JP5124131B2 - Conductive rubber roller - Google Patents

Description

  The present invention relates to a conductive rubber roller suitably used for an image forming apparatus such as an electrophotographic copying machine, a FAX, and a printer. More specifically, the present invention relates to a photoconductor and transfer of the above image forming apparatus. The present invention relates to a conductive rubber roller used in contact with a belt or the like.

  Conventionally, in a conductive rubber roller used in an image forming apparatus such as an electrophotographic system, a method of imparting electronic conductivity by incorporating carbon black has been used. However, it is very difficult to uniformly disperse carbon black in the polymer, and the manufacturing stability is such that the electrical resistance value of the conductive rubber roller changes greatly due to a slight deviation in the blending amount of carbon black. There is a problem of lacking. There is also a problem that the difference in electrical resistance value between when a low voltage is applied and when a high voltage is applied, that is, the voltage dependency of the electrical resistance value is large.

  In contrast to the above electronic conductivity type materials, ion conductivity type materials that obtain conductivity by using ion conductive substances can be dispersed relatively easily and uniformly in polymers. This is advantageous in that the fluctuation of the electric resistance value due to the deviation is small and the voltage dependency of the electric resistance value is low.

  As a conductive rubber roller using an ion conductive material, for example, a conductive rubber roller using an epichlorohydrin rubber having ion conductivity as a polymer has been proposed.

  Patent Document 1 proposes a conductive rubber roller having an elastic layer made of a rubber composition containing epichlorohydrin rubber and a polyether polyol having a weight average molecular weight (Mw) of 3000 to 10,000.

  Patent Document 2 discloses a rubber composition containing 50 to 85 parts by mass of acrylonitrile butadiene rubber having an acrylonitrile content of 10 to 20% by mass as a rubber component and 15 to 50 parts by mass of epichlorohydrin rubber occupying 50 mol% or more of ethylene oxide. And a conductive roll provided with a conductive foam having a maximum cell diameter of 200 μm or less, a minimum cell diameter of 10 μm or more, and a Shore E hardness of 20 to 50 has been proposed.

  However, when using epichlorohydrin rubber or blended rubber of epichlorohydrin rubber with other rubber, chlorine contained in the epichlorohydrin rubber deteriorates the stainless steel used as the support shaft, or harmful gas when incinerated after using the roller. There is a problem such as generating a load on the environment.

Accordingly, attention has been paid to conductive rubber rollers using a polymer containing no chlorine.
Patent Document 3 discloses an anion having a rubber component containing a mixture of an ethylene-propylene-diene copolymer and acrylonitrile butadiene rubber as a main component, and having a fluoro group and a sulfonyl group with respect to 100 parts by mass of the rubber component. A conductive layer containing a foamed layer foamed using a chemical foaming agent, the compression set of the foamed layer being 30% or less. Foam rolls have been proposed.

  In Patent Document 4, as a conductive elastic layer composed of a continuous phase and a discontinuous phase, an ionic conductive agent is added in an amount of 1 to 20 only in a discontinuous phase composed of an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer. The content of the polymer constituting the continuous phase is 60 parts by weight or more and less than 80 parts by weight with respect to a total of 100 parts by weight of the polymer constituting the continuous phase and the discontinuous phase. In addition, a conductive roll provided with a conductive elastic layer in which the content of the ethylene oxide-propylene oxide-allyl glycidyl ether copolymer containing a conductive agent is 1 part by mass or more and 25 parts by mass or less is proposed. ing.

However, when the resistance of the conductive rubber roller is reduced only with the ion conductive material, the electrical resistance can be reduced, but the contamination resistance, which is an important characteristic of the conductive rubber roller, is deteriorated. There are problems such as. That is, with the above technique, it is difficult to obtain a conductive rubber roller that satisfies the overall balance of performance.
JP 2006-39394 A JP 2006-259131 A JP 2004-170814 A JP 2006-105374 A

  The present invention has been made in view of the above problems, and is a conductive roller used for an image forming apparatus, for example, and maintains a low electric resistance value even when a polymer containing chlorine is not used. Both the voltage dependency of the electrical resistance value and the environmental dependency due to fluctuations in the usage environment are low, and it has good electrical characteristics due to the suppression of the increase in energization during continuous energization. It is an object of the present invention to provide a conductive rubber roller that does not contaminate parts (for example, a photoreceptor).

  More specifically, an object of the present invention is to provide a conductive rubber roller that can be suitably used as a developing roll, a charging roll, a transfer roll, and the like that are disposed in contact with a photoreceptor and a transfer belt.

The conductive rubber roller of the present invention has a conductive rubber layer, 1 to 20 mass of a polyalkylene oxide component comprising 100 parts by mass of a polymer component, and an alkali metal salt and / or alkaline earth metal salt and a polyalkylene oxide. Part and a conductive rubber composition containing 1 to 20 parts by mass of silica having a BET specific surface area of 170 m ² / g or more are used for the conductive rubber layer.

  In the conductive rubber roller of the present invention, the water absorption rate of silica is preferably in the range of 0.3 to 1.0% by mass.

