JP2017015944A - Image forming apparatus and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that suppresses the occurrence of seizing ghost occurring when a single image is continuously output and the occurrence of optical fatigue when photoreceptors are exposed to light.SOLUTION: There is provided an image forming apparatus 100 comprising: photoreceptors 7 each including a photosensitive layer containing at least one selected from the group consisting of a butadiene-based charge transport material (CT1), benzidine-based charge transport material (CT2), biphenyl copolymerized polycarbonate resin, a hindered phenolic antioxidant having a molecular weight of 300 or more, and a benzophenone-based ultraviolet absorber; charging means 8; electrostatic latent image forming means including a light-emitting diode as a light source; developing means 11; and transfer means 40.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus and a process cartridge.

  Conventionally, as an electrophotographic image forming apparatus, an electrophotographic photoreceptor (hereinafter sometimes referred to as “photoreceptor”) is used to sequentially perform processes such as charging, electrostatic latent image formation, development, transfer, and cleaning. Devices for performing are widely known.

  As an electrophotographic photosensitive member, a function-separated type photosensitive member in which a charge generating layer for generating charges and a charge transporting layer for transporting charges are stacked on a conductive substrate such as aluminum, or a charge is generated. Single-layer type photoreceptors in which the same layer performs the function and the function of transporting electric charge are known.

For example, in Patent Document 1, for example, in Patent Document 1, an electrophotographic photosensitive member containing a butadiene monomer-based charge transport material, a hindered phenol-based antioxidant, and a hindered amine-based antioxidant in a charge transport layer. Is disclosed.
Patent Document 2 discloses an electrophotographic photoreceptor in which a photosensitive layer contains a butadiene trimer charge transport material, a phenolic antioxidant, and a benzotriazole ultraviolet absorber.
Patent Document 3 discloses a photoreceptor in which an outermost surface layer contains a butadiene-based charge transport material and a hindered phenol-based antioxidant.

JP-A-7-261414 JP 2010-211057 A JP 2012-047959 A

  An object of the present invention is to provide a photosensitive layer comprising a charge generation material, a charge transport material represented by the general formula (CT1), a charge transport material represented by the general formula (CT2), and a biphenyl copolymerized polycarbonate resin. Furthermore, an electrophotographic photosensitive member containing at least one selected from the group consisting of hindered amine antioxidants and benzoate ultraviolet absorbers as antioxidants and ultraviolet absorbers, charging means, and a light emitting diode as a light source Compared with an image forming apparatus having an electrostatic latent image forming unit, a developing unit, and a transfer unit, the light generated when the same image is continuously output and the image ghost is generated and the light is exposed. An object of the present invention is to provide an image forming apparatus that suppresses the occurrence of fatigue.

  The above problem is solved by the following means.

The invention according to claim 1
A conductive substrate and a photosensitive layer disposed on the conductive substrate, the charge generation material, a charge transport material represented by the following general formula (CT1), a charge transport material represented by the following general formula (CT2), A photosensitive layer containing at least one selected from the group consisting of a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton, and a hindered phenol antioxidant having a molecular weight of 300 or more and a benzophenone ultraviolet absorber; An electrophotographic photoreceptor having
Charging means for charging the surface of the electrophotographic photosensitive member;
An electrostatic latent image forming unit that has a light emitting diode as a light source and forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member by exposure with the light emitting diode;
Developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
Transfer means for transferring the toner image to the surface of the recording medium;
An image forming apparatus comprising:

(In the general formula (CT1), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or a carbon number. It represents an alkoxy group having 1 to 20 carbon atoms or an aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure, where n and m are each Independently represents 0, 1 or 2.)

(In general formula (CT2), R ^C21 , R ^C22 , and R ^C23 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or And represents an aryl group having 6 to 10 carbon atoms.)

The invention according to claim 2
The charge transport material represented by the general formula (CT1), wherein R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 represent a hydrogen atom, and m and n represent 1. Image forming apparatus.

The invention according to claim 3
The charge transport material represented by the general formula (CT2), wherein R ^C21 and R ^C23 represent a hydrogen atom, and R ^C22 represents an alkyl group having 1 to 10 carbon atoms. Image forming apparatus.

The invention according to claim 4
The image forming apparatus according to claim 1, wherein the hindered phenol-based antioxidant is an antioxidant represented by the following general formula (HP).

(In General Formula (HP), R ^H1 and R ^H2 each independently represents a branched alkyl group having 4 to 8 carbon atoms. R ^H3 and R ^H4 each independently represent a hydrogen atom, Or, it represents an alkyl group having 1 to 10 carbon atoms, and R ^H5 represents an alkylene group having 1 to 10 carbon atoms.)

The invention according to claim 5
The image forming apparatus according to claim 4, wherein in the antioxidant represented by the general formula (HP), R ^H1 and R ^H2 represent a tert-butyl group.

The invention according to claim 6
The image forming apparatus according to claim 1, wherein the benzophenone-based ultraviolet absorber is an ultraviolet absorber represented by the following general formula (BP).

(In General Formula (BP), R ^B1 , R ^B2 , and R ^B3 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or And represents an aryl group having 6 to 10 carbon atoms.)

The invention according to claim 7 provides:
The image formation according to claim 6, wherein in the benzophenone-based ultraviolet absorber represented by the general formula (BP), R ^B1 and R ^B2 represent a hydrogen atom, and R ^B3 represents an alkoxy group having 1 to 4 carbon atoms. apparatus.

The invention according to claim 8 provides:
The image forming apparatus according to claim 1, wherein the charge generation material is a hydroxygallium phthalocyanine pigment.

The invention according to claim 9 is:
The biphenyl copolymer polycarbonate resin is a polycarbonate resin containing a structural unit represented by the following general formula (PCA) and a structural unit represented by the following general formula (PCB). The image forming apparatus according to claim 1.

(In the general formulas (PCA) and (PCB), R ^P1 , R ^P2 , R ^P3 , and R ^P4 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or 5 or more carbon atoms. 7 a cycloalkyl group, or, .X ^P1 representing an aryl group having 6 to 12 carbon atoms, a phenylene group, biphenylene group, naphthylene group, an alkylene group, or a cycloalkylene group.)

The invention according to claim 10 is:
The image forming apparatus according to claim 1, wherein the photosensitive layer further includes fluorine-containing resin particles and a fluorine-containing dispersant.

The invention according to claim 11 is:
A conductive substrate and a photosensitive layer disposed on the conductive substrate, the charge generation material, a charge transport material represented by the following general formula (CT1), a charge transport material represented by the following general formula (CT2), A photosensitive layer containing at least one selected from the group consisting of a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton, and a hindered phenol antioxidant having a molecular weight of 300 or more and a benzophenone ultraviolet absorber; An electrophotographic photoreceptor having
An electrostatic latent image forming unit that has a light emitting diode as a light source and forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member by exposure with the light emitting diode;
And a process cartridge that is detachably attached to the image forming apparatus.

(In the general formula (CT1), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or a carbon number. It represents an alkoxy group having 1 to 20 carbon atoms or an aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure, where n and m are each Independently represents 0, 1 or 2.)

(In general formula (CT2), R ^C21 , R ^C22 , and R ^C23 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or And represents an aryl group having 6 to 10 carbon atoms.)

  According to the first aspect of the present invention, the charge generation material, the charge transport material represented by the general formula (CT1), the charge transport material represented by the general formula (CT2), and the biphenyl copolymer polycarbonate resin are included. The photosensitive layer further includes at least one selected from the group consisting of a hindered amine antioxidant and a benzoate ultraviolet absorber as an antioxidant and an ultraviolet absorber, a charging unit, and a light source Compared to an image forming apparatus having an electrostatic latent image forming unit having a light emitting diode, a developing unit, and a transfer unit, the image was exposed to light along with the occurrence of a burning ghost that occurred when the same image was output continuously. There is provided an image forming apparatus in which occurrence of light fatigue that occurs sometimes is suppressed.

According to the second aspect of the invention, the same image is continuously displayed as compared with the image forming apparatus in which the charge transport material represented by the general formula (CT1) includes the electrophotographic photosensitive member that is the exemplary compound (CT1-1). Provided is an image forming apparatus that suppresses the occurrence of burn-in ghost that occurs when output and the occurrence of light fatigue that occurs when exposed to light.
According to the invention of claim 3, the same image is continuously displayed as compared with an image forming apparatus in which the charge transport material represented by the general formula (CT2) is provided with the electrophotographic photosensitive member which is the exemplary compound (CT2-1). Provided is an image forming apparatus that suppresses the occurrence of burn-in ghost that occurs when output and the occurrence of light fatigue that occurs when exposed to light.

  According to the invention according to claim 4 or 5, the antioxidant is the same as that of the image forming apparatus including the electrophotographic photosensitive member that is a hindered phenol-based antioxidant represented by the structural formula (CAO-1). Provided is an image forming apparatus that suppresses the occurrence of burn-in ghost that occurs when images are continuously output and the occurrence of light fatigue that occurs when exposed to light.

  According to the invention which concerns on Claim 6 or 7, compared with an image forming apparatus provided with the electrophotographic photoreceptor whose ultraviolet absorber is a benzoate type ultraviolet absorber shown by structural formula (CUA-1), the same image is displayed. Provided is an image forming apparatus that suppresses the occurrence of burn-in ghost that occurs when output continuously and the occurrence of light fatigue that occurs when exposed to light.

  The invention according to claim 8 includes a charge generation material, a charge transport material represented by the general formula (CT1), a charge transport material represented by the general formula (CT2), and a biphenyl copolymer polycarbonate resin. The photosensitive layer further includes at least one selected from the group consisting of a hindered amine antioxidant and a benzoate ultraviolet absorber as an antioxidant and an ultraviolet absorber, a charging unit, and a light source Compared to an image forming apparatus having an electrostatic latent image forming unit having a light emitting diode, a developing unit, and a transfer unit, even when the photosensitive layer contains a hydroxygallium phthalocyanine pigment, the same image is output continuously. Provided is an image forming apparatus that suppresses the occurrence of light fatigue caused by exposure to light as well as the occurrence of image sticking ghost.

  The invention according to claim 9 includes a charge generation material, a charge transport material represented by the general formula (CT1), a charge transport material represented by the general formula (CT2), and a biphenyl copolymer polycarbonate resin. The photosensitive layer further includes at least one selected from the group consisting of a hindered amine antioxidant and a benzoate ultraviolet absorber as an antioxidant and an ultraviolet absorber, a charging unit, and a light source As a homopolymeric polycarbonate resin of bisphenol Z, a structural unit represented by the general formula (PCA) as compared to an image forming apparatus comprising an electrostatic latent image forming unit having a light emitting diode, a developing unit, and a transfer unit, Even when the photosensitive layer contains a polycarbonate resin containing a structural unit represented by the following general formula (PCB), the same image is continuously displayed. The occurrence of seizing ghosts occurring when outputting Te, an image forming apparatus that suppresses the generation of light fatigue that occurs when light exposure is provided.

  The invention according to claim 10 includes a charge generation material, a charge transport material represented by the general formula (CT1), a charge transport material represented by the general formula (CT2), and a biphenyl copolymer polycarbonate resin. In comparison with an image forming apparatus, the photosensitive layer further comprises an electrophotographic photoreceptor containing at least one selected from the group consisting of a hindered amine antioxidant and a benzoate ultraviolet absorber as an antioxidant and an ultraviolet absorber. Even when fluorine-containing resin particles and a fluorine-containing dispersant are included in the photosensitive layer, the occurrence of light fatigue that occurs when exposed to light is generated along with the occurrence of a burning ghost that occurs when the same image is continuously output. A suppressed image forming apparatus is provided.

  According to the eleventh aspect of the present invention, the charge generation material, the charge transport material represented by the general formula (CT1), the charge transport material represented by the general formula (CT2), and the biphenyl copolymer polycarbonate resin are included. The photosensitive layer further includes at least one selected from the group consisting of a hindered amine antioxidant and a benzoate ultraviolet absorber as an antioxidant and an ultraviolet absorber, and a light emitting diode as a light source. Compared with a process cartridge having an electrostatic latent image forming means, it has a burn-in ghost that occurs when the same image is output continuously and a light fatigue that occurs when the electrophotographic photosensitive member is exposed to light. A suppressed process cartridge is provided.

1 is a schematic partial cross-sectional view illustrating an example of a layer configuration of an electrophotographic photoreceptor according to an exemplary embodiment. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows the other example of the image forming apparatus which concerns on this embodiment.

  Hereinafter, an embodiment which is an example of the present invention will be described with reference to the accompanying drawings. In the drawings, elements having similar functions are denoted by the same reference numerals, and redundant description is omitted.

<Image forming apparatus / process cartridge>
The image forming apparatus according to the present embodiment includes an electrophotographic photosensitive member, a charging unit that charges the surface of the electrophotographic photosensitive member, and a light emitting diode as a light source. An electrostatic latent image forming means for forming an electrostatic latent image on the surface; and a developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image. Transfer means for transferring the toner image onto the surface of the recording medium.
On the other hand, an electrophotographic photosensitive member (hereinafter also referred to as “photosensitive member” or “electrophotographic photosensitive member according to the present embodiment”) includes a conductive substrate and a photosensitive layer disposed on the conductive substrate. The photosensitive layer includes a charge generation material, a charge transport material represented by the general formula (CT1) (hereinafter also referred to as “butadiene-based charge transport material (CT1)”), and a charge transport material represented by the general formula (CT2). (Hereinafter also referred to as “benzidine-based charge transporting material (CT2)”), a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton (hereinafter also referred to as “BP polycarbonate resin”), and a hindered phenol having a molecular weight of 300 or more. And at least one selected from the group consisting of benzophenone-based UV absorbers (hereinafter also referred to simply as “hindered phenol-based antioxidants”).

