JP2016184033A - Image forming apparatus and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that has suppressed the occurrence of seizing ghost occurring when a single image is continuously output and the occurrence of optical fatigue occurring when an electrophotographic photoreceptor is exposed to light.SOLUTION: There is provided an image forming apparatus comprising: an electrophotographic photoreceptor that includes a photosensitive layer including a charge transport material of formula (CT1), a charge transport material having a specific structure, a biphenyl copolymerization type polycarbonate resin, and at least one of a hindered phenolic antioxidant and a benzophenone ultraviolet absorber; and charging means of a contact type or a proximity type that applies a voltage in which an AC voltage is superimposed on a DC voltage to charge the electrophotographic photoreceptor.SELECTED DRAWING: None

Description

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

  2. Description of the Related Art Conventionally, as an electrophotographic image forming apparatus, an apparatus that sequentially performs processes such as charging, electrostatic latent image formation, development, transfer, and cleaning using an electrophotographic photosensitive member is 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 charge generating material, a charge transporting material represented by the general formula (CT1), a charge transporting material represented by the general formula (CT2), and a biphenyl copolymerized polycarbonate comprising a structural unit having a biphenyl skeleton. A photosensitive layer containing a resin, and an electrophotographic photoreceptor further comprising 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; An image forming apparatus comprising a contact-type or proximity-type charging unit that applies a voltage obtained by superimposing an alternating voltage on a voltage to charge an electrophotographic photosensitive member, an electrostatic latent image forming unit, a developing unit, and a transfer unit. Compared to the case, the occurrence of burn-in ghost that occurs when the same image is output continuously and the occurrence of light fatigue when the electrophotographic photosensitive member is exposed to light. We are to provide an image forming apparatus which suppresses.

  The above problem is solved by the following means.

The invention according to claim 1
A conductive substrate, a photosensitive layer disposed on the conductive substrate, a charge generation material, a charge transport material represented by the following general formula (CT1), and a charge transport represented by the following general formula (CT2) A material, a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton, and at least one selected from the group consisting of a hindered phenol antioxidant having a molecular weight of 300 or more and a benzophenone ultraviolet absorber An electrophotographic photoreceptor having a photosensitive layer;
Contact-type or proximity-type charging means for applying a voltage obtained by superimposing an AC voltage on a DC voltage to charge the electrophotographic photosensitive member;
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
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.

(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. This is an 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. An 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
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 any one of claims 1 to 5, 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. Device.

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, a photosensitive layer disposed on the conductive substrate, a charge generation material, a charge transport material represented by the following general formula (CT1), and a charge transport represented by the following general formula (CT2) A material, a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton, and at least one selected from the group consisting of a hindered phenol antioxidant having a molecular weight of 300 or more and a benzophenone ultraviolet absorber An electrophotographic photoreceptor having a photosensitive layer;
A contact-type or proximity-type charging unit that applies a voltage obtained by superimposing an AC voltage on a DC voltage to charge the electrophotographic photosensitive member, and
It is a process cartridge that can be attached to and detached from 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 biphenyl including a structural unit having a biphenyl skeleton An electrophotographic photosensitive material further comprising at least one selected from the group consisting of a hindered amine-based antioxidant and a benzoate-based ultraviolet absorber as an antioxidant and an ultraviolet absorber in a photosensitive layer containing a copolymerized polycarbonate resin. A contact-type or proximity-type charging unit that charges the electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage, an electrostatic latent image forming unit, a developing unit, and a transfer unit. Compared to the case of image forming apparatuses, it occurs when an electrophotographic photosensitive member is exposed to light, together with the occurrence of burn-in ghosts that occur when the same image is output continuously. Image forming apparatus that suppresses the generation of light fatigue is provided.
According to the second aspect of the present invention, the same image is continuously output as compared with the case where the charge transporting 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 light fatigue that occurs when an electrophotographic photosensitive member is exposed to light along with the occurrence of a burning ghost that sometimes occurs.
According to the invention of claim 3, the same image is continuously output as compared with the case where the charge transporting material represented by the general formula (CT2) includes the electrophotographic photosensitive member which is the exemplary compound (CT2-1). Provided is an image forming apparatus that suppresses the occurrence of light fatigue that occurs when an electrophotographic photosensitive member is exposed to light along with the occurrence of a burning ghost that sometimes occurs.

  According to the invention which concerns on Claim 4 or 5, compared with the case where an antioxidant is provided with the electrophotographic photoreceptor which is a hindered phenolic antioxidant shown by Structural formula (CAO-1), it is the same image. Provided is an image forming apparatus that suppresses the occurrence of light fatigue that occurs when an electrophotographic photosensitive member is exposed to light as well as the occurrence of burn-in ghosts that occur when continuously output.

  According to the invention which concerns on Claim 6 or 7, compared with the case where an ultraviolet absorber is provided with the electrophotographic photoconductor which is a benzoate type ultraviolet absorber shown by Structural formula (CUA-1), the same image is continued. In addition, an image forming apparatus is provided that suppresses the occurrence of burn-in ghosts that occur when the electrophotographic photoreceptor is exposed to light and the occurrence of light fatigue that occurs when the electrophotographic photosensitive member is exposed to light.

