JP4386820B2 - Electrophotographic photoreceptor for wet development - Google Patents

Description

  The present invention relates to an electrophotographic photoreceptor excellent in solvent resistance for hydrocarbon solvents and durability when used in wet development.

In an electrophotographic image forming apparatus such as an electrostatic copying machine, a facsimile, or a laser beam printer, a photosensitive material containing a charge generating agent, a charge transporting agent, a binder resin, etc. on a conductive substrate as an electrophotographic photosensitive member. Organic photoreceptors having layers are widely used.
As a developing method of an image forming apparatus using an organic photoreceptor, a dry developing method using a powder toner (dry developer) is generally used, but a colorant and a polymer particle are contained in a solvent having high electrical insulation. There is also known a wet development (liquid development) method in which development is performed by electrophoresing toner particles onto an electrostatic latent image on the surface of a photoreceptor using a wet developer in which the toner is dispersed. The toner particles of the wet developer are charged to a predetermined charge by the binder resin and charge control agent that forms the toner particles, and are stably dispersed in the solvent. Therefore, the particle size of the toner particles is smaller than that of the dry developer. Can be reduced. In addition, according to wet development, problems such as leakage in dry development do not occur. Therefore, the wet development has a higher resolution than that of the dry development and can realize high-quality image formation.

  However, since wet developers are required to have high electrical insulation, generally, paraffinic solvents such as isoparaffin and n-paraffin are frequently used as solvents. Therefore, when the photoreceptor and the wet developer are in contact with each other for a long time, such as by repeatedly performing image formation, the charge transport agent in the photosensitive layer is eluted in the paraffinic solvent, and the sensitivity of the photoreceptor is increased. The problem of decreasing over time arises. Further, when the binder resin forming the photosensitive layer swells with a paraffinic solvent, there arises a problem that the photosensitive layer is softened, cracked, and deteriorated.

  On the other hand, in recent years, mainly for the purpose of improving the abrasion resistance of the photosensitive layer, a polycarbonate resin having a repeating unit represented by the following formula (i) and a repeating unit represented by the following general formula (ii) in a binder resin: A polycarbonate resin having a repeating unit represented by the following formula (i) and a repeating unit represented by the following formula (iii), or a polyarylate resin having a repeating unit represented by the following general formula (iv) Has been proposed (Patent Documents 1 and 2).

(In general formula (ii) and general formula (iii), R represents an alkyl group which may have a substituent, etc. m represents an integer of 0 to 4. In general formula (iv), R represents ^{a to} R ^h represent a hydrogen atom, an alkyl group, etc. Z ¹ and Z ² independently represent a hydrogen atom, an alkyl group, an aryl group, etc.)
JP 2001-215739 A JP-A-2-132453

  However, as a result of the study by the present inventor, as shown in a comparative example to be described later, even when the photosensitive layer is formed using the polycarbonate resin described in Patent Document 1, it is incorporated into the hydrocarbon solvent. The elution amount of the charge transfer agent is increased (that is, the solvent resistance of the hydrocarbon solvent is low), and there is a problem that the durability of the electrophotographic photosensitive member becomes poor when used for wet development.

  Further, even when a polyarylate resin is used as the binder resin for forming the photosensitive layer, among the polyarylate resins described in Patent Document 2, a bisphenol moiety in the repeating unit represented by the general formula (iv) If the structure is specifically disclosed in Patent Document 2, the solvent resistance of the hydrocarbon solvent is still low, and the durability when used in wet development is sufficiently improved. I can't.

  Accordingly, an object of the present invention is to solve the above-described problems and provide an electrophotographic photosensitive member that can suppress elution of a charge transfer agent and swelling and deterioration of a photosensitive layer even when used in wet development. That is.

In order to solve the above problems, the present invention provides:
(1) An electrophotographic photosensitive member having a photosensitive layer on a conductive substrate,
The photosensitive layer contains a charge generator, a charge transport agent and a binder resin,
The binder resin is a polyarylate resin having a repeating unit represented by the following general formula (1), and the charge transfer agent has a site represented by the following general formula (h1) or the following general formula (h2). An electrophotographic photosensitive member for wet development, comprising at least a hole transport agent having a molecular weight of 900 or more ,

(In general formula (1), R 1 and R 2 each independently represent a hydrogen atom or a methyl group. Ar represents an arylene group which may have an alkyl group. )

(In the general formula (h1) or the general formula (h2), R ^h1 , R ^h2 , R ^h3 , R ^h4 and R ^h5 are each independently a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, or an aralkyl group. A to e each independently represent an integer of 0 to 3. When a to e are 2 or 3, a plurality of substituents substituted on the same benzene ring are groups different from each other. In addition, when a to e are 2 or 3, two alkyl groups or alkenyl groups substituted on adjacent carbon atoms of the benzene ring are bonded to each other and are saturated or unsaturated together with the benzene ring. A hydrocarbon ring may be formed.)
(2) The polyarylate resin has two or more repeating units represented by the general formula (1) having different structures, and has an alkyl group corresponding to Ar in the repeating unit. A group that binds to the carbonyl group in a positional relationship in which the molecular chain of the polyarylate is linear, and a group that binds to the carbonyl group in a positional relationship that forms a bent portion in the molecular chain of the polyarylate, The electrophotographic photosensitive member for wet development according to the above (1), characterized by comprising:
(3) The photosensitive layer (1) or (2), wherein the photosensitive layer is a photosensitive layer composed of a single layer, and the charge transport agent includes a hole transport agent and an electron transport agent. ) Electrophotographic photosensitive member for wet development,
(4) The photosensitive layer is a laminated photosensitive layer comprising a charge generating layer containing the charge generating agent and a charge transporting layer containing the charge transporting agent, and the laminated photosensitive layer is on the conductive substrate side. The electrophotographic photosensitive member for wet development according to (1) or (2) above, wherein the charge generation layer and the charge transport layer are formed in this order.
(5) wherein the charge transport agent, characterized in that the molecular weight containing 600 or more electron-transporting agent, wherein (1) to wet-developing electrophotographic photoconductor according to any one of (4),
(6) the charge generating agent, characterized in that metal-free phthalocyanine, at least one selected from the group consisting of titanyl phthalocyanine, hydroxygallium phthalocyanine and chlorogallium phthalocyanine, either above (1) to (5) An electrophotographic photoreceptor for wet development according to claim 1,
Is to provide.

  According to the electrophotographic photoreceptor for wet development of the present invention, a charge transfer agent from the photosensitive layer can be used even when repeated image formation processing is performed by a wet development method using a wet developer containing a hydrocarbon solvent. Elution or swelling of the photosensitive layer can be suppressed. In addition, it is possible to suppress deterioration of the photosensitive layer such as softening and cracking even after repeated image formation processing by wet development.

  The electrophotographic photoreceptor for wet development of the present invention is excellent in solvent resistance for hydrocarbon solvents and durability when used in wet development, and is therefore suitable as an electrophotographic photoreceptor for wet development. is there.

