JP2019078870A - Electrophotographic photoreceptor, image forming apparatus, and process cartridge - Google Patents

Abstract

To provide an electrophotographic photoreceptor that can inhibit the occurrence of transfer memory.SOLUTION: An electrophotographic photoreceptor comprises a conductive substrate and a photosensitive layer. The photosensitive layer is a single layer and contains a charge generating agent, a hole transport agent, an electron transport agent, and a binder resin. The electron transport agent contains a first electron transport agent and a second electron transport agent. The first electron transport agent is a compound represented by the following general formula (1). The second electron transport agent is a compound having four types of specific structures.SELECTED DRAWING: None

Description

  The present invention relates to an electrophotographic photosensitive member, an image forming apparatus and a process cartridge.

  The electrophotographic photosensitive member is used as an image carrier in an electrophotographic image forming apparatus (for example, a printer and a multifunction peripheral). The electrophotographic photosensitive member comprises a photosensitive layer. Examples of the electrophotographic photosensitive member include a single layer type electrophotographic photosensitive member and a laminated type electrophotographic photosensitive member. The single-layer type electrophotographic photosensitive member is provided with a photosensitive layer having a charge generation function and a charge transport function. The multi-layered electrophotographic photosensitive member includes a photosensitive layer including a charge generation layer having a charge generation function and a charge transport layer having a charge transport function.

  The photosensitive layer provided in the electrophotographic photosensitive member described in Patent Document 1 contains a compound represented by the following chemical formula (ET-A).

Unexamined-Japanese-Patent No. 2013-117572

  However, according to the study of the present inventors, it has been found that it is difficult to suppress the generation of transfer memory in the electrophotographic photosensitive member described in Patent Document 1.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electrophotographic photosensitive member capable of suppressing the generation of a transfer memory. Another object of the present invention is to provide an image forming apparatus and a process cartridge which suppress the occurrence of image defects.

  The electrophotographic photosensitive member of the present invention comprises a conductive substrate and a photosensitive layer. The photosensitive layer is a single layer, and contains a charge generating agent, a hole transporting agent, an electron transporting agent and a binder resin. The electron transfer agent includes a first electron transfer agent and a second electron transfer agent. The first electron transfer agent is a compound represented by the following general formula (1). The second electron transfer agent is a compound represented by the following general formula (2), general formula (3), general formula (4) or general formula (5).

In the general formula (1), each of R ¹ and R ² independently represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom.

In formula (2), R ¹¹ and R ¹² each independently represent an alkyl group having 1 to 6 carbon atoms. In Formula (3), each of R ¹⁷ and R ¹⁸ independently represents an aryl group having 6 to 14 carbon atoms that may have an alkyl group having 1 to 4 carbon atoms. In the above general formula (4), R ¹⁹ and R ²⁰ each independently represent an alkyl group having 1 to 6 carbon atoms, and R ²¹ has 6 to 14 carbon atoms which may have a halogen atom. The following aryl groups are represented. In the general formula (5), R ²² , R ²³ , R ²⁴ and R ²⁵ each independently represent an alkyl group having 1 to 6 carbon atoms.

  The image forming apparatus of the present invention includes an image carrier, a charging unit, an exposure unit, a developing unit, and a transfer unit. The image carrier is the above-mentioned electrophotographic photosensitive member. The charging unit charges the surface of the image carrier. The charging polarity of the charging unit is positive. The exposure unit exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier. The developing unit develops the electrostatic latent image as a toner image. The transfer unit transfers the toner image from the image carrier to the transfer body while bringing the surface of the image carrier into contact with the transfer body.

  The process cartridge of the present invention comprises the above-described electrophotographic photosensitive member.

  The electrophotographic photosensitive member of the present invention can suppress the occurrence of transfer memory. In addition, the image forming apparatus and the process cartridge of the present invention can suppress the occurrence of image defects.

FIG. 1 is a partial cross-sectional view showing an example of the structure of an electrophotographic photosensitive member according to a first embodiment of the present invention. FIG. 1 is a partial cross-sectional view showing an example of the structure of an electrophotographic photosensitive member according to a first embodiment of the present invention. FIG. 1 is a partial cross-sectional view showing an example of the structure of an electrophotographic photosensitive member according to a first embodiment of the present invention. It is a figure showing an example of the image forming device concerning a second embodiment of the present invention. It is a figure which shows the image which the image ghost produced | generated.

  Hereinafter, although an embodiment of the present invention is described in detail, the present invention is not limited to the following embodiment at all, and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, although description may be suitably abbreviate | omitted about the location where description overlaps, it does not limit the summary of invention. Furthermore, in the present specification, a “system” may be added after the compound name to generically generically refer to the compound and the derivative thereof. When a “system” is added after the compound name to represent a polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative.

  Hereinafter, an alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, 6 carbon atoms Each of the above 14 or less aryl groups and halogen atoms has the following meanings.

  The alkyl group having 1 to 6 carbon atoms is linear or branched and unsubstituted. As an alkyl group having 1 to 6 carbon atoms, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, pentyl group, isopentyl group, neopentyl group And hexyl groups.

  The alkyl group having 1 or more and 4 or less carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an s-butyl group and a t-butyl group.

  The alkoxy group having 1 to 6 carbon atoms is linear or branched and unsubstituted. Examples of the alkoxy group having 1 or more and 6 or less carbon atoms include, for example, methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, s-butoxy group, t-butoxy group, pentyloxy group, iso Examples include pentyloxy group, neopentyloxy group, and hexyloxy group.

  The alkoxy group having 1 to 4 carbon atoms is linear or branched and unsubstituted. As a C1-C4 alkoxy group, a methoxy group, an ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, s-butoxy group, and t-butoxy group are mentioned, for example.

