U.S. patent number 3,705,767 [Application Number 05/056,852] was granted by the patent office on 1972-12-12 for electrophotographic device.
Invention is credited to Osamu Fukushima, Yasuo Tamai.
United States Patent |
3,705,767 |
Tamai , et al. |
December 12, 1972 |
ELECTROPHOTOGRAPHIC DEVICE
Abstract
An electrophotographic device for reproducing a colored original
characterized by the interconnection of a plurality of processing
units each having a corona charging means, a color-decomposing
filter of a color corresponding to a unique color constituent of
the colored original, and a developing means for applying a toner
of a color complementary to the color of the filter, the elements
of each developing unit being arranged in the sequence mentioned
above. The interconnected processing units are moved across the
surface of a stationary electrophotographic sensitive material on
which the image of the colored original is projected, the original
also being held in a stationary position whereby the colored
original is reproduced on the surface of the sensitive material
after all processing units are moved thereacross.
Inventors: |
Tamai; Yasuo (Asaka-shi,
JA), Fukushima; Osamu (Asaka-shi, JA) |
Family
ID: |
13058695 |
Appl.
No.: |
05/056,852 |
Filed: |
July 21, 1970 |
Foreign Application Priority Data
|
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|
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Jul 21, 1969 [JA] |
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44/57544 |
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Current U.S.
Class: |
399/178;
430/45.2; 430/45.3; 399/239; 399/249 |
Current CPC
Class: |
G03G
15/0142 (20130101) |
Current International
Class: |
G03G
15/01 (20060101); G03g 015/00 () |
Field of
Search: |
;355/4,3,8,10 ;96/1.2
;118/637 ;117/17.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Matthews; Samuel S.
Assistant Examiner: Greiner; Robert P.
Claims
What is claimed is:
1. An electrophotographic device for reproducing a colored original
comprising:
an electrophotographic sensitive layer;
means for holding said layer in a stationary position;
means for holding said colored original in a stationary
position;
means for imaging said colored original onto said sensitive
layer;
a plurality of processing units serially connected, each
including:
means for charging said sensitive layer disposed approximately at
one end of its processing unit;
color-decomposing filter means disposed approximately adjacent to
and farther from said one end than said charging means, each
color-decomposing filter means corresponding to a unique color
constituent of said colored original; and
developing means disposed approximately adjacent to and farther
from said one end than said color decomposing filter means for
developing latent images on said sensitive layer with a toner of a
color complementary to the color of said color-decomposing filter
means; and
means for moving said plurality of color processing units across
said sensitive layer so that said one end of each of said
processing units first encounters said sensitive layer as the
processing units are moved thereacross
whereby as the color-decomposing filter of each of said processing
units passes under the image of said colored original, a latent
image is formed on said sensitive layer, said latent image
corresponding to the color constituent of said colored original
having the color of the toner used in the processing unit being
moved across the sensitive layer, the latent image being
subsequently developed by said last-mentioned toner to form the
image of said last-mentioned color constituent on the sensitive
layer
whereby all color constituents of said original are reproduced on
said sensitive layer after all of said processing units have been
moved across said sensitive layer to thereby reproduce said colored
image.
2. A device as in claim 1 where each said processing unit includes
an opening extending vertically therethrough disposed between said
one end and said charging means so that the light of said colored
original image may substantially discharge any electrostatic charge
on said sensitive layer.
3. A device as in claim 1 where said developing means includes
means for contacting said sensitive layer with a liquid
developer.
4. A device as in claim 3 where said liquid developer contacting
means includes a roller having a porous portion containing said
liquid developer, said roller being held in contact with said
sensitive layer so that said latent image is developed by the toner
carried in said liquid developer when said latent image is
contacted by said roller.
5. A device as in claim 3 where each said processing unit includes
means for removing excess liquid developer on said sensitive layer,
said last-mentioned means being positioned approximately adjacent
to and further from said one end than said developing means.
6. A device as in claim 5 where said excess liquid developer
removing means includes a metallic roller held in contact with said
sensitive layer to squeeze said excess liquid developer off of said
sensitive layer.
7. A device as in claim 1 where said processing units are disposed
above said sensitive layer.
