JP2010139649A - Electrophotographic photoreceptor, electrophotographic photoreceptor cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single layer type electrophotographic photoreceptor in which stability of a coating liquid for forming a photosensitive layer is stable, and also, which has satisfactory electric properties. <P>SOLUTION: The electrophotographic photoreceptor having a single layer type photosensitive layer provided on a conductive support, comprises at least one kind of enamine compound expressed by formula (1). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member, an electrophotographic photosensitive member cartridge, and an image forming apparatus used for a copying machine, a printer, and the like. Specifically, a single-layer type electrophotographic photosensitive member having good electrical characteristics and excellent stability of a coating solution for forming a photosensitive layer, and an electrophotographic photosensitive member cartridge and image formation provided with the photosensitive member It relates to the device.

  Electrophotographic technology is widely used in the fields of copiers and various printers because of its immediacy and high quality images. An electrophotographic photosensitive material (hereinafter also simply referred to as “photosensitive material”) that is the core of electrophotographic technology is an organic photoconductive material that has the advantages of being pollution-free, easy to form, and easy to manufacture. A photoconductor using is used.

  In organic electrophotographic photoreceptors, so-called function-separated type photoreceptors that share the functions of charge generation and movement with separate compounds have a large room for material selection, and the characteristics of the photoreceptor can be easily controlled. Since then, it has become the mainstream of development. From the viewpoint of the layer structure, a single layer type electrophotographic photosensitive member (hereinafter referred to as a single layer type photosensitive member) having a charge generation material and a charge transport material in the same layer, a charge generation material and a charge transport material are provided. A laminated electrophotographic photoreceptor (hereinafter referred to as a laminated photoreceptor) that is separated and laminated in separate layers (charge generation layer and charge transport layer) is known.

  Of these, the laminated type photoreceptors are of this type because most of the current photoreceptors are of this type because the functions are easily optimized for each layer and the characteristics can be easily controlled from the viewpoint of the photoreceptor design. Most of such laminated photoreceptors have at least a charge generation layer and a charge transport layer in this order on a substrate. In the charge transport layer, there are very few suitable electron transport materials, whereas many hole transport materials having a good characteristic are known. For this reason, in a laminated photoreceptor using such a hole transport material, a negative charging method is adopted for charging. In such a negative charging method, when the photosensitive member is charged by negative corona discharge, the generated ozone may adversely affect the environment and the photosensitive member characteristics.

  On the other hand, since the single-layer type photoreceptor can be used for either a negative charging system or a positive charging system, if the positive charging system is used, the generation of ozone, which is a problem with the above-mentioned multilayer photoreceptor, is reduced. Can be suppressed. For this reason, some of the electrical characteristics are inferior to the negatively charged multi-layer photoreceptor, but some have been put into practical use. In addition to the effect on the generation of ozone, the single-layer type photosensitive member has advantages such as fewer coating steps and hardly causing interference fringes with semiconductor laser light. In addition to the advantages described above, the single-layer type photoreceptor absorbs most of the incident light near the surface of the photosensitive layer and generates charges, so that the diffusion of incident light in the photosensitive layer is almost negligible. Furthermore, there is an advantage that the distance of charge movement until the surface charge after charging is neutralized is shorter than that of the multilayer type photoreceptor. For this reason, image blur due to light diffusion and charge diffusion is difficult to occur, and not only high resolution can be expected, but also the degree of charge diffusion and incident light diffusion changes greatly even when the film thickness of the photosensitive layer is increased. In addition, the resolution does not decrease much (for example, see Patent Documents 1 to 5).

On the other hand, a single-layer type photoreceptor has a feature that the sensitivity and residual potential as a photoreceptor greatly change depending on the compatibility of materials because substances having various functions are collectively contained in the layer as compared with a multilayer photoreceptor. Therefore, a particularly suitable charge transport material has been demanded. Among them, when an azo compound or a perylene derivative is used as a charge generation material, it is known that a triarylamine-based diamine charge transport material exhibits a low residual potential (for example, Patent Documents 6 and 7). reference).
JP-A-61-77054 JP-A 61-188543 JP-A-2-228670 Japanese Examined Patent Publication No. 7-97223 Japanese Examined Patent Publication No. 7-97225 Japanese Patent Publication No. 5-20742 JP 2005-43814 A

  However, even when these triarylamine-based diamine charge transport materials are used, there have been cases in which the electrical properties are insufficient and the image density becomes low for recent high-performance machines.

  In addition, in the coating solution for forming a single layer type photoreceptor, there is always a problem of precipitation when the charge transport material of these triarylamine diamines is contained in the coating solution. In other words, there is no problem if the photoconductor is prepared immediately after preparation of the coating solution (prepared by coating, drying, etc.), but if the coating solution is to be applied after storage for several days or more, the triarylamine type is used in the coating solution. A diamine charge transport material is deposited. Increasing the amount of the charge transport material improves the electrical characteristics, but the deposition is further promoted, and this measure has the aspect that it is difficult to withstand actual use.

  The present invention has been made to solve such problems. That is, an object of the present invention is to provide a single-layer type electrophotographic photoreceptor excellent in the stability of a coating solution for forming a photosensitive layer and having good electrical characteristics, and an electrophotographic photoreceptor cartridge provided with the photoreceptor. And providing an image forming apparatus.

  As a result of intensive investigations, the present inventors have found that a coating solution for forming a photosensitive layer becomes stable and that the photoreceptor exhibits good electrical characteristics by containing a specific enamine compound in the single-layer photosensitive layer. As a result, the following invention was completed.

  1st this invention WHEREIN: In the electrophotographic photoreceptor which has a single layer type photosensitive layer on an electroconductive support body, this photosensitive layer contains at least 1 type of enamine type compound represented by following formula (1). An electrophotographic photosensitive member is characterized.

（式（１）中、Ａｒ^１〜Ａｒ^６は、同一または異なっていてもよく、それぞれ置換基を有していてもよいアリール基を表す。ｎは２以上の整数を表す。Ｚは一価の有機残基を表し、ｍは０〜４の整数を表す。ただし、Ａｒ^１およびＡｒ^２のうち、少なくとも一つは、置換基を有するアリール基である。）

(In formula (1), Ar ^{1 to} Ar ⁶ may be the same or different and each represents an aryl group which may have a substituent. N represents an integer of 2 or more. Z represents a monovalent group. And m represents an integer of 0 to 4. However, at least one of Ar ¹ and Ar ² is an aryl group having a substituent.)