The electrophotographic photoreceptor for wet development of the present invention comprises a photosensitive layer on a conductive substrate, the photosensitive layer contains a charge generating agent, a charge transport agent and a binder resin, and the binder resin further comprises: The molecular weight is 900, which is a polyarylate resin having a repeating unit represented by the general formula (1), and the charge transfer agent has a site represented by the general formula (h1) or the general formula (h2). It is characterized by containing at least the above hole transport agent .
In the electrophotographic photoreceptor for wet development of the present invention, the polyarylate resin may have only one type of repeating unit represented by the general formula (1) or two or more types.

In the repeating unit represented by the general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a methyl group. R ¹ and R ² are preferably both hydrogen atoms.
In the repeating unit represented by the general formula (1), Ar represents an arylene group that may have an alkyl group.

Examples of the arylene group that may have an alkyl group include phenylene, biphenylene, naphthylene, anthrylene, phenanthrylene, and the like. Of these, phenylene and biphenylene are preferable.
Examples of the alkyl group substituted on the arylene group include alkyl groups having 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, and t-butyl. .

  Two carbonyl groups are bonded to Ar (arylene group which may have an alkyl group) in the general formula (1). As for Ar in the general formula (1), preferably, for example, p-phenylene, 4,4′-biphenylene, 3,5′-biphenylene, 2,6′-biphenylene, 1,4-naphthylene, 1,5 A group that binds to a carbonyl group in a positional relationship in which the molecular chain of polyarylate is linear, such as naphthylene, 2,6-naphthylene, 2,7-phenanthrylene (hereinafter sometimes referred to as “linear group”) And m-phenylene, o-phenylene, 3,3′-biphenylene, 3,4′-biphenylene, 2,5-naphthylene, 2,7-naphthylene, 2,8-naphthylene, 1,8- Groups such as phenanthrylene and 3,6-phenanthrylene, which are bonded to a carbonyl group in a positional relationship that forms a bent portion in the polyarylate molecular chain (hereinafter referred to as “flexibility”). May be referred to. "With), it is preferable to include both.

  For example, when Ar is phenylene, it preferably contains both p-phenylene and m-phenylene or o-phenylene. When Ar is biphenylene, it is preferable to include both 4,4'-biphenylene or 3,5'-biphenylene and 3,3'-biphenylene, 3,4'-biphenylene, or the like. Further, for example, it may have a repeating unit in which Ar in the general formula (1) is m-phenylene and a repeating unit in which Ar is 4,4′-biphenylene. It may have a repeating unit in which Ar is p-phenylene and a repeating unit in which Ar is 3,3′-biphenylene.

  Note that Ar in the general formula (1) is, for example, p-phenylene, 4,4′-biphenylene, 3,5′-biphenylene, 1,4-naphthylene, 1,5-naphthylene, 2,6-naphthylene, When the molecular chain of polyarylate is only a group (linear group) bonded to a carbonyl group in a linear relationship such as 2,7-phenanthrylene, the polyarylate resin is easily crystallized. In addition, the solubility in a solvent may be reduced. Conversely, Ar in the above general formula (1) is, for example, m-phenylene, o-phenylene, 3,3′-biphenylene, 3,4′-biphenylene, 2,5-naphthylene, 2,7-naphthylene, 2; , 8-naphthylene, 1,8-phenanthrylene, 3,6-phenanthrylene, etc., only a group (flexible group) that binds to a carbonyl group in a positional relationship that forms a bent part in the molecular chain of polyarylate In this case, the polyarylate resin tends to aggregate and the solubility in the solvent may be reduced. On the other hand, when Ar in the general formula (1) has both the linear group and the flexible group, the crystallization and aggregation of the polyarylate resin is prevented, and the solubility in a solvent is reduced. Can be improved.

The content ratio (S: F) of the linear group S and the flexible group F in the polyarylate resin is not particularly limited, but is preferably 10:90 to 90:10 (molar ratio). More preferably, it is 20:80 to 80:20 (molar ratio).
In the electrophotographic photoreceptor for wet development of the present invention, as the binder resin, other polyarylate resins and other resins such as polycarbonate resins are used in combination with the polyarylate resin having the repeating unit (1). May be.

  The other resin is not particularly limited except that it is excellent in compatibility with the polyarylate resin having the repeating unit (1). For example, bisphenol A type, bisphenol F type, Examples include polycarbonate resins made of bisphenol such as bisphenol AD type, bisphenol Z type, bisphenol A type, bisphenol C type, and bisphenol ZC type; polyester resins, polystyrene resins, polymethacrylate resins, and polyacrylate resins.

The content ratio of the other polyarylate resin and the other resin is appropriately set within a range that does not impair the effects of the present invention. The content ratio of the other polyarylate resin and the other resin is preferably 80% by weight or less, and more preferably 50% by weight or less with respect to the whole binder resin.
In the case where the electrophotographic photoreceptor for wet development of the present invention is a laminated photoreceptor described later, if the polyarylate resin having the repeating unit (1) is used as the binder resin for forming the outermost layer. Well, the layer that is not the outermost layer is not limited to using the polyarylate resin having the repeating unit (1) as the binder resin.

  In the electrophotographic photoreceptor for wet development of the present invention, examples of the conductive substrate include various materials in which the substrate itself has conductivity or the surface of the substrate has conductivity. Specifically, for example, simple metals such as iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass; Examples thereof include laminated plastic materials; glass coated with aluminum iodide, tin oxide, indium oxide, and the like; and a resin substrate in which conductive fine particles such as carbon black are dispersed. As the shape of the conductive substrate, various shapes such as a sheet shape and a drum shape can be adopted depending on the structure of the image forming apparatus using the electrophotographic photoreceptor for wet development of the present invention.

In the electrophotographic photoreceptor for wet development of the present invention, the photosensitive layer has a single layer type photosensitive layer containing a charge generating agent and a charge transporting agent in the same layer, and a layer containing a charge generating agent. Any of the laminated photosensitive layers in which the (charge generation layer) and the layer containing the charge transport agent (charge transport layer) are separated may be used.
In the electrophotographic photoreceptor for wet development of the present invention, examples of the charge generator include phthalocyanine pigments such as metal-free phthalocyanine, titanyl phthalocyanine (TiOPc), hydroxygallium phthalocyanine, chlorogallium phthalocyanine; disazo pigment, disazo condensation pigment, Monoazo pigments, perylene pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azulenium pigments, cyanine pigments, pyrylium salts, ansanthrone pigments, triphenyl Examples include methane pigments, selenium pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments, and the like. The charge generating agent may be appropriately selected according to the wavelength of the exposure light source of the image forming apparatus. The charge generators exemplified above may be used alone or in admixture of two or more.

  A digital optical image forming apparatus such as a laser beam printer generally uses a semiconductor laser (LD) or a light emitting diode (LED) as an exposure light source, and its wavelength is around 680 to 830 nm (near infrared region). Mainstream. Therefore, when the electrophotographic photoreceptor for wet development of the present invention is used in an image forming apparatus of a digital optical system, it is preferable to use a metal-free phthalocyanine or titanyl having excellent sensitivity in the near infrared region as a charge generator. And phthalocyanine pigments such as phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine.

