JPH0358507B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer formed on a conductive support. Generally, in electrophotography, like the xerography method, a photoreceptor in which a photoconductor element such as selenium or cadmium sulfide is formed into a thin film on a metal drum is charged in a dark place, and a light image is irradiated (exposed). After forming an electrostatic latent image, a visible image is created with toner (development), and this is transferred and fixed onto paper, etc., or a photoconductive layer (photosensitive layer) is placed on paper as in the electrofax method. The photoreceptor is charged,
There is a method of obtaining a permanent visible image on the photoconductive layer by exposure, development and fixing. Inorganic compounds that are currently widely used as photoconductor materials for electrophotographic photoreceptors include amorphous selenium, cadmium sulfide, zinc sulfide, and the like. Amorphous selenium has good properties as a photoconductor material, but it is difficult to manufacture because it must be manufactured by vapor deposition, and the vapor-deposited film is not flexible and is highly toxic, so it must be handled with care. However, it also has the disadvantage of being expensive. Cadmium sulfide, zinc oxide is used in the form of a photoconductive layer dispersed in a binder resin, with a resin/photoconductor material weight ratio of 0.2.
Practical sensitivity cannot be obtained unless it is ~0.3 or less, and therefore it has drawbacks in mechanical properties such as flexibility, smoothness, hardness, tensile strength, and abrasion resistance. Therefore, it cannot withstand repeated use as it is. Hygiene issues with cadmium sulfide also need to be considered. On the other hand, polyvinylcarbazole (PVK), phthalocyanine, etc. are known as organic compounds. Although these photoconductor materials have excellent flexibility and processability, they do not have sufficient electrophotographic sensitivity for practical use when used alone, and they can be improved by combining chemical sensitization and optical sensitization. It becomes sensitized. Chemical sensitizers include polycyclic or heterocyclic nitro compounds such as 2,4,7-trinitro-9-fluorenone (TNF) and 2,4,5,7-tetranitro-9-fluorenone (TENF), anthraquinone, etc. quinones, and nitrile compounds such as tetracyanoethylene are known. Furthermore, xanthene dyes and quinoline dyes are known as optical sensitizers. However, if these substances are added to an electrophotographic photoreceptor until a practical level of sensitivity is obtained, these substances themselves have problems with charging resistance, light resistance, etc., and fatigue phenomena due to continuous charging and exposure to light will be significant. , there are practical problems. Further, as chemical sensitizers, TNF and TENF have particularly excellent sensitizing effects, and are actually often used for organic photoconductors and the like. However, these substances are expensive, and in order to obtain the sensitivity required for practical use, adding large amounts of these substances results in
Photoreceptors are not only expensive, but also have hygienic problems, and their use is questionable. In addition, some studies are also considering methods of using phthalocyanine derivatives for phthalocyanine.
This method requires a strong mechanical mixing treatment, and it is true that this method allows phthalocyanine and phthalocyanine derivative to be mixed uniformly, resulting in an electrophotographic photoreceptor with excellent electrophotographic properties. The mechanical mixing process, which lasts for quite a long time, requires a great deal of effort, and the implementation of this method is subject to significant industrial constraints. Furthermore, it can be seen that the physical properties required for an electrophotographic photoreceptor are not necessarily fully satisfied. On the other hand, various means for forming a charge generation layer and a charge transport layer on a dielectric support have been studied as a function-separated layered photoreceptor. Known laminated photoreceptors include those in which a charge generation layer/charge transport layer is formed on a dielectric support, or a charge generation layer/charge transport layer is formed by changing the lamination order. This laminated photoreceptor has the advantage that the induction effect caused by the trapping of generated charges, which is generally observed in single-layer photoreceptors, is reduced and the gradation is improved. The present invention provides a functionally separated laminated photoreceptor which has excellent electrophotographic properties such as sensitivity as well as gradation by using a specific phthalocyanine-based charge generating material as a charge generating layer. That is, 100 parts by weight of phthalocyanine and 0.01 parts by weight of a phthalocyanine derivative in which the benzene nucleus of the phthalocyanine molecule is substituted with at least one electron-withdrawing group selected from a nitro group, a cyano group, a halogen atom, a sulfone group, and a carboxyl group.
