JPH07117759B2 - Electrophotographic photoreceptor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel electrophotographic photoreceptor, and more specifically, an electrophotographic photoreceptor containing a disazo pigment having a specific molecular structure in a photosensitive layer. It is about.

[Conventional technology]

Electrophotography is a photoconductive method comprising a support coated with an insulating material in the dark, the electric resistance of which changes according to the amount of irradiation received during image exposure as shown in U.S. Pat. Use material. The basic characteristics required for an electrophotographic photosensitive member using this photoconductive material are (1) being able to be charged to an appropriate potential in a dark place (2) Little dissipation of charges in a dark place (3) It is possible to rapidly dissipate the electric charge by light irradiation.

Conventionally, as an electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer containing an inorganic photoconductive compound such as selenium, zinc oxide, or cadmium sulfide as a main component has been widely used. However, although these satisfy the above conditions (1) to (3), they are not necessarily satisfactory in terms of thermal stability, moisture resistance, durability and the like. For example, when selenium is crystallized, the characteristics as a photoreceptor are deteriorated, which is difficult to manufacture, and crystallization is caused by heat, fingerprints, etc., and the performance as a photoreceptor is deteriorated. Also, cadmium sulfide has problems in moisture resistance and durability, and zinc oxide has problems in smoothness, hardness, and abrasion resistance. Further, most of the inorganic photoconductors have a limited photosensitive wavelength region. For example, in selenium, the photosensitive wavelength region is in the blue region and there is almost no sensitivity in the red region. Therefore, various methods have been proposed to extend the photosensitivity to the long wavelength region, but there are many restrictions on the selection of the photosensitizing wavelength region. When using zinc oxide or cadmium sulfide as a photoreceptor,
The photosensitive wavelength region itself is narrow, and it is necessary to add various sensitizers.

In order to overcome the drawbacks of these inorganic photoconductors, electrophotographic photoconductors containing various organic photoconductive compounds as main components have been actively developed in recent years. For example, Japanese Examined Japanese Patent Publication 50-10496
U.S. Pat. No. 3,484,237 discloses poly-N-vinylcarbazole and 2,4,7-trinitrofluorenone-9.
There are a photoreceptor having a photosensitive layer containing -one, a sensitized poly-N-vinylcarbazole with a pyrylium salt dye (Japanese Patent Publication No. Sho 48-25658), and the like. These organic electrophotographic photoconductors have some drawbacks of the above-mentioned inorganic electrophotographic photoconductors, but generally have low photosensitivity and are not suitable for repeated use. In order to overcome these drawbacks, various photoconductors have been proposed as organic electrophotographic photoconductors in recent years. Among them, a layer containing a substance (hereinafter, referred to as a charge generation substance) that generates a charge carrier when irradiated with light (hereinafter, referred to as a charge generation substance). , A charge generation layer) and a layer (hereinafter, referred to as a charge transport layer) mainly containing a substance (hereinafter, referred to as a charge transport substance) that receives and transports the charge carriers generated by the charge generation layer. The photosensitive member of 1 is generally higher in sensitivity than conventional organic electrophotographic photosensitive members, and some of them have been put to practical use because they can withstand repeated use.

For example, U.S. Pat. No. 3,738,851 discloses a photoreceptor having a charge generation layer and a charge transport layer containing triallyl pyrazoline, and U.S. Pat. No. 3,871,882 discloses a charge generation layer composed of a derivative of a perylene pigment and 3-bromopyrene. Examples thereof include a photoreceptor having a charge transport layer made of a condensation product of formaldehyde.

Further, JP-A-59-33445, JP-A-56-46237, JP-A-60-111249 and the like are already known as photoreceptors using a bisazo pigment or trisazo pigment as a charge generating substance. However, these bisazo pigments or trisazo pigments are not always satisfactory in the characteristics of sensitivity, residual potential or stability upon repeated use.
In addition, the selection range of the charge transport material is limited, so that it does not sufficiently satisfy the wide requirements of the electrophotographic process.

[Problems to be solved by the invention]

An object of the present invention is to provide a novel photoconductive material.

A second object of the present invention is to provide an electrophotographic photosensitive member having stable potential characteristics when it is repeatedly used with practical high sensitivity characteristics in the visible region.

A third object of the present invention is to provide an electrophotographic photosensitive member which also matches a charge transport substance having a high oxidation potential.

