Electrophotographic member and its manufacturing method, process cartridge and electrophotographic image forming apparatus

Abstract

To provide a member for electrophotography that can quickly recover from deformation even with low-hardness urethane elastomer and prevent a streak-like image defect.SOLUTION: A member for electrophotography comprises a shaft core body and an elastic layer provided on an outer periphery of the shaft core body. The elastic layer includes urethane elastomer having a matrix and a plurality of domains dispersed in the matrix. The modulus of elasticity of the domains measured on a cross section in a thickness direction of the elastic layer is lower than the modulus of elasticity of the matrix. The micro rubber hardness of the elastic layer at a temperature of 23°C is 20 or more and 50 or less. In an indentation test for the elastic layer at 23°C using a nanoindenter, when a Vickers indenter is pressed at a loading speed of 10 mN / 30 sec, maintained at the load of 10 mN for 60 seconds, and then unloaded, the elastic layer has a strain of 1 μm or less after five seconds from the unloading.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an electrophotographic member used in an electrophotographic image forming apparatus (hereinafter also simply referred to as an "image forming apparatus") such as an electrophotographic copying machine or printer, and a method for manufacturing the same. The present disclosure also relates to a process cartridge and an electrophotographic image forming apparatus. [Background technology]

[0002] An image forming apparatus that employs electrophotography (such as a copier, facsimile, or printer that uses electrophotography) mainly consists of an electrophotographic photosensitive member (hereinafter also referred to as "photosensitive member"), a charging device, an exposure device, a developing device, a transfer device, and a fixing device. In an image forming apparatus, a photoconductor is first charged by a charging member (hereinafter also referred to as a "charging roller") and then exposed to light, forming an electrostatic latent image on the photoconductor. The toner in a toner container is applied to a toner carrier (hereinafter also referred to as a "developing roller") by a toner regulating member, and then transported to a development area by the developing roller. The toner transported to the development area develops the electrostatic latent image on the photoconductor at the contact point between the photoconductor and the developing roller. The toner on the photoconductor is then transferred to recording paper by a transfer means and fixed with heat and pressure. Any toner remaining on the photoconductor is removed by a cleaning member.

[0003] Conventionally, materials used for the elastic layer of such charging rollers and developing rollers include silicone rubber, acrylonitrile butadiene rubber, epichlorohydrin rubber, and urethane elastomers. Among these materials, urethane elastomers are preferred as the material for the elastic layer because of their excellent abrasion resistance. However, urethane elastomers are generally prone to compression set. Therefore, when a specific portion of a developing roller having an elastic layer containing a urethane elastomer comes into contact with a toner regulating member for a long period of time and deforms, the deformation does not easily recover. When a developing roller with a deformed specific portion is used for image formation, streak-like defects may occur in the resulting electrophotographic image at the position corresponding to the deformed portion. Similarly, with a charging roller having an elastic layer containing a urethane elastomer, poor charging due to deformation occurring in a specific portion of the charging roller may occur, resulting in defects in the electrophotographic image. The lower the hardness of the urethane elastomer, the greater the compression set, making the above-mentioned defects more likely to occur.

[0004] Patent Document 1 discloses a conductive roller having a conductive elastic layer made of a urethane elastomer obtained by reacting a polyisocyanate consisting of a hexamethylene diisocyanate trimer, a biuret, or a mixture thereof with a polyol containing a high molecular weight polypropylene polyol as a main component, at an isocyanate index of 80 to 120. Patent Document 1 discloses that the conductive elastic layer reduces the permanent deformation of the roller, thereby providing a conductive roller with excellent restorability against deformation caused by pressure contact with a photosensitive member or a roller or blade. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-34216 [Non-patent literature]

[0006] [Non-Patent Document 1] IEEE Transactions on SYSTEMS, MAN, AND CYBERNETICS, Vol. SMC-9, No. 1, January 1979, pp. 62-66 Summary of the Invention [Problem to be solved by the invention]

[0007] The present inventors have studied the conductive roller disclosed in Patent Document 1. As a result, they have found that the urethane elastomer disclosed in Patent Document 1 still has room for improvement as a constituent material for the elastic layers of developing rollers and charging rollers used in high-speed image forming apparatuses. One aspect of the present disclosure is directed to providing an electrophotographic member that has low hardness and fast recovery from deformation. Another aspect of the present disclosure is directed to a method for manufacturing an electrophotographic member that has low hardness and excellent deformation recovery force. Another aspect of the present disclosure is directed to providing a process cartridge that contributes to the formation of high-quality electrophotographic images. Still another aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that can form high-quality electrophotographic images. [Means for solving the problem]

[0008] According to one aspect of the present disclosure, An electrophotographic member comprising a mandrel and an elastic layer provided on the outer periphery thereof, the electrophotographic member is a developing roller, the elastic layer includes a urethane elastomer having a matrix and a plurality of domains dispersed in the matrix; The relationship between a parameter A indicating the viscoelastic term of the domain measured in a viscoelastic image of a cross section of the elastic layer in the thickness direction by a scanning probe microscope and a parameter B indicating the viscoelastic term of the matrix is ​​as follows: A <Bであり、 The elastic layer has a micro rubber hardness of 20 or more and 50 or less at a temperature of 23°C, and in an indentation test of the elastic layer using a nanoindenter at 23°C, a Vickers indenter is pressed at a loading rate of 10 mN / 30 seconds, the load of 10 mN is maintained for 60 seconds, and then the strain 5 seconds after the load is released is 1 μm or less. the law of nature, The measurement mode of the viscoelastic image by the scanning probe microscope is a micro-viscoelastic dynamic force mode, The micro-viscoelastic dynamic force mode is a mode in which a surface topography image is obtained while controlling the distance between the probe and the measurement sample so that the vibration and amplitude of the cantilever are constant while the cantilever is resonated, The cantilever is a silicon microcantilever with a spring constant of 1.9 N / m, and the scanning frequency is 0.5 Hz. Slices were prepared from a total of three cross sections of the elastic layer in the thickness direction, namely, a cross section of the elastic layer at the center in the longitudinal direction of the elastic layer, and a cross section of the elastic layer in the thickness direction at two locations at L / 4 (L is the length of the elastic layer in the longitudinal direction) from both ends of the elastic layer in the longitudinal direction toward the center, to obtain a total of three slices, As the observation regions for observing the viscoelasticity images in the three cross sections, observation regions of 50 μm square were arbitrarily selected in the thickness region from the outer surface of each of the three slices to a depth of 100 μm, and observation was performed in a total of three observation regions. After obtaining the viscoelastic image, when a parameter indicating a viscoelastic term is determined in a domain at 10 points for each of the three observation regions, the average value is parameter A; when a parameter indicating a viscoelastic term is determined in a matrix at 10 points for each of the three observation regions, the average value is parameter B; The unit of the parameter A and the parameter B is mV, and the larger the value, the higher the elasticity. , Characterized by An electrophotographic member is provided.

[0009] According to another aspect of the present disclosure, Electrophotography A process cartridge configured to be detachably mountable to an image forming apparatus, The process cartridge includes a developing roller, The developing roller is The electrophotographic member Yes R 、 Characterized by A process cartridge is provided.

[0010] According to another aspect of the present disclosure, An electrophotographic image forming apparatus having a developing roller, The developing roller is The electrophotographic member Yes R 、 Characterized by An electrophotographic imaging apparatus is provided.

[0011] Furthermore, according to another aspect of the present disclosure, The electrophotographic member Electrophotographic members for manufacturing A method for producing the electrophotographic member is a developing roller, The manufacturing method comprises: (i) reacting a first polyether having at least two isocyanate groups with a first polycarbonate polyol having at least two hydroxyl groups to obtain a urethane reactive emulsifier having at least two hydroxyl groups; (ii) obtaining a dispersion in which droplets containing at least a portion of the urethane reactive emulsifier are dispersed in a second polycarbonate polyol; (iii) obtaining a mixture for forming an elastic layer, the mixture comprising the dispersion and a polyisocyanate having at least two isocyanate groups; and (iv) reacting the urethane reactive emulsifier, the second polycarbonate polyol, and the polyisocyanate in the elastic layer-forming mixture on the surface of the mandrel to obtain the elastic layer; have 、 Characterized by A method for making an electrophotographic member is provided. [Effects of the Invention]

[0012] According to one aspect of the present disclosure, an electrophotographic member having low hardness and fast recovery from deformation can be obtained. According to one aspect of the present disclosure, a method for manufacturing an electrophotographic member having low hardness and fast recovery from deformation can be obtained. Furthermore, according to one aspect of the present disclosure, a process cartridge contributing to the formation of high-quality electrophotographic images can be obtained. Furthermore, according to one aspect of the present disclosure, an electrophotographic image forming apparatus capable of forming high-quality electrophotographic images can be obtained. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view illustrating an example of an electrophotographic member according to one embodiment of the present disclosure. [Figure 2] 1 is a schematic cross-sectional view of one embodiment of an elastic layer of an electrophotographic member according to one aspect of the present disclosure. [Figure 3] 10A and 10B are diagrams illustrating deformation of an elastic layer according to the present disclosure. [Figure 4] FIG. 10 is a diagram illustrating the position and direction of cutting out a cross section. [Figure 5] 1A to 1C are schematic diagrams illustrating a method for manufacturing an electrophotographic member according to one embodiment of the present disclosure. [Figure 6] 1 is a schematic cross-sectional view of an example of an image forming apparatus according to an embodiment of the present disclosure. [Figure 7]1 is a schematic cross-sectional view of an example of a process cartridge according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] In the present disclosure, unless otherwise specified, the expressions "XX to YY" and "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints. Furthermore, when a numerical range is described in stages, any combination of the upper and lower limits of each numerical range is disclosed. In recent years, with the increasing demand for ever-increasing printing speeds and ever-higher quality electrophotographic images, the elastic layers of developing rollers and charging rollers are required to recover faster from deformation. However, according to the inventors' investigations, the urethane elastomer disclosed in Patent Document 1 still lacks a sufficient recovery rate from deformation. Patent Document 1 describes that the compression set of the urethane elastomer disclosed in Patent Document 1 was measured in accordance with Japanese Industrial Standards (JIS) K6301, with compression conditions of 70°C for 22 hours. That is, Patent Document 1 presumably measures the compression set of the urethane elastomer disclosed in Patent Document 1 by compressing it at 70°C for 22 hours, then releasing it from the compressed state and leaving it for 30 minutes, after which the thickness is measured. However, even urethane elastomers exhibiting low compression set in these tests still have a slow recovery rate from deformation required for elastic layers for developing rollers and charging rollers used in high-speed image forming devices. Therefore, the inventors recognized the need to develop an elastic layer that exhibits faster recovery from deformation while maintaining flexibility.

