JP4712351B2 - Electrophotographic photosensitive member, image forming method using the same, image forming apparatus, and process cartridge for image forming apparatus - Google Patents

Description

  The present invention has high durability and high image quality over a long period of time by using a photosensitive layer that has high wear resistance and scratch resistance, is unlikely to cause cracks and film peeling, and has good electrical characteristics. The present invention relates to an electrophotographic photoreceptor capable of realizing the above. 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. This is because, for example, (1) optical characteristics such as the light absorption wavelength range and the amount of absorption, (2) electrical characteristics such as high sensitivity and stable charging characteristics, and (3) material selection range (4) Ease of manufacturing, (5) Low cost, (6) 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 crosslinkable charge transport layer is mainly composed of a low molecular charge transport material and an inert polymer. It has the disadvantage that wear is likely to occur due to mechanical loading by the system. In addition, due to the demand for higher image quality, the cleaning blade is required to increase its rubber hardness and contact pressure for the purpose of improving the cleaning property as the particle size of the toner particles is reduced. This also promotes wear of the photoreceptor. It is a factor. Such wear 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 above-mentioned wear amount in order to increase the durability of the organic photoreceptor, and this is the most pressing issue in this field. Techniques for improving the abrasion resistance of the photosensitive layer include (1) using a curable binder in the crosslinkable charge transport layer (see, for example, Patent Document 1), and (2) using a polymer charge transport material. (For example, see Patent Document 2), (3) those in which an inorganic filler is dispersed in a cross-linked charge transport layer (for example, see Patent Document 3), and the like. 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, although the polymer charge transport material (2) can improve the abrasion resistance to some extent, the durability required for the organic photoreceptor is not fully satisfied. Not reached. In addition, polymer charge transport materials are difficult to polymerize and purify, and it is difficult to obtain a high-purity material. Therefore, it is difficult to stabilize electrical characteristics between materials. Furthermore, production problems such as high viscosity of the coating solution may occur. The dispersion of the inorganic filler (3) exhibits higher abrasion resistance than a photoreceptor in which a normal low molecular charge transport material is dispersed in an inert polymer, but the charge present on the surface of the inorganic filler. The residual potential increases due to the trap, and the image density tends to decrease. In addition, when the unevenness of the inorganic filler and the binder resin on the surface of the photoconductor is large, defective cleaning may occur, which may cause toner filming and image flow. 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 acrylate monomer cured product in order to improve the abrasion resistance and scratch resistance of (1) is also known (see Patent Document 4). However, in this photoreceptor, although there is a description that the polyfunctional acrylate monomer cured product is contained in the protective layer provided on the photosensitive layer, the protective layer may contain a charge transport material. However, there is a problem of compatibility with the cured product when a cross-linked charge transport layer contains a low-molecular charge transport material. As a result, precipitation of a low-molecular charge transport material and white turbidity occur, and not only the image density is lowered but also the mechanical strength is lowered due to the increase of the exposed portion potential. Furthermore, since this photoconductor specifically reacts with the monomer in a state containing a polymer binder, the three-dimensional network structure does not proceed sufficiently, and the crosslink density becomes dilute, resulting in a dramatic wear resistance. Has not yet been able to demonstrate.

  As a wear resistance technology for a photosensitive layer that replaces these, a charge transport layer formed by using a coating liquid comprising a monomer having a carbon-carbon double bond, a charge transport material having a carbon-carbon double bond, and a binder resin. It is known to provide (for example, refer to Patent Document 5). This binder resin is thought to play a role of improving the adhesion between the charge generation layer and the curable charge transport layer, and further mitigating the internal stress of the film during thick film curing, and has a carbon-carbon double bond. These are roughly classified into those having reactivity with the charge transport material and those having no reactivity with the double bond. This photoconductor is remarkably compatible with wear resistance and good electrical properties, but when a non-reactive binder resin is used, the binder resin, the monomer and the charge transport agent are used. The compatibility with the cured product produced by this reaction is poor, and phase separation occurs in the cross-linked charge transport layer, which may cause scratches and sticking of external additives and paper powder in the toner.

  In addition, as described above, the three-dimensional network structure does not proceed sufficiently, and the cross-linking density becomes dilute. In addition, what is specifically described as the monomer used in this photoreceptor is bifunctional, and from these reasons, it has not yet been satisfactory in terms of wear resistance. Even when a reactive binder is used, the molecular weight of the cured product is increased, but the number of intermolecular crosslinks is small, and it is difficult to achieve a balance between the amount of the charge transporting substance and the crosslink density. Abrasion 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 (for example, see Patent Document 6). However, this photosensitive layer has high hardness because the crosslink density can be increased, but since the bulky hole transporting compound has two or more chain polymerizable functional groups, distortion occurs in the cured product and internal stress is reduced. In some cases, the cross-linked surface layer tends to crack and peel off when used for a long time. Even in the conventional photoconductors having a cross-linked photosensitive layer in which a charge transporting structure is chemically bonded, it cannot be said that the present invention has sufficient comprehensive characteristics.
In particular, in the case of a photoreceptor having a cross-linked surface layer, generation of a residual potential and accumulation of the residual potential when used for a long time are serious problems.

JP 56-48637 A JP-A 64-1728 JP-A-4-281461 Japanese Patent No. 3262488 Japanese Patent No. 3194392 JP 2000-66425 A

  An object of the present invention is to provide a high durability and high performance electrophotographic photosensitive member that has high wear resistance and scratch resistance and good electrical characteristics, and is less susceptible to cracks and film peeling especially in the photosensitive layer. It is to be. Another object of the present invention is to provide an image forming method, an image forming apparatus, and a process cartridge for an image forming apparatus, which use these highly durable and high performance photoconductors and realize high image quality over a long period of time.

