JP2007093885A - Conductive member and process cartridge having the same, and image forming apparatus having process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive member capable of uniformly charging the surface of an image carrier and improving durability while holding a stable gap between the image carrier and the conductive member in the beginning of the use of the conductive member and even in its use for a long period of time. <P>SOLUTION: The conductive member 10 has a conductive support 1, an electrical resistance adjusting layer 2 formed on the conductive support 1, and gap-holding members 4, 4 force-fitted to both ends of the electrical resistance adjusting layer 2. In the conductive member 10, the outer peripheral face of each of gap-holding members 4, 4 has a level difference with respect to the peripheral face of the electrical resistance adjusting layer 2 so that when the outer peripheral faces of the gap-holding members 4 are brought into contact with the image carrier, the gap of a fixed interval is formed between the outer peripheral face of the image carrier and the outer peripheral face of the conductive member 10. A difference between the maximum outer diameter and minimum outer diameter of each of the gap-holding members 4, 4 is set to 20 μm or less by annealing the gap-holding member 4, 4 before and after the members 4 are force-fitted to the conductive support 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive member used in an image forming apparatus such as a copying machine, a laser beam printer, and a facsimile, a process cartridge having the conductive member, and an image forming apparatus having the process cartridge.

  In an electrophotographic image forming apparatus such as a conventional electrophotographic copying machine, laser printer, or facsimile, a charging member that charges an image bearing member (photosensitive drum) and toner on the photosensitive member As a transfer member that performs the transfer process, a conductive member is used. FIG. 8 is an explanatory diagram of an electrophotographic image forming apparatus having a conventional charging roller.

  In FIG. 8, reference numeral 120 denotes a conventional electrophotographic image forming apparatus. A conventional electrophotographic image forming apparatus 120 includes an image carrier 101 on which an electrostatic latent image is formed, a charging roller 102 that performs charging processing in contact with the image carrier 101, an exposure unit 103 such as a laser beam, and an image. A developing roller 104 for attaching toner to the electrostatic latent image on the carrier 101, a power pack 105 for applying a DC voltage to the charging roller 102, and a transfer roller for transferring the toner image on the image carrier 101 to the recording paper 107 106, a cleaning device 108 for cleaning the image carrier 101 after the transfer process, and a surface potential meter 109 for measuring the surface potential of the image carrier 101.

  The conventional electrophotographic image forming apparatus 120 is a process cartridge detachable apparatus. That is, in the conventional electrophotographic image forming apparatus 120, the process equipment including the image carrier 101, the charging roller 102, the developing roller 104, and the cleaning device 108 can be detachably attached to the main body of the image forming apparatus. The process cartridge 110 is used. The process cartridge 110 only needs to include at least the image carrier 101 and the charging roller 102. The process cartridge 110 is connected to a drive system and an electrical system on the image forming apparatus main body side by being mounted at a predetermined position on the image forming apparatus. In FIG. 8, functional units normally required in other electrophotographic processes are omitted because they are not required in this specification.

  Next, a basic image forming operation of the conventional electrophotographic image forming apparatus 120 will be described.

  When a DC voltage is supplied from the power pack 105 to the charging roller 102 in contact with the image carrier 101, the surface of the image carrier 101 is uniformly charged to a high potential. Immediately after that, when image light is irradiated onto the surface of the image carrier 101 by the exposure means 103, the potential of the irradiated portion of the image carrier 101 decreases. It is known that such a charging mechanism to the surface of the image carrier 101 by the charging roller 102 is discharge according to Paschen's law in a minute space between the charging roller 102 and the image carrier 101.

  Since the image light has a light amount distribution according to white / black of the image, when the image light is irradiated, the potential distribution corresponding to the recorded image on the surface of the image carrier 101 by the irradiation of the image light, that is, An electrostatic latent image is formed. When the portion of the image carrier 101 on which the electrostatic latent image is formed in this way passes through the developing roller 104, toner adheres according to the level of the potential, and a toner image that visualizes the electrostatic image is formed. Is done. The recording paper 107 is conveyed to a portion of the image carrier 101 on which the toner image is formed by a registration roller (not shown) at a predetermined timing, and overlaps the toner image. Then, after the toner image is transferred to the recording paper 107 by the transfer roller 106, the recording paper 107 is separated from the image carrier 101. The separated recording paper 107 is conveyed through a conveyance path, heated and fixed by a fixing unit (not shown), and then discharged outside the apparatus. When the transfer is completed in this manner, the surface of the image carrier 101 is cleaned by the cleaning device 108, and residual charges are removed by a quenching lamp (not shown), so that the next image forming process is performed. Prepared for.

A conventional charging method using a charging roller includes a contact charging method in which a charging roller is brought into contact with an image carrier (see Patent Documents 1 and 2). ,
(1) The substance constituting the charging roller oozes out from the charging roller, and this adheres to the surface of the object to be charged and leaves a charging roller mark.
(2) When an AC voltage is applied to the charging roller, the charging roller that is in contact with the member to be charged vibrates, so that a charging noise is generated.
(3) Since the toner on the image carrier adheres to the charging roller (particularly, the above-mentioned oozing out makes toner adhesion more likely), so that the charging performance of the charging roller is reduced.
(4) the substance constituting the charging roller adheres to the image carrier, and
(5) The charging roller is permanently deformed when the image carrier is stopped for a long time.
There was a problem.

  As a technique for solving such a problem, a charging device using a proximity charging method (see Patent Documents 3 and 4) in which a charging roller is brought close to an image carrier has been proposed. In the charging device using the proximity charging method, the image bearing member is charged by applying a voltage to the charging roller with the charging roller facing the image bearing member at a closest distance (50 to 300 μm). It is a thing. In the charging device using the proximity charging method, the roller and the image carrier are not in contact with each other. Therefore, the substance constituting the charging roller, which has been a problem in the conventional charging device using the contact charging method, is transferred to the image carrier. There is no problem of adhesion or permanent deformation when the image carrier is stopped for a long time. Further, in the charging device using the proximity charging method, the toner adhering to the charging roller is reduced, so that the toner or the like on the image carrier is less likely to adhere to the charging roller. Therefore, it can be said that the charging device using the proximity charging method is an excellent charging device.