[0015] Generally, lowering the microrubber hardness of an elastic layer increases the compression set and slows the recovery rate from deformation. On the other hand, increasing the elastic modulus of the elastic layer is effective for achieving a low compression set and a fast recovery rate from deformation. However, increasing the elastic modulus of the elastic layer also increases the microrubber hardness. In other words, it has been extremely difficult to achieve a fast recovery rate from deformation while maintaining a low microrubber hardness. To address this issue, the inventors conducted further research. As a result, they discovered that using a polyurethane elastomer incorporating a matrix-domain structure, which has a matrix with a structure that can accelerate the recovery rate from deformation and a domain with a structure that contributes to suppressing an increase in microrubber hardness, as a constituent material for the elastic layer is effective in solving the above-mentioned problem. Hereinafter, preferred embodiments of the electrophotographic member and the like according to the present disclosure will be described in detail.

[0016] <Electrophotographic materials> 1(a) and 1(b) are schematic circumferential cross-sectional views of two embodiments of an electrophotographic member having a roller shape according to the present disclosure (hereinafter also referred to as an "electrophotographic roller"). The electrophotographic roller 1A shown in FIG. 1(a) has an electrically conductive mandrel 2 and an elastic layer 3 covering the surface (outer peripheral surface) of the mandrel 2. The electrophotographic roller 1B shown in FIG. 1(b) further has a surface layer 4 on the surface of the elastic layer 3 opposite to the side facing the mandrel 2 (hereinafter also referred to as the "outer surface"). The electrophotographic roller according to the present disclosure is not limited to these configurations, and may, for example, have an adhesive layer (not shown) between each layer.

[0017] (Core shaft) The shaft core 2 preferably has conductivity in order to supply power to the surface of the electrophotographic member through the shaft core. The electrical resistance value of the shaft core is preferably lower than that of the elastic layer, and the volume resistivity of the shaft core is preferably 103 Ω·cm or less. The conductive shaft core can be appropriately selected and used from those known in the field of electrophotographic members, and those made of metals such as aluminum, aluminum alloy, stainless steel, and iron are preferred. Further, in order to improve corrosion resistance and abrasion resistance, these metals may be subjected to plating treatment such as chromium and nickel. The shape of the shaft core may be any selected from a hollow shape (cylindrical shape) and a solid shape (columnar shape). For example, it is possible to use a solid cylindrical shaft core with a nickel plating layer about 5 μm thick on the surface of a carbon steel alloy. The outer diameter of the cylindrical or columnar shaft core can be appropriately selected according to the image forming apparatus to be mounted.

[0018] (Elastic layer) The elastic layer 2 satisfies the following requirements (1-1) to (1-4). Requirement (1-1): It contains a urethane elastomer, and the urethane elastomer has a matrix-domain structure having a matrix and a plurality of domains dispersed in the matrix. Requirement (1-2): When the parameter indicating the viscoelastic term of the domain measured in the viscoelastic image by a scanning probe microscope of the cross section in the thickness direction of the elastic layer is A, and the parameter indicating the viscoelastic term of the matrix measured in the viscoelastic image is B, A < B. That is, in the cross section in the thickness direction of the elastic layer according to the present disclosure, the matrix-domain structure of the urethane elastomer is observed. And the elastic modulus of the matrix of the urethane elastomer observed in the cross section is larger than the elastic modulus of the domain. Requirement (1-3): The micro rubber hardness of the elastic layer at a temperature of 23 °C is 20 or more and 50 or less. Requirement (1-4): In the indentation test using a nanoindenter at 23 °C of the elastic layer, a Vickers indenter is pushed in at a load rate of 10 mN / 30 seconds, maintained at a load of 10 mN for 60 seconds, and then unloaded. When unloaded, the strain 5 seconds after unloading is 1 μm or less. In the urethane elastomer according to the present disclosure, the matrix has the function of recovering from deformation, and the domains have the function of reducing the hardness of the urethane elastomer. By using such a urethane elastomer, the elastic layer according to the present disclosure exhibits the softness specified in the above requirement (1-3) and the fast recovery from deformation specified in the above requirement (1-4). On the other hand, even in general urethane elastomers, there is a difference in elastic modulus between the so-called hard segment and the soft segment. However, it is believed that there has not been a urethane elastomer that has the flexibility required by the above requirement (1-3) while also exhibiting the fast recovery rate from deformation required by requirement (1-4).

[0019] Fig. 2(a) is a partial cross-sectional view in the circumferential direction of an electrophotographic roller 1A according to one embodiment of the present disclosure, and Fig. 2(b) is a partial cross-sectional view in the longitudinal direction of a mandrel 2 of the electrophotographic roller 1A. Figures 2(a) and 2(b) show a schematic diagram of the matrix 31 of the urethane elastomer according to the present disclosure and multiple domains 32 dispersed in the matrix 31, as observed in a cross section of the elastic layer 3 in the thickness direction. As described above, the polyurethane elastomer has a matrix-domain structure comprising a matrix 31 and domains 32 dispersed within the matrix. The matrix 31 has a structure that can accelerate the deformation recovery rate, and the domains 32 have a structure that contributes to suppressing an increase in micro-rubber hardness. As a result, the matrix exhibits higher elasticity than the domains. Figures 3(a) and 3(b) are explanatory diagrams of the deformation recovery of the elastic layer 3 according to the present disclosure. As shown in Figure 3(a), multiple domains 32 are dispersed within the matrix 31. Because the domains 32 have lower elasticity than the matrix 31, when the elastic layer 3 is compressed in the direction of arrow F, as shown in Figure 3(b), the domains 32 deform preferentially. Therefore, even if the matrix 31 has high elasticity, the micro-rubber hardness of the elastic layer can be reduced. Furthermore, when the elastic layer is released from compression, the elasticity of the matrix 31, which is the continuous phase, allows the elastic layer to quickly return to its original thickness before compression.

[0020] (Micro rubber hardness of elastic layer) The hardness of the elastic layer is 20 or more and 50 or less in micro rubber hardness. By setting the micro rubber hardness to 50 or less, the nip width between the developing roller and the toner regulating member and the nip width between the charging roller and the photosensitive member are increased, preventing excessive contact pressure. This makes it less likely that toner on the developing roller will fuse to the developing roller, or that toner that has slipped through the cleaning member and adhered to the charging roller will fuse to the charging roller. Furthermore, by setting the micro rubber hardness to 20 or more, the mechanical strength is increased, making the edges of the elastic layer less likely to be worn away, even when used in long-life image forming devices. The micro rubber hardness is determined as follows. The locations for measuring the micro rubber hardness are three: the center of the elastic layer in the longitudinal direction, and two locations at L / 4 from both ends of the elastic layer toward the center, where L is the longitudinal length of the elastic layer. At each measurement location, the surface is measured at 23°C using a micro rubber hardness meter (product name: MD-1capa; manufactured by Kobunshi Keiki Co., Ltd.; indenter: Type A (cylindrical, diameter 0.16 mm, height 0.5 mm, outer diameter 4 mm, inner diameter 1.5 mm); measurement mode: peak hold mode), and the average value is calculated. This calculated average value is the micro rubber hardness in this disclosure.

[0021] (Parameter indicating the viscoelastic term) The difference in the relative elastic modulus between the matrix 31 and the domains 32 can be measured by cutting the elastic layer into thin slices and using a scanning probe microscope (SPM / AFM). Examples of scanning probe microscopes that can be used include "S-Image" (product name) manufactured by Hitachi High-Tech Science Corporation. Examples of methods for cutting into thin slices include a sharp razor, a microtome, and a focused ion beam (FIB) method. As shown in Figure 4, three slices were prepared from cross sections 41 to 43 in the thickness direction of the elastic layer, one at the center of the elastic layer in the longitudinal direction and the other at L / 4 from both ends of the elastic layer toward the center, where L is the longitudinal length of the elastic layer. Furthermore, the region that deforms when the electrophotographic member contacts another member is primarily the thickness region from the outer surface of the elastic layer to a depth of 100 μm. Therefore, for the observation regions of cross sections 41 to 43, a 50 μm square observation region was arbitrarily selected from the thickness region from the outer surface to a depth of 100 μm of each slice, and viscoelastic images were observed in a total of three observation regions. The measurement mode for the viscoelastic image using SPM was the Viscoelastic Dynamic Force Mode (VE-DFM). The cantilever used was a silicon microcantilever for DMF (SI-DF3 (product name), manufactured by Hitachi High-Tech Science Corporation, spring constant = 1.9 N / m). The scanning frequency was 0.5 Hz. Note that VE-DFM is a mode in which a surface topography image is obtained by controlling the distance between the probe and the sample to maintain a constant cantilever vibration and amplitude while the cantilever is resonating. After obtaining the viscoelastic image, parameters indicating the viscoelastic term were determined for 10 points each for the matrix and domain in each observation region, and their average values ​​were designated as parameter A indicating the viscoelastic term of the domain and parameter B indicating the viscoelastic term of the matrix in this disclosure. Note that the units of parameters A and B are mV, and the larger the value, the higher the elasticity. The ratio (A / B) of parameter A to parameter B is preferably 0.65 or less. The smaller the A / B, the greater the difference in viscoelasticity between the matrix and the domain, making it easier to achieve both hardness and recovery from deformation.

[0022] (Recovery from deformation) In an indentation test using a nanoindenter at a temperature of 23°C, the elastic layer 3 is indented with a Vickers indenter at a loading rate of 10 mN / 30 seconds, and the load of 10 mN is maintained for 60 seconds. After the load is released, the strain of the elastic layer 3 is 1 μm or less 5 seconds after the load is released. By keeping the strain after 5 seconds of unloading measured under the above conditions to 1 μm or less, streak-like image defects can be suppressed when used as a developing roller in a high-speed printer. This is because the deformation of the developing roller can recover to less than the size of a single toner particle in the short time between starting the high-speed printer and developing the electrostatic latent image. Furthermore, even when used as a charging roller, the fast recovery from deformation makes it less likely for uneven discharge to occur on the photoreceptor, preventing the occurrence of streak-like image defects caused by uneven charging of the photoreceptor. In this disclosure, a "Fisherscope HM2000" (product name, manufactured by Fisher Instruments Inc.) is used as the nanoindenter, and measurements taken at a temperature of 23°C are taken. The indenter used for the measurements is a square pyramidal Vickers indenter with an opposing angle of 136°. Furthermore, the measurement positions are three in total: the center of the elastic layer in the longitudinal direction, and two positions at L / 4 from both ends of the elastic layer toward the center, where L is the longitudinal length of the elastic layer. The average value of measurements taken using the nanoindenter at each measurement position is taken as the strain 5 seconds after unloading in this disclosure.

