JP2006154442A - Electrifying member and electrifying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging member which can be mounted on a high-speed/high-durability electrophotographic apparatus and is free from poor charging and doesn't require the use of a charging member cleaner and doesn't bring about abnormal images caused by sticking of toner or the like to stably form good images for a long period and to provide a electrifying device provided with the charging member. <P>SOLUTION: A charging member 2 for charging an object to be charged has a surface hardness of ≥40°, and B/A=Sa wherein A is a sum of actual contact areas in a nip part between the charging member and the object and A is an area of the entire nip part is increased 1.1 to 10 times when a contact force f1 to the object of the charging member is increased from 0.49N to 19.6N, that is, äSa(19.6N)/Sa(0.48N)} is 1.1 to 10. The charging device is provided with this charging member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charging member used in an electrophotographic apparatus such as a laser beam printer and a copying machine, and a charging device including the charging member.

  In a contact charging device for uniformly charging the surface of a photoreceptor in an electrophotographic apparatus, a charging member having a configuration in which a resistance layer made of rubber or resin is provided on a conductive substrate such as iron or SUS is generally used. Has been. A conductive material such as conductive carbon black or metal powder is added to the resistance layer to impart conductivity, and an appropriate elasticity is maintained in order to secure a contact portion (nip portion) with the photoreceptor. In order to give elasticity to the resistance layer, generally, softeners such as oil and plasticizer are added. However, these softeners are generally migratory and may contaminate the photoconductor. It is necessary to apply a surface layer that achieves both prevention of contamination and maintaining the elasticity of the charging member.

  As the conductive characteristics of the charging member, if the volume resistance is generally too high, abnormal images due to uneven charging of the photosensitive member or defective charging occur. On the other hand, if the resistance value of the charging member is lowered too much, abnormal images due to poor charging can be suppressed, but if a pinhole occurs on the surface of the photoreceptor due to manufacturing or handling, the image is reversed on the image corresponding to the pinhole portion. There is an appropriate region in the resistance of the charging member, such as a rhombus abnormal image being generated during development.

  The charging phenomenon between the charging member and the object to be charged includes a method in which a narrow space is formed at the contact or adjacent portion, and charging is performed by forming discharge in a dischargeable region that can be interpreted by Paschen's law, for example, a gap of several tens of μm. (See, for example, Patent Document 1).

  As a method for uniformly charging the surface of a photoconductor as a member to be charged in a conventional contact charging device, there is a method in which an AC voltage (AC) and a DC voltage (DC) are simultaneously applied to a charging member. In this method, the cost of the electrophotographic apparatus becomes higher as compared with the DC charging method in which only the DC voltage is applied to the charging member because the AC voltage source is used.

  Therefore, a proposal for a DC charging method has been made (see, for example, Patent Document 2).

  The DC charging method is generally lower in cost than the AC + DC charging method, but has a problem. That is, since there is no AC current leveling effect as in the case of AC + DC charging, non-uniformity in the electrical resistance of the charging roller itself is likely to appear in the image, and uniform charging is difficult as compared with the AC + DC charging method. Further, since there is no leveling effect, there is also a problem that image defects are easily caused due to dirt such as toner and paper dust adhering to the surface of the charging member.

  Although there is a merit such as low cost, the recent electrophotographic apparatus has increased in speed with respect to the DC charging method that seems to have little margin as the physical property of the charging member against the uniformity of charging and the adhesion to the surface of the charging member. High durability is advancing rapidly, and there is an urgent need to further improve the performance of the charging member.

  In order to improve the uniformity of charging, in the conventional technique, the charging member is controlled to a desired surface roughness, for example, flexible elastic particles such as silicone powder having a particle diameter of 7 to 30 μm are bonded to the surface layer, such as polyamide. There has been proposed a method of controlling the surface roughness of the charging member surface to a desired value by dispersing the resin in a resin (see, for example, Patent Document 3). Also, a method of coating a urethane resin layer in which cross-linked acrylic particles are dispersed on the surface layer (see, for example, Patent Document 4), a method of dispersing silica particles and polycarbonate particles that are high mold release but high in hardness (for example, Patent Documents) 5) has been proposed.

In order to increase the durability of an electrophotographic apparatus, it is required to suppress partial charging failure due to adhesion of toner, paper powder, etc. to the surface of the charging member, and to maintain stable charging uniformity over a long period of time. Yes. This is because the toner or paper dust that has passed through the cleaning member adheres to the charging member surface from the surface of the photosensitive member at the contact nip portion between the photosensitive member and the charging member, and is charged. It causes a defect. In order to increase the durability of the electrophotographic apparatus, the method of providing a cleaner on the charging member to suppress adhesion of toner or the like to the surface of the charging member increases the cost of the apparatus. A method has been proposed in which the roughness is made equal to or less than a predetermined surface roughness (see, for example, Patent Document 6).
JP 57-178257 A JP 05-341627 A Japanese Patent No. 3024248 Japanese Patent Laid-Open No. 08-286468 JP 2003-131460 A JP-A-11-249383

  However, by simply roughening the surface of the charging member in order to improve the charging uniformity, the charging uniformity can be improved. However, the surface area of the charging member at the nip portion with the photosensitive member being charged is reduced. In addition, since there is a minute dent in the charging member, toner, paper dust and the like are likely to move to the surface of the charging member, and further, toner and the like are liable to accumulate, leading to high durability of the electrophotographic apparatus. It has become difficult to respond. This tendency is more remarkable when high hardness particles such as crosslinked acrylic particles, polycarbonate particles, and silica particles are added.

  2 and 3 are conceptual diagrams of contact between the charging member and the member to be charged. A nip portion (nip region) 13 is formed between the charging member and the photosensitive member as the member to be charged by a predetermined contact force f1. In the contact between the charging member and the photosensitive member, a convex portion centered on the high hardness particle 61 and a concave portion 62 existing around the particle are formed in the nip portion 13. Since the shape of the unevenness hardly changes even in the nip portion, toner or paper dust or the like easily adheres and accumulates in the concave portion, and there is a problem that an abnormal image due to dirt on the surface of the charging member is generated in the concave portion.

  In Patent Document 3, flexible elastic particles such as silicone powder are dispersed in a low-hardness binder resin to form a surface layer. However, there is no specific description regarding the hardness of the binder resin, and the elastic particles There is no description of the properties related to the hardness of the material, and the reason why elastic particles are used is that the photoreceptor is not damaged. Therefore, it is appropriate to think that the binder resin forming the surface layer is also flexible. is there.

