JPH053585B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing an organic photoconductor, a charge-generating material made of an organic photoconductor, and an electrophotographic method, and more particularly, it relates to a method for producing an organic photoconductor, and more particularly to a method for producing a tetrazotized or hexazonium-based photoconductor by coexisting two or more types of diamines or triamines. The present invention relates to a method for producing an organic photoconductor, which is a pigment mixture obtained by coupling the organic photoconductor with a coupler, the use of the organic photoconductor as a charge-generating material, and an electrophotographic method. BACKGROUND 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 easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has been expanded. Photoconductive organic pigments and dyes have been proposed. For example, US Patent No. 4123270, US Patent No. 4147614, US Patent No.
No. 4251613, No. 4151614, No. 4256821, No. 4260672, No. 4268596, No. 4278747,
As disclosed in Japanese Patent No. 4,293,628, electrophotographic photoreceptors are known in which an azo 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. An electrophotographic photoreceptor using such an organic photoconductor can be produced by coating by appropriately selecting a binder, so it is possible to provide an extremely highly productive and inexpensive photoreceptor. Among the above charge-generating materials, azo pigments have the advantage of being easy to manufacture and having many structural variations, and many materials have been proposed in recent years. They sometimes have drawbacks such as insufficient sensitivity because the particle size is not fine and lack of potential stability during repeated use. On the other hand, since the particle size is not small, the dispersion stability of the pigment is poor, resulting in defects in the coating film and image unevenness. Problems to be Solved by the Invention An object of the present invention is to improve the dispersion stability of pigments, and to provide an electrophotographic photoreceptor that has practical high sensitivity characteristics and stable potential characteristics during repeated use through such improvement. . Another object of the present invention is to provide an electrophotographic photoreceptor with no defects in the photosensitive layer coating by improving the dispersibility of pigments. This object of the present invention can be achieved by using, as a charge-generating material, a pigment mixture obtained by tetrazotization or hexazonation in the coexistence of two or more types of diamines or triamines, followed by coupling reaction. Means and Effects for Solving the Problems The present invention relates to the production of a photoconductive azo pigment, which is characterized in that two or more diamines or triamines are tetrazotized or hexazonated in the coexistence and then coupled with a coupler. A charge generating material comprising an organic photoconductor which is a photoconductive azo pigment obtained by the method and the above method,
The charge generating material has an average particle size determined by centrifugal sedimentation.
It is 0.2 μ or less. Furthermore, the electrophotographic photoreceptor prepared by containing the charge generating material is at least charged,
It consists of an electrophotographic method characterized by repeated use through the steps of image exposure, development, transfer, cleaning, and pre-exposure. Pigments obtained through tetrazotization or hexazonation of a single diamine or triamine, sand mills, ball mills, attritors,
Even if a crushing means such as a roll mill is used, the particles are difficult to break down and do not become fine. On the other hand, it has been found that the pigment mixture produced by the method of the present invention has two or more types of pigments mixed together in the particles, and therefore the particles are extremely easy to loosen and become atomized. Incidentally, the average particle diameter of pigments obtained by conventional methods (based on centrifugal sedimentation method) is coarse particles of 0.4μ or more, but with the method of the present invention, it is reduced to 0.2μ or less, and even better, to 0.1μ or less. It became possible. Electrophotographic photoreceptors containing a large amount of coarse particles cause a decrease in carrier mobility due to an increase in the number of carriers generated due to a decrease in hiding power, and furthermore, the large unevenness of the surface of the charge generation layer makes it difficult to inject carriers into the charge transport layer. Although it has many drawbacks in terms of sensitivity, such as reduced efficiency, and poor potential stability during long-term use, the present invention has succeeded in making the pigment particles finer.
Potential stability during repeated use has been confirmed, and by setting the average particle size to 0.2μ or less, preferably 0.1μ or less, it is effective in suppressing the increase in bright area potential during repeated use, and furthermore, charge generation. It is possible to obtain a beautiful image with no unevenness in the layers and no image defects in the image rendering test results. The diamines and triamines used in the present invention include: Aromatic or heterocyclic amines such as the following are used. R ₁ to _{R 31} in the above formulas (1) to (11) are hydrogen atoms, halogen atoms such as chlorine atoms, bromine atoms, and iodine atoms, alkyl groups such as methyl, ethyl, and propyl, and methoxy, ethoxy, and propoxy groups. Represents an alkoxy group, phenoxy group, nitro group, etc., and X is -O-,
-S-, -N-R ₃₂ (R ₃₂ is an alkyl group); As the coupler, a coupler having an aromatic OH group is used. Particularly preferable couplers for electrophotography include, for example, the general formulas (12) and (13) shown below.
and (14). General formula (12) is

