JP2011164399A - Charging member, charging device, image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of an image defect such as a white spot and a black spot even if a charging voltage is lowered. <P>SOLUTION: This charging member includes: a shaft body; an elastic layer disposed at the outer periphery of the shaft body; and a surface layer disposed at the outer periphery of the elastic layer and containing insulating particles. Some of the insulating particles are buried in the surface layer, and the other thereof are projected from the surface of the surface layer. In the projecting part, the insulating particles are exposed, and the surface exposure proportion of the insulating particles in the projecting part is 9% or larger, and the ratio (H/D) of the projecting height (H) of the insulating particle to the volume mean particle diameter (D) of the insulating particle is 75% or smaller. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a charging member, a charging device, an image forming apparatus, and a process cartridge.

  As a charging device for image forming apparatuses such as copying machines and printers adopting an electrophotographic system, from the viewpoint of improving charging performance, a shaft body, a resistance adjusting layer formed on the outer periphery of the shaft body, and formed on the outer periphery thereof The surface of the resistance adjusting layer is formed into an uneven rough surface, and the rough surface forming particles are partly in the recesses on the surface of the resistance adjusting layer. In the state where the other portion is protruded from the surface of the resistance adjustment layer, and is fixed to the resistance adjustment layer through the surface layer coating film, the thickness of the surface layer coating film is 4 μm or less, A charging roll in which the theoretical exposure rate of the rough surface forming particles from the surface layer coating film is set to 50% or more is disclosed (for example, see Patent Document 1).

  Further, from the viewpoint of obtaining an image without horizontal streaks, a resistance adjustment layer is formed on the outer periphery of the shaft body, and a protective layer containing rough surface forming particles is formed on the outer periphery of the resistance adjustment layer. In the charging roll, convex portions due to the rough surface forming particles are distributed and formed on the surface of the protective layer, and the height of the convex portions is set to 2.0 to 9.5 μm. In addition, a charging roll is disclosed in which the ratio of the rough surface forming particles to the protective layer surface (specific surface area S) determined by a specific formula is set to 12 to 50% (see, for example, Patent Document 2).

  Furthermore, from the viewpoint of suppressing adhesion of foreign matters such as toner and external additives to the surface layer, a charging roll having a surface layer in which fine particle is contained in a resin binder and the ten-point average surface roughness Rz is adjusted is disclosed. (For example, refer to Patent Document 3).

JP 2007-225914 A JP 2007-178559 A JP 2008-083404 A

  An object of the present invention is to provide a charging member capable of suppressing the occurrence of image defects such as white spots and black spots even when the charging voltage is lowered.

Specific means for achieving the above object are as follows.
The invention according to claim 1
A shaft,
An elastic layer disposed on the outer periphery of the shaft body;
A surface layer containing insulating particles disposed on the outer periphery of the elastic layer,
A part of the insulating particles are embedded in the surface layer, and the other part protrudes from the surface of the surface layer, and the surface of the insulating particles is exposed in the protruding part.
The ratio at which the surface of the insulating particles in the protruding portion is exposed is 9% or more,
The charging member has a ratio (H / D) of a height (H) at which the insulating particles protrude to a volume average particle diameter (D) of the insulating particles is 75% or less.

The invention according to claim 2
The charging member according to claim 1, wherein the surface layer is formed of a coating liquid containing the insulating particles and a resin constituting the surface layer.

The invention according to claim 3
3. The charging member according to claim 1, wherein the resin constituting the surface layer and the insulating particles are formed of materials that are not compatible with each other.

The invention according to claim 4
The charging member according to claim 1, wherein the insulating particles are formed of a silicone resin.

The invention according to claim 5
The charging member according to claim 1, wherein a height (H) at which the insulating particles protrude is 8 μm or more.

The invention according to claim 6
The charging member according to claim 1, wherein the surface layer has a thickness of 5 μm or more.

The invention according to claim 7 provides:
A charging device comprising the charging member according to claim 1.

The invention according to claim 8 provides:
An image carrier,
The charging member according to claim 1, wherein the surface of the image carrier is charged.
A latent image forming apparatus for forming a latent image on the surface of the charged image carrier;
A developing device for developing a latent image formed on the surface of the image carrier with toner to form a toner image;
A transfer device for transferring a toner image formed on the surface of the image carrier to a recording medium;
An image forming apparatus.

The invention according to claim 9 is:
The image forming apparatus according to claim 8, wherein the image carrier includes a surface layer that is a cured film on a surface.

The invention according to claim 10 is:
An image carrier,
The charging member according to any one of claims 1 to 6, wherein the surface of the image carrier is charged.
A process cartridge that is detachably attached to the main body of the image forming apparatus.

  According to the first aspect of the present invention, a part of the insulating particles in the surface layer is embedded in the surface layer and the other part protrudes from the surface of the surface layer, and the surface of the insulating particles is exposed in the protruding part. If the ratio of the exposed surface of the insulating particles in the protruding portion is less than 9%, or the height (H) at which the insulating particles protrude relative to the volume average particle diameter (D) of the insulating particles Compared with the case where the ratio (H / D) of the ratio is larger than 75%, a charging member in which the occurrence of image defects such as white spots and black spots is suppressed even when the charging voltage is lowered is provided.

  According to the invention which concerns on Claim 2, compared with the case where the surface layer is not formed with the coating liquid containing the said insulating particle | grain and the resin which comprises a surface layer, it is insulating from a surface layer. Particle detachment is prevented.

  According to the invention of claim 3, when the surface layer and the insulating particles are compatible with each other, the insulating particles protrude from the surface of the surface layer and the charging voltage is lowered. Occurrence of image defects such as white spots and black spots can be further suppressed.

  According to the fourth aspect of the present invention, contamination by negatively chargeable toner is prevented as compared with the case where the insulating particles are formed of a material other than the silicone resin.

  According to the invention of claim 5, the image of white spots, black spots, etc. when the charging voltage is lowered as compared with the case where the height (H) at which the insulating particles protrude from the surface of the surface layer is less than 8 μm. The occurrence of defects is further suppressed.

  According to the invention which concerns on Claim 6, detachment | leave of the insulating particle | grains from a surface layer is prevented compared with the case where the film thickness of a surface layer is less than 5 micrometers.

