Electrophotographic roller, developing device, electrophotographic image forming apparatus, and process cartridge

Abstract

To provide an electrophotographic roller that can prevent inversion fogging through durability and stably form a high-quality electrophotographic image, and is trial-manufactured easily at an inexpensive price.SOLUTION: An electrophotographic roller comprises a conductive substrate, and a foam layer on an outer peripheral surface of the substrate. The foam layer is a surface layer of the electrophotographic roller. The foam layer has a skeleton including a binder resin and at least one conductive particle in the binder resin. The foam layer has a communication structure having at least one air gap opening in an outer surface of the foam layer and extending in a thickness direction of the foam layer. At least a part of an inner wall of the air gap is constituted of the skeleton. At least part of the at least one conductive particle is exposed on the inner wall. The foam layer has a thickness T of 2.0 mm or more. In cross-sectional observation of the foam layer by a scanning electron microscope, a ratio of the number of pixels having specific luminance is within a specific range.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrophotographic roller, a developing device, and a process cartridge used in an electrophotographic image forming apparatus.The present disclosure also relates to an electrophotographic image forming apparatus. [Background technology]

[0002] In an electrophotographic image forming apparatus (such as a copying machine, facsimile, or printer using an electrophotographic method, hereinafter also referred to as an "image forming apparatus"), an electrophotographic photoconductor (hereinafter also referred to as a "photoconductor") is charged by a charging roller and exposed to light, so that an electrostatic latent image is formed on the photoconductor. Next, the toner in the developer container is applied onto the developing roller by a toner supply roller and a toner regulating member. Next, the toner is transported to a developing area by the developing roller. The toner transported to the developing area develops the electrostatic latent image on the photoconductor between the photoconductor and the developing roller or a portion adjacent to the developing roller. Thereafter, the toner on the photoconductor is transferred to a recording paper by a transfer means and fixed by heat and pressure, and the toner remaining on the photoconductor is removed by a cleaning blade. In an electrophotographic image forming apparatus, for example, an electrophotographic roller having a foamed elastic layer is used as a toner supply roller. Patent Document 1 describes an invention relating to a conductive roller that can be used as a toner supply roller. The conductive roller is made of conductive polyurethane foam, and the conductive polyurethane foam has a base made of soft polyurethane foam and a conductive coating layer, the base is composed of a skeleton and a cell membrane, the conductive coating layer is provided on at least a part of the surface of each of the skeleton and the cell membrane, and the conductive coating layer contains carbon nanotubes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-139866 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the image forming process of an electrophotographic image forming apparatus, toner that should not adhere may adhere to non-image forming areas (white areas) of a photoconductor. This phenomenon is called "fog." When "fog" occurs, image quality is degraded, and the number of printable pages per toner cartridge is reduced due to increased toner consumption. Therefore, suppressing "fog" is one of the issues that must be resolved in order to further improve the image quality of electrophotographic images and reduce the frequency of cartridge replacement.

[0005] Among the types of "fogging," the "fogging" caused by toner charged with a polarity opposite to the normal polarity (hereinafter also referred to as "reverse toner") is also called "reverse fog." For example, when the normal polarity of the toner is negative, "reverse fog" occurs when the positively charged reverse toner is attracted to the photoconductor having a charging potential Vd that is more negative than the development potential Vdc.

[0006] In order to improve user benefits such as further improving the image quality of electrophotographic images and further reducing the frequency of cartridge replacement, the present inventors have come to realize that it is necessary to develop technology to further suppress "reverse fog." Here, the present inventors have knowledge that the charged state of the toner as a result of the charge being applied to the toner by the toner supply roller in an electrophotographic image forming apparatus has a significant effect on "reverse fog." And, according to the inventors' studies, when the conductive roller according to Patent Document 1 is used as a toner supply roller, In electrophotographic image forming apparatuses using a roller, the suppression of reverse fogging has not yet been sufficient.

[0007] At least one aspect of the present disclosure is directed to providing an electrophotographic roller capable of further suppressing reverse fogging. At least one aspect of the present disclosure is directed to providing a developing device that contributes to the formation of high-quality electrophotographic images. At least one aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that can stably output high-quality electrophotographic images. At least one aspect of the present disclosure is directed to providing a process cartridge that contributes to the formation of high-quality electrophotographic images. [Means for solving the problem]

[0008] According to at least one aspect of the present disclosure, there is provided an electrophotographic roller comprising a conductive substrate and a foam layer on an outer peripheral surface of the substrate, the foam layer is a surface layer of the electrophotographic roller, the foam layer has a skeleton including a binder resin and at least one conductive particle in the binder resin; the foam layer has an open structure having at least one void that opens to an outer surface of the foam layer and extends in a thickness direction of the foam layer; At least a part of the inner wall of the void is composed of the skeleton, At least a portion of the at least one conductive particle is exposed to the inner wall; The thickness T of the foam layer is 2.0 mm or more, The length of the foam layer in the longitudinal direction is L, and a cross section of the foam layer in the entire thickness direction along the circumferential direction of the electrophotographic roller is exposed at four points at an angle of 90 degrees in the circumferential direction of the foam layer, at a midpoint in the longitudinal direction of the foam layer and at three points of L / 4 from both ends toward the midpoint, For each of the 12 cross sections, the inner wall of at least one void present in a region from the outer surface of the foamed layer to a depth of 1.0 mm was observed with a scanning electron microscope, and a secondary electron image was obtained at a magnification of 5000 times, with a resolution of 18 nm / pixel, 256 gradations from the lowest gradation of 0 to the highest gradation of 255, a contrast of 1200, and an average brightness of 128±16. When the ratio Rs of the total number of pixels belonging to a brightness of 200 to 255 to the total number of pixels in the secondary electron image was calculated, the average value of Rs for the 12 locations was 0.5% or more, and For each of the 12 cross sections, the inner wall of at least one void present in a region up to a thickness of 1.0 mm from the surface of the foam layer facing the substrate toward the outer surface of the foam layer is observed with a scanning electron microscope to obtain a secondary electron image having a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gradations from a minimum gradation of 0 to a maximum gradation of 255, a contrast of 1200 and an average brightness of 128±16, and when the ratio Rt of the total number of pixels having a brightness of 200 to 255 to the total number of pixels in the secondary electron image is calculated, the average Rt value for the 12 locations is 0.5% or more.

[0009] According to at least one aspect of the present disclosure, there is provided a developing device including at least a developing roller and a toner supply roller that supplies toner to the developing roller, A voltage can be applied between the developing roller and the toner supply roller, A development apparatus is provided, wherein the toner donor roller is the electrophotographic roller described above.

[0010] According to at least one aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above-described developing device.

[0011] According to at least one aspect of the present disclosure, there is provided a process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, comprising: When the process cartridge is mounted in the main body, it is electrically connected to the electrical contact of the main body. a contact member to be connected, The process cartridge includes a developing roller and a toner supply roller for supplying toner to the developing roller. a voltage can be applied between the developing roller and the toner supply roller by electrical connection with the main body; The toner supply roller is the electrophotographic roller described above, and a process cartridge is provided. Effect of the Invention

[0012] According to at least one aspect of the present disclosure, an electrophotographic roller capable of further suppressing reverse fogging can be obtained. According to at least one aspect of the present disclosure, a developing device contributing to the formation of high-quality electrophotographic images can be obtained. Furthermore, according to at least one aspect of the present disclosure, an electrophotographic image forming apparatus capable of stably outputting high-quality electrophotographic images can be obtained. Furthermore, according to at least one aspect of the present disclosure, a process cartridge contributing to the formation of high-quality electrophotographic images can be obtained. [Brief description of the drawings]

[0013] [Figure 1] Schematic cross-sectional view of an electrophotographic roller according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a portion of a foam layer of an electrophotographic roller according to one embodiment of the present disclosure. [Diagram 3] FIG. 1 is a schematic diagram showing a process cartridge according to one embodiment of the present invention; [Figure 4] Schematic cross-sectional view of a mold for molding an electrophotographic roller according to one embodiment of the present invention. [Diagram 5] SEM image of cross section of foam layer [Figure 6] Schematic diagram of an opening on the outermost surface of a foam layer when observing the surface shape of the foam layer. [Figure 7] Schematic diagram of toner charge distribution DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In the present disclosure, the description of "XX or more and YY or less" or "XX to YY" expressing a numerical range means a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range can be arbitrarily combined. In addition, in the present disclosure, a description such as "at least one selected from the group consisting of XX, YY, and ZZ" means any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ.

