JP2009115952A - Conductive roller, manufacturing method for same and image forming apparatus using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive roller which has an elastic layer formed of ultraviolet curing type resin and can suppress occurrence of an image irregularity. <P>SOLUTION: The conductive roller 1 is provided with a shaft member 2 and the elastic layer 3 which is arranged outside the shaft member 2 in a radial direction and formed of the ultraviolet curing type resin, wherein the elastic layer 3 has the thickness of 0.5-2 mm and Asker C hardness of ≤70. Here, the ultraviolet curing type resin is formed by curing the material for the elastic layer, containing urethane (meth)acrylate oligomer (A), (meth)acrylate monomer (B), photoinitiator (C) and conductive agent (D), by ultraviolet irradiation. It is desirable that the urethane (meth)acrylate oligomer (A) has the number of functional groups of ≤2.0. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a conductive roller, a method for manufacturing the same, and an image forming apparatus using the conductive roller, and is particularly suitable as a developing roller, and has a low-hardness elastic layer and can suppress occurrence of image unevenness. The present invention relates to a conductive roller.

  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 member, i.e., a conductive roller, is often used. The conductive roller is usually attached to a shaft member that is supported by both ends in the length direction, and the shaft member. And one or more elastic layers disposed radially outward. In addition, a surface layer may be further provided on the surface of the elastic layer.

  For example, Japanese Patent Laying-Open No. 2005-352072 (Patent Document 1) discloses a radial direction of a shaft member having a metal hollow cylindrical body as a developing roller that is lightweight and has excellent durability without causing image defects. A developing roller having a resin layer made of an ultraviolet curable resin on the surface of an elastic layer disposed outside is disclosed. Japanese Patent Application Laid-Open No. 2004-191638 (Patent Document 2) discloses an ultraviolet curable resin on the surface of an elastic layer formed on the outer periphery of a shaft as a toner carrier capable of stably obtaining a good image. Alternatively, a toner carrier having an electron beam curable resin coating layer is disclosed.

  In JP-A-2005-352072 and JP-A-2004-191638, an ultraviolet curable resin is used for the surface layer arranged on the outer side in the radial direction of the elastic layer, and this is generally a layer made of an ultraviolet curable resin. This is because, for example, when UV curable resin is used for the elastic layer, it is easily affected by the surface accuracy of the shaft member such as roundness, runout, and unevenness because of its high hardness and thinness. As described above, when a conductive roller having an elastic layer made of an ultraviolet curable resin is used in an image forming apparatus, there is a problem that image unevenness occurs.

Japanese Patent Laying-Open No. 2005-352072 JP 2004-191638 A

  Accordingly, an object of the present invention is to solve the above-described problems of the prior art, and to have a conductive roller having an elastic layer made of an ultraviolet curable resin and capable of suppressing the occurrence of image unevenness, and the manufacture of the conductive roller. It is to provide a method. 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 has determined the thickness of the elastic layer and Asker C hardness in a conductive roller having an elastic layer made of an ultraviolet curable resin on the surface of the shaft member. It has been found that the occurrence of image unevenness can be suppressed by prescribing within the range, and the present invention has been completed.

That is, the conductive roller of the present invention includes a shaft member and an elastic layer made of an ultraviolet curable resin disposed on the outer side in the radial direction of the shaft member,
The elastic layer has a thickness of 0.5 to 2 mm and an Asker C hardness of 70 degrees or less. Here, “thickness” used in the present specification means an average thickness.

  In a preferred example of the conductive roller of the present invention, the ultraviolet curable resin comprises a urethane (meth) acrylate oligomer (A), a (meth) acrylate monomer (B), a photopolymerization initiator (C), and a conductive agent (D ), And the urethane (meth) acrylate oligomer (A) has a functional group number of 2.0 or less. In this case, it is possible to suppress an increase in the crosslinking density in the ultraviolet curable resin, and to reduce the Asker C hardness of the elastic layer. The urethane (meth) acrylate oligomer (A) preferably has 2.0 functional groups.

