JPH11255716A - Tetra-substituted diamine compound, organic electroluminescent element by using the compound, and organic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new tetra-substituted diamine compound having good luminous efficiency, high intensity luminescence, luminescence at a low driving voltage, or the like, capable of providing an organic EL element stable for a long period, and useful as a positive hole-injected and transporting layer compound in a transporting layer. SOLUTION: This compound is a tetra-substituted diamine compound of formula I Y is a 6-12C aryl, a 1-4C alkyl or a 7-14C aralkyl; X is a 6-12C arylene or the like; R1 and R2 are each H, a 1-4C alkyl or a 6-12C aryl, or form a group of formula II [(n) is 2 or 3; R4 and R5 are each H, a 1-4C alkyl or the like] by binding to each other through C atoms each bonding to the R1 or the R2 }. The compound of formula I in which X is a substituted phenylene is readily obtained, for example, by heating and refluxing an N-substituted diamino compound and an aldehyde derivative in an equivalent ratio of (1:3) to (1:5), and removing the formed water to the exterior of the reaction system. The compound is useful as a component of a positive hole-injected and transporting layer for an organic EL element having a base structure of a cathode/ a luminescent layer/an anode.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tetra-substituted diamine compound having a novel structure, an organic electroluminescence device and an organic photoreceptor using the compound, and more particularly, to a low driving voltage and good luminous efficiency. The present invention relates to a tetra-substituted diamine compound capable of constituting an organic electroluminescent device, an organic electroluminescent device using the compound, and an organic photoreceptor for a printer and a copying machine.

[0001]

2. Description of the Related Art In recent years, organic electroluminescent devices (hereinafter abbreviated as EL devices) have characteristics such as high self-luminous properties, high visibility recognition, and excellent solid-state impact resistance. Therefore, application to various displays, backlight lamps, and the like has attracted attention.

This EL element includes an inorganic EL element using an inorganic compound for a light emitting layer and an organic EL element using an organic compound.
There is an element. Among these EL devices, organic EL devices have been actively studied for practical use for the purpose of lowering the applied voltage and supporting full color.

An organic EL device has a basic structure of an anode / light-emitting layer / cathode, and a hole injection / transport layer having a function of efficiently transferring holes injected from the anode to the light-emitting layer, or an injection from the cathode. It is well known that an electron injecting and transporting layer having a function of efficiently transmitting the transferred electrons to the light emitting layer is appropriately provided.

Among the organic EL devices having such a structure, various devices having a structure of anode / hole injection / transport layer / light emitting layer / cathode have been proposed as having particularly excellent performance. (U.S. Pat.Nos. 4,539,507 and 4,769,292
JP-A-59-194393, JP-A-63-295695, etc.). For example, in the organic EL device having the above structure, by using a material having excellent thin film forming properties for the hole injecting and transporting layer, the total thickness of the hole injecting and transporting layer and the light emitting layer can be reduced to 150 n.
m, and as a result, high-luminance light emission has been successfully obtained with a drive voltage of 20 V or less.

[0005] Further, a triphenylamine-based hole injection / transport compound which does not transport electrons and acts as a barrier against electrons is used for the hole injection / transport layer, and an interface between the hole injection / transport layer and the light emitting layer is formed. By accumulating electrons at this interface in the light emitting layer due to the electron barrier existing in the light emitting layer, and further using an aluminum (III) complex as a material for the light emitting layer, 10 V
With the following low applied voltage, a green color with high luminance of 1000 cd / m ² is realized with a high luminous efficiency of 1.5 lumen / V.

Incidentally, since the organic EL element has a light-emitting mechanism of recombination of electrons and holes, it should be possible to drive at a low voltage (2 to 6 V) as much as a light-emitting diode.
However, at present, the driving voltage is 8 V or more. This is due to the energy barrier against hole injection existing at the interface between the anode and the hole injection transport layer or the energy barrier against electron injection existing at the interface between the light emitting layer and the cathode. Furthermore, it is said that the upper limit of the general quantum efficiency of light emission is about 40%, but it is still about 3% in an organic EL device.

As described above, the organic EL device having the structure of the anode / hole injection / transport layer / light emitting layer / cathode has better performance than the organic EL devices of other structures, The luminous efficiency is not always satisfactory. Further, the organic EL element is an inorganic EL element.
The problem that the deterioration characteristics of the constituent material is not as good as that of the element and the problem that the element cannot withstand long-time use has not been solved yet.