As a result of intensive studies, the present inventors have found that at least a charge generation layer, a charge transport layer, and a cross-linked charge transport layer are sequentially laminated on a conductive support, and the charge transport layer is composed of a low molecular charge transport material and a binder resin. In the electrophotographic photosensitive member mainly composed of a cured product of a charge transporting radical polymerizable monomer and a non-charge transporting polyfunctional radical polymerizable monomer, the crosslinkable charge transporting layer By incorporating the same low molecular charge transport material as the charge transport layer, it is possible to improve residual potential generation and residual potential accumulation when used for a long period of time, even with a photoreceptor having a crosslinked surface layer. I found. Preferably, the low molecular charge transport material contained in the crosslinkable charge transport layer is contained in the crosslinkable charge transport layer at a concentration of 5 to 25% by weight, and the low molecular charge transport is provided with a concentration gradient. By incorporating the material and having a region where the low-molecular charge transport material hardly exists on the surface side, and having a region contained on the charge transport layer side, the cross-linked charge transport layer is originally formed. It has been found that the required mechanical toughness and generation of residual potential and good electrical characteristics without residual potential accumulation when used for a long period of time can be achieved at the same time.
That is, the said subject is solved by (1)-( 5 ) of this invention.
(1) “At least a charge generation layer, a charge transport layer, and a crosslinkable charge transport layer are sequentially laminated on a conductive support, and the charge transport layer is mainly composed of a low molecular charge transport material and a binder resin, In the electrophotographic photosensitive member whose transport layer is mainly composed of a cured product of a charge transporting radical polymerizable monomer and a non-charge transporting polyfunctional radical polymerizable monomer, the crosslinkable charge transporting layer is further the same as the charge transporting layer. A region in which the low molecular charge transport material is contained at a concentration of 5 to 25% by weight, and the low molecular charge transport material to be contained in the cross-linked charge transport layer is added so that the concentration gradually decreases from the charge transport layer side. An electrophotographic photosensitive member characterized by comprising:
( 2 ) “The low-molecular charge transport material to be contained in the cross-linked charge transport layer has a region that hardly exists on the surface side, and has a region that is contained on the charge transport layer side. The electrophotographic photosensitive member according to item (1 ) ;
( 3 ) "Image forming method characterized in that at least charging, image exposure, development, and transfer are repeated using the electrophotographic photosensitive member according to item (1) or (2) ";
( 4 ) "Image forming apparatus comprising the electrophotographic photosensitive member according to item (1) or (2) ";
( 5 ) "At least one means selected from the group consisting of the electrophotographic photosensitive member according to item (1) or (2) and a charging means, a developing means, a transfer means, a cleaning means, and a static elimination means. And a process cartridge for an image forming apparatus, characterized in that the process cartridge for the image forming apparatus is detachable from the main body of the image forming apparatus.
Here, in the present invention, “the cross-linked charge transport layer further contains the same low-molecular charge transport material as that of the charge transport layer” means that the cross-linked charge transport layer film is formed from the interface between the charge transport layer and the cross-linked charge transport layer. This means that the same low-molecular charge transport material as that of the charge transport layer exists in a region exceeding 20% of the thickness, and “surface side” means a portion of the cross-linked charge transport layer film thickness of 20% from the photoreceptor surface. In addition, “nearly present” means that the abundance is less than 1%.

As is clear from the following detailed and specific description, according to the present invention, a conventional crosslinked protective layer can be formed by incorporating the same low molecular charge transport material as that of the lower charge transport layer in the crosslinked charge transport layer. Thus, it is possible to provide a photoconductor having excellent electrical characteristics with excellent wear resistance and less residual potential generation compared to a photoconductor without the photoconductor. In addition, it is possible to provide a photoconductor excellent in electric characteristics with less residual potential generation as compared with a conventional photoconductor having a crosslinked protective layer.
In addition, by setting the content of the low-molecular charge transporting material within a specific range, it is possible to provide a photoconductor excellent in both wear resistance and residual potential characteristics.
Furthermore, by incorporating low molecular charge transport materials with a concentration gradient so that the concentration gradually increases from the surface side to the charge transport layer, electrical properties such as residual potential characteristics can be maintained while maintaining a high level of wear resistance. A photoconductor excellent in characteristics can be provided.
Furthermore, by arranging the low molecular charge transport material to be hardly present on the surface side and to be contained on the charge transport layer side, the residual potential can be generated with the addition amount of the low molecular charge transport material as small as possible. It is possible to form a photoconductor excellent in electrical characteristics with few, and therefore, it is possible to provide a photoconductor excellent in electrical characteristics in a state of maximum wear resistance as a crosslinked film.
Therefore, by using this photoreceptor, it is possible to provide a high-performance and highly reliable image forming process, an image forming apparatus, and a process cartridge for the image forming apparatus that can provide a good image at a low running cost at a low cost.

Hereinafter, the present invention will be described in detail.
In the photoreceptor of the present invention, at least a charge generation layer, a charge transport layer and a cross-linked charge transport layer are sequentially laminated on a conductive support, and the charge transport layer is mainly composed of a low molecular charge transport material and a binder resin, In the electrophotographic photosensitive member whose main component is a cured product of a charge transporting radical polymerizable monomer and a non-charge transporting polyfunctional radical polymerizable monomer, the crosslinkable charge transporting layer further includes a charge in the crosslinkable charge transporting layer. The same low molecular charge transport material as that of the transport layer is contained at a concentration of 5 to 25% by weight, and the low molecular charge transport material contained in the cross-linked charge transport layer is gradually decreased in concentration from the charge transport layer side. It is characterized by having an added region .

  Here, the charge transporting radical polymerizable monomer means a compound skeleton having a property of transporting charges generated by light reception in the photosensitive layer by hopping conduction or the like and a conventionally known group such as a vinyl group, an acryloyloxy group, a methacryloyloxy group, and an aryl group. It refers to a compound having a radical polymerizable group. Conventionally known monomers can be applied as such charge transporting radical polymerizable monomers. For example, the compound of Unexamined-Japanese-Patent No. 2004-221959 etc. are mentioned.

  In addition, a preferable structure has a hole transporting structure such as triarylamine, hydrazone, pyrazoline, and carbazole, for example, an electron transporting structure such as condensed polycyclic quinone, diphenoquinone, an electron-withdrawing aromatic ring having a cyano group or a nitro group. And a compound having one radical polymerizable functional group. The radical polymerizable functional group may be any group having a carbon-carbon double bond and capable of radical polymerization.

Examples of these radical polymerizable functional groups include 1-substituted ethylene functional groups and 1,1-substituted ethylene functional groups shown below.
(1) Examples of the 1-substituted ethylene functional group include functional groups represented by the following formula (10).

（ただし、式中、Ｘ_１は、置換基を有していてもよいフェニレン基、ナフチレン基等のアリーレン基、置換基を有していてもよいアルケニレン基、−ＣＯ−基、−ＣＯＯ−基、−ＣＯＮ（Ｒ_１０）−基（Ｒ_１０は、水素、メチル基、エチル基等のアルキル基、ベンジル基、ナフチルメチル基、フェネチル基等のアラルキル基、フェニル基、ナフチル基等のアリール基を表わす。）、または−Ｓ−基を表わす。）

(In the formula, X ₁ is an arylene group such as a phenylene group or a naphthylene group which may have a substituent, an alkenylene group which may have a substituent, a —CO— group, a —COO— group. , —CON (R ₁₀ ) — group (R ₁₀ represents an alkyl group such as hydrogen, methyl group or ethyl group, an aralkyl group such as benzyl group, naphthylmethyl group or phenethyl group, or an aryl group such as phenyl group or naphthyl group. Or the —S— group.)

