Electrophotographic member, process cartridge, and electrophotographic image forming apparatus

Abstract

To provide an electrophotographic member that can prevent the generation of black dots in addition to prevention of white dots, even when it is applied to an extended electrophotographic image forming process on the body.SOLUTION: An electrophotographic member has a substrate having a conductive outer surface and a conductive layer on the outer surface of the substrate. The conductive layer has a matrix including first rubber and a plurality of domains dispersed in the matrix. A sample obtained from the conductive layer includes a specific number of domains with a specific volume resistivity. The domains include second rubber and an electronic conductive agent, and include a domain A having the volume gravity center in the domain. When an area from an outer edge of the domain up to a distance 10 nm toward the volume gravity center is defined as an outer peripheral area, and an area from the volume gravity center up to a distance 10 nm toward the outer edge of the domain is defined as an inner area, the outer peripheral area and the inner area do not overlap each other, and the modulus of elasticity of the outer peripheral area is higher than the modulus of elasticity of the inner area at a specific ratio.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 an electrophotographic photosensitive member to charge the surface of the electrophotographic photosensitive member, and it is necessary to achieve uniform charging of the electrophotographic photosensitive member. In recent years, in order to accommodate cleaner-less systems that eliminate the need for a cleaning member on the photosensitive drum surface in order to reduce the size of electrophotographic image forming apparatuses, and systems in which a cleaning member is brought into contact with the surface with light pressure, electrophotographic members that have a longer life than conventional ones are required.

[0004] Specifically, there is a demand for electrophotographic members that do not change in physical properties even when contaminants adhere to them, and that can maintain image quality for a long period of time. Patent Document 1 discloses a charging member in which the conductive layer is a rubber composition having a matrix-domain structure including a matrix containing a crosslinked product of a first rubber and a plurality of domains dispersed in the matrix, and the impedance of the conductive layer is 1.0×10 3 Ω or more 1.0×10 8 Ω or less, and the domain shape is close to a perfect circle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-067924 Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors conducted an evaluation in a process that has recently been designed to extend the service life, particularly in a cleaner process that severely contaminates charging members. The inventors confirmed that the excellent discharge characteristics of the matrix-domain structure of Patent Document 1 suppressed the occurrence of white spots, but recognized that there were still issues to be resolved from the perspective of extending the service life, and that there was room for improvement. Specifically, after the transfer process, toner remaining on the photosensitive member without being transferred to the intermediate transfer member or paper may reach the surface of the charging member, and as the charging member rotates over a long period of time, the surface may be repeatedly distorted, causing it to become highly resistant, resulting in black spots.

[0007] The present disclosure is directed to an electrophotographic member that can suppress the occurrence of black spots in addition to suppressing white spots even when applied to an electrophotographic image forming process of a main body with a long life. 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 substrate having an electrically conductive outer surface and an electrically conductive layer on the outer surface of the substrate, the conductive layer has a matrix containing a first rubber and a plurality of domains dispersed in the matrix; Among the cubic samples with a side length of 6 μm sampled from nine locations on the conductive layer, at least eight samples satisfy the following <Condition 1> and <Condition 2> in FIB-SEM measurement: <Condition 1> The ratio of the total volume of the plurality of domains to the volume of the sample is 10 to 40 volume %; <Condition 2> The number of the multiple domains in the sample is 10 to 2,400; The plurality of domains contained in each of the samples satisfying <Condition 1> and <Condition 2> includes at least one domain A, The domain A relates to an electrophotographic member that satisfies the following <Condition 3> to <Condition 6>: <Condition 3> The domain A contains a second rubber and an electronic conductive agent; <Condition 4> The center of gravity of the volume of the domain A exists within the domain; <Condition 5> In a cross section passing through the volume center of gravity of the domain A, when a region from the outer edge of the domain to a distance of 10 nm toward the volume center of gravity is defined as an outer circumferential region, and a region from the volume center of gravity to a distance of 10 nm toward the outer edge of the domain is defined as an inner region, the outer circumferential region and the inner region do not overlap; <Condition 6> When the elastic modulus measured in the outer peripheral region of the cross section in <Condition 5> is Eout and the elastic modulus measured in the inner region is Ein, Eout / Ein > 1.10. [Effects of the Invention]

[0009] According to at least one aspect of the present disclosure, there is provided an electrophotographic member that can suppress not only white spots but also black spots even when applied to an electrophotographic image forming process of a main body with a long life. 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 an external view of an electrophotographic roller. [Figure 2] FIG. 2 is a diagram showing a domain structure in a conductive layer. [Figure 3] FIG. 2 is a diagram showing domains in a conductive layer. [Figure 4] FIG. 10 is a diagram showing the state of a domain when compressed. [Figure 5]FIG. 10 is a diagram showing conditions for cutting out a sample for measuring physical properties. [Figure 6] FIG. 2 is a diagram illustrating a schematic configuration 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 relates to a cleanerless system and a system in which a cleaning member is brought into contact with a photosensitive drum with light pressure. In a system in which a large amount of contaminants reach a charging member, such as a system in which a large amount of contaminants reach a charging member, black spots are suppressed during long-term use. The present inventors speculate that the reason why black spots occur in the charging member according to Patent Document 1 is as follows.

[0014] The term "contaminant substances" refers to substances that, when toner and external additives are transferred to paper or an intermediate transfer body during the transfer process in an electrophotographic image forming process, are not transferred in their entirety and remain on the photosensitive drum surface, reaching and adhering to the charging member. The origin of the problem in this case is when these contaminant substances adhere and accumulate on the surface of the charging member over a long period of use of an electrophotographic image forming apparatus (hereinafter also referred to as "image forming apparatus").

[0015] Since black spots still appeared on the charging member after long-term use and after cleaning the contaminants, the inventors believe that the mechanism behind the occurrence of black spots is a change in the charging member caused by the contaminants described below. Generally, charging members are often designed with rubber elasticity to ensure proper contact with the drum. Therefore, the surface of the charging member with contaminants attached thereto will develop local depressions and distortion the moment it comes into contact with the drum. The distortion will then be relieved once the contact ends.

[0016] Furthermore, in order to ensure the conductivity of the charging member over a long period of time, it is common to add an electronic conductive agent such as carbon black, and use the electronic conductive agent as a conductive path to transport charges, thereby developing the conductivity. Therefore, when the contact with the drum at the area where the contaminants are attached causes repeated distortion and release, the connections between the electronic conductive agents in the charging member change, cutting the conductive path. This increases the resistance of the area, reducing the amount of discharge, which is thought to result in the black spots.

[0017] Even in a matrix-domain structure such as that described in Patent Document 1, in which an electronic conductive agent is filled and dispersed in spherical domains, it is possible to infer that the conductive paths of the carbon black present in the domains that exhibit conductivity change, resulting in high resistance. Based on the mechanism of black dot formation described above, the inventors have concluded that suppressing distortion of domains containing electronic conductive agents in a matrix-domain structure and suppressing fluctuations in the conductive paths is effective in suppressing black dots on images.

[0018] The inventors conducted a detailed analysis of the phenomenon in which a domain containing an electronic conductive agent in a matrix is ​​compressed under load, and found that the strain is greater in the central region of the domain than in the outer region of the domain. This means that the conductive paths inside the domain are more strongly affected by the compression phenomenon than the conductive paths outside the domain.

[0019] From these results of investigation, the inventors have investigated an electrophotographic member having a matrix-domain structure in which the domain has a core-shell structure and the shell portion contains a large amount of carbon black, which is an electron conductive agent. By distributing the electronic conductive agent, which contributes to conductivity, in the shell region, which is less distorted when the domain is compressed, conductivity is exerted only in the shell region, which is less affected by compression, and it is possible to suppress an increase in the resistance of the domain.

[0020] In addition, by distributing the electronic conductive agent in the shell region and minimizing the amount of electronic conductive agent in the core region, it was found that the elastic modulus of the core region can be significantly reduced compared to the shell region, and the strain in the core and shell regions can be concentrated more in the core region, further reducing the strain in the shell region. This tendency is more pronounced when the elastic modulus outside the domain is greater than that inside the domain. This is because when an object made of two materials with different elastic moduli undergoes compressive deformation, the flexible part deforms preferentially.

[0021] From the above, in order to suppress the occurrence of black spots caused by high resistance in the dirty areas, an electrophotographic member having a substrate with a conductive outer surface and a specific conductive layer on the outer surface can suppress black spots over a long period of time and provide high-quality images.

