JPH077214B2 - Electrophotographic photoreceptor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor containing a disazo pigment having a specific molecular structure in a photoconductive layer. .

[Prior Art] Conventionally, pigments and dyes exhibiting photoconductivity have been announced in many documents.

For example, “RCA Review” Vol.23, P.413 ~ P.419 (1962.
In 9), the photoconductivity of phthalocyanine pigment was announced, and electrophotographic photoreceptors using this phthalocyanine pigment were disclosed in US Pat. No. 3397086 and US Pat.
It is described in Japanese Patent Publication No. 816118. In addition, examples of organic semiconductors used for electrophotographic photoreceptors include US Pat. No. 4,315,983, US Pat. No. 4,327,169, and “Reseac”.
h Disclosure "20517 (1981.5), pyrylium-based dye, squaric acid methine dye described in U.S. Pat. No. 3824099, U.S. Pat. No. 3898084.
And the disazo pigments described in US Pat. No. 4,251,613 and the like.

Such an organic semiconductor is easier to synthesize than an inorganic semiconductor and can be synthesized as a compound having photoconductivity with respect to light in a required wavelength range. The electrophotographic photosensitive member formed on the conductive support has the advantage that the color sensitivity is improved,
It has problems in sensitivity and durability.

[Problems to be Solved by the Invention] It is an object of the present invention to provide a novel photoconductive material, which can be used in all the electrophotographic processes to date, and has practical high sensitivity characteristics and repetitive action. An object is to provide an electrophotographic photoreceptor having stable potential characteristics.

[Means and Actions for Solving Problems] The present invention relates to an electrophotographic photoreceptor having a photoconductive layer,
The photoconductive layer contains a disazo pigment represented by the following general formula (1), which is an electrophotographic photoreceptor.

General formula (1) In the formula, R ₁ represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, an alkoxy group or a halogen atom, a nitro group, a cyano group, R ₂ , R ₃ and R ₄
And R ₅ represent a hydrogen atom or an electron-withdrawing group, A and A ′ represent a coupler residue having a phenolic hydroxyl group, and A and A ′ may be the same or different,
Ar ₁ and Ar ₂ represent a substituted or unsubstituted carbocyclic aromatic ring group or a substituted or unsubstituted heterocyclic aromatic ring group, and Ar ₁ and Ar ₂ may be the same or different. .

Specifically, R ₁ is methyl, ethyl, propyl, isopropyl, butyl, s-butyl, t-butyl, methoxy, ethoxy, propoxy, phenoxy, phenyl, p-toluyl, benzyl, phenethyl, naphthylmethyl, fluorine atom, Groups such as chlorine atom, bromine atom, iodine atom, nitro, cyano, etc. are mentioned, and the substituents are halogen atom such as fluorine atom, chlorine atom, bromine atom, iodine atom, alkyl group such as methyl, ethyl, propyl, butyl and the like. Alkoxy groups such as methoxy, ethoxy, propoxy and phenoxy, nitro groups, cyano groups, dimethylamino, diethylamino, dibenzylamino, diphenylamino, morpholino, substituted amino groups such as piperidino and pyrrolidino.

Examples of the electron withdrawing group for R _{2 to} R ₅ include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, a cyano group and a nitro group.

More preferred specific examples of the coupler residue having a phenolic hydroxyl group of A and A'include the following general formulas (2) to
The residue shown by (8) is mentioned.

General formula In the formula, X is condensed with a benzene ring to form a polycyclic aromatic ring such as a naphthalene ring, anthracene ring, carbazole ring, benzcarbazole ring, dibenzofuran ring, dibenzonaphthofuran ring, or diphenylene sulfite ring, or a heterocyclic ring. Indicates the required residue.

The ring to which X is bonded is more preferably a naphthalene ring, an anthracene ring, a carbazole ring, or a benzcarbazole ring.

R ₆ and R ₇ are a hydrogen atom, an alkyl group which may have a substituent, an aryl, an aralkyl group, a heterocyclic group or R ₆ , R ₇
A cyclic amino group is shown together with the nitrogen atom to which is bonded.

Specific examples of the alkyl group include methyl, ethyl, propyl and butyl, specific examples of the aralkyl group include benzyl, phenethyl and naphthylmethyl, and specific examples of the aryl group include phenyl, diphenyl, naphthyl and anthryl, and a heterocyclic group. Specific examples of include carbazole, dibenzofuran, thiazole, pyridine, and the like.

