JP7638647B2 - Process cartridge and electrophotographic apparatus - Google Patents

Description

The present invention relates to a process cartridge and an electrophotographic device having an electrophotographic photosensitive member and a charging member.

The electrophotographic process related to electrophotographic photoreceptors (hereinafter simply referred to as "photoreceptors") mainly consists of four processes: charging, exposure, development, and transfer, with additional processes such as cleaning and pre-exposure as necessary. Among these, the charging process and exposure process are the key processes for forming electrostatic latent images, which control the charge distribution of the photoreceptor and make the photoreceptor surface have the desired potential distribution. The charging process generates discharge from the charging member (charging means) to the electrophotographic photoreceptor, charging the photoreceptor surface. In this case, if the electrical characteristics of the photoreceptor and the charging member and the frequency dependence of the electrical characteristics are not properly designed, excessive discharge can cause the photoreceptor to break down (hereinafter also referred to as "leak"), or poor charging can occur due to unstable discharge, which can be problematic. For this reason, a layer with controlled resistance (hereinafter referred to as the "bottom layer") has been provided directly above the support of the photoreceptor, separate from the photosensitive layer, to electrically conceal unevenness caused by burrs on the surface of the support, thereby suppressing leaks and poor charging.

When considering photoconductor characteristics from the perspective of electrical resistance, it is desirable for the electrical resistance to be high in order to suppress leakage and improve charging ability to suppress charging defects, but if the electrical resistance is made too high, the light sensitivity will deteriorate during the exposure process. In particular, when repeatedly printing images using a photoconductor with high electrical resistance, charge does not easily escape, and charge accumulates inside the photoconductor over long periods of use. This causes the light area potential to gradually increase (hereinafter also referred to as "potential fluctuation"), reducing the contrast with the dark area potential. Therefore, when considering the exposure process, it is preferable for the photoconductor to have low electrical resistance.

Conventionally, the electrical characteristics of the bottom layer and photoconductor have been designed based on the concept of impedance, and the electrical characteristics have been optimized taking into account frequency dependency. In this way, the above-mentioned problems have been addressed by optimizing the electrical characteristics in the frequency bands corresponding to the respective time constants for the different characteristic time scales of each electrophotographic process, such as the charging process and exposure process, to suit the process.

On the other hand, corona and roller types have traditionally been used as charging members that impart charge to the photoreceptor during the charging process. Of these, corona types require a higher applied voltage than roller types, which poses problems in terms of the size and cost of the power supply required. In contrast, roller types require a lower applied voltage, which allows the size and cost of the power supply to be kept small. However, roller types have the problem of being inferior to corona types in terms of charging uniformity and stability.

In addition, in the case of a roller-type charging member (hereinafter also referred to as the "charging roller"), the charging roller and the photoconductor are in direct contact with each other, so that the photoconductor may be locally scratched down to the lowest layer surface or have holes due to the intrusion of foreign matter into the photosensitive layer or dents caused by impact, and the voltage applied to the photoconductor in that local area is largely divided to the lowest layer. In such a case, a large current flows from the surface side of the photoconductor to the support side through that area. This causes an insufficient charge supply to the charging roller, and the discharge to the photoconductor surface is not sufficiently performed, resulting in linear charging defects in the longitudinal direction of the charging roller. When an image is printed in this state, an image with black lines drawn in the longitudinal direction of the photoconductor (hereinafter referred to as a "horizontal running image") is output. This phenomenon (hereinafter referred to as "horizontal running") was problematic because it was difficult to completely control the intrusion of foreign matter or the occurrence of dents caused by impact.

Patent document 1 describes a photoreceptor that has a photosensitive layer containing a photoconductive material on an aluminum substrate having an aluminum oxide coating on its surface. By controlling the impedance of the aluminum oxide coating, fogging due to localized charging defects can be suppressed.

Patent Document 2 describes a photoreceptor having an undercoat layer in which the angular frequency ω _max [rad] at which the complex impedance component becomes maximum satisfies 2≦ω _max ≦ 10. By controlling the impedance of the undercoat layer within the above-mentioned range, the occurrence of abnormal discharge caused by excessive charge movement in the undercoat layer during the charging process is suppressed, and streak-like image quality defects in low image density images are suppressed.

Patent Document 3 describes a rubber composition with an islands-in-a-sea structure including a polymer continuous phase made of an ionically conductive rubber material mainly composed of raw rubber A having a volume resistivity of 1× ¹⁰ Ω·cm or less, and a polymer particle phase made of an electronically conductive rubber material made conductive by blending conductive particles into raw rubber B, and an electrostatic charging member having an elastic layer formed from the rubber composition. The islands-in-a-sea structure of the ionically conductive rubber material and the electronically conductive rubber material provides the electrostatic charging member with excellent resistance stability.

Japanese Patent Application Publication No. 10-268541 JP 2016-139052 A JP 2002-3651 A

According to the inventors' investigations, it was difficult to suppress lateral movement while maintaining favorable potential fluctuations with the electrophotographic photoreceptors and charging members described in Patent Documents 1 to 3.

According to one aspect of the present invention, the present invention aims to provide a process cartridge that can suppress lateral movement while maintaining good potential fluctuation. Another aspect of the present invention aims to provide an electrophotographic device that can form high-quality electrophotographic images.

According to one aspect of the present invention, there is provided a process cartridge which has an electrophotographic photosensitive member and a charging member and is detachably mountable to a main body of an electrophotographic apparatus, the electrophotographic photosensitive member being an electrophotographic photosensitive member having a cylindrical first support, a bottom layer formed directly on the first support, and a photosensitive layer formed on the bottom layer , a needle electrode having a diameter of 1 mm connected to a high voltage side of an impedance measuring device is brought into contact with the bottom layer, a conductor on the earth side of the impedance measuring device is connected to the first support, and an AC voltage with an amplitude of 1 Vpp is applied to a surface of the first support while changing the frequency between 1.0×10 ^-2 [Hz] and 1.0×10 ⁶ [Hz] to measure impedance, and the maximum frequency at which the phase of the impedance is 45° is defined as f _OPC [Hz], the charging member is an electrophotographic charging member having a cylindrical second support and a second conductive layer formed on the second support, the second conductive layer having a matrix containing a first rubber and a plurality of domains dispersed in the matrix, the domains containing a second rubber and an electronic conductive agent, the volume resistivity _ρM of the matrix being 1.0×10 ⁵ times or more the volume resistivity _ρD of the domains, a strip- shaped metal thin film electrode having a longitudinal width of 1.5 cm is provided in the circumferential direction on the surface of the charging member, the metal thin film electrode is connected to one side of an impedance measuring device, the second support is connected to the other side of the impedance measuring device, and an AC voltage having an amplitude of 1 Vpp is applied while changing the frequency between 1.0×10 ^-2 [Hz] to 1.0×10 ⁶ [Hz] to measure the impedance, where f _C [Hz] is the maximum frequency at which the phase _of the impedance is 45°, There is provided a process cartridge in which _C satisfies the relationship of the following formula (D1) or the following formula (D2):
10≦f _OPC /f _C ≦10,000 Formula (D1)
0.0001≦f _OPC /f _C ≦0.1 Formula (D2).

According to another aspect of the present invention, there is provided an electrophotographic apparatus having an electrophotographic photosensitive member and a charging member, the electrophotographic photosensitive member having a cylindrical first support, a bottom layer formed directly on the first support, and a photosensitive layer formed on the bottom layer, a needle electrode having a diameter of 1 mm connected to a high voltage side of an impedance measuring device is brought into contact with the bottom layer, a portion of the first support where the core material is exposed is connected to the earth side of the impedance measuring device, and an AC voltage with an amplitude of 1 Vpp is applied to a surface of the first support while changing the frequency between 1.0×10 ^-2 [Hz] to 1.0×10 ⁶ [Hz] to measure impedance, and the maximum frequency at which the phase of the impedance is 45° is defined as f _OPC [Hz], the charging member is an electrophotographic charging member having a cylindrical second support and a second conductive layer formed on the second support, the second conductive layer having a matrix containing a first rubber and a plurality of domains dispersed in the matrix, the domains containing a second rubber and an electronic conductive agent, the volume resistivity _ρM of the matrix being 1.0×10 ⁵ times or more the volume resistivity _ρD of the domains, a metal thin film electrode is provided on the surface of the charging member, a metal sheet is wrapped around the metal thin film electrode, the metal sheet is connected to an electrode on the high voltage side of an impedance measuring device, the second support is connected to the earth side of the impedance measuring device, and an AC voltage having an amplitude of 1 Vpp is applied while changing the frequency between 1.0×10 ^-2 [Hz] to 1.0×10 ⁶ [Hz] to measure impedance, where the maximum frequency at which the phase of the impedance is 45° is f _C [Hz], then f _OPC and f There is provided an electrophotographic apparatus, in which _C satisfies the relationship of the following formula (D1) or the following formula (D2):
10≦f _OPC /f _C ≦10,000 Formula (D1)
0.0001≦f _OPC /f _C ≦0.1 Formula (D2).

According to one aspect of the present invention, a process cartridge can be obtained that can suppress lateral movement while maintaining favorable potential fluctuation. According to another aspect of the present invention, an electrophotographic device that can form high-quality electrophotographic images can be obtained.

FIG. 1 is a diagram showing an example of a schematic configuration of an electrophotographic apparatus having a process cartridge including an electrophotographic photosensitive member and a charging member. 1 is a schematic diagram of a sea-island structure of the charging member of the present invention. FIG. 2 is an explanatory diagram of impedance characteristics required in the present invention. FIG. 13 is an explanatory diagram of impedance characteristics in the fifth embodiment of the present invention. FIG. 13 is an explanatory diagram of impedance characteristics in the seventh embodiment of the present invention. FIG. 11 is an explanatory diagram of impedance characteristics in Comparative Example 4 of the present invention. FIG. 11 is an explanatory diagram of impedance characteristics in Comparative Example 1 of the present invention. FIG. 13 is an explanatory diagram of impedance characteristics in Comparative Example 6 of the present invention. FIG. 23 is an explanatory diagram of impedance characteristics in Example 17 of the present invention. FIG. 2 is a schematic diagram showing a state in which a measurement electrode is formed on the charging roller produced in the examples. FIG. 4 is a cross-sectional view of a charging roller with a measurement electrode formed thereon. FIG. 1 is a schematic diagram of an impedance measurement system. 5A to 5C are explanatory diagrams of a method for manufacturing the charging member. FIG. 1 is a schematic diagram of a leak test device.

The present invention will be described in detail below with reference to preferred embodiments.
As a result of the inventors' investigations, it was found that simply optimizing the impedance of the aluminum oxide coating or undercoat layer in conventional photoreceptors does not have the effect of suppressing the above-mentioned foreign matter contamination and lateral movement due to dents while maintaining good potential fluctuations.
Therefore, the inventors discovered that in order to optimize the combination of the photoconductor and the charging member and solve the above problems, the photoconductor and the charging member are designed as follows, and the combination is further optimized, thereby making it possible to suppress lateral movement while maintaining favorable potential fluctuation.

<Photoreceptor design>
The inventors have found that the photoreceptor needs to have a bottom layer on a cylindrical support (hereinafter, the support of the photoreceptor is referred to as the "first support") This bottom layer plays a role in preventing the first support from being completely exposed when foreign matter is mixed in or a dent occurs on the photoreceptor.

<Design of charging components>
The inventors also found that the charging member is a charging member having a conductive layer (hereinafter, the conductive layer of the charging member will be referred to as the "second conductive layer") formed on a cylindrical support (hereinafter, the support of the charging member will be referred to as the "second support"), and that the second conductive layer must have a sea-island structure (see FIG. 2), and further, the sea portion must have a certain level of resistance compared to the island portions.

Here, the "sea-island structure" of the second conductive layer refers to a structure having a matrix 6a which is a sea portion containing a first rubber, and domains 6b which are a plurality of island portions dispersed in the matrix 6a, and the domains 6b contain a second rubber and an electronic conductive agent 6c, as shown in Fig. 2. In addition, "the sea portion has a certain level of resistance or higher compared to the island portions" specifically means, for example, that the ratio _ρM / _ρD of the volume resistivity _ρM [Ω·cm] of the matrix 6a to the volume resistivity _ρD [Ω·cm] of the domains 6b is 1.0 x ¹⁰⁵ or more.

<Optimization of the combination of photoconductor and charging member>
In the present invention, when combining a photoconductor and a charging member, it is necessary to separate the reaction frequency of the photoconductor and the reaction frequency of the charging member by a certain amount or more, but not by a limit value or more.

