JPH0417428B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor in which a photosensitive layer contains a specific azo pigment. [Prior Art] Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components have been known. On the other hand, since it was discovered that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed. For example, organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene, carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones,
Organic pigments and dyes such as low-molecular organic photoconductors such as polyarylalkanes, phthalocyanine pigments, azo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindigo dyes, or methine squaritate dyes are used. Are known. In particular, organic pigments and dyes with photoconductivity are
Many photoconductive organic pigments and dyes have been proposed because they are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has expanded. For example, US Patent No. 4123270, US Patent No. 4247614, US Patent No.
No. 4251613, No. 4251614, No. 4256821, No. 4260672, No. 4268596, No. 4278747,
As disclosed in No. 4,293,628, electrophotographic photoreceptors are known in which a disazo pigment exhibiting photoconductivity is used as a charge-generating substance in a photosensitive layer that is functionally separated into a charge-generating layer and a charge-transporting layer. Electrophotographic photoreceptors using such organic photoconductors can be produced by coating by appropriately selecting a binder, so they can be produced with extremely high productivity and at low cost. Although this photoreceptor has the advantage of being able to freely control the sensitive wavelength range by selecting the photoreceptor, it has poor sensitivity and durability, and so far only a few have been put into practical use. [Problems to be Solved by the Invention] An object of the present invention is to provide a novel electrophotographic photoreceptor. Another object of the present invention is to provide an electrophotographic photoreceptor having practically excellent sensitivity and durability. [Means for solving the problem] That is, the present invention solves the following general formula (1) [Wherein, R represents hydrogen, nitroso, an alkyl group which may have a substituent, an aralkyl group, an aryl group, and an acyl group. However, R is −Ar ₅ −N=N−A
(In the formula, Ar ₅ represents an arylene group or a heterocyclic group which may have a substituent.)
Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ represent an arylene group or a heterocyclic group which may have a substituent, and A represents a coupler residue having a phenolic OH group. ] This is an electrophotographic photoreceptor characterized by containing an azo pigment represented by the following in a photosensitive layer. In the above general formula (1), the alkyl group is, for example, methyl, ethyl, propyl, butyl, etc., the aralkyl group is, for example, benzyl, phenethyl, naphthylmethyl, etc., and the aryl group is phenyl, diphenyl, naphthyl, etc. Examples of the acyl group include acetyl, propionyl, butyryl, and benzoyl. Further, examples of substituents that R may be substituted with include hydroxy group, halogen (chloro, bromo, iodo, etc.),
Alkyl (methyl, ethyl, propyl, butyl, etc.), alkoxy (methoxy, ethoxy, propoxy, butoxy, etc.), aryloxy group (phenyloxy, etc.), substituted amino (dimethylamino,
Diethylamino, dibenzylamino, pyrrolidino, piperidino, morpholino, etc.), nitro, cyano, acyl (acetyl, benzoyl, etc.), and the like. However, R is not _-Ar5 -N=NA. As definitions of Ar ₁ to _{Ar 5} , arylene includes, for example, phenylene, biphenylene, naphthylene, and anthrylene, and heterocyclic groups include, for example, divalent groups such as benzoxazole, benzothiazole, pyridine, quinoline, thiophene, and carbazole. may be further substituted with the substituents described above. Furthermore, the phenolic nature of A in general formula (1)
Examples of coupler residues having an OH group are represented by the following general formulas (2) to (8): (In the formula, X represents a residue _that forms a polycyclic aromatic ring or a heterocycle by condensing with a benzene ring, _and
represents hydrogen, an alkyl group, an aralkyl group, an aryl group, a heterocyclic group which may have a substituent, or a cyclic amino group bonded to each other to form a nitrogen atom, and R ₅ and R ₆ each have a substituent. Y represents an aromatic hydrocarbon divalent group or a heterocyclic divalent group having a nitrogen atom, and R ₇ and R ₈ each represent a substituent. an aryl group or a heterocyclic group which may have 5 to 6 together with the central carbon;
Indicates a residue forming a membered ring, this 5- to 6-membered ring may have a fused aromatic ring, R ₉ and R ₁₀ are hydrogen, an alkyl group that may have a substituent, an aralkyl group , represents an aryl group or a heterocyclic group. ) Examples of the polycyclic aromatic ring of X include naphthalene, anthracene, carbazole, benzcarbazole, dibenzofuran, benzonaphthofuran,
Examples include diphenyl sulfide. These may be substituted with the substituents described above. In addition,
