TITLE OF THE INVENTION ELECTROPHOTOGRAPHIC ELEMENT, PROCESS CARTRIDGE AND ELECTROPHOTOGRAPHIC IMAGE FORMING APPARATUS

Abstract

An electrophotographic element comprising: a support member having a conductive outer surface; and a conductive layer disposed on an outer surface of the support member, wherein the conductive layer comprises a matrix comprising a first rubber and a plurality of domains dispersed in the matrix, wherein the volume resistivity of the matrix is ​​1.00 × 10 12 Ω cm or less, the plurality of domains includes at least one domain A, and the domain A satisfies specific conditions, in a case where the impedance of the electrophotographic member is changed by applying a specific AC voltage while changing the frequency in a range of 1.0 × 10 -2 up to 1.0 × 10 7 Hz is measured and the specific recording is performed, a slope at a specific frequency is -0.80 to - 0.30, and the impedance at a specific frequency is 1.00 × 10 3 up to 1.00 × 10 7 Ω.

Description

BACKGROUND OF THE INVENTIONField of the Invention

[0001] The present disclosure relates to an electrophotographic element, a process cartridge, and an electrophotographic image forming apparatus that can be used for electrophotography. Description of the related prior art

[0002] In an electrophotographic image forming apparatus, conductive elements are used as electrophotographic elements, such as a charging element, a transfer element, and a developing element. The conductive elements play a role in transporting charges from a conductive support element to a surface of the conductive element and delivering charges to a contacted object through discharge or triboelectric charge. For example, an electrophotographic element composed of a conductive support element and a conductive layer disposed on the conductive support element is known as the conductive element.

[0003] The charging element is a component that, together with an electrophotographic photosensitive element, generates a discharge to charge the surface of the electrophotographic photosensitive element. It must perform uniform charging on the electrophotographic photosensitive element. Recently, a conductive element capable of producing high-quality images over a long period of time has been required in an electrophotographic image formation process that has become faster and has a longer service life.

[0004] Japanese Patent Application No. 2020-166210 discloses a conductive member that stably charges a charged element, even when used in a high-speed electrophotographic image forming process. This conductive member has a conductive layer including a matrix containing a first rubber and a plurality of domains dispersed in the matrix, and the domain contains a second rubber and an electrically conductive agent. SUMMARY OF THE INVENTION

[0005] Using the conductive member disclosed in Japanese Patent Application No. 2020-166210 as a charging member, the present inventors attempted to form images over a long period of time in a current electrophotographic image forming process, increasing its speed and extending its service life. As a result, it was confirmed that this conductive member excels in uniform charging performance on a charged member even in this faster electrophotographic image forming process. Specifically, when the micropotential unevenness formed on the surface of the charged member cannot be sufficiently uniformed before reaching the charging step, an image that does not need to be formed ("ghost image") is generated, overlapping an intended image due to these potential unevenness. However, such a ghost image was not formed.This result indicates that the conductive element according to Japanese Patent Application No. 2020-166210 sufficiently supports the faster electrophotographic image formation process.

[0006] However, the inventors noted that problems related to supporting a longer service life remain. Specifically, in some cases, an adhesive substance, such as toner, remaining on the photosensitive member without being transferred to the paper, is noticeably deposited on the surface of the charging member, overdischarge is generated at the locations where the adhesive substance is deposited, and white dot images are formed.

[0007] The present disclosure is directed to an electrophotographic element that can form a high-quality image for a long period of time even when this element is mounted on the electrophotographic image forming process of the main body having a longer life and a higher speed.

[0008] Furthermore, the present disclosure is directed to a process cartridge for forming a high-quality image. Furthermore, the present disclosure is directed to an electrophotographic image forming apparatus capable of forming a high-quality electrophotographic image.

[0009] The present disclosure provides an electrophotographic element comprising: a carrier element having a conductive outer surface; and a conductive layer disposed on an outer surface of the carrier element, wherein the conductive layer a matrix comprising a first rubber, and comprises a plurality of domains dispersed in the matrix, the volume resistivity of the matrix 1.00 × 10 12 Ω · cm or less, the plurality of domains comprises at least one domain A, and the domain A the following<Bedingung 1> until<Bedingung 3> fulfilled: <Bedingung 1> Domain A comprises a second rubber and an electrically conductive agent; <Bedingung 2> a volume center of mass of domain A exists in domain A; <Bedingung 3> on a cross-section of domain A passing through the volume center of gravity, the volume resistance of an outer peripheral region, which is a region with a distance of 100 nm from an outer edge of domain A in the direction of the volume center of gravity, is greater than 1.00 × 10 12Ω cm, and in a case where a platinum electrode is directly disposed on an outer surface of the electrophotographic member, the impedance is measured by applying an AC voltage having an amplitude of 1 V between the outer surface of the support member and the platinum electrode in an environment having a temperature of 23°C and 50% relative humidity, while changing the frequency in a range of 1.0 × 10 -2 up to 1.0 × 10 7 Hz, and the frequency is plotted on an abscissa and the impedance is plotted on an ordinate of a log-log graph, a slope at a frequency range of 1.0 × 10 5 up to 1.0 × 10 6 Hz is -0.80 to -0.30, and the impedance in a frequency range of 1.0 × 10 -2 up to 1.0 × 10 1 Hz 1.00 × 10 3 up to 1.00 × 10 7 Ω is.

[0010] The present disclosure provides a process cartridge detachably attached to a main body of an electrophotographic image forming apparatus, wherein the process cartridge includes: an electrophotographic photosensitive member; and a charging member arranged to be capable of charging the electrophotographic photosensitive member, and the charging member is the electrophotographic member of the present disclosure.

[0011] The present disclosure provides an electrophotographic image forming apparatus comprising: an electrophotographic photosensitive member; and a charging roller arranged to be capable of charging the electrophotographic photosensitive member, wherein the charging roller is the electrophotographic element of the present disclosure.

[0012] According to at least one aspect of the present disclosure, an electrophotographic member can be provided that can form high-quality images over a long period of time, even when this member is applied to the electrophotographic image forming process having a longer lifetime and a higher speed. Further, according to at least one aspect of the present disclosure, a process cartridge for forming high-quality electrophotographic images can be provided. Moreover, according to at least one aspect of the present disclosure, an electrophotographic image forming apparatus can be provided that can form high-quality electrophotographic images. Other features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1A to 1C are diagrams describing the surface potential irregularities; Fig. Figure 2 is a schematic diagram depicting the structure of a domain; Fig. 3 is a schematic diagram illustrating a charging roller; Fig. 4 is a schematic diagram for describing a structure of a conductive layer; Fig. 5A and Fig. 5B are diagrams for describing a cross-sectional cutting direction; Fig. 6 is a graph indicating the impedance characteristics; Fig. 7 is a graph describing the impedance behavior; Fig. 8 is a diagram for describing a shell circumference; Fig. 9 is a schematic diagram showing a process cartridge; Fig. 10 is a schematic diagram illustrating an electrophotographic apparatus; Fig.11 is a schematic diagram illustrating the state in which a measuring electrode is formed on a charging roller; Fig. 12 is a cross-sectional view illustrating a measuring electrode; Fig. 13 is a schematic diagram illustrating an impedance measurement system; Fig. 14 is a schematic diagram showing an image for evaluating a ghost image; and Fig. 15A and Fig. 15B are diagrams describing a volume center of gravity of a domain A. DESCRIPTION OF THE EMBODIMENTS

[0013] In the present disclosure, the terms "from XX to YY" and "XX to YY" representing a numerical value range, unless otherwise specified, represent a numerical value range including the lower limit and the upper limit of the range as endpoints. In a case where numerical value ranges are described in stages, the upper limits and the lower limits of the respective numerical value ranges can be arbitrarily combined. For example, in the present disclosure, a phrase such as "at least one selected from the group consisting of XX, YY, and ZZ" includes XX, YY, and ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, and a combination of XX, YY, and ZZ.

[0014] Embodiments of the present disclosure will be described in detail with reference to the drawings. However, the components described in the embodiments are merely examples and are not intended to limit the scope of the present disclosure.

[0015] The present disclosure not only solves the problem of generation of ghost images, which is a problem of increasing the speed in the electrophotographic process having a longer life and a faster speed, but also suppresses the generation of white point images which may be generated when using the electrophotographic process for a long time.

[0016] The present inventors estimated that the conductive member according to Japanese Patent Application No. 2020-166210 cannot implement both the suppression of ghost images and the suppression of the generation of white point images in image formation over a long period of time for the following reasons.

[0017] The contaminants in this disclosure are toner and external additives which are not transferred to the paper or an intermediate transfer member in the electrophotographic image forming process, and which remain on the surface of the photosensitive drum, and reach and adhere to the charging member.

[0018] The toner and external additives often have insulating properties to retain predetermined charges, which are electrostatically transferred from the developing roller to the photosensitive drum during the development process. The toner and external additives that remain on the surface of the photosensitive drum without being transferred from the photosensitive drum to the paper and the intermediate transfer member are affected by discharge at the transfer roller and friction with the paper before reaching the charging member again, and are charged in a predetermined distribution of positive and negative charges.

[0019] The charging member (hereinafter also referred to as the "charging roller"), on the other hand, is a member that generates a potential difference between the charging member and the surface of the photosensitive drum when a DC voltage is applied to discharge electricity to the photosensitive drum. Therefore, it is difficult to prevent the adhesion of components whose polarity (negative / positive) is opposite to the polarity of the charging bias voltage that generates the above potential difference to the charging roller side due to electrostatic attraction. In other words, for the charging member to be used for a long period of time, it is necessary to suppress the abnormal discharge caused by contaminants, even if the contaminants adhere to the charging roller as described below.

[0020] Next, we describe white dot images generated by abnormal discharge due to contaminants. The discharge phenomena are generated between the charging roller and the photosensitive member based on Paschen's law, and the photosensitive member is charged with negative or positive charges according to the applied voltage. The discharge is generated by neutral air being ionized in the electric field, so charges of the opposite polarity are also generated at the same time. In other words, the positive or negative charges, which have the opposite polarity of the discharge, are moved toward the surface of the charging member by the electric field.In a state where no contaminant substances adhere to the surface of the charging roller, the charges on the surface of the charging member normally escape to the conductive support member side due to the conductivity of the charging roller, even if the surface of the charging roller is charged with charges having an opposite polarity.

[0021] However, when contaminants (e.g., toner, external additives) with insulating properties adhere to the surface of the charging roller, charges of opposite polarity to the discharge moving toward the surface of the charging member are trapped on the surface without escaping to the conductive member. Here, charges of opposite polarity exist between the contaminants charged with opposite polarity to the discharge (charged with the opposite polarity of the voltage applied to the charging member) and the surface of the charging member around the area where the contaminants adhere, generating a very strong electric field. This very strong electric field can, in some cases, generate an abnormally strong discharge.

[0022] Therefore, if the charges charged due to adhering contaminants can be moved toward the conductive support member side, the abnormally strong charges cannot be generated and accordingly, white dot images cannot be generated.

[0023] Based on the above considerations, the reason why both the suppression of ghost images and the suppression of the generation of white point images in image formation over a long period of time cannot be implemented in the case of using the conductive member according to Japanese Patent Application No. 2020-166210 as the charging member will be described below.

[0024] The phenomena of ghost image generation are discussed with reference to Fig. 1A to 1C. Fig. 1A to 1C are diagrams describing the surface potential unevenness. Fig.1A is a schematic diagram depicting an electrophotographic process, Fig. 1B is a graph indicating a surface potential on the surface of the photosensitive drum, and Fig. Figure 1C is a graph indicating a charging potential when using the charging element according to Japanese Patent Application No. 2020-166210. Fig. 1C, the solid line portion indicates the charging potential on the surface of the charging member, and the dashed line portion indicates the surface potential on the surface of the photosensitive drum.

[0025] In Fig.In FIG. 1A, 11 indicates a charging element, 12 indicates a photosensitive drum, 13 indicates a surface potential measuring section before the charging process, and 14 indicates the surface potential measuring section after the charging process. Normally, the surface potential of the photosensitive drum after the transfer process has an unevenness, as shown in Fig. 1B. Therefore, the unevenness of the surface potential enters the charging process, and the charging potential unevenness, as indicated by the solid line in Fig. 1C indexed, is formed according to the above-mentioned surface potential unevenness. As a result, a ghost image is generated. Here, if the charging element has a charging function sufficient to make the surface unevenness uniform, a ghost image may not be generated.

[0026] The conductive element according to Japanese Patent Application No. 2020-166210 includes a matrix and a plurality of domains dispersed in the matrix, each domain containing an electrically conductive agent. By electrically separating each domain by an insulating region (matrix), sufficient charge can be more easily stored in the domain. This suppresses discharge leakage, and by simultaneously improving the individual discharge amount, the generation of a ghost image is more easily suppressed.

[0027] However, in Japanese Patent Application No. 2020-166210, it is impossible to move the charge, which is charged by the discharge in the opposite polarity to the contaminants deposited on the surface of the charging member, toward the conductive support member side when the matrix exists as an isolation region. As a result, white dot images are more easily generated in image formation over a long period of time. In other words, the present inventors estimate that the existence of the matrix as an isolation region not only suppresses the generation of ghost images, but is also the cause of the generation of white dot images in image formation over a long period of time.

[0028] Therefore, the inventors verified that the charging of the adhering contaminants is suppressed by adjusting the volume resistivity of the matrix, and confirmed that when the volume resistivity of the matrix is ​​set to 1.0 × 10 12Ω cm or less, the charges charged on the contaminant substances adhering to the charging member can be quickly moved across the matrix toward the supporting member side, and the generation of the white dot images can be suppressed.

[0029] As a consequence, the inventors realized that it is not easy to implement both the suppression of ghost image generation to support higher speeds and the suppression of white point images in image generation over a long period of time.

[0030] Then, the present inventors continued their intensive studies to obtain an electrophotographic element that implements both the suppression of ghost image generation and the suppression of white dot image generation. As a result, the present inventors found that the above requirements can be well met if the conductive layer having a matrix domain structure includes a domain A that meets the following requirements 1 to 3.

[0031] The present disclosure will now be described in detail with reference to the drawings. Electrophotographic element

[0032] The electrophotographic element includes a support member having a conductive outer surface and a conductive layer disposed on an outer surface of the support member. The electrophotographic element may, for example, be an electrophotographic drum. The electrophotographic element will now be described using an electrophotographic drum as an example.

[0033] Fig.3 is a schematic external view of an electrophotographic roller. This electrophotographic roller includes a conductive layer 32 on an outer periphery of the support member (shaft core) 31. The conductive layer 32 is, for example, an elastic layer. Both ends of the support member 31 may be exposed without being coated with the conductive layer 32. The electrophotographic roller may be a charging roller. The charging roller is arranged in the image forming apparatus as a charging means for charging a photosensitive member and has conductivity. Support element

[0034] The support member has a conductive outer surface. A material constituting the support member can be selected from materials known in the field of electrophotographic elements and materials that can be used for electrophotographic elements. For example, aluminum, stainless steel, synthetic resin exhibiting conductivity, a metal such as iron, and an alloy such as copper can be used. Furthermore, oxidation and plating treatment using chromium, nickel, or the like can be performed thereon.

[0035] Both electroplating and electroless plating can be used for plating. However, electroless plating is preferred in terms of dimensional stability. Nickel plating, copper plating, gold plating, and many other alloy plating types can be used for the electroless plating used here. The thickness of the plating is preferably 0.05 μm or more, and is more preferably 0.1 to 30 μm when considering the balance between operating efficiency and rust protection.

