JPH0417425B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to an electrophotographic photoreceptor. [Prior Art] Pigments and dyes exhibiting photoconductivity have been published in numerous publications. For example, “RCA Review” Vo1.23, P.413~
P.419 (September 1962), the photoconductivity of phthalocyanine pigments was announced, and electrophotographic photoreceptors using this phthalocyanine pigment were published in US Pat. No. 3,397,086, US Pat. No. 3,816,118, etc. It is shown. In addition, as organic semiconductors used in electrophotographic photoreceptors, for example, US Pat.
4315983, U.S. Patent No. 4327169, and pyrylium dyes disclosed in “Reseach Disclosure” 20517 (May 1981), U.S. Patent No.
Examples include methine squaritate dyes shown in US Pat. No. 3,824,099, and disazo pigments shown in US Pat. No. 3,898,084 and US Pat. No. 4,251,613. Such organic semiconductors are easier to synthesize than inorganic semiconductors, and can be synthesized as compounds that have photoconductivity for light in the required wavelength range. Electrophotographic photoreceptors formed on conductive supports have the advantage of improved color sensitivity, but only a few of them have good sensitivity and durability for practical use. [Problems to be Solved by the Invention] By using a new organic photoconductive material, the present invention achieves better practical sensitivity characteristics and durability than ever before, and in particular stability of potential characteristics during repeated use. The purpose of this invention was to provide an electrophotographic photoreceptor with high properties. [Means and Effects for Solving the Problems] That is, the present invention provides an electrophotographic photoreceptor comprising a photosensitive layer containing a disazo pigment represented by the following general formula [] on a conductive substrate. It is. General formula [] (In the formula, A represents a coupler residue having a phenolic OH group. _{Ar 1} and Ar ₂ are respectively a phenylene group which may have a substituent, a biphenylene group which may have a substituent, or a fused Represents a polycyclic aromatic group or a divalent heterocyclic group.However, Ar ₁ and Ar ₂
However, neither of them is a phenylene group which may have a substituent. ) In the above formula, Ar ₁ and Ar ₂ each represent a phenylene group which may have a substituent; a biphenylene group which may have a substituent; a hydrogen group from a naphthylene group, anthrylene group, fluorene, fluorenone, etc. A divalent fused polycyclic aromatic group such as a divalent group formed by removing two atoms; or a divalent heterocycle such as a divalent group formed by removing two hydrogen atoms from quinoline, carbazole, benzoxazole, etc. represents a group. Examples of atoms or groups that substitute the divalent groups represented by Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom, methyl group, and ethyl group. group, alkyl group such as propyl group, benzyl group, phenethyl group,
Aralkyl groups such as naphthylmethyl groups, phenyl groups, diphenyl groups, aryl groups such as naphthyl groups,
Examples include alkoxy groups such as methoxy, ethoxy and butoxy groups, acyl groups such as cyano, acetyl and benzoyl, and nitro groups. However, Ar ₁ and Ar ₂ are not both phenylene groups which may have a substituent. In addition, in the general formula [], A is phenolic
It represents a coupler residue having an OH group, and preferred specific examples include the following general formulas [], []~
Examples include groups represented by []. General formula [] In the formula, X is fused with a benzene ring to form a polycyclic aromatic ring which may have a substituent (e.g. naphthalene ring, anthracene ring) or a hetero ring (e.g. carbazole ring, benzcarbazole ring, dibenzofuran ring, benzene ring). Represents a residue necessary to form a naphthofuran ring or a diphenylene sulfite ring. More preferably, naphthalene ring,
They are anthracene ring, carbazole ring and benzcarbazole ring. R ₁ and R ₂ are each a hydrogen atom, an alkyl group that may have a substituent,
It represents an aralkyl group, an aryl group, or a heterocyclic group, or represents a residue necessary for forming a cyclic amino group with R ₁ and R ₂ together with the bonded nitrogen atom. Specific examples of alkyl groups include methyl group,
Examples include ethyl group, propyl group, butyl group, and the like. Specific examples of the aralkyl group include benzyl group, phenethyl group, naphthylmethyl group, and the like. Examples of the aryl group include phenyl group, diphenyl group, naphthyl group, and anthryl group. In particular, R ₁ is a hydrogen atom, R ₂ is a phenyl group having a halogen atom, an electron-withdrawing group such as a nitro group, a cyano group, a trifluoromethyl group, and an alkyl group such as an ethyl group, a methyl group, a butyl group, etc. In this case, the electrophotographic properties are good. Examples of the heterocyclic group include groups obtained by removing one hydrogen atom from a heterocyclic ring such as carbazole, dibenzofuran, benzimidazolone, benzothiazole, thiazole, and pyridine. As a cyclic amino group formed by R ₁ and R ₂ ,
Examples include pyrrolidino group, piperidino group, and morpholino group. In particular, in the general formula [], R ₁ is a hydrogen atom,
Preferred examples include those in which R ₂ is a phenyl group represented by the following general formula []. General formula [] In the formula, R ₃ is a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom), a nitro group,
Represents a cyano group, trifluoromethyl group, or acyl group (eg, acetyl group, benzoyl group, etc.).
Further, another suitable example of the general formula [] is represented by the following general formula []. General formula [] In the formula, R ₄ represents a phenyl group which may have a substituent. General formula [] In the formula, R ₅ represents an alkyl group, an aralkyl group, or an aryl group which may have a substituent. General formula [] In the formula, R ₆ represents an alkyl group, an aralkyl group, or an aryl group that may have a substituent. Specific examples of the alkyl group represented by R ₅ and R ₆ include a methyl group, an ethyl group, a propyl group, a butyl group, and the like. Specific examples of aralkyl groups include benzyl group, phenethyl group, naphthylmethyl group, etc. Aryl groups include phenyl group,
Examples include diphenyl group, naphthyl group, and anthryl group. Examples of atoms or groups substituting optionally substituent-containing groups in general formulas [], [], [], and [] include alkyl groups such as methyl, ethyl, and propyl groups, and methoxy groups. , alkoxy groups such as ethoxy groups and propoxy groups, halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, substituted amino groups such as nitro groups, cyano groups, dimethylamino groups, diethylamino groups, benzylamino groups, and diphenylamino groups. Examples include groups. General formula [] In the formula, Y ₁ represents a divalent aromatic hydrocarbon group bonded to two nitrogen atoms, or

