JPH01140166A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain practicable high sensitivity characteristics and stable potential characteristics at the time of repeated uses by incorporating a specified disazo pigment in a photoconductive layer formed on a conductive substrate. CONSTITUTION:The photoconductive layer formed on the conductive substrate contains the disazo pigment represented by formula I in which each of R1-R4 is H, halogen, alkyl, alkoxy, nitro, or cyano, optionally substituted aryl or aralkyl, each of R1 and R2 is not H, and R1 and R2, R3 and R4 may form an optionally substituted aromatic or hetero ring together with the adjacent benzene ring; and each of Ar1 and Ar2 is an optionally substituted aromatic ring or hetero ring optionally linked through a bonding group, each optionally same or different from each other, thus permitting practicable high sensitivity characteristics and stable potential characteristics even at the time of repeated uses to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor containing a specific disazo pigment in a photosensitive layer.

[Prior Art] Electrophotographic annular bodies using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components have been known.

On the other hand, since the discovery that certain organic compounds exhibit photoconductivity, a number of organic photoconductors have been developed. carbazole,
Low-molecular organic photoconductors such as anthracene, pyrazolines, oxadiazoles, hydrazones, polyarylalkanes, phthalocyanine pigments, azo pigments, cyanine pigments, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindigo dyes Alternatively, organic pigments and dyes such as methine squaric acid dyes are known. In particular, organic pigments and dyes with photoconductivity are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has been expanded.
Many photoconductive organic pigments and dyes have been proposed.

For example, U.S. Pat. No. 4,123,270, U.S. Pat.
47614 specification, 4251613 specification, 4251614 specification, 4256821 specification, 4260672 specification, 4268596
Specification of No. 4278747, No. 4293
Electrophotographic photoreceptors are known that use an azo pigment exhibiting photoconductivity as a charge-generating substance in a photosensitive layer that is functionally separated into a charge-generating layer and a charge-transporting layer, as disclosed in No. 628. .

Electrophotographic photoreceptors using such organic photoconductors can be produced by coating by appropriately selecting a binder, making it possible to provide photoreceptors with extremely high productivity and low cost. Although it has the advantage of being able to freely control the sensitive wavelength range, there are still many problems with sensitivity and durability.

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel photoconductive material and an electrophotographic photoreceptor having practical high sensitivity characteristics and stable potential characteristics when used for edge reversing. That's true.

[Means and effects for solving the problems] The present invention comprises an electrophotographic photoreceptor characterized in that a photosensitive layer laminated on a conductive support contains a disazo pigment represented by the following general formula (1). be done.

In the general formula, R1, R2, R3 and R4 represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a nitro group, a cyano group, an aryl group which may have a substituent, or an aralkyl group, provided that R2 and R3 are never hydrogen atoms.

Specifically, halogen atoms such as hydrogen atoms, fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, furkyl groups such as methyl, ethyl, and pugopyl, alkoxy groups such as methoxy, ethoxy, and propoxy, nitro groups, cyano groups, Examples include heptaryl groups such as phenyl and naphthyl, aralkyl groups such as benzyl and phenethyl, and substituents for aryl and aralkyl groups include halogen atoms such as fluorine, chlorine, bromine, and iodine atoms, methyl, Examples include aralkyl groups such as ethyl and propyl, alkoxy groups such as methoxy, ethoxy, and propoxy, haloalkyl groups such as trifluoromethyl, nitro groups, and cyano groups.

Moreover, R1 and R2 and R3 and R4 may form an aromatic ring or a heterocycle which may have a substituent together with the benzene ring to which they are bonded, specifically.

Examples include naphthalene ring, anthracene ring, carbazole ring, benzcarbazole ring, dibenzofuran ring, etc.
Examples of the substituent include the same groups as those for the above-mentioned aryl group and aralkyl group.

Arl and Ar2 represent an aromatic ring or a heterocycle which may have a substituent which may be bonded via a bonding group,
Ar1 and Ar2 may be the same or different, and specifically, aromatic hydrocarbon rings such as benzene, naphthalene, fluorene, phenanthrene, and anthracene,
Furan, thiophene, pyridine, indole, benzothiazole, carbazole, acridone, dibenzothiophene, benzoxazole, benzotriazole.

