JP2670821B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member containing a disazo pigment having a specific molecular structure in a photosensitive layer.

[Prior Art] Conventionally, as an electrophotographic photosensitive member made of an inorganic photoconductive substance, one using selenium, cadmium sulfide, zinc oxide or the like has been widely used.

On the other hand, as an electrophotographic photoreceptor using an organic photoconductive substance, a photoconductive polymer represented by poly-N-vinylcarbazole or 2,5-bis (p-diethylaminophenyl) -1,3,4- Known are those using a low-molecular organic photoconductive substance such as oxadiazole, and those obtained by combining such an organic photoconductive substance with various dyes and pigments.

An electrophotographic photoreceptor using an organic photoconductive substance has advantages in that it has good film-forming properties, can be produced by coating, and can provide an extremely high productivity and inexpensive photoreceptor. Further, there is an advantage that color sensitivity can be freely controlled by selecting a sensitizer such as a dye or a pigment to be used, and wide studies have been made so far. Particularly recently, the development of a function-separated type photoreceptor in which an organic photoconductive pigment is used as a charge generation layer and a charge transport layer made of the above-mentioned photoconductive polymer or a low molecular weight organic photoconductive substance is laminated, The sensitivity and durability, which have been the drawbacks of organic electrophotographic photoreceptors, have been remarkably improved.

A number of pigment compounds have been proposed as disazo pigments used in this type of photoreceptor, for example, as pigment compounds related to the present invention, JP-A-59-45444, JP-A-62-267365, JP-A-60-151644, JP-A-SHO
61-32063, JP 61-62563, JP 61-
The pigment compound described in Japanese Patent No. 259257 is known.

However, it cannot be said that the sensitivity and the stability upon repeated use are always sufficient, and only a few materials have been put to practical use.

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel photoconductive material,
An object of the present invention is to provide an electrophotographic photoreceptor having practically high sensitivity characteristics and stable potential characteristics upon repeated use.

[Means for Solving the Problems and Functions] An electrophotographic photoreceptor having a photosensitive layer on a conductive support comprises an electrophotographic photoreceptor characterized in that the photosensitive layer contains a disazo pigment represented by the following general formula (1).

General formula In the formula, A represents a coupler residue having a phenolic hydroxyl group, R ₁ and R ₂ represent a hydrogen atom, an alkyl group, an alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group or a cyano group. Show.

Specifically, in R ₁ and R ₂ , an alkyl group is a group such as methyl, ethyl and propyl, an alkoxy group is a group such as methoxy and ethoxy, an aryl group is a group such as phenyl, diphenyl and naphthyl, and an aralkyl group. Examples include groups such as benzyl and phenethyl.

Examples of the substituent of the above group include a halogen atom such as a fluorine atom, a chlorine atom, an iodine atom and a bromine atom, an alkyl group such as methyl, ethyl, propyl, isopropyl and butyl, an alkoxy group such as methoxy, ethoxy, propoxy and phenoxy. And substituted amino groups such as nitro group, cyano group, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino.

The coupler residue having a phenolic hydroxyl group represented by A is represented by the following general formulas (2) to (5).

In the formula, X is condensed with a benzene ring to form a naphthalene ring, an anthracene ring, a carbazole ring, a benzocarbazole ring,
A residue necessary for forming a polycyclic aromatic ring or a heterocyclic ring such as a dibenzofuran ring, a dibenzonaphthofuran ring, a diphenylene sulfide ring, and a fused ring of X is a naphthalene ring, an anthracene ring, a carbazole ring, a benzocarbazole ring Is more preferable.

R ₃ and R ₄ are a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, a heterocyclic group or R ₃ ,
A cyclic amino group containing a nitrogen atom to which R ₄ is attached in the ring is shown, a group such as methyl, ethyl, propyl and butyl as an alkyl group, a group such as phenyl, diphenyl, naphthyl and anthryl as an aryl group, an aralkyl group. Is a group such as benzyl, phenethyl, naphthylmethyl,
Examples of the heterocyclic group include groups such as carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine.

 Z represents an oxygen atom or a sulfur atom.

The alkyl group represented by R ₃ and R ₄ , an aryl group, an alkoxy group, a substituent which the heterocyclic group may have, for example, a fluorine atom, a chlorine atom, an iodine atom, a halogen atom such as a bromine atom, methyl, ethyl , Alkyl groups such as propyl, isopropyl and butyl, alkoxy groups such as methoxy, ethoxy, propoxy and phenoxy, nitro groups,
Examples include substituted amino groups such as cyano group, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino.

