JP2014153550A - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus including a charging device by a contact charging system applying a voltage in which an AC voltage is superimposed on a DC voltage, in which the residual potential increase of an electrophotographic photoreceptor is suppressed.SOLUTION: In the image forming apparatus comprising: a charging device 208 coming into direct contact with an electrophotographic photoreceptor 7 and applying the voltage in which the AC voltage is superimposed on the DC voltage, to charge the electrophotographic photoreceptor; an electrostatic latent image forming device 210; a developing device 211; and a transfer device 212, as the electrophotographic photoreceptor 7, an electrophotographic photoreceptor which includes a conductive substrate, an undercoat layer provided on the conductive substrate and containing a binder resin, metal oxide particles, and an electron accepting material, and a photoreceptive layer provided on the undercoat layer and in which when the impedance of the undercoat layer is measured at the AC voltage being in the range of 1 MHz to 1 mHz, the maximum point of the phase difference θ of the impedance is within the range of a frequency more than 0.15 Hz and less than 0.3 Hz is applied.

Description

  The present invention relates to an electrophotographic photosensitive member, a process cartridge, and an image forming apparatus.

  With respect to the electrophotographic photosensitive member, from the viewpoint of ensuring the stability of electrophotographic characteristics in repeated use, it has at least an undercoat layer and a photosensitive layer on a conductive substrate, and the undercoat layer contains metal oxide fine particles and the metal oxide. A substance containing an acceptor compound having a group capable of reacting with fine particles has been proposed (for example, see Patent Document 1).

  Patent Document 2 states that “at least a conductive substrate, an undercoat layer, and a charge generation layer are provided, the undercoat layer contains metal oxide particles, and the impedance of the undercoat layer is 1 MHz. An electrophotographic photosensitive member has been proposed in which the maximum point of the impedance phase difference θ is in the frequency range of 10 mHz to 150 mHz when measured with an AC voltage in the range of 1 to 1 mHz.

  Patent Document 3 states that “at least a conductive substrate, an undercoat layer, and a charge generation layer are provided, the undercoat layer contains metal oxide particles, and the impedance of the undercoat layer is 1 MHz. A contact charging type charging device to which only a DC voltage is applied, in which the maximum point of impedance phase difference θ is in a frequency range of 0.3 Hz to 10 kHz when measured with an AC voltage in a range from 1 to 1 mHz. An electrophotographic photosensitive member for use in an image forming apparatus having the same has been proposed.

JP 2006-030697 A JP 2012-073353 A JP 2012-063447 A

  The present invention relates to an image forming apparatus including a contact charging type charging device (hereinafter referred to as a “DC / AC contact charging device”) that applies a voltage obtained by superimposing an AC voltage on a DC voltage. It is an object of the present invention to provide an image forming apparatus that suppresses the rise and suppresses an afterimage phenomenon (hereinafter referred to as “ghost”) in which the history of the previous image remains.

  In order to solve the above problems, the following inventions are provided.

The invention according to claim 1
A conductive substrate; an undercoat layer provided on the conductive substrate and including a binder resin, metal oxide particles, and an electron-accepting substance; and a photosensitive layer provided on the undercoat layer. When the impedance of the undercoat layer is measured with an AC voltage in the range of 1 MHz to 1 mHz, the maximum point of the impedance phase difference θ is in the frequency range of 0.15 Hz to less than 0.3 Hz. When,
A charging device that directly contacts the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage in which an alternating voltage is superimposed on a direct current voltage;
An electrostatic latent image forming apparatus that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image on the surface of the electrophotographic photosensitive member;
A developing device for developing the electrostatic latent image into a toner image with a developer;
A transfer device for transferring the toner image to a transfer medium;
An image forming apparatus.

The invention according to claim 2
The image forming apparatus according to claim 1, wherein the maximum point of the impedance phase difference θ is within a frequency range of 0.15 Hz to 0.2 Hz.

The invention according to claim 3
The image forming apparatus according to claim 1, wherein a light source for exposing the electrophotographic photosensitive member is not provided other than the electrostatic latent image forming apparatus.

The invention according to claim 4
The image forming apparatus according to claim 1, wherein the electron accepting substance has anthraquinone as a basic skeleton.

The invention according to claim 5
The image forming apparatus according to claim 4, wherein the electron-accepting substance has a hydroxyl group and an alkoxy group.

The invention according to claim 6
The image forming apparatus according to claim 4, wherein the electron accepting substance has a hydroxyl group and an ethoxy group.

The invention according to claim 7 provides:
The image forming apparatus according to claim 4, wherein the electron-accepting substance has a hydroxyl group and one ethoxy group.

The invention according to claim 8 provides:
The image forming apparatus according to claim 1, wherein the metal oxide particles are surface-treated with a silane coupling agent represented by the following general formula (S).

(In general formula (S), R ¹ represents an alkoxy group or a halogen atom. R ² represents a hydrogen atom, a phenyl group, or an alkyl group having an amino group at the terminal.)

The invention according to claim 9 is:
A conductive substrate; an undercoat layer provided on the conductive substrate and including a binder resin, metal oxide particles, and an electron-accepting substance; and a photosensitive layer provided on the undercoat layer. When the impedance of the undercoat layer is measured with an AC voltage in the range of 1 MHz to 1 mHz, the maximum point of the impedance phase difference θ is in the frequency range of 0.15 Hz to less than 0.3 Hz. When,
A charging device that directly contacts the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage in which an alternating voltage is superimposed on a direct current voltage;
Have
A process cartridge attached to and detached from the image forming apparatus.

The invention according to claim 10 is:
A conductive substrate; an undercoat layer provided on the conductive substrate and including a binder resin, metal oxide particles, and an electron-accepting substance; and a photosensitive layer provided on the undercoat layer. ,
When the impedance of the undercoat layer is measured with an AC voltage in the range from 1 MHz to 1 mHz, the maximum point of the impedance phase difference θ is in the range of frequencies from 0.15 Hz to less than 0.3 Hz,
An electrophotographic photosensitive member used in an image forming apparatus having a charging device that directly contacts the electrophotographic photosensitive member and applies a voltage in which an alternating voltage is superimposed on a direct current voltage to charge the electrophotographic photosensitive member.

According to the first aspect of the present invention, compared to the case where the maximum point of the phase difference θ of the impedance of the undercoat layer on the electrophotographic photosensitive member is outside the frequency range of 0.15 Hz or more and less than 0.3 Hz, the direct current / alternating current In an image forming apparatus provided with a contact charging device, an image forming apparatus that realizes suppression of an increase in residual potential of an electrophotographic photosensitive member and suppresses ghost is provided.
According to the second aspect of the present invention, compared to the case where the maximum point of the phase difference θ of the impedance of the undercoat layer on the electrophotographic photosensitive member is outside the frequency range of 0.15 Hz to 0.2 Hz, the direct current / alternating current In an image forming apparatus provided with a contact charging device, an image forming apparatus that realizes suppression of an increase in residual potential of an electrophotographic photosensitive member is provided.
According to the third aspect of the present invention, the electrostatic latent image has an electrostatic latent potential higher than that in the case where the maximum point of the phase difference θ of the impedance of the undercoat layer is outside the frequency range of 0.15 Hz to less than 0.3 Hz. In addition to the image forming apparatus, an image forming apparatus that suppresses ghost is provided even in an image forming apparatus that does not have a light source for exposing an electrophotographic photosensitive member.

According to the invention of claim 4, in the image forming apparatus provided with the DC / AC contact charging device as compared with the case where a substance having a basic skeleton other than anthraquinone is applied as the electron-accepting substance, Provided is an image forming apparatus that suppresses an increase in potential and suppresses ghosts.
According to the invention according to claim 5, 6 or 7, the direct current / ac contact charging device is compared with the case where a material having no hydroxyl group and no alkoxy group is applied as the electron accepting material having anthraquinone as a basic skeleton. In the image forming apparatus provided, an image forming apparatus that realizes suppression of an increase in the residual potential of the electrophotographic photosensitive member and suppresses ghost is provided.
According to the eighth aspect of the invention, the increase in the residual potential of the electrophotographic photosensitive member is suppressed as compared with the case where the metal oxide particles are surface-treated with a material other than the silane coupling agent represented by the following general formula (S). And an image forming apparatus that suppresses ghosts.

  According to the ninth aspect of the present invention, compared to the case where the maximum point of the phase difference θ of the impedance of the undercoat layer on the electrophotographic photosensitive member is outside the frequency range of 0.15 Hz to less than 0.3 Hz, the In a process cartridge including a contact charging device, a process cartridge is provided that realizes suppression of an increase in residual potential of an electrophotographic photosensitive member.

