JP2007133223A - Developing roller and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller which will not contaminate photosensitive drum or deteriorate toner, and has small permanent compressive strain and low skin frictional resistance. <P>SOLUTION: The developing roller 1 is equipped with a shaft 2, an elastic layer 3 formed on the periphery of the shaft 2, and a surface covering layer 5 formed on the circumferential surface of the elastic layer 3, wherein urethane resin and/or acrylic urethane resin, obtained by crosslinking lactone-modified polyol with polyisocyanate and having siloxane bond-containing silicone introduced into its resin skeleton, is applied to the surface covering layer 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing roller and an image forming apparatus including the developing roller, and in particular, does not contaminate a photosensitive drum or deteriorate toner, and further develops a developing roller having low compression set and low surface frictional resistance, and the developing roller. The present invention relates to an image forming apparatus that includes a roller and can form a good image over a long period of time.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, as a developing method for visualizing a latent image by supplying toner to a photosensitive drum holding a latent image and attaching the toner to the latent image on the photosensitive drum. A pressure development method is known. In the pressure development method, for example, after the photosensitive drum is charged to a constant potential, an electrostatic latent image is formed on the photosensitive drum by an exposure machine, and further, a developing roller carrying toner is placed on the electrostatic latent image. Development is performed by bringing the toner into contact with the latent image on the photosensitive drum in contact with the held photosensitive drum.

  In the pressure development method described above, the developing roller must rotate while securely holding the photosensitive drum, so polyurethane, silicone rubber, acrylonitrile is placed on the outer periphery of the shaft made of a highly conductive material such as metal. -Semiconductive elastic body in which carbon black or metal powder is dispersed in an elastomer such as butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), epichlorohydrin rubber (ECO), or a foam obtained by foaming these. It has a structure in which a semiconductive elastic layer made of is formed. In addition, for the purpose of controlling the chargeability and adhesion to the toner, and preventing the photosensitive drum from being contaminated by the elastic layer, a surface coating layer is formed on the surface of the elastic layer, and the surface coating layer is further formed. In order to protect the elastic layer, an intermediate coating layer made of a water-based resin or the like may be disposed between the elastic layer and the surface coating layer.

  On the other hand, in recent years, with the increase in color, high speed, high image quality, and energy saving of image forming apparatuses, the number of image forming apparatuses using low-melting toner is increasing. Here, when using a low-melting toner, the low-melting toner is damaged by repeated compression or friction between the components, and the toner is aggregated and fused, and thus, such as fogging. Image defects are likely to occur. That is, since the toner deteriorates at the end of the life of the toner cartridge and the chargeability becomes non-uniform, there is a problem that an image defect occurs or the life is shortened. Therefore, there is a demand for a developing roller having a low hardness that hardly damages the toner.

  On the other hand, when a low-hardness developing roller is used in the image forming apparatus, there is a problem that pressure contact marks due to a photosensitive drum, a blade, a supply roller, and the like are easily generated on the surface of the developing roller. Therefore, in recent years, there is a demand for a developing roller having a low compression set in addition to a low hardness. However, since materials with low hardness tend to have large compression set, it has been very difficult to balance both hardness and compression set sufficiently low (see Patent Documents 1 to 3).

  Further, the developing roller provided with the surface coating layer has a problem that since the frictional resistance of the roller surface is relatively large, slippage during driving is bad or the roller surface is easily worn and has low durability. Therefore, when an image forming apparatus in which such a developing roller is incorporated is used for a long time, the surface of the developing roller is scraped, and there is a problem that an image defect is likely to occur.

JP-A-8-190263 JP 2001-75354 A JP 2004-67726 A

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a developing roller that does not contaminate the photosensitive drum or deteriorate the toner, has a small compression set, and has a low surface frictional resistance. There is to do. Another object of the present invention is to provide an image forming apparatus provided with such a developing roller and capable of stably forming a good image over a long period without causing image defects such as fogging. There is to do.

  As a result of intensive studies to achieve the above object, the present inventor has obtained a urethane resin and / or an acrylic urethane resin obtained by crosslinking a lactone-modified polyol with polyisocyanate in a developing roller having an elastic layer and a surface coating layer. By using a urethane resin and / or acrylic urethane resin in which a silicone having a siloxane bond in the resin skeleton is used for the surface coating layer, the hardness of the developing roller and the compression set are sufficiently reduced to deteriorate the toner. In addition, it is possible to improve the durability by reducing the coefficient of friction on the surface of the developing roller, and further, by incorporating the developing roller into the image forming apparatus, it is possible to stabilize a good image over a long period of time. As a result, the present invention was completed.

