JP2002124389A - Organic electroluminescence device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescence device having a low light emission starting voltage, a high light emission efficiency, and excellent durability. SOLUTION: It comprises a hole transport layer containing a carbazole polymer having a structural unit represented by the general formula (1). [R ¹ is a hydrogen atom, an alkyl group or a phenyl group,
R ² , R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group or a dialkylamino group, X is a single bond or a phenylene group, a carbonyl group or one or both of them And a divalent organic group containing ]

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device.

[0002]

2. Description of the Related Art In recent years, organic materials have begun to be used as a hole transporting material and an electron transporting material constituting an electroluminescent device. An organic electroluminescent device using such an organic material (hereinafter referred to as "organic EL device") has been developed.
Also called an "element." ) Is being actively researched. An organic material constituting such an organic EL element is required to have excellent durability and to obtain high luminous efficiency.

Conventionally, organic materials having a hole transporting property include diamine derivatives, N, N'-diphenyl-N,
Low molecular weight organic materials such as aromatic amine compounds such as N′-di (3-methylphenyl) -4,4 ′, diaminobiphenyl (hereinafter also referred to as “m-TPD”), and polymers such as polyvinylcarbazole Organic materials are known.
However, since the above-mentioned low-molecular organic material has poor physical or thermal durability, when the hole transport layer is formed by the low-molecular organic material, the organic EL element is driven or stored. During the hole transport layer will be altered,
There is a disadvantage that. In addition, since a high molecular weight organic material such as polyvinyl carbazole has a very high glass transition point (Tg), a hole transport layer having excellent durability, that is, a long service life can be obtained. And the luminous efficiency is low due to insufficient hole transport performance, which poses a practical problem.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made based on the above circumstances, and its object is to provide:
An object of the present invention is to provide an organic electroluminescence device having a low light emission starting voltage, high light emission efficiency, and excellent durability.

[0005]

An organic electroluminescent device according to the present invention comprises a hole transport layer containing a carbazole polymer having a structural unit represented by the following general formula (1). It is characterized by.

[0006]

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[Wherein, R¹Represents a hydrogen atom, an alkyl group or
Represents a phenyl group;^Two, R^Three, R ^FourAnd R^FiveIs
Each independently a hydrogen atom, an alkyl group, an alkoxy group,
It represents a phenyl group or a dialkylamino group. X is simply
Bond or phenylene group, carbonyl group or this
Represents a divalent organic group containing one or both of
You. ]

In the organic electroluminescent device of the present invention, the carbazole polymer preferably contains at least 5% by mass of the structural unit represented by the general formula (1). Further, when the hole transport layer contains a carbazole-based polymer having the structural unit represented by the general formula (1) and a polymer other than the carbazole-based polymer, It is preferable that the proportion of the structural unit represented by the general formula (1) in all the polymers constituting the hole transport layer is 5% by mass or more. Further, the organic electroluminescence device of the present invention preferably has at least an anode layer, the hole transport layer, a light emitting layer, and a cathode layer.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. FIG. 1 is an explanatory cross-sectional view showing the configuration of the organic electroluminescence element according to the first embodiment of the present invention. In this organic EL device, an anode layer (hole injection electrode layer) 2 is provided on a transparent substrate 1, and a hole transport layer 10 is provided on the anode layer 2. Is provided with a light-emitting layer 15.
A cathode layer (electron injection electrode layer) 3 is provided on 5. The anode layer 2 and the cathode layer 3 are connected to a DC power supply 5.

As the transparent substrate 1, a glass substrate, a transparent resin substrate, a quartz glass substrate or the like can be used.
The anode layer 2 is made of a material having a large work function (for example, 4 eV or more), for example, an ITO film, tin oxide (S
nO ₂ ) film, copper oxide (CuO) film, zinc oxide (ZnO)
A film or the like can be used. The hole transport layer 10 is formed of a carbazole polymer (hereinafter, referred to as a “specific structural unit”) having a structural unit represented by the general formula (1).
Also referred to as “specific carbazole-based polymer”. ).

In the general formula (1) representing a specific structural unit, R ¹ represents a hydrogen atom, an alkyl group or a phenyl group. Here, specific examples of the alkyl group include a methyl group,
Examples thereof include an alkyl group having 1 to 18 carbon atoms such as an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, and a dodecyl group. In the general formula (1), R ¹ is preferably an alkyl group having 1 to 3 carbon atoms such as a methyl group or an ethyl group, or a hydrogen atom.

