JPH052144B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an electrophotographic photoreceptor. More specifically, the present invention relates to a high-density electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductive substance. <Conventional technology> Conventionally, the photosensitive layer of an electrophotographic photoreceptor contains selenium,
Inorganic photoconductive materials such as cadmium sulfide and zinc oxide were widely used. In recent years, research has progressed in using organic photoconductive substances such as polyvinyl carbazole in the photosensitive layer of electrophotographic photoreceptors.
Some of them have been put into practical use. Organic photoconductive materials have advantages over inorganic materials, such as being lightweight, easy to form a film, and easy to manufacture photoreceptors. Despite having such many advantages, organic photoconductive materials have not been widely used as electrophotographic photoreceptors because they are inferior to inorganic materials in terms of sensitivity and durability. <Problems to be Solved by the Invention> Therefore, the present inventors have conducted intensive research on organic photoconductive materials that provide electrophotographic photoreceptors with high sensitivity and high durability. <Means for Solving the Problems> As a result, it was discovered that a specific azo compound is suitable, and the present invention was achieved. That is, the gist of the present invention resides in an electrophotographic photoreceptor characterized by having a photosensitive layer containing an azo compound represented by the following general formula [] on a conductive support. (In the above general formula [], cp represents a coupler residue selected from general groups (i) to (iii) shown below. (In the formula, X represents an organic group that is condensed with benzene ring A to form a naphthalene ring, anthracene ring, carbazole ring, benzocarbazole ring, or dibenzofuran ring together with benzene ring A, and R ¹ is an alkyl group, phenyl group, or naphthyl group. or dibenzofuranyl group, any of which may be substituted with an alkyl group, an alkoxy group, a halogen atom, a nitro group, a hydroxy group, a dialkylamino group, or a cyano group.) (In the formula, R ² represents an alkyl group, a benzyl group, or a phenyl group, and any of these may be substituted with an alkyl group, an alkoxy group, a halogen atom, or a hydroxy group.) (In the formula, Z represents a divalent group of an aromatic hydrocarbon or a divalent group of a heterocycle containing a nitrogen atom in the ring, and each of these is substituted with an alkyl group, a halogen atom, a nitro group, or a hydroxy group. To explain the present invention in detail below, the azo compound contained in the photosensitive layer of the electrophotographic photoreceptor of the present invention is represented by the above general formula []. In the general formula [], cp is the following general formula (i)
Represents a coupler residue selected from ~(iii). In the formula, X is an organic group that is condensed with benzene ring A to form a polycyclic aromatic hydrocarbon ring such as a naphthalene ring or anthracene ring, or a heterocycle such as a carbazole ring, benzocarbazole ring, or dibenzofuran ring. shows. R ¹ is an alkyl group (e.g. methyl group, ethyl group,
Propyl group, isopropyl group, butyl group, sec-
Butyl group, acyl group, hexyl group, octyl group,
2-ethylhexyl group, nonyl group, octadecyl group, benzyl group, etc.), phenyl group (e.g. phenyl group, tolyl group, xylyl group, biphenyl group,
Chlorophenyl group, dichlorophenyl group, trichlorophenyl group, bromophenyl group, dibromophenyl group, tribromophenyl group, methoxyphenyl group, ethoxyphenyl group, butoxyphenyl group, phenoxyphenyl group, nitrophenyl group,
Cyanophenyl group, hydroxyphenyl group, N,
N-dimethylaminophenyl group, N,N-diethylaminophenyl group, N,N-dibenzylaminophenyl group, etc.), naphthyl group (e.g. α-naphthyl group, β-naphthyl group, etc.) or dibenzofuranyl group (for example, dibenzofuranyl group, methoxybenzofuranyl group, etc.), and these are all alkyl groups, alkoxy groups, halogen atoms, nitro groups, hydroxy groups, cyano groups, or dialkylamino groups, as shown in the specific examples above. It may be substituted with a group. In the formula, ^R2 is an alkyl group (e.g. methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, isobutyl group, hexyl group,
Cyclohexyl group, octyl group, 2-ethylhexyl group, methoxymethyl group, ethoxymethyl group,
2-methoxyethyl group, 2-ethoxyethyl group,
2-hydroxyethyl group, 2-hydroxypropyl group, 3-phenoxypropyl group, 4-phenoxybutyl group, 2-chloroethyl group, 3-chloropropyl group, 4-chlorobutyl group, etc.), benzyl group (e.g. methylbenzyl group) , ethylbenzyl group, propylbenzyl group, isopropylbenzyl group, methoxybenzyl group, ethoxybenzyl group,
