JPH0830899B2 - Electrophotographic photoreceptor - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor containing a specific azo pigment.

[Prior Art] An electrophotographic photoreceptor using an inorganic photoconductor such as selenium, cadmium sulfide, or zinc oxide as a photosensitive component has been heretofore known.

On the other hand, a number of organic photoconductors have been developed since the discovery that specific organic compounds exhibit photoconductivity.
For example, organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene, carbazole,
Low molecular weight organic photoconductors such as anthracene, pyrazolines, oxadiazoles, hydrazones, polyarylalkanes and phthalocyanine pigments, azo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindigo dyes Alternatively, organic pigments and dyes such as squaric acid methine dye are known. In particular, organic pigments and dyes having photoconductivity are easier to synthesize than inorganic materials, and moreover, the variation in selecting a compound exhibiting photoconductivity in an appropriate wavelength range has been expanded.
Many photoconductive organic pigments and dyes have been proposed.

For example, U.S. Patent No. 4123270, No. 4247614, No. 4251613, No. 4251614,
No. 4,256,821, No. 4,260,672, No. 4,268
No. 596, No. 4,278,747, Azo pigment showing photoconductivity as a charge generating substance in a photosensitive layer functionally separated into a charge generating layer and a charge transporting layer as disclosed in the specification of No. 4,293,628, etc. An electrophotographic photoreceptor using the same is known.

An electrophotographic photosensitive member using such an organic photoconductor,
Since it can be produced by coating by properly selecting the binder, it has the advantage of being able to provide an extremely high-sensitivity and inexpensive photoreceptor, and being able to freely control the photosensitive wavelength range by selecting an organic pigment. However, this photoreceptor has practical problems in terms of sensitivity and durability, and has problems.

Conventional azo pigments are compounds having an amide structure at the coupler site (for example, JP-A-47-37543, JP-A-47-37543).
8-122967), compounds having a hydrazone structure (for example, JP-A-56-94358) and the like,
The present inventors, as a result of studies to solve the above problems,
It has been found that a compound having a structure represented by the general formula (I) described below is extremely effective when used as a coupler.

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel electrophotographic photosensitive member, and to provide an electrophotographic photosensitive member having practical high sensitivity characteristics and stable potential characteristics in repeated use. Is.

[Means for Solving the Problems and Action] The present invention relates to a substituted or unsubstituted aromatic group which may be bonded via a bonding group to an organic residue represented by the following general formula (I) on a conductive support. An electrophotographic photosensitive member comprising a photosensitive layer containing an azo pigment having a structure bonded to a hydrocarbon group or an aromatic heterocyclic group.

In the formula, X represents a residue necessary for forming an aromatic hydrocarbon group or an aromatic heterocyclic group which may be condensed with a benzene ring to form a substituent, and R ₁ is a substituent. Represents an aromatic hydrocarbon group or an aromatic heterocyclic group, n ₁ is 0 or 1
Is an integer.

The specific azo pigment in the present invention can be represented by the following general formula (II).

In the formula, Ar represents a substituted or unsubstituted aromatic hydrocarbon group or an aromatic heterocyclic group which may be bonded via a bonding group, and n is an integer of 1, 2, 3 or 4. In addition,
X, R ₁ and n ₁ have the same meaning as in formula (I).

Specifically, X is an aromatic hydrocarbon such as naphthalene, anthracene, carbazole, benzcarbazole, dibenzocarbazole, dibenzofuran, benzonaphthofuran, fluorenone, or diphenylsulfide, which may be condensed with a benzene ring and have a substituent. A group or a residue necessary for forming an aromatic heterocyclic group is mentioned, and as R ₁ , benzene which may have a substituent, naphthalene, fluorene, phenanthrene, anthracene, an aromatic hydrocarbon group such as pyrene, Furan, thiophene, pyridine, benzothiazole, carbazole, dibenzothiophene,
Examples thereof include aromatic heterocyclic groups such as benzoxazole, benzotriazole, oxadiazole, and thiadiazole.

