JP4208765B2 - Developing roller, process cartridge, and image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roller that presses against a photoreceptor to visualize a developer in an image forming apparatus, a process cartridge using the developing roller, and an image forming apparatus.

  In recent years, OA equipment such as copiers and printers has been improved in image quality, and accordingly, a contact development method has been proposed in which an elastic body is used as a developing roller and development is performed by uniformly pressing the photoreceptor.

  For example, in a printer using an electrophotographic method, a photosensitive member is uniformly charged by a charging roller, and an electrostatic latent image is formed by a laser or the like. Next, the developer in the developing container is uniformly applied on the developing roller with appropriate charges by the developer applying roller and the developer regulating member, and the developer is transferred (developed) at the contact portion between the photosensitive member and the developing roller. Done. Thereafter, the developer on the photoconductor is transferred onto a recording sheet by a transfer roller and fixed by heat and pressure. The developer remaining on the photoconductor is removed by a cleaning blade, and a series of processes is completed. In this case, the developing roller is always in pressure contact with the photosensitive member and the developer regulating member, and is in contact with the photosensitive member and the developer regulating member for a long time when stopped or not in use, so that the constituent members are easily deformed. It is necessary not to damage the abutting member. For this reason, as the constituent member that comes into contact with the photosensitive member or the developer regulating member, a member formed of a material made of a low hardness elastic body is used.

  Normally, a developing roller is used in which an elastic body layer made of a low-hardness elastic body is concentrically laminated on the outer periphery of a metal shaft center, which is necessary for imparting surface properties and charging properties. Depending on the case, a layer formed by laminating a coating layer is also used.

  Further, development rollers used in electrophotographic image forming apparatuses have various proposals for deformation recovery (that is, setability), which is important for maintaining an appropriate contact state. ing. In general, in the conventional proposal, the setting performance is improved by selecting a material excellent in compression set as the elastic material constituting the roller layer, and the roller layer is configured by laminating two or more kinds of materials. A similar approach has been used to do this.

  Further, in the prior art, an elastic roller has been proposed in which a flexible layer is provided as a surface layer on the outer peripheral surface of an elastic roller base (base layer). By adopting a laminated structure in which a flexible layer is provided as the surface layer, when the compression set of the elastic roller is set to 20% or less, a developing device that applies the elastic roller of this structure to the developing roller is used for a long time. Or, even after long-term storage, it is disclosed that deterioration in image quality due to deformation of the developing roller can be suppressed, and high-quality image quality similar to the case of using the developing roller immediately after manufacture can be obtained. . By providing a flexible layer as a surface layer, the load applied to the roller surface is received in a wide part, and as a result, not only the part that receives direct load but also other adjacent parts are deformed simultaneously. Thus, the change of the deformation amount in each part becomes gradual. Accompanying this effect, the influence of the distortion itself on the image quality is reduced, and if the sharp crease or sharp dent on the roller in which permanent distortion occurs is less likely to occur, the action of the technique is described (Patent Document 1). reference).

  In recent years, the required performance of elastic rollers used in electrophotographic image forming apparatuses has become more advanced as the speed of image forming apparatuses increases and the quality of image quality increases. In addition to deformation recovery (setability), there is a further demand for improvement in uniform conductivity required for high resolution and durability (adhesiveness) required for higher speed. It is not always easy to realize these required performances only by a conventionally known method. For example, in the case where a substrate having a lower hardness (for example, an elastic body layer) is employed for the purpose of further improving the deformation recovery property (set property) by applying the method of Patent Document 1, the surface layer is flexible. It is necessary to make the elastic modulus of the adhesive layer relatively high. When such a flexible material having a high elastic modulus is used, a problem is likely to occur in the adhesion of the base layer to the substrate, and as a result, the desired conductivity and durability can be sufficiently maintained during long-term use. Not achieved.

  In addition, there are other conventional techniques for explaining the hardness of the elastic layer, compression set characteristics, and creep characteristics of the surface layer material. It is not always a good idea to select materials with excellent compression set for all the layers that make up the roller layer for the purpose of further improving deformation recovery (setability). In most cases, it is balanced with other properties. Including "", it is not possible to provide sufficient performance to satisfy all of the plurality of requirement items.

Therefore, a configuration in which a roller layer having a laminated structure is formed on the outer peripheral surface of the shaft core body is used, and the hardness of the elastic layer (using the elastic layer mainly composed of rubber as the base layer) Asker-C) is selected in the range of 15 to 55 ° and the compression set is in the range of 0.5 to 5.0%, so that the base layer can derive good compression set, Therefore, it is possible to obtain an appropriate nip width because it is more easily deformed with respect to external input. On the other hand, a resin layer that covers at least the outer side of the elastic layer is used as a surface layer, and the resin layer is made permanent. By selecting the elongation in the range of 1 to 10%, it exhibits excellent adhesion and durability even with a large amount of deformation of the base layer, is rich in flexibility, and more excellent in setability (deformation recovery) A technique for forming a developing roller is also disclosed (see Patent Document 2). ).
JP-A-2-259785 JP 2002-257130 A