chlorobenzyl group, bromobenzyl group, etc.), or phonyl group (phenyl group, tolyl group, xylyl group, biphenyl group, chlorophenyl group, dichlorophenyl group, bromophenyl group, dibromophenyl group, methoxyphenyl group, ethoxyphenyl group) group, ethyl phenyl group, phenoxyphenyl group,
hydroxyphenyl group, etc.), and these are
As shown in the above specific examples, any of them may be substituted with an alkyl group, an alkoxy group, a halogen atom, or a hydroxy group. In the formula, Z represents a divalent aromatic hydrocarbon group or a heterocyclic divalent group containing a nitrogen atom in the ring, and each of these is substituted with an alkyl group, a halogen atom, a nitro group, or a hydroxy group. You can leave it there. Examples of divalent groups of aromatic hydrocarbons include o
- Divalent group of monocyclic aromatic hydrocarbon such as phenylene, o-naphthylene group, peri-naphthylene group,
2 of fused polycyclic aromatic hydrocarbons such as 1,2-anthraquinonylene group and 9,10-phenanthrylene group
Examples include valence groups. In addition, examples of heterocyclic divalent groups containing a nitrogen atom in the ring include 3,4-pyrazoledilyl group, 2,3-pyridiyl group, 4,5-
pyrimidinediyl group, 6,7-indazolediyl group, 5,6-benzimidazolediyl group,
Examples include divalent heterocyclic groups containing a 5- to 10-membered ring nitrogen atom, preferably 2 or less nitrogen atoms, such as a 6,7-quinolinediyl group. When considering sensitivity and durability, o-phenylene group, o-naphthylene group, peri-nafretin group, 2,3-pyridinediyl group, 4,5-pyrimidinediyl group, especially o-
-phenylene group and o-naphthylene group are preferred. These divalent groups may have substituents shown in specific examples below, as described above. Examples of such substituents include alkyl groups such as methyl group, ethyl group, propyl group, i-propyl group, n-butyl group, sec-butyl group, n-hexyl group, fluorine atom, chlorine atom, bromine atom, etc. Examples include halogen atoms, nitro groups, and hydroxyl groups. Specific examples of the azo compound useful in the present invention represented by the general formula () include those having the structural formula shown in Table 1 below.

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[Table] The azo compound of the present invention can be easily synthesized by a coupling reaction between a coupling component represented by the following formula () and an octazonium salt of a tetraamine represented by the following formula (). Such a coupling reaction is carried out according to a known method,
Usually water and/or dimethyl sulfoxide, N
- In an organic solvent such as methylpyrrolidone or N,N-dimethylformamide at a reaction temperature of 30°C or less, 1
It is sufficient to allow the reaction to occur for about 10 hours. The tetraamine represented by the above formula () can be easily synthesized, for example, according to the reaction formula shown below. The azo compound of the present invention can be obtained by the method described above, and the azo compound of the present invention can be obtained by the following general formula (-
Mixture of A) and (-B) (For details, see JP-A-Sho
57-176055) is used, It is obtained as a mixture of isomers represented by the following general formula (). (Here cp is

[expression] or

Represents [formula]. ) In the present invention, these mixtures can be used as they are. The electrophotographic photoreceptor of the present invention has a photosensitive layer containing one or more azo compounds represented by the above general formula (). Various forms of photosensitive layers are well known, and the photosensitive layer of the electrophotographic photoreceptor of the present invention may be any of them. Usually, the photosensitive layer is of the type exemplified below. A photosensitive layer made of an azo compound A photosensitive layer containing an azo compound dispersed in a binder A photosensitive layer containing an azo compound dispersed in a well-known charge transfer medium The photosensitive layer of ~ above serves as a charge generation layer, and a well-known charge transfer medium is added to the photosensitive layer. The azo compound represented by the general formula () is:
When it absorbs light, it generates charge carriers with extremely high efficiency. Although the generated carrier can be transferred using an azo compound as a medium, it is preferable to use a known charge transfer medium as a medium.
From this point of view, photosensitive layers in the form of and are particularly preferred, and the highest performance can be obtained with the form of.