The present invention has been made in view of the above problems, and has good luminous efficiency, high-luminance luminescence, luminescence at a low driving voltage, chemicals such as water or oxygen, and physical phenomena such as light and heat. An object is to provide an organic EL element with small deterioration.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to develop an EL device having the above-mentioned excellent characteristics, and as a result, the basic structure of the anode / light-emitting layer / cathode has at least transport. When the above-mentioned tetra-substituted diamine compound is used as the hole injection transport layer compound in the layer, the energy barrier of the charge injection existing at each interface is relaxed, and a lower drive voltage becomes possible, and high luminous efficiency and It has been found that a long-term stable organic EL element can be obtained, and the present invention has been completed. That is, according to the present invention, the formula (I)

Embedded image [In the formula, Y is a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, an alkyl group having 1 to 4 carbon atoms, and 7-14 carbon atoms.
X is a substituted or unsubstituted aralkyl group;
12 substituted or unsubstituted arylene groups, having 2 to 2 carbon atoms
6 substituted or unsubstituted cyclic or linear alkylene groups; R ₁ and R ₂ are the same or different and each are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted aryl having 6 to 12 carbon atoms. The group, or R ₁ and R ₂ , together with the carbon atom to which they are attached,

Embedded image (Where R ₄ and R ₅ are the same or different and form a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and n is 2 or 3). Good] is provided. Also,
According to the present invention, an anode, a hole injecting and transporting layer, a light emitting layer, and a cathode are laminated on a substrate in this order, and the hole injecting and transporting layer comprises a tetra-substituted diamine compound represented by the above formula (I). An organic electroluminescent device is provided.

BEST MODE FOR CARRYING OUT THE INVENTION The tetra-substituted diamine compound of the present invention is a compound having a novel structure. However, on the other hand, the synthesis method is generally well-known,
For example, the method described in Tetrahydrone Report No. 138, p3363 and the like can be applied.

The tetra-substituted diamine compound of the formula (I) of the present invention has the following structure

[0011]

Embedded image

Wherein Y is a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 14 carbon atoms;
Is a substituted or unsubstituted arylene group having 6 to 12 carbon atoms, a substituted or unsubstituted cyclic or linear alkylene group having 2 to 6 carbon atoms; R ₁ and R ₂ are the same or different and are each a hydrogen atom, 1-4 alkyl groups, 6-carbon atoms
The 12 substituted or unsubstituted aryl groups, or R ₁ and R ₂ , together with the carbon atom to which they are attached, have the formula

Embedded image (Where R ₄ and R ₅ are the same or different and form a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and n is 2 or 3). Good] and one of the features is that the width between the melting point (MP) and the glass transition point (Tg) is small.

The "aryl group having 6 to 12 carbon atoms" of the "substituted or unsubstituted aryl group having 6 to 12 carbon atoms" in Y includes, for example, phenyl group, tolyl group,
And a naphthyl group. Of these, a phenyl group and a naphthyl group are preferred. Examples of the “substituent of an aryl group” include, for example, a halogen atom, a lower (C _1-4 ) alkyl group (e.g., a methyl group, an ethyl group, a propyl group) and a lower (C
_1-4 ) Alkoxy groups (methoxy group, ethoxy group, propoxy group, etc.), trifluoromethyl group, nitro group, hydroxy group, amino group, phenyl group and the like. Among them, an electron donating group such as an alkyl group, an alkoxy group, a hydroxy group, and an amino group are preferable. Specific examples of the “substituted or unsubstituted aryl group having 6 to 12 carbon atoms” include, for example, a phenyl group, an α-naphthyl group, a β-naphthyl group,
-Tolyl group, m-methoxyphenyl group, p-methoxyphenyl group, o-methoxyphenyl group, m-ethoxyphenyl group, p-ethoxyphenyl group, o-ethoxyphenyl group, p-biphenyl group, 3,4-methylene Dioxyphenyl group, p-diphenylaminophenyl group, 3,4-
And a dimethylphenyl group.

"C1-C4 alkyl group" for Y
Examples thereof include a methyl group, an ethyl group, a propyl group, a t-butyl group, a butyl group and the like. "C 7
Examples of the “aralkyl group having 7 to 14 carbon atoms” of the “substituted or unsubstituted aralkyl group having 1 to 14 carbon atoms” include a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group,
Examples include a naphthylethyl group, and among them, a benzyl group is preferable. Further, as a substituent of the "aralkyl group",
The same substituents as in the case of the aryl group can be mentioned.

The "arylene group having 6 to 12 carbon atoms" of the "substituted or unsubstituted arylene group having 6 to 12 carbon atoms" in X includes, for example, phenylene group, tolylene group,
And a naphthylene group. Of these, a phenylene group and a naphthylene group are preferred. Examples of the “substituent of an arylene group” include, for example, a halogen atom, a lower (C _1-4 ) alkyl group (eg, a methyl group, an ethyl group and a propyl group), and a lower (C _1-4 ) alkoxy group (a methoxy group, Ethoxy group, propoxy group, etc.), trifluoromethyl group, nitro group, hydroxy group, amino group, phenyl group and the like. Of these, a halogen atom, a lower (C _1-4 ) alkyl group (eg, a methyl group, an ethyl group, a propyl group) and a lower (C _1-4 ) alkoxy group (eg, a methoxy group, an ethoxy group, a propoxy group) are preferred. Specific examples of the “substituted or unsubstituted arylene group having 6 to 12 carbon atoms” include o-
Phenylene group, m-phenylene group, p-phenylene group,
2-methyl-p-phenylene group, 4,4′-biphenylene group, 3,3′-dichloro-4,4′-biphenylene group, 3,3′-dimethyl-4,4′-biphenylene group,
3,3′-dimethoxy-4,4′-biphenylene group,
Examples thereof include a 1,5-diaminonaphthalene group.