[0023] (Matrix elastic modulus) The elastic modulus of the matrix 31 is preferably 2 MPa or more and 8 MPa or less. By making the elastic modulus of the matrix 2 MPa or more, the effect of the matrix as a spring is increased, and it is possible to speed up recovery from deformation. Furthermore, by making the elastic modulus of the matrix 8 MPa or less, the hardness of the matrix is ​​reduced, and it is possible to keep the micro-rubber hardness of the elastic layer low. The elastic modulus of the matrix can be measured by cutting the elastic layer into thin sections and using a scanning probe microscope (SPM / AFM). Examples of scanning probe microscopes that can be used include the Oxford Instruments MFP-3D-Origin (trade name). Examples of methods for cutting thin sections include a sharp razor, a microtome, and focused ion beam (FIB). As shown in Figure 4, three sections were prepared in the thickness direction of the elastic layer, one at the center of the elastic layer and the other at L / 4 from both ends of the elastic layer toward the center, where L is the longitudinal length of the elastic layer. Regarding the observation regions of cross sections 41-43, a 50-μm square observation region was arbitrarily selected within the thickness region from the outer surface to a depth of 100 μm on each section, and phase images were observed in a total of three observation regions. The phase image measurement mode using the SPM was AM-FM. The cantilever used was a dynamic mode silicon cantilever, such as the "OMCL-AC-160TS" (product name, manufactured by Olympus Corporation, spring constant = 47.08 N / m). The scanning frequency was 0.5 Hz. After acquiring the phase image, a force curve is measured using an SPM to measure the elastic modulus of the matrix. The force curve measurement mode is contact mode, with a force distance of 500 nm and a trigger point of 0.01 V. The cantilever used is a silicon cantilever for dynamic mode, such as the "OMCL-AC-160TS" (trade name, manufactured by Olympus Corporation, spring constant = 47.08 N / m), as described above. The scanning frequency is 1 Hz. The elastic modulus of the matrix was measured at 10 points in each observation region, and the average value was taken as the elastic modulus of the matrix in the present disclosure.

[0024] (Cross-sectional area and number of domains) The cross-sectional area and number of domains 32 of the polyurethane elastomer observed in a cross section of the elastic layer in the thickness direction will be described. When the longitudinal length of the elastic layer is L, three locations are designated: the longitudinal center of the elastic layer, and L / 4 from both ends of the elastic layer toward the center. For each of these three locations on the cross section of the elastic layer in the thickness direction, when a 50 μm square observation area is arbitrarily placed in the thickness region from the outer surface of the elastic layer to a depth of 100 μm, it is preferable that all three observation areas satisfy the following requirements (2-1) and (2-2). Requirement (2-1): The ratio of the sum of the cross-sectional areas of the domains present in the observation area to the area of ​​the observation area is 15% or more and 45% or less. Requirement (2-2): When the cross-sectional area of ​​each domain present in the observation area is calculated, the number of domains having a cross-sectional area of ​​0.1% or more and 13.0% or less of the area of ​​the observation area accounts for 70% or more by number of the total number of domains present in the observation area. Regarding the above requirement (2-1), by setting the ratio of the total cross-sectional area of ​​the domains to the area of ​​the observation region to 15% or more, the micro-rubber hardness of the elastic layer can be kept low. Furthermore, by setting this ratio to 45% or less, the elastic layer can recover quickly from deformation. Regarding requirement (2-2), by setting the number of domains having a cross-sectional area of ​​0.1 to 13.0% of the area of ​​the observation region to 70% or more of the total number of domains in the observation region, the number of domains large enough to deform sufficiently when the elastic layer is pressed against them is ensured. This allows the micro-rubber hardness of the elastic layer to be reduced. Furthermore, because the number of large domains that would deform excessively when a load is applied to the elastic layer is reduced, the micro-rubber hardness of the elastic layer can be prevented from becoming too low. The cross-sectional area and number of domains are determined as follows. First, slices are prepared using the same method as used to measure the elastic modulus of the matrix. The slices are prepared at two locations: the center of the elastic layer in the longitudinal direction and at a distance of L / 4 from both ends of the elastic layer toward the center, as shown in Figure 4. These locations expose cross sections 41, 42, and 43 of the elastic layer in the full thickness direction. Next, a 50-μm square observation area is set at any position within the thickness region of each slice, extending from the outer surface of the elastic layer to a depth of 100 μm. The cross-sectional area, number, and circularity of the domains are then measured for a total of three observation areas.

[0025] The cross-sectional area and number of domains in the observation region can be measured as follows. First, the cross section is observed using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a scanning probe microscope (SPM / AFM). The obtained cross-sectional image is converted into a 256-level monochrome image using image processing software such as "ImageProPlus" (product name, manufactured by MediaCybernetics). Next, a binarization process is performed using the image processing software to obtain a binary image. The binarization method is not particularly limited as long as it is possible to distinguish between domains and matrices in the monochrome image. For example, a method of setting a binarization threshold based on the Otsu algorithm described in Non-Patent Document 1 from the luminance distribution of the monochrome image can be used. Next, the counting function of the image processing software is used to obtain the cross-sectional area and number of domains present in the observation area of ​​the binarized image. Note that the obtained binarized image for analysis may contain minute dots due to noise. When analyzing a binarized image containing such minute dots due to noise using image processing software, the noise-derived dots may also be counted as domains. Therefore, among the domains determined to be domains using the counting function, domains with a cross-sectional area of ​​less than 0.05% of the 50 μm square observation area are preferably considered to be noise-derived domains and deleted from the data.

[0026] (Domain circularity) Furthermore, it is preferable that the number of domains of the polyurethane elastomer observed in a cross section of the elastic layer in the thickness direction have a circularity of 0.60 or more and 0.95 or less, and the proportion of the number of domains that exist in the observation area is 70% or more by number. When a domain has a circularity of a certain level or higher, anisotropy is unlikely to occur in the direction of recovery of the domain shape when the domain recovers from deformation. Furthermore, a large number (proportion) of domains with a circularity of a certain level or higher makes it unlikely for anisotropy to occur in the recovery of the elastic layer from deformation. As a result, wrinkles and other defects caused by anisotropy in the recovery of deformation are unlikely to occur in the elastic layer after recovery from deformation. Here, the circularity and number of domains can be determined by using the counting function of the image processing software at the same time as measuring the cross-sectional area and number of domains.

[0027] (Elastic layer material) A polyurethane elastomer capable of realizing the elastic layer according to the present disclosure will now be described. As described above, the polyurethane elastomer according to the present disclosure has a matrix-domain structure having a matrix 31 and domains 32 dispersed in the matrix. The matrix 31 has a structure that can increase the deformation recovery speed, and the domains 32 have a structure that contributes to suppressing an increase in micro rubber hardness. Such a polyurethane elastomer matrix 31 preferably has a polycarbonate structural unit represented by general formula (1) as a repeating structural unit. Furthermore, the alkylene group having 3 to 9 carbon atoms represented by R1 in the repeating structural unit represented by general formula (1) more preferably has a branched structure.

[0028] [ka] (R1 represents an alkylene group having 3 to 9 carbon atoms.)

[0029] In general, polyurethane obtained by reacting a polyol having a polycarbonate structure (polycarbonate polyol) with a polyisocyanate exhibits high elasticity due to the strong intermolecular forces between carbonate groups, and is therefore a preferred component of the matrix 31. When R1 is an alkylene group having 3 to 9 carbon atoms, incompatibility with domains containing polyether repeating structural units represented by general formula (2) described below is ensured, and clear phase separation between the matrix and the domains can be achieved. This allows the polyurethane elastomer according to the present disclosure to more reliably exhibit its two functions of softness and fast recovery from deformation. Furthermore, when R1 contains an alkylene group having a branched structure and 3 to 9 carbon atoms, the intermolecular force between carbonate groups is moderately suppressed, and the matrix can be prevented from becoming excessively elastic. R1 is, for example, -(CH2) m -(m=3 to 9), -CH2C(CH3)2CH2-, -CH2CH(CH3)CH2-, -(CH2)2CH(CH3)(CH2)2-, etc. These can be used alone or in combination of two or more. The number average molecular weights of the polycarbonate and the polyols described below can all be calculated using the hydroxyl value (mgKOH / g) and valence according to the following formula: For example, the number average molecular weight of a polyether polyol with a hydroxyl value of 56.1 mgKOH / g and a valence of 2 can be calculated to be 2,000. Number average molecular weight = 56.1 x 1000 x valence ÷ hydroxyl value The elastic modulus of the matrix can be adjusted by, for example, increasing the crosslink density using a polyisocyanate trimer compound or polymer compound. Normally, increasing the elastic modulus also increases the micro rubber hardness of the elastic layer, but in the present disclosure, multiple low-elasticity domains are dispersed in the matrix, making it possible to prevent excessive hardness.

[0030] It is preferable that domain 32 contains a polyether structural unit represented by general formula (2) as a repeating structural unit. Furthermore, it is more preferable that the alkylene group having 3 to 5 carbon atoms represented by R2 in the structural unit represented by general formula (2) has a branched structure.

[0031] [ka] (R2 represents an alkylene group having 3 to 5 carbon atoms.)

