JP2005189828A - Electrophotographic photosensitive member, image forming method, image forming apparatus, and process cartridge for image forming apparatus - Google Patents

Abstract

An object of the present invention is to provide an electrophotographic photosensitive member that has excellent image quality stability and can achieve high durability.
In an electrophotographic photosensitive member in which at least an undercoat layer, a photosensitive layer and a crosslinkable charge transport layer are sequentially laminated on a conductive support, the undercoat layer comprises an inorganic pigment-containing layer and an inorganic pigment. A radical polymerizable compound having a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a monofunctional charge transport structure comprising at least two layers not containing the crosslinkable charge transport layer And is cured.
[Selection figure] None

Description

  The present invention relates to an undercoat layer composed of at least two layers of an inorganic pigment-containing layer and an inorganic pigment-free layer, a photosensitive layer, and a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure. The present invention relates to an electrophotographic photosensitive member in which a crosslinkable charge transport layer obtained by curing a radical polymerizable compound having a monofunctional charge transport structure is laminated, an image forming apparatus using the same, and a process cartridge for the image forming apparatus.

  In recent years, the development of information processing system machines using electrophotography has been remarkable, and in particular, laser printers and digital copiers that record information using light by converting information into digital signals have significantly improved print quality and reliability. . These laser printers and digital copiers that are rapidly spreading are required to have higher speed and smaller size as well as higher image quality. Furthermore, recently, the demand for full-color laser printers and full-color digital copiers capable of full-color printing is rapidly increasing. When full-color printing is performed, it is necessary to superimpose toner images of at least four colors. In particular, speeding up and downsizing of the apparatus are even more important issues.

  In order to realize high speed and downsizing of the apparatus, it is necessary to improve the sensitivity of the electrophotographic photosensitive member used for them and to reduce the diameter of the photosensitive member. In particular, in the case of a tandem system effective for achieving both full color and high speed, since at least four photoreceptors are included in the apparatus, the degree of demand for reducing the diameter of the photoreceptor is very high. However, as the diameter of the photoconductor is reduced, the photoconductor is used in a harsher situation. Therefore, the replacement speed of the conventional photoconductor is greatly increased, especially in a high-speed machine. It becomes a serious problem. Therefore, in order to realize high speed and downsizing of the apparatus, it is indispensable to greatly increase the durability of the photoconductor used at the same time.

  In order to increase the durability of the photoreceptor, it is necessary to improve the stability of the image quality and particularly to suppress the occurrence of background stains. Background stain is a type of image defect in which countless minute spots are developed in a white background region. As a mechanism for the occurrence of scumming, when the photosensitive member is charged, a charge having a polarity opposite to that induced on the conductive support side leaks locally and is injected into the photosensitive layer and the surface of the photosensitive member. This is considered to be due to the fact that the portion is easily developed. In this case, even in the initial stage of the photoconductor, even if the scumming has not been revealed, the scumming is likely to be manifested due to fatigue of the photoconductor (reduction in charge) due to repeated use or increase in electric field strength due to wear of the photosensitive layer. Therefore, this is one of the major factors that determine the life of the photoreceptor.

In order to realize high durability of the photosensitive member, it is necessary to suppress the background contamination, and for that purpose, it is important to suppress the injection of charges from the conductive support. As these conventional techniques, a technique of providing an undercoat layer or an intermediate layer between a conductive support and a photosensitive layer has been proposed.
For example, Patent Document 1 includes a cellulose nitrate resin intermediate layer, Patent Document 2 includes a nylon resin intermediate layer, Patent Document 3 includes a maleic acid resin intermediate layer, and Patent Document 4 includes a polyvinyl alcohol resin intermediate layer. Are each disclosed.
However, the intermediate layer of these resins alone (single layer) has a high electric resistance, so that the residual potential is increased, and in negative / positive development, image density and gradation are lowered. In addition, since these intermediate layers exhibit ionic conductivity due to impurities and the like, the electrical resistance of the intermediate layers is particularly high under low temperature and low humidity, and the environmental dependence of the residual potential is increased. In order to reduce this, it was necessary to make the intermediate layer thin, and it was very difficult to achieve both soiling and residual potential.

In order to solve these problems, a method of dispersing a conductive additive in the intermediate layer has been proposed as a technique for controlling the electric resistance of the intermediate layer.
For example, Patent Document 5 includes an intermediate layer in which a carbon or chalcogen-based material is dispersed in a curable resin, and Patent Document 6 includes a thermal polymer intermediate layer using an isocyanate-based curing agent to which a quaternary ammonium salt is added, Patent Document 7 discloses a resin intermediate layer to which a resistance modifier is added, and Patent Document 8 discloses a resin intermediate layer to which an organometallic compound is added. However, these resin intermediate layers alone have a problem that light interference fringes appear in an image, that is, so-called moire in an image forming apparatus using coherent light such as laser light in recent years.

For the purpose of suppressing the occurrence of moire and simultaneously controlling the electric resistance of the intermediate layer, a photoreceptor containing a filler in the intermediate layer has been proposed.
For example, Patent Document 9 includes a resin intermediate layer in which an oxide of aluminum or tin is dispersed, Patent Document 10 includes a resin intermediate layer in which conductive particles are dispersed, and Patent Document 11 includes an intermediate layer in which magnetite is dispersed. In Patent Document 12, a resin intermediate layer in which titanium oxide and tin oxide are dispersed is dispersed. In Patent Documents 13 to 18, borides such as calcium, magnesium, and aluminum, nitrides, fluorides, and oxide powders are dispersed. A resin intermediate layer is disclosed.

  Although the intermediate layer in which the filler is dispersed is effective for suppressing moire, it is necessary to increase the filler content in order to reduce the residual potential. Thus, the coexistence of soiling and residual potential has not been achieved. Further, the adhesiveness to the conductive support is lowered, and there is a problem that peeling between the support and the intermediate layer is likely to occur, and there are many problems for improving the durability of the photoreceptor.

  In order to solve such problems, a concept of stacking intermediate layers has been proposed. The structure of lamination is roughly classified into two types. One is a structure in which a resin layer in which a filler is dispersed and a resin layer not containing a filler are sequentially laminated on a conductive support (see FIG. 1 (a)). In the other, a resin layer not containing a filler and a resin layer in which a filler is dispersed are sequentially provided on a conductive support (see FIG. 1B).

To elaborate the former configuration, in order to conceal defects in the conductive support, a conductive layer in which a low-resistance filler is dispersed is provided on the conductive support, and the resin layer is laminated thereon. is there. These are described in Patent Documents 19 to 27, for example.
On the other hand, as the latter configuration, a hole blocking resin single layer is provided on a conductive support, and a resin layer in which a low resistance filler or an electron conductive filler is dispersed is provided thereon. These are described in, for example, Patent Documents 28 and 29.

  Also disclosed is a method using an undercoat layer or an intermediate layer containing N-alkoxy (methoxy) methylated nylon in the undercoat layer. For example, Patent Document 30 discloses a method in which an undercoating layer contains an alkoxymethylated copolymer nylon having an alkoxymethylation degree of 5 to 30%, and Patent Document 31 crosslinks an intermediate layer as an inorganic pigment and a binder resin. According to Patent Document 32, the undercoat layer is made of N-alkoxymethylated nylon resin, and the elemental concentration of impurities Na, Ca and P atoms contained in the resin is 10 ppm each. The method described below is a method in which Patent Document 33 includes an N-alkoxymethylated polyamide copolymer containing λ-amino-n-lauric acid as a main component in the intermediate layer. A method of containing a polyamide resin having a unit component having a certain structure is disclosed.

  As described above, methods for laminating an undercoat layer or an intermediate layer and for containing N-alkoxymethylated nylon in the undercoat layer or the intermediate layer are well known, and suppress the injection of charges from the conductive support. It is effective as a means for enhancing the dirt suppression effect. However, as the electric field strength increases as the photoconductor wears, the scumming increases remarkably. Even at high electric field strength, attempts to enhance the charge blocking function of the undercoat layer or the intermediate layer cause a significant increase in residual potential. However, merely suppressing the injection of electric charges from the conductive support by the undercoat layer or the intermediate layer is not sufficient for suppressing the soiling in the repeated use of the photoconductor, and high durability of the photoconductor has been realized. There wasn't.

  In addition, only by increasing the wear resistance of the photoreceptor, the influence of the electric field strength over time is reduced, but the influence of the charge injection from the conductive support is also promoted by a decrease in charge due to fatigue of the photoreceptor. Therefore, the effect is not sufficient. Therefore, in order to suppress the occurrence of scumming due to repeated use of the photoconductor and to realize high durability of the photoconductor, it is possible to suppress charge injection from the conductive support and to wear due to repeated use of the photoconductor. It is necessary to reduce it.

  Conventional techniques for improving the abrasion resistance of the photosensitive layer include (i) using a curable binder in the crosslinkable charge transport layer (see, for example, Patent Document 35), and (ii) using a polymer charge transport material. (Iii) a material obtained by dispersing an inorganic filler in a crosslinkable charge transport layer (for example, see Patent Literature 37).

  As described above, since the fluctuation of the electric field strength with time can be reduced by increasing the wear resistance of the photoreceptor, a high effect can be obtained for the suppression of background contamination. However, among these technologies, those using the curable binder (i) have poor compatibility with the charge transport material, and the residual potential increases due to impurities such as polymerization initiators and unreacted residues. There is a tendency for image density reduction to occur easily.

  In addition, although the polymer type charge transport material (ii) 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 (iii) 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.

Even if these technologies (i), (ii), and (iii) may be effective in suppressing scumming, there are defects in residual potential, cleaning properties, etc., resulting in image defects resulting in durability. I haven't fully satisfied.
Furthermore, a photoreceptor containing a polyfunctional acrylate monomer cured product for improving the wear resistance and scratch resistance of (i) is also known (see Patent Document 38). 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 technique for a photosensitive layer that replaces these, a charge transport layer formed by using a coating solution comprising a monomer having a carbon-carbon double bond, a charge transport material having a carbon-carbon double bond, and a binder resin. It is known to provide (for example, refer to Patent Document 39). This binder resin is thought to play a role of improving the adhesion between the charge generation layer and the cross-linked charge transport layer, and also relaxing 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 transporting substance and those having no reactivity with the double bond.

  This photoconductor is remarkably compatible with wear resistance and good electrical properties. However, when a non-reactive binder resin is used, the binder resin, the monomer, and the charge transport material are used. The compatibility with the cured product produced by this reaction is poor, and layer 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 a bifunctional one, and in these respects, the abrasion resistance has not yet been satisfied. Even when a binder resin having reactivity is used, although the molecular weight of the cured product is increased, the number of cross-linking bonds between molecules is small, and it is difficult to achieve both the bonding amount and the cross-linking density of the charge transport material. The abrasion resistance was not sufficient.

  A photosensitive layer containing a compound obtained by curing a hole transporting compound having two or more chain polymerizable functional groups in the same molecule is also known (see, for example, Patent Document 40). 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 increases. In some cases, the crosslinked surface layer is liable to crack or peel off when used for a long period of 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.

  As described above, a number of conventional techniques for improving the wear resistance of a photoreceptor have been disclosed, and it is known that it is effective for suppressing scumming, but on the other hand, a residual potential rise is likely to occur. Humidity is likely to cause image flow, and filming is more likely to occur because the surface of the photoconductor is less likely to be refaced. In fact, the photoconductor has not been improved in durability since the image defect is induced and the stability of the image quality is greatly lowered.

  In order to completely suppress the occurrence of scumming, it cannot be achieved not only by suppressing the injection of charges from the conductive support but also by suppressing the decrease in the thickness of the photosensitive layer due to repeated use. In addition, the high durability of the photoconductor suppresses the occurrence of scumming, and the residual potential is highly stable over time, and also has improved wear resistance, resulting in image quality degradation such as filming, foreign matter adhesion, and image flow. This is achieved for the first time by reducing the side effects and maintaining high image quality over a long period of time even after repeated use. However, in the prior art, it has not been realized to make all of them compatible, and it has been the actual situation that high durability of the photoreceptor has not yet been achieved.

JP-A-47-6341 JP-A-60-66258 JP 52-10138 A JP 58-105155 A JP 51-65942 A JP 52-82238 A Japanese Patent Application Laid-Open No. 55-110451 JP 58-93062 A Japanese Patent Laid-Open No. 58-58556 Japanese Patent Laid-Open No. 60-111255 JP 59-17557 A JP-A-60-32054 JP-A 64-68762 JP-A 64-68763 JP-A 64-73352 JP-A 64-73353 JP-A-1-118848 Japanese Patent Laid-Open No. 1-118849 JP 58-95351 A JP 59-93453 A JP-A-4-170552 JP-A-6-208238 JP-A-6-222600 Japanese Patent Laid-Open No. 8-184979 Japanese Patent Laid-Open No. 9-43886 Japanese Patent Laid-Open No. 9-190005 JP-A-9-288367 Japanese Patent Laid-Open No. 5-80572 JP-A-6-19174 JP-A-9-265202 JP 2002-107984 A Japanese Patent No. 2718044 Japanese Patent No. 3086965 Japanese Patent No. 3226110 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 an electrophotographic photoreceptor excellent in image quality stability and capable of realizing high durability. Specifically, it suppresses the scumming caused by the charge injection from the conductive support, and also suppresses the increase of scumming promoted by the electrostatic fatigue due to repeated long-term use, and further the increase of the electric field strength due to wear. Rather, it has dramatically improved durability and stability by minimizing the occurrence of image defects such as filming, adhesion of foreign matter, and image flow due to increased residual potential, reduced charge, and improved wear resistance. It is an object to provide an electrophotographic photosensitive member having properties.

  Another object of the present invention is to provide an image forming apparatus that is stable and highly durable with less occurrence of abnormal images such as scumming even when image formation is repeated using the above-described photoreceptor. Specifically, it is an object to provide a high-speed, high-durability and highly stable image forming apparatus that solves the biggest problems in negative / positive development systems such as scumming and density reduction caused by repeated use. Furthermore, another object of the present invention is to provide a process cartridge for an image forming apparatus that uses the above-described photoreceptor and is highly durable, highly stable, and has good handling.

As a result of intensive studies on the above problems, the present inventors have found that an undercoat layer in which at least two layers of a layer containing an inorganic pigment and a layer not containing an inorganic pigment are laminated on a conductive support. And a photosensitive layer, and a cross-linked charge transport layer obtained by curing a tri- or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. It has been found that there is no side effect of potential increase, and the scumming durability in repeated use can be dramatically improved, and the present invention has been completed.
That is, the present invention is achieved by the following configurations.