[0015] The present inventors speculate that the reason why the conductive roller according to Patent Document 1 could not sufficiently suppress the inversion fog when used as a toner supply roller is as follows. In the conductive roller according to Patent Document 1, the conductive coating layer provided on at least a part of the skeleton of the base made of soft polyurethane foam and the cell membrane comes into contact with the toner, so that the toner is charged. At this time, it is considered that most of the carbon nanotubes, which are the conductive agent in the conductive coating layer, are embedded in the conductive coating layer. It is considered that the charge given to the toner in contact with such a conductive coating layer is mainly due to frictional charging. Therefore, it is considered that the toner in contact with the conductive coating layer also contains a certain amount of toner charged with a polarity opposite to the normal polarity. As a result, it is considered that the inversion fog could not be sufficiently suppressed. In light of such considerations, the present inventors have conducted further studies and have found that, for example, an electrophotographic roller according to the following embodiment contributes to further reducing reverse fog.

[0016] That is, an electrophotographic roller according to at least one embodiment of the present disclosure includes a substrate and a foam layer on an outer peripheral surface of the substrate. The foam layer is a surface layer of the electrophotographic roller and has a skeleton including a binder resin and at least one conductive particle in the binder resin. The foam layer has an interconnected structure having at least one void that opens to the outer surface of the foam layer and extends in the thickness direction of the foam layer. The inner wall of the void is formed of the skeleton, and at least a portion of the at least one conductive particle is exposed to the inner wall. The foam layer has a thickness T of 2.0 mm or more.

[0017] The length of the foam layer in the longitudinal direction is L, and cross sections of the foam layer in the direction along the circumferential direction of the electrophotographic roller are exposed at four locations every 90 degrees in the circumferential direction of the foam layer, the midpoint in the longitudinal direction of the foam layer, and three locations at an angle of L / 4 from both ends toward the midpoint. For each of these 12 cross sections, the inner wall of at least one void present in a region from the outer surface of the foam layer to a depth of 1.0 mm is observed with a scanning electron microscope to obtain a secondary electron image at a magnification of 5000 times, with a resolution of 18 nm / pixel, 256 gradations with the lowest gradation being 0 and the highest gradation being 255, a contrast of 1200, and an average brightness of 128±16. When the ratio Rs of the total number of pixels belonging to the brightness range of 200 to 255 to the total number of pixels in the secondary electron image is calculated, the average value of Rs of the 12 locations is 0.5% or more. Further, for each of the 12 cross sections, the inner wall of at least one void present in a region up to a thickness of 1.0 mm from the surface of the foamed layer facing the substrate toward the outer surface of the foamed layer is observed with a scanning electron microscope to obtain a secondary electron image at a magnification of 5000 times, with a resolution of 18 nm / pixel, 256 gradations from a minimum gradation of 0 to a maximum gradation of 255, a contrast of 1200, and an average brightness of 128±16. When the ratio Rt of the total number of pixels belonging to a brightness of 200 to 255 to the total number of pixels in the secondary electron image is calculated, the average value of Rt for the 12 locations is 0.5% or more.

[0018] The present inventors speculate as follows why the electrophotographic roller according to the above embodiment contributes to further reducing reverse fog. Note that the effect manifestation mechanism described below is merely speculation, and the technical scope of the electrophotographic roller according to the present disclosure is not limited by the effect manifestation mechanism described below.

[0019] In the electrophotographic roller according to the above embodiment, the foam layer has an open outer surface and at least one void extending in the thickness direction of the foam layer, the inner wall of the void is formed of the above skeleton, and at least one conductive particle is at least partially exposed to the inner wall, so that the toner can come into contact with at least a part of the conductive particle exposed inside the void.

[0020] In addition, the above Rs and Rt are indicators of the degree of exposure of the conductive particle part exposed on the inner wall of at least one void present in each of the region from the outer surface of the foamed layer to a depth of 1.0 mm in the cross section along the entire thickness of the foamed layer - the circumferential direction of the electrophotographic roller and the region from the surface of the foamed layer facing the substrate toward the outer surface of the foamed layer to a thickness of 1.0 mm. The average values ​​of Rs and Rt each being 0.5% or more indicate that a certain amount of the conductive particle part is exposed on the inner wall of the void present near the surface of the foamed layer and on the inner wall of the void present deep in the foamed layer. As a result, in the process in which the toner enters the voids of the foamed layer and flows inside the foamed layer, the toner comes into direct contact with the exposed part of the conductive particle on the inner wall of the void, and a sufficient opportunity is secured for the charge to be injected into the toner. As a result, the distribution of the charge held by the toner becomes narrower, and the proportion of toner charged opposite to the normal polarity decreases, which is thought to suppress the occurrence of inverted fogging. An electrophotographic roller according to one aspect of the present disclosure will be described below.

[0021] (1) Electrophotographic Roller An electrophotographic roller according to one embodiment of the present disclosure has a conductive substrate and a foam layer on the outer peripheral surface of the substrate. An example of the electrophotographic roller is shown in FIG. 1. The electrophotographic roller 1 shown in FIG. The electrophotographic roller 1 is made up of a conductive substrate 3 and a foam layer 2 provided on the outer peripheral surface thereof. The foam layer 2 is a surface layer of the electrophotographic roller 1 and forms the outer surface. The layer structure of the electrophotographic roller 1 is not limited to being composed only of the substrate 3 and the foam layer 2, and other layers such as a conductive elastic layer may be further provided between the substrate 3 and the foam layer 2. The structure of the electrophotographic roller will be described in detail below.

[0022] <Base> The conductive substrate 3 functions as a support member and an electrode for the electrophotographic roller. The substrate is made of a conductive material such as a metal or alloy, such as aluminum, copper alloy, or stainless steel, iron plated with chromium or nickel, or a conductive synthetic resin. For example, the substrate may be a core metal. The substrate is, for example, in the shape of a solid cylinder or a hollow cylinder.

[0023] <Foam layer> The foam layer 2 has a skeleton including a binder resin and at least one conductive particle in the binder resin. The foam layer 2 has voids between the skeletons. Furthermore, the foam layer 2 has an interconnected structure having at least one void that opens to the outer surface of the foam layer 2 and extends in the thickness direction of the foam layer 2. By providing such an interconnected structure and exposing the conductive particle to the inner wall, charge injection into the toner can be effectively performed. The surface of the skeleton inside the foam layer 2 is called the inner wall. That is, at least a part of the inner wall of the void is composed of the skeleton. It is preferable that the inner wall of the void is composed of the skeleton. It is more preferable that the inner wall of the void is formed of a binder resin and conductive particles in the binder resin. The inner wall has a structure in which at least a part of at least one conductive particle is exposed.

[0024] [Conductive particles] The conductive particles are not particularly limited, and can be appropriately selected from known resins. For example, fine particles of carbon black; conductive metals such as silver, gold, and copper; and conductive metal oxides such as zinc oxide, tin oxide, and titanium oxide can be used. At least one of these can be used. The conductive particles preferably contain at least one selected from the group consisting of conductive metals and carbon black, and more preferably contain at least one selected from the group consisting of silver, gold, and carbon black. Of these, carbon black is relatively easy to obtain and provides better conductivity. Therefore, it is more preferable that the conductive particles contain carbon black. In addition, other conductive agents such as ion conductive agents and fibrous carbon nanotubes (CNTs) can be used in combination with the conductive particles.

[0025] By exposing at least a part of the conductive particles in the foam layer from the inner wall of the foam layer, it is possible to directly inject charges into the toner, and it is possible to obtain the effect of suppressing reverse fogging. More specifically, it is preferable that at least a part of the conductive particles is also exposed to the inner wall of the cell opening on the outer surface. Hereinafter, a description will be given with reference to FIG. 2, which is a partially enlarged view of the inner wall of the foam layer of the electrophotographic roller according to one embodiment of the present disclosure.

[0026] The foam layer 2 has a plurality of voids 22 having a connected structure inside the foam layer 2. The foam layer 2 also contains a binder resin 23 and a plurality of conductive particles 24 dispersed in the binder resin 23. At least a portion of the plurality of conductive particles 24 is exposed to an inner wall 25 of the foam layer 2. The "exposure" of the particles means that at least a portion of one conductive particle 24 is not covered with the binder resin 23 and constitutes a part of the inner wall of the foam layer.