That is, the developing roller of the present invention is a developing roller comprising a shaft, an elastic layer formed on the outer periphery of the shaft, and a surface coating layer formed on the outer peripheral surface of the elastic layer.
The surface coating layer includes a urethane resin and / or an acrylic urethane resin obtained by crosslinking a lactone-modified polyol with polyisocyanate, and the urethane resin and / or the acrylic urethane resin has a silicone having a siloxane bond introduced into the resin skeleton. It is characterized by that.

  In a preferred example of the developing roller of the present invention, the urethane resin and / or the acrylic urethane resin has a siloxane bond and silicone having hydroxyl groups or amino groups at both ends introduced into the urethane portion.

  In another preferred embodiment of the developing roller of the present invention, the acrylic urethane resin has a siloxane bond and silicone having a methacryloxy group at one end introduced into the acrylic part.

  In another preferred embodiment of the developing roller of the present invention, the number average molecular weight of the silicone introduced into the resin skeleton is 500 to 10,000.

  In another preferred embodiment of the developing roller of the present invention, the elastic layer is made of foamed urethane obtained by mechanically stirring and foaming a urethane raw material.

  The developing roller of the present invention preferably further comprises an intermediate coating layer formed from a mixed solution containing a polymer and an aqueous solvent between the elastic layer and the surface coating layer.

In another preferred embodiment of the developing roller of the present invention, the surface coating layer has an elastic modulus of 10 ³ MPa or less.

  In another preferred embodiment of the developing roller of the present invention, at least one of the intermediate coating layer and the surface coating layer further contains a conductive agent. In this case, the conductivity of the intermediate coating layer and / or the surface coating layer can be easily controlled.

  In another preferred embodiment of the developing roller of the present invention, the surface coating layer has a thickness of 30 μm or less.

  The image forming apparatus of the present invention includes the developing roller.

  According to the present invention, there is provided a photosensitive drum in which a urethane resin and / or an acrylic urethane resin in which a lactone-modified polyol is crosslinked with a polyisocyanate and a silicone having a siloxane bond in a resin skeleton is introduced is used as a surface coating layer. It is possible to provide a developing roller that is not contaminated, does not deteriorate the toner, has a small compression set, and has a low surface frictional resistance. Further, it is possible to provide an image forming apparatus that includes the developing roller and can stably form a good image over a long period of time.

<Developing roller>
Hereinafter, the developing roller of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of an example of the developing roller of the present invention. The illustrated developing roller 1 includes a shaft 2, an elastic layer 3 formed on the outer periphery of the shaft 2, an intermediate coating layer 4 formed on the outer peripheral surface of the elastic layer 3, and an outer periphery of the intermediate coating layer 4. And a surface coating layer 5 formed on the surface. In the drawing, the intermediate coating layer 4 and the surface coating layer 5 are each composed of one layer, but the intermediate coating layer 4 and the surface coating layer 5 of the developing roller of the present invention may each be composed of two or more layers. Further, the developing roller of the present invention may not include the intermediate coating layer 4. In the developing roller of the present invention, since the surface coating layer 5 is disposed on the outer peripheral surface of the elastic layer 3, it is possible to sufficiently prevent the contaminants oozing out from the elastic layer 3 from contaminating the photosensitive drum. it can.

  In the developing roller of the present invention, the surface coating layer 5 includes a urethane resin and / or an acrylic urethane resin obtained by crosslinking a lactone-modified polyol with a polyisocyanate, and the urethane resin and / or the acrylic urethane resin is made of silicone having a siloxane bond. It is introduced into the resin skeleton. When the surface coating layer 5 contains the urethane resin and / or acrylic urethane resin, the hardness of the developing roller is reduced and the toner is not damaged, and the compression set of the developing roller is reduced, which is good. It is possible to form a clear image. Further, by introducing silicone having a siloxane bond into the resin skeleton of the urethane resin and / or acrylic urethane resin used for the surface coating layer 5, the friction resistance of the surface coating layer 5, that is, the developing roller surface is reduced, and the slip In addition to improving the durability of the developing roller, it is possible to improve slippage during driving.

  The shaft 2 of the developing roller of the present invention is not particularly limited as long as it has good electrical conductivity. For example, a metal core made of a metal such as iron, stainless steel, or aluminum, or a hollow interior is hollowed out. A metal shaft such as a metal cylinder or a highly conductive plastic shaft can be used.

  The elastic layer 3 of the developing roller of the present invention is preferably made of urethane foam obtained by mechanical stirring foaming of a urethane raw material, that is, mechanical floss foamed urethane. The urethane foam is produced by a method in which bubbles are mixed by mechanically stirring a urethane raw material without using a foaming agent. Here, examples of the urethane material include a polyol and a polyisocyanate, or a urethane prepolymer synthesized from a polyol and a polyisocyanate, and a chain extender. The urethane material further includes a catalyst, a foam stabilizer, a conductive agent, and the like. can do. In addition, the bubbles in the urethane foam are mainly closed cells, and the expansion ratio and density can be appropriately adjusted depending on how air is introduced.

