JP2007334028A - Conductive roller and manufacturing method thereof, process cartridge having the conductive roller, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a conductive roller having a dimensional accuracy such as an outer diameter and capable of outputting a good image using a cylindrical coating head.
SOLUTION: The structure recovery time of a rubber material coated around the shaft core is set to 0.1 to 60.0 seconds, the nozzle length L of a cylindrical coating head used for coating, and the cylindrical coating When the relation of the thickness t of the rubber material covered by the working head satisfies 0.2 ≦ L / t ≦ 25.0, a conductive roller having excellent dimensional accuracy such as an outer diameter and small resistance unevenness can be manufactured. I can do it.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a conductive roller disposed around a photosensitive drum in an image forming apparatus such as an electrophotographic apparatus, a printer, or an electrostatic recording apparatus. The present invention also relates to a conductive roller manufactured by the manufacturing method, a process cartridge having the conductive roller, and an image forming apparatus.

  A conventional electrophotographic apparatus will be described below. An image forming unit is installed inside the main body of the apparatus, and an image is formed through processes of cleaning, charging, latent image, development, transfer, and fixing. The image forming unit includes a photosensitive drum as an image carrier, and includes a cleaning unit, a charging unit, a latent image forming unit, a developing unit, and a transfer unit. The image on the photosensitive drum formed by the image forming unit is transferred to a recording material by a transfer member, conveyed, and then heated and pressed by a fixing unit, and output as a fixed recorded image.

  Next, among the cleaning, charging, latent image, development, transfer, and fixing processes, the charging, latent image formation, development, and transfer processes will be described.

  The charging member performs a primary charging process on the surface of the photosensitive drum so that the potential is uniform with a predetermined polarity. After being uniformly charged by the charging member, the target image information is exposed to form an electrostatic latent image corresponding to the target image on the surface of the photosensitive drum. This electrostatic latent image is visualized as a developer image by a developing device. The visualized developer image is transferred to the recording material by applying a voltage from the back surface of the recording material by the transfer means under the photosensitive drum. Thereafter, the recording material is conveyed to a fixing unit, subjected to image fixing, and output as an image formed product.

  In the developing device in the image forming apparatus such as the electrophotographic apparatus described above, since it is good to contact the photosensitive drum, a charging member, a developing member for visualizing a latent image, a rubber material or the like for a transfer unit, etc. A conductive roller made of an elastic body is used.

  The shape of the conductive roller used in these image forming apparatuses is required to have very high dimensional accuracy. If these dimensional accuracy is poor, for example, in the developing member, the amount of the developer supplied to the photosensitive drum becomes non-uniform, which causes problems such as image unevenness. Further, in the charging member, the photosensitive drum cannot be uniformly charged, resulting in problems such as adversely affecting the image.

  In order to meet this demand for high dimensional accuracy, various molding methods such as molding using a mold and molding by extrusion have been studied as methods for manufacturing various conductive rollers. In addition, various methods such as spray coating, dip coating, roll coating, blade coating, etc. have been studied as methods for directly applying a liquid material to the shaft core. When applied to a roller or the like that requires several millimeters, there are various problems.

  For example, in spray coating, if the viscosity of the paint is high, it is difficult to atomize uniformly, so it is necessary to keep the viscosity of the paint low. In the blade coating method and the roll coating method, for example, a blade or roll is disposed in the axial direction of the cylinder to be applied, and the coating liquid is applied by the blade or roll while rotating the cylinder. After rotating the cylindrical body by one to several revolutions, the blade or roll is moved backward to complete the coating. When the blade or roll is retracted at the end of coating, a part of the coating film on the cylindrical body is thicker than the other part due to the viscosity of the coating liquid, especially when the viscosity of the coating liquid is high. Since the part appears directly in the image, it is not preferable.

Under such circumstances, a coating method using a cylindrical coating head is disclosed as a method for directly coating a high-viscosity material (see Patent Document 1). By using a method in which the coating liquid is applied to the surface of the cylindrical body with the center line of the cylindrical body parallel to the horizontal direction, the coating process is limited by the viscosity of the coating liquid and the film thickness of the coating film. The present invention provides a coating method capable of forming a good and uniform coating film by removing and applying the coating liquid directly onto the surface of the cylindrical body with a simpler apparatus.
JP 2003-190870 A

  By using the above invention, a high-viscosity material can be directly applied to the shaft core body. However, in the application method using a cylindrical coating head, at the start and end of application of the material to be coated (both ends of the roller) Unlike the roller center, it is difficult to obtain stable characteristics such as the shape and physical properties of both ends due to the large change in the speed of the ring and the separation of the coating head and the coating material.

  The present invention solves the above problems, and provides a method for producing a conductive roller having excellent dimensional accuracy and small resistance unevenness in a method for producing a conductive roller using a cylindrical coating head. Is to provide a conductive roller obtained.

  The present inventors have intensively studied to solve the above-mentioned problems, and have reached the present invention.

  That is, according to the present invention, in the method for producing a conductive roller obtained by coating a rubber material around the shaft core and curing and curing, the structure recovery time of the rubber material to be coated is 0.1 to 60.0 seconds. Yes, the rubber material is coated using a cylindrical coating head, the nozzle length L (mm) of the cylindrical coating head and the thickness of the rubber material coated by the cylindrical coating head The present invention relates to a method for manufacturing a conductive roller, wherein the relationship of length t (mm) satisfies 0.2 ≦ L / t ≦ 25.0.

  Furthermore, the present invention is a method for producing a conductive roller, wherein the thickness t of the rubber material covered by the cylindrical coating head is 0.5 mm to 6.0 mm.

  Further, the present invention is the method for producing a conductive roller, wherein the cylindrical coating head has a nozzle length L of 1.0 to 30.0 mm.

  Furthermore, the present invention is the method for producing a conductive roller, wherein the rubber material is a silicone rubber containing a filler.

  Furthermore, the present invention is the method for producing a conductive roller, wherein the filler content in the rubber material is 5 to 60 parts by mass.

  Furthermore, the present invention is a method for producing a conductive roller, wherein at least one of the fillers contained in the rubber material is carbon black.

  Moreover, this invention is the electroconductive roller manufactured by one of the said manufacturing methods.

  Furthermore, the present invention is the conductive roller, wherein the conductive roller is any one of a developing roller and a charging roller.

  The present invention further includes a charging roller for supplying a charge to the surface of the photosensitive drum, an exposure unit for recording image information on the surface of the photosensitive drum, a developing roller for contacting the photosensitive drum and supplying a developer to the surface of the photosensitive drum, The electrophotographic process cartridge according to claim 1, wherein at least one of the developing roller and the charging roller is the conductive roller.

  The present invention further includes a charging roller for supplying a charge to the surface of the photosensitive drum, an exposure unit for recording image information on the surface of the photosensitive drum, a developing roller for contacting the photosensitive drum and supplying a developer to the surface of the photosensitive drum, An image forming apparatus comprising: a transfer roller that transfers the developer onto a transfer material; and a pressure roller that forms a nip portion with the fixing roller, the fixing roller, and presses and conveys the transfer material by the nip portion. In the image forming apparatus, at least one of the charging roller and the developing roller is the conductive roller.