  According to the invention of claim 7, a part of the insulating particles in the surface layer is embedded in the surface layer and the other part protrudes from the surface of the surface layer, and the surface of the insulating particle is exposed in the protruding part. The charging member, the charging member in which the surface ratio of the insulating particles in the protruding portion is less than 9%, or the height at which the insulating particles protrude relative to the volume average particle diameter (D) of the insulating particles ( Compared with a charging device including a charging member having a ratio (H / D) greater than 75%, the occurrence of image defects such as white spots and black spots can be suppressed even when the charging voltage is lowered.

  According to the invention of claim 8, a part of the insulating particles in the surface layer is embedded in the surface layer, and the other part protrudes from the surface of the surface layer, and the surface of the insulating particle is exposed in the protruding part. The charging member, the charging member in which the surface ratio of the insulating particles in the protruding portion is less than 9%, or the height at which the insulating particles protrude relative to the volume average particle diameter (D) of the insulating particles ( The occurrence of image defects such as white spots and black spots can be suppressed even when the charging voltage is lowered, as compared with an image forming apparatus provided with a charging member having a ratio (H / D) greater than 75%.

  According to the ninth aspect of the present invention, the flow of the electrostatic latent image on the photoconductor is suppressed and the life is long as compared with an image forming apparatus using a photoconductor that does not have a surface layer that is a cured film on the surface. Become.

  According to the invention described in claim 10, a part of the insulating particles in the surface layer is embedded in the surface layer, and the other part protrudes from the surface of the surface layer, and the surface of the insulating particle is in the protruding part. Charging member that is not exposed, charging member in which the surface of the insulating particles in the protruding portion is exposed to less than 9%, or the height at which the insulating particles protrude relative to the volume average particle diameter (D) of the insulating particles The occurrence of image defects such as white spots and black spots can be suppressed even when the charging voltage is lowered, as compared with a process cartridge including a charging member having a ratio (H / D) greater than 75%.

It is a schematic perspective view which shows the charging member which concerns on this embodiment. It is a schematic sectional drawing of the charging member which concerns on this embodiment. It is an expanded sectional view which shows the surface layer in the charging member which concerns on this embodiment. (A) (B) is an expanded sectional view which shows an example of the exposure state of the insulating particle | grains in a protrusion part. (C) is a top view when (B) is observed from the surface layer side (arrow direction) of the film thickness direction. (A) is a diagram illustrating a general charging member, and (B) is a diagram illustrating a discharge region when the charging member according to the present embodiment is brought into contact with the photosensitive member. 1 is a schematic perspective view of a charging device according to an embodiment. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows the process cartridge which concerns on this embodiment. 2 is an electron micrograph of a surface layer of a charging roll obtained in Example 1. FIG.

  Hereinafter, an embodiment which is an example of the present invention will be described with reference to the drawings.

(Charging member)
FIG. 1 is a schematic perspective view showing a charging member according to the present embodiment. FIG. 2 is a schematic cross-sectional view of the charging member according to the present embodiment. 2 is a cross-sectional view taken along the line AA in FIG.
FIG. 3 is an enlarged cross-sectional view showing a surface layer in the charging member according to the present embodiment. FIG. 4A is an enlarged cross-sectional view showing an example of the exposed state of the insulating particles in the protruding portion, and FIG. 4B shows another example of the exposed state of the insulating particles in the protruding portion. FIG. 4C is an enlarged cross-sectional view, and FIG. 4C is a plan view when FIG. 4B is observed from the surface layer side (arrow direction) in the film thickness direction.
FIG. 5A is a diagram for explaining a discharge region when a general charging member is brought into contact with the photoconductor, and FIG. 5B is a diagram in which the charging member according to this embodiment is brought into contact with the photoconductor. It is a figure explaining the discharge area at the time.

  As shown in FIGS. 1 and 2, the charging member 121 according to the present embodiment includes, for example, a shaft 30 that is a shaft body, an elastic layer 31 disposed on the outer peripheral surface of the shaft 30, and an outer periphery of the elastic layer 31. And a surface layer 32 disposed on the surface. And the surface layer 32 is comprised including resin 32A and particle | grains 32B, as shown in FIG.

  The charging member 121 according to the present embodiment is not limited to the above-described configuration, for example, an adhesive layer (primer layer) disposed between the elastic layer 31 and the shaft 30, or between the elastic layer 31 and the surface layer 32. A configuration may be provided in which a resistance adjusting layer or a migration preventing layer to be disposed and a coating layer (protective layer) disposed on the outer side (outermost surface) of the surface layer 32 are provided.

  The shaft 30 is a conductive rod-like member, and examples of the material thereof include metals such as iron (free-cutting steel), copper, brass, stainless steel, aluminum, nickel, and the like. Examples of the shaft 30 include a member (for example, a resin or a ceramic member) whose outer peripheral surface is plated, a member in which a conductive agent is dispersed (for example, a resin or a ceramic member), and the like. The shaft 30 may be a hollow member (cylindrical member) or a non-hollow member.

  The elastic layer 31 includes, for example, an elastic material, a conductive agent, and other additives as necessary.

  Elastic materials include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, polyurethane, silicone rubber, fluorine rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide- Examples include allyl glycidyl ether copolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber, and blend rubbers thereof. Among these, polyurethane, silicone rubber, EPDM, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, NBR, and blended rubbers thereof are desirably used. These elastic materials may be foamed or non-foamed.

Examples of the conductive agent include an electronic conductive agent and an ionic conductive agent. Examples of the electronic conductive agent include carbon black such as ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, stainless steel; tin oxide, indium oxide, titanium oxide And various conductive metal oxides such as tin oxide-antimony oxide solid solution and tin oxide-indium oxide solid solution; Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium; perchlorates and chlorates of alkaline earth metals ; These conductive agents may be used alone or in combination of two or more.
Note that the conductive agent means a material having a volume resistivity of less than 10 ¹³ Ωcm. Conductivity means that the volume resistivity is less than 10 ¹³ Ωcm. The same applies hereinafter.

  Here, specific examples of carbon black include “Special Black 350”, “Special Black 100”, “Special Black 250”, “Special Black 5”, “Special Black 4”, “Special Black 4A”, “Special Black 550”, “Special Black 6”, “Color Black FW200”, “Color Black FW2”, “Color Black FW2V”; “MONARCH1000” manufactured by Cabot, “ MONARCH1300 "," MONARCH1400 "," MOGUL-L "," REGAL400R ";" Asahi Thermal "manufactured by Asahi Carbon Corporation.