(1) In an electrophotographic photosensitive member in which at least an undercoat layer, a photosensitive layer and a crosslinkable charge transport layer are sequentially laminated on a conductive support, the undercoat layer contains an inorganic pigment-containing layer and an inorganic pigment. A trifunctional or higher functional radical polymerizable monomer having at least two layers, and the crosslinkable charge transporting layer having at least a charge transporting structure, and a radical polymerizable compound having a monofunctional charge transporting structure; An electrophotographic photosensitive member characterized by being formed by curing.
(2) The electrophotographic photosensitive member according to (1) above, wherein the photosensitive layer has a laminated structure in which a charge generation layer and a charge transport layer are sequentially laminated.
(3) The electrophotographic photoreceptor as described in (1) or (2) above, wherein a polyamide resin is contained in a layer not containing an inorganic pigment among the undercoat layer.
(4) The electrophotographic photoreceptor as described in (3) above, wherein the polyamide resin is N-methoxymethylated nylon.
(5) The electrophotographic photoreceptor as described in (4) above, wherein the N-methoxymethylated nylon is crosslinked by heating.

(6) The electrophotographic film as described in any one of (1) to (5) above, wherein a film thickness of a layer not containing an inorganic pigment among the undercoat layer is less than 2.0 μm. Photoconductor.
(7) The layer containing an inorganic pigment in the undercoat layer contains a metal oxide as an inorganic pigment, according to any one of (1) to (6) above Electrophotographic photoreceptor.
(8) The electrophotographic photosensitive member according to (7), wherein the metal oxide is titanium oxide.
(9) The inorganic pigment is a mixture of two or more inorganic pigments having different average primary particle sizes, and the average primary particle size of the inorganic pigment having the largest average primary particle size is D1, and the smallest average primary particle size is The electron according to any one of (1) to (8), wherein the relationship of 0.2 <(D2 / D1) ≦ 0.5 is satisfied when the average primary particle diameter of the inorganic pigment is D2 Photoconductor.
(10) The electrophotographic photosensitive member according to (9), wherein the D2 is less than 0.2 μm.
(11) The content ratio of two or more inorganic pigments having different average primary particle sizes is T1, the content of the inorganic pigment having the largest average primary particle size, and the content of the inorganic pigment having the smallest average primary particle size The electrophotographic photosensitive member as described in (9) or (10), wherein the relationship of 0.2 ≦ T2 / (T1 + T2) ≦ 0.8 is satisfied by weight where is T2.
(12) The electron according to any one of (1) to (11) above, wherein the layer containing an inorganic pigment among the undercoat layer includes a thermosetting resin as a binder resin. Photoconductor.
(13) The electrophotographic photosensitive member according to (12), wherein the thermosetting resin comprises an alkyd resin and a melamine resin.
(14) The electrophotographic photosensitive member according to (13), wherein a weight ratio of the alkyd resin to the melamine resin is in a range of 1/1 to 4/1.
(15) The volume ratio of the inorganic pigment to the binder resin contained in the layer containing the inorganic pigment is in the range of 1/1 to 3/1. (1) to (14) The electrophotographic photosensitive member according to any one of the above.
(16) The above-mentioned (1) to (15), wherein the thickness of the layer containing the inorganic pigment among the undercoat layers is larger than the thickness of the layer not containing the inorganic pigment. The electrophotographic photosensitive member according to any one of the above.
(17) Of the undercoat layer, the layer containing no inorganic pigment is directly formed on the conductive support, and the layer containing the inorganic pigment is laminated thereon. The electrophotographic photosensitive member according to any one of (1) to (16).

(18) The electrophotographic photosensitive member according to any one of (1) to (17), wherein the cross-linked charge transport layer is insoluble in an organic solvent.
(19) The functional group of a tri- or higher functional radical polymerizable monomer having no charge transporting structure used for the crosslinkable charge transport layer is an acryloyloxy group and / or a methacryloyloxy group. The electrophotographic photosensitive member according to any one of 1) to (18).
(20) The ratio of the molecular weight to the number of functional groups (molecular weight / number of functional groups) in a tri- or higher functional radical polymerizable monomer having no charge transporting structure used for the cross-linked charge transport layer is 250 or less. The electrophotographic photosensitive member according to any one of (1) to (19) above.
(21) The functional group of the radically polymerizable compound having a monofunctional charge transporting structure used for the crosslinkable charge transporting layer is an acryloyloxy group or a methacryloyloxy group. 20) The electrophotographic photosensitive member according to any one of the above.
(22) The above-mentioned (1) to (21), wherein the charge transport structure of the radical polymerizable compound having a monofunctional charge transport structure used for the crosslinked charge transport layer is a triarylamine structure. The electrophotographic photosensitive member according to any one of the above.

(23) The radical polymerizable compound having a monofunctional charge transporting structure used in the crosslinkable charge transporting layer is at least one compound represented by the following general formula (1) or (2). The electrophotographic photosensitive member according to any one of (1) to (22) above,

(Wherein R ₁ is 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 represents 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 Ali substituted or unsubstituted X may be the same or different, and X is 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, sulfur An atom and a vinylene group, Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, and an alkyleneoxycarbonyl divalent group, m and n represent an integer of 0 to 3.)
(24) The radical polymerizable compound having a monofunctional charge transport structure used for the cross-linked charge transport layer is at least one compound represented by the following general formula (3): The electrophotographic photosensitive member according to any one of (1) to (23).

  (Wherein, o, p and q are each an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent a substituent other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, And s and t each represent an integer of 0 to 3. Za represents a single bond, a methylene group, an ethylene group, or a group having the following structural formula.)

（２５）前記架橋型電荷輸送層に用いられる電荷輸送性構造を有しない３官能以上のラジカル重合性モノマーの成分割合が、架橋型電荷輸送層全量に対し３０〜７０重量％であることを特徴とする上記（１）〜（２４）のいずれかに記載の電子写真感光体。
（２６）前記架橋型電荷輸送層に用いられる１官能の電荷輸送性構造を有するラジカル重合性化合物の成分割合が、架橋型電荷輸送層全量に対し３０〜７０重量％であることを特徴とする上記（１）〜（２５）のいずれかに記載の電子写真感光体。
（２７）前記架橋型電荷輸送層の硬化が加熱又は光エネルギー照射手段によって行われたことを特徴とする上記（１）〜（２６）のいずれかに記載の電子写真感光体。
（２８）（１）乃至（２７）のいずれかに記載の電子写真感光体を用いて、少なくとも帯電、画像露光、現像、転写を繰り返し行うことを特徴とする画像形成方法。
（２９）少なくとも帯電手段、露光手段、現像手段、転写手段、及び電子写真感光体を具備してなる画像形成装置において、該電子写真感光体が上記（１）〜（２７）のいずれかに記載の電子写真感光体であることを特徴とする画像形成装置。
（３０）少なくとも帯電手段、露光手段、現像手段、転写手段、及び電子写真感光体からなる画像形成要素を複数配列したことを特徴とする上記（２９）に記載の画像形成装置。

(25) The proportion of the trifunctional or higher functional radical polymerizable monomer having no charge transport structure used in the crosslinkable charge transport layer is 30 to 70% by weight based on the total amount of the crosslinkable charge transport layer. The electrophotographic photosensitive member according to any one of (1) to (24) above.
(26) The component ratio of the radical polymerizable compound having a monofunctional charge transporting structure used in the crosslinkable charge transport layer is 30 to 70% by weight based on the total amount of the crosslinkable charge transport layer. The electrophotographic photosensitive member according to any one of (1) to (25) above.
(27) The electrophotographic photosensitive member according to any one of (1) to (26) above, wherein the crosslinking charge transport layer is cured by heating or light energy irradiation means.
(28) An image forming method, wherein at least charging, image exposure, development, and transfer are repeated using the electrophotographic photosensitive member according to any one of (1) to (27).
(29) An image forming apparatus comprising at least a charging unit, an exposure unit, a developing unit, a transfer unit, and an electrophotographic photosensitive member, wherein the electrophotographic photosensitive member is any one of the above (1) to (27). An image forming apparatus characterized by being an electrophotographic photosensitive member.
(30) The image forming apparatus as described in (29) above, wherein a plurality of image forming elements comprising at least charging means, exposure means, developing means, transfer means, and electrophotographic photosensitive member are arranged.

(31) The image forming apparatus as described in (29) or (30), wherein an AC superimposed voltage is applied to a charging unit used in the image forming apparatus.
(32) In an image forming apparatus comprising at least a charging unit, an exposing unit, a developing unit, a transfer unit, and an electrophotographic photosensitive member, the linear velocity of the photosensitive member during image formation is 250 mm / sec or more. The image forming apparatus according to any one of (29) to (31). (33) The image forming apparatus includes a process cartridge for an image forming apparatus in which at least an electrophotographic photosensitive member and at least one means selected from a charging unit, an exposure unit, a developing unit, and a cleaning unit are integrated. The image forming apparatus according to any one of (29) to (32), wherein the process cartridge for the image forming apparatus is detachable from the apparatus main body.
(34) In a process cartridge for an image forming apparatus in which at least an electrophotographic photosensitive member is integrated with at least one unit selected from a charging unit, an exposure unit, a developing unit, and a cleaning unit, the electrophotographic photosensitive member is the above ( A process cartridge for an image forming apparatus, which is the electrophotographic photosensitive member according to any one of 1) to (27).

According to the present invention, it has an undercoat layer in which at least two layers of a layer containing an inorganic pigment and a layer not containing an inorganic pigment are laminated, and at least a trifunctional or higher functional group having no charge transporting structure on the surface of the photoreceptor. By having a crosslinkable charge transport layer formed by curing a radical polymerizable monomer and a radical polymerizable compound having a monofunctional charge transport structure, it is possible to suppress the occurrence of scumming even in long-term repeated use. It is possible to provide an electrophotographic photosensitive member that can output a high-quality image stably over a long period of time and can suppress the occurrence of image defects such as image flow and filming. Is done.
In addition, by using the photoconductor, there is provided an image forming apparatus capable of stably outputting a high-quality image over a long period of time, with little occurrence of background smudges even when image formation is repeated, with less side effects such as image flow. Is done. Further, the realization of high durability and high stability of the photoconductor in this way enables the size and speed of the image forming apparatus to be reduced. Especially for tandem type image forming apparatuses and high speed image forming apparatuses. It can be used effectively.

The electrophotographic photosensitive member used in the present invention will be described in detail with reference to the drawings.
FIG. 2 (a) is a cross-sectional view showing a structural example of the electrophotographic photosensitive member used in the present invention, and on the conductive support, at least two layers of a layer not containing an inorganic pigment and a layer containing an inorganic pigment are shown. Cross-linked charge formed by curing an undercoat layer, a photosensitive layer, and at least a tri- or higher functional radical polymerizable monomer having no charge transporting structure and a radical polymerizable compound having a monofunctional charge transporting structure The transport layer is stacked.
FIG. 2B is a cross-sectional view showing another structural example of the electrophotographic photosensitive member used in the present invention, and includes at least a layer not containing an inorganic pigment and a layer containing an inorganic pigment on a conductive support. Two undercoat layers, a charge generation layer mainly composed of a charge generation material, a charge transport layer mainly composed of a charge transport material, and at least a trifunctional or higher-functional radical polymerizable monomer having no charge transport structure and 1 A crosslinkable charge transport layer formed by curing a radical polymerizable compound having a functional charge transport structure is sequentially laminated.

Examples of the conductive support include those having a volume resistance of 10 ¹⁰ Ω · cm or less, such as metals such as aluminum, nickel, chromium, nichrome, copper, gold, silver, and platinum, tin oxide, and indium oxide. Metal oxide coated with film or cylindrical plastic or paper by vapor deposition or sputtering, or a plate made of aluminum, aluminum alloy, nickel, stainless steel, etc. After the conversion, a tube subjected to surface treatment such as cutting, superfinishing or polishing can be used. Further, endless nickel belts and endless stainless steel belts disclosed in JP-A-52-36016 can also be used as the conductive support.

  In addition, the conductive support dispersed in a suitable binder resin on the support can be used as the conductive support 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. It is done.

  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.

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

  Next, the undercoat layer will be described. The undercoat layer in the present invention has a configuration in which at least two undercoat layers of a layer containing no inorganic pigment and a layer containing an inorganic pigment are laminated. The role of the undercoat layer is to suppress the injection of reverse polarity charges induced on the conductive support during charging of the photoconductor, to prevent moire, to conceal defects in the tube, and to adhere the photoconductive layer It has many roles such as enhancing sex. In the case of a single undercoat layer, the residual potential tends to increase when charge injection from the conductive support is suppressed, and conversely, if the residual potential is reduced, the soiling is worsened. As a result of functional separation of such a trade-off relationship by forming a plurality of undercoat layers, the scumming suppression effect can be significantly improved without significantly affecting the residual potential.

  First, of the undercoat layer of the present invention, an undercoat layer not containing an inorganic pigment whose main purpose is to suppress charge injection from the conductive support will be described. As a layer for suppressing charge injection, an anodized film typified by an aluminum oxide layer, an inorganic insulating layer typified by SiO, and a metal oxide glass as described in JP-A-3-191361 A layer formed of a quality network, a layer of polyphosphazene as described in JP-A-3-141363, a layer of an aminosilane reaction product as described in JP-A-3-101737, Other examples include a layer made of an insulating binder resin and a layer made of a curable binder resin. Among them, a layer composed of an insulating binder resin or a curable binder resin that can be formed by a wet coating method can be used favorably. Furthermore, since these undercoat layers are laminated with an undercoat layer or a photosensitive layer containing an inorganic pigment thereon, when these are provided by a wet coating method, they are insoluble in the coating solvent. It is important that the coating film is made of a material or composition that does not attack the coating film.

In the present invention, any conventionally known resin may be used as the resin used for the undercoat layer that does not contain an inorganic pigment. Resin is used. Examples of the binder resin include thermoplastic resins such as polyamide, polyester, vinyl chloride-vinyl acetate copolymer, and thermosetting resins such as active hydrogen (hydrogen such as —OH group, —NH ₂ group, and —NH group). A thermosetting resin obtained by thermally polymerizing a compound containing a plurality of compounds and a compound containing a plurality of isocyanate groups and / or a compound containing a plurality of epoxy groups can also be used.

  In this case, examples of the compound containing a plurality of active hydrogens include acrylic resins containing active hydrogen such as polyvinyl butyral, phenoxy resin, phenol resin, polyamide, polyester, polyethylene glycol, polypropylene glycol, polybutylene glycol, and hydroxyethyl methacrylate groups. System resin and the like. Examples of the compound containing a plurality of isocyanate groups include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and prepolymers thereof. Examples of the compound having a plurality of epoxy groups include bisphenol A type epoxy resin. can give. Further, a thermosetting resin obtained by thermally polymerizing an oil-free alkyd resin and an amino resin, for example, a butylated melamine resin, and a polyurethane having an unsaturated bond, a resin having an unsaturated bond such as an unsaturated polyester, A photocurable resin such as a combination with a photopolymerization initiator such as a thioxanthone compound or methylbenzyl formate can also be used as the binder resin.