Heterocycles such as oxadiazole, thiadiazole, and the above aromatic rings bonded directly or with aromatic or non-aromatic groups, such as triphenylamine, diphenylamine, N-methyldiphenylamine, biphenyl, terphenyl, binaphthyl. , fluorenone, phenanthrenequinone, anthraquinone, benzanthrone,
Diphenyloxadiazole, phenylbendiocosazole, diphenylmethane, diphenylsulfone, diphenyl ether, benzophenone, stilbene, distyrylbenzene, etc., and as a substituent for the above group,
Halogen atoms such as fluorine, chlorine, bromine, and iodine; alkyl groups such as methyl, ethyl, and propyl; flukoxy groups such as methoxy and ethoxy; dialkylamino groups such as dimethylamino and diethylamino; nitro groups; cyano groups; Examples include hydroxyl group.

Although the reason why the electrophotographic photoreceptor containing the disazo pigment represented by the general formula (1) in the present invention has excellent sensitivity is not clear, the bifunctional coupler forms the following intramolecular hydrogen bonds, and the pigment molecule This is presumed to be due to the fact that the pigment molecules have a large planar structure, which improves the overlapping of the pigment molecules due to intermolecular hydrogen bonds.

ArI Arλ Representative specific examples of the disazo pigment represented by the general formula (1) are listed below.

Exemplary Pigment (1) I OA Exemplary Pigment (2) x ci Exemplary Pigment (3) Exemplary Pigment (4) Exemplary Pigment (5) Exemplary Pigment (6) F NO Exemplary Pigment (7) Exemplary Pigment (8) Exemplary Pigment ( 9) Exemplary Pigment (10) Exemplary Pigment (11) Exemplary Pigment (12) Exemplary Pigment (13) Exemplary Pigment (14) Exemplary Pigment (15) Exemplary Pigment (16) Exemplary Pigment (17) Exemplary Pigment (18) Exemplary Pigment ( 19) Exemplary Pigment (20) Exemplary Pigment (21) Exemplary Pigment (22) Exemplary Pigment (23) Exemplary Pigment (24) Exemplary Pigment (25) Exemplary Pigment (26) Exemplary Pigment (27) Exemplary Pigment (28) Exemplary Pigment ( 29) Exemplary Pigment (30) Exemplary Pigment (31) Exemplary Pigment (32) Exemplary Pigment (33) Exemplary Pigment (34) Exemplary Pigment (35) Exemplary Pigment (36) Exemplary Pigment (37) Exemplary Pigment (38) Exemplary Pigment ( 39) The disazo pigment represented by general formula (1) is not limited to the above.

The disazo pigment represented by the general formula (1) is 1 e.g. R, 11
2R Co R Next, the amine corresponding to Arl and Ar2 is diazotized by a conventional method, and this is coupled with the above coupler in an alkaline aqueous solution such as caustic soda, or the diazotide is converted to a borofluoride salt, zinc chloride, etc. After that,
It is easily synthesized by coupling with the above coupler in an organic solvent such as N,N-dimethylformamide or dimethyl sulfoxide in the presence of a base such as sodium acetate, pyridine, triethylamine, or triethanolamine.

In addition, when Arl and Ar2 are different, they can be synthesized by condensing them.

Synthesis Example [Synthesis of Exemplified Pigment (8)] (i) Synthesis of Coupler 2-Hydroxy-3-naphthoic acid chloride Log (
0,0984 mol) and 18.1 g (0,0968 mol) of 2-hydroxy-3-naphthoic acid amide were added to 50 mol of toluene.
After refluxing for 2 hours in 0mu, the precipitated crystals were collected by filtration, washed with methanol and water, and then recrystallized with DMF/methyl cellosolve (if).
mjL (0,483 mol), aniline 15g (0,16
1 mol), stirred and cooled to 0℃, and added 1 mol of sodium nitrite.
A solution of 2.2 g (0,177 mol) dissolved in 20 ml of water was added dropwise over 10 minutes, and after stirring for an additional 15 minutes, carbon was added and filtered. A solution prepared by dissolving 35.1 g (0,322 mol) of sodium borofluoride in 70 mJl of water was added dropwise to the diazotization reaction solution to remove the precipitated borofluoride salt.