  The aryl group having 6 to 14 carbon atoms is unsubstituted. As an aryl group having 6 to 14 carbon atoms, for example, an unsubstituted aromatic monocyclic hydrocarbon group having 6 to 14 carbon atoms, an unsubstituted aromatic fused bicyclic having 6 to 14 carbon atoms Examples thereof include hydrocarbon groups and unsubstituted aromatic fused tricyclic hydrocarbon groups having 6 to 14 carbon atoms. More specific examples of the aryl group having 6 to 14 carbon atoms include a phenyl group, a naphthyl group, an anthryl group, and a phenanthryl group.

  As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned, for example.

  In addition, in the following, “may have an alkyl group having 1 to 4 carbon atoms” means that part or all of the hydrogen atoms of the functional group are substituted with an alkyl group having 1 to 4 carbon atoms. It means that you may. The same applies to “it may have a halogen atom”.

First Embodiment: Electrophotographic Photoreceptor
The structure of the electrophotographic photosensitive member (hereinafter, may be referred to as a photosensitive member) according to the first embodiment of the present invention will be described. FIGS. 1, 2 and 3 are partial cross-sectional views showing the structure of a photosensitive member 1 which is an example of the first embodiment. As shown in FIG. 1, the photosensitive member 1 includes a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 is a single layer photosensitive layer. As shown in FIG. 1, the photosensitive layer 3 may be provided directly on the conductive substrate 2. Further, as shown in FIG. 2, the photoreceptor 1 may include, for example, a conductive substrate 2, an intermediate layer 4 (for example, an undercoat layer), and a photosensitive layer 3. In the example shown in FIG. 2, the photosensitive layer 3 is provided indirectly on the conductive substrate 2 via the intermediate layer 4. Further, as shown in FIG. 3, the photosensitive member 1 may be provided with a protective layer 5 as the outermost surface layer.

  The elements of the photoreceptor 1 (conductive substrate 2, photosensitive layer 3 and intermediate layer 4) will be described below. Furthermore, a method of manufacturing the photosensitive member 1 will also be described.

[1. Conductive substrate]
The conductive substrate 2 is not particularly limited as long as it can be used as the conductive substrate of the photosensitive member 1. As the conductive substrate 2, a conductive substrate composed of a material having at least a surface portion having conductivity can be used. Examples of the conductive substrate 2 include a conductive substrate composed of a material having conductivity (conductive material), and a conductive substrate coated with a conductive material. Examples of the conductive material include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, and indium. These conductive materials may be used alone or in combination of two or more. As a combination of two or more, for example, an alloy (more specifically, an aluminum alloy, stainless steel, brass, etc.) can be mentioned. Among these conductive materials, aluminum and an aluminum alloy are preferable because charge transfer from the photosensitive layer 3 to the conductive substrate 2 is good.

  The shape of the conductive substrate 2 can be appropriately selected according to the structure of the image forming apparatus to be used. Examples of the shape of the conductive substrate 2 include a sheet and a drum. Further, the thickness of the conductive substrate 2 can be appropriately selected according to the shape of the conductive substrate 2.

[2. Photosensitive layer]
The photosensitive layer 3 contains a charge generating agent, a hole transporting agent, an electron transporting agent, and a binder resin. The photosensitive layer 3 may further contain an additive. The thickness of the photosensitive layer 3 is not particularly limited as long as it can sufficiently exhibit the function as the photosensitive layer. Specifically, the thickness of the photosensitive layer 3 may be 5 μm or more and 100 μm or less, and preferably 10 μm or more and 50 μm or less.

  Hereinafter, the charge generating agent, the hole transporting agent, the electron transporting agent, the binder resin and the additive which is an optional component will be described.

(Charge generating agent)
The charge generating agent is not particularly limited as long as it is a charge generating agent for a photoreceptor. Examples of charge generating agents include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squalene pigments, indigo pigments, azulenium pigments, cyanines Pigment, powder of inorganic photoconductive material (for example, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide and amorphous silicon), pyrylium pigment, ansanthrone pigment, triphenylmethane pigment, selenium pigment, toluidine pigment, And pyrazoline pigments and quinacridone pigments. The charge generating agent may be used alone or in combination of two or more.

  Examples of phthalocyanine pigments include metal-free phthalocyanines represented by the following chemical formula (C-1), and metal phthalocyanines. Examples of the metal phthalocyanine include titanyl phthalocyanine, hydroxygallium phthalocyanine and chlorogallium phthalocyanine represented by the following chemical formula (C-2). The phthalocyanine pigment may be crystalline or non-crystalline. The crystal form (for example, α-type, β-type, X-type, Y-type, V-type and II-type) of the phthalocyanine-based pigment is not particularly limited, and phthalocyanine-based pigments having various crystal forms are used.

  Examples of crystals of metal-free phthalocyanine include, for example, X-type crystals of metal-free phthalocyanine (hereinafter sometimes referred to as X-type metal-free phthalocyanine). Examples of crystals of titanyl phthalocyanine include α-type, β-type and Y-type crystals of titanyl phthalocyanine (hereinafter sometimes referred to as α-type, β-type and Y-type titanyl phthalocyanine, respectively). Examples of hydroxygallium phthalocyanine crystals include V-type crystals of hydroxygallium phthalocyanine.

  When the photosensitive member 1 is applied to a digital optical image forming apparatus (for example, a laser beam printer and a facsimile using a light source such as a semiconductor laser), a charge generating agent having sensitivity in a wavelength region of 700 nm or more It is preferable to use In this case, since the charge generating agent has a high quantum yield in a wavelength region of 700 nm or more, phthalocyanine pigments are preferable, and metal-free phthalocyanine and titanyl phthalocyanine are more preferable.

  When the photoreceptor 1 is applied to an image forming apparatus using a short wavelength laser light source (for example, a laser light source having a wavelength of 350 nm to 550 nm), as an electric charge generating agent, for example, anthanthrone pigment and perylene type Pigments are preferably used.

  From the viewpoint of further suppressing the occurrence of transfer memory, a charge generating agent is preferably an X-type metal-free phthalocyanine.

  The content of the charge generating agent is preferably 0.1 parts by mass or more and 50 parts by mass or less, and more preferably 0.5 parts by mass or more and 30 parts by mass with respect to 100 parts by mass of the binder resin. It is more preferable that it is a part or less, and it is especially preferable that it is 0.5 to 10 parts by mass.

