JP4248531B2 - Electrophotographic photoreceptor, method for producing the same, image forming method using the same, image forming apparatus, and process cartridge for image forming apparatus - Google Patents

Description

  The present invention is excellent by using a crosslinked surface protective layer that can maintain high wear resistance over a long period of time, has almost no variation in electrical characteristics, and has improved adhesion to the underlying photosensitive layer. The present invention relates to an electrophotographic photosensitive member that realizes stable electrical characteristics and high-quality image formation over a long period of time as well as durability, and a method for manufacturing the same. The present invention also relates to an image forming method, an image forming apparatus, and a process cartridge for the image forming apparatus using the long-life, high-performance photoconductor.

  In recent years, organic photoreceptors (OPC) have been widely used in copying machines, facsimile machines, laser printers, and composite machines in place of inorganic photoreceptors because of their good performance and various advantages. The reasons for this are, for example, (i) optical characteristics such as the light absorption wavelength range and the amount of absorption, (ii) electrical characteristics such as high sensitivity and stable charging characteristics, and (iii) material selection range. (Iv) ease of production, (v) low cost, (vi) non-toxicity, and the like.

On the other hand, the diameter of the photoconductor has recently been reduced due to the downsizing of the image forming apparatus, and the high speed of the machine and the maintenance-free movement have been added to increase the durability of the photoconductor. From this point of view, organophotoreceptors are generally soft because the surface layer is mainly composed of low-molecular charge transport materials and inert polymers, and when used repeatedly in electrophotographic processes, they are mechanically driven by development systems and cleaning systems. There is a drawback that wear is likely to occur due to a typical load. In addition, due to the demand for higher image quality, the rubber hardness of the cleaning blade and the contact pressure must be increased for the purpose of improving the cleaning property as the particle size of the toner particles is reduced. This also promotes the wear of the photoreceptor. It is a factor. Such abrasion of the photoreceptor deteriorates electrical characteristics such as sensitivity deterioration and chargeability, and causes abnormal images such as image density reduction and background stains. Further, scratches where wear is locally generated cause streak-like stain images due to poor cleaning. Under the present circumstances, the wear and scratches are rate-determined and the life of the photoconductor has been replaced.
Therefore, it is indispensable to reduce the amount of wear as described above in order to increase the durability of the organic photoreceptor, and an organic photoreceptor having a good surface property is required in order to impart excellent cleaning properties and transferability. These are the most pressing issues in the field.

  Techniques for improving the abrasion resistance of the photosensitive layer include (1) using a curable binder for the surface layer (Patent Document 1), and (2) using a polymeric charge transport material (Patent Document 2). (3) An inorganic filler dispersed in the surface layer (Patent Document 3). Among these techniques, those using the curable binder (1) have poor compatibility with the charge transport material, and the residual potential increases due to impurities such as polymerization initiators and unreacted residues, resulting in a decrease in image density. Tends to occur. In addition, (2) using a polymer type charge transport material and (3) dispersed inorganic filler are required for organic photoreceptors, although they can improve wear resistance to some extent. The durability has not been fully satisfied. Further, in the case where the inorganic filler (3) is dispersed, the residual potential increases due to traps present on the surface of the inorganic filler, and the image density tends to decrease. These technologies (1), (2), and (3) are sufficient to satisfy the overall durability including the electrical durability and mechanical durability required for the organic photoreceptor. Has not reached.

  Furthermore, a photoreceptor containing a polyfunctional curable acrylate monomer in order to improve the abrasion resistance and scratch resistance of (1) is also known (Patent Document 4). However, in this photoreceptor, although there is a description that the polyfunctional curable acrylate monomer is contained in the protective layer provided on the photosensitive layer, the protective layer may contain a charge transport material. However, when the surface layer contains a low-molecular charge transporting substance, there is a problem of compatibility with the cured product. In some cases, the molecular charge transport material is precipitated and cracks are generated, and the mechanical strength is also lowered. There is also a description that a polycarbonate resin is contained for improving compatibility, but the content of the curable acrylic monomer is reduced, and as a result, sufficient wear resistance cannot be achieved. In addition, regarding a photoconductor that does not include a charge transport material in the surface layer, there is a description that the surface layer is a thin film in order to reduce the potential of the exposed portion. In addition, the environmental stability of the charging potential and the exposure portion potential is poor, and the value fluctuates greatly due to the influence of the temperature and humidity environment, and it is not possible to maintain a sufficient value.

  As an alternative anti-wear technique for photosensitive layers, a charge transport layer formed by using a coating solution comprising a monomer having a carbon-carbon double bond, a charge transport material having a carbon-carbon double bond, and a binder resin is used. It is known (Patent Document 5) that this binder resin has a carbon-carbon double bond and is reactive to the charge transporting substance, and has no double bond. Those having no reactivity are included. This photoconductor is remarkably compatible with wear resistance and good electrical properties. However, when a non-reactive binder resin is used, the binder resin, the monomer, and the charge transport material are used. The compatibility with the cured product produced by this reaction was poor, and surface irregularities were generated during cross-linking from layer separation, and a tendency to cause poor cleaning was observed. Further, as described above, in this case, the binder resin prevents the curing of the monomer, and what is specifically described as the monomer used in the photoreceptor is a bifunctional one. The monomer has a small number of functional groups and a sufficient crosslinking density cannot be obtained, and it has not yet been satisfactory in terms of wear resistance. Further, even when a reactive binder is used, due to the low number of functional groups contained in the monomer and the binder resin, it is difficult to achieve both the binding amount and the crosslinking density of the charge transport material, and the electrical characteristics and The abrasion resistance was not sufficient.

  A photosensitive layer containing a compound obtained by curing a hole transporting compound having two or more chain polymerizable functional groups in the same molecule is also known (Patent Document 6). However, in this photosensitive layer, the bulky hole transporting compound has two or more chain-polymerizable functional groups, so that distortion occurs in the cured product, resulting in high internal stress, resulting in rough surface layers and cracks over time. It may be easy to do and does not have sufficient durability.

Furthermore, there is also known a cross-linked charge transport layer obtained by curing a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a monofunctional radical polymerizable compound having a charge transport structure (Patent Document 7, By using a monofunctional radically polymerizable compound having a charge transporting structure (Patent Documents 8 and 9), cracking of the photosensitive layer is suppressed simultaneously with mechanical and electrical durability. However, when this crosslinked surface layer is formed, an acrylic monomer having a large number of acrylic functional groups is cured for the purpose of high wear resistance. In such a case, the volumetric shrinkage of the acrylic cured product is remarkable, and therefore the adhesiveness with the underlying photosensitive layer may be insufficient. In such a case, when used in an image forming apparatus having a large mechanical hazard with respect to the electrophotographic photosensitive member, peeling of the crosslinked surface layer occurs, and there is a problem that sufficient wear resistance cannot be maintained over a long period of time. It was.
In addition, for electrophotographic photoreceptors containing charge transportable structural units that can be combined with organopolysiloxane resin on the cross-linked surface layer, a coating solution is prepared using a specific solvent to improve the adhesion The method of doing is also known (patent document 10, patent document 11). However, the number of polymerizable functional groups per unit weight contained in these coating solutions is large, and it is possible to realize a harder crosslinked film surface layer. Adhesiveness with a lower layer will fall and it has not reached achieving sufficient adhesiveness. That is, the cross-linked surface layer is easily peeled off, and sufficient wear resistance cannot be maintained for a long time. Furthermore, the thickness of the crosslinked surface layer cannot be increased from the viewpoint of the stability of electrostatic characteristics, and as a result, satisfactory high wear resistance has not been achieved.
For the above reasons, it cannot be said that a photoreceptor having a cross-linked photosensitive layer obtained by chemically bonding the charge transporting structure in these prior arts has sufficient comprehensive characteristics at present.

JP 56-48637 A JP-A 64-1728 JP-A-4-281461 Japanese Patent No. 3262488 Japanese Patent No. 3194392 JP 2000-66425 A JP 2004-302450 A JP 2004-302451 A JP 2004-302452 A JP 2001-183857 A JP 2001-183858 A

  An object of the present invention is to use a cross-linked surface layer that can maintain high wear resistance over a long period of time, has little fluctuation in electrical characteristics over a long period of time, and has improved adhesion to the underlying photosensitive layer. Thus, it is an object to provide an electrophotographic photosensitive member and a method for producing the same that have realized excellent electrical durability and stable electrical characteristics and high-quality image formation over a long period of time. Another object of the present invention is to provide an image forming method, an image forming apparatus, and a process cartridge for the image forming apparatus using the long life and high performance photoconductor.

In the electrophotographic photosensitive member having at least a photosensitive layer on a conductive support, the inventors of the present invention have a charge transporting property and a trifunctional or higher functional radical polymerizable monomer in which the surface layer of the photosensitive layer does not have at least a charge transporting structure. It is formed by curing a monofunctional radically polymerizable compound having a structure, and the number of radically polymerizable functional groups in 1 g of the solid content contained in the surface layer is 2.55 × 10 ²¹ or more, 7.50 × is 10 ²¹ or less, leading to the problem is the completion of the present invention to discover that can be achieved by the peel strength of the surface layer calculated from measurement by the SAICAS method is to 0.1 N / mm or more.

In the first aspect of the present invention, in an electrophotographic photoreceptor having at least a photosensitive layer on a conductive support, the surface layer of the photosensitive layer is at least (i) a trifunctional or higher functional radical polymer having no charge transporting structure. It is formed by polymerizing a monomer mixture containing a monomer and a monofunctional radically polymerizable compound having a (b) charge transporting structure, and the radical polymerizable functional group in 1 g of the solid content contained in the surface layer The number is 2.55 × 10 ²¹ or more and 7.50 × 10 ²¹ or less, and the peel strength of the surface layer calculated from the measurement by the SAICAS method is 0.1 N / mm or more. The present invention relates to an electrophotographic photoreceptor.
2. The electrophotographic photoreceptor according to claim 1, wherein the charge transporting structure (b) is selected from the group consisting of a triarylamine structure, a hydrazone structure, a pyrazoline structure, and a carbazole structure. About.
The third of the present invention, the is (ii) a charge transport structure is a triarylamine structure, the number of radically polymerizable functional groups is characterized in that it is a 2.58-3.68 × 10 ²¹ pieces the electrophotographic photosensitive member according to claim 1 or 2 wherein about.
In the fourth aspect of the present invention, the trifunctional or higher functional radical polymerizable monomer of (i) has three or more functional groups selected from the group consisting of acryloyloxy groups and methacryloyloxy groups. 3. The electrophotographic photosensitive member according to any one of 3 above.
The fifth aspect of the present invention is to saturate a polymerizable composition comprising (a) a tri- or higher functional radical polymerizable monomer having no charge transport structure and (b) a monofunctional radical polymerizable compound having a charge transport structure. The electrophotographic photosensitive member according to any one of claims 1 to 4, wherein a surface layer corresponding to the outermost layer is formed using a coating solution formed by dissolving in a solvent having a vapor pressure of 100 mmHg / 25 ° C or lower. It relates to the manufacturing method.
The sixth aspect of the present invention relates to the method for producing an electrophotographic photosensitive member according to claim 5, wherein the solvent has a boiling point of 60 ° C. to 150 ° C.
7th of this invention is related with the manufacturing method of the electrophotographic photoreceptor of Claim 5 or 6 whose solubility parameter of the said solvent is 8.5-11.0.
The eighth of the present invention relates to the method for producing an electrophotographic photosensitive member according to any one of claims 5 to 7, wherein the solvent is at least one selected from the group consisting of butyl acetate and cyclohexanone.
According to a ninth aspect of the present invention, there is provided an image forming method characterized in that at least charging, image exposure, development and transfer are repeated using the electrophotographic photosensitive member according to any one of claims 1 to 4.
A tenth aspect of the present invention relates to an image forming apparatus comprising the electrophotographic photosensitive member according to any one of the first to fourth aspects.
An eleventh aspect of the present invention comprises the electrophotographic photosensitive member according to any one of claims 1 to 4 and at least one means selected from the group consisting of a charging means, a developing means, a transfer means, a cleaning means, and a charge eliminating means. The present invention relates to a process cartridge for an image forming apparatus, which is detachable from a main body of the image forming apparatus.

The present invention will be described in detail below. The present invention is based on the following basic idea.
The photoreceptor of the present invention uses a tri- or higher functional radical polymerizable monomer having no charge transporting structure on the surface layer, thereby developing a three-dimensional network structure and a high hardness cross-linking having a very high cross-linking density. A surface layer is obtained and high wear resistance is achieved. On the other hand, when only a monomer having few radical polymerizable functional groups is used, the crosslink density in the cross-linked surface layer becomes dilute, and a dramatic improvement in wear resistance cannot be achieved. When the crosslinked surface layer contains another polymer material, the development of the three-dimensional network structure is hindered and the degree of crosslinking is lowered, so that sufficient wear resistance cannot be obtained as compared with the present invention. Further, other polymer materials contained therein and the radical polymerizable composition of the present invention (a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a monofunctional radical polymerizable compound having a charge transport structure) The compatibility with the cured product resulting from this reaction is poor, local wear occurs from the phase separation, and it appears as a scratch on the surface.

