JP2017026997A - Positively-charged single-layer electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positively-charged single-layer electrophotographic photoreceptor that can achieve both electrical characteristics and toner image transferability.SOLUTION: There is provided a positively-charged single-layer electrophotographic photoreceptor comprising a photosensitive layer that includes a specific tetracarboxylic acid dianhydride and a binder resin. The content of the tetracarboxylic acid dianhydride is 0.02 pts.mass or more and 7.00 pts.mass or less based on 100 pts.mass of the binder resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a positively charged single layer type electrophotographic photosensitive member, a process cartridge, and an image forming apparatus.

  The electrophotographic photosensitive member is used as an image carrier in an electrophotographic image forming apparatus (for example, a printer or a multifunction machine). In general, an electrophotographic photoreceptor includes a photosensitive layer. The photosensitive layer contains, for example, a charge generating agent, a charge transporting agent (more specifically, a hole transporting agent or an electron transporting agent), and a resin (binder resin) for binding them. For example, an electrophotographic photoreceptor contains a charge generating agent and a charge transport agent in the same layer (photosensitive layer), and has both functions of charge generation and charge transport in the same layer. Such an electrophotographic photoreceptor is referred to as a single layer type electrophotographic photoreceptor.

  Patent Document 1 describes an organic photoelectric conversion film. The organic photoelectric conversion film is used for, for example, an optical sensor or a solar cell. The organic photoelectric conversion film includes a p-type material layer and an n-type material layer. The n-type material layer is formed from 1,4,5,8-naphthalenetetracarboxylic dianhydride.

JP 2009-290190 A

  However, the technique described in Patent Document 1 is insufficient to improve the electrical characteristics of the electrophotographic photosensitive member and the transferability of the toner image by the electrophotographic photosensitive member.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a positively charged single layer type electrophotographic photosensitive member capable of achieving both electrical characteristics and toner image transferability. Another object of the present invention is to provide a process cartridge or an image forming apparatus capable of forming an image while achieving both electrical characteristics and transferability.

  The positively charged single layer type electrophotographic photosensitive member of the present invention includes a photosensitive layer. The photosensitive layer includes tetracarboxylic dianhydride and a binder resin. The tetracarboxylic dianhydride is a compound represented by the general formula (1), (2) or (3). Content of the said tetracarboxylic dianhydride is 0.02 mass part or more and 7.00 mass part or less with respect to 100 mass parts of said binder resins.

In the general formulas (1), (2) and (3), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ and R ¹⁴ are each independently a group consisting of an alkyl group, an alkoxy group and a halogen atom which may have a substituent selected from the group consisting of a hydrogen atom, a halogen atom, an alkoxy group and a halogen atom. Or an aryl group which may have a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom.

  The process cartridge of the present invention includes the above-described positively charged single layer type electrophotographic photosensitive member.

  The image forming apparatus of the present invention includes an image carrier and a charging unit. The image carrier is the positively charged single layer type electrophotographic photosensitive member described above. The charging unit charges the surface of the image carrier. The charging polarity of the charging unit is positive.

  According to the single layer type electrophotographic photosensitive member of the present invention, both electrical characteristics and toner image transferability can be achieved. In addition, according to the process cartridge or the image forming apparatus of the present invention, an image can be formed with both electrical characteristics and transferability compatible.

(A), (b), and (c) are schematic sectional drawings which show the structure of the positively charged single layer type electrophotographic photosensitive member according to the first embodiment. It is a schematic diagram which shows the image in which the image defect generate | occur | produced. It is the schematic which shows the structure of the one aspect | mode of the image forming apparatus which concerns on 2nd embodiment. It is the schematic which shows the structure of another aspect of the image forming apparatus which concerns on 2nd embodiment. It is a schematic diagram which shows the image for evaluation.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. The present invention can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, about the location where description overlaps, although description may be abbreviate | omitted suitably, the summary of invention is not limited.

  Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. In addition, when “polymer” is added after the compound name to indicate the polymer name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof.

<First Embodiment: Positively Charged Single Layer Type Electrophotographic Photoconductor>
The first embodiment relates to a positively charged single layer type electrophotographic photosensitive member (hereinafter sometimes referred to as “photosensitive member”). The photoreceptor can achieve both electrical characteristics (for example, sensitivity) and toner image transferability. The reason is presumed as follows.

  First, for the sake of convenience, a decrease in transferability will be described. An electrophotographic image forming apparatus includes, for example, an image carrier (photosensitive member), a charging unit, an exposure unit, a developing unit, and a transfer unit. The transfer unit transfers the toner image from the photoconductor to the transfer target. In the transfer process executed by the transfer unit, if the surface potential of the exposed area of the photoconductor is reduced to less than 0 V, the transfer efficiency of the toner image from the photoconductor to the transfer target may be reduced. Such a drop in toner image transferability is likely to occur particularly in a high temperature and high humidity environment.

  In the photoreceptor according to the first embodiment, the photosensitive layer contains a tetracarboxylic dianhydride represented by the general formula (1), (2), or (3). The content of tetracarboxylic dianhydride is 0.02 parts by mass or more and 7.00 parts by mass or less with respect to 100 parts by mass of the binder resin in the photosensitive layer. When the content of tetracarboxylic dianhydride is 0.02 parts by mass or more and 7.00 parts by mass or less, the photoreceptor tends to have an appropriate electrical resistance. As a result, in the photoconductor according to the first embodiment, it is considered that the surface potential of the photoconductor is stably held and the electrostatic latent image is stably held. On the other hand, when the content of tetracarboxylic dianhydride exceeds 7.00 parts by mass, tetracarboxylic dianhydride tends to crystallize in the photosensitive layer. When crystallized in the photosensitive layer, the sensitivity of the photoreceptor tends to decrease. Therefore, it is considered that the photoconductor according to the first embodiment can achieve both electrical characteristics and toner image transferability.

  The surface potential of the exposed region of the photoreceptor exposed by the exposure unit is preferably 0 V or more, and more preferably 0 V or more and +60 V or less. When the surface potential of the exposed area of the photoreceptor is 0 V or more, electrostatic attraction is less likely to act between the positively charged toner and the exposed area of the photoreceptor, so that the toner image is transferred from the photoreceptor to the transferred body. easy. The surface potential of the exposed area of the photoreceptor can be measured using a surface potential meter (“MODEL244” manufactured by Monroe Electronics). Further, the surface potential of the exposure area of the photoconductor is the same as that of the photoconductor in which the transfer unit transfers the toner image from the photoconductor to the transfer target in the image forming apparatus according to the second embodiment, which will be described later, and the charging unit is the next round. Measured before charging the surface. The method for measuring the surface potential of the exposed area of the photoreceptor will be described in detail later in the examples.

  The photoreceptor is described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing the structure of the photoreceptor 1. The photoreceptor 1 includes a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 is provided directly or indirectly on the conductive substrate 2. For example, as shown in FIG. 1A, the photosensitive layer 3 may be provided directly on the conductive substrate 2. For example, an intermediate layer 4 may be provided between the conductive substrate 2 and the photosensitive layer 3 as shown in FIG. Further, as shown in FIGS. 1A and 1B, the photosensitive layer 3 may be exposed as the outermost layer. As shown in FIG. 1C, a protective layer 5 may be provided on the photosensitive layer 3. Hereinafter, the conductive substrate, the photosensitive layer, and the intermediate layer will be described. In addition, a method for manufacturing the photoreceptor will 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 photoreceptor 1. As the conductive substrate 2, a conductive substrate formed of a material having at least a surface portion having conductivity can be used. Examples of the conductive substrate 2 include a conductive substrate made of a 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, indium, stainless steel, and brass. These conductive materials may be used alone or in combination of two or more (for example, as an alloy). Among these materials having conductivity, aluminum or an aluminum alloy is 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. For example, a sheet-like conductive substrate or a drum-shaped conductive substrate can be used. Further, the thickness of the conductive substrate 2 can be appropriately selected according to the shape of the conductive substrate 2.

[2. Photosensitive layer]
As already described, the photosensitive layer 3 includes tetracarboxylic dianhydride and a binder resin. The photosensitive layer 3 may contain a charge generating agent, an electron transport agent, a hole transport agent, and various additives as necessary. Hereinafter, a tetracarboxylic dianhydride, a charge generator, an electron transport agent, a hole transport agent, a binder resin, and an additive will be described.

(2-1. Tetracarboxylic acid dianhydride)
Tetracarboxylic dianhydride is a compound represented by the general formula (1), (2) or (3).