  In the conductive rubber roller of the present invention, the polymer component is preferably at least one selected from diene rubber and non-diene rubber.

  In the conductive rubber roller of the present invention, the polymer component is composed of a diene rubber component and a non-diene rubber component, and the ratio of the diene rubber component to the polymer component is in the range of 60 to 90% by mass. preferable.

  In the conductive rubber roller of the present invention, the Asker C hardness of the conductive rubber composition is preferably in the range of 15 to 70 °.

  In the conductive rubber roller of the present invention, the conductive rubber composition further includes a foaming agent in the range of 1 to 5 parts by mass with respect to 100 parts by mass of the polymer component, and the conductive rubber composition constitutes the conductive rubber. The Asker C hardness of the layer is preferably 70 ° or less.

  In the conductive rubber roller of the present invention, the content of alkali metal salt and / or alkaline earth metal salt in the polyalkylene oxide component is preferably in the range of 1 to 20% by mass.

  The conductive rubber roller of the present invention includes a support shaft and a single-layer or multiple-layer rubber layer formed on the outer periphery of the support shaft, and at least one of the rubber layers is any of the conductive rubber layers described above. It is preferable that

  According to the present invention, for example, for an image forming apparatus, a low electric resistance value is maintained even when a chlorine-containing polymer is not used, and the voltage dependency of the electric resistance value and the environmental dependency due to the change in the use environment. Both have low electrical currents and suppress the increase in energization during continuous energization, etc., and have excellent electrical characteristics. Furthermore, the overall performance does not contaminate contact parts (such as photoconductors) in the image forming apparatus. A satisfactory conductive rubber roller can be obtained.

The conductive rubber roller of the present invention has a conductive rubber layer, 1 to 20 mass of a polyalkylene oxide component comprising 100 parts by mass of a polymer component, and an alkali metal salt and / or alkaline earth metal salt and a polyalkylene oxide. Conductive rubber composition containing 1 part by mass and 1-20 parts by mass of silica having a BET specific surface area of 170 m ² / g or more is used for the conductive rubber layer.

  The polyalkylene oxide component used in the present invention has good ionic conductivity. The polyalkylene oxide itself also has ionic conductivity due to the alkylene oxide structure, but further excellent ionic conductivity is imparted by containing an alkali metal salt and / or an alkaline earth metal salt.

The conductive rubber composition used in the present invention contains silica having a BET specific surface area of 170 m ² / g or more. In the present invention, the polyalkylene oxide component as described above is used. However, if the content of the polyalkylene oxide component is too large, the contamination resistance of the conductive rubber roller may be lowered. In the present invention, silica having a controlled specific surface area is used in combination with the polyalkylene oxide component.

  Since the silica used in the present invention has a large specific surface area, it has a hygroscopic property. In addition to the effect of increasing the dissociation degree of alkali metal salt and / or alkaline earth metal salt by moisture absorption of silica, addition of silica has the effect of forming a channel of dissociated ions in the polyalkylene oxide component. can get. Due to these effects, the silica used in the present invention is considered to be excellent in the conductivity improving action of the conductive rubber composition.

  That is, in the conductive rubber composition used in the present invention, good ionic conductivity can be ensured even if the content of the polyalkylene oxide component is relatively small. It is possible to achieve both the stain resistance of the conductive rubber roller and the high ion conductivity. Therefore, according to the present invention, a low electrical resistance value is maintained even when a chlorine-containing polymer is not used, and the voltage dependency of the electrical resistance value and the environmental dependency due to changes in the usage environment are both low during continuous energization. A conductive rubber roller that has good electrical characteristics due to the suppression of the increase in energization of the toner and that does not contaminate contact parts (eg, a photoreceptor) in the image forming apparatus and that satisfies the overall performance is obtained. be able to.

[Polyalkylene oxide component]
In the conductive rubber composition used in the present invention, the content of the polyalkylene oxide component is in the range of 1 to 20 parts by mass with respect to 100 parts by mass of the polymer component. When the content of the polyalkylene oxide component is less than 1 part by mass, the conductive rubber roller cannot be provided with desired ionic conductivity, and the electrical resistance value becomes high. On the other hand, if the content exceeds 20 parts by mass, the contamination resistance of the conductive rubber roller is impaired due to the bleeding out of the polyalkylene oxide component. The content of the polyalkylene oxide component is more preferably 5 parts by mass or more, and more preferably 15 parts by mass or less.

  The content of the alkali metal salt and / or alkaline earth metal salt in the polyalkylene oxide component is preferably in the range of 1 to 20% by mass. When the content is 1% by mass or more, particularly good ionic conductivity is imparted. When the content exceeds 20% by mass, a remarkable improvement in the effect of lowering resistance cannot be expected even if the content is increased, but the tendency to decrease the stain resistance appears. Therefore, when the content is 20% by mass or less, it is preferable in terms of contamination resistance and cost. The content is more preferably 5% by mass or more, and more preferably 15% by mass or less.