  In the present invention, among these resins, polyamide is preferable, and N-methoxymethylated nylon is most preferable among them. The polyamide resin has a high effect of suppressing charge injection and has a relatively small influence on the residual potential. These polyamide resins are alcohol-soluble resins, are insoluble in ketone solvents, can form a uniform thin film even in dip coating, and have excellent coating properties. In particular, the undercoat layer needs to be a thin film and requires a uniform film thickness, so that the coatability is important in terms of image quality stability.

  In general, however, alcohol-soluble polyamide resins are highly dependent on humidity, which increases resistance in low humidity environments and increases residual potential.In high humidity environments, resistance decreases and causes a decrease in charge. A big problem was a big problem. Among polyamide resins, N-methoxymethylated nylon is most preferably used because its environmental dependency is greatly reduced and stable image quality can always be maintained even when the use environment of the image forming apparatus changes. It is done. In addition, when N-methoxymethylated nylon is used, the film thickness dependence of the residual potential is small, so that it is possible to reduce the influence on the residual potential and obtain a high scumming suppression effect.

  The substitution rate of the alkoxymethyl group in N-methoxymethylated nylon is not particularly limited, but is preferably 15 mol% or more. If the substitution rate of the alkoxymethyl group is lower than this, the humidity dependency will increase, and when it is used as an alcohol solution, it tends to become cloudy, and the stability over time of the coating solution may slightly decrease. is there.

  In the present invention, N-methoxymethylated nylon can be used alone, but in some cases, a crosslinking agent or an acid catalyst can be added. A commercially available material such as a conventionally known melamine resin or isocyanate resin is used as the crosslinking agent, an acidic catalyst is used as the catalyst, and a general-purpose catalyst such as tartaric acid can be used. However, since the insulating property of the undercoat layer is lowered by the addition of the acid catalyst, and the effect of suppressing soiling may be reduced, the addition amount needs to be very small. The addition amount is preferably 5 wt% or less with respect to the resin. In some cases, other binder resins can be mixed. As a miscible binder resin, a polyamide resin exhibiting alcohol solubility is used, and the stability of the liquid over time may be increased.

  In addition, a conductive polymer, an acceptor resin or a low molecular compound, and other various additives can be added in accordance with the charge polarity, which may be effective in reducing the residual potential. However, when the upper layer is laminated by dip coating, these additives may be dissolved out, so the addition amount needs to be kept to a minimum.

  As a coating solvent, a general organic solvent can be used. In the case of a polyamide-based resin, an alcohol-based solvent such as methanol, ethanol, propanol, butanol, or a mixed solvent thereof is used because it is alcohol-soluble.

  The undercoat layer is applied by a conventionally known dip coating method, spray coating, ring coating, bead coating, nozzle coating method or the like. After coating, the film formation is completed by drying by heating. However, in the case of curing, a curing treatment such as heating or light irradiation can be performed as necessary.

  The thickness of the undercoat layer is suitably from 0.1 μm to less than 2.0 μm, preferably from 0.3 μm to 1.0 μm. If the film thickness of the undercoat layer is larger than that, the residual potential is likely to increase due to repeated charging and exposure, and if the film thickness is too thin, the effect of suppressing scumming is poor.

  Next, the undercoat layer containing an inorganic pigment among the undercoat layers of the present invention will be described. The undercoat layer containing an inorganic pigment is mainly for the purpose of preventing moire, but it prevents charge injection from the conductive support, reduces residual potential increase due to fatigue, reduces dark decay, and enhances adhesion to the photosensitive layer. It also has a function.

  The aforementioned moire is a kind of image defect in which interference fringes called moire are formed in an image due to optical interference inside the photosensitive layer when writing with coherent light such as laser light. Basically, it is necessary to contain a material having a large refractive index in order to prevent the occurrence of moire by scattering the incident laser light by the undercoat layer. In order to prevent moiré, a configuration in which an inorganic pigment is dispersed in a binder resin is most effective. As the inorganic pigment used, a white pigment is effectively used, and metal oxides such as titanium oxide, calcium fluoride, zinc oxide, calcium oxide, silicon oxide, magnesium oxide, aluminum oxide, and tin oxide are good. Used for.

In addition, the undercoat layer preferably has a function of transferring a charge having the same polarity as the charge charged on the surface of the photoreceptor from the photosensitive layer to the conductive support side from the viewpoint of reducing the residual potential. It also plays that role. For example, in the case of a negatively charged type photoreceptor, the residual potential can be greatly reduced because the undercoat layer has electronic conductivity. As these inorganic pigments, the metal oxides described above are effectively used, but the effect of reducing the residual potential by using an inorganic pigment with low resistance or increasing the addition ratio of the inorganic pigment to the binder resin. On the other hand, the effect of suppressing soiling may be reduced. Therefore, it is necessary to achieve both suppression of background contamination and reduction of residual potential by properly using them according to the layer structure and film thickness of the undercoat layer in the photoreceptor and adjusting the addition amount.
Among the inorganic pigments, conductive pigments such as tin oxide are effective for suppressing the occurrence of residual potential, but there is a risk that the influence of background stains will increase. Titanium oxide is most suitable as a pigment that minimizes the effect on residual potential and soiling and has an excellent moire prevention effect.
The inorganic pigment used in the present invention preferably has a high purity in order to reduce an increase in residual potential. The purity is preferably 99.0% or more, more preferably 99.5% or more. The average primary particle size of the inorganic pigment of the present invention is preferably 0.01 μm to 0.8 μm, more preferably 0.05 μm to 0.5 μm. However, when only an inorganic pigment having an average primary particle size of 0.1 μm or less is used, it is effective for reducing background stains, but the moire prevention effect tends to be reduced, while the average primary particle size is When only a metal oxide larger than 0.4 μm is used, although the moire prevention effect is excellent, there is a tendency that the effect of suppressing background stains is slightly reduced. In this case, by mixing and using inorganic pigments having different average primary particle sizes, it may be possible to achieve both reduction of background stains and reduction of moire, and may be effective in reducing residual potential. It is.
In the present invention, when two or more kinds of inorganic pigments having different average primary particle sizes are mixed, the average primary particle size of the inorganic pigment having the largest average primary particle size is D1, and the inorganic pigment having the smallest average primary particle size When the average primary particle size of D2 is D2, it is preferable that the relationship 0.2 <(D2 / D1) ≦ 0.5 is satisfied. As a result, it is possible to achieve both a moire prevention effect and a background stain suppression effect. In this case, the average primary particle diameter D2 of the inorganic pigment having the smallest average primary particle diameter is preferably less than 0.2 μm. As a result, the background dirt suppressing effect is sufficiently exhibited.
In addition, the mixing ratio of two or more inorganic pigments having different average primary particle sizes is T1, the content of the inorganic pigment having the largest average primary particle size, and the content of the inorganic pigment having the smallest average primary particle size. Is T2, it is preferable to satisfy the relationship of 0.2 ≦ T2 / (T1 + T2) ≦ 0.8 by weight. If it is smaller than this, the background stain suppressing effect may be reduced, and if it is larger than this, the moire preventing effect may be reduced.

  Binder resins used in the undercoat layer containing these inorganic pigments include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as polyamide, copolymer nylon, and methoxymethylated nylon, and polyurethane. Curable resins that form a three-dimensional network structure, such as alkyd-melamine resins composed of phenol resins, alkyd resins and melamine resins, and epoxy resins. Among these resins, curable resins are most preferably used because they are hardened so that they are hardly affected by organic solvents when the photosensitive layer is applied onto the undercoat layer. Among the curable resins, alkyd-melamine resins are preferable from the viewpoint of residual potential and environmental stability.

  However, in this case, if the ratio of the main agent and the curing agent is not appropriate, volume shrinkage due to thermal curing is increased, and coating film defects are likely to occur or the residual potential may be increased. In particular, a coating layer defect in the undercoat layer causes charge leakage and promotes the occurrence of black spots and background stains, so care must be taken. Further, as the content of the curing agent increases, the residual potential tends to increase. In the present invention, when an alkyd-melamine resin is used as the resin for the undercoat layer, the content ratio of the alkyd resin to the melamine resin is preferably in the range of 1/1 to 4/1 by weight ratio. Thereby, there is no generation | occurrence | production of a coating-film defect, and it becomes possible to reduce the influence of a residual potential rise.

  The content ratio of the inorganic pigment and the binder resin needs to be adjusted according to the type and layer structure of the inorganic pigment to be used, and the thickness of the undercoat layer not containing the inorganic pigment. The volume ratio between the inorganic pigment and the binder resin is preferably in the range of 1/1 to 3/1. When the volume ratio of the two is less than 1/1, not only the moire prevention ability is lowered, but there is a possibility that the increase of the residual potential in repeated use is increased. On the other hand, in the region where the volume ratio is 3/1 or more, not only the binding ability of the binder resin is lowered, but also the coating film surface property is deteriorated, and the film forming property of the upper layer may be adversely affected. This effect is caused by the fact that the photosensitive layer is a laminated type, and when a thin layer such as a charge generation layer is formed as an upper layer, local charge reduction occurs due to a decrease in the uniformity of the film thickness of the charge generation layer. , There is a risk that the soil dirt suppression effect is reduced. Furthermore, when the volume ratio of the two is 3/1 or more, the coverage with the binder resin on the surface of the inorganic pigment is lowered, and there is a case where it has an adverse effect on soiling due to direct contact with the charge generating substance. .

  The thickness of the undercoat layer containing the inorganic pigment needs to be adjusted according to the type of inorganic pigment used, the layer structure, and the thickness of the undercoat layer not containing the inorganic pigment, but when titanium oxide is used as the inorganic pigment. Is 1 to 10 μm, preferably 2 to 6 μm in order to achieve both soiling and residual potential. If the film thickness is less than 1 μm, the moire prevention effect may decrease or the charge reduction due to fatigue may increase. If the film thickness is more than necessary, the residual potential may increase. When a conductive metal oxide is used for the inorganic pigment, the effect of the residual potential is small even if the film thickness is increased, and 3 to 20 μm, preferably 5 to 15 μm is appropriate. Moreover, in this invention, it is preferable that the film thickness of the undercoat layer containing an inorganic pigment is thicker than the undercoat layer which does not contain an inorganic pigment. As a result, it is possible to suppress a decrease in electrification due to fatigue, and it is effective in suppressing scumming.

  The inorganic pigment can be dispersed together with a solvent and a binder resin by a conventionally known method such as a ball mill, a sand mill, an attritor or the like to obtain a coating liquid. The binder resin may be added before dispersion or as a resin solution after dispersion. Moreover, it is possible and effective to add chemicals, solvents, additives, curing accelerators, and the like necessary for curing (crosslinking) as necessary. Using these coating liquids, they are formed on a conductive substrate using a conventionally known method such as dip coating, spray coating, ring coating, bead coating, or nozzle coating. After the application, it can be produced by drying or heating, and if necessary, drying or curing by a curing treatment such as light irradiation.

  In the present invention, a structure in which the undercoat layer is functionally separated and at least two layers are laminated is used in order to achieve both suppression of background contamination, reduction of residual potential and dark decay due to fatigue, prevention of moire, adhesion of the photosensitive layer, and the like. doing. In this case, two layer structures can be considered depending on whether the undercoat layer containing the inorganic pigment is formed in the upper layer or the lower layer of the undercoat layer not containing the inorganic pigment.

  The former undercoat layer containing an inorganic pigment, which is formed between an undercoat layer that does not contain an inorganic pigment formed on a conductive support and a photosensitive layer, exhibits a high anti-staining effect. However, the effect of charging deterioration due to residual potential rise and fatigue is very small, and the electrostatic stability is excellent. In addition, the adhesion to the photosensitive layer is improved, and the effectiveness is high in enhancing the durability of the photoreceptor. In this case, titanium oxide can be effectively used as the inorganic pigment among the metal oxides described above.

  On the other hand, when the subbing layer containing the latter inorganic pigment is formed between the conductive support and the subbing layer containing no inorganic pigment, the antifouling effect tends to increase slightly. However, the effects of increased residual potential and charging deterioration due to fatigue increase. In order to suppress this, it is possible to significantly increase the addition ratio of the inorganic pigment to the binder resin or to add a conductive inorganic pigment. The inorganic pigment used for this is preferably a conductive pigment such as tin oxide from the viewpoint of residual potential. In the present invention, it has a great effect on suppressing scumming and can be compatible with residual potential due to fatigue and stability over time of chargeability, and further has excellent concealment of defects of the conductive support and adhesion of the photosensitive layer. Therefore, the former configuration is suitable, and the effect of the present invention can be further enhanced.

  Next, the photosensitive layer will be described. The photosensitive layer may be a single-layered photosensitive layer containing a charge generation material and a charge transport material, but as described above, the laminated type composed of the charge generation layer and the charge transport layer is more sensitive, durable, and soiled. It exhibits excellent properties in suppression and is used favorably in the present invention.

  The charge generation layer is a layer mainly composed of a charge generation material. 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, cadmium sulfide, cadmium sulfide-selenium, amorphous silicon, and the like. In amorphous silicon, dangling bonds terminated with hydrogen atoms and halogen atoms, and those doped with boron atoms, phosphorus atoms and the like are preferably used.

  On the other hand, a known material can be used as the organic material. For example, disazo pigments, asymmetric disazo pigments, trisazo pigments, azo pigments having a carbazole skeleton (described in JP-A-53-95033), azo pigments having a distyrylbenzene skeleton (JP-A-53-133445) Azo pigments having a triphenylamine skeleton (described in JP-A-53-132347), azo pigments having a diphenylamine skeleton, and azo pigments having a dibenzothiophene skeleton (described in JP-A-54-21728). ), An azo pigment having a fluorenone skeleton (described in JP-A No. 54-22834), an azo pigment having an oxadiazol skeleton (described in JP-A No. 54-12742), an azo pigment having a bis-stilbene skeleton ( Described in JP-A-54-17733), having a distyryl oxadiazol skeleton Azo pigments such as zo pigments (described in JP-A No. 54-2129), azo pigments having a distyrylcarbazole skeleton (described in JP-A No. 54-14967), azulenium salt pigments, squares Acid methine pigment, perylene pigment, anthraquinone or polycyclic quinone pigment, quinoneimine pigment, diphenylmethane and triphenylmethane pigment, benzoquinone and naphthoquinone pigment, cyanine and azomethine pigment, indigoid pigment, bisbenzimidazole And phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine represented by the following formula:

  In the formula, M (center metal) represents an element of metal and metal free (hydrogen). M (center metal) mentioned here is H, Li, Be, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga , Ge, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, TI , La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa, U, Np, Am, etc., or oxide, chloride It consists of two or more elements such as fluoride, fluoride, hydroxide and bromide. The central metal is not limited to these elements.

  The charge generation material having a phthalocyanine skeleton in the present invention may have at least a basic skeleton of the general formula (N), a substance having a multimeric structure such as a dimer or trimer, and a higher order high-order substance. It may have a molecular structure. Also, the basic skeleton may have various substituents. Of these various phthalocyanines, oxotitanium phthalocyanine having TiO as the central metal, metal-free phthalocyanine, chlorogallium phthalocyanine, and the like are particularly preferable in view of the photoreceptor characteristics.