[Formula] represents the residue necessary to form a divalent heterocycle. General formula [] In the formula, Y ₁ represents a divalent aromatic hydrocarbon group bonded to two nitrogen atoms, or

[Specific description and examples of the invention]

Examples of the disazo pigment of the general formula [] used in the present invention include disazo pigments of the following pigment numbers and structural formulas. These disazo pigments may be used alone or in combination of two or more. The disazo pigment of the general formula [] can be synthesized as follows. That is, a diamine having a secondary amine represented by the general formula: H ₂ N-Ar ₁ -NH-Ar ₂ -NH ₂ (wherein Ar ₁ and Ar ₂ have the above-mentioned meanings) is tetrazotized by a conventional method. At the same time, the corresponding coupler is subjected to nitrosation, and then the corresponding coupler is coupled in an aqueous system in the presence of an alkali, or the tetrazonium salt of the diamine is isolated in the form of a borofluoride salt or zinc chloride double salt, and then a suitable solvent is used. For example, 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 disazo pigment used in the present invention is shown below. Synthesis Example 1 (Synthesis of Disazo Pigment No. 1 exemplified above) Add 80 ml of water and 16.6 ml (0.19 mol) of concentrated hydrochloric acid to a 500 ml beaker and add diamine while cooling in an ice water bath. 7.23g (0.029mol) was stirred and the liquid temperature was brought to 3°C.
Next, a solution prepared by dissolving 6.2 g (0.090 mol) of sodium nitrite 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 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, dimethylformamide 700 in 21 beakers
ml, add 53.6 g (0.53 mol) of triethylamine, and add 3-hydroxy-2-naphthoic acid anilide.
16.06 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 a water paste containing 23.05 g of crude pigment was obtained by calculating the solid content. Next, stirring filtration was repeated four times at room temperature using 400 ml of N,N-dimethylformamide. after that
After repeating stirring and filtration twice with 400ml of methyl ethyl ketone, dry under reduced pressure at room temperature to obtain purified pigment.
20.7g was obtained. The yield was 86.5%. Melting point 300
℃ or more. Elemental analysis Calculated value (%) Experimental value (%) C 72.63 72.79 H 4.14 4.10 N 13.55 13.66 The synthesis method of typical pigments has been described above, but other disazo pigments represented by general formula (1) can also be synthesized in the same manner. be done. The coating containing the aforementioned disazo pigment exhibits photoconductivity and is suitable for use in the photosensitive layer of an electrophotographic photoreceptor. That is, in a specific example of the present invention, an electrophotographic photoreceptor is prepared by coating the above-mentioned disazo pigment on a conductive support by vacuum evaporation, or by dispersing it in a suitable binder to form a coating. can do. In a preferred embodiment of the present invention, as a charge generation layer in an electrophotographic photoreceptor in which the photoreceptor of the electrophotographic photoreceptor is functionally separated into a charge generation layer and a charge transport layer,
Photoconductive coatings as described above can be applied. The charge generation layer contains as much of the above-mentioned disazo pigment as possible in order to obtain sufficient absorbance, and is a thin film layer, for example, 5μ or less, preferably 0.01~ to shorten the range of the generated charge carriers. Preferably, it is a thin film layer with a thickness of 1μ. This means that most of the amount of sunlight is absorbed by the charge generation layer, generating many charge carriers, and that the generated charge carriers are transported without being deactivated by recombination or trapping. This is due to the need to inject into the layer. The charge generation layer can be formed by dispersing the above-mentioned disazo pigment in a suitable binder and coating it on the substrate, or it can also be obtained by forming a vapor deposited film using a vacuum vapor deposition device. I can do it. The binder used in forming the charge generating layer by coating can be selected from a wide variety of insulating resins, and can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, Examples include insulating resins such as 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 it is preferable to select a solvent that does not dissolve the undercoat layer in the charge transport layer described below. Specific organic solvents include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone, methyl ethyl ketone, and dichlorohexanone, 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, plate 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 blown air for a period of time within 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 the charge transport layer is formed on the charge generation layer, the material that transports charge carriers in the charge transport layer (hereinafter simply referred to as charge transport material) is substantially in the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. Preferably, it is insensitive to. The term "electromagnetic waves" used herein includes a broad definition of "light rays" that includes gamma rays, X-rays, ultraviolet rays, visible light, near infrared rays, infrared rays, far infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps that of the charge generation layer, charge carriers generated in both layers capture each other, resulting in a decrease in sensitivity. Charge transport substances include electron transport substances and hole transport substances, and electron transport substances include chloranil, bromoanil, 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-absorbing substances such as 2,4,8-trinitrothioxanthone, and polymerized versions of these electron-absorbing 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-dimethylaminophenyl)pyrazoline, 1-[quinolyl(2)]-3-(p-diethylaminostyryl)-5-(p-dimethylaminophenyl)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-dimethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(α-methyl-p-
diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-phenyl-3-
(-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-dimethylaminophenyl)-4-(p-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2
Thiazole compounds such as -(p-diethylaminostyryl)-6-diethylaminobenzothiazole, bis(4-diethylamino-2-methylphenyl)-phenylmethane, triarylmethane compounds, 1,1-bis(4-N,N -diethylamino-2-methylphenyl)peptane, 1,