[Means for solving problems]

That is, the present invention is an electrophotographic photoreceptor 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 Ar and Ar 'in the general formula (1) represent a divalent aromatic hydrocarbon ring group or aromatic heterocyclic group which may have a substituent, and may be the same or different. Examples of the aromatic hydrocarbon ring group include phenylene, naphthylene, anthracenylene, and phenanthrylene. Examples of the aromatic heterocyclic group include pyridinediyl and quinolinediyl. Examples of the substituent of the aromatic hydrocarbon ring group and the aromatic heterocyclic group include fluorine, halogen groups such as chlorine, bromine and iodine, alkyl groups such as methyl, ethyl, propyl, isopropyl and butyl, methoxy and ethoxy, Examples thereof include alkoxy groups such as propoxy and phenoxy, nitro groups, cyano groups, substituted amino groups such as dimethylaminodibenzylamino, diphenylamino, morpholino, piperidino and pyrrolidino.

R ₁ represents a lower alkyl group having 2 or more halogen atoms and having up to 3 carbon atoms, or a cyano group, and specifically, a difluoromethyl group, a trifluoromethyl group, a 1,1,1-trifluoroethyl group, 1,1,1-trichloroethyl group, 1,1,1
-Trifluoroisopropyl group, 2,2,2-trifluoropropyl group and the like are shown.

A and A'in the general formula (1) are coupler residues having a phenolic OH group, and more preferable specific examples of the coupler residues represented by A and A'are general formulas (2) to (8). Indicated by.

General formula In the formula (2), 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, diphenylene sulphite ring, or a heterocyclic ring. The residues required to form are indicated.

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

In formula (2), R ₂ and R ₃ are a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, a heterocyclic group or a nitrogen atom to which R ₂ and R ₃ are bonded, and a cyclic amino group. Indicates.

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

General formula General formula R ₄ in the formulas (3) and (4) represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group or an aralkyl group. Specific examples of R ₄ are indicated by the same example as above R _3, R _4.

An alkyl group represented by the substituents R _{2 to} R _{4 in} the formulas (2) to (4),
Aryl group, aralkyl group, alkoxy group, and heterocyclic group are other substituents such as fluorine, halogen groups such as chlorine, iodine and bromine, alkyl groups such as methyl, ethyl, propyl, isopropyl and butyl, methoxy and ethoxy, It may be substituted with an alkoxy group such as propoxy and phenoxy, a nitro group, a cyano group, a substituted amino group such as dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino and pyrrolidino.

General formula General formula Y in the formulas (5) and (6) represents a divalent group of an aromatic hydrocarbon or a divalent group of a hetero ring contained in the ring of a nitrogen atom.

As the divalent group of the aromatic hydrocarbon, a divalent group of a monocyclic aromatic hydrocarbon such as o-phenylene, a condensed polycondensation group such as o-naphthylene, perinaphthylene, 1,2-anthrylene, and 9,10-phenanthrylene. A divalent group of a cyclic aromatic hydrocarbon may be mentioned. Further, as the divalent group of the hetero ring containing a nitrogen atom in the ring, 3,4-pyrazolediyl group, 2,3-pyridinediyl group, 4,5-pyrimidinediyl group, 6,7-indazolediyl group, A divalent group such as a 6,7-quinolinediyl group may be mentioned.

General formula R ₅ in the formula (7) represents an optionally substituted aryl group or heterocyclic group, and specifically represents a phenyl, naphthyl, anthryl, pyrenyl, pyridyl, thienyl, furyl or carbazoyl group.

The aryl group represented by R ₅ , as the substituent of the heterocyclic group, fluorine, chlorine, iodine, a halogen group such as bromine, an alkyl group such as methyl, ethyl, propyl, isopropyl, butyl,
Examples thereof include alkoxy groups such as methoxy, ethoxy, propoxy and phenoxy, and substituted amino groups such as nitro group, cyano group, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino and pyrrolidino.

Specific examples of X are shown by the same examples as X in formula (2).

General formula R ₆ and R ₇ in the formula (8) represent a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group or a heterocyclic group, and specifically methyl, ethyl, propyl and butyl. , Benzyl, phenethyl, naphthylmethyl,
It shows phenyl, naphthyl, anthryl, diphenyl, carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole and pyridine.

