Electrophotographic member, process cartridge, and electrophotographic image forming apparatus

Abstract

To provide an electrophotographic member that, even if used in a high-speed process over a long period, can prevent both a white dotted image caused by contamination substances and a fogged image derived from injection electrification.SOLUTION: An electrophotographic member has a support having a conductive outer surface and a conductive layer provided on the outer surface of the support. The conductive layer has a matrix and at least one domain dispersed in the matrix. The domain includes a domain A including second rubber and an electronic conductive agent. The conductive layer further has an insulating area. The volume resistivity of the matrix and the volume resistivity of the insulating area are within specific ranges. When a platinum electrode is provided directly on the outer surface of the electrophotographic member and impedance measurement is performed by applying 1 V DC voltage between the outer surface and the platinum electrode, an impedance X is within a specific range. An impedance Y measured while 10 V DC voltage is applied and the impedance X satisfies X / Y≥7.5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electrophotographic member, a process cartridge, and an electrophotographic image forming apparatus that can be used in electrophotography. [Background technology]

[0002] In electrophotographic image forming apparatuses, conductive members are used as electrophotographic members such as charging members, transfer members, and developing members. The conductive members transport electric charges from a conductive support to the surface of the conductive member and impart electric charges to a contacting object by discharge or frictional charging. For example, a known conductive member is an electrophotographic member having a conductive support and a conductive layer provided on the support.

[0003] The charging member is a member that generates a discharge between itself and the photosensitive drum to charge the surface of the photosensitive drum, and it is necessary to achieve uniform charging of the photosensitive drum. In recent years, the trend toward higher speeds and longer lifespans for electrophotographic devices has led to an increase in the amount of contaminants adhering to charging members, resulting in uneven discharge and thus adversely affecting images. Measures are also being sought to suppress adverse image effects resulting from injection charging of the photosensitive drum as the device rotates at high speeds. To extend the service life, Patent Document 1 discloses a charging member that removes the charge of contaminants on the charging member surface as a means of preventing image degradation even when contaminants adhere to the charging member surface. Specifically, the conductive layer has a matrix containing a crosslinked product of a first rubber and a plurality of domains in which conductive particles are dispersed in the matrix, and second conductive particles are further present as primary particles in the matrix. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-076450 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the investigations of the present inventors, when the charging member described in Patent Document 1 was evaluated using a process that has become faster and longer-lasting in recent years, it was possible to improve the white dot images caused by abnormal discharge due to charging of dirt adhering to the charging member. However, when the charging member rotates at high speed relative to the photosensitive drum, minute slippage occurs at the contact point, and white haze images may occur on the photosensitive drum due to injection charging from the charging member, and it was recognized that there is room for improvement.

[0006] As a result of further investigation into the cause of white haze images caused by injection charging, it was discovered that the cause was the improvement of the charge transport properties of the conductive layer in order to remove the charge of dirt adhering to the charging member. In other words, it was recognized that there is a trade-off between measures to prevent dirt in order to extend the life and measures to prevent injection charging due to high speed.

[0007] The present disclosure is directed to an electrophotographic member that can simultaneously suppress both white dot images caused by contaminants and white haze images caused by injection charging, even when used in a high-speed process over a long period of time. The present disclosure also relates to a process cartridge that contributes to high-quality electrophotographic image formation, and further to an electrophotographic image forming apparatus that can form high-quality electrophotographic images. [Means for solving the problem]

[0008] The present disclosure provides an electrophotographic member having a support having an electrically conductive outer surface and an electrically conductive layer disposed on the outer surface of the support, the conductive layer has a matrix including a first rubber and at least one domain dispersed in the matrix; The volume resistivity of the matrix is ​​1.00×10 8 ~1.00×10 12 Ω cm, The at least one domain includes a domain A including a second rubber and an electronic conductive agent; the conductive layer further has an insulating region comprising a third rubber; The volume resistivity of the insulating region is 1.00×10 12 is greater than Ω·cm, A platinum electrode was provided directly on the outer surface of the electrophotographic member, and the impedance was measured in an environment of a temperature of 23°C and a relative humidity of 50% while a DC voltage of 1 V and an AC voltage having an amplitude of 1 V were superimposed and applied between the outer surface of the support and the platinum electrode. Frequency 1.0 x 10 -1 Impedance X in Hz is 1.00 x 10 6 ~1.00×10 8 Ω, When the impedance was measured in a state where a DC voltage of 10 V and an AC voltage having an amplitude of 1 V were superimposed and applied between the outer surface of the support and the platinum electrode, Frequency 1.0 x 10 -1 The relationship between the impedance Y in Hz and the impedance X satisfies the following formula (1): X / Y≧7.5 ···(1). [Effects of the Invention]

[0009] According to at least one aspect of the present disclosure, there is provided an electrophotographic member capable of simultaneously suppressing both white dot images caused by contaminants and white haze images caused by injection charging, even when used in a high-speed process over a long period of time. Also, according to at least one aspect of the present disclosure, there is provided a process cartridge and an electrophotographic image forming apparatus that contribute to high-quality electrophotographic image formation. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram of a charging roller. [Figure 2] FIG. 1 is an explanatory diagram of the cross-sectional cutting direction; [Figure 3] FIG. 1 is a diagram for explaining a conductive layer structure; [Figure 4] Schematic diagram for sampling nine locations on the conductive layer. [Figure 5] FIG. 10 is an explanatory diagram of an envelope perimeter. [Figure 6] FIG. 2 is a schematic diagram of a process cartridge. [Figure 7] FIG. 1 is a diagram illustrating a schematic configuration of an electrophotographic image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the present disclosure, expressions such as "XX or more and YY or less" or "XX to YY" representing a numerical range mean a numerical range including the upper and lower limits, which are the endpoints, unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined arbitrarily. Furthermore, in the present disclosure, expressions such as "at least one selected from the group consisting of XX, YY, and ZZ" mean any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ.

[0012] Hereinafter, 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.

[0013] The present disclosure provides a method for preventing the formation of contaminants on the surface of an electrophotographic member even when used in a high-speed process for a long period of time. The present invention relates to a conductive member that can simultaneously suppress both white dot images, which are an image defect caused by charging of a substance, and white haze images, which occur due to injection charging into a photosensitive drum at high speeds. Hereinafter, a charging member will be described as an example of an electrophotographic member. The present inventors have hypothesized the following mechanism for suppressing white dot images, which occur in the charging member of Patent Document 1 due to the phenomenon in which dirt adhering to the charging member becomes charged, and the reason for the occurrence of image defects due to injection charging.

[0014] The term "contaminating substances" as used herein refers to substances that are not transferred in their entirety when toner and external additives are transferred to paper or an intermediate transfer body during a transfer process in an electrophotographic image forming process, but remain on the photosensitive drum surface, reach a charging member, and adhere to the charging member.

[0015] Toner and external additives often have insulating properties because they need to retain a certain charge in order to be electrostatically transferred from the developing roller to the photosensitive drum during the development process. The toner and external additives that are not transferred from the photosensitive drum to the paper or intermediate transfer member and remain on the surface of the photosensitive drum are affected by discharge at the transfer roller and friction with the paper before they reach the charging member again, and are charged with a certain distribution of positive and negative charges.

[0016] A charging member (hereinafter also referred to as a "charging roller") is a member that generates a potential difference between itself and the surface of a photosensitive drum when a DC voltage is applied to generate a discharge on the photosensitive drum. Therefore, it is difficult to prevent components of opposite polarity to the polarity of the charging bias that generates the potential difference from adhering to the charging roller due to electrostatic attraction. In other words, charging members intended for long-term use are required to suppress abnormal discharge caused by contaminants even if contaminants adhere to the charging roller, as explained below.

[0017] This section explains white spots that occur due to abnormal discharge caused by contaminants. A discharge phenomenon occurs between the charging roller and the photosensitive member according to Paschen's law, and the photosensitive member is charged with either a negative or positive charge depending on the applied voltage. Because discharge occurs when neutral air is ionized by an electric field, an opposite charge also occurs simultaneously. In other words, a positive or negative charge of the opposite polarity to the discharge is drawn toward the surface of the charging member by the electric field. If the charging roller surface is free of contaminants, even if the charging roller surface is charged up with a charge of the opposite polarity, the charge on the charging roller surface generally escapes toward the conductive support due to the conductivity of the charging roller.

[0018] However, if insulating contaminants, such as toner or external additives, are attached to the surface of the charging roller, the charge generated by the discharge, which has a polarity opposite to that of the discharge directed toward the surface of the charging member, is trapped on the surface without being released into the conductive member. At this time, a very strong electric field is generated between the contaminants, which have a polarity opposite to that of the discharge, i.e., the polarity opposite to that of the voltage applied to the charging member, and the surrounding surface of the charging member where the contaminants are attached, because a charge of the opposite polarity exists in close proximity. This very strong electric field can sometimes cause abnormally large discharges.

[0019] Therefore, if the charge built up due to the attached dirt can be transferred to the conductive support side, it is believed that abnormally excessive discharge will not occur and white dot images will not occur.

[0020] In Patent Document 1, a voltage is applied in a manner that is shared among the first rubber, the first conductive particles, and the domains in the matrix (hereinafter also referred to as "shared voltage"). However, because the first conductive particles in the matrix are conductors and exist independently, the shared voltage applied to the first conductive particles is significantly small, and most of the voltage applied to the conductive layer containing the first conductive particles is applied to the first rubber and the domains in the matrix.

[0021] As a result, charge is quickly supplied between domains or between a domain and the first conductive particles. Furthermore, the charge consumed by the discharge can be more quickly supplied by using the charge accumulated in the domain before the next discharge timing. This makes it possible to remove the charge of the opposite polarity to the charging bias of the contaminants adhering to the surface of the charging member and prevent excessive discharge.

[0022] However, the inventors have recognized that in high-speed processes, the means of improving the charge transport performance within the conductive layer of Patent Document 1 increases the amount of injected charge at the drum contact point, resulting in the generation of white haze images.

[0023] Injection charging is a phenomenon in which charge is transferred from a charging member to a photosensitive drum in accordance with a charging bias at the contact point with the photosensitive drum. Injection charging is a phenomenon directly linked to the charge transportability, and unevenness in the contact area between the charging member and the photosensitive drum can cause unevenness in the injected charge amount, which can further cause unevenness in the surface potential of the photosensitive drum.

[0024] In high-speed processes, unevenness in the injected charge amount due to minute variations in the contact area can become apparent as a white haze on the image, not only in drive rotation systems where the contact area with the drum tends to increase due to differences in peripheral speed between the charging member and the photosensitive drum, but also in driven rotation systems.

[0025] Even if the charging member is designed to have uniform contact pressure in the rotational and longitudinal directions, there will be some variation in shape, resulting in uneven contact area. However, there is a limit to how high the precision of the shape can be, so it is necessary to take measures to fundamentally suppress white haze images by designing the conductive layer.

[0026] The inventors conducted a study focusing on the difference in potential difference between injection charging at the contact portion of the photosensitive drum and charge transportability at the non-contact portion. First, at the contact portion of the photosensitive drum, the photosensitive drum is charged to several hundred volts due to discharge. Furthermore, at the contact portion between the charging member and the photosensitive drum, the actual contact area is less than 10% of the contact area calculated from the contact width and longitudinal direction due to the unevenness of the surface of the charging member. Since the gap with high resistance bears a shared voltage, the potential difference at the contact portion is low, at several volts or less. At this low potential difference, when charge transportability is high, injection charging occurs from the charging member to the photosensitive drum. In other words, at the contact portion of the photosensitive drum where the potential difference is low, it is necessary to suppress the conductivity of the charge to reduce injection charging.

[0027] On the other hand, areas other than the contact area are areas where a high electric field for discharge is applied, and non-discharge areas that do not face the drum, and are in a state where a potential of at least 10 V or more, and in some cases as high as 1000 V, is applied. Therefore, at this high potential difference, if the charge transport property of the conductive layer is high, it is possible to remove static electricity from dirt.

