JPH042948B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor in which a photosensitive layer contains a specific azo pigment. [Prior Art] Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components have been known. On the other hand, since it was discovered that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed. For example, organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene, carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones,
Organic pigments and dyes such as low-molecular organic photoconductors such as polyarylalkanes, phthalocyanine pigments, azo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindigo dyes, or methine squaritate dyes are used. Are known. In particular, organic pigments and dyes with photoconductivity are
Many photoconductive organic pigments and dyes have been proposed because they are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has expanded. For example, US Patent No. 4123270, US Patent No. 4247614, US Patent No.
No. 4251613, No. 4251614, No. 4256821, No. 4260672, No. 4268596, No. 4278747,
As disclosed in No. 4,293,628, electrophotographic photoreceptors are known in which a disazo pigment exhibiting photoconductivity is used as a charge-generating substance in a photosensitive layer that is functionally separated into a charge-generating layer and a charge-transporting layer. An electrophotographic photoreceptor using such an organic photoconductor can be produced by a coating method by appropriately selecting a binder, so it has extremely high productivity.
Although this photoreceptor has the advantage of being able to provide an inexpensive photoreceptor and the sensitivity wavelength range can be freely controlled by selecting organic pigments, this photoreceptor has poor sensitivity and durability, so it has not been put into practical use until now. There are very few things. [Problems to be Solved by the Invention] An object of the present invention is to provide a novel electrophotographic photoreceptor. Another object of the present invention is to provide an electrophotographic photoreceptor having practically excellent sensitivity and durability. [Means for solving the problem] That is, the present invention solves the following general formula (1) (In the formula, Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ and Ar ₅ each represent an arylene group which may have a substituent, and A represents a coupler residue having a phenolic OH group. However, Ar ₁ is an unsubstituted phenylene group or an unsubstituted biphenylene group, and all of Ar ₂ , Ar ₃ , Ar ₄ and Ar ₅ are phenylene groups which may have a substituent.) This is an electrophotographic photoreceptor characterized by containing the compound in a photosensitive layer. In the above general formula (1), Ar ₁ to _{Ar 5} are defined as arylene groups such as phenylene, biphenylene, naphthylene, and anthrylene. Ar ₁ to _{Ar 5} may further have a substituent. Such substituents include halogen (fluorine, chlorine, bromine, iodo), alkyl groups (methyl, ethyl, propyl, etc.), alkoxy groups (methoxy, ethoxy, propoxy, etc.), thioalkyl groups (thiomethyl, thioethyl, thiopropyl, etc.), nitro,
Examples include cyano and trifluoromethyl. Furthermore, the phenolic nature of A in general formula (1)
Coupler residues having an OH group are represented by the following general formulas (2) to (8), for example. (In the formula, X is a residue that forms a polycyclic aromatic ring or a heterocycle by condensing with a benzene ring, R ₃ and R ₄ are hydrogen,
Alkyl, aralkyl, aryl or heterocyclic groups which may have substituents or together form a cyclic amino group with a nitrogen atom; R ₅ and R ₆
represents alkyl, aralkyl, or aryl, each of which may have a substituent; Y is a divalent aromatic hydrocarbon group or together with a nitrogen atom forms a heterocyclic divalent group; R ₇ and R ₈ each represent an aryl group or a heterocyclic group which may have a substituent, or together form a 5-6 negative ring with carbon atoms; R ₉ and R ₁₀ each represent a hydrogen atom or a substituted (represents an alkyl, aralkyl, aryl or heterocyclic group which may have a group)
Examples of the polycyclic aromatic ring or heterocycle formed by condensing a benzene ring with a benzene ring include naphthalene, anthracene, carbazole, benzcarbazole, dibenzofuran, benzonaphthofuran, and diphenylene sulfide. These may be substituted with the substituents described above. In the case of R ₃ and R ₄ , anokyl is, for example, methyl, ethyl, propyl, butyl, etc., aralkyl is, for example, benzyl, phenethyl, naphthylmethyl, etc., and aryl is, for example, phenyl, diphenyl, naphthyl, anthryl, etc. In particular, R ₃ is hydrogen and R ₄ is halogen, nitro, cyano,