In X, the "C2-C6 substituted or unsubstituted cyclic or linear alkylene group"
Examples of the "cyclic or chain alkylene group Nos. To 6" include an ethylene group, a propylene group, a butylene group, a pentene group, a hexene group, a cyclopropylene group, a cyclobutylene group, a cyclopentene group, and a cyclohexene group. Examples of the “substituent for a cyclic or chain alkylene group” include a halogen atom, a lower (C _1-4 ) alkyl group (eg, a methyl group, an ethyl group, and a propyl group), and a lower (C _1-4 ) alkoxy group ( Methoxy, ethoxy, propoxy, etc.),
Examples include a trifluoromethyl group, a nitro group, a hydroxy group, an amino group, and a phenyl group. Specific examples of the "substituted or unsubstituted cyclic or chain alkylene group having 2 to 6 carbon atoms" include an ethylene group, a butadiene group, a 1,1-cyclohexalene group, and a 1,1-cyclopentalene group. Can be

The "alkyl group having 1 to 4 carbon atoms" for R ₁ and R ₂ includes a methyl group, an ethyl group, a propyl group and a butyl group.

The "aryl group having 6 to 12 carbon atoms" of the "substituted or unsubstituted aryl group having 6 to 12 carbon atoms" of R ₁ and R ₂ and the "substituent" thereof are the same as those in Y. . Among them, an electron donating substituent such as a methoxy group is preferable. This substituent is preferably substituted at the m-position and the p-position of the aryl group.

Further, "the number of carbon atoms 1 for R ₄ and R ₅
The “alkyl group of 4” is the same as defined for Y. Also,
Examples of the "alkoxy group having 1 to 4 carbon atoms" include a methoxy group, an ethoxy group, a propoxy group and a butoxy group. Among the above compounds (I), compounds of the formula (II)

[0020]

Embedded image

And formula (III)

[0022]

Embedded image

And formula (IV)

[0024]

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The compound of the formula (1) is preferred. Specific examples of the compound of the present invention are shown below.

[0026]

[Table 1] Of the compounds in Table 1, compounds in which R ₁ and R ₂ are both phenyl or naphthyl, ie, Nos. 1, 2,
3, 6, and 11 are preferable because they are excellent in terms of synthesis, cost, and organic EL characteristics.

[0027]

[Table 2]

Among the compounds in Table 2, Y is a phenyl group or a naphthyl group, a phenyl group substituted with an electron donating group,
A benzyl group substituted with an electron donating group, X is a p-phenylene group, and R ₁ and R ₂ are both hydrogen atoms are preferable from the viewpoint of materials. The electron donating group preferably has a van der Waals radius of 4 ° or less. In addition, the compounds shown in the above Table 2 correspond to the following formulas (A) and (B)

[0029]

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Is a kind of compound having a basic structure of formula (A) and (B), although the compound of the present invention has a high melting point as shown in Table 3, Relatively low melting point and excellent amorphous properties. For this reason, it is excellent in preparation and holding and stable crystallization of a stable coating solution. It is considered that the reason for this is that the symmetry point is largely broken by the substituent Y, and a bulky enamine compound having a high molecular weight is contained.

[0031]

[Table 3]

Next, a method for synthesizing the tetra-substituted diamine compound of the present invention, in particular, the compound (II) will be described.

[0033]

Embedded image

(Wherein, Y and R _{1 to} R ₃ have the same meanings as described above). Particularly, when the compound (IV) is synthesized, it can be represented by the following reaction formula.

[0035]

Embedded image

(Wherein X, Y, R ₄ , R ₅ and n have the same meanings as described above) In the above reaction, the N-substituted diamino compound and the aldehyde derivative are used in an equivalent ratio of about 1: 3 to 1: 5. The reaction can be easily carried out by heating under reflux in an organic solvent to remove generated water out of the reaction system. As the organic solvent at this time, a solvent in which the raw material compound is easily dissolved and is hardly miscible with water is preferable, and examples thereof include benzene, toluene, xylene, chlorobenzene, ethyl acetate, and n-butanol. These organic solvents are preferably added in a slight excess to prevent bumping. In order to smoothly carry out the above reaction, it is preferable to carry out the reaction in an acidic atmosphere, and in some cases, in an alkaline atmosphere. To create an acidic atmosphere, p
-A trace amount (for example, about 0.01 equivalent ratio) of toluenesulfonic acid or the like can be used. The reaction temperature is preferably near the boiling point of the solvent used, and the reaction time is suitably about 4 to 5 hours. As a method for removing generated water out of the system, an azeotropic method can be applied.

The organic EL device of the present invention is mainly constituted by laminating an anode, a hole injection / transport layer, a light emitting layer and a cathode on a substrate in this order. In addition, these substrate-anode, anode-hole injection transport layer, hole injection transport layer-light emitting layer, light emitting layer-
Optionally, an intermediate layer such as an electron injection layer, a charge blocking layer, and a buffer layer may be provided between the cathodes. In particular, it is preferable that an electron injection layer is formed between the light emitting layer and the cathode, and a charge barrier layer is formed facing the light emitting layer.