  However, in general, when a material having a low elastic modulus is used for the flexible layer of the surface layer and a material design that is simply flexible in order to obtain the followability of a low hardness elastic body layer, In some cases, the bleed material from the toner contaminates the photoconductor, or the toner deteriorated after long-term use of the developing roller melts and adheres to the surface of the developing roller, causing problems such as image defects and toner leakage.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and an object of the present invention is to prevent the toner from being melted and fixed on the surface of the developing roller caused by the deterioration of the toner after long-term use of the developing roller, and to develop during long-term storage or stop An object of the present invention is to provide a developing roller that adopts a novel material configuration that can achieve good deformation recovery (set property) in compression deformation of a roller surface pressure contact portion, and at the same time has excellent adhesion and durability. Another object of the present invention is to provide a process cartridge and an image forming apparatus using such a developing roller.

  In the present invention, a conductive elastic layer made of a low-hardness elastic body is concentrically laminated on the outer periphery of a metal shaft core body, and further a coating layer is laminated to impart surface properties and chargeability. In the developing roller composed of more than one layer, by selecting a material having sufficient flexibility and difficult to adhere deteriorated toner as the material of the outer layer (coating layer), the developing roller surface pressure contact portion It has been found that it is possible to obtain a developing roller that exhibits good deformation recovery (setting property) in compression deformation and is excellent in preventing the toner from being fused and fixed on the surface of the developing roller.

The present invention includes a mandrel, and the mandrel conductive elastic layer formed on the outer periphery of at least and a coating layer formed on the conductive elastic layer, said coating layer,
A polyol component (i),
3/7 to 8/2 (molar ratio (A A developing roller containing a polyurethane elastomer obtained from the isocyanate component (ii) contained in / B)) ,
The developing roller, wherein the polyol component (i) is polytetramethylene ether glycol .

The present invention also provides:
A process cartridge having a developer and the developing roller capable of supporting the developer in a thin film;
The developing roller is in contact with or pressed against the surface of a latent image carrier capable of forming an electrostatic latent image on the surface, and the developer carried on the surface of the developing roller is allowed to remove the latent image. It can be supplied and developed to an electrostatic latent image formed on the surface of the carrier,
The latent image carrier is a process cartridge provided in the process cartridge or the image forming apparatus.

The present invention also provides:
A latent image carrier, a charging device for charging the surface of the latent image carrier, an electrostatic latent image forming device for forming an electrostatic latent image on a charged region of the latent image carrier, and the latent image carrier. A developing device for supplying a developer to the electrostatic latent image formed on the surface of the image carrier to visualize the electrostatic latent image into an image, and a transfer for transferring the image to a transfer material An image forming apparatus comprising:
The image forming apparatus according to claim 1, wherein the developing roller includes the developing roller in a state of being in contact with or pressed against the surface of the latent image carrier.

  According to the present invention, the developing roller exhibits excellent deformation recoverability (setting property) in compressive deformation of the developing roller surface pressure contact portion, and becomes a developing roller excellent in prevention of melting and fixing of toner on the developing roller surface. For example, a material having a low hardness and excellent compression set is selected as an elastic layer mainly composed of silicone rubber, and a sufficiently soft and deteriorated toner is used as a coating layer using a urethane resin formed on the outer peripheral surface thereof. By selecting a material that is difficult to adhere, it is possible to provide a developing roller for an image forming apparatus that has low hardness, excellent set performance (deformation recovery property), and filming property. In addition, a process cartridge and an image forming apparatus using such a developing roller can be provided.

The developing roller of the present invention is a developing roller comprising at least a metal shaft core, a conductive elastic layer formed on the outer periphery of the shaft core, and a coating layer formed on the conductive elastic layer. The coating layer is
A polyol component (i),
3/7 to 8/2 (molar ratio (A / B)) and a polyurethane elastomer obtained from the isocyanate component (ii) contained therein.

  The modified isocyanate compound is a prepolymerized isocyanate compound obtained by reacting an isocyanate compound with a polyol compound to form a urethane prepolymer having an NCO group at the terminal. Here, as the modified isocyanate compound (A), diphenylmethane diisocyanate is used. A modified product of toluene diisocyanate with trimethylolpropane is used as the modified product of polypropylene polyol and modified isocyanate compound (B).

  As a number average molecular weight of the polypropylene polyol used for modification | denaturation of a modified isocyanate compound (A), the thing of 1000-3000 and 2-3 functional groups is preferable.

  The free isocyanate concentration (hereinafter abbreviated as NCO%) of the modified isocyanate compound (A) is preferably 2.6 to 9.8. Moreover, it is preferable that NCO% of a modified isocyanate compound (B) is 7-15.

  In the present invention, an isocyanate component (ii) containing the above-mentioned modified isocyanate compound (A) and modified isocyanate compound (B) in a ratio of 3/7 to 8/2 (molar ratio (A / B)) is used as a polyurethane elastomer. Used as a raw material. The mixing ratio of the two components is preferably 5/5 to 7/3 (molar ratio (A / B)).