[0028] In other words, we came to the conclusion that if we could suppress the transport of charges under low potential differences to reduce injected charging, and further promote the transport of charges under high potential differences to suppress the charge-up of dirt, it would be possible to design a conductive layer that could simultaneously suppress both white dot images and white haze images.

[0029] As a result of extensive research, the present inventors have found that the prevention of white dot images and white haze images can be achieved by using the following electrophotographic member. That is, the present disclosure provides an electrophotographic member having a support having an electrically conductive outer surface and an electrically conductive layer disposed on the outer surface of the support, the conductive layer has a matrix including a first rubber and at least one domain dispersed in the matrix; The volume resistivity of the matrix is ​​1.00×10 8 ~1.00×10 12 Ω cm, The at least one domain includes a domain A including a second rubber and an electronic conductive agent; the conductive layer further has an insulating region comprising a third rubber; The volume resistivity of the insulating region is 1.00×10 12 is greater than Ω·cm, A platinum electrode was provided directly on the outer surface of the electrophotographic member, and the impedance was measured in an environment of a temperature of 23°C and a relative humidity of 50% while a DC voltage of 1 V and an AC voltage having an amplitude of 1 V were superimposed and applied between the outer surface of the support and the platinum electrode. Frequency 1.0 x 10 -1 Impedance X in Hz is 1.00 x 10 6 ~1.00×10 8 Ω, When the impedance was measured in a state where a DC voltage of 10 V and an AC voltage having an amplitude of 1 V were superimposed and applied between the outer surface of the support and the platinum electrode, Frequency 1.0 x 10 -1 The relationship between the impedance Y in Hz and the impedance X satisfies the following formula (1): X / Y≧7.5 ···(1).

[0030] In the conductive layer having a domain matrix structure, the volume resistivity ρm of the matrix is ​​1.00×10 8 Ω cm or more 1.00×10 12 The conductive layer has a volume resistivity of 1.00×10 12 It has an insulating region of over Ω·cm. The charge transport properties are controlled at the interface between the matrix and the insulating region.

[0031] 1.00 x 10 for charge-up of dirt adhering to the surface of a charged member 12 A matrix with a volume resistivity of Ω·cm or less allows charge transport to be carried out within the matrix, rather than being limited to the domain. As the degree of freedom of charge within the matrix increases, the amount of charge injected into the photosensitive drum increases, but the 12 Insulating regions with volume resistivities above Ω·cm can be introduced into the matrix to eliminate the trade-off.

[0032] The inventors speculate that the reason for the improvement of this trade-off is as follows: 12 Ω·cm or less matrix and 1.00×10 12 At the interface of an insulating region exceeding Ω·cm, a tiny energy barrier is formed, and if the driving force of the charge due to the electric field is weak, the charge cannot cross the interface. On the other hand, when the electric field is large, the charge can move beyond the energy barrier at the interface. In other words, at low potential differences, excessive charge transport can be suppressed, thereby suppressing injection charging, while at the same time, at high potential differences, charge transport can be promoted.

[0033] The present inventors have further found that the above-mentioned charge transport property is preferably exhibited within the range of impedance characteristics shown below. A typical impedance measurement method involves gradually increasing the frequency and measuring the characteristics where the movement of electric charges becomes difficult to follow the oscillating voltage in the high range (several hundred Hz to 1 MHz).

[0034] Measurements performed while applying a low-frequency voltage can be assumed to simulate the amount of charge movement that occurs when the charge can follow the voltage oscillation. Therefore, the amount of charge movement at low frequencies is an index of the ease of charge movement between the charging member and the measurement electrode, and can also be used as an index of the amount of charge that can be transferred by discharge from the surface of the charging member to the photosensitive drum.

[0035] The inventors have discovered that the characteristics correlated with the injection charging that occurs at the drum contact portion where the potential difference is low and the phenomenon of static elimination of dirt that occurs at a high potential difference, as described above, correlate with the impedance characteristics in the low frequency range when the DC voltage is changed.

[0036] Specifically, a platinum electrode was directly provided on the outer surface of the electrophotographic member, and the temperature was 23°C and the relative humidity was 50 %, a DC voltage of 1 V and an AC voltage with an amplitude of 1 V are superimposed and applied between the outer surface of the support and the platinum electrode, and the impedance is measured. -1 The impedance X in Hz (absolute value of impedance X) is 1.00 x 10 6 ~1.00×10 8 It is Ω. The measurement of 1V DC voltage corresponds to the injection charging phenomenon at the contact point of the photosensitive drum. 6 Ω or more, this is a range in which injection charging can be suitably suppressed. In order to suppress charging failure due to high resistance of the conductive layer, the impedance X is set to 1.00×10 8 It is preferably Ω or less.

[0037] Furthermore, the measurement of impedance Y when a DC voltage of 10 V and an AC voltage with an amplitude of 1 V are applied in superposition corresponds to the charge transport phenomenon at a location where the photosensitive drum and charging roller do not face each other, or at a high potential difference in a discharge area. The impedance X and the impedance Y satisfy the relationship of the following formula (1). X / Y≧7.5 (1) When X / Y is 7.5 or more, high resistance occurs at the drum contact point where the potential difference is low, making it difficult for charges to move and suppressing injection charging. At the same time, low resistance occurs in the high potential difference area, promoting the charge transport phenomenon and suppressing white haze images.

[0038] As described above, by controlling the volume resistivity of the matrix and the insulating region and then making the impedance X and the impedance Y satisfy a specific relationship, it is possible to achieve both suppression of injection charging at a low potential difference and suppression of dirt charge-up at a high potential difference, and it is thought that it is possible to simultaneously suppress white dot images and white mist images.

[0039] In addition, in order to further suppress the injection charge and further improve the charge transportability for eliminating the charge buildup of dirt, the impedance X is set to 4.00 × 10 6 ~6.50×10 7 It is preferably Ω. The impedance X can be increased by, for example, selecting a polar polymer for the matrix, lengthening the mixing time, controlling the release temperature to a high level, or increasing the amount of filler. The impedance X can also be decreased by selecting a non-polar polymer for the matrix, lowering the release temperature, and appropriately controlling the mixing time to a short level.

[0040] From the same viewpoint, it is preferable that the impedance Y and the impedance X satisfy the following formula (2), and it is more preferable that they satisfy the formula (2-2). 20.0≧X / Y≧7.5 (2) 18.0≧X / Y≧7.5 (2-2) X / Y can be controlled by the selection of the matrix polymer, the mixing time, the release temperature, and the presence of insulating domains. For example, X / Y can be increased by selecting a polar matrix polymer, increasing the mixing time, and increasing the release temperature. X / Y can also be increased by the presence of insulating domains.

[0041] <Method of measuring impedance> Impedance can be measured by the following method. When measuring impedance, it is necessary to eliminate the influence of contact resistance between the electrophotographic member and the measurement electrode. To achieve this, a low-resistance thin film of platinum is deposited on the surface of the electrophotographic member, and this thin film is used as an electrode. The electrophotographic support is then used as a ground electrode, and the impedance is measured using two terminals.

[0042] Examples of the method for forming the electrode include metal vapor deposition, sputtering, application of metal paste, and application of metal tape. Among these, in the present disclosure, from the viewpoint of reducing the contact resistance with the electrophotographic member, a platinum electrode is formed by vapor deposition of a thin film of platinum. Form as.

[0043] When forming a platinum electrode on the surface of an electrophotographic member, in consideration of the simplicity and uniformity of the thin film, a mechanism capable of gripping the electrophotographic member is provided to the vacuum deposition apparatus. For electrophotographic members having a cylindrical cross section, it is preferable to use a vacuum deposition apparatus further equipped with a rotation mechanism. For electrophotographic members having a curved cross section, such as a circular cross section, it is difficult to connect the platinum electrode serving as the measurement electrode to the impedance measurement device, so it is preferable to use the following method.

[0044] Specifically, a platinum electrode having a width of about 10 mm to 20 mm is formed in the longitudinal direction of the electrophotographic member, and then a metal sheet is tightly wrapped around the electrophotographic member, and the metal sheet is connected to a measurement electrode extending from a measurement device for measurement. This allows the measurement device to suitably acquire an electrical signal from the conductive layer of the electrophotographic member, enabling impedance measurement. The metal sheet may be any metal sheet that has an electrical resistance value equivalent to that of the metal part of the connection cable of the measurement device when measuring impedance, and examples of such metal sheets include aluminum foil and metal tape.

[0045] The impedance measurement equipment is an impedance analyzer, a network analyzer, a spectrum analyzer, etc., and is 1.0 x 10 7 Any device capable of measuring impedance in a frequency range up to 100 Hz may be used. Among these, it is preferable to measure impedance using an impedance analyzer in the range of electrical resistance of electrophotographic members.

[0046] The impedance measurement conditions are as follows: An impedance measurement device was used, and the impedance was measured at 1.0 x 10 -2 Hz~1.0×10 7 Impedance is measured in the Hz frequency range. Measurements are performed in an environment with a temperature of 23°C and a humidity of 50% RH. To reduce measurement variations, it is preferable to set five or more measurement points per frequency digit. The amplitude of the AC voltage is 1V.

[0047] In this disclosure, assuming a low potential difference at the contact portion of the photosensitive drum and a high potential difference at the non-contact portion and non-discharge portion, measurements are performed while superimposing a DC voltage on top of an AC voltage. Specifically, a DC voltage of 1 V or 10 V and an oscillating voltage of 1 V and a frequency of 1.0 × 10 -1 Hz can be applied in a superimposed manner.

[0048] The arithmetic average value of five measurement positions is used for the impedance. The five positions should be positioned at equal intervals to avoid arbitrary measurements. Although it depends on the shape of the conductive layer, for example, if the conductive layer can be divided into five equal parts, sampling should be performed from the center of each of the five divisions. When measuring impedance on roller-shaped or cylindrical electrophotographic members, measurements should be performed at five locations in the center of each of the five areas when the axial direction (longitudinal direction) is divided into five equal parts, and the arithmetic average of the measured values ​​of the inclination at the five locations should be calculated.

[0049] <Electrophotographic materials> An electrophotographic member has a support having a conductive outer surface and a conductive layer provided on the outer surface of the support. Figure 1 shows a schematic view of the appearance of a charging member (hereinafter referred to as a charging roller) as an electrophotographic member. The charging roller has a structure in which a conductive conductive layer 2 is provided on the outer periphery of a support 1 having a conductive outer surface. Both ends of the support 1 are exposed and not covered with the conductive layer 2. The conductive layer 2 may be a single-layer conductive elastic layer, or may have a structure in which one or more conductive resin layers are provided on the outer periphery of the elastic layer.

[0050] <Support having a conductive outer surface> The support 1 used in the electrophotographic member has conductivity and has a conductive layer or the like provided on its periphery. The support has a function of supporting the substrate. Examples of materials include metals such as iron, copper, stainless steel, aluminum, and nickel, and alloys thereof. Furthermore, the surface of these metals may be subjected to plating treatment or the like in order to impart scratch resistance. Furthermore, the support may be a support in which the surface of a resin substrate is coated with a metal or the like to impart surface conductivity, or a support made from a conductive resin composition.

[0051] An adhesive layer (not shown) may be provided between the support 1 and the conductive layer 2. In this case, the adhesive is preferably conductive. To achieve conductivity, the adhesive may be appropriately selected from known conductive agents (e.g., ionic conductive agents and electronic conductive agents), and may be used alone or in combination of two or more.

[0052] Examples of binders for adhesives include thermosetting resins and thermoplastic resins, and known materials such as urethane-based, acrylic-based, polyester-based, polyether-based, and epoxy-based materials can be used. Commercially available adhesives can be used, such as Metalock N33 (manufactured by Toyo Kagaku Kenkyusho). Known methods for applying the adhesive can be used, such as roll coating, sponge coating, and spray coating.

[0053] The adhesive layer between the support 1 and the conductive layer 2 may be provided over the entire surface where the support 1 and the conductive layer 2 contact each other, or may be provided only in a range of 5 mm to 20 mm in width at both ends of the surface where the support 1 and the conductive layer 2 contact each other. The thickness of the adhesive layer is preferably 1 μm to 10 μm from the viewpoint of adhesion between the support and the conductive layer.