The "reaction frequency" referred to here means the maximum frequency at which the phase of the impedance is 45° when an AC voltage is applied to a photoconductor or a charging member while changing the frequency between 1.0×10 ^-2 [Hz] and 1.0×10 ⁶ [Hz] and the impedance is measured. The reaction frequency of the photoconductor is f _OPC [Hz], and the reaction frequency of the charging member is f _C [Hz]. In addition, "separated by a certain amount or more" referred to here means that the ratio of the reaction frequency of the photoconductor to the reaction frequency of the charging member is one digit or more, that is, f _OPC /f _C is 10 or more or 0.1 or less. In addition, "not separated by a limit value or more" referred to here means that the ratio of the reaction frequency of the photoconductor f _OPC to the reaction frequency of the charging member f _C is four digits or less, that is, f _OPC /f _C is 10,000 or less or 0.0001 or more. That is, f _OPC /f _C satisfies the relationship of the following formula (D1) or the following formula (D2).
10≦f _OPC /f _C ≦10,000 Formula (D1)
0.0001≦f _OPC /f _C ≦0.1 Formula (D2)

4, 5, 6, 7, 8, and 9 show the impedance measurement results of the bottom layer of the photoconductor and the charging member in the configuration of the embodiment of the present invention or the comparative example. 4, 5, and 6 show the impedance measurement results when the bottom layer is changed for the same charging member. In 4 and 5, the reaction frequency f _OPC of the bottom layer and the reaction frequency f _C of the charging member are separated by a certain amount or more, but not by a limit value or more, so the effect of the present invention is exerted. On the other hand, in 6, the reaction frequency f _OPC of the bottom layer and the reaction frequency f _C of the charging member are too close, so the effect of the present invention is not exerted. 7, 8, and 9 show the impedance measurement results when the charging member of 4, 5, and 6 is changed, respectively. In 7, the two reaction frequencies of the reaction frequency f _OPC of the bottom layer and the reaction frequency f _C of the charging member are too far apart, so the effect of the present invention is not exerted, and in 8, the two reaction frequencies are too close, so the effect of the present invention is not exerted. On the other hand, in FIG. 9, the ratio of the two reaction frequencies is within the required range, and therefore the effect of the present invention is exhibited.

（式（Ｅ１）及び（Ｅ２）中、ｉは虚数単位、ｆは周波数［Ｈｚ］である。） The relationship between impedance and reaction frequency will be explained below.
When measuring the impedance of a sample, the equivalent circuit can be roughly expressed as a parallel circuit (hereinafter also referred to as an "RC parallel circuit") of an electric resistance R [Ω], which is a resistance component, and an electrostatic capacitance C [Ω], which is a capacitance component. The impedance Z [Ω] and absolute value of the impedance |Z| [Ω] of the sample at this time are expressed by the following formulas (E1) and (E2), respectively.

(In formulas (E1) and (E2), i is the imaginary unit, and f is the frequency [Hz].)

これらの式から位相θを周波数ｆの関数として表すと、下記式（Ｅ４）となる。

Moreover, when considering the polar coordinate representation of Z, Z can be expressed by the following equation (E3) using the phase θ.

From these equations, when the phase θ is expressed as a function of the frequency f, the following equation (E4) is obtained.

Figure 3 shows the f-θ graph of formula (E4). In the case of the RC parallel circuit model shown here, R and C are constants specific to each sample, so when θ = 0°, f = 0. At this time, the impedance is dominated by the resistance component. On the other hand, when θ = 90°, f → ∞, and the impedance is dominated by the capacitance component. When θ = 45°, the RC parallel circuit is in a transitional period of two components, resistance R and capacitance C, and is highly reactive. In this invention, the frequency corresponding to θ = 45° is called the reaction frequency. Here, "high reactivity" refers to the characteristic that, for example, when a locally low-resistance part caused by a conductive foreign object piercing or hitting the photoconductor surface enters the charging process section and the shared voltage applied to the photoconductor changes suddenly, a large electrical load is applied to the charging member or photoconductor due to the sudden change in the shared voltage.

The inventors speculate that the reason why the combination of a photoconductor and a charging member is effective in suppressing lateral movement while maintaining favorable potential fluctuation is as follows.

First, by having a bottom layer, the photoconductor prevents the first support from being completely exposed even if the photoconductor layer is locally damaged by a conductive foreign object piercing or being struck. Therefore, the bottom layer stops the large current that is generated between the first support of the photoconductor and the charging roller through the localized damaged area during the charging process, thereby preventing lateral movement.

Secondly, the second conductive layer has a sea-island structure in which the matrix has a certain level of resistance compared to the domains, so that in the charging process, discharge onto the photoreceptor surface mainly occurs from the domains. Moreover, because the discharges in multiple domains are electrically isolated by the matrix, the discharges are prevented from combining and growing. This prevents large currents from flowing into the area even if the photoreceptor is locally damaged and the electrical resistance is reduced. As a result, insufficient discharge onto the photoreceptor surface due to insufficient charge supply to the charging roller is suppressed, and linear charging defects in the longitudinal direction of the charging roller, i.e., lateral running, are suppressed.

Thirdly, by separating the reaction frequency f _OPC of the photoconductor from the reaction frequency f _C of the charging member by a certain amount, it is possible to prevent the photoconductor and the charging member from being subjected to a large electrical load simultaneously with the same time constant during the charging process. When the surface of the photoconductor approaches the contact portion with the charging roller (hereinafter also referred to as "nip") as the charging roller rotates, a discharge occurs in a small gap near the nip. When a locally low-resistance portion caused by a conductive foreign object piercing or denting the surface of the photoconductor enters, a large current is likely to be generated suddenly on the surface of the photoconductor, while the shared voltage is likely to increase suddenly on the surface of the charging member corresponding to the low-resistance portion. Therefore, the inventors believe that when the reaction frequency f _OPC of the photoconductor and the reaction frequency f _C of the charging roller are close to each other, the electrical loads of both become large at the same time, and there is a high possibility that a large current will be generated. By separating the reaction frequency f _OPC of the photoconductor from the reaction frequency f _C of the charging roller by a certain amount, it is possible to avoid a large current flowing through the charging roller and the photoconductor. As a result, lateral movement is suppressed.

On the other hand, by not separating f _OPC and f _C by more than the limit value, the impedance characteristics such as the electrical resistance and capacitance of the photoconductor when discharge occurs from the charging member during the charging process change to a certain extent. As a result, various memories accumulated in the photoconductor by the previous processes such as exposure and transfer are alleviated, high-quality charging is performed by uniform and stable discharge, and good image quality can be maintained.

As described above, lateral travel is not controlled by the electrical resistance of the bottom layer of the photoconductor or the second conductive layer of the charging member, but by optimizing the combination of the reaction frequencies of the photoconductor and charging member, making it easier to independently control the electrical resistance to achieve good potential fluctuations. In addition, as per the mechanism described above, memory within the photoconductor is mitigated and high-quality charging is performed, which also contributes to achieving good potential fluctuations.

[Electrophotographic Photoreceptor]
The electrophotographic photoreceptor according to the present invention is characterized by having a bottom layer and a photosensitive layer formed on the bottom layer. Here, the bottom layer means a surface treatment layer, undercoat layer, or conductive layer (hereinafter, the conductive layer of the electrophotographic photoreceptor is also referred to as the "first conductive layer") formed by performing electrochemical treatment or the like on the surface of the first support, which is laminated directly on the first support. The surface treatment layer and the first conductive layer on the surface of the first support will be described later. The material constituting the bottom layer is preferably an inorganic material from the viewpoint of deterioration due to long-term use.

When the impedance of the bottom layer is measured, f _OPC [Hz] is preferably 5 [Hz] or more, and particularly preferably 100 [Hz] or more. By increasing f _OPC , the amount of discharge per discharge can be reduced and the number of discharges can be increased, resulting in improved lateral running and potential fluctuation.

Furthermore, the impedance per unit area z _OPC of the bottom layer at f _OPC /10 [Hz] is preferably 3.0×10 ⁵ [Ω·cm ² ] or more, and more preferably 1.0×10 ⁹ [Ω·cm ² ] or less.

f _OPC and z _OPC are controlled by various parameters such as the material of the resin constituting the bottom layer, the metal oxide and the surface treatment of the metal oxide, the film thickness, the mixture ratio and dispersion state of the resin and the metal oxide. For example, f _OPC can be controlled by a time constant τ=RC, where R means the resistance of the bottom layer and C means the capacitance of the bottom layer. In general, when R is increased, the phase change region in the impedance measurement shifts to the low frequency side, so that f _OPC can be reduced. The same effect can also be obtained by increasing C.

One method for producing such an electrophotographic photoreceptor is to prepare a coating liquid for each layer, which will be described later, and then coat and dry the layers in the desired order. In this case, methods for applying the coating liquid include dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, dip coating is preferred from the standpoint of efficiency and productivity.

Each layer will be described below.
<First Support>
The first support is preferably a conductive support having electrical conductivity. The shape of the first support may be a cylinder, a belt, a sheet, or the like. Of these, a cylinder is preferable. A surface treatment layer may be provided on the surface of the first support by blasting or cutting.

The material of the first support is preferably a metal, a resin, or a glass.
Examples of the metal include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among these, a support made of aluminum is preferable.
Furthermore, the resin or glass may be made conductive by a process such as mixing with or coating with a conductive material.

The first support may be provided with a surface treatment layer by anodizing the surface of the first support in an acidic liquid containing an oxidizing agent. In this case, for example, an inorganic acid such as sulfuric acid or chromic acid or an organic acid such as oxalic acid or sulfonic acid can be used as an electrolyte for the anodizing treatment. The conditions such as the applied voltage, current density, treatment temperature, and time can be selected according to the type of electrolyte and the film thickness. In addition, the anodized surface treatment layer used in the electrophotographic photoreceptor of the present invention may be subjected to a sealing treatment after electrolysis. As a method for the sealing treatment, hot water treatment, steam treatment, or various sealing agents such as nickel acetate and nickel fluoride may be used, but it is preferable to use nickel acetate, which can efficiently seal fine pores.

In particular, a surface treatment layer formed by anodizing the surface of an aluminum first support under appropriate conditions is called an anodized layer, and by appropriately controlling the above-mentioned treatment conditions, it can be used as the bottom layer in the present invention.
For example, f _OPC can be reduced by increasing the resistance R of the alumite layer by lengthening the anodization time of the first support.

<First Conductive Layer>
A conductive layer (hereinafter, the conductive layer of the photoreceptor is referred to as the "first conductive layer") may be provided on the first support. By providing the first conductive layer, scratches and irregularities on the surface of the first support can be concealed and light reflection on the surface of the first support can be controlled. The first conductive layer preferably contains conductive particles and a resin.

In particular, by controlling the selection of conductive particles and resin, their compounding ratio, the method of dispersing the conductive particles in the coating liquid for the first conductive layer, etc., it can be used as the bottom layer of the present invention.

The conductive particles may be made of a material such as metal oxide, metal, or carbon black.
Examples of metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, etc. Examples of metals include aluminum, nickel, iron, nichrome, copper, zinc, silver, etc.
Among these, it is preferable to use metal oxides as the conductive particles, and it is particularly preferable to use titanium oxide, tin oxide, or zinc oxide.

When metal oxides are used as conductive particles, the surface of the metal oxide may be treated with a silane coupling agent or the like, or the metal oxide may be doped with elements such as phosphorus or aluminum or their oxides. Examples of elements to be doped and their oxides include phosphorus, aluminum, niobium, and tantalum.

By controlling the relative dielectric constant of the conductive particles by changing the surface treatment method of the conductive particles or the metal oxide used, the capacitance C of the first conductive layer can be increased, thereby reducing f _OPC .

The conductive particles may also have a laminated structure having a core particle and a coating layer that covers the particle. Examples of the core particle include titanium oxide, barium sulfate, and zinc oxide. Examples of the coating layer include metal oxides such as tin oxide and titanium oxide.

In addition, when metal oxides are used as conductive particles, the volume average particle diameter is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, and alkyd resin.

The first conductive layer may further contain silicone oil, resin particles, titanium oxide, or other masking agents.

The average thickness of the first conductive layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less.

The first conductive layer can be formed by preparing a coating solution for the first conductive layer containing the above-mentioned materials and solvent, forming a coating film from this, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Examples of dispersion methods for dispersing the conductive particles in the coating solution for the first conductive layer include methods using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

<Undercoat layer>
An undercoat layer may be provided on the first support or the first conductive layer, which can improve adhesion between layers and provide a charge injection blocking function.
The undercoat layer preferably contains a resin. Alternatively, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.

Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinylphenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin, polyimide resin, polyamideimide resin, and cellulose resin.

