Electrophotographic member, method for manufacturing the same, process cartridge, and electrophotographic image forming apparatus

Abstract

An electrophotographic member including a core shaft and an elastic layer on an outer circumference of the core shaft, the elastic layer containing a polyurethane elastomer, the polyurethane elastomer containing a matrix and domains dispersed in the matrix, a parameter A and a parameter B satisfying a relationship of A < B, wherein the parameter A represents a viscoelastic term of each of the domains and the parameter B represents a viscoelastic term 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, and in an indentation test of the elastic layer at 23°C using a nanoindenter, wherein the test includes pressing into the elastic layer with a Vickers indenter at a loading rate of 10 mN / 30 sec, holding at a load of 10 mN for 60 seconds, and then unloading, the strain after unloading for 5 seconds is 1 µm or less.

Description

Technical Field

[0001] This disclosure relates to an electrophotographic component for an electrophotographic image forming apparatus (hereinafter sometimes simply referred to as "image forming apparatus"), such as a copier or printer using an electrophotographic system, and a method for manufacturing the electrophotographic component. This disclosure also relates to a processing cartridge and an electrophotographic image forming apparatus. Background Technology

[0002] Image forming equipment using an electrophotographic system (such as copiers, fax machines, or printers using an electrophotographic system) mainly includes an electrophotographic photosensitive element (sometimes referred to as "photosensitive element" below), a charging device, an exposure device, a developing device, a transfer device, and a fixing device.

[0003] In an image forming apparatus, the photosensitive element is first charged by a charging member (hereinafter sometimes referred to as a "charging roller") and then exposed. Thus, an electrostatic latent image is formed on the photosensitive element. Meanwhile, toner in a toner container is applied to a toner carrier member (hereinafter sometimes referred to as a "developing roller") via a toner adjusting member and transported to the developing area via the developing roller. The electrostatic latent image on the photosensitive element is then developed at the contact point between the photosensitive element and the developing roller using the toner transported to the developing area. Subsequently, the toner on the photosensitive element is transferred to a recording film by means of a transfer method and fixed using heat and pressure. Any toner remaining on the photosensitive element is removed by a cleaning member.

[0004] Silicone rubber, acrylonitrile-butadiene rubber, epichlorohydrin rubber, and urethane elastomers have been used to date as materials for the elastic layer in each of these charging and developing rollers. Among these materials, urethane elastomers have satisfactory abrasion resistance and are therefore suitable as materials for the elastic layer.

[0005] However, urethane elastomers are generally prone to compression set. Therefore, when a specific portion of a developing roller, including an elastic layer containing an urethane elastomer, comes into prolonged contact with a toner adjusting member and deforms at that portion, the deformation is difficult to recover. When image formation is performed on a developing roller with this deformed portion, the resulting electrophotographic image will have streaky defects at the location corresponding to the deformed area. Similarly, in charging rollers including an elastic layer containing an urethane elastomer, charging failures can occur due to deformation occurring at specific locations within the charging roller, resulting in defective electrophotographic images. When the hardness of the urethane elastomer is low, compression set tends to increase, and the aforementioned defects are more likely to occur.

[0006] Patent Document 1 discloses a conductive roller comprising a conductive elastic layer formed of a urethane elastomer, which is obtained by reacting a polyisocyanate formed from a trimer of hexamethylene diisocyanate, its biuret, or a mixture thereof with a polyol comprising high molecular weight polypropylene glycol as a main component at an isocyanate index of 80 to 120. Patent Document 1 discloses a conductive roller with excellent recovery from deformation caused by pressure contact with a photosensitive element and pressure contact with a roller or scraper, as the conductive elastic layer reduces permanent deformation of the roller.

[0007] [List of Citations]

[0008] [Patent Literature]

[0009] Patent Document 1: Japanese Patent Application Publication No. H09-34216

[0010] [Non-patent literature]

[0011] Non-patent literature 1: IEEE Transactions on Systems, MAN, and Cybernetics, Volume SMC-9, Issue 1, January 1979, pp. 62-66. Summary of the Invention

[0012] The problem the invention aims to solve

[0013] The inventors investigated the conductive roller according to Patent Document 1. As a result, the inventors found that the urethane elastomer according to Patent Document 1, as a constituent material of the elastic layer of each developing roller and charging roller in a high-speed image forming apparatus, still has room for improvement.

[0014] One aspect of this disclosure aims to provide an electrophotographic component with low hardness and rapid recovery from deformation. Another aspect of this disclosure aims to provide a method for manufacturing an electrophotographic component with low hardness and excellent deformation recovery. Yet another aspect of this disclosure relates to providing a processing cartridge that facilitates the formation of high-quality electrophotographic images. Still another aspect of this disclosure relates to providing an electrophotographic image forming apparatus capable of forming high-quality electrophotographic images.

[0015] Solution for solving the problem

[0016] According to one aspect of the present disclosure, there is provided an electrophotographic member including: a mandrel; an elastic layer provided on the outer periphery of the mandrel, the elastic layer containing a polyurethane elastomer, the polyurethane elastomer including a matrix and a plurality of domains dispersed in the matrix, and parameters A and B satisfying the relationship A < B, where parameter A represents the viscoelastic term of each of the plurality of domains and parameter B represents the viscoelastic term of the matrix, the parameters A and B being measured in a viscoelastic image of a cross section in the thickness direction of the elastic layer using a scanning probe microscope, the microrubber hardness of the elastic layer at a temperature of 23 °C being 20 or more and 50 or less, 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 sec and maintained at a load of 10 mN for 60 seconds and then unloaded, and the strain after 5 seconds of unloading is 1 μm or less.

[0017] According to another aspect of the present disclosure, there is provided a processing cartridge configured to be detachably mounted to an image forming apparatus, the processing cartridge including the above electrophotographic member.

[0018] According to still another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above electrophotographic member.

[0019] According to yet another aspect of the present disclosure, there is provided a method for manufacturing the electrophotographic member, the method including the steps of: (i) reacting a first polyether having at least two isocyanate groups and a first polycarbonate polyol having at least two hydroxyl groups with each other to obtain a urethane-reactive emulsifier having at least two hydroxyl groups; (ii) obtaining a dispersion in which droplets each containing at least a part of the urethane-reactive emulsifier are dispersed in a second polycarbonate polyol; (iii) obtaining an elastic layer-forming mixture containing 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 with each other on the surface of the mandrel to obtain an elastic layer.

[0020] The effects of the invention

[0021] According to one aspect of the present disclosure, there can be provided an electrophotographic member having low hardness and quickly recovering from deformation. According to another aspect of the present disclosure, there can be provided a method for manufacturing an electrophotographic member having low hardness and quickly recovering from deformation. Further, according to still another aspect of the present disclosure, there can be provided a processing cartridge contributing to the formation of a high-quality electrophotographic image. According to yet another aspect of the present disclosure, there can be provided an electrophotographic image forming apparatus capable of forming a high-quality electrophotographic image. Attached Figure Description

[0022] [ Figure 1A [A schematic cross-sectional view illustrating an example of an electrophotographic component according to one aspect of this disclosure.]

[0023] [ Figure 1B [A schematic cross-sectional view illustrating an example of an electrophotographic component according to one aspect of this disclosure.]

[0024] [ Figure 2A [This is a schematic cross-sectional view of an embodiment of an elastic layer of an electrophotographic component according to one aspect of this disclosure.]

[0025] [ Figure 2B [This is a schematic cross-sectional view of an embodiment of an elastic layer of an electrophotographic component according to one aspect of this disclosure.]

[0026] [ Figure 3 Each figure shows a deformation of the elastic layer according to this disclosure.

[0027] [ Figure 4 This is a diagram showing the cutout location and direction of the cross-section.

[0028] [ Figure 5 [A schematic diagram illustrating a method for manufacturing an electrophotographic component according to one embodiment of the present disclosure.]

[0029] [ Figure 6 [This is a schematic cross-sectional view of an example of an image forming device according to one embodiment of the present disclosure.]

[0030] [ Figure 7 [A schematic cross-sectional view of an example of a processing box according to one embodiment of the present disclosure.] Detailed Implementation

[0031] In this disclosure, unless otherwise stated, the descriptions "above XX and below YY" and "XX to YY" that represent numerical ranges respectively mean a numerical range including both the lower and upper limits as endpoints. Furthermore, the segmented description of numerical ranges discloses any combination of the upper and lower limits of each numerical range.

[0032] In recent years, with the increasing demand for higher printing speeds and higher quality electrophotographic images, there has been a growing requirement for faster recovery of the elastic layers of the developing and charging rollers from deformation. However, according to research conducted by the inventors, the recovery speed of the urethane elastomer according to Patent Document 1 is still insufficient. Patent Document 1 describes the measurement of the compression set of the urethane elastomer according to Patent Document 1 according to Japanese Industrial Standard (JIS) K6301, with compression conditions set at 70°C for 22 hours. Specifically, Patent Document 1 states that the measurement of the compression set of the urethane elastomer according to Patent Document 1 is performed by compressing the urethane elastomer at 70°C for 22 hours, releasing the urethane elastomer from the compressed state, allowing the result to stand for 30 minutes, and then measuring its thickness. However, in the results of this test, even urethane elastomers exhibiting small compression set still have a low recovery speed from deformation for providing elastic layers to each of the developing and charging rollers in high-speed image forming equipment. Therefore, the inventors have recognized the need to develop an elastic layer that exhibits faster deformation recovery while maintaining flexibility.

[0033] Generally, when the microrubber hardness of the elastic layer decreases, the compression set increases, and the recovery rate from deformation also decreases. Meanwhile, increasing the elastic modulus of the elastic layer is effective in obtaining an elastic layer with low compression set and rapid recovery from deformation. However, as the elastic modulus of the elastic layer increases, the microrubber hardness also increases. That is, it is very difficult to obtain an elastic layer with a high recovery rate from deformation while maintaining the microrubber elasticity of the elastic layer at a low level. To solve this problem, the inventors have repeatedly conducted further research. It has been found that using a polyurethane elastomer with a matrix-domain structure, comprising a matrix having a structure that improves the deformation recovery rate and domains having a structure that helps suppress the increase in microrubber hardness, is effective in solving the above problems.

[0034] The following describes in detail, through preferred embodiments, the electrophotographic component, etc., according to the present disclosure.

