Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus

The present invention relates to an electrophotographic photosensitive member and a method for producing the same, and a process cartridge and electrophotographic apparatus each using the electrophotographic photosensitive member.

For electrophotographic photosensitive members to be installed in a process cartridge or electrophotographic apparatus, electrophotographic photosensitive members containing an organic photoconductive material (charge generating material) are used. An electrophotographic photosensitive member generally includes a support and a photosensitive layer formed on the support.

For a photosensitive layer, a laminated photosensitive layer in which a charge transport layer containing a charge transporting material is laminated on a charge generation layer containing a charge generating material is suitably used.

An electrophotographic apparatus with a longer product life has been demanded in recent years, and hence it is desired to provide an electrophotographic photosensitive member having enhanced abrasion resistance to mechanical force and potential variation-suppressing effect to electric force in combination. To enhance the abrasion resistance, a protective layer is occasionally provided on a charge transport layer. For a protective layer, a cured material of a composition having a polymerizable functional group which is polymerized through external energy such as heat, light (e.g., ultraviolet rays) and radiation (e.g., electron beams) is suitably used.

However, adverse effects due to the presence of a protective layer are problematic, and to solve the problem various examinations have been made on polycarbonate resins to be used for a charge transport layer. Japanese Patent Application Laid-Open No. H06-011877 discloses a technique in which a particular polycarbonate resin is used as a countermeasure to cracks to be generated between a protective layer and a photosensitive layer in formation of the protective layer. Japanese Patent Application Laid-Open No. 2011-107363 discloses a technique in which a particular polycarbonate resin is used for reduction of image unevenness.

The present inventors conducted examination, and the results revealed that the polycarbonate resins described in Japanese Patent Application Laid-Open No. H06-011877 and Japanese Patent Application Laid-Open No. 2011-107363 may have insufficient potential variation-suppressing effect, and leave room for further improvement.

The present invention is directed to providing an electrophotographic photosensitive member with suppressed potential variation even in the case that a protective layer including a cured material of a composition having a polymerizable functional group is used, and a method for producing the electrophotographic photosensitive member. Further, the present invention is directed to providing a process cartridge and electrophotographic apparatus each including the electrophotographic photosensitive member.

The above objects are achieved by the present invention. Specifically, according to one aspect of the present invention, there is provided an electrophotographic photosensitive member comprising a support, a charge generation layer, a charge transport layer containing a charge transporting material, and a protective layer, in the order presented, wherein the charge transport layer contains a polycarbonate resin having a structure selected from a group A below and a structure selected from a group B below, and the protective layer includes a cured material of a composition containing a compound having at least a functional group selected from chain-polymerizable functional groups and sequential polymerizable functional groups.

Examples of the structure selected from a group A include structures represented by the following formulas (101) and (102).

In the formula (101), R 211 to R 214 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; R 215 represents an alkyl group, an aryl group, or an alkoxy group; R 216 and R 217 each independently represent an alkyl group having one to nine carbon atoms; and i1 represents an integer of 0 to 3, provided that R 215 and (CH 2 ) i1 CHR 216 R 217 are not the same.

In the formula (102), R 221 to R 224 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; R 225 and R 226 each independently represent an alkyl group having one to nine carbon atoms, provided that R 225 and R 226 are not the same; and i2 represents an integer of 0 to 3.

Examples of the structure selected from a group B include structures represented by the following formula (104), formula (105) and formula (106).

In the formula (104), R 241 to R 244 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; and X represents a single bond, an oxygen atom, a sulfur atom, or a sulfonyl group.

In the formula (105), R 251 to R 254 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; and R 256 and R 257 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a halogenated alkyl group.

In the formula (106), R 261 to R 264 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; and W represents a cycloalkylidene group having 5 to 12 carbon atoms.

Alternatively, the above objects are achieved by the present invention in the following. Specifically, according to another aspect of the present invention, there is provided an electrophotographic photosensitive member comprising a support, a charge generation layer, a charge transport layer containing a charge transporting material, and a protective layer, in the order presented, wherein the charge transport layer contains a polycarbonate resin having a structure represented by a formula (121) below and a structure represented by the formula (104), and the protective layer includes a cured material of a composition containing a compound having at least a functional group selected from chain-polymerizable functional groups and sequential polymerizable functional groups.

In the formula (121), R 11 to R 15 each independently represent a hydrogen atom, a methyl group, an ethyl group, or a phenyl group; and R 16 represents a linear alkyl group having 6 to 15 carbon atoms.

According to the present invention, an electrophotographic photosensitive member with suppressed potential variation even in the case that a protective layer including a cured material of a composition having a polymerizable functional group is used can be provided through use of a particular polycarbonate resin for a charge transport layer.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawing.

FIGURE is a diagram illustrating one example of the schematic configuration of an electrophotographic apparatus including a process cartridge including an electrophotographic photosensitive member according to the present invention.

Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawing.

Hereinafter, the present invention will be described in detail with reference to exemplary embodiments. The present inventors conducted examination, and found that use of an electrophotographic photosensitive member including a charge transport layer containing a particular polycarbonate resin enables achievement of enhancement of the abrasion resistance and potential variation-suppressing effect in combination, even in the case that a protective layer including a cured material of a composition having a polymerizable functional group is used. Specifically, the electrophotographic photosensitive member according to the present invention is an electrophotographic photosensitive member including a support, a charge generation layer, a charge transport layer containing a charge transporting material, and a protective layer, in the order presented, wherein the charge transport layer contains a polycarbonate resin having a structure selected from a group A below and a structure selected from a group B below, and the protective layer includes a cured material of a composition containing a compound having at least a functional group selected from chain-polymerizable functional groups and sequential polymerizable functional groups.

Examples of the structure selected from a group A include structures represented by the following formulas (101) and (102).

In the formula (101), R 211 to R 214 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; R 215 represents an alkyl group, an aryl group, or an alkoxy group; R 216 and R 217 each independently represent a substituted or unsubstituted alkyl group having one to nine carbon atoms; and i1 represents an integer of 0 to 3, provided that R 215 and (CH 2 ) i1 CHR 216 R 217 are not the same.