  In addition, the formation of the cross-linked surface layer of the present invention contains a monofunctional radical polymerizable compound having a charge transporting structure in addition to a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure. These were simultaneously polymerized and cured in a short time to form a high-hardness cross-linked bond, and an improvement in durability was achieved. Furthermore, it became possible to form a smooth surface layer by improving the curing rate, and it became possible to maintain a good cleaning property for a long period of time. Furthermore, a crosslinking layer is obtained by curing a trifunctional or higher-functional radical polymerizable monomer having a large number of reactive functional groups and a fast curing speed and having no charge transport structure and a monofunctional radical polymerizable compound having a charge transport structure. It is possible to form a uniform cross-linked film with less distortion therein, and as a result, the unreacted portion of the charge transport material is reduced in the cross-linked surface layer, and the homogeneity inside the cross-linked film is greatly improved. As a result, it was possible to achieve both of improved wear resistance and at the same time stable electrostatic properties and an electrophotographic photoreceptor free from cracks. In other words, various characteristics such as abrasion resistance, cleaning properties, and electrical characteristics of the photoconductor do not depend on the location of the photoconductor, and both stable wear resistance and long-term image formation are realized for long-term paper passing. In addition, since a monofunctional radically polymerizable compound having a charge transporting structure is incorporated in the cross-linked layer, stable electric characteristics are exhibited over a long period of time. On the other hand, when a low molecular charge transport material having no functional group is contained in the cross-linked surface layer, precipitation of the low molecular charge transport material and white turbidity occur due to its low compatibility, and the cross-linked surface layer The mechanical strength also decreases. In addition, when a bifunctional or higher functional charge transporting compound is used, it is fixed in the crosslinked structure by a plurality of bonds. However, since the charge transporting structure is very bulky, distortion occurs in the cured resin, and the inside of the crosslinked surface layer. Stress increases and cracks and scratches occur frequently due to carrier adhesion. In addition, since the intermediate structure (cation radical) at the time of charge transport cannot be stably maintained because a plurality of bonds are fixed in the crosslinked structure, the sensitivity is lowered due to charge trapping and the residual potential is increased. Such deterioration of the electrical characteristics appears as an image such as a decrease in image density and thinning of characters. Therefore, in the present invention, an electrophotographic photosensitive member that has improved wear resistance and has stable electrical characteristics over a long period of time, is free from cracks, and can maintain high-quality image output over a long period of time is realized. It became possible.

Furthermore, the number of radically polymerizable functional groups in 1 g of solid content contained in the crosslinked surface layer of the present invention is 2.55 × 10 ²¹ or more and 7.50 × 10 ²¹ or less. In this case, The number of radically polymerizable functional groups contained is sufficiently present, and a surface layer having a dense cross-linked structure with a higher degree of cross-linking can be constructed. That is, the three-dimensional network structure inside the crosslinked film is greatly developed, and a crosslinked surface layer having high hardness, high elastic modulus, and extremely high wear resistance can be realized.
The number of radically polymerizable functional groups in 1 g of solid content can be determined as follows.
(1) First, weight / molecular weight = number of moles.
(2) The number of moles x Avogadro number (6.02 × 10 ²³ mol ⁻¹ ) = number of molecules is determined.
(3) Calculate the number of molecules × the number of functional groups = the number of functional groups.
(4) The number of functional groups is determined for all materials having radical polymerizable functional groups, and the total number is divided by the total weight of the solid content to determine the number of radical polymerizable functional groups in 1 g of the solid content.

  Furthermore, in the present invention, a high hardness cross-linked surface layer having sufficient adhesion can be realized by constructing a cross-linked surface layer having a peel strength of 0.1 N / mm or more calculated from the measurement by the SAICAS method. As a result, peeling does not occur near the interface with the lower layer, and the characteristics of the crosslinked surface layer can be maintained throughout the crosslinked film, and high wear resistance and stable electrical characteristics can be maintained over a long period of time. Therefore, it is possible to realize an electrophotographic photosensitive member capable of maintaining high-quality image output for a long period of time.

In the present invention, a compound having a reactive functional group as a resin component constituting the cross-linked layer, more specifically, a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a charge transport structure 1 It is formed by polymerizing and curing a functional radical polymerizable compound, and the number of radical polymerizable functional groups in a solid content of 1 g contained in the surface layer is 2.55 × 10 ²¹ or more, 7.50 × 10 ^21. When the peel strength of the surface layer calculated from the measurement by the SAICAS method is 0.1 N / mm or more, the wear resistance is maintained for a long period of time, and the electrical characteristics are stabilized over a long period of time. It is possible to improve the sustainability of high-quality image formation.

Next, the constituent material of the crosslinked surface layer coating solution of the present invention will be described.
The trifunctional or higher functional radical polymerizable monomer having no charge transporting structure used in the present invention refers to a monomer having three or more radical polymerizable functional groups such as acryloyloxy group or methacryloyloxy group.
A compound having three or more acryloyloxy groups can be prepared by, for example, using a compound having three or more hydroxyl groups in the molecule and acrylic acid (salt), acrylic acid halide, or acrylic ester, and performing an ester reaction or a transesterification reaction. Obtainable. A compound having three or more methacryloyloxy groups can be obtained in the same manner. Further, the radical polymerizable functional groups in the monomer having three or more radical polymerizable functional groups may be the same or different.

Specific examples of the trifunctional or higher-functional radical polymerizable monomer (a) having no charge transporting structure include the following, but are not limited to these compounds.
That is, examples of the radical polymerizable monomer (A) used in the present invention include trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, HPA-modified (alkylene-modified) trimethylolpropane triacrylate, EO-modified ( (Ethyleneoxy modified) trimethylolpropane triacrylate, PO modified (propyleneoxy modified) trimethylolpropane triacrylate, caprolactone modified trimethylolpropane triacrylate, HPA modified trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate (PETTA) ), Glycerol triacrylate, ECH-modified (epichlorohydrin-modified) glycero Triacrylate, EO modified glycerol triacrylate, PO modified glycerol triacrylate, tris (acryloxyethyl) isocyanurate, dipentaerythritol hexaacrylate (DPHA), caprolactone modified dipentaerythritol hexaacrylate, dipentaerythritol hydroxypentaacrylate, alkyl modified Dipentaerythritol pentaacrylate, alkyl-modified dipentaerythritol tetraacrylate, alkyl-modified dipentaerythritol triacrylate, dimethylolpropane tetraacrylate (DTMPTA), pentaerythritol ethoxytetraacrylate, EO-modified phosphate triacrylate, 2, 2, 5, 5, -tetrahydroxymethylcyclopentanone tetra Such as acrylate and the like, which can be used in combination either alone or in combination. The reason for the modification is to lower the viscosity of the monomer and make it easier to handle.

  The trifunctional or higher functional radical polymerizable monomer having no charge transport structure used in the present invention is a ratio of molecular weight to the number of functional groups in the monomer in order to form a dense crosslink in the cross-linked surface layer. (Molecular weight / functional group number) is preferably 250 or less. Further, when this ratio is larger than 250, the crosslinked surface layer is soft and wear resistance is somewhat lowered. Therefore, among the monomers exemplified above, monomers having a modifying group such as HPA, EO, and PO are extremely long. It is not preferable to use one having a modifying group alone.

  Moreover, the component ratio of the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure used for the crosslinked surface layer is 20 to 80% by weight, preferably 30 to 70% by weight, based on the total amount of the crosslinked surface layer. When the monomer component is less than 20% by weight, the three-dimensional cross-linking density of the cross-linked surface layer is small, and a drastic improvement in wear resistance is not achieved as compared with the case of using a conventional thermoplastic binder resin. On the other hand, if it is 80% by weight or more, the content of the charge transporting compound is lowered, and the electrical characteristics are deteriorated. Since the required wear resistance and electrical characteristics differ depending on the process used, it cannot be said unconditionally, but considering the balance of both characteristics, the range of 30 to 70% by weight is most preferable.

  The monofunctional radically polymerizable compound having a (b) charge transporting structure used in the present invention is a hole transporting structure such as triarylamine, hydrazone, pyrazoline, carbazole, such as condensed polycyclic quinone, diphenoquinone, A compound having an electron transport structure such as an electron-withdrawing aromatic ring having a cyano group or a nitro group and having a radical polymerizable functional group. Examples of the radical polymerizable functional group include those shown in the above radical polymerizable monomer, and acryloyloxy group and methacryloyloxy group are particularly useful. As the charge transporting structure, a triarylamine structure is highly effective.

〔式中、Ｒ_１は水素原子、ハロゲン原子、置換基を有してもよいアルキル基、置換基を有してもよいアラルキル基、置換基を有してもよいアリール基、シアノ基、ニトロ基、アルコキシ基、−ＣＯＯＲ_２（Ｒ_２は水素原子、置換基を有してもよいアルキル基、置換基を有してもよいアラルキル基又は置換基を有してもよいアリール基）、ハロゲン化カルボニル基若しくはＣＯＮＲ_３Ｒ_４（Ｒ_３及びＲ_４は水素原子、ハロゲン原子、置換基を有してもよいアルキル基、置換基を有してもよいアラルキル基又は置換基を有してもよいアリール基を示し、互いに同一であっても異なっていてもよい）を表わし、Ａｒ_１、Ａｒ_２は置換もしくは未置換のアリーレン基を表わし、同一であっても異なってもよい。Ａｒ_３、Ａｒ_４は置換もしくは未置換のアリール基を表わし、同一であっても異なってもよい。Ｘは単結合、置換もしくは無置換のアルキレン基、置換もしくは無置換のシクロアルキレン基、置換もしくは無置換のアルキレンエーテル基、酸素原子、硫黄原子、ビニレン基を表わし、Ｚは置換もしくは無置換のアルキレン基、置換もしくは無置換のアルキレンエーテル基、アルキレンオキシカルボニル基を表わし、ｍとｎは０〜３の整数を表わす。〕 Furthermore, when a compound represented by the structure of the following general formula (1) or (2) is used, electrical characteristics such as sensitivity and residual potential are favorably maintained.

[Wherein, R ₁ represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, an aryl group which may have a substituent, a cyano group, a nitro group, Group, alkoxy group, —COOR ₂ (R ₂ is a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent or an aryl group which may have a substituent), halogen Carbonyl group or CONR ₃ R ₄ (R ₃ and R ₄ may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Represents a good aryl group, which may be the same or different from each other, and Ar ₁ and Ar ₂ represent a substituted or unsubstituted arylene group, which may be the same or different. Ar _{3 and} Ar ₄ represent a substituted or unsubstituted aryl group, and may be the same or different. X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group, and Z represents a substituted or unsubstituted alkylene. Represents a group, a substituted or unsubstituted alkylene ether group or an alkyleneoxycarbonyl group, and m and n each represents an integer of 0 to 3; ]

In the general formulas (1) and (2), examples of the alkyl group in R ₁ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the aryl group include a phenyl group and a naphthyl group. As benzyl group, phenethyl group, naphthylmethyl group, and alkoxy groups include methoxy group, ethoxy group, propoxy group, etc., which are halogen atom, nitro group, cyano group, methyl group, ethyl group, respectively. Or an alkyl group such as methoxy group or ethoxy group, an aryloxy group such as phenoxy group, an aryl group such as phenyl group or naphthyl group, an aralkyl group such as benzyl group or phenethyl group, etc. .
Particularly preferred among R ₁ are a hydrogen atom and a methyl group.

Examples of the aryl group of Ar ₃ and Ar ₄ include a condensed polycyclic hydrocarbon group, a non-condensed cyclic hydrocarbon group, and a heterocyclic group.
The condensed polycyclic hydrocarbon group preferably has 18 or less carbon atoms forming a ring, for example, a pentanyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptaenyl group, a biphenylenyl group, an As-indacenyl group. , S-indacenyl group, fluorenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrenyl group, aceanthrylenyl group, triphenylyl group, pyrenyl group , A chrycenyl group, a naphthacenyl group, and the like.
Examples of the non-fused cyclic hydrocarbon group include monovalent groups of monocyclic hydrocarbon compounds such as benzene, diphenyl ether, polyethylene diphenyl ether, diphenyl thioether and diphenyl sulfone, or biphenyl, polyphenyl, diphenylalkane, diphenylalkene, diphenylalkyne, Monovalent groups of non-condensed polycyclic hydrocarbon compounds such as triphenylmethane, distyrylbenzene, 1,1-diphenylcycloalkane, polyphenylalkane, and polyphenylalkene, or ring assemblies such as 9,9-diphenylfluorene And monovalent groups of hydrocarbon compounds.
Examples of the heterocyclic group include monovalent groups such as carbazole, dibenzofuran, dibenzothiophene, oxadiazole, and thiadiazole.

（式中、Ｒ_１０及びＲ_１１は各々独立に水素原子、前記（２）で定義したアルキル基、またはアリール基を表わす。アリール基としては、例えばフェニル基、ビフェニル基又はナフチル基が挙げられ、これらはＣ_１〜Ｃ_４のアルコキシ基、Ｃ_１〜Ｃ_４のアルキル基またはハロゲン原子を置換基として含有してもよい。Ｒ_１０及びＲ_１１は共同で環を形成してもよい）
具体的には、アミノ基、ジエチルアミノ基、Ｎ−メチル−Ｎ−フェニルアミノ基、Ｎ，Ｎ−ジフェニルアミノ基、Ｎ，Ｎ−ジ（トリール）アミノ基、ジベンジルアミノ基、ピペリジノ基、モルホリノ基、ピロリジノ基等が挙げられる。
（７）メチレンジオキシ基、又はメチレンジチオ基等のアルキレンジオキシ基又はアルキレンジチオ基等が挙げられる。
（８）置換又は無置換のスチリル基、置換又は無置換のβ−フェニルスチリル基、ジフェニルアミノフェニル基、ジトリルアミノフェニル基等。
前記Ａｒ_１、Ａｒ_２で表わされるアリーレン基としては、前記Ａｒ_３、Ａｒ_４で表されるアリール基から誘導される２価基である。 The aryl group represented by Ar ₃ or Ar ₄ may have a substituent as shown below, for example.
(1) Halogen atom, cyano group, nitro group and the like.
(2) Alkyl groups, preferably C ₁ -C _12, especially C ₁ -C ₈ , more preferably C ₁ -C ₄ linear or branched alkyl groups, further including fluorine atoms , a hydroxyl group, a cyano _group, an alkoxy group of C 1 -C _4, a phenyl group or a halogen _atom, which may have a phenyl group substituted by an alkoxy group C 1 -C ₄ alkyl or _C 1 -C ₄ Good. Specifically, methyl group, ethyl group, n-butyl group, i-propyl group, t-butyl group, s-butyl group, n-propyl group, trifluoromethyl group, 2-hydroxyethyl group, 2-ethoxyethyl Group, 2-cyanoethyl group, 2-methoxyethyl group, benzyl group, 4-chlorobenzyl group, 4-methylbenzyl group, 4-phenylbenzyl group and the like.
(3) An alkoxy group (—OR _a ), and R _a represents an alkyl group defined in (2). Specifically, methoxy group, ethoxy group, n-propoxy group, i-propoxy group, t-butoxy group, n-butoxy group, s-butoxy group, i-butoxy group, 2-hydroxyethoxy group, benzyloxy group And a trifluoromethoxy group.
(4) An aryloxy group, and examples of the aryl group include a phenyl group and a naphthyl group. It _may contain an alkoxy group having C 1 -C _4, alkyl group, or a halogen atom C 1 -C ₄ as a substituent. Specific examples include a phenoxy group, a 1-naphthyloxy group, a 2-naphthyloxy group, a 4-methoxyphenoxy group, and a 4-methylphenoxy group.
(5) Alkyl mercapto group or aryl mercapto group, and specific examples include methylthio group, ethylthio group, phenylthio group, p-methylphenylthio group and the like.
(6)

(Wherein R ₁₀ and R ₁₁ each independently represent a hydrogen atom, an alkyl group defined in (2) above, or an aryl group. Examples of the aryl group include a phenyl group, a biphenyl group, and a naphthyl group. these may form a ring _C 1 -C ₄ alkoxy _groups, C 1 -C good _{.R 10} and _{R 11} may contain, as a substituent, an alkyl group or a halogen atom ₄ in collaboration)
Specifically, amino group, diethylamino group, N-methyl-N-phenylamino group, N, N-diphenylamino group, N, N-di (tolyl) amino group, dibenzylamino group, piperidino group, morpholino group And pyrrolidino group.
(7) An alkylenedioxy group or an alkylenedithio group such as a methylenedioxy group or a methylenedithio group.
(8) A substituted or unsubstituted styryl group, a substituted or unsubstituted β-phenylstyryl group, a diphenylaminophenyl group, a ditolylaminophenyl group, and the like.
The arylene group represented by Ar ₁ and Ar ₂ is a divalent group derived from the aryl group represented by Ar ₃ and Ar ₄ .

