Electrophotography – Image formation – Development
Reexamination Certificate
2000-03-29
2001-03-13
Lee, Susan S. Y. (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06201942
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a developer-carrying member, a developing device and an image forming apparatus used for electrophotographic copying machines, laser beam printers, facsimile apparatus, printing apparatus, etc.
Conventional developer-carrying members are provided with roughened uneven surfaces for conveying a developer. As old proposals, Japanese Laid-Open Patent Application (JP-A) 54-79043 disclosed are provided with knurls principally for a two-component developer system and JP-A 55-26526 proposed one provided with a roughened surface principally for a mono-component developer system.
As a material for such a surface-roughness developer-carrying member, it has been proposed to use a relatively hard material for forming a surface-coating layer on a substrate. For example, JP-A 58-132768 has disclosed a developer-carrying member comprising an aluminum substrate surface-coated with a nitride such as TiN or CrN, a carbide such as TiC or B
4
C, or an Ni—P plating layer; JP-A 6-230676 has disclosed a developer-carrying member comprising a substrate of aluminum, brass, stainless steel, etc., surface-coated with Cr plating, an anodized aluminum film, Ni—P plating or nitriding layer; and JP-A 3-41485 has disclosed a developer-carrying member comprising a substrate of aluminum, stainless steel, etc., surface-coated with a plating layer of Cr, Cu—Cr, Ni—Cr, Cu—Ni—Cr or Ni—Cu—Ni—Cr.
The above-mentioned wear-resistant surface-coating layers include an electroless Ni—P plating layer which can provide such a highly wear-resistant plating layer as to show a high Vickers hardness of 900 or higher after being heat-treated at 300-500° C. (JP-A 58-132768). Such a heat treatment can substantially lower the product yield. This is because the substrate can cause a thermal deformation on the order of several tens of &mgr;m in a direction perpendicular to its longitudinal direction as a result of the heat treatment, so that the spacing between the electrostatic image-bearing member and the developer-carrying member fluctuates locally, thereby causing local toner image irregularity. Such an image irregularity poses a serious obstacle for providing high-quality toner images.
Electroplating provides a hard surface-coating layer exhibiting an excellent wear resistance without requiring a high-temperature heat treatment as in a post-treatment of the electroless Ni—P plating layer.
However, the use of an electroplating layer is accompanied with a problem for the purpose of providing a surface-coating layer having a prescribed desirable surface shape. More specifically, the developer-carrying member is generally required to have a surface exhibiting a prescribed degree of surface roughness in order to exhibit good developer-conveying performance, provide an appropriate level of charge to the developer by friction with the developer and prevent the developer sticking. It is difficult to provide an electroplating layer with such a prescribed surface roughness. This is for the following reason.
In the electroplating, metal is deposited from a plating liquid on a substrate in an amount proportional to a density of electric lines of force directed toward the substrate. However, the substrate surface is generally accompanied with minute projections and cracks, and the electric lines of force tend to concentrate onto peaks of the projections or edges of the cracks. As a result, the metal is abnormally or excessively deposited at these sites, thus failing to provide an electroplating layer with prescribed surface roughness.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a developer-carrying member coated with an electroplating layer having a high accuracy of surface roughness and free from abnormal local metal deposition sites.
Further objects of the present invention are to provide a developing device and an image forming apparatus including such a developer-carrying member.
According to the present invention, there is provided a developer-carrying member for carrying and conveying a developer along a surface thereof, comprising a substrate, and an intermediate electroless plating layer and an electroplating layer disposed in this order on the substrate.
The present invention further provides:
a developing device, comprising the above-mentioned developer-carrying member for carrying and conveying a developer along a surface thereof, disposed opposite to an electrostatic image-bearing member bearing an electrostatic image thereon; and
an image forming apparatus, comprising: an electrostatic image-bearing member for bearing an electrostatic image on a surface thereof, and a developing device for developing the electrostatic image comprising the above-mentioned developer-carrying member disposed opposite to the electrostatic image-bearing member.
In the developer-carrying member according to the present invention, an electroless plating layer is disposed as an intermediate layer between a substrate and an electroplating layer, whereby the electroplating layer exhibiting a high hardness can be formed with a high accuracy of surface roughness free from abnormal metal deposition sites. More specifically, in the electroless plating, a metal is deposited on the substrate by a chemical reaction, so that the metal deposition is not concentratively caused at minute projections or along edges of cracks present on the substrate surface. As a result, the shapes of such projections and cracks on the substrate surface are not copied or reflected on the surface of the intermediate electroless plating layer surface, so that the electroplating layer thereon are free from adverse influences of the projections and cracks on the substrate surface.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4368971 (1983-01-01), Watanabe et al.
patent: 4380966 (1983-04-01), Isaka et al.
patent: 4564285 (1986-01-01), Yasuda et al.
patent: 4866480 (1989-09-01), Hosoya et al.
patent: 4870461 (1989-09-01), Watanabe et al.
patent: 5563690 (1996-10-01), Hasegawa et al.
patent: 5697027 (1997-12-01), Takagi et al.
patent: 54-79043 (1979-06-01), None
patent: 55-026526 (1980-02-01), None
patent: 58-132768 (1983-08-01), None
patent: 6-230676 (1994-08-01), None
Hara Nobuaki
Honda Takao
Kashiwagi Hiromi
Tajima Hatsuo
Watanabe Tsuyoshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee Susan S. Y.
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