In the formula (102), R 221 to R 224 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; R 225 and R 226 each independently represent a substituted or unsubstituted alkyl group having one to nine carbon atoms, provided that R 225 and R 226 are not the same; and i2 represents an integer of 0 to 3.

Examples of the structure selected from a group B include structures represented by the following formula (104), formula (105) and formula (106).

In the formula (104), R 241 to R 244 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; and X represents a single bond, an oxygen atom, a sulfur atom, or a sulfonyl group.

In the formula (105), R 251 to R 254 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; R 256 and R 257 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a halogenated alkyl group; and the aryl group may be substituted with an alkyl group, an alkoxy group, or a halogen atom.

In the formula (106), R 261 to R 264 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; W represents a cycloalkylidene group having 5 to 12 carbon atoms; and the cycloalkylidene group may be substituted with an alkyl group.

Specifically, the electrophotographic photosensitive member according to the present invention is an electrophotographic photosensitive member including a support, a charge generation layer, a charge transport layer containing a charge transporting material, and a protective layer, in the order presented, wherein the charge transport layer contains a polycarbonate resin having a structure represented by a formula (121) below and a structure represented by the formula (104), and the protective layer includes a cured material of a composition containing a compound having at least a functional group selected from chain-polymerizable functional groups and sequential polymerizable functional groups.

In the formula (121), R 11 to R 15 each independently represent a hydrogen atom, a methyl group, an ethyl group, or a phenyl group; and R 16 represents a linear alkyl group having 6 to 15 carbon atoms.

Examples of methods for synthesizing a polycarbonate resin having a structure selected from the group A and a structure selected from the group B include the following two methods. The first method is a method in which at least one bisphenol compound selected from formulas (107) and (108) below and at least one bisphenol compound selected from formulas (110) to (112) below are directly reacted with phosgene (phosgene method). The second method is a method in which the at least two bisphenol compounds mentioned above are subjected to transesterification reaction with a bisaryl carbonate such as diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-tolyl carbonate, di-p-chlorophenyl carbonate, and dinaphthyl carbonate (transesterification method).

The same is applied to the method for synthesizing a polycarbonate resin having the structure represented by the formula (121) and the structure represented by the formula (104).

In the phosgene method, the above-mentioned at least two bisphenol compounds and phosgene are reacted typically in the presence of an acid-binding agent and a solvent. Examples of the acid-binding agent therefor include pyridine and hydroxides of alkali metal such as potassium hydroxide and sodium hydroxide. Examples of the solvent include methylene chloride and chloroform. Further, a catalyst or a molecular weight modifier may be appropriately added to promote condensation polymerization reaction. Examples of the catalyst include tertiary amines such as triethylamine and quaternary ammonium salts. Examples of the molecular weight modifier include monofunctional compounds such as phenol, p-cumylphenol, t-butylphenol, and long-chain alkyl-substituted phenols.

In synthesizing a polycarbonate resin, an antioxidant such as sodium sulfite and hydrosulfite; or a branching agent such as phloroglucin and isatinbisphenol may be used. The reaction temperature in synthesizing a polycarbonate resin is preferably 0 to 150° C., and more preferably 5 to 40° C. The reaction time depends on the reaction temperature. However the reaction time is preferably 0.5 minutes to 10 hours, and more preferably 1 minute to 2 hours in typical cases. The pH of the reaction system can be set to 10 or higher during reaction.

Specific examples of bisphenol compounds to be used for the synthesis are as follows.

(1) At least one bisphenol compound selected from formulas (107) and (108)

In the formula (107), R 211 to R 214 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; R 215 represents an alkyl group, an aryl group, or an alkoxy group; R 216 and R 217 each independently represent a substituted or unsubstituted alkyl group having one to nine carbon atoms; and i1 represents an integer of 0 to 3, provided that R 215 and (CH 2 ) i1 CHR 216 R 217 are not the same.

In the formula (108), R 221 to R 224 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; R 225 and R 226 each independently represent a substituted or unsubstituted alkyl group having one to nine carbon atoms, provided that R 225 and R 226 are not the same; and i2 represents an integer of 0 to 3.

Specific examples of bisphenol compounds represented by the formulas (107) and (108) include 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,2-bis(4-hydroxyphenyl)-5-methylhexane, 3,3-bis(4-hydroxyphenyl)-5-methylheptane, 2,2-bis(4-hydroxyphenyl)-3-methylbutane, 1,1-bis(4-hydroxyphenyl)-1-phenyl-2-methylpropane, 1,1-bis(4-hydroxyphenyl)-1-phenyl-3-methylbutane, 2,2-bis(4-hydroxyphenyl)-6-methylheptane, 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, and 1,1-bis(4-hydroxyphenyl)-1-phenyl-2-methylpentane. Two or more of these bisphenol compounds can be used in combination.

(2) At least one bisphenol compound selected from formulas (110) to (112)

In the formula (110), R 241 to R 244 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; and X represents a single bond, an oxygen atom, a sulfur atom, or a sulfonyl group.

In the formula (111), R 251 to R 254 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; R 256 and R 257 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a halogenated alkyl group; and the aryl group may be substituted with an alkyl group, an alkoxy group, or a halogen atom.

In the formula (112), R 261 to R 264 each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group; W represents a cycloalkylidene group having 5 to 12 carbon atoms; and the cycloalkylidene group may be substituted with an alkyl group.