In the formula, Y represents a divalent group of aromatic hydrocarbon or a heterocyclic divalent group containing a nitrogen atom in the ring, and the divalent group of aromatic hydrocarbon is a monocyclic ring such as o-phenylene. Aromatic hydrocarbon divalent group, o-naphthylene, perinaphthylene,
Examples include condensed aromatic hydrocarbon divalent groups such as 1,2-anthrylene and 9,10-phenanthrylene.Examples of the heterocyclic divalent group containing a nitrogen atom in the ring include 3,4-pyrazole And divalent groups such as a diyl group, a 2,3-pyridinediyl group, a 4,5-pyrimidinediyl group, a 6,7-indazolediyl group, and a 6,7-quinolinediyl group.

In the formula, R ₅ represents an aryl group or a heterocyclic group which may have a substituent, and specific examples thereof include phenyl, naphthyl, anthryl, pyrenyl, pyridyl, thienyl, furyl and carbazolyl groups.

Further, examples of the substituent of the aryl group and the heterocyclic group include a halogen atom such as a fluorine atom, a chlorine atom, an iodine atom, and a bromine atom; an alkyl group such as methyl, ethyl, propyl, isopropyl, and butyl; methoxy, ethoxy, propoxy, and phenoxy. And substituted amino groups such as alkoxy group, nitro group, cyano group, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino and pyrrolidino.

 X has the same meaning as X in the general formula (2).

In the formula, R ₆ and R ₇ represent a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group, an aryl group or a heterocyclic group, and specific examples of the alkyl group include methyl, ethyl, propyl and butyl. The aralkyl group includes benzyl, phenethyl, naphthylmethyl, the aryl group includes phenyl, diphenyl, naphthyl, anthryl, the heterocyclic group includes carbazole, thienyl, pyridyl and furyl groups, and the alkyl group and the aralkyl group. Examples of the substituent of the group, the aryl group and the heterocyclic group include a fluorine atom, a chlorine atom, an iodine atom, a halogen atom such as a bromine atom, an alkyl group such as methyl, ethyl, propyl, isopropyl and butyl, methoxy, ethoxy and propoxy,
Alkoxy groups such as phenoxy, nitro groups, cyano groups,
And substituted amino groups such as dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino.

 X has the same meaning as X in the general formula (2).

Hereinafter, typical examples of the disazo pigment represented by the general formula (1) will be listed.

However, these disazo pigments do not limit the claims of the present invention.

The description shall indicate only R ₁ , R ₂ , and A that change in the basic form.

Basic type Exemplified pigment (1) R ₁ , R ₂ : -H Exemplified pigment (2) R ₁ , R ₂ : -CH ₃ Exemplified Pigment (3) R ₁ , R ₂ : -C ₂ H ₅ Exemplified pigment (4) R ₁ , R ₂ : -CN Exemplified pigment (5) R ₁ : -CH ₃ R ₂ : -H Illustrative pigment (6) Exemplified pigment (7) R ₁ , R ₂ : -OCH ₃ A general method for producing the disazo pigment represented by the general formula (1) is 2,7-dinitro-9-10-phenanthrenequinone and diamine obtained by nitrating 9,10-phenanthrenequinone. Cyclize by dehydration reaction with and reduce two nitro groups,
Diamine Then, tetrazotized by a conventional method, in the presence of an alkali, after coupling with a corresponding coupler, or after converting the tetrazonium salt into a borofluoride salt or a zinc chloride double salt, N, N-dimethylformamide, dimethylsulfoxide, etc. In the presence of a base such as sodium acetate, pyridine, triethylamine, triethanolamine in a solvent,
It can be easily synthesized by coupling with a corresponding coupler.

The coating containing the disazo pigment represented by the general formula (1) has photoconductivity and can be used for a photosensitive layer of an electrophotographic photoreceptor.

That is, in the present invention, electrophotography is carried out by forming a film of the disazo pigment represented by the above-mentioned general formula (1) on the conductive support by a vacuum vapor deposition method or by forming a film by dispersing and containing it in a suitable binder. A photoreceptor can be configured.