[0054] <Conductive layer> The conductive layer must satisfy the following requirements in order to simultaneously suppress both white dot images and white haze images. (Condition 1) The conductive layer has a matrix containing a first rubber and at least one domain dispersed in the matrix, and the volume resistivity ρm of the matrix is ​​1.00×10 8 ~1.00×10 12 Ω·cm, and the at least one domain includes Domain A including a second rubber and an electronic conductive agent. (Condition 2) The conductive layer further has an insulating region containing a third rubber, and the volume resistivity of the insulating region is 1.00×10 12 It is over Ω·cm.

[0055] The above conditions will be explained below. Regarding Condition 1 The volume resistivity of the matrix, ρm, is 1.00×10 12By keeping the volume resistivity below Ω·cm, it is possible to eliminate the charge-up of contaminants adhering to the surface of the charging member. Because the charge-up of contaminants has the opposite polarity to the charging bias, by keeping the volume resistivity within the above range, the degree of freedom of the matrix charge is improved, and the charge-up can be transported and removed from the surface of the conductive layer toward the support having a conductive outer surface.

[0056] The volume resistivity of the matrix is ​​1.00×10 8 If ρm is less than the lower limit, the conductivity of the matrix increases, which excessively promotes the exchange of charges between conductive domains and tends to cause excessive current flow, and even when the insulating region of condition 2 is introduced, white haze due to injected charging may occur.

[0057] The volume resistivity ρm of the matrix is ​​preferably 4.00×10 8 ~1.00×10 10 The volume resistivity ρm of the matrix can be increased, for example, by decreasing the polarity of the polymer. The volume resistivity ρm of the matrix can also be decreased, for example, by increasing the polarity of the polymer or decreasing the viscosity of the matrix polymer.

[0058] <Method for measuring volume resistivity ρm of matrix> The volume resistivity ρm of the matrix can be measured, for example, by cutting a thin slice of a predetermined thickness (e.g., 1 μm) containing a matrix domain structure from the conductive layer and contacting the matrix in the thin slice with a microprobe of a scanning probe microscope (SPM) or an atomic force microscope (AFM).

[0059] For example, as shown in FIG. 2A, when the longitudinal direction of electrophotographic member 51 is defined as the X axis, the thickness direction of the conductive layer is defined as the Z axis, and the circumferential direction is defined as the Y axis, slices 52 are cut out so as to include at least a portion of cross section 52a parallel to the XZ plane. Alternatively, as shown in FIG. 2B, slices are cut out so as to include at least a portion of a YZ plane (e.g., 53a, 53b, 53c) perpendicular to the axial direction of electrophotographic member 51. In the present disclosure, the slices were cut out as shown in FIG. 2B. The cutting can be performed using, for example, a sharp razor, a microtome, a focused ion beam (FIB), etc. In the present disclosure, a microtome is used.

[0060] To measure volume resistivity, one side of a thin piece cut from the conductive layer is grounded. Next, a microprobe from a scanning probe microscope (SPM) or atomic force microscope (AFM) is contacted with the matrix on the side of the thin piece opposite the grounded surface, and a DC voltage of 50 V is applied for 5 seconds. The ground current value is measured over 5 seconds, and the arithmetic mean is calculated. The applied voltage is then divided by this calculated value to calculate the electrical resistance. Finally, the resistance value is converted to volume resistivity using the thickness of the thin piece. At this time, the SPM or AFM can measure the thickness of the thin piece at the same time as the resistance value. The specific procedure will be described later.

[0061] <First Rubber> The matrix includes a first rubber. The matrix includes, for example, a crosslinked product of the first rubber. The first rubber is a component that forms the matrix in the rubber mixture for forming the conductive layer. The volume resistivity ρm of the matrix is ​​set to 1.0×10 12 By setting the resistance to Ωcm or less, it is possible to remove the charge of contaminants adhering to the surface of the charging member. Furthermore, the first rubber is one that can phase-separate from the second rubber described below and form a matrix-domain structure. The cross-linked rubber determines the mechanical strength of the conductive layer. Therefore, it is preferable that the first rubber, after cross-linking, exhibits the strength required for a conductive member for electrophotography in the conductive layer.

[0062] The first rubber may be, for example, any of the rubber materials listed below. Examples of the first rubber include at least one 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, chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated NBR (H-NBR), and hydrin rubber. Among these, the first rubber preferably includes at least one selected from the group consisting of chloroprene rubber (CR) and acrylonitrile-butadiene rubber (NBR), more preferably includes NBR, and even more preferably is NBR.

[0063] If necessary, the matrix may contain a filler, a processing aid, a crosslinking agent, a crosslinking aid, a crosslinking accelerator, a crosslinking accelerator aid, a crosslinking retarder, an antioxidant, a softener, a dispersant, a colorant, and an electronic conductive agent. In order to set the volume resistivity of the matrix within the above range, it is preferable that the matrix does not contain an electronic conductive agent such as carbon black.

[0064] <Domain A having second rubber> At least one domain includes a domain A containing a second rubber and an electronic conductive agent. That is, the second rubber is a rubber that forms domain A containing an electronic conductive agent. The domain may contain a crosslinked product of the second rubber. As will be described later, in order to realize uniform conductivity by the domain matrix, the volume resistivity ρd of domain A is set to 1.00×10 1 ~1.00×10 4 Ω·cm is preferred, and 1.00×10 1 ~1.00×10 2 Ω·cm is more preferable, and 1.00×10 1 ~7.00×10 1 It is more preferable that the resistivity is Ω·cm.

[0065] The second rubber may be any rubber material that has a volume resistivity within the range when an electronic conductive material is added, and examples thereof include the following rubber materials: For example, at least one selected from the group consisting of natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butyl rubber (IIR), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), silicone rubber, and urethane rubber (U) is preferred.

[0066] The second rubber preferably contains at least one rubber selected from the group consisting of SBR, EPDM and IR, and more preferably is at least one rubber selected from the group consisting of SBR, EPDM and IR.

[0067] (Condition 2) The conductive layer contains a third rubber and has a volume resistivity of 1.00 × 10 12 It has an insulating area of ​​over Ω·cm. As mentioned above, the conductive layer has a volume resistivity of 10 × 10 12 Ω·cm or less matrix and 1.00×10 12 This creates an insulating region of over Ω·cm. It is speculated that this configuration creates a tiny energy barrier at the interface between the two, and if the driving force of the charge due to the electric field is weak, the charge will not be able to cross the interface. On the other hand, when the electric field is large, the charge can move beyond the energy barrier at the interface. That is, at low potential differences, excessive charge transport can be suppressed to suppress injected charging, while at the same time, at high potential differences, charge transport can be promoted.

[0068] The volume fraction of the insulating region, based on the total volume of the matrix and insulating region, is preferably 50% to 90%. A volume fraction of 50% or more increases the interfacial area within the matrix, making it possible to suppress charging injection at the drum contact portion. A volume fraction of 90% or less is preferable because it can suppress the phenomenon of increasing the volume resistance of the entire conductive layer and significantly reducing the charge transportability.

[0069] As described above, the insulating region may be within a range that allows the formation of an interface with the matrix, and may have a co-continuous structure with the matrix, or may exist as a domain within the matrix. The insulating region in the matrix preferably has a domain structure in the matrix in order to uniformly suppress charge transport at low potential differences and promote charge transport at high potential differences within the conductive layer. Hereinafter, the insulating domain in the matrix is ​​referred to as domain B. That is, it is preferable that at least one domain includes domain B, which constitutes the insulating region. It is preferable that the insulating region is an insulating region formed by domain B.

[0070] Furthermore, the results of the study revealed that there is a favorable correlation between the proportion of conductive domain A and insulating domain B in the conductive layer and their uniform arrangement. Specifically, FIB-SEM can be used to measure the matrix domain structure in the conductive layer in three dimensions, as well as the conductive and insulating regions within the domains.

[0071] FIB-SEM is a device that processes samples using a FIB (Focused Ion Beam) and then performs SEM (Scanning Electron Microscopy) of the exposed cross section. This is a technique for observing a sample using a scanning electron microscope (SEM). To examine the three-dimensional structure, a large number of photographs are taken through a series of repeated processing and observations, and then the SEM images are reconstructed in 3D using computer software to create a three-dimensional image of the sample structure.

[0072] Specifically, first, sampling is performed from nine points on the conductive layer. The nine points are positioned at equal intervals to avoid arbitrary positioning. Although it depends on the shape of the conductive layer, for example, if the conductive layer can be divided into nine equal parts, sampling is performed from the center of each of the nine divided parts. When the electrophotographic member is in the form of a roller, when the length in the axial direction (longitudinal direction) is L, three positions are positioned at (1 / 4)L, (2 / 4)L, and (3 / 4)L from the end, every 120 degrees around the circumference of the roller, and one sample is cut out from each of them.

[0073] Then, three-dimensional measurements were performed using FIB-SEM to measure images of cubes with sides of 3 μm and spaced 60 nm apart. Here, measurements were taken of the conductive layer cross sections at (1 / 4)L, (2 / 4)L, and (3 / 4)L cross sections every 120 degrees around the roller circumference, from the position of the core bar to the center of the surface. The obtained images were then analyzed using 3D visualization and analysis software Avizo (registered trademark, manufactured by FEI, Inc.) The single 9 μm-side cubic sample was divided into 27 unit cubes with sides of 3 μm.

[0074] An example is shown in Figures 4A and 4B. The electrophotographic member 100 has a conductive layer 2 on a conductive support (conductive mandrel) 1, the conductive layer 2 having a matrix containing a cross-linked first rubber and a plurality of domains dispersed in the matrix. If necessary, other layers may be provided on the conductive layer. First cubic samples 13, each 9 µm on a side, are obtained by sampling from nine locations on the conductive layer. The sample is divided into 27 unit cubes 14, each 3 µm on a side. The obtained unit cubes 14 are evaluated.

[0075] That is, it is preferable that at least eight of the cubic samples with sides of 9 μm taken from nine locations on the conductive layer satisfy the following condition (A). (A) One sample is divided into 27 unit cubes with a side length of 3 μm, and the volume Vd of the domain contained in the unit cube is calculated. Vd is 2.7 to 10.8 μm3 There are at least 23 unit cubes where

[0076] By satisfying (A), it is indicated that the domains are uniformly arranged, and the effects of suppressing injection charging at low potential differences and suppressing charge-up of contaminants at high potential differences can be favorably exhibited. In order to satisfy (A), for example, a method of reducing the domain size and finely dispersing the particles can be mentioned.

[0077] Regarding (A), the domain for which Vd is calculated includes both domain A and domain B. A domain included in a cubic sample refers to both a domain that is entirely included in the cubic sample and a domain that is only partially included in the cubic sample. In this case, an object that is counted as a domain is counted as a domain if it is partially included in the cubic sample. Fig. 3 shows a diagram illustrating the structure of a conductive layer having a matrix and a plurality of domains dispersed in the matrix. Fig. 3 is a schematic diagram of a unit cube 14. For example, the unit cube 14 has an insulating domain 22 and a conductive domain 23. The conductive domain 23 has conductive particles 24.

[0078] The volume resistivity of the matrix, ρm, is 1.0×10 12 Although the degree of freedom of charge transport is reduced by setting the resistance to Ωcm or less, it is preferable that the main conduction in the conductive layer is hopping conduction through the conductive domain A. Therefore, it is preferable that at least eight samples that satisfy the above (A) also satisfy the following (B). (B) The proportion of the number of domains A in the total number of domains (hereinafter simply referred to as the proportion of domains A) is 10 to 50% by number. When the proportion of domain A is within the above range, the interface area of ​​the insulating region in the matrix becomes more suitable, and the effects of suppressing injection charging and suppressing charge-up can be more suitably exhibited.

