JP2016184036A - Image forming apparatus - 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 a photoreceptor is exposed to light.SOLUTION: There is provided an image forming apparatus comprising: a photoreceptor that includes a photosensitive layer including a charge transport material of formula (CT1), a charge transport material having a specific structure, and at least one selected from the group consisting of a hindered phenolic antioxidant having a molecular weight of 300 or more and a benzophenone ultraviolet absorber; developing means that forms a toner image with a developer including a toner (volume average particle diameter of 3-4.5 μm); and transfer means that has a transfer current value of 0.03-0.13 μA/mm.SELECTED DRAWING: None

Description

  The present invention relates to an image forming apparatus.

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

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

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

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

  An object of the present invention is to provide a photosensitive layer containing a charge generation material, a charge transport material represented by the general formula (CT1), and a charge transport material represented by the general formula (CT2), an antioxidant and an ultraviolet absorber. An electrophotographic photosensitive member containing only at least one selected from the group consisting of a hindered amine antioxidant and a benzoate ultraviolet absorber as an agent, and transfer per unit length (mm) in the axial direction of the electrophotographic photosensitive member Compared with an image forming apparatus provided with a transfer means having a current value of 0.03 μA / mm or more and 0.13 μA / mm or less, along with the occurrence of a burn-in ghost that occurs when the same image is output continuously, An object of the present invention is to provide an image forming apparatus that suppresses the occurrence of light fatigue when an electrophotographic photosensitive member is exposed to light.

  The above problem is solved by the following means.

The invention according to claim 1
A conductive substrate, a photosensitive layer provided 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) An electrophotographic photoreceptor comprising a material and a photosensitive layer comprising 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;
Charging means for charging the surface of 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;
A developer containing a toner having a volume average particle size of 3 μm or more and 4.5 μm or less is accommodated, and the electrostatic latent image formed on the surface of the electrophotographic photosensitive member is developed with the developer to form a toner image. Developing means,
Transfer means for transferring the toner image to the surface of a recording medium, wherein a transfer current value is 0.03 μA / mm or more and 0.13 μA / mm or less per unit length (mm) in the axial direction of the electrophotographic photosensitive member. A transfer means,
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.

  According to the first, second, or third aspect of the invention, the photosensitive layer includes a charge generation material, a charge transport material represented by the general formula (CT1), and a charge transport material represented by the general formula (CT2). Furthermore, as an antioxidant and an ultraviolet absorber, an electrophotographic photosensitive member containing only at least one selected from the group consisting of a hindered amine antioxidant and a benzoate ultraviolet absorber, and an axial direction of the electrophotographic photosensitive member When the same image is output continuously as compared with an image forming apparatus provided with a transfer unit having a transfer current value per unit length (mm) of 0.03 μA / mm to 0.13 μA / mm. An image forming apparatus is provided that suppresses the occurrence of light fatigue that occurs when the electrophotographic photosensitive member is exposed to light as well as the occurrence of image sticking ghosts.

  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 eighth aspect of the present invention, the photosensitive layer containing the charge generation material, the charge transport material represented by the general formula (CT1), and the charge transport material represented by the general formula (CT2) is further oxidized. As compared with a case where an electrophotographic photosensitive member containing at least one selected from the group consisting of a hindered amine antioxidant and a benzoate ultraviolet absorber is included as a light-sensitive agent and an ultraviolet absorber, a photosensitive layer contains a hydroxygallium phthalocyanine pigment. Even when the same image is continuously output, an image forming apparatus that suppresses the occurrence of burn-in ghosts and the occurrence of light fatigue that occurs when the electrophotographic photosensitive member is exposed to light 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. It is a photograph which shows the evaluation criteria of the dot reproducibility (granularity) in an Example. It is a figure which shows the evaluation criteria of the burning ghost in an Example.

  Embodiments that are examples of the present invention will be described below.

<Image forming apparatus>
The image forming apparatus according to the present embodiment includes a charge generation material, a charge transport material represented by the following general formula (CT1), a charge transport material represented by the following general formula (CT2), and a molecular weight on a conductive substrate. And an electrophotographic photosensitive member (hereinafter also referred to as “photosensitive member”) having a photosensitive layer including at least one selected from the group consisting of 300 or more hindered phenolic antioxidants and benzophenone ultraviolet absorbers. .
The image forming apparatus according to the present embodiment further includes a charging unit that charges the surface of the photoconductor, an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the charged photoconductor, and a volume average particle size. A developing unit that contains a developer containing toner of 3 μm or more and 4.5 μm or less, and develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with the developer to form a toner image; Transfer means for transferring the image to the surface of the recording medium.
The transfer means is set so that the transfer current value is 0.03 μA / mm or more and 0.13 μA / mm or less per unit length (mm) in the axial direction of the electrophotographic photosensitive member.