  Examples of the polyol that can be used as the foamed urethane raw material include polyester polyol, polyether polyol, polytetramethylene glycol, polybutadiene polyol, propylene oxide (PO) -modified polybutadiene polyol, and polyisoprene polyol. Examples of the polyester polyol include polyhydric alcohols such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, propylene glycol, trimethylolethane, trimethylolpropane, adipic acid, and glutaric acid. , Succinic acid, sebacic acid, pimelic acid, suberic acid and other polybasic carboxylic acids, and the polyether polyol is, for example, polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, ethylene oxide and propylene It can be obtained by adding alkylene oxide such as oxide.

  Examples of the polyisocyanate that can be used as the urethane foam raw material include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI), isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, and hydrogenated tolylene diene. Isocyanates, hexamethylene diisocyanate (HDI), isocyanurate-modified products, carbodiimide-modified products, glycol-modified products, and the like can be used. The amount of these polyisocyanates used is appropriately selected so that the ratio (NCO / OH) of the isocyanate groups (NCO) of the polyisocyanates to the hydroxyl groups (OH) of the polyol is in the range of 95/100 to 110/100. It is preferable.

  The polyisocyanate may be reacted with the polyol by a one-shot method, or may be reacted with the polyol in advance to form a urethane prepolymer, and then reacted with a chain extender or the like in the presence of a catalyst. In addition, the NCO group content of the synthesized urethane prepolymer is preferably in the range of 3 to 30% by mass, more preferably in the range of 5 to 15% by mass, and the amount of polyisocyanate and polyol used in the synthesis of the urethane prepolymer is It is preferable that the NCO group content of the urethane prepolymer is appropriately selected so as to be in the above range. The chain extender is a compound that connects the urethane prepolymers, specifically, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, trimethylolpropane, polyether polyol. , Polytetramethylene glycol, polybutadiene polyol, polyisoprene polyol and the like. The amount of these chain extenders used is such that the ratio (NCO / OH) of the isocyanate group (NCO) of the urethane prepolymer to the hydroxyl group (OH) of the chain extender is in the range of 95/100 to 110/100. It is preferable to select appropriately.

  The catalyst that can be used for the foamed urethane raw material is a catalyst for urethanization reaction, specifically, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin thiocarboxylate, octene Organic tin compounds such as tin oxide; Organic lead compounds such as lead octenoate; Monoamines such as triethylamine and dimethylcyclohexylamine; Diamines such as tetramethylethylenediamine, tetramethylpropanediamine and tetramethylhexanediamine; Pentamethyldiethylenetriamine and penta Triamines such as methyldipropylenetriamine and tetramethylguanidine; triethylenediamine, dimethylpiperazine, methylethylpiperazine, methylmorpholine, di Cyclic amines such as tilaminoethylmorpholine and dimethylimidazole; alcohol amines such as dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethylethanolamine, methylhydroxyethylpiperazine, hydroxyethylmorpholine; bis (dimethylaminoethyl) ether, And ether amines such as ethylene glycol bis (dimethyl) aminopropyl ether. Of these catalysts, organotin compounds are preferred. These catalysts may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the catalyst used is preferably in the range of 0.001 to 2.0 parts by mass with respect to 100 parts by mass of the polyol or urethane prepolymer.

  Examples of the foam stabilizer that can be used for the urethane foam raw material include ionic surfactants and nonionic surfactants in addition to silicone foam stabilizers such as polyether-modified silicone oil. The amount of the foam stabilizer used is preferably in the range of 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the polyol or urethane prepolymer.

  Examples of the conductive agent that can be used for the urethane foam raw material include an electronic conductive agent and an ionic conductive agent. Electronic conductive agents include conductive carbon such as ketjen black and acetylene black, carbon black for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT and MT, and carbon black for color subjected to oxidation treatment. , Pyrolytic carbon black, natural graphite, artificial graphite, antimony-doped tin oxide, ITO, tin oxide, titanium oxide, zinc oxide and other metal oxides, nickel, copper, silver, germanium and other metals, polyaniline, polypyrrole, polyacetylene, etc. And conductive whiskers such as carbon whisker, graphite whisker, titanium carbide whisker, conductive potassium titanate whisker, conductive barium titanate whisker, conductive titanium oxide whisker, and conductive zinc oxide whisker. The blending amount of the electronic conductive agent is preferably in the range of 1 to 50 parts by mass, and in the range of 5 to 40 parts by mass with respect to the total of the polyol and polyisocyanate or the total of 100 parts by mass of the urethane prepolymer and the chain extender. Is more preferable.