  The photosensitive layer may be a function separation type photosensitive layer having a charge generation layer and a charge transport layer, or may be a single layer type photosensitive layer. In the case of the functional separation type photosensitive layer, the charge generation layer contains a charge generation agent, and the charge transport layer contains a butadiene-based charge transport material (CT1), a benzidine-based charge transport material (CT2), a BP polycarbonate resin, and a hinder. And at least one selected from the group consisting of a dophenol antioxidant and a benzophenone ultraviolet absorber.

  With the above configuration, the image forming apparatus according to the present embodiment suppresses the occurrence of burn-in ghost that occurs when the same image is continuously output and the occurrence of light fatigue that occurs when exposed to light. The reason is guessed as shown below.

  First, the butadiene based charge transport material (CT1) is suitable for obtaining a photosensitive layer (or charge transport layer) having high charge mobility and high charge transport ability. On the other hand, the butadiene-based charge transport material (CT1) has a low solubility in a solvent. For this reason, in order to obtain a photosensitive layer having a high charge transport capability, a benzidine charge transport material (CT2) having a relatively high charge mobility and a high solubility in a solvent is used together with the butadiene charge transport material (CT1). It is good to use together.

However, after using a photoconductor having a photosensitive layer containing both a butadiene-based charge transport material (CT1) and a benzidine-based charge transport material (CT2), the same image is continuously output (for example, 3000 sheets are continuously output). When a halftone image is output, the surface potential of the photoconductor in a continuously exposed portion due to the same image output decreases, and an image defect (positive ghost) called “burn-in ghost” in which the density increases may occur. is there.
In addition, if the photoconductor is exposed to room light or sunlight, for example, when the photoconductor is replaced, the chargeability of the photoexposed portion of the photoconductor deteriorates, and then a full-tone image is output. As a result, an image defect called “light fatigue” occurs in which the image density of the portion exposed to light appears to be deep.

Image defects called “burn-in ghosts” and “light fatigue” are caused by the continuous output of the same image and light exposure, the injection of charge from the charge generating material into the charge transport material in the photosensitive layer, and the charge This is considered to be caused by the occurrence of a state in which electrons are easily excited in the delocalized region of electrons that are entrusted to charge transfer between transport materials. In other words, this image defect is caused by the activation of charge generation and charge injection, resulting in a decrease in the charged potential of the area continuously exposed by the continuous output of the same image and the area exposed to light. It is thought to be caused by the rise.
The increase in the image density due to the decrease in the charging potential is particularly significant when the photosensitive layer contains both the butadiene-based charge transport material (CT1) and the benzidine-based charge transport material (CT2). This is because the butadiene-based charge transporting material (CT1) has a high charge transporting capability in the structure, so that the delocalized region of electrons in the molecule is large, and the benzidine-based charge transporting material (CT2) and the charge generating material This is thought to be due to a significant decrease in charging potential due to continuous output of the same image and exposure to light.

  Further, the photosensitive layer containing BP polycarbonate resin as the binder resin has improved wear resistance and can extend the life of the photoreceptor. However, even in a photoreceptor having a photosensitive layer containing a BP polycarbonate resin as a binder resin, “burn-in ghost” and “light fatigue” are particularly prominent. It is considered that the benzene ring of the biphenyl skeleton of the BP polycarbonate resin easily acts as a charge trap site (a region where charges are easily accumulated) by interacting with the charge transport material. If the charge is accumulated excessively in the photosensitive layer due to the charge trapping site, it is offset by the charge accumulated on the surface of the photoconductor after charging, so that "burn-in ghost" and "photo fatigue" are prominent. It is thought to occur.

  In addition, when a light emitting diode is used as the light source of the electrostatic latent image forming means for forming the electrostatic latent image on the photosensitive member, the apparatus can be reduced in size and cost compared with the case where a laser is used as the light source. However, since the light emitting diode generates less light than the laser, the electrostatic latent image forming means having the light emitting diode is disposed near the surface of the photoreceptor. Along with this, the developing means is arranged away from the exposure position on the surface of the photoreceptor of the light emitting diode, and the time from the formation of the electrostatic latent image by exposure to development (that is, the time from exposure to development [photosensitive The time until the surface of the body reaches the development area from the position irradiated with the exposure light] tends to be longer. Specifically, there is a tendency that the time from exposure to development is as long as 0.1 seconds to 0.5 seconds. As a result, due to the dark decay of the photosensitive layer of the photoreceptor, the charged potential of the area continuously exposed by the continuous output of the same image and the area exposed to light are more likely to be reduced. It is thought that “light fatigue” occurs remarkably.

  On the other hand, when a hindered phenolic antioxidant is further added to the photosensitive layer containing both the butadiene based charge transporting material (CT1) and the benzidine based charge transporting material (CT2) and the BP polycarbonate resin, the same. Reduction in charging potential due to continuous image output and light exposure is suppressed. This is because the hindered phenol-based antioxidant causes interactions such as charge transfer to and from the delocalized region of electrons, and the delocalized region of electrons due to continuous output of the same image and exposure to light. This is because it is considered that the change in the energy state of electrons is suppressed. When the molecular weight of the hindered phenol antioxidant is 300 or more, volatilization of the hindered phenol antioxidant in the drying step when forming the photosensitive layer is suppressed. That is, if the molecular weight of the hindered phenol antioxidant is 300 or more, it is considered that the hindered phenol antioxidant remains in the photosensitive layer in an amount that exhibits the above function.

  On the other hand, even if a photosensitive layer containing both a butadiene-based charge transport material (CT1) and a benzidine-based charge transport material (CT2) and a BP polycarbonate resin is further incorporated with a benzophenone-based UV absorber, continuous output of the same image is possible. In addition, a decrease in charging potential due to light exposure is suppressed. This is because the benzophenone UV absorber absorbs the light energy received by the photosensitive layer by continuous output of the same image and light exposure, and suppresses the change in the energy state of the electrons in the delocalized region of the electrons. Conceivable.

  Further, the hindered phenol-based antioxidant and the benzophenone-based ultraviolet absorber act on the benzene ring of the biphenyl skeleton of the BP polycarbonate resin and the charge transport material, and charge due to the interaction between the benzene ring of the biphenyl skeleton and the charge transport material. It is thought that the formation of trap sites is suppressed. For this reason, it is considered that excessive accumulation of charges in the photosensitive layer caused by charge trap sites due to the interaction between the benzene ring of the biphenyl skeleton and the charge transport material is suppressed.

  In addition, by providing the photosensitive member with the above-described configuration, and by providing an electrostatic latent image forming means having a light emitting diode as a light source, even if the time from exposure to development becomes long, continuous output of the same image and light exposure It is difficult for the charging potential to decrease due to.

  As described above, the image forming apparatus according to this embodiment includes an electrostatic latent image forming unit having a light emitting diode as a light source, and the time from exposure to development becomes longer, for example, from 0.1 second to 0.5 second. However, it is presumed that the occurrence of burn-in ghost that occurs when the same image is output continuously and the occurrence of light fatigue that occurs when exposed to light are suppressed.

  In the electrophotographic photosensitive member according to the present embodiment, since the BP polycarbonate resin is included in the photosensitive layer as the binder resin, the wear resistance of the photosensitive layer is improved and the life is extended.

  In addition, when the photosensitive layer contains a hydroxygallium phthalocyanine pigment having a high charge generation efficiency as a charge generation material, a large amount of charge is generated, and therefore, a decrease in the charged potential due to continuous output of the same image and exposure to light becomes noticeable. Attached ghost and light fatigue are likely to occur. However, in the electrophotographic photosensitive member according to the present embodiment, even when hydroxygallium phthalocyanine is included in the photosensitive layer, the light generated when exposed to light together with the occurrence of a burning ghost that occurs when the same image is continuously output. Reduces fatigue.

  Furthermore, when the photosensitive layer contains fluorine-containing resin particles and a fluorine-containing dispersant, the abrasion resistance of the photosensitive layer is improved and the life of the photoreceptor can be extended. On the other hand, when a fluorine-containing dispersant is contained in the photosensitive layer, it is considered that the fluorine-containing dispersant easily acts as a charge trap site (a region where charges are easily accumulated). If the charge is accumulated excessively in the photosensitive layer due to the charge trapping site, it is offset by the charge accumulated on the surface of the photoconductor after charging, so that "burn-in ghost" and "photo fatigue" are prominent. It is thought to occur. However, in the electrophotographic photosensitive member according to the present embodiment, even when fluorine-containing resin particles and a fluorine-containing dispersant are included in the photosensitive layer, along with the occurrence of a burning ghost that occurs when the same image is continuously output, Suppresses the occurrence of light fatigue when exposed to light.

  Here, the image forming apparatus according to the present embodiment includes a fixing unit that fixes the toner image transferred to the surface of the recording medium; the toner image formed on the surface of the electrophotographic photosensitive member is directly transferred to the recording medium. Direct transfer system device; primary transfer of the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the intermediate transfer member, and secondary transfer of the toner image transferred to the surface of the intermediate transfer member to the surface of the recording medium An intermediate transfer system device; a device provided with a cleaning means for cleaning the surface of the electrophotographic photosensitive member after the toner image is transferred and before charging; and after the toner image is transferred, the surface of the image holding member is discharged before charging. A known image forming apparatus such as an apparatus provided with a static eliminating means for removing electricity by irradiation; an apparatus provided with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature is applied.

  In the case of an intermediate transfer type apparatus, the transfer means includes, for example, an intermediate transfer body on which a toner image is transferred onto the surface, and a primary transfer that primarily transfers the toner image formed on the surface of the image holding body onto the surface of the intermediate transfer body. And a secondary transfer unit that secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of the recording medium.

  The image forming apparatus according to the present embodiment may be either a dry developing type image forming apparatus or a wet developing type (developing type using a liquid developer).

  Note that in the image forming apparatus according to the present embodiment, for example, the portion including the electrophotographic photosensitive member may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member according to the present embodiment and an electrostatic latent image forming unit having a light emitting diode as a light source is preferably used. In addition to the electrophotographic photosensitive member and the electrostatic latent image forming unit, the process cartridge may include, for example, at least one selected from the group consisting of a charging unit, a developing unit, and a transfer unit.

  Hereinafter, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto. In addition, the main part shown to a figure is demonstrated and the description is abbreviate | omitted about others.

FIG. 2 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment.
As shown in FIG. 2, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 including an electrophotographic photosensitive member 7, a transfer device 40 (primary transfer device), and an intermediate transfer member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where the electrophotographic photosensitive member 7 can be exposed from the opening of the process cartridge 300, and the transfer device 40 is interposed between the electrophotographic photosensitive member via the intermediate transfer member 50. 7, and a part of the intermediate transfer member 50 is disposed in contact with the electrophotographic photosensitive member 7. Although not shown, it also has a secondary transfer device that transfers the toner image transferred to the intermediate transfer member 50 to a recording medium (for example, paper). The intermediate transfer member 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) correspond to an example of a transfer unit.

  The process cartridge 300 in FIG. 2 includes an electrophotographic photosensitive member 7, a charging device 8 (an example of a charging unit), an exposure device 9 (an example of an electrostatic latent image forming unit), and a developing device 11 (of the developing unit) in a housing. An example) and a cleaning device 13 (an example of a cleaning means) are integrally supported. The cleaning device 13 includes a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is disposed so as to contact the surface of the electrophotographic photosensitive member 7. The cleaning member may be a conductive or insulating fibrous member instead of the cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

  In FIG. 2, as an image forming apparatus, a fibrous member 132 (roll shape) for supplying the lubricant 14 to the surface of the electrophotographic photosensitive member 7 and a fibrous member 133 (flat brush shape) for assisting in cleaning are shown. Examples are provided, but these are arranged as necessary.

  Hereinafter, each configuration of the image forming apparatus according to the present embodiment will be described.

<Electrophotographic photoreceptor>
Hereinafter, the electrophotographic photoreceptor according to the exemplary embodiment will be described with reference to the drawings.
FIG. 1 is a schematic partial cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor 7A according to this embodiment. The electrophotographic photoreceptor 7A shown in FIG. 1 has a structure in which an undercoat layer 1, a charge generation layer 2, and a charge transport layer 3 are laminated in this order on a conductive substrate 4. The charge generation layer 2 and the charge transport layer 3 constitute the photosensitive layer 5.

  The electrophotographic photoreceptor 7A may have a layer configuration in which the undercoat layer 1 is not provided. Further, the electrophotographic photoreceptor 7A may have a layer configuration in which a protective layer is further provided on the charge transport layer 3. Each electrophotographic photoreceptor 7A may be a single-layer type photosensitive layer in which the functions of the charge generation layer 2 and the charge transport layer 3 are integrated.

  Hereinafter, each element of the electrophotographic photosensitive member will be described. Note that the reference numerals of the elements of the electrophotographic photosensitive member will be omitted.

(Conductive substrate)
Examples of the conductive substrate include metal plates (eg, aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.), metal drums, metal belts, etc. Is mentioned. In addition, as the conductive substrate, for example, paper, resin film, belt, etc. coated, vapor-deposited or laminated with a conductive compound (for example, conductive polymer, indium oxide, etc.), metal (for example, aluminum, palladium, gold, etc.) or an alloy, etc. Also mentioned. Here, “conductive” means that the volume resistivity is less than 10 ¹³ Ωcm.

  When the electrophotographic photosensitive member is used in a laser printer, the surface of the conductive substrate has a center line average roughness Ra of 0.04 μm or more and 0.5 μm for the purpose of suppressing interference fringes generated when laser light is irradiated. The surface is preferably roughened below. When non-interfering light is used as a light source, roughening for preventing interference fringes is not particularly required, but it is suitable for extending the life because it suppresses generation of defects due to irregularities on the surface of the conductive substrate.

  Examples of the roughening method include wet honing by suspending an abrasive in water and spraying the conductive substrate, centerless grinding in which the conductive substrate is pressed against a rotating grindstone, and grinding is performed continuously. And anodizing treatment.

