JP2008216827A - Conductive particle and conductive member containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide conductive particles for obtaining a conductive member that has high wear resistance and high selflubricity, and to provide conductive members, such as a conductive roller and conductive sheet, which contain the conductive particles. <P>SOLUTION: The conductive particle 23 has a conductive layer 232 on the surface of an ultrahigh molecular weight polyethylene resin particle 231. The conductive member is a conductive roller, conductive sheet, or the like, in which an insulation material such as a rubber layer 22 contains the conductive particles 23. The wear resistance and selflubricity of the ultrahigh molecular weight polyethylene resin of the conductive particles make it possible to form a conductive member that has excellent wear resistance and high selflubricity, and prolong the lifetime. In addition, it is used to form a chargeable roller or sheet having a required electric resistance characteristic and improves the reliability of an image forming apparatus. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to conductive particles, and in particular, conductive particles suitable for forming conductive members such as charging rollers and developing rollers used in image forming apparatuses such as electrophotographic laser printers, copying machines, and facsimiles, and the like. It is related with the electroconductive member containing this.

  In the electrophotographic image forming apparatus, conductive rollers such as a developing roller, a charging roller, and a transfer roller are disposed along the circumference of the photosensitive drum, as will be apparent from the description of examples described later. The charging roller charges the surface of the photosensitive drum by applying a predetermined potential. The developing roller charges the developing toner adhering to the surface, and the developing toner adheres to the electrostatic latent image formed on the photosensitive drum by the exposure unit to make it visible. The transfer roller uses electrostatic force to transfer the developing toner formed on the photosensitive drum onto the sheet. Some image forming apparatuses use a transfer sheet formed in a belt shape instead of the transfer roller.

All of these rollers and sheets are required to have a charging property on the surface or a region close to this, and for this reason, the rollers and sheets are formed as conductive rollers or conductive sheets having required electric resistance characteristics. This type of roller or sheet is usually formed of a relatively flexible material such as rubber or resin in order to obtain a highly adhesive contact with the photosensitive drum or the like. A resistance layer is formed on the surface region of the sheet, and in order to form this resistance layer, a conductive material or conductive particles are contained in the base material of the rubber or resin constituting the roller or the sheet to obtain conductivity. Yes. For example, in Patent Document 1, a rubber roller includes conductive particles obtained by coating the surface of mother particles made of an organic polymer material such as low density polyethylene, high density polyethylene, epoxy resin, and polyester with a conductive material such as carbon black. ing. In addition, as a similar technique, in Patent Document 2, conductive composite particles obtained by coating the surface of mother particles made of an oxide or ceramic such as silica or titanium oxide with a conductive material such as carbon black or graphite are used as the resistance layer of the roller. Included.
JP 2003-162106 A Japanese Patent Laid-Open No. 2006-133591

  When this type of roller or sheet is rotated or moved in contact with the photosensitive drum or other member or paper, the surface of the roller or sheet is worn at the contact surface, and the conductive particles contained in the roller or sheet. Is exposed on the surface. At this time, since the wear resistance of the organic polymer material such as high-density polyethylene, epoxy resin, and polyester described above serving as the base particle of the conductive particles of Patent Document 1 is low, the conductive particles are also worn, and the charging property is high. The life of the image forming apparatus as a roller is shortened, for example, by deteriorating the image quality. On the other hand, since silica, ceramics, and the like, which are the base particles of the conductive particles of Patent Document 2, have high hardness, when the conductive particles are exposed to the surface due to wear of the surface of the roller or the sheet, the photosensitive material that comes into contact with the roller or the sheet is exposed. The drum and other members are damaged and the image quality is deteriorated. In addition, since the base particles of the conductive particles of Patent Documents 1 and 2 are both low in self-lubricating property, they have a large physical resistance upon contact with the photosensitive drum and other members, and smooth rotation and rotation are possible. The problem of being disturbed arises. Further, since the self-lubricating property is low, the developing toner adheres to the surface of the roller or the sheet, which causes fogging and smudges in the formed image.

  An object of the present invention is to provide conductive particles for improving wear resistance and obtaining a highly self-lubricating conductive member, and a conductive member such as a conductive roller or a conductive sheet containing the conductive particle. To do.

