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Claims  |
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What is claimed is:
1. An image-forming system, comprising:
a photosensitive/pressure sensitive recording medium which includes a
support and a uniform layer of photocurable microcapsules containing a
first color forming ingredient on the support;
charging means for uniformly charging said photosensitive/pressure
sensitive recording medium to a predetermined polarity;
a photosensitive member having a conductive layer and a photoconductive
layer arranged in a superposed manner, said conductive layer being coupled
to a first direct current power source having said predetermined polarity,
said photoconductive layer being located on an outermost surface of said
photosensitive member so as to be arranged in face-to-face relation with
respect to the uniform layer of said photocurable microcapsules on said
photosensitive/pressure sensitive recording medium;
developing means for charging a developer which is capable of combining
with the first color forming ingredient to develop an image, to a polarity
opposite to said predetermined polarity and for uniformly applying the
charged developer onto the photoconductive layer; and
exposing means for simultaneously irradiating an image information
containing light on both the photoconductive layer and the uniform coating
of the photocurable microcapsules.
2. The image-forming system according to claim 1, wherein said
photosensitive/pressure sensitive recording medium is an elongated web.
3. The image-forming system according to claim 1, wherein said charging
means includes a second direct current power source which charges said
photosensitive/pressure sensitive recording medium to said predetermined
polarity.
4. The image-forming system according to claim 3, wherein an absolute value
of a second voltage supplied by said second direct current power source is
lower than an absolute value of a first voltage supplied by said first
direct current power source.
5. The image-forming system according to claim 1, wherein said
photosensitive member comprises a photosensitive drum, said
photoconductive layer is provided on an outer peripheral surface of said
photosensitive drum, and said conductive layer is provided radially
inwardly from said photoconductive layer of said photosensitive drum.
6. The image-forming system according to claim 5, wherein the support of
said photosensitive/pressure sensitive recording medium is transparent and
capable of transmitting at least visible light therethrough.
7. The image-forming system according to claim 6, wherein said image
information containing light is irradiated on the photocurable
microcapsules after being transmitted through the support, and said
photoconductive layer is irradiated with said image information containing
light after said image information containing light has been transmitted
through the support.
8. The image-forming system according to claim 7, wherein said charging
means charges said photosensitive/pressure sensitive recording medium
before said exposing means irradiates image information containing light
onto both said photoconductive layer and said photocurable microcapsules.
9. The image-forming system according to claim 1, wherein said first color
forming ingredient includes dye-precursors, and said developer is capable
of reacting with said dye-precursors to develop colors.
10. An image-forming system, comprising:
a photosensitive/pressure sensitive recording medium which includes a
support and a uniform layer of photocurable microcapsules containing a
first color forming ingredient on the support, said
photosensitive/pressure sensitive recording medium being provided as an
elongated web;
charging means for uniformly charging said photosensitive/pressure
sensitive recording medium to a predetermined polarity;
a photosensitive member having a conductive layer and a photoconductive
layer arranged in a superposed manner, said conductive layer being coupled
to a first direct current power source having said predetermined polarity,
said photoconductive layer being located on an outermost surface of said
photosensitive member so as to be arranged in face-to-face relation with
respect to the uniform layer of said photocurable microcapsules;
developing means for charging a developer, which is capable of combining
with the first color forming ingredient to develop colors, to a polarity
opposite to said predetermined polarity and for uniformly applying the
developer onto the photoconductive layer;
irradiating means for simultaneously irradiating an image information
containing light on both the photoconductive layer and the uniform coating
of the photocurable microcapsule;
supplying means for storing and supplying a recording medium on which an
image is to be recorded;
pressure means for applying pressure to the recording medium and said
photosensitive/pressure sensitive recording medium when arranged in a
superposed manner to rupture uncured microcapsules; and
thermal fixing means for heating and fixing an image on said recording
medium.
11. The image-forming system according to claim 10, wherein said charging
means includes a second direct current power source which charges said
photosensitive/pressure sensitive recording medium to said predetermined
polarity.
12. The image-forming system according to claim 11, wherein an absolute
value of a second voltage supplied by said second direct current power
source is lower than an absolute value of a first voltage supplied by said
first direct current power source.
13. The image-forming system according to claim 10, wherein said
photosensitive member comprises a photosensitive drum, said
photoconductive layer being provided on an outer peripheral surface of
said photosensitive drum and said conductive layer being provided radially
inwardly of said photoconductive layer of said photosensitive drum.
14. The image-forming system according to claim 13, wherein the support of
said photosensitive/pressure sensitive recording medium is transparent and
capable of transmitting at least visible light therethrough.