  X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group.

The alkylene group in X is a C _{1 to} C ₁₂ , preferably C _{1 to} C ₈ , more preferably C _{1 to} C ₄ linear or branched alkylene group, and these alkylene groups further include fluorine. atom, a hydroxyl group, a cyano _group, optionally having a C 1 -C ₄ alkoxy group, a phenyl group or a halogen _atom, C 1 -C phenyl group substituted by ₄ alkyl or alkoxy group of _C 1 -C ₄ Also good. Specifically, methylene group, ethylene group, n-butylene group, i-propylene group, t-butylene group, s-butylene group, n-propylene group, trifluoromethylene group, 2-hydroxyethylene group, 2-ethoxyethylene Group, 2-cyanoethylene group, 2-methoxyethylene group, benzylidene group, phenylethylene group, 4-chlorophenylethylene group, 4-methylphenylethylene group, 4-biphenylethylene group and the like.

The cycloalkylene group in X is a C _{5 to} C ₇ cyclic alkylene group, and these cyclic alkylene groups include a fluorine atom, a hydroxyl group, a C _{1 to} C ₄ alkyl group, and a C _{1 to} C ₄ alkoxy group. And may have a substituent such as Specific examples of the cycloalkylene group include a cyclohexylidene group, a cyclohexylene group, and a 3,3-dimethylcyclohexylidene group.

  The alkylene ether group in X represents ethyleneoxy, propyleneoxy, ethylene glycol, propylene glycol, diethylene glycol, tetraethylene glycol, tripropylene glycol, and the alkylene group of the alkylene ether group includes a hydroxyl group, a methyl group, an ethyl group, and the like. You may have a substituent.

で表わされ、Ｒ_１２は水素、アルキル基〔前記（２）で定義されるアルキル基と同じ〕、アリール基（前記Ａｒ_３、Ａｒ_４で表わされるアリール基と同じ）、ａは１または２、ｂは１〜３を表わす。
前記Ｚは置換もしくは未置換のアルキレン基、置換もしくは無置換のアルキレンエーテル基、アルキレンオキシカルボニル基を表わす。置換もしくは未置換のアルキレン基としては、前記Ｘのアルキレン基と同様なものが挙げられる。置換もしくは無置換のアルキレンエーテル基としては、前記Ｘのアルキレンエーテル基が挙げられる。アルキレンオキシカルボニル基としては、カプロラクトン変性基が挙げられる。 The vinylene group in X is

R ₁₂ is hydrogen, an alkyl group (same as the alkyl group defined in (2) above), an aryl group (same as the aryl group represented by Ar ₃ or Ar ₄ above), a is 1 or 2 , B represents 1-3.
Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether group, or an alkyleneoxycarbonyl group. Examples of the substituted or unsubstituted alkylene group include the same alkylene groups as those described above for X. Examples of the substituted or unsubstituted alkylene ether group include the alkylene ether group represented by X. Examples of the alkyleneoxycarbonyl group include a caprolactone-modified group.

（式中、ｐ、ｑ、ｒはそれぞれ０又は１の整数、Ｒ_５は水素原子、メチル基を表わし、Ｒ_６、Ｒ_７は水素原子以外の置換基で炭素数１〜６のアルキル基を表わし、複数の場合は異なっても良い。ｓ、ｔは０〜３の整数を表わす。Ｚ_２は単結合、メチレン基、エチレン基、

を表わす。）
上記一般式で表わされる化合物としては、Ｒ_６、Ｒ_７の置換基として、特にメチル基、エチル基である化合物が好ましい。 Further, the radical polymerizable compound having a monofunctional charge transport structure of the present invention is more preferably a compound having a structure of the following general formula (3).

(In the formula, p, q and r are each an integer of 0 or 1, R ₅ represents a hydrogen atom or a methyl group, and R ₆ and R ₇ represent a substituent other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms. And a plurality of s and t each represent an integer of 0 to _3. Z ₂ represents a single bond, a methylene group, an ethylene group,

Represents. )
As the compound represented by the above general formula, a compound having a methyl group or an ethyl group is particularly preferable as a substituent for R ₆ and R ₇ .

  In the monofunctional radically polymerizable compound having a monofunctional charge transport structure of the above general formulas (1) and (2) and (3) used in the present invention, the carbon-carbon double bond is opened on both sides. In the polymer that is incorporated into the chain polymer and cross-linked by polymerization with a tri- or higher functional polymerizable monomer, it does not form a terminal structure and exists in the main chain of the polymer. And present in a cross-linked chain between the main chain and the main chain (this cross-linked chain includes an intermolecular cross-linked chain between one polymer and another polymer, and a main chain folded in one polymer. There is an intramolecular cross-linked chain that crosslinks a part of the main chain and another part derived from the polymerized monomer at a position distant from this in the main chain). Even when present in the chain, the triarylamine structure suspended from the chain moiety is It has at least three aryl groups arranged radially from the elementary atoms and is bulky, but it is not directly bonded to the chain part and is suspended from the chain part via a carbonyl group, etc. Since these triarylamine structures can be spatially arranged adjacent to each other in the polymer, there is little structural distortion in the molecule, and the electrophotographic photoreceptor In the case of the surface layer, it is presumed that an intramolecular structure that is relatively free from interruption of the charge transport path can be adopted.

  Specific examples of the monofunctional radically polymerizable compound having a charge transporting structure of the present invention are shown below, but are not limited to the compounds having these structures.

式中、Ａｒ_５は置換又は無置換の芳香族炭化水素骨格からなる一価基または二価基を表す。芳香族炭化水素としては、ベンゼン、ナフタレン、フェナントレン、ビフェニル、１，２，３，４−テトラヒドロナフタレン等が挙げられる。置換基としては、炭素数１〜１２のアルキル基、炭素数１〜１２のアルコキシ基、ベンジル基、ハロゲン原子が挙げられる。また、上記アルキル基、アルコキシ基は、さらにハロゲン原子、フェニル基を置換基として有していても良い。
Ａｒ_６は、少なくとも１個の３級アミノ基を有する芳香族炭化水素骨格からなる一価基または二価基もしくは少なくとも１個の３級アミノ基を有する複素環式化合物骨格からなる一価基または二価基を表すが、ここで、３級アミノ基を有する芳香族炭化水素骨格とは下記一般式（Ａ）で表される。

（式中、Ｒ_１３、Ｒ_１４はアシル基、置換もしくは無置換のアルキル基、置換もしくは無置換のアリール基を表し、Ａｒ_７はアリール基を表し、ｗは１〜３の整数を表す。）
Ｒ_１３、Ｒ_１４のアシル基としてはアセチル基、プロピオニル基、ベンゾイル基等が挙げられる。
Ｒ_１３、Ｒ_１４のアルキル基はＡｒ_５の置換基で述べたアルキル基と同様である。
Ｒ_１３、Ｒ_１４のアリール基は、フェニル基、ナフチル基、ビフェニリル基、ターフェニリル基、ピレニル基、フルオレニル基、９，９−ジメチル−２−フルオレニル基、アズレニル基、アントリル基、トリフェニレニル基、クリセニル基に加えて下記一般式（Ｂ）で表される基を挙げることができる。
Ｒ_１３、Ｒ_１４は、Ａｒ_５で定義されたアルキル基、アルコキシ基、ハロゲン原子を置換基として有していても良い。

（式中、Ｂは−Ｏ−、−Ｓ−、−ＳＯ−、−ＳＯ_２−、−ＣＯ−及び以下の２価基から選ばれる。

（ここで、Ｒ_２１は、水素原子、Ａｒ_５で定義された置換もしくは無置換のアルキル基、アルコキシ基、ハロゲン原子、Ｒ_１３で定義された置換もしくは無置換のアリール基、アミノ基、ニトロ基、シアノ基を表し、Ｒ_２２は、水素原子、Ａｒ_５で定義された置換もしくは無置換のアルキル基、Ｒ_１３で定義された置換もしくは無置換のアリール基を表し、ｉは１〜１２の整数、ｊは１〜３の整数を表す。）］
Ｒ_２１のアルコキシ基の具体例としてはメトキシ基、エトキシ基、ｎ−プロポキシ基、ｉ−プロポキシ基、ｎ−ブトキシ基、ｉ−ブトキシ基、ｓ−ブトキシ基、ｔ−ブトキシ基、２−ヒドロキシエトキシ基、２−シアノエトキシ基、ベンジルオキシ基、４−メチルベンジルオキシ基、トリフルオロメトキシ基等が挙げられる。
Ｒ_２１のハロゲン原子としてはフッ素原子、塩素原子、臭素原子、ヨウ素原子が挙げられる。
Ｒ_２１のアミノ基としては、ジフェニルアミノ基、ジトリルアミノ基、ジベンジルアミノ基、４−メチルベンジル基等が挙げられる。
Ａｒ_７のアリール基としてはフェニル基、ナフチル基、ビフェニリル基、ターフェニリル基、ピレニル基、フルオレニル基、９，９−ジメチル−２−フルオレニル基、アズレニル基、アントリル基、トリフェニレニル基、クリセニル基を挙げることができる。
Ａｒ_７は、Ａｒ_５で定義されたアルキル基、アルコキシ基、ハロゲン原子を置換基として有していても良い。
また、前記Ａｒ_６における３級アミノ基を有する複素環式化合物骨格としては、ピロール、ピラゾール、イミダゾール、トリアゾール、ジオキサゾール、インドール、イソインドール、ベンズイミダゾール、ベンゾトリアゾール、ベンゾイソキサジン、カルバゾール、フェノキサジン等のアミン構造を有する複素環化合物が挙げられる。これらは、Ａｒ_５で定義されたアルキル基、アルコキシ基、ハロゲン原子を置換基として有していても良い。
Ｂ_１、Ｂ_２はアクリロイルオキシ基、メタクリロイルオキシ基、ビニル基、アクリロイルオキシ基又はメタクリロイルオキシ基又はビニル基を有するアルキル基、アクリロイルオキシ基又はメタクリロイルオキシ基又はビニル基を有するアルコキシ基を表す。アルキル基、アルコキシ基は、Ａｒ_５で述べたものが同様に適用される。これら、Ｂ_１、とＢ_２は、どちらか一方のみが存在し、両方の存在は除外される。 In the present invention, the specific (meth) acrylic acid ester compound represented by the following general formula (4) can also be favorably used as the charge transporting compound (b) having one radical polymerizable functional group.

In the formula, Ar ₅ represents a monovalent group or a divalent group consisting of a substituted or unsubstituted aromatic hydrocarbon skeleton. Examples of the aromatic hydrocarbon include benzene, naphthalene, phenanthrene, biphenyl, 1,2,3,4-tetrahydronaphthalene and the like. Examples of the substituent include an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a benzyl group, and a halogen atom. The alkyl group and alkoxy group may further have a halogen atom or a phenyl group as a substituent.
Ar ₆ represents a monovalent group consisting of an aromatic hydrocarbon skeleton having at least one tertiary amino group, a monovalent group consisting of a divalent group or a heterocyclic compound skeleton having at least one tertiary amino group, or Although it represents a divalent group, the aromatic hydrocarbon skeleton having a tertiary amino group is represented by the following general formula (A).

(In the formula, R ₁₃ and R ₁₄ represent an acyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, Ar ₇ represents an aryl group, and w represents an integer of 1 to 3).
Examples of the acyl group for R ₁₃ and R ₁₄ include an acetyl group, a propionyl group, and a benzoyl group.
The alkyl group for R ₁₃ and R _{14 is the same as} the alkyl group described for the substituent for Ar ₅ .
The aryl groups of R ₁₃ and R ₁₄ are phenyl group, naphthyl group, biphenylyl group, terphenylyl group, pyrenyl group, fluorenyl group, 9,9-dimethyl-2-fluorenyl group, azulenyl group, anthryl group, triphenylenyl group, chrysenyl group. In addition, a group represented by the following general formula (B) can be exemplified.
R ₁₃ and R ₁₄ may have an alkyl group, an alkoxy group, or a halogen atom defined by Ar ₅ as a substituent.

(In the formula, B is selected from —O—, —S—, —SO—, —SO ₂ —, —CO—, and the following divalent groups.

