Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-01-18
2001-05-22
Pendergrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C355S030000, C399S098000
Reexamination Certificate
active
06236419
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid electrophotographic imaging system and, more particularly, to a liquid electrophotographic imaging system having an improved structure which prevents a carrier used during development from condensing at an output window of an optical scanning unit.
2. Description of the Related Art
In general, a liquid electrophotographic imaging system is an apparatus for forming an image on a photoreceptor medium such as a photoreceptor web or a photoreceptor drum by developer which is a mixture of a solid toner and a liquid carrier, and transferring the image to a sheet of print paper.
Referring to
FIG. 1
, a general liquid electrophotographic imaging system includes a photoreceptor medium
20
such as a photoreceptor web circulating around a predetermined path by being supported by a steering roller
11
, a driving roller
13
and a transfer backup roller
15
. The photoreceptor medium
20
is charged by a charger
23
to a predetermined electric potential. The charged electric potential varies in response to the light scanned by a laser scanning unit (LSU)
30
. A discharger
21
provided around the photoreceptor web
20
resets the electric potential formed on the photoreceptor medium
20
. The charger
23
charges the photoreceptor web
20
to a predetermined electric potential. The laser scanning unit
30
forms an electrostatic latent image corresponding to each color by scanning light onto the photoreceptor medium
20
. Development units
25
are provided, one for each corresponding color of yellow (Y), magenta (M), cyan (C) and black (K). An image is formed in an area where an electrostatic latent image corresponding to each color is formed. That is, each development unit
25
carries solid toner of a certain color using the liquid carrier to a development gap between the development unit
25
and the photoreceptor medium
20
. An image is formed in an area corresponding to the electrostatic latent image due to a difference between the electric potential applied to the photoreceptor medium
20
and the electric potential for development. Excess carrier left over on the photoreceptor web
20
is removed by a drying unit
27
. The image formed on the photoreceptor web
20
is transferred to a print paper P by a transfer unit
29
.
The structural elements including the photoreceptor medium
20
, the laser scanning unit
30
, and the development unit
25
are housed in a cabinet
10
having an inlet and an outlet through which the print paper P enters and exists, respectively. The cabinet
10
is for preventing the carrier which exists in a gaseous state by passing the drying unit
27
and the transfer unit
29
after being used during development from escaping to the outside .
Referring to
FIGS. 2 and 3
, the laser scanning unit
30
is comprised of a driving source
51
, a deflection disk
55
having a plurality of sectors, each having a hologram pattern, a light emitting means
40
disposed at one side of the deflection disk
55
for emitting light to the deflection disk
55
, an optical path changing means for changing a proceeding direction of the light deflected by the deflection disk
55
, and a housing
31
housing the above structural elements and having transparent windows
35
through which scanning light passes. To correspond to a color image, the light emitting means
40
is comprised of first through fourth light sources
41
,
43
,
45
and
47
suitable for yellow, magenta, cyan, and black, respectively. The light emitted from each of the first through fourth light sources
41
,
43
,
45
and
47
is incident on a predetermined position of the deflection disk
55
. Here, the light path changing means includes a plurality of flat mirrors M
11
, M
12
, M
21
, M
22
, M
31
, M
32
, M
41
, and M
42
, other flat mirrors M, curved mirrors CM
1
, CM
2
, CM
3
, and CM
4
, and holographic optical elements HOE
1
, HOE
2
, HOE
3
, and HOE
4
. The curved mirrors CM
1
-CM
4
are for focusing and reflecting scanning lines input through a plurality of optical paths via the flat mirrors M to make and maintain the scanning lines emitted to be parallel to each other. Also, the curved mirrors CM
1
-CM
4
correct diffraction of incident light due to the holographic pattern of the deflection disk
55
and bowing, a phenomenon in which the scanning line is bent, caused by forming the scanning line by rotation of the deflection disk
55
. By diffracting and transmitting the scanning line incident on the holographic optical elements HOE
1
-HOE
4
at a predetermined angle, the scanning line is made to proceed in a direction perpendicular to the photoreceptor medium
20
.
The housing
31
allows the above optical elements to be installed at predetermined positions inside the cabinet
10
and prevents the optical path changing means from being contaminated by developer in the cabinet
10
. The scanning lines proceeding toward the photoreceptor medium
20
via the holographic optical elements HOE
1
-HOE
4
pass through the transparent windows
35
.
The carrier in a gaseous state and/or vapor in the cabinet
10
adheres to an inside wall of the cabinet
10
, the housing
31
of the laser scanning unit, and the transparent windows
35
. Particularly, the carrier N and/or vapor (H
2
O) condensed on the transparent windows
35
form drops due to the surface energy of the transparent windows
35
. Such formation of drops is called beading.
When there is beading in an area where the scanning line
100
(see
FIG. 3
) passes, the scanning line disperses. Thus, as shown in
FIG. 4
, an unclear image
111
, i.e., color spreading on a desired image
110
, is formed on the photoreceptor medium
20
.
Therefore, since the carrier and/or vapor is formed on the transparent windows and the scanning lines disperse due to beading, resolution of an image is lowered and print quality is deteriorated.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide a liquid electrophotographic imaging system in which the carrier used during development is prevented from condensing on an exit window of the laser scanning unit.
To achieve the above objective, the present invention provides a liquid electrophotographic imaging system, which comprises a photoreceptor medium, a for scanning light onto the photoreceptor medium to form an electrostatic latent image on a photoreceptor surface of the photoreceptor medium, a development unit for developing an image on the photoreceptor surface corresponding to an electrostatic latent image formed by the laser scanning unit with toner carried by a liquid carrier, a cabinet enclosing the photoreceptor medium, the laser scanning unit, and the development unit to prevent the carrier in a gaseous state after being used during development from escaping to the outside. The laser scanning unit comprises a light emitting unit, a beam deflector for deflecting and scanning the light emitted from the light emitting unit, a housing enclosing the light emitting unit and the beam deflector and having at least one transparent window through which the light scanned by the beam deflector passes, and a temperature controlling unit installed outside the housing for maintaining a predetermined temperature around the transparent window, so that the carrier and/or vapor is prevented from beading on the transparent window and dispersion of light emitted to the photoreceptor medium is prevented.
REFERENCES:
patent: 5613174 (1997-03-01), Denton et al.
patent: 5904870 (1999-05-01), Fenner et al.
Pendergrass Joan
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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