JP2012159734A - Developing roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing roller which suppresses occurrence of fogging under a high temperature and high humidity environment without degrading an image under a low temperature and low humidity environment.SOLUTION: In an elastic roller having at least an elastic layer 2 provided in the outer periphery of a shaft 1, the elastic layer 2 contains an ultraviolet curable resin and an ion conductive agent, the surface potential after 0.4 seconds after a surface has been charged by corona discharge of 8 kV from a position which is 1 mm apart from the elastic layer 2 on conditions of a temperature of 32.5°C and a humidity of 80% RH is 25 V or more, and an intermediate layer 3 and a surface layer 4 are stacked on the elastic layer 2.

Description

  The present invention relates to a developing roller (hereinafter also simply referred to as “roller”), and more particularly to a developing roller used in an image forming process in an image forming apparatus such as a copying machine or a printer.

  Conventionally, as a developing method when a non-magnetic one-component developer is used as a developer (toner), toner is supplied to an image carrier such as a photosensitive drum holding an electrostatic latent image via a developing roller, and an image is obtained. A development method (pressure development method) is known in which a latent image is visualized by attaching toner to the latent image on the carrier. In this developing method, development is performed by bringing a developing roller carrying toner into contact with an image carrier holding an electrostatic latent image and attaching the toner to the latent image on the image carrier. The developing roller to be used needs to be formed of an elastic body having conductivity.

  FIG. 2 shows a configuration example of a developing device using a pressure developing method. In the illustrated developing device, a developing roller 10 is disposed in contact with a photosensitive drum 12 between a toner supply roller 11 for supplying toner and a photosensitive drum 12 holding an electrostatic latent image. As the developing roller 10, the photosensitive drum 12, and the toner supply roller 11 rotate in the directions of the arrows in the drawing, the toner 13 is supplied to the surface of the developing roller 10 by the toner supply roller 11. The supplied toner is adjusted to a uniform thin layer by the stratifying blade 14, and the developing roller 10 rotates in contact with the photosensitive drum 12 in this state, whereby the toner formed in the thin layer is transferred from the developing roller 10 to the photosensitive drum. The latent image is visualized by attaching to the 12 latent images. Note that reference numeral 15 in the drawing denotes a transfer portion, where a toner image is transferred to a recording medium such as paper. Reference numeral 16 denotes a cleaning unit, and toner remaining on the surface of the photosensitive drum 12 after transfer is removed by a cleaning blade 17.

  However, in the apparatus using the developing method as described above, the toner carried on the surface of the developing roller when a white solid image is printed in a high temperature and high humidity environment at a temperature of 32.5 ° C. and a humidity of about 80% RH. However, there is a case in which a so-called fog phenomenon occurs in which the toner is transferred to the white background portion of the printed image by adhering to the portion that should originally be white background on the image carrier. One of the causes of the occurrence of fog in such a high temperature and high humidity environment is insufficient charge amount of toner. This is because in a high temperature and high humidity environment, there is little static electricity and the electrostatic adhesion of toner to the developing roller is weakened. Therefore, conventionally, as a measure for preventing fogging in a high-temperature and high-humidity environment, studies for improving the toner charge amount have been made.

  For example, Patent Document 1 aims to provide a developing roller in which the occurrence of filming on the surface of the developing roller is suppressed, a high-quality toner image with high density and no fogging is obtained, and in-machine contamination is not generated. In a developing roller having a conductive coating layer formed on the outer periphery of a conductive shaft, the surface of the resin thin film after 1 second when a resin thin film made only of the resin forming the coating layer is charged by a charger. A technique is disclosed in which the potential Rv1 and the surface potential of the resin thin film after 10 seconds Rv2 have a relationship of 0.01 ≦ Rv2 / Rv1 ≦ 0.20.

JP 2008-233157 A (Claims etc.)

  In recent years, with the progress of technical improvements related to toner, toner having a high charge amount has been adopted in image forming apparatuses. However, when a developing roller design that promotes charging is performed on such a toner having a high charge amount, there is a problem in that image quality deteriorates in a low temperature and low humidity environment. Therefore, establishment of a technique for suppressing the occurrence of fogging in a high-temperature and high-humidity environment without deteriorating an image in a low-temperature and low-humidity environment has been demanded.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing roller that solves the above problems and suppresses the occurrence of fogging in a high temperature and high humidity environment without deteriorating an image in a low temperature and low humidity environment.

  As a result of diligent investigation, the present inventor has adopted a design for maintaining the charging property of the developing roller rather than a conventional method for improving the charge amount of the toner, that is, delaying the potential attenuation on the surface of the developing roller. Thus, the inventors have found that the above problems can be solved by maintaining the roller surface potential high for a certain period of time after charging, and have completed the present invention.

