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AssigneeMinolta Camera Kabushiki Kaisha
InventorsHiromi Kameda, Sanji Inagaki
Estimating the term…
An electrophotographic copying machine of the image transfer type includes a roller for pressing the copy image receiving substrate into virtual contact with the electrostatic image carrying drum. The roller includes a metal shaft and an outer layer formed of an electroconductive elastic sponge material having a resistivity of 10.sup.2 to 10.sup.6 ohm/cm which varies inversely with the compression of the material. The sponge material is produced by soaking an open pore soft polymeric sponge matrix temporarily expandable when exposed to alcohol in a liquid composition containing 10 parts of a water dispersable resin binder, 2 to 7 parts of a fine electroconductive powder and 10 to 200 parts of alcohol, expressing the excess liquid and then drying the liquid composition.
In an electrophotographic copying machine, including a photosensitive first substrate and means for forming an electrostatic latent image on said substrate, a mechanism for transferring said latent image from said first substrate to a second substrate having a conductive base overcoated with a dielectric layer, said mechanism comprising an electroconductive elastic sponge member urged toward engagement with said first substrate with said second substrate therebetween, said sponge member having an electrical resistivity in the range of 10.sup.2 to 10.sup.6 ohm/cm which varies inversely with the pressure applied thereto and comprising a foamed organic polymeric base material temporarily expandable by methyl or ethyl alcohol and coated with an electroconductive additive agent including a mixture of 10 parts by weight of a water dispersable binding resin, 2 to 7 parts by weight of a fine electroconductive powder and 10 to 200 parts by weight of said base material expandable alcohol.
In an electrophotographic copying machine which comprises:
An electroconductive elastic sponge member in the form of a roller for use in electrophotography as an electrostatic latent image transferring means comprising an electrically conducting substrate member formed thereover with an electroconductive elastic layer which comprises an elastic polymeric foam treated and coated with an electroconductive additive agent including a mixture of a water dispersable binding resin, a fine electroconductive powder and a fluid alcohol by which said polymeric foam is expandable, said member having an electrical resistivity of 10.sup.2 to 10.sup.6 ohm/cm with said resistivity varying inversely with the pressure applied to said member.
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
For transferring a pattern to a second base: of a charge pattern
After-treatment: impregnation
Electrography
Working-up
Term ended 3 Jan 1995 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The present invention relates generally to improvements in resilient electroconductive members, and it relates more particularly to an improved electroconductive elastic sponge member having an electrical resistivity in the range of 10.sup.2 to 10.sup.6 ohm/cm and possessing fine pliability and fine compression restorability, and it relates further to an electroconductive elastic sponge member for use in the field of electrophotography, such as in an electrostatic latent image transfer mechanism.
Conventionally, an electroconductive member in the form of a plate, roller or belt has been used in devices for electrophotography, printing, spinning and the likes for antistatic and for electrostatic charge injection purposes. Specifically in electrophotographic copying machines, an electroconductive member is used to remove excess electrostatic charge from a copy paper and/or to transfer an electrostatic latent image formed on a suitable photosensitive plate or substrate to a copy paper. Such electroconductive members are commonly prepared by coating or kneading an antistatic agent mainly comprising an anionic, cationic, or nonionic surfactant on an elastic material such as natural rubber, synthetic rubber or a synthetic resin.
However, the electroconductive elastic member thus obtained has a relatively high electrical resistivity of 10.sup.15 to 10.sup.7 ohm/cm due to the employment of an ion or salt for electroconductivity, and the electrical resistivity thereof is quite unstable in long use.
FIG. 1 is an enlarged fragmentary view of an electroconductive elastic sponge member in accordance with the present invention;
FIG. 2 is a schematic view of an electrophotographic copying apparatus embodying the present invention;
FIG. 3 is an enlarged view of a part of FIG. 2; and
An electroconductive elastic sponge member according to the present invention has been developed to satisfy the following conditions in which the sponge member has (1) an electroconductivity of 10.sup.2 to 10.sup.6 ohm/cm, (2) a pliable elastic character, (3) at least 80 percent restoratability of the elastic member subsequent to release from the application of pressure, (4) a simple and nonpolluting process of manufacture and (5) a good binding or adhesive characteristic between the base material and treating agent.
To satisfy the above conditions, the present invention contemplates the use of an elastic sponge member, such as a continuous open-cellular or reticulated cushion material, as a base and treating this base with an electroconductive additive agent to obtain the electroconductive elastic sponge or reticular member. Specifically, the base material selected for the device of the present invention may be of any soft foam adapted to temporarily swell or expand when treated with alcohol and generally includes a polyether or polyester type soft polyurethane foam. To this alcohol pretreated base, an electroconductive additive composition or agent is uniformly mixed and dispersed, the agent comprising a water soluble or emulsive resin, a fine electroconductive powder and alcohol. The water soluble or emulsive resin provides pliability to the coating and acts as a binding agent for fine binding between the electroconductive coating and the base material. The water soluble or emulsive resin may be an aminoalkyd, phenolalkyd, aminoacryl, acrylic ester, methacrylic acid, polyvinyl alcohol, polyacrylic acid resin, acrylic acetic vinyl copolymer, rubber latex, polyethyren, vinylidene chloride, vinyl acetate, or acryl resin. The fine electroconductive powder may be of any electroconductive material such as carbon black, acetylene black, graphite, silver, nickel, copper and the like. The alcohol may be of either methyl alcohol or ethyl alcohol.
As for the ratio of the three components of the additive composition, it varies in accordance with the desired electroconductivity. More specifically, the weight ratio between the binding agent and the fine electroconductive powder influences the electroconductivity, and the dilution ratio by alcohol also tends to vary the electroconductivity. Further, the electroconductivity is dependent on the material selected as the fine electroconductive powder. If acetylene black is used, only one third part by weight of this is needed to obtain the same electroconductivity as compared to one part by weight of carbon black. Thus, to obtain an electroconductive elastic sponge member having an electrical resistivity of 10.sup.2 to 10.sup.6 ohm/cm, the component or ingredient ratio of the composition should be 10 parts by weight of binding agent, 2 to 7 parts by weight of electroconductive fine powder and 10 to 200 parts by weight of alcohol. For the sake of comparison, to obtain an electroconductive elastic sponge member having a electrical resistivity of 10.sup.2 to 10.sup.12 ohm/cm, the mixing ratio for the additive agent should be such that to 10 to 50 parts by weight of binding agent, 2 to 30 parts by weight of the fine electroconductive powder and 10 to 200 parts by weight of alcohol should be mixed.