Conductive member, processing cartridge, and electrophotographic image forming apparatus

Abstract

The electroconductive member according to the present invention includes a support having conductivity and an electroconductive layer on the outer surface of the support, and is used as a member for electrophotography. The electroconductive layer has: a matrix containing a crosslinked product of a first rubber and first electroconductive particles; and domains each containing a crosslinked product of a second rubber and second electroconductive particles. At least a part of the first electroconductive particles are present as primary particles in the crosslinked product of the first rubber. Assuming that the length of the electroconductive layer in the length direction is L and the thickness of the electroconductive layer is T, when observing each cross section of the electroconductive layer in the thickness direction at 3 positions (i.e., the center in the length direction and positions L / 4 from both ends of the electroconductive layer toward the center) in a specific observation region, the electroconductive member satisfies the following conditions: the average primary particle diameter d1 of the first electroconductive particles in the matrix is 200 nm or more; the average primary particle diameter d2 of the second electroconductive particles in each domain is 50 nm or less; and in 80% or more of the domains, the ratio of the cross-sectional area of the second electroconductive particles contained in the domain to the cross-sectional area of the domain is 20% or more, and the circular equivalent diameter of the domain is 4 × d2 or more.

Description

Technical Field

[0001] The present invention relates to an electrophotographic conductive member, a processing cartridge, and an electrophotographic image forming apparatus. Background Art

[0002] An electrophotographic image forming apparatus includes a charging member, a transfer member, and a developing member. The charging member is a member for causing discharge between the charging member and an electrophotographic photosensitive member to charge the surface of the electrophotographic photosensitive member.

[0003] The developing member is a member for controlling the charge of a developer covering the surface of the developing member by triboelectric charging to impart a uniform charge amount distribution to the developer, and then uniformly transferring the developer onto the surface of the electrophotographic photosensitive member according to the applied electric field. The transfer member is a member for transferring the developer from the electrophotographic photosensitive member to a printing medium such as paper or an intermediate transfer member and simultaneously causing discharge to stabilize the transferred developer.

[0004] A conductive member is used as the above-described charging member, transfer member, and developing member. Each of these conductive members needs to achieve uniform charging of an abutting object such as an electrophotographic photosensitive member, an intermediate transfer member, or a printing medium. As such a conductive member, a conductive member having a configuration including a conductive support and a conductive layer provided on the support is known. The conductive member has a function of transporting charges from the conductive support to the surface of the conductive member and applying charges to the abutting object by discharge or triboelectric charging.

[0005] In Patent Document 1, a charging member for achieving uniform charging is disclosed. The charging member includes an elastomeric layer in which polymer particles having electronic conductivity are dispersed in a semiconductive polymer continuous layer having ionic conductivity.

[0006] In Patent Document 2, a charging member that can stably charge a charged object even when applied to a high-speed electrophotographic image forming process is disclosed. The charging member includes an elastomeric layer in which a matrix containing a first rubber and a plurality of domains dispersed in the matrix are dispersed, and each of the domains contains a second rubber and an electronic conductive material.

[0007] [Prior Art Documents]

[0008] [Patent Documents]

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-3651

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-166210 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] In recent years, electrophotographic image forming processes have become faster and longer-lasting, and for the purpose of miniaturizing the apparatus, there has been provided an electrophotographic image forming apparatus having a configuration (hereinafter sometimes referred to as a "cleaner-less configuration") that does not include a cleaning member configured to remove the developer (toner) remaining on the photosensitive member.

[0013] The present inventors have attempted long-term image formation by applying the respective charging members according to Patent Document 1 and Patent Document 2 to the above electrophotographic image forming apparatus. As a result, for example, attachments such as toner that remains on the photosensitive member and is not transferred onto the paper significantly accumulate on the surface of the charging member, and over-discharge occurs at the accumulation position, resulting in the appearance of an image in the shape of white spots (hereinafter sometimes referred to as a "white dot image") in some cases.

[0014] One aspect of the present invention relates to providing a conductive member that enables high-quality image formation to be achieved over a long period even when applied to a high-speed and long-lasting electrophotographic image forming process and even in a cleaner-less configuration. Another aspect of the present invention relates to providing a process cartridge that contributes to high-quality electrophotographic image formation. Another aspect of the present invention relates to providing an electrophotographic image forming apparatus that can form high-quality electrophotographic images.

[0015] Solutions for Solving the Problems

[0016] According to one aspect of the present invention, there is provided a conductive member including: a support having conductivity; and a conductive layer provided on an outer surface of the support, the conductive layer including: a matrix containing a crosslinked product of a first rubber and first conductive particles; and domains each containing a crosslinked product of a second rubber and second conductive particles, at least a part of the first conductive particles existing as primary particles in the crosslinked product of the first rubber, wherein when the length of the conductive layer in the length direction is defined as L and the thickness of the conductive layer is defined as T, and when observation regions of 15 μm square are provided at three positions including the center of the conductive layer in the length direction and positions L / 4 from both ends of the conductive layer toward the center, in each of the three cross-sections in the thickness direction of the conductive layer, and at any three positions in the thickness region from the outer surface of the conductive layer to a depth of 0.1 to 0.9T, the average primary particle diameter d1 of the first conductive particles existing as primary particles in the matrix observed in each of the total nine observation regions is 200 nm or more, and the average primary particle diameter d2 of the second conductive particles in the domains observed in each observation region is 50 nm or less, and 80% or more of the number of the domains observed in each observation region satisfy the following requirements (i) and (ii):

[0017] Requirement (i)

[0018] The ratio of the cross-sectional area of the second conductive particles contained in the domain to the cross-sectional area of the domain is 20% or more;

[0019] Requirement (ii)

[0020] The circular equivalent diameter of the domain is 4 × d2 or more.

[0021] According to at least one aspect of the present disclosure, there is provided a process cartridge detachably mounted to a main body of an electrophotographic image forming apparatus, the process cartridge including: an electrophotographic photosensitive member; and a charging member configured to be able to charge the electrophotographic photosensitive member, wherein the charging member is the above-described conductive member.

[0022] According to at least one aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including: an electrophotographic photosensitive member; and a charging roller configured to be able to charge the electrophotographic photosensitive member, wherein the charging roller is the above-described conductive member.

[0023] Effects of the Invention

[0024] According to the present invention, a conductive member that can be used as a charging member, a developing member, or a transfer member is obtained. The conductive member can maintain high image quality for a long time when applied to a high-speed and long-life electrophotographic image forming process and even in a configuration without a cleaner. In addition, according to other aspects of the present invention, an electrophotographic image forming apparatus capable of stably outputting high-quality electrophotographic images and a process cartridge for use therein are obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a graph for explaining the change over time of the discharge current amount in the electrophotographic process.

[0026] Figure 2 is a partial cross-sectional view of a conductive layer of a conductive member according to an embodiment of the present invention.

[0027] Figure 3 is a cross-sectional view of a conductive roller according to an embodiment of the present invention.

[0028] Figure 4 is a graph showing the change of the absolute value of impedance with respect to frequency.

[0029] Figure 5 is a cross-sectional view of a process cartridge including the conductive member according to the present invention.

[0030] Figure 6 ​​​​​​Schematic configuration diagram of an electrophotographic image forming apparatus including a conductive member according to the present invention.

[0031] Figure 7 Schematic diagram for explaining the state where a measurement electrode is formed on a charging roller.

[0032] Figure 8 Cross-sectional view of the state where a measurement electrode is formed on a charging roller. Detailed Description of the Invention

[0033] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the constituent elements described in the embodiments are merely exemplary and are not intended to limit the scope of the present invention to the exemplary embodiments.

[0034] An object of the present invention is to suppress the occurrence of white dot images due to dirt substances adhering to a charging member during high-speed and long-life electrophotographic image formation.

[0035] As used in the present invention, the term "dirt substance" refers to a substance that is not transferred in its entirety during the transfer process when toner and external additives on the surface of a photosensitive drum are transferred to paper or an intermediate transfer member, and a part of which remains on the surface of the photosensitive drum and reaches and adheres to the charging member.

[0036] Toner and external additives each need to have a certain charge so that they can be appropriately transferred to the photosensitive drum during the development process, and thus are often insulating. As a result, dirt substances from toner and external additives also have insulating properties. Inside a developing container, toner and external additives each carry charges with polarities greatly shifted in the positive or negative direction. On the other hand, dirt substances from toner and external additives that remain on the photosensitive drum and are not transferred to paper or an intermediate transfer member are affected by friction or the like before reaching the charging member, and thus become charged and have a certain distribution with respect to positive and negative polarities.

[0037] At the same time, a charging member (hereinafter sometimes referred to as "charging roller") is configured to discharge to the photosensitive drum. Specifically, a DC voltage is applied to the charging member to generate a potential difference between the charging member and the surface of the photosensitive drum. In this case, in the presence of a potential difference between the charging member and the photosensitive drum, it is difficult to prevent components having polarities opposite to the polarity of the charging bias from adhering to the charging member side due to electrostatic attraction. Therefore, for a charging member intended for long-term use, it is desirable to use means that suppress abnormal discharge caused by dirt substances even when dirt substances adhere to the charging roller as described below.

[0038] ​​Next, a white dot image caused by abnormal discharge due to dirt substances will be described. Discharge occurs between the charging roller and the photosensitive drum in accordance with Paschen's law, and the surface of the photosensitive drum is charged negatively or positively according to the applied voltage. Discharge occurs by ionizing neutral air with an electric field, so charges of opposite polarities are also generated at the same time. That is, positive or negative charges with polarities opposite to the discharge polarity are migrated toward the charging roller by means of the electric field. Since the charging roller is a conductive member, in a state where dirt substances do not adhere to the surface of the charging roller, even when the surface of the charging roller is charged with a charge having a polarity opposite to the discharge polarity, its conductivity causes the charge to escape from the surface to the substrate side. However, when insulating dirt substances (toner and external additives) adhere to the surface of the charging roller, charges with polarities opposite to the discharge polarity do not escape from the surface to the substrate side and are captured on the surface. At this time, the dirt substances adhering to the surface of the charging roller have a polarity opposite to the discharge polarity, that is, a polarity opposite to the polarity of the voltage applied to the charging roller. Between such dirt substances with opposite polarities and the surrounding area of the area where the dirt substances are adhered, charges of opposite polarities exist at a very close distance from each other. Therefore, an extremely strong electric field is generated, and in some cases, abnormal excessive discharge occurs due to the extremely strong electric field.