As the charge barrier layer facing the light emitting layer, there are two types, a hole barrier layer and an electron barrier layer, and the electron barrier layer is preferable because it is more efficient. The expression “formed so as to face the light emitting layer” means that in the case of an electron barrier layer, it is preferably provided between the light emitting layer and the hole injection / transport layer, preferably in contact with the anode side surface of the light emitting layer. In the case of a hole blocking layer, it is preferably provided between the light emitting layer and the cathode, preferably in contact with the cathode side surface of the light emitting layer.
Specifically, (1) anode / hole injection / transport layer / light emitting layer / cathode (2) anode / hole injection / transport layer / light emitting layer / electron injection / transport layer / cathode (3) anode / hole injection / transport layer / Electron barrier layer / light emitting layer / cathode (4) anode / hole injection / transport layer / electron barrier layer / light emitting layer / electron injection / transport layer / cathode (5) anode / hole injection / transport layer / electron barrier layer / light emitting layer / Hole barrier layer / electron injection / transport layer / cathode.

It is preferable that the organic EL device is supported on a substrate. The substrate is not particularly limited as long as it is generally used for an organic EL device, and examples thereof include a substrate made of glass, transparent plastic, and quartz. Further, a desired insulating layer, an element, a circuit, and the like, a desired insulating layer, and the like may be formed over these substrates. However, when the layer configuration is multi-layered, the organic EL
Since problems such as difficulty in controlling the production of the element also increase, it is preferable to make the element structure as simple as possible.

Examples of the anode in the present invention include a metal, an alloy, a conductive compound, a transparent conductive compound, and a mixture thereof having a large work function (4 eV or more) as an electrode material. Above all, it is common to take out light emission from the anode side, and thus a transparent conductive compound is preferable. The anode can be formed in a thin film shape by the above-mentioned metal or the like by a method such as vapor deposition or sputtering.

When light emission is taken out by the anode, it is necessary to increase the transmittance, so that the seal resistance is preferably about several tens Ω or less. The thickness of the anode varies depending on the electrode material used.
About 300 nm is preferable.

The hole injection / transport layer according to the present invention has a function of transmitting holes injected from the anode to the light emitting layer described later. The hole injection transport layer contains the compound represented by the above formula (I). The compound represented by the formula (I) is most suitable as a main material of the hole injecting / transporting layer because of its excellent thermal stability, high transfer efficiency, low driving voltage, retention of amorphousness, and the like.

The compound represented by the above formula (I) is
By optionally using it in combination with another transporting material, an organic EL element having higher luminance and lower driving voltage and higher luminous efficiency may be obtained in some cases. Such a transport material is selected from those conventionally known as a hole transport compound of an organic optical semiconductor and those conventionally known as a hole injection compound of an organic EL device. can do. For example, triazole compounds (US Pat. No. 3,112,197), pyrazoline compounds (US Pat. No. 3,180,729), arylamine compounds (US Pat. No. 3,567,450,
3,180,703), porphyrin compounds (JP-A-63-29569), styrylamine compounds (U.S. Pat. No. 4,127,412, JP-A-54-5844).
No. 5, JP-A-54-149634).
When these compounds are used in combination, thermal decomposition or the like is likely to occur due to the effect of mixing and fusion.

The light emitting layer according to the present invention is composed of an organic compound having a light emitting property in a solid state, and has at least (1) an injection performance capable of injecting holes from an anode or a hole injection layer when an electric field is applied; ) One of the following: a transport function for transferring injected charges (electrons or holes) by the force of an electric field; or (3) a light-emitting function for providing a field of recombination of electrons and holes and connecting the same to light emission; Preferably, it has all functions. The thickness of the light emitting layer is 10 nm to 200
A thin film having a thickness of about 0 nm is preferable. Note that the light-emitting layer may have a difference between the ease with which holes are injected and the ease with which electrons are injected, and may have a large or small transport function represented by the mobility of electrons and holes. It is preferable that at least one of the charges can be moved.

In the injection function of the above (1), the ionization energy of the light emitting layer is preferably about 6.0 eV or less, since it is relatively easy to inject holes if an appropriate anode material is selected. If a suitable cathode material is selected, electrons are relatively easy to inject, so the electron affinity is 2.5 eV
It is preferable that it is not more than about. As for the light emitting function of the above (3), it is desirable that the fluorescent property in the solid state is strong.

The organic compound constituting the light emitting layer is not particularly limited, and any compound can be selected from known compounds. For example, polycyclic fused aromatic compounds; fluorescent brighteners such as benzothiazole, benzimidazole, and benzoxazole; metal chelated oxinoid compounds; styryl compounds.

Examples of the polycyclic condensed compound include a condensed ring light emitting compound having an anthracene, naphthalene, phenathrene, pyrene, and perylene skeleton, and another condensed ring light emitting material having eight condensed rings.

As the fluorescent whitening agent, for example, JP-A-59
No. 194393.