In a preferred embodiment of the present invention, the above-described photoconductive coating can be applied as a charge generation layer in an electrophotographic photosensitive member in which the photosensitive layer of the electrophotographic photosensitive member is functionally separated into a charge generation layer and a charge transport layer.

The charge generation layer contains as much of the aforementioned photoconductive disazo pigment as possible to obtain sufficient absorbance,
In addition, it is desirable to use a thin film layer, for example, a thin film layer having a film thickness of 5 μm or less, preferably 0.01 to 1 μm, in order to shorten the range of the generated charge carrier.

As described above, the charge generation layer can be formed, for example, by dispersing the disazo pigment represented by the general formula (1) in a suitable binder and coating it on a conductive support. It can be obtained by forming a film.

The binder that can be used when forming the charge generation layer by coating can be selected from a wide range of insulating resins, and can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. Preferably, polyvinyl butyral, polyvinyl benzal, polyarylate (such as a condensation polymer of bisphenol A and phthalic acid), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinyl pyridine, cellulose resin, Examples include insulating resins such as urethane resins, casein, polyvinyl alcohol, and polyvinylpyrrolidone.

The amount of the resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less.

The solvent for dissolving these resins differs depending on the type of the resin, and is preferably selected from those which do not dissolve the charge transport layer or the undercoat layer described below.

Specific organic solvents include methanol, ethanol,
Alcohols such as isopropanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as dichlorohexane, N, N-dimethylformamide,
N, N- amides such as dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, ethers such as ethylene glycol monomethyl ether, methyl acetate, esters such as ethyl acetate, chloroform, methylene chloride, dichloroethylene, Aliphatic halogenated hydrocarbons such as carbon tetrachloride and trichloroethylene, and aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene can be used.

Coating can be performed using a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a Meyer bar coating method, a blade coating method, a roller coating method, and a curtain coating method.

Drying is preferably performed by touch drying at room temperature and then heating and drying. The heating and drying can be performed at a temperature of 30 to 200 ° C. for 5 minutes to 2 hours in a still or blown state.

The charge transport layer is electrically connected to the above-mentioned charge generation layer and has a function of receiving the injected charge carriers in the presence of an electric field and transporting these charge carriers to the surface. ing. In this case, the charge transport layer may be located farther from the charge generation layer than the conductive support, or may be located between the conductive support and the charge generation layer.

As the charge transporting substance, there are an electron transporting substance and a hole transporting substance, and as the electron transporting substance, chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,
5,7-tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-
There are electron-withdrawing substances such as tetranitroxanthone and 2,4,8-trinitrothioxanthone, and those obtained by polymerizing these electron-withdrawing substances.

As the hole transporting substance, pyrene, N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N
-Phenylhydrazino-3-methylidene-9-ethylcarbazole, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N, N-diphenylhydrazino-3-methylidene-10-ethylphenothiazine,
N, N-diphenylhydrazino-3-methylidene-10-ethylphenoxazine, p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, p-diethylaminobenzaldehyde-N-α-naphthyl-N-diphenylhydrazone, p-pyrrolidino Benzaldehyde-N, N
-Diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N, N-diphenylhydrazone,
hydrazone compounds such as p-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone,
2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1-phenyl-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl)
Pyrazoline, 1- [quinolyl (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (p
-Diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [6-methoxy-pyridyl (2)]-3- (p-diethylaminostyryl) -5
-(P-diethylaminophenyl) pyrazoline, 1-
[Pyridyl (3)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [lepidyl (2)]-3- (p-diethylaminostyryl) -5- (p-diethylamino) Phenyl) pyrazoline, 1- [pyridyl (2)]-3- (p-diethylaminostyryl) -4-methyl-5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]
-3- (α-methyl-p-diethylaminostyryl)-
5- (p-diethylaminophenyl) pyrazolin, 1-
Phenyl-3- (p-diethylaminostyryl) -4-
Pyrazoline compounds such as methyl-5- (p-diethylaminophenyl) pyrazoline, 1-phenyl-3- (α-benzyl-p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline and spiropyrazolin, α-phenyl- N, N-diphenylaminostilbene, N-ethyl-3- (α-phenylstyryl) carbazole, 9-p-dibenzylaminobenzylidene-9H
-Styryl compounds such as fluorenone, 5-p-ditolylaminobenzylidene-5H-dibenzo [a, d] cycloheptene, 2- (p-diethylaminostyryl) -6-
Oxazole compounds such as diethylaminobenzoxazole, 2- (p-diethylaminophenyl) -4- (p-dimethylaminophenyl) -5- (2-chlorophenyl) oxazole, 2- (p-diethylaminostyryl) -6-diethylaminobenzo Thiazole compounds such as thiazole, triazole methane compounds such as bis (4-diethylamino-2-methylphenyl) phenylmethane, 1,1-bis (4-N, N-diethylamino-2)
-Methylphenyl) heptane, polyarylalkane-based compounds such as 1,1,2,2-tetrakis (4-N, N-dimethylamino-2-methylphenyl) ethane, triphenylamine, poly-N-vinylcarbazole, Polyvinyl pyrene, polyvinyl anthracene, polyvinyl acridine, poly-9-vinyl anthracene, a pyrene-formaldehyde resin, an ethyl carbazole formaldehyde resin, and the like.