(Hole transport agent)
Examples of the hole transport agent include nitrogen-containing cyclic compounds and fused polycyclic compounds. Examples of nitrogen-containing cyclic compounds and condensed polycyclic compounds include triphenylamine derivatives; diamine derivatives (more specifically, N, N, N ′, N′-tetraphenylbenzidine derivatives, N, N, N) ', N'-tetraphenyl phenylene diamine derivative, N, N, N ', N'-tetraphenyl naphthylene diamine derivative, di (aminophenyl ethenyl) benzene derivative, N, N, N ', N'-tetraphenyl Phenanthrylene diamine derivatives etc.); Oxadiazole compounds (more specifically, 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole etc.); Styryl compounds (from Specifically, 9- (4-diethylaminostyryl) anthracene etc .; carbazole type compounds (more specifically, polyvinyl carbazole etc.); organic policy Compounds; pyrazoline compounds (more specifically, 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline etc.); hydrazone compounds; indole compounds; oxazole compounds; isoxazole compounds; thiazole compounds Thiadiazole compounds; imidazole compounds; pyrazole compounds; and triazole compounds. One of these hole transport agents may be used alone, or two or more thereof may be used in combination.

  Among these hole transfer agents, a compound represented by the following general formula (9) (hereinafter sometimes referred to as a hole transfer agent (9)) from the viewpoint of further suppressing the occurrence of transfer memory. preferable.

In General Formula (9), R ³¹ , R ³² and R ³³ each independently represent an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms. m1 and m2 each independently represent an integer of 1 or more and 3 or less. n1, n2 and n3 each independently represent an integer of 0 or more and 5 or less. When n1 represents an integer of 2 or more and 5 or less, the plurality of R ³¹ may be the same as or different from each other. When n2 represents an integer of 2 or more and 5 or less, the plurality of R ³² may be identical to or different from one another. When n3 represents an integer of 2 or more and 5 or less, plural R ^{33 s} may be the same as or different from each other.

In the general formula (9), R ³¹ , R ³² and R ³³ are each independently an alkyl group having 1 to 4 carbon atoms or 1 to 4 carbon atoms from the viewpoint of further suppressing generation of transfer memory. It is preferable to represent an alkoxy group of

  In the general formula (9), m1 and m2 preferably represent 2 or 3 from the viewpoint of further suppressing the occurrence of transfer memory.

  In the general formula (9), n1 preferably represents 1 or 2 from the viewpoint of further suppressing the occurrence of transfer memory. From the same point of view, n2 and n3 preferably represent 0 in the general formula (9).

  As the hole transfer agent (9), for example, compounds represented by the following chemical formulas (HT-1) to (HT-7) (hereinafter, hole transfer agents (HT-1) to (HT-7) and May be mentioned).

  Among these hole transport agents, hole transport agents (HT-1), (HT-3), (HT-4) and (HT-5) are preferable from the viewpoint of further suppressing the occurrence of transfer memory.

  The content of the hole transfer agent is preferably 10 parts by mass or more and 200 parts by mass or less, and more preferably 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the binder resin.

(Electron transport agent)
The electron transfer agent comprises a first electron transfer agent and a second electron transfer agent. The first electron transfer agent is a compound represented by the following general formula (1). The second electron transfer agent is a compound represented by the following general formula (2), general formula (3), general formula (4) or general formula (5). The photosensitive layer 3 contains one or more of a first electron transfer agent and one or more of a second electron transfer agent.

In general formula (1), R ¹ and R ² each independently represent an alkyl group having 1 to 6 carbon atoms, or a hydrogen atom.

In the general formula (2), R ¹¹ and R ¹² each independently represents a 1 to 6 alkyl group carbon atoms. In General Formula (3), R ¹⁷ and R ¹⁸ each independently represent an aryl group having 6 to 14 carbon atoms which may have an alkyl group having 1 to 4 carbon atoms. In General Formula (4), R ¹⁹ and R ²⁰ each independently represent an alkyl group having 1 to 6 carbon atoms, and R ²¹ has 6 to 14 carbon atoms which may have a halogen atom. Represents an aryl group of In general formula (5), R ²² , R ²³ , R ²⁴ and R ²⁵ each independently represent an alkyl group having 1 to 6 carbon atoms.

  The photoreceptor 1 can suppress the generation of the transfer memory by including the first electron transport agent and the second electron transport agent in the photosensitive layer 3. The reason is presumed as follows.

  The first electron-transporting agent tends to easily accept carriers (electrons) from the charge-generating agent because the electron-accepting ability is relatively high. In addition, since the second electron transfer agent has a relatively large π conjugated system, the π conjugated systems of the plurality of second electron transfer agents easily overlap each other, and carriers (electrons) between the molecules of the plurality of second electron transfer agents The moving distance of is relatively small. Therefore, the second electron transport agent tends to have high carrier (electron) transportability. Therefore, the photosensitive member 1 contains in the photosensitive layer 3 a first electron transport agent having relatively high carrier (electron) acceptance and a second electron transport agent having relatively high carrier (electron) transportability. Thus, it is considered that the residual charge in the photosensitive layer 3 can be reduced, and the generation of transfer memory can be suppressed.

In the general formula (1), R ¹ and R ² each preferably independently represent an alkyl group having 1 to 6 carbon atoms, from the viewpoint of suppressing generation of transfer memory more, and 1 or more carbon atoms It is more preferable to represent an alkyl group of 4 or less, and further preferable to represent a branched alkyl group having 1 to 4 carbon atoms.

In the general formula (2), R ¹¹ and R ¹² preferably each independently represent a branched alkyl group having 1 or more and 6 or less carbon atoms from the viewpoint of further suppressing the occurrence of transfer memory.

In the general formula (3), R ¹⁷ and R ¹⁸ preferably each independently represent a phenyl group having an alkyl group having 1 to 4 carbon atoms, from the viewpoint of further suppressing the occurrence of transfer memory, It is more preferable to represent a phenyl group having two alkyl groups each having 1 or more and 4 or less atoms.