  The addition amount of the conductive agent is not particularly limited, but in the case of the electronic conductive agent, it is preferably in the range of 1 part by mass to 30 parts by mass with respect to 100 parts by mass of the elastic material. It is more desirable that the amount be in the range of parts by mass or less. On the other hand, in the case of the ionic conductive agent, it is desirable that the amount be in the range of 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the elastic material, and 0.5 to 3.0 parts by weight. The following range is more desirable.

  Examples of other additives blended in the elastic layer 31 include a softener, a plasticizer, a curing agent, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a surfactant, a coupling agent, and a filler (silica, Examples thereof include materials that can be added to a normal elastic layer such as calcium carbonate).

The thickness of the elastic layer 31 is preferably about 1 mm to 10 mm in terms of average film thickness, and more preferably about 2 mm to 5 mm. The volume resistivity of the elastic layer is preferably 10 ³ Ωcm or more and 10 ¹⁴ Ωcm or less.

  As shown in FIG. 3, the surface layer 32 includes a resin 32A, insulating particles 32B, and a conductive agent and other additives as necessary. The particle 32B is partially embedded in the surface layer 32 (part A), and the other part protrudes from the surface of the surface layer 32 (part B), and the surface of the particle 32B is exposed at the protruding part B.

  A part of the particle 32B is embedded in the surface layer 32 and the other part protrudes from the surface of the surface layer 32, and it is confirmed by a micrograph whether the surface of the particle 32B is exposed at the protruding part. A method for forming such a shape will be described later.

  Note that the surface of the resin 32B may not be exposed in all of the protruding portions B, and as shown in FIGS. 4A and 4B, a portion of the protruding portion B may be covered with the resin 32A. It is desirable that it is exposed at least in a portion in contact with the photoreceptor.

  The exposure rate E (ratio not covered with the resin 32A) of the surface of the particle 32B in the protruding portion B is 9% or more, preferably 25% or more, and more preferably 36% or more.

This exposure rate E is the surface layer side in the film thickness direction (FIG. 4 (B)) when the ratio of the protrusion height H to the volume average particle diameter D of the particles 32B (H / D) is 50% or less. (In the direction of the arrow in FIG. 5) is observed with a microscope, and is calculated from the plane photograph by the projected area ratio. Specifically, it is the ratio (%) of the projected area of the portion where the surface of the particle 32B is exposed when the projected area of the protruding portion B is a standard (100%) in the planar photograph.
As an example, a method for calculating the exposure rate E will be described with reference to FIG. FIG. 4C is a plan view when FIG. 4B is observed from the surface layer side in the film thickness direction. The exposure rate E is the ratio (%) of the area indicated by oblique lines excluding the portion of the resin 32A shown in white inside the cross-sectional area of the protruding portion of the particle 32B.

On the other hand, when the ratio (H / D) of the protrusion height H to the volume average particle diameter D of the particles 32B exceeds 50%, there is a portion that is not observed in the plan view seen from the arrow direction in FIG. Therefore, the exposure rate E is obtained by observing the cross section with a micrograph. Specifically, in the cross-sectional photograph, the ratio (%) of the length of the portion where the surface of the particle 32B is exposed when the circumferential length of the protruding portion B of the particle 32B is defined as a standard (100%). Ask for.
As an example, a method for calculating the exposure rate E will be described with reference to FIG. The exposure rate E is the ratio of the length of the protruding portion B to which the resin 32A is not attached to the length of the portion protruding above the resin 32A in the cross-sectional circumference of the particle 32B ( %).

  Further, the ratio of the protrusion height H to the volume average particle diameter D of the particles 32B (H / D) is 75% or less and 71% or less so that the protruding particles 32B are not detached from the surface layer 32. Is desirable, and it is further desirable that it is 67% or less.

Furthermore, the protruding ratio S that the protruding particles 32B occupy in the surface layer 32, that is, the ratio S that the cross-sectional area of the protruding particles 32B occupies per unit area of the surface layer 32 is desirably 20% or more, and 30% or more. It is more desirable that the ratio is 50% or more.
Protrusion ratio S = cross sectional area of protruding particles 32B / unit area of surface layer 32 * 100

As the resin 32A, acrylic resin, cellulose resin, nylon resin, polyurethane resin, polycarbonate resin, polyester resin, polyethylene resin, polyvinyl resin, polyacrylate resin, polythiophene resin, tetrafluoroethylene (PFA), tetrafluoroethylene (FEP), Examples thereof include polyolefin resins such as polyethylene terephthalate (PET), styrene butadiene resins, melamine resins, epoxy resins, urethane resins, silicone resins, and urea resins.
Here, the nylon resin includes copolymer nylon, methoxymethylated nylon, ethoxymethylated nylon and the like. The copolymer nylon includes one or more of 610 nylon, 11 nylon, and 12 nylon as polymerized units, and other polymer units contained in the copolymer include 6 nylon. 66 nylon and the like.
Further, as the resin 32A, an elastic material blended in the elastic layer 31 may be applied. A suitable material for the resin 32A will be described later.

  Examples of the conductive agent blended in the surface layer 32 include the conductive agent blended in the elastic layer 31. As other additives, for example, conductive agents, softeners, plasticizers, curing agents, vulcanizing agents, vulcanization accelerators, antioxidants, surfactants, coupling agents and the like are usually added to the surface layer. Materials to be obtained are mentioned.

Here, the discharge to the photosensitive member by the charging member 121 will be described with reference to FIG.
As shown in FIG. 5A, when a general charging member is brought into contact with the photoconductor, a space is formed on the surface of the charging member so as to gradually move away from the surface of the photoconductor along its curvature. According to Paschen's law, discharge does not occur at a gap length (gap) of 8 μm or less. Therefore, when a voltage higher than the discharge start voltage is applied while a general charging member is in contact with the photoreceptor, the contact portion of the charging member In the region where the gap length is 8 μm or less, no discharge occurs and the photoreceptor is not charged. Further, when the distance from the photosensitive member to the surface of the charging member is larger than the maximum dischargeable distance G, the discharge is not performed. Therefore, the discharge region by a general charging member is the region C1.

  According to the research conducted by the inventors so far, it has been found that abnormal discharge is likely to occur in the vicinity of the maximum dischargeable distance G, and white spots are likely to be generated on the surface P of the photoreceptor discharged in the vicinity of the maximum distance G. is doing.