[0039] In addition, the discharge state during the high-speed process is analyzed in detail using an oscilloscope.

[0040] Specifically, in an electrophotographic process in which discharge occurs while the photosensitive drum is rotating, a point on the surface of the photosensitive drum is traced over time. Figure 1 FIG. is a diagram for explaining the change over time of the discharge current amount. In the electrophotographic process, discharge does not occur continuously from the starting point to the ending point of the discharge, but as shown in (a) of Figure 1 , multiple discharges occur repeatedly. As shown in (b) of Figure 1 , at a moment when discharge is not likely to occur in the high-frequency region, omission of discharge occurs. It is found that in some cases, as shown in (c) of Figure 1 , at a moment after each moment when discharge omission occurs, excessive charge may be supplied during discharge, resulting in discharge with a large discharge amount, that is, over-discharge.

[0041] In view of the above, the present inventors have found that the following conditions (a) and (b) need to be satisfied to suppress the appearance of white dot images in the electrophotographic image forming process with high speed and long life:

[0042] (a) Suppress excessive charging of dirt substances to avoid applying an extremely strong electric field to the part where dirt substances are adhered; and

[0043] (b) Suppress discharge omission even in a high-frequency region where discharge is not likely to occur, thereby avoiding supplying an excessive amount of charge to the surface immediately after discharge omission.

[0044] Furthermore, the present inventors conducted in-depth research and found that a charging roller satisfying the following requirements (A) and (B) satisfies the above conditions (a) and (b), and thus the appearance of white dot images can be suppressed even during the process of high-speed operation and long life.

[0045] Requirement (A):

[0046] The conductive layer includes: a matrix containing a cross-linked product of a first rubber and first conductive particles; and domains each containing a cross-linked product of a second rubber and second conductive particles. At least a part of the first conductive particles exist as primary particles in the cross-linked product of the first rubber. The length of the conductive layer in the longitudinal direction is represented by L and the thickness of the conductive layer is represented by T. In three positions including the center in the longitudinal direction of the conductive layer and positions L / 4 from both ends of the conductive layer toward the center, in each cross-section in the thickness direction of the conductive layer, in any three positions in the thickness region from the outer surface of the conductive layer to a depth of 0.1T to 0.9T, an observation region of 15 μm square is set. At this time, the average primary particle diameter d1 of the first conductive particles existing as primary particles in the matrix observed in each of the total nine observation regions is 200 nm or more.

[0047] Requirement (B):

[0048] The average primary particle diameter d2 of the second conductive particles in the domains observed in each observation region is 50 nm or less, and 80% or more of the domains observed in each observation region satisfy the following requirements (B1) and (B2).

[0049] Requirement (B1):

[0050] The ratio of the cross-sectional area of the second conductive particles contained in the domain to the cross-sectional area of the domain is 20% or more.

[0051] Requirement (B2):

[0052] The circular equivalent diameter of the domain is 4 × d2 or more.

[0053] The above requirement (A) indicates that the first conductive particles exist in the state of primary particles and do not form a structure in the matrix in the matrix-domain structure, and do not make the first conductive particles conductive. As used herein, the phrase "make... conductive" means that an electron conductive agent forms a structure through which charge moves, resulting in a significant reduction in resistance. The "state of primary particles" in the present invention is defined as a state in which there is no interface within the particles.

[0054] Requirement (B) above indicates that the second conductive particles in the domains dispersed in the matrix-domain structure have a small average primary particle size and achieve high filling, in which the domains are dispersed in the matrix and the domains are not connected to each other. That is, requirement (B) indicates that the interfacial area between the second rubber and the second conductive particles in the domains is very large, and the second conductive particles form a structure to exhibit high conductivity.

[0055] Figure 2 FIG. is a partial cross-sectional view of a conductive layer in a direction perpendicular to the length direction of a conductive member having a roller shape (hereinafter sometimes referred to as "conductive roller") according to an embodiment of the present invention. As Figure 2 shown, the conductive layer has a matrix-domain structure having a matrix 21 and domains 23. The matrix 21 includes a crosslinked product of a first rubber and first conductive particles 22. Each of the domains 23 includes a crosslinked product of a second rubber and second conductive particles 24.

[0056] In the above matrix-domain structure, based on requirement (A), the matrix 21 is made non-conductive. Based on requirement (B), the second conductive particles 24 have a small primary particle size and achieve high filling. Therefore, the interfacial area between the second rubber and the second conductive particles 24 is very large, so that a large amount of charge can be accumulated in the domains 23 near the interface between them and the matrix 21 in the domains. When the charge is consumed by discharge on the surface of the charging member, the charge accumulated in the domains is quickly supplied to the surface of the charging member due to the shared voltage applied to each of the first rubber in the matrix and the domains described later. By virtue of the characteristic of quickly supplying charge immediately after discharge, the occurrence of discharge omission as shown in (b) of such as Figure 1 can be suppressed. As a result, the phenomenon of inducing over-discharge by supplying excessive charge at the next discharge moment as shown in (c) of such as Figure 1 can be prevented.

[0057] When a voltage is applied from the side of the conductive support, the voltage is applied in a shared manner to each of the first rubber and the first conductive particles in the matrix and the domains (hereinafter sometimes referred to as "shared voltage"). However, the first conductive particles in the matrix are conductors and exist individually, so the interfacial area between the first conductive particles and the first rubber is small. Therefore, the shared voltage applied to the first conductive particles is significantly small, and most of the voltage applied to the conductive layer is applied to the first rubber in the matrix and the domains. As a result, when the first conductive particles exist in the matrix in the state of primary particles, the shared voltage applied to each of the first rubber and the domains in the matrix is increased. When the shared voltage applied to the domains is increased, when the charge accumulated in the domains is supplied to the surface, the charge is easily released. In addition, when the shared voltage applied to the first rubber in the matrix is increased, the supply of charge between the domains or between the domains and the first conductive particles is accelerated. Therefore, by using the charge accumulated in the domains, the charge consumed by discharge can be supplied more quickly until the next discharge moment.

[0058] In addition, as described above, the first conductive particles present in the matrix described in requirement (A) are conductors themselves and exist individually, thus having a small interfacial area with the first rubber. Therefore, unlike the domains, the first conductive particles have almost no charge accumulation ability. Therefore, when the dirt substances deposited on the surface of the charging member are subjected to discharge, the charges overcharged to the opposite polarity can escape to the conductive support side more quickly than in the domains.

[0059] In addition, the overcharged charges have a polarity opposite to the polarity of the voltage applied from the conductive support side, so they are attracted by the electric field and escape to the conductive support side. However, when the first conductive particles exist in the matrix as primary particles, as described above, the shared voltage applied to each of the matrix and the domains is also increased. Therefore, the overcharged charges escaping through the matrix and the domains can also escape to the conductive support side more quickly.

[0060] Therefore, the charging member that satisfies requirement (A) and requirement (B) satisfies the above conditions (a) and (b), so the appearance of white dot images can be suppressed in the electrophotographic image forming process with high speed and long life to provide stable images with high quality.

[0061] Taking a conductive roller as an example for reference Figure 3 to describe the conductive member according to the present invention. Figure 3 It is a cross-sectional view showing the constitution of a cross-section perpendicular to the length direction (axial direction) of the conductive roller. The conductive roller includes a cylindrical conductive support 31 and a conductive layer 32 formed on the outer peripheral surface (i.e., its outer surface) of the support 31.

[0062] <Conductive support>

[0063] Materials that can be appropriately selected from materials known in the field of electrophotographic conductive members and materials that can each be used as an electrophotographic conductive member can be used as the material for constituting the support 31. Examples of the material are aluminum, stainless steel, a synthetic resin having conductivity, or a metal or alloy such as an iron or copper alloy.

[0064] In addition, such materials can be subjected to an oxidation treatment or a plating treatment with chromium, nickel, or the like. As the type of plating, either electroplating or electroless plating can be used. Among them, from the viewpoint of dimensional stability, electroless plating is preferred. Examples of the type of electroless plating to be used herein can include nickel plating, copper plating, gold plating, and plating with various other alloys.

[0065] The thickness of the plating is preferably 0.05 μm or more, and in consideration of the balance between work efficiency and rust prevention ability, the thickness of the plating is preferably 0.10 μm or more and 30.00 μm or less. The cylindrical shape of the support 31 can be a solid cylindrical shape or a hollow cylindrical shape (cylindrical). In addition, the outer diameter of the support is preferably in the range of 3 mm or more and 10 mm or less.

[0066] <Conductive layer>

[0067] Meet the above requirements (A) and requirement (B), so that the appearance of white dot images is suppressed even in the electrophotographic process of high speed and long life. Specifically, by suppressing the overcharging of dirt substances and also suppressing the discharge omission in the high-frequency region, excessive charge is prevented from being supplied to the surface of the charging member.

[0068] Requirement (A) indicates that the first conductive particles exist in the state of primary particles and do not form a structure in the matrix in the matrix-domain structure, and since they exist in the state of primary particles, the matrix portion is not made conductive.

[0069] Requirement (B) indicates that the second conductive particles dispersed in the domain have a small average primary particle size and achieve high filling, so the interface area between the second rubber and the second conductive particles is very large and the domain exhibits high conductivity.

[0070] In addition to requirements (A) and requirement (B), it is more preferable to satisfy the following constitutions (i) to (v).

[0071] (i) The volume resistivity of the matrix is greater than 1.0×10 8 Ω·cm and 1.0×10 17 Ω·cm or less.

[0072] (ii) The volume resistivity of each domain is 1.0×10 1 Ω·cm or more and 1.0×104 Below 1.0×10

[0073] (iii) The distance between adjacent wall surfaces between domains falls within the range of 0.2 μm or more and 2.0 μm or less.

