JP2011107652A - Electroconductive rubber member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroconductive rubber member which is reduced in environmental dependence and stable in the electrical resistance value. <P>SOLUTION: The electroconductive rubber member includes: an electroconductive and elastic layer; and a coat layer formed by applying a coating liquid, which contains polyvinyl alcohol and electroconductive fine powder, onto the electroconductive and elastic layer and satisfies ¾LogR<SB>LL</SB>-LogR<SB>HH</SB>¾≤2.0 (wherein R<SB>LL</SB>(Ω) is the electrical resistance value in the LL environment (10°C, 15%RH); R<SB>HH</SB>(Ω) is the electrical resistance value in the HH environment (30°C, 80%RH)) when 100V is applied thereto. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention includes a conductive roll such as a charging roll, a developing roll, a transfer roll, a toner supply roll, and a cleaning roll used in an image forming apparatus such as an electrophotographic copying machine and printer, or a toner jet copying machine and printer, The present invention relates to a conductive rubber member suitable for a cleaning blade, a transfer belt, and the like.

  A conductive roll of an image forming apparatus such as a copying machine or a printer is required to have non-contamination, conductivity, and the like on a photoreceptor. Thus, conventionally, various types of coating layers provided on the surface of various elastic layers have been proposed. However, the conventional coating layer made of resin has the problem that the electrical resistance value is highly dependent on the environment, and the coating layer. Has a problem that it is compatible with the resin on the surface of the photoreceptor and is fixed.

  Therefore, a charging member having a polymer layer containing a specific water-soluble high molecular weight substance on a conductive elastic layer has been proposed (see Patent Document 1). The charging member disclosed in Patent Document 1 is difficult to adhere to the photosensitive member, has low toner contamination, and has a small change in electrical resistance due to environmental fluctuations.

  Although the charging member of Patent Document 1 has a low volume resistivity fluctuation even when it is moved to a low-temperature and low-humidity environment with a temperature of 15 ° C. and a humidity of 10% or an environment of a temperature of 22 ° C. and a humidity of 60%, When shifting from an environment to a high-temperature and high-humidity environment, the volume resistivity sometimes fluctuated greatly. For this reason, the thing with a small fluctuation | variation of volume resistivity is calculated | required also when transfering from a low temperature low humidity environment to a high temperature high humidity environment.

Japanese Patent No. 3056273

  In view of such circumstances, it is an object of the present invention to provide a conductive rubber member having a small environmental dependency and a stable electric resistance value.

A first aspect of the present invention that solves the above problems includes a conductive elastic layer, and a coating layer formed by applying a coating liquid containing polyvinyl alcohol and conductive fine powder on the conductive elastic layer. The electrical resistance value in the LL environment (10 ° C., 15% RH) when 100 V is applied is R _LL (Ω), and the electrical resistance value in the HH environment (30 ° C., 80% RH) is R _HH (Ω). The conductive rubber member satisfies the following formula.

According to a second aspect of the present invention, there is provided the conductive rubber member according to the first aspect, wherein the coat layer has an electric resistance value (Ω) of 1.0 × 10 ⁷ or less. In the member.

  According to a third aspect of the present invention, there is provided the conductive rubber member according to the first or second aspect, wherein the coat layer has a lower electrical resistance value than the conductive elastic layer. It is in.

  According to a fourth aspect of the present invention, in the conductive rubber member according to any one of the first to third aspects, the conductive fine powder is at least one of zinc oxide and carbon black. The conductive rubber member.

  According to a fifth aspect of the present invention, in the conductive rubber member according to any one of the first to fourth aspects, the conductive elastic layer is made of an ion conductive polymer. is there.

  According to a sixth aspect of the present invention, in the conductive rubber member according to the fifth aspect, the conductive elastic layer is made of epichlorohydrin rubber.

  According to a seventh aspect of the present invention, there is provided a conductive rubber roll comprising the conductive rubber member according to any one of the first to sixth aspects.

  According to the present invention, it is possible to provide a conductive rubber member that is less dependent on the environment and has a stable electrical resistance value.

It is a figure which shows the result of the reference test example 1. FIG. It is a figure which shows the result of the reference test example 2. FIG. It is a figure which shows the result of Test Example 1.