[0079] Furthermore, it is more preferable that at least eight samples that satisfy the above (A) satisfy the following (B2). (B2) The proportion of domain A in the total number of domains is 30 to 40% by number. By satisfying (B2), the effects of suppressing injection charging at a low potential difference and suppressing charge-up of dirt at a high potential difference can be more suitably exhibited.

[0080] The proportion of domain A can be increased by increasing the amount of electronic conductive material added to the domain, by increasing the amount of conductive domain added, or by increasing the release temperature when mixing domain A. The proportion of domain A can also be decreased by decreasing the amount of electronic conductive material or the amount of conductive domain added.

[0081] On the other hand, the proportion of the number of domains B in the total number of domains is preferably 50 to 90% by number, and more preferably 60 to 70% by number. In cubic samples with sides of 9 μm taken from nine locations on the conductive layer, the average number of domains A per sample is preferably 30 to 500, and more preferably 180 to 350. In cubic samples with sides of 9 μm taken from nine locations on the conductive layer, the average number of domains B per sample is preferably 200 to 1,000, and more preferably 250 to 800.

[0082] <The third rubber> The conductive layer has an insulating region containing a third rubber, and the volume resistivity ρI of the insulating region is 1.00×10 12 The insulating region includes, for example, a crosslinked product of a third rubber. The insulating region has a volume resistivity of 1.00×10 12 At the interface with the matrix of Ω·cm or less, it restricts charge transport at low potential differences and promotes charge transport at high potential differences. If the insulating region has a lower volume resistivity than the first rubber of the matrix, it becomes difficult to suppress injection charging due to low potential differences at the contact point with the photosensitive drum. Here, insulation means a material with a volume resistivity of 1.00×10 12 The volume resistivity ρI of the insulating region is, for example, 1.00×10 14 ~1.00×10 17 Ω·cm is preferred.

[0083] Preferred examples of the third rubber are listed below. Examples include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene propylene diene rubber (EPDM), and silicone rubber. The third rubber preferably includes at least one rubber selected from the group consisting of SBR, EPDM, and IR, and at least one rubber selected from the group consisting of SBR, EPDM, and IR. It is more preferable that the rubber is the same.

[0084] <Size of conductive domain A> Regarding the domain diameters of domain A and domain B, the domain diameter of domain A dispersed in the matrix is ​​preferably 0.2 to 2.0 μm. Also, the domain diameter of domain B is preferably 0.2 to 2.0 μm. Here, the domain diameter specifically refers to the maximum Feret diameter of the domains in the conductive phase.

[0085] By setting the domain diameter of Domain A to 2.0 μm or less, uniform conductivity can be obtained through the domain matrix structure, and the phenomenon of excessive current generation in areas with locally uneven conductivity, which promotes injection charging, can be further suppressed. By making the domain diameter of domain A 0.2 μm or more, the charge is generally retained in the insulating region having the third rubber, ensuring an appropriate amount of discharge as a charging member and suppressing the phenomenon of poor charging. The means for controlling the domain size will be described later in the description regarding the control of the domain matrix structure.

[0086] <Method for measuring the volume ratio and number of domains A and insulating regions (domains B)> Using FIB-SEM, it is possible to determine the three-dimensional matrix domain structure within the conductive layer, as well as the domain volume fraction and number.

[0087] FIB-SEM is a technique in which a sample is processed using a FIB (Focused Ion Beam) device and the exposed cross section is observed using a SEM (Scanning Electron Microscope). To examine the three-dimensional structure, a series of processing and observations are repeated to obtain numerous photographs, and then the SEM images are reconstructed in 3D using computer software, allowing the sample structure to be constructed as a three-dimensional image. The specific procedure will be described later.

[0088] <Electron conductive agent> Examples of the electronic conductive agent to be blended into domain A include oxides such as carbon black, graphite, titanium oxide, and tin oxide; metals such as Cu and Ag; and particles coated with an oxide or metal to make them conductive. If necessary, two or more of these conductive agents may be blended in appropriate amounts. The electronic conductive agent preferably contains carbon black or tin oxide, more preferably contains carbon black, and even more preferably is carbon black.

[0089] Among the above-mentioned electronic conductive agents, it is preferable to use conductive carbon black, which has a high affinity with rubber and allows easy control of the distance between the electronic conductive agents. The type of carbon black to be compounded into the domain is not particularly limited. Specific examples include gas furnace black, oil furnace black, thermal black, lamp black, acetylene black, and ketjen black.

[0090] Among them, DBP with an oil absorption of 40 cm can impart high conductivity to the domain. 3 / 100g or more 170cm 3Conductive carbon black having a density of 100 g or less can be suitably used.

[0091] The content of the electronic conductive agent such as conductive carbon black is preferably 20 parts by mass or more and 150 parts by mass or less, more preferably 50 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the second rubber contained in the domain, from the viewpoint of exhibiting stable conductivity.

[0092] It is preferable that a larger amount of conductive agent is blended compared to a general electrophotographic member for electrophotography. This makes it possible to increase the volume resistivity of the domain to 1.00×10 1 Ωcm or more 1.00×10 4 It can be easily controlled to a range of Ω·cm or less, and high resistance can be achieved by increasing the release temperature during mixing. In the step of preparing a rubber mixture for conductive domains (hereinafter also referred to as "DRC-A"), which will be described later, it is preferable to set the rubber release temperature at about 115 to 180°C.

[0093] <Method of manufacturing electrophotographic members> An example of a method for producing an electrophotographic member is shown below. In this example, the production method preferably includes the following steps (A) to (F), but is not particularly limited as long as the configuration of the present disclosure can be achieved.

[0094] Step (A): preparing a rubber mixture for a conductive domain (hereinafter also referred to as "DRC-A") containing an electronic conductive agent such as carbon black and a second rubber; Step (B): preparing a rubber mixture for an insulating domain (hereinafter also referred to as "DRC-B") containing a third rubber; Step (C): preparing a matrix-forming rubber composition (hereinafter also referred to as "MRC") containing a first rubber; Step (D): Mixing MRC and DRC-B to prepare a rubber mixture for the matrix and insulating domains (hereinafter also referred to as "M-DRC"); Step (E): A step of kneading DRC-A and M-DRC to prepare a rubber mixture for forming a conductive layer having a matrix domain structure and also having conductive and insulating domain structures. Step (F): A step of forming a layer of the rubber mixture for forming a conductive layer on the conductive support directly or via another layer, and curing the rubber mixture layer to form a conductive layer.

[0095] Step (F) may be the following step (F2). Step (F2): A step of forming a conductive layer on a conductive support by a known method such as extrusion molding, injection molding, or compression molding using the rubber mixture for forming a conductive layer prepared in steps (A) to (E).

[0096] The conductive layer may be adhered to the conductive support via an adhesive, if necessary. The conductive layer formed on the conductive support may be vulcanized, polished, and then subjected to a surface treatment such as ultraviolet treatment, if necessary. When vulcanization is performed, a vulcanizing agent may be further added to the rubber mixture for forming the conductive layer in step (F), and vulcanization may be performed during the curing. The vulcanizing agent is not particularly limited, and examples thereof include sulfur.

[0097] The amount of the second rubber relative to 100 parts by mass of the first rubber is preferably 50 to 200 parts by mass, more preferably 75 to 125 parts by mass. The amount of the third rubber relative to 100 parts by mass of the first rubber is preferably 50 to 200 parts by mass, more preferably 75 to 125 parts by mass.

[0098] <Method for controlling matrix domain structure> Regarding the dispersed particle diameter (domain size) D when two immiscible polymers are melt-kneaded, the Taylor equation, Wu's empirical formula, and Tokita's equation shown in the following formulas (4) to (7) have been proposed (see Sumitomo Chemical Technical Journal 2003-II, 42). Taylor's formula Formula (4) D=[C·σ / ηm·γ]·f(ηm / ηd) Wu's Empirical Formula Formula (5) γ·D·ηm / σ=4(ηd / ηm)0.84·ηd / ηm>1 Formula (6) γ·D·ηm / σ=4(ηd / ηm)-0.84·ηd / ηm<1 In formulas (4) to (7), D: domain size, C: constant, σ: interfacial tension, ηm: viscosity of matrix, ηd: viscosity of domain, where γ is the shear rate, η is the viscosity of the mixture, P is the probability of collision and coalescence, φ is the domain phase volume, and EDK is the domain phase cleavage energy.

[0099] From the above formula, it is effective to control the following four factors (a) to (d) with regard to the dispersion state of the domains. (a) Difference in interfacial tension σ between DRC-A, DRC-B, and MRC; (b) The ratio (ηm / ηd) of the viscosity of DRC-A or DRC-B (ηd) and the viscosity of MRC (ηm); (c) Shear rate (γ) and energy content during shear (EDK) during kneading of DRC-A, DRC-B, and MRC in step (E). (d) Volume fraction of DRC-A or DRC-B relative to the MRC in step (E).

[0100] (a) Difference in interfacial tension σ of each rubber material Generally, when two incompatible rubbers are mixed, phase separation occurs. This is because the interaction between the same polymers is stronger than the interaction between different polymers, so the same polymers aggregate together, reducing the free energy and stabilizing the mixture.

[0101] Because the interface of a phase-separated structure comes into contact with different polymers, the free energy is higher than the interior, which is stabilized by interactions between the same molecules. As a result, interfacial tension occurs, which tries to reduce the area of ​​contact with different polymers in order to reduce the free energy at the interface. When this interfacial tension is small, the different polymers tend to mix more uniformly in order to increase entropy. A uniformly mixed state is called dissolution, and the SP value (solubility parameter), which is an indicator of solubility, tends to correlate with interfacial tension. The method for measuring the SP value will be described later.

[0102] It is possible to control this by selecting the raw rubbers for the matrix and domain. The difference in absolute values ​​of the solubility parameters of the first rubber and the second rubber is 0.4 to 4.0 (J / cm 3 ) 0.5 A stable phase separation structure can be formed if the ion exchange rate is 0.4 to 2.2 (J / cm 3 ) 0.5 is. Within this range, a stable phase separation structure can be formed, and the maximum Feret diameter of the domains can be easily controlled to 0.2 to 2.0 μm.

[0103] It is also known that when three or more incompatible rubber materials are mixed, the dispersion state varies depending on the SP values ​​of the constituent rubber materials. When forming a conductive layer having a matrix-domain structure in which the domains have insulating regions, it is preferable that the SP value of the rubber material containing the electronic conductive agent is larger than that of both, or that the SP value of both is smaller than that of both.

[0104] On the other hand, when a vulcanizing agent is added to the domain containing the electronic conductive material and then the matrix-domain structure is mixed, the SP value is not limited to the above. Furthermore, when producing the domain containing the electronic conductive material by kneading, a method may be adopted in which the temperature and time during kneading are controlled to form a carbon gel around the electronic conductive material. In order to efficiently form the carbon gel, it is preferable that the temperature during kneading is high and the kneading time is long.

[0105] The matrix-domain structure of the present invention can also be produced using two types of rubber. Specifically, when produced in the same manner as above, a vulcanizing agent is added to the domain side in advance, and then the domain rubber and matrix rubber are mixed together to effectively form a phase-separated structure. For example, it is preferable that the insulating domain rubber mixture (DRC-B) contains a vulcanizing agent.

[0106] How to measure SP value The SP value can be calculated accurately by creating a calibration curve using materials with known SP values. This known SP value can also be the catalog value from the material manufacturer. For example, the SP value of NBR and SBR is not dependent on the molecular weight, but is largely determined by the content ratio of acrylonitrile and styrene.

[0107] Therefore, the rubber that constitutes the matrix and domains is analyzed for the acrylonitrile or styrene content using analytical techniques such as pyrolysis gas chromatography (Py-GC) and solid-state NMR, which allows the SP value to be calculated from a calibration curve obtained from materials with known SP values.

[0108] The SP value of isoprene rubber is determined by the isomer structure, such as 1,2-polyisoprene, 1,3-polyisoprene, 3,4-polyisoprene, cis-1,4-polyisoprene, trans-1,4-polyisoprene, etc. Therefore, as with SBR and NBR, the isomer content ratio can be analyzed using Py-GC and solid-state NMR, etc., and the SP value can be calculated from materials with known SP values. The SP values ​​of materials with known SP values ​​were determined by the Hansen sphere method.

