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

Abstract

The invention relates to an electrophotographic roller, a developing apparatus, an electrophotographic image forming apparatus, and a process cartridge. The electrophotographic roller includes: a conductive substrate; and a foaming layer on an outer peripheral surface of the base, in which the foaming layer is a surface layer of the electrophotographic roller, the foaming layer having a skeleton containing a binder resin and at least one conductive particle in the binder resin, the foaming layer having a communicating structure, and a communication structure that has at least one gap that opens in the outer surface of the foam layer and extends in the thickness direction of the foam layer, at least a portion of the inner wall of the gap includes a skeleton, at least a portion of the at least one conductive particle is exposed at the inner wall, and the thickness of the foam layer is 2.0 mm or more. When the cross-section of the foam layer is observed by a scanning electron microscope, the ratio of the number of pixels having a specific brightness is within a specific range.

Description

Technical Field

[0001] The present disclosure relates to an electrophotographic roller, a developing device, and a process cartridge for an electrophotographic image forming apparatus. In addition, the present disclosure relates to an electrophotographic image forming apparatus. Background Art

[0002] In an electrophotographic image forming apparatus (a copy machine, fax machine, printer, or the like using an electrophotographic system, hereinafter also referred to as an "image forming apparatus"), an electrophotographic photosensitive member (hereinafter also referred to as a "photosensitive member") is charged by a charging roller and exposed. Thus, an electrostatic latent image is formed on the photosensitive member. Then, the toner in the developer container is applied to the developing roller by a toner supply roller and a toner regulating member. Next, the developing roller transports the toner to the developing area. While the toner is being transported to the developing area, the electrostatic latent image on the photosensitive member is developed by the photosensitive member and the developing roller portion or the vicinity of the developing roller. Subsequently, the toner on the photosensitive member is transferred to the recording paper by a transfer means and fixed by heat and pressure. The toner remaining on the photosensitive member is removed by a cleaning blade.

[0003] In an electrophotographic image forming apparatus, an electrophotographic roller including a foamed elastic layer is used as a toner supply roller, for example. Japanese Patent Application Publication No. 2009-139866 describes an invention relating to a conductive roller that can be used as a toner supply roller. The conductive roller includes conductive polyurethane foam. The conductive polyurethane foam includes a substrate including soft polyurethane foam and a conductive coating. The substrate is formed of a skeleton and a cell film. The conductive coating is provided on at least a portion of each surface of the skeleton and the cell film, and the conductive coating contains carbon nanotubes. Summary of the invention

[0004] In the image forming process of the electrophotographic image forming apparatus, toner that should not be deposited may be deposited on the non-image forming portion (blank portion) of the photosensitive member. This phenomenon is called "fogging". When "fogging" occurs, the image quality deteriorates, and the toner consumption increases, reducing the number of printable sheets in one toner cartridge. Therefore, suppressing "fogging" is one of the problems to be solved in order to further improve the image quality of the electrophotographic image and reduce the replacement frequency of the cartridge.

[0005] Among the "fogging", the "fogging" caused by the toner having a charged polarity opposite to the normal polarity (hereinafter also referred to as "reverse toner") is also referred to as "reverse fogging". For example, when the normal polarity of the toner is negative, the "reverse fogging" is generated by attracting the positively charged reverse toner to the photosensitive member having a charged potential Vd more negative than the development potential Vdc.

[0006] In order to further improve the image quality of electrophotographic images and enhance user benefits such as further reducing the frequency of cartridge replacement, the present inventors have recognized the development of a technology to achieve further suppression of "reverse fogging". Here, the present inventors have found that the charged state of toner due to the imparting of charge to the toner by a toner supply roller in an electrophotographic image forming apparatus greatly affects "reverse fogging". Thus, according to the present inventors' research, in an electrophotographic image forming apparatus using a conductive roller for a toner supply roller according to Japanese Patent Application Publication No. 2009-139866, suppression of reverse fogging is still insufficient.

[0007] At least one aspect of the present disclosure is directed to providing an electrophotographic roller capable of further suppressing reverse fogging. In addition, at least one aspect of the present disclosure is directed to providing a developing device that facilitates the formation of high-quality electrophotographic images. In addition, at least one aspect of the present disclosure is directed to providing an electrophotographic image forming device that can stably output high-quality electrophotographic images. In addition, at least one aspect of the present disclosure is directed to providing a processing box that facilitates the formation of high-quality electrophotographic images.

[0008] At least one aspect of the present disclosure provides an electrophotographic roller comprising:

[0009] A conductive substrate; and a foaming layer on the outer peripheral surface of the substrate, wherein

[0010] The foaming layer is the surface layer of the electrophotographic roller.

[0011] The foamed layer has a skeleton including a binder resin and at least one conductive particle in the binder resin,

[0012] The foamed layer has a connected structure having at least one gap which opens on the outer surface of the foamed layer and extends in the thickness direction of the foamed layer,

[0013] At least a portion of the inner wall of the gap is formed by the frame,

[0014] At least a portion of at least one conductive particle is exposed at the inner wall,

[0015] The thickness T of the foam layer is 2.0 mm or more.

[0016] L is the length of the foam layer in the longitudinal direction, and a cross section having the total thickness of the foam layer in the direction along the circumferential direction of the electrophotographic roller is exposed at each of four locations at every 90-degree angle in the circumferential direction of the foam layer, at the midpoint in the longitudinal direction of the foam layer, and at each of three locations at a distance of L / 4 from each of the opposite ends toward the midpoint,

[0017] For each of the cross sections of a total of 12 locations, an inner wall of at least one gap existing in a region from the outer surface of the foaming layer to a depth of 1.0 mm was observed by a scanning electron microscope, thereby obtaining a secondary electron image with a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gray levels with a lowest gray level of 0 and a highest gray level of 255, a contrast of 1200, and an average brightness of 128±16, and when determining a ratio Rs of the sum of the number of pixels in the secondary electron image having a brightness of 200 to 255 relative to the total number of pixels in the secondary electron image, the average value of Rs for the 12 locations was 0.5% or more, and

[0018] For each of the cross-sections of a total of 12 locations, the inner wall of at least one gap existing in the area from the surface of the foamed layer on the side opposite to the substrate toward the outer surface of the foamed layer to a thickness of 1.0 mm was observed by a scanning electron microscope, thereby obtaining a secondary electron image with a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gray levels with the lowest gray level being 0 and the highest gray level being 255, a contrast of 1200, and an average brightness of 128±16, and when determining the ratio Rt of the sum of the number of pixels in the secondary electron image with a brightness of 200 to 255 relative to the total number of pixels in the secondary electron image, the average value of Rt for the 12 locations was greater than 0.5%.

[0019] At least one aspect of the present disclosure provides a developing device including at least a developing roller and a toner supplying roller for supplying toner to the developing roller, which is configured such that

[0020] A voltage may be applied between the developer roller and the toner supply roller, wherein

[0021] The toner supply roller is an electrophotographic roller.

[0022] At least one aspect of the present disclosure provides an electrophotographic image forming apparatus including a developing apparatus.

[0023] At least one aspect of the present disclosure provides a process cartridge detachable relative to a main body of an electrophotographic image forming apparatus,

[0024] The process cartridge has a contact point member electrically connected to an electrical contact point of the main body when the process cartridge is mounted to the main body,

[0025] The process cartridge includes a developing roller and a toner supplying roller for supplying toner to the developing roller.

[0026] The process cartridge is configured so that a voltage can be applied between the developing roller and the toner supplying roller through an electrical connection with the main body, and

[0027] The toner supply roller is an electrophotographic roller.

[0028] At least one aspect of the present disclosure may provide an electrophotographic roller capable of further suppressing reverse fogging. In addition, at least one aspect of the present disclosure may provide a developing device that facilitates the formation of high-quality electrophotographic images. In addition, at least one aspect of the present disclosure may provide an electrophotographic image forming device that can stably output high-quality electrophotographic images. In addition, at least one aspect of the present disclosure may provide a processing box that facilitates the formation of high-quality electrophotographic images.

