CONDUCTIVE MEMBER, ELECTROPHOTOGRAPHIC IMAGE FORMING APPARATUS, AND PROCESS CARTRIDGE

Abstract

To provide a conductive member for an electrophotographic image forming apparatus in which a resistance value changes by a small amount even when a large amount of current is caused to flow at a high voltage for a long period.SOLUTION: A conductive member has a support that has a conductive outer surface and a conductive layer that is provided on the outer surface of the support. The conductive layer has a matrix that includes a first rubber cross-linked material, and a plurality of domains that are dispersed in the matrix. The domains include a second rubber cross-linked material different from the first rubber, and an electronic conductive agent. The second rubber cross-linked material has, in a molecule, a structural unit indicated by the following structural formula (I). Structural formula (I): [-(CH2)n-O-]. In the structural formula (I), n indicates an integer of 1 to 3.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an electroconductive member for electrophotography, an electrophotographic image forming apparatus, and a process cartridge. [Background technology]

[0002] An electrophotographic image forming apparatus (hereinafter also referred to as "electrophotographic apparatus") typically comprises an image carrier such as a photoreceptor, a charging member which charges the surface of the image carrier, an exposure device which irradiates the surface of the image carrier with light modulated according to image information, a developing member which develops the image carrier with a developer (toner) to form a visible image (toner image), and a transfer member which transfers the visible image on the image carrier to a recording material.

[0003] In conductive members such as charging members, developing members, and transfer members, a medium resistance is desired, and therefore, a method of using a rubber having ionic conductivity such as epichlorohydrin rubber or a method of dispersing a conductive material such as carbon black in an insulating rubber material is known. In Patent Document 1, the volume resistivity is 1×10 12 The document discloses a rubber composition with an islands-in-a-sea structure that includes a polymer continuous phase made of an ionically conductive rubber material mainly composed of raw rubber A having a resistivity of Ω·cm or less, and a polymer particle phase made of an electronically conductive rubber material made by blending conductive particles into raw rubber B, and an electrostatic charging member having an elastomer layer formed from the rubber composition. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-3651 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in recent electrophotographic devices, high speed and long life are required, and performance corresponding to high speed and long life is also required for electrophotographic members. In order to increase the speed of electrophotographic devices, it is necessary to pass a large current at a higher voltage to the above-mentioned conductive member. Therefore, it is desired that the change in resistance value of the conductive member is small even when a large current is passed through the conductive member at a high voltage for a long period of time. However, as disclosed in Patent Document 1, when a high voltage is continuously applied to an electrophotographic member using carbon black as a conductive material for a long period of time, the conductivity changes, and the function as a conductive member for electrophotography may change over time.

[0006] One aspect of the present disclosure is to provide a conductive member that exhibits small changes in resistance even when a large amount of current is passed through it at a high voltage for a long period of time. Another aspect of the present disclosure is directed to providing a process cartridge that contributes to forming a high-quality electrophotographic image. Yet another aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that can form a high-quality electrophotographic image. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, A conductive member for electrophotography, comprising: a support having a conductive outer surface; and a conductive layer provided on the outer surface of the support, The conductive layer is A matrix containing a crosslinked product of a first rubber, and having a plurality of domains dispersed in the matrix; The domain includes a crosslinked product of a second rubber different from the first rubber and an electronic conductive agent, The crosslinked product of the second rubber has a structural unit represented by the following structural formula (I) in the molecule: death, [-(CH2)nO-] Structural formula (I) ( In structural formula (I), n represents an integer of 1 to 3. ) A conductive member in which, when a length in the longitudinal direction of the conductive layer is L and a thickness of the conductive layer is T, observation regions of 15 μm square are placed at any three locations in a thickness region from an outer surface of the conductive layer to a depth of 0.1T to 0.9T for each of three locations in a cross section of the conductive layer in the thickness direction, the center of the conductive layer in the longitudinal direction and three locations at L / 4 from both ends of the conductive layer toward the center, 80% by number or more of the domains observed in each of all nine observation regions satisfy the following requirement (1) and requirement (2): Requirement (1) The ratio of the cross-sectional area of ​​the carbon black contained in the domain to the cross-sectional area of ​​the domain is 20% or more; Requirement (2) There is provided a conductive member in which, when the perimeter of the domain is A and the envelope perimeter of the domain is B, A / B is 1.00 or more and 1.10 or less.

[0008] According to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above-mentioned conductive member. According to still another aspect of the present disclosure, there is provided a process cartridge for electrophotography that is configured to be detachably mountable to a main body of an electrophotographic image forming apparatus and that includes the above-mentioned conductive member. Effect of the Invention

[0009] According to one aspect of the present disclosure, it is possible to obtain a conductive member for electrophotography that exhibits small change in resistance even when a large current is passed through it at a high voltage for a long period of time. According to another aspect of the present disclosure, it is possible to obtain a process cartridge that contributes to the formation of high-quality electrophotographic images. According to yet another aspect of the present disclosure, it is possible to obtain an electrophotographic image forming apparatus that can form high-quality electrophotographic images. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a conductive member for electrophotography according to one embodiment of the present disclosure. [Diagram 2] This is an example of an apparatus that can be used to form a rubber tube (conductive layer), and is composed of an extruder, a microwave vulcanizer, a hot air vulcanizer, a take-off machine, and a cut-to-length machine. [Diagram 3] FIG. 1 is a schematic diagram of a matrix-domain structure according to one embodiment of the present disclosure. [Figure 4] FIG. 2 is a conceptual diagram illustrating the maximum Feret diameter of a domain. [Diagram 5] FIG. 1 is a conceptual diagram illustrating the envelope perimeter of a domain. [Figure 6] 1 is a schematic configuration diagram of an electrophotographic image forming apparatus according to one embodiment of the present disclosure. [Figure 7] FIG. 2 is a schematic diagram for explaining a cross section of a slice cut out for domain shape measurement or the like. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present inventors speculate that the reason why the conductivity of the conductive member disclosed in Patent Document 1 changes when a high voltage is continuously applied for a long period of time is as follows: The conductivity attributable to carbon black depends on the degree of development of the carbon black structure. It is believed that an increase in the current flowing through the carbon black changes the structure of the carbon black, causing a change in the conductivity of the conductive member. Therefore, the present inventors have considered that in order to suppress changes in the conductivity of a conductive member using carbon black as a conductive material when a high voltage is applied, it is effective to suppress the concentration of charge on the carbon black that constitutes the structure, thereby suppressing the change in the structure. Based on these considerations, further investigations led to the discovery that when a conductive layer provided on the outer surface of a conductive member has the following configuration, changes in the conductivity of the conductive member can be prevented when a high voltage is continuously applied thereto.

[0012] The composite material has a matrix containing a cross-linked product of a first rubber, and a plurality of domains dispersed in the matrix, the domains containing a cross-linked product of a second rubber different from the first rubber, and an electronic conductive agent; The crosslinked product of the second rubber has a structure having a structural unit represented by the following structural formula (I) in the molecule: [-(CH2) n -O-] Structural formula (I) (In structural formula (I), n represents an integer of 1 to 3.)

[0013] Hereinafter, the conductive member for electrophotography according to one embodiment of the present disclosure will be described using a roller-shaped conductive member for electrophotography (hereinafter, sometimes simply referred to as "electrophotography roller") as an example. FIG. 1 shows an example of an electrophotographic roller according to one embodiment of the present disclosure, which has a conductive elastic layer (conductive layer) 12 on the outer surface of a cylindrical or columnar support 11 having a conductive outer surface.