In the general formulas (1), (2) and (3), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ and R ¹⁴ are each independently an alkyl group, an alkoxy group and a halogen atom which may have a substituent selected from the group consisting of a hydrogen atom, a halogen atom, an alkoxy group and a halogen atom. An alkoxy group which may have a substituent selected, or an aryl group which may have a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom.

In general formulas (1) to (3), examples of the halogen atom represented by R ^{1 to} R ¹⁴ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Of these halogen atoms, a chlorine atom is preferred.

In general formulas (1) to (3), the alkyl group represented by R ^{1 to} R ¹⁴ is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, An alkyl group having 1 to 2 atoms (more specifically, a methyl group or an ethyl group) is more preferable. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, and tert. -A pentyl group or n-hexyl group is mentioned.

In general formulas (1) to (3), the alkyl group represented by R ^{1 to} R ¹⁴ may have a substituent. The substituent of the alkyl group represented by R ^{1 to} R ¹⁴ is a substituent selected from the group consisting of an alkoxy group and a halogen atom. Alkoxy groups, in later-described general formulas (1) to (3), is synonymous with the alkoxy group represented by R ¹ to R ^14. Halogen atom, in the general formula described above (1) to (3), is synonymous with a halogen atom represented by R ¹ to R ^14.

In general formulas (1) to (3), the alkoxy group represented by R ^{1 to} R ¹⁴ is preferably an alkoxy group having 1 to 6 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms, An alkoxy group having 1 to 2 atoms (more specifically, a methoxy group) is more preferable. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, n-pentoxy group, A tert-pentoxy group or an n-hexoxy group can be mentioned.

In general formulas (1) to (3), the alkoxy group represented by R ^{1 to} R ¹⁴ may have a substituent. The substituent of the alkoxy group represented by R ^{1 to} R ¹⁴ is a substituent selected from the group consisting of an alkoxy group and a halogen atom. As an alkoxy group as a substituent of an alkoxy group, a C1-C6 alkoxy group is mentioned, for example. Halogen atom, in the general formula described above (1) to (3), is synonymous with a halogen atom represented by R ¹ to R ^14.

In general formulas (1) to (3), the aryl group represented by R ^{1 to} R ¹⁴ is preferably an aryl group having 6 to 10 carbon atoms, and more preferably a phenyl group or a naphthyl group. In general formula (1), the aryl group represented by R ₁ and R ₂ may have a substituent. The substituent of the aryl group represented by R ₁ and R ₂ is a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom. Examples of the alkyl group as the substituent for the aryl group include an alkyl group having 1 to 6 carbon atoms. Examples of the alkoxy group as the substituent for the aryl group include an alkoxy group having 1 to 6 carbon atoms. Halogen atom, in the general formula described above (1) to (3), is synonymous with a halogen atom represented by R ¹ to R ^14.

In general formula (1), it is preferable that R < ¹ > -R < ⁴ > represents a hydrogen atom or a halogen atom each independently. In general formula (2), R ^{5 to} R ⁶ preferably represent a hydrogen atom. In general formula (3), R ^{7 to} R ¹⁴ preferably represent a hydrogen atom.

  Specific examples of tetracarboxylic dianhydrides may be described as compounds represented by chemical formulas (ADD-1) to (ADD-4) (hereinafter referred to as compounds (ADD-1) to (ADD-4)). ).

(2-2. Charge generator)
The charge generator is not particularly limited as long as it is a charge generator for a photoreceptor. Examples of the charge generator include phthalocyanine pigments, perylene pigments, bisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azurenium pigments, and cyanine pigments. , Powders of inorganic photoconductive materials (for example, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, or amorphous silicon), pyrylium salts, ansanthrone pigments, triphenylmethane pigments, selenium pigments, toluidine pigments, Examples thereof include pyrazoline pigments and quinacridone pigments.

  Examples of the phthalocyanine pigment include metal-free phthalocyanine represented by the chemical formula (CGM-1) or metal phthalocyanine. Examples of the metal phthalocyanine include titanyl phthalocyanine represented by the chemical formula (CGM-2) or phthalocyanine coordinated with a metal other than titanium oxide (for example, V-type hydroxygallium phthalocyanine). The phthalocyanine pigment may be crystalline or non-crystalline. The crystal shape (for example, α-type, β-type, or Y-type) of the phthalocyanine pigment is not particularly limited, and phthalocyanine pigments having various crystal shapes are used.

  Examples of the crystal of metal-free phthalocyanine include an X-type crystal of metal-free phthalocyanine (hereinafter sometimes referred to as “X-type metal-free phthalocyanine”). Examples of the titanyl phthalocyanine crystal include α-type crystal, β-type crystal, and Y-type crystal of titanyl phthalocyanine.

  A charge generator having an absorption wavelength in a desired region may be used alone, or two or more charge generators may be used in combination. Further, for example, in a digital optical image forming apparatus (for example, a laser beam printer or a facsimile using a light source such as a semiconductor laser), it is preferable to use the photoreceptor 1 having sensitivity in a wavelength region of 700 nm or more. . Therefore, for example, phthalocyanine pigments are preferable, and metal-free phthalocyanine or titanyl phthalocyanine is more preferable. A charge generating agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the photoreceptor 1 applied to an image forming apparatus using a short wavelength laser light source (for example, a laser light source having a wavelength of about 350 nm to 550 nm), an sanslon pigment or a perylene pigment is used as a charge generator. Preferably used.

  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 or less with respect to 100 parts by mass of the binder resin.

(2-3. Electron transport agent)
The electron transfer agent is not particularly limited as long as it can be applied to the photoreceptor 1. Examples of the electron transfer agent include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, Examples include dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, or dibromomaleic anhydride. Examples of quinone compounds include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds. These electron transfer agents may be used alone or in combination of two or more.

  Of these electron transfer agents, compounds represented by general formula (4), (5), (6), (7) or (8) are preferred, and compounds represented by general formula (4) are more preferred. .

In the general formula (4), R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ each independently have a substituent selected from the group consisting of a hydrogen atom, an alkoxy group and a halogen atom. An alkoxy group which may have a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom, or a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom Represents an aryl group. R ²⁰ and R ²¹ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom.

In general formula (4), the alkyl group which may have a substituent selected from the group consisting of an alkoxy group represented by R ^{15 to} R ¹⁹ and a halogen atom is R in general formulas (1) to (3). a substituent selected from the group consisting of an alkoxy group and a halogen atom represented by ¹ to R ¹⁴ is synonymous with an alkyl group which may. In general formula (4), the alkoxy group which may have a substituent selected from the group consisting of an alkoxy group represented by R ^{15 to} R ¹⁹ and a halogen atom is R in general formulas (1) to (3). a substituent selected from the group consisting of an alkoxy group and a halogen atom represented by ¹ to R ¹⁴ is synonymous with an alkoxy group which may. In the general formula (4), the aryl group which may have a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom represented by R ^{15 to} R ¹⁹ is represented by the general formulas (1) to (3). Among them, it is synonymous with an aryl group which may have a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom represented by R ^{1 to} R ¹⁴ .

In general formula (4), the alkyl group, alkoxy group and halogen atom represented by R ²⁰ and R ^{21 have} the same meanings as the alkyl group, alkoxy group and halogen atom represented by R ^{15 to} R ¹⁹ in general formula (4), respectively. It is.

In General Formula (4), R ^{15 to} R ²¹ each independently preferably represent a hydrogen atom or an alkyl group, and more preferably represent a hydrogen atom or an alkyl group having 1 to 2 carbon atoms.

In the general formulas (5), (6), (7) and (8), R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ , R ²⁷ , R ²⁸ , R ²⁹ , R ³⁰ , R ³¹ , R ³² , R ³³ and R ³⁴ are each independently a group consisting of an alkyl group, an alkoxy group and a halogen atom which may have a substituent selected from the group consisting of a hydrogen atom, a halogen atom, an alkoxy group and a halogen atom. Or an aryl group which may have a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom.

In the general formulas (5) to (8), the alkyl group which may have a substituent selected from the group consisting of an alkoxy group represented by R ^{22 to} R ³⁴ and a halogen atom is represented by the general formulas (1) to (3). In general, it is synonymous with an alkyl group which may have a substituent selected from the group consisting of an alkoxy group represented by R ^{1 to} R ¹⁴ and a halogen atom. In the general formulas (5) to (8), the alkoxy group which may have a substituent selected from the group consisting of an alkoxy group represented by R ^{22 to} R ³⁴ and a halogen atom is represented by the general formulas (1) to (3). ) Are the same as the alkoxy group which may have a substituent selected from the group consisting of an alkoxy group represented by R ^{1 to} R ¹⁴ and a halogen atom. In the general formulas (5) to (8), the aryl group which may have a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom represented by R ^{22 to} R ³⁴ is represented by the general formula (1). to (3), the alkyl group represented by R ¹ to R ^14, the same meaning as aryl group which may have a substituent selected from the group consisting of an alkoxy group and a halogen atom. In general formulas (5) to (8), the halogen atom represented by R ^{22 to} R ^{34 has} the same meaning as the halogen atom represented by R ^{1 to} R ¹⁴ in general formulas (1) to (3).