Examples of the metal chelated oxinoid compound include those described in JP-A-63-295695.

Examples of the styryl compound include those described in JP-A-62-31356 or JP-A-63-80257.

The light emitting layer may optionally have a laminated structure of two or more layers. For example, U.S. Pat.
As described in No. 292, a laminated structure of a host substance and a fluorescent substance may be used. In this case, the host material is a thin film-like layer, which is responsible for part of the functions of the light emitting layer, such as the injection / transport function and the light emitting function. The fluorescent material is present in the host material layer in a small amount (several%). In addition, it has only a part of the light emitting function of emitting light in accordance with the combination of electrons and holes.

The fluorescent substance used in the light emitting layer may be a compound having no thin film forming property.
1,4,4-tetraphenyl-1,3-butadiene and the like can also be used.

The method of thinning these organic light emitting materials is as follows.
For example, a spin coating method, a casting method, an LB method, an evaporation method and the like can be mentioned, and among them, an evaporation method is preferred, in which a uniform film is easily obtained and a pinhole is hardly generated. When using the evaporation method, the deposition conditions may, sublimation temperature of the organic material used, the thin film of interest state, crystalline, varies due orientation of the crystal, generally board heating temperature 50 to 500 ° C., vacuum degree of 10 ^{- 6} to 10 ^-3 Pa, deposition rate 0.01 to 50 nm / sec, substrate temperature -50 to +30
It can be appropriately selected within a range of 0 ° C. and a film thickness of 5 nm to 500 nm.

As the cathode in the present invention, metals, alloys, conductive compounds, and the like having a small work function (about 4 eV or less) can be used.
Examples thereof include those using a transparent conductive compound and a mixture thereof as an electrode material. In general, it is preferable that one of the anode and the cathode is transparent or translucent because the efficiency of extracting light emission is high. The cathode can be formed from the above-mentioned metal or the like into a thin film by a method such as vapor deposition or sputtering. Note that the cathode seal resistance, film thickness, and the like can be the same as those of the anode.

In the present invention, the optional electron injecting and transporting layer is made of an electron transporting compound, and has a function of transmitting electrons injected from the cathode to the light emitting layer. The electron transfer compound is not particularly limited, and may be appropriately selected from known compounds. Such compounds include, for example,
Nitro-substituted fluorenone compounds, thiovirane dioxide compounds, diphenylquinone compounds, anthraquinodimethane compounds (JP-A-57-149259 or 58-55)
No. 450), anthran compounds (JP-A-61-2251)
No. 51, No. 61-233750).

In the present invention, among the charge barrier layers which can be provided arbitrarily, the electron barrier layer has a role of retaining electrons which are going to the anode side from the light emitting layer in the light emitting layer. Preferably, the layer has an electron mobility lower than the electron mobility of the layer or a layer having an electron affinity lower than the electron affinity of the light emitting layer.

Such an electron barrier layer is made of a triphenyldiamine compound or a triphenylamine compound (for example, JP-A-59-194393 or JP-A-63-29556).
95, and inorganic amorphous compounds (for example, those described in JP-A-3-77299). Above all, the following formula (V)

[0058]

Embedded image

Wherein A is an oxygen atom, a bond, —CH
(R ₇₎ - or

[0060]

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(Where R ₇ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group, and m is 4 or 5), and B is an alkyl having 1 to 4 carbon atoms. A substituted or unsubstituted aryl group having 6 to 12 carbon atoms, and R ₆ represents a hydrogen atom, a halogen atom, a methylenedioxy group, an alkyl group having 1 to 4 carbon atoms,
Which is an alkoxy group of the formula (I).
The mobility of the amine compound has an appropriate correlation with the mobility of the compound of the formula (I), and
This is because the ionization energy is considered to be mostly between the light emitting material and the compound of the formula (I).

Examples of the "alkyl group having 1 to 4 carbon atoms" for R ₇ include a methyl group, an ethyl group, a propyl group, a butyl group and a t-butyl group. Examples of the “substituent” of the “substituted or unsubstituted phenyl group” include a methyl group, an ethyl group, a methoxy group, an ethoxy group, and a halogen atom.

"An alkyl group having 1 to 4 carbon atoms" in B
Is the same as in R _7. In addition, “C 6-12
The substituted or unsubstituted aryl group of "is the same as defined for Y in formula (I).

[0064] "alkyl group having 1 to 4 carbon atoms" in R _6, an "alkoxy group having 1 to 4 carbon atoms" are the same as in R _3.

Preferred examples of the compound (V) are shown below.

[0066]

Embedded image

[0067]

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The hole barrier layer has a role of keeping holes going to the cathode side from the light emitting layer in the light emitting layer, and has a hole mobility lower than the hole mobility of the light emitting layer. It is preferable that the light-emitting layer has a lower energy than the light-emitting layer. Such a hole blocking layer is made of an inorganic amorphous compound (JP-A-3-772).
No. 99) is preferred. Among them, N-type α-SiC is preferable. The charge barrier layer preferably has a thickness of 1 to 200 nm, preferably 50 nm or less.