Polyarylalkanes such as 1,2,2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, 4-diphenylamino-4'-
Stilbene compounds such as methoxystilbene, 4'-diethylaminostyryl-3-(9-ethyl)carbazole, triphenylamine, poly-N-
Examples include vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, and ethylcarbazole formaldehyde resin. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, 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, insulating resins such as acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, or poly-N- Mention may be made of organic photoconductive polymers such as vinylcarbazole, polyvinylanthracene, polyvinylpyrene. Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, it is 5-30μ, but the preferred range is 8-20μ. 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, conductive particles (e.g. aluminum powder, tin oxide, zinc oxide, titanium oxide, carbon black,
a substrate in which silver particles, etc.) are coated on plastic or the conductive substrate with a suitable binder;
A substrate made of plastic or paper impregnated with conductive particles, a plastic containing a conductive polymer, 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 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. The thickness of the undercoat layer is 0.1 to 5μ, preferably 0.5 to 3μ.
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 treating 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 developing method and the fixing method using the type of developer may be any known method or known methods, and are not limited to any particular method. 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. Electrical contrast occurs.
During development, it is necessary to use a positively charged toner, contrary to the case where an electron transporting substance is used. When using a photoreceptor in which a conductive layer, a charge transport layer, and a charge generation layer are laminated in this order, if the charge transport material is an electron transport material, the surface of the charge generation layer must be negatively 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 substrate. On the other hand, holes generated in the charge generation layer reach the surface and the surface potential is attenuated, creating an electrostatic contrast with the unexposed area. A visible image can be obtained by developing the electrostatic latent image thus formed with a positively 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 methods, and are not limited to specific ones. On the other hand, when the charge generation layer is made of a hole transporting substance, the surface of the charge generation layer must be positively charged.
When exposed to light after charging, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer and then reach the substrate. On the other hand, electrons generated in the charge generation layer reach the surface and the surface potential is attenuated, creating an electrostatic contrast with the unexposed area. During development, it is necessary to use a negatively charged toner, contrary to the case where an electron transporting substance is used. In another specific example of the present invention, organic photoconductive materials such as the aforementioned hydrazones, pyrazolines, oxazoles, thiazoles, triarylmethanes, polyarylalkanes, triphenylamines, poly-N-vinylcarbazoles, etc. The photosensitive film may contain the above-mentioned disazo pigment as a sensitizer for photoconductive substances and inorganic photoconductive substances such as zinc oxide, cadmium sulfide, and selenium. This photosensitive film is formed by coating these photoconductive substances and the above-mentioned disazo pigment together with a binder. Another specific example of the present invention is an electrophotographic photoreceptor containing the above-mentioned disazo pigment and a charge transport material in the same layer. In this case, in addition to the above-mentioned charge transport materials, a charge transfer complex compound consisting of poly-N-vinylcarbazole and trinitrofluorenone can be used. The electrophotographic photoreceptor of this example can be prepared by dispersing the aforementioned disazo pigment and charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran, and then forming a film thereon. The pigment used in any of the photoreceptors contains at least one pigment selected from disazo pigments represented by the general formula (1), and its crystal form may be amorphous or crystalline. Furthermore, if necessary, two or more types of disazo pigments represented by the general formula (1) may be used in combination for the purpose of increasing the sensitivity of the photoreceptor or obtaining a panchromatic photoreceptor by using a combination of pigments with different light absorption. Alternatively, it can be used in combination with a charge generating substance selected from known dyes and pigments. The electrophotographic photoreceptor of the present invention 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 40 An ammonia aqueous solution of casein (11.2% casein in aqueous ammonia, 1 g, 222 ml of water) was coated on an alumina plate using a Mayer bar so that the film thickness after drying was 1.0 μm and dried. Next, 5 g of the above-mentioned disazo pigment No. 1 was added to 9.5 ml of ethanol with butyral resin (butyralization degree).
63 mol%) was added to the solution and dispersed for 2 hours using a sand mill. This dispersion was applied onto the previously formed casein layer using a Mayer bar so that the film thickness after drying was 0.5 μm, 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.
The photoreceptor of Example 1 was prepared by dissolving the solution in 70 ml and coating it on the charge generation layer using a Mayer bar so that the dry film thickness was 12μ, and drying to form a charge transport layer. Photoreceptors corresponding to Examples 2 to 40 were prepared in exactly the same manner using other exemplary pigments shown in Table 1 in place of disazo pigment No. 1. The electrophotographic photoreceptor thus prepared was statically charged with corona at -5kV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., and held in a dark place for 1 second, then at an illuminance of 21ux. It was exposed to light and its charging characteristics were investigated. As for the charging characteristics, the surface potential (Vo) and the exposure amount (E _1/2 ) required to attenuate the potential by 1/2 when dark decaying for 1 second were measured. The results are shown in Table 1.