<Polyalkylene oxide>
Examples of the polyalkylene oxide contained in the polyalkylene oxide component include polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide random copolymer, epoxy (iso) butane, epoxy hexane, epoxy heptane, epoxy nonane, epoxy octane, An epoxy decane etc. can be illustrated. These are preferable in that they are excellent in balance between ion conductivity and suppression of hygroscopicity.

<Alkali metal salt and / or alkaline earth metal salt>
The alkali metal salt and the alkaline earth metal salt are composed of an alkali metal or alkaline earth metal cation (cation) and an anion (anion) dissociable from the cation. Examples of the cation include lithium ion (Li ⁺ ), sodium ion (Na ⁺ ), potassium ion (K ⁺ ), magnesium ion (Mg ⁺ ), calcium ion (Ca ⁺ ), and the like. The anions include ClO ₄ ⁻ , SCN ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₃ ) ₃ C ⁻ , BF ₄ ⁻ , F ⁻ , Cl ⁻ and Br. ^-, I ^- the like can be exemplified.

  By combining one or more of the above cations and one or more of the above anions, an alkali metal salt or alkaline earth metal salt preferably used in the present invention can be formed.

Especially, it is more preferable that a cation is at least any selected from a lithium ion, a sodium ion, and a potassium ion at the point which shows a high dissociation degree and electroconductivity. Examples of more preferable metal salts include LiClO ₄ , NaClO ₄ , KClO ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC (CF ₃ SO ₃ ) ₃ , KSCN, and NaSCN.

[silica]
The BET specific surface area of the silica used in the present invention is 170 m ² / g or more. When the BET specific surface area is less than 170 m ² / g, the effect of increasing the degree of dissociation of the alkali metal salt and / or alkaline earth metal salt is not sufficiently exhibited, and the effect of improving the ionic conductivity of the conductive rubber composition is desired. Can not get the degree of. The BET specific surface area of silica is more preferably 190 m ² / g or more.

In the conductive rubber composition, the content of silica having a BET specific surface area of 170 m ² / g or more is in the range of 1 to 20 parts by mass with respect to 100 parts by mass of the polymer component. When the content is less than 1 part by mass, the effect of improving the ionic conductivity cannot be exhibited to a desired extent. On the other hand, when the content exceeds 20 parts by mass, the change in the electrical resistance value due to the change in the usage environment of the conductive rubber roller, that is, the environmental dependency of the electrical resistance value increases, which is not suitable for use. The content is more preferably 5 parts by mass or more, and more preferably 15 parts by mass or less.

  The water absorption rate of the silica used in the present invention is preferably in the range of 0.3 to 1.0% by mass. When the water absorption is 0.3% by mass or more, the effect of improving the ionic conductivity is good, and when it is 1.0% by mass or less, it is preferable in that the environmental dependency of the electrical resistance value can be kept low.

The water absorption rate is the mass after drying at 120 ° C. for 4 hours as the initial mass, and after drying, the mass after standing for 12 hours in an environment of temperature 28 ° C. and humidity 85% is the mass after standing. As
Water absorption (%) = [{(mass after standing) − (initial mass)} / (initial mass)] × 100
Is the value obtained according to

  Specific examples of the silica used in the present invention include “Nip Seal VN3” manufactured by Tosoh Silica Co., Ltd., DSL. Examples thereof include “CARPLEX # 67” and “CARPLEX # 70” manufactured by Japan Corporation.

[Polymer component]
As the polymer component, diene rubber, non-diene rubber and the like can be used. Specific examples of the diene rubber include natural rubber, isoprene rubber, butadiene rubber, acrylonitrile-butadiene rubber, and styrene-butadiene rubber. Examples of non-diene rubbers include ethylene propylene rubber, butyl rubber, urethane rubber, silicone rubber, and acrylic rubber. These can be used alone or in combination of two or more.

  The polymer component of the present invention preferably contains no halogen such as chlorine. Since the conductive rubber composition used in the present invention has excellent ionic conductivity, the conductive rubber roller can be provided with excellent conductivity even when the polymer component does not contain halogen. When the polymer component does not contain halogen, it is possible to remarkably reduce the environmental load at the time of disposal after use of the roller and deterioration of peripheral members such as the support shaft of the conductive rubber roller.

  The polymer component is preferably composed of a diene rubber component and a non-diene rubber component. In this case, good physical properties can be obtained for the conductive rubber roller, and deterioration with respect to ozone and environmental dependency of the electric resistance value can be reduced. In this case, the proportion of the diene rubber component in the polymer component is preferably in the range of 60 to 90% by mass. When the proportion is 60% by mass or more, it is preferable in that good mechanical properties such as compression set, rebound resilience, and elongation can be obtained. When the proportion is 90% by mass or less, a non-diene rubber component Can be contained in an amount of 10% by mass or more, so that the effect of reducing deterioration of the conductive roller with respect to ozone can be obtained. The ratio is more preferably 70% by mass or more, and more preferably 80% by mass or less.

