JP5279237B2 - Conductive roller and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a conductive roller having an elastic layer and a coating layer, and an image forming apparatus including the conductive roller, and in particular, a conductive roller having improved durability and a good image including the conductive roller. The present invention relates to an image forming apparatus capable of forming the image.

  In general, in an electrophotographic image forming apparatus such as a copying machine, a facsimile, or a laser beam printer (LBP), a developing roller, a charging roller, a toner supply roller, a transfer roller, a paper feeding roller, a cleaning roller, and a pressure for fixing. As a roller or the like, a roll-shaped conductive elastic member, that is, a conductive roller is frequently used, and the conductive roller is usually mounted with a shaft member supported by both ends in the length direction, and the shaft member. And one or more elastic layers disposed on the outside in the radial direction. The conductive roller has a coating layer on the surface of the elastic layer for the purpose of improving the hardness of the roller, controlling chargeability and adhesion to toner, preventing contamination of the photosensitive drum by the elastic layer, and the like. There is a case to prepare.

  For the shaft member of the conductive roller, various resins such as engineering plastics are used in addition to metals such as iron and stainless steel. The elastic layer of the conductive roller uses an elastomer such as silicone rubber, acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), epichlorohydrin rubber (ECO), polyurethane, It is manufactured by injecting an elastomer raw material into a mold having a desired cavity shape and heating it to heat cure the elastomer raw material. Further, the coating layer is formed by dipping the roller body composed of the shaft member and the elastic layer into a solvent-based or aqueous coating liquid containing resin or spraying the coating liquid on the roller body, It is formed by drying and curing with hot air. Here, since long time drying is required for the formation of the coating layer, a long drying line is necessary for mass production, and the coating layer requires delicate conductivity and surface condition from its application. However, there is a problem in quality because variations in temperature distribution and air volume in the drying line greatly affect the performance of the coating layer.

  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 1).

JP 2002-310136 A

  However, a coating layer formed by ultraviolet curing an ultraviolet curable resin material usually has high hardness and does not have sufficient elongation characteristics. For this reason, when a conductive roller having such a coating film layer is used in an image forming apparatus, the coating film is scraped or broken during use, and image defects are likely to occur. In particular, when the elastic layer of the conductive roller is made of a foam (foam), coating film scraping and cracking remarkably appeared, and there was a problem in durability.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive roller that does not require a long drying line for production, has a stable quality coating layer, and has improved durability. 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 inventor of the present invention, in a conductive roller having a coating layer disposed on the surface of the elastic layer, the coating layer, (meth) acrylate oligomer, and (meth) By using an ultraviolet curable resin obtained by curing a raw material composition containing an acrylate monomer and a photopolymerization initiator by ultraviolet irradiation, a conductive roller having excellent elongation characteristics of the coating layer and excellent durability can be obtained. The inventors have found that the present invention can be obtained and have completed the present invention.

That is, the conductive roller of the present invention includes a shaft member, an elastic layer disposed on the outer side in the radial direction of the shaft member, and one or more coating layers disposed on the outer side in the radial direction of the elastic layer. Prepared,
At least the coating layer adjacent to the elastic layer is cured by irradiating the coating layer material containing (meth) acrylate oligomer (A), (meth) acrylate monomer (B) and photopolymerization initiator (C) with ultraviolet irradiation. UV curable resin
The ultraviolet curable resin has an elongation at break of 80% or more ,
The (meth) acrylate monomer (B) is at least one selected from the group consisting of acryloylmorpholine, N, N-diethylaminoethyl methacrylate, and isobornyl acrylate .

  In the conductive roller of the present invention, the (meth) acrylate oligomer (A) preferably has a weight average molecular weight of 4500 or more.

  In the conductive roller of the present invention, in order to exhibit excellent durability, the ultraviolet curable resin preferably has an elastic modulus of 280 MPa or less in addition to an elongation at break of 80% or more.

  In a preferred example of the conductive roller of the present invention, the (meth) acrylate oligomer (A) is a urethane-based (meth) acrylate oligomer.

  In the conductive roller of the present invention, the content of the (meth) acrylate monomer (B) in the total of the (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B) is 10 to 60. It is preferably in the range of mass%.