  According to the invention of claim 8, a charge generating material, a charge transporting material represented by the general formula (CT1), a charge transporting material represented by the general formula (CT2), and biphenyl containing a structural unit having a biphenyl skeleton An electrophotographic photosensitive material further comprising at least one selected from the group consisting of a hindered amine-based antioxidant and a benzoate-based ultraviolet absorber as an antioxidant and an ultraviolet absorber in a photosensitive layer containing a copolymerized polycarbonate resin. A contact-type or proximity-type charging unit that charges the electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage, an electrostatic latent image forming unit, a developing unit, and a transfer unit. Compared to image forming devices, even when hydroxygallium phthalocyanine pigment is included in the photosensitive layer, image sticking occurs when the same image is output continuously. The generation of paste, the electrophotographic photosensitive member is an image forming apparatus that suppresses the generation of light fatigue that occurs when light exposure is provided.

  According to the ninth aspect of the invention, 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 biphenyl including a structural unit having a biphenyl skeleton An electrophotographic photosensitive material further comprising at least one selected from the group consisting of a hindered amine-based antioxidant and a benzoate-based ultraviolet absorber as an antioxidant and an ultraviolet absorber in a photosensitive layer containing a copolymerized polycarbonate resin. A contact-type or proximity-type charging unit that charges the electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage, an electrostatic latent image forming unit, a developing unit, and a transfer unit. Compared to the case of the image forming apparatus, a polycarbonate including a structural unit represented by the general formula (PCA) and a structural unit represented by the general formula (PCB). An image forming apparatus that suppresses the occurrence of burn-in ghost that occurs when the same image is output continuously and the occurrence of light fatigue that occurs when the electrophotographic photosensitive member is exposed to light even when the resin is included in the photosensitive layer. Provided.

  According to the invention of claim 10, 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 biphenyl including a structural unit having a biphenyl skeleton An electrophotographic photosensitive material further comprising at least one selected from the group consisting of a hindered amine-based antioxidant and a benzoate-based ultraviolet absorber as an antioxidant and an ultraviolet absorber in a photosensitive layer containing a copolymerized polycarbonate resin. A contact-type or proximity-type charging unit that charges the electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage, an electrostatic latent image forming unit, a developing unit, and a transfer unit. Compared to the image forming apparatus, even when fluorine-containing resin particles and a fluorine-containing dispersant are contained in the photosensitive layer, it occurs when the same image is output continuously. Ghost the generation of per electrophotographic photosensitive member in the image forming apparatus that suppresses the generation of light fatigue that occurs when light exposure is provided.

  According to the invention of claim 11, a charge generating material, a charge transport material represented by the general formula (CT1), a charge transport material represented by the general formula (CT2), and biphenyl including a structural unit having a biphenyl skeleton An electrophotographic photosensitive material further comprising at least one selected from the group consisting of a hindered amine-based antioxidant and a benzoate-based ultraviolet absorber as an antioxidant and an ultraviolet absorber in a photosensitive layer containing a copolymerized polycarbonate resin. When the same image is output continuously compared to the case of a process cartridge comprising a body and a contact type or proximity type charging means for charging an electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage In addition to the occurrence of burn-in ghosts that occur in Cartridge is provided.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. 1 is a schematic partial cross-sectional view illustrating an example of a layer configuration of an electrophotographic photoreceptor according to an exemplary embodiment.

  Hereinafter, embodiments 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>
The image forming apparatus according to the present embodiment includes, on a conductive substrate, a charge generation material, a charge transport material represented by the following general formula (CT1) (hereinafter also referred to as “butadiene-based charge transport material (CT1)”), A charge transport material represented by the following general formula (CT2) (hereinafter also referred to as “benzidine-based charge transport material (CT2)”), a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton, and a hinder having a molecular weight of 300 or more An electrophotographic photosensitive member having a photosensitive layer comprising a dophenol antioxidant (hereinafter also simply referred to as “hindered phenol antioxidant”) and at least one selected from the group consisting of benzophenone ultraviolet absorbers ( (Hereinafter also referred to as “photoreceptor”).
The image forming apparatus according to the present embodiment further includes a contact-type or proximity-type charging unit that applies a voltage obtained by superimposing an AC voltage on a DC voltage to charge the photoconductor, and a surface of the charged photoconductor. An electrostatic latent image forming unit that forms an electrostatic latent image, a developing unit that develops the electrostatic latent image formed on the surface of the photosensitive member with a developer containing toner, and a toner image Transfer means for transferring to the surface of the recording medium.

  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, the same image is continuously output (for example, continuous output of 3000 sheets) using an image forming apparatus including a photoconductor having a photosensitive layer containing both a butadiene-based charge transport material (CT1) and a benzidine-based charge transport material (CT2). After that, for example, when a full-tone halftone image is output, the surface potential of the photoconductor in the portion continuously exposed by the same image output is lowered, and an image defect (positive ghost) called “burn-in ghost” in which the density becomes high is generated. May occur.
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.

  Furthermore, the photosensitive layer containing a biphenyl copolymerization type polycarbonate resin containing a structural unit having a biphenyl skeleton (hereinafter also referred to as “BP polycarbonate resin”) as a binder resin has improved wear resistance and extended life of the photoreceptor. Can be planned. 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.