[0032] Generally, polyethers are preferred as components of the domains because they exhibit a low modulus of elasticity due to weak intermolecular forces between ether groups. By containing an alkylene group having 3 to 5 carbon atoms, incompatibility with the urethane elastomer having the polycarbonate structural unit represented by general formula (1) is ensured, and clear phase separation between the matrix and the domain is achieved, which is preferable. Examples of R2 include -(CH2)m- (m = 3 to 5), -CH2CH(CH3)-, -CH2C(CH3)2CH2-, -CH2CH(CH3)CH2-, -(CH2)2CH(CH3)CH2-, etc. These can be used alone or in combination of two or more. The number average molecular weight of the polyether structural unit represented by general formula (2) is preferably 1,000 or more and 50,000 or less, and more preferably 1,200 or more and 30,000 or less. A number-average molecular weight of 1,000 or more is preferred because it ensures incompatibility with the urethane elastomer containing the polycarbonate structural unit represented by general formula (1) and makes the phase separation between the matrix and the domains clearer. A number-average molecular weight of 50,000 or less is preferred because it facilitates the formation of domains and stabilizes the phase separation morphology. The proportion of the total cross-sectional area of ​​the domains can be adjusted, for example, by changing the compounding ratio of the urethane elastomer containing the polycarbonate structural unit of general formula (1) in the matrix to the polyether structural unit of general formula (2) in the domains. Increasing the compounding ratio of the polyether structural unit of general formula (2) increases the proportion of the total cross-sectional area of ​​the domains. However, if the compounding ratio of the polyether structural unit of general formula (2) is increased too much, the matrix and domains may be inverted, and the polyether structural unit of general formula (2) may become the main component of the matrix. In addition, the cross-sectional area of ​​the domains can be increased, for example, by increasing the number-average molecular weight of the polyether structural unit of general formula (2). The chemical structures of the components contained in the matrix and the domains can be analyzed using, for example, spectroscopic analyzers such as an AFM infrared spectroscopic analyzer, a microscopic infrared spectroscopic analyzer, or a microscopic Raman spectroscopic analyzer, or a mass spectrometer.

[0033] (Method of manufacturing polyurethane elastomer) An example of the method for producing the polyurethane elastomer described above includes a method comprising the following steps (i) to (iii). Step (i) reacting a first polyether having at least two isocyanate groups with a first polycarbonate polyol having at least two hydroxyl groups to obtain a urethane reactive emulsifier having at least two hydroxyl groups. Step (ii) obtaining a dispersion in which droplets containing at least a portion of the urethane reactive emulsifier are dispersed in a second polycarbonate polyol. Step (iii) A step of preparing a mixture for forming an elastic layer containing the dispersion obtained in step (ii) and a polyisocyanate having at least two isocyanate groups, and then reacting the urethane reactive emulsifier, the second polycarbonate polyol, and the polyisocyanate in the mixture for forming an elastic layer.

[0034] Each step of the above manufacturing method will be explained with reference to FIG. In step (i), a first polyether 51 having at least two isocyanate groups is mixed with a first polycarbonate polyol 52 having at least two hydroxyl groups. The isocyanate groups and hydroxyl groups in the mixture are reacted in the presence of a catalyst to link them via a urethane bond, thereby obtaining a urethane-reactive emulsifier 53 having at least two hydroxyl groups. In step (ii), the urethane reactive emulsifier 53 obtained in step (i) is dispersed in a second polycarbonate polyol 55. The segments derived from the first polyether 51 contained in the urethane reactive emulsifier 53 are not compatible with the second polycarbonate polyol 55 and form droplets 54. Meanwhile, droplets 54 containing segments derived from the first polyether constituting part of the urethane reactive emulsifier are uniformly and stably dispersed in the second polycarbonate polyol 55 via the segments derived from the first polycarbonate polyol 52 contained in the urethane reactive emulsifier 53. As a result, a dispersion is obtained in which droplets 54 containing segments derived from the first polyether 51 of the urethane reactive emulsifier 53 are dispersed in the second polycarbonate polyol 55. Note that for the sake of explanation, steps (i) and (ii) are described separately, but these steps may also be a continuous series of steps.

[0035] In step (ii), the second polycarbonate polypolyol 55 in which the droplets 54 are dispersed can be the unreacted product of the first polycarbonate polyol used in step (i) with the first polyether. That is, by using an excess amount of the first polycarbonate polyol relative to the first polyether in step (i), it is possible to obtain the dispersion described in step (ii) in which the urethane reactive emulsifier 53 is dispersed in the excess first polycarbonate polyol, i.e., the second polycarbonate polyol 55. Even when an excess amount of the first polycarbonate polyol is used, it is possible to add additional polycarbonate polyol (second polycarbonate polyol) as a dispersion medium for the urethane reactive emulsifier. In this case, the added polycarbonate polyol may have the same chemical composition as the first polycarbonate polyol used in step (i), or it may have a different chemical composition.

[0036] On the other hand, in step (i), when the first polycarbonate polyol and the first polyether are reacted in equivalent amounts and the first polycarbonate polyol is completely consumed, a new polycarbonate polyol is used as the second polycarbonate polyol to prepare a dispersion in step (ii). In this case, the polycarbonate polyol used as the second polycarbonate polyol may have the same chemical composition as the first polycarbonate polyol or may have a different chemical composition.

[0037] Finally, in step (iii), an elastic layer-forming mixture is prepared, containing the dispersion prepared in step (ii) and a polyisocyanate 56 having at least two isocyanate groups. Next, the terminal hydroxyl groups of the urethane-reactive emulsifier 53 in the elastic layer-forming mixing section, the hydroxyl groups of the second polycarbonate polyol 55, and the isocyanate groups of the polyisocyanate 56 are reacted. Thus, a network structure is formed via urethane bonds, and the elastic layer-forming mixture is cured to obtain a polyurethane elastomer according to the present disclosure. The polyurethane elastomer 500 thus obtained has a matrix-domain structure in which domains 32 containing polyether derived from the first polyether 51 are dispersed in a matrix 31 containing a urethane elastomer having a polycarbonate derived from the first polycarbonate polyol 52 and the second polycarbonate polyol 55. Furthermore, the domains 32 are primarily composed of polyether structural moieties, and the interior of the domains can be substantially free of crosslinked structures. In other words, the domains 32 can be present in a substantially liquid state in the matrix, which allows the domains to have a low modulus of elasticity in the polyurethane elastomer according to the present disclosure.

[0038] Furthermore, the domains are not simply liquid portions confined within the matrix; rather, the domains and the matrix are chemically bonded by urethane bonds at their boundaries. Therefore, when a load applied to the polyurethane elastomer is removed, the recovery of the domains from deformation can be linked to the recovery of the matrix from deformation. That is, the substantially liquid domains have substantially no internal crosslinking structure. Therefore, it is difficult for domains deformed by the application of a load to a polyurethane elastomer to autonomously recover from the deformation. However, in the polyurethane elastomer according to the present disclosure, the domains are chemically bonded to the matrix at their boundaries, allowing the domains to recover from deformation together with the recovery of the matrix. This allows stable deformation (deformation amount) and stable recovery from the deformation to be achieved even when the polyurethane elastomer is repeatedly subjected to loading and unloading.

[0039] The above steps (i) and (ii) are steps for stably dispersing a polyether, which is inherently difficult to disperse stably and uniformly due to its low compatibility, in a polyol. That is, a first polyether 51 is reacted with a first polycarbonate polyol 52 to produce a urethane-reactive emulsifier 53. This is a step for obtaining a dispersion in which polyether segments derived from the first polyether 51 are stably and uniformly dispersed in a second polycarbonate polyol. This makes it possible to prepare a polyurethane elastomer in which domains 32 with high circularity and small sizes on the order of micrometers and a relatively uniform size distribution are dispersed in a polyurethane 31 matrix. Another method for mixing materials with low compatibility is, for example, mixing and dispersing them under high shear force. However, this method applies high shear force to the polyether, resulting in distorted domain shapes, reduced circularity, and uneven domain size. Furthermore, the dispersion state is unstable, and aggregation of domains progresses over a relatively long period of time. Furthermore, the incompatibility between the polyether and polycarbonate polyol is not ensured, and the phase separation between the matrix and domains of the resulting urethane elastomer becomes unclear. Therefore, it is difficult to obtain a polyurethane elastomer that provides an elastic body with flexibility and excellent deformation recovery, as disclosed herein.

[0040] The first polyether has at least two isocyanate groups and has a repeating structural unit represented by general formula (2). The first polyether can be obtained, for example, by a process of reacting a polyether polyol having at least two hydroxyl groups and having a repeating structural unit represented by general formula (2) with a polyisocyanate having at least two isocyanate groups. Examples of polyether polyols include polyether polyols containing an alkylene structure, such as polypropylene glycol, polytetramethylene glycol, a copolymer of tetrahydrofuran and neopentyl glycol, and a copolymer of tetrahydrofuran and 3-methyltetrahydrofuran, as well as random or block copolymers of these polyalkylene glycols, which can be used alone or in combination of two or more. Among polyether polyols, amorphous polyether polyols are preferred from the viewpoints of incompatibility with the second polycarbonate polyol and the ability to achieve low hardness. More preferably, the liquid contains at least one selected from polypropylene glycol, a copolymer of tetrahydrofuran and neopentyl glycol, and a copolymer of tetrahydrofuran and 3-methyltetrahydrofuran. The number-average molecular weight of the polyether polyol is preferably 1,000 or more and 50,000 or less, and more preferably 1,200 or more and 30,000 or less. A number-average molecular weight of 1,000 or more is preferred because it ensures incompatibility with the polycarbonate polyol and makes the phase separation between the matrix and domains of the resulting urethane elastomer clear. Furthermore, a number-average molecular weight of 50,000 or less is preferred because it facilitates domain formation and stabilizes the phase separation morphology.

[0041] Examples of polyisocyanates to be reacted with polyether polyols include pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, trimer compounds (isocyanurates) of these polyisocyanates, polymeric compounds, allophanate-type polyisocyanates, biuret-type polyisocyanates, water-dispersible polyisocyanates, etc. These polyisocyanates can be used alone or in combination of two or more. Among polyisocyanates, a bifunctional isocyanate having two isocyanate groups is preferred because of its high compatibility with the first polyether and ease of adjusting physical properties such as viscosity. More preferred is at least one selected from hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate. In the step of reacting the polyether polyol with the polyisocyanate, the isocyanate index is preferably in the range of 1.2 to 5.0. Having an isocyanate index in this range reduces the amount of components derived from the first polyether that remain without forming a network structure, and suppresses the exudation of liquid substances from the urethane elastomer. The isocyanate index indicates the ratio ([NCO] / [OH]) of the number of moles of isocyanate groups in the isocyanate compound to the number of moles of hydroxyl groups in the polyol compound. The first polyether obtained by the reaction of polyether polyol and polyisocyanate has a structure in which hydroxyl groups and isocyanate groups are linked via urethane bonds formed by the reaction. Its number average molecular weight is preferably 1,000 or more and 50,000 or less, more preferably 1,200 or more and 30,000 or less.