[0109] (b) The ratio (ηm / ηd) of the viscosity of DRC-A or DRC-B (ηd) to the viscosity of MRC (ηm) The closer the viscosity ratio (ηd / ηm) between DRC-A or DRC-B and DRC (DRC-A / DRC or DRC-B / DRC) is to 1, the smaller the domain diameter can be. Specifically, the viscosity ratio is preferably 1.0 or more and 2.0 or less. The viscosity ratio can be adjusted by selecting the Mooney viscosity of the raw rubber used for DRC-A or DRC-B and DRC, and by blending the type and amount of filler.

[0110] It is also possible to add a plasticizer such as paraffin oil to the extent that it does not interfere with the formation of a phase-separated structure.The viscosity ratio can also be adjusted by adjusting the temperature during kneading.

[0111] The viscosity of the rubber mixture is Mooney viscosity ML based on JIS K6300-1:2013. (1+4) It can be obtained by measuring the rubber temperature during kneading.

[0112] The closer the viscosity ratio (ηd / ηm) of the domain to the matrix (DRC-A / DRC or DRC-B / DRC) is to 1, the smaller the maximum Feret diameter of the domain can be. Specifically, it is preferable to set the viscosity ratio to 2.0 or less, since this allows for the acquisition of a desirable domain size.

[0113] (c) Shear rate (γ) and energy content during shear (EDK) during kneading of DRC-A, DRC-B, and MRC The higher the shear rate during mixing of DRC-A, DRC-B, and MRC, the greater the shear stress. The greater the amount of energy, the smaller the interdomain distance can be.

[0114] The shear rate can be increased by increasing the inner diameter of the agitating members such as the blades and screws of the mixer, reducing the gap between the end face of the agitating member and the inner wall of the mixer, or by increasing the rotation speed.Increasing the energy during shearing can also be achieved by increasing the rotation speed of the agitating members or by increasing the viscosity of the rubber.

[0115] The higher the shear rate / energy amount during mixing, the smaller the maximum Feret diameter of the domains. The shear rate can be increased by increasing the inner diameter of the mixing elements such as the blades and screws of the mixer, reducing the gap between the end face of the mixing element and the inner wall of the mixer, or by increasing the rotation speed.

[0116] (d) Volume fraction of DRC-A or DRC-B relative to the MRC. The volume fraction of DRC-A or DRC-B relative to the MRC correlates with the probability of collision and coalescence of the domain-forming rubber mixture with the matrix-forming rubber mixture. Specifically, reducing the volume fraction of the domain-forming rubber mixture relative to the matrix-forming rubber mixture reduces the probability of collision and coalescence between the domain-forming rubber mixture and the matrix-forming rubber mixture. In other words, the inter-domain distance can be reduced by reducing the volume fraction of the domains in the matrix within a range that achieves the required electrical conductivity.

[0117] <Domain shape> The present inventors have found that the amount of electronic conductive agent contained in a domain affects the external shape of the domain. That is, as the amount of electronic conductive agent in a domain increases, the external shape of the domain becomes closer to a sphere. The more domains that are close to a sphere, the more uniform the distance between the conductive domain A and the insulating domain B, which is preferable.

[0118] According to the inventors' investigations, although the reason for this is unclear, a domain in which the ratio of the total cross-sectional area of ​​the electronic conductive agent observed in the cross section to the cross-section of the domain is 20% or more can have a shape closer to a sphere. As a result, it is possible to have an outer shape that can significantly alleviate the concentration of electron transfer between domains, which is preferable. Specifically, it is preferable that the ratio of the cross-sectional area of ​​the electronic conductive agent contained in the domain to the cross-sectional area of ​​the domain is 20% or more.

[0119] Regarding a shape without irregularities on the peripheral surface of the domain, when the peripheral length of domain A is A and the envelope peripheral length of domain A is B, it is preferable that the following formula (5) is satisfied. 1.00≦A / B≦1.10 (5) (A: perimeter of domain A, B: envelope perimeter of domain A) Equation (5) represents the ratio of the perimeter A of domain A to the envelope perimeter B of domain A. Here, the envelope perimeter is the perimeter when connecting the convex portions of domain 81 observed in the observation area, as shown in FIG. 5.

[0120] The minimum ratio of the domain perimeter to the domain envelope perimeter is 1, which indicates that the domain has a cross-sectional shape with no recesses, such as a perfect circle or ellipse. If this ratio exceeds 1.10, the domain will have large recesses and protrusions, which means that the electric field will become anisotropic. If A / B satisfies formula (5), the concentration of the electric field can be reliably suppressed, and uniform discharge can be achieved.

[0121] A / B is preferably 1.00 to 1.07, more preferably 1.00 to 1.05. A / B can be increased by increasing the viscosity of the matrix and domains. Furthermore, A / B can be reduced by reducing the difference in viscosity between the matrix and the domain.

[0122] <Method for measuring each parameter related to domain shape> First, a slice is prepared in the same manner as in the measurement of the volume resistivity of the matrix described above. However, as described below, the slice is prepared along a cross section perpendicular to the longitudinal direction of the electrophotographic member, and the domain shape at the fracture surface of the slice is evaluated. The reason for this will be explained below. 2A and 2B show the shape of the electrophotographic member 51 in a three-dimensional manner along three axes, specifically, the X, Y, and Z axes. In Figures 2A and 2B, the X axis is parallel to the longitudinal direction (axial direction) of the electrophotographic member, and the Y and Z axes are perpendicular to the axial direction of the electrophotographic member. The thickness direction of the conductive layer is the Z axis.

[0123] 2A shows an image of an electrophotographic member cut out at a cross section 52a parallel to an XZ plane 52. The XZ plane can rotate 360° around the axis of the electrophotographic member. Considering that the electrophotographic member is in contact with the photosensitive drum and rotates, repeatedly coming into contact with the photosensitive drum, the cross section 52a parallel to the XZ plane 52 indicates a surface that simultaneously comes into contact with the photosensitive drum at a certain timing.

[0124] Therefore, to evaluate the domain shape, which correlates with the electric field concentration in the electrophotographic member, it is necessary to evaluate a cross section parallel to a YZ plane 53 perpendicular to the axial direction of the electrophotographic member, which allows evaluation of the domain shape including a certain amount of cross section 52a. For this evaluation, when the length in the longitudinal direction of the conductive layer is L, a total of three cross sections are selected: cross section 53b at the center of the conductive layer in the longitudinal direction, and two cross sections (53a and 53c) at L / 4 from both ends of the conductive layer toward the center (FIG. 2B).

[0125] Furthermore, with regard to the observation positions of the cross sections 53a to 53c, when the thickness of the conductive layer is T, measurements can be taken at a total of nine observation areas, with 15 μm square observation areas placed at three locations (0.2T, 0.5T, and 0.7T) in the thickness region of each slice from the outer surface to a depth of 0.1T to 0.9T.

[0126] The fracture surface can be formed by freeze fracturing, cross polishing, focused ion beam (FIB), or other methods. Considering the smoothness of the fracture surface and pretreatment for observation, the FIB method is preferred. Furthermore, to facilitate observation of the matrix domain structure, pretreatments such as staining and vapor deposition may be performed to favorably obtain contrast between the conductive and insulating phases.

[0127] The matrix domain structure can be observed on the fractured surface and pretreated sections using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Among these, observation with an SEM at 1000x to 100,000x magnification is preferred for accurate quantification of the domain area.

[0128] The domain perimeter, envelope perimeter, and domain number can be measured by quantifying the captured images. The fracture surface images obtained by SEM observation were processed using image processing software such as ImageProPlus (MediaCybernetics), and nine images were taken at each observation position. Each image was then processed using an 8-bit grayscale processor to extract a 15-μm square analysis area. A 256-level monochrome image was then obtained. The image was then inverted to show white domains within the fracture surface, and binarized to obtain a binary image for analysis.

[0129] <<Method for measuring the cross-sectional area ratio μr of electronic conductive material within a domain>> The cross-sectional area ratio of the electronic conductive agent in the domain can be measured by quantifying the above-mentioned binary image. The cross-sectional area S of the domain and the sum of the cross-sectional areas of the conductive agent in each domain, Sc, are calculated using the counting function of the image processing software ImageProPlus (Media Cybernetics) for the binary image. Then, the arithmetic mean value μr (%) of Sc / S can be calculated.

[0130] In the case of a cylindrical charging member, where the longitudinal length of the conductive layer is L and the thickness of the conductive layer is T, cross sections of the conductive layer in the thickness direction as shown in Fig. 2B are obtained at three locations: the longitudinal center of the conductive layer, and three locations at L / 4 from both ends of the conductive layer toward the center. For each of the obtained cross sections, the above measurements are made in three 15 µm square regions (0.2T, 0.5T, and 0.7T) in the thickness region from the outer surface of the conductive layer to a depth of 0.1T to 0.9T toward the support, and the value is calculated from the arithmetic average of the measurements from a total of nine regions.

[0131] <<Method for measuring domain perimeter A and envelope perimeter B>> The domain perimeter, envelope perimeter, and domain number can be measured by quantifying the binarized image. The binarized image is then subjected to a counting function in the image processing software ImageProPlus (MediaCybernetics) to calculate the perimeter A and envelope perimeter B of each domain in the domain size group, and the arithmetic mean of the domain perimeter ratio A / B is calculated.

[0132] In the case of a cylindrical charging member, where the longitudinal length of the conductive layer is L and the thickness of the conductive layer is T, cross sections of the conductive layer in the thickness direction as shown in Fig. 2B are obtained at three locations: the longitudinal center of the conductive layer, and three locations at L / 4 from both ends of the conductive layer toward the center. For each of the obtained cross sections, the above measurements are made in three 15 µm square regions (0.2T, 0.5T, and 0.7T) in the thickness region from the outer surface of the conductive layer to a depth of 0.1T to 0.9T toward the support, and the value is calculated from the arithmetic average of the measurements from a total of nine regions.

[0133] <<Method for measuring the shape index of a domain>> The shape index of a domain can be calculated by calculating the percentage of the total number of domains in which μr (%) is 20% or more and the domain perimeter ratio A / B satisfies the above formula (5).The count function of the image processing software ImageProPlus (manufactured by MediaCybernetics) is used to calculate the number of domains in the binarized image, and then the percentage of the number of domains that satisfy μr≧20 and the above formula (5) can be obtained.

[0134] In the case of a cylindrical charging member, where the longitudinal length of the conductive layer is L and the thickness of the conductive layer is T, cross sections of the conductive layer in the thickness direction as shown in Fig. 2B are obtained at three locations: the longitudinal center of the conductive layer, and three locations at L / 4 from both ends of the conductive layer toward the center. For each of the obtained cross sections, the above measurements are made in three 15 µm square regions (0.2T, 0.5T, and 0.7T) in the thickness region from the outer surface of the conductive layer to a depth of 0.1T to 0.9T toward the support, and the value is calculated from the arithmetic average of the measurements from a total of nine regions.

[0135] <Amount of electronic conductive agent added in domain A> The amount of electronic conductive agent added to the shell within the domain is preferably such that the ratio of the cross-sectional area of ​​the electronic conductive agent to the cross-sectional area of ​​the domain is at least 20%, preferably 25% to 30%. This range allows the electronic conductive agent to be densely packed into the domain. This also allows the external shape of the domain to approach a sphere and minimize irregularities. Furthermore, adding an electronic conductive agent improves the reinforcing properties of the shell and increases its elastic modulus, thereby reducing distortion in the shell.

[0136] To obtain a domain in which the electronic conductive agent is densely packed, the electronic conductive agent should have a DBP oil absorption of 40 to 80 cm 3 Carbon black having a DBP oil absorption (cm) / 100g is particularly suitable. 3 / 100g) is the volume of dibutyl phthalate (DBP) that can be adsorbed by 100g of carbon black, and is measured in accordance with Japanese Industrial Standards (JIS) K6217-4:2017 (Carbon black for rubber - Fundamental properties - Part 4: Determination of oil absorption (including compressed samples)).