  In the first aspect of the present invention, the single-layer type photosensitive layer preferably contains oxytitanium phthalocyanine.

  In the first aspect of the present invention, oxytitanium phthalocyanine preferably shows a clear peak at a Bragg angle 2θ ± 0.2 ° of 27.2 ° in powder X-ray diffraction using CuKα characteristic X-rays.

  In the first invention, the single-layer type photosensitive layer preferably contains a perylene derivative.

  In the first invention, it is preferable that an undercoat layer is provided between the conductive support and the single-layer type photosensitive layer, and the undercoat layer contains a phthalocyanine compound.

  According to a second aspect of the present invention, there is provided an electrophotographic photosensitive member according to the first aspect of the invention, a charging device for charging the electrophotographic photosensitive member, and exposure for forming an electrostatic latent image by exposing the charged electrophotographic photosensitive member. An electrophotographic photosensitive member cartridge comprising: an apparatus; and at least one selected from the group consisting of a developing device that develops an electrostatic latent image formed on the electrophotographic photosensitive member.

  According to a third aspect of the present invention, there is provided an electrophotographic photosensitive member according to the first aspect of the present invention, a charging device that charges the electrophotographic photosensitive member, an exposure device that forms an electrostatic latent image by exposing the charged electrophotographic photosensitive member, An image forming apparatus comprising: a developing device that develops an electrostatic latent image formed on the electrophotographic photosensitive member.

  In the third aspect of the present invention, the charging device is preferably a charging device that positively charges the electrophotographic photosensitive member.

  According to the electrophotographic photoreceptor of the present invention, the enamel compound having a specific structure is contained in the single-layer type photosensitive layer, so that the coating liquid for forming the photosensitive layer becomes stable, and the electrophotographic photoreceptor of the present invention. Can exhibit good electrical properties.

  Hereinafter, the best mode for carrying out the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

[Electrophotographic photoconductor]
The electrophotographic photoreceptor of the present invention has a single-layer type photosensitive layer (hereinafter also simply referred to as “photosensitive layer”) on a conductive support, and the photosensitive layer is represented by the following formula (1). Contains at least one enamine compound. This single-layer type photosensitive layer is obtained by dispersing a charge generating material in a layer containing a charge transport material and a binder resin. The enamine compound represented by the following formula (1) is contained in the photosensitive layer. Included as a charge transport material.

In the formula (1), Ar ^{1 to} Ar ⁶ may be the same or different and each represents an aryl group which may have a substituent. n represents an integer of 2 or more. Z represents a monovalent organic residue, and m represents an integer of 0 to 4. However, at least one of Ar ¹ and Ar ² is an aryl group having a substituent. )

In the formula (1), Ar ^{1 to} Ar ⁶ represent aryl groups which may have a substituent, and may be the same or different. Among them, an aryl group having 6 to 20 carbon atoms is preferable, and an aryl group having 6 to 12 carbon atoms is more preferable. Specific examples include a phenyl group, a naphthyl group, a fluorenyl group, an anthryl group, a phenanthryl group, and a pyrenyl group, and a phenyl group, a naphthyl group, and a fluorenyl group are preferable. From the viewpoint of production cost, an aryl group having 6 to 10 carbon atoms such as a phenyl group and a naphthyl group is particularly preferable. Further, when it has a substituent, the substituent is preferably a substituent having 1 to 10 carbon atoms and having a substituent constant σp of 0.20 or less according to Hammett's rule.

  Here, Hammett's rule is an empirical rule used to explain the effect of a substituent in an aromatic compound on the electronic state of an aromatic ring, and the substituent constant σp of the substituted benzene is the electron donation / It can be said that this is a value obtained by quantifying the degree of suction. If the σp value is positive, the substituted compound is more acidic than the unsubstituted one, that is, an electron-withdrawing substituent. Conversely, when the σp value is negative, an electron donating substituent is formed. The σp values of typical substituents are described in “Chemical Handbook Basic Edition II Revised Edition 4” edited by The Chemical Society of Japan (Maruzen Co., Ltd., published on September 30, 1993, p.364-365). Yes.

  Examples of such a substituent include an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylamino group having 2 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and the like. Specifically, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, methoxy group, ethoxy group, propoxy group, butoxy group, N, N-dimethylamino group N, N-diethylamino group, phenyl group, 4-tolyl group, 4-ethylphenyl group, 4-propylphenyl group, 4-butylphenyl group, naphthyl group and the like. Among these, from the viewpoint of electrical characteristics, an alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group and an ethyl group are particularly preferable.

  In the formula (1), n is an integer of usually 2 or more in terms of improving the electrical characteristics of the electrophotographic photoreceptor according to the present invention, and there is no particular upper limit as long as the electrical characteristics are not adversely affected. An integer of 5 or less is preferable, and an integer of 3 or less is more preferable. From the viewpoint of compatibility with the photosensitive layer and production cost, n is preferably 2 or 3, particularly preferably n = 2.

  In the formula (1), examples of the monovalent organic residue Z include, for example, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkylamino group having 2 to 4 carbon atoms, and 6 carbon atoms. -10 aryl groups and the like, specifically, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, methoxy, ethoxy, propoxy, butoxy, N, N-dimethylamino, N, N-diethylamino, phenyl, 4-tolyl, 4-ethylphenyl, 4-propylphenyl, 4-butylphenyl, naphthyl and the like can be mentioned. Among these, an alkyl group having 1 to 4 carbon atoms is particularly preferable from the viewpoint of electrical characteristics.

  In the formula (1), m is preferably an integer of 0 to 1, but m = 0 is particularly preferable from the viewpoint of production cost.

  As typical examples of the compound represented by the formula (1), the following exemplified compounds CT-1 to CT-14 may be mentioned. However, the compound represented by Formula (1) according to the present invention is not limited to these compounds.

  These compounds can be easily synthesized by known methods. For example, exemplary compound CT-1 of this invention can be manufactured according to the following reaction formula.