  These phthalocyanines are known to have various crystal systems. For example, in the case of oxotitanium phthalocyanine, α, β, γ, m, Y type, etc., in the case of copper phthalocyanine, α, β, γ, etc. It has a polycrystal system. Even in the phthalocyanine having the same central metal, various characteristics change as the crystal system changes. It has been reported that the characteristics of photoreceptors using phthalocyanine pigments having these various crystal systems also change accordingly (Electrophotographic Society Vol. 29, No. 4, 1990). For this reason, the selection of the crystal system of phthalocyanine is very important for the characteristics of the photoreceptor, and among these, Y-type oxotitanium phthalocyanine is particularly effective and useful for increasing the sensitivity. These charge generation materials can be used alone or as a mixture of two or more.

  The binder resin used in the charge generation layer as necessary includes polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, and poly-N-vinyl. Examples include carbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, and the like. . The amount of the binder resin used in the charge generation layer 35 is 0 to 500 parts by weight, preferably 0 to 200 parts by weight with respect to 100 parts by weight of the charge generation material. Moreover, various additives, such as leveling agents, a sensitizer, a dispersing agent, etc., such as dimethyl silicone oil and a methylphenyl silicone oil, can be added as needed.

  Examples of the solvent used here include isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, and ligroin. In particular, ketone solvents, ester solvents, and ether solvents are preferably used. These may be used alone or in combination of two or more. The coating liquid for forming the charge generation layer mainly comprises a charge generation substance, a solvent and a binder resin, and any of these additives such as a sensitizer, a dispersant, a surfactant, and silicone oil are included therein. An agent may be included.

  In the charge generation layer, the charge generation material is dispersed in a suitable solvent together with a binder resin as necessary using a ball mill, attritor, sand mill, ultrasonic wave, etc., and this is applied onto a conductive support and dried. Is formed. The binder resin may be added before or after dispersion.

  As a coating method of the coating liquid, methods such as dip coating, spray coating, bead coating, nozzle coating, spinner coating, and ring coating can be used. The thickness of the charge generation layer 35 is suitably about 0.01 to 5 μm, and preferably 0.05 to 2 μm.

  The charge transport layer can be formed by dissolving or dispersing a charge transport material and a binder resin in an appropriate solvent, and applying and drying the solution on the charge generation layer. Moreover, a plasticizer, a leveling agent, antioxidant, etc. can also be added as needed.

  Charge transport materials 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 benzoquinone derivatives.

  Examples of hole transport materials include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, polysilane, oxazole derivatives, Oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazolines Derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, etc., bisstilbene derivatives, enamine derivatives, etc. Other known materials may be mentioned. These charge transport materials may be used alone or in combination of two or more.

  Binder resins include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, poly Vinylidene chloride, polyarylate, 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, phenol Examples thereof include thermoplastic or thermosetting resins such as resins and alkyd resins.

  For the charge transport layer, a polymer charge transport material having both a function as a charge transport material and a function of a binder resin is also preferably used. The charge transport layer composed of these polymer charge transport materials is excellent in wear resistance. As the polymer charge transport material, known materials can be used, and in particular, a polycarbonate containing a triarylamine structure in the main chain and / or side chain is preferably used. Among these, polymer charge transport materials represented by the formulas (I) to (X) are preferably used, and these are exemplified below and specific examples are shown.

In the formula, R ₁ , R ₂ and R ₃ are each independently a substituted or unsubstituted alkyl group or a halogen atom, R ₄ is a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₅ and R ₆ are substituted or unsubstituted. Substituted aryl group, o, p and q are each independently an integer of 0 to 4, k and j are compositions, 0.1 ≦ k ≦ 1, 0 ≦ j ≦ 0.9, and n is the number of repeating units Represents an integer of 5 to 5000. X represents an aliphatic divalent group, a cycloaliphatic divalent group, or a divalent group represented by the following general formula. In the formula (I), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

R ₁₀₁ and R ₁₀₂ each independently represents a substituted or unsubstituted alkyl group, aryl group or halogen atom. l and m are integers of 0 to 4, Y is a single bond, a linear, branched or cyclic alkylene group having 1 to 12 carbon atoms, —O—, —S—, —SO—, —SO ₂ —. , -CO-, -CO-O-Z-O-CO- (wherein Z represents an aliphatic divalent group) or

(A represents an integer of 1 to 20, b represents an integer of 1 to 2000, and R ₁₀₃ and R ₁₀₄ represent a substituted or unsubstituted alkyl group or aryl group). Here, R ₁₀₁ and R ₁₀₂ , and R ₁₀₃ and R ₁₀₄ may be the same or different. )

In the formula, R ₇ and R ₈ represent a substituted or unsubstituted aryl group, and Ar ₁ , Ar ₂ , and Ar ₃ represent the same or different arylene groups. X, k, j and n are the same as in the case of formula (I). In the formula (II), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₉ and R ₁₀ represent a substituted or unsubstituted aryl group, and Ar ₄ , Ar ₅ , and Ar ₆ represent the same or different arylene groups. X, k, j and n are the same as in the case of formula (I). In the formula (III), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₁₁ and R ₁₂ are substituted or unsubstituted aryl groups, Ar ₇ , Ar ₈ and Ar ₉ are the same or different arylene groups, and p represents an integer of 1 to 5. X, k, j and n are the same as in the case of formula (I). In the formula (IV), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₁₃ and R ₁₄ are substituted or unsubstituted aryl groups, Ar ₁₀ , Ar ₁₁ and Ar ₁₂ are the same or different arylene groups, X ₁ and X ₂ are substituted or unsubstituted ethylene groups, or substituted or unsubstituted Represents a substituted vinylene group. X, k, j and n are the same as in the case of formula (I). In the formula (V), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₁₅ , R ₁₆ , R ₁₇ and R ₁₈ are substituted or unsubstituted aryl groups, Ar ₁₃ , Ar ₁₄ , Ar ₁₅ and Ar ₁₆ are the same or different arylene groups, and Y ₁ , Y ₂ and Y ₃ are 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 may be the same or different. X, k, j and n are the same as in the case of the formula (VI). In the formula (VI), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₁₉ and R _{20 each} represent a hydrogen atom or a substituted or unsubstituted aryl group, and R ₁₉ and R ₂₀ may form a ring. Ar ₁₇ , Ar ₁₈ and Ar ₁₉ represent the same or different arylene groups. X, k, j and n are the same as in the case of formula (I). In the formula (VII), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₂₁ represents a substituted or unsubstituted aryl group, and Ar ₂₀ , Ar ₂₁ , Ar ₂₂ , and Ar ₂₃ represent the same or different arylene groups. X, k, j and n are the same as in the case of formula (I). In the formula (VIII), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₂₂ , R ₂₃ , R ₂₄ and R ₂₅ represent substituted or unsubstituted aryl groups, and Ar ₂₄ , Ar ₂₅ , Ar ₂₆ , Ar ₂₇ and Ar ₂₈ represent the same or different arylene groups. X, k, j and n are the same as in the case of formula (I). In the formula (IX), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₂₆ and R ₂₇ represent a substituted or unsubstituted aryl group, and Ar ₂₉ , Ar ₃₀ and Ar ₃₁ represent the same or different arylene groups. X, k, j and n are the same as in the case of formula (I). In the formula (X), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

  The amount of the charge transport material is 20 to 300 parts by weight, preferably 40 to 150 parts by weight, based on 100 parts by weight of the binder resin. The thickness of the charge transport layer is 5 to 100 μm, preferably about 10 to 40 μm.

  As the solvent used here, tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, acetone and the like are used. Among them, it is desirable to use non-halogen solvents for the purpose of reducing environmental burdens. Specifically, cyclic ethers such as tetrahydrofuran, dioxolane and dioxane, aromatic hydrocarbons such as toluene and xylene, and derivatives thereof. However, it is also used favorably in terms of the antifouling effect.

  In the present invention, a plasticizer or a leveling agent may be added to the charge transport layer. As the plasticizer, those used as a plasticizer for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is suitably about 0 to 30% by weight based on the binder resin. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain are used, and the amount used is 0 to 1 with respect to the binder resin. Weight percent is appropriate.

  So far, the case where the photosensitive layer has a laminated structure has been described. However, in the present invention, the photosensitive layer may have a single layer structure. In order to make the photosensitive layer as a single layer, the photosensitive layer is formed by providing a single layer containing at least the above-described charge generating substance and a binder resin, and the binder resin is described in the description of the charge generating layer and the charge transport layer. The listed materials can be used satisfactorily.

  In addition, when a charge transport material is used in combination with the single-layer photosensitive layer, high photosensitivity, high charge transportability, and low residual potential are expressed and can be used favorably. At this time, as the charge transport material to be used, either a hole transport material or an electron transport material is selected according to the polarity charged on the surface of the photoreceptor. Furthermore, since the above-described polymer charge transporting material also has the functions of a binder resin and a charge transporting material, it is favorably used for a single-layer photosensitive layer.

  In the electrophotographic photoreceptor of the present invention, a cross-linked charge transport layer whose main purpose is to improve the abrasion resistance of the photoreceptor is laminated on the outermost surface of the photoreceptor. As a result, it is possible to suppress an increase in electric field strength due to repeated use, which is effective in suppressing scumming. In addition, there is little increase in residual potential, high scratch resistance on the surface of the photoreceptor, and filming and the like are less likely to occur, so it has the effect of reducing the occurrence of image defects and is effective in realizing high durability. Useful.

  The cross-linked charge transport layer reduces the effects of abrasion caused by repeated use of the photoconductor, increases the aging stain stability, and further increases the electrostatic stability and image quality stability to improve aging stability and durability. It is formed for the purpose of achieving both.

  Scratches formed on the surface of the photosensitive member and foreign matters (toner, toner external additives, carrier, paper dust, etc.) adhering to the surface decrease the cleaning property of the photosensitive member and significantly reduce the image quality stability. Therefore, in order to achieve high durability of the photoconductor, it is important not only to increase the wear resistance, but also to minimize the effects of scratches and filming on the surface of the photoconductor. It is preferable to form a highly elastic and smooth surface layer.

  Since the cross-linked charge transport layer formed on the surface of the present invention has a cross-linked structure obtained by curing a tri- or higher functional radical polymerizable monomer, a three-dimensional network structure is developed, and the cross-link density is very high. An elastic surface layer can be obtained, and it is uniform and smooth, and high wear resistance and scratch resistance are achieved. In this way, it is important to increase the crosslink density on the surface of the photoreceptor, that is, the number of crosslink bonds per unit volume. However, since a large number of bonds are instantaneously formed in the curing reaction, internal stress due to volume shrinkage occurs. Since this internal stress increases as the film thickness of the crosslinkable charge transport layer increases, cracks and film peeling tend to occur when the entire charge transport layer is cured. Even if this phenomenon does not appear initially, it may be likely to occur over time due to repeated use in the electrophotographic process and the influence of charging, development, transfer, cleaning hazards and thermal fluctuations.

  As a method for solving this problem, (1) a polymer component is introduced into the crosslinked layer and the crosslinked structure, (2) a large amount of monofunctional and bifunctional radically polymerizable monomers are used, and (3) a flexible group is introduced. Although the directionality which makes a cured resin layer soft, such as using the polyfunctional monomer which has, is mentioned, the crosslink density of a bridge | crosslinking layer becomes thin in any case, and remarkable wear resistance is not achieved. On the other hand, the photoconductor of the present invention is provided with a cross-linked charge transport layer having a high cross-linking density and having a three-dimensional network structure developed on the charge transport layer with a film thickness of 1 μm or more and 10 μm or less. No film peeling occurs and very high wear resistance is achieved. By selecting a film thickness of the crosslinkable charge transport layer of 2 μm or more and 8 μm or less, in addition to further improving the margin for the above problem, a material selection for increasing the crosslink density that leads to further improvement in wear resistance. Is possible.

  The reason why the photoconductor of the present invention can suppress cracking and film peeling is that the cross-linked charge transport layer can be made thin, so that the internal stress does not increase, and since the charge transport layer is provided in the lower layer, the surface of the cross-linked charge transport layer This is because internal stress can be relaxed. For this reason, it is not necessary to contain a large amount of polymer material in the cross-linked charge transport layer, and the polymer material and radical polymerizable composition (radical polymerizable monomer or radical polymerizable compound having a charge transport structure) generated at this time. Scratches and toner filming due to incompatibility with the cured product resulting from this reaction are unlikely to occur.

  Further, when a thick film over the entire charge transport layer is cured by light energy irradiation, light transmission from the absorption by the charge transport structure to the inside is limited, and a phenomenon in which the curing reaction does not proceed sufficiently may occur. In the cross-linked charge transport layer of the present invention, when it is a thin film having a thickness of 10 μm or less, the curing reaction proceeds particularly uniformly to the inside, and high wear resistance tends to be maintained inside as well as the surface. In addition, in the formation of the crosslinkable charge transport layer of the present invention, in addition to the trifunctional radical polymerizable monomer, a radical polymerizable compound having a monofunctional charge transporting structure is contained, which is the trifunctional Incorporated into the cross-linking bond at the time of curing the above radical polymerizable monomer.

  On the other hand, when a low molecular charge transport material having no functional group is contained in the cross-linked surface layer, precipitation of the low molecular charge transport material and white turbidity occur due to its low compatibility, and the cross-linked surface layer The mechanical strength also decreases. On the other hand, when a bifunctional or higher-functional charge transporting compound is used as the main component, the crosslink structure is fixed by a plurality of bonds and the crosslink density is further increased, but the charge transporting structure is very bulky, so that the cured resin structure is distorted. Becomes very large, which increases the internal stress of the cross-linked charge transport layer.

  Furthermore, the photoreceptor of the present invention has good electrical characteristics, and therefore has excellent repeated stability, realizing high durability and high stability. This is because a radically polymerizable compound having a monofunctional charge transporting structure is used as a constituent material of the crosslinkable charge transport layer and is immobilized in a pendant shape between the crosslinks. As described above, the charge transport material having no functional group causes precipitation and clouding phenomenon, and the electrical characteristics are remarkably deteriorated in repeated use such as reduction in sensitivity and increase in residual potential. When a bifunctional or higher-functional charge transporting compound is used as the main component, it is fixed in the crosslinked structure with a plurality of bonds, so the intermediate structure (cation radical) during charge transport cannot be kept stable, Sensitivity decreases due to traps and residual potential increases. Such deterioration of the electric characteristics appears as an image such as a decrease in image density and thinning of characters. Furthermore, in the photoreceptor of the present invention, the high charge mobility design with less charge trapping of the conventional photoreceptor can be applied as the lower charge transport layer, and the electrical side effects of the cross-linked charge transport layer can be minimized. it can.