  The present inventors have examined the uniformity of charging and the easiness of contamination of the charging member surface by dispersing flexible elastic particles in a flexible binder resin. The inventors have observed the periphery of the contact nip between the charging member and the object to be charged in detail. As a result, when the flexible elastic particles are dispersed in the flexible binder resin, the downstream that has passed through the nip of the charging member. It was found that it took time to restore the surface roughness on the side. For this reason, even if the charging member is made to have a desired surface roughness, the desired surface roughness cannot be ensured in the discharge region, and the uniformity of charging cannot be achieved particularly in an electrophotographic apparatus having a high printing speed. all right. In addition, since the surface roughness in the nip portion is excessively reduced and no discharge occurs in the nip portion, the charging uniformity cannot be maintained. Further, it has been found that there is a problem that the binder resin becomes sticky, and the charging member cannot be prevented from being soiled due to adhesion of toner or paper dust.

  On the other hand, a charging member that has a smooth charging member surface to prevent contamination of the charging member surface does not cause a discharge in the nip, and does not easily generate a desired discharge in the discharge region near the nip. In the recent situation where the speed of photographic devices is rapidly increasing, it is impossible to sufficiently achieve the uniformity of charging.

  As described above, as a conventional technique related to the surface resistance layer in which elastic particles are dispersed, as a structure of the surface resistance layer of the charging member, high hardness particles are dispersed in a high hardness binder resin, In order to prevent damage to the body to be charged, flexible particles were used, and as a result, the binder resin was also made of flexible resin or rubber. In addition, a method for suppressing contamination of the charging member has not been achieved.

  The present invention has been made in view of such circumstances, and it is possible to flexibly prevent the uniformity of charging from being reduced due to the smooth surface even when the electrophotographic apparatus is increased in speed and durability. Dispersion of various elastic particles in a flexible binder resin reduces the uniformity of charging, prevents abnormal images from adhering to toner, etc., and disperses particles with high hardness The present invention proposes a means for providing a charging member that can stably and uniformly charge for a long time without generating an abnormal image due to adhesion of toner or the like. Further, the present invention aims to change the surface shape of the charging member at the nip portion due to the contact force with the object to be charged, smooth the surface roughness, and restore the surface shape when passing through the nip portion. Therefore, it is very different from the conventional invention.

  Accordingly, the problem of the present invention is that it can be mounted on a high-speed, high-durability electrophotographic apparatus, has no charging failure, does not require the use of a charging member cleaner, does not generate abnormal images due to adhesion of toner, etc. It is an object to provide a charging member capable of stably forming a good image and a charging device including the charging member.

  According to a first aspect of the present invention, in a charging member that charges a member to be charged, the surface hardness of the charging member is 40 ° or more, and the contact force to the member to be charged is 0.49 N (50 g) to 19.6 N ( 2000g), the ratio (B / A = Sa) of the sum (B) of the actual contact area in the nip portion between the charging member and the member to be charged (B) and the area (A) of the entire nip portion is {Sa (19.6 N (2000 g)) / Sa (0.49 N (50 g))} is a charging member characterized by being 1.1 times or more and 10 times or less.

  As a result of detailed examination of the adhesion of toner, paper dust, etc. to the surface of the charging member as described above, the contact state in the nip portion between the charging member and the object to be charged has a great influence, and the discharge in the vicinity of the nip portion is also affected. It was found that the surface roughness in the region greatly affects the uniformity of charging.

  The reason why the contact force is set to 0.49 N and 19.6 N is that the charging member is generally provided with springs having a load of about 4.9 N (500 g) to 9.8 N (1000 g) at both ends, and the object to be charged is provided. It is in contact. Therefore, Sa (19.6 N) when a load of 19.6 N is applied is considered to reflect the nip state during actual use, and Sa (0.49 N) when a load of 0.49 N is applied is It is possible to reflect a discharge state in the vicinity of the nip, that is, a surface state close to a state where the contact force is lost. Therefore, controlling Sa (19.6 N) / Sa (0.49 N) within the range of the present invention can represent a change in the surface state in and near the nip portion.

  In the present invention, when the contact force f1 to the charged body is increased from 0.49N to 19.6N, the ratio of Sa {Sa (19.6N) / Sa (0.49N)} is 1.1 times or more. By configuring the charging member so as to satisfy the above, it is possible to reduce the dent depth on the surface of the charging member that becomes a pocket to which toner or the like adheres in the nip portion, and to suppress the adhesion. Further, when the contact force f1 to the charged body is increased from 0.49N to 19.6N, the roughness of the surface is restored on the downstream side passing through the nip portion by reducing the ratio of Sa to 10 times or less. Since the surface roughness in the discharge region can be set to a desired roughness, the charging uniformity can be improved. That is, by setting the ratio of Sa to 1.1 times or more and 10 times or less, it is possible to secure unevenness in the discharge region and reduce the depth of the dent on the surface of the charging member that becomes a pocket to which toner or the like adheres in the nip portion. Adhesion can be suppressed.

  Furthermore, by setting the surface hardness of the charging member to 40 ° or more, it is possible to maintain the uniformity of charging by generating discharge even in the nip portion, and to suppress the adhesion of the charging member surface, and after passing through the nip portion. The surface shape of the charging member can be quickly restored, and the surface shape of the charging member in the discharge region can be set to a desired roughness.

  According to a second aspect of the present invention, the charging member has a structure in which a resistance layer is coated on a conductive substrate, and the hardness of the base layer resistance layer excluding the surface resistance layer located on the surface of the charging member conforms to JIS K6253: 1997. Thus, the charging member is characterized by being measured at 50 ° or more.

  Since the surface resistance layer can be deformed by suppressing the deformation of the base resistance layer by setting the hardness of the base resistance layer to 50 ° or more in accordance with JIS K6253: 1997, the surface roughness of the nip portion of the charging member can be easily controlled. become.

  A third aspect of the present invention is the above charging member, wherein the charging member has a surface roughness of 4 μm or more and 15 μm or less in terms of a ten-point average roughness Rz based on JIS B0601-1994.

  By setting Rz to 4 μm or more, the surface roughness after passing through the nip portion can be increased, so that the uniformity of charging can be improved. By setting Rz to 15 μm or less, the dent on the surface of the charging member in the nip portion can be reduced. Stain can be suppressed.

  According to a fourth aspect of the present invention, the charging member has a structure in which a resistance layer is coated on a conductive substrate, the surface resistance layer located on the surface of the charging member is made of elastic particles, a binder resin, and conductive particles, The charging member according to claim 1, wherein a compression ratio of the elastic particles by a load of 0.0098 N (1 g) is 10% to 50% of the particle diameter.

  By making the particles dispersed in the surface resistance layer elastic particles having a compression rate of 10% or more, the depth of the concave portions formed around the convex portions formed by the elastic particles can be suppressed, and adhesion can be suppressed. As the hardness of the elastic particles, the amount of displacement with respect to the particle diameter when the elastic particles are compressed until a load of 0.0098 N is applied can be expressed as a compression ratio, and the compression ratio is 10% or more of the particle diameter. By selecting the elastic particles, the uniformity of charging can be improved, the depth of the concave portions formed around the convex portions formed by the elastic particles can be suppressed, and adhesion to the charging member surface can be suppressed. Further, by setting it to 50% or less, the surface shape downstream of the nip region (nip portion) can be made to easily generate a uniform discharge.