  Examples of the ionic conductive agent include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, denatured fatty acid dimethylethylammonium, and other perchlorates, chlorates, hydrochlorides, and bromates. Ammonium salts such as salts, iodates, borofluorides, sulfates, ethyl sulfates, carboxylates, sulfonates; alkaline metals such as lithium, sodium, potassium, calcium, magnesium, alkaline earth metals Examples include perchlorate, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, trifluoromethyl sulfate, and sulfonate. The blending amount of the ionic conductive agent is preferably in the range of 0.01 to 10 parts by mass, and in the range of 0.05 to 5 parts by mass with respect to the total of the polyol and polyisocyanate or the total of 100 parts by mass of the urethane prepolymer and the chain extender. Is more preferable. The said electrically conductive agent may be used individually by 1 type, may be used in combination of 2 or more type, and may combine an electronic conductive agent and an ionic conductive agent.

The elastic layer 3 preferably has a resistance value of 10 ³ to 10 ¹⁰ Ωcm, more preferably 10 ⁴ to 10 ⁸ Ωcm, depending on the blending of the conductive agent. If the resistance value of the elastic layer 3 is less than 10 ³ Ωcm, electric charges may leak to the photosensitive drum or the developing roller itself may be damaged by voltage, and if it exceeds 10 ¹⁰ Ωcm, ground fog is likely to occur.

  The developing roller of the present invention preferably includes an intermediate coating layer 4 formed from a mixed solution containing a polymer and an aqueous solvent between the elastic layer 3 and the surface coating layer 5. Here, the polymer may be any resin or rubber as long as it can be dissolved or dispersed in water. In the developing roller of the present invention, the intermediate coating layer 4 is preferably composed of two or more layers. The glass transition temperature of the intermediate coating layer 4 is preferably 10 ° C. or less, and the thickness of the intermediate coating layer 4 is preferably 100 μm or less. When the developing roller of the present invention includes the intermediate coating layer 4, the elastic layer 3 is a solvent in the coating material even when a coating material containing the raw material of the surface coating layer 5 is applied, for example, when forming the surface coating layer 5 described later. It can prevent dissolution or swelling.

  When the polymer used for forming the intermediate coating layer 4 is a resin, for example, a mixed solution containing the resin and water is prepared, and the mixed solution is applied onto the elastic layer 3 by dipping or spraying and dried. Thus, the intermediate coating layer 4 can be formed. The resin used for the intermediate coating layer 4 is preferably an aqueous resin. The aqueous resin may be any type such as a water-soluble type, an emulsion type, and a suspension type, and an aqueous resin having active hydrogen such as a carboxyl group, a hydroxyl group, and an amino group is preferable. Examples of the aqueous resin include warm water-soluble resins such as acrylic, urethane, polyester, and polydioxolane. Among these, acrylic resins and urethane resins are preferable. The acrylic resin is not particularly limited, but preferably has a glass transition temperature of 10 ° C. or lower. In addition, the acrylic resin includes a thermoplastic type and a crosslinking type such as self-crosslinking, melamine crosslinking, and isocyanate crosslinking. The thermoplastic type is preferable from the viewpoint of the coating film forming process and hardness.

  On the other hand, when the polymer used for forming the intermediate coating layer 4 is rubber, for example, after applying rubber latex onto the elastic layer 3 by dipping or the like, the latex is solidified with a coagulant, or the elastic After forming a coagulant layer on the layer 3 by dipping or the like, the intermediate coating layer 4 can be formed by applying a rubber latex on the layer 3 and coagulating it. Examples of the rubber component used for the intermediate coating layer 4 include styrene-butadiene copolymer rubber and natural rubber. For coagulation, a coagulant such as Colatex 93 (manufactured by Kawaguchi Chemical Co., Ltd.) is used. It is preferable to use an acidic solution dissolved in water or methanol. By causing an acid-alkali reaction between the alkaline latex and the acidic solution, the latex gels and solidifies. Here, in the formation of the intermediate coating layer 4 from the rubber latex, a drying step for removing water generated by the acid-alkali reaction and a washing step for removing the salt generated by the acid-alkali reaction are appropriately performed. Also good.

Similarly to the elastic layer 3, the intermediate coating layer 4 can be adjusted in conductivity by adding a conductive agent, and the volume resistivity of the intermediate coating layer 4 is in the range of 10 ³ to 10 ¹⁰ Ω · cm. It is preferable to add a conductive agent so as to be, and it is more preferable to add so as to be in the range of 10 ⁴ to 10 ⁸ Ω · cm. Examples of the conductive agent added to the intermediate coating layer 4 include the same conductive agents as those exemplified as the conductive agent that can be used for the foamed urethane raw material constituting the elastic layer 3. Here, the addition amount of the conductive agent in the intermediate coating layer 4 is preferably in the range of 0.1 to 20 parts by mass, more preferably in the range of 1 to 10 parts by mass with respect to 100 parts by mass of the polymer.

  If necessary, an appropriate amount of additives such as a thickener, a thixotropy imparting agent, and a structural viscosity imparting agent can be added to the intermediate coating layer 4 as necessary.