  In the charging device using the proximity charging method described in Patent Documents 3 and 4, spacer ring layers are provided at both ends of the charging roller in order to maintain a gap between the charging roller and the image carrier. However, since these charging devices using the proximity charging method have not been devised to precisely set the gap, the gap varies due to variations in the dimensional accuracy of the charging roller and the spacer ring. There is a problem in that the potential fluctuates, so that the toner adheres to a white background during image formation and an image defect occurs.

  In order to solve such a problem, a charging device (see Patent Document 5) provided with a tape-shaped gap holding means having a predetermined thickness has been proposed, but this tape-like gap holding means is provided. When the charging device is used for a long period of time, the tape-shaped gap holding means is worn, and the toner enters and adheres between the charging roller and the tape-shaped gap holding means. There was a problem that a gap could not be maintained between the surface and the surface of the charging roller. Further, in the charging device provided with the tape-like gap holding means, the thickness of the tape-like gap holding means varies, so the gap between the surface of the image carrier and the surface of the charging roller can be formed with high accuracy. There was also a problem that it was not possible.

  Moreover, in order to solve such a problem, the electroconductive member as shown in FIG. 9 (refer patent document 6) was proposed. The conductive member (charging member) 210 includes a conductive support 201, an electric resistance adjustment layer 202 formed on the conductive support 201, and a void holding formed at both ends of the electric resistance adjustment layer 202. Member 203. The gap holding member 203 is made of a thermoplastic resin that satisfies (b) durometer hardness: HDD30 to HDD70, and (b) wear mass of a Taber type abrasion tester: 10 mg / 1000 cycles or less. . In addition, a technique for precisely controlling the gap between the image bearing member and the charging roller by simultaneously removing the gap holding member 203 and the electric resistance adjusting layer 202 (see Patent Document 7) is also proposed. It was done.

However, in order to control the gap between the image carrier and the conductive member (charging roller) with high accuracy, the surface layer is not formed on the outer surface of the electric resistance adjusting layer even if integrated removal processing such as cutting is performed. If the heat curing treatment is performed on the coating material after the coating is performed, there is a problem that it is impossible to maintain a highly accurate controlled gap between the gap holding member and the electric resistance adjusting layer by an integrated removal process such as cutting. It was. Further, when the conductive support comes into contact with the image carrier, the contact area is reduced, so that the accuracy of the gap between the conductive support (charging roller) and the image carrier is lowered. It was.
JP-A 63-149668 JP-A-1-267667 Japanese Patent Laid-Open No. 3-240076 JP-A-4-358175 JP 2002-139893 A JP 2004-354477 A JP-A-2005-91818

  The present invention aims to solve this problem.

  That is, the present invention can maintain a stable gap between the image carrier and the conductive member even when used for an initial period and a long period of time, and can uniformly charge the surface of the image carrier and is durable. It is an object of the present invention to provide a conductive member with improved performance, a process cartridge having the conductive member, and an image forming apparatus having the process cartridge.

  The present inventors apply a surface layer on the outer surface of the electric resistance adjusting layer, and then perform a heat curing process on the outer surface of the electric resistance adjusting layer. As a result of intensive studies on the cause of the problem that it becomes impossible to maintain a highly precisely controlled gap, the internal strain accumulated when the gap holding member is molded and when the gap holding member is pressed into the conductive support is The stress of the internal strain is released by heat such as heat hardening of the gap holding member of the applied surface layer, the gap holding member slightly fluctuates, and the gap holding member that has been integrally removed by cutting, grinding, etc. It has been found that the shape is changed, so that a highly accurately controlled gap cannot be maintained between the gap holding member and the electric resistance adjusting layer. Therefore, the present inventors have a conductive support having a conductive support, an electric resistance adjusting layer formed on the conductive support, and a gap holding member press-fitted into both ends of the electric resistance adjusting layer. When the outer peripheral surface of the gap holding member is in contact with the image carrier, a gap having a constant interval is formed between the outer peripheral surface of the image carrier and the outer peripheral surface of the conductive member. In the conductive member in which the height difference between the outer peripheral surface of the gap holding member and the outer peripheral surface of the electrical resistance adjusting layer is provided, the gap holding member before being press-fitted into the conductive support is annealed. The void holding member is subjected to an annealing treatment after being subjected to the treatment and press-fitted into the conductive support, and the outer diameter of the gap holding member is obtained by the annealing treatment before the press-fitting into the conductive support and the annealing treatment after the press-fitting. When the difference between the maximum diameter and the minimum diameter is within 20μm Even when used for the initial and long term, the surface of the image carrier can be uniformly charged while maintaining a stable gap between the image carrier and the conductive member, and the durability can be improved. The present inventors have found that a conductive member can be provided and have completed the present invention.

That is, in order to achieve the above object, the invention described in claim 1 is a conductive support, an electric resistance adjustment layer formed on the conductive support, and both ends of the electric resistance adjustment layer. A conductive member having a gap holding member press-fitted into the outer peripheral surface of the image carrier and the outer circumference of the conductive member when the outer circumferential surface of the gap holding member abuts on the image carrier. In the conductive member provided with a difference in height with respect to the outer peripheral surface of the electric resistance adjusting layer on the outer peripheral surface of the gap holding member, so that a gap with a constant interval is formed between the surface and the surface.
The difference between the maximum diameter and the minimum diameter of the outer diameter of the gap holding member is within 20 μm by the annealing treatment before press-fitting the gap holding member into the conductive support and the annealing treatment after press-fitting. It is an electroconductive member characterized by these.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, the resin material forming the gap holding member is made of a synthetic resin having low moisture absorption and wear resistance. To do.

  The invention described in claim 3 is the invention described in claim 2, wherein the resin material is a resin material selected from high density polyethylene and high molecular weight polyethylene.

  The invention described in claim 4 is characterized in that, in the invention described in claim 2 or 3, the gap holding member is formed by molding a synthetic resin.

  The invention described in claim 5 is the invention described in any one of claims 1 to 4, wherein a difference in height of an outer peripheral surface of the gap holding member with respect to an outer peripheral surface of the electric resistance adjusting layer is the conductivity. Integral by removal processing such as cutting and grinding applied to the outer peripheral surface of the gap holding member installed on the conductive support and the outer peripheral surface of the electric resistance adjusting layer provided on the conductive support It is formed by processing.