  As described above, according to the present invention, in a method for manufacturing a conductive roller using a cylindrical coating head, it is possible to provide a conductive roller with high dimensional accuracy and small resistance unevenness over the entire length of the roller. I can do it.

  Hereinafter, embodiments of the present invention will be described in detail.

  Until now, when applying a liquid material using a cylindrical coating head, the material has been controlled to have a high viscosity, thereby preventing dripping of the material after coating and improving the shape accuracy. However, the material viscosity alone cannot completely correlate with the behavior of the material after coating, and it has been difficult to manufacture a roller having a highly accurate shape.

  As a result of intensive investigations to solve this problem, the inventors of the present invention appropriately set the nozzle length of the coating head with respect to the thickness of the material to be coated when the structural recovery time of the material to be coated is set within a certain range. It has been found that a roller having a very good shape accuracy can be produced by adjusting the length to an appropriate length.

  According to the present invention, it is desirable that the structure recovery time of the material covered by the cylindrical coating head is 0.1 second to 60.0 seconds. When the structure recovery time exceeds 60 seconds, it takes time for the structure of the material to become stable after coating the material, which causes problems such as dripping during that time, and the shape accuracy of the roller cannot be obtained. Further, when designing a material having a structural recovery time of less than 0.1 seconds, the type of filler that can be used is limited, and thus it may be difficult to design a material having appropriate physical properties.

  A more preferable range of the structure recovery time is 0.1 to 45.0 seconds. When it is in this range, dripping of the material is sufficiently suppressed, and a roller having a good shape accuracy is very easily obtained.

  In the present invention, the relationship between the nozzle length L of the coating head and the thickness t of the material to be applied is preferably in the range of 0.2 ≦ L / t ≦ 25.0. When L / t exceeds 25.0, since the nozzle length becomes long, the accuracy of the coating head itself may be lowered, which greatly affects the accuracy of the shape and physical property values of the roller itself. When L / t is smaller than 0.2, the length of the nozzle is short, and thus the roller is manufactured before the pressure distribution of the material is relaxed in the coating head. It is difficult to perform excellent roller molding. A more preferable range of L / t is 1.0 ≦ L / t ≦ 15.0.

  For the same reason, there is a preferable range of the nozzle length L, and as the range, L is preferably 1.0 mm or more and 30.0 mm or less.

  If the thickness of the coating to be applied exceeds 6.0 mm, dripping due to the weight of the material itself occurs and it becomes difficult to maintain dimensional stability. On the other hand, if the thickness of the coating is less than 0.5 mm, the coating cannot be applied satisfactorily because the shearing force applied to the material is increased and the recovery of the structurally broken material is hindered. The thickness of the coating to be applied is preferably 0.5 mm or more and 6.0 mm or less. More preferably, it is more than 2.0 mm and 4.5 mm or less.

  Moreover, in this examination, the preferable range of the filler contained in order to give structural recovery to a material is 5-60 mass parts with respect to the base polymer contained in a rubber material. When there is more filler content than 60 mass parts, since the elasticity of a rubber material is impaired, it is unpreferable. In addition, when the filler content is less than 5 parts by mass with respect to the base polymer, it is not preferable because the structural recovery of the material is difficult to occur or the structural recovery itself does not occur depending on the filler. The filler content is more preferably 5 parts by mass and 45 parts by mass with respect to the base polymer.

  The conductive roller manufactured by the manufacturing method of the present invention can be used as various rollers used in an image forming apparatus, for example, a developing roller, a charging roller, and the like. Hereinafter, these rollers will be described.

(Development roller)
A schematic diagram of a developing roller manufactured by the manufacturing method of the present invention is shown in FIG. FIG. 1A shows a cross section parallel to the longitudinal direction of the developing roller, and FIG. 1B shows a cross section perpendicular to the longitudinal direction.

  The shaft core 11 of the developing roller of the present invention may be any material as long as it is conductive, and can be appropriately selected from carbon steel, alloy steel, cast iron, conductive resin, and the like. Here, examples of the alloy steel include stainless steel, nickel chrome steel, nickel chrome molybdenum steel, chrome steel, chromium molybdenum steel, nitriding steel to which Al, Cr, Mo, and V are added, but from the viewpoint of strength. Metal is preferable. Furthermore, as a countermeasure against rust, the shaft core material can be plated and oxidized. As the type of plating, both electroplating and electroless plating can be used, but electroless plating is preferable from the viewpoint of dimensional stability. Examples of the electroless plating used here include nickel plating, copper plating, gold plating, Kanigen plating, and other various alloy platings. Examples of the nickel plating include Ni—P, Ni—B, Ni—WP, and Ni—P—PTFE composite plating. Each film thickness is preferably 0.05 μm or more, more preferably 0.1 to 30 μm.

  Further, the developing roller is always in pressure contact with the photosensitive drum, the developing blade, the toner, and the like. For this reason, in order to reduce the damage given to these members, it is important to obtain a good image by using a material having a low hardness and a small compression set. Further, it is desirable that the surface of the developing roller has wear resistance and the like and has high durability. For this reason, the developing roller used in the present invention has an elastic layer 12 around the shaft core body 11.

  At this time, the hardness of the elastic layer 12 is desirably Asker C hardness of 10 to 80 degrees for the above reason. If the hardness of the elastic layer is a low hardness of less than 10 degrees, the photosensitive drum may be contaminated. Further, when the hardness of the elastic layer is higher than 80 degrees, the toner may be damaged when contacting the toner, and the image quality of the output image may be deteriorated. Further, the elastic layer 12 does not have to be a single layer, and may be a multilayer.

  Examples of the material used for the elastic layer 12 include epoxy rubber, diallyl phthalate rubber, polycarbonate rubber, fluoro rubber, polypropylene rubber, urea rubber, melamine rubber, silicon rubber, polyester rubber, styrene rubber, vinyl acetate rubber, phenol rubber, polyamide rubber, Examples thereof include fiber base rubber, urethane rubber, silicone rubber, acrylic urethane rubber, and water-based rubber. These materials can be used alone or in combination. Furthermore, foams of these materials may be used for the elastic layer.

  In addition, the resin layer 13 may be formed on the outer periphery of the elastic layer 12 in order to improve wear resistance and the like as in the developing roller used in the present invention. Similarly to the elastic layer, the resin layer does not have to be a single layer, and may be a multilayer.

When the conductive roller obtained by the production method of the present invention is used as a developing roller, the volume resistivity of the elastic layer is preferably in the range of 1 × 10 ⁴ to 1 × 10 ¹¹ Ω · cm. If the volume resistivity of the elastic layer material is 1 × 10 ⁴ to 1 × 10 ¹¹ Ω · cm, uniform charge controllability can be obtained for the toner. A more preferable range of the volume resistivity of the elastic layer material is 1 × 10 ⁴ to 1 × 10 ⁹ Ω · cm.

  When measuring this volume resistivity, an appropriate heat treatment is performed according to the material, a test piece having a thickness of 2.0 mm is molded, and measurement is performed. When using a silicone material, a test piece was prepared under the following conditions and measured.