【table】

【table】

[Table] Comparative Examples 1 to 7 In place of the exemplified disazo pigments (1), (3), and (4), the central skeleton of the pigment was

[Formula] Azo pigment No. 2, No.
Comparative materials 1, 2, and 3 were created using pigments No. 1 and No. 3. Next, exemplified disazo pigments (1), (14), (19),
Instead of (34), the central skeleton of the pigment is Comparative Examples 4, 5, 6, and 7 were created using the comparative pigments. Regarding Comparative Materials 1 to 7 using Comparative Pigments 1 to 7, charge measurement was performed in the same manner as in Example 1. Table 2 shows the characteristics of comparative examples compared to the present invention.

[Table] * Extracted from the data in Table 1 As is clear from the results in Table 2, the photoreceptor of the present invention has a central skeleton of the pigment.

It was confirmed that electrophotographic sensitivity is significantly improved by having the group [Formula] and one or more polycyclic aromatic rings or heterocycles. Examples 41 to 46 Using the photoreceptors used in Examples 1, 3, 4, 12, 14, and 25, fluctuations in bright area potential and dark area electrons 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 copy paper as a cylinder is driven. Using this copier, set the initial light potential (V _L ) and dark potential (V _D ) to around -100V and -600V, respectively, and calculate the light potential (V _L ) and dark potential after using it 5000 times. It was measured.
The results are shown in Table 3.