  The invention described in claim 6 is characterized in that, in the invention described in any one of claims 1 to 5, a surface layer is formed on the electric resistance adjusting layer.

  The invention described in claim 7 is characterized in that, in the invention described in any one of claims 1 to 6, the conductive member has a cylindrical shape.

  The invention described in claim 8 is the invention described in any one of claims 1 to 7, wherein the conductive member is a charging member.

  According to a ninth aspect of the present invention, there is provided a process cartridge characterized in that the charging member according to the eighth aspect of the present invention is provided so as to be disposed close to a member to be charged.

  According to a tenth aspect of the present invention, there is provided an image forming apparatus having the process cartridge according to the ninth aspect.

  According to the invention described in claim 1, the maximum diameter and the minimum diameter of the outer diameter of the gap holding member are obtained by the annealing treatment before press-fitting the gap holding member into the conductive support and the annealing treatment after press-fitting. The difference between the distance between the image bearing member and the image carrier is improved, so that when the space is formed in contact with the image carrier, the contact area is increased and the surface is stabilized. The gap can be maintained, so that the surface of the image carrier can be uniformly charged by maintaining a stable gap between the image carrier and the conductive member even in the initial and long-term use. In addition, it is possible to provide a conductive member with improved durability.

  According to the second and third aspects of the present invention, since the resin material forming the gap holding member is composed of a synthetic resin having low hygroscopicity and wear resistance, the gap holding member serves as an image carrier. It can be prevented from being damaged, and toner can be prevented from adhering to the gap holding member.

  According to the invention described in claim 4, since the gap holding member is formed by molding a synthetic resin, the productivity of the gap holding member can be increased.

  According to the invention described in claim 5, the difference in height of the outer peripheral surface of the gap holding member with respect to the outer peripheral surface of the electric resistance adjusting layer is the outer peripheral surface of the gap holding member installed on the conductive support. And the outer peripheral surface of the electric resistance adjusting layer provided on the conductive support are formed by an integrated process by a removing process such as a cutting process or a grinding process. The difference in height with the resistance adjustment layer can be formed by integrated processing. For this reason, fluctuation (shake) of the gap formed between the outer peripheral surface of the image carrier and the outer peripheral surface of the conductive member is reduced. Thus, the accuracy of the gap can be further increased.

  According to the invention described in claim 6, since the heat-cured surface layer is formed on the electric resistance adjusting layer, the toner, the toner additive and the like are electrically conductive members over time. It is possible to prevent the amount of voids and electrical characteristics from changing due to adhesion to the surface, and to improve the fixability of the surface layer.

  According to the seventh aspect of the present invention, since the conductive member has a cylindrical shape, the conductive member can be rotated. For this reason, continuous discharge from the same location is prevented, thereby extending the life. be able to.

  According to the eighth aspect of the present invention, since the conductive member according to any one of the first to seventh aspects is used as a charging member, the charging member charges the surface of the image carrier in a non-contact manner. For this reason, the charging member can be prevented from being contaminated, and the charging member can be made of a hard material, so that the accuracy can be increased. Therefore, uneven charging can be prevented.

  According to the ninth aspect of the present invention, since the charging member according to the eighth aspect is a process cartridge provided so as to be disposed close to the member to be charged, a stable image quality can be obtained over a long period of time. In addition, the replacement can be simplified by the user maintenance.

  According to the invention described in claim 10, since the image forming apparatus having the process cartridge described in claim 9 is used, an image with high reliability and high image quality can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a conductive member (charging roller) showing an embodiment of the present invention. FIG. 2 is an explanatory view showing a method of forming a conductive member (charging roller) according to an embodiment of the present invention, wherein FIG. The shape after the removal processing such as cutting and grinding is performed on the surface is shown. (B) is a heat curing treatment on the surface layer formed on the outer peripheral surface of the electrical resistance adjusting layer subjected to the removal processing. (C) shows the shape after the heat curing treatment is applied to the surface layer formed on the outer peripheral surface of the electrical resistance adjusting layer that has been subjected to the removal process. FIG. 3 is an enlarged explanatory view of the gap holding member, where (a) shows the maximum outer diameter and the minimum outer diameter of the gap holding member before the surface layer is heat-cured, and (b) The maximum outer diameter and the minimum outer diameter of the gap holding member after the surface layer is heat-cured are shown. FIG. 4 shows an outer diameter generated when a gap holding member made of high-density polyethylene before being pressed into a conductive support in a conductive member (charging roller) showing an embodiment of the present invention is annealed. (A) shows the relationship between the annealing temperature [° C.] and the φ outer diameter shrinkage [mm] when the annealing time is set to a constant time: 60 minutes, and (b) ) Shows the relationship between the annealing time [min and φ outer diameter shrinkage [mm] when the annealing temperature is a constant temperature: 120 ° C. FIG. 5 is a schematic diagram showing a state in which a conductive member (charging roller) is disposed on the image carrier. FIG. 6 is an explanatory diagram of an image forming apparatus showing an embodiment of the present invention. FIG. 7 is an explanatory view showing a measurement location of the outer diameter of the gap holding member in the conductive member (charging roller) obtained in the example and the comparative example.

  In FIG. 1, reference numeral 10 denotes a conductive member (charging roller). The conductive member (charging roller) 10 includes a conductive support 1, an electric resistance adjustment layer 2 formed on the conductive support 1, and a gap held by being pressed into both ends of the electric resistance adjustment layer 2. As shown in FIG. 5, the conductive member (charging roller) 10 has an outer peripheral surface of the gap holding members 4, 4 as the image carrier 5. The outer peripheral surfaces of the gap holding members 4, 4 are formed such that gaps G are formed at regular intervals between the outer peripheral surface of the image carrier 5 and the outer peripheral surface of the conductive member 10. Further, a height difference is provided with respect to the outer peripheral surface of the electric resistance adjusting layer 2. The conductive member (charging roller) 10 is formed on the outside of the gap holding members 4, 4 by annealing treatment before press-fitting the gap holding members 4, 4 into the conductive support 1 and annealing treatment after press-fitting. The difference between the maximum diameter and the minimum diameter [see (b) in FIG. ] Within 20 μm. In the present invention, the press-fitted gap holding members 4 and 4 are used over a long period of time by applying an adhesive between this and the electric resistance adjusting layer 2 or between this and the conductive support 1. In this case, it is possible to avoid the gap holding members 4 and 4 from being detached.