8. A device as in claim 1 where said processing units are disposed
below said sensitive layer.
9. A device as in claim 8 where said developing means includes a
metallic roller disposed adjacent to said sensitive layer, said
metallic roller being partially disposed in a bath of said liquid
developer, said device including means for rotating said metallic
roller so that said liquid developer contacts said sensitive
layer.
10. A device as in claim 9 where said metallic roller is spaced
0.05 mm. to 1 mm. from said sensitive layer.
11. A device as in claim 1 including an opaque member disposed
outside of and adjacent to said one end of the first of said
processing units for preventing the illumination of said sensitive
layer by said image of the colored original, said opaque member
being connected in series with said processing units and moved by
said moving means so that said sensitive member is not exposed to
said image of the colored original until said processing units are
moved thereacross.
Description
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a novel electrophotographic device. The
device according to the present invention is suitable particularly
for color reproduction.
The electrophotographic process whereby an electrostatic latent
image is formed on the surface of a photoconductive sensitive layer
in conformity with a given image and the latent image is developed
by a toner has already been put to practical use. It is readily
conceived that it is sufficient to repeat this electrophotographic
process for each of the colors involved for the purpose of
electrophotographically reproducing an original containing color
images. For example, a color image can be obtained by repeating,
for varying combination of filters and toners, the process
consisting of the steps of exposing an electrically charged
xerographic plate to a given image through a color-decomposing
filter, developing the latent image with a toner possessed of a
complementary color with reference to the color filter, and
transferring the toner image onto a white paper. The method of
obtaining a color image by the so-called superposition developing
process which repeats the steps of electric charging, exposing to
color-decomposed image, and developing with color toner on one same
electrophotographic sensitive paper has already been reduced to
practical application as Remak's process.
However, these methods have suffered from the short-coming of
insufficient rapidity. To obtain a color image of desirable
quality, the process comprising the steps of electric charging,
exposing to light, and developing is required to be repeated at
least three times. In the course of repetition, there is involved a
problem of registration, namely, the requirement that the
positional relation between the original and the sensitive layer
should remain unchanged at the time of exposure to light. This and
other problems have prevented materialization of a method for
rapidly accomplishing color reproduction or a color reproducing
device capable of rapid treatment.
After various researches, the inventors have developed an
electrophotographic device whereby the positional relation between
the original and the sensitive layer can be maintained unchanged
during the process of color reproduction. This device is also
characterized by its capability of accomplishing the color
reproduction in an extremely short period. In the present
invention, the exposure to image is accomplished while the
processing unit consisting of a corona charging electrode, an
optical filter, a liquid developing device, and squeeze rollers is
passing over the surface of an immobilized sensitive layer. In the
case of color reproduction, the exposure to image is accomplished
continuously over the entire surface of a sensitive layer while a
plurality of such processing units are passing thereover.
Accordingly, absence of color registration cannot occur at all in
the resultant image because the original, the optical lens system,
and the sensitive layer remain stationary during color
reproduction. Further, this device can be utilized for not only
color reproduction but also monochrome reproduction. Therefore, the
object of this invention resides in providing a novel
electrophotographic device. Another important object of the
invention consists in providing an electrophotographic device
capable of rapidly accomplishing color reproduction. A still other
object of this invention is to provide an electrophotographic
device capable of producing color images without involving absence
of color registration.
BRIEF EXPLANATION OF THE DRAWINGS
FIG. 1 and FIG. 2 are side elevations in longitudinal section of
processing units to be used for the present invention;
FIG. 3 and FIG. 4 are side elevations in longitudinal section of
devices having a plurality of processing units interconnected so as
to carry out color reproduction, and
FIG. 5 is a side elevation in longitudinal section of an
electrophotographic device of the present invention.
The present invention will be described in further detail by
referring to the accompanying drawings.
FIG. 1 illustrates the condition in which the processing unit of
the present invention is passing over the sensitive layer from
right to left in the drawing. In obtaining a color reproduction, a
plurality of such processing units are interconnected and put to
use. On the supporting board 14, there is stationarily disposed an
electrophotographic sensitive paper having a photoconductive
insulative layer 1 formed on a base 2, with the surface of the
photoconductive insulative layer 1 facing upward. The exposure to
image is accomplished continuously onto the supporting board 14
from above this processing unit.
