JP2007212780A - Conductive roller and image forming apparatus equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive roller equipped with a coating film layer composed of ultraviolet curing resin, and having high performance to positively electrify toner. <P>SOLUTION: The conductive roller 1 is equipped with a shaft 2, an elastic layer 3 disposed on the outside in the radial direction of the shaft 2, and one or more coating film layers 4 disposed on the outside in the radial direction of the elastic layer. At least the outermost layer of the coating film layers 4 is composed of the ultraviolet curing resin, that is, material for the outermost layer containing an acrylate monomer expressed by a general formula (I) [in the formula, n is an integer ≥1 and R is an n-valent hydrocarbon radical] cured with UV irradiation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive roller and an image forming apparatus including the conductive roller, and more particularly to a conductive roller excellent in performance of imparting positive charge to toner.

  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 or the like 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, development is performed by bringing a developing roller carrying toner into contact with a photosensitive drum holding an electrostatic latent image and attaching the toner to the latent image on the photosensitive drum. Therefore, it is necessary to form the developing roller with a conductive elastic body.

  In the above pressure development method, the developing roller must rotate while securely holding the state in close contact with the photosensitive drum. Therefore, silicone rubber, acrylonitrile-butadiene are placed on the outer periphery of the shaft made of a highly conductive material such as metal. From conductive elastic bodies in which carbon black and metal powder are dispersed in elastomers such as rubber (NBR), ethylene-propylene-diene rubber (EPDM), epichlorohydrin rubber (ECO), polyurethane, etc., and foams obtained by foaming these. The conductive elastic layer is formed. In some cases, a coating layer is 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 of the developing roller.

  For example, Japanese Patent Laid-Open No. 2000-130429 discloses a semiconductive silicone rubber roll having a polyurethane resin layer having a contact charge amount of 0 to 15 nC as an outermost layer, and the semiconductive silicone rubber roll is formed on an elastic layer. It is said that it has a stable triboelectric charging characteristic without impairing the environmental resistance characteristics of the applied silicone rubber, and can impart a sufficient charge amount to the toner.

  Japanese Patent Laid-Open No. 11-249212 discloses a conductive roller in which an elastic layer is produced using a polyol containing polysiloxane having active hydrogen at both ends, thereby improving the charge imparting performance of the elastic layer itself. Is disclosed.

  By the way, conventionally, the coating layer is formed by dipping the roller in a solvent-based or aqueous coating solution or spraying the coating solution on the roller, followed by drying and curing with heat or hot air, for a long time. Therefore, a long drying line is necessary for mass production. The coating layer is required to have subtle electrical conductivity and surface condition depending on its use, but the quality distribution is affected by variations in temperature distribution and air volume in the drying line, which greatly affects the performance of the coating layer. There was a problem.

  On the other hand, as a method of forming a stable quality coating layer without requiring a long drying line, an ultraviolet curable resin material is applied to the surface of the elastic layer of the roller, and the resin material is cured, A technique for forming a coating layer made of an ultraviolet curable resin on the surface of an elastic layer has been proposed (see Patent Document 3).

JP 2000-130429 A JP-A-11-249212 JP 2002-310136 A

  As described above, the coating layer is made of an ultraviolet curable resin, so that a long drying line is not required and a stable quality coating layer can be formed. The conductive roller provided with the coating layer has insufficient ability to impart positive charge to the toner.

  Accordingly, an object of the present invention is to solve the above-described problems of the prior art and provide a conductive roller having a coating layer made of an ultraviolet curable resin and having high positive charge imparting performance to toner. Another object of the present invention is to provide an image forming apparatus that can stably form a good image using such a conductive roller.

  As a result of intensive studies to achieve the above object, the present inventors have cured a raw material composition containing a low-polarity acrylate monomer having a specific structure with ultraviolet irradiation to form at least the outermost layer of the coating layer. The inventors have found that a conductive roller excellent in the performance of imparting positive charge to toner can be obtained, and have completed the present invention.