  The isocyanate component (ii) can further contain other isocyanate compounds. For example, polynuclear bodies such as polymeric MDI, polyfunctional isocyanates, allophanate modified bodies, burette modified bodies, isocyanurate modified bodies and the like can also be contained. However, in order to sufficiently exhibit the effects of the present invention, the total content of the modified isocyanate compound (A) and the modified isocyanate compound (B) is preferably 80% by mass or more in the isocyanate component (ii). .

  The polyol component (i) used as a raw material for the polyurethane elastomer in the present invention is not particularly limited, and polytetramethylene ether glycol, polypropylene glycol, epoxide addition polyol, polyester polyol, polyether ester polyol, and the like can be used. . Especially, it is preferable that it is what has a polytetramethylene ether glycol as a main component. That is, it is possible to use polytetramethylene ether glycol alone or a material in which 0.1 to 10% by mass of a low molecular weight polyol is added within a range in which the film properties of the target coating layer can be achieved. As polytetramethylene ether glycol, those having a number average molecular weight of 650 to 3000 are preferably used. More preferably, it is the range of 1000-2000 number average molecular weight. Moreover, as the low molecular weight polyol, ethylene glycol, diethylene glycol, 1,4-butanediol, trimethylolpropane and the like are suitably used in addition to a polypropylene polyol having a number average molecular weight of less than 500 and a functional group number of 2-3.

  The present invention uses a polyurethane elastomer obtained from the polyol component (i) and the isocyanate component (ii) as described above. About the compounding ratio of the polyol component (i) and the isocyanate component (ii) which are raw materials of this polyurethane elastomer, when used as a material for forming a coating layer, it is appropriately selected so that the intended effect of the present invention can be exhibited. Can be set.

  Hereinafter, the present invention will be described in detail.

  An example of the structure of the developing roller of the present invention is schematically shown in FIG. 1 (perspective view) and FIG. 2 (cross-sectional view). The developing roller 1 of the present invention has a shaft core body 11 at the center, and a conductive elastic layer (base layer) 12 is fixed on the outer peripheral surface of the shaft core body 11 as a roller layer. A coating layer (surface layer) 13 is laminated on the outer peripheral surface.

  The shaft core body 11 itself has a columnar or hollow cylindrical shape and often uses a shaft core metal made of a conductive material such as metal. However, such a developing roller is electrically insulated. When used in a state in which the shaft core 11 is used, it may be made of a non-conductive material as long as the shape of the shaft core 11 itself can be firmly held against an external force applied to the developing roller. Even when such a developing roller is used with an electrical bias applied or grounded, the entire shaft core 11 is made of a conductive material instead of the conductive material. It is also possible to use a conductive treatment that satisfies the desired conductivity on the surface, for example, a structure having a coating with a highly conductive coating layer.

  Since the developing roller used in the image forming apparatus is generally used with an electrical bias applied or grounded, the shaft core 11 is made of a conductive base, so-called shaft core. A gold form is preferred. The shaft core is a support member, for example, a metal or alloy such as aluminum, copper alloy, stainless steel, iron plated with chromium, nickel, etc., synthetic resin, etc. The roller layer formed thereon is made of a conductive material sufficient to apply a predetermined voltage. The outer diameter of the shaft core in the developing roller used in the image forming apparatus is usually in the range of 4 to 10 mm.

  The conductive elastic layer 12 serving as a base layer can be formed as a molded body using a rubber component as a raw material main component. As the rubber component of the raw material main component of the conductive elastic layer 12, various conventionally used rubbers can be used. 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, NBR hydride, polysulfide rubber, urethane rubber and the like can be used alone or in admixture of two or more.

  In particular, it is preferable to use silicone rubber as a main component because low hardness and low compression set as described later are easily obtained. Silicone rubber includes polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polytrifluoropropylvinylsiloxane, polymethylphenylsiloxane, polyphenylvinylsiloxane, and two monomer units constituting them. Examples of the copolymer are as described above. The degree of polymerization of the silicone rubber is preferably in the range of 3000 to 15000. In addition to the silicone rubber used as the main component, an elastomer such as natural rubber, isoprene rubber, chloroprene rubber, EPDM, SBR, and NBR is used as the rubber component as long as the desired hardness and compression set are obtained as required. It can also contain in the ratio of 20 mass% or less.

  Furthermore, components necessary for the function required for the conductive elastic layer itself, such as a conductive agent and a non-conductive filler, and various additive components such as a cross-linking agent, a catalyst, and a dispersion accelerator are appropriately added. Can be blended.

  As a conductive agent added for the purpose of imparting conductivity to the conductive elastic layer, various conductive metals or alloys such as carbon black, graphite, aluminum, copper, tin, and stainless steel; tin oxide, zinc oxide, indium oxide, Various conductive metal oxides such as titanium oxide, tin oxide-antimony oxide solid solution, 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 can be obtained relatively easily and good chargeability can be obtained regardless of the type of the main rubber. As means for dispersing the finely divided conductive agent in the rubber material, conventionally used means such as a roll kneader, a Banbury mixer, a ball mill, a sand grinder, a paint shaker, etc. can be used depending on the main rubber material. Can be used as appropriate.