[0035] <Electronic photographic components>

[0036] Figure 1A and Figure 1B These are schematic cross-sectional views of two aspects of an electrophotographic component having a roller shape (hereinafter sometimes referred to as an "electrophotographic roller") according to the present disclosure. Figure 1AThe electrophotographic roller 1A shown includes a conductive mandrel 2 and an elastic layer 3 covering the surface (outer peripheral surface) of the mandrel 2. Additionally, Figure 1B The electrophotographic roller 1B shown further includes a surface layer 4 on the surface (hereinafter sometimes referred to as the "outer surface") of the elastic layer 3 on the side opposite to the side facing the mandrel 2. The electrophotographic roller according to the present disclosure is not limited to these configurations and may include, for example, an adhesive layer (not shown) between the respective layers.

[0037] (Mandrel)

[0038] Preferably, the mandrel 2 has conductivity to supply power to the surface of the electrophotographic member through the mandrel. Preferably, the resistance value of the mandrel is lower than the resistance value of the elastic layer, and the volume resistivity of the mandrel is 10 3 Ω·cm or less. A mandrel appropriately selected from those known in the field of electrophotographic members can be used as the conductive mandrel, preferably a mandrel made of a metal such as aluminum, aluminum alloy, stainless steel, or iron. Additionally, these metals can be subjected to plating treatment with chromium and nickel, etc. to improve corrosion resistance and abrasion resistance. The shape of the mandrel can be either a hollow shape (cylindrical shape) or a solid shape (cylindrical shape). For example, a solid cylindrical mandrel obtained by plating the surface of a carbon steel alloy with nickel having a thickness of about 5 μm can be used. A mandrel having a cylindrical shape or a cylindrical shape can be appropriately selected according to the image forming apparatus in which the mandrel is to be installed.

[0039] (Elastic layer)

[0040] The elastic layer 2 satisfies the following requirements (1-1) to (1-4).

[0041] Requirement (1-1): The elastic layer 2 contains a polyurethane elastomer having a matrix-domain structure including a matrix and a plurality of domains dispersed in the matrix.

[0042] Requirement (1-2): When the parameter representing the viscoelastic term of each domain measured in the viscoelastic image of the cross-section in the thickness direction of the elastic layer using a scanning probe microscope is represented by A, and the parameter representing the viscoelastic term of the matrix measured in the viscoelastic image is represented by B, it exhibits 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 polyurethane elastomer is observed. Additionally, the elastic modulus of the matrix of the polyurethane elastomer observed in the cross-section is greater than the elastic modulus of each domain.

[0043] 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.

[0044] Requirements (1-4): In the indentation test of the elastic layer using a nanoindenter at 23°C, when the Vickers indenter is pressed into the elastic layer at a loading rate of 10mN / 30sec and maintained under a load of 10mN for 60 seconds, and then unloaded, the strain after 5 seconds of unloading is less than 1μm.

[0045] In the polyurethane elastomers according to this disclosure, the function of restoring deformation is imparted to the matrix, and the function of reducing the hardness of the polyurethane elastomer is imparted to the domain. When such polyurethane elastomers are used, the elastic layer according to this disclosure expresses the softness as defined in requirements (1-3) and the rapid recovery from deformation as defined in requirements (1-4).

[0046] Meanwhile, typical polyurethane elastomers also exhibit a difference in elastic modulus between the so-called hard and soft segments. However, it is believed that there is no polyurethane elastomer that possesses both the softness defined in requirements (1-3) and the high recovery rate from deformation defined in requirements (1-4).

[0047] Figure 2A This is a partial circumferential cross-sectional view of an electrophotographic roller 1A according to one aspect of this disclosure. Additionally, Figure 2B This is a partial cross-sectional view of the electrophotographic roller 1A along the length direction of the spindle 2.

[0048] exist Figure 2A and Figure 2B Each figure schematically illustrates a matrix 31 included in the polyurethane elastomer according to the present disclosure and a plurality of domains 32 dispersed in the matrix 31 as observed in a cross section along the thickness direction of the elastic layer 3.

[0049] The polyurethane elastomer has a matrix-domain structure as described above, comprising a matrix 31 and domains 32 dispersed within the matrix. Furthermore, the matrix 31 has a structure capable of increasing deformation recovery rate, and each of the domains 32 has a structure that helps suppress the increase in micro-rubber hardness. As a result, the matrix exhibits higher elasticity than each domain. Figure 3 (a) and Figure 3 (b) are illustrations of the deformation resilience of the elastic layer 3 according to this disclosure. Figure 3 As shown in (a), multiple domains 32 are dispersed in the matrix 31. Furthermore, each domain 32 has less elasticity than the matrix 31; therefore, when the elastic layer 3... Figure 3 As shown in (b), when compressed in the direction indicated by arrow F, domain 32 deforms preferentially. Therefore, even when 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, due to the elasticity of the matrix 31 as a continuous phase, the thickness of the elastic layer can quickly recover to its pre-compression thickness.

[0050] (Micro-rubber hardness of the elastic layer)

[0051] The hardness of the elastic layer is 20 or higher and 50 or lower, measured by micro-rubber hardness. When the micro-rubber hardness is set to 50 or lower, the gap width between the developing roller and the toner adjusting member, as well as the gap width between the charging roller and the photosensitive member, increases without excessively increasing the contact pressure. As a result, toner on the developing roller is less likely to melt and adhere to the developing roller, and toner that has slid onto the developing roller through the cleaning member is less likely to melt and adhere to the charging roller. Furthermore, by setting the micro-rubber hardness to 20 or higher, mechanical strength is increased, and the ends of the elastic layer are less prone to wear, even when used in long-life image forming equipment.

[0052] The micro-rubber hardness is determined as described below. When the length of the elastic layer in the longitudinal direction is represented by L, the micro-rubber hardness is measured at a total of three locations, including 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. At each measurement location, the micro-rubber hardness of the surface of the elastic layer at a temperature of 23°C is measured using a micro-rubber hardness tester (trade 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 of the measured values ​​is calculated. In this disclosure, the calculated average value is used as the micro-rubber hardness.

[0053] (Parameter representing the viscoelasticity term)

[0054] The relative difference in elastic modulus between matrix 31 and domain 32 can be measured by preparing a thin sheet of the elastic layer and measuring the elastic modulus of the sheet using a scanning probe microscope (SPM / AFM). For example, the "S-Image" (trade name) manufactured by Hitachi High-Tech Science Corporation can be used as a scanning probe microscope. Other examples of means for preparing the thin sheet include a sharp razor, a microtome, and focused ion beam (FIB) methods.

[0055] Regarding the location for slice fabrication, when the length of the elastic layer is represented by L, the slices are fabricated at two positions: the center of the elastic layer along its length and L / 4 of the distance from both ends of the elastic layer towards the center. Figure 4 Three slices were prepared along the thickness direction of sections 41-43. Furthermore, the area of ​​deformation when the electron imaging component comes into contact with another component is primarily the thickness region from the outer surface of the elastic layer to a depth of 100 μm. Therefore, these sections 41-43 were selected as observation areas. An arbitrary 50 μm square observation area was chosen within the thickness region from the outer surface of each slice to a depth of 100 μm, and viscoelastic images were observed in all three observation areas.

[0056] The measurement mode for viscoelastic imaging using SPM is the micro-viscoelastic dynamic force mode (referred to as "viscoelastic dynamic force mode (VE-DFM)"). A silicon microcantilever ("SI-DF3" (trade name), manufactured by Hitachi High-Tech Science Corporation, with a spring constant of 1.9 N / m) is used as the cantilever in the DFM. The scanning frequency is set to 0.5 Hz. VE-DFM is a mode in which a surface profile image is obtained while controlling the distance between the probe and the measurement sample to keep the vibration and amplitude of the cantilever beam constant in a state of cantilever resonance.

[0057] After obtaining the viscoelastic image, parameters representing the viscoelastic terms in each observation region are determined at 10 points each in the matrix and the domain, and their average values ​​are used as parameter A representing the viscoelastic term of the domain and parameter B representing the viscoelastic term of the matrix in this disclosure. The units of parameter A and parameter B are mV, and the larger the value, the higher the elasticity.

[0058] The ratio of parameter A to parameter B (A / B) is preferably 0.65 or less. When the ratio (A / B) is small, the viscoelastic difference between the matrix and the domain increases, thus making it easy to obtain both hardness and recovery from deformation simultaneously.

[0059] (From the resilient nature of deformation)

[0060] In the indentation test of elastic layer 3 using a nanoindenter at a temperature of 23℃, when the Vickers indenter was pressed into the elastic layer at a loading rate of 10mN / 30sec and maintained under a load of 10mN for 60 seconds, and then unloaded, the strain after 5 seconds of unloading was less than 1μm.

[0061] When the strain after 5 seconds of unloading is set to less than 1 μm during measurement under the above conditions, striped image defects can be suppressed when the elastic layer is applied to the developing roller in a high-speed printer. This is because the deformation of the developing roller can recover to its normal size of less than one toner in a short time from the start of the high-speed printer to the development of the electrostatic latent image. Furthermore, even when the elastic layer is applied to the charging roller, the recovery from deformation is rapid, thus reducing the likelihood of uneven discharge to the photosensitive element. Therefore, striped image defects due to uneven charging of the photosensitive element can be prevented.

[0062] In this disclosure, a "FISCHERSCOPE HM2000" (trade name, manufactured by Fischer Instruments KK) is used as a nanoindenter, and measurements are taken at a temperature of 23°C. Additionally, a pyramidal Vickers indenter with a 136° face angle is used as the measuring indenter. Furthermore, when the length of the elastic layer in the longitudinal direction is represented by L, a total of three measurement locations are used, including 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. The average value of measurements taken at each measurement location using the nanoindenter is used as the strain after 5 seconds of unloading in this disclosure.

[0063] (Elastic modulus of the matrix)

[0064] The elastic modulus of the matrix 31 is preferably 2 MPa or higher and 8 MPa or lower. When the elastic modulus of the matrix is ​​set to 2 MPa or higher, the matrix's spring-like effect is enhanced, and recovery from deformation can be accelerated. In addition, when the elastic modulus of the matrix is ​​set to 8 MPa or lower, the matrix hardness is reduced, and the micro-rubber hardness of the elastic layer can be kept low.

