JP4996865B2 - Conductive elastic roller and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a conductive elastic roller and an image forming apparatus provided with the conductive elastic roller, and is particularly suitable as a developing roller, a charging roller, and the like, and has low hardness and a small compressive residual distortion, with respect to adjacent members such as a photoreceptor. The present invention relates to a conductive elastic roller having an elastic layer with improved contamination.

  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, i.e., a conductive elastic roller, is often used, and the conductive elastic roller is usually provided with a shaft member that is attached by being supported at both ends in the length direction, And one or more elastic layers disposed on the radially outer side of the shaft member.

  For the shaft member of the conductive elastic roller, various resins such as engineering plastics are used in addition to metals such as iron and stainless steel. On the other hand, various thermosetting resins such as a thermosetting urethane resin are used for the elastic layer of the conductive elastic roller, and a resin raw material is injected into a mold having a desired cavity shape and heated. It is manufactured by heat-curing a resin raw material (see Patent Document 1 below).

JP 2004-150610 A

  However, when producing a conductive elastic roller using a thermosetting urethane resin or the like for the elastic layer, it is necessary to heat and cure the resin raw material, which requires a large amount of heat energy, and is also suitable for curing. It took time. In addition, there is a problem that a large amount of equipment costs such as a curing furnace are required for heat curing.

  On the other hand, the present inventors examined a conductive elastic roller using an ultraviolet curable resin instead of a thermosetting resin for the elastic layer, but generally an ultraviolet curable resin has high hardness, It has been found that the elastic layer of the conductive elastic roller tends to be hard. Here, when a roller having a high hardness of the elastic layer is used as a developing roller or the like of the image forming apparatus, the toner is damaged due to repeated compression or friction between the rollers, and is aggregated and fused. Thus, image defects are likely to occur. Therefore, the elastic layer of the conductive elastic roller needs to have a sufficiently low hardness.

  On the other hand, when a conductive elastic roller having a low hardness elastic layer is used in the image forming apparatus, pressure contact marks due to a photoreceptor, blade, supply roller, etc. are likely to be generated on the roller surface. There is a problem that image defects are likely to occur. Therefore, the elastic layer of the conductive elastic roller needs to have a sufficiently small compressive residual strain (C set). However, since a material with low hardness tends to have a large compressive residual strain, it is generally difficult to balance both the hardness and the compressive residual strain sufficiently low.

  Further, the present inventors have further studied the conductive elastic roller using the above-mentioned ultraviolet curable resin, and as a result, the ultraviolet curable resin using a general urethane acrylate oligomer has a contamination property to adjacent members. I found it expensive. Here, when a roller having an elastic layer that is highly contaminating adjacent members is used as a developing roller or the like of an image forming apparatus, adjacent members such as a photoreceptor are contaminated, and image defects are likely to occur. Therefore, the elastic layer of the conductive elastic roller needs to have sufficiently low contamination to adjacent members.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, can be manufactured in a short time without requiring a large amount of heat energy, does not require a large amount of equipment cost, and further has a low hardness. Another object of the present invention is to provide a conductive elastic roller having an elastic layer having a small compressive residual strain and improved contamination with respect to adjacent members. Another object of the present invention is to provide an image forming apparatus that can stably form a good image using such a conductive elastic roller.

  As a result of intensive studies to achieve the above object, the present inventor has cured a raw material composition containing a urethane acrylate oligomer synthesized using a specific raw material, a photopolymerization initiator, and a conductive agent by ultraviolet irradiation to thereby form an elastic layer. Can be manufactured in a short time without requiring a large amount of heat energy, and does not require a large amount of equipment cost. Further, it has a low hardness and a small compressive residual strain. It has been found that a conductive elastic roller having an elastic layer with improved contamination is obtained, and the present invention has been completed.

That is, the conductive elastic roller of the present invention comprises a shaft member and one or more elastic layers disposed on the outer side in the radial direction of the shaft member,
At least one layer of the elastic layer is made of an ultraviolet curable resin obtained by curing a raw material for an elastic layer containing a urethane acrylate oligomer (A), a photopolymerization initiator (B), and a conductive agent (C) by ultraviolet irradiation,
The urethane acrylate oligomer (A) is a polyol represented by the following formula (I):
y ≦ 0.6 / x + 0.01 (I)
[In the formula, x is the hydroxyl value (mgKOH / g) of the polyol, and y is the total unsaturation degree (meq / g) of the polyol] alone, or the high-purity polyol and others It is a urethane acrylate oligomer synthesized by using a polyol.

  In general, commercially available polyols contain monool by-products such as unsaturated terminals as impurities. Therefore, in the present invention, the purity of the polyol used for the synthesis of the urethane acrylate oligomer (A) is defined by the total degree of unsaturation, and the total degree of unsaturation (meq / g) and the hydroxyl value (mgKOH / g) are as described above. It is necessary to use at least a part of the polyol satisfying the relationship of the formula (I). In addition, the total unsaturation degree and hydroxyl value of a polyol can be measured based on JISK1557: 1970.

  In a preferred example of the conductive elastic roller of the present invention, the high-purity polyol used for the synthesis of the urethane acrylate oligomer (A) has a molecular weight of 1,000 to 16,000.

  In another preferred embodiment of the conductive elastic roller of the present invention, the mass ratio (a1 / a2) of the high-purity polyol (a1) and the other polyol (a2) in the polyol used for the synthesis of the urethane acrylate oligomer (A). Is in the range of 100/0 to 30/70.