  As a roughening method, without roughening the surface of the conductive substrate, conductive or semiconductive powder is dispersed in the resin to form a layer on the surface of the conductive substrate. The method of roughening by the particle | grains disperse | distributed in a layer is also mentioned. As the roughening layer, an undercoat layer described later can also be used.

  In the roughening treatment by anodic oxidation, a metal (for example, aluminum) conductive substrate is used as an anode, and an oxide film is formed on the surface of the conductive substrate by anodizing in an electrolyte solution. Examples of the electrolyte solution include a sulfuric acid solution and an oxalic acid solution. However, the porous anodic oxide film formed by anodic oxidation is chemically active as it is, easily contaminated, and has a large resistance fluctuation due to the environment. Therefore, the pores of the oxide film are blocked by the volume expansion due to the hydration reaction in pressurized water vapor or boiling water (a metal salt such as nickel may be added) against the porous anodic oxide film, and more stable hydration oxidation It is preferable to perform a sealing treatment for changing to a product.

  The thickness of the anodized film is preferably, for example, 0.3 μm or more and 15 μm or less. When this film thickness is within the above range, the barrier property against implantation tends to be exhibited, and the increase in residual potential due to repeated use tends to be suppressed.

The conductive substrate may be treated with an acidic treatment liquid or boehmite treatment.
The treatment with the acidic treatment liquid is performed as follows, for example. First, an acidic treatment liquid containing phosphoric acid, chromic acid and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid and hydrofluoric acid in the acidic treatment liquid is, for example, in the range of 10% by mass to 11% by mass of phosphoric acid, in the range of 3% by mass to 5% by mass of chromic acid, The concentration of these acids is preferably in the range of 13.5% by mass or more and 18% by mass or less. The treatment temperature is preferably 42 ° C. or higher and 48 ° C. or lower, for example. The film thickness is preferably from 0.3 μm to 15 μm.

  The boehmite treatment is performed, for example, by immersing in pure water of 90 ° C. or higher and 100 ° C. or lower for 5 minutes to 60 minutes, or by contacting with heated steam of 90 ° C. or higher and 120 ° C. or lower for 5 minutes to 60 minutes. The film thickness is preferably 0.1 μm or more and 5 μm or less. This may be further anodized using an electrolyte solution with low film solubility such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, citrate, etc. Good.

(Undercoat layer)
The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

Examples of the inorganic particles include inorganic particles having a powder resistance (volume resistivity) of 10 ² Ωcm or more and 10 ¹¹ Ωcm or less.
Among these, as the inorganic particles having the resistance value, for example, metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles are preferable, and zinc oxide particles are particularly preferable.

The specific surface area of the inorganic particles by the BET method is preferably 10 m ² / g or more, for example.
The volume average particle diameter of the inorganic particles is, for example, preferably from 50 nm to 2000 nm (preferably from 60 nm to 1000 nm).

  For example, the content of the inorganic particles is preferably 10% by mass or more and 80% by mass or less, and more preferably 40% by mass or more and 80% by mass or less with respect to the binder resin.

  The inorganic particles may be subjected to a surface treatment. Two or more inorganic particles having different surface treatments or particles having different particle diameters may be mixed and used.

  Examples of the surface treatment agent include a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, and a surfactant. In particular, a silane coupling agent is preferable, and an amino group-containing silane coupling agent is more preferable.

  Examples of the silane coupling agent having an amino group include 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and N-2- (aminoethyl) -3-amino. Examples include, but are not limited to, propylmethyldimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, and the like.

  Two or more silane coupling agents may be used in combination. For example, a silane coupling agent having an amino group and another silane coupling agent may be used in combination. Other silane coupling agents include, for example, vinyltrimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycol. Sidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- ( Aminoethyl) -3-aminopropylmethyldimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, and the like, but are not limited thereto. It is not a thing.

  The surface treatment method using the surface treatment agent may be any method as long as it is a known method, and may be either a dry method or a wet method.

  The treatment amount of the surface treatment agent is preferably 0.5% by mass or more and 10% by mass or less with respect to the inorganic particles, for example.

  Here, the undercoat layer may contain an electron-accepting compound (acceptor compound) together with the inorganic particles from the viewpoint of enhancing the long-term stability of the electric characteristics and the carrier blocking property.

Examples of the electron accepting compound include quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, and the like. 2- (4-biphenyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (4-naphthyl) -1,3,4- Oxadiazole compounds such as oxadiazole and 2,5-bis (4-diethylaminophenyl) -1,3,4 oxadiazole; xanthone compounds; thiophene compounds; 3,3 ′, 5,5 ′ tetra- electron transporting substances such as diphenoquinone compounds such as t-butyldiphenoquinone;
In particular, the electron-accepting compound is preferably a compound having an anthraquinone structure. As the compound having an anthraquinone structure, for example, a hydroxyanthraquinone compound, an aminoanthraquinone compound, an aminohydroxyanthraquinone compound, and the like are preferable, and specifically, for example, anthraquinone, alizarin, quinizarin, anthralfin, and purpurin are preferable.

  The electron-accepting compound may be dispersed and included in the undercoat layer together with the inorganic particles, or may be included in a state of being attached to the surface of the inorganic particles.

  Examples of the method for attaching the electron accepting compound to the surface of the inorganic particles include a dry method and a wet method.

  In the dry method, for example, while stirring inorganic particles with a mixer having a large shearing force or the like, an electron-accepting compound dissolved directly or in an organic solvent is dropped and sprayed with dry air or nitrogen gas. It is a method of adhering to the surface of inorganic particles. When the electron-accepting compound is dropped or sprayed, it is preferably performed at a temperature not higher than the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be performed at 100 ° C. or higher. The baking is not particularly limited as long as it is a temperature and time for obtaining electrophotographic characteristics.

  In the wet method, for example, an electron-accepting compound is added while dispersing inorganic particles in a solvent by stirring, ultrasonic waves, a sand mill, an attritor, a ball mill, etc., and after stirring or dispersing, the solvent is removed to remove electrons. This is a method of attaching a receptive compound to the surface of inorganic particles. The solvent removal method is distilled off by filtration or distillation, for example. After removing the solvent, baking may be performed at 100 ° C. or higher. The baking is not particularly limited as long as it is a temperature and time for obtaining electrophotographic characteristics. In the wet method, the water content of the inorganic particles may be removed before adding the electron-accepting compound. Examples thereof include a method of removing while stirring and heating in a solvent, and a method of removing by azeotropic distillation with a solvent. Can be mentioned.

  The attachment of the electron-accepting compound may be performed before or after the surface treatment with the surface treatment agent is performed on the inorganic particles, or may be performed simultaneously with the attachment of the electron-accepting compound and the surface treatment with the surface treatment agent.

  The content of the electron-accepting compound is, for example, from 0.01% by mass to 20% by mass with respect to the inorganic particles, and preferably from 0.01% by mass to 10% by mass.

Examples of the binder resin used for the undercoat layer include acetal resins (eg, polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, and unsaturated polyesters. Resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, Known polymer compounds such as urethane resin, alkyd resin, epoxy resin; zirconium chelate compound; titanium chelate compound; aluminum chelate compound; titanium alkoxide compound ; Organic titanium compounds; known materials silane coupling agent, and the like.
Examples of the binder resin used for the undercoat layer include a charge transport resin having a charge transport group, a conductive resin (for example, polyaniline) and the like.

Among these, as the binder resin used for the undercoat layer, a resin insoluble in the upper coating solvent is preferable, and in particular, a urea resin, a phenol resin, a phenol-formaldehyde resin, a melamine resin, a urethane resin, and an unsaturated polyester. Thermosetting resins such as resins, alkyd resins, and epoxy resins; at least one resin selected from the group consisting of polyamide resins, polyester resins, polyether resins, methacrylic resins, acrylic resins, polyvinyl alcohol resins, and polyvinyl acetal resins; Resins obtained by reaction with curing agents are preferred.
When these binder resins are used in combination of two or more, the mixing ratio is set as necessary.

The undercoat layer may contain various additives for improving electrical characteristics, improving environmental stability, and improving image quality.
Additives include known materials such as electron transport pigments such as polycyclic condensation systems and azo systems, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. It is done. The silane coupling agent is used for the surface treatment of the inorganic particles as described above, but may be further added to the undercoat layer as an additive.

  Examples of the silane coupling agent as the additive include vinyltrimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3- Glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (Aminoethyl) -3-aminopropylmethylmethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane and the like can be mentioned.

  Examples of the zirconium chelate compound include zirconium butoxide, zirconium zirconium acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octoate, Zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, isostearate zirconium butoxide and the like.

  Examples of the titanium chelate compound include tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, and titanium lactate ammonium salt. , Titanium lactate, titanium lactate ethyl ester, titanium triethanolamate, polyhydroxy titanium stearate and the like.

  Examples of the aluminum chelate compound include aluminum isopropylate, monobutoxy aluminum diisopropylate, aluminum butyrate, diethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate) and the like.

  These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.

The undercoat layer preferably has a Vickers hardness of 35 or more.
The surface roughness (ten-point average roughness) of the undercoat layer is adjusted from 1 / 4n (n is the refractive index of the upper layer) to 1 / 2λ of the exposure laser wavelength λ used to suppress moire images. It should be done.
Resin particles or the like may be added to the undercoat layer for adjusting the surface roughness. Examples of the resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. Further, the surface of the undercoat layer may be polished for adjusting the surface roughness. Examples of the polishing method include buffing, sandblasting, wet honing, and grinding.

  There is no particular limitation on the formation of the undercoat layer, and a well-known formation method is used. For example, a coating film for forming an undercoat layer in which the above components are added to a solvent is formed, and the coating film is dried. And heating as necessary.

Solvents for preparing the coating solution for forming the undercoat layer include known organic solvents such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketone alcohol solvents, ether solvents. Examples include solvents and ester solvents.
Specific examples of these solvents include methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, Examples include ordinary organic solvents such as n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

  Examples of the dispersion method of the inorganic particles when preparing the coating liquid for forming the undercoat layer include known methods such as a roll mill, a ball mill, a vibration ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

  Examples of the method for applying the coating liquid for forming the undercoat layer onto the conductive substrate include, for example, a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method. The usual methods such as these are mentioned.

  The thickness of the undercoat layer is, for example, preferably set in the range of 15 μm or more, more preferably 18 μm or more and 50 μm or less.

(Middle layer)
Although illustration is omitted, an intermediate layer may be further provided between the undercoat layer and the photosensitive layer.
An intermediate | middle layer is a layer containing resin, for example. Examples of the resin used for the intermediate layer include an acetal resin (for example, polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, Polymer compounds such as polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, melamine resin, and the like can be given.
The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used for the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon.
The compounds used for these intermediate layers may be used alone or as a mixture or polycondensate of a plurality of compounds.

  Among these, the intermediate layer is preferably a layer containing an organometallic compound containing a zirconium atom or a silicon atom.

The formation of the intermediate layer is not particularly limited, and a well-known formation method is used. For example, a coating film of an intermediate layer forming coating solution in which the above components are added to a solvent is formed, and the coating film is dried and necessary. It is performed by heating according to.
As the coating method for forming the intermediate layer, usual methods such as a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a knife coating method, and a curtain coating method are used.

  For example, the thickness of the intermediate layer is preferably set in a range of 0.1 μm to 3 μm. An intermediate layer may be used as the undercoat layer.

(Charge generation layer)
The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. The charge generation layer may be a vapor deposition layer of a charge generation material. The vapor-deposited layer of the charge generation material is suitable when an incoherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array is used.

  Examples of the charge generating material include azo pigments such as bisazo and trisazo; fused aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide;

  Among these, in order to cope with near-infrared laser exposure, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generation material. Specifically, for example, hydroxygallium phthalocyanine disclosed in JP-A-5-263007, JP-A-5-279591, etc .; chlorogallium phthalocyanine disclosed in JP-A-5-98181; More preferred are dichlorotin phthalocyanines disclosed in JP-A No. 140472, JP-A No. 5-140473 and the like; and titanyl phthalocyanine disclosed in JP-A No. 4-189873.

  On the other hand, in order to cope with laser exposure in the near-ultraviolet region, as the charge generation material, condensed aromatic pigments such as dibromoanthanthrone; thioindigo pigments; porphyrazine compounds; zinc oxide; trigonal selenium; Bisazo pigments and the like disclosed in 2004-78147 and JP-A-2005-181992 are preferred.

  The above-described charge generation material may also be used in the case of using an incoherent light source such as an LED having a central wavelength of light emission of 450 nm to 780 nm and an organic EL image array. However, from the viewpoint of resolution, the photosensitive layer is 20 μm or less. When the thin film is used, the electric field strength in the photosensitive layer is increased, and a charge decrease due to charge injection from the substrate, that is, an image defect called a black spot is likely to occur. This becomes conspicuous when a charge generating material that easily generates a dark current is used in a p-type semiconductor such as trigonal selenium or a phthalocyanine pigment.

On the other hand, when an n-type semiconductor such as a condensed ring aromatic pigment, perylene pigment, azo pigment or the like is used as the charge generation material, dark current hardly occurs and even a thin film can suppress image defects called black spots. . Examples of the n-type charge generation material include compounds (CG-1) to (CG-27) described in paragraphs [0288] to [0291] of JP2012-155282A. It is not limited.
The n-type determination is performed by using a time-of-flight method that is usually used, and is determined by the polarity of the flowing photocurrent, and an n-type is more likely to flow electrons as carriers than holes.

Among these, the charge generation material is preferably a hydroxygallium phthalocyanine pigment, and more preferably a V-type hydroxygallium phthalocyanine pigment from the viewpoint of charge generation efficiency.
In particular, as a hydroxygallium phthalocyanine pigment, for example, in a spectral absorption spectrum in a wavelength region of 600 nm to 900 nm, a hydroxygallium phthalocyanine pigment having a maximum peak wavelength in a range of 810 nm to 839 nm can provide more excellent dispersibility. It is preferable from the viewpoint.