[0074] (iv) 90% or more of the number of the first conductive particles in the matrix exist as primary particles, and the distance between the first conductive particles in the matrix and the closest domain is 0.1 μm or more.

[0075] (v) When the number of the first conductive particles in the matrix is represented by N(A) and the number of domains is represented by N(B), N(A) / N(B) is 0.2 to 3.0.

[0076] <Configuration (i)>

[0077] In this configuration, as described above, the first conductive particles exist as primary particles in the matrix, so the shared voltage applied to the domains is increased to promote charge movement through the domains. Therefore, when the volume resistivity of the matrix falls within the range greater than 1.0×10 8 Ω·cm and 1.0×10 17 Ω·cm or less, the charge bypasses the domains and leaks within the matrix. Therefore, it is possible to prevent the establishment of a state as if a conductive path connected within the conductive layer 32 is formed.

[0078] In addition, the volume resistivity of the matrix is more preferably greater than 1.0×10 12 Ω·cm and 1.0×10 17 Ω·cm or less.

[0079] <Method for measuring the volume resistivity of the matrix>

[0080] The volume resistivity of the matrix can be measured with a microprobe for a thin film prepared from the conductive layer 32. As a means for preparing the thin film, for example, a sharp razor, a microtome, and a focused ion beam method (FIB) are given.

[0081] Regarding the production of the thin film, it is necessary to measure the volume resistivity of only the matrix by excluding the influence of the domains. For this purpose, it is preferable to produce a thin film with a thickness less than the distance between domains measured in advance using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), etc. Therefore, the means for preparing the thin film is preferably a means capable of producing a very thin sample, such as a microtome.

[0082] The measurement of the volume resistivity is carried out as described below. First, one side of the thin sheet is grounded, and then the positions of the matrix and the domains in the thin sheet are identified. The identification of these positions can be carried out by means such as a scanning probe microscope (SPM) or an atomic force microscope (AFM) that can measure the distribution of the volume resistivity or hardness of the matrix and the domains. Next, the probe is brought into contact with the matrix, and a DC voltage of 50 V is applied for 5 seconds. The arithmetic mean value of the grounded current value during the 5 - second period is measured, and the measured value is divided by the voltage to thereby calculate the resistance value. Then, the resistance value is converted to the volume resistivity by using the thickness of the thin sheet. In this case, means such as SPM or AFM that can also measure the shape of the thin sheet can measure the thickness of the thin sheet, whereby the volume resistivity can be measured, and thus it is suitable.

[0083] In the measurement of the volume resistivity of the matrix in the cylindrical conductive member, one thin - sheet sample is cut out from each region obtained by dividing the conductive layer into 4 parts in the circumferential direction and 5 parts in the length direction. The above - mentioned measured values are obtained for each thin - sheet sample, and then the arithmetic mean value of the volume resistivity of a total of 20 samples is calculated.

[0084] <Configuration (ii)>

[0085] When the volume resistivity of each domain is 1.0×10 1 Ω·cm or more and 1.0×10 4 Ω·cm or less, a state where the volume resistivity of each domain is sufficiently low can be ensured. As a result, while suppressing the accidental movement of charges in the matrix, the charge transport path can be restricted to a more effective path located between multiple domains.

[0086] Furthermore, the volume resistivity of each domain is more preferably 1.0×10 2 Ω·cm or less.

[0087] The volume resistivity of each domain is adjusted by using a conductive agent for the rubber component of the domain to set its conductivity to a predetermined value.

[0088] A rubber composition containing a rubber component for the matrix can be used as the rubber material for the domain. However, in this case, it is preferable to set the difference in solubility parameter (SP value) between the rubber material for the domain and the rubber material for forming the matrix within the following range to form the matrix - domain structure. That is, it is preferable to set the difference in SP value to be 0.4 (J / cm 3 ) 0.5 or more and 5.0 (J / cm 3 ) 0.5 or less, and, in particular, it is more preferable to set this difference to be 0.4 (J / cm 3 ) 0.5 or more and 2.2 (J / cm3 ) 0.5 as follows.

[0089] The volume resistivity of each domain can be adjusted by appropriately selecting the type and addition amount of the electronic conductive agent. The conductive agent for controlling the volume resistivity of each domain to 1.0×10 1 Ω·cm or more and 1.0×10 4 Ω·cm or less is preferably an electronic conductive agent, and the volume resistivity of the electronic conductive agent can be greatly changed from a high resistance to a low resistance according to its dispersion amount.

[0090] Examples of the electronic conductive agent to be compounded into each domain include: carbon black and graphite; oxides such as titanium oxide and tin oxide; metals such as Cu and Ag; and particles made conductive by covering their surfaces with oxides or metals. In addition, if necessary, two or more of these conductive agents can be used as a compound in an appropriate amount.

[0091] Among such electronic conductive agents as described above, conductive carbon black is preferably used because carbon black has a large affinity for rubber and the intermolecular distance of the electronic conductive agent is easily controlled. The type of carbon black to be compounded into each domain is not particularly limited, but using an electronic conductive agent with an average primary particle size of 50 nm or less can provide sufficient conductivity. The average primary particle size is more preferably 30 nm or less.

[0092] Relative to 100 parts by mass of the rubber component in the domain, an electronic conductive agent such as conductive carbon black is preferably compounded into each domain in an amount of 20 parts by mass or more and 150 parts by mass or less. A particularly preferred compounding ratio is 50 parts by mass or more and 100 parts by mass or less. When the conductive agent is compounded in such a ratio, it is preferred to compound the conductive agent in a larger amount compared to a normal electrophotographic conductive member. Therefore, the volume resistivity of each domain can be easily controlled within the range of 1.0×10 1 Ω·cm or more and 1.0×10 4 Ω·cm or less.

[0093] In addition, if necessary, fillers, processing aids, crosslinking aids, crosslinking accelerators, anti-aging agents, crosslinking accelerator aids, crosslinking retardants, softeners, dispersants, colorants, etc., which are usually used as compounding agents for rubber, can be added to the rubber composition for the domain to such an extent that the effects of the present invention are not hindered.

[0094] <Measurement method of volume resistivity of domain>

[0095] Except for changing the measurement site to the position corresponding to the domain and changing the applied voltage when measuring the measurement current value to 1 V, the volume resistivity of each domain can be measured by the same method as the measurement method of the volume resistivity of the above-mentioned matrix.

[0096] <Configuration (iii)>

[0097] When the distance between adjacent wall surfaces between domains (hereinafter sometimes referred to as "inter-domain distance") is 0.2 μm or more and 2.0 μm or less, the charge accumulated in the domains can be effectively supplied between the domains without the charge leaking from the domains to the matrix.

[0098] In addition, from the viewpoint of effectively supplying charge between domains, the inter-domain distance is preferably 2.0 μm or less. In addition, from the viewpoint of suppressing the leakage of charge to the matrix, the inter-domain distance is more preferably 0.3 μm or more.

[0099] <Method for measuring inter-domain distance>

[0100] The method for measuring the inter-domain distance can be carried out as described below.

[0101] First, a slice is produced by the same method as in the measurement of the volume resistivity of the above-mentioned matrix. Then, a fracture surface is formed by means such as, for example, freeze-fracture method, cross-polishing method or focused ion beam method (FIB). Considering the smoothness of the fracture surface and the pretreatment for observation, the FIB method is preferred. In addition, in order to obtain the difference in contrast between the domains and the matrix and the first conductive particles, it is preferable to stain the domains by a staining treatment.

[0102] The slice that has undergone the formation of the fracture surface and the pretreatment is observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) to confirm the presence of the matrix-domain structure.

[0103] In particular, from the viewpoint of the accuracy of quantification of the domain area, it is preferable to observe with an SEM at a magnification of 1,000 times to 100,000 times.

[0104] The measurement of the inter-domain distance is preferably carried out by quantifying the captured image of the fracture surface where the matrix-domain structure appears. The fracture surface image obtained by observing with an SEM is subjected to 8-bit grayscale conversion using image processing software (for example, "Luzex" (trade name, manufactured by Nireco Corporation)) to obtain a monochromatic image with 256 gray levels. Next, the black and white of the image is inverted so that the domains in the fracture surface become white and it is binarized. Next, the distance between the wall surfaces of the domain size group in the image is calculated. The distance between the wall surfaces at this time is the shortest distance between the closest domains.

[0105] In the case of a cylindrical charging member, when the length of the conductive layer in the longitudinal direction is represented by L and the thickness of the conductive layer is represented by T, cross-sections of the conductive layer in the thickness direction are obtained at three positions including the center in the longitudinal direction of the conductive layer and positions at L / 4 from both ends of the conductive layer toward the center. For each of the obtained cross-sections, a 50-μm square observation region is set at each of any three positions in the thickness region from the outer surface of the conductive layer to a depth of 0.1T to 0.9T toward the support. It is only necessary to measure the inter-domain distances observed in each of a total of nine observation regions. A slice is cut out in a direction in which a cross-section including a normal line starting from the central axis of the support can be observed, because it is necessary to observe the surface of the region including the region from the support to the outer surface of the conductive layer (the region corresponding to the charge movement direction).

[0106] <Configuration (iv)>

[0107] 90% or more of the number of the first conductive particles in the matrix exist as primary particles, and the distance between the first conductive particles in the matrix and the closest domain is 0.1 μm or more. This indicates that the first conductive particles in the matrix do not form a structure, and the first conductive particles in the matrix are not connected to the domain, and, for example, the first conductive particles are not connected to the domain, causing excessive charge movement. Therefore, charge can be accumulated in the domain.

[0108] Whether the first conductive particles do not form a structure in the matrix and whether the first conductive particles and the domain are not connected, causing significant charge movement, can also be determined by measuring the following impedance characteristics.