General formula In the formula, R ₈ and R ₉ represent a hydrogen atom, an alkyl group which may have a substituent, an aryl group or an aralkyl group. Specific examples of R ₈ and R ₉ are the same as those of R ₆ and R ₇ .

The alkyl group, the aryl group, the aralkyl group, the alkoxy group, and the heterocyclic group represented by the substituents R _{6 to} R _{9 in} the general formulas (2) to (4) may be other substituents such as a fluorine atom, a chlorine atom,
Halogen atom such as iodine atom, bromine atom, alkyl group such as methyl, ethyl, propyl, isopropyl, butyl, alkoxy group such as methoxy, ethoxy, propoxy, phenoxy, nitro group, cyano group, dimethylamino, dibenzylamino, diphenyl It may be substituted with a substituted amino group such as amino, morpholino, piperidino and pyrrolidino.

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

General formula In the formula, R ₁₀ represents an aryl group or a heterocyclic group which may have a substituent, and specifically represents a phenyl, naphthyl, anthryl, pyrenyl, pyridyl, thienyl, furyl or carbazolyl group. Further, as the substituent of the aryl group and the heterocyclic group, a halogen atom such as a fluorine atom, a chlorine atom, an iodine atom and a bromine atom, methyl, ethyl, propyl,
Alkyl groups such as isopropyl and butyl, alkoxy groups such as methoxy, ethoxy, propoxy and phenoxy,
Substituted amino groups such as nitro group, cyano group, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino can be mentioned.

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

General formula In the formula, R ₁₁ and R ₁₂ represent an alkyl group which may have a substituent, an aryl group, an aralkyl group or a heterocyclic group, and specifically, methyl, ethyl, propyl, butyl, benzyl, phenethyl, naphthylmethyl. , Phenyl, diphenyl, naphthyl, anthryl, carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine. Atom, halogen atom such as iodine atom, bromine atom, methyl, ethyl, propyl, isopropyl,
Examples thereof include an alkyl group such as butyl, an alkoxy group such as methoxy, ethoxy, propoxy and phenoxy, a nitro group, a cyano group, a substituted amino group such as dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino and pyrrolidino.

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

Ar ₁ and Ar ₂ in the general formula (1) are specifically phenyl,
Carbocyclic aromatic ring groups such as naphthyl and anthryl or heterocyclic aromatic ring groups such as furyl, pyroyl, thienyl, pyridyl and pyrazinyl are mentioned, and the substituents are fluorine atom, chlorine atom, iodine atom, bromine atom. Halogen atom such as, alkyl group such as methyl, ethyl, propyl, isopropyl, butyl, alkoxy group such as methoxy, ethoxy, propoxy, phenoxy, nitro group,
Examples of the substituted amino group include cyano group, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino.

Next, a general method for producing the disazo pigment used in the present invention will be described.

When A and A ′ are the same in the disazo pigment represented by the general formula (1), the diamine represented by the following general formula (9) is converted into a tetrazonium salt by a conventional method such as sodium nitrite or nitrosyl sulfuric acid. (In the formula, R _{1 to} R ₅ , Ar ₁ and Ar ₂ are synonymous with those in the general formula (1)) Either water coupling is performed with coupler components A and A ′, or the obtained tetrazolium salt is fluorinated. It can be synthesized by taking out as a stable salt such as a carboxylic acid salt and then coupling in an organic solvent such as DMF. When A and A'are different, the first coupler component and the cup are used in the coupling reaction. It can be synthesized by ring-forming the monoazo form and then coupling it with the second coupler component to form the disazo pigment, or by mixing two coupler components and subjecting them to the coupling reaction, but surely The former method is preferred for obtaining asymmetric pigments.

Typical examples of the disazo pigment represented by the general formula (1) of the present invention are listed below.

The disazo pigments shown in the above specific examples do not limit the claims of the present invention.

The film containing the above-mentioned disazo pigment exhibits photoconductivity, and therefore can be used for the photosensitive layer of the electrophotographic photoreceptor described below.

That is, in a specific example of the present invention, an electrophotographic photosensitive member is prepared by forming a film on the conductive support by the vacuum deposition method or by forming a film by dispersing and dispersing the disazo pigment in an appropriate binder. can do.

