Information
-
Patent Grant
-
6243161
-
Patent Number
6,243,161
-
Date Filed
Tuesday, December 29, 199825 years ago
-
Date Issued
Tuesday, June 5, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Adams; Russell
- Brown; Khaled
Agents
- Greenblum & Bernstein, P.L.C.
-
CPC
-
US Classifications
Field of Search
US
- 430 138
- 355 32
- 355 33
- 355 400
-
International Classifications
- G03B2700
- G03B2732
- G03L172
-
Abstract
An image-forming liquid medium comprised of a solution containing a surface-active agent, and at least two types of microcapsule mixed with the solution. A first type of microcapsule is filled with a first dye, and a second type of microcapsule is filled with a second dye. A first shell of the first type microcapsule is formed of a first resin that exhibits a first characteristic such that, when the first type microcapsule is squashed and broken under simultaneous application of a first pressure at a first temperature, the first dye seeps from the squashed and broken microcapsule. A second shell of the second type of microcapsule is formed of a second resin that exhibits a second characteristic such that, when the second type microcapsule is squashed and broken under simultaneous application of a second pressure at a second temperature, the second dye seeps from the squashed and broken microcapsule.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image-forming liquid medium containing microcapsules filled with dye or ink, and to an image-forming apparatus that forms an image on a sheet of recording paper by selectively developing monochromatic dots, when using such an image-forming liquid medium, in accordance with a series of digital image-pixel signals.
2. Description of the Related Art
Conventionally, an image-forming system, using an image-forming sheet coated with a layer of microcapsules filled with dye or ink, is known. In this image-forming sheet, a shell of each microcapsule is formed of a suitable photo-setting resin, and an optical image is recorded and formed as a latent image on the layer of microcapsules by exposing it to light rays in accordance with image-pixel signals. Then, the latent image is developed by exerting pressure on the microcapsule layer. Namely, the microcapsules, which are not exposed to the light rays, are squashed and broken, whereby the dye or ink seeps out of the squashed and broken microcapsules, and thus the latent image is visually developed by the seepage of the dye or ink.
Of course, in this conventional image-forming system, it is impossible to form an image on a sheet of ordinary printing paper without the layer of microcapsules. Nevertheless, usually, only a small portion of the microcapsules included in the layer contributes to the formation of an image on the image-forming sheet. In other words, a large portion of the microcapsules included in the layer are not utilized for the formation of an image on the image-forming sheet. Thus, in the conventional image-forming system, a large amount of ink or dye, encapsulated in the microcapsules, is wastefully consumed by not taking part in the formation of an image.
Also, each of the image-forming sheets must be packed so as to be protected from being exposed to light, resulting in wastage of materials. Further, the image-forming sheets must be handled such that they are not subjected to excess pressure due to the softness of unexposed microcapsules, resulting in an undesired seepage of the dye or ink.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a novel image-forming liquid medium containing a plurality of microcapsules filled with dye or ink, by which an image can be formed on a sheet of recording paper.
Another object of the present invention is to provide an image-forming apparatus that forms an image on a sheet of recording paper by selectively generating dots, when using the above-mentioned image-forming liquid medium, in accordance with a series of digital image-pixel signals, thereby developing monochromatic dots on a sheet of recording paper by squashing and breaking the microcapsules included in each drop.
In accordance with an aspect of the present invention, there is provided an image-forming liquid medium comprising a solution that contains a surface-active agent; and at least two types of microcapsule: a first type of microcapsule filled with a first dye, and a second type of microcapsule filled with a second dye, which are homogeneously mixed with the solution. The first type of microcapsule exhibits a first pressure/temperature characteristic such that, when the first type of microcapsule is squashed and broken under a first predetermined pressure at a first predetermined temperature, the first dye seeps from the squashed and broken microcapsule, and the second type of microcapsule exhibits a second pressure/temperature characteristic such that, when the second type of microcapsule is squashed and broken under a second predetermined pressure at a second predetermined temperature, the second dye seeps from the squashed and broken microcapsule.
The image-forming liquid medium may further comprise a third type of microcapsule filled with a third dye mixed with the solution together with the first and second types of microcapsule, and the third type of microcapsule exhibits a third pressure/temperature characteristic such that, when the third type of microcapsule is squashed and broken under a third predetermined pressure at a third predetermined temperature, the third dye seeps from the squashed and broken microcapsule.
In this image-forming liquid medium, the first type of microcapsule may have a first shell wall composed of a first resin which exhibits the first pressure/temperature characteristic, the second type of microcapsule may have a second shell wall composed of a second resin which exhibits the second pressure/temperature characteristic, and the third type of microcapsule has a third shell wall composed of a third resin which exhibits the third pressure/temperature characteristic.
Preferably, each of the first, second and third resins exhibit transparency, and each of the first, second and third dyes exhibit transparency, with the solution exhibiting transparency and further comprising a color developer that reacts with each of the first, second and third dyes, thereby developing a predetermined monochromatic color. Preferably, the respective first, second and third dyes comprise a first leuco-pigment and a second leuco-pigment, respectively, and the respective first, second, and third dyes exhibit a cyan pigmentation, a magenta pigmentation and a yellow pigmentation.
In accordance with a second aspect of the present invention, there is provided an image-forming apparatus, using the image-forming liquid medium, as mentioned above, which comprises: a transfer unit that selectively transfers a small part of the image-forming liquid medium as a first fluid drop to a sheet of recording medium in accordance with a first digital monochromatic image-pixel signal, corresponding to the first dye, and that selectively transfers a small part of the image-forming liquid medium as a second fluid drop to the sheet of recording medium in accordance with a second digital monochromatic image-pixel signal, corresponding to the second dye; and a pressure/temperature applicator unit that applies the first predetermined pressure and the first predetermined temperature to the first fluid drop, and that applies the second predetermined pressure and the second predetermined temperature to the second fluid drop.
The transfer unit and the pressure/temperature applicator unit may be combined with each other as a single thermal head assembly.
In this case, the image-forming apparatus further comprises a platen member that is associated with the single thermal head assembly, and the single thermal head assembly includes: an electrically-insulated base member; a first movable thermal head provided in the base member and having a first array of heater elements aligned with each other; a second movable thermal head provided in the base member and having a second array of heater elements aligned with each other, the first array of heater elements being in parallel with the second array of heater elements; a spacer member, having an opening, securely provided on the base member such that the first and second thermal heads are encompassed by the opening of the spacer member; and a sheet of film that covers the spacer member such that the opening of the spacer member is defined as a liquid medium space that stores the image-forming liquid medium, the sheet of film including a plurality of pores formed therein, with the pores being aligned with each other in a first row and a second row, which extend along the first and second arrays of heater elements, respectively, such that each of the heater elements is associated with a corresponding pore, the first fluid drop being produced from one of the pores in the first row by heating a corresponding one of the heater elements in the first array to the first predetermined temperature, the second fluid drop being produced from one of the pores in the second row by heating a corresponding one of the heater elements in the second array to the second predetermined temperature, the platen member urging the first and second thermal heads toward the interposed sheet of film, the sheet of recording medium being interposed between the platen member and the sheet of film during the production of the first and second fluid drops. The single thermal head assembly further includes a first resilient member that is associated with the first thermal head such that the first thermal head is elastically biased against the sheet of film, backed by the platen member, under the first predetermined pressure; and a second resilient member that is associated with the second thermal head such that the second thermal head is elastically biased against the sheet of film, backed by the platen member, under the second predetermined pressure.
Preferably, the single thermal head assembly includes a reservoir that holds the image-forming liquid medium to feed the liquid medium space of the spacer member with the image-forming liquid medium.
In accordance with a third aspect of the present invention, there is provided an image-forming apparatus, using the image-forming liquid medium, as mentioned above, which comprises: a transfer unit that selectively transfers a small part of the image-forming liquid medium as a fluid drop to a sheet of recording medium in accordance with at least one of a first digital monochromatic image-pixel signal and a second digital monochromatic image-pixel signal, which correspond to the first and second dyes, respectively; and a pressure/temperature applicator unit that selectively applies the first predetermined pressure and the first predetermined temperature to the fluid drop in accordance with the first digital monochromatic image-pixel signal, and that applies the second predetermined pressure and the second predetermined temperature to the fluid drop in accordance with the second digital monochromatic image-pixel signal.