  The image forming apparatus of the present invention is characterized by using the conductive roller.

  According to the present invention, the conductive roller having the coating layer disposed on the surface of the elastic layer includes (meth) acrylate oligomer (A), (meth) acrylate monomer (B), and photopolymerization initiator (C). By using a UV-curable resin with a breaking elongation of 80% or more, which is obtained by curing the raw material mixture by UV irradiation, as a coating layer (there is no need for a long drying line for manufacturing and it has a stable quality coating layer. The conductive roller having improved durability against scraping and cracking can be provided. The (meth) acrylate monomer (B) is preferably a (meth) acrylate monomer (B) having one functional group and a bulky substituent or polar group. Furthermore, durability is further improved by designing the elastic modulus of the UV curable resin used for the coating layer to be 280 MPa or more. As a result, an image forming apparatus including such a conductive roller and capable of stably forming a good image can be provided.

<Conductive roller>
Below, the conductive roller of this invention is demonstrated in detail, referring a figure. FIG. 1 is a cross-sectional view of an example of a conductive roller of the present invention. The conductive roller 1 in the illustrated example includes a shaft member 2, an elastic layer 3 disposed on the outer side in the radial direction of the shaft member 2, and a coating layer 4 disposed on the outer side in the radial direction of the elastic layer 3. Is provided. In addition, although the conductive roller 1 shown in FIG. 1 has only one coating layer 4, the conductive roller of the present invention may have two or more coating layers.

  In the conductive roller of the present invention, at least the coating layer 4 adjacent to the elastic layer 3 includes a (meth) acrylate oligomer (A), a (meth) acrylate monomer (B), and a photopolymerization initiator (C). It is made of an ultraviolet curable resin obtained by curing the layer raw material by ultraviolet irradiation, and the ultraviolet curable resin has a breaking elongation of 80% or more. Here, when the (meth) acrylate monomer (B) has a functional group number of 1 and a bulky substituent or polar group, in addition to reducing the viscosity of the coating layer raw material, it is suitable for an ultraviolet curable resin. Toughness and elongation properties can be imparted. Further, in the conductive roller of the present invention, since the breaking elongation of the ultraviolet curable resin is 80% or more, problems relating to the durability of the roller such as coating film scraping can be solved.

  In the conductive roller of the present invention, in addition to the elongation at break of the coating layer 4 adjacent to the elastic layer 3 being 80% or more, the durability can be further improved by setting the elastic modulus to 280 MPa or less. it can. The conductive roller is in direct contact with a member such as a photoconductor during printing and rotates while appropriately nipping. As a result, stress concentrates on the coating layer 4 that is the outermost layer. This stress increases as the elastic modulus of the coating layer 4 increases. Therefore, stress concentration on the coating film layer 4 can be prevented by setting the elastic modulus to 280 MPa or less. Thereby, the problems relating to the durability of the roller such as coating film scraping can be further solved.

  The shaft member 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 metal such as iron, stainless steel, aluminum, or the like is hollowed out. A metal shaft such as a metal cylinder or a highly conductive plastic shaft can be used.

  The elastic layer of the conductive roller of the present invention is formed of an elastomer, and may contain other components such as a conductive agent as necessary. Examples of the elastomer used for the elastic layer include polyurethane, silicone rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR). , Isoprene rubber (IR), polynorbornene rubber, butyl rubber (IIR), chloroprene rubber (CR), acrylic rubber, epichlorohydrin rubber (ECO), ethylene-vinyl acetate copolymer (EVA), and mixtures thereof. Among these, polyurethane is preferable. In the elastic layer, the elastomer may be used as a non-foamed material or a foamed material.

  Examples of the conductive agent that can be used for the elastic layer 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. Conductive whiskers such as conductive polymer, 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, more preferably in the range of 5 to 40 parts by mass with respect to 100 parts by mass of the elastomer.