The fused ring of X is preferably naphthalene, anthracene, or benzcarzole. Also R ₃ ,
In the case of R ₄ , alkyl is, for example, methyl, ethyl, propyl, butyl, etc., aralkyl is, for example, benzyl, phenethyl, naphthylmethyl, etc., and aryl is, for example, phenyl, diphenyl,
These include naphthyl and anthryl. Particularly preferred is a compound having a structure in which R ₃ is hydrogen and R ₄ is a phenyl group having an electron-withdrawing group such as halogen, nitro, cyano, or trifluoromethyl at the o-position. These may have substituents. Heterocycles include carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole,
Examples include pyridine. Specific examples of R ₅ and R ₆ include the same ones as exemplified above for R ₃ and R ₄ . These may be substituted with the substituents described above. Furthermore, R ₃ to _{R 6} are other substituents such as alkoxy groups such as methoxy, ethoxy, propoxy, chlorol, chloro, bromo,
It may be substituted with a halogen such as iodine, a nitro group, a cyano group, a substituted amino group such as dimethylamino, diethylamino, dibenzylamino, diphenylamino, etc. In the definition of Y, examples of the divalent aromatic hydrocarbon group include monocyclic aromatic hydrocarbon groups such as o-phenylene, o-naphthylene, perinaphthylene,
Examples include fused polycyclic aromatic hydrocarbon groups such as 1,2-antrylene and 9,10-phenanthrylene. Further, examples of forming a divalent heterocycle with a nitrogen atom include a 3,4-pyrazolediyl group, a 2,3-pyridinediyl group, a 4,5-pyrimidinediyl group, a 6,7-imidazolediyl group,
5,6-benzimidazolediyl group, 6,7-
Examples include 5- to 6-membered heterocyclic divalent groups such as quinolinediyl group. Examples of the aryl group or heterocyclic group for R ₇ and R ₈ include phenyl, naphthyl, anthryl, pyrenine, and the like; pyridyl, thienyl, furyl, carbazolyl, and the like. These may be substituted with the substituents described above. Substituents for the aryl group and heterocyclic group represented by R ₇ and R ₈ include halogens such as fluorine, chlorine, bromine, and iodine, alkyl groups such as methyl, ethyl, propyl, and butyl, methoxy, ethoxy, propoxy, butoxy, etc. alkoxy group, nitro group, cyano group,
Examples include substituted amino groups such as dimethylamino, diethylamino, dipropylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino. Furthermore, R ₇ and R ₈ represent residues that form a 5- to 6-membered ring together with the central carbon;
The ~6-membered ring may have a fused aromatic ring. Examples of such groups include cyclopentylidene, cyclohexylidene, 9-fluorenylidene, 9-xanthenylidene, and the like. R ₉ and R ₁₀ in formula (8) are hydrogen atoms, alkyl groups such as methyl, ethyl, propyl, and butyl which may have substituents, aralkyl groups such as benzyl, phenethyl, and naphthylmethyl, phenyl, naphthyl, It represents an aryl group such as anthryl and diphenyl, or a heterocyclic group such as carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine. An alkyl group, an aralkyl group represented by R ₉ and R ₁₀ ,
Substituents for aryl groups and heterocyclic groups include halogens such as fluorine, chlorine, bromine, and iodine, methyl,
Alkyl groups such as ethyl and propyl butyl, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, nitro groups, cyano groups, dimethylamino,
Examples include substituted amino groups such as dipropylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino. Although the present invention is not bound by theory, the aryl diamino that forms the skeleton of the azo pigment of general formula (1) has excellent sensitivity as a photoreceptor and ensures potential stability during long-term use. . High sensitivity is achieved in this way, making it possible to apply it to high-speed copying machines, laser beam printers, LED printers, liquid crystal printers, etc. Also, since a stable potential is ensured regardless of the previous history of the photoreceptor, stable and beautiful images can be produced. is obtained. Representative examples of azo pigments used in the present invention are listed below. These azo pigments can be used alone or in combination of two or more. Additionally, these pigments can be used, for example, with the general formula (However, R, Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ in the formula have the same meanings as the symbols in general formula (1).) The amine represented by the formula is diazotized by a conventional method, and then the corresponding coupler is added. After hydrogen coupling in the presence of an alkali, or once the diazonium salt of the amine described above is isolated in the form of a borofluoride salt or zinc chloride double salt, etc., it is dissolved in a suitable solvent such as N,N
- It can be easily produced by coupling with a coupler in a solvent such as dimethylformamide or dimethyl sulfoxide in the presence of an alkali. Next, a typical synthesis example of the azo pigment used in the present invention is shown below. Synthesis Example 1 (Synthesis of Azo Pigment No. 1 exemplified above): In a 500ml beaker, add 80ml of water and 16.6ml of concentrated hydrochloric acid (0.19ml).