In the general formula (4), R ^{15 to} R ¹⁹ each independently represents a hydrogen atom or an alkyl group, and R ²⁰ and R ²¹ preferably represent a hydrogen atom. In general formulas (5) to (7), R ^{22 to} R ²⁹ preferably represent an alkyl group, and R ³⁰ preferably represents a halogen atom. In the general formula (8), R ^{31 to} R ³⁴ are each independently a phenyl group having a halogen atom (more specifically, a dichlorophenyl group or the like) or an alkyl group having 1 to 5 carbon atoms (more specifically, Represents a methyl group, an isopropyl group, a tert-butyl group, a tert-pentyl group, or the like.

  Specific examples of the electron transporting agent include compounds represented by chemical formulas (ETM-1) to (ETM-5) (hereinafter sometimes referred to as compounds (ETM-1) to (ETM-5)). It is done.

  The content of the electron transport agent is preferably 5 parts by mass or more and 100 parts by mass or less, and more preferably 10 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the binder resin.

(2-4. Hole transport agent)
The hole transport agent is not particularly limited as long as it can be applied to the photoreceptor 1. As the hole transport agent, for example, a nitrogen-containing cyclic compound or a condensed polycyclic compound can be used. Examples of the nitrogen-containing cyclic compound and the condensed polycyclic compound include triphenylamine derivatives; diamine derivatives (for example, N, N, N ′, N′-tetraphenylbenzidine derivatives, N, N, N ′, N ′). -Tetraphenylphenylenediamine derivative, N, N, N ', N'-tetraphenylnaphthylenediamine derivative, or di (aminophenylethenyl) benzene derivative, or N, N, N', N'-tetraphenylphenanthri Range amine derivatives); oxadiazole compounds (eg, 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole); styryl compounds (eg, 9- (4-diethylaminostyryl) ) Anthracene); carbazole compounds (for example, polyvinyl carbazole); organic polysilane compounds; pyrazoline compounds ( For example, 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline); hydrazone compound; indole compound; oxazole compound; isoxazole compound; thiazole compound; thiadiazole compound; imidazole compound; Or triazole compounds. These hole transport agents may be used alone or in combination of two or more.

  Among these hole transporting agents, the compound represented by the general formula (9), (10), (11) or (12) is preferable, and the compound represented by the general formula (9) is more preferable.

In general formula (9), R ³⁵ , R ³⁶ , R ³⁷ and R ³⁸ each independently represents an alkyl group or arylalkenyl group which may have a substituent selected from the group consisting of an alkoxy group and a halogen atom. Represents. In the general formulas (10), (11) and (12), R ³⁹ , R ⁴⁰ , R ⁴¹ , R ⁴² , R ⁴³ , R ⁴⁴ and R ⁴⁵ are each independently a group consisting of an alkoxy group and a halogen atom. Represents an alkyl group which may have a substituent selected from: In general formulas (9) and (10), p, q, r, s, and t each independently represent an integer of 0 or more and 2 or less. In general formula (11), k, l, m, n, and u each independently represent 1 or 2.

In general formulas (9), (10), (11) and (12), the alkyl group which may have a substituent selected from the group consisting of an alkoxy group represented by R ^{35 to} R ⁴⁵ and a halogen atom, in the general formula (1) to (3), the same meaning as an alkyl group which may have a substituent selected from the group consisting of an alkoxy group and a halogen atom represented by R ¹ to R ^14. In the general formula (9), arylalkenyl group represented by R ³⁵ to R ³⁸ is a substituent and an aryl group and an alkenyl group is bonded, for example, phenylethenyl group. Aryl groups of the general formula (1) to (3), is synonymous with the aryl group represented by R ¹ to R ^14. Examples of the alkenyl group include an alkenyl group having 2 to 6 carbon atoms, and more specifically an alkenyl group having 2 to 4 carbon atoms (more specifically, an ethenyl group, a propenyl group, or a butenyl group). Is more preferable.

  Specific examples of the hole transporting agent include compounds represented by chemical formulas (HTM-1) to (HTM-6) (hereinafter sometimes referred to as compounds (HTM-1) to (HTM-6)). Can be mentioned.

  The total content of the hole transporting 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.

(2-5. Binder resin)
The photosensitive layer 3 can contain a binder resin. Examples of the binder resin include a thermoplastic resin, a thermosetting resin, and a photocurable resin. Examples of the thermoplastic resin include polyester resin, polycarbonate resin, styrene resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, styrene-acrylic acid copolymer, acrylic copolymer. Polymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, urethane resin, polyarylate resin , Polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, or polyether resin. Examples of thermosetting resins include silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, or other crosslinkable thermosetting resins. As an example of a photocurable resin, an epoxy acrylic acid resin or a urethane-acrylic acid copolymer is mentioned. One of these other resins may be used alone, or two or more thereof may be used in combination.

  Of these binder resins, polycarbonate resins are preferred. When the binder resin is a polycarbonate resin, it is easy to obtain the photosensitive layer 3 having an excellent balance of processability, mechanical properties, optical properties, and wear resistance. Among the polycarbonate resins, bisphenol Z-type polycarbonate resin, bisphenol CZ-type polycarbonate resin, or bisphenol C-type polycarbonate resin is preferable because the transferability of the toner image by the photoreceptor 1 is easy to improve. A resin represented by C) or (CZ) is more preferable. In chemical formulas (Z), (C) and (CZ), the suffix of the repeating unit indicates the molar ratio of the repeating unit to which the suffix is attached relative to the total number of moles of the repeating unit in the resin.

  The molecular weight of the binder resin is preferably 40,000 or more in terms of viscosity average molecular weight, and more preferably 40,000 or more and 52,500 or less. When the viscosity average molecular weight of the binder resin is 40,000 or more, it is easy to improve the wear resistance of the photoreceptor 1. When the molecular weight of the other binder resin is 52,500 or less, the binder resin is easily dissolved in a solvent when the photosensitive layer 3 is formed, and the viscosity of the coating solution for the photosensitive layer 3 does not become too high. As a result, the photosensitive layer 3 can be easily formed.

(2-6. Additives)
Additives include, for example, deterioration inhibitors (more specifically, antioxidants, radical scavengers, singlet quenchers, ultraviolet absorbers, etc.), softeners, surface modifiers, extenders, Examples include a sticking agent, a dispersion stabilizer, a wax, an acceptor, a donor, a surfactant, a plasticizer, a sensitizer, and a leveling agent. Examples of the antioxidant include hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone, or a derivative thereof, an organic sulfur compound, or an organic phosphorus compound.

[3. Middle layer]
In the photoreceptor 1, the intermediate layer 4 (particularly the undercoat layer) is located between the conductive substrate 2 and the photosensitive layer 3, for example. The intermediate layer 4 contains, for example, inorganic particles and a resin (interlayer resin) used for the intermediate layer 4. It is considered that the presence of the intermediate layer 4 maintains an insulating state that can suppress the occurrence of leakage. Further, it is considered that the presence of the intermediate layer 4 smoothes the flow of current generated when the photosensitive member 1 is exposed and suppresses the increase in resistance.

  As the inorganic particles, for example, metal (for example, aluminum, iron, or copper), metal oxide (for example, titanium oxide, alumina, zirconium oxide, tin oxide, or zinc oxide) particles, or non-metal oxide (for example, , Silica) particles. These inorganic particles may be used individually by 1 type, and may use 2 or more types together.

  The resin for the intermediate layer is not particularly limited as long as it is a resin that can be used as the resin for forming the intermediate layer 4.

  The intermediate layer 4 may contain various additives as long as the electrophotographic characteristics of the photoreceptor 1 are not adversely affected. The additives are the same as those for the photosensitive layer 3.

[4. Photoconductor manufacturing method]
With reference to FIG. 1, the manufacturing method of the photoreceptor 1 is demonstrated. The method for manufacturing the photoreceptor 1 includes a photosensitive layer forming step. Hereinafter, the photosensitive layer forming step will be described.