[0036] The shape of the support element is not particularly limited, but is preferably a cylindrical shape, for example. The cylindrical shape can be a solid cylindrical shape or a hollow cylindrical shape (tubular). The outer diameter of the support element is preferably ϕ 3 mm to ϕ 10 mm. Conductive layerMatrix domain structure

[0037] The conductive layer includes a matrix containing a first rubber and a plurality of domains dispersed in the matrix. In other words, the conductive layer has a matrix-domain structure. In the conductive layer, for example, the domain has a core-shell structure, with an electrically conductive agent (conductive particles), such as carbon black, filled in the core portion. Core-shell structure of the domain

[0038] An example of the core-shell structure of a domain 21 is shown in Fig. 2 shown. Fig. 2 is a cross-sectional view of the domain 21 cut in a plane passing through a volume centroid 24. In Fig. 2, domain 21 has a core-shell structure composed of a core 22 and a shell 23 surrounding the core 22. In Fig.2, the amount of electrically conductive agent is indexed by the density of the shading, which indicates that the amount of electrically conductive agent is higher, the darker the shading is.

[0039] The electrophotographic element meets the following requirements (1) to (3). Requirement (1)

[0040] The conductive layer includes a matrix containing a first rubber and a plurality of domains dispersed in the matrix, and the volume resistivity of the matrix is ​​1.00 × 10 12 Ω · cm or less. Requirement (2)

[0041] The plurality of domains dispersed in the matrix includes at least one domain A, and the domain A satisfies the following conditions<Bedingung 1> until<Bedingung 3> . <Bedingung 1> Domain A contains a second rubber and an electrically conductive agent. <Bedingung 2>A volume center of mass of domain A exists in domain A. <Bedingung 3> On a cross-section of domain A passing through the volume center of gravity, the volume resistance of an outer peripheral region, which is a region with a distance of 100 nm from an outer edge of domain A in the direction of the volume center of gravity, is greater than 1.00 × 10 12 Ω · cm. Requirement (3)

[0042] In a case where a platinum electrode is arranged on an outer surface of the electrophotographic member and the impedance is measured by applying an AC voltage having an amplitude of 1 V between the outer surface of the support member and the platinum electrode in an environment with a temperature of 23°C and a relative humidity of 50%, while the charging frequency is in a range of 1.0 × 10 -2 up to 1.0 × 10 7Hz, the frequency is plotted on the abscissa and the impedance is plotted on the ordinate of a log-log graph, the following requirements (3-1) and (3-2) are met. Requirement (3-1) A slope in a frequency range of 1.0 × 10 5 up to 1.0 × 10 6 Hz is -0.80 to -0.30. Requirement (3-2) The impedance in a frequency range of 1.0 × 10 -2 up to 1.0 × 10 1 Hz is 1.00 × 10 3 up to 1.00 × 10 7 Ω.

[0043] Requirements (1) to (3) are described in detail. Requirement (1)

[0044] By setting the volume resistance of the matrix to 1.00 × 10 12Ω cm or less, charges charged on the contaminants adhering to the electrophotographic member can be more easily moved toward the supporting member side. The charged charges have the opposite polarity to the voltage applied to the supporting member side, so the charges are attracted to the electric field and move toward the supporting member. Therefore, when the volume resistivity of the matrix is ​​set within the above-mentioned range, the charged charges can move more easily through the matrix. This makes it easier for the charged charges to move more quickly across the matrix toward the supporting member.

[0045] The volume resistivity of the matrix is ​​preferably 1.00 × 10 11 Ω · cm or less, and more preferably 1.00 × 10 10Ω cm or less. The lower limit is not limited, but can be, for example, 1.00 × 10 -1 up to 1.00 × 10 12 Ω · cm, or 1.00 × 10 0 up to 1.00 × 10 11 Ω · cm, or 1.00 × 10 0 up to 1.00 × 10 10 Ω · cm. Adjustment method of the volume resistance of the matrix

[0046] The volume resistivity of the matrix can be adjusted by the composition of the rubber used to form the matrix (hereinafter referred to as "MRC"). For example, a rubber material within the above-mentioned volume resistivity range is used, or the volume resistivity is adjusted to the above-mentioned range by using an additive required for a high volume resistivity rubber, as needed.

[0047] A first rubber that can be used for MRC is, for example, at least one rubber selected from the group consisting of natural rubber, butadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, urethane rubber, silicone rubber, fluororubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, polynorbornene rubber, and hydrin rubber. In particular, at least one rubber is preferably selected from the group consisting of acrylonitrile-butadiene rubber, chloroprene rubber, and hydrin rubber, and more preferably at least one rubber is selected from the group consisting of acrylonitrile-butadiene rubber and chloroprene rubber.

[0048] If necessary, the matrix may contain fillers, processing aids, crosslinking agents, crosslinking aids, crosslinking accelerators, crosslinking accelerators, crosslinking retarders, antioxidants, plasticizers, dispersants, dyes, or electrically conductive agents. To adjust the volume resistivity of the matrix to the above-mentioned range, it is preferable that the matrix not contain electrically conductive agents such as carbon black. Method of measuring the volume resistance of the matrix

[0049] To measure the volume resistivity, a thin slice containing the matrix-domain structure is cut out of the conductive layer with a predetermined thickness (e.g., 1 µm), and a microprobe of a scanning probe microscope (SPM) or an atomic force microscope (AFM) is contacted with the matrix and the domain of the thin slice.

[0050] The thin slice is cut out of the conductive layer such that the thin slice includes at least a part of a cross section 52a parallel with the XZ plane, where the X-axis is the longitudinal direction of the electrophotographic member 51, the Z-axis is the thickness direction of the conductive layer, and the Y-axis is the circumferential direction, as shown, for example, in Fig. 5A. The thin disc may also be cut out such that the thin disc includes at least a part of the YZ plane (e.g., 53a, 53b, 53c) vertical to the axial direction of the conductive element, as shown in Fig. 5B. In the present disclosure, the thin disc was prepared as shown in Fig. Cut out as shown in Figure 5B.

[0051] The excision is performed, for example, with a sharp razor, a microtome, a focused ion beam (FIB), or the like. A microtome was used in the present disclosure.

[0052] To measure volume resistivity, a surface of the thin slice cut from the conductive layer is grounded. Then, the microprobe of a scanning probe microscope (SPM) or atomic force microscope (AFM) is contacted with the matrix portion of the thin slice surface on the opposite side of the grounded surface, and a 50 V DC voltage is applied for 5 seconds. An arithmetic average is then calculated from the values ​​measured when the base current value is measured for 5 seconds. The electrical resistance value is calculated by dividing the applied voltage by this calculated value. Finally, the resistance value is converted to volume resistivity using the layer thickness of the thin slice. Here, SPM and AFM can measure the layer thickness of the thin slice along with the resistance value. The specific method will be described later. Requirement (2)

[0053] A plurality of domains includes at least one domain A, and the domain A contains an electrically conductive agent, and the volume resistivity of the outer peripheral region of the domain is greater than 1.00 × 10 12 Ω · cm, which allows domains to be electrically isolated from each other, even in a case where the volume resistivity of the matrix is ​​1.00 × 10 12 Ω cm or less. As a result, a sufficient amount of charge can be stored in the domains, leakage discharge is suppressed, and the generation of a ghost image can be suppressed. Domain A

[0054] Domain A fulfills the following<Bedingungen 1> until<Bedingung 3> . <Bedingung 1> Domain A contains a second rubber and an electrically conductive agent. <Bedingung 2> A volume center of mass of domain A exists in domain A. <Bedingung 3>On a cross-section of domain A passing through the volume center of gravity, the volume resistance of an outer peripheral region, which is a region with a distance of 100 nm from an outer edge of domain A in the direction of the volume center of gravity, is greater than 1.00 × 10 12 Ω · cm.

[0055] The above conditions are described in detail below. <Bedingung 1>

[0056] Domain A contains a second rubber and an electrically conductive agent. By including the second rubber and the electrically conductive agent, the transport path of charges through the domain can be more effectively limited, while the movement of non-essential charges in the matrix is ​​suppressed. <Bedingung 2>

[0057] A volume centroid of domain A exists within domain A. The shape of domain A is preferably spherical. The volume centroid preferably exists within the core of domain A. Fig. For example, 15A indicates a domain in which the volume center of gravity 24 does not exist within domain A, and Fig. 15B indicates a domain in which the volume center of gravity 24 exists within the domain. In the case where the volume center of gravity of domain A exists within domain A, this means that domain A has a spherical shape. When domain A has a spherical shape, a reduction in the electric field non-uniformity between the domains can be achieved. <Bedingung 3>

[0058] On the cross-section of domain A passing through the volume center of gravity, the volume resistance of an outer peripheral region, which is a region with a distance of 100 nm from an outer edge of domain A in the direction of the volume center of gravity, is greater than 1.00 × 10 12Ω cm. This allows the interior of domain A and the matrix to be electrically isolated by the outer peripheral region of domain A. As a result, a sufficient amount of charge can be more easily stored in the domain without charge leakage into the matrix. By reducing the amount of the electrically conductive agent in the outer peripheral region, the volume resistivity of the outer peripheral region can more easily enter the above-mentioned range. To adjust the volume resistivity of the outer peripheral region, as mentioned later, a method of making domain A into a core-shell structure and adjusting the volume resistivity of the shell to, for example, more than 1.00 × 10 12 Ω · cm, can be used.

[0059] The volume resistivity of the outer peripheral region is preferably 1.00 × 10 13 Ω · cm or more and is more preferably 8.00 × 10 13Ω cm or more. The upper limit of the volume resistivity of the outer peripheral region is not particularly limited, but may, for example, be more than 1.00 × 10 12 Ω · cm and 1.00 × 10 19 Ω cm or less, 1.00 × 10 13 Ω · cm or more and 1.00 × 10 18 Ω cm or less, or 8.00 × 10 13 Ω · cm or more and 1.00 × 10 18 Ω · cm or less.

[0060] It is preferred that domain A, which contains the above-mentioned<Bedingungen 1> until<Bedingung 3> fulfills, for example, has a core-shell structure composed of a core and a shell surrounding the core. It is more preferred that the core includes a second rubber and an electrically conductive agent contained in the second rubber. It is even more preferred that the electrically conductive agent is distributed unevenly to the core. If domain A has the core-shell structure and the electrically conductive agent is distributed unevenly to the core,<Bedingung 3> can be more easily fulfilled. In other words, the nuclei can be electrically insulated by the shell, and a sufficient amount of charge can be more easily stored in the domains without any charge escaping into the matrix.In the matrix-domain structure confirmation method mentioned later, if it is determined that a domain exists where the core is surrounded by a shell containing a low amount of the electrically conductive agent, it is determined that the domain has a core-shell structure composed of a core and a shell surrounding the core. The confirmation method for domain A will be described later.

[0061] Domain A may be composed of one type of rubber material, but is preferably composed of two types of rubber material.

[0062] In at least eight of the cubic samples, one side of which is 6 μm and which are taken from nine locations on the conductive layer, the higher the number ratio of the A domain relative to the total number of the plurality of domains, the better. As the number ratio of the A domains is higher, the movement of unnecessary charges in the matrix can be more easily suppressed. Specifically, the ratio may be 27% or more by quantity, and preferably more than 50% by quantity, and even more preferably 80% or more by quantity. The upper limit is not particularly limited, but may be 27% or more and 100% or less by quantity, more than 50% or more and 95% or less by quantity, or 80% or more and 90% or less by quantity.

[0063] In the case of increasing the ratio of domain A using two types of rubbers, the second rubber and the first rubber are kneaded into a cured second rubber, in which the electrically conductive agent and a vulcanizing agent are added to the second rubber used as the core and mixed by a pressure kneader. This makes it easier for the second rubber to be unevenly distributed in the outer peripheral region of domain A and increases the size of domain A. In the case of using the third rubber, in addition to the above means, the electrically conductive agent is mixed with the second rubber using a pressure kneader and prepared into a masterbatch, and further, the first rubber and the third rubber are mixed to prepare a masterbatch. By mixing these masterbatches, the number of domains having a domain A structure can be increased.

[0064] The second rubber used for the core and the third rubber used for the shell may be composed of the same rubber material. In this case, in the step of preparing the rubber composition for forming the core (hereinafter also called "CMB"), which will be described later, the temperature during kneading the second rubber and the electrically conductive agent is set to C (°C), and in the step of preparing the rubber composition for forming the matrix and the shell (hereinafter also called "MSC"), which will be described later, the temperature during kneading the first rubber and the third rubber is set to D (°C) so that the temperature C is higher than the temperature D.Here, the difference between temperature C and temperature D, which indicates the temperature difference, is preferably 20°C or higher, more preferably 30°C or higher, and even more preferably 40°C or higher. By setting temperature C higher than temperature D, the amount of the gel containing the electrically conductive agent can be increased during kneading of the second rubber and the electrically conductive agent. As a result, the electrically conductive agent is retained in the second rubber even in the later-mentioned step of preparing the rubber composition for forming the conductive layer, and the movement of the electrically conductive agent between the second rubber and the third rubber can be suppressed.

[0065] In particular, the value of temperature C is not limited as long as it does not exceed a temperature that causes deterioration of the rubber during kneading, and may be, for example, 110 to 170°C, 120 to 160°C, or 120 to 150°C. Within these ranges, the amount of the gel containing the electrically conductive agent may be slightly increased. It is also preferable that the temperature of the CMB in the step of preparing the rubber composition for forming the conductive layer (kneading step) be 110 to 170°C, 120 to 160°C, or 120 to 150°C.

[0066] In particular, the value of temperature D is not limited and may be, for example, 80 to 120° C or 90 to 110° C. It is also preferable that the temperature of MSC in the step of preparing the rubber composition for forming the conductive layer (kneading step) is 80 to 120° C or 90 to 110° C.

[0067] In order to arrange the center of gravity of the domain inside the domain, a method for uniformly forming the domains A can be used by increasing the kneading time in the step of forming the domains (step (iii)) or by enhancing the shear strength during kneading.

[0068] Matrix domain structure, confirming domains A, measuring the ratio of domains A to the total number of domains

[0069] In the present disclosure, the matrix domain structure, the confirmation of the domains A, and a numerical ratio between the number of domains A and the total number of domains can be determined by three-dimensional measurement of the conductive layer using an FIB-SEM.

[0070] FIB-SEM is a processing technique in which a sample is treated with a focused ion beam (FIB) and an exposed cross-section is viewed with a scanning electron microscope (SEM). To examine a three-dimensional structure, multiple images are acquired by repeating the processing and observation steps one after the other. These SEM images are then reconstructed three-dimensionally by computer-based software, thus constructing the sample structure as a three-dimensional stereoscopic image.

[0071] A concrete method for measuring the ratio of domains A to the total number of domains is to take a three-dimensional stereoscopic image, as in Fig. 4 using a FIB-SEM (manufactured by FEI Co.), and the above configuration is confirmed in this image. Fig.4 indexes 41 a unit cube, 42 indexes a matrix, 43 indexes a domain and 44 indexes a conductive particle.

[0072] In other words, sampling is performed at nine locations on the conductive layer. The nine locations should not be positioned randomly, but rather at equal intervals, for example. If the conductive layer can be evenly divided into nine regions, sampling is performed from the center of each of the nine divided regions, depending on the shape of the conductive layer.

[0073] In the case where the electrophotographic member is a roller shape and the length in the axial direction (longitudinal direction) is L, the positions are determined every 120° in the circumferential direction of the roller ((1 / 4))L, (2 / 4)L, (3 / 4)L) from the edge, and a sample is cut out from each position.

[0074] Subsequently, three-dimensional measurement is performed using FIB-SEM to measure the cube-shaped images, one side of which is 6 µm, at 60 nm intervals. On each cross section of (1 / 4)L, (2 / 4)L, and (3 / 4)L, the cross section of the conductive layer is measured every 120° in the central section between the core metal position and the surface in the circumferential direction of the roll.

[0075] To properly observe the domain structure, pretreatment is performed to obtain a good contrast between the domain and the matrix. A dye treatment can be performed here. Specifically, a dye can be selected to identify the first rubber and the second rubber, such as osmium tetroxide, ruthenium tetroxide, or phosphotungstic acid. In the examples mentioned later, osmium tetroxide is used for dyeing. The types of rubber can be determined, and the domain and the matrix can be distinguished by this, because dyeing progresses more when the amount of double bonds and benzene rings in the rubber is higher.