[0065] The elastic modulus of the matrix can be measured by preparing a thin sheet of the elastic layer and then measuring the elastic modulus of the sheet using a scanning probe microscope (SPM / AFM). For example, the "MFP-3D-Origin" (trade name) manufactured by Oxford Instruments plc can be used as a scanning probe microscope. Other examples of methods used for preparing thin sheets include sharp razors, microtome, and focused ion beam (FIB) methods.

[0066] Regarding the location for slice fabrication, when the length of the elastic layer is represented by L, the slices are fabricated at two positions: the center of the elastic layer along its length and L / 4 of the distance from both ends of the elastic layer towards the center. Figure 4 Three slices were fabricated along the thickness direction shown. Furthermore, for each of the observation areas at sections 41-43, an arbitrary 50μm square observation area was selected within a thickness region extending 100μm from the outer surface of each slice, and phase images were observed in all three observation areas. The measurement mode for the phase images using SPM was set to AM-FM. A silicon cantilever, such as "OMCL-AC-160TS" (trade name, manufactured by Olympus Corporation, spring constant = 47.08 N / m), was used as the cantilever for dynamic mode. The scan frequency was set to 0.5Hz.

[0067] After acquiring the phase image, a force profile was measured using SPM to determine the elastic modulus of the matrix. The force profile measurement mode was set to contact mode, the force distance was set to 500 nm, and the trigger point was set to 0.01 V. Additionally, in the same manner as above, a silicon cantilever, such as "OMCL-AC-160TS" (trade name, manufactured by Olympus Corporation, spring constant = 47.08 N / m), was used as the cantilever for dynamic mode. The scan frequency was set to 1 Hz.

[0068] The elastic modulus of the matrix is ​​determined at 10 points in each observation area, and the average value is used as the elastic modulus of the matrix in this disclosure.

[0069] (Cross-sectional area and number of domains)

[0070] Describe the cross-sectional area and number of domains 32 of the polyurethane elastomer observed in a section along the thickness direction of the elastic layer.

[0071] When the length of the elastic layer in the longitudinal direction is represented by L, three positions are specified, including the center of the elastic layer in the longitudinal direction and two positions L / 4 from both ends of the elastic layer toward the center. Regarding the cross-sections of the elastic layer in the thickness direction at these three positions, when a 50μm square observation area is arbitrarily set in a thickness region from the outer surface of the elastic layer to a depth of 100μm, it is preferable that all three positions of the observation area satisfy the following requirements (2-1) and (2-2).

[0072] Requirement (2-1): The sum of the cross-sectional areas of the domains existing in the observation area is more than 15% and less than 45% of the area of ​​the observation area.

[0073] Requirement (2-2): When calculating the cross-sectional area of ​​each domain in the observation area, the number of domains whose cross-sectional area is more than 0.1% and less than 13.0% of the area of ​​the observation area shall be more than 70% of the total number of domains in the observation area.

[0074] Regarding requirement (2-1), when the ratio of the sum of the cross-sectional areas of the domains to the area of ​​the observation region is set to 15% or more, the micro-rubber hardness of the elastic layer can be kept low. Furthermore, when this ratio is set to 45% or less, the recovery of the elastic layer from deformation can be accelerated.

[0075] Regarding requirement (2-2), when the number of regions whose respective cross-sectional area is 0.1% to 13.0% of the area of ​​the observation region is set to 70% or more of the total number of regions in the observation region, it ensures that each region has a size that allows it to deform sufficiently when in pressure contact with the elastic layer. Therefore, the micro-rubber hardness of the elastic layer can be reduced. Furthermore, the number of large regions that excessively deform when a load is applied to the elastic layer is small, thus suppressing excessive reduction in the micro-rubber hardness of the elastic layer.

[0076] Here, the cross-sectional area and number of domains are determined as described below. First, slices are prepared using the same method as for measuring the elastic modulus of the matrix described above. Regarding the location of the slices, when the length of the elastic layer in the longitudinal direction is represented by L, slices are prepared at the center of the elastic layer in the longitudinal direction and at two locations L / 4 from both ends of the elastic layer toward the center, as shown in the example. Figure 4 The cross-sections 41, 42, and 43 along the total thickness direction of the elastic layer are shown as exposed slices. Then, 50 μm square observation areas are set at arbitrary locations within the thickness region extending from the outer surface of the elastic layer to a depth of 100 μm in each slice. The cross-sectional area, number, and circularity of the domains are then measured in a total of three observation areas.

[0077] 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), transmission electron microscope (TEM), or scanning probe microscope (SPM / AFM). The resulting cross-sectional image is converted into a 256-grayscale monochrome image using image processing software such as "ImageProPlus" (trade name, manufactured by Media Cybernetics, Inc.). Then, binarization processing is performed using image processing software to provide a binarized image. The binarization method is not particularly limited, as long as the domains and matrix in the monochrome image can be distinguished, but a method is given, for example, involving setting the binarization threshold from the brightness distribution of the monochrome image based on the Otsu algorithm described in Non-Patent Document 1.

[0078] Next, the counting function of image processing software is used in the binarized image to provide the cross-sectional area of ​​each domain present in the observation area and the number of domains. In the resulting binarized image used for analysis, there may be tiny points originating from noise. When analyzing the binarized image containing such tiny points originating from noise using image processing software, these noise-originating points may also be counted as domains. Therefore, it is preferable that, among those domains determined as domains by the counting function, domains whose respective cross-sectional area is less than 0.05% of the 50 μm square observation area are considered noise-originating domains and removed from the data.

[0079] (Circularity of the domain)

[0080] Furthermore, preferably, the number of polyurethane elastomer domains observed in the cross-section along the thickness direction of the elastic layer with a circularity of 0.60 or higher and 0.95 or lower is at least 70% of the total number of domains present in the observed region.

[0081] Domains with a certain degree of roundness or higher are less likely to exhibit anisotropy in the direction of shape recovery when they recover from deformation. Furthermore, when the number (proportion) of domains with a certain degree of roundness or higher is large, anisotropy is less likely to occur in the elastic layer during deformation recovery. As a result, wrinkles and other defects caused by anisotropy during deformation recovery are less likely to occur in the elastic layer after deformation recovery.

[0082] Here, while measuring the cross-sectional area and number of the aforementioned domains, the circularity and number of domains can be determined using the counting function of image processing software.

[0083] (Material of the elastic layer)

[0084] The description describes a polyurethane elastomer that can realize the elastic layer according to the present disclosure. As described above, the polyurethane elastomer according to the present disclosure has a matrix-domain structure comprising a matrix 31 and domains 32 dispersed in the matrix. The matrix 31 has a structure that can increase the deformation recovery rate, and each of the domains 32 has a structure that helps to suppress the increase of micro-rubber hardness.

[0085] Preferably, the matrix 31 of this type of polyurethane elastomer has polycarbonate structural units represented by general formula (1) as repeating structural units. Further, more preferably, the alkylene groups represented by R1 in the repeating structural units represented by general formula (1) having a carbon number of 3 to 9 have a branched structure.

[0086]

[0087] General formula (1)

[0088] R1 represents an alkylene group having 3 to 9 carbon atoms.

[0089] Typically, polyurethanes obtained through the reaction between polyols with a polycarbonate structure (polycarbonate polyols) and polyisocyanates exhibit high elasticity due to the strong intermolecular forces between their carbonate groups. Therefore, such polyurethanes are preferred as a constituent component of matrix 31.

[0090] When R1 represents an alkylene group having 3 to 9 carbon atoms, incompatibility with domains of polyethers each containing repeating structural units represented by the general formula (2) described later is ensured, and the matrix and domains can be clearly phase-separated. Therefore, the polyurethane elastomer according to this disclosure can more reliably perform both the flexibility and rapid recovery from deformation.

[0091] In addition, when R1 contains a branched alkylene group with 3 to 9 carbon atoms, the intermolecular forces between carbonate groups can be appropriately suppressed, and the excessive increase in the elasticity of the matrix can be suppressed.

[0092] Examples of R1 include -(CH2) m -(m=3~9), -CH2C(CH3)2CH2-, -CH2CH(CH3)CH2- and -(CH2)2CH(CH3)(CH2)2-. These groups can be used alone or in combination of two or more.

[0093] The number-average molecular weights of the polyols, etc., described later, and the number-average molecular weights of the polycarbonates mentioned above can be calculated using the following mathematical formulas using the hydroxyl value (mgKOH / g) and valence. 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 as 2,000.

[0094] Number average molecular weight = 56.1 × 1,000 × valence number / hydroxyl value

[0095] The elastic modulus of the matrix can be adjusted, for example, by increasing the crosslinking density through the use of trimer or polymeric compounds of polyisocyanates. Typically, as the elastic modulus increases, the microrubber hardness of the elastic layer also increases. However, in this disclosure, multiple domains, each with low elasticity, are dispersed within the matrix, thus suppressing excessive increases in hardness.

[0096] Preferably, each of the domains 32 includes a polyether structural unit represented by general formula (2) as a repeating structural unit. Further, more preferably, the alkylene group represented by R2 in the structural unit represented by general formula (2) having a carbon number of 3 to 5 has a branched structure.

[0097]

[0098] General formula (2)

[0099] R2 represents an alkylene group having 3 to 5 carbon atoms.

[0100] Polyethers typically exhibit low elastic modulus due to the weak intermolecular forces between their ether groups, making them a preferred component of the domain.

[0101] Preferably, each domain comprises an alkylene group having 3 to 5 carbon atoms, which ensures incompatibility with polyurethane elastomers comprising polycarbonate structural units represented by general formula (1), and that the matrix and domains are clearly phase-separated.

[0102] Examples of R2 include -(CH2). m-(m=3~5), -CH2CH(CH3)-, -CH2C(CH3)2CH2-, -CH2CH(CH3)CH2- and -(CH2)2CH(CH3)CH2-. These groups can be used alone or in combination of two or more.

[0103] 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, more preferably 1,200 or more and 30,000 or less.

[0104] Preferably, the number average molecular weight is 1,000 or higher, because this ensures incompatibility with polyurethane elastomers comprising polycarbonate structural units represented by general formula (1) and makes phase separation between the matrix and the domains clear. Additionally, it is preferred that the number average molecular weight is 50,000 or lower, because the domains are easily formed and the phase separation pattern is stabilized.