[0042] The first polycarbonate polyol is a polycarbonate polyol having at least two hydroxyl groups and a repeating structural unit represented by general formula (1). Examples of the first polycarbonate polyol include a reaction product of a polyhydric alcohol and phosgene, and a ring-opening polymerization product of a cyclic carbonate ester (such as an alkylene carbonate). Examples of polyhydric alcohols include propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylene diol, 1,3-tetramethylene diol, 2-methyl-1,3-trimethylene diol, 1,5-pentamethylene diol, neopentyl glycol, 1,6-hexamethylene diol, 3-methyl-1,5-pentamethylene diol, 2,4-diethyl-1,5-pentamethylene diol, glycerin, trimethylolpropane, trimethylolethane, cyclohexanediols (such as 1,4-cyclohexanediol), and sugar alcohols (such as xylitol and sorbitol). Examples of alkylene carbonates include trimethylene carbonate, tetramethylene carbonate, and hexamethylene carbonate. The number-average molecular weight of the first polycarbonate polyol is preferably 500 or more and 10,000 or less, and more preferably 700 or more and 8,000 or less. When the number-average molecular weight is 500 or more, incompatibility with domains containing polyether repeating structural units represented by general formula (2) is ensured, and phase separation between the matrix and the domains can be made clearer. Furthermore, by setting the number-average molecular weight to 10,000 or less, an excessive increase in viscosity of the first polycarbonate polyol can be prevented. The second polycarbonate polyol used in step (ii) may be any of the polycarbonate polyols listed above for the first polycarbonate polyol. As described above, the first polycarbonate polyol and the second polycarbonate polyol may have the same chemical composition, or may be different from each other.

[0043] The polyisocyanate 56 having at least two isocyanate groups used in step (iii) may be the same as the polyisocyanates exemplified above as the raw material for the first polyether. These polyisocyanates may be used alone or in combination of two or more. From the viewpoint of increasing the elastic modulus of the matrix, the polyisocyanate 56 preferably includes a polyisocyanate having at least three isocyanate groups, such as a polyisocyanate trimer compound (isocyanurate), a polyisocyanate multimer compound, an allophanate polyisocyanate, or a biuret polyisocyanate, among the polyisocyanates exemplified above. More preferably, the polyisocyanate 56 includes any of a pentamethylene diisocyanate trimer compound (isocyanurate), a hexamethylene diisocyanate trimer compound (isocyanurate), and a diphenylmethane diisocyanate multimer compound.

[0044] As the catalyst, a conventionally known urethane catalyst or isocyanurate catalyst (isocyanate trimerization catalyst) can be used. These may be used alone or in combination. Examples of urethanization catalysts include tin-based urethanization catalysts such as dibutyltin dilaurate and stannous octoate, and amine-based urethanization catalysts such as triethylenediamine, tetramethylguanidine, pentamethyldiethylenetriamine, diethylimidazole, tetramethylpropanediamine, N,N,N'-trimethylaminoethylethanolamine and 1,4-diazabicyclo[2.2.2]octane-2-methanol. These may be used alone or in combination. Examples of isocyanurate catalysts include metal oxides such as LiO and (BuSn)O; hydride compounds such as NaBH; alkoxide compounds such as NaOCH, KO-(t-Bu), and borates; amine compounds such as N(C2H5)3, N(CH3)2CH2C2H5, and 1,4-ethylenepiperazine (DABCO); alkaline carboxylate salt compounds such as HCOONa, Na2CO3, PhCOONa / DMF, CH3COOK, (CH3COO)2Ca, alkali soap, and naphthenate; alkaline formate compounds; and quaternary ammonium salt compounds such as ((R)3-NR'OH)-OCOR". Furthermore, examples of combined catalysts (co-catalysts) used as isocyanurate catalysts include amine / epoxide, amine / carboxylic acid, and amine / alkyleneimide. These isocyanurate catalysts and combined catalysts may be used alone or in combination.

[0045] In the production method according to the present disclosure, a chain extender (a polyfunctional low-molecular-weight polyol) may be used as needed. Examples of chain extenders include glycols having a number-average molecular weight of 1,000 or less. Examples of glycols include ethylene glycol (EG), diethylene glycol (DEG), propylene glycol (PG), dipropylene glycol (DPG), 1,4-butanediol (1,4-BD), 1,6-hexanediol (1,6-HD), 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, xylylene glycol (terephthalyl alcohol), and triethylene glycol. Examples of chain extenders other than glycols include trihydric or higher polyhydric alcohols. Examples of trihydric or higher polyhydric alcohols include trimethylolpropane, glycerin, pentaerythritol, and sorbitol. These may be used alone or in combination. If necessary, additives such as pigments, plasticizers, waterproofing agents, antioxidants, conductive agents, ultraviolet absorbers, and light stabilizers may also be used in combination.

[0046] (Method of manufacturing elastic layer) The elastic layer can be formed, for example, by carrying out the reaction according to step (iii) in the above-described method for producing a polyurethane elastomer on the surface of the mandrel. Specifically, for example, a method of curing an elastic layer-forming mixture containing the dispersion prepared in the step (ii) and a polyisocyanate having at least two isocyanate groups on the circumferential surface of a mandrel can be mentioned. That is, the elastic layer according to the present disclosure can be produced by a method including, for example, the following steps (2-i) to (2-iv). Step (2-i) a step of reacting a first polyether having at least two isocyanate groups with a first polycarbonate polyol having at least two hydroxyl groups to obtain a urethane reactive emulsifier having at least two hydroxyl groups; Step (2-ii) a step of obtaining a dispersion in which droplets containing at least a portion of the urethane reactive emulsifier are dispersed in a second polycarbonate polyol; Step (2-iii) mixing the dispersion and a polyisocyanate having at least two isocyanate groups to obtain a mixture for forming an elastic layer; and and step (2-iv) reacting the urethane reactive emulsifier in the elastic layer-forming mixture, the second polycarbonate polyol, and the polyisocyanate on the surface of the mandrel to obtain the elastic layer. The method of hardening the elastic layer-forming mixture on the surface of the mandrel may be, for example, a method of injecting the material for the elastic layer into a mold in which a cylindrical pipe, a piece for holding the mandrel, and the mandrel are arranged, and then hardening by heating (cast molding method). Alternatively, a method of applying the elastic layer-forming mixture on the surface of the mandrel to form a coating film, and then hardening the coating by heating may be used.

[0047] (Surface layer) A surface layer can be provided on the surface of the elastic layer as needed. Materials for forming the surface layer include resin, natural rubber, and synthetic rubber. Thermosetting resin or thermoplastic resin can be used as the resin. In particular, fluororesin, polyamide resin, acrylic resin, polyurethane resin, silicone resin, or butyral resin is preferred as the resin because it is easy to control the viscosity of the paint. These resins can be used alone or in combination of two or more types. They may also be copolymers. The surface layer may contain a conductive agent to adjust the electrical resistance of the electrophotographic roller, and the volume resistivity of the surface layer may be adjusted by an ionic conductive agent or an electronic conductive agent.

[0048] Examples of ionic conductive agents include: inorganic ionic substances such as lithium perchlorate, sodium perchlorate, and calcium perchlorate; cationic surfactants such as lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, trioctyl propyl ammonium bromide, and modified aliphatic dimethyl ethyl ammonium ethosulfate; zwitterionic surfactants such as lauryl betaine, stearyl betaine, and dimethyl alkyl lauryl betaine; quaternary ammonium salts such as tetraethyl ammonium perchlorate, tetrabutyl ammonium perchlorate, and trimethyl octadecyl ammonium perchlorate; and organic acid lithium salts such as lithium trifluoromethanesulfonate. These may be used alone or in combination.

[0049] Examples of electronic conductive agents include: fine particles and fibers of metals such as aluminum, palladium, iron, copper, and silver; conductive metal oxides such as titanium oxide, tin oxide, and zinc oxide; composite particles in which the surfaces of the above-mentioned metal fine particles, fibers, and metal oxides are treated by electrolysis, spray coating, or mixing and shaking; and carbon powders such as furnace black, thermal black, acetylene black, ketjen black, PAN (polyacrylonitrile)-based carbon, and pitch-based carbon.

[0050] The surface layer may also contain other particles. Examples of such other particles include insulating particles. Examples of insulating particles include: polyamide resin, silicone resin, fluororesin, (meth)acrylic resin, styrene resin, phenolic resin, polyester resin, melamine resin, urethane resin, olefin resin, epoxy resin, copolymers, modified products, and derivatives thereof; rubbers such as ethylene-propylene-diene copolymer (EPDM), styrene-butadiene copolymer rubber (SBR), silicone rubber, urethane rubber, isoprene rubber (IR), butyl rubber, acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), and epichlorohydrin rubber; polyolefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, polystyrene-based thermoplastic elastomers, fluororubber-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polybutadiene-based thermoplastic elastomers, ethylene-vinyl acetate-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, and chlorinated polyethylene-based thermoplastic elastomers. Among these, (meth)acrylic resins, styrene resins, urethane resins, fluorine resins, and silicone resins are particularly preferred.

[0051] The materials constituting these surface layers can be dispersed using a conventionally known dispersing device that utilizes beads such as a sand mill, a paint shaker, a Dyno Mill, or a pearl mill. The method for applying the resulting dispersion is not particularly limited, but a dipping method is preferred because of its simple operation.