Examples of the polymerizable functional groups possessed by monomers having polymerizable functional groups include isocyanate groups, blocked isocyanate groups, methylol groups, alkylated methylol groups, epoxy groups, metal alkoxide groups, hydroxyl groups, amino groups, carboxyl groups, thiol groups, carboxylic anhydride groups, and carbon-carbon double bond groups.

For the purpose of improving electrical properties, the undercoat layer may further contain an electron transporting material, a metal oxide, a metal, a conductive polymer, etc. Among these, it is preferable to use an electron transporting material or a metal oxide.
Examples of the electron transport substance include a quinone compound, an imide compound, a benzimidazole compound, a cyclopentadienylidene compound, a fluorenone compound, a xanthone compound, a benzophenone compound, a cyanovinyl compound, an aryl halide compound, a silole compound, a boron-containing compound, etc. An electron transport substance having a polymerizable functional group may be used as the electron transport substance, and the undercoat layer may be formed as a cured film by copolymerizing the electron transport substance with a monomer having the polymerizable functional group.
Examples of metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, silicon dioxide, etc. Examples of metals include gold, silver, aluminum, etc.
The undercoat layer may further contain an additive.

The average thickness of the undercoat layer is preferably 0.1 μm or more and 50 μm or less, more preferably 0.2 μm or more and 40 μm or less, and particularly preferably 0.3 μm or more and 30 μm or less.

The undercoat layer can be formed by preparing a coating solution for the undercoat layer containing the above-mentioned materials and solvent, forming a coating film from this, and drying and/or curing it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

<Photosensitive layer>
The photosensitive layer of an electrophotographic photoreceptor is mainly classified into (1) a laminated type photosensitive layer and (2) a single-layer type photosensitive layer. (1) The laminated type photosensitive layer has a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. (2) The single-layer type photosensitive layer has a photosensitive layer containing both a charge generation material and a charge transport material.

(1) Multi-Layer Photosensitive Layer The multi-layer photosensitive layer has a charge generating layer and a charge transport layer.

(1-1) Charge Generation Layer The charge generation layer preferably contains a charge generation material and a resin.

Examples of the charge generating material include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferred. Among phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferred.
The content of the charge generating material in the charge generating layer is preferably from 40% by weight to 85% by weight, and more preferably from 60% by weight to 80% by weight, based on the total weight of the charge generating layer.

Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, polyvinyl chloride resin, etc. Among these, polyvinyl butyral resin is preferred.

The charge generating layer may further contain additives such as antioxidants and ultraviolet absorbers. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

The average thickness of the charge generating layer is preferably 0.10 μm or more and 1.00 μm or less, and more preferably 0.15 μm or more and 0.40 μm or less.

The charge generation layer can be formed by preparing a coating liquid for the charge generation layer containing the above-mentioned materials and solvent, forming a coating film from this, and drying it. Examples of solvents used in the coating liquid include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

(1-2) Charge Transport Layer The charge transport layer preferably contains a charge transport material and a resin.

Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these materials. Among these, triarylamine compounds and benzidine compounds are preferred.
The content of the charge transport material in the charge transport layer is preferably from 25% by weight to 70% by weight, and more preferably from 30% by weight to 55% by weight, based on the total weight of the charge transport layer.

Examples of the resin include polyester resin, polycarbonate resin, acrylic resin, polystyrene resin, etc. Among these, polycarbonate resin and polyester resin are preferable. As the polyester resin, polyarylate resin is particularly preferable.
The content ratio of the charge transport material to the resin is preferably from 4:10 to 20:10, and more preferably from 5:10 to 12:10, in terms of mass ratio.

The charge transport layer may also contain additives such as antioxidants, UV absorbers, plasticizers, leveling agents, slippage agents, and abrasion resistance improvers. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

The average thickness of the charge transport layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing the above-mentioned materials and solvent, forming a coating film from this, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents and aromatic hydrocarbon-based solvents are preferred.

(2) Single-layer type photosensitive layer The single-layer type photosensitive layer can be formed by preparing a coating solution for the photosensitive layer containing a charge generating material, a charge transporting material, a resin and a solvent, forming a coating film of this, and drying it. The charge generating material, the charge transporting material and the resin are the same as the examples of materials in the above "(1) Multi-layer type photosensitive layer".

<Protective Layer>
In the present invention, a protective layer may be provided on the photosensitive layer. By providing the protective layer, durability can be improved.

The protective layer preferably contains conductive particles and/or a charge transport material, and a resin.
The conductive particles include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide.
Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these materials. Among these, triarylamine compounds and benzidine compounds are preferred.
Examples of the resin include polyester, acrylic resin, phenoxy resin, polycarbonate, polystyrene, phenol resin, melamine resin, epoxy resin, etc. Among these, polycarbonate, polyester, and acrylic resin are preferable.

The protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. The reaction may be a thermal polymerization reaction, a photopolymerization reaction, or a radiation polymerization reaction. Examples of the polymerizable functional group possessed by the monomer having a polymerizable functional group include an acrylic group and a methacrylic group. A material having a charge transport function may be used as the monomer having a polymerizable functional group.

The protective layer may contain additives such as antioxidants, UV absorbers, plasticizers, leveling agents, slippage agents, and abrasion resistance improvers. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

The average thickness of the protective layer is preferably 0.5 μm or more and 10 μm or less, and more preferably 1 μm or more and 7 μm or less.

The protective layer can be formed by preparing a coating solution for the protective layer containing the above-mentioned materials and solvent, forming a coating film from this, and drying and/or curing it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

<Method for measuring impedance of bottom layer>
The impedance of the bottom layer can be measured by the following method.
In order to eliminate the influence of the contact resistance between the bottom layer and the measurement electrode when measuring impedance, there is a method in which a low-resistance thin film is deposited on the surface of the bottom layer, the thin film is used as an electrode, and the conductive first support is used as a ground electrode to measure impedance with two terminals. Methods for forming the thin film include metal deposition, sputtering, application of a metal paste, and application of a metal tape.

However, when electrodes are formed directly on a specific bottom layer using these methods, there is a concern that the electrodes or the solvent in which the electrodes are dispersed may contaminate the bottom layer. From this perspective, it is desirable to ground the surface of the bottom layer by contacting it with a needle electrode. The needle electrode is connected to a measuring device, and the first support side is connected to the earth side of the measuring device. This allows the electrical signal from the bottom layer to be conveniently acquired by the measuring device, and impedance measurements can be performed.

The impedance measuring device may be an impedance analyzer, a network analyzer, a spectrum analyzer, etc., as long as it is capable of measuring impedance in a frequency band up to 1.0×10 ⁶ Hz. Among these, it is preferable to measure the electrical resistance of the lowest layer using an impedance analyzer.

The impedance measurement conditions are as follows. An impedance measuring device is used to measure impedance in the frequency band of 1.0×10 ^-2 Hz to 1.0×10 ⁶ Hz. The measurement is performed in an environment with a temperature of 23° C. and a relative humidity of 50%, and it is preferable to provide five or more measurement points per digit of frequency in order to reduce measurement variation.

Regarding the measurement voltage, measurements may be performed while applying a DC voltage, taking into account the shared voltage applied to the bottom layer in the electrophotographic device. Specifically, measurements are performed while applying a DC voltage of 10 V or less superimposed on an oscillating voltage, which is suitable for quantifying the characteristics of charge transport and accumulation.

In the embodiment of the present invention, a needle electrode with a diameter of 1 mm was attached to the tip of the high-voltage side conductor of an impedance measuring device (Solatron 1260 and Solartron 1296, Solartron) and this needle electrode was vertically abutted against the bottom layer that had been exposed with an appropriate solvent or the like. A conductive clip was attached to the earth side conductor of the impedance device, and the conductive material was established by clamping the exposed core material of the first support. If necessary, the surface of the first support was polished with a file to ensure sufficient conductivity. Measurements were performed while applying a DC voltage of -8V superimposed with an AC voltage of 1Vpp, and measurements were performed at frequencies from 1.0 x 10 ^-2 Hz to 1.0 x 10 ⁶ Hz (10 points were measured at each frequency change of one digit).

[Charging member]
The charging member according to the present invention can be, for example, a charging roller having a second conductive layer.

The charging roller can be formed, for example, through a method including the following steps (1) to (4).
Step (1): A step of preparing a domain-forming rubber mixture (hereinafter also referred to as "CMB") containing an electronic conductive material and a second rubber.
Step (2): A step of preparing a matrix-forming rubber mixture (hereinafter also referred to as "MRC") containing a first rubber.
Step (3): A step of kneading the CMB and the MRC to prepare a rubber mixture having a matrix-domain structure.
Step (4): A step of forming a layer of the rubber mixture prepared in step (3) directly or through another layer on the surface of a conductive second support, and curing the layer of the rubber mixture to form the second conductive layer of the present invention.

<Second Support>
The second support is preferably a conductive support having electrical conductivity. The shape of the second support may be a cylinder, a belt, a sheet, or the like. Among these, a cylinder is preferable.
The material of the second support is preferably a metal, a resin, or a glass.
Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. These may also be subjected to oxidation treatment or plating with chromium, nickel, etc. As the type of plating, either electric plating or electroless plating can be used, but electroless plating is preferred from the viewpoint of dimensional stability. Examples of the type of electroless plating used here include nickel plating, copper plating, gold plating, and various other alloy platings. The plating thickness is preferably 0.05 μm or more, and considering the balance between work efficiency and rust prevention ability, the plating thickness is preferably 0.1 to 30 μm. The cylindrical shape of the second support may be a solid cylindrical shape or a hollow cylindrical shape (cylindrical shape). The outer diameter of this second support is preferably in the range of 3 mm to 10 mm.

<Middle class>
An intermediate layer may be provided between the second support and the second conductive layer, which enhances the adhesion between the layers and allows the charge supply capability to be controlled.
The intermediate layer is preferably a thin conductive resin layer such as a primer, from the viewpoint of quickly supplying charge after the charge is consumed by discharging during the charging process and stabilizing the charge.
As the primer, a known one can be selected and used depending on the rubber material for forming the second conductive layer and the material of the second support, etc. Examples of the primer material include thermosetting resins and thermoplastic resins such as phenolic resins, urethane resins, acrylic resins, polyester resins, polyether resins, and epoxy resins.

<Second Conductive Layer>
The second conductive layer is provided on the outer surface of the second support, and has a matrix containing a first rubber and a plurality of domains dispersed in the matrix. The domain contains a second rubber and an electronic conductive agent, and the volume resistivity _ρM of the matrix is 1.0×10 ⁵ times or more the volume resistivity _ρD of the domain. By making the volume resistivity _ρM of the matrix and the volume resistivity _ρD of the domain have the above relationship, a function of temporarily suspending charge at the interface between the matrix and the domain is realized. As a result, charge is abundantly accumulated in the domain, and the efficiency of charge transfer between the domains is improved due to the large amount of accumulation. In other words, when the difference between the volume resistivity _ρD of the domain and the volume resistivity _ρM of the matrix becomes large, the responsiveness in the conductive layer is improved, and the reaction frequency shifts to the high frequency side.

From the viewpoint of making the charge contrast on the photoconductor corresponding to the sea-island structure clearer, it is preferable that the volume resistivity _ρM of the matrix is 1.0×10 ¹² [Ω·cm] or more.

By setting the volume resistivity _ρM of the matrix to 1.0×10 ¹² [Ω·cm] or more, discharge and charge inflow from the matrix portion are significantly suppressed, and the discharge contrast in the discharge region during the charging process and the current contrast in the nip region are increased. As a result, the charge contrast on the photoconductor after the charging process, which corresponds to the sea-island structure of the charging roller, can be made clearer. In addition, it is preferable that the impedance _zC per unit area of the charging member at f _C /10 [Hz] is 1.0×10 ⁶ [Ω·cm ² ] [Hz] or more.

The thickness of the conductive layer is not particularly limited as long as it provides the desired function and effect of the electroconductive member, but it is preferably 1.0 mm or more and 4.5 mm or less.

<Method of measuring charged member impedance>
The impedance of the charging member can be measured by the following method.
In order to eliminate the influence of contact resistance between the charged member and the measurement electrode when measuring impedance, a low-resistance thin film is deposited on the surface of the charged member, and the thin film is used as an electrode while a conductive second support is used as a ground electrode to measure the impedance via two terminals.

Methods for forming the thin film include metal deposition, sputtering, application of metal paste, and application of metal tape. Among these, from the viewpoint of reducing the contact resistance with the conductive member, it is preferable to form the electrode by deposition of a thin metal film such as platinum or palladium.