Preferably, the transfer unit is formed as a first thermal head assembly, and the pressure/temperature applicator unit is formed as a second thermal head assembly, the first and second thermal head assemblies being arranged so as to partially define a path along which the sheet of recording medium is moved, the first thermal head assembly being positioned upstream of the second thermal head assembly in a direction of the movement of the sheet of recording medium.
In the third aspect of the present invention, the image-forming apparatus may further comprises a first platen member that is associated with the transfer unit, and a second platen member that is associated with the pressure/temperature applicator unit.
In this case, the first thermal head assembly may include: a first electrically-insulated base member; a thermal head provided in the first electrically-insulated base member and having an array of heater elements aligned with each other; a spacer member, having an opening, securely provided on the first electrically-insulated base member such that the thermal head is encompassed by the opening of the spacer member; a sheet of film that covers the spacer member such that the opening of the spacer member is defined as a liquid medium space that stores the image-forming liquid medium, the sheet of film including a plurality of pores formed therein, with the pores being aligned with each other in a single row, which extends along the array of heater elements, such that each of the heater elements is associated with a corresponding pore. The first platen member urges the thermal head toward the interposed sheet of film, and the fluid drop is selectively produced from one of the pores by heating a corresponding one of the heater elements in the array to a predetermined temperature in accordance with at least one of the first and second digital monochromatic image-pixel signals, with the sheet of recording medium being interposed between the first platen member and the sheet of film during the production of the fluid drop.
On the other hand, the pressure/temperature applicator unit may include: a second electrically-insulated base member; a first movable thermal head provided in the base member and having a first array of heater elements aligned with each other; a second movable thermal head provided in the base member and having a second array of heater elements aligned with each other, the first array of heater elements being in parallel with the second array of heater elements, and the second platen member contacting the first and second thermal heads; a first resilient member that is associated with the first thermal head such that the first thermal head elastically contacts the second platen with the first predetermined pressure, during a passage of the sheet of recording medium carrying the fluid drop through a nip between the second platen member and the elastically-contacted first thermal head, a corresponding one of the heater elements in the first array being selectively heated to the first predetermined temperature in accordance with the first digital monochromatic image-pixel signal; and a second resilient member that is associated with the second thermal head such that the second thermal head elastically contacts the sheet of film with the second predetermined pressure, during a passage of the sheet of recording medium carrying the fluid drop through a nip between the second platen member and the elastically-contacted second thermal head, a corresponding one of the heater elements in the second array being selectively heated to the second predetermined temperature in accordance with the second digital monochromatic image-pixel signal.
BRIEF DESCRIPTION OF THE DRAWINGS
These objects and other objects of this invention will be better understood from the following description, with reference to the accompanying drawings in which:
FIG. 1
is a schematic cross-sectional view showing three types of microcapsules: a cyan microcapsule filled with a cyan dye; a magenta microcapsule filled with a magenta dye; and a yellow microcapsule filled with a yellow dye, used to prepare an image-forming liquid medium according to the present invention;
FIG. 2
is a graph showing a characteristic curve of a longitudinal elasticity coefficient of a shape memory resin forming a shell wall of the cyan, magenta and yellow microcapsules shown in
FIG. 1
;
FIG. 3
is a graph showing pressure/temperature breaking characteristics of the respective cyan, magenta and yellow microcapsules shown in
FIG. 1
, with each of a cyan-developing area, a magenta-developing area and a yellow-developing area being indicated as a hatched area;
FIG. 4
is a schematic perspective exploded view of a first embodiment of an image-forming apparatus, using the image-forming liquid medium, according to the present invention;
FIG. 5
is a schematic cross-sectional view of the image-foaming apparatus shown in
FIG. 4
;
FIG. 6
is a block diagram of a control circuit of the image-forming apparatus shown in
FIGS. 4 and 5
;
FIG. 7
is a partial block diagram representatively showing a set of an AND-gate circuit and a transistor included in each of first, second and third driver circuits shown in
FIG. 6
;
FIG. 8
is a timing chart representatively showing a strobe signal and a control signal for electronically actuating the first driver circuit shown in
FIG. 6
;
FIG. 9
is a timing chart representatively showing a strobe signal and a control signal for electronically actuating the second driver circuit shown in
FIG. 6
;
FIG. 10
is a timing chart representatively showing a strobe signal and a control signal for electronically actuating the third driver circuit shown in
FIG. 6
;
FIG. 11
is a schematic partially-enlarged cross-sectional view of the image-forming apparatus shown in
FIGS. 4 and 5
, showing a representative first stage of an image-forming operation executed therein;
FIG. 12
is a schematic partially-enlarged cross-sectional view, similar to
FIG. 11
, showing a representative second stage of the image-forming operation executed in the image-forming apparatus shown in
FIGS. 4 and 5
;
FIG. 13
is a schematic partially-enlarged cross-sectional view, similar to
FIG. 11
, showing a representative third stage of the image-forming operation executed in the image-forming apparatus shown in
FIGS. 4 and 5
;
FIG. 14
is a schematic cross-sectional view of a second embodiment of the image-forming apparatus, using the image-forming liquid medium, according to the present invention;
FIG. 15
is a block diagram of a control circuit of the image-forming apparatus shown in
FIG. 14
;
FIG. 16
is a timing chart representatively showing a strobe signal and a control signal for electronically actuating an additional driver circuit shown in
FIG. 15
;
FIG. 17
is a schematic partially-enlarged cross-sectional view of a first thermal head assembly of the image-forming apparatus shown in
FIG. 14
, showing a representative first stage of an image-forming operation executed in the first thermal head assembly;
FIG. 18
is a schematic partially-enlarged cross-sectional view, similar to
FIG. 17
, showing a representative second stage of the image-foaming operation executed in the first thermal head assembly;
FIG. 19
is a schematic partially-enlarged cross-sectional view, similar to
FIG. 17
, showing a representative third stage of the image-forming operation executed in the first thermal head assembly; and
FIG. 20
is a schematic partially-enlarged cross-sectional view of a second thermal head assembly of the image-forming apparatus shown in
FIG. 14
, showing a representative stage of an image-forming operation executed in the second thermal head assembly.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1
shows three types of microcapsules: a first type of microcapsule
10
C filled with cyan liquid dye or ink, a second type of microcapsule
10
M filled with magenta liquid dye or ink, and a third type of microcapsule
10
Y filled with yellow liquid dye or ink, a plurality of which are utilized to prepare an image-forming liquid medium according to the present invention.
In each type of microcapsule (
10
C,
10
M,
10
Y), a shell wall of a microcapsule is formed of a suitable synthetic resin material. Also, in order to produce each of the types of microcapsules
10
C,
10
M and
10
Y, a well-known polymerization method, such as interfacial polymerization, in-situ polymerization or the like, may be utilized, and the microcapsules
10
C,
10
M and
10
Y may have an average diameter of several microns, for example, 1 μm to 5 μm.
In this embodiment, for the resin material of each type of microcapsule (
10
C,
10
M,
10
Y), a shape memory resin is utilized. For example, the shape memory resin is represented by a polyurethane-based-resin, such as polynorbornene, trans-1, 4-polyisoprene polyurethane. As other types of shape memory resin, a polyimide-based resin, a polyamide-based resin, a polyvinyl-chloride-based resin, a polyester-based resin and so on are also known.
In general, as shown in a graph of
FIG. 2
, the shape memory resin exhibits a coefficient of longitudinal elasticity, which abruptly changes at a glass-transition temperature boundary T
g
. In the shape memory resin, Brownian movement of the molecular chains is stopped in a low-temperature area “a”, which is below the glass-transition temperature T
g
, and thus the shape memory resin exhibits a glass-like phase. On the other hand, Brownian movement of the molecular chains becomes increasingly energetic in a high-temperature area “b”, which is above the glass-transition temperature T
g
, and thus the shape memory resin exhibits a rubber elasticity.