[0014] [Support 11] The support 11 supports the conductive layer 12 formed thereon. The support 11 is not particularly limited as long as it has conductivity for providing electrical continuity to the conductive layer 12, but is preferably made of a metal such as aluminum, an aluminum alloy, stainless steel, or iron. In addition, in order to improve corrosion resistance and abrasion resistance, these metals may be plated with chromium, nickel, or the like. The shape of the support 11 may be any shape selected from a hollow shape (cylindrical shape) and a solid shape (columnar shape). The outer diameter of the cylindrical or columnar support 11 can be appropriately selected depending on the electrophotographic image forming apparatus to be mounted, and may be, for example, 4 mm or more and 10 mm or less.

[0015] [Conductive layer 12] The outer diameter of the conductive layer can be appropriately selected depending on the electrophotographic image forming apparatus in which it is mounted, and may be, for example, from 7 mm to 20 mm.

[0016] The conductive layer 12 is A matrix containing a crosslinked product of a first rubber, and having a plurality of domains dispersed in a matrix, The domain includes a cross-linked product of a second rubber different from the first rubber, and an electronic conductive agent, and the cross-linked product of the second rubber has a structural unit represented by the following structural formula (I) in the molecule. [-(CH2) n -O-] Structural formula (I) In structural formula (I), n represents an integer of 1 to 3.

[0017] The present inventors presume that the reason why the conductive member for electrophotography according to this embodiment can prevent a change in conductivity even when a high voltage is continuously applied thereto is as follows. It is considered that the electronic conductive agent contained in the domain is covered with the crosslinked product of the second rubber having in its molecule a structural unit represented by structural formula (I) that is ion conductive. When electricity is passed in this state, the difference in electrical resistance between the electronic conductive agent and the crosslinked product of the second rubber is small, so that the charge flows through both the electronic conductive agent and the crosslinked product of the second rubber. This makes it possible to suppress the concentration of current in the electronic conductive agent. As a result, the electronic conductive agent is less likely to cause changes in the conductive path, and changes in conductivity can be suppressed. Specifically, for example, when the electronic conductive agent is carbon black, the above-mentioned configuration can suppress changes in the structure of the carbon black, thereby preventing changes in conductivity.

[0018] The volume resistivity ρd of the domain and the volume resistivity ρ of the conductive layer are preferably in the following ranges. 1.0×10 1 Ω cm ≦ ρd ≦ 1.0×10 4 Ω cm 1.0×10 5 Ω cm ≦ ρ ≦ 1.0×10 8 Ω cm The volume resistivity ρd of the domain is 1.0×10 1 By having a resistivity of Ω·cm or more, it is possible to prevent electric charges from concentrating and flowing in areas where the interdomain distance is locally short. In addition, the volume resistivity ρd is 1.0×10 4 With a resistivity of Ω·cm or less, the electronic conductivity in the domain becomes stronger than the ionic conductivity, which makes it possible to further reduce the environmental dependency of the electrical conductivity. The volume resistivity ρ of the conductive layer is 1.0×10 5 By having a resistivity of Ω·cm or more, it is possible to prevent electric charges from concentrating and flowing in areas where the interdomain distance is locally short. 8 By being Ω·cm or less, charges can flow without reducing the conductive path even in areas where the interdomain distance is locally long. Moreover, it is preferable that the volume resistivity ρm of the matrix is ​​in the following range. 1.0×10 8 Ω cm ≦ ρm ≦ 1.0×10 17 Ω cm The volume resistivity of the matrix is ​​1.0×10 8 By having a resistivity of 1.0×10 Ω·cm or more, the electric charge flowing through the matrix is ​​suppressed, thereby suppressing the resistance fluctuation of the matrix. 17 By being Ω·cm or less, charges can flow without reducing the conductive path even in areas where the interdomain distance is locally long.

[0019] <Method of measuring volume resistivity ρd of domain and volume resistivity ρm of matrix> The volume resistivity ρd of the domain can be measured, for example, by cutting a slice of a given thickness (e.g., 1 μm) containing a matrix domain structure from a conductive layer and contacting a microprobe (the tip of a cantilever) of a scanning probe microscope (SPM) or an atomic force microscope (AFM) with the domain in the slice. The slices are cut out from the elastic layer so as to include at least a part of a cross section parallel to the XZ plane, where the longitudinal direction of the conductive member is the X axis, the thickness direction of the conductive layer is the Z axis, and the circumferential direction is the Y axis, as shown in Fig. 7. Alternatively, the slices are cut out so as to include at least a part of a YZ plane 72 (e.g., cross sections 72a, 72b, 72c) perpendicular to the axial direction of the conductive member, as shown in Fig. 7. Examples of methods for cutting out the slices from the elastic layer include a method using a sharp razor or a microtome, and a focused ion beam method (FIB). The volume resistivity is measured as follows. First, one side of a flake cut from a conductive layer is grounded. Next, a microprobe of a scanning probe microscope (SPM) or atomic force microscope (AFM) is brought into contact with the domain part on the side of the flake opposite the grounded side, a DC voltage of 1V is applied for 5 seconds, and the ground current value measured for 5 seconds is used to calculate the arithmetic mean value, and the applied voltage is divided by this calculated value to calculate the electrical resistance value. Since the SPM and AFM can measure the thickness of the flake at the same time as the resistance value, the resistance value is converted to volume resistivity using the thickness of the flake. The volume resistivity value of the domain in a cylindrical charging member is determined, for example, by cutting out one thin sample from each of the regions obtained by dividing the conductive layer into four in the circumferential direction and five in the longitudinal direction, obtaining the above-mentioned measured values, and then calculating the arithmetic average value of the volume resistivities of a total of 20 samples. The volume resistivity ρm of the matrix can be measured in the same manner as in the measurement of the volume resistivity of the domain, except that the measurement location is changed to a location equivalent to the matrix and the applied voltage when measuring the current value is changed to 50 V.

[0020] <Domain shape> By making the cross-sectional shape of the domains appearing in the cross section in the thickness direction of the conductive layer closer to a circular shape, it is possible to minimize the electric field concentration caused by the convex shape of the conductive domains. Therefore, even when a high voltage is applied to the conductive member, the transfer of excess charge is suppressed, and the photoconductor can be charged more uniformly. As a result, the occurrence of fogging on the electrophotographic image can be suppressed. In the present disclosure, the cross-sectional shape of the domain (hereinafter simply referred to as the domain shape) is defined as the shape of the domain observed in each of the nine observation regions when 15 μm square observation regions are placed at three arbitrary positions in the thickness region from the outer surface of the conductive layer to a depth of 0.1T to 0.9T for each of the cross sections 72a, 72b, and 72c in the thickness direction of the conductive layer 71 as shown in FIG. 7, the three positions being the center of the conductive layer in the longitudinal direction and two positions at L / 4 from both ends of the conductive layer toward the center, where L is the longitudinal length of the conductive layer and T is the thickness of the conductive layer. The cross sections 72a, 72b, and 72c are cross sections parallel to the YZ plane 72, where the axial direction of the support is the X direction and the directions perpendicular thereto are the Y direction and the Z direction.

[0021] The domain according to this embodiment preferably has a cross-sectional shape that is closer to a circle when viewed in a cross section of the conductive layer in the thickness direction. Specifically, when a 15 μm square observation area is placed at any position on the cross section of the conductive layer in the thickness direction, it is preferable that 80% or more of the domains observed in the observation area satisfy the following formulas (1) and (2). 0.60≦4×S / (π×D f2 )≦1.00 Equation (1) (In formula (1), D f is the maximum Feret diameter of the domain cross section, and S is the area of ​​the domain cross section.) 1.00≦A / B≦1.10 Formula (2) (In formula (2), A represents the perimeter of the cross section of the domain, and B represents the envelope perimeter of the cross section of the domain.)