mole) and 7.64 g (0.019 mol) was added thereto and stirred while cooling in an ice water bath to bring the temperature of the solution to 3°C. Then sodium nitrite
A solution prepared by dissolving 4.2 g (0.061 mol) in 7 ml of water was added dropwise over 10 minutes while controlling the temperature within the range of 3 to 10°C, and after the dropwise addition was completed, the mixture was stirred for an additional 30 minutes at the same temperature. Carbon was added to the reaction solution and filtered to obtain a tetrazotized solution. Next, put 700ml of water into 2 beakers and dissolve 21g (0.53mol) of caustic soda, then naphthol AS.
(3-hydroxy-2-naphthoic acid anilide)
16.1 g (0.061 mol) was added and dissolved. Cool this coupler solution to 6℃ and reduce the liquid temperature to 6-10℃.
Add the above-mentioned tetrazotization solution while controlling the temperature at
The mixture was added dropwise over 30 minutes with stirring, and then stirred at room temperature for 2 hours and further left overnight. The reaction solution was filtered, washed with water, and filtered to obtain a water paste containing 21.2 g of crude pigment in terms of solid content. Next, stirring filtration was repeated four times at room temperature using 400 ml of N,N-dimethylformamide. next
After repeating stirring and filtration twice with 400ml of methyl ethyl ketone, drying under reduced pressure at room temperature yielded 19.7g of purified pigment.
I got it. The yield was 85%. Melting point > 250℃ Elemental analysis: Calculated value (%) Experimental value (%) C 74.93 74.90 H 4.52 4.53 N 12.65 12.58 Although the synthesis method of typical pigments has been described above, other triazo pigments represented by general formula (1) are synthesized in the same way. However, if the solubility of the coupler in an alkaline aqueous solution is low, or if the coupling reaction is performed using a coupler that is easily hydrolyzed, such as the type of coupler represented by general formula (7), the coupler should be dissolved in a solvent such as DMF or DMAc. It is desirable to react with a tetrazonium salt using an organic base such as sodium acetate, pyridine, trimethylamine, or triethylamine, while being careful not to hydrolyze the coupler or reaction solvent. In a preferred embodiment of the present invention, an azo pigment represented by the general formula (1) can be used as a charge-generating substance in an electrophotographic photoreceptor in which the photosensitive layer is functionally separated into a charge-generating layer and a charge-transporting layer. The charge generation layer contains as much of the azo pigment as possible in order to obtain sufficient absorbance and is a thin film layer, e.g. less than 5 microns, in order to prevent the generated charge carriers from being trapped within the charge generation layer. , preferably a thin film layer having a thickness of 0.01 micron to 1 micron. This means that most of the incident light is absorbed by the charge generation layer and generates a large number of charge carriers, and that the generated charge carriers are not deactivated by recombination or trapping, and the charge transport layer This is due to the need to inject. The charge generation layer can be formed by dispersing the above-mentioned azo pigment in a suitable binder and coating it on the substrate, or it can be obtained by forming a deposited film using a vacuum deposition device. can. The binder that can be used when forming the charge generating layer by coating can be selected from a wide variety of insulating resins, and can also be selected from organic conductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate (bisphenol A, Z type, etc.), polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, Examples include insulating resins such as polyvinylpyridine, cellulose resin, urethane resin, 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 resin, and is preferably selected from those that do not dissolve the charge transport layer or undercoat layer described below. Specific organic solvents include alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexane, N,N-dimethylformamide,
Amides such as N,N-dimethylacetamide,
Sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogens such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene. Hydrocarbons or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used. Coating can be carried out using coating methods such as dip coating, spray coating, spinner coating, bead coating, Meyer bar coating, blade coating, roller coating, and curtain coating. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying at a temperature of 30℃ to 200℃ for 5 minutes to 2
It can be carried out stationary or under ventilation for a range of hours. The charge transport layer is electrically connected to the charge generation layer described above, and has the 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, this charge transport layer may be laminated on or under the charge generation layer. When a charge transport layer is formed on a charge generation layer, the substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as a charge transport substance) is substantially in the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. Preferably, it is insensitive to. The reason is to prevent the charge transport layer from having a filter effect and reducing sensitivity. The “electromagnetic wave” mentioned here is γ