[0076] In the case where a plurality of domains are dispersed in the matrix and the matrix has a communicating structure, it is determined that a matrix-domain structure is observed. Based on the backscattered electron image of the image taken by FIB-SEM, it is also possible to easily determine whether the second rubber and the electrically conductive agent are contained. Furthermore, in the case where the matrix-domain structure is observed in at least eight of the nine samples, it is determined that the conductive layer has the matrix-domain structure.

[0077] The resulting image is analyzed using the 3D visualization analysis software Avizo (registered trademark, manufactured by FEI Co.). Here, the domain and matrix are binarized, and image analysis is performed.

[0078] Then, the total number of domains and the number of A domains contained in a cube-shaped sample (one side: 6 µm) are counted. This step is performed for nine samples, and a numerical ratio of A domains to the total number of domains is calculated in each sample.

[0079] As mentioned above, the electrically conductive agent contained in the outer peripheral region tends to be small. Therefore, a domain in which a region in which the content of the electrically conductive agent is small exists around the core containing the electrically conductive agent is called<Bedingung 3> and can be determined as the domain A. Furthermore, if the electrically conductive agent is contained in the domain, it is determined that<Bedingung 1> is satisfied, and if the shape of the domain is spherical, it is determined that<Bedingung 2> is fulfilled. Then a domain can be determined as domain A, which satisfies the <Bedingung 1> until<Bedingung 3> fulfilled.

[0080] In the case where domain A has a core-shell structure, the volume resistivity of the shell is preferably greater than 1.00 × 10 12Ω · cm. This allows<Bedingung 3> can be more easily fulfilled. In other words, it is easier to prevent the condition in which charges escape into the matrix and move within it, resulting in the creation of a conductive path inside the conductive layer. The volume resistivity of the shell is preferably 1.00 × 10 13 Ω · cm or greater, and is more preferably 8.00 × 10 13 Ω cm or greater. The upper limit of the volume resistance of the shell is not limited, but can be, for example, greater than 1.00 × 10 12 Ω · cm and 1.00 × 10 19 Ω · cm or smaller, 1.00 × 10 13 Ω · cm or greater and 1.00 × 10 18 Ω · cm or smaller, or 8.00 × 10 13 Ω · cm or greater and 1.00 × 10 18 Ω · cm or smaller.

[0081] The volume resistivity of the shell is determined by the composition of the shell. It is preferred that the shell contain a third rubber. For the third rubber, it is preferable to use a rubber material that has a high volume resistivity to electrically insulate the core. A rubber that can be used, for example, for the third rubber is at least one rubber selected from the group consisting of natural rubber, butadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, urethane rubber, silicone rubber, fluororubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, and polynorbornene rubber.Particularly preferred is at least one rubber selected from the group consisting of: natural rubber, butadiene rubber, butyl rubber, isoprene rubber, styrene-butadiene rubber, and ethylene-propylene rubber, and even more preferred is at least one rubber selected from the group consisting of: butadiene rubber, butyl rubber, isoprene rubber, styrene-butadiene rubber, and ethylene-propylene-diene rubber. The third rubber may be different from or the same as the second rubber, but is preferably different from the second rubber. When the third rubber and the second rubber are different, phase separation between the core and the shell is easier, and the core-shell structure can be easily formed.

[0082] Optionally, the shell may contain fillers, processing aids, crosslinking agents, crosslinking aids, crosslinking accelerators, crosslinking accelerators, crosslinking retarders, antioxidants, plasticizers, dispersants, or colorants. To adjust the volume resistivity of the shell to the above-mentioned range, it is preferable that the shell not contain electrically conductive agents such as carbon black. Measurement method of the volume resistivity of the outer peripheral region of domain A

[0083] To measure the volume resistivity of the outer peripheral region of domain A, the volume resistivity is measured each time a plurality of cross-sections are obtained by FIB-SEM. Then, the volume centroid is determined based on the three-dimensional image, and a measurement cross-section including the volume centroid is specified, and the volume resistivity of this measurement cross-section is determined.

[0084] Specifically, the domain is sectioned at 60 nm intervals using the FIB-SEM, and each time a plurality of cross-sections are obtained, the volume resistivity of domain A existing in the cross-sections is measured in the same way as for the matrix volume resistivity measurement method. Then, the volume centroid of the domain is calculated using an image analysis device (product name: LUZEX-AP, manufactured by Nireco Corp.), specifying the measurement cross-section containing the volume centroid. Furthermore, the volume resistivity for the outer peripheral region of the domain of this measurement cross-section is measured in the same way as for the matrix volume resistivity measurement method. The same steps of cross-section formation and volume resistivity measurement are repeated until the entire domain is sectioned.

[0085] The volume centroid is calculated for the three-dimensional image obtained by FIB-SEM using an image analysis device (product name: LUZEX-AP, manufactured by Nireco Corp.), and whether the volume centroid exists within the domain is analyzed. If the domain is domain A, the volume resistivity of the outer peripheral region of the domain in the cross-section closest to the volume centroid of the domain is considered the volume resistivity of the outer peripheral region of domain A. Thickness of the shell

[0086] The thinner the thickness of the shell, the better, since the amount of charge stored in domain A increases, as indicated in the following expression (1). C=εSd

[0087] In expression (1), d indicates the shell thickness, S indicates the shell surface area, C indicates the shell capacitance, and ε indicates the shell dielectric constant. As expressed in expression (1), as d is smaller, the shell capacitance C increases. This leads to an increase in the amount of charge stored in domain A, which is preferable.

[0088] Specifically, the thickness of the shell is preferably 1.00 µm or less, more preferably 0.70 µm or less, and ideally 0.50 µm or less. However, in order to reliably suppress charge leakage into the matrix by isolating the domains from each other with insulating regions, the thickness of the shell is preferably 0.10 µm or more, and ideally 0.20 µm or more. In other words, the thickness of the shell can be, for example, 0.10 to 1.00 µm, 0.10 to 0.70 µm, or 0.20 to 0.50 µm. Method of measuring the thickness of the shell

[0089] The measurement method of the shell thickness is the same as the measurement method of the volume resistivity of the outer peripheral region of domain A, except that the shell thickness is measured in each cross section instead of measuring the volume resistivity in each cross section.

[0090] To facilitate observation of the matrix domain structure, pretreatment is performed to obtain a clear contrast between the core and shell. Specifically, osmium tetroxide, ruthenium tetroxide, phosphotungstic acid, or the like can be used, and colorants for identifying the second rubber and the third rubber can be appropriately selected. In the examples mentioned later, osmium tetroxide is used for coloring. Since coloring progresses more when the amount of double bonds and benzene rings in the rubber is higher, the type of rubber is determined, and the core and shell can be distinguished.

[0091] After the fracture surface has been formed and pretreated, the slice is examined with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the presence of the matrix-domain structure is confirmed. For example, observation at 1,000 to 100,000x magnification using the SEM can accurately quantify the surface area of ​​the domain.

[0092] The thickness of the shell is measured by quantifying the captured image of the fracture surface, capturing the matrix-domain structure. The image of the fracture surface obtained by SEM observation is converted into an 8-bit grayscale image using the image analysis device (product name: LUZEX-AP (manufactured by Nireco Corp.)), thereby obtaining a 256-gradation monochrome image. Then, the white and black of the image are inverted so that the shell on the fracture surface becomes white, and binarization processing is performed.

[0093] The shell thickness is calculated as the thickness of the thinnest section of the shell forming a domain.

[0094] In the case of the cylindrical electrophotographic member where the length of the conductive layer in the longitudinal direction is L and the thickness of the conductive layer is T, cross sections in the thickness direction of the conductive layer are taken as in Fig. 5B, at three locations (center of the conductive layer in the longitudinal direction and locations at L / 4 from both ends of the conductive layer toward the center). For each of the obtained cross sections, a 15 µm square observation region is arranged at three locations (0.2T, 0.5T, and 0.7T) in the thickness region from the outer surface of the conductive layer toward the support member at a depth of 0.1T to 0.9T, and the thickness of each shell observed in the observation regions at the nine locations is measured.

[0095] The disc is cut out in a direction that allows viewing the cross-section, which includes a normal line starting from the central axis of the support element, since the surface, including the support element up to the outer surface of the conductive layer (charge movement direction), must be viewed. Requirement (3-1)

[0096] The fact that the slope in the frequency range of 1.0 × 10 5 up to 1.0 × 10 6 Hz, when the frequency is plotted on the abscissa and the impedance is plotted on the ordinate in a log-log graph (hereinafter also called "impedance slope"), is -0.80 to -0.30, indicating that charge stagnation is hardly generated in the electrophotographic element on the high-frequency side. When the impedance of a conventional electrophotographic element is measured and the absolute value of the impedance of the electrophotographic element is plotted on the ordinate and the frequency is plotted on the abscissa in the log-log graph, the slope on the high-frequency side is always -1. As shown in Fig.6, the "slope" here means the slope with respect to the abscissa when the absolute value of the impedance of the electrophotographic element is plotted on the ordinate and the frequency is plotted on the abscissa in the log-log graph. An equivalent circuit of the electrophotographic element is expressed by a parallel connection of the electrical resistance R and a capacitance C, and the absolute value |Z| of the impedance can be expressed by the following expression (2). Where, "f" in expression (2) indicates the frequency. |Z|=1R−2+(2πf)2C2

[0097] The reason why the high-frequency side becomes a line in which the slope is -1 is probably as follows. If the movement of the charges cannot follow the high-frequency voltage, the charges stagnate. From this, it can be deduced that the state where the electrical resistance R is increased to be very high, in other words, the isolated capacitance is measured. The state where the charges stagnate is assumed in expression (2) to be a state in which R is approximated to infinity. In expression (3), which is the expression when the element of the denominator in expression (2) is extracted, R -2 as a very small value with respect to (2 πf) 2 C 2 Therefore, expression (2) can be transformed into expression (4), which is obtained by removing R -2is generated based on the approximation. Finally, expression (4) is transformed so that both sides become logarithms, establishing expression (5) and the slope of log f becomes -1. R−2+(2 π f)2 C2 |Z|=1(2πf)2C2 log|Z|=−logf−log(2 π C)

[0098] The meaning of expressions (2) to (5) is defined with reference to Fig. 7. In Fig. 7, the ordinate indicates a logarithm of the absolute value of the impedance and the abscissa indicates a logarithm of the frequency of the measured oscillating voltage. Fig. 7 indicates a behavior of the impedance that is expressed by expression (2). As described above, the impedance that satisfies expression (2) decreases at a certain frequency as the frequency increases. This decreasing behavior produces in the log-log diagram in Fig.7 a line whose slope is -1, without the slope depending on the value of the electrical resistance and the capacitance of the electrical photographic element, as expressed in expression (5).

[0099] When the impedance characteristic of the electrophotographic element with insulation properties is measured, a line with a slope of -1 is generated. Therefore, the state in which a line with a slope of -1 is generated during the impedance measurement of the electrophotographic element is considered to indicate the state in which the characteristic expresses that the charge movement on the high-frequency side is stagnant. When the movement of charges on the high-frequency side is stagnant, the charge supply for the discharge cannot follow the discharge frequency. As a result, it is considered that a time point is generated at which the discharge is disabled, and the discharge escapes.

[0100] On the other hand, the conductive element, whose impedance slope in the high frequency range is 1.0 × 10 5 up to 1.0 × 10 6Hz is -0.80 to -0.30, stagnation of charge supply on the high-frequency side is less likely. In this case, charges can be supplied when the discharge is generated on the high-frequency side, where charges are prone to stagnation. Since the charges can be supplied evenly, discharge leakage can be suppressed and the overall discharge amount can be improved. This range of the high-frequency region appears to be a region where discharge leakage is prone to generation, probably because this is a region where the frequency is the highest among the discharge frequencies generated from the electrophotographic element.If the slope in this frequency range is greater than -1 in the above-mentioned range, a slope greater than -1 can be obtained even in the high-frequency range lower than this frequency range, and the generation of discharge leakage can be suppressed and the total amount of discharge can be improved. The impedance slope in a range where the frequency is 1.0 × 10 5 Hz to 1.0 × 10 6 Hz is preferably -0.72 to -0.35, and more preferably -0.72 to -0.55.

[0101] The inventors think that the discharge frequency in a case of using the combination of the charging roller as the electrophotographic member and the photosensitive drum will be in the following range.

[0102] A discharge area in the moving direction of the surface of the charging roller, which is arranged 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 the process speed of the electrophotographic device is a maximum of 100 to 500 mm / s, the time required for the surface of the photosensitive drum to pass through the discharge area is 10 -3 s to 10 -2 s or more. From a detailed examination of the discharge, the length of the discharge area by a single discharge is 0.01 mm to 0.1 mm, so it is assumed that the discharge is generated at least 5 to 100 times while a certain point on the surface of the charging roller passes through the discharge area. Therefore, the frequency of the discharge generated by the charging roller is estimated to be in the range of several Hz to 1.0 × 10 6Hz. As the process becomes faster, the discharge frequency must be increased to increase the number of discharges, so that even in the above range, the discharge control and conductive mechanism, especially in the high frequency range of 1.0 × 10 5 Hz to 1.0 × 10 6 Hz, is critical.

[0103] To increase the number of discharges, as mentioned above, it is effective to deviate the impedance slope from -1. This can better achieve the characteristics in which the discharge and charge supply for the next discharge occur quickly. Deviating the impedance slope from -1 means that the charge supply in the electrophotographic element does not stagnate, allowing this electrophotographic element to implement discharge leakage suppression characteristics. Requirement (3-2)

[0104] The fact that the impedance (hereinafter also called “low frequency impedance”) in the frequency range of 1.0 × 10 -2 up to 1.0 × 10 1 Hz 1.00 × 10 3 up to 1.00 × 10 7 Ω indicates that charge stagnation is less likely on the low-frequency side. As mentioned above, the absolute value |Z| of the impedance can be expressed by the above expression (2). In expression (2), when the frequency is approximately zero, the absolute value of the impedance is approximately the electrical resistance R, and the electrical resistance R indicates the electrical resistance when the charges move in a single direction. Therefore, measuring the impedance while applying a low-frequency voltage is likely like simulating an impedance based on the amount of movement of the charges in the state where the movement of the charges can follow the oscillation of the voltage.

[0105] In other words, low-frequency impedance is an index of how easily charges move between the electrophotographic element and the measuring electrode, and is also an index of the amount of charge that can be moved by discharge from the surface of the electrophotographic element to the photosensitive drum.

[0106] The amplitude of the AC voltage used for the impedance measurement according to requirement (3-1) and requirement (3-2) is 1 V. This AC voltage for the measurement is much lower than the voltage actually applied to the electrophotographic element in the electrophotographic image forming apparatus (which is several hundred to several thousand V). Therefore, by measuring the impedance according to requirement (3-1) and requirement (3-2), the ease of discharge generated from the surface of the electrophotographic element can be evaluated in a high dimension.

[0107] Furthermore, by fulfilling requirement (3-2), the discharge ease can be controlled within a suitable range. If the impedance is less than 1.00 × 10 3 Ω, the amount of a discharge step becomes too large, and the charge supply for the next discharge step cannot keep pace. As a result, discharge leakage tends to occur, which makes ghost suppression difficult. On the other hand, when the impedance is 1.00 × 10 7 Ω, the discharge ease decreases, and the discharge amount does not reach the level required to fill the surface potential unevenness.

[0108] The low frequency impedance is preferably 2.00 × 10 3 up to 1.00 × 10 6 Ω, and is preferably 2.00 × 10 3 up to 1.00 × 10 5 Ω.

[0109] As in Fig.As described in Figure 7, the absolute value of the impedance in the electrophotographic element becomes a constant value in the low frequency range. Therefore, the impedance can be in the range of 1.0 × 10 -2 up to 1.0 × 10 1 Hz can be replaced, for example, by a value of the impedance at 1 Hz frequency.