[0052] <Electrophotographic image forming apparatus> FIG. 6 shows a schematic configuration of an example of an electrophotographic image forming apparatus equipped with an electrophotographic member according to an embodiment of the present disclosure. In FIG. 6, the image forming apparatus includes a photosensitive member 61, a charging device, a latent image forming device, a developing device, a transfer device, a cleaning device, and a fixing device. The photoreceptor 61 is a rotating drum having a photosensitive layer on a conductive substrate, and is driven to rotate in the direction of the arrow at a predetermined peripheral speed (process speed). The charging device has a function of charging the photosensitive member 61, and has a contact-type charging roller 62 that is placed in contact with the photosensitive member 61 by being pressed against the photosensitive member 61 with a predetermined pressing force. The charging roller 62 rotates in the direction of the arrow in accordance with the rotation of the photosensitive member 61. The charging roller 62 charges the photosensitive member 61 to a predetermined potential by applying a predetermined DC voltage from a charging power source 63. A latent image forming device (not shown) performs exposure to light to form an electrostatic latent image on the photoreceptor 61. An exposure device such as a laser beam scanner is used as the latent image forming device. The latent image forming device forms an electrostatic latent image by irradiating the uniformly charged photoreceptor 61 with exposure light 64 corresponding to image information. The developing device has a function of developing a toner image, and includes a developing roller 65 disposed in close proximity to or in contact with the photosensitive member 61. The developing roller 65 develops the electrostatic latent image by reversal development using toner that has been electrostatically treated to have the same polarity as the charge polarity of the photosensitive member 61, thereby forming a toner image on the photosensitive member 61. The transfer device has a function of transferring the developed toner image onto recording material P, and has a contact-type transfer roller 66. The transfer roller 66 rotates in the direction of the arrow in accordance with the rotation of the photosensitive member 61, and transfers the toner image from the photosensitive member 61 onto recording material P, such as plain paper. The transfer material P is transported in the direction of the arrow by a paper feed system (not shown) having a transport member. The cleaning device has a function of collecting residual toner remaining on the photosensitive member 61, and includes a blade-type cleaning member 68 and a collection container 69. After the toner image is transferred to the recording material P, the cleaning device mechanically scrapes off and collects residual toner remaining on the photosensitive member 61. Here, by adopting a simultaneous development and cleaning method in which the developing device collects the transfer residual toner, it is possible to omit the cleaning device. The fixing device has the function of fixing the toner image and is composed of a fixing belt 67 having a heated roll. By rotating in the direction of the arrow, the toner image transferred onto the recording material P is fixed and the recording material P is discharged outside the machine. In the image forming apparatus, the electrophotographic member described above can be suitably used as the charging roller 62 or the developing roller 65.

[0053] <Process cartridge> A schematic configuration of one embodiment of a process cartridge according to one embodiment of the present disclosure is shown in Fig. 7. The process cartridge integrates a photosensitive member 71, a charging roller 72, a developing roller 73, and a cleaning member 74, and is configured to be detachably attachable to an image forming apparatus. The process cartridge is equipped with the electrophotographic member according to one embodiment of the present disclosure described above, and such electrophotographic member can be suitably used in particular as the charging roller 72 and the developing roller 73. [Example]

[0054] The following examples will further illustrate one embodiment of the present disclosure, but the present disclosure is not limited to the following examples.

[0055] Example 1 (Preparation of mixture for forming elastic layer) A polyether having two isocyanate groups was synthesized by adding 20.1 parts by mass of polypropylene glycol (trade name: PREMINOL S 4013F, manufactured by AGC Inc.), 19.2 parts by mass of polypropylene glycol (trade name: UNIOL D-4000, manufactured by NOF Corporation), and 2.5 parts by mass of xylylene diisocyanate (XDI) (manufactured by Tokyo Chemical Industry Co., Ltd.) with 500 ppm of 1,4-diazabicyclo[2.2.2]octane-2-methanol (trade name: RZETA, manufactured by Tosoh Corporation) as a curing catalyst, and stirring for 4 hours in a sealed mixer adjusted to 100°C. This was mixed with 50.3 parts by mass of polycarbonate diol (trade name: Duranol G3452, manufactured by Asahi Kasei Corporation). The mixture was then stirred for an additional 2 hours in a sealed mixer adjusted to 100°C, thereby synthesizing a urethane reactive emulsifier having two hydroxyl groups and obtaining a dispersion in which droplets containing the urethane reactive emulsifier were dispersed in the polycarbonate diol. To this dispersion were added 0.8 parts by mass of xylylene diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter sometimes referred to as "XDI"), 5.2 parts by mass of polyisocyanate (trade name: Millionate MR-200, manufactured by Tosoh Corporation, hereinafter sometimes referred to as "MR-200"), and 1.8 parts by mass of an ionic conductive agent (trade name: CIL-542, manufactured by Nippon Carlit Co., Ltd., hereinafter sometimes referred to as "CIL"), and the mixture was stirred for 2 minutes in a rotary vacuum degassing mixer at a revolution speed of 1600 rpm to obtain a mixture for forming an elastic layer.

[0056] (Production of electrophotographic roller) A primer (product name: Metalock N-33, manufactured by Toyo Kagaku Kenkyusho Co., Ltd.) was applied to a mandrel made of SUS304 with a diameter of 6 mm and a length of 250 mm, and baked at 130°C for 30 minutes. Next, this mandrel was placed concentrically in a cylindrical mold having an inner diameter of 11.5 mm, and the elastic layer-forming mixture was poured into the cylindrical mold preheated to 130° C. over 10 seconds. The cylindrical mold was heated at 130°C for 1 hour, then demolded and further aged at 80°C for 2 days to obtain an elastic layer. The ends of the elastic layer were then removed to obtain an electrophotographic roller with a length of 225 mm and an elastic layer thickness of 2.0 mm. The obtained electrophotographic roller was evaluated as follows.

[0057] Evaluation method for electrophotographic rollers (Evaluation 1: Review and analysis of the matrix (sometimes written as "M" in Table 4-1) and domain (sometimes written as "D" in Table 4-1)) Sections were prepared from the electrophotographic roller using a microtome at three locations in the thickness direction of the elastic layer: the center of the elastic layer in the longitudinal direction, and two locations at L / 4 from both ends of the elastic layer toward the center, where L is the longitudinal length of the elastic layer. Mapping measurements were performed using a three-dimensional microscopic laser Raman spectrometer (product name: Nanofinder 30, manufactured by Tokyo Instruments Inc.). The measurement mode was EM (Electron Multiplying), and measurements were taken at 60 × 60 points at 500 nm intervals, obtaining an integrated image from 0 to 400 cm-1. The obtained integrated image confirmed that the elastic layer contained a matrix with multiple domains dispersed within the matrix. Furthermore, there was clear phase separation between the matrix and the domains. Next, Raman spectra of the matrix and domains were measured from the integrated image. Measurements were performed using a Nd:YVO4 (wavelength 532 nm) light source, a laser intensity of 240 μW, a 100x objective lens, a diffraction grating of 300 gr / mm, a pinhole diameter of 100 μm, an exposure time of 30 seconds, and one integration. The Raman spectra obtained confirmed that the matrix contained a structure derived from polycarbonate urethane, and the domains contained a structure derived from polypropylene glycol (sometimes referred to as "PPG" in Table 4-1).

[0058] (Evaluation 2: Measurement of micro rubber hardness) The micro rubber hardness of the elastic layer was measured using a micro rubber hardness tester (product name: MD-1capa, manufactured by Kobunshi Keiki Co., Ltd.). For the measurement, the electrophotographic roller was left in an environment at a temperature of 23°C for 24 hours or more, and the measurement was performed using a measuring device placed in the same environment. The indenter used was a type A (height 0.50 mm, diameter 0.16 mm, cylindrical), and the measurement mode was peak hold mode. The locations where the micro rubber hardness was measured were three: the center of the elastic layer in the longitudinal direction, and two locations at L / 4 from both ends of the elastic layer toward the center, where L is the longitudinal length of the elastic layer. The average value of the micro rubber hardness measured at each measurement location at a temperature of 23°C was calculated.

[0059] (Evaluation 3: Measurement of parameters indicating viscoelasticity) Sections were prepared from the electrophotographic roller using a microtome at three locations in the thickness direction of the elastic layer: the center of the elastic layer in the longitudinal direction, and two locations at L / 4 from both ends of the elastic layer toward the center, where L is the longitudinal length of the elastic layer. Three 50-μm square observation areas were randomly selected from the outer surface of each section to a depth of 100 μm. Viscoelastic images were measured in three observation areas using a scanning probe microscope (product name: S-Image, manufactured by SII NanoTechnology Inc.). The viscoelastic image measurement mode was VE-DFM. The cantilever used was an "SI-DF3" (product name, manufactured by Hitachi High-Tech Science Corporation, spring constant = 1.9 N / m). The scanning frequency was 0.5 Hz. From the obtained viscoelastic images, parameters indicating the viscoelastic term in each observation region were calculated for 10 points each for the matrix and domain, and parameter A indicating the viscoelastic term of the domain and parameter B indicating the viscoelastic term of the matrix were obtained from the average values.

[0060] (Evaluation 4: Measurement of deformation recovery of elastic layer) The deformation recovery of the elastic layer was evaluated by an indentation test using a nanoindenter (product name: HM2000, manufactured by Fisher Instruments Inc.) at a temperature of 23°C. For the measurement, the electrophotographic roller was left in an environment at a temperature of 23°C for 24 hours or more, and the measurement was carried out using a measuring device placed in the same environment. The measurement locations were three locations: the center of the elastic layer in the longitudinal direction, and two locations at L / 4 from both ends of the elastic layer toward the center, where L is the longitudinal length of the elastic layer. In the indentation test, a Vickers indenter (square pyramid-shaped, facing angle 136°) was pressed into the elastic layer at a loading rate of 10 mN / 30 seconds, and the load of 10 mN was maintained for 60 seconds. After that, the load was released, and the strain measured at each measurement location 5 seconds after release was calculated as the average value.

[0061] (Rating 5: Elastic modulus of matrix) Sections were prepared from the electrophotographic roller using a microtome at three locations in the thickness direction of the elastic layer: the center of the elastic layer in the longitudinal direction, and two locations at L / 4 from both ends of the elastic layer toward the center, where L is the longitudinal length of the elastic layer. A 50-μm square observation area was selected from each section within a thickness range of 100 μm from the outer surface. A total of three observation areas were used to observe phase images using a scanning probe microscope (product name: MFP-3D-Origin, Oxford Instruments). The phase image measurement mode was AM-AFM. The cantilever used was an "OMCL-AC-160TS" (product name, Olympus Corporation, spring constant = 47.08 N / m). The scanning frequency was 0.5 Hz. The elastic modulus of the matrix was determined from the obtained phase image by measuring a force curve using the above-mentioned scanning electron microscope. The force curve measurement mode was contact mode, the force distance was 500 nm, and the trigger point was 0.01 V. The cantilever used was an "OMCL-AC-160TS" (trade name, manufactured by Olympus Corporation, spring constant = 47.08 N / m). The scanning frequency was 1 Hz. The elastic modulus of the matrix was determined at 10 points for each observation area, and the average value was calculated.