[0105] The proportion of the sum of the cross-sectional areas of the domains can be adjusted, for example, by the blending ratio of the polyurethane elastomer of the matrix comprising polycarbonate structural units of general formula (1) and the polyether structural units of the domains of general formula (2). When the blending ratio of the polyether structural units of general formula (2) increases, the proportion of the sum of the cross-sectional areas of the domains increases. However, when the blending ratio of the polyether structural units of general formula (2) increases excessively, the matrix and domains will be reversed, and the polyether structural units of general formula (2) will 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 units of general formula (2).

[0106] The chemical structure of the components in the matrix and domain can be analyzed using spectrometers such as AFM infrared spectrometer, micro infrared spectrometer, or micro Raman spectrometer, or mass spectrometer.

[0107] (Manufacturing method of polyurethane elastomer)

[0108] As an example of the above-mentioned method for manufacturing polyurethane elastomers, a method including the following steps (i) to (iii) is given:

[0109] Step (i): reacting a first polyether having at least two isocyanate groups and a first polycarbonate polyol having at least two hydroxyl groups with each other to obtain a urethane reactive emulsifier having at least two hydroxyl groups;

[0110] Step (ii): obtaining a dispersion in which droplets, each comprising at least a portion of a urethane reactive emulsifier, are dispersed in a second polycarbonate polyol; and

[0111] Step (iii): preparing a mixture for forming an elastic layer comprising 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 the elastic layer with each other.

[0112] Reference Figure 5 Explain each step of the above manufacturing method.

[0113] In step (i), a first polyether 51 having at least two isocyanate groups and a first polycarbonate polyol 52 having at least two hydroxyl groups are mixed. The isocyanate groups and hydroxyl groups in the mixture are reacted with each other in the presence of a catalyst to link together via urethane bonds. This yields a urethane reactive emulsifier 53 having at least two hydroxyl groups.

[0114] In step (ii), the urethane reactive emulsifier 53 obtained in step (i) is dispersed in the second polycarbonate polyol 55. Segments derived from the first polyether 51 contained in the urethane reactive emulsifier 53 incompatiblely form droplets 54 with the second polycarbonate polyol 55. Simultaneously, droplets 54 containing segments derived from the first polyether forming a portion of the urethane reactive emulsifier are uniformly and stably dispersed in the second polycarbonate polyol 55 by 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 of the first polyether 51 derived from the urethane reactive emulsifier 53 are dispersed in the second polycarbonate polyol 55. For ease of explanation, steps (i) and (ii) are described separately, but these steps can be a sequential series of steps.

[0115] In step (ii), the second polycarbonate polyol 55 in which droplets 54 are dispersed can be an unreacted product of the first polyether in the first polycarbonate polyol used in step (i). That is, by using an excess of the first polycarbonate polyol relative to the first polyether in step (i), a dispersion of the urethane reactive emulsifier 53 in the excess first polycarbonate polyol can be obtained, i.e., the second polycarbonate polyol 55 described in step (ii) can be obtained. Even when the first polycarbonate polyol is used in excess, a polycarbonate polyol (second polycarbonate polyol) used as a dispersion medium for the urethane reactive emulsifier can be added separately. In this case, the polycarbonate polyol to be added can have the same chemical composition as or different from the first polycarbonate polyol used in step (i).

[0116] Meanwhile, when the first polycarbonate polyol and the first polyether react with each other in equal amounts, and all of the first polycarbonate polyol is consumed in step (i), the new polycarbonate polyol is used as the second polycarbonate polyol to prepare the dispersion in step (ii). Similarly, in this case, the polycarbonate polyol used as the second polycarbonate polyol may have the same chemical composition as the first polycarbonate polyol, or it may be different.

[0117] Finally, in step (iii), an elastic layer forming mixture comprising the dispersion prepared in step (ii) and a polyisocyanate 56 having at least two isocyanate groups is prepared. Then, the terminal hydroxyl groups of the urethane reactive emulsifier 53, the hydroxyl groups of the second polycarbonate polyol 55, and the isocyanate groups of the polyisocyanate 56 in the elastic layer forming mixture are reacted with each other. Thus, a network structure through urethane bonds is formed, and the elastic layer forming mixture is cured to obtain the polyurethane elastomer according to the present disclosure. The resulting polyurethane elastomer 500 has a matrix-domain structure, wherein domains 32, each comprising a polyether derived from the first polyether 51, are dispersed in a matrix 31 comprising a polycarbonate elastomer comprising a polycarbonate derived from the polycarbonate polyol 52 and the second polycarbonate polyol 55. Furthermore, the domains 32 primarily comprise polyether structural portions, and the cross-linked structures may be substantially absent within the domains. In other words, the domains 32 may exist in a substantially liquid state within the matrix 31. With this configuration, the domains in the polyurethane elastomer according to the present disclosure can have a low elastic modulus.

[0118] Furthermore, regarding the domains, the liquid portion is not merely confined within the matrix; rather, the domains and the matrix are chemically bonded to each other via urethane bonds at the boundary between the domains and the matrix. Therefore, when the 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 domains in liquid form essentially lack cross-linking structures. Therefore, domains deformed by applying a load to the polyurethane elastomer are difficult to autonomously recover from deformation. However, in the polyurethane elastomer according to this disclosure, the domains are chemically bonded to the matrix at the boundary with it, and thus the domains can also recover from deformation along with the matrix. As a result, stable deformation (deformation amount) and stable recovery from deformation can be achieved even when the polyurethane elastomer is repeatedly subjected to load application and removal.

[0119] Steps (i) and (ii) above involve stably dispersing the polyether, which originally had low compatibility with the polyol and was difficult to disperse stably and uniformly, in the polyol. Specifically, steps (i) and (ii) involve reacting the first polyether 51 with the first polycarbonate polyol 52 to form a urethane reactive emulsifier 53, thereby obtaining a dispersion in which the polyether segments derived from the first polyether 51 are stably and uniformly dispersed in the second polycarbonate polyol. As a result, a polyurethane elastomer can be manufactured in which domains 32, each possessing high sphericity, micron-sized dimensions, and relatively uniform size distribution, are dispersed in the polyurethane 31 used as a matrix.

[0120] Other methods for mixing materials with low compatibility include, for example, methods involving mixing and dispersing materials with high shear forces. However, in this method, the shape of each domain is distorted due to the high shear force applied to the polyether, thereby reducing roundness, and the domain size may also become non-uniform. Furthermore, the dispersion is unstable, and domain aggregation occurs within a relatively short time. Additionally, the incompatibility between the polyether and the polycarbonate polyol cannot be guaranteed, resulting in unclear phase separation between the matrix and domains of the resulting polyurethane elastomer. Therefore, it is difficult to obtain a polyurethane elastomer that provides a soft elastomer with excellent deformation recovery according to this disclosure.

[0121] The first polyether is a polyether having at least two isocyanate groups and repeating structural units represented by general formula (2). The first polyether can be obtained by reacting a polyether polyol having at least two hydroxyl groups and repeating structural units represented by general formula (2) with a polyisocyanate having at least two isocyanate groups.

[0122] Examples of polyether polyols include polyether polyols containing alkylene structures, such as polypropylene glycol, polybutane glycol, copolymers of tetrahydrofuran and neopentyl glycol, copolymers of tetrahydrofuran and 3-methyltetrahydrofuran, and random or block copolymers of these polyalkylene glycols. These polyether polyols can be used alone or in combination of two or more.

[0123] From the viewpoint that it can achieve incompatibility with the second polycarbonate polyol and low hardness, amorphous polyether polyols are preferred.

[0124] More preferably, the polyether polyol includes at least one selected from polypropylene glycol, a copolymer of tetrahydrofuran and neopentyl glycol, and a copolymer of tetrahydrofuran and 3-methyltetrahydrofuran.

[0125] The number average molecular weight of the polyether polyol is preferably 1,000 or more and 50,000 or less, 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 polycarbonate polyols and results in clear phase separation between the matrix and domains of the obtained polyurethane elastomer. Furthermore, a number average molecular weight of 50,000 or less is preferred because domains are easily formed and the phase separation morphology is stabilized.

[0126] Examples of polyisocyanates permissible to react with polyether polyols include pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, phenylenediethylene diisocyanate, diphenylmethane diisocyanate, or trimers (isocyanurates) or polymers of any of these polyisocyanates, urea-formate polyisocyanates, biuret-formate polyisocyanates, and aqueous dispersion polyisocyanates. These polyisocyanates can be used alone or in combination of two or more.

[0127] Among polyisocyanates, bifunctional isocyanates having two isocyanate groups are preferred because they have high compatibility with the first polyether and their physical properties, such as viscosity, are easily adjustable. More preferably, the polyisocyanate includes at least one selected from hexamethylene diisocyanate, isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, phenylenediethylene diisocyanate, and diphenylmethane diisocyanate.

[0128] In the step of reacting the polyether polyol and the polyisocyanate with each other, the isocyanate index is preferably in the range of 1.2 to 5.0. When the isocyanate index falls within the above range, the amount of the component originating from the first polyether that has not formed a network structure and remains is reduced, and the exudation of liquid substances from the polyurethane elastomer can be suppressed. The isocyanate index represents the ratio of the molar number of cyanoisoester groups in the isocyanate compound to the molar number of hydroxyl groups in the polyol compound ([NCO] / [OH]).

[0129] The first polyether obtained by the reaction between a polyether polyol and a polyisocyanate has a structure in which hydroxyl groups react with isocyanate groups to link them together via urethane bonds. 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.

[0130] The first polycarbonate polyol is a polycarbonate polyol having at least two hydroxyl groups and repeating structural units represented by general formula (1). Examples of the first polycarbonate polyol include reaction products of polyols with phosgene and ring-opening polymers of cyclic carbonates (e.g., alkylene carbonates).

[0131] Examples of polyols include propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylene glycol, 1,3-tetramethylene glycol, 2-methyl-1,3-trimethylene glycol, 1,5-pentamethylene glycol, neopentyl glycol, 1,6-hexamethylene glycol, 3-methyl-1,5-pentamethylene glycol, 2,4-diethyl-1,5-pentamethylene glycol, glycerol, trimethylolpropane, trimethylolethane, cyclohexanediol (e.g., 1,4-cyclohexanediol), and sugar alcohols (e.g., xylitol and sorbitol).