  Two rubber sheets with a thickness of 2.0 mm were formed by placing them in a 130 ° C. oven as test pieces and heating them for 20 minutes, and then secondary vulcanization was carried out in a 200 ° C. oven for 4 hours. Then, after leaving the rubber sheet in an environment of temperature 25 ° C. and humidity 45% for 24 hours or more, measurement was performed by applying a voltage of 100 V using Hiresta IP (manufactured by Mitsubishi Oil Chemical Co., Ltd.) and obtained from two rubber sheets. The volume resistivity was determined from the average value of the resistance values obtained.

  As described above, as a means for making the elastic layer material conductive in accordance with the use, a method of making the material conductive by adding a conductivity imparting agent based on an ionic conduction mechanism or an electronic conduction mechanism to the material is widely known.

Examples of the conductivity-imparting agent based on the ionic conduction mechanism include LiCF ₃ SO ₃ , NaClO ₄ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , NaSCN, KSCN, NaCl and other group 1 metal salts, NH ₄ Cl, (NH _{4) 2} SO4, NH4NO ₃ ammonium salts such _{as, Ca (ClO4) 2, Ba} (ClO 4) 2 periodic table group II metal salts such as the salts and 1,4-butanediol, ethylene glycol, Complexes of polyhydric alcohols such as polyethylene glycol, propylene glycol and polypropylene glycol and their derivatives, salts thereof and monools such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether Complex with quaternary Cationic surfactants such as ammonium salts, aliphatic sulfonates, alkyl sulfates, anionic surfactants such as alkyl phosphate ester salt, and amphoteric surfactants such as betaines.

  In addition, as a conductivity imparting agent by an electronic conduction mechanism, carbon-based materials such as carbon black and graphite, metals or alloys such as aluminum, silver, gold, tin-lead alloy, copper-nickel alloy, zinc oxide, titanium oxide, oxidation Examples thereof include metal oxides such as aluminum, tin oxide, antimony oxide, indium oxide, and silver oxide, and materials obtained by applying conductive metal plating such as copper, nickel, and silver to various fillers. These conductivity-imparting agents based on the ion conduction mechanism and the electron conduction mechanism can be used alone or in a mixture of two or more in the form of powder or fiber. Among these, carbon black is often used from the viewpoint of easy control of conductivity and economy, and in the present invention, a method based on an electronic conduction mechanism using carbon black is used.

  Next, the resin layer 13 will be described. As in the embodiments of the present invention, the resin layer 13 may be formed around the elastic layer 12 in order to optimize the roller surface. Materials used for the resin layer 13 include epoxy resin, diallyl phthalate resin, polycarbonate resin, fluorine resin, polypropylene resin, urea resin, melamine resin, silicon resin, polyester resin, styrene resin, vinyl acetate resin, phenol resin, polyamide resin. , Fiber based resins, urethane resins, silicone resins, acrylic urethane resins, water based resins, and the like. It is also possible to use a combination of two or more of these. Among these, it is particularly preferable to use a nitrogen-containing compound such as a urethane resin or an acrylic urethane resin because the toner can be stably charged.

  The urethane resin used here is obtained from an isocyanate compound and a polyol.

  Diisocyanate-4,4′-diisocyanate, 1,5-naphthalene diisocyanate, 3,3′-dimethylbiphenyl-4,4′-diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, p-phenylene diisocyanate as isocyanate compounds Isophorone diisocyanate, carbodiimide-modified MDI, xylylene diisocyanate, trimethylhexamethylene diisocyanate, tolylene diisocyanate, naphthylene diisocyanate, paraphenylene diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl polyisocyanate and the like can be used. Moreover, these mixtures can also be used and the mixing ratio may be any ratio.

  In addition, as the polyol used here, as a divalent polyol (diol), ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, hexanediol, neopentyl glycol, 1,4-cyclohexanediol 1,4-cyclohexanedimethanol, xylene glycol, triethylene glycol, etc., and trivalent or higher polyols include 1,1,1-trimethylolpropane, glycerin, pentaerythritol, sorbitol, etc. be able to. Furthermore, polyols such as high molecular weight polyethylene glycol, polypropylene glycol, and ethylene oxide-propylene oxide block glycol obtained by adding ethylene oxide and propylene oxide to diol, triol, and the like can also be used. Moreover, these materials can also be mixed and used, and the mixing ratio may be any ratio.

  In addition, as a method for applying the resin layer 13, generally known coating methods such as a ring coating method, a dipping method, a roll coating method, and a spray coating method can be used, but the thickness of the resin layer 13 can be easily controlled. The dipping method is often used for such reasons. In the dipping method, it is preferable to use a material having a viscosity of 5 to 50 cps. If the viscosity is less than 5 cps, the shape collapses until the material is cured and stabilized, and the specifications as a developing roller are not satisfied. Further, when the viscosity of the material exceeds 50 cps, it becomes difficult to form the resin layer 13 uniformly on the surface of the elastic layer 12.

  Furthermore, the resin layer 13 can be used after imparting conductivity. As a method for imparting conductivity, it is possible to use a method similar to the above-described method for making the elastic layer conductive.

  Furthermore, the thickness of the resin layer 13 is preferably 1 to 500 μm. More preferably, the thickness of the resin layer 13 is 1 to 50 μm. If the resin layer 13 is too thin, there is a risk that when the image is output repeatedly, the role of the resin layer may not be fulfilled due to deterioration due to wear or the like. On the other hand, if the resin layer 13 is too thick, the hardness of the roller surface becomes high, which is not preferable because it promotes toner deterioration and causes toner fusion.

  Also, if the electrical resistance unevenness of the entire developing roller is smaller, the toner with a uniform charge can be sent from the developing roller to the photosensitive drum, so that the transferability of the toner is stabilized, so that a good image is obtained. Can be obtained. Here, the uneven resistance of the developing roller refers to a value obtained by 1- (minimum resistance value of the developing roller / maximum resistance value of the developing roller). The resistance unevenness in the developing roller is preferably at least 0 to 0.7. More preferably, the resistance unevenness is suppressed to 0 to 0.3.

  Further, the shape is given as a characteristic required for the developing roller. For example, when the circumferential deviation of the developing roller is large, the fluctuation in the nip width between the developing roller and the photosensitive drum becomes large in one round of the developing roller. When the variation in the nip width is large as described above, the toner conveying force to the drum is uneven, and the image may be shaded. In order to prevent this, it is better that the circumferential deviation of the developing roller is smaller. Specifically, the difference between (maximum value) and (minimum value) (maximum value)-(minimum value) of the distance from the center of the shaft core to the developing roller surface in one rotation of the developing roller is 0 to 50 μm. For example, the shading on the image can be suppressed. Further, if the value of (maximum value) − (minimum value) is 0 to 30 μm, the density on the image is almost uniform, and excellent image quality can be output.

  The roughness on the surface of the developing roller greatly affects the toner conveying force. Therefore, it is desirable that the Ra of the developing roller surface in the standard of JIS B 0601: 1994 surface roughness is 0.5 to 3.0 μm. When Ra is less than 0.5 μm, the toner conveying force is reduced, and the image density is not sufficiently obtained. On the other hand, if it exceeds 3.0 μm, the toner conveying force becomes too large, and thus the toner is conveyed more than necessary, so that the toner may remain on the photosensitive drum and the image may deteriorate. In addition, the smaller the unevenness of roughness in the circumference of the developing roller, the more uniformly the toner can be conveyed, and an image having a uniform density can be output. Therefore, the roughness unevenness in the developing roller is desirably 0 to 0.6. More preferably, the roughness unevenness is in the range of 0 to 0.3. Here, the roughness unevenness refers to a value obtained by subtracting the minimum roughness from the maximum roughness in the developing roller.