15. The image-forming system according to claim 14, wherein said image
information containing light is irradiated onto the photocurable
microcapsules after passing through the support, said light which passes
through said support also being irradiated onto said photoconductive
layer.
16. The image-forming system according to claim 15, wherein said charging
means charges said photosensitive/pressure sensitive recording medium
before said exposing means irradiates said image information containing
light on both said photoconductive layer and said photocurable
microcapsules.
17. The image-forming system according to claim 10, wherein said pressure
means comprises a pair of pressure rollers.
18. The image-forming system according to claim 10, wherein said first
color forming ingredient includes dye-precursors, and said developer is
capable of reacting with said dye-precursors to develop colors.
19. An image-forming system, comprising:
a photosensitive member having a conductive layer and a photoconductive
layer arranged in a superposed manner, said conductive layer being coupled
to a first charging means for charging said conductive layer to a first
voltage level having a predetermined polarity, said photoconductive layer
being located on an outermost surface of said photosensitive member;
second charging means for uniformly charging a substrate to a second
voltage level having said predetermined polarity, an absolute value of
said second voltage level being less than an absolute value of said first
voltage level;
particle applying means for uniformly applying particles charged to a
polarity opposite from said predetermined polarity onto said
photoconductive layer; and
exposing means for irradiating an image information containing light onto
said photoconductive layer after said charged particles have been
uniformly applied onto said photoconductive layer so that selected
portions of said photoconductive layer become conductive to have a voltage
level substantially equal to a voltage level supplied by said first
charging means, said particles being attracted to said selected conductive
portions of said photoconductive layer more strongly than to
non-conductive portions of said photoconductive layer.
20. The image-forming system according to claim 19, wherein said first
charging means includes a first direct current power source which charges
said conductive layer to said predetermined polarity, and said second
charging means includes a second direct current power source which charges
the substrate to said predetermined polarity.
21. The image-forming system according to claim 19, wherein said
photosensitive member comprises a photosensitive drum, said
photoconductive layer is provided on an outer peripheral surface of said
photosensitive drum, and said conductive layer is provided radially
inwardly from said photoconductive layer of said photosensitive drum.
22. The image-forming system according to claim 19, further comprising:
a substrate to which said particles located on said non-conductive portions
of said photoconductive layer are transferred.
23. The image-forming system according to claim 22, wherein said substrate
is transparent.
24. The image-forming system according to claim 22, further comprising:
supplying means for storing and supplying a recording medium on which an
image is to be recorded;
pressure means for applying pressure to the recording medium and said
selectively toner-applied substrate when arranged in a superposed manner;
and
thermal fixing means for heating and fixing an image on said recording
medium.
25. An image-forming system, comprising:
charging means for uniformly charging a substrate to a predetermined
polarity;
a photosensitive member having a conductive layer and a photoconductive
layer arranged in a superposed manner, said conductive layer being coupled
to a first direct current power source having said predetermined polarity,
said photoconductive layer being located on an outermost surface of said
photosensitive member;
particle applying means for uniformly applying particles charged to a
polarity opposite from said predetermined polarity onto said
photoconductive layer, so that said particles uniformly coat and are
weakly adhered to said photoconductive layer;
exposing means for irradiating an image information containing light onto
said photoconductive layer after said charged particles have been
uniformly coated onto and weakly adhered to said photoconductive layer so
that selected portions of said photoconductive layer become conductive to
have a voltage level substantially equal to a voltage level supplied by
said first direct current power source, said particles being attracted to
said selected conductive portions of said photoconductive layer more
strongly than to non-conductive portions of said photoconductive layer,
said particles remaining weakly adhered to said non-conductive portions of
said photoconductive layer; and
a transfer point where the particles weakly adhered to the non-conductive
portions of said photoconductive layer are transferred to a substrate
charged by said charging means to said predetermined polarity.
26. The image-forming system according to claim 25, wherein said charging
means includes a second direct current power source which charges the
substrate to said predetermined polarity.
27. The image-forming system according to claim 26, wherein an absolute
value of a second voltage supplied by said second direct current power
source is lower than an absolute value of a first voltage supplied by said
first direct current power source.
28. The image-forming system according to claim 25, wherein said
photosensitive member comprises a photosensitive drum, said
photoconductive layer is provided on an outer peripheral surface of said
photosensitive drum, and said conductive layer is provided radially
inwardly from said photoconductive layer of said photosensitive drum.
