Electrophotography – Image formation – Development
Reexamination Certificate
2001-07-30
2003-01-28
Pendegrass, Joan (Department: 2852)
Electrophotography
Image formation
Development
C492S056000
Reexamination Certificate
active
06512911
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates to a toner carrier and an image formation apparatus using the same. More particularly, the present invention is concerned with a toner carrier which is intended to form a visible image on the surface of an image formation body by supplying a toner to the image formation body such as a photosensitive body, paper or the like that preserves an electrostatic latent image in an image formation apparatus such as copying machinery, printers or the like, and which affords a high quality image free from image unevenness, is also minimized in variation of its characteristics during a long-term service, and is excellent in durability. The present invention also relates to an image formation apparatus using the same.
2. Description of the Related Arts
In regard to an electrophotographic image formation method including copying machinery, printers or the like, there is previously known a pressurized developing method as an image formation method which comprises supplying a unary toner to an image formation body such as a photosensitive body preserving an electrostatic latent image, and visualizing the latent image by allowing the toner to adhere to the latent image (refer to U.S. Pat. Nos. 3,152,012 and 3,731,146).
The pressurized developing method, which performs the image formation by bringing a toner carrier that supports a toner into contact with an image formation body such as a photosensitive body preserving an electrostatic latent image, and allowing the toner to adhere to the latent image on the aforesaid image formation body, thus requires the above-mentioned toner carrier to be constituted of an electroconductive elastic body having both electroconductivity and elasticity.
Specifically in the foregoing pressurized developing method the constitution is such that, for instance, as illustrated in
FIG. 2
, a toner carrier
1
(developing roller) is placed between a toner application roller
5
for supplying a toner and an image formation body
6
(photosensitive body, etc.) preserving an electrostatic latent image; the toner carrier
1
(developing roller), the image formation body
6
(photosensitive body, etc.) and the toner application roller
5
rotate each in the direction of the arrow in
FIG. 2
, thereby a toner
7
is supplied onto the surface of the toner carrier
1
(developing roller) with the toner application roller
5
; the toner carrier
1
(developing roller) rotates, while being in contact with the image formation body
6
(photosensitive body, etc.) in a state that the toner is arranged into a uniform thin film by a layer forming blade
8
; and the toner thus formed into a thin film is allowed to adhere to a latent image on the image formation body
6
(photosensitive body, etc.) from the toner carrier
1
(developing roller), whereby the aforesaid latent image is visualized.
In such image formation apparatus by means of pressurized developing system as the above, the toner carrier
1
is obliged to rotate, while maintaining the state of close contact with the image formation body
6
. For this reason, the constitution of the toner carrier
1
is such that as illustrated on the schematic cross section of the attached
FIG. 1
, a shaft
6
consisting of an electroconductive material such as a metal is equipped on its outside periphery with an electroconductive elastic layer
3
composed of an electroconductive elastic body which is imparted with electroconductivity by blending an electroconductivity imparting agent in elastic rubber such as silicone rubber, acrylonitrile butadien rubber, ethylene propylene rubber and polyurethane rubber or foam thereof. In addition, a coating layer
4
composed of a resin or the like is installed on the surface of the electroconductive elastic layer
3
for the purpose of controlling electrostatic property and adhesivity for the toner, controlling force of friction between the image formation body and the layer forming blade, or preventing fouling of the image formation body due to the elastic body.
On the other hand, a proposal is made on an image formation method for forming an image by allowing a toner supported on a toner carrier to directly jump over onto an image formation body composed of paper sheets such as paper, OHP paper sheet or the like via a perforated controlling electrode.
Another proposal is also made on a method for forming an image by supporting a non-magnetic toner layered into thin layer on the surface of a toner carrier which is in the form of sleeve and which is placed in a non-contact state in the vicinity of a photosensitive body, and allowing the toner to jump over onto the photosensitive body to form images {refer to Japanese Patent Application Laid Open No. 116559/1983 (Showa 58)}.
In both the above-mentioned methods, the electroconductive elastic layer for a toner carrier is equipped on the surface thereof with a coating layer composed of a resin or the like for the purpose of controlling electrostatic property and adhesivity for the toner, or decreasing force of friction with an other member such as the photosensitive body, layer forming blade, controlling electrode and the like.
It has been suggested by the present inventors that the friction and image characteristics can be improved by a toner carrier wherein such a resin as melamine resin, phenolic resin, alkyd resin, fluororesin and polyamide resin is employed in a coating layer.
However, accompanying the major currents in recent years towards high speed of a printer, improvement required of image fineness, colored image and the like, the requirements for image forming properties have come to be increasingly strict, thus actualizing a variety of problems with which conventional toner carriers can no longer cope. In particular, the problems still remain unsolved in that (a) an increase in toner damage caused by high speed tendency is grasped as an important problem which leads to defective image such as fog due to poor electrification of a toner upon long-term service of a toner carrier, and (b) while the demand for evenness in image quality is increasingly accentuated, there take place such defective images as fogging of white image, unevenness in half tone image and unevenness in density of black image accompanying increase in the number of printing sheets in the case of long-term service of a toner carrier by incorporating it in an image formation apparatus.
With respect to the durability of the toner carrier, there are caused as the case may be, the problems in that agglomerated toner which brings about filming or fusedly fixing attributable to toner damage scrapes off and wears the toner carrier or a member in contact therewith, thereby inducing toner leakage.
Appropriate elimination of damaged toner is the drastic measure of solving against various problems attributable to toner damage, but it is difficult with the state of the art to completely remove damaged toner from a developing system. In this case, as the countermeasure from the side of the toner carrier it is one of effective means for suppressing toner damage to decrease the hardness of the toner carrier so as to absorb as much as possible the pressure of contact with other members. On the other hand, however, it is known that in the case of the toner carrier being flexible and markedly low in hardness, when such carrier is incorporated in a printer or the like and is used for imaging after a long-term non-use state, deformation remains which is due to press contact between the carrier and a layer forming blade in half tone image, sometimes causing streaky trace (defective set image). On the basis of the knowledge, it is taken into consideration to adopt a method for enhancing wear resistance of the toner carrier by increasing the hardness thereof to the utmost, while limiting the the quantity of deformation due to press contact therebetween. Nevertheless in such a case, the stress applied to a toner is extremely increased, thus giving rise to an increase in damaged toner. As a result, varia
Arai Toshiaki
Murata Kazuya
Nihei Norio
Ohuchi Takao
Takagi Koji
Bridgestone Corporation
Oblon, Spivak, McClelland, Maier & Neusttadt, P.C.
Pendegrass Joan
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