JPH0448226B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor using a novel electrophotographic photosensitive material, and more specifically to a high-sensitivity electrophotographic photoreceptor containing a thiillium salt compound having a specific molecular structure in a photoconductive layer. The present invention relates to an electrophotographic photoreceptor. [Prior Art] Pigments and dyes exhibiting photoconductivity have been published in numerous publications. For example, "R.C.A. Review" (〓
RCA Review”) Vol.23, P.413-P.419 (1962.9)
published on the photoconductivity of phthalocyanine pigments, and electrophotographic photoreceptors using these phthalocyanine pigments have been disclosed in US Pat. No. 3,397,086 and US Pat. No. 3,816,118.
In addition, examples of organic semiconductors used in electrophotographic photoreceptors include US Pat. No. 4,315,983, US Pat. No. 4,327,169, and "Research Disclosure" 20517
(1981.5), methine squaritate dye shown in US Pat. No. 3,824,099, US Pat. No. 3,898,084,
Examples include disazo pigments disclosed in US Pat. No. 4,251,613. Such organic semiconductors are easier to synthesize than inorganic semiconductors, and can be synthesized as compounds that have photoconductivity for light in the required wavelength range. An electrophotographic photoreceptor formed on a conductive support has the advantage of improved color sensitivity, but only a few of them are practical in terms of sensitivity and durability. [Problems to be Solved by the Invention] The present inventors have completed the present invention as a result of intensive research aimed at improving the various drawbacks of organic semiconductor materials and obtaining a photoconductive material with excellent electrophotographic properties. Ivy. The first object of the present invention is to provide a novel organic semiconductor coating. A second object of the present invention is to provide an electrophotographic photoreceptor that can be used in all existing electrophotographic processes, improves the conventional drawbacks, and provides higher electrophotographic response gain. [Means for Solving the Problems] According to the present invention, there is provided an electrophotographic photoreceptor comprising a photoconductive layer containing a thiillium salt compound represented by the following general formula [] on a conductive substrate. is provided. General formula [] (However, in the formula, m and n represent integers of 0, 1, and 2, and B forms a benzothiylium ring, benzoxathiylium ring, naphthodithylium ring, or naphthoxathiylium ring that may have a substituent. Substituents include lower alkyl groups such as methyl, ethyl, propyl, butyl, lower alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, and halogens such as fluorine, chlorine, bromine, and iodine. Atoms or functional groups such as nitro groups are included. _{A 1 and} A ₂ represent sulfur or oxygen atoms,
X ^- represents an anionic functional group, specific examples include I ^- ,
Br ^- , Cl ^- , ClO ₄ ^- , BF ₄ ^- , PF ₆ ^- ,