  A diarylamine derivative (α) is condensed by reflux dehydration with diarylacetaldehyde (β) in the presence of an acid catalyst such as p-toluenesulfonic acid to obtain the target charge transport material CT-1. it can.

  The structure of the electrophotographic photosensitive member according to the present invention will be described below. The electrophotographic photosensitive member according to the present invention has a single-layer type photosensitive layer containing the compound represented by the general formula (1) described above on a conductive support.

[Conductive support]
As the conductive support, for example, a metal material such as aluminum, aluminum alloy, stainless steel, copper, nickel, or a resin material imparted with conductivity by adding conductive powder such as metal, carbon, tin oxide, Mainly used are resin, glass, paper, or the like obtained by depositing or coating a conductive material such as aluminum, nickel, ITO (indium-tin oxide) on its surface. As a form, a drum shape, a sheet shape, a belt shape or the like is used. A conductive material having an appropriate resistance value may be coated on a conductive support made of a metal material for controlling conductivity, surface property, etc., or for covering defects.

When a metal material such as an aluminum alloy is used as the conductive support, it may be used after anodizing, chemical conversion coating or the like. When anodizing is performed, it is desirable to perform sealing by a known method.
The surface of the conductive support may be smooth, or may be roughened by using a special cutting method or performing a polishing treatment. Further, it may be roughened by mixing particles having an appropriate particle diameter with the material constituting the conductive support.

[Underlayer]
An undercoat layer may be provided between the conductive support and the photosensitive layer in order to improve adhesion and blocking properties.
As the undercoat layer, a resin alone or a resin in which particles such as metal oxide or a dispersant such as an organic pigment are dispersed in the resin is used. Examples of metal oxide particles used for the undercoat layer include metal oxide particles containing one metal element such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zinc oxide, iron oxide, calcium titanate, titanium Examples thereof include metal oxide particles containing a plurality of metal elements such as strontium acid and barium titanate. In this way, only one type of particle may be used, or a plurality of types of particles may be mixed and used. Among these metal oxide particles, titanium oxide and aluminum oxide are preferable, and titanium oxide is particularly preferable. The surface of the titanium oxide particles may be treated with an inorganic substance such as tin oxide, aluminum oxide, antimony oxide, zirconium oxide, or silicon oxide, or an organic substance such as stearic acid, polyol, or silicone. As the crystal form of the titanium oxide particles, any of rutile, anatase, brookite, and amorphous can be used. A thing of a several crystalline state may be contained.

In addition, various particle diameters of the metal oxide particles can be used. Among these, from the viewpoint of characteristics and liquid stability, the average primary particle diameter is preferably 10 nm to 100 nm, and more preferably 10 nm to 50 nm. .
The undercoat layer is preferably formed in a form in which metal oxide particles are dispersed in a binder resin. As binder resin used for the undercoat layer, phenoxy, epoxy, polyvinylpyrrolidone, polyvinyl alcohol, casein, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide, etc. are used alone or in a cured form with a curing agent. Among them, alcohol-soluble copolymer polyamides, modified polyamides, and the like are preferable because they exhibit good dispersibility and coatability.

  In particular, in the single-layer type photoreceptor of the present invention, the charge generation layer constituting the multilayer photoreceptor can be substituted for the undercoat layer. In this case, a phthalocyanine pigment or an azo pigment dispersed in a binder resin is preferably used because it may have excellent electrical characteristics. Among these, it is more preferable to use a phthalocyanine pigment (phthalocyanine compound) from the viewpoint of electrical characteristics. As the binder resin, polyvinyl acetal resins are preferably used, and polyvinyl butyral resin is particularly preferably used.

The addition ratio of the dispersing agent such as particles and pigment to the binder resin can be arbitrarily selected, but it is preferably used in the range of 10% by mass or more and 500% by mass or less from the viewpoint of the stability of the dispersion and the coating property.
The thickness of the undercoat layer can be arbitrarily selected, but is preferably 0.1 μm to 25 μm from the viewpoint of photoreceptor characteristics and coatability. Moreover, you may add a well-known antioxidant etc. to an undercoat layer.

[Photosensitive layer]
In the single-layer type photosensitive layer of the present invention, the charge transport material is dissolved or dispersed in the binder resin and the charge generation material is dispersed to form the same layer. Specifically, for example, a coating liquid is prepared by dissolving or dispersing a charge transport material, a charge generation material, and the like and a binder resin in a solvent, and this is formed on a conductive support (if an undercoat layer is provided, an undercoat is provided). It can be obtained by coating on a layer and drying.

  Examples of the binder resin used in the photosensitive layer include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymers thereof, polycarbonate, polyarylate, polyester, polyester carbonate, polysulfone, polyimide, phenoxy, Examples thereof include epoxies and silicone resins, and these partially crosslinked cured products can also be used. Of the binder resins, polycarbonate resins and polyarylate resins are particularly preferable. These resins may be used alone or in combination.

  In the photosensitive layer of the present invention, at least one type of enamine compound represented by the above formula (1) is used as a charge transport material, but other enamine compounds having a different chemical structure, triarylamine compounds, and the like may be used. You may use together with a charge transport material.

  Furthermore, a conventionally known electron transport material may be used in combination as the charge transport material. The electron transport material used in combination is not particularly limited as long as it is a conventionally known material. For example, aromatic nitro compounds such as 2,4,7-trinitrofluorenone, and cyano compounds such as tetracyanoquinodimethane And electron withdrawing substances such as quinone compounds such as diphenoquinone, and conventionally known cyclic ketone compounds and perylene pigments (perylene derivatives). As an electron transport material, the compound which consists of a structure of following formula (I)-(XI) can be illustrated, for example.

  Preferable electron transport materials include perylene derivatives represented by the following general formulas P-1 to P-3.