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can be used.

These charge transport materials can be used alone or in combination of two or more. When the charge transport material does not have a film-forming property, a film can be formed by selecting an appropriate binder. Resins that can be used as the binder include, for example, acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-
Butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide,
Insulating resins such as polyamide and chlorinated rubber, or poly-N-vinylcarbazole, polyvinylanthracene,
Examples include organic photoconductive polymers such as polyvinylpyrene.

Since the charge transport layer has a limit for transporting charge carriers, it cannot be made thicker than necessary. Generally, it is 5 to 40 μm, but a preferable range is 15 to 30 μm.
It is.

When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

Such a photosensitive layer having a laminated structure of a charge generation layer and a charge transport layer is provided as a conductive support on a support having, for example, a conductive layer.

As the conductive support, the support itself has conductivity, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium,
Nickel, indium, gold, platinum, and the like can be used. In addition, plastics having a layer in which aluminum, an aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, or the like is formed by a vacuum evaporation method can be used. For example, a support in which conductive particles (eg, carbon black, silver particles, etc.) are coated on a plastic together with a suitable binder, conductive particles, such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, and polyfluoroethylene. And a support having a conductive polymer impregnated in plastic or paper.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive layer and the photosensitive layer. The undercoat layer is casein,
Polyvinyl alcohol, nitrocellulose, ethylene-
It can be formed of acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon and the like), polyurethane, gelatin, aluminum oxide and the like.

The thickness of the undercoat layer is 5 μm or less, preferably 0.1 to 3 μm.
m is appropriate.

When using a photoconductor arranged in the order of a conductive support, a charge generation layer, and a charge transport layer, when the charge transport material is made of an electron transport material, the surface of the charge transport layer must be positively charged. In the post-exposure, in the exposed area, the electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface to neutralize the positive charge, attenuate the surface potential, and generate static electricity between the unexposed area. Contrast occurs.

If the electrostatic latent image thus formed is developed with negatively charged toner, a visible image can be obtained. This can be fixed directly, or the toner image can be transferred to paper or a plastic film and then developed and fixed.

There is also a method in which an electrostatic latent image on a photoreceptor is transferred onto an insulating layer of transfer paper, and then developed and fixed. The type of the developer, the developing method, and the fixing method may be any of known agents and known methods, and are not limited to specific ones.

On the other hand, when the charge transport material is a hole transport material,
It is necessary to charge the surface of the charge transport layer negatively, and after the charge, when exposed, holes generated in the charge generation layer are injected into the charge transport layer in the exposed portion, and then reach the surface to neutralize the negative charge, The surface potential is attenuated, and an electrostatic contrast is generated between the exposed portion and the unexposed portion.

At the time of development, it is necessary to use a positively charged toner, contrary to the case where an electron transporting substance is used.

When using a photoreceptor in which a conductive support, a charge transport layer, and a charge generation layer are located in this order, and the charge transport material is an electron transport material, the charge generation layer surface must be negatively charged. When post-exposure is performed, in the exposed portion, electrons generated in the charge generation layer are injected into the charge transport layer and then reach the conductive support.

On the other hand, the holes generated in the charge generation layer reach the surface, attenuate the surface potential, and generate an electrostatic contrast with the unexposed portion.

A visible image can be obtained by developing the electrostatic latent image formed in this manner with positively charged toner. This can be fixed directly, or the toner image can be transferred to paper or a plastic film and then developed and fixed.