Specific examples of bisphenol compounds represented by the formulas (110) to (112) include 4,4′-dihydroxybiphenyl, 4,4′-dihydroxy-3,3′-dimethylbiphenyl, 4,4′-dihydroxy-2,2′-dimethylbiphenyl, 4,4′-dihydroxy-3,3′,5-trimethylbiphenyl, 4,4′-dihydroxy-3,3′,5,5′-tetramethylbiphenyl, 4,4′-dihydroxy-3,3′-dibutylbiphenyl, 4,4′-dihydroxy-3,3′-dicyclohexylbiphenyl, 3,3′-difluoro-4,4′-dihydroxybiphenyl, 4,4′-dihydroxy-3,3′-diphenylbiphenyl, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(3-methyl-4-hydroxyphenyl)ethane, 1,1-bis(3-fluoro-4-hydroxyphenyl)ethane, 1,1-bis(2-tert-butyl-4-hydroxy-3-methylphenyl)ethane, 1,2-bis(4-hydroxyphenyl)ethane, 1,2-bis(3-methyl-4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane, 2,2-bis(3-phenyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(3-fluoro-4-hydroxyphenyl)propane, 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 2,2-bis(3-bromo-4-hydroxyphenyl)propane, 2,2-bis(3,5-difluoro-4-hydroxyphenyl)propane, 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 2,2-bis(2-tert-butyl-4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxyphenyl) hexafluoropropane, 2,2-bis(3-methyl-4-hydroxyphenyl)hexafluoropropane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl) hexafluoropropane, 2,2-bis(3-phenyl-4-hydroxyphenyl)hexafluoropropane, 2,2-bis(3-fluoro-4-hydroxyphenyl) hexafluoropropane, 2,2-bis(3-chloro-4-hydroxyphenyl)hexafluoropropane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(3-cyclo-4-hydroxyphenyl)cyclohexane, 1,1-bis(3-phenyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(3-fluoro-4-hydroxyphenyl)cyclohexane, 1,1-bis(3-chloro-4-hydroxyphenyl)cyclohexane, 1,1-bis(3-bromo-4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-difluoro-4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-dichloro-4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-dibromo-4-hydroxyphenyl)cyclohexane, 1,1-bis(2-tert-butyl-4-hydroxy-3-methylphenyl)cyclohexane, bis(4-hydroxyphenyl)sulfone, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bis(4-hydroxyphenyl)diphenylmethane, 9,9-bis(4-hydroxyphenyl)-fluorene, and 2,2-bis(4-hydroxyphenyl)butane. Two or more of these bisphenol compounds can be used in combination.

The present inventors infer that the reason why the potential variation is suppressed through use of an electrophotographic photosensitive member in which the charge transport layer contains a polycarbonate resin having a structure selected from the group A and a structure selected from the group B and the protective layer includes a cured material of a composition containing a compound having at least a functional group selected from chain-polymerizable functional groups and sequential polymerizable functional groups is as follows.

A coating solution for a protective layer is applied onto a charge transport layer provided above a support and a charge generation layer, and a protective layer is then formed through external energy such as heat, light (e.g., ultraviolet rays) and radiation (e.g., electron beams). The protective layer is converted to a cured material through bonding between polymerizable functional groups, where the film density increases, and thereby a stress is presumably left in the layer. The residual stress acts on the interface between the charge transport layer and the protective layer. Mechanical and electric force continuously applied to the electrophotographic photosensitive member by electrophotographic process including a charging unit, a developing unit, a transferring unit, and a cleaning unit through long-term, repeated use may generate a minute detached portion in the interface between the charge transport layer and the protective layer to cause an image defect such as a spot on an image. Therefore, the charge transport layer can have a high ability to relax stress. The structure of the polycarbonate resin contained in the charge transport layer significantly contributes to relaxation of stress, and it is expected that the volume of a space pushed away in the charge transport layer increases by virtue of the presence of a structure of polycarbonate as a bisphenol structure having a branched chain in the center of the structure (a structure selected from the group A) and a structure different therefrom (a structure selected from the group B), and as a result overlapping of the structures of polycarbonate is prevented between the molecules of the polycarbonate resin in the polycarbonate resin.

On the other hand, the presence of a structure of polycarbonate as a bisphenol structure having a branched chain in the center of the structure (a structure selected from the group A) has been proved to impart a high charge transporting ability to the polycarbonate resin. The present inventors infer that this is because the volume of a space pushed away in the charge transport layer increases to further homogenize the distances between the polycarbonate resins and between the polycarbonate resin and the charge transporting material, and the charge transporting ability becomes higher; and expect that the charge transporting material is homogeneously present in the charge transport layer, and thus homogeneously present also in the interface between the protective layer and the charge transport layer, which allows quick transfer and acceptance of charge in the interface, and thus the accumulation of charge is prevented and eventually potential variation is suppressed. By virtue of suppressed potential variation, the stability of image density is kept high even after long-term, repeated use of the electrophotographic photosensitive member.

Now, the structure selected from the group A will be described in detail.

Among structures selected from the group A, a polycarbonate resin having a structure represented by any of formulas (A-101) to (A-105), (A-201) to (A-205) and (A-401) to (A-405) below can be used from the viewpoint of potential variation-suppressing effect. Especially, the formulas (A-101) to (A-105) and (A-201) to (A-205) below are preferred, in each of which one of the moieties bonding to a carbon element at the center of a bisphenol structure is not a hydrogen element. The present inventors infer that this is because the volume of a space pushed away in the charge transport layer is higher than that in the case of the structure in which one of the moieties bonding to a carbon element at the center of a bisphenol structure is a hydrogen element. Moreover, the formulas (A-101), (A-102), (A-104), (A-105), (A-201) and (A-203) below are preferred, in which one of the moieties bonding to a carbon element at the center of a bisphenol structure is a methyl group (R 215 in the above formula (101) is CH 3 ), and the formulas (A-101), (A-102), (A-104) and (A-105) below are more preferred, in which the branched chains in the center of a bisphenol structure are the same (R 216 and R 217 in (CH 2 ) i1 CHR 216 R 217 in the formula (101) are the same). The present inventors infer that this is because the volume of a space pushed away in the charge transport layer is in the most preferable range for the advantageous effects of the present invention by virtue of the structure in which one of the moieties bonding to a carbon element at the center of a bisphenol structure is a methyl group and the branched chains in the center of a bisphenol structure are the same.

Now, the structure selected from the group B will be described in detail.