  On the other hand, in the case where deterioration due to ozone is not a problem when using a conductive roller, a polymer component composed of at least one selected from diene rubber and non-diene rubber may be used. In this case, good mechanical properties such as compression set, impact resilience, and elongation can be obtained.

  In the conductive rubber roller of the present invention, the polymer component particularly preferably contains acrylonitrile-butadiene rubber. Acrylonitrile-butadiene rubber is advantageous in that it exhibits ionic conductivity among polymers not containing chlorine.

  In the conductive rubber roller of the present invention, the Asker C hardness of the conductive rubber composition is preferably in the range of 15 to 70 °. When the Asker C hardness is 15 ° or more, the compression set and durability of the conductive rubber roller are good. When the Asker C hardness is 70 ° or less, the flexibility of the conductive rubber roller is not impaired, and the paper feedability and stable conductivity are improved. Roller performance such as a wide nip width for imparting good properties can be maintained satisfactorily.

  In addition, said Asker C hardness is the value which selected and measured Asker C hardness in order to show 20 points or less in the measurement by Asker A based on JISK6253.

  In addition to the above, the conductive rubber composition used in the present invention may contain a known rubber compounding agent such as a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a softening agent, and a filler as necessary. May be contained.

  Examples of the vulcanizing agent include sulfur and sulfur-based organic compounds such as sulfur, tetraalkyltyramium-disulfide, morpholine-disulfide, and alkyl-phenol-disulfide, metal compounds such as magnesium oxide, 1,1-disulfide. (T-hexylperoxy) cyclohexane, 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-butylperoxy) -2-methylcyclohexane, n -Peroxyketals such as butyl, 4,4-di (t-methylperoxy) valerate, 1,1-di (t-butylperoxy) cyclohexane, dicumyl peroxide, di (2-t-butylper) Oxopropyl) benzene, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di (t-butyl) -Oxy) hexane, dialkyl peroxides such as 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, di (3-t-methylbenzoyl) peroxide, di (4-t-methyl) Diacyl peroxides such as benzoyl) peroxide, peroxyesters such as 2,5-dimethyl-2,5-di (benzoylperoxy) -hexane, t-hexylperoxybenzoate, t-butylperoxybenzoate, etc. However, sulfur or a sulfur-based organic compound is preferable in that it is inexpensive and easily available, has a sufficiently large vulcanization effect, and has excellent wear resistance on the rubber surface. These vulcanizing agents may be used alone or in combination of two or more.

  As the vulcanization accelerator, a commonly used vulcanization accelerator can be appropriately blended. For example, dibenzothiazoyl disulfide (DM), 2-mercaptobenzothiazole (D), 2-mercaptobenzothiazole zinc salt (MZ ), Thiazoles such as diisopropyl sulfenamide (DIBS), cyclohexyl sulfenamide (CZ), tetramethyltyrium disulfide (TT), tetraethyltylium disulfide (TET), di Thiraum such as pentamethylene tyrium-tetrasulfide (TRA), dithioacid salts such as dimethyldithiocarbamate zinc salt (PZ), diethyldithiocarbamate zinc salt (EZ), other guanidines, thioureas, aldehyde ammonia salts, xanthates There is kind. These vulcanization accelerators may be used alone or in combination of two or more.

  As the anti-aging agent, for example, a known anti-aging agent can be appropriately blended, and phenyl-α-naphthylamine, N, N′-di-β-naphthyl-p-phenylenediamine, N-phenyl-N′-isopropyl, for example. Examples include amines such as -p-phenylenediamine, phenols such as di-tert-butyl-p-cresol and styrenated phenol, and imidazoles such as 2-mercaptobenzimidazole.

  As the softener, for example, a known softener can be appropriately blended, and mineral oil, vegetable oil, synthetic softener and the like can be used. As mineral oils, paraffinic mineral oils in which the number of paraffin chain carbon accounts for 50% or more of the total carbon, naphthenic mineral oils in which the number of naphthenic ring carbons accounts for 30 to 45% of the total carbon, and the total number of aromatic carbons Aromatic mineral oils that occupy 35% or more of carbon. Examples of vegetable oils include fatty oil-based softeners, pine tar oil, tall oil, factis and the like. Examples of synthetic softeners include aliphatic dibasic acid ester-based, ether-based, polyester-based softeners.

As the filler, for example, a known filler can be appropriately blended, and carbon black, calcium carbonate, magnesium carbonate, clay, cork, talc, zeolite, alumina, mica, graphite, aluminum hydroxide, barium sulfate, aluminum sulfate , Dibasic phosphite, wood chips, glass powder, ceramic powder and the like. In addition to the silica blended in the present invention, a silica having a BET specific surface area of less than 170 m ² / g may be used in combination. These fillers may be used alone or in combination of two or more.

  In addition, known plasticizers and processing aids can be added and mixed. Examples of processing aids include fatty acids such as stearic acid and oleic acid, metal oxides such as zinc white, and the like.

  The conductive rubber layer formed in the present invention may be a solid rubber layer made of hard rubber or a sponge rubber layer made of foamed rubber, and is applied to an image forming apparatus to which the conductive rubber roller of the present invention is applied. What is necessary is just to select suitably according to the desired performance.