[0137] Generally, carbon black has a cluster-like high-order structure in which primary particles with an average particle size of 10 nm to 50 nm are aggregated. This cluster-like high-order structure is called a structure, and its degree is measured by the DBP oil absorption (cm 3The DBP oil absorption is quantified in units of 1 / 100g. Conductive carbon black with a DBP oil absorption within the above range has an underdeveloped structure, resulting in less carbon black aggregation and good dispersibility in rubber. This allows for a larger loading amount in the domain, which in turn makes it easier to obtain domains with an outer shape closer to a sphere. Furthermore, conductive carbon black with a DBP oil absorption within the above range is effective because it is less likely to form aggregates.

[0138] The electronic conductive agent is, for example, conductive particles. Among the conductive particles, conductive particles containing conductive carbon black as a main component are preferred for reasons such as high conductivity, high affinity with rubber, and ease of control of the distance between conductive particles. The type of conductive carbon black to be blended into the domain is not particularly limited. Specific examples include gas furnace black, oil furnace black, thermal black, lamp black, acetylene black, and ketjen black. Among these, as will be described later, those with DBP absorption of 40 to 80 cm 3 Carbon black having a particle size of 1 / 100g can be particularly preferably used.

[0139] Adding a large amount of carbon black to the shell within the domains makes the domain shape more spherical. The reason for this is believed to be that the amount of carbon gel can be increased, as follows: Carbon gel is a particulate substance that is pseudo-crosslinked when rubber molecules are adsorbed onto the carbon black. Carbon gel does not dissolve even in organic solvents that dissolve raw rubber. In other words, it is three-dimensionally crosslinked by the physical and chemical adsorption of rubber molecules onto the carbon black surface, and it is thought to behave as rubber particles. It is believed that the rubber particles formed by the carbon gel act as nuclei to form domains. To increase the amount of carbon gel, it is preferable to compound a large amount of carbon black relative to the rubber, which simply increases the amount of carbon black that functions as an adsorbent.

[0140] <Reinforcing material> In order to improve the ratio of the elastic modulus of the domain, it is also possible to compound reinforcing carbon black as a reinforcing agent. Examples of reinforcing carbon black used here include FEF, GPF, SRF, and MT carbon, which have low electrical conductivity.

[0141] Furthermore, if necessary, fillers, processing aids, vulcanization aids, vulcanization accelerators, vulcanization acceleration aids, vulcanization retarders, antioxidants, softeners, dispersants, colorants, and the like, which are generally used as compounding agents for rubber, may be added.

[0142] <Process cartridge> At least one aspect of the present disclosure provides a process cartridge equipped with the electrophotographic member of the present disclosure. Fig. 6 is a schematic cross-sectional view of a process cartridge for electrophotography equipped with the electrophotographic member according to one embodiment of the present disclosure as a charging member (charging roller). This process cartridge integrates a developing device and a charging device, and is configured to be detachably mountable to the main body of an electrophotographic device. This was done. The developing device is an integrated unit of at least a developing roller 93, a toner container 96, and toner 99, and may also include a toner supply roller 94, a developing blade 98, and an agitating blade 910 as required.

[0143] The charging device is an integrated device that includes at least the photosensitive drum 91 and the charging roller 92, and may also include a cleaning blade 95 and a waste toner container 97. The charging roller 92, the developing roller 93, the toner supply roller 94, and the developing blade 98 are each configured to have a voltage applied thereto.

[0144] The electrophotographic member according to the present disclosure can be used as a charging roller, a developing roller, a developing blade, and a toner supply roller. The electrophotographic member is preferably a charging member, and more preferably a charging roller.

[0145] <Electrophotographic image forming apparatus> At least one aspect of the present disclosure provides an electrophotographic image forming apparatus including an electrophotographic member according to the present disclosure. Fig. 7 is a schematic diagram of an electrophotographic image forming apparatus 200 using an electrophotographic member according to one embodiment of the present disclosure as a charging member (charging roller). This apparatus is a color electrophotographic apparatus in which the process cartridges are detachably mounted. Each process cartridge uses toner of each color: black (BK), magenta (M), yellow (Y), and cyan (C).

[0146] Photosensitive drum 201 rotates in the direction of the arrow and is uniformly charged by charging roller 202 to which a voltage is applied from a charging bias power supply, and an electrostatic latent image is formed on its surface by exposure light 211. Meanwhile, toner 209 stored in toner container 206 is supplied to toner supply roller 204 by stirring blade 210 and transported onto developing roller 203. Then, developing blade 208, which is arranged in contact with developing roller 203, uniformly coats the surface of developing roller 203 with toner 209, and imparts an electric charge to toner 209 by frictional charging. The electrostatic latent image is developed by the toner 209 transported by developing roller 203, which is arranged in contact with photosensitive drum 201, and is visualized as a toner image.

[0147] The visualized toner image on the photosensitive drum is transferred by a primary transfer roller 212, to which a voltage is applied by a primary transfer bias power supply, onto an intermediate transfer belt 215, which is supported and driven by a tension roller 213 and an intermediate transfer belt drive roller 214. The toner images of each color are sequentially superimposed to form a color image on the intermediate transfer belt.

[0148] A transfer material 219 is fed into the device by a paper feed roller and transported between an intermediate transfer belt 215 and a secondary transfer roller 216. A voltage is applied to the secondary transfer roller 216 from a secondary transfer bias power supply, and the secondary transfer roller 216 transfers the color image on the intermediate transfer belt 215 onto the transfer material 219. The transfer material 219 onto which the color image has been transferred is fixed by a fixing device 218, and is then discarded outside the device, completing the printing operation.

[0149] Meanwhile, the toner remaining on the photosensitive drum without being transferred is scraped off by a cleaning blade 205 and stored in a waste toner container 207, and the above-mentioned process is repeated for the cleaned photosensitive drum 201. In addition, the toner remaining on the primary transfer belt without being transferred is also scraped off by a cleaning device 217.

[0150] Although a color electrophotographic apparatus is shown as an example, in a monochrome electrophotographic apparatus (not shown), the process cartridge uses only black toner. The monochrome image is formed directly onto the transfer material by the process cartridge and the primary transfer roller (no secondary transfer roller). The image is then fixed by the fixing unit, and the paper is ejected from the device, completing the printing operation. [Example]

[0151] The present disclosure will be described below based on examples, but the technical scope of the present disclosure is not limited to these examples.

[0152] The electrophotographic members in the examples and comparative examples were prepared using the materials shown below. <nbr> NBR (product name: JSR NBR N230SV, acrylonitrile content: 35%, Mooney viscosity ML (1+4) 100°C: 32, SP value: 20.0 (J / cm3) 0.5 , manufactured by JSR Corporation, abbreviation: N230SV)

[0153] <Isoprene rubber IR> Isoprene rubber (trade name: Nipol IR2200L, Mooney viscosity ML (1+4) at 100°C: 70, SP value: 16.5 (J / cm 3 ) 0.5 , manufactured by Zeon Corporation, abbreviated name: IR2200L)

[0154] <Butadiene rubber BR> Butadiene rubber (product name: UBEPOL BR150B, Mooney viscosity ML (1+4) 100°C: 40, SP value: 16.8 (J / cm 3 ) 0.5 , manufactured by Ube Industries, abbreviated name: BR150B)

[0155] <sbr> SBR (product name: Tufden 2003, styrene content: 25%, Mooney viscosity ML (1+4) 100°C: 33, SP value: 17.0 (J / cm 3 ) 0.5 , manufactured by Asahi Kasei Corporation, abbreviation: T2003)

[0156] <Chloroprene rubber (CR)> Chloroprene rubber (product name: SKYPRENE B31, Mooney viscosity ML (1+4) at 100°C: 40, SP value: 17.4 (J / cm 3 ) 0.5 , manufactured by Tosoh Corporation, abbreviation: B31)

[0157] <epdm> EPDM (product name: Esprene 505A, Mooney viscosity ML (1+4) 100°C: 47, SP value: 16.0 (J / cm 3 ) 0.5 , manufactured by Sumitomo Chemical Co., Ltd., abbreviation: E505A)

[0158] <Butyl rubber> Butyl (trade name: Butyl 065, Mooney viscosity ML (1+4) at 100°C: 32, SP value: 15.8 (J / cm 3 ) 0.5 , manufactured by JSR Corporation, abbreviation: Butyl065)

[0159] <Electro-conductive agent (conductive particles)> Carbon black (2) (product name: TOKABLACK♯7360SB, DBP absorption capacity: 87 cm 3 / 100g, manufactured by Tokai Carbon Co., Ltd., abbreviation: #7360) Carbon black (3) (product name: TOKABLACK♯7270SB, DBP absorption capacity: 62 cm 3 / 100g, manufactured by Tokai Carbon Co., Ltd., abbreviation: #7270) Conductive tin oxide (Product name: S-2000, DBP absorption capacity: 80cm 3 / 100g, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd., abbreviated name: tin oxide)

[0160] <Vulcanizing agent> Vulcanizing agent (1) (product name: SULFAX PMC, sulfur content 97.5%, manufactured by Tsurumi Chemical Industry Co., Ltd., abbreviated name: sulfur)

[0161] <Vulcanization accelerator> Vulcanization accelerator (1) (trade name: Sancerer TBZTD, tetrabenzyl thiuram disulfide, manufactured by Sanshin Chemical Industry Co., Ltd., abbreviation: TBZTD)

[0162] <Filler> Filler (1) (product name: Nanox #30, calcium carbonate, manufactured by Maruo Calcium Co., Ltd., abbreviation: #30)

[0163] Example 1 1. Preparation of unvulcanized rubber composition for forming conductive layer [1-1. Preparation of carbon masterbatch in the domain (rubber mixture DRC-A for conductive domain)] The materials shown in Table 1 were mixed in the amounts shown in Table 1 in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Corporation) to obtain a rubber mixture for the conductive domain. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and a mixing time of 16 minutes. The rubber discharge temperature was 160°C.

[0164] [Table 1]

[0165] [1-2. Preparation of rubber mixture for insulating domain (DRC-B)] The materials of the types and amounts shown in Table 2 were mixed in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Corporation) to obtain a rubber mixture for the insulating domains. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and 16 minutes.

[0166] [Table 2]

[0167] [1-3. Preparation of matrix-forming rubber mixture (MRC)] The materials shown in Table 3 were mixed in the amounts shown in Table 3 in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.) to obtain a rubber mixture for forming a matrix. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and a time of 16 minutes.

[0168] [Table 3]

[0169] [1-4. Preparation of Rubber Mixture for Forming Matrix and Insulating Domain (M-DRC)] The materials shown in Table 4 were mixed in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Corporation) to obtain a rubber mixture for forming the matrix and insulating domains (M-DRC). The mixing conditions were a loading of 70 vol%, a blade rotation speed of 30 rpm, and 16 minutes.

[0170] [Table 4]

[0171] [1-5. Preparation of rubber mixture for forming conductive layer] The materials shown in Table 5 were mixed in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Corporation) to obtain a rubber mixture for forming the conductive layer. The mixing conditions were a filling amount of 70 vol%, a blade rotation speed of 30 rpm, and 16 minutes.

[0172] [Table 5]

[0173] [1-6. Preparation of unvulcanized rubber composition for forming conductive layer] The materials of the types and amounts shown in Table 6 were mixed using an open roll to obtain an unvulcanized rubber composition for forming the conductive layer. The mixer used was an open roll with a roll diameter of 12 inches. The mixing conditions were a front roll rotation speed of 10 rpm, a rear roll rotation speed of 8 rpm, a roll gap of 2 mm, and a total of 20 left and right turns, followed by 10 thin passes with a roll gap of 1.0 mm.

