JP5730051B2 - Charging member - Google Patents

Description

  The present invention relates to a charging member.

  In an electrophotographic apparatus, as a charging member used for contact charging of an electrophotographic photosensitive member, resin particles are contained in the surface layer, and convex portions derived from the resin particles are formed on the surface to adjust the surface roughness. A charging member is proposed (Patent Document 1).

JP 2008-276026 A

  In the charging member for contact charging, the convex portion on the surface is considered to be an important configuration for more reliably generating a discharge phenomenon in the vicinity of the nip with the electrophotographic photosensitive member.

  However, with the recent increase in image quality of electrophotographic images, the particle size of toner has become smaller. In addition, various external additives have come to be used as the function of the toner is enhanced. As a result, toner or the like adheres to the surface of the charging member having a convex portion on the surface, and it becomes easy to get dirty. In particular, the present inventors have accumulated toner and external additives between the convex portions (valleys) on the surface of the charging member when a charging member having convex portions formed on the surface is used for a long period of time. It was confirmed. Further, it was confirmed that a streak-like or dot-like defect occurred in the electrophotographic image with the accumulation of toner or the like between the convex portions. From this, the present inventors have estimated that the accumulation of toner or the like between the convex portions is a factor that destabilizes the discharge from the charging member to the photosensitive member.

  Accordingly, the present invention is directed to providing a charging member that can stably charge an electrophotographic photosensitive member even after long-term use.

  The present invention is also directed to providing an electrophotographic apparatus and a process cartridge that can stably provide high-quality electrophotographic images over a long period of time.

According to the present invention, there is provided a charging member having a conductive substrate, an elastic layer, and a surface layer in this order, the surface layer being dispersed in the binder resin and the binder resin, and a convex portion on the surface of the surface layer. Solid resin particles that are produced,
The elastic layer includes a rubber as a binder and hollow particles dispersed in the rubber, the hollow particles have a shell containing a thermoplastic resin, and enclose gas.
The diameter of the projected circle of the resin particles in the laminating direction of the elastic layer and the surface layer is smaller than the diameter of the projected circle of the hollow particles in the laminating direction,
When a circle having a diameter that is three times the diameter of the projected circle of the resin particles in the laminating direction and centering on a point obtained by projecting the apex of the convex portion in the laminating direction is projected in the laminating direction In addition, a charging member is provided in which the total area of the projected circles of the hollow particles contained in the circle region is 80% or more of the area of the circle.

  According to the present invention, there is provided a process cartridge comprising the charging member and an electrophotographic photosensitive member and configured to be detachable from the main body of the electrophotographic apparatus.

Furthermore, according to the present invention, there is provided an electrophotographic apparatus provided with the charging member and an electrophotographic photosensitive member .

  According to the present invention, it is possible to obtain a charging member in which toner or the like hardly accumulates between convex portions even after long-term use, and the charging performance hardly changes with time. Further, by using such a charging member, an electrophotographic apparatus and a process cartridge that can stably form a high-quality electrophotographic image can be obtained.

(A) It is sectional drawing of the charging member which concerns on this invention. (B) It is a projection figure of the lamination direction of the charging member which concerns on this invention. It is the schematic of the projection circle | round | yen of the lamination direction of a resin particle and a hollow particle, and sectional drawing of a charging member. It is the schematic which shows the ratio for which the area of the projection circle | round | yen of the hollow particle contained in the 3 times circular area | region of the diameter of the projection circle | round | yen of the resin particle accounts to the area of this 3 times circular area | region. (A) It is sectional drawing at the time of immersing an elastic layer in the coating solution for surface layers. (B) It is sectional drawing of the drying process which apply | coats the coating solution for surface layers on the elastic layer surface. (C) It is sectional drawing after apply | coating the coating solution for surface layers on the elastic layer surface, and drying. (A) It is sectional drawing of the roller-shaped charging member which concerns on this invention. (B) It is sectional drawing of the flat-shaped charging member which concerns on this invention. It is the schematic of the measuring apparatus at the time of the electrical resistance value measurement of the charging member which concerns on this invention. (A) It is a schematic sectional drawing of a single layer crosshead extrusion molding machine. (B) It is a cross-sectional schematic diagram of a metal mold | die. 1 is a schematic cross-sectional view illustrating an example of an electrophotographic apparatus including a charging member according to the present invention.

  The charging member according to the present invention has a conductive substrate, an elastic layer, and a surface layer in this order, and is used for charging a member to be charged. The surface layer includes a binder resin and solid resin particles that are dispersed in the binder resin and have convex portions formed on the surface of the surface layer. The elastic layer includes a rubber as a binder and hollow particles dispersed in the rubber. The hollow particles have a shell containing a thermoplastic resin and contain a gas.

  The diameter of the projected circle of the resin particles in the stacking direction of the elastic layer and the surface layer is smaller than the diameter of the projected circle of the hollow particles in the stacking direction.

  Further, a circle having a diameter that is three times the diameter of the projected circle of the resin particles in the laminating direction and centering on a point obtained by projecting the apex of the convex portion in the laminating direction is projected in the laminating direction. Then, the total area of the projected circles of the hollow particles contained in the circle region is 80% or more of the area of the circle.

  With such a configuration, when the electrophotographic photosensitive member and the charging member come into contact with each other, it is possible to prevent the resin particles from sinking into the elastic layer side and depositing dirt on the concave portion of the charging member surface. The hollow particles in the elastic layer enclose a gas, and when deformation is applied, the internal pressure of the hollow particles increases and expresses high resilience. Therefore, when the contact between the electrophotographic photosensitive member and the charging member is released, the shape is quickly restored, and the convex portion due to the resin particles is restored.

  Therefore, immediately before and after the nip, the surface of the charging member and the surface of the electrophotographic photosensitive member are close to each other, and in the region where the discharge occurs most actively (discharge region), there is an effect of charging stabilization due to the presence of the convex portion. Demonstrated. As a result, the accumulation of dirt such as toner and external additives on the surface of the charging member is suppressed, and at the same time, the effect of uniform charging is demonstrated over a long period of time. Generation of streaks and dots due to surface contamination is suppressed. In the charging member according to the present invention, the relationship between the resin particles and the hollow particles is controlled as follows.

  FIG. 1A shows a cross-sectional view of an example of a charging member according to the present invention. The charging member according to the present invention has an elastic layer 2 and a surface layer 5. The elastic layer 2 contains hollow particles 3 and the surface layer 5 contains resin particles 4. FIG. 1B shows a projection 8 of the hollow particles 3 and a projection 7 of the resin particles 4 in the stacking direction of the elastic layer 2 and the surface layer 5. In the present invention, the diameter of the projected circle of the resin particles 4 is smaller than the diameter of the projected circle of the hollow particles 3. That is, the ratio of the diameter of the projected circle of the resin particle 4 to the diameter of the projected circle of the hollow particle 3 is less than 1. The diameter of the projected circle of the hollow particles 3 and the diameter of the projected circle of the resin particles 4 are calculated by the following method.

  An arbitrary point of the elastic layer 2 of the charging member is cut out from the surface layer 5 by 20 nm over 500 μm by a focused ion beam (trade name: FB-2000C, manufactured by Hitachi, Ltd.), and a cross-sectional image is taken. To do. A three-dimensional image is calculated by combining the captured images. As shown in FIG. 2, a projection view in the stacking direction is created from the three-dimensional image of the hollow particles 3, and the projection area is obtained. Next, the diameter of a circle having an area equal to the projected area is obtained. Similarly, a projected area of another hollow particle 3 is obtained, a diameter of a circle having an area equal to the projected area is obtained, and an arithmetic average of the diameters of these circles is obtained. This operation is performed for 10 hollow particles in the field of view. Further, the same measurement is performed for 10 points in the longitudinal direction of the charging member, and an average value of a total of 100 obtained is calculated and set as the diameter of the projected circle of the hollow particles 3.

  A three-dimensional image of the resin particles 4 in the surface layer 5 is calculated by the same method as the measurement of the volume average particle diameter of the hollow particles 3. As shown in FIG. 2, a projection view of the resin particle 4 is created from the stereoscopic image of the resin particle 4, and the diameter of the projection circle of the resin particle 4 is calculated in the same manner as the diameter of the projection circle of the hollow particle 3.

  Moreover, as shown in FIG. 3, it has a diameter three times the diameter of the projected circle in the laminating direction of the resin particles 4 causing the convex portions on the surface, and the apex of the convex portion is projected in the laminating direction. When a circle centered on the point is projected in the stacking direction, a region 10 of the circle is virtually set on the surface of the charging member. Here, the vertex of the convex portion indicates a point farthest from the elastic layer 2 in the convex portion in the stacking direction. Hereinafter, the region 10 is also referred to as a triple circular region. The region 10 is assumed to be a region that needs to be distorted in order to cause the resin particles 4 that form convex portions by contact with the electrophotographic photosensitive member to be embedded in the elastic layer 2. In the present invention, the total area of the projected circles of the hollow particles 3 included in the region 10 occupies 80% or more of the area of the region 10. In order to further exhibit the characteristics of the hollow particles 3, it is preferable that the total area of the projected circles of the hollow particles 3 included in the region 10 occupy 90% or more of the area of the region 10. The area ratio is calculated by the following method.

  The point which projected the vertex of the convex part of arbitrary resin particles 4 which has a diameter 3 times the diameter of the projected circle of resin particle 4 calculated by the above-mentioned method in the lamination direction on the surface. A center circle is projected in the stacking direction and set on the surface of the charging member. This is a triple circle region. In addition, the position of the vertex of a convex part can be determined from the said three-dimensional image. By a method similar to the method of calculating the diameter of the projected circle of the hollow particles 3, the threefold circular regions are cut out every 20 nm in the stacking direction, and a three-dimensional image of the hollow particles 3 is calculated. All the hollow particles 3 in this three-dimensional image are projected in the stacking direction, the area of the projected portion of the hollow particles 3 included in the triple circle region is obtained, and the ratio to the area of the triple circle region is calculated. . Further, the same measurement is performed for 10 points in the longitudinal direction of the charging member, and the average value is calculated.