[0109] When measuring the impedance at a frequency of 1.0×10 -1 Hz with a DC voltage superimposed on an AC voltage, the impedance at a DC voltage of 0 V is defined as impedance A, and the impedance at a DC voltage of 10 V is defined as impedance B. The above determination is based on whether "impedance A / impedance B" is 60 or less. In the case where the first conductive particles form a structure in the matrix or in the case where the first conductive particles are connected to the domain, causing significant charge movement, when the DC voltage increases, it becomes difficult to accumulate charge in the domain. Therefore, impedance B when a DC voltage of 10 V is applied is significantly smaller than impedance A when no DC voltage is applied. As a result, "impedance A / impedance B" increases. The present inventors have determined that when impedance A / impedance B ≤ 60, sufficient charge can be accumulated in the domain. Here, impedance A is preferably 1.0×10 3 Ω to 1.0×10 8 Ω.

[0110] <Impedance measurement method>

[0111] When measuring impedance, in order to eliminate the influence of the contact resistance between the conductive member and the measurement electrode, a low-resistance thin film is deposited on the surface of the conductive member, and the thin film is used as the electrode and the conductive support is used as the ground electrode, and the impedance is measured with two terminals.

[0112] As a method for forming the thin film, a method for forming a metal film can be given, such as metal evaporation, sputtering, coating of a metal paste, and attachment of a metal strip. Among them, from the viewpoint of reducing the contact resistance with the conductive member, a method of forming a metal thin film such as platinum or palladium as the electrode by evaporation is preferred.

[0113] When forming a metal thin film on the surface of the conductive member, in consideration of simplicity and uniformity of the thin film, it is preferable to provide a vacuum evaporation apparatus having a mechanism capable of holding the charging member. In addition, for a conductive member having a cylindrical cross-section, it is preferable to use a vacuum evaporation apparatus further provided with a rotation mechanism.

[0114] For a conductive member having a cross-section composed of a curved surface such as a circular shape, for example, a cylindrical conductive member, it is difficult to connect the above-mentioned metal thin film used as the measurement electrode and the impedance measurement device. Therefore, it is preferable to use the following method. Specifically, it is suitable to perform the measurement as follows: a metal thin film electrode having a width of about 10 mm to about 20 mm in the length direction of the conductive member is formed, and then the metal sheet is wound without a gap, and the metal sheet is connected to the measurement electrode from the measurement device. Thereby, an electric signal from the conductive layer of the conductive member can be appropriately obtained by the measurement device, and impedance measurement can be performed. When measuring impedance, the metal sheet only needs to be a metal sheet having a resistance value equivalent to that of the metal portion of the connection cable of the measurement device, and, for example, aluminum foil or a metal strip can be used.

[0115] The impedance measurement device only needs to be a device capable of measuring impedance in a frequency region up to 1.0×10 7 Hz, such as an impedance analyzer, a network analyzer, or a spectrum analyzer. In consideration of the resistance region of the conductive member, among these devices, it is preferable to perform the measurement with an impedance analyzer.

[0116] The measurement conditions of the impedance are described. The impedance in the frequency region of 1.0×10 -1 Hz is measured with an impedance measurement device. The measurement is performed in an environment where the temperature is 23°C and the humidity is 50%RH. In order to reduce measurement variations, it is preferable to set 5 or more measurement points for each order of magnitude of the frequency. In addition, the amplitude of the AC voltage is 1V.

[0117] Regarding measuring voltage, first, measure using only AC voltage without applying any DC voltage, and then, measure while applying a DC voltage to be superimposed on the above AC voltage. The DC voltage to be superimposed is preferably 10V. This is because the common voltage applied to the charging roller in a general electrophotographic image forming apparatus is about 10V.

[0118] <(v) constitution>

[0119] In the present invention, the domain highly filled with the second conductive particles accumulates charges on the interface side with the matrix in the domain. However, as described above, the first conductive particles existing in the state of primary particles in the matrix hardly accumulate charges. Therefore, the common voltage applied to each of the first rubber in the matrix and the domain is increased. Thus, after discharging the charges on the surface of the charging member, the charges accumulated in the domain can be quickly supplied. As a result, excessive charge movement can be prevented by preventing discharge omission in the high-frequency region. In addition, the charges carried by the dirt substances being overcharged can quickly escape to the conductive substrate side. Thereby, the appearance of white dot images can be prevented.

[0120] When the number of the first conductive particles in the matrix is represented by N(A) and the number of domains is represented by N(B), it is preferable that N(A) / N(B) is 0.2 to 3.0. When N(A) / N(B) is less than 0.2, the number of the first conductive particles is insufficient, and thus the above effects cannot be fully obtained. In addition, when N(A) / N(B) exceeds 3.0, since the number of the first conductive particles is large, the proportion of the first conductive particles existing as primary particles described in (iv) constitution decreases, and the region where the domain is connected to the first conductive particles easily appears. N(A) / N(B) is more preferably 0.35 to 0.70.

[0121] In the present invention, it is more desirable to satisfy the following impedance characteristics.

[0122] <First requirement>

[0123] The slope of the impedance at a frequency of 1.0×10 5 Hz to 1.0×10 6 Hz (hereinafter sometimes referred to as "the slope of the high-frequency impedance") is -0.8 or more.

[0124] <Second requirement>

[0125] The impedance at a frequency of 1.0×10 -2 Hz to 1.0×10 1 Hz (hereinafter sometimes referred to as "the low-frequency impedance") is 1.0×10 3 Ω or more and 1.0×10 8 Ω or less.

[0126] The equivalent circuit of the conductive member is represented by a parallel circuit of a resistor R and a capacitance C, and the absolute value Z of the impedance can be expressed by the following formula (1).

[0127] [Mathematical formula 1]

[0128]

[0129] The first requirement indicates that almost no charge stagnation occurs in the conductive member on the high-frequency side. It can be speculated that the movement of charges cannot follow the high-frequency voltage and the state of stagnation is the so-called insulating capacitance state where the measured resistance value R increases significantly. The state of charge stagnation can be considered as the state where R in formula (1) is approximately infinite, and the following approximation can be made: in the following formula (2) obtained by extracting the elements of the denominator of formula (1), R -2 compared to (2πf) 2 C 2 has a very small value. Therefore, formula (1) can be approximately transformed by applying the approximation into the following formula (3) (removing R -2 from it). Finally, when an equation transformation of taking the logarithm of both sides of formula (3) is performed, the following formula (4) is obtained and the slope of logf becomes -1.

[0130] [Mathematical formula 2]

[0131] R -2 +(2πf) 2 C 2 (2)

[0132]

[0133] log|Z| = -logf - log(2πC) (4)

[0134] In other words, the case where the slope of the high-frequency impedance is -1 means that the movement of charges cannot follow the high-frequency voltage. In this case, the supply of charges for discharging cannot follow the discharge frequency, resulting in a moment when discharging cannot be performed. The occurrence of the moment when discharging cannot be performed means that the accumulated charges may move all at once at the subsequent discharging moment. When a large amount of charges move all at once, over-discharge may be induced.

[0135] Meanwhile, in such a conductive member where the slope of the high-frequency impedance is -0.8 or more, the supply of charge hardly stagnates on the high-frequency side. As a result, charge supply can be performed with respect to discharge at frequencies from the low-frequency region where the impedance has a constant value to the high-frequency region, particularly discharge on the high-frequency side where charge stagnation is likely to occur. Charge supply can be sufficiently achieved, so discharge omission does not occur. The one-time movement of charge is suppressed, so over-discharge can be suppressed.

[0136] It is considered that the high-frequency region corresponds to the region where discharge omission is likely to occur because this range is the highest-frequency region where discharge occurs among the frequencies at which discharge occurs in the conductive member.

[0137] In other words, this range is the region where discharge omission is likely to occur and over-discharge is likely to be induced immediately thereafter at the discharge time. When the slope shows a value within the above range exceeding -1 in such a frequency region, the occurrence of over-discharge caused by discharge omission can be suppressed.

[0138] Regarding the measurement frequency region of the high-frequency impedance, the present inventors consider that in the case of combining an electrophotographic charging roller used as a charging member and a photosensitive drum, the normal discharge frequency is predicted to fall within such a range as described below.

[0139] The discharge region along the moving direction of the surface of the charging roller, which is set to face the outer surface of the photosensitive drum and rotates synchronously with the photosensitive drum, is set to 0.5 mm to 1 mm. When assuming that the processing speed of the electrophotographic image forming apparatus is 100 mm / second to 500 mm / second at maximum, the time for the surface of the photosensitive drum to pass through the discharge region is 1.0×10 -3 seconds to 1.0×10 -2 seconds or more. In addition, when observing the discharge in detail, the length of the discharge region for a single discharge is 0.01 mm to 0.1 mm, so it is estimated that at least 5 to 100 discharges occur during the same point on the surface of the charging roller passing through the discharge region. Therefore, it is estimated that the frequency of discharge caused by the charging roller falls within the range of several Hz to 1.0×10 6 Hz. As the processing speed becomes higher, it is necessary to increase the number of discharges by making the discharge frequency higher. Therefore, it is considered that control of the discharge and conduction mechanism is important in the above range, particularly in the high-frequency region of, for example, 1.0×10 5 Hz to 1.0×10 6 Hz.

[0140] The low-frequency impedance of the second requirement represents such a characteristic that charge hardly stagnates. When the frequency is approximated to 0, the absolute value of the impedance can be approximated to the resistance value R. Therefore, it is found that the resistance value R represents the ability when charge moves in a single direction.

[0141] Therefore, it can be assumed that the measurement simulation synchronized with the application of the low-frequency voltage measures the amount of charge movement in a state where the movement of the charge can follow the vibration of the voltage.

[0142] The amount of charge movement at low frequencies is an index of the ease of charge movement between the charging member and the measurement electrode. In addition, this amount can be used as an index of the amount of charge that moves from the surface of the charging member to the photosensitive drum by discharging.

[0143] The amplitude of the alternating voltage to be used for impedance measurement is 1 V. Considering the fact that the voltage actually applied to the charging member in an electrophotographic image forming apparatus is several hundreds of volts to several thousands of volts, the vibration voltage for measurement is significantly low. Therefore, it is considered that the measurement of impedance according to the first requirement and the second requirement enables the ease of discharge from the surface of the charging member to be evaluated at a higher level.

[0144] When the low-frequency impedance is lower than 1.0×10 3 Ω, the amount of primary discharge may become too large and induce over-discharge when the dirt substance is overcharged.