[0027] The exposure rate of the conductive particles from the inner wall can be calculated by image analysis of an image taken by a scanning electron microscope (SEM) described later. Specifically, the length of the foam layer 2 in the longitudinal direction is L, and the cross section of the entire thickness of the foam layer in the circumferential direction of the electrophotographic roller is exposed at four points at an angle of 90 degrees in the circumferential direction of the foam layer, the midpoint in the longitudinal direction of the foam layer, and three points at L / 4 from both ends toward the midpoint. For each of the 12 cross sections, the inner wall of at least one void present in the region from the outer surface of the foamed layer to a depth of 1.0 mm is observed with a scanning electron microscope. A secondary electron image is obtained at a magnification of 5000 times, with a resolution of 18 nm / pixel, 256 gradations from the lowest gradation of 0 to the highest gradation of 255, a contrast of 1200, and an average brightness of 128±16. The ratio of the total number of pixels with a brightness of 200 to 255 to the total number of pixels in the secondary electron image is defined as Rs. The average value of Rs for these 12 locations is 0.5% or more.

[0028] Also, for each of the 12 cross sections, the inner wall of at least one void present in a region from the surface of the foam layer facing the substrate toward the outer surface of the foam layer to a thickness of 1.0 mm is observed with a scanning electron microscope. A secondary electron image is obtained at a magnification of 5000 times, with a resolution of 18 nm / pixel, 256 gradations from the lowest gradation of 0 to the highest gradation of 255, a contrast of 1200, and an average brightness of 128±16. The ratio of the total number of pixels belonging to the brightness range of 200 to 255 to the total number of pixels in the secondary electron image is defined as Rt. The average value of Rt for these 12 locations is 0.5% or more.

[0029] In order to suppress the amount of reversed toner, it is effective to inject charge into the toner from a toner supply roller having a foam layer. In order to obtain a high charge injection effect into the toner through durable use, it is necessary that conductive particles are exposed on the inner wall of the foam layer. In the present disclosure, as described above, it is necessary that the average value of the exposure rate of the conductive particles in the region from the outer surface of the foam layer to a depth of 1.0 mm and the average value of the exposure rate in the region from the base of the foam layer to the outer surface of the foam layer to a thickness of 1.0 mm are both 0.5% or more. Pixels belonging to a brightness of 200 to 255 observed under the above conditions indicate the presence of conductive particles. Since the foam layer has a connected structure, when the average value of Rs and the average value of Rt are satisfied, it is considered that the conductive particles are exposed not only near the surface of the foam layer but also to the inner wall inside the foam layer. In other words, it is considered that the conductive particles are exposed to the inner wall throughout the thickness direction of the foam layer. When the average value of Rs and the average value of Rt satisfy the above range, it is possible to directly inject charges into the toner, and the effect of suppressing inversion fogging is obtained. The reason for this is considered to be that if the average value of Rs and the average value of Rt are 0.5% or more, the contact opportunity between the toner and the conductive particles can be sufficiently secured in the process of the toner flowing inside the foam layer.

[0030] The method for obtaining the electrophotographic roller according to the present disclosure is not particularly limited. In order to obtain an electrophotographic roller having a conductive foamed layer in which the inner walls of the voids are formed by the skeleton of the foamed layer and the conductive particles are exposed on the inner walls so as to satisfy the average values ​​of Rs and Rt, a method of using a liquid mixture containing conductive particles (hereinafter, also simply referred to as "liquid mixture") for forming the foamed layer can be mentioned.

[0031] As an example of a method for obtaining a foamed layer having voids with at least a portion of the conductive particles exposed on the inner wall, a method in which the polymerization of the polymer constituting the skeleton is sufficiently delayed relative to the generation of gas by the foaming agent is effective. For example, taking as an example a case in which the liquid mixture contains a polyol, an isocyanate compound, water as a foaming agent, a urethane catalyst, and conductive particles, the estimated mechanism by which the above method forms a foamed layer having voids in which at least a portion of the conductive particles are exposed to the inner wall will be explained.

[0032] The liquid mixture of the above composition foams when carbon dioxide (CO2) is generated by the reaction between water and the isocyanate compound. If a urethane reaction occurs simultaneously between the polyol and the isocyanate compound, the viscosity of the liquid compound also rises rapidly. Therefore, when the surrounding resin components are pushed apart by the pressure generated by the expansion of the voids created by the generated CO2, the conductive particles are also pushed apart together with the resin components, and the conductive particles are embedded in the resin skeleton.

[0033] On the other hand, if the urethane reaction occurs sufficiently late in the foaming, when the voids created by the generated CO2 expand, the viscosity of the resin component around the voids remains low, so even if the resin component around the voids is pushed out by the pressure when the voids expand, the conductive particles are unlikely to move. It is believed that this difference in mobility between the resin component and the conductive particles against the foaming pressure allows the formation of a foam having voids with at least a portion of the conductive particles exposed on the inner wall. From the above mechanism, it is preferable to use a material for the conductive particles that is difficult to move even under foaming pressure. From this viewpoint, it is preferable that the conductive particles contain at least carbon black, and it is particularly preferable that the conductive particles are carbon black.

[0034] As described above, in the process of forming a foam layer containing polyurethane, a foaming reaction for forming a foam structure and a resinification reaction of polyurethane proceed. The resinification reaction can be sufficiently delayed from the foaming reaction by selecting a catalyst. In other words, by using a temperature-sensitive catalyst as a urethane-forming catalyst that controls the resinification reaction, the progress of the resinification reaction in the foaming process can be suppressed, and the resin component in the liquid mixture can be prevented from becoming highly viscous.

[0035] Although the temperature-sensitive catalyst has low catalytic activity at room temperature, it rapidly becomes active as a resinification catalyst when it reaches a certain temperature. The catalytic activity is low in the early stage of the reaction when the solution temperature starts to rise, but increases significantly in the later stage of the reaction when the temperature rises. Therefore, it is assumed that the foaming reaction can be advanced in advance when the viscosity of the solution is low, especially in the early stage of the reaction, and the conductive particles can be exposed on the inner wall. By using an electrophotographic roller with this foam layer, charge injection into the toner can be effectively performed.

[0036] In the case of the liquid mixture exemplified above, water and an isocyanate compound react at a temperature of, for example, about 40 to 50°C to generate CO2. Therefore, as the temperature-sensitive catalyst, a catalyst that has low activity at a temperature of about 40 to 50°C and rapidly exhibits activity at high temperatures is preferably used. Examples of such a temperature-sensitive catalyst include 2-ethylhexanoate of 1,5-diazabicyclo(4,3,0)nonene-7 (active temperature 100°C), phenol salt of 1,8-diazabicyclo(5,4,0)undecene-7 (active temperature 80°C), and 2-ethylhexanoate of 1,8-diazabicyclo(5,4,0)undecene-7 (active temperature 100°C). The active temperature is the temperature at which the catalytic activity of the temperature-sensitive catalyst is the highest.

[0037] The above-mentioned phenol salt of 1,8-diazabicyclo(5,4,0)undecene-7 is commercially available, for example, under the trade name "U-CAT SA1" (manufactured by San-Apro Co., Ltd.). The above-mentioned 2-ethylhexanoate of 1,8-diazabicyclo(5,4,0)undecene-7 is commercially available, for example, as "U-CAT SA102" (trade name, manufactured by San-Apro Co., Ltd.). It is being done.

[0038] As described above, the average value of Rs and the average value of Rt can be easily controlled within the above range by forming a foam layer using a temperature-sensitive catalyst. The average value of Rs and the average value of Rt can be increased by using a temperature-sensitive catalyst with a higher activation temperature than the curing reaction.

[0039] The average value of Rs is preferably 1.0% or more, more preferably 2.0% or more, and even more preferably 4.0% or more. The average value of Rt is preferably 1.0% or more, more preferably 2.0% or more, and even more preferably 4.0% or more. The higher the exposure rate, the higher the possibility that the exposed conductive particles come into contact with the toner, and the more efficiently the reversed toner can be reduced. Therefore, although there is no particular upper limit, the average value of Rs is preferably 1.0 to 20.0%, more preferably 2.0 to 16.0% or more, and even more preferably 4.0 to 14.0%. The average value of Rt is preferably 1.0 to 20.0%, more preferably 2.0 to 16.0% or more, and even more preferably 4.0 to 14.0%.

[0040] The ratio (Rs / Rt) of the average value of Rs at 12 points to the average value of Rt at 12 points is preferably 0.8 to 1.2, and more preferably 0.9 to 1.1.