[0022] <Electrophotographic materials> The electrophotographic member has a substrate having a conductive outer surface and a conductive layer on the outer surface of the substrate. The electrophotographic member may be, for example, an electrophotographic roller. The electrophotographic member will be described below using an electrophotographic roller as an example. FIG. 1 is a schematic diagram showing the appearance of an electrophotographic roller. The electrophotographic roller has a conductive layer 2 on the outer periphery of a substrate 1 (mandrel 1). The conductive layer 2 is, for example, an elastic layer. Both ends of the substrate 1 may be exposed without being covered with the conductive layer 2. The electrophotographic roller may also be a charging roller. The charging roller is provided as a charging means for charging a photosensitive member in an image forming apparatus. Specifically, the charging roller contacts the photosensitive drum, moves relative to the photosensitive member of the photosensitive drum, and performs charging by friction at the contact point between the photosensitive drum and the charging roller.

[0023] <Substrate (conductive support)> The substrate 1 used in the electrophotographic roller is conductive and has the function of supporting a conductive layer or the like provided on its outer periphery. Examples of materials include metals such as iron, copper, stainless steel, aluminum, and nickel, and alloys thereof. Furthermore, the surface of these may be plated or otherwise treated to impart scratch resistance. Furthermore, a mandrel in which the surface of a resin base material is coated with a metal or the like to impart surface conductivity, or a mandrel manufactured from a conductive resin composition, can also be used as the substrate.

[0024] An adhesive layer (not shown) may be provided between the substrate 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.

[0025] 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.

[0026] The adhesive layer between the base 1 and the conductive layer 2 may be provided over the entire surface where the base 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 base 1 and the conductive layer 2 contact each other. The thickness of the adhesive layer is preferably 1 to 10 μm from the viewpoint of adhesion between the base and the conductive layer.

[0027] <Conductive layer> <Matrix-Domain Structure> The conductive layer has a matrix containing a first rubber and a plurality of domains dispersed in the matrix. That is, it has a matrix-domain structure. As described above, in the conductive layer, the domains may have, for example, a core-shell structure, and the shell may be filled with an electronic conductive agent (conductive particles) such as carbon black.

[0028] <Core-shell structure of domains> Furthermore, examples of core-shell structures within domains are shown in Figures 2A to 2F. 2A to 2F are cross-sectional views of the domain taken along a plane passing through the center of gravity of the volume. In Figures 2A to 2F, the amount of electronic conductive agent is indicated by the density of the shading, with the darker the shading, the more electronic conductive agent there is.

[0029] In Figure 2A, the outline is the boundary 4 between the matrix and shell. The domain has a boundary 3 between the core and shell. Figure 2A shows a domain structure in which the shell portion 14 contains a relatively larger amount of electronic conductive agent than the core portion 13, and during compression, the core portion 13 deforms preferentially, suppressing deformation of the shell portion 14. This prevents the domain from becoming highly resistive and suppresses black spots.

[0030] 2B shows a domain structure in which the core portion 13 contains a second rubber that does not contain an electronic conductive agent, and the shell portion 14 contains a second rubber that does contain an electronic conductive agent, and when compressed, the core portion 13 deforms more preferentially than in FIG. 2A, and deformation of the shell portion 14 can be suppressed. Therefore, the increase in resistance of the domain can be suppressed more than in the structure of FIG. 2A, and black spots can be suppressed.

[0031] 2C shows a domain structure in which the amount of electronic conductive agent gradually increases from the core portion 13 toward the outer edge of the domain, and since the elastic modulus of the shell portion 14 is higher than that of the core portion 13, the core portion 13 deforms preferentially during compression, suppressing deformation of the shell portion 14. This prevents the domain from becoming highly resistive, and suppresses black spots.

[0032] Figure 2D shows a domain in which conductive particles are contained in the core portion 13 other than near the center of gravity. Although the effect is smaller than that of Figure 2A, the elastic modulus of the shell portion 14 is higher than that of the core portion 13, so the core portion 13 deforms preferentially during compression, preventing the domain from becoming highly resistive and suppressing black spots.

[0033] In Figure 2E, the electronic conductive agent is unevenly distributed across the core portion 13 and the shell portion 14. Because the proportion of electronic conductive agent near the center of gravity is small, or because the shell portion 14 contains a higher proportion of electronic conductive agent than the core portion 13, the elastic modulus of the shell portion 14 is higher than that of the core portion 13. Therefore, the core portion 13 has a larger area that deforms preferentially, and compression of the shell portion 14 can be suppressed. This prevents high resistance and black spots.

[0034] FIG. 2F shows a domain structure in which the core portion 13 contains a third rubber that does not contain an electronic conductive agent, and the shell portion 14 contains a second rubber that contains an electronic conductive agent. By separating the rubbers in the core portion 13 and shell portion 14, the electronic conductive agent can be clearly separated. Furthermore, depending on the rubber used in the shell portion 14, the elastic modulus of the shell portion 14 can be further increased. Therefore, the core portion 13 can be preferentially deformed during compression, and deformation of the shell portion 14 can be significantly suppressed, which prevents the domain from becoming highly resistive and effectively suppresses black spots.

[0035] <Structure with minimal effect in suppressing black spots> Next, configurations that the inventors have investigated but which do not exhibit the effect of suppressing black dots are shown in FIGS. 3A to 3C. Figure 3A shows a cross section of an electrophotographic member. Figure 3A shows an electrophotographic member with a non-matrix-domain structure in which an electronic conductive agent is dispersed in a single type of rubber. Since there is no distortion suppression effect, the suppression effect of black spots is small.

[0036] Figure 3B is a cross-sectional view of a domain. Figure 3B shows a structure in which an electronic conductive agent is uniformly dispersed in the domain. The flexible matrix, which does not contain an electronic conductive agent, alleviates the distortion of the domain, which is more advantageous than Figure 3A in preventing the occurrence of black spots, but it is not sufficient.

[0037] FIG. 3C is a cross-sectional view of a domain, which has a hollow structure without a core. In FIG. 3C, the domain core does not contain rubber, and the shell contains rubber and an electronic conductive agent. This structure In the case of , distortion occurs at the core-side interface of the shell when the domain is compressed, so the effect of suppressing black spots is small.

[0038] From the above investigations, the present inventors have found that the following conditions are necessary for a conductive layer that can suppress black spots.

[0039] The conductive layer has a matrix containing a first rubber and a plurality of domains dispersed in the matrix, and at least eight of the 6 μm-side cubic samples taken from nine locations on the conductive layer satisfy the following <Condition 1> and <Condition 2> in FIB-SEM measurement. <Condition 1> The ratio of the total volume of the plurality of domains to the volume of the sample is 10 to 40% by volume; <Condition 2> The number of domains in the sample is 10 to 2,400

[0040] Furthermore, the multiple domains contained in each of the samples satisfying <Condition 1> and <Condition 2> include at least one domain A, and the domain A satisfies the following <Condition 3> to <Condition 6>. <Condition 3> The domain A contains a second rubber and an electronic conductive agent; <Condition 4> The center of gravity of the volume of the domain A exists within the domain; <Condition 5> In a cross section passing through the volume center of gravity of the domain A, when a region from the outer edge of the domain to a distance of 10 nm toward the volume center of gravity is defined as an outer circumferential region, and a region from the volume center of gravity to a distance of 10 nm toward the outer edge of the domain is defined as an inner region, the outer circumferential region and the inner region do not overlap; <Condition 6> When the elastic modulus measured in the outer peripheral region of the cross section in the above <Condition 5> is Eout and the elastic modulus measured in the inner region is Ein, Eout / Ein > 1.10

[0041] The above conditions are described in detail below. <Condition 1> and <Condition 2> The conductive layer is sampled from nine locations on the conductive layer, and at least eight of the 6 μm-side cubic samples satisfy <Condition 1> and <Condition 2>. That is, the ratio of the total volume of the domains to the volume of the sample (domain volume ratio) is 10 to 40 volume %. Furthermore, the number of the domains contained in the sample is 10 to 2400.

[0042] <Condition 1> and <Condition 2> are parameters that indicate the volume and number of domains present in the matrix of the electrophotographic member (hereinafter also referred to as the conductive roller).<Condition 1> and <Condition 2> are indicators of the volume occupied by the domains in the conductive layer, and therefore, the magnitude of compression applied to each domain can be controlled.

[0043] In this case, a domain included in a cubic sample refers to both a domain that includes the entire domain in the cubic sample and a domain that includes only a portion of the domain in the cubic sample. In <Condition 1> and <Condition 2>, the domain counted is a domain that includes the shell of a core-shell structure in the cubic sample. In other words, if even a portion of the shell is included, it is counted as a domain in <Condition 1> and <Condition 2>.

[0044] Regarding <Condition 1>, if the domain volume ratio in the cubic sample is 10% or more by volume relative to the total volume of the cubic sample, the diameter of the domain will exceed a certain size. Therefore, expansion and contraction during domain compression will be concentrated in the core of the domain, and the domain This can prevent the resistance in the domain from increasing. Also, from the viewpoint of making the domain size closer to a sphere and preventing the shell portion of the domain from being compressed, the volume fraction of the domain is set to 40% by volume or less. From the viewpoint of achieving both, the volume fraction of the domain is preferably 20 to 40% by volume, and more preferably 20 to 30% by volume. The arithmetic mean value of the domain volume fraction in the samples that satisfy <Condition 1> among the nine samples is, for example, 10 to 40% by volume, preferably 20 to 40% by volume, and more preferably 20 to 30% by volume.