[0174] [Table 6]

[0175] 2. Preparation of electrophotographic components [2-1. Formation of conductive layer] As a support, a core bar with a total length of 252 mm and an outer diameter of 6 mm, made of free-cutting steel with an electroless nickel-plated surface, was prepared. This core bar was used as a support, which is a conductive mandrel. Using a roll coater, an adhesive (product name: Metalock U-20, manufactured by Toyo Kagaku Kenkyusho Co., Ltd.) was applied over the entire circumference of the core bar, within a range of 230 mm, excluding 11 mm at each end. In this example, the core bar coated with the adhesive was used as a conductive support.

[0176] Next, a die with an inner diameter of 10.0 mm was attached to the tip of a crosshead extruder having a mechanism for feeding the conductive support and a mechanism for discharging the unvulcanized rubber roller, and the temperatures of the extruder and crosshead were adjusted to 100°C, and the conveying speed of the conductive support was adjusted to 60 mm / sec. Under these conditions, the unvulcanized rubber composition for forming the conductive layer was fed from the extruder, and the outer periphery of the conductive support was coated with the unvulcanized rubber composition for forming the conductive layer in the crosshead, thereby obtaining an unvulcanized rubber roller. Next, the unvulcanized rubber roller was placed in a hot air vulcanizing furnace at 170°C and heated for 60 minutes to vulcanize the unvulcanized rubber composition, thereby obtaining a conductive roller with a conductive layer formed on the outer periphery of the conductive support. After that, 10 mm of each end of the conductive layer was cut off, and the length of the conductive layer in the longitudinal direction was reduced to 2. It was set to 32mm.

[0177] [2-2. Conductive layer polishing] Next, the surface of the conductive layer was polished under the polishing conditions described in the following polishing condition 1 to obtain a crown-shaped charging roller 1 having a diameter of 8.5 mm at the center and a diameter of 8.44 mm at each position 90 mm from the center to both ends.

[0178] (polishing condition 1) A cylindrical grinding wheel (manufactured by Teiken Co., Ltd.) with a diameter of 305 mm and a length of 235 mm was prepared. The type of abrasive grain, grain size, degree of bonding, bonding agent, and structure (abrasive grain ratio) were as follows: Abrasive material: GC (green silicon carbide), (JISR6111-2002) Abrasive grain size: #80 (average grain size 177 μm JIS B4130) Abrasive grain bond: HH (JISR6210) Binder: V4PO (vitrified) Abrasive grain structure (abrasive grain ratio): 23 (abrasive grain content 16% JIS R6242) The polishing conditions were a grinding wheel rotation speed of 2100 rpm and an electrophotographic member rotation speed of 250 rpm. In the rough grinding process, the grinding wheel penetrated the electrophotographic member at a speed of 20 mm / sec, penetrating 0.24 mm after contacting the outer peripheral surface of the electrophotographic member. In the fine polishing process, the penetration speed was changed to 0.5 mm / sec, penetrating 0.01 mm. The grinding wheel was then removed from the electrophotographic member to complete the polishing. The polishing method used was the upper cut method, in which the grinding wheel and electrophotographic member rotate in the same direction.

[0179] (Examples 2 to 23, Comparative Examples 1 and 2) Electrophotographic members (charging rollers of Examples 2 to 23 and Comparative Examples 1 and 2) were prepared in the same manner except that the rubber, filler, conductive particles, and sulfur in the rubber composition formulation, and the rubber mixture for forming the conductive layer were formulated as shown in Table 7.

[0180] (Comparative Example 3) An electrophotographic member was produced in the same manner as in Example 6, except that the mixing conditions for mixing the rubber for forming the conductive layer were a blade rotation speed of 35 rpm, a mixing time of 20 minutes, and an amount of calcium carbonate for mixing the matrix of 65 parts.

[0181] Comparative Example 4 An electrophotographic member was produced in the same manner as in Example 21, except that the mixing conditions for the matrix and the rubber mixture for forming the insulating domain (M-DRC) were changed to a blade rotation speed of 35 rpm and a mixing time of 25 minutes.

[0182] (Comparative Example 5) An electrophotographic member was prepared in the same manner as in Example 5, except that the mixing conditions for preparing the matrix were a blade rotation speed of 35 rpm, a mixing time of 25 minutes, and an amount of calcium carbonate when mixing the matrix of 70 parts.

[0183] (Comparative Example 6) An electrophotographic member was produced in the same manner as in Example 22, except that the mixing conditions for the rubber mixture for insulating domains (DRC-B) were changed to a blade rotation speed of 25 rpm and a mixing time of 12 minutes.

[0184] [Table 7] In the table, A indicates the domain A release temperature, M indicates the Mooney viscosity, and SP indicates the SP value. .

[0185] 3. Characterization [3-1. Confirmation of the presence or absence of matrix domain structure] The presence of a matrix domain structure in the conductive layer was confirmed by the following method. A slice (500 μm thick) was cut using a razor so that a cross section perpendicular to the longitudinal direction of the conductive layer of the electrophotographic member could be observed. Platinum was then vapor-deposited on the surface of the slice corresponding to the cross section of the conductive layer. The platinum-deposited surface of the slice was photographed at 5000x magnification using a scanning electron microscope (SEM) (product name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image. When the SEM image confirmed that multiple domains were dispersed in the matrix and that the matrix was interconnected, it was determined that the matrix domain structure was "present."

[0186] [3-2. Measurement of matrix volume resistivity ρm] 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 Corporation) as follows: The measurement environment was a temperature of 23°C and a relative humidity of 50%.

[0187] First, a microtome (trade name: Leica EMFCS, manufactured by Leica Microsystems) was used to cut out slices of approximately 2 μm thickness from the conductive layer of the charging roller 1 at a cutting temperature of -100°C. As described above, cross sections in the thickness direction of the conductive layer were obtained as shown in FIG. 2B. For each of the obtained cross sections, measurements were made in three 15 μm square regions (0.2T, 0.5T, and 0.7T) in the thickness range from the outer surface of the conductive layer to a depth of 0.1T to 0.9T toward the support, and the value was calculated from the arithmetic mean of the measurement values ​​at a total of nine points. Next, the slice was placed on a metal plate so that one side of the slice corresponding to the cross section of the conductive layer was in contact with the surface of the metal plate. Then, on the side of the slice opposite to the side in contact with the surface of the metal plate, a cantilever of an SPM was brought into contact with the portion corresponding to the matrix. A voltage of 50 V was then applied to the cantilever, and the current value was measured. The surface shape of the slice was also observed with the SPM, and the thickness of the measurement point was calculated from the obtained height profile. Furthermore, the area of ​​the recess at the contact point of the cantilever was calculated from the surface shape observation results. The volume resistivity was calculated from the thickness and the area of ​​the recess, and this was taken as the volume resistivity of the matrix.

[0188] [3-3. Measurement of volume resistivity ρd of conductive domain A] The volume resistivity ρd of the conductive domain A was measured in the same manner as in the measurement method for the matrix volume resistivity in 3-2 above, except that the contact position of the cantilever was set to the point corresponding to the conductive domain A and the voltage applied to the cantilever was set to 1 V. The average value of the values ​​at each measurement point was calculated.

[0189] [3-4. Measurement of volume resistivity ρI of insulating region and insulating domain B] The measurement was performed in the same manner as in 3-2 above, except that the contact position of the cantilever was set to the insulating region, a location corresponding to insulating domain B, and the voltage applied to the cantilever was set to 10 V. The average value of the values ​​at each measurement location was calculated. The domain A and the insulating region were distinguished as follows. From the backscattered electron images taken with the FIB-SEM, it is possible to determine whether a second rubber and conductive particles are included based on the contrast between the matrix and domains. Specifically, an image analyzer (product name: LUZEX-AP, manufactured by Nireco Corporation) is used to distinguish between the matrix and domains by utilizing the contrast difference inside the domains, and it is possible to identify and analyze the area of ​​conductive particles, such as carbon black, within each domain.

[0190] [3-5. Measurement of domain volume and number] The volume Vd, which indicates the state of the conductive domain A and the insulating region (domain B) in the matrix, the number ratio of domain A to domain B, and the domain diameter of domain B were calculated by FIB-SEM measurement as described below.

[0191] FIB-SEM is a technique in which a sample is processed using a FIB (Focused Ion Beam) device and the exposed cross section is observed using a SEM (scanning electron microscope).

[0192] Specifically, first, sampling of the conductive layer is performed from nine locations on the conductive layer. In the case of a roller, when the longitudinal length is L, one sample is cut out from each of three locations at approximately (1 / 4)L, (2 / 4)L, and (3 / 4)L from the end, at 120-degree intervals around the circumference of the roller.

[0193] Then, three-dimensional measurement was performed using a focused ion beam by FIB-SEM to measure images of cubes with sides of 9 μm and 60 nm intervals. Here, the cross sections of the conductive layer at each of the (1 / 4)L, (2 / 4)L, and (3 / 4)L cross sections were measured every 120 degrees around the circumference of the roller, from the position of the core bar to the center of the surface.

[0194] Next, in order to properly observe the domain structure, a pretreatment is carried out to obtain a good contrast between the domain and the matrix. A staining treatment is preferably used here. Specific examples include osmium tetroxide, ruthenium tetroxide, and phosphotungstic acid, and a staining agent that can distinguish the first rubber and the second rubber can be appropriately selected. In the examples, osmium tetroxide was used for staining. Since the greater the number of double bonds and benzene rings in the rubber, the greater the staining, the rubber type was identified and the domains and matrix were distinguished. Domain A and Domain B were distinguished by utilizing the contrast difference within the domains to distinguish between the matrix and the domains, and the conductive particles, typically carbon black, within each domain could be identified and their area analyzed.

[0195] The obtained images were then analyzed using 3D visualization and analysis software Avizo (registered trademark, manufactured by FEI, Inc.). The 9 μm-side cubic sample was divided into 27 unit cubes with sides of 3 μm. The volume Vd of the domain contained in each unit cube was then calculated.

[0196] Specifically, when the volume Vd of the domains including the domain A and domain B observed above contained in the unit cube is calculated, Vd is 2.7 to 10.8 μm 3 The number of unit cubes was counted and the number of samples that satisfied (A) was confirmed.

[0197] Furthermore, using the above method, the number of domains A containing the electronic conductive agent and the number of insulating domains B were counted, and the proportion of the number of domains A in the total number of domains was calculated.

[0198] [3-6. Evaluation of domain shape] The shape of the domains contained in the conductive layer was evaluated by the following method of quantifying images obtained by scanning electron microscope (SEM) through image processing.

[0199] A thin piece having a thickness of 1 mm was cut out in the same manner as in the measurement of the volume resistivity of the matrix [3-2] above. At this time, a plane perpendicular to the axis of the conductive support and a cross section parallel to that plane were obtained from the thin piece. The cutting positions from the conductive layer were the center in the longitudinal direction, and three positions at L / 4 from both ends of the conductive layer toward the center, where L is the length in the longitudinal direction of the conductive layer. Platinum was vapor-deposited onto the section to obtain a vapor-deposited section. The surface of the vapor-deposited section was then photographed at 1,000x magnification using a scanning electron microscope (SEM) (product name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an observation image.

[0200] Next, when the thickness of the conductive layer is T, 15 μm square areas at three locations (0.2T, 0.5T, and 0.7T) in the thickness region from the outer surface of the conductive layer to a depth of 0.1T to 0.9T on each of the three slices obtained from the three measurement positions above were extracted as analysis images, for a total of nine locations. Next, to quantify the shape of the domains in the analysis image, image processing software ImageProPlus (product name, manufactured by MediaCybernetics) was used to convert the image to 8-bit grayscale, obtaining a monochrome image with 256 gradations. The image was then inverted to obtain a binary image, so that the domains in the fracture surface appeared white. The following items were then calculated for the domain group A present in the binary image using a counting function for the binary image. ·Perimeter length A (μm) ·Envelope perimeter B (μm) Domain A and Domain B can be distinguished from each other by analyzing the image and determining whether or not they contain conductive particles.