  In another preferred embodiment of the conductive elastic roller of the present invention, the elastic layer material further contains an acrylate monomer (D).

  In another preferred embodiment of the conductive elastic roller of the present invention, the conductive agent (C) is an ionic conductive agent.

In the conductive elastic roller of the present invention, the elastic layer material used for the ultraviolet curable resin has a mass ratio (A / D) between the urethane acrylate oligomer (A) and the acrylate monomer (D) of 100/0. In the range of ~ 10/90,
For a total of 100 parts by mass of the urethane acrylate oligomer (A) and the acrylate monomer (D), the photopolymerization initiator (B) is 0.2 to 5.0 parts by mass, and the conductive agent (C) is 0.1 to 5.0 parts by mass. It is preferable to contain a part.

In another preferred embodiment of the conductive elastic roller of the present invention, 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 4.0 to 8.0 mm, and the outer diameter of the resin base material is 10 to 25 mm.

  In the conductive elastic roller of the present invention, the elastic layer preferably has an Asker C hardness of 30 to 70 degrees and a compressive residual strain of 3.0% or less.

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

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

  According to the present invention, an elastic layer material comprising a urethane acrylate oligomer (A) synthesized using a high-purity polyol that satisfies the relationship of the above formula (I), a photopolymerization initiator (B), and a conductive agent (C). By curing with ultraviolet irradiation to form at least one elastic layer, it can be manufactured in a short time without requiring a large amount of heat energy, and does not require a large amount of equipment cost. It is possible to provide a conductive elastic roller having an elastic layer that is hard and has a small compressive residual strain and improved contamination on adjacent members. Further, it is possible to provide an image forming apparatus that includes such a conductive elastic roller and can stably form a good image.

<Conductive elastic roller>
Hereinafter, the conductive elastic roller of the present invention will be described in detail with reference to FIG. FIG. 1 is a cross-sectional view of an example of the conductive elastic roller of the present invention. The conductive elastic roller 1 in the illustrated example includes a shaft member 2 that is attached with both end portions in the length direction being pivotally supported, and an elastic layer 3 that is disposed on the outer side in the radial direction of the shaft member 2. The conductive elastic roller 1 shown in FIG. 1 has only one elastic layer 3, but the conductive elastic roller of the present invention may have two or more elastic layers. Although not shown, the conductive elastic roller of the present invention may include a coating layer on the radially outer side of the elastic layer 3.

  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 outer side in the radial direction of the metal shaft 2A. The shaft member of the conductive elastic roller of the present invention is As long as it has good electrical conductivity, there is no particular limitation, and it may be composed only of the metal shaft 2A, may be composed only of a highly rigid resin base material, or is made of a metal whose interior is hollowed Alternatively, it may be a cylindrical body made of a highly rigid resin. 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 highly rigid resins may be used alone or in combination of two or more.

  When the shaft member is a metal shaft or a shaft having a highly rigid resin base disposed on the outside of the metal shaft, the outer diameter of the metal shaft is preferably in the range of 4.0 to 8.0 mm. Further, 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 25 mm. In addition, even if the outer diameter of a shaft member is enlarged by using high rigidity resin for the said shaft member, the increase in the mass of a shaft member can be suppressed.

  The conductive elastic roller of the present invention is obtained by curing an elastic layer raw material containing at least one elastic layer containing a urethane acrylate oligomer (A), a photopolymerization initiator (B) and a conductive agent (C) by ultraviolet irradiation. Made of an ultraviolet curable resin. 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 acrylate oligomer (A) used as the elastic layer raw material is synthesized by using a high-purity polyol satisfying the above formula (I) alone or using the high-purity polyol and other polyols as an acryloyloxy group. It is a compound having one or more (CH ₂ ═CHCOO—) and a plurality of urethane bonds (—NHCOO—). The urethane acrylate oligomer (A) is, for example, (I) a high-purity polyol alone or a mixture of a high-purity polyol and other polyols and a urethane prepolymer synthesized from a polyisocyanate, and an acrylate having a hydroxyl group is added. (II) An acrylate having a hydroxyl group in a mixture of a high-purity polyol alone or a urethane prepolymer synthesized from a mixture of a high-purity polyol and other polyols and a polyisocyanate, and a urethane prepolymer synthesized from another polyol and a polyisocyanate Can be synthesized by adding. The high-purity polyol used for the synthesis of the urethane prepolymer is, for example, ethylene glycol, propylene glycol, glycerin, neopentyl in the presence of a catalyst such as diethyl zinc, iron chloride, metal porphyrin, double metal cyanide complex, cesium compound, etc. It can be synthesized by adding an alkylene oxide such as propylene oxide (PO) or ethylene oxide (EO) to a polyhydric alcohol such as glycol, trimethylolpropane, pentaerythritol and a compound obtained by reacting these with an alkylene oxide. There are few monool by-products, such as an unsaturated terminal, and it is highly pure compared with the conventional polyol.