  Furthermore, in the formation of the crosslinkable charge transport layer of the present invention, the drastic wear resistance is exhibited particularly by making the crosslinkable charge transport layer insoluble in the organic solvent. The cross-linked charge transport layer of the present invention is formed by curing a tri- or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. Although a three-dimensional network structure develops and has a high crosslinking density, it contains from other than the above components (for example, mono- or bifunctional monomers, polymer binders, antioxidants, leveling agents, plasticizers and other additives and lower layers) In some cases, the cross-linking density is locally dilute or the aggregate is formed of fine cured products cross-linked with high density.

  Such a crosslinkable charge transport layer has a weak bonding force between cured products and is soluble in an organic solvent, and is repeatedly used in an electrophotographic process. Elimination is likely to occur. By making the cross-linkable charge transport layer insoluble in an organic solvent as in the present invention, the original three-dimensional network structure is developed and has a high degree of cross-linking, and the chain reaction proceeds in a wide range to obtain a cured product. Since the polymer has a high molecular weight, a dramatic improvement in wear resistance is achieved.

  Next, the constituent materials of the crosslinkable charge transport layer coating solution of the present invention will be described. The trifunctional or higher functional radical polymerizable monomer having no charge transporting property used in the present invention is a hole transporting structure such as triarylamine, hydrazone, pyrazoline, carbazole, such as condensed polycyclic quinone, diphenoquinone, cyano group. And a monomer having no electron transport structure such as an electron-withdrawing aromatic ring having a nitro group and having three or more radical 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. Examples of these radical polymerizable functional groups include 1-substituted ethylene functional groups and 1,1-substituted ethylene functional groups shown below.

(1) 1-Substituted Ethylene Functional Group Examples of the 1-substituted ethylene functional group include functional groups represented by the following formulas.
CH ₂ = CH—X ₁ −... Formula 10
(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 represents an —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) 1,1-Substituted Ethylene Functional Group Examples of the 1,1-substituted ethylene functional group include functional groups represented by the following formulas.
_{CH 2 = C (Y) -X} 2 - ···· formula 11
(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 Ara such phenethyl group, Kill group or substituent a phenyl group which may have a represents an aryl group such as phenyl or naphthyl, 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 and Y include, for example, a halogen atom, a nitro group, an alkyl group such as a cyano group, a methyl group, and an ethyl group, an alkoxy group such as a methoxy group and an ethoxy group, Examples thereof include aryloxy groups such as phenoxy group, aryl groups such as phenyl group and naphthyl group, aralkyl groups such as benzyl group and phenethyl group. Among these radical polymerizable functional groups, acryloyloxy group and methacryloyloxy group are particularly useful, and a compound having three or more acryloyloxy groups is, for example, a compound having three 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 three or more methacryloyloxy groups can be obtained in the same manner. Further, the radical polymerizable functional groups in the monomer having three or more radical polymerizable functional groups may be the same or different.

Specific examples of the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure include the following, but are not limited to these compounds.
That is, examples of the radical polymerizable monomer used in the present invention include trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, trimethylolpropane alkylene-modified triacrylate, trimethylolpropane ethyleneoxy-modified (hereinafter referred to as EO modification). ) 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) Acrylate, glycerol EO modified triacrylate, glycerol PO modified triacrylate, tris (acryloxyethyl) isocyanurate, dipentaerythritol hexaacrylate (DPHA), dipentaerythritol caprolactone modified hexaacrylate, dipentaerythritol hydroxypentaacrylate, alkylated di Pentaerythritol pentaacrylate, alkylated dipentaerythritol tetraacrylate, alkylated dipentaerythritol triacrylate, dimethylolpropane tetraacrylate (DTMPTA), pentaerythritol ethoxytetraacrylate, phosphoric acid EO-modified triacrylate, 2, 2, 5, 5 , -Tetrahydroxymethylcyclopentanone tetraacrylate And the like, which can be used in combination either alone or in combination.

  The trifunctional or higher functional radical polymerizable monomer having no charge transport structure used in the present invention has a molecular weight relative to the number of functional groups in the monomer in order to form a dense crosslink in the crosslinkable charge transport layer. The ratio (molecular weight / functional group number) 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.

Further, the proportion of the trifunctional or higher functional radical polymerizable monomer having no charge transport structure 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. %. 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 is 80% by weight or more, 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.

  The radical polymerizable compound having a monofunctional charge transport structure used in the crosslinked charge transport layer of the present invention is, for example, a hole transport structure such as triarylamine, hydrazone, pyrazoline, carbazole, such as condensed polycyclic quinone. , A compound having an electron transport structure such as diphenoquinone, an electron-withdrawing aromatic ring having a cyano group or a nitro group, and having one radical polymerizable functional group. Examples of the radical polymerizable functional group include those shown in the above radical polymerizable monomer, and acryloyloxy group and methacryloyloxy group are particularly useful. In addition, a triarylamine structure has a high effect 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 Is well maintained.

(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 those represented by the 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 carbazole, dibenzofuran, dibenzothiophene, oxadiazole, and thiadiazole.
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) Group represented by the following general formula

(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.
A vinylene group is represented by the following general formula.

Here, 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, b Represents 1-3.

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.
Further, the radical polymerizable compound having a monofunctional charge transport structure of the present invention is more preferably a compound having a structure of the following general formula (3).

  (Wherein, o, p and q are each an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent a substituent other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, And s and t each represent an integer of 0 to 3. Za represents a single bond, a methylene group, an ethylene group, or a compound represented by the following general formula.)

  As the compound represented by the above general formula, a compound having a methyl group or an ethyl group as a substituent for Rb and Rc is particularly preferable.

  The radically polymerizable compound having a monofunctional charge transport structure represented by the general formulas (1) and (2), particularly (3) used in the present invention is polymerized with the carbon-carbon double bond open on both sides. Therefore, in a polymer that is not a terminal structure but is incorporated in a chain polymer and crosslinked by polymerization with a tri- or higher functional radical polymerizable monomer, it exists in the main chain of the polymer, and Present in the cross-linked chain between the chain and the main chain (this cross-linked chain has an intermolecular cross-linked chain between one polymer and another polymer, and a site where the main chain is folded in one polymer. And other intramolecular cross-linked chains that are cross-linked with other sites derived from the polymerized monomer at positions away from this in the main chain), but even if they are present in the main chain, Even if present, the triarylamine structure suspended from the chain moiety is It has at least three aryl groups arranged in the radial direction and is bulky, but is not directly bonded to the chain part, but is suspended from the chain part via a carbonyl group, etc. Since these triarylamine structures can be arranged adjacent to each other in the polymer, there is little structural distortion in the molecule, and the surface of the electrophotographic photosensitive member is also fixed. In the case of a layer, it is presumed that an intramolecular structure that is relatively free from interruption of the charge transport pathway can be adopted.

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

    Further, the radical polymerizable compound having a monofunctional charge transport structure used in the present invention is important for imparting the charge transport performance of the crosslinked charge transport layer. -80% by weight, preferably 30-70% by weight. If this component is less than 20% by weight, the charge transport performance of the crosslinkable charge transport layer cannot be maintained sufficiently, and deterioration of electrical characteristics such as a decrease in sensitivity and an increase in residual potential will occur with repeated use. On the other hand, if it is 80% by weight or more, the content of the trifunctional monomer having no charge transport structure is lowered, and the crosslink density is lowered, so that 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.

  The crosslinkable charge transport layer of the present invention is obtained by curing at least a trifunctional or higher radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. Monofunctional and bifunctional radically polymerizable monomers and radically polymerizable oligomers are used in combination for the purpose of imparting functions such as viscosity adjustment during coating, stress relaxation of the cross-linked charge transport layer, lower surface energy and reduced friction coefficient. be able to. 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, and neopentyl glycol diacrylate.

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.

  The crosslinked charge transport layer of the present invention is obtained by curing at least a trifunctional or higher radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. Accordingly, a polymerization initiator may be contained in the crosslinking type charge transport layer coating solution in order to allow the curing reaction to proceed efficiently.

  Examples of the thermal polymerization initiator include 2,5-dimethylhexane-2,5-dihydroperoxide, dicumyl peroxide, benzoyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di ( Peroxybenzoyl) hexyne-3, di-t-butyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, lauroyl peroxide, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) B) Peroxide-based initiators such as propane, azo-based compounds such as azobisisobutylnitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 4,4′-azobis-4-cyanovaleric acid Initiators are mentioned.

  Examples of the photopolymerization initiator include diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 4- (2-hydroxyethoxy) phenyl- (2 -Hydroxy-2-propyl) ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2- Acetophenone-based or ketal-based photopolymerization initiators such as methyl-2-morpholino (4-methylthiophenyl) propan-1-one, 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime, Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether Benzoin ether photopolymerization initiators such as benzoin isopropyl ether, benzophenone, 4-hydroxybenzophenone, methyl o-benzoylbenzoate, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoylphenyl ether, acrylated benzophenone, Benzophenone photopolymerization initiators such as 1,4-benzoylbenzene, thioxanthones such as 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone Examples of photopolymerization initiators and other photopolymerization initiators include ethyl anthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoic acid. Phenylethoxyphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,4-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10 -Phenanthrene, an acridine type compound, a triazine type compound, an imidazole type compound is mentioned. Moreover, what has a photopolymerization 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 crosslinkable charge transport layer coating liquid of the present invention is optionally provided with various plasticizers (added for the purpose of stress relaxation and adhesion improvement), leveling agents, and low molecular charge transport materials having no radical reactivity. Such additives can be contained. 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 will be described later with a coating liquid containing at least a trifunctional or higher-functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. It is formed by coating and curing on the charge transport layer. When the radically polymerizable monomer is a liquid, such a 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 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 distortion, a large number of unreacted residues, and reaction termination terminals are generated in the cross-linked charge transport layer. In order to advance the curing reaction uniformly, it is also effective to complete the reaction by heating at a relatively low temperature of less than 100 ° C. and then heating to 100 ° C. or more.

As the energy of light, UV irradiation light sources such as high-pressure mercury lamps and metal halide lamps, which mainly have an emission wavelength in ultraviolet light, can be used, but a visible light source can also be selected according to the absorption wavelength of radically polymerizable substances and photopolymerization initiators. Is possible. Irradiation light amount is 50 mW / cm ² or more, preferably 1000 mW / cm ² or less, it takes time for the curing reaction is less than 50 mW / cm ^2. If it is higher than 1000 mW / cm ^2, the progress of the reaction becomes non-uniform, and 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 effect of radical trapping by oxygen. This effect is noticeable when the surface layer is 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, contaminants spread throughout the layer, which inhibits the curing reaction and lowers the crosslink density. For these reasons, the cross-linkable charge transport layer of the present invention has good wear resistance and scratch resistance at a film thickness of 1 μm or more, but it can be locally scraped to the lower charge transport layer in repeated use. The wear of the portion increases, and the density unevenness of the halftone image tends to occur due to the chargeability and sensitivity fluctuation. Therefore, it is desirable that the film thickness of the crosslinkable charge transport layer be 2 μm or more for a longer life and higher image quality.

  In the present invention, the charge generation layer, the charge transport layer, and the crosslinkable charge transport layer are sequentially laminated. When the outermost crosslinkable charge transport layer is insoluble in the organic solvent, the wear resistance, scratch resistance, It is characterized by achieving sex. As a method for testing the solubility in an organic solvent, a drop of an organic solvent having high solubility in a polymer substance, for example, tetrahydrofuran, dichloromethane, or the like, is dropped on the surface layer of the photoconductor, and the surface shape of the photoconductor is dried after natural drying. It can be determined by observing the change with a stereomicroscope. Dissolving photoconductors have a phenomenon that the central part of the droplet becomes concave and the surroundings swell up, the charge transport material precipitates and becomes cloudy or cloudy due to crystallization, and the surface swells and then shrinks, causing wrinkles Changes such as phenomena are observed. In contrast, an insoluble photoconductor does not exhibit the above-described phenomenon, and does not change at all as before dropping.

  In the configuration of the present invention, in order to make the crosslinkable charge transport layer insoluble in an organic solvent, (1) the composition of the crosslinkable charge transport layer coating solution, adjustment of the content ratio thereof, (2) the crosslinkable charge Dilution solvent of transport layer coating solution, adjustment of solid content concentration, (3) Selection of coating method for crosslinkable charge transport layer, (4) Control of curing conditions for crosslinkable charge transport layer, (5) Lower layer charge It is important to control these, such as making the transport layer difficult to dissolve, but it is not achieved by a single factor.

  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 Tend to be soluble. 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.

  Regarding the diluting solvent of the crosslinkable charge transport layer coating solution, if a solvent with a low evaporation rate is used, the remaining solvent may interfere with curing or increase the amount of the lower layer component mixed, resulting in uneven curing. And the cured density is reduced. For this reason, it tends to be soluble in organic solvents. Specifically, tetrahydrofuran, a mixed solvent of tetrahydrofuran and methanol, ethyl acetate, methyl ethyl ketone, ethyl cellosolve and the like are useful, but are selected according to the coating method.

  Moreover, regarding the solid content concentration, if it is too low for the same reason, it tends to be soluble in an organic solvent. Conversely, the upper limit concentration is constrained by the limitations of film thickness and coating solution viscosity. Specifically, it is desirable to use in the range of 10 to 50% by weight. As the coating method for the cross-linked charge transport layer, for the same reason, the solvent content at the time of forming the coating film, the method of reducing the contact time with the solvent is preferable, specifically, the spray coating method, the amount of coating liquid A ring coat method in which the above is regulated is preferable. In order to suppress the amount of the lower layer component mixed, it is also effective to use a polymer charge transport material as the charge transport layer and to provide an insoluble intermediate layer for the coating solvent for the cross-linked charge transport layer.

  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., 10 minutes to 3 hours, and the curing conditions by UV light irradiation are 50 to 1000 mW / cm 2, 5 seconds to 5 minutes, and It is desirable to control the temperature rise to 50 ° C. or less to suppress non-uniform curing reaction.

In the structure of the present invention, an example of a method for making the crosslinkable charge transport layer insoluble in an organic solvent is, for example, an acrylate monomer having three acryloyloxy groups and a triaryl having one acryloyloxy group as a coating solution. In the case of using an amine compound, the ratio of use is 7: 3 to 3: 7, and a polymerization initiator is added in an amount of 3 to 20% by weight based on the total amount of these acrylate compounds, and a solvent is added to the coating solution. To prepare. For example, in the charge transport layer that is the lower layer of the cross-linked charge transport layer, when the surface layer is formed by spray coating using a triarylamine donor as the charge transport material and polycarbonate as the binder resin, the above coating is used. As the solvent of the liquid, tetrahydrofuran, 2-butanone, ethyl acetate and the like are preferable, and the use ratio is 3 to 10 times the total amount of the acrylate compound.

  Next, for example, the prepared coating solution is applied by spraying or the like on a photoreceptor in which an undercoat layer, a charge generation layer, and the charge transport layer are sequentially laminated on a support such as an aluminum cylinder. Thereafter, it is naturally dried or dried at a relatively low temperature for a short time (25 to 80 ° C., 1 to 10 minutes) and cured by UV irradiation or heating.