[0041] The foam layer has a thickness T of 2.0 mm or more. By having the thickness T of 2.0 mm or more, a stable contact state with other members such as the developing roller can be maintained. The foam layer has a thickness T of preferably 2.0 to 5.0 mm, more preferably 3.0 to 4.0 mm.

[0042] There is no particular restriction on the primary particle diameter of the conductive particles (the arithmetic mean value of the Feret diameters of the particles including the unexposed parts). However, in order to ensure a contact area with the toner, it is preferable that the size is at least a certain size, specifically, 10 nm or more. In order to prevent the particles from falling off the foam layer during use of the electrophotographic roller, it is preferable that the particle diameter is less than a certain size, specifically, 10 μm or less. The arithmetic mean value of the Feret diameters of the conductive particles is preferably 10 nm to 10 μm, more preferably 10 to 100 nm, and even more preferably 15 to 50 nm.

[0043] To measure the average particle size of the particles, first heat the foam layer at 500°C under a nitrogen atmosphere to decompose the binder. Then, collect the residue and take an image of the particles using a known microscope. The Feret's diameter is measured when the image is parallel to the top and bottom directions. The arithmetic mean value of 100 particles is used.

[0044] The content of the conductive particles in the foam layer is not particularly limited as long as the exposure rate of the conductive particles can be controlled within the above range. The content of the conductive particles in the foam layer is preferably 1.0 to 25.0 parts by mass, more preferably 1.0 to 20.0 parts by mass, even more preferably 1.0 to 15.0 parts by mass, and even more preferably 2.0 to 15.0 parts by mass, relative to 100 parts by mass of the binder resin contained in the foam layer.

[0045] [Binder resin] The foam layer preferably contains a foamable binder resin. For example, the foam layer is preferably formed by dispersing particles in a binder resin. The resin for the foam layer is not particularly limited, and may be appropriately selected from known resins. Examples of the resin include epoxy resin, urea resin, ester resin, amide resin, imide resin, amide-imide resin, phenol resin, vinyl resin, silicone resin, and fluororesin. The following rubber materials are also preferably used as the resin for the foam layer. Examples of the rubber material include ethylene-propylene-diene copolymer rubber, acrylonitrile-butadiene rubber, chloroprene rubber, natural rubber, isoprene rubber, styrene-butadiene rubber, silicone rubber, epichlorohydrin rubber, and polyurethane.

[0046] The binder resin preferably contains polyurethane. Since polyurethane has an electron-donating nitrogen element in its structure, it increases the charge amount of the toner by contacting with the negatively charged toner. In addition, polyurethane has a low solution viscosity during foaming, so that the conductive particles can be easily exposed on the inner wall by selecting a catalyst, which will be described later. In other words, it is preferable that the foam layer contains polyurethane as a binder resin.

[0047] For the polyurethane, for example, a known reaction product of polyol and isocyanate can be used. The polyol is not particularly limited, and can be appropriately selected from various polyols known as polyurethane raw materials. For example, it can be appropriately selected from known polyols such as polyether polyols and polyester polyols that are generally used in the production of flexible polyurethane foams. The polyols can be used alone or in combination of two or more. Among the above polyols, the use of polyether polyols is suitable for producing a flexible, highly elastic polyurethane foam having excellent durability against wet heat. For example, polyethylene propylene ether triol is preferred.

[0048] The hardness of the polyurethane constituting the skeleton of the voids of the foam layer is expressed as the average modulus of elasticity measured, for example, on the surface of the inner wall using SPM. The average modulus of elasticity is preferably 2200 MPa or less, particularly preferably 2000 MPa or less, and further preferably 1900 MPa or less. When the skeleton measured on the surface of the inner wall has such an average modulus of elasticity, the stress on the toner can be sufficiently alleviated. In addition, a good contact state with the developing roller can be formed, the residual toner after development can be effectively collected, and the toner injected with the charge can be smoothly supplied to the developing roller. The lower limit of the average modulus of elasticity is not particularly limited, but is preferably 1000 MPa or more, particularly 1300 MPa or more, in order to make the mechanical strength of the foam layer more sufficient and to exhibit a more reliable scraping property of the toner on the surface of the developing roller. The preferred range of the average modulus of elasticity is 1000 to 2200 MPa, or 1000 to 2000 MPa, particularly 1300 to 2000 MPa, and further 1300 to 1900 MPa.

[0049] In order to make the average elastic modulus 2200 MPa or less, for example, the number average molecular weight of the polyol is controlled, and the amount of aromatic isocyanate is suppressed to a certain amount or less. Specifically, for example, it is effective to make the number average molecular weight of the polyol 2000 to 7000, particularly 3000 to 5000. By making the number average molecular weight of the polyol within the above range, the length of the soft segment between the urethane bonds can be secured, and it becomes easier to control the average elastic modulus within the above range. Furthermore, the ratio (molar ratio) of isocyanate groups to the amount of hydroxyl groups in the polyol (1.0) is preferably 1.1 or less, and more preferably 1.05 or less.

[0050] There is no particular limitation on the isocyanate, and it can be appropriately selected and used from various isocyanates conventionally known as raw materials for polyurethane. For example, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), tolidine diisocyanate (TODI), naphthylene diisocyanate (NDI), xylylene diisocyanate (XDI), 4,4'-diphenylmethane diisocyanate (MDI), carbodiimide-modified MDI, polymethylene polyphenyl isocyanate, polymeric isocyanate, etc. may be used alone or in combination of two or more. In addition, isocyanate-terminated prepolymers obtained by reacting isocyanate with one or more known active hydrogen compounds can also be used as the isocyanate.

[0051] In order to keep the viscosity of the solution low during foaming, an isocyanate with a relatively small molecular weight is preferred. The isocyanate preferably includes at least one selected from the group consisting of 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), and 4,4'-diphenylmethane diisocyanate (MDI).

[0052] The foam layer has an open structure having at least one void that opens on the outer surface of the foam layer and extends in the thickness direction of the foam layer. The foam layer preferably has an open or semi-open cell structure, and more preferably has an open cell structure. For example, the foam layer more preferably has an open cell structure in which a skeleton containing a binder resin and conductive particles forms cells. In particular, in a foam layer having an open cell structure, toner penetrates into the foam layer, and charge injection is easily performed from the exposed conductive particles, so that reverse toner can be more effectively reduced.

[0053] The porosity of the foam layer is not particularly limited, but is preferably 50 to 97% by volume. If it is 50% by volume or more, the toner has good fluidity in the voids of the foam layer, and if it is 97% or less, the contact opportunity of the toner with the conductive particles on the inner wall can be well maintained. It is more preferably 75 to 93% by volume, and even more preferably 82 to 90% by volume. The porosity can be controlled by the amount of foaming agent, and further, in the case of cast curing described later, the amount of the foaming agent poured into the mold.

[0054] [catalyst] The catalyst is not particularly limited and can be appropriately selected from various known catalysts, but in order to expose the conductive particles on the inner wall, it is preferable to use a temperature-sensitive catalyst that is active in the resinification reaction of urethane. Examples of the temperature-sensitive catalyst include 2-ethylhexanoate of 1,5-diazabicyclo(4,3,0)nonene-7 (active temperature 100°C), 1,8-diazabicyclo Examples include phenol salt of (5,4,0)undecene-7 (active temperature 80°C) and 2-ethylhexanoate of 1,8-diazabicyclo(5,4,0)undecene-7 (active temperature 100°C). The active temperature is the temperature at which the catalytic activity of the temperature-sensitive catalyst is the highest.

[0055] Furthermore, a catalyst active in the resinification reaction and foaming reaction of polyurethane can be appropriately selected and used. For example, amine catalysts (triethylenediamine, bis(dimethylaminoethyl)ether, N,N,N',N'-tetramethylhexanediamine, 1,8-diazabicyclo(5,4,0)undecene-7, 1,5-diazabicyclo(4,3,0)nonene-5, 1,2-dimethylimidazole, N-ethylmorpholine, N-methylmorpholine, etc.), organometallic catalysts (tin octoate, tin oleate, dibutyltin dilaurate, dibutyltin diacetate, tetra-i-propoxytitanium, tetra-n-butoxytitanium, tetrakis(2-ethylhexyloxy)titanium, etc.), and acid salt catalysts (carboxylates, formates, octoates, borates, etc.) in which the initial activity of the amine catalysts and organometallic catalysts has been reduced may be used alone or in combination with a temperature-sensitive catalyst.