  The charging member according to the present invention has a convex portion on the surface of the surface layer 5. When the surface of the charging member and the surface of the electrophotographic photosensitive member are at a predetermined distance before and after the nip between the charging member and the electrophotographic photosensitive member, point discharge is preferentially performed from the convex portion. Compared with the case where there is no convex portion, the battery is always discharged from a specific position, so that the effect of equalizing the charging performance can be obtained. The charging member according to the present invention preferably has a surface ten-point average roughness (Rz) (μm) of 2 ≦ Rz ≦ 100. Moreover, it is preferable that surface uneven | corrugated average space | interval (Sm) (micrometer) is 15 <= Sm <= 200. By setting Rz and Sm of the charging member within this range, the charging uniformity effect is more reliably exhibited. Rz and Sm are calculated by the following method.

  The surface ten-point average roughness (Rz) is measured according to JIS B 0601-1994 surface roughness standards using a surface roughness measuring instrument (trade name: SE-3500, manufactured by Kosaka Laboratory Ltd.). The measurement is performed at six random locations on the charging member, and the average value is defined as Rz.

  The surface unevenness average interval (Sm) is obtained by measuring 10 unevenness intervals at an arbitrary portion of the charging member, and taking the average as Sm of the measurement portion. The measurement is performed on six random portions of the charging member, and the average value is Sm.

  When the vertex 1 of the convex portion is projected in the stacking direction, 80% or more of the projected point 6 is preferably included in the projection diagram 8 of the hollow particle 3 as shown in FIG. As a result, when the resin particles 4 sink into the elastic layer 2 in contact with the electrophotographic photosensitive member, the effect of returning the shape when released is more surely exhibited. The ratio is calculated by the following method.

  A three-dimensional image is calculated by a method similar to the method of measuring the diameter of the projected circle of the resin particles 4. From the three-dimensional image of the obtained resin particle 4, the vertex 1 of the convex part of the arbitrary resin particle which forms a convex part on the surface is determined. It is confirmed whether or not the point 6 obtained by projecting the vertex 1 in the stacking direction is included in the projection 8 of the hollow particle 3 measured by the above method. Such an operation is carried out for 10 arbitrary resin particles that form convex portions on the surface within the field of view. Further, the same measurement is performed for any 10 points in the longitudinal direction of the charging member. For a total of 100 resin particles 4 obtained, the ratio at which the point 6 obtained by projecting the apex 1 of the convex portion in the stacking direction is included in the projection 8 of the hollow particle 3 is calculated.

  As a method for controlling the hollow particles 3 and the resin particles 4 to have a specific positional relationship, there is a method of adjusting the permeation amount of the solvent in the coating solution for forming the surface layer 5 with respect to the elastic layer 2 when the surface layer 5 is formed. . The present inventors consider the mechanism that can control the positional relationship between the hollow particles 3 and the resin particles 4 as follows.

  In the step of applying the coating solution for forming the surface layer 5 to the surface of the elastic layer 2, the elastic layer 2 is immersed in the coating solution for forming the surface layer 5. At the time of immersion, the solvent in the coating solution is absorbed into the elastic layer 2 as shown in FIG. At this time, the absorption amount of the solvent of the elastic layer 2 is reduced in the portion where the hollow particles 3 exist in the elastic layer 2. This is because the volume which can hold | maintain a solvent becomes relatively small because the void | hole which concerns on the hollow particle 3 exists.

  In the drying step after the coating solution is applied, the coating solution on the elastic layer 2 in which the hollow particles 3 are present is dried faster because the amount of the solvent retained in the elastic layer 2 is small, and the hollow particles 3 are formed. The solid content concentration in the coating solution on the existing elastic layer 2 is increased. Therefore, as shown in FIG. 4B, from the coating solution on the elastic layer 2 in which the hollow particles 3 containing a large amount of the solvent are not present, the elastic particles 2 on the elastic layer 2 in which the hollow particles 3 with a low solvent retention amount and quick drying exist A flow occurs to supplement the solvent toward the coating solution. With this flow, after the coating solution is dried, as shown in FIG. 4C, the resin particles 4 dispersed in the coating solution move onto the elastic layer 2 where the hollow particles 3 are present, thereby forming convex portions.

  In order to make a difference in the amount of absorption of the solvent as described above depending on the presence or absence of the hollow particles 3, the solvent in the coating solution has a relatively high affinity for the material of the elastic layer 2 compared to the material of the hollow particles 3, It is preferable to select one that easily penetrates. In order to adjust the permeation amount of the solvent in the coating solution for forming the surface layer 5 with respect to the elastic layer 2, specifically, the following adjustment is performed.

  As the rubber used as the binder for the elastic layer 2, it is preferable to use a rubber having high solvent permeability in the coating solution for forming the surface layer 5. For example, urethane rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), acrylic rubber and epichlorohydrin rubber. In particular, epichlorohydrin rubber and NBR are more preferable. These may be used alone or in combination of two or more.

  The shell material of the hollow particles 3 in the elastic layer 2 has a low affinity with the solvent used for the coating solution for forming the surface layer 5 and preferably suppresses the penetration of the coating solution for forming the surface layer 5 into the elastic layer 2. . Specifically, those having a large difference in solubility parameter (hereinafter referred to as “sp value”) with the solvent are preferable as compared with the rubber of the elastic layer 2. Examples thereof include acrylonitrile resin, vinyl chloride resin, vinylidene chloride resin, methacrylic acid resin, urethane resin, amide resin, methacrylonitrile resin, and the like. In particular, it is preferable to use at least one thermoplastic resin selected from acrylonitrile resin, vinylidene chloride resin, and methacrylonitrile resin.

  The surface layer 5 can be formed by a coating method such as dipping coating in which the elastic layer 2 is dipped in a coating solution for forming the surface layer 5 and coated.

  As the solvent used in the coating solution for forming the surface layer 5, it is preferable to use a solvent having high affinity for the rubber used for the elastic layer 2 and low affinity for the shell material of the hollow particles 3. In particular, a solvent having a small difference in sp value from the rubber used for the elastic layer 2 and a large difference in sp value from the shell material of the hollow particles 3 in the elastic layer 2 is preferable. Specifically, ketones such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone, esters such as methyl acetate and ethyl acetate, and aromatic compounds such as xylene. These may use only 1 type and may use 2 or more types together. In particular, methyl ethyl ketone, methyl isobutyl ketone and the like are preferable.

  The binder resin used for the coating solution for forming the surface layer 5 is not particularly limited as long as it is a binder resin dissolved in the solvent.

  Furthermore, in order to express the above effects more reliably, the following adjustments can be made.

  The volume average particle diameter of the resin particles 4 and the hollow particles 3 to be added can be adjusted. Specifically, the volume average particle diameter of the resin particles 4 is made smaller than the volume average particle diameter of the hollow particles 3. By adjusting and using the volume average particle diameters of the resin particles 4 and the hollow particles 3, the diameter of the projected circle of the hollow particles 3 is 10 μm or more and 1200 μm or less, and the diameter of the projected circle of the resin particles 4 is 5 μm or more and 120 μm or less. It is preferable to do. Furthermore, the ratio of the diameter of the projected circle of the resin particle 4 to the diameter of the projected circle of the hollow particle 3 is preferably 0.15 or more and less than 1. As a result, the resin particles 4 sink into the elastic layer 2 at the time of contact with the electrophotographic photosensitive member, and the effect of returning the shape at the time of opening is more surely expressed. The volume average particle size of the hollow particles 3 and the volume average particle size of the resin particles 4 are calculated by the following method.

  An arbitrary point of the elastic layer 2 of the charging member is cut out from the surface layer 5 by 20 nm over 500 μm by a focused ion beam (trade name: FB-2000C, manufactured by Hitachi, Ltd.), and a cross-sectional image is taken. To do. A three-dimensional image is calculated by combining the captured images. The volume of the hollow particle 3 is calculated from this stereoscopic image, and the diameter of a sphere having a volume equal to this volume is obtained. This operation is performed for 10 hollow particles in the field of view. Furthermore, the same measurement is performed for 10 points in the longitudinal direction of the charging member, and an average value of a total of 100 obtained is calculated as the volume average particle diameter of the hollow particles 3.

  A three-dimensional image of the resin particles 4 in the surface layer 5 is calculated by the same method as the measurement of the volume average particle diameter of the hollow particles 3. The volume of the resin particles 4 is calculated from this stereoscopic image, and the diameter of a sphere having a volume equal to this volume is obtained. This operation is performed for 10 resin particles in the field of view. Furthermore, the same measurement is performed for 10 points in the longitudinal direction of the charging member, and an average value of a total of 100 obtained is calculated as the volume average particle diameter of the resin particles 4.

  Further, the porosity of the elastic layer 2 can be adjusted. Specifically, the porosity of the elastic layer 2 can be adjusted by the number of the hollow particles 3 and the volume average particle diameter. The number of hollow particles 3 represents the number of hollow particles 3 present in a unit volume of the elastic layer 2. The porosity indicates the ratio (%) of the volume of the gas contained in the hollow particles 3 contained in the unit volume of the elastic layer 2. The porosity is preferably 50% or more and 95% or less. By setting the porosity within this range, the convex portion of the surface layer 5 tends to sink into the elastic layer 2 side when the electrophotographic photosensitive member and the charging member are in contact with each other, and when the contact is released, the convex portion is quickly formed. The returning characteristic can be imparted more effectively. The porosity of the elastic layer 2 is calculated by the following method.

