JP2007206443A - Conductive elastic roller and image forming apparatus equipped with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive elastic roller which can be produced in a short time without requiring a large amount of heat energy, and which requires no huge plant cost and includes an elastic layer having small dependence of volume resistivity on the environment. <P>SOLUTION: The conductive elastic roller 1 comprises a shaft member 2 and one or more elastic layers 3 disposed on the radial outside of the shaft member 2, wherein at least one layer of the elastic layers 3 is made of an ultraviolet curing resin obtained by curing raw material for an elastic layer containing a urethane acrylate oligomer (A), a photopolymerization initiator (B) and a lithium salt (C) by ultraviolet irradiation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive elastic roller and an image forming apparatus including the conductive elastic roller. It is about.

  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 an ultraviolet curable type in which a general ionic conductive agent is dispersed. It was found that the resin has a large environmental dependency of the volume resistivity. Here, when a roller whose volume resistivity of the elastic layer greatly depends on the environment is used as a developing roller or the like of the image forming apparatus, the roller resistance greatly changes depending on the use environment, and image defects are likely to occur. Therefore, the elastic layer of the conductive elastic roller needs to have a sufficiently small environment dependency of the volume resistivity.

  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, is specific to the volume. It is an object of the present invention to provide a conductive elastic roller having an elastic layer whose resistance is less dependent on the environment. 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 hardens a raw material composition containing a lithium salt as an ionic conductive agent together with a urethane acrylate oligomer and a photopolymerization initiator by ultraviolet irradiation to form an elastic layer. Therefore, a conductive elastic roller having an elastic layer that does not require a large amount of heat energy, can be manufactured in a short time, does not require a large amount of equipment cost, and has low volume resistivity and environmental dependency. The inventors have found that the present invention can be obtained and have completed the present invention.

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 an elastic layer material containing a urethane acrylate oligomer (A), a photopolymerization initiator (B), and a lithium salt (C) by ultraviolet irradiation. And

  In the suitable example of the electroconductive elastic roller of this invention, content of the said lithium salt (C) in the said raw material for elastic layers is 0.1-5.0 mass%.

  In another preferred embodiment of the conductive elastic roller of the present invention, the elastic layer material further contains an acrylate monomer (D). Here, the acrylate monomer (D) preferably has a functional group number of 1.0 to 10 and a molecular weight of 100 to 2000.

In the conductive elastic roller of the present invention, 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,
It is preferable to contain 0.2-5.0 mass parts of said photoinitiators (B) with respect to a total of 100 mass parts of said urethane acrylate oligomer (A) and said acrylate monomer (D).

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 a volume resistivity of 10 ⁴ to 10 ¹⁰ Ωcm and a thickness of 1 to 3000 μm.

  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, the elastic layer material containing the urethane acrylate oligomer (A) and the photopolymerization initiator (B) and further containing the lithium salt (C) as the ionic conductive agent is cured by ultraviolet irradiation, and the elastic layer By forming at least one layer, it is possible to manufacture in a short time without requiring a large amount of heat energy, and does not require a large amount of equipment cost. A conductive elastic roller can be provided. 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 ends 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. Although the conductive elastic roller 1 shown in FIG. 1 has only one elastic layer 3, 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 lithium salt (C) by ultraviolet irradiation. Made of UV 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 for the elastic layer material is a compound having one or more acryloyloxy groups (CH ₂ ═CHCOO—) and a plurality of urethane bonds (—NHCOO—). The number of functional groups and the molecular weight of the urethane acrylate oligomer (A) are not particularly limited. The urethane acrylate oligomer (A) can be produced, for example, by synthesizing a urethane prepolymer from a polyol and a polyisocyanate, and adding an acrylate having a hydroxyl group to the urethane prepolymer.

