alkali metal evaporates. When the organic electron transport material and the alkali metal are co-evaporated, the organic electron transport material is put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is depressurized with a suitable vacuum pump. Thereafter, each crucible and dispenser can be simultaneously heated and evaporated to form a cathode buffer layer 8 on the substrate 1 placed facing the crucible and dispenser. At this time, co-evaporation is uniformly performed in the film thickness direction of the cathode buffer layer 8, but there may be a concentration distribution in the film thickness direction.

(Cathode 9)
The cathode 9 is formed on the cathode buffer layer 8 when the cathode buffer layer 8 is provided, and on the electron transport layer 7 when the electron transport layer 7 is provided without the cathode buffer layer 8. When the hole blocking layer 6 is provided without the transport layer 7, the cathode blocking layer 6, the electron transport layer 7, and the hole blocking layer 6 are not provided above the light emitting layer 5. Formed. The cathode 9 plays a role of injecting electrons into adjacent layers on the anode 2 side (cathode buffer layer 8, electron transport layer 7, etc.).

As the material of the cathode 9, the material used for the anode 2 can be used. Among them, it is preferable to use a metal having a low work function for efficient electron injection. As such a metal, for example, a metal such as tin, magnesium, indium, calcium, aluminum, silver, or an alloy thereof is used. Specific examples of the material for forming the low work function alloy electrode include aluminum, magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.
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, a metal layer having a high work function and stable to the atmosphere can be further laminated on the cathode 9. Examples of metals suitable for this purpose include metals such as aluminum, silver, copper, nickel, chromium, gold, and platinum.

(Other component layers)
In the present embodiment, the organic electroluminescent element 10 may have any other layer in addition to the above-described layers between the anode 2 and the cathode 9 as long as the performance is not impaired. Moreover, you may abbreviate | omit arbitrary layers other than the lowest layer organic layer which plays the role of the light emitting layer 5. FIG.
Further, for the same purpose as the hole blocking layer 6, an electron blocking layer adjacent to the light emitting layer 5 on the anode 2 side can be provided. The electron blocking layer prevents electrons moving from the light emitting layer 5 from reaching the hole injection layer 3 or the hole transport layer 4, thereby recombination probability of holes and electrons in the light emitting layer 5. And the generated excitons are confined in the light emitting layer 5 and holes injected from the layer on the anode 2 side are efficiently injected into the light emitting layer 5.

Furthermore, a structure in which a plurality of layers shown in FIG. 1 are stacked (a structure in which a plurality of light emitting units are stacked) may be employed. In this case, for example, V ₂ O ₅ or the like is used as the charge generation layer (CGL) instead of the interface layer between the steps (between the light emitting units) (two layers when the anode 2 is ITO and the cathode 9 is Al). Thus, the barrier between the stages is reduced, which is more preferable from the viewpoint of light emission efficiency and driving voltage. In the present embodiment, the organic electroluminescent element 10 is applied to any of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. Can do.
Further, in the organic electroluminescence device 10 of the present embodiment, by using a transparent cathode as the cathode 9, it is formed as a top emission type device that extracts light emission from above (from the surface opposite to the substrate 1). Is also possible.

(Organic EL display)
Next, an organic EL display will be described.
The organic EL display to which the present embodiment is applied has at least a transparent support substrate and an organic electroluminescent element laminated on the transparent support substrate. As the organic electroluminescent element, the organic electroluminescent element material described above or By using an organic electroluminescent device comprising an organic layer formed using a composition for organic electroluminescent devices, for example, “Organic EL Display” (Ohm Co., Ltd., issued on August 20, 2004, Shizushi Tokito An organic EL display as described in Chiyaya Adachi and Hideyuki Murata) can be formed.

  Hereinafter, the present invention will be described in more detail based on examples. The present invention is not limited to the following examples without departing from the gist thereof. In addition, unless otherwise indicated, in the following description, a part refers to a weight part.

(Measurement of solubility of condensed polycyclic hydrocarbon derivatives in toluene)
Into a glass sample bottle having an internal volume of 2 mL to 10 mL, a condensed polycyclic hydrocarbon derivative having a diphenylamino group (usually in the range of 3 mg to 10 mg) and toluene are charged, and the lid of the glass sample bottle is closed. Sonication or heat treatment is performed to accelerate dissolution of the solute as much as possible. Next, the glass sample bottle was allowed to stand at 25 ° C. for 10 hours or more, and then the solubility was measured.