It encompasses a broad definition of "light" that includes radiation, X-rays, ultraviolet rays, visible light, near-infrared rays, infrared rays, far-infrared rays, and the like. Charge transport substances include electron transport substances and hole transport substances, and electron transport substances include chloranil, promoanil, tetracyanoethylene, tetracyanoquinodimethane, and 2,4,7-trinitro-9-fluorenone. , 2, 4, 5, 7-
Tetranitro-9-fluorenone, 2,4,7-
trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone,
Examples include electron-withdrawing substances such as 2,4,8-trinitrothioxanthone, and polymerized versions of these electron-withdrawing substances. Examples of hole-transporting substances include 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-
Pyrrolidinobenzaldehyde-N,N-diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N,N-diphenylhydrazone, P-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone hydrazones such as 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-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, 2
-(P-diethylaminostyryl)-6-diethylaminobenzothiazole and other thiazole compounds,
Triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane, 1,1-bis(4-N,N-diethylamino-2-methylphenyl)heptane, 1,1,
Polyarylalkanes such as 2,2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, triphenylamine, stilbene derivatives, polycyclic aromatic compounds having a styryl group,
Examples include heterocyclic compounds, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin, and the like. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-thermal amorphous silicon, and cadmium sulfide can also be used. Moreover, these charge transport substances may be one or two types.
More than one species can be used in combination. When the charge transport material does not have film-forming properties,
A film can be formed by selecting an appropriate binder. Resins that can be used as binders are:
For example, acrylic resin, polyarylate, polyester, polycarbonate (bisphenol A, Z
type, etc.), polystyrene, acrylonitrile-
Insulating resins such as styrene copolymers, acrylonitrile-butadiene copolymers, polyvinyl butyral, polyvinyl formal, polysulfones, polyacrylamides, polyamides, chlorinated rubber, or organic photoconductive materials such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. Polymers may be mentioned. Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Typically it is between 5 microns and 30 microns, with a preferred range between 8 microns and 20 microns. When forming the charge transport layer by coating, an appropriate coating method as described above can be used. A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. As the substrate having a conductive layer, materials that are themselves conductive can be used, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum. In addition, plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene, terephthalate, , acrylic resin, polyethylene fluoride, etc.), conductive particles (e.g. carbon black, silver particles, etc.) coated on plastic with a suitable binder, substrates made of plastic or paper impregnated with conductive particles, and conductive materials. Plastics with polymers, etc. can be used. A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer. The undercoat 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. The thickness of the undercoat layer is 0.1 micron to 5 micron.
Preferably, 0.5 micron to 3 micron is appropriate. When 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, the surface of the charge transport layer must be positively charged, and exposure after charging is required. Then, in the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface and neutralize the positive charge, causing a decrease in surface potential and creating an electrostatic contrast with the unexposed area. . A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. This can be directly fixed, or the toner image can be transferred to paper, plastic film, etc. and then developed and fixed. Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or known methods, and are not limited to specific ones. On the other hand, when the charge transport material consists of a hole transport material, the surface of the charge transport layer must be negatively charged.
After charging, when exposed to light, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer, and then reach the surface and neutralize the negative charge, causing a decrease in the surface potential and static electricity between the exposed area and the unexposed area. Electrocontrast occurs. During development, it is necessary to use a positively charged toner, contrary to the case where an electron transport material is used. Another specific example of the present invention is an electrophotographic photoreceptor in which the azo pigment described above is contained in the same layer as a charge transport material. At this time, a charge transfer complex compound consisting of poly-N-vinylcarbazole and trinitrofluorenone can be used in addition to the above-mentioned charge transport substance. The electrophotographic photoreceptor of this example can be prepared by dispersing the aforementioned azo pigment and charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran, and forming a film using the resulting coating liquid. In any of the photoreceptors, the pigment used contains at least one type of pigment selected from azo pigments represented by general formula (1), and its crystal form may be amorphous or crystalline. . If necessary, a disazo pigment represented by general formula (1) may be used in combination to increase the sensitivity of the photoreceptor or to obtain a panchromatic photoreceptor.
