JP2007316524A - Developing roller, its manufacturing method, electrophotographic process cartridge and electrophotographic image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller with which irregular density and fogging are restrained from occurring and an image is formed with appropriate density. <P>SOLUTION: The developing roller comprises a shaft core body, an elastic layer and a surface layer, and the surface layer is a thermoplastic resin layer whose thickness is ≥5.0 nm and <2.0μm, and the micro rubber hardness Hd of the elastic layer is ≥21 and ≤50, a difference (Hs-Hd) from the micro rubber hardness Hs of the roller is ≥0 and ≤5, and a difference between the surface roughness Ra<SB>1</SB>of the elastic layer and the surface roughness Ra<SB>2</SB>of the developing roller is from -0.20μm to 0.20μm. It is desirable that Ra<SB>1</SB>is within a range from 0.01μm to 2.00μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing roller used in an electrophotographic apparatus such as a copying machine or a laser printer, a manufacturing method thereof, an electrophotographic process cartridge including the developing roller, and an electrophotographic image forming apparatus.

  In a conventional printer using an electrophotographic system, an image forming unit is installed therein. The image is formed through processes of cleaning, charging, latent image formation, development, transfer, and fixing. The image forming section includes a cleaning drum, a charging section, a latent image forming section, a developing section, and a transfer section around a photosensitive drum that is an electrophotographic photosensitive member. The toner image formed on the photosensitive drum in the developing unit of the image forming unit is transferred to the recording material in the transfer unit and then conveyed to the fixing unit, where it is heated and pressurized to form a fixed recorded image. The

  In recent years, OA devices such as printers have been improved in image quality and lifetime. Along with this, in a development process in which an electrostatic latent image is a toner image on a photosensitive drum, a developing roller having an elastic layer such as rubber is used. Proposed.

  However, the low molecular weight substance contained in the elastic body is likely to ooze out due to the pressure contact with the photosensitive drum, and the low molecular weight substance adheres to the member in pressure contact and often adversely affects the obtained image and life. Therefore, in general, the developing roller has a surface layer further formed on the elastic layer, thereby taking measures to prevent the low molecular weight material from exuding from the elastic body (see Patent Document 1).

  Further, in the developing roller of the contact developing system, it is required to reduce the hardness of the developing roller itself in consideration of a load on the photosensitive drum and developer that are in pressure contact (see Patent Document 2).

  Furthermore, an appropriate surface roughness is required for the developing roller to convey an appropriate amount of developer (toner) (see Patent Document 3).

  However, in the technique described in Patent Document 1, when the film thickness of the surface layer is increased, the developing roller becomes harder, so that stress on the photosensitive drum that is in pressure contact increases, leading to a reduction in life. Further, the load on the developer passing through the pressure contact portion between the developing roller and the other member is large, and when continuous image formation is performed, the so-called “fogging” phenomenon in which the developer adheres to the photosensitive drum also in the non-image portion gradually. It ’s getting bigger.

  In addition, as in Patent Document 2, it has been studied to reduce the hardness of the elastic body in consideration of the reduction in the hardness of the developing roller. However, the hardness of the roller is kept uniform by reducing the hardness of the elastic body. In the developing roller using such an elastic body, uneven density tends to occur in the image.

Moreover, in patent document 3, in order to optimize the surface roughness of a developing roller, an uneven | corrugated shape is formed in the surface by disperse | distributing and mixing an inorganic or organic powder in a surface layer. However, if the thickness of the surface layer is reduced, it becomes difficult to control the surface roughness with such means.
JP-A 63-217375 Japanese Patent Laid-Open No. 10-268631 Japanese Patent Laid-Open No. 07-054836

  Accordingly, an object of the present invention is to provide a developing roller capable of suppressing density unevenness and fogging and forming an image with an appropriate density.

  As a result of intensive studies to solve the above problems, the present inventors have found that a developing roller that is favorable when the elastic layer and the surface layer formed on the shaft core have a specific relationship with respect to the hardness and surface roughness. In addition, the inventors have found that the developing roller can be easily manufactured by specifying the method for forming the surface layer, and finally the present invention has been achieved.

That is, the present invention has at least one elastic layer on the shaft core and at least one surface layer on the outer periphery thereof, carries and conveys the developer, and comes into contact with the photosensitive drum to allow an electrostatic latent image. In the developing roller for visualizing, the surface layer is made of a thermoplastic resin, the thickness thereof is 5.0 nm or more and less than 2.0 μm, the micro rubber hardness Hd of the elastic layer surface is 21 or more and 50 or less, The difference (Hs−Hd) between the micro rubber hardness Hd of the elastic layer surface and the micro rubber hardness Hs of the developing roller surface is 0 or more and 5 or less, the surface roughness Ra ₁ of the elastic layer surface and the surface roughness of the developing roller The developing roller is characterized in that a difference of Ra ₂ (Ra ₁ −Ra ₂ ) is between −0.20 μm and 0.20 μm.

The surface roughness Ra ₁ of the elastic layer surface is preferably 0.01 μm or more and 2.00 μm or less.

  Furthermore, it is preferable that the thermoplastic resin forming the surface layer is selected from the group consisting of fluorine resin, thermoplastic polyimide, polyamide, polyethylene, polypropylene, and polystyrene.

  The present invention also has at least one elastic layer on the shaft core and at least one surface layer on the outer periphery thereof, carries and conveys the developer, contacts the photosensitive drum, and electrostatic latent image In the method for producing a developing roller for visualizing the surface, the surface layer is formed by a physical vapor deposition (PVD) method using a thermoplastic resin.

  The PVD method is preferably vacuum deposition or sputtering.

  Furthermore, the present invention is a developing roller manufactured by the above-described developing roller manufacturing method.

  According to another aspect of the present invention, there is provided the electrophotographic process cartridge, wherein the developing roller is any one of the developing rollers described above, wherein the developing roller is detachably attached to the main body of the electrophotographic image forming apparatus.

  Furthermore, according to the present invention, in the electrophotographic image forming apparatus having a developing roller disposed in contact with a photosensitive drum for holding an electrostatic latent image, the developing roller is any one of the above developing rollers. An electrophotographic image forming apparatus characterized by the above.