When forming a thin metal film on the surface of a charged member, taking into consideration the ease of use and uniformity of the thin film, it is preferable to use a vacuum deposition device equipped with a mechanism for gripping the charged member, and for conductive members with a cylindrical cross section, to further provide a rotation mechanism.

For charged members with a cross section that is curved, such as a circular shape, for example a cylindrical charged member, it is difficult to connect the above-mentioned metal thin film as the measurement electrode to the impedance measuring device, so it is preferable to use the following method. Specifically, a metal thin film electrode with a width of about 10 mm to 20 mm is formed in the longitudinal direction of the charged member, and then a metal sheet is tightly wrapped around it, and the metal sheet is connected to the measurement electrode coming out of the measuring device for measurement. This allows the measuring device to conveniently acquire the electrical signal from the second conductive layer of the charged member, and impedance measurement can be performed. The metal sheet may be any metal sheet that has an electrical resistance value equivalent to that of the metal part of the connecting cable of the measuring device when measuring impedance, and for example aluminum foil or metal tape can be used.

The impedance measuring device may be an impedance analyzer, a network analyzer, a spectrum analyzer, etc., as long as it is capable of measuring impedance in a frequency band up to 1.0×10 ⁶ Hz. Among these, it is preferable to measure the impedance using an impedance analyzer because of the electric resistance range of the charging member.

The impedance is measured using an impedance measuring device in a frequency band of 1.0×10 ⁻² Hz to 1.0×10 ⁶ Hz. The measurement is performed in an environment of a temperature of 23° C. and a relative humidity of 50%. In order to reduce measurement variation, it is preferable to provide five or more measurement points per digit of frequency.

Regarding the measurement voltage, measurements may be performed while applying a DC voltage, taking into account the shared voltage applied to the charging member in the electrophotographic device. Specifically, measurements are performed while applying a DC voltage of 10 V or less superimposed on an oscillating voltage, which is suitable for quantifying the characteristics of charge transport and accumulation.

In the embodiment of the present invention, first, as a pretreatment, a measurement electrode was created by vacuum-depositing platinum on the fabricated charged member while rotating it. At this time, masking tape was used to create a strip-shaped electrode with a longitudinal width of 1.5 cm that was uniform in the circumferential direction. By forming this electrode, the influence of the contact resistance between the measurement electrode and the conductive member due to the surface roughness of the conductive member can be minimized. Next, an aluminum sheet was tightly wrapped around the electrode to form the measurement electrode on the conductive member side.

Figure 10 shows a schematic diagram of the state in which the measurement electrode is formed on the charging roller. In Figure 10, 111 is a conductive second support, 112 is a second conductive layer having a matrix domain structure, 113 is a platinum vapor deposition layer, and 114 is an aluminum sheet.

Figure 11 shows a cross-sectional view of a charging roller with a measurement electrode formed thereon. 121 is a conductive second support, 122 is a second conductive layer with a matrix domain structure, 123 is a platinum vapor deposition layer, and 124 is an aluminum sheet. As shown in Figure 11, it is important to sandwich the second conductive layer with a matrix domain structure between the conductive second support and the measurement electrode.

Figure 12 shows a schematic diagram of this measurement system. The aluminum sheet 124 is connected to the measurement electrode on the impedance measurement device 125 (for example, Solartron 1260 and Solartron 1296 manufactured by Solartron, etc.). Impedance measurement is performed by using the conductive second support 121 and the aluminum sheet 124 as the two electrodes of the impedance measurement device 125 for measurement.

When measuring the impedance, the charging member is left in an environment of a temperature of 23° C. and a relative humidity of 50% for 48 hours to saturate the moisture content of the charging member.
The impedance is measured in an environment of 23° C. and 50% relative humidity at an AC voltage of 1 Vpp amplitude and a frequency of 1.0×10 ⁻² Hz to 1.0×10 ⁶ Hz (measurements are taken at five points when the frequency changes by one digit) to obtain a measured impedance value.

<Method of Controlling ρ _D , ρ _M , and Domain Matrix Structure>
In order to control the domain volume resistivity ρ _D [Ω·cm], matrix volume resistivity ρ _M [Ω·cm], and domain matrix structure of the second conductive layer of the present invention, the type and content of the materials used in each of the steps (1) to (4) for producing the charging roller described above may be selected and the production conditions may be adjusted.

First, the volume resistivity _ρD of the domain can be controlled by the amount of the electronic conductive agent in the CMB.
For example, suppose that conductive carbon black having a dibutyl phthalate oil absorption (DBP oil absorption) of 40 [ ^cm3 ]/100 [g] or more and 170 [ ^cm3 ]/100 [g] or less is used as the electronic conductive agent. In this case, by adjusting the CMB so that it contains 40 mass % or more and 200 mass % or less of conductive carbon black based on the total mass of the CMB, _ρD can be controlled to 1.0× ¹⁰¹ [Ω·cm] or more and 1.0× ¹⁰⁴ [Ω·cm] or less.

As the rubber material for the domains, a rubber composition containing a rubber component for the matrix can be used. From the viewpoint of facilitating the formation of a sea-island structure, the difference in SP value between the rubber material for the domains and the rubber material for forming the matrix is preferably 0.4 [(J/ ^cm3 ) ^0.5 ] or more and 5.0 [(J/ ^cm3 ) ^0.5 ] or less, and more preferably 0.4 [(J/ ^cm3 ) ^0.5 ] or more and 2.2 [(J/ ^cm3 ) ^0.5 ] or less.

The volume resistivity of the domain can be adjusted by appropriately selecting the type of electronic conductive agent and the amount of the agent added. Examples of electronic conductive agents that can be added to the domain include oxides such as carbon black, graphite, titanium oxide, and tin oxide, metals such as Cu and Ag, and particles that have been coated with the oxides of these metals to make them conductive. If necessary, two or more types of these conductive agents may be mixed in appropriate amounts and used.

Among the above electronic conductive agents, it is preferable to use conductive carbon black, which has a high affinity with rubber and allows easy control of the distance between the electronic conductive agents. Examples of carbon black that can be blended into the domain include, but are not limited to, gas furnace black, oil furnace black, thermal black, lamp black, acetylene black, and ketjen black.

Among these, from the viewpoint of being able to impart high electrical conductivity to the domain, conductive carbon black having a DBP oil absorption of 40 [cm ³ ]/100 [g] or more and 170 [cm ³ ]/100 [g] or less can be preferably used.

The conductive agent, such as conductive carbon black, is preferably blended into the domain in an amount of 20 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the rubber component contained in the domain. A particularly preferred blending ratio is 50 parts by mass or more and 100 parts by mass or less. The blending ratio of the conductive agent in these ratios preferably contains a larger amount of conductive agent than in typical electrophotographic charging members.

If necessary, fillers, processing aids, crosslinking aids, crosslinking accelerators, antiaging agents, crosslinking accelerators, crosslinking retarders, softeners, dispersants, colorants, and the like, which are commonly used as compounding agents for rubber, may be added to the rubber composition for the domains to the extent that they do not impair the effects of the present invention.

The volume resistivity _ρM of the matrix can then be controlled by the composition of the MRC.
For example, the first rubber used in the MRC may be natural rubber, butadiene rubber, butyl rubber, acrylonitrile butadiene rubber, urethane rubber, silicone rubber, fluororubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, polynorbornene rubber, or the like, which have low electrical conductivity.

Furthermore, to the MRC, fillers, processing aids, crosslinking agents, crosslinking assistant agents, crosslinking accelerators, crosslinking accelerator assistant agents, crosslinking retarders, antioxidants, softeners, dispersants, and colorants may be added as necessary.
On the other hand, in order to satisfy ρ _M /ρ _D ≧10 ⁵ and ρ _M ≧1.0×10 ¹² , it is preferable that the MRC does not contain an electronic conductive agent such as carbon black.

Finally, the domain matrix structure can be effectively controlled by adjusting the following four items (a) to (d):
(a) The difference in interfacial tension σ between CMB and MRC.
(b) The ratio η _D /η _M of the viscosity of CMB, _{η D} , and the viscosity of MRC, η _M .
(c) The shear rate γ during kneading of the CMB and the MRC in the manufacturing process (3) of the charging roller, and the amount of energy E _DK during shear.
(d) The volume fraction of CMB relative to the MRC in the manufacturing process (3) of the charging roller.

Each step will be described below.
(a) Interfacial tension difference between CMB and MRC Generally, when two types of incompatible rubber are mixed, phase separation occurs. This is because the interaction between the same polymers is stronger than the interaction between different polymers, so the same polymers aggregate to reduce the free energy and stabilize. Since the interface of the phase-separated structure comes into contact with different polymers, the free energy is higher than the interior, which is stabilized by the interaction between the same molecules. As a result, in order to reduce the free energy of the interface, an interfacial tension is generated that tries to reduce the area of contact with the different polymers. When this interfacial tension is small, the different polymers tend to be mixed more uniformly in order to increase the entropy. The state of uniform mixing is dissolution, and the solubility parameter (hereinafter referred to as the SP value), which is an indicator of solubility, tends to correlate with the interfacial tension.

In other words, the difference in interfacial tension σ between the CMB and the MRC is considered to correlate with the SP value difference between the rubbers contained therein. It is preferable to select rubbers for the first rubber in the MRC and the second rubber in the CMB such that the difference in absolute SP value is 0.4 [(J/cm ³ ) ^0.5 ] or more and 5.0 [(J/cm ³ ) ^0.5 ] or less, particularly 0.4 [(J/cm ³ ) ^0.5 ] or more and 2.2 [(J/cm ³ ) ^0.5 ] or less. Within this range, a stable phase separation structure can be formed, and the domain diameter of the CMB can be reduced.

Specific examples of the second rubber that can be used in the CMB include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), ethylene-propylene rubber (EPM, EPDM), chloroprene rubber (CR), nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), silicone rubber, and urethane rubber (U).

(b) Viscosity ratio of CMB to MRC The closer the viscosity ratio η _D /η _M of CMB to MRC is to 1, the smaller the maximum Feret diameter of the domain can be. Specifically, η _D /η _M is preferably 1.0≦η _D /η _M ≦2.0. _{η D} /η _M can be adjusted by selecting the Mooney viscosity of the raw rubber used for CMB and MRC, or by blending the type and amount of filler. It can also be adjusted by adding a plasticizer such as paraffin oil to an extent that does not interfere with the formation of a phase separation structure. The viscosity ratio can also be adjusted by adjusting the temperature during kneading. The viscosity of the rubber mixture for forming the domain or the rubber mixture for forming the matrix can be obtained by measuring the Mooney viscosity ML (1+4) at the rubber temperature during kneading based on JIS K 6300-1:2013.

(c) Shear rate and amount of energy during shearing when kneading CMB and MRC The faster the shear rate γ when kneading CMB and MRC, and the larger the amount of energy E _DK during shearing, the smaller the interdomain distance can be.

γ can be increased by increasing the inner diameter of the stirring members such as the blades and screws of the kneader, decreasing the gap between the end face of the stirring member and the inner wall of the kneader, and increasing the rotation speed. E _DK can be increased by increasing the rotation speed of the stirring members and increasing the viscosity of the second rubber in the CMB and the first rubber in the MRC.

(d) CMB volume fraction relative to MRC The volume fraction of CMB relative to MRC correlates with the probability of collision and merging between CMBs. Specifically, when the volume fraction of CMB relative to MRC is reduced, the probability of collision and merging between CMBs decreases. In other words, the interdomain distance can be reduced by reducing the volume fraction of CMB relative to MRC within a range in which the required electrical conductivity can be obtained. From this viewpoint, it is preferable that the volume fraction of CMB relative to MRC is 15% or more and 40% or less.

By controlling ρ _D and ρ _M using the above method and forming a sea-island structure, a second conductive layer that satisfies ρ _M /ρ _D ≧1.0×10 ⁵ and ρ _M ≧1.0×10 ¹² can be obtained.

<How to confirm the island structure>
The presence of the sea-island structure in the second conductive layer can be confirmed by preparing a thin piece from the second conductive layer and closely observing the fracture surface formed in the thin piece.

Examples of means for thinning include a sharp razor, a microtome, and an FIB. In order to observe the sea-island structure more accurately, the thin sections for observation may be pretreated with a dyeing process, deposition process, or other pretreatment that favorably improves the contrast between the domain and the matrix.

The presence of the sea-island structure can be confirmed by observing the fracture surface of the formed and, if necessary, pre-treated thin sections using a laser microscope, a scanning electron microscope (SEM) or a transmission electron microscope (TEM). From the viewpoint of being able to easily and accurately confirm the sea-island structure, it is preferable to observe using a scanning electron microscope (SEM).