In the conductive roller of the present invention, the ultraviolet curable resin comprises a urethane (meth) acrylate oligomer (A) having a functional group number of 2.0 or less, a (meth) acrylate monomer (B), a photopolymerization initiator (C), and a conductive agent. When the elastic layer material containing (D) is cured by ultraviolet irradiation, the glass transition point (Tg ₁ ) of the ultraviolet curable resin is represented by the following formula (I):
_{Tg 1 -5 ≦ m A × Tg} A + m B × Tg B ≦ Tg 1 +5 ··· (I)
[Wherein, Tg ₁ is the glass transition point (° C.) of the UV curable resin, and Tg _A is the glass transition point (° C.) of the polymer obtained when the urethane (meth) acrylate oligomer (A) is polymerized. Yes, Tg _B is the glass transition temperature (° C) of the polymer obtained by polymerizing the (meth) acrylate monomer (B), and m _A is the urethane (meth) acrylate oligomer (A) and (meth) acrylate monomer It is a ratio of the urethane (meth) acrylate oligomer (A) in the total mass of (B), and m _B accounts for the total mass of the urethane (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B). The ratio of (meth) acrylate monomer (B)] is preferably satisfied. In this case, since the distortion of the elastic layer curable resin and the ultraviolet curable resin is reduced, image unevenness and film peeling are improved.

  The conductive roller of the present invention is suitable as a developing roller.

  Moreover, the manufacturing method of the electroconductive roller of this invention is the urethane (meth) acrylate oligomer (A), the (meth) acrylate monomer (B), the photoinitiator (C), and the electrically conductive agent (on the outer surface of the shaft member. After the elastic layer material containing D) is applied by a die coating method, the elastic layer material is cured by ultraviolet irradiation.

  Furthermore, the image forming apparatus of the present invention is characterized by using the above conductive roller.

  According to the present invention, a conductive roller having a specific thickness and Asker C hardness on the surface of a shaft member and having an elastic layer made of an ultraviolet curable resin and capable of suppressing the occurrence of image unevenness. And the manufacturing method of this electroconductive roller can be provided. Further, it is possible to provide an image forming apparatus provided with such a conductive roller and capable of stably forming a good image.

<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 illustrated conductive roller 1 includes a shaft member 2 that is pivotally supported at both ends in the length direction, and an elastic layer 3 made of an ultraviolet curable resin that is disposed on the outer side in the radial direction of the shaft member 2. . 1 has the elastic layer 3 formed from only one layer, the conductive roller of the present invention may form the elastic layer from two or more layers.

  In FIG. 1, the shaft member 2 is composed of a metal shaft 2A and a highly rigid resin base material 2B disposed on the radially outer side of the metal shaft 2A. The shaft member of the conductive roller of the present invention is There is no particular limitation as long as it has good conductivity. For example, it may be composed of only the metal shaft 2A, may be composed of only a highly rigid resin base material, or is a metal hollowed inside. A cylindrical body made of high-rigidity resin or the like may be used. In addition, when using highly rigid resin for the shaft member 2, it is preferable to ensure sufficient electroconductivity by adding and dispersing a conductive agent in the 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 of the metal shaft 2A and the metal cylinder include iron, stainless steel, and aluminum. The material of the high-rigidity resin base material 2B includes polyacetal, polyamide 6, polyamide 6 · 6, polyamide 12, polyamide 4 · 6, polyamide 6 · 10, polyamide 6 · 12, polyamide 11, polyamide MXD6, poly Butylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polyethersulfone, polycarbonate, polyimide, polyamideimide, polyetherimide, polysulfone, polyetheretherketone, polyethylene terephthalate, polyarylate, liquid crystal polymer, polytetrafluoroethylene, polypropylene, ABS resin, Examples include polystyrene, polyethylene, melamine resin, phenol resin, and silicone resin. Among these, polyacetal, polyamide 6/6, polyamide MXD6, polyamide 6/12, polybutylene terephthalate, polyphenylene ether, polyphenylene sulfide, and polycarbonate are preferable. These high-rigidity resins may be used alone or in combination of two or more.

  When the shaft member is a metal shaft or a shaft in which a highly rigid resin base material is disposed outside the metal shaft, the outer diameter of the metal shaft is preferably in the range of 4 to 12 mm. When the shaft member is a shaft in which a highly rigid resin base material is disposed outside the metal shaft, the outer diameter of the resin base material is preferably in the range of 10 to 30 mm. In addition, even if the outer diameter of a shaft member is enlarged by using a resin material for the said shaft member, the increase in the mass of a shaft member can be suppressed.