  In the developing roller of the present invention, since the surface layer is a very thin layer of thermoplastic resin, the hardness of the elastic layer and the hardness of the developing roller can be made extremely small, and the hardness of the elastic layer can be used as the developing roller. It became possible to produce with the required hardness. That is, it becomes easy to form an elastic layer having a uniform hardness before the surface layer is formed, and the entire hardness unevenness of the developing roller is extremely small. Accordingly, when the developing roller of the present invention is used as a developing roller in an electrophotographic process cartridge or an electrophotographic image forming apparatus, an image having no density unevenness can be obtained.

  In the production method of the present invention, since a physical vapor deposition (PVD) method which is a dry method is used, a thin film layer of a thermoplastic resin can be easily formed as a surface layer. Since the surface layer is formed to be sufficiently thin, the difference in hardness is small between the elastic body and the developing roller after the surface layer is formed, and the elastic body is sufficiently hard and uniform in required hardness. Can be used. Accordingly, there is provided a developing roller capable of increasing the hardness accuracy of the entire developing roller and obtaining an image having no density unevenness when used in an electrophotographic image forming apparatus. Further, a developing roller having a sufficiently low surface hardness and suppressing occurrence of fogging even in continuous image formation is provided.

Furthermore, the developing roller of the present invention has a desired surface roughness because the difference between the surface roughness Ra ₁ of the elastic layer surface and the surface roughness Ra ₂ of the developing roller after forming the elastic body is small. Easy to produce.

  A sectional view of an example of the developing roller of the present invention is shown in FIG.

  The developing roller of the present invention usually has a shaft core 1 made of a conductive material such as metal, and an elastic layer 2 is fixed on the outer peripheral surface of the shaft core 1, and the outer peripheral surface of the elastic layer 2. It has a structure in which the surface layer 3 is laminated. The shaft core body 1 has a columnar shape or a hollow cylindrical shape, and is often made of a conductive material such as metal. In the case where the developing roller is used in an electrically insulated state, a non-conductive material may be used as long as the shaft core itself can firmly hold its shape against an applied external force. .

  The developing roller is generally used with an electric bias applied or grounded. Therefore, the shaft core body 1 is preferably a support member, and at least the surface is preferably conductive as a conductive material. That is, a conductive material sufficient to apply a predetermined voltage to the elastic layer 2 having at least the outer peripheral surface formed thereon, for example, a metal or alloy such as aluminum, copper alloy, stainless steel, or chromium, nickel It is made of iron, synthetic resin, etc. that has been plated with, for example. In the developing roller used in the electrophotographic image forming apparatus, it is appropriate that the shaft core body 1 has an outer diameter in the range of 4 mm to 10 mm.

  The elastic layer 2 is a molded body using rubber as a raw material main component. Various rubbers conventionally used for developing rollers can be used as the raw material rubber of the elastic layer 2. Specifically, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR). ), Fluorine rubber, silicone rubber, epichlorohydrin rubber, hydride of NBR, polysulfide rubber, urethane rubber and the like. And these are used individually or in mixture of 2 or more types.

  The hardness of the elastic layer 2 which is a molded body formed mainly of rubber is preferably 21 or more and 50 or less, more preferably 25 or more and 40 or less in terms of micro rubber hardness. In the following, unless otherwise specified, the micro rubber hardness is expressed as “MD hardness”.

  If the MD hardness of the elastic layer 2 is less than 21, it is difficult to obtain the uniformity of the hardness of the entire elastic layer. When the developed developing roller is used in an image forming apparatus, density unevenness occurs in the image. Cheap. Further, when the MD hardness of the elastic layer 2 is more than 50, the pressure contact pressure between the developing roller and the other member pressed against the developing roller becomes high, and fogging occurs when continuous image formation is performed.

  The MD hardness is a micro rubber hardness meter “MD-1 type” (trade name) manufactured by Kobunshi Keiki Co., Ltd.・ Measured under normal humidity and averaged.

  In particular, it is preferable to use a silicone rubber as the main component rubber because low hardness and low compression set are easily obtained. Examples of the silicone rubber include polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polytrifluoropropylvinylsiloxane, polymethylphenylsiloxane, polyphenylvinylsiloxane, and copolymers of these polysiloxanes. .

  When the rubber molded body is used, its compression set and the like are in a preferable range, and therefore the degree of polymerization of the silicone rubber is preferably in the range of 3000 to 15000. In addition to the silicone rubber, natural rubber, isoprene rubber, chloroprene rubber, EPDM, SBR, NBR, etc., as long as the hardness remains within the required range in the rubber molded body forming the conductive elastic layer as necessary. May be included at a ratio of 20% by mass or less of the rubber molded body.

  Furthermore, in the developing roller of the present invention, when forming a rubber molded body for forming the elastic layer, components necessary for the function required for the elastic layer itself, such as a conductive agent, a non-conductive filler, etc., and rubber Various additive components used in forming a molded body, for example, various additives such as a crosslinking agent, a catalyst, and a dispersion accelerator can be appropriately blended in the main rubber material.

  As a conductive agent added for the purpose of imparting conductivity to the elastic layer, various conductive metals or alloys such as carbon black, graphite, aluminum, copper, tin, stainless steel, tin oxide, zinc oxide, indium oxide, titanium oxide, Various conductive metal oxides such as tin oxide-antimony oxide solid solution and tin oxide-indium oxide solid solution, and fine powders such as insulating substances coated with these conductive materials can be used.

  Among these, carbon black can be suitably used because it is relatively inexpensive and easily available, and good chargeability is obtained regardless of the type of the main rubber material. As a means for dispersing the finely powdered conductive agent in the main rubber material, conventionally used means such as a roll kneader, a Banbury mixer, a ball mill, a sand grinder, a paint shaker, etc. may be used. What is necessary is just to use suitably according to material.

In addition, as a means for imparting conductivity to the elastic layer, a technique of adding a conductive polymer compound instead of or together with the conductive agent can be used. The conductive polymer compound is a polymer compound obtained by using a polymer having a conjugated system such as polyacetylene as a host polymer, and doping it with a dopant such as I ₂ to make it conductive. Examples of the host polymer include polyacetylene, poly (p-phenylene), polypyrrole, polythiophenine, poly (p-phenylene oxide), poly (p-phenylene sulfide), poly (p-ferene vinylene), poly (2, 6 -Dimethylphenylene oxide), poly (bisphenol A carbonate), polyvinylcarbazole, polydiacetylene, poly (N-methyl-4-vinylpyridine), polyaniline, polyquinoline, poly (phenylene ether sulfone), etc. For example, AsF ₅ , I ₂ , Br ₂ , SO ₃ , Na, K, ClO ₄ , FeCl ₃ , F, Cl, Br, I, Kr, and other ions, Li, TCNQ (7, 7, 8, 8- Tetracyanoquinodimethane) and the like.