In addition, as a means for imparting conductivity to the conductive elastic layer, a technique of adding a conductive polymer compound instead of the conductive agent or together with the conductive agent can be used. For example, as a conductive polymer compound, as a host polymer, 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) and the like. These are used as dopants, such as 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) Thing is, it is possible to use.

  The amount of the component imparting conductivity can be appropriately selected from the amount necessary to achieve the desired properties of the conductive elastic layer.

  Examples of the non-conductive filler include diatomaceous earth, quartz powder, dry silica, wet silica, titanium oxide, zinc oxide, aluminosilicate, calcium carbonate and the like.

  As a crosslinking agent, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, t-butylperoxybenzoate, p-chlorobenzoylper An oxide etc. can be mentioned. For example, when liquid silicone rubber is used as the rubber component, it is preferable to crosslink the rubber components using polyorganohydrogensiloxane as a crosslinking component and a platinum-based catalyst.

  The hardness (Asker-C) of the conductive elastic layer is preferably in the range of 15 to 55 °. If the conductive elastic layer hardness (Asker-C) is less than 15 °, it is difficult to obtain rubber elasticity that contributes to the desired set performance, whereas if it exceeds 55 °, the other performances of the present invention are lost. Therefore, it becomes difficult to obtain an appropriate nip width. The conductive elastic layer hardness (Asker-C) is more preferably in the range of 20 to 40 °. Here, the hardness (Asker-C) is determined according to a rubber material hardness measurement method. Specifically, an Asker rubber hardness tester is used by using a test piece separately prepared in accordance with a standard standard Asker C-type SRIS (Japan Rubber Association Standard) 0101. It is defined by the hardness measured by (manufactured by Kobunshi Keiki Co., Ltd.).

  At the same time, the compression set of the conductive elastic layer is preferably in the range of 0.5 to 5.0%. If the compression set is less than 0.5%, rubber elasticity itself may not be exhibited. On the other hand, if the compression set exceeds 5.0%, when the amount of deformation of the conductive elastic layer itself increases, if it is stored for a long time in the deformed state, the recovery of the deformation cannot be sufficiently achieved. When used in an image forming apparatus, good image formation similar to that at the beginning of manufacture may not be possible. The compression set of the conductive elastic layer is more preferably in the range of 0.5 to 3.0%. Here, the compression set is defined by a value measured according to a JIS K-6301 vulcanized rubber test method (10. compression set test) using a separately prepared test piece.

  When contacting the developing roller, in order to ensure a uniform nip width, and in addition to satisfy a suitable setting property, the thickness of the conductive elastic layer is preferably 0.5 mm or more, More preferably, it is 1.0 mm or more. Although there is no upper limit on the thickness of the conductive elastic layer unless the outer diameter accuracy of the developing roller to be produced is impaired, generally, if the thickness of the conductive elastic layer is excessively increased, the manufacturing cost of the conductive elastic layer In view of this practical limitation, the thickness of the conductive elastic layer is preferably 6.0 mm or less, and more preferably 5.0 mm or less. The thickness of the conductive elastic layer is appropriately selected according to the hardness in order to achieve the target nip width.

  In the developing roller of the present invention, the conductive elastic layer is used as a base layer, and a coating layer covering the outer surface is formed as a surface layer.

  The coating layer of the developing roller of the present invention contains the polyurethane elastomer as described above. The content is preferably 50 to 100% by mass and more preferably 70 to 100% by mass with respect to the entire coating layer.

  Further, other resin components can be contained in the coating layer of the developing roller of the present invention. For example, amino resin components such as urea resin and melamine resin, acrylic resin components, silicone resin components, and the like can be used. The content is preferably 20% by mass or less with respect to the entire coating layer.

  Furthermore, in the developing roller of the present invention, components necessary for the functions required for the coating layer itself, for example, a conductive agent, a non-conductive filler, etc., and a resin film body are used according to the application. Various additive components such as a catalyst, a dispersion accelerator and the like can be appropriately blended. In addition, a conductive agent and a nonelectroconductive filler can be suitably selected from what was illustrated as an additive which can be previously contained in a conductive elastic layer. Moreover, the addition amount of these components can be suitably selected according to the addition purpose, as long as the characteristic of the coating layer to be formed can be within the range in which the effect of the present invention is exhibited. In particular, it is preferable to contain a conductive substance.

  The thickness of the coating layer is preferably 1 μm or more in order to ensure sufficient wear resistance and to facilitate uniform application and formation. On the other hand, the thickness of the coating layer is limited to 100 μm or less in order to achieve uniform conductivity when the developing roller has conductivity and to reduce the influence on the deformability of the entire developing roller. Is preferred. The thickness of the coating layer may be appropriately selected in the above range in consideration of its hardness and the like.

  For forming the coating layer, a method can be used in which the resin raw material used as the raw material for the resin film body is applied in a liquid state to the surface of the conductive elastic layer. The method for applying the resin raw material is not particularly limited, but it is preferable that the resin raw material is uniformly applied to the surface of the conductive elastic layer at a desired thickness by a method such as air spray, roll coating, curtain coating, dipping or the like. . Thereafter, heat treatment may be performed as necessary.