  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 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, 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, 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 to be added to the urethane prepolymer 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 lithium salt (C) used as the raw material for the elastic layer is a kind of ionic conductive agent and has a function of imparting conductivity to the elastic layer. Since the lithium salt has a small environmental dependency of the conductivity imparting effect, the environmental dependency of the volume resistivity of the elastic layer can be reduced. In addition, since the lithium salt dissolves in the urethane acrylate oligomer (A) and has transparency, even when the elastic layer raw material is applied thickly on the shaft member, the ultraviolet rays sufficiently reach the inside of the coating film. The raw material for the elastic layer can be sufficiently cured. The lithium salt may be a salt of an organic acid such as sulfonic acid or trifluoromethanesulfonic acid, or may be a salt of an inorganic acid such as perchloric acid or tetrafluoroboric acid. Here, as the lithium salt, Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiAsF ₆ , LiC ₄ Examples thereof include F ₉ SO ₃ , and among these, Li (CF ₃ SO ₂ ) ₂ N is preferable. These lithium salts may be used individually by 1 type, and may use 2 or more types together. The lithium salt may be dissolved in various solvents and mixed with the elastic layer raw material. Here, as the solvent for dissolving the lithium salt, it is preferable to use a solvent that does not impair the object of the present invention. For example, a polyol used for the synthesis of the urethane acrylate oligomer (A) described above or an acrylate monomer described later. It is preferable to use (D) or the like.

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. Here, the functional group refers to an acryloyloxy group. If the number of functional groups of the acrylate monomer (D) is 1.0 or more, unreacted acrylate monomer hardly remains in the elastic layer, while if it is 10 or less, the hardness of the elastic layer does not become too high.

The acrylate monomer (D) preferably has a molecular weight of 100 to 2000, and more preferably 100 to 1000. If the molecular weight of the acrylate monomer (D) is 100 or more, the hardness can be adjusted and the viscosity of the compounded liquid can be adjusted while maintaining good resin properties.
On the other hand, if it is 2000 or less, the compression residual strain is good and the viscosity can be adjusted.

  Examples of the acrylate monomer (D) include methoxytriethylene glycol acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, isoamyl acrylate, glycidyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydipropylene glycol acrylate, phenoxyethyl acrylate, Examples include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, pentaerythritol triacrylate and the like. 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 content of the lithium salt (C) in the elastic layer raw material is preferably in the range of 0.1 to 5.0 mass%. If the lithium salt content is less than 0.1% by mass, the conductivity of the elastic layer is low, and it may not be possible to impart the desired conductivity to the conductive elastic roller. On the other hand, if it exceeds 5.0% by mass, the conductivity of the elastic layer May not be high, and physical properties such as compression residual strain may be reduced, and a good image may not 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. 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 elastic layer preferably has a volume resistivity of 10 ⁴ to 10 ¹⁰ Ωcm. If the volume resistivity of the elastic layer is less than 10 ⁴ Ωcm, when used as a developing roller, there is a risk of charge leaking to the photosensitive drum, etc., or the roller itself may be destroyed by voltage, while 10 ¹⁰ Ωcm If it exceeds, ground cover is likely to occur.

  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 surely UV-cured, and the amount of the expensive UV-curing resin raw material can be reduced.

The elastic layer is not particularly limited, but the Asker C hardness is preferably 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. The elastic layer preferably has a compression residual strain (compression permanent strain) of 5% 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%. 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 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 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 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 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
Urethane acrylate oligomer “UA-340P [manufactured by Shin-Nakamura Chemical Co., Ltd.]” 80.0 parts by mass, acrylate monomer “light acrylate MTG-A” 20.0 parts by mass of Kyoeisha Chemical Co., Ltd., Ciba Specialty Chemicals Co., Ltd. 0.5 parts by mass of photopolymerization initiator “Irgacure 184D” manufactured by Sanko Chemical Co., Ltd. “80% by mass of polyalkylene oxide polyol and Li (CF ₃ SO _2)” ) at ₂ mixture of N 20 wt%) "2.0 parts by mass of stirrer, liquid temperature 70 ° C., with stirring for 1 hour mixing at 60 revs / min, the mixture was filtered to obtain a raw UV-curing resin material .