In this case, the charge generation layer may be formed by applying a coating solution obtained by dissolving or dispersing an azo compound represented by the general formula () in an appropriate solvent alone or in a binder polymer onto the conductive support. ,
Obtained by drying. Butylamine, butylamine,
Chlorinated solvents such as ethylenediamine; ethers such as tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane, and diethylene glycol dimethyl ether; ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene and xylene; N,N-dimethylformamide, Non-brotic polar solvents such as acetonitrile, N-methylpyrrolidone, dimethylsulfoxide;
Examples include alcohols such as methanol, ethanol, and isopropanol; esters such as ethyl acetate, methyl formate, and methyl cellosolve acetate; and chlorinated hydrocarbons such as dichloroethane and chloroform. These solvents can be used alone or in combination of two or more. When using a binder polymer, it is desirable to use one that dissolves the polymer. Binder polymers include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic esters, and methacrylic esters;
Examples include polyester, polycarbonate, polysulfone, polyvinyl butyral, phenoxy resin, cellulose ester, cellulose ether, urethane resin, and epoxy resin. The amount of binder polymer used is usually in the range of 0.1 to 5 times the weight of the azo compound. In addition, the azo compound has a thickness of 1 μm in the binder.
It is preferable to make it exist in the following fine particle state.
The thickness of the charge generation layer is usually several μm or less, especially 1 μm.
The following are preferred. As the conductive support on which the charge generation layer is coated, any of those employed in well-known electrophotographic sensitive materials can be used. Specific examples include metal drums and sheets made of aluminum, copper, etc., and laminates and vapor deposits of these metal foils. Further examples include plastic films, plastic drums, paper, paper tubes, etc., which are coated with a conductive substance such as metal powder, carbon black, copper iodide, or polymer electrolyte together with a suitable binder to conductivity treatment. In addition, metal powder, carbon black,
Examples include plastic sheets and drums that contain conductive substances such as carbon fibers and are made conductive. A charge transfer layer is formed by stacking on the charge generation layer. Conversely, a charge transfer layer may be formed on a conductive support and a charge generation layer may be laminated on top of the charge transfer layer, but since the thickness of the charge generation layer is usually thin, it is difficult to protect the charge generation layer from wear and dirt. The former type is often used for this purpose. The charge transport layer is a layer that transports charge carriers generated in the charge generation layer and contains a charge carrier transport medium. Charge carrier transfer media are generally classified into two types: electron transfer media and hole transfer media, and both can be used in the photosensitive layer of the photoreceptor of the present invention, and a mixture thereof can also be used. As an electron transfer medium, an electron-withdrawing compound having an electron-withdrawing group such as a nitro group, a cyano group, or an ester group, such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, etc. Examples include nitrated fluorenone or tetracyanoquinodimethane. In addition, electron-donating organic photoconductive compounds such as carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, pyrazole, and pyrazoline (1,3-diphenyl-5-(p-dimethylamino phenyl)-2
-pyrazoline, etc.), heterocyclic compounds such as thiazazole, derivatives of aniline, hydrazine derivatives, hydrazone, or polymers having a group consisting of these compounds in the main chain or side chain (polyvinylcarbazole, polyglycidylcarbazole), and the like. Among these, especially the following general formula () (In the above formula, R ³ represents an alkyl group, substituted alkyl group, or aralkyl group, R ⁴ represents an alkyl group, allyl group, substituted alkyl group, phenyl group, naphthyl group, or aralkyl group, and Z ¹ represents a hydrogen atom. , represents an alkyl group, an alkoxy group or a halogen atom) (see JP-A-54-150128) or the following general formula () (In the formula, X ¹ , Y ¹ and Z ² represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, a phenoxy group or an arylalkoxy group, and R ⁵ represents a hydrogen atom,
It represents a lower alkyl group, allyl group, phenyl group or aralkyl group, m and l represent 1 or 2, and p represents 0 or 1. ) is preferably used alone or in combination. When the charge carrier transport medium is a low-molecular compound, the charge transport layer is formed in a state in which it is dissolved in a binder polymer. The charge carrier transfer medium is normally used in an amount of 0.2 to 1.5 parts by weight, preferably 0.3 to 1.2 times the weight of the binder polymer. As the binder polymer, a polymer similar to that used for the charge generation layer is used, and it is dissolved in a solvent together with the charge carrier transfer medium to prepare a coating solution, which is coated and dried to form the charge transfer layer. The thickness of the charge transfer layer is 5 to 50 μm, preferably 10 to 30 μm. Of course, the photosensitive layer of the electrophotographic photoreceptor of the present invention may contain a known sensitizer. Suitable sensitizers include Lewis acids and dyes that form charge transfer complexes with organic photoconductive materials. Examples of Lewis acids include chloranil, 2,3-dichloro-