In addition, R ² , R ³ ,
R ⁴ and R ⁵ represent a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group or a dialkylamino group, all of which may be the same or a part or all thereof may be different. Here, as the alkyl group,
Although not particularly limited, a methyl group, an ethyl group,
An alkyl group having 1 to 8 carbon atoms such as a propyl group, a butyl group, a hexyl group and an octyl group is preferred. In particular, a methyl group is preferable in that high hole transport performance is obtained, and an alkyl group having a large number of carbon atoms (for example, having 8 carbon atoms) is preferable in terms of obtaining a polymer having high solubility in an organic solvent. preferable. The alkoxy group is not particularly limited, but is preferably an alkoxy group having 1 to 8 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. Particularly, a point at which high hole transport performance is obtained. Then
A methoxy group is preferred. As the dialkylamino group,
Although not particularly limited, a dimethylamino group, a diethylamino group, a dipropylamino group or the like having 1 carbon atom
Those having an alkyl group of from 8 to 8 are preferable, and a di-n-propylamino group and a di-i-propylamino group are particularly preferable in that high hole transport performance is obtained. And
In the general formula (1), as a combination of R ² and R ³ , one of the two is a hydrogen atom and the other is an alkyl group, and the combination of R ⁴ and R ^{5 is} a combination of the two. It is preferable that one of them is a hydrogen atom and the other is an alkyl group. Also, R
^When each of ^{2 to} R ⁵ is other than a hydrogen atom, the respective positions are preferably in the meta or para position.

In the general formula (1), X represents a single bond, a phenylene group, a carbonyl group, or a divalent organic group containing one or both of them. Examples of the divalent organic group containing a carbonyl group include -COO-
(Oxycarbonyl group), -CONH- (iminocarbonyl group) or -CONHC
And a group represented by O- (ureylene group). Examples of the divalent organic group containing a phenylene group include -C
_And a group represented by ₆ H ₄ CH ₂ O—. Examples of the divalent organic group containing both a carbonyl group and a phenylene group include a group represented by the following formula (A) and a group represented by the following formula (B). here,
A phenylene group and a divalent organic group containing the same are represented by o
-, M-, or p-form,
It is preferably a body. In the general formula (1), X is preferably a group represented by the formula (A), a group represented by the formula (B), or a phenylene group.

[0014]

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[0015]

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[In the formula (b), the number of repetitions n is 1
Is an integer of 10 to 10. ]

Such a specific structural unit is obtained from a carbazole derivative represented by the following general formula (2) (hereinafter, also referred to as “specific monomer”). Specific examples include those represented by the following formula (a), those represented by the following formula (b),
Examples include those represented by the following formula (c) and those represented by the following formula (d).

[0018]

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[Wherein, R¹Represents a hydrogen atom, an alkyl group or
Represents a phenyl group;^Two, R^Three, R ^FourAnd R^FiveIs
Each independently a hydrogen atom, an alkyl group, an alkoxy group,
It represents a phenyl group or a dialkylamino group. X is simply
Bond or phenylene group, carbonyl group or this
Represents a divalent organic group containing one or both of
You. ]

[0020]

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[0021]

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Such specific monomers can be obtained by, for example, starting from carbazole, various substitutions for the hydrogen atom bonded to the nitrogen of the carbazole and the hydrogen atom bonded to each carbon atom at the position numbers 3 and 6. It is obtained by performing a reaction. As a specific example, a method for producing the carbazole derivative represented by the above formula (a) will be described.
First, by reacting carbazole with, for example, nitrobenzene, a hydrogen atom bonded to the nitrogen of the carbazole is replaced with a nitrophenyl group, and further, for example, by reacting with bromine, each carbon atom at the position numbers 3 and 6 is reacted. Is replaced with a bromine atom, whereby the intermediate product (A) (3,6-dibromo [N-
(P-nitrophenyl) carbazole]). This synthesis step is shown in reaction formula (i).

[0023]

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The intermediate product (A) thus obtained
And the intermediate product (B) (3,6-bis (m-tolylphenylamino) [N- (p -Nitrophenyl) carbazole]), and the nitro group is converted to an amino group by, for example, performing a hydrogenation reaction on the intermediate product (B), whereby the intermediate product (C) (3,6- Bis (m-tolylphenylamino) [N- (p-aminophenyl) carbazole] is obtained. This synthesis step is represented by the reaction formula (ii)
And the reaction formula (iii).

[0025]

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[0026]

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By reacting the obtained intermediate product (C) with, for example, methacryloyl chloride, a carbazole derivative represented by the formula (a) can be produced.

The method for producing the carbazole derivative represented by the formula (b) will be described. Similar to the method for producing the carbazole derivative represented by the formula (a), the intermediate product is prepared by using carbazole as a starting material. The carbazole derivative represented by the formula (b) can be produced by synthesizing the product (C) and reacting the intermediate product (C) with, for example, 2-isocyanatoethyl methacrylate.

The specific carbazole-based polymer is composed of only a specific structural unit, that is, a homopolymer of a specific monomer, but having a specific structural unit and another structural unit, ie, a specific monomer. It may be a copolymer of a polymer and a monomer copolymerizable therewith (hereinafter, referred to as a “copolymerizable monomer”).

When the specific carbazole polymer is a copolymer of a specific monomer and a copolymerizable monomer, the content of the specific structural unit is 5% by mass or more, particularly 10% by mass or more. It is preferred that Content ratio of specific structural unit is 5
If it is less than 10% by mass, the resulting hole transport layer 10
Tends to have low hole transport performance and durability.