The hydroxygallium phthalocyanine pigment having the maximum peak wavelength in the range of 810 nm or more and 839 nm or less preferably has an average particle diameter in a specific range and a BET specific surface area in a specific range. Specifically, the average particle size is preferably 0.20 μm or less, and more preferably 0.01 μm or more and 0.15 μm or less. On the other hand, the BET specific surface area is preferably 45 m ² / g or more, more preferably 50 m ² / g or more, and particularly preferably 55 m ² / g or more and 120 m ² / g or less. The average particle size is a volume average particle size (d50 average particle size) measured by a laser diffraction / scattering particle size distribution analyzer (LA-700, manufactured by Horiba, Ltd.). Moreover, it is the value measured by the nitrogen substitution method using the BET-type specific surface area measuring device (Shimadzu Corporation make: Flow soap II2300).

  The maximum particle size (maximum primary particle size) of the hydroxygallium phthalocyanine pigment is preferably 1.2 μm or less, more preferably 1.0 μm or less, and still more preferably 0.3 μm or less.

The hydroxygallium phthalocyanine pigment preferably has an average particle size of 0.2 μm or less, a maximum particle size of 1.2 μm or less, and a specific surface area value of 45 m ² / g or more.

  The hydroxygallium phthalocyanine pigment has a Bragg angle (2θ ± 0.2 °) of at least 7.3 °, 16.0 °, 24.9 °, 28.0 ° in an X-ray diffraction spectrum using CuKα characteristic X-rays. It is preferable that it is V type which has a diffraction peak.

  The charge generation material may be used alone or in combination of two or more.

The binder resin used for the charge generation layer is selected from a wide range of insulating resins, and the binder resin is selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinyl anthracene, polyvinyl pyrene, and polysilane. You may choose.
As the binder resin, for example, polyvinyl butyral resin, polyarylate resin (polycondensate of bisphenol and aromatic divalent carboxylic acid, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, Examples thereof include polyamide resin, acrylic resin, polyacrylamide resin, polyvinyl pyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinyl pyrrolidone resin, and the like. Here, “insulating” means that the volume resistivity is 10 ¹³ Ωcm or more.
These binder resins are used singly or in combination of two or more.

  The mixing ratio of the charge generation material and the binder resin is preferably in the range of 10: 1 to 1:10 by mass ratio.

  In addition, the charge generation layer may contain a known additive.

  The formation of the charge generation layer is not particularly limited, and a known formation method is used. For example, a coating film of a charge generation layer forming coating solution in which the above components are added to a solvent is formed, and the coating film is dried. And heating as necessary. The charge generation layer may be formed by vapor deposition of a charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when a condensed ring aromatic pigment or perylene pigment is used as the charge generation material.

  Solvents for preparing the charge generation layer forming coating solution include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-acetate. -Butyl, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene and the like. These solvents are used alone or in combination of two or more.

Examples of a method for dispersing particles (for example, a charge generation material) in a coating solution for forming a charge generation layer include, for example, a media disperser such as a ball mill, a vibrating ball mill, an attritor, a sand mill, a horizontal sand mill, a stirring, an ultrasonic disperser, etc. Medialess dispersers such as roll mills and high-pressure homogenizers are used. Examples of the high-pressure homogenizer include a collision method in which a dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high pressure state, and a penetration method in which a fine flow path is dispersed in a high pressure state.
In this dispersion, it is effective that the average particle size of the charge generation material in the coating solution for forming the charge generation layer is 0.5 μm or less, preferably 0.3 μm or less, more preferably 0.15 μm or less. .

  Examples of methods for applying the charge generation layer forming coating solution on the undercoat layer (or on the intermediate layer) include blade coating, wire bar coating, spray coating, dip coating, bead coating, and air knife coating. And usual methods such as a curtain coating method.

  The film thickness of the charge generation layer is, for example, preferably set in the range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

(Charge transport layer)
The charge transport layer is, for example, a layer containing a charge transport material and a binder resin.
As the charge transport material, a butadiene-based charge transport material (CT1) and a benzidine-based charge transport material (CT2) are applied. The charge transport layer containing the butadiene-based charge transport material (CT1) and the benzidine-based charge transport material (CT2) further includes at least selected from the group consisting of a hindered phenol-based antioxidant and a benzophenone-based ultraviolet absorber. Contains one species. Furthermore, the charge transport layer may contain fluorine-containing resin particles and a fluorine-containing dispersant.

-Charge transport material-
The butadiene based charge transport material (CT1) will be described.
The butadiene-based charge transport material (CT1) is a charge transport material represented by the following general formula (CT1).

In the general formula (CT1), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 carbon atom. It represents an alkoxy group having 20 or less or an aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure.
n and m each independently represents 0, 1 or 2.

In the general formula (CT1), examples of the halogen atom represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, as a halogen atom, a fluorine atom and a chlorine atom are preferable and a chlorine atom is more preferable.

In the general formula (CT1), the alkyl group represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 has 1 to 20 carbon atoms (preferably 1 to 6 or less, more preferably 1 4 or less), a linear or branched alkyl group.
Specific examples of the linear alkyl group include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n- Nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n- Nonadecyl group, n-icosyl group, etc. are mentioned.
Specific examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, and tert-hexyl group. , Isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert- Decyl group, isoundecyl group, sec-undecyl group, tert-undecyl group, neoundecyl group, isododecyl group, sec-dodecyl group, tert-dodecyl group, neododecyl group, isotridecyl group, sec-tridecyl group, tert-tridecyl group, neotridecyl group Group, isotetradecyl group, sec-tetradecyl group, tert-tetradecyl group, neotetradecyl group, 1-isobutyl-4-ethyloctyl group, isopentadecyl group, sec-pentadecyl group, tert-pentadecyl group, neopenta Decyl group, isohexadecyl group, sec-hexadecyl group, tert-hexadecyl group, neohexadecyl group, 1-methylpentadecyl group, isoheptadecyl group, sec-heptadecyl group, tert-heptadecyl group, neoheptadecyl group, isooctadecyl group, sec-octadecyl group, tert-octadecyl group, neooctadecyl group, isonononadecyl group, sec-nonadecyl group, tert-nonadecyl group, neononadecyl group, 1-methyloctyl group, isoicosyl group, sec-icosyl group, te t- eicosyl group, Neoikoshiru group and the like.
Among these, the alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, or an isopropyl group.

In the general formula (CT1), the alkoxy group represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 has 1 to 20 carbon atoms (preferably 1 to 6 or less, more preferably 1 Or a linear or branched alkoxy group of 4 or less).
Specific examples of the linear alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, and an n-octyloxy group. Group, n-nonyloxy group, n-decyloxy group, n-undecyloxy group, n-dodecyloxy group, n-tridecyloxy group, n-tetradecyloxy group, n-pentadecyloxy group, n-hexadecyl group An oxy group, n-heptadecyloxy group, n-octadecyloxy group, n-nonadecyloxy group, n-icosyloxy group, etc. are mentioned.
Specific examples of the branched alkoxy group include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec -Hexyloxy group, tert-hexyloxy group, isoheptyloxy group, sec-heptyloxy group, tert-heptyloxy group, isooctyloxy group, sec-octyloxy group, tert-octyloxy group, isononyloxy group, sec-nonyloxy group, tert-nonyloxy group, isodecyloxy group, sec-decyloxy group, tert-decyloxy group, isoundecyloxy group, sec-undecyloxy group, tert-undecyloxy group, neoundecyloxy group , Isodo Siloxy group, sec-dodecyloxy group, tert-dodecyloxy group, neododecyloxy group, isotridecyloxy group, sec-tridecyloxy group, tert-tridecyloxy group, neotridecyloxy group, isotetradecyloxy group Group, sec-tetradecyloxy group, tert-tetradecyloxy group, neotetradecyloxy group, 1-isobutyl-4-ethyloctyloxy group, isopentadecyloxy group, sec-pentadecyloxy group, tert-pentadecyl group Oxy group, neopentadecyloxy group, isohexadecyloxy group, sec-hexadecyloxy group, tert-hexadecyloxy group, neohexadecyloxy group, 1-methylpentadecyloxy group, isoheptadecyloxy group, sec -Heptadecyloxy Group, tert-heptadecyloxy group, neoheptadecyloxy group, isooctadecyloxy group, sec-octadecyloxy group, tert-octadecyloxy group, neooctadecyloxy group, isononadecyloxy group, sec-nonadecyloxy group, tert- Examples include nonadecyloxy group, neononadecyloxy group, 1-methyloctyloxy group, isoicosyloxy group, sec-icosyloxy group, tert-icosyloxy group, neoicosyloxy group and the like.
Among these, as an alkoxy group, a methoxy group is preferable.

In the general formula (CT1), the aryl group represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 has 6 to 30 carbon atoms (preferably 6 to 20 or less, more preferably 6 And aryl groups of 16 or less).
Specific examples of the aryl group include a phenyl group, a naphthyl group, a phenanthryl group, and a biphenylyl group.
Among these, the aryl group is preferably a phenyl group or a naphthyl group.

Note that in the general formula (CT1), each of the substituents represented by R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 further includes a group having a substituent. Examples of the substituent include the atoms and groups exemplified above (for example, a halogen atom, an alkyl group, an alkoxy group, an aryl group, etc.).

In the general formula (CT1), two adjacent substituents of R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 (for example, R ^C11 and R ^C12 , R ^C13 and R ^C14 , R R ^In the hydrocarbon ring structure in which ^C15 and R ^C16 are connected, the groups connecting the substituents are a single bond, 2,2′-methylene group, 2,2′-ethylene group, 2,2′- A vinylene group etc. are mentioned, Among these, a single bond and a 2,2'-methylene group are preferable.
Here, specific examples of the hydrocarbon ring structure include a cycloalkane structure, a cycloalkene structure, a cycloalkanepolyene structure, and the like.

  In general formula (CT1), n and m are preferably 1.

In the general formula (CT1), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 are hydrogen atoms and have 1 or more carbon atoms from the viewpoint of forming a photosensitive layer (charge transport layer) having a high charge transport capability. It represents an alkyl group having 20 or less or an alkoxy group having 1 to 20 carbon atoms, and m and n preferably represent 1 or 2, and R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R More preferably, ^C16 represents a hydrogen atom, and m and n represent 1.
That is, the butadiene-based charge transport material (CT1) is more preferably a charge transport material (exemplary compound (CT1-3)) represented by the following structural formula (CT1A).

  Specific examples of the butadiene-based charge transport material (CT1) are shown below, but are not limited thereto.

In addition, the abbreviations in the above exemplary compounds have the following meanings. Moreover, the number attached | subjected before a substituent has shown the substitution position with respect to a benzene ring.
· -CH _3: methyl groups · -OCH _3: methoxy

  A butadiene type charge transport material (CT1) may be used individually by 1 type, and may use 2 or more types together.

The benzidine charge transport material (CT2) will be described.
The benzidine charge transport material (CT2) is a charge transport material represented by the following general formula (CT2).

In the general formula (CT2), R ^C21 , R ^C22 , and R ^C23 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or Represents an aryl group having 6 to 10 carbon atoms.

In the general formula (CT2), examples of the halogen atom represented by R ^C21 , R ^C22 , and R ^C23 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, as a halogen atom, a fluorine atom and a chlorine atom are preferable and a chlorine atom is more preferable.

In the general formula (CT2), the alkyl group represented by R ^C21 , R ^C22 , and R ^C23 is a linear or straight chain having 1 to 10 carbon atoms (preferably 1 to 6 or less, more preferably 1 to 4 or less). A branched alkyl group is exemplified.
Specific examples of the linear alkyl group include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n- Nonyl group, n-decyl group, etc. are mentioned.
Specific examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, and tert-hexyl group. , Isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert- A decyl group etc. are mentioned.
Among these, the alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, or an isopropyl group.

In the general formula (CT2), the alkoxy group represented by R ^C21 , R ^C22 , and R ^C23 is a straight chain having 1 to 10 carbon atoms (preferably 1 to 6 and more preferably 1 to 4). A branched alkoxy group is mentioned.
Specific examples of the linear alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, and an n-octyloxy group. Group, n-nonyloxy group, n-decyloxy group and the like.
Specific examples of the branched alkoxy group include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec -Hexyloxy group, tert-hexyloxy group, isoheptyloxy group, sec-heptyloxy group, tert-heptyloxy group, isooctyloxy group, sec-octyloxy group, tert-octyloxy group, isononyloxy group, A sec-nonyloxy group, a tert-nonyloxy group, an isodecyloxy group, a sec-decyloxy group, a tert-decyloxy group and the like can be mentioned.
Among these, as an alkoxy group, a methoxy group is preferable.

In the general formula (CT2), examples of the aryl group represented by R ^C21 , R ^C22 , and R ^C23 include aryl groups having 6 to 10 carbon atoms (preferably 6 to 9 and more preferably 6 to 8). It is done.
Specific examples of the aryl group include a phenyl group and a naphthyl group.
Among these, as the aryl group, a phenyl group is preferable.

Note that in the general formula (CT2), each of the substituents represented by R ^C21 , R ^C22 , and R ^C23 further includes a group having a substituent. Examples of the substituent include the atoms and groups exemplified above (for example, a halogen atom, an alkyl group, an alkoxy group, an aryl group, etc.).

In general formula (CT2), R ^C21 , R ^C22 , and R ^C23 are each independently a hydrogen atom or a carbon number of 1 or more, particularly from the viewpoint of forming a photosensitive layer (charge transport layer) having a high charge transport capability. Preferably, it represents an alkyl group having 10 or less, more preferably R ^C21 and R ^C23 represent a hydrogen atom, and R ^C22 represents an alkyl group having 1 to 10 carbon atoms (particularly a methyl group).
Specifically, the benzidine charge transport material (CT2) is particularly preferably a charge transport material (exemplary compound (CT2-2)) represented by the following structural formula (CT2A).

