JP2003072128A - Gradation control apparatus for self coloring type color recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel gradation control apparatus capable of applying a gradation representation to each coloring dot formed on a multicolor recording medium by heating elements. SOLUTION: A pressure sensitive and thermally sensitive coloring layer of the multicolor recording medium includes a thermally sensitive coloring component and multiple pressure sensitive microcapsules each of which has a pressure-temperature coloring characteristic of creating a first color by being broken at a predetermined pressure in a first temperature range. The thermally sensitive coloring component has a temperature coloring characteristic of crating a second color different from the first color in a second temperature range between a first temperature included in the first temperature range and a second temperature exceeding the upper limit of the first temperature range. A gradation control apparatus applies the gradation representation by a dot gradation method to a mixture of colors in a color mixing temperature region of the first color and the second color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation control device for a self-coloring type color recording medium which is capable of developing at least two colors.

[0002]

2. Description of the Related Art As a self-coloring type color recording medium as described above, a color-adding type multicolor heat-sensitive recording paper capable of developing two or more colors is already known. For example, when two colors are developed with such a color-sensitive thermal paper, a thermosensitive coloring layer is formed on the sheet paper, and when the thermosensitive coloring layer has a single layer structure, two types of leuco dyes, That is, when the first leuco dye and the second leuco dye are uniformly distributed together with the color developer, and the thermosensitive coloring layer has a two-layer structure, one type of leuco dye is provided in each layer together with the color developer. It is evenly distributed. In any case, the color development temperature of one type of leuco dye, that is, the first leuco dye is appropriately selected so as to be lower than the color development temperature of the other type of leuco dye, that is, the second leuco dye, and if necessary. In order to adjust the color development temperature of these leuco dyes, a sensitizer is appropriately added to the thermosensitive color development layer.

As is well known, the leuco dye itself is usually a milky white or translucent powder, and such a leuco dye develops a color by a chemical color reaction with a color developer to give a predetermined color. In order to induce a chemical color reaction between the leuco dye and the color developer to obtain a sufficient density of color development, it is a condition that both the leuco dye and the color developer are in a heat-melted state. .

Therefore, when the heat-melting temperature of the first leuco dye is applied to the thermosensitive coloring layer, only the first leuco dye develops a first color, and the thermosensitive coloring layer contains the second leuco dye. When the heat-melting temperature is applied, both the first and second leuco dyes develop color, respectively, resulting in a color mixture of the first and second colors. In short, by selectively applying a low temperature and a high temperature to the thermosensitive coloring layer, color development by the first leuco dye and color mixing by the color development of the first and second leuco dyes can be obtained. For example, when the first and second leuco dyes are selected to develop magenta and cyan, respectively, a magenta color is obtained on the low temperature side, and a mixed color of magenta and cyan, that is, a blue color is obtained on the high temperature side. .

A thermal printer is generally used to record characters, images and the like on the color-added multicolor heat-sensitive recording paper described above. As is well known, a thermal head is incorporated in a thermal printer, and a large number of electric resistance elements, that is, heating elements are embedded in the thermal head in a predetermined arrangement. When each heating element is heated to a temperature equal to or higher than a predetermined temperature by being energized, a so-called dot has a desired color as a pixel unit (magenta or blue in the above example).
In this way, characters and images are recorded in multicolor on the additive type multicolor thermosensitive recording paper by such colored dots. The size of the colored dots, that is, the dot diameter is generally about 50 to 100 μm.

Initially, characters and images recorded by a thermal head were obtained as a binarized image, but in recent years, it has been possible to express gradation in characters and images by changing the coloring density of each coloring dot. Has also been done. As such a gradation expression method, two types are known, and one method is called an energy gradation method in which gradation expression is obtained by controlling the heat generation temperature of a heating element of a thermal head. The other method is called a dot gradation method that obtains gradation expression by controlling the heat generation time of the heating element of the thermal head. In the energy gradation method, the energization amount (current) is gradually changed in a state where the heat generation time of each heat generating element is kept constant, whereby the color density of each color forming dot is controlled. In addition, the dot gradation method is one of so-called area gradation methods, and the heat generation time is changed stepwise in a state where the energization amount (current) of each heating element is kept constant, whereby individual color development is achieved. The color development area of the dots (dot size) is controlled.

Now, as one of the main problems of the above-mentioned color-addition type multicolor thermal recording paper, although only one of the basic colors can be independently developed, the other basic colors are It cannot develop color independently. For example, when magenta and cyan are selected as the basic colors as in the above example, if one of the colors, for example, magenta, is independently colored, blue obtained by mixing magenta and cyan is obtained. However, cyan cannot be independently colored. Thus, the conventional color-added multicolor heat-sensitive recording paper is inferior in terms of coloring efficiency.

In Japanese Patent Application No. 2001-099132 and Japanese Patent Application No. 2001-104428, as a novel self-coloring type color recording medium, not only two basic colors can be independently developed, but also both basic colors are formed. There is disclosed a multicolor pressure-sensitive thermosensitive recording medium configured so as to be capable of developing a mixed color. This multicolor pressure-sensitive thermal recording medium comprises a support and a color-developing layer formed on one surface of the support. The coloring layer contains at least one thermosensitive coloring component, and a large number of pressure-sensitive microcapsules enclosing a coloring material having a desired hue are uniformly distributed in the coloring layer. The pressure-sensitive microcapsules are provided with a pressure-temperature color-developing property which is ruptured and develops color under a predetermined pressure within the first temperature range, while the thermosensitive color-developing component is contained within the first temperature range. In the second temperature range between the first temperature and the second temperature exceeding the upper limit temperature of the first temperature range, a color different from that of the color material of the pressure-sensitive microcapsule is developed. Thermal color development characteristics are provided.

In such a multicolor pressure-sensitive thermosensitive recording medium, the heat-generating temperature of each heat-generating element is appropriately controlled while the thermal head is pressed under a predetermined pressure, so that the pressure-sensitive microcapsule Coloring only with color materials,
Coloring only by the heat-sensitive coloring component and color mixture coloring by both colors are obtained. For example, if the color development of the pressure-sensitive microcapsule is magenta and the color development of the thermosensitive coloring component is cyan, magenta color development occurs between the lower limit temperature of the first temperature range and the first temperature. The obtained blue color is obtained between the first temperature and the upper limit temperature of the first temperature range by mixing the magenta color and the cyan color.
Cyan color development is obtained between the upper limit of the temperature range and the upper limit temperature.

[0010]

By the way, in such a multicolor pressure-sensitive thermal recording medium, there is a technique for expressing gradation in a character, an image or the like by changing the density of individual colored dots obtained by a thermal head. It has not been established yet.

Therefore, an object of the present invention is to change the density of each color-developed dot obtained by the thermal head in the multicolor pressure-sensitive thermosensitive recording medium as described above to express gradation in characters, images and the like. The present invention is to provide a new gradation control device.

[0012]

A gradation control device according to the present invention is a multicolor recording medium comprising a support and a pressure-sensitive thermosensitive coloring layer formed on one surface of the support. The pressure-sensitive thermosensitive coloring layer contains a thermosensitive coloring component and a large number of pressure-sensitive microcapsules that encapsulate a predetermined coloring material and are evenly distributed. A pressure-temperature color-developing characteristic which is destroyed in the temperature range of 1 to develop the first color, and the thermosensitive color-developing component has the first temperature and the first temperature within the first temperature range. A second color temperature which is different from the first color in the second temperature range between the first temperature range and the second temperature exceeding the upper limit temperature. Between the first temperature and the upper limit temperature of the first temperature range, assuming a multicolor recording medium The first color and the color mixing color mixing temperature range and a second color that is defined is to try to give the gradation expression. The gradation control device according to the present invention includes a heating element applied to the pressure-sensitive thermosensitive coloring layer under the above-described predetermined pressure, and first coloring density data for controlling the coloring density of the first color. Calculation means for calculating the color density ratio with the second color density data for controlling the color density of the second color, and heat generation temperature control for heating the heat generating element to a temperature within the color mixture temperature region corresponding to the color density ratio. Means for controlling the heat generation time of the heating element in accordance with any one of the color density of the first color density data and the color density data of the second color, and changing the density to a mixed color of the first color and the second color. And a heat generation time control means for providing a color tone expression by a dot gray scale method for a color mixture of the first color and the second color.

In the gradation control device according to the present invention, when the first color-developing density data and the second color-developing density data are equal to each other, the heat-generating time of the heat-generating element by the heat-generating time control means is the first color-density. It can be performed according to either the data or the second color density data.

When the second color-developing density data is the non-color-developing density data, the first color-developing density data is equal to or higher than the lower limit temperature within the first temperature range according to the magnitude of the color-developing density. Is assigned to a temperature within the temperature range of In this case, the heat generation temperature control means controls the heat generation temperature of the heat generating element to be the allocated temperature,
In addition, the heat generation time control means controls the heat generation time of the heat generating element to be the maximum heat generation time, and thus the gradation expression by the energy gradation method is given to the color development of the first color. The maximum heat generation time of the heat generating element is the time for which a full-sized colored dot is obtained by the heat generating element.

When the second color-developing density data is the non-color-developing density data, the heat-generating temperature of the heat-generating element is controlled by the heat-generating temperature control means so as to be the first temperature, and the heat-generating element generates heat. The time may be controlled by the heat generation time control means according to the first color density data, and at this time, the gradation expression by the dot gradation method is given to the color development of the first color.

When the first color-developing density data is the non-color-developing density data, heat is generated so that the heat-generating temperature of the heating element is equal to or higher than the upper limit temperature of the first temperature range and is within the second temperature range. It is possible to control by the temperature control means and to control the heat generation time of the heat generating element by the heat generation time control means according to the second color density data.
At this time, gradation expression by the dot gradation method is given to the color development of the second color.

In one aspect of the present invention, the support of the multicolor recording medium is formed of a transparent material, the pressure-sensitive thermosensitive coloring layer is formed as a transparent layer, and the thermosensitive coloring layer is formed on the other surface of the support. May be formed, and at this time, the thermosensitive coloring layer is different from the first and second colors in a third temperature range independent of the first and second temperature ranges of the pressure-sensitive thermosensitive coloring layer. The third color is used to develop the temperature color development characteristic.
The third color density data for controlling the color density of the color is assigned to a temperature within the third temperature range according to the magnitude of the color density. In such a case, the gradation control device according to the present invention is further applied to the thermosensitive coloring layer in order to give the gradation expression by the energy gradation method to the coloring of the third color. The heat-generating element for the color-developing layer, the heat-generating time controlling means for the heat-sensitive color-developing layer for controlling the heat-generating time of the heat-generating element for the heat-sensitive color-developing layer to the maximum heat-generating time, and the heat-generating temperature of the heat-generating element for the heat-sensitive color-developing layer are set to the third value. A heat generation temperature control means for the heat-sensitive color forming layer may be provided to control the temperature so that the temperature is assigned within the temperature range. The maximum heat generation time of the heat-generating element for heat-sensitive color-developing layer is the time for which a full-sized color dot can be obtained by the heat-generating element for heat-sensitive color-forming layer.

Further, in the above situation, it is possible to give the gradation expression by the dot gradation method to the color development of the third color. In that case, the gradation control device according to the present invention Further, a heat-generating element for heat-sensitive color-developing layer applied to the heat-sensitive color-developing layer, and heat generation for heat-sensitive color-developing layer for controlling the heat-generating temperature of the heat-generating element for heat-sensitive color-developing layer to the upper limit temperature of the third temperature range. The temperature control means and the heat generation time control means for the heat-sensitive color development layer for controlling the heat generation time of the heat generation element for the heat-sensitive color development layer according to the third color development density data for controlling the color development density of the third color may be provided.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a gradation control system according to the present invention will be described with reference to the accompanying drawings.

First, referring to FIG. 1, a multicolor pressure-sensitive thermal recording medium, which is a target of the gradation control method according to the present invention, is indicated generally by the reference numeral 10.
0 is configured as a full color recording medium. The full-color recording medium 10 comprises a suitable transparent support 12 and this support 1.
2, the pressure-sensitive thermosensitive coloring layer 14 coated on one surface, and the thermosensitive coloring layer 16 coated on the other surface of the support 12,
A reflective coating layer 18 is formed on the thermosensitive coloring layer 16. The support 12 is formed as a sheet 12 made of, for example, transparent polyethylene terephthalate resin (PET) and has a thickness of about 50 to 100 μm. The sheet 12 not only functions as a supporting substrate for forming the pressure-sensitive thermosensitive coloring layer 14 and the thermosensitive coloring layer 16, but also as a heat insulating layer for thermally insulating both coloring layers 14 and 16 as described later. Also works as. The reflective coating layer 18 is made of a polyethylene terephthalate resin (PET) film sheet having a thickness of 6 μm, and the film sheet is colored white.

The pressure-sensitive thermosensitive coloring layer 14 is formed by uniformly distributing a large number of pressure-sensitive microcapsules 20 in the thermosensitive coloring layer composed of a leuco dye component for cyan coloring and a developer component. For convenience, the leuco dye component for cyan color development is indicated by "□", and the developer component is indicated by the symbol "x" for convenience. For the cyan color forming leuco dye, for example, it is available as NC-Blue-3 from Hodogaya Chemical Co.,
The thermal melting temperature of this NC-Blue-3 is about 190 ℃. The developer component is available, for example, from Asahi Denka Kogyo Co., Ltd. as K-5, which shows a thermal melting temperature of about 145 ° C. Although not shown in FIG. 1, low-melting-point stearic acid amide is appropriately added as a sensitizer component to the pressure-sensitive thermosensitive coloring layer 14.

