JP2007279562A - Developing roller and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost developing roller which can be manufactured with a small number of steps. <P>SOLUTION: The developing roller 1 is equipped with a shaft 2, an elastic layer 3 formed on the outer circumference of the shaft 2, an intermediate coating layer 4 formed on the outer circumferential surface of the elastic layer 3 and a surface coating layer 5 formed on the outer circumferential surface of the intermediate coating layer 4, wherein urethane foam obtained by foaming urethane material by mechanical stirring is used for the elastic layer 3, the intermediate coating layer 4 and the surface coating layer 4 are composed of coating material containing resin, organic solvent and particulates. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing roller and an image forming apparatus including the developing roller, and particularly relates to a low-cost developing roller that can be manufactured with a small number of steps and an image forming apparatus including the developing roller.

  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, a resin coating layer may be further formed on the surface of the elastic layer for the purpose of controlling chargeability and adhesion to the toner and preventing contamination of the photosensitive drum by the elastic layer.

  In general, a conventional resin coating layer is a solvent system containing two to three water-based resin coating layers disposed on the outer periphery of the elastic layer and particles disposed on the outer periphery of the water-based resin coating layer. And a surface coating layer. Here, by providing the water-based resin coating layer on the outer periphery of the elastic layer, dissolution / breakage of the elastic layer due to the solvent contained in the raw material paint of the solvent-based surface coating layer containing particles and the like can be prevented. (See Patent Document 1).

Japanese Patent Laid-Open No. 7-119733

  As described above, the conventional developing roller has the advantage that the elastic layer can be protected from the solvent by disposing the aqueous resin coating layer, but the conventional aqueous coating material for forming the aqueous resin coating layer has an emulsifier. Therefore, if the water-based resin coating layer is the outermost layer of the developing roller, there is a problem that the photosensitive drum that comes into contact with it is contaminated. Therefore, when a water-based resin coating layer is disposed on the outer peripheral surface of the elastic layer, a solvent-based surface coating layer that does not contain an emulsifier needs to be disposed on the outer peripheral surface of the water-based resin coating layer. Therefore, in order to produce a developing roller having a conventional configuration, it is necessary to go through two or more dipping processes of the raw material paint and a sufficient drying process for water-based resin coating after the formation of the elastic layer. The manufacturing cost was inevitably high.

  On the other hand, the competition for price reduction of image forming apparatuses has been intense recently, and it is necessary to manufacture each part used in the image forming apparatus at a lower cost. Development of a developing roller capable of reducing the manufacturing cost is strongly demanded.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a low-cost developing roller that can solve the problems of the prior art and can be manufactured with a small number of steps. Another object of the present invention is to provide an image forming apparatus provided with such a developing roller.

  As a result of intensive studies to achieve the above object, the present inventors have a structure in which a solvent-based intermediate coating layer and a surface coating layer are disposed on the outer peripheral surface of the elastic layer without forming a water-based resin coating layer. The intermediate coating layer and the surface coating layer are formed from a paint containing resin, fine particles and an organic solvent, so that a resin coating layer having a thickness sufficient to supplement the elastic layer dissolved by the solvent is formed on the outer peripheral surface of the elastic layer. It was found that the obtained developing roller has various performances sufficient for application to an image forming apparatus, and the present invention has been completed.

That is, the developing roller of the present invention is formed on the shaft, the elastic layer formed on the outer periphery of the shaft, the intermediate coating layer formed on the outer peripheral surface of the elastic layer, and the outer peripheral surface of the intermediate coating layer. A surface coating layer,
The elastic layer is made of urethane foam obtained by mechanically foaming a urethane raw material,
The intermediate coating layer and the surface coating layer are formed from a paint containing a resin, an organic solvent, and fine particles.

  In a preferred example of the developing roller of the present invention, the foamed urethane bubbles are closed cells.

  In the developing roller of the present invention, it is preferable that the intermediate coating layer and the surface coating layer are formed of the same paint.

  In another preferred embodiment of the developing roller of the present invention, the intermediate coating layer has a thickness of 5 to 40 μm.

  In another preferred embodiment of the developing roller of the present invention, the average particle size of the fine particles is 20 μm or less.

  In another preferred embodiment of the developing roller of the present invention, the thickness of the surface coating layer is smaller than the average particle diameter of the fine particles.

  The developing roller of the present invention preferably has a JIS 10-point average roughness (Rz) of 5 to 10 μm.