  A fifth invention is the above-mentioned charging member, wherein the charging member has a surface hardness of 50 ° or more and 55 ° or less.

  By making the surface hardness of the charging member 50 ° or more, the recovery of the surface roughness after passing through the nip portion is further accelerated, and by making the surface hardness 55 ° or less, the depth of the concave portion formed around the convex portion formed by the elastic particles. Can be suppressed, and adhesion to the surface of the charging member can be suppressed.

  A sixth invention is the above-mentioned charging member, characterized in that the elastic particles are composed of a spherical resin made of a hollow porous material.

  By making the elastic particles hollow spherical resin, the reinforcement speed with the binder resin increases, so even if the surface shape changes due to contact with the charged body, the restoration speed after passing through the nip part Can be expedited.

  A sixth aspect of the present invention is a charging device including the above charging member.

  In Patent Document 3, there is a description related to the function and effect of the present invention in which the surface shape of the charging member, in particular, the unevenness of the surface is smoothed at the contact nip portion to suppress contamination of the charging member. Nothing at all.

  As described above, the charging member according to the claimed invention can be mounted on a high-speed, high-durability electrophotographic apparatus, has no charging failure, does not require the use of a charging member cleaner, and is abnormal due to adhesion of toner or the like. There is no generation of an image, and a good image can be stably formed over a long period of time.

  Specific examples of the charging member of the present invention will be described below. FIG. 6 is a schematic cross-sectional view showing a contact portion between the charging member of the present invention and a member to be charged, FIG. 1 is a diagram conceptually showing a charging device incorporating the charging member of the present invention, and FIG. It is the schematic which shows the example of the electrophotographic apparatus incorporating the charging member of this invention.

  The charging device according to the present invention shown in FIG. 1 includes a charging member 2 according to the present invention, a photosensitive drum 10 serving as a member to be charged, and a power source 3 that applies a charging bias to the charging member 2. The charging member 2 covers a conductive substrate 5 with a resistance layer 6, and the resistance layer is composed of a surface resistance layer 8 located on the surface of the charging member and a base layer resistance layer 7 excluding the surface resistance layer.

  In general, as shown in FIG. 2, the charging member is in contact with the member to be charged 10 by the contact force f <b> 1 applied to the conductive substrate 5 to form a nip portion (nip region) 13.

  In the present invention, as shown in FIG. 6, the surface of the charging member is deformed by the contact force f1 at the nip portion 13 so that the unevenness is crushed, and is in contact with the member to be charged. In FIG. 5, the sum (B) of the actual contact area (area of the contact portion b) centered on the convex portion of the charging member in the nip portion 13 with the member to be charged and the area of the entire nip portion (A ) Ratio (B / A = Sa) increases by increasing the contact force.

  In the present invention, the charging member has a ratio (B / A = Sa) of the sum (B) of the actual contact area in the nip portion of the charging member with the member to be charged and the area (A) of the entire nip portion (B / A = Sa). Sa (19.6 N) / Sa (0.49 N) is configured to be 1.1 times or more and 10 times or less when the abutting force is increased from 0.49 N to 19.6 N. As a method for controlling the ratio (B / A = Sa) of the sum (B) of the actual contact area of the charging member with the member to be charged (B) and the area (A) of the entire nip portion, the hardness of the base resistance layer In addition, a method of controlling the film hardness of the surface resistance layer (when only elastic particles are not added), and the compressibility of the elastic and sex particles described below can be mentioned. Particularly preferable Sa (19.6N) / Sa (0.49N) is 4 times or more and 8 times or less, and in this range, it is possible to obtain a charging member which prevents particularly uniform charging and surface contamination.

  The sum (B) of the actual contact area at the nip is a portion where the charging member is pressed against a glass cylindrical drum having the same shape as the body to be charged with a predetermined load and is actually in contact using a CCD camera or the like. And a non-contact portion is binarized by image processing, and the area of the portion in contact with the glass surface is summed. Moreover, the area (A) of the whole nib part can be calculated | required by calculating the whole area | region which connected the outermost contact location in the part which is actually contacting. An image of an example in which a nip portion is observed from the inside of a cylindrical drum using a CCD camera is shown. In FIG. 5, the actual contact portions B formed by the convex portions on the surface of the charging member are observed scattered. The nip part A was an area connecting the outermost parts of the contact part B. The space portion C is a region where the charging member is not in contact with the cylindrical drum. The ratio (B / A = Sa) between the area of the nip portion A and the actual contact area sum B (B / A = Sa) is calculated for each of the 0.49N load and 19.6N load, and the ratio Sa (19.6N) / Sa ( 0.49N), which was defined as the rate of change in contact.

  In the present invention, the film hardness of the surface resistance layer is preferably set to 45 ° or more when the charging member is formed with the same film thickness without adding only elastic particles. Forming a surface resistance layer by adding elastic particles to a film having a surface hardness of 45 ° or more, creating a surface resistance layer that makes it easy to obtain a desired surface roughness downstream of the nip and suppresses adhesiveness. Easy to do.

  In the present invention, it is preferable to use elastic particles having a compressibility of 5% or more. Further, the addition amount is preferably 20 parts by mass or more of elastic particles with respect to 100 parts by mass of the binder resin in order to ensure the roughness in the discharge region, and 100 masses of elastic particles in order to obtain smoothness at the nip part. Part or less is preferred. The average particle size of the elastic particles is preferably 10% or more and 130% or less with respect to the thickness of the surface resistance layer, because deformation occurs in the nip portion and shape recovery occurs downstream of the nip portion. The surface hardness of the surface resistance layer is preferably 45 ° or more when the charging member is formed with the same film thickness without adding only the elastic particles. Forming a surface resistance layer by adding elastic particles to a film having a surface hardness of 45 ° or more, creating a surface resistance layer that makes it easy to obtain a desired surface roughness downstream of the nip and suppresses adhesiveness. Easy to do.

  The material of the conductive substrate (core metal) 5 is not particularly limited, but a material having strength as a substrate and exhibiting conductivity is suitable. These materials include iron, stainless steel, aluminum, and conductive plastic.

The volume resistance value of the base resistance layer 7 is preferably 1 × 10 ² Ω · cm or more so that excessive voltage application does not occur in the surface resistance layer, and 1 × 10 ² in order to charge the surface of the object to be charged. ¹³ Ω · cm or less is preferable.

  The thickness of the base resistance layer is not particularly limited, but is usually about 1 mm or more and about 10 mm because of contact with the photosensitive drum.

  The hardness of the base resistance layer is determined by the ratio (B / A = Sa) of the sum (B) of the actual contact area in the nip portion of the charging member with the member to be charged and the area (A) of the entire nip portion (B / A = Sa). When the abutment force f1 is increased from 0.49N to 19.6N, an appropriate hardness is required to increase from 1.1 times to 10 times, and therefore preferably in JIS K6253: 1997. It is 50 ° or more as measured in conformity.