(Measurement of glass transition temperature (Tg) of condensed polycyclic hydrocarbon derivatives)
The glass transition temperature (Tg) of the condensed polycyclic hydrocarbon derivative having a diphenylamino group was measured with a differential scanning calorimeter (SII Nanotechnology Inc., DSC 6220).

(Synthesis of condensed polycyclic hydrocarbon derivatives having a diphenylamino group)
As shown below, condensed polycyclic hydrocarbon derivatives having three types of diphenylamino groups (DDD-3, DDD-4, and DDD-5) were synthesized.

[Synthesis of Compound DDD-3]
9,10-phenanthrenequinone (5.20 g, 25 mmol), isopropylphenylamine (10.99 g, 81.3 mmol) and pyridine (1.25 g, 15.8 mmol) were dissolved in 78 ml of toluene and stirred at 5 ° C. . A solution of TiCl ₄ (3.8 g) dissolved in 7.5 ml of toluene was added dropwise to the reaction solution, and after completion of the addition, the temperature was gradually raised to room temperature and stirred for 9 hours. After adding 100 ml of demineralized water in which NaOH (6.4 g) is dissolved, liquid separation is performed, the organic layer is evaporated, and the resulting solid is washed with 50 ml of methanol and filtered to obtain compound (A). It was. The chemical formula of compound (A) is shown below. Compound (A) was used in the next reaction without further purification.

Next, p-cyclohexyliodobenzene (5.30 g, 18.5 mmol), the aforementioned compound (A) (1.87 g, 4.2 mmol), Cu (0.80 g, 12.6 mmol), potassium carbonate (2. 32 g, 16.8 mmol) was suspended in 8 ml of tetraglyme and refluxed at 220 ° C. for 20 hours. The reaction solution was filtered to remove inorganic substances, 20 ml of demineralized water was added, and after separation, the solvent was distilled off. Subsequently, the column was purified with hexane / AcoEt = 20/1 and recrystallized with hexane / ethyl acetate = 50/1 to obtain 0.93 g of a yellow solid (compound DDD-3) having a purity of 99%. The measurement result of ¹ H-NMR of compound DDD-3 is as follows.
(NMR measurement results)
1.07 (dd, 12H), 1.10-1.80 (m, 20H), 2.25 (m, 2H), 2.65 (m, 2H)
6.6-6.8 (m, 16H), 7.42 (t, 2H), 7.61 (t, 2H), 7.91 (d, 2H), 8.74 (d, 2H),

  Compound DDD-3 has a glass transition temperature Tg of 103 ° C. and a solubility in toluene of 3% by weight. Further, the chemical formula of the compound DDD-3 is shown below.

[Synthesis of Compound DDD-4]
In addition to using 1,4-chrysene diketone compound K1 (6.45 g, 25 mmol) shown below in place of 9,10-phenanthrenequinone (5.20 g, 25 mmol) in the synthesis of compound DDD-3 described above, The synthesis was performed in the same manner under other conditions to obtain 1.05 g of a yellow solid (compound DDD-4) having a purity of 99%.

The measurement result of ¹ H-NMR of compound DDD-4 is as follows.
(NMR measurement results)
1.07 (dd, 12H), 1.10-1.80 (m, 20H), 2.25 (m, 2H), 2.65 (m, 2H)
6.975-7.10 (m, 18H), 7.55-7.75 (m, 2H), 77.82 (d, 2H), 7.90 (d, 2H), 8.05 (d, 2H), 8.29 (d, 2H), 8.39 (d, 2H), 8.64 (d, 2H)

  Compound DDD-4 has a glass transition temperature Tg of 94 ° C. and a solubility in toluene of 5% by weight. Further, the chemical formula of the compound DDD-4 is shown below.

[Synthesis of Compound DDD5]
5,8-dibromobenzophenanthrene (compound BR4) (3.86 g, 10 mmol), toluene 100 ml, compound AM4 (5.23 g.22 mmol), tris-tertiary butylphosphine (0.2 g) and tertiary A solution containing butyl sodium (2.1 g) was stirred for 30 minutes while bubbling nitrogen, and then nitrogen tris (dibenzylideneacetone) dipadium (0) (0.18 g) was added. The reaction solution was then heated to 80 ° C. and held for 4 hours. Subsequently, the reaction solution was returned to room temperature, 100 ml of demineralized water was added, and the mixture was separated, and the organic layer was evaporated. Then, a column (Wako Pure Chemical Industries, Ltd .: Purification with silica Wakogel C-200) yielded 3.5 g of a 99% pure yellow solid (compound DDD-5).
The chemical formulas of Compound BR4 and Compound AM4 are shown below.