  In the conductive roller of the present invention, the elastic layer made of the ultraviolet curable resin has a thickness of 0.5 to 2 mm and an Asker C hardness of 70 degrees or less. In general, in an image forming apparatus using a conductive roller having an elastic layer made of an ultraviolet curable resin, the elastic layer is easily affected by the surface accuracy of the shaft member such as roundness, vibration, unevenness, etc. Cause unevenness. However, since the conductive roller of the present invention has an elastic layer thickness of 0.5 to 2 mm and an Asker C hardness of 70 degrees or less, it can absorb the influence caused by the surface accuracy of the shaft member described above, When such a conductive roller is used in an image forming apparatus, the occurrence of image unevenness can be significantly reduced.

  The elastic layer of the conductive roller of the present invention requires a thickness of 0.5 to 2 mm, and preferably 0.5 to 1.5 mm. Here, if the thickness of the elastic layer is within the specified range, the influence caused by the surface accuracy of the shaft member can be effectively reduced. Further, if the thickness of the elastic layer is less than 0.5 mm, the influence due to the surface accuracy of the shaft member cannot be sufficiently mitigated. On the other hand, if the thickness exceeds 2 mm, formation of the elastic layer becomes difficult.

  The elastic layer of the conductive roller of the present invention requires an Asker C hardness of 70 degrees or less, and preferably 35 to 70 degrees. Here, the Asker C hardness is a value when a flat portion of a cylindrical sample having a height of 12.7 mm and a diameter of 29 mm is measured. By setting the Asker C hardness to 70 degrees or less, the influence caused by the surface accuracy of the shaft member can be sufficiently absorbed, and the occurrence of image unevenness can be significantly reduced. In addition, this Asker C hardness can be adjusted by selecting suitably the component, composition, etc. which are contained in the raw material for elastic layers which forms an elastic layer.

  The elastic layer of the conductive roller of the present invention is made of an ultraviolet curable resin. For example, the urethane (meth) acrylate oligomer (A), the (meth) acrylate monomer (B), the photopolymerization initiator (C), and the conductive agent ( It comprises an ultraviolet curable resin obtained by curing the elastic layer material containing D) with ultraviolet irradiation. In addition, various additives can be mix | blended with this raw material for elastic layers, unless the objective of this invention is impaired.

The urethane (meth) acrylate oligomer (A) used for the elastic layer material has one or more acryloyloxy groups (CH ₂ ═CHCOO—) or methacryloyloxy groups (CH ₂ ═C (CH ₃ ) COO—). And a compound having a plurality of urethane bonds (—NHCOO—). The urethane (meth) acrylate oligomer (A) preferably has a functional group number of 2.0 or less, and more preferably 2.0. Here, the functional group refers to an acryloyloxy group and a methacryloyloxy group. If the number of functional groups of the urethane (meth) acrylate oligomer (A) is 2.0 or less, an increase in the crosslinking density in the ultraviolet curable resin can be suppressed, and the Asker C hardness of the elastic layer can be reduced.

  The urethane (meth) acrylate oligomer (A) preferably has a molecular weight of 5,000 to 100,000. The molecular weight is a number average molecular weight in terms of polystyrene. When the molecular weight of the urethane (meth) acrylate oligomer (A) is less than 5,000, the hardness of the elastic layer may be too high. On the other hand, when it exceeds 100,000, the compressive residual strain of the elastic layer may be too large.

  The urethane (meth) acrylate oligomer (A) is not particularly limited. For example, it is produced by synthesizing a urethane prepolymer from a polyol and a polyisocyanate and adding a (meth) acrylate having a hydroxyl group to the urethane prepolymer. can do.

  The polyol used for the synthesis of the urethane prepolymer is a compound having a plurality of hydroxyl groups (OH groups). Specific examples of the polyol include polyether polyol, polyester polyol, polytetramethylene glycol, polybutadiene polyol, and alkylene oxide modification. Examples include polybutadiene polyol and polyisoprene polyol. The polyether polyol is obtained, for example, by adding an alkylene oxide such as ethylene oxide or propylene oxide to a polyhydric alcohol such as ethylene glycol, propylene glycol, or glycerin. The polyester polyol is, for example, ethylene glycol. , Diethylene glycol, 1,4-butanediol, 1,6-hexanediol, propylene glycol, trimethylolethane, trimethylolpropane and other polyhydric alcohols and adipic acid, glutaric acid, succinic acid, sebacic acid, pimelic acid, suberin It is obtained from a polyvalent carboxylic acid such as an acid. These polyols may be used alone or in a blend of two or more.