[0110] The electrophotographic element that meets both requirements (3-1) and (3-2) can achieve a discharge amount at a level that eliminates the surface potential unevenness of the photosensitive drum and suppresses ghost images in the frequency ranges from the low-frequency side to the high-frequency side. Furthermore, by meeting requirements (3-1), discharge leakage on the high-frequency side can be suppressed. By meeting requirements (3-2), the discharge performance is further improved, and the generation of ghost images can be effectively suppressed. Impedance measurement method

[0111] The impedance can be measured by the following method.

[0112] When measuring impedance, the influence of contact resistance between the electrophotographic element and the measuring electrode must be eliminated. Therefore, a low-resistance thin film is deposited on the surface of the electrophotographic element, and this thin film is used as an electrode. On the other hand, a conductive support element is used as a ground electrode, and the impedance is measured using these two terminals.

[0113] To form the thin film, an electrode formation method such as metal deposition, sputtering, metal paste coating, and metal tape application can be used. In the present disclosure, a platinum thin film is deposited as a platinum electrode to reduce the contact resistance with the electrophotographic element.

[0114] In the case of forming the platinum electrode on the surface of the electrophotographic member, it is preferable to attach a mechanism that holds the electrophotographic member to the vacuum deposition apparatus in view of simplicity and production of a uniform thin film. For an electrophotographic member whose cross section is circular, it is preferable to use a vacuum deposition apparatus further incorporating a rotation mechanism. For example, in the case of a cylindrical electrophotographic member whose cross section is a curved surface (e.g., circular), it is preferable to use the following method because the connection of the platinum electrode (measuring electrode) and the impedance measuring device is difficult.

[0115] Specifically, after forming a platinum electrode (10 mm to 20 mm wide) in the longitudinal direction of the electrophotographic element, a metal foil is wrapped around it without a gap, and this metal foil and the measuring electrode exposed by the measuring device are bonded together, and the impedance is measured. This allows electrical signals from the conductive layer of the electrophotographic element to be smoothly picked up by the measuring device, and impedance measurement can be performed. The metal foil can be made of any metal whose electrical resistance value is similar to the metal portion of the lead wire of the measuring device when measuring impedance, and aluminum foil, metal tape, or the like can be used.

[0116] The impedance measuring device can be any device that measures the impedance up to the frequency range 1.0 × 10 7Hz, such as an impedance analyzer, a network analyzer, and a spectrum analyzer. Regarding the electrical resistance range of the electrophotographic element, measurement by an impedance analyzer is preferred.

[0117] The impedance measurement conditions are described. Using the impedance measuring device, the impedance is measured in the frequency range of 1.0 × 10 -2 up to 1.0 × 10 7Hz. The measurement is performed at an ambient temperature of 23°C and a relative humidity of 50%. To reduce measurement variation, five measurement points are set for each digit of the frequency. The positions of the five measurement points are chosen at equal intervals, for example, to avoid arbitrary placement. In the case where the electrophotographic element can be evenly divided into five parts, a measurement point is placed at the center of each of the five divided areas, although this may depend on the shape of the electrophotographic element. The amplitude of the AC voltage is 1 V.

[0118] The measurement voltage can be measured while applying a DC voltage, while taking into account the divided voltage applied to the electrophotographic element within the electrophotographic device. In particular, measurement while superimposing a DC voltage of 10 V or less with an AC voltage is preferred to quantify the charge transport and storage characteristics.

[0119] Next, a method for calculating the impedance slope is described. For the measurement result under the above conditions, the absolute value of the impedance is plotted with respect to the measurement frequency in the log-log graph using spreadsheet software (e.g., "Microsoft Excel (product name)" (manufactured by Microsoft Corp.). In the graph obtained by this log-log graph, the impedance slope in the frequency range of 1.0 × 10 5 up to 1.0 × 106 Hz using the measurement points in the frequency range of 1.0 × 10 5 up to 1.0 × 10 6 Hz determined.

[0120] Specifically, an approximate line of the linear function is calculated in the graph in this frequency range using the least squares method, and the slope of the determined approximate line is calculated. Then, the arithmetic mean of the values ​​at the measurement points in the frequency range of 1.0 × 10 -2 up to 1.0 × 10 1 Hz in this log-log graph, and the obtained value is considered as the impedance on the low frequency side.

[0121] In the case of measuring the impedance slope in the cylindrical electrophotographic element, the electrophotographic element is equally divided into five regions in the longitudinal direction (axial direction), and the measurement is performed at five locations which are the center portions of the five regions, respectively, and an arithmetic average of the measured slope values ​​at the five locations is calculated.

[0122] It is preferable that the electrophotographic element satisfies the following configuration (1). It is also preferable that the electrophotographic element satisfies the following configuration (2). It is more preferable that the electrophotographic element satisfies the following configurations (1) and (2). This allows the electrophotographic element to easily satisfy the above-mentioned requirement (3).

[0123] Configuration (1) The volume resistance of the core is 1.00 × 10 1 up to 1.00 × 10 4 Ω · cm.

[0124] Configuration (2) The arithmetic mean Dm of the distances between the nuclei is 0.20 to 2.00 µm. Configuration (1)

[0125] The volume resistivity of the core is preferably 1.00 × 10 1 up to 1.00 × 10 4 Ω cm. By adjusting the volume resistance of the core to a lower state, the transport path of charges can be more effectively limited to the path across the domain, while suppressing the movement of purposeless charges in the matrix.

[0126] Furthermore, the volume resistivity of the core is more preferably 1.00 × 10 2 Ω cm or less. By lowering the volume resistance of the core to this range, the amount of charge moving within the domain can be dramatically increased, so that the impedance of the conductive layer in the frequency range of 1.0 × 10 -2 up to 1.0 × 10 1Hz easier to an even lower range, such as 1.00 × 10 5 Ω cm or less. As a result, the transport path of the charges can be more effectively limited to the path across the domain. In other words, the volume resistance of the core is ideally 1.00 × 10 1 up to 1.00 × 10 2 Ω cm. The volume resistivity of the core can be adjusted by the electrically conductive agent contained in the core, so that the conductivity of the electrically conductive agent becomes a predetermined value. Specifically, this adjustment can be achieved by appropriately selecting the type of electrically conductive agent and the amount of the electrically conductive agent added.

[0127] The electrically conductive agent used to control the volume resistivity of the core to 1.00 × 10 1 up to 1.00 × 10 4Ω cm is used is not particularly limited, but is preferably an electrically conductive agent that can largely change the volume resistivity from high resistance to low resistance by the amount to be dispersed.

[0128] Examples of the electrically conductive agent mixed with the core include carbon black, graphite, oxide (e.g., titanium oxide, tin oxide), metal (e.g., Cu, Ag), or particles coated on the surface with an oxide or metal to provide conductivity. If necessary, two or more types of these electrically conductive agents can be mixed at an appropriate ratio. The electrically conductive agent preferably contains carbon black or tin oxide.

[0129] Among the above-mentioned electrically conductive agents, conductive carbon black is preferred because of its high affinity for rubber and the easy control of the distance between the particles of the electrically conductive agent. The type of carbon black blended into the domain is not limited. For example, furnace black, oil furnace black, thermal black, lamp black, acetylene black, Ketjen black, and the like can be used.

[0130] Particularly preferred is the conductive carbon black whose DBP oil absorption is 40 cm 3 / 100g up to 170 cm 3 / 100g, as the core can be given high conductivity.

[0131] The content of the electrically conductive agent, such as conductive carbon black, is preferably from 20 parts by mass to 150 parts by mass when the second rubber contained in the core is 100 parts by mass. The content is even more preferably from 50 parts by mass to 100 parts by mass.

[0132] The volume resistivity of the core can be adjusted by the content of the electrically conductive agent in the core. For example, in the case of using a conductive carbon black whose DBP oil absorption is 40 cm 3 / 100g up to 170 cm 3 / 100g as the electrically conductive agent, the content of the electrically conductive agent in the core is preferably 40 mass% to 200 mass% with respect to the total mass of the core.

[0133] It is preferable to mix a larger amount of the conductive agent compared to the case of the conductive agent used for a general electrophotographic element. This makes it easier to control the volume resistivity of the core within a desired range. If necessary, the core may contain fillers, processing aids, crosslinking aids, crosslinking accelerators, antioxidants, crosslinking accelerator aids, crosslinking retarders, plasticizers, dispersants, dyes, or the like.

[0134] The second rubber is, for example, at least one rubber selected from the group consisting of natural rubber, butadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, urethane rubber, silicone rubber, fluororubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, polynorbornene rubber, ethylene-propylene-diene rubber, nitrile rubber and hydrogenated nitrile rubber.In particular, at least one rubber selected from the group consisting of natural rubber, butadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, urethane rubber, silicone rubber, fluororubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber and polynorbornene rubber is preferable, and at least one rubber selected from the group consisting of butadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, isoprene rubber and ethylene-propylene-diene rubber is more preferable. Method of measuring the volume resistance of the core

[0135] The measurement method of the volume resistivity of the core is the same as the above-mentioned measurement method of the volume resistivity of the shell, except that the measurement location is a location corresponding to the core, and the applied voltage to measure the current value is 1 V. Configuration (2)

[0136] The number of nuclei contained in domain A is not limited to one. If domain A contains multiple nuclei, the nuclei preferentially maintain at least a certain distance or more from each other.

[0137] Specifically, it is preferred that domain A includes a plurality of nuclei and an arithmetic mean Dm of the distance between the nuclei is 0.20 to 2.00 µm.

[0138] The arithmetic mean Dm of the distance between the nuclei is preferably 2.00 µm or less, more preferably 1.00 µm or less, and even more preferably 0.80 µm or less. When the arithmetic mean Dm of the distance between the nuclei is in this range, the impedance on the low frequency side can be more easily adjusted to the above-mentioned range. On the other hand, in terms of storing a sufficient amount of charge in the domain by clearly isolating each nucleus by the insulating region, the arithmetic mean Dm of the distance between the nuclei is preferably 0.20 µm or more, and is ideally 0.30 µm or more. In other words, the arithmetic mean Dm of the distance between the nuclei can be, for example, 0.20 to 2.00 µm, 0.30 to 1.00 µm, or 0.30 to 0.80 µm. The setting procedure of the arithmetic mean Dm of the distance between the nuclei will be described later. <Messverfahren des arithmetischen Mittelwerts Dm der Distanz zwischen den Kernen>

[0139] The arithmetic mean Dm of the distance between the cores is measured as follows. First, slices are prepared using the same method as the matrix volume resistivity measurement method described above. Then, the fracture surface is formed using methods such as freeze-fracture, cross-polishing, and focused ion beam (FIB) etching. The FIB method is preferred for the smoothness of the fracture surface and the pretreatment for observation. To clearly observe the matrix domain structure, pretreatment is performed so that a clear contrast between the core and domain can be observed. Specifically, a colorant for identifying the second rubber and the third rubber, such as osmium tetroxide, ruthenium tetroxide, or phosphotungstic acid, can be selected. In the examples mentioned later, phosphotungstic acid was used for coloring.The types of rubber can be determined and the core and shell can be distinguished because the dyeing proceeds faster when the amount of double bonds and benzene rings in the rubber is greater. After the fracture surface has been formed and the pretreatment has been performed, the slice is examined using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the presence of the matrix-domain structure is confirmed. For example, observation is performed at a magnification of 1000x to 100,000x using the SEM, allowing for accurate quantification of the domain surface area.

[0140] The arithmetic mean Dm of the distance between the nuclei is measured by quantizing the fracture surface image where the matrix domain structure appears. The fracture surface image is obtained by SEM observation and is converted into an 8-bit grayscale image using image processing software (product name: "LUZEX-AP" (made by Nireco Corp.)), resulting in a 256-grayscale monochrome image. Then, the white and black of the image are inverted so that the nucleus on the fracture surface becomes white, and binarization processing is performed. Next, the distance between the cores in the image is calculated. The distance between the cores here is the shortest distance between adjacent cores. In the case of the cylindrical electrophotographic element, where the length of the conductive layer in the longitudinal direction is L and the thickness of the conductive layer is T, cross sections are obtained in the thickness direction of the conductive layer, as indicated in FIG. 5B, at three locations (the center of the conductive layer in the longitudinal direction and locations at L / 4 from both ends of the conductive layer toward the center). For each of the obtained cross sections, a 15 μm square observation area is arranged at three locations (0.2T, 0.5T, and 0.7T) in the thickness range from the outer surface of the conductive layer toward the support member at the depth of 0.1T to 0.9T, and the distance between each core observed at each of these nine locations is measured.

[0141] The disc is cut out in a direction that allows the observation of the cross-section, which includes a normal line starting at the central axis of the support element, since the surface including the support element up to the outer surface of the conductive layer (charge movement direction) must be observed. Manufacturing process of an electrophotographic element

[0142] An example of the manufacturing method of the electrophotographic member is described below. In this example, the manufacturing method of the electrophotographic member includes the following steps (i) to (iv), but the present invention is not limited to this as long as the configuration described in the present disclosure can be implemented.

[0143] The manufacturing process of the electrophotographic element differs depending on whether the electrophotographic element is formed using two types of rubber materials or three types of rubber materials. For example, in the case of using three types of rubber materials, the following steps (i) to (iv) are performed. Step (i): a step of preparing a rubber composition for forming the core (hereinafter also called “CMB”) containing an electrically conductive agent (e.g., carbon black) and the second rubber Step (ii): a step of preparing a rubber composition for forming the matrix and the shell (hereinafter also called “MSC”) containing the first and third rubbers Step (iii): a step of kneading CMB and MSC to prepare a rubber composition for forming the conductive layer, which has the matrix-domain structure, wherein the domain has the core-shell structure Step (iv): a step of forming the layer of the rubber composition for forming the conductive layer directly on the support member or over another layer and curing the layer of the rubber composition to form the conductive layer

[0144] The conductive layer can be formed on the support member using a rubber composition for forming the conductive layer based on a known method (e.g., extrusion molding, injection molding, compression molding). If necessary, the conductive layer can be adhered to the support member by an adhesive. The conductive layer formed on the support member can also be vulcanized, if necessary, and such a surface treatment as UV treatment can be performed thereon after polishing. In the case of performing vulcanization, a vulcanizing agent can be added to the rubber composition for forming the conductive layer in step (iv). Then, vulcanization can be performed in the above-mentioned curing. The vulcanizing agent is not particularly limited and may be, for example, sulfur.

[0145] The amount of the second rubber with respect to 100 parts by mass of the first rubber is preferably 10 to 100 parts by mass, and is more preferably 20 to 50 parts by mass.

[0146] The amount of the third rubber based on 100 parts by mass of the first rubber is preferably 10 to 100 parts by mass, and is more preferably 10 to 30 parts by mass.

[0147] In order to adjust the arithmetic mean volume Dm of the distance between the nuclei in the above range, it is effective to control the following (a) to (d). (a) Difference of the respective interfacial tensions σ of CMB and MSC (b) Ratio (ηm / ηd) of viscosity (ηd) of CMB and viscosity (ηm) of MSC (c) Shear rate (γ) and shear energy (EDK) when CMB and MSC are kneaded in step (iii) (d) Volume fraction of CMB with respect to MSC in step (iii) (a) Difference in interfacial tensions of CMB and MSC

[0148] When two or more types of incompatible rubbers are mixed, phase separation usually occurs. This is because the interaction between the same polymers is stronger than the interaction between different polymers, and the same polymers tend to aggregate, which lowers the free energy for stabilizing the state.

[0149] The interface of the phase separation structure contacts different polymers, so the free energy becomes higher than inside the structure, which is stabilized by interactions between the same molecules. As a result, interfacial tension is generated, which tends to reduce the area in contact with different polymers to lower the free energy at the interface. If this interfacial tension is small, even different polymers will mix evenly, increasing the entropy. The evenly mixed state indicates dissolution, and the SP value (solubility parameter), which is an index of solubility, tends to correlate with the interfacial tension. In other words, the difference in interfacial tension between CMB and MSC can correlate with the SP value difference of the rubbers contained in CMB and MSC.