The shape memory resin is named due to the following shape memory characteristic: once a mass of the shape memory resin is worked into a finished article in the low-temperature area “a”, and is heated to beyond the glass-transition temperature T
g
, the article becomes freely deformable. After the shaped article is deformed into another shape, and cooled to below the glass-transition temperature T
g
, the most recent shape of the article is fixed and maintained. Nevertheless, when the deformed article is again heated to above the glass-transition temperature T
g
, without being subjected to any load or external force, the deformed article returns to the original shape.
In this embodiment, the shape memory characteristic per se is not utilized, but the characteristic abrupt change of the shape memory resin in the longitudinal elasticity coefficient is utilized, such that the three types of cyan, magenta and yellow microcapsules
10
C,
10
M and
10
Y can be selectively squashed and broken at a predetermined temperature and under a predetermined pressure.
As shown in a graph of
FIG. 3
, a shape memory resin of the cyan microcapsule
10
C is prepared so as to exhibit a characteristic longitudinal elasticity coefficient, indicated by a solid line, having a glass-transition temperature T
1
; a shape memory resin of the magenta microcapsule
10
M is prepared so as to exhibit a characteristic longitudinal elasticity coefficient, indicated by a single-chained line, having a glass-transition temperature T
2
; and a shape memory resin of the yellow microcapsule
10
Y is prepared so as to exhibit a characteristic longitudinal elasticity coefficient, indicated by a double-chained line, having a glass-transition temperature T
3
.
Note, by suitably varying compositions of the shape memory resin and/or by selecting a suitable one from among various types of shape memory resin, it is possible to obtain the respective shape memory resins, with the glass-transition temperatures T
1
, T
2
and T
3
.
Also, as shown in
FIG. 1
, the microcapsule walls of the cyan microcapsule
10
C, magenta microcapsule
10
M, and yellow microcapsule
10
Y, respectively, have differing thicknesses W
C
, W
M
and W
Y
. The thickness W
C
of the cyan microcapsule
10
C is larger than the thickness W
M
of the magenta microcapsule
10
M, and the thickness W
M
of the magenta microcapsule
10
M is larger than the thickness W
Y
of the yellow microcapsule
10
Y.
The wall thickness W
C
of the cyan microcapsule
10
C is selected such that each cyan microcapsule
10
C is compacted and broken under a breaking pressure that lies between a critical breaking pressure P
3
and an upper limit pressure P
UL
(FIG.
3
), when each cyan microcapsule
10
C is heated to a temperature between the glass-transition temperatures T
1
and T
2
; the wall thickness W
M
of the magenta microcapsule
10
M is selected such that each magenta microcapsule
10
M is compacted and broken under a breaking pressure that lies between a critical breaking pressure P
2
and the critical breaking pressure P
3
(FIG.
3
), when each magenta microcapsule
10
M is heated to a temperature between the glass-transition temperatures T
2
and T
3
; and the wall thickness W
Y
of the yellow microcapsule
10
Y is selected such that each yellow microcapsule
10
Y is compacted and broken under a breaking pressure that lies between a critical breaking pressure P
1
and the critical breaking pressure P
2
(FIG.
3
), when each yellow microcapsule
10
Y is heated to a temperature between the glass-transition temperature T
3
and an upper limit temperature T
UL
.
Note, the upper limit pressure P
UL
and the upper limit temperature T
UL
are suitably set in view of the characteristics of the used shape memory resins.
According to the present invention, same amounts of the cyan, magenta and yellow microcapsules
10
C,
10
M and
10
Y are homogeneously mixed with a suitable solution, such as a water solution, organic solution, or the like, containing a dispersant or surface-active agent to form a suspension, which is utilized as the image-forming liquid medium.
As is apparent from
FIG. 1
, preferably, the shape memory resins of the cyan, magenta and yellow microcapsules
10
C,
10
M and
10
Y should be transparent. In this case, for respective cyan, magenta and yellow dyes to be encapsulated in the cyan, magenta and yellow microcapsules
10
C,
10
M and
10
Y, cyan, magenta and yellow leuco-pigments are utilized, and color developer is contained in the solution. Usually, each leuco-pigment per se and the color developer pre se exhibit transparency, but the leuco-pigment develops a given monochromatic color (cyan, magenta, yellow) when chemically reacting with the color developer.
According to the present invention, the image-forming liquid medium is applied as a drop to a sheet of recording medium, and the cyan, magenta and yellow microcapsules
10
C,
10
M and
10
Y included in the drop are selectively compacted and broken by suitably selecting a heating temperature and a breaking pressure, which should be exerted on the drop.
For example, if the selected heating temperature and breaking pressure fall within a hatched cyan-developing area C (FIG.
3
), defined by a temperature range between the glass-transition temperatures T
1
and T
2
and by a pressure range between the critical breaking pressure P
3
and the upper limit pressure P
UL
, only the cyan microcapsules
10
C are compacted and broken. The cyan leuco-pigment, seeped from the compacted and broken microcapsules
10
C, generates cyan by chemically reacting with the color developer, and thus the drop is developed as a cyan dot on the sheet of recording paper.
Also, if the selected heating temperature and breaking pressure fall within a hatched magenta-developing area M, defined by a temperature range between the glass-transition temperatures T
2
and T
3
and by a pressure range between the critical breaking pressures P
2
and P
3
, only the magenta microcapsules
10
M are compacted and broken. The magenta leuco-pigment, seeped from the compacted and broken microcapsules
10
M, generates magenta by chemically reacting with the color developer, and thus the drop is developed as a magenta dot on the sheet of recording paper.
Similarly, if the selected heating temperature and breaking pressure fall within a hatched yellow-developing area Y, defined by a temperature range between the glass-transition temperature T
3
and the upper limit temperature T
UL
and by a pressure range between the critical breaking pressures P
1
and P
2
, only the yellow microcapsules
10
Y are compacted and broken. The yellow leuco-pigment, seeped from the compacted and broken microcapsules
10
Y, generates yellow by chemically reacting with the color developer, and thus the drop is developed as a yellow dot on the sheet of recording paper.
FIGS. 4 and 5
schematically show a first embodiment of an image-forming apparatus, using the image-forming liquid medium, which is constituted as a line printer so as to form a color image on a sheet of recording paper.
The printer is provided with a thermal head assembly
12
that includes an elongated rectangular base plate
14
formed of, for example, a suitable ceramic material, with the base plate
14
being formed with three elongated grooves
16
C,
16
M and
16
Y, as shown in FIG.
5
. The thermal head assembly
12
also includes three elongated thermal heads
18
C,
18
M and
18
Y, which are slidably accommodated in the elongated grooves
16
C,
16
M and
16
Y, respectively. Each of the thermal heads (
18
C,
18
M,
18
Y) is provided with plural spring elements (
20
C,
20
M,
20
Y), symbolically shown in
FIG. 5
, which are confined in the corresponding groove (
16
C,
16
M,
16
Y), so as to resiliently act on the corresponding thermal head (
18
C,
18
M,
18
Y), so that the thermal head (
18
C,
18
M,
18
Y) concerned is elastically biased outward from the corresponding groove (
16
C,
16
M,
16
Y). Note, each of the thermal heads
18
C,
18
M and
18
Y may also be formed of a suitable ceramic material.
As best shown in
FIG. 4
, the thermal head
18
C has an array of n electric resistance elements or electric heater elements longitudinally aligned on and embedded in an outer or lower surface thereof, with one of the n electric heater elements being representatively indicated by reference R
cn
. Similarly, the respective thermal heads
18
M and
18
Y have arrays of n electric heater elements R
mn
and S
yn
longitudinally aligned on and embedded in outer or lower surfaces thereof. Note, as is apparent from
FIG. 4
, the n electric heater elements R
cn
, the n electric heater elements R
mn
and the n electric heater elements R
yn
are aligned at a same pitch with respect to each other.
The thermal head assembly
12
further includes an elongated frame or spacer member
22
, which is formed with a rectangular opening
24
, and which is securely attached to the lower surface of the base plate
14
such that the arrays of electric heater elements R
cn
, R
mn
and R
yn
are encompassed by the rectangular opening
24
of the frame or spacer member
22
, which may be formed of an electrically insulating material, such as a suitable synthetic resin.
