Electrophotography – Image formation – Development
Reexamination Certificate
1999-07-01
2001-06-26
Braun, Fred L (Department: 2852)
Electrophotography
Image formation
Development
C399S284000
Reexamination Certificate
active
06253052
ABSTRACT:
RELATED APPLICATION
Reference is made to our co-pending provisional application Ser. No. 60/044,598 filed Apr. 22, 1997 entitled Conductive Coating For Charging Blade In Electrostatic Printing Processes.
BACKGROUND OF THE INVENTION
This invention relates generally to the field of electrostatic printing processes, and more particularly to an improved coating applied to an elastomeric charging blade pressure against a developing roller which forms part of the developer apparatus used to develop an electrostatic image normally using single component toner.
One component toner, also known as monocomponent toner, is widely used in electrophotographic printers. The toner may also contain other additives used to improve flow characteristic and to control charging. The toner is triboelectrically charged by the friction developed in its movement through the developer apparatus. This friction occurs at the developer roller surface which is usually textured, and is increased by the use of an elastomeric blade placed in contact with the developer surface. The elastomeric blade also meters the layer of toner on the developer roller prior to image development.
Developer rollers used with monocomponent toners can create unequal charge distribution among different size toner particles. U.S. Pat. No. 4,989,044 discloses the variation in toner charge and related particles in the toner layer on the developer roller. The solution to equalize the charge, according to this patent, is to use a conductive coating on the developer roller surface. U.S. Pat. No. 5,027,745 discloses that the conductive coating described in U.S. Pat. No. 4,989,044 is usually short lived. This short life is even more pronounced with developer rollers using elastomeric blades pressed against them to increase the friction on the toner passing over the developer roller surface. The elastomeric blades significantly increase the wear of the developer roller surface.
The need for a conductive coating to equalize the toner charge is of particular importance in developer systems that use toner projection development, a process which is described in U.S. Pat. No. 4,292,387. The AC voltage applied to the developer roller causes sorting of the toner particles by size with the smaller higher charged particles migrating to the inside of the toner layer on the developer roller. This toner particle sorting by size results in lower image density and developer roller ghosting.
SUMMARY OF THE INVENTION
Briefly stated, the invention contemplates the provision of an improved flexible electrically conductive coating adapted to be applied to the charging blade, or at least the surface thereof which contacts the developer roller. In one embodiment, the coating is applied by dipping, painting, or spraying. In another embodiment, the coating material is incorporated into the material forming the charging blade prior to extruding or casting the same. In a third embodiment, particularly useful in reconditioning used blades, the coating applied to an adhesive strip which is subsequently applied to the operative surface of the blade.
REFERENCES:
patent: 5085171 (1992-02-01), Aulick et al.
patent: 5168312 (1992-12-01), Aoto et al.
patent: 5570166 (1996-10-01), Ohzeki et al.
patent: 5623718 (1997-04-01), Bracken et al.
patent: 5702812 (1997-12-01), Bracken et al.
patent: 5853868 (1998-12-01), Bracken et al.
Cornelius Lester
Kacinsky Robert
Braun Fred L
Temko Charles E.
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