  Examples of the ionic conductive agent include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, modified fatty acid dimethylethylammonium, perchlorate, chlorate, hydrochloride, bromate, and the like. 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 compounding amount of the ionic conductive agent is preferably in the range of 0.01 to 10 parts by mass, more preferably in the range of 0.05 to 5 parts by mass with respect to 100 parts by mass of the elastomer. 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 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 elastic layer may contain a crosslinking agent such as an organic peroxide and a vulcanizing agent such as sulfur in order to make the elastomer into a rubbery material, if necessary. Accelerators, vulcanization accelerators, vulcanization retarders, and the like may be included. In addition, the elastic layer further comprises a rubber compounding agent such as a filler, a peptizer, a foaming agent, a plasticizer, a softener, a tackifier, an anti-tacking agent, a separating agent, a release agent, a bulking agent, and a coloring agent An agent may be contained.

  The elastic layer of the conductive roller of the present invention is preferably composed of urethane foam obtained by mechanically foaming 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 raw material include a polyol and a polyisocyanate, or a urethane prepolymer and a chain extender synthesized from a polyol and a polyisocyanate. The urethane raw material further includes a catalyst, a foam stabilizer, the above-described conductive agent, and the like. Can be added. 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 and 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.

  The elastomer raw material, preferably a urethane raw material foamed by mechanical stirring, is poured into a cylindrical mold in which the shaft member 2 is arranged in advance, and is cured by reaction, whereby the elastic layer 3 is formed radially outward of the shaft member 2. Can be obtained.

  The conductive roller of the present invention increases the hardness of the roller, controls the chargeability and adhesion to the toner, reduces the frictional force with the photosensitive drum and the stratified blade, etc. In order to prevent contamination, one or more coating layers are provided on the radially outer side of the elastic layer. And at least the layer adjacent to the elastic layer in the coating layer comprises a (meth) acrylate oligomer (A), a (meth) acrylate monomer (B) and a photopolymerization initiator (C). It is made of an ultraviolet curable resin that is cured by ultraviolet irradiation. In the conductive roller of the present invention, it suffices that at least the coating layer adjacent to the elastic layer is formed from this ultraviolet curable resin, and when the conductive roller has two or more coating layers, The other coating layer is not limited to this.

The (meth) acrylate oligomer (A) used as the raw material for the coating layer is an oligomer having one or more acryloyloxy groups (CH ₂ ═CHCOO—) or methacryloyloxy groups (CH ₂ ═C (CH ₃ ) COO—). It is. The number of functional groups of the (meth) acrylate oligomer (A) is not particularly limited. As the (meth) acrylate oligomer (A), urethane (meth) acrylate oligomer, epoxy (meth) acrylate oligomer, ether (meth) acrylate oligomer, ester (meth) acrylate oligomer, polycarbonate (meth) acrylate Examples include oligomers, fluorine-based (meth) acrylate oligomers, and silicone-based (meth) acrylate oligomers. Among these, urethane-based (meth) acrylate oligomers are preferable. The (meth) acrylate oligomer (A) includes polyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol, bisphenol A type epoxy resin, phenol novolac type epoxy resin, adduct of polyhydric alcohol and ε-caprolactone, and the like. It can be synthesized by reaction with (meth) acrylic acid or by urethanizing a polyisocyanate compound and a (meth) acrylate compound having a hydroxyl group.

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

  The (meth) acrylate oligomer (A) is not particularly limited, but the weight average molecular weight is preferably 4500 or more, more preferably 6000 or more, and the weight average molecular weight is 40000 or less. preferable. Here, if the weight average molecular weight is 4500 or more, elongation characteristics can be imparted to the coating layer, and the durability of the roller is improved. On the other hand, when the weight average molecular weight exceeds 40,000, the adhesiveness of the coating layer is lowered, and workability may be lowered.

The (meth) acrylate monomer (B) used for the raw material for the coating layer is a monomer having a functional group number of 1 and can be cured by ultraviolet irradiation and can impart elongation characteristics to the ultraviolet curable resin. Here, the functional group refers to an acryloyloxy group (CH ₂ ═CHCOO—) or a methacryloyloxy group (CH ₂ ═C (CH ₃ ) COO—). If the number of functional groups of the (meth) acrylate monomer (B) is 2 or more, the elongation of the coating layer is impaired and the durability of the roller is deteriorated.