[0150] It is known that in the case of blending three or more kinds of incompatible rubber materials, the dispersion states will vary depending on the SP values ​​of the rubber materials being blended.

[0151] In the case of forming the conductive layer having the matrix-domain structure, wherein the domain has the core-shell structure, it is preferable to select rubber materials such that the SP value of the rubber material forming the shell has an intermediate value between the SP values ​​of the rubber materials forming the matrix and the core, and it is preferable that the SP value of the rubber material forming the shell is smaller than the SP value of the rubber material forming the matrix, and the SP value of the rubber material forming the shell exceeds the SP value of the rubber material forming the core.Rubbers having similar SP values ​​have high affinity, so when the SP value of the rubber material forming the matrix, the SP value of the rubber material forming the shell, and the SP value of the rubber material forming the core have the above relationship, domain A can more easily exhibit the core-shell structure.

[0152] The difference between the absolute values ​​of the solubility parameters of each of the rubber materials is preferably 0.4 to 5.0 (J / cm 3 ) 0,5 , and is more preferably 0.4 to 2.2 (J / cm 3 ) 0,5 . In this region, a stable phase separation structure can be formed and the domain diameter D can be reduced.

[0153] In particular, the thickness of the conductive layer is not limited as long as the desired functions and effects of the electrophotographic element can be maintained. The thickness of the conductive layer is preferably from 1.0 mm to 4.5 mm. Method of measuring the SP value

[0154] The SP value can be precisely calculated by generating a calibration curve using a material whose SP value is already known. A catalog value from a material manufacturer can be used for this SP value. For example, the SP values ​​of NBR and SBR are virtually determined by the content ratios of acrylonitrile and styrene, regardless of molecular weight.

[0155] Therefore, the acrylonitrile or styrene content ratio of the rubbers composing the matrix and the domain is analyzed using an analytical method such as pyrolysis gas chromatography (Py-GC) or solid-state NMR. Subsequently, the SP values ​​can be calculated using the calibration curve obtained from a material whose SP value is known.

[0156] The SP value of isoprene rubber can be determined using an isomer structure such as 1,2-polyisoprene, 1,3-polyisoprene, 3,4-polyisoprene, cis-1,4-polyisoprene, and trans-1,4-polyisoprene. Therefore, as in the case of SBR and NBR, the isomer content ratio is analyzed using Py-GC, solid-state NMR, or the like, and the SP value can be calculated based on a material whose SP value is known.

[0157] The SP value of the material whose SP value is known was determined by the Hansen solubility sphere method. (b) Viscosity ratio of CMB and MSC

[0158] Since the viscosity ratio (ηd / ηm) of CMB and MSC is closer to 1, the domain diameter can be smaller. Specifically, the viscosity ratio is preferably from 1.0 to 2.0. The viscosity ratio of CMB and MSC can be adjusted by selecting the Mooney viscosities of the material rubbers used for CMB and MSC and the type and amount of filler blended.

[0159] It is also possible to add a plasticizer (e.g., paraffin oil) in an amount that does not disrupt the formation of the phase separation structure. The viscosity ratio can be adjusted by adjusting the temperature during kneading.

[0160] The viscosity of the rubber composition for forming the core and the viscosity of the rubber composition for forming the shell are determined by measuring the Mooney viscosity ML (1+4) at the rubber temperature during kneading, based on JISK6300-1: 2013. (c) Shear rate and energy amount during shearing when MSC and CMB are kneaded

[0161] When MSC and CMB are kneaded, the distance between the domains can be reduced with increasing shear rate and larger amount of shearing energy.

[0162] The shear rate can be increased by increasing the inner diameter of the agitating elements (e.g., the blade and screw of the kneading machine) to reduce the space between the face of the agitating elements and the inner wall of the kneading machine, and by increasing the rotation frequency. To increase the energy during shearing, the rotation frequency of the agitating elements is increased, or the viscosity of the second rubber in CMB and the first and third rubbers in MSC are increased. (d) Volume fraction of CMB relative to MSC in step (iii)

[0163] The volume fraction of CMB, relative to MSC, correlates with the collision / union probability of the core-forming rubber composition with the matrix-shell rubber composition. Specifically, the collision / union probability of the core-forming rubber composition with the matrix-shell rubber composition decreases as the volume fraction of the core-forming rubber composition relative to the matrix-shell rubber composition is reduced. In other words, in a range where the required conductivity is maintained, the distance between the cores can be reduced by reducing the volume fraction of the core in the matrix.

[0164] The volume fraction of CMB with respect to MSC is preferably 15 volume% to 40 volume%.

[0165] It is preferable that the conductive layer satisfies the following configuration (3). It is preferable that the conductive layer satisfies the following configuration (4). It is more preferable that the conductive layer satisfies the following configuration (3) and configuration (4). Configuration (3) A ratio of a cross-sectional area of ​​the electrically conductive agent contained in the core with respect to a cross-sectional area of ​​the core is 20 area % or more.

[0166] Configuration (4) In a case where a perimeter of the core is A and a hull perimeter of the core is B, A and B satisfy the following expression (6). (6)

[0167] Configurations (3) and (4) can be considered as components related to the core shape. "Core shape" is defined as a cross-sectional shape of the core that appears in the cross-section of the conductive layer in the thickness direction.

[0168] The shape of the core is measured as follows. In the case of a cylindrical charging element whose length of the conductive layer in the longitudinal direction is L and the thickness of the conductive layer is T, cross sections of the conductive layer in the thickness direction are measured as shown in Fig. 5B, taken at three locations: at the center of the conductive layer in the longitudinal direction and at positions at L / 4 from both ends of the conductive layer toward the center. For each of the cross-sections taken, the 15 µm square viewing areas are located at three locations (0.2T, 0.5T, and 0.7T) in the thickness ranges at a depth of 0.1T to 0.9T from the outer surface of the conductive layer toward the support member. The shape of the core is defined by the shape of each core viewed in each of the nine viewing areas.

[0169] It is preferable that the shape of the core be such that its peripheral surface is free of unevenness. By reducing the unevenness, the unevenness of the electric fields between the cores can be reduced, i.e., the locations where an electric field concentration is generated are reduced, and the transport phenomena of excessive charges in the shells can be further reduced.

[0170] The present inventors have discovered that the amount of electrically conductive agent contained in a core affects the outer shape of the core. In other words, the present inventors have discovered that as the amount of electrically conductive agent contained in a core increases, the outer shape of the core becomes more spherical. Furthermore, as the number of spherical nuclei increases, the concentration points of electron transfer between nuclei can be reduced. According to a study by the present inventors, a core whose ratio to the total cross-sectional area of ​​the electrically conductive agent viewed in that cross section is 20.0 area% or more is more likely to have a spherical shape, although the reason for this is not clear.As a result, it is preferred because it can assume an outer shape that can significantly reduce the concentration of electron transfer between the nuclei. In other words, it is preferable that the ratio of the cross-sectional area of ​​the conductive particles contained in the core to the cross-sectional area of ​​the core be 20.0 area% or more. The upper limit of the ratio of the cross-sectional area of ​​the conductive particles is not particularly limited, but may be, for example, 20.0 to 30.0 area% or 20.0 to 28.0 area%.

[0171] To implement the core shape without asperities on the peripheral surface, it is preferable to satisfy the following expression (6). When there are no large asperities, the unevenness of the electric field between the cores can be reduced, that is, the locations where the electric fields are concentrated are reduced, and the transport of excessive charges in the shell can be further suppressed. 1.00≤A / B≤1.10 (A: circumference of the core; B: circumference of the shell of the core)

[0172] Expression (6) indicates a relationship between the circumference A of the core with respect to the hull circumference B of the core. The hull circumference here means the circumference when the protruding portions of the core 81 observed in the observation area are connected as shown in Fig. 8 shown.

[0173] The ratio of the core circumference to the core shell circumference is at least 1, and state 1 indicates that the core has no irregularities in its cross-sectional shape (e.g., a perfect circle, ellipse). If this ratio is greater than 1.1, a larger irregularity exists in the core, which means that an anisotropy of the electric field is generated. Measurement method for each parameter in relation to the shape of the core

[0174] First, the shape of the core on each cross section is evaluated using the same method as the above-described measurement method for the volume resistivity of the outer peripheral region of domain A, as follows. However, as mentioned below, the disc is manufactured through a cross section perpendicular to the longitudinal direction of the electrophotographic element, and the shape of the core on the fracture surface of this disc is evaluated. The reason for this is described below.

[0175] Fig. 5A and Fig. 5B are diagrams in which the shape of the electrophotographic element 51 is depicted three-dimensionally in three axes (X, Y and Z). In Fig. 5A and Fig. In FIG. 5B, the X-axis indicates a direction parallel to the longitudinal direction (axial direction) of the electrophotographic element, and the Y and Z axes indicate directions perpendicular to the axial direction of the electrophotographic element. The Z-axis is the thickness direction of the conductive layer.

[0176] Fig.5A is a diagram showing an image when a slice is cut from the electrophotographic element at a cross section 52a parallel with an XZ plane 52. The XZ plane 52 can be rotated 360° around the axial direction of the electrophotographic element. Considering that the electrophotographic element contacts the photosensitive drum and rotates, and that electricity is discharged when it passes through the gap with the photosensitive drum, the cross section 52a parallel to the XZ plane 52 indicates a plane where the discharge is generated simultaneously at a certain time. When a surface corresponding to a predetermined amount of the cross section 52a passes, the surface potential is generated on the photosensitive drum.

[0177] Therefore, in order to evaluate the shape of the core, which correlates with the electric field concentration inside the electrophotographic element, it is necessary to evaluate the cross section parallel to the XY plane 53, which is perpendicular to the axial direction of the electrophotographic element, whereby the core shape including the predetermined amount of the cross section 52a can be evaluated. For this evaluation, when the length of the conductive layer in the longitudinal direction is L, three locations are selected, that is, the cross section 53b at the center of the conductive layer in the longitudinal direction and the two cross sections (53a and 53c) at the positions at L / 4 from both ends of the conductive layer toward the center ( Fig. 5B).

[0178] In order to observe the cross sections 53a to 53c when the thickness of the conductive layer is T, the observation areas of 15 µm square are arranged at three locations (0.2T, 0.5T and 0.7T) in the thickness ranges at a depth of 0.1T to 0.9T from the outer surface of each slice (a total of nine locations), and the measurement is performed at the nine locations.

[0179] The fracture surface can be formed using methods such as freeze fracturing, cross-polishing, and focused ion beam (FIB) etching. Considering the smoothness of the fracture surface and the pretreatment required for observation, the FIB method is preferred. To observe the matrix domain structure, pretreatment such as staining and deposition can be performed so that a clear contrast between the conductive phase and the insulating phase can be observed.

[0180] After the fracture surface is formed and the pretreatment is performed, the matrix-domain structure in the slice can be observed using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). In particular, considering the accuracy of quantifying the domain area, observation at a magnification of 1000x to 100,000x using the SEM is preferred.

[0181] As mentioned above, the circumference and shell circumference of the core can be measured by quantizing the acquired image. For the fracture surface images obtained by the SEM, the analysis areas of 15 μm square are extracted from the nine images obtained at each viewing position using image processing software such as Image Pro Plus (from Media Cybernetics Co.), and 8-bit grayscale processing is performed, resulting in 256-gradation monochrome images. Then, the white and black of an image are inverted so that the domain on the fracture surface becomes white, and the image is binarized to obtain a binary image for analysis. Method of measuring the cross-sectional area ratio of the electrically conductive agent in the core

[0182] The cross-sectional area ratio of the electrically conductive agent in the core can be measured by quantizing the above-mentioned binary image. For the binary image, the cross-sectional area S of the domain and the total number Sc of cross-sectional areas of the section composed of the conductive agent in each core are calculated using the counting function included in the image processing software Image Pro Plus (manufactured by Media Cybernetics Co.). Then, the arithmetic mean (%) of (Sc / S) × 100 is calculated.

[0183] In the case of a cylindrical charging element whose length of the conductive layer in the longitudinal direction is L and the thickness of the conductive layer is T, cross sections of the conductive layer in the thickness direction are taken as shown in Fig.5B, were taken at three locations, that is, at the center of the conductive layer in the longitudinal direction and at positions at L / 4 from both ends of the conductive layer toward the center. For each of the recorded cross sections, the above-mentioned measurement was performed in the 15 µm square range at three locations (0.2T, 0.5T, and 0.7T) in the thickness ranges at a depth of 0.1T to 0.9T from the outer surface of the conductive layer toward the support member, and the arithmetic mean of the measured values ​​determined at a total of nine locations was calculated. Method of measuring the circumference A and the shell circumference B of the core

[0184] The perimeter and hull perimeter of the kernel can be measured by quantizing the above-mentioned binary image. The perimeter A and hull perimeter B of each kernel in a domain group in the image are calculated using the counting function of the image processing software Image Pro Plus (from Media Cybernetics Co.) for the binary image, and thereby the arithmetic mean of the kernel perimeter ratio A / B can be calculated.

[0185] In the case of a cylindrical charging element in which the length of the conductive layer in the longitudinal direction is L and the thickness of the conductive layer is T, cross sections of the conductive layer in the thickness direction are taken as shown in Fig.5B, were taken at three locations, that is, at the center of the conductive layer in the longitudinal direction and at positions at L / 4 from both ends of the conductive layer toward the center. For each of the recorded cross sections, the above-mentioned measurement was performed in the 15 µm square range at three locations (0.2T, 0.5T, and 0.7T) in the thickness ranges at a depth of 0.1T to 0.9T from the outer surface of the conductive layer toward the support member, and the arithmetic mean of the measured values ​​determined at a total of nine locations was calculated.

[0186] As specified in configuration (3), by filling the conductive particles into the core at high density, the outer shape of the core can be close to spherical and the surface unevenness can be reduced as specified in configuration (4).

[0187] In order to obtain a domain in which the electrically conductive agent is filled at high density, carbon black whose DBP oil absorption amount is 40 to 80 cm 3 / 100g is particularly preferred as the electrically conductive agent. The DBP oil absorption amount (cm 3 / 100g) is a volume of dibutyl phthalate (DBP) that can adsorb 100g of carbon black and is measured according to Japan Industrial Standard (JIS) K6217-4: 2017 (Carbon black for rubber - Basic properties - Part 4: Determination of oil absorption amount (including compressed sample)).

[0188] Soot usually exhibits a higher-order cluster structure where primary particles (average particle diameter: 10 nm to 50 nm) are aggregated. This higher-order cluster structure is simply referred to as "structure," and the level of structure is measured by the DBP oil absorption amount (cm 3 / 100g) was quantified.

[0189] When the DBP oil absorption amount of the conductive carbon black is within the above range, the structure is underdeveloped and the aggregation of the carbon black is lower, meaning the carbon black is well dispersed in the rubber. Therefore, the filling amount of the carbon black in the core can be increased, and as a result, the outer shape of the core can be spherical. Furthermore, the conductive carbon black in which the DBP oil absorption amount is within the above-described range is effective in creating a domain that meets requirement (4) because it is difficult to form aggregates.

[0190] The charge attenuation rate of the electrophotographic element is not particularly limited, but is preferably 50 to 95%, and more preferably 65 to 95%. Within this range, charges accumulated by adhering contaminants can be more easily moved toward the support member side. The charge attenuation rate can be reduced by increasing the volume resistivity of the matrix, for example, by reducing the volume resistivity of the matrix. Calculation method of the charge damping rate

[0191] The charge attenuation rate can be calculated by measuring the surface potential of the charged surface of the electrophotographic member. For example, a voltage is applied to a corona discharge device to discharge current, thereby charging the surface of the electrophotographic member. Then, the surface potential of the charging roller immediately after charging is completed and the surface potential of the charged roller 10 seconds later are measured. Based on the change between the surface potential immediately after discharge and the surface potential 10 seconds later, the charge attenuation rate can be calculated. A specific method for this will be described later. process cartridge

[0192] The present disclosure provides a process cartridge detachably attached to a main body of an electrophotographic image forming apparatus, wherein the process cartridge includes: an electrophotographic photosensitive member and a charging member arranged to be capable of charging the electrophotographic photosensitive member, and the charging element is the electrophotographic element of the present disclosure.