[0029] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic cross-sectional view of an electrophotographic roller according to one aspect of the present invention;

[0031] Figure 2 is an enlarged cross-sectional view of a portion of a foamed layer of an electrophotographic roller according to one aspect of the present disclosure;

[0032] Figure 3 is a schematic block diagram showing a process cartridge according to an aspect of the present invention;

[0033] FIG. 4A to FIG. 4C Each is a schematic cross-sectional view of a mold when an electrophotographic roller is formed according to an aspect of the present invention;

[0034] Figure 5 is the SEM image of the cut surface of the foam layer;

[0035] Fig. 6A and Figure 6B Each is a schematic diagram of an opening of the outermost surface of a foamed layer when observing the surface profile of the foamed layer; and

[0036] Figure 7 It is a schematic diagram of the charge amount distribution of toner. DETAILED DESCRIPTION

[0037] In the present disclosure, the expression "from XX to YY" or "XX to YY (or XX to YY)" indicating a numerical range refers to a numerical range including the lower limit and the upper limit of the endpoints, unless otherwise specified. When describing the numerical range in sections, the upper limit and the lower limit of each numerical range can be arbitrarily combined. In addition, in the present disclosure, for example, expressions such as "at least one selected from the group consisting of XX, YY and ZZ" refer to any one 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.

[0038] The present inventors speculate that the reason why reverse fogging cannot be sufficiently suppressed when the conductive roller of Japanese Patent Application Publication No. 2009-139866 is used as a toner supply roller is as follows. In the case of the conductive roller according to Japanese Patent Application Publication No. 2009-139866, the conductive coating provided at at least a portion of the skeleton of the substrate including soft polyurethane foam and cellular membrane is in contact with the toner, so that the toner is applied with an electric charge. In this step, it is conceivable that most of the carbon nanotubes, i.e., the conductive agent in the conductive coating, are embedded in the conductive coating. It is believed that the charge applied to the toner in contact with such a conductive coating is mainly caused by frictional charging. Therefore, it is believed that the toner in contact with the conductive coating also contains a certain amount of toner charged to a polarity opposite to the conventional polarity. As can be imagined, the result is that reverse fogging cannot be sufficiently suppressed.

[0039] Based on such considerations, the present inventors conducted further studies. As a result, the present inventors found that, for example, an electrophotographic roller according to the following aspects contributes to further reducing reverse fogging.

[0040] That is, an electrophotographic roller according to at least one aspect of the present disclosure includes a substrate and a foamed layer on the outer peripheral surface of the substrate. The foamed 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.

[0041] The foamed layer has a connected structure having at least one gap that opens on the outer surface of the foamed layer and extends in the thickness direction of the foamed layer. The inner wall of the gap includes a skeleton, and at least a portion of at least one conductive particle is exposed at the inner wall. The thickness T of the foamed layer is 2.0 mm or more.

[0042] Then, at each of the four locations at every 90-degree angle along the circumferential direction of the foaming layer, at the midpoint in the length direction of the foaming layer, and at each of the three locations at a distance of L / 4 from each opposite end toward the midpoint, where L represents the length in the length direction of the foaming layer, a cross section having the total thickness of the foaming layer in the direction along the circumferential direction of the electrophotographic roller is exposed. For each of the cross sections at a total of 12 locations, the inner wall of at least one gap existing in the region from the outer surface of the foaming layer to a depth of 1.0 mm is observed by a scanning electron microscope, thereby obtaining a secondary electron image with a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gray levels with a minimum grayscale of 0 and a maximum grayscale of 255, a contrast of 1200, and an average brightness of 128±16. When the ratio Rs of the sum of the number of pixels in the secondary electron image belonging to a brightness of 200 to 255 relative to the total number of pixels in the secondary electron image is determined, the average value of Rs for the 12 locations is 0.5% or more.

[0043] In addition, for each of the cross sections at a total of 12 locations, the inner wall of at least one gap existing in the region from the surface of the foamed layer on the side opposite to the substrate toward the outer surface of the foamed layer to a thickness of 1.0 mm was observed by a scanning electron microscope, thereby obtaining a secondary electron image with a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gray levels with a lowest grayscale of 0 and a highest grayscale of 255, a contrast of 1200, and an average brightness of 128±16. When the ratio Rt of the sum of the number of pixels belonging to the brightness of 200 to 255 in the secondary electron image to the total number of pixels in the secondary electron image was determined, the average value of Rt for the 12 locations was 0.5% or more.

[0044] The inventors speculate that the reason why the electrophotographic roller according to this aspect contributes to further reducing reverse fogging is as follows. In addition, the effect presentation mechanism described below is strictly speculative, and the technical scope of the electrophotographic roller according to the present disclosure is not limited by the following effect presentation mechanism.

[0045] The electrophotographic roller according to the present aspect has a communication structure having at least one gap that opens on the outer surface of the foamed layer and extends in the thickness direction of the foamed layer. The inner wall of the gap includes a skeleton, and at least a portion of at least one conductive particle is exposed at the inner wall. Thus, the toner can contact at least a portion of the conductive particles exposed in the internal gap.

[0046] In addition, Rs and Rt are indices of the degree of exposure of the portion of the conductive particles exposed at the inner wall of at least one gap present in each of the region from the outer surface of the foamed layer to a depth of 1.0 mm at the cross section having the total thickness of the foamed layer in the direction along the circumferential direction of the electrophotographic roller, and the region from the surface of the foamed layer opposite to the substrate toward the outer surface of the foamed layer to a thickness of 1.0 mm. And, the average values ​​of each of Rs and Rt being 0.5% or more indicate that a portion of the conductive particles is exposed in a given amount at the inner wall of the gap present near the surface of the foamed layer, and at the inner wall of the gap present in the deep part of the foamed layer. As a result, in the process of the toner entering the gap of the foamed layer and flowing inside the foamed layer, the toner directly contacts the exposed portion of the conductive particles of the inner wall of the gap, thereby fully ensuring the timing of charge injection into the toner. As a result, it is conceivable that the distribution of the charge held by the toner is narrowed, and the proportion of the toner charged to the polarity opposite to the normal polarity is reduced, so that the generation of reverse fogging can be suppressed.

[0047] Next, a description will be given of an electrophotographic roller according to an aspect of the present disclosure.

[0048] (1) Electrophotographic roller

[0049] An electrophotographic roller according to one aspect of the present disclosure has a conductive substrate and a foamed layer on an outer peripheral surface of the substrate. Figure 1 An example of an electrophotographic roller is shown in . Figure 1 The electrophotographic roller 1 shown includes a conductive substrate 3 and a foamed layer 2 provided on the peripheral surface thereof. The foamed layer 2 is a surface layer of the electrophotographic roller 1, and forms the outer surface.

[0050] The layer structure of the electrophotographic roller 1 is not limited to the layer structure including only the substrate 3 and the foam layer 2. The layer structure may include other layers such as a conductive elastic layer between the substrate 3 and the foam layer 2. The structure of the electrophotographic roller is described in detail below.

[0051] Matrix

[0052] The conductive substrate 3 is used as a support layer and electrode of the electrophotographic roller. The substrate includes a conductive material, which includes a metal such as aluminum, a copper alloy or stainless steel or an alloy thereof, iron plated with chromium or nickel, or a synthetic resin having conductivity. For example, the substrate may be a core metal. The substrate has, for example, a solid cylindrical shape or a hollow cylindrical shape.

[0053] Foam layer

[0054] The foamed layer 2 has a skeleton containing a binder resin and at least one conductive particle in the binder resin. The foamed layer 2 has gaps, i.e., spaces between the skeletons. In addition, the foamed layer 2 has a connected structure having at least one gap that opens on the outer surface of the foamed layer 2 and extends in the thickness direction of the foamed layer 2. By making the foamed layer have such a connected structure and exposing the conductive particles at the inner wall, charge injection into the toner can be effectively performed.

[0055] The skeleton surface inside the foaming layer 2 is referred to as the inner wall. That is, at least a portion of the inner wall of the gap includes the skeleton. The inner wall of the gap preferably includes the skeleton. The inner wall of the gap is more preferably formed by a binder resin and conductive particles in the binder resin. The inner wall has a structure in which at least a portion of at least one conductive particle is exposed.