(4-1. Photosensitive layer forming step)
In the photosensitive layer forming step, a photosensitive layer forming coating solution (hereinafter sometimes referred to as a coating solution) is applied onto the conductive substrate 2, and at least part of the solvent of the applied coating solution is removed. The photosensitive layer 3 is formed. The photosensitive layer forming step includes, for example, a coating solution preparing step, a coating step, and a drying step. Hereinafter, a coating liquid preparation process, a coating process, and a drying process will be described.

(4-1-1. Coating liquid preparation step)
In the coating liquid preparation step, a coating liquid is prepared. A coating liquid contains the tetracarboxylic dianhydride represented by general formula (1), (2) or (3), binder resin, and a solvent at least. The coating solution may contain a charge generator, a hole transport agent, or an additive as necessary. The coating liquid is, for example, a tetracarboxylic dianhydride represented by the general formula (1), (2) or (3), a binder resin, and optional components (more specifically, a charge generator, hole transport Agents or additives) can be prepared by dissolving or dispersing them in a solvent.

  The solvent contained in the coating solution is not particularly limited as long as each component contained in the coating solution can be dissolved or dispersed. Examples of the solvent include alcohols (for example, methanol, ethanol, isopropanol, or butanol), aliphatic hydrocarbons (for example, n-hexane, octane, or cyclohexane), aromatic hydrocarbons (for example, benzene, toluene, Or xylene), halogenated hydrocarbons (eg, dichloromethane, dichloroethane, carbon tetrachloride, or chlorobenzene), ethers (eg, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, or diethylene glycol dimethyl ether), ketones (eg, acetone) , Methyl ethyl ketone, or cyclohexanone), esters (for example, ethyl acetate or methyl acetate), dimethylformaldehyde, N, N-dimethylformamide (D F), or dimethyl sulfoxide. These solvents may be used alone or in combination of two or more. Of these solvents, non-halogen solvents are preferred.

  The coating solution is prepared by mixing each component and dissolving or dispersing in a solvent. For mixing, dissolving, or dispersing, for example, a bead mill, a roll mill, a ball mill, an attritor, a paint shaker, or an ultrasonic disperser can be used.

  The coating liquid may contain, for example, a surfactant or a leveling agent in order to improve the dispersibility of each component or the surface smoothness of each layer formed.

(4-1-2. Application process)
In the coating process, a coating solution is applied onto the conductive substrate 2. The method for applying the coating solution is not particularly limited as long as it is a method that can uniformly apply the coating solution on the conductive substrate 2. Examples of the coating method include a dip coating method, a spray coating method, a spin coating method, and a bar coating method.

  Since it is easy to adjust the thickness of the photosensitive layer 3 to a desired value, a dip coating method is preferable as a method of applying the coating solution. When the coating process is performed by a dip coating method, in the coating process, the conductive substrate 2 is immersed in a coating solution. Subsequently, the immersed conductive substrate 2 is pulled up from the coating solution. As a result, the coating liquid is applied to the conductive substrate 2.

(4-1-3. Drying step)
In the drying step, at least a part of the solvent contained in the coating solution applied on the conductive substrate 2 is removed. The method for removing the solvent contained in the coating solution is not particularly limited as long as it is a method capable of evaporating the solvent in the coating solution. Examples of the removal method include heating, reduced pressure, or combined use of heating and reduced pressure. More specifically, a method of performing heat treatment (hot air drying) using a high-temperature dryer or a vacuum dryer can be mentioned. The heat treatment conditions are, for example, a temperature of 40 ° C. or higher and 150 ° C. or lower and a time of 3 minutes or longer and 120 minutes or shorter.

  In addition, the manufacturing method of the photoreceptor 1 may further include one or both of a step of forming the intermediate layer 4 and a step of forming the protective layer 5 as necessary. In the step of forming the intermediate layer 4 and the step of forming the protective layer 5, a known method is appropriately selected.

  Heretofore, the photoreceptor 1 according to the first embodiment has been described with reference to FIG. According to the photoreceptor 1 according to the first embodiment, both electrical characteristics and transferability of the toner image by the photoreceptor 1 can be achieved.

<Second Embodiment: Image Forming Apparatus>
The second embodiment relates to an image forming apparatus. The image forming apparatus includes a photoreceptor 1 as an image carrier. As described in the first embodiment, the photoreceptor 1 can suppress a decrease in toner image transferability due to the photoreceptor 1. Therefore, it is considered that the image forming apparatus can form an image with both electrical characteristics and transferability by providing such a photoreceptor 1. Hereinafter, image defects that occur when the electrical characteristics and the transferability cannot be compatible will be described. As an example of the image defect, an image defect caused by a decrease in toner image transferability will be described.

  When the transferability of the toner image is reduced as described above, the toner that could not be transferred to the transfer medium remains on the image carrier 1. The remaining toner may be transferred to an image formed in the next round of the image carrier 1. An image defect in which an image reflecting the image of the previous round of the image carrier 1 is formed is an image defect caused by a decrease in transferability.

  With reference to FIG. 2, an image in which an image defect has occurred will be further described. FIG. 2 is a schematic diagram showing an image in which an image defect has occurred due to a decrease in transferability of the toner image by the photoreceptor 1. The image 100 has a region 102, a region 104, and a region 106. The region 102, the region 104, and the region 106 are regions corresponding to one turn of the image carrier 1. The image 108 in the region 102 includes a rectangular solid image (image density 100%). The area 104 and the area 106 each include an entire blank image (image density 0%) on the design image. The image 108 in the region 102 is first formed along the direction a (conveying direction a) in which the recording medium is conveyed, then the blank image in the region 104 is formed, and finally, the blank image in the region 106 is formed. The blank paper image in the area 104 is an image corresponding to one round of the next rotation of the image carrier 1, and 1 of the image carrier 1 in the second round with reference to the first round of the image carrier 1 forming the image 108. It is an image corresponding to the circumference. The blank image in the area 106 is an image corresponding to one round of the next rotation of the image carrier 1, and 1 of the image carrier 1 on the third round with reference to the first round of the image carrier 1 forming the image 108. It is an image corresponding to the circumference.

  A blank image in the area 110 of the area 104 is an image corresponding to the image 108 in the second turn of the image carrier 1. A blank image in the area 112 of the area 102 is an image corresponding to the image 108 in the third round of the photoconductor. In this case, an image reflecting the image 108 is formed in the area 110 and / or the area 112 as an image defect. As described above, the image defect due to the decrease in transferability of the toner image by the photosensitive member 1 occurs in a cycle with the peripheral length of the image carrier 1 as a unit. Images reflecting the image 108 are easily formed on both ends of the recording medium. This is considered to be because the pressing force to both ends of the recording medium is relatively strong. Here, the both end portions of the recording medium are, for example, both end portions in the vertical direction b (region 110L and region 110R) in the region 110 of the recording medium, and both end portions (region 112L and region 112R in the vertical direction b in the region 112. ).

  Hereinafter, the image forming apparatus according to the second embodiment will be described with reference to FIGS. 3 and 4. First, the case where the image forming apparatus adopts the intermediate transfer method will be described as an example with reference to FIG. FIG. 3 is a schematic diagram illustrating a configuration of one aspect of the image forming apparatus according to the second embodiment. The image forming apparatus 6 includes the photoreceptor 1 according to the first embodiment as an image carrier.

  The image forming apparatus 6 according to the second embodiment includes, for example, the image carrier 1, a charging unit 27 corresponding to a charging device, an exposure unit 28 corresponding to an exposure device, a developing unit 29 corresponding to a developing unit, A transfer unit 26. The charging unit 27 charges the surface of the image carrier 1. The charging polarity of the charging unit 27 is positive. The exposure unit 28 exposes the charged surface of the image carrier 1 to form an electrostatic latent image on the surface of the image carrier 1. The developing unit 29 develops the electrostatic latent image as a toner image. The transfer unit 26 transfers the toner image from the image carrier 1 to the transfer target 38. As shown in FIG. 3, when the image forming apparatus 6 adopts the intermediate transfer method, the transfer unit 26 corresponds to the primary transfer roller 33. Further, the transfer body 38 corresponds to an intermediate transfer body (for example, the intermediate transfer belt 20).

  The image forming apparatus 6 is not particularly limited as long as it is an electrophotographic image forming apparatus. The image forming apparatus 6 may be, for example, a monochrome image forming apparatus or a color image forming apparatus. The image forming apparatus 6 may be a tandem color image forming apparatus in order to form toner images of the respective colors using different color toners.