  What is necessary is just to comprise with a normal resin and a rubber material as a raw material of a base layer resistance layer. For example, polybutadiene, natural rubber, polyisoprene, SBR (styrene butadiene rubber), CR (chloroprene rubber), EPDM (ethylene propylene dienter rubber), IIR (butyl rubber), NBR (nitrile butadiene rubber), silicone rubber, urethane rubber, epichlorohydrin Rubbers such as rubber, polystyrene resins such as RB (butadiene resin) and SBS (styrene / butadiene / styrene elastomer), polyolefin resins, polyester resins, polyurethane, PVC (polyvinyl chloride), acrylic resins, styrene / What gave elasticity to high molecular materials, such as a vinyl acetate copolymer and a butadiene acrylonitrile copolymer, can be used. In order to form the resistance layer, one kind of these materials may be used or two or more kinds may be used in combination.

  Conductive base particles can be formed by dispersing conductive particles described later in these raw materials.

  The base resistance layer 7 may be solid or foamed (sponge-like), but the solid is preferable because the deformation due to the contact force can be concentrated on the surface resistance layer, so that the surface shape of the charging member in the nip portion can be easily smoothed.

  The surface of the base resistance layer 7 may be a polished surface, a surface onto which the mold inner surface is transferred, or a skin surface, and is not particularly limited. In particular, a surface on which a smooth inner surface of the mold is transferred or a surface obtained by polishing a solid body is preferable for uniform contact with the photosensitive drum.

  When a foam is produced by using a foaming agent, an inorganic foaming agent, an organic foaming agent, a polymer foaming agent, or the like can be used as the foaming agent. Examples of the inorganic foaming agent include sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate. D. C. A. (Azodicarbonamide) series, D.I. P. T.A. (Di-nitrosopentamethylenetetramine) system, O.D. B. S. H. (4,4'-oxybis-benzenesulfonyl-hydrazide) system, T.W. S. H. (P-trienesulfonylhydrazide) system, A.I. I. B. N. (Azobisisobutyronitrile) and the like can be used. D. C. A. System, O.D. B. S. H. With the blend of the system, a dense foam and a vulcanized tight (high crosslink density) foam can be obtained. Furthermore, as the polymer foaming agent, a polyethylene foaming agent, a polypropylene foaming agent, a vinyl chloride foaming agent, a vinylidene chloride foaming agent, an acrylic foaming agent, or the like can be used. A foaming agent may use 1 type or may use 2 or more types together.

  The base resistance layer 7 is blended with a vulcanizing agent as necessary. As vulcanizing agents, depending on the type of rubber used, sulfur vulcanizing agents, organic peroxides, quinoid vulcanizing agents, resin crosslinking agents, metal oxide crosslinking agents, amine crosslinking agents, triazine crosslinking agents, maleimides A known vulcanizing agent such as a system crosslinking agent can be appropriately used.

  In addition to this, a vulcanization accelerator, an anti-aging agent, a plasticizer, and the like may be added to the base layer resistance layer.

  A known method can be used to manufacture the base layer resistance layer. An elastic material is extruded, heated, vulcanized and cured, pressed into a core, and then polished into a desired shape. Elastic material Injection, transfer, and the like are injected into a mold having a predetermined shape.

In this manner, a base resistance layer having a volume resistance of 1 × 10 ² Ω · cm or more and 1 × 10 ¹³ Ω · cm or less and a hardness of 50 ° or more in accordance with JIS K6253: 1997 can be produced.

  The surface resistance layer 8 includes at least a conductive material, elastic particles, and a binder resin as constituent elements. The surface resistance layer needs to have a surface hardness of 40 ° or more and a ratio of a contact area in the nip portion to a desired value. As a method for controlling the ratio (B / A = Sa) of the sum (B) of the actual contact area of the charging member with the member to be charged (B) and the area (A) of the entire nip portion, the hardness of the base resistance layer At the same time, it is possible by controlling the film hardness of the surface resistance layer and the compressibility of the elastic particles.

  The material of the binder resin used for the surface resistance layer is preferably a crosslinkable resin from the viewpoint of preventing bleeding of the material of the base layer resistance layer and preventing adhesion of toner, etc., and BR (butadiene resin), SBS (styrene butadiene)・ Polystyrene resins such as styrene elastomers, polyolefin resins, polyester resins, polyurethane resins, PVC (polyvinyl chloride), acrylic resins, styrene / vinyl acetate copolymers, butadiene / acrylonitrile copolymers, etc. Materials can be used. In order to form the resistance layer, one kind of these materials may be used or two or more kinds may be used in combination. In addition, when a crosslinking agent is blended in the surface resistance layer, conventionally used crosslinking agents such as isocyanate crosslinking agents, melamine crosslinking agents, and amine crosslinking agents can be used as the crosslinking agent.

  As the elastic particles dispersed in the surface resistance layer, elastic particles having a compressibility of 5% or more can be used. As the material, acrylic resin, urethane resin, styrene resin, silicone resin, etc. can be used, and particularly preferable. Is a particle having a compressibility of 10% or more. As a specific shape, elastic particles made of a hollow porous spherical resin are particularly preferable because the characteristics of the charging member can be improved as described above.

  The conductive substance contained in the base layer resistance layer and the surface resistance layer used in the present invention can be appropriately selected from an ion conductive type conductive substance, a conductive polymer, and an electronic conductive type conductive substance. For example, conductive polymers such as polyaniline, polypyrrole and polyacetylene, quaternary ammonium salts such as trimethyloctadecyl ammonium perchlorate and benzyltrimethyl ammonium chloride, perchlorates such as lithium perchlorate and potassium perchlorate, and tetraalkyls. Ammonium salts, phosphate esters, aliphatic alcohol sulfate salts, aliphatic polyhydric alcohols, ionic surfactants, metals and metal oxides such as graphite, tin, ruthenium, titanium, nickel, copper, silver, germanium Alternatively, ketjen black, acetylene black, carbon black such as HAF, SAF, ISAF, SRF, and FT can be used. As a dispersing means for the polymer raw material, a roll kneader, a Banbury mixer, a ball mill, a sand grinder, a paint shaker, or the like may be used as appropriate.

The volume resistance value of the surface resistance layer 8 is preferably 1 × 10 ⁴ Ω · cm or more from the viewpoint of preventing excessive current to the charged body, and 1 × 10 ¹³ Ω for charging the surface of the charged body. -Cm or less is preferable. The thickness of the surface resistance layer is not particularly limited, but is usually about 1 μm to 50 μm.