[0056] Conductive particles

[0057] The conductive particles are not particularly limited and may be appropriately selected from known resins for use.

[0058] For example, fine particles of carbon black can be used; fine particles of conductive metals such as silver, gold or copper; or fine particles of conductive metal oxides such as zinc oxide, tin oxide or titanium oxide. 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. Among them, carbon black is relatively easy to obtain and can provide good conductivity. Therefore, the conductive particles further preferably contain carbon black. Alternatively, other conductive agents such as ionic conductive agents and fibrous carbon nanotubes (CNTs) can also be used in combination with conductive particles.

[0059] At least a portion of the conductive particles in the foaming layer is exposed from the inner wall of the foaming layer. Thus, charge can be injected into the toner and the effect of suppressing reverse fogging can be obtained. More specifically, at least a portion of the conductive particles is preferably also exposed at the inner wall of the cell opening at the outer surface.

[0060] Next, we will refer to Figure 2 A description is given of a partially enlarged view of an inner wall of a foamed layer of an electrophotographic roller according to one aspect of the present disclosure.

[0061] The foamed layer 2 has a plurality of gaps 22 having a connection structure inside the foamed layer 2. In addition, the foamed layer 2 contains a binder resin 23 and a plurality of conductive particles 24 dispersed in the binder resin 23. Then, at least a portion of the plurality of conductive particles 24 is exposed at the inner wall 25 of the foamed layer 2. In addition, the term "exposed" of the particle means that at least a portion of one conductive particle 24 is not covered by the binder resin 23 and forms a portion of the inner wall of the foamed layer 2.

[0062] The exposure rate of the conductive particles from the inner wall can be calculated by image analysis of an image taken with a scanning electron microscope (SEM) described later. Specifically, it is assumed that the length of the foam layer 2 in the longitudinal direction is L. A cross section having the total thickness of the foam layer 2 in the direction along the circumferential direction of the electrophotographic roller is exposed at four locations at every 90-degree angle along the circumferential direction of the foam layer 2, at the midpoint in the longitudinal direction of the foam layer 2, and at three locations at a distance of L / 4 from each of the opposite ends toward the midpoint.

[0063] For each of the cross sections at 12 locations, the inner wall of at least one gap existing in the region from the outer surface of the foaming layer 2 to a depth of 1.0 mm was observed by a scanning electron microscope, and a secondary electron image with a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gray levels with a minimum grayscale of 0 and a maximum grayscale of 255, a contrast of 1200, and an average brightness of 128±16 was obtained. Rs represents the ratio of the sum of the number of pixels in the secondary electron image with a brightness of 200 to 255 to the total number of pixels in the secondary electron image. The average value of Rs for the 12 locations is greater than 0.5%.

[0064] However, for each of the 12 cross sections in total, the inner wall of at least one gap existing in the region from the surface of the foaming layer 2 opposite to the substrate 3 toward the outer surface of the foaming layer 2 to the thickness of 1.0 mm was observed by a scanning electron microscope, and a secondary electron image with a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gray levels with a minimum grayscale of 0 and a maximum grayscale of 255, a contrast of 1200, and an average brightness of 128±16 was obtained. Rt represents the ratio of the sum of the number of pixels belonging to brightness 200 to 255 in the secondary electron image to the total number of pixels in the secondary electron image. The average value of Rt of the 12 locations is more than 0.5%.

[0065] 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. However, in order to obtain a high charge injection effect through durability test use, it is necessary to expose conductive particles at the inner wall inside the foam layer.

[0066] In the present disclosure, as described above, it is required that the average value of the exposure rate of the conductive particles in the area from the outer surface of the foaming layer to the depth of 1.0 mm, and the average value of the exposure rate in the area from the side of the foaming layer close to the substrate toward the outer surface of the foaming layer to the thickness of 1.0 mm are both 0.5% or more. Pixels belonging to the brightness of 200 to 255 observed under the above conditions indicate the presence of conductive particles. The foaming layer has a connected structure. Therefore, 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 foaming layer, but also at the inner wall inside the foaming layer. That is, it is considered that the conductive particles are exposed at the inner wall along the thickness direction of the foaming layer. The average value of Rs and the average value of Rt satisfy the aforementioned range. This can directly inject charge into the toner and can provide an effect of suppressing reverse fogging. The reason is considered to be as follows. When 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 fully ensured during the flow of the toner inside the foaming layer.

[0067] 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 wall of the gap is formed by the skeleton of the foamed layer and the conductive particles are exposed at the inner wall so that the average value of Rs and the average value of Rt can be satisfied, a method in which a liquid mixture containing conductive particles (which will also be referred to as "liquid mixture" hereinafter) is used to form the foamed layer can be mentioned.

[0068] As an example of a method for obtaining a foamed layer having gaps in which at least a part of the conductive particles are exposed on the inner wall, a method in which polymerization of a polymer constituting a skeleton is sufficiently delayed by gas generated by a foaming agent is effective.

[0069] For example, the presumed mechanism of forming a foamed layer having gaps in which at least a portion of the conductive particles are exposed on the inner wall by the above method is explained by taking the case where a liquid mixture contains a polyol, an isocyanate compound, water as a foaming agent, a urethanization catalyst and conductive particles as an example.

[0070] The liquid mixture having the aforementioned composition is foamed by generating carbon dioxide (CO2) due to the reaction between water and the isocyanate compound. In this step, when the urethanization reaction due to the reaction between the polyol and the isocyanate compound occurs simultaneously, the viscosity of the liquid compound also increases rapidly. Therefore, when the surrounding resin component is expanded by the pressure when the gap is expanded due to the generated CO2, the conductive particles are also expanded together with the resin component, so that the conductive particles are embedded in the resin skeleton.

[0071] On the other hand, in the case where the foaming is sufficiently delayed to cause the urethanization reaction, when the gap generated by the generated CO2 expands, the viscosity of the surrounding resin component of the gap is still low. Therefore, even when the surrounding resin component of the gap is expanded by the pressure when the gap expands, the conductive particles rarely move. It is conceivable that such a difference in mobility between the resin component and the conductive particles relative to the foaming pressure can form a foamed product having a gap in which at least a part of the conductive particles is exposed at its inner wall.

[0072] Due to this mechanism, for the conductive particles, it is preferred to use a material that is less likely to move even by foaming pressure. Then, from this viewpoint, the conductive particles preferably contain at least carbon black, and particularly preferably carbon black.

[0073] As described above, in the process of forming the foamed layer containing polyurethane, the foaming reaction for forming the foamed structure and the resinification reaction of the polyurethane proceed. Then, by selecting the catalyst, it is possible to achieve that the resinification reaction is sufficiently delayed relative to the foaming reaction. That is, by using a temperature-sensitive catalyst as a urethanization catalyst for controlling the resinification reaction, the progress of the resinification reaction during the foaming process is suppressed. As a result, the viscosity of the resin component in the liquid mixture can be prevented from increasing.

[0074] Although the temperature-sensitive catalyst has low catalytic activity at normal temperature, it rapidly exhibits activity as a resinification catalyst when a given temperature is reached. In the initial stage of the reaction when the solution temperature begins to rise, the catalytic activity is low. However, in the later stage of the reaction when the temperature rises, the catalytic activity also greatly increases. Therefore, in the initial state of the reaction, when the viscosity of the solution is low, the foaming reaction can be carried out in advance. Therefore, it is conceivable that the conductive particles can be exposed at the inner wall. Thus, by using an electrophotographic roller having a foaming layer, it is possible to effectively inject charges into the toner.

[0075] In the case of the liquid mixture shown above, water and the isocyanate compound react with each other at a temperature of, for example, about 40 to 50° C., thereby generating CO 2 . Therefore, as a temperature-sensitive catalyst, it is preferred to use a catalyst that has low activity at a temperature of about 40 to 50° C. and rapidly exhibits activity at a high temperature. Examples of such temperature-sensitive catalysts may include 2-ethylhexanoate of 1,5-diazabicyclo (4,3,0) nonene-7 (active temperature 100° C.), phenolate 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 becomes the highest.