A layer containing a charge generation material (charge generation layer) and a charge transport layer obtained by mixing ~20 parts by weight with an inorganic acid capable of forming a salt with phthalocyanine and precipitating it with water or a basic substance. This is an electrophotographic photoreceptor formed on a conductive support. The phthalocyanine according to the present invention is a metal-free phthalocyanine, a metal phthalocyanine, or a mixture thereof. The metals of metal phthalocyanine include copper, silver, beryllium, magnesium, calcium, zinc, cadmium, barium,
Mercury, aluminum, gallium, indium, lanthanum, neodymium, samarium, europium,
Gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, titanium, tin, hafnium, lead, thorium, vanadium, antimony, chromium, molybdenum, uranium, manganese, iron, cobalt, nickel, rhodium, palladium, osmium, and Platinum et al. Furthermore, the central core of the phthalocyanine may not be a metal atom, but a metal halide having a valence of 3 or more. Metal-free phthalocyanines and metal phthalocyanines such as copper, cobalt, lead, and zinc are preferred. Furthermore, it may be a low halogenated phthalocyanine. Note that phthalocyanine is a compound well known as a pigment, but in the present invention, phthalocyanine obtained by any manufacturing method may be used. Of course, pigmented phthalocyanine may also be used. The phthalocyanine derivative according to the present invention is one in which the benzene nucleus of the phthalocyanine molecule is substituted with at least one electron-withdrawing group selected from a nitro group, a cyano group, a halogen atom, a sulfone group, and a carboxyl group. This phthalocyanine derivative can be obtained by using phthalonitrile, phthalic acid, phthalic anhydride, or phthalimide substituted with the above substituents as the raw material for phthalocyanine during phthalocyanine synthesis; It can be obtained by using both. The method for producing the phthalocyanine derivative is not particularly limited.
Further, the number of substituents in one molecule of the phthalocyanine derivative is 1 to 16, preferably 1 to 8,
More preferably, it is 1 to 4 pieces. The number of substituents is
Although it varies depending on the manufacturing method, different numbers are often mixed. As the phthalocyanine derivative, for example, one having a nitro group and a cyano group, a phthalocyanine derivative having a nitro group, and a phthalocyanine derivative having a cyano group may be used in combination. Furthermore, some phthalocyanine derivatives other than the phthalocyanine derivatives of the present invention can also be used in combination. The phthalocyanine derivatives include metal-free phthalocyanines or metal phthalocyanines such as copper, nickel, cobalt, iron, sodium, lithium, calcium, magnesium, and aluminum. The composition ratio of phthalocyanine and phthalocyanine derivative is phthalocyanine
Phthalocyanine derivative: 0.01 per 100 parts by weight
~20 parts by weight. Preferably, the amount of the phthalocyanine derivative is 0.1 to 5 parts by weight. If it is less than 0.01 parts by weight, sufficient sensitivity cannot be obtained, and if it exceeds 20 parts by weight, the dark decay rate increases and it cannot be put to practical use. Next, typical examples of methods for producing phthalocyanine and phthalocyanine derivatives will be given. First, phthalodinitrile and/or phthalodinitrile substituted with nitro or cyano groups are heated in the presence or absence of a metal salt in an organic solvent such as alcohol with a strong base catalyst such as ammonia alcoholate. There is a nitrile method, a method in which phthalic anhydride and/or phthalic anhydride substituted with a nitro group or a cyano group, urea, or a metal salt is heated in the presence or absence of a solvent using molybdic acid, ammonium, etc. as a catalyst. Alternatively, a method using aminoiminoisoindolenine or the like may be used. Examples of inorganic acids that can form salts with the phthalocyanine used in the present invention include sulfuric acid, orthophosphoric acid, pyrophosphoric acid, chlorosulfonic acid, bases, hydroiodic acid, hydrofluoric acid, and hydrobromic acid.
These inorganic acids are those used in conventionally known methods such as phthalocyanine acid pasting method and acid slurry method. Further, as a method, a conventionally known method is applied. For example, a method in which phthalocyanine is dissolved in the above-mentioned inorganic acid and then the solution is injected into water, etc. (acid pasting method), a method in which a slurry of an inorganic acid salt of phthalocyanine is made, and the solution is injected into water, etc. (acid slurry method). Alternatively, there is a method of decomposing an inorganic acid salt of phthalocyanine with a basic substance such as ammonia gas to precipitate phthalocyanine. The charge generating material obtained as described above is coated with a binder resin to form a charge generating layer on a conductive support or on a charge transport layer, or a charge generating layer is formed by coating with a solvent. Alternatively, the charge generation layer can be formed by a vapor deposition method, a sputtering method, or the like. In addition, in the latter two methods, except for the method in which a protective layer is further provided, the lamination order of conductive support/charge generation layer/charge transport layer is preferable. When forming the charge generation layer together with a binder resin,
The mixture is uniformly dispersed together with a binder resin, a solvent, etc. using a kneading/dispersing machine such as a ball mill or attritor, and then coated on a conductive support to form a charge generation layer. Binder resins include melamine resin, epoxy resin, silicone resin, polyurethane resin, polyester resin, alkyd resin, acrylic resin, xylene resin, vinyl chloride-vinyl acetate copolymer resin,
A binder resin having an insulating property with a volume resistivity of 10 Ωcm or more, such as polycarbonate resin or a cellulose derivative, or a binder resin such as polyvinyl carbazole. A composition containing this charge-generating material, binder resin, etc. is coated on a conductive support such as an aluminum plate, conductivity-treated paper, or plastic film, which is commonly used in electrophotographic photoreceptors, to form a photosensitive layer.