  The surface resistance layer is coated by a method of extruding into a tube using an extruder or the like and coating on the base resistance layer. Preferably, the surface resistance layer is sprayed, dipped, roll coater, coil coater, curtain. Providing a surface resistance layer using liquid coating or powder coating as appropriate by coating such as flow coater, electrodeposition coating, electrostatic coating, powder coating, etc. Adhesiveness with the base layer resistance layer, stable charging member shape In particular, when the charging member is in the form of a roll, ring coating does not swell the base layer resistance layer, and the thickness of the surface resistance layer in the axial direction can be easily controlled to improve shape accuracy. It is preferable because it is excellent.

  Further, as shown in FIG. 1, a photosensitive drum 10 which is a drum-shaped electrophotographic photosensitive member has an OPC (organic photosensitive member), amorphous silicon, selenium, and a photosensitive drum base 11 which is rotatable in the R direction and grounded. The photosensitive layer 12 made of zinc oxide or the like is covered.

  The photoreceptor 10 is not limited to a drum shape, and may be a belt shape or a sheet shape. The charging member 2 is a roller-shaped member, but may be a non-rotating roller, a blade-shaped pad member, or the like.

  The charging member 2 abuts on the photoconductor 10 and is connected to the photoconductor 10 via the power source 3 to constitute an electric circuit. The power supply 3 charges the vicinity of the nip portion 13 between the contact charging member 2 and the photosensitive member 10, and the nip portion 13 moves as the photosensitive member 10 moves, so that the entire surface of the photosensitive member 10 is charged.

  FIG. 4 is a schematic view showing an example in which a conductive member is applied to an electrophotographic apparatus as a charging member.

  The electrophotographic apparatus has a charging member 2 and a photosensitive drum 10 as shown in FIGS. 1 and 3, and is further integrated with a developing device 31, a transfer member 32, a fixing device 33, a cleaner 34, and the electrophotographic device. A process cartridge is provided as a detachable unit.

  As shown in FIG. 4, after the entire surface of the photoconductor 10 is charged, it is exposed with laser light L in accordance with image information to form a latent image on the surface of the photoconductor 10 and then developed with toner in the developing unit 31. In the transfer portion, the image is transferred to a transfer material by the transfer member 32 and thermally fixed by the fixing device 33. On the other hand, the photosensitive drum 10 is cleaned by a post-transfer cleaner 34 to prepare for the next image formation.

  Here, the process cartridge is a cartridge in which an electrophotographic photosensitive member as an image carrier and at least one of a charging unit, a developing unit, or a cleaning unit as an operation unit are integrally formed into a cartridge. For example, a copying machine, LBP, etc.) are detachable from the main body. The process cartridge only needs to include at least a photosensitive drum and a charging member.

  The photosensitive drum 10 is configured as follows.

  The photoreceptor 10 is provided on the photosensitive drum base 11. As the photosensitive drum substrate 11, the support itself can be made of a conductive material such as aluminum, aluminum alloy, stainless steel, nickel, etc. In addition, aluminum, aluminum alloy, indium oxide-tin oxide alloy, etc. A plastic having a layer formed by vacuum deposition, a support in which conductive particles (for example, carbon black, tin oxide particles, etc.) are applied to a metal or plastic together with an appropriate binder resin, a plastic having a conductive binder resin, etc. Can be used.

An undercoat layer having a barrier function and an adhesive function may be provided between the photosensitive drum substrate 11 and the photosensitive member 12. The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, etc.), polyurethane, gelatin, aluminum oxide, or the like. The thickness of the undercoat layer is preferably 5 μm or less, particularly preferably 0.5 μm to 3 μm. The undercoat layer is preferably 10 × 10 ⁷ Ω · cm or more in order to exhibit its function.

  The photoreceptor 12 can be formed by applying an organic or inorganic photoconductor together with a binder resin as necessary, or can be formed by vapor deposition. The form of the photosensitive layer (photoreceptor) is preferably a function-separated type laminated photosensitive layer of a charge generation layer and a charge transport layer.

  The charge generation layer can be formed by depositing a charge generation material such as an azo pigment, a phthalocyanine pigment, a quinone pigment, or a perylene pigment, or by coating with a suitable binder resin (or without a binder resin). The film thickness of the charge generation layer is preferably 0.01 μm to 5 μm, particularly preferably 0.05 μm to 2 μm.

  The charge transport layer can be formed by dissolving a charge transport material such as a hydrazone compound, a styryl compound, an osissazole compound, or a triarylamine compound in a film-forming binder resin. The film thickness of the charge transport layer is preferably 5 μm to 50 μm, particularly preferably 10 μm to 30 μm.

  Hereinafter, the present invention will be described by way of examples. In the examples, “part” means part by mass.

<Example 1>
The charging member used in this example was manufactured by the following method.

  100 parts of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (trade name: Epichromer CG102, manufactured by Daiso Corporation) as a raw material for the base resistance layer, 1 part of zinc stearate as a processing aid, vulcanization acceleration 5 parts of zinc oxide as an auxiliary agent, 30 parts of MT carbon black (trade name: Thermacs Flow Foam N990, manufactured by CANCAB) as a filler, dipentamethylene thiuram tetrasulfide (trade name: Noxeller TRA, large) as a vulcanizing agent 2 parts of Uchinshinko Chemical Co., Ltd.) were mixed with an open roll to obtain an unvulcanized rubber composition.

  Next, it was extruded into a tube shape by a vent type rubber extruder (φ50 mm vent extruder L / D = 16 manufactured by EM Giken Co., Ltd.), subjected to primary vulcanization at 160 ° C. for 30 minutes with pressurized steam using a vulcanizing can, A rubber tube having a diameter of 15 mm, an inner diameter of 5.5 mm, and a length of 250 mm was obtained.

  Next, a core metal having a length of 256 mm and a diameter of 6 mm made of SUM which has been dried after applying a thermosetting adhesive (trade name: METALOC U-20, manufactured by Toyo Chemical Laboratories) is inserted into the rubber tube. Then, secondary vulcanization and adhesion treatment were performed in a hot air oven at 160 ° C. for 2 hours.

  A sample piece was prepared using the material for the base layer resistance layer, and the hardness of the base layer resistance layer was measured according to JIS K6253: 1997 to be 52 °.

  Next, after cutting both ends so as to have a rubber length of 224 mm, using an NC grinder, a crown-shaped base layer resistance layer material with a rubber part end diameter of 12.00 mm and a center part diameter of 12.10 mm was obtained. Obtained.