[0076] The phenol salt of 1,8-diazabicyclo(5,4,0)undecene-7 is commercially available as, for example, "U-CAT SA1" (trade name, manufactured by San-Apro Ltd.). In addition, the 2-ethylhexanoic acid salt of 1,8-diazabicyclo(5,4,0)undecene-7 is commercially available as, for example, "U-CAT SA102" (trade name, manufactured by San-Apro Ltd.).

[0077] By forming the foamed layer using the temperature-sensitive catalyst as described above, the average values ​​of Rs and Rt become easier to control within the aforementioned range. By using a temperature-sensitive catalyst having an active temperature higher than the curing reaction temperature, the average values ​​of Rs and Rt can be increased.

[0078] The average value of Rs is preferably 1.0% or more, more preferably 2.0% or more, and further preferably 4.0% or more. The average value of Rt is preferably 1.0% or more, more preferably 2.0% or more, and further preferably 4.0% or more. The greater the exposure rate, the higher the possibility of contact between the exposed conductive particles and the toner. Therefore, the reverse toner can be effectively reduced.

[0079] Therefore, the upper limit is not particularly limited. The average value of Rs is preferably 1.0 to 20.0%, more preferably 2.0 to 16.0%, and further preferably 4.0 to 14.0%. On the other hand, the average value of Rt is preferably 1.0 to 20.0%, more preferably 2.0 to 16.0%, and further preferably 4.0 to 14.0%.

[0080] The ratio of the average value of Rs at 12 sites to the average value of Rt at 12 sites (Rs / Rt) is preferably 0.8 to 1.2, and more preferably 0.9 to 1.1.

[0081] The thickness T of the foam layer is 2.0 mm or more. A thickness T of 2.0 mm or more can maintain a stable contact state with other members such as a developing roller. The thickness T of the foam layer is preferably 2.0 to 5.0 mm, more preferably 3.0 to 4.0 mm.

[0082] The primary particle size of the conductive particles (including the arithmetic mean of the Feret diameter of the particles in the unexposed portion) is not particularly limited. However, in order to ensure the contact area with the toner, the primary particle size is preferably above a given size, and particularly preferably above 10 nm. In addition, in order to make it difficult for the particles to fall off from the foaming layer during the use of the electrophotographic roller, the primary particle size is preferably set to a given particle size or less, specifically preferably below 10 μm. The arithmetic mean of the Feret diameter of the conductive particles is preferably 10 nm to 10 μm, more preferably 10 to 100 nm, and further preferably 15 to 50 nm.

[0083] In order to measure the average particle size of the particles, first, the foaming layer is heated at 500° C. in a nitrogen atmosphere to decompose the binder. Subsequently, the residue is collected and an image of the particles is taken using a known microscope or the like. The Feret diameter set in a direction parallel to the vertical direction of the image is measured for determination. One hundred arithmetic averages are adopted.

[0084] The content of the conductive particles in the foaming 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 foaming layer is preferably 1.0 to 25.0 parts by mass, more preferably 1.0 to 20.0 parts by mass, further preferably 1.0 to 15.0 parts by mass, and further preferably 2.0 to 15.0 parts by mass per 100 parts by mass of the binder resin contained in the foaming layer.

[0085] Binder resin

[0086] The foaming layer preferably has a foamable binder resin. For example, the foaming layer preferably contains particles dispersed in the binder resin. The resin of the foaming layer is not particularly limited and can be appropriately selected from known resins for use.

[0087] Examples thereof may include epoxy resins, urea-formaldehyde resins, ester resins, amide resins, imide resins, amide-imide resins, phenolic resins, vinyl resins, silicone resins, and fluororesins. As the resin of the foaming layer, the following rubber materials may also be preferably used. As the rubber material, mention may be made of ethylene-propylene-diene copolymer rubber, acrylonitrile-butadiene rubber, chloroprene rubber, natural rubber, isoprene rubber, styrene-butadiene rubber, silicone rubber, epichlorohydrin rubber, and polyurethane, etc.

[0088] The binder resin preferably includes polyurethane. Polyurethane has an electron-donating nitrogen element in its structure, and therefore, the charge amount of the toner can be increased by contacting with a negatively charged toner. Therefore, polyurethane is preferably used. In addition, the solution viscosity of polyurethane is low during foaming, and therefore, by selecting a catalyst described later, the exposure of the conductive particles at the inner wall can be easily achieved. That is, the foaming layer preferably includes polyurethane as a binder resin.

[0089] As the polyurethane, for example, a reaction product of a known polyol and an isocyanate can be used.

[0090] The polyol is not particularly limited and can be appropriately selected from various known polyols as the raw material of the polyurethane used. For example, the polyol can be appropriately selected from known polyols such as polyether polyols and polyester polyols that are commonly used to make soft polyurethane foams. The polyol can be used alone or in combination of two or more thereof.

[0091] It should be noted that, among the polyols, polyether polyols are preferably used for producing flexible and highly elastic polyurethane foams having excellent wet heat durability. For example, polyethylene propylene ethertriol is preferably used.

[0092] In addition, the hardness of the polyurethane of the skeleton of the gap constituting the foaming layer is, for example, expressed as the average elastic modulus measured using SPM at the surface of the inner wall. This average elastic modulus is preferably below 2200MPa, particularly preferably below 2000MPa, and further preferably below 1900MPa. The skeleton measured at the inner wall surface has such an average elastic modulus, which can relax the stress on the toner. In addition, a good contact state with the developing roller can be formed, which can effectively collect the residual toner of the developer, and can smoothly supply the toner injected with the charge by the developing roller. The lower limit of the average elastic modulus is not particularly limited. In order to make the mechanical strength of the foaming layer more sufficient, and to show more reliable scratchiness of the toner on the surface of the developing roller, the lower limit of the average elastic modulus is preferably set to more than 1000MPa, and particularly set to more than 1300MPa. The preferred range of the average elastic modulus is 1000 to 2200 MPa, further 1000 to 2000 MPa, particularly 1300 to 2000 MPa, and further 1300 to 1900 MPa.

[0093] In order to set the average elastic modulus to 2200 MPa or less, for example, controlling the number average molecular weight of the polyol, and suppressing the amount of aromatic isocyanate to a prescribed amount or less can be mentioned. Specifically, for example, it is effective to set the number average molecular weight of the polyol to 2000 to 7000, and particularly 3000 to 5000. By setting the number average molecular weight of the polyol within the above range, the length of the soft segment between the urethane bonds can be ensured, and it becomes easier to control the average elastic modulus within the above range.

[0094] The ratio (molar ratio) of the isocyanate group to 1.0 of the hydroxyl group in the polyol is preferably 1.1 or less, more preferably 1.05 or less.

[0095] Isocyanate is not particularly limited and can be appropriately selected from various conventionally known isocyanates as a raw material for polyurethane. For example, 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), dimethyl diphenyl diisocyanate (TODI), naphthalene diisocyanate (NDI), xylylene diisocyanate (XDI), 4,4'-diphenylmethane diisocyanate (MDI), carbodiimide-modified MDI, polymethylene polyphenyl isocyanate and polymeric isocyanate etc. can be used alone, or two or more thereof can be used in combination. In addition, an isocyanate-terminated prepolymer obtained by reacting an isocyanate with one or more known active hydrogen compounds can also be used as an isocyanate.

[0096] In order to suppress the low viscosity of the solution during foaming, isocyanates with relatively small molecular weight are preferred. The isocyanate preferably includes at least one selected from the group consisting of 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI) and 4,4'-diphenylmethane diisocyanate (MDI).

[0097] The foaming layer has a connected structure having at least one gap that opens on the outer surface of the foaming layer and extends in the thickness direction of the foaming layer. The foaming layer preferably has a cell structure of continuous foam or semi-continuous foam, and more preferably has a cell structure of continuous foam. For example, for the foaming layer, the skeleton containing the binder resin and the conductive particles more preferably has a continuous foaming structure forming cells. In particular, for the foaming layer having a cell structure of continuous foaming, since the toner penetrates into the inside of the foaming layer, the charge tends to be injected from the exposed conductive particles, so that the reverse toner can be more effectively reduced.