[0045] Regarding <Condition 2>, by ensuring that the number of domains in a sample is 10 or more, the size of each domain increases, thereby suppressing the increase in shell resistance during domain compression. From the perspective of the size of each domain, the number of domains is 2,400 or less. The number of domains is preferably 100 to 1,100, more preferably 200 to 600, and even more preferably 200 to 500.

[0046] The number of domains per sample that satisfies <Condition 2> is, for example, 10 to 2400, preferably 100 to 1100, more preferably 200 to 600, and even more preferably 200 to 500.

[0047] <Method for controlling the volume and number of domains> The volume and number of domains can be controlled by controlling the domain diameter in the conductive layer. Specifically, the diameter of the domains dispersed in the matrix is ​​preferably 0.30 μm or more and 2.1 μm or less. Here, the domain size specifically refers to the maximum Feret diameter of the domains in the conductive layer.

[0048] When the domain diameter is 0.30 μm or more, the effect of concentrating strain in the core portion can be enhanced when the conductive roller contacts the drum and compressive force is applied to the domains in the conductive roller.On the other hand, when the domain diameter is 2.1 μm or less, the discharge characteristics of the matrix-domain structure can be easily maintained. The means for controlling the domain size will be described later in the description regarding the control of the domain matrix structure.

[0049] The domain volume fraction within the sample can be controlled by increasing or decreasing the amount of rubber used in the domains. The number of domains in a sample can be controlled by selecting a rubber with a large difference in viscosity and SP value between the rubber used in the matrix and the rubber used in the domains, or by the shear force when mixing the rubber. The larger the difference in viscosity and SP value between the rubber in the matrix and the domains, the more domains there can be, and the smaller the difference, the fewer domains there can be. Additionally, the number can be increased by increasing the shear force when mixing the rubber, and decreased by decreasing the shear force.

[0050] <Domain A count ratio> The multiple domains contained in each of the samples satisfying <Condition 1> and <Condition 2> include at least one domain A. The domain A is a domain that satisfies the following <Condition 3> to <Condition 6>.

[0051] Designing domain A within the following ranges provides a greater effect in suppressing high resistance. The proportion of domain A in the total number of domains may be, for example, 1% or more by number in order to suppress high resistance, and is preferably 30% or more by number, more preferably 50% or more by number, even more preferably 70% or more by number, and even more preferably 80% or more by number. There is no particular upper limit, and examples include 100% or less by number, 95% or less by number, and 90% or less by number. The proportion of domain A is preferably 30 to 100% by number, more preferably 50 to 95% by number, More preferably, it is 70 to 95% by number, and even more preferably, it is 80 to 90% by number.

[0052] In a preferred embodiment, the conductive layer that satisfies <Condition 1> and <Condition 2> further satisfies the following <Condition 7>. <Condition 7> The proportion of Domain A among the total number of multiple domains is 70% or more.

[0053] When increasing the proportion of domain A using two types of rubber, a vulcanizing agent is added to the second rubber to be used as the domain, and the two rubbers are mixed in a pressure kneader to harden the resulting second rubber. The second rubber and the first rubber containing an electronic conductive agent are then kneaded together. This makes it easier to distribute the electronic conductive agent in the peripheral regions of the domains, increasing domain A. When a third rubber is used, in addition to the above-mentioned methods, the electronic conductive agent can be mixed with the second rubber in a pressure kneader, turned into a masterbatch, and then mixed with the third rubber to increase the number of domains with a structure that will become domain A.

[0054] <Area ratio of core and shell in domain A> Domain A preferably has a core-shell structure having a core and a shell surrounding the core. Preferably, the outer region is at least a part of the shell, and the inner region is at least a part of the core. By satisfying the above, the region where strain occurs can be concentrated in the core, thereby further reducing strain on the shell.

[0055] Furthermore, the ratio of the core area to the area of ​​domain A observed in the cross section under <Condition 5> (core area / domain area × 100) is preferably 10 to 80 area%, more preferably 30 to 80 area%, even more preferably 50 to 80 area%, and even more preferably 50 to 70 area%. Within this range, the core portion deforms preferentially during domain deformation, thereby enhancing the effect of suppressing the domain from increasing in resistance. (Core area / Domain area x 100) can be controlled by increasing or decreasing the amount of rubber used in the core and the amount of rubber used in the shell.

[0056] Furthermore, for domain A, the ratio (A1 / A2×100) of the total area A1 of the electronic conductive agent observed in the cross section under <Condition 5> to the area A2 of the cross section is preferably 15.0 to 80.0 area%, more preferably 19.0 to 30.0 area%, and even more preferably 19.0 to 27.0 area%. By being in the above range, the excellent discharge characteristics of the matrix-domain structure can be maintained. (A1 / A2×100) can be controlled by increasing or decreasing the amount of electronic conductive agent blended into the domain.

[0057] From the viewpoint of stable discharge and suppression of high resistance, the ratio (A3 / A4 × 100) of the total area A3 of the electronic conductive agent in the peripheral region to the area A4 of the peripheral region, as observed in the cross section under <Condition 5>, for the domain A is preferably 20 to 50 area %, more preferably 30 to 50 area %, and even more preferably 40 to 50 area %. Within this range, high discharge characteristics are maintained while the amount of domain deformation is reduced by the improved elastic modulus of the peripheral region, further suppressing high resistance. (A3 / A4×100) can be controlled by increasing or decreasing the amount of electronic conductive agent mixed with the rubber used as the shell.

[0058] <Confirmation of matrix domain structure, and measurement method of domain volume ratio and domain number <Condition 1> and <Condition 2>> The volume of the domain can be determined by three-dimensionally measuring the matrix domain structure in the conductive layer and the core-shell structure in the domain using FIB-SEM. What is FIB-SEM? FIB (Focused Ion Beam) This technique involves processing a sample using a device and observing the exposed cross section with a scanning electron microscope (SEM). 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 to create a three-dimensional image of the sample structure.

[0059] Specifically, first, sampling of the conductive layer 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.

[0060] Then, three-dimensional measurements were performed using FIB-SEM to measure images of cubes with sides of 6 μm and 60 nm intervals. Here, measurements were taken of the conductive layer cross sections at each of the (1 / 4)L, (2 / 4)L, and (3 / 4)L cross sections every 120 degrees around the circumference of the roller, from the position of the core bar to the center of the surface.

[0061] 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 described later, osnium tetroxide was used for dyeing. Since the dyeing progresses more as the amount of double bonds and benzene rings in the rubber increases, the rubber type was identified and the domain and matrix were distinguished.

[0062] A conductive layer is judged to have a matrix domain structure when multiple domains are dispersed in a matrix and the matrix has a structure in which the matrix is ​​interconnected. If a matrix domain structure is observed in at least eight of the nine samples, the conductive layer is judged to have a matrix domain structure.

[0063] The obtained images are then analyzed using 3D visualization and analysis software Avizo (registered trademark, manufactured by FEI Inc.), which performs binarization of the domains and matrices and image analysis. Then, the total volume of domains contained in one sample of a cubic shape with one side measuring 6 μm is calculated, and the ratio of the total volume of the domains to the volume of the sample (volume ratio of the domains) is calculated. The number of domains in the sample is also calculated, and the number of samples that satisfy <Condition 1> and <Condition 2> is determined from the nine samples.

[0064] <Condition 3> The multiple domains contained in each of the samples that satisfy <Condition 1> and <Condition 2> include at least one domain A. The domain A includes a second rubber and an electronic conductive agent.

[0065] By distributing the electronic conductive agent unevenly in the shell portion where the strain in the domain is small, it is possible to suppress the increase in the resistance of the domain. Furthermore, it is possible to realize a configuration in which the reinforcing properties of the shell portion are increased and the difference in elastic modulus between the shell portion and the core portion is large. As a result, it is possible to further suppress the strain in the shell portion and to suppress the increase in the resistance due to repeated strain.

[0066] Furthermore, by using an electronic conductive agent such as carbon black, which exhibits conductivity through a conductive path, rather than a material such as an ionic conductive material, which exhibits conductivity through the movement of ions, it is possible to prevent the resistance from increasing over long-term use.

[0067] From the viewpoint of discharge characteristics, compared to a configuration in which the entire domain is filled with carbon black, assuming the same amount of mobile charge, the path through which the charge moves is narrowed, thereby improving the charge density. In other words, the conductive mechanism of only the shell portion enables the efficiency of the charge transport function. As a result, while demonstrating the effect of suppressing high resistance, the inventors believe that the presence of an insulating core portion within the domain does not result in a phenomenon such as a decrease in the amount of discharge and poor charging.