The case 3 of the processing unit is made of metal plate, for
example. It serves to enclose the processing unit only on its
lateral sides. In the diagram of FIG. 1, the processing unit is
moved from right to left for its service. Inside the processing
unit, there is provided a vacant space. Through this vacant space,
therefor, rays of light conforming to the image projected from
above the processing unit can reach the sensitive layer without
being intercepted. When a plurality of interconnected processing
units is moved, this vacant space 4 serves the purpose of
eliminating electrostatic charge remaining on the surface of
sensitive layer by virtue of light.
In the direction of advance, the corona charging member consisting
of a shielding plate 6 and a corona discharge electrode 5 is
positioned next to the space. The surface of the sensitive layer 1
is electrically charged by having this member pass over the
electrophotographic sensitive layer. In this drawing, the corona
discharge electrode 5 is illustrated as one composed of thin
metallic wire. It goes without saying that what may be formed by
placing needle-shaped electrodes side by side can be used as such.
This corona discharge electrode 5 is connected to a remote
high-voltage power source. The shielding plate 6 is made of metal
and is grounded electrically. The distance between the corona
discharge electrode 5 and the sensitive layer 1 is determined by
the magnitude of the electric potential applied by the corona
discharge electrode 5 and the speed at which the processing unit is
moved.
Next to the corona charging member is disposed the optical filter
7. While the processing unit is moving over the sensitive layer 1,
exposure to image is performed continuously from above the
processing unit. Consequently, the sensitive layer which has
already charged electrically is exposed to the image which is
color-decomposed through the optical filter 7 so as to acquire a
latent image conforming to the image. As a result, there is formed
an electrostatic latent image on the surface of sensitive layer 1
which is situated below the optical filter 7. As the processing
unit moves on, the electrostatic latent image thus formed comes
into contact with the roller 8. This roller 8 has a porous surface
capable of easily absorbing a liquid and is made of an insulative
material. The roller 8 contains an insulative liquid and therefore
can wet the surface of sensitive layer having the electrostatic
latent image formed thereon. This treatment is intended to minimize
possible fogging in the course of development. Where fogging does
not pose any serious problem, therefore, this roller 8 can
naturally be omitted. Then the surface of latent image is treated
with the developing roller 9. This roller 9 has a porous surface
capable of easily absorbing and retaining a liquid and contains on
the surface an electrophotographic light developing agent. While
this roller 9 is held in contact with the surface of the sensitive
layer, the toner in the liquid developing agent contained in the
roller 9 is caused to deposit on the surface of sensitive layer in
conformity to the electrostatic latent image formed on the surface
of sensitive layer. Thus is developed the latent image. The surface
of sensitive layer which has undergone the step of developing and
consequently has been wetted with the liquid developing agent is
then squeezed by the roller 10. The roller 10 is made of an element
having a smooth surface, such as a metallic roller possessed of a
surface of mirror-face finish. As the development and the squeezing
are performed, the liquid developing agent collects on the surface
of sensitive layer which is positioned between the developing
roller 9 and the squeeze roller 10. Such excess liquid developing
agent is absorbed by the pad 11 which is capable of absorbing
liquid. This pad 11 is held in intimate yet smooth contact with the
squeeze roller 10. Thus, the surface of the squeeze roller 10 is
kept clean at all times. The liquid developing agent which has been
absorbed by the liquid-absorbing pad 11 is returned to the
developing roller 9 as the amount of liquid developing agent within
the developing roller 9 becomes small. This transfer of liquid
developing agent occurs because the pad 11 and the developing
roller 9 are held in light contact with each other.
Removal of the excess developing agent deposited on the surface of
sensitive layer may be accomplished without necessarily resorting
to such squeeze roller. It may be accomplished by blowing a current
of air against the surface, for example.
After the processing unit has passed over, there remains an image
on the surface of sensitive layer as a result of development. The
upper section of the processing unit is optically shielded against
light coming from above, except the vacant space 7 and the optical
filter member 7. The shielding plate 12 is intended to provide such
optical shielding. The pipe 13 is intended to supply the insulative
liquid to the roller 8.