  The polyol used for the synthesis of the urethane prepolymer preferably has a molecular weight in the range of 500 to 15,000. If the molecular weight of the polyol used for the synthesis of the urethane prepolymer is less than 500, the hardness becomes high, so that it is not suitable for the elastic layer of the conductive roller.On the other hand, if it exceeds 15,000, the compressive residual strain increases, resulting in poor image quality. It tends to occur.

  The polyisocyanate is a compound having a plurality of isocyanate groups (NCO groups). Specifically, the polyisocyanate includes tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI), Examples include isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, hexamethylene diisocyanate (HDI), these isocyanurate-modified products, carbodiimide-modified products, and glycol-modified products. These polyisocyanates may be used alone or in a blend of two or more.

In the synthesis of the urethane prepolymer, the ratio of polyol and polyisocyanate can be appropriately selected according to the purpose. Here, the urethane prepolymer preferably has an isocyanate index in the range of 110 to 200, and more preferably in the range of 115 to 200. The isocyanate index is the following formula:
(Isocyanate index) = (B / A) × 100
[Wherein, A is the number of OH groups of the polyol, and B is the number of NCO groups of the polyisocyanate]. If the isocyanate index of the urethane prepolymer is less than 110, the compression residual strain increases and image defects are likely to occur. On the other hand, if it exceeds 200, the isocyanate that does not react with the polyol increases and the physical properties deteriorate.

  In the synthesis of the urethane prepolymer, it is preferable to use a catalyst for urethanization reaction. Examples of the catalyst for urethanization reaction include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin thiocarboxylate, tin octenoate, monobutyltin oxide, etc .; stannous chloride, etc. Inorganic lead compounds; organic lead compounds such as lead octenoate; monoamines such as triethylamine and dimethylcyclohexylamine; diamines such as tetramethylethylenediamine, tetramethylpropanediamine and tetramethylhexanediamine; pentamethyldiethylenetriamine and pentamethyldipropylene Triamines such as triamine and tetramethylguanidine; triethylenediamine, dimethylpiperazine, methylethylpiperazine, methylmorpholine, dimethyl Cyclic amines such as ruaminoethylmorpholine, dimethylimidazole, pyridine; alcohol amines such as dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethylethanolamine, methylhydroxyethylpiperazine, hydroxyethylmorpholine; bis (dimethylaminoethyl) Ethers, ether amines such as ethylene glycol bis (dimethyl) aminopropyl ether; organic sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid and fluorosulfuric acid; inorganic acids such as sulfuric acid, phosphoric acid and perchloric acid; sodium alcoholate Bases such as lithium hydroxide, aluminum alcoholate and sodium hydroxide; titanium compounds such as tetrabutyl titanate, tetraethyl titanate and tetraisopropyl titanate; Smus compounds; quaternary ammonium salts and the like. 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.

The (meth) acrylate having a hydroxyl group to be added to the urethane prepolymer has one or more hydroxyl groups, and is an acryloyloxy group (CH ₂ ═CHCOO—) or a methacryloyloxy group (CH ₂ ═C (CH ₃ ) COO. It is a compound having one or more-). The (meth) acrylate having a hydroxyl group can be added to the isocyanate group of the urethane prepolymer. Examples of the (meth) acrylate having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and the like. These acrylates having a hydroxyl group may be used alone or in combination of two or more.

The (meth) acrylate monomer (B) used for the elastic layer raw material is a monomer having one or more acryloyloxy groups (CH ₂ ═CHCOO—) or methacryloyloxy groups (CH ₂ ═C (CH ₃ ) COO—). Yes, it acts as a reactive diluent, that is, it can be cured with ultraviolet rays, and the viscosity of the elastic layer material can be lowered.

  The (meth) acrylate monomer (B) preferably has a functional group number of 2.0 or less. Here, the functional group refers to an acryloyloxy group and a methacryloyloxy group. When the number of functional groups of the (meth) acrylate monomer (B) exceeds 2.0, the crosslink density in the ultraviolet curable resin increases, so that the hardness of the elastic layer may increase rapidly. However, when the elastic layer material contains a (meth) acrylate monomer (B) having a functional group number of 2.0, the glass transition point (Tg) of the (meth) acrylate monomer (B) is If it is 50 ° C. or higher, the hardness of the elastic layer may be increased. In this case, the number of functional groups in the total of the urethane (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B) Is preferably 2.0 and the ratio of the (meth) acrylate monomer (B) having a glass transition point (Tg) of 50 ° C. or higher is preferably adjusted to 5% by mass or less. The (meth) acrylate monomer (B) having a functional group number of 2.0 is the sum of the urethane (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B) regardless of the glass transition point (Tg). If the proportion of the (meth) acrylate monomer (B) having a functional group number of 2.0 exceeds 15% by mass, the hardness of the elastic layer may be too high.