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

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

The charge generation layer contains a disazo pigment exhibiting the above-mentioned photoconductivity as much as possible in order to obtain sufficient absorption, and a thin film layer for shortening the range of the generated charge carriers,
For example, a thin film layer having a thickness of 5 μm or less, preferably 0.01 to 1 μm is preferable.

This means that most of the incident light is absorbed in the charge generation layer to generate many charge carriers, and the generated carriers need to be injected into the charge transport layer without being deactivated by recombination or trapping. It is due to being there.

The charge generation layer can be formed by dispersing the disazo pigment in an appropriate binder and coating the dispersion on a substrate, or can be obtained by forming a vapor deposition film using a vacuum vapor deposition device.

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 is also selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.),
Examples of the insulating resin include polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinyl pyridine, cellulosic resin, polyurethane, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone.

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

The solvent that dissolves these resins varies depending on the type of the resin, and is preferably selected from those that do not dissolve the charge transport layer and the undercoat layer described below.

Specific organic solvents include methanol, ethanol,
Alcohols such as isopropanol, acetone, methyl ethyl ketone, ketones such as cyclohexanone, N,
N-dimethylformamide, N, N-dimethylacetamide and other amides, dimethyl sulfoxide and other sulfoxides, tetrahydrofuran, dioxane, ethylene glycol monomethyl ether and other ethers, methyl acetate, ethyl acetate and other esters, chloroform, methylene chloride It is possible to use aliphatic halogenated hydrocarbons such as dichloroethylene, carbon tetrachloride, and trichloroethylene, or aromatic hydrocarbons such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene.

The coating can be performed using a coating method such as a dip coating method or a spray coating method.

Drying is preferably a method of drying by touching at room temperature and then drying by heating. The heat drying can be performed at a temperature of 30 to 200 ° C. for a time in the range of 5 minutes to 2 hours while still or under blowing air.

The charge transport layer is electrically connected to the aforementioned charge generation layer, and has a function of receiving charge carriers injected from the charge generation layer in the presence of an electric field and capable of transporting these charge carriers to the surface. ing. At this time, the charge transport layer may be laminated on or below the charge generation layer.

When the charge-transporting layer is formed on the charge-generating layer, the charge-transporting substance includes an electron-transporting substance and a hole-transporting substance, and the electron-transporting substance includes chloranil, bromoanil, tetracyanoethylene, and tetracyanoquinodimethane. , 2,4,
7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone, 2, There are electron-withdrawing substances such as 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-phenylhydrazone, p-pyrrolidino Benzaldehyde-N, N-
Hydrazones such as diphenylhydrazone, 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1-phenyl-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) Pyrazoline, 1- [quinolyl (2)]-2- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (p-diethylaminostyryl) -5- (P-Diethylaminophenyl) pyrazoline, 1-phenyl-3- (p-diethylaminostyryl) -4-methyl-5- (p-diethylaminophenyl) pyrazoline, 1-phenyl-3- (α-benzyl-p-diethylaminostyryl) ) -5- (p-Diethylaminophenyl) pyrazoline, spiropyrazoline and other pyrazolines, 2 -(P-diethylaminostyryl) -6-diethylaminobenzoxazole, 2-
Oxazole compounds such as (p-diethylaminophenyl) -4- (p-dimethylaminophenyl) -5- (2-chlorophenyl) oxazole, thiazole compounds such as 2- (p-diethylaminostyryl) -6-diethylaminobenzothiazole , Triarylmethane compounds such as bis (4-diethylamino-2-methylphenyl) -phenylmethane, 1,1-bis (4-N, N-diethylamino-2-methylphenyl) heptane, 1,1,2, Polyarylalkanes such as 2-tetrakis (4-N, N-dimethylamino-2-methylphenyl) ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9- Vinylphenylanthracene, pyrene-formaldehyde Fat,
Examples include ethylcarbazole-formaldehyde resin.

In addition to this organic charge transport material, selenium, selenium-tellurium,
Inorganic materials such as amorphous silicon and cadmium sulfide can also be used. These charge transport substances can be used alone or in combination of two or more.

When the charge transport material has no film-forming property, a film can be formed by selecting an appropriate binder. The resin that can be used as the binder is, for example, an acrylic resin,
Polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer,
Examples thereof include insulating resins such as acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, and chlorinated rubber, and organic photoconductive polymers such as poly-N-vinylcarbazole polyvinylanthracene and polyvinylpyrene.