[0062] (Evaluation 6: Measurement of domain cross-sectional area and number) Sections were prepared from the electrophotographic roller using a microtome. The sections were prepared at three locations: the center of the elastic layer in the longitudinal direction, and two locations at L / 4 from both ends of the elastic layer toward the center, exposing the cross section of the elastic layer in the full thickness direction. A square observation area measuring 50 μm on a side was placed at a random position within the thickness region of each section, extending from the outer surface of the elastic layer to a depth of 100 μm. Viscoelastic images were measured in a total of three observation areas using a scanning probe microscope (product name: S-Image, manufactured by SII Nano Technology, Inc.). The measurement mode for the viscoelastic image was the Viscoelastic Dynamic Force Mode (VE-DFM). The cantilever used was a silicon microcantilever for DMF (SI-DF3, manufactured by Hitachi High-Tech Science Corporation, spring constant = 1.9 N / m). The scanning frequency was 0.5 Hz. The obtained cross-sectional images were converted into 256-level monochrome images using image processing software (product name: ImageProPlus, manufactured by MediaCybernetics), and then binarized to obtain binary images for analysis. The threshold value for binarization was determined from the luminance distribution of the monochrome images based on Otsu's algorithm described in Non-Patent Document 1. The cross-sectional area and number of domains were calculated from the obtained binarized image using the counting function of the image processing software. However, among the domains determined as domains by the counting function, domains with a cross-sectional area of ​​less than 0.05% of the 50 μm square observation area were considered to be domains caused by noise and were removed from the data. Then, the ratio (%) of the total cross-sectional area of ​​the domains in each observation area to the area of ​​the observation area was calculated. In addition, the number of domains in each observation area whose cross-sectional area was 0.1% or more and 13.0% or less of the area of ​​the observation area was counted, and the ratio (%) of the observation area to the total number of domains was calculated.

[0063] (Evaluation 7: Measurement of domain circularity and number) The circularity of the domains was calculated from the binary images obtained in Evaluation 6 above using the counting function of the image processing software. However, as in Evaluation 6, domains resulting from noise were removed from the data. Then, the number of domains in each observation area with a circularity of 0.60 or more and 0.95 or less was counted, and the percentage (%) of this number relative to the total number of domains in each observation area was calculated.

[0064] (Evaluation 8: Evaluation of streaky image defects) A color laser printer (product name: LBP7700C, manufactured by Canon Inc.) and a process cartridge incorporating an electrophotographic roller as a developing roller were acclimatized to an environment of 23°C temperature and 50% RH for 24 hours, and then image evaluation was performed. Specifically, a process cartridge incorporating an electrophotographic roller as a developing roller was installed in the color laser printer, and 10 halftone images (images depicting horizontal lines with a width of 1 dot and an interval of 2 dots in the direction perpendicular to the rotation direction of the photosensitive member) were printed consecutively. The images obtained were visually observed, and the presence of streak-like image defects was evaluated according to the following two criteria. <Evaluation of streaky image defects 8-1> Rank A: No streaky image defects are observed from the first sheet. Rank B: Streaky image defects are observed only on the first sheet. Rank C: Streaky image defects are observed on the second and subsequent sheets. <Evaluation of streaky image defects 8-2> Rank A: No streak-like image defects are observed over the entire length of the electrophotographic roller. Rank B: Streaky image defects are observed in some areas in the longitudinal direction of the electrophotographic roller. Rank C: Streak-like image defects are observed over a wide range in the longitudinal direction of the electrophotographic roller and are noticeable.

[0065] (Evaluation 9: Evaluation of edge scraping, toner fusion, and image defects caused by toner fusion) The color laser printer and a process cartridge incorporating the electrophotographic roller as a developing roller were allowed to acclimate to an environment of temperature 23° C. and humidity 50% RH for 24 hours. Thereafter, the electrophotographic roller was attached as a developing roller to the color laser printer, and an image of horizontal lines with a width of 2 dots and an interval of 50 dots was continuously output on 10,000 sheets. During the continuous output of 10,000 sheets, the developing roller was taken out every 1,000 sheets and visually inspected, and scraping of the edge of the developing roller and fusion of toner were evaluated according to the following criteria. <Evaluation 9-1: Evaluation of edge wear> Rank A: No wear on the edges is observed even after printing 10,000 sheets. Rank B: No edge wear was observed after 8,000 sheets were printed, but was observed after 9,000 sheets were printed. Rank C: No scraping of the edges is observed after printing 5,000 sheets, but is observed after printing 8,000 sheets. Rank D: Edge wear is observed after printing 5,000 sheets. <Evaluation 9-2: Evaluation of toner fusion> Rank A: No toner fusion is observed even after printing 10,000 sheets. Rank B: Toner fusion is not observed after 8,000 sheets are output, but is observed after 9,000 sheets are output. Rank C: Toner fusion is not observed after 5,000 sheets are output, but is observed after 8,000 sheets are output. Rank D: Toner fusion is observed after 5,000 sheets are printed. <Evaluation 9-3: Evaluation of image defects caused by toner fusion> While 10,000 sheets were continuously output, the images output every 10 sheets were checked. If there was an image defect, such as toner being transferred to the paper at intervals of one rotation of the electrophotographic roller in areas other than the horizontal lines, output was temporarily stopped and the electrophotographic roller was removed from the process cartridge. If the location where the image defect occurred matched the location and size of the fused toner part on the electrophotographic roller, the number of sheets output at the time of temporary stop was counted as the number of sheets with image defects caused by fused toner.

[0066] <Examples 2 to 7, 9 to 12, 14, 15, and 18> An elastic layer-forming mixture was prepared in the same manner as in Example 1, except that the materials shown in Table 3 were used in the blending amounts shown in Table 3. An elastic layer was formed in the same manner as in the Examples, except that the elastic layer-forming mixture was used, and an electrophotographic roller according to each Example was produced. The obtained electrophotographic roller was evaluated in the same manner as in Example 1. The details of the material types in Table 3 are shown in Tables 1 and 2. The same applies to the following examples.

[0067] Example 8 An elastic layer-forming mixture was prepared in the same manner as in Example 1, except that the materials shown in Table 3 were used in the blending amounts shown in Table 3. An elastic layer was formed in the same manner as in Example 1, except that the elastic layer-forming mixture was used and that the injection of the elastic layer-forming mixture into the cylindrical mold was carried out for 5 seconds, thereby producing an electrophotographic roller according to this example. The obtained electrophotographic roller was evaluated in the same manner as in Example 1.

[0068] <Examples 13, 16, and 17> An elastic layer-forming mixture was prepared in the same manner as in Example 1, except that the materials shown in Table 3 were used in the blending amounts shown in Table 3. An elastic layer was formed in the same manner as in Example 1, except that the elastic layer-forming mixture was used and that the injection of the elastic layer-forming mixture into the cylindrical tubular mold was carried out for 3 seconds, thereby producing an electrophotographic roller according to each Example. The obtained electrophotographic roller was evaluated in the same manner as in Example 1.

[0069] [Table 1] The tetrahydrofuran-neopentyl glycol copolymer of A5 above is a polyether glycol represented by the structural formula: HO-(CH2CH2CH2CH2O)m-(CH2C(CH3)2CH2O)n-.

[0070] [Table 2] The above-mentioned B2 relates to Kuraray Polyol C-2090 (a polycarbonate polyol manufactured by Kuraray Co., Ltd.; number average molecular weight: 1993; hydroxyl value: 56.3 mg KOH / g; a polycarbonate polyol having a structure derived from 1,6-hexanediol and a structure derived from 3-methyl-1,5-pentanediol).

[0071] [Table 3]

[0072] <Comparative Example 1> (Preparation of mixture for forming elastic layer) A polyether having two isocyanate groups was synthesized by adding 24.9 parts by mass of polypropylene glycol (trade name: PREMINOL S4013F, manufactured by AGC Inc.), 24.0 parts by mass of polypropylene glycol (trade name: UNIOL D-4000, manufactured by NOF Corporation), and 3.1 parts by mass of xylylene diisocyanate (XDI) (manufactured by Tokyo Chemical Industry Co., Ltd.) and 500 ppm of a curing catalyst (trade name: RZETA, manufactured by Tosoh Corporation), and stirring for 4 hours in a sealed mixer adjusted to 100°C. This was mixed with 41.5 parts by mass of polycarbonate diol (Duranol G3452, manufactured by Asahi Kasei Corporation). After that, the mixture was stirred for an additional 2 hours in a sealed mixer adjusted to 100°C, thereby synthesizing a urethane reactive emulsifier having two hydroxyl groups and obtaining a dispersion in which droplets containing the urethane reactive emulsifier were dispersed in the polycarbonate diol. To this dispersion, 4.7 parts by mass of polyisocyanate (trade name: Millionate MR-200, manufactured by Tosoh Corporation) and 1.8 parts by mass of an ionic conductive agent (trade name: CIL-542, manufactured by Nippon Carlit Co., Ltd.) were added, and the mixture was stirred for 2 minutes at a revolution speed of 1600 rpm using a rotary-revolution vacuum degassing mixer, to obtain a mixture for forming an elastic layer. Except for using the mixture for forming an elastic layer thus obtained, an electrophotographic roller according to this comparative example was obtained in the same manner as in Example 1. The obtained electrophotographic roller was evaluated in the same manner as in Example 1.

[0073] The results of Evaluation 1 showed that the matrix and domains were clearly phase-separated. It was also confirmed that the matrix contained a urethane elastomer composed of polyether, and the domains contained a urethane elastomer composed of polycarbonate. In other words, the domain-matrix relationship was reversed from that of the polyurethane elastomer of Example 1.

[0074] <Comparative Example 2> (Preparation of mixture for forming elastic layer) 20.1 parts by weight of polypropylene glycol (trade name: PREMINOL S4013F, manufactured by AGC Inc.) and 19.2 parts by weight of polypropylene glycol (trade name: UNIOL D-4000, manufactured by NOF Corporation) were added to 50.3 parts by weight of polycarbonate diol (trade name: DURANOL G3452, manufactured by Asahi Kasei Corporation) and 500 ppm of curing catalyst (trade name: RZETA, manufactured by Tosoh Corporation), and the mixture was stirred for 2 hours in a closed mixer adjusted to 100°C. To this mixture was added 3.3 parts by weight of xylylene diisocyanate (XDI) (manufactured by Tokyo Chemical Industry Co., Ltd.), 5.2 parts by weight of polyisocyanate (trade name: MILLIONATE MR-200, manufactured by Tosoh Corporation), and 1.8 parts by weight of an ion conductive agent (trade name: CIL-542, manufactured by Nippon Carlit Co., Ltd.). The resulting mixture was stirred for 2 minutes in a closed vacuum mixer to obtain a mixture for forming the elastic layer. Except for using the elastic layer-forming mixture, an elastic layer was formed in the same manner as in Example 1 to produce an electrophotographic roller according to this comparative example. The obtained electrophotographic roller was evaluated in the same manner as in Example 1.