After washing with cold water, it was dried under reduced pressure.

Yield 20.1 g, yield 65% (ii+) Synthesis of pigment Next, in a beaker 11, N,N-dimethylformamide 5
00mJl and 10g of coupler synthesized together (0,
After dissolving 0280 mol) and cooling to 5℃, @
-N; aF+t 1.3 g (0,0588 mol) was dissolved, triethylamine 6.1 g (0,060 mol)
was added dropwise and stirred at the same temperature for 2 hours.
N,N-dimethylformamide 500m! After washing with L four times and replacing with acetone, it was dried under reduced pressure.

Yield 13.9g, yield 88% Elemental analysis Calculated value (%) Actual value (%) C72.1
972,26 H4,114,07 N 12.38 12.45 Coatings with the aforementioned disazo pigments exhibit photoconductivity and can therefore be used in photosensitive layers of subsequent electrophotographic photoreceptors.

In a preferred embodiment of the present invention, a photoconductive coating containing the above-mentioned disazo pigment is used 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. can be applied.

The charge generation layer contains as much as possible of the above-mentioned specific disazo pigments exhibiting photoconductivity in order to obtain sufficient absorbance, and in order to shorten the range of the generated charge carriers a thin film layer, e.g. It is desirable to form a thin film layer with a thickness of 5W or less, preferably 0.01 to 1L.

This means that most of the incident light is absorbed by the charge generation layer, generating many charge carriers, and that the generated charge carriers are not deactivated by recombination or trapping, but are transferred to the charge transport layer. This is due to the need for injection.

The charge generation layer can be formed by dispersing the aforementioned specific disazo pigment in a suitable binder and coating it on a conductive substrate, or it can be obtained by forming a vapor deposited film using a vacuum vapor deposition device. . The binder that can be used to form 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.

Preferred are polyvinyl butyral, polyvinyl benzal, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, and cellulose resin.

Examples include insulating resins such as urethane 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 underlying charge transport layer or subbing layer.

Specific organic solvents include methanol, ethanol,
Alcohols such as isopropanol, ketones such as acetone, methyl ethyl ketone, cyclohexane, N,
Amides such as N-dimethylformamide and N,N-dimethylacetamide, and sulfoxides such as dimethylsulfoxide.

Ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, or benzene, Examples include aromatics such as toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene.

Coating is done by dip coating method, spray coating method,
spinner coating method, bead coating method, Meyer bar coating method, blade coating method,
This can be carried out using a coating method such as a roller coating method or a curtain coating method.

For drying, it is preferable to dry to the touch at room temperature and then heat dry.Heat drying is performed at a temperature of 30 to 200°C for 5 minutes to 2 minutes.
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 and taking charge carriers injected from the charge generation layer in the presence of an electric field, and transporting these charge carriers to the surface. have.

At this time, the 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 referred to as charge transport material) is substantially in the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. The electromagnetic waves referred to herein, which are preferably insensitive, include gamma rays, XI! It encompasses a broad definition of light, including ultraviolet light, visible light, near-infrared light, infrared light, far-infrared light, 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 trap each other, resulting in a decrease in sensitivity.

Charge-transporting substances include electron-transporting substances and hole-transporting substances, and electron-transporting substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4.7-)unitro-9- fluorenone,
2,4,5.7-1-tetranitro-9-fluorenone, 2,4,7-)linitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone,
2゜4.8-) Electron-withdrawing substances such as linitrothioxanthone and polymerized products of these electron-withdrawing substances are available.