There is also a method in which an electrostatic latent image on a photoreceptor is transferred onto an insulating layer of transfer paper, and then developed and fixed. The type of the developer, the developing method, and the fixing method may be any of known agents and known methods, and are not limited to specific ones.

On the other hand, when the charge transporting substance is a hole transporting substance, the surface of the charge generating layer needs to be positively charged. It is injected into the transport layer and then reaches the electrically conductive support.

On the other hand, the electrons generated in the charge generation layer reach the surface, attenuate the surface potential, and generate an electrostatic contrast with the unexposed portion. At the time of development, it is necessary to use a negatively chargeable toner, contrary to the case of using an electron transporting substance.

In another specific example of the present invention, the above-mentioned hydrazone compound, pyrazoline compound, styryl compound, oxazole compound, thiazole compound, triarylmethane compound, polyarylalkane compound, triphenylamine, poly- A photosensitive film containing a disazo pigment represented by the aforementioned general formula (1) as a sensitizer for an organic photoconductive substance such as an N-vinylcarbazole compound or an inorganic photoconductive substance such as zinc oxide, cadmium sulfide, or selenium; can do. This photosensitive film is formed by coating these photoconductive substances and the above-mentioned disazo pigment represented by the general formula (1) with a binder.

Further, as the electrophotographic photoreceptor of the present invention, an electrophotographic photoreceptor in which the disazo pigment represented by the above general formula (1) is contained in the same layer together with the charge transporting substance can be mentioned.

At this time, in addition to the charge transport material, a charge transfer complex compound composed of poly-N-vinylcarbazole and trinitrofluorenone can be used.

The electrophotographic photoreceptor of this example is manufactured by dispersing a disazo pigment represented by the above general formula (1) and a charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran and then forming a film.

The pigment used in any of the electrophotographic photosensitive members is at least one selected from disazo pigments represented by the general formula (1).
Contains different types of pigments.

If necessary, two or more disazo pigments represented by the above general formula (1) may be used in combination for the purpose of increasing the sensitivity of the photoreceptor by using a combination of pigments having different light absorptions and obtaining a panchromatic photoreceptor. Alternatively, it can be used in combination with a charge generating substance selected from known dyes and pigments.

The electrophotographic photoreceptor of the present invention is used for an electrophotographic copying machine, a laser beam printer, a CRT printer, and an LED.
It can be widely used in electrophotographic application fields such as printers, liquid crystal printers, and laser plate making.

Examples Examples 1 to 6 An undercoat layer made of a 0.1 μm vinyl chloride-maleic anhydride-vinyl acetate copolymer was provided on an aluminum plate.

Next, 5 g of the above exemplified pigment (1) was added to 95 ml of cyclohexanone.
Was dissolved in a solution of 2 g of butyral resin (butyralization degree: 63 mol%, number average molecular weight: 20,000), and dispersed by a sand mill for 20 hours. This dispersion was applied on a previously formed undercoat layer with a Meyer bar so that the dried roundness was 0.5 μm, and dried to form a charge generation layer.

Next, p-diethylaminobenzaldehyde-N-α
5 g of naphthyl-N-phenylhydrazone and 5 g of polymethyl methacrylate (number average molecular weight 100,000)
The solution was dissolved in 70 ml, and this solution was applied on a charge generation layer with a Meyer bar so that the film thickness after drying was 20 μm, and dried to form a charge transport layer. Thus, an electrophotographic photosensitive member of Example 1 was prepared.

Example 2 The following example pigment was used in place of the example pigment (1) used, and other conditions were the same as in example 1
Electrophotographic photoreceptors corresponding to ~ 6 were prepared.

The electrophotographic photoreceptor thus prepared was corona-charged at −5.5 KV in a static manner using an electrostatic copying paper tester (Model SP-428, manufactured by Kawaguchi Electric Co., Ltd.) and held for 1 second in a dark place. Thereafter, the substrate was exposed to light with an illuminance of 2 lux, and charging characteristics were examined.

As the charging characteristics, the surface potential (V _O ) and the exposure amount (E 1/2) required to attenuate the potential after dark decay for one second to half were measured. The results are shown. Examples Exemplified pigment V ₀ (−V) E 1/2 (lux, sec) 1 (1) 695 3.0 2 (2) 670 4.1 3 (3) 705 3.9 4 (4) 680 3.2 5 (5) 670 1.5 6 (6) 700 2.2 Comparative Examples 1 and 2 In place of Exemplified Pigment (1) used in Example 1, an azo pigment represented by the following structural formula was used, and a photosensitive member was prepared in the same manner as in Example 1. And evaluated similarly. The results are shown.