[Formula] Contains anions such as CH ₃ SO ₃ ^- , C ₂ H ₅ SO ₃ ^- , CH ₃ SO ₄ ^- , etc. Q represents an optionally substituted benzene, naphthalene, anthracene, pyrrole, furan, thiophene, or isoxazole residue, and substituents include lower alkyl groups such as methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, and butoxy. It includes lower alkoxy groups such as, halogen atoms such as fluorine, chlorine, bromine, and iodine, and functional groups such as nitro groups. R ₁ , R ₂ , R ₃ , and R ₄ indicate that at least one of them is a substituent other than a hydrogen atom, and includes a lower alkyl group such as methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, butoxy It includes lower alkoxy groups such as, halogen atoms such as fluorine, chlorine, and iodine, and cyano groups. Next, a general method for producing the thiillium salt compound used in the present invention will be described. The compound represented by the general formula [] is It is generally synthesized by methods such as Specific examples of the thiillium salt compounds used in the present invention are listed below. The thiillium compound having the above structure does not limit the scope of the claims of the present invention. The film containing the thiillium salt compound described above exhibits photoconductivity, and therefore can be used as a photosensitive layer, in other words, a photoconductive layer, of the electrophotographic photoreceptor described below. That is, in a specific example of the present invention, an electrophotographic photoreceptor is formed by forming a film of the above-mentioned thiylium salt compound on a conductive support by vacuum evaporation, or by dispersing it in a suitable binder and forming a film. It can be prepared. In a preferred embodiment of the present invention, the photoconductive coating described above can be applied as a charge generation layer 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 of the above-mentioned photoconductive compound as possible in order to obtain sufficient absorbance, and is a thin film layer, for example, 5μ or less, in order to shorten the range of the generated charge carriers. Preferably
A thin film layer having a thickness of 0.01 to 1 μm is preferable. 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 compound 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 apparatus. . The binder that can be used when forming the charge generation layer by coating can be selected from a wide range of insulating resins.
It can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene. Preferably, polyvinylbutyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.) polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, Examples include insulating resins such as urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less. The solvent that dissolves these resins varies depending on the type of resin, and 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 methods include dip coating method, spray coating method, spinner coating method, bead coating method, Meyer bar coating method, blade coating method, roller coating method,
This can be done using a coating method such as a curtain coating method. 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° C. 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. 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 transport substances include electron transport substances and hole transport substances, and electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, and 2,4,7-trinitro-9-fluorenone. , 2, 4, 5, 7-
Tetranitro-9-fluorenone, 2,4,7-
trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone,
Examples include electron-withdrawing substances such as 2,4,8-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-hydrazine 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, spirazoline and other pyrazolines, 2-(p-diethylaminostyryl)-6
-diethylaminobenzoxazole, 2-(p
Oxazole compounds such as -diethylaminophenyl)-4-(p-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2-(p-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole,
-diethylaminostyryl) -thiazole compounds such as 6-diethylaminobenzothiazole, bis(4-diethylamino-2-methylphenyl)
-Trialmethane compounds such as phenylmethane, 1,1-bis(4-N,N-diethylamino-2-methylphenyl)heptane, 1,1,2,
2-tetrakis(4-N,N-dimethylamino-
Polyarylalkanes such as 2-methylphenyl)ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9
-Vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin, etc. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium amorphous silicon, and cadmium sulfide can also be used. Moreover, these charge transport substances may be one or two types.
More than one species can be used in combination. When the charge transport material does not have film-forming properties,
A film can be formed by selecting an appropriate binder. Resins that can be used as binders are:
For example, insulating resins such as acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, or poly-N- Mention may be made of organic photoconductive polymers such as vinylcarbazole, polyvinylanthracene, polyvinylpyrene. Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, it is 5-30μ, but the preferred range is 8-20μ. When forming the charge transport layer by coating, an appropriate coating method as described above can be used. A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. The substrate having a conductive layer, that is, the conductive substrate, is one that itself has conductivity, 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.
A substrate made of plastic coated with carbon black, silver particles, etc.) along 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 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 transporting substance is used. When using a photoreceptor in which a conductive layer, a charge transport layer, and a charge generation layer are laminated in this order, if the charge transport substance is an electron transport substance, the surface of the charge generation layer must be negatively charged, and after charging, When exposed to light, in the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer and then reach the substrate, while holes generated in the charge generation layer reach the surface.
Attenuation of the surface potential occurs and electrostatic contrast occurs between the surface potential and the unexposed area. A visible image can be obtained by developing the electrostatic latent image thus formed with a positively charged toner. This can be directly fixed, or the toner image can be transferred to paper, plastic film, etc. and then developed and fixed. Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or known methods, and are not limited to specific ones. On the other hand, when the charge transport material is a hole transport material, it is necessary to positively charge the surface of the charge generation layer, 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. After that, the electrons generated in the charge generation layer reach the surface, and the surface potential attenuates, creating an electrostatic contrast with the unexposed area. During development, it is necessary to use a negatively charged toner, contrary to the case where an electron transporting substance is used. In another specific example of the present invention, organic photoconductive materials such as the aforementioned hydrazones, pyrazolines, oxazoles, thiazoles, triarylmethanes, polyarylalkanes, triphenylamines, poly-N-vinylcarbazoles, etc. The photosensitive film may contain the above-described thiillium salt compound as a sensitizer for inorganic photoconductive substances such as photoconductive substances, zinc oxide, cadmium sulfide, and selenium. This photosensitive film is formed by coating these photoconductive substances and the above-mentioned thiillium salt compound together with a binder. Further, as another specific example of the present invention, JP-A-49-
It can also be used as a type of photoreceptor in which a charge generating material is added to a charge transfer complex as disclosed in Publication No. 916483 (Photoconductive Member). Any photoreceptor should contain at least one type of thiillium salt compound selected from the compounds represented by the general formula [], and if necessary, be used in combination with other photoconductive pigments or dyes with different light absorption. Depending on the method, the sensitivity of this photoreceptor can be increased or it can be prepared as a bank chromatic photoreceptor. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers and CRTs.
It can also be widely used in electrophotographic applications such as printers. Hereinafter, the present invention will be explained according to examples. Examples 1 to 21 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 1.0μ, and dried. Next, to a solution of 2 g of butyral resin (degree of butyralization: 63 mol %) dissolved in 95 ml of isopropyl alcohol, 5 g of each of the 21 types of thiillium salt compounds mentioned in the specific examples were added to prepare 21 types of coating liquids. After dispersing each coating solution in a sand mill, each coating solution was applied onto the casein undercoat layer using a Mayer bar so that the film thickness after drying was 0.1 μm, and dried to form a charge generation layer. Then, the structural formula 5 g of hydrazine 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 21 types of electrophotographic photoreceptors prepared in this way were tested using an electrostatic copying paper tester Model SP- manufactured by Kawaguchi Electric Co., Ltd.
428 using the dynamic method at -5kV, held in the dark for 1 second, and then charged at 4kV with an illuminance of 5lux.
It was exposed to light for seconds and the charging characteristics were examined. As for the charging characteristics, the initial charging potential V ₀ and the exposure amount (E _1/2 ) required to attenuate the potential by 1/2 when dark decaying for 1 second were measured. The results are shown in Table 1. In addition, the residual potential after 20 lux·sec exposure was expressed as _VR .