In the above formulas (P-1) to (P-3), R ¹ , R ² and R ⁵ each independently have hydrogen, an alkyl group which may have a substituent, or a substituent. Represents a good aryl group. In the alkyl group which may have a substituent, an alkyl group having 6 or less carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert-butyl group, a pentyl group, and a hexyl group is preferable. Alkyl groups having 3 or less carbon atoms such as methyl group, ethyl group, propyl group and isopropyl group are particularly preferable. Examples of the substituent that the alkyl group may have include an alkyl group or an aryl group, and an alkyl group having 3 or less carbon atoms or an aryl group having 2 or less rings is preferable. In the aryl group which may have a substituent, an aryl group having 3 or less rings such as a phenyl group, a naphthyl group and an anthryl group is preferable, and a phenyl group is particularly preferable. Examples of the substituent that the aryl group may have include an alkyl group and an aryl group, preferably an alkyl group having 3 or less carbon atoms or an aryl group having 2 or less rings.

In the formulas (P-1) to (P-3), R ³ , R ⁴ , and R ⁶ are preferably divalent aromatic hydrocarbons, and particularly preferably phenylene groups.
Among the above formulas (P-1) to (P-3), a perylene derivative represented by the following formula (P-4), wherein R ¹ and R ² are aryl groups which may have a substituent, Preferable examples can be given.

In the following formulae, R ^{7 to} R ¹⁰ each independently represent a lower alkyl group. Examples of the lower alkyl group include alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, tert-butyl group, pentyl group, and hexyl group.

  Specific examples of the perylene derivative represented by the above formula (P-4) include N, N′-bis (3,5-dimethylphenyl) perylene-3,4,9,10-tetracarboxydiimide, N, N '-Bis (3-methyl-5-ethylphenyl) perylene-3,4,9,10-tetracarboxydiimide, N, N'-bis (3,5-diethylphenyl) perylene-3,4,9,10 -Tetracarboxydiimide, N, N'-bis (3,5-dipropylphenyl) perylene-3,4,9,10-tetracarboxydiimide, N, N '-(3,5-diisopropylphenyl) perylene-3 , 4,9,10-tetracarboxydiimide, N, N'-bis (3-methyl-5-isopropylphenyl) perylene-3,4,9,10-tetracarboxydiimide, N, N'- Su (3-ethyl-5-isopropylphenyl) perylene-3,4,9,10-tetracarboxydiimide, N, N′-bis (3,5-dibutylphenyl) perylene-3,4,9,10-tetra Carboxydiimide, N, N′-bis (3-methyl-5-di-tert-butylphenyl) perylene-3,4,9,10-tetracarboxydiimide, N, N′-bis (3,5-dipentylphenyl) ) Perylene-3,4,9,10-tetracarboxydiimide, N, N′-bis (3,5-dihexylphenyl) perylene-3,4,9,10-tetracarboxydiimide, and the like. May be used alone or in admixture of two or more.

  When the perylene derivative is contained as an electron transport material, the content ratio of the perylene derivative is not particularly limited. For example, it is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin in the photosensitive layer. Particularly preferably, it is 2 parts by mass or more and 10 parts by mass or less.

  Moreover, in this invention, you may use together other hole transport materials other than the said enamine type compound which is a hole transport material. The hole transport material used in combination is not particularly limited as long as it is a conventionally known material. For example, heterocyclic rings such as carbazole derivatives, indole derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, thiadiazole derivatives, benzofuran derivatives, etc. Compounds, aniline derivatives, hydrazone derivatives, aromatic amine derivatives, arylamine derivatives, stilbene derivatives, butadiene derivatives, enamine derivatives and those in which multiple types of these compounds are bonded, or groups consisting of these compounds in the main chain or side Examples thereof include an electron donating substance such as a polymer in the chain. Among these, carbazole derivatives, aromatic amine derivatives, arylamine derivatives, stilbene derivatives, butadiene derivatives, enamine derivatives, and those in which a plurality of these compounds are bonded, or a group composed of these compounds is a main chain or side. Examples thereof include an electron donating substance such as a polymer in the chain. Among these, carbazole derivatives, aromatic amine derivatives, arylamine derivatives, stilbene derivatives, butadiene derivatives, enamine derivatives and those in which a plurality of these compounds are bonded are preferable. In addition, there is no restriction | limiting in particular also in the number of these hole transport materials used together.

  When the previously known hole transport material described above is used in combination, the compound of the present invention can improve the electrical characteristics even with a small amount of mixing, so the enamine compound of the present invention relative to the total amount of other hole transport materials. It is preferable to use it so that a mass ratio may be 5 mass% or more, It is more preferable to use together so that it may become 20 mass% or more, 30 mass% or more is especially preferable.

  The mixing ratio of the binder resin constituting the photosensitive layer and the charge transporting material (electron transporting material and / or hole transporting material) is arbitrary, but usually 20 parts by weight of the charge transporting material with respect to 100 parts by weight of the binder resin. Mix at a ratio of at least parts. Among these, from the viewpoint of reducing the residual potential, it is preferable to blend the charge transport material at a ratio of 30 parts by mass or more with respect to 100 parts by mass of the binder resin, and from the viewpoint of stability and charge mobility when repeatedly used. More preferably, the charge transport material is blended in a proportion of 40 parts by mass or more. On the other hand, from the viewpoint of the thermal stability of the photosensitive layer, the charge transport material is preferably blended at a ratio of 150 parts by weight or less with respect to 100 parts by weight of the binder resin, and the compatibility between the charge transport material and the binder resin is further improved. From a viewpoint, it is preferable to mix | blend a charge transport material in the ratio of 120 mass parts or less, and also from a printing durability viewpoint, it is more preferable to mix | blend a charge transport material in the ratio of 100 mass parts or less, and also a flaw resistance From the viewpoint of safety, it is particularly preferable to blend the charge transport material in a proportion of 80 parts by mass or less. In addition, when using several charge transport material, it is made for the sum total of those charge transport materials to be in the said range.

  Examples of the charge generating material include selenium and its alloys, cadmium sulfide, other inorganic photoconductive materials, phthalocyanine pigments, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthanthrone pigments, benzimidazoles. Various photoconductive materials such as organic pigments such as pigments can be used, and organic pigments, phthalocyanine pigments, azo pigments, and perylene pigments are particularly preferable, and phthalocyanine pigments are particularly preferable.