The resistance value of the developing roller of the present invention is preferably 10 ⁴ to 10 ¹⁰ Ω. The resistance value is defined by the resistance value when the conductive roller is pressed against a cylindrical metal roller (Φ60) with a constant pressure load of 500 g on one side and a DC voltage of 100 V is applied.

  As described above, in the developing roller of the present invention, the conductive elastic layer has low hardness and good compression set characteristics, and the coating layer has good deformation followability and is difficult to creep. Even when the developing roller is greatly deformed during the period, problems such as adhesion and wrinkles do not occur. In particular, due to its low hardness, it is easy to obtain an appropriate nip width, an excellent setting property, a good image can be obtained due to the adhesiveness between two layers, and it is possible to prevent the adhesion of deteriorated toner. Its good image can be maintained after long-term use. Further, the above-described advantages become more remarkable under the condition that the image forming apparatus used is increased in speed and the process speed, that is, the speed of the surface of the photoreceptor is increased.

The developing roller as described above is suitable for use as a developing roller of an image forming apparatus. That is, as one of the preferred embodiments of the present invention,
A latent image carrier, a charging device for charging the surface of the latent image carrier, an electrostatic latent image forming device for forming an electrostatic latent image on a charged region of the latent image carrier, and the latent image carrier. A developing device for supplying a developer to the electrostatic latent image formed on the surface of the image carrier to visualize the electrostatic latent image into an image, and a transfer for transferring the image to a transfer material An image forming apparatus having the developing roller as a developing roller included in the developing device in a state of being in contact with or pressed against the surface of the latent image carrier. And an image forming apparatus.

  An example of the configuration of the image forming apparatus of the present invention is shown in FIG. In the image forming apparatus of FIG. 3, the developing roller 25 is provided in a state of being in contact with and facing the surface of the photosensitive member 21 as a latent image carrier. The surface of the photosensitive member 21 is charged by a charging roller 22 provided in the charging device, and then a predetermined amount is applied to the surface of the photosensitive member 21 by a laser beam 23 transmitted from a laser beam transmitting device provided in the electrostatic latent image forming device. An electrostatic latent image is formed. On the other hand, in the developing device 24, the developer 28 put in the developing container 34 is supplied to the surface of the developing roller 25 by the developer supplying roller 26, and is carried on the surface of the developing roller 25 in a thin film state by the developer regulating member 27. Is done. Then, the developer carried on the surface of the developing roller 25 is supplied to the electrostatic latent image formed on the surface of the photoconductor 21 and visualized to form an image. Thereafter, the paper 33 passes between the photosensitive member 21 and the transfer roller 29 of the transfer device, whereby the image is transferred to the paper, and the image is fixed on the paper by the fixing roller 32. The developer remaining on the photoreceptor 21 is scraped off by the cleaning blade 30 and dropped into the waste toner container 31.

The developing device 24 in the image forming apparatus is preferably detachable as a process cartridge. That is, as one of the preferred embodiments of the present invention,
A process cartridge having a developer and the above-described developing roller capable of supporting the developer in a thin film, wherein the developing roller is formed on a surface of a latent image carrier capable of forming an electrostatic latent image on the surface. The developer can be developed by supplying the developer carried on the surface of the developing roller to the electrostatic latent image formed on the surface of the latent image carrier in a state of facing or pressing against each other. The latent image carrier is provided in the process cartridge or the image forming apparatus. With such a configuration, the developing roller included in the developing device 24 can be easily replaced.

  The configuration of the process cartridge of the present invention may be a configuration capable of exhibiting the above functions, and may be configured by only the developing device 24 in the image forming apparatus of FIG. 3 (in this case, a photoconductor). 21 may be installed in advance in the image forming apparatus), and may include a developing device 24 and a photosensitive member 21. In either case, the developing roller 25 is in contact with or pressed against the surface of the photosensitive member 21 as a latent image carrier, and the developer carried on the surface of the developing roller 25 is charged with the photosensitive member 21. It can be developed by supplying it to an electrostatic latent image formed on the surface. In particular, a process cartridge including only the developing device 24 is preferable. 3 includes a developer 28, a developer container 34 for containing the developer 28, a developing roller 25, a developer supply roller 26 that can supply the developer 28 to the surface of the developing roller 25, In addition, a developer regulating member 27 that regulates the developer 28 so as to form a thin film on the surface of the developing roller 25 is configured.

Hereinafter, the present invention will be described more specifically with reference to examples. Examples 1 to 6 are examples of the present invention, and examples 7 and 8 are reference examples related to the present invention. These examples are examples of the best mode of the present invention, but the present invention is not limited to the examples. The developing roller produced by the method shown in the embodiment can be suitably used as a developing roller used in the image forming apparatus.

  In the specific examples described below, commercially available high-purity products were used as reagents used in the respective examples unless otherwise specified. Tables 1 and 2 show the compositions of the polyol component (i) and the isocyanate component (ii), which are the raw materials of the urethane elastomer used in the production of the coating layer of the developing roller in each example and comparative example.