Furthermore, the thermal head assembly
12
includes a sheet of film
26
securely adhered to the frame or spacer member
22
such that the rectangular opening
24
is covered with the film sheet
26
, thereby defining a liquid medium space
28
, as best shown in FIG.
5
. The film sheet
26
may have a thickness of about 0.03 to about 0.08 mm, and is preferably formed of a suitable synthetic resin material, exhibiting a moderate elasticity, a wear-resistant property and a thermal-resistant property. For example, polytetrafluoroethylene can be advantageously used for the film sheet
26
.
As shown in
FIG. 4
, the thermal head assembly
12
is provided with a reservoir
30
, in which the above-mentioned image-forming liquid medium is held, such that the liquid medium space
28
is fed with the image-forming liquid medium from the reservoir
30
. In particular, the reservoir
30
has an elongated spout
32
formed therein, which is securely joined to a wide passage
34
, formed in and extending along one of the longitudinal sides of the frame or spacer member
22
, such that the reservoir
30
is in communication with the liquid medium space
28
via the wide passage
34
. Thus, the image-forming liquid medium, held in the reservoir
30
, can be drawn into the liquid medium space
28
, and the liquid medium space
28
is fed and filled with the image-forming liquid medium from the reservoir
30
.
Preferably, the reservoir
30
is provided with a roller-type agitator
38
rotatably provided therein, and the agitator
38
is rotationally driven during a printing operation of the printer, thereby ensuring a good homogenous suspension of the cyan, magenta and yellow microcapsules
10
C,
10
M and
10
Y in the image-forming liquid medium held in the reservoir
30
. Note, the reservoir
30
is suitably and securely supported by a structural frame (not shown) of the printer.
As best shown in
FIG. 4
, the film sheet
26
is provided with a plurality of pores
40
formed therein, and these pores
40
are aligned with each other in three rows, and the three respective rows of pores
40
extend below and along the arrays of electric heater elements R
cn
, R
mn
and R
yn
, such that each heater element (R
cn
, R
mn
, R
yn
) is associated with a corresponding pore
40
. Note, in
FIGS. 4 and 5
, although the pores
40
are exaggeratively illustrated, in reality, the pores
40
are microscopic.
For example, it is possible to produce the film sheet
26
, as follows:
Initially, a blank sheet of film is omnidirectionally pulled so as to be elastically expanded, and is then pierced by fine needles or fine lasers, such that a plurality of fine pores (
40
) is formed in the blank film sheet. Thereafter, the pierced blank film sheet is released from the pulling forces, and is then trimmed or shaped as the film sheet
26
with the pores
40
.
Note, when the pierced blank film sheet is released from the pulling forces, the pores
40
usually elastically close, so that the image-forming liquid medium, held in the liquid medium space
28
, cannot permeate and penetrate through the pores
40
.
Furthermore, as shown in
FIG. 4
, the printer is provided with a roller platen
42
constituted as a rubber roller, and the roller platen
42
is rotatably provided below and in contact with the film sheet
26
(
FIG. 5
) such that a rotational axis of the roller platen
42
is in parallel with the arrays of electric heater elements R
cn
, R
mn
and R
yn
. During a printing operation of the printer, the roller platen
42
is rotated, in a direction indicated by an arrow A in
FIG. 5
, with a suitable electric motor (not shown), and a sheet of recording paper to be printed, generally indicated by reference P in
FIG. 5
, is introduced into a nip between the film sheet
26
and the roller platen
42
, and is moved in a direction indicated by an arrow B in
FIG. 5
, due to the recording paper sheet P being subjected to a traction force from the rotating roller platen
42
.
A resilient force of the spring elements
20
C is set so that the thermal head
18
C is elastically pressed against the film sheet
26
, backed by the roller platen
42
, at a pressure range between the critical breaking pressure P
3
and the upper limit pressure P
UL
. Also, a resilient force of the spring elements
20
M is set so that the thermal head
18
M is elastically pressed against the film sheet
26
, backed by the roller platen
42
, at a pressure range between the critical breaking pressures P
2
and P
3
. Further, a resilient force of the spring elements
20
Y is set so that the thermal head
18
Y is elastically pressed against the film sheet
26
, backed by the roller platen
42
, at a pressure range between the critical breaking pressures P
1
and P
2
.
FIG. 6
shows a schematic block diagram of a control circuit
44
for the printer shown in
FIGS. 4 and 5
. As shown in this drawing, the control circuit
44
comprises a printer controller
46
including a microcomputer. The printer controller
46
receives a series of digital color image-pixel signals from a personal computer or a word processor (not shown) through an interface circuit (I/F)
48
. The received digital color image-pixel signals are once stored in a memory
50
.
Also, the control circuit
44
is provided with a motor driver circuit
52
for driving an electric motor
54
, such as a stepping motor, a servo motor, or the like, which is used to rotationally drive the roller platen
42
in accordance with a series of drive pulses outputted from the motor driver circuit
52
. The outputting of the drive pulses from the motor driver circuit
52
to the motor
54
is controlled by the printer controller
46
.
As shown in
FIG. 6
, the control circuit
44
is further provided with a first driver circuit
56
C, a second driver circuit
56
M and a third driver circuit
56
Y, which are controlled by the printer controller
46
to drive the thermal heads
18
C,
18
M and
18
Y, respectively. Namely, the driver circuits
56
C,
56
M and
56
Y are controlled by n sets of strobe signals “STC” and control signals “DAC”, n sets of strobe signals “STM” and control signals “DAM”, and n sets of strobe signals “STY” and control signals “DAY”, respectively, outputted from the printer controller
46
, thereby carrying out the selective energization of the heater elements R
c1
to R
cn
, the selective energization of the heater elements R
m1
to R
mn
and the selective energization of the heater elements R
y1
to R
yn
, as stated in detail below.
In each driver circuit (
56
C,
56
M,
56
Y), n sets of AND-gate circuits and transistors are provided with respect to the respective electric heater elements (R
cn
, R
mn
, R
yn
). With reference to
FIG. 7
, an AND-gate circuit and a transistor in one set are representatively shown and indicated by references
58
and
60
, respectively. A set of a strobe signal (STC, STM or STY) and a control signal (DAC, DAM or DAY) is inputted from the printer controller
46
to two input terminals of the AND-gate circuit
58
. A base of the transistor
60
is connected to an output terminal of the AND-gate circuit
58
; a corrector of the transistor
60
is connected to an electric power source (V
cc
); and an emitter of the transistor
60
is connected to a corresponding electric heater element (R
cn
, R
mn
, R
yn
).
When the AND-gate circuit
58
, as shown in
FIG. 7
, is one included in the first driver circuit
31
C, a set of a strobe signal “STC” and a control signal “DAC” is inputted to the input terminals of the AND-gate circuit
58
. As shown in a timing chart of
FIG. 8
, the strobe signal “STC” has a pulse width “PWC”. On the other hand, the control signal “DAC” varies in accordance with binary values of a digital cyan image-pixel signal. Namely, when the digital cyan image-pixel signal has a value “1”, the control signal “DAC” is outputted as a high-level pulse having the same pulse width as that of the strobe signal “STC”, whereas, when the digital cyan image-pixel signal has a value “0”, the control signal “DAC” is maintained at a low-level.
Accordingly, only when the digital cyan image-pixel signal has the value “1”, is a corresponding transistor (
60
) switched ON during a period corresponding to the pulse width “PWC” of the strobe signal “STC”, so that a corresponding electric heater element (R
c1
to R
cn
) is electrically energized, whereby the electric heater element concerned is heated to the temperature between the glass-transition temperatures T
1
and T
2
.
Also, when the AND-gate circuit
58
, as shown in
FIG. 7
, is one included in the second driver circuit
56
M, a set of a strobe signal “STM” and a control signal “DAM” is inputted to the input terminals of the AND-gate circuit
58
. As shown in a timing chart of
FIG. 9
, the strobe signal “STM” has a pulse width “PWM”, being longer than that of the strobe signal “STC”. On the other hand, the control signal “DAM” varies in accordance with binary values of a digital magenta image-pixel signal. Namely, when the digital magenta image-pixel signal has a value “1”, the control signal “DAM” is outputted as a high-level pulse having the same pulse width as that of the strobe signal “STM”, whereas, when the digital magenta image-pixel signal has a value “0”, the control signal “DAM” is maintained at a low-level.