Among structures selected from the group B, a polycarbonate resin having a structure represented by any of formulas (B-101) to (B-105), (B-201) to (B-205), (B-301) to (B-308) and (B-401) to (B-405) below can be used from the viewpoint of potential variation-suppressing effect. Especially, the formulas (B-101) to (B-105) below are more preferred from the view point of potential variation-suppressing effect. The present inventors infer that this is because the volume of a space pushed away in the charge transport layer increases to further homogenize the distances between the polycarbonate resins and between the polycarbonate resin and the charge transporting material, and the charge transporting ability becomes higher. Moreover, the formulas (B-201) to (B-205) below are preferred from the viewpoint of further preventing generation of an image defect such as a spot on an image. The present inventors infer that denser packing of the polycarbonate resin lowers the film density and increases the contact area between the resin site of the charge transport layer and the protective layer in the interface to increase the adhesive force, and as a result generation of an image defect can be further prevented. Furthermore, the formulas (B-301) to (B-308) and (B-401) to (B-405) below are preferred from the viewpoint of the solubility of a copolymerized polycarbonate resin. High affinity to the structure selected from the group A presumably contributes to enhancement of the solubility of the resin in a solvent in a coating solution for a charge transport layer.

The present inventors infer that the reason why potential variation is suppressed when an electrophotographic photosensitive member in which the charge transport layer contains a polycarbonate resin having the structure represented by the formula (121) and the structure represented by the formula (104) and the protective layer includes a cured material of a composition containing a compound having at least a functional group selected from chain-polymerizable functional groups and sequential polymerizable functional groups is used is as follows.

A coating solution for a protective layer is applied onto a charge transport layer provided above a support and a charge generation layer, and a protective layer is then formed through external energy such as heat, light (e.g., ultraviolet rays) and radiation (e.g., electron beams). The protective layer is converted to a cured material through bonding between polymerizable functional groups, where the film density increases, and thereby a stress is presumably left in the layer. The residual stress acts on the interface between the charge transport layer and the protective layer. Mechanical and electric force continuously applied to the electrophotographic photosensitive member by electrophotographic process including a charging unit, a developing unit, a transferring unit, and a cleaning unit through long-term, repeated use may generate a minute detached portion in the interface between the charge transport layer and the protective layer to cause an image defect such as a spot on an image. Therefore, the charge transport layer can have a high ability to relax stress. The structure of the polycarbonate resin contained in the charge transport layer significantly contributes to relaxation of stress, and it is expected that, by virtue of the presence of the structure represented by the formula (121), in which the center of the structure is folded and thus the structure is bulky, and the structure represented by the formula (104), in which the center of the structure is small, overlapping of the structures of polycarbonate is prevented between the molecules of the polycarbonate resin in the polycarbonate resin.

Further, the present inventors infer that the distances between the polycarbonate resins and between the polycarbonate resin and the charge transporting material becomes more homogenous through the prevention of overlapping, and the charge transporting material is homogeneously present to fill the space, and the charge transporting ability becomes higher; and expect that the charge transporting material is homogeneously present similarly in the interface between the protective layer and the charge transport layer, which allows quick transfer and acceptance of charge in the interface, and the accumulation of charge is prevented and eventually potential variation is suppressed. By virtue of suppressed potential variation, the stability of image density is kept high even after long-term, repeated use of the electrophotographic photosensitive member.

Now, the structure represented by the formula (121) will be described in detail.

Among the structures represented by the formula (121), a polycarbonate resin having a structure represented by any of formulas (C-101) to (C-105) below can be used from the viewpoint of potential variation-suppressing effect. Especially, the formulas (C-101) to (C-103) below are preferred, in each of which one of the moieties bonding to a carbon element at the center of a bisphenol structure is a hydrogen element. The present inventors infer that this is because a long linear alkyl group is folded by virtue of the structure in which one of the moieties bonding to a carbon element at the center of a bisphenol structure is a hydrogen element, and as a result the volume of a space pushed away in the charge transport layer is in the most preferable range for the advantageous effects of the present invention.

In the present invention, the content ratio of the structure selected from the group A to the polycarbonate resin is preferably 20 mol % or higher and 80 mol % or lower, and more preferably 25 mol % or higher and 49 mol % or lower.

In the present invention, the content ratio of the structure represented by the formula (121) to the polycarbonate resin is preferably 20 mol % or higher and 80 mol % or lower, and more preferably 25 mol % or higher and 49 mol % or lower.

In the present invention, the viscosity-average molecular weight (Mw) of the polycarbonate resin is preferably 20,000 or higher and 70,000 or lower, and more preferably 25,000 or higher and 60,000 or lower. If the viscosity-average molecular weight of the polycarbonate resin is lower than 20,000, the viscosity of the coating solution for a charge transport layer is low, and a charge transport layer having a desired film thickness may not be obtained. If the viscosity-average molecular weight of the polycarbonate resin is higher than 70,000, on the other hand, the coating solution for a charge transport layer may have insufficient storage stability. The weight-average molecular weight (Mw) of the polycarbonate resin is preferably 25,000 or higher and 100,000 or lower, and more preferably 30,000 or higher and 80,000 or lower.

For measurement of the viscosity-average molecular weight of a polycarbonate resin in Examples described later, the intrinsic viscosity [q] was measured by using a Ubbelohde viscometer for a 0.5 w/v % dichloromethane solution of polycarbonate at 20° C. with a Huggins constant of 0.45, and the viscosity-average molecular weight was determined by using the following equation.

[η]=1.23×10−4×( Mv )0.83

The weight-average molecular weight of a polycarbonate resin was measured for a sample of a 0.25 w/v % chloroform solution through gel permeation chromatography (GPC) [measurement apparatus: Alliance HPLC system (manufactured by Waters Corporation)] with two Shodex KF-805L columns (manufactured by Showa Denko K.K.) and an eluent of chloroform at 1 mL/min under UV detection at 254 nm, and calculated as a value in terms of polystyrene.

The intrinsic viscosity of the polycarbonate resin can be 0.3 dL/g to 2.0 dL/g.

Now, specific examples of the polycarbonate resin will be described in detail.

Specific examples of the polycarbonate resin having a structure selected from the group A and a structure selected from the group B are listed in Tables 1 to 12.

Specific examples of the polycarbonate resin having the structure represented by the formula (121) and the structure represented by the formula (104) are listed in the following Tables 13 and 14.