The leuco dye for cyan color development (NC-Blue-
3), the developer component (K-5) and the sensitizer component (low melting point stearic acid amide) are all white powders, but as described below, they are water-soluble as a binder added during layer formation. Due to the refractive index characteristics, all of the above-mentioned materials are made semitransparent or transparent due to the characteristic polyester in a dry state, and the pressure-sensitive thermosensitive coloring layer 14 on the sheet 12 becomes invisible.

The pressure-sensitive microcapsule 20 contains, for example, a magenta-based coloring material.
A suitable vehicle in which a leuco dye for magenta coloring is dissolved is used. In the present embodiment, a suitable transparent oil is used as the vehicle, and such a transparent oil is available, for example, from RKS (Rutgers Kureha Solvents Gmbh) as KMC-113 (2,7 diisopropylnaphthalene). As the magenta coloring leuco dye, for example, Red-3 manufactured by Yamamoto Kasei Co. can be used. That is, as the magenta color material to be encapsulated in the pressure-sensitive microcapsule 20, KMC-113 in which Red-3 is dissolved is used. In FIG. 1, the pressure-sensitive microcapsules 20 are shown.
The magenta color material enclosed inside is indicated by "M" representing magenta. The magenta coloring leuco dye itself is a translucent powder, but when dissolved in transparent oil (KMC-113), the magenta coloring material itself becomes transparent.

The wall film of the pressure-sensitive microcapsules 20 is formed of a suitable melamine resin, which is transparent or translucent. Such a pressure-sensitive microcapsule 20 can be manufactured by a well-known microcapsule manufacturing method such as in situ (in sit).
u) It can be manufactured by a polymerization method or the like, and its average particle size is about 3 μm to 4 μm, and the wall thickness of the pressure-sensitive microcapsules 20 is 0.5 MPa or more accompanied by shearing force. It is designed so that it can be destroyed under pressure, and its heat resistance temperature is about 300 ° C under no load.

The pressure-sensitive microcapsules 20 which can be broken under the pressure of 0.5 MPa or more accompanied by shearing force are as follows.
Examples for the production of (average particle size of about 3 μm to about 4 μm) are shown. 1) First, the following three solutions are prepared. (A) Magenta coloring material solution KMC-113 (2,7 diisopropylnaphthalene)… 100g Red-3… 4g (B) Protective colloid solution Partial sodium salt of polyvinylbenzenesulfonic acid… 5g Purified water… 95g (C) Melamine- Formalin prepolymer aqueous solution Melamine… 14g Formalin… 36g Purified water… 50g (Note that formalin is a 2% aqueous solution of sodium hydroxide at pH
37% formaldehyde prepared in 9 is used. 36g of this formalin and 14g of melamine are mixed and heated to 70 ° C,
After the melamine was dissolved, add 50 g of purified water and stir, (C)
(A melamine-formalin prepolymer aqueous solution was obtained)

2) Next, (A) magenta coloring material solution and (B) protective colloid aqueous solution are mixed, and this mixed solution is stirred by a homogenizer to prepare (D) emulsion dispersion (O / W emulsion). . At this time, the emulsion dispersion was dispersed by adjusting the number of revolutions of the homogenizer and the stirring time so that the magenta coloring material solution (A) became droplets having an average particle size of about 2.5 μm.

3) Next, the (C) melamine-formalin prepolymer aqueous solution was added to and mixed with the above emulsified dispersion, and the mixture was slowly stirred while maintaining the temperature at 30 ° C.
Aqueous acetic acid solution is appropriately added to set the mixed solution at pH 3 to pH 6. Then, the temperature of the mixed solution is kept at 60
The temperature was raised to 0 ° C., and the polycondensation reaction was allowed to proceed with stirring for about 1 hour to obtain pressure-sensitive microcapsules 20 having an average particle size of about 3 μm.

The thickness of the wall film of the pressure-sensitive microcapsule 20 thus obtained is such that it can be broken under a pressure of 0.5 MPa or more accompanied by shearing force. The thickness of the wall film of the pressure-sensitive microcapsule 20 mainly depends on the amount of melamine in the melamine-formalin prepolymer aqueous solution, and the larger the amount, the thicker the film thickness.

The thermosensitive coloring layer 16 is composed of a leuco dye component and a developer component. In FIG. 1, the leuco dye component is indicated by a symbol "○" and the developer component is indicated by a symbol "x". As the leuco dye component "○", a leuco dye for yellow color development is used, and such a leuco dye for yellow color development is available, for example, from Ciba Specialty Chemicals as I-3R (Pergascript Yellow), Its heat melting temperature is about 170 ° C. As the developer component "x", K-5, which is the same as the developer component in the case of the pressure-sensitive thermosensitive color developing layer 14, is used. Although not shown in FIG. 1, low melting point stearic acid amide as a sensitizer is appropriately added to the thermosensitive coloring layer 16. The yellow color forming leuco dye (I-3R) is a white powder.

Next, the full-color recording medium 1 described above
A production example of No. 0 is shown below. In order to form the pressure-sensitive thermosensitive coloring layer 14, a composition liquid A having the composition shown in the following table is prepared. Composition Weight part (1) 25W% aqueous dispersion of microcapsules… 1.0 (2) 17W% NC-Blue-3 aqueous dispersion… 0.5 (3) 16W% K-5 aqueous dispersion… 1.5 (4) 16W % Low melting point stearic acid amide aqueous dispersion 0.7 (5) 20W% binder aqueous solution 0.5 0.5 where composition (1) is purified water and pressure sensitive microcapsules 20
25% by weight is added to disperse (suspend). Composition (2) is prepared by adding 17% by weight of NC-Blue-3 (leuco dye for cyan color development) to purified water and dispersing (suspending) it. This leuco dye is a powder with an average particle size of 1 μm or less. is there. The composition (3) is prepared by adding 17% by weight of K-5 (developing agent) to purified water and dispersing (suspending) it, and the developing agent is a powder having an average particle size of 1 μm or less. Composition (4) is 16% by weight of low melting point stearic acid amide (sensitizer) added to purified water and dispersed (suspended), and the sensitizer is a powder having an average particle size of 1 μm or less. . The composition (5) is made by adding purified water to Gabsen ES-901A (water-soluble polyester) as a binder material to make 20% by weight. Especially, after drying, all the materials are made transparent so that they cannot be directly viewed on the sheet 12. Used to do so. Gabsen
ES-901A is available from Teikoku Kagaku.

By applying the above-mentioned composition liquid A on one surface of the sheet (PET) 12 with Meyer bar No. 8 and drying it, a pressure-sensitive thermosensitive coloring layer 14 as shown in FIG. 1 is obtained. . When the above composition liquid A is applied using Meyer bar No. 8, it is about 4 to 5 per square meter.
A coating weight of gram is obtained. In addition, because of the use of Gabsen ES-901A (water-soluble polyester) as a binder, the pressure-sensitive thermosensitive coloring layer 14 becomes translucent or transparent after drying, and thus a full-color image is formed on the full-color recording medium 10 as described later. When it is formed, the full-color image is visually observed from the pressure-sensitive thermosensitive coloring layer 14 side.

Since the transparent pressure-sensitive thermosensitive coloring layer 14 thus obtained contains a low melting point stearic acid amide as a sensitizer, the thermal melting temperature of the developer (K-5) is about 14
It is lowered from 5 ℃ to about 85 ℃, and the onset temperature of NC-Blue-3 (leuco dye for cyan color development) is lowered to 120 ℃ due to the eutectic effect with the sensitizer.

In order to form the thermosensitive coloring layer 16, a composition liquid B having the composition shown in the following table is prepared. Composition Weight part (1) 17W% I-3R aqueous dispersion …… 0.5 (2) 16W% K-5 aqueous dispersion …… 1.0 (3) 16W% low melting point stearamide aqueous dispersion …… 0.5 (4) Aqueous solution of 10W% binder ... 0.5 Here, composition (1) is I-3R (leuco dye for yellow color development) added to purified water in an amount of 17% by weight and dispersed (suspended). It is a white powder having an average particle size of 1 μm or less. The composition (2) is prepared by dispersing (suspending) 16% by weight of K-5 (developing agent) in purified water, and the developing agent is a powder having an average particle size of 1 μm or less. The composition (3) is prepared by dispersing (suspending) 16% by weight of a low-melting point stearic acid amide (sensitizer) in purified water, and the sensitizer itself is a powder having an average particle size of 1 μm or less. is there. Composition (4) is prepared by adding 10% by weight of PVA (polyvinyl alcohol) having a degree of polymerization of 500 as a binder material to purified water and dissolving it.

By applying the above composition liquid B on the other surface of the sheet (PET) 12 with Meyer bar No. 6 and drying it, a thermosensitive coloring layer 16 as shown in FIG. 1 can be obtained. When the above composition liquid B is applied using Meyer bar No. 6, an application amount of about 3 to 5 grams per square meter is obtained.

Since the low-melting-point stearic acid amide is contained as a sensitizer in the heat-sensitive color forming layer 16 thus obtained, the color development start temperature of the yellow color forming leuco dye (I-3R) is different from that of the sensitizer. It is lowered to about 110 ℃ by eutectic effect. Note that, unlike the transparent pressure-sensitive thermosensitive coloring layer 14, the thermosensitive coloring layer 16 does not need to be particularly transparent in view of hue in the present invention. Therefore, PVA is used as a binder for the thermosensitive coloring layer 16, and thus the thermosensitive coloring layer 16 is used. The coloring layer 16 itself becomes white after being dried.

After the thermosensitive coloring layer 16 is completely dried, a white film sheet (polyethylene terephthalate) having a thickness of 6 μm is attached thereto to form a reflection film layer 18. Thus, the full-color recording medium 1 as shown in FIG.
0 will be obtained. Regarding the attachment of the white film sheet to the thermosensitive coloring layer 16, preferably,
The surface of the thermosensitive coloring layer 16 is coated with a leuco dye (I-3
It is carried out by heating to 80 ° C. to 100 ° C., which is lower than the color development start temperature of R), to heat-melt the developer component (K-5) of the heat-sensitive color developing layer 16 and press-bond a white film sheet thereto.
Of course, other attachment methods include water-soluble adhesives such as
A white film sheet may be attached to the surface of the thermosensitive coloring layer 16 using a PVA (polyvinyl alcohol) aqueous solution. The thermosensitive coloring layer 1 is used instead of the white film sheet.
A fine white powder such as titanium oxide or silica may be further coated on 6 together with a binder to form a white reflective coating layer.

As will be described in detail later, a magenta image and a cyan image are formed in dot pixel units on the transparent pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10, and the thermosensitive coloring layer 16 is based on yellow image data. As a result, a yellow image is formed in dot pixel units, and gradation expression is given to each color image. In this case, light incident from the transparent pressure-sensitive color developing layer 14 side is reflected by the reflective film layer 18 and is emitted again from the transparent pressure-sensitive color developing layer, so that the above-described three primary color images are transparent pressure-sensitive color developing layer 14. It will be visible as a full-color image from the side. That is, the area where the magenta image and the cyan image overlap is observed as a blue color image, the area where the cyan image and the yellow image overlap is observed as a green color image, and the area where the yellow image and the magenta image overlap is red. An area that is observed as a color image and the images of the three primary colors overlap is observed as a black image.

Referring to FIG. 2, there is schematically shown an image recording apparatus for performing full-color image recording on the full-color recording medium 10 having the above-described structure. The image recording apparatus is configured as a thermal line printer. To be done.

As shown in FIG. 2, the printer includes a housing 22 having a substantially rectangular parallelepiped shape, and an inlet 24 for introducing the full-color recording medium 10 is formed on the upper side wall of the housing 22. A discharge port 26 for discharging the full-color recording medium 10 is provided on one of the side walls of the housing 22.
Is formed. In FIG. 2, the movement path of the full-color recording medium 10 is indicated by a chain line 28. During image recording, the full-color recording medium 10 is introduced into the introduction port 24, moved along the movement route 28, and then from the discharge port 26. Is discharged.
A guide plate 30 for guiding the movement of the full-color recording medium 10 is provided in the housing 22, and the guide plate 30 defines a part of the movement path 28.

The guide plate 30 is formed with a _first elongated hole 32 ₁ extending in a direction perpendicular to the moving path 28, and the first elongated hole 32 ₁ has a cross section thereof as shown in FIG. It is tapered upward. First slot 3
The first platen roller 34 ₁ is arranged along the upper opening surface of 2 _1, the platen roller 34 ₁ of the first is rotatably appropriately supported by the frame structure within the housing 22 (not shown). Further, the first thermal head 36 ₁ is inserted into the first elongated hole 32 ₁ from below and is elastically pressed against the axial center of the _first platen roller 34 ₁ . That is, the first thermal head 36
₁ is combined with the _first pressure spring applying means 38 ₁ and by this first pressure spring applying means 38 ₁ , for example 2.0 MPa
It is constantly pressed against the _first platen roller 34 ₁ by the pressing force of.