  The crystal form of the phthalocyanine pigment is not particularly limited. For example, the metal-free phthalocyanine is preferably X-type or τ-type. The titanyl phthalocyanine has α type (having main diffraction peaks at Bragg angles (2θ ± 0.2 °) of 7.6 ° and 28.6 ° in X-ray diffraction spectrum) or Y type (Bragg angle (2θ (± 0.2 °) having a main diffraction peak at 27.2 °) is preferable. The hydroxygallium phthalocyanine is preferably V type, and the chlorogallium phthalocyanine is preferably type II.

When the electrophotographic photoreceptor for wet development of the present invention is used in an analog optical image forming apparatus that uses a white light source such as a halogen lamp as an exposure light source, the charge generator is preferably sensitive to the visible region. And perylene pigments having a bisazo pigment.
In the electrophotographic photoreceptor for wet development of the present invention, as the charge transfer agent, holes having a molecular weight of 900 or more having a site represented by the general formula (h1) or the general formula (h2) as described above. There is no particular limitation except that at least a transport agent is included, and other various hole transport agents and electron transport agents can be appropriately selected and used in combination with the hole transport agent .

  As the hole transport agent, for example, a compound obtained by substituting one, two or three diarylamino groups which may have a substituent on an aromatic hydrocarbon which may have a substituent (specifically, For example, N, N, N ′, N′-tetraphenylbenzidine compound, N, N, N ′, N′-tetraphenylphenylenediamine compound, N, N, N ′, N′-tetraphenylnaphthylenediamine Compounds, N, N, N ′, N′-tetraphenylphenanthrylenediamine compounds, for example, styryl compounds such as 9- (4-diethylaminostyryl) anthracene, etc.); 2,5-di (4- Oxadiazole compounds such as methylaminophenyl) -1,3,4-oxadiazole; carbazole compounds such as polyvinylcarbazole; 1-phenyl- -Pyrazoline compounds such as (p-dimethylaminophenyl) pyrazoline; organic polysilane compounds, hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds Compounds, triazole compounds, and the like.

  In the above-mentioned “compound formed by substituting one, two or three diarylamino groups which may have a substituent on an aromatic hydrocarbon which may have a substituent”, an aromatic which may have a substituent Examples of the aromatic hydrocarbon of the hydrocarbon include benzene, naphthalene, phenanthrene, anthracene, biphenyl, o-, m-, p-terphenyl, binaphthalene, stilbene, styryl stilbene, and the like.

  In addition, examples of the substituent of the aromatic hydrocarbon which may have a substituent include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group, and an arylalkenyl group. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, sec-pentyl, 2-methylpentyl, tert- C1-C6 alkyl groups, such as pentyl, n-hexyl, and isohexyl, are mentioned. Examples of the cycloalkyl group include cycloalkyl groups having 3 to 8 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of the alkenyl group include alkenyl groups having 1 to 6 carbon atoms such as vinyl, 1-propenyl, allyl, isopropenyl, 2-butenyl, 1,3-butadienyl, 1-pentenyl, 2-hexenyl and the like. . Examples of the aryl group include phenyl, o, m or p-tolyl, 2,3-, 2,4-, 2,5-, 3,4- or 3,5-xylyl, o, m or p-cumenyl. , Aryl groups having 6 to 18 carbon atoms, such as mesityl, naphthyl and biphenyl. Examples of the aralkyl group include benzyl, 1-phenylethyl, phenethyl, 1-phenylpropyl, benzhydryl, o, m or p-methylbenzyl, 2,3-, 2,4-, 2,5-, 3,4 -Or an aralkyl group having 7 to 18 carbon atoms such as 3,5-dimethylbenzyl. Examples of the arylalkenyl group include arylalkenyl groups having 8 to 12 carbon atoms such as styryl and cinnamyl.

In addition, in the above-mentioned “compound formed by substituting one, two or three diarylamino groups which may have a substituent on an aromatic hydrocarbon which may have a substituent”, it may have a substituent. Examples of the diarylamino group of the diarylamino group include diphenylamino, dinaphthylamino, dibenzylamino, distyrylamino and the like.
Examples of the substituent of the diarylamino group that may have a substituent include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group, and an arylalkenyl group. Examples of these groups include the same groups as those exemplified above.

Oite wet developing electrophotographic photoconductor of the present invention, as a hole transporting agent has a portion represented by at least the general formula (h1) or the general formula (h2), the molecular weight is used more than 900 compounds Thus, as is clear from the results of the examples described later, when the image forming process is repeatedly performed using a wet developer containing a hydrocarbon solvent, the elution amount of the hole transport agent is further suppressed. Can do.

  Examples of the electron transfer agent include benzoquinone compounds, naphthoquinone compounds, anthraquinone compounds, diphenoquinone compounds, dinaphthoquinone compounds, naphthalene tetracarboxylic acid diimide compounds, fluorenone compounds, malononitrile compounds, thiopyran compounds, tri Examples thereof include nitrothioxanthone compounds, dinitroanthracene compounds, dinitroacridine compounds, nitroantharaquinone compounds, and dinitroanthraquinone compounds.

  The electron transport agent used in the electrophotographic photoreceptor for wet development of the present invention is preferably a compound having a molecular weight of 600 or more among those exemplified above. By using such an electron transfer agent, as is clear from the results of Examples described later, when the image forming process is repeatedly performed using a wet developer containing a hydrocarbon solvent, the electron transfer agent and the positive transfer agent are used. The elution amount of the pore transport agent can be further suppressed.

  In the case where the electrophotographic photoreceptor for wet development of the present invention is a so-called single layer type photoreceptor having a single layer type photosensitive layer, the photosensitive layer includes, for example, the charge generator, the charge transport agent, and The polyarylate resin (binder resin) having the repeating unit represented by the above general formula (1) is dispersed or dissolved in a dispersion medium described later together with other components described later as required, and thus the photosensitive material thus obtained. It can be produced by applying a coating liquid for layer formation onto a conductive substrate and drying it. The photosensitive layer may be formed directly on the conductive substrate or may be formed via an undercoat layer (barrier layer). Further, a protective layer may be formed on the surface of the photoreceptor.

  Examples of the dispersion medium for preparing a coating solution for forming a photosensitive layer include alcohols such as methanol, ethanol, isopropanol, and butanol; aliphatic hydrocarbons such as n-hexane, octane, and cyclohexane; benzene, toluene, Aromatic hydrocarbons such as xylene; Halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, chlorobenzene; Ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether; Acetone, methyl ethyl ketone Ketones such as cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethylformaldehyde, dimethylformamide, and dimethylsulfoxide It is below. These dispersion media may be used alone or in combination of two or more.