The measurement result of ¹ H-NMR of compound DDD-5 is as follows.
(NMR measurement results)
1.07 (dd, 12H), 1.10-1.80 (m, 20H), 2.25 (m, 2H), 2.65 (m, 2H)
6.95-7.10 (m, 16H), 7.392 (s, 2H), 7.46 (t, 2H), 7.62 (t, 2H), 8.17 (d, 2H), 9 .04 (d, 2H)

  Compound DDD-5 has a glass transition temperature Tg of 129 ° C. and a solubility in toluene of 5% by weight. Further, the chemical formula of the compound DDD-5 is shown below.

(Compound CCC-2, Compound CCC-3, Compound CCC-4)
In order to perform a comparative experiment, as shown below, the compound CCC-2, the compound CCC-3, and the compound CCC- in which a diphenylamino group as a substituent is bonded to the 6th and 12th carbon atoms of the chrysene ring. 4 was synthesized.
The solubilities of Compound CCC-2, Compound CCC-3, and Compound CCC-4 in toluene are 2% by weight, less than 0.1% by weight, and less than 0.1% by weight, respectively.
In addition, Compound CCC-4 had a glass transition temperature Tg of 101 ° C. For compounds CCC-2 and CCC-3, no clear glass transition temperature Tg was observed.

( Reference Example 1)
Using the compound DDD-3 described above, an organic electroluminescence device having a light emission area portion of 2 mm × 2 mm in size was prepared according to the following operation.

(Formation of anode)
An indium tin oxide (ITO) transparent conductive film was formed on a glass substrate with a thickness of 150 nm (sputtered film, sheet resistance 15Ω). This transparent conductive film was patterned into a stripe having a width of 2 mm by an ordinary photolithography technique to form an anode.
The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, and then dried with nitrogen blow to perform ultraviolet ozone cleaning.

(Formation of hole injection layer)
Subsequently, a hole injection layer was formed on the anode. As a material for the hole injection layer, a non-conjugated polymer compound (PB-1: weight average molecular weight 29,400, number average molecular weight 12,600) having an aromatic amino group having the structural formula shown below is used, and photoreaction is performed. It spin-coated on the anode with the initiator (A-1). Table 7 shows the spin coating conditions. Moreover, the use ratio of the non-conjugated polymer compound (PB-1) and the photoreaction initiator (A-1) was (PB-1) :( A-1) = 10: 4 (weight ratio). After spin coating, drying was performed at 260 ° C. for 180 minutes to form a uniform hole injection layer thin film having a thickness of 30 nm.

(Hole transport layer)
A hole transport layer was formed on the formed hole injection layer. A hole transport layer was formed by spin coating using the following compound (HT-1) as a material for the hole transport layer. Table 8 shows the spin coating conditions. After spin coating, drying was performed at 230 ° C. for 60 minutes to form a uniform hole transport layer thin film having a thickness of 20 nm.

(Light emitting layer)
Next, a light emitting layer was formed on the formed hole transport layer. As a material for the light emitting layer, a light emitting layer was formed by spin coating using a composition obtained by dissolving the compound H-1 shown below and the synthesized compound DDD-3 in toluene under the following conditions. Table 9 shows the spin coating conditions. The ratio of compound H-1 to compound DDD-3 was (compound H-1) :( DDD-3) = 10: 1 (weight ratio). After spin coating, drying was performed at 100 ° C. for 60 minutes to form a uniform light emitting layer thin film having a thickness of 50 nm.

(Hole blocking layer / charge transport layer)
Subsequently, a hole blocking layer was formed on the formed light emitting layer, and an electron transport layer was further formed on the hole blocking layer. A hole blocking layer having a thickness of 10 nm was formed by vacuum deposition using HB-1 shown below as a material for the hole blocking layer. Next, an electronic element layer having a thickness of 30 nm was formed by vacuum deposition using ET-1 shown below as a material for the electron transport layer.

(Cathode buffer layer / cathode)
Next, a cathode buffer layer was formed on the charge transport layer, and a cathode was further formed on the cathode buffer layer. As the cathode buffer layer, lithium fluoride (LiF) was used, and a cathode buffer layer having a thickness of 0.5 nm was formed by a vacuum deposition method in the same manner as the organic layer. Also, aluminum was used as the cathode material, and cathodes with a film thickness of 80 nm were stacked in a 2 mm-wide stripe shape that was orthogonal to the ITO stripe that was the anode.