[0056] [others] If necessary, a foam stabilizer and other auxiliaries may be used. When the binder resin of the foam layer according to the present disclosure is polyurethane or polyurea, water can be used as a foaming agent as described above, whereby carbon dioxide gas can be generated by reaction with an isocyanate compound, but other foaming agents may also be used in combination with water.

[0057] The foam stabilizer is not particularly limited, and may be appropriately selected from various known foam stabilizers. As other auxiliary agents, crosslinking agents, vulcanizing agents, vulcanization accelerators, vulcanization assistants, flame retardants, colorants, ultraviolet absorbers, antioxidants, and the like may be used as necessary within a range that does not impair the effects of the present disclosure.

[0058] (Method of forming foam layer) There is no particular limitation on the foaming method of the foam layer. Any method can be used, such as a method using a foaming agent or a method of mixing air bubbles by mechanical stirring. The foaming ratio can be appropriately determined and is not particularly limited. The foam layer is preferably a foamed and cured product of a liquid mixture for forming the foam layer (hereinafter, also simply referred to as a "liquid mixture"). For example, when the binder resin is polyurethane, the foamed layer according to the present disclosure can be obtained by foaming and curing a liquid mixture for forming a foamed layer, which is a mixture of the following materials 1 to 4 (preferably 1 to 5). That is, the method for producing an electrophotographic roller preferably includes a step of foaming and curing a liquid mixture for forming a foamed layer, which contains the following materials 1 to 4, preferably the following materials 1 to 5, to obtain a foamed layer.

[0059] 1. As a material for forming binder resin, Polyols such as polyether polyols and polyester polyols ·Isocyanate compounds 2.Conductive particles 3. Catalyst (preferably a catalyst containing a temperature-sensitive catalyst) 4. Foaming agent 5.Foam stabilizer There is no particular limitation on the method of joining the substrate and the foam layer. A method in which the substrate is placed in advance inside a mold (molding die), the liquid mixture is poured into a mold for casting, and foamed and cured (cast molding method), or a method in which the foamed and cured liquid mixture is molded in advance, molded into the shape of the foam layer, and bonded to the substrate (premolding method) can be used. In either method, a conductive adhesive layer can be provided between the substrate and the foam layer as necessary. Known materials such as adhesives and hot melt sheets can be used as this adhesive layer.

[0060] When using the cast molding method, a release agent may be applied to the inner wall of the mold in advance. As the release agent, a known release agent can be used. For example, an aqueous release agent containing an olefin component and a silicone component, or a release agent in which a fluorine component is dissolved in a fluorine-based solvent can be used. In order to easily form an opening on the outer surface of the foam layer, it is preferable to use an aqueous release agent containing an olefin component and a silicone component.

[0061] When the pre-molding method is used, the method for producing the foamed and cured product from the liquid mixture is not particularly limited. For example, in addition to the above-mentioned method of casting into a mold of a predetermined shape, a method of cutting a block-state foam (so-called slab foam) to a predetermined size by cutting and then grinding it into a cylindrical shape, or a method of molding to a predetermined size by an extruder can be used.

[0062] In order to efficiently supply the toner injected with the charge by the toner supply roller to the developing roller, it is necessary to scrape off the toner on the developing roller that has returned to the developing container without being developed by the toner supply roller with the toner supply roller. The toner scraping ability of the toner supply roller is greatly affected by the shape of the foam layer surface. In particular, when the shape of the foam layer surface surrounding the opening with a small height change in the roller radial direction at the edge of the opening, the continuous edge can effectively scrape off the toner on the developing roller.

[0063] Specifically, the outer peripheral surface of the electrophotographic roller is brought into contact with one surface of the glass plate, that is, a first surface, so that the amount of depression of the glass plate against the electrophotographic roller is 1.0 mm. In this state, the contact portion between the electrophotographic roller and the glass plate is observed from the second surface side opposite to the first surface of the glass plate. At this time, it is preferable that the edge of the opening of the gap surrounds the opening. The pushing amount is defined as the amount of pushing when a horizontally held glass plate is brought close to the electrophotographic roller to be observed from vertically above, the electrophotographic roller and the first surface of the glass plate first come into contact with each other, and the glass plate is then moved toward the electrophotographic roller from that point. Refers to quantity (distance). In order to form a surface shape in which the edge surrounds the opening as observed above, it is preferable to mold the foam layer by a method in which the urethane rubber composition is poured into a mold of a predetermined shape and then foamed and cured.

[0064] The type of resin in the foam layer was determined by known methods such as pyrolysis GC / MS, FT-IR, 13 This can be confirmed by C-NMR, etc. The type and composition ratio of the conductive particles can be confirmed by known energy dispersive X-ray analysis (EDS) or X-ray diffraction (XRD). The metal element type and composition ratio of the particles can be obtained by EDS analysis. Furthermore, if the particles are crystalline, the foam layer can be thermally decomposed in a nitrogen atmosphere, and the remaining particle powder can be subjected to XRD to obtain a detailed composition formula.

[0065] (2) Process cartridge The present disclosure provides a process cartridge that is detachably mountable to a main body of an electrophotographic image forming apparatus and includes the electrophotographic roller. The process cartridge preferably includes a photoconductor and a developing roller that conveys toner to the surface of the photoconductor. The process cartridge preferably includes a toner supply roller that supplies toner to the surface of the developing roller. And, the electrophotographic roller is preferably the toner supply roller.

[0066] The process cartridge according to one embodiment of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited thereto. Fig. 3 is a schematic diagram showing an example of a process cartridge using an electrophotographic roller according to one embodiment of the present disclosure as a toner supply roller 34.

[0067] The process cartridge shown in FIG. 3 has a cleaning blade 31, a charging roller 32, a developing roller 33, a toner supply roller 34, a toner 35, a toner regulating member 36, and a photosensitive member 37, and is configured to be detachably attached to the main body of the electrophotographic device.

[0068] The photoconductor 37 is charged by the charging roller 32 and rotated in the direction of the arrow R1. The process cartridge has a contact member that is electrically connected to an electrical contact of the main body when the process cartridge is mounted in the main body of the electrophotographic image forming apparatus. This electrical connection allows a voltage to be applied between the developing roller 33 and the toner supply roller 34, and charge can be injected into the toner inside the foam layer. The toner supply roller 34 rotates in contact with the developing roller 33, supplying toner to the surface of the developing roller 33. A toner regulating member 36 contacts the developing roller 33 and regulates the amount of toner on the surface of the developing roller 33. The developing roller 33 rotates in the direction of the arrow R2 to transport toner to a development area where the developing roller 33 and the photoconductor 37 face each other.

[0069] The process cartridge according to this embodiment employs a so-called contact development method in which the developing roller 33 is disposed in contact with the photoreceptor 37. Toner remaining on the photoreceptor 37 after being transferred to paper is scraped off by the cleaning blade 31 and stored in a cleaner container.

[0070] (3) Developing device The electrophotographic roller may be used as a toner supply roller in a developing device including at least a developing roller and a toner supply roller for supplying toner to the developing roller. A voltage can be applied between the developing roller and the toner supply roller, and charge can be injected into the toner inside the foam layer.

[0071] (4) Electrophotographic image forming apparatus The present disclosure provides an electrophotographic image forming apparatus including the electrophotographic roller described above. The electrophotographic image forming apparatus may be, for example, an electrophotographic image forming apparatus including the developing device described above. The electrophotographic image forming apparatus includes, for example, a photoconductor, a developing roller for conveying toner to the surface of the photoconductor, a toner supply roller for supplying the toner to the surface of the developing roller, and a cleaning roller for cleaning the photoconductor. The electrophotographic roller is preferably the toner supply roller. EXAMPLES

[0072] The present disclosure will be described below with reference to examples and comparative examples, but the present disclosure is not limited to these examples, etc. In the examples and comparative examples, "parts" are all by mass unless otherwise specified.

[0073] Example 1 As shown in Figures 4A to 4C, a mold consisting of a cylindrical member 42 with an inner diameter of 11 mm whose inner surface was coated with a release agent, an upper bridge member 43, and a lower bridge member 41, and a base body 44 made of stainless steel (SUS304) with an outer diameter of 4 mm were prepared, and all were preheated to 80°C. Cylindrical member 42 was attached to lower bridge member 41, and base 44 was placed (FIG. 4A). The following materials (A) to (F) were mixed in advance and designated as liquid B, and material (G) was designated as liquid A. Urethane rubber composition 45, which was a liquid mixture for forming a foam layer obtained by mixing liquid A and liquid B, was injected from the gap between the cylindrical member and base 44 (FIG. 4B). Liquid A and liquid B were mixed immediately before the injection. After injecting urethane rubber composition 45, upper bridge member 43 was attached to the upper end surface of cylindrical member 42, and upper bridge member 43 and lower bridge member 41 held base body 44 concentrically with cylindrical member 42 (FIG. 4C). The amount of urethane rubber composition 45 injected was 2.3 g.