[0193] Fig. 9 is a schematic cross-sectional view of the process cartridge for electrophotographers incorporating the electrophotographic element according to the present invention as the charging roller. This process cartridge is an integration of a developing device and a charging device and is detachably attached to the main body of the electrophotographic apparatus.

[0194] The developing device is an integration of at least a developing roller 93 and a toner container 96, and may also include a toner supply roller 94, toner 99, a developing blade 98, and a stirring blade 910 if necessary.

[0195] The charging device is an integration of at least a photosensitive drum 91, a cleaning blade 95, and a charging roller 92, and may also include a waste toner container 97. Voltage is applied to the charging roller 92, the developing roller 93, the toner supply roller 94, and the developing blade 98, respectively.

[0196] The electrophotographic member according to the present disclosure can be used as the charging roller, the developing roller, the developing blade, and the toner supply roller. The electrophotographic member is preferably a charging member and is more preferably a roller. Electrophotographic image forming device

[0197] The present disclosure provides an electrophotographic image forming apparatus comprising: an electrophotographic photosensitive member; and a charging member arranged to be capable of charging the electrophotographic photosensitive member, wherein the charging member is the electrophotographic member of the present disclosure.

[0198] Fig. Figure 10 is a schematic cross-sectional view of the electrophotographic image forming apparatus using the electrophotographic member of the present invention as the charging roller. This electrophotographic image forming apparatus is a color electrophotographic apparatus to which the process cartridge is detachably attached. Toner of each color (Black BK, Magenta M, Yellow Y, and Cyan C) is used for each process cartridge.

[0199] A photosensitive drum 101 rotates in the direction of the arrow and is uniformly charged by a charging roller 102 to which a voltage is applied from a charging bias power supply, and an electrostatic latent image is formed on the surface of the photosensitive drum 101 by an exposure lamp 1011. Toner 109 stored in a toner container 106 is supplied to a toner supply roller 104 by a stirring blade 1010 and conveyed onto a developing roller 103. Then, the toner 109 is evenly coated on the surface of the developing roller 103 by a developing blade 108 arranged in contact with the developing roller 103, and charges are provided to the toner 109 by triboelectric charging.The above-mentioned electrostatic latent image is developed by the toner 109 conveyed by the developing roller 103 arranged in contact with the photosensitive drum 101, and is thereby visualized as a toner image.

[0200] The visualized toner image on the photosensitive drum is transferred by a primary transfer roller 1012, to which power is applied by a primary transfer bias power supply, to an intermediate transfer belt 1015, which is supported and driven by a tension roller 1013 and an intermediate transfer belt drive roller 1014. A toner image of each color is sequentially superimposed, and a color image is formed on the intermediate transfer belt.

[0201] A transfer material 1019 is fed into the device through a paper feed roller and conveyed between the intermediate transfer belt 1015 and a secondary transfer roller 1016. The secondary transfer roller 1016, to which a voltage is applied from a secondary transfer bias power supply, transfers the color image on the intermediate transfer belt 1015 to the transfer material 1019. The color image transferred to the transfer material 1019 is fixed by a fixing unit 1018, and then the transfer material 1019 is discharged from the device, and the printing operation ends.

[0202] The untransferred toner remaining on the photosensitive drum is scraped off by a cleaning blade 105, stored in a waste toner container 107, and the cleaned photosensitive drum 101 undergoes a repetition of the above steps. The untransferred toner remaining on the primary transfer belt is scraped off by a cleaning device 1017.

[0203] The above is an example of a color electrophotographic device, but in the case of a monochrome electrophotographic device (not shown), only a process cartridge containing black toner is used. The monochrome image is formed directly onto the transfer member by the process cartridge and the primary transfer roller (there is no secondary transfer roller), without using the intermediate transfer belt. The monochrome image is then fixed by the fixing unit, and the transfer material is ejected from the device, completing the printing process. Examples

[0204] Examples of the present disclosure are described below, but the technical scope of the present disclosure is not limited thereto.

[0205] Examples and Comparative Examples are described below. The electrophotographic elements described in the Examples and Comparative Examples were fabricated using the materials indicated in Table 1. [Table 1] Material type Material abbreviation Material name Product name Manufacturer name Rubber material N230SV Acrylonitrile butadiene rubber (NBR) NBR N230SV JSR Corp. N202S Acrylonitrile butadiene rubber (NBR) NBR N202S JSR Corp. A303 Styrene-butadiene rubber (SBR) Asaprene 303 Asahi Kasei Corp. T2003 Styrene-butadiene rubber (SBR) Tufdene 2003 Asahi Kasei Corp. Esplene505A Ethylene-propylene-diene rubber (EPDM) Esplene505A Sumitomo Chemical Co., Ltd. Esplene301A Ethylene-propylene-diene rubber (EPDM) Esplene301A Sumitomo Chemical Co., Ltd. BR150B Polybutadiene rubber (BR) UBEPOLBR150B Ube Corp. IR2200L Isoprene rubber (IR) Nipol IR2200L ZeonCorp. B31 Chloroprene rubber (CR) SKYPRENEB31 TosohCorp. Butyl 065 Butyl rubber (butyl) Butyl 065 JSR Corp. CG102 Epichlorohydrin rubber EpichloromerCG 102 OsakaSoda Co.,Ltd. Conductive agent #7360SB Conductive soot DBP adsorption : 87cm3 / 100g TOKABLACK#7360SB TokaiCarbonCo., Ltd. Tin oxide Tin oxide type DBP adsorption: 80 cm3 / 100g S-2000 MitsubishiMaterialsElectronicChemicalsCo., Ltd. EC100J Conductive sootDBP adsorption: EC100J LionSpecialty 350 cm3 / 100g Chemicals Co., Ltd. Vulcanizing agent PMC sulfur SULFAX PMC TsurumiChemicalIndustryCo., Ltd. Vulcanization accelerator TB to TD Tetrabenzylthiuram disulfide SancelerTBzTD SanshinChemicalIndustryCo., Ltd. filler #30 Calcium carbonate Nanox #30 MaruoCalcium Co., Ltd. Example 11. Preparation of an unvulcanized rubber composition used to form a conductive layer. 1-1. Preparation of carbon masterbatch (CMB) for forming the core.

[0206] Each material indicated in Table 2 by type and mixing amount was mixed using a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.) to obtain the CMB for core formation. The mixing conditions were: a loading ratio of 70 vol%, a blade rotation frequency of 30 rpm, and a kneader temperature of 130°C for 16 minutes. [Table 2] Material name Mixed quantity (parts by mass) Second rubber EPDM (Product name: Esplene 505A, manufactured by Sumitomo Chemical Co., Ltd.) 100 Electrically conductive agent Carbon black (Product name: Toka black#7360SB, manufactured by TokaiCarbon Co., Ltd.) 60 Vulcanization accelerator Zinc Oxide (Product Name: Zinc Oxide Grade 2, manufactured by Sakai Chemical Industry Co. Ltd.) 5 Process aids Zinc Stearate (Product Name: SZ-2000, manufactured by Sakai Chemical Industry Co.Ltd.) 2 1-2. Preparation of the rubber composition (MSC) for the formation of matrix and shell

[0207] Each material, indexed by type and mixing amount in Table 3, was mixed using a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.) to obtain the rubber composition for forming a matrix and a shell. The mixing conditions were: a loading ratio of 70 vol%, a blade rotation frequency of 30 rpm, and a kneader temperature of 100°C for 16 minutes. [Table 3] Material name Mixed quantity (parts by mass) First rubber NBR (Product name: JSRNBR N230SV, manufactured by JSR Co., Ltd.) 80 Third rubber EPDM (Product name: Esplene505A, manufactured by Sumitomo Chemical Co., Ltd.) 20 filler Calcium Carbonate (Product Name: Nanox#30, manufactured by Maruo Calcium Co., Ltd.) 40 Vulcanization accelerator Zinc Oxide (Product Name: Zinc Oxide Two Types, manufactured by Sakai Chemical Industry Co., Ltd.) 5 Process aids Zinc Stearate (Product Name: SZ2000, manufactured by Sakai Chemical Industry Co., Ltd.) 2 1-3. Preparation of an unvulcanized rubber composition for forming a conductive layer

[0208] Each material, indexed by type and mixing amount in Table 4, was mixed using a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.) to obtain the unvulcanized rubber composition. The mixing conditions were: a loading ratio of 70 vol%, a blade rotation frequency of 30 rpm, and a kneader temperature of 100°C for 16 minutes. [Table 4] Material name Mixed quantity (parts by mass) Material rubber Rubber composition for forming the core (CMB) 26 Material rubber Rubber composition for forming the matrix and shell (MSC) 74

[0209] Each material indicated in Table 5 with type and blending amount was mixed using an open roll to obtain an unvulcanized rubber composition for forming a conductive layer.

[0210] The mixing machine used here was an open roller with a roller diameter of 12 inches. The mixing conditions were: a front roller rotation frequency of 10 rpm and a rear roller rotation frequency of 8 rpm. After the left and right rollers were changed a total of 20 times with a roller gap of 2 mm, dense grinding was performed 10 times with a roller gap of 1.0 mm. [Table 5] Material name Mixed quantity (parts by mass) Material rubber Non-vulcanized rubber composition 100 Vulcanizing agent Sulfur (Product name: Sulflax PMC, sulfur content of 97.5%, manufactured by Tsurumi Chemical Industry Co., Ltd.) 3 Vulcanization accelerator1 Tetrabenzylthiuram disulfide (Product name: Sanceler TBzTD, manufactured by Sanshin Chemical Industry Co., Ltd.) 1 Vulcanization accelerator2 Nt-butyl-2-benzothiazolesulfenimide (Product name: SANTOCRE-TBSI, manufactured by FLEXSYS Corp.) 0,5 2. Manufacturing the electrophotographic element (conductive element) 2-1. Forming a conductive layer

[0211] For the support element, a core metal (252 mm long, 6 mm outer diameter) was prepared by electroless nickel plating the surface of free-cutting steel. This core metal was used as a conductive shaft core (support element). Then, using a roll coating machine, an adhesive (product name: Metaloc U-20, manufactured by Toyokagaku Kenkyusho, Co. Ltd.) was applied to the entire surface of the core metal within a 230 mm area, except for 11 mm at each end. In this example, the adhesive-coated core metal was used as the conductive support element.

[0212] Then, a die (inner diameter: 10.0 mm) was attached to a tip of the crosshead extruder, which included a feeding mechanism for the conductive support member and a discharging mechanism for the unvulcanized rubber roller. The temperature of the extender and the crosshead was set to 100 °C, and the conveying speed of the conductive support member was set to 60 mm / sec. Under these conditions, the unvulcanized rubber composition for forming a conductive layer was fed using the extruder, and the outer peripheral portion of the conductive member was coated with the unvulcanized rubber composition for forming a conductive layer within the crosshead, thereby obtaining an unvulcanized rubber roller.

[0213] Then, the unvulcanized rubber roller was placed in a hot-air vulcanization oven (170 °C) and heated for 60 minutes, thereby vulcanizing the unvulcanized rubber composition and obtaining the conductive layer. A conductive layer was formed on the outer peripheral portion of the conductive support member. Then, 10 mm was cut off from each end of the conductive layer, so that the longitudinal length of the conductive layer was 232 mm. 2-2. Polishing the conductive layer

[0214] Then, by polishing the surface of the conductive layer according to the polishing conditions mentioned in the following Polishing Conditions 1, a crown-shaped charging roller 1 (diameter of the central portion is 8.5 mm and each diameter at 90 mm positions from the center to both ends is 8.44 mm) was obtained. Polishing conditions 1

[0215] A cylindrical whetstone (from Teiken Corp.) with a diameter of 305 mm and a length of 235 mm was provided. The grain type, grain size, bonding degree, binder, and structure (grain fraction) are as follows. - Grain material: GC (green silicon carbide), (JISR6111-2002) - Grain size: #80 (average grain diameter: 177 µm, JISB4130) - Grain binding degree: HH (JISR6210) - Binder: V4PO (vitrified) - Grain structure (grain content): 23 (grain content percentage: 16% JISR 6242)

[0216] The polishing conditions are as follows. The rotation speed of the grindstone was 2100 rpm, and the rotation speed of the conductive element was 250 rpm. In the rough polishing step, the entry speed of the grindstone to the conductive element was 20 mm / s, and the grindstone was allowed to penetrate 0.24 mm after contact with the outer peripheral surface of the conductive element. In the fine polishing step, the entry speed was changed to 0.5 mm / s, and the grindstone was allowed to penetrate 0.01 mm. The grindstone was then separated from the conductive element, and polishing was completed. The polishing process used an upper cutting method in which the rotation directions of the grindstone and the conductive element were the same. 3. Property Evaluation 3-1. Measurement of the Volume Resistivity of the Matrix

[0217] The volume resistivity of the matrix was measured in contact mode using a scanning probe microscope (SPM) (product name: Q-Scope 250, manufactured by Quesant Instrument Corp.) as follows. The measurement environment was a temperature of 23°C and a relative humidity of 50%.

[0218] First, a slice approximately 2 µm thick was cut from the conductive layer of the charging roller 1 at a cutting temperature of -100 °C using a microtome (product name: Leica EMFCS, manufactured by Leica Microsystems). For the cutout, as mentioned above, cross sections of the conductive layer were cut in the thickness direction of the conductive layer, as shown in Fig.5B. For each of the obtained cross-sections, a 15 µm square observation area was arranged at three locations (0.2T, 0.5T, and 0.7T) in the thickness range from the outer surface of the conductive layer toward the support element at depths of 0.1T and 0.9T, a measurement was performed, and the arithmetic mean of the measured values ​​was calculated at a total of nine locations.

[0219] Then, this disk was placed on a metal plate so that a surface of the disk corresponding to the cross-section of the conductive layer came into contact with the surface of the metal plate. Then, a cantilever of the SPM was contacted at a location corresponding to the matrix on the disk surface, opposite the surface in contact with the metal plate. A voltage of 50 V was then applied to the cantilever, and the current value was measured. Furthermore, the surface profile of this disk was observed using the SPM, and the thickness of the measurement point was calculated based on the obtained height profile. The surface area of ​​the depressed portions of the portion contacting the cantilever was also calculated based on the observation result of the surface profile.Then, the volume resistivity of this thickness and the surface area of ​​the depressed sections was calculated, and the result was regarded as the volume resistivity of the matrix. 3-2. Measurement of the volume resistance of the shell

[0220] A slice was cut using the same method as for measuring the volume resistivity of the matrix. Then, the slice was sectioned at 60 nm intervals using the FIB-SEM, and a volume centroid was calculated for the acquired cross-section using an image analysis device (product name: LUZEX-AP, manufactured by Nireco Corp.). The shell of the cross-section at the position where the cantilever was in contact was measured using the same method described for measuring the volume resistivity of the matrix. The arithmetic mean of the values ​​measured at the measurement positions was then calculated.

[0221] The same step was repeated until the entire domain was sectioned. For the three-dimensional image obtained by FIB-SEM, the volume centroid was calculated using an image analysis device (product name: LUZEX-AP, manufactured by Nireco Corp.), and whether the volume centroid existed within the domain was analyzed. If the domain was domain A, the volume resistivity of the outer peripheral region of the domain on the cross-section closest to the volume centroid of the domain was considered the volume resistivity of the shell. 3-3. Measuring the thickness of the shell

[0222] To evaluate the thickness of the shell, the following measurement was performed.