[0145] Meanwhile, when the low-frequency impedance exceeds 1.0×10 8 Ω, the discharge performance is reduced, and when a dirt substance is present on the surface of the charging member, a sufficient amount of charge cannot be applied to the photosensitive member, and as a result, a difference in the amount of discharge occurs according to the difference in the amount of the dirt substance. Therefore, in some cases, the uneven deposition amount of the dirt substance is manifested as uneven potential of the photosensitive member.

[0146] Figure 4 Shows the change of the absolute value Z (Ω) of the impedance with respect to the frequency "f" (Hz). As Figure 4 shown, in the charging member, the absolute value of the impedance has a constant value in the low-frequency region. The impedance at 1.0×10 -2 Hz to 1.0×10 1 Hz can be replaced by the value of the impedance at a frequency of 0.1 Hz, for example.

[0147] The conductive member according to the present invention can be formed by a method including, for example, the following steps (a) to (d):

[0148] Step (a): A step of preparing a domain-forming rubber mixture (hereinafter also referred to as "CMB") containing second conductive particles and a second rubber;

[0149] Step (b): A step of preparing a matrix-forming rubber mixture (hereinafter also referred to as "MRC") containing first conductive particles and a first rubber;

[0150] Step (c): a step of kneading CMB and MRC to prepare a rubber mixture having a matrix - domain structure; and

[0151] Step (d): a step of directly forming the rubber composition prepared in step (c) on a conductive support or via any other layer, and then curing the layer of the rubber composition to form a conductive layer according to the present invention.

[0152] As described above, MRC contains a first rubber and first conductive particles.

[0153] <First rubber>

[0154] The compounding ratio of the first rubber is the largest in the rubber mixture for forming the conductive layer, and the cross - linked product of the first rubber dominates the mechanical strength of the conductive layer. Therefore, a rubber that exhibits the required strength for an electrophotographic conductive member in the conductive layer after cross - linking is used as the first rubber.

[0155] Preferred examples of the first rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene - butadiene rubber (SBR), butyl rubber (IIR), ethylene - propylene rubber (EPM), ethylene - propylene - diene terpolymer rubber (EPDM), chloroprene rubber (CR), acrylonitrile - butadiene rubber (NBR), hydrogenated product of NBR (H - NBR), epichlorohydrin homopolymer, epichlorohydrin - ethylene oxide copolymer, epichlorohydrin - ethylene oxide - allyl glycidyl ether terpolymer, and silicone rubber.

[0156] In addition, if necessary, fillers, processing aids, cross - linkers, cross - link accelerators, or anti - aging agents, etc. can be added.

[0157] <First conductive particles>

[0158] Examples of the first conductive particles include carbon black and conductive metal oxides such as titanium oxide. However, as described above, in order to accumulate a sufficient amount of charge in the domains, the conductive particles need to exist in the state of primary particles without forming a structure. For example, in the case of carbon black, carbon black having a large primary particle size and a small DBP absorption amount is preferably selected.

[0159] The primary particle size of the carbon black preferably satisfying the above characteristics is 200 nm or more, and the DBP absorption amount is less than 40 cm 3 / 100 g. A specific example thereof is MT carbon.

[0160] The DBP absorption is the volume of dibutyl phthalate (DBP) that can be absorbed by 100 g of carbon black, and is measured in accordance with JIS K 6217. The carbon black has a hierarchical structure in which primary particles are aggregated into clusters (hereinafter referred to as "structure"), and the degree of the structure is quantified by the DBP absorption (cm 3 / 100 g).

[0161] The primary particle size of the conductive metal oxide is preferably 200 nm or more.

[0162] <Measurement method of the primary particle size of the first conductive particles>

[0163] The primary particle size of the first conductive particles can be observed by the method described in the above-described method for identifying the first conductive particles. For the calculation of the particle size, adjustment is performed by binarization processing or the like so that the first conductive particles become white and the matrix polymer part becomes black, and image processing software is used to calculate the particle size. When the length of the conductive layer of the conductive member in the longitudinal direction is represented by L, the sampling positions of the slices are a total of three positions including the center of the conductive layer in the longitudinal direction and two positions at L / 4 from both ends of the conductive layer toward the center. Slices are cut out from each of these three positions. When the thickness of the conductive layer is represented by T, the measurement positions are a total of nine positions including any three positions in the matrix part in the thickness region from the outer surface of each slice to a depth of 0.1T to 0.9T. For these nine positions, the particle sizes of all the first conductive particles are calculated, and the arithmetic mean thereof is adopted as the average particle size of the first conductive particles.

[0164] As described above, the domains each contain the second rubber and the second conductive particles.

[0165] <Second rubber>

[0166] Specific examples of the second rubber are at least one selected from the group consisting of natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), silicone rubber, and polyurethane rubber (U).

[0167] <Second conductive particles>

[0168] Examples of the second conductive particles include: carbon materials such as conductive carbon black and graphite; and metal oxides such as titanium oxide and tin oxide. Two or more of these conductive particles can be appropriately compounded. In addition, the second conductive particles to be compounded into each domain are preferably added in an amount such that the ratio of the cross-sectional area of the conductive particles to the cross-sectional area of the domain is at least 20% or more, preferably 25% or more. There is no particular limitation on the upper limit of the ratio of the cross-sectional area of the conductive particles to the cross-sectional area of the domain, but it is preferably 30% or less.

[0169] Conductive carbon black is appropriately used as the second conductive particles to be compounded into each domain because carbon black has high conductivity efficiency and high affinity for rubber, and the distance between the conductive particles can be easily controlled.

[0170] There is no particular limitation on the type of conductive carbon black to be compounded into each domain. Specific examples thereof include furnace black, oil furnace black, thermal black, lamp black, acetylene black, and Ketjen black. However, from the viewpoint of the above charge supply, it is preferable that the primary particle size of the carbon black is 50 nm or less and the DBP oil absorption amount is 40 cm 3 / 100 g or more and 170 cm 3 / 100 g or less.

[0171] It is also preferable that the primary particle size of the conductive metal oxide such as titanium oxide or tin oxide is 50 nm or less.

[0172] <Process Cartridge>

[0173] Figure 5 FIG. is a schematic cross-sectional view of an electrophotographic process cartridge including the conductive member according to the present invention as a charging roller. The process cartridge is formed by integrating a developing device and a charging device, and is detachably mounted to the main body of an electrophotographic image forming apparatus. The developing device is obtained by integrating at least a developing roller 53 and a toner container 56, and may include, as needed, a toner supply roller 54, toner 59, a developing blade 58, and a stirring blade 510. The charging device is obtained by integrating at least a photosensitive drum 51 and a charging roller 52, and may include a cleaning blade 55 and a waste toner container 57. A non-cleaning configuration is a state in which the cleaning blade 55 and the waste toner container 57 are not present. A voltage is applied to each of the charging roller 52, the developing roller 53, the toner supply roller 54, and the developing blade 58. The charging roller 52, which is a charging member, is arranged so as to be able to charge the photosensitive drum 51, which is an electrophotographic photosensitive member.

[0174] <Electrophotographic Image Forming Apparatus>

[0175] Figure 6Schematic configuration diagram of an electrophotographic image forming apparatus using the electroconductive member according to the present invention as a charging roller. The electrophotographic image forming apparatus includes an electrophotographic photosensitive member, a charging device, a latent image forming device, a developing device, a transfer device, a cleaning device, a fixing device, and the like. The charging device charges the electrophotographic photosensitive member. The latent image forming device exposes the electrophotographic photosensitive member to form an electrostatic latent image. The developing device develops the electrostatic latent image into a toner image. The transfer device transfers the toner image onto a transfer material. The cleaning device recovers the residual transferred toner on the electrophotographic photosensitive member. The fixing device fixes the toner image onto the transfer material. In the case of a configuration without a cleaner, this configuration does not have any cleaning device configured to recover transfer residues. An electrophotographic roller according to the present invention can be used as the electrophotographic roller included in the charging device of the electrophotographic image forming apparatus. The electrophotographic roller as a charging member is arranged so as to be able to charge the electrophotographic photosensitive member.

[0176] The electrophotographic photosensitive member 62 is a rotary drum type having a photosensitive layer on a conductive substrate. The electrophotographic photosensitive member 62 is rotationally driven in the arrow direction at a predetermined circumferential speed (processing speed). The charging device includes a contact charging roller 61 that is arranged in contact with the electrophotographic photosensitive member 62 with a predetermined pressing force. The charging roller 61 is configured to perform such rotational driving so as to rotate as the electrophotographic photosensitive member 62 rotates. When a predetermined DC voltage is applied from a charging power source 69 to the charging roller 61, the charging roller 61 charges the electrophotographic photosensitive member 62 to a predetermined potential. For example, an exposure device such as a laser beam scanner is used as the latent image forming device (not shown) configured to form an electrostatic latent image on the electrophotographic photosensitive member 62. The uniformly charged electrophotographic photosensitive member 62 is irradiated with exposure light 67 corresponding to image information to form an electrostatic latent image.

[0177] The developing device includes a developing sleeve or a developing roller 63 arranged close to or in contact with the electrophotographic photosensitive member 62. The developing device develops the electrostatic latent image into a toner image by using toner that has been electrostatically treated to have the same polarity as the charging polarity of the electrophotographic photosensitive member 62, by reverse development. The transfer device includes a contact transfer roller 64. The toner image is transferred from the electrophotographic photosensitive member 62 onto a transfer material such as plain paper. The transfer material is conveyed by a paper feeding system including a conveying member.

[0178] The cleaning device includes a blade type cleaning member 66 and a recovery container 68.

[0179] After transferring the developed toner image onto the transfer material, the cleaning device mechanically scrapes and recovers the transfer residual toner remaining on the electrophotographic photosensitive member 62. When using a developing while cleaning system involving recovering the transfer residual toner with a developing device, the cleaning device can be omitted. The toner image transferred onto the transfer material passes through the gap between the fixing belt 65 heated by a heating device (not shown) and the roller arranged to face the fixing belt 65, and is thereby fixed onto the transfer material.