［式中、ｎは１以上の整数であり、Ｒはｎ価の炭化水素基である］で表されるアクリレートモノマーを含む最表層用原料を紫外線照射で硬化させた紫外線硬化型樹脂からなることを特徴とする。 That is, the conductive roller of the present invention includes a shaft, an elastic layer disposed on the radially outer side of the shaft, and one or more coating layers disposed on the radially outer side of the elastic layer,
At least the outermost layer of the coating layer has the following general formula (I):

[In the formula, n is an integer of 1 or more, and R is an n-valent hydrocarbon group] and consists of an ultraviolet curable resin obtained by curing an outermost layer raw material containing an acrylate monomer by ultraviolet irradiation. It is characterized by.

  In a preferred example of the conductive roller of the present invention, n in the general formula (I) is 1, and R is an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group.

  In another preferred embodiment of the conductive roller of the present invention, n in the general formula (I) is 2, and R is an alkylene group, a cycloalkylene group, an arylene group or an aralkylene group.

  An image forming apparatus according to the present invention includes the above-described conductive roller.

  According to the present invention, a raw material composition containing a low-polarity acrylate monomer having a specific structure is cured by ultraviolet irradiation to form at least the outermost layer of the coating layer, thereby imparting positive charge to the toner of the conductive roller. Performance can be improved. Further, it is possible to provide an image forming apparatus that includes such a conductive roller and can stably form a good image.

<Conductive roller>
Below, the electroconductive roller of this invention is demonstrated in detail. FIG. 1 is a cross-sectional view of an example of a conductive roller of the present invention. The illustrated conductive roller 1 includes a shaft 2, an elastic layer 3 formed on the outer periphery of the shaft 2, and a coating layer 4 formed on the outer peripheral surface of the elastic layer 3. In addition, although the coating film layer 4 consists of one layer in the electroconductive roller of the example of illustration, the coating film layer 4 of the electroconductive roller of this invention may be comprised from two or more layers.

  Here, the conductive roller of the present invention is an ultraviolet curable resin in which at least the outermost layer of the coating layer is formed by curing an outermost layer material containing the acrylate monomer represented by the general formula (I) by ultraviolet irradiation. It is characterized by becoming. Generally, the toner is charged by friction (friction charging phenomenon) with the outermost layer of the conductive roller. Here, the ease of charging the toner is determined by the charging order of the elastic layer and the coating layer. The acrylate monomer of the above formula (I) has a lower polarity than a normal acrylate monomer containing an ethyleneoxy group (EO), a propyleneoxy (PO) group, etc., and a low polarity acrylate monomer. The coating layer formed as is easier to positively charge the toner than the conventional coating layer. Therefore, the conductive roller of the present invention is excellent in the performance of imparting positive charge to the toner.

  The coating layer of the present invention is composed of an ultraviolet curable resin obtained by curing at least the outermost layer material containing the acrylate monomer represented by the above general formula (I) by ultraviolet irradiation, but other than the outermost layer. The coating layer is not particularly limited, and may be the same as or different from the outermost layer. In addition, it is preferable that the raw material for outermost layers of a coating layer contains an acrylate oligomer, a photoinitiator, microparticles | fine-particles, etc. other than the said acrylate monomer.

  The acrylate monomer represented by the general formula (I) acts as a reactive diluent, that is, it can be cured with ultraviolet rays and can reduce the viscosity of the outermost layer raw material. In the acrylate monomer represented by the general formula (I), n is an integer of 1 or more, and R is an n-valent hydrocarbon group. The acrylate monomer of formula (I) is more polar than acrylate monomers containing oxygen such as ethyleneoxy group (EO) or propyleneoxy (PO) group because R in formula (I) is an n-valent hydrocarbon group Is low. Here, n is an integer of 1 or more, and is preferably 1 or 2. The hydrocarbon group may be an aromatic hydrocarbon group, a linear or branched aliphatic hydrocarbon group, or an alicyclic hydrocarbon group.