  The surface coating layer 5 of the developing roller of the present invention is a urethane resin and / or an acrylic urethane resin obtained by crosslinking a lactone-modified polyol with polyisocyanate, and a urethane resin in which silicone having a siloxane bond is introduced in the resin skeleton. It mainly contains an acrylic urethane resin and, if necessary, contains other components such as a conductive agent. The lactone-modified polyol can be produced by modifying the end of the polyol with a lactone such as ε-caprolactone, and a commercially available product can also be used. The lactone-modified polyol preferably has a weight average molecular weight (Mw) of 500 or more, more preferably 1000 or more.

  Polyols modified with the lactone include polyether polyols obtained by addition polymerization of alkylene oxides such as ethylene oxide and propylene oxide to glycerin, polytetramethylene glycol, glycerin, ethylene glycol, propylene glycol, butanediol, pentanediol, hexane Examples include diol, octanediol, polybutadiene polyol, polyisoprene polyol, and polyester polyol.

  Polyisocyanates that crosslink the lactone-modified polyol include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI), isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diene. Examples include isocyanate and hexamethylene diisocyanate (HDI). These polyisocyanates may be used alone or in combination of two or more.

  As for the acrylic urethane resin used for the said surface coating layer 5, even if the silicone which has a siloxane bond is introduced into the urethane part, the silicone which has a siloxane bond may be introduced into the acrylic part. The silicone introduced into the urethane part of the urethane resin and / or acrylic urethane resin is preferably a silicone having a siloxane bond and having hydroxyl groups or amino groups at both ends, and is introduced into the acrylic part of the acrylic urethane resin. As the silicone, a silicone having a siloxane bond and having a methacryloxy group at one end is preferable. Further, as the silicone introduced into the resin skeleton of the urethane resin and / or acrylic urethane resin, those having a number average molecular weight (Mn) of 500 to 10,000 are preferable. In the urethane resin and acrylic urethane resin, the content of the silicone part having a siloxane bond in the resin is preferably in the range of 5 to 40% by mass, and the content of the silicone part is less than 5% by mass, the surface coating layer The effect of reducing the frictional resistance of 5 and improving the slipperiness of the developing roller is not sufficient, and if it exceeds 40% by mass, the cost increases.

  In the acrylic urethane resin, the urethane part and the acrylic part may be bonded in a block type or in a graft type, but the urethane part is a main chain, and the acrylic part is a side chain in the main chain. A combined type is preferred. The acrylic urethane resin comprises, for example, a polymer in which a hydroxyl group is introduced into an acrylic polymer with 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and the like, and a urethane prepolymer having an isocyanate group at the molecular end. It can be produced by reacting or radically polymerizing a urethane prepolymer containing a mercapto group at the terminal or side chain by adding (meth) acrylate in the presence of a peroxide. In the latter case, a mercapto group generates a radical by peroxide, and (meth) acrylate undergoes radical polymerization with the radical as a base point. Here, in the present invention, by using a urethane prepolymer synthesized from the lactone-modified polyol and polyisocyanate and, for example, a silicone having a siloxane bond and having hydroxyl groups or amino groups at both ends, a urethane part is used. An acrylic urethane resin into which the lactone-modified polyol and the silicone having a siloxane bond are introduced is obtained. Moreover, in the synthesis | combination of the said acrylic polymer, the acrylic urethane resin by which the silicone which has a siloxane bond and the silicone which has a methacryloxy group in the one end was introduce | transduced into the acrylic part is obtained. On the other hand, the urethane resin can be produced from, for example, the lactone-modified polyol, the polyisocyanate, and silicone having a siloxane bond and having hydroxyl groups or amino groups at both ends. The developing roller of the present invention may use a urethane resin and / or an acrylic urethane resin obtained by a method other than the above method.

  As the acrylic component of the acrylic urethane resin, in addition to 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, etc., methyl (meth) acrylate, ethyl (meth) acrylate, isobutyl (meth) Examples include (meth) acrylates such as acrylate, n-butyl (meth) acrylate, and glycidyl (meth) acrylate. In the acrylic urethane resin, the acrylic content in the resin is preferably in the range of 5 to 80% by mass, more preferably in the range of 10 to 60% by mass, and still more preferably in the range of 20 to 50% by mass. .

  The surface coating layer 5 can further contain a catalyst for promoting a crosslinking reaction between the lactone-modified polyol and the polyisocyanate. Examples of the catalyst include those similar to those exemplified as the catalyst used for the urethane foam constituting the elastic layer 3, and the amount of the catalyst used is 100 parts by mass of the lactone-modified polyol. A range of 0.001 to 2.0 parts by mass is preferable. In addition, this catalyst can also accelerate | stimulate the crosslinking reaction of the silicone which has the said siloxane bond and has a hydroxyl group or an amino group at both ends, and the said polyisocyanate.