The (meth) acrylate monomer (B) preferably has a bulky substituent or polar group in addition to the acryloyloxy group or methacryloyloxy group. As a result of having a bulky substituent or polar group in the (meth) acrylate monomer (B), the polymer chain after polymerization becomes sterically bulky, or the polar group interaction in the polymer chain becomes stronger. The crystallinity of the polymer decreases. In general, amorphous polymers tend to have better elongation characteristics than crystalline polymers, and thus the (meth) acrylate monomer (B) is considered to be effective in imparting elongation characteristics. Here, examples of the bulky substituent include a substituent having a cyclic structure or a branched chain structure, and a substituent having a cyclic structure is preferable. The cyclic structure may be either monocyclic or polycyclic, but preferably has a strong cyclic structure in which the movement of the ring is limited, and is a cyclic conjugated structure or three or more rings. A polycyclic bridged cyclic structure formed from is more preferable. The cyclic structure may be a cyclic hydrocarbon or a heterocyclic ring. The cyclic conjugated structure is preferably a benzene ring, naphthalene ring, pyridine ring or the like. On the other hand, a polycyclic bridged cyclic structure formed from three or more rings is bicyclo [2.2. 1] A heptane ring, a bicyclo [2.2.1] heptene ring, a tricyclo [3.3.1.1 ^3,7 ] decane ring, a tricyclo [5.2.1.0 ^2,6 ] decane ring and the like are preferable. . Accordingly, specific examples of the bulky substituent include a phenoxyethyl group, an isobornyl group, a norbornyl group, a norbornenyl group, an adamantyl group, a tricyclo [5.2.1.0 ^2,6 ] decyl group, and the like. Among these, a phenoxyethyl group and an isobornyl group are preferable. On the other hand, the polar group is preferably a polar group containing nitrogen or oxygen, and is an amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, nitrogen-containing heterocyclic group. More preferred are oxygen-containing heterocyclic groups, and more preferred are amino groups, nitrogen-containing heterocyclic groups and oxygen-containing heterocyclic groups. Note that the polar group containing nitrogen or oxygen may further contain other heteroatoms. Here, the amino group is preferably a dialkylamino group, a diarylamino group, or the like. The dialkylamino group is more preferably a dialkylamino group having an alkyl group having 1 to 10 carbon atoms, more preferably a diethylamino group, a dimethylamino group, or the like. On the other hand, as the diarylamino group, a diarylamino group having an unsubstituted or substituted aryl group having 6 to 10 carbon atoms in the ring showing an aromatic attribute is more preferable, and a diphenylamino group is more preferable. Specific examples of the nitrogen-containing heterocyclic group include a morpholino group, and specific examples of the oxygen-containing heterocyclic group include a tetrahydrofuryl group.

  From the above, specific examples of the (meth) acrylate monomer (B) include acryloylmorpholine, N, N-diethylaminoethyl methacrylate, isobornyl acrylate, phenoxyethyl acrylate, and the like. In addition, a (meth) acrylate monomer (B) may be used individually by 1 type, and may be used in combination of 2 or more type.

In the conductive roller of the present invention, the coating layer raw material may contain a (meth) acrylate monomer (D) other than the (meth) acrylate monomer (B) as a reactive diluent. The (meth) acrylate monomer (D) is a monomer having one or more acryloyloxy groups (CH ₂ ═CHCOO—) or methacryloyloxy groups (CH ₂ ═C (CH ₃ ) COO—) for coating layers. It acts as a reactive diluent in the raw material, that is, it can be cured with ultraviolet rays and the viscosity of the raw material for the coating layer can be lowered. The (meth) acrylate monomer (D) preferably has a functional group number of 1.0 to 10 and more preferably 1.0 to 3.5. The acrylate monomer (D) preferably has a molecular weight of 100 to 2000, and more preferably 100 to 1000.

  As the (meth) acrylate monomer (D), 2-butyl-2-ethyl-1,3-propanediol diacrylate, 1,6-hexanediol diacrylate, isomyristyl acrylate, methoxytriethylene glycol acrylate, ethyl acrylate , Isobutyl acrylate, n-butyl acrylate, isoamyl acrylate, glycidyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydipropylene glycol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, pentaerythritol triacrylate, etc. Among these, 2-butyl-2-ethyl-1,3-propanediol diacrylate and 1,6-hexanediol diacrylate are Masui. These (meth) acrylate monomers (D) may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the coating layer raw material, the (meth) acrylate monomer (A), the (meth) acrylate monomer (B), and the (meth) acrylate monomer (D) in the total of the (meth) acrylate monomer (D) that can be optionally contained ( The proportion of B) is preferably in the range of 10 to 60% by mass. If the content of the (meth) acrylate monomer (B) is less than 10% by mass, the UV-cured film may have a tackiness, which may cause abrasion due to friction. Unreacted monomer tends to remain in the film, and bleeding of uncured components becomes a problem.