  FIG. 2 is a schematic view showing an apparatus to which the coating method of the embodiment of the present invention is applied. As an example, in the coating apparatus of the present embodiment, as shown in FIG. 2, a column 202 is mounted substantially vertically on the mount 201, and a precision ball screw 203 is mounted approximately vertically on the mount 201 and the column 202. It has been. Two linear guides 214 are attached to the column 202 in parallel with the precision ball screw 203.

  The LM guide 204 is connected to a linear guide 214 and a precision ball screw 203 so that a rotary motion is transmitted from a servo motor 205 via a pulley 206 so that the LM guide 204 can move up and down.

  A cylindrical coating head 208 for discharging the coating liquid is attached to the column 202 on the outer peripheral surface of the shaft core body.

  Further, a bracket 207 is attached to the LM guide 204, and a lower work holding shaft 209 for holding and fixing the developing roller shaft core 11 is attached to the bracket 207 substantially vertically, and the opposite developing roller shaft core 11 is attached. The center axis of the workpiece upper holding shaft 210 is attached to the upper portion of the bracket 207, and the workpiece upper holding shaft is disposed so as to be substantially concentric facing the workpiece lower holding shaft 209 to hold the shaft core body. Yes. Further, the central axis of the cylindrical coating head 208 is supported so as to be parallel to the moving direction of the workpiece lower holding shaft 209 and the workpiece upper holding shaft 210. Further, when the workpiece lower holding shaft 209 and the workpiece upper holding shaft 210 are moved up and down, the central axis of the discharge port formed in an annular slit opened inside the coating head 208, the workpiece lower holding shaft 209, and the workpiece upper holding shaft 210 are arranged. The center axis is adjusted to be substantially concentric. With such a configuration, the central axis of the discharge port which is an annular slit of the coating head 208 can be aligned substantially concentrically with the central axis of the axial core body, and the inner peripheral surface of the cylindrical coating head and the axial core A uniform gap is formed between the outer peripheral surface of the body 11.

  The coating solution supply port 211 is connected to a material supply valve 213 via a coating solution transporting pipe 212. The material supply valve 213 includes a mixing mixer, a material supply pump, a material fixed amount discharge device, a material tank, and the like in front of the material supply valve 213, and can continuously discharge a constant amount (a constant amount per unit time) during coating. It has become.

  In the present invention, the elastic layer material is applied using the cylindrical coating head as described above. During this application, the distance between the roller to be applied and the application head in the radial direction is fixed by an apparatus as shown in FIG. For this reason, it is possible to uniformly apply the elastic layer material.

  A schematic view of the vicinity of the cylindrical coating head discharge port is shown in FIG. Here, the nozzle length L indicates the length from the upper part of the discharge port to the point where the coated material is separated from the coating head. The thickness t of the rubber material refers to the thickness of the material applied to the shaft core at a point where the material is separated from the coating head.

When the elastic layer material is applied from the coating head, a roller having a certain shape can be stably manufactured by discharging a certain amount per unit time. Discharge amount of this time the elastic layer material is preferably from 50~15000mm ³ / sec, more preferably 100~10000mm ³ / sec. When the discharge amount of the elastic layer material is within these ranges, the material can be stably applied at a high application speed.
(Charging roller)
Next, an example of the charging roller manufactured by the present invention is shown in FIG. 4A shows a cross section parallel to the longitudinal direction, and FIG. 4B shows a cross section perpendicular to the longitudinal direction.

  The charging roller desirably has an appropriate elasticity in order to ensure good uniform adhesion to the photosensitive drum. Therefore, the charging roller used in the present invention has a configuration in which an elastic layer 42 is provided around the shaft core body 41 as in the developing roller. The hardness of the elastic layer 42 used for the charging roller is desirably Asker C hardness 20 to 40 degrees for the purpose of ensuring adhesion. At this time, like the developing roller, the elastic layer 42 does not have to be a single layer, and may be a multilayer. Further, when imparting conductivity to the elastic layer 42 as in the developing roller, the conductivity of the elastic layer 42 is adjusted by adding a conductive agent such as carbon black.

  Further, a resin layer 43 may be provided on the surface of the elastic layer 42 in order to maintain the slipperiness and smoothness of the charging roller surface. Similarly to the elastic layer, the resin layer 43 does not have to be a single layer, and may have a multilayer structure.

  Specific materials of the elastic layer 42 used for the charging roller include, for example, natural rubber, ethylene propylene diene methylene rubber (EPDM), styrene-butadiene rubber (SBR), silicone rubber, urethane rubber, epichlorohydrin rubber, isoprene rubber ( IR), butadiene rubber (BR), nitrile-butadiene rubber (NBR), chloroprene rubber (CR), and other synthetic rubbers, as well as polyamide rubber and fluorine rubber. These materials can be used alone or in combination. Moreover, you may use the foam of these materials for an elastic layer.

  Moreover, as a material used for the resin layer 43, resin, such as a polyamide resin, a urethane resin, an acrylic resin, a fluororesin, and a silicone resin, Furthermore, an epichlorohydrin resin, a chloroprene resin, an acrylonitrile resin, etc. are mentioned. These materials can be used alone or in combination. As a coating method of the resin layer material, generally known coating methods such as a ring coating method, a dipping method, a roll coating method, and a spray coating method can be used as in the case of the developing roller.

  Regardless of whether the charging roller is in contact or non-contact with the photosensitive drum, if the surface of the charging roller is rough, subtle uneven charging occurs due to the unevenness. As a result, image defects may occur. Therefore, the surface of the charging roller is preferably smoother, and it is desirable that Rz in the standard of JIS B 0601 surface roughness is 0 to 30 μm. In particular, the thickness is desirably 15 μm or less.

  The thickness of the resin layer is desirably 1 to 500 μm. If the thickness of the resin layer is less than 1 μm, there is a possibility that it cannot withstand friction with the photosensitive drum. Moreover, when the thickness of the resin layer exceeds 500 μm, it is difficult to make full use of the function of the elastic layer.

  In addition, when the electrical resistance unevenness of the entire charging roller is smaller, the photosensitive drum can be uniformly charged, so that a good image can be obtained.

  In addition, when the circumferential deviation of the charging roller is large, the variation in the nip width between the charging roller and the photosensitive drum within the circumference of the charging roller becomes large, so that the photosensitive drum may not be uniformly charged. In order to prevent this, it is better that the circumferential deflection of the charging roller is smaller. Specifically, the difference between (maximum value) and (minimum value) (maximum value)-(minimum value) of the distance from the center of the shaft core to the surface of the charging roller in one charging roller circumference is 0 to 30 μm. In this range, the photosensitive drum can be charged almost uniformly.

In addition, when the roller obtained by the production method of the present invention is used as a charging roller, it is important to function as an electrode, and it is elastic and obtains a sufficient contact state, and at the same time charges a moving charged object. It is necessary to have a sufficiently low resistance. However, on the other hand, it is necessary to prevent voltage leakage in the case where a defect site such as a pinhole exists in the member to be charged. Therefore, when an electrophotographic photosensitive drum is used as the member to be charged, a resistance of 1 × 10 ³ to 1 × 10 ⁹ Ω · cm is required as the resistance value of the elastic layer in order to obtain sufficient chargeability and leakage resistance. It is desirable to have.