1,4-naphthoquinone, 2-methylanthraquinone, 1-nitroanthraquinone, 1-chloro-5
- quinones such as nitroanthraquinone, 2-chloroanthraquinone, phenanthrenequinone,
Aldehydes such as 4-nitrobenzaldehyde, 9-benzoylanthracene, indanedione, 3,5-dinitrobenzophenone, 3,3',
Ketones such as 5,5'-tetranitrobenzophenone, acid anhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride, tetracyanoethylene, terephthalalmalononitrile, 4-nitrobenzalmalononitrile, 4- (p-nitrobenzoyloxy)
Cyano compounds such as benzalmalononitrile; 3-
Benzalphthalide, 3-(α-cyano-p-nitrobenzal)phthalide, 3-(α-cyano-p-
Examples include electron-withdrawing compounds such as phthalides such as (nitrobenzal)-4,5,6,7-tetrachlorophthalide. Examples of dyes include triphenylmethane dyes such as methyl violet, brilliant green, and crystal violet, thiazine dyes such as methylene blue, quinone dyes such as quinizarin, cyanine dyes, pyrylium salts, thiapyrylium salts, and benzopyrylium salts. It will be done. Furthermore, the photosensitive layer of the electrophotographic photoreceptor of the present invention may contain a well-known plasticizer in order to improve film formability, flexibility, and mechanical strength. Examples of the plasticizer include phthalate esters, phosphate esters, epoxy compounds, chlorinated paraffins, chlorinated fatty acid esters, aromatic compounds such as methylnaphthalene, and the like. It goes without saying that it may also have an adhesive layer, an intermediate layer, and a transparent insulating layer, if necessary. <Effects of the Invention> The photoreceptor using the azo compound of the present invention has high sensitivity and good color sensitivity, and when used repeatedly, there is little variation in sensitivity and chargeability, and there is little optical fatigue. It has extremely high durability. Furthermore, the photoreceptor of the present invention has a maximum spectral sensitivity wavelength of 600
It is in the range of ~650 nm and can be widely used in electrophotographic applications such as electrophotographic copying machines and photoconductors for printers that use lasers, LEDs, OFT (Optical Fiber Tubes), etc. as light sources. <Examples> Next, the present invention will be explained in more detail with reference to production examples and examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded. Production example (Synthesis of compound No. 1-1 in Table 1) (1) Synthesis of tetra(p-aminophenyl)ethylene 5g of p,p'-diaminobenzophenone was added to 35%
It was added to 180 ml of hydrochloric acid and heated to 60-70°C to dissolve.
Next, 50 g of zinc was added at the same temperature and reacted for 5 hours. The precipitated crystals were collected, washed with ethanol, added to 200 ml of 10% caustic soda solution, and stirred at room temperature for 30 minutes. Subsequently, it was filtered, washed with water and methanol, and then dried to obtain the desired product. Yield 2.8g (2) Tetra(p-aminophenyl)ethylene 1.0
Dissolve g in 100 g of water and 2.7 g of concentrated hydrochloric acid and keep at 0°C. Next, add a saturated aqueous solution of 0.7g of sodium nitrite.
The mixture was added dropwise over 10 minutes, stirred at the same temperature for 2 hours, and then 1.3 g of a 42% hydroborofluoric acid aqueous solution was added and stirred at the same temperature for 1 hour. Then naphthol AS
A solution of 3.0 g of dimeryl sulfoxide (1) was added, and then a saturated methanol solution of 10 g of sodium acetate was added dropwise over 15 minutes. After stirring at room temperature for 2 hours, the precipitated dark brown solid was collected and purified by suspension washing with dimethylformamide, demineralized water, methanol, and tetrahydrofuran, respectively, to obtain 2.5 g of tetrakisazo application material. From the elemental analysis values and infrared absorption spectrum, it was confirmed that this compound was a tetrakisazo compound represented by the following structural formula. Elemental analysis value as C ₉₄ H ₆₄ N ₁₂ O ₈ Calculated value: C75.81% H4.30% N11.29% Actual value: C75.42% H3.90% N10.73% Production example 2 (Table-1 Synthesis of Compound No. 1-23) Production Example 1 Coupling with the same octazo component as in Production Example 1 was carried out using N-methyl-4-hydroxynaphthalimide as the coupling component.
A black and colored tetrakisazo application material was obtained using a method similar to the above. It was confirmed from elemental analysis and infrared absorption spectrum that this compound was a tetrakisazo compound represented by the following structural formula. Elemental analysis value as C ₇₈ H ₄₈ N ₁₂ O ₁₂ Calculated value: C69.64% H3.57% N12.50% Actual value: C69.25% H3.22% N12.15% Similarly, Table 1 Compound No. 1-5, 6, 10,
11, 12, 13, 16, 19, 20, 21, 23, 25, 27, 30,
34, 35, 36, 37, 38, 39, 40, 42, 43 and 44 were synthesized. Example 1 10 parts by weight of the tetrakisazo compound synthesized in Production Example 1 (Table 1 No. 1-1), 5 parts by weight of phenoxy resin (PKHH manufactured by Union Carbide Co., Ltd.), and polyvinyl butyral resin (BH manufactured by Sekisui Chemical Co., Ltd.)