29. The image-forming system according to claim 25, further comprising:
a substrate to which said particles located on said non-conductive portions
of said photoconductive layer are transferred.
30. The image-forming system according to claim 29, wherein said substrate
is transparent.
31. The image-forming system according to claim 29, further comprising:
supplying means for storing and supplying a recording medium on which an
image is to be recorded;
pressure means for applying pressure to the recording medium and said
selectively toner-applied substrate when arranged in a superposed manner;
an
thermal fixing means for heating and fixing an image on said recording
medium. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to image-forming systems of the type wherein images
are recorded by selectively applying a color developer onto a
photosensitive/pressure sensitive recording medium which contains
photocurable microcapsules.
2. Description of the Related Art
As is known in the art, color developers usually include ultrafine
particles dispersed in aqueous solvents. A color developer sheet is
fabricated by adding properly controlled binders and additives to the
color developer, and then applying the mixture to a paper sheet. An
image-forming technique using this type of color developer sheet is
disclosed, for example, in U.S. Pat. Nos. 4,399,209, 4,483,912, 4,842,976
and others. The terminology image-forming technique as used herein is
intended to mean all image forming techniques wherein two or more
ingredients which have been initially separated from each other are
brought into contact and combined with each other by application of a
physical external force such as pressure and/or temperature, so that an
optical variation, a variation in optical absorption region, or an
absorption intensity is caused to occur, thereby rendering visible
information present in the ingredients.
For example, one of the conventional image-forming techniques uses
photocurable microcapsules as described below. This technique uses three
types of photocurable microcapsules which, respectively, contain yellow,
magenta and cyan dye precursors, dyes or pigments. The respective
photocurable microcapsules have the following characteristics. The
photocurable microcapsules which contain a cyan precursor, dye or pigment
are cured by exposure to red light having a wavelength of approximately
650 nm. The photocurable microcapsules containing a magenta dye precursor,
dye or pigment are cured by exposure to green light having a wavelength of
approximately 550 nm. The photocurable microcapsules containing a yellow
dye precursor, dye or pigment are cured by exposure to blue light having a
wavelength of approximately 450 nm.
In order to record images utilizing the abovedescribed characteristics of
the photocurable microcapsules, a photosensitive/pressure sensitive
recording medium having these photocurable microcapsules applied thereon
is used with a medium on which the image is to be recorded (a recording
medium), and which has a color developer pre-coated thereon.
The photosensitive/pressure sensitive recording medium comprises a support
(such as, for example, a web) having a photocurable microcapsule layer
formed thereon. The support can have the photocurable microcapsule layer
formed thereon by uniformly applying the three types of photocurable
microcapsules onto the support. The recording medium (i.e., the medium
which is to ultimately receive the image) also comprises a support having
a color developer layer (which reacts with the dye-precursors or absorbs
the pigments or dyes) uniformly coated on the support. If a dye precursor
is contained in the respective photocurable microcapsules, the color
developer provided on the recording medium is able to develop a color by
reacting with the dye precursor (which is usually colorless). This
reaction occurs when the recording medium is contacted with the
photosensitive/pressure sensitive recording medium, and pressure or heat
is applied to the combined mediums resulting in breakage of the
microcapsules. Alternatively, when the photocurable microcapsules contain
a dye or pigment (instead of the dye-precursor), the color is developed by
absorption of the dyes or pigments by a dye-receiving material (on the
recording medium) after breakage of the photocurable microcapsules as
described above.
When red, green and blue light rays are irradiated, according to an
original image, on the photocurable microcapsule layer of the
photosensitive/pressure sensitive recording medium (which can be done
simultaneously or at separate times for each different color), only the
photocurable microcapsules which have been exposed to light having the
predetermined wavelengths described above are cured. (This curing results
in a change of the viscosity of the contents of the microcapsules, which
in the described examples is an increase in viscosity, resulting in
hardening of the microcapsules. This phenomenon is well known in the art.)
This eventually leads to formation of a chemical latent image
(corresponding to the original image) being formed on the photocurable
microcapsules located on the support. Subsequently, the
photosensitive/pressure sensitive recording medium and the recording
medium are superposed such that the photocurable microcapsule layer on
which the chemical latent image has been formed and the coated layer of
color developer are in face-to-face contact. The superposed mediums are
then passed between a pair of pressure rollers and/or heated to break
uncured microcapsules by pressure and/or heat. The contents of the broken
microcapsules are transferred to the recording medium, thereby developing
and recording a desired image on the recording medium.