  When using a phthalocyanine compound as the charge generation material, specifically, a metal such as metal-free phthalocyanine, copper, indium, gallium, tin, titanium, zinc, vanadium, silicon, germanium, or an oxide or halide thereof. Phthalocyanines are used. Examples of the ligand to a metal atom having 3 or more valences include a hydroxyl group and an alkoxy group in addition to the oxygen atom and chlorine atom shown above. Particularly preferred are X-type, τ-type metal-free phthalocyanine having high sensitivity, oxytitanium phthalocyanine such as A-type and B-type, oxyvanadium phthalocyanine, chloroindium phthalocyanine, chlorogallium phthalocyanine, and hydroxygallium phthalocyanine. Of the crystal types of oxytitanium phthalocyanine mentioned here, A type and B type are described in W.W. It has been shown by Heller et al. As phase I and phase II, respectively (Zeit. Kristallogr. 159 (1982) 173), and type A is known as a stable type. And in this invention, it is preferable to use the crystal type characterized by the diffraction angle 2θ ± 0.2 ° showing a clear peak at 27.2 ° in powder X-ray diffraction using CuKα rays. As the phthalocyanine compound, only a single compound may be used, or several mixed states may be used. As the mixed state in the phthalocyanine compound or crystal state here, the respective constituent elements may be mixed and used later, or a mixed state is generated in the production / treatment process of phthalocyanine compound such as synthesis, pigmentation, crystallization, etc. It can be stuffed. As such treatment, acid paste treatment, grinding treatment, solvent treatment and the like are known.

  In this case, the particle size of the charge generating material needs to be sufficiently small, and is preferably 1 μm or less, more preferably 0.5 μm or less. If the amount of the charge generating material dispersed in the photosensitive layer is too small, sufficient sensitivity cannot be obtained, and if it is too large, there are adverse effects such as reduced chargeability and reduced sensitivity. The amount is preferably in the range of 0.5 to 50% by mass, more preferably in the range of 1 to 20% by mass, and particularly preferably in the range of 1 to 5% by mass. The photosensitive layer is formed in such a form that these charge transport material and charge generation material are bound to a binder resin. The photosensitive layer is preferably composed of a single layer, but may be a laminate of a plurality of layers having different constituent components or composition ratios. Even in the latter case, it is called a single-layer type photoreceptor because of the function of the material in the layer.

  The film thickness of the photosensitive layer is usually 5 to 50 μm, more preferably 10 to 45 μm. Also in this case, known plasticizers for improving film formability, flexibility, mechanical strength, additives for suppressing residual potential, dispersion aids for improving dispersion stability, coatability A leveling agent or a surfactant, for example, a silicone oil, a fluorinated oil or other additives for improving the viscosity may be added.

A protective layer may be provided on the photosensitive layer for the purpose of preventing wear of the photosensitive layer or preventing or reducing deterioration of the photosensitive layer due to discharge products generated from a charger or the like.
Further, for the purpose of reducing frictional resistance and wear on the surface of the photoreceptor, the surface layer may contain a fluorine-based resin, a silicone resin, or the like. Moreover, the particle | grains which consist of these resin, and the particle | grains of an inorganic compound may be included.

[Method for preparing electrophotographic photoreceptor]
The method for preparing the electrophotographic photosensitive member to which the exemplary embodiment is applied is not particularly limited. Usually, the layer constituting the photosensitive member is a dip coating method or a spray known as a method for forming a photosensitive layer of the electrophotographic photosensitive member. It is formed by coating on a support by a coating method, a nozzle coating method, a bar coating method, a roll coating method, a blade coating method or the like. Among these, the dip coating method is preferable because of its high productivity.
As a method for forming the layer, a known method such as sequential application of a coating solution obtained by dissolving or dispersing a substance contained in the layer in a solvent can be applied.

[Image forming apparatus]
Next, an embodiment of an image forming apparatus using the electrophotographic photosensitive member of the present invention will be described with reference to FIG. However, the embodiment is not limited to the following description, and can be arbitrarily modified without departing from the gist of the present invention.
As shown in FIG. 1, the image forming apparatus includes an electrophotographic photosensitive member 1, a charging device 2, an exposure device 3, and a developing device 4, and further, a transfer device 5, a cleaning device 6, and a fixing device as necessary. A device 7 is provided.

  The electrophotographic photoreceptor 1 is not particularly limited as long as it is the above-described electrophotographic photoreceptor of the present invention, but in FIG. 1, as an example, a drum in which the above-described photosensitive layer is formed on the surface of a cylindrical conductive support. The photoconductor is shown. A charging device 2, an exposure device 3, a developing device 4, a transfer device 5, and a cleaning device 6 are arranged along the outer peripheral surface of the electrophotographic photoreceptor 1.

  The charging device 2 charges the electrophotographic photoreceptor 1 positively, and uniformly charges the surface of the electrophotographic photoreceptor 1 to a predetermined potential. In FIG. 1, a roller type charging device (charging roller) is shown as an example of the charging device 2, but a corona charging device such as a corotron or a scorotron, a contact type charging device such as a charging brush, etc. are often used.

  In many cases, the electrophotographic photosensitive member 1 and the charging device 2 are designed to be removable from the main body of the image forming apparatus as a cartridge including both of them (hereinafter referred to as a photosensitive cartridge as appropriate). For example, when the electrophotographic photoreceptor 1 or the charging device 2 is deteriorated, the photoreceptor cartridge can be detached from the image forming apparatus main body, and another new photoreceptor cartridge can be mounted on the image forming apparatus main body. It has become. Also, in many cases, the toner described later is stored in the toner cartridge and designed to be removable from the main body of the image forming apparatus. When the toner in the used toner cartridge runs out, It can be removed from the main body of the image forming apparatus and another new toner cartridge can be mounted. Further, a cartridge equipped with all of the electrophotographic photosensitive member 1, the charging device 2, and the toner may be used.

  The type of the exposure apparatus 3 is not particularly limited as long as it can expose the electrophotographic photoreceptor 1 to form an electrostatic latent image on the photosensitive surface of the electrophotographic photoreceptor 1. Specific examples include halogen lamps, fluorescent lamps, lasers such as semiconductor lasers and He—Ne lasers, LEDs, and the like. Further, exposure may be performed by a photoreceptor internal exposure method. The light at the time of exposure is arbitrary, but for example, exposure may be performed with monochromatic light with a wavelength of 780 nm, monochromatic light with a wavelength slightly shorter than 600 nm to 700 nm, monochromatic light with a wavelength shorter than 380 nm to 500 nm, or the like. .