That is, the present invention provides an elastic roller having at least an elastic layer on the outer periphery of the shaft.
When the elastic layer contains an ultraviolet curable resin and an ionic conductive agent, and the surface is charged by 8 kV corona discharge from a position 1 mm away under conditions of a temperature of 32.5 ° C. and a humidity of 80% RH. The surface potential after 0.4 seconds is 25 V or more.

In the developing roller of the present invention, the resistance value under the conditions of a temperature of 10 ° C. and a humidity of 15% RH is preferably 10 ⁴ to 10 ⁸ Ω. In the roller of the present invention, an intermediate layer and a surface layer are laminated on the elastic layer, and the surface layer comprises polybutadiene polyol or hydrogenated polybutadiene polyol, polyisocyanate, and (meth) acrylate having a hydroxyl group. It is preferable to contain the urethane (meth) acrylate oligomer made to react.

Furthermore, in the roller of the present invention, an intermediate layer and a surface layer are laminated on the elastic layer, and the intermediate layer contains 1 part by mass or more of carbon black with respect to 100 parts by mass of the ultraviolet curable resin, A photopolymerization initiator having an extinction coefficient at 254 nm of 2 × 10 ⁴ ml / g · cm or more and a photopolymerization initiator having an extinction coefficient at 365 nm of 4 × 10 ² ml / g · cm or more. preferable.

  According to the present invention, with the above configuration, it is possible to realize a developing roller that suppresses the occurrence of fogging in a high temperature and high humidity environment without deteriorating an image in a low temperature and low humidity environment. .

FIG. 3 is a longitudinal sectional view according to an example of the developing roller of the present invention. It is a schematic explanatory drawing which shows one structural example of the image development apparatus using a pressure development method. It is a schematic explanatory drawing which shows the measuring apparatus of the surface potential used in the Example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view according to an example of the developing roller of the present invention. As shown in the figure, the developing roller 10 of the present invention includes at least an elastic layer 2 on the outer periphery of the shaft 1, and further preferably has an intermediate layer 3 and a surface layer 4 laminated thereon.

  In the present invention, the elastic layer 2 contains an ultraviolet (UV) curable resin and an ionic conductive agent, and is 8 kV corona from a position 1 mm away under conditions of a temperature of 32.5 ° C. and a humidity of 80% RH. It is important that the surface potential after 0.4 seconds when the surface is charged by discharge is 25 V or more. By prescribing in this way and keeping the surface potential of the developing roller high for a certain time after charging in a high-temperature and high-humidity environment, the toner is reliably supported on the surface of the developing roller and moves to the image carrier. Therefore, the occurrence of fogging in a high temperature and high humidity environment can be suppressed, and a good print image quality can be realized. Further, in the present invention, unlike the conventional technique by improving the toner charge amount, the image does not deteriorate under a low temperature and low humidity environment.

  In the present invention, the surface potential after 0.4 seconds from the charging under the predetermined condition is preferably 25 to 100V, more preferably 40 to 100V, and further preferably 60 to 100V. If this surface potential is less than 25 V, the effect of suppressing the generation of fog cannot be obtained. On the other hand, if the surface potential is too high, the electrostatic adhesion force of the toner becomes too strong in a low-temperature and low-humidity environment. Here, the problem of the temperature of 32.5 ° C. and the humidity of 80% RH is that the conditions of the high temperature and high humidity environment are clarified. In addition, the charging condition is a case where the surface is charged by a corona discharge of 8 kV from a position 1 mm away, which defines a general charging condition in an actual image forming apparatus. Further, the problem of the surface potential after 0.4 seconds is that after the roller surface is charged by corona discharge, it becomes 0.4 until the charged portion on the surface of the image carrier and the developing roller surface comes close to each other. This is because it is considered to take about 2 seconds.

  In the present invention, the elastic layer 2 is mainly composed of a UV curable resin and an ionic conductive agent, whereby a developing roller that satisfies the conditions relating to the surface potential can be obtained. More specifically, in the present invention, the elastic layer 2 is formed of an elastic layer forming composition containing a UV curable resin, a photopolymerization initiator, and an ionic conductive agent.

  Although it does not restrict | limit especially as UV curable resin used for the elastic layer 2, For example, the thing containing (A) urethane (meth) acrylate oligomer and (B) (meth) acrylate monomer is used suitably. be able to.

The (A) urethane (meth) acrylate oligomer has one or more acryloyloxy groups (CH ₂ ═CHCOO—) or methacryloyloxy groups (CH ₂ ═C (CH ₃ ) COO—), and a urethane bond (—NHCOO). A compound having a plurality of-). This (A) urethane (meth) acrylate oligomer has a functional group number of 3.0 or less, particularly preferably 1.5 to 2.5. Here, the functional group refers to an acryloyloxy group and a methacryloyloxy group, and the number of functional groups refers to the average number of functional groups. (A) If the number of functional groups of the urethane (meth) acrylate oligomer is 3.0 or less, the crosslinking density in the UV curable resin will increase moderately, so the amount of acetone extracted is reduced without increasing the layer hardness. The effect of improving the contamination of adjacent members such as a photoconductor can be obtained. In addition, when a trifunctional urethane (meth) acrylate oligomer is contained in the (A) urethane (meth) acrylate oligomer, the hardness of the layer may be increased.