  According to the tenth aspect of the present invention, the DC / AC contact charging device is provided as compared with the case where the maximum point of the phase difference θ of the impedance of the undercoat layer is outside the frequency range of 0.15 Hz or more and less than 0.3 Hz. When used in an image forming apparatus, there is provided an electrophotographic photosensitive member that realizes suppression of an increase in residual potential.

1 is a schematic cross-sectional view illustrating an example of an electrophotographic photosensitive member of the present embodiment. It is a schematic cross-sectional view showing another example of the electrophotographic photosensitive member of the present embodiment. 1 is a schematic diagram illustrating a basic configuration of an image forming apparatus according to a first embodiment. It is the schematic which shows the basic composition of the image forming apparatus of 2nd Embodiment. FIG. 3 is a schematic diagram illustrating a basic configuration of an example of a process cartridge according to the present embodiment. In an Example, it is a figure which shows the evaluation pattern and evaluation criteria of a ghost.

  Hereinafter, embodiments will be described in detail. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and repeated description is omitted as appropriate.

<Electrophotographic photoreceptor>
The electrophotographic photosensitive member of this embodiment is provided with a conductive substrate, an undercoat layer provided on the conductive substrate and containing metal oxide particles and an electron-accepting substance, and a photosensitive material provided on the undercoat layer. And a layer.
When the impedance of the undercoat layer is measured with an AC voltage in the range of 1 MHz to 1 mHz, the maximum point of the impedance phase difference θ is set within a frequency range of 0.15 Hz to less than 0.3 Hz.
Note that the electrophotographic photosensitive member of this embodiment is a DC / AC contact charging device (charging that directly contacts the electrophotographic photosensitive member and applies a voltage in which an AC voltage is superimposed on the DC voltage to charge the electrophotographic photosensitive member. Device).

  Here, as a charging method of the electrophotographic photosensitive member, there is a contact-type charging method using a charging roll or a brush in addition to a non-contact type using a corotron or the like. The contact charging method is being adopted because it is an environmentally superior method, but it is known that the residual potential is likely to increase as compared with the non-contact charging method. In addition, among the contact charging methods, it is clear that in the charging method in which a voltage obtained by superimposing an AC voltage on a DC voltage is applied, the increase in the residual potential is increased compared to the charging method in which only a DC voltage is applied. It is coming. It has also become clear that ghost (an afterimage phenomenon in which the history of the previous image remains) is likely to occur.

  When the residual potential rises, for example, it causes image quality defects such as density abnormalities and fogging on images. The cause of this is not clear, but it is thought to be due to the fact that abnormal discharge tends to occur. Further, although the cause of the ghost is not clear, it is considered that it is caused by the carrier remaining in the photoreceptor.

As a result of examining these phenomena, when the maximum point of the impedance phase difference θ in the undercoat layer is within a specific frequency range, even if it is used for an image forming apparatus having a DC / AC contact charging device, the residual potential is reduced. It was found that both rise and ghost were suppressed.
Note that the DC / AC contact charging device is a method in which a specific region in contact with the electrophotographic photosensitive member is charged by applying a voltage in which the AC voltage is superimposed on the DC voltage at the time of contact. It has been found that adjusting the charging responsiveness to an appropriate range is effective in suppressing both the residual potential rise and the ghost, and the electrophotographic photosensitive member of this embodiment has been achieved.

  As described above, the electrophotographic photosensitive member of the present exemplary embodiment increases the residual potential of the electrophotographic photosensitive member by appropriately adjusting the maximum point of the impedance phase difference θ in the undercoat layer to be within a specific frequency range. Is suppressed, and ghost is suppressed. Note that, by setting the maximum point to a frequency of less than 0.3 Hz, it is easy to suppress the occurrence of image unevenness due to the charge responsiveness being too high.

In particular, in the case of an image forming apparatus equipped with a DC / AC contact charging device using a charging roller, the residual potential generally tends to increase. However, this can be improved by applying the electrophotographic photosensitive member of this embodiment. Is done.
In addition to the electrostatic latent image forming apparatus, an image forming apparatus that does not have a light source (for example, a charge eliminating device) that exposes the electrophotographic photosensitive member is likely to generate ghosts. However, when the electrophotographic photosensitive member of the present embodiment is applied. This will be improved.

  In the electrophotographic photosensitive member of the present embodiment, it is desirable that the maximum point of the impedance phase difference θ is 0.15 Hz or more and 0.2 Hz or less from the viewpoint of suppressing the residual potential rise and further suppressing the ghost.

Here, a method for measuring the maximum point of the impedance phase difference θ in the undercoat layer will be described.
For measurement of impedance, SI 1287 electrical interface (manufactured by Toyo Technica) is used as a power source and ammeter, and 1296 dielectric interface (manufactured by Toyo Technica) is used as a current amplifier.

  First, an aluminum pipe is dipped and applied in the undercoat layer coating liquid described below, and then dried under the same conditions as those for forming the undercoat layer in the electrophotographic photosensitive member, and applied to the electrophotographic photosensitive member. An undercoat monolayer film having the same thickness as the layer is formed. For example, when an electrophotographic photosensitive member having an undercoat layer having a thickness of 15 μm that has been dried and cured at 170 ° C. for 24 minutes is produced, the undercoat monolayer film for the impedance measurement sample is also dried and cured at 170 ° C. for 24 minutes. Thus, the film thickness is set to 15 μm. About this undercoat single layer film, a gold electrode of 100 nm is deposited as a counter electrode by a vacuum deposition method to prepare a measurement sample.

  Using the aluminum pipe of the prepared measurement sample as a cathode and a gold electrode as an anode, an AC voltage of 1 Vp-p was applied from the high frequency side in a frequency range of 1 MHz to 1 mHz in an environment of a temperature of 20 ° C. and a humidity of 50 RH%, Measure impedance.

  Impedance is expressed by two parameters, the amplitude ratio of the response current to the applied voltage and the phase difference between the applied voltage and the response current. The phase difference between the applied voltage and the response current is plotted against the frequency of the applied voltage, and the phase difference θ is maximized. Find the frequency at which

  In the electrophotographic photosensitive member of this embodiment, the subbing layer in which the maximum point of the impedance phase difference θ is in the frequency range of 0.15 Hz to 0.3 Hz can reduce the addition of a substance that traps charges. This can be achieved by changing the curing conditions or designing so that the charge can easily move. Depending on the heating temperature and heating time in curing, the trapping ability of the substance that traps the charge may decrease, so it is necessary to consider multiple factors. It is important not to prescribe, but to prescribe comprehensively as a frequency range indicating the maximum point of the impedance phase difference θ. A specific method for adjusting the undercoat layer will be described later.

Hereinafter, the electrophotographic photoreceptor according to the exemplary embodiment will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of the electrophotographic photosensitive member of this embodiment. FIG. 2 is a schematic cross-sectional view showing another example of the electrophotographic photosensitive member of the present embodiment.

  The electrophotographic photoreceptor 7A shown in FIG. 1 has a structure in which an undercoat layer 1 is provided on a conductive substrate 4, and a charge generation layer 2 and a charge transport layer 3 are sequentially formed thereon. An electrophotographic photoreceptor 7B shown in FIG. 2 has a structure in which an undercoat layer 1 is provided on a conductive substrate 4, and a charge transport layer 3 and a charge generation layer 2 are sequentially formed thereon. .

In the electrophotographic photoreceptors 7A and 7B shown in FIGS. 1 and 2, the undercoat layer 1 has the above-described configuration.
The electrophotographic photoreceptor shown in FIGS. 1 and 2 is an example of a function-separated type electrophotographic photoreceptor having a charge generation layer and a charge transport layer as the photosensitive layer.

  Hereinafter, each element will be described based on the electrophotographic photosensitive member 7A shown in FIG. 1 as a representative example. In the following description, reference numerals are omitted.

[Conductive substrate]
The conductive substrate will be described. “Conductivity” means, for example, a volume resistivity of 10 ¹³ Ω · cm or less.
Any conductive substrate may be used as long as it is conventionally used. For example, thin films (eg, metals such as aluminum, nickel, chromium, and stainless steel, and films such as aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, and indium tin oxide (ITO)) And a resin film coated or impregnated with a conductivity-imparting agent, a resin film coated or impregnated with a conductivity-imparting agent, and the like. The shape of the conductive substrate is not limited to a cylindrical shape, and may be a sheet shape or a plate shape.

  When a metal pipe is used as the conductive substrate, the surface may be left as it is, and processing such as mirror cutting, etching, anodizing, rough cutting, centerless grinding, sand blasting, wet honing has been performed in advance. Also good.