  On the other hand, as shown in FIG. 5B, when the charging member 121 of the present embodiment is brought into contact with the photosensitive member, particles protruding from the surface of the surface layer 32 of the charging member 121 (the outer peripheral surface of the charging member 121). 32B contacts the photoconductor, and the surface of the surface layer 32 is separated from the photoconductor to form a space. Therefore, even when a voltage is applied to the charging member 121 in a state where the charging member 121 is in contact with the photoconductor, discharge is performed in a space formed in a region where the photoconductor and the charging member 121 are in contact.

  Here, since the particles 32B are insulative, the particles 32B do not discharge as shown in FIG. For this reason, when the particle 32B is present at a position where the maximum dischargeable distance G is present, discharge is performed at a distance shorter than the maximum dischargeable distance G (maximum distance G ′), and generation of white spots is suppressed. The Here, when the region 32A in which the particles 32B are not formed reaches the maximum distance G, there is a concern that white spots may occur as in the conventional case. However, FIG. 5 is a cross-sectional view of the charging member 121 in the radial direction. Actually, since the particles 32B are randomly scattered in the axial direction of the charging member 121, white spots are generated by the division effect described later. Is suppressed.

  In addition, since the discharge region is divided by the particles 32B, a conductive path for concentrating current at a specific place is also divided. By such an action, abnormal discharge due to current concentration is suppressed, and occurrence of image defects due to abnormal discharge such as white spots and black spots is reduced. In conventional charging members, if the resistance value of the surface layer is not set in a narrow range, once abnormal discharge occurs, current concentrates immediately and image defects such as white spots and black spots occur. In the charging member 121 of the present embodiment, current concentration can be suppressed, so that the resistance value of the surface layer can be designed in a wider range than before.

  In addition, when a part of the insulating particles 32B is not embedded in the surface layer 32, a void is formed between the particle 32B and the surface layer, and a discharge occurs in the void, and the discharge causes the particle 32B to be discharged. It is presumed that the discharge region is not divided because charges are accumulated, and when the charged potential of the particles 32B due to the charges exceeds the discharge start voltage, the particles are discharged toward the photoreceptor. Furthermore, unlike the semiconductive case, the discharge from such an insulator causes charge accumulation and discharge to occur alternately. Therefore, the amount of electric charge discharged during discharge tends to increase, and image quality defects associated with abnormal discharge are likely to occur. It is estimated that the occurrence tends to increase.

  In the charging member 121 of the present embodiment, the discharge region is divided, but the surface of the surface layer 32 existing around the particle 32B is separated from the photoconductor, so that it is actively discharged and non-discharged by the particle 32B. Complementing this part, the surface of the photoreceptor is uniformly charged.

  Furthermore, in the charging member 121 of the present embodiment, inhibition of discharge due to foreign matters such as toner and external additives attached to the surface of the charging member can be suppressed. Foreign matters such as toner and external additives adhere to the convex portions on the surface of the surface layer 32 and do not adhere much to the concave portions. Therefore, in the charging member 121 of the present invention, toner or the like does not adhere to the surface of the surface layer 32 corresponding to the recess that is the discharge region, and the discharge is not hindered. Further, the protruding particles 32B corresponding to the convex portions of the surface layer do not discharge because they are insulative, and even if foreign matter adheres to the convex portions of the surface layer, charging is not hindered.

  The charging member 121 of the present embodiment can be used with the charging voltage applied to the charging member lowered. In conventional charging members, the voltage applied to the charging member has been increased in order to suppress the occurrence of image defects such as white spots and black spots. However, in the charging member 121 of the present embodiment, image defects such as white spots and black spots have been increased. Can be used without increasing the charging voltage. As a result, the load on the power source is reduced. Furthermore, since the voltage applied to the charging member 121 can be lowered and used, damage to the photosensitive member due to discharge can be reduced, and the wear rate of the photosensitive member can be reduced to achieve a longer life.

The particle 32B is an insulator as described above so as to prevent discharge at the maximum dischargeable distance G and to divide the discharge region. Here, “insulator” means a volume resistivity of 10 ¹³ Ωcm or more. Hereinafter, non-conductivity is also synonymous.
The particles 32B are insulating resin particles such as polyimide resin particles, methacrylic resin particles, polystyrene resin particles, fluorine resin particles, and silicone resin particles; insulating particles such as clay particles, kaolin particles, talc particles, silica particles, and alumina particles. Inorganic particles or ceramic particles can be used.

The particles 32B are preferably composed of the same type of resin as the resin 32A from the viewpoint of preventing peeling from the surface layer 32. However, as will be described later, when the surface layer 32 is formed from a coating liquid containing the particles 32B and the resin 32A, the particles 32B protrude from the surface layer 32 and the surfaces of the particles 32B are exposed at the protruding portions. Moreover, it is desirable that the particles 32B be formed of a material that is not compatible with the resin 32A.
A suitable combination of the particles 32B and the resin 32A will be described later.

  The height H at which the particles 32B protrude from the surface of the surface layer 32 is preferably 8 μm or more, more preferably 9 μm or more and 50 μm or less, and further preferably 15 μm or more and 30 μm or less. When the protrusion height H of the particles 32B is in the above range, it is easy to prevent discharge at the maximum dischargeable distance G and to divide the discharge region.

  The height H of the protrusion from the surface is confirmed and measured by a micrograph of the cross section of the surface layer 32. About ten particles 32B protruding from the surface of the surface layer 32, the height H protruding from the surface is measured, and an average value is obtained.

The volume average particle diameter D of the particles 32B is desirably 12 μm or more and 100 μm or less, and more desirably 12 μm or more and 60 μm or less. When the volume average particle diameter of the particles 32B is within the above range, it is easy to prevent discharge at the maximum dischargeable distance G and to divide the discharge region.
The volume average particle diameter D of the particles 32B is a value measured using a Coulter Counter TA-II type (manufactured by Coulter). In this case, measurement is performed using an optimum aperture according to the particle size level of the particles.
When measuring the volume average particle diameter D of the particles 32 </ b> B from the manufactured charging member, it is measured by a micrograph of a cross section of the surface layer 32.

  The particles 32B may be spherical or irregular.