[0180] Example

[0181] Specific examples and comparative examples according to the present invention are described below. The conductive members in the examples and comparative examples of the present invention are produced using the materials shown in Table 1.

[0182] [Table 1]

[0183]

[0184] The term "phr" in the table shown below is an abbreviation of "per hundred rubber", which represents the compounding amount relative to 100 parts by mass of rubber. In Examples 1 to 30 and Comparative Examples 1 to 4 below, the charging rollers of Examples 1 to 30 are respectively referred to as "charging roller 1" to "charging roller 30", and the charging rollers of Comparative Examples 1 to 4 are respectively referred to as "charging roller 31" to "charging roller 34".

[0185] (Example 1)

[0186] 1. Preparation of the uncured rubber composition for forming the conductive layer to be used for forming the conductive layers according to the examples and comparative examples

[0187] [1-1. Preparation of the carbon masterbatch (CMB) for domain formation]

[0188] Each material of the types and compounding amounts shown in Table 2 was mixed using a 6-liter pressure kneader (trade name: TD6-15MDX, manufactured by Toshin Co., Ltd.) to provide the CMB for domain formation. The mixing conditions were set to a filling rate of 70% by volume, a blade rotation speed of 30 rpm, and 16 minutes.

[0189] [Table 2]

[0190]

[0191] [1-2. Preparation of the rubber composition (MRC) for matrix formation]

[0192] Mix the materials of the types and compounding amounts shown in Table 3 using a 6-liter pressure kneader (trade name: TD6-15MDX, manufactured by Toshin Co., Ltd.) to provide a rubber composition for forming a matrix. Set the mixing conditions to a filling rate of 70% by volume, a blade rotation speed of 30 rpm, and 16 minutes.

[0193] [Table 3]

[0194]

[0195] [1-3. Preparation of Unvulcanized Rubber Composition for Forming Conductive Layer]

[0196] Mix the materials of the types and compounding amounts shown in Table 4 using an open mill to prepare a rubber composition for forming a conductive resin layer. Use an open mill with a roll diameter of 12 inches as the mixer. The mixing is carried out under the following conditions: The mixture is cut bilaterally with a front roll speed of 10 rpm, a rear roll speed of 8 rpm, and a roll nip of 2 mm for a total of 20 times, and then passed through the nip at 1.0 mm for 10 times.

[0197] [Table 4]

[0198]

[0199] 2. Production of Conductive Member

[0200] [2-1. Formation of Conductive Layer]

[0201] Prepare a mandrel with a total length of 252 mm and an outer diameter of 6 mm, which has been electroless nickel-plated on the surface of free-cutting steel, as a support. Use the mandrel as a support for the conductive mandrel. Apply an adhesive (trade name: METALOC U-20, manufactured by Toyokagaku Kenkyusho Co., Ltd.) to the entire circumference within a range of 230 mm except for 11 mm from each end of the mandrel using a roll coater. In this example, use the mandrel coated with the adhesive as the conductive support.

[0202] Next, install a die with an inner diameter of 10.0 mm at the front end of a crosshead extruder including a supply mechanism for the conductive support and a discharge mechanism for the unvulcanized rubber roll. Adjust the temperatures of the extruder and the crosshead to 100 °C, and adjust the conveying speed of the conductive support to 60 mm / second. Under these conditions, supply the rubber composition for forming a conductive resin layer from the extruder, and the outer peripheral portion of the conductive support is covered with the rubber composition for forming a conductive resin layer within the crosshead. Thus, an unvulcanized rubber roll is obtained.

[0203] Next, the unvulcanized rubber roller is put into a hot air vulcanizing furnace at 170°C and heated for 60 minutes to vulcanize the unvulcanized rubber composition. Thus, a conductive roller having a conductive resin layer formed on the outer peripheral portion of the conductive support is obtained. Thereafter, both ends of the conductive resin layer are each cut off by 10 mm to set the length of the conductive resin layer portion in the length direction to 232 mm.

[0204] [2-2. Grinding of the conductive layer]

[0205] Next, the surface of the conductive layer is ground under the grinding conditions described in the following Grinding Condition 1. Thus, a charging roller 1 having a crown shape is obtained, where the diameter of the central portion is 8.5 mm, and the diameter at each position 90 mm from the central portion toward both end portions is 8.44 mm.

[0206] (Grinding Condition 1)

[0207] Prepare a cylindrical grinding stone with a diameter of 305 mm and a length of 235 mm (manufactured by TEIKEN Corporation). The type, grain size, bond strength, binder, and structure (abrasive grain ratio) of the abrasive grains are as described below.

[0208] · Abrasive grain material: green silicon carbide (GC), (JIS R6111-2002)

[0209] · Grain size of the abrasive grains: #80 (average particle size: 177 μm JIS B4130)

[0210] · Bond strength of the abrasive grains: HH (JIS R6210)

[0211] · Binder: V4PO (vitrified)

[0212] · Structure of the abrasive grains (abrasive grain ratio): 23 (content rate of the abrasive grains: 16%, JIS R6242)

[0213] The grinding conditions are as described below. Set the rotational speed of the grinding stone to 2,100 rpm, and set the rotational speed of the conductive member to 250 rpm. In the rough grinding process, after the grinding stone contacts the outer peripheral surface of the conductive member, penetrate the conductive member at a penetration speed of 20 mm / second by 0.24 mm. In the precision grinding process, change the penetration speed to 0.5 mm / second, and penetrate the grinding stone by 0.01 mm. Thereafter, separate the grinding stone from the conductive member to complete the grinding.

[0214] As the grinding method, an up-cut method in which the rotational directions of the grinding stone and the conductive member are set to the same direction is adopted.

[0215] 3. Characteristic evaluation

[0216] [3-1. Confirmation of the presence or absence of the matrix-domain structure]

[0217] The presence of the matrix-domain structure in the conductive layer is confirmed by the following method.

[0218] A section (thickness: 500 μm) is cut out with a razor blade so that a cross-section perpendicular to the length direction of the conductive layer of the conductive member can be observed. Next, platinum is vapor-deposited on the surface of the cross-section of the section corresponding to the conductive layer. The platinum-vapor-deposited surface of the section is photographed at a magnification of 5,000 times with a scanning electron microscope (SEM) (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image. In the SEM image, when a structure in which a plurality of domains are dispersed in the matrix and the matrixes are connected to each other is confirmed, the matrix-domain structure is determined to be "present".

[0219] [3-2. Measurement of the volume resistivity of the matrix]

[0220] The volume resistivity of the matrix is measured in contact mode with a scanning probe microscope (SPM) (trade name: Q-Scope 250, manufactured by Quesant Instrument Corporation) as described below. The measurement is carried out in an environment where the temperature is 23°C and the relative humidity is 50%.

[0221] First, a section with a thickness of about 2 μm is cut out from the conductive layer of the charging roller 1 at a cutting temperature of -100°C using a microtome (trade name: Leica EM FCS, manufactured by Leica Microsystems). Next, the section is placed on a metal plate so that one side of the cross-section of the section corresponding to the conductive layer is in contact with the surface of the metal plate. Then, the cantilever of the SPM is brought into contact with the portion of the section corresponding to the matrix on the opposite side of the surface in contact with the surface of the metal plate. Next, a voltage of 50 V is applied to the cantilever, and the current value is measured.

[0222] In addition, the surface shape of the section is observed with the SPM, and the thickness of the measurement point is calculated from the obtained height profile. In addition, from the observation result of the surface shape, the area of the concave portion of the contact portion of the cantilever is calculated. The volume resistivity is calculated from the thickness and the concave portion area and used as the volume resistivity of the matrix.

[0223] [3-3. Measurement of the volume resistivity of the domain]

[0224] The volume resistivity of the domain is measured in the same manner as the method for measuring the volume resistivity of the matrix in Section 3-2 above, except that the contact position of the cantilever is set to the portion corresponding to the domain and the voltage applied to the cantilever is set to 1 V. The average value of the values at each measurement site is calculated.

[0225] [Measurement of inter-domain distance]

[0226] The sections prepared in the measurement of the volume resistivity of the substrate in Section 3-2 above are stained with phosphotungstic acid for only the second rubber in each domain. Thereafter, platinum is vapor-deposited on the surface corresponding to the cross-section of the conductive layer. Next, an SEM image (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) is taken at a magnification of 10,000 times of the platinum vapor-deposited surface.

[0227] Next, the SEM image is subjected to 8-bit grayscale conversion using an image processing analyzer (trade name: LUZEX-AP, manufactured by Nireco Corporation) to obtain a monochromatic image with 256 gray levels. Next, for the binary image, the black and white of the image are inverted so that the stained domains in the monochromatic image become white, and a binary threshold is set for the brightness distribution of the image based on the algorithm of Otsu's discriminant analysis method to thereby obtain a binary image. In the binary image, when the thickness of the conductive layer is represented by T, in each of the 3 sections, in any 3 positions (i.e., a total of 9 positions) in the region corresponding to the thickness region from the outer surface to a depth of 0.1T to 0.9T, an observation region of 15 μm square is set. The inter-domain distance is calculated in each observation region, and the average value of the inter-domain distance measurement values in the observation regions at a total of 9 positions is calculated.

[0228] [Measurement of the proportion of the first conductive particles present as primary particles]

[0229] Using the SEM image obtained in the measurement of the inter-domain distance in Section 3-4 above, the number N of the first conductive particles dispersed in the substrate and the number N(C) of the particles among the first conductive particles that have no interface within the particles are counted. The proportion of the first conductive particles present as primary particles is calculated by (N(C) / N)×100.

[0230] [Measurement of the average primary particle diameter of the first conductive particles]

[0231] In the SEM image analyzed in the measurement of the proportion of the first conductive particles present as primary particles in Section 3-5 above, the average diameter of the particles present as primary particles is calculated.