As such a copolymerizable monomer, for example, N
Carbazole derivatives other than specific monomers such as -vinylcarbazole, N- (4-vinylphenyl) carbazole, N-biphenylvinylcarbazole, compounds represented by the following formula (e), and represented by the following formula (f) Compounds, vinyl aromatic amines such as compounds represented by the following formula (g), monomers having a hole-transporting ability such as p-vinyltriphenylamine, p-methacryloyltriphenylamine, and the like, Particularly, N-vinylcarbazole is preferred. These copolymerizable monomers can be used alone or in combination of two or more.

[0032]

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The weight average molecular weight of the specific carbazole polymer is, for example, 1000 to 1,000,000 in terms of polystyrene by gel permeation chromatography.
In particular, it is preferably 5,000 to 300,000. When the weight average molecular weight is less than 1000, the polymer may have insufficient heat resistance, stability in a thin film state, and mechanical strength. On the other hand, when this weight average molecular weight exceeds 1,000,000, the polymer tends to have a significantly high solution viscosity, and when the hole transport layer 10 is formed by a wet method, the handling property is reduced. It is not preferable because the stringiness of the hole transport layer forming solution occurs. The ratio Mw / Mn between the weight average molecular weight and the number average molecular weight is not particularly limited, but is a polymer having a uniform molecular weight, that is, a ratio Mw / Mn.
Those having relatively small Mn are preferable.

The specific carbazole-based polymer is prepared by mixing a specific monomer or a mixture of a specific monomer and a copolymerizable monomer with an appropriate polymerization method, for example, a radical polymerization method, an anion polymerization method or a cationic polymerization method. It can be produced by polymerizing by a polymerization method. In order to obtain a carbazole polymer having a narrow molecular weight distribution, a living radical polymerization method, a living anion polymerization method or a living cation polymerization method is used.

When a specific carbazole polymer is obtained by a usual radical polymerization method, an azo compound such as azobisisobutyronitrile (AIBN), a peroxide such as benzoyl peroxide (BPO), and tetraethylthiuram disulfide are used. A radical polymerization method using a known radical initiator such as a dithiocarbamate derivative as a polymerization catalyst can be used. When a specific carbazole polymer is obtained by a living radical polymerization method, an N-oxy radical such as 2,2,6,6-tetramethyl-1-piperidine-N-oxide (TEMPO) and the above-mentioned N-oxy radical are used. A living radical polymerization method using a catalyst system combined with a radical polymerization initiator, a living radical polymerization method using atom transfer polymerization or the like can be used. The usage ratio of such a radical polymerization catalyst is 1 to 0.00001 mol per 1 mol of the monomer. In such a radical polymerization method, as a polymerization solvent, dimethylformamide, dimethylacetamide,
Amide solvents such as N-methylpyrrolidone, benzene,
Hydrocarbon solvents such as toluene, xylene, hexane, and cyclohexane; ester solvents such as γ-butyrolactone and ethyl lactate; ketone solvents such as cyclohexylbenzophenone, cyclohexanone, 2-ethylpentanone and ethyl isoamyl ketone; and cyclic compounds such as tetrahydrofuran Ether solvents such as ethers and aliphatic ethers such as diethylene glycol dimethyl ether can be used. The reaction temperature is, for example, 0 to 20.
0 ° C., and the reaction time is, for example, 0.5 to 72 hours.

When a specific carbazole polymer is obtained by a usual anionic polymerization method, for example, an olefin catalyst such as naphthyl sodium, an alkyl lithium such as methyllithium, ethyllithium, butyllithium, etc.
Anionic polymerization using an organometallic compound of a metal such as an alkali metal or an alkaline earth metal such as an aryl lithium such as phenyllithium, an alkyl zinc such as diethyl zinc, an alkyl complex such as lithium alkyl magnesium or lithium alkyl barium as an anion polymerization catalyst. Legal can be used. In particular, it is preferable to use an organic lithium compound such as n-butyllithium, sec-butyllithium, and phenyllithium as the anion polymerization catalyst. When a specific carbazole-based polymer is obtained by a living anion polymerization method, a living anion polymerization method using a catalyst such as butyllithium, ethyllithium, or ethylsodium can be used. The use ratio of such an anionic polymerization catalyst is 1.0 to 0.0001 mol per 1 mol of the monomer. In such an anionic polymerization method, as a polymerization solvent,
Hydrocarbons such as benzene, toluene, hexane, heptane and cyclohexane, and ether compounds such as tetrahydrofuran and dioxane can be used. The reaction temperature is, for example, -50 to 100C, and the reaction time is, for example, 0.25 to 48 hours.

In the case of obtaining a specific carbazole-based polymer by a usual cationic polymerization method, known cation polymerization resins such as trifluoroborate, tin tetrachloride and other Lewis acids, sulfuric acid, hydrochloric acid and other inorganic acids, and cation exchange resins. Cationic polymerization using a catalyst can be used. When a specific carbazole-based polymer is obtained by a living cationic polymerization method, a living cationic polymerization method using a catalyst such as HI or HI-ZnI ₂ can be used. The use ratio of such a cationic polymerization catalyst is 0.01 to 0.00001 mol per 1 mol of the monomer. In such a cationic polymerization method, polymerization solvents include halogenated hydrocarbons represented by methylene chloride and chlorobenzene, cyclic ethers such as dibutyl ether, diphenyl ether, dioxane and tetrahydrofuran, and highly polar solvents such as acetonitrile and nitrobenzene. Etc. can be used. The reaction temperature is, for example, -150 to 50 ° C, and the reaction time is, for example, 0.5 minutes to 24 hours.