[0068] <Electron conductive agent> Examples of the electronic conductive agent to be blended into the domain 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.

[0069] 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.

[0070] Among them, DBP with an oil absorption of 40 cm can impart high conductivity to the domain. 3 / 100g or more 170cm 3 Conductive carbon black having a density of 100 g or less can be suitably used.

[0071] 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 30 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.

[0072] It is preferable that a larger amount of conductive agent is blended compared to a general conductive member for electrophotography. This makes it easier to control the volume resistivity of the domain, particularly the volume resistivity of the shell, within a preferred range. The volume resistivity of the shell is preferably 1.00×10 1 ~1.00×10 4 Ω·cm, and more preferably 1.00×10 1 ~5.00×10 3 Ω·cm. The volume resistivity of the core is preferably 1.00 x 10 10 ~1.00×10 19 Ω·cm, and more preferably 1.00×10 13 ~1.00×10 18 Ω·cm.

[0073] <Method for measuring the volume resistivity of the matrix or the volume resistivity of the core or shell in the domain> The volume resistivity can be measured, for example, by cutting a thin piece of a predetermined thickness (e.g., 1 μm) containing a matrix domain structure from the conductive layer and contacting the matrix and domain in the thin piece with a microprobe of a scanning probe microscope (SPM) or an atomic force microscope (AFM).

[0074] For example, as shown in FIG. 5A, when the longitudinal direction of the electrophotographic member 51 is the X axis, the thickness direction of the conductive layer is the Z axis, and the circumferential direction is the Y axis, a thin piece 52 is cut out from the conductive layer. The thin piece 53 is cut out so as to include at least a portion of a cross section 52a parallel to the XZ plane. Alternatively, as shown in Fig. 5B, the thin piece 53 is 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 the conductive member. In the present disclosure, the thin piece 53 is cut out as shown in 5B. The cutting is performed using, for example, a sharp razor, a microtome, a focused ion beam method (FIB), etc. In the present disclosure, a microtome is used.

[0075] 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 portion of the surface opposite the grounded surface of the thin piece, and a DC voltage of 50 V is applied for 5 seconds. The ground current value is measured for 5 seconds, and the arithmetic mean is calculated from the measured value. 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.

[0076] <Condition 4> The volume center of gravity of domain A must be located within the domain. The shape of the domain is preferably close to spherical. The volume center of gravity is preferably located within the core of the domain. Figures 4A to 4D show domains where the volume center of gravity is located and not located within the domain.

[0077] Figure 4A shows a domain in which the volume center of gravity 5 does not exist within the domain. Figure 4B shows the state of the domain in Figure 4A when compressive forces are applied from above and below. A domain with a shape like that of Figure 4A bends in the compression direction, and strain concentrates in the shell at the bent portion. Therefore, the effect of suppressing the increase in resistance in the shell portion of the domain containing the electronic conductive agent cannot be obtained. In the domain of Figure 4C, the volume center of gravity 5 is located within the domain. Figure 4D shows what happens when compressive forces are applied from above and below the domain of Figure 4C. As shown in Figure 4D, strain is concentrated inside the domain when compressed from above and below. This suppresses strain in the shell portion containing the electronic conductive agent, thereby preventing high resistance.

[0078] <Condition 5> In the cross section of domain A, the region from the outer edge of the domain toward the volume center of gravity up to a distance of 10 nm is defined as the outer periphery region, and the region from the volume center of gravity toward the outer edge of the domain up to a distance of 10 nm is defined as the inner region. The outer periphery region and the inner region do not overlap. The fact that the outer periphery region and the inner region do not overlap indicates that the domain has a shape close to a sphere. Since a shape close to a sphere causes stress to concentrate in the inner region during compression, it is possible to concentrate strain in the core portion of the domain and reduce strain in the shell portion.

[0079] <Condition 6> Furthermore, in domain A, the elastic moduli of the domain's internal region and its peripheral region satisfy a specific relationship. Specifically, when the elastic modulus measured in the peripheral region of a cross section of a domain that satisfies <Condition 5> is Eout and the elastic modulus measured in the internal region is Ein, Eout / Ein > 1.10. Within this range, the core region deforms preferentially, suppressing distortion in the shell region and preventing the domain from becoming highly resistive.

[0080] From the viewpoint of further suppressing distortion of the shell portion, Eout / Ein ≥ 1.11 is preferable, and Eout / Ein ≥ 1.30 is more preferable. Eout / Ein is preferably more than 1.10 and not more than 2.00, more preferably 1.11 to 1.50, and even more preferably 1.30 to 1.50.

[0081] Eout is preferably 10 to 100 MPa, more preferably 20 to 60 MPa and more preferably 30 to 50 MPa. When Eout is in this range, the elasticity of the conductive layer is not impaired and distortion of the shell portion can be suppressed. Ein is preferably 10 to 90 MPa, more preferably 20 to 50 MPa, and even more preferably 25 to 40 MPa.

[0082] (How to check if Domain A meets <Conditions 3> to <Conditions 6>) Using the measurement method using the FIB-SEM described above, multiple domains contained in a sample that satisfies <Condition 1> and <Condition 2> are measured, and it is confirmed whether each domain satisfies <Condition 3> to <Condition 6>, which are the conditions for Domain A.

[0083] Regarding <Condition 3> From the backscattered electron images of the images taken by FIB-SEM under <Condition 1> and <Condition 2>, the matrix It is possible to determine whether a second rubber and an electronic conductive agent are included from the contrast between the matrix and the domain. Specifically, an image analyzer (product name: LUZEX-AP, manufactured by Nireco Corporation) is used to distinguish between the matrix and the domain by utilizing the contrast difference inside the domain, and it is possible to identify and analyze the area of ​​the electronic conductive agent, typically carbon black, within each domain.

[0084] Regarding Condition 4 For the 3D images obtained by FIB-SEM under <Condition 1> and <Condition 2> The volume center of gravity is calculated using an image analyzer (product name: LUZEX-AP, manufactured by Nireco Corporation), and an analysis is performed to determine whether the volume center of gravity exists within the domain.

[0085] Regarding <Condition 5> Three-dimensional FIB-SEM measurements are performed on cubic images with sides of 6 μm at 60 nm intervals. After calculating the volume center of gravity using the method described in <Condition 4>, an image analyzer (product name: LUZEX-AP, manufactured by Nireco Corporation) is used to confirm that the 10 nm distance from the outer edge of the domain toward the volume center of gravity does not overlap with the 10 nm distance from the volume center of gravity to the outer edge of the domain. If no image passing through the center of gravity is found among the captured cross-sectional images, the cross-sectional image closest to the center of gravity is selected, and the center of gravity is determined by moving the position perpendicular to the cross section.

[0086] Regarding <Condition 6> For each cross section cut at 60 nm intervals using an FIB-SEM, the center of gravity is calculated using an image analyzer (product name: LUZEX-AP, manufactured by Nireco Corporation), and the elastic modulus of the cut cross section is measured using an SPM (MFP-3Dorigin). The elastic modulus Ein is measured in a 10 nm region from the center of gravity toward the outer edge, and the elastic modulus Eout is measured in a 10 nm region from the outer edge toward the center of gravity. Ten force curve measurements are performed for each, and the elastic modulus is calculated from the force curve using the Hertz method. The maximum and minimum values ​​are excluded from the calculated elastic modulus at eight points, and the average is taken as the elastic modulus. The same process is repeated until the entire domain is cut. The volume center of gravity of the entire domain is calculated using the method described in <Condition 4> above, and Ein and Eout of the cross section closest to the volume center of gravity are taken as Ein and Eout of the cross section passing through the volume center of gravity of the domain.

[0087] Also, calculate (A1 / A2 x 100). Specifically, after confirming domain A, calculate (A1 / A2 x 100) on a cross section passing through the center of gravity of domain A obtained in <Condition 5>. Use the arithmetic average value of all domains A among the multiple domains observed.

[0088] In addition, (A3 / A4 × 100) is calculated. Specifically, after confirming domain A, (A3 / A4 × 100) is calculated on the cross section passing through the center of gravity of domain A obtained by confirming <Condition 5>. 0) is calculated. The arithmetic mean value of all domains A among the multiple domains observed is used.

[0089] In addition, calculate (core area / domain area x 100). Specifically, after confirming domain A, calculate (core area / domain area x 100) in a cross section passing through the center of gravity of domain A obtained in the confirmation of <Condition 5>. Use the arithmetic average value of all domains A among the multiple domains observed.

[0090] Furthermore, for <Condition 7>, the ratio of domain A to the total number of multiple domains is calculated.