  Hereinafter, the image forming apparatus 6 will be described by taking a tandem color image forming apparatus as an example. The image forming apparatus 6 includes a plurality of image carriers 1 arranged in parallel in a predetermined direction and a plurality of developing units 29. Each of the plurality of developing units 29 is disposed to face the image carrier 1. Each of the plurality of developing units 29 includes a developing roller. The developing roller carries and conveys toner, and supplies the toner to the surface of the corresponding image carrier 1.

  As shown in FIG. 3, the image forming apparatus 6 further includes a box-shaped device housing 7. In the device housing 7, a paper feeding unit 8, an image forming unit 9, and a fixing unit 10 are provided. The paper feed unit 8 feeds the paper P. The image forming unit 9 transfers the toner image based on the image data to the paper P while conveying the paper P fed from the paper feeding unit 8. The fixing unit 10 fixes the unfixed toner image transferred on the paper P by the image forming unit 9 to the paper P. Further, a paper discharge unit 11 is provided on the upper surface of the device housing 7. The paper discharge unit 11 discharges the paper P fixed by the fixing unit 10.

  The paper feed unit 8 includes a paper feed cassette 12, a first pickup roller 13, a plurality of paper feed rollers 14, and a registration roller pair 17. The paper feed cassette 12 is provided so as to be detachable from the device housing 7. Various sizes of paper P are stored in the paper feed cassette 12. The first pickup roller 13 is provided at the upper left position of the paper feed cassette 12. The first pickup roller 13 takes out the sheets P stored in the sheet feeding cassette 12 one by one. The plurality of paper feed rollers 14 transport the paper P picked up by the first pickup roller 13. The registration roller pair 17 temporarily waits for the paper P conveyed by the plurality of paper feed rollers 14 and then supplies the paper P to the image forming unit 9 at a predetermined timing.

  The paper feed unit 8 may further include a manual feed tray (not shown) and a second pickup roller 18. The manual feed tray is attached to the left side surface of the device housing 7. The second pickup roller 18 takes out the paper P placed on the manual feed tray. The paper P taken out by the second pickup roller 18 is conveyed by a plurality of paper feed rollers 14 and is supplied to the image forming unit 9 by a registration roller pair 17 at a predetermined timing.

  The image forming unit 9 includes an image forming unit 19, an intermediate transfer belt 20, and a secondary transfer roller 21. A toner image is primarily transferred onto the intermediate transfer belt 20 by the image forming unit 19 on the peripheral surface of the intermediate transfer belt 20 (contact surface with the surface of the image carrier 1). The toner image to be primarily transferred is formed based on image data transmitted from a host device such as a computer. The secondary transfer roller 21 secondarily transfers the toner image on the intermediate transfer belt 20 onto the paper P fed from the paper feed cassette 12.

  The image forming unit 19 includes a yellow toner supply unit 25, a magenta toner supply unit 24, a cyan toner supply unit 23, and a black toner supply unit 22. The image forming unit 19 includes a yellow toner supply unit 25 and a magenta toner supply from the upstream side (right side in FIG. 3) to the downstream side in the rotation direction of the intermediate transfer belt 20 with the yellow toner supply unit 25 as a reference. A unit 24, a cyan toner supply unit 23, and a black toner supply unit 22 are sequentially arranged. In each of the units 22 to 25, the image carrier 1 is disposed at the center position of each unit. The image carrier 1 is arranged to be rotatable in the direction of an arrow (clockwise). The units 22 to 25 may be process cartridges described later that are detachable from the main body of the image forming apparatus 6.

  Around each image carrier 1, a charging unit 27, an exposure unit 28, and a developing unit 29 are sequentially arranged from the upstream side in the rotation direction of each image carrier 1 with respect to the charging unit 27.

  A static eliminator (not shown) and a cleaning device (not shown) may be provided on the upstream side of the charging unit 27 in the rotation direction of the image carrier 1. The static eliminator neutralizes the peripheral surface (surface) of the image carrier 1 after the primary transfer of the toner image to the intermediate transfer belt 20 is completed. The surface of the image carrier 1 cleaned by the cleaning device or the surface of the image carrier 1 neutralized by the static eliminator is sent to the charging unit 27 and newly charged. When the image forming apparatus 6 includes a cleaning device and a charge eliminator, the charging unit 27, the exposure unit 28, the developing unit 29, the transfer unit 26, and the cleaning unit with respect to the charging unit 27 from the upstream side in the rotation direction of each image carrier 1. Arranged in the order of device and static eliminator. The developing unit 29 can also function as a cleaning device. Details of the developing unit 29 will be described later.

  As already described, the charging unit 27 charges the surface of the image carrier 1. Specifically, the charging unit 27 uniformly charges the surface of the image carrier 1. The charging unit 27 is not particularly limited as long as the surface of the image carrier 1 can be uniformly charged. The charging unit 27 may be a non-contact type charging unit or a contact type charging unit. The non-contact charging unit 27 applies a voltage without contacting the image carrier 1. Examples of the non-contact charging unit 27 include a corona discharge charging unit, and more specifically, a corotron charger or a scorotron charger. The contact-type charging unit applies a voltage in contact with the image carrier 1. Examples of the contact-type charging unit include a charging roller or a charging brush. When a contact-type charging unit is used, discharge of active gas (for example, ozone or nitrogen oxide) generated from the charging unit 27 can be suppressed. As a result, the deterioration of the photosensitive layer 3 due to the active gas is suppressed, and a design in consideration of the office environment can be achieved.

  The charging unit 27 can charge the surface of the image carrier 1 while being in contact with the image carrier 1 as described above. That is, the image forming apparatus 6 according to the second embodiment can employ a so-called contact charging method. In the image forming apparatus 6 that employs such a contact charging method, since the charging unit 27 and the image carrier 1 are usually in contact with each other during development, the surface potential of the image carrier 1 is likely to decrease. In the image forming apparatus 6 according to the second embodiment, since the surface potential of the image carrier 1 is not easily lowered as described above, it is possible to suppress a reduction in transferability of the toner image by the image carrier 1. For this reason, even if the image forming apparatus 6 according to the second embodiment adopts the contact charging method, it is possible to suppress the occurrence of image defects due to a decrease in transferability.

  Examples of the charging roller include a charging roller that rotates depending on the rotation of the image carrier 1 while being in contact with the surface of the image carrier 1. Further, for example, at least the surface portion of the charging roller is made of resin. Specifically, the charging roller includes a core metal that is rotatably supported, a resin layer formed on the core metal, and a voltage application unit that applies a voltage to the core metal. The charging unit 27 provided with such a charging roller can charge the surface of the image carrier 1 that is in contact with the resin through the resin layer when the voltage application unit applies a voltage to the cored bar.

  The resin constituting the resin layer of the charging roller is not particularly limited as long as the surface of the image carrier 1 can be satisfactorily charged. Specific examples of the resin constituting the resin layer include a silicone resin, a urethane resin, or a silicone-modified resin. The resin layer may contain an inorganic filler.

  The voltage applied by the charging unit 27 is not particularly limited. Examples of the voltage applied by the charging unit 27 include an AC voltage, a superimposed voltage obtained by superimposing the AC voltage on the DC voltage, or a DC voltage. Especially, it is preferable that the charging unit 27 applies only a DC voltage. The charging unit 27 that applies only the DC voltage has the following advantages compared to the charging unit 27 that applies the AC voltage or the charging unit 27 that applies the superimposed voltage. When the charging unit 27 applies only a DC voltage, the voltage value applied to the image carrier 1 is constant, so that the surface of the image carrier 1 is easily charged uniformly to a constant potential. Further, when the charging unit 27 applies only a DC voltage, the wear amount of the photosensitive layer 3 tends to decrease. As a result, it is considered that a suitable image can be formed. The DC voltage applied to the image carrier 1 by the charging unit 27 is preferably 1,000 V or more and 2,000 V or less, more preferably 1,200 V or more and 1,800 V or less, and 1,400 V or more, 1, A voltage of 600 V or less is particularly preferable.

  Examples of the exposure unit 28 include a laser scanning unit. The exposure unit 28 exposes the charged surface of the image carrier 1 to form an electrostatic latent image on the surface of the image carrier 1. Specifically, the exposure unit 28 irradiates the surface of the image carrier 1 uniformly charged by the charging unit 27 with laser light based on image data input from a host device such as a personal computer. Thereby, an electrostatic latent image based on the image data is formed on the surface of the image carrier 1.

  As already described, the developing unit 29 develops the electrostatic latent image as a toner image. Specifically, the developing unit 29 supplies toner to the surface of the image carrier 1 on which the electrostatic latent image is formed, and forms a toner image based on the image data. Then, the formed toner image is primarily transferred to the intermediate transfer belt 20. Note that the charging polarity of the toner is positive.