  Specific examples of the benzidine-based charge transport material (CT2) are shown below, but are not limited thereto.

In addition, the abbreviations in the above exemplary compounds have the following meanings. Moreover, the number attached | subjected before a substituent has shown the substitution position with respect to a benzene ring.
· -CH _3: methyl groups · _-C 2 _{H 5:} ethyl · -OCH _3: methoxy · _-OC 2 _{H 5:} ethoxy

  A benzidine type charge transport material (CT2) may be used individually by 1 type, and may use 2 or more types together.

The hindered phenol antioxidant will be described.
The hindered phenol-based antioxidant is a compound having a hindered phenol ring and having a molecular weight of 300 or more.

  In the hindered phenol antioxidant, the hindered phenol ring is, for example, a phenol ring in which at least one alkyl group having 4 to 8 carbon atoms (for example, a branched alkyl group having 4 to 8 carbon atoms) is substituted. It is. More specifically, the hindered phenol ring is, for example, a phenol ring in which the ortho position with respect to the phenolic hydroxyl group is substituted with a tertiary alkyl group (for example, tert-butyl group).

As a hindered phenolic antioxidant,
1) an antioxidant having one hindered phenol ring,
2) A linking group having 2 to 4 hindered phenol rings and comprising a linear or branched divalent to tetravalent aliphatic hydrocarbon group, or a divalent to tetravalent aliphatic group. A linking group in which at least one of an ester bond (—C (═O) O—) and an ether bond (—O—) is interposed between carbon-carbon bonds of a hydrocarbon group, and is a hinder of 2 or more and 4 or less Antioxidant to which dophenol ring is linked 3) 2 or more and 4 or less hindered phenol rings and one benzene ring (unsubstituted or substituted benzene ring substituted with alkyl group or the like) or isocyanurate ring And an antioxidant in which 2 or more and 4 or less hindered phenol rings are each linked to a benzene ring or an isocyanurate ring via an alkylene group.

  Specifically, as the hindered phenol-based antioxidant, an antioxidant represented by the following general formula (HP) is preferable from the viewpoint of suppressing ghosting and light fatigue.

In General Formula (HP), R ^H1 and R ^H2 each independently represent a branched alkyl group having 4 to 8 carbon atoms.
R ^H3 and R ^H4 each independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.
R ^H5 represents an alkylene group having 1 to 10 carbon atoms.

In the general formula (HP), examples of the alkyl group represented by R ^H1 and R ^H2 include branched alkyl groups having 4 to 8 carbon atoms (preferably 4 to 6 carbon atoms).
Specific examples of the branched alkyl group include isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group. , Sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group and tert-octyl group.
Among these, as an alkyl group, a tert-butyl group and a tert-pentyl group are preferable, and a tert-butyl group is more preferable.

In General Formula (HP), examples of R ^H3 and R ^H4 include linear or branched alkyl groups having 1 to 10 carbon atoms (preferably 1 to 4 carbon atoms).
Specific examples of the linear alkyl group include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n- Nonyl group, n-decyl group, etc. are mentioned.
Specific examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, and tert-hexyl group. , Isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert- A decyl group etc. are mentioned.
Among these, the alkyl group is preferably a lower alkyl group such as a methyl group or an ethyl group.

In General Formula (HP), R ^H5 represents a linear or branched alkylene group having 1 to 10 carbon atoms (preferably 1 to 4 carbon atoms).
Specifically as a linear alkylene group, a methylene group, ethylene group, n-propylene group, n-butylene group, n-pentylene group, n-hexylene group, n-heptylene group, n-octylene group, n- Nonylene group, n-decylene group, etc. are mentioned.
Specific examples of the branched alkylene group include isopropylene group, isobutylene group, sec-butylene group, tert-butylene group, isopentylene group, neopentylene group, tert-pentylene group, isohexylene group, sec-hexylene group, tert-hexylene. Group, isoheptylene group, sec-heptylene group, tert-heptylene group, isooctylene group, sec-octylene group, tert-octylene group, isononylene group, sec-nonylene group, tert-nonylene group, isodecylene group, sec-decylene group, tert -A decylene group etc. are mentioned.
Among these, the alkylene group is preferably a lower alkylene group such as a methylene group, an ethylene group, or a butylene group.

In the general formula (HP), each of the substituents represented by R ^H1 , R ^H2 , R ^H3 , R ^H4 , and R ^H5 further includes a group having a substituent. Examples of the substituent include a halogen atom (for example, a fluorine atom and a chlorine atom), an alkoxy group (for example, an alkoxy group having 1 to 4 carbon atoms), an aryl group (for example, a phenyl group, a naphthyl group, and the like).

In formula (HP), in particular, from the viewpoint of suppression of seizure ghost and optical ^{fatigue, R H1,} and preferably representing the ^{R H2} is tert- butyl ^{group, R H1,} and ^{R H2} is a tert- butyl group R ^H3 and R ^H4 preferably represent an alkyl group having 1 to 3 carbon atoms (particularly a methyl group), and R ^H5 preferably represents an alkylene group having 1 to 4 carbon atoms (particularly a methylene group).
Specifically, the hindered phenol antioxidant is particularly preferably a hindered phenol antioxidant represented by the exemplified compound (HP-3).

  The molecular weight of the hindered phenol-based antioxidant is preferably 300 or more and 1000 or less, more preferably 300 or more and 900 or less, and still more preferably 300 or more and 800 or less, from the viewpoint of suppression of seizure ghost and light fatigue.

  Although the specific example of a hindered phenolic antioxidant is shown below, it is not necessarily limited to this.

  A hindered phenolic antioxidant may be used individually by 1 type, and may use 2 or more types together.

Next, the benzophenone ultraviolet absorber will be described.
A benzophenone-based ultraviolet absorber is a compound having a benzophenone skeleton.

  As the benzophenone-based ultraviolet absorber, 1) a compound in which two benzene rings are unsubstituted, 2) two benzene rings each independently comprising a hydroxyl group, a halogen atom, an alkyl group, an alkoxy group, and an aryl group And a compound substituted with at least one substituent selected from: In particular, the benzophenone-based ultraviolet absorber is preferably a compound in which at least one hydroxyl group is substituted on one of the two benzene rings (particularly, at a position ortho to the —C (═O) — group).

  Specifically, as the benzophenone-based ultraviolet absorber, an ultraviolet absorber represented by the following general formula (BP) is preferable from the viewpoint of suppressing seizure ghost and light fatigue.

In General Formula (BP), R ^B1 , R ^B2 , and R ^B3 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or Represents an aryl group having 6 to 10 carbon atoms.

In the general formula (BP), examples of the halogen atom represented by R ^B1 , R ^B2 , and R ^B3 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, as a halogen atom, a fluorine atom and a chlorine atom are preferable and a chlorine atom is more preferable.

In the general formula (BP), the alkyl group represented by R ^B1 , R ^B2 , and R ^B3 is a straight chain having 1 to 10 carbon atoms (preferably 1 to 6 and more preferably 1 to 4). A branched alkyl group is exemplified.
Specific examples of the linear alkyl group include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n- Nonyl group, n-decyl group, etc. are mentioned.
Specific examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, and tert-hexyl group. , Isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert- A decyl group etc. are mentioned.
Among these, the alkyl group is preferably a lower alkyl group such as a methyl group, an ethyl group, or an isopropyl group.

In the general formula (BP), the alkoxy group represented by R ^B1 , R ^B2 , and R ^B3 is a straight chain having 1 to 10 carbon atoms (preferably 1 to 6 and more preferably 1 to 4). A branched alkoxy group is mentioned.
Specific examples of the linear alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, and an n-octyloxy group. Group, n-nonyloxy group, n-decyloxy group and the like.
Specific examples of the branched alkoxy group include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec -Hexyloxy group, tert-hexyloxy group, isoheptyloxy group, sec-heptyloxy group, tert-heptyloxy group, isooctyloxy group, sec-octyloxy group, tert-octyloxy group, isononyloxy group, A sec-nonyloxy group, a tert-nonyloxy group, an isodecyloxy group, a sec-decyloxy group, a tert-decyloxy group and the like can be mentioned.
Among these, as an alkoxy group, a methoxy group is preferable.

In the general formula (BP), examples of the aryl group represented by R ^B1 , R ^B2 , and R ^B3 include aryl groups having 6 to 10 carbon atoms (preferably 6 to 9 or less, more preferably 6 or more and 8 or less). It is done.
Specific examples of the aryl group include a phenyl group and a naphthyl group.
Among these, as the aryl group, a phenyl group is preferable.

Note that in the general formula (BP), each of the substituents represented by R ^B1 , R ^B2 , and R ^B3 further includes a group having a substituent. Examples of the substituent include the atoms and groups exemplified above (for example, a halogen atom, an alkyl group, an alkoxy group, an aryl group, etc.).

In general formula (BP), it is preferable that R ^B1 and R ^B2 represent a hydrogen atom and R ^B3 represents an alkoxy group having 1 to 3 carbon atoms, particularly from the viewpoint of suppressing seizure ghost and light fatigue. .
Specifically, the ultraviolet absorber is particularly preferably a charge transport material (Exemplary Compound (BP-3)) represented by the following structural formula (BPA).

  Specific examples of the charge transport material represented by the general formula (CT1) are shown below, but are not limited thereto.

In addition, the abbreviations in the above exemplary compounds have the following meanings. Moreover, the number attached | subjected before a substituent has shown the substitution position with respect to a benzene ring.
· -CH _3: methyl groups · _-C 2 _{H 5:} ethyl _{· - (CH 2) 7 -CH} 3: octyl · -OCH _3: methoxy · -OH: hydroxy groups

  A benzophenone type ultraviolet absorber may be used individually by 1 type, and may use 2 or more types together.

Next, the contents of the charge transport material, the antioxidant and the ultraviolet absorber will be described.
The content of the butadiene-based charge transporting material (CT1) is 0 in terms of the blending ratio of CT1 and the binder resin (mass ratio CT1: binder resin) from the viewpoint of forming a photosensitive layer (charge transport layer) having a high charge transport ability. Preferably in the range from 1: 9.9 to 4.0: 6.0, more preferably in the range from 0.4: 9.6 to 3.5: 6.5, More preferably, it is in the range of 0.6: 9.4 to 3.0: 7.0.

  The content of the benzidine-based charge transport material (CT2) is the blending ratio of CT2 and the binder resin (mass ratio CT2: binder resin) in terms of forming a photosensitive layer (charge transport layer) having a high charge transport capability. : Preferably in the range from 9 to 7: 3, more preferably in the range from 2: 8 to 6: 4, still more preferably in the range from 2: 8 to 4: 6. .

Mass ratio of content of butadiene based charge transport material (CT1) and content of benzidine based charge transport material (CT2) (content of butadiene based charge transport material (CT1) / content of benzidine based charge transport material (CT2) The amount is preferably from 1/9 to 5/5, more preferably from 1/9 to 4/6, and from 1/9 to 3 /, from the viewpoint of forming a photosensitive layer (charge transport layer) having a high charge transport capability. 7 or less is more preferable.
In particular, if the mass ratio of the content of the butadiene-based charge transport material (CT1) and the content of the benzidine-based charge transport material (CT2) is within the above range, seizure ghost and light fatigue are likely to occur. The occurrence of seizure ghost and light fatigue is suppressed by at least one selected from the group consisting of a system antioxidant and a benzophenone ultraviolet absorber.

  In addition, you may use together charge transport materials other than a butadiene type charge transport material (CT1) and a benzidine type charge transport material (CT2). However, in that case, the content of the other charge transport material in the total charge transport material is preferably 10% by mass or less (preferably 5% by mass or less).

  The content of the hindered phenolic antioxidant is preferably 0.5% by mass or more and 30.0% by mass or less with respect to 100% by mass of the total charge transporting material from the viewpoint of suppression of seizure ghost and light fatigue, 0.5 mass% or more and 15 mass% or less are more preferable, and 0.5 mass% or more and 9.0 mass% or less are still more preferable. In addition, content of this hinder phenolic antioxidant has shown the number of parts (mass part) when content of all the charge transport materials is 100 mass parts.

  The content of the benzophenone-based ultraviolet absorber is preferably 0.5% by mass or more and 30.0% by mass or less with respect to 100% by mass of the total charge transporting material from the viewpoint of suppression of seizure ghost and light fatigue. More preferably, it is 0.5 mass% or more and 15 mass% or less, and 0.5 mass% or more and 9.0 mass% or less are still more preferable. In addition, content of this benzophenone series ultraviolet absorber has shown the number of parts (mass part) when content of all the charge transport materials is 100 mass parts.

  It should be noted that the content of the hindered phenolic antioxidant and the benzophenone ultraviolet absorber is 30.0% by mass or less, so that the antioxidant and the ultraviolet absorber can inhibit the charge transporting ability of the charge transporting material. It is suppressed. That is, the inhibition of formation of an electrostatic latent image on the surface of the photoreceptor due to light irradiation is suppressed, and an image having a target density can be easily obtained.

Next, the binder resin will be described.
The binder resin used for the charge transport layer is BP polycarbonate resin. The BP polycarbonate resin is a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton.

Examples of the BP polycarbonate resin include biphenyl copolymerized polycarbonate resins having a structural unit represented by the following general formula (PCA) as a structural unit having a biphenyl skeleton and another structural unit.
Examples of other structural units include structural units having a bisphenol skeleton (for example, bisphenol A, bisphenol B, bisphenol BP, bisphenol C, bisphenol F, bisphenol Z, etc.).