[0223] The slice was cut out in the same way as in the shell volume resistivity measurement described above. This slice was then stained using phosphotungstic acid. The slice was then sectioned at 60 nm intervals using an FIB-SEM, and a volume center of gravity was calculated for the obtained cross-sections using an image analyzer (product name: LUZEX-AP, manufactured by Nireco Corp.). Platinum was then deposited on the obtained cross-section, and an image of the platinum-deposited surface was taken using an SEM (product name: S-4800, manufactured by Hitachi High Tech Corp.) at 10,000x magnification to obtain an SEM image.

[0224] Subsequently, this SEM image was processed in 8-bit grayscale using an image analysis device (product name: LUZEX-AP, manufactured by Nireco Corp.), obtaining a 256-gradation monochrome image. Then, the black and white of the binary image were inverted so that the colored shell becomes white in the monochrome image. The image was then binarized by setting a binarization threshold for the brightness distribution of the image based on the Otsu discriminant analysis method algorithm. The thickness of the shell was calculated from the obtained binary image. This step was repeated until the entire domain was sectioned. For the three-dimensional image obtained by the FIB-SEM, the volume centroid was calculated using the image analysis device (product name: LUZEX-AP, manufactured by Nireco Corp.), and it was analyzed whether the volume centroid existed within the domain.When the domain was domain A, the shell thickness on the cross-section closest to the volume centroid of the domain was considered as the shell thickness of domain A.

[0225] When the thickness of the conductive layer was T, a 15 µm square observation region was placed at three locations (0.2T, 0.5T, and 0.7T) in the thickness region from the outer surface of each of the three layers at depths of 0.1T to 0.9T (a total of nine locations). In each observation region, the thickness of the shell was calculated, and the arithmetic mean of the measured values ​​of the thickness of each shell at nine locations was calculated. 3-4. Measurement of the volume resistance of the core

[0226] The volume resistivity of the core was measured in the same manner as the above-mentioned method for the volume resistivity of the shell, except that the contact position of the cantilever was a location corresponding to the core, and the voltage applied to the cantilever was 1 V. Then, the average value of the values ​​measured at the measurement positions was calculated. 3-5. Measuring the distance between the cores

[0227] For the disk prepared for measuring the volume resistivity of the matrix, only the second rubber contained in the core was dyed using phosphotungstic acid. Platinum was then deposited on the surface corresponding to the cross-section of the conductive layer. An image of the platinum-deposited surface was subsequently taken using an SEM (product name: S-4800, Hitachi High Tech Corp.) at 10,000x magnification to obtain an SEM image.

[0228] Subsequently, 8-bit grayscale processing was performed on this SEM image using an image analysis device (product name: LUZEX-AP, manufactured by Nireco Corp.), obtaining a 256-gradation monochrome image. Then, the black and white of the binary image were inverted so that the colored nucleus in the monochrome image becomes white. The image was then binarized by setting a binarization threshold for the brightness distribution of the image based on the Otsu discriminant analysis method algorithm.

[0229] For the obtained binary image, when the thickness of the conductive layer was T, a 15 µm square observation region was placed at three locations (0.2T, 0.5T, and 0.7T) in the region corresponding to the thickness region from the outer surface of each of the three layers at a depth of 0.1T to 0.9T (a total of nine locations). In each observation region, the inter-nuclear distance was calculated, and the arithmetic mean of the measured values ​​of each inter-nuclear distance was calculated at a total of nine locations. 3-6. Evaluation of the shape of the core

[0230] The shape of a core contained in the conductive layer was evaluated by the following method of quantizing the observation image obtained using the scanning electron microscope (SEM) through image processing.

[0231] A thin slice (1 mm thick) was cut out in the same way as in the above-described measurement of the volume resistivity of the shell. For the thin slice, a surface perpendicular to the axis of the conductive support member and a fracture surface of a cross-section parallel to this surface were taken. When the length of the conductive layer in the longitudinal direction was L, the cut-out positions from the conductive layer were obtained at three locations: the center in the longitudinal direction and the positions at L / 4 from both ends of the conductive layer toward the center. Then, the cut-out slice was sectioned at 60 nm intervals using an FIB-SEM, and platinum was deposited on the obtained cross-section. Next, the image was imaged using a scanning electron microscope (SEM) (product name: S-4800, manufactured by Hitachi High Tech Corp.) at 1 nm.000x magnification, an image of the platinum-deposited surface was taken to obtain a viewing image.

[0232] This step was repeated until the entire domain was sectioned. For the resulting three-dimensional image, the volume centroid was calculated using the image analysis device (product name: LUZEX-AP, manufactured by Nireco Corp.), and whether the volume centroid was within the domain was analyzed to determine whether this domain was Domain A. For the core of Domain A, the shape was evaluated using the following method.

[0233] Then, when the thickness of the conductive layer was T, the areas of 15 µm square arranged at three locations (0.2T, 0.5T and 0.7T) in the thickness range from the outer surface of the conductive layers in the depth of 0.1T to 0.9T (a total of nine locations) of each of the three slices obtained from the three above-mentioned measuring positions were extracted as analysis images.

[0234] To subsequently quantify the domain shape in this analysis image, 8-bit grayscale processing was performed using the image processing software Image Pro Plus (from Media Cybernetics Corp.), resulting in a 256-gradation monochrome image. The black and white of the image were then inverted so that the nuclei on the fracture surface became white, thus obtaining a binary image. Using the counting function, the following points were then calculated for the nuclei group present in this binary image. - Circumference A (µm) - Shell circumference B (µm)

[0235] These values ​​were substituted into Expression (6), and the numerical ratio of the number of nuclei satisfying the condition of Expression (6) was calculated as the quantity % with respect to the total number of nuclei groups in each evaluation image, and an index of the shape of the nucleus was determined by calculating an arithmetic mean of the evaluation images at the nine locations. 1.00≤A / B≤1.10 (A: Core circumference; B: Core shell circumference) 3-7. Measurement of the charge damping rate on the charging roller surface

[0236] The surface potential of the charging roller after corona discharge was measured using a charge quantity measuring device (product name: DRA-2000L, manufactured by QEA Inc.). Specifically, a corona discharge device of the charge quantity measuring device was positioned so that the gap between a portion of the grid and the surface of the charging roller became 1 mm. Then, by applying a voltage of 8 kV to the corona discharge device, a discharge was generated to charge the charging roller surface. The surface potential immediately after this charging (immediately after the end of the discharge) and the surface potential of the charging roller 10 seconds later were measured.

[0237] The charge attenuation rate Q (%) was then calculated using the following expression (7), where E0 was the surface potential immediately after charging and E10 was the surface potential 10 seconds later after the end of discharge (or after charging). Q={(E0−E10) / E0}×100 3-8. Impedance measurement

[0238] As a pretreatment, platinum was deposited on the outer surface of the charging roller (electrophotographic element) while the charging roller rotated, creating a measuring electrode (platinum electrode). Using masking tape, a 1.5 cm wide electrode was created that was uniform in the circumferential direction. By creating this electrode, the negative influence of the surface roughness of the electrophotographic element on the contact area between the measuring electrode and the electrophotographic element can be minimized.

[0239] Then, an aluminum foil was wrapped around this electrode without any gaps, creating the measurement sample. An impedance measuring device (product name: Solartron 1260 and Solartron 1296, manufactured by Solartron Co.) was then connected to the measuring electrode and the outer surface of the support element via the aluminum foil.

[0240] Fig. 11 and Fig. 12 are schematic diagrams showing a state in which the measuring electrode has been formed on the charging roller. In Fig. 11, 111 is the conductive support element, 112 is the conductive layer, 113 is the platinum-deposited layer, and 114 is the aluminum foil. In Fig. 12, 121 is the conductive support element, 122 is the conductive layer having a matrix domain structure, 123 is the aluminum deposited layer and 124 is the aluminum foil.

[0241] Fig. 12 is a cross-sectional view illustrating a state in which the measuring electrode is formed on the charging roller. As shown in Fig. As shown in Figure 12, it is important to place the conductive layer, which has the matrix domain structure, between the conductive support element and the measuring electrode. Then, as shown in Fig.As shown in Figure 13, the aluminum foil and the outer surface of the support member were connected to the measuring electrodes on the side of the impedance measuring device (product name: Solartron 1260 and Solartron 1296, manufactured by Solartron Co.). The impedance was measured using the conductive support member and the aluminum foil as two measuring electrodes.

[0242] The impedance was measured in an environment with a temperature of 23 °C and a relative humidity of 50%, at an amplitude of 1 V and a frequency of 1.0 × 10 -2 up to 1.0 × 10 7Hz. The measurement points were changed every time the frequency changed by one digit, and the measurement was performed at five locations each time. The measurement points were the central section of each area, which was determined by equally dividing the longitudinal (axial) direction of the electrophotographic element into five sections. The absolute value of the impedance was determined by taking the arithmetic mean of these measured values.

[0243] Then, using the measurement result, the absolute value of the impedance was plotted on the ordinate and the frequency on the abscissa in the log-log graph. The slope of the impedance in the frequency range was 1.0 × 10 -2 up to 1.0 × 10 1 Hz (low frequency impedance) and the slope of the impedance in the frequency range 1.0 × 10 5 up to 1.0 × 10 6 Hz (high frequency impedance) is calculated. 4. Image Evaluation 4-1. Evaluation of Loading Capacity

[0244] The following evaluation was conducted to confirm the discharge leakage suppression function of the charging roller 1.

[0245] First, an electrophotographic laser printer (product name: Laserjet M608dn, manufactured by HP Co.) was prepared as the electrophotographic device. Then, the charging roller 1, the electrophotographic device, and the process cartridge were left in an environment of 23°C / 50% RH for 48 hours to adapt to the measurement environment.

[0246] To conduct the evaluation in a high-speed process, this laser printer was modified so that the number of sheets output per unit minute was 75 sheets / minute (A4 paper), which was greater than the original output number. The recording media output speed was set to 370 mm / sec and the image resolution was set to 1200 dpi. The pre-exposure device in the laser printer was removed. Furthermore, the process cartridge was modified so that the drum surface potential could be measured after charging using a surface potential probe (main body: Model 347, probe: Model 3800S-2, manufactured by Trek Co. Ltd.).

[0247] The charging roller 1, which was left in the above-mentioned environment, was set as the charging roller of the process cartridge and was attached to the laser printer.

[0248] In the same environment as above, using an external power supply (Trek 615, manufactured by Trek Japan Co.), a voltage of -1000 V was applied to the charging roller 1, and a white and a black solid image were output. Then, the difference (black and white potential difference) between the surface potential of the photosensitive drum after charging when the black solid image was output and the surface potential of the photosensitive drum after charging when the white solid image was output was calculated. Table 8 and Table 11 are the results. A low black and white potential difference means that the charging capability of the charging roller is high. 4-2. Evaluation of the ghost image

[0249] The effect of generating a uniform discharge in the high-speed process of the charging roller 1 even when the surface potential of the photosensitive drum before charging is uneven was confirmed by the following method.

[0250] The laser printer used for the above-mentioned "Chargeability Evaluation" was used to generate an evaluation image. Just as in the "Chargeability Evaluation," the charging roller 1, the laser printer, and the process cartridge were left in an environment of 23°C / 50% RH for 48 hours to adapt to the measurement environment, and the evaluation image was generated in the same environment. The evaluation image featured the letters "E" in the upper part of the image and a halftone image below the central portion of the image. Table 8 and Table 11 are the results.

[0251] Specifically, the letters "E" (size: 4 pt.) were printed in the upper 10 cm area of ​​the image to cover 4% of the A4 paper. This allows the surface potential (before the charging process) of the photosensitive drum to form an initial unevenness along the surface potential after the transfer process, corresponding to the letters "E" in an area covered by one cycle of the photosensitive drum. Fig. Figure 14 is a diagram describing this evaluation image.

[0252] Furthermore, a halftone image (an image created by drawing horizontal lines with a width of 1 dot and a distance of 2 dots perpendicular to the rotation direction of the photosensitive drum) was output below the upper 10 cm. This halftone image was visually observed and evaluated based on the following standards. Table 8 and Table 11 are the results.

[0253] Evaluation of the letters "E" on the halftone image. Rank A: No image unevenness caused by the letters "E" is visible on the halftone image, even when using a microscope. Rank B: No image unevenness caused by the letters "E" is visually visible on the halftone image, but it is visible in part of the halftone image when using a microscope. Rank C: An image of the letters “E” is visually recognizable on a part of the halftone image. Rank D: An image of the letters “E” is visually recognizable over the entire area of ​​the halftone image. 4-3. Evaluation of the white point image

[0254] The following evaluation was conducted to confirm the contamination resistance performance when the charging roller 1 is used for a long period of time.

[0255] First, an electrophotographic laser printer (product name: Laserjet Pro M203dw, manufactured by HP Co.) was prepared as the electrophotographic device. To conduct the evaluation in a high-speed process, this laser printer was subsequently modified so that the number of sheets output per minute was 75 sheets / minute (A4-sized paper), which was more than the original number of output sheets. The output speed of the recording media was set to 370 mm / sec.

[0256] Then, the charging roller 1, the electrophotographic image forming device, and the process cartridge were left in an environment of 15 °C / 30% RH for 48 hours to adapt to the measurement environment.

[0257] Charging roller 1, which was left in the above-mentioned environment, was set as the process cartridge charging roller and attached to the laser printer. Then, a total of 50,000 sheets of images were sequentially output in the same environment.

[0258] For the output image, the letters “E” (size: 4 pt.) were printed at a print ratio of 1.0% on A4 paper.

[0259] Then, a halftone image (an image created by drawing horizontal lines with a width of 1 dot and a distance of 2 dots perpendicular to the rotation direction of the photosensitive drum) was output. This halftone image was visually observed, and the white dot images were evaluated based on the following standards.

[0260] Evaluation of white point images on halftone images Rank A: No white point is visible on the halftone image, even when using a microscope. Rank B: There is no white point visually visible on the halftone image, but it can be seen when using a microscope. Rank C: A white point is visible on part of the halftone image. Rank D: A white point is visible over the entire area of ​​the halftone image. Examples 2 to 24