Incidentally, the first platen roller 34₁Is shown
Counterclockwise in Figure 2 by a suitable drive motor not
Is driven to rotate in the opposite direction, and thus the first platen roller
34 ₁And the first thermal head 36₁Full color between
When the recording medium 10 is introduced, the full-color recording medium 10
Is the first platen roller 34₁From along the travel route 28
Receives the carrying force.

Further, the guide plate 30 has a first elongated hole 32 ₁
A second slot 32 ₂ extending in the direction perpendicular to the movement path 28 is formed on the downstream side of the second slot 32 ₂ , and the second slot 32 ₂ also has the first slot 32 ₂ .
Similar to the elongated hole of FIG. 2, it is tapered upward in its cross section as shown in FIG. A second platen roller 34 ₂ is accommodated in the second elongated hole 32 ₂ from below,
In addition, it is rotatably supported by the frame structure in the housing 22. The second thermal head 36 ₂ is disposed along a second upper opening surface of the slot 32 _2, elastic with respect to the second thermal head 36 ₂ and the second axial center of the platen roller 34 ₂ Be pressed against each other. That is, the second thermal head 36 ₂ in combination with the second pressure spring applying means 38 _2, the second platen roller with the pressing force of the appropriate pressure for example 0.2MPa by the second pressure spring applying means 38 ₂ It is constantly pressed against 34 ₂ .

Contrary to the case of the first platen roller 34 ₁ , the second platen roller 34 ₂ is driven to rotate in the clockwise direction in FIG. 2, and therefore, the second platen roller 34 ₂ and the second platen roller 34 ₂ are rotated. When the full-color recording medium 10 is introduced between the thermal head 36 ₂ and the thermal head 36 ₂ , the full-color recording medium 10 moves from the second platen roller 34 ₂ to the moving path 2
Receives the conveying force along the line 8.

In FIG. 2, reference numeral 40 indicates a control circuit board for controlling the operation of the printer, and reference numeral 42.
Indicates a power supply device, and the power supply device 42 supplies electric power to the drive motors of the first and second thermal heads 36 ₁ and 36 ₂ , the drive motors of the first and second platen rollers 34 ₁ and 34 ₂ , and the control circuit board 40. Is done.

Each of the first and second thermal heads 36 ₁ and 36 ₂ includes n electric resistance elements, that is, heat generating elements, and these n heat generating elements extend in the direction traversing the movement path 28. They are arranged in a straight line. Here, a thermistor is used as an electric resistance element, and as is well known,
A thermistor is a semiconductor device whose resistance value changes with temperature.

Referring to FIG. 3, n thermistors included in the first thermal head 36 ₁ are designated by the reference numeral TH ₁₁ ,
TH _12, TH _13, indicated by ... and TH _1n, also are n thermistor included in the ₂ second thermal head 36 indicated by reference numeral _{TH 21, TH 22, TH 23} ... and TH _2n.
N thermistors T of the first thermal head 36 _{1.
H 1 1, TH 12, TH} 13, ... TH 1n and the second thermal head 36 ₂ of n _{TH 21, TH 22, TH 23} , ... are aligned with each other, respectively along the movement path 28 and TH _2n Are in correspondence.

[0047] During recording operation, a full-color recording medium 10 with the thermal head 36 ₁ and the first platen roller 34 ₁ of the first so that the sensitive pressure sensitive thermal coloring layer 14 is contacted with _one first thermal head 36 It is passed through between, this time the first thermal head 36 ₁ of the individual thermistor (TH
_{11, TH 12, TH 13,} ... when TH _1n) is exothermic is energized, magenta dots, or color dots of cyan dots and blue dots are allowed to develop on sensitive pressure-sensitive heat-coloring layer 14, a magenta dot Which color dot, cyan dot or blue dot, is colored depends on the heat generation temperature of each thermistor. The color (magenta, cyan, blue) color development process in the pressure-sensitive and heat-sensitive color development layer 14 will be described in detail later.

On the other hand, after the full-color recording medium 10 has passed between the first thermal head 36 ₁ and the first platen roller 34 _1, it is between the second thermal head 36 ₂ and the second platen roller 34 _2. The thermosensitive coloring layer 16 of the full-color recording medium 10 is brought into contact with the second thermal head 36 _{2 while} the thermistors (TH ₂₁ , TH ₂₂ , TH, and TH 2 of the second thermal head 36 ₂ are contacted.
_23, ... TH _2n) are heating is energized, thereby the yellow dots are allowed to develop on top thermosensitive coloring layer 16.

As described above, the n thermistors TH ₁₁ , TH ₁₂ , TH ₁₃ , ... Of the first thermal head 36 ₁ are.
TH _1n and n TH _{21 of} the second thermal head 36 ₂ ,
TH _{2 2,} TH _23, ... TH _2n that there is a corresponding relationship be aligned with one another along their movement path 28, a pair of thermistors (TH ₁₁ and TH in correspondence with each other this time
₂₁ ; TH ₁₂ and TH ₂₂ ; TH ₁₃ and TH ₂₃ ; ... TH _1n and TH
_2n ) cooperate with each other to develop any of white dots, magenta dots, cyan dots, blue dots, yellow dots, red dots, green dots and black dots on the full-color recording medium 10.

More specifically, regarding the energization timing of each thermistor of the _second thermal head 36 ₂ during the recording operation, the full-color recording medium 10 is moved more than the energization timing of each thermistor of the _first thermal head 36 _1. Speed and first and second thermal heads 36 ₁ and 3
Delayed by an appropriate time according to the distance of 6 _2, thereby a pair of thermistors in correspondence with each other (T
H ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n ; TH ₂₁ , TH ₂₂ , T
The color dots obtained by H ₂₃ , ... TH _2n ) are aligned with each other via the transparent sheet 12. For example, the color (magenta, cyan, blue) dots colored by the thermistor TH ₁₁ on the pressure-sensitive thermosensitive coloring layer 14 and the yellow dots colored by the thermistor TH ₂₁ are aligned with each other through the transparent sheet 12.

Therefore, if the color dots colored by the thermistor TH ₁₁ are magenta and the yellow dots are colored by the thermistor TH ₂₁ , both dots are full color recording medium 10.
Will be observed as red dots from the pressure-sensitive and thermosensitive coloring layer 14 side. Further, if the color dot colored by the thermistor TH ₁₁ is cyan and the yellow dot is colored by the thermistor TH ₂₁ , both dots are full color recording medium 10.
The green dots are observed from the pressure-sensitive and thermosensitive coloring layer 14 side. Furthermore, if the color dots colored by the thermistor TH ₁₁ are blue and the yellow dots are colored by the thermistor TH ₂₁ , both dots are full color recording medium 1.
It will be observed as a black dot from the pressure-sensitive thermosensitive coloring layer 14 side of 0. Of course, if the thermistor TH ₂₁ does not color the yellow dots, the color (magenta, cyan, blue) dots colored on the pressure-sensitive thermosensitive coloring layer 14 by the thermistor TH ₁₁ are observed, and another set is formed. If both of the thermistors TH ₁₁ and TH ₂₁ are not energized, they will be observed as non-coloring (white) dots.

The size of the color dots formed on the pressure-sensitive and heat-sensitive coloring layers 14 and 16 of the full-color recording medium 10 depends on the size of each thermistor. That is, the dot diameter is about 50 μm to 100 μm.

Next, the coloring process of the color (magenta, cyan, blue) dots in the pressure-sensitive thermosensitive coloring layer 14 will be described.

[0054] full-color recording when the medium 10 is passed between the first thermal head 36 ₁ and the first platen roller 34 _1, the first thermal head 36 ₁ of the individual thermistor (TH _11, TH _12, TH ₁₃ , ... TH _1n ) is 85
When heated to a temperature between ℃ and 120 ℃, the developer component "x" in the pressure-sensitive thermosensitive coloring layer 14 is eutectic with the sensitizer component (low melting point stearamide). It is heat-softened, so that the thermistor penetrates into the pressure-sensitive thermosensitive coloring layer 14 as schematically shown in FIG. Thus, a pressure of about 2.0 MPa, which is much higher than the breaking pressure of 0.5 MPa, is applied to the pressure-sensitive microcapsules 20 by the thermistor, whereby the pressure-sensitive microcapsules 20 are broken and the magenta coloring material is released therefrom. To be done.

On the other hand, when the full-color recording medium 10 is passed between the first thermal head 36 ₁ and the first platen roller 34 ₁ , the individual thermistors (TH ₁₁ , TH) of the first thermal head 36 ₁ are passed. ₁₂ , TH ₁₃ , ... T
When H _1n ) is heated to a temperature of 120 ° C. or higher, the developer component “×” of the pressure-sensitive thermosensitive coloring layer 14 is melted by heat. At this time, the color development starting temperature of the cyan color forming leuco dye component "□" is lowered to 120 ° C due to the eutectic action of the developer component "x" and the sensitizer component (low melting point stearamide). Therefore, the leuco dye component “□” for cyan color development is made to develop a cyan color by the color reaction with the developer component “x” by the thermistor heated to 120 ° C. or higher.
At the same time, a pressure of about 2.0 MPa, which is much higher than the breaking pressure of 0.5 MPa, is directly applied to the pressure-sensitive microcapsules 20 by the thermistor, so that the pressure-sensitive microcapsules 20 are broken and, as a result, the magenta system Magenta coloring by the coloring material can also be obtained. Thus, the pressure-sensitive thermosensitive coloring layer 14
A blue dot is formed by mixing cyan and magenta.

[0056] As described above, the first thermal head 36 ₁ of the individual thermistor (TH _11, TH _12,
TH ₁₃ , ... TH _1n ) is 2.0M with respect to the pressure-sensitive thermosensitive coloring layer 14.
When the heating temperature of each thermistor exceeds 85 ° C. while exerting the pressure of Pa, the pressure-sensitive microcapsules 20 start to break (that is, magenta coloration). When the exothermic temperature of each thermistor is gradually increased from 85 ° C. under such a condition, the number of pressure-sensitive microcapsules 20 destroyed by each thermistor also increases, and the magenta color density also increases accordingly. The thermistor heat generation temperature is 12
When the temperature reaches 0 ° C., the number of pressure-sensitive microcapsules 20 destroyed by each thermistor becomes maximum, and the magenta color density also becomes maximum.

Therefore, the heat generation temperature of each thermistor is 12
At 0 ° C or higher, the magenta color density is considered to be maintained at the maximum level. However, surprisingly,
The heat generation temperature range of the thermistor where the maximum magenta color density is maintained is limited to 120 ° C to 145 ° C. When the heat temperature of each thermistor exceeds 145 ° C, the magenta color density gradually decreases and It was found that when the exothermic temperature of the thermistor exceeds 180 ° C, magenta color development is not observed. Of course, this means that when the heat generation temperature of each thermistor exceeds 145 ° C., a part of the pressure-sensitive microcapsule 20 is escaped from destruction in the region where the pressure of about 2.0 MPa is exerted by the thermistor. It means that when the heat generation temperature of the thermistor exceeds 180 ° C., all of the pressure-sensitive microcapsules 20 contained in the region are escaped from destruction.

The phenomenon of the destruction of the pressure-sensitive microcapsule 20 as described above has been confirmed by an experiment, and the experiment will be described below.

The graph of FIG. 5 shows the above experimental results. In this experiment, the set pressure of the first pressure applying spring means 38 ₁ of the above-mentioned printer (FIG. 2) was changed between 0.35 MPa and 2.8 MPa, and the thermistors TH ₁₁ and TH of the first thermal head 36 ₁ were changed. The color of the color dots obtained on the pressure-sensitive thermosensitive coloring layer 14 was examined when the individual exothermic temperatures of ₁₂ , TH ₁₃ , ... TH _1n were changed between 55 ° C and 200 ° C.

In the graph shown in FIG. 5, the shaded area indicated by "MA" indicates the magenta coloring area, the shaded area indicated by "CY" indicates the cyan coloring area, and the magenta coloring area "MA" and the cyan coloring area. An overlapping area “MA / CY” overlapping with “CY” indicates a blue coloring area. As is clear from the graph, the first pressure applying spring means 3
When the set pressure of 8 ₁ is 2.0 MPa, that is, by the thermistor of the first thermal head 36 ₁ , the pressure-sensitive thermosensitive coloring layer 1
When the pressure exerted on 4 is 2.0MPa, the temperature range for obtaining magenta dots is 85 ℃ and 180 ℃.
Is defined as a temperature range between and, and the temperature range in which cyan dots are obtained is defined as a temperature range of 120 ° C or higher, and the temperature range in which blue dots are obtained is 120 ° C and 180 ° C. Is defined as the temperature range between.

