Electrophotography – Image formation – Development
Reexamination Certificate
2001-04-02
2002-12-10
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06493531
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid electrophotographic printer and, more particularly, to a photoreceptor web drying unit of a liquid electrophotographic printer for drying and vaporizing liquid carrier including toner adhering to an electrostatic latent image formed on a photoreceptor web.
Priority is claimed from Korean Patent Application No. 01-917, filed on Jan. 8, 2001, which is incorporated herein by reference.
2. Description of the Related Art
In general, an electrophotographic printer is an image forming apparatus for obtaining a desired image by forming an electrostatic latent image on a photosensitive medium such as a photoreceptor web, developing the electrostatic latent image with toner of a predetermined color, and transferring the developed image to a sheet of print paper. The electrophotographic printer is divided into a dry type and a liquid type according to the type of toner in use. The dry electrophotographic printer uses toner in a powdered state while the liquid electrophotographic printer uses liquid developer which is a mixture of volatile liquid carrier and toner. The use of the liquid electrophotographic printer is gradually increasing because the quality of print is superior to that of the dry electrophotographic printer, and simultaneously because damage caused by toxic toner dust is prevented.
FIG. 1
shows the structure of a conventional liquid electrophotographic color printer. Referring to the drawing, a liquid electrophotogrpahic printer
100
adopts a photoreceptor web
110
installed to be capable of circulating along an endless path being supported by a transfer backup roller
121
, a steering roller
122
and a driving roller
123
, as a photosensitive medium.
A laser scanning unit (LSU)
130
and a developing unit
140
are installed under the photoreceptor web
110
. The laser scanning unit
130
forms an electrostatic latent image through exposure by scanning a laser beam onto the photoreceptor web
110
according to an image signal. The developing unit
140
forms the electrostatic latent image formed on the photoreceptor web
110
by making developer including toner of a predetermined color adhere to the electrostatic latent image. For color printing, a plurality of the laser scanning units (LSU)
130
and the developing units
140
are installed so that the electrostatic latent image can be developed for respective colors, as shown in the drawing.
The photoreceptor web
110
circulates in a direction of the arrows indicating the direction of the respective rollers. The photoreceptor web
110
is charged to a predetermined voltage as a charging unit
150
applies charges to the photoreceptor web
110
. Here, the laser scanning unit
130
scans a laser beam corresponding to a pattern portion of a particular color onto the photoreceptor web
110
. Accordingly, a portion of the photoreceptor web
110
receiving the laser beam is discharged so that a difference in voltage is generated between the portion receiving the laser beam and a portion that does not receive the laser beam.
The developing unit
140
develops developer of a particular color at the portion of the photoreceptor web
110
where charges are lost . A toner image adhering to the electrostatic latent image on the photoreceptor web
110
by the developing unit
140
is transferred to a transfer roller
124
which is installed parallel to the transfer backup roller
121
while the photoreceptor web
110
is interposed between the transfer roller
124
and the transfer backup roller
121
. Then, the toner image transferred to the transfer roller
124
is transferred again to a sheet of print paper
126
provided between the transfer roller
124
and a fusing roller
125
installed parallel to the transfer roller
124
. Thus, a desired image can be printed.
However, ink provided to the photoreceptor web
110
from the developing unit
140
is a mixture of solid toner and liquid carrier. The toner actually has a color to be printed on the print paper
126
and the carrier serves as a solvent for carrying the toner. Thus, the carrier is dried and vaporized by a drying unit
160
before printing and removed from a transfer surface of the photoreceptor web
110
. The developer in a liquid state adhering to the electrostatic latent image of the photoreceptor web
110
is dried because a liquid component of the developer is removed as it passes through the drying unit
160
.
The drying unit
160
is installed to be capable of rotating in contact with part of the transfer surface of the photoreceptor web
110
. The drying unit
160
includes a drying roller
161
having a heat source
162
for generating heat at the center axis of rotation, a pair of reproduction rollers
163
each having a heat source
164
for generating heat, for example, a heat lamp, at the center axis of rotation as a heating means for heating the drying roller
161
and installed to rotate by being engaged to the drying roller
161
, and a manifold
165
encompassing the drying roller
161
and the reproduction rollers
163
.
The drying roller
161
has a high temperature because of the heat source
162
installed at the center axis of rotation and the surface of the drying roller
161
is formed of a material capable of absorbing liquid carrier. Also, the drying roller
161
contacts the photoreceptor web
110
by a pressing apparatus (not shown). The reproduction rollers
163
contact the drying roller
161
by the pressing apparatus.
According to the drying unit
160
having the above structure, the drying roller
161
rotating in contact with the photoreceptor web
110
presses liquid carrier of the image ink adhering to the transfer surface of the photoreceptor web
110
so that it adheres to the surface of the drying roller
161
. Part of the liquid carrier is vaporized on the surface of the drying roller
161
.
The reproduction rollers
163
are heated by each heat source
164
to a particular temperature, drying and vaporizing the liquid carrier absorbed by the drying roller
161
. The vaporized carrier is collected by the manifold
165
.
However, since the conventional photoreceptor web drying unit
160
, as above, vaporizes and absorbs the liquid carrier on a contact surface between the drying roller
161
and the photoreceptor web
110
, the contact time therebetween is so short that a sufficient amount of liquid carrier cannot be absorbed. Accordingly, the liquid carrier which is not vaporized and remains on the photoreceptor web
110
is absorbed by the transfer roller
124
so that a paper jam phenomenon occurs.
Also, when images are continuously printed, since the image on the photoreceptor web is not sufficiently dried, an image defect phenomenon, that is, an image is not transferred to a sheet of print paper, is generated.
Further, since the conventional photoreceptor web drying unit
160
uses a contact method, the image on the surface of the photoreceptor web
110
is picked up and transferred to the surface of the drying roller
161
and/or the reproduction rollers
163
. Thus, the performance of the drying roller
161
and the reproduction rollers
163
is lowered. The picking up of the image from the surface of the photoreceptor web
110
causes a deterioration of image printing quality.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a photoreceptor web drying unit of a liquid electrophotographic printer having an improved structure which can improve efficiency in drying and vaporization of liquid carrier adhering to the photoreceptor web.
Accordingly, to achieve the above objective, there is provided a photoreceptor web drying unit of a liquid electrophotographic printer comprising a plurality of heating sources, a manifold, a circulation line, an inlet duct, and a blowing duct.
The plurality of heating sources generate heat and are installed close to, but not contacting, a photoreceptor web, thereby drying and vaporizing liquid carrier on the surface of the photorecept
Brase Sandra
Samsung Electronics Co,. Ltd.
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