In the organic EL device of the present invention, even if the hole transport layer 10 is composed of only a specific carbazole-based polymer, the hole-transporting layer 10 includes a specific carbazole-based polymer and a material other than the specific carbazole-based polymer. And a polymer (hereinafter, referred to as “another polymer”).
Here, the specific carbazole-based polymer can be used alone or in combination of two or more.

When the hole transport layer 10 is formed of a specific carbazole polymer and another polymer, the content of the specific structural unit in the total polymer is 5% by mass or more, particularly 10% by mass or more. Preferably, there is. When the content ratio of the specific structural unit is less than 5% by mass, the obtained organic EL element tends to have a high luminescence starting voltage, low luminous efficiency, and low durability.

Other polymers constituting the hole transport layer 10 include, for example, polyvinyl carbazole, poly (4-vinylphenyl) carbazole, polyvinyltriphenylamine, vinylcarbazole and 2- (4-vinylphenyl) -5- Examples thereof include known polymers having a hole-transporting ability such as a copolymer with naphthyl-1,3,5-oxadiazole, and preferably poly (4-vinylphenyl) carbazole and polyvinyltriphenylamine. ,
Vinyl carbazole and 2- (4-vinylphenyl) -5
-Naphthyl-1,3,5-oxadiazole. These other polymers can be used alone or in combination of two or more.

In the hole transport layer 10, various dyes,
A laser dye or the like may be contained, and the ratio is preferably 0.1 to 10% by mass of all materials constituting the hole transport layer 10. By containing such dyes, laser dyes, and the like in the hole transport layer 10,
The obtained organic EL element has a longer use life while emitting light is promoted.

The light emitting material constituting the light emitting layer 15 includes:
A metal complex of hydroxyquinoline represented by trisquinolinolate aluminum, a metal complex of hydroxybenzoxazole, and a metal complex of hydroxybenzothiazole can be used. The cathode layer 3 is made of a material having a small work function (for example, 4 eV or less), for example, a metal film made of aluminum, calcium, magnesium, lithium, indium, or the like, an alloy film of these metals, or a mixture of these metals and other materials. And an alloy film with such a metal can be used. The thickness of each of the hole transport layer 10 and the light emitting layer 15 is not particularly limited.
It is selected in the range of 10 to 1000 nm, preferably 50 to 200 nm.

Such an organic EL device can be manufactured, for example, as follows. First, an anode layer 2 is formed on the surface of a transparent substrate 1. On the surface of the anode layer 2, a specific carbazole-based polymer and other materials used as necessary are dissolved in an appropriate organic solvent. The resulting hole transport layer forming solution is applied, and the resulting coating film is subjected to a heat treatment, whereby the organic solvent in the coating film is removed and the hole transport layer 10 is formed. Next, the hole transport layer 10
A light emitting layer 15 is formed on the surface of the light emitting layer 15, and then a cathode layer 3 is formed on the surface of the light emitting layer 15.
An L element is manufactured.

In the above, as a method for forming the anode layer 2, a vacuum evaporation method, a sputtering method, or the like can be used. Alternatively, a commercially available material in which, for example, an ITO film is formed on the surface of a transparent substrate such as a glass substrate can be used.

As an organic solvent for preparing the solution for forming the hole transport layer, a material for forming the hole transport layer 10 (a specific carbazole polymer and other materials used as necessary) is dissolved. Examples thereof include chloroform, chlorobenzene, halogenated hydrocarbons such as tetrachloroethane, dimethylformamide, amide solvents such as N-methylpyrrolidone,
Ethyl lactate, pegmere, ethyl ethoxypropionate, methyl amyl ketone, and the like. These organic solvents can be used alone or in combination of two or more. Among them, it is preferable to use an organic solvent having an appropriate evaporation rate, specifically, an organic solvent having a boiling point of about 70 to 150 ° C., in that a thin film having a uniform thickness can be obtained. The proportion of the organic solvent used is in the hole transport layer 1
The concentration of the material for forming the hole transport layer 10 in the solution for forming the hole transport layer is usually 0.1 to 10% by weight, although it depends on the type of the material for forming 0. As a means for applying the hole transport layer forming solution, for example, a spin coating method, a dipping method, a roll coating method, or the like can be used.