  As a coating for the surface resistance layer, 150 parts of a lactone-modified acrylic polyol (trade name: Plaxel DC2009, manufactured by Daicel Chemical Industries) having a solid content of 70% and a hydroxyl value of 90%, 500 parts of methyl isobutyl ketone, a leveling agent 0.05 parts of silicone oil (trade name: SH28PA, manufactured by Toray Dow Silicone Co., Ltd.) and 30 parts of conductive tin oxide powder (trade name: SN-100P, manufactured by Ishihara Sangyo Co., Ltd.) as conductive particles 30 parts of elastic particles obtained by dividing non-crosslinked acrylic particles (trade name: M-200, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) as elastic particles using an elbow jet into an average particle size of 2 μm, and paint shaker For 6 hours. To 370 parts of the resulting dispersion, 25 parts of isophorone diisocyanate nurate type (trade name: Bestanat B1370, manufactured by Degussa Huls), hexamethylene diisocyanate nurate type (trade name: Duranate TPA-B80E, Asahi Kasei Corporation) 16 parts) was mixed and stirred with a ball mill for 1 hour to obtain a coating for a surface resistance layer having a viscosity of 9 mPa · s. The compression rate of the elastic particles used was 5%.

  The compression ratio of the elastic particles is the particle diameter when the load is unloaded using a micro compression tester MCTM / MCTE (manufactured by Shimadzu Corporation) and the elastic particles are compressed until a load of 0.0098 N is applied. The amount of displacement was expressed as a percentage and was taken as the compression rate.

  The surface resistance layer coating material was applied to the base layer resistance layer material by dipping at a lifting speed of 300 mm / min, air-dried for 30 minutes, then dipped again with the axis direction reversed and dried in the same manner. Subsequently, it dried at 160 degreeC for 1 hour, and obtained the charging member 1 whose thickness of a surface resistance layer is 20 micrometers.

  The charging member 1 had a current value of 250 μA and a ten-point average roughness Rz of 1 μm. The charging member 1 had a surface hardness of 55 ° and a contact change rate of 1.1 times.

  The current value of the charging member is determined by contacting the conductive substrate and the metal in a state where the charging member is brought into contact with a cylindrical metal drum using springs having a spring pressure of 4.9 N (500 g) at both ends and rotated. A voltage of DC 200V was applied between the drums, and the voltage applied to the resistor connected in series with the metal drum was measured to obtain the current value of the charging roller.

  The ten-point average roughness Rz was measured for a total of six points, 3 in the axial direction and 2 in the circumferential direction, using Surfcoder SE3400 (manufactured by Kosaka Laboratory) based on the surface roughness of JIS B0601-1994. Averaged. The surface hardness was measured with a micro rubber hardness meter MD-1 type A (manufactured by Kobunshi Keiki Co., Ltd.) in the state of the charging member.

  The ratio (Sa) of the actual contact area in the nip width between the charging member and the member to be charged is the spring having a spring pressure of 0.49 N or 1000 g when the charging member is a glass cylindrical drum having the same shape as the member to be charged. Was used for both ends, and the contact state was observed. The nip portion is observed from the inside of the cylindrical drum using a CCD camera, and the ratio (B / A = Sa) of the sum (B) of the actual contact area (B) to the total area (A) of the entire nip portion is set to 0.49 N load. The ratio Sa (1000 g) / Sa (0.49 N) was calculated for each load of 1000 g, and the change rate of contact was taken.

  Using the charging member 1, a contact charging device 1 schematically illustrated in FIG. In this embodiment, a photosensitive drum covered with an OPC photosensitive member is used. A charging member was pressed against the photosensitive drum by using a spring having a spring pressure of 4.9 N (500 g) at both ends to make contact.

  As for the contact charging device using the charging member 1, the toner is used at the initial stage of actual use under the two conditions of the peripheral speed of the photosensitive member of 47 mm / s and 94 mm / s, and after endurance of 20,000 sheets and 80000 sheets at 94 mm / s. An image due to adhesion of etc. was observed. The results are shown in Table 1. A DC voltage of −1500 V was applied to the charging member 1 in the contact charging device.

Here, the evaluation of the occurrence of abnormal images is
◯: In the halftone image, there are no black spots due to poor charging.
Δ: In the halftone image, although black spots are generated due to charging failure, there is no problem in actual use.
X: In a halftone image, black spots are generated due to defective charging.
It was.

  When the charging member 1 is mounted on the electrophotographic apparatus 1 and image evaluation is performed, the initial image and continuous paper passing at a peripheral speed of 47 mm / s and a peripheral speed of 94 mm / s are not problematic for actual use. Black spots due to slight charging failure were observed.

  From the above, it can be seen that the charging member 1 has no problem in actual use and has good image characteristics.

<Example 2>
As a coating for the surface resistance layer, 150 parts of a lactone-modified acrylic polyol having a solid content of 70% and a hydroxyl value of 90% (trade name: Plaxel DC2009), 500 parts of methyl isobutyl ketone, 0.05 part of silicone oil (SH28PA), 30 parts of conductive tin oxide powder (SN-100P), non-crosslinked acrylic particles (trade name: M-100, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) as elastic particles are divided into an average particle size of 18 μm using an elbow jet. 30 parts of spherical elastic particles were blended and dispersed for 6 hours with a paint shaker. 12.5 parts of isophorone diisocyanate nurate type (Vestanat B1370) and 8 parts of hexamethylene diisocyanate nurate type (Duranate TPA-B80E) were mixed with 370 parts of the resulting dispersion, stirred for 1 hour with a ball mill, and a viscosity of 8 mPa.s. -The coating material for surface resistance layers of s was obtained. The compression rate of the elastic particles used was 5%.

  The coating material for the surface resistance layer was applied to the base layer resistance layer material obtained in the same manner as in Example 1 in the same manner to produce a charging member 2 having a surface resistance layer thickness of 15 μm.

  The charging member 2 had a current value of 150 μA and a ten-point average roughness Rz of 18 μm. The charging member 2 had a surface hardness of 40 ° and a contact change rate of 10 times.

  When the charging member 2 was mounted on the electrophotographic apparatus 1 and image evaluation was performed, a good image was obtained with an initial image at peripheral speeds of 47 mm / s and 94 mm / s. Although there was no problem, an image due to adhesion of toner or the like was observed.

  From the above, it can be seen that the charging member 2 has no problem in actual use and has good image characteristics.

<Example 3>
As a coating for the surface resistance layer, 150 parts of a lactone-modified acrylic polyol having a solid content of 70% and a hydroxyl value of 90% (trade name: Plaxel DC2009), 500 parts of methyl isobutyl ketone, 0.05 part of silicone oil (SH28PA), 30 parts of conductive tin oxide powder (SN-100P), 30 parts of non-crosslinked acrylic particles (M-100) as elastic particles, and 30 parts of elastic particles with an average particle size of 15 μm using elbow jet, paint Dispersed for 6 hours on a shaker. 18 parts of isophorone diisocyanate nurate type (Vestanat B1370) and 12 parts of hexamethylene diisocyanate nurate type (Duranate TPA-B80E) were mixed with 370 parts of the resulting dispersion, stirred for 1 hour with a ball mill, and a viscosity of 10 mPa · s. A coating for the surface resistance layer was obtained. The compression rate of the elastic particles used was 5%.

  The coating material for the surface resistance layer was applied to the base layer resistance layer material obtained in the same manner as in Example 1 in the same manner to prepare the charging member 3 having a surface resistance layer thickness of 25 μm.