  Examples of the non-conductive filler that can be added to the rubber molded body include diatomaceous earth, quartz powder, dry silica, wet silica, titanium oxide, zinc oxide, aluminosilicate, calcium carbonate, and the like.

  When producing a rubber molding, for example, when liquid silicone rubber is used, the rubber components are cross-linked using a platinum-based catalyst with polyorganohydrogensiloxane as a cross-linking component.

  In order to ensure contact with the photosensitive drum to ensure a uniform nip width and to satisfy a suitable setting property, the thickness of the elastic layer is preferably 0.5 mm or more, more preferably. Is preferably 1.0 mm or more. There is no upper limit on the thickness of the elastic layer as long as the accuracy of the outer diameter of the produced elastic roller is not impaired. However, if the thickness of the elastic layer is excessively increased, only the production cost is required. In practice, the thickness of the elastic layer is suitably 6.0 mm or less, more preferably 5.0 mm or less. Further, the thickness of the elastic layer is appropriately selected according to the hardness thereof in order to achieve the target nip width.

  The method for forming the elastic layer on the shaft core is not particularly limited, and examples thereof include the following methods. Any of them may be used in the present invention.

  Necessary components such as a conductive agent, a vulcanizing agent, a stabilizer and a filler are mixed with the main component rubber to obtain an elastic layer raw material composition. Next, the raw material composition is poured into a cylindrical mold containing the shaft core, and extruded from the extruder together with the shaft core, or first extruded into a cylindrical shape to obtain a tube of the raw material composition. The shaft core is inserted into the tube, and an elastic layer is formed on the shaft core.

  After injecting the raw material composition into the mold, the elastic layer is preferably fixed in the mold. The thermoplastic rubber is cooled and solidified, and the vulcanized cured rubber is heated and vulcanized. In addition, after taking out from a metal mold | die, it is preferable to put in a heating furnace in order to take a distortion or to perform secondary vulcanization.

  In the method of extruding the shaft core together with the raw material composition, the raw material composition layer extruded together with the shaft core is cooled and solidified or heated and vulcanized. At this time, if necessary, the end portion can be cut off and the length and the end portion of the elastic layer can be adjusted.

  Also, the raw material composition is extruded into a cylindrical shape, cooled and solidified or heat vulcanized to obtain a tube, then cut into a predetermined length, and a shaft core body is inserted. Heat vulcanization is performed after the shaft core body is inserted. May be.

  In addition to these, the raw material composition can be used as a paint, and an elastic layer can be formed on the shaft core body by a method such as brush coating, spray coating, roller coating, or dip coating on the shaft core body.

  The surface of the elastic layer thus provided is usually prepared by polishing, blasting or the like before the surface layer is formed.

The surface of the developing roller having an appropriate roughness is preferable for uniformly supporting the developer and charging it uniformly. For this reason, it is preferable that the surface of the elastic layer produced as described above is subjected to uneven processing in a predetermined shape. The surface roughness of the elastic layer surface (hereinafter referred to as “Ra ₁ ”) is preferably 0.01 μm or more and 2.50 μm or less, more preferably 0.50 μm or more and 1.00 μm or less in terms of arithmetic average roughness. It is. When Ra ₁ is less than 0.01 μm, the toner transportability is lowered and sufficient image density may not be obtained. On the other hand, when Ra ₁ exceeds 1.50 μm, the amount of toner transport becomes too large and the toner may not be sufficiently charged. Here, when there are a plurality of elastic layers, Ra ₁ is the surface roughness measured on the layer forming the surface layer.

  The surface roughness of the elastic layer surface and the roller surface was measured using, for example, a surface roughness measuring machine “Surf Coder SE-3500” (trade name) manufactured by Kosaka Laboratory Ltd., and a feed speed of 0.5 mm / sec. Evaluation length 2.5 mm, roughness cutoff λc = 0.8 mm, can be measured with auto leveling ON in the horizontal direction.

  Examples of means for subjecting the elastic layer surface to a predetermined uneven process include a blasting method and a polishing method, and a polishing method is preferable in consideration of operability and reproducibility. In the polishing method, for example, by using a rubber roll grinder “LEO-600-F2” (trade name) manufactured by Mizuguchi Seisakusho Co., Ltd., it is possible to easily obtain an elastic roller having a desired surface roughness. it can.

  As described above, the developing roller of the present invention has a surface layer on the elastic layer. The surface layer is preferably made of a thermoplastic resin, more preferably a fluorine resin, polyimide, polyamide, polyethylene, polypropylene or polystyrene.

  In the developing roller of the present invention, the thickness of the surface layer is preferably 5.0 nm or more and less than 2.0 μm, more preferably 100.0 nm or more and 1.0 μm or less. When the thickness of the surface layer is less than 5.0 nm, the surface layer is peeled off immediately due to the seepage or wear of the low molecular weight substance from the elastic body. On the other hand, when the thickness of the surface layer is 2.0 μm or more, stress is generated in the surface layer, and cracks and wrinkles are likely to occur. The surface layer may be a single layer or a multilayer. The thickness of the surface layer can be measured by using a transmission electron microscope “Hitachi Electron Microscope H-7500” (trade name) manufactured by Hitachi High-Tech Co., Ltd., for example.

  This surface layer may be formed by wet methods such as dip coating, spray coating, roll coating, or physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, ion plating, plasma CVD, thermal CVD, laser CVD, etc. It is formed on the elastic layer by a dry method using a chemical vapor deposition (CVD) method.

  Note that it is preferable to use a dry method for forming the surface layer as compared with a wet method. The reason will be described with reference to the schematic cross-sectional view of the surface layer portion shown in FIG.

  FIG. 2A shows a case where a surface layer is formed by a wet method, where liquid accumulates in a concave portion on the surface of the elastic layer, a liquid flow occurs in the convex portion, and the uneven shape of the formed surface layer is easily changed. . Therefore, in order to manufacture a developing roller having a desired surface shape, it is necessary to consider various conditions such as the shape of the surface of the elastic layer and the parameters of the liquid used as the surface layer.