Further, in the method for producing the developing roller of the present invention, after forming the elastic layer by mechanical stirring foaming on the outer periphery of the shaft,
After applying a paint containing resin, organic solvent and fine particles by dip method and drying for 1-10 minutes at a temperature of 25 ± 5 ° C and humidity of 30-80% RH, forming an intermediate coating layer,
Again, a surface coating layer is formed by coating a paint containing a resin, an organic solvent, and fine particles by a dip method.

  Furthermore, an image forming apparatus according to the present invention includes the developing roller.

  According to the present invention, an intermediate coating layer and a surface coating layer formed from a paint containing a resin, an organic solvent, and fine particles are provided on the outer periphery of the elastic layer. A developing roller can be provided. In addition, an image forming apparatus provided with the developing roller can be provided.

<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. The illustrated elastic layer 3 includes a foam layer 3a positioned on the outer periphery of the shaft 2 and a skin layer 3b positioned on the outer peripheral surface of the foam layer 3a. 3b may not be included.

  The developing roller of the present invention is characterized in that the intermediate coating layer 4 and the surface coating layer 5 are formed of a paint containing a resin, an organic solvent, and fine particles. By forming two resin coating layers (that is, the intermediate coating layer 4 and the surface coating layer 5) on the outer peripheral surface of the elastic layer 3, the thickness is sufficient to make up the elastic layer 3 dissolved by the solvent in the paint. Can be formed on the outer peripheral surface of the elastic layer 3, and the developing roller 1 thus obtained has various performances sufficient for use in an image forming apparatus. Here, when the resin coating layer formed on the outer peripheral surface of the elastic layer 3 is a single layer, in order to form a resin coating layer having a thickness sufficient to supplement the elastic layer 3 dissolved by the solvent in the paint, There is no choice but to increase the resin concentration in the paint, but when the resin concentration in the paint increases, there is a problem that the viscosity of the paint increases and the productivity deteriorates or the uniformity of the paint is impaired. In addition, when fine particles are included to control the roughness of the resin coating layer, if the thickness of the single resin coating layer is large, the fine particles are buried in the resin coating layer to ensure the roughness. I can't do that. On the other hand, the developing roller of the present invention has two resin coating layers composed of the intermediate coating layer 4 and the surface coating layer 5, and contains fine particles by ensuring a sufficient thickness of the intermediate coating layer 4. The thickness of the surface coating layer 5 can be reduced, and fine particles can be prevented from being buried in the surface coating layer 5 to ensure a sufficient roughness. The developing roller of the present invention has a simple structure in which the intermediate coating layer 4 and the surface coating layer 5 are formed on the outer peripheral surface of the elastic layer 3 without the aqueous resin coating layer that takes time to dry after coating. Yes, since the coating for the intermediate coating layer 4 can be applied to the outer surface of the elastic layer 3 and dried at room temperature, the coating for the surface coating layer 5 can be applied, so that compared to a developing roller having a conventional aqueous resin coating layer. Thus, the manufacturing cost can be greatly reduced.

  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 made of urethane foam obtained by mechanically agitating and foaming a urethane raw material, that is, mechanical floss method 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 roller raw material having the elastic layer 3 on the outer periphery of the shaft 2 can be obtained by injecting the urethane raw material foamed by mechanical stirring into a cylindrical mold in which the shaft 2 is arranged in advance and reaction hardening. it can. Here, the roller main body taken out from the mold usually has a thin film-like film, that is, a skin layer 3b in a portion in contact with the mold. Therefore, when the elastic layer 3 is composed of the foam layer 3a and the skin layer 3b, the roller main body taken out from the mold may be directly dipped or the like in the paint described later without polishing. The thickness of the skin layer 3b is not particularly limited, but is usually about 1 to 50 μm. The developing roller of the present invention preferably has a skin layer 3b from the viewpoint of suppressing dissolution of the elastic layer 3 by a solvent in the paint.

  The developing roller of the present invention controls the chargeability and adhesion to the toner, reduces the frictional force with the photosensitive drum and the stratified blade, and prevents the photosensitive drum from being contaminated by the elastic layer 3. An intermediate coating layer 4 and a surface coating layer 5 are provided on the outer peripheral surface of the elastic layer 3. Here, the intermediate | middle coating layer 4 and the surface coating layer 5 are formed from the coating material containing resin, an organic solvent, and microparticles | fine-particles.