The conductive rubber member of the present invention comprises a conductive elastic layer and a coating layer formed by applying a coating liquid containing polyvinyl alcohol and conductive fine powder on the conductive elastic layer. Here, the present invention is based on the knowledge that polyvinyl alcohol has a relatively high hygroscopicity, and the amount of moisture absorption becomes very large under a high temperature and high humidity environment, resulting in a decrease in volume resistivity. By blending fine powder, the effect of conductive mechanism by conductive fine powder is made larger than the effect of change in volume resistivity by moisture absorption, that is, by making the conductive mechanism dependent on conductive fine powder, polyvinyl alcohol greatly absorbs moisture. Even if it does, it will realize what the electrical resistance value does not drop significantly. The conductive rubber member of the present invention has a small environmental dependency and a stable electric resistance value. Thus, the electrical resistance of the LL environment (10 ° C., 15% RH) when 100 V is applied is obtained by blending the conductive fine powder with polyvinyl alcohol and making the conductive mechanism of the coat layer depend on the conductive fine powder. When the value is R _LL (Ω) and the electrical resistance value in the HH environment (30 ° C., 80% RH) is R _HH (Ω), the following equation is satisfied.

  That is, by making the conductive mechanism depend on the conductive fine powder, it is possible to obtain a conductive rubber member having a small environmental dependency that satisfies the above formula. The conductive rubber member satisfying the above formula is generally considered to have a small environmental fluctuation, and can be suitably used in any application. For example, when used as a developing roll of an image forming apparatus, good image formation can be performed.

  The coating layer is formed by applying a coating liquid containing polyvinyl alcohol and conductive fine powder on the conductive elastic layer. The coating solution is composed of an aqueous solution containing polyvinyl alcohol and conductive fine powder. By including polyvinyl alcohol in the coating solution, it is possible to form a coat layer that is difficult to adhere to the photoreceptor and has low toner stainability. By blending a predetermined amount of conductive fine powder, the conductive mechanism of the coat layer is made conductive. It is possible to make it less dependent on the environment by depending on the fine powder. In addition, since polyvinyl alcohol has a high SP value of 12.6, it can effectively bleed plasticizers having a low SP value (for example, paraffinic oil: 6 to 8, dioctyl phthalate: 7.9) and low molecular weight compounds. Can be prevented.

  The conductive fine powder used in the present invention is of a water dispersion type. The water-dispersed type here refers to those that have been subjected to various treatments so as to be dispersed in water, such as those to which a surfactant has been added, those that have been dispersed by stirring blades, ball mills, ultrasonic irradiation, or the like. . Specific examples of the conductive fine powder include metal oxides such as zinc oxide, tin oxide, and indium oxide, carbon black, and carbon nanotube, and these may be used in combination. In particular, zinc oxide and carbon black having a wide variety of particle diameters and sizes affecting dispersibility and conductivity are suitable.

  A method for applying the coating solution is not particularly limited, but a dip coating method, a roll coating method, a spray coating method, a doctor coating method and the like are preferable.

The coat layer preferably has an electric resistance value (Ω) of 1.0 × 10 ⁷ or less. Thereby, the conductive mechanism of the coat layer can be made to depend on the conductive fine powder, and the environment dependency can be reduced. Here, the change of the electrical resistance value with respect to the moisture absorption amount of polyvinyl alcohol will be described.

(Reference Example 1)
Polyvinyl alcohol (PVA) (manufactured by Wako) 3 wt% aqueous solution was prepared, poured into a metal container, and after natural drying at 23 ° C. and 55% RH, water remaining in the coating film was eliminated. By drying at 120 ° C. for 1 hour, a sample of Reference Example 1 consisting of a polyvinyl alcohol film having a size of 10 cm × 10 cm × thickness 10 μm was produced.

(Reference Test Example 1) Electrical Resistance Value Measurement For the sample of Reference Example 1, the humidity was changed at 25 ° C., and the moisture content (wt%) and the electrical resistance value of the sample at each humidity were measured. The moisture content of the sample was determined by measuring with an automatic moisture vaporizer (CA-06; manufactured by Mitsubishi Chemical Analytech Co., Ltd.). Moreover, the electrical resistance value was measured using ULTRA HIGH RESISTANCE METER R8340A (made by Advantest Corporation) according to the double ring electrode method (JIS K6271). In addition, each measurement was performed 3 times and the average value was calculated | required. The applied voltage at this time was DC-100V. The results are shown in Table 1 and FIG.