[0074] (A) Polyol (polyethylene propylene ether triol having a number average molecular weight of 3100, trade name: Actocol EP-550N, manufactured by Mitsui Chemicals, Inc.): 100.0 parts (B) Conductive particles (trade name: Lionite CB, manufactured by Lion Specialty Chemicals): 3.0 parts (C) Foam stabilizer (product name: Niax Silicone L-3640, manufactured by Momentive Performance Materials, Inc.): 0.4 parts (D) Temperature-sensitive catalyst (2-ethylhexanoate of 1,5-diazabicyclo(4,3,0)nonene-7, trade name: U-CAT 1102, manufactured by San-Apro Co., Ltd.): 0.25 parts (E) Tertiary amine catalyst (mixture of triethylenediamine and dipropylene glycol, trade name: DABCO 33 LV, manufactured by Evonik): 0.5 parts (F) Foaming agent (water): 1.5 parts (G) Isocyanate mixture (containing 45% NCO and 20% MDI, product name: Cosmonate TM20, manufactured by Mitsui Chemicals): 24.4 parts

[0075] Next, the cylindrical member 42, upper bridge member 43, and lower bridge member 41 were heated to 80°C while integrated, and maintained in this state for 10 minutes to foam and harden the urethane rubber composition 45. After cooling to 50°C, the upper bridge member 43 and lower bridge member 41 were removed, and the base body 44 having a foam layer formed on its outer circumferential surface was demolded from the cylindrical member 42, thereby obtaining the electrophotographic roller Y-1 according to Example 1. The thickness T of the foam layer was 3.5 mm.

[0076] [Measurement of the average conductive particle exposure rate Rs and average conductive particle exposure rate Rt] The foam layer was cut out from the surface of the electrophotographic roller Y-1 perpendicular to the longitudinal direction of the substrate. In other words, a cross section of the foam layer in the direction along the entire thickness-circumferential direction of the electrophotographic roller was exposed. Platinum was evaporated (product name: E-1045, Hitachi High-Tech) on the surface of the obtained slice corresponding to the cross section of the foam layer. An observation sample was prepared by discharging the discharged battery (manufactured by Huawei Technologies Co., Ltd., discharge voltage: 15 mA, discharge time: 30 seconds). Next, the inner walls of the voids present in the region from the outer surface of the cut surface to a depth of 1.0 mm were observed using an SEM (product name: JSM-7800F, manufactured by JEOL). Specifically, as shown in FIG. 5, the center 53 of the inscribed circle 52 of the cell 51 in the cut surface was placed in the center of the observation screen. Next, a secondary electron image was obtained at that position with the magnification increased to 5000 times. At this time, if even a part of the connecting hole 54 was reflected in the observation screen, the cell was not photographed. The SEM measurement conditions were as follows: measurement magnification: 5000x, resolution: 18nm / pixel, acceleration voltage: 2kV, irradiation current: 8, contrast: 1200, brightness: adjusted so that the average brightness when converted into a monochrome image with 256 gradations was 128±16.

[0077] Furthermore, the obtained secondary electron image was imported into the image processing software ImageJ and converted into a monochrome image with 256 levels (brightness 0 is black and 255 is white), and the ratio Rs of the sum of the number of pixels with brightness between 200 and 255 to the total number of pixels in the entire image area was calculated. The above operation was performed at a total of 12 points, that is, at the midpoint in the longitudinal direction of the foamed layer and at three points at L / 4 from both ends toward the midpoint, i.e., at four points each rotated 90° in the circumferential direction on the cross section at positions L / 4, L / 2, and 3L / 4, where L is the total length of the foamed layer in the longitudinal direction. The arithmetic mean value of the Rs obtained at the 12 points was calculated. The same procedure was carried out in a region of the foam layer extending from the substrate toward the outer surface of the foam layer up to a thickness of 1.0 mm, and the arithmetic mean value of Rt was calculated.

[0078] [Observation of the surface shape of the foam layer] The outer peripheral surface of the electrophotographic roller Y-1 and the first surface of the glass plate are brought into contact with the electrophotographic roller Y-2. With the glass plate pressed against the electrophotographic roller by 1.0 mm, the contact portion between the electrophotographic roller and the glass plate was observed from the second surface of the glass plate opposite to the first surface, and it was confirmed whether the edge of the opening surrounded the opening. The state in which the edge of the opening surrounds the opening refers to a state in which the opening 26 is surrounded by a continuous edge of the binder resin 23, as shown in Fig. 6A. Fig. 6B shows an example in which the opening is not surrounded. In the present disclosure, 100 apertures were observed, and if 98% or more were surrounded, it was determined that the edges of the apertures of that electrophotographic roller surrounded the apertures. The above-mentioned indentation amount refers to the amount (distance) by which the glass plate is moved toward the electrophotographic roller to be observed, from a position vertically above the electrophotographic roller, with the indentation amount being defined as 0.0 mm when the electrophotographic roller and the first surface of the glass plate first come into contact with each other.

[0079] [SPM elastic modulus measurement] The cross section of the electrophotographic roller Y-1 was cut into thin pieces using a cryomicrotome (product name: EMFC6, manufactured by Leica Microsystems) while being kept at -110°C, using a diamond knife. Furthermore, a sample with a size of 100 μm square and a width of 100 μm in the depth direction was prepared from the thin piece. The elastic modulus of the surface of the inner wall containing the polyurethane resin skeleton was measured. For the measurement, an SPM device (product name: MFP-3D-Origin, manufactured by Oxford Instruments) and a probe (product name: AC160, manufactured by Olympus) were used. At this time, the force curve was measured 25 times in total at 5 vertical positions and 5 horizontal positions, and the arithmetic average of 23 points excluding the highest and lowest values ​​was obtained, and the elastic modulus was calculated using the Hertz theory.

[0080] [Porosity measurement] The electrophotographic roller Y-1 was cut into a cylindrical shape of 10 mm together with the substrate, and a three-dimensional image was obtained using a three-dimensional measuring X-ray CT device (model: TDM1001-II, manufactured by Yamato Scientific Co., Ltd.). The porosity was calculated from the three-dimensional image using the following formula (1). The measurement conditions were as follows: target material: tungsten, filament material: tungsten, X-ray intensity: 100 kV. Porosity (volume%) = void volume / (cylinder volume - substrate volume) (1)

[0081] [Measurement of the conductive particle content per 100 parts by mass of binder resin] When determining the content of the conductive particles from the electrophotographic roller, the following method can be used. The foam layer is removed from the core metal and its mass is measured, then it is heated at 500°C in a nitrogen atmosphere to decompose the binder resin, after which the conductive particle residue is collected and its mass is measured. The mass of the binder resin is calculated as (mass of the foam layer - mass of the conductive particles). From these masses, the content of the conductive particles per 100 parts by mass of the binder resin can be calculated.

[0082] [Image evaluation] The electrophotographic roller to be evaluated was a toner supply roller, and fogging was evaluated. First, a color laser printer (product name: Laser Beam Printer Satera The toner supply roller was removed from a black cartridge (LBP674C, manufactured by Canon Inc.), and the toner supply roller to be evaluated was installed. The cartridge and the laser printer were placed in a high-temperature, high-humidity environment (temperature: 30.0°C, relative humidity: 80%) and left to stand for 12 hours or more. Next, one solid white image with 0% printing was output, and its reflectance (%) was measured with a reflection densitometer (product name: TC-6DS / A, manufactured by Tokyo Denshoku Co., Ltd.) The value obtained by subtracting the obtained reflectance from the reflectance (%) of an unused printout paper (standard paper) measured in the same manner was defined as the initial fogging value (%).

[0083] Subsequently, halfway through outputting a solid white image, the color laser printer was turned off and the process cartridge was removed. Next, the ratio of inverted toner to the toner on the developing roller was measured using a charge amount / particle size distribution measuring instrument (product name: E-spart Analyzer Model EST-III, manufactured by Hosokawa Micron Corporation). Toner with a charge amount Q / M (μC / g) exceeding 0 was considered to be inverted toner, and the ratio was calculated (Figure 7), which was taken as the initial positive toner ratio (%). The number of particles measured was approximately 3,000. Thereafter, 5,000 sheets of 1% print images were continuously output, and the same operations as above were carried out to measure the fog value (%) after durability and the positive toner ratio (%) after durability.