[0091] Also, confirm whether Domain A has a core-shell structure. In a cross section passing through the volume center of gravity of Domain A, if the region including the volume center of gravity of Domain A and the outer edge region are made of different rubbers, it is determined to have a core-shell structure. Furthermore, if there is only one type of rubber inside Domain A, draw a concentric circle with the volume center of gravity at its center and covering 10% of the cross-sectional area of ​​Domain A, and obtain Ratio 1 of the electronic conductive agent within the concentric circle. Also obtain Ratio 2 of the electronic conductive agent in 90% of the area outside the concentric circle. If Ratio 2 is greater than Ratio 1, it is determined to have a core-shell structure.

[0092] <Method for Controlling Eout / Ein> In order to increase Eout / Ein, there are means such as increasing the ratio of the electron conductive agent being unevenly distributed in the shell part or adopting different rubbers for the core part and the shell part. More specifically, when different rubbers are used for the core part and the shell part, there is a means such as selecting a polymer with a high elastic modulus for the shell part and a polymer with a low elastic modulus for the core part.

[0093] Furthermore, in the case of different rubbers for the shell and the core, by mixing the electron conductive agent into the rubber of the shell and then mixing it with the rubber of the core, the electron conductive agent can be easily unevenly distributed in the shell, so it is easier to unevenly distribute the electron conductive agent in the shell part compared to a configuration where the domain is composed of a single polymer. For these reasons, it is more desirable that the core and the shell are made of different polymers.

[0094] Moreover, by adding more of the electron conductive agent added to the shell part, the elastic modulus of the shell part can be improved, which is preferable. As will be described later, by selecting the DBP absorption amount of carbon black, the addition amount of carbon black can be increased.

[0095] The domain includes at least one domain A. Domain A has a core part and a shell part, and it is preferable that the shell part contains an electron conductive agent. By blending more of the electron conductive agent in the polymer serving as the shell, the effect of suppressing the increase in the high resistance of the domain can be more easily obtained. Details will be described later, but such a method for manufacturing a domain may, for example, form the core and the shell using the same polymer, or manufacture them using different polymers respectively.

[0096] When making a domain with a core-shell structure using the same polymer for the core and the shell, the first rubber is used as the matrix and the second rubber is used as the domain. The formation of a domain with a core-shell structure where the electron conductive agent is unevenly distributed in the shell can be achieved by appropriately selecting changes in the manufacturing method, or the electron conductive agent, rubber type, and kneading manufacturing conditions during rubber mixing.

[0097] For example, a domain matrix structure is formed by mixing a vulcanizing agent into a second rubber in a pressure kneader, curing the resulting second rubber, and then kneading a masterbatch of the second rubber containing an electronic conductive agent and the first rubber in an open roll. This two-stage molding process allows the electronic conductive agent to be unevenly distributed in the shell portion of the domain. Specifically, the temperature C when the second rubber and the electronic conductive agent are mixed and the temperature C when the third rubber is added and mixed are One method is to make temperature C higher than temperature D during kneading (a temperature difference of 20°C or more). By increasing the amount of carbon gel during kneading of the second rubber and electronic conductive agent, the electronic conductive agent is retained in the second rubber, and migration of the electronic conductive agent between the second rubber and the third rubber can be suppressed.

[0098] When creating a domain with a core-shell structure using different polymers for the core and shell, it is possible to create a core-shell structure with a high content of electronic conductive agent in the shell by controlling the SP value and blending amount. Three types of rubber are used: the first rubber is the matrix, the second rubber is the shell of the domain, and the third rubber is the core of the domain. A structure in which the electronic conductive agent is unevenly distributed in the second rubber can be formed by selecting the appropriate rubber based on the relationship between the SP values ​​of the three types of rubber used.

[0099] First, when rubbers with SP values ​​in the order of first rubber > second rubber > third rubber are mixed, the resulting structure is one in which the first rubber is in the matrix, the second rubber is in the shell, and the third rubber is in the core. Therefore, by mixing the electronic conductive agent with the second rubber in a pressure kneader in advance and creating a masterbatch, it is possible to form a structure in which the electronic conductive agent is unevenly distributed in the shell.

[0100] From the viewpoint of forming a core-shell structure, the relationship between the SP values ​​of the first rubber to the third rubber may be "SP value of the first rubber > SP value of the second rubber = SP value of the third rubber", and is preferably "SP value of the first rubber > SP value of the second rubber > SP value of the third rubber". Furthermore, a method of forming domains using different polymers for the core and shell is preferable because it allows for a clear interface between the core and shell and reduces the compression applied to the shell. Therefore, it is preferable that the shell contains a second rubber and an electronic conductive agent, and the core contains a third rubber, the second rubber and the third rubber being different rubbers.

[0101] <First Rubber> The matrix includes a first rubber. The matrix includes, for example, a cross-linked product of the first rubber. The first rubber is the component with the largest compounding ratio in the rubber composition for forming the conductive layer, and the cross-linked product of the first rubber determines the mechanical strength of the conductive layer. Therefore, the first rubber is one that, after cross-linking, imparts to the conductive layer the strength required for a conductive member for electrophotography, and is one that can phase-separate from the second rubber described below and form a matrix-domain structure.

[0102] Preferred examples of the first 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 terpolymer rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated NBR (H-NBR), and silicone rubber.

[0103] <Second Rubber> The domain comprises the second rubber, for example a crosslinked product of the second rubber. Preferably, the shell comprises the second rubber, for example a crosslinked product of the second rubber. Specific examples of the second rubber include 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).

[0104] <The third rubber> The core preferably contains a third rubber, for example a crosslinked product of the third rubber. Specific examples of the third rubber include 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).

[0105] The first rubber is preferably at least one selected from the group consisting of NBR, SBR, and CR, and more preferably at least one selected from the group consisting of NBR and CR. The second rubber is preferably at least one selected from the group consisting of EPDM, BR, IR, IIR, and NBR. The third rubber is preferably at least one selected from the group consisting of EPDM, BR, IR, IIR, and SBR, and more preferably at least one selected from the group consisting of EPDM, BR, IR, and SBR. It is particularly preferred that the first rubber is NBR, the second rubber is EPDM, and the third rubber is SBR.

[0106] <Method of manufacturing electrophotographic members> An example of a method for producing an electrophotographic member is shown 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 the present disclosure can be achieved. Step (A): preparing a shell-forming rubber composition (hereinafter also referred to as "SCMB") containing carbon black and a second rubber; Step (B): preparing a core-forming rubber composition (hereinafter also referred to as "CRC") containing a third rubber; Step (C): preparing a matrix-forming rubber composition (hereinafter also referred to as "MRC") containing a first rubber; Step (D): Kneading the SCMB and the CRC to prepare a domain-forming rubber composition (hereinafter also referred to as "DRC"); Step (E): A step of kneading the DRC and the MRC to prepare a rubber composition for forming a conductive layer having a matrix domain structure, the domains of which have a core-shell structure. Step (F): A step of forming a layer of a rubber composition for forming a conductive layer on a substrate directly or via another layer, and curing the rubber composition layer to form a conductive layer.

[0107] Alternatively, a conductive layer may be formed on a substrate using a rubber composition for forming a conductive layer by a known method such as extrusion molding, injection molding, or compression molding. The conductive layer may be adhered to the substrate via an adhesive, if necessary. The conductive layer formed on the substrate may be vulcanized as needed, polished, and then subjected to a surface treatment such as ultraviolet treatment. When vulcanization is performed, a vulcanizing agent may be further added to the rubber composition for forming the conductive layer in step (F). Then, vulcanization may be performed during the curing. The vulcanizing agent is not particularly limited and examples thereof include sulfur.

[0108] 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 30 to 80 parts by mass. The amount of the third rubber relative to 100 parts by mass of the first rubber is preferably 5 to 60 parts by mass, more preferably 20 to 50 parts by mass.

[0109] <Method for controlling matrix domain structure> The dispersed particle diameter (domain size) D when two incompatible polymers are melt-kneaded is calculated using the Taylor formula, Wu's empirical formula, and Tokita's formula shown in the following formulas (4) to (7). has been proposed (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.

[0110] 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 SCMB, CRC, and MRC; (b) The ratio (ηm / ηd) of the viscosity of the DRC (ηd) and the viscosity of the MRC (ηm); (c) Shear rate (γ) and energy amount during shearing (EDK) during kneading of DRC and MRC in step (E). (d) Volume fraction of DRC relative to MRC in step (E).

[0111] (a) Difference in interfacial tension σ between SCMB, CRC, and MRC 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.

[0112] 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.

[0113] 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 0.30 μm or more and 2.1 μm or less.