  Further, when a contact type or proximity type charging unit is adopted as a charging unit for charging the photosensitive member, the generation of discharge products and the like can be suppressed, and the apparatus can be reduced in size and cost. Further, among contact-type or proximity-type charging means, a charging method (hereinafter also referred to as “superimposed voltage application method”) in which a photosensitive member is charged by applying a voltage in which an AC voltage is superimposed on a DC voltage is adopted. This makes it easier to obtain uniform charging. However, the contact type or proximity type charging means using the superimposed voltage application method is easier to lower the charging potential and more likely to remain a history than the non-contact type charging means (for example, scorotron charger). Charging performance tends to be inferior. For this reason, when the contact voltage or proximity type charging means of the superimposed voltage application method is employed, “burn-in ghost” and “light fatigue” are more likely to occur.

  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.

  The hindered phenol-based antioxidant and the benzophenone-based UV absorber act on the benzene ring of the biphenyl skeleton of the BP polycarbonate resin and the charge transport material, and trap the charge by the interaction between the benzene ring of the biphenyl skeleton and the charge transport material. It is thought that site formation 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.

  Furthermore, in this embodiment, since the photoreceptor is configured as described above, as described above, a decrease in charging potential due to continuous output of the same image and exposure to light is suppressed. Even when used in combination with a mold charging means, "burn-in ghost" and "light fatigue" are less likely to occur.

  From the above, the image forming apparatus according to this 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 the photoconductor is exposed to light. Inferred.

  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 image forming apparatus according to the present embodiment, even when hydroxygallium phthalocyanine is included in the photosensitive layer, the light fatigue caused by the exposure to light along with the generation of the burning ghost that occurs when the same image is continuously output. Suppresses the occurrence of

  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 image forming apparatus according to the present embodiment, even when fluorine-containing resin particles and a fluorine-containing dispersant are included in the photosensitive layer, a light ghost that occurs when the same image is output continuously is generated. Suppresses the occurrence of light fatigue that occurs when exposed.

  Hereinafter, the image forming apparatus according to the present embodiment will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram illustrating an example of a configuration of an image forming apparatus according to the present embodiment.
As shown in FIG. 1, for example, an electrophotographic photoreceptor 7 is provided in an image forming apparatus 10 according to the present embodiment. The photoconductor 7 has a cylindrical shape and is connected to a drive motor 27 (an example of a drive unit) via a drive force propagation member (not shown) such as a gear, and is driven to rotate by the drive motor 27 (FIG. 1). Middle arrow A direction).

  Around the photosensitive member 7 (an example of an image carrier), for example, a charging device 15 (an example of a charging unit), an electrostatic latent image forming device 16 (an example of an electrostatic latent image forming unit), and a developing device 18 (development) An example of a device), a transfer device 31 (an example of a transfer device), a cleaning device (an example of a cleaning device) 22 (an example of a cleaning device), and a static eliminator 24 (an example of a static eliminator) are arranged along the rotation direction of the photoreceptor 7. They are arranged in order. The image forming apparatus 10 according to the present embodiment is also provided with a fixing device 26. Furthermore, a control device 36 that is connected to each device and each member in the image forming apparatus 10 and controls the operation of each device and each member is also provided.

The photoreceptor 7 includes, for example, a conductive substrate, an undercoat layer formed on the conductive substrate, and a photosensitive layer formed on the undercoat layer. This photosensitive layer may have a two-layer structure of a charge generation layer and a charge transport layer. The photosensitive layer may have a configuration in which a protective layer is provided on the outermost surface, or may have a configuration in which no undercoat layer is formed.
The detailed configuration of the photoconductor 7 will be described later.

  Details of each part of the image forming apparatus 10 will be described below.

(Charging device)
The charging device 15 (an example of a charging unit) in the present embodiment is a contact type or proximity type charging device that applies a voltage in which an AC voltage is superimposed on a DC voltage to charge the photoreceptor 7.
The contact-type or proximity-type charging device 15 is a charging device that is disposed in contact with or close to the surface of the photoconductor 7 and charges the surface of the photoconductor 7. Here, to arrange the charging device 15 close to each other means, for example, that the charging device 15 (conductive member (charging member 14)) is arranged away from the surface of the photoreceptor 7 in a range of 1 μm to 200 μm. Show.

In the present embodiment, a superimposed voltage application method is adopted as a method for applying a voltage to the photoconductor 7. The superimposed voltage application method is a method of charging the surface of the photoconductor 7 by applying a voltage obtained by superimposing an AC voltage on a DC voltage.
As charging conditions, the peak-to-peak voltage of the AC voltage is preferably 400 V to 3000 V, more preferably 800 V to 2800 V, and still more preferably 1200 V to 2800 V. The frequency of the AC voltage is preferably 50 Hz to 20000 Hz, more preferably 100 Hz to 5000 Hz. Further, the direct current voltage superimposed on the alternating current voltage is preferably positive or negative and is 50 V or more and 2000 V or less, more preferably positive or negative is 100 V or more and 1500 V or less.
The selection of the voltage application method (superimposed voltage application method, AC voltage application method, or DC voltage application method) is appropriately selected according to market needs (maintenance costs, price, presence / absence of static eliminator, scale, etc.). For example, when the superimposed voltage application method is employed, it is easy to obtain charging uniformity.