  The developing unit 29 can develop the electrostatic latent image as a toner image while in contact with the image carrier 1. That is, the image forming apparatus 6 according to the second embodiment can employ a so-called contact development method. In the image forming apparatus 6 that employs such a contact development method, the developing roller and the image carrier 1 are usually in contact with each other during development, and thus the surface potential of the image carrier 1 is likely to decrease. In the image forming apparatus 6 according to the second embodiment, since the surface potential of the image carrier 1 is not easily lowered as described above, it is possible to suppress a reduction in transferability of the toner image by the image carrier 1. For this reason, even if the image forming apparatus 6 according to the second embodiment adopts the contact development method, it is possible to suppress the occurrence of image defects due to a decrease in transferability of the toner image by the image carrier 1.

  The developing unit 29 can clean the surface of the image carrier 1. That is, the developing unit 29 can remove components remaining on the surface of the image carrier 1 (hereinafter, may be referred to as “residual components”). Examples of the residual component include a toner component (more specifically, a toner or a free external additive) or a non-toner component (more specifically, a paper powder). Since these residual components can lower the surface potential of the image carrier 1, when the developing unit 29 cleans the surface of the image carrier 1, the image forming apparatus 6 according to the second embodiment uses the toner from the image carrier 1. It is possible to further suppress image defects due to a decrease in image transferability.

In order for the developing unit 29 to efficiently clean the surface of the image carrier 1, it is preferable to satisfy the following conditions (1) and (2).
Condition (1): A contact developing method is adopted, and a peripheral speed difference is provided between the image carrier and the developing roller.
Condition (2): The difference between the surface potential of the image carrier 1 and the potential of the developing bias satisfies the following formulas (2-1) and (2-2).
0 (V) <potential of developing bias (V) <surface potential of unexposed area of image carrier (V) Formula (2-1)
Development bias potential (V)> Image carrier surface exposure potential (V)> 0 (V) Expression (2-2)
In formula (2-1), the surface potential of the unexposed area of the image carrier 1 that has not been exposed by the exposure unit 28. In Formula (2-2), the surface potential of the exposure region of the image carrier 1 exposed by the exposure unit 28. Note that the surface potential of the unexposed area of the image carrier 1 and the surface potential of the exposed area of the image carrier 1 are the same as the surface potential of the unexposed area of the image carrier 1. The transfer unit 26 transfers the toner image from the image carrier 1 to the transfer body. After the transfer, measurement is performed before the charging unit 27 charges the surface of the image carrier 1 for the next round.

  When the contact development method shown in condition (1) is employed and a peripheral speed difference is provided between the image carrier 1 and the development roller, the surface of the image carrier contacts the development roller, and the surface of the image carrier 1 Residual components are removed by friction with the developing roller.

The rotational speed of the image carrier 1 is preferably 120 mm / second or more and 350 mm / second or less. The rotation speed of the developing roller is preferably 133 mm / second or more and 700 mm / second or less. Further, it is preferable that the ratio between the rotation speed V _P of the image carrier 1 and the rotation speed V _D of the developing roller satisfies the formula (1-1). When this ratio is other than 1, it indicates that a peripheral speed difference is provided between the image carrier 1 and the developing roller.
0.5 ≦ V _P / V _D ≦ 0.8 Expression (1-1)

  In the condition (2), a case where the toner charging polarity is positively charged and the developing method is a reversal developing method will be described as an example. If there is a difference between the potential of the developing bias shown in condition (2) and the surface potential of the image carrier 1, the surface potential (charging potential) of the image carrier 1 and the potential of the developing bias in the unexposed area. In order to satisfy Equation (2-1), the electrostatic repulsive force acting between the residual toner (hereinafter sometimes referred to as “residual toner”) and the unexposed area of the image carrier 1 causes the residual toner to develop. Larger than the electrostatic repulsive force acting between the rollers. Therefore, the residual toner moves from the surface of the image carrier 1 to the developing roller and is collected. The toner hardly adheres to the unexposed area of the image carrier 1.

  If a difference is provided between the potential of the developing bias shown in condition (2) and the surface potential of the image carrier 1, the surface potential (sensitivity potential) of the image carrier 1 and the potential of the developing bias in the exposure region are expressed by mathematical formulas. In order to satisfy (2-2), the electrostatic repulsive force acting between the residual toner and the exposure area of the image carrier 1 is smaller than the electrostatic repulsive force acting between the toner and the developing roller. Therefore, residual toner on the surface of the image carrier 1 is held on the surface of the image carrier 1. The toner adheres to the exposed area of the image carrier 1.

  The potential of the developing bias is, for example, + 250V or more and + 400V or less. The charging potential of the image carrier 1 is, for example, not less than + 450V and not more than + 900V. The sensitivity potential of the image carrier 1 is, for example, not less than + 50V and not more than + 200V. The difference between the potential of the developing bias and the charging potential of the image carrier 1 is, for example, + 100V or more and + 700V or less. The difference between the potential of the developing bias and the sensitivity potential of the image carrier 1 is, for example, not less than + 150V and not more than + 300V. Here, the potential difference indicates the absolute value of the difference. Conditions for providing such a potential difference are, for example, a developing bias potential +330 V, a charging potential +600 V of the image carrier 1, and a sensitivity potential +100 V of the image carrier 1.

  The intermediate transfer belt 20 is an endless belt rotating body. The intermediate transfer belt 20 is stretched around a driving roller 30, a driven roller 31, a backup roller 32, and a plurality of primary transfer rollers 33. The intermediate transfer belt 20 is disposed so that the surfaces of the plurality of image carriers 1 are in contact with the peripheral surface of the intermediate transfer belt 20.

  The intermediate transfer belt 20 is pressed against the image carrier 1 by the primary transfer roller 33. In the pressed state, the intermediate transfer belt 20 rotates endlessly in the arrow (counterclockwise) direction by the drive roller 30. The driving roller 30 is rotationally driven by a driving source such as a stepping motor, and gives a driving force for rotating the intermediate transfer belt 20 endlessly. The driven roller 31, the backup roller 32, and the plurality of primary transfer rollers 33 are rotatably provided and rotate following the endless rotation of the intermediate transfer belt 20 by the driving roller 30. The driven roller 31, the backup roller 32, and the primary transfer roller 33 support the intermediate transfer belt 20.

  The primary transfer roller 33 is disposed to face each image carrier 1. The primary transfer roller 33 transfers the toner image from the image carrier 1 to the intermediate transfer belt 20. Specifically, the primary transfer roller 33 applies a primary transfer bias (specifically, a bias having a polarity opposite to the charging polarity of the toner) to the intermediate transfer belt 20. As a result, the toner image formed on each image carrier 1 is sequentially transferred (primary transfer) between each image carrier 1 and the primary transfer roller 33 to the circulating intermediate transfer belt 20. .

  The secondary transfer roller 21 applies a secondary transfer bias (specifically, a bias having a polarity opposite to that of the toner image) to the paper P. As a result, the toner image primarily transferred onto the intermediate transfer belt 20 is transferred onto the paper P between the secondary transfer roller 21 and the backup roller 32. As a result, an unfixed toner image is transferred onto the paper P.

  The fixing unit 10 fixes the unfixed toner image transferred to the paper P by the image forming unit 9. The fixing unit 10 includes a heating roller 34 and a pressure roller 35. The heating roller 34 is heated by an energized heating element. The pressure roller 35 is disposed to face the heating roller 34, and the circumferential surface of the pressure roller 35 is pressed against the circumferential surface of the heating roller 34.

  The transfer image transferred to the paper P by the secondary transfer roller 21 in the image forming unit 9 is fixed to the paper P by a fixing process by heating when the paper P passes between the heating roller 34 and the pressure roller 35. The Then, the paper P subjected to the fixing process is discharged to the paper discharge unit 11. In addition, a plurality of transport rollers 36 are disposed at appropriate positions between the fixing unit 10 and the paper discharge unit 11.

  The paper discharge unit 11 is formed by recessing the top of the device housing 7. A paper discharge tray 37 that receives the discharged paper P is provided at the bottom of the recessed portion. The image forming apparatus 6 according to the second embodiment has been described above with reference to FIG.