  The foamed rubber can be formed by adding a foaming agent and, if necessary, a foaming aid during preparation of the conductive rubber composition, and preferably vulcanizing and molding under sealed conditions.

  For example, a chemical foaming agent is preferably used as the foaming agent, and the chemical foaming agent is classified into an organic type and an inorganic type. Organic foaming agents include azo compounds such as azodicarbonamide (ADCA), azobisisobutyronitrile (AIBN), barium azodicarboxylate (Ba / AC), N, N′-dinitrosopentamethylenetetra Nitroso compounds such as amine (DPT), hydrazine derivatives such as benzenesulfonyl hydrazide (BSH), 4,4 oxybis (benzenesulfonyl hydrazide) (OBSH), toluenesulfonyl hydrazide (TSH), hydrazodicarbonamide (HDCA) can be used. . As an inorganic foaming agent, sodium bicarbonate (sodium bicarbonate), ammonium bicarbonate, ammonium carbonate, sodium bicarbonate and the like can be used. These foaming agents may be used alone or in combination of two or more.

  Of these, azodicarbonamide (ADCA), 4,4 oxybis (benzenesulfonylhydrazide) (OBSH), and N, N′-dinitrosopentamethylenetetraamine (DPT) are particularly preferable.

  It is preferable that the compounding quantity of a foaming agent shall be in the range of 1-5 mass parts with respect to 100 mass parts of a polymer component. When the blending amount is 1 part by mass or more, good foaming is possible. On the other hand, when the blending amount is 5 parts by mass or less, problems such as deterioration in workability due to insufficient vulcanization due to vulcanization inhibition and increase in environmental dependency of electrical resistance value are unlikely to occur. The blending amount of the foaming agent is more preferably 2 parts by mass or more, and more preferably 4 parts by mass or less.

  As the foaming aid, for example, urea-based aids can be used in addition to organic acid-based aids such as salicylic acid.

  In the present invention, when a conductive rubber layer comprising a conductive rubber composition containing a foaming agent, that is, a sponge rubber layer is formed, the Asker C hardness of the sponge rubber layer may be 70 ° or less. preferable. In this case, the cushioning resistance of the sponge rubber layer is good, and a sufficient nip width can be obtained when a sponge roller is used, so that stable transferability or chargeability can be imparted, and a good image can be obtained. It is done. The Asker C hardness of the sponge rubber layer is more preferably 60 ° or less. On the other hand, if the Asker C hardness of the sponge rubber layer is too low, the compression set of the sponge rubber layer may increase or the durability may decrease. From such a viewpoint, it is preferable that the sponge rubber layer has an Asker C hardness of 15 ° or more, and more preferably 20 ° or more.

  The conductive rubber roller of the present invention includes a support shaft and a single-layer or multiple-layer rubber layer formed on the outer periphery of the support shaft, and at least one of the rubber layers is any of the conductive rubber layers described above. It is preferable that As a result, it is possible to improve the contamination resistance and the manufacturing stability, reduce the voltage dependency and the environment dependency of the electrical resistance value, and reduce the increase in energization.

  1 and 2 are cross-sectional views showing examples of the configuration of the conductive rubber roller according to the present invention. The conductive rubber roller 1 has a configuration in which a conductive rubber layer 12 used in the present invention is formed as a rubber layer on the outer periphery of a support shaft 11. The conductive rubber roller 2 has a configuration in which conductive rubber layers 22 and 23 used in the present invention are formed on the outer periphery of the support shaft 21 as rubber layers. In FIG. 2, the two layers constituting the rubber layer are both conductive rubber layers used in the present invention. For example, instead of the conductive rubber layer 23, a carbon conductive layer is used. It may be formed.

  Moreover, you may form the resin layer which consists of a fluororesin, a silicone resin, a urethane resin, an acrylic resin etc. on the outer side of a rubber layer, for example. In this case, the frictional resistance and adhesive force on the surface of the conductive rubber roller are reduced, and the toner releasability and cleaning properties are improved.

  Moreover, it is preferable that the electrical resistance values of the resin layer and the rubber layer are as close as possible. In this case, the variation of the electric resistance value when the thickness of the resin layer is changed is small, which is convenient in manufacturing process management.

  In the present invention, a surface treatment that reduces the frictional resistance and adhesive force by carbonizing the surface of the conductive rubber roller by ultraviolet irradiation or the like is also useful. When such a surface treatment is performed, the frictional resistance and adhesive force against the photoconductor, transfer belt, toner, cleaning plate and the like are reduced, so that paper contamination and contamination from the conductive rubber roller can be prevented.

  In the present invention, a layer other than the conductive rubber layer may be provided as the rubber layer, and even if the conductive rubber layer is formed on a portion that is not the outermost surface of the conductive rubber roller, contamination resistance and production stability are improved. Although the improvement effect and the voltage dependency reduction effect of the electrical resistance value can be obtained, in particular, in order to ensure better contamination resistance, the conductive rubber layer in the present invention is formed on the outermost surface of the conductive rubber roller. Preferably, the resin layer is formed or only the resin layer is formed outside the conductive rubber layer.