The presence / absence of light emission and light emission color as a light emitting element when a voltage of 7 V was applied to the organic electroluminescent element having a light emitting area of 2 mm × 2 mm prepared by the above operation were evaluated.
As a result, blue light emission was obtained. Furthermore, using a coating solution containing compound DDD-3 (compound DDD-3 concentration 0.5% / solvent toluene), the 50 nm molecular film of compound DDD-3 formed on the glass substrate was irradiated with ultraviolet light (366 nm). Then, blue light emission was obtained.

(Example 2)
In place of DDD-3, the above-described compound DDD-5 was used, and the same operation as in Example 1 was performed to prepare an organic electroluminescent device having a light emitting area portion of 2 mm × 2 mm in size. Next, in the same manner as in Example 1, the presence or absence of light emission as a light emitting element and the light emission color when a voltage of 7 V was applied to the organic electroluminescent element thus prepared were evaluated.
As a result, blue light emission was obtained from the organic electroluminescent element prepared using Compound DDD-5. Furthermore, using a coating solution containing compound DDD-5 (compound DDD-5 concentration 0.5% / solvent toluene), a 50 nm molecular film of compound DDD-5 formed on a glass substrate is irradiated with ultraviolet light (366 nm). Then, blue light emission was obtained.

(Example 3)
Using the coating solution containing the compound DDD-4 (compound DDD-4 concentration 0.5% / solvent toluene), the 50 nm molecular film of the compound DDD-4 formed on the glass substrate is irradiated with ultraviolet light (366 nm). Then, blue light emission was obtained.
Thereby, it is thought that an organic electroluminescent element is obtained by using compound DDD-4 similarly to compound DDD-3 mentioned above.

(Comparative Example 1)
By the same operation as in Example 1, an organic electroluminescent device having a light emitting area portion of 2 mm × 2 mm in size was prepared using the compound CCC-2 described above. As a result, blue light emission was obtained from this organic electroluminescence device, but the solubility of compound CCC-2 was lower than that of compound DDD-4, making it difficult to produce an organic electroluminescence device.

(Comparative Example 2)
Since the compound CCC-3 described above has low solubility in toluene (less than 0.1% by weight), an organic electroluminescent device could not be formed by a wet film formation method.

(Comparative Example 3)
Since the compound CCC-4 described above has low solubility in toluene (less than 0.1% by weight), an organic electroluminescent device could not be formed by a wet film formation method.

It is a cross-sectional schematic diagram which shows the suitable structural example of the organic electroluminescent element to which this Embodiment is applied.

Explanation of symbols

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 ... Cathode buffer layer, 9 ... Cathode, 10 ... Organic electroluminescence device

Claims (8)

An organic electroluminescent element material comprising a condensed polycyclic hydrocarbon derivative having a diphenylamino group, the compound having a structure represented by the following formula (1):

(In formula (1), Ar ¹ represents a chrysenyl group, an aromatic condensed polycyclic hydrocarbon group selected from the group consisting of base down zone phenanthrenyl group. However, when Ar ¹ is a chrysenyl group, ring diphenylamino groups a ¹ and ring ^{B 1} is bonded is .Cy ¹ which binds at the position of the 1-position and 4-position of the chrysenyl group, a cycloalkyl group. ring ^{a 1} is a substituted besides Cy ¹ A benzene ring which may have a group is represented, a ring B ¹ represents a benzene ring which may have a substituent, and n represents an integer of 1 or more.   The organic electroluminescent element material according to claim 1, wherein the solubility of the condensed polycyclic hydrocarbon derivative in toluene is 1% by weight or more.   The organic electroluminescent element material according to claim 1, wherein the material is used for wet film formation. A composition for an organic electroluminescent element used for forming an organic electroluminescent element,
The composition for organic electroluminescent elements of any one of Claims 1 thru | or 3 and the predetermined | prescribed solvent are included. An organic electroluminescent device comprising an anode, a cathode, and an organic layer provided between the anode and the cathode,
The said organic layer contains the organic electroluminescent element material of any one of Claim 1 thru | or 3, The organic electroluminescent element characterized by the above-mentioned.   The organic electroluminescent device according to claim 5, wherein the organic layer is a light emitting layer.   The organic electroluminescent device according to claim 5 or 6, wherein the organic layer is formed by a wet film forming method using a composition containing the material for an organic electroluminescent device and a predetermined solvent. An organic EL display having a transparent support substrate and an organic electroluminescent element laminated on the transparent support substrate,
The organic electroluminescence device according to claim 5, wherein the organic electroluminescence device is the organic electroluminescence device according to claim 5.

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