  When an elastic layer is formed by UV irradiation using a general urethane acrylate oligomer, it is highly contaminated to adjacent members of the roller, but surprisingly, it is synthesized using a high-purity polyol that satisfies the relationship of formula (I) above. By forming an elastic layer by irradiating ultraviolet rays using the urethane acrylate oligomer (A), it is possible to reduce the contamination of the adjacent members of the roller while reducing the compression residual strain. This is because the elasticity of the elastic layer raw material containing the urethane acrylate oligomer (A) synthesized using a high-purity polyol is higher than the ultraviolet hardening of the elastic layer raw material containing a general urethane acrylate oligomer. This is thought to be caused by this. Here, in the case where an elastic layer is formed using a urethane acrylate oligomer synthesized using only a polyol that does not satisfy the relationship of the above formula (I) as a polyol, in addition to the fact that the contamination with respect to adjacent members of the roller cannot be sufficiently reduced. As a result, the compressive residual strain of the elastic layer cannot be sufficiently reduced, so that the press-contact marks of the adjacent members remain on the roller, and image defects are likely to occur. In addition, from the viewpoint of reducing the contamination to the adjacent members of the roller while reducing the compression residual strain, the total unsaturation degree of the high-purity polyol is preferably 0.05 meq / g or less, and 0.025 meq / g or less. More preferably, it is 0.01 meq / g or less.

  The high-purity polyol used for the synthesis of the urethane acrylate oligomer (A) preferably has a molecular weight of 1,000 to 16,000. The molecular weight is a weight average molecular weight (Mw). If the molecular weight of the high-purity polyol is less than 1,000, the hardness of the resin will be high and the image will deteriorate, making it unsuitable for the elastic roller material. Is likely to occur.

  In addition, in the synthesis of the urethane acrylate oligomer (A), another polyol that can be used together with the high-purity polyol is a compound having a plurality of hydroxyl groups (OH groups). As the polyol, specifically, a polyether Examples include polyols, polyester polyols, polybutadiene polyols, alkylene oxide-modified polybutadiene polyols, and polyisoprene polyols. 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.

  In the synthesis of the urethane acrylate oligomer (A), when another polyol (a2) is used together with the high purity polyol (a1), the mass ratio (a1 /) of the high purity polyol (a1) and the other polyol (a2) is used. a2) is preferably in the range of 100/0 to 30/70. By setting the ratio of the high purity polyol (a1) in the total amount (a1 + a2) of the high purity polyol (a1) and the other polyol (a2) to 30% by mass or more (that is, the ratio of the other polyol (a2) is By setting it to 70% by mass or less, the contamination of the conductive elastic roller with respect to adjacent members such as the photosensitive member can be sufficiently reduced while reducing the compression residual strain of the elastic layer.

  The polyisocyanate that can be used for the synthesis of the urethane acrylate oligomer (A) is a compound having a plurality of isocyanate groups (NCO groups). Specifically, the polyisocyanate includes tolylene diisocyanate (TDI) and diphenylmethane. Diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI), isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, hexamethylene diisocyanate (HDI), their isocyanurate modified products, carbodiimide modified products, glycols Examples include modified products. These polyisocyanates may be used alone or in a blend of two or more.

  In the synthesis of the urethane acrylate oligomer (A), 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, and the like; 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, 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 acrylate having a hydroxyl group that can be used for the synthesis of the urethane acrylate oligomer (A) is a compound having one or more hydroxyl groups and one or more acryloyloxy groups (CH ₂ ═CHCOO—). The acrylate having a hydroxyl group can be added to the isocyanate group of the urethane prepolymer. Examples of the acrylate having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and pentaerythritol triacrylate. These acrylates having a hydroxyl group may be used alone or in combination of two or more.

  The photopolymerization initiator (B) used for the elastic layer raw material has an action of initiating polymerization of the above-described urethane acrylate oligomer (A) and further an acrylate monomer (D) described later by being irradiated with ultraviolet rays. . Examples of the photopolymerization initiator (B) 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 conductive agent (C) used as the elastic layer material has a function of imparting conductivity to the elastic layer. As this electrically conductive agent (C), 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 acrylate oligomer (A) and has transparency, when the ionic conductive agent is used as the conductive agent (C), the elastic layer material is applied thickly on the shaft member. However, 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 and the like perchlorate, chlorate, hydrochloride, bromate 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.

The elastic layer material preferably further contains an acrylate monomer (D). The acrylate monomer (D) is a monomer having one or more acryloyloxy groups (CH ₂ ═CHCOO—), which acts as a reactive diluent, that is, is cured with ultraviolet rays and has a viscosity of the elastic layer material. It can be reduced. The 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.

  Examples of the acrylate monomer (D) include isomyristyl acrylate, methoxytriethylene glycol acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, isoamyl acrylate, glycidyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydipropylene glycol acrylate, Examples include phenoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and pentaerythritol triacrylate. These acrylate monomers may be used alone or in combination of two or more.

  In the elastic layer raw material, the mass ratio (A / D) of the urethane acrylate oligomer (A) and the acrylate monomer (D) is preferably in the range of 100/0 to 10/90. By making the ratio of the urethane acrylate oligomer (A) in the total amount of the urethane acrylate oligomer (A) and the acrylate monomer (D) 10% by mass or more (that is, the ratio of the acrylate monomer (D) is 90% by mass or less. Thus, it is possible to obtain an elastic layer with low hardness and low compression residual strain suitable for the conductive elastic roller.

  Moreover, the compounding quantity of the photoinitiator (B) in the said raw material for elastic layers is 0.2-5.0 mass parts with respect to a total of 100 mass parts of the said urethane acrylate oligomer (A) and the said acrylate monomer (D). The range of is preferable. When the blending amount of the photopolymerization initiator (B) is 0.2 parts by mass or less, the effect of initiating UV curing of the elastic layer raw material is small, whereas when it exceeds 5.0 parts by mass, the effect of initiating UV curing is saturated. Further, physical properties such as compression residual strain are lowered, and the cost of the elastic layer raw material is increased.