As the substituents for X and R ₁ above, methyl,
Alkyl groups such as ethyl and propyl, alkoxy groups such as methoxy and ethoxy, substituted amino groups such as diethylamino and dimethylamino, halogen atoms such as fluorine atom, chlorine atom and bromine atom, nitro group, cyano group, trifluoromethyl etc. Examples thereof include halomethyl group.

Examples of Ar (a substituted or unsubstituted aromatic hydrocarbon group or aromatic heterocyclic group which may be bonded via a bonding group to which the organic residue represented by the general formula (I) is bonded) include benzene, naphthalene and fluorene. , Aromatic hydrocarbon groups such as phenanthrene, anthracene, and pyrene; aromatic heterocyclic groups such as furan, thiophene, pyridine, indole, benzothiazole, carbazole, acridone, dibenzothiophene, benzoxazole, benzotriazole, oxadiazole, and thiadiazole. Further, those which are bonded to the above aromatic groups directly or by an aromatic or non-aromatic group, for example, triphenylamine, diphenylamine, N-methyldiphenylamine, biphenyl, terphenyl, binaphthyl, fluorenone, phenanthrenequinone, anthraquinone. , Nzuantoron, diphenyl oxadiazole, phenyl benzoxazole, diphenylmethane, diphenyl sulfone, diphenyl ether, benzophenone, stilbene, distyryl benzene, tetraphenyl -p- phenylenediamine, etc. tetraphenyl benzidine and the like.

Examples of the substituent in Ar include alkyl groups such as methyl, ethyl, propyl and butyl, alkoxy groups such as methoxy and ethoxy, dialkylamino groups such as diethylamino and dimethylamino, halogen atoms such as fluorine atom, chlorine atom and bromine atom. , Hydroxy group, nitro group,
Cyano group, halomethyl group or general formula -N = N-Cp (II
I) (in the formula, Cp represents a coupler residue having a phenolic hydroxyl group).

Preferred examples of Cp in the general formula (III) include groups having a structure represented by the following general formula.

In the above general formula, X and R ₁ have the same meanings as in general formula (I), and R ₂ and R ₃ are hydrogen atoms, optionally substituted alkyl groups, aralkyl groups, aryl groups, heterocyclic groups or R ₂
And R ₃ represent a cyclic amino group containing a nitrogen atom to be bonded in the ring, and R ₄ and R ₅ represent a hydrogen atom, an optionally substituted alkyl group, an aralkyl group, an aryl group or a heterocyclic group. , R ₆ represents an alkyl group, an aralkyl group, an aryl group or a heterocyclic group which may have a substituent, and Y ₁ represents a divalent aromatic hydrocarbon group or a heterocyclic group which may have a substituent. , Including Y ₁ as, Etc., Y ₂ represents a divalent aromatic hydrocarbon group which may have a substituent, such as o-phenylene, o-naphthylene, perinaphthylene, 1,2-anthrylene, and 9,10-phenanthrene. Group, Y ₃ represents a divalent aromatic hydrocarbon group which may have a substituent or a divalent heterocyclic group containing a nitrogen atom in the ring, and represents a divalent aromatic hydrocarbon group. Include groups such as o-phenylene, o-naphthylene, perinaphthylene, 1,2-anthrylene, and 9,10-phenanthrene, and a divalent heterocyclic group containing a nitrogen atom in the ring is 3,4-pyrazolediyl. , 2,3-pyridinediyl, 4,5-pyrimidinediyl, 6,7-indazolediyl, 5,6-benzimidazolediyl, 6,7-quinolinediyl and the like groups, Z is an oxygen atom or a sulfur atom. B is an oxygen atom, a sulfur atom or N Substituted, it represents an unsubstituted imino group, N- examples of the substituent optionally substituted alkyl group, an aralkyl group, an aryl group.

Examples of the alkyl group in the above expression include groups such as methyl, ethyl, propyl and butyl, examples of the aralkyl group include groups such as benzyl, phenethyl and naphthylmethyl, and examples of the aryl group include phenyl, diphenyl, naphthyl and anthryl. Examples of the heterocyclic group include pyridyl, thienyl, furyl, thiazolyl, carbazolyl, dibenzofuryl, benzimidazolyl, and benzothiazolyl groups, and the cyclic amino group containing a nitrogen atom in the ring includes pyrrole, pyrroline, Examples include cyclic amino groups derived from pyrrolidine, pyrrolidone, indole, indoline, isoindole, carbazole, benzoindole, imidazole, pyrazole, pyrazoline, oxazine, phenoxazine, benzocarbazole and the like.