[0201] The results are shown in Table 8. In Table 8, the value obtained by substituting into formula (5) is shown as the "perimeter ratio A / B." 1.00≦A / B≦1.10 (5) (A: perimeter of domain, B: envelope perimeter of domain)

[0202] [Impedance measurement] The impedance was measured by the following method. First, as a pretreatment, platinum was vapor-deposited onto the outer surface of the electrophotographic member, a charging roller, while it was rotating, to create a measurement electrode (metal film). Masking tape was used to create a 1.5 cm wide, uniform electrode in the circumferential direction. By forming this electrode, the contribution of the contact area between the measuring electrode and the electrophotographic member, due to the surface roughness of the electrophotographic member, can be minimized. Next, an aluminum sheet was tightly wrapped around the electrode to form a measurement sample.

[0203] An impedance measuring device (product name: Solartron 1260 96W, manufactured by Solartron) was connected to the aluminum sheet and to the outer surface of the support. The impedance was measured in an environment of 23°C temperature and 50% relative humidity using a DC voltage of 1 V or 10 V, an oscillating voltage of 1 V, and a frequency of 1.0 × 10 -1 The impedance when a DC voltage of 1 V was applied was defined as impedance X. The impedance when a DC voltage of 10 V was applied was defined as impedance Y.

[0204] The charging roller (longitudinal length: 230 mm) was divided into five equal regions in the longitudinal direction, and a measurement electrode was formed at one point in the center of each region, for a total of five points, and the above measurement was performed. The average value of these was taken as the impedance of the charging roller.

[0205] 4. Image Evaluation In order to confirm the stain resistance performance of the charging roller 1 under long life conditions, the following evaluation was carried out. First, an electrophotographic laser printer (product name: LaserJetProM203dw manufactured by HP) was prepared as an electrophotographic image forming apparatus. In order to evaluate a high-speed process, the laser printer was set to output as many pages per minute as the original. The printer was modified to print 50 sheets of A4 paper per minute, which is more than the required number of sheets. The output speed of the recording media was set to 370 mm / sec. Next, the charging roller 1, the electrophotographic image forming apparatus, and the process cartridge were left in an environment of 15° C. / 10% RH for 48 hours in order to acclimate them to the evaluation environment.

[0206] The charging roller 1 that had been left in the above environment was set as a charging roller for a process cartridge and incorporated into a laser printer, after which images were output continuously on a total of 50,000 sheets under the same environment. The image output was a 4-point alphabet letter "E" printed on an A4 size sheet of paper with a print rate of 1.0%. Then, a halftone image (an image in which horizontal lines with a width of 1 dot and an interval of 2 dots are drawn in the direction perpendicular to the rotation direction of the photosensitive drum) was output. This halftone image was visually observed, and the white dot image and the black dot image were evaluated according to the following criteria.

[0207] [Evaluation of white spots on halftone images] Rank A: No white spots are visible on the halftone image even when observed under a microscope. Rank B: No white dots are visible on the halftone image when observed with the naked eye, but they are visible when observed under a microscope. Rank C: White spots are visible in some parts of the halftone image. Rank D: White dots are visible all over the halftone image.

[0208] [White haze image evaluation] Furthermore, in order to acclimate the charging roller 1, the electrophotographic image forming apparatus, and the process cartridge to the evaluation environment, they were left in an environment of 30°C / 80% RH for 48 hours. In order to evaluate the white haze image, the charging roller 1 was prepared with a circumferential outer diameter deviation of 40 μm at the center. The charging roller 1 that had been left in the above environment was set as a charging roller for a process cartridge and incorporated into a laser printer, after which images were output continuously on a total of 50,000 sheets under the same environment. The image output was a 4-point alphabet letter "E" printed on an A4 size sheet of paper with a print rate of 1.0%.

[0209] Thereafter, a halftone image (an image in which horizontal lines with a width of 1 dot and an interval of 2 dots are drawn in the direction perpendicular to the rotation direction of the photosensitive drum) was output. This halftone image was visually observed, and the white haze image was evaluated according to the following criteria. [Evaluation of white haze images on halftone images] Rank A: No white mist image is visible on the halftone image even when observed under a microscope. Rank B: No white mist image is visible on the halftone image when observed with the naked eye, but can be seen when observed under a microscope. Rank C: White mist images are visible in parts of the halftone image. Rank D: A white haze image is visible across the entire halftone image.

[0210] The results are shown in Table 8 [Table 8]

[0211] In the table, "1 to 9" in the DRC-A column represent samples taken from nine locations on the conductive layer. In the pull, Vd is 2.7 to 10.8 μm 3 This indicates the number of unit cubes that satisfy (A). That is, in Examples 7 to 23, there were at least eight samples that satisfied (A). DA indicates the average number of domains A per sample among the nine samples. DB indicates the average number of domains B per sample among the nine samples. In each example, the proportion of the number of domains B in the total number of domains was 100 - proportion of domains A (number %).

[0212] The present disclosure relates to the following configurations. (Configuration 1) 1. An electrophotographic member having a support having an electrically conductive outer surface, and an electrically conductive layer disposed on the outer surface of the support, the conductive layer has a matrix including a first rubber and at least one domain dispersed in the matrix; The volume resistivity of the matrix is ​​1.00×10 8 ~1.00×10 12 Ω cm, The at least one domain includes a domain A including a second rubber and an electronic conductive agent; the conductive layer further has an insulating region comprising a third rubber; The volume resistivity of the insulating region is 1.00×10 12 is greater than Ω·cm, A platinum electrode was provided directly on the outer surface of the electrophotographic member, and the impedance was measured in an environment of a temperature of 23°C and a relative humidity of 50% while a DC voltage of 1 V and an AC voltage having an amplitude of 1 V were superimposed and applied between the outer surface of the support and the platinum electrode. Frequency 1.0 x 10 -1 Impedance X in Hz is 1.00 x 10 6 ~1.00×10 8 Ω, When the impedance was measured in a state where a DC voltage of 10 V and an AC voltage having an amplitude of 1 V were superimposed and applied between the outer surface of the support and the platinum electrode, Frequency 1.0 x 10 -1 An electrophotographic member characterized in that the relationship between impedance Y in Hz and impedance X satisfies the following formula (1): X / Y≧7.5 ···(1). (Configuration 2) 2. The electrophotographic member of claim 1, wherein the at least one domain includes a domain B that constitutes the insulating region. (Configuration 3) The electrophotographic member according to constitution 2, wherein at least eight of the cubic samples with a side of 9 μm taken from nine locations on the conductive layer satisfy the following (A): (A) when one sample is divided into 27 unit cubes with a side of 3 μm and the volume Vd of the domain contained in each unit cube is calculated, Vd is 2.7 to 10.8 μm 3 The number of unit cubes in which (Configuration 4) 4. The electrophotographic member according to claim 3, wherein at least eight samples satisfying (A) above satisfy the following (B): (B) The proportion of the number of domains A in the total number of domains is 10 to 50% by number. (Configuration 5) The conductive member according to configuration 4, wherein at least eight samples satisfying (A) above satisfy the following (B2): (B2) The proportion of the number of domains A in the total number of domains is 30 to 40% by number. (Configuration 6) The impedance Y and the impedance X satisfy the following formula (2): 6. An electrophotographic member according to any one of claims 1 to 5, 20.0≧X / Y≧7.5 ···(2). (Configuration 7) 7. The electrophotographic member according to any one of configurations 1 to 6, wherein the electronic conductive agent is carbon black. (Configuration 8) The electrophotographic member according to any one of Configurations 1 to 7, wherein when the perimeter of the domain A is A and the envelope perimeter of the domain A is B, the following formula (5) is satisfied: 1.00≦A / B≦1.10 ···(5). (Configuration 9) The first rubber is NBR, The second rubber is at least one rubber selected from the group consisting of SBR, EPDM, and IR, 9. The electrophotographic member according to any one of configurations 1 to 8, wherein the third rubber is at least one rubber selected from the group consisting of SBR, EPDM, and IR. (Configuration 10) The volume resistivity of the domain A is 1.00×10 1 ~1.00×10 4 10. The electrophotographic member according to any one of configurations 1 to 9, wherein the resistivity is Ω·cm. (Configuration 11) The electrophotographic member according to any one of configurations 1 to 10, wherein the electrophotographic member is a charging member. (Configuration 12) A process cartridge detachably mountable to an electrophotographic image forming apparatus, 12. A process cartridge comprising the electrophotographic member according to any one of Configurations 1 to 11. (Configuration 13) An electrophotographic image forming apparatus, 12. An electrophotographic image forming apparatus comprising the electrophotographic member according to any one of Configurations 1 to 11. [Explanation of symbols]

[0213] 1 Support 2 Conductive layer< / epdm> < / sbr> < / nbr>

Claims

1. 1. An electrophotographic member having a support having an electrically conductive outer surface, and an electrically conductive layer disposed on the outer surface of the support, the conductive layer has a matrix including a first rubber and at least one domain dispersed in the matrix; The volume resistivity of the matrix is ​​1.00×10 ８ ~1.00 x 10 １２ Ω cm, The at least one domain includes a domain A including a second rubber and an electronic conductive agent; the conductive layer further has an insulating region comprising a third rubber; The volume resistivity of the insulating region is 1.00×10 １２ greater than Ω cm, A platinum electrode was provided directly on the outer surface of the electrophotographic member, and a DC voltage of 1 V and an AC voltage having an amplitude of 1 V were superimposed and applied between the outer surface of the support and the platinum electrode in an environment of a temperature of 23° C. and a relative humidity of 50%, and the impedance was measured. Frequency 1.0 x 10 －１ Impedance X in Hz is 1.00 x 10 ６ ~1.00 x 10 ８ Ω, When the impedance was measured in a state where a DC voltage of 10 V and an AC voltage having an amplitude of 1 V were superimposed and applied between the outer surface of the support and the platinum electrode, Frequency 1.0 x 10 －１ 1. An electrophotographic member characterized in that the relationship between impedance Y in Hz and impedance X satisfies the following formula (1): X / Y≧7.5 (1).

2. 2. An electrophotographic member according to claim 1, wherein said at least one domain includes a domain B that constitutes said insulating region.

3. 3. The electrophotographic member according to claim 2, wherein at least eight of the cubic samples, each 9 μm on a side, sampled from nine locations on the conductive layer satisfy the following condition (A): (A) One sample is divided into 27 unit cubes each having a side length of 3 μm, and the volume Vd of the domain contained in the unit cube is calculated. Vd is 2.7 to 10.8 μm. ３ The number of unit cubes in which

4. 4. The electrophotographic member of claim 3, wherein at least eight samples satisfying (A) satisfy the following (B): (B) The proportion of the number of domains A in the total number of domains is 10 to 50% by number.

5. The conductive member according to claim 4, wherein at least eight samples that satisfy (A) satisfy the following (B2): (B2) The proportion of the number of domains A in the total number of domains is 30 to 40% by number.

6. 2. The electrophotographic member according to claim 1, wherein the impedance Y and the impedance X satisfy the following formula (2): 20.0≧X / Y≧7.5...(2).

7. 2. An electrophotographic member according to claim 1, wherein said electronically conductive agent is carbon black.

8. 2. The electrophotographic member according to claim 1, wherein the following formula (5) is satisfied, where A is the perimeter of the domain A and B is the envelope perimeter of the domain A: 1.00≦A / B≦1.10 (5).

9. The first rubber is NBR, The second rubber is at least one rubber selected from the group consisting of SBR, EPDM, and IR, 2. An electrophotographic member according to claim 1, wherein said third rubber is at least one rubber selected from the group consisting of SBR, EPDM, and IR.

10. The volume resistivity of the domain A is 1.00×10 １ ~1.00 x 10 ４ 3. The electrophotographic member of claim 1, wherein the surface resistivity is Ω·cm.

11. 2. The electrophotographic member according to claim 1, wherein the electrophotographic member is a charging member.

12. A process cartridge detachably mountable to an electrophotographic image forming apparatus, 12. A process cartridge comprising the electrophotographic member according to claim 1.

13. An electrophotographic image forming apparatus, 12. An electrophotographic image forming apparatus comprising the electrophotographic member according to claim 1.

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