The method of forming the light emitting layer 15 is as follows: (1) a dry method of forming the light emitting layer 15 by vacuum-depositing a light emitting material on the surface of the hole transport layer 10;
(2) A light emitting layer forming solution in which a light emitting material is dissolved in an appropriate organic solvent is applied to the surface of the hole transport layer 15 and subjected to a heat treatment, thereby utilizing a wet method or the like for forming the light emitting layer 15. can do. In the case of using the wet method, as the organic solvent for preparing the light emitting layer forming solution, various ones can be used as long as they can dissolve the light emitting material, and specific examples thereof include toluene, Aromatic hydrocarbons such as xylene, ketones such as methyl isobutyl ketone and cyclohexanone, ethyl lactate, γ-
Esters such as butyrolactone; amides such as N-methylpyrrolidone; alcohols such as 2-ethylhexanol; and halogen compounds such as tetrachloroethane. The usage ratio of the organic solvent varies depending on the type of the light emitting material, but is usually a ratio at which the concentration of the light emitting material in the light emitting layer forming solution is 0.5 to 10% by weight. As a means for applying the light emitting layer forming solution, for example, a spin coating method, a dipping method, a roll coating method, or the like can be used. As a method for forming the cathode layer 3, a vacuum evaporation method, a sputtering method, or the like can be used.

In the organic EL device according to the first embodiment, the anode layer 2 and the cathode layer 3 are
When a DC voltage is applied between the positive electrode and the negative electrode, the hole transport layer 10 and the light emitting layer 15 emit light, and this light is emitted via the anode layer 2 and the glass substrate 1. Organic EL having such a configuration
Since the hole transport layer 10 contains a specific carbazole-based polymer, the device has a low luminescence starting voltage, high luminous efficiency, and excellent durability.

FIG. 2 is an explanatory sectional view showing the structure of an organic EL device according to a second embodiment of the present invention. The organic EL device according to the first embodiment is different from the organic EL device according to the first embodiment except that the electron transport layer 20 is provided on the light emitting layer 15 and the cathode layer 3 is provided on the electron transport layer 20. It has the same configuration as the element. Examples of the material constituting the electron transport layer 20 include a metal complex of a quinoline-based compound such as an 8-hydroxyquinoline derivative, bisnaphthyloxadiazole,
Oxadiazole-based compounds such as -t-butylphenyl-biphenyl-oxadiazole and 2-naphthyl-5-phenyl-oxadiazole, or polymers containing these residues in the side chain can be used. Such an electron transport layer 20 may be formed by a dry method such as a vacuum evaporation method or a sputtering method, or by dissolving an electron transport material in an appropriate solvent.
The solution can be formed by a wet method in which the solution is applied by a spin coating method, a dipping method, an ink jet method, a printing method, or the like, and dried. In particular, it is preferable to form the electron transport layer 20 by co-evaporating the above-described electron transport material and an alkali metal or an alkaline earth metal. According to the organic EL device according to the second embodiment, the same effects as those of the organic EL device according to the above-described first embodiment can be obtained. In addition, since the electron transport layer 20 is formed, the escape of holes (holes) is prevented, the transport of electrons is smoothed, the emission start voltage is further reduced, and the emission efficiency is further improved. Can be achieved.

FIG. 3 is an explanatory sectional view showing the structure of an organic EL device according to a third embodiment of the present invention. The organic EL device according to the second embodiment is different from the organic EL device according to the second embodiment except that an electron injection layer 25 is provided on the electron transport layer 20 and the cathode layer 3 is provided on the electron injection layer 25. EL
It has the same configuration as the element. As a material constituting the electron injection layer 25, the anode and the electron transport layer are formed from a compound such as a metal fluoride such as LiF, MgF ₂ or CsF, a metal oxide such as AlO ₃ or SrO, or a metal complex such as aluminum. The electron injection layer 25, which can be appropriately selected in consideration of the work function of the constituent material and the LUMO level,
It may be formed on the entire surface of the electron transport layer 20 or may be formed scattered on the surface, and the thickness may be about 0.1 to 20 nm. Such an electron injection layer 25 can be formed by a dry method such as a vacuum evaporation method and a sputtering method. According to the organic EL device according to the third embodiment, the same effects as those of the organic EL devices according to the above-described first and second embodiments can be obtained. Further, since the electron injection layer 25 is formed, the injection of electrons from the anode becomes smooth, the light emission starting voltage is further reduced, and the light emission efficiency can be further improved.

FIG. 4 is an explanatory sectional view showing the structure of an organic EL device according to a fourth embodiment of the present invention. The organic EL device according to the first embodiment is different from the first embodiment except that a hole injection layer 30 is provided on the anode layer 2 and a hole transport layer 10 is provided on the hole injection layer 30. Organic EL related to
It has the same configuration as the element. Examples of the material constituting the hole injection layer 30 include copper phthalocyanine, polyaniline, polythiophene, and a complex of polyethylene dioxythiophene and polystyrene sulfonic acid, which are commercially available under the trade name “PEDOT” (manufactured by Bayer). it can.
Such a hole injection layer 30 may be formed by a dry method such as a vacuum evaporation method or a sputtering method, or by dissolving an electron transport material in an appropriate solvent, and then applying the solution to a spin coating method, a dipping method, an inkjet method, a printing method, or the like. It can be formed by a wet method of coating and drying. In addition, the thickness is 1 to
100 nm. The organic E according to the fourth embodiment
According to the L element, the organic E according to the first embodiment described above is used.
The same effect as that of the L element can be obtained. The hole injection layer 30
Is formed, it is possible to prevent hole injection failure.