Specific examples of these substituents include a vinyl group, a styryl group, a 2-methyl-1,3-butadienyl group, a vinylcarbonyl group, an acryloyloxy group, an acryloylamide group, and a vinyl thioether group.
(2) Examples of the 1,1-substituted ethylene functional group include functional groups represented by the following formula (11).

（ただし、式中、Ｙは、置換基を有していてもよいアルキル基、置換基を有していてもよいアラルキル基、置換基を有していてもよいフェニル基、ナフチル基等のアリール基、ハロゲン原子、シアノ基、ニトロ基、メトキシ基あるいはエトキシ基等のアルコキシ基、−ＣＯＯＲ_１１基（Ｒ_１１は、水素原子、置換基を有していてもよいメチル基、エチル基等のアルキル基、置換基を有していてもよいベンジル、フェネチル基等のアラルキル基、置換基を有していてもよいフェニル基、ナフチル基等のアリール基）、または−ＣＯＮＲ_１２Ｒ_１３（Ｒ_１２およびＲ_１３は、水素原子、置換基を有していてもよいメチル基、エチル基等のアルキル基、置換基を有していてもよいベンジル基、ナフチルメチル基、あるいはフェネチル基等のアラルキル基、または置換基を有していてもよいフェニル基、ナフチル基等のアリール基を表わし、互いに同一または異なっていてもよい。）、また、Ｘ_２は上記式１０のＸ_１と同一の置換基及び単結合、アルキレン基を表わす。ただし、Ｙ，Ｘ_２の少なくとも何れか一方がオキシカルボニル基、シアノ基、アルケニレン基、及び芳香族環である。）

(In the formula, Y is an aryl group such as an alkyl group which may have a substituent, an aralkyl group which may have a substituent, a phenyl group which may have a substituent, or a naphthyl group. Group, halogen atom, cyano group, nitro group, alkoxy group such as methoxy group or ethoxy group, -COOR ₁₁ group (R ₁₁ is a hydrogen atom, an alkyl such as an optionally substituted methyl group or ethyl group) Group, an aralkyl group such as benzyl which may have a substituent, a phenethyl group or the like, an aryl group such as a phenyl group or a naphthyl group which may have a substituent, or -CONR ₁₂ R ₁₃ (R ₁₂ and R ₁₃ is a hydrogen atom, which may have a substituent an alkyl group such as methyl group and ethyl group, which may have a substituent group benzyl group, naphthylmethyl group, or a, such as a phenethyl group, Alkyl group or a substituent a phenyl group which may have a, an aryl group such as a naphthyl group, which may be the same or different from each other.) Further, X ₂ is the same as X ₁ in the formula 10 A substituent, a single bond, or an alkylene group, provided that at least one of Y and X ₂ is an oxycarbonyl group, a cyano group, an alkenylene group, and an aromatic ring.

Specific examples of these substituents include an α-acryloyloxy chloride group, a methacryloyloxy group, an α-cyanoethylene group, an α-cyanoacryloyloxy group, an α-cyanophenylene group, and a methacryloylamino group.
In addition, examples of the substituent further substituted with the substituent for X ₁ , X ₂ , and Y include, for example, a halogen atom, a nitro group, a cyano group, a methyl group, an alkyl group such as an ethyl group, a methoxy group, an ethoxy group, and the like And an aryloxy group such as a phenoxy group, an aryl group such as a phenyl group and a naphthyl group, and an aralkyl group such as a benzyl group and a phenethyl group.

  In particular, an acryloyloxy group and a methacryloyloxy group are useful. In addition, a triarylamine structure is highly effective as a charge transporting structure, and in particular, 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 good. To last.

（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_７（Ｒ_７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_８Ｒ_９（Ｒ_８及びＲ_９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、ビニレン基を表わす。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２価基、アルキレンオキシカルボニル２価基を表わす。ｍ、ｎは０〜３の整数を表わす。）

(In the formula, 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 ₇ (R ₇ 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 ₈ R ₉ (R ₈ and R ₉ 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. Ar ₁ and Ar ₂ each represent a substituted or unsubstituted arylene group, and may be the same or different.Ar ₃ , which may be the same or different from each other. Ar ₄ may be substituted Represents an unsubstituted aryl group, which 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, O represents an oxygen atom, a sulfur atom, or a vinylene group, Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group, and m and n are integers of 0 to 3. Represents.)

Specific examples of general formulas (1) and (2) are shown below.
In the general formulas (1) and (2), in the substituent of R ₁ , examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group, and examples of the aryl group include a phenyl group and a naphthyl group. The aralkyl group includes a benzyl group, a phenethyl group, and a naphthylmethyl group, and the alkoxy group includes a methoxy group, an ethoxy group, a propoxy group, and the like. These include a halogen atom, a nitro group, a cyano group, and a methyl group. Substituted with an alkyl group such as an ethyl group, an alkoxy group such as a methoxy group or an ethoxy group, an aryloxy group such as a phenoxy group, an aryl group such as a phenyl group or a naphthyl group, an aralkyl group such as a benzyl group or a phenethyl group, etc. May be.
Of the substituents for R ₁ , particularly preferred are a hydrogen atom and a methyl group.
Substituted or unsubstituted Ar ₃ and Ar ₄ are aryl groups, and examples of the aryl group include condensed polycyclic hydrocarbon groups, non-fused cyclic hydrocarbon groups, and heterocyclic groups.

  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 carbazolyl, dibenzofuranyl, dibenzothiophenyl, oxadiazolyl, and thiadiazolyl.

Further, 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 ₂ ), and R ₂ represents the 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)

（式中、Ｒ_３及びＲ_４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_３及びＲ_４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。

(In the formula, R ₃ and R ₄ 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 a alkyl group or a halogen atom ₄ which may contain as substituents .R ₃ and _{R 4} jointly)
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 substituted or unsubstituted alkylene group is a C ₁ -C ₁₂ , preferably C ₁ -C ₈ , more preferably C ₁ -C ₄ linear or branched alkylene group, and these alkylene groups include a fluorine atom, a hydroxyl group, a cyano _group, an alkoxy group of C 1 -C _4, a phenyl group or a halogen _atom, a phenyl group substituted with an alkyl group or a _C 1 -C ₄ alkoxy group C 1 -C ₄ It may be. 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 substituted or unsubstituted cycloalkylene _group, a cyclic alkylene group of C 5 -C _7, these are the cyclic alkylene group fluorine atom, a hydroxyl _group, an alkyl group of C 1 -C _4, a C 1 -C ₄ It may have an alkoxy group. Specific examples include a cyclohexylidene group, a cyclohexylene group, and a 3,3-dimethylcyclohexylidene group.

