JP2008020634A - Image formation roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image formation roller which is not damaged by polishing of a conductive elastic material while having a resin-based shaft, and suppresses lowering of dimensional accuracy even after formation of a resin coating layer. <P>SOLUTION: The image formation roller comprises: a shaft formed from a resin composition containing an aromatic polyamide, glass fibers, a conductive material, and optionally, an aliphatic polyamide and having a flexural strength of ≥250 MPa and a flexural modulus of ≥15 GPa; a surface-polished conductive elastic layer disposed on an outer peripheral face of the shaft; and a coating layer disposed on an outer peripheral face of the conductive elastic layer, wherein the coating layer comprises an ultraviolet-cured resin or an electron beam-cured resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming roller used in an image forming unit of an image forming apparatus based on an electrophotographic system such as a copying machine, a printer, and a facsimile, and more particularly to an image forming roller including a resin shaft.

  In an image forming unit of an image forming apparatus based on an electrophotographic system such as a copying machine, a printer, or a facsimile, an image forming roller related to image forming such as a transfer roller, a toner supply roller, a developing roller, and a cleaning roller is used. Conventionally, such an image forming roller has a configuration in which a conductive elastic layer is provided on the outer periphery of a metal shaft. However, in recent years, due to demands for reducing the size and weight of image forming apparatuses, the shaft is made of resin. Attempts have been made to form with compositions. For example, Patent Document 1 and Patent Document 2 disclose a nonmagnetic developing roller made of a resin composition containing a synthetic resin such as polyamide and a conductive agent, and optionally fibers. Patent Document 3 discloses a developing roller having a shaft made of a conductive resin composition containing a polyamide resin and a conductive material.

  However, as described in Patent Document 2, the conventional resin-based shaft is obtained by foaming a conductive elastic material in a mold provided with the resin-based shaft or by foaming. After forming the material into a predetermined shape, the conductive elastic layer is provided only by adhering the material to the resin-based shaft, or as described in Patent Document 3, the semi-conductive material is provided on the resin-based shaft. There is no problem when a semiconductive layer is provided only by coating, but after covering the outer periphery of the resin shaft with a conductive elastic material, etc., the shaft is supported by the journal portion of the resin shaft, When polishing the coated conductive elastic material to form a conductive elastic layer, the resin shaft is destroyed at the journal during polishing, and an image forming roller cannot be manufactured. Cormorant problem arises.

The image forming roller has a conductive elastic layer formed on the outer periphery of the shaft as described above. On the conductive elastic layer, the elastic layer is prevented from being contaminated, the wear resistance is improved, and the toner is charged. For the purpose of optimizing properties, it is common to provide a resin coating layer. However, it has been found that when the shaft is formed of resin, the dimensional accuracy of the image forming roller is lowered due to the influence of heat applied when the resin coating layer is formed, and the deflection accuracy is lowered.
JP 2001-215780 A JP 2003-195601 A Japanese Patent Laid-Open No. 2002-40798

  Accordingly, the present invention provides an image forming roller having a resin-based shaft, which is not damaged by polishing of a conductive elastic material, and in which a reduction in dimensional accuracy is suppressed even after a resin coating layer is formed. For the purpose.

  According to the present invention, a shaft formed of a resin composition containing an aromatic polyamide, glass fiber, a conductive material, and optionally an aliphatic polyamide, having a bending strength of 250 MPa or more and a bending elastic modulus of 15 GPa or more, and the shaft A conductive elastic layer provided so as to cover the outer peripheral surface and having a polished surface, and a coating layer provided so as to cover the outer peripheral surface of the conductive elastic layer, the coating layer comprising an ultraviolet curable resin or an electron beam An image forming roller is provided that includes a cured resin.

  In the image forming roller of the present invention, although the shaft is formed of a resin composition, it is not damaged by polishing of the conductive elastic material, and the decrease in dimensional accuracy is suppressed even after the coating layer is formed. ing.