(Wherein R ₂₁ is a hydrogen atom, a substituted or unsubstituted alkyl group defined by Ar ₅ , an alkoxy group, a halogen atom, a substituted or unsubstituted aryl group defined by R ₁₃ , an amino group, a nitro group; Represents a cyano group, R ₂₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group defined by Ar ₅ , a substituted or unsubstituted aryl group defined by R ₁₃ , and i is an integer of 1 to 12 , J represents an integer of 1 to 3)]
Specific examples of the alkoxy group of R ₂₁ include methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group, s-butoxy group, t-butoxy group, 2-hydroxyethoxy. Group, 2-cyanoethoxy group, benzyloxy group, 4-methylbenzyloxy group, trifluoromethoxy group and the like.
Examples of the halogen atom for R ₂₁ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the amino group of R ₂₁ include a diphenylamino group, a ditolylamino group, a dibenzylamino group, and a 4-methylbenzyl group.
Examples of the aryl group of Ar ₇ include a phenyl group, a naphthyl group, a biphenylyl group, a terphenylyl group, a pyrenyl group, a fluorenyl group, a 9,9-dimethyl-2-fluorenyl group, an azulenyl group, an anthryl group, a triphenylenyl group, and a chrysenyl group. Can do.
Ar ₇ may have an alkyl group, an alkoxy group, or a halogen atom defined by Ar ₅ as a substituent.
Examples of the heterocyclic compound skeleton having a tertiary amino group in Ar ₆ include pyrrole, pyrazole, imidazole, triazole, dioxazole, indole, isoindole, benzimidazole, benzotriazole, benzoisoxazine, carbazole, phenoxy. Examples include heterocyclic compounds having an amine structure such as sajin. These may have an alkyl group, an alkoxy group, or a halogen atom defined by Ar ₅ as a substituent.
B ₁ and B ₂ represent an acryloyloxy group, a methacryloyloxy group, a vinyl group, an acryloyloxy group, a methacryloyloxy group, an alkyl group having a vinyl group, an acryloyloxy group, a methacryloyloxy group, or an alkoxy group having a vinyl group. As the alkyl group and alkoxy group, those described for Ar ₅ are similarly applied. Only _{one of} these B ₁ and B ₂ is present, and both are excluded.

式中、Ｒ_８、Ｒ_９は、置換もしくは無置換のアルキル基、置換もしくは無置換のアルコキシ基、ハロゲン原子を表し、Ａｒ_７、Ａｒ_８は、置換もしくは無置換のアリール基またはアリレン基、置換又は無置換のベンジル基をあらわす。置換もしくは無置換のアルキル基、置換もしくは無置換のアルコキシ基、ハロゲン原子は前記Ａｒ_５で述べたものが同様に適用される。
置換もしくは無置換のアリール基は、Ｒ_１３、Ｒ_１４で定義されたアリール基と同様である。置換もしくは無置換のアリレン基は、そのアリール基から誘導される二価基である。
Ｂ_１〜Ｂ_４は、一般式（４）におけるＢ_１、Ｂ_２と同様であり、Ｂ_１〜Ｂ_４の内、どれか一つだけが存在し、二つ以上の存在は除外される。ｕは０〜５の整数、ｖは０〜４の整数を表す。 As a more preferred structure in the (meth) acrylic acid ester compound of the general formula (4), the compound of the general formula (5) can be exemplified.

In the formula, R ₈ and R ₉ represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group or a halogen atom, and Ar ₇ and Ar ₈ represent a substituted or unsubstituted aryl group or an arylene group, substituted Or an unsubstituted benzyl group is represented. As for the substituted or unsubstituted alkyl group, the substituted or unsubstituted alkoxy group, and the halogen atom, those described in the above Ar ₅ are similarly applied.
The substituted or unsubstituted aryl group is the same as the aryl group defined by R ₁₃ and R ₁₄ . A substituted or unsubstituted arylene group is a divalent group derived from the aryl group.
B _{1 to} B ₄ are the same as B ₁ and B ₂ in the general formula (4), and only one of B _{1 to} B ₄ is present, and the presence of two or more is excluded. u represents an integer of 0 to 5, and v represents an integer of 0 to 4.

  The specific (meth) acrylic acid ester compound represented by the general formula (5) has the following characteristics. It is a tertiary amine compound having a stilbene-type conjugated structure, and has a developed conjugated system. By using a charge transporting compound with such a conjugated system, the charge injection property at the interface part of the cross-linked layer becomes very good, and intermolecular interaction is inhibited even when immobilized between cross-linked bonds. It is difficult and has good characteristics with respect to charge mobility. Moreover, it has one acryloyloxy group or methacryloyloxy group having high radical polymerizability in the molecule, so that it rapidly gels during radical polymerization and does not cause excessive crosslinking strain. The double bond at the stilbene structure in the molecule partially participates in the polymerization, and the polymerization is lower than the acryloyloxy group or methacryloyloxy group. In addition, since the number of cross-linking reactions per molecular weight can be increased due to the use of double bonds in the molecule, the cross-linking density can be increased, and further improvement in wear resistance can be realized. . In addition, the degree of polymerization of this double bond can be adjusted depending on the crosslinking conditions, and an optimum crosslinked film can be easily produced. Such cross-linking participation in radical polymerization is a unique feature of an acrylate compound and does not occur in an α-phenylstilbene type structure.

  From the above, the use of a charge transporting compound having a radical polymerizable functional group represented by the general formula (4), particularly the general formula (5), while maintaining good electrical characteristics and generating cracks and the like. A film having a very high crosslinking density can be formed without causing any problems, thereby satisfying various characteristics of the photoconductor, preventing silica fine particles from being stuck in the photoconductor, and reducing image defects such as white spots. be able to.

  Specific examples of the charge transporting compound having a radical polymerizable functional group represented by the general formula (4) as a charge transporting structure are shown below, but are not limited to the compounds having these structures.

  In addition, the charge transporting compound (B) having a radical polymerizable functional group used in the present invention is important for imparting the charge transport performance of the crosslinked surface layer, and this component is 20 to 80 with respect to the total amount of the crosslinked surface layer. The content of the coating liquid component is adjusted so as to be 5% by weight, preferably 30 to 70% by weight. When this component is less than 20% by weight, the charge transport performance of the crosslinked surface layer cannot be maintained sufficiently, and deterioration of electrical characteristics such as a decrease in sensitivity and an increase in residual potential appears with repeated use. On the other hand, if it exceeds 80% by weight, the content of the trifunctional or higher-functional radical polymerizable monomer having no charge transport structure is lowered, and the crosslink density is lowered, so that high wear resistance is not exhibited. Although the electrical characteristics and abrasion resistance required differ depending on the process used, it cannot be said unconditionally, but considering the balance of both characteristics, the range of 30 to 70% by weight is most preferable.

Next, the present invention is further characterized in that the peel strength of the crosslinked surface layer is 0.1 N / mm or more. The peel strength of the present invention is measured by cutting and peeling a single crystal diamond cutting blade having a blade angle of 60 °, a rake angle of 20 ° and a burr angle of 10 ° from the sample surface to the interface at an ultra-low speed. The data to be specifically measured are the horizontal force, vertical force and vertical displacement applied to the cutting edge, and the peel strength can be calculated as the horizontal force per blade width. The peel strength is measured under a constant temperature and humidity. In the present invention, the peel strength is a measured value of the above test conducted under environmental conditions of a temperature of 22 ° C. and a relative humidity of 55%.
In the present invention, a SAICAS device DN-20 type (manufactured by Daipura Wintes) and a cutting blade having a blade width of 0.5 mm are used, but values measured by any device having equivalent performance can be used. Good. In the measurement, the photoreceptor having the crosslinked surface layer of the present invention was prepared on an aluminum cylinder, which was appropriately cut and used (specific measurement conditions are described in [0156]). Adhesive strength between the crosslinked surface layer and the lower photosensitive layer can be sufficiently ensured by setting the peel strength in the crosslinked surface layer to 0.1 N / mm or more, without causing peeling of the crosslinked surface layer. Thus, an electrophotographic photosensitive member capable of maintaining high wear resistance and stable electrical characteristics in the entire cross-linked layer and capable of outputting a high-quality image for a long period of time has been realized.

  Further, as the solvent used in the present invention, a solvent having a saturated vapor pressure of 100 mmHg / 25 ° C. or less is preferable from the viewpoint of improving the adhesion of the crosslinked surface layer. By using such a solvent, the amount of solvent removal at the time of forming the coating film of the crosslinked surface layer is reduced, so that the surface of the underlying photosensitive layer swells or slightly dissolves, and the interface between the crosslinked surface layer and the photosensitive layer is caused. It is presumed that a region having continuity is formed in the vicinity. By forming such a layer, there is no region with abrupt changes in physical properties between the crosslinked surface layer and the photosensitive layer, the adhesiveness can be sufficiently maintained, and the entire crosslinked surface layer has high durability. It became possible to maintain. That is, in the present invention, the amount of residual solvent in the coating film is changed by changing the solvent used in the crosslinked surface layer coating solution to the solvent used in the photosensitive layer coating solution (those having a low vapor pressure have a large residual amount). If the solubility parameter is the same as that of the photosensitive layer constituent resin component, the interface between the surface layer and the photosensitive layer is made continuous by dissolving the photosensitive layer constituent resin during the coating film formation and compatibility with the crosslinked film constituent material. In other words, the adhesion of the crosslinked surface layer is improved. In the present invention, the presence of a slight amount of solvent in the coating film during the formation of the coating film accelerates the radical reaction of the crosslinked surface layer by the solvent. As a result, the uniform curing property of the entire crosslinked surface layer is also improved. An electrophotographic photoreceptor that can be improved has been realized. In other words, by diluting with a solvent having a saturated vapor pressure of 100 mmHg / 25 ° C. or less, internal stress inside the crosslinked surface layer is not accumulated locally, and a uniform crosslinked surface layer without distortion can be constructed. In addition, it is possible to realize an electrophotographic photoreceptor having stable electrical characteristics over a long period of time while maintaining high durability over the entire cross-linked surface layer by ensuring sufficient adhesion, and at the same time, cracks do not occur. did it. Further, from the viewpoint of the amount of residual solvent in the coating film during formation, the solvent preferably has a saturated vapor pressure of 50 mmHg / 25 ° C. or less, more preferably 20 mmHg / 25 ° C. or less.

  Although it is considered to be similar to the effect of saturated vapor pressure, when the boiling point of the solvent is 60 ° C. to 150 ° C., a continuous region between the crosslinked surface layer and the underlying photosensitive layer can be formed satisfactorily. Sufficient sex can be secured. In view of the solvent removal step such as heat drying, the boiling point of the solvent is more preferably 100 ° C. to 130 ° C. Further, in the solvent used in the present invention, when the solubility parameter is 8.5 to 11.0, more preferably 9.0 to 9.7, the coating is made with polycarbonate which is the main constituent material of the lower photosensitive layer. It is possible to construct a cross-linked surface layer that has a higher affinity with the working solution, improves the compatibility of each constituent material at the interface between the cross-linked surface layer and the photosensitive layer, and can maintain sufficient adhesion. It becomes.

  Examples of the solvent used in the present invention include heptane, octane, trimethylpentane, isooctane, nonane, 2,2,5-trimethylhexane, decane, benzene, toluene, xylene, ethylbenzene, isopropylbenzene, styrene, ethylcyclohexanone, cyclohexene and the like. Hydrocarbons, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2- Methyl-1-butanol, tert-pentyl alcohol, 3-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pe Tanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol, 3-heptanol, allyl alcohol, propargyl alcohol, benzyl alcohol, cyclohexanol, 1,2-ethanodiol, 1,2-propanediol, etc. Alcohols, phenols such as phenol and cresol, ethers such as dipropyl ether, diisopropyl ether, dibutyl ether, butyl vinyl ether, benzyl ethyl ether, dioxane, anisole, phenetole, 1,2-epoxybutane, acetal, 1, Acetal type such as 2-dimethoxyethane, 1,2-diethoxyethane, methyl ethyl ketone, 2-pentanone, 2-hexanone, 2-heptanone, diisobutyl ketone, methyl oxide, cyclohexanone, methyl Ketones such as cyclohexanone, 4-methyl-2-pentanone, acetylacetone, acetonylacetone, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, 3-methoxybutyl acetate, diethyl carbonate, 2-methoxyethyl acetate, etc. Esters, halogen compounds such as chlorobenzene, sulfur compounds such as tetrahydrothiophene, or 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, 1-methoxy-2-propanol, 1 -Ethoxy-2-propanol, diacetone alcohol, furfural, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, propylene glycol propyl ether, propylene glycol-1-monomethyl Examples thereof include compounds having a plurality of functional groups such as tilether-2-acetate. Among these, from the viewpoint of adhesiveness, butyl acetate, chlorobenzene, acetylacetone, xylene, 2-methoxyethyl acetate, propylene glycol-1-monomethyl ether-2-acetate, and cyclohexanone are preferable. These solvents may be used alone or in combination of two or more.

  The dilution ratio with the solvent varies depending on the solubility of the composition, the coating method, and the target film thickness, and is optional, but the amount of residual solvent in the coating film during the coating film formation is maintained, and sufficient adhesion to the crosslinked surface layer From the viewpoint of imparting water, the solid content concentration of the coating liquid is preferably 25% by weight or less, and more preferably 3 to 15% by weight. By doing so, compatibility with the lower layer is improved, and even when the polyfunctional monomer is cured, the adhesiveness is not lowered, that is, no film peeling or cracking occurs, and a high resistance to the entire crosslinked surface layer. Abrasion was achieved.

  The cross-linked surface layer of the present invention is a tri- or higher functional radical polymerizable compound in which the surface layer of the photosensitive layer has at least (i) a charge transporting structure in an electrophotographic photosensitive member having at least a photosensitive layer on a conductive support. It is formed by curing a monomer and (b) a monofunctional radically polymerizable compound having a charge transporting structure. In addition to this, viscosity adjustment during coating, stress relaxation of the crosslinked surface layer, lower surface energy, Monofunctional and bifunctional radically polymerizable monomers, functional monomers and radically polymerizable oligomers can be used in combination for the purpose of imparting a function such as a reduction in friction coefficient. Known radical polymerizable monomers and oligomers can be used.

  Examples of the monofunctional radical monomer include 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, 2-ethylhexyl carbitol acrylate, 3-methoxybutyl acrylate, benzyl acrylate, and cyclohexyl acrylate. , Isoamyl acrylate, isobutyl acrylate, methoxytriethylene glycol acrylate, phenoxytetraethylene glycol acrylate, cetyl acrylate, isostearyl acrylate, stearyl acrylate, styrene monomer, and the like.