[0084] (Examples 2 to 8, 10 to 11) (B) Except for changing the type and amount of the conductive particles as shown in Table 1-1, electrophotographic rollers Y-2 to Y-8 and Y-10 to Y-11 according to Examples 2 to 8 and 10 to 11 were produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The materials (product names) used are as follows: Toka Black #5500 (Tokai Carbon Co., Ltd.) Ketjenblack EC600JD (Lion Specialty Chemicals Co., Ltd.) Ag nanoparticles (Sigma-Aldrich) Au nanoparticles (Sigma-Aldrich)

[0085] Example 9 (B) An electrophotographic roller Y-9 according to Example 9 was produced in the same manner as in Example 1, except that the amount of conductive particles was changed to 1.3 parts, and 2 parts of carbon nanotubes (product name: FloTube9100, manufactured by CNano Corporation) were further added as a conductive agent other than the conductive particles, and evaluated in the same manner as in Example 1.

[0086] (Examples 12 to 14) (D) Except for changing the type and amount of the temperature-sensitive catalyst as shown in Table 1-2, electrophotographic rollers Y-12 to Y-14 according to Examples 12 to 14 were produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The materials (product names) used are as follows. U-CAT SA102 (product name, manufactured by San-Apro Ltd.) 2-Ethylhexanoate of 1,8-diazabicyclo[5.4.0]undecene-7 (DBU) Active temperature: 100℃ [ka]

[0087] U-CAT SA1 (product name, San-Apro Ltd.) Phenol salt of 1,8-diazabicyclo[5.4.0]undecene-7 Active temperature: 80℃ [ka]

[0088] Example 15 An electrophotographic roller Y-15 according to Example 15 was produced in the same manner as in Example 1, except that the type of (A) polyol was changed to a polyester polyol having a number average molecular weight of 1000 (product name: Kuraray Polyol P-1020, manufactured by Kuraray Co., Ltd.) and the amount of (G) isocyanate mixture was changed to 31.7 parts. The electrophotographic roller Y-15 according to Example 15 was then evaluated in the same manner as in Example 1.

[0089] (Examples 16 to 20) Except for changing the amount of (F) water and the amount of (G) isocyanate mixture as shown in Table 1-2, electrophotographic rollers Y-16 to Y-20 according to Examples 16 to 20 were produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

[0090] (Examples 21 to 23) The cylindrical member 42 shown in Figs. 4A to 4C was changed to have an inner diameter of 13 mm, and 3.4 g of a urethane rubber composition 45 prepared by mixing the materials shown in Table 1-2 was injected into the cylindrical member 42. Then, foaming and curing were performed in the same manner as in Example 1 to prepare a roller. Furthermore, the outer peripheral surface of the obtained roller was polished at a rotation speed of 1800 rpm and a feed speed of 800 mm / min so that the outer diameter became 11 mm, thereby preparing electrophotographic rollers Y-21 to Y-23 according to Examples 21 to 23. Furthermore, evaluations were performed in the same manner as in Example 1.

[0091] Comparative Example 1 (B) An electrophotographic roller X-1 was produced in the same manner as in Example 1, except that instead of adding the conductive particles, 5 parts of silica (SiO2, product name: MSN-002, manufactured by Teika Corporation) was blended, and evaluated in the same manner as in Example 1.

[0092] Comparative Example 2 (B) Instead of adding conductive particles, an ionic conductive agent (Li-TFSI, product name: E An electrophotographic roller X-2 was produced in the same manner as in Example 1, except that 1 part of F-N115 (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was added, and evaluated in the same manner as in Example 1.

[0093] Comparative Example 3 (B) An electrophotographic roller X-3 was produced in the same manner as in Example 1, except that no conductive particles were added, and was evaluated in the same manner as in Example 1.

[0094] Comparative Example 4 (D) An electrophotographic roller X-4 was produced in the same manner as in Example 1, except that no temperature-sensitive catalyst was added, and evaluated in the same manner as in Example 1.

[0095] Comparative Example 5 The electrophotographic roller X-4 was irradiated with a low pressure mercury lamp (product name: GLQ500US / 11, manufactured by Harrison Toshiba Lighting Co., Ltd.) to perform a surface treatment, to prepare an electrophotographic roller X-5. The surface treatment was performed by rotating the roller and measuring the sensitivity of the sensor at 254 nm at 4000 mJ / cm 2 With this surface treatment, the exposed rate Rs of the conductive particles in the region from the outer surface to a depth of 1.0 mm was 3.0%.

[0096] [Table 1-1]

[0097] [Table 1-2] In the table, the parts relative to the binder resin indicates the parts by mass of the conductive particles relative to 100 parts by mass of the binder resin.

[0098] [Table 2]

[0099] The evaluation results of each of the Examples and Comparative Examples are shown in Tables 3-1, 3-2, and 4. In Examples 1 to 23, the average conductive particle exposure rates Rs and Rt are both 0.5% or more, so the charge injection effect into the toner is large, and the positive toner rate is low even after 5,000 sheets of durability. This resulted in the suppression of fogging on the paper. Among them, in Examples 1 to 3, 5, 7 to 8, 10 to 15, and 20 to 22, both Rs and Rt were 4.0% or more, and therefore a higher effect of suppressing fogging on paper was obtained. Furthermore, in Examples 2 to 3, 7 to 8, and 13 to 15, Rs and Rt were both 4.0% or more, the porosity was 82% by volume to 90% by volume, the conductive particles were carbon black, the edges of the openings in the foam layer surrounded the openings, and the average elastic modulus of the inner wall of the foam layer was 2000 MPa or less, so that a particularly high effect of suppressing fogging on paper was obtained.

[0100] In addition, in Examples 1-2 and 4, Rs and Rt are both 0.5% or more, and the shape of the opening is such that the opening is surrounded with a small radial height change at the edge of the opening on the foam layer surface, so that more toner injected with charge can be supplied to the developing roller. Therefore, it is considered that Examples 1-2 and 4 have a lower positive toner ratio than Examples 21-23, and thus have a greater effect of suppressing fogging on paper.

[0101] In Comparative Examples 1 to 4, Rs and Rt were both less than 0.5%, so the effect of injecting charge into the toner was low, and the positive toner rate was high even after 5,000 sheets of printing, so the effect of suppressing fogging on paper was not obtained.

[0102] In Comparative Example 2, since it contains an ionic conductive agent, the initial fogging on the paper is good, but after the 5,000 sheets of durability test, fogging on the paper occurs frequently. It is considered that the charge injection effect after the durability test is reduced because the ionic conductive agent is deteriorated in electrical conductivity due to durability test.

[0103] In Comparative Example 5, Rs is 0.5% or more due to ultraviolet irradiation, but Rt is less than 0.5%, which is thought to be why a sufficient charge injection effect into the toner was not obtained, and the effect of suppressing fogging on paper was not obtained.

[0104] [Table 3-1]

[0105] [Table 3-2]

[0106] [Table 4]