The substituted or unsubstituted alkylene ether group represents ethyleneoxy, propyleneoxy, ethylene glycol, propylene glycol, diethylene glycol, tetraethylene glycol, tripropylene glycol, alkylene ether group alkylene group is hydroxyl group, methyl group, ethyl group, etc. You may have the substituent of.
The vinylene group is

で表わされ、
Ｒ_５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。

Represented by
R ₅ 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, and b is 1 to 2 3 is represented.

Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent 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 divalent group include the divalent group of the alkylene ether group of X.
Examples of the alkyleneoxycarbonyl divalent group include a caprolactone-modified divalent group.

  Examples of the non-charge transporting polyfunctional radical polymerizable monomer include hole-transporting structures such as triarylamine, hydrazone, pyrazoline, and carbazole, for example, electron-withdrawing aromatics having condensed polycyclic quinone, diphenoquinone, cyano group, and nitro group. A monomer having no electron transport structure such as an aromatic ring and having two or more, preferably three or more radically polymerizable functional groups. The radical polymerizable functional group may be any group as long as it has a carbon-carbon double bond and is capable of radical polymerization.

These radical polymerizable functional groups are the same as the charge transporting radical polymerizable monomer.
Among these radical polymerizable functional groups, acryloyloxy group and methacryloyloxy group are particularly useful. For example, a compound having two or more acryloyloxy groups may be a compound having two or more hydroxyl groups in the molecule and an acrylic group. It can be obtained by using an acid (salt), an acrylic acid halide, or an acrylic ester to cause an ester reaction or a transesterification reaction. A compound having two or more methacryloyloxy groups can be obtained in the same manner. Further, the radical polymerizable functional groups in the monomer having two or more radical polymerizable functional groups may be the same or different.

  Specific examples of the non-charge transporting polyfunctional radical polymerizable monomer include the following, but are not limited to these compounds.

  For example, trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, trimethylolpropane alkylene modified triacrylate, trimethylolpropane ethyleneoxy modified (hereinafter EO modified) triacrylate, trimethylolpropane propyleneoxy modified (hereinafter PO modified) Triacrylate, trimethylolpropane caprolactone modified triacrylate, trimethylolpropane alkylene modified trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate (PETTA), glycerol triacrylate, glycerol epichlorohydrin modified (hereinafter ECH modified) triacrylate, Glycerol EO-modified triacrylate, glycerol P Modified triacrylate, tris (acryloxyethyl) isocyanurate, dipentaerythritol hexaacrylate (DPHA), dipentaerythritol caprolactone modified hexaacrylate, dipentaerythritol hydroxypentaacrylate, alkylated dipentaerythritol pentaacrylate, alkylated dipentaerythritol Tetraacrylate, alkylated dipentaerythritol triacrylate, dimethylolpropane tetraacrylate (DTMPTA), pentaerythritol ethoxytetraacrylate, phosphoric acid EO-modified triacrylate, 2,2,5,5, -tetrahydroxymethylcyclopentanone tetraacrylate These may be used alone or in combination of two or more. .

  In addition, as the non-charge transporting polyfunctional radical polymerizable monomer used in the present invention, in order to form a dense crosslink in the crosslinkable charge transport layer, the ratio of molecular weight to the number of functional groups in the monomer (molecular weight / The number of functional groups) is preferably 250 or less. Further, when this ratio is larger than 250, the cross-linked charge transport layer is soft and wear resistance is somewhat lowered. Therefore, among monomers exemplified above, monomers having a modifying group such as EO, PO, caprolactone, etc. It is not preferable to use a compound having a long modifying group alone. The component ratio of the non-charge transporting polyfunctional radical polymerizable monomer used in the crosslinkable charge transport layer is 20 to 80% by weight, preferably 30 to 70% by weight, based on the total amount of the crosslinkable charge transport layer. Specifically, it depends on the ratio of the bifunctional or higher radical polymerization reactive monomer in the solid content of the coating liquid. When the monomer component is less than 20% by weight, the three-dimensional crosslink density of the crosslinkable charge transport 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 exceeds 80% by weight, the content of the charge transporting compound is lowered, and the electrical characteristics are deteriorated. The electrical characteristics and abrasion resistance required differ depending on the process used, and the film thickness of the cross-linked charge transport layer of the photoreceptor varies accordingly. A range of 70% by weight is most preferred.

  In addition, the inclusion of the charge transporting radical polymerizable monomer used in the crosslinkable charge transport layer of the present invention and the same low molecular charge transport material as the charge transport layer is important for imparting the charge transport performance of the crosslinkable charge transport layer. Thus, this component is 20 to 80% by weight, preferably 30 to 70% by weight, based on the cross-linked charge transport layer. If these components are less than 20% by weight, the charge transport performance of the cross-linked charge transport layer cannot be maintained sufficiently, and repeated use causes deterioration of electrical characteristics such as a decrease in sensitivity and an increase in residual potential. On the other hand, if it exceeds 80% by weight, the content of the monomer having no charge transport structure is lowered, resulting in a decrease in the crosslink density and high wear resistance is not exhibited. The electrical characteristics and abrasion resistance required differ depending on the process used, and the film thickness of the cross-linked charge transport layer of the photoreceptor varies accordingly. A range of 70% by weight is most preferred.

Among these, the content of the low-molecular charge transport material is 5 to 25% by weight.
If the low-molecular-weight charge-transporting material is less than 5 wt%, the residual potential reduction effect is small, when exceeding 25 wt% can not maintain a high level of wear resistance weakens the strength of the crosslinked charge transporting layer.

In order to achieve a high level of both mechanical strength and residual potential characteristics, it is preferable that the concentration gradient is such that the low-molecular charge transport material is less on the surface side and thicker on the charge transport layer side in the cross-linked charge transport layer. More preferably, it is hardly contained on the surface and is preferably contained from the middle of the film to the charge transport layer side.
When many low-molecular charge transport materials are present on the surface side, light is absorbed on the surface side in the case of photocrosslinking, and the curing reaction of the entire crosslinkable charge transport layer is caused by the radical generation region being biased toward the film surface. It seems that the wear resistance decreases due to difficulty in progress.

  In order to avoid this, it is preferable to form a region having almost no low molecular charge transporting material on the surface side, and preferably no low molecular charge transporting material is contained in the 1 to 2 μm region from the surface side. Good. On the other hand, on the charge transport layer side, a low molecular charge transport material is contained in an amount of 10 to 150 mol% with respect to the charge transportable radical polymerizable monomer in order to smoothly inject and move charges from the charge transport layer. It is preferable.