In the general formula (4), R ¹⁹ and R ²⁰ preferably each independently represent an alkyl group having 1 or more and 4 or less carbon atoms from the viewpoint of further suppressing the occurrence of transfer memory. From the same viewpoint, in general formula (4), R ²¹ preferably represents a phenyl group having a halogen atom, and more preferably represents a phenyl group having a chlorine atom.

In the general formula (5), R ²² , R ²³ , R ²⁴ and R ²⁵ preferably each independently represent an alkyl group having 1 to 4 carbon atoms, from the viewpoint of further suppressing the occurrence of transfer memory. .

  From the viewpoint of further suppressing the occurrence of transfer memory, the second electron transfer agent is preferably a compound represented by General Formula (2), General Formula (4) or General Formula (5).

  As a 1st electron transport agent, the compound (Hereafter, it may describe as an electron transport agent (ET-1).) Represented by following Chemical formula (ET-1) is mentioned. In addition, as the second electron transfer agent, for example, compounds represented by the following chemical formulas (ET-2) to (ET-5) (hereinafter referred to as electron transfer agents (ET-2) to (ET-5), respectively) May be mentioned).

  The content ratio of the first electron transfer agent to the second electron transfer agent is 1/4 or more as the mass ratio (first electron transfer agent / second electron transfer agent) from the viewpoint of further suppressing the generation of transfer memory. It is preferable that it is / 1 or less.

  The photosensitive layer 3 may contain another electron transfer agent in addition to the first electron transfer agent and the second electron transfer agent described above. Other electron transfer agents include, for example, quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds , Dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride, the first electron Compounds of different structure than the transport agent and the second electron transport agent can be used. The total content of the first electron transfer agent and the second electron transfer agent relative to the total mass of the electron transfer agent is preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass. Being particularly preferred.

  The content of the electron transfer agent is preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 10 parts by mass or more and 80 parts by mass or less, and more preferably 30 parts by mass or more based on 100 parts by mass of the binder resin. It is particularly preferable that the amount is 60 parts by mass or less.

(Binder resin)
As binder resin, a thermoplastic resin, a thermosetting resin, and a photocurable resin are mentioned, for example. As a thermoplastic resin, for example, polycarbonate resin, polyarylate resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic acid polymer, styrene-acrylic acid copolymer, Polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, urethane resin, polysulfone resin, diallyl phthalate Resin, ketone resin, polyvinyl butyral resin, polyester resin and polyether resin are mentioned. As a thermosetting resin, a silicone resin, an epoxy resin, a phenol resin, a urea resin, and a melamine resin are mentioned, for example. Examples of the photocurable resin include epoxy-acrylic acid resins (acrylic acid adducts of epoxy compounds) and urethane-acrylic acid copolymers (acrylic acid adducts of urethane compounds). One of these binder resins may be used alone, or two or more thereof may be used in combination.

  Among these resins, polycarbonate resins are preferable because the photosensitive layer 3 excellent in the balance of processability, mechanical properties, optical properties and abrasion resistance can be obtained. Examples of polycarbonate resins include bisphenol Z-type polycarbonate resins represented by the following chemical formula, bisphenol ZC-type polycarbonate resins, bisphenol C-type polycarbonate resins, and bisphenol A-type polycarbonate resins.

  The viscosity average molecular weight of the binder resin is preferably 30,000 or more, and more preferably 35,000 to 55,000. When the viscosity average molecular weight of the binder resin is 35,000 or more, the abrasion resistance of the photosensitive layer 3 can be easily improved. When the viscosity average molecular weight of the binder resin is 55,000 or less, the binder resin is easily dissolved in the solvent when the photosensitive layer 3 is formed, and the viscosity of the coating solution for the photosensitive layer does not become too high. As a result, the photosensitive layer 3 can be easily formed.

(Additive)
As an additive which is an optional component, for example, antidegradants (more specifically, antioxidants, radical scavengers, quenchers, ultraviolet absorbers, etc.), softeners, surface modifiers, extenders, These include thickeners, dispersion stabilizers, waxes, donors, surfactants, and leveling agents. When an additive is added, one of these additives may be used alone, or two or more thereof may be used in combination.

  As an antioxidant, a hindered phenol compound, a hindered amine compound, a thioether compound, and a phosphite compound are mentioned, for example. Among these antioxidants, hindered phenol compounds and hindered amine compounds are preferred.

[3. Middle layer]
As described above, the photoreceptor 1 may have an intermediate layer 4 (for example, an undercoat layer). The intermediate layer 4 contains, for example, inorganic particles and a resin (intermediate layer resin) used for the intermediate layer. When the intermediate layer 4 is interposed, the flow of current generated when the photosensitive member 1 is exposed can be smoothed and an increase in electrical resistance can be suppressed while maintaining the insulation state to a degree that can suppress the occurrence of leakage.

  As the inorganic particles, for example, particles of metal (more specifically, aluminum, iron, copper etc.), metal oxides (more specifically, titanium oxide, alumina, zirconium oxide, tin oxide, zinc oxide etc.) And particles of nonmetallic oxides (more specifically, silica etc.). These inorganic particles may be used alone or in combination of two or more. The inorganic particles may be subjected to surface treatment.

  It will not specifically limit, if it can use as resin which forms an intermediate | middle layer as resin for intermediate | middle layers.

[4. Method of manufacturing photoreceptor]
The method of manufacturing the photosensitive member 1 will be described. The method of manufacturing the photosensitive member 1 includes, for example, a photosensitive layer forming step. In the photosensitive layer forming step, a coating solution for photosensitive layer for forming the photosensitive layer 3 is prepared. Next, the coating solution for photosensitive layer is applied onto the conductive substrate 2. Next, the photosensitive layer 3 is formed by removing at least a part of the solvent contained in the applied coating solution for photosensitive layer by drying by an appropriate method. The coating solution for the photosensitive layer contains, for example, a charge generating agent, a hole transporting agent, an electron transporting agent, a binder resin, and a solvent. Such a coating solution for a photosensitive layer is prepared by dissolving or dispersing a charge generating agent, a hole transporting agent, an electron transporting agent, and a binder resin in a solvent. If necessary, various additives may be added to the coating solution for the photosensitive layer.