As shown in FIG. 1, the electrical resistance value of the sample made of polyvinyl alcohol decreases as the water content increases. When the water content increases to some extent, the rate of decrease in the electrical resistance value with respect to the increase in the water content decreases. The change point at which the rate of decrease in the electrical resistance value with respect to the increase in the amount of water was reduced was 1.0 × 10 ⁷ Ω. By blending the conductive fine powder so that the electric resistance value of the coat layer is 1.0 × 10 ⁷ Ω or less, that is, the electric resistance value of the coat layer is 1.0 × 10 ⁷ Ω or less, Dependency can be reduced. When polyvinyl alcohol absorbs moisture, the electrical resistance value decreases, but the electrical resistance value of the coat layer is kept lower by adding conductive fine powder to polyvinyl alcohol, that is, the influence of the conductive mechanism by the conductive fine powder. Is made larger than the influence of the change in the electrical resistance value due to moisture absorption, the change in the electrical resistance value due to the environment can be suppressed.

  The conductive fine powder is preferably blended so as to form a conductive mechanism, and the blending amount of the conductive fine powder varies depending on the type of the conductive fine powder. For example, zinc oxide is preferably blended so that the volume concentration of zinc oxide in the solid content of the coating solution (polyvinyl alcohol and zinc oxide) is 35 vol% or more.

(Reference Example 2)
Polyvinyl alcohol (PVA) (manufactured by Wako) 3 wt% aqueous solution and water-dispersed zinc oxide (pasette GK water dispersion: manufactured by Hux Itec Corp.) 20 wt% aqueous solution are mixed to obtain a solid content (polyvinyl alcohol and zinc oxide). In order to eliminate the water remaining in the coating film after removing the coating liquid having a volume concentration of 3% by volume of zinc oxide in a metal container, pouring it into a metal container, and naturally drying at 23 ° C. and 55% RH. A sample of Reference Example 2 having a size of 10 cm × 10 cm × thickness of 10 μm was produced by drying at a temperature of 1 ° C. for 1 hour.

(Reference Example 3)
A sample of Reference Example 3 was prepared in the same manner as Reference Example 2, except that the coating liquid had a volume concentration of zinc oxide of 10 vol%.

(Reference Example 4)
A sample of Reference Example 4 was prepared in the same manner as Reference Example 2 except that the coating solution had a volume concentration of zinc oxide of 20 vol%.

(Reference Example 5)
A sample of Reference Example 5 was produced in the same manner as Reference Example 2 except that the coating solution had a volume concentration of zinc oxide of 28 vol%.

(Reference Example 6)
A sample of Reference Example 6 was produced in the same manner as Reference Example 2 except that the coating solution had a volume concentration of zinc oxide of 37 vol%.

(Reference Test Example 2) Electrical Resistance Value Measurement For the samples of each reference example, the electrical resistance value R in the NN environment (23 ° C., 55% RH) is determined according to the double ring electrode method (JIS K6271), ULTRA HIGH RESISTANCE METER. It measured using R8340A (made by Advantest Corporation). In addition, each measurement was performed 3 times and the average value was calculated | required. The applied voltage at this time was DC-100V. The results are shown in Table 2 and FIG.

When the volume concentration of zinc oxide in the solid content of the coating solution was 37 vol% (Reference Example 6), it was 5.94 × 10 ⁶ Ω. Also, from FIG. 2, the electrical resistance value of the coating layer is 1.0 × 10 ⁷ Ω or less because the volume concentration of zinc oxide in the solid content (polyvinyl alcohol and zinc oxide) of the coating solution is 35 vol% or more. Can be guessed.

  In the conductive rubber member, it is preferable that the coat layer has a lower electrical resistance value than the conductive elastic layer. Thereby, the conductive mechanism of the conductive rubber member can be made to depend on the conductive fine powder of the coat layer, and the environment dependency can be reduced. For example, a conductive elastic layer composed of an ion conductive polymer or a conductive elastic layer containing an ionic conductive agent has a relatively large environmental dependency, but by making the conductive mechanism of the conductive rubber member dependent on the coat layer, It can be set as the conductive rubber member with small environmental dependence.

  The rubber base material used for the conductive elastic layer of the conductive rubber member of the present invention is not particularly limited. For example, epichlorohydrin rubber, polyurethane, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), styrene rubber (SBR), Examples include acrylic rubber (ACM), ethylene / propylene rubber (EPDM), silicone rubber (Q), and a polymer containing alkylene oxide. These may be used alone or in admixture of two or more.