[0075] <Comparative Example 3> (Preparation of mixture for forming elastic layer) 7.0 parts by mass of polypropylene glycol (trade name: Uniol D-2000, manufactured by NOF Corporation) was mixed with 79.0 parts by mass of polycarbonate diol (Duranol T6002, manufactured by Asahi Kasei Corporation) and 500 ppm of a curing catalyst (trade name: RZETA, manufactured by Tosoh Corporation), and the mixture was stirred for 2 hours in a sealed mixer adjusted to 100°C. To this was added 4.3 parts by mass of xylylene diisocyanate (XDI) (manufactured by Tokyo Chemical Industry Co., Ltd.), 8.0 parts by mass of polyisocyanate (trade name: Millionate MR-200, manufactured by Tosoh Corporation), and 1.8 parts by mass of an ion conductive agent (trade name: CIL-542, manufactured by Nippon Carlit Co., Ltd.) The resulting mixture was stirred for 2 minutes in a sealed vacuum mixer to obtain a mixture for forming an elastic layer. Except for using the elastic layer-forming mixture, an elastic layer was formed in the same manner as in Example 1 to produce an electrophotographic roller according to this comparative example. The obtained electrophotographic roller was evaluated in the same manner as in Example 1.

[0076] <Comparative Example 4> (Preparation of mixture for forming elastic layer) 46.7 parts by mass of polycarbonate diol (trade name: Kuraray Polyol C-2090, manufactured by Kuraray Co., Ltd.) and 44.8 parts by mass of silicone particles (trade name: KMP-598, manufactured by Shin-Etsu Chemical Co., Ltd.), which are soft resin particles, were added with 500 ppm of a curing catalyst (trade name: RZETA, manufactured by Tosoh Corporation), and the mixture was stirred for 4 hours in a sealed vacuum mixer adjusted to 100°C. To this was added 2.6 parts by mass of xylylene diisocyanate (XDI) (manufactured by Tokyo Chemical Industry Co., Ltd.), 84.2 parts by mass of polyisocyanate (trade name: Millionate MR-200, manufactured by Tosoh Corporation), and 1.8 parts by mass of an ion conductive agent (trade name: CIL-542, manufactured by Nippon Carlit Co., Ltd.) The resulting mixture was stirred for 2 minutes in a planetary vacuum degassing mixer at a revolution speed of 1600 rpm to obtain a mixture for forming an elastic layer. An elastic layer was formed in the same manner as in Example 1, except that the elastic layer-forming mixture was used, to produce an electrophotographic roller according to this comparative example. The obtained electrophotographic roller was evaluated in the same manner as in Example 1. In the evaluation of the electrophotographic roller according to this comparative example, the silicone particles were regarded as domains. The evaluation results of Examples 1 to 18 and Comparative Examples 1 to 4 are shown in Tables 4-1 to 4-4 and 5.

[0077] [Table 4-1]

[0078] [Table 4-2]

[0079] [Table 4-3]

[0080] [Table 4-4]

[0081] [Table 5]

[0082] The electrophotographic rollers according to Examples 1 to 18 had low micro rubber hardness in the elastic layer, and multiple domains dispersed in a matrix containing a urethane elastomer. Furthermore, parameter B, which indicates the viscoelasticity of the matrix, was larger than parameter A, which indicates the viscoelasticity of the domain, and the strain after unloading in an indentation test using a nanoindenter was small, so good results were obtained in the evaluation of streak-like image defects. Furthermore, although toner fusion was observed in some electrophotographic rollers, no image defects due to toner fusion occurred within the time it took to output 10,000 sheets. On the other hand, in the electrophotographic roller according to Comparative Example 1, parameter A, which indicates the viscoelasticity term of the domain, was larger than parameter B, which indicates the viscoelasticity term of the matrix. As a result, the micro rubber hardness was excessively reduced and the distortion after unloading was large, and the evaluation of streak-like image defects was also not good. In the electrophotographic roller according to Comparative Example 2, a matrix-domain structure was formed by mechanical phase separation without using a polyether and urethane reactive emulsifier. As a result, the phase separation was unclear. In addition, the circularity of the domains was also reduced, which resulted in an excessive decrease in micro rubber hardness and increased distortion after unloading, and the evaluation of streak-like image defects was also poor. The electrophotographic roller of Comparative Example 3 was mechanically phase-separated without using a urethane reactive emulsifier, as in Comparative Example 2. As a result, phase separation was unclear. Furthermore, the circularity of the domains was reduced, resulting in increased distortion after unloading and poor evaluation of streak-like image defects. Furthermore, the distortion did not recover easily, and toner adhered to the distorted areas and further fused, resulting in image defects due to toner fusion at 8,410 sheets. The electrophotographic roller of Comparative Example 4 used soft particles for the domains. However, to maintain the particle shape, parameter A, which indicates the viscoelasticity term, was significantly larger than that of the domains of the present disclosure. Furthermore, parameter B, which indicates the viscoelasticity term of the matrix, also had to be increased. As a result, the micro-rubber hardness became excessively high, resulting in toner fusion. Furthermore, the micro-rubber hardness was too high, further promoting toner fusion, resulting in image defects due to toner fusion at 5,550 sheets.

[0083] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the present disclosure. Therefore, the following claims are appended to apprise the public of the scope of the present disclosure. [Explanation of symbols]

[0084] 1A, 1B Electrophotographic member, 2: Mandrel, 3: Elastic layer, 31: Matrix, 32: Domain

Claims

1. An electrophotographic member comprising a mandrel and an elastic layer provided on the outer periphery thereof, the electrophotographic member is a developing roller, the elastic layer includes a urethane elastomer having a matrix and a plurality of domains dispersed in the matrix; a parameter A indicating the viscoelastic term of the domain measured in a viscoelastic image of a cross section of the elastic layer in the thickness direction by a scanning probe microscope and a parameter B indicating the viscoelastic term of the matrix satisfy the relationship A<B; the elastic layer has a micro rubber hardness of 20 or more and 50 or less at a temperature of 23°C, and in an indentation test of the elastic layer using a nanoindenter at 23°C, a Vickers indenter is pressed into the elastic layer at a loading rate of 10 mN / 30 seconds, the load of 10 mN is maintained for 60 seconds, and then the strain 5 seconds after unloading is 1 μm or less; The measurement mode of the viscoelastic image by the scanning probe microscope is a micro-viscoelastic dynamic force mode, The micro-viscoelastic dynamic force mode is a mode in which a surface topography image is obtained while controlling the distance between the probe and the measurement sample so that the vibration and amplitude of the cantilever are constant while the cantilever is resonated, The cantilever is a silicon microcantilever with a spring constant of 1.9 N / m, and the scanning frequency is 0.5 Hz. Slices were prepared from a total of three cross sections of the elastic layer in the thickness direction at the center of the elastic layer in the longitudinal direction, and from two cross sections of the elastic layer in the thickness direction at L / 4 (L is the length of the elastic layer in the longitudinal direction) from both ends of the elastic layer toward the center in the longitudinal direction, to obtain three slices in total. As the observation regions for observing the viscoelasticity images in the three cross sections, observation regions of 50 μm square are arbitrarily selected in the thickness region from the outer surface of each of the three slices to a depth of 100 μm, and observation is performed in a total of three observation regions; After obtaining the viscoelastic image, when a parameter indicating a viscoelastic term is determined in a domain at 10 points for each of the three observation regions, the average value is parameter A; when a parameter indicating a viscoelastic term is determined in a matrix at 10 points for each of the three observation regions, the average value is parameter B; The unit of the parameter A and the parameter B is mV, and the larger the value, the higher the elasticity. Electrophotographic member characterized by:

2. 2. The electrophotographic member according to claim 1, wherein the matrix has an elastic modulus of 2 MPa or more and 8 MPa or less.

3. 3. The electrophotographic member according to claim 1 or 2, wherein all of the three observation regions satisfy the following requirements (1) and (2): Requirement (1) The ratio of the total cross-sectional area of ​​the domains to the total cross-sectional area of ​​the observation area is 15% or more and 45% or less. Requirement (2) The proportion of the number of domains whose cross-sectional area is 0.1% or more and 13.0% or less of the observation area is 70% or more by number.

4. 4. The electrophotographic member according to claim 1, wherein the ratio of the number of domains having a circularity of 0.60 or more and 0.95 or less in all three observation regions is 70% or more by number.

5. The matrix contains a urethane elastomer having a polycarbonate structural unit represented by the following general formula (1) as a repeating structural unit, and The domain contains, as a repeating structural unit, a polyether structural unit represented by the following general formula (2): The electrophotographic member according to any one of claims 1 to 4. 【Chemistry 1】 (R １ represents an alkylene group having 3 to 9 carbon atoms. 【Chemistry 2】 (R ２ represents an alkylene group having 3 to 5 carbon atoms.

6. R in the repeating structural unit represented by the general formula (1) １ 6. The electrophotographic member according to claim 5, wherein is an alkylene group having a branched structure and having 3 to 9 carbon atoms.

7. R in the repeating structural unit represented by the general formula (2) ２ 7. The electrophotographic member according to claim 5, wherein is an alkylene group having a branched structure and having 3 to 5 carbon atoms.

8. A process cartridge configured to be detachably attached to an electrophotographic image forming apparatus, The process cartridge includes a developing roller, The developing roller is the electrophotographic member according to any one of claims 1 to 7. A process cartridge characterized by:

9. An electrophotographic image forming apparatus having a developing roller, The developing roller is the electrophotographic member according to any one of claims 1 to 7. Electrophotographic image forming apparatus characterized in that:

10. A method for producing an electrophotographic member according to any one of claims 1 to 7, comprising the steps of: the electrophotographic member is a developing roller, The manufacturing method comprises: (i) reacting a first polyether having at least two isocyanate groups with a first polycarbonate polyol having at least two hydroxyl groups to obtain a urethane reactive emulsifier having at least two hydroxyl groups; (ii) obtaining a dispersion in which droplets containing at least a portion of the urethane reactive emulsifier are dispersed in a second polycarbonate polyol; (iii) mixing the dispersion and a polyisocyanate having at least two isocyanate groups to obtain a mixture for forming an elastic layer; and (iv) a step of reacting the urethane reactive emulsifier, the second polycarbonate polyol, and the polyisocyanate in the elastic layer-forming mixture on the surface of the mandrel to obtain the elastic layer; having 10. A method for producing an electrophotographic member, comprising:

Images