The processing unit which has been explained by referring to the
diagram of FIG. 1 above, is suitable for the development wherein
the projection of light is made downwardly.
Now a description is made of the case wherein the projection of
light is made upwardly. The condition of such projection is shown
in FIG. 2. In this case, the electrophotographic sensitive paper
composed of the base 22 and the sensitive layer 21 is fixed on the
supporting board 23, with the surface of sensitive layer looking
downwardly.
The processing unit is housed in the case 24 which is covered only
on its lateral sides. The processing unit is made to travel from
right to left. In the processing unit, there are arranged the
vacant space 25, the corona electrode 26, the shielding plate 27,
and the optical filter 28 in sequence in the direction of travel as
in the case of the embodiment illustrated in FIG. 1. By these
components, the surface of the sensitive layer is electrically
charged and then exposed to the color-decomposed image. On the
surface of electrostatic latent image thus obtained, an insulative
liquid is spread by the roller 29 similarly to the roller 8 of the
former embodiment. Below the roller 29 is situated the reservoir 32
for the insulative liquid. The insulative liquid is preserved
within the container 33 and constantly keeps the roller 29 wet. The
development is made by the developing roller 30. The developing
roller may be similar to the developing roller 9 which was
described in the embodiment of FIG. 1. In this case, the roller 30
may be brought into direct contact with the surface of latent image
on the sensitive layer. Otherwise, the roller 30 may be a simple
metallic roller. If there is provided a mechanism whereby the
developing roller 30 is revolved with the travel of the processing
unit, then the liquid developing agent 37 is taken up by the
surface of the roller 30 and is then applied to the surface of
sensitive layer. In case where the roller 30 is made of metal, it
is not desirable for the roller 30 to achieve either linear contact
or surface contact directly with the surface of the sensitive layer
21. Such contact has the possibility of destroying the
electrostatic latent image.
In such case, the roller 30 is so adjusted that it will keep a
fixed opening from the surface of sensitive layer. The opening is
suitable in the range of from 0.05 mm to 1 mm. The lower limit
depends on the smoothness of the surface of the sensitive layer and
the mechanical precision of the mechanism in question, while the
upper limit is determined by the viscosity of the liquid developing
agent. With this mechanism, there may be employed the so-called
toner sheet process by having a porous roller. In this case, the
roller may be held in contact with the sensitive layer. Numeral 38
denotes the container for holding the liquid developing agent. The
surface containing the developed image is squeezed by the squeeze
roller 31. The excess developing agent which has been squeezed out
falls back into the container 38. After the processing unit has
travelled from right to left, there is left on the surface of the
sensitive layer an image which has undergone the treatment of
development.
In the processing unit illustrated in FIG. 2, it is desirable that
the shielding plate 27, the container 33, and the container 38 are
made of materials impervious to light. This is for the purpose of
shielding the processing unit against the passage of light coming
from below, with the exception of the filter 28 and the vacant
space 25.
In the embodiments illustrated in FIG. 1 and FIG. 2, the vacant
spaces 4 and 25 respectively are intended to eliminate, by virtue
of light, the electrostatic charge remaining on the surface of the
sensitive layer. Therefore, a lamp may be placed in such space to
project light for the same purpose. Otherwise, an AC corona
discharge electrode may be disposed to accomplish this purpose.
In the case of the development of monochrome image, the step of
electric charging is required only once. Therefore, the vacant
space is not required. In the case of color reproduction, such
processing units as shown in FIG. 1 or FIG. 2 are interconnected
and used in that state. Needless to add, such vacant space is not
required in the processing unit (the first one of the series as
seen in the direction travel) to be used for the first color either
in this case.
Referring to FIG. 1 and FIG. 2, examples of the processing unit to
be used for the present invention have been described. Now, the
following description covers the operation of color reproduction
involving the use of a plurality of such processing units
interconnected with one another.