  The conductive particles of the present invention are characterized by having a conductive layer on the surface of ultrahigh molecular weight polyethylene resin particles. Moreover, the electroconductive member of this invention contains the electroconductive particle concerning the said this invention in an insulating material, It is characterized by the above-mentioned. For example, rubber or resin is used as the insulating material. The conductive member of the present invention is configured as a roller or a sheet.

  According to the conductive particles of the present invention, it is possible to form a conductive member having excellent wear resistance and high self-lubricating property due to the wear resistance and self-lubricating property of the ultrahigh molecular weight polyethylene resin. Long life can be realized. In addition, according to the conductive member of the present invention, when a chargeable conductive roller or conductive sheet having the required electrical resistance characteristics containing conductive particles is formed, the wear resistance and self-lubricating property are improved. An excellent conductive roller or conductive sheet can be realized.

  The conductive particles of the present invention are formed by coating carbon black or other conductive material on the surface of spherical or nearly spherical base particles made of ultrahigh molecular weight polyethylene resin. In addition, when the conductive member of the present invention is configured as a charging roller, a developing roller, a transfer roller, a transfer sheet, or the like of an image forming apparatus, a high-quality apparatus that suppresses a decrease in image quality of the image forming apparatus is realized. it can.

  Next, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an electrophotographic image forming apparatus. A charging roller 2, an exposure device 3, a developing device 4 having a developing roller 5, and a transfer roller 6 along the circumference of a cylindrical photosensitive drum 1. A cleaner device 7 is provided. The charging roller 2 charges the surface of the photosensitive drum 1 by applying a predetermined potential V1. The developing roller 5 is charged by applying a predetermined potential V2, and the developing toner is charged and adhered to the surface. Then, an electrostatic latent image formed by optically drawing a required pattern on the photosensitive drum 1 by the exposure device 3 including a laser scanning device is attached to the electrostatic latent image to be visualized. The transfer roller 6 is charged by the applied predetermined potential V3, and the developing toner formed on the photosensitive drum 1 is transferred onto the paper P using the electrostatic force. Further, the developing toner remaining on the surface of the photosensitive drum 1 is removed by the cleaner device 7. Here, the charging roller 2, the developing roller 5, and the transfer roller 6 are each configured as a conductive roller according to the present invention.

FIG. 2 is a cross-sectional view of the charging roller 2 representatively showing the conductive roller according to the present invention. A conductive shaft 21 made of a good conductor typified by metal such as iron, copper, and stainless steel, and the conductive shaft 21 A rubber layer 22 is integrally formed around the periphery to form a roll body having a required diameter. The rubber layer 22 is made of synthetic rubber such as natural rubber or EPDM (ethylene propylene rubber). The rubber layer 22 contains a large number of conductive particles 23 as shown in the schematic diagram partially enlarged in the same figure, and the volume resistance of the rubber layer 22 is 1 by the conductive particles 23. Conductivity of × 10 to 1 × 10 ¹⁰ Ω · cm is imparted.

  As shown in the enlarged view in FIG. 2, the conductive particles 23 are composed of mother particles 231 and a conductive layer 232 formed on the surface of the mother particles 231. The mother particle 231 is made of ultra high molecular weight polyethylene resin, and is formed in a spherical shape having a particle size of about 1 to 50 μm or a polygonal body close thereto. The conductive layer 232 is made of carbon black and is coated on the surface of the mother particle 231. The rubber layer 22 is formed by mixing the conductive particles 23 in a suspended state in a rubber material before curing. Moreover, the value of the volume resistance of the rubber layer 22 to be formed can be adjusted by adjusting the particle size and the amount of the conductive particles 23 to be contained, that is, the density of the conductive particles 23 in the rubber layer 22. For example, when used for each roller of the image forming apparatus as in the first embodiment, the volume ratio of the conductive particles 23 in the rubber material is preferably 10 to 80%.

  In the charging roller 2 configured as described above, the surface of the rubber layer 22 is brought into contact with the surface of the photosensitive drum 1 with a required pressing force when disposed in the image forming apparatus shown in FIG. It is configured to be rotationally driven in the same surface direction at the surface speed. In addition, a predetermined voltage (for example, DC voltage) V1 is applied to the conductive shaft 21 of the charging roller 2, and an electric field due to this potential reaches the surface through the conductive particles 23 in the rubber layer 22, and thus contacts the surface. The surface of the photosensitive drum 1 is charged to a predetermined magnetic potential.