A slice of the second conductive layer is obtained using the above-mentioned method, and an image is obtained by observing the surface of the slice at 1,000 to 10,000 times magnification. Then, image processing software (product name: ImageProPlus, manufactured by Media Cybernetics) or the like is used to convert the image to 8-bit grayscale, obtaining a monochrome image with 256 gradations. Next, the image is inverted so that the domains in the fracture surface become white, and a binarization threshold is set for the brightness distribution of the image based on the algorithm of Otsu's discriminant analysis method, obtaining a binarized image. Finally, the presence or absence of a matrix domain structure can be determined from the analysis image, which has been image-processed to distinguish the domains and matrix through binarization.

When the analysis image includes a structure in which multiple domains 6b exist in an isolated state in a matrix 6a as shown in FIG. 2, the presence of a sea-island structure in the second conductive layer can be confirmed. The isolated state of the domains 6b may be such that each domain 6b is arranged in a state where it is not connected to other domains 6b, the matrix 6a is connected in the image, and the domains 6b are divided by the matrix 6a. Specifically, when a 50-μm square in the analysis image is set as the analysis region, the state in which the number of domains that exist in an isolated state as described above is 80 percent or more of the total number of domains that do not contact the border of the analysis region is considered to have a sea-island structure.

The above confirmation can be carried out by dividing the second conductive layer of the conductive member into 5 equal parts in the longitudinal direction and 4 equal parts in the circumferential direction, and then randomly selecting one point from each area to create the relevant slices, for a total of 20 points, and then carrying out the above measurements.

In the embodiment of the present invention, a slice was cut using a razor so that a cross section perpendicular to the longitudinal direction of the second conductive layer could be observed, platinum was evaporated, and then a scanning electron microscope (SEM) (product name: S-4800, manufactured by Hitachi High-Technologies) was used to take a photograph at 1,000x magnification to obtain a cross-sectional image.

Next, in the embodiment of the present invention, the percentage K of the number of domains 6b that are isolated and not connected to each other was calculated from the total number of domains 6b that exist within a 50 μm square area and have no contact points with the frame lines of the binary image using a counting function for the binary image obtained using the above image processing software and method. In this case, as shown in Figure 2, a plurality of domains 6b are dispersed in a matrix 6a, and the domains 6b are independent and not connected to each other, while on the other hand, a group of domains in which the matrix 6a is connected within the image was confirmed.

Finally, in the examples of the present invention, the presence or absence of a sea-island structure was determined as follows. That is, the second conductive layer was divided equally into 5 equal parts in the longitudinal direction and 4 equal parts in the circumferential direction, and slices were prepared at random points from each of the obtained regions, for a total of 20 points, and the above measurements were performed. If the arithmetic mean value K (number %) obtained in this way was 80 or more, the sea-island structure was evaluated as "present," and if the arithmetic mean value K (number %) was less than 80, the sea-island structure was evaluated as "absent."

<Method of measuring volume resistivity _ρD of domain>
The volume resistivity _ρD of the domain can be measured by a microprobe after slicing the second conductive layer, for example, by a sharp razor, a microtome, or a focused ion beam (FIB) method.

When preparing the thin sections, it is necessary to eliminate the effects of the matrix and measure the volume resistivity of only the domains, so it is necessary to prepare thin sections with a thickness smaller than the interdomain distance previously measured using a scanning electron microscope (SEM) or transmission electron microscope (TEM). Therefore, the preferred method of thinning is to use a method that can produce very thin samples, such as a microtome.

To measure the volume resistivity, first, one side of the flake is grounded, and then the locations of the matrix and domain in the flake are identified. These locations can be identified using a means capable of measuring the volume resistivity or hardness distribution of the matrix and domain, such as a scanning probe microscope (SPM) or an atomic force microscope (AFM). Next, a probe is brought into contact with the matrix, and a DC voltage of 1 [V] is applied for 5 seconds to measure the arithmetic average of the ground current value for 5 seconds, and the electrical resistance value is calculated by dividing the applied voltage by the measured value. Finally, the resistance value can be converted to volume resistivity using the film thickness of the flake. In this case, a means capable of shape measurement, such as an SPM or AFM, is preferable because it can measure the film thickness of the flake at the same time as the resistance value.

The measurement of _ρD in a cylindrical charging member can be carried out by cutting out one thin sample from each of the regions obtained by dividing the second conductive layer into four in the circumferential direction and five in the longitudinal direction, obtaining the above-mentioned measured values, and then calculating the arithmetic average value of the volume resistivities of a total of 20 samples.

In the embodiment, ultra-thin slices with a thickness of 1 μm were cut from the second conductive layer using a microtome (product name: Leica EM FCS, manufactured by Leica Microsystems) at a cutting temperature of -100°C. When cutting the long thin slices, the direction of the cross section was set perpendicular to the longitudinal direction of the charged member, taking into account the direction in which the charge is transported for discharge.

Next, in the embodiment, in an environment with a temperature of 23°C and a relative humidity of 50%, the ultrathin slice was placed on a metal plate, and a portion of the slice that was in direct contact with the metal plate was selected. The portion that corresponded to the domain was brought into contact with the cantilever of a scanning probe microscope (SPM) (product name: Q-Scope 250, manufactured by Quesant Instrument Corporation), and a voltage of 1 V was applied to the cantilever for 5 seconds, the current value was measured, and the arithmetic average value for the 5 seconds was calculated.

Next, in the embodiment of the present invention, the surface shape of the measurement piece was observed with the SPM, and the thickness of the measurement point was calculated from the obtained height profile. Furthermore, the recess area of the contact part of the cantilever was calculated from the surface shape observation results. The volume resistivity was calculated from the thickness and the recess area.

Finally, in the embodiment of the present invention, the second conductive layer was divided into 5 equal parts in the longitudinal direction and 4 equal parts in the circumferential direction, and one piece was randomly prepared from each of the obtained regions, totaling 20 pieces, and the above measurement was performed on the slices. The average value was determined as the volume resistivity _ρD of the domain.
In the embodiment of the present invention, the SPM was used for scanning in contact mode.

<Method for measuring volume resistivity _ρM of matrix>
The volume resistivity _ρM of the matrix may be measured in the same manner as in the <Method of measuring the volume resistivity _ρD of the domain>, except that the measurement location is changed to a location corresponding to the matrix, and the applied voltage during measurement of the current value is changed to 50 V.

In the examples of the present invention, the same method as in the example of the present invention in the above <Method of measuring volume resistivity _ρD of domain> was used, except that the measurement location was changed to a location corresponding to the matrix, and the applied voltage during measurement of the current value was changed to 50 V.

<Method of Measuring SP Value>
The SP value can be calculated with high accuracy by creating a calibration curve using a material with a known SP value. The known SP value can also be a catalog value of the material manufacturer. For example, the SP value of NBR and SBR is determined almost entirely by the content ratio of acrylonitrile and styrene, regardless of the molecular weight. Therefore, by using analytical techniques such as pyrolysis gas chromatography (Py-GC) and solid-state NMR for the rubber constituting the matrix and domain, the content ratio of acrylonitrile or styrene can be analyzed, and the SP value can be calculated by combining the analytical curve obtained from a material with a known SP value. In addition, the SP value of isoprene rubber is determined by the isomeric structure of 1,2-polyisoprene, 1,3-polyisoprene, 3,4-polyisoprene, cis-1,4-polyisoprene, trans-1,4-polyisoprene, etc. Therefore, the SP value can be calculated by analyzing the isomer content ratio by Py-GC, solid-state NMR, etc., in the same manner as for SBR and NBR, and combining it with a calibration curve obtained from a material with a known SP value. The SP value of a material with a known SP value is determined by the Hansen ball method.

[Process Cartridge, Electrophotographic Apparatus]
The process cartridge of the present invention is characterized in that it integrally supports the electrophotographic photosensitive member and the charging member described above and is detachably mountable to the main body of the electrophotographic apparatus. The process cartridge of the present invention may also integrally support at least one means selected from the group consisting of a developing means, a transfer means and a cleaning means.

The electrophotographic apparatus of the present invention is characterized by having an exposure means, a development means, and a transfer means in addition to the electrophotographic photoreceptor and charging member described above.

The photoconductor and charging member of the process cartridge of the present invention preferably have a relationship f _OPC /f _C between f _OPC [Hz] of the photoconductor and f _C [Hz] of the charging member that satisfies the following formula (D3) or the following formula (D4).
30≦f _OPC /f _C ≦3,000 Formula (D3)
0.0003≦f _OPC /f _C ≦0.03 Formula (D4)

Furthermore, from the viewpoint of suppressing lateral movement by balancing the electrical resistance of the photosensitive member and the charging member, it is preferable that the impedance per unit area z _OPC [Ω·cm ² ] of the bottom layer at f _OPC /10 [Hz] and the impedance per unit area z _C [Ω·cm ² ] of the charging member at f _C /10 [Hz] satisfy the relationship of the following formula (D5).
(z _OPC ×z _C )≧1.0×10 Formula ⁶ (D5)

Figure 1 shows an example of the schematic configuration of an electrophotographic device having a process cartridge equipped with an electrophotographic photosensitive member and a charging member.

A cylindrical electrophotographic photoreceptor 1 is rotated around an axis 2 in the direction of the arrow at a predetermined peripheral speed. The surface of the electrophotographic photoreceptor 1 is charged to a predetermined positive or negative potential by a charging member 3. As shown in FIG. 1, the charging member of the present invention is a roller charging type using a roller-type charging member. The surface of the charged electrophotographic photoreceptor 1 is irradiated with exposure light 4 from an exposure means (not shown), and an electrostatic latent image corresponding to the target image information is formed. The electrostatic latent image formed on the surface of the electrophotographic photoreceptor 1 is developed with toner contained in the developing means 5, and a toner image is formed on the surface of the electrophotographic photoreceptor 1. The toner image formed on the surface of the electrophotographic photoreceptor 1 is transferred to a transfer material 7 by a transfer means 6. The transfer material 7 to which the toner image has been transferred is transported to a fixing means 8, where the toner image is fixed and printed out outside the electrophotographic device. The electrophotographic device may have a cleaning means 9 for removing adhesions such as toner remaining on the surface of the electrophotographic photoreceptor 1 after transfer. Also, a so-called cleanerless system may be used in which a separate cleaning means is not provided and deposits are removed by a developing means or the like. The electrophotographic device may have a charge removing mechanism that removes charge from the surface of the electrophotographic photoreceptor 1 by pre-exposure light 10 from a pre-exposure means (not shown). Also, a guide means 12 such as a rail may be provided to mount and remove the process cartridge 11 of the present invention to and from the main body of the electrophotographic device.

Electrophotographic photoreceptors can be used in laser beam printers, LED printers, copiers, facsimiles, and combination machines of these.

The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples, so long as the gist of the invention is not exceeded. In the following description of the examples, "parts" are by weight unless otherwise specified.

The thickness of each layer of the electrophotographic photoreceptor in the examples and comparative examples, except for the charge generation layer, was measured using an eddy current film thickness meter (product name: Fischerscope, manufactured by Fisher Instruments) or by converting the specific gravity from the mass per unit area. The film thickness of the charge generation layer was measured by converting the Macbeth density value of the photoreceptor using a calibration curve previously obtained from the Macbeth density value measured by pressing a spectrodensitometer (product name: X-Rite 504/508, manufactured by X-Rite) against the surface of the photoreceptor and the film thickness measurement value obtained by observing a cross-sectional SEM image.

<Production of Electrophotographic Photoreceptor>
The first support, the first conductive layer, the undercoat layer, the charge generating layer, and the charge transport layer were prepared by the following method to manufacture an electrophotographic photoreceptor. The combination of the surface treatment layer, the first conductive layer, and the undercoat layer in the manufactured photoreceptor is shown in Table 1.

<Preparation of first support>
An aluminum cylinder (JIS-A3003, aluminum alloy) having a diameter of φ24 mm and a length of 257 mm was obtained by hot extrusion. If necessary, a surface treatment layer was formed by the method described later to obtain a first support.

(Preparation of Surface Treatment Layer 1)
The first support was subjected to cutting using a sintered diamond cutting tool.
In the cleaning process, the cylinder was degreased, etched with a 2 wt % sodium hydroxide solution for 1 minute, neutralized, and then washed with pure water, in that order.
Next, anodization was performed for 10 minutes in a 14 wt % sulfuric acid solution at a DC voltage of 20 V to form an anodized film on the cylinder surface. Next, after washing with water, the cylinder was immersed in a 0.8 wt % nickel acetate solution at a temperature of 72° C. for 15 minutes to perform a sealing treatment. Further, it was washed with pure water and dried to obtain a surface treatment layer 1.