[0107] The present disclosure relates to the following configurations. (Configuration 1) An electrophotographic roller comprising a conductive substrate and a foam layer on an outer peripheral surface of the substrate, the foam layer is a surface layer of the electrophotographic roller, The foam layer includes a binder resin and at least one conductive particle in the binder resin. and having a skeleton comprising the foam layer has an open structure having at least one void that opens to an outer surface of the foam layer and extends in a thickness direction of the foam layer; At least a part of the inner wall of the void is composed of the skeleton, At least a portion of the at least one conductive particle is exposed to the inner wall; The thickness T of the foam layer is 2.0 mm or more, The length of the foam layer in the longitudinal direction is L, and a cross section of the foam layer in the entire thickness direction along the circumferential direction of the electrophotographic roller is exposed at four points at an angle of 90 degrees in the circumferential direction of the foam layer, at a midpoint in the longitudinal direction of the foam layer and at three points of L / 4 from both ends toward the midpoint, For each of the 12 cross sections, the inner wall of at least one void present in a region from the outer surface of the foamed layer to a depth of 1.0 mm was observed with a scanning electron microscope, and a secondary electron image was obtained at a magnification of 5000 times, with a resolution of 18 nm / pixel, 256 gradations from the lowest gradation of 0 to the highest gradation of 255, a contrast of 1200, and an average brightness of 128±16. When the ratio Rs of the total number of pixels belonging to a brightness of 200 to 255 to the total number of pixels in the secondary electron image was calculated, the average value of Rs for the 12 locations was 0.5% or more, and an inner wall of at least one void present in a region up to a thickness of 1.0 mm from the surface of the foam layer facing the substrate toward the outer surface of the foam layer for each of the 12 cross sections is observed with a scanning electron microscope to obtain a secondary electron image at a magnification of 5000 times, with a resolution of 18 nm / pixel, 256 gradations from a minimum gradation of 0 to a maximum gradation of 255, a contrast of 1200 and an average luminance of 128±16; and when a ratio Rt of the total number of pixels having a luminance of 200 to 255 to the total number of pixels in the secondary electron image is calculated, the average Rt value for the 12 locations is 0.5% or more. (Configuration 2) 2. The electrophotographic roller according to claim 1, wherein the inner wall of the gap is formed of the skeleton. (Configuration 3) when the outer circumferential surface of the electrophotographic roller and a first surface, which is one surface of a glass flat plate, are brought into contact with each other such that the amount of depression of the glass flat plate against the electrophotographic roller is 1.0 mm, and the contact portion between the electrophotographic roller and the glass flat plate is observed from the side of a second surface of the glass flat plate opposite to the first surface, the edge of the opening surrounds the opening, The push-in amount refers to the amount (distance) by which the glass plate, held horizontally, is moved toward the electrophotographic roller to be observed from vertically above the electrophotographic roller, the amount of push-in being 0.0 mm when the electrophotographic roller and the first surface of the glass plate first come into contact with each other, and the amount of push-in refers to the amount (distance) by which the glass plate is moved toward the electrophotographic roller from that point. (Configuration 4) 4. The electrophotographic roller according to any one of Configurations 1 to 3, wherein the binder resin contains polyurethane. (Configuration 5) 5. The electrophotographic roller according to any one of Configurations 1 to 4, wherein the content of the conductive particles is 1.0 to 15.0 parts by mass with respect to 100 parts by mass of the binder resin contained in the foam layer. (Configuration 6) 6. The electrophotographic roller according to any one of Configurations 1 to 5, wherein the conductive particles include at least one selected from the group consisting of conductive metals and carbon black. (Configuration 7) 7. The electrophotographic roller according to any one of Configurations 1 to 6, wherein the conductive particles contain carbon black. (Configuration 8) 8. The electrophotographic roller according to any one of Configurations 1 to 7, wherein the average elastic modulus of the surface of the inner wall measured with an SPM is 2000 MPa or less. (Configuration 9) 9. The electrophotographic roller according to any one of Configurations 1 to 8, wherein the foam layer has a porosity of 50 to 97% by volume. (Configuration 10) 10. The electrophotographic roller according to any one of claims 1 to 9, wherein the foam layer has a porosity of 82 to 90% by volume. (Configuration 11) A developing device including at least a developing roller and a toner supply roller that supplies toner to the developing roller, A voltage can be applied between the developing roller and the toner supply roller, 11. A developing device, wherein the toner supply roller is the electrophotographic roller according to any one of configurations 1 to 10. (Configuration 12) 12. An electrophotographic image forming apparatus comprising the developing device according to claim 11. (Configuration 13) A process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, the process cartridge has a contact member which is electrically connected to an electrical contact of the main body when the process cartridge is mounted in the main body; The process cartridge includes a developing roller and a toner supply roller for supplying toner to the developing roller. a voltage can be applied between the developing roller and the toner supply roller by electrical connection with the main body; 11. A process cartridge, wherein the toner supply roller is the electrophotographic roller according to any one of Configurations 1 to 10. [Explanation of symbols]

[0108] 1 electrophotographic roller, 2 foam layer, 3 substrate, 22 void, 23 binder resin, 24 Conductive particles, 25 inner wall, 26 opening 31 cleaning blade, 32 charging roller, 33 developing roller, 34 toner supply roller, 35 toner, 36 toner regulating member, 37 photoconductor, 41 Lower bridge member, 42 Cylindrical member, 43 Upper bridge member, 44 Core metal (base), 45 Urethane rubber composition, 51 Cell on cut surface, 52 Inscribed circle of cell, 53 Center of inscribed circle, 54 Connecting hole

Claims

1. An electrophotographic roller comprising a conductive substrate and a foam layer on an outer peripheral surface of the substrate, the foam layer is a surface layer of the electrophotographic roller, the foam layer has a skeleton including a binder resin and at least one conductive particle in the binder resin; the foam layer has an open structure having at least one void that opens to an outer surface of the foam layer and extends in a thickness direction of the foam layer; At least a part of the inner wall of the void is composed of the skeleton, At least a portion of the at least one conductive particle is exposed to the inner wall; The thickness T of the foam layer is 2.0 mm or more, The length of the foam layer in the longitudinal direction is L, and a cross section of the foam layer in the entire thickness direction - the circumferential direction of the electrophotographic roller is exposed at four points every 90 degrees in the circumferential direction of the foam layer, at a midpoint in the longitudinal direction of the foam layer and at three points of L / 4 from both ends toward the midpoint, For each of the 12 cross sections, the inner wall of at least one void present in a region from the outer surface of the foamed layer to a depth of 1.0 mm is observed with a scanning electron microscope to obtain a secondary electron image having a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gradations from a minimum gradation of 0 to a maximum gradation of 255, a contrast of 1200, and an average brightness of 128±16. When the ratio Rs of the total number of pixels belonging to a brightness of 200 to 255 to the total number of pixels in the secondary electron image is calculated, the average value of Rs for the 12 locations is 0.5% or more, and an inner wall of at least one void present in a region up to a thickness of 1.0 mm from the surface of the foam layer facing the substrate toward the outer surface of the foam layer for each of the 12 cross sections is observed with a scanning electron microscope to obtain a secondary electron image having a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gradations from a minimum gradation of 0 to a maximum gradation of 255, a contrast of 1200 and an average luminance of 128±16; and when a ratio Rt of the total number of pixels having a luminance of 200 to 255 to the total number of pixels in the secondary electron image is calculated, an average value of Rt for the 12 cross sections is 0.5% or more.

2. 2. The electrophotographic roller according to claim 1, wherein said inner walls of said gaps are formed of said skeleton.

3. when the outer circumferential surface of the electrophotographic roller and a first surface, which is one surface of a glass flat plate, are brought into contact with each other such that the amount of depression of the glass flat plate against the electrophotographic roller is 1.0 mm, and the contact portion between the electrophotographic roller and the glass flat plate is observed from a second surface side of the glass flat plate opposite to the first surface, the edge of the opening surrounds the opening, The electrophotographic roller according to claim 1, wherein the push-in amount is defined as a push-in amount of 0.0 mm when the horizontally held glass plate is brought into contact with the electrophotographic roller from vertically above the electrophotographic roller to be observed, and refers to an amount (distance) by which the glass plate is moved toward the electrophotographic roller from that point.

4. The electrophotographic roller of claim 1 , wherein the binder resin comprises a polyurethane.

5. 2. The electrophotographic roller according to claim 1, wherein the content of the conductive particles is 1.0 to 15.0 parts by mass with respect to 100 parts by mass of the binder resin contained in the foam layer.

6. 2. The electrophotographic roller of claim 1, wherein said conductive particles comprise at least one selected from the group consisting of conductive metals and carbon black.

7. 2. The electrophotographic roller of claim 1, wherein said conductive particles comprise carbon black.

8. 2. The electrophotographic roller according to claim 1, wherein the average elastic modulus of the surface of said inner wall is 2000 MPa or less as measured by SPM.

9. 2. The electrophotographic roller according to claim 1, wherein the foam layer has a porosity of 50 to 97% by volume.

10. 2. The electrophotographic roller according to claim 1, wherein the foam layer has a porosity of 82 to 90% by volume.

11. A developing device including at least a developing roller and a toner supply roller that supplies toner to the developing roller, A voltage can be applied between the developing roller and the toner supply roller, A developing device, wherein the toner supply roller is the electrophotographic roller according to any one of claims 1 to 10.

12. 12. An electrophotographic image forming apparatus comprising the developing device according to claim 11.

13. A process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, the process cartridge has a contact member which is electrically connected to an electrical contact of the main body when the process cartridge is mounted in the main body; The process cartridge includes a developing roller and a toner supply roller for supplying toner to the developing roller. a voltage can be applied between the developing roller and the toner supply roller by electrical connection with the main body; 11. A process cartridge, wherein the toner supply roller is the electrophotographic roller according to claim 1.

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