JP2003001950A - Multicolor recording medium using pressure sensitive microcapsule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicolor recording medium capable of guaranteeing color developing of a desired tinge for at least one color of basic colors. SOLUTION: The multicolor recording medium 10 comprises a support 12 and a color developing layer 14 coating on a surface of the support 12. The developing layer is formed to uniformly distribute many pressure sensitive microcapsules 16, and many heat sensitive and pressure sensitive microcapsules 18 in a binder layer. Temperature characteristics for heat melting at a predetermined temperature is imparted to the binder layer. The microcapsule seals a first color material, and pressure breaking characteristics for breaking the microcapsule at a first pressure or more are imparted to the microcapsule. The heat sensitive microcapsule seals a second color material, and pressure breaking characteristics for breaking the microcapsule at a second pressure or more higher than the first pressure are imparted to the heat sensitive microcapsule.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-color recording medium configured to develop at least two colors.

[0002]

2. Description of the Related Art As a multi-color recording medium as described above, a color-adding type multi-color thermal paper capable of developing two or more colors is already known. For example, in the case of developing two colors with such a color-added thermosensitive 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, the first
(Leuco dye and second leuco dye) and a developer are uniformly distributed, and the thermosensitive coloring layer has a multi-layer structure (two-layer structure).
When, the leuco dye and the color developer of one kind are uniformly distributed in each layer. The color developer is appropriately selected so that the color development temperature of the first leuco dye is lower than the color development temperature of the second leuco dye, and if necessary, thermosensitive color development is performed to adjust the color development temperature of these leuco dyes. A sensitizer is appropriately added to the 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 heat-sensitive color-developing layer, the first leuco dye develops a first color and the heat-sensitive color-developing layer exhibits the heat of the second leuco dye. When the 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 only the first leuco dye and color mixing by both 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. .

Further, in the conventional additive type multi-color thermosensitive recording medium, the coloring temperature of the low temperature side leuco dye (that is, the magenta coloring leuco dye in the above example) of the first and second leuco dyes. Is set to at least 100 ° C or higher. This is because the multi-color thermosensitive recording medium can often be exposed to a temperature of around 100 ° C. under ordinary conditions. That is, if the color development temperature of the low temperature side leuco dye is set to, for example, 80 ° C., the multi-color thermal recording medium is inadvertently exposed to a temperature of 80 ° C. or higher, and erroneous color development such as background stain occurs. Because it will be. On the other hand, when the color development temperature of the low temperature side leuco dye is set to at least 100 ° C., the color development temperature of the high temperature side leuco dye (that is, the cyan color development leuco dye in the above example) is the color development temperature of the low temperature side leuco dye. (at least
It is necessary to set the temperature sufficiently higher than 100 ° C. This is because if the temperature difference between the color development temperature of the low temperature side leuco dye and the color development temperature of the high temperature side leuco dye is not sufficiently separated, the high temperature side leuco dye develops at a low concentration when the low temperature side leuco dye develops color. This is because a phenomenon called "fog" may occur. As a result, the overall required printing energy for conventional multi-color thermal recording media is significantly high.

[0006] JP 08-282115 A and JP 09-7663
No. 4, in the additive multicolor thermal recording medium as described above, fog is caused even if the temperature difference between the color forming temperature of the low temperature side leuco dye and the color forming temperature of the high temperature side leuco dye is relatively close. It is disclosed that a leuco dye on the high temperature side is encapsulated in a heat-sensitive microcapsule in order to prevent the occurrence of That is, when the heat-sensitive microcapsules are heat-melted at a predetermined temperature (coloring temperature of the high-temperature side leuco dye), the high-temperature side leuco dye flows out to cause a color-forming reaction with the color developing agent. Until the heat melting, the color development of the high temperature side leuco dye is completely prevented,
Fog is prevented from occurring when the low temperature side leuco dye is developed.