  Note that the image forming apparatus according to the present embodiment may include, for example, a control device that performs constant current control so that the transfer current value falls within the above range.

  In this embodiment, the “transfer current value” indicates a current value of a transfer current that flows from the transfer unit to the electrophotographic photosensitive member when the toner image is transferred from the electrophotographic photosensitive member to the transfer target. .

  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 the electrophotographic photosensitive member is exposed to light. To do. 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.

In addition, in order to achieve high image quality and high resolution, a toner having a smaller particle diameter than the conventional one (hereinafter referred to as “small particle diameter toner”) may be employed as the toner used in the image forming apparatus. (In this embodiment, a toner having a volume average particle diameter of 3 μm to 4.5 μm is used). However, the chargeability of the individual toner is lower in the small particle size toner than in the conventional toner (for example, the volume average particle size is 6 μm or more). Therefore, the transfer current is set higher than the conventional one (in this embodiment, the transfer current value is set to 0.03 μA / mm or more and 0.13 μA / mm or less per unit length (mm) in the axial direction of the electrophotographic photosensitive member. When the toner image is transferred from the photoconductor, the toner image formed on the photoconductor can be easily transferred by setting the value of the current flowing through the photoconductor to be higher than the conventional value.
On the other hand, when a toner having a small particle diameter is employed and the toner image is transferred from the photoconductor, the current value flowing through the photoconductor is set to be higher than the conventional value (unit in the axial direction of the electrophotographic photoconductor). 0.03 μA / mm or more and 0.13 μA / mm or less per length (mm), the amount of electric charge flowing through the photosensitive layer during transfer increases, so that an electrical load (electrical stress) generated on the photoconductor Tends to increase. For this reason, a decrease in charging potential due to continuous output of the same image and exposure to light becomes remarkable, and the occurrence of the above-mentioned “burn-in ghost” and “light fatigue” may be more noticeable.

  In contrast, when a photosensitive layer containing both the butadiene-based charge transport material (CT1) and the benzidine-based charge transport material (CT2) is further incorporated with a hindered phenol-based antioxidant, continuous output of the same image is performed. In addition, a decrease in charging potential due to 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 the photosensitive layer containing both the butadiene-based charge transporting material (CT1) and the benzidine-based charge transporting material (CT2) is further incorporated with a benzophenone-based ultraviolet absorber, the charging potential due to continuous output of the same image and 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.

  From the above, the image forming apparatus according to the present embodiment uses toner having a volume average particle diameter of 3 μm or more and 4.5 μm or less, and the transfer current value is 0 per unit length (mm) in the axial direction of the electrophotographic photosensitive member. Even when it is set to be in the range of 0.03 μA / mm or more and 0.13 μA / mm or less, the electrophotographic photosensitive member becomes light with the occurrence of a burn-in ghost that occurs when the same image is continuously output. It is presumed to suppress the occurrence of light fatigue that occurs when exposed.

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

  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. The 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) charges the surface of the photoreceptor 7. The charging device 15 includes, for example, a power supply 28 (an example of a voltage applying unit for a charging member) that applies a charging potential 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 charging member 14 of the charging device 15 is provided, for example, in contact with or non-contact with the surface of the photoreceptor 7. Examples of the charging member 14 include a contact-type charger using a conductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, and the like. Further, for example, a non-contact type roller charger, a known charger such as a scorotron charger using a corona discharge or a corotron charger may be used.

  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 information image is formed on the photoconductor 7, and the exposed surface of the photoconductor has a post-exposure potential corresponding to the exposure light amount of the electrostatic latent image forming apparatus.

  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 emitting diode) 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.
In the present embodiment, a developer containing toner having a volume average particle diameter of 3 μm or more and 4.5 μm or less is stored in the storage unit.

  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. Details of the developer containing toner having a volume average particle diameter of 3 μm or more and 4.5 μm or less will be described later.

  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 a cylindrical shape, for example, 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 the transfer voltage is applied from the power supply 32 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.

(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. FIG. 1 illustrates a heat roller fixing device including a heating roll 26A and a pressure roll 26B arranged to face the heating roll 26A.

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, a USB (Universal Serial Bus) memory, etc. And a device for writing data. 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 having a volume average particle size of 3 μm or more and 4.5 μm or less. 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, an image having high image quality and high resolution is formed on the recording medium P by forming an image using toner having a volume average particle diameter of 3 μm or more and 4.5 μm or less. Is done. 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.

The image forming apparatus 10 is set such that the transfer current value is in the range of 0.03 μA / mm or more and 0.13 μA / mm or less per unit length (mm) in the axial direction of the electrophotographic photosensitive member.
In the control device 36, for example, a preset transfer current value is in the range of 0.03 μA / mm or more and 0.13 μA / mm or less per unit length (mm) in the axial direction of the electrophotographic photosensitive member. Thus, constant current control may be performed.