-3) 100 parts by weight of 4-methoxy-4-methylpentanone-2 was added to 5 parts by weight and pulverized and dispersed using a sand grind mill. The azo compound dispersion thus obtained was applied with a film applicator onto an aluminum vapor-deposited layer deposited on a polyester film having a thickness of 100 μm to a dry film thickness of 0.6 g/m ² and then dried. N-ethylcarbazole-3
- 80 parts by weight of aldehyde diphenylhydrazone and methacrylic resin (Dyanal, manufactured by Mitsubishi Rayon Co., Ltd.)
A solution prepared by dissolving 100 parts by weight of BR-85) in 550 parts of toluene was applied to give a dry film thickness of 15 μm to form a charge transfer layer, thereby producing a laminated photoreceptor No.-1. Examples 2 to 26 Charge transfer substances used in Example 1 and Table 2 below
Photoreceptors Nos. 2 to 26 were obtained in the same manner as in Example 1 except that the azo compounds shown in . These photoreceptors were tested using an electrostatic copying paper tester (Model SP-428 manufactured by Kawaguchi Electric Seisakusho).
First, it is charged by -6.5KV corona discharge in a dark place, then exposed to white light with an illuminance of 5lux, and the amount of exposure is enough to attenuate the surface potential to half of the initial surface potential.
E _1/2 (lux・sec) was calculated. The results are shown in Table 2 below.

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[Table] Also, the surface potential of photoreceptor No.-18 is -
After corona discharge to 500V, we repeated a cycle of exposure to white light at 400lux for 2 seconds and examined the change in sensitivity, and found that the initial sensitivity was E _1/2 with white exposure at 5lux. is 4.5lux・sec,
E _1/5 is 9.1 lux sec (however, E _1/2 has the same meaning as above, and E _1/5 indicates the amount of exposure necessary for the surface potential to attenuate to one-fifth). Yes, the sensitivity after 2000 repetitions is 4.3lux sec for E _1/2 and 8.8lux sec for E _1/5
It was hot. This photoreceptor can also be used in a copying machine (SF-
755) and repeated charging and exposure,
The change in surface potential between the initial stage and after 2000 cycles was 3%. From the above results, it was found that the variation in electrical characteristics of the photoreceptor of the present invention due to repeated use is extremely small. Furthermore, when copying a test chart (manufactured by Dataquest), clear images with no fogging were obtained. Example 27 After pulverizing 0.3 parts of azo compounds No. 1-13 in Table 1, they were added to 20 parts of cyclohexanone and dispersed using an ultrasonic disperser. To this were added 30 parts of tetrahydrofuran, 10 parts of polyester (Trademark Byron 200 manufactured by Toyobo Co., Ltd.) and 10 parts of 1,3-diphenyl-5-(p-dimethylaminophenyl)-2-pyrazoline and dissolved therein.
This coating liquid was applied with a film applicator onto an aluminum vapor-deposited layer deposited on a polyester film having a thickness of 100 μm to provide a photosensitive layer having a dry film thickness of 15 μm. When we measured the sensitivity of this photoreceptor, E _1/2 was 9lux when using +6KV corona discharge.
sec, and in the case of -6KV corona discharge charging, it was 12lux sec.

Claims (1)

[Scope of Claims] 1. A photoreceptor for electrophotography, comprising a photosensitive layer containing an azo compound represented by the following general formula () on a conductive support. (In the above general formula (), cp represents a coupler residue selected from general formulas (i) to (iii) shown below. (In the formula, X represents an organic group that is condensed with benzene ring A to form a naphthalene ring, anthracene ring, carbazole ring, benzocarbazole ring, or dibenzofuran ring together with benzene ring A, and R ¹ is an alkyl group, a phenyl group, naphthyl group,
or a dibenzofuranyl group, any of which may be substituted with an alkyl group, an alkoxy group, a halogen atom, a nitro group, a hydroxy group, a dialkylamino group, or a cyano group. ) (In the formula, R ² represents an alkyl group, a benzyl group, or a phenyl group, and any of these may be substituted with an alkyl group, an alkoxy group, a halogen atom, or a hydroxy group.) (In the formula, Z represents a divalent group of an aromatic hydrocarbon or a divalent group of a heterocycle containing a nitrogen atom in the ring, and each of these is substituted with an alkyl group, a halogen atom, a nitro group, or a hydroxy group. ))