  On the other hand, when the surface layer is formed by the dry method, as shown in FIG. 2B, the surface layer can be formed into a film that maintains substantially the same shape so as to follow the shape of the elastic layer. For this reason, when manufacturing a developing roller having a desired surface shape, only the shape of the elastic layer needs to be predetermined, and the desired surface layer can be easily formed.

  As described above, the dry method is optimal as a method for forming a thin surface layer. Among them, the PVD method is considered in consideration of the adhesion between the elastic layer and the surface layer, processing time and processing temperature, simplicity of the apparatus, and the like. preferable. Further, in the PVD method, vacuum evaporation or sputtering is a particularly preferable method when handling a thermoplastic resin.

  A schematic diagram of an example of a vacuum deposition apparatus used in the present invention is shown in FIG.

In the vacuum deposition apparatus 201, a roller 202 having an elastic layer on which a surface layer is formed is set, and an alumina (Al ₂ O ₃ ) crucible 204 that heats and evaporates the evaporation substance 203 that becomes the surface layer, a vacuum pump, etc. An exhaust means 205 for reducing the pressure inside the apparatus 201 is disposed.

  Formation of the surface layer by the vacuum deposition process is performed according to the following procedure.

  The raw material roller 202 is set in the vacuum vapor deposition apparatus 201, and the evaporated substance 203 is put in the crucible 204. Next, the inside of the apparatus 201 is depressurized by the exhaust means 205. Here, the degree of vacuum in the apparatus 201 is 10 Torr (1.333 kPa) or less, although it varies depending on the type of the evaporated substance or the desired physical property of the developing roller to be obtained. If the degree of vacuum exceeds this range, the deposition rate of the surface layer is extremely reduced, and at the same time, the adhesion between the surface layer of the developing roller and the elastic layer tends to be insufficient.

  After reaching a predetermined degree of vacuum, the crucible 204 is raised to a temperature determined in accordance with the evaporation substance, and the evaporation substance 203 serving as a surface layer is evaporated and adhered to the surface of the roller 202 to form a surface layer. At this time, when the roller is driven to rotate, a highly uniform surface layer can be formed in the circumferential direction. The thickness of the surface layer can be controlled by, for example, the deposition time.

  A schematic diagram of an example of a sputtering apparatus used in the present invention is shown in FIG.

  The sputtering apparatus 301 includes a roller 202 having an elastic layer on which a surface layer is formed, a target 302 serving as a surface layer, a gas introduction port 303, an exhaust means 304 for evacuating the interior of the apparatus 301 such as a vacuum pump, and an applied power source for sputtering. (DC 305, AC power supply 306) are arranged as shown.

  The formation of the surface layer by the sputtering process is performed according to the following procedure.

The inside of the apparatus 301 in which the roller 202 on which the surface layer is formed and the target 203 serving as the surface layer is set is decompressed by the exhaust means 304, and then an inert gas is introduced from the gas inlet 303. At this time, argon gas is usually used as the inert gas because of cost and sputtering strength. The degree of vacuum in the apparatus after gas introduction is determined in consideration of the type of target to be used, the set physical properties of the developing roller to be manufactured, and the stability of the plasma generated in the apparatus, but usually 10 ⁻³ Torr. A range of (0.1333 Pa) to 1 Torr (133.3 Pa) is preferable.

  When a voltage is applied between the electrodes in the apparatus 301 after introducing the gas, plasma is generated, and atoms and ions are released from the surface of the target 302 into the plasma. These atoms and ions reach the elastic layer surface of the roller 202 installed so as to face the target, and a thin film is formed. Here, when the target is a conductive material, a DC power source 305 is used. When the target is an insulating material, an AC power source 306 is used to form a thin film on the roller. Is possible. Further, it is possible to form a surface layer having a uniform film thickness by rotating the roller in the circumferential direction while applying a voltage.

  In forming the surface layer by these methods, almost all inorganic materials, polymer materials, metal-based materials, etc. can be used as the surface layer material. However, in consideration of the flexibility required for the developing roller, the chargeability of the developer, the cost and the processing time in the manufacturing process, the material of the surface layer to be formed is preferably a thermoplastic resin. More preferably, it is a fluororesin, polyimide, polyamide, polyethylene, polypropylene or polystyrene.

  Further, the difference (Hs−Hd) between the MD hardness Hd of the elastic layer and the MD hardness Hs of the developing roller after forming the surface layer is preferably 0 or more and 5 or less, more preferably 2 or more and 4 or less. If this difference is greater than 5, when the developing roller is brought into pressure contact with another member such as a photoreceptor, a difference occurs in the amount of compressive deformation between the elastic layer and the surface layer, and the surface layer is liable to peel off.

Further, the difference (Ra ₁ −Ra ₂ ) between the surface roughness of the developing roller (hereinafter referred to as “Ra ₂ ”) after the surface layer is formed and the surface roughness Ra ₁ of the elastic layer is −0. It is preferably 20 μm or more and 0.20 μm or less, more preferably −0.15 μm or more and 0.15 μm or less. If the difference in surface roughness is larger than 0.20 μm in absolute value, various considerations such as selection of the shape of the elastic layer surface and setting of conditions for forming the surface layer are required when producing a developing roller having a desired shape. .

  FIG. 5 is a schematic explanatory view of an example of the electrophotographic image forming apparatus of the present invention.

  The photosensitive drum 5 serving as an electrostatic latent image carrier rotates in the direction of the arrow, and is uniformly charged by a charging roller 6 for charging the photosensitive drum 5, and is an exposure unit that writes an electrostatic latent image on the photosensitive drum 5. An electrostatic latent image is formed on the surface of the laser beam 7. The electrostatic latent image is developed by applying toner from a developing roller 8 disposed in contact with the photosensitive drum 5 and visualized as a toner image.

  Development is so-called reversal development in which a toner image is formed on the exposed portion. The visualized toner image on the photosensitive drum 5 is transferred to a recording material 10 such as paper by a transfer roller 9. The recording material 10 to which the toner image has been transferred is subjected to fixing processing by the fixing device 11 and is discharged out of the device, thus completing the printing operation.

  On the other hand, toner remaining on the photosensitive drum 5 without being transferred is peeled off by a cleaning blade 12 for cleaning the surface of the photosensitive drum. The cleaned photosensitive drum 5 repeats the above operation.