  The charging device 15 includes, for example, a power supply 28 (an example of a voltage application unit for a charging member) that applies a charging voltage to the charging member 14 that charges the surface of the photoreceptor 7. The power source 28 is electrically connected to the charging member 14. The power supply 28 in the present embodiment is a power supply that applies a voltage obtained by superimposing an AC voltage on a DC voltage.

  The charging member 14 is provided in contact with or close to the surface of the photoreceptor 7. Examples of the charging member 14 include a contact-type charger in which a conductive or semi-conductive member such as a charging roller, a charging brush, a charging film, a charging rubber blade, or a charging tube is provided in contact with the surface of the photoconductor 7, And a proximity charger in which a conductive or semiconductive member is provided apart from the surface of the photoreceptor 7.

In the present embodiment, it is preferable to use a charging roll as a contact charger or a proximity charger from the viewpoint of charging characteristics and versatility.
As the charging roll, for example, a conductive elastic layer and, if necessary, a surface layer are sequentially formed on a conductive support (shaft).

  As the material of the conductive support (shaft) of the charging roll, free-cutting steel, stainless steel, etc. are used, and the material and surface treatment method are appropriately selected according to the application such as slidability, and it does not have conductivity. The material may be processed by a general process such as a plating process and subjected to a conductive process.

The conductive elastic layer of the charging roll is, for example, an elastic material such as rubber having elasticity, a conductive agent such as carbon black or ionic conductive material that adjusts the resistance of the conductive elastic layer, a softener, a plasticizer, if necessary, Materials that can normally be added to rubber, such as curing agents, vulcanizing agents, vulcanization accelerators, anti-aging agents, fillers such as silica and calcium carbonate, may be added. It is formed by coating a peripheral surface of a conductive support with a mixture in which materials usually added to rubber are added.
The conductive elastic layer is a material such as carbon black, conductive metal oxide particles, or ionic conductive agent as a conductive agent for adjusting the resistance value, and is electrically conductive using at least one of electrons and ions as a charge carrier. A material in which a material to be dispersed is dispersed can be used.
The conductive elastic layer may be a foam.

Further, the surface layer of the charging roll is formed for the purpose of preventing contamination by foreign matters such as toner.
The material for the surface layer may be any of resin, rubber and the like, and is not particularly limited. For example, polyester, polyimide, copolymer nylon, silicone resin, acrylic resin, polyvinyl butyral, ethylene tetrafluoroethylene copolymer Examples thereof include coalescence, melamine resin, fluororubber, epoxy resin, polycarbonate, polyvinyl alcohol, cellulose, polyvinylidene chloride, polyvinyl chloride, polyethylene, and ethylene vinyl acetate copolymer.

  Further, the surface layer may contain a conductive agent similar to that used for the conductive elastic layer to adjust the resistance value. Further, a fluorine-based or silicone-based resin, insulating particles or the like may be added to the surface layer.

  The charging device 15 (including the power supply 28) is electrically connected to, for example, a control device 36 provided in the image forming apparatus 10 and is driven and controlled by the control device 36 to apply a charging voltage to the charging member 14. To do. The charging member 14 to which the charging voltage is applied from the power supply 28 charges the photoconductor 7 to a charging potential corresponding to the applied charging voltage. For this reason, by adjusting the charging voltage applied from the power supply 28, the photoconductor 7 is charged to different charging potentials.

(Electrostatic latent image forming device)
The electrostatic latent image forming device (exposure device) 16 (an example of an electrostatic latent image forming unit) forms an electrostatic latent image on the surface of the charged photoreceptor 7.
Specifically, for example, the electrostatic latent image forming device 16 is electrically connected to a control device 36 provided in the image forming device 10, is driven and controlled by the control device 36, and is charged by the charging member 14. The light L modulated based on the image information of the image to be formed is exposed on the surface of the photoconductor 7 thus formed. Then, an electrostatic latent image corresponding to the image of the image information is formed on the photoreceptor 7.

  Examples of the electrostatic latent image forming apparatus 16 include optical system equipment having a light source that exposes light such as semiconductor laser light, light emitting diode (LED) light, and liquid crystal shutter light imagewise. An exposure apparatus is mentioned. The wavelength of the light source is preferably in the spectral sensitivity region of the electrophotographic photoreceptor 7. The wavelength of the semiconductor laser is preferably near infrared having an oscillation wavelength of around 780 nm, for example. However, the present invention is not limited to this wavelength, and an oscillation wavelength laser in the 600 nm range or a laser having an oscillation wavelength of 400 nm to 450 nm as a blue laser may be used. Further, as the electrostatic latent image forming device 16, for example, a surface emitting laser light source of a multi-beam output type is also effective for color image formation.

(Developer)
The developing device 18 is provided, for example, on the downstream side in the rotation direction of the photoconductor 7 from the irradiation position of the light L by the electrostatic latent image forming device 16. In the developing device 18, an accommodating portion for accommodating the developer is provided.
Note that the developer housed in the developing device 18 may be a single-component developer containing toner alone or a two-component developer containing toner and carrier. Further, the developer may be magnetic or non-magnetic.
The developing device 18 includes, for example, a developing member 18A that develops an electrostatic latent image formed on the surface of the photoreceptor 7 with a developer containing toner, and a power source 32 (for developing member) that applies a developing voltage to the developing member 18A. An example of the voltage application unit of The developing member 18A is electrically connected to the power source 32, for example.