[0022] The maximum Feret diameter D in Eq. (1) f As shown in FIG. 4, the value is the value when the length of the perpendicular line is the longest when the periphery of the cross section 41 of the observed domain is sandwiched between two parallel lines and the two parallel lines are connected by a perpendicular line. Formula (1) shows the ratio of the actual area S of the cross section of the domain to the area of ​​the circle equivalent to the maximum Feret diameter obtained from the cross section of the domain. The maximum value of this ratio is 1.00, and a state of 1.00 indicates that the cross section of the domain is a perfect circle. If the ratio is less than 0.60, the shape of the domain has a large anisotropy, and electric field concentration is likely to occur at the end of the domain in the longitudinal direction. Equation (2) shows the ratio between the perimeter of the domain cross section and the envelope perimeter of the domain cross section. The envelope perimeter is defined as the perimeter of the convex hull of the domain. Specifically, as shown in FIG. 5, it is the perimeter (dashed line 52) when the convex parts of the domain cross section 51 observed in the observation area are connected and the perimeter of the concave parts is ignored. The ratio of the domain cross-sectional perimeter A to the domain cross-sectional envelope perimeter B in formula (2) is at a minimum value of 1.00, and a state of 1.00 indicates that the domain cross-section is a perfect circle or an ellipse. If the ratio exceeds 1.10, the domain will have a large uneven shape, that is, electric field concentration will be likely to occur. If the above formula (2) is satisfied, the electric field concentration is suppressed, and it is possible to suppress fogging. The size of the domain in this embodiment is preferably within a certain range, and the maximum Feret diameter, which is an index of domain size, is preferably 0.1 μm or more and 5.0 μm or less. If the maximum Feret diameter is within this range, the cross-sectional shape of the domain shape that appears in the cross-section of the conductive layer in the thickness direction tends to be circular. As a result, fogging is reduced, and the fineness of the conductive domain makes the discharge finer, which enables high image quality. In this embodiment, it is more preferable that the average number of domains is 20 to 300 in an observation area of ​​15 μm square. If there are 20 or more domains, sufficient conductivity as a conductive member can be obtained, and sufficient charge supply can be achieved even in a high-speed process. Also, if there are 300 or less domains, a sufficient distance between the domains can be maintained and aggregation of the domains due to repeated image output can be suppressed, making it easy to achieve uniform discharge even in long-term use.

[0023] In addition, in this embodiment, when carbon black is contained in the domains as an electronic conductive agent, it is preferable that 80% or more by number of the domains observed in each of all nine observation regions described above satisfy the following requirements (1) and (2). Requirement (1): The ratio of the cross-sectional area of ​​the domain containing carbon black to the cross-sectional area of ​​the domain is 20% or more; Requirement (2): If the perimeter of the domain is A and the envelope perimeter of the domain is B, then A / B must be greater than or equal to 1.00 and less than or equal to 1.10. Requirement (2) is synonymous with formula (2) above. Regarding requirement (1), the present inventors have found that the amount of electronic conductive agent (carbon black particles) contained in one domain affects the external shape of the domain. In other words, the present inventors have found that as the amount of carbon black particles packed in one domain increases, the shape of the domain becomes closer to a sphere. The more domains that are closer to a sphere, the fewer the points of concentration of electron transfer between domains can be. According to the study by the present inventors, although the reason is not clear, a domain in which the ratio of the total cross-sectional area of ​​the carbon black particles observed in the cross-section is 20% or more based on the cross-sectional area of ​​one domain can have a shape closer to a sphere. As a result, it is preferable because it can have an external shape that can significantly alleviate the concentration of electron transfer between domains. Considering that the carbon black particles are kept within the domain, the ratio of the cross-sectional area of ​​the carbon black particles is preferably 40% or less, more preferably 30% or less.

[0024] [Conductive layer composition] The conductive layer 12 has a matrix containing a cross-linked product of a first rubber and a plurality of domains dispersed in the matrix, the domains containing a cross-linked product of a second rubber different from the first rubber and an electronic conductive agent, and the cross-linked product of the second rubber has a structural unit represented by the following structural formula (I) in its molecule. [-(CH2) n -O-] Structural formula (I) In structural formula (I), n represents an integer of 1 to 3.

[0025] Examples of the electronic conductive agent to be blended in the domain include carbon materials such as carbon black and graphite, conductive oxides such as titanium oxide and tin oxide, metals such as Cu and Ag, and particles that are coated with a conductive oxide or metal to make them conductive. If necessary, two or more of these electronic conductive agents may be blended in combination. Among the above electronic conductive agents, electronic conductive agents mainly composed of conductive carbon black are preferred because they prevent a significant decrease in rubber elasticity, have high conductivity efficiency, have high affinity with rubber, and facilitate control of the distance between electronic conductive agents, etc. The type of conductive carbon black is not particularly limited, but specific examples include gas furnace black, oil furnace black, thermal black, lamp black, and acetylene black.

[0026] In the following description, the rubber components in the uncrosslinked composition are referred to as the "first rubber" and the "second rubber", and the crosslinked ones are referred to as the "crosslinked product of the first rubber" and the "crosslinked product of the second rubber", respectively. The second rubber preferably contains 50 to 98 mol %, more preferably 50 to 75 mol %, of the structural unit represented by structural formula (I). When the second rubber contains 50 mol % or more of the structural unit represented by structural formula (I), sufficient ion conductivity is obtained as a polymer, charge concentration in the electronic conductive agent is suppressed, and the effect of suppressing deterioration is increased. In addition, when the second rubber contains 98 mol % or less, more preferably 75 mol % or less of the structural unit represented by structural formula (I), it has excellent affinity with the matrix and allows fine dispersion of domains. The second rubber preferably has a structural unit derived from allyl glycidyl ether (AGE), and more preferably, the ratio of the number of structural units derived from allyl glycidyl ether is 2 to 15 mol%. When the ratio of the number of structural units derived from allyl glycidyl ether is 2 mol% or more, crosslinking is performed appropriately by sulfur crosslinking, and deformation of the conductive layer is unlikely to occur. Furthermore, when the ratio is 15 mol% or less, there are few double bonds remaining without being crosslinked by sulfur, and a decrease in conductivity due to denaturation of the rubber caused by current flow is unlikely to occur. Furthermore, the second rubber is preferably an epichlorohydrin-alkylene oxide-allyl glycidyl ether terpolymer, because the presence of structural units derived from epichlorohydrin makes the rubber less susceptible to modification by electrical current. Furthermore, it is preferable that the structural unit represented by the structural formula (I) contains either or both of an ethylene oxide structural unit (n=2) and a propylene oxide structural unit (n=3). By containing either or both of an ethylene oxide structural unit and a propylene oxide structural unit as the structural unit represented by the structural formula (I), the second rubber can obtain better ion conductivity.

[0027] Carbon black, which acts as an electronic conductor in the domain, absorbs DBP at a rate of 40 cm 3 / 100g or more, 200cm 3 The DBP absorption is closely related to the electronic conductivity of carbon black, and the DBP absorption is preferably 40 cm 3 If the DBP absorption is 200cm or more, electronic conductivity is exhibited when mixed with the second rubber, and it is easy to suppress the resistivity fluctuation due to the environment. 3 By keeping the weight per unit area at 100 g or less, the electronic conductivity of the carbon black and the ionic conductivity of the second rubber are well balanced, resulting in smaller changes in resistance when electricity is passed through them. In addition, DBP absorption (cm 3 / 100g) is the volume of dibutyl phthalate (DBP) that can be absorbed by 100g of carbon black, and is measured in accordance with Japan Industrial Standards (JIS) K 6217-4:2017 (Carbon black for rubber - Basic properties - Part 4: Determination of oil absorption (including compressed samples)). Generally, carbon black has a tufted higher-order structure in which primary particles with an average particle size of 10 nm to 50 nm are aggregated. This tufted higher-order structure is called structure, and its degree is expressed as DBP absorption (cm 3 / 100g).