Examples of hole-transporting substances include pyrene, N-ethylcal/<
Sol, N-isopropylcarbazole, N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino- 3-methylidene-10-ditylphenothiazine, N,N-diphenylhydrazino-3-methylidene-10-ditylphenoxazine, p-diethylaminobenzaldehyde-N,N-diphenylhydrazone, p
-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone, p-pyrrolidinobenzaldehyde N, N-diphenylhydrazone, 1,3.3-
1-limethylindolenine - ω-fuldehyde N, N-diphenylhydrazone, p-diethylbenzaldehyde
hydrazones such as 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-diethyl 7minophenyl)pyrazoline, 1-[6-medoxyviridyl(2)] -
3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[pyridyl(3
)] -3-(p-diethylaminostyryl)-5-(
p-diethylaminophenyl)pyrazoline, l-[lepidyl (2)] -3-(p-diethylaminostyryl)
-5-(p-diethylaminophenyl)pyrazoline, l
-[pyridyl(2)] -3-(p-diethylaminostyryl)-4-methyl-5-(p-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)] -3-(
α-Methyl-p-diethylaminostyryl)-5-(p
-diethylaminophenyl)pyrazoline, l-phenyl-3-(p-diethylaminostyryl)-4-methyl-
5-(p-diethylaminophenyl)hilazoline, l-
Pyrazolines such as phenyl-3-(α-benzyl-P-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline and spiropyrazoline, α-phenyl-4-N, N-diphenylaminostilbene, N
- styryl compounds such as ethyl-3-(α-phenylstyryl)carbazole, 9-dibenzylaminobenzylidene-9H-fluorenone, 5-p-ditolylaminobenzylidene-5H-dibenzo[a,d]cycloheptene, 2- Oxazole compounds such as (p-diethylaminostyryl)-6-dinithylaminobenzoxazole, 2-(p-diethylaminophenyl)-4-(p-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2- Thiazole compounds such as (p-diethylaminostyryl)-6-dinithylaminobenzothiazole, triarylmethane compounds such as bis(,4-diethylamino-2-methylphenyl)-phenylmethane, 1,1-bis(4 -N,N-diethylamino-2-methylphenyl)hebutane, 1,1,2.2
Polyarylalkanes such as tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylanthracene , pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin, and the like.

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

Further, these charge transport substances can be used alone or in combination of two or more.

When the charge transport material does not have film-forming properties, a film can be formed by selecting an appropriate binder. Examples of resins that can be used as binders include acrylic resin,
Insulating resins such as polyarylate, polyester, polycarbonate polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, or poly-N-vinylcarbazole, polyvinylanthracene , organic photoconductive polymers such as polyvinylpyrene, and the like.

Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary.The thickness is generally 5 to 30 μl, but the preferred range is 8 to 20 μl. 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 such a substrate, materials such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum, etc., which have conductivity can be used. Plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluoride (e.g. ethylene), substrates made of plastic coated with conductive particles (e.g. carbon black, silver particles, etc.) together with a suitable binder, substrates made of plastic or paper impregnated with conductive particles, and conductive polymers. It is possible to use plastics that have

An undercoat layer having barrier and adhesive functions can also be provided between the conductive substrate and the photosensitive layer. Is the undercoat layer casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer? -, polyamide, (nylon 6,
It can be formed from nylon 66, nylon sio, composite nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc.

The thickness of the subbing layer is 0.1 to 5 mm, preferably 0.5 to 3 mm.
IL is appropriate.

When using a photoreceptor in which a conductive substrate, 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 after charging, When exposed to light, electrons generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the surface and neutralize the positive charges, resulting in attenuation of the surface potential.
Electrostatic contrast occurs between the exposed area and the unexposed area.

A visible image is 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 or plastic film 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 one or any known method, and are not limited to specific ones.

On the other hand, when the charge transport material is a hole transport material, the surface of the charge transport layer must be negatively charged, and when exposed to light after charging, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. After that, it reaches the surface and neutralizes the negative charge, resulting in attenuation of the surface potential and an electrostatic contrast between it and the unexposed area. During development, it is necessary to use a positively charged toner, contrary to when an electron transporting substance is used.

When using an electrophotographic photoreceptor in which a conductive substrate, a charge transport layer, and a charge generation layer are laminated in this order, when the charge transport material is an electron transport material.

It is necessary to negatively charge the surface of the charge generation layer, and when it is exposed to light after being charged, electrons generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the substrate. On the other hand, holes generated in the charge generation layer reach the surface, attenuation of the surface potential occurs, and electrostatic contrast occurs between the layer and the unexposed area. A visible image is 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 or plastic film 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 transport material, the surface of the charge generation layer must be positively charged, and when exposed to light after charging, the holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. , then reaches the substrate. On the other hand, electrons generated in the charge generation layer reach the surface and attenuation of one surface potential occurs, 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.