[Underlayer]
Next, the undercoat layer will be described.
The undercoat layer 1 includes a binder resin, metal oxide particles, and an electron accepting substance.

-Binder resin-
As the binder resin, for example, acetal resin such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, Known vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, unsaturated urethane resin, polyester resin, alkyd resin, epoxy resin, etc. A polymeric resin compound is mentioned. Examples of the binder resin include a charge transporting resin having a charge transporting group and a conductive resin such as polyaniline.
Among these, as the binder resin, a resin insoluble in the upper layer coating solvent is desirable, and in particular, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, epoxy resin. Such as thermosetting resins such as polyamide resins, polyester resins, polyether resins, acrylic resins, polyvinyl alcohol resins, and polyvinyl acetal resins, and a resin obtained by reaction of a curing agent with at least one resin selected from the group consisting of polyvinyl acetal resins Is preferred.
When these binder resins are used in combination of two or more, the mixing ratio is set as necessary.

-Metal oxide particles-
Examples of the metal oxide particles include metal oxide particles such as zinc oxide, titanium oxide, tin oxide, and zirconium oxide, and it is desirable to use zinc oxide and titanium oxide. The metal oxide particles may be used alone or in combination of two or more.

The average particle diameter of the metal oxide particles is desirably 50 nm or more and 200 nm or less, more desirably 60 nm or more and 150 nm or less, and further desirably 70 nm or more and 100 nm or less. The metal oxide particles having an average particle diameter within the above range of the metal oxide particles have a maximum point of impedance phase difference θ in the undercoat layer 1 within a frequency range of 0.15 Hz to 0.3 Hz. Desirable from.
In general, when the average particle diameter is increased without changing the addition amount of the metal oxide particles, the maximum point of the impedance phase difference θ in the undercoat layer 1 moves to the high frequency side. Therefore, in view of the maximum point of the phase difference θ, it is desirable to select the average particle diameter of the metal oxide particles to be used.

  The average particle diameter of the metal oxide particles is measured using a laser diffraction particle size distribution measuring device (LA-700: manufactured by Horiba, Ltd.). As a measuring method, the sample in the state of dispersion is adjusted to 2 g in solid content, ion-exchanged water is added thereto to make 40 ml, and this is put into a cell until an appropriate concentration is obtained. Measure after 2 minutes. The obtained volume average particle diameter for each channel is accumulated from the smaller one, and the place where the accumulation reaches 50% is defined as the average particle diameter (that is, volume average particle diameter).

The content of the metal oxide particles is desirably 30% by mass to 90% by mass, more desirably 55% by mass to 80% by mass, and desirably 60% by mass to 75% by mass. More desirable.
Generally, when the content of the metal oxide particles is increased, the maximum point of the impedance phase difference θ in the undercoat layer 1 moves to the low frequency side. Therefore, it is desirable to adjust the content of the metal oxide particles in view of the frequency at the maximum point of the phase difference θ.

  The metal oxide particles may be surface-treated with a surface treatment agent. The surface treatment agent is not particularly limited as long as desired characteristics can be obtained, and is selected from known materials. For example, a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, and the like can be given. Powder resistance is controlled by surface treatment with a silane coupling agent. A silane coupling agent having an amino group is desirably used in order to give a good blocking property to the undercoat layer.

  In general, since the coupling agent has a property of trapping charges, when the amount of the coupling agent is increased, the maximum point of the impedance phase difference θ in the undercoat layer 1 moves to the low frequency side. Therefore, it is desirable to adjust the processing amount of the coupling agent in view of the frequency at the maximum point of the phase difference θ.

  From the viewpoint of setting the frequency at the maximum point of impedance phase difference θ in the undercoat layer within the above range, when using a coupling agent, it is desirable to use a silane coupling agent containing an amino group, It is further desirable to use a silane coupling agent represented by the general formula (S).

In general formula (S), R ¹ represents an alkoxy group or a halogen atom. R ² represents a hydrogen atom, a phenyl group, or an alkyl group having an amino group at the terminal.
The number of carbon atoms of the alkoxy group represented by R ¹ is preferably 1 or 2. Three R < ¹ > may represent the same group (or atom), and may represent a different group (or atom).
The number of carbon atoms of the alkyl group represented by R ² (alkyl group having an amino group) may be 2 or 3. Three R ² may represent the same group (or atom), or may represent different groups (or atoms).

Here, the silane coupling agent represented by the general formula (S) is preferably a silane coupling agent in which R ¹ represents a methoxy group and R ² represents an aminoethyl group.

Specific examples of the silane coupling agent represented by the general formula (S) include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane and N-2- (aminoethyl) -3-aminopropyl. Trimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3- Dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and the like.
Among these, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane is preferable.

  The treatment amount of the coupling agent (particularly the silane coupling agent represented by the general formula (S)) is preferably 0.75% by mass or more and 1.5% by mass or less with respect to the metal oxide particles.

-Electron acceptor-
When the electron-accepting substance contains the undercoat layer together with the metal oxide particles, an undercoat layer excellent in long-term stability of electric characteristics and carrier blocking properties can be obtained.

As the electron-accepting substance, any substance can be used as long as the desired characteristics can be obtained. Examples thereof include compounds having a quinone group.
As an electron accepting substance, an electron accepting substance having an anthraquinone as a basic skeleton (an electron accepting substance having an anthraquinone structure) is particularly preferable from the viewpoint of suppressing an increase in residual potential and further suppressing ghosts. An electron accepting substance having an anthraquinone having a basic skeleton (an electron accepting substance having an anthraquinone structure having a hydroxyl group) is desirable.
Examples of the electron accepting substance having an anthraquinone as a basic skeleton include a hydroxyanthraquinone compound and an aminohydroxyanthraquinone compound. Specific examples of the electron-accepting material include alizarin, quinizarin, anthralphine, purpurin, 1-hydroxyanthraquinone, 2-amino-3-hydroxyanthraquinone, 1-amino-4-hydroxyanthraquinone, 4-methoxy-1,2 -Dihydroxy-9,10-anthraquinone, 4-ethoxy-1,2-dihydroxy-9,10-anthraquinone, 4-butoxy-1,2-dihydroxy-9,10-anthraquinone and the like.
Among these, from the viewpoint of suppressing increase in residual potential and further suppressing ghost, the electron accepting substance having anthraquinone as a basic skeleton includes a hydroxyl group and an alkoxy group (for example, having 1 to 10 carbon atoms, preferably 1 or more carbon atoms). It is preferably an electron-accepting substance having 8 or less, more preferably 1 or more and 6 or less alkoxy groups.
In particular, from the same viewpoint, the electron accepting substance having anthraquinone as a basic skeleton is preferably an electron accepting substance having a hydroxyl group and an ethoxy group, and more preferably an electron accepting substance having a hydroxyl group and one ethoxy group. .

  The content of the electron-accepting substance is not limited as long as the desired characteristics can be obtained, but it is preferably in the range of 0.01% by mass to 20% by mass with respect to the metal oxide particles. . Furthermore, it is desirable to add in the range of 0.05 mass% or more and 10 mass% or less from the viewpoint of preventing charge accumulation and preventing aggregation of metal oxide particles.

  In general, when the addition amount of the electron accepting substance is increased, the maximum point of the impedance phase difference θ in the undercoat layer moves to the low frequency side. Therefore, in view of the maximum point of the phase difference θ, it is desirable to select the addition amount of the electron accepting substance to be used.

  The electron-accepting substance may be dispersed in the binder resin separately from the metal oxide particles and contained in the undercoat layer, or may be included in the undercoat layer while adhering to the surface of the metal oxide particles. May be included.

  Examples of the method for attaching the electron accepting substance to the surface of the metal oxide particles include a dry method and a wet method.

  In the dry method, an electron-accepting substance is dropped by spraying it together with dry air or nitrogen gas while stirring the metal oxide particles directly or in an organic solvent while stirring with a mixer having a large shearing force. Is attached to the surface of the metal oxide particles. The addition or spraying is preferably performed at a temperature below the boiling point of the solvent. When sprayed at a temperature lower than the boiling point of the solvent, local distribution of the electron accepting substance is suppressed. After addition or spraying, baking may be performed at 100 ° C. or higher. Baking is carried out within a target range as long as the temperature and time allow desired electrophotographic characteristics to be obtained.

  In the wet method, the metal oxide particles are stirred in a solvent, dispersed using an ultrasonic wave, a sand mill, an attritor, a ball mill, etc., added with an electron-accepting substance, stirred or dispersed, and then removed by removing the solvent. In this method, the accepting substance is attached to the surface of the metal oxide particles. The solvent removal method is distilled off by filtration or distillation. 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 moisture contained in the metal oxide particles may be removed before adding the electron-accepting substance. For example, a method of removing with stirring and heating in the solvent used for the electron-accepting substance, A method of removing it by boiling may be used.