A sheet sample of 2.0 mm was prepared by sandwiching the UV curable resin raw material between two quartz glass plates provided with a 2.0 mm spacer. If necessary, the sheet sample can be easily peeled by sandwiching the PTFE sheet between the quartz glass on the side opposite to the UV irradiation surface and the UV curable resin. The sample thus obtained was allowed to stand at 20 ° C. and 50% RH (NN conditions) for 2 days, then set in a JIS BOX resistance measurement box, and the resistance was measured at an applied voltage of 100 V using an Advantest resistance measuring instrument. However, the volume resistivity was 1.31 × 10 ⁷ Ωcm (10 ^7.12 Ωcm). Similarly, when the resistance was measured after standing at 12 ° C. and 10% RH (LL condition) for 2 days, the volume resistivity was 3.99 × 10 ⁷ Ωcm (10 ^7.60 Ωcm). Further, after standing for 2 days at 32.5 ° C. and 85% RH (HH condition), the resistance was measured in the same manner. As a result, the volume resistivity was 3.27 × 10 ⁶ Ωcm (10 ^6.51 Ωcm). The difference in volume resistivity between the LL condition and the HH condition was 1.09 to the logarithmic value.

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 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. This roller was incorporated into an electrophotographic apparatus as a developing roller, and after leaving for 2 days under NN, LL, and HH conditions, and printing a gray image, a good image could be obtained under each condition.

(Example 2)
Urethane acrylate oligomer “UA-340P [manufactured by Shin-Nakamura Chemical Co., Ltd.]” 80.0 parts by mass, acrylate monomer “light acrylate MTG-A” 20.0 parts by mass of Kyoeisha Chemical Co., Ltd., Ciba Specialty Chemicals Co., Ltd. 0.5 parts by mass of a photopolymerization initiator “Irgacure 184D” manufactured by Sanko Chemical Co., Ltd. “Sanconol (registered trademark) PETA-20R (80% by mass of pentaerythritol triacrylate) and Li (CF ₃ SO ₂₎ ) at ₂ mixture of N 20 wt%) "2.0 parts by mass stirrer, liquid temperature 70 ° C., mixed with stirring for 1 hour at 60 rev / min, the mixture was filtered to obtain a raw UV-curing resin material .

A sheet sample of 2.0 mm was prepared by sandwiching the UV curable resin raw material between two quartz glass plates provided with a 2.0 mm spacer. If necessary, the sheet sample can be easily peeled by sandwiching the PTFE sheet between the quartz glass on the side opposite to the UV irradiation surface and the UV curable resin. The sample thus obtained was allowed to stand at 20 ° C. and 50% RH (NN conditions) for 2 days, then set in a JIS BOX resistance measurement box, and the resistance was measured at an applied voltage of 100 V using an Advantest resistance measuring instrument. However, the volume resistivity was 1.34 × 10 ⁷ Ωcm (10 ^7.13 Ωcm). Similarly, when the resistance was measured after standing at 12 ° C. and 10% RH (LL condition) for 2 days, the volume resistivity was 4.03 × 10 ⁷ Ωcm (10 ^7.61 Ωcm). Further, after standing for 2 days at 32.5 ° C. and 85% RH (HH condition), the resistance was measured in the same manner. As a result, the volume resistivity was 3.58 × 10 ⁶ Ωcm (10 ^6.55 Ωcm). The difference in volume resistivity between the LL condition and the HH condition was 1.06 to the logarithmic value.

Next, the above UV curable resin raw material is applied to a PBT resin conductive roller base material having an outer diameter of 17.0 mm inserted with a metal shaft having an outer diameter of 6.0 mm with a die coater at a thickness of 1500 μm, and is applied by spot UV irradiation while being applied. The resin raw material was cured. 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. This roller is incorporated into an electrophotographic apparatus as a developing roller, and after leaving for 2 days under NN, LL, and HH conditions, white solid, black solid, and gray scale images are printed, and a good image is obtained under each condition. I was able to.

(Comparative Example 1)
Urethane acrylate oligomer “UA-340P [manufactured by Shin-Nakamura Chemical Co., Ltd.]” 80.0 parts by mass, acrylate monomer “light acrylate MTG-A” 20.0 parts by mass of Kyoeisha Chemical Co., Ltd., Ciba Specialty Chemicals Co., Ltd. 0.5 parts by weight of photopolymerization initiator “Irgacure 184D” manufactured by Akishima Chemical Industry Co., Ltd. “MP-100 (mixture of sodium perchlorate polyol complex salt 60-80% and polyol 20-40%) ) ”2.6 parts by mass was stirred and mixed for 1 hour at a liquid temperature of 70 ° C. and 60 rpm with a stirrer, and the mixed solution was filtered to obtain a UV curable resin raw material.