[0232] The observed image was 8-bit grayscale processed using the image processing software "Image-pro plus" (trade name, manufactured by Media Cybernetics, Inc.) to obtain a monochromatic image with 256 gray levels. Next, the black and white of the image were inverted to make the domains in the monochromatic image white, and a binarization threshold was set for the brightness distribution of the image based on the algorithm of Otsu's discriminant analysis method to thereby obtain a binarized image. Next, an observation region of the size of one first conductive particle in the accommodating matrix was extracted from the obtained binarized image. Then, by using a counting function, the cross-sectional area S1 of the first conductive particle was calculated, and the average primary particle diameter d1 was calculated by d1 = (S1 / 2π) 0.5 The average primary particle diameter d1 was calculated.

[0233] [Measurement of the average distance between the first conductive particle and the closest domain]

[0234] In the same manner as in the measurement of the volume resistivity of the matrix in Section 3-2 above, a slice with a thickness of about 2 μm was cut from the conductive layer of the charging roller 1 at a cutting temperature of -100°C using a slicer (trade name: Leica EM FCS, manufactured by Leica Microsystems). Thereafter, platinum was vapor-deposited on the surface corresponding to the cross-section of the conductive layer. Next, the platinum vapor-deposited surface was photographed at a magnification of 10,000 times with an SEM (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image.

[0235] Next, the SEM image is subjected to 8-bit grayscale conversion using an image processing analyzer (trade name: LUZEX-AP, manufactured by Nireco Corporation) to obtain a monochromatic image with 256 gray levels. For the binary image, the black and white of the image are inverted so that the domains and the first conductive particles in the monochromatic image become white, and a binary threshold is set based on the algorithm of Otsu's discriminant analysis method to thereby obtain a binary image. In the binary image, when the thickness of the conductive layer is represented by T, in each of the three slices, in any three positions (i.e., a total of nine positions) in the region corresponding to the thickness region from the outer surface to a depth of 0.1T to 0.9T, an observation region of 15 μm square is set. In each observation region, the positions of the first conductive particles are determined from the observation image before binarization, and only the distances between the first conductive particles and the domains adjacent to them are calculated. For one first conductive particle, the distances to a plurality of adjacent domains are calculated, but the shortest distance among them is taken as the distance between the first conductive particle and the closest domain. The same measurement is performed on all the first conductive particles in the above observation regions, and then their average value is calculated. Thus, the average distance between the first conductive particles and the closest domains is calculated.

[0236] [Measurement of the ratio of the first conductive particles to the domains]

[0237] Using the SEM image obtained in the measurement of the volume resistivity of the substrate in Section 3-2 above, the number N(B) of domains present in the observation image region and the number N(A) of the first conductive particles present therein are counted. Then, N(A) / N(B) is calculated as the ratio of the first conductive particles to the domains.

[0238] [Measurement of the cross-sectional area ratio of the second conductive particles in the domains]

[0239] A slice having a thickness of about 100 nm is cut from the conductive layer of the charging roller 1 at a cutting temperature of -100°C using a microtome (trade name: Leica EM FCS, manufactured by Leica Microsystems), and platinum is evaporated on the surface corresponding to the cross-section of the conductive layer. Next, the platinum-evaporated surface is photographed at a magnification of 20,000 times with an SEM (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image.

[0240] Next, binarization is performed using the image processing software "Image-pro plus" (trade name, manufactured by MediaCybernetics, Inc.) so that the carbon black in the domain can be distinguished. Next, an observation region that accommodates the size of one domain is extracted from the obtained binarized image. Further, by using a counting function, the cross-sectional area S of the domain and the cross-sectional area Sc of the carbon black serving as the second conductive particles contained in the domain are calculated, and the cross-sectional area ratio of the second conductive particles in the domain is calculated by Sc / S.

[0241] [3-10. Measurement of the equivalent circular diameter of the second conductive particles in the domain]

[0242] Using the cross-sectional area S of the domain measured in Section 3-9 above, the equivalent circular diameter D of the domain is calculated by D = (S / 2π) 0.5 to calculate the equivalent circular diameter D of the domain.

[0243] [3-11. Measurement of the primary particle size of the second conductive particles]

[0244] The section used for measuring the cross-sectional area ratio of the second conductive particles in the domain in Section 3-9 above is used and photographed at a magnification of 50,000 times with a TEM (trade name: JEM-2800, manufactured by JEOL Ltd.) to obtain a TEM image. The observation region is set to include the domain portion.

[0245] Next, binarization is performed using the image processing software "Image-pro plus" (trade name, manufactured by MediaCybernetics, Inc.) so that the carbon black serving as the second conductive particles in the domain can be distinguished. Then, by using a counting function, the primary particle size of the second conductive particles is calculated, and its average value is taken as the primary particle size of the second conductive particles.

[0246] [3-12. Measurement of the charge decay rate on the surface of the charging roller]

[0247] The surface potential of the charging roller based on corona discharge is measured using a charge amount measuring device (trade name: DRA-2000L, manufactured by QEA). Specifically, the corona discharger of the charge amount measuring device is configured so that the gap between the grid portion and the surface of the charging roller becomes 1 mm. Next, a voltage of 8 kV is applied to the corona discharger to cause discharge, thereby charging the surface of the charging roller, and the surface potential of the charging roller immediately after the discharge is completed and immediately after the discharge is completed and after 10 seconds is measured. The surface potential immediately after the discharge is completed (or immediately after charging) is represented by E0, and the surface potential after 10 seconds from the completion of the discharge (or the completion of charging) is represented by E 10 is represented, and the charge decay rate Q is calculated by the following formula (5). The charge decay rate Q is preferably 83% or more.

[0248] [Mathematical formula 3]

[0249]

[0250] [3-13. Impedance measurement]

[0251] As a pretreatment, while rotating the roller, platinum is vapor-deposited on the outer surface of the charging roller to produce a measurement electrode. In this case, an electrode with a width of 1.5 cm and uniform along the circumferential direction is produced by using a masking tape. By forming the electrode, the contribution of the contact area between the measurement electrode and the conductive member can be minimized by the surface roughness of the charging roller.

[0252] Next, an aluminum sheet is wound around the electrode without any gaps, and the electrode is connected from the aluminum sheet to the measurement electrode of an impedance measurement device (trade names: Solartron 1260 and Solartron 1296, manufactured by Solartron).

[0253] Figure 7 Schematic diagram of the state where the measurement electrode is formed on the charging roller. In Figure 7 , the conductive support 71, the conductive layer 72 having a matrix-domain structure, the platinum vapor-deposited layer 73, and the aluminum sheet 74 are shown.

[0254] Figure 8 Cross-sectional view of the state where the measurement electrode is formed on the charging roller. The conductive support 81, the conductive layer 82 having a matrix-domain structure, the platinum vapor-deposited layer 83, and the aluminum sheet 84 are shown. As Figure 8 shown in, it is important to establish a state where the conductive layer having a matrix-domain structure is clamped between the conductive support 81 and the measurement electrode.

[0255] Then, the aluminum sheet is connected to the measurement electrode on the side of the impedance measurement device (Solartron 1260 and Solartron 1296, manufactured by Solartron). By using the conductive support and the aluminum sheet as the two electrodes for measurement, impedance measurement is performed.

[0256] In an environment with a temperature of 23 °C and a relative humidity of 50%, at an AC voltage of 1 Vpp and a frequency of 1.0×10 -2 Hz to 1.0×10 7 Hz, impedance measurement is performed (when the frequency changes by one order of magnitude, it is measured at 5 points) to obtain the absolute value of the impedance. Then, by using the measurement results, a graph is plotted by double logarithmic plotting of the absolute value of the impedance and the frequency. From the graph, the impedance Z0 at a frequency of 1.0×10 -2 Hz to 1.0×10 1 Hz and 1.0×10 5Hz to 1.0×10 6 The slope of the impedance at Hz.

[0257] Next, the same measurement is performed while applying a DC voltage of 10 V to superimpose on the AC voltage of 1 V, and the impedance Z is calculated 10 is calculated, and Z0 / Z representing the influence degree of the DC voltage is calculated 10 .

[0258] 4. Image evaluation

[0259] The following evaluation is performed to confirm the stain resistance performance of the charging roller 1 under high-life conditions.

[0260] First, a laser printer (product name: Laser Jet Pro M203dw, manufactured by Hewlett-Packard Company) of an electrophotographic system is prepared as an electrophotographic image forming apparatus. In order to perform the evaluation during the high-speed process, the laser printer is modified so that the number of sheets output per minute becomes 75 sheets / min for A4 size paper, which is larger than the original output number. The output speed of the recording medium at this time is set to 370 mm / second.

[0261] Next, for the purpose of adapting to the evaluation environment, the charging roller 1, the electrophotographic image forming apparatus, and the processing cartridge are left standing in an environment of 15°C / 30%RH for 48 hours.

[0262] The charging roller 1 that has been left standing in the above environment is set as the charging roller of the processing cartridge and assembled into the laser printer. Thereafter, in the same environment, image output is continuously performed for a total of 50,000 sheets.

[0263] The output image is as follows: The letter "E" with a size of 4 dots is formed on A4 size paper so that the printing rate is 1.0%.

[0264] Thereafter, a halftone image (an image in which horizontal lines with a width of 1 dot and an interval of 2 dots are drawn in a direction perpendicular to the rotation direction of the photosensitive drum) is output. The halftone image is visually observed, and the white dot image is evaluated according to the following criteria.

[0265] [Evaluation of white dot image on halftone image]

[0266] Grade A: No white dot image can be found on the halftone image even by observing with a microscope.

[0267] Grade B: No white dot-like image can be found on the halftone image by visual observation, but it can be found by observing with a microscope.

[0268] Grade C: A white dot-like image is visually found in a part of the halftone image.

[0269] Grade D: An image with white dot-like appearances is visually found on the entire surface of the halftone image.

[0270] (Examples 2 to 28)

[0271] Except for changing the starting materials shown in Table 5, the charging rollers 2 to 28 are produced by the same method as the charging roller 1 of Example 1. The mass parts and physical properties of the starting materials used for producing each conductive member are shown in Tables 5 and 6. The results of the characteristic evaluation and image evaluation of the completed charging rollers 2 to 28 are shown in Tables 7-1, 7-2, and 8.

[0272] (Example 29)

[0273] Except for using the starting materials shown in Table 5, forming the conductive layer by the following method, and the production not involving any grinding process, the charging roller 29 is produced in the same manner as in Example 4.