Examples of the substituent in the above expression include an alkyl group such as methyl, ethyl and propyl, an alkoxy group such as methoxy and ethoxy, a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and an alkylamino such as dimethylamino and diethylamino. And halomethyl groups such as phenylcarbamoyl group, nitro group, cyano group and trifluoromethyl.

Listed below are representative examples of the specific azo pigments used in the present invention.

The coupler component represented by the following general formula (XIV) used in the synthesis of the azo pigment used in the present invention includes a corresponding acid halogen compound represented by the general formula (XV) and a corresponding guanidino compound or amidino compound represented by the general formula (XVI). It is easily synthesized by reacting with a compound by a known method.

(In the formula, R ₁ , X and n ₁ have the same meanings as in formula (I), and X ′ represents a halogen atom.) The specific azo pigment used in the present invention is prepared by diazotizing a corresponding amino compound by a conventional method. , After coupling with the coupler synthesized above in the presence of an alkali, or once isolating the corresponding diazonium salt of an amino compound in the form of a salt such as a borofluoride salt or a zinc chloride double salt, for example, N, N- It can be produced by coupling in an organic solvent such as dimethylformamide or dimethylsulfoxide in the presence of a base such as sodium acetate, pyridine or triethylamine.

Further, among the above-mentioned specific azo pigments, in the case of disazo pigments, trisazo pigments, and tetrakisazo pigments, other couplers can be used if one or more coupler components represented by the general formula (XIV) are contained in the same molecule. It may contain components.

In this case, the synthesis method is such that after diazotizing the amino compound represented by the general formula (XVII) and coupling with the coupler represented by the general formula (XIV), (CH ₃ CONH) _m —Ar— (NH ₂ ) _l ( XVII) (wherein Ar has the same meaning as in the general formula (II), l and m are integers of 1, 2 or 3 and l + m is 2, 3 or 4) Hydrolyzed with a mineral acid such as hydrochloric acid , May be synthesized by adding diazo again and coupling with another coupler having a phenolic hydroxyl group, or ArNH ₂ ) _n (XVIII) (wherein Ar has the same meaning as in the general formula (II), n Represents an integer of 2, 3 or 4) in the usual manner to form a diazonium salt, which is mixed with a coupler represented by the general formula (XIV) and a coupler other than the coupler to dissolve it. You may synthesize by coupling with.

Alternatively, the first coupler component may be first coupled to form a monoazo compound, and then a coupler may be sequentially added to each of the same components and coupled to synthesize a corresponding azo pigment.

Synthesis Example (Synthesis of Exemplified Pigment (2-1)) 200 ml of water and 48 ml (0.5 mol) of concentrated hydrochloric acid were put in a 500 ml beaker, and while cooling in an ice-water bath, 20.0 g of o-dianisidine
(0.082 mol) was added, and the liquid temperature was adjusted to 0 to 3 ° C with stirring. Next, a solution prepared by dissolving 12.0 g (0.174 mol) of sodium nitrite in 20 ml of water was added dropwise over 10 minutes while keeping the liquid temperature at 5 ° C. or lower, and after the addition was completed, the mixture was stirred at the same temperature for 30 minutes. Activated carbon (5 g) was added to the reaction solution, and after filtration, sodium borofluoride 2
A solution prepared by dissolving 7.0 g (0.246 mol) in 40 ml of water was added dropwise, and the precipitated borofluoride salt was collected by filtration, washed with water and dried in vacuum.