[0098] The porosity of the foaming layer is not particularly limited, and is preferably 50 to 97% by volume. A porosity of 50% by volume or more results in good fluidity of the toner in the gaps of the foaming layer, and a porosity of 97% or less can well maintain the contact timing between the toner and the conductive particles of the inner wall. The porosity is more preferably 75 to 93% by volume, and further preferably 82 to 90% by volume. The porosity can be controlled by the amount of the foaming agent, and in the case of cast curing described later, can also be controlled by the amount of casting into the forming mold.

[0099] catalyst

[0100] The catalyst is not particularly limited and can be appropriately selected from various known catalysts for use. In order to expose the conductive particles on the inner wall, it is preferred to use a temperature-sensitive catalyst that is active in the resinification reaction of the polyurethane. As temperature-sensitive catalysts, 2-ethylhexanoate of 1,5-diazabicyclo (4,3,0) nonene-7 (active temperature 100°C), phenolate 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) can be mentioned. The active temperature indicates the temperature at which the catalytic activity of the temperature-sensitive catalyst becomes the highest.

[0101] Further, a catalyst active in the resinification reaction of polyurethane and its foaming reaction can be appropriately selected for use. For example, one of amine catalysts (such as 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 and N-methylmorpholine), organometallic catalysts (such as tin octoate, tin oleate, dibutyltin dilaurate, dibutyltin diacetate, tetraisopropoxytitanium, tetra-n-butoxytitanium and tetra(2-ethylhexyloxy)titanium), acid salt catalysts obtained by reducing the initial activity of amine catalysts and organometallic catalysts (such as carboxylates and formates, octoates, and borates), or a combination of two or more thereof can be used in combination with a temperature-sensitive catalyst.

[0102] other

[0103] Foam stabilizers and other additives may be used as required.

[0104] When the binder resin in the foaming layer according to the present disclosure is polyurethane or polyurea, by using water as a foaming agent as described above, carbonic acid gas can be generated by reaction with an isocyanate compound. Other foaming agents and water may be used in combination.

[0105] The foam stabilizer is not particularly limited and may be appropriately selected from various known foam stabilizers for use.

[0106] As other auxiliary agents, a crosslinking agent, a vulcanizing agent, a vulcanization accelerator, a vulcanization auxiliary agent, a flame retardant, a colorant, an ultraviolet absorber, an antioxidant, and the like may be used as necessary within a range not impairing the effects of the present disclosure.

[0107] Method for forming foamed layer

[0108] The foaming method of the foaming layer is not particularly limited. Any of a method using a foaming agent, a method of mixing bubbles by mechanical stirring, and other methods can be used. In addition, the foaming rate can be appropriately determined and is not particularly limited. The foaming layer is preferably a foamed / cured product of a liquid mixture for forming the foaming layer (hereinafter also referred to as "liquid mixture").

[0109] For example, when the binder resin is polyurethane, a liquid mixture for forming a foam layer obtained by mixing the following materials 1 to 4 (preferably 1 to 5) is foamed and cured. As a result, a foam layer according to the present disclosure can be obtained. That is, the method for manufacturing an electrophotographic roller preferably has a step of foaming and curing a liquid mixture for forming a foam layer containing the following materials 1 to 4, preferably the following materials 1 to 5.

[0110] 1. As a material for forming a binder resin,

[0111] Polyols, such as polyether polyols or polyester polyols

[0112] Isocyanate compounds

[0113] 2. Conductive particles

[0114] 3. Catalyst (preferably a catalyst comprising a temperature-sensitive catalyst)

[0115] 4. Foaming agent

[0116] 5. Foam stabilizer

[0117] There is no particular limitation on the method for joining the substrate and the foaming layer. The following methods can be used. A method in which the substrate is pre-set in a mold (forming mold), the liquid mixture is injected into a mold for casting, and foamed / cured (casting molding method); and a method in which the foamed / cured product of the liquid mixture is pre-formed and then formed into the shape of the foaming layer to be bonded to the substrate (existing forming method); and other methods. As required, for any method, an adhesive layer having conductivity can be provided between the substrate and the foaming layer. As the adhesive layer, known materials such as adhesives and hot melt sheets can be used.

[0118] In the case of using a casting forming method, a release agent can be applied to the inner wall of the forming mold in advance. As a release agent, a known release agent can be used. Examples thereof can include aqueous release agents comprising an olefin component and a polysiloxane component, and release agents obtained by dissolving a fluorine component in a fluorine-based solvent. In order to easily form an opening on the outer surface of the foaming layer, it is preferred to use an aqueous release agent comprising an olefin component and a polysiloxane component.

[0119] In the case of using an existing forming method, the method for producing the foamed / solidified product of the liquid mixture is not particularly limited. In addition to the method of casting into a mold in a prescribed shape, examples thereof may include a method of cutting a product of a prescribed size from a block foamed product (so-called slab foam) by cutting, and then grinding it into a cylindrical shape, and a method of forming it into a prescribed size by an extrusion machine.

[0120] In order to effectively supply the toner injected with the charge to the developing roller through the toner supply roller, it is necessary to scrape off the toner on the developing roller that is not developed and returned to the developer container through the toner supply roller. The scraping property of the toner supply roller on the toner is greatly affected by the shape of the surface of the foaming layer. In particular, at the edge of the opening, in the case of the shape of the foaming layer surface surrounding the opening in a manner with a small height change in the radial direction of the roller, the continuous edge can effectively scrape off the toner on the developing roller.

[0121] Specifically, the outer peripheral surface of the electrophotographic roller and the first surface, that is, one surface of the glass plate, are in contact with each other so that the amount of indentation of the glass plate relative to the electrophotographic roller may become 1.0 mm. In this state, the contact portion between the electrophotographic roller and the glass plate is observed from the side of the second surface of the glass plate opposite to the first surface. In this step, the opening edge of the gap preferably surrounds the opening.

[0122] In addition, the indentation amount represents the amount (distance) that the glass plate moves from the position toward the electrophotographic roller when the horizontal glass plate is brought closer to the vertical upper side of the observed electrophotographic roller and assuming that the indentation amount when the electrophotographic roller and the first surface of the glass plate first contact each other is 0.0 mm.

[0123] From this observation, in order to form a surface profile in which the edge surrounds the opening, it is preferred to cast the polyurethane rubber composition into a mold of a prescribed shape, thereby forming a foamed layer by a foaming and curing method.

[0124] The type of resin in the foaming layer can be determined by known pyrolysis GC / MS, FT-IR or 13 C-NMR and other confirmations.

[0125] The type and composition ratio of the conductive particles can be confirmed by known energy dispersive X-ray spectroscopy (EDS) or X-ray diffraction (XRD) etc. EDS analysis can provide the type and composition ratio of the metal elements of the particles. In addition, when the particles are crystalline, XRD of the particle powder left when the foaming layer is pyrolyzed in a nitrogen atmosphere can provide a more specific composition formula.

[0126] (2) Processing box

[0127] The present disclosure provides a process cartridge configured to be detachable relative to the main body of an electrophotographic image forming apparatus and including the above-mentioned electrophotographic roller. The process cartridge preferably includes a developing roller for conveying toner to a photosensitive member and a surface of the photosensitive member. The process cartridge preferably includes a toner supplying roller for supplying toner to the surface of the developing roller. Then, the electrophotographic roller is preferably a toner supplying roller.

[0128] A process cartridge according to one aspect of the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited thereto. Figure 3 : is a schematic sectional view showing one example of a process cartridge using the electrophotographic roller according to one aspect of the present disclosure as the toner supplying roller 34 .

[0129] Figure 3The illustrated process cartridge has a cleaning blade 31, a charging roller 32, a developing roller 33, a toner supplying roller 34, a toner 35, a toner regulating member 36, and a photosensitive member 37, and has a detachable configuration relative to the main body of the electrophotographic apparatus.