  Specific examples of the BP polycarbonate resin include a copolymer of a dihydroxybiphenyl compound and a dihydroxybisphenol compound. This copolymer can be obtained, for example, by a method such as polycondensation with a carbonate ester-forming compound such as phosgene or transesterification with bisaryl carbonate using a dihydroxybiphenyl compound and a dihydroxybisphenol compound as raw materials.

The dihydroxybiphenyl compound is a biphenyl compound having a biphenyl skeleton and having one hydroxyl group on each of the two benzene rings of the biphenyl skeleton. Examples of the dihydroxybiphenyl compound include 4,4′-dihydroxybiphenyl, 4,4′-dihydroxy-3,3′-dimethylbiphenyl, 4,4′-dihydroxy-2,2′-dimethylbiphenyl, and 4,4 ′. -Dihydroxy-3,3'-dicyclohexylbiphenyl, 3,3'-difluoro-4,4'-dihydroxybiphenyl, 4,4'-dihydroxy-3,3'-diphenylbiphenyl and the like.
These dihydroxybiphenyl compounds may be used alone or in combination.

The dihydroxy bisphenol compound is a bisphenol compound having a bisphenol skeleton, and each having one hydroxyl group on two benzene rings of the bisphenol skeleton. Examples of the dihydroxybisphenol compound include bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 1,2-bis (4-hydroxyphenyl) ethane, and 2,2-bis (4 -Hydroxyphenyl) propane, 2,2-bis (3-methyl-4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) octane, 4 , 4-bis (4-hydroxyphenyl) heptane, 1,1-bis (4-hydroxyphenyl) -1,1-diphenylmethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1 -Bis (4-hydroxyphenyl) -1-phenylmethane, bis (4-hydroxyphenyl) ether, bis (4-hydroxy Loxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) cyclopentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (3-methyl) -4-hydroxyphenyl) propane, 2- (3-methyl-4-hydroxyphenyl) -2- (4-hydroxyphenyl) -1-phenylethane, bis (3-methyl-4-hydroxyphenyl) sulfide, bis ( 3-methyl-4-hydroxyphenyl) sulfone, bis (3-methyl-4-hydroxyphenyl) methane, 1,1-bis (3-methyl-4-hydroxyphenyl) cyclohexane, 2,2-bis (2-methyl) -4-hydroxyphenyl) propane, 1,1-bis (2-butyl-4-hydroxy-5-methyl) Phenyl) butane, 1,1-bis (2-tert-butyl-4-hydroxy-3-methylphenyl) ethane, 1,1-bis (2-tert-butyl-4-hydroxy-5-methylphenyl) propane, 1,1-bis (2-tert-butyl-4-hydroxy-5-methylphenyl) butane, 1,1-bis (2-tert-butyl-4-hydroxy-5-methylphenyl) isobutane, 1,1- Bis (2-tert-butyl-4-hydroxy-5-methylphenyl) heptane, 1,1-bis (2-tert-butyl-4-hydroxy-5-methylphenyl) -1-phenylmethane, 1,1- Bis (2-tert-amyl-4-hydroxy-5-methylphenyl) butane, bis (3-chloro-4-hydroxyphenyl) methane, bis (3,5-di- Bromo-4-hydroxyphenyl) methane, 2,2-bis (3-chloro-4-hydroxyphenyl) propane, 2,2-bis (3-fluoro-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 (3-bromo-4-hydroxy-5-chlorophenyl) propane, 2,2-bis (3,5-dichloro-4) -Hydroxyphenyl) butane, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) butane, 1-phenyl-1,1-bis (3-fluoro-4) Hydroxyphenyl) ethane, bis (3-fluoro-4-hydroxyphenyl) ether, 1,1-bis (3-cyclohexyl-4-hydroxyphenyl) cyclohexane.
These bisphenol compounds may be used alone or in combination.

  Among these, BP polycarbonate resin is a structural unit represented by the following general formula (PCA), a structural unit represented by the following general formula (PCB), from the point of wear resistance of the photosensitive layer (charge transport layer), Polycarbonate resin containing is preferable.

In the general formulas (PCA) and (PCB), R ^P1 , R ^P2 , R ^P3 , and R ^P4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or 5 to 7 carbon atoms. The following cycloalkyl group or an aryl group having 6 to 12 carbon atoms is represented. X ^P1 represents a phenylene group, a biphenylene group, a naphthylene group, an alkylene group, or a cycloalkylene group.

In general formulas (PCA) and (PCB), the alkyl group represented by R ^P1 , R ^P2 , R ^P3 , and R ^P4 is a straight chain having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms). Or a branched alkyl group is mentioned.
Specific examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and an n-hexyl group.
Specific examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, and tert-hexyl group. Etc.
Among these, the alkyl group is preferably a lower alkyl group such as a methyl group or an ethyl group.

Examples of the cycloalkyl group represented by R ^P1 , R ^P2 , R ^P3 , and R ^{P4 in the} general formulas (PCA) and (PCB) include cyclopentyl, cyclohexyl, and cycloheptyl.

In the general formulas (PCA) and (PCB), examples of the aryl group represented by R ^P1 , R ^P2 , R ^P3 , and R ^P4 include a phenyl group, a naphthyl group, and a biphenylyl group.

In the general formula (PCA) and ^(PCB), the alkylene group represented by ^{X P1,} 1 to 12 carbon atoms (preferably having from 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms) linear Or a branched alkylene group is mentioned.
Specifically as a linear alkylene group, a methylene group, ethylene group, n-propylene group, n-butylene group, n-pentylene group, n-hexylene group, n-heptylene group, n-octylene group, n- Nonylene group, n-decylene group, n-undecylene group, n-dodecylene group and the like can be mentioned.
Specific examples of the branched alkylene group include isopropylene group, isobutylene group, sec-butylene group, tert-butylene group, isopentylene group, neopentylene group, tert-pentylene group, isohexylene group, sec-hexylene group, tert-hexylene. Group, isoheptylene group, sec-heptylene group, tert-heptylene group, isooctylene group, sec-octylene group, tert-octylene group, isononylene group, sec-nonylene group, tert-nonylene group, isodecylene group, sec-decylene group, tert -Decylene group, isoundecylene group, sec-undecylene group, tert-undecylene group, neoundecylene group, isododecylene group, sec-dodecylene group, tert-dodecylene group, neododecylene group, etc.
Among these, the alkylene group is preferably a lower alkyl group such as a methylene group, an ethylene group, or a butylene group.

In general formulas (PCA) and (PCB), the cycloalkylene group represented by ^XP1 is a cycloalkylene group having 3 to 12 carbon atoms (preferably 3 to 10 carbon atoms, more preferably 5 to 8 carbon atoms). Groups.
Specific examples of the cycloalkyl group include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, and a cyclododecanyl group.
Among these, as the cycloalkyl group, a cyclohexyl group is preferable.

In the general formulas (PCA) and (PCB), each of the substituents represented by R ^P1 , R ^P2 , R ^P3 , R ^P4 , and X ^P1 further includes a group having a substituent. Examples of the substituent include a halogen atom (for example, a fluorine atom and a chlorine atom), an alkyl group (for example, an alkyl group having 1 to 6 carbon atoms), and a cycloalkyl group (for example, a cycloalkyl group having 5 to 7 carbon atoms). , An alkoxy group (for example, an alkoxy group having 1 to 4 carbon atoms), an aryl group (for example, a phenyl group, a naphthyl group, a biphenylyl group, and the like).

In General Formula (PCA), R ^P1 and R ^P2 each independently preferably represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ^P1 and R ^P2 represent a hydrogen atom. It is more preferable.
In the general formula (PCB), R ^P3 and R ^P4 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and X ^P1 preferably represents an alkylene group or a cycloalkylene group. .

  Specific examples of the BP polycarbonate resin include the following, but are not limited thereto. In the exemplified compounds, pm and pn represent copolymerization ratios.

Here, in the BP polycarbonate resin, the content (copolymerization ratio) of the structural unit represented by the general formula (PCA) is in the range of 5 mol% to 95 mol% with respect to all the structural units constituting the BP polycarbonate resin. From the viewpoint of improving the abrasion resistance of the photosensitive layer (charge transport layer), it is preferably in the range of 5 to 50 mol%, more preferably in the range of 15 to 30 mol%.
Specifically, in the above exemplary compounds of the BP polycarbonate resin, pm and pn indicate a copolymerization ratio (molar ratio), but pm: pn = 95: 5 to 5:95, 50:50 to 5:95. More preferably, the range of 15:85 to 30:70 is mentioned.

The viscosity average molecular weight of the BP polycarbonate resin is preferably, for example, 20,000 or more and 80,000 or less.
In addition, as a measuring method of the viscosity average molecular weight of BP polycarbonate resin, it is a value measured by the following method. 1 g of resin was uniformly dissolved in 100 cm ³ of methylene chloride, and its specific viscosity ηsp was measured with an Ubbelohde viscometer in a measurement environment at 25 ° C., and a relational expression of ηsp / c = [η] +0.45 [η] 2c ( However c is determined the concentration (g / cm ³⁾ than the intrinsic viscosity [η] (cm3 / g), the equations given by H.Schnell, [η] = 1.23 × 10-4Mv0.83 relationship Further, the viscosity average molecular weight Mv is obtained.

  The BP polycarbonate resin may be used in combination with other binder resins. However, the other binder resin is preferably used in an amount of 10% by mass (preferably 5% by mass or less) with respect to the total binder resin.

Here, the content of the BP polycarbonate resin is preferably 10% by mass or more and 90% by mass or less, and more preferably 30% by mass or more and 90% by mass or less with respect to the total solid content of the photosensitive layer (charge transport layer). 50 mass% or more and 90 mass% or less is still more preferable.
In addition, the blending ratio (mass ratio = binder resin: charge transport material) of all the binder resins and the charge transport material is desirably 10: 1 to 1: 5.

Next, the fluorine-containing resin particles will be described.
Examples of the fluorine-containing resin particles include a tetrafluoroethylene resin, a trifluorinated ethylene chloride resin, a hexafluoropropylene resin, a vinyl fluoride resin, a vinylidene fluoride resin, a difluorodiethylene chloride resin, and their co-polymerization. It is desirable to select one or more of the coalesced particles. Among these, as the fluorine-containing resin particles, tetrafluoroethylene resin particles and vinylidene fluoride resin particles are particularly desirable.

The primary particle size of the fluorine-containing resin particles is preferably 0.05 μm or more and 1 μm or less, and preferably 0.1 μm or more and 0.5 μm or less.
The primary particles are obtained by obtaining a sample piece from the photosensitive layer (charge transport layer) and observing it with a SEM (scanning electron microscope) at a magnification of, for example, 5000 times or more. The maximum diameter of the fluororesin particles in the primary particle state And measure this as the average value of 50 particles. Note that a JSM-6700F manufactured by JEOL Ltd. is used as the SEM, and a secondary electron image with an acceleration voltage of 5 kV is observed.

  Examples of commercially available fluororesin particles include Lubron (registered trademark) series (manufactured by Daikin Industries, Ltd.), Teflon (registered trademark) series (manufactured by DuPont), Dinion (registered trademark) series (manufactured by Sumitomo 3M), and the like. It is done.

  The content of the fluorine-containing resin particles is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass with respect to the total solid content of the photosensitive layer (charge transport layer). More preferably, the content is 15% by mass or less.

Next, the fluorine-containing dispersant will be described.
Examples of the fluorine-containing dispersant include a polymer obtained by homopolymerizing or copolymerizing a polymerizable compound having a fluorinated alkyl group (hereinafter also referred to as “fluorinated alkyl group-containing polymer”).

Specifically, as a fluorine-containing dispersant, a homopolymer of a (meth) acrylate having a fluorinated alkyl group, a random or block copolymer of a (meth) acrylate having a fluorinated alkyl group and a monomer having no fluorine atom Examples include coalescence. In addition, (meth) acrylate means both acrylate and methacrylate.
Examples of the (meth) acrylate having a fluorinated alkyl group include 2,2,2-trifluoroethyl (meth) acrylate and 2,2,3,3,3-pentafluoropropyl (meth) acrylate.
Examples of the monomer having no fluorine atom include (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and isobornyl. (Meth) acrylate, cyclohexyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 2-ethoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, benzyl (meth) Acrylate, ethyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4- Droxybutyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, hydroxyethyl o-phenylphenol (meth) acrylate, o -Phenylphenol glycidyl ether (meth) acrylate.

  In addition, specific examples of the fluorine-containing dispersant include block or branch polymers disclosed in US Pat. No. 5,637,142 and US Pat. No. 4,251,662. Furthermore, specific examples of the fluorine-containing dispersant include fluorine-based surfactants.

  Among these, as the fluorine-containing dispersant, a fluorinated alkyl group-containing polymer having a structural unit represented by the following general formula (FA) is preferable. The structural unit represented by the following general formula (FA) and the following general formula A fluorinated alkyl group-containing polymer having a structural unit represented by (FB) is more preferred.

  Hereinafter, the fluorinated alkyl group-containing polymer having a structural unit represented by the following general formula (FA) and a structural unit represented by the following general formula (FB) will be described.

In general formulas (FA) and (FB), R ^F1 , R ^F2 , R ^F3 and R ^F4 each independently represent a hydrogen atom or an alkyl group.
X ^F1 represents an alkylene chain, a halogen-substituted alkylene chain, —S—, —O—, —NH—, or a single bond.
Y ^F1 represents an alkylene chain, a halogen-substituted alkylene chain,-(C _fx H _2fx-1 (OH))-or a single bond.
Q ^F1 represents —O— or —NH—.
fl, fm, and fn each independently represent an integer of 1 or more.
fp, fq, fr and fs each independently represent 0 or an integer of 1 or more.
ft represents an integer of 1 to 7.
fx represents an integer of 1 or more.

In general formulas (FA) and (FB), groups representing R ^F1 , R ^F2 , R ^F3 and R ^F4 are preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, etc., more preferably a hydrogen atom or a methyl group. Preferably, a methyl group is more preferable.