  The developing member 18A of the developing device 18 is selected according to the type of developer, and examples thereof include a developing roll having a developing sleeve with a built-in magnet.

The developing device 18 (including the power supply 32) is electrically connected to, for example, a control device 36 provided in the image forming apparatus 10, and is driven and controlled by the control device 36 to apply a developing voltage to the developing member 18A. To do. The developing member 18A to which the developing voltage is applied from the power source 32 is charged to a developing potential corresponding to the applied developing voltage.
The developing member 18A charged to the developing potential holds, for example, the developer accommodated in the developing device 18 on the surface, and the toner contained in the developer is transferred from the developing device 18 to the surface of the photoconductor 7. And supply.

For example, the toner supplied onto the photoreceptor 7 adheres to the electrostatic latent image on the photoreceptor 7 by electrostatic force. Specifically, for example, the toner contained in the developer by the potential difference in the area where the photoreceptor 7 and the developing member 18A face each other, that is, the potential difference between the surface potential of the photoreceptor 7 and the developing potential of the developing member 18A in this area. Is supplied to the area where the electrostatic latent image is formed on the photosensitive member 7 and the developer contains a carrier, the carrier is returned to the developing device 18 while being held by the developing member 18A.
Thereby, for example, the electrostatic latent image on the photoconductor 7 is developed by the toner supplied from the developing member 18 </ b> A, and a toner image corresponding to the electrostatic latent image is formed on the photoconductor 7.

(Transfer device)
The transfer device 31 (an example of a transfer unit) is provided, for example, on the downstream side in the rotation direction of the photosensitive member 7 from the position where the developing member 18A is disposed.
The transfer device 31 includes, for example, a transfer member 20 that transfers a toner image formed on the surface of the photoreceptor 7 to a recording medium P (an example of a transfer target), and a power source 30 (transfer) that applies a transfer voltage to the transfer member 20. An example of a voltage application unit for a member). The transfer member 20 has, for example, a cylindrical shape, is rotated in the direction of arrow C in FIG. 1, and conveys the recording medium P with the photoreceptor 7 therebetween. The transfer member 20 is electrically connected to, for example, a power supply 30.

  As the transfer member 20 of the transfer device 31, for example, a contact transfer charger using a belt, a roller, a film, a rubber blade or the like, a scorotron transfer charger using a corona discharge, a corotron transfer charger, or the like is known per se. A non-contact type transfer charger is exemplified.

  The transfer device 31 (including the power supply 30) is electrically connected to a control device 36 provided in the image forming apparatus 10, for example, and is driven and controlled by the control device 36 to apply a transfer voltage to the transfer member 20. To do. The transfer member 20 to which a transfer voltage is applied from the power supply 30 is charged to a transfer potential corresponding to the applied transfer voltage.

  When a transfer voltage having a polarity opposite to that of the toner constituting the toner image formed on the photoconductor 7 is applied from the power source 30 of the transfer member 20 to the transfer member 20, for example, between the photoconductor 7 and the transfer member 20. In the facing area (see transfer area T in FIG. 1), an electric field having an electric field strength is formed to move each toner constituting the toner image on the photoreceptor 7 from the photoreceptor 7 to the transfer member 20 side by electrostatic force. The

  The recording medium P (an example of a transfer target) is accommodated in, for example, a storage unit (not illustrated), and is transported along the transport path 34 by a plurality of transport members (not illustrated) from the storage unit. 7 and a transfer region T that is a region where the transfer member 20 and the transfer member 20 face each other. In the example shown in FIG. 1, it is conveyed in the direction of arrow B. For example, when a transfer voltage is applied to the transfer member 20, the toner image on the photoconductor 7 is transferred to the recording medium P that has reached the transfer region T by a transfer electric field formed in this region. That is, for example, the toner image is transferred onto the recording medium P by the movement of the toner from the surface of the photoreceptor 7 to the recording medium P.

  The toner image on the photoreceptor 7 is transferred onto the recording medium P by a transfer electric field. The magnitude of the transfer electric field is controlled based on the transfer current value. The transfer current value is a current value detected by the transfer device 31 when a transfer electric field is applied by constant current control. The transfer current value represents the magnitude of the transfer electric field.

(Cleaning device)
A cleaning device (cleaning device) 22 (an example of a cleaning unit) is provided downstream of the transfer region T in the rotation direction of the photoconductor 7.
After the toner image is transferred to the recording medium P, the cleaning device 22 removes the deposits attached to the photoconductor 7.
The cleaning device 22 removes deposits such as residual toner and paper dust on the photoreceptor 7. Examples of the cleaning device 22 include a configuration having a cleaning blade (cleaning blade) 22 </ b> A that contacts the photoconductor 7 with a predetermined linear pressure. The cleaning blade 22A is preferably in contact with the photoconductor 7 at a linear pressure of 10 g / cm or more and 150 g / cm or less, for example.

(Staticizer)
The static eliminator 24 (an example of the static eliminator) is provided, for example, on the downstream side in the rotation direction of the photoconductor 7 from the cleaning device 22.
After the toner image is transferred, the neutralization device 24 exposes the surface of the photoreceptor 7 to neutralize the charge.
Specifically, for example, the static eliminator 24 is electrically connected to a control device 36 provided in the image forming apparatus 10, and is driven and controlled by the control device 36 so that the entire surface of the photoreceptor 7 (specifically, For example, the entire surface of the image forming area is exposed to remove electricity.