Accordingly, only when the digital magenta image-pixel signal is “1”, is a corresponding transistor (
60
) switched ON during a period corresponding to the pulse width “PWM” of the strobe signal “STM”, so that a corresponding electric heater element (R
m1
to R
mn
) is electrically energized, whereby the electric heater element concerned is heated to the temperature between the glass-transition temperatures T
2
and T
3
.
Similarly, when the AND-gate circuit
58
, as shown in
FIG. 7
, is one included in the third driver circuit
56
Y, a set of a strobe signal “STY” and a control signal “DAY” is inputted to the input terminals of the AND-gate circuit
58
. As shown in a timing chart of
FIG. 10
, the strobe signal “STY” has a pulse width “PWY”, being longer than that of the strobe signal “STM”. On the other hand, the control signal “DAY” varies in accordance with binary values of a corresponding digital yellow image-pixel signal. Namely, when the digital yellow image-pixel signal has a value “1”, the control signal “DAY” is outputted as a high-level pulse having the same pulse width as that of the strobe signal “STY”, whereas, when the digital yellow image-pixel signal has a value “0”, the control signal “DAY” is maintained at a low-level.
Accordingly, only when the digital yellow image-pixel signal is “1”, is a corresponding transistor (
60
) switched ON during a period corresponding to the pulse width “PWY” of the strobe signal “STY”, so that a corresponding electric heater element (R
y1
to R
yn
) is electrically energized, whereby the heater element concerned is heated to the temperature between the glass-transition temperature T
3
and the upper limit temperature T
UL
.
As conceptually shown in
FIG. 11
, although an electric heater element (R
cn
, R
mn
, R
yn
) is elastically pressed against the film sheet
26
, backed by the roller platen
42
, as mentioned above, a small part of the image-forming liquid medium, held in the liquid medium space
28
, exists as a fluid film between the electric heater element concerned and the film sheet
26
. Note, if necessary, an exposed face of each electric heater element (R
cn
, R
mn
, R
yn
) may be roughly treated, to thereby ensure the existence of the image-forming liquid medium between the electric heater element and the film sheet
26
.
Thus, for example, when one of the electric heater elements R
cn
is heated by the electrical energization thereof, as mentioned above, a part of the solution component of the image-forming liquid medium in contact with the heated heater element concerned, is vaporized, thereby producing a bubble
62
, as conceptually shown in FIG.
12
. Also, a local area of the film sheet
26
, corresponding to the heated heater element concerned, is heated so that a modulus of elasticity of the heated local area is decreased. As a result, the heated local area of the film sheet
26
inflates due to the decrease in the modulus of elasticity thereof and due to the vapor pressure generated in the bubble
62
. Further, a part of the image-forming liquid medium, pressurized by the vapor pressure, can permeate and penetrate into a corresponding pore
40
associated with the heated heater element concerned, and thus the pore
40
is widened, as shown in FIG.
12
.
Accordingly, the permeated and penetrated image-forming liquid medium is generated as a fluid drop
64
on the inflated local area, corresponding to the heated heater element concerned, of the film sheet
26
(FIG.
12
). If the recording paper sheet P is interposed between the film sheet
26
and the roller platen
42
(FIG.
5
), the fluid drop
64
is transferred to the recording paper sheet P, and, as conceptually shown in
FIG. 13
, only a microcapsule component
66
of the fluid drop is deposited on a surface of the recording paper sheet P, due to a solution component of the fluid drop
64
being absorbed by the recording paper sheet P. Note, in
FIG. 13
, although the deposited microcapsule component
66
is conveniently shown as a clod on the recording paper sheet P, in reality, a large part of the deposited microcapsule component
66
penetrates the fibrous-tissue surface of the recording paper sheet P.
When the electrical energization of the heater element concerned is stopped, the bubble
62
condenses and the heated and inflated local area of the film sheet
26
is cooled by the surrounding image-forming liquid medium held in the liquid medium space
29
, leading to a return to the original condition, as shown in FIG.
11
.
As is apparent from the foregoing, since the deposited microcapsule component
66
is subjected to the heating temperature and breaking pressure falling within the hatched cyan-developing area C (FIG.
3
), by the electric heater element (R
cn
) concerned, only the cyan microcapsules
10
C included in the deposited microcapsule component
66
are compacted and broken, and thus the cyan leuco-pigment, seeped from the compacted and broken microcapsules
10
C, is developed as a cyan dot on the recording paper sheet P.
The same is true for the electric heater elements R
mn
and R
yn
. Namely, when one of the electric heater elements R
mn
is heated by the electrical energization thereof, a magenta dot is developed on the recording paper sheet P, and, when one of the electric heater elements R
yn
is heated by the electrical energization thereof, a yellow dot is developed on the recording paper sheet P Note, each of the developed cyan, magenta and yellow dots may have a size of about 50 μm to about 100 μm.
FIG. 14
schematically shows a second embodiment of the image-forming apparatus, using the image-forming liquid medium, which is also constituted as a line printer so as to form a color image on a sheet of recording paper. The printer is provided with a first thermal head assembly
68
and a second thermal head assembly
70
, which are aligned with each other so as to define a part of a path through which a sheet of recording paper is passed.
The first thermal head assembly
68
includes an elongated rectangular base plate
72
formed of, for example, a suitable ceramic material, and the base plate
72
has an elongated thermal head
74
securely attached to a lower surface of the base plate
72
. The thermal head
74
has an array of n electric resistance elements or electric heater elements longitudinally aligned on and in an outer or lower surface thereof, one of the n electric heater elements being representatively indicated by reference R
n
in FIG.
14
.
The first thermal head assembly
68
also includes an elongated frame or spacer member
76
, which is formed with a rectangular opening, and which is securely attached to the lower surface of the base plate
72
such that the array of electric heater elements R
n
is encompassed by the rectangular opening of the frame or spacer member
76
, which may be formed of an electrically insulating material, such as a suitable synthetic resin.
The first thermal head assembly
68
further includes a sheet of film
78
securely adhered to the frame or spacer member
76
such that the rectangular opening of the spacer member
76
is covered with the film sheet
78
, thereby defining a liquid medium space
80
. Similar to the above-mentioned film sheet
26
, the film sheet
78
also may have a thickness of about 0.03 to about 0.08 mm, and is preferably formed of a suitable synthetic resin material, such as polytetrafluoroethylene.
The film sheet
78
is provided with a plurality of pores
82
formed therein, and these pores
82
are aligned with each other in a single row, and the row of pores
82
extend below and along the array of electric heater elements R
n
, such that each heater element (R
n
) is associated with a corresponding pore
82
. Similar to the pores
40
shown in
FIGS. 4 and 5
, although the pores
82
are exaggeratively illustrated in
FIG. 14
, in reality, the pores
82
are microscopic. Note, the film sheet
78
having the pores
82
may be produced in substantially the same manner as the film sheet
26
.
As shown in
FIG. 14
, the first thermal head assembly
68
is provided with a reservoir
84
, in which the above-mentioned image-forming liquid medium is held, such that the liquid medium space
80
is fed with the image-forming liquid medium from the reservoir
84
. Namely, the reservoir
84
is constituted in substantially the same manner as the previous reservoir
30
, and is arranged so as to be in communication with the liquid medium space
80
such that the image-forming liquid medium, hold in the reservoir
84
, can be drawn into the liquid medium space
80
. Note, the reservoir
84
may be provided with a roller-type agitator, as indicated by reference
38
in
FIG. 4
, thereby ensuring a good homogenous suspension of the cyan, magenta and yellow microcapsules
10
C,
10
M and
10
Y in the image-forming liquid medium held in the reservoir
84
.
The second thermal head assembly
70
includes an elongated rectangular base plate
86
formed of, for example, a suitable ceramic material, with the base plate
86
being formed with three elongated grooves
88
C,
88
M and
88
Y, as shown in FIG.