  When n in the formula (I) is 1, R includes an alkyl group, a cycloalkyl group, an aryl group, and an aralkyl group. Here, as the alkyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, etc. Examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a methylcyclopentyl group, a methylcyclohexyl group, an octylcyclopentyl group, an octylcyclohexyl group, a decylcyclopentyl group, a decylcyclohexyl group, a dodecylcyclopentyl group, and a dodecylcyclohexyl group. Examples of the aryl group include a phenyl group, a hexylphenyl group, an ethylnaphthyl group, a nonylphenyl group, a pentylnaphthyl group, a dodecylphenyl group, and an octylnaphthyl group. The Kill group, a benzyl group, a phenyl hexyl group, a phenyl nonyl group, and a phenyl dodecyl group and the like.

  When n in the formula (I) is 2, R includes an alkylene group, a cycloalkylene group, an arylene group, and an aralkylene group. Here, examples of the alkylene group include a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, a nonamethylene group, and a decamethylene group. Examples of the cycloalkylene group include a cyclopentylene group, a cyclohexylene group, and a trimethylene group. Cyclodecanediyl group, methyltricyclodecanediyl group, ethyltricyclodecanediyl group, dimethyltricyclodecanediyl group, diethyltricyclodecanediyl group, methylethyltricyclodecanediyl group and the like, and as arylene group, Examples thereof include a phenylene group, a naphthylene group, and a biphenylylene group, and examples of the aralkylene group include a xylylene group. As the acrylate monomer represented by the formula (I) and n = 2, specifically, 1,6-hexanediol diacrylate, dimethyltricyclodecane diacrylate and the like are preferable.

  The content of the acrylate monomer represented by the formula (I) in the raw material for the outermost layer of the coating layer is preferably in the range of 30 to 60% by mass. When the content of the acrylate monomer of the formula (I) in the raw material for the outermost layer is less than 30% by mass, the effect of improving the positive charge imparting property to the toner of the conductive roller is small. Both the elongation and strength of the film are reduced, and the film cannot withstand the friction with the photoreceptor and may be broken.

  Suitable acrylate oligomers for the coating layer material include urethane acrylate oligomers, epoxy acrylate oligomers, ether acrylate oligomers, ester acrylate oligomers, polycarbonate acrylate oligomers, fluorine acrylate oligomers, and silicone acrylates. An oligomer etc. are mentioned. The acrylate oligomer is produced by a reaction of acrylic acid with polyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol, bisphenol A type epoxy resin, phenol novolac type epoxy resin, adduct of polyhydric alcohol and ε-caprolactone, etc. Alternatively, it can be synthesized by urethanizing a polyisocyanate compound and an acrylate compound having a hydroxyl group.

  The urethane acrylate oligomer can be obtained by urethanizing a polyol, an isocyanate compound, and an acrylate compound having a hydroxyl group. The epoxy acrylate oligomer is preferably a reaction product of a compound having a glycidyl group and acrylic acid, and has a cyclic structure such as a benzene ring, a naphthalene ring, a spiro ring, dicyclopentadiene, tricyclodecane, and the like. A reaction product of a compound having a glycidyl group and acrylic acid is more preferable. Furthermore, the ether-based acrylate oligomer, ester-based acrylate oligomer and polycarbonate-based acrylate oligomer can be obtained by reacting polyol (polyether polyol, polyester polyol and polycarbonate polyol) with acrylic acid.