Another technique which is similar to the image-forming technique described
above is described below. In the above-described image-forming technique,
images are formed on a recording medium on which a developer has been
pre-coated. The technique to be described below enables images to be
formed on any arbitrary type of recording medium. In this second
technique, color developer powder is electrostatically applied onto an
arbitrary medium (such as, for example, plain paper), thereby forming a
recording medium. Then, the same procedures (superposing, etc.) as in the
first described technique are performed.
This second type of technique is known as a color developer application
technique, and is disclosed in U.S. Pat. No. 5,038,710. According to the
color developer application technique, an electrode is placed on the back
side of any arbitrary recording medium. An electric field is generated
between the electrode and a carrier (for example, a photosensitive drum)
which is used to carry the color developer powder, so that the color
developer powder is then electrostatically attracted to the recording
medium. This results in the color developer powder being applied onto the
entire surface of the arbitrary recording medium.
The application of the color developer particles onto the entire surface of
the recording medium as described above has the following problem. When an
image is formed on the recording medium which has the color developer
powder applied on the entire surface thereof, the developer powder remains
on the white or background regions even though no color developing
function is required for these background regions. In the described
example, the regions which are free of any image correspond to the area of
the recording medium which was superposed with regions of the
photosensitive/pressure sensitive recording medium that contained all
cured microcapsules, and thus no color. Thus, the developer powder located
on the background regions is wasted, increasing a cost per unit output
image (hard copy). Moreover, the color developer powder located on the
white (background) regions becomes discolored by prolonged exposure to
light or air. This discoloration of the developer lowers the image
contrast and degrades the storage properties of the resulting output
image.
To avoid this problem, there has been proposed, for example, in U.S. Pat.
No. 4,985,727, a selective application process of a color developer
wherein color developer particles are selectively applied only onto
portions of the photosensitive/pressure sensitive recording medium where
color images are to be formed. In this process, however, the step of
curing microcapsules by exposure of the photosensitive/pressure sensitive
recording medium to a light image and the step of selectively applying a
color developer onto the uncured portions of the light exposed
photosensitive/pressure sensitive medium are performed separately.
Accordingly, it is very difficult to register the selectively applied
color developer and the uncured microcapsules. If the color developer and
the latent microcapsule image are not accurately registered, not only a
portion of the color developer is wasted by not contributing to the color
development process, but also a portion of the desired image (i.e., the
uncured microcapsules that were not coated with developer) are not color
developed. Thus, there arises the problem that the image is incomplete and
unclear.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an image-forming
system wherein a color developer can be selectively applied only to
portions of a recording medium on which images, including letters and
characters (i.e., colored images) are to be formed, whereby waste of the
color developer can be avoided.
It is another object of the invention to provide an image-forming system
which forms images having improved durability.
In order to achieve the foregoing and other objects, and to overcome the
shortcomings discussed above, according to the invention, an image-forming
system comprises: a photosensitive/pressure sensitive recording medium
which includes, on a support, a uniform layer of photocurable
microcapsules containing a first color forming ingredient (e.g., dye
precursors) charging means for uniformly charging said
photosensitive/pressure sensitive recording medium to a predetermined
polarity; a photosensitive member which has a superposed structure
including a conductive layer connected to a direct current power source
having said predetermined polarity and a photoconductive layer, said
photoconductive layer being arranged in face-to-face relation with respect
to the uniform coating of photocurable microcapsules on said
photosensitive/pressure sensitive recording medium; developing means for
charging a color developer, capable of combining (e.g, by reaction or
absorption) with the first color forming ingredient in the microcapsules
to develop desired colors, to a polarity opposite to the predetermined
polarity, and for uniformly applying the color developer onto said
photoconductive layer of said photosensitive member; and exposing means
for irradiating image information-containing light simultaneously onto
both the photoconductive layer and the uniform layer of photocurable
microcapsules so that portions of the photoconductive layer exposed to
white light become conductive so as to strongly attract the color
developer applied thereon, and portions of the photoconductive layer
exposed to colored light weakly attract the color developer applied
thereto so that the weakly attracted color developer is transferred from
said photoconductive member onto portions of said photosensitive/pressure
sensitive recording medium exposed to colored light, while the strongly
attracted color developer remains on said photosensitive member.
According to the image-forming system of the present invention, the
photosensitive/pressure sensitive recording medium is uniformly charged to
a predetermined polarity by the charging means. The developing means
uniformly charges a color developer to a polarity opposite to the
predetermined polarity and also uniformly applies the color developer onto
the photoconductive layer of the photosensitive member. The system further
comprises an exposing means by which light having image information is
irradiated simultaneously onto the photoconductive layer of the
photosensitive member and the photocurable microcapsule layer of the
photosensitive/pressure sensitive recording medium. By this process,
portions of the photoconductive layer irradiated with white light are
rendered conductive and strongly attract the color developer thereto.