  The photopolymerization initiator (C) used as the raw material for the coating layer is the above-mentioned (meth) acrylate oligomer (A), (meth) acrylate monomer (B) and (meth) acrylate monomer when irradiated with ultraviolet rays. (D) has an action of initiating polymerization. Examples of the photopolymerization initiator (C) 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, alkyl benzoylbenzoate, bis (4-dialkylaminophenyl) ketone, benzyl, benzylmethyl ketal, etc. Benzyl derivatives of benzoin, benzoin derivatives such as benzoin and benzoin isobutyl ether, benzoin isopropyl ether, 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, 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. Is mentioned. These photoinitiators may be used individually by 1 type, and may use 2 or more types together. The blending amount of the photopolymerization initiator (C) 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 oligomer and monomer. When the blending amount of the photopolymerization initiator (C) is 0.2 parts by mass or less, the effect of initiating UV curing of the coating layer raw material is small, while when it exceeds 5.0 parts by mass, the effect of initiating UV curing is saturated. On the other hand, the cost increases.

  In the raw material for the coating layer, a tertiary amine photopolymerization accelerator such as triethylamine or triethanolamine, or a phosphine light such as triphenylphosphine is used to promote the polymerization reaction by the photopolymerization initiator (C). A polymerization accelerator, a thioether photopolymerization accelerator such as thiodiglycol, and the like may be further added to the paint. The addition amount of these photopolymerization accelerators is preferably in the range of 0.01 to 10 parts by mass with respect to 100 parts by mass in total of the oligomer and the monomer.

  In the conductive roller of the present invention, the raw material for the coating layer includes the (meth) acrylate oligomer (A), the (meth) acrylate monomer (B), the photopolymerization initiator (C), and optionally the (meth) acrylate monomer. In addition to (D) and a photopolymerization accelerator, it is preferable to contain a conductive agent, fine particles, a polymerization inhibitor, and the like. In the conductive roller of the present invention, the coating layer other than the coating layer adjacent to the elastic layer is not particularly limited, and may be the same as or different from the coating layer adjacent to the elastic layer.

  In the conductive roller of the present invention, the raw material for the coating layer may contain a conductive agent in order to impart conductivity, and the conductive agent can be used for the elastic layer described above. The same thing is mentioned.

  In the conductive roller of the present invention, the coating layer material may further contain fine particles. By including fine particles in the raw material for the coating layer, appropriate fine 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. In addition, 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 oligomer and the monomer.

  In the conductive roller of the present invention, the raw material for the coating layer may further contain a polymerization inhibitor. By adding a polymerization inhibitor, thermal polymerization before ultraviolet irradiation can be prevented. Polymerization inhibitors include hydroquinone, hydroquinone monomethyl ether, p-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-p-cresol, butylhydroxyanisole, 3 -Hydroxythiophenol, α-nitroso-β-naphthol, p-benzoquinone, 2,5-dihydroxy-p-quinone and the like. In addition, the content of the polymerization inhibitor is preferably in the range of 0.001 to 0.2 parts by mass with respect to 100 parts by mass in total of the oligomer and the monomer.

  In the conductive roller of the present invention, the ultraviolet curable resin forming the coating layer adjacent to the elastic layer needs to have an elongation at break of 80% or more, and preferably 80 to 600%. If the elongation at break of the ultraviolet curable resin is less than 80%, the elongation of the coating layer is impaired, and the durability of the roller is deteriorated. As a result, the coating film is cracked or the coating film is scraped during printing.

  In the conductive roller of the present invention, the ultraviolet curable resin forming the coating layer adjacent to the elastic layer has an elastic modulus of 280 MPa or less, preferably 5 to 5 in addition to the elongation at break of 80% or more. By setting the pressure within the range of 200 MPa, the durability can be further improved. If the elastic modulus of the ultraviolet curable resin exceeds 280 MPa, stress concentrates on the coating layer and the durability of the roller deteriorates, resulting in coating cracking and coating scraping during printing.