-Others-
Resin particles may be added to the undercoat layer in order to adjust the surface roughness. Examples of the resin particles include silicone resin particles and cross-linked polymethyl methacrylate (PMMA) resin particles. The surface may be polished after forming the undercoat layer for adjusting the surface roughness. As a polishing method, buffing, sandblasting, wet honing, grinding, or the like is used.

-Formation of undercoat layer-
The formation of the undercoat layer is not particularly limited, and a well-known formation method is used. For example, a coating film of a coating solution for forming an undercoat layer 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.
Examples of such solvents include aromatic hydrocarbon solvents such as toluene and chlorobenzene, aliphatic alcohol solvents such as methanol, ethanol, n-propanol, iso-propanol, and n-butanol, acetone, cyclohexanone, and 2-butanone. Ketone solvents, halogenated aliphatic hydrocarbon solvents such as methylene chloride, chloroform, ethylene chloride, cyclic or linear ether solvents such as tetrahydrofuran, dioxane, ethylene glycol, diethyl ether, methyl acetate, ethyl acetate, n acetate -Organic solvents, such as ester solvents, such as butyl. These solvents may be used alone or in combination of two or more.

  When dispersing each particle in the coating liquid for forming the undercoat layer, as a dispersion method, for example, a media disperser such as a ball mill, a vibration ball mill, an attritor, a sand mill, a horizontal sand mill, an agitator, an ultrasonic disperser, Medialess dispersers such as roll mills and high-pressure homogenizers are used. Here, examples of the high-pressure homogenizer include a collision method in which the 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. Can be mentioned.

  Examples of the method for applying the coating solution for forming the undercoat layer on the conductive substrate include dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, curtain coating, and the like. Is mentioned.

After application, the undercoat layer 1 is formed by drying. The drying temperature is desirably 100 ° C. or more and 200 ° C. or less, more desirably 150 ° C. or more and 190 ° C. or less, and further desirably 165 ° C. or more and 175 ° C. or less. The drying time is preferably 15 minutes or more and 90 minutes or less, more preferably 20 minutes or more and 60 minutes or less, and further preferably 20 minutes or more and 30 minutes or less.
If the heating temperature for drying is increased and the curing conditions are made stricter, the charge trap sites caused by residual solvents in the film can be reduced, and the charge can be easily transferred. The maximum point of the phase difference θ moves to the high frequency side. Therefore, it is desirable to adjust the drying conditions in view of the frequency at the maximum point of the phase difference θ.

  The thickness of the undercoat layer is, for example, preferably set in the range of 15 μm or more, more preferably 15 μm or more and 40 μm or less.

[Middle layer]
Here, although not shown in the figure, an intermediate layer (between the undercoat layer and the photosensitive layer) is provided on the undercoat layer in order to improve electrical characteristics, improve image quality, improve image quality maintainability, and improve adhesiveness of the photosensitive layer. Additional layers may be provided.

  As the binder resin used for the intermediate layer, acetal resins such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl In addition to polymer resins such as acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, melamine resin, zirconium, titanium, aluminum, manganese, silicon atom, etc. An organometallic compound containing These compounds may be used alone, as a mixture of a plurality of compounds, or as a polycondensate. Among these, zirconium or an organometallic compound containing a silicon atom is preferable.

  The formation of the intermediate layer is not particularly limited, and a well-known formation method is used. For example, a coating film of the intermediate layer forming coating solution in which the above components are added to the solvent is formed, and the coating film is dried and necessary. It is performed by heating according to.

  Examples of the method for applying the intermediate layer forming coating solution onto the undercoat layer include dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating. Conventional methods are used.

  In addition to improving the coatability of the upper layer, the intermediate layer also serves as an electrical blocking layer.However, if the film thickness is too large, the electrical barrier becomes too strong, leading to increased desensitization and potential increase due to repetition. It may happen. Therefore, when forming the intermediate layer, it is preferable to set the film thickness within the range of 0.1 μm to 3 μm.

[Charge generation layer]
Next, the charge generation layer will be described.
The charge generation layer includes, for example, a charge generation material and a binder resin. Note that the charge generation layer may be formed of, for example, a vapor generation film of a charge generation material.

  Examples of the charge generation material include phthalocyanine pigments such as metal-free phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine. Chlorogallium phthalocyanine crystal having strong diffraction peaks at least at 7.4 °, 16.6 °, 25.5 ° and 28.3 °, Bragg angle (2θ ± 0.2 °) to CuKα characteristic X-ray of at least 7. Metal-free phthalocyanine crystals having strong diffraction peaks at 7 °, 9.3 °, 16.9 °, 17.5 °, 22.4 ° and 28.8 °, Bragg angle (2θ ± 0. 2 °) at least 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18.6 °, Hydroxygallium phthalocyanine crystals with strong diffraction peaks at 5.1 ° and 28.3 °, Bragg angles (2θ ± 0.2 °) to CuKα characteristic X-rays of at least 9.6 °, 24.1 ° and 27.2 A titanyl phthalocyanine crystal having a strong diffraction peak at 0 ° can be mentioned.

In addition, examples of the charge generation material include quinone pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, anthrone pigments, quinacridone pigments, and the like.
These charge generation materials may be used alone or in combination of two or more.

  Examples of the binder resin in the charge generation layer include polycarbonate resin (for example, polycarbonate resin such as bisphenol A or bisphenol Z type), acrylic resin, methacrylic resin, polyarylate resin, polyester resin, polyvinyl chloride resin, polystyrene resin, Acrylonitrile-styrene copolymer resin, acrylonitrile-butadiene copolymer, polyvinyl acetate resin, polyvinyl formal resin, polysulfone resin, styrene-butadiene copolymer resin, vinylidene chloride-acrylonitrile copolymer resin, vinyl chloride-vinyl acetate- Examples thereof include maleic anhydride resin, silicone resin, phenol-formaldehyde resin, polyacrylamide resin, polyamide resin, poly-N-vinylcarbazole resin and the like. These binder resins may be used alone or in combination of two or more.

  The blending ratio of the charge generating material and the binder resin is preferably in the range of 10: 1 to 1:10, for example.

  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. This is done by heating as necessary. The charge generation layer may be formed by vapor deposition of a charge generation material.

  Examples of the method for applying the charge generation layer forming coating liquid on the undercoat layer (or on the intermediate layer) include dip coating, push-up coating, wire bar coating, spray coating, blade coating, and knife coating. Method, curtain coating method and the like.

  In addition, as a method of dispersing particles (for example, charge generation material) in the coating solution for forming the charge generation layer, for example, a media dispersion machine such as a ball mill, a vibration ball mill, an attritor, a sand mill, a horizontal sand mill, agitation, ultrasonic Medialess dispersers such as dispersers, 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.

  The thickness of the charge generation layer is desirably set in the range of 0.01 μm to 5 μm, more desirably 0.05 μm to 2.0 μm.

[Charge transport layer]
For example, the charge transport layer includes a charge transport material and a binder resin, or includes a polymer charge transport material.

Examples of the charge transport material include known materials, such as oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, Phenyl-pyrazolin, pyrazoline derivatives such as 1- [pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline, triphenylamine, tris [4- (4,4- Diphenyl-1,3-butadienyl) phenyl] amine, N, N′-bis (3,4-dimethylphenyl) biphenyl-4-amine, tri (p-methylphenyl) aminyl-4-amine, dibenzylaniline, etc. Aromatic tertiary amino compounds, aromatic tertiary diaminos such as N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine Compound, 1,2,4-triazine derivatives such as 3- (4′-dimethylaminophenyl) -5,6-di- (4′-methoxyphenyl) -1,2,4-triazine, 4-diethylaminobenzaldehyde Hydrazone derivatives such as -1,1-diphenylhydrazone, quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) benzofuran, p- ( 2,2-diphenylvinyl) -N, N-diphenylaniline and other α-stilbene derivatives, enamine derivatives, carbazole derivatives such as N-ethylcarbazole, hole transport materials such as poly-N-vinylcarbazole and its derivatives, chloranil , Quinone compounds such as bromoanthraquinone, tetracyanoquinodimethane compounds Group consisting mainly of fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone, electron transport materials such as xanthone compounds and thiophene compounds, and the above compounds. Examples thereof include a polymer having a chain or a side chain.
These charge transport materials may be used alone or in combination of two or more.