  Furthermore, the compounding quantity of the electrically conductive agent (C) in the said raw material for elastic layers is the range of 0.1-5.0 mass parts with respect to a total of 100 mass parts of the said urethane acrylate oligomer (A) and the said acrylate monomer (D). Is preferred. If the blending amount of the conductive agent (C) is less than 0.1 parts by mass, the conductivity of the elastic layer may be low and desired conductivity may not be imparted to the conductive elastic roller. On the other hand, if it exceeds 5.0 parts by mass, the elastic layer In some cases, the electrical conductivity of the film does not increase, and physical properties such as compressive residual strain decrease and a good image cannot be obtained.

  Moreover, you may add 0.001-0.2 mass part of polymerization inhibitors with respect to the said raw material for elastic layers further with respect to a total of 100 mass parts of the said urethane acrylate oligomer (A) and the said acrylate monomer (D). By adding a polymerization inhibitor, thermal polymerization before ultraviolet irradiation can be prevented. Examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, p-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-p-cresol, butylhydroxyanisole, Examples include 3-hydroxythiophenol, α-nitroso-β-naphthol, p-benzoquinone, 2,5-dihydroxy-p-quinone, and the like.

  The elastic layer preferably has an Asker C hardness of 30 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. If the Asker C hardness is 30 degrees or more, sufficient hardness can be secured as a conductive elastic roller such as a developing roller, while if it is 70 degrees or less, followability with other rollers and blades is good. Thus, aggregation and fusion of the low melting point toner can be sufficiently prevented.

  The elastic layer preferably has a compressive residual strain (compression permanent strain) of 3.0% or less. Here, the compressive residual strain can be measured in accordance with JIS K 6262 (1997). Specifically, a cylindrical sample having a height of 12.7 mm and a diameter of 29 mm is subjected to a prescribed heat treatment condition (22 at 70 ° C.). Time), the sample can be determined by compressing it in the height direction by 25%. If the compressive residual strain of the elastic layer is 3.0% or less, when the conductive elastic roller is incorporated in an image forming apparatus as a developing roller, pressure contact marks due to a photosensitive drum, blade, supply roller, etc. are hardly generated on the roller surface. Thus, streak-like image defects are less likely to occur in the formed image.

  The elastic layer preferably has a thickness of 1 to 3000 μm. If the thickness of the elastic layer is 1 μm or more, the conductive elastic roller has sufficient elasticity and the damage to the toner is sufficiently small. Is sufficiently reached, the raw material for the elastic layer can be reliably UV-cured, and the amount of high-priced UV-curing resin raw material used can be reduced.

The elastic layer is not particularly limited, but preferably has a volume resistivity of 10 ⁴ to 10 ¹⁰ Ωcm. Furthermore, the conductive elastic roller of the present invention preferably has a roller resistance of 10 ⁴ to 10 ¹⁰ Ω at an applied voltage of 100V. Here, the resistance value is obtained from a current value at that time by applying a voltage of 100 V between the shaft and the counter electrode by pressing the outer peripheral surface of the conductive elastic roller to a flat plate or a cylindrical counter electrode with a predetermined pressure. be able to.

  The conductive elastic 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 irradiating it with ultraviolet rays. Therefore, the conductive elastic 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, and a die coating method. 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 elastic 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. Particularly suitable as a developing roller and a charging roller.

<Image forming apparatus>
The image forming apparatus of the present invention includes the above-described conductive elastic roller, and preferably includes at least one of a developing roller and a charging roller. The image forming apparatus of the present invention is not particularly limited except that the conductive elastic roller is used, and can be manufactured by a known method.

  The image forming apparatus of the present invention will be described in detail below with reference to FIG. FIG. 2 is a partial cross-sectional view of an example of the image forming apparatus of the present invention. The image forming apparatus of the illustrated example supplies a photosensitive member 4 holding an electrostatic latent image, a charging roller 5 that is positioned in the vicinity of the photosensitive member 4 (upward in the drawing) and charges the photosensitive member 4, and a toner 6. A toner supply roller 7, a developing roller 8 disposed between the toner supply roller 7 and the photosensitive member 4, a stratification blade 9 provided in the vicinity of the developing roller 8 (upward in the drawing), and a photosensitive member. 4 is provided with a transfer roller 10 located near (lower in the drawing) 4 and a cleaning roller 11 disposed adjacent to the photoreceptor 4. The image forming apparatus of the present invention can further include a known component (not shown) that is usually used in the image layer forming apparatus.

  In the illustrated image forming apparatus, the charging roller 5 is brought into contact with the photosensitive member 4 and a voltage is applied between the photosensitive member 4 and the charging roller 5 to charge the photosensitive member 4 to a constant potential. Then, an electrostatic latent image is formed on the photoreceptor 4 by an exposure machine (not shown). Next, the photosensitive member 4, the toner supply roller 7, and the developing roller 8 rotate in the direction of the arrow in the figure, so that the toner 6 on the toner supply roller 7 is sent to the photosensitive member 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 member 4 are in contact with each other, whereby the toner 6 is transferred from the developing roller 8 to the photosensitive member 4. It adheres to the electrostatic latent image and the latent image becomes visible. The toner 6 attached to the latent image is transferred to a recording medium such as paper by the transfer roller 10, and the toner 6 remaining on the photoreceptor 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 at least the charging roller 5 and the developing roller 8. On the other hand, it is possible to stably form an excellent image by using the above-described conductive elastic roller of the present invention.