The substituents of the alkyl group, aryl group, aralkyl group and heterocyclic group represented by R ₆ and R ₇ in the formula (8) are halogen groups such as fluorine, chlorine, iodine and bromine, methyl, ethyl, propyl and isopropyl. Alkyl groups such as butyl,
Examples thereof include alkoxy groups 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 following bisazo pigments having a diphenylamine skeleton as a central skeleton, which are related to the present invention, are already known.

JP-A-58-80643 JP 60-140351 A JP 61-228453 Cp represents a coupler residue.

These bisazo pigments are not always satisfactory in the characteristics of sensitivity, residual potential or stability upon repeated use. The inventor believes that one of these causes is due to the strength of the donor property of the central skeleton, and the structure of the central skeleton of the pigment reduces the ionization potential of the pigment molecule itself, which affects sensitivity and other properties. It seems that there is. Further, these pigments have high sensitivity only when they are combined with a charge transfer substance having a low oxidation potential, and there is a problem in terms of durability since a charge transport substance having a high oxidation potential cannot be used.

However, the electrophotographic photosensitive member using the disazo pigment according to the present invention has no substitution or electron donating substitution by introducing an electron withdrawing group consisting of a halogenated alkyl group and a cyano group as an N-substituent on the central skeleton. Group, and further, the central skeleton can be made more acceptor as compared with that of a weak electron-withdrawing group such as acetyl group. Therefore, when the disazo pigment according to the present invention is used as a charge generation layer, the oxidation potential of A high charge transport material (Eox (V) = 0.70 or more) can be used and high sensitivity can be realized. Among the alkyl halides, the effect of the trifluoromethyl group is particularly excellent. Also, since a charge transport material with a high oxidation potential (Eox (V) = 0.70 or more) can be used, it is excellent in chemical stability such as ozone oxidation due to corona discharge on the surface of the electrophotographic photosensitive member, and especially when repeated. Potential stability can now be maintained.

The oxidation potential of the charge-transporting substance indicates the peak value (Eox) of the first oxidation wave. In practice, methanol, ethanol, acetonitrile, etc. are used as a solvent, and tetra-n-butylammonium perchlorate, a perchlorate is used as a supporting electrolyte. It can be measured by cyclic voltammetry using salts such as lithium chlorate and tetraethylammonium p-tolueneate and a saturated calomel electrode as an electrode. However, the measurement is not limited to this method, and it can be obtained by potentiometry or polarography.

In the present invention, the oxidation potential was measured by cyclic voltammetry using acetonitrile as a solvent, tetra-n-butylammonium perchlorate as a supporting electrolyte, and a saturated calomel electrode as an electrode.

A general method for producing the disazo pigment of the general formula (1) 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 using sodium nitrite or nitrosylsulfuric acid, and the coupler component is used. It can be obtained by performing an aqueous coupling with a certain A, A ', or taking out the obtained tetrazonium salt as a stable salt such as a borohydride salt and then performing the coupling in an organic solvent such as dimethylformamide. A,
When A ′ is different, in the coupling reaction, first coupling is performed with the first coupler component to form a monoazo compound, and then coupling is performed with the second coupler component to obtain a disazo pigment or a mixture of two coupler components. Can be obtained by carrying out a coupling reaction. Further, as another method, it can be obtained by the following method.

General formula Here, Ar, Ar ′ and R ₁ have the same meanings as in claim (1).

That is, the acetylamino compound represented by the general formula (10) is diazotized to obtain a coupler having a phenolic hydroxyl group. After coupling, they are hydrolyzed with mineral acids such as hydrochloric acid or alkalis such as sodium hydroxide to give amino compounds. (Cp represents a coupler residue having a phenolic hydroxyl group.), Diazotized again and coupled with another coupler residue to obtain an asymmetric pigment.

Next, specific examples of the disazo pigment used in the present invention are given below. However, these disazo pigments do not limit the claims of the present invention.

Next, typical synthetic examples of the disazo pigment used in the present invention are shown.

Synthesis Example 1 (Synthesis of Azo Pigment No. 1 exemplified above) 100 ml of water and 24 ml (0.27 mol) of concentrated hydrochloric acid were put into a 300 ml beaker, and N-trifluoromethyl-4, while cooling with an ice-water bath.
11.0 g (0.041 mol) of 4'-diphenylamine was added, and the liquid temperature was adjusted to 3 ° C with stirring.