[0114] 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. In the case of forming a conductive layer having a matrix-domain structure in which the domains have a core-shell structure, it is preferable to select a rubber material such that the SP value of the rubber material forming the shell is intermediate between the SP values ​​of the rubber materials forming the matrix and the core.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] (b) The ratio (ηm / ηd) of the viscosity of the DRC (ηd) and the viscosity of the MRC (ηm); The closer the viscosity ratio (DRC / MRC) (ηd / ηm) between DRC and MRC 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 between DRC and MRC can be adjusted by selecting the Mooney viscosity of the raw rubber used for the DRC and MRC, and by blending the type and amount of filler.

[0119] 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. The viscosity of the domain-forming rubber composition and the matrix-forming rubber composition is determined based on the Mooney viscosity ML (1+4) It can be obtained by measuring the rubber temperature during kneading.

[0120] The maximum Feret diameter of the domains can be reduced as the viscosity ratio (ηd / ηm) of the domains to the matrix approaches 1. Specifically, a desirable domain diameter can be obtained by setting the viscosity ratio to 2.0 or less.

[0121] (c) Shear rate (γ) and energy content during shearing (EDK) when mixing DRC and MRC The faster the shear rate during kneading of DRC and MRC, and the greater the amount of energy during shearing, the smaller the interdomain distance can be. 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, and increasing the rotation speed.Increasing the energy during shear can also be achieved by increasing the rotation speed of the mixing elements and by increasing the viscosity of the rubber in the DRC and the rubber in the MRC.

[0122] 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.

[0123] (d) Volume fraction of DRC relative to MRC in step (iii). The volume fraction of the DRC to the MRC is the domain volume fraction of the matrix-forming rubber composition. This correlates with the probability of collision and coalescence of the rubber composition for forming a domain. Specifically, reducing the volume fraction of the rubber composition for forming a domain relative to the rubber composition for forming a matrix reduces the probability of collision and coalescence of the rubber composition for forming a domain and the rubber composition for forming a matrix. 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 allows the required conductivity to be obtained.

[0124] <Domain shape> The 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 closer to a sphere, the closer the center of gravity within the domain becomes to the center of the domain, which reduces distortion of the shell containing the electronic conductive agent. Furthermore, the closer the external shape of the domain is to a sphere, the easier it is to satisfy <Condition 4> and <Condition 5>.

[0125] 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.

[0126] It is preferable that the shape of the domain without irregularities on the peripheral surface satisfies the following formula (5). When there are fewer irregularities, distortion of the shell portion containing the electronic conductive agent can be more effectively suppressed, and therefore, high resistance can be more effectively suppressed. 1.00≦A / B≦1.10 (5) (A: perimeter of the domain, B: envelope perimeter of the domain) Equation (5) represents the ratio of the domain perimeter A to the domain envelope perimeter B. Here, the envelope perimeter is the perimeter when connecting the convex portions of the domain 71 observed in the observation area, as shown in FIG.

[0127] 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 1.1, the domain will have large recesses and protrusions, which means that anisotropy of the electric field will occur.

[0128] <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. 5A and 5B show the shape of an electrophotographic member 51 in a three-dimensional manner along three axes, specifically, the X, Y, and Z axes. In Figures 5A and 5B, 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.

[0129] FIG. 5A 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 the state in which the electrophotographic member is in contact with the photosensitive drum and rotates, and repeatedly comes into contact with the photosensitive drum, the cross section 52a parallel to the XZ plane 52 will be cut out at a certain timing. This means that the surface of the ring contacts the photosensitive drum at the same time.

[0130] 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. 5B).

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] <<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.

[0136] 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. 5B 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 performed 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 depths 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.

[0137] <<Method for measuring domain perimeter A and envelope perimeter B>> The domain perimeter, envelope perimeter, and number of domains can be measured by quantifying the above binary image. Using the counting function of us (MediaCybernetics), the perimeter A of each domain in the domain size group within the image and the domain envelope perimeter B can be calculated, and the arithmetic mean value of the domain perimeter ratio A / B can be calculated.

[0138] 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. 5B 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 performed 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 depths 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.

[0139] <<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.

[0140] 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. 5B 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 performed 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 depths 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.

[0141] <Amount of electronic conductive agent added in the shell> 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, while minimizing 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.

[0142] 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)).

[0143] 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 3 The 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.

[0144] 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.

[0145] 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.

[0146] <Reinforcing material> In addition, reinforcing carbon black can be added as a reinforcing agent to improve the ratio of the modulus of elasticity of the core to that of the shell in the domain. Examples of reinforcing carbon black used here include FEF, GPF, SRF, and MT carbon, which have low electrical conductivity.

[0147] 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.

[0148] <Matrix> The matrix contains a crosslinked product of the first rubber. The volume resistivity of the matrix is ​​1.0×10 8 ~1.0×10 17 Ωcm is preferred. The volume resistivity of the matrix is ​​1.0×10 8When the resistivity is Ωcm or more, the influence of the conductivity of the matrix on the transfer of charges between conductive domains can be suppressed. In particular, when the conductivity of the matrix is ​​high (volume resistivity is low) and it exhibits ionic conductivity, the matrix excessively promotes the transfer of charges between conductive domains, and if electric field concentration occurs due to a slight change in the domain shape, excessive current may flow. Therefore, in order to suppress the ionic conductivity of the matrix, the volume resistivity should be set to 1.0 x 10 8 It is preferable that the resistivity is Ωcm or more.

[0149] Volume resistivity is 1.0×10 17 When the resistivity is Ωcm or less, the necessary conductivity can be obtained as a whole of the conductive layer without interfering with the transfer of charges between conductive domains, and therefore image defects due to insufficient charging can be prevented.

[0150] The volume resistivity is more preferably 3.0×10 8 Ωcm or more 1.0×10 17 Within this range, the influence of the ionic conductivity of the matrix can be suppressed, and a better volume resistivity can be obtained for the electrophotographic member. The most preferable range of the volume resistivity is 4.0×10 8 Ωcm or more 1.0×10 17 Within this range, even when a high voltage is applied, electric field concentration can be strongly suppressed, and a more favorable volume resistivity can be obtained for the electrophotographic member.

[0151] <Process cartridge> At least one aspect of the present disclosure provides a process cartridge equipped with the electrophotographic member of the present disclosure. Figure 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 attachable to the main body of the electrophotographic device. 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.

[0152] 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.

[0153] 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.

[0154] <Electrophotographic image forming apparatus> At least one aspect of the present disclosure provides an electrophotographic image forming apparatus equipped with the electrophotographic member of the present disclosure. Fig. 7 is a schematic diagram of an electrophotographic image forming apparatus 200 using the 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 above-mentioned process cartridges are detachably mounted. Each process cartridge uses toner of each color: black (BK), magenta (M), yellow (Y), and cyan (C).

[0155] 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.

[0156] 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.

[0157] 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 ejected outside the device, completing the printing operation.

[0158] On the other hand, the toner that has not been transferred and remains on the photosensitive drum is removed by the cleaning blade 205. The above-mentioned process is repeated for the cleaned photosensitive drum 201. The toner remaining on the primary transfer belt without being transferred is also scraped off by the cleaning device 217.

[0159] Although a color electrophotographic device is shown as an example, in a monochrome electrophotographic device (not shown), the process cartridge uses only black toner. A monochrome image is formed directly on the transfer material by the process cartridge and primary transfer roller (no secondary transfer roller) without using an intermediate transfer belt. The image is then fixed by a fixing device, and the printing operation is completed when the paper is ejected from the device. [Example]

[0160] The present disclosure will be described below based on examples, but the technical scope of the present disclosure is not limited to these examples.

[0161] 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)

[0162] <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)

[0163] <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)

[0164] <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)

[0165] <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)

[0166] <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)

[0167] <Butyl rubber> Butyl rubber (product name: JSR Butyl, Mooney viscosity ML (1+4) at 100°C: 32, SP value: 15.8 (J / cm 3 ) 0.5 , manufactured by JSR Corporation, abbreviation: Butyl065)

[0168] <Electro-conductive agent (conductive particles)> Carbon black (product name: TOKABLACK♯7360SB, DBP absorption capacity: 87 cm 3 / 100g, manufactured by Tokai Carbon Co., Ltd., abbreviation: #7360SB) Tin oxide (Product name: S-2000, DBP absorption capacity: 80cm 3 / 100g, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd., abbreviated name: tin oxide) Carbon black (Product name: Ketjen Black, DBP absorption capacity: 350 cm 3 / 100g, manufactured by Lion Specialty Chemicals, abbreviated name: EC100J)

[0169] Example 1 1. Preparation of unvulcanized rubber composition for forming conductive layer [1-1. Preparation of carbon masterbatch (SCMB) for forming shells in domains] The materials shown in Table 1 in their types and amounts (parts by mass) were mixed in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Corporation) to obtain SCMB for forming the domain shell. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, a kneader temperature of 130°C, and 16 minutes.