  The image forming roller according to the present invention has a shaft formed of a resin composition containing aromatic polyamide, glass fiber, and conductive material particles, and a conductive elastic layer is provided on the outer periphery of the shaft. A predetermined resin coating layer is formed on the outer peripheral surface of the conductive elastic layer.

  The resin shaft of the image forming roller according to the present invention exhibits a bending strength of 250 MPa or more and a bending elastic modulus of 15 GPa or more. If the bending strength and flexural modulus are less than these values, cracks will occur when a conductive elastic layer such as conductive rubber is provided on the shaft and then the conductive elastic layer is ground and polished with a grindstone. obtain. The bending strength is usually 500 MPa or less, and the bending elastic modulus is usually 30 GPa or less.

  The shaft of the image forming roller according to the present invention preferably further exhibits a glass transition point of 70 ° C. or higher. The image forming roller is usually assembled as a unit and stored at about 60 ° C. in a stressed state. Further, the journal part may be heated to a temperature of about 60 ° C. during the cutting process. When the glass transition point is less than 70 ° C., there is a possibility that deflection occurs during the storage, and deformation occurs during the cutting process, which may reduce the surface accuracy. The glass transition point is usually 100 ° C. or lower.

  The shaft of the image forming roller according to the present invention preferably further exhibits a specific gravity of 1.8 or less. If the specific gravity exceeds 1.8, there is a possibility that the request for weight reduction cannot be sufficiently met. The specific gravity is usually 1.0 or more.

Furthermore, the shaft of the image forming roller according to the present invention preferably exhibits a volume resistivity of 1 × 10 ⁵ Ω · cm or less. The volume resistivity exceeding 1 × 10 ⁵ Ω · cm is higher than the resistance value required for the conductive elastic layer provided on the outer periphery of the shaft, which may adversely affect printing. The volume resistivity is usually 1 × 10 ⁰ Ω · cm or more.

  As described above, the shaft having the above physical properties is formed from a resin composition that includes aromatic polyamide, glass fiber, and conductive material particles, and may further include aliphatic polyamide.

  The aromatic polyamide is a polyamide having an aromatic group in the main chain, and is obtained by a polycondensation reaction between metaxylylenediamine and an α, ω-aliphatic dicarboxylic acid such as adipic acid, succinic acid, glutaric acid or pimelic acid. It is obtained. An aromatic polyamide obtained from metaxylylenediamine and adipic acid is known as polyamide MXD6.

  The aliphatic polyamide has a polycondensate structure of polymethylene diamine such as hexamethylene diamine and an aliphatic dicarboxylic acid, and includes polyamide 6, polyamide 6,6 and the like.

  As the glass fiber, those known per se can be used. The diameter of the glass fiber is preferably 1 to 50 μm, and the length is preferably 0.1 to 10 mm.

  As the conductive material, carbon black such as channel black, furnace black, thermal black, lamp black, ketjen black, and acetylene black, carbon fiber, and the like can be suitably used. The diameter of the carbon fiber is preferably 1 to 50 μm, and the length is preferably 0.1 to 10 mm. As the conductive material, carbon black and carbon fiber can be used in combination.

  In order to bring the physical properties to the shaft, the resin composition has a glass fiber of 10 to 300 parts by mass and a conductive material of 0.1 to 20 parts by mass with respect to a total of 100 parts by mass of the aromatic polyamide and the aliphatic polyamide. It is preferable to contain in the ratio. The mass ratio of the aromatic polyamide and the aliphatic polyamide is preferably 100: 0 to 50:50.

  The shaft of the image forming roller of the present invention can be formed by a method such as injection molding. After injection molding, the journal part can be finished by cutting. More specifically, the shaft of the image forming roller of the present invention has a shaft main body and journal portions integrally provided at both ends of the shaft main body.