  Next, an outline of an electrophotographic process cartridge and an image forming apparatus incorporating the developing roller and charging roller of the present invention will be described with reference to FIG.

  The surface of the photosensitive drum 501 is charged by the charging roller 502 so that the electric potential is uniform with a predetermined polarity, and then subjected to exposure 503 of target image information. An electrostatic latent image corresponding to is formed. This electrostatic latent image is visualized as a toner image by the toner 505 supplied by the developing roller 504. The visualized toner image is transferred to the recording material 507 by applying a voltage from the back surface of the recording material 507 conveyed by the paper supply roller 506 by the transfer roller 508, and is configured by the fixing roller 509 and the pressure roller 510. It is conveyed to the fixing unit, undergoes image fixing, and is output as an image formed product. The photosensitive drum 501 is cleaned by a cleaning unit 511 in order to remove toner, dust, and the like remaining on the photosensitive drum 501, neutralized by a neutralizing member (not shown), and proceeds to the charging process again. Note that the toner removed by the cleaning unit 511 is collected in a waste toner container 512. In addition, a cleaning roller can be used as a member of the cleaning unit 511.

  On the other hand, the surface of the developing roller 504 is supplied with toner from the toner storage tank 514 by the toner supply roller 513, and the toner supply roller 513 and the developing blade 515 are in contact with each other so that the developing blade 515 has a uniform thickness. . Toner that is not used when developing the electrostatic latent image on the photosensitive drum on the developing roller 504 is scraped off from the developing roller 504 once by the toner supply roller 513. The charging roller 502, the developing roller 504, and the transfer roller 508 are applied with a necessary voltage by a bias application power source. The electrophotographic process cartridge is a unit in which members such as those described here, excluding the transfer roller and the fixing unit, are integrated.

  In addition, by arranging four color electrophotographic process cartridges of black, magenta, cyan, and yellow, transferring each toner to a recording material, and performing image fixing, a color image formed product can be output. .

  The present invention can be applied not only to conductive rollers such as developing rollers and charging rollers used in electrophotographic apparatuses, but also to advantageous effects when applied to conductive rollers for various industries. Moreover, it is not limited to the following Example.

(Example)
Hereinafter, the present invention will be described by way of examples. First, details of various measurements and evaluation methods will be described.

(Structure recovery time measurement)
A method for measuring the structure recovery time of a liquid rubber material using a viscoelasticity measuring device is described below.

  As a viscoelasticity measuring device, RheoStress 600 manufactured by Haake was used.

  About 1 g of sample was collected and placed on the sample stage, the cone plate was gradually approached, and a measurement gap was set at a position of about 50 μm from the sample stage. ). At that time, the material extruded around was removed cleanly so as not to affect the measurement. The temperature of the plate base was set so that the material temperature would be 23 ° C., and the measurement was started after leaving the sample for 10 minutes.

  The stress applied to the sample was 2000 Pa, and the stress was continuously applied for 60 seconds while rotating the cone plate in the same direction. After that, the stress was set to 2 Pa and the stress was continuously applied for 120 seconds while changing the rotation direction at a cycle of 1 Hz, and the changes in the storage elastic modulus G and loss elastic modulus G were measured. The time until the storage elastic modulus G ′ and the loss elastic modulus G ″ intersect after reaching a constant value in the region was defined as the structure recovery time. FIG. 6 is a schematic diagram showing the structure recovery time in the present invention.

(Measurement and evaluation method of outer diameter accuracy of conductive roller)
The conductive roller obtained in this study was left in an environment of temperature 25 ° C. and humidity 45% for 24 hours or more, and then the following measurements were performed.

The outer diameter of the point 30 mm from both ends of the rubber roller and the central portion in the longitudinal direction of the rubber roller is measured by a laser length measuring machine (LS-5000 manufactured by Keyence). This was performed while rotating 360 °, and the average was taken as the outer diameter at each point of the conductive roller. Furthermore, the three measured outer diameters are compared, the difference between the maximum value and the minimum value is taken, and if the value is less than 30 μm, ◎,
○ if it is 30 μm or more and less than 50 μm,
If it is 50 μm or more, it was evaluated as Δ.

(Measurement and evaluation method of resistance and resistance unevenness of conductive roller)
The conductive roller obtained in this study was left in an environment of temperature 25 ° C. and humidity 45% for 24 hours or more, and then the following measurements were performed.

  Details will be described with reference to FIG. A load of 500 g is applied to both ends of the shaft core of the conductive roller 71 and pressed against the metal drum 72 rotating at 60 rpm. After applying a voltage of 100 V between the shaft of the metal drum 72 and the conductive roller 71, The resistance value of the conductive roller is calculated from the value of the current flowing through the 10 kΩ resistor connected in series with the conductive roller, and the average value of the maximum and minimum values of the conductive roller resistance in one round is calculated as the resistance of the conductive roller. Value. Also, the maximum and minimum resistance values in one round of the conductive roller are taken, and the value of 1- (minimum resistance value / maximum resistance value) is defined as the resistance unevenness of the conductive roller.

If the resistance unevenness is 0 or more and less than 0.3, ◎,
When resistance unevenness is 0.3 or more and less than 0.7, ○,
When the resistance unevenness was 0.7 or more and 1 or less, the evaluation was made as Δ.
(Measurement and evaluation method for circumferential runout of conductive roller)
The conductive roller obtained in this study was left in an environment of temperature 25 ° C. and humidity 45% for 24 hours or more, and then the following measurements were performed.

  For each point obtained by equally dividing the conductive roller into six parts in the longitudinal direction, the conductive roller is rotated in steps of 1 ° around the center of the shaft core, and the distance from the center of the shaft core to the surface of the conductive roller is measured by a laser measuring machine (LS made by Keyence -5000). After the conductive roller makes one turn, a value obtained by subtracting the minimum distance value from the maximum distance value in the obtained 360-point distance is defined as a circumferential deflection value at each point of the conductive roller. Further, the five measured values of circumferential deflection are compared, and the maximum circumferential deflection value is taken as the circumferential deflection value of the conductive roller.

When the circumferential deflection value is 0 μm or more and less than 30 μm, ◎,
When the circumferential runout is 30 μm or more and less than 50 μm,
When the circumferential deflection value was 50 μm or more, the evaluation was made as Δ.

(Conductive roller image evaluation method)
The conductive roller obtained by this study was incorporated into a cartridge as various rollers, and image evaluation was performed. For example, when image evaluation is performed using the obtained developing roller, a conductive roller is incorporated in the cartridge as a developing roller (a cylindrical coating head having an inner diameter of 12.6 mm is manufactured by HP Color Laser Jet 3700, inner diameter Manufactured by Canon Inc., LASER SHOT LBP-2510 manufactured by Canon Inc.), an image for evaluation was output, and image evaluation was performed.

