Liquid developer imaging system

Details Liquid developer imaging system Liquid developer imaging system

2002-05-13

2004-07-20

Grimley, Arthur T. (Department: 2852)

Electrophotography

Image formation

Development

C399S240000

Reexamination Certificate

active

06766130

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid developer imaging system and, more particularly, to a method of developing an image and to a liquid developer imaging system that has a simple structure and uses a high-density developing solution.
2. Description of the Related Art
In a general liquid developer imaging system, light is scanned onto a photosensitive object to form an electrostatic latent image corresponding to a desired image. Next, the obtained electrostatic latent image is developed with a developing solution that is a mixture of powdered toner and a liquid solvent. Then, the developed resultant is printed on paper.
FIG. 1
is a view of an example of a general liquid developer imaging system disclosed in U.S. Pat. No. 5,255,058. Referring to
FIG. 1
, the general liquid developer imaging system includes: a photosensitive object
10
electrically charged to a predetermined voltage level by a charger
14
; an optical scanning device
16
which forms an electrostatic latent image of a desired image by scanning light onto the charged photosensitive object
10
and forming a relative voltage difference thereon; a developing solution supply unit, which supplies developing solution to the photosensitive object
10
to form the electrostatic latent image; and a transferring roller
30
that receives an image developed on the photosensitive object
10
and prints the received image on paper.
The developing solution supply unit generally supplies the developing solution including less than 3% solid toner to the portion between the photosensitive object
10
and a developing roller
38
. The developing solution supply unit includes: enriched cartridges
82
and
84
containing enriched developing solution of about 25% solid; a solvent cartridge
86
containing a pure solvent; mixing tanks
55
,
57
,
59
and
61
that are classified according to colors and mix the developing solution and solvent in the cartridges
82
,
84
and
86
to prepare the developing solution of regular concentration, e.g., 2~3% solid; a supplier
20
for pumping the developing solution prepared in the mixing tanks
55
,
57
,
59
and
61
by pumps
90
,
92
,
94
and
96
, and supplying the same to the developing roller
38
; and a retriever for retrieving the developing solution remaining after the development of an electrostatic latent image. The retriever includes: a collecting container
50
which collects the developing solution remaining after the developing solution is supplied to the developing roller
38
and the photosensitive object
10
, and then returns the remaining developing solution to the mixing tanks
55
,
57
,
59
and
61
; a squeezing roller
26
, which compresses the photosensitive object
10
where an image is developed and squeezes the developing solution out of the developed image; and a separator
66
for retrieving the squeezed developing solution from the collecting container
50
, extracting a toner and a solvent from the developing solution and supplying the extracted solvent to the solvent tank
65
.
To develop an image using the above general liquid developer imaging system, four colors of developing solutions containing 2-3% solid, i.e., yellow Y, magenta M, cyan C and black K, are prepared in the mixing tanks
55
,
57
,
59
and
61
, respectively. In the developing system, for a black and white image, only one color developing solution is required, whereas in a liquid developer imaging system, which develops color images, developing solutions of four different colors are needed. To prepare four developing solutions of different colors, the developing solution supply unit extracts enriched developing solution from the enriched cartridges
82
and
84
and a pure solvent from the solvent cartridge
86
and supplies them to the mixing tanks
55
,
57
,
59
and
61
to prepare developing solutions containing 2~3% solid. In general, each of the mixing tanks
55
,
57
,
59
and
61
includes a concentration sensor (not shown) for measuring the concentration of the mixed developing solution. When the developing solutions are prepared, an image is developed as described below.
First, while the photosensitive object
10
is charged with a predetermined electrical charge by the charger
14
, light is scanned onto the charged photosensitive object
10
by the optical scanning device
16
and as a result, an electrical potential of the photosensitive object
10
is lowered, thus forming a desired electrostatic latent image. Next, the pumps
90
,
92
,
94
and
96
are operated to supply the developing solutions from the mixing tanks
55
,
57
,
59
and
61
to the region between the developing roller
38
and the photosensitive object
10
, through the supplier
20
, thereby developing the electrostatic latent image. Then, the developed image is transferred onto the transferring roller
30
. Next, if the image is composed of one color, then the transferred image is directly printed on paper
72
. However, if a desired image is a color image, the above process must be repeated for each respective color, i.e., yellow Y, magenta M, cyan C and black K, so that images developed per color are overlapped on the transferring roller
30
forming a color image. Thereafter, the formed color image is printed on paper
72
, which passes all the way through and between the transferring roller
30
and a compressing roller
71
.
Such a general liquid developer imaging system is not easy to use because of the complexities in preparing the developing solution, supplying the solution between a developing roller and a photosensitive object, and retrieving it. The complexity in the system is due to the fact that enriched high-density developing solution is not used directly in the general liquid developer imaging system but must be diluted to less than 3% solid by concentration. The use of diluted developing solution makes the fluidity thereof better, thus reducing regional deviation of toner density in a developed image. However, diluting developing solution makes a process of developing an image more complicated. In detail, enriched developing solution and solvent are prepared in each of the enriched cartridges
82
,
84
and
86
to be supplied to the mixing tanks
55
,
57
,
59
and
61
, mixed to have a low solid concentration of less than 3% and used to form an electrostatic latent image. Then, the solvent contained in the developed image is squeezed to be retrieved, so that the developing solution has a high concentration to be adapted to print the image. Accordingly, the general liquid developer imaging system becomes larger and more expensive to manufacture. For this reason, there is a growing need for a new liquid developer imaging system to solve this problem.
SUMMARY OF THE INVENTION
To solve the above problem, it is an aspect of the present invention to provide an improved liquid developer imaging system in which high-density developing solution can be used without squeezing a solvent from the solution.
Accordingly, to achieve the above aspect, the present invention includes a liquid developer imaging system that has a cartridge for storing a developing solution; a developing container for receiving the developing solution supplied from the cartridge via a predetermined supply line; a developing roller installed for rotating facing a photosensitive object, and partly submerged in the developing solution contained in the developing container; and metering means for scraping off developing solution coated on the surface of the developing roller to a predetermined thickness.
Furthermore, to achieve the above aspect, the present invention includes a method of developing a print image comprising of supplying a developing solution from a cartridge to a developing container by the movement of a piston for compression and expansion of a tube; applying a bias voltage to a development roller, partly submerged in the developing solution contained in the developing container, and to a deposit roller for charging particles of a toner i

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