  Examples of the bifunctional radical polymerizable monomer include 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol diacrylate, 1, Examples include 6-hexanediol dimethacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, bisphenol A-EO modified diacrylate, bisphenol F-EO modified diacrylate, neopentyl glycol diacrylate, and the like.

  Examples of the functional monomer include those substituted with a fluorine atom such as octafluoropentyl acrylate, 2-perfluorooctylethyl acrylate, 2-perfluorooctylethyl methacrylate, 2-perfluoroisononylethyl acrylate, No. 60503, JP-B-6-45770, siloxane repeating units: 20-70 acryloyl polydimethylsiloxane ethyl, methacryloyl polydimethylsiloxane ethyl, acryloyl polydimethylsiloxane propyl, acryloyl polydimethylsiloxane butyl, diacryloyl polydimethylsiloxane Examples include vinyl monomers having a polysiloxane group such as diethyl, acrylates and methacrylates.

  Examples of the radical polymerizable oligomer include epoxy acrylate, urethane acrylate, and polyester acrylate oligomers.

  However, when a large amount of monofunctional and bifunctional radically polymerizable monomers and radically polymerizable oligomers are contained, the three-dimensional cross-linking density of the cross-linked surface layer is substantially reduced, resulting in a decrease in wear resistance. For this reason, the content of these monomers and oligomers is limited to 50 parts by weight or less, preferably 30 parts by weight or less, with respect to 100 parts by weight of the tri- or higher functional radical polymerizable monomer.

  The surface layer of the present invention is an electrophotographic photosensitive member having at least a photosensitive layer on a conductive support, and the surface of the photosensitive layer has at least a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure and a charge. It is formed by applying a solvent solution composition (coating solution) of a monomer mixture containing a monofunctional radically polymerizable compound having a transporting structure, drying, polymerizing and curing the composition. If necessary, a polymerization initiator (for example, a thermal polymerization initiator or a photopolymerization initiator) may be used in the solvent solution composition in order to allow the crosslinking reaction to proceed efficiently.

  Examples of the thermal polymerization initiator include 2,5-dimethylhexane-2,5-dihydroperoxide, dicumyl peroxide, benzoyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di ( Peroxybenzoyl) hexyne-3, di-t-butyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, peroxide initiators such as lauroyl peroxide, azobisisobutylnitrile, azobiscyclohexanecarbonitrile Azo initiators such as methyl azobisisobutyrate, azobisisobutylamidine hydrochloride, and 4,4′-azobis-4-cyanovaleric acid.

  Examples of the photopolymerization initiator include diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 4- (2-hydroxyethoxy) phenyl- (2 -Hydroxy-2-propyl) ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2- Acetophenone-based or ketal-based photopolymerization initiators such as methyl-2-morpholino (4-methylthiophenyl) propan-1-one, 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime, Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether Benzoin ether photopolymerization initiators such as benzoin isopropyl ether, benzophenone, 4-hydroxybenzophenone, methyl o-benzoylbenzoate, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoylphenyl ether, acrylated benzophenone, Benzophenone photopolymerization initiators such as 1,4-benzoylbenzene, thioxanthones such as 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone Examples of photopolymerization initiators and other photopolymerization initiators include ethyl anthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoic acid. Phenylethoxyphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,4-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10 -Phenanthrene, an acridine type compound, a triazine type compound, an imidazole type compound is mentioned. Moreover, what has a photopolymerization promotion effect can also be used individually or in combination with the said photoinitiator. Examples include triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino) ethyl benzoate, 4,4′-dimethylaminobenzophenone, and the like.

  These polymerization initiators may be used alone or in combination of two or more. The content of the polymerization initiator is 0.5 to 40 parts by weight, preferably 1 to 20 parts by weight with respect to 100 parts by weight of the total content having radical polymerizability.

  Furthermore, the coating liquid of the present invention can contain additives such as various plasticizers (for the purpose of stress relaxation and adhesion improvement), leveling agents, and low molecular charge transport materials having no radical reactivity as required. As these additives, known additives can be used, and as plasticizers, those used in general resins such as dibutyl phthalate and dioctyl phthalate can be used, and the amount used is the total solid content of the coating liquid. To 20 wt% or less, preferably 10 wt% or less. As leveling agents, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain can be used, and the amount used is based on the total solid content of the coating liquid. 3% by weight or less is appropriate.

  The surface layer of the present invention is an electrophotographic photosensitive member having at least a photosensitive layer on a conductive support, and the surface layer of the photosensitive layer is at least (i) a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure. And (b) formed by polymerizing and curing a monomer mixture containing a monofunctional radically polymerizable compound having a charge transporting structure. Examples of coating methods include dip coating, spray coating, and bead coating. A ring coating method can be used, but a spray coating method that can appropriately adjust the amount of residual solvent in the coating film during coating can be selected more preferably.

In the present invention, after applying such a coating solution, energy is applied from the outside and cured to form a crosslinked surface layer. The external energy used at this time includes heat, light, and radiation. The heat energy is applied by heating from the coating surface side or the support side using a gas such as air or nitrogen, steam, various heat media, infrared rays, or electromagnetic waves. The heating temperature is preferably 100 ° C. or higher and 170 ° C. or lower. If the heating temperature is lower than 100 ° C., the reaction rate is slow and the reaction is not completely completed. At a temperature higher than 170 ° C., the reaction proceeds non-uniformly and a large strain is generated in the crosslinked surface layer. In order to advance the curing reaction uniformly, it is also effective to complete the reaction by heating at a relatively low temperature of less than 100 ° C. and then heating to 100 ° C. or more. As the energy of light, UV irradiation light sources such as high-pressure mercury lamps and metal halide lamps, which mainly have an emission wavelength in ultraviolet light, can be used, but a visible light source can also be selected according to the absorption wavelength of radically polymerizable substances and photopolymerization initiators. Is possible. Irradiation light amount is 50 mW / cm ² or more, preferably 1000 mW / cm ² or less, it takes time for the curing reaction is less than 50 mW / cm ^2. If it is higher than 1000 mW / cm ^2, the progress of the reaction becomes non-uniform and the cross-linked surface layer becomes very rough. Examples of radiation energy include those using electron beams. Among these energies, those using heat and light energy are useful because of the ease of reaction rate control and the simplicity of the apparatus.

  Since the film thickness of the surface layer of the present invention varies depending on the layer structure of the photoreceptor in which the surface layer is used, it is described in accordance with the following description of the layer structure.

<About the layer structure of the electrophotographic photoreceptor>
The electrophotographic photosensitive member used in the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an electrophotographic photosensitive member of the present invention, in which a single layer structure in which a photosensitive layer (33) having a charge generating function and a charge transporting function is provided on a conductive support (31). This is a photoreceptor. FIG. 1A shows the case where the cross-linked surface layer is the entire photosensitive layer, and FIG. 1-B shows the case where the cross-linked surface layer is the surface portion of the photosensitive layer.
FIG. 2 shows a photoreceptor having a laminated structure in which a charge generation layer (35) having a charge generation function and a charge transport layer (37) having a charge transport function are laminated on a conductive support (31). . FIG. 2-A shows the case where the cross-linked surface layer is the entire charge transport layer, and FIG. 2-B shows the case where the cross-linked surface layer is the surface portion of the charge transport layer.

<About conductive support>
As the conductive support (31), a material having a volume resistance of 10 ¹⁰ Ω · cm or less, for example, a metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, tin oxide, oxidation Metal oxide such as indium is deposited or sputtered to form film or cylindrical plastic, paper coated, or aluminum, aluminum alloy, nickel, stainless steel, etc. After conversion, a tube that has been subjected to surface treatment such as cutting, superfinishing, or polishing can be used. Further, an endless nickel belt and an endless stainless steel belt disclosed in Japanese Patent Application Laid-Open No. 52-36016 can be used as the conductive support (31).

In addition, the conductive support dispersed in a suitable binder resin and coated on the support can also be used as the conductive support (31) of the present invention.
Examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc and silver, or metal oxide powder such as conductive tin oxide and ITO. Can be mentioned. The binder resin used at the same time is polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, Examples thereof include thermoplastic, thermosetting resins, and photocurable resins such as melamine resin, urethane resin, phenol resin, and alkyd resin. Such a conductive layer can be provided by dispersing and coating these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, and toluene.

  Furthermore, it is electrically conductive by a heat-shrinkable tube in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, Teflon (registered trademark) on a suitable cylindrical substrate. Those provided with a conductive layer can also be used favorably as the conductive support (31) of the present invention.

<About photosensitive layer>
Next, the photosensitive layer will be described. The photosensitive layer may have a laminated structure or a single layer structure.
In the case of a laminated structure, the photosensitive layer is composed of a charge generation layer having a charge generation function and a charge transport layer having a charge transport function. In the case of a single layer structure, the photosensitive layer is a layer having a charge generation function and a charge transport function at the same time.
Hereinafter, each of the photosensitive layer having a laminated structure and the photosensitive layer having a single layer structure will be described.

<Photosensitive layer comprising a charge generation layer and a charge transport layer>
(Charge generation layer)
The charge generation layer (35) is a layer mainly composed of a charge generation material having a charge generation function, and a binder resin can be used in combination as necessary. As the charge generation material, inorganic materials and organic materials can be used.

Examples of the inorganic material as the charge generation material include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compound, amorphous silicon, and the like. In amorphous silicon, dangling bonds that are terminated with hydrogen atoms or halogen atoms, or those that are doped with boron atoms, phosphorus atoms, or the like are preferably used.
On the other hand, a known material can be used as the organic material as the charge generating substance. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having carbazole skeleton, azo pigments having triphenylamine skeleton, azo pigments having diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having fluorenone skeleton, azo pigments having oxadiazole skeleton, azo pigments having bis-stilbene skeleton, azo pigments having distyryl oxadiazole skeleton, azo pigments having distyrylcarbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Goido based pigments, and bisbenzimidazole pigments.
These charge generation materials can be used alone or as a mixture of two or more.

The binder resin used as necessary for the charge generation layer (35) includes polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-. Examples thereof include vinyl carbazole and polyacrylamide. These binder resins can be used alone or as a mixture of two or more. In addition to the binder resin described above as a binder resin for the charge generation layer, a polymer charge transport material having a charge transport function, such as an arylamine skeleton, benzidine skeleton, hydrazone skeleton, carbazole skeleton, stilbene skeleton, pyrazoline skeleton, etc. Polymer materials such as polycarbonate, polyester, polyurethane, polyether, polysiloxane, and acrylic resin, polymer materials having a polysilane skeleton, and the like can be used.
Specific examples of the binder resin include JP-A-01-001728, JP-A-01-009964, JP-A-01-013061, JP-A-01-019049, JP-A-01-241559. JP, 04-011627, JP 04-175337, JP 04-183719, JP 04-22514, JP 04-230767, JP 04-320420, Japanese Laid-Open Patent Publication Nos. 05-232727, 05-310904, 06-234836, 06-234837, 06-234838, 06-234839, 06 -234840, JP-A-06-234441, JP-A-06-239 49, JP 06-236050, JP 06-236051, JP 06-295077, JP 07-056374, JP 08-176293, JP 08-208820. JP-A-08-212640, JP-A-08-253568, JP-A-08-269183, JP-A-09-062019, JP-A-09-038883, JP-A-09-71642, JP-A 09-87376, JP-A 09-104746, JP 09-110974, JP 09-110976, JP 09-157378, JP 09-221544, JP JP 09-227669 A, JP 09-235367 A, JP 09-24 A. 369, JP-A 09-268226, JP-A 09-272735, JP-A 09-302084, JP-A 09-302085, JP-A 09-328539, and the like. Examples include polymer materials.
Specific examples of the polymer material having the charge transport function include, for example, JP-A-63-285552, JP-A-05-19497, JP-A-05-70595, and JP-A-10-73944. And the polysilylene polymers described in the above.

The charge generation layer (35) may contain a low molecular charge transport material.
Low molecular charge transport materials that can be used in combination with the charge generation layer (35) include electron transport materials and hole transport materials.

  Examples of the electron transporting material include chloroanil, bromanyl, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-tri Examples thereof include electron-accepting substances such as nitrodibenzothiophene-5,5-dioxide and diphenoquinone derivatives. These electron transport materials can be used alone or as a mixture of two or more.

  Examples of the hole transporting material include the electron donating materials shown below and are used favorably. As hole transport materials, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triaryls Other known materials such as methane derivatives, 9-styrylanthracene derivatives, pyrazoline derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, bisstilbene derivatives, enamine derivatives, and the like can be given. These hole transport materials can be used alone or as a mixture of two or more.

Methods for forming the charge generation layer (35) include a vacuum thin film preparation method and a casting method from a solution dispersion system.
As the former method, a vacuum deposition method, a glow discharge decomposition method, an ion plating method, a sputtering method, a reactive sputtering method, a CVD method, or the like is used, and the above-described inorganic materials and organic materials can be satisfactorily formed.
In addition, in order to provide a charge generation layer by the casting method described later, if necessary, the inorganic or organic charge generation material together with a binder resin, tetrahydrofuran, dioxane, dioxolane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, cyclohexane. Can be formed by dispersing with a ball mill, attritor, sand mill, bead mill, etc. using a solvent such as pentanone, anisole, xylene, methyl ethyl ketone, acetone, ethyl acetate, butyl acetate, etc. . Moreover, leveling agents, such as a dimethyl silicone oil and a methylphenyl silicone oil, can be added as needed. The coating can be performed using a dip coating method, spray coating, bead coating, ring coating method or the like.

  The thickness of the charge generation layer provided as described above is suitably about 0.01 to 5 μm, preferably 0.05 to 2 μm.

(About charge transport layer)
The charge transport layer (37) is a layer having a charge transport function, and the crosslinked surface layer (32) having the charge transport structure of the present invention is useful as a charge transport layer. As shown in FIG. 2A, when the cross-linked surface layer (32) is the entire charge transport layer (37), the present invention is formed on the charge generation layer (35) as described in the cross-linked surface layer preparation method. Coating solution containing at least a radically polymerizable composition (a monomer composition containing at least a radically polymerizable monomer having no charge transporting structure and a charge transporting compound having a radically polymerizable functional group; the same shall apply hereinafter) After coating and drying as necessary, the curing reaction is started by external energy, and a crosslinked surface layer is formed.