  The conductive elastic layer provided on the outer periphery of the shaft body is based on a rubber material such as silicone rubber, acrylonitrile butadiene rubber, urethane rubber, ethylene propylene rubber, etc. In order to impart conductivity to this, conductive material such as carbon black or metal powder is used. It can be formed of a conductive rubber material containing a substance. The conductive elastic layer is formed by coating a conductive rubber material on the outer periphery of the shaft body and then polishing and grinding with a grindstone or the like by a conventional method. Alternatively, the conductive elastic layer can also be formed by adhering a tube body made of a conductive elastic material to the outer periphery of the shaft body and polishing and grinding the tube body by a conventional method. In either case, the polishing is performed while supporting the shaft having the conductive elastic material provided on the outer periphery of the main body with both journal portions and rotating the shaft. The thickness of the final conductive elastic layer (after polishing) is preferably 0.2 mm or more from the viewpoint of polishing accuracy. The thickness of the conductive elastic layer after polishing is usually 10 mm or less.

  By the way, when the conductive elastic layer is made of a conductive rubber tube cured in advance, if the inner diameter of the conductive rubber tube is excessive with respect to the outer diameter of the resin-based shaft, when the tube is polished later, The tube slips on the resin shaft, and the decrease in dimensional accuracy of the tube causes a decrease in runout accuracy. On the other hand, if the inside diameter of the cured conductive rubber tube is too small, the shaft is pressed into the tube. The distortion generated in the tube remains in the tube, causing a decrease in the accuracy of tube outer diameter deflection. In order to solve this problem, the ratio de / ds of the inner diameter de of the cured conductive rubber tube to the outer diameter ds of the resin-based shaft is set to 0.75 to 0.97 and / or the outer diameter of the resin-based shaft. The difference ds−de between ds and the inner diameter de of the cured conductive rubber tube is preferably set to 0.3 mm or more and 2.5 mm or less.

  By having such a relationship between the outer diameter ds of the resin-based shaft and the inner diameter de of the tube, the tube does not slip with respect to the resin-based shaft when the cured tube is polished, and the shaft is press-fitted into the tube. Thus, the image forming roller having excellent dimensional accuracy is obtained without causing distortion generated in the tube to remain in the tube. The ratio de / ds is preferably 0.8 to 0.95. The difference ds-de is preferably 0.5 to 2.5 mm.

  Conductive rubber tube is based on rubber materials such as silicone rubber, acrylonitrile butadiene rubber, urethane rubber, ethylene propylene rubber, etc., and it is a conductive material that contains conductive materials such as carbon black and metal powder to give it conductivity. It can be formed of a rubber material. The tube can be formed by extruding an uncured conductive rubber material into a tube shape and curing it. Here, depending on the material of the tube, there may be a case where only primary curing is sufficient, and it is preferable to perform primary curing and secondary curing. For example, for acrylonitrile butadiene rubber and urethane rubber, it is sufficient only to perform primary curing at 80 ° C. to 180 ° C. for 5 minutes to 24 hours. On the other hand, the silicone rubber is preferably subjected to primary curing at 100 ° C. to 400 ° C. for 1 minute to 10 hours and then secondary curing at 150 ° C. to 250 ° C. for 1 hour to 24 hours. The ethylene propylene rubber is preferably subjected to primary curing at 80 ° C. to 180 ° C. for 5 minutes to 24 hours and then secondary curing at 70 ° C. to 150 ° C. for 1 hour to 6 hours. .

  While expanding the diameter of the cured conductive rubber tube thus obtained with compressed air, a resin-based shaft is pressed into the tube. Thereafter, the cured conductive rubber tube (conductive elastic layer) is polished and ground with a grindstone or the like by a conventional method. The thickness of the final conductive elastic layer (after polishing) is preferably 0.2 mm or more and 10 mm or less from the viewpoint of polishing accuracy. It is not necessary to provide an adhesive, a primer, or the like between the outer periphery of the resin shaft and the inner periphery of the tube, and the outer periphery of the resin shaft and the inner periphery of the tube can be brought into direct contact.

