Electrophotography – Image formation – Development
Reexamination Certificate
2000-07-13
2001-09-18
Beatty, Robert (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06292642
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a squeegee roller for a liquid electrophotographic printer and, more particularly, to a squeegee roller for a liquid electrophotographic printer in which the roughness of a surface of an elastic rubber layer thereof is improved so that the efficiency of squeegeeing is improved.
2. Description of the Related Art
In general, a liquid electrophotographic printer, such as a color laser printer or a copier, produces a desired image by electrically attaching developer, which is a mixture of a solid toner having a predetermined color and a liquid carrier functioning as a solvent, to an area for an electrostatic latent image formed on a surface of a photoreceptor medium such as a photoreceptor web. A development unit for developing the developer in the area for an electrostatic latent image of the photoreceptor medium is provided in the printer.
Referring to
FIG. 1
, a development unit of the conventional liquid electrophotographic printer includes a development tray
12
for finally collecting developer D after being used for development, a development roller
14
arranged to maintain a predetermined distance of development gap G with respect to a photoreceptor web
10
, a manifold
116
through which developer D is injected to the development gap G, a development container
13
for containing the collected developer D which is injected to the development roller
14
, a development roller cleaning apparatus for removing the developer adhering to the outer circumferential surface of the development roller
14
, and a squeegee roller
15
for making toner of the developer remaining on the photoreceptor web
10
a film and for separating carrier from the photoreceptor web
10
.
The development roller cleaning apparatus rotates in contact with the development roller
14
and includes a brush roller
18
, part of which is submerged in the developer D, and a blade
14
b
for removing foreign materials adhering to the surface of the development roller
14
which remain between the brush roller
18
and the development roller
14
after cleaning. Reference numeral
17
denotes a squeegee blade for squeegeeing developer while contacting a surface of the squeegee roller
15
in a drip-line removing mode after development.
FIG. 2
is a view for explaining the operation of the squeegee roller
15
which removes carrier. As shown in the drawing, after development, developer still remains between the photoreceptor web
10
and the squeegee roller
15
. The remaining developer is referred to as a drip-line (DL). To remove the drip-line (DL), the blade
17
is allowed to contact the squeegee roller
15
and the circulating speed of the photoreceptor web
10
is reduced. In this state, a pressing force applied to the squeegee roller
15
contacting the photoreceptor web
10
is slightly reduced and the squeegee roller
15
is rotated in a direction reverse to the direction in which the photoreceptor web
10
circulates. Then, the drip line (DL) is removed and flows down along an outer circumferential surface of the squeegee roller
15
. The developer is squeegeed by the blade
17
and falls into the developer tray
12
.
However, the squeegee roller
15
is made by coating an elastic material around a metal core. There is no optimized specifications for the roughness of a surface thereof and the shape of a surface pattern. Thus, when the roughness of the surface of the squeegee roller
15
is less than or equal to 1.0 &mgr;m, the surface of the squeegee roller
15
becomes too slippery. Then, as shown in
FIG. 3
, developer at A, B and C remaining on the photoreceptor web
10
flows in a direction reverse to a direction in which the photoreceptor web
10
proceeds, by the pressing force of the squeegee roller
15
. Consequently, the printed image is deteriorated.
Meanwhile, when the roughness of the surface of the squeegee roller
15
is greater than or equal to 3.0 &mgr;m, the surface of the squeegee roller
15
becomes too rough. Thus, the developer on the surface of the photoreceptor web
10
is not squeegeed by the squeegee roller
15
and continuously remains on the photoreceptor web
10
. Therefore, the efficiency of squeegeeing is lowered.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a squeegee roller for a liquid electrophotographic printer in which the roughness of the surface thereof is maintained between 1.5-2.5 &mgr;m and a pattern with grooves is formed about 45° on the surface thereof, to improve the efficiency of squeegeeing.
Accordingly, to achieve the above objective, there is provided a squeegee roller for a liquid electrophotographic printer which comprises a steel core and an elastic rubber layer coated on an outer circumferential surface of the steel core and forming a squeegee nip by contacting a photoreceptor web, thereby to make a toner of the excess developer, which is developed in an area for an electrostatic latent image of the photoreceptor web, into a thin film in the area for electrostatic latent image and to squeeze the remaining carrier, in which the roughness (Ra) of a surface of the elastic rubber layer satisfies the condition, 1.5 &mgr;m≦Ra≦2.5 &mgr;m.
In this case, it is preferred in the present invention that a groove pattern having an inclination of about 45° with respect to an axial direction of the squeegee roller is formed on a surface of the elastic rubber layer to guide exhaust of excess developer squeegeed from the squeegee nip to the surface of the elastic rubber layer.
REFERENCES:
patent: 4091404 (1978-05-01), Schornig et al.
patent: 4127082 (1978-11-01), Kawabata
patent: 5576815 (1996-11-01), Teschendorf et al.
patent: 6104901 (2000-08-01), Imamiya
patent: 6144827 (2000-11-01), Iikura
patent: 61-272771 (1986-12-01), None
Chang Kee-son
Kwak Jin-geun
Beatty Robert
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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