For UV irradiation, uses a metal halide lamp, illuminance 50 mW / cm ² or more, 1000 mW / cm ² or less, preferably about 5 minutes 5 seconds as the time, the drum temperature is controlled so as not to exceed 50 ° C. .
In the case of thermosetting, the heating temperature is preferably 100 to 170 ° C. For example, when a blowing oven is used as a heating means and the heating temperature is set to 150 ° C, the heating time is 20 minutes to 3 hours.
After completion of curing, the photosensitive member of the present invention is obtained by further heating at 100 to 150 ° C. for 10 to 30 minutes to reduce the residual solvent.

Next, the image forming apparatus of the present invention will be described in detail with reference to the drawings.
FIG. 3 is a schematic diagram for explaining the image forming process and the image forming apparatus of the present invention, and modifications as described below also belong to the category of the present invention.
In FIG. 4, the photoreceptor 1 has at least two undercoat layers of a layer containing no inorganic pigment and a layer containing an inorganic pigment on a conductive support, and the photosensitive layer and a specific cross-linked charge transport layer. Are laminated. The photosensitive member 1 has a drum shape, but may be a sheet shape or an endless belt shape. The charging roller 3, the pre-transfer charger 7, the transfer charger 10, the separation charger 11, and the pre-cleaning charger 13 are known in the art such as a corotron, a scorotron, a solid state charger, a charging roller, and a transfer roller. Means are used.

  As a charging method, a corona discharge method typified by a conventionally known scorotron, a contact charging method in which a charging roller or a charging brush is brought into contact with a photosensitive member, and a photosensitive member and a charging member in an image forming region are 200 μm or less, preferably A proximity arrangement method (see FIG. 4) having a gap (gap) of 100 μm or less is preferably used. Such a charging method has a defect that dielectric breakdown of the photosensitive member is likely to occur because a high voltage is applied. However, the photosensitive member used in the present invention has a plurality of undercoat layers, and thus has a photosensitive layer. The body's pressure resistance is extremely high. For this reason, the photoconductor is highly resistant to dielectric breakdown, image quality deterioration due to dielectric breakdown is suppressed, and a longer life of the photoconductor is realized. Further, it is possible to superimpose an AC voltage on a DC voltage when a voltage is applied, which is effective in suppressing charging unevenness.

  Although the photosensitive member is charged by such a charging member, in a normal image forming apparatus, since background contamination due to the photosensitive member is likely to occur, the electric field strength applied to the photosensitive member is set to be low ( 40V / μm or less, preferably 30V / μm or less). This is because the occurrence of soiling depends on the electric field strength, and the probability of soiling increases as the electric field strength increases. However, reducing the electric field strength applied to the photoreceptor reduces the efficiency of photocarrier generation and reduces the photosensitivity. In addition, since the electric field strength applied between the surface of the photosensitive member and the conductive support is reduced, the straightness of the photocarrier generated in the photosensitive layer is reduced, and diffusion due to clone repulsion is increased, resulting in a reduction in resolution. Arise. On the other hand, by using the electrophotographic photosensitive member of the present invention, the probability of occurrence of soiling can be extremely reduced, so there is no need to reduce the electric field intensity more than necessary, and it can be used even under an electric field intensity of 40 V / μm or more. become able to. For this reason, a sufficient amount of gain in the attenuation of the photoreceptor light can be secured, a large margin can be created for development (potential) described later, and development can be performed without reducing the resolution.

  For the image exposure unit 5, a light source capable of ensuring high luminance such as a light emitting diode (LED), a semiconductor laser (LD), or electroluminescence (EL) is used. As a light source such as the static elimination lamp 2, general light emitting 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. Among these light sources, light emitting diodes and semiconductor lasers have high irradiation energy and long wavelength light of 600 to 800 nm, so that the above-mentioned phthalocyanine pigment, which is a charge generation material, exhibits high sensitivity and is used well. The Such a light source or the like irradiates the photosensitive member with light by providing a process such as a transfer process, a charge eliminating process, a cleaning process, or a pre-exposure using light irradiation in addition to the process shown in FIG.

  The toner developed on the photoreceptor 1 by the developing unit 6 is transferred to the transfer paper 9, but not all is transferred, and some toner remains on the photoreceptor 1. Such toner is removed from the photoreceptor by the fur brush 14 and the blade 15. Cleaning may be performed only with a cleaning brush, and a known brush such as a fur brush or a mag fur brush is used as the cleaning brush.

When the electrophotographic 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. If this is developed with toner of negative (positive) polarity (electrodetection fine particles), a positive image is obtained, and if developed with toner of positive (negative) polarity, a negative image is obtained. A known method is applied to the developing unit, and a known method is also used for the charge eliminating unit.
The above illustrated electrophotographic process is illustrative of an embodiment of the present invention, and of course other embodiments are possible.

  The image forming means as described above may be fixedly incorporated in a copying apparatus, a facsimile, or a printer, but may be incorporated in these apparatuses in the form of a process cartridge. The process cartridge is a single device (part) that contains a photosensitive member and includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, a charge eliminating unit, and the like. There are many shapes and the like of the process cartridge, but a general example is shown in FIG. The photoreceptor 1 is formed by laminating at least a plurality of undercoat layers, a photosensitive layer, and a specific cross-linked charge transport layer on a conductive support.

  FIG. 6 is a schematic diagram for explaining the tandem-type full-color electrophotographic apparatus of the present invention, and the following modifications also belong to the category of the present invention. In FIG. 6, reference numerals 1C, 1M, 1Y and 1K are drum-shaped photoconductors, and the photoconductor 1 is the photoconductor of the present invention.

  The photoreceptors 1C, 1M, 1Y, and 1K rotate in the direction of the arrow in the drawing, and at least around them, the charging members 2C, 2M, 2Y, and 2K, the developing members 4C, 4M, 4Y, and 4K, the cleaning member 5C, and the like. 5M, 5Y, and 5K are arranged. The charging members 2C, 2M, 2Y, and 2K are charging members that constitute a charging device for uniformly charging the surface of the photoreceptor. Laser light 3C, 3M, 3Y, 3K from an exposure member (not shown) is irradiated from the back side of the photosensitive member between the charging members 2C, 2M, 2Y, 2K and the developing members 4C, 4M, 4Y, 4K, and the photosensitive member. Electrostatic latent images are formed on 1C, 1M, 1Y, and 1K.

  Then, four image forming elements 6C, 6M, 6Y, and 6K centering on such photoreceptors 1C, 1M, 1Y, and 1K are juxtaposed along a transfer conveyance belt 10 that is a transfer material conveyance unit. The transfer conveyance belt 10 contacts the photoreceptors 1C, 1M, 1Y, and 1K between the developing members 4C, 4M, 4Y, and 4K of the image forming units 6C, 6M, 6Y, and 6K and the cleaning members 5C, 5M, 5Y, and 5K. Transfer brushes 11C, 11M, 11Y, and 11K for applying a transfer bias are disposed on a surface (back surface) that is in contact with the back side of the transfer conveyance belt 10 on the photoconductor side. Each of the image forming elements 6C, 6M, 6Y, and 6K is different in the color of the toner inside the developing device, and the others are the same in configuration.

  In the color electrophotographic apparatus having the configuration shown in FIG. 6, the image forming operation is performed as follows. First, in each of the image forming elements 6C, 6M, 6Y, and 6K, the photoreceptors 1C, 1M, 1Y, and 1K are charged by the charging members 2C, 2M, 2Y, and 2K that rotate in the direction of the arrow (the direction along with the photoreceptor). Next, an electrostatic latent image corresponding to each color image to be created is formed by laser beams 3C, 3M, 3Y, and 3K at an exposure unit (not shown) arranged outside the photoreceptor.

  Next, the latent image is developed by developing members 4C, 4M, 4Y, and 4K to form a toner image. The developing members 4C, 4M, 4Y, and 4K are developing members that perform development with toners of C (cyan), M (magenta), Y (yellow), and K (black), respectively, and the four photosensitive members 1C, 1M, and 1Y. , 1K toner images of each color are superimposed on the transfer paper. The transfer paper 7 is sent out from the tray by a paper feed roller 8, temporarily stopped by a pair of registration rollers 9, and sent to the transfer conveyance belt 10 in synchronism with the image formation on the photosensitive member. The transfer paper 7 held on the transfer conveyance belt 10 is conveyed, and the toner images of each color are transferred at the contact positions (transfer portions) with the photoconductors 1C, 1M, 1Y, 1K.

  The toner image on the photoconductor is transferred onto the transfer paper 7 by an electric field formed from a potential difference between the transfer bias applied to the transfer brushes 11C, 11M, 11Y, and 11K and the photoconductors 1C, 1M, 1Y, and 1K. The Then, the recording paper 7 on which the four color toner images are passed through the four transfer portions is conveyed to the fixing device 12, where the toner is fixed, and is discharged to a paper discharge portion (not shown). Further, the residual toner remaining on the photoreceptors 1C, 1M, 1Y, and 1K without being transferred by the transfer unit is collected by the cleaning devices 5C, 5M, 5Y, and 5K.

  In the example of FIG. 6, the image forming elements are arranged in the order of C (cyan), M (magenta), Y (yellow), and K (black) from the upstream side to the downstream side in the transfer paper conveyance direction. However, it is not limited to this order, and the color order is arbitrarily set. Further, when a black-only document is created, it is particularly effective to use the present invention to provide a mechanism for stopping the image forming elements (6C, 6M, 6Y) other than black. Further, in FIG. 6, the charging member is in contact with the photosensitive member, but by using a charging mechanism as shown in FIG. 6, an appropriate gap (about 10-200 μm) is provided between them. In addition, the wear amount of the both can be reduced, and toner filming on the charging member can be reduced and the toner can be used satisfactorily.

  The image forming means as described above may be fixedly incorporated in a copying apparatus, facsimile, or printer, but each electrophotographic element may be incorporated in the apparatus in the form of a process cartridge. The process cartridge is a single device (part) that contains a photosensitive member and includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, a charge eliminating unit, and the like.

Hereinafter, although an example is given and the present invention is explained, the present invention is not restricted by an example. All parts are parts by weight. First, a synthesis example of a compound having a monofunctional charge transport structure used in the present invention will be described.

<Synthesis example of compound having monofunctional charge transport structure>
The compound having a monofunctional charge transport structure in the present invention is synthesized, for example, by the method described in Japanese Patent No. 3164426. An example of this is shown below.
(1) Synthesis of hydroxy group-substituted triarylamine compound (the following structural formula B) 113.85 parts (0.3 mol) of a methoxy group-substituted triarylamine compound (the following structural formula A) and 138 parts of sodium iodide (0. 92 mol) was added 240 parts of sulfolane and heated to 60 ° C. in a nitrogen stream. In this liquid, 99 parts (0.91 mol) of trimethylchlorosilane was added dropwise over 1 hour and stirred at a temperature of about 60 ° C. for 4 and a half hours to complete the reaction. About 1500 parts of toluene was added to the reaction solution, cooled to room temperature, and washed repeatedly with water and an aqueous sodium carbonate solution. Thereafter, the solvent was removed from the toluene solution, and purification was performed by column chromatography (adsorption medium: silica gel, developing solvent: toluene: ethyl acetate = 20: 1). Cyclohexane was added to the obtained pale yellow oil to precipitate crystals. In this way, 88.1 parts (yield = 80.4%) of white crystals of the following structural formula B were obtained.
Its melting point was 64.0-66.0 ° C. The elemental analysis values are shown in Table 1 below.

(2) Triarylamino group-substituted acrylate compound (Exemplary Compound No. 54 in Table 1)
82.9 parts (0.227 mol) of the hydroxy group-substituted triarylamine compound (Structural Formula B) obtained in (1) above is dissolved in 400 parts of tetrahydrofuran, and an aqueous sodium hydroxide solution (NaOH: 12.2. 4 parts, water: 100 parts) was added dropwise. The solution was cooled to 5 ° C., and 25.2 parts (0.272 mol) of acrylic acid chloride was added dropwise over 40 minutes. Then, it stirred at 5 degreeC for 3 hours, and reaction was complete | finished. The reaction solution was poured into water and extracted with toluene. This extract was repeatedly washed with an aqueous sodium bicarbonate solution and water. Thereafter, the solvent was removed from the toluene solution, and purification was performed by column chromatography (adsorption medium: silica gel, developing solvent: toluene). N-Hexane was added to the obtained colorless oil to precipitate crystals. In this way, Exemplified Compound No. 54.73 parts of white crystals (yield = 84.8%) were obtained.
Its melting point was 117.5-119.0 ° C. The elemental analysis values are shown in Table 2 below.

Next, a method for producing an electrophotographic photoreceptor will be described.
<Example 1>
An undercoating layer 1 coating solution, an undercoating layer 2 coating solution, a charge generation layer coating solution, a charge transport layer coating solution and a crosslinkable charge transport layer coating solution having the following composition on an aluminum cylinder having a diameter of 30 mm Are sequentially applied and dried, and a 0.7 μm undercoat layer 1, a 3.5 μm undercoat layer 2, a charge generation layer, a 19 μm charge transport layer, and a 5.0 μm crosslinkable charge transport layer are laminated to form an electron. A photographic photoreceptor was prepared.
This is referred to as an electrophotographic photoreceptor 1. The cross-linked charge transport layer is spray-coated and air-dried for 20 minutes, followed by light irradiation under conditions of a metal halide lamp: 160 W / cm, irradiation intensity: 500 mW / cm 2, irradiation time: 60 seconds. Was cured. After the coating of each layer, after touch drying, the undercoat layer 1 is 130 ° C., the undercoat layer 2 is 130 ° C., the charge generation layer is 130 ° C., the charge transport layer is 130 ° C., and the crosslinked charge transport layer. Was heat-dried at 130 ° C.

(Coating liquid for undercoat layer 1)
N-methoxymethylated nylon (FR101: manufactured by Lead City) 5 parts Methanol 70 parts n-butanol 30 parts

(Coating liquid for undercoat layer 2)
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.25 μm)
60 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 12 parts Melamine resin [Super Becamine L-145-60 (solid content 60%), Dainippon Ink & Chemicals, Inc. 7 parts 2-butanone 70 parts The volume ratio of the inorganic pigment to the binder resin is about 2/1. The weight ratio of the alkyd resin to the melamine resin is about 1.5 / 1.

(Charge generation layer coating solution)
Bisazo pigment of the following structural formula (I) 2.5 parts Polyvinyl butyral (XYHL, manufactured by UCC) 0.5 part Cyclohexanone 200 parts Methyl ethyl ketone 80 parts

(Charge transport layer coating solution)
Polycarbonate (TS2050: manufactured by Teijin Chemicals Ltd.) 10 parts 7 parts of charge transport material having the following structural formula

Tetrahydrofuran 100 parts Silicone oil in tetrahydrofuran (KF-
50 (100 cs): Shin-Etsu Chemical Co., Ltd.) 0.2 parts

(Coating liquid for crosslinkable charge transport layer)
10 parts of a tri- or more functional radical polymerizable monomer having no charge transporting structure (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 a radically polymerizable compound having a monofunctional charge transporting structure (Exemplary Compound No. 54)
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 2 was produced in the same manner as in Example 1 except that the undercoat layer 2 coating solution in Example 1 was changed to a coating solution having the following composition.