Next, a solution prepared by dissolving 6.0 g (0.087 mol) of sodium nitrite in 10 ml of water was added dropwise over 10 minutes while controlling the liquid temperature at 5 ° C or lower, and after completion of the addition, the mixture was stirred at the same temperature for 30 minutes.
Activated carbon was added to the reaction solution, and after filtration, a solution prepared by dissolving 13.5 g (0.123 mol) of sodium borohydride in 20 ml of water was added dropwise, and the precipitated borohydride salt was collected by filtration, washed with water, and dried in vacuum. Yield 15.4g Yield 81.0% DMF 200ml was put into one beaker, and 2-hydroxy-3-naphthoic acid-2'-fluoroanilide 2.81g.
(0.01 mol) was dissolved, the liquid temperature was cooled to 5 ° C., 4.65 g (0.01 mol) of the borohydride salt obtained above was dissolved, and 1.02 g (0.01 mol) of triethylamine was added dropwise over 10 minutes, Then, the mixture was stirred for 2 hours. The reaction solution was filtered, washed with 200 ml of N, N-dimethylformamide four times, replaced with acetone, and dried under vacuum to obtain the desired azo pigment No. 1. Yield 7.
26g Yield 85.2% (based on borofluoride salt) Elemental analysis Calculated value Actual value C 66.27% 66.35% H 3.55% 3.50% N 11.51% 11.59% The coating containing the disazo pigment of the general formula (1) is photoconductive. And therefore can be used in the photosensitive layer of an electrophotographic photoreceptor.

That is, in the present invention, the general formula (1) is formed on the conductive support.
An electrophotographic photosensitive member can be formed by forming a film of the disazo pigment of 1 above by a vacuum vapor deposition method or by forming a film by dispersing and containing it in an appropriate binder.

In a preferred embodiment of the present invention, the above-mentioned photoconductive coating film may 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. it can.

The charge generation layer contains as much of the above-mentioned photoconductive compound as possible in order to obtain sufficient absorbance, and is a thin film layer, for example, 5 μm or less, preferably in order to shorten the range of the generated charge carrier. Is preferably a thin film layer having a film thickness of 0.01 to 1 μm. This means that most of the amount of incident light is absorbed by the charge generation layer to generate a large number of charge carriers, and the generated charge carriers are not deactivated by recombination or capture (trap) to the charge transport layer. It is due to the need to inject.

As described above, the charge generation layer can be formed, for example, by dispersing the disazo pigment of the general formula (1) in a suitable binder and coating it on a support, or by forming a vapor deposition film by a vacuum vapor deposition device. It can also be obtained by doing. 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 also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (polycondensation polymer of bisphenol A and phthalic acid, etc.) polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinyl pyridine, cellulosic resin, urethane Insulating resins such as resins, epoxy resins, casein, polyvinyl alcohol, and polyvinylpyrrolidone can be mentioned. 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 differs depending on the type of 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, amides such as N, N-dimethylacetamide, and dimethyl sulfoxide. Ethers such as sulfoxides, tetrahydrofuran, dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride and trichloroethylene. Or benzene, toluene,
Aromatic compounds such as xylene, ligroin, monochlorobenzene, and dichlorobenzene can be used.

The coating can be performed by using a coating method such as a dip coating method, a spray coating method, a Meyer bar coating method, a blade coating method, a roller coating method, a curtain coating method and the like.

Drying is preferably a method of drying by touching at room temperature and then drying by heating. Heat drying at a temperature of 30 ℃ to 200 ℃ for 5 minutes to 2
It can be performed statically or under blast for a time range of hours.

The charge transport layer is electrically connected to the above-mentioned charge generation layer, and has a function of receiving the 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 located on the side farther from the charge generation layer than the conductive support, or may be located between the conductive support and the charge generation layer.