A sheet sample of 2.0 mm was prepared by sandwiching the UV curable resin raw material between two quartz glass plates provided with a 2.0 mm spacer. If necessary, the sheet sample can be easily peeled by sandwiching the PTFE sheet between the quartz glass on the side opposite to the UV irradiation surface and the UV curable resin. The sample thus obtained was allowed to stand at 20 ° C. and 50% RH (NN conditions) for 2 days, then set in a JIS BOX resistance measurement box, and the resistance was measured at an applied voltage of 100 V using an Advantest resistance measuring instrument. However, the volume resistivity was 2.96 × 10 ⁶ Ωcm (10 ^6.47 Ωcm). Similarly, when the resistance was measured after standing at 12 ° C. and 10% RH (LL condition) for 2 days, the volume resistivity was 3.14 × 10 ⁷ Ωcm (10 ^7.50 Ωcm). Further, after standing at 32.5 ° C. and 85% RH (HH condition) for 2 days, the resistance was measured in the same manner, and the volume resistivity was 7.25 × 10 ⁵ Ωcm (10 ^5.86 Ωcm). The difference in volume resistivity between the LL condition and the HH condition was 1.64 to the logarithmic value.

Next, the above UV curable resin raw material is applied to a PBT resin conductive roller base material having an outer diameter of 17.0 mm inserted with a metal shaft having an outer diameter of 6.0 mm with a die coater at a thickness of 1500 μm, and is applied by spot UV irradiation while being applied. The resin raw material was cured. 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.

  The surface of the roller with the elastic layer made of UV curable resin thus obtained is coated with a UV curable resin raw material containing particles having a hardness higher than that of the elastic layer with a roll coater, irradiated with UV, and a UV coating is applied to the surface. A UV resin roller having an outer diameter of 20.0 mm and having a low hardness was obtained. This roller was incorporated into an electrophotographic apparatus as a developing roller, and after leaving for 2 days under NN, LL, and HH conditions, and printing a gray image, good images were obtained under NN and LL conditions. Under HH conditions, the image density was low and color unevenness occurred.

(Comparative Example 2)
Urethane acrylate oligomer “UA-340P [manufactured by Shin-Nakamura Chemical Co., Ltd.]” 80.0 parts by mass, acrylate monomer “light acrylate MTG-A” 20.0 parts by mass of Kyoeisha Chemical Co., Ltd., Ciba Specialty Chemicals Co., Ltd. 0.5 parts by mass of photopolymerization initiator “Irgacure 184D” manufactured by Kao Co., Ltd., “KS555 (quaternary ammonium salt / perchlorate, RNCH ₃ (CH ₂ CH ₂ OH) ₂ .ClO” manufactured by Kao Corporation ₄ ) “2.6 parts by mass of the mixture was stirred and mixed with a stirrer at a liquid temperature of 70 ° C. and 60 rpm for 1 hour, and the mixed solution was filtered to obtain a UV curable resin raw material.

A sheet sample of 2.0 mm was prepared by sandwiching the UV curable resin raw material between two quartz glass plates provided with a 2.0 mm spacer. If necessary, the sheet sample can be easily peeled by sandwiching the PTFE sheet between the quartz glass on the side opposite to the UV irradiation surface and the UV curable resin. The sample thus obtained was allowed to stand at 20 ° C. and 50% RH (NN conditions) for 2 days, then set in a JIS BOX resistance measurement box, and the resistance was measured at an applied voltage of 100 V using an Advantest resistance measuring instrument. However, the volume resistivity was 2.14 × 10 ⁷ Ωcm (10 ^7.33 Ωcm). Similarly, when the resistance was measured after standing for 2 days at 12 ° C. and 10% RH (LL condition), the volume resistivity was 1.87 × 10 ⁸ Ωcm (10 ^8.27 Ωcm). Further, after standing for 2 days at 32.5 ° C. and 85% RH (HH condition), the resistance was measured in the same manner. As a result, the volume resistivity was 2.00 × 10 ⁶ Ωcm (10 ^6.30 Ωcm). The difference in volume resistivity between the LL condition and the HH condition was 1.97 to the logarithmic value.