  Other components include, for example, dispersants, sensitizers; antioxidants, radical scavengers, singlet quenchers, UV absorbers and other deterioration inhibitors; softeners, plasticizers, surface modifiers, extenders , Thickeners, dispersion stabilizers, waxes, acceptors, donors; surfactants for improving the dispersibility of charge transport agents and charge generators, smoothness of the photosensitive layer surface, leveling agents, and the like. Examples of the dispersant include a dispersant for improving the dispersibility of the charge generating agent in the binder resin. Examples of such a dispersant include disazo yellow, dianisidine orange, pyrazolone orange, Examples include azo pigments such as pyrazolone red. Examples of the sensitizer include terphenyl, halonaphthoquinones, acenaphthylene, and the like.

The photosensitive layer forming coating solution is obtained by, for example, dispersing and mixing a charge generator, a charge transport agent, a binder resin, and the like together with a dispersion medium using a roll mill, a ball mill, an attritor, a paint shaker, an ultrasonic disperser, and the like. Can be prepared.
The thickness of the single-layer type photosensitive layer is not particularly limited, but is preferably 5 to 100 μm, and more preferably 10 to 50 μm.

  In the single-layer type photosensitive layer, the content ratio of the charge generator is not particularly limited, but is preferably 0.1 to 50 parts by weight, more preferably 0.5 to 30 parts by weight with respect to 100 parts by weight of the binder resin. Part. Although the content rate of a positive hole transport agent is not specifically limited, Preferably it is 10-200 weight part with respect to 100 weight part of binder resin, More preferably, it is 20-100 weight part. Although the content rate of an electron transfer agent is not specifically limited, Preferably it is 5-100 weight part with respect to 100 weight part of binder resin, More preferably, it is 10-80 weight part. In the case where the hole transport agent and the electron transport agent are used in combination, the total amount of the hole transport agent and the electron transport agent is not particularly limited, but is preferably 20 to 300 parts by weight with respect to 100 parts by weight of the binder resin. More preferably, it is 30 to 200 parts by weight.

In the case where the electrophotographic photoreceptor for wet development of the present invention is a so-called laminated photoreceptor having a laminated photosensitive layer, the photosensitive layer is formed, for example, by first forming a charge generation layer on a conductive substrate. Thus, it can be manufactured by forming a charge transport layer on the surface of the charge generation layer.
The charge generation layer is formed by, for example, forming the charge generation layer obtained by dispersing or dissolving the charge generation agent and the binder resin in the dispersion medium together with the charge transport agent and the other components as necessary. It can be produced by applying a coating solution for coating on a conductive substrate and drying it. The charge transport layer may be, for example, the above-described charge transport agent and the polyarylate resin (binder resin) having the repeating unit represented by the general formula (1), together with the above other components, if necessary, It can be prepared by dispersing or dissolving in a medium, coating the charge transport layer forming coating solution thus obtained on the charge generation layer and drying.

  The stacking order of the charge generation layer and the charge transport layer may be the reverse order of the above case, but in general, the charge generation layer is thin and the strength is not sufficient. The stacking order is preferable. Of the charge generation layer and the charge transport layer, the layer formed on the conductive substrate side may be formed directly on the conductive substrate or may be formed via an undercoat layer. Further, a protective layer may be formed on the surface of the charge generation layer and the charge transport layer formed on the outer surface side of the photoreceptor.

Examples of the dispersion medium in the charge generation layer forming coating solution and the charge transport layer forming coating solution include the same ones as described above.
The charge generation layer forming coating liquid and the charge transport layer forming coating liquid are, for example, a predetermined component such as a charge generating agent, a charge transporting agent, a binder resin, a dispersion medium, a roll mill, a ball mill, an attritor, a paint shaker, It can be prepared by dispersing and mixing using an ultrasonic disperser or the like.

The thickness of the multilayer photosensitive layer is not particularly limited, but the charge generation layer is preferably 0.01 to 5 μm, more preferably 0.1 to 3 μm, and the charge transport layer is preferably 2 to 2 μm. It is 100 micrometers, More preferably, it is 5-50 micrometers.
In the charge generation layer of the multilayer photosensitive layer, the content ratio of the charge generation agent is not particularly limited, but is preferably 5 to 1000 parts by weight, more preferably 30 to 500 parts with respect to 100 parts by weight of the binder resin. Parts by weight. In the charge transport layer of the multilayer photosensitive layer, the content ratio of the charge transport agent (hole transport agent or electron transport agent) is not particularly limited, but is preferably 10 to 500 parts by weight, more preferably 25 to 25 parts by weight. 200 parts by weight.

  The electrophotographic photosensitive member of the present invention executes image formation by wet development using an image forming apparatus such as an electrostatic copying machine, a facsimile machine, or a laser beam printer, in particular, using a wet developer using a paraffinic solvent. The image forming apparatus is suitable.

EXAMPLES Next, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited by the following Example.
<Synthesis of polyarylate resin>
Reference example 1
1,1-bis (4-hydroxyphenyl) ethane 42.9 g (0.20 mol), t-butylphenol 1.5 g (0.010 mol), sodium hydroxide 16.0 g (0.40 mol), and water 1.1 liters was blended to prepare an alkaline aqueous solution, and trimethylbenzylammonium chloride as a polymerization catalyst was further added. The addition amount of the polymerization catalyst was adjusted to 0.5 mol% with respect to 1,1-vir (4-hydroxyphenyl) ethane, and the alkaline aqueous solution was vigorously stirred after the addition of the polymerization catalyst. On the other hand, 20.2 g (0.10 mol) of terephthaloyl chloride and 20.2 g (0.10 mol) of isophthaloyl chloride were dissolved in 0.75 liter of dichloromethane to prepare a dichloromethane solution.

  Next, the dichloromethane solution was added to the alkaline aqueous solution under stirring to initiate the polymerization reaction. The polymerization reaction was carried out for 3 hours under stirring, and the temperature of the reaction solution during the polymerization reaction was adjusted to 20 ° C. After 3 hours from the addition of the dichloromethane solution, acetic acid was added to the reaction solution to terminate the polymerization reaction, and the reaction solution was washed with water. Washing was repeated until the aqueous layer after separation became neutral.

Next, the organic layer taken out from the reaction solution after washing by water is slowly added to methanol under stirring, and the precipitate is separated by furnace and dried, whereby 60 g of polyarylate resin (Resin-1) is obtained. Got.
The polyarylate resin (Resin-1) is a polyarylate having a repeating unit represented by the general formula (1), specifically, a repeating unit represented by the following formula (RU-1a), The repeating unit represented by the formula (RU-1b) is contained at a molar ratio of 50:50.

The viscosity average molecular weight Mv of the polyarylate resin (Resin-1) was 50,000.
The viscosity average molecular weight Mv of the polyarylate resin was calculated by a viscosity method as a conversion value using bisphenol A type polycarbonate resin as a standard substance. The viscosity average molecular weight Mv of the standard material was calculated first based on the intrinsic viscosity [η] (20 ° C., solvent: methylene chloride) of the standard material, and then based on the Schnell equation shown below. In calculating the intrinsic viscosity, the viscosity of the diluted solution was measured with an Ostwald viscometer.
[Η] = 1.23 × 10 ⁻⁴ Mv ^0.83
Reference example 2
Other than using a combination of 27.8 g (0.10 mol) of 4,4′-biphenyldicarbonyl dichloride and 20.2 g (0.10 mol) of isophthaloyl chloride in place of the combination of terephthaloyl chloride and isophthaloyl chloride. Prepared a dichloromethane solution in the same manner as in Reference Example 1. In addition, except that the same alkaline aqueous solution as used in Reference Example 1 and the above dichloromethane solution were used, the polymerization reaction was carried out in the same manner as in Reference Example 1 to obtain 61 g of polyarylate resin (Resin-2). Obtained.