  (A) The urethane (meth) acrylate oligomer is preferably 5,000 to 100,000 in terms of polystyrene-equivalent number average molecular weight. (A) If the molecular weight of the urethane (meth) acrylate oligomer is less than 5,000, the hardness of the layer may be too high, while if it exceeds 100,000, the compressive residual strain of the layer may be too high. .

  Although it does not restrict | limit especially as said (A) urethane (meth) acrylate oligomer, For example, by synthesize | combining a urethane prepolymer from a polyol and polyisocyanate, and adding the (meth) acrylate which has a hydroxyl group to this urethane prepolymer. What was manufactured can be used conveniently.

  The polyol used for the synthesis of the urethane prepolymer is a compound having a plurality of hydroxyl groups (OH groups). Specific examples of such polyol include polyether polyol, polyester polyol, polytetramethylene glycol, polybutadiene polyol, alkylene oxide-modified polybutadiene polyol, and polyisoprene polyol. Among these, polyether polyol is particularly preferable. Specific examples of the polyether polyol include polyoxypropylene glycol, polyoxyethylene glycol, polyoxymethylene glycol, polyoxytetramethylene glycol, and polyoxybutylene glycol. By selecting these suitable polyether polyols as the polyol used for the synthesis of the urethane prepolymer, the effect of increasing the hydrophobicity of the layer and making it difficult to incorporate moisture into the layer can be obtained. For this reason, the layer exhibits resistance to degradation reactions such as hydrolysis, and the amount of acetone extracted can be reduced. As a result, the effect of improving the contamination of adjacent members such as a photoreceptor can be obtained. 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. These polyols may be used alone or in a blend of two or more.

  The polyol used for the synthesis of the urethane prepolymer preferably has a molecular weight in the range of 500 to 15,000. If the molecular weight of the polyol used for the synthesis of the urethane prepolymer is less than 500, the hardness becomes high, so that it becomes unsuitable for the layer of the developing roller. On the other hand, if it exceeds 15,000, the compressive residual strain increases, resulting in poor image quality. It tends to occur.

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

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

  In the synthesis of the urethane prepolymer, it is preferable to use a catalyst for urethanization reaction. Examples of the catalyst for urethanization reaction include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin thiocarboxylate, tin octenoate, monobutyltin oxide 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, Cyclic amines such as methylaminoethylmorpholine, 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, sodium hydroxide; tita such as tetrabutyl titanate, tetraethyl titanate, tetraisopropyl titanate Compounds; bismuth compounds; quaternary ammonium salts, and the like. Of these catalysts, organotin compounds are preferred. These catalysts may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the catalyst used is preferably in the range of 0.001 to 2.0 parts by mass with respect to 100 parts by mass of the polyol.

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

The (B) (meth) acrylate monomer is a monomer having one or more acryloyloxy groups (CH ₂ ═CHCOO—) or methacryloyloxy groups (CH ₂ ═C (CH ₃ ) COO—). This (B) (meth) acrylate monomer acts as a reactive diluent, that is, it can be cured with UV, and the viscosity of the elastic layer forming composition can be lowered.

  The (B) (meth) acrylate monomer preferably has a functional group number of 3.0 or less, more preferably 1-2. Here, the functional group refers to an acryloyloxy group and a methacryloyloxy group, and the number of functional groups refers to the average number of functional groups. (B) If the number of functional groups of the (meth) acrylate monomer is 3.0 or less, the crosslinking density in the UV curable resin will increase moderately, so that the amount of acetone extracted is reduced without increasing the hardness of the layer. And the effect of improving the contamination of adjacent members such as a photoconductor can be obtained. Moreover, when the said (B) (meth) acrylate monomer contains a bifunctional (meth) acrylate monomer, bifunctional in the sum total of the said urethane (meth) acrylate oligomer (A) and (meth) acrylate monomer (B). The content of the (meth) acrylate monomer is preferably 1 to 15 masses. If the content of the bifunctional (meth) acrylate monomer is less than 1% by mass, the crosslinking density in the UV curable resin cannot be increased sufficiently. On the other hand, if it exceeds 15% by mass, the crosslinking density increases. This may increase the hardness of the layer.

  The (B) (meth) acrylate monomer preferably has a glass transition point (Tg) of 50 ° C. or lower. Here, the (B) (meth) acrylate monomer having a glass transition point (Tg) of 50 ° C. or less generally has a large proportion of the portion excluding the functional group in the monomer molecule, and (B) (meth) When the acrylate monomer is polymerized with the (A) urethane (meth) acrylate oligomer, the movement of the polymer excluding the functional group of the (B) (meth) acrylate monomer increases, resulting in layer hardness. Reduce.