(Coating liquid for undercoat layer 2)
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.25 μm)
80 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 14 parts Melamine resin [Super Becamine L-145-60 (solid content 60%), Dainippon Ink & Chemicals, Inc. Made by Industry] 6 parts 2-butanone 90 parts The volume ratio of the inorganic pigment to the binder resin is about 2.5 / 1. The weight ratio of the alkyd resin to the melamine resin is about 2/1.

<Example 3>
In Example 1, an electrophotographic photosensitive member 3 was produced in the same manner as in Example 1 except that the thickness of the undercoat layer 1 was changed to 0.4 μm.

<Example 4>
An electrophotographic photosensitive member 4 was produced in the same manner as in Example 1 except that the thickness of the undercoat layer 1 was changed to 2.0 μm in Example 1.

<Example 5>
In Example 1, the electrophotographic photosensitive member 6 was produced in the same manner as in Example 1 except that the coating liquid for the undercoat layer 2 was changed to the following composition and the film thickness was changed to 6 μm.

(Coating liquid for undercoat layer 2)
Zinc oxide (SAZEX 4000: manufactured by Sakai Chemical Co., Ltd.) 60 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink and Chemicals, Inc.] 14 parts Melamine resin [Super Becamine L-121-60 (solid Min. 60%), manufactured by Dainippon Ink & Chemicals, Inc.] 8 parts 2-butanone 90 parts The volume ratio of the inorganic pigment to the binder resin is about 1.3 / 1. The weight ratio of the alkyd resin to the melamine resin is about 1.5 / 1.

<Example 6>
In Example 5, an electrophotographic photosensitive film was formed in the same manner as in Example 5 except that an undercoat layer 2 having a thickness of 8 μm was formed on a conductive support and an undercoat layer 1 having a thickness of 0.5 μm was formed thereon. A body 6 was produced.

<Comparative Example 1>
In Example 1, an electrophotographic photosensitive member 7 was produced in the same manner as in Example 1 except that the undercoat layer 1 was not formed.

<Comparative example 2>
In Example 1, an electrophotographic photosensitive member 8 was produced in the same manner as in Example 1 except that the undercoat layer 2 was not formed.

<Comparative Example 3>
An electrophotographic photosensitive member 9 was produced in the same manner as in Example 1 except that neither the undercoat layer 1 nor the undercoat layer 2 was formed in Example 1.

<Comparative example 4>
In Example 1, an electrophotographic photoreceptor 10 was produced in the same manner as in Example 1 except that the coating liquid for the undercoat layer 2 was changed to the following composition.

(Coating liquid for undercoat layer 2)
Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 14 parts Melamine resin [Super Becamine L-121-60 (solid content 60%), manufactured by Dainippon Ink & Chemicals, Inc. ] 8 parts 2-butanone 140 parts The inorganic pigment is not added. The weight ratio of alkyd resin to melamine resin is about 1.5 / 1.

<Example 7>
In Example 1, an electrophotographic photosensitive member 11 was produced in the same manner as in Example 1 except that the coating solution for the undercoat layer 1 was changed to one having the following composition.

(Coating liquid for undercoat layer 1)
N-methoxymethylated nylon (FR101: manufactured by Lead City) 5 parts Methanol solution of tartaric acid (solid content 10%) 3 parts Methanol 70 parts n-butanol 30 parts

<Example 8>
In Example 5, an electrophotographic photosensitive member 12 was produced in the same manner as in Example 5 except that the coating solution for the undercoat layer 1 was changed to one having the following composition.

(Coating liquid for undercoat layer 1)
N-methoxymethylated nylon (FR101: manufactured by Lead City) 5 parts Melamine resin [Super Becamine L-145-60 (solid content 60%), manufactured by Dainippon Ink & Chemicals, Inc.) 8 parts Methanol solution of tartaric acid (solid content 10 %) 5 parts methanol 120 parts n-butanol 50 parts

<Example 9>
In Example 1, an electrophotographic photosensitive member 13 was produced in the same manner as in Example 1 except that the coating liquid for the undercoat layer 1 was changed to one having the following composition.

(Coating liquid for undercoat layer 1)
Copolymer nylon (Amilan CM8000: manufactured by Toray) 5 parts Methanol 70 parts n-Butanol 30 parts

<Example 10>
An electrophotographic photoreceptor 14 was produced in the same manner as in the photoreceptor preparation example 13 except that the thickness of the undercoat layer 1 was changed to 0.4 μm in the photoreceptor preparation example 13.

<Example 11>
An electrophotographic photoreceptor 15 was produced in the same manner as in the photoreceptor preparation example 13 except that the thickness of the undercoat layer 1 was changed to 1.1 μm in the photoreceptor preparation example 13.

<Example 12>
In Example 1, a radical polymerizable monomer having a monofunctional charge transporting structure is replaced with the following monomer instead of the trifunctional or higher radical polymerizable monomer having no charge transporting structure contained in the crosslinkable charge transport layer coating solution. The polymerizable compound was exemplified as Compound No. 1. Except for changing to 138 and 10 parts, the electrophotographic photosensitive member 16 was produced in the same manner as in Example 1.
Trifunctional or higher functional radical polymerizable monomer having no charge transporting structure 10 parts Pentaerythritol tetraacrylate (SR-295, manufactured by Kayaku Sartomer)
Molecular weight: 352, number of functional groups: 4 functions, molecular weight / number of functional groups = 88

<Example 13>
In Example 1, the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure contained in the coating liquid for the crosslinkable charge transport layer is replaced with the following monomer, and the film thickness of the crosslinkable charge transport layer is changed. An electrophotographic photosensitive member 17 was produced in the same manner as in Example 1 except that the thickness was 7.0 μm.
Trifunctional or more radical polymerizable monomer having no charge transport structure 10 parts Caprolactone-modified dipentaerythritol hexaacrylate (KAYARAD DPCA-120, manufactured by Nippon Kayaku Co., Ltd.)
Molecular weight: 1947, number of functional groups: 6 functions, molecular weight / number of functional groups = 325

<Example 14>
In Example 1, the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure contained in the coating liquid for the crosslinkable charge transporting layer is changed to the following monomer, and the photopolymerization initiator is changed to the following compound 1 The electrophotographic photosensitive member 18 was produced in the same manner as in Example 1 except that the thickness of the cross-linked charge transport layer was changed to 9.0 μm.
Trifunctional or more radical polymerizable monomer having no charge transport structure 10 parts Caprolactone-modified dipentaerythritol hexaacrylate (KAYARAD DPCA-60, manufactured by Nippon Kayaku Co., Ltd.)
Molecular weight: 1263, number of functional groups: 6 functions, molecular weight / number of functional groups = 211
Photoinitiator 1 part 2,2-Dimethoxy-1,2-diphenylethane-1-one (Irgacure 651, manufactured by Ciba Specialty Chemicals)

<Example 15>
In Example 1, the radically polymerizable compound having a charge transporting structure contained in the coating liquid for the crosslinkable charge transporting layer was converted into a monofunctional exemplified compound No. An electrophotographic photoreceptor 19 was prepared in the same manner as in Example 1 except that 54 and 9 parts and 1 part of a bifunctional compound having the following structure were used and the film thickness of the cross-linked charge transport layer was 6.0 μm.
9 parts of a radically polymerizable compound having a monofunctional charge transporting structure
(Exemplary Compound No. 54)
1 part of radically polymerizable compound having a bifunctional charge transporting structure

<Comparative Example 5>
The trifunctional or higher functional radical polymerizable monomer having no charge transporting structure contained in the coating liquid for the crosslinkable charge transporting layer of Example 1 is converted into a bifunctional radical having no charge transporting structure represented by the following structural formula. An electrophotographic photoreceptor 20 was produced in the same manner as in Example 1 except that the thickness of the cross-linked charge transport layer was changed to 6.0 μm instead of 10 parts of the polymerizable monomer.
Bifunctional radical polymerizable monomer having no charge transporting structure 10 parts 1,6-hexanediol diacrylate (manufactured by Wako Pure Chemical Industries, Ltd.)
Molecular weight: 226, number of functional groups: bifunctional, molecular weight / number of functional groups = 113

<Comparative Example 6>
In Example 1, a radical having a monofunctional charge transporting structure, which is a composition of a coating solution for a crosslinkable charge transporting layer, containing no monofunctional charge transporting structure and having no charge transporting structure is used. An electrophotographic photoreceptor 21 was produced in the same manner as in Example 1 except that the amount of the polymerizable monomer was changed to 20 parts and the film thickness of the cross-linked charge transport layer was changed to 4.5 μm.

<Comparative Example 7>
In Example 1, a radically polymerizable compound having a monofunctional charge transporting structure, which is a composition of a coating liquid for a crosslinkable charge transport layer, is not contained, but instead contained in the charge transport layer coating liquid. An electrophotographic photosensitive member 22 was produced in the same manner as in Example 1 except that 10 parts of the low molecular charge transport material having the following structural formula was contained and the film thickness of the cross-linked charge transport layer was 5.5 μm.

<Example 16>
In Example 1, an electrophotographic photosensitive member 23 was produced in the same manner as in Example 1 except that the charge transport layer coating solution was changed to one having the following composition.

(Charge transport layer coating solution)
Polymer charge transport material having the following composition (weight average molecular weight: about 135000) 10 parts Methylene chloride 100 parts

<Comparative Example 8>
An electrophotographic photosensitive member 24 was prepared in the same manner as in Example 1 except that instead of the cross-linked charge transport layer in Example 1, an inorganic pigment-containing charge transport layer having the following composition was replaced and the film thickness was changed to 6.0 μm. Produced.

(Inorganic pigment-containing charge transport layer coating solution)
Alumina (average primary particle size: 0.4 μm, Sumicorundum AA-03: manufactured by Sumitomo Chemical Co., Ltd.) 2 parts Wetting and dispersing agent (solid content 50%, BYK-P104: manufactured by BYK Chemie) 0.025 parts Polycarbonate (TS2050: Teijin) Kasei Co., Ltd., viscosity average molecular weight: 50,000) 10 parts Charge transport material of the following structural formula 7 parts Cyclohexanone 500 parts Tetrahydrofuran 150 parts

<Comparative Example 9>
In Example 1, the thickness of the charge transport layer was set to 19 μm, and a protective layer coating solution having the following composition was applied and dried on the charge transport layer, and an electron was formed in the same manner as in Example 1 except that a 5 μm protective layer was provided. A photoconductor 25 was produced.

(Protective layer coating solution)
Methyltrimethoxysilane 100 parts 3% acetic acid 20 parts 35 parts of a charge transporting compound having the following structure

<Comparative Example 10>
In Example 1, an electrophotographic photosensitive member 26 was produced in the same manner as in Example 1 except that the thickness of the charge transport layer was 24 μm and the cross-linked charge transport layer provided on the outermost surface was not formed.

<Example 17>
In Example 1, an electrophotographic photosensitive member 27 was produced in the same manner as in Example 1 except that the undercoat layer 1 coating solution was changed to a coating solution having the following composition.
(Coating liquid for undercoat layer 1)
Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 14 parts Melamine resin [Super Becamine L-121-60 (solid content 60%), manufactured by Dainippon Ink & Chemicals, Inc. ] 8 parts 2-butanone 110 parts

<Comparative Example 11>
In Example 1, an electrophotographic photosensitive member 28 was produced in the same manner as in Example 1 except that the undercoat layer 1 coating solution was changed to a coating solution having the following composition.
(Coating liquid for undercoat layer 1)
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.25 μm)
15 parts N-methoxymethylated nylon (FR101: manufactured by Lead City) 5 parts Methanol 70 parts n-Butanol 30 parts

<Example 18>
In Example 1, an electrophotographic photosensitive member 29 was produced in the same manner as in Example 1 except that the undercoat layer 2 coating solution was changed to a coating solution having the following composition.
(Coating liquid for undercoat layer 2)
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.25 μm)
45 parts titanium oxide (PT-401M: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.07 μm)
35 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 16 parts Melamine resin [Super Becamine L-145-60 (solid content 60%), Dainippon Ink & Chemicals, Inc. 9 parts 2-butanone 100 parts The volume ratio of the inorganic pigment to the binder resin is about 2/1. The weight ratio of the alkyd resin to the melamine resin is about 1.5 / 1. D2 / D1 is 0.28, and the mixing ratio of the inorganic pigment is about 0.44.

<Example 19>
An electrophotographic photoreceptor 30 was prepared in the same manner as in Example 1 except that the undercoat layer 2 coating solution in Example 1 was changed to a coating solution having the following composition.
(Coating liquid for undercoat layer 2)
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.25 μm)
40 parts titanium oxide (TTO-F1: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.04 μm)
40 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 16 parts Melamine resin [Super Becamine L-145-60 (solid content 60%), Dainippon Ink & Chemicals, Inc. 9 parts 2-butanone 100 parts The volume ratio of the inorganic pigment to the binder resin is about 2/1. The weight ratio of the alkyd resin to the melamine resin is about 1.5 / 1. D2 / D1 is 0.16, and the mixing ratio of the inorganic pigment is about 0.5.

<Example 20>
An electrophotographic photoreceptor 31 was produced in the same manner as in Example 1 except that the undercoat layer 2 coating solution in Example 1 was changed to a coating solution having the following composition.
(Coating liquid for undercoat layer 2)
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.25 μm)
65 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 14 parts Melamine resin [Super Becamine L-145-60 (solid content 60%), Dainippon Ink & Chemicals, Inc. Made by industry] 13 parts 2-butanone 80 parts The volume ratio of the inorganic pigment to the binder resin is about 1.5 / 1. The weight ratio of alkyd resin to melamine resin is about 0.9 / 1.

<Example 21>
An electrophotographic photosensitive member 32 was produced in the same manner as in Example 1 except that the undercoat layer 2 coating solution in Example 1 was changed to a coating solution having the following composition.
(Coating liquid for undercoat layer 2)
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.25 μm)
50 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 25 parts Melamine resin [Super Becamine L-145-60 (solid content 60%), Dainippon Ink & Chemicals, Inc. Made by Industry] 10 parts 2-butanone 70 parts The volume ratio of the inorganic pigment to the binder resin is about 0.9 / 1. The weight ratio of the alkyd resin to the melamine resin is about 2/1.

<Example 22>
In Example 1, an electrophotographic photosensitive member 33 was produced in the same manner as in Example 1 except that the undercoat layer 2 coating solution was changed to a coating solution having the following composition.
(Coating liquid for undercoat layer 2)
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.25 μm)
125 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 16 parts Melamine resin [Super Becamine L-145-60 (solid content 60%), Dainippon Ink & Chemicals, Inc. 9 parts 2-butanone 140 parts The volume ratio of the inorganic pigment to the binder resin is about 3.1 / 1. The weight ratio of the alkyd resin to the melamine resin is about 1.5 / 1.