<Isocyanate compound used>
Urethane-modified MDI (modified isocyanate compound (A)):
Modified product of diphenylmethane diisocyanate with polypropylene polyol (NCO%: 4.7, solid content: 65% by mass, manufactured by Nippon Polyurethane Industry Co., Ltd., number average molecular weight of polypropylene polyol: equivalent to 1000)
・ Polymeric MDI:
Polynuclear body of diphenylmethane diisocyanate (NCO%: 14.2, solid content: 80% by mass, manufactured by Nippon Polyurethane Industry Co., Ltd.)
TMP-modified TDI (modified isocyanate compound (B)):
Modified product of toluene diisocyanate with trimethylolpropane (NCO%: 7.0, solid content: 55% by mass, manufactured by Mitsui Takeda Chemical Co., Ltd.)
-Urethane modified TDI:
Modified product of toluene diisocyanate with polypropylene polyol (NCO%: 4.1, solid content: 100% by mass, manufactured by Nippon Polyurethane Industry Co., Ltd., number average molecular weight of polypropylene polyol: equivalent to 1500)
Example 1
The developing roller (1) was produced by the following method. In addition, both the base layer and the surface layer constituting the roller layer are imparted with conductivity, and specifically, carbon black is appropriately added as a conductive agent in each of the conductive elastic layer of the base layer and the coating layer of the surface layer, The amount of the conductive agent carbon black added was adjusted so that the electric resistance when the developing roller was brought into contact was 10 ⁶ Ω.

  As the shaft core body, a SUS metal core having a surface plated with nickel and further coated with an adhesive on its outer peripheral surface and baked was used. This shaft core was placed in a mold, and liquid silicone rubber 1 (made by Toray Dow Corning Silicone) was injected into a cavity formed in the mold. Subsequently, the mold was heated, and the injected silicone rubber was cured by heating at 150 ° C. for 30 minutes. After cooling, the mold was removed, and further a heat treatment was performed at 150 ° C. for 30 minutes, thereby providing a conductive elastic layer having a thickness of 4 mm and mainly composed of silicone rubber on the outer peripheral surface of the shaft core. The obtained conductive elastic layer had an Asker-C hardness of 32 ° and a compression set of 1.9%.

  As a raw material of the urethane elastomer for forming the coating layer, 50 parts by mass of the isocyanate component (ii) shown below with respect to 100 parts by mass of polytetramethylene ether glycol (PTMEG 3000, number average molecular weight: 3000, manufactured by Sanyo Chemical Industries, Ltd.) Part was added and stirred thoroughly. As the isocyanate component (ii), a mixture of urethane-modified MDI and TMP-modified TDI so as to have a molar ratio of 5/5 was used. The value of [NCO] / [OH] was 1.2. An organic solvent (methyl ethyl ketone) was added to the above raw material mixture to adjust the solid content to 20% by mass, 20 parts by mass of carbon black (trade name: MA100, manufactured by Mitsubishi Chemical Corporation) and urethane spherical filler (trade name: C400, manufactured by Negami Kogyo Co., Ltd., average particle diameter of 15 μm), 15 parts by mass) were added and uniformly dispersed and mixed to obtain a resin raw material liquid.

  The shaft core after the formation of the conductive elastic layer was immersed in this resin raw material liquid to coat the outer surface of the conductive elastic layer, and then pulled up and allowed to dry naturally. Next, the coated resin raw material was cured by heat treatment at 140 ° C. for 60 minutes, and a coating layer having a thickness of 20 μm was formed on the outer peripheral surface of the conductive elastic layer.

(Example 2)
As a raw material for the urethane elastomer forming the coating layer, an isocyanate component (ii) having the same composition as that of Example 1 is used with respect to 100 parts by mass of polytetramethylene ether glycol (PTMEG2000, number average molecular weight: 2000, manufactured by Sanyo Chemical Industries, Ltd.). A developing roller (2) was produced in the same manner as in Example 1 except that 75 parts by weight of) was added.

(Example 3)
As a raw material of the urethane elastomer for forming the coating layer, an isocyanate component (ii) having the same composition as that of Example 1 with respect to 100 parts by mass of polytetramethylene ether glycol (PTMEG1000, number average molecular weight: 1000, manufactured by Sanyo Chemical Industries, Ltd.) A developing roller (3) was produced in the same manner as in Example 1 except that 150 parts by mass of) was added.

(Example 4)
As a raw material for the urethane elastomer forming the coating layer, an isocyanate component (ii) having the same composition as that of Example 1 is used with respect to 100 parts by mass of polytetramethylene ether glycol (PTMEG650, number average molecular weight: 650, manufactured by Sanyo Chemical Industries, Ltd.). A developing roller (4) was produced in the same manner as in Example 1 except that a material having 230 parts by mass of) was added.

(Example 5)
As a raw material of the urethane elastomer for forming the coating layer, an isocyanate component in which urethane-modified MDI and TMP-modified TDI are mixed at a molar ratio of 3/7 to 100 parts by mass of polytetramethylene ether glycol (PTMEG2000) ( A developing roller (5) was produced in the same manner as in Example 1 except that 64 parts by mass of ii) was used.