  Examples of the static eliminating device 24 include a device having a light source such as a tungsten lamp that emits white light and a light emitting diode (LED) that emits red light.

(Fixing device)
The fixing device 26 (an example of a fixing unit) is provided, for example, on the downstream side in the transport direction of the transport path 34 of the recording medium P from the transfer region T.
For example, the fixing device 26 fixes the toner image transferred onto the recording medium P.
Specifically, for example, the fixing device 26 is electrically connected to a control device 36 provided in the image forming apparatus 10, and is toner that is driven and controlled by the control device 36 and transferred onto the recording medium P. The image is fixed on the recording medium P by heat or heat and pressure.

  Examples of the fixing device 26 include a fixing device known per se, such as a heat roller fixing device and an oven fixing device.

Here, the recording medium P that is transported along the transport path 34 and to which the toner image is transferred by passing through a region (transfer region T) where the photoconductor 7 and the transfer member 20 face each other is omitted, for example. The conveying member further reaches the installation position of the fixing device 26 along the conveying path 34 and the toner image on the recording medium P is fixed.
The recording medium P on which an image is formed by fixing the toner image is discharged to the outside of the image forming apparatus 10 by a plurality of conveyance members (not shown).
The photosensitive member 7 is charged again by the charging device 15 after the charge removal by the charge removal device 24.

(Control device)
The control device 36 is configured as a computer that controls the entire device and performs various calculations. Specifically, the control device 36 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) storing various programs, and a RAM (Random Access Memory) used as a work area when executing the programs. ), A nonvolatile memory for storing various information, and an input / output interface (I / O). Each of the CPU, ROM, RAM, nonvolatile memory, and I / O is connected via a bus. The I / O includes a photoreceptor 7 (including a drive motor 27), a charging device 15 (including a power source 28), an electrostatic latent image forming device 16, a developing device 18 (including a power source 32), and a transfer device 31. Each part of the image forming apparatus 10 (including the power supply 30), the static eliminating device 24, the fixing device 26, and the like is connected.

  Note that the CPU executes, for example, a program (for example, a control program for an image forming sequence or a recovery sequence) stored in a ROM or a non-volatile memory, and controls the operation of each unit of the image forming apparatus 10. The RAM is used as a work memory. The ROM and the non-volatile memory store, for example, programs executed by the CPU and data necessary for the processing of the CPU. Note that the control program and various data may be stored in another storage device such as a storage unit, or may be acquired from the outside via the communication unit.

  Various drives may be connected to the control device 36. As various drives, data is read from a computer-readable portable recording medium P such as a flexible disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, and a USB memory, and data is written to the recording medium P. The apparatus which performs is mentioned. When various drives are provided, the control program may be recorded on the portable recording medium P, and this may be read and executed by the corresponding drive.

(Image forming operation)
An image forming operation of the image forming apparatus 10 will be described.
First, the surface of the photoreceptor 7 is charged by the charging device 15. The electrostatic latent image forming device 16 exposes the surface of the charged photoconductor 7 based on the image information. As a result, an electrostatic latent image corresponding to the image information is formed on the photoreceptor 7. In the developing device 18, the electrostatic latent image formed on the surface of the photoreceptor 7 is developed by a developer containing toner. As a result, a toner image is formed on the surface of the photoreceptor 7. In the transfer device 31, the toner image formed on the surface of the photoreceptor 7 is transferred to the recording medium P. The toner image transferred to the recording medium P is fixed by the fixing device 26. As described above, by forming an image using toner, an image showing high image quality and high resolution is formed on the recording medium P. On the other hand, the surface of the photoconductor 7 after the toner image is transferred is cleaned by the cleaning device 22 and discharged by the discharging device 24.

In FIG. 1, the transfer device 31 is described as an example of a direct transfer type device that directly transfers the toner image formed on the surface of the electrophotographic photosensitive member to the recording medium P, but according to the present embodiment. The image forming apparatus 10 is not limited to the above configuration.
In the image forming apparatus 10 of the present embodiment, as the transfer device 31, although not shown, the toner image formed on the surface of the electrophotographic photosensitive member is primarily transferred to the surface of the intermediate transfer member and transferred to the surface of the intermediate transfer member. An intermediate transfer apparatus that secondarily transfers the toner image to the surface of the recording medium may be applied.
In the case of an intermediate transfer type apparatus, for example, an intermediate transfer body on which a toner image is transferred onto the surface, a primary transfer unit that primarily transfers a toner image formed on the surface of the image holding body onto the surface of the intermediate transfer body, A configuration having secondary transfer means for secondary transfer of the toner image transferred to the surface of the transfer body to the surface of the recording medium is applied.