Comparative Example 1 Comparative azo pigment V _O : −680V E 1/2: 6.9luv, sec Comparative Example 2 Comparative azo pigment V _O : −660V E 1/2: 8.2lux, sec From these results, it can be seen that the electrophotographic photosensitive members of the present invention have sufficient charging ability and excellent sensitivity.

Example 7 Using the electrophotographic photosensitive member prepared in Example 3, the fluctuations in the light portion potential and the dark portion potential during repeated use were measured.

The measurement method is -5.6 KV corona charger, exposure optical system,
The photoreceptor was affixed to a cylinder of an electrophotographic copying machine equipped with a developing unit, a transfer charger, a charge erasing exposure optical system and a cleaner. This copying machine is configured so that an image can be obtained on a transfer paper by driving a cylinder.

With this copying machine, the initial light potential (V _L) and the dark potential (V _D), respectively set -100 V, in the vicinity of -600 V, 5,
The light potential (V _L ) and dark potential (V _D ) after 000 use were measured. Get results.

From the above results, it can be seen that the sensitivity is good and the potential stability during durable use is also good.

Example 8 A polyvinyl alcohol film having a thickness of 0.5 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film.

Next, a dispersion of the disazo pigment of Exemplified Pigment (1) used in Example 1 was applied onto the polyvinyl alcohol layer previously formed by a Meyer bar so that the film thickness after drying was 0.5 μm, and dried. Thus, a charge generation layer was formed.

Next, the structural formula 5 g of benzylidene compound and 5 g of bisphenol Z-type polycarbonate (viscosity average molecular weight 30,000)
The thickness of the liquid dissolved in 2.5 ml after drying on the charge generation layer is 2
It was applied to a thickness of 0 μm and dried to form a charge transport layer.

The charging characteristics of the electrophotographic photosensitive member thus prepared were measured by the same method as in Examples 1 and 7. The results are shown.

V _O : −680V E 1/2: 2.8lux, sec Initial V _D : −600V V _L : −100V After 5,000 sheets endurance V _D : −585V V _L : −115V [Effect of the invention] Electrophotography of the present invention By using a specific disazo pigment in the photosensitive layer, it is estimated that either or both of the carrier generation efficiency and the carrier transport efficiency inside the photosensitive layer are improved, resulting in high sensitivity and durability. In particular, it is an electrophotographic photoreceptor having excellent potential stability during durable use.

Claims (2)

(57) [Claims] An electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a disazo pigment represented by the following general formula (1). General formula In the formula, A represents a coupler residue having a phenolic hydroxyl group represented by the following general formulas (2) to (5), R ₁ and R ₂ are a hydrogen atom, an alkyl group, an alkoxy group, a substituted or unsubstituted aryl group. Alternatively, it represents a substituted or unsubstituted aralkyl group or cyano group. General formula In the formula, X represents a residue necessary for forming a polycyclic aromatic ring or a heterocyclic ring by being condensed with a benzene ring, R ₃ and R ₄ are a hydrogen atom, an alkyl group which may have a substituent, It represents an aryl group, an aralkyl group, a heterocyclic group or a cyclic amino group containing in the ring a nitrogen atom to which R ₃ and R ₄ are bonded, and Z represents an oxygen atom or a sulfur atom. General formula In the formula, Y represents a divalent group of an aromatic hydrocarbon or a divalent group of a heterocycle containing a nitrogen atom in the ring. General formula In the formula, X represents a residue necessary for forming a polycyclic aromatic ring or a heterocycle by being condensed with a benzene ring, and R ₅ represents an aryl group or a heterocyclic group which may have a substituent. General formula In the formula, X represents a residue necessary for forming a polycyclic aromatic ring or a heterocyclic ring by condensing with a benzene ring, R ₆ and R ₇ are a hydrogen atom, an alkyl group which may have a substituent, An aralkyl group, an aryl group or a heterocyclic group is shown. 2. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer comprises at least two layers of a charge generating layer containing a disazo pigment represented by the general formula (1) and a charge transporting layer.