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

  In the present invention, the proportion of the (A) urethane (meth) acrylate oligomer in the total amount of the (A) urethane (meth) acrylate oligomer and the (B) (meth) acrylate monomer is preferably 50% by mass or more. Preferably it is 60-90 mass%. (A) If the content rate of a urethane (meth) acrylate oligomer is less than 50 mass%, since the ratio of a monomer will increase, a low molecular weight polymer will increase, As a result, there exists a possibility that acetone extraction amount may increase.

  The photoinitiator used for the elastic layer 2 has the effect | action which starts superposition | polymerization of the said (A) urethane (meth) acrylate oligomer and (B) (meth) acrylate monomer by irradiating with an ultraviolet-ray. Such photopolymerization initiators include 4-dimethylaminobenzoic acid, 4-dimethylaminobenzoic acid ester, 2,2-dimethoxy-2-phenylacetophenone, acetophenone diethyl ketal, alkoxyacetophenone, benzyldimethyl ketal, benzophenone and 3,3. -Benzyl derivatives such as dimethyl-4-methoxybenzophenone, 4,4-dimethoxybenzophenone, 4,4-diaminobenzophenone, alkyl benzoylbenzoate, bis (4-dialkylaminophenyl) ketone, benzyl and benzylmethyl ketal Benzoin derivatives such as benzoin and benzoin isobutyl ether, benzoin isopropyl ether, 2-hydroxy-2-methylpropiophenone, 1-hydroxysilane Rohexyl phenyl ketone, xanthone, thioxanthone and thioxanthone derivatives, fluorene, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2 , 4,6-trimethylbenzoyl) -phenylphosphine oxide, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropane-1,2-benzyl-2-dimethylamino-1- (morpholinophenyl) -Butanone-1 etc. are mentioned. Specific examples include IRGACURE 651, 184, 500, 2959, 127, 1800, 784, 907, 369, 379, 819, DAROCUR 1173, 4265, TPO (all manufactured by BASF Japan Ltd.) and the like. These photopolymerization initiators may be used alone or in combination of two or more. In addition, the compounding quantity of the photoinitiator in the composition for elastic layer formation is 100 mass in total of the said (A) urethane (meth) acrylate oligomer which comprises UV curable resin, and the said (B) (meth) acrylate monomer. A range of 0.2 to 5.0 parts by mass, particularly 0.5 to 2 parts by mass is preferable with respect to parts.

  The ionic conductive agent used for the elastic layer 2 has a function of imparting conductivity to the elastic layer. In addition to being dissolved in the (A) urethane (meth) acrylate oligomer, the ionic conductive agent has transparency, so even if the elastic layer forming composition is applied thickly on the shaft, the ultraviolet rays are sufficiently inside the coating film. And the elastic layer forming composition can be sufficiently cured. Examples of the ionic conductive agent include perchlorates, chlorates, hydrochlorides, bromates such as tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, and modified fatty acid dimethylethylammonium. 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.

  More specifically, in the present invention, by selecting an ionic conductive agent used for the elastic layer 2 from the viewpoints of ion mobility and resistance adjustment, a developing roller that satisfies the above-described surface potential conditions can be obtained. it can. Suitable ionic conductive agents include, for example, sodium perchlorate (MP-100, manufactured by Showa Chemical Industry Co., Ltd.), an acrylic monomer solution of lithium imide (Sanconol MTGA-50R, manufactured by Sanko Chemical Co., Ltd.), and the like. Can be mentioned. These electrically conductive agents may be used individually by 1 type, and may use 2 or more types together. The compounding amount of the ionic conductive agent in the elastic layer forming composition depends on its type, but is the total of (A) urethane (meth) acrylate oligomer and (B) (meth) acrylate monomer constituting the UV curable resin. The range of 0.1 to 5.0 parts by mass, particularly 0.4 to 2.0 parts by mass, and further 0.4 to 1.2 parts by mass is preferable with respect to 100 parts by mass.

  Further, in the elastic layer forming composition, the polymerization inhibitor is further added to a total of 100 parts by mass of the (A) urethane (meth) acrylate oligomer and the (B) (meth) acrylate monomer constituting the UV curable resin. On the other hand, you may add in 0.001-0.2 mass part. By adding a polymerization inhibitor, thermal polymerization before ultraviolet irradiation can be prevented. Such polymerization inhibitors 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.

  In addition to the above, various known additives can be added to the elastic layer forming composition as long as the desired effects of the present invention are not impaired. In the present invention, the thickness of the elastic layer 2 is preferably 0.5 to 4 mm.

  Next, the intermediate layer 3 in the roller of the present invention can be formed of an intermediate layer forming composition containing a UV curable resin, a photopolymerization initiator, and a conductive agent. As the UV curable resin and the photopolymerization initiator, the same materials as those used for the elastic layer can be used, and are not particularly limited.