  In the image forming apparatus of this embodiment, as described above, the transfer current value is in the range of 0.03 μA / mm or more and 0.13 μA / mm or less per unit length (mm) in the axial direction of the electrophotographic photosensitive member. Is set to From the viewpoint of high image quality and high resolution, it is preferably in the range of 0.05 μA / mm to 0.12 μA / mm, more preferably in the range of 0.06 μA / mm to 0.11 μA / mm. preferable.

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

  If the transfer device is an intermediate transfer type device and includes a primary transfer unit and a secondary transfer unit, the transfer current value in the present embodiment corresponds to the transfer current value of the primary transfer unit.

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. Such an image forming apparatus is not limited to the above configuration.
In the image forming apparatus according to the present embodiment, the static eliminator is not shown, but is, for example, a cleaning device (cleaning device) around the electrophotographic photosensitive member and downstream of the transfer device in the rotation direction of the electrophotographic photosensitive member. The first toner neutralizing device may be provided on the upstream side of the rotation direction of the electrophotographic photosensitive member relative to the device) so that the polarity of the remaining toner is aligned and easy to remove with a cleaning brush. Alternatively, the second static eliminating device for neutralizing the surface of the electrophotographic photosensitive member may be provided downstream of the electrophotographic photosensitive member in the rotational direction and upstream of the charging device in the rotational direction of the electrophotographic photosensitive member. For example, the form which does not provide a static elimination apparatus may be sufficient.

  Note that in the image forming apparatus according to the present embodiment, for example, the portion including the electrophotographic photosensitive member may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member 7 according to this embodiment is preferably used. In addition to the electrophotographic photosensitive member, the process cartridge may include at least one selected from the group consisting of a charging unit, an electrostatic latent image forming unit, a developing unit, and a transfer unit.

  The image forming apparatus according to the present embodiment may be a tandem multicolor image forming apparatus equipped with four process cartridges as described above. For example, as such an image forming apparatus, there is an apparatus in which four process cartridges are arranged in parallel on an intermediate transfer member, and one electrophotographic photosensitive member is used for one color. Can be mentioned.

[Electrophotographic photoreceptor]
Next, the electrophotographic photosensitive member according to this embodiment will be described.
The photoconductor includes a conductive substrate and a photosensitive layer disposed on the conductive substrate. The photosensitive layer comprises a charge generation material, a charge transport material represented by the general formula (CT1) (hereinafter also referred to as “butadiene-based charge transport material (CT1)”), and a charge transport represented by the general formula (CT2). A material (hereinafter also referred to as “benzidine-based charge transport material (CT2)”), a hindered phenol-based antioxidant having a molecular weight of 300 or more (hereinafter also simply referred to as “hindered phenol-based antioxidant”), and a benzophenone-based ultraviolet ray And at least one selected from the group consisting of absorbents.

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

  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. 1 has a structure in which an undercoat layer 1, a charge generation layer 2, and a charge transport layer 3 are laminated in this order on a conductive substrate 4. The charge generation layer 2 and the charge transport layer 3 constitute the photosensitive layer 5.

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

  Hereinafter, each element of the electrophotographic photosensitive member will be described. In addition, the code | symbol of each element is abbreviate | omitted and demonstrated.

(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.

  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 20 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 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, an agitator, and an ultrasonic disperser. 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 fluorine-containing resin particles and a fluorine-containing dispersant, and is a hindered phenol-based antioxidant. And at least one selected from the group consisting of benzophenone-based ultraviolet absorbers.

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 group · OCH ₃ : methoxy group

  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 and 10 or less from the viewpoint of forming a photosensitive layer (charge transport layer) having a high charge transport capability. It is preferable that R ^C21 and R ^C23 represent a hydrogen atom, and R ^C22 more preferably 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: a methyl group _· C 2 _{H 5:} ethyl · OH _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), from the viewpoint of suppression of seizure ghost and optical ^{fatigue, R H1,} and it is preferred ^{that R H2} represents a tert- butyl ^{group, R H1,} and ^{R H2} represents a tert- butyl group, More preferably, R ^H3 and R ^H4 represent an alkyl group having 1 to 3 carbon atoms (particularly a methyl group), and R ^H5 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.

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

As benzophenone UV absorbers,
1) a compound in which two benzene rings are unsubstituted,
2) A compound in which two benzene rings are each independently substituted with at least one substituent selected from the group consisting of a hydroxyl group, a halogen atom, an alkyl group, an alkoxy group, and an aryl group. 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)) charge transport material 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: a methyl group _· C 2 _{H 5:} ethyl _{· (CH 2) 7 CH 3} : octyl · OCH _3: methoxy · OH: hydroxy groups

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

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

  The content of the benzidine-based charge transport material (CT2) is 1 in terms of the blending ratio of CT2 and the binder resin (mass ratio CT2: binder resin) from the viewpoint of forming a photosensitive layer (charge transport layer) having a high charge transport capability. : Preferably in the range from 9 to 7: 3, more preferably in the range from 2: 8 to 6: 4, still more preferably in the range from 2: 8 to 4: 6. .