Next, the above UV curable resin raw material is applied to a PBT resin conductive roller base material having an outer diameter of 17.0 mm inserted with a metal shaft having an outer diameter of 6.0 mm with a die coater at a thickness of 1500 μm, and is applied by spot UV irradiation while being applied. The resin raw material was cured. 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.

  The surface of the roller with the elastic layer made of UV curable resin thus obtained is coated with a UV curable resin raw material containing particles having a hardness higher than that of the elastic layer with a roll coater, irradiated with UV, and a UV coating is applied to the surface. A UV resin roller having an outer diameter of 20.0 mm and having a low hardness was obtained. This roller was incorporated into an electrophotographic apparatus as a developing roller, and after leaving for 2 days under NN conditions, LL conditions, and HH conditions, and printing a gray image, good images were obtained under NN conditions and HH conditions. Under the LL condition, the image density was low and color unevenness occurred.

(Comparative Example 3)
100.0 parts by mass of polyether polyol “Exenol 851 [Asahi Glass Co., Ltd.]”, 0.002 parts by mass of dibutyltin dilaurate, and 2.8 parts by mass of ionic conductive agent “MP-100 [Akishima Chemical Industry Co., Ltd.]” were stirred. The mixture was stirred and mixed at a liquid temperature of 25 ° C. and 60 rpm for 10 minutes, and the resulting mixture was designated as A solution. Also, the isocyanate “Sumijoule PF [Sumika Bayer Urethane Co., Ltd.]” was designated as B liquid. 102.802 parts by mass of the A liquid and 8.5 parts by mass of the B liquid were stirred and mixed to obtain a urethane resin raw material.

Immediately after stirring and mixing the urethane resin raw material, it was poured into an aluminum mold with a lid having a cavity of 2.0 × 100 × 100 mm, and heat cured at 100 ° C. for 1 hour to prepare a sheet sample having a thickness of 2.0 mm. . This sample was allowed to stand at 20 ° C. and 50% RH (NN conditions) for 2 days, then placed in a JIS BOX type resistance measuring box and measured for resistance at an applied voltage of 100 V using an Advantest resistance measuring instrument. Was 2.82 × 10 ⁷ Ωcm (10 ^7.45 Ωcm). Similarly, when the resistance was measured after standing for 2 days at 12 ° C. and 10% RH (LL condition), the volume resistivity was 2.89 × 10 ⁸ Ωcm (10 ^8.46 Ωcm). Further, after standing for 2 days at 32.5 ° C. and 85% RH (HH condition), the resistance was measured in the same manner. As a result, the volume resistivity was 5.01 × 10 ⁶ Ωcm (10 ^6.70 Ωcm). The difference in volume resistivity between the LL condition and the HH condition was 1.76 to the logarithmic value.

  Next, a PBT resin conductive roller base material with an outer diameter of 6.0 mm inserted with a metal shaft with an outer diameter of 6.0 mm is set in a pipe mold with an inner diameter of 20.0 mm via a metal shaft fixing cap, and the urethane The resin raw material was injected under pressure, cured by heating at 100 ° C. for 1 hour, and then taken out from the mold.

  Roller coater is coated with a UV curable resin raw material containing fine particles having hardness higher than that of the elastic layer on the surface of the roller with elastic layer made of urethane resin thus obtained. A low hardness roller with an outer diameter of 20.0 mm was obtained. When this roller was incorporated into an electrophotographic apparatus as a developing roller and left for 2 days under NN, LL, and HH conditions, and a gray image was printed, a good image was obtained under NN and HH conditions. Under the LL conditions, the image density was low and color unevenness occurred.