  Note that it is particularly advantageous to apply the precured conductive rubber tube to a resin shaft having a glass transition point of 100 ° C. or less. This is because the resin shaft having such a low glass transition point is particularly easily deformed at a high temperature at which the primary curing and the secondary curing are performed. In particular, when the resin-based shaft of the present invention is heated at a temperature exceeding + 45 ° C. from its glass transition point, deformation is likely to occur significantly.

  In the image forming roller of the present invention, a resin coating layer is provided on the outer peripheral surface of the conductive elastic layer for the purpose of preventing contamination of the elastic layer, improving wear resistance, and optimizing the chargeability with respect to the toner. Yes. In the present invention, the resin coating layer contains an ultraviolet curable resin or an electron beam curable resin. Such an ultraviolet or electron beam curable resin can be obtained by curing an acrylate monomer such as polyester acrylate, fluorine acrylate, epoxy acrylate, urethane acrylate, or silicone acrylate with ultraviolet rays or an electron beam. More specifically, an ultraviolet ray or electron beam curable composition in which a photoinitiator such as benzoyl ether type, thiooxane type, or benzophenone type is blended with these acrylate monomers is applied to the outer peripheral surface of the conductive elastic layer, and ultraviolet rays or electrons are applied. A cured resin coating layer is formed by irradiating a line. The quantity of the photoinitiator mix | blended with a ultraviolet-ray or an electron beam curable composition is 0.1-10 mass parts normally per 100 mass parts of acrylate monomers. A polymerization accelerator can be blended with the ultraviolet ray or electron beam curable composition in order to accelerate the curing reaction by the photoinitiator. As the polymerization accelerator, a tertiary amine, alkylphosphine, thioether, or other polymerization accelerator can be used. The compounding quantity of a polymerization accelerator is 0.01-10 mass parts normally per 100 mass parts of acrylate monomers. Furthermore, a reactive diluent can be mix | blended with an ultraviolet-ray or an electron beam curable composition. The reactive diluent is used to adjust the viscosity of the ultraviolet ray or electron beam curable composition, and since it is reactive, it is incorporated into the cured product (resin) of the curable composition. Thus, it is not necessary to apply heat for removal. Examples of the reactive diluent include a monofunctional, difunctional and polyfunctional polymerizable compound in which acrylic acid is bonded to a compound containing an amino acid or a hydroxyl group by an amidation reaction or an esterification reaction. it can. More specifically, it is a diacrylate of butanediol, diethylene glycol, polyethylene glycol, or neopentyl glycol. The amount of the reactive diluent added to the ultraviolet ray or electron beam curable composition is usually 10 to 200 parts by mass per 100 parts by mass of the acrylate monomer.

  The thickness of the resin coating layer is usually 5 to 100 μm. If the thickness is less than 5 μm, the durability may be inferior, and if the thickness exceeds 100 μm, the surface becomes too hard and the toner or the photoreceptor surface may be damaged.

  According to the present invention, by constituting the resin coating layer with an ultraviolet curable resin or an electron beam curable resin, the resin-based shaft is not subjected to a high temperature (a temperature exceeding + 45 ° C. from the glass transition point), and depends on the heat. Deformation is prevented.

  Any of the image forming rollers of the present invention can be provided as a transfer roller, a toner supply roller, a cleaning roller, etc. in addition to a developing roller.

  Examples of the present invention will be described below together with comparative examples, but the present invention is not limited to these examples.