FIG. 3 illustrates the condition in which the development is made
by using three processing units of FIG. 1 interconnected with one
another. The interconnected unit moves from right to left with
reference to the drawing. In the device of FIG. 3, projection of
light is made downward. The exposure to light is carried out
continuously while the interconnected processing unit passes over
the electrophotographic paper 35 which is fixed immovably on the
supporting board 36. In the case of the device shown in FIG. 3,
exposure to light begins at the moment that the optical filter 43
of the first processing unit arrives at the right edge of the
sensitive paper 35 and continues until the optical filter 51 of the
third processing unit has passed the left edge of the sensitive
paper 35. Such continuous exposure to light characterizes the
present invention.
According to the present invention, since the optical filter for
color decomposition is incorporated in the processing unit, there
is no need for inserting any optical filter in the optical system
for image projection (near the lens or in front of the original,
for example). Consequently, the original is illuminated by a light
source of white color so that the image which is not
color-decomposed in any way is projected through the lens system
onto the processing unit, with the focus adjusted to the surface of
the electrophotographic sensitive layer.
Now, as one end of the interconnected processing unit follows the
light-shielding screen 53 and approaches one end (right end in the
drawing) of the sensitive paper 35, the aforementioned projection
of color image is started. In the first unit of the interconnected
processing unit, the vacant space portion 41 is shielded against
passage of light. As the unit further travels, the sensitive layer
is electrically charged by the corona charge element 42. In the
present example, the first unit is used for developing an image in
magenta color, the unit in the middle for developing an image in
cyan color, and the last unit for developing an image in yellow
color respectively. In such case as this, the optical filter 43 to
be used in the magenta color developing unit should be in green
color. Consequently, an image of light excluding the constituent of
magenta color is projected onto the sensitive layer. By making such
color-decomposed projection, the data on the magenta color
constituent of the original image are formed on the surface of
sensitive layer as a static latent image. The surface containing
this latent image is immediately wetted by the insulative liquid
with the aid of the roller 44 and then brought into contact with
the developing roller 45. The developing roller 45 contains the
liquid developing agent which incorporates a toner of magenta
color. Thus, the area which has remained undischarged by the light
passed through the green filter 43 is now developed in the magenta
color (attraction development). This action continues while the
processing unit passes over the entire surface of the sensitive
layer. The surface containing the developed image is squeezed by
the squeeze roller 46. It is generally known that, according to
such method of developing as this, the development cannot be
achieved to the extent of completely eliminating the electric
charge on the surface of sensitive layer. The electric charge
remaining on the surface is eliminated by the light from the image
which passes through the vacant space 47 of the unit in the middle.
The light which passes the vacant space 47 originates from the
projection of the original image. If this is the light from the
color image, the light of image including the magenta color
constituent penetrates through the toner image of magenta color and
reaches the surface of sensitive layer. Consequently, the electric
charge remaining in the surface of sensitive layer beneath the
image of magenta toner is eliminated. If the image of the original
happens to be in black color, the electric charge below the image
of magenta toner is not eliminated. This has no adverse effect
whatever on this invention. The reason is that, where the image of
original is in black color, the second and third toners are
required to deposit on top. As the interconnected processing unit
travels further to left, the portion which has acquired the image
of magenta toner by means of the first unit is immediately charged
electrically by the corona charge element 48 of the second
processing unit and then exposed to light through the optical
filter 49. This optical filter 49 is in red color. By making such
color-decomposed projection, the data on the cyan color of the
original are formed on the surface of sensitive layer as a static
latent image. This latent image is developed by the developing
roller 50. This developing roller 50 contains a liquid developing
agent which incorporates therein a toner of cyan color. Thus, the
area which has remained undischarged by the light passed through
the red filter 49 is developed in cyan color. In the last unit, the
optical filter 51 is in blue color and the developing roller 52
contain a liquid developing agent incorporating therein a toner of
yellow color. Also in this case, development is made by the same
mechanism, with a yellow image formed on top on the surface of
sensitive layer. The projection of light is discontinued the moment
that the optical filter 51 has passed the entire surface of the
sensitive layer. The reproduction of color image is accomplished by
having the interconnected processing unit pass over the surface of
sensitive layer while the projection of image is in
continuation.