(Example 6)
As a raw material of the urethane elastomer for forming the coating layer, an isocyanate component in which urethane-modified MDI and TMP-modified TDI are mixed at a molar ratio of 8/2 with respect to 100 parts by mass of polytetramethylene ether glycol (PTMEG2000). A developing roller (6) was produced in the same manner as in Example 1 except that 64 parts by mass of ii) was used.

(Comparative Example 1)
As a raw material of the urethane elastomer for forming the coating layer, an isocyanate component in which urethane-modified MDI and TMP-modified TDI are mixed at a molar ratio of 9/1 with respect to 100 parts by mass of polytetramethylene ether glycol (PTMEG2000). A developing roller (7) was produced in the same manner as in Example 1 except that 100 parts by mass of ii) was used.

(Comparative Example 2)
The same procedure as in Example 1 was used except that 107 parts by mass of urethane-modified MDI was added to 100 parts by mass of polytetramethylene ether glycol (PTMEG2000) as a raw material for the urethane elastomer forming the coating layer. A developing roller (8) was produced.

(Comparative Example 3)
As a raw material for the urethane elastomer for forming the coating layer, an isocyanate component in which urethane-modified MDI and TMP-modified TDI are mixed at a molar ratio of 2/8 to 100 parts by mass of polytetramethylene ether glycol (PTMEG2000) ( A developing roller (9) was produced in the same manner as in Example 1, except that 71 parts by mass of ii) was used.

(Comparative Example 4)
The same method as in Example 1 except that 60 parts by mass of TMP-modified TDI was added to 100 parts by mass of polytetramethylene ether glycol (PTMEG2000) as a raw material for the urethane elastomer forming the coating layer. Thus, a developing roller (10) was produced.

(Example 7)
Isocyanate component (ii) having the same composition as in Example 1 as a raw material for the urethane elastomer forming the coating layer with respect to 100 parts by mass of polypropylene polyol (number average molecular weight: 3000, f = 2, manufactured by Mitsui Takeda Chemical Co., Ltd.). A developing roller (11) was produced in the same manner as in Example 1 except that 50 parts by mass of the toner was added.

(Example 8)
An isocyanate component having the same composition as that of Example 1 with respect to 100 parts by mass of a polyester polyol (number average molecular weight: 2000, f = 2, EA type, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a raw material for the urethane elastomer forming the coating layer. A developing roller (12) was produced in the same manner as in Example 1 except that 75 parts by mass of (ii) was used.

(Comparative Example 5)
As a raw material of urethane elastomer for forming the coating layer, an isocyanate component (ii) in which urethane-modified MDI and urethane-modified TDI are mixed at a molar ratio of 5/5 with respect to 100 parts by mass of polytetramethylene ether glycol (PTMEG2000). A developing roller (13) was produced in the same manner as in Example 1 except that 64 parts by mass of) was added.

(Comparative Example 6)
As a raw material of urethane elastomer for forming a coating layer, an isocyanate component (ii) in which polymeric MDI and TMP-modified TDI are mixed at a molar ratio of 5/5 with respect to 100 parts by mass of polytetramethylene ether glycol (PTMEG2000). A developing roller (14) was produced in the same manner as in Example 1 except that 64 parts by mass of) was added.

(Characteristic evaluation)
For the developing rollers (1) to (14) produced in Examples 1 to 8 and Comparative Examples 1 to 6, the set performance (deformation recovery), filming, and images (initial, after 12k), Evaluation was performed as follows. Table 3 shows the evaluation results.

  In the development process, image formation was performed under the same bias conditions for the photoreceptor.

<Evaluation of set performance (deformation recovery)>
The set performance is as follows: the developing roller is installed in the cartridge, left in an L / L environment (15 ° C., 10% RH) for 6 days, then moved to a J / J environment (normal temperature, normal humidity) and left for 1 day. A cartridge having the configuration shown in FIG. 3 was incorporated in the image forming apparatus, and solid and halftone images were evaluated. The cartridge includes a developing roller, a developer supply roller, a developer regulating member, a developer, and a developing container.
◎: No pressure trace is seen on the image ○: The pressure trace is very thin but does not affect the image △: The pressure trace is thin but does not affect the image ×: The pressure trace is not present What is clearly seen and affects the image. Examples 1 to 3 and 5 to 7 and Comparative Examples 1, 2 and 5 showed almost no pressure contact marks on the developing roller, and good results were obtained. In the developing rollers produced in Examples 4 and 8 and Comparative Example 6, the pressure contact trace was confirmed to be thin, but it was at a level causing no practical problem. In the developing rollers prepared in Comparative Examples 3 and 4, the pressure contact marks were clearly seen, and the image was problematic. From this result, there is a correlation between the molar ratio of the isocyanate compound in the isocyanate component (ii) and the setting performance, and when the molar ratio of the urethane-modified MDI is 30% or more, good setting performance was obtained.