  A three-dimensional image is calculated by a method similar to the method of measuring the diameter of the projected circle of the hollow particles 3. From the stereoscopic image, the total volume of the voids in the image is obtained. The ratio of the total volume of the pores to the volume of the elastic layer 2 in the image is calculated. Further, the same measurement is performed for any 10 points in the longitudinal direction of the charging member, and an average value of the obtained values is calculated. This is the porosity of the elastic layer 2.

  Here, the relationship between the number of hollow particles 3 and the number of resin particles 4 forming convex portions on the surface is such that the ratio of the number of resin particles 4 forming convex portions on the surface to the number of hollow particles 3 is 3 or more. 50 or less. The number of resin particles 4 that form convex portions on the surface represents the number of resin particles 4 that form convex portions on the surface existing in the unit volume of the surface layer 5. By setting the ratio between the number of the resin particles 4 that form the convex portions on the surface and the number of the hollow particles 3 within this range, the indentation of the resin particles 4 that form the convex portions on the surface to the elastic layer 2 side is uniformly stabilized. . As a result, the resin particles 4 that form convex portions on the surface at the time of contact with the electrophotographic photosensitive member are dented by deformation of the hollow particles 3, and the convex shape quickly returns when the contact is released. It can be demonstrated reliably. The ratio between the number of hollow particles 3 and the number of resin particles 4 that form convex portions on the surface is calculated by the following method.

  A three-dimensional image is calculated by a method similar to the method of calculating the diameter of the projected circle of the resin particles 4 and the hollow particles 3. The number of resin particles 4 that form convex portions on the surface is counted from the three-dimensional image in the surface layer 5. Further, the number of the hollow particles 3 is counted from the stereoscopic image in the elastic layer 2. Thereby, the ratio of the number of resin particles 4 that form convex portions on the surface and the number of hollow particles 3 is calculated. Further, the same measurement is performed for any 10 points in the longitudinal direction of the charging member, and an average value of the obtained values is calculated. This is the ratio between the number of hollow particles 3 and the number of resin particles 4 that form convex portions on the surface.

<Charging member>
5A and 5B are schematic cross-sectional views of an example of the charging member according to the present invention. FIG. 5A shows a roller-shaped charging member, and FIG. 5B shows a flat plate-shaped charging member. Hereinafter, the roller-shaped charging member shown in FIG. 5A, that is, the charging roller will be described in detail. The charging roller shown in FIG. 5A has a conductive substrate 12, an elastic layer 2 formed on the conductive substrate 12, and a surface layer 5 formed on the elastic layer 2. The elastic layer 2 contains hollow particles 3 and the surface layer 5 contains resin particles 4.

  The conductive substrate 12 and the elastic layer 2 or the layers sequentially laminated (for example, the elastic layer 2 and the surface layer 5 shown in FIG. 5A) may be bonded via an adhesive. In this case, the adhesive is preferably conductive. In order to impart conductivity, the adhesive may contain a known conductive agent. Examples of the binder for the adhesive include thermosetting resins and thermoplastic resins. For example, known materials such as urethane, acrylic, polyester, polyether, and epoxy can be used. As a conductive agent for imparting conductivity to the adhesive, it can be appropriately selected from conductive agents described in detail later, and can be used alone or in combination of two or more.

The charging roller according to the present invention has an electric resistance of 1 × 10 ³ Ω or more and 1 × 10 ⁹ Ω or less in an environment of a temperature of 23 ° C./humidity of 50% RH in order to improve the charging of the electrophotographic photosensitive member. It is preferable. FIG. 6 shows a method for measuring the electrical resistance of the charging roller 17. Both ends of the conductive substrate 12 are brought into contact with a cylindrical metal 13 having the same curvature as that of the electrophotographic photosensitive member by a bearing 14 under load. In this state, the cylindrical metal 13 is rotated by a motor, and a DC voltage of −200 V is applied from the stabilized power supply 15 while the charging roller 17 that is in contact with the rotation is driven. The current flowing at this time is measured by an ammeter 16 and the resistance of the charging roller 17 is calculated. The load is 4.9 N each, the diameter of the metal cylinder is 30 mm, and the rotation of the metal cylinder is 45 mm / sec.

  As described above, the charging roller according to the present invention preferably has a surface ten-point average roughness (Rz) (μm) of 2 ≦ Rz ≦ 100. Moreover, it is preferable that surface uneven | corrugated average space | interval (Sm) (micrometer) is 15 <= Sm <= 200.

[Conductive substrate]
The conductive substrate 12 according to the present invention is conductive and has a function of supporting the elastic layer 2 and the like provided thereon. Examples of the material include metals such as iron, copper, stainless steel, aluminum, nickel, and alloys thereof.

[Elastic layer]
The elastic layer 2 according to the present invention contains rubber as a binder and hollow particles 3 dispersed in the rubber.

  As described above, it is preferable to use a rubber having high solvent permeability in the coating solution for forming the surface layer 5 as the rubber used as the binder for the elastic layer 2. Examples thereof include urethane rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), acrylic rubber, and epichlorohydrin rubber. These may be used alone or in combination of two or more. Among these, epichlorohydrin rubber and NBR are more preferable because of the high permeability of the solvent in the coating solution for forming the surface layer 5 and easy resistance adjustment. These have an advantage that resistance control and hardness control of the elastic layer 2 can be easily performed.

The volume resistivity of the elastic layer 2 is preferably 10 ² Ω · cm or more and 10 ¹⁰ Ω · cm or less when measured in a temperature 23 ° C./humidity 50% RH environment. The volume resistivity of the elastic layer 2 is obtained by the following method. First, the elastic layer 2 is cut into a strip shape of about 5 mm × 5 mm from the charging roller. A sample for measurement is obtained by vapor-depositing metal on both sides to produce an electrode and a guard electrode. A voltage of 200 V is applied to the obtained measurement sample using a microammeter (trade name: ADVANTEST R8340A ULTRA HIGH RESISTANCE METER, manufactured by Advantest). The current after 30 seconds is measured, and the volume resistivity is obtained from the sample thickness and the electrode area.

  A known conductive agent can be appropriately added to the elastic layer 2 according to the present invention in order to adjust the volume resistivity. Examples of the conductive agent include ionic conductive agents and electronic conductive agents.

  Examples of the ion conductive agent include the following. Inorganic ionic substances such as lithium perchlorate, sodium perchlorate, calcium perchlorate, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, trioctylpropylammonium Cationic surfactants such as bromide, modified aliphatic dimethylethylammonium ethosulphate, zwitterionic surfactants such as lauryl betaine, stearyl betaine, dimethylalkyl lauryl betaine, tetraethylammonium perchlorate, tetrabutylammonium perchlorate, Quaternary ammonium salts such as trimethyloctadecyl ammonium perchlorate, trifluoro Organic acid lithium salts such as lithium methanesulfonate or the like. These can be used alone or in combination of two or more. Among these ionic conductive agents, quaternary ammonium perchlorate is particularly preferably used because of its stable resistance to environmental changes.

  Examples of the electronic conductive agent include the following. Electrolytic treatment and spray coating on metal fine particles and fibers such as aluminum, palladium, iron, copper and silver, metal oxides such as titanium oxide, tin oxide and zinc oxide, metal fine particles, fibers and metal oxide surfaces Composite particles surface-treated by mixed shaking, carbon black, carbon-based fine particles, and the like. These can be used alone or in combination of two or more. The surface of the conductive agent may be surface-treated.

  In addition, additives such as softening oil and plasticizer may be added to the elastic layer 2 in order to adjust the hardness and the like. Furthermore, the elastic layer 2 may appropriately contain materials that impart various functions. Examples of these include anti-aging agents and fillers.

(Hollow particles)
The hollow particles 3 according to the present invention have a shell containing a thermoplastic resin and contain a gas. As the hollow particles 3, particles in which the inside of the particles are bubbles may be used, or the inclusion substance is included in the inside of the particles, and the inclusion substance is vaporized and expanded by applying heat to form the hollow particles 3. So-called thermally expandable microcapsules may be used. When the thermally expandable microcapsule is used, the shell containing the thermoplastic resin expands due to heat during vulcanization of the elastic layer 2. By adjusting the temperature conditions at the time of molding, the capsule can be molded with the shell structure maintained without melting or rupturing.

  As described above, the thermoplastic resin used for the shell of the hollow particle 3 has low affinity with the solvent used for the coating solution for forming the surface layer 5, and the coating solution for forming the surface layer 5 penetrates into the elastic layer 2. It is preferable to suppress this. Examples thereof include acrylonitrile resin, vinyl chloride resin, vinylidene chloride resin, methacrylic acid resin, urethane resin, amide resin, methacrylonitrile resin, and the like. Among these, those having low affinity with the solvent used for the coating solution for forming the surface layer 5 and exhibiting high impact resilience are preferable. Specifically, compared to the rubber of the elastic layer 2, the difference in solubility parameter (hereinafter referred to as “sp value”) with the solvent is large and the gas permeability is low. From acrylonitrile resin, vinylidene chloride resin, and methacrylonitrile resin. It is preferable to use at least one selected thermoplastic resin. These thermoplastic resins can be used alone or in combination of two or more. Furthermore, these thermoplastic resin monomers may be copolymerized and used as a copolymer.

  In the case of using a thermally expandable microcapsule, a substance that expands as a gas at a temperature lower than the softening point of the shell material of the hollow particles 3 can be used as the inclusion substance to be included in the capsule. For example, the following substances can be used. Low boiling liquids such as propane, propylene, butene, normal butane, isobutane, normal pentane, and isopentane, and high boiling liquids such as normal hexane, isohexane, normal heptane, normal octane, isooctane, normal decane, and isodecane. These may be used alone or in combination of two or more.