  Suitable resins for forming the intermediate coating layer 4 and the surface coating layer 5 include resins that self-crosslink with heat, catalyst, oxygen, water, ultraviolet rays, electron beams, etc., and reactions with crosslinking agents and other crosslinkable resins. The resin which bridge | crosslinks by is mentioned. Such resins include reactive groups such as hydroxyl groups, carboxyl groups, acid anhydride groups, amino groups, imino groups, isocyanate groups, methylol groups, alkoxymethyl groups, aldehyde groups, mercapto groups, epoxy groups, and unsaturated groups. Polyester resin, polyether resin, fluororesin, epoxy resin, amino resin, polyamide resin, acrylic resin, acrylic urethane resin, urethane resin, alkyd resin, phenol resin, melamine resin, urea resin, silicone resin, polyvinyl butyral resin, etc. These resins may be used alone or in a combination of two or more. Among these resins, fluororesins, polyamide resins, acrylic urethane resins, alkyd resins, phenols from the viewpoints of toner charging ability, non-contamination to toner, reduction of frictional force with other members, non-contamination to photosensitive drums, etc. Resins, melamine resins and silicone resins are preferred. The resin used for the intermediate coating layer 4 and the resin used for the surface coating layer 5 may be the same or different.

  Examples of the catalyst for crosslinking the resin include radical catalysts such as peroxides and azo compounds, acid catalysts, basic catalysts, and alkaline catalysts. The crosslinking agent for crosslinking the resin includes hydroxyl group, carboxyl group, acid anhydride group, amino group, imino group, isocyanate group, methylol group, alkoxymethyl group, aldehyde group, mercapto group, epoxy group, unsaturated group. A compound having 2 or more reactive groups in one molecule and a molecular weight of 1000 or less is preferable, and a compound having a molecular weight of 500 or less is more preferable. Specifically, a polyol compound, a polyisocyanate compound, a polyaldehyde compound, Examples include polyamino compounds and polyepoxy compounds.

  On the other hand, the organic solvent used in the coating is not particularly limited, and alcohol solvents such as methanol, ethanol, isopropanol and butanol, ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone, and aromatic hydrocarbons such as toluene and xylene. Solvents, aliphatic hydrocarbon solvents such as hexane, alicyclic hydrocarbon solvents such as cyclohexane, ester solvents such as ethyl acetate, ether solvents such as isopropyl ether and tetrahydrofuran, amide solvents such as dimethylsulfamide And halogenated hydrocarbon solvents such as chloroform and dichloroethane. These organic solvents may be used alone or in combination of two or more. In addition, the solvent used for the coating material for intermediate | middle coating layers and the solvent used for the coating material for surface coating layers may be the same, or may differ.

A conductive agent can be added to the paint used for forming the intermediate coating layer 4 and the surface coating layer 5 for the purpose of controlling the conductivity of the intermediate coating layer 4 and the surface coating layer 5. Examples of the conductive agent that can be used for the urethane foam raw material constituting the elastic layer 3 are the same as those exemplified above. Here, the blending amount of the conductive agent in the intermediate coating layer 4 and the surface coating layer 5 is preferably 20 parts by mass or less with respect to 100 parts by mass of the resin constituting the intermediate coating layer 4 and the surface coating layer 5, and 0.01 to 20 parts by mass. Is more preferable, and a range of 1 to 10 parts by mass is even more preferable. The intermediate coating layer 4 and the surface coating layer 5 are preferably adjusted so as to have a volume resistance in the range of 10 ³ to 10 ¹² Ω · cm by addition of the conductive agent, and 10 ⁵ to 10 ¹⁰ Ω. -It is more preferable to adjust so that it may become the range of cm.

  The coating material used for forming the intermediate coating layer 4 and the surface coating layer 5 further contains fine particles. By including fine particles in the intermediate coating layer 4 and the surface coating layer 5 and controlling the average particle size and particle size distribution of the fine particles, the toner transportability of the developing roller can be controlled. Here, as the fine particles, rubber or synthetic resin fine particles, carbon fine particles, and inorganic fine particles such as silica-based fine particles are preferable. Silicone rubber, silicone resin, fluororesin, urethane elastomer, polyolefin resin, epoxy resin, polystyrene Resin, urethane acrylate, melamine resin, phenol resin, (meth) acrylic resin, glassy carbon fine particles and silica fine particles are particularly preferable. These fine particles may be used alone or in combination of two or more. Further, the content of the fine particles is preferably in the range of 0.1 to 100 parts by mass, more preferably in the range of 5 to 80 parts by mass with respect to 100 parts by mass of the resin constituting the intermediate coating layer 4 and the surface coating layer 5. Furthermore, the average particle size of the fine particles is preferably in the range of 1 to 30 μm, more preferably in the range of 1 to 20 μm, and even more preferably in the range of 1 to 10 μm. Fine particles having an average particle size of 20 μm or less have a narrow particle size distribution, and therefore the surface roughness of the developing roller can be easily controlled by using the fine particles.