  The conductive rubber roller of the present invention can be manufactured, for example, by the following method. In the following, a case where the rubber layer is a single conductive rubber layer and a resin layer is provided on the outer periphery of the rubber layer will be described as an example. First, a conductive rubber layer is formed on the outer periphery of a conductive support shaft. The conductive rubber layer can be manufactured, for example, by the following method.

  That is, the compounding component of the conductive rubber composition is kneaded with a roll, a Banbury mixer, a kneader or the like to prepare a rubber compound, which is extruded into a cylindrical shape. This is, for example, steam vulcanized at 150 ° C. for 50 minutes under a load of 0.4 MPa, and inserted into a cored bar made of stainless steel or the like that serves as a support shaft for the conductive rubber roller. A rubber layer can be obtained. Alternatively, the rubber compound may be covered with a metal core, followed by press vulcanization to form a cylindrical rubber layer, and the rubber surface may be polished. When using an organic peroxide as a vulcanizing agent, it is preferable to perform vulcanization in a state of being sealed from air by sealing.

  The rubber surface can be polished using, for example, a dry polishing machine using a grindstone or the like, a wet polishing machine, or the like. By polishing, a rubber layer having good dimensional accuracy and a uniform surface shape can be formed.

  Although the support shaft and the rubber layer may be bonded, the inner diameter of the rubber layer is set to about 80 to 95% of the outer diameter of the support shaft in order to improve recyclability and reduce manufacturing costs, and use the press-fitting margin. A method of pressing and holding rubber on the support shaft is more preferable. Moreover, when bonding a support shaft and a rubber layer, it is preferable to use a conductive adhesive in order to prevent an increase in electric resistance value.

  Next, on the outer periphery of the rubber layer, a resin such as fluorine resin, silicone resin, urethane resin, acrylic resin, spray coating, electrostatic coating, dipping coating or the like, or tube so as to have a predetermined dry thickness The resin formed into a shape is formed by, for example, a method of covering the rubber layer, and dried at an ambient temperature of 150 ° C. for 1 hour, for example, to form a resin layer. The conductive rubber roller of the present invention can be manufactured by the above method.

[Example]
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
60 parts by mass of acrylonitrile-butadiene rubber, 40 parts by mass of ethylene-propylene rubber, and 15 parts by mass of a polyalkylene oxide component containing an alkali metal salt are masticated with an open roller, and 1 part by mass of stearic acid, 5 parts by mass of zinc white, 10 parts by mass of carbon black, 5 parts by mass of silica with a surface area of 195 m ² / g, 10 parts by mass of naphthenic oil as a softening agent, 1 part by mass of sulfur as a vulcanizing agent, vulcanization acceleration 2 parts by mass of the agent 1 and 1.5 parts by mass of the vulcanization accelerator 2 were put in order into an open roller and kneaded to obtain a rubber compound.

  This rubber compound is extruded into a cylindrical shape, vulcanized in a steam vulcanizer at a steam pressure of 0.5 Mpa for 1 hour, and then subjected to secondary vulcanization at 160 ° C. for 2 hours in an electric drying furnace. A cylindrical rubber tube was obtained. After cooling the rubber tube, the rubber tube is cut to an appropriate length, inserted into a stainless steel core bar having a diameter of 8 mm, which becomes a support shaft of the conductive rubber roller, and then the rubber surface is polished to a rubber outer diameter of 16 mm by a grindstone grinder. As a result, a conductive rubber roller was obtained.

<Examples 2 to 11 and Comparative Examples 1 to 11>
Conductive rubber rollers were obtained in the same manner as in Example 1 with the formulations shown in Tables 1 to 4 (unit: parts by mass). In Example 11 and Comparative Example 11, 2 parts by mass of the foaming agent was added last when the compounding ingredients were introduced into the open roller.

<Example 12>
A conductive rubber roller having a rubber layer composed of two layers of an inner layer and an outer layer was obtained with the composition shown in Table 5 (unit: part by mass).

  First, in the same manner as in Example 1, an inner layer rubber compound and an outer layer rubber compound were obtained. In the preparation of the rubber compound for the inner layer, 2 parts by mass of the foaming agent was added last when the compounding ingredients were introduced into the open roller.

  Next, the rubber compound for the inner layer and the rubber compound for the outer layer were extruded into a cylindrical shape, vulcanized with a steam vulcanizer at a steam pressure of 0.5 Mpa for 1 hour, and then 160 ° C. with an electric drying furnace. Secondary vulcanization for 2 hours was performed to obtain a cylindrical rubber tube. The rubber tube was cooled and then cut to an appropriate length. The rubber tube for the inner layer was inserted into a stainless steel core bar having a diameter of 8 mm that became a support shaft of the conductive rubber roller, and then the rubber surface was polished to a rubber outer diameter of 16 mm by a grindstone grinder. Subsequently, after pressing the rubber tube for the outer layer, the rubber surface was polished to a diameter of 16.8 mm with a grindstone grinder to obtain a conductive rubber roller on which two rubber layers were formed.