[0028] The first rubber constituting the matrix is ​​not particularly limited as long as it can be phase-separated from the second rubber to form a matrix-domain structure. Preferred examples of the first rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene-propylene-diene terpolymer rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated NBR (H-NBR), and silicone rubber. In order to make the shape of the domain appearing in the cross section of the conductive layer in the thickness direction closer to a circle and to reduce the Feret diameter, it is preferable that the SP value difference between the first rubber and the second rubber is in an appropriate range. 3 ) 0.5 More than 2.2(J / cm 3 ) 0.5 Materials with an SP value difference of 0.4 (J / cm 3 ) 0.5 By setting the SP value difference to 2.2 (J / cm or more), the first rubber and the second rubber can form a stable phase separation structure. 3 ) 0.5 By being equal to or less than 15%, the Ferret diameter of the domain can be made small. In order to make the SP value difference with the second rubber fall within the above-mentioned appropriate range, the type of the first rubber is preferably acrylonitrile-butadiene rubber (NBR). In particular, it is more preferable that the content ratio of acrylonitrile (AN) in the crosslinked product of NBR is 15% by mass or more and 25% by mass or less. If the content ratio of AN is 15% by mass or more, the resistance value does not become too high, and if it is 25% by mass or less, an appropriate butadiene content can be secured to obtain a sufficient degree of crosslinking by vulcanization. The content of the electronic conductive agent such as carbon black in the matrix is ​​preferably 10 mass % or less, and more preferably the matrix does not substantially contain the electronic conductive agent (0 mass %). By substantially not containing the electronic conductive agent in the matrix, the conductivity of the matrix can be suppressed, and a conductive path can be formed by the domain. The rubber composition further contains sulfur for crosslinking (sulfur vulcanization). The sulfur content can be appropriately determined depending on the degree of crosslinking, etc., and is not particularly limited, but as a guideline, it is preferably 1.0 to 4.0 mass % with respect to the total amount of the rubber composition. The rubber composition used to form the conductive layer 12 may contain rubber components other than the first rubber and the second rubber, vulcanization aids, foaming agents, vulcanization accelerators, and other additives as necessary. However, the content ratio of the first rubber and the second rubber to the total content of the rubber components in the rubber composition is preferably 95 mass% or more, and more preferably 98 mass% or more. Furthermore, it is particularly preferable that the rubber components in the rubber composition consist only of the first rubber and the second rubber, excluding impurities.

[0029] [Vulcanization aid] Examples of vulcanization aids that may be contained in the rubber composition used to form the conductive layer 12 include zinc oxide, zinc stearate, and stearic acid.

[0030] [Foaming Agent] Examples of foaming agent components that may be contained in the rubber composition used to form the conductive layer 12 include azodicarbonamide, sodium hydrogen carbonate, and p,p'-oxybis(benzenesulfonylhydrazide) (OBSH).

[0031] [Vulcanization accelerator] Examples of vulcanization accelerators that may be contained in the rubber composition used to form the conductive layer 12 include thiuram-based, thiazole-based, guanidine-based, sulfenamide-based, dithiocarbamate-based, and thiourea-based vulcanization accelerators.

[0032] [Other additives] Furthermore, the rubber composition used to form the conductive layer 12 may contain other ingredients such as silica and calcium carbonate within the range that does not impair the functions of the essential components contained in the rubber composition.

[0033] [Method of manufacturing electroconductive members for electrophotography] An example of a method for producing a conductive member according to this embodiment is described below. In this example, the production method is characterized by including the following steps (A) to (C), but is not particularly limited as long as the configuration of this embodiment can be achieved. (A) preparing an electronic conductive master batch (CMB) for domain formation, comprising carbon black and rubber; (B) preparing a matrix-forming rubber composition (MRC); (C) A step of kneading CMB and MRC to prepare a rubber composition having a matrix-domain structure.

[0034] First, the second rubber to be the domain, the electronic conductive agent, and additives as necessary are kneaded using an internal kneader such as a Banbury mixer or a kneader. Then, the obtained mixture is further kneaded with the first rubber, and vulcanization aids and additives as necessary using an internal kneader such as a Banbury mixer or a kneader. Furthermore, sulfur, vulcanization accelerators, foaming agents, etc. are added and kneaded as necessary using an open roll. Then, the kneaded mixture is formed into a ribbon shape using a ribbon forming and dispensing machine.

[0035] Next, a rubber tube that will become the conductive layer is formed in a rubber tube forming device that is composed of an extruder 21, a microwave vulcanizer 22, a hot air vulcanizer 23, a take-up machine 24, and a cut-to-length machine 25 shown in FIG. First, the obtained ribbon-shaped molded product is fed into an extruder 21, and a rubber tube is extruded. Next, the obtained rubber tube is vulcanized and foamed as necessary. Vulcanization and foaming can be performed using known means such as a microwave vulcanizer, a hot air vulcanizer, an electric furnace, and a vulcanizing can. Among them, considering the production cost due to the heating efficiency of the rubber, it is more preferable to perform vulcanization and foaming using a microwave vulcanizer. When vulcanization and foaming are performed using a vulcanizer including a microwave vulcanizer 22, uniform heat conduction to the rubber tube is possible, so that a desired conductive layer according to the material characteristics is easily obtained. In addition, after vulcanization and foaming using the microwave vulcanizer 22, it is preferable to further vulcanize and foam using a hot air vulcanizer 23. The vulcanized and foamed rubber tube is transported from the microwave vulcanizer 22 and the hot air vulcanizer 23 by a take-off machine 24, and cut to a desired size by a cutter 25. The rubber tube may be subjected to a cooling process before or after cutting. The support is pressed into the hollow part of the rubber tube thus obtained. The method of fixing the rubber tube and the substrate can be appropriately selected from a method of applying a conductive adhesive onto the support, a method of pressing a substrate having an outer diameter larger than the inner diameter of the rubber tube, and the like. Furthermore, after pressing the substrate, both ends of the rubber tube may be cut to a desired length as necessary. Usually, the length of the support is set to be longer than the length of the rubber tube, and a part of the support 11 is exposed from both ends of the conductive layer 12 (rubber tube) as shown in FIG. 1. The rubber tube with the support pressed into it is polished by a polishing machine to produce a conductive member 10 for electrophotography having the conductive layer 12 on the support 11.

[0036] [Electrophotographic Image Forming Apparatus] The electrophotographic image forming apparatus according to one embodiment of the present disclosure includes an electrophotographic photoreceptor, a transfer member arranged in contact with the electrophotographic photoreceptor, a charging member arranged so as to be able to charge the electrophotographic photoreceptor, and a developing member arranged in contact with the electrophotographic photoreceptor. The electrophotographic conductive member according to one embodiment of the present disclosure can be used for members required to have an elastic conductive layer, such as a transfer member, a charging member, and a developing member. Here, an example of an electrophotographic image forming apparatus in which the above-mentioned electroconductive member for electrophotography is applied as a transfer member will be described in detail below.