  The polyarylate resin (Resin-2) is a polyarylate having a repeating unit represented by the general formula (1), specifically, a repeating unit represented by the following formula (RU-2a), The repeating unit represented by the formula (RU-1b) is contained at a molar ratio of 50:50.

The viscosity average molecular weight Mv of the polyarylate resin (Resin-2) was 50200.
<Manufacture of electrophotographic photoreceptor>
Example 1
4 parts by weight of an X-type metal-free phthalocyanine represented by the following formula (CGM-1) as a charge generating agent, 40 parts by weight of a stilbene amine compound represented by the following formula (HTM-1) as a hole transporting agent, electron transport 50 parts by weight of a naphthoquinone compound represented by the following formula (ETM-1) as an agent, 100 parts by weight of polyarylate resin (Resin-1) obtained in Reference Example 1 as a binder resin, and dimethyl silicone as a leveling agent 0.1 parts by weight of oil (product number “KF-96-50CS” manufactured by Shin-Etsu Chemical Co., Ltd.) and 750 parts by weight of tetrahydrofuran as a solvent are mixed and dispersed for 50 hours with an ultrasonic disperser. Thus, a coating solution for a single-layer type photosensitive layer was prepared.

The molecular weight of the stilbene amine compound (C ₈₀ H ₆₄ N ₂ ) represented by the above formula (HTM-1) is 1057.45, and the naphthoquinone compound (C ₃₉ H ₂₈ O represented by the above formula (ETM-1)). ₈ ) The molecular weight is 624.65.
Next, the coating solution is applied to the surface of an anodized steel pipe (diameter 30 mm, length 254 mm) having a mirror-finished surface, and is dried with hot air at 140 ° C. for 20 minutes to obtain a film thickness of 20 μm. An electrophotographic photosensitive member (photosensitive drum) having a single-layer type photosensitive layer was manufactured.

Example 2
As binder resin, it replaced with the said polyarylate resin (Resin-1), and carried out similarly to Example 1 except having used 100 weight part of polyarylate resin (Resin-2) obtained by the said reference example 2. A coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used.

Comparative Example 1
Instead of the polyarylate resin (Resin-1), 100 parts by weight of a polycarbonate resin (Resin-3; viscosity average molecular weight Mv49500) composed of a repeating unit represented by the following formula (RU-3a) was used as the binder resin. Except for the above, a coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used.

Comparative Example 2
As a binder resin, instead of the polyarylate resin (Resin-1), a repeating unit represented by the following formula (RU-4a) and a repeating unit represented by the following formula (RU-4b) have a molar ratio of 50:50. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 100 parts by weight of the polyarylate resin (Resin-4; viscosity average molecular weight Mv43900) contained in 1 was used. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used.

Comparative Example 3
As a binder resin, instead of the polyarylate resin (Resin-1), a repeating unit represented by the following formula (RU-5a) and a repeating unit represented by the following formula (RU-5b) are in a molar ratio of 50:50. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 100 parts by weight of the polyarylate resin (Resin-5; viscosity average molecular weight Mv51200) contained in 1 was used. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used.

Comparative Example 4
As a binder resin, instead of the polyarylate resin (Resin-1), a repeating unit represented by the following formula (RU-6a) and a repeating unit represented by the following formula (RU-6b) are in a molar ratio of 50:50. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 100 parts by weight of the polyarylate resin (Resin-6; viscosity average molecular weight Mv50000) contained in 1 was used. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used.

Comparative Example 5
Instead of the polyarylate resin (Resin-1), 100 parts by weight of a polyarylate resin (Resin-7; viscosity average molecular weight Mv49800) having a repeating unit represented by the following formula (RU-7) was used as the binder resin. Except for this, a coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. In addition, the bisphenol part of the following repeating unit (RU-7) corresponds to the bisphenol part (B-1) described in Patent Document 2.

Comparative Example 6
As a binder resin, instead of the polyarylate resin (Resin-1), a repeating unit represented by the following formula (RU-8a) and a repeating unit represented by the following formula (RU-8b) have a molar ratio of 50:50. A coating solution for a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 100 parts by weight of the polyarylate resin (Resin-8; viscosity average molecular weight Mv49600) contained in 1 was used. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. In addition, the bisphenol part of the following repeating units (RU-8a) and (RU-8b) corresponds to the bisphenol part (B-17) described in Patent Document 2.

<Performance evaluation of electrophotographic photoreceptor>
The electrophotographic photoreceptors obtained in Examples 1 and 2 and Comparative Examples 1 to 6 were subjected to performance evaluation shown in the following (I) to (IV).
(I) Measurement of Bright Potential The sensitivity of the electrophotographic photoreceptors obtained in Examples 1-2 and Comparative Examples 1-6 was measured using a drum sensitivity tester manufactured by GENTEC. The measurement was performed according to the following procedure. First, an applied voltage is applied to the surface of the electrophotographic photosensitive member to charge the surface potential to +850 V, and then a single color having a wavelength of 780 nm is extracted from white light from a halogen lamp (exposure light source) using a bandpass filter. The surface of the electrophotographic photosensitive member was exposed by irradiation with light (half-width 20 nm, light intensity 1.0 μJ · cm ⁻² ) for 40 milliseconds. Thus, the surface potential (bright potential; unit V) at the time when 0.5 seconds elapsed from the start of exposure was measured, and this value was used as the sensitivity of the electrophotographic photosensitive member. The smaller the bright potential value, the higher the sensitivity of the electrophotographic photosensitive member.

(II) Measurement of elution amount of hole transport agent The electrophotographic photoreceptors (photoreceptor drums) obtained in Examples 1 to 2 and Comparative Examples 1 to 6, respectively, were isoparaffinic solvents (manufactured by Exxon Chemical Co., Ltd.). (Product name “Isopar L”) was immersed in 500 mL and allowed to stand for 600 hours. Next, the isoparaffinic solvent is taken out, the absorbance thereof is measured, and the content of the hole transport agent (HTM) in the isoparaffinic solvent (that is, the amount of HTM elution) based on the calibration curve prepared in advance. Unit g / cm ³ ) was calculated. It shows that the smaller the elution amount of the hole transfer agent, the better the solvent resistance of the hydrocarbon solvent and the durability when used in wet development.

(III) Sensitivity change after immersion in solvent The method described in (I) above was used except that the electrophotographic photoreceptor used in the above (II) “Measurement of HTM elution amount” was used. The light potential (unit V) of the electrophotographic photosensitive member was measured. Next, in each Example and Comparative Example, a change amount ΔV (unit V) with respect to the bright potential measured in the above (1) was calculated to evaluate a sensitivity change after immersion in the solvent. The smaller the absolute value of the change amount ΔV, the smaller the change in sensitivity after repeated use by wet development, indicating that the solvent resistance of hydrocarbon solvents and the durability when used in wet development are excellent. .