  Examples of the binder resin in the charge transport layer include polycarbonate resin (for example, polycarbonate resin such as bisphenol A or bisphenol Z type), acrylic resin, methacrylic resin, polyarylate resin, polyester resin, polyvinyl chloride resin, polystyrene resin, Acrylonitrile-styrene copolymer resin, acrylonitrile-butadiene copolymer resin, polyvinyl acetate resin, polyvinyl formal resin, polysulfone resin, styrene-butadiene copolymer resin, vinylidene chloride-acrylonitrile copolymer resin, vinyl chloride-vinyl acetate -Insulating resins such as maleic anhydride resin, silicone resin, phenol-formaldehyde resin, polyacrylamide resin, polyamide resin, chlorine rubber, and polyvinylcarbazo Le, polyvinyl anthracene, organic photoconductive polymers such as polyvinyl pyrene, and the like. These binder resins may be 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, for example, by mass.

  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.

  Examples of the method for applying the charge transport layer forming coating solution onto the charge generation layer include dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, curtain coating, and the like. The usual method is used.

  When dispersing the particles in the coating liquid for forming the charge transport layer, the dispersion method may be, for example, a media disperser such as a ball mill, a vibration ball mill, an attritor, a sand mill, a horizontal sand mill, a stirring, an ultrasonic disperser, or the like. 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.

  The film thickness of the charge transport layer is, for example, preferably set in the range of 5 μm to 50 μm, more preferably 10 μm to 40 μm.

[Outermost surface layer]
Although not shown in FIGS. 1 and 2, a protective layer may be provided as the outermost surface layer of the electrophotographic photosensitive member. The protective layer includes, for example, a conductive material and a binder resin. Moreover, the protective layer may be comprised with the cured film of the charge transport material which has a polymeric functional group, for example. The cured film may contain other resins as necessary. A well-known structure is employ | adopted for the structure of a protective layer.

  The layer that becomes the outermost surface layer of the electrophotographic photosensitive member (for example, a protective layer or a charge transport layer) is further provided with lubricity so that the surface layer is less likely to be worn or scratched. In order to improve the cleaning property of the developer adhered to the surface of the photoreceptor, it contains lubricating particles (for example, silica particles, fluorine resin particles such as alumina particles and polytetrafluoroethylene (PTFE), silicone resin particles). It is preferable. These lubricating particles may be used as a mixture of two or more. In particular, fluorine resin particles are desirably used.

Examples of the fluorine resin particles include fluorine resin particles such as ethylene tetrafluoride, ethylene trifluoride, propylene hexafluoride, vinyl fluoride and vinylidene fluoride, and a resin obtained by copolymerizing a fluorine resin and a monomer having a hydroxyl group. Particles. In particular, particles of tetrafluoroethylene resin and vinylidene fluoride resin are preferable.
The primary particle size of the fluororesin particles is preferably 0.05 μm or more and 1 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. When the primary particle size is less than 0.05 μm, aggregation during dispersion tends to proceed. On the other hand, if it exceeds 1 μm, image quality defects are likely to occur.

  When the charge transport layer is the outermost surface layer, the content of the fluorine resin particles with respect to the total solid content of the charge transport layer is preferably 2% by mass or more and 15% by mass or less. In addition, when content of the fluorine-type resin particle with respect to the total solid of a charge transport layer is less than 2 mass%, modification | reformation of the charge transport layer by fluorine-type resin particle dispersion may become inadequate. Moreover, when the said content exceeds 15 mass%, a dispersibility may deteriorate and the film | membrane intensity | strength may fall.

  As a dispersion method of the coating liquid for dispersing the fluororesin particles in the outermost surface layer, a media dispersion machine such as a ball mill, a vibration ball mill, an attritor, a sand mill, a horizontal sand mill, a stirring, an ultrasonic dispersion machine, a roll mill, Medialess dispersers such as high-pressure homogenizers and nanomizers are used. Further, examples of the high-pressure homogenizer include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high pressure state, and a penetration method in which the fine liquid is penetrated and dispersed in a high pressure state.

Moreover, the dispersibility as a coating liquid is stabilized by using a fluorine-type surfactant and a fluorine-type graft polymer as a dispersion stabilizer of the fluorine-type resin particle in an outermost surface layer. As the fluorine-based graft polymer, a macromonomer composed of an acrylic ester compound, a methacrylic ester compound, a styrene compound, or the like, and a resin graft-polymerized from perfluoroalkylethyl methacrylate are preferable.
The content of the fluorosurfactant or the fluorograft polymer is preferably 1% by mass or more and 5% by mass or less based on the total mass of the fluororesin particles.

  Furthermore, a fluorine-modified silicone oil may be added to the outermost surface layer for the purpose of improving the smoothness of the surface. The fluorine-modified silicone oil preferably has a fluoroalkyl group.

  For the same purpose, an oil such as silicone oil may be added to the outermost surface layer. Examples of the silicone oil include silicone oils such as dimethylpolysiloxane, diphenylpolysiloxane, and phenylmethylsiloxane, amino-modified polysiloxane, epoxy-modified polysiloxane, carboxyl-modified polysiloxane, carbinol-modified polysiloxane, fluorine-modified polysiloxane, Examples thereof include reactive silicone oils such as methacryl-modified polysiloxane, mercapto-modified polysiloxane, and phenol-modified polysiloxane. Among these, from the viewpoint of improving the smoothness of the surface, fluorine-modified silicone oil is desirable, and one having a fluoroalkyl group is more desirable.

  The amount of the fluorine-modified silicone oil is not limited as long as the desired characteristics are obtained. For example, the fluorine-modified silicone oil is used in the charge transport layer coating solution in the range of 0.1 ppm to 1000 ppm, and in the range of 0.5 ppm to 500 ppm. Is desirable. When the addition amount of the fluorine-modified silicone oil is within the above range, a sufficiently smooth surface can be obtained, and an increase in residual potential can be suppressed when the electrophotographic photosensitive member is repeatedly used.

[Other ingredients]
In order to prevent deterioration of the electrophotographic photosensitive member due to ozone, nitrogen oxide, or light and heat generated in the image forming apparatus, an antioxidant, a light stabilizer, a heat stabilizer, etc. are included in each layer constituting the photosensitive layer. Additives may be added.
For example, examples of the antioxidant include hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, and organic phosphorus compounds. Examples of light stabilizers include derivatives such as benzophenone, benzoazole, dithiocarbamate, and tetramethylpipen.

<Image forming apparatus>
Next, an image forming apparatus provided with the electrophotographic photosensitive member according to this embodiment will be described.
-First embodiment-
FIG. 3 schematically shows the basic configuration of the image forming apparatus according to the first embodiment. An image forming apparatus 200 shown in FIG. 3 is charged by the electrophotographic photosensitive member 7 of the present embodiment, a contact charging type charging device 208 that is connected to the power source 209 and charges the electrophotographic photosensitive member 7, and the charging device 208. An electrostatic latent image forming device (exposure device) 210 that exposes the electrophotographic photosensitive member 7 to form an electrostatic latent image, and development that includes the electrostatic latent image formed by the electrostatic latent image forming device 210 with toner. A developing device 211 that forms a toner image by developing with an agent; a transfer device 212 that transfers the toner image formed on the surface of the electrophotographic photosensitive member 7 to the transfer medium 500; A toner removing device 213 that removes toner remaining on the surface; and a fixing device 215 that fixes the toner image transferred to the transfer medium 500 to the transfer medium 500.
The image forming apparatus 200 shown in FIG. 3 does not include an erasing device that removes charges remaining on the surface of the electrophotographic photosensitive member after the toner image on the surface of the electrophotographic photosensitive member is transferred. It is.

The charging device 208 is a DC / AC contact charging device (charging device that directly contacts the electrophotographic photosensitive member 7 and charges the electrophotographic photosensitive member 7 by applying a voltage in which the AC voltage is superimposed on the DC voltage).
Specifically, the charging device 208 has a charging member, and when the electrophotographic photosensitive member 7 is charged, a voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging member. The voltage range is preferably 50 V or more and 2000 V or less, more preferably 100 V or more and 1500 V or less, depending on the photosensitive member charging potential as a DC voltage component.
As an AC voltage component, the peak-to-peak voltage is 400V to 1800V, preferably 800V to 1600V, and more preferably 1200V to 1600V. The frequency of the AC voltage is 50 Hz to 20000 Hz, preferably 100 Hz to 5000 Hz.