14
. The second thermal head assembly
70
also includes three elongated thermal heads
90
C,
90
M and
90
Y, which are slidably accommodated in the elongated grooves
88
C,
88
M and
88
Y, respectively. Each of the thermal heads (
90
C,
90
M,
90
Y) is provided with plural spring elements (
92
C,
92
M,
92
Y), symbolically shown in
FIG. 14
, which are confined in the corresponding groove (
88
C,
88
M,
88
Y), so as to resiliently act on the corresponding thermal head (
90
C,
90
M,
90
Y), so that the thermal head (
90
C,
90
M,
90
Y) concerned is elastically biased outward from the corresponding groove (
88
C,
88
M,
88
Y). Note, each of the thermal heads
90
C,
90
M and
90
Y also may be formed of a suitable ceramic material.
Each of the thermal heads
90
C,
90
M and
90
Y has an array of n electric resistance elements or electric heater elements longitudinally aligned on and embedded in an outer or lower surface thereof, one of the n electric heater elements
90
C, one of the n electric heater elements
90
M and one of the electric heater elements
90
Y are representatively indicated by references R
cn
, R
mn
and R
yn
, respectively.
Note, the n electric heater elements R
n
of the thermal head
74
of the first thermal head assembly
68
and the n electric heater elements R
cn
, n electric heater elements R
mn
and n electric heater elements R
yn
are all aligned at a same pitch with respect to each other.
As is apparent from
FIG. 14
, the printer is provided with a first roller platen
94
and a second roller platen
96
, each of which is constituted as a rubber roller. The first roller platen
94
is rotatably provided below and in contact with the film sheet
78
such that a rotational axis of the roller platen
94
is in parallel with the array of the electric heater elements R
n
. Also, the second roller platen
96
is rotatably provided below and in contact with the thermal heads
90
C,
90
M and
90
Y, such that a rotational axis of the roller platen
96
is in parallel with the arrays of electric heater elements R
cn
, R
mn
and R
yn
.
During a printing operation of the printer, the respective platen rollers
94
and
96
are rotated in a clockwise direction (
FIG. 14
) by suitable electrical motors (not shown), with a same peripheral speed, and a sheet of recording paper to be printed, generally indicated by reference P in
FIG. 14
, is passed through a nip between the film sheet
78
and the roller platen
94
, and then nips between the thermal heads
90
C,
90
M and
90
Y and the roller platen
96
, so as to be moved in a direction indicated by an arrow C in
FIG. 14
, due to the recording paper sheet P being subjected to a traction force from the rotating platen rollers
94
and
96
.
Similar to the first embodiment of the printer shown in
FIGS. 4 and 5
, a resilient force of the spring elements
92
C is set so that the thermal head
90
C is elastically pressed against the roller platen
96
, at a pressure ranging between the critical breaking pressure P
3
and the upper limit pressure P
UL
. Also, a resilient force of the spring elements
92
M is set so that the thermal head
90
M is elastically pressed against the roller platen
96
, at a pressure ranging between the critical breaking pressures P
2
and P
3
. Further, a resilient force of the spring elements
92
Y is set so that the thermal head
90
Y is elastically pressed against the roller platen
96
, at a pressure ranging between the critical breaking pressures P
1
and P
2
.
FIG. 15
shows a schematic block diagram of a control circuit
98
for the printer shown in FIG.
14
. As shown in this drawing, the control circuit
98
comprises a printer controller
100
including a microcomputer. The printer controller
100
receives a series of digital color image-pixel signals from a personal computer or a word processor (not shown) through an interface circuit (I/F)
102
. The received digital color image-pixel signals are once stored in a memory
104
.
Also, the control circuit
98
is provided with a motor driver circuit
106
for driving electric motors
108
and
110
, each of which may be a stepping motor, a servo motor, or the like. The respective motors
108
and
110
are used to rotationally drive the roller platens
94
and
96
in accordance with a series of drive pulses outputted from the motor driver circuit
106
. The outputting of the drive pulses from the motor driver circuit
106
to the motors
108
and
110
is controlled by the printer controller
100
.
As shown in
FIG. 15
, the control circuit
98
is further provided with a first driver circuit
56
C′, a second driver circuit
56
M′ and a third driver circuit
56
Y′, which are arranged in substantially the same manner as the first, second and third driver circuits
56
C,
56
M and
56
Y of the control circuit
44
shown in
FIG. 6
, respectively, and which are controlled by the printer controller
100
to drive the respective thermal heads
90
C,
90
M and
90
Y of the second thermal head assembly
70
. Namely, the driver circuits
56
C′,
56
M′ and
56
Y′ are controlled by n sets of strobe signals “STC” and control signals “DAC”, n sets of strobe signals “STM” and control signals “DAM”, and n sets of strobe signals “STY” and control signals “DAY”, respectively, outputted from the printer controller
100
, thereby carrying out the selective energization of the heater elements R
cl
to R
cn
, the selective energization of the heater elements R
m1
to R
mn
and the selective energization of the heater elements R
y1
to R
yn
, in substantially the same manner as explained with reference to the timing charts of
FIGS. 8
,
9
and
10
in the first embodiment of the printer shown in
FIGS. 4 and 5
.
Furthermore, the control circuit
98
is provided with an additional driver circuit
112
, which is arranged in substantially the same manner as each of the first, second and third driver circuits
56
C,
56
M and
56
Y of the control circuit
44
shown in
FIG. 6
, and which is controlled by the printer controller
100
to drive the thermal head
74
of the first thermal head assembly
68
. Namely, the driver circuit
112
includes n sets of AND-gate circuits (
58
) and transistors (
60
), as shown in
FIG. 7
, provided for the respective electric heater elements R
n
, and is controlled by n sets of strobe signals “ST” and control signals “DA” outputted from the printer controller
100
, thereby carrying out the selective energization of the heater elements R
1
to R
n
.
In particular, a set of a strobe signal ST and a control signal DA is inputted from the printer controller
100
to two input terminals of an AND-gate circuit (
58
) concerned of the additional driver circuit
112
. As shown in a timing chart of
FIG. 16
, the strobe signal “ST” has a pulse width “PW”. On the other hand, the control signal “DA” varies in accordance with a set of a digital cyan image-pixel signal, a digital magenta image-pixel signal and a digital yellow image-pixel signal, which controls respective outputtings of the control signals “DAC”, “DAM” and “DAY”, corresponding to each other. Namely, when at least one of the digital color (cyan, magenta and yellow) image-pixel signals included in each set has a value “1”, the control signal “DA” is outputted as a high-level pulse having the same pulse width as that of the strobe signal “ST”, whereas, when all of the digital color (cyan, magenta and yellow) image-pixel signals included in each set have a value “0”, the control signal “DA” is maintained at a low-level.
Accordingly, only when the control signal “DA” is outputted as a high-level pulse, is a corresponding transistor (
60
) switched ON during a period corresponding to the pulse width “PW” of the strobe signal “ST”, so that a corresponding electric heater element (R
1
to R
n
) of the thermal head
74
is electrically energized, whereby the electric heater element concerned is heated to a predetermined suitable temperature, which is of course lower than the upper limit temperature T
UL
(FIG.
3
).
When one of the electric heater elements R
n
of the thermal head
74
is not electrically energized, a corresponding pore
82
elastically closes, so that the image-forming liquid medium, held in the liquid medium space
80
, cannot permeate and penetrate through the pore concerned, as conceptually shown in FIG.
17
.
On the other hand, when one of the heater elements R
n
of the thermal head
74
is heated by the electrical energization thereof, due to at least one digital color (cyan, magenta, yellow) image-pixel signal included in a set having a value “1”, as mentioned above, a part of the solution component of the image-forming liquid medium in contact with the heated heater element (R
n
) concerned, is vaporized, thereby producing a bubble
114
, as conceptually shown in FIG.
18
. Also, a local area of the film sheet
78
, corresponding to the heated heater element (R
n
) concerned, is heated so that a modulus of elasticity of the heated local area is decreased. As a result, the heated local area of the film sheet
78
inflates due to the decrease in the modulus of elasticity thereof and due to the vapor pressure generated in the bubble
114
. Further, a part of the image-forming liquid medium, pressurized by the vapor pressure, can permeate and penetrate into a corresponding pore
82
associated with the heated heater element concerned, and thus the pore
82
is widened, as shown in FIG.