  The crosslinkable charge transport layer of the present invention comprises a charge transporting radical polymerizable monomer, a non-charge transporting polyfunctional radical polymerizable monomer, and the same low molecular charge transporting material as the charge transporting layer. Monofunctional and bifunctional radically polymerizable monomers and radically polymerizable oligomers can be used in combination for the purpose of imparting functions such as viscosity adjustment, stress relaxation of the crosslinkable charge transport layer, lower surface energy and reduced 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, if a large amount of monofunctional and bifunctional radically polymerizable monomers and radically polymerizable oligomers are contained, the three-dimensional crosslink density of the crosslinkable charge transport layer is substantially decreased, leading to 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. In addition, the crosslinkable charge transport layer of the present invention may contain a polymerization initiator in the crosslinkable charge transport layer coating solution in order to allow the curing reaction to proceed efficiently as required.

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)
Hexin-3, di-t-butyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, lauroyl peroxide, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, etc. And azo initiators such as azobisisobutylnitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 4,4′-azobis-4-cyanovaleric acid It is done.

  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-based photopolymerization initiators such as 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 acceleration 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 crosslinking type charge transport layer coating liquid of the present invention may contain additives such as various plasticizers (for the purpose of stress relaxation and adhesion improvement) and leveling agents 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 crosslinkable charge transport layer of the present invention is prepared by applying a coating liquid containing at least the charge transportable radical polymerizable monomer, the non-charge transportable polyfunctional radical polymerizable monomer, and the same low molecular charge transport material as the charge transport layer later. It is formed by applying and curing on the described charge transport layer. When the radically polymerizable monomer is a liquid, the coating liquid can be applied by dissolving other components in the liquid, but if necessary, it is diluted with a solvent and applied. Solvents used at this time include alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, tetrahydrofuran, dioxane and propyl ether. And ethers such as dichloromethane, dichloroethane, trichloroethane and chlorobenzene, aromatics such as benzene, toluene and xylene, cellosolves such as methyl cellosolve, ethyl cellosolve and cellosolve acetate. 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 arbitrary. The coating can be performed using a dip coating method, spray coating, bead coating, ring coating method or the like.

  In addition, by selecting various solvents that are soluble in the charge transport layer and controlling the drying speed during coating, only the low molecular charge transport material component is transferred from the charge transport layer into the cross-linked charge transport layer. Can be made. In this case, it is not necessary to previously add the same low molecular charge transport material as that of the charge transport layer to the crosslinkable charge transport layer coating solution. According to this method, the cross-linked charge transport layer can be easily contained with a concentration gradient so that the concentration of the low molecular charge transport material decreases toward the surface side. The movement from the charge transport layer to the cross-linked charge transport layer can be controlled by the type of solvent, coating method, temperature and humidity, drying speed, coating solution concentration, etc. Absent.

  A preferred coating method is the spray coating method described above. The permeability of the low-molecular charge transport material can be easily controlled by changing the type of solvent, coating distance, coating amount, coating solution concentration, feed rate, number of coatings, and number of substrate rotations.

  As for the solvent, when a solvent having a high solubility in the charge transport layer material and a slow evaporation rate is used, the interface between the charge transport layer and the crosslinkable charge transport layer becomes unclear, and the crosslinkable charge transport layer It causes poor curing and does not become a durable photoreceptor. The electrophotographic photosensitive member of the present application has a layer structure in which the interface between the charge transport layer and the crosslinkable charge transport layer is clearly observed when the cross section of the photoconductor is observed, but an appropriate amount of the low molecular charge transport material is a crosslinkable charge. It is also contained in the transport layer. Therefore, it is necessary to examine and select the solvent to be used and the coating conditions according to the charge transport material and the cross-linked charge transport material to be used.

When a suitable amount of the same low molecular charge transport material as that of the lower layer is mixed in the crosslinking type charge transport layer coating solution in advance, the coating may be performed under the condition that there is little soaking from the lower layer. In the case where a suitable amount of a low molecular charge transport material is intentionally soaked from the lower layer depending on the coating condition of the crosslinkable charge transport layer, it is necessary to examine the conditions while analyzing the concentration of the charge transport material in the film. As the analysis method, a thin film section obtained by obliquely cutting the cross section of the photosensitive layer of the formed photoreceptor is taken out, and the characteristic absorption peak intensity between the low molecular charge transport material and the charge transportable radical polymerizable monomer is analyzed by microscopic Raman spectroscopy. Can be easily analyzed.
According to this method, the charge transport material concentration distribution in the cross-linked charge transport layer can also be seen.

In the present invention, after applying such a crosslinkable charge transport layer coating solution, energy is applied from the outside and cured to form a crosslinkable charge transport layer. The external energy used at this time includes heat, light, and the like. , There is 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 more and 170 ° C. or less, and if it is less than 100 ° C., the reaction rate is slow and the curing reaction is not completely completed. When the temperature is higher than 170 ° C., the curing reaction proceeds non-uniformly, and large strains, a large number of unreacted residues, and reaction termination terminals are generated in the cross-linked charge transport layer. In order to proceed 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. UV light source such as high-pressure mercury lamp or metal halide lamp that has emission wavelength mainly in ultraviolet light can be used as light energy, but the visible light source can also be selected according to the absorption wavelength of radical 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 local flaws are generated on the surface of the cross-linked charge transport layer, or many unreacted residues and reaction termination ends are generated. In addition, internal stress increases due to rapid crosslinking, which causes cracks and film peeling. 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.

  The film thickness of the crosslinked charge transport layer of the present invention is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less. If it is thicker than 10 μm, cracks and film peeling are likely to occur as described above, and if it is 8 μm or less, the margin is further improved, so that the crosslink density can be increased, and material selection and curing that further increases wear resistance. Conditions can be set. On the other hand, the radical polymerization reaction is prone to oxygen inhibition, that is, the surface in contact with the air is not easily cross-linked or non-uniform due to the influence of radical trapping by oxygen. This effect appears remarkably in the surface layer of 1 μm or less, and the cross-linked charge transport layer having a thickness of less than this thickness is liable to cause a decrease in wear resistance or uneven wear. In addition, mixing of the lower layer charge transport layer component occurs during the application of the crosslinkable charge transport layer. If the coating thickness of the crosslinkable charge transport layer is thin, the contaminants spread throughout the layer, which inhibits the curing reaction and lowers the crosslink density. For these reasons, the cross-linked charge transport layer of the present invention has a good wear resistance and scratch resistance at a film thickness of 1 μm or more, but a portion that is locally scraped to the lower charge transport layer is formed in repeated use. And the wear of the portion increases, and the density unevenness of the halftone image is likely to occur due to the chargeability and sensitivity fluctuation. Therefore, it is desirable that the film thickness of the cross-linked charge transport layer be 2 μm or more for a longer life and higher image quality.