Examples of the charging member include a roller, a brush, and a film. Among them, as the roller-shaped charging member (hereinafter sometimes referred to as “charging roller”), for example, a member composed of a material whose electric resistance is adjusted to a range of 10 ³ Ω to 10 ⁸ Ω can be mentioned. . The charging roller may be a single layer or may be composed of a plurality of layers.
When a charging roller is used as the charging member, the pressure contacting the electrophotographic photosensitive member 7 is, for example, in the range of 250 mgf to 600 mgf.

Examples of the material constituting the charging member include synthetic rubber such as urethane rubber, silicon rubber, fluorine rubber, chloroprene rubber, butadiene rubber, EPDM (ethylene-propylene-diene copolymer rubber), epichlorohydrin rubber, polyolefin, and polystyrene. In addition, an elastomer composed of vinyl chloride or the like as a main material and a suitable amount of a conductivity imparting agent such as conductive carbon, metal oxide, or ionic conductive agent may be used.
Furthermore, a resin such as nylon, polyester, polystyrene, polyurethane, silicone is made into a paint, and an appropriate amount of a conductivity imparting agent such as conductive carbon, metal oxide, or ionic conductive agent is blended therein, and the resulting paint is immersed, sprayed, You may use by laminating | stacking by methods, such as roll application | coating.

  When a charging roll is used as the charging member, the charging roll is brought into contact with the surface of the electrophotographic photosensitive member 7 to rotate by following the electrophotographic photosensitive member 7 even if the charging unit does not have a driving unit. A driving means may be attached to the charging roll and rotated at a peripheral speed different from that of the electrophotographic photosensitive member 7.

  As the electrostatic latent image forming apparatus (exposure apparatus) 210, an optical apparatus that exposes the surface of the electrophotographic photosensitive member 7 in a desired image-like manner with a light source such as a semiconductor laser, an LED (Light Emitting Diode), or a liquid crystal shutter. Is used.

  As the developing device 211, a known developing device using a normal or reversal developer such as a one-component system or a two-component system is used. The shape of the toner used in the developing device 211 is not particularly limited, and an irregular shape, a spherical shape, or other specific shape may be used.

  Examples of the transfer device 212 include a roller-type contact-type charging member, a contact-type transfer charger using a belt, a film, a rubber blade, or the like, or a scorotron transfer charger using a corona discharge or a corotron transfer charger. Can be mentioned.

  The toner removing device 213 is for removing residual toner adhering to the surface of the electrophotographic photosensitive member 7 after the transfer process, and the electrophotographic photosensitive member 7 thus cleaned is repeatedly subjected to the above image forming process. Provided. As the toner removing device 213, a foreign matter removing member (cleaning blade), brush cleaning, roll cleaning, and the like are used. Among these, it is desirable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

-Second Embodiment-
FIG. 4 schematically shows a basic configuration of the image forming apparatus according to the second embodiment. An image forming apparatus 220 shown in FIG. 4 is an intermediate transfer type image forming apparatus. In the housing 400, four electrophotographic photoreceptors 7a, 7b, 7c, and 7d are arranged in parallel with each other along the intermediate transfer belt 409. ing. For example, an image is formed in which the electrophotographic photoreceptor 71a is yellow, the electrophotographic photoreceptor 71b is magenta, the electrophotographic photoreceptor 71c is cyan, and the electrophotographic photoreceptor 71d is black.

Here, the electrophotographic photoreceptors 7a, 7b, 7c, and 7d mounted on the image forming apparatus 220 are the electrophotographic photoreceptors of the present embodiment, respectively.
The electrophotographic photoreceptors 7a, 7b, 7c, and 7d rotate in one direction (counterclockwise on the paper surface), and charging rolls 402a, 402b, 402c, and 402d, and developing devices 404a, 404b, and 404c along the rotation direction. 404d, primary transfer rolls 410a, 410b, 410c, 410d and cleaning blades 415a, 415b, 415c, 415d. The developing devices 404a, 404b, 404c, and 404d supply toners of four colors, yellow, magenta, cyan, and black, stored in the toner cartridges 405a, 405b, 405c, and 405d, respectively, and the primary transfer rolls 410a, 410b, 410c and 410d are in contact with the electrophotographic photoreceptors 7a, 7b, 7c and 7d through the intermediate transfer belt 409, respectively. The rolls 402a, 402b, 402c, and 402d are in direct contact with the child photographic photoreceptors 7a, 7b, 7c, and 7d, respectively, to charge the electrophotographic photoreceptors 7a, 7b, 7c, and 7d.

  Further, a laser light source (exposure device) 403 is disposed in the housing 400, and irradiates the surfaces of the charged electrophotographic photoreceptors 7a, 7b, 7c, and 7d with laser light emitted from the laser light source 403. As a result, in the rotation process of the electrophotographic photoreceptors 7a, 7b, 7c, and 7d, the charging, exposure, development, primary transfer, and cleaning (removal of foreign matters such as toner) are sequentially performed, and the toner images of the respective colors are intermediate. The image is transferred onto the transfer belt 409 in an overlapping manner. The intermediate transfer belt 409 is supported with tension by a drive roll 406, a back roll 408, and a support roll 407, and rotates without causing deflection due to the rotation of these rolls. Further, the secondary transfer roll 413 is disposed so as to be in contact with the back roll 408 through the intermediate transfer belt 409. The intermediate transfer belt 409 that has passed between the back roll 408 and the secondary transfer roll 413 is cleaned by, for example, a cleaning blade 416 disposed opposite to the drive roll 406 and then repeatedly in the next image forming process. Provided.

  In addition, a container 411 that accommodates a transfer medium is provided in the housing 400, and the transfer medium 500 such as paper in the container 411 is moved between the intermediate transfer belt 409 and the secondary transfer roll 413 by a transfer roll 412. In addition, after being sequentially transferred between two fixing rolls 414 that are in contact with each other, the paper is discharged to the outside of the housing 400.

  In the above description, the case where the intermediate transfer belt 409 is used as the intermediate transfer member has been described. However, the intermediate transfer member may have a belt shape like the intermediate transfer belt 409 or a drum shape. May be. In the case of a belt shape, a known resin is used as the resin material constituting the base material of the intermediate transfer member. For example, polyimide resin, polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene terephthalate (PAT), ethylenetetrafluoroethylene copolymer (ETFE) / PC, ETFE / PAT, PC / PAT blend material, polyester Resin materials such as polyether ether ketone and polyamide, and resin materials using these as main raw materials. Further, a resin material and an elastic material may be blended and used.

  The transfer medium according to the above embodiment is not particularly limited as long as it is a medium that transfers a toner image formed on the surface of the electrophotographic photosensitive member. For example, when the image is directly transferred from the electrophotographic photosensitive member 7 to a transfer medium such as paper as in the first embodiment shown in FIG. 3, the paper or the like is the transfer medium. In the case where an intermediate transfer member is used as in the second embodiment shown in FIG. 4, the intermediate transfer member is a transfer medium.

<Process cartridge>
FIG. 5 schematically shows a basic configuration of an example of a process cartridge including the electrophotographic photosensitive member of the present embodiment. The process cartridge 300 includes, together with the electrophotographic photosensitive member 7, a contact charging type charging device 208 that charges the electrophotographic photosensitive member 7, and developing an electrostatic latent image formed on the electrophotographic photosensitive member 7 by exposure with toner. A mounting device 216 is used to combine a developing device 211 that develops a toner image with an agent, a toner removing device 213 that removes toner remaining on the surface of the electrophotographic photoreceptor 7 after transfer, and an opening 218 for exposure. Integrated.

The process cartridge 300 includes a transfer device 212 that transfers the toner image formed on the surface of the electrophotographic photosensitive member 7 to the transfer medium 500, and the toner image transferred to the transfer medium 500 to the transfer medium 500. The image forming apparatus includes a fixing device 215 to be fixed and other components (not shown). The image forming apparatus is configured together with the image forming apparatus.
In addition to the electrophotographic photosensitive member 1, the charging device 208, the developing device 211, the toner removing device 213, and the opening 218 for exposure, the process cartridge 300 exposes the surface of the electrophotographic photosensitive member 1 (see FIG. The toner removing device 213 may be provided.
The process cartridge according to the present embodiment only needs to include at least the electrophotographic photosensitive member 1 and the charging device 208.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example and a comparative example, this invention is not limited to a following example.