Yield 29.4g, Yield 81% Next, add 400ml of DMF to 1 beaker and add 1- (3-
Hydroxy-2-naphthoyl) -3-phenylguanidine 12.21 g (0.0400 mol) was dissolved, the liquid temperature was cooled to 5 ° C., and 8.48 g (0.0192 mol) of the borofluoride salt obtained above was dissolved, followed by triethylamine. 3.88 g (0.0384 mol) of 10
The mixture was added dropwise for 1 minute and then stirred for 2 hours. The reaction solution was filtered, washed with 400 ml of N, N-dimethylformamide 5 times, replaced with acetone, and dried under vacuum to obtain the desired pigment.

Yield 14.30 g, yield 85.0% (based on borofluoride salt) Elemental analysis Calculated value (%) Measured value (%) C 68.48 68.45 H 4.60 4.62 N 15.97 15.95 The film having the azo pigment described above exhibits photoconductivity, Therefore, it can be used for the photosensitive layer of the electrophotographic photoreceptor described below.

In a preferred specific embodiment of the present invention, the specific azo pigment described above can be used as the charge generating substance in the electrophotographic photosensitive member in which the photosensitive layer of the electrophotographic photosensitive member is functionally separated into a charge generating layer and a charge transporting layer.

The charge generation layer contains as much charge generation substance as possible in order to obtain sufficient absorbance, and is a thin film layer, for example, 5 μm or less, preferably 0.01 to less than, in order to shorten the traveling distance of the generated charge carrier. A thin film layer having a film thickness of 1 micron is preferable.

This means that most of the amount of incident light is absorbed by the charge generation layer, generating a large number of charge carriers, and the generated charge carriers are not deactivated by recombination or trapping (trap) and are transferred to the charge transport layer. This is due to the need to inject.

The charge generation layer can be formed by dispersing the above-mentioned specific azo pigment in a suitable binder and coating this on a conductive support.

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 at most 80% by weight, preferably at most 40% by weight.

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 a method of drying by touching at room temperature and then drying by heating. The heat drying can be carried out at a temperature of 30 to 200 ° C. for 5 minutes to 2 hours while still or under blowing air.

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 isopropyl alcohol, acetone, methyl ethyl ketone, ketones such as cyclohexanone, amides such as N, N-dimethylformamide, N, N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, ethylene glycol monomethyl ether Ethers such as, methyl acetate, esters such as ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene or benzene, toluene, xylene, ligroin, monochlorobenzene , Aromatics such as dichlorobenzene, etc. can be used.

The charge transport layer is electrically connected to the charge generation layer described above, and has a function of receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. ing.

At this time, the charge transport layer may be laminated on the charge generation layer or may be laminated below.

However, the charge transport layer is preferably laminated on the charge generation layer.

Since the photoconductor generally has the function of transporting charge carriers, the charge transport layer can be formed by this photoconductor.

The substance that transports the charge carrier in the charge transport layer (hereinafter referred to as the charge transport substance) is preferably substantially insensitive to the wavelength range of the electromagnetic wave to which the above-mentioned charge generation layer is sensitive.

The electromagnetic wave as used herein includes a broad definition of light rays including γ rays, X rays, ultraviolet rays, visible rays, near infrared rays, infrared rays, and far infrared rays.

When the photosensitive wavelength region of the charge transport layer coincides with or overlaps that of the charge generation layer, the charge carriers generated by the two capture each other, resulting in a decrease in sensitivity.

There are electron transporting substances and hole transporting substances as charge transporting substances, and as the electron transporting substances, 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-tetranitroxanthone, 2,4,8-trinitrothioxanthone and the like, and these There is a polymer of an electron-withdrawing substance.