Further, as another specific example of the present invention, the above-mentioned hydrazones, pyrazolines, styryl compounds, oxazoles,
Sensitization of organic photoconductive substances such as thiazoles, triarylmethanes, polyarylalkanes, triphenylamine, and poly-N-vinylcarbazoles, and inorganic photoconductive substances such as zinc monoxide, cadmium sulfide, and selenium. A photosensitive film containing a disazo pigment represented by the above-mentioned general formula (1) as an agent can be provided. A film is formed by coating these photoconductive substances and the disazo pigment represented by the general formula (1) together with a binder.

Another specific example of the present invention is an electrophotographic photoreceptor in which -F contains a disazo pigment represented by the general formula (1) together with the charge transport substance. At this time, in addition to the above-mentioned charge transport substance, 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 disazo pigment represented by the general formula (1) and the charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran, and then forming a film thereon.

The pigment used in any electrophotographic photoreceptor contains at least one type of pigment selected from disazo pigments represented by general formula (1), and its crystal form may be amorphous or crystalline. .

In addition, if necessary, the disazo pigment represented by the general formula (1) may be used in combination to increase the sensitivity of the photoreceptor or to obtain a photoreceptor with panchromatic ivy.
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, CRT printers, L
It can also be widely used in electrophotographic applications such as ED printers, liquid crystal printers, and laser engraving.

[Example] Examples 1 to 20 Ammonia aqueous solution of casein (casein 1
1.2 g of ammonia water, 1 g of ammonia water, and 222 ml of water) were applied using a Mayer bar so that the film thickness after drying was 1.0 l, and dried.

Next, 5 g of the exemplary pigment (11) was added to 95 ml of cyclohexanone with a butyral resin (butyralization degree 63 mol%).
) was added to the solution in which 2 g of the solution had been dissolved, and the mixture was dispersed using a sand mill for 20 hours. This dispersion was applied onto the previously formed casein layer using a Mayer bar so that the film thickness after drying would be 0.21 L, and dried to form a charge generation layer.

5g of hydrazone compound and polymethyl methacrylate (
A charge transport layer was formed by dissolving 5 g of the number average molecular weight (100,000 m) in 70 m of benzene, and applying this onto the charge generation layer using a Mayer bar so that the film thickness after drying would be 201 L, and drying. An electrophotographic photoreceptor of Example 1 was prepared.

Electrophotographic photoreceptors corresponding to Examples 2 to 20 were prepared in exactly the same manner using other exemplary pigments in place of exemplary pigment (11).

The electrophotographic photoreceptor thus prepared was statically charged with a corona at 15 KV using an electrostatic copying paper tester (Model 5P-428, manufactured by Kawaguchi Denki ■), held in a dark place for 1 second, and then subjected to an illuminance of 10 lux. The charging characteristics were investigated by exposing the sample to light.

The charging characteristics include the surface potential (vO) and the exposure amount (El/
2) was measured. Show the results.

1 (11) 700 1.52
(1) 710 3.13 (3)
680 3.44 (4) 69
0 3.85 (7) 700 3
．． 6s (9) 720 1.87
(10) 710 2.38 (15)
710 2.59 (18) 6
90 2.610 (22) 880
2.111 (24) 680 2.0
12 (25) 700 1.913
(27) 710 1.614 (28
) 710 2.415 (31)
670 1.416 (32), 6
85 1.517 (35) 6
80 1.818 (36)
690 2.419 (37)
720 2.020 (38)
730 2.5 Comparative Example An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 1 except that chlordian blue, a typical disazo pigment, was used instead of the exemplified pigment (11), and the charging characteristics were evaluated. . Show the results.

VO knee 730V E1/2:6. From the results for Blux and se, it can be seen that the electrophotographic photoreceptors of the present invention all have excellent sensitivity characteristics.

Examples 21 to 25 Using the electrophotographic photoreceptors prepared in Examples 2.6, 10, 13, and 16, fluctuations in bright area potential and dark area potential during use of eel-gaesing were measured.

The method is -5.6KV corona charger.

The photoreceptor was attached to the cylinder of an electrophotographic copying machine equipped with an exposure optical system, a developing device, 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 the cylinder is driven. Using this copying machine, the initial bright area potential (VL) and dark area potential (
Vo ) were set around -200V and -700V, respectively.