Since the charge transport layer has a limit of transporting charge carriers, the film thickness cannot be increased more than necessary. Generally, it is 5 to 30 μm, but the preferred range is 8 to 20 μm.
Is. When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

The photosensitive layer having such a laminated structure of the charge generation layer and the charge transport layer is provided on the substrate having the conductive layer. As the substrate having a conductive layer, a substrate having conductivity itself, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold or platinum is used.

In addition, a plastic having a layer formed by vacuum deposition of aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluoride). Ethylene, etc.), conductive particles (eg, carbon black, silver particles, etc.) coated on a plastic with an appropriate binder, a substrate in which conductive particles are impregnated into plastic or paper, and a plastic having a conductive polymer, etc. Can be used.

An undercoat layer having a barrier function and an adhesive function can be provided between the conductive layer and the photosensitive layer. The subbing layer can be formed of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. . The thickness of the undercoat layer is 0.
1 to 5 μm, preferably 0.5 to 3 μm is suitable.

In the case of using a photoreceptor in which a conductive layer, a charge generation layer and a charge transport layer are laminated in this order and the charge transport material is an electron transport material, it is necessary to positively charge the surface of the charge transport layer. Then, 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 and the surface potential is attenuated, resulting in electrostatic contrast with the unexposed area. Occurs.

A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively chargeable toner.

This can be fixed directly, or the toner image can be transferred to paper or a plastic film and then developed and fixed.

Further, there is also a method in which the electrostatic latent image on the photoconductor is transferred onto the insulating layer of the transfer paper and then developed and fixed. The developer, the developing method, and the fixing method may be selected from known ones and known ones, and are not limited to particular ones.

On the other hand, when the charge transport material is a hole transport material, the surface of the charge transport layer needs to be negatively charged, and after exposure after charging, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. After that, it reaches the surface to neutralize the negative charges, the surface potential is attenuated, and an electrostatic contrast is generated with the unexposed portion. At the time of development, it is necessary to use a positively chargeable toner, contrary to the case of using an electron transport substance.

In the case of using an electrophotographic photoreceptor in which a conductive layer, a charge transport layer, and a charge generation layer are laminated in this order, when the charge transport substance is an electron transport substance, the charge generation layer surface must be negatively charged, When exposed after charging, electrons generated in the charge generation layer in the exposed portion are injected into the charge transport layer and then reach the substrate. On the other hand, the holes generated in the charge generation layer reach the surface, the surface potential is attenuated, and electrostatic contrast is generated between the hole and the unexposed portion. A visible image can be obtained by developing the electrostatic latent image thus formed with a positively chargeable toner. This can be fixed directly, or the toner image can be transferred to paper or a plastic film and then developed and fixed.

Further, there is also a method in which the electrostatic latent image on the photoconductor is transferred onto the insulating layer of the transfer paper and then developed and fixed. The developer, the developing method, and the fixing method may be selected from known ones and known ones, and are not limited to particular ones.

On the other hand, when the charge generating layer is made of a hole transporting substance, the surface of the charge generating layer needs to be positively charged, and when exposed after charging, holes generated in the charge generating layer are injected into the charge transporting layer in the exposed portion. , Then reach the substrate. On the other hand, the electrons generated in the charge generation layer reach the surface, the surface potential is attenuated, and electrostatic contrast is generated between the electron and the unexposed portion. At the time of development, it is necessary to use a negatively chargeable toner, contrary to the case where an electron transporting substance is used.

Further, in another embodiment of the present invention, the above-mentioned hydrazones, pyrazolines, oxazoles, thiazoles, triarylmethanes, polyarylalkanes, triphenylamine, poly-N-vinylcarbazoles, and other organic photoconductive materials are used. The photosensitive film may contain the disazo pigment represented by the general formula (1) as a sensitizer of a substance or an inorganic photoconductive substance such as zinc oxide, cadmium sulfide or selenium. This photosensitive film is formed by coating these photoconductive substance and the disazo pigment together with a binder. Further, as another specific example of the present invention, an electrophotographic photoreceptor containing the disazo pigment represented by the general formula (1) in the same layer together with the charge transporting substance can be mentioned. In this case, a charge transfer complex compound composed of poly-N-vinylcarbazole and trinitrofluorenone can be used in addition to the above charge transport material.

The electrophotographic photoreceptor of this example can be prepared by dispersing the above-mentioned disazo pigment and the charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran and then forming a film.