It will be seen easily that similar reproduction can be
accomplished by using an interconnected processing unit which is
formed by combining a plurality of processing units of FIG. 2 in
series. The condition of this reproduction is illustrated in FIG.
4. Detailed description of this operation is omitted to avoid
repetition. Referring to FIG. 4, 62 denotes a supporting board, 61
an electrophotographic sensitive layer fixed on the supporting
board with the surface of sensitive layer looking downwardly, and
63 a light-shielding screen. The image is projected continuously
upwardly to the entire surface of the sensitive layer. The
interconnected processing unit is disposed in much the same way as
shown in FIG. 3. In the direction of travel, the first unit
consists of the optically closed vacant space 64, corona discharge
element 65, green filter 66, roller 67 for applying the insulative
liquid, liquid developing agent 68 containing a toner of magenta
color, developing roller 69, and squeeze roller 70. The unit in the
middle has vacant space 71, corona charging element 72, red filter
73, and others, with the liquid developing agent 74 incorporating a
toner of cyan color. In the last unit, the filter 75 is in blue
color, and the liquid developing agent 76 contains a toner of
yellow color. In the other respects, this unit is similar to the
other units. Where projection of light and development are made
upwardly as shown in the drawing of FIG. 4, the interconnected
processing unit is mounted on guard rails (not shown) which are
laid on both lateral sides exterior to the sensitive paper section
as seen in the direction of travel. It is made to travel along the
surface of the sensitive layer.
The electrophotographic sensitive paper to be used in the device of
the present invention is desired to have sensitivity to light of
the entire visible zone. Where the decomposing sensitivity in the
visible zone is not uniform, it is desirable to control the
position of the corona electrode disposed inside each processing
unit (with reference to the distance from the sensitive layer) or
the width of filter as measured in the direction of travel. By such
control, the optical density of each color image can be
uniformalized with ease. Where the sensitive paper suffers from low
sensitivity, an image of good quality can readily be obtained by
suitably lowering the speed at which the unit passes over the
paper. In case where the speed of the travel is lowered, it is
desirable to either lower the electric potential to be applied to
the corona electrode or prevent overcharge by increasing the
distance of the corona electrode from the surface of sensitive
layer.
Where the sensitive paper has high degree of sensitivity, the
processing unit can be made to travel at an increased rate. There
is a possibility that excessively high speed of travel may fail to
provide sufficient development. In such case, the speed of travel
can be lowered by decreasing the width of filter. Where there is
shortage of electric charging, the corona electrode has only to be
brought closer to the surface of sensitive layer.
Accordingly, in the device of the present invention, the adjustment
of color balance can be accomplished by increasing or decreasing
the distance between the corona electrode and the sensitive layer
and the length of the filter.
Since the optimum combination can vary with the kind of sensitive
material (including variation between production lots), the kind of
developing agent, and the like, there must be provided a mechanism
for adjusting the distance between the corona electrode and the
sensitive layer and mechanism for adjusting the length of the
filter, together with ample space for such mechanisms, within the
device. They will serve the purpose of heightening the practical
utility of the device.
In the explanation referring to FIG. 3 and FIG. 4, the development
was conducted in the sequence of magenta, cyan, and yellow. This
sequence is not necessarily definite. The sequence is determined by
the light absorbing property of each toner and the electric
charging property on the surface of sensitive layer.
One example of the electrophotographic device according to the
present invention is shown in FIG. 5. In this device, the sensitive
paper 85 is rolled up and preserved in that state. The reproduction
of color image is accomplished by using the interconnected
combination 88 of three developing units. The processing unit used
herein in the one shown in FIG. 2. Such processing units are
interconnected as shown in FIG. 4 and used in that state. In the
device of FIG. 5, however, the processing unit is made to travel
from left to right with reference to the drawing.
At the time of exposure and development, the sensitive paper 85 is
laid out and fixed in the focal plane of the optical system onto
the pressing plate 86. Although this pressing plate 86 may be a
simple plate, it is desired to have such mechanism that air is
sucked from behind through holes or grooves provided thereon,
whereby the sensitive paper will be held fast against the
plate.