  At this time, the film thickness of the crosslinked surface layer is 10 to 30 μm, preferably 10 to 25 μm. If it is thinner than 10 μm, a sufficient charging potential cannot be maintained, and if it is thicker than 30 μm, peeling from the lower layer tends to occur due to volume shrinkage during curing.

  As shown in FIG. 2B, when the cross-linked surface layer has a laminated structure formed on the surface portion of the charge transport layer (37), the charge transport layer (37) includes a charge transport material having a charge transport function and A binder resin is dissolved or dispersed in a suitable solvent, and this is formed by coating and drying on the charge generation layer (35), and a coating liquid containing the above-mentioned radical polymerizable composition of the present invention thereon. Is applied and cross-linked and cured by external energy.

As the charge transport material, the electron transport material, hole transport material and polymer charge transport material described in the charge generation layer (35) can be used. As described above, the use of the polymer charge transport material can reduce the solubility of the lower layer when the surface layer is applied, and is particularly useful.
The amount of the charge transport material is appropriately 20 to 300 parts by weight, preferably 40 to 150 parts by weight, based on 100 parts by weight of the binder resin. However, when a polymer charge transport material is used, it can be used alone or in combination with a binder resin.

  As the binder resin, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, Polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin And thermoplastic or thermosetting resins such as phenol resins and alkyd resins.

As the solvent used for the application of the charge transport layer (37) shown in FIG. 2B, the same solvent as the charge generation layer can be used, but a solvent that dissolves the charge transport material and the binder resin well is suitable. Yes. These solvents may be used alone or in combination of two or more. The charge transport layer can be formed by the same coating method as that for the charge generation layer (35).
If necessary, a plasticizer and a leveling agent can be added.
As the plasticizer that can be used in combination with the charge transport layer (37) shown in FIG. 2B, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are. About 0 to 30 parts by weight is appropriate for 100 parts by weight of the resin.
Leveling agents that can be used in combination with the charge transport layer (37) shown in FIG. 2B include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in the side chain. The amount used is suitably about 0 to 1 part by weight per 100 parts by weight of the binder resin.
The film thickness of the charge transport layer (37) shown in FIG. 2B is suitably about 5 to 40 μm, preferably about 10 to 30 μm.

  When the cross-linked surface layer (32) shown in FIG. 2B is the surface portion of the charge transport layer (37), as described in the above-mentioned method for preparing a cross-linked surface layer, ) And (b) are applied, and if necessary, after drying, a curing reaction is initiated by external energy such as heat or light to form a crosslinked surface layer. At this time, the film thickness of the crosslinked surface layer is 1 to 20 μm, preferably 2 to 10 μm. If the thickness is less than 1 μm, the durability varies due to uneven film thickness. If the thickness is more than 20 μm, the thickness of the laminated surface layer (32) and the charge transport layer (37) becomes thick, and the image reproducibility is due to the diffusion of charges. descend. In the formation of the crosslinked surface layer of the present invention, better results were obtained when the coating, irradiation (crosslinking), and drying were performed in this order than the coating, drying, and irradiation (crosslinking). Yes. The reason is considered as follows. For one thing, if the drying is performed first, the solvent disappears and the viscosity increases, so that the polymerization reaction is suppressed. Secondly, there is a possibility that the polymerization initiator sublimes by drying.

<Single photosensitive layer>
As shown in FIG. 1A, the photosensitive layer having a single layer structure is a layer having both a charge generation function and a charge transport function, and the cross-linked surface layer having the charge transport structure of the present invention contains a charge generation material having a charge generation function. By containing, it is useful as a photosensitive layer having a single layer structure. As described in the method for forming a charge generation layer, the charge generation material is dispersed together with a coating solution containing a radical polymerizable composition, applied onto the charge generation layer (35), and dried if necessary. The curing reaction is initiated by external energy, and a crosslinked surface layer is formed. In addition, you may add the liquid in which the charge generation material was previously disperse | distributed with the solvent to this coating material for bridge | crosslinking surface layers. At this time, the film thickness of the crosslinked surface layer is 10 to 30 μm, preferably 10 to 25 μm. If the thickness is less than 10 μm, a sufficient charging potential cannot be maintained. If the thickness is more than 30 μm, peeling from the conductive substrate or the undercoat layer tends to occur due to volume shrinkage during curing.

  Further, as shown in FIG. 1B, when the cross-linked surface layer (32) is a surface portion of a photosensitive layer having a single layer structure, the lower layer portion of the photosensitive layer has a charge generating material having a charge generating function and a charge transporting function. It can be formed by dissolving or dispersing the charge transport material and the binder resin in an appropriate solvent, and applying and drying the solution. Moreover, a plasticizer, a leveling agent, etc. can also be added as needed. The method for dispersing the charge generation material, the charge generation material, the charge transport material, the plasticizer, and the leveling agent are as already described in the charge generation layer (35) and the charge transport layer (37). As the binder resin, in addition to the binder resin previously mentioned in the section of the charge transport layer (37), the binder resin mentioned in the charge generation layer (35) may be mixed and used. In addition, the polymer charge transport materials listed above can also be used, which is useful in that contamination of the lower layer photosensitive layer composition into the crosslinked surface layer can be reduced. The thickness of the lower layer portion of the photosensitive layer is suitably about 5 to 30 μm, preferably about 10 to 25 μm.

When the crosslinked surface layer is the surface portion of the photosensitive layer (33) as shown in FIG. 1B, the radically polymerizable composition of the present invention and the charge generating material are contained on the lower layer portion of the photosensitive layer as described above. The coating liquid to be applied is applied, dried as necessary, and then cured by heat or light external energy to form a crosslinked surface layer. At this time, the film thickness of the crosslinked surface layer is 1 to 20 μm, preferably 2 to 10 μm. When the thickness is less than 1 μm, the durability varies due to the film thickness unevenness.
The charge generation material contained in the photosensitive layer having a single layer structure is preferably 1 to 30% by weight based on the total amount of the photosensitive layer, and the binder resin contained in the lower layer portion of the photosensitive layer is 20 to 80% by weight of the total amount. The transport material is preferably used in an amount of 10 to 70 parts by weight.

<About the intermediate layer>
In the photoreceptor of the present invention, when the crosslinked surface layer is the surface portion of the photosensitive layer, it is possible to provide an intermediate layer for the purpose of suppressing mixing of lower layer components into the crosslinked surface layer or improving adhesion with the lower layer. is there. This intermediate layer prevents inhibition of the curing reaction and unevenness of the crosslinked surface layer caused by mixing of the lower photosensitive layer composition in the outermost surface layer containing the radical polymerizable composition. It is also possible to improve the adhesion between the lower photosensitive layer and the surface cross-linked layer.
In the intermediate layer, a binder resin is generally used as a main component. Examples of these resins include polyamide, alcohol-soluble nylon, water-soluble polyvinyl butyral, polyvinyl butyral, and polyvinyl alcohol. As a method for forming the intermediate layer, a generally used coating method is employed as described above. The thickness of the intermediate layer is suitably about 0.05 to 2 μm.

<About the undercoat layer>
In the photoreceptor of the present invention, an undercoat layer can be provided between the conductive support (31) and the photosensitive layer. In general, the undercoat layer is mainly composed of a resin. However, considering that the photosensitive layer is coated with a solvent on these resins, the resin may be a resin having high solvent resistance with respect to a general organic solvent. desirable. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, and epoxy. Examples thereof include a curable resin that forms a three-dimensional network structure such as a resin. Further, a metal oxide fine powder pigment exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like may be added to the undercoat layer in order to prevent moire and reduce residual potential.

These undercoat layers can be formed using an appropriate solvent and a coating method like the above-mentioned photosensitive layer. Furthermore, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the undercoat layer of the present invention. In addition, in the undercoat layer of the present invention, Al ₂ O ₃ is provided by anodic oxidation, organic matter such as polyparaxylylene (parylene), SiO ₂ , SnO ₂ , TiO ₂ , ITO, CeO ₂ A material provided with an inorganic material such as a vacuum thin film can also be used favorably. In addition, known ones can be used. The thickness of the undercoat layer is suitably from 0 to 5 μm.

<Addition of antioxidant to each layer>
In the present invention, in order to improve environmental resistance, in order to prevent a decrease in sensitivity and an increase in residual potential, a surface cross-linked layer, a photosensitive layer, a charge generation layer, a charge transport layer, an undercoat layer, an intermediate layer An antioxidant can be added to each layer such as a layer. The addition amount of the antioxidant in this invention is 0.01 to 10 weight% with respect to the total weight of the layer to add.

The following are mentioned as antioxidant which can be used for this invention.
(Phenolic compounds)
2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3,5-di-t-butyl-4 -Hydroxyphenyl) propionate, 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis- (4-ethyl-6-tert-butylphenol), 4, 4'-thiobis- (3-methyl-6-tert-butylphenol), 4,4'-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1,3-tris- (2-methyl-4 -Hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [meth -3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3'-bis (4'-hydroxy-3'-t-butylphenyl) butyl Rick acid] glycol ester, tocopherols and the like.
(Paraphenylenediamines)
N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-phenylenediamine, N, N'- Di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine and the like.
(Hydroquinones)
2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2- (2-octadecenyl) ) -5-methylhydroquinone and the like.
(Organic sulfur compounds)
Dilauryl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate and the like.
(Organic phosphorus compounds)
Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.
These compounds are known as antioxidants such as rubbers, plastics and fats and oils, and commercially available products can be easily obtained.

<Image Forming Method and Apparatus>
Next, the image forming method and the image forming apparatus of the present invention will be described in detail with reference to the drawings.
The image forming method and the image forming apparatus of the present invention use a photoconductor having a smooth charge transporting surface cross-linked layer. For example, at least after the photoconductor is subjected to charging, image exposure, and development processes, an image is formed. An image forming method and an image forming apparatus including a process of transferring a toner image onto a holding member (transfer paper), fixing, and cleaning of the surface of the photoreceptor.
In some cases, an image forming method or the like in which an electrostatic latent image is directly transferred to a transfer member and developed does not necessarily have the above-described process arranged on a photosensitive member.

  FIG. 3 is a schematic diagram illustrating an example of an image forming apparatus. A charging charger (3) is used as a means for charging the photoconductor on average. As the charging means, a corotron device, a scorotron device, a solid discharge element, a needle electrode device, a roller charging device, a conductive brush device, or the like is used, and a known system can be used.

  In particular, the configuration of the present invention is effective when a charging unit such as a contact charging method or a non-contact proximity arrangement charging method is used in which the photosensitive composition is decomposed by proximity discharge from the charging unit. Here, the contact charging method is a charging method in which a charging roller, a charging brush, a charging blade, or the like is in direct contact with the photosensitive member. On the other hand, the proximity charging method is, for example, a type in which the charging roller is arranged in a non-contact state so as to have a gap of 200 μm or less between the surface of the photoreceptor and the charging means. If this gap is too large, the charging tends to become unstable, and if it is too small, the surface of the charging member may be contaminated when toner remaining on the photoreceptor exists. is there. Accordingly, the gap is suitably 10 to 200 μm, preferably 10 to 100 μm.

  An image exposure unit (5) is used to form an electrostatic latent image on the uniformly charged photoreceptor (1). As the light source, all luminescent materials such as a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), and an electroluminescence (EL) can be used. Various types of filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used to irradiate only light in a desired wavelength range.

  A developing unit (6) is used to visualize the electrostatic latent image formed on the photoreceptor (1). Development methods include a one-component development method using a dry toner, a two-component development method, and a wet development method using a wet toner. When the photosensitive member is positively (negatively) charged and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the photosensitive member. A positive image can be obtained by developing this with negative (positive) toner (electrodetection fine particles), and a negative image can be obtained by developing with positive (negative) toner.

  In order to transfer the toner image visualized on the photosensitive member onto the transfer member (9), a transfer charger (10) is used. In addition, a pre-transfer charger (7) may be used for better transfer. As these transfer means, a transfer charger, an electrostatic transfer method using a bias roller, a mechanical transfer method such as an adhesive transfer method and a pressure transfer method, and a magnetic transfer method can be used. As the electrostatic transfer method, the charging means can be used.

  A separation charger (11) and a separation claw (12) are used as means for separating the transfer body (9) from the photoreceptor (1). As other separation means, electrostatic adsorption induction separation, side end belt separation, tip grip conveyance, curvature separation, and the like are used. As the separation charger (11), the charging means can be used.

  In order to clean the toner remaining on the photoconductor after the transfer, a fur brush (14) and a cleaning blade (15) are used. Further, a pre-cleaning charger (13) may be used in order to perform cleaning more efficiently. Other cleaning means include a web method, a magnet brush method, and the like, but each may be used alone or in combination.

  Next, a neutralizing unit is used for the purpose of removing the latent image on the photoreceptor as required. As the charge removal means, a charge removal lamp (2) and a charge removal charger are used, and the exposure light source and the charging means can be used respectively.

  In addition, known processes can be used for reading, feeding, fixing, paper discharge and the like that are not close to the photoconductor.

The present invention provides an image forming method and an image forming apparatus using the electrophotographic photoreceptor according to the present invention in such image forming means.
The image forming means may be fixedly incorporated in a copying apparatus, facsimile, or printer, but may be incorporated in these apparatuses in the form of a process cartridge and detachable. An example of the process cartridge is shown in FIG.

  The process cartridge for the image forming apparatus in FIG. 4 includes a photoreceptor (101), and in addition, a charging unit (102), a developing unit (104), a transfer unit (106), a cleaning unit (107), and a charge eliminating unit ( And an apparatus (part) that is detachable from the main body of the image forming apparatus.

  Referring to the image forming process by the apparatus illustrated in FIG. 4, the surface of the photoreceptor (101) is exposed by charging by the charging means (102) and exposure by the exposure means (103) while rotating in the direction of the arrow. An electrostatic latent image corresponding to the image is formed, and the electrostatic latent image is developed with toner by the developing means (104). The toner development is transferred to the transfer body (105) by the transfer means (106), and printed. Out. Next, the surface of the photoconductor after the image transfer is cleaned by a cleaning unit (107), and further neutralized by a neutralizing unit (not shown), and the above operation is repeated again.