In general formulas (FA) and (FB), the alkylene chain (unsubstituted alkylene chain, halogen-substituted alkylene chain) representing X ^F1 and Y ^F1 is a linear or branched alkylene chain having 1 to 10 carbon atoms. Is preferred.
_{Fx in} — (C _fx H _2fx-1 (OH)) — representing Y ^F1 preferably represents an integer of 1 or more and 10 or less.
It is preferable that fp, fq, fr and fs each independently represent 0 or an integer of 1 or more and 10 or less.
For example, fn is preferably 1 or more and 60 or less.

  Here, in the fluorine-containing dispersant, the ratio of the structural unit represented by the general formula (FA) to the structural unit represented by the general formula (FB), that is, fl: fm is from 1: 9 to 9: 1. A range is preferable, and a range from 3: 7 to 7: 3 is more preferable.

  In addition to the fluorine-containing dispersant, the structural unit represented by the general formula (FA) and the structural unit represented by the general formula (FB), it may further have a structural unit represented by the general formula (FC). . The content ratio of the structural unit represented by the general formula (FC) is the sum of the structural units represented by the general formulas (FA) and (FB), that is, the ratio (fl + fm: fz) to fl + fm from 10: 0 to 7: A range of up to 3 is preferred, and a range of 9: 1 to 7: 3 is more preferred.

In general formula (FC), R ^F5 and R ^F6 each independently represent a hydrogen atom or an alkyl group. fz represents an integer of 1 or more.

In the general formula (FC), the group representing R ^F5 and R ^F6 is preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, more preferably a hydrogen atom or a methyl group, and even more preferably a methyl group.

  Commercially available fluorine-containing dispersants include, for example, GF300, GF400 (manufactured by Toagosei Co., Ltd.), Surflon series (manufactured by AGC Seikekikal), Footage series (manufactured by Neos), PF series (manufactured by Kitamura Chemical), Examples include the MegaFuck series (manufactured by DIC) and FC series (manufactured by 3M).

The weight average molecular weight of the fluorine-containing dispersant is, for example, preferably from 2000 to 250,000, more preferably from 3000 to 150,000, and still more preferably from 50,000 to 100,000.
The weight average molecular weight of the fluorine-containing dispersant is a value measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed using, for example, a Tosoh GPC / HLC-8120 as a measuring apparatus, a Tosoh column / TSKgel GMHHR-M + TSKgel GMHHR-M (7.8 mm ID 30 cm), and a chloroform solvent. From this measurement result, a molecular weight calibration curve prepared with a monodisperse polystyrene standard sample is used for calculation.

The content of the fluorinated alkyl group-containing copolymer is, for example, preferably from 0.5% by mass to 10% by mass, and more preferably from 1% by mass to 7% by mass with respect to the mass of the fluorine-containing resin particles.
In addition, a fluoroalkyl group containing copolymer may be used individually by 1 type, or may use 2 or more types together.

  In addition, the charge transport layer may contain a known additive.

  The formation of the charge transport layer is not particularly limited, and a well-known formation method is used. This is done by heating as necessary.

  Solvents for preparing the coating solution for forming the charge transport layer include aromatic hydrocarbons such as benzene, toluene, xylene and chlorobenzene; ketones such as acetone and 2-butanone; methylene chloride, chloroform and ethylene chloride. Halogenated aliphatic hydrocarbons: Usual organic solvents such as cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents are used alone or in combination of two or more.

  Coating methods for applying the charge transport layer forming coating solution on the charge generation layer include blade coating method, wire bar coating method, spray coating method, dip coating method, bead coating method, air knife coating method, curtain A usual method such as a coating method may be mentioned.

  The film thickness of the charge transport layer is, for example, preferably set in the range of 5 μm to 50 μm, more preferably 10 μm to 30 μm.

(Protective layer)
The protective layer is provided on the photosensitive layer as necessary. The protective layer is provided, for example, for the purpose of preventing chemical change of the photosensitive layer during charging or further improving the mechanical strength of the photosensitive layer.
Therefore, it is preferable to apply a layer composed of a cured film (crosslinked film) as the protective layer. Examples of these layers include the layers shown in 1) or 2) below.

1) A layer composed of a cured film of a composition containing a reactive group-containing charge transporting material having a reactive group and a charge transporting skeleton in the same molecule (that is, a polymer or cross-linking of the reactive group-containing charge transporting material) Layer containing body)
2) a layer composed of a cured film of a composition comprising a non-reactive charge transport material and a reactive group-containing non-charge transport material having a reactive group and having no charge transport skeleton (that is, A layer comprising a non-reactive charge transport material and a polymer or a cross-linked product of the reactive group-containing non-charge transport material)

The reactive group of the reactive group-containing charge transport material includes a chain polymerizable group, an epoxy group, —OH, —OR [wherein R represents an alkyl group], —NH ₂ , —SH, —COOH, —SiR. ^Q1 _3-Qn (OR ^Q2 ) _Qn [wherein R ^Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group, and R ^Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group. Qn represents an integer of 1 to 3], and the like, and other well-known reactive groups.

  The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization. For example, it is a functional group having a group containing at least a carbon double bond. Specific examples include groups containing at least one selected from vinyl groups, vinyl ether groups, vinyl thioether groups, styryl groups, vinylphenyl groups, acryloyl groups, methacryloyl groups, and derivatives thereof. Among them, the chain polymerizable group is a group containing at least one selected from a vinyl group, a vinylphenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof because of its excellent reactivity. preferable.

  The charge transporting skeleton of the reactive group-containing charge transporting material is not particularly limited as long as it is a known structure in an electrophotographic photoreceptor, and examples thereof include triarylamine compounds, benzidine compounds, hydrazone compounds, and the like. And a structure conjugated from a nitrogen-containing hole transporting compound and conjugated with a nitrogen atom. Among these, a triarylamine skeleton is preferable.

  The reactive group-containing charge transport material having a reactive group and a charge transport skeleton, a non-reactive charge transport material, and a reactive group-containing non-charge transport material may be selected from well-known materials.

  In addition, the protective layer may contain known additives.

  The formation of the protective layer is not particularly limited, and a well-known forming method is used. It is performed by performing a curing process such as heating as necessary.

Solvents for preparing the coating solution for forming the protective layer include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; tetrahydrofuran And ether solvents such as dioxane; cellosolv solvents such as ethylene glycol monomethyl ether; alcohol solvents such as isopropyl alcohol and butanol. These solvents are used alone or in combination of two or more.
The protective layer forming coating solution may be a solventless coating solution.

  As a method for applying the coating solution for forming the protective layer on the photosensitive layer (for example, charge transport layer), dip coating method, push-up coating method, wire bar coating method, spray coating method, blade coating method, knife coating method, curtain coating method. Ordinary methods such as a method may be mentioned.

  The thickness of the protective layer is, for example, preferably set in the range of 1 μm to 20 μm, more preferably 2 μm to 10 μm.

(Single layer type photosensitive layer)
The single-layer type photosensitive layer (charge generation / charge transport layer) is, for example, a layer containing a charge generation material, a charge transport material, a binder resin, and, if necessary, other known additives. Note that these materials are the same as those described for the charge generation layer and the charge transport layer.
In the single-layer type photosensitive layer, the content of the charge generating material is preferably 10% by mass or more and 85% by mass or less, and preferably 20% by mass or more and 50% by mass or less with respect to the total solid content.
On the other hand, the content of the charge transport material, the binder resin (BP polycarbonate resin), the antioxidant and the ultraviolet absorber in the single layer type photosensitive layer is the same as the content in the charge transport layer.
The method for forming the single-layer type photosensitive layer is the same as the method for forming the charge generation layer and the charge transport layer.
The film thickness of the single-layer type photosensitive layer is, for example, from 5 μm to 50 μm, and preferably from 10 μm to 40 μm.

<Charging device>
As the charging device 8, for example, a contact type charger using a conductive or semiconductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube or the like is used. Further, a non-contact type roller charger, a known charger such as a scorotron charger using a corona discharge or a corotron charger may be used.

<Exposure device>
As the exposure device 9, for example, an optical device or the like that exposes light of a light emitting diode in a predetermined image-like manner on the surface of the electrophotographic photosensitive member 7 is applied. That is, the exposure apparatus 9 is an exposure apparatus having a light emitting diode (LED: light emitting diode) as a light source.
Specifically, as the exposure apparatus 9 having LEDs as light sources, for example, an LED array in which a large number of LEDs are arranged on a long substrate and a lens in which a large number of gradient index rod lenses are arranged. And an LED print head with an array. Here, the array means an element array in which elements such as a plurality of LEDs and a plurality of lenses are arranged one-dimensionally or two-dimensionally. In the LED array, for example, 1200 pixels per inch (that is, 1200 dpi (dot per inch)), and a large number of LEDs are arranged corresponding to the number of pixels in the main scanning direction. A cylindrical rod lens is used as the gradient index rod lens.
In addition, it is preferable that the LED has a wavelength of light to be irradiated in the spectral sensitivity region of the electrophotographic photosensitive member 7.

<Developing device>
Examples of the developing device 11 include a general developing device that performs development by bringing a developer into contact or non-contact with the developer. The developing device 11 is not particularly limited as long as it has the functions described above, and is selected according to the purpose. For example, a known developing device having a function of attaching a one-component developer or a two-component developer to the electrophotographic photosensitive member 7 using a brush, a roller, or the like can be used. Among these, those using a developing roller holding the developer on the surface are preferable.

  The developer used in the developing device 11 may be a one-component developer including a toner alone or a two-component developer including a toner and a carrier. Further, the developer may be magnetic or non-magnetic. A well-known thing is applied for these developers.

<Cleaning device>
As the cleaning device 13, a cleaning blade type device including a cleaning blade 131 is used.
In addition to the cleaning blade method, a fur brush cleaning method and a simultaneous development cleaning method may be employed.

<Transfer device>
As the transfer device 40, for example, a contact transfer charger using a belt, a roller, a film, a rubber blade, etc., or a known transfer charger such as a scorotron transfer charger using a corona discharge or a corotron transfer charger. Can be mentioned.

<Intermediate transfer member>
As the intermediate transfer member 50, a belt-like member (intermediate transfer belt) containing polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber or the like having semiconductivity is used. Further, as the form of the intermediate transfer member, a drum-like one may be used in addition to the belt-like.

FIG. 3 is a schematic configuration diagram illustrating another example of the image forming apparatus according to the present embodiment.
An image forming apparatus 120 shown in FIG. 3 is a tandem multicolor image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, four process cartridges 300 are arranged in parallel on the intermediate transfer member 50, and one electrophotographic photosensitive member is used for one color. The image forming apparatus 120 has the same configuration as that of the image forming apparatus 100 except that it is a tandem system.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

<Production of photoconductor>
[Photoreceptor 1]
100 parts by mass of zinc oxide (trade name: MZ 300, manufactured by Teika Co., Ltd.), 10 parts by mass of a 10% by mass toluene solution of N-2- (aminoethyl) -3-aminopropyltriethoxysilane as a silane coupling agent Then, 200 parts by mass of toluene was mixed and stirred, and refluxed for 2 hours. Thereafter, toluene was distilled off under reduced pressure at 10 mmHg and baked at 135 ° C. for 2 hours to carry out surface treatment of zinc oxide with a silane coupling agent.
Surface-treated zinc oxide: 33 parts by mass, blocked isocyanate (trade name: Sumidur 3175, manufactured by Sumitomo Bayern Urethane Co., Ltd.): 6 parts by mass, compound represented by the following structural formula (AK-1): 1 part by mass, methyl ethyl ketone : 25 parts by mass mixed for 30 minutes, butyral resin (trade name: ESREC BM-1, manufactured by Sekisui Chemical Co., Ltd.): 5 parts by mass, silicone ball (trade name: Tospearl 120, manufactured by Momentive Performance Materials Co., Ltd.) ): 3 parts by mass, silicone oil as a leveling agent (trade name: SH29PA, manufactured by Toray Dow Corning Silicone): 0.01 parts by mass was added, dispersed for 3 hours in a sand mill, and applied for forming an undercoat layer A liquid was obtained.
Further, the coating solution for forming the undercoat layer is applied on an aluminum substrate having a diameter of 30 mm, a length of 340 mm, and a wall thickness of 0.7 mm by dip coating, followed by drying and curing at 185 ° C. for 30 minutes, An undercoat layer having a thickness of 30 μm was obtained.

Next, the hydroxygallium phthalocyanine pigment “Cukα characteristic X-ray using a Cukα characteristic X-ray has a Bragg angle (2θ ± 0.2 °) of at least 7.3 °, 16.0 °, 24.9 as a charge generation material. V-type hydroxygallium phthalocyanine pigment having a diffraction peak at a position of °, 28.0 ° (maximum peak wavelength in spectral absorption spectrum in wavelength range of 600 nm to 900 nm = 820 nm, average particle diameter = 0.12 μm, maximum particle Diameter = 0.2 μm, specific surface area value = 60 m ² / g) ”, vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, manufactured by Nihon Unicar) as a binder resin, and n-butyl acetate. The mixture is placed in a 100 mL glass bottle with a 1.0 mmφ glass bead at a filling rate of 50% and 2 using a paint shaker. Dispersion treatment was performed for 5 hours to obtain a charge generation layer coating solution. With respect to the mixture of the hydroxygallium phthalocyanine pigment and the vinyl chloride-vinyl acetate copolymer resin, the content of the hydroxygallium phthalocyanine pigment was 55.0% by volume, and the solid content of the dispersion was 6.0% by mass. Content, hydroxygallium phthalocyanine pigment density of 1.606g / cm ³ of vinyl chloride - calculated as specific gravity 1.35 g / cm ³ vinyl acetate copolymer resin.
The obtained coating solution for forming a charge generation layer was dip-coated on the undercoat layer and dried at 100 ° C. for 5 minutes to form a charge generation layer having a thickness of 0.20 μm.