The surface coating layer 5 can be blended with a conductive agent for the purpose of controlling its conductivity, and the conductive agent is exemplified as a conductive agent that can be used for the foamed urethane raw material constituting the elastic layer 3. The thing similar to what was done can be illustrated. Here, in the case of an ionic conductive agent, the blending amount of the conductive agent in the surface coating layer 5 is preferably 20 parts by mass or less with respect to a total of 100 parts by mass of the urethane resin and the acrylic urethane resin constituting the surface coating layer 5. The range of 0.01 to 20 parts by mass is more preferable, and the range of 1 to 10 parts by mass is even more preferable. On the other hand, in the case of an electronic conductive agent, the total of the urethane resin and the acrylic urethane resin constituting the surface coating layer 5 The range of 1 to 70 parts by mass is preferable with respect to 100 parts by mass, and the range of 5 to 50 parts by mass is more preferable. The surface coating layer 5 is preferably adjusted so that the volume resistivity is in the range of 10 ³ to 10 ¹⁰ Ω · cm, and is in the range of 10 ⁴ to 10 ⁸ Ω · cm by adding the conductive agent. It is more preferable to adjust so that it becomes.

The surface-coating layer 5 preferably has a modulus of elasticity at 10 ³ MPa or less. When the elastic modulus of the surface coating layer 5 exceeds 10 ³ MPa, the toner deteriorates when the toner collides with the surface coating layer 5, and an image defect occurs.

  The thickness of the surface coating layer 5 is not particularly limited, but is preferably 30 μm or less, and more preferably in the range of 1 to 15 μm. If the thickness of the surface coating layer 5 exceeds 30 μm, the surface coating layer 5 may become hard and the flexibility may be impaired, and durability may be reduced and cracks may occur due to use or damage to the toner. There is a possibility that the toner adheres to the photosensitive drum or the stratified blade, resulting in an image defect. Moreover, it is preferable that the total thickness of the said intermediate | middle coating layer 4 and the surface coating layer 5 is 100 micrometers or less from a viewpoint which does not impair the softness | flexibility of the said elastic layer 3. FIG.

  The method for forming the surface coating layer 5 is not particularly limited, and a coating material containing each component constituting the surface coating layer 5 is prepared and applied by a dipping method, a spray method, or a roll coater method. A drying method is preferably used.

  As for the surface roughness of the developing roller of the present invention, the JIS 10-point average roughness (Rz) is preferably 10 μm or less. When the JIS 10-point average roughness (Rz) of the developing roller exceeds 10 μm, the toner conveyance amount tends to increase, but the toner charge amount is insufficient, causing background fogging and poor gradation in the image. .

The resistance value of the developing roller of the present invention is not particularly limited, but in order to obtain a good image, the electric resistance is preferably 10 ³ to 10 ¹⁰ Ω, and 10 ⁴ to 10 ⁸ Ω. Is more preferable. When the resistance value of the developing roller is less than 10 ³ Omega, gradation control is extremely difficult, also sometimes when the bias leak was defective on the photosensitive drum is generated. On the other hand, if the resistance value exceeds 10 ¹⁰ Ω, for example, when developing toner on a photosensitive drum, the developing bias causes a voltage drop due to the high resistance of the developing roller itself, and a sufficient developing bias for development cannot be secured. Thus, a sufficient image density cannot be obtained. The resistance value is measured, for example, by pressing the outer peripheral surface of the developing roller against a flat plate or cylindrical counter electrode with a predetermined pressure, applying a voltage of 100 V between the shaft and the counter electrode, and obtaining from the current value at that time. be able to. In this way, by appropriately and uniformly controlling the resistance value of the developing roller, the electric field strength for moving the toner can be kept appropriate and uniform.

  The developing roller of the present invention preferably has an Asker C hardness of 60 ° or less. If it is a low-hardness developing roller with Asker C hardness of 60 ° or less, the toner will be damaged between the developing roller and the photosensitive drum, blade, toner supply roller and the like when incorporated in the image forming apparatus. And a sufficiently good image can be formed.

<Image forming apparatus>
The image forming apparatus of the present invention includes the above-described developing roller that does not contaminate the photosensitive drum, does not deteriorate the toner, and has a small compression set and a small frictional resistance on the surface. It does not occur, and a good image can be stably formed over a long period of time. The image forming apparatus of the present invention is not particularly limited except that the developing roller is used, and can be manufactured by a known method.