  The present invention provides a process cartridge for an image forming apparatus in which a photosensitive member having a smooth charge transporting surface cross-linked layer and at least one of charging, developing, transferring, cleaning, and discharging means are integrated.

  As is apparent from the above description, the electrophotographic photosensitive member of the present invention is not only used in electrophotographic copying machines, but also in electrophotographic application fields such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making. Can also be used widely.

  The electrophotographic photosensitive member of the present invention can maintain a high abrasion resistance for a long period of time, has little fluctuation in electrical characteristics over a long period of time, and has a crosslinked surface layer with improved adhesion to the underlying photosensitive layer. By using it, it is possible to form stable electrical characteristics and high-quality images over a long period of time as well as excellent durability.

  Hereinafter, the present invention will be described more specifically with reference examples, examples, and comparative examples, but the present invention is not limited to these examples. Note that “parts” used in the examples all represent parts by weight.

[Reference example]
<Synthesis example of monofunctional radically polymerizable compound having charge transporting structure>
The compound having a charge transporting structure in the present invention is synthesized, for example, by the method described in Japanese Patent No. 3164426. An example of this is shown below.
(1) Synthesis of hydroxy group-substituted triarylamine compound (the following structural formula B) 113.85 g (0.3 mol) of a methoxy group-substituted triarylamine compound (the following structural formula A) and 138 g (0.92 mol) of sodium iodide To this, 240 ml of sulfolane was added and heated to 60 ° C. in a nitrogen stream. In this solution, 99 g (0.91 mol) of trimethylchlorosilane was added dropwise over 1 hour and stirred at a temperature of about 60 ° C. for 4 and a half hours to complete the reaction. About 1.5 L of toluene was added to the reaction solution, cooled to room temperature, and washed repeatedly with water and an aqueous sodium carbonate solution. Thereafter, the solvent was removed from the toluene solution and purified by column chromatography (adsorption medium: silica gel, developing solvent: toluene: ethyl acetate = 20: 1). Cyclohexane was added to the obtained pale yellow oil to precipitate crystals. In this way, 88.1 g (yield = 80.4%) of white crystals of the following structural formula B was obtained.
Melting point: 64.0-66.0 ° C
Elemental analysis value (%)

(2) Synthesis of triarylamino group-substituted acrylate compound (Exemplary Compound No. 54) 82.9 g (0.227 mol) of the hydroxy group-substituted triarylamine compound (Structural Formula B) obtained in (1) above was added to 400 ml of tetrahydrofuran. In a nitrogen stream, an aqueous sodium hydroxide solution (NaOH: 12.4 g, water: 100 ml) was added dropwise. The solution was cooled to 5 ° C., and 25.2 g (0.272 mol) of acrylic acid chloride was added dropwise over 40 minutes. Then, it stirred at 5 degreeC for 3 hours, and reaction was complete | finished. The reaction solution was poured into water and extracted with toluene. This extract was repeatedly washed with an aqueous sodium bicarbonate solution and water. Thereafter, the solvent was removed from the toluene solution and purified by column chromatography (adsorption medium: silica gel, developing solvent: toluene). N-Hexane was added to the obtained colorless oil to precipitate crystals. Thus, Exemplified Compound No. As a result, 80.73 g (yield = 84.8%) of 54 white crystals were obtained.
Melting point: 117.5-119.0 ° C
Elemental analysis value (%)

(3) Synthesis example of acrylic ester compound (a) Preparation of diethyl 2-hydroxybenzylphosphonate 2-Hydroxybenzyl alcohol (manufactured by Tokyo Chemical Industry) in a reaction vessel equipped with a stirrer, thermometer, and dropping funnel. 4 g and 80 ml of o-xylene were added, 62.8 g of triethyl phosphite (manufactured by Tokyo Chemical Industry Co., Ltd.) was slowly added dropwise at 80 ° C. under a nitrogen stream, and the reaction was further performed at the same temperature for 1 hour. Thereafter, the produced ethanol, the solvent o-xylene, and unreacted triethyl phosphite were removed by distillation under reduced pressure to obtain 66 g of diethyl 2-hydroxybenzylphosphonate. (Boiling point 120.0 ° C./1.5 mmHg) (yield 90%)
(B) Preparation of 2-hydroxy-4 '-[N, N-bis (4-methylphenyl) amino] stilbene Into a reaction vessel equipped with a stirrer, a thermometer and a dropping funnel, 14.8 g of potassium tert-butoxide. A solution of 9.90 g of diethyl 2-hydroxybenzylphosphonate and 5.44 g of 4- [N, N-bis (4-methylphenyl) amino] benzaldehyde dissolved in tetrahydrofuran was added under a nitrogen stream. The solution was slowly added dropwise at room temperature, and then reacted at the same temperature for 2 hours. Thereafter, water was added under water cooling, and then 2N hydrochloric acid aqueous solution was added for acidification. Tetrahydrofuran was removed by an evaporator, and the crude product was extracted with toluene. The toluene phase was washed with water, an aqueous sodium hydrogen carbonate solution and saturated brine in this order, and dehydrated by adding magnesium sulfate. After filtration, toluene was removed to obtain an oily crude product, which was further purified with silica gel and then crystallized in hexane to give 5.09 g of 2-hydroxy-4 '-(N, N-bis). (4-Methylphenyl) amino) stilbene was obtained. (Yield 72%, melting point 136.0-138.0 ° C.)
(C) Preparation of 4 '-[N, N-bis (4-methylphenyl) amino] stilben-2-yl acrylate Into a reaction vessel equipped with a stirrer, thermometer and dropping funnel, 2-hydroxy-4'- [1, N-bis (4-methylphenyl) amino] stilbene (14.9 g), tetrahydrofuran (100 ml), 12% strength aqueous sodium hydroxide solution (21.5 g) were added, and acrylic acid chloride (5.17 g) was added at 5 ° C. under a nitrogen stream. It was added dropwise over 30 minutes. Then, it was made to react at the same temperature for 3 hours. The reaction solution was poured into water, extracted with toluene, concentrated and subjected to column purification with silica gel. The obtained crude product was recrystallized with ethanol, and 4 ′-[N, N-bis (4-methylphenyl) amino] stilben-2-yl acrylate (Exemplary Compound No. II) in the form of yellow needles 13. 5 g was obtained. (Yield 79.8%, melting point 104.1-105.2 ° C.)
The elemental analysis results are shown below.
Elemental analysis value (%)

  As described above, a number of 2-hydroxystilbene derivatives are synthesized by reacting 2-hydroxybenzylphosphonic acid ester derivatives with various amino-substituted benzaldehyde derivatives. An ester compound can be synthesized.

Example 1
By coating and drying an undercoat layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution in the following order on a φ30 mm aluminum cylinder in sequence, an undercoat layer of 3.5 μm A 0.2 μm charge generation layer and a 23 μm charge transport layer were formed. A coating solution for a crosslinked surface layer having the following composition is spray-coated on this charge transport layer, and using a Fusion UV lamp system, the bulb type: H bulb, lamp output: 200 W / cm, irradiation intensity: 450 mW / cm ^2. Irradiation time: Light irradiation was performed under conditions of 30 seconds, followed by drying at 130 ° C. for 20 minutes to provide a 5 μm surface cross-linked layer to obtain an electrophotographic photoreceptor of the present invention.

[Coating liquid for undercoat layer]
Alkyd resin: 6 parts (Beckosol 1307-60-EL, manufactured by Dainippon Ink & Chemicals, Inc.)
Melamine resin: 4 parts (Super Becamine G-821-60, manufactured by Dainippon Ink & Chemicals, Inc.)
Titanium oxide: 40 parts Methyl ethyl ketone: 50 parts

[Coating liquid for charge generation layer]
Bisazo pigment of the following structural formula (I): 2.5 parts polyvinyl butyral (XYHL, manufactured by UCC): 0.5 parts cyclohexanone: 200 parts methyl ethyl ketone: 80 parts

[Coating liquid for charge transport layer]
Bisphenol Z polycarbonate: 10 parts (Panlite TS-2050, manufactured by Teijin Chemicals)
Low molecular charge transport material of the following structural formula (II): 7 parts Tetrahydrofuran: 100 parts Tetrahydrofuran solution of 1% silicone oil: 0.2 parts (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

[Coating liquid for cross-linked surface layer]
Trifunctional or higher functional radical polymerizable monomer having no charge transporting structure: 10 parts Trimethylolpropane triacrylate (molecular weight: 296, functional group number: trifunctional)
(KAYARAD TMPTA, Nippon Kayaku)
Charge transporting compound having the following radical polymerizable functional group: 10 parts Acrylic ester triarylamine Exemplified Compound No. XII
(Molecular weight: 445, number of functional groups: 1)
Photopolymerization initiator: 1 part Irgacure 184: 1-hydroxycyclohexyl phenyl ketone (molecular weight: 204, number of functional groups: none)
(Nippon Kayaku)
Solvent: 120 parts butyl acetate (boiling point: 126 ° C., saturated vapor pressure: 13 mmHg / 25 ° C.)
Among these, materials having a radical polymerizable functional group include trimethylolpropane triacrylate and acrylate triarylamine exemplified compound No. XII. When the number of acrylic groups of each material is calculated | required using the described weight part, molecular weight, and the number of functional groups, it is as follows.
(1) Number of acrylic groups of trimethylolpropane triacrylate 10 × 6.02 × 10 ²³ × 3/296 = 6.10 × 10 ²² (2) Acrylic ester triarylamine exemplified compound No. Number of acrylic groups of XII 10 × 6.02 × 10 ²³ /445=1.35×10 ²² (3) The total number of acrylic groups is divided by the total weight of the solid content concentration, and the radical polymerizable functional group in 1 g of the solid content Calculate the number.
(6.10 × 10 ²² + 1.35 × 10 ²² ) / (10 + 10 + 1)
= 3.55 × 10 ²¹

Example 2
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the solvent of Example 1 was changed to 90 parts of tetrahydrofuran and 30 parts of butyl acetate (boiling point: 126 ° C., saturated vapor pressure: 13 mmHg / 25 ° C.).

Example 3
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that butyl acetate in Example 2 was replaced with cyclohexanone (boiling point: 156 ° C., saturated vapor pressure: 3.95 mmHg / 25 ° C.).

Example 4
An electrophotographic photosensitive member was produced in the same manner as in Example 2, except that butyl acetate in Example 2 was replaced with 2-propanol (boiling point: 82 ° C., saturated vapor pressure: 32.4 mmHg / 25 ° C.).

Example 5
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that butyl acetate in Example 2 was replaced with xylene (solubility parameter: 8.8).

Example 6
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that butyl acetate in Example 2 was replaced with dioxane (solubility parameter: 9.9).

Example 7
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that butyl acetate in Example 2 was replaced with chlorobenzene (solubility parameter: 9.5).

Example 8
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that butyl acetate in Example 1 was replaced with 63 parts of cyclohexanone.

Example 9
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the amount of butyl acetate used in Example 1 was changed to 399 parts.

Example 10
The charge transporting compound having a radical polymerizable functional group of Example 1 was converted to acrylate triarylamine exemplified compound No. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that VII (molecular weight: 431, functional group number: 1 functional) was used.

Example 11
The charge transporting compound having a radical polymerizable functional group of Example 1 was converted to acrylate triarylamine exemplified compound No. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that XV (molecular weight: 828, functional group number: 1 functional) was used.

Example 12
The charge transporting compound having a radical polymerizable functional group of Example 1 is represented by triarylamine exemplified compound No. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the molecular weight was changed to 54 (molecular weight: 419, functional group number: 1 functional).

Example 13
The charge transporting compound having a radical polymerizable functional group of Example 1 is represented by triarylamine exemplified compound No. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the molecular weight was changed to 16 (molecular weight: 371, number of functional groups: 1).

Example 14
The charge transporting compound having a radical polymerizable functional group of Example 1 is represented by triarylamine exemplified compound No. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the molecular weight was changed to 24 (molecular weight: 419, functional group number: 1 functional).

（式中、ａおよびｂは、カタログによればａ＝５、ｂ＝１またはａ＝６、ｂ＝０となっており、官能基数も５．５官能と記載されている。） Example 15
The trifunctional or higher functional radical polymerizable monomer having no charge transport structure of Example 2 is KAYARAD TMPTA (trimethylolpropane triacrylate): 5 parts and KAYARAD DPHA represented by the following formula (manufactured by Nippon Kayaku, dipentaerythritol) Hexaacrylate, average molecular weight: 536, functional group number: 5.5 functional): An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the content was changed to 5 parts.

(In the formula, a and b are a = 5, b = 1 or a = 6, b = 0 according to the catalog, and the number of functional groups is also described as 5.5.)

Example 16
The trifunctional or higher functional radical polymerizable monomer having no charge transport structure of Example 12 is KAYARAD TMPTA (trimethylolpropane triacrylate): 5 parts, KAYARAD DPCA-120 (manufactured by Nippon Kayaku, dipentaerythritol hexaacrylate, Average molecular weight: 1948, number of functional groups: 6 functional): An electrophotographic photosensitive member was produced in the same manner as in Example 12 except that the amount was changed to 5 parts.

Comparative Example 1
The tri- or more functional radical polymerizable monomer having no charge transport structure of Example 1 was changed to KAYARAD FM-280 (manufactured by Nippon Kayaku, PO-modified glycerol acrylate, average molecular weight: 463, number of functional groups: trifunctional). An electrophotographic photosensitive member was produced in the same manner as in Example 1 except for the above. In this case, the number of acrylic groups in 1 g of the solid content, that is, the number of radical polymerizable functional groups is less than 2.55 × 10 ²¹ .

Comparative Example 2
Electrophotography similar to Example 1 except that the two types of radical polymerizable monomers of Example 1 were changed to only 1,6-hexanediol diacrylate (manufactured by Wako Pure Chemical Industries, molecular weight: 226, functional group number: bifunctional). A photoconductor was prepared. In this case, a trifunctional or higher functional monomer is not used.