  The (meth) acrylate monomer (B) preferably has a glass transition point (Tg) of 100 ° C. or lower. Here, the (meth) acrylate monomer (B) having a glass transition point (Tg) of 100 ° C. or less generally has a large proportion of the portion excluding the functional group in the monomer molecule, and the (meth) acrylate monomer In the case where (B) is polymerized with the above oligomer (A), the movement of the polymer excluding the functional group of the (meth) acrylate monomer (B) increases, and as a result, the hardness of the elastic layer is increased. Reduce.

  Examples of the (meth) acrylate monomer (B) include lauryl (meth) acrylate, morpholine (meth) acrylate, methoxytriethylene glycol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isomyristyl (meth) acrylate, Ethylene glycol di (meth) acrylate, β- (meth) acryloyloxyethyl hydrogen succinate, isobornyl (meth) acrylate, ethyl (meth) acrylate, isobutyl (meth) acrylate, n-butyl (meth) acrylate, isoamyl (meth) ) Acrylate, glycidyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate Examples include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and the like. These (meth) acrylate monomers (B) may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the elastic layer raw material, the mass ratio (A / B) of the urethane (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B) is preferably in the range of 100/0 to 10/90. . By setting the ratio of the urethane (meth) acrylate oligomer (A) in the total of the urethane (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B) to 10% by mass or more (that is, (meth) acrylate By setting the ratio of the monomer (B) to 90% by mass or less, an elastic layer having a low hardness can be obtained.

In the conductive roller of the present invention, the ultraviolet curable resin forming the elastic layer is a urethane (meth) acrylate oligomer (A), (meth) acrylate monomer (B) having a functional group number of 2.0 or less, and photopolymerization is started. When the elastic layer material containing the agent (C) and the conductive agent (D) is cured by ultraviolet irradiation, the glass transition point (Tg ₁ ) of the ultraviolet curable resin satisfies the relationship of the above formula (I). It is preferable. If the glass transition point (Tg ₁ ) of the ultraviolet curable resin does not satisfy the relationship of the above formula (I), image unevenness may occur.

  The photopolymerization initiator (C) used for the elastic layer raw material has an action of initiating polymerization of the urethane (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B) described above when irradiated with ultraviolet rays. Have 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. In addition, the compounding quantity of the photoinitiator (C) in the said raw material for elastic layers is with respect to a total of 100 mass parts of the said urethane (meth) acrylate oligomer (A) and the said (meth) acrylate monomer (B). The range of 0.2 to 5.0 parts by mass is preferable.

  The conductive agent (D) used as the elastic layer material has a function of imparting conductivity to the elastic layer. As this electrically conductive agent (D), what can permeate | transmit an ultraviolet-ray is preferable, It is preferable to use an ionic conductive agent and a transparent electronic conductive agent, and it is especially preferable to use an ionic conductive agent. Since the ionic conductive agent dissolves in the urethane (meth) acrylate oligomer (A) and has transparency, when the ionic conductive agent is used as the conductive agent (D), the elastic layer material is formed on the shaft member. Even if it is thickly applied, the ultraviolet rays sufficiently reach the inside of the coating film, and the elastic layer material can be sufficiently cured. Here, as the ionic conductive agent, tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, modified fatty acid dimethylethylammonium perchlorate, chlorate, hydrochloride, bromate, etc. 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. In addition, transparent electronic conductive agents include fine particles of metal oxides such as ITO, tin oxide, titanium oxide, and zinc oxide; fine particles of metals such as nickel, copper, silver, and germanium: conductive titanium oxide whiskers, conductive titanium Examples include conductive whiskers such as barium acid whiskers. These electrically conductive agents may be used individually by 1 type, and may use 2 or more types together. In addition, the compounding quantity of the electrically conductive agent (D) in the said raw material for elastic layers is 0.1-5.0 mass with respect to a total of 100 mass parts of the said urethane (meth) acrylate oligomer (A) and the said acrylate monomer (D). A range of parts is preferred.