A compound having a structure of a phenyl group having an electron-withdrawing group such as trifluoromethyl is preferred. These may have substituents. Examples of the heterocycle include carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine. Specific examples of R ₅ and R ₆ include the same ones as exemplified above for R ₃ and R ₄ . These may be substituted with the substituents described above. In the definition of Y, examples of the divalent aromatic hydrocarbon group include monocyclic aromatic hydrocarbon groups such as o-phenylene, o-naphthylene, perinaphthylene,
Examples include fused polycyclic aromatic hydrocarbon groups such as 1,2-antrylene and 9,10-phenanthrylene. Examples of divalent heterocycles that are combined with nitrogen atoms include 3,4-pyrazolediyl group, 2,3-pyridinediyl group, 4,5-pyrimidinediyl group, and 6,7-indazolediyl group. basis,
5,6-benzimidazolediyl group, 6,7-
Examples include 5- to 6-membered heterocyclic divalent groups such as quinolinediyl group. The aryl group or heterocyclic group for R ₇ and R ₈ is phenyl, naphthyl, anthryl,
Pyrenyl and the like; examples include pyridyl, thienyl, furyl, carbazolyl and the like. These may be substituted with the substituents described above. Further, R ₇ and R ₈ can be combined with carbon atoms to form a 5-6 negative ring. The 5-6 negative rings may have a fused aromatic ring. Examples of such groups include cyclopentylidene, cyclohexylidene, 19-fluorenylidene, 19-xanthenylidene, and the like. Specific examples of alkyl, aryl, and aralkyl for R ₉ and R ₁₀ are the same as those listed above. Heterocycles include carbazole, dibenzofuran, benzimidazolone, benzthiazole,
Examples include thiazole and pyridine. These may be substituted with the substituents described above. Although the present invention is not bound by theory, by using arylene diamine in the skeleton of the tetrakisazo pigment of general formula (1), the polarity of the pigment is changed, and the carrier production efficiency or the carrier transportability is changed. Since either one or both of these conditions are good, the sensitivity of a photoreceptor using a photosensitive layer containing this azo pigment is improved, and potential stability during long-term use is ensured. Laser beam printer, KED because high sensitivity is achieved
It can be applied to printers, liquid crystal printers, etc., and stable and beautiful images can be obtained because a stable potential is ensured regardless of the previous history of the photoreceptor. Representative examples of the tetrakisazo pigments used in the present invention are listed below. Tetrakisazo pigment No. and its structural formula These strakisazo pigments are one or two types.
More than one species can be used in combination. Additionally, these pigments may have, for example, the general formula (However, Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ , and Ar ₅ in the formula have the same meanings as the symbols in general formula (1).) The amino group of the compound represented by the formula is diazotized by a conventional method, and then After hydrogen coupling the corresponding coupler in the presence of an alkali, or once isolating the diazonium salt of the amino group in the form of a borofluoride salt or a zinc chloride double salt, a suitable solvent such as N,
It can be easily produced by coupling with a coupler in a solvent such as N-dimethylformamide or dimethylsulfoxide in the presence of an alkali. However, if the solubility of the coupler in an alkaline aqueous solution is low, or if the coupling reaction is performed using a coupler that is easily hydrolyzed, such as the type of coupler represented by general formula (7), the coupler should be
Sodium acetate dissolved in a solvent such as DMF, DMAC,
It is preferable to react with a tetrazolium salt using an organic base such as pyridine, trimethylamine, or triethylamine, while being careful not to hydrolyze the coupler or reaction solvent. In a preferred embodiment of the present invention, a tetrakisazo pigment represented by the general formula (1) can be used as a charge generation substance in an electrophotographic photoreceptor in which a photosensitive layer is functionally separated into a charge generation layer and a charge transport layer. The charge generation layer contains as much of the tetrakisazo pigment as possible in order to obtain sufficient absorbance and is coated with a thin film layer, for example 5 microns, to prevent the generated charge carriers from being trapped within the charge generation layer. Hereinafter, the thin film layer preferably has a thickness of 0.01 micron to 1 micron. 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 tetrakisazo pigment in a suitable binder and coating it on the substrate, or it can be obtained by forming a vapor deposited film using a vacuum vapor deposition device. I can do it. The binder that can be used to form the charge generation layer by coating can be selected from a wide range of insulating resins, as well as organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. can.
Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.) polycarbonate (bisphenol A, Z type, etc.) polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinyl Examples include insulating resins such as pyridine, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less. The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the charge transport layer or undercoat layer described below. Specific organic solvents include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, N,N-dimethylformamide,
Amides such as N,N-dimethylacetamide,
Sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate, butyl acetate, chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, etc. Aliphatic halogenated hydrocarbons or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used. Coating can be carried out using coating methods such as dip coating, spray coating, spinner coating, bead coating, Meyer bar coating, blade coating, roller coating, and curtain coating. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying at a temperature of 30℃ to 200℃ for 5 minutes to 2
It can be carried out stationary or under ventilation for a range of hours. The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. ing. At this time, this charge transport layer may be laminated on or under the charge generation layer. When the charge transport layer is formed on the charge generation layer, the substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as the charge transport layer) is substantially in the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. Preferably, it is non-sensitive. The reason is to prevent the charge transport layer from having a filter effect and reducing sensitivity. The “electromagnetic wave” mentioned here is γ
It includes a broad definition of "light ray" that includes radiation, X-rays, ultraviolet rays, visible light, near infrared rays, infrared rays, far infrared rays, and the like. Charge-transporting substances include electron-transporting substances and hole-transporting substances, and electron-transporting substances include chloranil, promoanil, 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
-Hydrazones such as methylbenzthiazolinone-2-hydrazone, 2,5-bis(P-diethylaminophenyl)-1,3,4-oxadiazole,
1-phenyl-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[quinolyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl) ) Pyrazoline, 1-[pyridyl(2)]-3-(P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[6-methoxy-pyridyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1- [pyridyl(3)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-
3-(P-diethylaminostyryl)-4-methyl-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(α-methyl-P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-phenyl-3-
(P-diethylaminostyryl)-4-methyl-5
-(P-diethylaminophenyl)pyrazoline,
1-Phenyl-3-(α-benzyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, spiropyrazoline and other pyrazolines, 2-(P-diethylaminostyryl)
-6-diethylaminobenzoxazole, 2-
Oxazole compounds such as (P-diethylaminophenyl)-4-(P-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2
-(P-diethylaminostyryl)-6-diethylaminobezothiazole and other thiazole compounds,
Triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane, 1,1-bis(4-N,N-diethylamino-2-methylphenyl)heptane, 1,1,
Polyarylalkanes such as 2,2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, triphenylamine, stilbene derivatives, aromatic polycyclic compounds having a styryl group,
heterocyclic compound poly-N-vinylcarbazole,
Polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin,
Examples include ethyl carbazole formaldehyde resin. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-theramorphous silicon, and cadmium sulfide can also be used. In addition, 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:
Insulating resins such as acrylic resin polyarylate, polyester, polycarbonate (bisphenol A, Z type) polystyrene acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, Alternatively, organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene can be mentioned. Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Typically it is between 5 microns and 30 microns, with a preferred range between 8 microns and 20 microns. When forming the charge transport layer by coating, an appropriate coating method as described above can be used. A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. As the substrate having 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.), or conductive particles (e.g. carbon black, silver particles, etc.) coated on plastic with a suitable binder; substrates made of plastic or paper impregnated with conductive particles; Plastics with polymers, etc. can be used. A subbing layer having a barrier function and an adhesive function 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 micron to 5 micron.
Preferably, 0.5 micron to 3 micron is appropriate. When using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, and the charge transport material is an electron transport material, the surface of the charge transport layer must be positively charged, and exposure after charging is required. Then, in the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface and neutralize the positive charge, causing a decrease in surface potential and creating an electrostatic contrast with the unexposed area. . A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. This can be directly fixed, or the toner image can be transferred to paper, plastic film, etc. and then developed and fixed. Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or known methods, and are not limited to specific ones. On the other hand, when the charge transport material consists of a hole transport material, the surface of the charge transport layer must be negatively charged.
After charging, when exposed to light, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer, and then reach the surface and neutralize the negative charge, causing a decrease in the surface potential and static electricity between the exposed area and the unexposed area. Electrocontrast occurs. During development, it is necessary to use a positively charged toner, contrary to the case where an electron transport material is used. Another specific example of the present invention is an electrophotographic photoreceptor containing the above-mentioned tetrakisazo pigment and a charge transport material in the same layer. At this time, a charge transfer complex compound consisting of poly-N-vinylcarbazole and trinitrofluorenone can be used in addition to the above-mentioned charge transport materials. The electrophotographic photoreceptor of this example can be prepared by dispersing the aforementioned tetrakisazo pigment 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 tetrakisazo pigments represented by general formula (1), and its crystal form may be amorphous or crystalline. . If necessary, two types of tetrakisazo pigments represented by the general formula (1) may be used in combination to increase the sensitivity of the photoreceptor or to obtain a panchromatic photoreceptor by combining pigments with different light absorption. It is also possible to use a combination of the above, or a combination with a charge generating substance selected from known dyes and pigments. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers and CRTs.