  Examples of the conductive agent used for the intermediate layer 3 include conductive carbon black such as ketjen black and acetylene black, carbon black for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT, and oxidized carbon black. Various carbon blacks such as carbon black for ink and pyrolytic carbon black can be used. The blending amount of such carbon black is preferably at least 1 part by mass with respect to a total of 100 parts by mass of (A) urethane (meth) acrylate oligomer and (B) (meth) acrylate monomer constituting the UV curable resin. Is in the range of 2 to 15 parts by mass, more preferably 2 to 6 parts by mass. In the present invention, by blending carbon black in an amount in the above range, the resistance value of the intermediate layer 3 can be reduced, and a desired resistance value can be obtained for the entire roller, and the roller resistance associated with environmental changes can be obtained. The effect of suppressing fluctuation is obtained. However, if the amount of carbon black is too large, the intermediate layer 3 may be poorly cured.

The photopolymerization initiator used for the intermediate layer 3 can be the same as that used for the elastic layer 2 and is not particularly limited, but preferably has an extinction coefficient of 2 at 254 nm. A photopolymerization initiator having × 10 ⁴ ml / g · cm or more and a photopolymerization initiator having an extinction coefficient at 365 nm of 4 × 10 ² ml / g · cm or more are used in combination. In general, when UV light is applied to a layer containing carbon black, the UV light may not reach the inside of the layer and may cause poor curing of the resin, but by using a plurality of such photopolymerization initiators in combination, It can absorb multiple wavelengths of light and allow the curing reaction to proceed. Even in a layer containing more than a certain amount of carbon black as a conductive agent, it efficiently absorbs the light emitted from the light source and UV cures the resin. Can be reliably completed. The problem with photoinitiators with a high extinction coefficient at 254 nm and photoinitiators with a high extinction coefficient at 365 nm is that these 254 nm and 365 nm are the main emission wavelengths in a typical UV light source. Because.

Examples of the photopolymerization initiator having an extinction coefficient at 254 nm of 2 × 10 ⁴ ml / g · cm or more include IRGACURE 651, 184, 500, 2959, 127, 1800, 784, DAROCUR 1173, 4265 (both are BASF Japan Ltd. )) And the like. Examples of the photopolymerization initiator having an extinction coefficient at 365 nm of 4 × 10 ² ml / g · cm or more include IRGACURE 907, 369, 379, 819, 1800, 784, DAROCUR 4265, TPO (all of which are BASF Japan )) And the like. The blending amounts of these two kinds of photopolymerization initiators in the composition for forming an intermediate layer are the sum of (A) urethane (meth) acrylate oligomer and (B) (meth) acrylate monomer, respectively, constituting the UV curable resin. A range of 0.2 to 5.0 parts by mass, particularly 0.5 to 2 parts by mass is preferable with respect to 100 parts by mass.

  Furthermore, in addition to the above, various known additives can be blended in the intermediate layer forming composition as long as the desired effects of the present invention are not impaired. In the present invention, the thickness of the intermediate layer 3 is preferably 1 to 10 μm.

  Next, the surface layer 4 in the roller of the present invention can be formed of a surface layer forming composition containing a UV curable resin and a photopolymerization initiator and not containing a conductive agent. As the UV curable resin, the same resin as that used for the elastic layer can be used, and preferably a polybutadiene polyol or hydrogenated polybutadiene polyol, a polyisocyanate, and a (meth) acrylate having a hydroxyl group. And those containing a urethane (meth) acrylate oligomer obtained by reacting with. That is, as the (A) urethane (meth) acrylate oligomer, a UV curable resin using a urethane (meth) acrylate oligomer using a polybutadiene polyol or a hydrogenated polybutadiene polyol as a polyol is suitable. Thereby, in the surface layer 4, while being able to obtain a high resistance value, that is, a high insulating property, a high surface potential can be maintained. Therefore, it is possible to maintain the charging property of the toner in the developing roller and improve the printing quality, particularly the quality of fine line printing at the 1-dot level, without the occurrence of durable printing fog or the like.

  The polybutadiene polyol or hydrogenated polybutadiene polyol used for the surface layer 4 preferably has a weight average molecular weight of 1200 to 20000. If the weight average molecular weight is too small, the cured film tends to break and surface layer abrasion occurs. On the other hand, in order to increase the weight average molecular weight, the polyol / isocyanate ratio must be increased, and the compatibility between the hydrophobic polybutadiene polyol and the hydrophilic isocyanate deteriorates, increasing the number of unreacted components. End up. This causes toner sticking and adversely affects print quality. For this reason, those deviating from the aforementioned weight average molecular weight are not preferred.

  As a photoinitiator used for the surface layer 4, the thing similar to what was used for the said elastic layer 2 can be used, and it does not restrict | limit in particular. Further, the blending amount can be appropriately selected within the same range as in the case of the elastic layer 2. Furthermore, in addition to the above, various known additives can be added to the surface layer forming composition as long as the desired effects of the present invention are not impaired. In the present invention, the thickness of the surface layer 4 is preferably 1 to 20 μm.