As apparent from the graph of FIG. 5, when the set pressure of the _first pressure applying spring means 38 ₁ is 2.0 MPa and the heating temperature of the thermistor of the _first thermal head 36 ₁ exceeds 180 ° C. It can be seen that the color development of the pressure-sensitive microcapsules 20 is not observed and the destruction is less likely to occur. Further, it can be seen that when the set pressure of the first pressure applying spring means 38 ₁ is 2.0 MPa or less, the break-out phenomenon of the pressure-sensitive microcapsules 20 occurs even at a temperature lower than 180 ° C. From this, the individual thermistors (TH ₁₁ , T
As the form of heat transfer to the pressure-sensitive thermosensitive coloring layer 14 due to H ₁₂ , TH ₁₃ , ... TH _1n ) becomes higher, the ratio of heat radiation increases rather than heat conduction, and a sensitizer, a developer and a cyan color develop. When each of the leuco dyes for use instantaneously becomes in a high heat melting state and the fluidity increases, it acts like a lubricant, and as a result,
Seat 12 and thermistor (TH ₁₁ , TH ₁₂ , TH ₁₃ , ...
TH _1n ), the pressure-sensitive microcapsules 20 sandwiched between them do not receive sufficient pressure, and the pressure-sensitive microcapsules 20 slip through or fluidize from there without smashing into the color forming layer 14. It is speculated that sufficient breaking shear pressure does not work.

In short, in the pressure-sensitive thermosensitive coloring layer 14 as shown in FIG. 1, individual thermistors (TH ₁₁ , T
H ₁₂ , TH ₁₃ , ... TH _1n ), the pressure-sensitive thermosensitive coloring layer 1
When the pressure to be exerted on 4 is set to a predetermined pressure, by appropriately controlling the heat generation temperature of each thermistor,
It is possible not only to independently develop the basic colors magenta and cyan, but also to develop a mixed color of both basic colors, that is, blue.

Referring to the graph of FIG. 6, when the pressure of the first pressure applying spring means 38 ₁ is set to 2.0 MPa, the heating temperature of each thermistor (TH ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n ). Shows the respective density changes of magenta dots and cyan dots when the color dots are developed on the pressure-sensitive thermosensitive coloring layer 14 by gradually increasing the temperature from 85 ° C to 200 ° C. That is, the curve MD shows the density change of magenta dots, and the curve CD shows the density change of cyan dots. As is clear from the graph, the magenta coloring range is defined as a temperature range of 85 ° C or higher and 120 ° C or lower, and the blue coloring temperature range is defined as a temperature range exceeding 120 ° C, for example, a temperature range of 121 ° C or higher and 180 ° C or lower. , Cyan color temperature range is
It is defined as a temperature range exceeding 180 ° C, for example, a temperature range above 181 ° C.

As is apparent from FIG. 6, the magenta coloring temperature
In the temperature range (85 ℃ to 120 ℃), the magenta color density is 85 ℃.
Is the minimum concentration value, and 120 ° C is the maximum concentration value.
Color density gradually increases from 85 ℃ to 120 ℃.
It Therefore, the gradation expression is given to the magenta dot.
For each individual thermistor (TH₁₁, TH₁₂, T
H ₁₃, ... TH_1n) Of the individual thermistors with a constant energizing time
By changing the energization amount (current) of the star,
The so-called energy gradation method that controls the color density of the dot
It will be suitable.

On the other hand, the cyan coloring temperature range is defined as a temperature range of 181 ° C. or higher, and at this time, the cyan coloring density has already reached the maximum density value. Therefore, in order to give a gradation expression to the cyan dot, each thermistor (T
The heat generation temperature of H ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n ) is, for example,
A so-called dot gradation method is adopted in which the cyan color density is controlled by setting the temperature to 181 ° C and changing the energization time.

In the blue color development temperature range defined as a temperature range between 121 ° C. and 180 ° C., so-called true blue color development occurs at a temperature of 150 ° C. at which the ratio of magenta color development component to cyan color development component is 1: 1. As a result, when the temperature goes from 150 ° C to 120 ° C, the blue coloration gradually takes on a magenta hue, and on the contrary, from the temperature of 150 ° C to 180 ° C, the blue color takes on a cyanish hue. That is, the boundary temperature
At around 120 ° C, the hue of blue color is extremely close to magenta, and at the boundary temperature of around 180 ° C, the hue of blue color is extremely close to cyan. In short, in the blue color development temperature range defined as the temperature range between 121 ° C and 180 ° C, individual thermistors (TH ₁₁ , T
By varying the heat generation temperature of H ₁₂ , TH ₁₃ , ... TH _1n ), blue coloring of various hues can be obtained. Therefore,
In order to give gradation expression to blue dots of various hues, individual thermistors (TH ₁₁ , TH ₁₂ , TH ₁₃ , ...
A so-called dot gradation method is employed in which the heat generation temperature of TH _1n ) is set to a temperature corresponding to the hue and the energization time is changed to control the blue color density of each hue.

[0067] Referring to the graph of FIG. 7, the second thermal head 36 ₂ of the individual thermistor (TH _21, TH _22,
The relationship between the exothermic temperature of TH ₂₃ , ..., TH _2n ) and the color density of yellow dots obtained on the thermosensitive coloring layer 16 is shown. That is, the curve YD shows the density change of the yellow dots.

As described above, since the thermosensitive coloring layer 16 contains the low-melting-point stearic acid amide as a sensitizer,
The color development start temperature of the leuco dye (I-3R) for yellow color formation is lowered to about 110 ° C. due to the eutectic action with the sensitizer, and the individual thermistor thermistors (TH ₂₁ , TH ₂₂ , TH ₂₃ , ...
When the exothermic temperature of (TH _2n ) reaches 110 ° C, the thermosensitive coloring layer 16
In, the yellow color is developed at the minimum density value, the yellow color density gradually increases with a temperature rise from 110 ° C., and the yellow color density reaches the maximum density value at a temperature of 190 ° C. Therefore, in order to give the gradation expression to the yellow dots, the individual thermistors (TH ₂₁ , TH ₂₂ , TH
_The so-called energy gray scale method in which the color density of yellow dots is controlled by changing the energization amount (current) of each thermistor while keeping the energization time of ₂₃ , ... TH _2n ) constant is suitable.

Referring again to FIG. 3, as shown in FIG. 3, the control circuit board 40 includes a printer controller 44.
And the n thermal thermistors T of the first thermal head 36 _1.
First for driving H ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n
And the driving device 46 _1, the second thermal head 36 ₂ of n thermistor _{TH 21, TH 22, TH 23} , ... and the ₂ second driving device 46 for driving the TH _2n is provided. Each of the n thermistors of the first and second thermal heads 36 ₁ and 36 ₂ is a printer controller 44.
The first and second drive devices 46 ₁ and 46 ₂ under the control of
In accordance with the color pixel data for one line, it is selectively energized to generate heat.

Each of the n color pixel data included in one line is composed of density (gradation) data of three primary colors, that is, magenta density data, cyan density data, and yellow density data. 2 thermal heads 3
6 ₁ and 36 ₂ are used to drive a pair of corresponding thermistors (TH ₁₁ and TH ₂₁ ; TH ₁₂ and TH ₂₂ ; TH ₁₃ and TH ₂₃ ; ... TH _1n and TH _2n ). It That is, the magenta density data and the cyan density data that form the individual color pixel data are one thermistor of the set of thermistors, that is, the first thermal head 3.
The yellow density data used to drive the thermistor (eg TH ₁₁ ) included in 6 ₁ and constituting individual color pixel data is the other thermistor of the set of thermistors, that is, the second thermal head 36 ₂ Used to drive a thermistor (eg TH ₂₁ ) contained in

In the present embodiment, each of the magenta density data, the cyan density data and the yellow density data is made up of 8 bits, which makes it possible to give an expression of 256 gradations to the magenta dots, the cyan dots and the yellow dots. It is possible, and for convenience of the following description, each 8-bit density data will be represented as follows for convenience. Magenta density data: D _M [m] Cyan density data: D _C [c] Yellow density data: D _Y [y] where m, c and y are decimal numbers, and 000 to 2
Integer up to 55

For example, when the magenta density data is D _M [000], D _M [000] = [00000000], and when the magenta density data is D _M [255], D _M [255] = [11111111]. Become. Similarly, when the cyan density data and the yellow density data are D _C [000] and D _Y [000], respectively, D _C [000] = [000
00000] and D _Y [000] = [00000000], and cyan density data and yellow density data are D _C [255] and D, respectively.
_{When Y} [255], D _C [255] = [11111111] and D _Y [255] = [1
1111111] becomes. Next, heat generation temperature control of the corresponding thermistors (TH ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n ) for magenta density data D _M [m] and cyan density data D _C [c] will be described below.

When m of the magenta density data D _M [m] is 000, it indicates that the magenta density is zero, and when c of the cyan density data D _C [c] is 000, the cyan density is zero. Is shown. When both m and c of D _M [m] and D _C [c] are 000, the first thermal head 36 ₁
The corresponding thermistor is not energized.

[0074] Cyan density data D c of _C [c] is a 000, when m of the magenta density data D _M [m] is a numerical value other than 000, magenta density data D _M [m] in FIG. 6 The temperature is set to correspond to any temperature in the magenta color development temperature range (from 85 ° C. to 120 ° C.), and the temperature is set as the heat generation temperature of the thermistor of the first thermal head 36 ₁ , and the heat generation time, that is, the corresponding thermistor. The energization time is set to a predetermined maximum time.

More specifically, when m of the cyan density data D _C [m] is 000, the magenta density data D _M [001] to D _M [255] are in the magenta color development temperature range (85 ° C. to 120 ° C.). , The magenta density data D _M [001] corresponds to 85 ° C. (magenta coloring start temperature) at which the magenta coloring density becomes the minimum value.
The magenta density data D _M [255] corresponds to 120 ° C. where the magenta color density is the maximum value. Therefore, for example, when m of the magenta density data D _M [m] is 128, the magenta density data D _M [128] indicates the magenta color development temperature range (85 ° C. to 120 ° C.).
Corresponding to an intermediate temperature of 103 ° C (up to ℃), at which time the heat generation temperature of the corresponding thermistor of the _first thermal head 36 ₁ is 103 ° C.
℃ Thus, magenta dots are formed on the pressure-sensitive thermosensitive coloring layer 14 at a predetermined density by a so-called energy gradation method.

_{C of} cyan density data D _C [c] takes a value other than 000, and m of magenta density data D _M [m] is also 0.
When a numerical value other than 00 is taken, the hue data T _B [b] of blue color development is calculated based on the ratio of the magenta density data D _M [m] to the cyan density data D _C [c], and at this time, the hue data T _B [b] is also 8-bit data. In addition, here, b of the hue data T _B [b] is a decimal value and is 001
It can be any value from 1 to 256.

More specifically, regarding the calculation of the hue data T _B [b], when D _M [m] / D _C [c] = 1 (decimal number),
That is, when m = c, T _B [001] = [00000000],
In this case, the hue data T _B [001] represents true blue,
The hue data T _B [001] is associated with 150 ° C. (FIG. 6). The true blue density is represented by either magenta density data D _M [m] or cyan density data D _C [c] (m = c, of course). In short, when the hue data T _B [001] = [00000000], the heat generation temperature of the corresponding thermistor of the first thermal head 36 ₁ is set to 150 ° C. At this time, the energization time of the thermistor is magenta density data D _M [ m] or cyan density data D _C [c], so that true blue dots are formed at a predetermined density on the pressure-sensitive thermosensitive coloring layer 14 by a so-called dot gradation method.

On the other hand, when D _M [m] / D _C [c]> 1 (decimal number), the hue data T _B [b] is calculated by the following equation (1). b = INT [D _M [m] / D _C [c]] (1) Here, in general, when the division e / f is performed, the operator INT [e / f] is the division e / f. Represents a quotient, and b is an integer from 255 to 002.

If D _M [m] / D _C [c]> 1, the blue color obtained by mixing the magenta density data D _M [m] and the cyan density data D _C [c] is magenta blue. At this time, b of the hue data T _B [b] can take one of integers from 255 to 002 by the calculation of the above equation (1). For example, hue data T _B [256] = [11111111]
In this case, the blue represented by this hue data is the most magenta blue, and the hue data T _B [002] =
At [00000001], the blue represented by this hue data is the blue closest to the true blue.

When the blue color obtained by mixing the magenta density data D _M [m] and the cyan density data D _C [c] is magenta blue, as shown in FIG.
As shown in the graph, the hue data T _B [256] is a temperature of 121
The hue data T _B [002] is made to correspond to 145 ° C. and the hue data T _B [255] to T _B [003] is made to 121 ° C.
And the temperature range between 145 ° C and 145 ° C. In addition, the density of magenta blue is represented by magenta density data D _M [m] (m> of course).
c). In short, b of the hue data T _B [b] is 256 to 002.
When any one of the above values is taken, the heat generation temperature of the corresponding thermistor of the first thermal head 36 ₁ is the hue data T _B.
The temperature corresponding to [b] is set, and in this case, the energization time of the thermistor is controlled based on the magenta density data D _M [m]. It is generated at a predetermined density by a so-called dot gradation method.

When D _M [m] / D _C [c] <1 (decimal number),
The calculation of the hue data T _B [b] is performed by the following equation (2). b = 1 / INT [D _C [c] / D _M [m]] (2) where b is 255 from 1/001 to 1/255 (fraction is an integer)
Any number on the street.

If D _M [m] / D _C [c] <1, then the blue color obtained by mixing the magenta density data D _M [m] and the cyan density data D _C [c] is cyanish blue. In this case, b of the hue data T _B [b] can take one of the fractions (denominator is an integer) from 1/001 to 1/255 by the calculation of the equation (2). For example, when the hue data T _B [1/001] = [00000000], the blue represented by this hue data is the blue closest to the true blue, and the hue data T _B [1/255] = [11111110] At this time, the blue represented by this hue data is the blue with the most cyan.