(IV) Change in drum appearance The surface state of the electrophotographic photosensitive member (photosensitive drum) subjected to the “measurement of HTM elution amount” in (II) above is visually observed, and the photosensitive layer is damaged such as cracks ( By confirming whether or not (cracks) had occurred, the appearance change after repeated use by wet development (solvent resistance with respect to hydrocarbon solvents) was evaluated. The criteria for evaluation are as follows.
A: No damage (crack) on the surface of the photosensitive drum was observed.
B: A practically inappropriate amount of damage (cracks) was observed on the surface of the photosensitive drum.
C: Many damages (cracks) were observed on the surface of the photosensitive drum.

  The evaluation results of the performance evaluation shown in the above (I) to (IV) are shown in Table 1 together with the formula number of the binder resin used for forming the photosensitive layer.

  As is clear from the results shown in Table 1, in Examples 1 and 2 in which the binder resin forming the photosensitive layer is a polyarylate resin having a repeating unit represented by the general formula (1), high sensitivity is maintained. However, elution of the hole transport agent into the wet developer, reduction in sensitivity after repeated use due to wet development, and deterioration of the appearance of the photosensitive drum can be suppressed. Solvent resistance and wetness of hydrocarbon solvents Durability when used for development could be improved.

In contrast, in Comparative Examples 1 to 6, where the binder resin forming the photosensitive layer is a polycarbonate resin or a polyarylate resin having no repeating unit represented by the general formula (1), the sensitivity is high. The elution amount of the hole transport agent in the hydrocarbon solvent was large, and the sensitivity was lowered after repeated use by wet development and the appearance of the photosensitive drum was remarkably deteriorated.
<Manufacture of electrophotographic photoreceptor>
Example 3
In the same manner as in Example 1, except that 4 parts by weight of titanyl phthalocyanine represented by the following formula (CGM-2) was used in place of X-type metal-free phthalocyanine (CGM-1) as the charge generating agent. A coating solution for a layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. In addition, the titanyl phthalocyanine shown by a following formula (CGM-2) can be produced according to the method described in the manufacture example 1 of patent 3463032, for example.

Example 4
As a charge generating agent, in place of X-type metal-free phthalocyanine (CGM-1), except that 4 parts by weight of hydroxygallium phthalocyanine represented by the following formula (CGM-3) was used, the same as in Example 1, A coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used.

Example 5
As a charge generating agent, in place of X-type metal-free phthalocyanine (CGM-1), except that 4 parts by weight of chlorogallium phthalocyanine represented by the following formula (CGM-4) was used, the same as in Example 1, A coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used.

<Performance evaluation of electrophotographic photoreceptor>
The electrophotographic photoreceptors obtained in Examples 3 to 5 were subjected to the performance evaluations (I) to (IV). The evaluation results are shown in Table 2 together with the formula number of the charge generating agent (CGM) used for forming the photosensitive layer.

  As is clear from the results shown in Table 2, the electrophotographic photoreceptors obtained in Examples 3 to 5 are the same as the electrophotographic photoreceptor obtained in Example 1 except that the binder resin forming the photosensitive layer is the above. Since it is a polyarylate resin having a repeating unit represented by the general formula (1), elution of a hole transport agent with respect to a wet developer, sensitivity reduction after repeated use by wet development, and photosensitivity while maintaining high sensitivity. The appearance deterioration of the body drum could be suppressed, and the solvent resistance against the wet developer could be improved.

<Manufacture of electrophotographic photoreceptor>
Comparative Example 7
Example, except that 40 parts by weight of a biphenylenediamine compound represented by the following formula (HTM-2) was used in place of the stilbeneamine compound represented by the above formula (HTM-1) as the hole transport agent. In the same manner as in No. 1, a coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. The molecular weight of the biphenylenediamine compound (C ₇₀ H ₆₄ N ₂ ) represented by the following formula (HTM-2) is 916.25.

Example 6
Examples Except that 40 parts by weight of a stilbene amine compound represented by the following formula (HTM-3) was used in place of the stilbene amine compound represented by the above formula (HTM-1) as a hole transport agent. In the same manner as in No. 1, a coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. The molecular weight of the stilbene amine compound (C ₇₈ H ₄₀ N ₂ ) represented by the following formula (HTM-3) is 1045.52.

(In the formula (HTM-3), nC ₈ H ₁₇ represents a linear octyl group.)
Example 7
Example except that 40 parts by weight of a stilbene amine compound represented by the following formula (HTM-4) was used instead of the stilbene amine compound represented by the above formula (HTM-1) as a hole transport agent. In the same manner as in No. 1, a coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. The molecular weight of the stilbene amine compound (C ₁₁₇ H ₉₉ N ₃ ) represented by the following formula (HTM-4) is 1547.11.

Comparative Example 8
Example except that 40 parts by weight of a stilbene amine compound represented by the following formula (HTM-5) was used instead of the stilbene amine compound represented by the above formula (HTM-1) as a hole transport agent. In the same manner as in No. 1, a coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. The molecular weight of the stilbene amine compound (C ₅₂ H ₄₈ N ₂ ) represented by the following formula (HTM-5) is 700.95.

Comparative Example 9
Except that 40 parts by weight of the triphenylamine compound represented by the following formula (HTM-6) was used in place of the stilbeneamine compound represented by the above formula (HTM-1) as the hole transport agent. In the same manner as in Example 1, a coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. The molecular weight of the triphenylamine compound (C ₃₄ H ₂₉ N) represented by the following formula (HTM-6) is 451.60.

<Performance evaluation of electrophotographic photoreceptor>
For the electrophotographic photoreceptors obtained in Examples 6 and 7 and Comparative Examples 7 to 9 , performance evaluations (I) to (IV) were performed. The evaluation results are shown in Table 3 together with the formula number of the hole transfer agent (HTM) used for forming the photosensitive layer.

As is clear from the results shown in Table 3, the electrophotographic photoreceptors obtained in Examples 6 and 7 are the same as the electrophotographic photoreceptor obtained in Example 1, except that the binder resin forming the photosensitive layer is the above. Since it is a polyarylate resin having a repeating unit represented by the general formula (1), elution of a hole transport agent with respect to a wet developer, sensitivity reduction after repeated use by wet development, and photosensitivity while maintaining high sensitivity. The appearance deterioration of the body drum could be suppressed, and the solvent resistance against the wet developer could be improved.

In addition, Examples 1, 6, and 7 using a hole transporting agent having a molecular weight of 900 or more having a site represented by the general formula (h1) or the general formula (h2), and the general formula (H1) or Comparative Example 7 using a material having no site represented by the general formula (h2) and a site represented by the general formula (h1) or the general formula (h2), but having a molecular weight of 900 As is clear from the comparison with Comparative Examples 8 and 9 using less than the above, in Examples 1, 6 , and 7 , the elution amount of the hole transport agent with respect to the wet developer is further reduced. I was able to.