[0170] [Table 1]

[0171] [1-2. Preparation of Core-forming Rubber Compound (CRC) in Domains] A rubber composition for forming the domain core was obtained by mixing the materials in the types and amounts (parts by mass) shown in Table 2 in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Corporation). The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, a kneader temperature of 100°C, and 16 minutes.

[0172] [Table 2]

[0173] [1-3. Preparation of matrix-forming rubber composition (MRC)] The materials shown in Table 3 in the types and amounts (parts by mass) were mixed in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Corporation) to obtain a rubber composition for forming a matrix. The mixing conditions were a filling rate of 70 vol%, a temperature inside the kneader of 100°C, a blade rotation speed of 30 rpm, and a mixing time of 16 minutes.

[0174] [Table 3]

[0175] [1-4. Preparation of domain-forming rubber composition (DRC)] The materials shown in Table 4 were mixed (parts by mass) in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Corporation) to obtain a domain-forming rubber composition (DRC). The mixing conditions were a filling amount of 70 vol%, a kneader temperature of 130°C, a blade rotation speed of 30 rpm, and a duration of 16 minutes.

[0176] [Table 4]

[0177] [1-5. Preparation of Rubber Composition for Forming Conductive Layer] The materials (parts by mass) shown in Table 5 were mixed in a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Corporation) to obtain a domain-forming rubber composition (DRC). The mixing conditions were a filling amount of 70 vol%, a kneader temperature of 100°C, a blade rotation speed of 30 rpm, and a time of 16 minutes.

[0178] [Table 5]

[0179] [1-6. Preparation of unvulcanized rubber composition for forming conductive layer] The materials in the types and amounts (parts by mass) shown in Table 6 were mixed using an open roll to obtain an unvulcanized rubber composition for forming a 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.

[0180] [Table 6]

[0181] 2. Preparation of electrophotographic materials (conductive materials) [2-1. Formation of conductive layer] 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 as the substrate. This core bar was used as the substrate, which is a conductive shaft body. 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 the conductive support.

[0182] 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, resulting in 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, leaving a longitudinal length of 232 mm for the conductive layer.

[0183] [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.

[0184] (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 a conductive member rotation speed of 250 rpm. In the rough cutting process, the grinding wheel penetrated the conductive member at a speed of 20 mm / sec, penetrating 0.24 mm after contacting the outer surface of the conductive 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 conductive member to complete the polishing. The polishing method used was the upper cut method, in which the grinding wheel and conductive member rotate in the same direction.

[0185] Examples 2 to 25 Conductive members (charging rollers of Examples 2 to 25) were produced in the same manner as in Example 1, except that the blending of the rubber and the electronic conductive agent in the unvulcanized rubber composition for forming the conductive layer was as shown in Table 7.

[0186] (Comparative Example 1) A conductive member was produced in the same manner as in Example 1, except that the rubber and electronic conductive agent in the unvulcanized rubber composition for forming the conductive layer were blended as shown in Table 7 and the SCMB kneader temperature was set to 100°C.

[0187] (Comparative Example 2) A conductive member was produced in the same manner as in Example 1, except that the blending ratio of the rubber and the electronic conductive agent in the unvulcanized rubber composition for forming the conductive layer was as shown in Table 7. In Comparative Example 2, the electronic conductive agent was mixed with MRC.

[0188] (Comparative Example 3) The unvulcanized rubber composition for forming the conductive layer contained the rubber and the electronic conductive agent in the formulation shown in Table 7. Mixing with an open roll during preparation of the unvulcanized rubber composition for forming the conductive layer was performed with a front roll rotation speed of 10 rpm, a rear roll rotation speed of 8 rpm, and a roll gap of 4 mm, with the mixture turned left and right a total of 20 times, and no thin-threading was performed. A conductive member was produced under the same conditions as in Example 1, except for these conditions.

[0189] Comparative Example 4 A conductive member was produced in the same manner as in Example 1, except that the composition of the shell-forming carbon master batch (SCMB) in the domain was as follows. Raw rubber: 100 parts by weight Epichlorohydrin rubber (EO-EP-AGE ternary compound) (trade name: Epion ON301, manufactured by Osaka Soda Co., Ltd.), Mooney viscosity ML (1+4) 100°C: 32, SP value: 15.8 (J / cm 3 ) 0.5 Filler: 60 parts by weight Calcium carbonate (product name: Nanox #30, manufactured by Maruo Calcium Co., Ltd.) Plasticizer: 10 parts by weight Aliphatic polyester plasticizer (product name: Polycizer P-202, manufactured by Dainippon Ink and Chemicals, Inc.) Vulcanization accelerator: 5 parts by mass Zinc oxide (trade name: zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd.) Processing aid: 1 part by weight Zinc stearate (product name: SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.)

[0190] [Table 7] In the table, M indicates Mooney viscosity, and SP indicates the SP value.

[0191] 3. Characterization [Measurement of matrix volume resistivity] 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%.

[0192] First, a microtome (trade name: Leica EMFCS, manufactured by Leica Microsystems) was used to cut out slices of approximately 2 μm thick 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. 5B. 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.

[0193] [Shell volume resistivity measurement] The volume resistivity was measured in the same manner as the above-mentioned method for measuring the volume resistivity of the matrix, except that the contact position of the cantilever was set to the point corresponding to the shell and the voltage applied to the cantilever was set to 1 V. The average value of the values ​​at each measurement point was calculated.

[0194] [Core volume resistivity measurement] The volume resistivity of the core was measured in the same manner as the above-mentioned method for measuring the volume resistivity of the matrix, except that the contact position of the cantilever was set to the point corresponding to the core and the voltage applied to the cantilever was set to 1 V. The average value of the values ​​at each measurement point was calculated.

[0195] [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.

[0196] A thin slice having a thickness of 1 mm was cut out using the same method as in the measurement of the volume resistivity of the matrix. At this time, a plane perpendicular to the axis of the conductive support and a cross section parallel to that plane were obtained. The slice was cut out from the conductive layer at three locations: the center in the longitudinal direction, and L / 4 from both ends of the conductive layer toward the center, where L is the longitudinal length of the conductive layer. Platinum was vapor-deposited on the slice to obtain a vapor-deposited slice. The surface of the vapor-deposited slice 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.

[0197] 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, we used the image processing software Imag Using eProPlus (product name, manufactured by Media Cybernetics), the image was converted 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 within the fracture surface appeared white. The count function for the binary image was then used to calculate the following items for the domains present in the binary image. ·Perimeter length A (μm) ·Envelope perimeter B (μm)

[0198] These values ​​were substituted into the following formula (5), and the proportion of the number of domains that satisfied the conditions of formula (5) was calculated as a percentage of the total number of domains in each evaluation image.Furthermore, the average value of the nine evaluation images was calculated and used as an index of the domain shape.The results are shown in Table 8.In Table 8, the value obtained by substituting 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)

[0199] [Method for measuring the elastic modulus of the core and shell parts of a domain] The domain modulus was measured using the procedure described above.

[0200] 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. To evaluate the high-speed process, the laser printer was modified so that it could output 50 sheets per minute on A4-sized paper, which was higher than the original output rate. The output speed of the recording media was set to 246 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.

[0201] 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.

[0202] [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.

[0203] [Evaluation of black dots on halftone images] Rank A: No black dots are visible on the halftone image even when observed under a microscope. Rank B: No black dots are visible on the halftone image when observed with the naked eye, but they are visible when observed under a microscope. Rank C: Black dots are visible in some parts of the halftone image. Rank D: Black dots are visible all over the halftone image.

[0204] The charging rollers of Examples 2 to 25 and Comparative Examples 1 to 4 were evaluated in the same manner as charging roller 1. The results are shown in Table 8.

[0205] [Table 8]

[0206] In the table, for example, 5.00E+08 is 5.00 x 10 8 The perimeter ratio A / B indicates the ratio of the perimeter A of the domain to the envelope perimeter B of the domain. In Examples 1 to 25, at least eight of the samples taken from nine locations on the conductive layer satisfied the conditions <Condition 1> and <Condition 2>. In Example 25, all nine samples satisfied the conditions <Condition 1> and <Condition 2>. Comparative Example 1 did not satisfy Eout / Ein > 1.10 and did not have a core-shell structure. Comparative Example 2 did not have a domain-matrix structure. Comparative Example 3 did not have domain A, whose volume center of gravity is located within a domain. Comparative Example 4 did not satisfy Eout / Ein > 1.10. Moreover, Examples 1 to 25 also satisfied <Condition 3> to <Condition 6>. The "volume fraction" of the domain is the volume fraction of the domain in the sample that satisfies <Condition 1>. The "number" of domains is the arithmetic mean value of the total number of domains. The "number" of domains is the number of domains per sample that meets <Condition 2>. C / D (%) indicates the ratio of the core area to the area of ​​domain A (core area / domain area x 100). The number of A % indicates the ratio of domain A to the total number of multiple domains.