[0037] FIG. 6 is a schematic diagram of an electrophotographic image forming apparatus according to one embodiment of the present disclosure. In Fig. 6, a cylindrical electrophotographic photoreceptor 61 is rotated clockwise around an axis 62 at a predetermined peripheral speed. The surface of the electrophotographic photoreceptor 61 being rotated is uniformly charged to a predetermined positive or negative potential by a charging member 63 such as a charging roller during the rotation process. Next, the charged surface of the electrophotographic photoreceptor 61 is subjected to exposure light 64 whose intensity is modulated in response to a time-series electric digital image signal of target image information output from an exposure means (not shown) such as slit exposure or laser beam scanning exposure. In this way, electrostatic latent images corresponding to the target images are formed sequentially on the surface of the electrophotographic photoreceptor 61. The electrostatic latent image formed on the surface of the electrophotographic photoreceptor 61 is developed into a toner image by normal development or reversal development with the toner contained in the developer of the developing member 65. Next, the toner images formed and carried on the surface of the electrophotographic photoreceptor 61 are sequentially transferred to a transfer material P such as paper by a transfer bias from a transfer member 66, which is a transfer member having the above-mentioned conductive member. The transfer material P is taken out from a transfer material supply member (not shown) in synchronization with the rotation of the electrophotographic photoreceptor 61 and fed between the electrophotographic photoreceptor 61 and the transfer member 66 (contact portion). A bias voltage of a polarity opposite to the charge held by the toner is applied to the transfer member 66 from a bias power source (not shown). The transfer material P to which the toner image has been transferred is separated from the surface of the electrophotographic photosensitive member 61 and transported to the fixing member 68, where the toner image is fixed, and then transported outside the device as an image-formed product (print, copy).

[0038] After the toner image is transferred, the surface of the electrophotographic photoreceptor 61 is cleaned by removing the residual developer (residual toner) by a cleaning member 67 such as a cleaning blade. It is also possible to apply a cleanerless system in which the residual toner is directly removed by a developing device or the like. Next, the charge is removed by pre-exposure light (not shown) from a pre-exposure means (not shown), and then the charge is repeatedly used for image formation. Note that, as shown in FIG. 6, when the charging member 63 is a contact charging member using a charging roller or the like, pre-exposure is not necessarily required. Among the components such as the electrophotographic photoreceptor 61, the charging member 63, the developing member 65, and the cleaning member 67, a plurality of components including at least the electrophotographic photoreceptor 61 may be selected, housed in a container, and integrally supported as a process cartridge. Then, this process cartridge may be configured to be detachably attached to the main body of an electrophotographic image forming apparatus such as a copying machine or a laser beam printer. In FIG. 6, the electrophotographic photoreceptor 6, the charging member 63, the developing member 65, and the cleaning member 67 are integrally supported to form a cartridge. A guide member 610 such as a rail of the main body of the electrophotographic image forming apparatus 60 is used to form a process cartridge 69 that is detachably attached to the main body of the electrophotographic image forming apparatus. In the case of a process cartridge, the conductive member according to this embodiment can be applied to the charging member and the developing member. Note that the electrophotographic image forming apparatus shown in FIG. 6 has a cleaning member 67 and a fixing member 68, but these are not necessarily provided.

[0039] For example, when the electrophotographic image forming apparatus 60 is a copier or a printer, the exposure light 64 is reflected light or transmitted light from an original document, or the exposure light 64 is light irradiated by scanning a laser beam, driving an LED array, driving a liquid crystal shutter array, or the like, in accordance with a signal obtained by reading the original document with a sensor and converting the signal into a signal. When the conductive member according to the present embodiment is used as a transfer member (transfer roller), scattering of toner on an image due to abnormal discharge can be suppressed. Also, when the conductive member according to the present embodiment is used as a charging member (charging roller), fogging of an image due to abnormal discharge can be suppressed. EXAMPLES

[0040] Next, the present disclosure will be described in more detail by taking a transfer member as an example of a conductive member for electrophotography, but the present disclosure is not limited thereto. First, the materials shown in Table 1 were prepared as the first rubber, the second rubber, and the electronic conductive agent.

[0041] [Table 1]

[0042] In addition, the materials shown in Table 2 were prepared as a vulcanization aid, a filler, a vulcanizing agent, a foaming agent, and a vulcanization accelerator.

[0043] [Table 2]

[0044] <Example I-1> 1. Preparation of Rubber Composition [1-1. Preparation of domain-forming electronic conductive agent masterbatch (CMB) 1] The materials in the following material formulation (1) were mixed. (Material recipe (1)) Second rubber (R2-1) 30 parts by mass Electronic conductive agent (C-1) 25 parts by weight ·Vulcanization aid No.1 1.5 parts by mass

[0045] The resulting mixture was placed in a 7 L internal kneader (device name: WDS7-30, manufactured by Nihon Spindle Mfg. Co., Ltd.) and kneaded for 16 minutes at a rotor speed of 30 rpm to obtain CMB1.

[0046] [1-2. Preparation of matrix-forming rubber composition (MRC) 1] Similarly, the materials of the following material formulation (2) were mixed. (Material recipe (2)) First rubber (R1-1) 70 parts by mass ·Vulcanization aid No.1 3.5 parts by mass The resulting mixture was placed in a 7 L internal kneader (device name: WDS7-30, manufactured by Nihon Spindle Mfg. Co., Ltd.) and kneaded for 16 minutes at a rotor speed of 30 rpm to obtain MRC1.

[0047] The materials in the following material formulation (3) were mixed. (Material recipe (3)) ·CMB1 56.5 parts by mass ·MRC1 73.5 parts by mass Foaming agent No. 1 2.5 parts by weight Vulcanization accelerator No. 1 1.5 parts by weight Vulcanization accelerator No. 2 2.0 parts by weight Vulcanizing agent No. 1 3.0 parts by weight

[0048] The obtained mixture was placed in an open roll (device name: 12-inch open roll, manufactured by Kansai Roll Co., Ltd.) and kneaded and dispersed for 15 minutes while cooling so as to maintain the temperature of the mixture at 80° C. or less. Finally, the mixture was shaped into a ribbon to prepare a rubber composition for the conductive layer.

[0049] 2. Preparation of conductive members A rubber tube for the conductive layer was produced using the manufacturing apparatus shown in FIG. 2. First, the rubber composition for the conductive layer prepared above was fed to a vented rubber extruder 21 (apparatus name: 60 mm uniaxial vented rubber extruder, manufactured by Mitsuba Manufacturing Co., Ltd.) and extruded into a tube. Next, the tubular extrudate was vulcanized and foamed by a vulcanizing apparatus (apparatus name: 3.0 kJ / s (3.0 kW) microwave continuous rubber vulcanization line, manufactured by Micro Electronics Co., Ltd.) including a microwave vulcanizing apparatus 22 to produce a rubber tube. The microwave vulcanizing apparatus was set to a frequency of 2450±50 MHz, an output of 1.0 kJ / s (1.0 kW), and a furnace temperature of 200° C. After vulcanization and foaming in the microwave vulcanizing apparatus, further vulcanization and foaming were performed in a hot air vulcanizing apparatus 23 with a furnace temperature set to 200° C. The outer diameter of the tube after vulcanization and foaming was 15.0 mm, and the inner diameter was 4.0 mm. The rubber tube was transported at a speed of 2.0 m / min through the microwave vulcanizer and the hot air vulcanizer by a take-off machine 24. After vulcanization and foaming, the surface temperature of the rubber tube was cooled to 100° C. or less by cold air, and then the rubber tube was cut to a length of 230 mm by a cutter 25. Next, a stainless steel support having an outer diameter of 5 mm and a length of 240 mm was pressed into the hollow part of the rubber tube, and then both ends of the rubber tube were cut to obtain a roller having a rubber length of 216 mm. The outer peripheral surface of the roller was polished with a polishing wheel rotation speed of 1800 rpm and a feed rate of 800 mm / min so that the outer diameter became 12.5 mm, thereby producing a conductive member I-1 having a conductive layer on the outer periphery of the support.