Comparative Example 3
A trifunctional or higher-functional radical polymerizable monomer having no charge transporting structure without containing a charge transporting compound having a radical polymerizable functional group, which is the composition of the coating solution for the crosslinked surface layer of Example 1, is made of polyethylene. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that 20 parts of glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., molecular weight: 308, functional group number: 2) was used. This case corresponds to a case not including the component (b) in claim 1.

Comparative Example 4
A trifunctional or higher functional radical polymerizable monomer having no charge transporting structure and having no radical transportable functional group, which is the composition of the coating solution for the crosslinked surface layer of Example 1, is used. An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that 20 parts of pentyl glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., molecular weight: 212, functional group number: 2) was used. This case corresponds to a case not including the component (b) in claim 1.

Comparative Example 5
The amount of the charge transporting compound having a radical polymerizable functional group without containing a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure which is the composition of the coating solution for the crosslinked surface layer of Example 1 An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the amount was changed to 20 parts.

Comparative Example 6
The amount of the radically polymerizable monomer having a trifunctional or higher functionality that does not contain the charge transporting compound having the radically polymerizable functional group that is the composition of the coating solution for the crosslinked surface layer of Example 1 and does not have the charge transporting structure. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the amount was changed to 20 parts.

Comparative Example 7
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the charge transporting compound having a radical polymerizable functional group contained in the crosslinked surface layer coating solution in Example 1 was changed to the following materials. This case corresponds to a case not including the component (b) in claim 1.
Charge transporting compound having radically polymerizable functional group

Comparative Example 8
No. 1 contained in the crosslinked surface layer coating solution in Example 1. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the radical polymerizable compound having a charge transporting structure represented by XII was changed to the following material (a material having no radical polymerizable property).

Comparative Example 9
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the surface layer was not provided in Example 1 and the thickness of the charge transport layer was 27 μm.

Comparative Example 10
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that a crosslinked surface protective layer having a film thickness of 5 μm was provided according to Example 4 of the published patent publication (Patent Application Number: Japanese Patent Application Laid-Open No. 2004-302451). In this case, the monomer component satisfies the condition of claim 1 but does not satisfy the peel strength condition.

Comparative Example 11
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that a crosslinked surface protective layer having a thickness of 5 μm was provided according to Example 9 of the published patent publication (Patent Application Number: Japanese Patent Application Laid-Open No. 2004-302452). In this case, the monomer component satisfies the condition of claim 1 but does not satisfy the peel strength condition.

Comparative Example 12
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that a crosslinked surface protective layer having a film thickness of 5 μm was provided in accordance with Example 1 of the published patent publication (Patent Application Number: JP-A-2001-183858). This case is a case that does not satisfy the conditions of the number of radical polymerizable functional groups and the peel strength in 1 g of solid content.

The test method evaluated below is shown.
<Peel strength test>
As a method for evaluating the peel strength of the crosslinked surface layer, a Saikas apparatus DN-20 type (manufactured by Daipura Wintes) was used, a cutting blade with a blade width of 0.5 mm was used, and a horizontal cutting speed was 0.1 μm / sec. Vertical cutting speed: Measurement was performed in a constant cutting speed mode of 0.01 μm / sec. The test time was determined so that the depth of cut to be tested was larger than the film thickness of the crosslinked surface layer. The peel strength was calculated by dividing the horizontal load at the depth of cut corresponding to the cross-linked surface layer thickness by the blade width.

<Curing test>
A solubility test for an organic solvent is performed as an index of the curing progress of the crosslinked surface layer. One drop of tetrahydrofuran (hereinafter abbreviated as THF) is dropped on the photoreceptor, and the change in the surface shape after natural drying is visually observed. In the case where the curing has not progressed, a part of the surface is dissolved, and ring-shaped unevenness and cloudiness occur.

<Durability test>
Using a lapping film having a surface roughness of 0.3 μm (manufactured by Sumitomo 3M), the crosslinked surface layer having a width of 10 cm in the axial direction of the photoconductor was abraded by about 3.5 μm at an arbitrary position of the photoconductor. This Ricoh imagio MF 2200 machine was remodeled so that the photoconductor was mounted on a process cartridge for an electrophotographic apparatus, a semiconductor laser of 655 nm was used as an image exposure light source, and the contact pressure of the cleaning blade was 1.5 times. Then, the initial dark portion potential is set to -700 V in the portion where the crosslinked surface is not worn by the wrapping film. Thereafter, a paper feeding test is started, and film thickness measurement and image evaluation are performed at an initial stage and at every 10,000 sheets where the wrapping film is worn, and image passing is performed for A4 size 30,000 sheets. As electrical characteristics at the end of paper passing, the dark part and exposed part potentials are measured at the same place as the initial dark part potential measurement part. The film thickness of the photosensitive member was measured using an eddy current film thickness measuring device (manufactured by Fischer Instrument).

<Crack acceleration test>
Finger oil was attached to the surface of the electrophotographic photosensitive member and allowed to stand at 50 ° C. and normal pressure for 3 days, and then the crystallization state of the crosslinked surface layer was observed.

Table 4 shows the peel strength of the crosslinked surface layer and the solubility in THF for the electrophotographic photoreceptors of Examples 1 to 16 and Comparative Examples 1 to 12.

The photoreceptors of Examples 1 to 16 of the present invention have 2.55 × 10 ²¹ or more radical polymerizable functional groups per gram of the solid content in the crosslinked surface layer and at the same time have a peel strength of 0.1 N / mm or more. You can see that In other words, it is considered that both the construction of a dense three-dimensional network structure and the securing of adhesion with the underlying photosensitive layer have been achieved, and the results of the curability test are insoluble in any of the photoreceptors of the examples. Good curability is obtained. In Examples 2 to 4, as the solvent used for the cross-linked surface layer, the smaller the saturated vapor pressure or the higher the boiling point, the greater the peel strength. Further, in Examples 5 to 7, the peel strength is increased by setting the solubility parameter of the solvent to 8.5 to 11.0, more preferably 9.0 to 9.7. Furthermore, it can be seen from Examples 1 and 8 and 9 that the peel strength increases by lowering the solid content concentration of the coating solution for the crosslinked surface layer. Furthermore, it can be seen from Examples 15 and 16 that sufficient peel strength is secured even when a polyfunctional monomer having 5 or more functional groups is cured.
On the other hand, a photoreceptor using the bifunctional monomer of Comparative Example 2 for the crosslinked surface layer, a photoreceptor using only the charge transport compound having a radical polymerizable group of Comparative Example 5 for the crosslinked surface layer, and Comparative Example 8 A photoreceptor using a low molecular charge transport material for the crosslinked surface layer, and a photoreceptor not provided with the crosslinked surface layer of Comparative Example 9 are soluble in an organic solvent and cured for the crosslinked surface layers of Comparative Examples 2, 5, and 8. Is insufficient. Further, the photoreceptor of Comparative Example 1 has a small number of radical polymerizable functional groups per gram of solid content in the crosslinked surface layer of 2.50 × 10 ²¹ , and the photoreceptors of Comparative Examples 6, 7, 10, ¹¹ , and 12 are sufficient. It is considered that the peel strength is small with respect to the number of radically polymerizable functional groups, and the adhesiveness with the underlying photosensitive layer is insufficient. In Comparative Examples 3 and 4, the number of radically polymerizable functional groups per gram of solid content, peel strength, and curability test all showed good results. Since the content ratio of the charge transporting compound having a functional group is too low, the surface potential of the exposed area is high from the beginning, and the image density is lowered (see Table 5).

Table 5 shows the results of durability tests on the electrophotographic photoreceptors of Examples 1 to 16 and Comparative Examples 1, 3, 4, 6, 7, 9, 10, 11, and 12.

  The photoconductors of Examples 1 to 16 of the present invention have a small amount of wear and a stable amount of wear. Furthermore, there is little fluctuation of the exposure portion potential at the initial stage and before and after the durability test of 30,000 sheets. Therefore, in the present invention, a photoconductor that maintains high durability even in the vicinity of the interface between the crosslinked surface protective layer and the underlying photosensitive layer and further achieves stable electrical characteristics has been realized. On the other hand, in the case of the comparative example 1 having a small number of radical polymerizable functional groups, sufficient wear resistance is not realized. Further, of Comparative Examples 6, 7, 10, 11, and 12 having a low peel strength, Comparative Example 6 does not have a charge transporting structure in the crosslinked surface layer, so that the exposed portion potential is remarkably high from the beginning. It can also be seen that the exposed portion potential is high from the beginning by increasing the film thickness to 5 μm. Moreover, about Comparative Example 12, the amount of wear is also large, and it can be determined that the adhesiveness of the crosslinked surface layer is not sufficient. In Comparative Examples 7, 10, and 11, since the peel strength was small, a rapid film thickness reduction was observed in the paper passing evaluation. In Comparative Examples 3 and 4, since the charge transporting structure is not provided, the exposed portion potential is remarkably increased from the beginning. It can be seen from Comparative Example 9 that an electrophotographic photoreceptor having both high wear resistance and stable electrical characteristics can be realized by providing the crosslinked surface protective layer of the present invention.

Table 6 shows the results of the crack acceleration test performed on the electrophotographic photoreceptors of Examples 1 to 16.

It can be seen that no cracks are generated in the electrophotographic photoreceptor of the present invention, and the compound having a charge transporting structure in the crosslinked film is uniformly incorporated in the crosslinked film. As a result, improvement of wear resistance over a long period of time and maintenance of high-quality image output are realized.
Accordingly, in the electrophotographic photosensitive member having at least a photosensitive layer on the conductive support of the present invention, the surface layer of the photosensitive layer has at least a trifunctional or higher-functional radical polymerizable monomer and a charge transporting structure. The number of radical polymerizable functional groups in 1 g of the solid content contained in the surface layer is 2.55 × 10 ²¹ or more, 7.50 × 10 ^The electrophotographic photosensitive member is characterized in that the peel strength of the surface layer calculated from measurement by SAICAS method is 0.1 N / mm or more, and has high durability over the entire cross-linked surface protective layer. It has been found that it is possible to provide a photoreceptor that can maintain and have stable electrical characteristics and can realize high-quality image output over a long period of time. Further, it has been found that the image forming process, the image forming apparatus, and the process cartridge for the image forming apparatus using the photoconductor of the present invention have high performance and high reliability.

FIG. 1 is a cross-sectional view showing an electrophotographic photosensitive member of the present invention, in which a single layer structure in which a photosensitive layer (33) having a charge generating function and a charge transporting function is provided on a conductive support (31). This is a photoreceptor. FIG. 1-A shows the case where the crosslinked surface layer is the entire photosensitive layer, and FIG. 1-B shows the portion where the crosslinked surface layer is the surface portion of the photosensitive layer. FIG. 2 shows a photoreceptor having a laminated structure in which a charge generation layer (35) having a charge generation function and a charge transport layer (37) having a charge transport function are laminated on a conductive support (31). . FIG. 2-A shows the case where the cross-linked surface layer is the entire charge transport layer, and FIG. 2-B shows the case where the cross-linked surface layer is the surface portion of the charge transport layer. 1 is a schematic diagram illustrating an example of an image forming apparatus. It is the schematic which shows the image formation process using an image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Static elimination lamp 3 Charger charger 4 Eraser 5 Image exposure part 6 Developing unit 7 Charger before transfer 8 Registration roller 9 Transfer body 10 Transfer charger 11 Separation charger 12 Separation claw 13 Charger before cleaning 14 Fur brush 15 Cleaning blade 31 Conductivity Support 32 Surface layer (crosslinked surface layer)
33 Photosensitive layer 35 Charge generation layer 37 Charge transport layer 101 Photoconductor 102 Charging means 103 Exposure means 104 Developing means 105 Transfer body 106 Transfer means 107 Cleaning means

Claims (11)

In an electrophotographic photosensitive member having at least a photosensitive layer on a conductive support, the surface layer of the photosensitive layer is at least (i) a trifunctional or higher-functional radical polymerizable monomer having no charge transporting structure and (b) charge transporting. Formed by polymerizing a monomer mixture containing a monofunctional radically polymerizable compound having a crystalline structure, and the number of radically polymerizable functional groups in 1 g of the solid content contained in the surface layer is 2.55 × 10 ^21. An electrophotographic photosensitive member characterized by being ²¹ or more and 7.50 × 10 ²¹ or less and having a peel strength of the surface layer calculated from measurement by SAICAS method of 0.1 N / mm or more.   2. The electrophotographic photoreceptor according to claim 1, wherein the charge transporting structure (b) is selected from the group consisting of a triarylamine structure, a hydrazone structure, a pyrazoline structure and a carbazole structure. The charge transport structure (B) is a triaryl amine structure, according to claim 1-2, wherein the number of radically polymerizable functional groups is characterized in that it is a 2.58-3.68 × ^{10 21} pieces Electrophotographic photoreceptor.   The electrophotograph according to any one of claims 1 to 3, wherein the trifunctional or higher-functional radical polymerizable monomer (a) has three or more functional groups selected from the group consisting of an acryloyloxy group and a methacryloyloxy group. Photoconductor. (A) A polymerizable composition containing a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and (b) a monofunctional radical polymerizable compound having a charge transport structure has a saturated vapor pressure of 100 mmHg / 25 ° C. The method for producing an electrophotographic photosensitive member according to any one of claims 1 to 4, wherein a surface layer corresponding to the outermost layer is formed using a coating solution dissolved in the following solvent.   The method for producing an electrophotographic photosensitive member according to claim 5, wherein the solvent has a boiling point of 60 ° C. to 150 ° C.   The method for producing an electrophotographic photosensitive member according to claim 5 or 6, wherein the solubility parameter of the solvent is 8.5 to 11.0.   The method for producing an electrophotographic photosensitive member according to claim 5, wherein the solvent is at least one selected from the group consisting of butyl acetate and cyclohexanone.   An image forming method, wherein at least charging, image exposure, development, and transfer are repeated using the electrophotographic photosensitive member according to claim 1.   An image forming apparatus comprising the electrophotographic photosensitive member according to claim 1.   An image forming apparatus comprising: the electrophotographic photosensitive member according to claim 1; and at least one unit selected from the group consisting of a charging unit, a developing unit, a transfer unit, a cleaning unit, and a charge eliminating unit. A process cartridge for an image forming apparatus, wherein the process cartridge is removable from the apparatus main body.

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