FIG. 5 is an explanatory sectional view showing a structure of an organic EL device according to a fifth embodiment of the present invention. The organic EL device according to the fourth embodiment is different from the organic EL device according to the fourth embodiment except that the electron transport layer 20 is provided on the light emitting layer 15 and the cathode layer 3 is provided on the electron transport layer 20. It has the same configuration as the element. As a material constituting the electron transport layer 20, the same material as the organic EL device according to the second embodiment can be used. According to the organic EL device according to the fifth embodiment, the organic EL devices according to the first, second, and fourth embodiments described above.
The same effect as the element can be obtained.

FIG. 6 is an explanatory sectional view showing the structure of an organic EL device according to a sixth embodiment of the present invention. The organic EL device according to the fifth embodiment is different from the organic EL device according to the fifth embodiment except that an electron injection layer 25 is provided on the electron transport layer 20 and the cathode layer 3 is provided on the electron injection layer 25. EL
It has the same configuration as the element. The same material as that of the organic EL device according to the third embodiment can be used as a material forming the electron injection layer 25. According to the organic EL device according to the sixth embodiment, the same effects as those of the organic EL devices according to the above-described first to fourth embodiments can be obtained.

[0053]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to these. In the following, “parts” means “parts by mass”.

[Synthesis of Carbazole Derivative] <Derivative Synthesis Example 1> In a flask equipped with a reflux device, 20 g of carbazole as a starting material, 15 g of potassium hydroxide as a metalating agent, and 80 ml of nitrobenzene were added in this order and added at room temperature. After stirring at 80 ° C., the temperature was raised to 80 ° C. over 1 hour while stirring the system.
After stirring for an hour, the system was immediately heated to 90 ° C.
The reaction solution was obtained by stirring for 5 hours. The obtained reaction solution was cooled and then filtered, and the obtained reaction product was dissolved in acetic acid and recrystallized to obtain a reaction product 15.
g was collected. It was confirmed that the obtained reaction product was N- (p-nitrophenyl) carbazole (hereinafter, referred to as “compound (1)”).

5 g of compound (1) and 80 ml of acetic acid were charged into a three-necked flask equipped with a dropping funnel, and after dissolving compound (1) in acetic acid, 8.2 g of bromine was added dropwise to this system at room temperature for 5 minutes. A reaction solution was obtained by reacting for an hour. The obtained reaction solution was poured into 400 ml of ice water, and the reaction product was precipitated and collected, and was dissolved in tetrahydrofuran (THF) and recrystallized.
7 g of reaction product were obtained. The reaction product obtained is 3,6
-Dibromo [N- (p-nitrophenyl) carbazole] (hereinafter, referred to as “compound (2)”).

In an inert gas atmosphere, 5 g of compound (2) and tris (dibenzylideneacetone) dipalladium (Pd ₂ (db) were placed in a three-necked flask equipped with a reflux device.
a) ₃ ) 3100 mg and 3 g of sodium-t-butoxide were dissolved in 300 ml of m-xylene, and 6.2 g of m-tolylphenylamine and 91 mg of tris (t-butyl) phosphine were added thereto. After stirring at room temperature, the reaction was carried out by heating the system at 120 ° C. for 2 hours. The reaction solution was analyzed by high performance liquid chromatography (HPLC) to confirm that the reaction was completed. The reaction solution was washed with brine, then extracted with ether, dehydrated and dried, and then the solvent was removed. Then, a reaction product (solid) was obtained. The reaction product was dissolved in acetone, and purified by precipitation using methanol to recover 6 g of a reaction product. It was confirmed that the obtained reaction product was 3,6-bis (m-tolylphenylamino) [N- (p-nitrophenyl) carbazole] (hereinafter, referred to as “compound (3)”). .

A pressure reactor was charged with 5 g of compound (3) and palladium carbon (supporting 5% of palladium) in an amount of 10% by mass as a catalyst, and subjected to a hydrogenation reaction in the presence of a dimethylformamide (DMF) solvent. I let it. Thereafter, the catalyst was separated by filtration and purified using a column to obtain a reaction product. The obtained reaction product was 3,6-bis (m-tolylphenylamino) [N-
(P-aminophenyl) carbazole] (hereinafter referred to as “compound (4)”), and its purity was 97% and yield was 85%.

After reacting 3.1 g of compound (4) with 0.53 g of methacryloyl chloride in the presence of twice as much molar amount of triethylamine (dehydrochlorinating agent) as compound (4), triethylamine produced The reaction product was obtained by removing the hydrochloride and the remaining triethylamine. It was confirmed that the obtained reaction product was a carbazole derivative represented by the formula (a) (hereinafter, referred to as “derivative (1)”). In addition, the derivative (1)
Was 85%.