<Method for Synthesizing Polycarbonate Resin>

As an example, a method for synthesizing the exemplary compound 1001 is illustrated below. The other polycarbonate resins can be synthesized through appropriately changing the type and quantity to be added for a raw material of the structure of the group A and a raw material of the structure of the group B in a method for synthesizing the exemplary compound 1001 below. The viscosity-average molecular weight of a resin can be adjusted through appropriately changing the quantity of a molecular weight modifier to be added.

(Method for Synthesizing Exemplary Compound 1001)

In 1100 mL of 5% by mass aqueous solution of sodium hydroxide, 53.0 g (0.196 mol) of 2,2-bis(4-hydroxyphenyl)-4-methylpentane (manufactured by Tokyo Chemical Industry Co., Ltd., product code: D3267) as a raw material of the structure of the group A, 41.2 g (0.204 mol) of bis(4-hydroxyphenyl) ether (manufactured by Tokyo Chemical Industry Co., Ltd., product code: D2121) as a raw material of the structure of the group B, and 0.1 g of hydrosulfite were dissolved together. Thereto, 500 mL of methylene chloride was added with stirring, and 60 g of phosgene was then blown therein over 60 minutes while the temperature was kept at 15° C.

After the completion of blowing of phosgene, 1.3 g of p-t-butylphenol (manufactured by Tokyo Chemical Industry Co., Ltd., product code: B0383) was added as a molecular weight modifier, and the reaction solution was stirred to emulsify. After the emulsification, 0.4 mL of triethylamine was added, and the reaction solution was stirred at 23° C. for 1 hour to polymerize.

After the completion of polymerization, the reaction solution was separated into an aqueous phase and an organic phase, and the organic phase was neutralized with phosphoric acid, and washing was repeated until the electroconductivity of the washing solution (aqueous phase) reached 10 μS/cm or lower. The polymer solution obtained was dropped in warm water kept at 45° C., and the solvent was removed through evaporation to afford a precipitate of a white powder. The precipitate obtained was filtered out, and dried at 110° C. for 24 hours to afford a polycarbonate resin of the exemplary compound 1001 derived from copolymerization of a structure of the group A, A-101, and the structure of the group B, B-101.

The infrared absorption spectrum of the polycarbonate resin obtained was analyzed, and absorptions derived from a carbonyl group and an ether bond were found around 1770 cm −1 and around 1240 cm −1 , respectively, and thus the resin was confirmed to be a polycarbonate resin.

[Electrophotographic Photosensitive Member]

The electrophotographic photosensitive member according to the present invention includes a support, a charge generation layer, a charge transport layer, and a protective layer, in the order presented. Between the support and the charge transport layer, an additional layer (electroconductive layer, undercoat layer) may be provided. Now, the layers will be described.

Examples of methods for producing the electrophotographic photosensitive member include a method in which coating solutions for the layers, which will be described later, are prepared, and applied and dried in a desired order of layers. Examples of the method for applying a coating solution include a dip application method (dip coating method), a spray coating method, a curtain coating method, and a spin coating method. Among these methods, a dip application method can be used from the viewpoint of efficiency and productivity.

<Support>

In the present invention, the support can be an electroconductive support with electroconductivity. Examples of electroconductive supports include supports formed of metal such as aluminum, iron, nickel, copper and gold or alloy; and supports including a thin film of metal such as aluminum, chromium, silver and gold, a thin film of an electroconductive material such as indium oxide, tin oxide, and zinc oxide, or a thin film of an electroconductive ink with silver nanowires, on an insulating support such as polyester resin, polycarbonate resin, polyimide resin, and glass.

The surface of the support may be subjected to electrochemical treatment such as anodic oxidation, wet honing, blasting, cutting or the like, to improve the electric characteristics or reduce interference fringes.

Examples of the shape of the support include a cylinder and a film.

<Electroconductive Layer>

In the present invention, an electroconductive layer may be provided on the support. The electroconductive layer provided can cover unevenness or defects of the support and prevent the occurrence of interference fringes. The average thickness of the electroconductive layer is preferably 5 μm or larger and 40 μm or smaller, and more preferably 10 μm or larger and 30 μm or smaller.

The electroconductive layer can contain an electroconductive particle and a binder resin. Examples of the electroconductive particle include carbon black, metal particles, and metal oxide particles.

Examples of the metal oxide particle include particles of zinc oxide, white lead, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, indium oxide with tin doped therein, and tin oxide with antimony or tantalum doped therein. Two or more of these particles may be used in combination. Among these particles, particles of zinc oxide, tin oxide, and titanium oxide are preferred. The particle of titanium oxide absorbs very little visible light and near-infrared light and the color is white, and thus the particle of titanium oxide is particularly preferred from the viewpoint of achievement of high sensitivity. Examples of the crystal form of titanium oxide include rutile type, anatase type, brookite type, and amorphous type, and any of these crystal forms may be used. In addition, a particle of titanium oxide with needle crystals or granular crystals may be used. The particle is more preferably a particle of rutile-type crystals of titanium oxide. The average primary particle diameter based on the number of metal oxide particles is preferably 0.05 to 1 μm, and more preferably 0.1 to 0.5 μm.

Examples of the binder resin include phenol resin, polyurethane resin, polyamide resin, polyimide resin, polyamideimide resin, polyvinyl acetal resin, epoxy resin, acrylic resin, melamine resin, and polyester resin. Two or more of these binder resins may be used in combination. Among these binder resins, curable resins are preferred from the viewpoint of resistance to a solvent in a coating solution for formation of another layer, close adhesion to an electroconductive support, and dispersibility/dispersion stability of a metal oxide particle. Thermosetting resins are more preferred. Examples of thermosetting resins include thermosetting phenol resin and thermosetting polyurethane resin.

<Undercoat Layer>

In the present invention, an undercoat layer may be provided on the support or the electroconductive layer. The undercoat layer provided enhances the barrier function and bonding function. The average film thickness of the undercoat layer can be 0.3 μm or larger and 5.0 μm or smaller.

The undercoat layer can contain a charge transporting material or metal oxide particle and a binder resin. This configuration allows electrons, among charges generated in the charge generation layer, to be transported to the support, and thus the frequency of deactivation or trapping of charge in the charge generation layer can be prevented from increasing, even in the situation that the charge transporting ability of the charge transport layer is enhanced. Accordingly, the initial electric characteristics and the electric characteristics in repeated use are enhanced.