  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.

Example 1
Bifunctional, high-purity polyol with a molecular weight of 4,000 [Preminol S-X4004, Asahi Glass Co., Ltd., polyol consisting of PO chain, hydroxyl value = 27.9 mgKOH / g, total unsaturation = 0.007 meq / g, right side of formula (I) (0.6 / x + 0.01) = 0.03] 100 parts by weight, isophorone diisocyanate 8.29 parts by weight [isocyanate group / hydroxyl group of polyol = 3/2 = 1.50 (molar ratio)], and 0.01 parts by weight of dibutyltin dilaurate were mixed with heating. However, the reaction was carried out at 70 ° C. for 2 hours to synthesize a urethane prepolymer having isocyanate groups at both ends of the molecular chain. Furthermore, 2.88 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 synthesize a urethane acrylate oligomer (A-1) having a molecular weight of 9,000. . The obtained urethane acrylate oligomer (A-1) had a viscosity at 25 ° C. of 80,000 mPas / sec as measured with a B-type viscometer.

  70.0 parts by mass of the urethane acrylate oligomer (A-1), 30.0 parts by mass of an acrylate monomer “light acrylate IM-A (isomyristyl acrylate)” manufactured by Kyoeisha Chemical Co., Ltd., photopolymerization manufactured by Ciba Specialty Chemicals Co., Ltd. Initiator "Irgacure 184D" 0.5 parts by mass and Akishima Chemical Industry Co., Ltd. ionic conductive agent "MP-100" 2.0 parts by mass with a stirrer at a liquid temperature of 70 ° C and 60 rpm for 1 hour After mixing, the mixed solution was filtered to obtain a UV curable resin raw material. The obtained UV curable resin raw material had a viscosity of 10,000 mPas / sec.

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. This sample had an Asker C hardness (manufactured by Kobunshi Keiki Co., Ltd.) of the flat portion of 56 degrees. Further, the compression residual strain of this sample was measured according to JIS K 6262 (1997), and it was 1.8%.

Next, the above 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 into which a metal shaft having an outer diameter of 6.0 mm is inserted, with a thickness of 1500 μm using a die coater. The UV curable resin raw material was cured by spot UV irradiation. The UV-cured resin elastic layer-formed roller 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.

  On the surface of the roller with an elastic layer made of UV curable resin thus obtained, a UV curable resin material containing fine particles having hardness higher than that of the elastic layer is applied with a roll coater, and irradiated with UV to form a UV coating on the surface. A low hardness UV resin roller having an outer diameter of 20.0 mm was obtained. When this roller was incorporated into an electrophotographic apparatus as a developing roller and solid white, black solid, and gray scale images were printed, a good image could be obtained.

  Next, for the photoreceptor contamination test, the cartridge incorporating the roller was left in a hot air circulation oven shielded from light at 50 ° C. for 5 days, then taken out and left for 1 hour in an environment of 20 ° C. and 50% RH. Later, when 50 gray images were printed, a good image was obtained, and no image defect due to photoconductor contamination and roller deformation was observed.

(Example 2)
Bifunctional, high-purity polyol with a molecular weight of 2,000 [Preminol S-X4001, Asahi Glass Co., Ltd., polyol consisting of PO chain, hydroxyl value = 55.3 mgKOH / g, total unsaturation = 0.008 meq / g, right side of formula (I) (0.6 / x + 0.01) = 0.02] 100 parts by mass, 13.70 parts by mass of isophorone diisocyanate [isocyanate group / hydroxyl group of polyol = 5/4 = 1.25 (molar ratio)], and 0.01 parts by mass of dibutyltin dilaurate were mixed with heating. However, the reaction was carried out at 70 ° C. for 2 hours to synthesize a urethane prepolymer having isocyanate groups at both ends of the molecular chain. Further, 2.86 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 synthesize a urethane acrylate oligomer (A-2) having a molecular weight of 9,000. . The obtained urethane acrylate oligomer (A-2) had a viscosity of 170,000 mPas / sec at 25 ° C. measured with a B-type viscometer.

  70.0 parts by mass of the above urethane acrylate oligomer (A-2), 30.0 parts by mass of acrylate monomer “light acrylate IM-A (isomyristyl acrylate)” manufactured by Kyoeisha Chemical Co., Ltd., photopolymerization manufactured by Ciba Specialty Chemicals Co., Ltd. Initiator "Irgacure 184D" 0.5 parts by mass and Akishima Chemical Industry Co., Ltd. ionic conductive agent "MP-100" 2.0 parts by mass with a stirrer at a liquid temperature of 70 ° C and 60 rpm for 1 hour After mixing, the mixed solution was filtered to obtain a UV curable resin raw material. The obtained UV curable resin raw material had a viscosity of 15,000 mPas / sec.

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. This sample had an Asker C hardness (manufactured by Kobunshi Keiki Co., Ltd.) of 54 degrees in the plane portion. Further, the compression residual strain of this sample was measured in accordance with JIS K 6262 (1997) and found to be 1.6%.

Next, the above 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 into which a metal shaft having an outer diameter of 6.0 mm is inserted, with a thickness of 1500 μm using a die coater. The UV curable resin raw material was cured by spot UV irradiation. The UV-cured resin elastic layer-formed roller 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.