Examples 1-10
90 parts by mass of polyamide MXD6 manufactured by Mitsubishi Engineering Plastics as aromatic polyamide, 10 parts by mass of Novamid (registered trademark) 1007J manufactured by Mitsubishi Engineering Plastics as aliphatic polyamide, and CS03-JAFT2 manufactured by Asahi Fiber Glass Co., Ltd. as glass fiber Using a composition containing 100 parts by mass, 12 parts by mass of Mitsubishi Chemical Corporation # 3050B as carbon black, a shaft having a diameter of 10 mm and a surface length (rubber processed part) of 235 mm is injection-molded, and the journal part is finished by cutting. A resin shaft used as a developing roller for a printer HL-1850 manufactured by Brother Industries, Ltd. was obtained. The resin shaft was not damaged at all.

The bending elastic modulus, bending strength, glass transition point, specific gravity, and surface resistance of each obtained shaft were measured. The flexural modulus and flexural strength were measured with a strograph V10-C manufactured by Toyo Seiki Seisakusho, the glass transition point was measured with a differential thermal analyzer DSC-60 manufactured by Shimadzu, and the specific gravity was an electronic hydrometer MD- manufactured by Alpha Mirage. With 200S, the volume resistivity was measured with a resistance meter R8340 manufactured by Advantest Corporation. The glass transition point was measured by heating the resin shaft at a heating rate of 5 ° C./min. The bending elastic modulus was 18 GPa, the bending strength was 340 MPa, the glass transition point was 78 ° C., the specific gravity was 1.5, and the volume resistivity was 3 × 10 ² .

  On the other hand, an uncured silicone rubber material (DY32-4036 manufactured by Toray Dow Corning Co., Ltd.) containing carbon black is extruded into a tube shape, cured at 400 ° C. for 2 minutes (primary curing), and then a predetermined length. And cured at 200 ° C. for 4 hours (secondary curing) to obtain a tube having an inner diameter de of 7.5 to 9.7 mm and an outer diameter of 20 mm.

While expanding the diameter of each tube with compressed air, the resin-based shaft was press-fitted into the tube, and then the surface was polished to produce a roller having an outer diameter of 20 mm. The volume resistivity of the conductive silicone rubber tube was 10 ⁶ Ω · cm, and the JIS A hardness was 45 °.

  Further, the runout of some of the rollers thus obtained was measured by a conventional method. That is, the maximum value and the minimum value of the shaft displacement at three locations in the longitudinal direction of the shaft when each roller is supported by the journal portion and the shaft is rotated are optically measured using a laser-side long machine RSV15100 manufactured by Tokyo Koden Kogyo. The difference was determined as the shaft runout. The results are shown in the following Table 1 as “runout (before forming the resin coating layer)”.

Next, after conducting plasma treatment for 10 seconds on the surface of the conductive silicone rubber tube of each roller (Plasma processor ST-7000 manufactured by Keyence Corporation), an ultraviolet curable resin composition or an electron beam curable resin having the following composition: The composition was applied by dip coating, and ultraviolet rays (irradiation device: EXH880 manufactured by Eye Graphics Co., Ltd .; exposure amount: 400 mJ / cm ² ) or electron beam (irradiation device: LB-HP01 manufactured by Iwasaki Electric Co., Ltd .; absorbed dose: 40 KGy) at 25 ° C. And cured by forming a resin coating layer having a thickness of 10 μm, respectively, to obtain an image forming roller.

<Ultraviolet curable resin composition>
Monomer: 100 parts by mass of urethane acrylate (UA series) manufactured by Shin-Nakamura Chemical Co., Ltd. Reactive diluent: 30 parts by mass of diethylene glycol diacrylate Photoinitiator: 5 parts by mass of 2-hydroxy-4-n-octyloxybenzophenone <Electron beam curability Resin composition>
Monomer: 100 parts by mass of urethane acrylate (UA series) manufactured by Shin-Nakamura Chemical Co., Ltd. Photoinitiator: 5 parts by mass of 2-hydroxy-4-n-octyloxybenzophenone.

  For some of the image forming rollers thus obtained, the shake was measured in the same manner as described above. The results are shown in Table 1 as “runout (after forming the resin coating layer)”.