[0207] The present disclosure relates to the following configurations. (Configuration 1) 1. An electrophotographic member having a substrate having an electrically conductive outer surface, and a conductive layer on the outer surface of the substrate, comprising: the conductive layer has a matrix containing a first rubber and a plurality of domains dispersed in the matrix; Among the cubic samples with a side length of 6 μm sampled from nine locations on the conductive layer, at least eight samples satisfy the following <Condition 1> and <Condition 2> in FIB-SEM measurement: <Condition 1> The ratio of the total volume of the plurality of domains to the volume of the sample is 10 to 40 volume %; <Condition 2> The number of the multiple domains in the sample is 10 to 2,400; The plurality of domains contained in each of the samples satisfying <Condition 1> and <Condition 2> includes at least one domain A, The domain A satisfies the following <Condition 3> to <Condition 6>: <Condition 3> The domain A contains a second rubber and an electronic conductive agent; <Condition 4> The center of gravity of the volume of the domain A exists within the domain; <Condition 5> In a cross section passing through the volume center of gravity of the domain A, when a region from the outer edge of the domain to a distance of 10 nm toward the volume center of gravity is defined as an outer circumferential region, and a region from the volume center of gravity to a distance of 10 nm toward the outer edge of the domain is defined as an inner region, the outer circumferential region and the inner region do not overlap; <Condition 6> When the elastic modulus measured in the outer peripheral region of the cross section in <Condition 5> is Eout and the elastic modulus measured in the inner region is Ein, Eout / Ein > 1.10. (Configuration 2) 2. The electrophotographic member according to Configuration 1, wherein Eout and Ein satisfy Eout / Ein≧1.30. (Configuration 3) 3. The electrophotographic member according to configuration 1 or 2, wherein the Eout is 10 to 100 MPa. (Configuration 4) 4. The electrophotographic member according to any one of Configurations 1 to 3, wherein, with respect to the domain A, a ratio (A1 / A2×100) of a total area A1 of the electronic conductive agent observed in the cross section under <Condition 5> to an area A2 of the cross section of the domain A is 15.0 to 80.0 area %. (Configuration 5) The electrophotographic member according to Structure 4, wherein, with respect to the domain A, the ratio (A3 / A4×100) of the total area A3 of the electronic conductive agent in the outer peripheral region to the area A4 of the outer peripheral region observed in the cross section under the <Condition 5> is 20 to 50 area %. (Structure 6) The domain A has a core-shell structure consisting of a core and a shell surrounding the core, 6. The electrophotographic member according to any one of Configurations 1 to 5, wherein the outer peripheral region is at least a part of the shell, and the inner region is at least a part of the core. (Configuration 7) 7. The electrophotographic member according to configuration 6, wherein the ratio of the area of ​​the core to the area of ​​the domain A observed in the cross section under <Condition 5> (core area / domain area×100) is 10 to 80 area %. (Configuration 8) the shell includes the second rubber and the electronic conductive agent, the core includes a third rubber, 8. The electrophotographic member according to aspect 6 or 7, wherein the second rubber and the third rubber are different. (Configuration 9) The first rubber is NBR, the second rubber is EPDM, 9. The electrophotographic member according to claim 8, wherein the third rubber is SBR. (Configuration 10) 10. The electrophotographic member according to any one of configurations 1 to 9, wherein the electronic conductive agent is carbon black. (Configuration 11) The electrophotographic member according to any one of configurations 1 to 10, wherein the conductive layer that satisfies the above <Condition 1> and <Condition 2> further satisfies the following <Condition 7>: <Condition 7> The proportion of the domain A in the total number of the plurality of domains is 70% or more by number. (Configuration 12) The volume resistivity of the matrix is ​​1.0×10 8 ~1.0×10 17 12. The electrophotographic member according to any one of aspects 1 to 11, wherein the resistivity is Ωcm. (Configuration 13) the domain has a core-shell structure consisting of a core and a shell surrounding the core, The volume resistivity of the shell is 1.00×10 1 ~1.00×10 4 13. The electrophotographic member according to any one of aspects 1 to 12, wherein the resistivity is Ω·cm. (Configuration 14) The electrophotographic member according to any one of Configurations 1 to 13, wherein the electrophotographic member is a charging member. (Configuration 15) A process cartridge detachably mountable to an electrophotographic image forming apparatus, The process cartridge comprises the electrophotographic member according to any one of Configurations 1 to 14. (Configuration 16) An electrophotographic image forming apparatus, The electrophotographic image forming apparatus comprises the electrophotographic member according to any one of the first to fourteenth aspects. [Explanation of symbols]

[0208] 1 substrate, 2 conductive layer, 3 core-shell boundary, 4 matrix-shell boundary, 30 matrix, 5 domain centroid< / epdm> < / sbr> < / nbr>

Claims

1. 1. An electrophotographic member having a substrate having an electrically conductive outer surface, and a conductive layer on the outer surface of the substrate, comprising: the conductive layer has a matrix containing a first rubber and a plurality of domains dispersed in the matrix; Among the cubic samples with a side length of 6 μm sampled from nine locations on the conductive layer, at least eight samples satisfy the following <Condition 1> and <Condition 2> in FIB-SEM measurement: <Condition 1> The ratio of the total volume of the domains to the volume of the sample is 10 to 40 volume %; <Condition 2> The number of domains in the sample is 10 to 2,400; The plurality of domains contained in each of the samples that satisfy <Condition 1> and <Condition 2> includes at least one domain A, The domain A satisfies the following <Condition 3> to <Condition 6>: <Condition 3> The domain A contains a second rubber and an electronic conductive agent; <Condition 4> The center of gravity of the domain A exists within the domain; <Condition 5> In a cross section passing through the volume center of gravity of the domain A, when a region from the outer edge of the domain to a distance of 10 nm toward the volume center of gravity is defined as an outer circumferential region, and a region from the volume center of gravity to a distance of 10 nm toward the outer edge of the domain is defined as an inner region, the outer circumferential region and the inner region do not overlap; <Condition 6> When the elastic modulus measured in the outer peripheral region of the cross section in <Condition 5> is Eout and the elastic modulus measured in the inner region is Ein, Eout / Ein > 1.

10.

2. 2. The electrophotographic member of claim 1, wherein said Eout and said Ein satisfy Eout / Ein≥1.

30.

3. 2. The electrophotographic member of claim 1, wherein Eout is from 10 to 100 MPa.

4. 2. The electrophotographic member according to claim 1, wherein, with respect to the domain A, a ratio (A1 / A2×100) of a total area A1 of the electronic conductive agent observed in the cross section under <Condition 5> to an area A2 of the cross section of the domain A is 15.0 to 80.0 area %.

5. 5. The electrophotographic member according to claim 4, wherein, with respect to the domain A, a ratio (A3 / A4×100) of a total area A3 of the electronic conductive agent in the outer peripheral region to an area A4 of the outer peripheral region observed in the cross section under <Condition 5> is 20 to 50 area %.

6. The domain A has a core-shell structure consisting of a core and a shell surrounding the core, 2. The electrophotographic member of claim 1, wherein said outer peripheral region is at least a portion of said shell and said inner region is at least a portion of said core.

7. 7. The electrophotographic member according to claim 6, wherein the ratio of the area of ​​the core to the area of ​​the domain A observed in the cross section under <Condition 5> (core area / domain area×100) is 10 to 80 area %.

8. the shell includes the second rubber and the electronic conductive agent, the core includes a third rubber, 7. An electrophotographic member according to claim 6, wherein said second rubber and said third rubber are different.

9. The first rubber is NBR, The second rubber is EPDM, 9. An electrophotographic member according to claim 8, wherein said third rubber is SBR.

10. 2. The electrophotographic member of claim 1 wherein said electronically conductive agent is carbon black.

11. 2. The electrophotographic member according to claim 1, wherein the conductive layer that satisfies the <Condition 1> and <Condition 2> further satisfies the following <Condition 7>: <Condition 7> The proportion of the domain A in the total number of the plurality of domains is 70% or more by number.

12. The volume resistivity of the matrix is ​​1.0×10 ８ ~1.0 x 10 １７ 3. The electrophotographic member of claim 1, wherein the surface resistivity is Ωcm.

13. the domain has a core-shell structure consisting of a core and a shell surrounding the core, The volume resistivity of the shell is 1.00×10 １ ~1.00 x 10 ４ 3. The electrophotographic member of claim 1, wherein the surface resistivity is Ω·cm.

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

15. A process cartridge detachably mountable to an electrophotographic image forming apparatus, The process cartridge comprises the electrophotographic member according to any one of claims 1 to 14.

16. An electrophotographic image forming apparatus, The electrophotographic image forming apparatus comprises the electrophotographic member according to any one of claims 1 to 14.

Images