The environment for outputting the evaluation image was set to a temperature of 25 ° C. and a humidity of 45%, and the evaluation cartridge was left in this environment for 24 hours or more before evaluation. For the evaluation image, an image in which a horizontal line having a width of 1 dot and an interval of 2 dots was written in the direction perpendicular to the rotation direction of the photosensitive member was used. After that, if the image quality is very good visually, ◎
Defects such as slightly low concentration are seen, but if it is at a level that does not cause any problem in practice,
The image evaluation after endurance was evaluated as Δ if there was a bad image such as a low density.

(Comprehensive evaluation method)
As a comprehensive evaluation,
◎ if there is no item of △,
○ when there is only one item of △,
When there were two or more items of Δ, the evaluation was made as Δ.

  The developing roller was manufactured according to the following procedure.

[Preparation of elastic layer material]
The elastic layer material was prepared by the following procedure.
Liquid silicone rubber (molecular weight: 100,000) 100 parts by mass Carbon black (Tokai Black (registered trademark) # 4400, manufactured by Tokai Carbon Co., Ltd.) 14 parts by mass The above composition is mixed and defoamed with a planetary mixer for 30 minutes to obtain a silicone base material It was. Furthermore, 0.02 parts by mass of an isopropyl alcohol solution of chloroplatinic acid (platinum content: 3% by mass) is added to 100 parts by mass of this base material to obtain a mixture A, and an organohydrogenpolysiloxane having a viscosity of 10 cps (SiH content) 1% by mass) 1.5 parts by mass was added and mixed to obtain a mixture B. The mixtures A and B are set in the raw material tanks 1 and 2 attached to the coating machine, respectively, sent to a static mixer using a pressure feed pump, and the mixtures A and B are mixed at a ratio of 1: 1 to obtain an elastic layer material. Got.

  The structure recovery time of this elastic layer material was 0.5 seconds.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  Using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm, ejection of the elastic layer material was started at 680 mm 3 / sec. The elastic layer material was applied by passing a shaft core (diameter: 11.4 mm, t = 0.6 mm) through the cylindrical coating head at 30 mm / sec in the longitudinal direction. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and heat-cured for 1 minute with an infrared heater (HYL25, manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

[Preparation of resin layer material]
100 parts by mass of polyurethane polyol prepolymer (Takelac (registered trademark) TE5060, manufactured by Mitsui Takeda Chemical Co., Ltd.), 77 parts by mass of isocyanate (2521 Nippon Polyurethane, Coronate (registered trademark)), and carbon black (MA100, manufactured by Mitsubishi Chemical Corporation) ) 24 parts by mass and 24 parts by mass of urethane particles (C400 manufactured by Negami Kogyo Co., Ltd.) were mixed, methyl ethyl ketone was added, and the mixture was dispersed with a sand mill for 1 hour. Methyl ethyl ketone was further added so that the solid content after dispersion was 20 to 30% by mass to obtain a resin layer material.

(Resin layer application)
The conductive roller was immersed in the resin layer material to coat the resin layer, and then pulled up and allowed to dry naturally. Next, the coated resin layer material was cured by heat treatment at 140 ° C. for 60 minutes, and the conductive resin layer was laminated on the outer peripheral surface of the elastic layer to obtain the developing roller of the present invention.

  The developing roller obtained by the above method was measured and evaluated for outer diameter accuracy, resistance unevenness, circumferential runout and image. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that the coating head having a nozzle length of 9.0 mm was used in [Elastic layer application] in Example 1.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that the coating head having a nozzle length of 15.0 mm was used in [Elastic layer application] in Example 1.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that [Elastic layer application] in Example 1 was changed as follows.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 2160 mm 3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter: 8.2 mm, t = 2.2 mm) through the ring-type coating head at 30 mm / sec in the longitudinal direction. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and heat-cured for 3 minutes with an infrared heater (HYL25 manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 4 except that a coating head having a nozzle length of 2.2 mm was used in [Application of elastic layer] in Example 4.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 4 except that a coating head having a nozzle length of 30.0 mm was used in [Elastic layer application] in Example 4.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that [Elastic layer application] in Example 1 was changed as follows.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 2895 mm3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter 6.0 mm, t = 3.3 mm) through the ring-type coating head in the longitudinal direction at 30 mm / sec. The roller coated with the elastic layer material was rotated at 30 rpm in a horizontal state, and was heated and cured for 4 minutes with an infrared heater (HYL25, manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 7 except that the coating head having a nozzle length of 15.0 mm was used in [Elastic layer application] in Example 7.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 7 except that a coating head having a nozzle length of 30.0 mm was used in [Elastic layer application] in Example 7.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that [Elastic layer application] in Example 1 was changed as follows.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 5140 mm 3 / sec using a cylindrical coating head having an inner diameter of 16.8 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter: 8.0 mm, t = 4.4 mm) through the ring-type coating head in the longitudinal direction at 30 mm / sec. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and was heated and cured for 5 minutes with an infrared heater (HYL25, manufactured by Highbeck Co., Ltd .: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 10 except that the coating head having a nozzle length of 15.0 mm was used in [Elastic layer application] in Example 10.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 10 except that a coating head with a nozzle length of 30.0 mm was used in [Elastic layer application] in Example 10.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that [Elastic layer application] in Example 1 was changed as follows.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 6010 mm 3 / sec using a cylindrical coating head having an inner diameter of 16.8 mm and a nozzle length L of 1.2 mm. The elastic layer material was applied by passing a shaft core (diameter: 5.2 mm, t = 5.8 mm) through the ring-type coating head in the longitudinal direction at 30 mm / sec. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and was heated and cured for 6 minutes with an infrared heater (HYL25, manufactured by Hibeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 13 except that a coating head having a nozzle length of 15.0 mm was used in [Elastic layer application] in Example 13.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 13 except that a coating head having a nozzle length of 30.0 mm was used in [Elastic layer application] in Example 13.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that [Preparation of elastic layer material] and [Application of elastic layer] in Example 1 were changed as follows.

[Preparation of elastic layer material]
The elastic layer material was prepared by the following procedure.

Liquid silicone rubber (molecular weight: 100,000) 100 parts by mass Carbon black (Tokai Carbon Co., Ltd. # 4400) 8 parts by mass Carbon black (Mitsubishi Chemical Corporation # 2600) 21 parts by mass Silica (Aerosil, Japan Aerosil) Trademark) 50) 9 parts by mass quartz (Min-Usil manufactured by Pennsylvania Glass Sand) 20 parts by mass The above blend was mixed and defoamed with a planetary mixer for 30 minutes to obtain a silicone base material. Furthermore, 0.02 parts by mass of an isopropyl alcohol solution of chloroplatinic acid (platinum content: 3% by mass) is added to 100 parts by mass of this base material to obtain a mixture A, and an organohydrogenpolysiloxane having a viscosity of 10 cps (SiH content) 1% by mass) 1.5 parts by mass was added and mixed to obtain a mixture B. The mixtures A and B are set in the raw material tanks 1 and 2 attached to the coating machine, respectively, sent to a static mixer using a pressure feed pump, and the mixtures A and B are mixed at a ratio of 1: 1 to obtain an elastic layer material. Got.