[0261] Charging rollers 2 to 24 were each manufactured according to the same method as charging roller 1 of Example 1, except that the raw materials were changed as indicated in Table 6 and Table 7. In Example 7, the temperature in the kneader when preparing the carbon masterbatch (CMB) for forming the core was changed to 150°C. Table 6 and Table 7 indicate the mass fractions and physical properties of each raw material used to manufacture each charging roller of the core. Table 8 shows the results of property evaluation and image analysis of the finished charging rollers 2 to 24. [Table 6] Non-vulcanized rubber composition for forming the conductive layer Rubber composition for matrix and shell formation (MSC) First rubber Third rubber filler zinc oxide Zinc stearate Rubber type abbreviation Mooney viscosity SP value parts Rubber type abbreviation Mooney viscosity SP value parts abbreviation parts parts parts E-1 NBR N230SV 32 20 80 EPDM E505A 47 16 20 #30 40 5 2 E-2 CR B31 40 17,4 80 EPDM E505A 47 16 20 #30 40 5 2 E-3 NBR N230SV 32 20 80 BR BR150B 40 16,8 20 #30 40 5 2 E-4 NBR N230SV 32 20 80 IR IR2200L 70 16,5 20 #30 40 5 2 E-5 NBR N230SV 32 20 80 Butyl JSRButyl065 32 15,8 20 #30 40 5 2 E-6 NBR N230SV 32 20 80 EPDM E505A 47 16 20 #30 40 5 2 E-7 NBR N230SV 32 20 80 EPDM E505A 47 16 20 #30 40 5 2 E-8 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-9 CR B31 40 17,4 80 SBR T2003 33 17 20 #30 40 5 2 E-10 NBR N230SV 32 20 80 IR IR2200L 70 16,5 20 #30 40 5 2 E-11 NBR N230S 32 20 80 BR BR150B 40 16 20 #30 40 5 2 V ,8 E-12 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-13 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-14 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-15 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-16 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-17 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-18 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-19 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-20 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-21 NBR N230SV 32 20 80 SBR T2003 33 17 20 #30 40 5 2 E-22 NBR N230SV 32 20 90 SBR T2003 33 17 10 #30 40 5 2 E-23 NBR N230SV 32 20 70 SBR T2003 33 17 30 #30 40 5 2 E-24 NBR N230SV 32 20 60 SBR T2003 33 17 40 #30 40 5 2 [Table 7] Non-vulcanized rubber composition for forming a conductive layer Rubber composition for forming the core (CMB) Mixing ratio Second rubber Electrically conductive agent zinc oxide Zinc stearate MSC CMB Rubber type abbreviation Mooney viscosity SP-We rt parts abbreviation parts parts parts parts parts E-1 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 E-2 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 E-3 BR BR150B 40 17 100 #7360SB 60 5 2 74 26 E-4 IR IR2200L 70 17 100 #7360SB 60 5 2 74 26 E-5 Butyl JSR Butyl065 32 16 100 #7360SB 60 5 2 74 26 E-6 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 E-7 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 E-8 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 E-9 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 E-10 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 E-11 EPDM E505A 47 16 100 #7360S 60 5 2 74 26 B E-12 IR IR2200L 70 17 100 #7360SB 60 5 2 74 26 E-13 BR BR150B 40 17 100 #7360SB 60 5 2 74 26 E-14 NBR N230SV 32 20 100 #7360SB 60 5 2 74 26 E-15 Butyl JSR Butyl065 32 16 100 #7360SB 60 5 2 74 26 E-16 EPDM E505A 47 16 100 #7360SB 30 5 2 74 26 E-17 EPDM E505A 47 16 100 #7360SB 40 5 2 74 26 E-18 EPDM E505A 47 16 100 #7360SB 80 5 2 74 26 E-19 EPDM E505A 47 16 100 Tin oxide 60 5 2 74 26 E-20 EPDM E505A 47 16 100 #7360SB 60 5 2 82 18 E-21 EPDM E505A 47 16 100 #7360SB 60 5 2 64 36 E-22 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 E-23 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 E-24 EPDM E505A 47 16 100 #7360SB 60 5 2 74 26 [Table 8] Example Loading roller no. Non-vulcanized rubber composition for forming a conductive layer Physical properties of the roller matrix domain DomainAQuality-% Image Evaluation 1 (Mind) Image Evaluation 2 (White Dots) core Peel Black / white potential difference / V Ghost image White point rank@50K Low frequency impedance / Ω Slope of high-frequency impedance Charge damping rate % Volume resistance / Ω·cm Volume resistance / Ω·cm Distance between nuclei / µm Electrically conductive mediumCross-sectional area ratio % Circumference ratio A / B Volume resistance / Ω·cm Thickness / µm 1 1 E-1 8,90E+04 -0,61 73 2,11E+09 5,94E+01 0,25 26 1,06 2,11E+09 042 31 38 B A 2 2 E-2 2,28E+04 -0,5 58 5,20E+10 4,75E+01 0,27 26,2 1,05 5,20E+10 014 33 39 B B 3 3 E-3 8,72E+04 -0,62 72 2,37E+09 4,96E+01 0,29 26,4 1,05 2,37E+09 032 29 28 B A 4 4 E-4 7,59E+04 -0,61 72 1,90E+09 5,86E+01 0,28 25,9 1,04 1,90E+09 024 34 26 B A 5 5 E-5 6,21E+03 -0,43 75 1,86E+09 6,21E+01 0,28 26,3 1,07 1,86E+09 0- 6 6 31 26 B A 6 6 E-6 6,58E+03 -0,44 71 2,11E+09 5,55E+01 0,25 25,8 1,06 2,11E+09 045 53 19 A A 7 7 E-7 2,22E+03 -0,35 69 2,01E+09 5,88E+01 0,26 26,1 1,07 2,01E+09 042 81 7 A A 8 8 E-8 8,40E+04 -0,46 70 2,31E+09 6,13E+01 0,27 26 1,07 2,31E+09 025 71 19 A A 9 9 E-9 8,31E+04 -0,52 56 5,33E+10 4,57E+01 0,28 26,3 1,05 5,33E+10 016 70 16 A B 10 10 E-10 6,10E+03 -0,46 71 1,95E+09 5,29E+01 0,22 26,1 1,07 1,95E+09 03 1 73 8 A A 1 11 E-11 2,28E+ -0,52 72 2,10 6,39 0, 26 1,05 2,10 0 70 11 A A 1 04 E+09 E+01 24 E+09 ,26 12 12 E-12 8,43E+04 -0,54 70 2,04E+09 5,47E+01 0,22 26,2 1,06 2,04E+09 0, 3 1 69 19 A A 13 13 E-13 8,72E+04 -0,53 73 1,86E+09 4,82E+01 0,21 26,2 1,07 1,86E+09 0, 29 71 18 A A 14 14 E-14 8,40E+04 -0,72 73 1,89E+09 4,98E+01 0,26 26,4 1,05 1,89E+09 0,3 30 41 C A 15 15 E-15 8,26E+04 -0,53 71 2,00E+09 4,44E+01 0,53 25,9 1,06 2,00E+09 032 71 15 A A 16 16 E-16 2,52E+05 -0,52 66 2,31E+09 4,87E+01 0,27 19,4 1,12 2,31E+09 0, 29 69 32 B A 17 17 E-17 8,91E+04 -0,48 71 2,52E+00 4,19E+03 0,26 20,7 1,1 2,52E+00 0,33 70 20 A A 18 18 E-18 4,23E+04 -0,42 78 2,22E+09 2,10E+01 0,27 27,4 1,02 2,22E+09 032 73 14 A A 19 19 E-19 9,14E+04 -0,51 69 1,59E+00 5,66E+01 0,3 26 1,1 1,59E+00 0,3 71 19 A A 1 20 20 E-20 8,11E+04 -0,36 72 2,25E+09 5,89E+01 0,21 26,1 1,05 2,25E+09 0,52 81 4 A A 21 21 E-21 8,45E+04 -0,54 71 1,97E+09 4,76E+01 0,72 26 1,05 1,97E+09 025 57 25 B A 22 22 E-22 8,64E+04 -0,37 71 1,94E+09 4,89E+01 0,3 25,9 1,05 1,94E+09 0,23 68 6 A A 23 23 E-23 8,55E+04 -0,42 69 2,06E+09 5,27E+01 0,28 26,3 1,07 2,06E+09 041 72 20 A A 24 24 E-24 8,10E+04 -0,48 68 2,05E+09 4,78E+01 0,29 26,1 1,04 2,05E+09 0,68 75 24 A A

[0262] For example, in the tables above, 8.90E + 04 indicates 8.90 × 10 4 . This is the same for each of the following tables. Comparative examples 1 to 6

[0263] Charging rollers 25 to 30 were each manufactured according to the same method as in Example 1, except that the materials to be used were changed as indicated in Table 9 and Table 10. Table 11 shows the results of the property evaluation and image evaluation of the finished charging rollers 25 to 30.

[0264] In Comparative Example 1, the volume resistivity of the matrix was high, allowing charging to occur within the domain and suppressing ghosting. On the other hand, the volume resistivity in the outer peripheral region of the domain (i.e., the matrix) was high, resulting in a low charge attenuation rate and the generation of white spots.

[0265] In Comparative Example 2, the volume resistivity of the matrix was low, so the charge attenuation rate was high and white spots could be suppressed. On the other hand, the volume resistivity in the outer peripheral region (i.e., in the matrix) was low, so sufficient charging could not occur in the domain, and ghost images were generated.

[0266] In Comparative Example 3, the matrix domain structure was not included, and the effect of the domain to suppress the movement of charges could not be obtained, so ghost images were generated.

[0267] In Comparative Example 4, the value of the low-frequency impedance is 5.50 × 10 10 Ω, which is higher than 1.00 × 10 7 Ω. Therefore, uniform discharge was reduced, and the discharge amount did not reach the level needed to fill the surface potential irregularities. As a result, ghost images were generated.

[0268] In Comparative Example 5, a material with high DBP oil absorption was used for the electrically conductive agent, and the kneading time to form the unvulcanized rubber composition was 5 minutes. Since the volume center of gravity of the domain in this structure did not exist within the domain, conduction was not uniform, and localization-dependent discharges were generated, resulting in ghost images.

[0269] In Comparative Example 6, the core does not contain the electrically conductive agent and is ionically conductive. In the case of an ionically conductive core, there was no charge storage capability at the interface between the electrically conductive agent and the second rubber in the domain, and the effect of suppressing charge leakage into the domain decreased, resulting in ghost images. Furthermore, in the ionic conductive configuration, the charge transport rate is slower than electrical conduction, and the high impedance slope is -0.90, which is smaller than -0.80. Therefore, discharge leakage was more easily generated, and white spots were generated. [Table 9] Non-vulcanized rubber composition for forming a conductive layer Rubber composition for forming the matrix and shell (MSC) First rubber Third rubber filler zinc oxide Zinc stearate Rubber type abbreviation Mooney viscosity SP value parts Rubber type abbreviation Mooney viscosity SP value parts abbreviation parts parts parts E-25 SBR T2003 33 17 100 - - - - - #30 40 5 2 E-26 NBR N230SV 32 20 100 - - - - - #30 40 5 2 E-27 - - - - - - - - - - - - - - E-28 NBR N230SV 32 20 80 EPDM E505A 47 16 20 #30 40 5 2 E-29 NBR N230SV 32 20 80 EPDM E505A 47 16 20 #30 40 5 2 E-30 NBR N202S 57 20, 4 80 NBR N230SV 32 20 80 #30 40 5 2 [Table 10] Non-vulcanized rubber composition for forming a conductive layer Rubber composition for forming the core (CMB) Mixing ratio Second rubber Electrically conductive agent zinc oxide Zinc stearate MSC CMB Rubber type abbreviation Mooney viscosity SP-Wor t parts abbreviation parts parts parts parts parts E-25 NBR N230SV 32 20 100 #7360SB 60 5 2 74 26 E-26 SBR T2003 33 17 100 #7360SB 60 5 2 74 26 E-27 EPDM E505A 47 16 100 #7360SB 60 5 2 0 100 E-28 EPDM E505A 47 16 100 #7360SB 60 5 2 95 5 E-29 EPDM E505A 47 16 100 EC100J 5 5 2 74 26 E-30 ECO CG102 64 18,5 100 - - 5 2 74 26 [Table 11] Example Loading roller no. Non-vulcanized rubber composition for forming a conductive layer Physical properties of the roller matrix domain Domain AQuantity-% Image Evaluation 1 (Mind) Image evaluation 2 (white dots) core Peel Low frequency impedance / Ω Slope of high-frequency impedance Charge damping rate % Volume resistance / Ω·cm Volume resistance / Ω·cm Distance between nuclei / µm Electrically conductive mediumCross-sectional area ratio % Circumference ratio A / B Volume resistance / Ω·cm Thickness / µm Black / White potential difference / V Ghost image White point rank@50K Comparison example 1 25 E-25 8,78E+04 -0,63 36 5,92E+12 6,99E+01 0,26 26,6 1,08 - - - 36 B D Comparison example 2 26 E-26 1,57E+07 -1 71 2,58E+09 5,21E+01 0,23 26,3 1,04 - - - 62 D A Comparison example 3 27 E-27 2,55E+08 -1 85 - - - - - - - - 65 D B Comparison example 4 28 E-28 5,50E+10 -0,85 75 3,55E+09 2,22E+01 1,22 26,2 1,02 5,50E+16 032 12 62 D B Comparison example 5 29 E-29 2,20E+05 -0,86 65 5,50E+09 2,30E+01 1,55 12,1 1,15 3,50E+16 055 5 60 D B Comparison example 6 30 E-30 5,50E+09 -0,9 33 2,20E+09 2,50E+06 0,23 - 1,1 3,20E+16 0,34 25 64 D D

[0270] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be broadly interpreted to include all such modifications and equivalent structures and functions. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2020-166210 [0004, 0005, 0016, 0023, 0024, 0026, 0027]

Claims

[1] An electrophotographic element comprising: a carrier element having a conductive outer surface; and a conductive layer disposed on an outer surface of the carrier element, wherein the conductive layer a matrix comprising a first rubber, and a multitude of domains dispersed in the matrix, includes, the volume resistivity of the matrix 1.00 × 10 12 Ω · cm or less, the plurality of domains comprises at least one domain A, and the domain A the following<Bedingung 1> until<Bedingung 3> fulfilled: <Bedingung 1> Domain A comprises a second rubber and an electrically conductive agent; <Bedingung 2> a volume center of mass of domain A exists in domain A; <Bedingung 3>on a cross-section of domain A passing through the volume center of gravity, the volume resistance of an outer peripheral region, which is a region with a distance of 100 nm from an outer edge of domain A in the direction of the volume center of gravity, is more than 1.00 × 10 12 Ω · cm, and where In a case where a platinum electrode is directly disposed on an outer surface of the electrophotographic member, the impedance is measured by applying an AC voltage having an amplitude of 1 V between the outer surface of the support member and the platinum electrode in an environment having a temperature of 23°C and 50% relative humidity, while changing the frequency in a range of 1.0 × 10 -2 up to 1.0 × 10 7 Hz, and the frequency is plotted on an abscissa and the impedance is plotted on an ordinate of a log-log graph, a slope in a frequency range of 1.0 × 10 5up to 1.0 × 10 6 Hz is -0.80 to -0.30, and the impedance in a frequency range of 1.0 × 10 -2 up to 1.0 × 10 1 Hz 1.00 × 10 3 up to 1.00 × 10 7 Ω is. [2] An electrophotographic member according to claim 1, wherein in at least eight samples from cubic samples of which one side is 6 µm and which are taken from nine locations of the conductive layer, a ratio of the number of domains A with respect to a total number of pluralities of domains is more than 50 quantity%. [3] An electrophotographic element according to claim 1 or 2, wherein domain A has a core-shell structure composed of a core and a shell surrounding the core, the shell comprises a third rubber, the core comprises the second rubber and the electrically conductive agent in the second rubber, and the third rubber and the second rubber are different from each other. [4] An electrophotographic member according to claim 3, wherein the volume resistivity of the core is 1.00 × 10 1 up to 1.00 × 10 4 Ω · cm. [5] The electrophotographic member according to claim 3 or 4, wherein a ratio of a cross-sectional area of ​​the electrically conductive agent included in the core with respect to a cross-sectional area of ​​the core is 20 area% or more. [6] An electrophotographic element according to any one of claims 3 to 5, wherein the electrically conductive agent is carbon black. [7] An electrophotographic member according to any one of claims 3 to 6, wherein in a case where a circumference of the core is A and a shell circumference of the core is B, A and B satisfy the following expression (6): 1.00≤A / B≤1.10 [8] An electrophotographic element according to any one of claims 3 to 7, wherein the domain A comprises a plurality of nuclei and an arithmetic mean value Dm of a distance between the nuclei is 0.20 to 2.00 µm. [9] An electrophotographic member according to any one of claims 3 to 8, wherein the third rubber is at least one rubber selected from the group consisting of natural rubber, butadiene rubber, butyl rubber, isoprene rubber, styrene-butadiene rubber and ethylene-propylene rubber. [10] An electrophotographic member according to any one of claims 1 to 9, wherein the first rubber is at least one rubber selected from the group consisting of acrylonitrile butadiene rubber, chloroprene rubber and hydrin rubber. [11] An electrophotographic member according to any one of claims 1 to 10, wherein the second rubber is at least one rubber selected from the group consisting of natural rubber, butadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, urethane rubber, silicone rubber, fluororubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber and polynorbornene rubber. [12] A process cartridge detachably attached to a main body of an electrophotographic image forming apparatus, the process cartridge comprising: an electrophotographic photosensitive member; and a charging member arranged to be capable of charging the electrophotographic photosensitive member, and the charging member is the electrophotographic member according to any one of claims 1 to 11. [13] An electrophotographic image forming apparatus comprising: an electrophotographic photosensitive member; and a charging roller arranged to be capable of charging the electrophotographic photosensitive member, wherein the charging roller is the electrophotographic member according to any one of claims 1 to 11.

Images