18
.
Accordingly, the permeated and penetrated image-forming liquid medium is generated as a fluid drop
116
on the inflated local area, corresponding to the heated heater element concerned, of the film sheet
78
(FIG.
18
). If the recording paper sheet P is interposed between the film sheet
78
and the first roller platen
94
(FIG.
14
), the fluid drop
116
is transferred to the recording paper sheet P, and, as conceptually shown in
FIG. 19
, only a microcapsule component
118
of the fluid drop is deposited on the surface of the recording paper sheet P, due to a solution component of the fluid drop
116
being absorbed by the recording paper sheet P. Note, in
FIG. 19
, although the deposited microcapsule component
118
is conveniently illustrated as a clod on the recording paper sheet P, in reality, a large part of the deposited microcapsule component
118
penetrates the fibrous-tissue surface of the recording paper sheet P.
When the electrical energization of the heater element (R
n
) concerned is stopped, the bubble
114
condenses and the heated and inflated local area of the film sheet
78
is cooled by the surrounding image-forming liquid medium held in the liquid medium space
80
, leading to a return to the original condition, as shown in FIG.
19
. Then, the deposited microcapsule component
118
is successively passed through the nips between the thermal heads
90
C,
90
M and
90
Y and the second roller platen
96
, due to the movement of the recording paper sheet P.
During the passage of the deposited microcapsule component
118
through the nip between the thermal head
90
C and the second roller platen
96
, if only the digital cyan image-pixel signal of the digital color image-pixel signals included in the set concerned has a value “1”, by a corresponding heater element R
cn
, the deposited microcapsule component
118
is subjected to the heating temperature and breaking pressure that fall within the hatched cyan-developing area C (FIG.
3
), so that only the cyan microcapsules
10
C included in the deposited microcapsule component
118
are compacted and broken, and thus the cyan leuco-pigment, seeped from the compacted and broken microcapsules
10
C, is developed as a cyan dot on the recording paper sheet P.
During the passage of the deposited microcapsule component
118
through the nip between the thermal head
90
M and the second roller platen
96
, if only the digital magenta image-pixel signal of the digital color image-pixel signals included in the set concerned has a value “1”, by a corresponding heater element R
mn
, the deposited microcapsule component
118
is subjected to the heating temperature and breaking pressure that fall within the hatched magenta-developing area M (FIG.
3
), so that only the magenta microcapsules
10
M included in the deposited microcapsule component
118
are compacted and broken, and thus the magenta leuco-pigment, seeped from the compacted and broken microcapsules
10
M, is developed as a magenta dot on the recording paper shoot P.
During the passage of the deposited microcapsule component
118
through the nip between the thermal head
90
Y and the second roller platen
96
, if only the digital yellow image-pixel signal of the digital color image-pixel signals included in the set concerned has a value “1”, by a corresponding heater element R
yn
, the deposited microcapsule component
118
is subjected to the heating temperature and breaking pressure that fall within the hatched yellow-developing area Y (FIG.
3
), so that only the yellow microcapsules
10
Y included in the deposited microcapsule component
118
are compacted and broken, and thus the yellow leuco-pigment, seeped from the compacted and broken microcapsules
10
Y, is developed as a yellow dot on the recording paper sheet P.
Note, of course, if both the digital cyan and magenta image-pixel signals of the digital color image-pixel signals included in the set concerned have a value “1”, the deposited microcapsule component
118
is developed as a blue dot on the recording paper sheet P; if both the digital magenta and yellow image-pixel signals of the digital color image-pixel signals included in the set concerned have a value “1”, the deposited microcapsule component
118
is developed as a red dot on the recording paper sheet P; if both the digital cyan and yellow image-pixel signals of the digital color image-pixel signals included in the set concerned have a value “1”, the deposited microcapsule component
118
is developed as a green dot on the recording paper sheet P; and if all of the digital color image-pixel signals included in the set concerned have a value “1”, the deposited microcapsule component
118
is developed as a black dot on the recording paper sheet P.
If only white-colored sheets of recording paper are used, the shape memory resins of the cyan, magenta and yellow microcapsules
10
C,
10
M and
10
Y may be colored with a white pigment. In this case, respective cyan, magenta and yellow dyes or ink, which directly exhibit cyan, magenta and yellow pigmentations, may be encapsulated in the cyan, magenta and yellow microcapsules
10
C,
10
M and
10
Y without the need of a specific color development in the solution.
Finally, it will be understood by those skilled in the art that the foregoing description is of preferred embodiments of the printer, and that various changes and modifications may be made to the present invention without departing from the spirit and scope thereof.
The present disclosure relates to a subject matter contained in Japanese Patent Application No. 10-12136 (filed on Jan. 6, 1998) which is expressly incorporated herein, by reference, in its entirety.
Claims
- 1. An image-forming liquid medium comprising:a solution that contains a surface-active agent; at least two types of microcapsule, a first type of microcapsule filled with a first dye, and a second type of microcapsule filled with a second dye, said two types of microcapsules being mixed with said solution, wherein said first type of microcapsule exhibits a first pressure/temperature characteristic such that, when said first type of microcapsule is squashed and broken upon being simultaneously subjected to a first predetermined pressure and a first predetermined temperature, said first dye seeps from said squashed and broken microcapsule, and said second type of microcapsule exhibits a second pressure/temperature characteristic such that, when said second type of microcapsule is squashed and broken upon being simultaneously subjected to a second predetermined pressure and a second predetermined temperature, said second dye seeps from said squashed and broken microcapsule, said first predetermined pressure being higher than said second predetermined pressure and said first predetermined temperature being lower than said second predetermined temperature.
- 2. An image-forming liquid medium as set forth in claim 1, wherein said first type of microcapsule has a first shell wall composed of a first resin which exhibits said first pressure/temperature characteristic, and said second type of microcapsule has a second shell wall composed of a second resin which exhibits said second pressure/temperature characteristic.
- 3. An image-forming liquid medium as set forth in claim 2, wherein each of said first and second resins exhibit transparency, and each of said first and second dyes exhibit transparency, with said solution exhibiting transparency and further comprising a color developer that reacts with each of said first and second dyes, thereby developing a predetermined monochromatic color.
- 4. An image-forming liquid medium as set forth in claim 3, wherein said respective first and second dyes comprise a first leuco-pigment and a second leuco-pigment, respectively.
- 5. An image-forming liquid medium as set forth in claim 1, further comprising a third type of microcapsule filled with a third dye mixed with said solution together with said first and second types of microcapsule, wherein said third type of microcapsule exhibits a third pressure/temperature characteristic such that, when said third type of microcapsule is squashed and broken under a third predetermined pressure at a third predetermined temperature, said third dye seeps from said squashed and broken microcapsule.
- 6. An image-forming liquid medium as set forth in claim 5, wherein said first type of microcapsule has a first shell wall composed of a first resin which exhibits said first pressure/temperature characteristic, said second type of microcapsule has a second shell wall composed of a second resin which exhibits said second pressure/temperature characteristic, and said third type of microcapsule has a third shell wall composed of a third resin which exhibits said third pressure/temperature characteristic.
- 7. An image-forming liquid medium as set forth in claim 6, wherein each of said first, second and third resins exhibit transparency, and each of said first, second and third dyes exhibit transparency, with said solution exhibiting transparency and further comprising a color developer that reacts with each of said first, second and third dyes, thereby developing a predetermined monochromatic color.
- 8. An image-forming liquid medium as set forth in claim 7, wherein said respective first, second and third dyes comprise a first leuco-pigment, a second leuco-pigment and a third leuco-pigment, respectively.
- 9. An image-forming liquid medium as set forth in claim 5, wherein said first, second, and third dyes exhibit a pigmentation, a magenta pigmentation and a yellow pigmentation, respectively.