  The details of the photosensitive layer formation process will be described below. The solvent contained in the photosensitive layer coating solution is not particularly limited as long as it can dissolve or disperse each component contained in the photosensitive layer coating solution. As the solvent, for example, alcohol (more specifically, methanol, ethanol, isopropanol, butanol etc.), aliphatic hydrocarbon (more specifically, n-hexane, octane, cyclohexane etc.), aromatic hydrocarbon (more specifically, More specifically, benzene, toluene, xylene and the like), halogenated hydrocarbons (more specifically, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene and the like), ethers (more specifically, dimethyl ether, diethyl ether, Tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc.), ketones (more specifically, acetone, methyl ethyl ketone, cyclohexanone etc.), esters (more specifically, ethyl acetate, methyl acetate etc.), dimethyl formaldehyde Methyl formamide, and dimethylsulfoxide. These solvents may be used alone or in combination of two or more. Among these solvents, non-halogen solvents are preferably used.

  The coating solution for the photosensitive layer is prepared by mixing the respective components and dispersing in a solvent. For mixing or dispersing, for example, a bead mill, roll mill, ball mill, attritor, paint shaker, or ultrasonic disperser can be used.

  The coating solution for photosensitive layer may contain, for example, a surfactant in order to improve the dispersibility of each component.

  The method for applying the photosensitive layer coating solution is not particularly limited as long as it can uniformly apply the photosensitive layer coating solution. Examples of the coating method include dip coating, spray coating, spin coating, and bar coating.

  The method for removing at least a part of the solvent contained in the coating solution for the photosensitive layer is not particularly limited as long as it is a method by which at least a part of the solvent in the coating solution for the photosensitive layer can be evaporated. Examples of the method of removal include heating, reduced pressure, or a combination of heating and reduced pressure. More specifically, the method of heat-processing (hot-air drying) using a high temperature dryer, a pressure reduction dryer, etc. is mentioned. The heat treatment conditions are, for example, a temperature of 40 ° C. to 150 ° C., and a time of 3 minutes to 120 minutes.

  The method of manufacturing the photosensitive member 1 may further include a step of forming the intermediate layer 4 and the like as necessary. The step of forming the intermediate layer 4 can be appropriately selected from known methods.

  The photoreceptor of the present embodiment described above can suppress the generation of the transfer memory, and thus can be suitably used in various image forming apparatuses.

Second Embodiment Image Forming Apparatus
Hereinafter, one aspect of the image forming apparatus according to the second embodiment will be described by taking a tandem-type color image forming apparatus as an example. FIG. 4 is a view showing an example of the image forming apparatus according to the second embodiment. The image forming apparatus 100 according to the second embodiment includes an image carrier 30, a charging unit 42, an exposure unit 44, a developing unit 46, and a transfer unit 48. The image carrier 30 is a photosensitive member according to the first embodiment. The charging unit 42 charges the surface of the image carrier 30. The charging polarity of the charging unit 42 is positive. The exposure unit 44 exposes the charged surface of the image carrier 30 to form an electrostatic latent image on the surface of the image carrier 30. The developing unit 46 develops the electrostatic latent image as a toner image. The transfer unit 48 transfers the toner image from the image carrier 30 to the recording medium P while bringing the surface of the image carrier 30 into contact with the recording medium P (transferred material). The outline of the image forming apparatus 100 according to the second embodiment has been described above.

  The image forming apparatus 100 according to the second embodiment can suppress the occurrence of image defects. The reason is presumed as follows. The image forming apparatus 100 according to the second embodiment includes the photoreceptor according to the first embodiment as the image carrier 30. The photoreceptor according to the first embodiment can suppress the occurrence of transfer memory. Therefore, the image forming apparatus 100 according to the second embodiment can suppress the occurrence of an image defect such as an image ghost to be described later. Hereinafter, the image ghost resulting from the generation of the transfer memory will be described.

  When a transfer memory is generated in the image forming process, the non-exposure area of the reference circumference (any one rotation when an image is continuously formed) on the surface of the image carrier 30 is the exposure area of the reference circumference. As compared with the above, there is a tendency that the potential decreases at the time of charging of the next round of the reference round. For this reason, the non-exposed area of the reference circumference attracts positively charged toner more easily in the next development process than in the normal state. As a result, in the next round of the reference circumference, an image reflecting the non-image portion (non-exposure area) of the reference circumference is likely to be formed. An image defect in which an image reflecting such a non-image portion on the reference circumference is formed in the next round is an image ghost generated due to the transfer memory.

  The image ghost will be described with reference to FIG. FIG. 5 is a view showing an image 60 in which an image ghost has occurred. Image 60 includes area 62 and area 64. The area 62 is an area corresponding to one rotation of the image carrier (one rotation of the reference circumference), and the region 64 is an area corresponding to one rotation of the image carrier (one rotation next to the reference circumference). Region 62 includes image 66. The image 66 is composed of a square solid image. Region 64 includes image 68 and image 69. Image 68 is a square shaped halftone image. The image 69 is a halftone image of the area 64 excluding the image 68. The design image of the area 64 is a full halftone image. As shown in FIG. 5, the image 69 has a higher image density than the image 68. The image 69 is an image defect (image ghost) that reflects the non-exposure region of the region 62 and is darker than the design image density.

  Hereinafter, each part of the image forming apparatus 100 will be described in detail with reference to FIG.

  The image forming apparatus 100 employs a direct transfer method. That is, in the image forming apparatus 100, the transfer unit 48 transfers the toner image to the recording medium P while bringing the surface of the image carrier 30 into contact with the recording medium P. Usually, in an image forming apparatus adopting a direct transfer method, a transfer memory tends to be generated because an image carrier is easily affected by a transfer bias. However, the image forming apparatus 100 according to the second embodiment includes the photosensitive member according to the first embodiment as the image carrier 30. The photoreceptor according to the first embodiment can suppress the occurrence of transfer memory. Therefore, when the photosensitive member according to the first embodiment is provided as the image carrier 30, even in the case of the image forming apparatus 100 adopting the direct transfer method, the occurrence of the image defect due to the transfer memory is suppressed.