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-diethylaminebenzaldehyde-N, N-diphenylhydrazone, p-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone, p-pyrrolidino Benzaldehyde-N, N-
Diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N, N-diphenylhydrazone, p
Hydrazones such as -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-methoxypyridyl (2)]-3- (p-diethylaminostyryl) -5
(P-Diethylaminophenyl) pyrazoline, 1- [pyridyl (3)]-3- (p-diethylaminostyryl)
-5- (p-diethylaminophenyl) pyrazoline, 1
-[Lepidyl (2)]-3- (p-diethylaminoaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (p-diethylaminostyryl) -4-methyl -5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3-
(Α-methyl-p-diethylaminostyryl) -5-
(P-diethylaminophenyl) pyrazoline, 1-phenyl-3- (p-diethylaminostyryl) -4-methyl-5- (p-diethylaminophenyl) pyrazoline,
Pyrazolines such as 1-phenyl-3- (α-benzyl-p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline and spiropyrazoline;
Phenyl-4-N, N-diphenylaminostilbene, N
Styryl compounds such as -ethyl-3- (α-phenylstyryl) carbazole, 9-dibenzylaminobenzylidene-9H-fluorenone, 5-p-ditolylaminobenzylidene-5H-dibenzo [a, d] cycloheptene;
2- (p-diethylaminostyryl) -6-diethylaminobenzoxazole, 2- (p-diethylaminophenyl) -4- (p-dimethylaminophenyl) -5
Oxazole-based compounds such as (2-chlorophenyl) oxazole, 2- (p-diethylaminostyryl) -6
-Thiazole compounds such as diethylaminobenzothiazole, triarylmethane compounds such as bis (4-diethylamino-2-methylphenyl) -phenylmethane, 1,1-bis (4-N, N-diethylamino-2-methylphenyl) ) Heptane, polyarylalkanes such as 1,1,2,2 tetrakis (4-N, N-dimethylamino-2-methylphenyl) ethane, triphenylamine, poly-N-
Examples thereof include vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylanthracene, pyrene-formaldehyde resin, ethylcarbazoleformaldehyde 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 also 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 binders include, for example, acrylic resins, polyarylates, polyesters, polycarbonate polystyrene, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, and insulating resins such as chlorinated rubber. Or poly-N-vinylcarbazole,
Examples thereof include organic photoconductive polymers such as polyvinyl anthracene and polyvinyl pyrene.

Since the charge transport layer has a limit for transporting charge carriers, it cannot be made thicker than necessary. Generally 5-40 microns, but the preferred range is 10-25
Micron. 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 on a conductive support. 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 (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and acrylic resin) having a layer in which aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc. are formed by a vacuum deposition method , Polyfluoroethylene, etc.), a support in which conductive particles (eg, carbon black, silver particles, etc.) are coated on a plastic together with a suitable binder,
A support obtained by impregnating conductive particles into plastic or paper, plastic having a conductive polymer, or the like can be used.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer.

The undercoat 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 microns, preferably 0.5 to
3 microns is suitable.

When using an electrophotographic photosensitive member having a conductive support, a charge generation layer, and a charge transport layer laminated in this order, when the charge transport material is composed of an electron transport material, the surface of the charge transport layer must be positively charged. When exposed after charging, in the exposed area, the electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface, neutralize the positive charge, attenuate the surface potential, and between the unexposed area Electrostatic contrast occurs.

A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively chargeable toner. Fix this directly, or
Alternatively, the toner image can be transferred to paper or a plastic film and then developed and fixed.

Further, there is a method in which an electrostatic latent image on a photoreceptor is transferred onto an insulating layer of transfer paper, 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,
It is necessary to charge the surface of the charge transport layer negatively, and when exposed after charging, in the exposed area, holes generated in the charge generation layer are injected into the charge transport layer, and then reach the surface to neutralize negative charges and reduce the surface potential. Attenuation occurs and an electrostatic contrast is generated between the unexposed portion.

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

Further, examples of the electrophotographic photosensitive member of the present invention include the electrophotographic photosensitive member containing the above-mentioned azo pigment in the same layer together with the charge transporting substance.

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

The electrophotographic photosensitive member of this example can be prepared by dispersing the above-mentioned azo pigment and 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 kind of pigment selected from azo pigments having an organic residue represented by the general formula (1), and if necessary, a pigment having different light absorption may be combined. Two or more kinds of azo pigments having an organic residue represented by the general formula (1) are combined, or known dyes or pigments are used for the purpose of increasing the sensitivity of the photoreceptor and obtaining a panchromatic photoreceptor. It is also possible to use it in combination with a charge generating substance selected from

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 beam printers, CRT printers and laser plate making.

[Examples] Examples 1 to 15 Aqueous ammonia solution of casein (casein
11.2 g, 28% ammonia water 1 g, and water 222 ml) were applied by a Meyer bar so that the film thickness after drying would be 1.0 micron and dried.