[0274] A mandrel coated with an adhesive is used as the conductive support. A die with an inner diameter of 8.4 mm is attached to the front end of a crosshead extruder including a supply mechanism for the conductive support and a discharge mechanism for an unvulcanized rubber roller. The temperatures of the extruder and the crosshead are each set to 100 °C, and extrusion is carried out while changing the conveying speed of the conductive support. Forming is carried out so that the unvulcanized rubber roller has an outer diameter larger than that of the die. Thus, an unvulcanized rubber roller having a crown shape is obtained, where the outer diameter of the central portion is 8.5 mm, and the respective diameters at positions 90 mm each from the central portion toward both end portions are 8.44 mm.

[0275] Next, the unvulcanized rubber roller is put into a hot air vulcanizing furnace at 170 °C and heated for 60 minutes to vulcanize the unvulcanized rubber composition. Thus, a conductive roller having a conductive resin layer formed on the outer peripheral portion of the conductive support is obtained. Thereafter, each of the two end portions of the conductive resin layer is cut off by 10 mm to set the length of the conductive resin layer portion in the longitudinal direction to 232 mm. Thus, the charging roller 29 is produced.

[0276] (Example 30)

[0277] Except for using the starting materials shown in Table 5, the charging roller 30 is produced in the same manner as in Example 29.

[0278] [Table 5]

[0279]

[0280] [Table 6]

[0281]

[0282] [Table 7-1]

[0283]

[0284] [Table 7-2]

[0285]

[0286] [Table 8]

[0287]

[0288] Comparative Example

[0289] (Comparative Example 1)

[0290] The charging roller 31 of Comparative Example 1 was produced in the same manner as in Example 1, except that the materials to be used in Example 1 were changed to the materials shown in E-31 of Tables 9 and 10. The results of the characteristic evaluation and image evaluation of the completed charging roller 31 are shown in Tables 11-1, 11-2, and 12.

[0291] (Comparative Example 2)

[0292] The charging roller 32 of Comparative Example 2 was produced in the same manner as in Example 1, except that the materials to be used in Example 1 were changed to the materials shown in E-32 of Tables 9 and 10. The results of the characteristic evaluation and image evaluation of the completed charging roller 32 are shown in Tables 11-1, 11-2, and 12.

[0293] (Comparative Example 3)

[0294] The charging roller 33 of Comparative Example 3 was produced in the same manner as in Example 1, except that the materials to be used in Example 1 were changed to the materials shown in E-33 of Tables 9 and 10. The results of the characteristic evaluation and image evaluation of the completed charging roller 33 are shown in Tables 11-1, 11-2, and 12.

[0295] (Comparative Example 4)

[0296] The charging roller 34 of Comparative Example 4 was produced in the same manner as in Example 1, except that the materials to be used in Example 1 were changed to the materials shown in E-34 of Tables 9 and 10. The results of the characteristic evaluation and image evaluation of the completed charging roller 34 are shown in Tables 11-1, 11-2, and 12.

[0297] [Table 9]

[0298]

[0299] [Table 10]

[0300]

[0301] [Table 11-1]

[0302]

[0303] [Table 11-2]

[0304]

[0305] [Table 12]

[0306]

[0307] The present disclosure is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present invention. The appended claims are hereby attached to disclose the scope of the present disclosure.

[0308] This application claims priority based on Japanese Patent Application No. 2020-186694 filed on November 9, 2020, and Japanese Patent Application No. 2021-164209 filed on October 5, 2021, and the entire contents of the above applications are incorporated herein by reference.

[0309] Explanation of Reference Numerals

[0310] 21 Substrate

[0311] 22 First Conductive Particle

[0312] 23 Domain

[0313] 24 Second Conductive Particle

[0314] 31 Support

[0315] 32 Conductive Layer

Claims

1. A conductive member, characterized in that, It includes: A support with conductivity; And A conductive layer provided on the outer surface of the support, The conductive layer includes: A matrix, the matrix contains: The cross-linked product of the first rubber; and The first conductive particles; and Regions, each of the regions contains: The cross-linked product of the second rubber; and The second conductive particles, At least a part of the first conductive particles exist as primary particles in the cross-linked product of the first rubber, where When the length of the conductive layer in the length direction is defined as L and the thickness of the conductive layer is defined as T, and when at three positions including the center of the conductive layer in the length direction and the positions L / 4 from both ends of the conductive layer toward the center, on each cross-section in the thickness direction of the conductive layer, and at any three positions in the thickness region from the outer surface of the conductive layer to a depth of 0.1 to 0.9T, observation regions of 15 μm square are set, The average primary particle size d1 of the first conductive particles existing as primary particles in the matrix observed in each of the total nine observation regions is 200 nm or more, and The average primary particle size d2 of the second conductive particles in the regions observed in each of the observation regions is 50 nm or less, and where In each of the observation regions, 80% or more of the number of the regions observed satisfy the following requirement (i) and requirement (ii): Requirement (i) The ratio of the cross-sectional area of the second conductive particles contained in the region to the cross-sectional area of the region is 20% or more; Requirement (ii) The equivalent circular diameter of the region is 4 × d2 or more.

2. The conductive member according to claim 1, wherein, Among the first conductive particles, 90% or more of the number of the first conductive particles exist as primary particles in the matrix.

3. The conductive member according to claim 1, wherein when a metal film is provided on the outer surface of the conductive member, and when impedance A is measured by applying an AC voltage with an amplitude of 1 V and a frequency of 1.0×10 -1 Hz between the outer surface of the support and the metal film in an environment at a temperature of 23°C and a humidity of 50% RH, and impedance B is measured by applying an AC voltage with an amplitude of 1 V and a frequency of 1.0×10 -1 Hz and a DC voltage of 10 V between the outer surface of the support and the metal film in an environment at a temperature of 23°C and a humidity of 50% RH, impedance A and impedance B satisfy the following relationship: Impedance A / Impedance B ≤ 60.

4. The electrically conductive member according to claim 1, wherein, When the length of the conductive layer in the length direction is defined as L and the thickness of the conductive layer is defined as T, and when at three positions including the center of the conductive layer in the length direction and the positions L / 4 from both ends of the conductive layer toward the center, on each cross-section in the thickness direction of the conductive layer, and at any three positions in the thickness region from the outer surface of the conductive layer to a depth of 0.1 to 0.9T, observation regions of 15 μm square are set, N(A) and N(B) satisfy the following relationship, where N(A) represents the number of the first conductive particles observed in each of the total nine observation regions, and N(B) represents the number of the regions observed therein, 0.2 ≤ N(A) / N(B) ≤ 3.

0.

5. The conductive member according to claim 4, wherein N(A) and N(B) satisfy the following relationship: 0.35 ≤ N(A) / N(B) ≤ 0.

70.

6. The conductive member according to claim 1, wherein the arithmetic average of the distances between the first conductive particles and the closest regions is 0.1 μm or more.

7. The conductive member according to claim 1, wherein the arithmetic average of the distances between the regions is 0.2 μm or more and 2.0 μm or less.

8. The conductive member according to claim 1, wherein the volume resistivity of the matrix is greater than 1.0×10 8 Ω·cm and 1.0×10 17 Ω·cm or less.

9. The electrically conductive member according to claim 1, wherein, When the surface of the conductive member is charged with the corona discharger by setting the distance between the grid portion of the corona discharger and the surface of the conductive member to 1.0 mm and applying a voltage of 8 kV to the grid portion, and when the surface potential of the surface of the conductive member is represented by E0 immediately after charging and the surface potential of the surface of the conductive member is represented by E10 10 seconds after the end of charging, the charge decay rate Q represented by the following formula is 83% or more. [Mathematical formula 1] 10. The conductive member according to claim 1, wherein the first rubber is at least one selected from the group consisting of: natural rubber NR, isoprene rubber IR, butadiene rubber BR, styrene-butadiene rubber SBR, butyl rubber IIR, ethylene-propylene rubber EPM, ethylene-propylene-diene terpolymer rubber EPDM, chloroprene rubber CR, acrylonitrile-butadiene rubber NBR, hydrogenated product of NBR H-NBR, epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide copolymer, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer, and silicone rubber.

11. The conductive member according to claim 1, wherein the second rubber is at least one selected from the group consisting of: natural rubber NR, isoprene rubber IR, butadiene rubber BR, acrylonitrile-butadiene rubber NBR, styrene-butadiene rubber SBR, butyl rubber IIR, ethylene-propylene rubber EPM, ethylene-propylene-diene rubber EPDM, chloroprene rubber CR, nitrile rubber NBR, hydrogenated nitrile rubber H-NBR, silicone rubber, and polyurethane rubber U.

12. The conductive member according to claim 1, wherein the difference in solubility parameter, i.e., the SP value, between the rubber material for the domain and the rubber material for the matrix is 0.4 to 5.0 (J / cm 3 ) 0.5 .

13. The conductive member according to claim 1, wherein the first rubber is SBR and the second rubber is NBR.

14. The conductive member according to claim 1, wherein the first rubber is NBR and the second rubber is SBR.

15. The conductive member according to claim 1, wherein the first conductive particles are at least one selected from the group consisting of carbon black and titanium oxide.

16. The electrically conductive member according to claim 15, wherein the DBP absorption amount of the carbon black is less than 40 cm 3 / 100 g.

17. The conductive member according to claim 1, wherein the second conductive particles are conductive carbon black.

18. The conductive member according to claim 17, wherein the DBP absorption amount of the conductive carbon black is 40 to 170 cm 3 / 100 g.

19. A process cartridge detachably mounted to a main body of an electrophotographic image forming apparatus, the process cartridge including: an electrophotographic photosensitive member; and a charging member configured to be able to charge the electrophotographic photosensitive member, characterized in that the charging member is the conductive member according to any one of claims 1 to 18.

20. An electrophotographic image forming apparatus, including: an electrophotographic photosensitive member; and a charging roller configured to be able to charge the electrophotographic photosensitive member, characterized in that the charging roller is the conductive member according to any one of claims 1 to 18.

Images