[0050] 3. Characterization <3-1. Measurement of matrix volume resistivity> First, a slice having a thickness of about 2 μm was cut from the conductive layer of the conductive member I-1 using a microtome (trade name: Leica EM FCS, manufactured by Leica Microsystems) at a cutting temperature of −100° C. The slices were cut from a total of three cross sections perpendicular to the longitudinal direction at the center of the conductive layer in the longitudinal direction and at a position of L / 4 from both ends of the conductive layer toward the center, where the length of the longitudinal direction of the conductive layer of the conductive member I-1 is L, and included a sample including the entire thickness of the conductive layer. Platinum was vapor-deposited on the surface of the obtained sample corresponding to the cross section of the conductive layer. Next, the platinum-deposited surface was photographed at a magnification of 5,000 times using a scanning electron microscope (SEM) (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image. From this SEM image, it was confirmed that the conductive layer formed a matrix-domain structure and that carbon black was present in the domain. For the conductive members according to the other examples, the presence of the matrix-domain structure and the presence of carbon black in the domain were confirmed in the same manner as above. The volume resistivity of the matrix was measured in contact mode using a scanning probe microscope (SPM) (product name: Q-Scope250, manufactured by Quesant Instrument Corporation) as follows. The measurement environment was a temperature of 23°C and a relative humidity of 50%. First, a sample was cut out from the conductive layer in the same manner as above. Next, the sample was placed on a metal plate so that one surface of the sample corresponding to the cross section of the conductive layer was in contact with the surface of the metal plate. Then, the cantilever of the SPM was brought into contact with the portion of the surface of the sample opposite to the surface in contact with the surface of the metal plate that corresponds to the matrix. Next, a voltage of 50 V was applied to the cantilever, and the current value was measured. The surface shape of the measurement piece was observed with an SPM, and the thickness of the measurement point was calculated from the obtained height profile. The volume resistivity was calculated from the thickness and the current value, and was taken as the volume resistivity of the matrix. The measurement positions were three arbitrary positions in the matrix portion of each slice from the outer surface to a depth of 0.1T to 0.9T, totaling nine positions, where T is the thickness of the conductive layer. The average value was regarded as the volume resistivity of the matrix.

[0051] <3-2. Measurement of domain volume resistivity> The volume resistivity of the domain was measured in the same manner as in measuring the volume resistivity of the matrix, except that the cantilever of the SPM was brought into contact with the location corresponding to the domain and the current value was measured.

[0052] <3-3. Measurement of volume resistivity of conductive layer> A sample was cut out from the conductive layer of the conductive member I-1 in the same manner as above. The volume resistivity of the sample was measured using a measuring tool (device name: MPC probe UR-SS: manufactured by Mitsubishi Chemical Analytech Co., Ltd.) and a high resistance measuring device (device name: R8340A digital high resistance / micro current meter: manufactured by Advantest Corporation) in accordance with Japan Industrial Standards (JIS) K 6911 (1995). Specifically, the volume resistivity was calculated from the current value when a voltage adjusted so that the electric field (applied voltage / measurement sample) was 1000V / cm was applied to the sample for 30 seconds.

[0053] <3-4. Measurement of maximum Feret diameter, area, perimeter, envelope perimeter, and number of domains> The maximum Feret diameter, area, perimeter, envelope perimeter, and number of domains of the cross section of the domain according to the present disclosure were measured as follows. First, a sample was cut out from the conductive layer of the conductive member 1 in the same manner as described above. The samples were cut out from a total of three cross sections perpendicular to the longitudinal direction at the center of the longitudinal direction of the conductive layer and at a position of L / 4 from both ends of the conductive layer toward the center, where L is the longitudinal length of the conductive layer of the conductive member I-1. Platinum was vapor-deposited on a surface corresponding to a cross section in the thickness direction of the conductive layer of the obtained sample. Next, the platinum-deposited surface of the sample was photographed at 5,000 times magnification using a scanning electron microscope (SEM) (product name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image. Next, this SEM image was converted to 8-bit grayscale using image processing software "Image-pro plus" (product name, manufactured by Media Cybernetics Co., Ltd.) to obtain a monochrome image with 256 gradations. Next, the black and white of the image was inverted so that the domains in the monochrome image became white, and a binarization threshold was set for the brightness distribution of the image based on the algorithm of Otsu's discriminant analysis method to obtain a binarized image. Next, for the obtained binarized image, when the thickness of the conductive layer is T, square observation areas with sides of 15 μm were placed at three arbitrary locations in the thickness region from the outer surface of each of the three slices to a depth of 0.1T to 0.9T, and the maximum Feret's diameter, area, perimeter, and envelope perimeter were calculated for each of the domains present in each observation area using the count function of the image processing software.

[0054] The maximum Feret diameter, area, perimeter, and envelope perimeter measured for each domain observed in each observation area were calculated as 4×S / (π×D f 2 ) and the value of A / B were calculated. Then, the number of domains (percentage of the number) that satisfied the above requirement (2) (formula (2)) among all the observed domains was calculated. In addition, the average number of domains in each observation area was calculated.

[0055] <3-5. Ratio of the cross-sectional area of ​​the carbon black contained in the domain to the cross-sectional area of ​​the domain> The platinum-deposited surface of the sample prepared in 3-4. above was photographed at a magnification of 20,000 times at a location corresponding to the observation area with a side length of 15 μm placed on the binary image in the evaluation in 3-4. above using a scanning electron microscope (SEM) (product name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image. The SEM image was converted to 8-bit grayscale using an image analyzer (product name: LUZEX-AP, manufactured by Nireco Corporation) to obtain a monochrome image with 256 gradations. Next, the black and white of the image were inverted so that the domains in the fracture surface became white, and a binarization threshold was set for the brightness distribution of the image based on the algorithm of Otsu's discriminant analysis method to obtain a binary image. Next, an observation area large enough to accommodate at least one domain was extracted from the above binary image, and the cross-sectional area of ​​the domain and the cross-sectional area of ​​the carbon black in the domain were calculated. From these results, the ratio (number %) of the number of domains satisfying requirement (1) to the number of all domains observed was calculated. In addition, based on the results of 3-4 above, the ratio (number %) of the number of domains satisfying requirements (1) and (2) was calculated. Furthermore, the arithmetic mean value of the maximum Feret's diameter was calculated for the domains satisfying requirements (1) and (2).

[0056] 4. Change in electrical resistance before and after voltage application The prepared conductive member I-1 was left in a low-temperature, low-humidity environment at a temperature of 15°C and a relative humidity of 10% for 48 hours or more. In the same environment, it was pressed onto a stainless steel drum with an outer diameter of 30 mm, and a load of 500 g was applied to both ends of the support of the conductive member I-1. In this state, the stainless steel drum was rotated at a speed of 30 rpm / min, and the conductive member I-1 was rotated by the rotation, while a voltage of 1000 V was applied between the support and the stainless steel drum, and the current value flowing at that time was measured. From the current value, the electrical resistance value (LogR conversion value, the same applies below) was calculated according to Ohm's law, and the electrical resistance value 1 of the conductive member I-1 was determined. Thereafter, the conductive member I-1 was pressure-bonded to a stainless steel drum having an outer diameter of 30 mm in a low-temperature, low-humidity environment, and a load of 500 g was applied to each end of the support of the conductive member I-1. In this state, the stainless steel drum was rotated at a speed of 10 rpm / min to rotate the conductive member I-1, while a current of 20 μA was passed between the support and the stainless steel drum for 30 hours. After energization, the current value of the conductive member I-1 was measured in the same manner as for the electrical resistance value 1, and the electrical resistance value was calculated, which was defined as the electrical resistance value 2 of the conductive member I-1. In addition, after measuring the electrical resistance value 2, the conductive member I-1 was left in a high-temperature and high-humidity environment at a temperature of 30° C. and a relative humidity of 80% for 48 hours or more. Thereafter, the current value of the conductive member I-1 was measured in the same manner, and the electrical resistance value was calculated, which was defined as the electrical resistance value 3 of the conductive member I-1. The change in the electrical resistance value of the conductive member I-1 after energization for 30 hours and before energization (electrical resistance value 2-electrical resistance value 1) and the change in the electrical resistance value due to the environmental difference after energization for 30 hours (electrical resistance value 2-electrical resistance value 3) were obtained and evaluated according to the following criteria.