  The charging member 3 had a current value of 160 μA and a ten-point average roughness Rz of 10 μm. The charging member 3 had a surface hardness of 45 ° and a contact change rate of 8 times.

  When the charging member 3 was mounted on the electrophotographic apparatus 1 and image evaluation was performed, a good image was obtained with an initial image at peripheral speeds of 47 mm / s and 94 mm / s. Although there was no problem, an image due to adhesion of toner or the like was observed.

  From the above, it can be seen that the charging member 3 has no problem in actual use and has good image characteristics.

<Example 4>
As a coating for a surface resistance layer, 150 parts of a lactone-modified acrylic polyol (trade name: Plaxel DC2009) having a solid content of 70% and a hydroxyl value of 90%, 500 parts of methyl isobutyl ketone, and 0 of silicone oil (SH28PA) as a leveling agent .05 parts, 30 parts of conductive tin oxide powder (SN-100P), 30 parts of elastic particles obtained by dividing non-crosslinked acrylic particles (M-200) as elastic particles into an average particle size of 6 μm using an elbow jet Blended and dispersed for 6 hours in paint shaker. 25 parts of the isophorone diisocyanate nurate type (Bestanat B1370) and 16 parts of the hexamethylene diisocyanate nurate type (Duranate TPA-B80E) were mixed with 370 parts of the resulting dispersion, stirred for 1 hour with a ball mill, and a viscosity of 9 mPa · s. A coating for the surface resistance layer was obtained. The compression rate of the elastic particles used was 5%.

  The coating material for the surface resistance layer was applied to the base layer resistance layer material obtained in the same manner as in Example 1 in the same manner to produce the charging member 4 having a surface resistance layer thickness of 18 μm.

  The charging member 4 had a current value of 160 μA and a ten-point average roughness Rz of 4 μm. The charging member 4 had a surface hardness of 53 ° and a contact change rate of 1.5 times.

  When the charging member 4 was mounted on the electrophotographic apparatus 1 and image evaluation was performed, good initial images were obtained at peripheral speeds of 47 mm / s and 94 mm / s. In continuous paper passing, no abnormal image due to adhesion of toner or the like is observed up to 20000 sheets after paper passing, but in 80000 sheets, there is no problem in actual use, but images due to slight adhesion of toner or the like are observed. It was done.

  From the above, it can be seen that the charging member 4 has no problem in actual use and has good image characteristics.

<Example 5>
As a coating for a surface resistance layer, 150 parts of a lactone-modified acrylic polyol (trade name: Plaxel DC2009) having a solid content of 70% and a hydroxyl value of 90%, 500 parts of methyl isobutyl ketone, and 0 of silicone oil (SH28PA) as a leveling agent .05 parts, 30 parts of conductive tin oxide powder (SN-100P), urethane particles (trade name: CZ-400, manufactured by Negami Kogyo Co., Ltd.) as elastic particles, and an average particle diameter of 8 μm using an elbow jet 30 parts of the divided elastic particles were mixed and dispersed for 6 hours with a paint shaker. 18 parts of the isophorone diisocyanate nurate type (Bestanat B1370) and 12 parts of the hexamethylene diisocyanate nurate type (Duranate TPA-B80E) were mixed with 370 parts of the resulting dispersion, stirred for 1 hour with a ball mill, and a viscosity of 9 mPa · s. A coating for the surface resistance layer was obtained. The compression rate of the elastic particles used was 12%.

  The coating material for the surface resistance layer was applied to the base layer resistance layer material obtained in the same manner as in Example 1 in the same manner, and the charging member 5 having a surface resistance layer thickness of 15 μm was prepared.

  The charging member 5 had a current value of 160 μA and a ten-point average roughness Rz of 6 μm. The charging member 5 had a surface hardness of 50 ° and a contact change rate of 4 times.

  When the charging member 5 was mounted on the electrophotographic apparatus 1 and image evaluation was performed, good initial images were obtained at peripheral speeds of 47 mm / s and 94 mm / s. In continuous paper passing, no abnormal image due to adhesion of toner or the like is observed up to 20000 sheets after paper passing, but in 80000 sheets, there is no problem in actual use, but images due to slight adhesion of toner or the like are observed. It was done.

  From the above, it can be seen that the charging member 5 has no problem in actual use and has good image characteristics.

<Example 6>
As a coating for a surface resistance layer, 150 parts of a lactone-modified acrylic polyol (trade name: Plaxel DC2009) having a solid content of 70% and a hydroxyl value of 90%, 500 parts of methyl isobutyl ketone, and 0 of silicone oil (SH28PA) as a leveling agent .05 parts, 30 parts of conductive tin oxide powder (SN-100P), urethane particles (trade name: C-800, manufactured by Negami Kogyo Co., Ltd.) as elastic particles using an elbow jet to an average particle size of 8 μm 30 parts of the divided elastic particles were blended and dispersed for 6 hours with a paint shaker. 22 parts of isophorone diisocyanate nurate type (Vestanat B1370) and 14 parts of hexamethylene diisocyanate nurate type (Duranate TPA-B80E) were mixed with 370 parts of the resulting dispersion, stirred for 1 hour with a ball mill, and a viscosity of 9 mPa · s. A coating for the surface resistance layer was obtained. The compression rate of the elastic particles used was 32%.

  The coating material for the surface resistance layer was applied to the base layer resistance layer material obtained in the same manner as in Example 1 in the same manner, and the charging member 6 having a surface resistance layer thickness of 18 μm was prepared.

  The charging member 6 had a current value of 160 μA and a ten-point average roughness Rz of 6 μm. The charging member 6 had a surface hardness of 55 ° and a contact change rate of 8 times.

  When the charging member 6 was mounted on the electrophotographic apparatus 1 and image evaluation was performed, good initial images were observed at peripheral speeds of 47 mm / s and 94 mm / s. In the continuous paper passing test, good images were obtained even at 80000 sheets.

  From the above, it can be seen that the charging member 6 has good image characteristics.

<Example 7>
As a coating for a surface resistance layer, 150 parts of a lactone-modified acrylic polyol (trade name: Plaxel DC2009) having a solid content of 70% and a hydroxyl value of 90%, 500 parts of methyl isobutyl ketone, and 0 of silicone oil (SH28PA) as a leveling agent .05 parts, conductive tin oxide powder (SN-100P) 30 parts, hollow porous acrylic particles (M-610 Matsumoto Yushi Seiyaku Co., Ltd.) as elastic particles, spheroidized to an average particle size of 5 μm using elbow jet 30 parts of the resulting elastic particles were blended and dispersed for 6 hours with a paint shaker. 20 parts of the isophorone diisocyanate nurate type (Bestanat B1370) and 13 parts of the hexamethylene diisocyanate nurate type (Duranate TPA-B80E) were mixed with 370 parts of the resulting dispersion, stirred for 1 hour with a ball mill, and a viscosity of 9 mPa · s. A coating for the surface resistance layer was obtained. The compression rate of the elastic particles used was 12%.