【table】

[Table] Example 47 On the charge generation layer created 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 4. Table 4 V _p 590 volts E _1/2 ; 3.31 ux·sec Example 48 A polyvinyl alcohol film with a thickness of 0.5 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. Next, the dispersion of the disazo pigment used in Example 1 was placed on the polyvinyl alcohol layer formed previously.
It was coated with a Mayer bar so that the film thickness after drying was 0.5μ, and dried to form a charge generation layer. 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 was placed on the charge generation layer to determine the film thickness after drying.
It was applied to a thickness of 10μ 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 4. The results are shown in Table 5. Table 5 V _p :600V E _1/2 ;3.81ux・sec Durability characteristics Initial After 5000 sheets V _p V _L V _p V _L −600V −1000V −630V −125 Better sensitivity and durability than the results in Table 5 Potential stability during use is also good. Example 49 An ammonia aqueous solution of casein was coated on 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-vinylcarbazole (number average molecular weight 300,000) were added to 70 ml of tetrahydrofuran.
to form a charge transfer complex. This charge transfer complex compound and the above-mentioned disazo pigment No.
(26) 1 g was added to a solution in which 5 g of polyester resin (Vylon, manufactured by Toyobo) was dissolved in 70 ml of tetrahydrofuran, and dispersed. This dispersion was applied onto the undercoat layer so that the film thickness after drying was 12 microns.
Dry. 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 6. However, the charging polarity was determined. Table 6 V _p : 580V E _1/2 ; 4.41ux・sec Example 50 The charge transport layer and charge generation layer of Example 1 were sequentially applied on the casein layer of the casein layer-coated aluminum plate used in Example 1. A photoforming layer was formed in the same manner as in Example 1 except that the layer structure was different from that of Example 1.
The charge was measured in the same manner as above. However, the charging polarity was determined. Charging characteristics are shown in Table 7. Table 7 V _p : 600V E _1/2 ; 4.51ux・sec Example 51 An ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 22.2 ml of water) was coated on an aluminum cylinder by dip coating. , and dried to form a subbing layer with a coating weight of 1.0 g/m ² . Next, 1 part by weight of the above-mentioned disazo pigment No. 58, butyral resin (Eslec BM-2: Sekisui Chemical Co., Ltd.)
1 part by weight) and 30 parts by weight of isopropyl alcohol were dispersed for 4 hours using a ball mill disperser. This dispersion was applied onto the previously formed subbing layer by a dip coating method and dried to form a charge generation layer. The film thickness at this time was 0.3 microns. Next, 1 part by weight of the hydrazone compound used in Example 1, 1 part by weight of polysulfone resin (P1700: manufactured by Union Carbide) and 6 parts by weight of monochlorobenzene were added.
Parts by weight were mixed and dissolved by stirring with a stirrer. This liquid was applied onto the charge generation layer by dip coating and dried to form a charge transport layer. The film thickness at this time was 12 microns. A -5 kV corona discharge was applied to the photoreceptor thus prepared. The surface potential at this time was measured (initial potential V _p ). Further, the surface potential of the photoreceptor was measured after it was left in the dark for 5 seconds (dark decay V _K ). Sensitivity was evaluated by measuring the exposure amount (E _1/2 microjoule/cm ² ) required to attenuate the potential V _K by 1/2 after dark decay. At this time, a potassium/aluminum/arsenic ternary semiconductor laser (output: 5 mW; oscillation wavelength: 778 nm) was used as a light source. The results were as follows. V _p : -520 volts V _K : 94% E _1/2 : 1.3 microjoules/cm ^Second , a laser beam printer (Canon's LBP- CX), replace the above photoconductor with the photoconductor of LBP-CX, and set it.
An actual imaging test was used. The conditions are as follows. Surface potential after primary charging: -700V, surface potential after image exposure: -150V (exposure amount: 2 μJ/cm ² ), transfer potential:
+700V, developer polarity: negative polarity, process speed: 50mm/sec, development conditions (development bias): -
450V, image exposure scan method; image scan,