<Evaluation of image>
The image was evaluated by incorporating the produced developing roller into an image forming apparatus having the configuration shown in FIG. 3 to form solid and halftone images, and formed at the initial stage and after 12k (after printing 12,000 sheets). The presence or absence of image problems was determined. Based on the judgment, evaluation was made according to the following criteria.
◎: Good image ○: Very light shading and fogging confirmed, but no problem △: Light shading and fogging confirmed, but no problem x: Light shading and fogging clearly confirmed The developing rollers produced in Examples 1 to 7 and Comparative Example 3 have good initial images. Even with the developing rollers produced in Example 8 and Comparative Examples 1, 2, 4, and 6, the initial images were obtained. There was no problem above. In the image evaluation after 12k, the developing rollers produced in Examples 7 and 8 and Comparative Examples 1 and 6 produced slight shading and fogging, but the level was satisfactory. The developing roller produced in Comparative Example 2 had a poor fog state. In the developing roller produced in Comparative Example 7, unevenness in density and fogging were confirmed even in the initial image, and the image after durability could not be evaluated.

<Filming evaluation>
The filming was evaluated by observing the surface of the developing roller after image evaluation 12k with a microscope to confirm the level of toner fixing on the roller surface. Based on the result of this visual inspection, the evaluation was made according to the following criteria.
◎: No sticking observed ○: Some sticking is observed but no problem on image Δ: Some sticking is observed and there is a problem on image ×: Bad fixing and toner leakage occurs Example 1 8. In the developing rollers produced in Comparative Examples 3, 4, and 6, the fixing level of the toner was good, or the toner was fixed, but there was no problem on the image. The developing rollers produced in Comparative Examples 1, 2, and 5 were stuck, causing image problems. In Comparative Example 7, toner sticking occurred at the initial image evaluation stage. From this result, there was a correlation between the molar ratio of the isocyanate compound in the isocyanate component (ii) and filming, and it was effective for filming by setting the molar ratio of TMP-modified TDI to 20% or more.

Based on the above evaluation results, a comprehensive performance evaluation was performed, and the following four categories were evaluated.
A: Extremely good O: Good Δ: Slightly difficult, but no problem in practical use ×: Clear problem, not at a practical level When evaluated comprehensively, the developing rollers produced in Examples 1 to 8 In all of the items of set performance, image (initial and after durability), and filming, there were no practical problems, and it was evaluated as good or better. Among them, the developing rollers produced in Examples 2, 3, 5, and 6 show good characteristics including image characteristics (after 12 k), and are comprehensively evaluated as being extremely good.

  In addition, this invention is not limited to the conditions shown in the specific example mentioned above, It can implement after changing embodiment according to various uses within the technical scope of this invention. . Incidentally, in the above-described specific example, an example in which coating by dipping is used for forming the coating layer is shown. However, a developing roller having a coating layer applied and formed by a spray method, a roll coater method, or other methods. It is good.

It is a typical perspective view which shows the structure of the developing roller of this invention. It is a typical sectional view showing the composition of the development roller of the present invention. 1 is a diagram illustrating an example of a configuration of an image forming apparatus of the present invention.

Explanation of symbols

1: Developing roller 11: Shaft core 12: Conductive elastic layer (base layer)
13: Coating layer (surface layer)
21: Photoconductor 22: Charging roller 23: Laser beam 24: Developing device 25: Developing roller 26: Developer supplying roller 27: Developer regulating member 28: Developer 29: Transfer roller 30: Cleaning blade 31: Waste toner container 32 : Fixing roller 33: Paper 34: Developer container

Claims (6)

A mandrel, and the mandrel conductive elastic layer formed on the outer periphery of at least and a coating layer formed on the conductive elastic layer, said coating layer,
A polyol component (i),
3 / 7-8 / 2 (molar ratio (A A developing roller containing a polyurethane elastomer obtained from the isocyanate component (ii) contained in / B)) ,
The developing roller, wherein the polyol component (i) is polytetramethylene ether glycol . The developing roller according to claim 1 , wherein the coating layer further contains a conductive substance. The conductive elastic layer, the developing roller according to claim 1 or 2, characterized in that it is formed of a material mainly containing silicon rubber. Claim 1, the hardness of the conductive elastic layer (Asker-C) is 15 to 55 °, and compression set of the conductive elastic layer is characterized by a 0.5 to 5.0% The developing roller according to any one of? A process cartridge comprising: a developer; and the developing roller according to any one of claims 1 to 4 , which can carry the developer in a thin film.
The developing roller is in contact with or pressed against the surface of a latent image carrier capable of forming an electrostatic latent image on the surface, and the developer carried on the surface of the developing roller is allowed to remove the latent image. It can be supplied and developed to an electrostatic latent image formed on the surface of the carrier,
The process cartridge, wherein the latent image carrier is provided in the process cartridge or the image forming apparatus. A latent image carrier, a charging device for charging the surface of the latent image carrier, an electrostatic latent image forming device for forming an electrostatic latent image on a charged region of the latent image carrier, and the latent image carrier. A developing device for supplying a developer to the electrostatic latent image formed on the surface of the image carrier to visualize the electrostatic latent image into an image, and a transfer for transferring the image to a transfer material An image forming apparatus comprising:
As a developing roller, wherein the developing device comprises an image characterized by having a state in which the developing roller according to any one of claims 1 to 4, and opposite to contact or pressed against the surface of the latent image bearing member Forming equipment.

Images