When the blue color obtained by mixing the magenta density data D _M [m] and the cyan density data D _C [c] is cyanish blue,
As shown in the graph of 9, the hue data T _B [1/001] is the temperature 1
Is made to correspond to 55 ° C., the hue data T _B [1/255] is caused to correspond to 180 ° C., hue data T _B [1/002] to T _B [1/254]
Are evenly assigned to the temperature range between 155 ° C and 180 ° C. The density of such magenta blue is represented by cyan density data D _C [c]. In short, when b of the hue data T _B [b] takes any value from 1/001 to 1/255, the heat generation temperature of the corresponding thermistor of the first thermal head 36 ₁ is the hue data T _B [b]. ], In which case the energization time of the thermistor is controlled based on the cyan density data D _C [c], so that cyan-colored blue dots are so-called dots on the pressure-sensitive thermosensitive coloring layer 14. It is generated with a predetermined density by the gradation method.

_{C of} cyan density data D _C [c] takes a value other than 000, and m of magenta density data D _M [m] is 000.
, The hue data T _B [b] is conveniently used to determine the cyan maximum density color development temperature. In this case, 1/256 is set to b of the hue data T _B [b], and this hue data T _B [1/256] represents pure cyan. Such hue data T _B [1/256] is associated with 181 ° C. (FIG. 6). Further, such a pure cyan density is of course represented by cyan density data D _C [c].
In short, when the hue data T _B [1/256], the heat generation temperature of the corresponding thermistor of the _first thermal head 36 ₁ is 181 ° C.
And the energization time of the thermistor is controlled based on the cyan density data D _C [c] at this time, thus pure cyan dots are formed on the pressure-sensitive thermosensitive coloring layer 14 at a predetermined density by a so-called dot gradation method. Is caused.

The individual thermistors (TH ₁₁ , TH ₁₂ , TH ₁₃ , ... T included in the first thermal head 36 ₁₎ .
As for the heat generation temperature of H _1n ), the cyan color development temperature of 181 ° C. is the maximum heat generation temperature, and the above-mentioned magenta color development start temperature 85
C becomes the minimum heat generation temperature of the individual thermistors (TH ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n ) of the first thermal head 36 ₁ .

Then, the corresponding thermistors (TH ₂₁ , TH ₂₂ , TH ₂₃ , ...) For the yellow density data D _Y [y].
The heat generation temperature control of TH _2n ) will be described below.

When y of the yellow density data D _Y [y] is 000, it indicates that the yellow density is zero. In this case, the corresponding thermistor of the _second thermal head 36 ₂ is not energized. On the other hand, y of the yellow density data D _Y [y]
Is a value other than 000, yellow density data D
_Y [y] is the yellow color development temperature range shown in FIG.
Temperature (up to ° C), and that temperature is set as the heat generation temperature of the corresponding thermistor of the second thermal head 36 ₂ , and the heat generation time, that is, the energization time of the corresponding thermistor is set to a predetermined maximum time. It

More specifically, the yellow density data D _Y [001]
To D _Y [255] are in the yellow color development temperature range (110 ° C to 190 ° C)
(Up to ° C) corresponding to the temperature evenly assigned,
At this time, the yellow density data D _Y [001] corresponds to 110 ° C. (yellow color development start temperature) where the yellow color density is the minimum value, and the yellow density data D _Y [255] is 190 ° C. where the magenta color density is the maximum value. Corresponding to. Therefore, for example, when y of the yellow density data D _Y [y] is 128, the yellow density data D _Y [128] indicates the yellow color development temperature range (110 ° C.).
To 190 ° C.), the heat generation temperature of the corresponding thermistor of the second thermal head 36 ₂ is 150 ° C. Thus, yellow dots are formed at a predetermined density on the pressure-sensitive and thermosensitive coloring layer 14 by the so-called energy gradation method.

Here, the principle of giving gradation expression to the colored dots by the energy gradation (density gradation) method will be described.
For example, if case will be described to provide a gradation in accordance with the energy gradation method in magenta dot, the first thermal head 36 ₁ of the individual thermistor (TH _11, TH _12,
The heat generation time of TH ₁₃ , ... TH _1n ) is set to a heat generation time (for example, 5.10 ms) at which a full size dot is obtained, and the heat generation temperature is controlled based on the 8-bit magenta density data D _M [m]. .. Magenta density data D _M [m] is the density data 256 from D _M [000] As described above until D _M [255]. Needless to say, the heat generation time of 5.10 ms for obtaining a full-size dot is equivalent to that of the full-color recording medium 1.
This is related to a feed rate of 0, in other words, for the feed rate of the full-color recording medium 10, the time is 5.10 ms.
It is assumed that the distance travels for each dot size (about 50 μm to 100 μm).

Referring to FIG. 10, magenta density data D _M [m] and individual thermistors (TH _{1 1} , TH ₁₂ , T).
The relationship between the heat generation temperature of H ₁₃ , ... TH _1n ) is shown in the graph. As is clear from the graph, when the magenta density data D _M [000], the corresponding thermistor is not energized, and therefore the magenta dot is not colored, which is indicated by the temperature t _{m [000]} of the corresponding thermistor at that time. Be done. In the case of magenta density data D _M [001], the corresponding thermistor is energized so as to generate heat up to a magenta color development start temperature of 85 ° C. On the other hand, in the case of magenta density data D _M [255], the corresponding thermistor is energized so as to generate heat up to a temperature of 120 ° C. at which the magenta coloring density becomes maximum.

For example, if the magenta density data are represented by D _M [063], D _M [127] and D _M [191] respectively, the temperature at which the corresponding thermistor should generate heat according to the respective magenta density data is given. t _{M [063]} , t _{M [127]} and t
_{Given M [191]} , these temperatures are determined by the following calculations. t _{M [063]} ≈ (120-85) * (063/256) +85 t _{M [127]} ≈ (120-85) * (127/256) +85 t _{M [191]} ≈ (120-85) * (191 / 256) +85

Referring to FIG. 11A, a magenta dot obtained when the heat generation temperature of the thermistor is the maximum heat generation temperature (120 ° C.) is schematically shown, and the magenta color density is the maximum color density. On the other hand, in FIG. 11B, the magenta obtained at the heat generation temperature t _{M [063]} corresponding to approximately 1/4 of the temperature difference between the minimum color development temperature of 85 ° C. and the maximum color development temperature of 120 ° C. Dots are shown, and the color density thereof corresponds to the heat generation temperature t _{M [063]} , which is about 1/4 of the maximum color density. In addition, in (C) of FIG.
A magenta dot obtained at a heat generation temperature t _{M [127]} corresponding to approximately half the temperature difference between the minimum color development temperature of 85 ° C. and the maximum color development temperature of 120 ° C. is shown, and the magenta color density is the heat generation temperature t. It corresponds to _{M [127]} , and is about half of the maximum color density. Further, FIG. 11D shows that the temperature difference between the minimum color development temperature of 85 ° C. and the maximum color development temperature of 120 ° C. is approximately 3/4.
The magenta dot obtained at the heat generation temperature t _{M [191]} corresponding to is shown, and the magenta color density is the heat generation temperature t.
It corresponds to _{M [191],} and is approximately 3 / of the maximum color density.
It will be about 4. In this way, by making the heat generation time (energization time) of the thermistor constant and controlling the heat generation temperature, it is possible to give an energy gradation expression to the colored dots. Note that in FIGS. 11B, 11C, and 11D, the color density difference of the color dots is displayed as the hatching density difference for convenience.

Next, the principle of giving gradation expression to colored dots by the dot gradation (density gradation) method will be described. For example, if case will be described to provide a gradation according to the dot gradation method cyan dots, as described above, cyan density data D c of _C [c] takes a value other than 000, and the magenta density data D _M [ When m of m] is set to 000, the hue data T is used to determine the cyan maximum density coloring temperature.
_B is b in [b] is set 1/256, this time the first thermal head 36 ₁ of the thermistor (TH _11, TH _12, T
H ₁₃ , ... TH _1n ) is the maximum exothermic temperature (cyan color development temperature) 18
The heat is generated up to 1 ° C., and at this time, the energization time of the thermistor is controlled according to the cyan density data D _C [c]. That is, the thermistor (TH ₁₁ , TH ₁₂ , TH ₁₃ , ... T
H _1n ) has a constant heat generation temperature, that is, the cyan color development temperature is 181 ° C.
The heat generation time, that is, the energization time to the thermistor is controlled based on the 8-bit cyan density data D _C [c].

In this embodiment, for example, the full size (50
The maximum heat generation time (maximum energization time) for obtaining cyan dots of (μm to 100 μm) is, for example, 5.1 ms. As already mentioned, D _C [25 cyan density data D _C [000]
There are 256 kinds of density data up to 5], and the cyan density data D _C [000] to D _C [255] are assigned to the energization time range from 0 ms to 5.1 ms. That is, when the cyan density data D _C [000], the energization time of the corresponding thermistor is 0 m.
s, the energization time is 0.02 each time the cyan density data increases by 1.
It can be increased by ms.

Referring to FIG. 12, the relationship between the 8-bit cyan density data D _C [c] and the heat generation time (energization time) of each thermistor is shown in the form of a graph. As is clear from the graph, when the cyan density data D _C [000], the corresponding thermistor is not energized. Cyan density data D
When either _C [001] to [255], the corresponding thermistor is energized with the maximum current, which causes the thermistor to instantly generate heat up to 181 ° C. at which the cyan color density becomes maximum. In the case of the cyan density data D _C [001], the heat generation time of the corresponding thermistor, that is, the energization time is 0.02 ms, and the energization time increases by 0.02 ms each time the cyan density data increases by 1, and the cyan density data D _C [255] ], The energization time of the corresponding thermistor is the maximum energization time of 5.10 ms, at which time the cyan colored dots are full size.

With reference to FIG. 13A, a full-size cyan dot obtained when the energization time of the thermistor is the maximum energization time of 5.10 ms (that is, cyan density data D _C [255]) is schematically shown. . On the other hand, FIG. 13 (B)
Shows a partially colored cyan dot obtained when the energization time is 1.26 ms (that is, cyan density data D _C [063]), which corresponds to approximately 1/4 of the maximum energization time of 5.10 ms. The color development area of the cyan dot corresponds to the energization time of 1.26 ms. Also, in FIG. 13C, the energization time is 2.54 ms, which is almost half of the maximum energization time of 5.10 ms.
That is, a partially colored cyan dot obtained in the case of cyan density data D _C [127] is shown, and the colored area of this partially colored cyan dot corresponds to the energization time of 2.54 ms. Further, in FIG. 13D, the energization time and the maximum energization time
A partially colored cyan dot obtained when the energization time is 3.82 ms (that is, cyan density data D _C [191]) corresponding to approximately 3/4 of 5.10 ms is shown, and the colored area of this partially colored cyan dot is It corresponds to the energization time of 3.82 ms. In this way, by making the heat generation temperature of the thermistor constant and controlling the heat generation time, that is, the energization time, it is possible to give the dot gradation expression to the cyan dot.

Referring to FIG. 14, details of the printer controller 44 shown in FIG. 3 are shown. As shown in FIG. 14, the printer controller 44 is configured as a microcomputer. That is, the printer controller 44 includes a central processing unit (CPU) 44A, a read-only memory (ROM) 44B for storing programs for executing various routines, constants, etc., and a writable / readable memory for temporarily storing data and the like. It comprises a memory (RAM) 44C, a frame memory 44D for temporarily storing color pixel data for one frame to be recorded, an input / output interface (I / O) 44E and the like. The printer controller 44 is used to control the overall operation of the printer, and the printer controller 44 also controls the rotation drive of the platen roller 24, for example.

When the printer is operating, the printer controller 44 is connected to, for example, a personal computer or the like via the I / O 44E. In the printer controller 44,
When character code data, image data, etc. for one frame are sequentially received from the personal computer, the character code data, image data, etc. are processed and color pixel data for one frame is created. That is, the character code data is converted into character pattern pixel data by a character generator (not shown), and the image data is converted into bitmap pixel data, so that color pixel data for one frame is created. As described above, the individual color pixel data are density (gradation) data of the three primary colors, that is, magenta density data D _M [m], cyan density data D _C [c] and yellow density data D _Y [y].
And each density data is configured as 8-bit data.

In the present embodiment, the magenta density data D _M [m] and the cyan density data D _C [c] of the density data of the three primary colors included in the individual color pixel data are included.
Are further processed so that the individual thermistors (TH ₁₁ , TH ₁₂ , TH 1 of the first thermal head 36 ₁ are
_13, ... heating temperature TH _1n) is set in a manner as described below.

First, individual color pixel data is included.
Cyan density data D_CDetermine whether c in [c] is 000
And if c = 000 (when there is no cyan color)
Mackerel density data D_Mon the most significant bit side of [m]
2 bits [00] are added to form a 10-bit structure.
First thermal head 36₁Applicable thermistor (T
H ₁₁, TH₁₂, TH₁₃, ... TH_1n) About heat generation temperature
Is its 10-bit data [[00] D_M[m]]
Is set.