The pigment used in any electrophotographic photoreceptor contains at least one pigment selected from the disazo pigments represented by the general formula (1), and its crystal form may be amorphous or crystalline. Good. Further, if necessary, pigments having different light absorption may be used in combination to enhance the sensitivity of the photoconductor and to obtain a panchromatic photoconductor.
It is also possible to use two or more disazo pigments represented by the above or to use in combination with a charge generating substance selected from known dye pigments.

The electrophotographic photoreceptor of the present invention can be widely used not only in electrophotographic copying machines but also in electrophotographic application fields such as laser printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

[Examples] Examples 1 to 25 Aqueous ammonia solution of casein (casein 1
1.2%, 1 g of ammonia water, 222 ml of water) were applied by a Meyer bar so that the film thickness after drying was 1.0 μm, and dried.

Next, 5 g of the above-exemplified disazo pigment (1) was added to ethanol 95
2 g of butyral resin (butyralization degree: 63 mol%) was dissolved in ml, and the mixture was dispersed in a sand mill for 2 hours. The film thickness after drying this dispersion on the casein layer previously formed is 0.
A charge generating layer was formed by coating with a Meyer bar to a thickness of 5 μm and drying.

Then the structural formula Hydrazone compound (5 g) and polymethylmethacrylate (number average molecular weight 100,000) (5 g) are dissolved in 70 ml of benzene, and this is applied to the charge generation layer with a Meyer bar so that the film thickness after drying is 12 μm and dried. The charge transport layer was formed to prepare the electrophotographic photosensitive member of Example 1. Electrophotographic photoreceptors corresponding to Examples 2 to 25 were prepared in the same manner by using other exemplified pigments instead of the exemplified pigment (1).

The electrophotographic photoconductor thus prepared was corona-charged at -5 KV by a static method using an electrostatic copying paper tester (SP-428), kept in the dark for 1 second, and then exposed at an illumination of 2 lux. , Charging characteristics were investigated.

As the charging characteristics, the surface potential (V ₀ ) and the exposure amount (E1 / 2) required to attenuate the potential when dark-decayed for 1 second to 1/2 were measured. The results are shown.

Further, using the electrophotographic photoconductors used in Examples 2, 10, 11, 14, and 23, fluctuations in the light portion potential and the dark portion potential during repeated use were measured.

As a method, -5.6KV corona charger, exposure optical system,
The photoconductor was attached to a cylinder of an electrophotographic copying machine equipped with a developing device, a transfer charger, a static elimination exposure optical system and a cleaner. This copying machine is configured so that an image can be obtained on a transfer paper as the cylinder is driven.

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

This result is shown.

Example 26 5 g of 2,4,7-trinitro-9-fluorenone and 5 g of poly-4,4-dioxydiphenyl-2,2-propane carbonate (molecular weight 300,000) were formed on the charge generation layer formed in Example 2. Was dissolved in 70 ml of tetrahydrofuran to prepare a coating solution,
It was applied and dried so that the coating amount after drying was 10 g / m ² .

The electrophotographic photosensitive member thus prepared was subjected to charge measurement in the same manner as in Example 1. At this time, the charging polarity was +. The results are shown.

V ₀ : 580V, E1 / 2: 3.0lux, sec Example 27 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, the dispersion liquid of the disazo pigment used in Example 13 was applied on the polyvinyl alcohol layer previously formed by a Meyer bar so that the film thickness after drying was 0.5 μm, and dried to form a charge shipping layer. .

Then Of pyrazoline compound (5 g) and polyarylate (bisphenol A and terephthalic acid-isophthalic acid condensation polymer) (5 g) dissolved in 70 ml of tetrahydrofuran are applied on the charge generation layer so that the film thickness after drying is 10 μm and dried. Then, the charge transport layer was formed. The charging characteristics and durability characteristics of the thus prepared photoconductor were measured by the same method as in Example 1. The results are shown.

V ₀ : −645V, E1 / 2: 2.5lux, sec Endurance characteristics Initial V _D : −600V, V _L : −100V After 5,000 sheets endurance V _D : −605V, V _L : −101V As the result above, The sensitivity is also good, and the potential stability during durable use is also good.

Example 28 An ammonia solution of casein was applied onto an aluminum plate having a thickness of 100 μm and dried to form an undercoat layer having a thickness of 0.5 μm.

Next, 5 g of 2,4,7-trinitro-9-fluorenone and poly-
A charge transfer complex compound was prepared by dissolving 5 g of N-vinylcarbazole (number average molecular weight 300,000) in 70 ml of tetrahydrofuran.