  On the surface of the roller with an elastic layer made of UV curable resin thus obtained, a UV curable resin material containing fine particles having hardness higher than that of the elastic layer is applied with a roll coater, and irradiated with UV to form a UV coating on the surface. A low hardness UV resin roller having an outer diameter of 20.0 mm was obtained. When this roller was incorporated into an electrophotographic apparatus as a developing roller and solid white, black solid, and gray scale images were printed, a good image could be obtained.

  Next, for the photoreceptor contamination test, the cartridge incorporating the roller was left in a hot air circulation oven shielded from light at 50 ° C. for 5 days, then taken out and left for 1 hour in an environment of 20 ° C. and 50% RH. Later, when 50 gray images were printed, a good image was obtained, and no image defect due to photoconductor contamination and roller deformation was observed.

(Example 3)
Bifunctional, high-purity polyol with a molecular weight of 3,200 [Acclaim 3205, Sumika Bayer Urethane Co., Ltd., polyol mainly composed of PO chains and a small amount of EO chains, hydroxyl value = 35.0 mgKOH / g, total unsaturation = 0.002 meq / g 100 parts by mass of right side of formula (I) (0.6 / x + 0.01) = 0.03, 10.41 parts by mass of isophorone diisocyanate [isocyanate group / hydroxyl group of polyol = 3/2 = 1.50 (molar ratio)], and 0.01 mass of dibutyltin dilaurate The parts were reacted at 70 ° C. for 2 hours while heating and stirring to synthesize a urethane prepolymer having isocyanate groups at both ends of the molecular chain. Further, 3.63 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 synthesize a urethane acrylate oligomer (A-3) having a molecular weight of 7,000. . The obtained urethane acrylate oligomer (A-3) had a viscosity at 25 ° C. of 70,000 mPas / sec as measured with a B-type viscometer.

  70.0 parts by mass of the urethane acrylate oligomer (A-3), 30.0 parts by mass of an acrylate monomer “light acrylate IM-A (isomyristyl acrylate)” manufactured by Kyoeisha Chemical Co., Ltd., photopolymerization manufactured by Ciba Specialty Chemicals Co., Ltd. Initiator "Irgacure 184D" 0.5 parts by mass and Akishima Chemical Industry Co., Ltd. ionic conductive agent "MP-100" 2.0 parts by mass with a stirrer at a liquid temperature of 70 ° C and 60 rpm for 1 hour After mixing, the mixed solution was filtered to obtain a UV curable resin raw material. The obtained UV curable resin raw material had a viscosity of 10,000 mPas / sec.

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. This sample had an Asker C hardness (manufactured by Kobunshi Keiki Co., Ltd.) of the flat portion of 60 degrees. Further, the compression residual strain of this sample was measured in accordance with JIS K 6262 (1997) and found to be 1.2%.

Next, the above 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 into which a metal shaft having an outer diameter of 6.0 mm is inserted, with a thickness of 1500 μm using a die coater. The UV curable resin raw material was cured by spot UV irradiation. The UV-cured resin elastic layer-formed roller 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.

  On the surface of the roller with an elastic layer made of UV curable resin thus obtained, a UV curable resin material containing fine particles having hardness higher than that of the elastic layer is applied with a roll coater, and irradiated with UV to form a UV coating on the surface. A low hardness UV resin roller having an outer diameter of 20.0 mm was obtained. When this roller was incorporated into an electrophotographic apparatus as a developing roller and solid white, black solid, and gray scale images were printed, a good image could be obtained.

  Next, for the photoreceptor contamination test, the cartridge incorporating the roller was left in a hot air circulation oven shielded from light at 50 ° C. for 5 days, then taken out and left for 1 hour in an environment of 20 ° C. and 50% RH. Later, when 50 gray images were printed, a good image was obtained, and no image defect due to photoconductor contamination and roller deformation was observed.

Example 4
Bifunctional, high-purity polyol with a molecular weight of 5,500 [Preminol S-4006, Asahi Glass Co., Ltd., polyol consisting of PO chain, hydroxyl value = 21.1 mgKOH / g, total unsaturation = 0.006 meq / g, right side of formula (I) (0.6 / x + 0.01) = 0.04] 100 parts by weight, 6.69 parts by weight of isophorone diisocyanate [isocyanate group / hydroxyl group of polyol = 8/5 = 1.60 (molar ratio)], and 0.01 parts by weight of dibutyltin dilaurate were mixed with heating. However, the reaction was carried out at 70 ° C. for 2 hours to synthesize a urethane prepolymer having isocyanate groups at both ends of the molecular chain. Further, 2.6 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 synthesize a urethane acrylate oligomer (A-4) having a molecular weight of 11,000. . The obtained urethane acrylate oligomer (A-4) had a viscosity at 25 ° C. of 60,000 mPas / sec as measured with a B-type viscometer.

  70.0 parts by mass of the urethane acrylate oligomer (A-4), 30.0 parts by mass of an acrylate monomer “light acrylate IM-A (isomyristyl acrylate)” manufactured by Kyoeisha Chemical Co., Ltd., photopolymerization manufactured by Ciba Specialty Chemicals Co., Ltd. Initiator "Irgacure 184D" 0.5 parts by mass and Akishima Chemical Industry Co., Ltd. ionic conductive agent "MP-100" 2.0 parts by mass with a stirrer at a liquid temperature of 70 ° C and 60 rpm for 1 hour After mixing, the mixed solution was filtered to obtain a UV curable resin raw material. The obtained UV curable resin raw material had a viscosity of 9,000 mPas / sec.