[0057] Rank A: The change in electrical resistance is less than LogR1.3 in both cases. Rank B: The larger change in electrical resistance is LogR1.3 or more and less than LogR1.5 Rank C: The larger change in electrical resistance is LogR1.5 or more and less than LogR1.7 Rank D: The larger change in electrical resistance is LogR1.7 or more.

[0058] 5. Image Evaluation [5-1] Splash evaluation The electrophotographic image formed using the conductive member I-1 as a transfer roller was evaluated for toner scattering as follows. First, a laser printer (product name: Laserjet M608dn, manufactured by Hewlett-Packard Company) was prepared as an electrophotographic image forming apparatus. This electrophotographic image forming apparatus was modified so that a voltage could be applied to the transfer member from an external power source (product name: Model 615, manufactured by Trek Japan Co., Ltd.). Next, the laser printer with the conductive member I-1 attached as a transfer roller was left in an environment of 15°C temperature and 10% relative humidity for 48 hours. Subsequently, in the same environment, a transfer voltage was applied from an external power source to the conductive member I-1, and a horizontal line image of 2 dots and 98 spaces was output. The transfer voltage value was set as follows. That is, the lower of the electric resistance value (electric resistance value 1) in a low temperature and low humidity environment before energization and the electric resistance value (electric resistance value 3) in a high temperature and high humidity environment after energization for 30 hours, both measured in 4 above, and the electric resistance value of paper as the transfer material was calculated as 1×10 8 The voltage value that gave a transfer current value of 10 μA was determined as the transfer voltage value. When a sufficient amount of charge is supplied from the transfer roller to the back surface of the paper (the surface opposite to the toner image carrying surface of the paper), the developer transferred to the toner image carrying surface of the paper is held by the charge. On the other hand, when the charge supplied from the transfer roller to the back surface of the paper is insufficient, the developer transferred to the toner image carrying surface of the paper scatters due to the repulsion of the charges between the developer particles. The degree of scattering was evaluated by the following method.

[0059] (Measurement of the amount of scattering) A horizontal line image of 2 dots and 98 spaces (a horizontal line image in which horizontal lines of 2 dots wide extending in a direction perpendicular to the rotation direction of an electrophotographic photoreceptor are drawn at intervals of 98 dots in the rotation direction) was printed, and 9 arbitrary points 100 μm away from the horizontal lines on the paper after image formation were observed at 500x magnification using an optical microscope, and the developer present in an observation area of ​​400 μm square was counted, and the number of developer particles was taken as the amount of scattering, which was evaluated according to the following criteria. If the amount of scattering was 60 or less, a good image with little scattering was obtained. Grade A: 60 or less scattered particles; Rank B: 61 or more particles scattered.

[0060] <Examples I-2 to I-11> Conductive members I-2 to I-11 were produced in the same manner as in Example I-1 except that the material formulation was changed as shown in Tables 3 and 4, and were evaluated in the same manner as in Example I-1.

[0061] <Example II-1> A rubber composition for a conductive layer was prepared in the same manner as in Example I-1, except that the foaming agent in the material formulation (3) of the rubber composition was not added. Next, a round bar with a total length of 252 mm and an outer diameter of 6 mm was prepared, the surface of which was made of free-cutting steel and electroless nickel plating was applied. Using a roll coater, an adhesive (product name: Metalock U-20, manufactured by Toyo Kagaku Kenkyusho) was applied over the entire circumference of the round bar, a range of 230 mm, excluding 11 mm at each end. In this example, the round bar coated with the adhesive was used as a conductive support. Next, a die with an inner diameter of 12.5 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 temperature of the extruder and the crosshead was adjusted to 100° C., and the conveying speed of the conductive support was adjusted to 60 mm / sec. Under these conditions, the rubber composition for the conductive layer was fed from the extruder, and the outer periphery of the conductive support was coated with the rubber composition for the conductive layer in the crosshead, to obtain 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, obtaining a 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 to make the length of the conductive layer in the longitudinal direction 231 mm. Finally, the surface of the conductive layer was polished with a rotary grindstone. As a result, a conductive member II-1 was obtained in which the diameter at each position 90 mm from the center to both ends was 8.44 mm, and the central diameter was 8.5 mm. The obtained conductive member II-1 was subjected to the evaluation of the change in electrical resistance before and after the above-mentioned voltage application, and the evaluation of scattering. Regarding the evaluation of scattering, the conductive member II-1 was adjusted in the spring length and the support receiving member because the outer diameter of the support and the outer diameter of the roller are different from those of the conductive member I-1 in Example I-1.

[0062] [5-2] Fog evaluation In order to confirm the degree of discharge unevenness when the conductive member II-1 was used as a charging member, the following fogging evaluation was carried out. First, a laser printer (product name: Laserjet M608dn, manufactured by HP) was prepared as an electrophotographic image forming apparatus. This electrophotographic image forming apparatus was modified so that a voltage could be applied to the charging member and the developing member from an external power source (product name: Model 615, manufactured by Trek Japan). Next, the conductive member II-1, the modified electrophotographic image forming apparatus, and the process cartridge were left in an environment of a temperature of 30° C. and a relative humidity of 80% for 48 hours. Next, the process cartridge in which the conductive member II-1 was mounted as a charging roller was loaded into the electrophotographic image forming apparatus. Then, a DC voltage of −1700 V was applied from an external power source to the conductive support of the conductive member II-1, and a DC voltage of V was applied to the developing member. back A voltage was applied from an external power source so that the voltage obtained by subtracting the voltage applied to the developing member from the surface potential of the photoreceptor was −300 V, and a solid white image was output. The developer in this electrophotographic image forming apparatus is negatively charged, so that normally when a solid white image is output, the developer does not transfer onto the photoconductor or paper. However, when a positively charged developer is present, a phenomenon known as inversion fogging occurs, in which the positively charged developer transfers to an overcharged portion of the photoconductor surface caused by a strong localized discharge from the charging member. As a result, toner that should not be present on the solid white image is present, resulting in the so-called "fogging." This phenomenon can be prevented by applying a voltage of -300V, such as V back This is significantly more likely to occur when is large. Using the electrophotographic image forming apparatus thus set, a white solid image was output in an environment of a temperature of 30° C. and a relative humidity of 80%, and the amount of fog was measured. The amount of fog was measured by the following method.

[0063] (Measurement of fog on paper) Nine random points on a solid white image were observed at 500x magnification using an optical microscope, and the number of black dots caused by toner particles present in a 400 μm square observation area was counted. The number was taken as the amount of fogging on the paper and evaluated according to the following criteria. Rank A: 60 or less spots on paper Rank B: 61 or more spots on paper

[0064] <Examples II-2 to II-4> Except for changing the material formulation as shown in Table 5, conductive members II-2 to II-4 were produced in the same manner as in Example II-1, and were subjected to the same evaluation as for conductive member II-1 of Example II-1.