  The total thickness of the coating layer is preferably in the range of 0.5 μm to 150 μm. If the total thickness of the coating layer is less than 0.5 μm, the effect of disposing the coating layer is small, and if it exceeds 150 μm, the surface of the conductive roller becomes hard and flexibility is impaired.

  The conductive roller of the present invention is not particularly limited, and for example, the elasticity of the roller main body obtained by preparing a coating layer raw material (paint) containing each component constituting the coating layer and obtained by the above-described method. After coating on the layer, it can be prepared by irradiating with ultraviolet rays to form a coating layer. Moreover, in the electroconductive roller which has two or more coating film layers, it can produce by repeating the same procedure. In this case, the conductive roller of the present invention does not require a long drying line for production, and has a coating layer having a stable quality. In addition, as a method of apply | coating the raw material for coating-film layers (paint) to the outer surface of an elastic layer and a coating-film layer, 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 and coating amounts contained in various raw materials, and the irradiation intensity, the integrated light amount, etc. may be adjusted as appropriate.

  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 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 supplies a photosensitive drum 5 holding an electrostatic latent image, a charging roller 6 for charging the photosensitive drum 5 located near (upward in the drawing), 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 stratification 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 known components (not shown) that are normally used in the image 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 stratifying blade 10 and rotates while the developing roller 9 and the photosensitive drum 5 are in contact with each other, so that the toner 7 is transferred from the developing roller 9 to the photosensitive drum 5. 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, at least one of the charging roller 6, the toner supply roller 8, the developing roller 9, the transfer roller 11, and the cleaning roller 12, for example, the elastic layer 3 and the coating layer described above. 4 and the conductive roller 1 having excellent durability can be used to stably form an excellent image.

  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.

  First, the roller main body which has the elastic layer of the specification common to Examples 1-14 and Comparative Examples 1-9 was produced based on the following prescription.

(Production of roller body)
100 parts by mass of an isocyanate component which is a polyol-modified tolylene diisocyanate having a NCO content of 6.7% prepolymerized with a polyether polyol, 2.0 parts by mass of conductive carbon black, a poly having an average functional group number of 3 and a hydroxyl value of 37.0 mgKOH / g 21 parts by mass of ether polyol, 19 parts by mass of polyether polyol having a hydroxyl value of 388 mgKOH / g and an average number of functional groups of 3 and 5 parts by mass of reactive silicone foam stabilizer (polydimethylsiloxane / polyethylene oxide copolymer) having a hydroxyl value of 34 mgKOH / g Then, 0.3 parts by mass of sodium perchlorate and 0.2 parts 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.

(Examples 1-14 and Comparative Examples 1-6)
Next, the coating material for the coating layer having the formulation shown in Tables 1 to 3 is applied to the surface of the roller body with a roll coater, and UV irradiation is performed at a UV irradiation intensity of 1500 mW / cm ² for 5 seconds, and the surface is irradiated with UV. A conductive roller having a coating film [thickness: 20 μm] was obtained. For the obtained conductive roller, the printing durability test was evaluated by the following method. Further, the elongation at break and the elastic modulus of the ultraviolet curable resin obtained by curing the paint for coating layer by ultraviolet irradiation were also measured by the following methods. The results are shown in Tables 1-3.

(1) Printing durability test The conductive roller was incorporated in the image forming apparatus as a developing roller, and after printing 5,000 sheets, the degree of roller abrasion of the conductive roller was visually determined according to the following criteria.
`` Good '' if the line on the surface of the roller is not visible or can not be confirmed even if it is visible, but the step on the surface of the roller cannot be confirmed, but the elastic modulus of the UV curable resin that forms the coating layer is too high As a result, “slightly good” means that the spec crack occurs, and “bad” means that the level difference on the roller surface can be clearly confirmed.