Next, 5 g of the exemplified pigment (2-1) was added to 95 ml of tetrahydrofuran, and 2 g of butyral resin (degree of butyralization was 63 mol%).
Was added to the melted solution and dispersed by a sand mill for 2 hours. This dispersion was applied onto the casein layer previously formed by a Meyer bar so that the film thickness after drying was 0.4 μm, and dried to form a charge generation layer.

Next, the structural formula Hydrazone compound (5 g) and polymethylmethacrylate (number average molecular weight 100,000) (5 g) are dissolved in benzene (70 ml), and this solution is applied on the charge generation layer with a Meyer bar to a dry film thickness of 19 microns and dried. To form a charge transport layer,
An electrophotographic photosensitive member of Example 1 was prepared.

Example 2 was replaced with Example pigment (2-1) and the following example pigment was used.
An electrophotographic photosensitive member corresponding to ~ 15 was prepared.

The electrophotographic photosensitive member thus prepared was corona-charged at −5.5 KV by a static method using an electrostatic copying paper tester (Model Sp-428 manufactured by Kawaguchi Electric Co., Ltd.) and held for 1 second in a dark place. Exposure was carried out at an illuminance of 5 lux and the charging characteristics were examined.

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.

Comparative Examples 1-3 Photoconductors were prepared in exactly the same manner as in Examples 1, 2, and 3 except that the azo pigment used in Examples 1, 2, and 3 was replaced with an azo pigment having the following structural formula. evaluated. The results are shown.

(Comparative Example 1) V ₀ : −690V E1 / 2: 9.7lux, sec (Comparative example 2) V ₀ : −690V E1 / 2: 7.3lux, sec (Comparative example 3) V ₀ : −700V E1 / 2: 7.5lux, sec Examples 16 to 17 Each of the electrophotographic photosensitive members prepared in Examples 10 and 14 was tested at 780 nm.
The semiconductor laser and its scanning unit were replaced with a tungsten light source, and electrostatic discharge paper testing equipment (a modified model of Model Sp-428 manufactured by Kawaguchi Denki Co., Ltd.) was used to statically corona electrify at −5.5 KV, and store in the dark. After holding for 1 second, it was exposed to a laser beam to examine the charging characteristics.

As the charging characteristics, the surface potential (V ₀ ) and the exposure amount (E1 / 5) required to attenuate the potential when dark-decayed for 1 second to 1/5 were measured. The results are shown.

From the above results, it is recognized that the electrophotographic photoreceptors of the present invention all have excellent sensitivity to laser light.

Examples 18 to 22 The electrophotographic photoreceptors prepared in Examples 1, 2, 4, 6, and 11 were used to measure the fluctuations in the light potential and the dark potential during repeated use.

The measurement method is -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.

Using this copier, the initial light potential (V _L ) and the dark potential (V _D ) were set to −200 V and −700 V, respectively, and the light potential (V _L ) and the dark potential after repeated use 5,000 times. (V _D ) was measured.

Comparative Examples 4 to 6 The electrophotographic photosensitive members prepared in Comparative Examples 1 to 3 are used in Examples 18 to
The same method as 22 was used to measure the potential fluctuation during repeated use. The results are shown.

From the above results, it can be seen that the electrophotographic photosensitive member of the present invention has excellent characteristics with little potential fluctuation during repeated use.

Example 23 On the charge generation layer prepared in Example 6, 5 g of 2,4,7-trinitro-9-fluorenone and poly-4,4'-dioxydiphenyl-2,2-propane carbonate (molecular weight 30
A coating solution prepared by dissolving 5 g of the compound in 70 ml of tetrahydrofuran was applied so that the coating amount after drying was 10 g / m ^2, and dried.

The charging characteristics of the electrophotographic photosensitive member thus prepared were measured in the same manner as in Example 1.

 At this time, the charging polarity was +. The results are shown.

V ₀ : + 690V, E1 / 2: 3.8lux, sec Example 24 A polyvinyl alcohol film having a thickness of 0.5 micron was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film.