As for the coating method, if necessary, a solvent is added to the composition to adjust the viscosity, and a film is formed using an air doctor coater, blade coater, rod coater, reverse roll coater, spray coater, hot coater, squeeze coater, gravure coater, etc. I do. After coating, perform appropriate drying if necessary. In addition, the charge generation layer according to the present invention has a resin/charge generation material weight ratio of 1 or more, and has a larger amount of resin than in the case of a photoreceptor using zinc oxide, and the film has physical strength and is flexible. Highly flexible. It also has excellent practical characteristics such as high adhesive strength with the conductive support, good moisture resistance, little change over time, no toxicity problems, and easy production and low cost. The thickness of the charge generation layer is about 0.01 to 10 μm,
For methods other than vapor deposition and sputtering, 0.5 to 10 μm
The thickness is approximately 0.01 to 2 μm using vapor deposition methods. The charge transport layer laminated on the charge generation layer is a layer that transports the charges generated in the charge generation layer to the surface of the photoreceptor, and is preferably transparent to light from the photosensitive area of the charge generation layer. The material is formed alone or in the form of a dispersed or dissolved material in a resin on the charge generation layer or on the conductive support. As the sole charge transporting material, polyvinylcarbazole and its derivatives, or a selenium vapor-deposited film can also be used. On the other hand, when dispersing or dissolving in a resin, polycarbonate, polyester, etc. can be used as the resin, and in this case, the weight ratio of the charge transport material to the resin is preferably 0.1 to 0.8, preferably 0.3 to 0.6. Further, the thickness of the charge transport layer is not particularly limited, but it is usually appropriate to set it to 5 to 50 μm. Examples of the charge transport material in the present invention include carbazole, N-ethylcarbazole, N-vinylcarbazole, N-isopropylcarbazole, N-phenylcarbazole, tetracene, chrysene, pyrene, perylene, 2-phenylnaphthalene, azapyrene, 2.3 −Benzochrysene, 3.4−
Benzopyrene, fluorene, 1.2-benzofluorene, 2.3-benzofluorene, 4-(2-fluorenylazo)resorcinol, 4-(2-fluorenylazo)m-cresol, 2-P-anisoleaminofluorene, P-diethylamino-azobenzene, 1- (2-Thiazolylazo)-2-naphthol, 4-anisoleaminoazobenzene, cation, N,N-dimethyl-P-phenylazoaniline, P-(dimethylamino)stilbene, 1.4
-bis(2-methylstyryl)benzene, 9-
(4-diethylaminostyryl)anthracene,
2.5-bis(4-diethylaminophenol)-
1.3.5-Oxadiazole, 1-phenyl-3-
(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-phenyl-3-methyl-5-pyrazolone and 2-(m-
Examples include (naphthyl)-3-phenyloxazole, P-diethylaminobenzaldehyde (diphenylhydrazone), and the like. In addition, as the resin (binder), polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polycarbonate, polystyrene, styrene-butadiene copolymer, polyester, polyvinylcarbazole, polyurethane, epoxy resin, phenoxy resin, polyamide, Examples include acrylic resins and silicone resins. In the present invention, the charge generation layer and/or the charge transport layer may optionally contain ε-type phthalocyanine,
β-type phthalocyanine, photoconductor elements other than phthalocyanine, sensitizers, and other additives can be added. The electrophotographic photoreceptor of the present invention can also be used as an electrophotographic material for producing printing plates. The electrophotographic photoreceptor of the present invention has good gradation due to the reduced induction effect,
It has excellent sensitivity, and furthermore, the structure of conductive support/charge generation layer/charge transport layer has the advantage that fatigue phenomena associated with repeated processes such as charging and exposure are particularly improved. The present invention will be explained below with reference to Examples and Comparative Examples. In the examples, "parts" indicate parts by weight. Example 1 40 parts of copper phthalocyanine and 1 part of mononitro copper phthalocyanine are dissolved in 500 parts of 98% concentrated sulfuric acid with thorough stirring. The dissolved solution was poured into 1000 parts of water with sufficient stirring to precipitate the copper phthalocyanine and mononitro copper phthalocyanine compositions, which were then filtered, washed with water, and dried at 120°C under reduced pressure. A composition consisting of 10 parts of this composition, 36 parts of acrylic polyol (manufactured by Takeda Pharmaceutical Co., Ltd.), 5 parts of epoxy resin (manufactured by Ciel Chemical Co., Ltd.), and 50 parts of methyl ethyl ketone:cellosolve acetate (1:1) was mixed using a ball mill. By kneading for 24 hours, the photoconductive paint is prepared, and this paint is deposited on an aluminum support with approx.