  The image forming apparatus 100 includes image forming units 40 a, 40 b, 40 c and 40 d, a transfer belt 50, and a fixing unit 54. Hereinafter, each of the image forming units 40 a, 40 b, 40 c, and 40 d will be referred to as an image forming unit 40 if it is not necessary to distinguish.

  The image forming unit 40 includes an image carrier 30, a charging unit 42, an exposure unit 44, a developing unit 46, a transfer unit 48, and a cleaning unit 52 for cleaning the surface of the image carrier 30. The cleaning unit 52 is a cleaning blade. Usually, in an image forming apparatus provided with a cleaning blade, the image carrier is likely to be frictionally charged due to the contact between the image carrier and the cleaning blade. Therefore, in the image forming apparatus provided with the cleaning blade, the transfer memory is easily generated by the charge generated by the frictional charge remaining in the image carrier. However, the image forming apparatus 100 according to the second embodiment includes the photosensitive member according to the first embodiment as the image carrier 30. The photoreceptor according to the first embodiment can suppress the occurrence of transfer memory. Therefore, when the photosensitive member according to the first embodiment is provided as the image carrier 30, even in the case of the image forming apparatus 100 provided with the cleaning blade, the occurrence of the image defect due to the transfer memory is suppressed.

  The image carrier 30 is provided rotatably at a central position of the image forming unit 40 in the arrow direction (counterclockwise direction). A charging unit 42, an exposure unit 44, a developing unit 46, a transfer unit 48, and a cleaning unit 52 are provided around the image carrier 30 sequentially from the upstream side of the rotational direction of the image carrier 30 with respect to the charging unit 42. Be The image forming unit 40 may further include a charge removal unit (not shown).

  The toner images of a plurality of colors (for example, four colors of black, cyan, magenta and yellow) are sequentially superimposed on the recording medium P on the transfer belt 50 by each of the image forming units 40a to 40d.

  The charging unit 42 is a charging roller. The charging roller charges the surface of the image carrier 30 while in contact with the surface of the image carrier 30. In general, in an image forming apparatus provided with a charging roller, an image failure caused by a transfer memory is likely to occur. However, the image forming apparatus 100 according to the second embodiment includes the photosensitive member according to the first embodiment as the image carrier 30. The photoreceptor according to the first embodiment can suppress the occurrence of transfer memory. Therefore, even in the case of the image forming apparatus 100 including the charging roller as the charging unit 42, the occurrence of the image defect due to the transfer memory is suppressed. In addition, as a charging part of another contact charging system, a charging brush is mentioned, for example. Also, the charging unit may be of a non-contact type. Examples of the non-contact type charging unit include a corotron charging unit and a scorotron charging unit.

  The voltage applied by the charging unit 42 is not particularly limited. Examples of the voltage applied by the charging unit 42 include direct current voltage, alternating current voltage, and superimposed voltage (voltage in which alternating current voltage is superimposed on direct current voltage), and more preferably direct current voltage. The DC voltage has the following advantages over the AC voltage and the superimposed voltage. When the charging unit 42 applies only a DC voltage, the surface of the image carrier 30 can be uniformly charged to a constant potential since the voltage value applied to the image carrier 30 is constant. In addition, when the charging unit 42 applies only a DC voltage, the amount of wear of the photosensitive layer tends to decrease. As a result, a suitable image can be formed.

  The exposure unit 44 exposes the charged surface of the image carrier 30. Thereby, an electrostatic latent image is formed on the surface of the image carrier 30. The electrostatic latent image is formed based on the image data input to the image forming apparatus 100.

  The developing unit 46 supplies toner to the surface of the image carrier 30, and develops the electrostatic latent image as a toner image. As the developing unit 46, for example, a developing unit which develops an electrostatic latent image as a toner image while being in contact with the surface of the image carrier 30 can be employed.

  The transfer belt 50 conveys the recording medium P between the image carrier 30 and the transfer unit 48. The transfer belt 50 is an endless belt. The transfer belt 50 is provided rotatably in the arrow direction (clockwise).

  The transfer unit 48 transfers the toner image developed by the developing unit 46 from the surface of the image carrier 30 to the recording medium P. When the toner image is transferred from the image carrier 30 to the recording medium P, the image carrier 30 is in contact with the recording medium P. Examples of the transfer unit 48 include a transfer roller.

  The fixing unit 54 heats and / or pressurizes the unfixed toner image transferred to the recording medium P by the transfer unit 48. The fixing unit 54 is, for example, a heating roller and / or a pressure roller. The toner image is fixed on the recording medium P by heating and / or pressurizing the toner image. As a result, an image is formed on the recording medium P.

  As described above, an example of the image forming apparatus according to the second embodiment has been described, but the image forming apparatus according to the second embodiment is not limited to the image forming apparatus 100 described above. For example, although the image forming apparatus 100 described above is a tandem type image forming apparatus, the image forming apparatus according to the second embodiment is not limited to this, and may be, for example, a rotary type image forming apparatus. The image forming apparatus according to the second embodiment may be a monochrome image forming apparatus. In this case, the image forming apparatus may have, for example, only one image forming unit. The image forming apparatus according to the second embodiment may employ an intermediate transfer method. When the image forming apparatus according to the second embodiment employs an intermediate transfer method, the transfer target corresponds to an intermediate transfer belt.

Third Embodiment Process Cartridge
The process cartridge according to the third embodiment includes the photosensitive member according to the first embodiment. Continuing, with reference to FIG. 4, the process cartridge according to the third embodiment will be described.