  The type of the developing device 4 is not particularly limited, and any device such as a dry development method such as cascade development, one-component conductive toner development, two-component magnetic brush development, or a wet development method can be used. In FIG. 1, the developing device 4 includes a developing tank 41, an agitator 42, a supply roller 43, a developing roller 44, and a regulating member 45, and has a configuration in which toner T is stored inside the developing tank 41. . Further, a replenishing device (not shown) for replenishing the toner T may be attached to the developing device 4 as necessary. This replenishing device is configured to be able to replenish toner T from a container such as a bottle or a cartridge.

  The supply roller 43 is formed from a conductive sponge or the like. The developing roller 44 is made of a metal roll such as iron, stainless steel, aluminum, or nickel, or a resin roll obtained by coating such a metal roll with a silicone resin, a urethane resin, a fluororesin, or the like. The surface of the developing roller 44 may be smoothed or roughened as necessary.

  The developing roller 44 is disposed between the electrophotographic photoreceptor 1 and the supply roller 43 and is in contact with the electrophotographic photoreceptor 1 and the supply roller 43, respectively. The supply roller 43 and the developing roller 44 are rotated by a rotation drive mechanism (not shown). The supply roller 43 carries the stored toner T and supplies it to the developing roller 44. The developing roller 44 carries the toner T supplied by the supply roller 43 and contacts the surface of the electrophotographic photosensitive member 1.

  The regulating member 45 is formed of a resin blade such as a silicone resin or a urethane resin, a metal blade such as stainless steel, aluminum, copper, brass, phosphor bronze, or a blade obtained by coating such a metal blade with a resin. The regulating member 45 contacts the developing roller 44 and is pressed against the developing roller 44 side with a predetermined force by a spring or the like (general blade linear pressure is 0.05 to 5 N / cm). If necessary, the regulating member 45 may be provided with a function of imparting charging to the toner T by frictional charging with the toner T.

The agitator 42 is rotated by a rotation driving mechanism, and agitates the toner T and conveys the toner T to the supply roller 43 side. A plurality of agitators 42 may be provided with different blade shapes and sizes.
The type of the toner T is arbitrary, and in addition to the powdery toner, a polymerized toner using a suspension polymerization method, an emulsion polymerization method, or the like can be used. In particular, when a polymerized toner is used, a toner having a small particle diameter of about 4 to 8 μm is preferable, and the toner particles are used in various shapes ranging from a nearly spherical shape to a shape outside the spherical shape on the potato. be able to. The polymerized toner is excellent in charging uniformity and transferability and is suitably used for high image quality.

  The type of the transfer device 5 is not particularly limited, and an apparatus using an arbitrary system such as an electrostatic transfer method such as corona transfer, roller transfer, or belt transfer, a pressure transfer method, or an adhesive transfer method can be used. . Here, it is assumed that the transfer device 5 includes a transfer charger, a transfer roller, a transfer belt, and the like disposed so as to face the electrophotographic photoreceptor 1. The transfer device 5 applies a predetermined voltage value (transfer voltage) having a polarity opposite to the charging potential of the toner T, and transfers the toner image formed on the electrophotographic photosensitive member 1 to a recording paper (paper, medium) P. Is.

  There is no restriction | limiting in particular about the cleaning apparatus 6, Arbitrary cleaning apparatuses, such as a brush cleaner, a magnetic brush cleaner, an electrostatic brush cleaner, a magnetic roller cleaner, a blade cleaner, can be used. The cleaning device 6 is for scraping off residual toner adhering to the photoreceptor 1 with a cleaning member and collecting the residual toner.

  The fixing device 7 includes an upper fixing member (pressure roller) 71 and a lower fixing member (fixing roller) 72, and a heating device 73 is provided inside the fixing member 71 or 72. FIG. 1 shows an example in which a heating device 73 is provided inside the upper fixing member 71. Each of the upper and lower fixing members 71 and 72 includes a fixing roll in which a metal base tube such as stainless steel or aluminum is coated with silicon rubber, a fixing roll in which Teflon (registered trademark) resin is coated, a fixing sheet, or the like. A fixing member can be used. Further, the fixing members 71 and 72 may be configured to supply a release agent such as silicone oil in order to improve the releasability, or may be configured to forcibly apply pressure to each other by a spring or the like.

When the toner transferred onto the recording paper P passes between the upper fixing member 71 and the lower fixing member 72 heated to a predetermined temperature, the toner is heated to a molten state and cooled after passing through the recording paper. Toner is fixed on P.
The type of the fixing device is not particularly limited, and a fixing device of an arbitrary method such as heat roller fixing, flash fixing, oven fixing, pressure fixing, or the like can be provided.

In the electrophotographic apparatus configured as described above, an image is recorded as follows. That is, first, the surface (photosensitive surface) of the photoreceptor 1 is charged to a predetermined positive potential (for example, +600 V) by the charging device 2. At this time, charging may be performed by a DC voltage, or charging may be performed by superimposing an AC voltage on the DC voltage.
Subsequently, the photosensitive surface of the charged photoreceptor 1 is exposed by the exposure device 3 according to the image to be recorded, and an electrostatic latent image is formed on the photosensitive surface. The developing device 4 develops the electrostatic latent image formed on the photosensitive surface of the photoreceptor 1.

The developing device 4 thins the toner T supplied by the supply roller 43 by a regulating member (developing blade) 45 and has a predetermined polarity (here, the same polarity as the charging potential of the photosensitive member 1) and positive polarity. ), And conveyed while being carried on the developing roller 44 to be brought into contact with the surface of the photoreceptor 1.
When the charged toner T carried on the developing roller 44 comes into contact with the surface of the photoreceptor 1, a toner image corresponding to the electrostatic latent image is formed on the photosensitive surface of the photoreceptor 1. This toner image is transferred onto the recording paper P by the transfer device 5. Thereafter, the toner remaining on the photosensitive surface of the photoreceptor 1 without being transferred is removed by the cleaning device 6.