  The thermally expandable microcapsule can be produced by a known production method such as a suspension polymerization method, an interfacial polymerization method, an interfacial precipitation method, or a submerged drying method. The volume average particle diameter of the hollow particles 3 is not particularly limited, but is preferably 10 to 1000 μm and more preferably 50 to 500 μm in order to make the diameter of the projected circle of the hollow particles 3 be in the above range. By setting it as this range, the resin particle 4 which forms a convex part on the surface can fully sink into the elastic layer 2, and can fully exhibit the resilience with respect to sinking.

(Formation of elastic layer)
A method for forming the elastic layer 2 is not particularly limited, and a known method can be appropriately used. For example, the elastic layer 2 is formed using a known method such as mixing the above-mentioned various rubber components and other components with a ribbon blender, Nauter mixer, Henschel mixer, super mixer, Banbury mixer, pressure kneader, etc. An unvulcanized rubber composition is obtained. Using an extruder equipped with a cross head, the conductive base 12 and the produced unvulcanized rubber composition can be integrally extruded to produce an elastic roller preform. The crosshead is an extrusion mold that is used at the tip of a cylinder of an extruder, which is used to form a coating layer for electric wires and wires. The elastic roller preform is placed in a cylindrical or split mold having a cylindrical cavity and heated and foamed to obtain an elastic roller having an elastic layer 2 of a predetermined size. Further, it is also possible to use a method in which the elastic roller preform is freely foamed in a high-temperature atmosphere such as a hot stove and then polished with a plunge cut type cylindrical polishing machine to obtain an elastic roller having a predetermined outer diameter. it can.

[Surface layer]
In the charging member according to the present invention, the surface layer 5 is formed on the elastic layer 2. The surface layer 5 includes a binder resin and solid resin particles 4 that are dispersed in the binder resin and have convex portions formed on the surface of the surface layer 5.

The volume resistivity of the surface layer 5 is preferably 1 × 10 ³ Ω · cm or more and 1 × 10 ¹⁵ Ω · cm or less in a temperature 23 ° C./humidity 50% RH environment. When the volume resistivity of the surface layer 5 is smaller than the above range, when a pinhole is generated in the electrophotographic photosensitive member, an excessive current flows through the pinhole and the applied voltage drops, and the entire length of the pinhole portion is reduced. Band-shaped image unevenness may occur. On the other hand, when the volume resistivity is larger than the above range, it is difficult for current to flow through the charging roller, and the electrophotographic photosensitive member cannot be charged to a predetermined potential, and the image may not have a desired density.

  The volume resistivity of the surface layer 5 is obtained by the following method. First, the surface layer 5 is peeled off from the charging roller and cut into a strip shape of about 5 mm × 5 mm. A metal is vapor-deposited on both surfaces to produce an electrode and a guard electrode, and a measurement sample is obtained. Alternatively, it is applied on an aluminum sheet to form a surface layer coating film, and a metal is deposited on the coating film surface to obtain a measurement sample. For the obtained measurement sample, the volume resistivity is calculated from the film thickness and the electrode area in the same manner as the volume resistivity measurement method of the elastic layer 2. The volume resistivity of the surface layer 5 can be adjusted by adding a conductive agent such as the above-described ionic conductive agent or electronic conductive agent. Note that the conductive agent may be subjected to a surface treatment. When carbon black is used as the conductive agent for the surface layer 5, composite conductive fine particles obtained by coating carbon black on metal oxide fine particles may be used.

  The surface layer 5 preferably has a film thickness of 0.1 μm or more and 100 μm or less. The film thickness of the surface layer 5 is more preferably 1 μm or more and 50 μm or less. The film thickness of the surface layer 5 can be measured by cutting the charging roller section with a sharp blade and observing with an optical microscope or an electron microscope.

  The surface layer 5 may be subjected to a surface treatment. Examples of the surface treatment include a surface processing treatment using UV or electron beam, and a surface modification treatment for adhering and / or impregnating a compound or the like on the surface.

(Formation of surface layer)
The surface layer 5 can be formed by a coating method such as dipping coating in which the elastic layer 2 is dipped in a coating solution for forming the surface layer 5 and coated.

  As described above, it is preferable to use a solvent having a high affinity for the rubber used for the elastic layer 2 and a low affinity for the hollow particles 3 as the solvent used for the coating solution for forming the surface layer 5. In particular, a solvent having a small difference in sp value from the rubber used for the elastic layer 2 and a large difference in sp value from the hollow particles 3 in the elastic layer 2 is preferable. Specifically, the following solvents can be used. Ketones such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and ethyl acetate; and aromatic compounds such as xylene. These may use only 1 type and may use 2 or more types together. In particular, methyl ethyl ketone, methyl isobutyl ketone and the like are preferable.

  As a method for dispersing the binder, the conductive agent, the resin particles and the like in the coating solution for forming the surface layer 5, known solution dispersing means such as a ball mill, a sand mill, a paint shaker, a dyno mill, and a pearl mill can be used.

  The binder resin used for the surface layer 5 is not particularly limited as long as it is a binder resin that dissolves in the solvent. For example, a thermosetting resin or a thermoplastic resin can be used. Of these, polyamide resin, acrylic resin, polyurethane resin, acrylic urethane resin, silicone resin and the like are preferable. These may be used alone or in combination of two or more. Further, monomers of these resins may be copolymerized and used as a copolymer.

(Resin particles)
Examples of the solid resin particles 4 according to the present invention include particles made of a polymer compound. For example, the particle | grains which consist of a compound shown below are mentioned. Polyamide resin, silicone resin, fluororesin, (meth) acrylic resin, styrene resin, phenol resin, polyester resin, melamine resin, urethane resin, olefin resin, epoxy resin, resins such as copolymers, modified products, and derivatives, Ethylene-propylene-diene copolymer (EPDM), styrene-butadiene copolymer rubber (SBR), silicone rubber, urethane rubber, isoprene rubber (IR), butyl rubber, chloroprene rubber (CR), polyolefin-based thermoplastic elastomer, urethane-based Thermoplastic elastomer, polystyrene thermoplastic elastomer, fluoro rubber thermoplastic elastomer, polyester thermoplastic elastomer, polyamide thermoplastic elastomer, polybutadiene thermoplastic elastomer, ethylene vinyl acetate Thermoplastic elastomers, polyvinyl chloride thermoplastic elastomer, a thermoplastic elastomer such as chlorinated polyethylene based thermoplastic elastomer.

  Among these, it is preferable to use (meth) acrylic resin, styrene resin, urethane resin, fluorine resin, or silicone resin. These resin particles 4 may be used alone or in combination of two or more. Moreover, surface treatment, modification, introduction of a functional group or molecular chain, coating, or the like may be performed. In the present invention, the solid resin particle 4 indicates a state in which bubbles are not substantially contained in the resin particle 4 and the resin particle 4 is filled with resin.

  In order to control the uneven shape on the surface of the charging roller, the volume average particle diameter of the resin particles 4 is preferably 5 μm or more and 100 μm or less. The volume average particle diameter of the resin particles 4 is more preferably 8 μm or more and 80 μm or less. The surface layer 5 can contain other particles as long as the effects of the present invention are not impaired.

<Process cartridge, electrophotographic device>
FIG. 8 shows a schematic configuration of an example of an electrophotographic apparatus including the charging member according to the present invention. The electrophotographic apparatus shown in FIG. 8 includes an electrophotographic photosensitive member 23, a charging device that charges the electrophotographic photosensitive member 23, a latent image forming device 29 that performs exposure, a developing device that develops a toner image, and a transfer device that transfers to a transfer material. And a cleaning device for collecting the transfer toner on the electrophotographic photosensitive member and a fixing device for fixing the toner image.

  The electrophotographic photosensitive member 23 is a rotary drum type having a photosensitive layer on a conductive substrate. The electrophotographic photosensitive member 23 is rotationally driven at a predetermined peripheral speed (process speed) in the direction of the arrow. The charging device includes a contact-type charging roller 17 disposed in contact with the electrophotographic photosensitive member 23 by contacting with the electrophotographic photosensitive member 23 with a predetermined pressing force. The electrophotographic apparatus according to the present invention uses the charging member according to the present invention as the charging roller 17. The charging roller 17 is driven to rotate in accordance with the rotation of the electrophotographic photosensitive member 23, and a predetermined DC voltage is applied from the charging power supply 31 to charge the electrophotographic photosensitive member 23 to a predetermined potential. For the latent image forming device 29 that forms an electrostatic latent image on the electrophotographic photosensitive member 23, an exposure device such as a laser beam scanner is used. An electrostatic latent image is formed by exposing the uniformly charged electrophotographic photosensitive member 23 according to image information.

  The developing device includes a developing sleeve or a developing roller 24 that is disposed close to or in contact with the electrophotographic photosensitive member 23. The toner electrostatically processed to the same polarity as the charged polarity of the electrophotographic photosensitive member 23 is reversely developed to visualize and develop the electrostatic latent image as a toner image. The transfer device has a contact-type transfer roller 26. The toner image is transferred from the electrophotographic photosensitive member 23 to a transfer material 25 such as plain paper (the transfer material 25 is conveyed by a paper feeding system having a conveying member). The cleaning device has a blade-type cleaning member 28 and a collection container 30 and mechanically scrapes off and collects the transfer residual toner remaining on the electrophotographic photosensitive member 23 after transfer. It is possible to omit the cleaning device by adopting a development simultaneous cleaning system in which the transfer residual toner is collected by the developing device. The fixing device 27 is composed of a heated roll or the like, and fixes the transferred toner image on the transfer material 25 and discharges it outside the apparatus.

  A process cartridge in which the charging member is at least integrated with the member to be charged and is configured to be detachable from the main body of the electrophotographic apparatus can be used. For example, a process cartridge that is integrated with an electrophotographic photosensitive member, a charging device, a developing device, a cleaning device, and the like and is designed to be detachable from the electrophotographic device. The process cartridge according to the present invention includes the charging member according to the present invention as a charging member.

  Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples.