[Formula], where Z is a residue condensed with a benzene ring to form a naphthalene ring, anthracene ring, carbazole ring, benzcarbazole ring or dibenzofuran ring, and Y is -CONR ₃₃ R ₃₄ (However, R ₃₃ is a group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, and a phenyl group; R ₃₄ represents a group selected from the group consisting of a substituted or unsubstituted alkyl group, phenyl group, and naphthyl group); represent. Substituents for the R ₃₃ and R ₃₄ groups include alkyl groups such as methyl, ethyl, propyl, butyl, halogen atoms, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, acyl groups such as acetyl and benzoyl, methylthio, Arylthio groups such as ethylthio, aryl groups such as phenyl,
Examples include aralkyl groups such as benzyl and phenethio, nitro groups, cyano groups, and dialkylamino groups such as dimethylamino and diethylamino. General formulas (13) and (14) are

【formula】

Represented by [Formula]. In the formula, R ₃₅ represents a group selected from the group consisting of substituted or unsubstituted alkyl groups and phenyl groups. Specifically, _R35 is methyl, ethyl, propyl,
Alkyl groups such as butyl, hydroxyalkyl groups such as hydroxymethyl and hydroxyethyl, alkoxyalkyl groups such as methoxymethyl and ethoxyethyl, cyanoalkyl groups, aminoalkyl groups, N
-alkylaminoalkyl group, N,N-dialkylamino group, halogenated alkyl group, benzyl,
Aralkyl groups such as phenethyl, phenyl groups and substituted phenyl groups (substituents include general formula (12))
Examples include groups similar to R ₃₃ and R ₃₄ ). The amine and coupler used in the present invention are not particularly limited to the exemplified compounds. The pigment is produced by converting two or more amines or triamines into tetrazotized or hexazonated forms (in this specification, diamines such as the above-mentioned general formulas (3) and (10) are also expressed as tetrazotized), and then converted into a coupler. in the presence of an alkali, or once the tetrazonium salt or hexazonium salt of the diamine or triamine is isolated in the form of a borofluoride salt or zinc chloride double salt, etc., in a suitable solvent such as N,N-dimethyl. It can be easily produced by coupling with a coupler in a solvent such as formamide or dimethyl sulfoxide in the presence of an alkali. The amount of different amines used in the production of the azo pigment is preferably 10 to 50% by weight, particularly preferably 30 to 50% by weight of the total amines used, from the viewpoint of pigment crushability.
It is. In addition, the number of types of amines used is three rather than two.
It has been found that more than one type is more effective in terms of pigment crushability. In a preferred embodiment of the invention, the photoconductive azo pigment of the invention is used as an organic photoconductor as a charge generation material in an electrophotographic photoreceptor in which the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer. The charge generation layer contains as much charge generation substance as possible in order to obtain sufficient absorbance and is a thin film layer, for example 5 μm, in order to shorten the range of the generated charge carriers.
Hereinafter, it is preferable to use a thin film layer having a thickness of preferably 0.01μ. 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 above-mentioned organic photoconductor in a suitable binder and coating it on the substrate, or by forming a deposited film using a vacuum deposition apparatus. be able to. Binders that can be used to form the charge generating layer by coating can be selected from a wide range of insulating resins, and can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. . Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, urethane Examples include insulating resins such as resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is suitably 60% 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 cyclohexanone, 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 can be carried out at a temperature of 30 to 200° C. for a period of time ranging from 5 minutes to 2 hours, either stationary or under ventilation. 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. However, it is desirable that the charge transport layer is laminated on the charge generation layer. The substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as charge transport substance) is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. 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 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-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone,
2,4,5,7-tetranitroxanthone, 2,
Examples include electron-withdrawing substances such as 4,8-trinitrothioxanthone, and polymerization 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
Thiazole compounds such as -(P-diethylaminostyryl)-6-diethylaminobenzothiazole, triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane, 1,1-bis(4-N,N -diethylamino-2-methylphenyl)heptane, 1,
Polyarylalkanes such as 1,2,2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, triphenylamine, poly-
N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine,
Examples include 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 butyrate, 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 the 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,
A substrate made of plastic coated with silver particles (silver particles, etc.) together 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 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 is made of a hole transport material, it is necessary to charge the charge transport surface negatively, 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, causing a decrease in surface potential and creating an electrostatic contrast with the unexposed area.