Portions of the photoconductive layer irradiated with colored light are
not rendered conductive, so that the color developer is transferred from
the photoconductive layer to colored light-exposed portions of the
photosensitive/pressure sensitive recording medium. In this manner, the
color developer is selectively applied only onto portions of the
photosensitive/pressure sensitive recording medium which contain
microcapsules which are to be ruptured.
According to the invention, the photosensitive/pressure sensitive recording
medium and the photosensitive member are exposed to light at the same
time, so that the selective curing of the microcapsules and the selective
charging of the photoconductive layer of the photosensitive member are
effected simultaneously, preferably by the same rays of light. As a
consequence of this light exposure, the color developer on the
photosensitive member is selectively, strongly electrostatically attracted
to portions of the photosensitive member which received white light so
that the selectively attracted color developer is not deposited onto the
microcapsules which also received the white light (and thus will not be
subsequently ruptured). Thus, only the selected color developer which
takes part in the color development with rupturable microcapsules is
deposited onto the photosensitive/pressure sensitive recording medium. The
color developer located on portions of the photosensitive member exposed
to white light, which would not take part in the color development process
is not deposited onto the photosensitive/pressure sensitive recording
medium. Thus, discoloration does not take place and waste of the color
developer can be eliminated.
The present invention can also be used to selectively apply conventional
toner powder (or microcapsular toner powder) which forms images without
combining with any other material onto a support such as, for example,
plain paper.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention will be described in detail
with reference to the following drawings, in which like reference numerals
designate like elements, and wherein:
FIG. 1 is a schematic view of an image-forming system according to one
preferred embodiment of the present invention;
FIG. 2A is a schematic view illustrating the operating principle of an
exposing unit used in the preferred embodiment of the present invention;
FIG. 2B is a schematic view illustrating light intensities of the
respective reflected light rays and a conduction state of a
photoconductive layer when exposed to the respective light rays; and
FIG. 3 is a schematic view illustrating color development through breakage
of microcapsules and combination with color developer particles, and the
transfer of the combined materials onto an arbitrary recording medium.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention are described with reference to the
accompanying drawings. Reference is first made to FIG. 2A which
illustrates an arrangement of a photosensitive/pressure sensitive
recording medium K used in the described embodiments of the invention.
Photosensitive/pressure sensitive recording medium K includes a substrate
31 made of a transparent plastic capable of transmitting at least visible
light therethrough (for example, polyethylene terephthalate, polypropylene
or the like) and a layer of photocurable microcapsules 32 uniformly coated
on one side of plastic film substrate 31. Each microcapsule contains, for
example, a dye precursor such as Crystal Violet lactone,
3-diethyl-amino-7-chlorofluoran or the like. The dye precursors are
sensitive to three types of colors including yellow, magenta and cyan.
Three types of microcapsules 32C, 32M and 32Y which respectively contain
these dye precursors are uniformly coated on one side of plastic film
substrate 31. Microcapsules 32 also contain or are made of a photocurable
resin. The photocurable resin has a viscosity which changes (via curing)
depending on the amount and color of light applied thereto, which leads to
a variation in a mechanical strength (i.e., hardness) of the microcapsules
32.
The respective photocurable microcapsules can be cured in the following
manner. The microcapsule 32C containing a cyan dye precursor is cured by
exposure to red light having a wavelength of approximately 650 nm. The
microcapsule 32M containing a magenta dye precursor is cured by exposure
to green light having a wavelength of approximately 550 nm. The
microcapsule 32Y containing a yellow dye precursor is cured by exposure to
blue light having a wavelength of approximately 450 nm. These
microcapsules and their use are well known in the art as illustrated by
the above-referenced U.S. patents.
Referring now to FIG. 1, the image-forming system according to the present
invention is described.
An image-forming system M includes a housing 1 having an original mount 2
at the upper surface of housing and is arranged to hold an original 3 (the
original document to be copied) below original mount 2. The original mount
2, while keeping the original 3 in position is movable in the left or
right direction as viewed in FIG. 1 by conventional drive means (not
shown). Generally, the image-forming system M accommodates therein an
exposure unit 10, a developing unit 20, a transfer unit 30, and a thermal
fixing unit 40.
The exposure unit 10 is located below the original mount 2 and includes a
light source 4, a reflection mirror 5 and a filter unit 6. Light s | | |