  The structure recovery time of this elastic layer material was 10.3 seconds.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 680 mm 3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter: 11.4 mm, t = 0.6 mm) through the ring-type coating head in the longitudinal direction at 30 mm / sec. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and heat-cured for 1 minute with an infrared heater (HYL25, manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 16 except that a coating head having a nozzle length of 9.0 mm was used in [Application of elastic layer] in Example 16.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 16 except that a coating head with a nozzle length of 15.0 mm was used in [Elastic layer application] in Example 16.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 16 except that [Application of Elastic Layer] in Example 16 was changed as follows.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 2160 mm 3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter: 8.2 mm, t = 2.2 mm) through the ring-type coating head at 30 mm / sec in the longitudinal direction. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and heat-cured for 3 minutes with an infrared heater (HYL25 manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 19 except that a coating head having a nozzle length of 2.2 mm was used in [Elastic layer application] in Example 19.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 19 except that a coating head having a nozzle length of 30.0 mm was used in [Elastic layer application] in Example 19.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 16 except that [Application of Elastic Layer] in Example 16 was changed as follows.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 2895 mm3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter 6.0 mm, t = 3.3 mm) through the ring-type coating head in the longitudinal direction at 30 mm / sec. The roller coated with the elastic layer material was rotated at 30 rpm in a horizontal state, and was heated and cured for 4 minutes with an infrared heater (HYL25, manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 22 except that a coating head having a nozzle length of 15.0 mm was used in [Elastic layer application] in Example 22.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 22 except that a coating head with a nozzle length of 30.0 mm was used in [Elastic layer application] in Example 22.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that [Preparation of elastic layer material] and [Application of elastic layer] in Example 1 were changed as follows.

[Preparation of elastic layer material]
The elastic layer material was prepared by the following procedure.

Liquid silicone rubber (molecular weight: 100,000) 100 parts by mass Carbon black (Tokai Carbon (registered trademark) # 4400 manufactured by Tokai Carbon Co., Ltd.) 8 parts by mass Carbon black (# 2600 manufactured by Mitsubishi Chemical Corporation) 15 parts by mass Silica (Aerosil manufactured by Nippon Aerosil Co., Ltd.) Trademark) 50) 7 parts by mass quartz (Min-Usil manufactured by Pennsylvania Glass Sand) 15 parts by mass The above blend was mixed and defoamed with a planetary mixer for 30 minutes to obtain a silicone base material. Furthermore, 0.02 parts by mass of an isopropyl alcohol solution of chloroplatinic acid (platinum content: 3% by mass) is added to 100 parts by mass of this base material to obtain a mixture A, and an organohydrogenpolysiloxane having a viscosity of 10 cps (SiH content) 1% by mass) 1.5 parts by mass was added and mixed to obtain a mixture B. The mixtures A and B are set in the raw material tanks 1 and 2 attached to the coating machine, respectively, sent to a static mixer using a pressure feed pump, and the mixtures A and B are mixed at a ratio of 1: 1 to obtain an elastic layer material. Got.

  The structure recovery time of this elastic layer material was 38.2 seconds.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 680 mm 3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter: 11.4 mm, t = 0.6 mm) through the ring-type coating head in the longitudinal direction at 30 mm / sec. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and heat-cured for 1 minute with an infrared heater (HYL25, manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 25 except that the coating head having a nozzle length of 9.0 mm was used in [Elastic layer application] in Example 25.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 25 except that a coating head with a nozzle length of 15.0 mm was used in [Elastic layer application] in Example 25.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 25 except that [Application of Elastic Layer] in Example 25 was changed as follows.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 2160 mm 3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter: 8.2 mm, t = 2.2 mm) through the ring-type coating head at 30 mm / sec in the longitudinal direction. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and heat-cured for 3 minutes with an infrared heater (HYL25 manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 28 except that the coating head having a nozzle length of 2.2 mm was used in [Elastic layer application] in Example 28.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 28 except that the coating head having a nozzle length of 30.0 mm was used in [Elastic layer application] in Example 28.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that [Preparation of elastic layer material] and [Application of elastic layer] in Example 1 were changed as follows.

[Preparation of elastic layer material]
The elastic layer material was prepared by the following procedure.

Liquid silicone rubber (molecular weight: 100,000) 100 parts by mass Carbon black (Toka Black (registered trademark) # 4400, manufactured by Tokai Carbon Co., Ltd.) 6 parts by mass Silica (AELOSIL 50, manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass The mixture was degassed to obtain a silicone base material. Furthermore, 0.02 parts by mass of an isopropyl alcohol solution of chloroplatinic acid (platinum content: 3% by mass) is added to 100 parts by mass of this base material to obtain a mixture A, and an organohydrogenpolysiloxane having a viscosity of 10 cps (SiH content) 1% by mass) 1.5 parts by mass was added and mixed to obtain a mixture B. The mixtures A and B are set in the raw material tanks 1 and 2 attached to the coating machine, respectively, sent to a static mixer using a pressure feed pump, and the mixtures A and B are mixed at a ratio of 1: 1 to obtain an elastic layer material. Got.

  The structure recovery time of this elastic layer material was 44.3 seconds.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 680 mm 3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter: 11.4 mm, t = 0.6 mm) through the ring-type coating head in the longitudinal direction at 30 mm / sec. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and heat-cured for 1 minute with an infrared heater (HYL25, manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 31 except that a coating head having a nozzle length of 9.0 mm was used in [Elastic layer application] in Example 31.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  In [Elastic layer application] of Example 31, a developing roller was obtained in the same manner as in Example 31 except that a coating head having a nozzle length of 15.0 mm was used.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 31, except that [Elastic layer application] in Example 31 was changed as follows.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 2160 mm 3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter: 8.2 mm, t = 2.2 mm) through the ring-type coating head at 30 mm / sec in the longitudinal direction. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and heat-cured for 3 minutes with an infrared heater (HYL25 manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 34 except that, in [Applying elastic layer] in Example 34, a coating head having a nozzle length of 2.2 mm was used.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 34 except that the coating head having a nozzle length of 30.0 mm was used in [Application of elastic layer] in Example 34.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 1 except that [Preparation of elastic layer material] and [Application of elastic layer] in Example 1 were changed as follows.

[Preparation of elastic layer material]
The elastic layer material was prepared by the following procedure.

Liquid silicone rubber (molecular weight: 100,000) 100 parts by mass Carbon black (Toka Black (registered trademark) # 4400 manufactured by Tokai Carbon Co., Ltd.) 6 parts by mass Quartz (Pennsilvania Glass Sand manufactured by Min-Usil) 2 parts by mass The mixture was degassed for 30 minutes with a mixer to obtain a silicone base material. Furthermore, 0.02 parts by mass of an isopropyl alcohol solution of chloroplatinic acid (platinum content: 3% by mass) is added to 100 parts by mass of this base material to obtain a mixture A, and an organohydrogenpolysiloxane having a viscosity of 10 cps (SiH content) 1% by mass) 1.5 parts by mass was added and mixed to obtain a mixture B. The mixtures A and B are set in the raw material tanks 1 and 2 attached to the coating machine, respectively, sent to a static mixer using a pressure feed pump, and the mixtures A and B are mixed at a ratio of 1: 1 to obtain an elastic layer material. Got.

  The structure recovery time of this elastic layer material was 57.3 seconds.