The charge-transporting substance in the charge-transporting layer includes an electron-transporting substance and a hole-transporting substance, and the electron-transporting substance includes 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,
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-ethylphene Nothiazin,
N, N-diphenylhydrazino-3-methylidene-10-ethylphenoxazine, p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, p-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone, p-pyrrolidinobenzaldehyde-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-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-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,
1-phenyl-3- (α-pentyl-p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, pyrazolines such as spiropyrazoline, α-
Phenyl-4-N, N-diphenylaminostilbene, N
-Ethyl-3 (α-phenylstyryl) carbazole,
Styryl compounds such as 9-p-dibenzylaminobenzylidene-9H-fluorenone and 5-p-ditolylaminobenzylidene-5H-dibenzo [a, d] cycloheptene.
2- (p-diethylaminostyryl) -6-diethylaminobenzoxazole, 2- (p-diethylaminophenyl) -4- (p-dimethylaminophenyl) -5
Oxazole compounds such as (2-chlorophenyl) oxazole, 2- (p-diethylaminostyryl) -6-
Thiazole compounds such as diethylaminobenzothiazole, bis (4-diethylamino-2-methylphenyl)
-Triarylmethane compounds such as phenylmethane, 1,
1-bis (4-N, N-diethylamino-2-methylphenyl) heptane, 1,1,2,2-tetrakis (4-N, N-dimethylamino-2-methylphenyl) ethane, etc. There are phenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazoleformaldehyde resin and the like.

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

Further, these charge transport materials 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,
Acrylonitrile-butanediene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone,
Examples thereof include insulating resins such as 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 for transporting the charge carrier, the film thickness cannot be increased more than necessary. Generally, it is 5 to 40 μm, but the preferable range is 15 to 30 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 conductive support. As the conductive support, one having conductivity itself, for example, aluminum, aluminum alloy, copper, zinc, stainless steel,
Vanadium, molybdenum, chromium, titanium, nickel,
Indium, gold, platinum, etc. can be used, and in addition, aluminum, aluminum alloy, indium oxide,
Plastics (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluoroethylene, etc.) having a layer formed by coating a film of tin oxide, indium oxide-tin oxide alloy or the like by a vacuum deposition method, conductive particles (for example, , Titanium oxide, tin oxide, carbon black, silver particles, etc.) with a suitable binder, or a support in which the above metal support is coated on the plastic, or a support or conductive polymer in which the conductive particles are impregnated in the plastic or paper. It is possible to use a plastic or the like that has.

An undercoat layer having a buyer function and an adhesive function can be provided between the conductive support and the photosensitive layer. The subbing layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. it can.

The thickness of the undercoat layer is 0.05 to 5 μm, preferably 0.5 to 3
μm is suitable.

In another embodiment of the present invention, the above-mentioned hydrazones,
Organic photoconductive substances such as pyrazolines, styryl compounds, oxazoles, thiazoles, triarylmethanes, polyarylalkanes, triphenylamine, poly-N-vinylcarbazoles, zinc oxide, cadmium sulfide, selenium, etc. A photosensitive film containing the disazo pigment of the general formula (1) as a sensitizer for the inorganic photoconductive substance can be obtained. This photosensitive film is formed by coating these photoconductive substances and the above-mentioned disazo pigment of the general formula (1) together with a binder.

Another specific example of the present invention is an electrophotographic photosensitive member containing the disazo pigment represented by the general formula (1) in the same layer together with a 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 above charge transport material. The electrophotographic photoreceptor of this example can be prepared by dispersing the disazo pigment of the general formula (1) and the charge transfer complex compound in a solution of polyester dissolved in tetrahydrofuran, and then forming a film.

The pigment used in any of the photoconductors contains at least one kind of pigment selected from the disazo pigments represented by the general formula (1), and the crystal form thereof may be amorphous or crystalline. Further, two kinds of disazo pigments represented by the general formula (1) are used for the purpose of increasing the sensitivity of the photoconductor by using a combination of pigments having different light absorptions as required, and obtaining a panchromatic photoconductor. It is also possible to use a combination of the above or a known charge generating substance selected from dyes and 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.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Examples 1 to 9 0.1 μm vinyl chloride-maleic anhydride-on an aluminum plate
An undercoat layer made of a vinyl acetate copolymer resin was provided.

Next, 3,5 g of the above-mentioned disazo pigment No. 3 was added to a solution prepared by dissolving 2 g of butyral resin (degree of butyralization: 63 mol% number average molecular weight 20000) in 95 ml of cyclohexanone, and dispersed by a sand mill for 2 hours. This dispersion was applied onto the previously formed undercoat layer with a Meyer bar so that the film thickness after drying was 0.2 μm, and dried to form a charge generation layer. Next, 5 g of the benzylidene compound of No. 11 as a charge transport substance and polymethylmethacrylate resin (number average molecular weight 100000)
5 g was dissolved in 70 ml of chlorobenzene, and this was coated on the 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. Created.