After the transfer of the toner image onto the recording paper P, the final image is obtained by passing the fixing device 7 and thermally fixing the toner image onto the recording paper P.
In addition to the above-described configuration, the image forming apparatus may be configured to perform, for example, a static elimination process. The neutralization step is a step of neutralizing the electrophotographic photosensitive member by exposing the electrophotographic photosensitive member, and a fluorescent lamp, an LED, or the like is used as the neutralizing device. In addition, the light used in the static elimination process is often light having an exposure energy that is at least three times that of the exposure light.

  The image forming apparatus may be further modified. For example, the image forming apparatus may be configured to perform a pre-exposure process, an auxiliary charging process, or the like, or may be configured to perform offset printing. A full-color tandem system configuration using toner may be used.

  Hereinafter, the present embodiment will be described more specifically based on examples. In addition, the following examples are shown in order to describe the present invention in detail, and the present invention is not limited to the examples shown below unless it is contrary to the gist thereof. In addition, the description of “parts” in the following examples, comparative examples, and reference examples indicates “parts by mass” unless otherwise specified.

<Manufacture of photosensitive drum>
Example 1
High-speed fluidized mixing of rutile type titanium oxide having an average primary particle size of 40 nm (“TTO55N” manufactured by Ishihara Sangyo Co., Ltd.) and 3% by mass of methyldimethoxysilane (“TSL8117” manufactured by Toshiba Silicone Co., Ltd.) The surface-treated titanium oxide obtained by charging into a kneading machine (“SMG300” manufactured by Kawata Corporation) and mixing at high speed at a rotational peripheral speed of 34.5 m / sec is dispersed by a ball mill in a mixed solvent of methanol / 1-propanol. As a result, a dispersion slurry of hydrophobized titanium oxide was obtained. The dispersion slurry, a mixed solvent of methanol / 1-propanol / toluene, and ε-caprolactam [compound represented by the following formula (A)] / bis (4-amino-3-methylcyclohexyl) methane [the following formula ( Compound represented by B)] / hexamethylenediamine [compound represented by the following formula (C)] / decamethylene dicarboxylic acid [compound represented by the following formula (D)] / octadecamethylene dicarboxylic acid [following formula The compound represented by (E)] has a composition molar ratio of 60% / 15% / 5% / 15% / 5% and is agitated and mixed with pellets of copolymerized polyamide to dissolve the polyamide pellets. Then, ultrasonic dispersion treatment is performed, so that the mass ratio of methanol / 1-propanol / toluene is 7/1/2, and the hydrophobically treated titanium oxide / copolymerized polymer. Containing de mass ratio 3/1 was undercoat layer dispersion having a solid concentration of 18.0 mass%.

  The undercoat layer forming coating solution thus obtained is dried on a cylinder made of an aluminum alloy having an outer diameter of 30 mm, a length of 244 mm, and a wall thickness of 0.75 mm so that the film thickness after drying becomes 1.2 μm. An undercoat layer was provided by dip coating and drying.

  Next, in X-ray diffraction by CuKα ray, a Bragg angle (2θ ± 0.2) shows a strong diffraction peak at 27.3 °, and 5 parts by mass of oxytitanium phthalocyanine having a powder X-ray diffraction spectrum shown in FIG. Dispersed together with 70 parts by mass by a sand grind mill. Similarly, 8 parts by mass of a perylene derivative which is an electron transport material represented by the following structure was dispersed together with 112 parts by mass of toluene by a sand grind mill. On the other hand, 60 parts by mass of the hole transport material (CT-3) in the specific example shown above and 100 parts by mass of polycarbonate resin having the following structure as a repeating unit are dissolved in 420 parts by mass of toluene, and silicone is used as a leveling agent. 0.05 parts by mass of oil was added, and the above two dispersions were mixed with a homogenizer so as to be uniform. The coating solution thus prepared was dip-coated on the above-described undercoat layer so that the film thickness after drying was 25 μm to form a photosensitive layer, whereby a single-layer type photoreceptor A was obtained.

(Example 2)
In Example 1, the same procedure as in Example 1 was performed except that (CT-4) in the specific example shown above was used instead of (CT-3) as the hole transport material, and a single-layer type photosensitive material was used. Body B was obtained.

(Example 3)
In X-ray diffraction by CuKα ray, Bragg angle (2θ ± 0.2) shows a strong diffraction peak at 27.3 °, and 10 parts by mass of oxytitanium phthalocyanine having a powder X-ray diffraction spectrum shown in FIG. In addition to 150 parts by mass of dimethoxyethane, pulverization and dispersion treatment was performed with a sand grind mill to prepare a pigment dispersion. 160 parts by mass of the pigment dispersion thus obtained was added to 100 parts by mass of a 5% 1,2-dimethoxyethane solution of polyvinyl butyral (trade name # 6000C, manufactured by Denki Kagaku Kogyo Co., Ltd.) and an appropriate amount of 1,2-dimethoxyethane. In addition, a dispersion having a solid content concentration of 4.0% by mass was finally produced.
This dispersion is dip-coated on a cylinder made of an aluminum alloy having an outer diameter of 30 mm, a length of 244 mm, and a wall thickness of 0.75 mm so that the film thickness after drying is 0.4 μm, and then dried and subtracted. A layer was formed. On this, the same photosensitive layer as in Example 2 was dip-coated by 25 μm to obtain a single-layer type photoreceptor C.

Example 4
In Example 3, instead of using 60 parts of hole transport material (CT-4), all except that 20 parts of (CT-4) and 60 parts of hole transport material-1 having the following structural formula were used. The same procedure as in Example 3 was performed to obtain a single layer type photoreceptor D.

(Example 5)
In Example 4, in place of 20 parts of the hole transport material (CT-4), except that 20 parts of (CT-12) in the specific example shown above was used, everything was carried out in the same manner as in Example 4, A single-layer type photoreceptor E was obtained.

(Example 6)
In Example 4, in place of 20 parts of the hole transport material (CT-4), except that 20 parts of (CT-2) in the specific examples shown above were used, everything was carried out in the same manner as in Example 4, A single layer type photoreceptor F was obtained.

(Example 7)
In Example 3, instead of using the oxytitanium phthalocyanine having the powder X-ray diffraction spectrum shown in FIG. 2 as the charge generation material, oxytitanium phthalocyanine having the powder X-ray diffraction spectrum shown in FIG. 3 (B type) is used. A single layer type photoreceptor G was obtained in the same manner as in Example 3 except that it was used.