  Hereinafter, an image forming apparatus according to another aspect of the second embodiment will be described with reference to FIG. FIG. 4 is a schematic diagram illustrating a configuration of another aspect of the image forming apparatus according to the second embodiment. The image forming apparatus 6 shown in FIG. 4 differs from the image forming apparatus 6 shown in FIG. 3 in that the intermediate transfer belt 20 (intermediate transfer member) is not provided. In the image forming apparatus 6 illustrated in FIG. 4, the transfer unit corresponds to the transfer roller 41. In the image forming apparatus 6 shown in FIG. 4, the transfer target corresponds to a recording medium (paper P). That is, the image forming apparatus shown in FIG. 4 employs a direct transfer method. In FIG. 4, elements corresponding to those in FIG. 3 are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 4, the transfer belt 40 is an endless belt-like rotating body. The transfer belt 40 is stretched around a driving roller 30, a driven roller 31, a backup roller 32, and a plurality of transfer rollers 41. The transfer belt 40 is installed so that the circumferential surface of each image carrier 1 is in contact with the surface (contact surface) of the transfer belt 40. The transfer roller 41 is disposed to face the image carrier 1. The transfer belt 40 is pressed against the image carrier 1 by each transfer roller 41. In the pressed state, the transfer belt 40 is rotated endlessly by the plurality of rollers 30, 31, 32, and 41. The driving roller 30 is rotationally driven by a driving source such as a stepping motor, and gives a driving force for rotating the transfer belt 40 endlessly. The driven roller 31, the backup roller 32, and the transfer roller 41 are rotatably provided. With the endless rotation of the transfer belt 40 by the driving roller 30, the driven roller 31, the backup roller 32, and the plurality of transfer rollers 41 are driven to rotate. These rollers 31, 32 and 41 are driven to rotate and support the transfer belt 40. The paper P supplied from the registration roller pair 17 is sucked onto the transfer belt 40 by the suction roller 42. The sheet P adsorbed on the transfer belt 40 passes between each image carrier 1 and the transfer roller 41 as the transfer belt 40 rotates.

  The transfer unit transfers the toner image from the image carrier 1 to the paper P while the image carrier 1 and the paper P are in contact with each other. Specifically, each transfer roller 41 applies a transfer bias (specifically, a bias having a polarity opposite to the toner charging polarity) to the paper P adsorbed on the transfer belt 40. As a result, the toner image formed on the image carrier 1 is transferred onto the paper P between each image carrier 1 and the transfer roller 41. The transfer belt 40 circulates in the arrow (clockwise) direction by driving the driving roller 30. Along with this, the paper P sucked on the transfer belt 40 sequentially passes between each image carrier 1 and the transfer roller 41. When passing, the corresponding color toner images formed on each image carrier 1 are sequentially transferred onto the paper P in a stacked state. Thereafter, each image carrier 1 further rotates and shifts to the next process. The image forming apparatus that employs the direct transfer method according to another aspect of the second embodiment has been described above with reference to FIG.

  As described with reference to FIGS. 3 and 4, the image forming apparatus 6 according to the second embodiment includes the photosensitive member 1 according to the first embodiment as an image carrier. The photoreceptor 1 can suppress a decrease in transferability of the toner image. By providing such a photoreceptor 1 as an image carrier, the image forming apparatus 6 according to the second embodiment can form an image with both electrical characteristics and transferability compatible.

<Third embodiment: Process cartridge>
The third embodiment relates to a process cartridge. The process cartridge according to the third embodiment includes, for example, the photoreceptor 1 according to the first embodiment that is unitized. The process cartridge may be designed to be detachable from the image forming apparatus 6 according to the second embodiment. For example, in addition to the photoreceptor 1, the process cartridge includes a plurality of configurations described in the second embodiment (more specifically, a charging unit 27, an exposure unit 28, a developing unit 29, a transfer unit 26, a cleaning device, A configuration in which at least one selected from the group consisting of a static eliminator and the like is unitized is adopted.

  The process cartridge according to the third embodiment has been described above. The process cartridge according to the third embodiment includes the photoreceptor 1 according to the first embodiment. The photoreceptor 1 can suppress a decrease in transferability. Therefore, the process cartridge according to the third embodiment can form an image while achieving both electrical characteristics and transferability. Further, since such a process cartridge is easy to handle, when the sensitivity characteristic of the image carrier 1 is deteriorated, the process cartridge including the image carrier 1 can be easily and quickly replaced.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the scope of the examples.

[1. Photoconductor Material]
The following charge generator, hole transport agent, electron transport agent, and binder resin were prepared as materials for forming the photosensitive layer of the photoreceptor.

  A compound (CGM-1X) was prepared as a charge generator. The compound (CGM-1X) was a metal-free phthalocyanine represented by the chemical formula (CGM-1) described in the first embodiment. Furthermore, the crystal structure of the compound (CGM-1X) was X-type.

  Compounds (HTM-1) to (HTM-6) were prepared as hole transporting agents. The compounds (HTM-1) to (HTM-6) have been described in the first embodiment.

  Compounds (ETM-1) to (ETM-5) were prepared as electron transport agents. The compounds (ETM-1) to (ETM-5) have been described in the first embodiment.

  A polycarbonate resin (Za) was prepared as a binder resin. The polycarbonate resin (Za) was a polycarbonate resin represented by the chemical formula (Z) described in the first embodiment.

[2. Production of photoconductor]
Photoconductors (A-1) to (A-39) and photoconductors (B-1) to (B-12) were produced using materials for forming the photosensitive layer of the prepared photoconductor.

(2-1. Production of Photosensitive Member (A-1))
First, a conductive substrate was prepared. This conductive substrate was an aluminum conductive substrate having a diameter of 160 mm, a length of 365 mm, and a thickness of 2 mm.

  Next, a photosensitive layer forming step was performed. First, a coating solution was prepared. 2 parts by mass of a compound (CGM-1X) as a charge generating agent, 60 parts by mass of a compound (HTM-3) as a hole transporting agent, 35 parts by mass of a compound (ETM-1) as an electron transporting agent, and a binder 100 parts by mass of polycarbonate resin (Za) as a resin and 800 parts by mass of tetrahydrofuran as a solvent were put in a container. The contents of the container were mixed and dispersed for 50 hours using a ball mill to obtain a coating solution.

  Next, using a dip coating method, a coating solution was applied on the conductive substrate obtained in the oxide film forming step, and a coating film was formed on the conductive substrate. Specifically, the conductive substrate was immersed in the coating solution. Next, the immersed conductive substrate was pulled up from the coating solution. Thereby, the coating liquid was applied to the conductive substrate.

  Next, the conductive substrate coated with the coating solution was dried with hot air at 100 ° C. for 40 minutes. As a result, the solvent (tetrahydrofuran) contained in the coating solution applied to the conductive substrate was removed. As a result, a photosensitive layer was formed on the conductive substrate. Thereby, the photoreceptor (A-1) was obtained.

(2-2. Production of photoconductors (A-2) to (A-39) and photoconductors (B-1) to (B-12))
The photoconductors (A-2) to (A-39) and the photoconductors (B-1) to (B-12) were produced in the same manner as in the production of the photoconductor (A-1) except that the following points were changed. ) Was manufactured.

  In the production of the photoreceptor (A-1), a compound (ADD-1) as a tetracarboxylic dianhydride, a compound (ETM-1) as an electron transporting agent, and a hole transporting agent used for preparing the coating solution The compound (HTM-1) was changed to the tetracarboxylic dianhydride, electron transport agent, and hole transport agent of the type shown in Table 1 or Table 2, respectively. Moreover, 1.00 mass part of tetracarboxylic dianhydride content with respect to 100 mass parts of binder resin was changed into content shown in Table 1 or Table 2.

[3. Measuring method]
(3-1. Measurement of surface potential of photoreceptor)
Using a surface potential meter (“MODEL244” manufactured by Monroe Electronics), a surface potential probe (“MODEL1017AS” manufactured by Monroe Electronics, Inc.) was installed at the position after transfer, temperature 23 ° C., humidity 50% RH, drum linear velocity 165 mm. / Second, grid voltage 600V, flow-in current 300μA, measurement was performed.

[4. Evaluation method]
(4-1. Evaluation of sensitivity of photoreceptor)
Using a surface potentiometer (“MODEL244” manufactured by Monroe Electronics), a surface potential probe (“MODEL1017AE” manufactured by Monroe Electronics) was installed at the position of the developing unit, temperature 23 ° C., humidity 50% RH, charging potential 600 V, exposure Measurement was performed under the conditions of a wavelength of 780 nm and an exposure amount of 1.2 μJ / cm ² .