  The blending amount of the particles 32B is desirably 5 parts by mass or more and 90 parts by mass or less, more desirably 15 parts by mass or more and 70 parts by mass or less, and further desirably 25 parts by mass with respect to 100 parts by mass of the resin 32A. Part to 60 parts by weight. When the blending amount of the particles 32B is within the above range, it is easy to prevent discharge at the maximum dischargeable distance G and to divide the discharge region.

  The thickness (overall thickness) of the surface layer 32 is desirably 3 μm or more in terms of average film thickness, more desirably 25% or more and 90% of the diameter of the particle 32B to be added. It is more desirable that the thickness corresponds to 35% or more and 80% or less of the diameter of 32B. When the thickness of the surface layer 32 is within the above range, separation of the particles 32B from the surface layer 32 is suppressed.

  Here, the relationship between the volume average particle diameter D of the particles 32B and the average film thickness T1 of the surface layer 32 preferably satisfies the formula: D−T1 ≧ 8 μm. When this relational expression is satisfied, it becomes easy to prevent discharge at the maximum dischargeable distance G and to divide the discharge region.

The volume resistivity of the surface layer 32 is desirably 10 ³ Ωcm or more and 10 ¹⁴ Ωcm or less.

The charging member 121 according to this embodiment is manufactured by sequentially forming the elastic layer 31 and the surface layer 32 on the outer peripheral surface of the shaft 30.
As a method for forming the elastic layer 31, for example, an injection method using a molding die, an extrusion method, or the like is used on the outer peripheral surface of the shaft 30.

As a method for forming the surface layer 32, (1) a method of first applying particles 32 </ b> B to the elastic layer 31, and then applying a material constituting the other surface layer 32 such as a resin 32 </ b>A; After forming a layer with a material constituting the surface layer 32 other than 32B, a method of applying the particles 32B, (3) preparing a coating liquid containing the particles 32B, the resin 32A, and other components as necessary. And a method of applying this coating liquid.
Among these forming methods, the method (3) is desirable from the viewpoint of the simplicity of the manufacturing process.

  The coating liquid for forming the surface layer 32 includes particles 32B and a resin 32A, and further includes other additives such as a conductive agent and a solvent as necessary. When this production method (3) is employed, it is desirable that the particles 32B and the resin 32A are formed of materials that are not compatible with each other. By using such a combination of materials, the particles 32B protrude from the surface layer 32, and the surface of the particles 32B can be easily exposed at the protruding portions.

  Note that when the particles 32B are formed of a silicone resin, the silicone resin has low compatibility with other resins, so that the choice of the resin 32A to be combined is expanded. Moreover, when the silicone resin is modified with carbinol, the compatibility is adjusted. Furthermore, since the silicone resin is negatively charged and general toners are negatively charged, they repel each other, and contamination of the charging member 121 with the toner is prevented.

  Specific examples of suitable combinations of the particles 32B and the resin 32A include the following.

1)
Resin 32A: Copolymer nylon resin or alcohol-soluble polyamide resin Particle 32B: Fluororesin (Teflon (registered trademark), etc.), hydrophobic silica, silicone-acryl block copolymer, silicone resin, or cross-linked polystyrene resin

2)
Resin 32A: Acrylic resin Particle 32B: Silicone resin

3)
Resin 32A: acrylic resin, cellulose resin, polyamide resin, methoxymethylated nylon, ethoxymethylated nylon, polyurethane resin, polycarbonate resin, polyester resin, polyethylene resin, polyvinyl resin, polyacrylate resin, polythiophene resin, tetrafluoroethylene (PFA) Polyolefin resin such as tetrafluoroethylene (FEP) and polyethylene terephthalate (PET), styrene butadiene resin, melamine resin, epoxy resin, urethane resin, silicone resin, urea resin, or copolymer nylon resin Particle 32B: Carbinol-modified Silicone resin

  In the method of forming the surface layer 32 with the mixed coating liquid, a combination in which the particles 32B and the resin 32A exhibit high compatibility with each other is not suitable. Therefore, what is not suitable as a combination of the particle 32B and the resin 32A in the method using the mixed coating liquid includes the following.

Resin 32A: Copolymer nylon resin or alcohol-soluble polyamide resin Particle 32B: Porous 12 nylon, porous calcium carbonate, or melamine / silica composite fine particles

  Further, in the forming method using this mixed coating liquid, it is desirable that the particles 32B are not porous. If the particles 32B are porous, the resin 32A may enter the holes of the particles 32B, and the resin 32A that has entered the holes when contacting the photoreceptor may contaminate the photoreceptor. Further, when the particles 32B are porous, the particles 32B become familiar with the resin 32A, and the particles 32B are difficult to protrude from the surface layer 32, and the surfaces of the particles 32B are difficult to be exposed at the protruding portions.

  The above phenomenon when the particle 32B is porous also occurs in the particle 32B having large irregularities on the particle surface. Therefore, it is desirable to adjust the surface roughness of the particles 32B depending on the type of the resin 32A to be combined.

The coating liquid is prepared by mixing the particles 32B and the resin 32A and, if necessary, other additives such as a conductive agent and a solvent and stirring them by a known method such as a bead mill.
For example, a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, or the like is used as a coating method for the coating liquid.

  Note that the combination of the particles 32B and the resin 32A is the method (3) in which the surface layer 32 is formed by the mixed coating liquid, and is formed by other methods such as (1) and (2). The combination is not particularly limited. However, the combination of the methods (1) and (2) is also desirable from the viewpoint of causing the particles 32B to protrude from the surface layer 32 and exposing the surfaces of the particles 32B at the protruding portions.

  In the charging member 121 according to the present embodiment described above, the insulating particles 32B are partly embedded in the surface layer 32, and the other part protrudes from the surface of the surface layer 32, and the surface of the particle 32B is in the protruding part. Exposed. Further, the ratio of the surface of the particle 32B exposed at the protruding portion is 9% or more, and the ratio (H / D) of the height (H) at which the particle 32B protrudes with respect to the volume average particle diameter (D) of the particle 32B. Is 75% or less. As a result, the particles 32B are not discharged, the discharge at the maximum distance G that can be discharged is prevented, and the discharge region is divided. As a result, even when a voltage is applied to the charging member 121 in a state where the charging member 121 is in contact with the photosensitive member, discharge is performed, occurrence of image defects such as white spots and black spots is suppressed, and the surface of the photosensitive member is uniformly charged. It becomes. In addition, the inhibition of discharge due to foreign matters such as toner and external additives attached to the surface of the charging member can be suppressed.

