Electrophotography – Image formation – Transfer
Reexamination Certificate
2001-09-18
2003-07-29
Ngo, Hoang (Department: 2852)
Electrophotography
Image formation
Transfer
C430S126200
Reexamination Certificate
active
06600893
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a transfer member, a process for producing the transfer member, and an image-forming apparatus having the transfer member.
2. Related Background Art
Image-forming apparatus making use of an intermediate transfer member which is one of transfer members are effective as full-color image-forming apparatus or multi-color image-forming apparatus in which a plurality of component color images corresponding to full-color image information or multi-color image information are sequentially superimposingly transferred to output image-formed articles on which full-color images or multi-color images have synthetically been reproduced, or as image-forming apparatus made to have the function of full-color image formation or the function of multi-color image formation.
An example of an image forming apparatus employing an intermediate transfer belt which is a belt-form transfer member is schematically shown in FIG.
1
.
The apparatus shown in
FIG. 1
is a full-color image-forming apparatus (copying machine or laser beam printer) utilizing an electrophotographic process. A medium-resistance elastic material is used in an intermediate transfer belt
20
.
Reference numeral
1
denotes a drum-shaped electrophotographic photosensitive member repeatedly used as a first image bearing member (latent-image-bearing member), which is rotatingly driven at a prescribed peripheral speed (process speed) in the direction of an arrow.
The photosensitive drum
1
is, in the course of its rotation, uniformly charged to prescribed polarity and potential by means of a primary charging assembly
2
, and then imagewise exposed to light
3
by an exposure means (e.g., a color-original image color-separating/image-forming optical system, or a scanning exposure system comprising a laser scanner that outputs laser beams modulated in accordance with time-sequential electrical digital pixel signals of image information). Thus, an electrostatic latent image is formed which corresponds to a first color component image (e.g., a yellow color component image) of the intended color image.
Next, the electrostatic latent image formed is developed with a first-color yellow toner Y by means of a first developing assembly (yellow color developing assembly
41
). At this stage, second to fourth developing assemblies (magenta color developing assembly
42
, cyan color developing assembly
43
and black color developing assembly
44
) each stand unoperated and do not act on the electrophotographic photosensitive member
1
, and hence the first-color yellow toner image is not affected by the second to fourth developing assemblies.
The intermediate transfer belt
20
is clockwise rotatingly driven at the same peripheral speed as the electrophotographic photosensitive member
1
.
The first-color yellow toner image formed and held on the electrophotographic photosensitive member
1
passes a nip formed between the electrophotographic photosensitive member
1
and the intermediate transfer belt
20
, in the course of which it is successively intermediately transferred to the periphery of the intermediate transfer belt
20
(primary transfer) by the aid of an electric field formed by a primary transfer bias applied to the intermediate transfer belt
20
through a primary transfer roller
62
.
The electrophotographic photosensitive member
1
surface from which the first-color yellow toner image has been transferred to the intermediate transfer belt
20
, is cleaned by a cleaning assembly
13
.
Subsequently, the second-color magenta toner image, the third-color magenta toner image and the fourth-color black toner image are sequentially similarly transferred superimposingly onto the intermediate transfer belt
20
. Thus, synthesized color toner images corresponding to the intended full-color image is formed.
Reference numeral
63
denotes a secondary transfer roller, which is provided in such a way that it is axially supported in parallel to a secondary transfer opposing roller
64
and stands separable from the bottom surface of the intermediate transfer belt
20
.
The primary transfer bias for sequentially superimposingly transferring the first- to fourth-color toner images from the electrophotographic photosensitive member
1
to the intermediate transfer belt
20
is applied from a bias source
29
in a polarity (+) reverse to that of each toner. The voltage thus applied is, e.g., in the range of from +100 V to +2 kV.
In the step of primary transfer of the first- to third-color toner images from the electrophotographic photosensitive member
1
to the intermediate transfer belt
20
, the secondary transfer roller
63
may also be set separable from the intermediate transfer belt
20
.
The synthesized color toner images transferred to the intermediate transfer belt
20
are transferred to a second image bearing member, transfer medium P, in the following way: The secondary transfer roller
63
is brought into contact with the intermediate transfer belt
20
and simultaneously the transfer medium P is fed at a prescribed timing from a paper feed roller
11
through a transfer medium guide
10
until it reaches a contact nip formed between the intermediate transfer belt
20
and the secondary transfer roller
63
, where a secondary transfer bias is applied to the secondary transfer roller
63
from a power source
28
. On account of this secondary transfer bias, the synthesized color toner images are transferred from the intermediate transfer belt
20
to the second image bearing member transfer medium P (secondary transfer). The transfer medium P to which the toner images have been transferred are guided into a fixing assembly
15
and are heat-fixed there.
After the toner images have been transferred to the transfer medium P, a charging member
7
for cleaning is brought into contact with the intermediate transfer belt
20
, and a bias with a polarity reverse to that of the electrophotographic photosensitive member
1
is applied, whereupon electric charges with a polarity reverse to that of the electrophotographic photosensitive member
1
are imparted to toners not transferred to the transfer medium P and remaining on the intermediate transfer belt
20
(i.e., transfer residual toners). Reference numeral
26
denotes a bias power source.
The transfer residual toners are electrostatically transferred to the electrophotographic photosensitive member
1
at the nip between the electrophotographic photosensitive member
1
and the intermediate transfer belt
20
and the vicinity thereof, thus they are removed from the intermediate transfer belt
20
.
Compared with a prior art transfer unit in which toner images are transferred from a first image bearing member to a second image bearing member (transfer medium) fastened or attracted onto a transfer drum as disclosed in, e.g., Japanese Patent Application Laid-open No. 63-301960, full-color electrophotographic apparatus having an image-forming apparatus making use of the intermediate transfer member described above have an advantage that a variety of second image bearing member transfer mediums can be selected without regard to their width and length, including thin paper (40 g/m
2
paper) and up to thick paper (200 g/m
2
paper) such as envelopes, post cards and labels. This is because any processing or control (e.g., the transfer material is held with a gripper, attracted, and made to have a curvature) is not required for the second image bearing member transfer material.
Because of such advantages, full-color copying machines and full-color printers making use of intermediate transfer belts have already begun to be available in the market.
An example of an image-forming apparatus employing a belt-form transfer-transport belt as a transfer-transport (image-transferring and paper-transporting) member which is one of transfer members is schematically shown below in FIG.
2
.
The image forming apparatus shown in
FIG. 2
is, as one type of a full-color image-forming apparatus of color-separated imag
Ashibe Tsunenori
Kobayashi Hiroyuki
Kusaba Takashi
Matsuda Hidekazu
Nakazawa Akihiko
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