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 organic photoconductor, which is the photoconductive azo pigment of the present invention, is contained in the same layer together with a charge transport material. In this case, 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 organic photoconductor and charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran, and then forming a film thereon. In any of the photoreceptors, the pigment used contains at least one type of pigment selected from the photoconductive azo pigments of the present invention, and if necessary, pigments with different light absorptions may be combined to improve the sensitivity of the photoreceptor. The photoconductive azo pigment of the present invention may be used in combination with two or more types of photoconductive azo pigments of the present invention, or in combination with a charge generating substance selected from known dyes and pigments, for the purpose of increasing the photoconductivity or obtaining a panchromatic photoreceptor. is also possible. The organic photoconductor of the present invention can be widely used not only in ordinary electrophotographic copying machines but also in electrophotographic applications such as color copying machines, laser printers, and CRT printers. Further, the organic photoconductor of the present invention can also be used in solar cells and optical sensors in addition to the above-mentioned electrophotographic photoreceptor. Solar cells can be prepared, for example, by sandwiching the aforementioned organic photoconductors with indium oxide and aluminum. Hereinafter, the present invention will be explained according to examples. Example 1 3.38 g (0.015 mol) of 6-amino-2-(P-aminophenyl)benzoxazole as an amine and 2.68 g (0.01 mol) of 2,5-bis(P-aminophenyl)thiadiazole as an amine were mixed with 65 ml of water and concentrated hydrochloric acid. Add 3.54 g (0.051 mol) of sodium nitrite to 10.6 ml of water dissolved in 13.24 ml (0.15 mol).
While maintaining the solution temperature between 4.5 and 7℃,
The mixture was added dropwise over a period of minutes, and then stirred at the same temperature for 30 minutes. Next, the above tetrazotized solution was added to a solution in which 10.57 g (0.0525 mol) of 3-hydroxy-naphthalene-2-carboxylic acid methylamide and 16.8 g (0.42 mol) of caustic soda were dissolved in 420 ml of water while keeping the temperature of the solution at 4 to 10°C. was added dropwise over 10 minutes, stirred at the same temperature for 2 hours, and then left overnight. After sequentially washing with filtration, water, DMF, and acetone, it was vacuum dried to obtain 13.3 g of pigment. Next, place an ammonia solution of casein on an aluminum plate (11.2 g of casein, 1 g of 28% ammonia water, 222 g of water).
ml) was applied using the dipping method so that the film thickness after drying was 1.5μ, and then dried. Add 5 g of the organic photoconductor of the pigment mixture to a solution of 2 g of butyral resin (butyralization degree 63 mol%) in 95 ml of ethanol, and mix with a ball mill for 5 g.
Spread out time. This dispersion was applied onto the previously formed casein layer by a dipping method 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.
Dissolve it in 70ml and apply it on the charge generation layer using the dipping method so that the film thickness after drying is 12μ.
It was dried to form a charge transport layer. The electrophotographic photoreceptor thus prepared was statically charged with corona at -5 KV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd.
After keeping it in the dark for 10 seconds, it was exposed to light at an illuminance of 5 lux to examine the charging characteristics. As for the charging characteristics, the surface potential (Vo) and the exposure amount (E1/2) required to attenuate the potential by 1/2 when dark decaying for 1 second were measured. The results are shown in Table 1. Furthermore, in order to measure the fluctuations in bright area potential and dark area potential during repeated use, the photoreceptor fabricated in this example was equipped with a -5.6KV corona charger, an exposure optical system, a developer, a transfer charger, and a static eliminator. It was attached to the cylinder of an electrophotographic copying machine equipped with exposure optics and a cleaner. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copier, the initial bright area potential (V _L )
The light potential (V _L ) after 5000 uses with the dark potential (V _D ) and dark potential (V D ) set to around -600V and -100V, respectively.
and dark potential (V _D ) were measured. This result is the second
Shown in the table. Comparative Example 1 Next, for comparison, 5.63 g (0.025 mol) of amine alone was used instead of the amine of Example (1),
A disazo pigment of a single composition was synthesized in exactly the same manner as in Example 1 to obtain 13.0 g of pigment. Pigment was dispersed in exactly the same manner as in Example 1, and the particle size was measured using a Horiba particle size distribution analyzer CAPA-500. The average particle size of the pigment dispersion of Comparative Example 1 was
The average particle size of the pigment dispersion of Example 1 was 0.4μ, whereas the average particle size of the pigment dispersion of Example 1 was 0.06μ, which was an extremely fine dispersion, and the effect of the present invention was clearly recognized in terms of dispersibility. Next, a photoreceptor was prepared in exactly the same manner as in Example 1 using the pigment of Comparative Example instead of the pigment mixture of Example 1, and the characteristics were investigated and the results are shown in Tables 1 and 2.