  The composition of the crosslinkable charge transport layer coating liquid includes radical polymerization in addition to the above-described trifunctional or higher radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. When a large amount of additives such as binder resins, antioxidants, and plasticizers that do not have a functional functional group are included, the crosslinking density is reduced, the cured product resulting from the reaction and phase separation of the above additives occur, and the organic solvent It becomes soluble to. Specifically, it is important to suppress the total content to 20% by weight or less with respect to the total solid content of the coating liquid. Further, in order not to dilute the crosslinking density, the total content of monofunctional or bifunctional radical polymerizable monomers, reactive oligomers, and reactive polymers is 20% by weight or less based on the trifunctional radical polymerizable monomers. It is desirable. Further, when a large amount of a radical polymerizable compound having a bifunctional or higher functional charge transporting structure is contained, a bulky structure is fixed in the crosslinked structure by a plurality of bonds, so that distortion is likely to occur. It is easy to become an aggregate. This can cause solubility in organic solvents. Although different depending on the compound structure, the content of the radical polymerizable compound having a bifunctional or higher functional charge transporting structure is preferably 10% by weight or less based on the radical polymerizable compound having a monofunctional charge transporting structure.

As curing conditions for the cross-linked charge transport layer, if the energy of heating or light irradiation is low, the curing is not completely completed and the solubility in the organic solvent is increased. On the other hand, when cured with very high energy, the curing reaction becomes non-uniform, and it tends to increase the number of uncrosslinked parts and radical stopping parts and to form an aggregate of minute cured products. For this reason, it may become soluble in an organic solvent. In order to insolubilize in an organic solvent, the heat curing conditions are preferably 100 to 170 ° C. and 10 minutes to 3 hours, and the curing conditions by UV light irradiation are 50 to 1000 mW / cm ² and 5 seconds to 5 minutes. In addition, it is desirable to control the temperature rise to 50 ° C. or less to suppress non-uniform curing reaction.

Hereinafter, the present invention will be described according to 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. On a conductive support (31), a charge generation layer (35) having a charge generation function and a charge transport layer having a charge transport material function are shown. (37) and a cross-linked charge transport layer (39).

<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 by vapor deposition or sputtering, 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. In addition, an endless nickel belt and an endless stainless steel belt disclosed in JP-A-52-36016 can also 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-vinyl carbazole, 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.

  Further, 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, polytetrafluoroethylene-based fluororesin on a suitable cylindrical substrate. Those provided with a conductive layer can be used favorably as the conductive support (31) of the present invention.

<About photosensitive 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. Inorganic materials include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compounds, and amorphous silicon. 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.

  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) is 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 former include JP-A-01-001728, JP-A-01-009964, JP-A-01-013061, JP-A-01-019049, JP-A-01-241559, Japanese Unexamined Patent Publication Nos. 04-011627, 04-175337, 04-183719, 04-2225014, 04-230767, 04-320420, 05 -232727, JP-A 05-310904, JP-A 06-234836, JP-A 06-234837, JP-A 06-234838, JP-A 06-234839, JP-A 06-234840. No. 1, JP-A 06-234841, JP-A 06-239049, Japanese Unexamined Patent Publication Nos. 06-236050, 06-236051, 06-295077, 07-0756374, 08-176293, 08-208820, 08 No. -21640, JP 08-253568, JP 08-269183, JP 09-062019, JP 09-043883, JP 09-71642, JP 09-87376. JP-A 09-104746, JP-A 09-110974, JP-A 09-110976, JP-A 09-157378, JP-A 09-221544, JP-A 09-227669. JP 09-235367 A, JP 09-241369 A Charge transporting polymer materials described in JP 09-268226 A, JP 09-272735 A, JP 09-302084 A, JP 09-302085 A, JP 09-328539 A, etc. Can be mentioned. Specific examples of the latter include polysilylene polymers described in, for example, JP-A No. 63-285552, JP-A No. 05-19497, JP-A No. 05-70595, JP-A No. 10-73944, and the like. Illustrated.

  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 hole transport materials and electron transport materials. Examples of the electron transporting material include chloroanil, bromoanil, 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. A charge transport material having a charge transport function and a binder resin are dissolved or dispersed in an appropriate solvent, and this is coated on the charge generation layer (35) and dried. To form. 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 cross-linked charge transport layer is applied, and is particularly useful.

  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-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin And thermoplastic or thermosetting resins such as phenol resins and alkyd resins. 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 solvent used for coating the charge transport layer, the same solvent as that used for the charge generation layer can be used, but a solvent that dissolves the charge transport material and the binder resin well is suitable. These solvents may be used alone or in combination of two or more. The lower layer portion of the charge transport layer can be formed by a coating method similar to that for the charge generation layer (35).

  If necessary, a plasticizer and a leveling agent can be added. As a plasticizer that can be used in combination with the charge transport layer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is 0 with respect to 100 parts by weight of the binder resin. About 30 parts by weight is appropriate. Leveling agents that can be used in combination with the charge transport layer 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 a binder resin. About 0 to 1 part by weight is appropriate for 100 parts by weight. The thickness of the charge transport layer is suitably about 5 to 40 μm, preferably about 10 to 30 μm. On the charge transport layer thus formed, the above-described crosslinkable charge transport layer coating solution is applied, dried as necessary, and a curing reaction is started by external energy of heat or light irradiation, thereby crosslinkable charge. A transport layer is formed.

<About the intermediate layer>
In the photoreceptor of the present invention, an intermediate layer is provided between the charge transport layer and the cross-linked charge transport layer for the purpose of suppressing charge transport layer component mixing into the cross-linked charge transport layer or improving adhesion between the two layers. It is possible. For this reason, as the intermediate layer, those which are insoluble or hardly soluble in the cross-linked charge transport layer coating solution are suitable, and generally a binder resin is 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. In addition, about 0.05-2 micrometers is suitable for the thickness of an intermediate | middle layer.

<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, it may be a resin having a 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 anodization, organic substances 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>
Further, in the present invention, in order to improve environmental resistance, in particular, for the purpose of preventing a decrease in sensitivity and an increase in residual potential, a cross-linked charge transport layer, a charge transport layer, a charge generation layer, an undercoat layer, an intermediate layer An antioxidant can be added to each layer.

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- [methylene- -(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3'-bis (4'-hydroxy-3'-t-butylphenyl) butyric acid ] Cryol 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. The addition amount of the antioxidant in the present invention is 0.01 to 10% by weight based on the total weight of the layer to be added.