  Further, the developing roller 5 formed in the same structure as the charging roller 2 is not shown, but the surface of the rubber layer is in contact with the surface of the photosensitive drum 1, and the predetermined potential V2 applied to the conductive shaft. As a result, the surface of the rubber layer is charged, and the developing toner loaded in the developing device 4 is electrostatically adsorbed to charge the developing toner. Then, the developing toner accompanying the rotation of the developing roller 5 is attached to the electrostatic latent image formed on the surface of the photosensitive drum 1 by an electrostatic force to be visualized.

  Further, the transfer roller 6 formed in the same manner as the charging roller 2 is not shown in the figure, but the surface of the rubber layer is in contact with the surface of the photosensitive drum 1 with a required pressing force. A sheet P is supplied between the first sheet and the second sheet. The transfer roller 6 is charged on the surface of the rubber layer by a predetermined potential V3 applied to the conductive shaft, and the developing toner adhering to the surface of the photosensitive drum 1 is transferred onto the surface of the paper P by the electrostatic force generated by the charging.

As described above, the charging roller 2, the developing roller 5, and the transfer roller 6 are rotationally driven while being in contact with the photosensitive drum 1 and the paper P after the surface of the rubber layer is charged by the applied potential. The surface of the rubber layer of each roller is worn by friction. However, in each roller of Example 1, as described in the charging roller 2 shown in FIG. 2, the conductive particles 23 included in the rubber layer 22 have the base particles 231 formed of an ultra high molecular polyethylene resin. This ultra-high molecular weight polyethylene resin has an average molecular weight of 5 million or more and is extremely large compared to the molecular weight of 5 to 500,000 of ordinary high-density polyethylene resin. It has wear resistance, self-lubricity, chemical resistance, and low temperature characteristics. In addition, it has various characteristics such as non-water absorption, and is particularly excellent in wear resistance and self-lubrication. That is,
(A) Abrasion resistance: 6 times that of a fluororesin, 5 times that of a nylon resin, and several times that of a polymer resin such as a normal polymer polyethylene.
(B) Self-lubricating property: The sliding property is equivalent to that of a fluororesin and higher than that of a normal polymer resin.

  Therefore, even when the charging roller 2 is worn on the surface of the rubber layer 22, the progress of wear is suppressed by the wear resistance of the ultra-high molecular polyethylene resin constituting the conductive particles 23. Further, the self-lubricating property of the ultra-high molecular weight polyethylene resin constituting the conductive particles 23 enables smooth rotation of the roller on the contact surface with the photosensitive drum 1. Similarly, the developing roller 5 and the transfer roller 6 can be wear-resistant and smoothly rotated. Further, the developing roller is prevented from adhering to the transfer roller 6 by self-lubricating property. As a result, the charging roller 2, the developing roller 5, and the transfer roller 6 of the first embodiment maintain a good contact state with each surface of the photosensitive drum 1 and the paper P while maintaining a state suitable for charging. Image formation becomes possible.

  FIG. 3 is a configuration diagram of Example 2 in which the conductive member of the present invention is applied to a transfer sheet of an image forming apparatus. The parts equivalent to those in FIG. The transfer sheet 6A is disposed on the downstream side in the rotation direction of the developing device 4 at a part of the circumference of the photosensitive drum 1, and is formed in an endless belt shape with a resin such as polyimide resin or polycarbonate resin (here, 3 This is rotated around a guide roller 9 and is in contact with the photosensitive drum 1 in a part of the rotation direction. Further, an electrostatic transfer device 8 is provided inside a portion in contact with the photosensitive drum 1, and the developing toner attached to the surface of the photosensitive drum 1 is transferred to the transfer sheet 6 </ b> A by electrostatic force. In the transfer sheet 6A, the sheet P is pressed by the pressing roller 10 on the side opposite to the photosensitive drum 1, and the developing toner transferred to the transfer sheet 6A is transferred to the sheet P. At the time of this transfer, the sheet P may be charged by a predetermined potential applied to the pressing roller 10 and transferred by an electrostatic force.