  The photopolymerization initiator used for the raw material for the coating layer has an action of initiating polymerization of the acrylate monomer and acrylate oligomer described above when irradiated with ultraviolet rays. Examples of the photopolymerization initiator include 4-dimethylaminobenzoic acid, 4-dimethylaminobenzoic acid ester, 2,2-dimethoxy-2-phenylacetophenone, acetophenone diethyl ketal, alkoxyacetophenone, benzyldimethyl ketal, benzophenone and 3,3. -Dimethyl-4-methoxybenzophenone, benzophenone derivatives such as 4,4-dimethoxybenzophenone, 4,4-diaminobenzophenone, benzoylalkyl benzoate, bis (4-dialkylaminophenyl) ketone, benzyl derivatives such as benzyl and benzylmethyl ketal Benzoin derivatives such as benzoin and benzoin isobutyl ether, benzoin isopropyl ether, 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, xanthone Thioxanthone and thioxanthone derivatives, fluorene, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) ) -Phenylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1,2-benzyl-2-dimethylamino-1- (morpholinophenyl) -butanone-1, etc. It is done. These photoinitiators may be used individually by 1 type, and may use 2 or more types together.

  The blending amount of the photopolymerization initiator in the coating layer raw material is preferably in the range of 0.2 to 5.0 parts by mass with respect to 100 parts by mass in total of the acrylate monomer and the acrylate oligomer. When the blending amount of the photopolymerization initiator is 0.2 parts by mass or less, the effect of initiating UV curing of the coating layer raw material is small. On the other hand, when it exceeds 5.0 parts by mass, the effect of initiating UV curing is saturated. The cost of the raw material for the film layer increases.

  The raw material for the coating layer may further contain fine particles. By including fine particles in the raw material mixture of the coating layer, appropriate minute irregularities can be formed on the surface of the conductive roller. As the fine particles, inorganic fine particles such as fine particles made of rubber, urethane or synthetic resin, fine particles made of carbon and silica fine particles are preferable. Silicone rubber, silicone resin, fluororesin, urethane resin, 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 preferred. These fine particles may be used alone or in combination of two or more. The content of the fine particles is preferably in the range of 0.1 to 100 parts by mass with respect to 100 parts by mass in total of the acrylate monomer and the acrylate oligomer.

  The thickness of the coating layer 4 is preferably in the range of 5 to 30 μm. If the thickness of the coating layer is less than 5 μm, the effect of disposing the coating layer is small, and if it exceeds 30 μm, the surface of the conductive roller becomes hard and the flexibility is impaired.

  The shaft of the conductive roller of the present invention is not particularly limited as long as it has good conductivity. For example, a metal core made of a solid metal, a metal cylindrical body hollowed inside, or a highly rigid resin For example, a cylindrical body made of metal. In addition, when using highly rigid resin for a shaft, it is preferable to ensure sufficient electroconductivity by adding and disperse | distributing a electrically conductive agent to highly rigid resin. Here, as the conductive agent dispersed in the high-rigidity resin, carbon black powder, graphite powder, carbon fiber, metal powder such as aluminum, copper and nickel, metal oxide powder such as tin oxide, titanium oxide and zinc oxide, conductive A powdery conductive agent such as conductive glass powder is preferred. These electrically conductive agents may be used individually by 1 type, and may be used in combination of 2 or more type. The blending amount of the conductive agent is not particularly limited, but is preferably in the range of 5 to 40% by mass, and more preferably in the range of 5 to 20% by mass with respect to the entire highly rigid resin.

  Examples of the material for the metal core bar and the metal cylinder include iron, stainless steel, and aluminum. The material of the high-rigidity resin base material is polyacetal, polyamide 6, polyamide 6 · 6, polyamide 12, polyamide 4 · 6, polyamide 6 · 10, polyamide 6 · 12, polyamide 11, polyamide MXD6, polybutylene. Terephthalate, polyphenylene oxide, polyphenylene sulfide, polyethersulfone, polycarbonate, polyimide, polyamideimide, polyetherimide, polysulfone, polyetheretherketone, polyethylene terephthalate, polyarylate, liquid crystal polymer, polytetrafluoroethylene, polypropylene, ABS resin, polystyrene , Polyethylene, melamine resin, phenol resin, silicone resin and the like. Among these, polyacetal, polyamide 6/6, polyamide MXD6, polyamide 6/12, polybutylene terephthalate, polyphenylene ether, polyphenylene sulfide, and polycarbonate are preferable. These highly rigid resins may be used alone or in combination of two or more.