(Preparation of Surface Treatment Layer 2)
The first support was subjected to cutting using a sintered diamond cutting tool.
In the cleaning process, the cylinder was degreased, etched with a 2 wt % sodium hydroxide solution for 1 minute, neutralized, and then washed with pure water, in that order.
Next, anodization was performed for 20 minutes in a 10 wt % sulfuric acid solution at a DC voltage of 15 V to form an anodized film on the cylinder surface. After washing with water, the cylinder was immersed in a 1 wt % nickel acetate solution at a temperature of 80° C. for 15 minutes to perform a sealing treatment. Further, it was washed with pure water and dried to obtain a surface treatment layer 2.

(Preparation of Surface Treatment Layer 3)
A surface treatment layer 3 was obtained in the same manner as in the preparation of the surface treatment layer 2, except that the anodization time was changed to 30 seconds.

(Preparation of Surface Treatment Layer 4)
A surface treatment layer 4 was obtained in the same manner as in the preparation of the surface treatment layer 2, except that the anodization time was changed to 20 seconds.

(Preparation of Surface Treatment Layer 5)
A surface treatment layer 5 was obtained in the same manner as in the preparation of the surface treatment layer 2, except that the anodization time was changed to 10 seconds.

<Preparation of First Conductive Layer>
(Conductive Layer 1-1)
60 parts of barium sulfate particles coated with tin oxide (trade name: PASTRAN PC1, manufactured by Mitsui Mining & Smelting Co., Ltd.), 15 parts of titanium oxide particles (trade name: TITANIX JR, manufactured by Teika Co., Ltd.), 43 parts of resol-type phenolic resin (trade name: Phenolite J-325, manufactured by DIC, solid content 70% by mass), 0.015 parts of silicone oil (trade name: SH28PA, manufactured by Dow Corning Toray Co., Ltd.), 3.6 parts of silicone resin particles (trade name: Tospearl 120, manufactured by Momentive Performance Materials Japan LLC), 50 parts of 2-methoxy-1-propanol, and 50 parts of methanol were placed in a ball mill and dispersed for 20 hours to prepare a first conductive layer coating liquid 1. The first conductive layer coating liquid 1 was dip-coated on the above-mentioned first support to form a coating film, and the coating film was heated at a temperature of 145 ° C. for 1 hour to harden, thereby forming a conductive layer 1-1 having a film thickness of 25 μm.

(Conductive Layer 1-2)
100 parts of zinc oxide particles (average primary particle size: 50 nm, specific surface area: 19 m ² /g, powder resistance: 4.7×10 ⁶ Ω·cm, manufactured by Teica) were mixed with 500 parts of toluene while stirring. 1.25 parts of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane (product name: KBM602, manufactured by Shin-Etsu Chemical) was added as a surface treatment agent, and the mixture was mixed while stirring for 4 hours. Thereafter, the toluene was distilled off under reduced pressure, and the mixture was dried at a temperature of 130° C. for 4 hours to obtain surface-treated zinc oxide particles.

100 parts of titanium oxide particles (product name: JR-405, manufactured by Teika Co., Ltd., average primary particle size: 210 nm) were mixed with 500 parts of toluene and stirred, and 0.75 parts of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane was added and stirred for 2 hours. After that, the toluene was removed by vacuum distillation, and the mixture was baked at a temperature of 120°C for 3 hours to obtain surface-treated titanium oxide particles.

続いて、上記表面処理された酸化亜鉛粒子７５部、式（Ａ２）で示されるブロック化されたイソシアネート化合物（商品名：スミジュール３１７５、固形分：７５質量％、住友バイエルウレタン製）１６部、ポリビニルブチラール樹脂（商品名：エスレックＢＭ－１、積水化学工業製）９部、２，３，４－トリヒドロキシベンゾフェノン（東京化成工業製）１部、干渉縞を防止する目的で表面処理された酸化チタン粒子８．６５部を、メチルエチルケトン６０部とシクロヘキサノン６０部の混合溶剤に加えて分散液を調製した。この分散液に、平均粒径１．０ｍｍのガラスビーズを用いて縦型サンドミルにて温度２３℃雰囲気下、回転数１，５００ｒｐｍで３時間分散処理した。分散処理後、得られた分散液に架橋ポリメタクリル酸メチル粒子（商品名：ＳＳＸ－１０３、平均粒径：３μｍ、積水化学工業製）５部と、シリコーンオイル（商品名：ＳＨ２８ＰＡ、東レ・ダウコーニング製）０．０１部を添加して攪拌することで、第１導電層用塗布液２を調製した。第１導電層用塗布液２を第１支持体上に浸漬塗布して塗膜を形成し、塗膜を温度１６０℃で４０分間加熱、重合させることによって、膜厚が３０μｍの導電層１－２を形成した。

Subsequently, 75 parts of the above-mentioned surface-treated zinc oxide particles, 16 parts of a blocked isocyanate compound represented by formula (A2) (trade name: Sumidur 3175, solid content: 75 mass%, manufactured by Sumitomo Bayer Urethane), 9 parts of a polyvinyl butyral resin (trade name: S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.), 1 part of 2,3,4-trihydroxybenzophenone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 8.65 parts of titanium oxide particles that had been surface-treated for the purpose of preventing interference fringes were added to a mixed solvent of 60 parts of methyl ethyl ketone and 60 parts of cyclohexanone to prepare a dispersion liquid. This dispersion liquid was subjected to a dispersion treatment in a vertical sand mill using glass beads having an average particle size of 1.0 mm in an atmosphere at a temperature of 23° C. and a rotation speed of 1,500 rpm for 3 hours. After the dispersion treatment, 5 parts of crosslinked polymethyl methacrylate particles (product name: SSX-103, average particle size: 3 μm, manufactured by Sekisui Chemical Co., Ltd.) and 0.01 parts of silicone oil (product name: SH28PA, manufactured by Dow Corning Toray Co., Ltd.) were added to the obtained dispersion and stirred to prepare a first conductive layer coating liquid 2. The first conductive layer coating liquid 2 was dip-coated onto the first support to form a coating film, and the coating film was heated at a temperature of 160° C. for 40 minutes and polymerized to form a conductive layer 1-2 having a film thickness of 30 μm.

(Conductive Layer 1-3)
214 parts of titanium oxide (TiO _{2 ) particles coated with oxygen-deficient tin oxide (SnO 2 )} as metal oxide particles, 132 parts of phenol resin (phenol resin monomer/oligomer) as a binder material (product name: Plyofen J-325, manufactured by Dainippon Ink and Chemicals, Inc., resin solids content: 60% by mass), and 98 parts of 1-methoxy-2-propanol as a solvent were placed in a sand mill using 450 parts of glass beads with a diameter of 0.8 mm, and dispersion treatment was carried out under the conditions of rotation speed: 2000 rpm, dispersion treatment time: 4.5 hours, and cooling water temperature setting: 18° C. to obtain a dispersion. The glass beads were removed from this dispersion using a mesh (mesh size: 150 μm). Silicone resin particles (trade name: Tospearl 120, manufactured by Momentive Performance Materials, Inc., average particle size: 2 μm) as a surface roughening agent were added to the dispersion so as to be 10% by mass relative to the total mass of the metal oxide particles and the binding material in the dispersion after removing the glass beads. In addition, silicone oil (trade name: SH28PA, manufactured by Dow Corning Toray Co., Ltd.) as a leveling agent was added to the dispersion so as to be 0.01% by mass relative to the total mass of the metal oxide particles and the binding material in the dispersion and stirred to prepare a first conductive layer coating liquid 3. This first conductive layer coating liquid 3 was applied by dip coating onto the first support, and the resulting coating film was dried and heat-cured at a temperature of 150° C. for 30 minutes to form a conductive layer 1-3 having a film thickness of 30 μm.

(Conductive Layers 1-4)
The anatase type titanium dioxide core material can be produced by the known sulfuric acid method, in which a solution containing titanium sulfate and titanyl sulfate is heated and hydrolyzed to produce a metatitanic acid slurry, which is then dehydrated and fired.

As the core particles, anatase type titanium oxide particles with an average primary particle size of 200 nm were used. A titanium niobium sulfate solution containing 33.7 parts of titanium in terms of _TiO2 and 2.9 parts of _niobium in terms of _Nb2O5 was prepared. 100 parts of the core particles were dispersed in pure water to prepare a suspension of 1000 parts, which was then heated to a temperature of 60°C. The titanium niobium sulfate solution and 10 mol/L sodium hydroxide were dropped over 3 hours so that the pH of the suspension was 2 to 3. After the entire amount was dropped, the pH was adjusted to near neutral, and a flocculant was added to allow the solids to settle. The supernatant was removed, filtered and washed, and dried at a temperature of 110°C to obtain an intermediate containing 0.1 wt% of organic matter derived from the flocculant in terms of C. This intermediate was fired in nitrogen at a temperature of 750°C for 1 hour, and then fired in air at a temperature of 450°C to produce titanium oxide particles 1. The obtained particles had an average particle size (average primary particle size) of 220 nm as determined by the particle size measurement method using a scanning electron microscope described above.

Next, 80 parts of a phenolic resin (phenolic resin monomer/oligomer) (product name: Plyofen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g/cm ³ ) serving as a binder material was dissolved in 60 parts of 1-methoxy-2-propanol serving as a solvent to obtain a solution.
100 parts of metal oxide particles 1 were added to this solution, and the solution was placed in a vertical sand mill using 200 parts of glass beads with an average particle size of 1.0 mm as a dispersion medium, and dispersion treatment was performed for 2 hours under conditions of a dispersion temperature of 23±3° C. and a rotation speed of 1500 rpm (circumferential speed of 5.5 m/s) to obtain a dispersion. The glass beads were removed from this dispersion using a mesh. The dispersion after removing the glass beads was pressure-filtered using PTFE filter paper (trade name: PF060, manufactured by Advantec Toyo). 0.015 parts of silicone oil (trade name: SH28 PAINT ADDITIVE, manufactured by Dow Corning Toray) as a leveling agent and 15 parts of silicone resin particles (trade name: KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., average particle size: 2 μm, density: 1.3 g/cm ³ ) as a surface roughness imparting material were added to the dispersion after pressure filtration, and the mixture was stirred to prepare a first conductive layer coating liquid 4. This first conductive layer coating liquid 4 was dip-coated onto the above-mentioned first support to form a coating film, and the coating film was heated at a temperature of 145° C. for 1 hour to be cured, thereby forming a conductive layer 1-4 having a film thickness of 25 μm.

<Preparation of Undercoat Layer>
(Undercoat layer 1)
An undercoat solution was prepared by dissolving 25 parts of N-methoxymethylated nylon 6 (trade name: Toresin EF-30T, manufactured by Nagase Chemtex) in 480 parts of a 2/1 mixed solution of methanol/n-butanol (heat dissolution at a temperature of 65° C.). The solution was then filtered through a membrane filter (trade name: FP-022, pore size: 0.22 μm, manufactured by Sumitomo Electric Industries, Ltd.) to prepare undercoat layer coating solution 1. This undercoat layer coating solution 1 was dip-coated onto the first support or the first conductive layer, and the resulting coating film was dried to form an undercoat layer 1 having a film thickness of 0.8 μm.

前記エチルトリメトキシシランで表面処理済みされたルチル型酸化チタン粒子１８部、Ｎ－メトキシメチル化ナイロン（商品名：トレジンＥＦ－３０Ｔ、ナガセケムテックス製）４．５部、共重合ナイロン樹脂（商品名：アミランＣＭ８０００、東レ製）１．５部を、メタノール９０部と、１－ブタノール６０部と及びジメチルケトンアセトン１５部の混合溶剤に加えて分散液を調製した。この分散液を、直径１．０ｍｍのガラスビーズを用いて縦型サンドミルにて５時間分散処理することにより、下引き層用塗布液２を調製した。この下引き層用塗布液２を第１支持体または第１導電層上に浸漬塗布し、得られた塗膜を乾燥させることによって、膜厚が０．８μｍの下引き層２を形成した。 (Undercoat layer 2)
100 parts of rutile-type titanium oxide particles (average primary particle size: 50 nm, manufactured by Teika) were mixed with 500 parts of toluene by stirring, and 3.0 parts of ethyltrimethoxysilane, a compound represented by formula (A3) in which n=1 and R ¹ is a methyl group, was added and stirred for 8 hours. Thereafter, the toluene was distilled off under reduced pressure, and the mixture was dried at a temperature of 120° C. for 3 hours to obtain rutile-type titanium oxide particles surface-treated with ethyltrimethoxysilane.