  The shaft 1 used for the developing roller of the present invention is not particularly limited as long as it has good conductivity. A metal shaft, a resin shaft having a high rigidity disposed on the outer periphery of the metal shaft, a high rigidity Any of a resin base material, a metal hollow inside, or a cylindrical body made of high-rigidity resin may be used.

  Examples of the material for the metal shaft and the metal cylinder include iron, stainless steel, and aluminum. Examples of the high-rigidity resin include polyacetal, polyamide 6, polyamide 6 and 6, polyamide 12, polyamide 4 and 6, polyamide 6 and 10, polyamide 6 and 12, polyamide 11, polyamide MXD6, polybutylene terephthalate, polyphenylene oxide, Polyphenylene sulfide, polyethersulfone, polycarbonate, polyimide, polyamideimide, polyetherimide, polysulfone, polyetheretherketone, polyethylene terephthalate, polyarylate, liquid crystal polymer, polytetrafluoroethylene, polypropylene, acrylonitrile-butadiene-styrene (ABS) resin , Polystyrene, polyethylene, melamine resin, phenol resin, silicone resin and the like. Among these, polyacetal, polyamide 6 · 6, polyamide MXD6, polyamide 6 · 12, polybutylene terephthalate, polyphenylene ether, polyphenylene sulfide, and polycarbonate are preferable. These high-rigidity resins may be used alone or in combination of two or more.

  In addition, when using highly rigid resin for the shaft 1, it is preferable to ensure sufficient electroconductivity by adding and disperse | distributing a electrically conductive agent in 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. Moreover, the compounding quantity of these electrically conductive agents is although it does not restrict | limit in particular, The range of 5-40 mass% is preferable with respect to the whole highly rigid resin composition, and the range of 5-20 mass% is more preferable.

  The outer diameter of the shaft 1 is preferably 5 to 20 mm, particularly 5 to 10 mm. In addition, when a resin material is used for the shaft 1, there is an advantage that an increase in the mass of the shaft 1 can be suppressed even if the outer diameter of the shaft 1 is increased.

In the developing roller of the present invention, the resistance value under conditions of a temperature of 10 ° C. and a humidity of 15% RH is 10 ⁴ to 10 ⁸ Ω, particularly 10 ⁵ to 10 ⁸ Ω, more preferably 10 ⁵ to 10 ⁷ Ω. It is preferable. Thereby, it is possible to improve the print image quality in a low temperature and low humidity environment.

  The developing roller of the present invention preferably comprises the elastic layer 2, the intermediate layer 3 and the surface layer 4 on the outer periphery of the shaft 1 using the elastic layer forming composition, the intermediate layer forming composition and the surface layer forming composition. Can be manufactured in sequence. Specifically, first, the elastic layer 2 is formed by applying the elastic layer forming composition to the outer periphery of the shaft 1 and then curing it by irradiating with UV light. Next, the intermediate layer 3 is formed by applying the intermediate layer forming composition to the outer periphery of the formed elastic layer 2 and then curing it by irradiating with UV light. Furthermore, after applying the surface layer forming composition to the outer periphery of the formed intermediate layer 3, the surface layer 4 is formed by irradiating and curing the UV light to obtain a suitable developing roller of the present invention. Can do. In the developing roller of the present invention, the elastic layer 2, in particular, the entire layer composed of the intermediate layer 3 and the surface layer 4 can be formed using a UV curable resin, so that a large amount of heat energy is required for production. The roller can be manufactured in a short time. In addition, since a curing furnace or the like is not required for forming each layer, a large amount of equipment costs are not required.

  In the present invention, examples of the method for applying the composition for forming each layer to the outer periphery of a shaft and the like include a spray method, a roll coater method, a dipping method, a die coating method, and the like. By using the die coating method, each layer can be applied quickly and reliably, and the working efficiency during roller production can be greatly improved.

  In the present invention, the UV light source used for curing each layer is not particularly limited, and examples thereof include a mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, and a xenon lamp. In particular, as a UV light source used for curing the intermediate layer, a non-powered UV lamp manufactured by Fusion UV Systems is suitable because it has a light emission wavelength of 254 nm center to 365 nm center and a strong light quantity. Among these, an H valve or a D valve can be preferably used. When a general mercury-filled UV lamp is used, the low-pressure mercury lamp has an emission wavelength of only up to about 254 nm, and is not suitable for curing the intermediate layer. Therefore, it is preferable to use a high-pressure mercury lamp having an emission wavelength up to about 365 nm for curing the intermediate layer. In addition, irradiation conditions such as irradiation intensity and integrated light amount upon UV light irradiation can be appropriately selected according to the components, composition, coating amount, and the like included in the composition for forming each layer, and are not particularly limited.