The light area potential (VL) and dark area potential (VD) after using 5.000 @ were measured. Show the results.

23 (to) 700 20525
(1B) 700 205 Comparative Example 2 The potential fluctuation of the photoreceptor prepared in Comparative Example was measured in the same manner as in Example 21.

Show the results.

Initial VD knee 700V ゛VL knee 19
5V After printing 5,000 sheets Vo Knee 600V VL Knee 250V From the above results, it can be seen that the electrophotographic photoreceptor of the present invention has little potential fluctuation when used with the edges turned over.

Example 26 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 3
A residue prepared by dissolving 5 g of 0.000000000000 g in 70 mM of tetrahydrofuran was applied and dried so that the film thickness after drying would be 15 mm.

The charging characteristics of the produced electrophotographic photoreceptor were examined in the same manner as in Example 1. The charging polarity was positive.

Show the results.

vo: +650V El/2: 4.0JLux, sec Example 27 An ammonia aqueous solution of casein was applied onto an aluminum plate and dried to form a subbing layer with a thickness of 0.5L.

Next, 2.4.7-) 5 g of Rinitro 9-fluorenone and poly-N-vinylcarbazole (number average molecular weight 300,000)
A charge transfer complex was formed by dissolving 5 g in 70 rnl of tetrahydro7ran.

This charge transfer complex compound and Ig of the above-mentioned exemplary pigment (15) were mixed into 5 g of polyester resin (trade name: Vylon, manufactured by Toyobo Co., Ltd.).
was dissolved in 70rnl of tetrahydrofuran and dispersed. This dispersion was applied onto the subbing layer and dried.

The charging characteristics of the electrophotographic photoreceptor thus prepared were measured in the same manner as in Example 1. The charging polarity was positive. Show the results.

VO: +710V El/2: 4.81ux, see Example 28 On the casein layer of the aluminum substrate on which the casein layer used in Example 1 was formed, the same charge transport layer and charge generation layer as in Example 1 were sequentially laminated. An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 1, except that the one-layer structure was different, and the charging characteristics were measured in the same manner as in Example 1. The charging polarity was positive. Show the results.

Vt): +680V El/2: 2.6 x ux, sec Examples 29 to 31 The photoreceptor prepared in Examples 15, 16, and 17 was heated to 780 nm.
The film was exposed to light using a semiconductor laser having an oscillation wavelength of 2, and the half-life exposure amount (El/2) was measured.

Show the results.

29 15 2.0 30 16 2.1 31 17 1.6 [Effects of the Invention] The electrophotographic photoreceptor of the present invention has high sensitivity and durability during long-term use by containing a specific disazo pigment in the photosensitive layer. It is an electrophotographic photoreceptor with excellent potential stability. Furthermore, it is an excellent electrophotographic photoreceptor that can obtain good images with high sensitivity even in the oscillation wavelength range of semiconductor lasers.

Claims (2)

[Claims] (1) An electrophotographic photoreceptor characterized in that a photosensitive layer laminated on a conductive support contains a disazo pigment represented by the following general formula (1). General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (1) In the formula, R_1, R_2, R_3 and R_4 have a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a nitro group, a cyano group, or a substituent. aryl and aralkyl groups, provided that R_2 and R_3 are not hydrogen atoms, and R_1 and R_2 and R_3 and R_
4 may form an aromatic ring or a heterocyclic ring which may have a substituent together with the benzene ring to which it is bonded, and Ar_1 and Ar_2 may have a substituent which may be bonded via a bonding group. Indicates a good aromatic ring or heterocycle, Ar_
1 and Ar_2 may be the same or different. (2) The disazo pigment is a disazo pigment represented by the following general formula (2), which has a structure in which R_1 and R_2 and R_3 and R_4 form an aromatic ring or a heterocyclic ring together with the benzene ring to which R_1 and R_2 and R_3 and R_4 are bonded in the general formula (1). An electrophotographic photoreceptor according to claim 1. General formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (2) In the formula, Ar_1 and Ar_2 have the same meanings as in general formula (1), and X combines with the benzene ring to form an aromatic ring or a heterocycle. Indicates the group.