<Derivative Synthesis Example 2> Compound (4) was synthesized in the same manner as in Synthesis Example 1, 5 g of this compound (4) was dissolved in toluene in a flask equipped with a dropping funnel, and 2-isocyanatoethyl was added to the solution. Methacrylate 1.3
g was contacted dropwise at -70 ° C, and the temperature of the system was gradually raised to 30 ° C to complete the reaction. This reaction was quantitative. A reaction product was obtained by separating the obtained reaction solution using a column. It was confirmed that the obtained reaction product was a carbazole derivative represented by the formula (b) (hereinafter, referred to as “derivative (2)”). Further, the purity of the derivative (2) was 98%.

[Synthesis of Specific Carbazole-Based Polymer] <Polymer Synthesis Example 1> After the inside of a pressure-resistant bottle having a volume of 50 ml was replaced with nitrogen gas, the derivative (1) was placed in the pressure-resistant bottle under a nitrogen stream. 20 mmol and 10 ml of N, N-dimethylformamide were charged, and the derivative (1) was dissolved in N, N-dimethylformamide.
While stirring this solution, 2 mmol of azobisisobutyronitrile as a radical polymerization catalyst was added to the solution, and the temperature of the system was raised from room temperature to 70 ° C. to increase the reaction temperature to 70 ° C.
Radical polymerization was carried out at a temperature of 18 ° C. for a reaction time of 18 hours to obtain a polymer solution. The polymer was coagulated by pouring the obtained polymer solution into 50 times the amount of methanol to recover the polymer. The polymer was purified by reprecipitation by a conventional method, and then dried under reduced pressure at 50 ° C. for 1 day. Hereinafter, the obtained polymer is referred to as polymer (A-
1). It was confirmed that the obtained polymer (A-1) was a carbazole-based polymer composed of the specific structural unit represented by the formula (a). Further, the polymer (A-
The weight average molecular weight Mw of 1) was 10,300 in terms of polystyrene by gel permeation chromatography (solvent: tetrahydrofuran), and the ratio Mw / Mn of the weight average molecular weight to the number average molecular weight was 1.5.

Polymer Synthesis Example 2 A polymer was obtained in the same manner as in Polymer Synthesis Example 1 except that 20 mmol of the derivative (1) was used instead of 20 mmol of the derivative (1). Hereinafter, the obtained polymer is referred to as polymer (A-2). It was confirmed that the obtained polymer (A-2) was a carbazole polymer composed of the specific structural unit represented by the formula (b). Further, the weight average molecular weight Mw of the polymer (A-2)
Is 280 in terms of polystyrene by gel permeation chromatography (solvent: tetrahydrofuran).
00, the ratio Mw between the weight average molecular weight and the number average molecular weight.
/ Mn was 1.65.

<Synthesis Example 3> Same as Synthesis Example 1 except that 20 mmol of the derivative (2) was used instead of 20 mmol of the derivative (1), and 20 mmol of N-vinylcarbazole was used together. To obtain a polymer. Hereinafter, the obtained polymer is referred to as a polymer (A-3). Also,
This carbazole-based polymer (A-3) has the formula (b)
And a structural unit derived from N-vinylcarbazole was confirmed to be a carbazole-based polymer. The weight average molecular weight Mw of the polymer (A-3) is 20,000 in terms of polystyrene by gel permeation chromatography (solvent: tetrahydrofuran), and the ratio Mw / Mn of the weight average molecular weight to the number average molecular weight is: 1.65. And the polymer (A-3) contained a specific structural unit of 50% by mass.

<Synthesis Example 4> Except that 20 mmol of the derivative (1) was used instead of 20 mmol of the derivative (1), and 10 mmol of the compound represented by the formula (c) was used together. A polymer was obtained in the same manner as in Combination Synthesis Example 1. Hereinafter, the obtained polymer is referred to as a polymer (A-4).
The carbazole polymer (A-4) is composed of a specific structural unit represented by the formula (b) and a structural unit derived from the copolymerizable monomer represented by the formula (c). It was confirmed that this was a carbazole polymer. The weight average molecular weight Mw of the polymer (A-4) is determined by gel permeation chromatography (solvent: tetrahydrofuran).
And the ratio Mw / Mn of the weight average molecular weight to the number average molecular weight was 1.65. And the polymer (A-4) contained a specific structural unit in an amount of 70% by mass.

Example 1 A hole transport layer forming solution was prepared by dissolving 1.5 parts of the polymer (A-1) in 100 parts of tetrachloroethane. A laminated material in which an ITO film (anode layer) is formed on the surface of a transparent substrate made of 5 cm square glass is prepared.
After applying the prepared hole transport layer forming solution to the surface of the O film by a spin coater, the organic solvent was removed by a heat treatment to form a hole transport layer having a thickness of 25 nm. Next, a light emitting layer made of trisquinolinolate aluminum having a thickness of 50 nm is formed on the hole transporting layer by a vacuum evaporation method, and a surface of the light emitting layer having a thickness of 200 nm and a 5 mm square is formed on the surface of the light emitting layer. By forming an alloy film (cathode layer) of magnesium and silver, an organic EL device having the configuration shown in FIG. 1 was manufactured.

Example 2 An organic EL device was manufactured in the same manner as in Example 1 except that the polymer (A-2) was used instead of the polymer (A-1).