Production Example 1 (Production of Thermally Expandable Microcapsule 1)
To the polymerization reaction vessel, 4000 parts by mass of ion-exchanged water, 5 parts by mass of colloidal silica as a dispersion stabilizer, and 0.15 parts by mass of polyvinylpyrrolidone were added to prepare a water-soluble dispersion medium. 100 parts by mass of acrylonitrile as a raw material monomer to be a shell material, 13 parts by mass of normal hexane as an inclusion substance, 0.8 part by mass of dicumyl peroxide as a polymerization initiator, and 0.5 part by mass of methyl methacrylate as a crosslinking substance An oily mixed solution consisting of The oily mixed solution was added to the water-soluble dispersion medium, and 0.4 parts by mass of sodium hydroxide was further added to prepare a dispersion.

  The resulting dispersion was stirred and mixed using a homogenizer, charged into a nitrogen-substituted polymerization reaction vessel, pressurized, and reacted at a temperature of 60 ° C. for 20 hours to prepare a reaction product. The obtained reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules 1. By classifying the obtained thermally expandable microcapsules 1, the volume average particle diameter was set to 35 μm, and the thermally expanded microcapsules 1 after classification were obtained.

Production Example 2 [Production of Thermally Expandable Microcapsule 2]
A thermally expandable microcapsule 2 was produced in the same manner as in Production Example 1, except that methacrylonitrile was used as the raw material monomer in Production Example 1. By classifying the obtained thermally expandable microcapsules 2, the volume average particle size was set to 65 μm, and the thermally expandable microcapsules 2 after classification were obtained.

Production Example 3 (Production of Thermally Expandable Microcapsule 3)
A thermally expandable microcapsule 3 was produced in the same manner as in Production Example 1 except that the raw material monomer was vinylidene chloride in Production Example 1. By classifying the obtained thermally expandable microcapsules 3, the volume average particle size was set to 28 μm, and the thermally expanded microcapsules 3 after classification were obtained.

Production Example 4 (Production of Thermally Expandable Microcapsule 4)
A thermally expandable microcapsule 4 was produced in the same manner as in Production Example 1 except that styrene was used as the raw material monomer in Production Example 1. By classifying the obtained thermally expandable microcapsules 4, the volume average particle size was set to 25 μm, and the thermally expandable microcapsules 4 after classification were obtained.

Production Example 5 (Production of Thermally Expandable Microcapsule 5)
In the polymerization reaction vessel, 400 parts by mass of ion-exchanged water and 1 part by mass of sodium dodecylbenzenesulfonate were added to prepare a water-soluble dispersion medium. 100 parts by mass of vinyl chloride as a raw material monomer to be a shell material, 200 parts by mass of normal hexane, 100 parts by mass of n-butyl acrylate, 2 parts by mass of trimethylolpropane triacrylate, 2 parts by mass of 2,2-azobisisobutyronitrile An oily mixture consisting of The oily mixture was added to the water-soluble dispersion medium to prepare a dispersion.

  The resulting dispersion was stirred and mixed using a homogenizer, charged into a nitrogen-substituted polymerization reaction vessel, and reacted at a temperature of 80 ° C. for 30 minutes to prepare a reaction product. The obtained reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules 5. By classifying the obtained thermally expandable microcapsules 5, the volume average particle size was set to 35 μm, and the thermally expandable microcapsules 5 after classification were obtained.

Production Example 6 [Production of Thermally Expandable Microcapsule 6]
1000 parts by mass of toluene and 142 parts by mass of isophorone diisocyanate (IPDI) were added to 650 parts by mass of polyethylene terephthalate, reacted at 120 ° C. for 5 hours under reflux of toluene, and then cooled to room temperature. Furthermore, 25 parts by mass of hexamethylenediamine and 20 parts by mass of diethylenetriamine were added, and the reaction was performed at 60 ° C. for 5 hours. Thereafter, toluene was distilled off under reduced pressure to obtain a urethane resin having hydroxyl groups at both ends and having urethane and urea bonds. 400 parts by mass of the obtained resin, 12 parts by mass of yellow iron oxide, 62 parts by mass of normal hexane, and 380 parts by mass of ethyl acetate were mixed, and a 0.5% by mass aqueous polyvinyl alcohol solution 2000 prepared in advance from this mixture. A reaction product was obtained by dispersing the solution while dropping in parts by mass. The obtained reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules 6. By classifying the obtained thermally expandable microcapsules 6, the volume average particle diameter was set to 35 μm, and the thermally expandable microcapsules 6 after classification were obtained.

Production Examples 7 to 20 [Production of Thermally Expandable Microcapsules 7 to 20]
The thermally expandable microcapsules 7 to 20 after classification were prepared by classifying the thermally expandable microcapsules 1 to 6 that were prepared by the same method as in Production Examples 1 to 6. Table 1 shows the thermally expandable microcapsule numbers before and after classification, the shell material, and the volume average particle size of the thermally expandable microcapsules after classification.

[Example 1]
[Preparation of unvulcanized rubber composition A-1 for forming elastic layer 2]
The materials listed in Table 2 were kneaded for 15 minutes in a closed mixer adjusted to 50 ° C.

  To this, 9.25 parts by mass of the thermally expandable microcapsule 1 after classification prepared in Production Example 1, 1.2 parts by mass of sulfur as a vulcanizing agent, and tetrabenzyl thiuram disulfide (trade name) as a vulcanization accelerator. : Parkasit TBzTD, manufactured by Flexis Co., Ltd.) 4.5 parts by mass. This was kneaded for 10 minutes with a two-roll mill cooled to 25 ° C. to obtain an unvulcanized rubber composition A-1 for forming the elastic layer 2.

[Production of Elastic Roller A-1]
A thermosetting adhesive (trade name: METALOC U-20, manufactured by Toyo Chemical Laboratory Co., Ltd.) is applied to a stainless steel rod having a diameter of 6 mm and a length of 258 mm, and left in a hot air oven at 180 ° C. for 30 minutes. A conductive substrate 12 was obtained.

  An extrusion apparatus provided with the crosshead 20 shown in FIG. The conductive substrate 12 is fed to the crosshead 20 by a feed roll 21 and the unvulcanized rubber composition A-1 extruded by the extruder 18 with the conductive substrate 12 as a central axis is formed on the conductive substrate 12 in a cylindrical shape. Covered. Thereby, an elastic roller preform 19 having an outer diameter of 10 mm was obtained. The end portion of the unvulcanized rubber composition layer of the elastic roller preform 19 was removed, and the end portion of the conductive base 12 was exposed.

  Next, as shown in FIG. 7B, the elastic roller preform 19 is placed in a mold having a cylindrical cavity 22 having an inner diameter of 12 mm, and the elastic roller preform 19 is heated at 160 ° C. for 20 minutes. A roller was obtained by foaming. Further, the obtained roller was subjected to secondary vulcanization in a hot stove at 160 ° C. for 30 minutes to obtain an elastic roller A-1 having an outer diameter of 12 mm and a length of 224.2 mm.

[Preparation of Coating Solution A-1 for Forming Surface Layer 5]
Methyl isobutyl ketone (MIBK) was added to a caprolactone-modified acrylic polyol solution (trade name: Plaxel DC2016, manufactured by Daicel Chemical Industries) to adjust the solid content of acrylic polyol to 17% by mass. The materials listed in Table 3 were added to 588.24 parts by mass of this solution (100 parts by mass of acrylic polyol solid content) to prepare a mixed solution. The mixed amount of the blocked isocyanate mixture was such that isocyanate / polyol was NCO / OH = 1.0.

  200 g of the mixed solution and 200 g of glass beads having a volume average particle diameter of 0.8 mm as a medium were placed in a glass bottle having an internal volume of 450 mL, and dispersed for 28 hours using a paint shaker disperser. After dispersion, 11 parts by mass of silicone resin particles having a volume average particle diameter of 30 μm as resin particles 4 was added to 100 parts by mass of the acrylic polyol solid content. Thereafter, dispersion was performed for 5 minutes, and the glass beads were removed to obtain a coating solution A-1 for forming the surface layer 5.

[Production of Charging Roller A-1]
The coating solution A-1 for forming the surface layer 5 was dipped on the elastic roller A-1 once. After the coating, the roller is air-dried for 30 minutes or more at room temperature, and then dried with a hot air circulating dryer at 80 ° C. for 1 hour and further at 160 ° C. for 1 hour, and the charging roller A-1 having the surface layer 5 formed on the elastic layer 2 Got. As dipping coating conditions, the dipping time was 9 seconds, the dipping coating lifting speed was an initial speed of 20 mm / s, and a final speed of 2 mm / s, during which the speed was changed linearly with respect to time.

  The produced charging roller A-1 was evaluated by the following method.

[Measurement of the volume average particle diameter of the hollow particles 3 and the diameter of the projected circle of the hollow particles 3]
An arbitrary portion of the elastic layer 2 of the charging roller A-1 is cut out from the surface layer 5 by 20 nm over 500 μm by a focused ion beam (trade name: FB-2000C, manufactured by Hitachi, Ltd.), and its cross section An image was taken. The captured images were combined to calculate a stereoscopic image. The volume of the hollow particles 3 was calculated from this stereoscopic image, and the diameter of a sphere having a volume equal to this volume was determined. This operation was performed for 10 hollow particles in the field of view. Furthermore, the same measurement was performed for 10 points in the longitudinal direction of the charging roller A-1, and the average value of a total of 100 obtained was calculated as the volume average particle diameter of the hollow particles 3.

  Moreover, as shown in FIG. 2, the projection figure of the lamination direction was created from the three-dimensional image of the said hollow particle 3, and the projection area was calculated | required. Next, the diameter of a circle having an area equal to the projected area was determined. Similarly, the projected area of another hollow particle 3 was determined, the diameter of a circle having an area equal to the projected area was determined, and the arithmetic average of the diameters of these circles was determined. This operation was performed for 10 hollow particles in the field of view. Further, the same measurement was performed for 10 points in the longitudinal direction of the charging roller A-1, and an average value of a total of 100 obtained values was calculated as the diameter of the projected circle of the hollow particles 3.