If both c of cyan density data D _C [c] and m of magenta density data D _M [m] take values other than 000, magenta density data D _M [for cyan density data D _C [c] m] is calculated, and if D _M [m] / D _C [c]>
If it is 1, the hue data T _B [b] is calculated according to the above equation (1), and 2 bits [01] are added to the most significant bit side of the hue data T _B [b] to form a 10-bit configuration. It is, for heating temperature at this time the first thermal head 36 ₁ of the relevant thermistor is set according to the data from which it 10-bit configuration _{[[01] T B [b} ]].

If c of cyan density data D _C [c] and m of magenta density data D _M [m] are both values other than 000, D _M [m] / D _C [c] = 1. At times, as already described, 001 is set in b of the hue data T _B [b]. Even in such a case, 2 bits [01] are added to the most significant bit side of the hue data T _B [001] to form a 10-bit structure, and at this time, the heating temperature of the corresponding thermistor of the _first thermal head 36 ₁ (That is, 150 ℃), 10
It is set according to data which is a bit configuration _{[[01] T B [001} ]].

On the other hand, if D _M [m] / D _C [c] <1, then the hue data T _B [b] is calculated according to the above equation (2),
2 bits [1 on the most significant bit side of the hue data T _B [b]
0] is added to form a 10-bit structure. At this time, regarding the heat generation temperature of the corresponding thermistor of the first thermal head 36 ₁ , the data of the 10-bit structure [[10] T
It is set according to _B [b]].

If the cyan density data D _C [c] has a value c other than 000, and the magenta density data D _M [m] is m.
Is 000 (when there is no magenta color development), b of the hue data T _B [b] is set to 1/256, as described above. Even in such a case, the hue data T _B [1 / 256] the most significant bit of the two bits [10] is Load 10 bits, for this time, the first thermal head 36 ₁ of the relevant thermistor heating temperature (i.e., 181 ° C.), the Ten
It is set according to data which is a bit configuration _{[[10] T B [1/256} ]].

Referring to FIG. 15, the thermistor drive circuit constituting the _first drive device 46 ₁ is indicated by the reference numeral 48 ₁ , and the first drive device 46 ₁ includes n _first thermal heads 36 ₁ . The thermistor (TH ₁₁ , TH
₁₂ , TH ₁₃ , ... TH _1n ), n thermistor drive circuits 48 ₁ are provided.

The thermistor drive circuit 48 ₁ has a digital /
An analog (D / A) converter 50, an operational amplifier 52, and a transistor _Tr are provided. The input terminal (LATCH) of the D / A converter 50 is the I / O of the printer controller 44.
It is connected to the strobe signal output port of O44E. Further, the output terminal (OUT) of the D / A converter 50 is connected to the plus side input terminal of the operational amplifier 42 via the resistor R ₁ having an appropriate resistance value, and the output terminal of the operational amplifier 52 has an appropriate resistance value. It is connected to the base of the transistor T _r via the resistor R ₂ . The collector of the transistor T _r is connected to a suitable power supply voltage V _CC, and its emitter via a resistor R ₃ having an appropriate resistance value thermistor (TH _11, TH _12,
TH ₁₃ ... TH _1n ), and the other terminal of the thermistor is grounded. The negative input terminal of the operational amplifier 52 has a resistor R ₃ and a thermistor (TH ₁₁ , T
H _12, TH _13, ... are connected between the TH _1n).

Data of 10-bit configuration is sent from the printer controller 44 via the I / O 44E to the D / A converter 50.
Is sequentially output at a predetermined timing. In addition, such 10-bit data is stored in the individual thermistors (TH ₁₁ , TH ₁₂ , TH ₁₃₎ of the first thermal head 36 ₁ .
... TH _1n ) for setting the heat generation temperature,
[[00] D _M [m]], [[01] T _B [b]], and [[01] T described above.
_B [001]], which corresponds to any of _{[[10] T B [b} ]] and _{[[01] T B [1/256} ]].

As shown in FIG. 15, I / O 44E to D
8 of the 10-bit input lines to the A / A converter 50
For convenience, the input line for 2 bits and the input line for 2 bits are shown separately. The 8-bit input line is for inputting 8-bit magenta density data D _M [m] or 8-bit hue data T _B [b] to the D / A converter 50, and is a 2-bit input line. The line is 2 bits [00] added to the most significant bit side of magenta density data D _M [m] or 2 bits [01] or [10] added to the most significant bit side of hue data T _B [b]. Is input to the D / A converter 50.

When the strobe signal (STB) is output as a pulse signal from the strobe signal output port of the I / O 44E and the strobe signal is input to the input terminal (LATCH) of the D / A converter 50, the D / A conversion is performed. Container 50
It takes in 10-bit data and converts it to an analog voltage according to the value and outputs it to the output terminal (OU) of the D / A converter 50.
Output from T). In this embodiment, the output time interval of the strobe signal (pulse signal) corresponds to the time 5.10 ms required to obtain a full-sized colored dot, and the D / A converter 50 is latched during that time. That is, the output of the analog voltage from the output terminal (OUT) of the D / A converter 50 is maintained over the output time interval (5.10 ms) of the strobe signal.

When the analog voltage output from the output terminal (OUT) of the D / A converter 50 is input to the positive side input terminal of the operational amplifier 52, a predetermined voltage is output from the output terminal of the operational amplifier 52 to the base of the transistor T _r . To turn on the transistor T _r . When the transistor T _r is turned on, the thermistor (TH ₁ ,
TH ₂ , TH ₃ , ... TH _n ) are energized to generate heat,
At this time, the energization amount (current amount) of the thermistor is determined by the magnitude of the analog voltage applied to the plus side input terminal of the operational amplifier 52. That is, the operational amplifier 52 uses the resistor R ₃
The voltage drop due to is detected at its negative input terminal, and the energization amount of the thermistor is feedback-controlled so that the detected voltage matches the analog voltage applied to the positive input terminal of the operational amplifier 52. The energization amount of is according to the magnitude of the input analog voltage of the plus side input terminal of the operational amplifier 52.

In short, the thermistors (TH ₁₁ , TH ₁₂ ,
The heat generation temperature of TH ₁₃ , ... TH _1n is the energization amount (current amount)
As a result, the heat generation temperature of the thermistor is controlled by the value of the 10-bit data described above. For example, 10-bit data is [[00] D
_{When M} [001]], the operational amplifier 52 has an analog voltage of such a value that 85 ° C can be obtained as the thermistor heat generation temperature.
Of the input to the positive input terminal, when 10-bit data is _{[[01] T B [001} ]] is positive analog voltage operational amplifier 52 of 0.99 ° C. is sized such as a heating temperature of the thermistor It is input to the input terminal. Similarly, for example, when the 10-bit data is [[01] T _B [1/256]], an analog voltage of such a magnitude that 181 ° C. can be obtained as the heat generation temperature of the thermistor is input to the positive side of the operational amplifier 52. It will be input to the terminal.

When both c of cyan density data D _C [c] and m of magenta density data D _M [m] are 000, 10-bit data [[00] D _M [000]] is [0000000000]. ]
In this case, the output terminal of the D / A converter 50 (O
The analog voltage output from (UT) becomes zero, the transistor _Tr is turned off, and the thermistor is not energized.

Thermistors (TH ₁₁ , TH ₁₂ , TH ₁₃ , ...
The thermistor drive circuit 48 ₁ further includes a binary counter 54, a flip-flop 56, and an open collector gate 58 in order to control the heat generation time of TH _1n ).
And an inverter 60 are provided. As shown in FIG. 15, the output terminal (inverted Q) of the binary counter 54 is connected to the input terminal (D) of the flip-flop 56, and the output terminal (Q) of the flip-flop 56 is connected to the input terminal of the open collector gate 58. To be done. The input terminal (CLR) of the binary counter 54 is the printer controller 44.
I / O44E strobe signal output port. On the other hand, the input terminal of the inverter 60 is connected to the clock pulse output port of the I / O 44E, its output terminal is connected to the input terminal (CLK) of the flip-flop 56, and the input of the binary counter 54 is input to the clock pulse output port. It is also connected to the terminal (CLK). Furthermore,
The input terminal (inversion CLR) of the flip-flop 56 is I /
It is connected to the enable signal output port of O44E.

I / O 44E of the printer controller 44
When the enable signal output from the enable signal output port of 1 changes from the low level to the high level, the flip-flop 56 becomes operable. A clock pulse (CLOCK) having a predetermined frequency is continuously output from the clock pulse output port of the I / O 44E, and this clock pulse is input to both the input terminal (CLK) of the binary counter 54 and the input terminal of the inverter 60. It In addition,
The clock pulse output from the inverter 60 becomes a clock pulse (inversion CLOCK) whose phase is shifted by π with respect to the input clock pulse.

8-bit data is sent from the printer controller 44 via the I / O 44E to the binary counter 54.
Is sequentially output at a predetermined timing. I / O4
When the strobe signal (STB) is output from the strobe signal output port of 4E and input to the input terminal (CLR) of the binary counter 54, the set value of the binary counter 54 is once cleared and a new 8-bit data is created. A corresponding numerical value is set, and then counting of the number of input clock pulses for the input terminal (CLK) of the binary counter 54 is started.

Input terminal of the binary counter 54 (CL
When the count number of the input clock pulse for K) reaches the set value of the binary counter 54, the output level of the output terminal (inversion Q) of the binary counter 54 is changed from the low level to the high level. Binary counter 54
The output level of the output terminal (Q) of the flip-flop 56 is low level in synchronization with the rise of the inverted clock pulse output from the inverter 60 after the output level of the output terminal (inverted Q) of the To a high level, the open collector gate 58 is turned on at this time, and the voltage level of the positive side input terminal of the operational amplifier 52 is dropped to the ground level, which causes the thermistors (TH ₁ , TH ₂ , TH ₃ , (TH _n ) is forcibly stopped from being energized. In short, the open collector gate 58 functions as a switch means for forcibly grounding the positive side input terminal of the operational amplifier, and this switch means changes the output level of the output terminal (Q) of the flip-flop 56 from low level to high level. When it changes, it turns on and forcibly stops energizing the thermistor.

Therefore, if the frequency of the clock pulse (CLOCK) is 50 kHz, the output interval of each clock pulse is 0.02 ms, which causes the thermistor (TH ₁ ,
It is possible to control the energization time of TH ₂ , TH ₃ , ... TH _n ) in units of 0.02 ms. For example, 8-bit data
If it corresponds to decimal 63, the binary counter 54
Is set to 63, and at this time the thermistor energization time is 1.26.
It is set to (63 × 0.02) ms. Similarly, 8-bit data is 10
If it corresponds to the decimal number 127, the binary counter 54
Is set to 127, and the energization time of the thermistor is 2.5
4 (127 × 0.02) ms, 8-bit data in decimal
If it corresponds to 255, the binary counter 54 is set to 255, and the energization time of the thermistor is 5.10 (255
× 0.02) ms.

When the 10-bit data input to the D / A converter 50 is [[00] D _M [m]], that is, when c of the cyan density data D _C [c] is 000 (in short, , In the case of developing magenta dots on the pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10), the binary counter 54 has 10
8-bit data corresponding to the decimal number 255 is set, and therefore the corresponding thermistor (TH ₁₁ , TH ₁₂ , TH ₁₃ , ... TH) is set.
_1n ) energization time is 5.10ms, which is the maximum energization time for obtaining full-size magenta dots. At this time, the heat generation temperature of the thermistor is 10-bit data [[00] D
Figure 1 for magenta dots to follow _M [m]]
The gradation expression by the energy gradation method as exemplified in 1 is given.

Further, the 10-bit data input to the D / A converter 50 is [[01] T _B [b]] and [[01] T _B [001]].
, That is, when a magenta blue dot or a true blue dot is developed on the pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10, the binary counter 54
Corresponding to 8-bit magenta density data D _M [m]
A decimal number is set, so the corresponding thermistor (T
The energization time of H ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n ) corresponds to the magenta density data D _M [m], and thus FIG. 13 is used for magenta or true blue dots. The gradation expression by the dot gradation method as illustrated in FIG.

Furthermore, the 10-bit data input to the D / A converter 50 is [[10] T _B [b]] and [[01] T _B [1/25].
6]], that is, when cyan blue dots or pure cyan dots are developed on the pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10, the binary counter 54 displays 8-bit cyan density data D _C [ The decimal number corresponding to c] is set, so that the energization time of the corresponding thermistor (TH ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n ) corresponds to the cyan density data D _C [c]. Thus, the gradation expression by the dot gradation method as illustrated in FIG. 13 is given to the cyan-colored blue dot or the pure cyan dot.

Referring to FIG. 16, the thermistor drive circuit which constitutes the _second drive device 46 ₂ is indicated by the reference numeral 48 ₂ , and the second drive device 46 ₂ has n _second thermal heads 36 ₂ . The thermistor (TH ₂₁ , TH
₂₂ , TH ₂₃ , ... TH _2n ), n thermistor drive circuits 48 ₂ are provided.

As is apparent from FIG. 16, the thermistor drive circuit 48 ₂ has substantially the same configuration as the thermistor drive circuit 48 ₁ included in the first drive device 46 ₁ ,
6, the same reference numerals are used for the same components as in FIG. As is clear from the comparison between FIG. 15 and FIG. 16, 10-bit data is input to the D / A converter 50 of the thermistor drive circuit 48 ₁ , whereas the thermistor drive circuit 48 ₂ is input. the D / a converters 50 are adapted to 8-bit data is input, but they are different in this regard, those functions itself thermistor drive circuit 48 ₂ is the thermistor driving circuit 48 ₁ and substantially Are the same.