(Elastic layer coating)
For the shaft core, use iron whose surface is chemically nickel-plated, apply a primer to the surface (DY39-051: manufactured by Toray Dow Corning Silicone), and heat-treat it at 150 degrees for 30 minutes in an electric furnace. It was. After the primer treatment, the shaft core was placed on the ring coater work holding shaft, clamped by the upper holding shaft and the lower holding shaft, and then the shaft core was lowered to the coating start position and stopped.

  The elastic layer material was discharged at 680 mm 3 / sec using a cylindrical coating head having an inner diameter of 12.6 mm and a nozzle length L of 1.0 mm. The elastic layer material was applied by passing a shaft core (diameter: 11.4 mm, t = 0.6 mm) through the ring-type coating head in the longitudinal direction at 30 mm / sec. The roller to which the elastic layer material was applied was rotated at 30 rpm in a horizontal state, and heat-cured for 1 minute with an infrared heater (HYL25, manufactured by Hybeck: work heater distance 60 mm, output 780 W). Thereafter, heat treatment was carried out at 180 ° C. for 2 hours in an electric furnace for the purpose of stabilizing physical properties of the elastic layer material and removing reaction residues and unreacted low molecular components in the elastic layer material, thereby obtaining a conductive roller. .

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 37 except that a coating head having a nozzle length of 9.0 mm was used in [Elastic layer application] in Example 37.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  A developing roller was obtained in the same manner as in Example 37 except that the coating head having a nozzle length of 15.0 mm was used in [Elastic layer application] in Example 37.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

  The roll created in Example 8 was used as a charging roll and incorporated in an image forming apparatus for image evaluation. As a result, an excellent image could be obtained.

(Comparative Example 1)
A developing roller was obtained in the same manner as in Example 8, except that the following changes were made in [Preparation of elastic layer material] in Example 8.

[Preparation of elastic layer material]
The elastic layer material was prepared by the following procedure.

Liquid silicone rubber (molecular weight: 100,000) 100 parts by mass Carbon black (Toka Black (registered trademark) # 4400 manufactured by Tokai Carbon Co., Ltd.) 5 parts by mass Quartz (Pennsilvania Glass Sand manufactured by Min-Usil) 8 parts by mass The mixture was degassed for 30 minutes with a mixer to obtain a silicone base material. Furthermore, 0.02 parts by mass of an isopropyl alcohol solution of chloroplatinic acid (platinum content: 3% by mass) is added to 100 parts by mass of this base material to obtain a mixture A, and an organohydrogenpolysiloxane having a viscosity of 10 cps (SiH content) 1% by mass) 1.5 parts by mass was added and mixed to obtain a mixture B. The mixtures A and B are set in the raw material tanks 1 and 2 attached to the coating machine, respectively, sent to a static mixer using a pressure feed pump, and the mixtures A and B are mixed at a ratio of 1: 1 to obtain an elastic layer material. Got.

  The structure recovery time of this elastic layer material was 103.5 seconds.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

(Comparative Example 2)
A developing roller was obtained in the same manner as in Example 8 except that a coating head having a nozzle length of 0.2 mm was used in [Application of elastic layer] in Example 8.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

(Comparative Example 3)
A developing roller was obtained in the same manner as in Example 1 except that a coating head having a nozzle length of 30.0 mm was used in [Elastic layer application] in Example 1.

  The same evaluation as in Example 1 was performed on the developing roller obtained by the above method. The results are shown in Table 1.

It is sectional drawing which shows the developing roller of this invention. (A) Development roller longitudinal direction, (B) Development roller axial direction It is a coating machine having a ring-type coating head used in the present invention. It is the schematic of the cylindrical coating head discharge port vicinity used by this invention. It is sectional drawing which shows the charging roller of this invention. (A) Charge roller longitudinal direction, (B) Charge roller axial direction 1 is a schematic view showing an outline of an image forming apparatus of the present invention. It is the schematic for showing the structure recovery time in this invention. It is the schematic of the apparatus which measures the resistance of the conductive roller of this invention.

Explanation of symbols

11 Shaft core (Developing roller)
12 Elastic layer (developing roller)
13 Resin layer (developing roller)
DESCRIPTION OF SYMBOLS 201 Base 202 Column 203 Precision ball screw 204 LM guide 205 Servo motor 206 Pulley 207 Bracket 208 Coating head 209 Workpiece holding shaft 210 Workpiece holding shaft 211 Coating liquid supply port 212 Coating liquid conveyance pipe 213 Material supply valve 214 Linear Guide 31 Shaft core 32 Top of discharge port L Nozzle length t Thickness of coated rubber material 41 Shaft core (charging roller)
42 Elastic layer (charging roller)
43 Resin layer (charging roller)
501 Photosensitive drum 502 Charging roller 503 Exposure 504 Developing roller 505 Toner 506 Feeding roller 507 Recording material 508 Transfer roller 509 Fixing roller 510 Pressure roller 511 Cleaning unit 512 Waste toner container 513 Toner supply roller 514 Toner storage tank 515 Developing blade 71 Conductive roller 71 72 Metal drum

Claims (10)

  In the method for producing a conductive roller obtained by coating a rubber material around the shaft core and vulcanizing and curing, the structure recovery time of the rubber material to be coated is 0.1 second or more and 60.0 seconds or less, A rubber material is coated using a cylindrical coating head, and the relationship between the nozzle length L of the cylindrical coating head and the thickness t of the rubber material coated with the cylindrical coating head is 0. .2 ≦ L / t ≦ 25.0 is satisfied, A method for producing a conductive roller is provided.   2. The method of manufacturing a conductive roller according to claim 1, wherein a thickness t of the rubber material covered by the cylindrical coating head is 0.5 mm or more and 6.0 mm or less.   3. The method of manufacturing a conductive roller according to claim 1, wherein a nozzle length L of the cylindrical coating head is 1.0 mm or more and 30.0 mm or less.   The method for producing a conductive roller according to claim 1, wherein the rubber material is a silicone rubber containing a filler.   The method for producing a conductive roller according to claim 1, wherein a filler content in the rubber material is 5 parts by mass or more and 60 parts by mass or less.   The method for producing a conductive roller according to claim 1, wherein at least one of the fillers contained in the rubber material is carbon black.   The electroconductive roller manufactured by the manufacturing method in any one of Claims 1-6.   The conductive roller according to claim 7, wherein the conductive roller is one of a developing roller and a charging roller.   A charging roller that contacts a rotatable photosensitive drum to supply charges to the surface of the photosensitive drum, an exposure unit that records image information on the surface of the photosensitive drum, and a developer that contacts the photosensitive drum and contacts the surface of the photosensitive drum. An electrophotographic process cartridge having a developing roller for supplying the electrophotographic process cartridge, wherein at least one of the developing roller and the charging roller is the conductive roller according to claim 8.   A charging roller that contacts a rotatable photosensitive drum to supply charges to the surface of the photosensitive drum, an exposure unit that records image information on the surface of the photosensitive drum, and a developer that contacts the photosensitive drum and contacts the surface of the photosensitive drum. A developing roller for supplying the developer, a transfer roller for transferring the developer to the transfer material, a pressure roller for forming a nip portion with the fixing roller, the fixing roller, and conveying the transfer material in pressure contact with the nip portion. The image forming apparatus according to claim 8, wherein at least one of the charging roller and the developing roller is the conductive roller according to claim 8.

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