[0130] The photosensitive member 37 is charged by the charging roller 32 and rotates in the direction of arrow R1. The process cartridge has a contact point member that is electrically connected to the electrical contacts of the main body when the process cartridge is mounted to the main body of the electrophotographic image forming apparatus. The electrical connection provides a structure that enables a voltage to be applied between the developing roller 33 and the toner supplying roller 34, and that enables charge injection of the toner inside the foaming layer to be performed. The toner supplying roller 34 contacts and rotates with the developing roller 33, thereby supplying toner to the surface of the developing roller 33. The toner regulating member 36 contacts with the developing roller 33, thereby regulating the amount of toner on the surface of the developing roller 33. The developing roller 33 rotates in the direction of arrow R2, thereby conveying the toner to the developing area where the developing roller 33 and the photosensitive member 37 are opposite to each other.

[0131] The process cartridge according to the present disclosure adopts a so-called contact developing system configured such that the developing roller 33 is arranged in contact with the photosensitive member 37. The toner remaining on the photosensitive member 37 after transfer onto paper is scraped off by the cleaning blade 31 and contained in a cleaner container.

[0132] (3) Development equipment

[0133] The electrophotographic roller can be used as a toner supply roller of a developing device, which includes at least a developing roller and a toner supply roller for supplying toner to the developing roller, and is configured so that a voltage can be applied between the developing roller and the toner supply roller, and electric charge can be injected into the toner inside the foaming layer.

[0134] (4) Electrophotographic image forming equipment

[0135] The present disclosure provides an electrophotographic image forming apparatus including the above-mentioned electrophotographic roller. The electrophotographic image forming apparatus may be, for example, an electrophotographic image forming apparatus including a developing apparatus.

[0136] In addition, the electrophotographic image forming apparatus includes, for example, a photosensitive member, a developing roller for conveying toner to the surface of the photosensitive member, a toner supplying roller for supplying toner to the surface of the developing roller, and a cleaning roller for cleaning the photosensitive member. Then, the electrophotographic roller is preferably a toner supplying roller.

[0137] Example

[0138] Hereinafter, the present disclosure will be described by way of examples and comparative examples. However, the present disclosure is not limited to the examples and the like. In addition, the term "part" in the examples and comparative examples is based on mass unless otherwise specified.

[0139] Example 1

[0140] like Figure 4A to Figure 4C As shown, a mold including a cylindrical member 42 with an inner diameter of 11 mm and a release agent coated on its inner surface, an upper bridge member 43 and a lower bridge member 41, and a substrate 44 with an outer diameter of 4 mm made of stainless steel (SUS304) as a substrate are prepared and all are preheated to 80°C.

[0141] The cylindrical member 42 is mounted on the lower bridge member 41, and the base 44 ( Figure 4A The solution obtained by premixing the following materials (A) to (F) is referred to as solution B, and the material (G) is referred to as solution A. The polyurethane rubber composition 45, i.e., the liquid mixture for forming a foaming layer obtained by mixing solution A and solution B, is injected from the space between the cylindrical member 42 and the base 44. Figure 4B ). In addition, the mixing of solution A and solution B was performed immediately before injection.

[0142] After the polyurethane rubber composition 45 is injected, the upper bridge member 43 is mounted on the upper end surface of the cylindrical member 42, and the base 44 is held concentrically with the cylindrical member 42 by the upper bridge member 43 and the lower bridge member 41 ( Figure 4C ) The injection amount of the polyurethane rubber composition 45 was set to 2.3 g.

[0143] (A) Polyol (polyethylene propylene ether triol having a number average molecular weight of 3100, trade name: ACTOCOL EP-550N, manufactured by MITSUI CHEMICAL Inc.): 100.0 parts

[0144] (B) Conductive particles (trade name: LIONITE CB, manufactured by Lion Specialty Chemicals Co., Ltd.): 3.0 parts

[0145] (C) Foam stabilizer (trade name: Niax Silicone L-3640, manufactured by Momentive Performance Materials Inc.): 0.4 parts

[0146] (D) Temperature sensitive catalyst (2-ethylhexanoate of 1,5-diazabicyclo(4,3,0)nonene-7, trade name: U-CAT 1102, manufactured by San-Apro Ltd.): 0.25 parts

[0147] (E) Tertiary amine catalyst (a mixture of triethylenediamine and dipropylene glycol, trade name: DABCO 33LV, manufactured by Evonik Co.): 0.5 parts

[0148] (F) Foaming agent (water): 1.5 parts

[0149] (G) Isocyanate mixture (comprising NCO=45%, MDI=20%, trade name: COSMONATE TM20, manufactured by MITSUI CHEMICAL Inc.): 24.4 parts

[0150] Next, the state heated to 80° C. was maintained for 10 minutes while the cylindrical member 42, the upper bridge member 43, and the lower bridge member 41 were integrated, thereby foaming and curing the polyurethane rubber composition 45. After cooling to 50° C., the upper bridge member 43 and the lower bridge member 41 were removed, and the base 44 including the foamed layer formed on the outer peripheral surface was demolded from the cylindrical member 42 to obtain the electrophotographic roller Y-1 according to Example 1. The thickness T of the foamed layer was 3.5 mm.

[0151] Measurement of average values ​​of exposure rates Rs and Rt of conductive particles

[0152] The foamed layer was cut from the surface of the electrophotographic roller Y-1 perpendicular to the longitudinal direction of the substrate. That is, a cross section having the total thickness of the foamed layer in the direction along the circumferential direction of the electrophotographic roller was exposed. The surface of the obtained cross section corresponding to the cross section of the foamed layer was subjected to platinum vacuum evaporation (trade name E-1045, manufactured by Hitachi High-Tech Corporation, discharge voltage: 15 mA, discharge time: 30 seconds), thereby preparing an observation sample.

[0153] Then, for the cross section, the inner wall of the gap existing in the region from the outer surface of the cut cross section to a depth of 1.0 mm was observed using SEM (trade name: JSM-7800F, manufactured by JEOL Co.). Figure 5 As shown, the center 53 of the inscribed circle 52 of the cell 51 at the cut surface is arranged at the center of the observation screen. Then, while keeping the position unchanged, the magnification is increased to 5000 times to obtain a secondary electron image. In this step, when the connecting hole 54 is reflected even at a part of the observation screen, the cell is not photographed.

[0154] In addition, the measurement conditions of SEM are as follows: measurement magnification: 5000 times, resolution: 18 nm / pixel, acceleration voltage: 2 kV, irradiation current: 8, contrast: 1200, and brightness: adjusted so that the average brightness when converted into a monochrome image of 256 grayscales can become 128±16.

[0155] In addition, the obtained secondary electron image was imported into the image processing software Image J and converted into a monochrome image with 256 grayscale (brightness 0 is black and 255 is white), thereby calculating the ratio Rs of the sum of the number of pixels with brightness 200 to 255 in the entire image area to the total number of pixels.

[0156] The operation was performed at a total of 12 locations, including the midpoint in the length direction of the foaming layer, and three locations at a distance of L / 4 from each opposite end toward the midpoint, i.e., the cross sections at the positions of L / 4, L / 2, and 3L / 4, and 4 points at every 90-degree angle along the circumferential direction, where L represents the full length of the foaming layer in the length direction. The arithmetic mean of the Rs obtained at the 12 locations was calculated.

[0157] The same operation was also performed in a region from the base of the foamed layer toward the outer surface of the foamed layer to a thickness of 1.0 mm, whereby the arithmetic mean value of Rt was calculated.

[0158] Observation of the surface profile of the foam layer

[0159] While the outer peripheral surface of the electrophotographic roller Y-1 and the first surface of the glass plate are brought into contact with each other so that the amount of indentation of the glass plate with respect to the electrophotographic roller Y-1 can become 1.0 mm, the contact portion of the electrophotographic roller Y-1 and the glass plate is observed from the side of the second surface opposite to the first surface of the glass plate. Then, it is confirmed whether the edge of the opening surrounds the opening.