  The developing roller 9 is located at an opening extending in the longitudinal direction of a developing container (not shown) containing non-magnetic toner that is a one-component developer, and is disposed opposite to the photosensitive drum 5. During image formation, the developing roller 9 carrying toner contacts the photosensitive drum 5 with a contact width, and develops and visualizes the electrostatic latent image on the photosensitive drum 5.

  The developing container is provided with a toner applying member 13 for applying and carrying toner on the surface of the developing roller 9 and a toner regulating blade 14 for regulating the amount of toner applied. The toner application member 13 is in contact with the developing roller 9 upstream of the rotation direction of the developing roller 9 with respect to the contact portion of the toner regulating blade 14 with the developing roller 9, and rotates at a rotational speed different from the rotation of the developing roller 9. It is possible. The toner application member 13 serves to peel off the toner returned from the surface of the developing roller 9 without being developed for developing the electrostatic latent image. It is preferable to rotate in the counter direction.

  As the structure of the toner application member 13, a foamed skeleton-like sponge structure or a fur brush structure in which fibers such as rayon or polyamide are planted on the shaft core is used to supply toner to the developing roller 9 and strip off undeveloped toner. From the point of view, it is preferable. For example, an elastic roller in which polyurethane foam is provided on the shaft core can be used. The contact width of the toner application member 13 with respect to the developing roller 9 is preferably in the range of 1 mm to 8 mm.

  As the toner regulating blade 14, a member in which an elastic body is fixed to a metal sheet metal, a member having a spring property such as a thin plate of SUS or phosphor bronze, or a member in which resin or rubber is laminated on the surface thereof is used. Further, it is possible to control the toner layer thickness on the developing roller by applying a voltage higher than the voltage applied to the developing roller 9 to the toner regulating blade 14, and for this purpose, the toner regulating blade 14 is made of SUS. It is preferable to use a thin plate of phosphor bronze.

  In the electrophotographic process cartridge of the present invention, at least the photosensitive drum 5 and the developing device (the developing roller 9, the toner applying member 13, the regulating blade 14, and the developing container) are integrated. As the developing roller 9, the developing roller of the present invention is incorporated. A cleaning member (cleaning blade 12 and waste toner container (not shown)) may also be incorporated.

  The above-described electrophotographic image forming apparatus specifically shows a developing unit. In a color image forming apparatus such as a color copying machine, cyan, magenta, yellow and black units are arranged in a tandem type. There is also a cylindrical arrangement around the drum. In addition, as a method for forming a color toner image on a recording material, the toner image formed by each unit is directly superimposed on the recording material, or the recording image is once superimposed on a belt or a drum. Some are batch transferred. These may be in any form. Thereafter, the recording material on which the color toner image is formed is conveyed to a fixing device, and the color image is fixed to the recording material.

  As described above, the developing roller of the present invention has a surface layer made of a thermoplastic resin on the surface, and the thickness of the surface layer is thin, and at the same time, the difference in hardness and surface roughness before and after the surface layer is formed. Since it is small, it is possible to form an image having a predetermined density in which the occurrence of fog and density unevenness is suppressed.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited by this. The reagents used are commercially available high-purity products unless otherwise specified.

  The various data below were measured as follows.

1) Viscosity of addition reaction crosslinkable liquid silicone rubber Using a BH viscometer, rotor no. 7 was rotated at 4 rpm and measured at 25 ° C.

2) Micro rubber (MD) hardness of the elastic layer surface and developing roller Using a micro rubber hardness meter “MD-1 type” (trade name) manufactured by Kobunshi Keiki Co., Ltd. The hardness of a total of nine places was measured in the environment of normal temperature and normal humidity, and the obtained value was averaged. The measured value on the elastic layer surface is Hd, and the measured value on the roller surface is Hs.

3) Surface roughness of the elastic layer surface and the developing roller surface (arithmetic average roughness)
Using a surface roughness measuring machine “Surf Coder SE-3500” (trade name) manufactured by Kosaka Laboratory Ltd., a feed speed of 0.5 mm / sec. Evaluation length 2.5 mm, roughness cut-off λc = 0.8 mm, measured with horizontal auto-leveling ON. The measured value of the elastic layer surface is Ra ₁ and the measured value of the roller surface is Ra ₂ .

4) Thickness of surface layer The developing roller was cut at the center, and an end surface of the roller was prepared with a ultramicrotome “Cryosectioning System FCS” (trade name) manufactured by Leica, and a sample having a thickness of 100 nm at −100 ° C. was produced. Next, this sample was measured with a transmission electron microscope “Hitachi Electron Microscope H-7500” (trade name) manufactured by Hitachi High-Tech Co., Ltd. The acceleration voltage was 1.0 kV and the measurement magnification was 100,000 times.

Further, the produced developing roller is incorporated as a developing roller of a cartridge of an electrophotographic laser printer “Laser Shot LBP-1310” (trade name) manufactured by Canon Inc., and an image is output to evaluate the image (evaluation item: fog, Density unevenness, image density). The LBP-1310 used for this image evaluation is an A4 vertical output machine, which has a recording media output speed of 16 ppm and an image resolution of 1200 dpi. Further, the contact pressure and the amount of the developing roller contacting the photosensitive drum were such that the developer carrying amount on the developing roller was 0.35 mg / cm ² . Further, for evaluation, a solid black image and a halftone image were output in the initial stage, and after the endurance of 10,000 sheets, a solid black image and a solid white image were output.

(Fog)
The obtained solid white image was measured with a photovolt reflection densitometer “TC-6DS / A” (trade name) manufactured by Tokyo Denshoku Co., Ltd., and the difference from the unprinted portion was fogged (%). And evaluated according to the following criteria.
A: Less than 1.5%.
○: 1.5% or more and less than 3.0%.
X: 3.0% or more.

(Uneven density)
The halftone image was visually observed and evaluated according to the following criteria.
(Double-circle): Density nonuniformity is not confirmed with the naked eye, but it is favorable.
○: Slight density unevenness can be confirmed with the naked eye, but there is no practical problem.
X: Density unevenness can be confirmed with the naked eye, and there is a problem in practical use.

(Image density)
The solid black image was subjected to density measurement with a Macbeth densitometer “Macbeth Color Checker RD-1255” (trade name) manufactured by Macbeth Co., Ltd., and evaluated according to the following criteria.
(Double-circle): 1.3 or more and less than 1.6 both in the initial stage and after durability.
○: One of the initial and after durability is 1.3 or more and less than 1.6, and the other is less than 1.3 or 1.6 or more.
Δ: Less than 1.3 or 1.6 or more both at the initial stage and after endurance.