1 g of this charge transfer complex compound and the exemplified pigment (22) was added to and dispersed in a solution of 5 g of a polyester resin in 70 ml of tetrahydrofuran. This dispersion was applied onto the undercoat layer and dried to give a film thickness of 12 μm.

The charging characteristics of the produced electrophotographic photosensitive member were measured by the same method as in Example 1. However, the charging polarity was +. The results are shown.

V ₀ : + 600V, E1 / 2: 3.5lux, sec Example 29 A charge transport layer and a charge generating layer similar to those in Example 20 were sequentially laminated on the casein layer of the aluminum substrate provided with the casein layer used in Example 28. Then, a photoreceptor was prepared in the same manner except that the layer structure was different.

The charging characteristics were measured by the same method as in Example 1.

However, the charging polarity was +.

V ₀ : + 620V, E1 / 2: 3.7lux, sec [Effects of the Invention] The electrophotographic photoreceptor of the present invention uses a specific disazo pigment in the photosensitive layer, so that the carrier inside the photosensitive layer containing the disazo pigment can be used. It is presumed that either or both of the generation efficiency and the carrier transportation efficiency are improved, and a remarkable effect is exhibited as a high sensitivity and excellent potential stability during durable use.

Claims (8)

[Claims] 1. An electrophotographic photoreceptor having a photoconductive layer, wherein the photoconductive layer contains a disazo pigment represented by the following general formula (1). General formula (1) In the formula, R ₁ represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, an alkoxy group or a halogen atom, a nitro group, a cyano group, R ₂ , R ₃ and R ₄
And R ₅ represents a hydrogen atom or an electron-withdrawing group, A and A ′ represent a coupler residue having a phenolic hydroxyl group, and A and A ′ may be the same or different,
Ar ₁ and Ar ₂ represent a substituted or unsubstituted carbocyclic aromatic ring group or a substituted or unsubstituted heterocyclic aromatic ring group, and Ar ₁ and Ar ₂ may be the same or different. . 2. The electron according to claim 1, wherein one or both of A and A'in the general formula (1) is a coupler residue having a phenolic hydroxyl group represented by the following general formula (2). Photoreceptor. General formula In the formula, X is 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 hydrogen atoms,
It represents a cyclic amino group together with an optionally substituted alkyl group, aryl group, aralkyl group, heterocyclic group or nitrogen atom to which R ₆ and R ₇ are bonded. 3. The electron according to claim 1, wherein one or both of A and A'in the general formula (1) is a coupler residue having a phenolic hydroxyl group represented by the following general formula (3). Photoreceptor. General formula In the formula, R ₆ represents an optionally substituted alkyl group, aryl group or aralkyl group. 4. The electron according to claim 1, wherein one or both of A and A'in the general formula (1) is a coupler residue having a phenolic hydroxyl group represented by the following general formula (4). Photoreceptor. General formula In the formula, R ₉ represents an alkyl group which may have a substituent, an aryl group or an aralkyl group. 5. The electron according to claim 1, wherein one or both of A and A'in the general formula (1) is a coupler residue having a phenolic hydroxyl group represented by the following general formula (5). Photoreceptor. General formula In the formula, Y represents a divalent group of an aromatic hydrocarbon or a heterocyclic divalent group containing a nitrogen atom in the ring. 6. The electron according to claim 1, wherein one or both of A and A'in the general formula (1) is a coupler residue having a phenolic hydroxyl group represented by the following general formula (6). Photoreceptor. General formula In the formula, Y represents a divalent group of an aromatic hydrocarbon or a heterocyclic divalent group containing a nitrogen atom in the ring. 7. The electron according to claim 1, wherein one or both of A and A'in the general formula (1) is a coupler residue having a phenolic hydroxyl group represented by the following general formula (7). Photoreceptor. General formula In the formula, R ₁₀ represents an aryl group or a heterocyclic group which may have a substituent, and X has the same meaning as X in the general formula (2). 8. The electron according to claim 1, wherein one or both of A and A'in the general formula (1) is a coupler residue having a phenolic hydroxyl group represented by the following general formula (8). Photoreceptor. General formula In the formula, R ₁₁ and R ₁₂ represent an alkyl group, an aryl group, an aralkyl group or a heterocyclic group which may have a substituent, and X has the same meaning as X in the above general formula (2).