Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2000-12-28
2004-01-06
Kiliman, Leszek B (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036920, C428S323000, C428S327000, C428S331000, C428S473500, C399S307000, C522S162000, C522S164000
Reexamination Certificate
active
06673407
ABSTRACT:
BACKGROUND OF THE INVENTION
[Technical Field Pertinent to the Invention]
This invention relates to an image formation apparatus using electrophotography such as a copier and a printer and semiconductive members such as a semiconductive belt and a semiconductive roll used appropriate with the image formation apparatus and in particular to a charging roll for uniformly charging the surface of an image support in a copier, a printer, etc., a transfer roll for transferring a toner image formed on the image support to a record medium, a transfer toll for once transferring a toner image formed on the image support to an intermediate transfer body, a transfer roll for transferring the toner image once transferred to the intermediate transfer body to a record medium such as paper, a semiconductive roll used with a cleaning roll, etc., for removing the toner image on the image support, a semiconductive belt used as a paper transport body for transporting the intermediate transfer body and paper, and an image formation apparatus comprising at least one of the semiconductive members.
[Related arts]
An image formation apparatus using electrophotography forms uniform charges on an image support made of a photoconductive photosensitive body made of an inorganic or organic material and forms an electrostatic latent image with laser light, etc., modulated based on an image signal, then develops the electrostatic latent image in charged toner to form a visible toner image. The image formation apparatus electrostatically transfers the toner image via an intermediate transfer body or directly to a transfer body of paper, etc., thereby providing any desired reproduced image.
Particularly, as an image formation apparatus adopting the system of primarily transferring the toner image formed on the image support to the intermediate transfer body and further secondarily transferring the toner image on the intermediate transfer body to paper, an apparatus disclosed in JP-A-62-206567, etc., is known.
It is proposed to use a semiconductive endless belt comprising carbon black loaded to thermoplastic resin of polycarbonate resin (JP-A-3-89357, JP-A-06-095521), PVDF (polyvinylidene fluoride) (JP-A-5-200904, JP-A-6-228335), polyalkylene phthalate (JP-A-6-149081), PC (polycarbonate)/PAT (polyalkylene terephthalate) blend material (U.S. Pat. No. 2,845,059), ETFE (ethylene tetrafluoroethylene copolymer)/PC, ETFE/PAT, PC/PAT blend material (JP-A-6-149079), etc., as material of the intermediate transfer body used with the image formation apparatus adopting the intermediate transfer body system.
However, it is very difficult to control the resistance value of a resin material in a semiconductive region and it is almost impossible to stably provide any desired resistance value with normal conductive carbon black loaded to a normal resin material. Thus, the resistance values of all semiconductive endless belts need to be measured for selection and therefore costs are increased.
As described in “Koubunshikakou, vol.43, Nov. 4, 1977, SUMITA et al.,” as carbon black is loaded into a high polymer of resin material, etc., conductivity is small while a small amount of carbon black is loaded. From one threshold value, carbon black forms a conductor circuit and conductivity is enhanced rapidly and a medium resistance value cannot be provided.
Further, as a belt material used with the image formation apparatus adopting the intermediate transfer body system, JP-A-9-305038 and JP-A-10-240020 propose an elastic belt containing a reinforcing material comprising woven cloth of ester, etc., and elastic member laminated on each other.
However, the elastic belt involves a problem of occurrence of age extension caused by belt tension at the driving time.
JP-A-10-264268 discloses an attempt to decrease age extension of a belt at the driving time by heating resin or rubber reinforced with fibers in an expansion state for decreasing variations in inner peripheral length and providing a belt excellent in dimension stability.
However, this method has the disadvantage that it takes much time and labor as a manufacturing method, increasing the manufacturing costs.
Thus, although a large number of attempts have been made, variations in resistance values in members are large and it is difficult to stably provide members having uniform resistance values and decrease age extension at the belt driving time at low costs.
If in-plane variations in volume resistivity of intermediate transfer body (&Dgr;R) are large, particularly in a color image, a partial color loss is caused by a partial transfer efficiency difference and uniform high image quality cannot be provided; this is a problem.
The volume resistivity of an intermediate transfer body must be controlled in a predetermined range to provide high transfer image quality, in-plane variations in the intermediate transfer body (resistance value difference between the maximum and minimum values) must be small, and if the operating environmental condition changes, the volume resistivity must not largely change and high quality must be provided stably. For example, in practical use, it is required that volume resistivity change in a low-temperature and low-humidity environment of 10° C. and 15%RH and a high-temperature and high-humidity environment of 28° C. and 85%RH be within 1.5 orders of magnitude (log&OHgr; cm).
To give conductivity to material forming an intermediate transfer body, a method of giving a conductive agent giving electronic conductivity into composition material and a method of giving a conductive agent giving ion conductivity are available.
With a resin material comprising carbon black of a conductive agent giving electronic conductivity dispersed solely, the volume resistivity responsive to environmental change of temperature and humidity less varies, but it is difficult to uniformly disperse carbon black and thus in-plane variations in volume resistivity become easily large; this is a problem.
To give a conductive agent giving ion conductivity, volume resistivity change in the plane of the intermediate transfer body is extremely small, namely, 0.6 orders of magnitude (log&OHgr; cm) or less. In contrast, the volume resistivity responsive to environmental change of temperature and humidity varies largely. For example, the resistance value difference between the high-temperature and high-humidity environment of 28° C. and 85%RH (H/H environment) and the low-temperature and low-humidity environment of 10° C. and 15%RH (L/L environment) is 1.5 to tour orders of magnitude (log&OHgr; cm); this is a problem.
In an electrophotographic image formation apparatus, a semiconductive roll is often adopted. As the semiconductive roll, the following roll is often used: A conductive substance of carbon black, metal oxide, organic or inorganic electrolyte, etc., is dispersed in general elastomer (elastic body) such as EPDM (ethylene propylene diene rubber), NBR (nitrile butadiene rubber), SBR (styrene butadience rubber), polyurethane rubber, silicone rubber, or Norsorex to give conductivity, and the outer periphery of a conductive metal core is coated with a conductive foam elastic body foamed by machine foaming in air, nitrogen or with a chemical foaming agent to form a roll.
To control the electrical characteristic of a semiconductive roll, a method of changing the conductive agent blend amount in a conductive foam is known, but it is difficult to balance resistance because the hardness and resistance of the conductive foam is contrary to each other. With a semiconductive roll having electronic conductivity, control in a medium resistance region of 10
6
to 10
12
&OHgr; cm is hard to perform, and resistance variations in semiconductive roll or between rolls are large; this is a problem.
It is very difficult to control the resistance value of a resin material in a semiconductive region; as with the above-mentioned semiconductive endless belt, it is almost impossible to provide any desired resistance value with normal conductive carbon black loaded to a normal resin materia
Hara Yukio
Kuroda Masuo
Morita Shoichi
Watanabe Jiro
Fuji 'Xerox Co., Ltd.
Kiliman Leszek B
Oliff & Berridg,e PLC
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