Hereinafter, the present invention will be described in more detail with reference to examples.
The elastic layer materials shown in Tables 3 to 8 below were kneaded with a planetary mixer at 60 rpm for 1 hour to prepare an elastic layer forming composition. The obtained elastic layer forming composition was traverse-coated with a roll coater on the outer periphery of a shaft (outer diameter: 13 mm, material: aluminum). While rotating the coated shaft, the coated shaft was irradiated with UV light for 5 seconds using a non-powered UV lamp H bulb manufactured by Fusion UV Systems, and an elastic layer having a thickness of 1.5 mm was formed. Formed.

  Next, according to the intermediate | middle layer mixing | blending shown in the following table | surface, it carried out similarly to the above, and prepared the composition for intermediate | middle layer formation. The obtained intermediate layer forming composition was traverse-coated with a roll coater on the outer periphery of the shaft on which the elastic layer was formed. While rotating the coated shaft, the coated shaft was irradiated with UV light for 5 seconds using a non-powered UV lamp H bulb manufactured by Fusion UV Systems to form an intermediate layer having a thickness of 3 μm. .

  Next, a composition for forming a surface layer was prepared in the same manner as described above in accordance with the surface layer composition shown in the following table. The obtained surface layer-forming composition was traverse-coated with a roll coater on the outer periphery of the shaft on which the elastic layer and the intermediate layer were formed. While rotating the coated shaft, the coated shaft was irradiated with UV light for 5 seconds using a non-powered UV lamp H bulb manufactured by Fusion UV Systems to form a surface layer having a thickness of 2 μm. The developing roller of each Example and Comparative Example was obtained.

<Surface potential after 0.4 seconds in high temperature and high humidity (HH) environment>
With respect to the obtained developing rollers of the examples and comparative examples, using a measuring apparatus shown in FIG. 3, the corona of 8 kV from a position 1 mm away under a high temperature and high humidity condition of temperature 32.5 ° C. and humidity 80% RH. The surface potential after 0.4 seconds when the surface was charged by corona discharge from the discharger 21 was measured by the surface potential meter probe 22.

<Evaluation of fogging in high temperature and high humidity (HH) environment>
About the developing roller of each obtained Example and Comparative Example, a commercially available printing machine (manufactured by Brother Co., Ltd., HL-4040CN) was installed under high temperature and high humidity conditions of a temperature of 32.5 ° C. and a humidity of 80% RH, 3000 sheets of 1% density were printed to check for fog. As a result, it was determined that the toner was printed on a white background portion, and was defective (X) if it was visible.

<Resistance value in low temperature and low humidity (LL) environment>
With respect to the obtained developing rollers of Examples and Comparative Examples, the resistance values were measured under conditions of a temperature of 10 ° C. and a humidity of 15% RH.

<Evaluation of print quality in low temperature and low humidity (LL) environment>
For the developing rollers of each of the Examples and Comparative Examples obtained, a commercially available printing machine (manufactured by Brother Co., Ltd., HL-4040CN) was installed under a low temperature and low humidity condition of a temperature of 10 ° C. and a humidity of 15% RH. After performing density printing of 1000 sheets, after leaving overnight, a 100% density black image was printed, and the transmission density was measured, which was used as a reference for printing image quality. The result was x when the transmission density was 1.85 or less, Δ when the transmission density was more than 1.85 and less than 1.90, and ◯ when the transmission density was 1.90 or more. X-Rite 310T manufactured by Sakata Inx Engineering Co., Ltd. was used for measurement of the transmission density.

  The above results are also shown in the following table.

＊１）ウレタンアクリレートオリゴマー：ＮＸ４４−３１（亜細亜工業（株）製）
＊２）アクリルモノマー：ＨＯＡ（共栄社化学（株）製）
＊３）リチウムイミドのアクリルモノマー溶液：サンコノールＭＴＧＡ−５０Ｒ（三光化学工業（株）製）
＊４）過塩素酸ナトリウム：ＭＰ−１００（昭和化学工業（株）製）
＊５）４級アンモニウム過塩素酸塩：ＫＳ５５５（花王（株）製）
＊６）４級アンモニウム硫酸アルキル塩：ＫＳ４８（花王（株）製）
＊７）ホウ酸塩：ＰＥＬ４６（日本カーリット（株）製）
＊８）４級アンモニウムエチル硫酸塩：エレガン２６４ＷＡＸ（日油（株）製）
＊９）光重合開始剤：ＩＲＧＡＣＵＲＥ１８４（ＢＡＳＦジャパン（株）製）

* 1) Urethane acrylate oligomer: NX44-31 (Asia Kogyo Co., Ltd.)
* 2) Acrylic monomer: HOA (manufactured by Kyoeisha Chemical Co., Ltd.)
* 3) Acrylic monomer solution of lithium imide: Sanconol MTGA-50R (manufactured by Sanko Chemical Co., Ltd.)
* 4) Sodium perchlorate: MP-100 (manufactured by Showa Chemical Industry Co., Ltd.)
* 5) Quaternary ammonium perchlorate: KS555 (manufactured by Kao Corporation)
* 6) Quaternary ammonium sulfate alkyl salt: KS48 (manufactured by Kao Corporation)
* 7) Borate: PEL46 (manufactured by Nippon Carlit Co., Ltd.)
* 8) Quaternary ammonium ethyl sulfate: Elegan 264WAX (manufactured by NOF Corporation)
* 9) Photopolymerization initiator: IRGACURE184 (manufactured by BASF Japan Ltd.)