Next, as a charge transport material, 8.0 parts by mass of a butadiene-based charge transport material (CT1) “exemplary compound (CT1-1)” and a benzidine-based charge transport material (CT2) “exemplary compound (CT2-1)” 32. 0 part by mass, as binder resin, BP polycarbonate resin “Exemplary compound (PC-1), pm: pn = 25: 75, viscosity average molecular weight = 50,000” 60.0 parts by mass, and fluorine-containing resin particles, Tetrafluoroethylene resin particles (volume average particle diameter 200 nm): 8 parts by mass, and as a fluorine-containing dispersant, GF400 (manufactured by Toa Gosei Co., Ltd .: a surfactant having at least a methacrylate having a fluoroalkyl group as a polymerization component): 0.3 parts by weight and 3.2 parts by weight of a hindered phenol antioxidant “Exemplary Compound (HP-1), molecular weight 775” (total charge transport material) 8.0 mass%) and the total amount 100 mass%, and dissolved in tetrahydrofuran 340.0 parts by mass, to obtain a charge transport layer coating solution.
The obtained charge transport layer forming coating solution was dip-coated on the charge generation layer and dried at 140 ° C. for 25 minutes to form a charge transport layer having a thickness of 25 μm.

  The photoreceptor 1 was obtained through the above steps.

[Photosensitive members 2 to 4]
According to Table 1, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 1 except that the type of the charge transport material and the type of the hindered phenol antioxidant were changed.

[Photoreceptor 5]
Instead of the hindered phenolic antioxidant as the antioxidant, 3.2 parts by weight of the benzophenone-based ultraviolet absorber “Exemplary Compound (BP-1)” as the ultraviolet absorber (total amount of all charge transport materials 100% by mass) An electrophotographic photosensitive member was produced in the same manner as the photosensitive member 1 except that 8.0% by mass) was used.

[Photosensitive members 6 to 8]
According to Table 1, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 5 except that the type of the charge transport material and the type of the benzophenone-based ultraviolet absorber were changed.

[Photoreceptor 9]
As an antioxidant, together with 3.2 parts by weight of a hindered phenolic antioxidant “Exemplary Compound (HP-1), Molecular Weight 775” (8.0% by mass relative to 100% by mass of the total charge transporting material), Furthermore, except that 3.2 parts by mass of the benzophenone-based UV absorber “Exemplary Compound (BP-1)” (8.0% by mass with respect to 100% by mass of the total charge transporting material) was used as the UV absorber. In the same manner as the photoconductor 1, an electrophotographic photoconductor was produced.

[Photosensitive member 10]
According to Table 1, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 9, except that the type of hindered phenol antioxidant and the type of benzophenone ultraviolet absorber were changed.

[Photosensitive members 11 to 20]
According to Table 1, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 9, except that the type of charge transport material, the type of hindered phenolic antioxidant, and the type of benzophenone ultraviolet absorber were changed. did.

[Photosensitive members 21 to 25]
According to Table 1, electrophotographic photosensitivity was obtained in the same manner as the photoreceptor 20 except that the amount of hindered phenolic antioxidant as an antioxidant and the amount of benzophenone ultraviolet absorber as an ultraviolet absorber were changed. The body was made.

[Photosensitive members 26 to 37]
According to Table 2, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 9, except that the type and amount of the charge transport material, the type and amount of the antioxidant, and the type and amount of the ultraviolet absorber were changed. did.

[Photoconductor 38]
Except for using 60.0 parts by mass of bisphenol Z polycarbonate resin PCZ400 (bisphenol Z homopolymer polycarbonate resin, viscosity average molecular weight 39,000) instead of BP polycarbonate resin, the same as photoconductor 32 An electrophotographic photosensitive member was produced.

<Example 1>
The obtained electrophotographic photosensitive member (photosensitive member 1) was mounted on an electrophotographic image forming apparatus (manufactured by Fuji Xerox Co., Ltd .: DocuCentre SC2021 modified machine), and this modified machine was used as the image forming apparatus of Example 1. The electrostatic latent image forming apparatus mounted on the remodeling machine is an electrostatic latent image forming apparatus using a light emitting diode as a light source.

<Examples 2-31 and Comparative Examples 1-7>
An image forming apparatus (Examples 2 to 25 and Comparative Examples 1 to 7) similar to that of Example 1 was obtained except that the type of the photoreceptor was changed according to Tables 3 and 4.

<Evaluation>
Using the image forming apparatus of each example, “burn-in ghost”, “light fatigue”, and “halftone image density” were evaluated in the following manner.

(Evaluation of seizure ghost)
Using the image forming apparatus of each example, after continuously outputting 3000 lattice pattern charts on A3 size paper, an entire halftone image (Cyan color full halftone image) having an image density of 20% is printed on A3 size paper. One sheet was output.
Then, the output whole-surface halftone image was observed, and visual sensory evaluation (grade determination) was performed on the density difference between the continuous image output portion and the discontinuous image output portion of the lattice pattern. Grade determination is performed in increments of 0.5G from 0G to 5G. The smaller the G number, the smaller the density difference, indicating that no ghosting has occurred. The allowable grade of seizure ghost is 3.5G or less. All image output was performed in an environment of 28 ° C. and 85% RH. The results are shown in Tables 3-5.

(Evaluation of light fatigue)
First, before the electrophotographic photosensitive member (photosensitive members 1 to 38) is mounted on the image forming apparatus of each example, it is wound around black paper having a 2 cm square window so that only the window opening portion is exposed to light. Then, the electrophotographic photosensitive member was exposed to light by leaving it under a white fluorescent lamp (1000 Lux) for 10 minutes.
Next, the light-exposed electrophotographic photosensitive member was mounted on the image forming apparatus of each example, and one full-tone halftone image (Cyan) having an image density of 50% was output on A3 size paper.
Then, the output half-tone image was observed, and visual sensory evaluation (grade determination) was performed on the density difference between the light exposed portion and the non-light exposed portion. Grade determination is performed in increments of 0.5G from 0G to 5G, and the smaller the G number, the smaller the density difference and the less light fatigue occurs. The allowable grade of light fatigue is 3.5G or less. All image output was performed in an environment of 28 ° C. and 85% RH. The results are shown in Tables 3-4.

(Evaluation of halftone image density)
Using the image forming apparatus of each example, one full-tone halftone image (Cyan) having an image density of 50% was output on A3 size paper.
Then, the output entire halftone image was observed to check whether the target image density was output. All image output was performed in an environment of 28 ° C. and 85% RH. The results are shown in Tables 3-4.

From the above results, it can be seen that “burn-in ghost” and “light fatigue” are suppressed in this example as compared with the comparative example.
In addition, Examples 1 to 20 in which the blending amounts of the hindered phenol-based antioxidant and the benzophenone-based ultraviolet absorber are appropriate have a target halftone image density as compared with Examples 21 to 25. Recognize.

  Here, as an exposure apparatus for writing an electrostatic latent image on a photoreceptor, an image forming apparatus (from exposure to development) having a laser ROS (Raster Output Scanner) type exposure apparatus that scans light emitted from a laser light source with a polygon mirror. The photoconductor 1 (the photoconductor corresponding to the example) was mounted at a time of 0.07 seconds, and “burn-in ghost” and “light fatigue” were evaluated. Light fatigue "was 2.0G. From this, it can be seen that in an image forming apparatus including an exposure device having a light emitting diode as a light source, “burn-in ghost” and “light fatigue” are likely to occur, and these are improved in this embodiment.

Details of the abbreviations in Tables 1 and 2 are as follows.
CT1-1: Exemplary compound (CT1-1) of butadiene-based charge transport material (CT1)
CT1-2: Exemplified compound (CT1-2) of butadiene-based charge transport material (CT1)
CT1-3: Exemplified compound (CT1-3) of butadiene based charge transport material (CT1)
CT2-1: Exemplary compound (CT2-1) of benzidine charge transport material (CT2)
CT2-2: Exemplary compound (CT2-2) of benzidine charge transport material (CT2)
PC-1: BP polycarbonate resin exemplified compound (PC-1)
PCZ400: bisphenol Z type polycarbonate resin (homopolymerized polycarbonate resin of bisphenol Z, viscosity average molecular weight 39,000)
-HP-1: Illustrative compound of a hindered phenolic antioxidant (HP-1)
-HP-2: Example compound (HP-2) of hindered phenolic antioxidant
HP-3: Exemplary compound of hindered phenolic antioxidant (HP-3)
CAO-1: Comparative compound of antioxidant (see hindered phenol-based antioxidant represented by the following structural formula (CAO-1))
CAO-2: antioxidant comparison compound (see hindered amine antioxidant represented by the following structural formula (CAO-2))

BP-1: Exemplary compound of benzophenone ultraviolet absorber (BP-1)
-BP-2: Illustrative compound (BP-2) of benzophenone UV absorber
BP-3: Exemplary compound (BP-3) of benzophenone ultraviolet absorber
CUA-1: Comparative compound of UV absorber (see benzoate UV absorber represented by the following structural formula (CUA-1))

  DESCRIPTION OF SYMBOLS 1 Subbing layer, 2 Charge generation layer, 3 Charge transport layer, 4 Conductive substrate, 7A, 7 Electrophotographic photosensitive member, 8 Charging device, 9 Exposure device, 11 Developing device, 13 Cleaning device, 14 Lubricant, 40 Transfer Apparatus, 50 intermediate transfer member, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll shape), 133 fibrous member (flat brush shape), 300 process cartridge

Claims (11)

A conductive substrate and a photosensitive layer disposed on the conductive substrate, the charge generation material, a charge transport material represented by the following general formula (CT1), a charge transport material represented by the following general formula (CT2), A photosensitive layer containing at least one selected from the group consisting of a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton, and a hindered phenol antioxidant having a molecular weight of 300 or more and a benzophenone ultraviolet absorber; An electrophotographic photoreceptor having
Charging means for charging the surface of the electrophotographic photosensitive member;
An electrostatic latent image forming unit that has a light emitting diode as a light source and forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member by exposure with the light emitting diode;
Developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
Transfer means for transferring the toner image to the surface of the recording medium;
An image forming apparatus comprising:

(In the general formula (CT1), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or a carbon number. It represents an alkoxy group having 1 to 20 carbon atoms or an aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure, where n and m are each Independently represents 0, 1 or 2.)

(In general formula (CT2), R ^C21 , R ^C22 , and R ^C23 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or And represents an aryl group having 6 to 10 carbon atoms.) The charge transport material represented by the general formula (CT1), wherein R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 represent a hydrogen atom, and m and n represent 1. Image forming apparatus. The charge transport material represented by the general formula (CT2), wherein R ^C21 and R ^C23 represent a hydrogen atom, and R ^C22 represents an alkyl group having 1 to 10 carbon atoms. Image forming apparatus. The image forming apparatus according to claim 1, wherein the hindered phenol-based antioxidant is an antioxidant represented by the following general formula (HP).

(In General Formula (HP), R ^H1 and R ^H2 each independently represents a branched alkyl group having 4 to 8 carbon atoms. R ^H3 and R ^H4 each independently represent a hydrogen atom, Or, it represents an alkyl group having 1 to 10 carbon atoms, and R ^H5 represents an alkylene group having 1 to 10 carbon atoms.) The image forming apparatus according to claim 4, wherein in the antioxidant represented by the general formula (HP), R ^H1 and R ^H2 represent a tert-butyl group. The image forming apparatus according to claim 1, wherein the benzophenone-based ultraviolet absorber is an ultraviolet absorber represented by the following general formula (BP).

(In General Formula (BP), R ^B1 , R ^B2 , and R ^B3 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or And represents an aryl group having 6 to 10 carbon atoms.) The image formation according to claim 6, wherein in the benzophenone-based ultraviolet absorber represented by the general formula (BP), R ^B1 and R ^B2 represent a hydrogen atom, and R ^B3 represents an alkoxy group having 1 to 4 carbon atoms. apparatus.   The image forming apparatus according to claim 1, wherein the charge generation material is a hydroxygallium phthalocyanine pigment. The biphenyl copolymer polycarbonate resin is a polycarbonate resin containing a structural unit represented by the following general formula (PCA) and a structural unit represented by the following general formula (PCB). The image forming apparatus according to claim 1.

(In the general formulas (PCA) and (PCB), R ^P1 , R ^P2 , R ^P3 , and R ^P4 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or 5 or more carbon atoms. 7 a cycloalkyl group, or, .X ^P1 representing an aryl group having 6 to 12 carbon atoms, a phenylene group, biphenylene group, naphthylene group, an alkylene group, or a cycloalkylene group.)   The image forming apparatus according to claim 1, wherein the photosensitive layer further includes fluorine-containing resin particles and a fluorine-containing dispersant. A conductive substrate and a photosensitive layer disposed on the conductive substrate, the charge generation material, a charge transport material represented by the following general formula (CT1), a charge transport material represented by the following general formula (CT2), A photosensitive layer containing at least one selected from the group consisting of a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton, and a hindered phenol antioxidant having a molecular weight of 300 or more and a benzophenone ultraviolet absorber; An electrophotographic photoreceptor having
An electrostatic latent image forming unit that has a light emitting diode as a light source and forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member by exposure with the light emitting diode;
And a process cartridge that is detachably attached to the image forming apparatus.

(In the general formula (CT1), R ^C11 , R ^C12 , R ^C13 , R ^C14 , R ^C15 , and R ^C16 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or a carbon number. It represents an alkoxy group having 1 to 20 carbon atoms or an aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure, where n and m are each Independently represents 0, 1 or 2.)

(In general formula (CT2), R ^C21 , R ^C22 , and R ^C23 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or And represents an aryl group having 6 to 10 carbon atoms.)