[Measurement of Volume Average Particle Diameter of Resin Particle 4 and Diameter of Projected Circle of Resin Particle 4]
A three-dimensional image of the resin particles 4 in the surface layer 5 was calculated by the same method as the measurement of the volume average particle diameter of the hollow particles 3. The volume of the resin particles 4 was calculated from this stereoscopic image, and the diameter of a sphere having a volume equal to this volume was determined. This operation was performed for 10 resin particles in the field of view. Furthermore, the same measurement was performed for 10 points in the longitudinal direction of the charging roller A-1, and the average value of a total of 100 obtained was calculated as the volume average particle diameter of the resin particles 4. Further, as shown in FIG. 2, a projection view of the resin particle 4 is created from the three-dimensional image of the resin particle 4, and the diameter of the projection circle of the resin particle is calculated in the same manner as the diameter of the projection circle of the hollow particle 3. .

[Measurement of surface ten-point average roughness and surface irregularity average interval]
The surface ten-point average roughness (Rz) of the charging roller A-1 is in accordance with the standard of JIS B 0601-1994 surface roughness using a surface roughness measuring instrument (trade name: SE-3500, manufactured by Kosaka Laboratory). Measured accordingly. The measurement was performed at six random locations on the charging roller A-1, and the average value was defined as Rz.

  For the surface unevenness average interval (Sm), 10 unevenness intervals were measured at an arbitrary location on the charging roller A-1, and the average was defined as Sm of the measurement location. The measurement was performed on six random locations of the charging roller A-1, and the average value was taken as Sm of the charging roller A-1.

[Ratio of the diameter of the projected circle of the hollow particles 3 to the diameter of the projected circle of the resin particles 4]
From the diameter of the projected circle of the hollow particles 3 and the diameter of the projected circle of the resin particles 4 obtained by the above method, the ratio of the diameter of the projected circle of the hollow particles 3 and the diameter of the projected circle of the resin particles 4 was calculated. In Table 6, this ratio is expressed as resin particle projected circle diameter / hollow particle projected circle diameter.

[Measurement of the ratio of the area of the projected circle of the hollow particles 3 included in the triple circular area to the area of the circular area of the triple diameter of the projected circle of the resin particles 4]
The point which projected the vertex of the convex part of arbitrary resin particles 4 which has a diameter 3 times the diameter of the projected circle of resin particle 4 calculated by the above-mentioned method in the lamination direction on the surface. The center circle was projected in the stacking direction and set on the surface of the charging roller A-1. In addition, the position of the vertex of a convex part can be determined from the said three-dimensional image.

  By a method similar to the method of calculating the diameter of the projected circle of the hollow particles 3, the three-fold circular region was cut out every 20 nm in the stacking direction, and a three-dimensional image of the hollow particles 3 was calculated. All the hollow particles 3 in this three-dimensional image are projected in the stacking direction, the area of the projected portion of the hollow particles 3 included in the triple circular region is obtained, and the ratio to the area of the triple circular region is calculated. . Further, the same measurement was performed for 10 points in the longitudinal direction of the charging roller A-1, and the average value was calculated. This value was defined as the ratio of the area of the projected circle of the hollow particles 3 included in the triple circle area to the area of the triple circle area of the diameter of the projected circle of the resin particles 4. In Table 6, this ratio is expressed as the ratio of the area occupied by the hollow particle projection circle in the triple circle region.

[Measurement of ratio of point where projection of convex part of resin particle 4 is projected in stacking direction included in projected view of hollow particle 3]
A three-dimensional image was calculated by a method similar to the method of measuring the diameter of the projected circle of the resin particles 4. From the obtained three-dimensional image of the resin particles 4, the vertexes of the convex portions of the arbitrary resin particles 4 that form the convex portions on the surface were determined. It was confirmed whether the point which projected the vertex to the lamination direction was included in the projection figure of the hollow particle 3 measured by the said method. Such an operation was performed for 10 arbitrary resin particles that form convex portions on the surface within the field of view. Further, the same measurement was performed for any 10 points in the longitudinal direction of the charging roller A-1. For a total of 100 resin particles 4 obtained, the ratio of the points at which the vertices of the projections were projected in the stacking direction was included in the projection diagram of the hollow particles 3 was calculated. In Table 6, this ratio is expressed as the ratio at which the points where the resin particle convex portions are projected are included in the hollow particle projection diagram.

[Measurement of ratio between the number of resin particles 4 forming convex portions on the surface and the number of hollow particles 3]
A three-dimensional image was calculated by a method similar to the method of calculating the diameters of the projected circles of the resin particles 4 and the hollow particles 3. The number of resin particles 4 forming convex portions on the surface was counted from the three-dimensional image in the surface layer 5. Further, the number of the hollow particles 3 was counted from the stereoscopic image in the elastic layer 2. Thereby, the ratio between the number of the resin particles 4 forming the convex portions on the surface and the number of the hollow particles 3 was calculated. Furthermore, the same measurement was performed for any 10 points in the longitudinal direction of the charging roller A-1, and the average value of the obtained values was calculated. This was defined as the ratio of the number of resin particles 4 forming convex portions on the surface and the number of hollow particles 3. In Table 6, this ratio is expressed as convexity-forming resin particles / hollow particles.

[Measurement of porosity of elastic layer 2]
A three-dimensional image was calculated by a method similar to the method of measuring the diameter of the projected circle of the hollow particles 3. From the stereoscopic image, the total volume of the voids in the image was obtained. The ratio of the total volume of the pores to the volume of the elastic layer 2 in the image was calculated. Furthermore, the same measurement was performed for any 10 points in the longitudinal direction of the charging roller A-1, and the average value of the obtained values was calculated. This was defined as the porosity of the elastic layer 2. In Table 6, this value is expressed as elastic layer porosity.

[Durability evaluation]
Durability evaluation was performed using a color laser printer (trade name: HP Color LaserJet 4700dn, manufactured by Hewlett-Packard) having the configuration of the electrophotographic apparatus shown in FIG. 8 and a printer process cartridge. The printer was used so that it could output the recording medium at 200 mm / sec (A4 portrait output). The primary charging output was a DC voltage (Vdc) of −1100V. The resolution of the image was 600 dpi. The charging roller was removed from the process cartridge, and the manufactured charging roller A-1 was set. Further, the charging roller A-1 was brought into contact with the electrophotographic photosensitive member with a pressing force of a spring of 4.9 N at one end and a total of 9.8 N at both ends.

The process cartridge in which the charging roller A-1 is set has a temperature of 15 ° C./humidity of 10% RH environment (environment 1), a temperature of 23 ° C./humidity of 50% RH environment (environment 2), and a temperature of 30 ° C./humidity of 80% RH environment ( After being left in the environment 3) for 24 hours, durability evaluation was performed in each environment. Specifically, a two-sheet intermittent endurance test (endurance after stopping the rotation of the printer for 3 seconds for every two sheets) was performed on a 1% print density image at a process speed of 200 mm / sec. During the initial and endurance tests (at the time of initial image output, at the end of 18000 sheets, and at the end of 36000 sheets), a halftone image (horizontal line with a width of 1 dot and an interval of 2 dots in the direction perpendicular to the rotation direction of the electrophotographic photoreceptor) Image) was output and evaluated. In the evaluation, the obtained halftone image was visually observed, and the presence or absence of streak-like and dot-like image defects caused by the contamination on the surface of the charging roller A-1 was determined according to the following criteria.
Rank 1: No streak-like or dot-like image defects are observed.
Rank 2: Slight or dot image defects are slightly observed.
Rank 3: streak-like or dot-like image defects are observed.
Rank 4: A streak-like or dot-like image defect is noticeable.

[Example 2]
As the thermally expandable microcapsule, the thermally expanded microcapsule 6 after classification was used. Otherwise, the charging roller A-2 was prepared and evaluated in the same manner as in Example 1.

[Example 3]
As the resin particles, methyl methacrylate particles were used. Otherwise, the charging roller A-3 was prepared and evaluated in the same manner as in Example 1.

[Example 4]
The thermally expandable microcapsule 7 after classification was used as the thermally expandable microcapsule, and the added part was 28 parts by mass. Moreover, the addition part number of the resin particle was 31 mass parts. Otherwise, the charging roller A-4 was prepared and evaluated in the same manner as in Example 1.

[Example 5]
[Production of unvulcanized rubber composition A-5 for forming elastic layer 2]
The materials listed in Table 4 were kneaded for 10 minutes in a closed mixer adjusted to 50 ° C.

  To this, 28 parts by mass of the thermally expandable microcapsule 7 after classification produced in Production Example 7 and 0.8 part by mass of sulfur as a vulcanizing agent were added. Furthermore, as a vulcanization accelerator, 1 part by mass of dibenzothiazyl sulfide (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.) and tetramethylthiuram monosulfide (trade name: Noxeller TS, manufactured by Ouchi New Chemical Co., Ltd.) ) 0.5 parts by weight was added. This was kneaded for 10 minutes with a two-roll mill cooled to 25 ° C. to obtain an unvulcanized rubber composition A-5 for forming the elastic layer 2.

  A charging roller A-5 was prepared and evaluated in the same manner as in Example 4 except that the unvulcanized rubber composition A-5 was used.

[Example 6]
As the thermally expandable microcapsule, the thermally expanded microcapsule 8 after classification was used, and the number of added parts was 5 parts by mass. Moreover, the addition part number of the resin particle was 20 mass parts. Otherwise, the charging roller A-6 was prepared and evaluated in the same manner as in Example 1.