Example 3 An organic EL device was manufactured in the same manner as in Example 1 except that the polymer (A-3) was used instead of the polymer (A-1).

Example 4 An organic EL device was manufactured in the same manner as in Example 1 except that the polymer (A-4) was used instead of the polymer (A-1).

Example 5 Instead of the polymer (A-1), the polymer (A-2) was mixed with N-vinylcarbazole and 2- (4-vinylphenyl) -5-naphthyl-1,
3,4-oxadiazole copolymer (molar ratio 9: 1)
An organic EL device was manufactured in the same manner as in Example 1 except that a mixture of a compound having a weight average molecular weight (Mw) of 19000) and a weight ratio of 1: 1 was used. In this organic EL device, the proportion of the specific structural unit in all the polymers constituting the hole transport layer is 50% by mass.

Comparative Example 1 Except that N-polyvinylcarbazole was used instead of the polymer (A-1),
An organic EL device for comparison was manufactured in the same manner as in Example 1.

[Evaluation of Organic EL Element] (1) Emission starting voltage and maximum emission luminance: For each of the organic EL elements according to Examples 1 to 5 and Comparative Example 1, an ITO film was used as an anode, and magnesium and By applying a DC voltage using the silver alloy film as a cathode, the light emitting layer emits light, and the maximum light emission luminance is measured by a luminance meter “L”.
S-100 "(manufactured by Minolta). Also,
The light emission starting voltage at that time is indicated by a voltmeter “R8240” (AD
VANTEST). (2) Durability: With respect to each of the organic EL elements according to Examples 1 to 5 and Comparative Example 1, the light emitting layer was caused to emit light with the applied current kept constant at 15 mA, and the light emission luminance was initially set from the start of light emission. The half-life of the organic EL element according to Comparative Example 1 was measured by measuring the time (half-life) until the emission luminance was reduced to half (hereinafter, “half-life”).
That. ). The results are shown in Table 1 below.

[0071]

[Table 1]

As is clear from Table 1, the organic EL devices according to Examples 1 to 5 have a lower light emission starting voltage, a higher light emission luminance, and a higher luminance than the organic EL device according to Comparative Example 1. It was confirmed that the product had excellent durability.

[0073]

As described above, according to the present invention,
It is possible to provide an organic electroluminescence device having a low light emission starting voltage, high light emission efficiency, and excellent durability.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing a configuration of an organic electroluminescence element according to a first embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view showing a configuration of an organic electroluminescence element according to a second embodiment of the present invention.

FIG. 3 is an explanatory cross-sectional view showing a configuration of an organic electroluminescence element according to a third embodiment of the present invention.

FIG. 4 is an explanatory cross-sectional view showing a configuration of an organic electroluminescence element according to a fourth embodiment of the present invention.

FIG. 5 is an explanatory cross-sectional view showing a configuration of an organic electroluminescence element according to a fifth embodiment of the present invention.

FIG. 6 is an explanatory cross-sectional view showing a configuration of an organic electroluminescence element according to a sixth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Anode layer 3 Cathode layer 5 DC power supply 10 Hole transport layer 15 Light emitting layer 20 Electron transport layer 25 Electron injection layer 30 Hole injection layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09K 11/06 690 C09K 11/06 690 H05B 33/14 H05B 33/14 A (72) Inventor Mitsuhiko Sakakibara Tokyo 2-11-24 Tsukiji, Chuo-ku, Tokyo, Japan JSR Co., Ltd. (72) Inventor Hiroyuki Yasuda 2-11-24 Tsukiji, Chuo-ku, Tokyo Inside JR Srl, Inc. (72) Inventor Yasunori Negoro, Tsukiji Chuo-ku, Tokyo F-term (reference) within 2-11-11 JSR Co., Ltd. 3K007 AB02 AB06 AB11 CA01 CB01 DA01 DB03 EB00 4J100 AB07P AL08P AM21P BA27P BA37P BC43P BC65P CA01 DA01 DA04 FA03 JA32

Claims (3)

[Claims] 1. A structural unit represented by the following general formula (1):
Transport layer containing carbazole-based polymer having
An organic electroluminescent device characterized by comprising
Sense element. Embedded image[Wherein, R¹Is a hydrogen atom, an alkyl group or a phenyl group
And R^Two, R^Three, R ^FourAnd R^FiveAre independent
To hydrogen, alkyl, alkoxy, phenyl, etc.
Or a dialkylamino group. X is a single bond or
Is a phenylene group, a carbonyl group or one of them
Or a divalent organic group containing both. ] 2. The carbazole polymer has the general formula (1)
The organic electroluminescence device according to claim 1, wherein the organic electroluminescence device contains 5% by mass or more of a structural unit represented by: 3. The hole transporting layer comprises a carbazole polymer having a structural unit represented by the general formula (1) and a polymer other than the carbazole polymer. 3. The organic electroluminescent device according to claim 1, wherein the proportion of the structural unit represented by the general formula (1) in all the polymers constituting the layer is 5% by mass or more. 4.