  The elastic layer of the conductive roller of the present invention contains an elastomer and, if necessary, other components such as a conductive agent. Examples of the elastomer used for the elastic layer include polyurethane, silicone rubber, butyl rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), natural rubber, styrene-butadiene rubber (SBR), chloroprene rubber, acrylic rubber, Examples include epichlorohydrin rubber (ECO), ethylene-vinyl acetate copolymer (EVA), and mixtures thereof. In the elastic layer, the elastomer may be used as a foam by chemically foaming the elastomer using a foaming agent, or mechanically entraining and foaming air like a polyurethane foam. The elastic layer of the conductive roller of the present invention may be composed of an ultraviolet curable resin formed by ultraviolet curing a raw material containing an acrylate oligomer, an acrylate monomer, or the like used for the coating layer described above.

  Examples of the conductive agent used for the elastic layer include an ionic conductive agent and an electronic conductive agent. Examples of ionic conducting agents include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, and modified fatty acid dimethylethylammonium perchlorate, chlorate, hydrochloride, bromate, iodine Ammonium salts such as acid salts, borofluoride salts, sulfate salts, ethyl sulfate salts, carboxylate salts, sulfonate salts; alkali metals such as lithium, sodium, potassium, calcium, magnesium, and perchloric acids of alkaline earth metals Salt, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, trifluoromethyl sulfate, sulfonate, and the like. Conductive carbon such as acetylene black, SAF, I Carbon black for rubber such as AF, HAF, FEF, GPF, SRF, FT, MT, carbon black for color with oxidation treatment, pyrolytic carbon black, natural graphite, artificial graphite, antimony-doped tin oxide, ITO, oxidation Metal oxides such as tin, titanium oxide and zinc oxide, metals such as nickel, copper, silver and germanium, conductive polymers such as polyaniline, polypyrrole and polyacetylene, carbon whiskers, graphite whiskers, titanium carbide whiskers, conductive potassium titanate Examples include whiskers, conductive barium titanate whiskers, conductive titanium oxide whiskers, and conductive zinc oxide whiskers.

The elastic layer 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 is less than 10 ³ Ωcm, the electric charge may leak to the photosensitive drum or the like, or the conductive roller itself may be broken by voltage, and if it exceeds 10 ¹⁰ Ωcm, the ground cover tends to occur.

  The hardness of the elastic layer is not particularly limited, but is preferably 80 degrees or less in terms of Asker C hardness, and more preferably 20 to 70 degrees. If the Asker C hardness of the elastic layer exceeds 80 degrees, the contact area between the conductive roller and the photosensitive drum may be reduced, and good development may not be performed. Also, the toner may be damaged and the photosensitive drum or the stratified blade may be damaged. The toner sticks and the like occurs and image defects are likely to occur. On the other hand, if the elastic layer is too low in hardness, the frictional force with the photosensitive drum or the stratified blade increases, which may cause image defects such as jitter. Since the elastic layer is used in contact with a photosensitive drum, a stratified blade or the like, even when the hardness is set to a low hardness, it is preferable to make the compression set as small as possible, specifically 20% or less. It is preferable.

  The conductive roller of the present invention can be produced, for example, by applying the outermost layer raw material to the outer surface of a roller body formed with an elastic layer on the outer periphery of the shaft and then irradiating it with ultraviolet rays. In addition, when there are a plurality of coating layers, after forming a coating layer other than the outermost layer on the outer surface of the roller body, the outermost layer raw material is applied and irradiated with ultraviolet rays. Can be made. In addition, as a coating method of the raw material for outermost layers, a spray method, a roll coater method, a dipping method, a die coating method, etc. are mentioned. Examples of the light source used for ultraviolet irradiation include a mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, and a xenon lamp. The conditions for ultraviolet irradiation are appropriately selected according to the components, composition, coating amount, and the like contained in the raw material for the outermost layer, and the irradiation intensity, integrated light amount, and the like may be appropriately adjusted.