The electrophotographic photoconductor thus prepared is manufactured by Kawaguchi Electric Co., Ltd.
The electrostatic characteristics of the electrostatic copying paper tester Model SP-428 were statically charged at -5.5 KV for corona charging, held in the dark for 1 second, and then exposed at an illuminance of 2 lux to examine the charging characteristics.

As the charging characteristics, the surface potential (Vo) and the exposure dose (E 1/2) required to reduce the potential when dark-decayed for 1 second to 1/2 were measured. Similarly, with respect to the disazo pigments Nos. 3, 10, and 22, charge-transporting substances Nos. (11), (12), and (13) were used to prepare photoconductors corresponding to Examples 2 to 9, respectively. It was measured by the method. The results are shown in Table 1, and the oxidation potential Eox (V) of the charge transport material is shown in Table 2.

Comparative Examples 1 to 12 In place of the disazo pigments of Examples 1 to 9, disazo pigments of the following structural formulas (Comparative Pigment Nos. 1 to 3) were used, and in addition to the charge transporting substances of Examples 1 to 9, the structural formula ( 14) Using a hydrazone compound, a photoconductor was prepared and evaluated in exactly the same manner as in Examples 1-9. The results are shown in Table 3.

Comparative pigment No. Comparative Example 1 corresponds to Example 1, Comparative Example 2 corresponds to Example 6 and Comparative Example 3 corresponds to Example 11, respectively, and the disazo pigment of Comparative Example has a high level when combined with a charge transfer substance having a low oxidation potential. Although it is sensitive, it can be seen that the sensitivity is low when combined with a material having a high oxidation potential. From the above,
It can be seen that the disazo pigment according to the present invention has excellent sensitivity when combined with a charge transport material having a high oxidation potential (Eox = 0.70 V or higher).

Examples 9 to 20 Instead of the disazo pigments of Examples 1 to 9, disazo pigment N
Using o.4,6,7,8,13,15,17,18,28,34,38, a photoreceptor was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 4.

Examples 21 to 24 The photoreceptors used in Examples 1, 9, 12, and 16 were used to measure the fluctuations in the light potential and the dark potential during repeated use. As a method, a copier with a -5.6KV corona charger, an exposure optical system, a developing device, a transfer charger, a static elimination exposure optical system, and a cleaner was attached to the cylinder of the electrophotographic copying machine. An image can be obtained on the transfer paper with the driving. Using this copier, set the initial light potential (V _L ) and dark potential (V _D ) near -100V and -600V, respectively, and after using 5000 times, the light potential ( _VL ) and dark potential. (V _D ) was measured. The results are shown in Table 5.

Example 25 On the charge generation layer prepared in Example 1, 5 g of 2,4,7-trinitro-9-fluorenone and poly-4,4'-dioxydiphenyl-2,2'-propane carbonate (molecular weight 300,0
A coating solution prepared by dissolving 5 g of 00) in 70 ml of tetrahydrofuran was applied so that the coating amount after drying would be 10 g / m ^2, and dried.

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 set to +.
The results are shown below.

Vo: 675 volts E _1/2 : 5.9 lux · sec Example 26 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 polyvinyl alcohol layer on which the disazo pigment dispersion used in Example 1 was formed was coated with a Meyer bar so that the film thickness after drying was 0.2 μm, and dried to form a charge generation layer.

Then structural formula (12) Hydrazone compound 5g (Eox (V) = 0.57) and bisphenol Z type polycarbonate resin (viscosity average molecular weight 3000
0) A solution prepared by dissolving 5 g in 32.5 ml of monochlorobenzene was applied onto the charge generation layer so that the film thickness after drying was 20 μm, and dried to form a charge transport layer. The charging property and durability property of the thus prepared photoconductor were measured by the same method as in Example 21. The results are shown in Table 6.

Vo: 605 volts E _1/2 : 2.5lux ・ sec From the results in Table 6, the sensitivity is good and the potential stability during durable use is also good.

Example 27 Soluble nylon (6-66-610-
5% methanol solution of 12 quaternary nylon copolymer) was applied and dried to form an undercoat layer having a film thickness of 0.5 μm.