  In addition, a polymerization inhibitor is added to the elastic layer raw material in an amount of 0.001 to 0.2 parts by mass with respect to a total of 100 parts by mass of the urethane (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B). May be. 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.

  The conductive roller of the present invention can be produced by applying the elastic layer raw material to the outer surface of the shaft member and then curing it by ultraviolet irradiation. Therefore, the conductive roller of the present invention does not require a large amount of heat energy for the production of the elastic layer, and can produce the elastic layer in a short time. Moreover, since a curing furnace or the like is not required for forming the elastic layer, a large amount of equipment costs are not required. Examples of the method for applying the elastic layer raw material to the outer surface of the shaft member include a spray method, a roll coater method, a dipping method, a die coating method, and the like. Among these methods, the die coating method is preferable. When forming the elastic layer, applying the elastic layer raw material by a die coating method achieves quick and reliable application of the elastic layer raw material, and greatly reduces the work efficiency of manufacturing the conductive roller. be able to. 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 elastic layer raw material, and the irradiation intensity and the integrated light amount 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 feeding roller, a cleaning roller, a fixing pressure roller, etc. in an image forming apparatus. It is particularly suitable as a roller.

<Image forming apparatus>
The image forming apparatus of the present invention includes the above-described conductive roller, and is preferably provided as a developing roller. 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 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 4 holding an electrostatic latent image, a charging roller 5 that is positioned near (upward in the drawing) of the photosensitive drum 4 and charges the photosensitive drum 4, and toner 6. A toner supply roller 7, a developing roller 8 disposed between the toner supply roller 7 and the photosensitive drum 4, a stratification blade 9 provided in the vicinity of the developing roller 8 (upward in the drawing), and a photosensitive drum. 4 is provided with a transfer roller 10 located in the vicinity (downward in the drawing) 4 and a cleaning roller 11 disposed adjacent to the photosensitive drum 4. 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 5 is brought into contact with the photosensitive drum 4 and a voltage is applied between the photosensitive drum 4 and the charging roller 5 to charge the photosensitive drum 4 to a constant potential. Then, an electrostatic latent image is formed on the photosensitive drum 4 by an exposure machine (not shown). Next, the photosensitive drum 4, the toner supply roller 7, and the developing roller 8 rotate in the direction of the arrow in the drawing, so that the toner 6 on the toner supply roller 7 is sent to the photosensitive drum 4 through the developing roller 8. It is done. The toner 6 on the developing roller 8 is adjusted to a uniform thin layer by the stratifying blade 9 and rotates while the developing roller 8 and the photosensitive drum 4 are in contact with each other, so that the toner 6 is transferred from the developing roller 8 to the photosensitive drum 4. It adheres to the electrostatic latent image and the latent image becomes visible. The toner 6 adhered to the latent image is transferred to a recording medium such as paper by the transfer roller 10, and the toner 6 remaining on the photosensitive drum 4 after the transfer is removed by the cleaning roller 11. Here, in the image forming apparatus of the present invention, at least one of the charging roller 5, the toner supply roller 7, the developing roller 8, the transfer roller 10, and the cleaning roller 11, preferably the developing roller 8, the present invention described above. By using the conductive roller, excellent images can be stably formed.

  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.

<Synthesis of oligomer (A-1)>
While stirring and mixing 100 parts by weight of polyoxypropylene glycol with a molecular weight of 3000, 100 parts by weight of polyoxypropylene glycol, 10.4 parts by weight of isophorone diisocyanate (isocyanate index = 140), and 0.01 parts by weight of dibutyltin dilaurate, A urethane prepolymer having isocyanate groups at both ends was synthesized. The obtained urethane prepolymer had an NCO group content of 1.19%. Further, 3.3 parts by mass of 2-hydroxyethyl acrylate (HEA) was mixed with 100 parts by mass of this urethane prepolymer and reacted at 70 ° C. for 2 hours to give an oligomer (A-1) having 2 functional groups and a molecular weight of 14,000. ) Was synthesized.

<Synthesis of oligomer (A-2)>
Similar to the above oligomer (A-1), except that a bifunctional polyoxyethylene glycol having a molecular weight of 4000 was used in place of the bifunctional polyoxypropylene glycol having a molecular weight of 3000, the number of functional groups was 2 and the molecular weight was 18000. The oligomer (A-2) was synthesized.