In the present invention, an optional buffer layer may be further provided. The buffer layer is a layer for the purpose of preventing the separation phenomenon and improving the injection efficiency of holes or electrons. These buffer layers are composed of various phthalocyanine pigments,
Various organic metal compounds (for example, trialkoxyaluminum, zinc stearate, aluminum triacetylacetone, magnesium diacetylacetone), carbon black, and the like. The position of the buffer layer is
Although not particularly limited, in the case of the above (1) where the peeling phenomenon is likely to occur, the distance between the anode and the hole injection / transport layer is
It is effective to provide between the light emitting layer and the cathode, and in the above cases (2) to (5), between the anode and the hole injection and transport layer and between the electron injection and transport layer and the cathode. The thickness of the buffer layer varies depending on where it is provided.
About nm is preferable.

Next, a preferred method of manufacturing the organic EL device of the present invention will be described. The organic EL device having the configuration of (1) anode / hole injection / transport layer / light emitting layer / cathode can be manufactured as follows.

First, a thin film made of a desired anode material is formed on a suitable substrate in a thickness of 500 nm or less, preferably 10 to 300 nm.
An anode is formed by a method such as evaporation or sputtering so that the thickness is in the range of nm. Next, the compound of the present invention is formed into a thin film on the anode by a method such as vapor deposition or spin coating to form a hole injection / transport layer. In this case, the film thickness is preferably about 5 to 200 nm in order to increase the transparency when light is emitted from the substrate side. Subsequently, an organic luminescent material was deposited on the hole injection transport layer composed of the compound of the present invention by an evaporation method for 5 to 1500 n.
The light emitting layer is formed by stacking layers having a thickness in the range of m. afterwards,
On the light-emitting layer, a thin film made of a material for a cathode is laminated with a thickness of 500 nm or less, preferably in a range of 10 to 300 nm by a method such as vapor deposition or sputtering to form a cathode. Note that the above method may be performed in the reverse process from the cathode side.

The organic EL device having the constitution of (2) anode / hole injecting / transporting layer / light emitting layer / electron injecting / transporting layer / cathode has a structure in which an organic compound is formed on the light emitting layer by vapor deposition or sputtering or plasma CVD. N-type a-SiC is formed into a thin film by the method, an electron injection / transport layer having a thickness of about 100 nm or less is formed, and then a cathode is formed in the same manner as in (1) above. it can.

The organic E having the above-mentioned constitutions (3) to (5)
The L element can also be manufactured according to the above (1) and (2).

The organic EL of the present invention thus obtained
When a DC voltage is applied to the device, when a voltage of about 1 to 30 V is applied with a positive polarity of the anode and a negative polarity of the cathode, light emission can be observed from the transparent or translucent electrode side. Note that no light emission occurs even when a voltage is applied with the opposite polarity. When an AC voltage is applied, light is emitted when the anode is in the positive state and the cathode is in the negative state. The waveform of the applied AC voltage may be arbitrary.

Hereinafter, examples of the tetra-substituted diamine compound of the present invention, a method for producing the same, and an organic electroluminescent device will be described.

Synthesis Example 1 (Synthesis of Exemplified Compound 1) 18.4 g of p-aminodiphenylamine and 65.0 g of diphenylacetaldehyde were dissolved in 500 ml of benzene. About 0.1 g of p-toluenesulfonic acid was added thereto, and the mixture was heated and refluxed in an oil bath, and the generated water was removed from the system by a Dean-Stark tube.

Further, benzene dehydrated with anhydrous sodium sulfate was added to the above mixture, and the mixture was heated under reflux until the presence of water was no longer observed. Activated carbon and a small amount of benzene were added to the residue, followed by filtration, and then a small amount of ethanol was added, whereby yellowish-white crystals were deposited on the entire surface. The precipitate was taken out and recrystallized from 1000 ml of ethyl acetate. The thus obtained crystal was a yellow-white crystal having a little blue fluorescence and weighed 38.4 g. Melting point 198.5-20
0.0 ° C., the glass transition point was 124.5 ° C. IR (KBr) disappearance of 3380 cm ^-1 (NH) 16
10 cm ^-1 (C = C) MS (m / z) 718 (M ⁺ ) Note that other compounds in Table 1 can be synthesized according to Synthesis Example 1 described above.

Synthesis Example 2: Synthesis of Exemplified Compound 12 3.6 g of p-aminodiphenylamine and 10 g of 1-formyl-1,2,3,4-tetrohydronaphthalene were dissolved in 100 ml of dry benzene. 0.2 g of p-toluenesulfonic acid was added thereto, and the mixture was heated to reflux using a Dean-Stark tube. Dry benzene was supplied from the dropping funnel so that about 50 ml of benzene always remained. With water completely removed, the insolubles during the hot reaction were removed, and benzene was further removed. The obtained yellow-white powder was recrystallized from IPA to obtain 7.3 g of white granular crystals. Melting point 118.5 ° C. MS (m / z) 601 (M ⁺ )

Examples 1-4 As a transparent electrode, a glass substrate (25 mm × 75 mm × 1.1 mm) on which a 5 nm-thick ITO was deposited was used as a transparent support substrate. This transparent support substrate was subjected to ultrasonic cleaning with ethanol and then with acetone. Thereafter, the transparent support substrate was dried with dry nitrogen gas. The transparent support substrate thus obtained was fixed to a substrate holder of a vacuum evaporation apparatus, and sublimated and purified in a molybdenum resistance heating boat in an amount of 200 mg of each tetra-substituted diamine compound shown in Table 4 below.
The pressure inside the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa.