  The conductive member (charging roller) 10 of the present invention is manufactured through the following steps, for example. That is, the conductive member (charging roller) 10 according to the present invention is, as shown in FIG. 2, (a) annealing the gap holding members 4 and 4 before being pressed into the conductive support 1. After press-fitting into the conductive support 1, the gap holding members 4 and 4 are annealed, and then the outer peripheral surface of the gap holding members 4 and 4 and the outer peripheral surface of the electric resistance adjusting layer 2 are cut and ground. (B) forming the surface layer 3 on the outer peripheral surface of the electrical resistance adjusting layer 2 that has been subjected to removal processing such as cutting and grinding, and (c) cutting and grinding. The electrical resistance adjusting layer 2 that has been subjected to the removal process such as heating is heated and subjected to a heat curing process on the surface layer 3 formed on the outer peripheral surface thereof. Remove the gap retaining member before applying (i.e., cutting, grinding, etc.) The gap holding members 4, 4 have the shape shown in FIG. 3A, and the gap holding members 4, after the surface layer 3 is heat-cured and simultaneously annealed to the gap holding members 4, 4. 4 has the shape shown in FIG.

  There has been no conventional conductive member (charging roller) in which the difference between the maximum diameter and the minimum diameter of the gap holding member is within 20 μm. However, in the present invention, the gap holding member before being press-fitted into the conductive support is annealed and the gap holding member is also annealed after being pressed into the conductive support. , 4 by the annealing treatment before press-fitting into the conductive support and the annealing treatment after press-fitting can make the difference between the maximum diameter and the minimum diameter of the gap holding members 4 and 4 within 20 μm. It was. As in the prior art, when the difference between the maximum outer diameter and the minimum diameter of the gap holding members 4 and 4 exceeds 20 μm, the flatness of the gap holding members 4 and 4 deteriorates and comes into contact with the image carrier 5. When the gap G is formed, the contact area is increased, so that the stable gap G cannot be maintained. However, according to the present invention, the maximum diameter and the maximum outer diameter of the gap holding members 4 and 4 can be prevented. Since the difference from the small diameter is within 20 μm, the flatness of the gap holding members 4, 4 is improved. For this reason, when the gap G is formed in contact with the image carrier 5, the contact area becomes wide. Thus, the stable gap G can be maintained.

  Therefore, as in the present invention, the maximum diameter of the outer diameters of the gap holding members 4 and 4 is obtained by the annealing treatment before press-fitting the gap holding members 4 and 4 into the conductive support and the annealing treatment after press-fitting. When the difference from the minimum diameter is within 20 μm, the flatness of the gap holding members 4, 4 is improved. Therefore, when the gap G is formed in contact with the image carrier 5, the contact area is reduced. By increasing the width, a stable gap G can be maintained. Therefore, even when used for an initial period and for a long period of time, the stable gap G is maintained between the image carrier 5 and the conductive member 10, and the image carrier is maintained. The surface of the body 5 can be uniformly charged, and the conductive member 10 with improved durability can be provided.

Various resin materials can be used as the gap holding members 4 and 4. As a necessary characteristic of the material constituting the gap holding members 4, 4, an insulating material is preferable, and a volume resistivity is preferably 10 ¹³ Ω · cm or more. The reason why electrical insulation is necessary is to eliminate the occurrence of a short-circuit current with the base layer of the image carrier 5. In addition, the gap G with the image carrier 5 is stably maintained over a long period (time). For this purpose, a material having low hygroscopicity and wear resistance is preferable. The resin material for forming such gap holding members 4 and 4 is preferably made of a synthetic resin having low hygroscopicity and wear resistance. The resin material that constitutes the gap retaining members 4 and 4 is appropriately selected according to various conditions, but is preferably polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), polystyrene. (PS), a polystyrene copolymer (AS, ABS), a resin material selected from PC, polyurethane, and a fluororesin, and more preferably a resin material selected from high-density polyethylene and high-molecular-weight polyethylene. . Thus, when the resin material forming the gap holding members 4 and 4 is made of a synthetic resin having low hygroscopicity and wear resistance, the gap holding members 4 and 4 may damage the image carrier 5. In addition, the toner can be prevented from adhering to the gap holding members 4 and 4.

  In the present invention, the gap holding members 4 and 4 are preferably formed by a molding process such as injection molding or extrusion molding of a synthetic resin. As described above, when the gap holding members 4 and 4 are formed by molding a synthetic resin, the productivity of the gap holding members 4 and 4 can be increased.

  The present inventors have experimented and investigated the change in outer diameter that occurs when an annealing treatment is performed on a single gap holding member made of high-density polyethylene before being pressed into the conductive support in the conductive member (charging roller). As shown in FIG. 4 (a), the outer diameter shrinkage increases as the annealing temperature increases (that is, the shrinkage change increases), and the outer diameter shrinkage increases as the annealing time increases. Was constant (that is, the shrinkage change was saturated when the annealing time was longer than 60 minutes).

  FIG. 5 is a schematic diagram showing a state in which a conductive member (charging roller) is disposed on the image carrier. As shown in FIG. 5, the conductive member 10 is disposed in contact with the image carrier 5 with an arbitrary pressure. The gap holding members 4 and 4 are formed in a non-image forming area excluding the image forming area. In this state, the image carrier 5 can be charged by applying a voltage to the conductive member (charging roller) 10. When the conductive member 10 is used as a transfer member, it can be performed in the same manner. The gap G between the conductive member (charging roller) 10 and the image carrier 5 needs to be kept at a predetermined value, and is preferably 100 μm or less. When the gap G becomes large, electrical deterioration and abnormal discharge of the image carrier 5 are likely to occur, so it is necessary to increase the voltage application condition to the conductive member 10.