(Charging device)
Hereinafter, the charging device according to the present embodiment will be described. FIG. 6 is a schematic perspective view of the charging device according to the present embodiment. The charging device according to the present embodiment is a form in which the charging member according to the present embodiment is applied as a charging member.

  As shown in FIG. 6, the charging device 12 according to the present embodiment is disposed, for example, in which a charging member 121 and a cleaning member 122 are in contact with each other with a specific biting amount. Both ends of the shaft 30 of the charging member 121 and the shaft 122A of the cleaning member 122 in the axial direction are held by a conductive bearing 123 (conductive bearing) so that each member can rotate. A power supply 124 is connected to one of the conductive bearings 123. Note that the charging device according to the present embodiment is not limited to the above-described configuration, and may be a form that does not include the cleaning member 122, for example.

  The cleaning member 122 is a cleaning member for cleaning the surface of the charging member 121, and is formed in a roll shape, for example. The cleaning member 122 includes, for example, a shaft 122A and an elastic layer 122B on the outer peripheral surface of the shaft 122A.

  The shaft 122A is a conductive rod-like member, and examples of the material thereof include metals such as iron (free-cutting steel and the like), copper, brass, stainless steel, aluminum, and nickel. Examples of the shaft 122A include a member (for example, a resin or a ceramic member) whose outer peripheral surface is plated, a member in which a conductive agent is dispersed (for example, a resin or a ceramic member), and the like. The shaft 122A may be a hollow member (cylindrical member) or a non-hollow member.

  The elastic layer 122B is made of a foam having a porous three-dimensional structure, and preferably has a cavity and a concavo-convex portion (hereinafter referred to as a cell) inside and on the surface and has elasticity. The elastic layer 122B is made of polyurethane, polyethylene, polyamide, olefin, melamine or polypropylene, NBR (acrylonitrile-butadiene copolymer rubber), EPDM (ethylene-propylene-diene copolymer rubber), natural rubber, styrene butadiene rubber, chloroprene, silicone, It includes a foamable resin material such as nitrile or a rubber material.

  Among these foamable resin materials or rubber materials, polyurethane which is strong against tearing and tensile strength is particularly preferably applied. With this material, foreign matters such as toner and external additives are efficiently cleaned by driven sliding friction with the charging member 121, and it is difficult to scratch the surface of the charging member 121 due to rubbing of the cleaning member 122. In addition, it is difficult to cause tearing and breakage over a long period of time.

  The polyurethane is not particularly limited. For example, polyol (for example, polyester polyol, polyether polyester, acrylic polyol, etc.) and isocyanate (2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4, 4-diphenylmethane diisocyanate, tolidine diisocyanate, 1,6-hexamethylene diisocyanate, etc.), and reaction products of these chain extenders (eg, 1,4-butanediol, trimethylolpropane, etc.) Good. Polyurethane is generally foamed using a foaming agent (water or an azo compound (azodicarbonamide, azobisisobutyronitrile, etc.).

  The number of cells per 25 mm (number / 25 mm) of the elastic layer 122B is preferably 20/25 mm or more and 80/25 mm or less, more preferably 30/25 mm or more and 80/25 mm or less, and 30/25 mm or more. It is particularly desirable that it is 50/25 mm or less.

  The hardness of the elastic layer 122B is preferably 100N to 500N, more preferably 100N to 400N, and particularly preferably 150N to 400N.

  The conductive bearing 123 is a member that holds the charging member 121 and the cleaning member 122 integrally and rotatably, and also holds an inter-axis distance between the members. The conductive bearing 123 may be of any material and form as long as it is made of a conductive material. For example, a conductive bearing or a conductive sliding bearing is applied.

  The power supply 124 is a device that charges the charging member 121 by applying a voltage to the conductive bearing 123, and a known high-voltage power supply device can be used.

  In the charging device 12 according to the present embodiment, the charging member 121 is charged to the same polarity by applying a voltage from the power source 124 to the conductive bearing 123. As a result, foreign matter (for example, toner or external additives) on the surface of the image carrier is prevented from accumulating on the surfaces of the cleaning member 122 and the charging member 121 and can be transferred to the image carrier, and the foreign matter is collected by the image carrier cleaning device. Is done. Therefore, accumulation of dirt on the charging member 121 and the cleaning member 122 is suppressed over a long period of time, and charging performance is maintained.

(Image forming device, process cartridge)
The image forming apparatus according to the present embodiment includes an image carrier, a charging device that charges the surface of the image carrier, a latent image forming device that forms a latent image on the charged surface of the image carrier, and the image. And a developing device that forms a toner image by developing the latent image formed on the surface of the holding member with toner, and a transfer device that transfers the toner image formed on the surface of the image holding member to a recording medium. The charging device according to the present embodiment is applied as the charging device.

  On the other hand, the process cartridge according to the present embodiment includes, for example, an image carrier that is detached from the image forming apparatus having the above-described configuration, and a charging device that charges the image carrier. The charging device according to the present embodiment is applied as the charging device. The process cartridge according to the present embodiment includes, as necessary, a developing device that develops a latent image formed on the surface of the image carrier with toner to form a toner image, and a toner image formed on the surface of the image carrier. At least one device selected from the group consisting of a transfer device that transfers the toner onto a recording medium and a cleaning device that removes residual toner on the surface of the image carrier after transfer.

  Next, an image forming apparatus and a process cartridge according to the present embodiment will be described with reference to the drawings. FIG. 7 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment. FIG. 8 is a schematic configuration diagram illustrating an example of a process cartridge according to the present embodiment.

  As shown in FIG. 7, the image forming apparatus 101 according to the present embodiment includes an image carrier 10, a charging device 12 that charges the image carrier around the image carrier 10, and an image carrier charged by the charging device 12. An exposure device 14 as a latent image forming device that exposes 10 to form a latent image, a developing device 16 that develops the latent image formed by the exposure device 14 with toner and forms a toner image, and a developing device 16 A transfer device 18 that transfers the toner image to the recording medium A, a cleaning device 20 that removes residual toner on the surface of the image carrier 10 after the transfer, and a static elimination device 26 that removes residual potential on the surface of the image carrier 10. . Further, a fixing device 22 for fixing the toner image transferred to the recording medium A by the transfer device 18 is provided.