Printers, LED printers, LCD printers,
It can also be widely used in electrophotographic applications such as laser engraving. The present invention will be explained below with reference to Examples. Examples 1 to 10 Ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 ml of water) on an aluminum plate
was applied with a Mayer bar so that the film thickness after drying was 1.0 microns, and dried. Next, the above-mentioned exemplified tetrakisazo pigment No. 5
g 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 sand mill for 2 hours. This dispersion was applied onto the previously formed casein layer using a Mayer bar so that the film thickness after drying would be 0.5 microns, and dried to form a charge generation layer. Then, the structural formula 5 g of hydrazone compound and 5 g of polymethyl methacrylate resin (number average molecular weight 100,000) were added to benzene.
A photoreceptor was prepared by dissolving the solution in 70 ml and applying it onto the charge generation layer using a Mayer bar so that the dry film thickness would be 12 microns, and drying to form a charge transport layer. Photoreceptors of Examples 2 to 10 were prepared in the same manner using the azo pigments shown in Table 1 instead of Azo Pigment No. 1. The electrophotographic photoreceptor thus prepared was statically charged with corona at -5kV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., and then held in a dark place for 1 second. The charging characteristics were measured by exposing the sample to light. As for charging characteristics, the surface potential (V ₀ ) and the exposure amount E1/2 (1ux·sec) required to attenuate the potential to 1/2 when dark decayed for 1 second were measured. Results first
Shown in the table.

【table】

[Table] Example 11 Using the photoreceptor used in Example 36, fluctuations in bright area potential and dark area potential during repeated use were measured. The photoreceptor was attached to the cylinder of an electrophotographic copying machine equipped with a -5.6 kV corona charger, an exposure optical system, a developer, a transfer charger, a static elimination exposure optical system, and a cleaner. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copier, the initial bright area potential (V _L )
and dark potential (V _D ) are -100V and -100V, respectively.
The bright area potential (V _L ) and dark area potential (V _D ) were measured after being set at around 600 V and used 5000 times. The results are shown in Table 2.

[Table] The photoreceptor of the present invention had good stability in V _D and V _L even during repeated use.

Claims (1)

[Claims] First-order general formula (In the formula, Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ and Ar ₅ each represent an arylene group which may have a substituent, and A represents a coupler residue having a phenolic OH group. However, Ar ₁ is an unsubstituted phenylene group or an unsubstituted biphenylene group, and all of Ar ₂ , Ar ₃ , Ar ₄ and Ar ₅ are phenylene groups which may have a substituent.) An electrophotographic photoreceptor characterized in that the content is contained in a photosensitive layer. 2 A in the above general formula (1) is the following general formula (2) to (8)
An electrophotographic photoreceptor according to claim 1, which is represented by: (In the formula, X is a residue that forms a polycyclic aromatic ring or a heterocycle by condensing with a benzene ring, R ₃ and R ₄ are hydrogen,
Alkyl, aralkyl, aryl or heterocyclic groups which may have substituents or together form a cyclic amino group with a nitrogen atom; R ₅ and R ₆
represents alkyl, aralkyl, or aryl, each of which may have a substituent; Y is a divalent aromatic hydrocarbon group or together with a nitrogen atom forms a heterocyclic divalent group; R ₇ and R ₈ each represent an aryl group or a heterocyclic group which may have a substituent, or together form a 5-6 negative ring with carbon atoms; R ₉ and R ₁₀ each represent a hydrogen atom, a substituted represents an alkyl, aralkyl, aryl or heterocyclic group which may have a group). 3. The photosensitive layer is of a functionally separated type consisting of a charge generation layer and a charge transport layer, and the charge generation layer has the above general formula.
An electrophotographic photoreceptor according to claim 1, which contains an azo pigment represented by (1). 4 R ₃ in the above general formula (2) is hydrogen, and R ₄
The electrophotographic photoreceptor according to claim 2, wherein is a substituted phenyl represented by the following general formula [Formula] (wherein R ₁₁ is a substituent selected from halogen, nitro, cyano, and trifluoromethyl).