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. This sample had an Asker C hardness [manufactured by Kobunshi Keiki Co., Ltd.] of the flat portion of 55 degrees. Moreover, it was 1.7% when the compression residual strain of this sample was measured based on JISK6262 (1997).

Next, the above 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 into which a metal shaft having an outer diameter of 6.0 mm is inserted, with a thickness of 1500 μm using a die coater. The UV curable resin raw material was cured by spot UV irradiation. The UV-cured resin elastic layer-formed roller 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.

  On the surface of the roller with an elastic layer made of UV curable resin thus obtained, a UV curable resin material containing fine particles having hardness higher than that of the elastic layer is applied with a roll coater, and irradiated with UV to form a UV coating on the surface. A low hardness UV resin roller having an outer diameter of 20.0 mm was obtained. When this roller was incorporated into an electrophotographic apparatus as a developing roller and solid white, black solid, and gray scale images were printed, a good image could be obtained.

  Next, for the photoreceptor contamination test, the cartridge incorporating the roller was left in a hot air circulation oven shielded from light at 50 ° C. for 5 days, then taken out and left for 1 hour in an environment of 20 ° C. and 50% RH. Later, when 50 gray images were printed, a good image was obtained, and no image defect due to photoconductor contamination and roller deformation was observed.

(Comparative Example 1)
Bifunctional polyol having a molecular weight of 3,200 [EXCENOL 3020, Asahi Glass Co., Ltd., polyol consisting of PO chain, hydroxyl value = 37.4 mg KOH / g, total unsaturation = 0.084 meq / g, right side of formula (I) (0.6 / x + 0.00 01) = 0.03] 100 parts by weight, 10.40 parts by weight of isophorone diisocyanate [isocyanate group / hydroxyl group of polyol = 3/2 = 1.50 (molar ratio)], and 0.01 parts by weight of dibutyltin dilaurate at 70 ° C. while heating and mixing. By reacting for 2 hours, a urethane prepolymer having isocyanate groups at both ends of the molecular chain was synthesized. Further, 3.30 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 synthesize a urethane acrylate oligomer (A-5) having a molecular weight of 7,000. . The obtained urethane acrylate oligomer (A-5) had a viscosity at 25 ° C. of 30,000 mPas / sec as measured with a B-type viscometer.

  70.0 parts by mass of the urethane acrylate oligomer (A-5), 30.0 parts by mass of an acrylate monomer “light acrylate IM-A (isomyristyl acrylate)” manufactured by Kyoeisha Chemical Co., Ltd., photopolymerization manufactured by Ciba Specialty Chemicals Co., Ltd. Initiator "Irgacure 184D" 0.5 parts by mass and Akishima Chemical Industry Co., Ltd. ionic conductive agent "MP-100" 2.0 parts by mass with a stirrer at a liquid temperature of 70 ° C and 60 rpm for 1 hour After mixing, the mixed solution was filtered to obtain a UV curable resin raw material. The obtained UV curable resin raw material had a viscosity of 5,000 mPas / sec.

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. This sample had an Asker C hardness (manufactured by Kobunshi Keiki Co., Ltd.) of 54 degrees in the plane portion. Further, the compression residual strain of this sample was measured in accordance with JIS K 6262 (1997) and found to be 3.5%.

Next, the above 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 into which a metal shaft having an outer diameter of 6.0 mm is inserted, with a thickness of 1500 μm using a die coater. The UV curable resin raw material was cured by spot UV irradiation. The UV-cured resin elastic layer-formed roller 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.

  On the surface of the roller with an elastic layer made of UV curable resin thus obtained, a UV curable resin material containing fine particles having hardness higher than that of the elastic layer is applied with a roll coater, and irradiated with UV to form a UV coating on the surface. A low hardness UV resin roller having an outer diameter of 20.0 mm was obtained. When this roller was incorporated into an electrophotographic apparatus as a developing roller and solid white, black solid, and gray scale images were printed, a good image could be obtained.

  Next, for the photoreceptor contamination test, the cartridge incorporating this roller was left in a hot air circulation oven shielded from light at 50 ° C. for 5 days, then taken out and left for 1 hour in an environment of 20 ° C. and 50% RH. Later, when 50 gray images were printed, equally spaced white lines appeared in the image, and it was confirmed that the image was defective due to photoconductor contamination and blade pressure contact marks from the distance of the interval.

(Comparative Example 2)
Bifunctional polyol having a molecular weight of 3,200 [EXCENOL 3020, Asahi Glass Co., Ltd., polyol consisting of PO chain, hydroxyl value = 37.4 mg KOH / g, total unsaturation = 0.084 meq / g, right side of formula (I) (0.6 / x + 0.00 01) = 0.03] 100 parts by mass, 9.20 parts by mass of isophorone diisocyanate [isocyanate group / hydroxyl group of polyol = 4/3 = 1.33 (molar ratio)], and 0.01 parts by mass of dibutyltin dilaurate at 70 ° C. while heating and mixing. By reacting for 2 hours, a urethane prepolymer having isocyanate groups at both ends of the molecular chain was synthesized. Further, 2.20 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 synthesize a urethane acrylate oligomer (A-6) having a molecular weight of 11,000. . The obtained urethane acrylate oligomer (A-6) had a viscosity at 25 ° C. of 60,000 mPas / sec as measured with a B-type viscometer.