[0132] Examples of alkylene carbonates include trimethylene carbonate, tetramethylene carbonate, and hexamethylene carbonate.

[0133] The number average molecular weight of the first polycarbonate polyol is preferably 500 or more and 10,000 or less, more preferably 700 or more and 8,000 or less. When the number average molecular weight is 500 or more, incompatibility with domains of polyethers each containing repeating structural units represented by general formula (2) is ensured, and phase separation between the matrix and the domains can be made clearer. In addition, when the number average molecular weight is set to 10,000 or less, excessive increase in viscosity of the first polycarbonate polyol can be prevented.

[0134] As the second polycarbonate polyol used in step (ii), the polycarbonate polyol given in the first polycarbonate polyol described above can be used. As mentioned above, the first polycarbonate polyol and the second polycarbonate polyol can have the same chemical composition, or first polycarbonate polyol and second polycarbonate polyol with different chemical compositions can be used.

[0135] The polyisocyanate 56 having at least two isocyanate groups used in step (iii) can be any of the polyisocyanates listed above that are the same as the raw materials of the first polyether described above. These polyisocyanates can be used alone or in combination of two or more of them.

[0136] From the viewpoint of increasing the elastic modulus of the matrix, polyisocyanate 56 preferably comprises a polyisocyanate having at least three isocyanate groups, such as a trimer (isocyanurate) or polymer of a polyisocyanate, a urea-formate type polyisocyanate, or a biuret type polyisocyanate. Polyisocyanate 56 is more preferably comprised of any one of a trimer (isocyanurate) of pentamethylene diisocyanate, a trimer (isocyanurate) of hexamethylene diisocyanate, or a polymer of diphenylmethane diisocyanate.

[0137] As catalysts, urethane esterification catalysts and isocyanate esterification catalysts (isocyanate trimerization catalysts) that are known to date can be used individually. These catalysts can be used alone or as a mixture thereof.

[0138] Examples of carbamate catalysts include: tin-based carbamate catalysts, such as dibutyltin dilaurate and stannous octanoate; and amine-based carbamate catalysts, such as triethylenediamine, tetramethylguanidine, pentamethyldiethylenetriamine, diethylimidazole, tetramethylpropylenediamine, N,N,N′-trimethylaminoethylethanolamine, and 1,4-diazabicyclo[2.2.2]octane-2-methanol. These carbamate catalysts can be used alone or as mixtures thereof.

[0139] Examples of isocyanate esterification catalysts include: metal oxides such as Li₂O and (Bu₃Sn)₂O; hydrides such as NaBH₄; alkoxides such as NaOCH₃, KO-(t-Bu), and borates; amines such as N(C₂H₅)₃, N(CH₃)₂CH₂C₂H₅, and 1,4-ethylidene piperazine (DABCO); basic carboxylate compounds such as HCOONa, Na₂CO₃, PhCOONa / DMF, CH₃COOK, (CH₃COO)₂Ca, basic soaps, and naphthenates; basic formate compounds; and quaternary ammonium compounds such as ((R)₃-NR′OH)-OCOR″. Additionally, examples of combined catalysts (co-catalysts) used as isocyanate esterification catalysts include amine / epoxide, amine / carboxylic acid, and amine / alkylimide. These isocyanate esterification catalysts and combined catalysts can be used alone or as mixtures thereof.

[0140] According to the manufacturing method of this disclosure, a chain extender (a multifunctional low molecular weight polyol) may be used as needed. The chain extender is, for example, a diol with a number average molecular weight of 1,000 or less. Examples of diols 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-cyclohexanediol, xylenediol (terephthalic acid diethanolamide), and triethylene glycol. In addition, chain extenders other than diols may be, for example, polyols with three or more nucleotides. Examples of polyols with three or more nucleotides include trimethylolpropane, glycerol, pentaerythritol, and sorbitol. These diols may be used alone or as mixtures thereof.

[0141] In addition, additives such as pigments, plasticizers, water repellents, antioxidants, conductive agents, UV absorbers, and light stabilizers can be used as needed.

[0142] (Manufacturing method of elastic layer)

[0143] The elastic layer can be formed, for example, by performing the reaction according to step (iii) in the above-described method for manufacturing polyurethane elastomer on the surface of the mandrel.

[0144] Specifically, for example, a method may be provided involving curing a mixture comprising the dispersion prepared in step (ii) and a polyisocyanate having at least two isocyanate groups on the outer peripheral surface of a mandrel for forming an elastic layer. That is, as a method for manufacturing the elastic layer according to this disclosure, for example, the elastic layer may be manufactured by a method including the steps (2-i) to (2-iv):

[0145] Step (2-i): reacting a first polyether having at least two isocyanate groups and a first polycarbonate polyol having at least two hydroxyl groups with each other to obtain a urethane reactive emulsifier having at least two hydroxyl groups;

[0146] Step (2-ii): obtaining a dispersion in which droplets, each comprising at least a portion of a urethane reactive emulsifier, are dispersed in a second polycarbonate polyol;

[0147] Step (2-iii): The step of mixing the dispersion and a polyisocyanate having at least two isocyanate groups with each other to obtain a mixture for forming an elastic layer; and

[0148] Step (2-iv): The elastic layer is formed by reacting the urethane reactive emulsifier, the second polycarbonate polyol and the polyisocyanate in the mixture with each other on the surface of the mandrel to obtain the elastic layer.

[0149] As a method for curing an elastic layer with a mixture on the surface of a mandrel, for example, a method involving injecting the material of the elastic layer into a mold comprising a cylindrical tube, a bridge for holding the mandrel, and the mandrel, and then heating and curing it (casting method) can be used. Alternatively, a method involving coating the surface of the mandrel with an elastic layer forming mixture to form a coating film and heating and curing the coating film can also be used.

[0150] (Surface layer)

[0151] A surface layer may also be formed on the surface of the elastic layer, if necessary. Examples of materials used to form the surface layer include resins, natural rubber, and synthetic rubber. Thermosetting or thermoplastic resins can be used as resins. In particular, fluoropolymers, polyamides, acrylics, polyurethanes, silicones, or butyrals are preferred as resins because the viscosity of the coating can be easily controlled. These resins can be used alone or in combination of two or more. The materials may also be copolymers.

[0152] To adjust the resistance of the electrophotographic roller, a conductive agent can be blended into the surface layer. The volume resistivity of the surface layer can be adjusted using either an ionic or an electronic conductive agent.

[0153] Examples of ionic conductive agents include: inorganic ionic substances such as lithium perchlorate, sodium perchlorate, and calcium perchlorate; cationic surfactants such as dodecyltrimethylammonium chloride, stearyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, trioctylpropylammonium bromide, and modified aliphatic dimethylethylammonium ethosulfate; zwitterionic surfactants such as lauryl betaine, stearyl betaine, and dimethylalkyl lauryl betaine; quaternary ammonium salts such as tetraethylammonium perchlorate, tetrabutylammonium perchlorate, and trimethyloctadecylammonium perchlorate; and organic lithium acid salts such as lithium trifluoromethanesulfonate. Ionic conductive agents can be used alone or in combination of two or more.

[0154] Examples of electronically conductive agents include: fine metal particles or fibers, such as aluminum, palladium, iron, copper, and silver; conductive metal oxides, such as titanium oxide, tin oxide, and zinc oxide; composite particles whose surfaces are treated by electrolysis, spraying, or mixing / vibration; and toners, such as furnace black, thermal cracking black, acetylene black, Ketjen black, polyacrylonitrile (PAN)-based carbon, and pitch-based carbon.

[0155] The surface layer may contain other particles. Examples of other particles may include insulating particles. Examples of insulating particles include: polyamide resins, silicone resins, fluoropolymers, (meth)acrylic resins, styrene resins, phenolic resins, polyester resins, melamine resins, polyurethane resins, olefin resins, epoxy resins, or copolymers, modified products, or derivatives thereof; rubbers, such as ethylene-propylene-diene copolymer (EPDM), styrene-butadiene copolymer rubber (SBR), silicone rubber, polyurethane rubber, isoprene rubber (IR), butyl rubber, acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), epichlorohydrin rubber; and polyolefin thermoplastic elastomers, polyurethane thermoplastic elastomers, polystyrene thermoplastic elastomers, fluororubber thermoplastic elastomers, polyester thermoplastic elastomers, polyamide thermoplastic elastomers, polybutadiene thermoplastic elastomers, ethylene-vinyl acetate thermoplastic elastomers, polyvinyl chloride thermoplastic elastomers, and chlorinated polyethylene thermoplastic elastomers. In particular, (meth)acrylic resins, styrene resins, polyurethane resins, fluoropolymers, or silicone resins are preferred.

[0156] The materials used to form the surface layer can be dispersed using dispersion devices known to date that employ beads, such as sand mills, paint mixers, Dieno mills, or bead mills. There are no particular limitations on the method of applying the resulting dispersion, but impregnation is preferred due to its simplicity.

[0157] Electrophotographic image forming equipment

[0158] A schematic construction of an example of an electrophotographic image forming apparatus including an electrophotographic component according to one embodiment of the present disclosure is shown in the figure. Figure 6 .

[0159] Figure 6 In this image forming apparatus, there are photosensitive elements 61, charging devices, latent image forming devices, developing devices, transfer devices, cleaning devices, and fixing devices.

[0160] The photosensitive element 61 is a rotating drum having a photosensitive layer on a conductive substrate. The photosensitive element 61 is driven to rotate at a predetermined circumferential speed (processing speed) in the direction indicated by the arrow.

[0161] The charging device has the function of charging the photosensitive element 61 and includes a contact-type charging roller 62 configured to contact the photosensitive element 61 by abutting it with a predetermined pressure. The charging roller 62 rotates in the direction indicated by the arrow as the photosensitive element 61 rotates. The charging roller 62 charges the photosensitive element 61 to a predetermined potential by applying a predetermined DC voltage from a power supply 63 for charging.

[0162] A latent image forming apparatus (not shown) performs exposure to form an electrostatic latent image on the photosensitive member 61. An exposure apparatus such as a laser beam scanner is used as the latent image forming apparatus. The latent image forming apparatus forms an electrostatic latent image by irradiating the uniformly charged photosensitive member 61 with exposure light 64 corresponding to image information.