  In addition, as an ion conductive polymer mentioned above, the polymer etc. which contain acrylonitrile butadiene rubber (NBR), epichlorohydrin rubber, an alkylene oxide, etc. are mentioned. The epichlorohydrin rubber includes epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide copolymer, epichlorohydrin-allyl glycidyl ether copolymer, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl. Examples thereof include glycidyl ether quaternary copolymers and derivatives thereof. Polymers containing alkylene oxide include ethylene oxide homopolymer, ethylene oxide-propylene oxide copolymer, ethylene oxide-allyl glycidyl ether copolymer, ethylene oxide-propylene oxide-allyl glycidyl ether terpolymer and derivatives thereof. And so on.

  When the conductivity imparting material is blended with the rubber substrate, various carbon blacks are preferable, but an electronic conductivity imparting material such as metal powder, an ionic conductivity imparting material, or a mixture of both can be used. Examples of the ionic conductivity-imparting material include organic salts, inorganic salts, metal complexes, ionic liquids, and the like. Examples of organic salts and inorganic salts include lithium perchlorate, quaternary ammonium salts, and sodium trifluoride acetate. Moreover, as a metal complex, a halogenated ferric-ethylene glycol etc. can be mentioned, Specifically, the diethylene glycol-ferric chloride complex etc. which were described in patent 3655364 can be mentioned. On the other hand, the ionic liquid is a molten salt that is liquid at room temperature, and is also called a room temperature molten salt, and particularly refers to a melting point of 70 ° C. or lower, preferably 30 ° C. or lower. Specifically, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-butyl-3-ethylimidazolium trifluoromethylsulfonyl) imide described in JP-A No. 2003-202722, and the like Can be mentioned.

Although the electrical resistance value of a conductive elastic layer is not specifically limited, For example, it is preferable that it is 1.0 * 10 < ⁴ > -1.0 * 10 < ⁹ > (omega | ohm).

  The conductive rubber member according to the present invention is suitable for, for example, a roll, a blade, a belt, etc., and suitable for a charging roll, a developing roll, a transfer roll, a toner supply roll, a cleaning roll, a cleaning blade, a transfer belt, and the like. It is.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this.

Example 1
<Manufacture of rolls>
100 parts by mass of epichlorohydrin rubber (ECO), 25 parts by weight of Asahi Thermal, 1.5 parts by weight of Sunseller TET (manufactured by Sanshin Chemical Industry), 1.5 parts by weight of Sunseller CZ (manufactured by Sanshin Chemical Industry), sulfur 1 0.0 parts by weight were added and kneaded with a roll mixer, pressed on a metal shaft surface with a diameter of 6 mm under vulcanization conditions at 160 ° C. for 30 minutes, and the outer surface was polished to a diameter of 12 mm, A roll member 1 having an elastic layer formed on the surface of the core metal was obtained.

<Preparation of coating solution>
A 3 wt% aqueous solution of polyvinyl alcohol (PVA) (manufactured by Wako) and an aqueous dispersion type zinc oxide (ZnO) (pasette GK aqueous dispersion: manufactured by Hux Itec Corp.) are mixed with a 20 wt% aqueous solution to obtain a solid content (polyvinyl alcohol and A coating solution having a zinc oxide volume concentration of 37 vol% in zinc oxide) was prepared.

  The above coating solution is applied to the roll member 1 by dipping method, naturally dried at 23 ° C. and 55% RH, and then dried at 120 ° C. for 1 hour in order to eliminate moisture remaining in the coating film. A coating layer was formed to provide a conductive roll of Example 1.

(Example 2)
A conductive roll of Example 2 was obtained in the same manner as in Example 1 except that the coating liquid had a volume concentration of zinc oxide of 51 vol%.

(Comparative Example 1)
The electroconductive roll of the comparative example 1 was obtained like Example 1 except having used the polyvinyl alcohol (PVA) (made by Wako) 3 wt% aqueous solution as a coating liquid.

(Comparative Example 2)
A conductive roll of Comparative Example 2 was obtained in the same manner as in Example 1 except that the coating solution had a volume concentration of zinc oxide of 3 vol%.

(Comparative Example 3)
A conductive roll of Comparative Example 3 was obtained in the same manner as in Example 1 except that the coating solution had a volume concentration of zinc oxide of 10 vol%.

(Comparative Example 4)
A conductive roll of Comparative Example 4 was obtained in the same manner as in Example 1 except that the coating solution had a volume concentration of zinc oxide of 20 vol%.