  The image forming apparatus of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a partial cross-sectional view of an example of the image forming apparatus of the present invention. The image forming apparatus of the illustrated example includes the toner supply roller 7 for supplying the toner 6, the photosensitive drum 8 holding the electrostatic latent image, and the above-described toner disposed between the toner supply roller 7 and the photosensitive drum 8. The developing roller 1, the stratified blade 9 provided in the vicinity of the developing roller 1 (upper part in the figure), the charging roller 10 located in the vicinity of the photosensitive drum 8 (upward in the figure), and the vicinity of the photosensitive drum 8 (in the figure) A transfer roller 11 positioned on the lower side and a cleaning unit 12 provided adjacent to the photosensitive drum 8. The image forming apparatus of the present invention can further include a known component (not shown) that is usually used in the image layer forming apparatus.

  In the image forming apparatus of the illustrated example, after the photosensitive drum 8 is charged to a constant potential by the charging roller 10, an electrostatic latent image is formed on the photosensitive drum 8 by an exposure machine (not shown). Next, the toner supply roller 7, the developing roller 1, and the photosensitive drum 8 rotate in the direction of the arrow in the figure, so that the toner 6 on the toner supply roller 7 is sent to the photosensitive drum 8 through the developing roller 1. It is done. The toner 6 on the developing roller 1 is adjusted to a uniform thin layer by the stratifying blade 9 and rotates while the developing roller 1 and the photosensitive drum 8 are in contact with each other, so that the toner 6 is transferred from the developing roller 1 to the photosensitive drum 8. It adheres to the electrostatic latent image and the latent image becomes visible. The toner 6 attached to the latent image is transferred to a recording medium such as paper by the transfer roller 11, and the toner 6 remaining on the photosensitive drum 8 after the transfer is removed by the cleaning blade 13 of the cleaning unit 12. Here, in the image forming apparatus of the present invention, the developing roller 1 of the present invention that does not contaminate the above-described photosensitive drum, does not deteriorate the toner, and has low compression set and frictional resistance on the surface is provided. By using it, a good image can be stably formed over a long period of time.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Production of roller body)
100 parts by mass of urethane prepolymer synthesized from tolylene diisocyanate (TDI) and polyether polyol and 2 parts by mass of acetylene black are mixed to prepare a urethane prepolymer in which acetylene black is dispersed. did. On the other hand, 30 parts by mass of polyether polyol and 0.1 part by mass of sodium perchlorate (NaClO ₄ ) were mixed while heating to 70 ° C., and 4.5 parts by mass of polyether-modified silicone oil (foam stabilizer), dibutyltin dilaurate (Catalyst) 0.2 parts by mass was mixed to prepare a mixture, which was used as component B. Next, the A component and the B component are foamed by a mechanical floss method, and further injected into a cylindrical mold set with a core metal, and a roller body having an elastic layer made of foamed polyurethane is formed by RIM molding. Produced.

Example 1
100 parts by mass of an aqueous acrylic resin [manufactured by Nogawa Chemical Co., Ltd.] and 5 parts by mass of carbon black were dispersed to prepare a coating for an intermediate coating layer. Also, 100 parts by mass of caprolactone-modified acrylic urethane [manufactured by Asia: silicone introduced into urethane part], 35 parts by mass of carbon black, and 50 parts by mass of nurate-modified HDI [manufactured by Nippon Polyurethane: Coronate HX] are methyl ethyl ketone (MEK). A paint for surface coating was prepared by dispersing in 300 parts by mass. After the intermediate coating layer obtained is applied to the outer periphery of the roller body having the elastic layer made of foamed polyurethane to form the intermediate coating layer, the surface coating layer is further applied to form the surface coating layer. A developing roller was produced. Next, the roller resistance, JIS 10-point average roughness (Rz), Asker C hardness, friction coefficient, and toner chargeability of the obtained developing roller were evaluated by known methods, and the developing roller was mounted on a laser printer. Printing was performed and image characteristics were evaluated. Further, the obtained developing roller was assembled in a cartridge and stored in an environment of 50 ° C. and 90% RH for one week, and then the presence or absence of contamination of the photosensitive drum and the presence or absence of blade pressure contact marks on the surface of the developing roller were examined. The results are shown in Table 1.

(Example 2)
100 parts by mass of an aqueous urethane resin [Daiichi Kogyo Seiyaku Co., Ltd.] and 5 parts by mass of carbon black were dispersed to prepare a coating for an intermediate coating layer. Also, 100 parts by mass of caprolactone-modified acrylic urethane [manufactured by Asia: Silicone introduced into acrylic part], 35 parts by mass of carbon black, and 50 parts by mass of nurate-modified HDI [manufactured by Nippon Polyurethane: Coronate HX] 300 parts by mass of MEK To prepare a coating material for surface coating. A developing roller was prepared and evaluated by using the coating material for intermediate coating layer and the coating material for surface coating thus obtained in place of the coating material prepared in Example 1. The results are shown in Table 1.