Examples of the charge transporting material include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, naphthylimide compounds, and peryleneimide compounds. The charge transporting material can have a polymerizable functional group such as a hydroxy group, a thiol group, an amino group, a carboxyl group, and a methoxy group.

The metal oxide particle and binder resin are the same as those described above for the electroconductive layer.

<Charge Generation Layer>

In the present invention, a charge generation layer is provided between the support and the charge transport layer. The charge generation layer can be adjacent to the charge transport layer. The film thickness of the charge generation layer is preferably 0.05 μm or larger and 1 μm or smaller, and more preferably 0.1 μm or larger and 0.3 μm or smaller.

In the present invention, the charge generation layer can contain a charge generating material and a binder resin.

The content of the charge generating material in the charge generation layer is preferably 40% by mass or more and 85% by mass or less, and more preferably 60% by mass or more and 80% by mass or less.

Examples of the charge generating material include azo pigments such as monoazo, disazo and trisazo pigments; phthalocyanine pigments such as metal phthalocyanine and non-metal phthalocyanine pigments; indigo pigment; perylene pigment; polycyclic quinone pigments; squarylium dyes; thiapyrylium salts; triphenylmethane dyes; quinacridone pigment; azlenium salt pigments; cyanine dyes; xanthene dyes; quinonimine dyes; and styryl dyes. Among these charge generating materials, phthalocyanine pigments are preferred, and gallium phthalocyanine crystals are more preferred.

Among gallium phthalocyanine crystals, a hydroxy gallium phthalocyanine crystal, chloro gallium phthalocyanine crystal, bromo gallium phthalocyanine crystal, and iodo gallium phthalocyanine crystal, each having excellent sensitivity, are preferred. Especially, a hydroxy gallium phthalocyanine crystal and chloro gallium phthalocyanine crystal are particularly preferred. In the hydroxy gallium phthalocyanine crystal, a gallium atom has hydroxy groups as axial ligands. In the chloro gallium phthalocyanine crystal, a gallium atom has chlorine atoms as axial ligands. In the bromo gallium phthalocyanine crystal, a gallium atom has bromine atoms as axial ligands. In the iodo gallium phthalocyanine crystal, a gallium atom has iodine atoms as axial ligands. From the viewpoint of enhancement of the sensitivity, the hydroxy gallium phthalocyanine crystal, which has peaks at Bragg angles, 2θ, of 7.4°±0.3° and 28.30±0.3° in X-ray diffraction with CuKα radiation, and the chloro gallium phthalocyanine crystal, which has peaks at Bragg angles, 20±0.2°, of 7.4°, 16.6°, 25.5° and 28.3° in X-ray diffraction with CuKα radiation, are more preferred.

The gallium phthalocyanine crystal can be a gallium phthalocyanine crystal containing an amide compound shown below in the crystal.

Specific examples of the amide compound include N-methylformamide, N,N-dimethylformamide, N-propylformamide, and N-vinylformamide.

The content of the amide compound is preferably 0.1% by mass or more and 3.0% by mass or less, and more preferably 0.3% by mass or more and 1.5% by mass or less, based on gallium phthalocyanine in the gallium phthalocyanine crystal. The present inventors infer that, in the case that the content of the amide compound is 0.1% by mass or more and 3.0% by mass or less, a lower dark current is generated from the charge generation layer when electric field intensity increases, and the fogging-preventing effect of the charge transport layer of the present invention can be further enhanced. The content of the amide compound can be measured by using a 1 H-NMR method.

The gallium phthalocyanine crystal containing the amide compound in the crystal can be obtained through a process in which a solvent containing gallium phthalocyanine treated by using an acid pasting method or dry milling and the amide compound is subjected to wet milling to convert to a crystal.

Wet milling is a process performed by using a milling apparatus such as a sand mill and a ball mill with a dispersing medium such as glass beads, steel beads, and alumina balls.

Examples of the binder resin include resins including polyester, acrylic resin, polycarbonate, polyvinylbutyral, polystyrene, polyvinyl acetate, polysulfone, acrylonitrile copolymer, and polyvinylbenzal. Among these binder resins, polyvinylbutyral and polyvinylbenzal can be used as a resin to disperse the gallium phthalocyanine crystal therein.

<Charge Transport Layer>

In the present invention, the charge transport layer contains a charge transporting material and a polycarbonate resin having a structure selected from the group A and a structure selected from the group B. A crystallization inhibitor for the purpose of inhibiting the precipitation of the charge transporting material, or a leveling agent for the purpose of enhancing the film formability may be further contained.

In the present invention, to form the charge transport layer, a charge transporting material and a polycarbonate resin are mixed with a solvent to prepare a coating solution for a charge transport layer, and a coating film of the coating solution for a charge transport layer is formed on the charge generation layer, and the coating film is dried.

Examples of the solvent to be used for a coating solution for a charge transport layer include ketone solvents such as acetone and methyl ethyl ketone; ester solvents such as methyl acetate and ethyl acetate; aromatic hydrocarbon solvents such as toluene, xylene and chlorobenzene; ether solvents such as 1,4-dioxane and tetrahydrofuran; and halogen atom-substituted hydrocarbon solvents such as chloroform. Two or more of these solvents may be used in combination. Among these solvents, solvents having a dipole moment of 1.0 D or lower can be used. Examples of solvents having a dipole moment of 1.0 D or lower include o-xylene (dipole moment=0.64 D) and methylal (dimethoxymethane) (dipole moment=0.91 D).

The film thickness of the charge transport layer is preferably 5 μm or larger and 40 μm or smaller, more preferably 7 μm or larger and 25 μm or smaller, and particularly preferably 15 μm or larger and 20 μm or smaller.

The content of the charge transporting material in the charge transport layer can be 80% by mass or more and 200% by mass or less based on the content of the polycarbonate resin, from the viewpoint of the potential variation-suppressing effect of the electrophotographic photosensitive member.

