Electrophotography – Image formation – Development
Reexamination Certificate
1999-12-20
2001-06-05
Beatty, Robert (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06243553
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developer cleaning method in a liquid electrophotographic printer, and more particularly, to a developer cleaning method for a liquid electrophotographic printer for removing powdered toner particles from the developer remaining on a photoreceptor medium and a development roller, after termination of a development mode, so that contamination of the photoreceptor medium and a transfer roller can be reduced.
2. Description of the Related Art
In general, a liquid electrophotographic printer such as a laser printer or copier develops an electrostatic latent image formed on a photoreceptor medium such as a photoreceptor web, using developer. The developed image is transferred to a sheet of paper via a transfer roller. The developer is formed by mixing toner powder having a predetermined color, and a liquid carrier.
Referring to
FIG. 1
, a conventional liquid electrophotographic printer includes a photoreceptor web
10
circulating by being supported by a plurality of guide rollers
11
. In a development mode, while the photoreceptor web
10
circulates, a surface of the photoreceptor web
10
is charged to an electrical potential of about 600 V by a main corona
12
. Subsequently, the charged surface of the photoreceptor web
10
is charged to an exposure electrical potential of about 150 V by a beam scanned by a laser scanning unit (LSU)
13
according to image signals so that an electrostatic latent image is formed. Reference numeral
28
denotes a topping corona for increasing the electrical potential of the photoreceptor web
10
lowered after passing a development unit
20
so that the electrical potential thereof can be maintained constantly.
Also, as shown in
FIG. 2
, developer is injected from an injection nozzle
23
toward the outer circumference of a development roller
22
. The developer is transferred from the outer circumference of the development roller
22
to an area for the electrostatic latent image charged to an exposure electrical potential lower than that of the development roller
22
due to the difference in electrical potential, to develop the electrostatic latent image.
Extra developer on the surface of the photoreceptor web
10
is removed by a squeegee roller
24
. The developed image is dried by a drying unit
15
and then transferred to a transfer roller
16
due to the difference in a surface energy. The transferred image is printed on a sheet of paper P passing between the transfer roller
16
and a fixation roller
17
.
When the development mode is terminated, the supply of developer from the injection nozzle
23
is stopped. In a state in which a development electrical potential is continuously applied to the development roller
22
, as shown in
FIG. 3
, the development roller
22
is lowered a predetermined distance and developer D dripping from the photoreceptor web
10
is removed. For this, the squeegee roller
24
is reversed in a state in which the pressing force of the squeegee roller
24
to the photoreceptor web
10
is reduced. Then, the developer D is removed from the photoreceptor web
10
by the squeegee roller
24
and cleaned by a squeegee blade
26
contacting the squeegee roller
24
.
Reference numeral
25
denotes a cleaning blade installed at the injection nozzle
23
for cleaning developer adhering to the outer circumference of the development roller
22
and reference numeral
27
denotes a brush roller for cleaning the outer circumferential surface of the development roller
22
by rotating in contact with the development roller
22
.
However, remaining developer B remains, as shown in
FIG. 4
, at a contact portion between the squeegee roller
24
and the squeegee blade
26
after the drip developer D removing mode is terminated. The remaining developer B contains toner particles of about 3-3.5 wt % which causes to contaminate the photoreceptor web
10
and the transfer roller (
16
of
FIG. 1
) in the subsequent development mode.
Also, when the supply of developer is stopped as the development mode is terminated, developer already supplied remains due to a surface tension between the injection nozzle
23
, the development roller
22
and the cleaning blade
25
. As the remaining developer is hardened as the time passes, the image area is contaminated in the subsequent print mode.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide a developer cleaning method for a liquid electrophotographic printer in which the content of toner in the developer remaining on the photoreceptor web between the development roller and the squeegee roll is reduced to reduce contamination of the photoreceptor web and the transfer roller.
Also, it is another object of the present invention to provide a developer cleaning method for a liquid electrophotographic printer by which the developer remaining between the injection roller and development roller can be removed.
Accordingly, to achieve the above objective, there is provided a developer cleaning method for a liquid electrophotographic printer including the steps of developing an electrostatic latent image by supplying developer supplied from an injection nozzle to a photoreceptor medium via a development roller, removing drip developer formed on the photoreceptor web between a squeegee roller and the development roller, and reducing an electrical potential of the development roller after development so that toner particles included in the drip developer is transferred to the development roller due to a difference in electrical potential.
It is preferred in the present invention that the step of reducing an electrical potential includes the sub-steps of maintaining a constant charged electrical potential of the photoreceptor web and making the electrical potential difference between the development roller and the photoreceptor web to be equal to or greater than the electrical potential difference between the development roller and the electrostatic latent image.
Also, it is preferred in the present invention that the step of removing developer remaining between the injection nozzle and the development roller includes the sub-steps of continuously driving the photoreceptor web and the development roller after supply of the developer is terminated, transferring the developer remaining between the injection nozzle and the development roller to the development roller, and removing the transferred developer by a brush roller and a cleaning blade contacting the development roller.
Also, it is preferred in the present invention that the step of removing drip developer includes the sub-steps of lowering the development roller such that the development roller cannot contact the drip developer, decelerating the proceeding speed of the photoreceptor web, reducing a pressing force against the photoreceptor web by the squeegee roller, allowing a squeegee blade for removing developer on the outer circumferential surface of the squeegee roller, to contact the squeegee roller, and reversing the squeegee roller.
REFERENCES:
patent: Re. 31964 (1985-08-01), Schaefer et al.
patent: 4311780 (1982-01-01), Mochizuki et al.
patent: 4400079 (1983-08-01), Landa
patent: 4833500 (1989-05-01), Mochizuki et al.
patent: 5598253 (1997-01-01), Yagi
patent: 5689780 (1997-11-01), Tamura et al.
patent: 5805963 (1998-09-01), Teschendorf et al.
patent: 4-156485 (1992-05-01), None
patent: 6-314030 (1994-11-01), None
patent: 8-6404 (1996-01-01), None
Kwak Jin-geun
Lee Chang-Soo
Lee Jin-Soo
Beatty Robert
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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