<Example 1>
(Production of elastic layer)
Vinyl groups are substituted at both ends, 100 parts by mass of dimethylpolysiloxane having a viscosity of 120 Pa · s, 7 parts by mass of quartz powder (Min-USil, manufactured by Pennsylvania Glass Sand) as a filler, carbon black (Electrochemical Co., Ltd.) A blend of 10 parts by mass (manufactured by Denka Black, powdered product) was used as the base material for the liquid silicone rubber.

  After a small amount of a platinum compound is blended as a curing catalyst in this base material, an organohydrogenpolysiloxane (Si-H group content: 0.8 mass%) blended with a small amount of a curing retarder is used at a mass ratio of 1: 1. It mixed so that it might become.

  The obtained liquid mixture is poured into a pipe type set with a SUS nickel-plated shaft core having a diameter of 6 mm and a length of 300 mm, and heated and vulcanized at 200 ° C. for 2 hours to conduct a rubber part having a length of 240 mm and a thickness of 4 mm. A roller having an elastic elastic layer was obtained.

Next, the obtained roller was polished by a polishing machine (LEO-600-F2 (product name) dedicated to rubber rolls manufactured by Mizuguchi Seisakusho Co., Ltd.) equipped with a grinding wheel GC80, and the outer diameter was 12.0 mm. An elastic roller having a surface roughness Ra ₁ of 0.50 μm was produced. The polishing conditions were a workpiece rotation speed of 200 RPM, a polishing wheel rotation speed of 2000 RPM, and a feed speed of 500 mm / min. The obtained elastic roller had an MD hardness Hd of 30.

(Preparation of surface layer)
The prepared elastic roller is placed in the vacuum vapor deposition apparatus shown in FIG. 3, and the fluororesin “Polyflon _™ PTFE M-391 (trade name, manufactured by Daikin Industries, Ltd.) is put in the crucible, and then the inside of the apparatus is 0.1 Torr. In this state, the temperature of the crucible was adjusted to 650 ° C., and the placed roller was placed in the apparatus for 1 minute while rotating at 30 rpm to form a surface layer. The surface layer of the obtained developing roller was 100 nm, the MD hardness Hs was 32, and the surface roughness Ra ₂ was 0.40 μm.

<Example 2>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that the rotation speed of the grinding wheel was set to 1000 RPM. The surface roughness Ra ₁ of the elastic layer was 0.72 μm.

(Preparation of surface layer)
In the sputtering apparatus shown in FIG. 4, the elastic roller produced above and a sheet-like fluororesin “Teflon” (trade name, manufactured by DuPont) as a target were installed, and the inside of the apparatus was depressurized by a vacuum pump. Thereafter, argon gas was introduced into the apparatus and adjusted to 5 mTorr (0.6667 Pa). After the adjustment, 120 W of electric power was applied to the high frequency power source and the treatment was performed for 12 minutes. The thickness of the surface layer of the obtained developing roller was 500 nm, the MD hardness Hs was 33, and the surface roughness Ra ₂ was 0.85 μm.

<Example 3>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that the rotational speed of the grinding wheel was changed to 500 RPM. The surface roughness Ra ₁ of the elastic layer was 1.00 μm.

(Preparation of surface layer)
A developing roller was obtained in the same manner as in Example 2 except that the elastic roller produced above was used and the processing time was 25 minutes. The thickness of the surface layer of the obtained developing roller was 1.0 μm, the MD hardness Hs was 34, and the surface roughness Ra ₂ was 1.15 μm.

<Example 4>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 200 Pa · s was used. The elastic layer had an MD hardness Hd of 25 and a surface roughness Ra ₁ of 0.50 μm.

(Preparation of surface layer)
A developing roller was obtained in the same manner as in Example 1 except that the elastic roller produced above was used and the processing time was 5 minutes. The thickness of the surface layer of the obtained developing roller was 500 nm, the MD hardness Hs was 27, and the surface roughness Ra ₂ was 0.38 μm.

<Example 5>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 2 except that dimethylpolysiloxane having a viscosity of 80 Pa · s was used. The MD hardness Hd of the elastic layer was 40, and the surface roughness Ra ₁ was 0.75 μm.

(Preparation of surface layer)
A developing roller was obtained in the same manner as in Example 4 except that the elastic roller produced above was used. The thickness of the surface layer of the obtained developing roller was 500 nm, the MD hardness Hs was 43, and the surface roughness Ra ₂ was 0.65 μm.

<Example 6>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 2 except that the feed rate of the grinding stone was 1000 mm / min. The elastic layer had an MD hardness Hd of 30, and a surface roughness Ra ₁ of 0.30 μm.

(Preparation of surface layer)
A developing roller was obtained in the same manner as in Example 2 except that the elastic roller produced above was used. The film thickness of the surface layer of the obtained developing roller was 500 nm, the MD hardness Hs was 33, and the surface roughness Ra ₂ was 0.45 μm.

<Example 7>
(Production of elastic layer)
An elastic roller was prepared in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 100 Pa · s was used and the elastic layer was polished at a polishing wheel rotational speed of 1000 RPM and a feed speed of 250 mm / min. The elastic layer had an MD hardness Hd of 35 and a surface roughness Ra ₁ of 1.50 μm.

(Preparation of surface layer)
In the sputtering apparatus shown in FIG. 4, 1 mm-thick sheet polystyrene “G9401” (trade name, manufactured by PS Japan Co., Ltd.) was installed as the produced elastic roller and target, and the inside of the apparatus was depressurized by a vacuum pump. Thereafter, argon gas was introduced into the apparatus and adjusted to 5 mTorr (0.6667 Pa). After the adjustment, a power of 120 W was applied to the high frequency power source and the treatment was performed for 20 minutes. The thickness of the surface layer of the obtained developing roller was 100 nm, the MD hardness Hs was 38, and the surface roughness Ra ₂ was 1.65 μm.

<Example 8>
(Production of elastic layer)
An elastic roller was prepared in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 80 Pa · s was used and the elastic layer was polished at a polishing wheel rotational speed of 1000 RPM and a feed speed of 150 mm / min. The elastic layer had an MD hardness Hd of 40 and a surface roughness Ra ₁ of 1.55 μm.