<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 multilayer photoreceptor having a cross-linked charge transport layer on the surface, which has very high wear resistance and scratch resistance and is less likely to cause cracks or film peeling. An image forming method and an image forming apparatus including a process of charging, image exposure, and development of a photosensitive member, and a process of transferring a toner image onto an image carrier (transfer paper), fixing, and cleaning of the surface of the photosensitive member. 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 the photosensitive member.

  FIG. 2 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 method can be used. In particular, the structure of the present invention is particularly 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.

  Next, the 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. Next, the 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. Next, a transfer charger (10) is used to transfer the toner image visualized on the photoconductor onto the transfer body (9). 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. Next, 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.

  Next, a fur brush (14) and a cleaning blade (15) are used to clean the toner remaining on the photoreceptor after transfer. 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 is an image forming method and an image forming apparatus using the electrophotographic photoreceptor according to the present invention for 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 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 discharging unit (not shown). ), And an apparatus (part) that can be attached to and detached from the image forming apparatus main body. Referring to the image forming process by the apparatus illustrated in FIG. 3, the surface of the photoconductor (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 is a laminate type photoconductor having a cross-linked charge transport layer on its surface that has very high wear resistance and scratch resistance and is unlikely to cause cracks or film peeling, and at least one of charging, developing, transferring, cleaning, and neutralizing means. The present invention provides a process cartridge for an image forming apparatus in which the two 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.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to a following example. Note that “parts” used in the examples all represent parts by weight.

<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 an 18 μm charge transport layer were formed. On this charge transport layer, a coating solution for a cross-linked charge transport layer having the following composition is spray-coated and naturally dried for 20 minutes, and then a metal halide lamp: 160 W / cm, irradiation distance: 120 mm, irradiation intensity: 500 mW / cm ^2. , Irradiation time: Light irradiation was performed under the condition of 240 seconds to cure the coating film. Furthermore, drying was performed at 130 ° C. for 20 minutes, and a 5.0 μm cross-linked charge transport layer was provided to obtain an electrophotographic photoreceptor of the present invention.

[Coating liquid for undercoat layer]
Alkyd resin 6 parts (Beccosol 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]
2.5 parts of bisazo pigment of the following structural formula (I)

ポリビニルブチラール（ＸＹＨＬ、ＵＣＣ製） ０．５部
シクロヘキサノン ２００部
メチルエチルケトン ８０部

Polyvinyl butyral (XYHL, manufactured by UCC) 0.5 part Cyclohexanone 200 parts Methyl ethyl ketone 80 parts

[Coating liquid for charge transport layer]
10 parts of bisphenol Z polycarbonate (Panlite TS-2050, manufactured by Teijin Chemicals)
7 parts of a low molecular charge transport material (D-1) having the following structural formula (II)

テトラヒドロフラン １００部
１％シリコーンオイルのテトラヒドロフラン溶液 ０．２部
（ＫＦ５０−１００ＣＳ、信越化学工業製）

Tetrahydrofuran 100 parts 1% silicone oil tetrahydrofuran solution 0.2 parts (KF50-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.)

[Coating liquid for cross-linked charge transport layer]
Non-charge transportable polyfunctional radical polymerizable monomer 10 parts Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99
9 parts of the following charge transportable radical polymerizable monomer

前記低分子電荷輸送物質（Ｄ−１） １部
光重合開始剤 １部
１−ヒドロキシ−シクロヘキシル−フェニル−ケトン
（イルガキュア１８４、チバ・スペシャルティ・ケミカルズ製）
テトラヒドロフラン １００部

Low molecular charge transport material (D-1) 1 part Photopolymerization initiator 1 part 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
Tetrahydrofuran 100 parts

<Example 2>
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 8 parts of the charge transporting radical polymerizable monomer and 2 parts of the low molecular charge transporting substance were used.

<Example 3>
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that 6 parts of charge transporting radical polymerizable monomer and 4 parts of low molecular charge transporting substance were used.

<Example 4>
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 5 parts of the charge transporting radical polymerizable monomer and 5 parts of the low molecular charge transporting substance were used.

Example 5 Reference Example An electrophotographic photosensitive member was prepared in the same manner as in Reference Example 1, except that 4 parts of the charge transporting radical polymerizable monomer and 6 parts of the low molecular charge transporting substance were used.

<Example 6>
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the coating solution for the crosslinkable charge transport layer was changed as follows.

[Coating liquid for cross-linked charge transport layer]
Non-charge transportable polyfunctional radical polymerizable monomer 10 parts Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99
10 parts of the following charge transportable radically polymerizable monomer (formula III)
Photoinitiator 1 part 1-Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
Tetrahydrofuran 200 parts

<Example 7>
An electrophotographic photosensitive member was prepared in the same manner as in Example 6 except that the solvent of the crosslinking type charge transport layer coating solution was changed to 170 parts of tetrahydrofuran.

<Example 8>
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the coating solution for the crosslinkable charge transport layer was changed as follows.

[Coating liquid for cross-linked charge transport layer]
Non-charge transportable polyfunctional radical polymerizable monomer 10 parts Trimethylolpropane triacrylate (KAYARAD TMPTA, manufactured by Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99
10 parts of the following charge transportable radical polymerizable monomer

光重合開始剤 １部
１−ヒドロキシ−シクロヘキシル−フェニル−ケトン
（イルガキュア１８４、チバ・スペシャルティ・ケミカルズ製）
テトラヒドロフラン ２００部

Photoinitiator 1 part 1-Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
Tetrahydrofuran 200 parts

<Comparative Example 1>
In Example 1, the crosslinkable protective layer was not provided, and the charge transport layer was formed to a thickness of 23 μm to produce an electrophotographic photoreceptor.

<Comparative Example 2>
The same as Example 1 except that 10 parts of the charge transporting polyfunctional radical polymerizable monomer is used without using the low molecular charge transporting substance (D-1) contained in the coating liquid for the crosslinkable charge transporting layer. Thus, an electrophotographic photosensitive member was produced.

<Comparative Example 3>
The same procedure as in Example 3 except that a low molecular charge transporting material of the following compound different from that used in the charge transporting layer is used as the low molecular charge transporting material contained in the coating liquid for the crosslinkable charge transporting layer. An electrophotographic photosensitive member was produced.

<Comparative example 4>
An electrophotographic photosensitive member was produced in the same manner as in Example 8, except that the solvent of the crosslinking type charge transport layer coating solution was changed to 100 parts of tetrahydrofuran.

<Comparative Example 5>
The same procedure as in Example 3 except that a low molecular charge transporting material of the following compound different from that used in the charge transporting layer is used as the low molecular charge transporting material contained in the coating liquid for the crosslinkable charge transporting layer. An electrophotographic photosensitive member was produced.