Next, 5 g of 2,4,7-trinitro-9-fluorenone and poly-
5 g of N-vinylcarbazole (number average molecular weight 300,000) was dissolved in 70 ml of tetrahydrofuran to form a charge transfer complex compound. This charge transfer complex compound and 1 g of the above-mentioned disazo pigment No. 13 were added to polymethylmethacrylate-styrene copolymer resin (molecular weight 250,000) 5 g to tetrahydrofuran 70
It was added to the liquid dissolved in ml and dispersed. This dispersion was applied onto the undercoat layer and dried to prepare a 20 μm photosensitive member.

The charging characteristics of the thus prepared photoconductor were measured by the same method as in Example 1. The results are shown below. However, the charging polarity was.

Vo: 570V E _1/2 : 7.5lux · sec Example 28 A layer structure in which the charge transport layer and the charge generation layer of Example 1 were sequentially laminated on the nylon layer of the aluminum substrate used in Example 1 and provided with the nylon layer. A photoconductor was formed in exactly the same manner as in Example 1 except that the charging characteristics were measured. However, the charging polarity was set.

The results are shown below.

Vo: 575V E _1/2 : 3.5lux · sec [Effect of the Invention] According to the present invention, by using a specific disazo pigment in the photosensitive layer, either the carrier generation efficiency or the carrier transport efficiency inside the photosensitive layer can be improved. It is presumed that one or both of them will be improved, and as a result, an electrophotographic photosensitive member having high sensitivity and excellent durability, and particularly excellent potential stability during durable use can be constructed.

Claims (9)

[Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a disazo pigment represented by the general formula (1). General formula [Wherein A and A'are phenolic coupler residues,
It may be the same or different. Ar and Ar ′ represent a divalent aromatic hydrocarbon ring group which may have a substituent or an aromatic heterocyclic group, and may be the same or different. R ₁ represents a lower alkyl group having 2 or more halogen atoms and having up to 3 carbon atoms, or a cyano group. ] 2. The electrophotographic photosensitive member according to claim 1, wherein A and A'in the general formula (1) are represented by the following general formula (2). General formula In formula (2), X represents a residue necessary for forming a polycyclic aromatic ring or a heterocyclic ring by condensing with a benzene ring. In formula (2), R ₂ and R ₃ are a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, a heterocyclic group, or a nitrogen atom bonded to R ₂ and R ₃ together with a cyclic amino group. Indicates a group. 3. The electrophotographic photosensitive member according to claim 1, wherein A and A'in the general formula (1) are represented by the following general formula (3). General formula R ₄ in the formula (3) represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, or an aralkyl group. 4. The electrophotographic photosensitive member according to claim 1, wherein A and A'in the general formula (1) are represented by the following general formula (4). General formula R ₄ in the formula (4) represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, or an aralkyl group. 5. The electrophotographic photosensitive member according to claim 1, wherein A and A'in the general formula (1) are represented by the following general formula (5). General formula Y in the formula (5) represents a divalent group of an aromatic hydrocarbon or a divalent group of a hetero ring contained in the ring of a nitrogen atom. 6. The electrophotographic photosensitive member according to claim 1, wherein A and A'in the general formula (1) are represented by the following general formula (6). General formula Y in the formula (6) represents a divalent group of an aromatic hydrocarbon or a divalent group of a hetero ring containing a nitrogen atom in the ring. 7. The electrophotographic photosensitive member according to claim 1, wherein A and A'in the general formula (1) are represented by the following general formula (7). General formula R ₅ in the formula (7) represents an aryl group or heterocyclic group which may have a substituent, and X is necessary for forming a polycyclic aromatic ring or hetero ring by condensing with a benzene ring. Indicates a residue. 8. The electrophotographic photosensitive member according to claim 1, wherein A and A'in the general formula (1) are represented by the following general formula (8). General formula R ₆ and R ₇ in the formula (8) represent a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group or a heterocyclic group. X represents a residue necessary for forming a polycyclic aromatic ring or a heterocyclic ring by condensing with a benzene ring. 9. The photosensitive layer has a laminated structure of a charge generating layer and a charge transporting layer, the charge generating layer contains a disazo pigment represented by the general formula (1), and the charge transporting layer comprises The electrophotographic photosensitive member according to claim (1), which contains a charge transport substance having an oxidation potential of 0.7 (V) or more.