<Manufacture of electrophotographic photoreceptor>
Example 8
The same electron transporting agent as in Example 1 except that 50 parts by weight of a naphthoquinone compound represented by the following formula (ETM-2) was used instead of the naphthoquinone compound represented by the above formula (ETM-1). Thus, a coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. The molecular weight of the naphthoquinone compound (C ₄₂ H ₃₀ O ₁₀ ) represented by the following formula (ETM-2) is 718.72.

Example 9
The same electron transporting agent as in Example 1 except that 50 parts by weight of a naphthoquinone compound represented by the following formula (ETM-3) was used instead of the naphthoquinone compound represented by the above formula (ETM-1). Thus, a coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. The molecular weight of the naphthoquinone compound (C ₂₄ H ₁₆ O ₄ ) represented by the following formula (ETM-3) is 368.38.

Example 10
As an electron transporting agent, in place of the naphthoquinone compound represented by the above formula (ETM-1), the same as Example 1 except that 50 parts by weight of the diphenoquinone compound represented by the following formula (ETM-4) was used. Thus, a coating solution for a single-layer type photosensitive layer was prepared. Next, an electrophotographic photosensitive member having a single-layer type photosensitive layer having a thickness of 20 μm was produced in the same manner as in Example 1 except that the coating solution thus obtained was used. The molecular weight of the diphenoquinone compound (C ₂₂ H ₂₈ O ₂ ) represented by the following formula (ETM-4) is 324.46.

<Performance evaluation of electrophotographic photoreceptor>
With respect to the electrophotographic photoreceptors obtained in Examples 8 to 10 , performance evaluations (I) to (IV) were performed. The evaluation results are shown in Table 4 together with the formula number of the electron transfer agent (ETM) used for forming the photosensitive layer.

As is clear from the results shown in Table 4, in the electrophotographic photoreceptors obtained in Examples 8 to 10 , the binder resin forming the photosensitive layer is the same as the electrophotographic photoreceptor obtained in Example 1. Since it is a polyarylate resin having a repeating unit represented by the general formula (1), elution of a hole transport agent with respect to a wet developer, sensitivity reduction after repeated use by wet development, and photosensitivity while maintaining high sensitivity. The appearance deterioration of the body drum could be suppressed, and the solvent resistance against the wet developer could be improved.

Further, as is clear from the comparison between Examples 1 and 8 using an electron transporting agent having a molecular weight of 600 or more and Examples 9 and 10 using a molecular weight of less than 600, the electron transporting agent is clear. By using an agent having a molecular weight of 600 or more, the elution amount of the hole transport agent with respect to the wet developer could be further reduced. Usually, when the molecular weight of the electron transport agent is less than 600, elution of the electron transport agent to the wet developer tends to occur relatively easily, and in general, the electron transport agent is present in the same photosensitive layer. However, when the molecular weight of the electron transport agent is 600 or more, the elution of the electron transport agent to the wet developer is less likely to occur. It is assumed that the elution can be suppressed.

<Manufacture of electrophotographic photoreceptor>
Example 11
1 part by weight of titanyl phthalocyanine represented by the above formula (CGM-1) as a charge generating agent, 1 part by weight of polyvinyl butyral (trade name “ESREC BM-1” manufactured by Sekisui Chemical Co., Ltd.) as a binder resin, and Then, 50 parts by weight of diacetone alcohol as a solvent was blended and dispersed and dissolved by a ball mill to prepare a coating solution for a charge generation layer.

  On the other hand, 60 parts by weight of a stilbene amine compound represented by the above formula (HTM-1) as a hole transport agent, 100 parts by weight of the polyarylate resin (Resin-1) as a binder resin, and dimethyl silicone oil ( The coating solution for the charge transport layer is prepared by blending 0.1 parts by weight of the above-mentioned “KF-96-50CS”) and 700 parts by weight of tetrahydrofuran as a solvent, and mixing and dispersing with an ultrasonic disperser. did.

  The charge generation layer coating solution is applied to the surface of an alumite steel tube (diameter 30 mm, length 254 mm) having a mirror-finished surface as a conductive substrate by a dipping method. A charge generation layer having a thickness of 0.3 μm was formed by heating and drying for minutes. Next, the charge transport layer coating solution was applied to the surface of the charge generation layer thus obtained by dipping, and heated and dried at 130 ° C. for 30 minutes to form a charge transport layer having a thickness of 25 μm. In this way, an electrophotographic photosensitive member (photosensitive drum) including a laminated photosensitive layer obtained by laminating the charge generation layer and the charge transport layer in this order on a conductive substrate was produced.

Example 12
As in Example 11 , except that 100 parts by weight of the polyarylate resin (Resin-2) was used instead of the polyarylate resin (Resin-1) as the binder resin of the coating solution for forming the charge transport layer. Thus, a coating solution for the charge transport layer was prepared. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Comparative Example 10
As in Example 11 , except that 100 parts by weight of the polycarbonate resin (Resin-3) was used instead of the polyarylate resin (Resin-1) as the binder resin of the charge transport layer forming coating solution. A coating solution for the charge transport layer was prepared. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Comparative Example 11
As in Example 11 , except that 100 parts by weight of the polyarylate resin (Resin-4) was used in place of the polyarylate resin (Resin-1) as the binder resin of the coating solution for forming the charge transport layer. Thus, a coating solution for the charge transport layer was prepared. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Comparative Example 12
As in Example 11 , except that 100 parts by weight of the polyarylate resin (Resin-5) was used instead of the polyarylate resin (Resin-1) as the binder resin of the coating solution for forming the charge transport layer. Thus, a coating solution for the charge transport layer was prepared. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Comparative Example 13
As in Example 11 , except that 100 parts by weight of the polyarylate resin (Resin-6) was used instead of the polyarylate resin (Resin-1) as the binder resin of the coating solution for forming the charge transport layer. Thus, a coating solution for the charge transport layer was prepared. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Comparative Example 14
As in Example 11 , except that 100 parts by weight of the polyarylate resin (Resin-7) was used in place of the polyarylate resin (Resin-1) as the binder resin of the coating solution for forming the charge transport layer. Thus, a coating solution for the charge transport layer was prepared. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Comparative Example 15
As in Example 11 , except that 100 parts by weight of the polyarylate resin (Resin-8) was used in place of the polyarylate resin (Resin-1) as the binder resin of the coating solution for forming the charge transport layer. Thus, a coating solution for the charge transport layer was prepared. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

<Performance evaluation of electrophotographic photoreceptor>
The electrophotographic photoreceptors obtained in Examples 11 and 12 and Comparative Examples 10 to 15 were subjected to the performance evaluation shown in the above (I) to (IV). The evaluation results are shown in Table 5 together with the formula number of the charge generating agent (CGM) used for forming the photosensitive layer.