(Comparative Example 5)
A conductive roll of Comparative Example 5 was obtained in the same manner as in Example 1 except that the coating solution had a volume concentration of zinc oxide of 28 vol%.

(Example 3)
<Preparation of coating solution>
Polyvinyl alcohol (PVA) (manufactured by Wako) 3.0 wt% aqueous solution and water dispersion type carbon black (Lion paste W-310A: manufactured by Lion Corporation) 20 wt% aqueous solution are mixed to obtain a solid content (polyvinyl alcohol and carbon). A coating solution having a carbon black volume concentration of 1.25 vol% was prepared.

  The above coating solution is applied to the roll member 1 by dipping method, naturally dried at 23 ° C. and 55% RH, and then dried at 120 ° C. for 1 hour in order to eliminate moisture remaining in the coating film. A coating layer was formed to provide a conductive roll of Example 3.

Example 4
A conductive roll of Example 4 was obtained in the same manner as Example 3 except that the coating liquid had a volume concentration of carbon black of 3.36 vol%.

(Comparative Example 6)
A conductive roll of Comparative Example 6 was obtained in the same manner as in Example 3 except that the coating liquid had a carbon black volume concentration of 0.37 vol%.

(Test example 1) Electrical resistance value measurement The electrical resistance value R was measured about the conductive roll of each Example and each comparative example. The electrical resistance value is obtained by placing an electrically conductive roll on an electrode member made of SUS304 plate and applying a load of 100 g to both ends of the core metal, and measuring the electrical resistance between the core metal and the electrode member as ULTRA HIGH RESISTANCE. Measurement was performed using METER R8340A (manufactured by Advantest Corporation). The measurement was performed three times each in an LL environment (10 ° C., 15% RH), an NN environment (23 ° C., 55% RH), and an HH environment (30 ° C., 80% RH), and an average value was obtained. . The applied voltage at this time was DC-100V. The results are shown in Tables 3 and 4.

(Summary of results)
As shown in FIG. 3, the conductive rubber members of Examples 1 and 2 using a coating solution in which the volume concentration of zinc oxide is 37 vol% or more are LL environments (10 ° C., 15% RH) when 100 V is applied. the electrical resistance value _{R LL} of (Omega), HH environment (30 ℃, RH 80%) when the electrical resistance value of the _{R HH (Ω), | LogR} LL -LogR HH | is less than 2.0, It turns out that the environmental dependency is small.

On the other hand, the conductive rubber member of Comparative Example 1 in which no conductive fine powder such as zinc oxide was blended had very large environmental dependence. In addition, the conductive rubber members of Comparative Examples 2 to 5 using the coating solution having a zinc oxide volume concentration of 28 vol% or less have | LogR _LL -LogR _HH | larger than 2 and a large environmental dependency. I understood it.

On the other hand, the conductive rubber members of Examples 3 and 4 using the coating liquid having a carbon black concentration of 1.25 vol% or more had an electrical resistance value in an LL environment (10 ° C., 15% RH) when 100 V was applied. Is R _LL (Ω), and the electrical resistance value of the HH environment (30 ° C., 80% RH) is R _HH (Ω), | LogR _LL −LogR _HH | I found it to be small.

On the other hand, the conductive rubber member of Comparative Example 6 using a coating liquid having a carbon black concentration of 0.37 vol% has a | LogR _LL -LogR _HH | of greater than 2 and a large environmental dependency. I understood.

Claims (7)

A conductive elastic layer; and a coating layer formed by applying a coating liquid containing polyvinyl alcohol and conductive fine powder on the conductive elastic layer, and forming an LL environment (10 ° C, Conductivity characterized by satisfying the following formula where the electrical resistance value of 15% RH is R _LL (Ω) and the electrical resistance value of HH environment (30 ° C., 80% RH) is R _HH (Ω). Rubber member.
2. The conductive rubber member according to claim 1, wherein the coat layer has an electric resistance value (Ω) of 1.0 × 10 ⁷ or less. 3. The conductive rubber member according to claim 1, wherein the coat layer has an electrical resistance value lower than that of the conductive elastic layer. The conductive rubber member according to any one of claims 1 to 3, wherein the conductive fine powder is at least one of zinc oxide and carbon black. The conductive rubber member according to any one of claims 1 to 4, wherein the conductive elastic layer is made of an ion conductive polymer. 6. The conductive rubber member according to claim 5, wherein the conductive elastic layer is made of epichlorohydrin rubber. A conductive rubber roll comprising the conductive rubber member according to any one of claims 1 to 6.