  Further, as shown in FIG. 5, in the present invention, the height difference of the outer peripheral surface of the gap holding members 4, 4 with respect to the outer peripheral surface of the electric resistance adjusting layer 2 is on the conductive support 1. Integral by removal processing such as cutting and grinding applied to the outer peripheral surface of the installed gap holding members 4 and 4 and the outer peripheral surface of the electric resistance adjusting layer 2 provided on the conductive support 1 It is formed by processing. As described above, the difference in height between the outer peripheral surfaces of the gap holding members 4 and 4 with respect to the outer peripheral surface of the electrical resistance adjusting layer 2 is the outer peripheral surface of the gap holding members 4 and 4 installed on the conductive support 1. And the gap holding member 4 when formed integrally by removal processing such as cutting and grinding applied to the outer peripheral surface of the electrical resistance adjusting layer 2 provided on the conductive support 1. , 4 and the electric resistance adjusting layer 2 can be formed by integral processing. For this reason, a gap formed between the outer peripheral surface of the image carrier 5 and the outer peripheral surface of the conductive member 10 is formed. The accuracy (gap) of G can be reduced to further increase the accuracy of the gap G.

The electric resistance adjusting layer 2 in the present invention is formed of a thermoplastic resin composition containing a polymer type ion conductive material. The volume resistivity of the electric resistance adjusting layer 2 is preferably 10 ⁶ to 10 ⁹ Ωcm. When the volume resistivity of the electric resistance adjusting layer 2 exceeds 10 ⁹ Ωcm, charging ability and transfer capability are insufficient, and when the volume resistivity of the electric resistance adjusting layer 2 is less than 10 ⁶ Ωcm, image holding is performed. Leakage due to voltage concentration on the entire body 5 occurs. The thermoplastic resin used for the thermoplastic resin is not particularly limited, but is preferably polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), polystyrene (PS), and polystyrene. It is a thermoplastic resin selected from copolymers (AS, ABS), or a thermoplastic resin selected from polycarbonate (PC), polyacetal, polyurethane, and fluororesin.

  The polymer ion conductive material is preferably a resin mainly composed of polyetheresteramide. As described above, when the polymer ion conductive material is a resin having a polyether ester amide as a main component, the resin having the polyether ester amide as a main component is uniformly blended in the thermoplastic resin. Leakage to the image carrier (photoconductor) 5 does not occur, bleeding out to the surface hardly occurs, and electric resistance due to poor dispersion as seen in a composition in which a conductive agent such as carbon black is dispersed. There is no variation in value. In general, when a conductive agent such as carbon black is used, the electric charge is discharged to the image carrier through the carbon black, so that minute discharge unevenness due to the dispersion state of the carbon black is likely to occur, and the image quality is improved. Hinder. In particular, this phenomenon becomes significant when a high voltage is applied.

  The blending ratio of the thermoplastic resin and the polymer ion conductive material is preferably 30 to 70% by weight of the thermoplastic resin and 70 to 30% by weight of the polymer ion conductive material. With such a blending ratio, the electric resistance value of the electric resistance adjusting layer 2 can be set to a desired value. There is no restriction | limiting in particular about the manufacturing method of the semiconductive resin composition which comprises the electrical resistance adjustment layer 2, It can manufacture easily by melt-kneading the mixture of each material with a biaxial kneader, a kneader, etc. The electric resistance adjusting layer 2 is easily formed on the conductive support 1 by covering the conductive support 1 with the semiconductive resin composition by a molding means such as extrusion molding or injection molding. be able to.

If only the electric resistance adjusting layer 2 is formed on the conductive support 1 to form the conductive member 10, toner or the like may adhere to the electric resistance adjusting layer 2 and the performance may deteriorate. Such a problem can be eliminated by forming the surface layer 3 on the electric resistance adjusting layer 2. The electric resistance value of the surface layer 3 is formed so as to be larger than that of the electric resistance adjusting layer 2, thereby avoiding voltage concentration and abnormal discharge (leakage) on the defect portion of the image carrier 5. . However, if the electric resistance value of the surface layer 3 is too high, the charging ability and the transfer ability will be insufficient, so the difference in electric resistance value between the surface layer 3 and the electric resistance adjusting layer 2 should be 10 ³ Ωcm or less. Is preferred. As a material for forming the surface layer 3, a thermoplastic resin is preferable in that the film-forming property is good. Such a thermoplastic resin is preferably a thermoplastic resin such as a fluororesin, a silicone resin, a polyamide resin, or a polyester resin that is excellent in non-adhesiveness and excellent in terms of preventing toner sticking. Moreover, since such a thermoplastic resin is electrically insulating, the electrical resistance of the surface layer 3 is adjusted by dispersing various conductive materials. The surface layer 3 is formed on the electric resistance adjusting layer 2 by, for example, dispersing a thermoplastic resin constituting the surface layer 3 in an organic solvent to prepare a coating material, and coating by spray coating, dipping or the like. The film thickness is preferably about 10 to 30 μm.

  Since the electric resistance adjusting layer 2 and the gap holding members 4 and 4 adjacent to the electric resistance adjusting layer 2 are made of a thermoplastic resin, they are formed by a molding process such as injection molding or extrusion molding. Then, after the gap holding members 4 and 4 are press-fitted into the end portions of the electric resistance adjusting layer 2, the outer surfaces of the gap holding members 4 and 4 and the outer surface of the electric resistance adjusting layer 2 are integrally removed. And finish cutting to provide a step for setting a certain gap.

  In the present invention, the surface layer 3 is applied on the electric resistance adjusting layer 2. The fixing of the surface layer 3 is performed by curing the resin constituting the surface layer 3 by heating. Thus, when the surface layer 3 is heat-cured, the fixability of the surface layer 3 is improved.

  In general, in the heat curing of the surface layer 3, the electric resistance adjusting layer 2 and the gap holding members 4 and 4 are also heated. As described above, when the electrical resistance adjusting layer 2 and the gap holding members 4 and 4 are heated, a highly accurate gap G is formed by the integrated removal processing of the electrical resistance adjusting layer 2 and the gap holding members 4 and 4. Even if it exists, since the internal strain accumulated at the time of forming the gap holding members 4, 4 or processing such as the installation of the gap holding members 4, 4 is released by heat, the gap G slightly fluctuates. In addition, a highly accurate gap G cannot be maintained. Further, since the contact area decreases when the conductive member (charging roller) 10 contacts the image carrier 5, the accuracy of the gap G between the conductive member (charging roller) 10 and the image carrier 5 is reduced. There will be problems with stability and reliability during long-term use.