A dispersion was prepared by adding 18 parts of the rutile-type titanium oxide particles that had been surface-treated with the ethyltrimethoxysilane, 4.5 parts of N-methoxymethylated nylon (product name: Toresin EF-30T, manufactured by Nagase Chemtex), and 1.5 parts of copolymer nylon resin (product name: Amilan CM8000, manufactured by Toray) to a mixed solvent of 90 parts of methanol, 60 parts of 1-butanol, and 15 parts of dimethyl ketone acetone. The dispersion was dispersed for 5 hours in a vertical sand mill using glass beads having a diameter of 1.0 mm, to prepare an undercoat layer coating solution 2. The undercoat layer coating solution 2 was dip-coated on the first support or the first conductive layer, and the resulting coating film was dried to form an undercoat layer 2 having a thickness of 0.8 μm.

<Charge Generation Layer>
10 parts of titanyl phthalocyanine crystals (charge generating material) having a strong peak at 27.2±0.3° of Bragg angle 2θ in CuKα characteristic X-ray diffraction, 5 parts of polyvinyl butyral (product name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.) and 250 parts of cyclohexanone were placed in a sand mill using glass beads with a diameter of 0.8 mm, and dispersed under the condition of dispersion treatment time: 3 hours, and then 250 parts of ethyl acetate were added to prepare a coating liquid for a charge generating layer. This coating liquid for a charge generating layer was dip-coated on the first support, the first conductive layer or the undercoat layer, and the resulting coating film was dried at a temperature of 100° C. for 10 minutes to form a charge generating layer with a Macbeth concentration value of 0.95.

<Charge Transport Layer>
A coating liquid for a charge transport layer was prepared by mixing 90 parts of the charge transport material represented by formula (A4), 100 parts of a polyarylate resin having a repeating unit represented by formula (A5) as a binder resin, and 0.05 parts of silicone oil (trade name: KF-96, manufactured by Shin-Etsu Silicones Co., Ltd.) as a leveling agent in a mixed solvent of 480 parts of tetrahydrofuran and 120 parts of toluene. The coating liquid for a charge transport layer was dip-coated on the charge generating layer, and the resulting coating was dried at a temperature of 140° C. for 30 minutes to form a charge transport layer having a thickness of 20 μm.

[Production of unvulcanized rubber mixture for domain formation (CMB)]
<Production Example of CMB1>
100 parts of butyl rubber (trade name: JSR Butyl 065, manufactured by JSR Corporation) as raw rubber, 60 parts of carbon black (trade name: Toka Black #5500, manufactured by Tokai Carbon) as an electronic conductive agent, 5 parts of zinc oxide (trade name: zinc oxide type 2, manufactured by Sakai Chemical Industry Co., Ltd.) as a vulcanization accelerator, and 2 parts of zinc stearate (trade name: SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.) as a processing aid were mixed using a 6-liter pressure kneader (trade name: TD6-15MDX, manufactured by Toshin) to produce CMB1. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and 20 minutes.

At this time, the SP value and Mooney viscosity of the raw rubber and the Mooney viscosity of CMB1 were measured by the above-mentioned method. The results are shown in Table 2 together with the composition of each material of CMB1.
The abbreviations for the raw material rubbers in Table 2 are shown in Table 4, and the abbreviations for the electronic conductive agents are shown in Table 5.
In Table 2, "parts by mass" refers to parts by mass of the electronic conductive agent relative to 100 parts of the raw rubber material.

<Production Examples of CMB2 to 8>
CMB2 to 8 were produced in the same manner as in the production example of CMB1, except that the raw material rubber type and the electronic conductive agent were changed as shown in Table 2.
Similarly to CMB1, the SP value and Mooney viscosity of the raw rubbers of CMB2 to 8, and the Mooney viscosity of CMB2 to 8 were measured. The results are shown in Table 2 together with the material configurations of CMB2 to 8. The material abbreviations of the raw rubber types in Table 2 are shown in Table 4, and the material abbreviations of the electronic conductive agents are shown in Table 5.

表中のムーニー粘度に関し、原料ゴムのムーニー粘度の値は各社のカタログ値である。ＣＭＢのムーニー粘度の値は、ＪＩＳ Ｋ６３００－１：２０１３に基づくムーニー粘度ＭＬ（１＋４）であり、ＣＭＢを構成する材料すべてを混練している時のゴム温度で測定されたものである。

Regarding the Mooney viscosity in the table, the Mooney viscosity values of the raw rubber are the catalog values of each company. The Mooney viscosity value of CMB is the Mooney viscosity ML (1+4) based on JIS K6300-1:2013, and was measured at the rubber temperature when all the materials constituting the CMB were being kneaded.

[Production of matrix-forming rubber mixture (MRC)]
<Production Example of MRC1>
100 parts of styrene butadiene rubber (trade name: T1000, manufactured by Asahi Kasei) as raw rubber, 70 parts of calcium carbonate (trade name: Nanox #30, manufactured by Maruo Calcium Co., Ltd.) as filler, 7 parts of zinc oxide (trade name: zinc oxide type 2, manufactured by Sakai Chemical Industry Co., Ltd.) as vulcanization accelerator, and 2.8 parts of zinc stearate (trade name: SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.) as processing aid were mixed using a 6-liter pressure kneader (trade name: TD6-15MDX, manufactured by Toshin) to produce MRC1. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and 16 minutes.

At this time, the SP value and Mooney viscosity of the raw rubber and the Mooney viscosity of MRC1 were measured by the above-mentioned methods. The results are shown in Table 3 together with the material composition of MRC1.
In addition, "parts by mass" in Table 3 means parts by mass of the conductive agent relative to 100 parts of the raw material rubber type. In addition, the material abbreviations of the raw material rubber types in Table 3 are shown in Table 4.

<Production examples of MRC2 to 7>
MRC2 to 7 were produced in the same manner as in the production example of MRC1, except that the raw material rubber type was changed as shown in Table 3.
In addition, in the same manner as in the manufacturing example of MRC1, the SP value and Mooney viscosity of the raw material rubber of MRC2 to 7 and the Mooney viscosity of MRC2 to 7 were measured. The results are shown in Table 3 together with the material configurations of MRC2 to 7.

<Production of Charging Member>
(Manufacturing Example of Charging Roller 1)
As a cylindrical second support, a round bar having a total length of 252 mm and an outer diameter of 6 mm and made of stainless steel (SUS304) whose surface was subjected to electroless nickel plating was prepared.

Next, 25 parts of CMB1 and 75 parts of MRC1 were mixed using a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin). The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and 16 minutes.

Next, 100 parts of the mixture of CMB1 and MRC1, 3 parts of sulfur (product name: SULFAX PMC, manufactured by Tsurumi Chemical Industry Co., Ltd.) as a vulcanizing agent, and 3 parts of tetramethylthiuram disulfide (product name: Noccela TT-P, manufactured by Ouchi Shinko Chemical Co., Ltd.) as a vulcanizing aid were mixed using an open roll with a roll diameter of 12 inches to prepare an unvulcanized rubber mixture for forming the second conductive layer. The mixing conditions were a front roll rotation speed of 10 rpm, a rear roll rotation speed of 8 rpm, and a roll gap of 2 mm, with a total of 20 left and right turns, followed by 10 thin passes with a roll gap of 0.5 mm.

Next, an unvulcanized rubber roller was manufactured using the device shown in FIG. 13. A die with an inner diameter of 10 mm was attached to the tip of the extruder of the crosshead 163 having the supply mechanism 164 for the second support 161 and the discharge mechanism for the unvulcanized rubber roller, and the temperature of the extruder 162 and the crosshead 163 was adjusted to 80°C, and the conveying speed of the second support 161 was adjusted to 60 mm/sec. Under these conditions, the unvulcanized rubber mixture for forming the second conductive layer was supplied from the extruder 162, and the outer periphery of the second support 161 was covered with the unvulcanized rubber mixture for forming the second conductive layer in the crosshead 163, to obtain the unvulcanized rubber roller 165.

Next, the unvulcanized rubber roller 165 was placed in a hot air vulcanizing furnace at a temperature of 160°C and heated for 60 minutes to vulcanize the unvulcanized rubber mixture for forming the second conductive layer, forming a second conductive layer on the outer periphery of the second support 161. After that, 10 mm was cut off from each end of the second conductive layer, making the longitudinal length of the second conductive layer 232 mm, and the roller 166 was obtained.

Finally, the surface of the second conductive layer of the roller 166 was polished with a rotary grindstone. This produced a crown-shaped charging roller 1 with a diameter of 8.4 mm at each end 90 mm from the center and a diameter of 8.5 mm at the center.

The volume resistivity ρ _D [Ω·cm] of the domain and the volume resistivity ρ _M [Ω·cm] of the matrix of the obtained charging roller 1 were measured by the above-mentioned method. The results are shown in Table 6 together with the configuration of the charging roller 1.
The abbreviations of the materials for the vulcanizing agents and vulcanization accelerators in Table 6 are shown in Table 7.

(Manufacturing Examples of Charging Rollers 2 to 15)
Charge rollers 2 to 15 were manufactured in the same manner as in the manufacturing example of charge roller 1, except that in the manufacturing example of charge roller 1, CMB, MRC, the mixing ratio of CMB and MRC, and the vulcanization accelerator were changed as shown in Table 6.
Moreover, the domain volume resistivity ρ _D [Ω·cm] and matrix volume resistivity ρ _M [Ω·cm] of charging rollers 2 to 15 were measured in the same manner as charging roller 1. The results are shown in Table 6 together with the configurations of charging rollers 2 to 15.

[Example 1]
The photoreceptor 1 and the charging member 1 were mounted in a process cartridge of a laser beam printer (product name: Color Laser Jet Enterprise M653dn) manufactured by Hewlett-Packard Company, to prepare the process cartridge of Example 1.
The measured values of f _OPC and z _OPC of the photoreceptor 1 used at this time, the measured values of f _C and z _C of the charging member 1, the calculated value of ρ _M /ρ _D , and the calculated value of f _OPC /f _C and (z _OPC ×z _C ) ^0.5 when the photoreceptor 1 and the charging member 1 were combined are shown in Table 8.

[Examples 2 to 36, Comparative Examples 1 to 6]
In Example 1, except that the photoconductor 1 and the charging member 1 were changed as shown in Table 8, the process cartridges of Examples 2 to 36 and Comparative Examples 1 to 6 were prepared in the same manner as in Example 1.
Table 8 also shows the measured values of f _OPC and z _OPC of the photoconductor used, the measured values of f _C and z _C of the charging member, the calculated value of ρ _M /ρ _D , and the calculated value of f _OPC /f _C and (z _OPC ×z _C ) ^0.5 when the photoconductor and charging member are combined.

[evaluation]
The process cartridges of the examples and comparative examples were evaluated as follows.

<Evaluation device>
A laser beam printer (product name: Color Laser Jet Enterprise M653dn) manufactured by Hewlett-Packard was prepared as an electrophotographic device for evaluation. The motor that rotates the photosensitive drum and the like was modified to 80 rpm, and the motor was further modified so that the voltage applied to the charging roller, and the pre-exposure amount and image exposure amount to the photosensitive member could be adjusted and measured.
Three process cartridges each of the example and comparative example were prepared. These process cartridges were installed only in the magenta process cartridge station, so that the laser beam printer could operate without installing process cartridges for the other colors (cyan, yellow, black) in the main body.
When outputting an image, only the magenta process cartridge was attached to the laser beam printer body, and a monochromatic image was output using only magenta toner.

<Running sideways>
First, two photoconductors were removed from the process cartridge. A rotating drill was inserted perpendicularly into the center of the surface of the photoconductor, and holes of 2 mm in diameter were drilled until the undercoat layer was exposed. Five holes were drilled for each photoconductor, shifted in the circumferential direction of the photoconductor, so that there were no multiple holes on the same axis in the longitudinal direction of the photoconductor. A lateral running test was performed using the photoconductor and charging member 1 as follows.

Figure 14 shows the leak test device. The lateral run test is performed in a high temperature and high humidity environment (temperature 30°C/relative humidity 80%). Both ends of the electrophotographic photoreceptor 21 are placed on the fixing table 23 and fixed so as not to move. The contact portion 24 of the electrophotographic photoreceptor 21 with the first support is connected to earth via a reference resistor 25 of 100 kΩ. Next, the charging member 26 is abutted at one end 5N so as to contact the center of the photosensitive layer 27 of the electrophotographic photoreceptor 21. A power source 28 for applying voltage is connected to the charging member 26. The electrophotographic photoreceptor 21 can be rotated around the longitudinal axis by the contact portion 24 with the first support.