  The conductive roller of the present invention described above can be used as a developing roller, a charging roller, a toner supply roller, a transfer roller, a paper feed roller, a cleaning roller, a fixing pressure roller, and the like of an image forming apparatus.

<Image forming apparatus>
The image forming apparatus of the present invention includes the conductive roller described above. The image forming apparatus of the present invention is not particularly limited except that the conductive elastic 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 FIG. FIG. 2 is a partial cross-sectional view of an example of the image forming apparatus of the present invention. The image forming apparatus in the illustrated example supplies a photosensitive drum 5 that holds an electrostatic latent image, a charging roller 6 that is positioned near (upward in the drawing) of the photosensitive drum 5 and charges the photosensitive drum 5, and toner 7. A toner supply roller 8, a developing roller 9 disposed between the toner supply roller 8 and the photosensitive drum 5, a developing blade 10 provided in the vicinity of the developing roller 9 (upward in the drawing), and a photosensitive drum. 5 is provided with a transfer roller 11 located in the vicinity (downward in the drawing) 5 and a cleaning roller 12 disposed adjacent to the photosensitive drum 5. 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 illustrated image forming apparatus, the charging roller 6 is brought into contact with the photosensitive drum 5 and a voltage is applied between the photosensitive drum 5 and the charging roller 6 to charge the photosensitive drum 5 to a constant potential. Then, an electrostatic latent image is formed on the photosensitive drum 5 by an exposure machine (not shown). Next, the photosensitive drum 5, the toner supply roller 8, and the developing roller 9 rotate in the direction of the arrow in the figure, so that the toner 7 on the toner supply roller 8 is sent to the photosensitive drum 5 through the developing roller 9. It is done. The toner 7 on the developing roller 9 is adjusted to a uniform thin layer by the developing blade 10, and the toner 7 is transferred from the developing roller 9 to the photosensitive drum 5 by rotating while the developing roller 9 and the photosensitive drum 5 are in contact with each other. It adheres to the electrostatic latent image and the latent image becomes visible. The toner 7 attached to the latent image is transferred to a recording medium such as paper by the transfer roller 11, and the toner 7 remaining on the photosensitive drum 5 after the transfer is removed by the cleaning roller 12. Here, in the image forming apparatus of the present invention, for example, by using the above-described conductive roller of the present invention as the developing roller 9, the toner 7 contacted with the developing roller 9 is surely frictionally charged. Can be formed stably.

  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.

<Preparation of base material with urethane solid as elastic layer>
After adding 1.6 parts by weight of conductive carbon and 0.15 parts by weight of dibutyltin dilaurate to 100 parts by weight of a trifunctional and 9,000 molecular weight polyether polyol obtained by adding propylene oxide to glycerin and stirring sufficiently, the mixture is stirred for 20 minutes under reduced pressure. This was defoamed and used as a polyol component. The hydroxyl value of the polyol component was 19 mgKOH / g. On the other hand, polypropylene glycol-modified polymeric MDI having an NCO content of 11% was degassed for 20 minutes while stirring under reduced pressure, and this was used as an isocyanate component. The polyol component and isocyanate component are mixed at a high speed of 3000 rpm with a two-component casting machine so that the ratio of the polyol component to the isocyanate component is 101.75 / 13.70 (isocyanate index: 103). Was poured into a cylindrical mold set with a cored bar of φ6 mm, and heated and cured in a hot air circulating oven at 90 ° C. for 60 minutes. The cored urethane roller was taken out from the cylindrical mold to obtain a substrate having urethane solid as an elastic layer.