【table】

[Table] As shown in Table 1, Example 1 has higher sensitivity, and this is because the particle size of the pigment in Example 1 is finer.
This seems to be because there are fewer voids between pigment particles than in the comparative example, making it difficult for the carrier to be trapped inside the charge generation layer. The durability properties shown in Table 2 also show better effects in Example 1, but this is also considered to be due to the same reasons as mentioned in the section on initial properties. The results of imaging using the apparatus described in Example 1 show that the photoconductor of Example 1 produces a beautiful image with few defects, while the photoconductor of Comparative Example 1 produces an image with many white spots. Summer. This is also true in the case of the pigment dispersion of Example 1, where the particle size of the pigment is smaller and the pigment maintains a good dispersion state, and there is no defect in the coating film of the charge generation layer, whereas in the comparative example, the particle size of the pigment dispersion is smaller. It was confirmed that the coating was rough and had many bumps, which promoted coating defects when a charge transport layer was applied. Here, FIG. 1 shows the change in particle size depending on the dispersion method and time, and FIG. 2 shows the relationship between the average pigment particle size investigated from the charging characteristics of the photoreceptor and the increase in bright area potential during durability of 5,000 sheets. Example 2 3.02 g (0.0125 mol) of 6-amino-2-P-aminophenylben as the amine, 1.59 g of 4,4'-diaminoazobenzene as the amine
(0.0075 mol), 1.76 g of 2,4,6-tris(P-aminophenyl)pyridine as amine
(0.005 mol) dissolved in 65 ml of water and 13.24 ml (0.15 mol) of concentrated hydrochloric acid, add 3.54 g (0.051 mol) of sodium nitrite.
mol) in 10.6 ml of water at a temperature of 4.5 to 7.
Drop for 5 minutes while keeping at ℃, then at the same temperature.
Stir for 30 minutes. Next, 13.18 g (0.058 mol) of 4-hydroxy-N-methylnaphthalitukuimide and soda carbonate
Add 10% of the above tetrazotized solution to a solution of 27.6g (0.26mol) dissolved in 600ml of water while keeping the temperature at 4-10℃.
The mixture was added dropwise over a period of minutes, stirred at the same temperature for 2 hours, and then left overnight. After sequentially washing with filtration, water, DMF, and acetone, it was vacuum dried to obtain 16.0 g of pigment. Next, place an ammonia solution of casein on an aluminum plate (11.2 g of casein, 1 g of 28% ammonia water, 222 g of water).
ml) was applied with a Mayer bar so that the film thickness after drying was 1.5μ, and dried. 5 g of organic photoconductor of the disazo pigment mixture
was added to a solution prepared by dissolving 2 g of butyral resin (degree of butyralization: 63 mol %) in 95 ml of ethanol, and dispersed in a ball mill for 5 hours. 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 solution was dissolved in 70 ml and applied onto the charge generation layer using a Mayer bar so that the film thickness after drying was 12μ, and dried to form a charge transport layer. The electrophotographic photoreceptor thus prepared was statically charged with corona at -5 KV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd.
After keeping it in the dark for 10 seconds, it was exposed to light at an illuminance of 5 lux to examine the charging characteristics. As for the charging characteristics, the surface potential (Vo) and the exposure amount (E1/2) required to attenuate the potential by 1/2 when dark decaying for 1 second were measured. The results are shown in Table 3. Furthermore, in order to measure the fluctuations in bright area potential and dark area potential during repeated use, the photoreceptor fabricated in this example was equipped with a -5.6KV corona charger, an exposure optical system, a developer, a transfer charger, and a static eliminator. It was attached to the cylinder of an electrophotographic copying machine equipped with exposure optics and a cleaner. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copier, the initial bright area potential (V _L )
and dark area potential (V _D ) are set to around -600V and -100V, respectively, and the light area potential (V _L ) after 5000 uses.
and the dark potential (V _D ) were measured. This result is the fourth
Shown in the table. Comparative Example 2 Next, for comparison, the amine of Example 2,
Using 6.03g (0.025mol) of amine only instead of
A disazo pigment having a single composition was synthesized in exactly the same manner as in Example 2 to obtain 14.7 g of pigment. Pigment was dispersed in exactly the same manner as in Example 1, and the particle size was measured using a particle size distribution analyzer CAPA-500 manufactured by Horiba. The average particle size of the pigment dispersion of Comparative Example 2 was 0.42μ, whereas in Example 1, the average particle size was 0.42μ. The average particle diameter of the pigment dispersion of Example 2 was 0.03μ, which was an extremely fine dispersion, and the effect of the present invention was clearly observed in terms of dispersibility. Next, a photoreceptor was prepared in exactly the same manner as in Example 1 using the pigment of Comparative Example 2 instead of the pigment mixture of Example 2. The characteristics were investigated and the results are shown in Tables 3 and 4.
Shown in the table.