<Comparative Example 12>
In Example 1, an electrophotographic photosensitive member 34 was produced in the same manner as in Example 1 except that the undercoat layer 2 coating solution was changed to a coating solution having the following composition.
(Coating liquid for undercoat layer 2)
Organic pigment (silicone resin fine particles: manufactured by Toshiba Silicone Co., Ltd., average primary particle size: about 0.5 μm) 80 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 16 parts Melamine resin [Superbecamine L-145-60 (solid content 60%), manufactured by Dainippon Ink & Chemicals, Inc.] 9 parts 2-butanone 140 parts The volume ratio of the inorganic pigment to the binder resin is about 2/1. The weight ratio of the alkyd resin to the melamine resin is about 1.5 / 1.

<Comparative Example 13>
In Example 6, the electrophotographic process was performed in the same manner as in Example 6 except that the undercoat layer 2 coating solution was changed to a coating solution having the following composition and the thickness of the undercoat layer 2 was changed to 3.0 μm. A photoreceptor 35 was produced.
(Coating liquid for undercoat layer 2)
Alkyd resin [Beckolite M6401-50-S (solid content 50%), manufactured by Dainippon Ink & Chemicals, Inc.] 10 parts Melamine resin [Super Becamine L-145-60 (solid content 60%), manufactured by Dainippon Ink & Chemicals, Inc. ] 6 parts 2-butanone 90 parts No inorganic pigment added. The weight ratio of alkyd resin to melamine resin is about 1.4 / 1.

<Comparative example 14>
In Example 6, the electrophotographic photosensitive film was all treated in the same manner as in Example 6 except that the undercoat layer 1 coating solution was changed to a coating solution having the following composition and the thickness of the undercoat layer 1 was changed to 1.0 μm. A body 36 was produced.
(Coating liquid for undercoat layer 1)
Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: about 0.25 μm)
15 parts N-methoxymethylated nylon (FR101: manufactured by Lead City) 5 parts Methanol 70 parts n-Butanol 30 parts

[Examples 1 to 22, Comparative Examples 1 to 14]
With respect to the electrophotographic photoreceptors 1 to 36 produced as described above, the appearance was visually observed to determine the presence or absence of cracks and film peeling. Next, as a solubility test in an organic solvent, one drop of tetrahydrofuran (hereinafter abbreviated as THF) and dichloromethane (hereinafter abbreviated as MDC) was dropped, and the change in the surface shape after natural drying was observed. The results are shown in Table 3.

  From the results of Table 3, the photoreceptors of the present invention shown in Examples 1 to 22 were free from cracks and film peeling during the formation of the cross-linked charge transport layer, and a photoreceptor having a good appearance was obtained. . On the other hand, in the photoreceptor using the radical polymerizable compound having a bifunctional charge transport structure as the crosslinkable charge transport layer component of Comparative Example 5, cracks occurred when the crosslinkable charge transport layer was formed. Further, when a low molecular charge transport material is contained without containing a radical polymerizable compound having a charge transport structure as in Comparative Example 7, the charge transport material is precipitated and crosslinking is insufficient. I found out. Further, as seen in Comparative Examples 8 and 10, when the surface layer was not cured, it was confirmed that both showed solubility.

Further, the electrophotographic photosensitive members 1 to 36 of Examples 1 to 22 and Comparative Examples 1 to 14 produced as described above were mounted on a process cartridge and set in a tandem type full color laser printer remodeling machine. As the image exposure light source, a 655 nm semiconductor laser (image writing by a polygon mirror) was used, and the charging member was placed close to the photoreceptor by winding a 50 μm thick insulating tape around the non-image forming regions at both ends of the charging roller. At that time, the DC bias was 750 (−V), the AC bias (Vpp (Peak to peak): 1.8 kV, frequency: 900 Hz) was superimposed, and the developing bias was 500 (−V). The process cartridge loaded with each photoconductor sample is filled with the same developer, set in the cyan station, magenta station, cyan station, and black station, and a total of 100,000 images while rotating the station every 10,000 sheets. Output was repeated and image evaluation was then performed. The test environment was 23 ° C. and 60% RH. The level of image evaluation was expressed in the following four stages.
A: Very good level B: Slight image quality degradation but no problem Δ: Level where image defects are clearly recognized ×: Image defect is greatly affected and image quality is very bad.
The amount of wear was calculated from the difference in film thickness before and after the test. These results are shown in Tables 4-1 and 4-2.

  The electrophotographic photosensitive member of the present invention has high wear resistance even after printing on 100,000 sheets, maintains good image quality with little background contamination, and has good cleaning properties, filming and There were no side effects such as image flow. On the other hand, when the undercoat layer is a single layer, or when the undercoat layer is not formed, or when any of the undercoat layers contains an inorganic pigment, the durability of scumming is greatly reduced. On the other hand, when no inorganic pigment was contained in any of the undercoat layers, moire was generated from the beginning, or the image density was lowered due to a significant increase in the potential of the exposed area, resulting in image quality deterioration. In the cross-linked charge transport layer of the outermost surface layer, a bifunctional radical polymerizable monomer may be used instead of a trifunctional radical polymerizable monomer having no charge transport structure, or a monofunctional charge transport structure. In the case where a low molecular charge transporting material was contained instead of the radically polymerizable compound having, the wear resistance was greatly reduced, and the occurrence of scumming was noticeable. Furthermore, when the radically polymerizable compound having a monofunctional charge transporting structure was not contained, the exposed portion potential was significantly increased and the image density was lowered. In the present invention, a subbing layer comprising at least two layers of an inorganic pigment-containing layer and a non-containing layer, and a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure on the outermost surface; Combining a cross-linked charge transport layer obtained by curing a radically polymerizable compound having a monofunctional charge transport structure can suppress scumming and improve wear resistance, and can also provide filming and cleaning. An electrophotographic photosensitive member capable of stably obtaining a high-quality image over a long period of time without occurrence of image defects such as defects and adhesion of foreign matter, and an image forming apparatus using the same are realized.

  The photoconductor of the present invention can suppress the occurrence of background stains even after repeated use over a long period of time, and there is very little change in the exposure portion potential with time, and image defects such as image flow and filming can also occur. Since the image quality can be suppressed and a high-quality image can be output stably over a long period of time, it is possible to reduce the size and speed of the image forming apparatus. In particular, it can be effectively used for a tandem-type full-color image forming apparatus and a high-speed image forming apparatus that require high durability and image stability.

It is sectional drawing which shows an example of the laminated constitution of the electrophotographic photoreceptor of this invention. It is a figure which shows an example of the laminated constitution of the electrophotographic photoreceptor of this invention. It is the schematic for demonstrating the image formation process by the image forming apparatus of this invention. 1 is a schematic diagram for explaining an image forming apparatus of the present invention. It is a figure which shows an example of a structure of the process cartridge of this invention. 1 is a diagram illustrating an example of a configuration of a tandem full-color electrophotographic apparatus according to the present invention.

Explanation of symbols

(About FIGS. 1-5)
DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Static elimination lamp 3 Charging roller 5 Image exposure part 6 Developing unit 7 Pre-transfer charger 8 Registration roller 9 Transfer paper 10 Transfer charger 11 Separation charger 12 Separation claw 13 Pre-cleaning charger 14 Fur brush 15 Cleaning brush 21 Gap formation member 22 Metal shaft 23 Image forming area 24 Non-image forming area 101 Photoconductor 102 Charging means 103 Exposure means 104 Developing means 105 Transfer means 106 Transfer means 107 Cleaning means (about FIG. 6)
1C, 1M, 1Y, 1K Photoconductor 2C, 2M, 2Y, 2K Charging member 3C, 3M, 3Y, 3K Laser beam 4C, 4M, 4Y, 4K Developing member 5C, 5M, 5Y, 5K Cleaning member 6C, 6M, 6Y , 6K image forming element 10 transfer conveying belt 11C, 11M, 11Y, 11K transfer brush 12 fixing device

Claims (34)

  In an electrophotographic photosensitive member in which at least an undercoat layer, a photosensitive layer, and a crosslinkable charge transport layer are sequentially laminated on a conductive support, the undercoat layer contains a layer containing an inorganic pigment and no inorganic pigment. A cross-linkable charge transporting layer which cures at least a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure and a radical polymerizable compound having a monofunctional charge transporting structure. An electrophotographic photosensitive member formed by the method described above.   2. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer has a laminated structure in which a charge generation layer and a charge transport layer are sequentially laminated.   3. The electrophotographic photosensitive member according to claim 1, wherein a polyamide resin is contained in a layer that does not contain an inorganic pigment among the undercoat layer.   The electrophotographic photosensitive member according to claim 3, wherein the polyamide resin is N-methoxymethylated nylon.   The electrophotographic photosensitive member according to claim 4, wherein the N-methoxymethylated nylon is crosslinked by heating.   The electrophotographic photosensitive member according to any one of claims 1 to 5, wherein a thickness of a layer not containing an inorganic pigment in the undercoat layer is less than 2.0 µm.   The electrophotographic photosensitive member according to claim 1, wherein a metal oxide is contained as an inorganic pigment in a layer containing an inorganic pigment among the undercoat layer.   The electrophotographic photosensitive member according to claim 7, wherein the metal oxide is titanium oxide.   The inorganic pigment is a mixture of two or more kinds of inorganic pigments having different average primary particle sizes, the average primary particle size of the inorganic pigment having the largest average primary particle size is D1, and the inorganic pigment having the smallest average primary particle size The electrophotographic photosensitive member according to claim 1, wherein a relationship of 0.2 <(D2 / D1) ≦ 0.5 is satisfied, where D1 is an average primary particle size.   The electrophotographic photosensitive member according to claim 9, wherein the D2 is less than 0.2 μm.   The mixing ratio of two or more kinds of inorganic pigments having different average primary particle diameters is T1, the content of the inorganic pigment having the largest average primary particle diameter is T1, and the content of the inorganic pigment having the smallest average primary particle diameter is T2. 11. The electrophotographic photosensitive member according to claim 9, wherein a weight ratio satisfies a relationship of 0.2 ≦ T2 / (T1 + T2) ≦ 0.8.   The electrophotographic photoreceptor according to claim 1, wherein a layer containing an inorganic pigment in the undercoat layer contains a thermosetting resin as a binder resin.   The electrophotographic photosensitive member according to claim 12, wherein the thermosetting resin comprises an alkyd resin and a melamine resin.   The electrophotographic photosensitive member according to claim 13, wherein a weight ratio of the alkyd resin to the melamine resin is in a range of 1/1 to 4/1.   The volume ratio between the inorganic pigment and the binder resin contained in the layer containing the inorganic pigment is in a range of 1/1 to 3/1. Electrophotographic photoreceptor.   The film thickness of the layer which contains an inorganic pigment among the said undercoat layers is larger than the film thickness of the layer which does not contain an inorganic pigment, The Claim 1 characterized by the above-mentioned. Electrophotographic photoreceptor.   The layer which does not contain an inorganic pigment among the undercoat layers is directly formed on a conductive support, and a layer containing an inorganic pigment is laminated thereon. The electrophotographic photosensitive member according to any one of 16.   The electrophotographic photosensitive member according to claim 1, wherein the crosslinkable charge transport layer is insoluble in an organic solvent.   The functional group of a tri- or higher functional radical polymerizable monomer having no charge transport structure used in the cross-linked charge transport layer is an acryloyloxy group and / or a methacryloyloxy group. The electrophotographic photosensitive member according to any one of the above.   The ratio of the molecular weight to the number of functional groups (molecular weight / number of functional groups) in a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure used for the crosslinkable charge transporting layer is 250 or less. The electrophotographic photosensitive member according to any one of 1 to 19.   21. The functional group of the radical polymerizable compound having a monofunctional charge transport structure used for the cross-linked charge transport layer is an acryloyloxy group or a methacryloyloxy group. The electrophotographic photosensitive member described.   The charge transport structure of the radical polymerizable compound having a monofunctional charge transport structure used for the cross-linked charge transport layer is a triarylamine structure. Electrophotographic photoreceptor. The radical polymerizable compound having a monofunctional charge transporting structure used in the cross-linked charge transporting layer is at least one compound represented by the following general formula (1) or (2). The electrophotographic photosensitive member according to claim 1.

(Wherein R ₁ is 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 represents 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 Ali substituted or unsubstituted X may be the same or different, and X is 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, sulfur An atom and a vinylene group, Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, and an alkyleneoxycarbonyl divalent group, m and n represent an integer of 0 to 3.) The radical polymerizable compound having a monofunctional charge transport structure used in the cross-linked charge transport layer is at least one compound represented by the following general formula (3). 24. The electrophotographic photosensitive member according to any one of 23.

(Wherein, o, p and q are each an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent a substituent other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, And s and t each represents an integer of 0 to 3. Za is a single bond, a methylene group, an ethylene group,

Represents. )   The proportion of the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure used in the crosslinkable charge transport layer is 30 to 70% by weight based on the total amount of the crosslinkable charge transport layer. Item 25. The electrophotographic photosensitive member according to any one of Items 1 to 24.   2. The component ratio of the radical polymerizable compound having a monofunctional charge transporting structure used in the crosslinkable charge transport layer is 30 to 70% by weight based on the total amount of the crosslinkable charge transport layer. The electrophotographic photosensitive member according to any one of ˜25.   27. The electrophotographic photosensitive member according to claim 1, wherein the crosslinking type charge transport layer is cured by heating or light energy irradiation means.   An image forming method, wherein at least charging, image exposure, development, and transfer are repeated using the electrophotographic photosensitive member according to claim 1.   28. An image forming apparatus comprising at least a charging unit, an exposing unit, a developing unit, a transfer unit, and an electrophotographic photosensitive member, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to any one of claims 1 to 27. An image forming apparatus, comprising:   30. The image forming apparatus according to claim 29, wherein a plurality of image forming elements comprising at least charging means, exposure means, developing means, transfer means, and electrophotographic photosensitive member are arranged.   31. The image forming apparatus according to claim 29, wherein an AC superimposed voltage is applied to a charging unit used in the image forming apparatus.   An image forming apparatus comprising at least a charging unit, an exposing unit, a developing unit, a transfer unit, and an electrophotographic photosensitive member, wherein the linear velocity of the photosensitive member during image formation is 250 mm / sec or more. Item 32. The image forming apparatus according to any one of Items 29 to 31.   The image forming apparatus includes a process cartridge for an image forming apparatus in which at least an electrophotographic photosensitive member and at least one means selected from a charging unit, an exposure unit, a developing unit, and a cleaning unit are integrated. 33. The image forming apparatus according to claim 29, wherein the process cartridge for the apparatus is detachable from the apparatus main body. A process cartridge for an image forming apparatus comprising at least an electrophotographic photosensitive member, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to any one of claims 1 to 27. .

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