  Therefore, in the present invention, the gap holding members 4 and 4 formed in an arbitrary shape in advance by molding means such as injection molding and extrusion molding are annealed at a predetermined temperature for a predetermined time and the gap holding member 4 is used. , 4 are also annealed again at a predetermined temperature and within a predetermined time for the gap holding members 4 and 4 in a state where they are installed by press-fitting at both ends of the conductive support 1. Then, the gap holding members 4 and 4 and the electric resistance adjusting layer 2 are integrally removed, and subsequently, the surface layer 3 is applied to the outer surface of the electric resistance adjusting layer 2, and then the surface layer 3 is subjected to heat curing treatment. Apply.

  The stress at the time of molding and the stress at the time of processing can be relieved by these two annealing processes. In addition, it is possible to maintain the gap G with high accuracy even in a situation where heat is applied to the gap holding member in the heating process at the manufacturing stage. In the present invention, the step to be formed is 40 μm. This is because the larger the distance between the charging member and the image carrier during charging, the more serious the generation of ozone, NOx, etc. due to corona charging.

  In the present invention, the shapes of the conductive member 10 and the image carrier 5 are not particularly limited, and the image carrier 5 can take either a belt shape or a cylindrical shape. The electroconductive member 10 described in any one of Claims 1-7, Preferably, it is a cylindrical shape. When the conductive member 10 and the image carrier 5 are rotated in a cylindrical shape, continuous discharge from the same location can be prevented, and therefore chemical degradation of the surface due to energization stress can be reduced. . For example, as shown in FIG. 5, the rotation direction of the conductive member 10 can be selected in the same direction as the image carrier 5 or in the opposite direction. It is also possible to make a difference in peripheral speed from the image carrier 5 (rotate faster than image carrier 5 or rotate slower). In addition, intermittent rotation with respect to the rotation of the image carrier 5 is possible within a range where the function is not impaired. The gap G between the conductive member 10 and the image carrier 5 needs to be kept at a predetermined value, and is preferably 100 μm or less. This is because when the gap G becomes large, it is necessary to increase the voltage application condition to the conductive member 10, and electrical deterioration and abnormal discharge of the image carrier 5 are likely to occur.

  The conductive member 10 described in any one of claims 1 to 7 is preferably a charging member. Thus, when the conductive member 10 according to any one of claims 1 to 7 is a charging member, the charging member can charge the surface of the image carrier 5 in a non-contact manner. In addition to preventing the charging member from being soiled, the charging member can be made of a hard material, so that the accuracy can be increased, and thus uneven charging can be prevented.

  The conductive member (charging member) 10 described in claim 8 is a detachable process cartridge (see 110 in FIG. 8) provided so as to be disposed close to the member to be charged. As described above, when the process cartridge is provided so that the conductive member (charging member) 10 according to claim 8 is disposed close to the member to be charged, stable image quality can be obtained over a long period of time, and In addition, user maintenance is possible and simplified.

  In the present invention, an image forming apparatus having the process cartridge (see 110 in FIG. 8) according to claim 9 is provided. Thus, when the image forming apparatus having the process cartridge according to the ninth aspect is used, an image with high reliability and high image quality can be obtained.

  As shown in FIG. 6, in the image forming apparatus of the present invention, a paper feed unit 22 at the lower part of the apparatus main body, an image forming unit having the image carrier 5 above it, and a paper discharge unit above it. A pair of paper discharge rollers 26 and 27 are provided, and an image is formed by the image forming unit corresponding to the left side surface of the transfer paper P fed from the paper feed unit 22, and the transfer paper P is discharged. The rollers 26 and 27 are discharged to the bin tray 20 or the discharge tray 21. The paper feed unit 22 is provided with trays 28 and 29 in two upper and lower stages, and a paper feed roller 30 is provided in each of the paper feed stages. Reference numeral 23 denotes a writing unit which irradiates light onto the uniformly charged surface of the image carrier 5 to write an image there. Further, a registration roller pair 13 for correcting the skew of the transfer paper and matching the transfer timing of the image on the image carrier 5 and the transfer paper is provided upstream of the image carrier 5 in the transfer paper transport direction. Provided.

  Further, a fixing unit 25 is provided on the downstream side in the transfer paper conveyance direction with respect to the image carrier 5. As shown in FIG. 6, the image carrier 5 is provided in the image forming section so as to be rotatable in the direction of arrow A, and a charging device (see 102 in FIG. 8) is disposed around the image carrier 5. A developing device (see 104 in FIG. 8) that visualizes the electrostatic latent image on the image carrier 5 written by the writing unit 23 on the surface charged by the charging device to form a toner image, and the developing device. A transfer conveyance belt 6 for transferring the toner image onto the transfer paper P, a cleaning device for removing residual toner remaining on the image carrier 5 after the transfer of the toner image (see 108 in FIG. 8), and an image carrier. A neutralizing lamp (not shown) for neutralizing unnecessary charges on the unit 5 is provided. In this image forming apparatus, when an image forming operation is started, the image carrier 5 shown in FIG. 6 rotates in the direction of arrow A, and the surface thereof is neutralized by a neutralizing lamp and averaged to a reference potential. Next, the surface of the image carrier 5 is uniformly charged by a charging roller (see 102 in FIG. 8), and the charged surface is irradiated with light according to image information from the writing unit 23. An electrostatic latent image is formed there. When the latent image is moved to the position of the developing device (see 104 in FIG. 8) by rotating the image carrier 5 in the direction indicated by the arrow A, the toner is attached by the developing sleeve (not shown). As a result, a toner image (visualized image) is formed.