(Example 3)
100 parts by weight of an aqueous latex [manufactured by High Pressure Gas Industry: NR] and 5 parts by weight of carbon black were dispersed to prepare a coating for an intermediate coating layer. Also, 100 parts by mass of caprolactone-modified acrylic urethane [manufactured by Asia: Silicone introduced into acrylic part], 35 parts by mass of carbon black, and 50 parts by mass of nurate-modified HDI [manufactured by Nippon Polyurethane: Coronate HX] 300 parts by mass of MEK To prepare a coating material for surface coating. A developing roller was prepared and evaluated by using the coating material for intermediate coating layer and the coating material for surface coating thus obtained in place of the coating material prepared in Example 1. The results are shown in Table 1.

Example 4
Disperse 100 parts by mass of caprolactone-modified acrylic urethane [manufactured by Asia: silicone introduced into the acrylic part], 35 parts by mass of carbon black, and 50 parts by mass of nurate-modified HDI [manufactured by Nippon Polyurethane: Coronate HX] in 300 parts by mass of MEK. Thus, a coating material for surface coating was prepared. Without forming an intermediate coating layer, the surface coating material obtained as described above was used in place of the coating material prepared in Example 1, to form a surface coating layer, to produce a developing roller, evaluated. The results are shown in Table 1.

(Comparative Example 1)
100 parts by mass of an aqueous acrylic resin [manufactured by Nogawa Chemical Co., Ltd.] and 5 parts by mass of carbon black were dispersed to prepare a coating for an intermediate coating layer. In addition, 100 parts by mass of urethane acrylic paint [manufactured by Asia] without silicone, 35 parts by mass of carbon black, and 50 parts by mass of nurate-modified HDI [manufactured by Nippon Polyurethane: Coronate HX] are dispersed in 300 parts by mass of MEK. Thus, a coating material for surface coating was prepared. A developing roller was prepared and evaluated by using the coating material for intermediate coating layer and the coating material for surface coating thus obtained in place of the coating material prepared in Example 1. The results are shown in Table 1.

(Comparative Example 2)
100 parts by mass of an aqueous urethane resin [Daiichi Kogyo Seiyaku Co., Ltd.] and 5 parts by mass of carbon black were dispersed to prepare a coating for an intermediate coating layer. In addition, 100 parts by mass of urethane acrylic paint [manufactured by Asia] without silicone, 35 parts by mass of carbon black, and 50 parts by mass of nurate-modified HDI [manufactured by Nippon Polyurethane: Coronate HX] are dispersed in 300 parts by mass of MEK. Thus, a coating material for surface coating was prepared. A developing roller was prepared and evaluated by using the coating material for intermediate coating layer and the coating material for surface coating thus obtained in place of the coating material prepared in Example 1. The results are shown in Table 1.

  As is apparent from Table 1, the developing roller according to the embodiment of the present invention does not contaminate the photosensitive drum, and has a small compression set, so that there is no pressure contact mark of the blade and the surface has a low frictional resistance. In addition, since the damage to the toner is small, a good image can be stably formed.

It is sectional drawing of an example of the developing roller of this invention. 1 is a partial cross-sectional view of an example of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing roller 2 Shaft 3 Elastic layer 4 Intermediate coating layer 5 Surface coating layer 6 Toner 7 Toner supply roller 8 Photosensitive drum 9 Layering blade 10 Charging roller 11 Transfer roller 12 Cleaning part 13 Cleaning blade 13

Claims (10)

In a developing roller comprising a shaft, an elastic layer formed on the outer periphery of the shaft, and a surface coating layer formed on the outer peripheral surface of the elastic layer,
The surface coating layer includes a urethane resin and / or an acrylic urethane resin obtained by crosslinking a lactone-modified polyol with polyisocyanate, and the urethane resin and / or the acrylic urethane resin has a silicone having a siloxane bond introduced into the resin skeleton. A developing roller characterized by that.   2. The developing roller according to claim 1, wherein the urethane resin and / or the acrylic urethane resin has a siloxane bond and silicone having a hydroxyl group or an amino group at both ends is introduced into the urethane portion.   2. The developing roller according to claim 1, wherein the acrylic urethane resin has a siloxane bond and silicone having a methacryloxy group at one end is introduced into the acrylic part.   The developing roller according to claim 1, wherein the number average molecular weight of the silicone introduced into the resin skeleton is 500 to 10,000.   The developing roller according to claim 1, wherein the elastic layer is made of urethane foam obtained by mechanically foaming a urethane raw material.   The developing roller according to claim 1, further comprising an intermediate coating layer formed from a mixed solution containing a polymer and an aqueous solvent between the elastic layer and the surface coating layer. The developing roller according to claim 1, wherein the surface coating layer has an elastic modulus of 10 ³ MPa or less.   The developing roller according to claim 1, wherein at least one of the intermediate coating layer and the surface coating layer further contains a conductive agent.   The developing roller according to claim 1, wherein the surface coating layer has a thickness of 30 μm or less.   An image forming apparatus comprising the developing roller according to claim 1.

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