- 10. An image-forming apparatus, using said image-forming liquid medium as set forth in claim 1, comprising:a transfer unit that selectively transfers a small part of said image-forming liquid medium as a first fluid drop to a sheet of recording medium in accordance with a first digital monochromatic image-pixel signal, corresponding to said first dye, and that selectively transfers a small part of said image-forming liquid medium as a second fluid drop to said sheet of recording medium in accordance with a second digital monochromatic image-pixel signal, corresponding to said second dye; and a pressure/temperature applicator unit that applies said first predetermined pressure and said first predetermined temperature to said first fluid drop, and that applies said second predetermined pressure and said second predetermined temperature to said second fluid drop.
- 11. An image-forming apparatus as set forth in claim 10, wherein said transfer unit and said pressure/temperature applicator unit are combined with each other as a single thermal head assembly.
- 12. An image-forming apparatus as set forth in claim 11, further comprising:a platen member that is associated with said single thermal head assembly, said single thermal head assembly including: an electrically-insulated base member; a first movable thermal head provided in said base member and having a first array of heater elements aligned with each other; a second movable thermal head provided in said base member and having a second array of heater elements aligned with each other, said first array of heater elements being in parallel with said second array of heater elements; a spacer member, having an opening, securely provided on said base member such that said first and second thermal heads are encompassed by said opening of said spacer member; a sheet of film that covers said spacer member such that said opening of said spacer member is defined as a liquid medium space that stores said image-forming liquid medium, said sheet of film including a plurality of pores formed therein, said pores being aligned with each other in a first row and a second row, which extend along said first and second arrays of heater elements, respectively, such that each of said heater elements is associated with a corresponding pore, said first fluid drop being produced from one of said pores in said first row by heating a corresponding one of said heater elements in said first array to said first predetermined temperature, said second fluid drop being produced from one of said pores in said second row by heating a corresponding one of said heater elements in said second array to said second predetermined temperature, said platen member urging said first and second thermal heads toward the interposed sheet of film, said sheet of recording medium being interposed between said platen member and said sheet of film during said production of said first and second fluid drops; a first resilient member that is associated with said first thermal head such that said first thermal head is elastically biased against said sheet of film, backed by said platen member, under said first predetermined pressure; and a second resilient member that is associated with it said second thermal head such that said second thermal head is elastically biased against said sheet of film, backed by said platen member, under said second predetermined pressure.
- 13. An image-forming apparatus as set forth in claim 12, wherein said single thermal head assembly further includes a reservoir that holds said image-forming liquid medium to feed said liquid medium space with said image-forming liquid medium.
- 14. An image-forming apparatus, using said image-forming liquid medium as set forth in claim 1, comprising:a transfer unit that selectively transfers a small part of said image-forming liquid medium as a fluid drop to a sheet of recording medium in accordance with at least one of a first digital monochromatic image-pixel signal and a second digital monochromatic image-pixel signal, which correspond to said first and second dyes, respectively; and a pressure/temperature applicator unit that selectively applies said first predetermined pressure and said first predetermined temperature to said fluid drop in accordance with said first digital monochromatic image-pixel signal, and that applies said second predetermined pressure and said second predetermined temperature to said fluid drop in accordance with said second digital monochromatic image-pixel signal.
- 15. An image-forming apparatus as set forth in claim 14, wherein said transfer unit is formed as a first thermal head assembly, and said pressure/temperature applicator unit is formed as a second thermal head assembly, said first and second thermal head assemblies being arranged so as to partially define a path along which said sheet of recording medium is moved, said first thermal head assembly being positioned upstream of said second thermal head assembly in a direction of said movement of said sheet of recording medium.
- 16. An image-forming apparatus as set forth in claim 15, further comprising:a first platen member that is associated with said transfer unit; and a second platen member that is associated with said pressure/temperature applicator unit, said first thermal head assembly including: a first electrically-insulated base member; a thermal head provided in said first electrically-insulated base member and having an array of heater elements aligned with each other; a spacer member, having an opening, securely provided on said first electrically-insulated base member such that said thermal head is encompassed by said opening of said spacer member; a sheet of film that covers said spacer member such that said opening of said spacer member is defined as a liquid medium space that stores said image-forming liquid medium, said sheet of film including a plurality of pores formed therein, said pores being aligned with each other in a single row, which extends along said array of heater elements, such that each of said heater elements is associated with a corresponding pore, wherein said first platen member urges said thermal head toward the interposed sheet of film, and said fluid drop is selectively produced from one of said pores by heating a corresponding one of said heater elements in said array to a predetermined temperature in accordance with at least one of said first and second digital monochromatic image-pixel signals, with said sheet of recording medium being interposed between said first platen member and said sheet of film during said production of said fluid drop, said pressure/temperature applicator unit including: a second electrically-insulated base member; a first movable thermal head provided in said base member and having a first array of heater elements aligned with each other; a second movable thermal head provided in said base member and having a second array of heater elements aligned with each other, said first array of heater elements being in parallel with said second array of heater elements, and said second platen member contacting said first and second thermal heads; a first resilient member that is associated with said first thermal head such that said first thermal head elastically contacts said second platen with said first predetermined pressure, during a passage of said sheet of recording medium carrying said fluid drop through a nip between said second platen member and said elastically-contacted first thermal head, a corresponding one of said heater elements in said first array being selectively heated to said first predetermined temperature in accordance with said first digital monochromatic image-pixel signal; and a second resilient member that is associated with said second thermal head such that said second thermal head elastically contacts said sheet of film with said second predetermined pressure, during a passage of said sheet of recording medium carrying said fluid drop through a nip between said second platen member and said elastically-contacted second thermal head, a corresponding one of said heater elements in said second array being selectively heated to said second predetermined temperature in accordance with said second digital monochromatic image-pixel signal.
- 17. An image-forming apparatus comprising:a transfer unit that selectively transfers a small part of an image-forming liquid medium as a fluid drop onto a sheet of recording medium in accordance with at least one of a first digital monochromatic image-pixel signal and a second digital monochromatic image-pixel signal; a pressure/temperature applicator unit that selectively applies a first predetermined pressure and a first predetermined temperature to said fluid drop in accordance with said first digital monochromatic image-pixel signal, and that applies a second predetermined pressure and a second predetermined temperature to said fluid drop in accordance with said second digital monochromatic image pixel signal; said transfer unit being formed as a first thermal head assembly, said pressure/temperature applicator unit being formed as a second thermal head assembly, said first and second thermal head assemblies being arranged so as to partially define a path along which a sheet of recording medium is moved, said first thermal head assembly being positioned upstream of said second thermal head assembly in a direction of movement of the sheet of recording medium; said image-forming liquid medium comprising: a solution that contains a surface active agent; at least two types of microcapsules, a first type of microcapsule filled with a first dye, and a second type of microcapsule filled with a second dye, said two types of microcapsules being mixed with said solution; wherein said first type of microcapsule exhibits a first pressure/temperature characteristic such that, when said first type of microcapsule is squashed and broken upon being subjected to a first predetermined pressure at a first predetermined temperature, said first dye seeps from said squashed and broken microcapsule, and said second type of microcapsule exhibits a second pressure/temperature characteristic, such that, when said second type of microcapsule is squashed and broken upon being subjected to a second predetermined pressure at a second predetermined temperature, said second dye seeps from said squashed and broken microcapsule, said first digital monochromatic image pixel signal corresponding to said first dye and said second digital monochromatic image pixel signal corresponding to said second dye.
- 18. The image-forming apparatus according to claim 17, wherein said first type of microcapsule has a first shell wall comprising a first resin which exhibits said first pressure/temperature characteristic, and said second type of microcapsule has a second shell wall comprising a second resin which exhibits said second pressure/temperature characteristic.
- 19. The image-forming liquid medium according to claim 1, each said first predetermined temperature and said second predetermined temperature being above an ambient temperature, each said first predetermined pressure and said second predetermined pressure being above an ambient pressure.
- 20. The image-forming apparatus according to claim 17, each said first predetermined temperature and said second predetermined temperature being above an ambient temperature, each said first predetermined pressure and said second predetermined pressure being above an ambient pressure.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-012136 |
Jan 1998 |
JP |
|
US Referenced Citations (10)
Foreign Referenced Citations (1)
Number |
Date |
Country |
4-4960 |
Jan 1992 |
JP |