Comparative Examples 1-10
300 parts by mass of butyl acetate was added to 100 parts by mass of fluorine-containing polyol (Daikin Kogyo Zeffle) and 5 parts by mass of conductive carbon black (Cabot), and the mixture was dispersed using a disperser. To this dispersion, 5 parts by mass of volatile silicone oil (KF96L manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred to obtain a main agent. A coating material in which urethane-modified hexamethylene diisocyanate (Duranate manufactured by Asahi Kasei Kogyo Co., Ltd.) as a curing agent is blended with this main agent so that the equivalent of the hydroxyl group in the main agent and the equivalent of the isocyanate group in the curing agent are 1: 1. Was prepared. This coating material was spray-coated on the surface of the conductive silicone rubber tube of the roller (before forming the resin coating layer) prepared in Examples 1 to 5 so as to have a thickness of 10 μm, air-dried, and then heated at 160 ° C. at 40 ° C. A minute porous coating layer was formed by heating for a minute to obtain a developing roller. The developing roller runout was measured in the same manner as described above. The results are shown in Table 2.

  The developing rollers obtained in Examples 1 to 10 and Comparative Examples 1 to 10 were incorporated into a printer HL-1850 manufactured by Brother Industries, Ltd., 10 sheets were tested, and images were evaluated according to the following criteria.

<Image evaluation criteria>
No image unevenness ... ○
There is some unevenness in the image, but there is no practical problem ... △
Uneven with image unevenness ... ×
The results are shown in Table 1 for Examples 1 to 10 and in Table 2 for Comparative Examples 1 to 10.

  As is apparent from the results shown in Table 1, in the developing rollers of Examples 1 to 10, the resin coating layer was cured at a temperature lower than the temperature of [glass transition point of resin shaft + 45 ° C.] by irradiation with ultraviolet rays or electron beams. Therefore, it is possible to provide a developing roller that has no deformation and therefore has a small shake and gives a clear image. On the other hand, as shown in Table 2, since the developing rollers of Comparative Examples 1 to 10 use a high temperature of 160 ° C. when forming the coating layer, deformation is large and density unevenness occurs.

Claims (7)

  A shaft formed of a resin composition containing an aromatic polyamide, glass fiber, a conductive material and optionally an aliphatic polyamide, having a bending strength of 250 MPa or more and a bending elastic modulus of 15 GPa or more, and covering the outer peripheral surface of the shaft A conductive elastic layer whose surface is polished and a coating layer provided to cover the outer peripheral surface of the conductive elastic layer, the coating layer containing an ultraviolet curable resin or an electron beam curable resin. Characteristic imaging roller.   The resin composition contains 10 to 300 parts by mass of the glass fiber and 0.1 to 20 parts by mass of the conductive material with respect to 100 parts by mass in total of the aromatic polyamide and the aliphatic polyamide. The image forming roller according to claim 1, wherein a mass ratio of the aromatic polyamide to the aliphatic polyamide is 100: 0 to 50:50.   The image forming roller according to claim 1, wherein the conductive elastic layer includes a rubber material selected from the group consisting of silicone rubber, acrylonitrile butadiene rubber, urethane rubber, and ethylene propylene rubber as an elastic material.   The image forming roller according to any one of claims 1 to 3, wherein the conductive elastic layer is formed of a conductive rubber tube cured in advance.   The ratio de / ds of the inner diameter de of the tube to the outer diameter ds of the shaft is 0.75 to 0.97, and / or the difference ds-de between the outer diameter ds of the shaft and the inner diameter de of the tube. The image forming roller according to claim 4, wherein is 0.3 mm or more and 2.5 mm or less.   The image forming roller according to claim 1, wherein the coating layer includes an acrylate resin.   The image forming roller according to claim 6, wherein the coating layer includes a cured product of polyester acrylate, fluorine acrylate, epoxy acrylate, urethane acrylate, or silicone acrylate.