<Examples 1-15 and Comparative Examples 1-2>
Using the above oligomers (A-1) to (A-2), the raw material mixture having the formulation shown in Tables 1 to 3 was stirred and mixed for 1 hour at a liquid temperature of 70 ° C. and 60 rpm with a stirrer. The liquid was filtered to obtain a UV curable resin raw material.

The above UV curable resin raw material is poured into a mold having a cavity with a depth of 12.7 mm and an inner diameter of 29 mm, covered with a quartz glass plate, and then irradiated with UV at a UV irradiation intensity of 700 mW / cm ² for 10 seconds to measure cylindrical physical properties. A UV curable resin sample was obtained. About the obtained sample, the Asker C hardness [manufactured by Kobunshi Keiki Co., Ltd.] of the plane portion was measured. The results are shown in Tables 1-3.

Next, the UV curable resin raw material is applied to a conductive roller base material made of polybutylene terephthalate (PBT) resin having an outer diameter of 17.0 mm with a metal shaft having an outer diameter of 6.0 mm inserted by a die coater to a thickness of 1500 μm. The UV curable resin raw material was cured by spot UV irradiation. The roller with an elastic layer made of UV curable resin thus formed was further irradiated with UV at a UV irradiation intensity of 700 mW / cm ² for 5 seconds while rotating in a nitrogen atmosphere to obtain a conductive roller. In the obtained conductive roller, the thickness of the elastic layer was measured, and image unevenness was evaluated by the following method. The results are shown in Tables 1-3.

(1) Image unevenness The above conductive roller was incorporated as a developing roller in an image forming apparatus, a 1 dot 2 space halftone image was printed, and sensory evaluation of image unevenness and density difference measurement with a Macbeth densitometer were performed. In the sensory evaluation, the case where the image unevenness was not visible was set as “OK”, and the case where the image was visible was set as “NG”. In the measurement of the density difference with the Macbeth densitometer, the density measurement was performed along the longitudinal direction of the printed image, and the density difference of less than 0.3 was set to “OK”, and the density difference of 0.3 or more was set to “NG”. From the results of the sensory evaluation and the measurement of the density difference, in both cases, “OK” gave a comprehensive evaluation of image unevenness as “OK”, while “NG” gave a comprehensive evaluation of image unevenness as “NG”.

* 1 Nippon Synthetic Chemical Industry Co., Ltd., number of functional groups = 2, molecular weight = 18000.
* 2 Lauryl acrylate, manufactured by Kyoeisha Chemical Co., Ltd., number of functional groups = 1, Tg = -3 ° C.
* 3 Morpholine acrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., number of functional groups = 1, Tg = 150 ° C.
* 4 Methoxytriethylene glycol acrylate, manufactured by Kyoeisha Chemical Co., Ltd., number of functional groups = 1, Tg = -60 ° C.
* 5 Phenoxyethyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd., number of functional groups = 1, Tg = -22 ° C.
* 6 Tetrahydrofurfuryl acrylate, manufactured by Kyoeisha Chemical Co., Ltd., number of functional groups = 1, Tg = -40 ° C.
* 7 Isomyristyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd., number of functional groups = 1, Tg = -56 ° C.
* 8 Triethylene glycol diacrylate, manufactured by Kyoeisha Chemical Co., Ltd., number of functional groups = 2, Tg = 80 ° C.
* 9 β-acryloyloxyethyl hydrogen succinate, manufactured by Shin-Nakamura Chemical Co., Ltd., functional group number = 1, Tg = -10 ° C.
* 10 Made by Ciba Specialty Chemicals.
* 11 Made by Akishima Chemical Industry Co., Ltd.
* 12 Isobornyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd., number of functional groups = 1, Tg = 94 ° C.
* 13 # 600 diacrylate, manufactured by Kyoeisha Chemical Co., Ltd., number of functional groups = 2, Tg = -5 ° C.
* 14 This is the glass transition point (° C) of the UV curable resin that forms the elastic layer.
* 15 This is the glass transition temperature (° C) of the polymer obtained when the urethane (meth) acrylate oligomer (A) is polymerized.
* 16 This is the glass transition point (° C) of the polymer obtained by polymerizing the (meth) acrylate monomer (B).
* 17 Ratio of urethane (meth) acrylate oligomer (A) in the total mass of urethane (meth) acrylate oligomer (A) and (meth) acrylate monomer (B).
* 18 Ratio of (meth) acrylate monomer (B) to the total mass of urethane (meth) acrylate oligomer (A) and (meth) acrylate monomer (B).