  The image forming apparatus 101 according to the present embodiment includes, as the charging device 12, for example, a charging member 121, a cleaning member 122 disposed in contact with the charging member 121, and both axial ends of the charging member 121 and the cleaning member 122. The charging device of the present embodiment is provided with a conductive bearing 123 (conductive bearing) that holds each member so as to be rotatable, and a power source 124 connected to one of the conductive bearings 123. Has been applied. As described above, the charging device 12 may not include the cleaning member 122.

  In the image forming apparatus 101 including the charging device of the present embodiment, the charging voltage can be lowered. Therefore, the amount of wear of the photoconductor is reduced by reducing the discharge damage to the photoconductor, and the life of the photoconductor is extended. Is planned.

  In the image forming apparatus 101 of the present embodiment, known configurations are conventionally applied as components of an electrophotographic image forming apparatus, except for the charging device 12 (charging member 121). Hereinafter, an example of each configuration will be described.

  The image carrier 10 is not particularly limited, and a known photoreceptor can be used. An organic photoreceptor having a so-called function separation type structure in which a charge generation layer and a charge transport layer are separated is preferably used.

In addition, a photoreceptor having a surface layer that is a cured film on the surface is also suitably applied to the image carrier 10. In general, a photoconductor provided with a surface layer that is a cured film has a long life, but the surface of the photoconductor is hardly scraped by a cleaning blade, and discharge products attached to the surface of the photoconductor tend to remain. When the accumulated discharge product absorbs water in a high humidity environment, the surface resistance of the photoreceptor decreases and the latent image formed on the photoreceptor easily flows. Furthermore, when contaminants such as discharge products accumulate on the photoreceptor, the coefficient of friction of the photoreceptor increases, the wear amount of the photoreceptor and the cleaning blade increases, and the photoreceptor and the cleaning blade are easily damaged.
On the other hand, the charging member 121 of the present embodiment can be used with a lower charging voltage, and it is difficult for discharge products or the like to accumulate on the photoreceptor, and the amount of wear can be suppressed even in a photoreceptor having a surface layer. Longer life is achieved. Therefore, the photoconductor including the surface layer in which the amount of wear is suppressed by the charging member 121 of the present embodiment is also suitably applied to an image forming apparatus having a high processing speed.

  As a material constituting the surface layer of the image carrier 10, a siloxane-based resin or a phenol-based resin having a charge transporting property and a crosslinked structure is preferably used.

  As the exposure apparatus 14, for example, a laser optical system, an LED array, or the like is applied.

  For example, the developing device 16 brings a toner image onto the latent image on the surface of the image carrier 10 by bringing a developer carrier having a developer layer formed on the surface thereof into contact with or close to the image carrier 10. A developing device to be formed. As a developing method of the developing device 16, a developing method using a two-component developer is suitably applied as a known method. Examples of the developing method using the two-component developer include a cascade method and a magnetic brush method.

  Examples of the transfer device 18 include a non-contact transfer method such as corotron and scorotron, and a contact transfer method in which a conductive transfer roll is brought into contact with the image carrier 10 via the recording medium A to transfer a toner image to the recording medium A. Either may be applied.

  The cleaning device 20 is, for example, a member that removes toner, paper dust, dust, and the like adhering to the surface by bringing a cleaning blade into direct contact with the surface of the image carrier 10. As the cleaning device 20, a cleaning brush, a cleaning roll, or the like may be applied in addition to the cleaning blade.

The static eliminator 26 erases the electrostatic latent image remaining on the image carrier 10 after the toner image is transferred to the recording medium A by removing the residual charges on the image carrier 10, and the image carrier The surface of 10 is set as a static elimination potential.
The neutralization device 26 may be any device that erases the electrostatic latent image remaining on the image carrier 10 by setting the surface of the image carrier 10 to a predetermined static elimination potential. For example, as this static elimination apparatus 26, the static elimination apparatus 26 which performs static elimination by irradiating light is mentioned. Examples of the static elimination device 26 that performs static elimination by light irradiation include a light source that emits white light such as a tungsten lamp and infrared light such as LED light.

  As the fixing device 22, a heat fixing device using a heat roll is suitably applied. The heat fixing device includes, for example, a fixing roller in which a so-called release layer is formed of a heat-resistant resin coating layer or a heat-resistant rubber coating layer on the outer peripheral surface thereof with a heater lamp for heating inside a cylindrical metal core, A pressure roller or a pressure belt that is disposed in contact with the fixing roller at a specific contact pressure and has a heat-resistant elastic body layer formed on the outer peripheral surface of the cylindrical metal core or the surface of the belt-like base material. . The fixing process of the unfixed toner image is performed, for example, by inserting the recording medium A onto which the unfixed toner image is transferred between a fixing roller and a pressure roller or a pressure belt, and binding resin in the toner, Fixing by heat melting of additives and the like.

  The image forming apparatus 101 according to the present embodiment is not limited to the above configuration. For example, an intermediate transfer type image forming apparatus using an intermediate transfer member and an image forming unit that forms toner images of each color are arranged in parallel. A so-called tandem image forming apparatus may be used.

On the other hand, as shown in FIG. 8, the process cartridge 102 according to the present embodiment includes an opening 24A for exposure, an opening 24B for static elimination exposure, and a mounting rail 24C in the image forming apparatus shown in FIG. By the housing 24 provided, the image carrier 10, the charging device 12 that charges the image carrier, the developing device 16 that develops the latent image formed by the exposure device 14 with toner and forms a toner image, and the transfer The process cartridge 102 is configured to be integrally combined with a cleaning device 20 that removes residual toner on the surface of the subsequent image carrier 10. The process cartridge 102 is detachably attached to the image forming apparatus 101 shown in FIG.
If the process cartridge 102 according to this embodiment includes at least the image carrier 10 and the charging device 12 that charges the image carrier, the developing device 16 and the cleaning device 20 are appropriately selected and combined. It is done.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited by the following Example. Unless otherwise specified, “part” means “part by mass”.