[0160] like Fig. 6A As shown, the state in which the edge of the opening surrounds the opening refers to a state in which the opening 26 is surrounded by the continuous edge of the binder resin 23 . Figure 6B is an instance of a situation where there is no surround.

[0161] In the present disclosure, 100 openings were observed. When 98% or more were surrounded, it was determined that for the electrophotographic roller, the edge of the opening surrounded the opening.

[0162] In addition, the indentation amount represents the amount (distance) that the glass plate moves from the position toward the electrophotographic roller when the horizontal glass plate is brought closer to the vertical upper side of the observed electrophotographic roller and the indentation amount when the electrophotographic roller first contacts the first surface of the glass plate is assumed to be 0.0 mm.

[0163] Measurement of SPM elastic modulus

[0164] The cross section of the electrophotographic roller Y-1 was cut into thin slices by using a diamond knife cutting process while maintaining at -110°C with the help of CRYOMICROTOME (trade name: EMFC6, manufactured by Leica Microsystems Co.). In addition, a sample of 100 μm square and 100 μm width in the depth direction was made from the thin slice. The elastic modulus of the surface of the inner wall of the skeleton containing the polyurethane resin was measured. For the measurement, an SPM device (trade name: MFP-3D-Origin, manufactured by Oxford Instruments Co.) and a probe (trade name: AC160, manufactured by Olympus Corporation) were used. In this step, the force curve was measured a total of 25 times at 5 vertical × 5 horizontal locations, and was determined as the arithmetic mean of those at 23 points excluding the highest and lowest values, and the elastic modulus was calculated using Hertz's theory.

[0165] Porosity measurement

[0166] The electrophotographic roller Y-1 was cut into a 10 mm cylindrical shape together with the substrate, and a three-dimensional image was obtained using a three-dimensional measurement X-ray CT device (model: TDM1001-II, manufactured by Yamato Scientific Co., Ltd.). From the obtained three-dimensional image, the porosity was calculated using the following formula (1). In addition, the measurement conditions were as follows. Target material: tungsten, filament material: tungsten, X-ray intensity: 100 kV.

[0167] Porosity (volume %) = volume of gaps / (volume of cylinder - volume of matrix) (1)

[0168] Measurement of the content of conductive particles per 100 parts by mass of binder resin

[0169] When determining the content of the conductive particles from the electrophotographic roller, the following method can be used.

[0170] After the foaming layer is removed from the core metal and the mass is measured, the binder resin is decomposed by heating at 500°C in a nitrogen atmosphere. Next, the residue of the conductive particles is collected and the mass is measured. (The mass of the foaming layer - the mass of the conductive particles) is referred to as the mass of the binder resin. The content of the conductive particles per 100 parts by mass of the binder resin is calculated from the mass.

[0171] Image evaluation

[0172] The electrophotographic roller to be evaluated was assumed to be a toner supplying roller, and the evaluation of fogging was performed.

[0173] First, the toner supply roller was removed from the black cartridge of a color laser printer (trade name: laser beam printer Satera LBP674C, manufactured by Canon Corp.), and the toner supply roller to be evaluated was mounted thereto. The cartridge and the laser printer were placed in a high temperature and high humidity environment (temperature: 30.0° C., relative humidity: 80%), and then left to stand for more than 12 hours.

[0174] Then, a 0% printed solid white image was output, and the reflectance (%) was measured by a reflection densitometer (trade name: TC-6DS / A, manufactured by Tokyo Denshoku Co., Ltd.) The value obtained by subtracting the obtained reflectance from the reflectance (%) of unused print output paper (standard paper) measured in the same manner was referred to as the initial fogging value (%).

[0175] Next, during the output of the solid white image, the power of the color laser printer was turned off and the process cartridge was removed. Then, the ratio of the reverse toner in the toner on the developing roller was measured using a charge quantity and particle size distribution measuring instrument (trade name: E-spart Analyzer Model EST-III, manufactured by HOSOKAWAMICRON CORPORATION). The toner having a charge quantity Q / M (μC / g) greater than 0 was regarded as the reverse toner, and its ratio ( Figure 7 ), which is referred to as the initial positive toner ratio (%). In addition, the number of particles to be measured is set to about 3,000.

[0176] Then, 5000 1% printed images were continuously outputted, and then the same operation as above was performed, thereby measuring the fog value (%) after the durability test and the positive toner ratio (%) after the durability test.

[0177] Examples 2 to 8, and 10 to 11

[0178] (B) Except for changing the kind and mixing amount of the conductive particles as described in Table 1-1, the electrophotographic rollers Y-2 to Y-8, Y-10 and Y-11 according to Examples 2 to 8, 10 and 11 were manufactured in the same manner as in Example 1 and evaluated in the same manner as in Example 1.

[0179] The materials (trade names) used are as follows.

[0180] TOOKABLACK#5500(TOKAI CARBON CO.,LTD.)

[0181] Ketjen Black EC600JD (Lion Specialty Chemicals Co., Ltd.)

[0182] Silver nanoparticles (Sigma Aldrich)

[0183] Gold nanoparticles (Sigma Aldrich)

[0184] Example 9

[0185] (B) An electrophotographic roller Y-9 according to Example 9 was manufactured in the same manner as in Example 1, except that the mixing amount of the conductive particles was changed to 1.3 parts and 2 parts of carbon nanotubes (trade name: FloTube 9100, manufactured by CNanoCo.) as a conductive agent other than the conductive particles were further added, and evaluated in the same manner as in Example 1.

[0186] Embodiments 12 to 14

[0187] (D) Electrophotographic rollers Y-12 to Y-14 according to Examples 12 to 14 were manufactured in the same manner as in Example 1, except that the kind and the mixing amount of the temperature sensitive catalyst were changed as described in Table 1-2, and evaluated in the same manner as in Example 1.

[0188] The materials (trade names) used are as follows.

[0189] U-CAT SA102 (trade name, manufactured by San-Apro Ltd.)

[0190] 2-Ethylhexanoate of 8-diazabicyclo[5.4.0]undecene-7(DBU)

[0191] Active temperature: 100°C

[0192]

[0193] U-CAT SA1 (trade name, manufactured by San-Apro Ltd.)

[0194] 1,8-Diazabicyclo[5.4.0]undecene-7-phenolate

[0195] Active temperature: 80℃

[0196]

[0197] Embodiment 15

[0198] (A) An electrophotographic roller Y-15 according to Example 15 was manufactured in the same manner as in Example 1, except that the type of polyol was changed to a polyester polyol having a number average molecular weight of 1000 (trade name: Curaray polyol P-1020, manufactured by Kuraray Co., Ltd.), and the mixing amount of the (G) isocyanate mixture was changed to 31.7 parts, and was evaluated in the same manner as in Example 1.

[0199] Embodiments 16 to 20

[0200] (F) Electrophotographic rollers Y-16 to Y-20 according to Examples 16 to 20 were manufactured in the same manner as in Example 1, except that the amount of water and the mixing amount of the (G) isocyanate mixture were changed as described in Table 1-2, and evaluated in the same manner as in Example 1.

[0201] Examples 21 to 23

[0202] Will Figure 4A to Figure 4C The inner diameter of the cylindrical member 42 shown was changed to an inner diameter of 13 mm, and a polyurethane rubber composition 45 obtained by mixing the materials shown in Table 1-2 was injected into the cylindrical member 42 in an amount of 3.4 g. Next, a roller was manufactured by foaming and curing in the same manner as in Example 1. In addition, the outer peripheral surface of the obtained roller was ground at a rotation speed of 1800 rpm and a feed speed of 800 mm / min so that the outer diameter could become 11 mm, thereby manufacturing electrophotographic rollers Y-21 to Y-23 according to Examples 21 to 23. In addition, evaluation was performed in the same manner as in Example 1.

[0203] Comparative Example 1

[0204] Electrophotographic roller X-1 was manufactured in the same manner as in Example 1 except that silica (SiO2, trade name: MSN-002, manufactured by TAYCA CORPORATION) was added in an amount of 5 parts instead of adding (B) conductive particles, and evaluated in the same manner as in Example 1.