In FIG. 1, as an example of the charge removal apparatus, an apparatus including a charge removal unit that removes charge by irradiating the surface of the photoconductor with charge removal light after the transfer of the toner image is described as an example. The image forming apparatus 10 is not limited to the above configuration.
In the image forming apparatus 10 according to the present embodiment, the static eliminator 24 is not shown, but is, for example, around the electrophotographic photosensitive member 7 and downstream of the transfer device 31 in the rotation direction of the electrophotographic photosensitive member 7. Even if the first neutralization device is provided on the upstream side of the rotation direction of the electrophotographic photosensitive member relative to the cleaning device (cleaning device) 22, the polarity of the remaining toner is aligned and easily removed by the cleaning brush. In addition, a second static elimination device that neutralizes the surface of the electrophotographic photosensitive member 7 is provided downstream of the cleaning device 22 in the rotational direction of the electrophotographic photosensitive member and upstream of the charging device 15 in the rotational direction of the electrophotographic photosensitive member. The form may be sufficient. For example, the form which does not provide the static elimination apparatus 24 may be sufficient.

<Process cartridge>
The process cartridge according to the present embodiment includes a biphenyl copolymer including a charge generation material, a butadiene-based charge transport material (CT1), a benzidine-based charge transport material (CT2), and a structural unit having a biphenyl skeleton on a conductive substrate. An electrophotographic photoreceptor having a photosensitive layer comprising a polymerization type polycarbonate resin and at least one selected from the group consisting of a hindered phenolic antioxidant and a benzophenone ultraviolet absorber.
The process cartridge according to the present embodiment further includes a contact type or proximity type charging unit that applies a voltage obtained by superimposing an AC voltage on a DC voltage to charge the photosensitive member, and is attached to and detached from the image forming apparatus. Is done.
In the present embodiment, for example, in the image forming apparatus 10, a process cartridge including the electrophotographic photosensitive member 7 and a charging device 15 (an example of a charging unit) is preferably used. In addition to the electrophotographic photosensitive member and the charging unit, the process cartridge may include at least one selected from the group consisting of an electrostatic latent image forming unit, a developing unit, and a transfer unit.

Hereinafter, the electrophotographic photoreceptor according to the exemplary embodiment will be described with reference to the drawings.
FIG. 2 is a schematic partial cross-sectional view showing an example of the layer configuration of the electrophotographic photoreceptor 7A according to the present embodiment. The electrophotographic photoreceptor 7A shown in FIG. 2 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 photosensitive layer 5 may be a function-separated type photosensitive layer having the charge generation layer 2 and the charge transport layer 3, or a single layer in which the functions of the charge generation layer 2 and the charge transport layer 3 are integrated. It may be a mold type photosensitive layer. In the case of a functional separation type photosensitive layer, the charge generation layer 2 contains a charge generation agent, the charge transport layer 3 includes a butadiene-based charge transport material (CT1), a benzidine-based charge transport material (CT2), and a BP polycarbonate resin. And at least one selected from the group consisting of hindered phenol antioxidants and benzophenone ultraviolet absorbers.

  Further, 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.

  Hereinafter, each element of the electrophotographic photosensitive member will be described. Note that the reference numerals of the respective elements are 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 roughening methods 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 generation 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 to 4 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 benzophenone-based ultraviolet absorber (exemplary compound (BP-3)) represented by the following structural formula (BPA).

  Specific examples of the benzophenone-based ultraviolet absorber (benzophenone-based ultraviolet absorber represented by the general formula (BP)) 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 charge transporting material (CT2) is from the viewpoint of forming a photosensitive layer (charge transporting layer) having a high charge transporting ability, and the mixing ratio of CT2 to the binder resin is from 1: 9 to 7: 3 by mass ratio. Is preferably within the range of 2: 8 to 6: 4, more preferably within the range of 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] ^(cm 3 / g), the equations given by H.Schnell, [η] = 1.23 × relationship 10-4Mv0.83 The viscosity average molecular weight Mv is obtained from the equation.

  The BP polycarbonate resin may be used in combination with other binder resins. However, other binder resins may be used in combination at 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. 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 Mega-Fuck series (manufactured by DIC) and the FC series (made 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 known formation method is used. For example, a coating film of a charge transport layer forming coating solution in which the above components are added to a solvent is formed, and the coating film is dried. 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 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 known formation method is used.For example, a coating film of a coating liquid for forming a protective layer in which the above components are added to a solvent is formed, and the coating film is dried. 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) includes, for example, a charge generation material, a charge transport material, a binder resin (BP polycarbonate resin), and other known additives as necessary. It is. 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.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples. In the following description, “part” and “%” are all based on mass unless otherwise specified.

<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 47 mm, a length of 357 mm, and a thickness of 1 mm by dip coating, followed by drying and curing at 180 ° C. for 30 minutes, and a film thickness of 25 μm. Undercoat layer 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, butadiene based charge transport material (CT1) “8.0 parts by weight of exemplary compound (CT1-1) and benzidine based charge transport material (CT2)“ exemplary compound (CT2-1) ”32.0 6 parts by mass of BP polycarbonate resin “Exemplary Compound (PC-1), pm: pn = 25: 75, Viscosity Average Molecular Weight = 50,000”, 4 parts of fluorine resin particles Fluorinated ethylene resin particles (volume average particle diameter 200 nm): 8 parts by mass, and fluorine-containing dispersant, GF400 (manufactured by Toa Gosei Co., Ltd .: surfactant having at least a methacrylate having a fluorinated alkyl group as a polymerization component): 0 .3 parts by mass and, as an antioxidant, hindered phenolic antioxidant “Exemplary Compound (HP-1), molecular weight 775” 3.2 parts by mass (total charge transport material 8.0% by weight) and relative to the weighing 100 wt%, 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 150 ° C. for 40 minutes to form a charge transport layer having a thickness of 34 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 31]
According to Table 2, the amount of butadiene-based charge transport material (CT1) “example compound (CT1-3) and benzidine-based charge transport material (CT2)“ example compound (CT2-2) ”was changed as the charge transport material. An electrophotographic photosensitive member was produced in the same manner as the photosensitive member 20 except that.