The original containing a color image which is to be reproduced is
held under pressure against a transparent glass 92. The original is
illuminated by the light source 95 while the interconnected
processing unit 88 passes over the sensitive paper. Strictly
speaking, it is desirable that the illumination starts a little
before the passage of the interconnected processing unit 88 over
the sensitive paper. This is because the color temperature is
required to be stabilized after the temperature of light source has
risen sufficiently. The shutter 97 is opened after the illumination
is started but before the interconnected processing unit 88 begins
to travel. The image projected through the lens system 93 is formed
via the mirror 94 onto the surface of sensitive layer. At the front
end of the processing unit, there is disposed the light-shielding
screen 96. This serves the purpose of obstructing the passage of
light before the processing unit 88 reaches the surface of
sensitive paper. Where the sensitive paper to be used has such
electric charging property that it will hardly experience
exhaustion due to pre-exposure, this light-shielding screen 96 is
not necessarily required. The front end of this light-shielding
screen 96 is pulled by a chain or a wire 90. As the processing unit
crosses the front surface of the sensitive paper and travels at an
equal speed, the wire 90 and the light-shielding screen 96 are
wound up on the shaft 91. When the interconnected processing unit
88 has passed the front surface of sensitive paper, the shutter 97
is closed and the light source 95 is extinguished.
After the interconnected processing unit 88 has passed the front
surface of sensitive paper, the pressing plate which holds the
sensitive paper fast goes up and the sensitive paper which now
carries a color image is forwarded to the right with reference to
the drawing to be cut by the sheeter (cutter) 87 and discharged in
the shape of a sheet. The processing unit 88 which has been moved
to the right in the drawing after the step of developing is
returned to its original position (left in the drawing) by virtue
of the wire. This is done because the wire connected to the shaft
91 is wound up. As a matter of course, the mechanism which has
caused the wire 90 and the light-shielding screen 96 to be wound up
on the shaft 91 is released at this point. During the return travel
of the processing unit 88, none of the rollers incorporated in the
processing unit 88 is allowed to come into contact with the surface
of sensitive paper. For this purpose, the pressing plate may go up
while holding the sensitive paper thereon or the processing unit
may return to its original position while in a slightly lowered
state. The tanks 81, 82, 83, and 84 are used for holding liquid
developing agents of different colors and the insulative liquid.
When liquids held in the processing unit 88 are running short,
corresponding liquids are supplied from these tanks via pipes (not
shown in the drawing) into the interconnected processing unit 88.
The corona discharge electrode provided in each processing unit is
connected to the DC high-voltage power source 98 provided within
the device by means of a long flexible high-voltage cable. High
voltage is applied to the corona discharge electrode only while the
processing unit 88 is traveling over the front surface of sensitive
paper.
As is evident from the foregoing concrete examples, the present
invention accomplishes color reproduction with extreme ease by
causing the interconnected processing unit possessed of a special
mechanism as mentioned above to travel over the electrophotographic
sensitive paper which is continuously exposed to light projected
through a given image. While reproduction is in progress, the
positional relation among the original, the optical lens system,
and the sensitive paper remains perfectly unchanged. Therefore, the
so-called absence of color registration cannot be observed at all
in the resultant color image. It is also a conspicuous
characteristic that a color copy can be obtained in a decidedly
shorter time than is required by the conventional color reproducing
method without the aid of human hand.
Although the foregoing description of the present invention has
been limited to the liquid developing process utilizing rollers for
image development, it is apparent that other electrophotographic
developing processes, such as magnetic brush process and cascade
developing process, can be applied similarly. Of various possible
processes, the liquid developing process produces the most
desirable results. In the case of liquid developing operation,
there may be employed the development of wet toner sheet process in
the place of the liquid developing process utilizing rollers. In
the case of utilizing rollers, although only one roller is being
used in the foregoing description, it is naturally able to use
plural rollers. Further, it is apparent that not only linear but
also an image of continuous gradation can be reproduced
satisfactorily by suitably selecting a developing process, for
example, a liquid developing process utilizing a developing plate
electrode.
As is clear from the foregoing description, the present invention
can sufficiently satisfy the mounting demand for "faithful
reproduction of an original containing a color image" prevailing in
the market and therefore proves to be extremely important
industrially.
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