A voltage of -1500 V was applied to the charging member 26 while the electrophotographic photoreceptor 21 was rotated at a rotation speed of 200 rpm. At this time, in the current profile flowing from the electrophotographic photoreceptor 21 to earth, the current that rushed into the portion where the undercoat layer was exposed (the portion where the current was detected to be larger than other portions) was taken as the lateral current. The measurement results of the lateral current at this time are shown in Table 9.

Next, process cartridges using a perforated photoconductor were prepared again for each example and comparative example, and each process cartridge was attached to the evaluation machine one by one. The voltage applied to the charging roller and the image exposure amount to the photoconductor were set so that the dark area potential was -750V and the light area potential was -130V. The pre-exposure amount was three times the image exposure amount. To measure the surface potential of the photoconductor when setting the potential, a potential probe (product name: model 6000B-8, manufactured by Trek Japan) was attached to the development position of the process cartridge, and a surface potential meter (product name: model 344, manufactured by Trek Japan) was used.

Using the same voltage applied to the charging roller and the same amount of pre-exposure and image exposure to the electrophotographic photoreceptor as above, 10,000 halftone images of a 1-dot knight pattern were printed.

In the present invention, the image results corresponding to the five perforated portions in the halftone image output on the 10,000th sheet were ranked according to the following criteria. The evaluation criteria A to D were deemed to represent the effects of the present invention. The evaluation results are shown in Table 9.
A: Only sunspots are observed in all five locations.
B: Short, thin horizontal black streaks observed in one or two out of five locations.
C: Short, thin horizontal black streaks observed in 3 or more of 5 locations.
D: Long horizontal black streaks extending across the entire image area are observed in one or two out of five locations.
E: Long horizontal black streaks extending across the entire image area are observed in 3 or more of 5 locations.

<Electric potential fluctuation>
First, the process cartridges of the examples and the comparative examples were prepared again, and the process cartridges and the electrophotographic device were left in a low temperature and low humidity environment (L/L: temperature 15°C/relative humidity 20%) for 24 hours or more, and then the process cartridges were mounted in the magenta process cartridge station of the electrophotographic device.

The voltage applied to the charging roller and the image exposure to the photoconductor were set so that the dark area potential was -750 V and the light area potential was -130 V. The pre-exposure was three times the image exposure. To measure the surface potential of the photoconductor when setting the potential, a potential probe (product name: model 6000B-8, manufactured by Trek Japan) was attached to the development position of the process cartridge, and a surface potential meter (product name: model 344, manufactured by Trek Japan) was used.

After leaving the process cartridge and electrophotographic device in a low temperature and low humidity (L/L: temperature 15°C/relative humidity 20%) environment for 24 hours or more, the process cartridge was attached to the magenta process cartridge station of the electrophotographic device. The voltage applied to the charging roller and the image exposure amount to the photoconductor were set so that the dark area potential was -750V and the light area potential was -130V. The pre-exposure amount was three times the image exposure amount. Using this process cartridge and electrophotographic device, a print operation was performed in an intermittent mode in which a character image with a print rate of 2% was output one sheet at a time on A4 size plain paper, and a paper feed durability test was performed by outputting 10,000 sheets of images.

Next, immediately after the 10,000-sheet paper-passing durability test, the applied voltage was set again so that the dark potential was −750 V. The voltage applied to the charging roller and the image exposure amount to the photoconductor were set so that the dark potential was −750 V and the light potential was −130 V, and the dark potential and the light potential were measured with the pre-exposure amount being three times the image exposure amount. The measured light potential was defined as V _L [V], and the potential change amount before and after the 10,000-sheet paper-passing durability test was calculated as ΔV _L = |V _L + 130|.

In the present invention, the values of _ΔVL were ranked according to the following criteria. The evaluation criteria A to D were deemed to represent the effects of the present invention. The evaluation results are shown in Table 9.
A: ΔV _L ≦15
B: 15<ΔV _L ≦25
C: 25<ΔV _L ≦35
D: 35<ΔV _L ≦45
E: 45<ΔV _L

REFERENCE SIGNS LIST 1 Electrophotographic photoreceptor 2 Shaft 3 Charging member 4 Exposure light 5 Developing means 6 Transfer means 7 Transfer material 8 Fixing means 9 Cleaning means 10 Pre-exposure light 11 Process cartridge 12 Guide means 6a Matrix 6b Domain 6c Conductive particles 81 Charging member 111 Second support 112 Second conductive layer 113 Platinum vapor deposition layer 114 Aluminum sheet 121 Second support 122 Second conductive layer 123 Platinum vapor deposition layer 124 Aluminum sheet 125 Impedance measuring device 161 Conductive mandrel 162 Extruder 163 Two-layer crosshead 164 Core feed roller 165 Unvulcanized rubber roller 166 Roller 21 Electrophotographic photoreceptor 23 Fixing base 24 Part in contact with support 25 Reference resistance 26 Stepped core 27 Photosensitive layer 28 Power supply

Claims (10)

A process cartridge having an electrophotographic photosensitive member and a charging member, and being detachably mountable to a main body of an electrophotographic apparatus,
The electrophotographic photoreceptor has a cylindrical first support, a bottom layer formed directly on the first support, and a photosensitive layer formed on the bottom layer,
A needle electrode having a diameter of 1 mm connected to the high voltage side of an impedance measuring device is brought into contact with the bottom layer, and the earth side lead of the impedance measuring device is connected to the first support. An AC voltage with an amplitude of 1 Vpp is applied to the surface of the first support at a DC voltage of -8 V while varying the frequency between 1.0 x 10 ^-2 [Hz] - 1.0 x 10 ⁶ [Hz] to measure the impedance. The maximum frequency at which the phase of the impedance is 45° is defined as f _OPC [Hz],
The charging member is an electrophotographic charging member having a cylindrical second support and a second conductive layer formed on the second support,
the second conductive layer has a matrix including a first rubber and a plurality of domains dispersed in the matrix;
the domain comprises a second rubber and an electronic conductive agent;
The volume resistivity _ρM of the matrix is 1.0× ¹⁰⁵ or more times the volume resistivity _ρD of the domain,
A band-shaped thin metal film electrode having a longitudinal width of 1.5 cm is provided in the circumferential direction on the surface of the charging member, the thin metal film electrode is connected to one side of an impedance measuring device, the second support is connected to the other side of the impedance measuring device, and an AC voltage with an amplitude of 1 Vpp is applied while changing the frequency between 1.0×10 ^-2 [Hz] and 1.0×10 ⁶ [Hz] to measure the impedance. When the maximum frequency at which the phase of the impedance is 45° is taken as f _C [Hz],
A process cartridge, characterized in that f _OPC and f _C satisfy the relationship of the following formula (D1) or the following formula (D2):
10≦f _OPC /f _C ≦10,000 Formula (D1)
0.0001≦f _OPC /f _C ≦0.1 Formula (D2). 2. The process cartridge according to claim 1, wherein in the electrophotographic photosensitive member and the charging member, the f _OPC and the f _C satisfy the following formula (D3) or the following formula (D4):
30≦f _OPC /f _C ≦3,000 Formula (D3)
0.0003≦f _OPC /f _C ≦0.03 formula (D4). 3. The process cartridge according to claim 1, wherein the f _OPC of the electrophotographic photosensitive member is 5 Hz or more. 4. The process cartridge according to claim 1, wherein the f _OPC of the electrophotographic photosensitive member is 100 Hz or more. a needle electrode having a diameter of 1 mm connected to a high voltage side of an impedance measuring device is brought into contact with the bottommost layer of the electrophotographic photosensitive member, a lead wire on the earth side of the impedance measuring device is connected to the first support, and a DC voltage of -8 V and an AC voltage with an amplitude of 1 Vpp are applied to the surface of the first support while varying the frequency between 1.0 x 10 ^-2 [Hz] to 1.0 x 10 ⁶ [Hz] to measure the impedance per unit area of the bottommost layer at a frequency of f _OPC /10 [Hz], the measured value is defined as z _OPC [Ω·cm ² ],
A band-shaped metal thin film electrode having a longitudinal width of 1.5 cm is provided in the circumferential direction on the surface of the charged member, the metal thin film electrode is connected to one side of an impedance measuring device, the second support is connected to the other side of the impedance measuring device, and an AC voltage with an amplitude of 1 Vpp is applied while changing the frequency between 1.0 ×10 ^-2 [Hz] and 1.0×10 ⁶ [Hz] to measure the impedance per unit area of the charged member at a frequency of f _C /10 [Hz] . When the measured value is expressed as z _C [Ω·cm ² ],
The process cartridge according to any one of claims 1 to 4, wherein z _OPC and z _C satisfy the relationship of the following formula (D5):
(z _OPC ×z _C )≧1.0×10 ⁶ formula (D5). The process cartridge according to any one of claims 1 to 5, wherein when a needle electrode having a diameter of 1 mm connected to a high voltage side of an impedance measuring device is brought into contact with the bottommost layer of the electrophotographic photosensitive member, a lead wire on the earth side of the impedance measuring device is connected to the first support, and an AC voltage of an amplitude of 1 Vpp is applied to a surface of the first support while changing a DC voltage of -8 V between the surface of the first support and a frequency of 1.0 x 10 ^-2 [Hz] to 1.0 x 10 ⁶ [Hz], the impedance per unit area of the bottommost layer at a frequency of f _OPC /10 [Hz] is measured, the measured value z _OPC is 3.0 x 10 ⁵ [Ω·cm ² ] or more. The process cartridge according to any one of claims 1 to 6, wherein when a needle electrode having a diameter of 1 mm connected to a high voltage side of an impedance measuring device is brought into contact with the bottommost layer of the electrophotographic photosensitive member, a lead wire on the earth side of the impedance measuring device is connected to the first support, and an AC voltage of an amplitude of 1 Vpp is applied to a surface of the first support while changing a DC voltage of -8 V between the surface of the first support and a frequency between 1.0 x 10 ^-2 [Hz] and 1.0 x 10 ⁶ [Hz], the impedance per unit area of the bottommost layer at a frequency of f _OPC /10 [Hz] is measured, the measured value z _OPC is 1.0 x 10 ⁹ [Ω cm ² ] or less. The process cartridge according to any one of claims 1 to 7, wherein a band-shaped thin metal film electrode having a longitudinal width of 1.5 cm is provided in the circumferential direction on a surface of the charging member, the thin metal film electrode is connected to one side of an impedance measuring device, the second support is connected to the other side of the impedance measuring device, and an AC voltage having an amplitude of 1 Vpp is applied while changing the frequency between 1.0 x 10 ^-2 [Hz] and 1.0 ^x 10 6 [Hz] to measure the impedance per unit area of the charging member at a frequency of f C /10 [Hz], the measured value _{z C} is 1.0 x 10 ⁶ [Ω·cm ² ] or more . 9. The process cartridge according to claim 1, wherein in said charging member, said matrix has a volume resistivity _ρM of 1.0×10 ¹² [Ω·cm] or more. An electrophotographic apparatus having an electrophotographic photoreceptor and a charging member,
The electrophotographic photoreceptor has a cylindrical first support, a bottom layer formed directly on the first support, and a photosensitive layer formed on the bottom layer,
A needle electrode having a diameter of 1 mm connected to the high voltage side of an impedance measuring device is brought into contact with the bottom layer, and the part of the first support where the core material is exposed is connected to the earth side of the impedance measuring device. An AC voltage with an amplitude of 1 Vpp is applied to the surface of the first support at a DC voltage of -8 V while varying the frequency between 1.0 x 10 ^-2 [Hz] - 1.0 x 10 ⁶ [Hz] to measure the impedance. The maximum frequency at which the phase of the impedance is 45° is defined as f _OPC [Hz],
The charging member is an electrophotographic charging member having a cylindrical second support and a second conductive layer formed on the second support,
the second conductive layer has a matrix including a first rubber and a plurality of domains dispersed in the matrix;
the domain comprises a second rubber and an electronic conductive agent;
The volume resistivity _ρM of the matrix is 1.0× ¹⁰⁵ or more times the volume resistivity _ρD of the domain,
A thin metal film electrode is provided on the surface of the charged member, a metal sheet is wrapped around the thin metal film electrode, the metal sheet is connected to the high-voltage side electrode of an impedance measuring device, the second support is connected to the earth side of the impedance measuring device, and an AC voltage with an amplitude of 1 Vpp is applied while changing the frequency between 1.0×10 ^-2 [Hz] and 1.0×10 ⁶ [Hz] to measure the impedance. If the maximum frequency at which the phase of the impedance is 45° is taken as f _C [Hz], then:
An electrophotographic apparatus, characterized in that f _OPC and f _C satisfy the relationship of the following formula (D1) or the following formula (D2):
10≦f _OPC /f _C ≦10,000 Formula (D1)
0.0001≦f _OPC /f _C ≦0.1 Formula (D2).

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