(4-2. Evaluation of transferability of toner image by photoreceptor)
The photoconductor was mounted on an evaluation machine. As an evaluation machine, a printer (“FS-1300D” manufactured by Kyocera Document Solutions Co., Ltd., a dry electrophotographic printer using a semiconductor laser) was used. The evaluator was provided with a charging roller as a charging unit. A DC voltage was applied to the charging roller. The evaluation machine was provided with a direct transfer type transfer section (transfer roller). The evaluator was equipped with a contact developing type developing unit. For the transferability evaluation, “Kyocera Document Solutions Brand Paper VM-A4 (A4 size)” sold by Kyocera Document Solutions Inc. was used as the paper. For transferability evaluation, “TK-131” manufactured by Kyocera Document Solutions Co., Ltd. was used as the toner. The measurement of the transferability evaluation was performed in a high temperature and high humidity (temperature: 32.5 ° C., humidity: 80% RH) environment.

  An evaluation image was formed on a sheet using an evaluation machine equipped with a photoreceptor and toner. Details of the evaluation image will be described later with reference to FIG. The image forming condition was set to a linear velocity of 165 mm / sec. The current applied by the transfer roller to the photoconductor was set to -25 μA.

  Next, the obtained image was visually confirmed, and the presence or absence of an image corresponding to the image 208 was confirmed in the area 210 and the area 212. From the obtained visual observation results, the transferability of the toner image by the photoconductor was evaluated according to the following criteria. ◎ (Very good) and ○ (Good) were accepted.

  The evaluation image will be described with reference to FIG. FIG. 5 is a schematic diagram showing an evaluation image. The evaluation image 200 includes a region 202, a region 204, and a region 206. A region 202 is a region corresponding to one rotation of the image carrier. The image 208 in the region 202 includes a solid image (image density 100%). This solid image had a rectangular shape. The region 204 and the region 206 are regions corresponding to one rotation of the image carrier, and each includes a blank paper image (image density 0%). First, the image 208 of the region 202 was formed along the transport direction a, and then blank images of the region 204 and the region 206 were formed. The blank image in the area 204 is an image formed on the second turn with reference to the circumference on which the image 208 is formed. An area 210 is an area corresponding to the image 208 in the area 204. A blank paper image in the area 206 is an image formed on the third circumference with the circumference on which the image 108 is formed as a reference. An area 212 is an area corresponding to the image 208 in the area 204.

(Evaluation criteria for transferability)
A (very good): The image corresponding to the image 208 was not confirmed in the area 210 and the area 212.
○ (Good): Images corresponding to the image 208 were slightly confirmed at both ends of the area 210 in the vertical direction b. An image corresponding to the image 208 was not confirmed in the area 212.
Δ (bad): Images corresponding to the image 208 were clearly confirmed at both ends of the area 210 in the vertical direction b. An image corresponding to the image 208 was not confirmed in the area 212.
X (very bad): Images corresponding to the image 208 were clearly confirmed at both ends of the area 210 and the area 212 in the vertical direction b.

  As shown in Tables 1 and 2, in the photoreceptors (A-1) to (A-39), the photosensitive layer contains a tetracarboxylic dianhydride represented by the general formula (1), and tetra The content of carboxylic dianhydride was 0.02 parts by mass or more and 5.00 parts by mass or less with respect to 100 parts by mass of the binder resin.

  As shown in Table 2, in the photoreceptor (B-1) and the photoreceptor (B-2), each of the photosensitive layers contains a tetracarboxylic dianhydride represented by the general formula (1). The content of tetracarboxylic dianhydride was 0.01 parts by mass and 10 parts by mass with respect to 100 parts by mass of the binder resin, respectively. In the photoreceptors (B-3) to (B-12), none of the photosensitive layers had the tetracarboxylic dianhydride represented by the general formula (1).

  As shown in Tables 3 and 4, in the photoconductors (A-1) to (A-39), the sensitivity evaluation results are all “good”, and the toner image transferability evaluation results of the photoconductors All were ○ (good). As shown in Table 4, in the photoreceptor (B-1) and the photoreceptors (B-3) to (B-12), the evaluation results of the transferability of the toner image by the photoreceptor are all x (bad). It was. In the photoreceptor (B-2), the sensitivity evaluation result was x (poor).

  As described above, the photoconductors (A-1) to (A-39) have both electrical characteristics and transferability of the toner image by the photoconductor as compared with the photoconductors (B-1) to (B-12). Can do.

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

1 Photoconductor (Single-layer type electrophotographic photoconductor)
2 Conductive substrate 3 Photosensitive layer 6 Image forming apparatus 26 Transfer unit 27 Charging unit 28 Exposure unit 29 Development unit 38 Transfer object

Claims (11)

A positively charged single layer type electrophotographic photosensitive member provided with a photosensitive layer,
The photosensitive layer includes tetracarboxylic dianhydride and a binder resin,
The tetracarboxylic dianhydride is a compound represented by the general formula (1), (2) or (3),
The positively charged single layer type electrophotographic photoreceptor, wherein the content of the tetracarboxylic dianhydride is 0.02 parts by mass or more and 7.00 parts by mass or less with respect to 100 parts by mass of the binder resin.

In the general formulas (1), (2) and (3),
R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ and R ¹⁴ are each independently a hydrogen atom, An alkyl group which may have a substituent selected from the group consisting of a halogen atom, an alkoxy group and a halogen atom, an alkoxy group which may have a substituent selected from the group consisting of an alkoxy group and a halogen atom, or An aryl group which may have a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom. In the general formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom or a halogen atom,
In the general formula (2), R ⁵ and R ⁶ represent a hydrogen atom,
The positively charged single layer type electron according to claim 1, wherein, in the general formula (3), R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ and R ¹⁴ represent a hydrogen atom. Photoconductor. The positively charged single layer according to claim 1 or 2, wherein the photosensitive layer further contains a compound represented by the general formula (4), (5), (6), (7) or (8) as an electron transport agent. Layer type electrophotographic photoreceptor.

In the general formula (4),
R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ are each independently an alkyl group, an alkoxy group and a halogen which may have a substituent selected from the group consisting of a hydrogen atom, an alkoxy group and a halogen atom. alkoxy group which may have a substituent selected from the group consisting of atom, or an alkyl group, an aryl group which may have a substituent selected from the group consisting of an alkoxy group and a halogen atom, R ²⁰ And R ²¹ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom.

In the general formulas (5), (6), (7) and (8), R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ , R ²⁷ , R ²⁸ , R ²⁹ , R ³⁰ , R ³¹ , R ³² , R ³³ and R ³⁴ each independently comprises an alkyl group, an alkoxy group and a halogen atom which may have a substituent selected from the group consisting of a hydrogen atom, a halogen atom, an alkoxy group and a halogen atom. An alkoxy group which may have a substituent selected from the group, or an aryl group which may have a substituent selected from the group consisting of an alkyl group, an alkoxy group and a halogen atom. In the general formula (4), R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ each independently represent a hydrogen atom or an alkyl group, R ²⁰ and R ²¹ represent a hydrogen atom,
In the general formulas (5), (6), and (7), R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ , R ²⁷ , R ²⁸ , and R ²⁹ represent an alkyl group, and R ³⁰ is halogen. Represents an atom,
4. The positively charged single-layer electrophotographic image according to claim 3, wherein in the general formula (8), R ³¹ , R ³² , R ³³ and R ³⁴ each independently represents an alkyl group or a phenyl group having a halogen atom. Photoconductor. A positively charged single layer type electrophotographic photoreceptor provided in an image forming apparatus,
The image forming apparatus exposes the surface of the image carrier, the charging unit for charging the surface of the image carrier, and the charged surface of the image carrier. An exposure unit that forms an image, a developing unit that develops the electrostatic latent image as a toner image, and a transfer unit that transfers the toner image from the image carrier to a transfer target,
The charging polarity of the charging unit is positive.
After the transfer unit has transferred the toner image from the image carrier to the transfer target, the charging unit has been exposed by the exposure unit before charging the surface of the image carrier in the next round. The positively charged single layer type electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the surface potential of the exposure region of the image carrier is 0 V or more.   A process cartridge comprising the positively charged single layer type electrophotographic photosensitive member according to any one of claims 1 to 5. An image carrier;
A charging unit that charges the surface of the image carrier;
An image forming apparatus comprising:
The charging polarity of the charging part is positive.
The image forming apparatus according to claim 1, wherein the image carrier is a positively charged single layer type electrophotographic photosensitive member according to claim 1. A developing section;
The image forming apparatus according to claim 7, wherein the developing unit develops the electrostatic latent image as a toner image while being in contact with the image carrier.   The image forming apparatus according to claim 8, wherein the developing unit cleans the surface of the image carrier. A transfer section;
The image forming apparatus according to claim 8, wherein the transfer unit transfers the toner image from the image carrier to a recording medium.   The image forming apparatus according to claim 7, wherein the charging unit is a charging roller.

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