<Comparative Example 6>
The same procedure as in Example 3 except that a low molecular charge transporting material of the following compound different from that used in the charge transporting layer is used as the low molecular charge transporting material contained in the coating liquid for the crosslinkable charge transporting layer. An electrophotographic photosensitive member was produced.

<Comparative Example 7>
The same procedure as in Example 3 except that a low molecular charge transporting material of the following compound different from that used in the charge transporting layer is used as the low molecular charge transporting material contained in the coating liquid for the crosslinkable charge transporting layer. An electrophotographic photosensitive member was produced.

With respect to the electrophotographic photoreceptors of Examples 1 to 8 and Comparative Examples 1 to 4 produced as described above, the appearance was visually observed to determine the presence or absence of cracks and film peeling.
The results are shown in Table 1.

From the results of Table 1, all of them exhibited a good surface.
Moreover, about Examples 1-8, content of the low molecular charge transport material same as the lower layer charge transport layer in a bridge | crosslinking type charge transport layer was investigated. Similarly, the laminated part of the cross-linked charge transport layer and the charge transport layer of the photoconductor was peeled off, fixed with an adhesive resin, and a cross-section was taken out in the vertical direction of the film with a microtome, and the cross-linked charge transport layer and the charge transport layer were After confirming that the interface was clearly formed, oblique cutting was performed with a microtome, and the cross section of the cross-linked charge transport layer was enlarged 100 times in the vertical direction. This sample piece was measured for the characteristic absorption peak of the charge-transporting radical polymerizable monomer and the low-molecular charge-transporting material with a micro-Raman spectrophotometer, and the low-molecular charge was obtained using a calibration curve obtained in advance from a mixed sample of known concentration. The content of the transport material with respect to the charge transporting radical polymerizable monomer was determined by changing the film thickness point. The Raman measurement conditions are described below.

<Raman measurement conditions>
Excitation wavelength: 532.07 nm
Integration count: 16 times Manual attenuation filter: 25% 50%
Diffraction grating: 1800 (high resolution)
Center wavelength: 1280 cm ⁻¹
Multiplier: × 100 (Spatial resolution 1μ)
Exposure time: 10 sec

  Table 2 below shows the content ratio of the low-molecular charge transporting material and the average content ratio in the cross-linked charge transporting layer for each 1 μm thickness obtained from the above. The content ratio was calculated on the assumption that there was no composition change except for the charge transporting material.

Next, using a photoconductor of Examples 1 to 8 (Example 5 is a reference example) and Comparative Examples 1 to 4, a paper passing test of 50,000 sheets of A4 size was performed. First, the photosensitive member was mounted on a process cartridge for an electrophotographic apparatus, and the initial dark portion potential was set to −700 V with a Ricoh imagio Neo 270 remodeling machine using a 655 nm semiconductor laser as an image exposure light source. Thereafter, a paper passing test was started, and the dark portion and exposed portion potentials after the initial and 50,000 copies were measured. Further, the film thickness of all layers after the initial copy and after copying 50,000 sheets was measured, and the wear amount was calculated from the difference. The results are shown in Table 3.

From the results of Table 2 and Table 3, in the system in which the cross-linked charge transport layer contains the same low molecular charge transport material as the lower charge transport layer, the initial exposure part potential is low and the exposed part potential after repeated use is low. It can be seen that the rise is also small. This indicates that the generation of residual potential in the photosensitive layer is suppressed to a low level. In terms of the addition amount of the low-molecular charge transport material, both the exposed portion potential characteristics and the wear resistance are measured at a high level in the range of 5 wt% to 25 wt% in the cross-linked charge transport layer. In Example 5 (reference example) exceeding 25% by weight, the wear resistance started to show a tendency to rapidly decrease. Further, Comparative Example 2 and Comparative Example 4 containing almost no low-molecular charge transporting material are excellent in wear resistance, but the exposed portion potential characteristics are poor.

Moreover, in the case of the comparative example 3 and comparative examples 5-7 using the low molecular charge transport material different from a charge transport layer, the effect which improves an exposure part electric potential is not seen.
In addition, Examples 6 to 8 in which the low molecular charge transporting material is added so that the concentration is gradually decreased from the charge transporting layer side when compared with those having the same content of the low molecular charge transporting material. Compared to 4, it is understood that both the high wear resistance and the excellent exposed portion potential characteristics are compatible.
Further, as in Examples 6 to 8, a photoreceptor having a structure in which a low molecular charge transport material hardly exists on the surface side and a region contained on the charge transport layer side has a small average content. It shows that the exposed portion potential characteristics are excellent regardless of the ratio, and that it is extremely preferable for achieving both high-level wear resistance and residual potential characteristics.
In addition, 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.

It is a figure which shows an example of sectional drawing of the electrophotographic photoreceptor in this invention. It is a figure which shows an example of the image forming apparatus in this invention. FIG. 3 is a diagram illustrating an example of a process cartridge for an image forming apparatus according to the present invention.

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 paper 10 Transfer charger 11 Separation charger 12 Separation claw 13 Charger before cleaning 14 Fur brush 15 Cleaning blade 31 Conductivity Support 33 Photosensitive layer 35 Charge generation layer 37 Charge transport layer 39 Crosslinkable charge transport layer 101 Photosensitive drum 102 Charging device 103 Exposure 104 Developing device 105 Transfer body 106 Transfer device 107 Cleaning blade

Claims (5)

At least a charge generation layer, a charge transport layer, and a crosslinkable charge transport layer are sequentially laminated on a conductive support, the charge transport layer is mainly composed of a low molecular charge transport material and a binder resin, and the crosslinkable charge transport layer is charged. In the electrophotographic photosensitive member mainly composed of a cured product of a transportable radical polymerizable monomer and a non-charge transportable polyfunctional radical polymerizable monomer, the same low molecular charge transport as that of the charge transport layer is further included in the crosslinkable charge transport layer. A material having a concentration of 5 to 25% by weight , and a low molecular charge transport material to be contained in the cross-linked charge transport layer has a region to which the concentration is gradually decreased from the charge transport layer side. An electrophotographic photosensitive member. Low molecular weight charge transport material to be contained in the cross-linked charge transport layer has a region where there is little on the surface side, to claim 1, the charge transport layer side and having a region that is contained The electrophotographic photosensitive member described. 3. An image forming method, wherein at least charging, image exposure, development and transfer are repeated using the electrophotographic photosensitive member according to claim 1 or 2 . An image forming apparatus, comprising an electrophotographic photosensitive member according to claim 1 or 2. 3. An image forming apparatus main body 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.

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