  The process cartridge includes a unitized part. The unitized portion includes the image carrier 30. The unitized portion may include, in addition to the image carrier 30, at least one selected from the group consisting of the charging unit 42, the exposure unit 44, the developing unit 46, the transfer unit 48, and the cleaning unit 52. The process cartridge corresponds to, for example, each of the image forming units 40 a to 40 d. The process cartridge may further include a static eliminator (not shown). The process cartridge is designed to be detachable from, for example, the image forming apparatus 100. The process cartridge in this case is easy to handle, and can be easily and quickly replaced including the image carrier 30 when the sensitivity characteristics and the like of the image carrier 30 deteriorate.

  The process cartridge according to the third embodiment has been described above. The process cartridge according to the third embodiment can suppress the occurrence of image defects by including the photosensitive member according to the first embodiment as an image carrier.

  Hereinafter, the present invention will be more specifically described using examples. The present invention is not limited to the scope of the examples.

<Materials used in Examples and Comparative Examples>
The following charge generating agent, hole transporting agent, and electron transporting agent were prepared as materials for producing a photosensitive layer.

[Charge generating agent]
An X-type metal-free phthalocyanine (hereinafter referred to as charge generator (CG-1)) and a Y-type titanyl phthalocyanine (hereinafter referred to as charge generator (CG-2)) were prepared.

[Hole transport agent]
The hole transfer agents (HT-1) to (HT-7) described in the first embodiment were prepared as the hole transfer agents. Furthermore, hole transport agents (HT-8) and (HT-9) were also prepared. The hole transfer agents (HT-8) and (HT-9) are hole transfer agents represented by chemical formulas (HT-8) and (HT-9) shown below, respectively.

[Electron transport agent]
The electron transfer agents (ET-1) to (ET-5) described in the first embodiment were prepared. Furthermore, electron transport agents (ET-A) and (ET-B) were also prepared. Electron transport agents (ET-A) and (ET-B) are electron transport agents represented by chemical formulas (ET-A) and (ET-B) shown below, respectively.

<Production of Photoreceptor>
Photosensitive members (A-1) to (A-16) and (B-1) to (B-12) were produced by the methods described below.

[Production of Photoreceptor (A-1)]
Charge generator (CG-1) (5.0 parts by mass), hole transfer agent (HT-5) (50.0 parts by mass), electron transfer agent (ET-1) (17.5 parts by mass) And an electron transfer agent (ET-2) (17.5 parts by mass), and a bisphenol Z-type polycarbonate resin as a binder resin ("PCZ 500" manufactured by Mitsubishi Gas Chemical Co., Ltd., viscosity average molecular weight 50,000) (100.0) Parts by mass) and tetrahydrofuran (800.0 parts by mass) as a solvent were charged into the ball mill. These materials and a solvent were mixed by a ball mill for 50 hours to disperse the materials in the solvent. Thus, a coating solution for photosensitive layer was obtained. The coating solution for the photosensitive layer was applied on an aluminum drum-shaped support as a conductive substrate by dip coating. The coating solution for photosensitive layer applied was dried with hot air at 100 ° C. for 40 minutes. As a result, a photosensitive layer (film thickness of 30 μm) was formed on the conductive substrate to obtain a photosensitive member (A-1) which is a single layer type photosensitive member.

[Preparation of Photoreceptors (A-2) to (A-16) and (B-1) to (B-12)]
The photosensitive members (A-2) to (A-16) and (B-1) to (B-12) were prepared in the same manner as in the preparation of the photosensitive member (A-1) except that the following points were changed. Made.

(change point)
The charge generating agent (CG-1) used in preparation of the photosensitive member (A-1) was changed to the charge generating agent shown in Table 1. The hole transfer agent (HT-5) used for preparation of a photoreceptor (A-1) was changed into the hole transfer agent shown in Table 1. While changing the electron transfer agents (ET-1) and (ET-2) used for preparation of a photoreceptor (A-1) to the electron transfer agent shown in Table 1, the content ratio of the electron transfer agent is shown in Table 1 It changed to the mass ratio shown to. The total mass of each of the electron transfer agents used in the preparation of the photoreceptors (A-2) to (A-16) and (B-1) to (B-12) is for the preparation of the photoreceptor (A-1) It was the same as the total mass of the electron transport agent used.

<Evaluation of photoconductor>
[Measurement of post exposure potential and transfer memory potential]
For each of the photosensitive members (A-1) to (A-16) and (B-1) to (B-12), the measurement of the potential after exposure and the transfer memory potential were performed. For the evaluation, an image forming apparatus ("FS-C5250 DN" manufactured by KYOCERA Document Solutions Inc.) was used. This image forming apparatus adopts a method of transferring a toner image from the photosensitive member to the intermediate transfer belt while bringing the surface of the photosensitive member into contact with the intermediate transfer belt. Further, this image forming apparatus is provided with a contact type charging roller for applying a DC voltage as a charging unit. The charging roller was provided with an elastic layer made of a chargeable rubber in which conductive carbon is dispersed in epichlorohydrin resin.

  First, the photosensitive member was attached to the above-mentioned image forming apparatus, the charging voltage of the charging unit was adjusted, and the charging potential of the photosensitive member corresponding to the developing portion position at non-exposure was set to + 570V ± 10V.

Next, monochromatic light (wavelength 780 nm, half width 20 nm, light intensity 1.16 μJ / m ² ) was extracted from white light of the halogen lamp using a band pass filter. A part of the surface of the photosensitive member was exposed with the taken-out monochromatic light, and the surface potential was measured for each of the exposed region and the non-exposed region of the photosensitive member corresponding to the position of the development portion. The surface potential of the measured exposure area was taken as a potential after exposure V _L (unit: V). Further, the surface potential of the measured non-exposed area (white paper portion) was taken as the white paper portion potential V ₃ (unit: V). The post-exposure potential V _L and the white sheet part potential V ₃ were measured with the transfer bias turned off.

Then, by applying a transfer bias of -2.0 kV, except that measured when you turn on the transfer bias were measured the surface potential of the unexposed regions under the same conditions as the measurement of the blank portion potential V _3. The surface potential of the unexposed areas obtained (blank section) and a blank portion potential V _4. From the resulting V ₃ and V ₄ Metropolitan using Equation "transfer memory potential ΔVtc = V ₃ -V _4" transfer memory potential DerutaVtc (Unit: V) was obtained. The measurement environment was a temperature of 23 ° C. and a humidity of 50% RH.