(Comparative Example 1)
In Example 4, a single layer type photoreceptor H was obtained in the same manner as Example 4 except that only 80 parts of the hole transport material-1 having the above structural formula was used as the hole transport material.

(Comparative Example 2)
In Example 3, in place of the hole transporting material (CT-4), except that the hole transporting material-2 having the following structural formula was used, everything was performed in the same manner as in Example 3, and the single layer type photoreceptor I was prepared. Obtained.

(Comparative Example 3)
In Example 3, a single-layer photoreceptor J was obtained in the same manner as in Example 3 except that hole transport material-1 was used instead of hole transport material (CT-4).

(Comparative Example 4)
In Example 4, except that 20 parts of hole transport material-2 was used instead of 20 parts of hole transport material (CT-4), all was performed in the same manner as in Example 4 to obtain a single layer type photoreceptor K. It was.

All the photoreceptors produced in the above examples were uniform and a coating film without precipitation was obtained. These coating solutions were stored at 25 ° C. for 2 months and recoated in the same manner to confirm the presence or absence of precipitation on the photosensitive layer. The results are shown in Table 1.
The produced photoreceptor drums A to K were subjected to the following electrical property test and image evaluation test, and the results are summarized in Table 1.

<Electrical characteristics test>
Using the electrophotographic characteristic evaluation apparatus manufactured in accordance with the electrophotographic society measurement standard (Electrophotographic Society, edited by “Basic and Application of Electrophotographic Technology”, Corona 1996, pages 404 to 405) The drum was rotated at a constant rotational speed of 60 pm, and an electrical property evaluation test was performed by a cycle of charging, exposure, potential measurement, and static elimination. At that time, the surface potential after exposure when the photosensitive member was charged so that the initial surface potential becomes +700 and the light of the halogen lamp was changed to monochromatic light of 780 nm with an interference filter at 1.0 μJ / cm ² ( Hereinafter, it may be referred to as VL). In the VL measurement, the time required from the exposure to the potential measurement was 100 ms. The measurement environment was a temperature of 25 ° C. and a relative humidity of 50%.

<Image evaluation test>
The photosensitive drum is mounted on a drum cartridge (DR510) of a commercially available laser printer HL-5140 (manufactured by Brother) used for positive charging, and a halftone image is output, and an image using a standard drum (DR510 genuine) is used. And the presence or absence of black spots were confirmed. The image density is indicated by “deep”, “good”, “thin”, “extremely thin”, and “black spot” is indicated only when a black spot occurs. There was no photoreceptor with a “dark” image.

From the above results, the single-layer electrophotographic photosensitive member shows a sufficiently low light potential only by using the enamine compound of the present invention as a charge transport material, and the photosensitive layer forming coating solution has a charge transport property. It was found that the material was stable without causing precipitation.
In particular, as in the comparative example, the conventionally used triphenylamine compound cannot obtain a light part potential low enough to obtain a sufficient concentration, but it goes without saying that the compound of the present invention is used alone. However, it was found that a sufficient effect can be obtained even by adding a small amount.
In addition, as in Example 3, it was also revealed that a lower bright part potential can be achieved by using a phthalocyanine compound for the undercoat layer.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. The electrophotographic photosensitive member, the electrophotographic photosensitive member cartridge, and the image forming apparatus can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. Should also be understood as being included within the scope of the present invention.

1 is a conceptual diagram illustrating an embodiment of an image forming apparatus using an electrophotographic photosensitive member of the present invention. 2 is an X-ray diffraction pattern of oxytitanium phthalocyanine used in Example 1 and the like. FIG. 6 is an X-ray diffraction pattern of oxytitanium phthalocyanine used in Example 7. FIG.

Explanation of symbols

1 Photoconductor 2 Charging device (charging roller)
DESCRIPTION OF SYMBOLS 3 Exposure apparatus 4 Developing apparatus 5 Transfer apparatus 6 Cleaning apparatus 7 Fixing apparatus 41 Developing tank 42 Agitator 43 Supply roller 44 Developing roller 45 Control member 71 Upper fixing member (pressure roller)
72 Lower fixing member (fixing roller)
73 Heating device T Toner P Recording paper

Claims (8)

An electrophotographic photosensitive member having a monolayer type photosensitive layer on a conductive support, wherein the photosensitive layer contains at least one enamine compound represented by the following formula (1): body.

(In formula (1), Ar ^{1 to} Ar ⁶ may be the same or different and each represents an aryl group which may have a substituent. N represents an integer of 2 or more. Z represents a monovalent group. And m represents an integer of 0 to 4. However, at least one of Ar ¹ and Ar ² is an aryl group having a substituent.) 2. The electrophotographic photosensitive member according to claim 1, wherein the single-layer type photosensitive layer contains oxytitanium phthalocyanine. 3. The electron according to claim 2, wherein the oxytitanium phthalocyanine exhibits a clear peak at a Bragg angle 2θ ± 0.2 ° of 27.2 ° in powder X-ray diffraction using CuKα characteristic X-rays. Photoconductor. The electrophotographic photosensitive member according to claim 1, wherein the single-layer type photosensitive layer contains a perylene derivative. 5. The electron according to claim 1, further comprising an undercoat layer between the conductive support and the single-layer photosensitive layer, wherein the undercoat layer contains a phthalocyanine compound. Photoconductor. 6. The electrophotographic photosensitive member according to claim 1, a charging device for charging the electrophotographic photosensitive member, an exposure device for forming an electrostatic latent image by exposing the charged electrophotographic photosensitive member, And an electrophotographic photosensitive member cartridge comprising: at least one selected from the group consisting of a developing device that develops an electrostatic latent image formed on the electrophotographic photosensitive member. The electrophotographic photosensitive member according to any one of claims 1 to 5, a charging device for charging the electrophotographic photosensitive member, an exposure device for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image, and An image forming apparatus comprising: a developing device that develops an electrostatic latent image formed on the electrophotographic photosensitive member. The image forming apparatus according to claim 7, wherein the charging device is a charging device that positively charges the electrophotographic photosensitive member.

Images