The molecular weight of the charge transporting material can be 300 or higher and 1,000 or lower.

Examples of the charge transporting material include triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, thiazole compounds, and triallylmethane compounds. Two or more of these charge transporting materials may be used in combination. Among these charge transporting materials, triarylamine compounds can be used.

Here, general formulas and exemplary compounds satisfying each general formula are illustrated as specific examples of the charge transporting material.

In the formula (CTM-1), Ar 101 and Ar 102 each independently represent a substituted or unsubstituted aryl group; R 101 and R 102 each independently represent a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group; and the substituent of the substituted aryl group is an alkyl group, an alkoxy group, or a halogen atom.

Exemplary compounds of the general formula (CTM-1) are shown in the following.

In the formula (CTM-2), Ar 103 to Ar 106 each independently represent a substituted or unsubstituted aryl group; Z 101 represents a substituted or unsubstituted arylene group, or a divalent group derived from a plurality of arylene groups bonding together via a vinylene group; two adjacent substituents on Ar 103 to Ar 106 may be bonding together to form a ring; and the substituent of the substituted aryl group and the substituted arylene group is an alkyl group, an alkoxy group, or a halogen atom.

Exemplary compounds of the general formula (CTM-2) are shown in the following.

In the formula (CTM-3), R 103 represents an alkyl group, a cycloalkyl group, or a substituted or unsubstituted aryl group; R 104 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group; Ar 107 represents a substituted or unsubstituted aryl group; Z 102 represents a substituted or unsubstituted arylene group; n1 represents an integer of 1 to 3 and m represents an integer of 0 to 2, where m+n1=3; in the case that m is 2, the moieties R 103 may be the same or different; two adjacent substituents on the moieties R 103 may be bonding together to form a ring; R 103 and Z 102 may be bonding together to form a ring; Ar 107 and R 104 may be bonding together via a vinylene group to form a ring; and the substituent of the substituted aryl group and the substituted arylene group is an alkyl group, an alkoxy group, or a halogen atom.

Exemplary compounds of the general formula (CTM-3) are shown in the following.

In the formula (CTM-4), Ar 108 to Ar 111 each independently represent a substituted or unsubstituted aryl group; and the substituent of the substituted aryl group is an alkyl group, an alkoxy group, a halogen atom, or a 4-phenyl-but-1,3-dienyl group.

Exemplary compounds of the general formula (CTM-4) are shown in the following.

In the formula (CTM-5), Ar 112 to Ar 117 each independently represent a substituted or unsubstituted aryl group; Z 103 represents a phenylene group, a biphenylene group, or a divalent group derived from two phenylene groups bonding together via an alkylene group; and the substituent of the substituted aryl group is an alkyl group, an alkoxy group, or a halogen atom.

Exemplary compounds of the general formula (CTM-5) are shown in the following.

In the formula (CTM-6), at least one of R 105 to R 108 represents a monovalent group represented by a formula (6-1) below and the others each independently represent an alkyl group or a substituted or unsubstituted aryl group; Z 104 represents a substituted or unsubstituted arylene group, or a divalent group derived from a plurality of arylene groups bonding together via a vinylene group; n2 represents 0 or 1; and the substituent of the substituted aryl group and the substituted arylene group is an alkyl group, an alkoxy group, or a halogen atom.

In the formula (6-1), R 109 and R 110 each independently represent a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group; Ar 118 represents a substituted or unsubstituted aryl group; Z 105 represents a substituted or unsubstituted arylene group; n3 represents an integer of 1 to 3; the substituent of the substituted aryl group is an alkyl group, an alkoxy group, a dialkylamino group, or a diarylamino group; and the substituent of the substituted arylene group is an alkyl group, an alkoxy group, or a halogen atom.

Exemplary compounds of the general formula (CTM-6) are shown in the following.

In the formula (CTM-7), Ar 119 represents a substituted or unsubstituted aryl group, or a monovalent group represented by a formula (7-1) or formula (7-2) below; Ar 120 and Ar 121 each independently represent a substituted or unsubstituted aryl group; and the substituent of the substituted aryl group is an alkyl group, an alkoxy group, or a halogen atom.

In the formula (7-1), Ar 122 and Ar 123 each independently represent a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group; and the substituent of the substituted aryl group and the substituted aralkyl group is an alkyl group, an alkoxy group, or a halogen atom.

In the formula (7-2), R 111 and R 112 each independently represent a substituted or unsubstituted aryl group; Z 106 represents a substituted or unsubstituted arylene group; and the substituent of the substituted aryl group and the substituted arylene group is an alkyl group, an alkoxy group, or a halogen atom.

Exemplary compounds of the general formula (CTM-7) are shown in the following.

<Protective Layer>

In the present invention, a protective layer is provided on the charge transport layer. The protective layer includes a cured material of a composition containing a compound having at least a functional group selected from chain-polymerizable functional groups and sequential polymerizable functional groups, to enhance the abrasion resistance to mechanical force. A polymerization initiator for the purpose of initiation of polymerization reaction, a release agent for the purpose of enhancing the transfer efficiency for a toner, an anti-fingerprint agent for the purpose of prevention of fouling or the like, a filler for the purpose of prevention of chipping, or a lubricant for the purpose of enhancing the lubricity may be further contained.

In the present invention, for the protective layer, a composition containing a compound having at least a functional group selected from chain-polymerizable functional groups and sequential polymerizable functional groups is mixed with a solvent to prepare a coating solution for a protective layer, and a coating film of the coating solution for a protective layer is formed on the charge transport layer, and the coating film is dried and external energy such as heat, light (e.g., ultraviolet rays) and radiation (e.g., electron beams) is applied to the coating film to form a cured material.

A composition containing a compound having a chain-polymerizable functional group is cured through chain polymerization. Examples of the chain-polymerizable functional group include an acryloyloxy group, a methacryloyloxy group, an alkoxysilyl group, and an epoxy group.

A composition containing a compound having a sequential polymerizable functional group is cured through sequential polymerization. Examples of the sequential polymerizable functional group include a hydroxy group, a thiol group, an amino group, a carboxyl group, and a methoxy group.