[Example 7]
Urethane resin particles were used as the resin particles. Otherwise, a charging roller A-7 was prepared and evaluated in the same manner as in Example 6.

[Example 8]
The thermally expandable microcapsule 9 after classification was used as the thermally expandable microcapsule, and the number of added parts was 8 parts by mass. Moreover, the addition part number of the resin particle was 25 mass parts. Otherwise, a charging roller A-8 was prepared and evaluated in the same manner as in Example 1.

[Example 9]
As the thermally expandable microcapsule, the thermally expanded microcapsule 3 after classification was used. Otherwise, a charging roller A-9 was prepared and evaluated in the same manner as in Example 8.

[Example 10]
The thermally expandable microcapsule 10 after classification was used as the thermally expandable microcapsule, and the number of added parts was 9 parts by mass. Moreover, the methyl methacrylate particle | grains were used as a resin particle, and the addition part number was 10 mass parts. Otherwise, a charging roller A-10 was prepared and evaluated in the same manner as in Example 1.

[Example 11]
[Preparation of unvulcanized rubber composition A-11 for forming elastic layer 2]
The materials listed in Table 5 were kneaded for 15 minutes in a closed mixer adjusted to 80 ° C.

  To this, 9 parts by mass of the thermally expandable microcapsule 10 after classification produced in Production Example 10 and 1 part by mass of sulfur as a vulcanizing agent were added. Furthermore, as a vulcanization accelerator, 1 part by mass of dibenzothiazyl sulfide (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.) and tetramethylthiuram monosulfide (trade name: Noxeller TS, manufactured by Ouchi New Chemical Co., Ltd.) ) 1 part by mass was added. This was kneaded for 10 minutes with a two-roll mill cooled to 25 ° C. to obtain an unvulcanized rubber composition A-11 for forming the elastic layer 2.

  A charging roller A-11 was prepared and evaluated in the same manner as in Example 10 except that the unvulcanized rubber composition A-11 was used.

[Example 12]
The thermally expandable microcapsule 11 after classification was used as the thermally expandable microcapsule, and the number of added parts was 30 parts by mass. Moreover, the addition part number of the resin particle was 20 mass parts. Otherwise, a charging roller A-12 was prepared and evaluated in the same manner as in Example 1.

[Example 13]
As the thermally expandable microcapsule, the thermally expanded microcapsule 4 after classification was used. Otherwise, a charging roller A-13 was prepared and evaluated in the same manner as in Example 12.

[Example 14]
The thermally expandable microcapsule 11 after classification was used as the thermally expandable microcapsule, and the number of added parts was 25 parts by mass. Moreover, the addition part number of the resin particle was 10 mass parts. Otherwise, a charging roller A-14 was prepared and evaluated in the same manner as in Example 1.

[Example 15]
The thermally expandable microcapsule 7 after classification was used as the thermally expandable microcapsule, and the added part was 16 parts by mass. Moreover, the addition part number of the resin particle was 5 mass parts. Otherwise, a charging roller A-15 was prepared and evaluated in the same manner as in Example 1.

[Example 16]
The added part of the hollow particles was 16 parts by mass, and the added part of the resin particles was 5 parts by mass. Otherwise, a charging roller A-16 was prepared and evaluated in the same manner as in Example 5.

[Example 17]
As the thermally expandable microcapsule, the thermally expanded microcapsule 12 after classification was used, and the number of added parts was 13 parts by mass. Moreover, the addition part number of the resin particle was 20 mass parts. Otherwise, a charging roller A-17 was prepared and evaluated in the same manner as in Example 1.

[Example 18]
As the thermally expandable microcapsule, the thermally expanded microcapsule 2 after classification was used. Otherwise, a charging roller A-18 was produced in the same manner as in Example 17, and evaluated.

[Example 19]
The thermally expandable microcapsule 8 after classification was used as the thermally expandable microcapsule, and the number of added parts was 14 parts by mass. Moreover, the methyl methacrylate resin particle was used as a resin particle, and the addition part number was 30 mass parts. Otherwise, a charging roller A-19 was prepared and evaluated in the same manner as in Example 1.

[Example 20]
Styrene resin particles were used as the resin particles. Otherwise, a charging roller A-20 was prepared and evaluated in the same manner as in Example 19.

[Example 21]
The added part of the hollow particles was 5.5 parts by mass, and the added part of the resin particles was 17 parts by mass. Otherwise, the charging roller A-21 was prepared and evaluated in the same manner as in Example 1.

[Example 22]
As the thermally expandable microcapsule, the thermally expanded microcapsule 5 after classification was used. Otherwise, a charging roller A-22 was prepared and evaluated in the same manner as in Example 21.

[Example 23]
The thermally expandable microcapsule 11 after classification was used as the thermally expandable microcapsule, and the number of added parts was 12 parts by mass. Moreover, the addition part number of the resin particle was 35 mass parts. Otherwise, the charging roller A-23 was prepared and evaluated in the same manner as in Example 1.

[Example 24]
The thermally expandable microcapsule 7 after classification was used as the thermally expandable microcapsule, and the added part was 6.5 parts by mass. Moreover, the addition part number of the resin particle was 18 mass parts. Otherwise, a charging roller A-24 was prepared and evaluated in the same manner as in Example 1.

[Example 25]
As the thermally expandable microcapsule, the thermally expanded microcapsule 13 after classification was used. Otherwise, a charging roller A-25 was prepared and evaluated in the same manner as in Example 24.

[Example 26]
The added part of the hollow particles was 6.5 parts by mass, and the added part of the resin particles was 18 parts by mass. Otherwise, a charging roller A-26 was prepared and evaluated in the same manner as in Example 5.

[Example 27]
The thermally expandable microcapsule 12 after classification was used as the thermally expandable microcapsule, and the added part was 6 parts by mass. Moreover, the addition part number of the resin particle was 30 mass parts. Otherwise, a charging roller A-27 was prepared and evaluated in the same manner as in Example 1.

[Example 28]
Styrene resin particles were used as the resin particles. Otherwise, a charging roller A-28 was prepared in the same manner as in Example 27 and evaluated.

[Example 29]
The added part of the hollow particles was 3.5 parts by mass, and the added part of the resin particles was 25 parts by mass. Otherwise, a charging roller A-29 was prepared and evaluated in the same manner as in Example 1.

[Example 30]
As the thermally expandable microcapsule, the thermally expanded microcapsule 1 after classification was used, and the number of added parts was 3.5 parts by mass. Moreover, the silicone resin particle was used as the resin particle, and the addition part was 25 mass parts. Otherwise, a charging roller A-30 was prepared and evaluated in the same manner as in Example 11.

[Example 31]
The thermally expandable microcapsule 8 after classification was used as the thermally expandable microcapsule, and the added part was 18 parts by mass. Moreover, the addition part number of the resin particle was 8 mass parts. Otherwise, a charging roller A-31 was prepared and evaluated in the same manner as in Example 1.

[Example 32]
Methyl methacrylate resin particles were used as the resin particles. Otherwise, a charging roller A-32 was prepared and evaluated in the same manner as in Example 31.

[Example 33]
The added part of the hollow particles was 6 parts by mass, and the added part of the resin particles was 30 parts by mass. Otherwise, the charging roller A-33 was prepared and evaluated in the same manner as in Example 1.

[Example 34]
As the thermally expandable microcapsule, the thermally expanded microcapsule 14 after classification was used. Otherwise, a charging roller A-34 was prepared and evaluated in the same manner as in Example 33.

[Example 35]
As the thermally expandable microcapsule, the thermally expanded microcapsule 6 after classification was used. Otherwise, a charging roller A-35 was prepared and evaluated in the same manner as in Example 33.

[Example 36]
The thermally expandable microcapsule 8 after classification was used as the thermally expandable microcapsule, and the added part was 4 parts by mass. Moreover, the addition part number of the resin particle was 40 mass parts. Otherwise, a charging roller A-36 was prepared and evaluated in the same manner as in Example 1.

[Example 37]
Urethane resin particles were used as the resin particles. Otherwise, a charging roller A-37 was prepared and evaluated in the same manner as in Example 36.

[Example 38]
As the thermally expandable microcapsule, the thermally expanded microcapsule 15 after classification was used, and the number of added parts was 3.5 parts by mass. Moreover, the methyl methacrylate resin particle was used as a resin particle, and the addition part number was 20 mass parts. Otherwise, a charging roller A-38 was prepared and evaluated in the same manner as in Example 1.

[Example 39]
As the thermally expandable microcapsule, the thermally expanded microcapsule 15 after classification was used, and the number of added parts was 3.5 parts by mass. Moreover, the methyl methacrylate resin particle was used as a resin particle, and the addition part number was 20 mass parts. Otherwise, a charging roller A-39 was prepared and evaluated in the same manner as in Example 5.

[Example 40]
The thermally expandable microcapsule 12 after classification was used as the thermally expandable microcapsule, and the number of added parts was 30 parts by mass. Moreover, the methyl methacrylate resin particle was used as a resin particle, and the addition part number was 2 mass parts. Otherwise, the charging roller A-40 was prepared and evaluated in the same manner as in Example 1.

[Example 41]
As the thermally expandable microcapsule, the thermally expanded microcapsule 16 after classification was used. Otherwise, a charging roller A-41 was prepared and evaluated in the same manner as in Example 40.

[Example 42]
As the thermally expandable microcapsule, the thermally expanded microcapsule 17 after classification was used. Otherwise, a charging roller A-42 was prepared and evaluated in the same manner as in Example 40.

[Example 43]
The thermally expandable microcapsule 7 after classification was used as the thermally expandable microcapsule, and the number of added parts was 3.5 parts by mass. Moreover, the addition part number of the resin particle was 25 mass parts. Otherwise, a charging roller A-43 was prepared and evaluated in the same manner as in Example 1.