(2) Breaking Elongation and Elastic Modulus of Ultraviolet Curing Resin Evaluation was made by a JIS method plastic film and sheet tensile test method (JIS K 7127-1989). Specifically, the resin coating was UV cured in a glass mold to prepare a resin plate, which was cut into strips having a total length of 20 cm and a width of 1 to 2.5 cm to obtain samples. With respect to this sample, the distance between chucks was set to 10 cm, and the elongation at break was recorded with a tensile tester [STA-1150 manufactured by Orientec Co., Ltd.]. The elastic modulus was calculated from the stress at 5% elongation of the sample.

* 1 Urethane acrylate oligomer, manufactured by Kyoeisha Chemical Co., Ltd., weight average molecular weight: 4500.
* 2 Epoxy acrylate oligomer, manufactured by Kyoeisha Chemical Co., Ltd., weight average molecular weight: 600.
* 3 Polar group-containing acrylate monomer, acryloylmorpholine, manufactured by Shin-Nakamura Chemical Co., Ltd.
* 4 Polar group-containing methacrylate monomer, N, N-diethylaminoethyl methacrylate, manufactured by Kyoeisha Chemical Co., Ltd.
* 5 Bulky substituent-containing acrylate monomer, isobornyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.
* 6 Bulky substituent-containing acrylate monomer, phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.
* 7 2-Butyl-2-ethyl-1,3-propanediol diacrylate, manufactured by Kyoeisha Chemical Co., Ltd.
* 8 1,6-hexanediol diacrylate, manufactured by Kyoeisha Chemical Co., Ltd.
* 9 1-Hydroxycyclohexyl phenyl ketone, manufactured by Ciba Specialty Chemicals.
* 10 Urethane acrylate oligomer, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., weight average molecular weight: 18000.
* 11 Urethane acrylate oligomer, Nippon Kayaku Co., Ltd., weight average molecular weight: 8100.
* 12 Urethane acrylate oligomer, Nippon Kayaku Co., Ltd., weight average molecular weight: 11500.
* 13 Urethane acrylate oligomer, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., weight average molecular weight: 10000.
* 14 Urethane acrylate oligomer, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., weight average molecular weight: 10000.
* 15 Urethane acrylate oligomer, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., weight average molecular weight: 5000.

  From Tables 1 to 3, the conductive roller of the example is a coating layer coating containing a (meth) acrylate monomer (B) having a functional group number of 1 and a bulky substituent or polar group, which is cured by ultraviolet irradiation. It was found that the durability was better than that of the conductive roller of the comparative example by using the coating layer made of an ultraviolet curable resin having an elongation at break of 80% or more. Further, from the results of Examples 1, 2, 7, 12, and 13, the conductive roller of the present invention comprises a (meth) acrylate monomer containing a bulky substituent and a (meth) acrylate monomer containing a polar group. It was found that even when combined, the roller was excellent in durability. Furthermore, from the results of Examples 5 and 12, it was found that the conductive roller of the present invention may contain a (meth) acrylate monomer other than the (meth) acrylate monomer (B).

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 member 3 Elastic layer 4 Coating layer 5 Photosensitive drum 6 Charging roller 7 Toner 8 Toner supply roller 9 Developing roller 10 Layering blade 11 Transfer roller 12 Cleaning roller

Claims (5)

In a conductive roller comprising a shaft member, an elastic layer disposed on the radially outer side of the shaft member, and one or more coating layers disposed on the radially outer side of the elastic layer,
At least the coating layer adjacent to the elastic layer is cured by irradiating the coating layer material containing (meth) acrylate oligomer (A), (meth) acrylate monomer (B) and photopolymerization initiator (C) with ultraviolet irradiation. UV curable resin
The ultraviolet curable resin has an elongation at break of 80% or more ,
The conductive roller, wherein the (meth) acrylate monomer (B) is at least one selected from the group consisting of acryloylmorpholine, N, N-diethylaminoethyl methacrylate, and isobornyl acrylate .   The conductive roller according to claim 1, wherein the (meth) acrylate oligomer (A) has a weight average molecular weight of 4500 or more.   The conductive roller according to claim 1, wherein the (meth) acrylate oligomer (A) is a urethane-based (meth) acrylate oligomer.   The content of the (meth) acrylate monomer (B) in the total of the (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B) is in the range of 10 to 60% by mass. The conductive roller according to claim 1. An image forming apparatus using the conductive roller according to claim 1 .

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