It was applied to a thickness of 1μ to form a charge generation layer. Next, polycarbonate resin (manufactured by Teijin Kasei) 10
and 3 parts of polyester resin (manufactured by Gutdeyer) were mixed with tetrahydrofuran and 100 parts of toluene solvent. The weight ratio of solvents is 9:1. Then p
9 parts of -diethylaminobenzaldehyde-(diphenylhydrazone) were added together with 0.02 part of silicone oil. This liquid was applied onto the charge generation layer to a thickness of about 15 μm and dried at 80° C. to form a charge transport layer to obtain a laminated photoreceptor. Example 2 30 parts of metal-free phthalocyanine and 0.5 part of dinitrocopper phthalocyanine are dissolved in 500 parts of 98% concentrated sulfuric acid with thorough stirring. The dissolved solution is poured into 3000 parts of water to precipitate the phthalocyanine composition, which is then filtered, washed with water, and dried at 120°C under reduced pressure. 5 parts of this composition and thermoplastic acrylic resin OXL-97 (manufactured by Mitsui Toatsu)
A photoconductive paint was prepared by kneading a composition consisting of 20 parts by weight and 30 parts of butyl acetate:cellosolve acetate (1:1) in a ball mill for 24 hours, and this paint was spread on an aluminum support to a thickness of about 1μ. A charge generation layer was formed. Next, polycarbonate resin (manufactured by Teijin Kasei) 10
5 parts of polyester resin (manufactured by Gutsdoyer),
Five parts of acrylic resin (manufactured by Mitsubishi Kasei) was dissolved in 150 parts of tetrahydrofuran:toluene (9:1).
Next, 12 parts of 2,5-bis(4-diethylaminophenyl) 1,3,4-oxadiazole was added to this together with 0.02 part of silicone oil. This liquid was coated on the charge generation layer to a thickness of about 15 μm and dried at 80° C. to form a charge transport layer to obtain a laminated photoreceptor. Example 3 In forming the charge transport layer of Example 2, 2,5-
Bis(4-diethylaminophenyl)1,3,4
-1-phenyl-3 instead of oxadiazole
A photoreceptor was prepared in exactly the same manner as in Example 2 except that -(p-diethylaminostyryl)-5-(p-diethylaminophenyl)-2-pyrazoline was added. Comparative Example 1 10 parts of β-type copper phthalocyanine, 32 parts of thermosetting acrylic resin, 8 parts of melamine resin, and butyl acetate:
A photoconductive paint was prepared by kneading a composition consisting of 50 parts of cellosolve acetate (1:1) in a ball mill for 24 hours, and this paint was coated on an aluminum support to a thickness of approximately 1μ to form a charge generating layer. Formed. Next, in the same manner as the charge transport layer of Example 1, it was coated on the charge generation layer to a thickness of about 15 μm and dried at 80° C. to form a charge transport layer to obtain a laminated photoreceptor. Comparative Example 2 A photoreceptor was prepared in exactly the same manner as in Comparative Example 1, except that β-type copper phthalocyanine was replaced with metal-free phthalocyanine in the formulation of Comparative Example. Next, the above photoconductor was corona charged at -6.5KV by 0.2 using a commercially available Carlson electrophotographic copying machine.
The surface potential (V) and the amount of exposure required to reduce each V to 1/2 (E1/2) were measured, and the results shown in the following table were obtained.

[Table] As can be seen from the above results, the electrophotographic photoreceptor of the present invention has extremely high sensitivity and maintains sensitivity in the long wavelength range, which is a characteristic of phthalocyanine pigments. (λ=750～
This is an excellent photoreceptor that can also be used in printers that use a light source of 850 μm).

Claims (1)

[Claims] 1 On a conductive support, 100 parts by weight of phthalocyanine and the benzene nucleus of the phthalocyanine molecule are substituted with at least one electron-withdrawing group selected from a nitro group, a cyano group, a halogen atom, a sulfone group, and a carboxyl group. A layer containing a charge-generating substance and a charge-transporting layer are obtained by mixing 0.01 to 20 parts by weight of the phthalocyanine derivative with an inorganic acid capable of forming a salt with the phthalocyanine, and precipitating the mixture with water or a basic substance. An electrophotographic photoreceptor characterized in that it is formed by forming.