[Example 44]
The thermally expandable microcapsule 7 after classification was used as the thermally expandable microcapsule, and the number of added parts was 3.5 parts by mass. Moreover, the silicone resin particle was used as the resin particle, and the addition part was 25 mass parts. Otherwise, a charging roller A-44 was prepared and evaluated in the same manner as in Example 11.

[Example 45]
The added part of the hollow particles was 3 parts by mass, and the added part of the resin particles was 30 parts by mass. Otherwise, a charging roller A-45 was prepared and evaluated in the same manner as in Example 1.

[Example 46]
As the thermally expandable microcapsule, the thermally expanded microcapsule 6 after classification was used. Otherwise, a charging roller A-46 was prepared and evaluated in the same manner as in Example 45.

[Example 47]
Urethane resin particles were used as the resin particles. Otherwise, a charging roller A-47 was prepared and evaluated in the same manner as in Example 45.

[Example 48]
The added part of the hollow particles was 3.25 parts by mass, and the added part of the resin particles was 45 parts by mass. Otherwise, a charging roller A-48 was prepared and evaluated in the same manner as in Example 1.

[Example 49]
The thermally expandable microcapsule 1 after classification was used as the thermally expandable microcapsule, and the number of parts added was 3.25 parts by mass. Moreover, the addition part number of the resin particle was 45 mass parts. Otherwise, a charging roller A-49 was prepared and evaluated in the same manner as in Example 5.

[Example 50]
The thermally expandable microcapsule 12 after classification was used as the thermally expandable microcapsule, and the number of parts added was 3.25 parts by mass. Moreover, the addition part number of the resin particle was 20 mass parts. Otherwise, a charging roller A-50 was prepared and evaluated in the same manner as in Example 1.

[Example 51]
As the thermally expandable microcapsule, the thermally expanded microcapsule 17 after classification was used. Otherwise, a charging roller A-51 was prepared and evaluated in the same manner as in Example 50.

[Example 52]
The thermally expandable microcapsule 7 after classification was used as the thermally expandable microcapsule, and the number of added parts was 6 parts by mass. Moreover, the addition part number of the resin particle was 50 mass parts. Otherwise, a charging roller A-52 was prepared and evaluated in the same manner as in Example 1.

[Example 53]
The thermally expandable microcapsule 7 after classification was used as the thermally expandable microcapsule, and the number of added parts was 6 parts by mass. Moreover, the addition part number of the resin particle was 50 mass parts. Otherwise, a charging roller A-53 was prepared and evaluated in the same manner as in Example 1.

[Example 54]
As the thermally expandable microcapsule, the thermally expanded microcapsule 1 after classification was used. Otherwise, a charging roller A-54 was prepared and evaluated in the same manner as in Example 52.

[Example 55]
The number of added parts of the hollow particles was 13 parts by mass. Moreover, the methyl methacrylate resin particle was used as a resin particle, and the addition part number was 2 mass parts. Otherwise, a charging roller A-55 was produced and evaluated in the same manner as in Example 1.

[Example 56]
As the thermally expandable microcapsule, the thermally expanded microcapsule 1 after classification was used, and the number of added parts was 13 parts by mass. Moreover, the methyl methacrylate resin particle was used as a resin particle, and the addition part number was 2 mass parts. Otherwise, a charging roller A-56 was prepared and evaluated in the same manner as in Example 5.

[Example 57]
The thermally expandable microcapsule 12 after classification was used as the thermally expandable microcapsule, and the number of added parts was 30 parts by mass. Moreover, the addition part of the resin particle was 2 mass parts. Otherwise, a charging roller A-57 was prepared and evaluated in the same manner as in Example 1.

[Example 58]
As the thermally expandable microcapsule, the thermally expanded microcapsule 18 after classification was used. Otherwise, a charging roller A-58 was prepared and evaluated in the same manner as in Example 57.

[Example 59]
As the thermally expandable microcapsule, the thermally expanded microcapsule 7 after classification was used, and the number of added parts was 30 parts by mass. Moreover, the addition part number of the resin particle was 1 mass part. Otherwise, a charging roller A-59 was prepared and evaluated in the same manner as in Example 1.

[Example 60]
Styrene resin particles were used as the resin particles. Otherwise, a charging roller A-60 was prepared and evaluated in the same manner as in Example 59.

[Example 61]
The added part of the hollow particles was 30 parts by mass, and the added part of the resin particles was 8 parts by mass. Otherwise, a charging roller A-61 was prepared and evaluated in the same manner as in Example 1.

[Example 62]
As the thermally expandable microcapsule, the thermally expanded microcapsule 5 after classification was used. Otherwise, the charging roller A-62 was prepared and evaluated in the same manner as in Example 61.

[Example 63]
As the thermally expandable microcapsule, the thermally expanded microcapsule 19 after classification was used. Otherwise, a charging roller A-63 was produced in the same manner as in Example 61 and evaluated.

[Example 64]
The thermally expandable microcapsule 10 after classification was used as the thermally expandable microcapsule, and the number of added parts was 3.5 parts by mass. Moreover, the methyl methacrylate resin particle was used as a resin particle, and the addition part number was 5 mass parts. Otherwise, the charging roller A-64 was prepared and evaluated in the same manner as in Example 1.

[Example 65]
The thermally expandable microcapsule 10 after classification was used as the thermally expandable microcapsule, and the number of added parts was 3.5 parts by mass. Moreover, the methyl methacrylate resin particle was used as a resin particle, and the addition part number was 5 mass parts. Otherwise, the charging roller A-65 was prepared and evaluated in the same manner as in Example 1.

[Comparative Example 1]
The thermally expandable microcapsule 20 after classification was used as the thermally expandable microcapsule, and the number of added parts was 1 part by mass. Moreover, the addition part number of the resin particle was 20 mass parts. Otherwise, the charging roller B-1 was prepared and evaluated in the same manner as in Example 1.

[Comparative Example 2]
The thermally expandable microcapsule 8 after classification was used as the thermally expandable microcapsule, and the number of added parts was 0.3 parts by mass. Moreover, the addition part number of the resin particle was 30 mass parts. Otherwise, the charging roller B-2 was prepared and evaluated in the same manner as in Example 1.

[Comparative Example 3]
The thermally expandable microcapsule 9 after classification was used as the thermally expandable microcapsule, and the added part was 3 parts by mass. Moreover, the addition part number of the resin particle was 50 mass parts. Otherwise, the charging roller B-3 was prepared and evaluated in the same manner as in Example 1.

[Comparative Example 4]
The thermally expandable microcapsule 20 after classification was used as the thermally expandable microcapsule, and the number of added parts was 0.05 parts by mass. Moreover, the addition part number of the resin particle was 80 mass parts. Otherwise, the charging roller B-4 was prepared and evaluated in the same manner as in Example 1.

[Comparative Example 5]
The thermally expandable microcapsule 20 after classification was used as the thermally expandable microcapsule, and the number of added parts was 0.1 parts by mass. Moreover, the addition part number of the resin particle was 90 mass parts. Otherwise, a charging roller B-5 was prepared and evaluated in the same manner as in Example 1.

[Comparative Example 6]
As the thermally expandable microcapsule, the thermally expanded microcapsule 20 after classification was used, and the number of added parts was 0.2 parts by mass. Moreover, the addition part number of the resin particle was 100 mass parts. Otherwise, the charging roller B-6 was prepared and evaluated in the same manner as in Example 1.

[Comparative Example 7]
No thermally expandable microcapsules were added. Moreover, the methyl methacrylate resin particle was used as a resin particle, and the addition part number was 10 mass parts. Otherwise, a charging roller B-7 was prepared and evaluated in the same manner as in Example 1.

  Tables 6 and 7 show various measurement results of the charging rollers according to Examples 1 to 65 and Comparative Examples 1 to 7. Tables 8 and 9 show the results of evaluation of electrophotographic images obtained as a result of using the charging rollers according to Examples 1 to 65 and Comparative Examples 1 to 7 for a long time under various environments.

DESCRIPTION OF SYMBOLS 1 The vertex of the convex part of the resin particle which forms a convex part on the surface 2 Elastic layer 3 Hollow particle 4 Resin particle 5 Surface layer 6 The vertex of the convex part of the resin particle which forms a convex part on the surface was projected in the lamination direction Point 7 Projection of resin particles 8 Projection of hollow particles

Claims (6)

A charging member having a conductive substrate, an elastic layer, and a surface layer in this order,
The surface layer is
A binder resin,
Solid resin particles dispersed in the binder resin and formed with convex portions on the surface of the surface layer,
The elastic layer,
Rubber as a binder,
Hollow particles dispersed in the rubber, the hollow particles have a shell containing a thermoplastic resin, and contain a gas,
The diameter of the projected circle of the resin particles in the laminating direction of the elastic layer and the surface layer is smaller than the diameter of the projected circle of the hollow particles in the laminating direction,
When a circle having a diameter that is three times the diameter of the projected circle of the resin particles in the laminating direction and centering on a point obtained by projecting the apex of the convex portion in the laminating direction is projected in the laminating direction And the total area of the projected circles of the hollow particles contained in the region of the circle is 80% or more of the area of the circle. The charging member according to claim 1, wherein a diameter of a projected circle of the hollow particles is 10 μm or more and 1200 μm or less. The charging member according to claim 1 or 2, wherein a diameter of a projected circle of the resin particles is 5 µm or more and 120 µm or less. The charging member according to any one of claims 1 to 3, wherein a ratio of a diameter of the projected circle of the resin particles to a diameter of the projected circle of the hollow particles is 0.15 or more and less than 1. A process cartridge comprising the charging member according to any one of claims 1 to 4 and an electrophotographic photosensitive member , wherein the process cartridge is configured to be detachable from a main body of the electrophotographic apparatus . Electrophotographic apparatus characterized in that it comprises a charging member and an electrophotographic photosensitive member according to any one of claims 1 to 4.

Images