It is also possible to use a combination of more than one kind, or a combination with a charge generating substance selected from known dyes and pigments. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers and CRTs.
Printers, LED printers, LCD printers,
It can also be widely used in electrophotographic applications such as laser engraving. The present invention will be explained below with reference to Examples. Examples 1 to 32 Ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 ml of water) on an aluminum plate
was applied with a Mayer bar so that the film thickness after drying was 1.0 microns, and dried. Next, 5 g of the above-exemplified azo pigment No. (1) was added to a solution of 2 g of butyral resin (butyralization degree 63 mol%) dissolved in 95 ml of ethanol, and
Spread out time. This dispersion was applied onto the previously formed casein layer using a Mayer bar so that the film thickness after drying would be 0.5 microns, and dried to form a charge generation layer. Then, the structural formula 5 g of hydrazone compound and 5 g of polymethyl methacrylate resin (number average molecular weight 100,000) were added to benzene.
A photoreceptor was prepared by dissolving the solution in 70 ml and applying it onto the charge generation layer using a Mayer bar so that the dry film thickness would be 12 microns, and drying to form a charge transport layer. Photoreceptors of Examples 2 to 40 were prepared in the same manner using the azo pigments shown in Table 1 instead of Azo Pigment No. 1. The electrophotographic photoreceptor thus prepared was statically charged with corona at -5 kV using an electrostatic copying machine testing device Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., and held in a dark place for 1 second, then the illuminance was 2 lux. The charging characteristics were measured by exposing the sample to light. As for charging characteristics, the surface potential (V _D ) and the exposure amount E1/2 (lux·sec) required to attenuate the potential of a pair of dark decays for 1 second to 1/2 were measured. Results first
Shown in the table.

【table】

[Table] As is clear from the results in Table 1, it was confirmed that all the photoreceptors of the present invention had extremely high electrophotographic sensitivity. Examples 33 to 36 Using the photoreceptors used in Examples 1, 6, 25, and 30, fluctuations in bright area potential and dark area potential during repeated use were measured. The photoreceptor was attached to the cylinder of an electrophotographic copying machine equipped with a -5.6 kV corona charger, an exposure optical system, a developer, a transfer charger, a static elimination exposure optical system, and a cleaner. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copying machine, the initial bright area potential (V _L ) and dark area potential (V _D ) are calculated as −
The bright area potential (V _L ) and dark area potential were measured after being set at around 100 V and -600 V and used 5000 times. The results are shown in Table 2.

[Table] The photoreceptor of the present invention had extremely good stability in V _D and V _L even during repeated use. Example 37 On the charge generation layer prepared in Example 1, 2,
A coating solution prepared by dissolving 5 g of 4,7-trinitro-9-fluorenone and 5 g of poly-4,4'-dioxydiphenyl-2,2'-propane carbonate (molecular weight 300,000) in 70 ml of tetrahydrofuran was dried. It was coated at a coating weight of 10 g/m ² and dried. The electrostatic charge of the electrophotographic photoreceptor thus prepared was measured in the same manner as in Example 1. At this time, the charging polarity was set. The results are shown in Table 3. Table 3 V _D : 570 volts E1/2: 5.6 lux·sec Example 38 A polyvinyl alcohol film having a thickness of 0.5 microns was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. Next, the azo pigment dispersion used in Example 1 was applied onto the previously formed polyvinyl alcohol layer using a Mayer bar so that the film thickness after drying was 0.5 microns, and dried to form a charge generating layer. was formed. Then, the structural formula A solution prepared by dissolving 5 g of pyrazoline compound and 5 g of polyarylate resin (condensation polymer of bisphenol A and terephthalic acid-isophthalic acid) in 70 ml of tetrahydrofuran is placed on the charge generation layer so that the film thickness after drying is 10