  As shown in the above table, in Examples 1 to 3 where the surface potential in the HH environment is high and the resistance in the LL environment is low, there is no occurrence of fogging in the HH environment, and the LL environment Good results are also obtained for the print quality below. On the other hand, in Comparative Example 1, since no ionic conductive agent is added, the surface potential in the HH environment is high, but the resistance in the LL environment is too high, resulting in poor print image quality. . Further, in Comparative Example 2, since the amount of the ionic conductive agent added is too large, the surface potential in the HH environment becomes too low and fogging occurs. It was confirmed that the sodium perchlorate used in Examples 4 to 7 was effective in maintaining the surface potential, and the resistance value could be adjusted to an appropriate range. Defects such as pipe rusting occur.

  In Examples 8 and 9, quaternary ammonium perchlorate sodium salt is used as the ionic conductive agent, but quaternary ammonium perchlorate sodium salt has a poor resistance-reducing effect, so the addition amount is increased to some extent. Otherwise, the image quality under the LL environment will not improve. On the other hand, the sodium perchlorate salt of quaternary ammonium has a high charge transport capability. Therefore, when the amount added is excessive as in Comparative Example 4, fogging occurs in an HH environment.

  In Examples 10 to 12, quaternary ammonium diethyl sulfate is used as the ionic conductive agent. However, since quaternary ammonium diethyl sulfate has a poor resistance reduction effect, the image quality in the LL environment must be increased to some extent. Does not improve. On the other hand, since quaternary ammonium diethyl sulfate has a high charge transport capability, fogging occurs in an HH environment when the amount added is excessive as in Comparative Example 5.

  In Examples 13 to 15, borate is used as the ionic conductive agent, but borate has a poor resistance reduction effect, so the image quality in the LL environment is not improved unless the addition amount is increased to some extent. On the other hand, since borate has a high charge transport capability, fogging occurs in an HH environment when the addition amount is excessive as in Comparative Example 6.

  In Examples 16 to 18, quaternary ammonium ethyl sulfate was used as the ionic conductive agent. In this case, although fog was not generated, quaternary ammonium ethyl sulfate was not effective in reducing resistance. Even if the amount was increased, the image quality under the LL environment was not improved.

  As described above, by maintaining a high surface potential after charging in the HH environment in the developing roller, it is possible to prevent the occurrence of fogging in the HH environment, and to reduce the resistance in the LL environment. It was confirmed that by setting the value to a predetermined low value, good results can be obtained for the print image quality under the LL environment.

DESCRIPTION OF SYMBOLS 1 Shaft 2 Elastic layer 3 Intermediate | middle layer 4 Surface layer 10 Developing roller 11 Toner supply roller 12 Photosensitive drum 13 Toner 14 Layering blade 15 Transfer part 16 Cleaning part 17 Cleaning blade 21 Corona discharger 22 Surface potential meter probe

Claims (4)

In an elastic roller having at least an elastic layer on the outer periphery of the shaft,
When the elastic layer contains an ultraviolet curable resin and an ionic conductive agent, and the surface is charged by 8 kV corona discharge from a position 1 mm away under conditions of a temperature of 32.5 ° C. and a humidity of 80% RH. The developing roller having a surface potential of 25 V or more after 0.4 seconds. The developing roller according to claim 1, wherein the resistance value is 10 ⁴ to 10 ⁸ Ω under conditions of a temperature of 10 ° C. and humidity of 15% RH.   An intermediate layer and a surface layer are laminated on the elastic layer, and the surface layer is a urethane (meth) acrylate obtained by reacting a polybutadiene polyol or hydrogenated polybutadiene polyol, a polyisocyanate, and a (meth) acrylate having a hydroxyl group. The developing roller according to claim 1 or 2, which contains an oligomer. An intermediate layer and a surface layer are laminated on the elastic layer, and the intermediate layer contains 1 part by mass or more of carbon black with respect to 100 parts by mass of the ultraviolet curable resin, and further has an extinction coefficient of 2 × 10 2 at 254 nm. ^The photopolymerization initiator having ⁴ ml / g · cm or more and a photopolymerization initiator having an extinction coefficient at 365 nm of 4 × 10 ² ml / g · cm or more. The developing roller as described.

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