<Performance evaluation>
(Compression set)
This was performed based on JIS K 6262. In the above process, a test piece having a diameter of 18 mm and a height of 12.5 mm obtained by vulcanization at 150 ° C. for 15 minutes was used as a measurement sample. With respect to the measurement sample, compression set was measured under the conditions of compression ratio: 25%, test temperature: 70 ° C., test time: 24 hours.

(Electric resistance value)
FIG. 3 is a schematic diagram for explaining a method of measuring an electric resistance value in Examples and Comparative Examples. As shown in FIG. 3, a conductive rubber roller 32 is brought into contact with a rotating metal roll 31 having a diameter of 30 mm at both ends of 0.5 kg for a total of 1 kg, and a resistance meter 33 (trade name: R8340A, manufactured by Advantest Corp.) is used. The average value of the maximum value and the minimum value of the volume resistance value in the measurement for 10 seconds was defined as the electric resistance value.

Environmental dependency of electrical resistance value The electrical resistance value is LL (temperature 10 ° C, humidity 15%), NN (temperature 22 ° C, humidity 55%), HH (temperature 28 ° C, humidity 85%). Each of the conductive rubber rollers left for 24 hours or longer was measured.

From the measurement results, the following formula:
(Environment dependency index) = (resistance value under LL environment (logΩ)) − (resistance value under HH environment (logΩ))
The environmental dependence index was calculated according to

(Contamination resistance)
The conductive rubber roller produced as described above was left in contact with the photoreceptor for a week in an environment of a temperature of 50 ° C. and a humidity of 90%. Image evaluation was performed using the photoreceptor after being left. “No” if no abnormal image such as color loss due to the contacted portion of the conductive rubber roller is found, and abnormal image such as color loss is recognized only for the first image of the image evaluation and not after the second image Was judged as “bad” when abnormal images such as “slightly bad” and color loss occurred even after the fifth image evaluation.

(Asker C hardness)
In accordance with JIS K 6253, the conductive rubber roller was brought into contact with the Asker C hardness meter at 1 kg, and the hardness after 5 seconds was measured.

Note 1: NBR is nitrile rubber “DN401” manufactured by Nippon Zeon.
Note 2: EPDM is an ethylene-propylene-diene terpolymer "EPT4021" manufactured by Mitsui Chemicals.
Note 3: The polyalkylene oxide component is ethylene oxide-propylene oxide containing 10% by mass of LiCF ₃ SO ₃ .
Note 4: Carbon black is “Asahi Thermal” manufactured by Asahi Carbon.
Note 5: Silica 1 is “Nip Seal VN3” (BET specific surface area: 195 m ² / g) manufactured by Nippon Silica.
Note 6: Silica 2 is “Carplex # 67” (BET specific surface area: 429 m ² / g) manufactured by Degussa Japan.
Note 7: Silica 3 is “Carplex # 80” (BET specific surface area: 193 m ² / g) manufactured by Degussa Japan.
Note 8: Silica 4 is “Nip Seal ER” (BET specific surface area: 90 m ² / g) manufactured by Nippon Silica.
Note 9: Silica 5 is “Carplex # 1120” (BET specific surface area: 109 m ² / g) manufactured by Degussa Japan.
Note 10: Stearic acid is “Fatty Acid SA-200” manufactured by Asahi Denka.
Note 11: Zinc Hana is “Zinc Hana Special, Zodo Chemical” manufactured by Shodo Chemical.
Note 12: Softener is “Sansen 450” manufactured by Nippon San Oil.
Note 13: The release agent is silicon oil “KF96-50” manufactured by Shin-Etsu Chemical Co., Ltd.
Note 14: Sulfur is "Sulfax A" manufactured by Tsurumi Chemical.
Note 15: Vulcanization accelerator 1 is “Accel DM” manufactured by Kawaguchi Chemical.
Note 16: Vulcanization accelerator 2 is “Accel TT” manufactured by Kawaguchi Chemical.
Note 17: The foaming agent is OBSH type foaming agent “Neoselbon # 1000M” manufactured by Eiwa Kasei.
Note 18: Peroxide is dicumyl peroxide.

Table 6 shows specific surface areas and water absorption rates of silicas 1 to 5 used in Examples and Comparative Examples. The water absorption rate of silica is the mass after drying each silica at 120 ° C. for 4 hours as the initial mass, and after drying, the mass after being left in an environment at a temperature of 28 ° C. and a humidity of 85% for 12 hours. As the mass after standing,
Water absorption (%) = [{(mass after standing) − (initial mass)} / (initial mass)] × 100
Sought according to.

FIG. 4 is a diagram showing the results of volume resistance values measured in Examples 1 to 4 and Comparative Examples 1 and 2. In addition, the compounding quantity (phr) in a figure shows the compounding quantity (mass part) with respect to 100 mass parts of polymer components. From the results shown in Table 1 and FIG. 4, when 100 parts by mass of the polymer component is blended with 15 parts by mass of the polyalkylene oxide component, and when silica with a BET specific surface area of 195 m ² / g is blended, the polymer component It can be seen that as the amount of silica added to 100 parts by mass increases, the effect of reducing the volume resistance value is better.