[0163] The developing apparatus has the function of developing toner images and includes a developing roller 65 configured to be close to or in contact with the photosensitive member 61. The developing roller 65 develops an electrostatic latent image by reverse development to form a toner image on the photosensitive member 61 using a toner that has been electrostatically treated to have the same polarity as the charged electrode of the photosensitive member 61.

[0164] The transfer apparatus has the function of transferring a developed toner image onto a recording material P, and includes a contact-type transfer roller 66. The transfer roller 66 rotates in the direction indicated by the arrow as the photosensitive member 61 rotates, transferring the toner image from the photosensitive member 61 onto the recording material P, such as plain paper. The recording material P is conveyed by a paper feeding system (not shown) including a conveying member in the direction indicated by the arrow.

[0165] The cleaning device has the function of collecting residual toner on the photosensitive element 61 and includes a scraper-type cleaning element 68 and a collection container 69. After the toner image has been transferred onto the recording material P, the cleaning device mechanically scrapes off and collects the residual toner remaining on the photosensitive element 61.

[0166] Here, the cleaning unit can be omitted by using a simultaneous cleaning system where the residual toner from the transfer is collected by the developing unit.

[0167] The fixing device has the function of fixing a toner image and includes a fixing belt 67 with a heated roller. When the fixing device rotates in the direction indicated by the arrow, it fixes the toner image transferred onto the recording material P and transports the recording material P out of the equipment.

[0168] In an image forming apparatus, the aforementioned electrophotographic component can be suitably used as a charging roller 62 or a developing roller 65.

[0169] <Processing Box>

[0170] A schematic construction of a processing box according to one embodiment of this disclosure is shown in... Figure 7 The processing cartridge integrates a photosensitive element 71, a charging roller 72, a developing roller 73, and a cleaning element 74, and is detachably mounted to an image forming apparatus. The processing cartridge includes an electrophotographic element according to one embodiment of the present disclosure, and this electrophotographic element may be particularly suitable for use as either the charging roller 72 or the developing roller 73.

[0171] [Example]

[0172] One embodiment of this disclosure is described in more detail below through examples. However, this disclosure is not limited to the following examples.

[0173] <Example 1>

[0174] (Preparation of the mixture for forming the elastic layer)

[0175] 500 ppm of 1,4-diazabicyclo[2.2.2]octane-2-methanol (trade name: RZETA, manufactured by Tosoh Corporation) used as a curing catalyst was added to 20.1 parts by weight of polypropylene glycol (trade name: PREMINOLS4013F, manufactured by AGC Inc.), 19.2 parts by weight of polypropylene glycol (trade name: UNOL D-4000, manufactured by NOFCorporation), and 2.5 parts by weight of phthalimide diisocyanate (XDI) (manufactured by Tokyo Chemical Industry Co., Ltd.). The mixture was stirred in a closed mixer adjusted to 100°C for 4 hours to synthesize a polyether having two isocyanate groups.

[0176] 50.3 parts by weight of polycarbonate diol (product name: DURANOL G3452, manufactured by Asahi Kasei Corporation) were mixed with the result. The mixture was then further stirred for 2 hours using a closed mixer adjusted to 100°C to synthesize a urethane reactive emulsifier having two hydroxyl groups, and to obtain a dispersion in which droplets of the urethane reactive emulsifier were dispersed in polycarbonate diol.

[0177] 0.8 parts by mass of phthalimide 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 ionic conductive agent (trade name: CIL-542, manufactured by Japan Carlit Co., Ltd., hereinafter sometimes referred to as "CIL") were added to the dispersion. The mixture was stirred for 2 minutes at 1,600 rpm using a rotary vacuum degassing mixer to obtain a mixture for forming an elastic layer.

[0178] (Manufacturing of the Electrophotographic Roller)

[0179] The primer (trade name: METALOC N-33, manufactured by Toyokagaku Kenkyusho Co., Ltd.) was applied to a mandrel made of SUS304 with a diameter of 6mm and a length of 250mm, and baked at 130°C for 30 minutes.

[0180] Then, the mandrel is placed concentrically in a cylindrical mold with an inner diameter of 11.5 mm, and the mixture for forming the elastic layer is injected into the cylindrical mold preheated to 130°C within 10 seconds.

[0181] After heating a cylindrical mold at 130°C for 1 hour, the mixture was removed from the mold. The resulting material was further aged at 80°C for 2 days to obtain an elastic layer. The ends of the elastic layer were then removed. This yielded 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.

[0182] Evaluation methods for electrophotographic rollers

[0183] (Evaluation 1: Identification and analysis of matrix (sometimes referred to as “M” in Table 4-1) and domain (sometimes referred to as “D” in Table 4-1))

[0184] A slicer is used to make slices from an electrophotographic roller. Regarding the location for making slices, when the length of the elastic layer in the longitudinal direction is represented by L, slices are made in the thickness direction of the elastic layer at a total of three locations, including 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.

[0185] Each slice was mapped using a three-dimensional micro-laser Raman spectroscopy analyzer (trade name: Nanofinder 30, manufactured by Tokyo Instruments, Inc.). The measurement mode was set to electron multiplication (EM), and measurements were taken at 60×60 points at 500 nm intervals, yielding a result of 0 cm⁻¹. -1 ~400cm -1 The integral image was obtained. From the obtained integral image, the matrix and multiple domains dispersed in the matrix were identified in the elastic layer. Furthermore, the matrix and domains were clearly phase-separated.

[0186] Next, Raman spectra of the matrix and domain portions were measured from the integral image. Measurements were performed using the following parameters: Nd:YVO4 light source (wavelength: 532 nm), laser intensity: 240 μW, objective magnification: 100x, diffraction grating: 300 gr / mm, pinhole diameter: 100 μm, exposure time: 30 seconds, and scan count: 1. The obtained Raman spectra revealed that the matrix has a structure derived from polycarbonate urethane, and the domain has a structure derived from polypropylene glycol (sometimes referred to as "PPG" in Table 4-1).

[0187] (Evaluation 2: Measurement of micro-rubber hardness)

[0188] The micro-rubber hardness of the elastic layer was measured using a micro-rubber hardness tester (trade name: MD-1capa, manufactured by Kobunshi Keiki Co., Ltd.). During the measurement, the electrophotographic roller was placed at a temperature of 23°C for more than 24 hours, and measurements were taken using a measuring device placed under the same conditions. Furthermore, an A-type indenter (height: 0.50 mm, diameter: 0.16 mm, cylindrical) was used, and the measurement mode was set to peak hold mode.

[0189] When the length of the elastic layer is represented by L, the micro-rubber hardness is measured at a total of three locations, including the center of the elastic layer along its length and two locations at L / 4 points from both ends of the elastic layer toward the center. The average value of the micro-rubber hardness measured at each location is calculated at a temperature of 23°C.

[0190] (Evaluation 3: Measurement of parameters representing the viscoelasticity term)

[0191] A slicer is used to make slices from an electrophotographic roller. Regarding the location for making slices, when the length of the elastic layer in the longitudinal direction is represented by L, slices are made in the thickness direction of the elastic layer at a total of three locations, including 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.

[0192] A square observation area of ​​arbitrary 50 μm was selected within a thickness region extending from the outer surface of each slice to a depth of 100 μm, and viscoelastic images were measured in a total of three observation areas using a scanning probe microscope (trade name: S-Image, manufactured by SII NanoTechnology). The measurement mode for the viscoelastic images was set to VE-DFM. Additionally, a "SI-DF3" (trade name, manufactured by Hitachi High-Tech Science Corporation, spring constant = 1.9 N / m) was used as the cantilever. Furthermore, the scanning frequency was set to 0.5 Hz.

[0193] From the obtained viscoelastic image, the parameters representing the viscoelastic terms in each observation region are calculated at 10 points in the matrix and 10 points in the domain, and the parameters representing the viscoelastic terms in each domain and the viscoelastic terms in the matrix are determined from their average values.

[0194] (Evaluation 4: Measurement of the deformation recovery of the elastic layer)

[0195] The deformation recovery of the elastic layer was evaluated in an indentation test conducted at 23°C using a nanoindenter (trade name: HM2000, manufactured by Fischer Instruments KK). In the measurement, the electrophotographic roller was placed at 23°C for more than 24 hours, and measurements were taken using a measuring device placed under the same conditions.

[0196] When the length of the elastic layer is denoted by L, deformation recovery is measured at a total of three locations, including the center of the elastic layer along its length and two locations at L / 4 from both ends of the elastic layer toward the center. In the indentation test, a Vickers indenter (square pyramidal, face angle: 136°) is pressed into the elastic layer at a loading rate of 10 mN / 30 sec and maintained under a load of 10 mN for 60 seconds. Then, the average strain is calculated 5 seconds after unloading at each measurement location.

[0197] (Evaluation 5: Elastic modulus of the matrix)

[0198] A slicer is used to make slices from an electrophotographic roller. Regarding the location for making slices, when the length of the elastic layer in the longitudinal direction is represented by L, slices are made in the thickness direction of the elastic layer at a total of three locations, including 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.

[0199] A square observation area of ​​arbitrary 50 μm was selected within a thickness region extending from the outer surface of each slice to a depth of 100 μm. Phase images were observed in a total of three observation areas using a scanning probe microscope (trade name: MFP-3D-Origin, manufactured by Oxford Instruments plc). The observation mode for the phase images was set to AM-AFM. Additionally, an "OMCL-AC-160TS" (trade name, manufactured by Olympus Corporation, spring constant = 47.08 N / m) was used as a cantilever. The scanning frequency was set to 0.5 Hz.

[0200] The elastic modulus of the matrix was determined from the resulting phase image by measuring the force curve using a scanning electron microscope. The force curve measurement mode was set to contact mode, the force distance was set to 500 nm, and the trigger point was set to 0.01 V. An "OMCL-AC-160TS" (trade name, manufactured by Olympus Corporation, spring constant = 47.08 N / m) was used as the cantilever. The scanning frequency was set to 1 Hz. The elastic modulus of the matrix was determined at 10 points in each observation area, and its average value was calculated.

[0201] (Evaluation 6: Measurement of the cross-sectional area and number of domains)

[0202] A slicer is used to make slices from an electrophotographic roller. Regarding the location for making slices, when the length of the elastic layer in the longitudinal direction is represented by L, slices are made at a total of three locations, including 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, each exposing a section in the thickness direction of the elastic layer.