(Preparation of surface layer)
After installing the produced roller in the vacuum deposition apparatus shown in FIG. 3, the polyethylene pellet “Nipolon Hard 6100A” (trade name, manufactured by Tosoh Corporation) is put in the crucible, and then the inside of the apparatus is 0.1 Torr (13.33 Pa). The pressure was reduced to. In this state, the temperature of the crucible was adjusted to 550 ° C., and the surface roller was placed in the apparatus for 10 minutes while rotating the installed roller at 30 rpm to form a surface layer to obtain a developing roller. The surface layer of the obtained developing roller had a thickness of 1.0 μm, an MD hardness of 42, and a surface roughness Ra ₂ of 1.45 μm.

<Example 9>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 100 Pa · s was used and the elastic layer was polished at a rotational speed of a polishing grindstone of 1000 RPM and a feed rate of 200 mm / min. The elastic layer had an MD hardness Hd of 35 and a surface roughness Ra ₁ of 1.20 μm.

(Preparation of surface layer)
In the sputtering apparatus shown in FIG. 4, the produced elastic roller and the target sheet-like polypropylene sheet “Sumilite NS-3400” (trade name, manufactured by Sumitomo Bakelite Co., Ltd.) as a target are installed, and the inside of the apparatus is a vacuum pump Reduced pressure. Thereafter, argon gas was introduced into the apparatus and adjusted to 5 mTorr (0.6667 Pa). After the adjustment, a power of 120 W was applied to the high frequency power source, and the treatment was performed for 30 minutes. The thickness of the surface layer of the obtained developing roller was 1.5 μm, the MD hardness Hs was 39, and the surface roughness Ra ₂ was 1.35 μm.

<Example 10>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 250 Pa · s was used, and the elastic layer was polished at a rotational speed of a polishing grindstone of 2000 RPM and a feed rate of 200 mm / min. The MD hardness of the elastic layer was 22, and the surface roughness Ra ₁ was 0.90 μm.

(Preparation of surface layer)
The produced roller is placed in the vacuum vapor deposition apparatus shown in FIG. 3, and a polyamide resin “UBE nylon 1022B” (trade name, manufactured by Ube Industries Co., Ltd.) is placed in a crucible, and then the inside of the apparatus is 0.1 Torr (13. The pressure was reduced to 33 Pa). In this state, the crucible temperature was adjusted to 650 ° C., and the placed roller was placed in the apparatus for 1 minute while rotating at 30 rpm to form a surface layer to obtain a developing roller. The surface layer of the obtained developing roller had a thickness of 10 nm, an MD hardness Hs of 27, and a surface roughness Ra ₂ of 0.85 μm.

<Example 11>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 60 Pa · s was used, and the elastic layer was polished at a rotational speed of a grinding wheel of 2000 RPM and a feed rate of 500 mm / min. The elastic layer had an MD hardness Hd of 45 and a surface roughness Ra ₁ of 0.10 μm.

(Preparation of surface layer)
In the sputtering apparatus shown in FIG. 4, a 1 mm thick sheet-like polyamide resin “UBE nylon 1022B” (trade name, manufactured by Ube Industries Co., Ltd.) is installed as the elastic roller and target obtained above, and the inside of the apparatus is depressurized by a vacuum pump. I made it. Thereafter, argon gas was introduced into the apparatus and adjusted to 5 mTorr (0.6667 Pa). After the adjustment, 120 W of electric power was applied to the high frequency power source, and the treatment was performed for 5 minutes. The thickness of the surface layer of the obtained developing roller was 100 nm, the MD hardness Hs was 49, and the surface roughness Ra ₂ was 0.30 μm.

<Example 12>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 80 Pa · s was used and the elastic layer was polished at a rotational speed of a polishing grindstone of 1000 RPM and a feed rate of 250 mm / min. The elastic layer had an MD hardness Hd of 40 and a surface roughness Ra ₁ of 1.50 μm.

(Preparation of surface layer)
The produced elastic roller is placed on the vacuum vapor deposition apparatus shown in FIG. 3, and a polypropylene resin “Mitsui Polypro E110G” (trade name, manufactured by Mitsui Chemicals, Inc.) is placed in the crucible, and then the inside of the apparatus is 0.1 Torr (13 The pressure was reduced to 33 Pa). In this state, the crucible temperature was adjusted to 550 ° C., and the surface roller was formed by allowing the placed roller to stand in the apparatus for 20 minutes while rotating at 30 rpm to obtain a developing roller. The surface layer of the obtained developing roller had a thickness of 2.0 μm, an MD hardness Hs of 43, and a surface roughness Ra ₂ of 1.30 μm.

<Example 13>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 40 Pa · s was used, and the elastic layer was polished at a rotational speed of a grinding wheel of 500 RPM and a feed rate of 500 mm / min. The elastic layer had an MD hardness Hd of 50 and a surface roughness Ra ₁ of 2.00 μm.

(Preparation of surface layer)
In the sputtering apparatus shown in FIG. 4, a 1 mm-thick sheet-shaped polyimide resin “Upilex Board RB-100” (trade name, manufactured by Ube Industries) is installed as a target elastic roller and target, and the inside of the apparatus is vacuum pumped Reduced pressure. Thereafter, argon gas was introduced into the apparatus and adjusted to 5 mTorr (0.6667 Pa). After the adjustment, 120 W of electric power was applied to the high frequency power source and the treatment was performed for 1 minute. The thickness of the surface layer of the obtained developing roller was 5 nm, the MD hardness Hs was 51, and the surface roughness Ra ₂ was 2.20 μm.

<Example 14>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that a mold having an outer diameter of the elastic layer of 12 mm was used and the elastic layer after molding was not polished. The elastic layer had an MD hardness Hd of 30, and a surface roughness Ra ₁ of 0.10 μm.

(Preparation of surface layer)
A developing roller was obtained in the same manner as in Example 2 except that the elastic roller produced above was used. The thickness of the surface layer of the obtained developing roller was 500 nm, the MD hardness Hs was 33, and the surface roughness Ra ₂ was 0.13 μm.