As is clear from the above description, the individual thermistors (TH ₂₁ , TH) of the second thermal head 36 ₂ are
₂₂ , TH ₂₃ , ... TH _2n ) are used to develop yellow dots on the thermosensitive coloring layer 16 of the full-color recording medium 10, and each thermistor drive circuit 48 ₂ has its corresponding yellow density data D _Y [. y]. Binary counter 5 of thermistor drive circuit 48 ₂
8-bit data corresponding to decimal number 255 is always set in 4, and therefore the corresponding thermistor (TH ₂₁ , TH ₂₂ , T
H ₂₃ , ... TH _2n ) energization time is 5.10 ms, which is the maximum energization time for obtaining full-size yellow dots.
At this time, since the heat generation temperature of the thermistor follows the 8-bit yellow density data D _Y [y], the gradation expression by the energy gradation method as illustrated in FIG. 11 is given to the yellow dot.

As described above, when the printer controller 44 receives character code data or image data for one frame from the personal computer, for example, when the printer is operating, the character code data, image data, etc. are received. Color pixel data for one frame is created by processing. When such color pixel data is created, the magenta density data D _M [m] and the cyan density data D _C [c] of the individual color pixel data are immediately processed, whereby the first driving device 46 is processed. 10-bit data to be output to the D / A converter 50 of ₁ is created.

Referring to FIG. 17, the magenta / cyan density for processing the magenta density data D _M [m] and the cyan density data D _C [c] of the density data of the three primary colors included in each color pixel data. A flowchart of a data processing routine is shown.

In step 1701, the counter i is first initialized to 1. The counter i counts the number of times of sequential processing of the cyan density data D _C [c] and the magenta density data D _M [m] included in each of the n color pixel data for one line. Here, in order to individually distinguish the n pieces of cyan density data, the cyan density data is represented by D _C [c _i ], and in order to individually distinguish the n pieces of magenta density data, The magenta density data will be represented by D _M [m _i ].

At step 1702, it is judged whether or not c _{i of} the cyan density data D _C [c _i ] is not 000. If c
When _i ≠ 000, that is, when the color of at least a cyan dot on sensitive pressure-sensitive heat-coloring layer 14 of the full-color recording medium 10 is performed, the process proceeds to step 1703, where the m _i magenta density data D _M [m _i] 000 If not, it is determined.
If m _i ≠ 000, that is, when cyan dots and magenta dots are formed on the pressure-sensitive and heat-sensitive color forming layer 14 of the full-color recording medium 10 (in short, when blue dots are formed), step 1704 is entered. move on.

In step 1704, the ratio of the magenta density data D _M [m _i ] to the cyan density data D _C [c _i ], that is, D _M [m _i ] / D _C [c _i ] is calculated, and the ratio is calculated. It is determined whether it is equal to 1. If D _M [m _i ] / D _C [c _i ] = 1, that is, the pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10.
When true blue is developed above, step 170
Proceed to 5, where it is 001 set to b _i of the hue data T _B [b _i], then the process proceeds to step 1706, where the most significant bit of the color data T _B [b _i] is 2 bit [01] Load Is
The 10-bit data [[01] T _B [b _i ]] is stored in a predetermined address of the frame memory 44D.

At step 1704, D _M [m _i ] / D _C [c _i ] ≠
When it is 1, the routine proceeds from step 1704 to step 1707, where it is judged whether D _M [m _i ] / D _C [c _i ]> 1. If D _M [m _i ] / D _C [c _i ]> 1, that is, when magenta blue is developed on the pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10, step 170 is performed.
8 where the following operations are performed. b _i ← INT [D _M [m _i ] / D _C [c _i ]] Then, the procedure proceeds to step 1706, where the hue data T
Two bits [01] are added to the most significant bit side of _B [b _i ], and the 10-bit data [[01] T _B [b _i ]] is added to the frame memory 4
It is stored at a predetermined address of 4D.

At step 1707, D _M [m _i ] / D _C [c _i ] <
When it is 1, that is, when cyan-blue is developed on the pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10, the process proceeds from Step 1707 to Step 1709.
Therefore, the following calculation is executed. b _i ← 1 / INT [D _C [c _i ] / D _M [m _i ]] Then, the procedure proceeds to step 1710, where the hue data T
_B [b _i] is Load 2 bits [10] to the most significant bit of the 10-bit data [[10] T _B [b _i]] is a frame memory 4
It is stored at a predetermined address of 4D.

In step 1703, when m _i of the magenta density data D _M [m _i ] is 000, that is, only pure cyan dots are formed on the pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10. At this time, the process proceeds from step 1703 to step 1711, where the hue data T _B [b _i ] b _i
Is set to 1/256, then proceed to step 1710,
Therefore, 2 bits are placed on the most significant bit side of the hue data T _B [b _i ].
[10] is shark, the 10-bit data [[10] T _B [b _i]]
Is stored at a predetermined address in the frame memory 44D.

In step 1702, cyan density data D
When c _i of _C [c _i] is 000, that is, when the color only is made of pure magenta dots on sensitive pressure-sensitive heat-coloring layer 14 of the full-color recording medium 10, the process proceeds from step 1702 to step 1712, where the magenta Density data D _M [m _i ]
2 bits [00] are added to the most significant bit side of
The bit data [[00] D _M [m _i ]] is the frame memory 44D.
Is stored at a predetermined address of.

In any case, when any of the above 10-bit data is created, the process proceeds to step 1713, where the counter i is incremented by 1,
Next, in step 1714, it is determined whether or not the count number of the counter i has reached n. If i ≠
If it is n, the process returns to step 1702, and the processes of steps 1702 to 1714 are repeated until the count number of the counter i reaches n.

When it is confirmed in step 1714 that the count number of the counter i has reached n, step 171
5, all magenta density data D _M [m _i ] and cyan density data D _C [c of color pixel signals for one frame are processed.
_It is determined whether the process for _i ] is completed. If the processing for all magenta density data D _M [m _i ] and cyan density data D _C [c _i ] of the color pixel signal for one frame is not completed, the process returns to step 1701.
Until all the magenta density data D _M [m _i ] and the cyan density data D _C [c _i ] of the color pixel signal for one frame are processed, steps 1702 to 1714 are completed.
The process of is repeated.

Referring to FIG. 18, there is shown a flowchart of a recording operation routine when full color recording is performed on the full color recording medium 10 using the image recording apparatus shown in FIG.

In step 1801, the full-color recording medium is used.
The body 10 is the first thermal head 36 ₁Start recording for
Whether or not the position has been reached is monitored. Full color recording medium
The body 10 is the first thermal head 36₁Start recording for
If it is confirmed that the position has been reached, step 1802
Where the first drive device 46₁Actuating rouch
Command is issued. This operation routine is shown in FIG.
This will be described in detail later with reference to FIG.

In step 1803, the full-color recording medium is
The body 10 is the second thermal head 36. ₂Start recording for
Whether or not the position has been reached is monitored. Full color recording medium
The body 10 is the second thermal head 36.₂Start recording for
If it is confirmed that the position has been reached, step 1804
Where the second drive device 46₂Actuating rouch
Command is issued. The operation routine is shown in FIG.
This will be described later in detail with reference to 0.

At step 1805, it is monitored whether or not the recording operation for all pages has been completed. If the recording operation for all pages has not been completed, the process returns to step 1801 to perform recording on a new full-color recording medium 10. The operation is repeated. When it is confirmed that the recording operation for all pages is completed, this recording operation routine ends.

Referring to FIG. 19, there is shown a flowchart of a first drive device operation routine executed as a subroutine in step 1802 of the recording operation routine of FIG.

In the description of the first drive device operation routine shown in FIG. 19, the magenta / magenta shown in FIG.
10-bit data ([[00] D _M [m _i ]], [[01] T _B [b _i ]], [[10] T _B [b] obtained by the cyan density data processing routine.
_i ]]) is generally denoted by TEN-BIT _i . In addition, the thermistors (TH ₁₁ and T ₁₎ of the A / D converter and the binary counter included in the thermistor drive circuit 48 ₁ of the first drive data 46 ₁ are also included.
Those corresponding to H ₁₂ , TH ₁₃ , ... TH _1n ) are designated by reference numerals 50 _1i and 54 _1i .

At step 1901, the counter i is initialized to 1. The counter i has the same function as that used in the magenta / cyan density data processing routine shown in FIG.

At step 1902, the 10-bit data T
EN-BIT _i is read from the frame memory 44D. Next, in step 1903, the 10-bit data TEN-BIT _i is output to the D / A converter 50 _1i included in the first drive device 46 ₁ , which causes the heat generation temperature of the corresponding thermistor TH _1i. It is determined.

At step 1904, the 10-bit data T
It is determined whether or not the two bits on the most significant bit side of EN-BIT _i are [00]. If 2 bits are [00], that is, the pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10.
Step 1 when only magenta dots are colored on top
In step 905, 8-bit data corresponding to decimal number 256 is output to the binary counter 54 _1i . That is,
The energization time of the thermistor TH _1i is set to the longest energization time (5.10 ms) at which a full size dot is obtained.

In step 1904, 10-bit data TEN is set.
-When the two bits on the most significant bit side of BIT _i are other than [00], the process proceeds from step 1904 to step 1906, where it is determined whether or not the two bits are [01]. If the 2 bits are [01], that is, if magenta blue dots or true blue dots are formed on the pressure-sensitive color forming layer 14 of the full-color recording medium 10, the process proceeds to step 1907, where the binary The magenta density data D _M [m _i ] is output to the counter 54 _1i .
Thus, the energization time of the thermistor TH _1i corresponds to the magenta density data D _M [m _i ].

In step 1906, 10-bit data TEN is set.
-BIT_i2 bits on the most significant bit side of is other than [01]
2 bits, the 2-bit data becomes [10]. That is, full
Cyan is present on the pressure-sensitive and thermosensitive coloring layer 14 of the color recording medium 10.
Blue dots or pure cyan dots are colored
In this case, from step 1906
Proceed to step 1908, where binary counter 54_1i
Cyan density data D _C[c_i] Is output. Thus,
Thermistor TH_1iEnergization time of cyan density data D_C[c
_i] Will be supported.

In any case, when the heat generation temperature and energization time for the thermistor TH _1i are determined, step 19
In step 0910, the counter i is incremented by 1. Then, in step 1910, it is determined whether or not the count number of the counter i reaches n. If i <n, the process returns to step 1902 and n thermistors (T
_{H 11, TH 12, TH 13} , heating temperature and an energization time is determined successively for ... TH _1n).

When it is confirmed in step 1910 that the count number of the counter i has reached n, that is, the heat generation temperature and energization time for all _n thermistors (TH ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n ). Is determined, the process proceeds to step 1911 where all the n thermistor drive circuits 48 ₁ are enabled by the I / O 44E.
(ENABLE) and strobe signal (STB) are monitored. When the outputs of the enable signal (ENABLE) and the strobe signal (STB) are confirmed, the process proceeds to step 1912, where there is 10-bit data TEN-B for one frame.
It is monitored whether the recording based on IT _i is completed. When the recording based on the 10-bit data TEN-BIT _i for one frame is not completed, the process returns to step 1901 and the first thermal head 36 ₁ is operated in the above-described manner.
The recording is repeated line by line. When it is confirmed that the recording based on the 10-bit data TEN-BIT _i for one frame is completed, this routine ends.

Referring to FIG. 20, there is shown a flowchart of a second drive device operation routine executed as a subroutine in step 1804 of the recording operation routine of FIG.

In the description of the first drive device operation routine of FIG. 20, each of the A / D converter and the binary counter included in each thermistor drive circuit 48 ₂ of the second drive data 46 ₂ is described. Thermistor (T
Those corresponding to H ₂₁ , TH ₂₂ , TH ₂₃ , ... TH _2n ) are designated by reference numerals 50 _2i and 54 _2i .

In step 2001, the counter i is initialized to 1. The counter i also has the same function as that used in the magenta / cyan density data processing routine shown in FIG.

In step 2002, the yellow density data D _Y [y _i ] is read from the frame memory 44D.
Next, the routine proceeds to step 2003, where the yellow density data D _Y [y _i ] is output to the D / A converter 50 _2i included in the second drive device 46 ₂ so that the corresponding thermistor TH _2i generates heat. The temperature is determined.

At step 2004, the binary counter 54 _2i included in the second drive device 46 ₂ is set to the decimal number 2
8-bit data corresponding to 56 is output. That is, the energization time of the thermistor TH _2i is set to the longest energization time (5.10 ms) for obtaining a full size dot.

At step 2005, the counter i is incremented by 1, and then at step 2006, it is judged whether or not the count number of the counter i reaches n. If the count number of the counter i has not reached n, the process returns to step 2002 and the n thermistors (T
H ₂₁ , TH ₂₂ , TH ₂₃ , ... TH _2n ) are sequentially determined for the heat generation temperature and the energization time.