[Photoconductors 32-37]
According to Table 2, 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 antioxidant, and the type of ultraviolet absorber were changed.

[Photoconductor 38]
Except for using 60.0 parts by mass of PCZ500 “bisphenol Z type polycarbonate resin (homopolymerized polycarbonate resin of bisphenol Z, viscosity average molecular weight 50,000)” instead of BP polycarbonate resin, An electrophotographic photosensitive member was produced.

<Example 1>
The obtained electrophotographic photosensitive member (photosensitive member 1) is mounted on an electrophotographic image forming apparatus (manufactured by Fuji Xerox Co., Ltd .: DocuCentre-IV C5570 modified machine), and this modified machine is used as the image forming apparatus of Example 1. . The charging device installed in the remodeling machine is a contact-type superimposed voltage application type charging device that applies a voltage obtained by superimposing an AC voltage on a DC voltage, and charging conditions are a peak voltage of AC voltage 2.3 kV, a frequency The frequency was 0.4 kHz and the DC voltage was −1.0 kV. A charging roll was used as the charging member.

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

[Evaluation]
Using the image forming apparatus of each example, “burn-in ghost”, “light fatigue”, “halftone image density”, and “abrasion resistance” 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 G0 to G5, and the smaller the G number, the smaller the density difference, indicating that no ghosting has occurred. The allowable grade of seizure ghost is G3.5 or less. All image output was performed in an environment of 28 ° C. and 85% RH. The results are shown in Tables 3 and 4.

(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 G0 to G5, and the smaller the G number, the smaller the density difference and the less light fatigue occurs. The allowable grade of light fatigue is G3.5 or less. All image output was performed in an environment of 28 ° C. and 85% RH. The results are shown in Tables 3 and 4.

(Evaluation of halftone image density)
An electrophotographic photosensitive member (photosensitive members 1 to 38) was mounted on the image forming apparatus of each example, and one half-tone 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 and 4.

(Abrasion resistance evaluation)
An electrophotographic photosensitive member (photosensitive members 1 to 38) is mounted on the image forming apparatus of each example, and after 20000 sheets of an image density of 5% are continuously output on A3 size paper, the electrophotographic photosensitive member (photosensitive member) The film thickness of the photosensitive layer 1 to 38) was measured. The film thickness of the photosensitive layer was measured using an eddy current film thickness measuring device (manufactured by Fischer Instruments). And the difference (micrometer) of the film thickness of the photosensitive layer before and behind continuous output of 20000 sheets was calculated | required. The results are shown in Tables 3 and 4.

  Tables 1 and 2 show the configurations of the electrophotographic photoreceptors used in the examples and comparative examples. The evaluation results of each example are listed in Tables 3 to 4. In Tables 1 and 2, the column “Amount (mass%)” of the antioxidant and the ultraviolet absorber indicates the ratio with respect to the total amount of 100% by mass of the total charge transporting material.

<Explanation of Tables 3 and 4>
Voltage application method; superimposed voltage represents a superimposed voltage application method.

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.
Moreover, in this example, it can be seen that the wear resistance is higher than that of Comparative Example 7.

  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)
PCZ500: bisphenol Z type polycarbonate resin (homopolymerized polycarbonate resin of bisphenol Z, viscosity average molecular weight 50,000)

-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, 10 Image forming apparatus, 14 Charging member, 15 Charging apparatus, 16 Electrostatic latent image forming apparatus (exposure Device), 18 developing device, 20 transfer member, 22 cleaning device (cleaning device), 22A cleaning blade (cleaning blade), 24 static eliminator, 26 fixing device, 27 drive unit, 28 power source, 30 power source, 31 transfer device

Claims (11)

A conductive substrate, a photosensitive layer disposed on the conductive substrate, a charge generation material, a charge transport material represented by the following general formula (CT1), and a charge transport represented by the following general formula (CT2) A material, a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton, and at least one selected from the group consisting of a hindered phenol antioxidant having a molecular weight of 300 or more and a benzophenone ultraviolet absorber An electrophotographic photoreceptor having a photosensitive layer;
Contact-type or proximity-type charging means for applying a voltage obtained by superimposing an AC voltage on a DC voltage to charge the electrophotographic photosensitive member;
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
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, a photosensitive layer disposed on the conductive substrate, a charge generation material, a charge transport material represented by the following general formula (CT1), and a charge transport represented by the following general formula (CT2) A material, a biphenyl copolymerized polycarbonate resin containing a structural unit having a biphenyl skeleton, and at least one selected from the group consisting of a hindered phenol antioxidant having a molecular weight of 300 or more and a benzophenone ultraviolet absorber An electrophotographic photoreceptor having a photosensitive layer;
A contact-type or proximity-type charging unit that applies a voltage obtained by superimposing an AC voltage on a DC voltage to charge the electrophotographic photosensitive member, and
A process cartridge that can be attached to and detached from an 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.)