[0203] In each slice, a square observation area with a side length of 50 μm was set at arbitrary locations within a thickness region extending from the outer surface of the elastic layer to a depth of 100 μm. Viscoelastic images were then measured in a total of three observation areas using a scanning probe microscope (trade name: S-Image, manufactured by SII NanoTechnology).

[0204] The measurement mode for the viscoelastic image was set to micro-viscoelastic dynamic mode (VE-DFM). Furthermore, a microcantilever (SI-DF3, manufactured by Hitachi High-Tech Science Corporation, spring constant = 1.9 N / m) made of silicon was used as the cantilever for the DFM. The scanning frequency was set to 0.5 Hz.

[0205] The resulting cross-sectional image was converted into a 256-grayscale monochrome image using image processing software (trade name: ImageProPlus, manufactured by Media Cybernetics, Inc.). Then, binarization was performed to provide a binarized image for analysis. The binarization threshold was determined from the brightness distribution of the monochrome image based on the Otsu algorithm described in Non-Patent Document 1.

[0206] The cross-sectional area and number of domains were calculated from the obtained binarized image using the counting function of image processing software. Among the domains identified as domains by the counting function, those with a cross-sectional area less than 0.05% of the 50μm square observation area were considered noise-induced domains and removed from the data. Furthermore, the ratio (%) of the sum of the cross-sectional areas of the domains in each observation area to the area of ​​the observation area was calculated. Additionally, the number of domains in each observation area whose respective cross-sectional area was 0.1% to 13.0% of the observation area was determined, and the ratio (%) of the determined number of domains to the total number of domains in the observation area was calculated.

[0207] (Evaluation 7: Measurement of the circularity and number of domains)

[0208] The circularity of each region was calculated from the binarized image obtained in Evaluation 6 using the counting function of image processing software. Regions originating from noise were removed from the data in the same manner as in Evaluation 6. Then, in each observation region, the number of regions with a circularity of 0.60 or higher and 0.95 or lower was counted, and the percentage (%) of the counted regions relative to the total number of regions in each observation region was calculated.

[0209] (Evaluation 8: Evaluation of striped image defects)

[0210] A color laser printer (trade name: LBP7700C, manufactured by Canon Inc.) and its processing cassette, incorporating an electrophotographic roller as a developing roller, were placed in an environment with a temperature of 23°C and a humidity of 50%RH for 24 hours, and then the images were evaluated.

[0211] Specifically, a processing cartridge in which an electrophotographic roller is incorporated as a developing roller is installed in a color laser printer. Then, halftone images (images in which horizontal lines with a width of 1 point and a spacing of 2 points are drawn in a direction perpendicular to the rotation direction of the photosensitive element) are continuously output on 10 sheets, and the resulting images are visually observed, and striped image defects are judged based on the following two criteria.

[0212] <Evaluation of striped image defects 8-1>

[0213] Grade A: No striped image defect was identified from the first image.

[0214] Grade B: Striped image defects are identified only on the first image.

[0215] Grade C: Striped image defects were also identified on the second and subsequent images.

[0216] <Evaluation of striped image defects 8-2>

[0217] Grade A: No striped image defects were detected along the entire length of the electrophotographic roller.

[0218] Grade B: Striped image defects are identified in a portion of the length of the electrophotographic roller.

[0219] Grade C: Striped image defects are identifiable and obvious over a wide range along the length of the electrophotographic roller.

[0220] (Evaluation 9: Evaluation of image defects such as end wear, toner melt adhesion, and toner-derived melt adhesion)

[0221] The processing chamber, in which the aforementioned color laser printer and electrophotographic roller are introduced as developing rollers, is placed for 24 hours in an environment with a temperature of 23°C and a humidity of 50%RH.

[0222] The electrophotographic roller is then installed as a developing roller in a color laser printer, and images in which horizontal lines with a width of 2 dots and a spacing of 50 dots are drawn are continuously output on 10,000 sheets.

[0223] During a continuous output of 10,000 sheets, the developing roller is removed every 1,000 sheets and visually inspected. Wear at the end of the developing roller and toner melt adhesion are determined based on the following criteria.

[0224] <Evaluation 9-1: Evaluation of End Wear>

[0225] Grade A: No wear at the ends was detected even after 10,000 prints were output.

[0226] Grade B: No end wear was detected after 8,000 prints, but end wear was detected after 9,000 prints.

[0227] Grade C: No wear at the ends was detected after 5,000 prints, but wear at the ends was detected after 8,000 prints.

[0228] Grade D: Identifies end wear after 5,000 prints.

[0229] <Evaluation 9-2: Evaluation of the melt adhesion of toner>

[0230] Grade A: No toner melt adhesion was detected even after 10,000 prints were output.

[0231] Grade B: No toner melt adhesion was detected after 8,000 prints, but toner melt adhesion was detected after 9,000 prints.

[0232] Grade C: No toner melt adhesion was detected after 5,000 prints, but toner melt adhesion was detected after 8,000 prints.

[0233] Grade D: Toner melt adhesion is detected after 5,000 prints.

[0234] <Evaluation 9-3: Evaluation of image defects originating from toner melt adhesion>

[0235] During continuous output of 10,000 images, the output image is identified every 10 images. When an image defect exists outside the horizontal line, such as when toner transfers onto the paper during the interval of one rotation of the electrophotographic roller, output is temporarily stopped, and the electrophotographic roller is removed from the processing cassette. When the location of the image defect matches the location and size of the fused portion of toner on the electrophotographic roller, the number of output images at the time of temporary stop is taken as the number of image defects originating from toner melt adhesion.

[0236] <Examples 2-7, 9-12, 14, 15 and 18>

[0237] Except for using the materials shown in Table 3 at the blending amounts shown in Table 3, the mixture for forming the elastic layer was prepared in the same manner as in Example 1. Except for using the mixture for forming the elastic layer, the electrophotographic roller according to the embodiment was manufactured by forming the elastic layer in the same manner as in Example 1. The resulting electrophotographic roller was evaluated in the same manner as in Example 1.

[0238] Details of the material types in Table 3 are shown in Tables 1 and 2. The following examples are also applicable.

[0239] <Example 8>

[0240] Except that the materials shown in Table 3 are used in the blending amounts shown in Table 3, the elastic layer forming mixture is prepared in the same manner as in Example 1. Except that the elastic layer forming mixture is used and the injection of the elastic layer forming mixture into the cylindrical mold is performed for 5 seconds, the electrophotographic roller according to this embodiment is manufactured by forming the elastic layer in the same manner as in Example 1. The obtained electrophotographic roller is evaluated in the same manner as in Example 1.

[0241] <Examples 13, 16 and 17>

[0242] Except that the materials shown in Table 3 are used in the blending amounts shown in Table 3, the elastic layer forming mixture is prepared in the same manner as in Example 1. Except that the elastic layer forming mixture is used and the injection of the elastic layer forming mixture into the cylindrical mold is performed for 3 seconds, the electrophotographic roller according to the embodiment is manufactured by forming the elastic layer in the same manner as in Example 1. The obtained electrophotographic roller is evaluated in the same manner as in Example 1.

[0243] [Table 1]

[0244]

[0245] The tetrahydrofuran-neopentyl glycol copolymer in item A5 above is a polyether glycol represented by the following structural formula: HO-(CH2CH2CH2CH2O) m -(CH2C(CH3)2CH2O)n -

[0246] [Table 2]

[0247]

[0248] According to item B2 above, KURARAY POLYOL C-2090 (a polycarbonate polyol manufactured by Kuraray Co., Ltd.; number average molecular weight: 1,993; hydroxyl value: 56.3 mg KOH / g) is a polycarbonate polyol having a 1,6-hexanediol-derived structure and a 3-methyl-1,5-pentanediol-derived structure.

[0249] [Table 3]

[0250]

[0251] <Comparative Example 1>

[0252] (Preparation of the mixture for forming the elastic layer)

[0253] 500 ppm of curing catalyst (trade name: RZETA, manufactured by Tosoh Corporation) was added to 24.9 parts by weight of polypropylene glycol (trade name: PREMINOL S4013F, manufactured by AGC Inc.), 24.0 parts by weight of polypropylene glycol (trade name: UNIOL D-4000, manufactured by NOF Corporation), and 3.1 parts by weight of diphenylmethylene diisocyanate (XDI) (manufactured by Tokyo Chemical Industry Co., Ltd.). The mixture was stirred in a closed mixer adjusted to 100°C for 4 hours to synthesize a polyether having two isocyanate groups.

[0254] 41.5 parts by weight of polycarbonate diol (DURANOL G3452, manufactured by Asahi Kasei Corporation) were mixed with the result. The mixture was then further stirred for 2 hours using a closed mixer adjusted to 100°C to synthesize a urethane reactive emulsifier having two hydroxyl groups and to obtain a dispersion in which droplets of the urethane reactive emulsifier were dispersed in polycarbonate diol.

[0255] 4.7 parts by mass of polyisocyanate (trade name: Millionate MR-200, manufactured by Tosoh Corporation) and 1.8 parts by mass of ionic conductive agent (trade name: CIL-542, manufactured by Japan Carlit Co., Ltd.) were added to the dispersion. The mixture was stirred for 2 minutes at 1,600 rpm using a rotary vacuum degassing mixer to obtain a mixture for forming an elastic layer. Except for using the elastic layer forming mixture 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.

[0256] Regarding the results of Evaluation 1, the matrix and domains were clearly phase-separated. Furthermore, the matrix was identified as comprising a polyurethane elastomer containing polyether, and the domains as comprising a polyurethane elastomer containing polycarbonate. That is, the relationship between the domains and the matrix is ​​the reverse of the relationship in the polyurethane elastomer according to Example 1.

[0257] <Comparative Example 2>

[0258] (Preparation of the mixture for forming the elastic layer)

[0259] 500 ppm of curing catalyst (trade name: RZETA, manufactured by Tosoh Corporation) was added to 20.1 parts by weight of polypropylene glycol (trade name: PREMINOL S4013F, manufactured by AGC Inc.), 19.2 parts by weight of polypropylene glycol (trade name: UNIOL D-4000, manufactured by NOF Corporation), and 50.3 parts by weight of polycarbonate glycol (trade name: DURANOLG3452, manufactured by Asahi Kasei Corporation). The mixture was stirred for 2 hours using a closed mixer adjusted to 100°C. Add 3.3 parts by weight of phthalimide 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 ionic conductive agent (trade name: CIL-542, manufactured by Japan Carlit Co., Ltd.) to the mixture. Stir the resulting mixture in a closed vacuum mixer for 2 minutes to obtain a mixture for forming an elastic layer.