It was applied to a micron thickness and dried to form a charge transport layer. The charging characteristics and durability characteristics of the photoreceptor thus prepared were measured in the same manner as in Examples 1 and 33. The results are shown in Table 4. Table 4 V _D : −580V E1/2: 4.3lux・sec Durability characteristics Initial state After 5000 sheets of durability V _D V _L V _{D V L} −580V −100V −590V −120V Sensitivity is better than the results in Table 4 and durability Potential stability during use is also good. Example 39 An ammonia aqueous solution of casein was applied onto an aluminum plate with a thickness of 100 microns and dried to form a subbing layer with a thickness of 0.5 microns. Next, 5 g of 2,4,7-trinitro-9-fluorenone and 5 g of poly-N-vilcarbazole (number average molecular weight 300,000) were dissolved in 70 ml of tetrahydrofuran to form a charge transfer complex. This charge transfer complex compound and 1 g of the above-mentioned azo pigment No. (32)
, polyester resin (Vylon: manufactured by Toyobo) 5
g was dissolved in 70 ml of tetrahydrofuran and dispersed. This dispersion was applied onto the undercoat layer so that the film thickness after drying would be 12 microns, and then dried. The charging characteristics and durability characteristics of the photoreceptor thus prepared were measured in the same manner as in Example 1. The results are shown in Table 5. However, the charging polarity was determined. Table 5 V _D : +590V E1/2: 5.2lux・sec Initial durability characteristics After 5000 sheets durability V _D V _L V _D V _L +590V +110V +600V +120V Example 40 Aluminum substrate with casein layer used in Example 1 The charge transport layer and charge generation layer of Example 1 were sequentially laminated on the casein layer of Example 1, and a photoreceptor was formed in the same manner as in Example 1 except that the layer structure was different, and charged in the same manner as in Example 1. It was measured. However, the charging polarity was taken into account. Charging characteristics are shown in Table 6. Table 6 V _D : +590V E1/2: 4.7 lux・sec [Effects of the Invention] The present invention uses a specific azo pigment in the photosensitive layer to improve carrier generation efficiency within the photosensitive layer containing the azo pigment. It is assumed that one or both of the carrier transport efficiency will be improved, and a photoreceptor with excellent sensitivity and potential stability during long-term use can be obtained.

Claims (1)

[Claims] First-order general formula (1) [Wherein, R represents hydrogen, nitroso, an alkyl group which may have a substituent, an aralkyl group, an aryl group, and an acyl group. However, R is −Ar ₅ −N=N−A
(In the formula, Ar ₅ represents an arylene group or a heterocyclic group which may have a substituent.)
Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ represent an arylene group or a heterocyclic group which may have a substituent, and A represents a coupler residue having a phenolic OH group. ] An electrophotographic photoreceptor characterized by containing an azo pigment represented by the following in a photosensitive layer. 2 A in the above general formula (1) is the following general formula (2) to (8)
An electrophotographic photoreceptor according to claim 1, which is represented by: (In the formula, X represents a residue _that forms a polycyclic aromatic ring or a heterocycle by condensing with a benzene ring, _and
represents hydrogen, an alkyl group, an aralkyl group, an aryl group, a heterocyclic group which may have a substituent, or a cyclic amino group bonded to each other to form a nitrogen atom, and R ₅ and R ₆ each have a substituent. Y represents an aromatic hydrocarbon divalent group or a heterocyclic divalent group having a nitrogen atom, and R ₇ and R ₈ each represent a substituent. an aryl group or a heterocyclic group which may have 5 to 6 together with the central carbon;
Indicates a residue forming a membered ring, this 5- to 6-membered ring may have a fused aromatic ring, R ₉ and R ₁₀ are hydrogen, an alkyl group that may have a substituent, an aralkyl group , represents an aryl group or a heterocyclic group. ) 3. The photosensitive layer according to claim 1, wherein the photosensitive layer is a functionally separated type consisting of a charge generation layer and a charge transport layer, and the charge generation layer contains an azo pigment represented by the above general formula (1). Electrophotographic photoreceptor. 4 R ₃ in the above general formula (2) is hydrogen, and R ₄
is the general formula The electrophotographic photoreceptor according to claim 2, wherein R ₁₁ is a substituted phenyl represented by the following formula: (wherein R 11 is a substituent selected from halogen, nitro, cyano, and trifluoromethyl).