[0205] Comparative Example 2

[0206] Electrophotographic roller X-2 was manufactured in the same manner as in Example 1 except that an ion conductive agent (Li-TFSI, trade name: EF-N115, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was added in an amount of 1 part instead of (B) the conductive particles, and evaluated in the same manner as in Example 1.

[0207] Comparative Example 3

[0208] An electrophotographic roller X-3 was produced in the same manner as in Example 1, except that the (B) conductive particles were not added, and was evaluated in the same manner as in Example 1.

[0209] Comparative Example 4

[0210] An electrophotographic roller X-4 was produced in the same manner as in Example 1, except that the (D) temperature-sensitive catalyst was not added, and evaluated in the same manner as in Example 1.

[0211] Comparative Example 5

[0212] Electrophotographic Roller X-4 was irradiated with a low-pressure mercury lamp (trade name: GLQ500US / 11, manufactured by HARRISON TOSHIBA LIGHTING, Inc.) to perform surface treatment, thereby manufacturing Electrophotographic Roller X-5, and evaluated in the same manner as in Example 1.

[0213] For the surface treatment, the roller was rotated while the sensor sensitivity was 254 nm with 4000 mJ / cm 2 As a result of the surface treatment, the exposure rate Rs of the conductive particles in the region at a depth of 1.0 mm from the outer surface became 3.0%.

[0214] Table 1-1

[0215]

[0216] Table 1-2

[0217]

[0218] In the table, the number of parts of the binder resin indicates the mass parts of the conductive particles per 100 mass parts of the binder resin.

[0219] Table 2

[0220]

[0221] The evaluation results of each example and comparative example are shown in Table 3-1, Table 3-2, and Table 4.

[0222] In Examples 1 to 23, the average values ​​of the exposure rates of the conductive particles, Rs and Rt, were both 0.5% or more. Therefore, the charge injection effect on the toner was large, and the positive toner ratio was low even after a durability test of 5,000 sheets of paper. Therefore, the effect of suppressing fogging on paper can be obtained.

[0223] Among them, in Examples 1 to 3, Example 5, Examples 7 and 8, Examples 10 to 15, and Examples 20 to 22, Rs and Rt were both 4.0% or more. Therefore, a higher effect of suppressing fogging on paper can be obtained.

[0224] In Examples 2 to 3, Examples 7 and 8, and Examples 13 to 15, Rs and Rt are both 4.0% or more, and the porosity is 82% to 90% by volume, and the conductive particles are carbon black, and the structure is such that the edge of the opening of the foam layer surrounds the opening, and the average elastic modulus of the inner wall of the foam layer is 2000 MPa or less. Therefore, a particularly high effect of suppressing fogging on paper can be obtained.

[0225] In addition, in Examples 1 and 2 and Example 4, Rs and Rt are both 0.5% or more, and at the edge of the opening on the surface of the foaming layer, the shape is such that the opening is surrounded in a manner with a small height change in the radial direction. Therefore, a larger amount of charged toner can be supplied to the developing roller. Therefore, in Examples 1, 2, and 4, it is conceivable that the ratio of positive toner is also lower than that of Examples 21 to 23, and a higher effect of suppressing fogging on paper can be obtained.

[0226] In Comparative Examples 1 to 4, Rs and Rt are both less than 0.5%. Therefore, the charge injection effect on the toner is low. Therefore, even after the durability test of 5000 sheets of paper, the positive toner ratio is high. Therefore, the effect of suppressing fogging on paper cannot be obtained.

[0227] In Comparative Example 2, although the presence of the ion conductive agent resulted in good initial fogging on the paper, a large amount of fogging on the paper occurred after the endurance test of 5,000 sheets of paper. The consideration is as follows. The ion conductive agent undergoes electrical degradation due to use in the endurance test. Therefore, the charge injection effect after use in the endurance test is reduced.

[0228] In Comparative Example 5, although Rs became 0.5% or more due to ultraviolet irradiation, Rt was less than 0.5%. Therefore, it is considered as follows: A sufficient charge injection effect to the toner could not be obtained, and therefore, an effect of suppressing fogging on paper could not be obtained.

[0229] Table 3-1

[0230]

[0231] Table 3-2

[0232]

[0233] Table 4

[0234]

[0235] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An electrophotographic roller comprising: Conductive substrate; and a foaming layer on the outer peripheral surface of the substrate, wherein The foaming layer is the surface layer of the electrophotographic roller, The foamed layer has a skeleton including a binder resin and at least one conductive particle in the binder resin, The foamed layer has a connected structure having at least one gap that opens on the outer surface of the foamed layer and extends in the thickness direction of the foamed layer, At least a portion of the inner wall of the gap is formed by the frame, At least a portion of the at least one conductive particle is exposed at the inner wall, The thickness T of the foaming layer is greater than 2.0 mm. With L being the length of the foam layer in the longitudinal direction, a cross section having the total thickness of the foam layer in the direction along the circumferential direction of the electrophotographic roller is exposed at four locations at every 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 each of three locations at a distance of L / 4 from each of the opposite ends toward the midpoint, For each of the cross sections of a total of 12 locations, an inner wall of at least one gap existing in a region from the outer surface of the foaming layer to a depth of 1.0 mm is observed by a scanning electron microscope, thereby obtaining a secondary electron image with a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gray levels with a lowest grayscale of 0 and a highest grayscale of 255, a contrast of 1200, and an average brightness of 128±16, and when determining a ratio Rs of the sum of the number of pixels in the secondary electron image having a brightness of 200 to 255 relative to the total number of pixels in the secondary electron image, the average value of Rs for the 12 locations is 0.5% or more, and For each of the cross-sections at a total of 12 locations, the inner wall of at least one gap existing in the area from the surface of the foamed layer on the side opposite to the substrate toward the outer surface of the foamed layer to a thickness of 1.0 mm is observed by a scanning electron microscope, thereby obtaining a secondary electron image with a magnification of 5000 times, a resolution of 18 nm / pixel, 256 gray levels with a lowest grayscale of 0 and a highest grayscale of 255, a contrast of 1200 and an average brightness of 128±16, and when determining the ratio Rt of the sum of the number of pixels in the secondary electron image with a brightness of 200 to 255 to the total number of pixels in the secondary electron image, the average value of Rt for the 12 locations is greater than 0.5%.

2. The electrophotographic roller according to claim 1, wherein The inner wall of the gap is formed by a frame.

3. The electrophotographic roller according to claim 1 or 2, wherein When the outer peripheral surface of the electrophotographic roller and a first surface as one surface of a glass flat plate are brought into contact with each other in such a manner that the amount of indentation of the glass flat plate with respect to the electrophotographic roller is 1.0 mm, 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, in, The indentation amount is the amount, i.e., the distance, of movement of the glass plate from the glass plate toward the electrophotographic roller when the horizontally maintained glass plate is brought closer vertically above the electrophotographic roller to be observed and the first surfaces of the electrophotographic roller and the glass plate contact each other for the first time, assuming that the indentation amount is 0.0 mm.

4. The electrophotographic roller according to claim 1 or 2, wherein The binder resin includes polyurethane.

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

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

7. The electrophotographic roller according to claim 1 or 2, wherein The conductive particles include carbon black.

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

9. The electrophotographic roller according to claim 1 or 2, wherein The porosity of the foamed layer is 50 to 97 volume %.

10. The electrophotographic roller according to claim 1 or 2, wherein The porosity of the foamed layer is 82 to 90 volume %.

11. A developing device, comprising at least: Developing roller; and a toner supplying roller for supplying toner to the developing roller, wherein A voltage can be applied between the developing roller and the toner supply roller, and The toner supply roller is an electrophotographic roller according to any one of claims 1 to 10 .

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

13. A process cartridge detachable relative to a main body of an electrophotographic image forming apparatus, The process cartridge has a contact point member electrically connected to an electrical contact point of the main body when the process cartridge is mounted to the main body, The process cartridge includes a developing roller and a toner supplying roller for supplying toner to the developing roller, A voltage can be applied through an electrical connection to the main body between the developing roller and the toner supply roller, and The toner supply roller is an electrophotographic roller according to any one of claims 1 to 10 .

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