  On the other hand, the transfer paper P is fed from one of the trays 28 and 29 of the paper feed unit 22 shown in FIG. 6 by the paper feed roller 30, and is temporarily stopped by the pair of registration rollers 13. The leading edge and the leading edge of the image on the image carrier 5 are conveyed at an accurate timing, and the toner image on the image carrier 5 is transferred onto the transfer paper P by the transfer conveyance belt 6. The transfer paper P is transported by the transfer transport belt 6, and is separated from the transfer transport belt 6 by the curvature separation by the waist of the transfer paper P by the driving roller unit 6a, and transported to the fixing unit 25, where heat and pressure are transferred. Is added to the transfer paper P, and the toner is discharged to a designated paper discharge location, that is, one of the paper discharge tray 21 and the bin tray 20. Thereafter, the residual toner remaining on the image carrier 5 rotates and moves to a cleaning position which is the next process, and is scraped off by a cleaning blade (see 108 in FIG. 8) of the cleaning device, and again in the next image forming process. Move on.

  In the present embodiment, the description has been mainly given of the charging roller in which the conductive member 10 is embodied. However, the conductive member 10 in the present invention may be used as a toner carrier or a transfer member as long as it does not contradict the object of the present invention. Absent.

Example 1
50% by weight of ABS resin (Denka ABS GR-0500, manufactured by Denki Kagaku Kogyo Co., Ltd.) and 50% by weight of polyether ester amide (IRGASTAT P18, manufactured by Ciba Specialty Chemicals Co., Ltd.) are used as a resin composition. After blending 4.5 parts by weight of a polycarbonate-glycidyl methacrylate-styrene-acrylonitrile copolymer (Modifier CL440-G, manufactured by NOF Corporation) with 100 parts by weight of the product, these are melt-kneaded to obtain a melt-kneaded resin composition, This melt-kneaded composition was coated on a 10 mm outer conductive support (core shaft) made of nickel-plated sulfur free cutting steel (SUM) by injection molding, and an electric resistance adjusting layer (volume resistivity: 2. 1 × 10 ⁸ Ωcm) was formed. Then, a high-density polyethylene resin (Novatech PP HY540, manufactured by Nippon Polychem) is injection-molded into a ring shape, and the injection-molded gap retaining member is annealed at 120 ° C. for 1 hour in an oven, and injection-molded. The distortion of time was removed. Next, the gap holding member subjected to the annealing treatment is inserted and bonded to both ends of the electric resistance adjusting layer, and the gap holding member inserted and bonded to both ends of the electric resistance adjusting layer is annealed at 120 ° C. for 1.5 hours. It applied in oven and removed the distortion at the time of shaping | molding of an electrical resistance adjustment layer, and the process distortion at the time of insertion of a space | gap holding member. Next, simultaneous finishing was performed by cutting so that the outer diameter (maximum diameter) of the gap holding member was 12.7 mm and the outer diameter of the electric resistance adjusting layer was 12.6 [see FIG. Thereafter, a resin composition comprising an acrylic silicone resin (3000 VH-P, manufactured by Kawakami Paint Co., Ltd.), an isocyanate curing agent, and carbon black (30% by weight with respect to the total solid content) is formed on the surface of the electric resistance adjusting layer. Spray coating is performed to form a surface layer having a thickness of about 10 μm [see FIG. 2 (b). Subsequently, the surface layer was heat-cured at 80 ° C. for 1 hour in an oven to obtain a conductive member having a finished product level difference of 40 ± 10 μm.

(Example 2)
A conductive member was obtained in the same manner as in Example 1 except that the gap holding member inserted and bonded to both ends of the electric resistance adjusting layer was annealed at 120 ° C. for 1 hour in an oven.

(Example 3)
The injection-molded gap holding member is annealed at 120 ° C. for 0.5 hour in the oven, and the gap holding member inserted and bonded to both ends of the electric resistance adjusting layer is heated at 120 ° C. for 1 hour. A conductive member was obtained in the same manner as in Example 1 except that it was applied inside.

(Comparative Example 1)
50% by weight of ABS resin (Denka ABS GR-0500, manufactured by Denki Kagaku Kogyo Co., Ltd.) and 50% by weight of polyether ester amide (IRGASTAT P18, manufactured by Ciba Specialty Chemicals Co., Ltd.) are used as a resin composition. After blending 4.5 parts by weight of a polycarbonate-glycidyl methacrylate-styrene-acrylonitrile copolymer (Modifier CL440-G, manufactured by NOF Corporation) with 100 parts by weight of the product, these are melt-kneaded to obtain a melt-kneaded resin composition, This melt-kneaded composition was coated on a 10 mm outer conductive support (core shaft) made of nickel-plated sulfur free cutting steel (SUM) by injection molding, and an electric resistance adjusting layer (volume resistivity: 2. 1 × 10 ⁸ Ωcm) was formed. Then, a high-density polyethylene resin (Novatech PP HY540, manufactured by Nippon Polychem) is injection-molded into a ring shape to form a gap holding member. Simultaneous finishing was performed with the outer diameter (maximum diameter) of the holding member being 12.7 mm and the outer diameter of the electric resistance adjusting layer being 12.6. Next, after finishing the outer diameter (maximum diameter) of the gap holding member to 12.7 mm and the outer diameter of the electric resistance adjusting layer to 12.6 by cutting, acrylic silicone is applied to the surface of the electric resistance adjusting layer. A resin composition consisting of a resin (3000 VH-P, manufactured by Kawakami Paint Co., Ltd.), an isocyanate curing agent, and carbon black (30% by weight with respect to the total solid content) is spray coated to form a surface layer having a thickness of about 10 μm. Subsequently, the surface layer was heat-cured at 80 ° C. for 1 hour in an oven to obtain a conductive member.

(Comparative Example 2)
A conductive member was obtained in the same manner as in Comparative Example 1 except that polyacetal resin (Iupital V20-HE, manufactured by Mitsubishi Enginiering Co., Ltd.) was used as the gap retaining member.

(Comparative Example 3)
A conductive member was obtained in the same manner as in Comparative Example 1 except that ABS resin (Denka ABS GR-3000, manufactured by Denki Kagaku Kogyo Co., Ltd.) was used as the gap retaining member.