  70.0 parts by mass of the urethane acrylate oligomer (A-6), 30.0 parts by mass of an acrylate monomer “light acrylate IM-A (isomyristyl acrylate)” manufactured by Kyoeisha Chemical Co., Ltd., photopolymerization manufactured by Ciba Specialty Chemicals Co., Ltd. Initiator "Irgacure 184D" 0.5 parts by mass and Akishima Chemical Industry Co., Ltd. ionic conductive agent "MP-100" 2.0 parts by mass with a stirrer at a liquid temperature of 70 ° C and 60 rpm for 1 hour After mixing, the mixed solution was filtered to obtain a UV curable resin raw material. The obtained UV curable resin raw material had a viscosity of 8,000 mPas / sec.

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. This sample had an Asker C hardness [manufactured by Kobunshi Keiki Co., Ltd.] of 48 degrees in the plane portion. Further, the compression residual strain of this sample was measured in accordance with JIS K 6262 (1997) and found to be 4.8%.

Next, the above 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 into which a metal shaft having an outer diameter of 6.0 mm is inserted, with a thickness of 1500 μm using a die coater. The UV curable resin raw material was cured by spot UV irradiation. The UV-cured resin elastic layer-formed roller 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.

  On the surface of the roller with an elastic layer made of UV curable resin thus obtained, a UV curable resin material containing fine particles having hardness higher than that of the elastic layer is applied with a roll coater, and irradiated with UV to form a UV coating on the surface. A low hardness UV resin roller having an outer diameter of 20.0 mm was obtained. When this roller was incorporated into an electrophotographic apparatus as a developing roller and solid white, black solid, and gray scale images were printed, a good image could be obtained.

  Next, for the photoreceptor contamination test, the cartridge incorporating this roller was left in a hot air circulation oven shielded from light at 50 ° C. for 5 days, then taken out and left for 1 hour in an environment of 20 ° C. and 50% RH. Later, when 50 gray images were printed, equally spaced white lines appeared in the image, and it was confirmed that the image was defective due to photoconductor contamination and blade pressure contact marks from the distance of the interval.

  From Examples 1 to 4, for an elastic layer comprising a urethane acrylate oligomer (A) synthesized with a high-purity polyol that satisfies the relationship of the above formula (I), a photopolymerization initiator (B), and a conductive agent (C) It can be seen that a conductive elastic roller having an elastic layer made of an ultraviolet curable resin obtained by curing a raw material by ultraviolet irradiation has a low hardness and a small compressive residual strain, and does not contaminate the photoreceptor.

  On the other hand, when an elastic layer is formed from Comparative Examples 1 and 2 using a urethane acrylate oligomer synthesized using only a polyol that does not satisfy the relationship of the above formula (I) as a polyol, the conductive elastic roller contaminates the photoreceptor. At the same time, since the pressure contact marks of the blade remain, it can be seen that an image defect occurs.

It is sectional drawing of an example of the electroconductive elastic 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 Photoconductor 5 Charging roller 6 Toner 7 Toner supply roller 8 Developing roller 9 Stratified blade 10 Transfer roller 11 Cleaning roller

Claims (10)

In a conductive elastic roller comprising a shaft member and one or more elastic layers disposed radially outside the shaft member,
At least one layer of the elastic layer is made of an ultraviolet curable resin obtained by curing a raw material for an elastic layer containing a urethane acrylate oligomer (A), a photopolymerization initiator (B), and a conductive agent (C) by ultraviolet irradiation,
The urethane acrylate oligomer (A) is a polyol represented by the following formula (I):
y ≦ 0.6 / x + 0.01 (I)
[In the formula, x is the hydroxyl value (mgKOH / g) of the polyol, and y is the total unsaturation degree (meq / g) of the polyol] alone, or the high-purity polyol and others A conductive elastic roller, characterized in that it is a urethane acrylate oligomer synthesized using a polyol.   The conductive elastic roller according to claim 1, wherein the high-purity polyol used for the synthesis of the urethane acrylate oligomer (A) has a molecular weight of 1,000 to 16,000.   The mass ratio (a1 / a2) between the high-purity polyol (a1) and the other polyol (a2) in the polyol used for the synthesis of the urethane acrylate oligomer (A) is in the range of 100/0 to 30/70. The conductive elastic roller according to claim 1.   The conductive elastic roller according to claim 1, wherein the elastic layer material further contains an acrylate monomer (D).   The conductive elastic roller according to claim 1, wherein the conductive agent (C) is an ionic conductive agent. The elastic layer material used for the ultraviolet curable resin is:
The mass ratio (A / D) of the urethane acrylate oligomer (A) and the acrylate monomer (D) is in the range of 100/0 to 10/90,
For a total of 100 parts by mass of the urethane acrylate oligomer (A) and the acrylate monomer (D), the photopolymerization initiator (B) is 0.2 to 5.0 parts by mass, and the conductive agent (C) is 0.1 to 5.0 parts by mass. 5. The conductive elastic roller according to claim 1, comprising a part. The shaft member is a metal shaft or a shaft in which a highly rigid resin base material is disposed outside the metal shaft;
2. The conductive elastic roller according to claim 1, wherein an outer diameter of the metal shaft is 4.0 to 8.0 mm and an outer diameter of the resin base material is 10 to 25 mm.   The conductive elastic roller according to claim 1, wherein the elastic layer has an Asker C hardness of 30 to 70 degrees and a compressive residual strain of 3.0% or less.   The conductive elastic roller according to claim 1, wherein the conductive elastic roller is a developing roller or a charging roller.   An image forming apparatus using the conductive elastic roller according to claim 1.

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