The glass transition points Tg ₁ , Tg _A and Tg _B were measured by the following methods.

(2) Glass transition point (° C)
A UV irradiation intensity of 500 mJ / cm ² with a high-pressure mercury lamp in a solution of urethane (meth) acrylate oligomer (A) or (meth) acrylate monomer (B) in which 1% by mass of IRGACURE 184 [manufactured by Ciba Specialty Chemicals Co., Ltd.] was dissolved. Then, a cured sample of oligomer (A) or monomer (B) was produced. The sample was processed into a size of 10 mm × 50 mm × 1 mm, and Tg _A (° C.) and Tg _B (° C.) were measured according to JIS C 6481 using RHEOVIBRON DDV-01FP manufactured by ORIENTEC. Further, Tg ₁ (° C.) was measured in the same manner using the above UV curable resin raw material.

  From Tables 1 to 3, since the conductive roller of the example has an elastic layer thickness of 0.5 to 2 mm and an Asker C hardness of 70 degrees or less, an image forming apparatus incorporating the conductive roller as a developing roller is It can be seen that a good image can be formed without image unevenness.

  From the comparison of Examples 8 to 10 and Comparative Example 2, when the (meth) acrylate monomer (B) having a functional group number of 2.0 and a glass transition point (Tg) of 50 ° C. or higher is contained in the elastic layer raw material, urethane is used. Ratio of (meth) acrylate monomer (B) having a functional group number of 2.0 and a glass transition point (Tg) of 50 ° C. or higher in the total of (meth) acrylate oligomer (A) and (meth) acrylate monomer (B) When the content exceeds 5% by mass, the hardness of the elastic layer increases, and it is found that image unevenness occurs.

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 elastic roller 2 Shaft member 2A Metal shaft 2B High-rigidity resin base material 3 Elastic layer 4 Photosensitive drum 5 Charging roller 6 Toner 7 Toner supply roller 8 Developing roller 9 Laminated blade 10 Transfer roller 11 Cleaning roller

Claims (7)

In a conductive roller comprising a shaft member and an elastic layer made of an ultraviolet curable resin disposed on the outer side in the radial direction of the shaft member,
The conductive roller is characterized in that the elastic layer has a thickness of 0.5 to 2 mm and an Asker C hardness of 70 degrees or less. The ultraviolet curable resin cures the elastic layer material containing the urethane (meth) acrylate oligomer (A), the (meth) acrylate monomer (B), the photopolymerization initiator (C) and the conductive agent (D) by ultraviolet irradiation. Being
The conductive roller according to claim 1, wherein the urethane (meth) acrylate oligomer (A) has a functional group number of 2.0 or less.   The conductive roller according to claim 2, wherein the urethane (meth) acrylate oligomer (A) has a functional group number of 2.0. The glass transition point (Tg ₁ ) of the ultraviolet curable resin is represented by the following formula (I):
_{Tg 1 -5 ≦ m A × Tg} A + m B × Tg B ≦ Tg 1 +5 ··· (I)
[Wherein, Tg ₁ is the glass transition point (° C.) of the UV curable resin, and Tg _A is the glass transition point (° C.) of the polymer obtained when the urethane (meth) acrylate oligomer (A) is polymerized. Yes, Tg _B is the glass transition temperature (° C) of the polymer obtained by polymerizing the (meth) acrylate monomer (B), and m _A is the urethane (meth) acrylate oligomer (A) and (meth) acrylate monomer It is a ratio of the urethane (meth) acrylate oligomer (A) in the total mass of (B), and m _B accounts for the total mass of the urethane (meth) acrylate oligomer (A) and the (meth) acrylate monomer (B). The ratio of (meth) acrylate monomer (B)] is satisfied. The conductive roller according to claim 2.   The conductive roller according to claim 1, wherein the conductive roller is a developing roller.   The raw material for the elastic layer containing urethane (meth) acrylate oligomer (A), (meth) acrylate monomer (B), photopolymerization initiator (C) and conductive agent (D) is applied to the outer surface of the shaft member by a die coating method. The method for producing a conductive roller according to claim 1, wherein the elastic layer material is cured by ultraviolet irradiation.   An image forming apparatus using the conductive roller according to claim 1.

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