First, the boat containing the tetra-substituted diamine compound was heated to 230 to 240 ° C.
A hole injection / transport layer having a thickness of 50 to 75 nm was deposited on the substrate at a deposition rate of 秒 0.3 nm / sec. The substrate temperature at this time was room temperature. Without taking out the hole injection transport layer thus obtained from the vacuum chamber, tris- (8-hydroxyquinolinol) aluminum was deposited thereon at a boat temperature of 250 ° C. and a deposition rate of 0.1 to 0.2.
The light emitting layer was deposited on the substrate at a rate of 5 nm / sec to form a 50 nm thick light emitting layer.

This was taken out of the vacuum chamber, and a stainless steel mask was placed on the light emitting layer side, and fixed again to the substrate holder. Then, 0.5 g of silver (Ag) wire is put in a tungsten basket, 1 g of magnesium (Mg) is put in a molybdenum boat, the pressure in the vacuum chamber is reduced to 1 × 10 ⁻⁴ Pa, and Mg and Ag are co-deposited. A cathode was formed into a film to produce an organic EL device. With respect to each of the organic EL devices thus manufactured, the current flowing in the air when a DC voltage of 15 V was applied, the luminance at that time, and the light emission start voltage value were measured. Table 4 shows the results.
Shown in

[0082]

[Table 4]

As is clear from Table 4, the organic E using the tetra-substituted diamine compound of the present invention as a hole transport material
It turned out that the L element starts emitting light at a very close driving voltage, has a high luminance, and has excellent organic EL characteristics.

Examples 5 to 7 In the same manner as in Example 1, Exemplified Compound 1 was used as a hole injecting and transporting material, and an amine compound 3 shown in Table 5 was placed between the hole injecting and transporting layer and the light emitting layer. Each kind of electron barrier layer was produced. The manufacturing conditions are as follows.
The pressure was reduced to about × 10 ⁻⁴ Pa and the temperature was 250 ° C. The thickness of this electron barrier layer was about 20 nm.

The current value, luminance, and light emission starting voltage of each of these organic EL devices were measured according to Examples 1 to 4.
Table 5 shows the results.

[0086]

[Table 5]

As is clear from Table 5, by newly providing an electron barrier layer, light emission with higher luminance and a lower light emission start drive voltage became possible.

Example 8 The organic EL device prepared in Example 1 was subjected to a temperature of 0 ° C. and a humidity of 50.
%, And stored for one month in an environment of%, the luminance and the light emission start drive voltage were measured in the same manner as in Example 1. The values at this time were exactly the same as the values in Table 4. Also, 500c
Even after emission for 24 hours at d / m ² , generation of voids due to crystallization of Exemplified Compound 1, occurrence of delamination between layers, and degradation of light emission attributed to these were not observed. This is because the tetra-substituted diamine compound of the present invention is
It can be said that this is largely related to having a high glass transition point for the melting point, an asymmetric structure that is hardly crystallized in terms of structure, and a high hole transporting compound.

Example 9 The following structural formula

[0090]

Embedded image

0.5 g of the bisazo pigment represented by the above formula and 0.4 g of a vinyl acetate: vinyl chloride copolymer (acid value: 8) were added to 10 ml of methyl ethyl ketone, and the mixture was stirred for about 1 hour with a paint conditioner. Next, 40 ml of dioxane was added to the obtained dispersion, and the mixture was exposed to ultrasonic waves for about 10 minutes to prepare a charge generation layer liquid.

Separately, the tetra-substituted diamine compounds of the present invention (exemplified compounds 12, 13, 14, 18, 19,
21, 23, 25), 1 g of polyarylate resin
And 0.03 g of α-tocopherol were dissolved in methylene chloride to prepare a charge injection transport layer solution having a solid concentration of 15%. 8 g of each of the thus prepared charge injection transport layer liquids was used.
They were placed in test tubes, and they were allowed to stand at room temperature (20 ° C.) and at a cold temperature (5 ° C.) for one week. The change in appearance and the change in viscosity at this time were examined.

Table 6 shows the results. In addition, about the change of the viscosity, the cal pipette with a capacity of 3 cc was used. Using compounds (A) and (B) in Table 3 as comparative compounds,
A similar test was performed.

[0094]

[Table 6]

As is evident from Table 6, the solutions other than No. 8 of the charge injecting and transporting solution of the present invention were found to have excellent stability over time. In contrast, equations (A) and (B)
It has been found that the compound represented by the formula (1) has a relatively small molecular weight and, despite its simple structure, when used as a charge injecting / transporting liquid, the stability over time is significantly deteriorated.