Next, the film thickness after drying was applied on the polyvinyl alcohol layer on which the dispersion liquid of the disazo pigment used in Example 3 was previously formed.
A charge generating layer was formed by coating with a Meyer bar to a thickness of 0.5 micron and drying.

Then 5 g of polyarylate (bisphenol A and terephthalic acid-isophthalic acid condensation polymer) 5 g of tetrahydrofuran
A solution of 70 ml dissolved on the charge generation layer has a thickness of 18 after drying.
It was coated so as to have a size of micron and dried to form a charge transport layer.

The charging characteristics and durability characteristics of the electrophotographic photosensitive member thus prepared were measured in the same manner as in Example 1 and Example 18. The results are shown.

V ₀ : -700V, E1 / 2: 2.1lux, sec Endurance characteristics Initial V _D : -700V, _VL : -200V After endurance of 5,000 sheets V _D : -690V, _VL : -210V Example 25 100 micron thickness Aqueous ammonia solution of casein (described above) was applied on the aluminum plate and dried to form an undercoat layer having a thickness of 0.5 micron.

Next, 5 g of 2,4,7-trinitro-9-fluorenone and 5 g of poly-N-vinylcarbazole (number average molecular weight 300,000) were dissolved in 70 ml of tetrahydrofuran to prepare a charge transfer complex compound.

This charge transfer complex compound and 1 g of Exemplified Pigment (2-3) were added to and dispersed in a solution of 5 g of a polyester resin (Vylon, manufactured by Toyobo Co., Ltd.) in 70 ml of tetrahydrofuran. This dispersion was applied onto the undercoat layer so that the film thickness after drying would be 16 microns, and dried. The charging characteristics of the produced electrophotographic photosensitive member were measured by the same method as in Example 1. The results are shown. However, the charging polarity was +.

V ₀ : + 690V E1 / 2: 4.5lux, sec Example 26 An undercoat layer of casein was provided on an aluminum plate, and the charge transport layer and the charge generation layer used in Example 4 were laminated in this order on the aluminum plate. An electrophotographic photosensitive member was prepared in the same manner as in Example 4 except that the constitution was different, and the charging characteristics were measured in the same manner. However, the charging polarity was +.

V ₀ : + 690V E1 / 2: 3.7lux, sec [Effects of the Invention] The electrophotographic photoreceptor of the present invention uses a specific azo pigment in the photosensitive layer, so that carriers are generated inside the photosensitive layer containing the azo pigment. One or both of efficiency and carrier transportation efficiency are improved, and the electrophotographic photoreceptor has high sensitivity and good potential stability during durable use.

Claims (3)

[Claims] 1. A substituted or unsubstituted aromatic hydrocarbon group or aromatic heterocycle in which an organic residue represented by the following general formula (I) may be bonded to a conductive support through a bonding group. An electrophotographic photoreceptor having a photosensitive layer containing an azo pigment having a structure bonded to a group. In the formula, X represents a residue necessary for forming an aromatic hydrocarbon group or an aromatic heterocyclic group which may be condensed with a benzene ring to form a substituent, and R ₁ is a substituent. Is an aromatic hydrocarbon group or an aromatic heterocyclic group, and n ₁ is 0 or an integer of 1. 2. The electrophotographic photosensitive member according to claim 1, wherein the azo pigment is an azo pigment represented by the following general formula (II). In the formula, Ar represents a substituted or unsubstituted aromatic hydrocarbon group or an aromatic heterocyclic group which may be bonded via a bonding group, and n is an integer of 1, 2, 3 or 4. In addition,
X, R ₁ and n ₁ have the same meanings as in formula (I). 3. An organic residue represented by the following general formula (III), wherein the azo pigment has at least one organic residue selected from the organic residues represented by the general formula (I) and is different from the selected organic residue. An azo pigment having a structure in which at least one of the groups is bonded to a substituted or unsubstituted aromatic hydrocarbon group or aromatic heterocyclic group which may be bonded via a bonding group in the same molecule. 2. The electrophotographic photosensitive member according to 1. -N = N-Cp (III) In the formula, Cp represents a coupler residue having a phenolic hydroxyl group.