[Example 1]
-Formation of undercoat layer-
100 parts by mass of zinc oxide particles (average particle size: 70 nm, manufactured by Teica, specific surface area value: 15 m ² / g) are stirred and mixed with 500 parts by mass of methanol, and KBM-903 (3-aminopropyl) is used as a silane coupling agent. 1 part by mass of trimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred for 2 hours. Thereafter, methanol was distilled off under reduced pressure, baking was performed at 120 ° C. for 3 hours, and zinc oxide particles-1 surface-treated with a silane coupling agent were obtained.
Surface-treated zinc oxide particles-1: 25 parts by mass, 0.6 parts by mass of 4-ethoxy-1,2-dihydroxy-9,10-anthraquinone, and blocked isocyanate (Sumidu 3173, Sumitomo Bayern Urethane as a curing agent) 13.5 parts by mass) and 15 parts by mass of butyral resin (Esreck BM-1, Sekisui Chemical Co., Ltd.) in 38 parts by mass of methyl ethyl ketone and 25 parts by mass of methyl ethyl ketone were mixed. Then, dispersion was performed for 4 hours using a glass mill having a diameter of 1 mm in a sand mill. To the obtained dispersion, 0.005 parts by mass of dioctyltin dilaurate and 4.0 parts by mass of silicone resin particles (Tospearl 145, manufactured by GE Toshiba Silicone) are added as a catalyst, and a coating liquid for forming an undercoat layer is added. Obtained. This coating solution was applied on an aluminum substrate having a diameter of 30 mm by a dip coating method, followed by drying and curing at 170 ° C. for 24 minutes to obtain an undercoat layer having a thickness of 15 μm.

-Formation of charge generation layer-
Next, as a charge generation material, it has strong diffraction peaks at Bragg angles (2θ ± 0.2 °) with respect to CuKα characteristic X-rays of at least 7.4 °, 16.6 °, 25.5 ° and 28.3 °. Using a glass bead having a diameter of 1 mm, a mixture of 15 parts by mass of chlorogallium phthalocyanine crystal, 10 parts by mass of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Union Carbide) and 300 parts by mass of n-butyl alcohol was used. Then, it was dispersed in a sand mill for 4 hours to obtain a coating solution for forming a charge generation layer. This coating solution was dip-coated on the undercoat layer and dried to obtain a charge generation layer having a thickness of 0.2 μm.

-Formation of charge transport layer-
Next, 8 parts by mass of tetrafluoroethylene resin particles (average particle size: 0.2 μm) and 0.01 parts by mass of a fluorinated alkyl group-containing methacrylic copolymer (weight average molecular weight 30000), 4 parts by mass of tetrahydrofuran, toluene The mixture was kept at a liquid temperature of 20 ° C. together with 1 part by mass and stirred for 48 hours to obtain a tetrafluoroethylene resin particle suspension A.

  Next, 4 parts by mass of N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1 ′] biphenyl-4,4′-diamine as a charge transport material, and bisphenol Z type 6 parts by mass of polycarbonate resin (viscosity average molecular weight: 40,000), 0.1 part by mass of 2,6-di-t-butyl-4-methylphenol as an antioxidant are mixed, 24 parts by mass of tetrahydrofuran and 11 of toluene. Mass parts were mixed and dissolved to obtain a mixed solution B.

  Dispersion after increasing the pressure to 500 kgf / cm 2 using a high pressure homogenizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.) equipped with a penetrating chamber having a fine flow path after adding the A liquid to the B liquid and stirring and mixing. 5 ppm of fluorine-modified silicone oil (trade name: FL-100 manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the solution obtained by repeating the treatment 6 times, and the mixture was sufficiently stirred to obtain a coating solution for forming a charge transport layer. This coating solution was applied to the charge generation layer at 21.0 μm and dried at 140 ° C. for 25 minutes to form a charge transport layer, whereby the photoreceptor 1 of Example 1 was obtained.

[Comparative Example 1]
In the coating liquid for forming the undercoat layer of Example 1, a comparison was made in the same manner as in Example 1 except that 0.6 parts by mass of 4-ethoxy-1,2-dihydroxy-9,10-anthraquinone was not added. The comparative photoreceptor 1 of Example 1 was produced.

[Example 2]
In the coating liquid for forming the undercoat layer of Example 1, in the same manner as in Example 1 except that the addition amount of 4-ethoxy-1,2-dihydroxy-9,10-anthraquinone was changed to 1 part by mass, A photoreceptor 2 of Example 2 was produced.

[Example 3]
Except that the zinc oxide particle-1 used in the coating liquid for forming the undercoat layer of Example 2 was replaced with the following zinc oxide particle-2 subjected to the surface treatment of the silane coupling agent, the same as Example 2 was performed. A photoconductor of Example 3 was produced.

(Preparation of zinc oxide particles-2)
100 parts by mass of zinc oxide particles are stirred and mixed with 500 parts by mass of methanol, and KBM-603 (N-2- (aminoethyl) -3-aminopropyltrimethoxysilane: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 is used as a silane coupling agent. .25 parts by mass was added and stirred for 2 hours. Thereafter, methanol was distilled off under reduced pressure, baking was performed at 120 ° C. for 3 hours, and zinc oxide particles-2 surface-treated with a silane coupling agent were obtained.

[Example 4]
The zinc oxide particles-1 used in the coating liquid for forming the undercoat layer of Example 2 were replaced with the following zinc oxide particles-3 that had been surface-treated with a silane coupling agent, and the drying and curing conditions of the undercoat layer were 180 ° C. The photoreceptor 4 of Example 4 was produced in the same manner as in Example 2 except that the time was 40 minutes.

(Preparation of zinc oxide particles-3)
100 parts by mass of zinc oxide particles are mixed with 500 parts by mass of methanol, and 1.25 parts by mass of KBM-903 (3-aminopropyltrimethoxysilane: manufactured by Shin-Etsu Chemical Co., Ltd.) is added as a silane coupling agent. Stir for hours. Thereafter, methanol was distilled off under reduced pressure, baking was performed at 120 ° C. for 3 hours, and zinc oxide particles-3 surface-treated with a silane coupling agent were obtained.

[Comparative Example 2]
The zinc oxide particles-1 used in the coating solution for forming the undercoat layer of Comparative Example 1 were replaced with zinc oxide particles-4 subjected to surface treatment with a silane coupling agent, and 0.6 parts by mass of alizarin was further added. A comparative photoconductor 2 of Comparative Example 2 was produced in the same manner as in Comparative Example 2 except that.

(Preparation of zinc oxide particles-4)
100 parts by mass of zinc oxide particles are mixed with 500 parts by mass of methanol, and 2 parts by mass of KBM-903 (3-aminopropyltrimethoxysilane: manufactured by Shin-Etsu Chemical Co., Ltd.) is added as a silane coupling agent and stirred for 2 hours. did. Then, methanol was distilled off under reduced pressure, baking was performed at 120 ° C. for 3 hours, and zinc oxide particles-4 surface-treated with a silane coupling agent were obtained.

[Comparative Example 3]
In the same manner as in Comparative Example 1, except that the zinc oxide particles-1 used in the coating solution for forming the undercoat layer of Comparative Example 1 were replaced with the following zinc oxide particles-5 subjected to the surface treatment of the silane coupling agent. A comparative photoreceptor 3 of Comparative Example 3 was produced.

(Preparation of zinc oxide particles-5)
100 parts by mass of zinc oxide particles are mixed with 500 parts by mass of methanol, and KBM-603 (N-2- (aminoethyl) -3-aminopropyltrimethoxysilane: manufactured by Shin-Etsu Chemical Co., Ltd.) 2 is used as a silane coupling agent. .5 parts by mass was added and stirred for 2 hours. Thereafter, methanol was removed by distillation under reduced pressure, baking was performed at 120 ° C. for 3 hours, and zinc oxide particles-5 surface-treated with a silane coupling agent were obtained.

[Comparative Example 4]
The zinc oxide particles used in the coating solution for forming the undercoat layer are replaced with the following zinc oxide particles-6 subjected to silane coupling agent surface treatment, and 4-ethoxy-1,2-dihydroxy-9,10-anthraquinone. A comparative photoconductor 4 of Comparative Example 4 was produced in the same manner as in Example 3 except that the amount added was changed to 0.6 parts by mass.

(Preparation of zinc oxide particles-6)
100 parts by mass of zinc oxide particles are mixed with 500 parts by mass of methanol, and KBM-603 (N-2- (aminoethyl) -3-aminopropyltrimethoxysilane: manufactured by Shin-Etsu Chemical Co., Ltd.) is used as a silane coupling agent. .5 parts by mass was added and stirred for 2 hours. Thereafter, methanol was removed by distillation under reduced pressure, baking was performed at 120 ° C. for 3 hours, and zinc oxide particles-6 surface-treated with a silane coupling agent were obtained.

[Comparative Example 5]
Comparative Example 1 was made in the same manner as Comparative Example 1 except that the zinc oxide particles used in the coating solution for forming the undercoat layer of the comparative example 1 were replaced with the following zinc oxide particles-7 subjected to the surface treatment of the silane coupling agent. 5 was prepared.