<Example 15>
(Preparation of surface layer)
Ester-based thermoplastic polyurethane “Rezamin ME3612LP” (trade name, manufactured by Dainichi Seika Co., Ltd.) 100 parts by mass and carbon black “Mitsubishi Carbon Black # 1000” (trade name, manufactured by Mitsubishi Chemical Corporation, pH 3.0) 28 parts by mass The solid content was adjusted to 40% by mass with methyl ethyl ketone (MEK). Next, this mixed liquid was circulated and dispersed with a wet ultrafine particle dispersion grinder “Ready Mill” (trade name) manufactured by Imex Co., Ltd. until no solid black carbon aggregates could be confirmed. The obtained paint stock solution was diluted with MEK so that the viscosity was 5 mPa · s to obtain a paint for the surface layer.

The elastic roller produced in Example 1 was dipped at 50 mm / sec into the overflow dip coater and circulated so as to always overflow. Thereafter, the pulling speed was gradually changed from 200 mm / min to 50 mm / min while linearly changing to dip coat the outer surface of the elastic layer. This was naturally dried for 30 minutes, and then cured by heating at 140 ° C. for 60 minutes to produce a developing roller having a surface layer made of an ester-based thermoplastic polyurethane. The thickness of the surface layer of the developing roller is 2 μm, the MD hardness Hs is 33, and further. The surface roughness Ra ₂ was 0.30 μm.

<Comparative Example 1>
(Preparation of surface layer)
In the sputtering apparatus shown in FIG. 4, the Si-based target “Sputtering Target SX” (trade name, manufactured by Asahi Glass Ceramics Co., Ltd.) is installed as the elastic roller and the roller and the target manufactured in Example 1, and the inside of the apparatus is vacuum pumped. Reduced pressure. Thereafter, argon gas was introduced into the apparatus and adjusted to 5 mTorr (0.6667 Pa). After the adjustment, 200 W of electric power was applied to the DC power source and the treatment was performed for 5 minutes. The thickness of the surface layer of the obtained developing roller was 500 nm, the MD hardness Hs was 43, and the surface roughness Ra ₂ was 0.80 μm.

<Comparative example 2>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 10 Pa · s was used. The MD hardness Hd of the elastic layer was 55, and the surface roughness Ra ₁ was 1.20 μm.

(Preparation of surface layer)
A developing roller was obtained in the same manner as in Example 2 except that the elastic roller produced above was used. The thickness of the surface layer of the obtained developing roller was 500 nm, the MD hardness Hs was 58, and the surface roughness Ra ₂ was 1.30 μm.

<Comparative Example 3>
(Production of elastic layer)
An elastic roller was produced in the same manner as in Example 1 except that dimethylpolysiloxane having a viscosity of 300 Pa · s was used. The MD hardness of the elastic layer was 18, and the surface roughness Ra ₁ was 1.50 μm.

(Preparation of surface layer)
A developing roller was obtained in the same manner as in Example 2 except that the elastic roller produced above was used. The thickness of the surface layer of the obtained developing roller was 500 nm, the MD hardness Hs was 21, and the surface roughness Ra ₂ was 1.60 μm.

<Comparative example 4>
(Preparation of surface layer)
A developing roller was obtained in the same manner as in Example 15 except that the surface layer coating material was adjusted to have a viscosity of 10 mPa · s with MEK. The thickness of the surface layer of the obtained developing roller was 3.0 mm, the MD hardness Hs was 36, and the surface roughness Ra ₂ was 0.29 μm.

  Image evaluation was performed using the developing roller produced by the said Example and the comparative example. The obtained results are shown in Table 1.

μ

μ

It is sectional drawing of one example of a developing roller. It is a schematic cross section ((A) wet method and (B) dry method) of the surface layer part of the developing roller at the time of surface layer formation. It is a schematic diagram of the vacuum evaporation apparatus for surface layer formation. It is a schematic diagram of the sputtering device for surface layer formation. 1 is a schematic diagram of an example of an electrophotographic image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft core body 2 Elastic layer 3 Surface layer 5 Photoconductor 6 Charging roller 7 Laser beam 8 Developing roller 9 Transfer roller 10 Recording medium 11 Fixing device 12 Cleaning blade 13 Toner applying member 14 Toner regulating blade 15 Bias power supply 16 for charging roller Developing Bias power supply for roller 17 Bias power supply for regulating blade 18 Bias power supply for transfer roller 201 Vacuum deposition apparatus 202 Roller 203 Evaporating substance 204 Crucible 205 Exhaust means 301 Sputtering apparatus 302 Target 303 Gas inlet 304 Exhaust means 305 DC power supply 306 AC power supply

Claims (8)

A developing roller which has at least one elastic layer on the shaft core and at least one surface layer on the outer periphery thereof, carries and conveys the developer, and contacts the photosensitive drum to visualize the electrostatic latent image In
The surface layer is made of a thermoplastic resin, and the thickness is 5.0 nm or more and less than 2.0 μm,
The micro rubber hardness Hd of the elastic layer surface is 21 or more and 50 or less,
The difference (Hs−Hd) between the micro rubber hardness Hd of the elastic layer surface and the micro rubber hardness Hs of the developing roller surface is 0 or more and 5 or less,
A developing roller, wherein a difference (Ra ₁ -Ra ₂ ) between the surface roughness Ra ₁ of the elastic layer surface and the surface roughness Ra ₂ of the developing roller is between −0.20 μm and 0.20 μm. The developing roller according to claim ₁ , wherein the surface roughness Ra ₁ of the elastic layer surface is 0.01 μm or more and 2.00 μm or less.   The developing roller according to claim 1 or 2, wherein the thermoplastic resin is selected from the group consisting of fluorine resin, thermoplastic polyimide, polyamide, polyethylene, polypropylene, and polystyrene.   A developing roller that has at least one elastic layer on the shaft core and at least one surface layer on the outer periphery thereof, carries the developer, contacts the photosensitive drum, and visualizes the electrostatic latent image. In the production method, the surface layer is formed by a physical vapor deposition (PVD) method using a thermoplastic resin.   The method for producing a developing roller according to claim 4, wherein the PVD method is vacuum deposition or sputtering.   A developing roller produced by the method for producing a developing roller according to claim 4.   An electrophotographic process cartridge that is detachably attached to an electrophotographic image forming apparatus main body, wherein the developing roller is the developing roller according to any one of claims 1 to 3 and 6. Process cartridge.   7. The electrophotographic image forming apparatus having a developing roller disposed in contact with a photosensitive drum for holding an electrostatic latent image, wherein the developing roller is a developing roller according to claim 1. An electrophotographic image forming apparatus characterized by the above.

Images