[0260] Except for using the obtained elastic layer forming mixture, the electrophotographic roller according to this comparative example is manufactured by forming the elastic layer in the same manner as in Example 1. The obtained electrophotographic roller is evaluated in the same manner as in Example 1.

[0261] <Comparative Example 3>

[0262] (Preparation of the mixture for forming the elastic layer)

[0263] 500 ppm of curing catalyst (trade name: RZETA, manufactured by Tosoh Corporation) was added to 7.0 parts by weight of polypropylene glycol (trade name: UNIOL D-2000, manufactured by NOF Corporation) and 79.0 parts by weight of polycarbonate glycol (DURANOL T6002, manufactured by Asahi Kasei Corporation). The mixture was stirred for 2 hours using a closed mixer adjusted to 100°C.

[0264] Add 4.3 parts by weight of phthalimide diisocyanate (XDI) (manufactured by Tokyo Chemical Industry Co., Ltd.), 8.0 parts by weight of polyisocyanate (trade name: Millionate MR-200, manufactured by Tosoh Corporation), and 1.8 parts by weight of ionic conductive agent (trade name: CIL-542, manufactured by Japan Carlit Co., Ltd.) to the mixture. Stir the resulting mixture in a closed vacuum mixer for 2 minutes to obtain a mixture for forming an elastic layer.

[0265] Except for using the obtained elastic layer forming mixture, the electrophotographic roller according to this comparative example is manufactured by forming the elastic layer in the same manner as in Example 1. The obtained electrophotographic roller is evaluated in the same manner as in Example 1.

[0266] <Comparative Example 4>

[0267] (Preparation of the mixture for forming the elastic layer)

[0268] 500 ppm of curing catalyst (trade name: RZETA, manufactured by Tosoh Corporation) was added to 46.7 parts by weight of polycarbonate diol (trade name: KURARAY POLYOL C-2090, manufactured by Kuraray Co., Ltd.) and 44.8 parts by weight of silicone particles (trade name: KMP-598, manufactured by Shin-Etsu Chemical Co., Ltd.) as soft resin particles. The mixture was stirred for 4 hours using a closed vacuum mixer adjusted to 100°C.

[0269] To the mixture, 2.6 parts by mass of phthalimide 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 ionic conductive agent (trade name: CIL-542, manufactured by Japan Carlit Co., Ltd.) were added. The resulting mixture was stirred for 2 minutes at 1,600 rpm using a rotary vacuum degassing mixer to obtain a mixture for forming an elastic layer.

[0270] Except for using the obtained elastic layer forming mixture, the electrophotographic roller according to this comparative example was manufactured by forming the elastic layer in the same manner as in Example 1. 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 evaluation was performed by considering the silicone particles as domains.

[0271] The evaluation results of Examples 1 to 18 and Comparative Examples 1 to 4 are shown in Tables 4-1 to 4-4 and Table 5.

[0272]

[0273]

[0274]

[0275]

[0276] [Table 5]

[0277]

[0278] In each of the electrophotographic rollers according to Examples 1-18, the micro-rubber hardness of the elastic layer is low, and multiple domains are dispersed in a matrix containing a polyurethane elastomer. Furthermore, the parameter B, representing the viscoelasticity of the matrix, is greater than the parameter A, representing the viscoelasticity of each domain, and the strain after unloading in the indentation test performed using a nanoindenter is small. Therefore, satisfactory results were obtained in the evaluation of striped image defects. Additionally, although toner melt adhesion was observed in some electrophotographic rollers, no image defects originating from toner melt adhesion occurred until images were output on 10,000 sheets.

[0279] Meanwhile, in the electrophotographic roller according to Comparative Example 1, parameter A, representing the viscoelasticity of each domain, is greater than parameter B, representing the viscoelasticity of the matrix. Therefore, excessive reduction in micro-rubber hardness and large strain after unloading occur, and the evaluation of striped image defects is unsatisfactory.

[0280] In the electrophotographic roller according to Comparative Example 2, a matrix-domain structure is formed by mechanical phase separation instead of by a polyether and urethane reactive emulsifier. Therefore, phase separation is unclear. Furthermore, the roundness of each domain decreases. As a result, excessive reduction in micro-rubber hardness and large strain after unloading occur, and the evaluation of striped image defects is unsatisfactory.

[0281] Similarly, in the electrophotographic roller according to Comparative Example 3, phase separation was mechanically induced without the use of a urethane reactive emulsifier, in the same manner as in Comparative Example 2. Therefore, the phase separation was unclear. Furthermore, the roundness of each domain decreased. As a result, the strain after unloading increased, and the evaluation of striped image defects was unsatisfactory. Moreover, even after this, the strain did not easily recover, and the toner adhered to the strained portions and further fused, resulting in image defects originating from toner melt adhesion on 8,410 sheets. In the electrophotographic roller according to Comparative Example 4, flexible particles were used as domains. However, in order to maintain the shape of each particle, the parameter A representing the viscoelastic term of each domain according to this disclosure became very large, and the parameter B representing the viscoelastic term of the matrix needed to be increased. As a result, the microhardness increased excessively, leading to toner melt adhesion. Furthermore, due to the excessively high micro-rubber hardness, toner melt adhesion further developed, and image defects originating from toner melt adhesion occurred on 5,550 sheets.

[0282] This disclosure is not limited to the above-described embodiments, and various changes and modifications may be made without departing from the spirit and scope of this disclosure. The appended claims are intended to clarify the scope of this disclosure.

[0283] This application claims priority based on Japanese Patent Application No. 2021-074334, filed April 26, 2021; Japanese Patent Application No. 2021-161240, filed September 30, 2021; Japanese Patent Application No. 2022-011865, filed January 28, 2022; and Japanese Patent Application No. 2022-044046, filed March 18, 2022, the entire contents of which are incorporated herein by reference.

[0284] Explanation of reference numerals in the attached figures

[0285] 1A: Electrophotographic components

[0286] 1B: Electrophotographic components

[0287] 2: Spindle

[0288] 3: Elastic layer

[0289] 4: Surface layer

[0290] 31: Matrix

[0291] 32: Domain

Claims

1. An electrophotographic component, characterized in that, It includes: a mandrel; and an elastic layer provided on the outer periphery of the mandrel, the elastic layer contains a polyurethane elastomer, and the polyurethane elastomer includes a matrix and a plurality of domains dispersed in the matrix, parameter A and parameter B satisfy the relationship A < B, where, the parameter A represents the viscoelastic term of each of the plurality of domains and the parameter B represents the viscoelastic term of the matrix, and the parameter A and parameter B are measured in the viscoelastic image of the cross-section in the thickness direction of the elastic layer using a scanning probe microscope, after obtaining the viscoelastic image, parameters representing the viscoelastic terms in each observation region are determined at 10 points each in the matrix and the domain, and their respective average values are used as the parameter A representing the viscoelastic term of the domain and the parameter B representing the viscoelastic term of the matrix; the units of the parameter A and the parameter B are both mV, and the larger the value, the higher the elasticity, the micro rubber hardness of the elastic layer at 23°C is 20 or more and 50 or less, and in the indentation test of the elastic layer using a nanoindentation instrument at 23°C, a Vickers indenter is pressed into the elastic layer at a loading rate of 10 mN / 30 sec and maintained for 60 seconds under a load of 10 mN, and then unloaded, and the strain after 5 seconds of unloading is 1 µm or less.

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

3. The electrophotographic member according to claim 1, wherein, when the length in the length direction of the elastic layer is defined as L, in each cross-section in the thickness direction of the elastic layer at three positions of the elastic layer, square observation regions with side lengths of 50 µm are arbitrarily set in the thickness region from the outer surface of the elastic layer to a depth of 100 µm, and the three positions are the center in the length direction of the elastic layer and L / 4 from both ends of the elastic layer toward the center, all three of the observation regions each satisfy the following requirements (1) and requirement (2): Requirement (1): The proportion of the total cross-sectional area of the plurality of domains is 15% or more and 45% or less of the area of the observation region; Requirement (2): The proportion of the number of the plurality of domains each having a cross-sectional area of 0.1% or more and 13.0% or less with respect to each observation region is 70 number % or more.

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

5. The electrophotographic member according to claim 1, where the matrix contains a polyurethane elastomer, and the polyurethane elastomer includes a polycarbonate structural unit represented by the general formula (1) as a repeating structural unit, and where each of the plurality of domains includes a polyether structural unit represented by the general formula (2) as a repeating structural unit: General formula (1) in, R1 represents an alkylene group having 3 to 9 carbon atoms; General formula (2) where R2 represents an alkylene group having 3 to 5 carbon atoms.

6. The electrophotographic component according to claim 5, wherein R1 in the repeating structural unit represented by general formula (1) represents a branched alkylene group having 3 to 9 carbon atoms.

7. The electrophotographic component according to claim 5, wherein R2 in the repeating structural unit represented by general formula (2) represents a branched alkylene group having 3 to 5 carbon atoms.

8. A processing cartridge configured to be detachably mounted to an image forming apparatus, characterized in that, The processing box includes an electrophotographic component according to any one of claims 1 to 7.

9. An electrophotographic image forming apparatus, characterized in that, It includes an electrophotographic component according to any one of claims 1 to 7.

10. A method for manufacturing an electrophotographic component, characterized in that, The electrophotographic component is an electrophotographic component according to any one of claims 1 to 7, and the method includes the following steps: (i) Reacting a first polyether having at least two isocyanate groups and a first polycarbonate polyol having at least two hydroxyl groups with each other to obtain a urethane reactive emulsifier having at least two hydroxyl groups; (ii) Obtaining a dispersion in which droplets, each comprising 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 together to obtain a mixture for forming an elastic layer; and (iv) The elastic layer is formed by reacting the urethane reactive emulsifier, the second polycarbonate polyol, and the polyisocyanate in the mixture with each other on the surface of the mandrel to obtain the elastic layer.

Images