In formation of the protective layer, a leaving group is generated on curing through sequential polymerization of a hydroxy group, a thiol group, an amino group, a carboxyl group, a methoxy group, or the like, and in contrast chain polymerization of an acryloyloxy group, a methacryloyloxy group, an alkoxysilyl group, an epoxy group, or the like is considered to be less likely to cause increase in the film density on curing, and thus more preferred.

For the external energy to cure the protective layer, use of an ultraviolet ray or radiation, which has high energy, is preferred, and use of radiation is more preferred in order to decrease the number of polymerizable functional groups unnecessary for charge transfer to reduce the barrier for charge transport in the interface to the charge transport layer.

To reduce the barrier for charge transport in the interface to the charge transport layer and enhance the charge transporting ability in the protective layer, it would be preferred that the protective layer include a cured material having a homogeneous three-dimensional crosslinked structure. To allow the protective layer to have a homogeneous three-dimensional crosslinked structure, the composition containing a compound having a polymerizable functional group can contain at least one compound having three or more polymerizable functional groups.

To enhance the potential variation-suppressing effect of the present invention, the protective layer can have charge transporting function. Examples of methods for allowing the protective layer to have charge transporting function include allowing the composition for formation of the protective layer to contain a charge transporting material having a polymerizable functional group, and allowing the composition for formation of the protective layer to contain a charge transporting material having no polymerizable functional group.

To achieve enhancement of the abrasion resistance to mechanical force, which is a traditional object of laminating a protective layer on a charge transport layer, and potential variation-suppressing effect to electric force in the present invention in combination at a higher level, it is more preferred to allow the composition for formation of the protective layer to contain a charge transporting material having a polymerizable functional group.

The film thickness of the protective layer is preferably 2 μm or larger and 10 μm or smaller, more preferably 3 μm or larger and 8 μm or smaller, and particularly preferably 4 μm or larger and 6 μm or smaller.

To enhance the potential variation-suppressing effect of the present invention, the ratio of the film thickness of the protective layer to the film thickness of the charge transport layer (film thickness of protective layer/film thickness of charge transport layer) is preferably 0.20 to 0.40, and more preferably 0.25 to 0.35.

[Process Cartridge, Electrophotographic Apparatus]

FIGURE is a diagram illustrating one example of the schematic configuration of an electrophotographic apparatus including a process cartridge including the electrophotographic photosensitive member according to the present invention.

The reference sign 1 indicates a cylindrical (drum-shaped) electrophotographic photosensitive member, which is rotary-driven around a shaft 2 at a predetermined rotational speed (process speed) in the direction of the arrow. The surface of the electrophotographic photosensitive member 1 is charged to a predetermined positive or negative potential by a charging unit 3 in the course of rotation. The surface of the electrophotographic photosensitive member 1 after being charged is then irradiated with exposure light 4 from an exposing unit (not illustrated), and an electrostatic latent image corresponding to intended image information is formed. The exposure light 4 is light output from an image-exposing unit such as units for slit exposure and beam scanning exposure, and having been subjected to intensity modulation according to a time series of electric digital image signals of intended image information.

The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 1 is developed (normal development or reversal development) with a toner contained in a developing unit 5 , and a toner image is formed on the surface of the electrophotographic photosensitive member 1 . The toner image formed on the surface of the electrophotographic photosensitive member 1 is transferred to a transfer member 7 by a transferring unit 6 . Then, a bias voltage with a polarity opposite to the charge possessed by the toner is applied from a bias power supply (not illustrated) to the transferring unit 6 . In the case that the transfer member 7 is a paper, the transfer member 7 is taken out from a feeding unit (not illustrated) and fed between the electrophotographic photosensitive member 1 and the transferring unit 6 in synchronization with the rotation of the electrophotographic photosensitive member 1 .

The transfer member 7 to which the toner image has been transferred from the electrophotographic photosensitive member 1 is separated from the surface of the electrophotographic photosensitive member 1 , and conveyed to a fixing unit 8 and subjected to fixing for the toner image, and thus printed out of the electrophotographic apparatus as an image-bearing product (print, copy).

The surface of the electrophotographic photosensitive member 1 after transferring the toner image to the transfer member 7 is cleaned by a cleaning unit 9 through removal of a deposit such as a toner (untransferred residual toner). In recent years, a cleanerless system has been developed, and an untransferred residual toner can be removed directly, for example, in a developing device. Further, the surface of the electrophotographic photosensitive member 1 is subjected to charge removal with pre-exposure light 10 from a pre-exposing unit (not illustrated), and thereafter repeatedly used for image formation. In the case that the charging unit 3 is a contact charging unit with a charging roller or the like, the pre-exposing unit is not necessarily required.

In the present invention, a plurality of components selected from the above-described electrophotographic photosensitive member 1 , charging unit 3 , developing unit 5 , transferring unit 6 , cleaning unit 9 , and so on, may be contained in a container and integrally supported to form a process cartridge. The process cartridge can be configured to be attachable to and detachable from a main body of an electrophotographic apparatus. For example, at least one selected from the group consisting of the charging unit 3 , the developing unit 5 , and the cleaning unit 9 is supported integrally with the electrophotographic photosensitive member 1 to produce a cartridge. Then, a guiding unit 12 such as a rail in a main body of an electrophotographic apparatus is used, and thus a process cartridge 11 being attachable to and detachable from a main body of an electrophotographic apparatus can be produced.

In the case that the electrophotographic apparatus is a copier or printer, the exposure light 4 may be reflected light or transmitted light from an original image. Alternatively, the exposure light 4 may be laser beam scanning according to signals obtained through reading and subsequent signalization of an original image by a sensor, or light emitted through the drive of an LED array or the drive of a liquid crystal shutter array.

The electrophotographic photosensitive member 1 according to the present invention can be widely applied to the application field of electrophotography including laser beam printers, CRT printers, LED printers, FAX, liquid crystal printers, and laser engraving.

Hereinafter, the present invention will be described in more detail by using Examples and Comparative Examples. The present invention is never limited to Examples below as long as the Examples do not depart from the gist of the present invention. In the description in the following Examples, “part” is in terms of mass unless otherwise specified.