  The thickness of the intermediate coating layer 4 is not particularly limited, but is preferably 5 to 40 μm. On the other hand, the thickness of the surface coating layer 5 is preferably smaller than the average particle size of the fine particles used. Here, the thickness refers to the average thickness. If the thickness of the intermediate coating layer 4 exceeds 40 μm, the intermediate coating layer 4 may become hard and the flexibility may be impaired, and durability may be reduced, cracking may occur due to use, or toner may be damaged. There is a possibility that the toner adheres to the photosensitive drum or the stratified blade, resulting in an image defect. Further, when the thickness of the surface coating layer 5 is equal to or larger than the average particle diameter of the fine particles used, the fine particles are buried in the surface coating layer, and the surface roughness of the developing roller may not be sufficiently secured.

  The formation method of the said intermediate | middle coating layer 4 and the surface coating layer 5 is not specifically limited, For example, the coating material containing each component which comprises the intermediate | middle coating layer 4 and the surface coating layer 5 is prepared, respectively, and an intermediate | middle coating layer Apply the coating material on the elastic layer 3 by dip method, roll coater method, doctor blade method, spray method, etc., air-dry at a temperature of 20-30 ° C and humidity of 30-80% RH, and then dip the coating material for the surface coating layer A method in which the coating is applied on the intermediate coating layer 4 by a method such as a roll coater method, a doctor blade method, or a spray method, dried at room temperature or under heating at about 50 to 170 ° C., and cured by cross-linking is suitably employed. . Here, after applying the coating for the intermediate coating layer, the drying process by heat can be reduced by air drying at a temperature of 25 ± 5 ° C, a humidity of 30-80% RH, and a drying time of 1-10 minutes. The manufacturing cost of the roller can be reduced.

  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, and preferably 5 to 10 μm. 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 average roughness (Rz) can be controlled by selecting the average particle size and particle size distribution of the fine particles.

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>
Since the image forming apparatus of the present invention includes the low-cost developing roller, the price can be reduced. The image forming apparatus of the present invention is not particularly limited except that it includes the developing roller, 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, it is possible to reduce the manufacturing cost of the image forming apparatus itself by using the above-described low-cost developing roller for the developing roller 1.

  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 an isocyanate component which is a polyol-modified tolylene diisocyanate having a NOC content of 6.7% prepolymerized with a polyether polyol, 2.0 parts by mass of conductive carbon black, a polyether polyol having a hydroxyl value of 37.0 mgKOH and an average functionality of 3 21 parts by mass, 19 parts by mass of a polyether polyol having a hydroxyl value of 388 mgKOH and an average functionality of 3; 5 parts by mass of a reactive silicone foam stabilizer (polydimethylsiloxane / polyethylene oxide copolymer) having a hydroxyl value of 34 mgKOH; Part by mass and 0.2 part by mass of dibutyltin dilaurate were mixed to prepare a polyurethane raw material. This polyurethane raw material was foamed by a mechanical floss method. By casting this foamed polyurethane raw material into a mold on which a metal shaft was set, a roller body having an elastic layer of urethane foam around the shaft was produced. The foaming ratio of the obtained urethane foam was 1.6 times.

(Preparation of coating A for intermediate coating layer)
Caprolactone-modified polyol [Daicel Chemical Industries: PCL220AL] 100 parts by mass, carbon black 20 parts by mass and urethane particles [Dainippon Ink and Chemicals: CFB101-40 (average particle size 12 μm)] 10 parts by mass and nurate-modified HDI [Japan Polyurethane Industry Co., Ltd .: Coronero HX] 30 parts by mass was dispersed in 300 parts by mass of methyl ethyl ketone (MEK) to prepare a coating A for forming an intermediate coating layer.

(Preparation of coating B for intermediate coating layer and surface coating layer)
Caprolactone-modified polyol [manufactured by Daicel Chemical Industries: PCL220AL] 100 parts by mass, carbon black 20 parts by mass, acrylic particles [manufactured by Soken Chemical Co., Ltd .: MX1500 (average particle size 15 μm)], and 10 parts by weight nurate-modified HDI [manufactured by Nippon Polyurethane Industry: Coronero 30 parts by mass of HX] was dispersed in 300 parts by mass of methyl ethyl ketone (MEK) to prepare paint B for forming an intermediate coating layer and a surface coating layer.