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

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

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

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

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

The binder resin used for the charge transport layer is polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, Vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N -Vinylcarbazole, polysilane, etc. are mentioned. Among these, as the binder resin, a polycarbonate resin or a polyarylate resin is preferable. These binder resins are used alone or in combination of two or more.
The mixing ratio of the charge transport material and the binder resin is preferably 10: 1 to 1: 5 by mass ratio.

  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) is, for example, a layer containing a charge generation material, a charge transport material, and, if necessary, a binder resin and other known additives. Note that these materials are the same as those described for the charge generation layer and the charge transport layer.
In the single-layer type photosensitive layer, the content of the charge generating material is preferably 10% by mass or more and 85% by mass or less, and preferably 20% by mass or more and 50% by mass or less with respect to the total solid content.
On the other hand, the content of the charge transport material, the 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.

(toner)
Hereinafter, the toner used for the developing device 18 will be described.
In the image forming apparatus of this embodiment, a toner having a volume average particle size in the range of 3 μm to 4.5 μm is used.
Here, the volume average particle diameter of the toner corresponds to the volume average particle diameter of the toner particles, for example, in the case of toner including toner particles and an external additive.

The volume average particle diameter of the toner (toner particles) is measured as follows.
First, 0.5 mg to 50 mg of a measurement sample was added to 2 ml of a 5 mass% aqueous solution of a surfactant (desirably sodium alkylbenzenesulfonate) as a dispersant, and this was added to 100 ml to 150 ml of an electrolytic solution. The electrolytic solution in which the measurement sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for 1 minute, and a particle size of 100 μm is used with an aperture having a diameter of 100 μm by a Coulter Multisizer II type (manufactured by Beckman-Coulter). The particle size distribution of particles in the range of 2.0 μm to 60 μm is measured. The number of particles to be measured is 50,000.
For the particle size range (channel) obtained by dividing the obtained particle size distribution, the volume cumulative distribution is subtracted from the small particle size side, and the particle size that becomes 50% cumulative is defined as the volume average particle size D50v.

The average circularity of the toner (toner particles) is preferably 0.900 or more and 0.998 or less, and more preferably 0.950 or more and 0.980 or less.
The average circularity of the toner (toner particles) is determined by (equivalent circumference of circle) / (perimeter) [(perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)]. . Specifically, a flow-type particle image analyzer (for example, a particle image is captured as a still image by sucking and collecting the toner to be measured, forming a flat flow, and emitting light with a strobe light, and analyzing the particle image (for example, , FPIA-2100 manufactured by Sysmex Corporation). The number of samplings when obtaining the average circularity is 3500.

The shape factor SF1 of the toner (toner particles) is preferably 100 or more and 130 or less, and more preferably 110 or more and 120 or less.
The shape factor SF1 of the toner (toner particles) is obtained by the following formula.
Formula: SF1 = 100π × (ML) ² / (4 × A)
In the above formula, ML is the maximum particle length, and A is the projected area of the particle. The maximum length and projected area of the particles are determined by observing the particles sampled on the slide glass with an optical microscope, taking them into an image analysis apparatus (LUZEX III, manufactured by NIRECO) through a video camera, and performing image analysis. In this case, the number of sampling is 100 or more, and the shape factor shown in the above equation is obtained using the average value.

-Toner composition-
The toner may be composed of toner particles alone or may be composed of toner particles and an external additive.

  The toner particles are configured to contain, for example, a binder resin, a colorant, a release agent, and other internal additives.

  The binder resin is not particularly limited, but styrenes (eg, styrene, chlorostyrene, etc.), monoolefins (eg, ethylene, propylene, butylene, isoprene, etc.), vinyl esters (eg, vinyl acetate, vinyl propionate, Vinyl benzoate, vinyl butyrate, etc.), 1-methylene aliphatic monocarboxylic acid esters (for example, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, methacrylic acid) Ethyl acetate, butyl methacrylate, dodecyl methacrylate, etc.), vinyl ethers (eg, vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether), vinyl ketones (eg, vinyl methyl ketone, vinyl hexyl ketone, vinyl isopro) Homopolymers and copolymers of Niruketon etc.), etc., and polyester resins by copolymerization of dicarboxylic acids and diols.

Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include a polymer, a polyethylene resin, a polypropylene resin, and a polyester resin.
Typical binder resins include polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like.

  Examples of the colorant include magnetic powder (eg, magnetite, ferrite, etc.), carbon black, aniline blue, caryl blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, Lamp Black, Rose Bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3 is a typical example.

  Examples of mold release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; and ester waxes such as fatty acid esters and montanic acid esters. However, it is not limited to this.