【table】

【table】

[Table] A photoreceptor was prepared in exactly the same manner as in Example 1 except that the above comparative compound was replaced with the thiillium salt compound of Example 1, and the characteristics were investigated and the results are shown in Table 2.

[Table] All comparative examples have lower sensitivity and higher residual potential than the examples. Furthermore, using the charge measuring device of Example 1, the same charge exposure operation as in Example 1 was repeated 5000 times using a dynamic method, and the changes in the initial charging potential V ₀ and the residual potential V _R after exposure were investigated and shown in Table 3. .
Note that the same measurements were performed on the photoreceptors of Examples 1, 20, and 21.

[Table] Although the photoreceptors of the comparative examples all have high initial residual potentials, the residual potentials during repeated use are extremely high, and this pushes up the V ₀ as well, which is a major problem due to lack of stability in practical use. On the other hand, the properties of the examples according to the present invention are extremely stable even after repeated use, and it is clear that they have excellent properties in practical use. Examples 25 to 27 A casein subbing layer was coated on an aluminum plate in the same manner as in Example 1. Next, the charge transport layer containing the hydrazine compound used in Example 1 as a charge transport material was dried to a thickness of 12 μm.
A charge transport layer was formed by coating with a Mayer bar and drying. Next, the three coating solutions of Examples 1, 9, and 16 were applied onto the charge transport layer using a Mayer bar so that the film thickness after drying was 0.1 μm, and dried to form a charge generation layer. The charging characteristics of the three types of electrophotographic photoreceptors thus prepared were examined in the same manner as in Example 1. In this case, it was corona charged at +5kV. The results are shown in Table 4.

〔Effect of the invention〕

According to the present invention, it is possible to obtain an electrophotographic photoreceptor that has extremely stable properties even after repeated use and has extremely excellent properties for practical use.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photoconductive layer containing a thiillium salt compound represented by the following general formula [] on a conductive substrate. General formula [] (However, in the formula, m and n represent integers of 0, 1, and 2,
B is a benzothirium ring which may have a substituent,
It shows the residues necessary to form a benzoxathylium ring, a naphthodithyllium ring, and a naphthoxathiylium ring, A ₁ and A ₂ represent sulfur or oxygen atoms, and X ^- represents an anionic functional group. Q represents an optionally substituted benzene, naphthalene, anthracene, pyrrole, furan, or thiophene residue, and R ₁ , R ₂ , R ₃ , and R ₄ represent at least one substituent other than a hydrogen atom. show. )