(Preparation of zinc oxide particles-7)
100 parts by mass of zinc oxide particles are stirred and mixed with 500 parts by mass of methanol, and 4.8 parts by mass of KBM-573 (N-phenyl-3-aminopropyltrimethoxysilane: manufactured by Shin-Etsu Chemical Co., Ltd.) is used as a silane coupling agent. Added and stirred for 2 hours. Thereafter, methanol was removed by distillation under reduced pressure, baking was performed at 120 ° C. for 3 hours, and zinc oxide particles-5 surface-treated with a silane coupling agent were obtained.

[Measurement of impedance of undercoat layer]
-Preparation of measurement sample-
The undercoat layer coating solution used in preparing the photoconductors of the above examples and comparative examples was dip-coated on aluminum pipes, respectively, and dried under the same conditions as those for preparing the photoconductor undercoat layer ( For example, in the examples, drying and curing was performed at 170 ° C. for 24 minutes), and an undercoat single layer film having a thickness of 15 μm was formed. About this undercoat single layer film, a gold electrode with a thickness of 100 nm was attached as a counter electrode by a vacuum vapor deposition method to obtain a sample for impedance measurement.

-Measurement method-
For impedance measurement, SI 1287 electrical interface (manufactured by Toyo Technica) was used as a power source, SI 1260 impedance / gain phase analyzer (manufactured by Toyo Technica) was used as an ammeter, and 1296 selective interface (manufactured by Toyo Technica) was used as a current amplifier.

With the aluminum pipe in the impedance measurement sample as the cathode and the gold electrode as the anode, an AC voltage of 1 Vp-p was applied from the high frequency side in the frequency range from 1 MHz to 1 mHz, and the impedance of each sample was measured. The impedance is expressed by two parameters, that is, the amplitude ratio of the response current to the applied voltage and the phase difference between the applied voltage and the response current. Table 1 shows the frequency at which the phase difference θ of the impedance measurement sample was maximized.
The frequency at which the phase difference θ is maximized is the “maximum point of the impedance phase difference θ”.

[Evaluation]
The photoreceptor manufactured as described above was incorporated into a modified DocuCentre C3300, and ghost evaluation and residual potential measurement were performed under conditions of high temperature and high humidity (28 ° C., 85% RH). The obtained results are shown in Table 1.
The charging device mounted on the modified DocuCentre 505a is a contact charging type charging device in which a voltage obtained by superimposing an AC voltage on a DC voltage is applied. The applied voltage is -700V, and the peak voltage between AC voltages is 1400V. To charge the photoreceptor.

-Ghost evaluation criteria-
In the ghost evaluation, as shown in FIG. 6A, 10,000 charts of patterns having the letter “G” and the “black solid area” are output, and the letter “G” (ghost) in the black solid area is output. The appearance was visually observed and evaluated according to the following criteria.
A +: Even if 10,000 charts are output, the letter “G” is not confirmed in the black solid area as shown in FIG.
A: As shown in FIG. 6A, the letter “G” is not confirmed in the black solid region.
B: As shown in FIG. 6B, the letter “G” is slightly confirmed in the black solid region.
C: As shown in FIG. 6C, the letter “G” is clearly confirmed in the black solid region.

-Measurement of residual potential-
The residual potential of the photoconductor is measured by attaching a potential probe in the experimental machine, outputting 10,000 half-tone images with an image density of 30% on A4 paper, and the initial (before image output) and after the image output. The residual potential was measured and the difference was calculated.
A: The difference is less than 38V A: The difference is 38V or more and less than 45V B: The difference is 45V or more and less than 60V C: The difference is 60V or more

As shown in Table 1, in the photoreceptors of Examples 1 to 4, that is, the photoreceptor in which the maximum point of the impedance phase difference θ is 0.15 Hz or more and 0.3 Hz or less, the AC voltage is superimposed on the DC voltage. When used in an image forming apparatus having a contact charging type charging device to which a voltage is applied, an increase in residual potential and a ghost over time related to the life are suppressed.
On the other hand, the photoreceptors of Comparative Examples 1 to 5 having a maximum point outside the frequency range of 0.15 Hz or more and 0.3 Hz or less are all applied with a voltage in which an AC voltage is superimposed on a DC voltage. When used in an image forming apparatus having a charging type charging device, an increase in residual potential and a ghost occurred.

  The relationship between the configuration of the undercoat layer and the frequency at which the phase difference θ takes a maximum is shown below.

  The undercoat layers 12, 13 and 14 in the above table were prepared in the same manner as in the undercoat layer of Example 1, except that the average particle diameter or addition amount of zinc oxide particles was changed as shown in the above table.

  The undercoat layer 21 in the above table was prepared in the same manner as the undercoat layer of Example 4 except that the drying conditions were changed as shown in the above table. The undercoat layers 23, 24 and 26 were prepared in the same manner as the undercoat layer of Example 5 except that the drying conditions were changed as shown in the above table.

DESCRIPTION OF SYMBOLS 1 ... Undercoat layer, 2 ... Charge generation layer, 3 ... Charge transport layer, 4 ... Conductive substrate, 7, 7A, 7B ... Electrophotographic photosensitive member, 200 ... Image forming device, 208 ... Charging device, 210 ... Electrostatic Latent image forming device (exposure device), 211 ... developing device, 212 ... transfer device, 213 ... toner removing device, 215 ... fixing device, 216 ... mounting rail, 218 ... opening for exposure, 220 ... image forming device, 300 ... Process cartridge, 402a, 402b, 402c, 402d ... Charging roll, 500 ... Transfer medium

Claims (10)

A conductive substrate; an undercoat layer provided on the conductive substrate and including a binder resin, metal oxide particles, and an electron-accepting substance; and a photosensitive layer provided on the undercoat layer. When the impedance of the undercoat layer is measured with an AC voltage in the range of 1 MHz to 1 mHz, the maximum point of the impedance phase difference θ is in the frequency range of 0.15 Hz to less than 0.3 Hz. When,
A charging device that directly contacts the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage in which an alternating voltage is superimposed on a direct current voltage;
An electrostatic latent image forming apparatus that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image on the surface of the electrophotographic photosensitive member;
A developing device for developing the electrostatic latent image into a toner image with a developer;
A transfer device for transferring the toner image to a transfer medium;
An image forming apparatus.   The image forming apparatus according to claim 1, wherein the maximum point of the impedance phase difference θ is within a frequency range of 0.15 Hz to 0.2 Hz.   The image forming apparatus according to claim 1, wherein a light source for exposing the electrophotographic photosensitive member is not provided other than the electrostatic latent image forming apparatus.   The image forming apparatus according to claim 1, wherein the electron accepting substance has anthraquinone as a basic skeleton.   The image forming apparatus according to claim 4, wherein the electron-accepting substance has a hydroxyl group and an alkoxy group.   The image forming apparatus according to claim 4, wherein the electron accepting substance has a hydroxyl group and an ethoxy group.   The image forming apparatus according to claim 4, wherein the electron-accepting substance has a hydroxyl group and one ethoxy group. The image forming apparatus according to claim 1, wherein the metal oxide particles are surface-treated with a silane coupling agent represented by the following general formula (S).

(In general formula (S), R ¹ represents an alkoxy group or a halogen atom. R ² represents a hydrogen atom, a phenyl group, or an alkyl group having an amino group at the terminal.) A conductive substrate; an undercoat layer provided on the conductive substrate and including a binder resin, metal oxide particles, and an electron-accepting substance; and a photosensitive layer provided on the undercoat layer. When the impedance of the undercoat layer is measured with an AC voltage in the range of 1 MHz to 1 mHz, the maximum point of the impedance phase difference θ is in the frequency range of 0.15 Hz to less than 0.3 Hz. When,
A charging device that directly contacts the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage in which an alternating voltage is superimposed on a direct current voltage;
Have
A process cartridge attached to and detached from the image forming apparatus. A conductive substrate; an undercoat layer provided on the conductive substrate and including a binder resin, metal oxide particles, and an electron-accepting substance; and a photosensitive layer provided on the undercoat layer. ,
When the impedance of the undercoat layer is measured with an AC voltage in the range from 1 MHz to 1 mHz, the maximum point of the impedance phase difference θ is in the range of frequencies from 0.15 Hz to less than 0.3 Hz,
An electrophotographic photosensitive member used in an image forming apparatus having a charging device that directly contacts the electrophotographic photosensitive member and applies a voltage in which an alternating voltage is superimposed on a direct current voltage to charge the electrophotographic photosensitive member.