  Examples of other internal additives include magnetic materials, charge control agents, inorganic powders, and the like.

Examples of the external additive include inorganic particles. Examples of the inorganic particles include SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , MgO, BaO, and CaO. , K ₂ O, Na ₂ O, ZrO ₂ , CaO · SiO ₂ , K ₂ O · (TiO ₂ ) n, Al ₂ O ₃ · 2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO _{4 and the} like. .

  The surface of the external additive may be hydrophobized in advance. The hydrophobic treatment is performed, for example, by immersing inorganic particles in a hydrophobic treatment agent. The hydrophobizing agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, aluminum coupling agents and the like. These may be used individually by 1 type and may use 2 or more types together.

-Toner production method-
For example, after obtaining toner particles, the toner may be mixed with an external additive.
The method for producing the toner particles is not particularly limited by the production method. For example, kneading and pulverization in which a binder resin, other colorant, release agent, and other internal additives are added and kneaded, pulverized, and classified. Method: Method of changing the shape of particles obtained by kneading and pulverization method by mechanical impact force or thermal energy; Emulsion polymerization of polymerizable monomer of binder resin, and formed dispersion or other coloring An emulsion polymerization aggregation method in which a dispersing agent, a release agent and other internal additives are mixed, agglomerated and heat-fused; a polymerizable monomer for obtaining a binder resin, other colorants, a release agent Suspension polymerization method in which a solution of other internal additives is suspended in an aqueous solvent for polymerization; a binder resin, other colorant, release agent, and other internal additive solutions are suspended in an aqueous solvent. For example, a dissolution suspension method for granulation.
The toner particles may be core-shell toner particles obtained by using the toner particles obtained by the above method as a core, and further adhering and aggregating aggregated particles.
As a method for producing the toner particles, a suspension polymerization method, an emulsion polymerization aggregation method, and a dissolution suspension method in which an aqueous solvent is used are desirable from the viewpoint of shape control and particle size distribution control, and an emulsion polymerization aggregation method is particularly desirable.

  When the toner includes an external additive, the toner is manufactured by mixing the toner particles and the external additive with a Henschel mixer or a V blender. Further, when the toner particles are produced by a wet method, they may be externally added by a wet method.

(Career)
Examples of the carrier include iron powder, glass beads, ferrite powder, nickel powder, or those having a resin coating on the surface thereof.
The mixing ratio (mass ratio) of the toner and the carrier is, for example, in the range of toner: carrier = 1: 100 to 30: 100.

  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 Teica), 10 parts by mass of a 10% by mass toluene solution of N-2- (aminoethyl) -3-aminopropyltriethoxysilane as a silane coupling agent, 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.
Furthermore, the coating solution for forming the undercoat layer is applied onto an aluminum substrate having a diameter of 47 mm, a length of 357 mm, and a thickness of 1 mm by dip coating, and is dried and cured at 180 ° C. for 30 minutes, and has a film thickness of 30 μm. Undercoat layer was obtained.

Next, hydroxygallium phthalocyanine pigment as a charge generation material “X-ray diffraction spectrum Bragg angle (2θ ± 0.2 °) using CuKα characteristic X-ray is at least 7.3 °, 16.0 °, 24.9 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. Based on 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 130 ° C. for 5 minutes to form a charge generation layer having a thickness of 0.20 μm.

Next, as the charge transport material, 8 parts by mass of a butadiene-based charge transport material (CT1) “exemplary compound (CT1-3)” and 32 parts by mass of a benzidine-based charge transport material (CT2) “exemplary compound (CT2-2)” As a binder resin, 58 parts by mass of a bisphenol Z-type polycarbonate resin (bisphenol Z homopolymer polycarbonate resin, viscosity average molecular weight 40,000), and as an antioxidant, a hindered phenol-based antioxidant “Exemplary Compound (HP- 1), 2 parts by mass of molecular weight 775 ”(5% by mass with respect to 100% by mass of the total charge transporting material) was added to 340 parts by mass of tetrahydrofuran and dissolved to obtain a coating solution for forming a charge transport layer.
The resulting charge transport layer forming coating solution was dip coated on the charge generation layer and dried at 145 ° C. for 30 minutes to form a charge transport layer having a thickness of 30 μm.

  The photoreceptor 1 was obtained through the above steps.

[Photoreceptor 2]
As an antioxidant, together with 1 part by mass of hindered phenolic antioxidant “Exemplary Compound (HP-1), Molecular Weight 775” (2.5% by mass with respect to 100% by mass of the total charge transport material), Photosensitive member 1 except that 1 part by mass of benzophenone-based ultraviolet absorber “Exemplary Compound (BP-1)” (2.5% by mass with respect to 100% by mass of the total charge transporting material) was used as the ultraviolet absorber. In the same manner as above, an electrophotographic photosensitive member was produced.