[0065] <Comparative Example 1> A comparative rubber composition C1 according to Patent Document 1 was prepared as follows. 100 parts of an ethylene-propylene-diene terpolymer (product name: EPT4045, manufactured by Mitsui Chemicals) as a domain material, 10 parts of carbon black (product name: Ketjen Black EC600JD, manufactured by Ketjen Black International) as conductive particles, 30 parts of paraffin oil (product name: PW-380, manufactured by Idemitsu Kosan) as a softener, and 1 part of stearic acid as a processing aid were kneaded in a pressure kneader to obtain masterbatch C1. Next, 75 parts of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (product name: Epichromer CG, manufactured by Osaka Soda Co., Ltd.) as a matrix material, 1 part of stearic acid as a processing aid, 35.25 parts of masterbatch C1, 2.5 parts of 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne (product name: Perhexa 25B-40, manufactured by Nippon Oil & Fats Co., Ltd.) as a vulcanizing agent, and 1.5 parts of triallyl isocyanurate (product name: TAIC-M60, manufactured by Nippon Kasei Co., Ltd.) as a crosslinking aid were mixed using an open roll to obtain a comparative rubber composition C1. Using the comparative rubber composition C1, the conductive member C-1 was obtained by the same manufacturing method as in Example II-1. The obtained conductive member C-1 was subjected to the same evaluation as that of the conductive member II-1 according to Example II-1.

[0066] <Comparative Example 2> A conductive member C2 was obtained in the same manner as in Example I-1, except that the electronic conductive agent (C-1) was not added. The obtained conductive member C2 was subjected to the same evaluation as the conductive member I-1 according to Example I-1.

[0067] The evaluation results of Examples I-1 to I-11, Examples II-1 to II-4, and Comparative Examples 1 and 2 are shown in Tables 6 to 9. From the results of the Examples, it was confirmed that the conductive member according to one embodiment of the present disclosure is a conductive member for electrophotography that can suppress high resistance caused by deterioration of carbon black. It was also confirmed that the conductive member according to one embodiment of the present disclosure can be used as a charging member that can suppress fogging even when the charging bias is increased. Since Comparative Example 1 does not have an ionically conductive polymer in the domain, it becomes highly resistant by applying a high voltage for a long time. Since Comparative Example 2 does not have an electronic conductive agent and has only conductivity due to the ionically conductive rubber, the resistance fluctuation due to the environment is large, and the resistance fluctuation becomes even larger by applying a current for a long time.

[0068] [Table 3]

[0069] [Table 4]

[0070] [Table 5]

[0071] [Table 6]

[0072] [Table 7]

[0073] [Table 8]

[0074] [Table 9] [Explanation of symbols]

[0075] 10 Conductive materials 11 Support 12 Conductive layer 31 Matrix 32 Domain 33 Electronic Conductive Agents 21 Extruder 22 Microwave vulcanizing equipment 23 Hot air vulcanizing equipment 24 Collection machine 25 Standard length cutting machine 41 Domain cross section 51 Domain cross section 52 Perimeter 61 Electrophotographic photoreceptor 62 Axis 63 Electrostatic materials 64 Exposure light 65 Developing materials 66 Transfer material 67 Cleaning materials 68 Fixing member 69 Process Cartridge 610 Guide member 71 Conductive layer 72 YZ plane 72a cross section 72b cross section 73c cross section Maximum Feret diameter of the cross section of the D1 domain L is the longitudinal length of the conductive layer of the conductive member P Transferred material

Claims

1. A conductive member for electrophotography having a support having a conductive outer surface and a conductive layer provided on the outer surface of the support, The conductive layer is A matrix including a crosslinked product of a first rubber, and having a plurality of domains dispersed in the matrix; The domain includes a crosslinked product of a second rubber different from the first rubber and an electronic conductive agent, The crosslinked product of the second rubber has a structural unit represented by the following structural formula (I) in the molecule: [-(CH2)n-O-] Structural formula (I) (In structural formula (I), n represents an integer of 1 to 3.) A conductive member in which, when the length in the longitudinal direction of the conductive layer is L and the thickness of the conductive layer is T, observation regions of 15 μm square are placed at any three locations in a thickness region from an outer surface of the conductive layer to a depth of 0.1T to 0.9T for each of a cross section of the conductive layer in the thickness direction at three locations, namely, the center in the longitudinal direction of the conductive layer and at L / 4 from both ends of the conductive layer toward the center, 80% or more by number of the domains observed in each of all nine observation regions satisfy the following requirement (1) and requirement (2): Requirement (1) The ratio of the cross-sectional area of ​​the carbon black contained in the domain to the cross-sectional area of ​​the domain is 20% or more; Requirement (2): When the perimeter of the domain is A and the envelope perimeter of the domain is B, A / B is 1.00 or more and 1.10 or less.

2. 2. The conductive member according to claim 1, wherein the volume resistivity ρd of the domain and the volume resistivity ρ of the conductive layer are in the following ranges: 1.0×10 １ Ω・cm ≦ ρδ ≦ 1.0×10 ４ Ohm・cm 1.0×10 ５ Ω・cm ≦ p ≦ 1.0×10 ８ Ohm・cm.

3. The volume resistivity ρm of the matrix is ​​1.0×10 ８ Ω・cm or more, 1.0×10 １７ The conductive member according to claim 1 or 2, having a resistivity of Ω·cm or less.

4. The conductive member according to any one of claims 1 to 3, wherein the cross-linked product of the second rubber further has a structural unit derived from allyl glycidyl ether.

5. The conductive member according to any one of claims 1 to 4, wherein the cross-linked product of the second rubber is a cross-linked product of an epichlorohydrin-alkylene oxide-allyl glycidyl ether terpolymer.

6. 6. The conductive member according to claim 1, wherein the structural unit represented by the structural formula (I) has at least one of an ethylene oxide structural unit and a propylene oxide structural unit.

7. The conductive member according to any one of claims 1 to 6, wherein the electronic conductive agent is carbon black.

8. The DBP absorption of the carbon black is 40 cm ３ / 100g or more, 200cm ３ The conductive member according to claim 7, wherein the surface roughness is 100 g or less.

9. The conductive member according to claim 8, wherein the average of the maximum Feret diameters Df of the domains contained in each of the domains satisfying the requirements (1) and (2) is in the range of 0.1 μm or more and 5.0 μm or less.

10. 10. The conductive member according to claim 8, wherein an average number of the domains present in the observation region is 20 to 300.

11. The conductive member according to any one of claims 7 to 10, wherein a ratio of a cross-sectional area of ​​the carbon black to a cross-sectional area of ​​the domain is 30% or less.

12. The conductive member according to any one of claims 1 to 11, wherein the first rubber is an acrylonitrile-butadiene rubber.

13. The conductive member according to claim 12 , wherein the content of acrylonitrile in the cross-linked product of the first rubber is 15% by mass or more and 25% by mass or less.

14. The conductive member according to any one of claims 1 to 13, wherein the conductive member has a roller shape.

15. The conductive member according to any one of claims 1 to 14, which is a transfer member.

16. An electrophotographic image forming apparatus comprising the conductive member according to claim 1.

17. 17. An electrophotographic image forming apparatus according to claim 16, wherein the conductive member is provided as a transfer member.

18. 15. A process cartridge for electrophotography, which is configured to be detachably mountable to a main body of an electrophotographic image forming apparatus, comprising the conductive member according to claim 1.

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