Primary pre-charging exposure: 501 ux·sec full red exposure Image formation was performed by line-scanning a laser beam in accordance with character signals and image signals, and good prints were obtained for both character images.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing a disazo pigment represented by the following general formula [] on a conductive substrate. General formula [] (In the formula, A represents a coupler residue having a phenolic OH group. _{Ar 1} and Ar ₂ are respectively a phenylene group which may have a substituent, a biphenylene group which may have a substituent, or a fused Represents a polycyclic aromatic group or a divalent heterocyclic group.However, Ar ₁ and Ar ₂
However, neither of them is a phenylene group which may have a substituent. ) 2. The electrophotographic photoreceptor according to claim 1, wherein A in the general formula [] is represented by the following general formula []. General formula [] (In the formula, X represents a residue necessary to form a polycyclic aromatic ring or a heterocycle which may have a substituent by condensation with a benzene ring. R ₁ and R ₂ are each , represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic group which may have a substituent, or R ₁ and R ₂ together with the bonding nitrogen atom form a cyclic amino group. ) 3 R ₁ is a hydrogen atom, and R ₂ is the following general formula []
Claim 2, which is a phenyl group represented by
The electrophotographic photoreceptor described in . General formula [] (In the formula, R ₃ represents a halogen atom, a nitro group, a cyano group, a trifluoromethyl group, or an acyl group.) 4. Claim 2, wherein A is represented by the following general formula [] electrophotographic photoreceptor. General formula [] (In the formula, R ₄ represents a phenyl group which may have a substituent.) 5. Claim 1, wherein A in the general formula [] is represented by the following general formula [] electrophotographic photoreceptor. General formula [] (In the formula, R ₅ represents an alkyl group, an aralkyl group, or an aryl group that may have a substituent.) 6. A patent claim in which A in the general formula [] is represented by the following general formula [] The electrophotographic photoreceptor according to item 1. General formula [] (In the formula, R ₆ represents an alkyl group, an aralkyl group, or an aryl group that may have a substituent.) 7. A patent claim in which A in the general formula [] is represented by the following general formula [] The electrophotographic photoreceptor according to range 1. General formula [] (In the formula, Y ₁ represents a divalent aromatic hydrocarbon group bonded to two nitrogen atoms, or
[Formula] represents a residue necessary to form a divalent heterocyclic group. ) 8 The electrophotographic photoreceptor according to claim 1, wherein A in the general formula [] is represented by the following general formula []. General formula [] (In the formula, Y ₁ represents a divalent aromatic hydrocarbon group bonded to two nitrogen atoms, or
[Formula] represents a residue necessary to form a divalent heterocyclic group. ) 9 The electrophotographic photoreceptor according to claim 1, wherein A in the general formula [] is represented by the following general formula []. General formula [] (In the formula, Z ₁ represents a residue necessary to form a polycyclic aromatic ring or a heterocycle which may have a substituent by condensation with a benzene ring. _{R 7} and R ₈ are each represents a hydrogen atom, an optionally substituted aryl group or a heterocyclic group, or R ₇
together with the carbon atom to which R ₈ is bonded, a 5-membered ring or a 6-membered ring
Represents a residue necessary to form a membered ring, and these 5- or 6-membered rings may have a fused aromatic ring. ) 10 The electrophotographic photoreceptor according to claim 1, wherein A in the general formula [] is represented by the following general formula []. General formula [] (In the formula, Z ₂ represents a residue necessary to form a polycyclic aromatic ring or a heterocycle which may have a substituent by condensation as a benzene ring. R ₉ and R ₁₀
each represents a hydrogen atom, an optionally substituted alkyl group, an aralkyl group, an aryl group, or a heterocyclic group. ) 11. Claims 1 to 10, wherein the photosensitive layer has a laminated structure consisting of a charge generation layer containing at least one disazo pigment of the general formula [] and a charge transport layer. The electrophotographic photoreceptor according to item 1.