[Photoreceptor 3]
Instead of the hindered phenol-based antioxidant as the antioxidant, 2 parts by mass of the benzophenone-based ultraviolet absorbent “Exemplary Compound (BP-1)” as the ultraviolet absorber (based on 100% by mass of the total amount of all charge transport materials) The electrophotographic photosensitive member was produced in the same manner as the photosensitive member 1 except that 5.0% by mass) was used.

[Photosensitive members 4 to 6]
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 was changed.

[Photoreceptors 7, 8]
According to Table 1, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 1 except that the kind of the hindered phenol antioxidant was changed.

[Photosensitive members 9, 10]
According to Table 1, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 3 except that the kind of the benzophenone-based ultraviolet absorber was changed.

[Photoreceptor 11]
According to Table 1, electrophotographic photosensitization was performed in the same manner as the photoreceptor 2 except that the type of hindered phenolic antioxidant as an antioxidant and the type of benzophenone ultraviolet absorber as an ultraviolet absorber were changed. The body was made.

[Photosensitive members 12 to 14]
According to Table 1, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 1 except that the kind of the charge transport material and the amount of the hindered phenol antioxidant were changed.

[Photosensitive members 15 and 16]
According to Table 1, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 3 except that the type of the charge transport material and the amount of the benzophenone-based ultraviolet absorber were changed.

[Photosensitive member 17]
According to Table 1, electrophotographic photosensitization was performed in the same manner as the photoreceptor 2 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 18 to 28]
According to Table 1, an electrophotographic photosensitive member was produced in the same manner as the photosensitive member 1, except that the amount of the charge transport material, the type and amount of the antioxidant, and the type and amount of the ultraviolet absorber were changed.

<Production of developer>
[Developer 1]
(Preparation of toner particles 1)
-Preparation of resin particle dispersion-
A nonionic surfactant (Nonipol 400: manufactured by Sanyo Kasei Kogyo Co., Ltd.) 6 g obtained by mixing and dissolving 370 g of styrene, 30 g of n-butyl acrylate, 8 g of acrylic acid, 24 g of dodecanethiol, and 4 g of carbon tetrabromide And 10 g of an anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) are added to a flask containing an aqueous solution dissolved in 550 g of ion-exchanged water, and emulsion polymerization is performed while slowly mixing for 10 minutes. An aqueous solution in which 4 g of ammonium persulfate was dissolved in 50 g of ion-exchanged water was added.
After carrying out nitrogen substitution, while stirring the liquid in the flask, the contents were heated in an oil bath until the content reached 70 ° C., and emulsion polymerization was continued for 5 hours.
As a result, a resin particle dispersion was obtained in which resin particles having a volume average particle size of 150 nm, a glass transition temperature Tg of 58 ° C., and a weight average molecular weight Mw of 11500 were dispersed. The solid content concentration of this dispersion was 40% by mass.

-Preparation of colorant particle dispersion-
-Cyan pigment (CI Pigment Blue 15: 3) 60 g
-Nonionic surfactant (Nonipol 400: Sanyo Chemical Industries) 6g
・ Ion exchange water 240g
The above components are mixed and dissolved, stirred for 10 minutes using a homogenizer (Ultra Turrax T50: manufactured by IKA), and then dispersed with an optimizer to give a colorant having a volume average particle diameter of 250 nm ( A colorant particle dispersion in which cyan) particles were dispersed was prepared.

-Preparation of release agent particle dispersion-
-Paraffin wax (HNP0190: Nippon Seiwa Co., Ltd., melting temperature 85 ° C.) 100 g
・ Cationic surfactant (Sanisol B50: manufactured by Kao Corporation) 5g
・ Ion exchange water 240g
The above components were dispersed in a round stainless steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA) for 10 minutes, and then dispersed with a pressure discharge homogenizer, and the volume average particle diameter was 550 nm. A release agent particle dispersion in which the release agent particles are dispersed was prepared.

-Production of toner particles 1-
-234 parts of resin particle dispersion-30 parts of colorant particle dispersion-40 parts of release agent particle dispersion-0.5 part of polyaluminum hydroxide (Pho2S manufactured by Asada Chemical Co., Ltd.)-600 parts of ion-exchanged water Were mixed and dispersed in a round stainless steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA), and then heated to 30 ° C. while stirring the inside of the flask in a heating oil bath. After holding at 30 ° C. for 20 minutes, it was confirmed that aggregated particles having a volume average particle diameter D50 of 3.0 μm were produced.