<Preparation of substrate using UV resin as elastic layer>
Conductive roller base material made of polybutylene terephthalate (PBT) resin with an outer diameter of 17.0 mm inserted with a metal shaft with an outer diameter of 6.0 mm, 60 parts by mass of urethane acrylate oligomer UV3700B [manufactured by Nippon Synthetic Chemical Co., Ltd.], acrylate monomer MTG- A [methoxytriethylene glycol acrylate, manufactured by Kyoeisha Chemical Co., Ltd.] 40 parts by mass, photoinitiator IRGACURE651 [2,2-dimethoxy-1,2-diphenylethane-1-one, Ciba Specialty Chemicals Co., Ltd. )] 1 part by weight, ion conductive agent MP100 [polyol complex salt of sodium perchlorate, manufactured by Akishima Chemical Co., Ltd.] 2 parts by weight of the elastic layer material was applied by a die coater to a thickness of 1500 μm, under a nitrogen atmosphere While rotating, UV irradiation was performed at a UV irradiation intensity of 700 mW / cm ² for 5 seconds to obtain a base material having a UV resin as an elastic layer.

(Examples 1-3 and Comparative Examples 1-4)
Next, the raw material for the coating layer having the composition shown in Table 1 was applied to the surface of the substrate with a roll coater, and UV irradiation was performed at a UV irradiation intensity of 700 mW / cm ² for 5 seconds. A conductive roller having a thickness of 10 μm] was obtained. The obtained conductive roller was evaluated for toner charge amount, durable sheet number, resistance value, and average surface roughness by the following methods. The results are shown in Table 1.

(1) Toner charge amount The toner charge amount is 210HS-2A Q / m Meter [manufactured by Trek Co., Ltd.], and the toner adhering to the roller surface after the cyan 1% density printing is sucked from the tip nozzle portion. The amount was determined by measurement. The toner charge amount was defined as a Q / M value (toner charge amount per unit mass), and the charge amount was divided by the suction toner mass.

(2) Durable number of sheets Using a commercially available laser printer, cyan was printed at 1% density, and a durability test was conducted. In the durability test, the number of prints on which the toner started to adhere to the white background (non-printed portion) during continuous printing was defined as the durable number (fogging occurrence number).

(3) Resistance value The resistance value is set between the shaft and the roller surface by using R8340A ULTRA HIGH RESISTANCE METER [manufactured by ADVANTEST] in a static state after placing a roller on a metal plate and applying a load of 500 g to both end metal shafts. A voltage of 100 V was applied to the surface, and the surface resistance was measured.

(4) Average surface roughness The average surface roughness (Ra value) was calculated by using Surfcom 590A [manufactured by Tokyo Seimitsu Co., Ltd.] and tracing the uneven shape on the roller surface with a tip needle.

  As is apparent from Table 1, a conductive roller having a coating layer (outermost layer) formed by ultraviolet curing a raw material containing the acrylate monomer represented by the general formula (I) has a high toner charge amount. By incorporating such a conductive roller as a developing roller in the image forming apparatus, the durability of the image forming apparatus can be improved.

It is sectional drawing of an example of the electroconductive 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 Conductive roller 2 Shaft 3 Elastic layer 4 Coating layer 5 Photosensitive drum 6 Charging roller 7 Toner 8 Toner supply roller 9 Developing roller 10 Developing blade 11 Transfer roller 12 Cleaning roller

Claims (4)

In a conductive roller comprising a shaft, an elastic layer disposed on the radially outer side of the shaft, and one or more coating layers disposed on the radially outer side of the elastic layer,
At least the outermost layer of the coating layer has the following general formula (I):

[In the formula, n is an integer of 1 or more, and R is an n-valent hydrocarbon group] and consists of an ultraviolet curable resin obtained by curing an outermost layer raw material containing an acrylate monomer by ultraviolet irradiation. A conductive roller characterized by.   2. The conductive roller according to claim 1, wherein n in the general formula (I) is 1 and R is an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group.   2. The conductive roller according to claim 1, wherein n in the general formula (I) is 2 and R is an alkylene group, a cycloalkylene group, an arylene group, or an aralkylene group.   An image forming apparatus comprising the conductive roller according to claim 1.

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