Example 1
The roller body having the elastic layer made of polyurethane foam is coated with the intermediate coating layer coating A by the dip coating method, dried for 5 minutes in an environment of a temperature of 24 ° C. and a humidity of 52% RH, and then coated with the coating B for the surface coating layer. Dip painted. The produced roller had an intermediate coating layer thickness of 35.2 μm and a surface coating layer thickness of 10.2 μm.

(Example 2)
The roller body having the elastic layer made of polyurethane foam is coated with the intermediate coating layer coating B by the dip coating method, dried for 5 minutes in an environment of temperature 24 ° C. and humidity 52% RH, and then coated with the surface coating layer coating B. Dip painted. The produced roller had an intermediate coating layer thickness of 12.9 μm and a surface coating layer thickness of 9.8 μm.

(Example 3)
The roller body having the elastic layer made of polyurethane foam is coated with the intermediate coating layer coating B by the dip coating method, dried for 5 minutes in an environment of temperature 24 ° C. and humidity 52% RH, and then coated with the surface coating layer coating B. Dip painted. The produced roller had an intermediate coating layer thickness of 35.0 μm and a surface coating layer thickness of 9.5 μm.

Example 4
The roller body having the elastic layer made of polyurethane foam is coated with the intermediate coating layer coating B by the dip coating method, dried for 5 minutes in an environment of temperature 24 ° C. and humidity 52% RH, and then coated with the surface coating layer coating B. Dip painted. The produced roller had an intermediate coating layer thickness of 4.5 μm and a surface coating layer thickness of 9.7 μm.

(Example 5)
The roller body having the elastic layer made of polyurethane foam is coated with the intermediate coating layer coating B by the dip coating method, dried for 5 minutes in an environment of temperature 24 ° C. and humidity 52% RH, and then coated with the surface coating layer coating B. Dip painted. The produced roller had an intermediate coating layer thickness of 54.3 μm and a surface coating layer thickness of 9.6 μm.

(Comparative Example 1)
The surface coating layer coating material B was dip-coated without forming an intermediate coating layer on the outer periphery of the roller body having the elastic layer made of the polyurethane foam. The produced roller had a surface coating layer thickness of 11.6 μm.

  Next, the roller resistance, JIS 10-point average roughness (Rz), and Asker C hardness of the developing roller obtained as described above are evaluated by known methods, and the developing roller is attached to a laser printer for printing. 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.

  The developing rollers of Examples 1 to 4 did not contaminate the photosensitive drum, did not cause pressure contact marks on the blade, and had good image characteristics.

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 3a Foam layer 3b Skin 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 unit 13 Cleaning blade 13

Claims (9)

A developing roller comprising a shaft, an elastic layer formed on the outer periphery of the shaft, an intermediate coating layer formed on the outer peripheral surface of the elastic layer, and a surface coating layer formed on the outer peripheral surface of the intermediate coating layer In
The elastic layer is made of urethane foam obtained by mechanically foaming a urethane raw material,
The developing roller, wherein the intermediate coating layer and the surface coating layer are formed of a paint containing a resin, an organic solvent, and fine particles.   The developing roller according to claim 1, wherein bubbles of the urethane foam are closed cells.   The developing roller according to claim 1, wherein the intermediate coating layer and the surface coating layer are formed of the same paint.   The developing roller according to claim 1, wherein the intermediate coating layer has a thickness of 5 to 40 μm.   The developing roller according to claim 1, wherein an average particle diameter of the fine particles is 20 μm or less.   The developing roller according to claim 1, wherein a thickness of the surface coating layer is smaller than an average particle diameter of the fine particles.   The developing roller according to claim 1, wherein the JIS 10-point average roughness (Rz) is 5 to 10 μm. After forming an elastic layer on the outer periphery of the shaft by mechanical stirring foaming,
After applying a coating containing resin, organic solvent and fine particles by dip method and drying for 1-10 minutes at a temperature of 25 ± 5 ° C and a humidity of 30-80% RH, an intermediate coating layer is formed,
A method for producing a developing roller, wherein the surface coating layer is formed again by applying a paint containing a resin, an organic solvent, and fine particles by a dipping method.   An image forming apparatus comprising the developing roller according to claim 1.

Images