[Example 1]
(Preparation of charging roll)
-Formation of elastic layer-
With respect to 100 parts by mass of an elastic material (epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber), 15 parts by mass of a conductive agent (carbon black Asahi Thermal: manufactured by Asahi Carbon Co., Ltd.), a vulcanizing agent (sulfur 200 mesh: Tsurumi Chemical Co., Ltd.) A mixture of 1 part by mass and 2 parts by mass of a vulcanization accelerator (Noxeller DM: manufactured by Ouchi Shinsei Chemical Co., Ltd.) was kneaded with an open roll, and a shaft (conductive support) made of SUS303. An elastic layer having a thickness of 3.5 mm was formed on the outer peripheral surface of the body and the shaft body through a bonding layer using a press molding machine to obtain a roll having a diameter of 15 mm. Thereafter, a conductive elastic roll having a diameter of 14 mm having an elastic layer having a thickness of 3 mm was obtained by polishing.

-Formation of surface layer-
Curing agent (amino resin solution Super Becamine G-821-60: manufactured by Dainippon Ink & Chemicals, Inc.) 26.3 parts by mass with respect to 100 parts by mass of copolymer nylon resin (“CM8000”, manufactured by Toray Industries, Inc.), conductive agent In a bead mill, a mixture in which 10 parts by mass of (carbon black) and 30 parts by mass of silicone resin particles (filler) (“Tospearl”, manufactured by Momentive Performance Materials Japan GK, volume average particle diameter 12 μm) was added. This was dispersed and diluted with methyl ethyl ketone to prepare a coating solution.
The conductive elastic roll was dipped and applied in the prepared coating liquid, and dried by heating at 180 ° C. for 20 minutes to obtain a surface layer having a thickness of 4 μm.
In this way, a charging roll was obtained.

(Evaluation of charging roll)
-Observation of surface layer-
As described above, the height (H) at which the particles (filler) protrude from the surface layer was determined from a micrograph. Further, the exposure rate was determined by setting Y to indicate that the particles (filler) were exposed at the protruding portion, and N to indicate that the particles were not exposed.
In FIG. 9, the microscope picture of the surface layer of the charging roll obtained in Example 1 is shown. As shown in FIG. 9, in the surface layer of the charging roll of Example 1, particles (filler) protrude from the surface layer, and the surface of the particle (filler) is exposed at the protruding portion.

-Evaluation of image defects-
If the above-mentioned charging roll is incorporated into the toner cartridge of Fuji Xerox color copier DocuCenter Color a450, 500,000 sheets are printed. If no streaks due to white spots or black spots occur, rank A, if minor streaks are observed Rank B, rank C if dark streaks occur. An experiment was conducted in the range of 0.3 mm to 0.8 mm with respect to the width in the rotation direction of the portion (nip portion) where the charging roll and the photoconductor contact.

[Examples 2 to 9]
According to Table 1, except that the thickness of the surface layer, the particle diameter of the particles (filler), the type of resin of the surface layer, the type of particles (filler), or the blending ratio of the particles (filler) in the coating liquid were changed. A charging roll was produced in the same manner as in Example 1. The obtained charging roll was evaluated in the same manner as in Example 1.

[Comparative Examples 1 to 3]
According to Table 1, the charging roll is the same as in Example 1 except that the thickness of the surface layer, the type of resin of the surface layer, the type of particles (filler), or the blending ratio of the particles (filler) in the coating liquid are changed. Was made. The obtained charging roll was evaluated in the same manner as in Example 1.

[Comparative Example 4]
A charging roll described in Example 1 of JP 2007-225914 A was produced.

In Table 1, resin types 1 and 2 represent the following.
Type 1: Copolymer nylon resin (CM8000, manufactured by Toray Industries, Inc.)
Type 2: Alcohol-soluble polyamide resin (Fine Resin FR-101, manufactured by Lead City Corporation)

In Table 1, types 1 to 4 of particles (fillers) represent the following: Type 1: Silicone resin particles (Tospearl, manufactured by Momentive Performance Materials Japan GK)
Type 2: Fluorine resin particles (Polyflon M-112, Daikin Industries, Ltd.)
Type 3: Cross-linked polystyrene (SBX-12, manufactured by Sekisui Plastics Co., Ltd.)
Type 4: Porous 12 nylon (2001 UD Nat1, manufactured by ARKEMA)

  From the above results, it can be seen that in this embodiment, the generation of image streaks due to white spots and black spots is suppressed as compared with the comparative example.

DESCRIPTION OF SYMBOLS 10 Image carrier 12 Charging device 14 Exposure device 16 Development device 18 Transfer device 20 Cleaning device 22 Fixing device 24 Housing 24A Opening 24B Opening 24C Mounting rail 26 Static elimination device 30 Shaft 31 Elastic layer 32 Surface layer 32A Resin 32B Insulating Particle 101 Image forming apparatus 102 Process cartridge 121 Charging member 122 Cleaning member 123 Conductive bearing 122A Shaft 122B Elastic layer 124 Power source

Claims (10)

A shaft,
An elastic layer disposed on the outer periphery of the shaft body;
A surface layer containing insulating particles disposed on the outer periphery of the elastic layer,
A part of the insulating particles are embedded in the surface layer, the other part protrudes from the surface of the surface layer, and the insulating particles are exposed in the protruding part,
The ratio at which the surface of the insulating particles in the protruding portion is exposed is 9% or more,
A charging member having a ratio (H / D) of a height (H) at which insulating particles protrude to a volume average particle diameter (D) of the insulating particles is 75% or less.   The charging member according to claim 1, wherein the surface layer is formed by a coating liquid containing the insulating particles and a resin constituting the surface layer.   The charging member according to claim 1, wherein the resin constituting the surface layer and the insulating particles are formed of materials that are not compatible with each other.   The charging member according to claim 1, wherein the insulating particles are formed of a silicone resin.   The charging member according to claim 1, wherein a height (H) at which the insulating particles protrude is 8 μm or more.   The charging member according to claim 1, wherein the surface layer has a thickness of 5 μm or more.   A charging device comprising the charging member according to claim 1. An image carrier,
The charging member according to claim 1, wherein the surface of the image carrier is charged.
A latent image forming apparatus for forming a latent image on the surface of the charged image carrier;
A developing device for developing a latent image formed on the surface of the image carrier with toner to form a toner image;
A transfer device for transferring a toner image formed on the surface of the image carrier to a recording medium;
An image forming apparatus comprising:   The image forming apparatus according to claim 8, wherein the image carrier includes a surface layer that is a cured film on a surface. An image carrier,
The charging member according to any one of claims 1 to 6, wherein the surface of the image carrier is charged.
A process cartridge that is detachably attached to the main body of the image forming apparatus.