The obtained post-exposure potential V _L and transfer memory potential ΔVtc are shown in Table 2. The smaller the absolute value of the post-exposure potential V _L, the better the sensitivity characteristics of the photosensitive member. The smaller the absolute value of the transfer memory potential ΔVtc, the more the generation of the transfer memory is suppressed.

  As shown in Table 1, in the photosensitive members (A-1) to (A-16), the photosensitive layer is composed of the electron transfer agent included in the general formula (1), the general formula (2), and the general formula (3). And the electron transport agent included in the general formula (4) or the general formula (5).

  As shown in Table 2, in the photosensitive members (A-1) to (A-16), ΔVtc was 12 V or more and 24 V or less.

  As shown in Table 1, photoreceptors (B-1), (B-2), (B-4), (B-6), (B-7) and (B-9) to (B-11) In the above, the photosensitive layer did not contain the electron transfer agent included in the general formula (2), the general formula (3), the general formula (4) and the general formula (5). In the photosensitive members (B-3) to (B-5), (B-8) and (B-12), the photosensitive layer did not contain the electron transfer agent included in the general formula (1).

  As shown in Table 2, in the photosensitive members (B-1) to (B-12), ΔVtc was 28 V or more.

  As is clear from the above results, the photoreceptors (A-1) to (A-16) were able to suppress the generation of transfer memory as compared with the photoreceptors (B-1) to (B-12).

  The photoreceptor according to the present invention can be used in an image forming apparatus.

1 electrophotographic photosensitive member 2 conductive substrate 3 photosensitive layer

Claims (11)

An electrophotographic photosensitive member comprising a conductive substrate and a photosensitive layer,
The photosensitive layer is a single layer, and includes a charge generating agent, a hole transporting agent, an electron transporting agent, and a binder resin.
The electron transfer agent includes a first electron transfer agent and a second electron transfer agent,
The first electron transfer agent is a compound represented by the following general formula (1),
The electrophotographic photosensitive member, wherein the second electron transfer agent is a compound represented by the following general formula (2), general formula (3), general formula (4) or general formula (5).

(In the general formula (1), R ¹ and R ² each independently represent an alkyl group having 1 to 6 carbon atoms, or a hydrogen atom.)

(In the above general formula (2), R ¹¹ and R ¹² each independently represent an alkyl group having 1 to 6 carbon atoms,
In the general formula (3), each of R ¹⁷ and R ¹⁸ independently represents an aryl group having 6 to 14 carbon atoms which may have an alkyl group having 1 to 4 carbon atoms,
In the general formula (4),
R ¹⁹ and R ²⁰ each independently represent an alkyl group having 1 to 6 carbon atoms,
R ²¹ represents an aryl group having 6 to 14 carbon atoms which may have a halogen atom,
In the general formula (5), R ²² , R ²³ , R ²⁴ and R ²⁵ each independently represent an alkyl group having 1 to 6 carbon atoms. )   The electrophotographic photosensitive member according to claim 1, wherein the second electron transfer agent is a compound represented by the general formula (2), the general formula (4) or the general formula (5). In the above general formula (1), R ¹ and R ² each independently represent an alkyl group having 1 to 6 carbon atoms,
In the general formula (3), each of R ¹⁷ and R ¹⁸ independently represents a phenyl group having an alkyl group having 1 or more and 4 or less carbon atoms,
The electrophotographic photosensitive member according to claim 1, wherein in the general formula (4), R ²¹ represents a phenyl group having a halogen atom. The first electron transfer agent includes a compound represented by the following chemical formula (ET-1),
The second electron transfer agent according to claim 3, wherein the second electron transfer agent comprises a compound represented by the following chemical formula (ET-2), chemical formula (ET-3), chemical formula (ET-4) or chemical formula (ET-5). Electrophotographic photosensitive member.

The electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the hole transfer agent contains a compound represented by the following general formula (9).

(In the general formula (9),
R ³¹ , R ³² and R ³³ each independently represent an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms,
m1 and m2 each independently represent an integer of 1 or more and 3 or less,
n1, n2 and n3 each independently represent an integer of 0 or more and 5 or less,
When n1 represents an integer of 2 or more and 5 or less, plural R ^{31 s} may be the same as or different from each other,
When n2 represents an integer of 2 or more and 5 or less, plural R ^{32 s} may be the same as or different from each other,
When n3 represents an integer of 2 or more and 5 or less, plural R ^{33 s} may be the same as or different from each other. ) In the general formula (9),
m1 and m2 represent 2 or 3;
n1 represents 1 or 2;
The electrophotographic photosensitive member according to claim 5, wherein n2 and n3 represent 0. The hole transport agent is represented by the following chemical formula (HT-1), chemical formula (HT-2), chemical formula (HT-3), chemical formula (HT-4), chemical formula (HT-5), chemical formula (HT-6) or The electrophotographic photosensitive member according to claim 6, comprising a compound represented by a chemical formula (HT-7).

An image carrier,
A charging unit that charges the surface of the image carrier;
An exposure unit for exposing the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier;
A developing unit for developing the electrostatic latent image as a toner image;
An image forming apparatus including: a transfer unit configured to transfer the toner image from the image carrier to a transfer target;
The image carrier is the electrophotographic photosensitive member according to any one of claims 1 to 7,
The charging polarity of the charging unit is positive,
The image forming apparatus according to claim 1, wherein the transfer unit transfers the toner image from the image carrier to the transfer medium while bringing the surface of the image carrier into contact with the transfer medium.   The image forming apparatus according to claim 8, wherein the transfer target is a recording medium.   The image forming apparatus according to claim 8, wherein the charging unit charges the surface of the image carrier while being in contact with the surface of the image carrier.   A process cartridge comprising the electrophotographic photosensitive member according to any one of claims 1 to 7.

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