As is apparent from shown to result in Table 5, the binder resin forming the photosensitive layer, the polyarylate resin Examples 11 and 12 having a repeating unit represented by the above general formula (1), a high sensitivity While maintaining, it is possible to suppress elution of the hole transport agent with respect to the wet developer, reduction in sensitivity after repeated use due to wet development, and deterioration of the appearance of the photoreceptor drum, and to improve the solvent resistance against the wet developer. I was able to.

In contrast, in Comparative Examples 10 to 15 in which the binder resin forming the photosensitive layer is a polycarbonate resin or a polyarylate resin having no repeating unit represented by the general formula (1), the sensitivity is high. The amount of elution of the hole transport agent with respect to the wet developer was large, and the sensitivity was lowered after repeated use by wet development and the appearance deterioration of the photosensitive drum was remarkable.
<Manufacture of electrophotographic photoreceptor>
Comparative Example 16
In place of the stilbene amine compound represented by the above formula (HTM-1), the biphenylenediamine compound (C ₇₀ H) represented by the above formula (HTM-2) may be used as the hole transport agent in the charge transport layer forming coating solution. A coating solution for the charge transport layer was prepared in the same manner as in Example 11 except that 40 parts by weight of ₆₄ N ₂ C; molecular weight 916.25) was used. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Example 13
Instead of the stilbene amine compound represented by the above formula (HTM-1), the stilbene amine compound (C ₇₈ H) represented by the above formula (HTM-3) may be used as the hole transport agent for the charge transport layer forming coating solution. A coating solution for a charge transport layer was prepared in the same manner as in Example 11 except that 40 parts by weight of ₄₀ N ₂ ; molecular weight 1045.52) was used. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Example 14
Instead of the stilbene amine compound represented by the above formula (HTM-1), the stilbene amine compound (C ₁₁₇ H) represented by the above formula (HTM-4) may be used as the hole transport agent for the coating solution for forming the charge transport layer. A coating solution for a charge transport layer was prepared in the same manner as in Example 11 except that 40 parts by weight of ₉₉ N ₃ ; molecular weight 1547.11) was used. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Comparative Example 17
Instead of the stilbene amine compound represented by the above formula (HTM-1), the stilbene amine compound (C ₅₂ H) represented by the above formula (HTM-5) may be used as the hole transport agent for the charge transport layer forming coating solution. ₄₈ N ₂ ; molecular weight 700.95) was used in the same manner as in Example 11 except that 40 parts by weight was used to prepare a coating solution for the charge transport layer. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

Comparative Example 18
Instead of the stilbene amine compound represented by the above formula (HTM-1), the triphenylamine compound (C ₃₄ ) represented by the above formula (HTM-6) may be used as the hole transport agent for the coating solution for forming the charge transport layer. A coating solution for a charge transport layer was prepared in the same manner as in Example 11 except that 40 parts by weight of H ₂₉ N; molecular weight 451.60) was used. Next, a film thickness was formed on the conductive substrate in the same manner as in Example 11 except that the same charge generating layer coating solution as used in Example 11 and the above charge transport layer coating solution were used. An electrophotographic photoreceptor was produced by laminating a 0.3 μm charge generation layer and a 25 μm charge transport layer in this order.

<Performance evaluation of electrophotographic photoreceptor>
For the electrophotographic photosensitive members obtained in Examples 13 and 14 and Comparative Examples 16 to 18 , the performance evaluations (I) to (IV) were performed. The evaluation results are shown in Table 6 together with the formula number of the hole transfer agent (HTM) used for forming the photosensitive layer.

As shown in Table 6, the electrophotographic photoconductors obtained in Examples 13 and 14 have the same binder resin that forms the outermost charge transport layer as the electrophotographic photoconductor obtained in Example 11. Since it is a polyarylate resin having a repeating unit represented by the general formula (1), elution of a hole transport agent with respect to a wet developer, sensitivity reduction after repeated use by wet development, while maintaining high sensitivity, and Deterioration of the appearance of the photosensitive drum could be suppressed, and the solvent resistance against the wet developer could be improved.

In addition, Examples 11 , 13 , and 14 using a hole transport agent having a molecular weight of 900 or more having a site represented by the general formula (h1) or the general formula (h2), and the general formula (H1) or Comparative Example 16 using a material having no site represented by the general formula (h2) and a site represented by the general formula (h1) or the general formula (h2), but having a molecular weight of 900 As is clear from the comparison with Comparative Examples 17 and 18 that use less than the above, in Examples 11 , 13 , and 14 , the elution amount of the hole transport agent with respect to the wet developer is further reduced. I was able to.

  The present invention is not limited to the above description, and various design changes can be made within the scope of the matters described in the claims.

Claims (6)

An electrophotographic photoreceptor comprising a photosensitive layer on a conductive substrate,
The photosensitive layer contains a charge generator, a charge transport agent and a binder resin,
The binder resin is a polyarylate resin having a repeating unit represented by the following general formula (1), and the charge transfer agent has a site represented by the following general formula (h1) or the following general formula (h2). An electrophotographic photoreceptor for wet development, comprising at least a hole transporting agent having a molecular weight of 900 or more .

(In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a methyl group. Ar represents an arylene group that may have an alkyl group.)

(In the general formula (h1) or the general formula (h2), R ^h1 , R ^h2 , R ^h3 , R ^h4 and R ^h5 are each independently a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, or an aralkyl group. A to e each independently represent an integer of 0 to 3. When a to e are 2 or 3, a plurality of substituents substituted on the same benzene ring are groups different from each other. In addition, when a to e are 2 or 3, two alkyl groups or alkenyl groups substituted on adjacent carbon atoms of the benzene ring are bonded to each other and are saturated or unsaturated together with the benzene ring. A hydrocarbon ring may be formed.)   The polyarylate resin may have two or more repeating units having different structures, represented by the general formula (1), and may have an alkyl group corresponding to Ar in the repeating unit. The arylene group includes a group that binds to the carbonyl group in a positional relationship where the molecular chain of the polyarylate is linear, and a group that binds to the carbonyl group in a positional relationship that forms a bent portion in the molecular chain of the polyarylate. The electrophotographic photosensitive member for wet development according to claim 1, wherein   The wet development according to claim 1, wherein the photosensitive layer is a photosensitive layer composed of a single layer, and the charge transport agent includes a hole transport agent and an electron transport agent. For electrophotographic photoreceptors.   The photosensitive layer is a laminated photosensitive layer comprising a charge generating layer containing the charge generating agent and a charge transporting layer containing the charge transporting agent, and the laminated photosensitive layer is charged from the conductive substrate side. 3. The electrophotographic photoreceptor for wet development according to claim 1, wherein the generation layer and the charge transport layer are formed in this order. Wherein the charge transport agent, characterized in that the molecular weight contains 600 or more electron-transporting agent, a wet developing electrophotographic photoconductor according to any one of claims 1-4. Wherein the charge generating agent, characterized in that metal-free phthalocyanine, at least one selected from the group consisting of titanyl phthalocyanine, hydroxygallium phthalocyanine and chlorogallium phthalocyanine, wet development according to any one of claims 1 to 5 For electrophotographic photoreceptors.