As shown in a perspective view in which a part of the transfer sheet 6A is broken in FIG. 4, the transfer sheet 6A is composed of a rubber sheet or a resin sheet. The conductive particles 23 are included in the structure to form a conductive sheet. That is, the conductive particles 23 are composed of mother particles 231 and a conductive layer 232 formed on the surface of the mother particles 231 as shown in an enlarged cross section in FIG. The mother particle 231 is made of a super high molecular weight polyethylene resin having a spherical shape with a particle size of about 1 to 50 μm or a polygonal shape close to this. The conductive layer 232 is made of carbon black and is coated on the surface of the mother particle 231 as in the first embodiment. By mixing the conductive particles 23 in a suspended state in the rubber or resin forming the transfer sheet 6A, the conductive sheet 23 is configured as a conductive sheet having a volume resistance of 1 × 10 to 1 × 10 ¹⁰ Ω · cm.

  In Example 2, as shown in FIG. 4, a thin strip-shaped guide tape 61 is integrally bonded in an endless manner to regions along both ends of the inner surface of the transfer sheet 6A. 61 is fitted in the concave grooves 9a provided at both ends of the peripheral surface of the guide roller 9, so that when the transfer sheet 6A is rotated, the position is moved in the direction of the rotation axis of the guide roller 9, so-called meandering. It is possible to prevent. The guide tape 61 is formed by, for example, forming a polyurethane resin in a strip shape having a thickness of about 1 mm and a width of about 5 mm, and affixing it to the inner surface of the transfer sheet 6A using a double-sided tape or the like.

  The transfer sheet 6A of Example 2 is in a situation where wear due to contact with the photosensitive drum 1 or wear due to contact with the guide roller 9 proceeds, but the conductive material contained in the rubber or resin constituting the sheet. The progress of wear is suppressed by the wear resistance of the ultra-high molecular weight polyethylene resin constituting the conductive particles 23. As a result, it is possible to maintain a good contact state with the surface of the photosensitive drum 1, the guide roller 9, and the paper P while maintaining a state suitable for charging, and a high-quality image can be formed. Further, due to the self-lubricating property of the ultra-high molecular polyethylene resin constituting the conductive particles 23, the transfer sheet 6A can be smoothly rotated by contact with the photosensitive drum 1, the guide roller 9, and the paper P. Further, the self-lubricating property of the transfer sheet 6A by the conductive particles 23 of the ultra high molecular polyethylene resin prevents the development toner from being fixed, and the development toner remaining on the transfer sheet after transfer can be suitably removed. It becomes possible.

  In the above description, the first embodiment applies the present invention to a rubber roller, but the present invention can also be applied to a resin roller. The present invention is not limited to the conductive roller or conductive sheet for the image forming apparatus, and the present invention is similarly applied to any conductive roller or sheet having conductivity or other shape. Is possible.

  In Examples 1 and 2, the conductive particles of the present invention are contained in the entire rubber or resin. However, the conductive member of the present invention has a resistance layer only on the surface region of the insulating material such as rubber or resin. It is also possible to form and form the resistance layer to contain the conductive particles of the present invention.

1 is a conceptual configuration diagram of an image forming apparatus according to Embodiment 1. FIG. It is an expanded sectional view of a charging roller and conductive particles. FIG. 3 is a conceptual configuration diagram of an image forming apparatus according to a second exemplary embodiment. It is an expanded sectional view of a transfer sheet and conductive particles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Exposure apparatus 4 Developing apparatus 5 Developing roller 6 Transfer roller 6A Transfer sheet 7 Cleaner apparatus 8 Electrostatic transfer device 9 Guide roller 10 Press roller 21 Conductive shaft 22 Rubber layer (insulating material)
23 conductive particles 231 mother particles (ultra high molecular weight polyethylene resin)
232 Conductive layer 61 Guide tape P Paper

Claims (3)

  Conductive particles comprising a conductive layer on the surface of ultrahigh molecular weight polyethylene resin particles.   The electroconductive member characterized by including the electroconductive particle of Claim 1 in an insulating material. The conductive member according to claim 2, wherein the insulating material is rubber or resin and is configured as a roller or a sheet.

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