  From the results shown in Table 2, it can be seen that when the silica is not blended, the volume resistance value is reduced as the blending amount of the polyalkylene oxide component is increased, but at the same time the contamination resistance is deteriorated. That is, it can be seen that the contamination resistance cannot be sufficiently secured if an attempt is made to reduce the electric resistance value only with the polyalkylene oxide component without blending silica. Further, in Comparative Example 7 in which only the silica was blended without blending the polyalkylene oxide component, the electrical resistance value was higher than that in Comparative Example 3 in which the polyalkylene oxide component and silica were not blended. It can be seen that when only silica is blended without blending, the electrical resistance value is increased by the silica.

  From the results shown in Table 1 and Table 3, by blending the predetermined polyalkylene oxide component and silica of the present invention, both the effect of reducing the electrical resistance value and ensuring the contamination resistance can be achieved even if the composition of the polymer component is changed. I understand that I can do it.

FIG. 5 is a graph showing the results of volume resistance values measured in Examples 8 to 10 and Comparative Examples 9 and 10. From the results shown in Table 4 and FIG. 5, in Comparative Examples 9 and 10 in which silicas having BET specific surface areas of 90 m ² / g and 109 m ² / g were blended, respectively, the electrical resistance value was compared with Comparative Example 8 in which no silica was blended. Example 8 in which silica having a BET specific surface area of 170 m ² / g or more, specifically, 193 m ² / g, 195 m ² / g, and 429 m ² / g, respectively, was blended. 9 and 10, it can be seen that the effect of reducing the electrical resistance value is remarkably obtained.

  From the results shown in Table 5, in Example 11 in which the polyalkylene oxide component and silica were also blended in the sponge rubber, compared with Comparative Example 11 in which only the polyalkylene oxide component was blended, the effect of reducing the electrical resistance value and resistance It can be seen that the contamination was good. Also in Example 12 in which a rubber layer composed of two layers of sponge rubber and solid rubber was provided, it was possible to ensure good electrical characteristics and contamination resistance by blending the polyalkylene oxide component and silica. I understand.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The conductive rubber roller of the present invention can be suitably applied to an image forming apparatus such as an electrophotographic copying machine, a FAX, or a printer, and more specifically, a photoconductor of the above image forming apparatus, It can be suitably applied as a conductive rubber roller that is used in contact with a transfer belt or the like.

It is sectional drawing which shows the example of a structure of the conductive rubber roller which concerns on this invention. It is sectional drawing which shows the example of a structure of the conductive rubber roller which concerns on this invention. It is a schematic diagram explaining the measuring method of the electrical resistance value in an Example and a comparative example. It is a figure which shows the result of the volume resistance value measured in Examples 1-4 and Comparative Examples 1 and 2. FIG. It is a figure which shows the result of the volume resistance value measured in Examples 8-10 and Comparative Examples 9 and 10.

Explanation of symbols

  1, 2, 32 Conductive rubber roller, 11, 21 Support shaft, 12, 22, 23 Conductive rubber layer, 31 Rotating metal roll, 33 Resistance meter.

Claims (7)

A conductive rubber roller having a conductive rubber layer,
100 parts by mass of a polymer component, 1 to 20 parts by mass of a polyalkylene oxide component comprising an alkali metal salt and / or alkaline earth metal salt and a polyalkylene oxide, and a silica having a BET specific surface area of 170 m ² / g or more and 1 to 20 parts by mass, the conductive rubber composition comprising Ri name used in the conductive rubber layer,
The conductive rubber roller , wherein the polymer component includes at least acrylonitrile-butadiene rubber and ethylene-propylene-diene terpolymer .   The conductive rubber roller according to claim 1, wherein the silica has a water absorption rate within a range of 0.3 to 1.0 mass%. The conductive rubber roller according to claim 1 or 2 , wherein the polymer component has a ratio of the acrylonitrile-butadiene rubber in a range of 60 to 90% by mass. The Asker C hardness of the conductive rubber composition is in the range of 15 to 70 °, the conductive rubber roller according to any one of claims 1-3. The conductive rubber composition further includes a foaming agent in a range of 1 to 5 parts by mass with respect to 100 parts by mass of the polymer component, and the Asker C of the conductive rubber layer that the conductive rubber composition constitutes. The conductive rubber roller according to any one of claims 1 to 4 , which has a hardness of 70 ° or less. The content of the polyalkylene oxide of the alkali metal salt and / or the alkaline earth metal salt in the component is in the range of 1 to 20 mass%, a conductive rubber roller as claimed in any one of claims 1 to 5 . A support shaft, and a rubber layer of a single layer or multiple layer formed on the outer periphery of the support shaft, at least one layer of the rubber layer is the conductive rubber layer, claim 1-6 The conductive rubber roller described in 1.

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