  As described above, the following Test 1 and Test 2 were performed on the electric resistance adjusting layers of the conductive members obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

(Test 1)
About 10 conductive members (samples) obtained in Examples 1 to 3 and Comparative Examples 1 to 3, immediately after providing a predetermined step by integral removal processing, and after heat-curing and conditioning the surface layer for a predetermined time The outer diameter of the gap holding member was measured with a laser measuring device. Measurement points were measured at a total of five locations (see FIG. 7), two on the left and right at a pitch of 0.75 mm from the center position of the gap holding member, and the difference between the maximum diameter and the minimum diameter was confirmed.

(Test 2)
Each of the two conductive members (samples) obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are mounted on the image forming apparatus shown in FIG. 8, and applied voltages are DC = −800 V, AC = 2400 Vpp (frequency = 2 kHz) and the state of the gap holding member after passing 600,000 sheets was evaluated. The evaluation environment was 23 ° C. and 60% RH, and PxP toner (particle diameter 5 μm) was used as the evaluation toner.

  The evaluation results are shown in the following Table 1.

The overall judgment in Table 1 is
○: No problem in practical use
×: Things that have practical problems
It was.

  Table 1 shows the following. That is, in Examples 1 to 3, the difference between the maximum and minimum outer diameters in the gap holding member as the fluctuation of the gap holding member before and after the heat curing of the surface layer is about 15 μm, and the maximum deviation exceeds 20 μm. The thing could not be confirmed. The meaning of having an outer diameter difference of 20 μm in this test is considering the tolerance from the formation step of 40 ± 10 μm. Further, toner adhesion was not observed on both the gap holding member and the surface layer.

  On the other hand, in Comparative Examples 1 to 3, there was no one in which the maximum deviation of the maximum outer diameter and the minimum outer diameter of the gap holding member was within 20 μm. The reason for this is that due to insufficient annealing of the gap holding member, the gap holding member is released from the internal distortion due to the heat of the heat curing process of the paint resin, and the flatness of the gap holding member due to the integral removal process cannot be maintained, and the original shape is restored. It is because it fluctuates and does not return. Further, the gap holding member after the paper passing test had a sample in which toner fixation due to entering toner was observed due to an outer diameter difference of 20 μm or more. Furthermore, due to the influence of the outer diameter difference, uneven wear (change in flare) occurred in the gap holding member after passing 600,000 sheets.

It is sectional drawing of the electroconductive member (charging roller) which shows one embodiment of this invention. It is explanatory drawing which shows the method to form the electroconductive member (charging roller) which shows one embodiment of this invention, Comprising: (a) is cut into the outer peripheral surface of a space | gap holding member, and the outer peripheral surface of an electrical resistance adjustment layer. The shape after removal processing such as processing and grinding is shown, and (b) shows the surface layer formed on the outer peripheral surface of the electrical resistance adjustment layer subjected to the removal processing before being subjected to heat curing treatment. The shape is shown, and (c) shows the shape after the heat curing treatment is applied to the surface layer formed on the outer peripheral surface of the electric resistance adjusting layer subjected to the removal processing. It is expansion explanatory drawing of a space | gap holding member, (a) shows the maximum outer diameter and minimum outer diameter of the space | gap holding member before performing a heat-hardening process to a surface layer, and (b) is a surface layer. The maximum outer diameter and the minimum outer diameter of the space | gap holding member after performing a heat-hardening process are shown. An outer diameter change that occurs when a gap holding member made of high-density polyethylene before press-fitting into a conductive support in a conductive member (charging roller) showing an embodiment of the present invention is annealed will be described. It is a graph, (a) shows the relationship between the annealing temperature [° C.] and the φ outer diameter shrinkage [mm] when the annealing time is a fixed time: 60 minutes, and (b) shows the annealing The relationship between the annealing time [min and φ outer diameter shrinkage [mm] when the temperature is a constant temperature: 120 ° C. is shown. FIG. 3 is a schematic diagram illustrating a state where a conductive member (charging roller) is disposed on an image carrier. 1 is an explanatory diagram of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the measurement location of the outer diameter of the space | gap holding member in the electroconductive member (charging roller) obtained by the Example and the comparative example. It is an explanatory view of a conventional electrophotographic image forming apparatus. It is sectional drawing of the conventional electroconductive member (charging roller).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Electrical resistance adjustment layer 3 Surface layer 4 Gap holding member 5 Image carrier G Gap 10 Conductive member (charging roller)

Claims (10)

A conductive member having a conductive support, an electric resistance adjusting layer formed on the conductive support, and a gap holding member press-fitted into both ends of the electric resistance adjusting layer, wherein the gap When the outer peripheral surface of the holding member comes into contact with the image carrier, the gap holding member is formed such that a gap is formed between the outer peripheral surface of the image carrier and the outer peripheral surface of the conductive member. In the conductive member provided with a height difference with respect to the outer peripheral surface of the electrical resistance adjusting layer,
The difference between the maximum diameter and the minimum diameter of the outer diameter of the gap holding member is within 20 μm by the annealing treatment before press-fitting the gap holding member into the conductive support and the annealing treatment after press-fitting. A conductive member characterized by the above.   2. The conductive member according to claim 1, wherein the resin material forming the gap holding member is made of a synthetic resin having low hygroscopicity and wear resistance.   The conductive member according to claim 2, wherein the resin material is a resin material selected from high density polyethylene and high molecular weight polyethylene.   The conductive member according to claim 2 or 3, wherein the gap holding member is formed by molding a synthetic resin.   The difference in height of the outer peripheral surface of the gap holding member with respect to the outer peripheral surface of the electric resistance adjusting layer is the outer peripheral surface of the gap holding member installed on the conductive support and the conductive support provided on the conductive support. 5. The conductive member according to claim 1, wherein the conductive member is formed by an integrated process by a removal process such as a cutting process or a grinding process applied to the outer peripheral surface of the electrical resistance adjusting layer. .   The conductive member according to claim 1, wherein a surface layer is formed on the electric resistance adjusting layer.   The conductive member according to claim 1, wherein the conductive member has a cylindrical shape.   The conductive member according to claim 1, wherein the conductive member is a charging member.   9. A process cartridge, wherein the charging member according to claim 8 is provided so as to be disposed close to a member to be charged.   An image forming apparatus comprising the process cartridge according to claim 9.

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