Example 10 The charge generation layer solution prepared in Example 9 was placed on a support having an aluminum surface anodized (alumite layer: 7 μm).
Coated and dried by the doctor blade method, thickness 0.2μ
Was produced. On this charge generation layer, eight kinds of charge injection / transport layer liquids (solid concentration: 12%) of Example 9 mainly containing the tetra-substituted diamine compound of the present invention were applied by a squeezing doctor. The dry film thickness of this layer is 3
It was 5 μm. An electrophotographic recording paper measuring device (Kawaguchi Electric:
SP-428) to evaluate the electrophotographic characteristics. Table 7 shows the results.

[0097]

[Table 7]

The measuring conditions were as follows: applied voltage: -6 V, applied method: STATIC-3, light source: halogen lamp (irradiation light: 10 lux). A portion of the photoreceptor thus prepared was attached to a drum of a copying machine (SF-2030) manufactured by Sharp Corporation, and after 10,000 copies were continuously performed, the rate of decrease in film thickness was determined. Was determined by exfoliation using tetrahydrofuran. Table 7 also shows the percentage (%) of this decrease. As is clear from Table 7, the photoreceptor using the tetra-substituted diamine compound of the present invention as the charge transport layer was not inferior to the conventional photoreceptor in sensitivity and potential characteristics. Another feature is high printing durability (high abrasion) based on the unique structure. Further, easiness of synthesis is one of the great features as compared with the structure.

[0099]

According to the present invention, an organic EL device having good luminous efficiency, high-luminance luminescence, luminescence at a low driving voltage, and low physical and chemical deterioration due to a substance such as water or oxygen such as light and heat. Can be provided. Further, the present invention can be applied to a charge injection / transport material of an organic photoreceptor for a printer or a copying machine.

Claims (14)

[Claims] 1. A compound of the formula (I) [In the formula, Y is a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, an alkyl group having 1 to 4 carbon atoms, and 7-14 carbon atoms.
X is a substituted or unsubstituted aralkyl group;
12 substituted or unsubstituted arylene groups, having 2 to 2 carbon atoms
6 substituted or unsubstituted cyclic or linear alkylene groups; R ₁ and R ₂ are the same or different and each are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted aryl having 6 to 12 carbon atoms. The radicals, or R ₁ and R ₂ , together with the carbon atom to which they are attached, have the formula: (Where R ₄ and R ₅ are the same or different and form a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and n is 2 or 3). Good]. 2. X is a substituted phenylene group (wherein the substituent is R ₃ : a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms); Formula (II) (Wherein Y, R ₁ and R ₂ have the same meanings as in formula (I)). 3. R ₁ and R ₂ are both a phenyl group and R ₃ is a hydrogen atom, and have the following sub-formula (III): 3. The tetra-substituted diamine compound according to claim 2, wherein Y is as defined in the formula (I). 4. The tetra-substituted diamine compound according to claim 1, wherein Y is a phenyl group which is unsubstituted or substituted with an electron donating group. 5. R ₁ and R ₂ together with the carbon atom to which they are attached, have the formula: Wherein R ₄ and R ₅ have the same meanings as in formula (I), and form the following sub-formula (IV): (Wherein n, R ₄ and R ₅ have the same meanings as in formula (I)). 6. The tetra-substituted diamine compound according to claim 5, wherein R ₄ and R ₅ are both hydrogen atoms, Y is a phenyl group, and X is a p-phenylene group. 7. The tetra-substituted diamine compound according to claim 5, wherein R ₄ and R ₅ are both hydrogen atoms and Y is a phenyl group substituted with an electron donating group. 8. The tetra-substituted diamine compound according to claim 5, wherein R ₄ and R ₅ are both hydrogen atoms and Y is a naphthyl group which is unsubstituted or substituted with an electron donating group. 9. An anode, a hole injecting and transporting layer, a light emitting layer and a cathode are laminated on a substrate in this order, and the hole injecting and transporting layer contains a tetra-substituted diamine compound represented by the formula (I). An organic electroluminescent device, comprising: 10. The organic electroluminescent device according to claim 9, wherein an electron injection / transport layer is further laminated between the light emitting layer and the cathode. 11. The organic electroluminescent device according to claim 9, wherein an electron barrier layer is provided facing the light emitting layer. 12. The method according to claim 11, wherein the electron barrier layer has the formula (V) Wherein A is an oxygen atom, a bond, —CH (R ₇ ) — or (Where R ₇ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group, m is 4 or 5), B is an alkyl group having 1 to 4 carbon atoms, Number 6
A 12 substituted or unsubstituted aryl group, R ₆
Is a hydrogen atom, a halogen atom, a methylenedioxy group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms]. Light emitting element. 13. The organic electroluminescent device according to claim 11, wherein the electron barrier layer contains an amine compound of the formula (V) wherein A is a bond. 14. A charge generation layer and a charge injection / transport layer are laminated on a conductive substrate in this order, and the charge injection / transport layer comprises the tetra-substituted diamine compound of the formula (I) according to claim 1. An organic photoreceptor characterized by containing.