When it is confirmed in step 2006 that the count number of the counter i has reached n, that is, the heat generation temperature and the energization time for all n thermistors (TH ₂₁ , TH ₂₂ , TH ₂₃ , ... TH _2n ). Is determined, the process proceeds to step 2007, where the enable signals from the I / O 44E are sent to all the n thermistor drive circuits 48 ₂ .
(ENABLE) and strobe signal (STB) are monitored. When the outputs of the enable signal (ENABLE) and the strobe signal (STB) are confirmed, the process proceeds to step 2008, where the yellow density data D _Y [y for one frame is detected.
_It is monitored whether the recording based on _i ] is completed. When the recording based on the one-frame yellow density data D _Y [y _i ] is not completed, the process returns to step 2001, and the recording by each line by the _second thermal head 36 ₂ is repeated in the manner as described above. . When it is confirmed that the recording based on the yellow density data D _Y [y _i ] for one frame is confirmed, this routine ends.

According to the recording operation as described above, the magenta image, the blue image and the cyan image are formed on the pressure-sensitive thermosensitive coloring layer 14 of the full-color recording medium 10 based on the 10-bit data TEN-BIT _i for one frame. On the other hand, a yellow image is recorded on the thermosensitive coloring layer 16 of the full-color recording medium 10 on the basis of the yellow density data D _Y [y _i ] for one frame. A complete full-color image can be observed from the pressure-sensitive thermosensitive coloring layer 14 of the medium 10.

As described above, the sheet 12 not only functions as a supporting substrate for forming the pressure-sensitive and heat-sensitive color forming layers 14 and 16, but also both color-forming layers 14 and 1 are formed.
Since it also functions as a heat insulating layer for thermally insulating 6, the both coloring layers are not thermally affected by each other.

Needless to say, the yellow image is formed as a mirror image of the magenta image, blue image and cyan image formed on the transparent pressure-sensitive thermosensitive coloring layer 14, whereby the yellow image is formed on the transparent pressure-sensitive thermosensitive coloring layer 14. It is properly aligned with the magenta, blue and cyan images formed therein when viewed from the side.

In addition, in the full-color recording medium 10,
If necessary, the reflection coating layer 18 may be eliminated. In this case, a high refractive index substance such as titanium oxide or silica is added to the thermosensitive coloring layer 16 to increase the whiteness of the thermosensitive coloring layer 16 itself. It can be observed from the transparent pressure-sensitive thermosensitive coloring layer 14 side.

Further, by changing the binder of the thermosensitive coloring layer 16 from PVA to Gabsen ES-901A, the thermosensitive coloring layer 16 is made transparent, and the reflective film layer 18 is removed, so that a full-color image can be observed from both sides through the transmitted light. Can, for example
It can be used for OHP.

Thermosensitive coloring layer 1 from full color recording medium 10
6 may be eliminated to form a multicolor recording medium, and in this case, the sheet 12 does not necessarily have to be a transparent body. Further, in this case, since the pressure-sensitive and heat-sensitive coloring layer 14 does not need to be a transparent layer, as a coloring material in the microcapsule 20, its wall film is colored in the same color as the sheet 12 (usually white). It is possible to use a dye other than the leuco dye under the condition.

In the above-mentioned embodiment, the energy gradation method is adopted to give the gradation expression to the color development of the magenta dot, but the gradation expression is given to the color development of the magenta dot by the dot gradation method. It is also possible. That is, when the magenta dot is colored, the heat generation temperature of the corresponding thermistor (TH ₁₁ , TH ₁₂ , TH ₁₃ , ... TH _1n )
By setting 120 ° C with 10-bit data [[00] D _M [255]] and setting the heat generation time according to magenta density data D _M [m], the dot gradation method is used for the color development of magenta dots. It is possible to give gradation expression.

Similarly, it is also possible to give a gradation expression by the dot gradation method to the color development of yellow dots. In this case, when the yellow dot is colored, the corresponding thermistor (TH ₂₁ , TH ₂₂ , TH ₂₃ , ... T)
The heat generation temperature of H _2n ) is set to 190 ° C. by the yellow density data D _Y [255], and the heat generation time is set according to the yellow density data D _Y [y].

[0163]

As is clear from the above description, according to the present invention, in the multicolor pressure-sensitive thermal recording medium as described above, the density of each colored dot obtained by the thermal head is changed. Provided is a novel gradation control technique capable of giving gradation expression to characters and images.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view schematically showing a part of a full-color recording medium capable of providing gradation expression by a gradation control device according to the present invention.

FIG. 2 is a schematic sectional view showing an example of an image recording apparatus for recording a full-color image on the full-color recording medium shown in FIG.

FIG. 3 is a control block diagram of first and second thermal heads included in the image recording apparatus of FIG.

4 is a schematic cross-sectional view schematically showing a state in which colored dots of a predetermined color are formed on the pressure-sensitive thermosensitive coloring layer of the full-color recording medium of FIG. 1 using the first thermal head of the recording apparatus shown in FIG. Is.

5 is a graph showing pressure-temperature color development characteristics of the pressure-sensitive heat-sensitive color development layer of the full-color recording medium shown in FIG.

FIG. 6 is a graph showing changes in color density of magenta and cyan when magenta and cyan are colored in the pressure-sensitive and thermosensitive coloring layers of the full-color recording medium according to the pressure-temperature coloring characteristics shown in FIG.

FIG. 7 is a graph showing a change in color density of yellow when yellow is developed in the thermosensitive coloring layer of the full-color recording medium.

FIG. 8 is a graph showing a relationship between hue data and temperature in a magenta blue coloring area in which the magenta coloring area and the cyan coloring area shown in FIG. 6 overlap each other.

9 is a graph showing a relationship between hue data and temperature in a cyan-colored blue coloring area in which the magenta coloring area and the cyan coloring area shown in FIG. 6 overlap each other.

FIG. 10 is a graph showing an example of heat generation temperature control when giving a gradation expression to a colored dot by an energy gradation method while keeping the heat generation time of each heat generation element of the thermal head constant.

FIG. 11 is a schematic diagram for explaining gradation expression by an energy gradation method.

FIG. 12 is a graph showing an example of heat generation time control when a gradation expression is given to a colored dot by a dot gradation method with a constant heat generation temperature of each heat generation element of the thermal head.

FIG. 13 is a schematic diagram for explaining gradation expression by a dot gradation method.

FIG. 14 is a block diagram similar to the block diagram shown in FIG. 3, showing the printer controller in detail.

FIG. 15 is a thermistor drive circuit diagram forming a part of the first drive device shown in FIG.

16 is a thermistor drive circuit diagram forming a part of the second drive device shown in FIG. 14. FIG.

FIG. 17 is a flowchart of a magenta / cyan density data processing routine executed by the printer controller.

FIG. 18 is a flowchart of a recording operation routine executed by the printer controller.

FIG. 19 is a flowchart of a first drive device operation routine executed as a subroutine during execution of the recording operation routine of FIG.

20 is a flowchart of a second drive device operation routine executed as a subroutine during execution of the recording operation routine of FIG.

[Explanation of symbols]

10 Full Color Recording Medium 12 Support (Sheet) 14 Pressure-Sensitive Coloring Layer 16 Thermosensitive Coloring Layer 18 Reflective Coating Layer 20 Pressure-sensitive Microcapsule 22 Housing 28 Moving Path 30 Guide Plate 34 ₁ First Platen Roller 34 ₂ Second Platen Roller 36 ₁ First thermal head 36 ₂ Second thermal head 38 ₁ First pressure spring applying means 38 ₂ Second pressure spring applying means 40 Control circuit board 42 Power supply device 44 Printer controller 46 ₁ First driving device 46 ₂ Second Driving Device 48 ₁ Thermistor Driving Circuit of _First Driving Device 46 ₁ 48 ₂ Thermistor Driving Circuit of Second Driving Device 46 ₂ Digital / Analog (D / A) Converter 52 Operational Amplifier T _r Transistor R ₁ · R ₂ · R ₃ resistor 54 binary counter 56 flip-flop 58 open collector gate 60 Converter TH _11, ... TH _1n the first thermal head 36 ₁ of the thermistor TH _21, ... TH _2n second thermal head 36 ₂ of the thermistor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B41M 5/34 B41J 3/20 117C F term (reference) 2C065 AA01 AB01 AC02 AF01 DC03 DC04 DC24 2C066 AB09 AC01 AD03 CD01 CD04 CD06 CD10 CD11 CD14 CD17 CD19 CD23 2H026 AA07 AA15 AA30 BB01 EE05 FF05 FF07 FF24 GG10 2H085 AA07 AA11 AA13 AA20 BB01 CD04 EE05 FE14

Claims (10)

[Claims] 1. A multicolor recording medium comprising a support and a pressure-sensitive thermosensitive coloring layer formed on one surface of the support, wherein the pressure-sensitive thermosensitive coloring layer comprises a thermosensitive coloring component and a predetermined color. The present invention includes a number of pressure-sensitive microcapsules which are filled with a coloring material and uniformly distributed, and the pressure-sensitive microcapsules are destroyed under a predetermined pressure and within a first temperature range to obtain a first color. A pressure-temperature color-developing characteristic that allows color development is given, and the thermosensitive color-developing component has a first temperature included in the first temperature range and a second temperature exceeding an upper limit temperature of the first temperature range. Between the first color and the second color different from the first color within a second temperature range between
Of the first color and the second color defined between the temperature of the first color temperature range and the upper limit temperature of the first temperature range. A heating element applied to the pressure-sensitive thermosensitive coloring layer under the predetermined pressure, first coloring density data controlling the coloring density of the first color, and coloring density of the second color. Controlling means for calculating a color density ratio with the second color density data, heat generation temperature control means for heating the heat generating element to a temperature within the color mixture temperature region corresponding to the color density ratio, The heat generation time of the heating element is controlled according to the color density of one of the first color density data and the second color density data to change the color density to a mixed color of the first color and the second color. And a heat generation time control means for providing the gradation control device. 2. The gradation control device according to claim 1, wherein when the first color density data and the second color density data are equal to each other, the heat generation time of the heat generating element by the heat generation time control means is set. The gradation control device is characterized in that it is performed according to one of the first color density data and the second color density data. 3. The gradation control device according to claim 1, wherein when the second color-developing density data is non-color-developing density data, the first color-developing density data indicates a magnitude of the color-developing density. Accordingly, the heat generation temperature control means is assigned to a temperature within the temperature range that is equal to or higher than the lower limit temperature within the first temperature range and is equal to or lower than the first temperature, and the heat generation temperature of the heat generating element is the assigned temperature. The gradation control device is characterized by being controlled by the heat generation time control means so that the heat generation time of the heat generating element becomes the maximum heat generation time. 4. The gradation control device according to claim 3, wherein the maximum heat generation time of the heating element is a time for which a full-sized colored dot is obtained by the heating element. . 5. The gradation control device according to claim 1, wherein when the second color-developing density data is non-color-developing density data, the heating temperature of the heating element becomes the first temperature. And a heat generation time of the heat generating element is controlled by the heat generation time control means according to the first color density data. 6. The gradation control device according to claim 1, wherein when the first color-developing density data is non-color-developing density data, the heating temperature of the heating element is the first The heat generation temperature control means controls the temperature so that the temperature is within the second temperature range above the upper limit temperature of the first temperature range, and the heat generation time of the heat generating element is the second time.
The gradation control device is controlled by the heat generation time control means in accordance with the color density data. 7. The gradation control device according to claim 1, wherein the support of the multicolor recording medium is formed of a transparent material, and the pressure-sensitive thermosensitive coloring layer is a transparent layer. And a thermosensitive coloring layer is formed on the other surface of the support, and the thermosensitive coloring layer has a third temperature range independent of the first and second temperature ranges of the pressure-sensitive thermosensitive coloring layer. A third color development density data for controlling the color development density of the third color is provided, which is provided with a temperature color development characteristic that develops a third color different from the first and second colors. The heating element for the thermosensitive coloring layer applied to the thermosensitive coloring layer, and the heat generation time of the heating element for the thermosensitive coloring layer. Heat generation time control hand for the thermosensitive color developing layer that controls the maximum heat generation time And,
A gradation control device comprising: a heat-sensitive color-developing layer heat-generating temperature control means for controlling the heat-generating temperature of the heat-sensitive color-developing layer heating element to be an assigned temperature within the third temperature range. . 8. The gradation control device according to claim 7, wherein the maximum heat generation time of the heat-sensitive color-developing layer heating element is a time when a full-size color-developed dot is obtained by the heat-sensitive color-developing layer heat-generating element. A gradation control device characterized by: 9. The gradation control device according to claim 1, wherein the support of the multicolor recording medium is formed of a transparent material, and the pressure-sensitive thermosensitive coloring layer is a transparent layer. And a thermosensitive coloring layer is formed on the other surface of the support, and the thermosensitive coloring layer has a third temperature range independent of the first and second temperature ranges of the pressure-sensitive thermosensitive coloring layer. A thermosensitive coloring layer heating element applied to the thermosensitive coloring layer, which is provided with a temperature coloring characteristic that a third color different from the first and second colors is developed; Heat-sensitive color-forming layer heat-generating temperature control means for controlling the heat-generating temperature of the heat-sensitive color-forming layer heating element to be the upper limit temperature of the third temperature range; and third color-forming for controlling the color density of the third color. The heating time of the heating element for the thermosensitive color developing layer is controlled according to the density data. And a heat generation time control means for the heat-sensitive color forming layer. 10. The gradation control device according to claim 7, wherein the first, second and third gradation control devices are provided.
The gradation control device is characterized in that the above colors are three primary colors based on subtractive color mixing.