(Comparative Example 4)
100.0 parts by mass of polyether polyol “Exenol 851 [Asahi Glass Co., Ltd.]”, 0.002 parts by mass of dibutyltin dilaurate, and 2.8 parts by mass of ionic conductive agent “KS555 [manufactured by Kao Corporation]” at a liquid temperature of 25 ° C. The mixture was stirred and mixed at 60 rpm for 10 minutes, and the resulting mixture was designated as solution A. Also, the isocyanate “Sumijoule PF [Sumika Bayer Urethane Co., Ltd.]” was designated as B liquid. 102.802 parts by mass of the A liquid and 8.5 parts by mass of the B liquid were stirred and mixed to obtain a urethane resin raw material.

Immediately after stirring and mixing the urethane resin raw material, it was poured into an aluminum mold with a lid having a cavity of 2.0 × 100 × 100 mm, and heat cured at 100 ° C. for 1 hour to prepare a sheet sample having a thickness of 2.0 mm. . This sample was allowed to stand at 20 ° C. and 50% RH (NN conditions) for 2 days, then placed in a JIS BOX type resistance measuring box and measured for resistance at an applied voltage of 100 V using an Advantest resistance measuring instrument. Was 2.04 × 10 ⁸ Ωcm (10 ^8.31 Ωcm). Similarly, when the resistance was measured after standing at 12 ° C. and 10% RH (LL condition) for 2 days, the volume resistivity was 1.81 × 10 ⁹ Ωcm (10 ^9.26 Ωcm). Further, after standing for 2 days at 32.5 ° C. and 85% RH (HH condition), the resistance was measured in the same manner. As a result, the volume resistivity was 1.87 × 10 ⁷ Ωcm (10 ^7.27 Ωcm). The difference in volume resistivity between the LL and HH conditions was 1.99 to the logarithmic value.

  Next, a PBT resin conductive roller base material with an outer diameter of 6.0 mm inserted with a metal shaft with an outer diameter of 6.0 mm is set in a pipe mold with an inner diameter of 20.0 mm via a metal shaft fixing cap, and the urethane The resin raw material was injected under pressure, cured by heating at 100 ° C. for 1 hour, and then taken out from the mold.

  Roller coater is coated with a UV curable resin raw material containing fine particles having hardness higher than that of the elastic layer on the surface of the roller with elastic layer made of urethane resin thus obtained. A low hardness roller with an outer diameter of 20.0 mm was obtained. This roller was incorporated into an electrophotographic apparatus as a developing roller, and after being left for 2 days under NN, LL, and HH conditions, a gray image was printed. A good image was obtained under HH conditions. Under the LL conditions, the image density was low and color unevenness occurred.

  From Examples 1 and 2, ultraviolet curing in which a raw material for an elastic layer containing a urethane acrylate oligomer (A) and a photopolymerization initiator (B) and further containing a lithium salt (C) as an ionic conductive agent was cured by ultraviolet irradiation. It can be seen that the conductive elastic roller having the elastic layer made of the mold resin has a small environmental dependency of the volume resistivity of the elastic layer.

  On the other hand, from the results of Comparative Examples 1 to 4, it can be seen that the use of an ionic conductive agent other than the lithium salt (C) significantly increases the environmental dependency of the volume resistivity of the elastic layer.

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 Photosensitive drum 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 an elastic layer material containing a urethane acrylate oligomer (A), a photopolymerization initiator (B), and a lithium salt (C) by ultraviolet irradiation. Conductive elastic roller.   2. The conductive elastic roller according to claim 1, wherein a content of the lithium salt in the elastic layer raw material is 0.1 to 5.0 mass%.   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 3, wherein the acrylate monomer (D) has a functional group number of 1.0 to 10 and a molecular weight of 100 to 2,000. 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,
The photopolymerization initiator (B) is contained in an amount of 0.2 to 5.0 parts by mass with respect to a total of 100 parts by mass of the urethane acrylate oligomer (A) and the acrylate monomer (D). The conductive elastic roller according to 1. The conductive elastic roller according to claim 1, wherein the elastic layer has a volume resistivity of 10 ⁴ to 10 ¹⁰ Ωcm. 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 a thickness of 1 to 3000 μm.   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.

Images