  Furthermore, the temperature of the heating oil bath was raised and held at 45 ° C. for 1 hour, and the volume average particle diameter D50 was 3.8 μm. Thereafter, 26 parts of the resin particle dispersion was added to the dispersion containing the aggregate particles, and then the temperature of the heating oil bath was raised to 50 ° C. and held for 20 minutes. After adding 1N sodium hydroxide to the dispersion containing the aggregate particles and adjusting the pH of the system to 5.0, the stainless steel flask was sealed, and stirring was continued using a magnetic seal. Heated to 0 ° C. and held for 3 hours. After cooling, the resulting toner particles were filtered off, washed four times with ion exchange water, and then lyophilized to obtain toner particles 1. Toner particles 1 had a volume average particle diameter D50 of 4.1 μm and a shape factor SF1 of 105.

(Preparation of carrier 1)
• Ferrite particles (average particle size: 50 μm) 100 parts • Toluene 14 parts • Styrene / methacrylate copolymer (component ratio: 90/10) 2 parts • Carbon black (R330: manufactured by Cabot) 0.2 parts First, ferrite The above components except the particles were stirred with a stirrer for 10 minutes to prepare a dispersed coating solution. Next, the coating liquid and the ferrite particles were put in a vacuum degassing kneader and stirred at 60 ° C. for 30 minutes, and then degassed and degassed while heating, and dried to obtain a carrier 1. This carrier 1 had a volume resistivity value of 10 ¹¹ Ωcm when an applied electric field of 1000 V / cm was applied.

(Preparation of developer 1)
1100 parts of the toner particles 1, 1 part of rutile type titanium oxide particles (particle size 20 nm, n-decyltrimethoxysilane treatment), and silica particles (particle size 40 nm, silicone oil treatment, gas phase oxidation method) 2.0 Part, cerium oxide particles (average particle size 0.7 μm) 1 part, higher fatty acid alcohol (molecular weight 700) and tetrafluoroethylene resin (Lublon L-2) at a mass ratio of 5: 1 by jet mill After mixing with 0.3 parts of a pulverized average particle size of 8.0 μm with a 5 L Henschel mixer for 15 minutes at a peripheral speed of 30 m / s, coarse using a sieve with 45 μm openings Particles were removed to obtain toner 1.
Further, 100 parts of the carrier 1 and 5 parts of the toner 1 were stirred with a V-blender for 20 minutes under a condition of 40 rpm, and sieved with a sieve having an opening of 212 μm, thereby developing agent 1. Got.

[Preparation of Developer 2]
(Preparation of toner particles 2)
-234 parts of resin particle dispersion-30 parts of colorant particle dispersion-40 parts of release agent particle dispersion-0.5 part of polyaluminum hydroxide (Pho2S manufactured by Asada Chemical Co., Ltd.)-600 parts of ion-exchanged water Were mixed and dispersed in a round stainless steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA), and then heated to 40 ° C. while stirring the inside of the flask in a heating oil bath. After maintaining at 40 ° C. for 30 minutes, it was confirmed that aggregated particles having a volume average particle diameter D50 of 4.5 μm were generated.
Further, the temperature of the heating oil bath was raised and maintained at 53 ° C. for 1 hour, and the volume average particle diameter D50 was 5.2 μm. Thereafter, 26 parts of the resin particle dispersion was added to the dispersion containing the aggregate particles, and then the temperature of the heating oil bath was raised to 50 ° C. and held for 30 minutes. After adding 1N sodium hydroxide to the dispersion containing the aggregated particles to adjust the pH of the system to 7.0, the stainless steel flask was sealed, and stirring was continued using a magnetic seal at 80 ° C. And held for 3.5 hours. After cooling, the obtained toner particles were separated by filtration, washed four times with ion exchange water, and then lyophilized to obtain toner particles 2. Toner particles 2 had a volume average particle diameter D50 of 6.0 μm and a shape factor SF1 of 135.

(Preparation of developer 2)
Toner 2 was obtained in the same manner as toner 1 except that toner particle 2 was used instead of toner particle 1.
Further, 100 parts of the carrier 1 and 5 parts of the toner 2 were stirred with a V-blender for 20 minutes at 40 rpm, and sieved with a sieve having an opening of 212 μm, thereby developing agent 2. Got.

<Examples 1 to 28 and Comparative Examples 1 to 9>
The obtained electrophotographic photosensitive member (photosensitive member 1 to photosensitive member 28) is mounted on a modified machine of an image forming apparatus (manufactured by Fuji Xerox Co., Ltd .: Versant 2100 Press), and the transfer current value is a value shown in Table 2 and Table 3. The image forming apparatus using a combination of the developers shown in Tables 2 and 3 was evaluated in the following manner.

[Image density evaluation]
Using the above image forming apparatus, a halftone image having an image density of 20% and a solid image having an image density of 100% are formed in cyan (Cyan) color in an environment of 22 ° C. and 55% humidity. -Rite 938) was used to measure the image density (Dout), and evaluation was performed according to the following criteria.