【table】

[Table] As shown in Table 3, Example 2 has higher sensitivity,
The reason is considered to be the same as in the first embodiment. The durability characteristics shown in Table 4 also showed better results in Example 2. As a result of image formation using the apparatus described in Example 1, the photoreceptor of Example 2 produced a beautiful image with few defects, while the photoreceptor of Comparative Example 2 produced an image with many white spots. Ta. Example 3 On the charge generation layer prepared in Example 1, 2,
4,5,7-tetranitro-9-fluorenone 5
g and poly-4,4'-dioxydiphenyl-2,2
- A coating solution prepared by dissolving 5 g of propane carbonate (molecular weight 300,000) in 70 ml of tetrahydrofuran was applied so that the coating amount after drying was 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 Tables 5 and 6.

【table】

[Table] Example 4 A polyvinyl alcohol film having a thickness of 2 μm 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 0.5μ, 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 polyacrylate resin (condensation polymer of bisphenol A and terephthalic acid-isophthalic acid) in 70 ml of tetrahydrofuran was placed on the charge generation layer 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 Example 1.
The results are shown in Tables 7 and 8.

【table】

[Table] Example 5 An ammonia aqueous solution of casein was coated on an aluminum plate with a thickness of 100 μm and dried to form a subbing layer with a thickness of 2 μm. 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 1 g of the disazo pigment photoconductor shown in Example 2 were mixed with a polyester resin (Vylon:
Toyobo Co., Ltd.) 5 g was dissolved in 70 ml of tetrahydrofuran and dispersed in a sand mill for 3 hours. The average particle size measured using the same equipment as in Example 1 was 0.15μ. This dispersion is applied onto the undercoat layer so that the film thickness after drying is
It was applied to a thickness of 12μ and 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 Tables 9 and 10. However, the charging polarity was determined.

【table】

[Table] Examples 6 to 8 Pigments having the following compositions were synthesized according to Example 1, photoreceptors were prepared in exactly the same manner as in Example 1, and the characteristics were investigated. However, the material used for the charge transport layer was changed from the pyrazoline compound of Example 1. The compound was changed to the hydrazone compound shown below. Table 11 shows the initial properties and average particle size of the pigment dispersion. An image forming test was conducted using each photoreceptor, and excellent images with no defects were obtained. Example 6 Average particle size 0.13μ Example 7 Average particle size 0.08μ Example 8 Average particle size 0.07μ

[Table] Effects of the Invention The present invention has developed a method for easily producing photoconductive azo pigments with an average particle size of 0.2μ or less by centrifugal sedimentation, which could not be obtained by conventional methods. By using a conductor as a charge-generating material, it is possible to create an electrophotographic photoreceptor with excellent characteristics such as sensitivity and potential stability, which were not successful with the conventional method of using pigments consisting of coarse particles. It was possible to obtain beautiful images with no defects.

[Brief explanation of the drawing]

Figure 1 shows the dispersion method and particle size change depending on time in Example 1, and Figure 2 shows the pigment average from the charging characteristics of the photoreceptor prepared in Example 1 with only the difference in dispersion time. This figure shows the relationship between the particle size and the increase in bright area potential during durability of 5000 sheets.

Claims (1)

[Scope of Claims] 1. A method for producing a photoconductive azo pigment, which comprises tetrazotizing or hexazonium-forming two or more types of diamines or triamines in the coexistence, and then coupling them with a coupler. 2. A charge-generating material comprising an organic photoconductor which is a photoconductive azo pigment obtained by tetrazotizing or hexazonating two or more types of diamines or triamines in the coexistence and then coupling with a coupler. 3. The charge-generating material according to claim 2, which has an average particle diameter of 0.2 μm or less as determined by centrifugal sedimentation. 4. An electrophotographic photoreceptor prepared using an organic photoconductor, which is a photoconductive azo pigment obtained by tetrazotizing or hexazonium-forming two or more diamines or triamines in the coexistence and coupling it with a coupler, as a charge-generating material. An electrophotographic method characterized by repeating at least the steps of charging, image exposure, development, transfer, cleaning, and pre-exposure.