  The coating material for the surface resistance layer was applied to the base layer resistance layer material obtained in the same manner as in Example 1 in the same manner to produce a charging member 7 having a surface resistance layer thickness of 15 μm.

  The charging member 7 had a current value of 200 μA and a ten-point average roughness Rz of 3 μm. The charging member 7 had a surface hardness of 50 ° and a contact change rate of 4 times.

  When the charging member 7 was mounted on the electrophotographic apparatus 1 and image evaluation was performed, good initial images were obtained at both peripheral speeds of 47 mm / s and 94 mm / s. In continuous paper feeding, images due to adhesion of toner and the like and abnormal images due to poor charging did not occur up to 80000 sheets after paper feeding.

  From the above, it can be seen that the charging member 7 has good image characteristics.

<Comparative Example 1>
As a coating for a surface resistance layer, 150 parts of a lactone-modified acrylic polyol (trade name: Plaxel DC2009) having a solid content of 70% and a hydroxyl value of 90%, 500 parts of methyl isobutyl ketone, and 0 of silicone oil (SH28PA) as a leveling agent .05 parts, 30 parts of conductive tin oxide powder (SN-100P), 30 parts of crosslinked acrylic particles (trade name: MBX-8, Sekisui Plastics Co., Ltd.) having an average particle diameter of 8 μm as elastic particles, and paint shaker For 6 hours. 25 parts of the isophorone diisocyanate nurate type (Bestanat B1370) and 16 parts of the hexamethylene diisocyanate nurate type (Duranate TPA-B80E) were mixed with 370 parts of the resulting dispersion, stirred for 1 hour with a ball mill, and a viscosity of 9 mPa · s. A coating for the surface resistance layer was obtained. The compression rate of the elastic particles used was 2%.

  The coating material for the surface resistance layer was applied to the base layer resistance layer material obtained in the same manner as in Example 1 in the same manner to produce a charging member 8 having a surface resistance layer thickness of 18 μm.

  The charging member 8 had a current value of 130 μA and a ten-point average roughness Rz of 7 μm. The charging member 8 had a surface hardness of 55 ° and a contact change rate of 1.01.

When the charging member 8 was mounted on the electrophotographic apparatus 1 and image evaluation was performed, an image due to a charging failure was observed at a peripheral speed of 47 mm / s, although there was no problem in actual use, but charging was performed at 94 mm / s. The uniformity of the image could not be maintained due to the defect. In continuous paper passing, image failure and charging failure due to toner adhesion occurred on 20000 and 80000 paper after passing <Comparative Example 2>
As a coating for the surface resistance layer, 150 parts of a lactone-modified acrylic polyol having a solid content of 70% and a hydroxyl value of 12% (Placcel DC2026 Daicel Chemical Industries), 500 parts of methyl isobutyl ketone and 0 of silicone oil (SH28PA) as a leveling agent .05 parts, 30 parts of conductive tin oxide powder (SN-100P), 30 parts of urethane particles (trade name: C-800, manufactured by Negami Kogyo Co., Ltd.) as elastic particles, and dispersed for 6 hours with a paint shaker did. 4 parts of the isophorone diisocyanate nurate type (Vestanat B1370) and 2 parts of the hexamethylene diisocyanate nurate type (Duranate TPA-B80E) were mixed with 370 parts of the resulting dispersion, stirred for 1 hour with a ball mill, and a viscosity of 9 mPa · s. A coating for the surface resistance layer was obtained. The compression rate of the elastic particles used was 32%.

  The coating material for the surface resistance layer was applied to the base layer resistance layer material obtained in the same manner as in Example 1 in the same manner to produce a charging member 9 having a surface resistance layer thickness of 15 μm.

  The charging member 9 had a current value of 150 μA and a ten-point average roughness Rz of 7 μm. The charging member 9 had a surface hardness of 38 ° and a contact change rate of 13 times.

  When the charging member 9 was mounted on the electrophotographic apparatus 1 and image evaluation was performed, an image due to a charging failure was observed at a peripheral speed of 47 mm / s, although there was no problem in actual use, but charging was performed at 94 mm / s. The uniformity of the image could not be maintained due to the defect. Further, in continuous paper passing, image defects and charging defects due to toner adhesion occurred on 20000 sheets and 80000 sheets after paper passing.

The block diagram of the contact charging device to which the charging member of this invention is applied. Schematic of contact between a conventional charging member and a photosensitive drum. Schematic of contact between a conventional charging member and a photosensitive drum. 1 is a configuration diagram of an electrophotographic apparatus to which a charging member of the present invention is applied. Schematic of the contact part of the charging member of this invention and a to-be-charged body. The schematic sectional drawing of the contact part of the charging member of this invention and a to-be-charged body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Contact charging device 2 Charging member 3 Power supply 5 Conductive base | substrate (core metal)
6 Resistance layer 7 Base resistance layer 8 Surface resistance layer 10 Charged body (photosensitive body, photosensitive drum)
11 Photosensitive drum base 12 Photosensitive layer 13 Nip part (nip area)
31 Developing Device 32 Transfer Member 33 Fixing Device 34 Cleaner 61 High Hardness Particle 62 Concave L Laser Light f1 Abutting Force A Total Area of the Nip Part b Actual Contact Part in the Nip Part B Actual Contact Area in the Nip Part Area)

Claims (7)

  In the charging member that charges the member to be charged, when the surface hardness of the charging member is 40 ° or more and the contact force to the member to be charged is increased from 0.49 N to 19.6 N, the charging member The ratio (B / A = Sa) of the sum (B) of the actual contact area in the nip portion with the member to be charged and the area (A) of the entire nip portion is {Sa (19.6N) / Sa (0. 49N)} and is 1.1 times or more and 10 times or less.   The charging member has a structure in which a resistance layer is coated on a conductive substrate, and the hardness of the base layer resistance layer excluding the surface resistance layer located on the surface of the charging member is 50 according to JIS K6253: 1997. The charging member according to claim 1, wherein the charging member is at least °.   The charging member according to claim 1, wherein the charging member has a surface roughness of 4 μm or more and 15 μm or less in terms of a ten-point average roughness Rz based on JIS B0601-1994.   The charging member has a structure in which a resistance layer is coated on a conductive substrate, the surface resistance layer located on the surface of the charging member is made of elastic particles, a binder resin, and conductive particles, and 0.0098 N of the elastic particles. The charging member according to any one of claims 1 to 3, wherein a compressibility by a load is 10% or more and 50% or less of a particle diameter.   The charging member according to claim 1, wherein the charging member has a surface hardness of 50 ° to 55 °.   6. The charging member according to claim 4, wherein the elastic particles are made of a spherical resin made of a hollow porous material.   A charging device comprising the charging member according to claim 1.

Images