(Evaluation criteria for halftone images with 20% image density)
A: 0.15 <Dout ≦ 0.25
B: 0.1 <Dout ≦ 0.15 or 0.25 <Dout ≦ 0.3
C: Dout ≦ 0.1 or 0.3 <Dout

(Evaluation criteria for 100% solid image)
A: 1.4 ≦ Dout
B: 1.35 ≦ Dout <1.4
C: 1.3 ≦ Dout <1.35
D: Dout <1.3

[Dot reproducibility (granularity) evaluation]
About the image formed by said image evaluation, dot reproducibility (granularity) was evaluated according to the following reference | standard. Note that the photograph shown in FIG. 3 is a photograph obtained by enlarging the halftone image (Cyan) with an image density of 20% formed by the above image evaluation 100 times with a microscope (manufactured by KEYENCE, model number: VHX-900). is there. The evaluation results are shown in Table 2 and Table 3.
A: The dots are not disturbed as shown in FIG. 3A. B: The dots are slightly scattered as shown in FIG. 3B. C: The toner is scattered as shown in FIG. 3C.

[Evaluation of seizure ghost]
Using the above-described image forming apparatus, after forming 3000 grid-like chart images (Cyan color) as shown in FIG. 4A on an A3 size paper in an environment of 28 ° C. and 85% RH, Then, an entire halftone image (Cyan color) with an image density of 20% was output, and the appearance of a lattice-like image (ghost) was visually observed and evaluated according to the following criteria. The evaluation results are shown in Table 2 and Table 3.
A: A grid-like image is not confirmed as shown in FIG.
B: As shown in FIG. 4C, a lattice-like image is slightly confirmed.
C: A lattice-like image is clearly confirmed as shown in FIG.

[Evaluation of light fatigue]
First, an electrophotographic photosensitive member (photosensitive member 1 to photosensitive member 22) is mounted on the image forming apparatus, the image forming apparatus is adjusted so as to have the transfer current values shown in Tables 2 and 3, and then the electrophotographic photosensitive member is adjusted. I took my body out.
A black paper with a window of 5 cm in length and 10 cm in width was prepared, and the black paper was wrapped around the electrophotographic photosensitive member so that the axially central portion of the extracted electrophotographic photosensitive member and the window opening portion were aligned. Next, the electrophotographic photosensitive member was light-fatigued by leaving it under a white fluorescent lamp (1000 Lux) for 10 minutes so that only the window opening portion was light-fatigue.
Then, after the photo-fatigue electrophotographic photosensitive member is mounted on the adjusted image forming apparatus again, and the post-exposure potential is measured without changing the adjustment, the light-fatigue portion is exposed The potential VL1 and the post-exposure potential VL2 of the light-fatigue portion were measured, and a change ΔVL = VL1-VL2 due to the photo-fatigue of the post-exposure potential was obtained. The results are shown in Table 2 and Table 3.
A: ΔVL <30
B: 30 ≦ ΔVL <40
C: 40 ≦ ΔVL

  Each example and each comparative example and their evaluation results are listed in Tables 1 to 3. In Table 1, 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 transport material. In Tables 2 and 3, “halftone” indicates a halftone image with an image density of 20%, and “solid” indicates a solid image with an image density of 100%.

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, the example using the toner having a volume average particle size of 4.1 μm has better dot reproducibility and image density evaluation results than the comparative example using the toner having a volume average particle size of 6.0 μm. It can be seen that it is.

  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)

-HP-1: Illustrative compound (HP-1) of a hindered phenol-based antioxidant
HP-2: Illustrative compound (HP-2) of a hindered phenolic antioxidant
-HP-3: Exemplary compound (HP-3) of a hindered phenol-based antioxidant
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: Exemplified compound of benzophenone ultraviolet absorber (BP-1)
BP-2: Illustrative compound of benzophenone ultraviolet absorber (BP-2)
BP-3: exemplary compound of a benzophenone ultraviolet absorber (BP-3)
CUA-1: Comparative compound of UV absorber (see benzoate UV absorber represented by the following structural formula (CUA-1))

  DESCRIPTION OF SYMBOLS 1 Undercoat layer, 2 Charge generation layer, 3 Charge transport layer, 4 Conductive substrate, 7A, 7 Electrophotographic photosensitive member, 10 Image forming apparatus, 15 Charging apparatus, 16 Electrostatic latent image forming apparatus (exposure apparatus), 18 Development 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 (8)

A conductive substrate, a photosensitive layer provided 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) An electrophotographic photoreceptor comprising a material and a photosensitive layer comprising 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;
Charging means for charging the surface of 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;
A developer containing a toner having a volume average particle size of 3 μm or more and 4.5 μm or less is accommodated, and the electrostatic latent image formed on the surface of the electrophotographic photosensitive member is developed with the developer to form a toner image. Developing means,
Transfer means for transferring the toner image to the surface of a recording medium, wherein a transfer current value is 0.03 μA / mm or more and 0.13 μA / mm or less per unit length (mm) in the axial direction of the electrophotographic photosensitive member. A transfer means,
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.