Member for developing electrostatic latent images

Details Member for developing electrostatic latent images Member for developing electrostatic latent images

1996-08-29

2001-10-30

Copenheaver, Blaine (Department: 1771)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

C428S421000, C428S458000, C428S465000, C428S483000, C428S522000, C428S906000, C430S102000, C355S117000

Reissue Patent

active

RE037429

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a member for developing electrostatic latent images for use in a development unit using a non-magnetic one-component toner.
As a development method using a non-magnetic one-component toner, a so-called contact development method is in general use, by which an electrostatic latent image bearing member is brought into contact with a toner transporting member for transporting toner particles charged to a predetermined polarity onto electrostatic latent images for developing the same to visible images.
The toner transporting member (hereinafter referred to as a development roller) is required to have many functions and to meet, for instance, the following requirements: When the electrostatic latent image bearing member is made of a rigid material, the development roller to be used with the electrostatic latent image bearing member is required to have the following properties: (1) appropriate elasticity with a low hardness in order to obtain a nip necessary for development, (2) sufficient recovery properties from compression caused by the contact with the electrostatic latent image bearing member, and (3) allowing a layer to be uniformly coated onto the core of the development characteristics, (4) providing the toner particles on the development roller with the desired charge polarity and charge quantity, (5) sufficient releasability from the toner particles so as not to cause the filming phenomenon, (6) appropriate surface roughness for forming a uniformly thin toner layer on the surface of the development roller, (7) sufficient lubricity to reduce the chatter caused by the frictional resistance during the contact development, and (8) wear-resistance.
To meet the above-mentioned requirements, an elastic body having a low hardness, as usually referred to rubber, is conventionally employed as a coating material for the core of the development roller.
Specific examples of such a rubber are polar polymer such as nitrile-butadiene rubber (NBR), epichlorohydrin rubber (ECO), acrylic rubber, and chloroprene rubber, and high resistance rubbers such as silicone rubber, ethylene-propylene rubber, and styrene-butadiene rubber, in which particles with a low electric resistivity such as carbon and metal powder, serving as resistance adjusting
agent

agents
, are dispersed. These rubbers are molded into a development roller on a cylindrical core by a conventional molding method such as press-molding and vapor-molding.
However, the conventional development rollers can not satisfy all of the above requirements.
In particular, the above-mentioned requirements (1) through (3) are essential for the contact development method. However, it is difficult to obtain a development roller which satisfies not only requirements (1) to (3), but also the requirements (4) to (8) for the surface properties of the development roller.
This difficulty stems from, for example, the following facts. When the hardness of a rubber used for the development roller is decreased, sufficient surface grinding properties cannot be obtained, resulting in the difficulty in finishing the surface of the rubber with a desired surface roughness (Rz) expressed as a value of the order of less than several &mgr;m. In addition, such a rubber has not only a tendency to have a large frictional resistance to the member which comes into contact therewith because of its surface adhesiveness, but also a tendency to easily wear because of its low hardness. When the polar rubber is used for the development roller, toner particles persistently adhere to the surface of the development roller due to its poor releasability from toner, resulting in the toner filming. Accordingly, the charge quantity of the toner is changed, so that the deposition amount of the toner on the development member becomes non-uniform, and accordingly images become non-uniform in quality.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a development member with improved toner releasability and resistance to abrasion, from which the above-mentioned conventional shortcomings are eliminated.
Another object of the present invention
is

are
to provide a function-separated type development roller by providing a second coating layer having a uniform volume resistivity.
The above objects of the present invention
is

are
attained by a development member which comprises a first coating layer made of an elastic material formed on a support, and a second coating layer made of a flexible synthetic resin formed on the first coating layer, which development member may be a development roller, and is brought into contact with an electrostatic latent image bearing member for development of electrostatic latent images to visible toner images.
In particular, to attain the above-mentioned objects, it is preferable to form the second coating layer by coating onto the first coating layer a solvent-type semiconductive coating liquid which is prepared by dispersing carbon black uniformly in a flexible synthetic curable resin solution.


REFERENCES:
patent: 4041207 (1977-08-01), Takada et al.
patent: 4263391 (1981-04-01), Saito et al.
patent: 4286543 (1981-09-01), Ohnuma et al.
patent: 4755847 (1988-07-01), Matsushiro et al.
patent: 4760422 (1988-07-01), Seimiya et al.
patent: 4764841 (1988-08-01), Brewington et al.
patent: 4819020 (1989-04-01), Matsushiro et al.
patent: 4827868 (1989-05-01), Tarumi et al.
patent: 4908665 (1990-03-01), Takeda et al.
patent: 4958193 (1990-09-01), Nojima et al.
patent: 58-194061 (1983-11-01), None
patent: 63-100396 (1988-02-01), None
Electronic Packaging, Microelectronics, and Interconnection Dictionary, Charles A. Haper & Martin B. Miller, McGraw-Hill Inc., New York, Dec. 1993, p. 210.

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