[0007]

It has been pointed out that, as a problem of the additive type multi-color thermosensitive recording medium described above, a desired color may not be obtained in some cases. For example, various types of magenta colors are known, but the magenta colors are limited to those obtained with leuco dyes, and when considering combinations with other colors of leuco dyes. In consideration of the color development temperature condition, the selection range of magenta colors can be further narrowed. There is a demand among users of multi-color thermosensitive recording media to obtain a desired color tone for at least one color, but the desired color tone cannot be obtained by only one type of leuco dye. As long as it is not possible to meet the demands of such users. On the other hand, even if a magenta-type leuco dye is appropriately mixed to obtain a magenta color having a desired hue, the mixed leuco dye does not always obtain a desired coloring temperature. Furthermore,
When trying to obtain three or more colors, it is almost impossible to obtain a desired tint for a certain color because the selection range of the leuco dye is further narrowed.

Therefore, it is an object of the present invention to provide a multi-color recording medium constructed so as to guarantee a desired hue of at least one of the basic colors.

On the other hand, another problem is that the total required printing energy for the conventional additive type multi-color thermosensitive recording medium is large. JP 08-282115 A and JP 09-7663
In the additive type multi-color thermal recording medium as disclosed in Japanese Patent Publication No. 4, even if the coloring temperature of the high temperature side leuco dye can be set to a relatively low temperature side, the false coloration of the low temperature side leuco dye such as background stain In order to prevent this, it is necessary to set the color development temperature to a high temperature of at least 100 ° C. or higher.

Therefore, another object of the present invention is a multi-color recording medium of the type described above, in which, even if the color-forming temperature of one of the basic colors is set to 100 ° C. or less, the background stain and the like will not occur. An object of the present invention is to provide a multi-color recording medium capable of preventing erroneous color development.

[0011]

A multicolor recording medium according to the present invention comprises a support and a color-developing layer coated on the surface of the support. The coloring layer is formed by uniformly distributing a large number of pressure-sensitive microcapsules and a large number of heat-sensitive pressure-sensitive microcapsules in the binder layer, and the binder layer is provided with a temperature characteristic of being melted by heat at the first temperature. To be
The pressure-sensitive microcapsules are encapsulated with the first coloring material, and are given a pressure rupture characteristic such that they are destroyed under the first pressure, and the thermosensitive microcapsules are encapsulated with the second coloring material. In addition, the temperature-pressure rupture characteristic is provided so that the rupture occurs at the second temperature higher than the first temperature and under the second pressure higher than the first pressure.

Each of the first and second coloring materials can be prepared as a coloring material based on a leuco dye, in which case the binder layer is formed as a developer layer of the leuco dye. It Preferably, the first temperature is set to at most 100 ° C. Also preferably, the heat and pressure sensitive microcapsules are coated with a wax material adapted to be heat melted at a second temperature.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of a multi-color recording medium according to the present invention will be described with reference to the accompanying drawings.

Referring first to FIG. 1, one embodiment of a multi-color recording medium according to the present invention is indicated generally by the reference numeral 10, which multi-color recording medium 10 comprises a suitable support, such as a sheet of paper 12, The color forming layer 14 is applied to one surface of the sheet paper 12. In this embodiment, the color-developing layer 14 is the pressure-sensitive microcapsule 1 in the developer layer.
6 and the heat-sensitive pressure-sensitive microcapsules 18 are evenly distributed. The developer layer comprises a developer component for the leuco dye, which developer component is conveniently indicated by the symbol "x" in FIG. As the developer component “x”, K-5 manufactured by Asahi Denka Kogyo Co., Ltd. is used, and this K-5 is a white powder having a thermal melting temperature of about 145 ° C.

The pressure-sensitive microcapsule 16 contains, for example, a magenta coloring material, and this magenta coloring material comprises a magenta dye dissolved or dispersed in a suitable vehicle. For the vehicle, use a suitable transparent oil that is liquid at room temperature or a suitable low melting point wax (melting point 90 ° C or less)
Can be used. As the magenta dye, any magenta dye can be appropriately selected. In this embodiment, the vehicle is RKS (Rutgers Kureha Sol).
A transparent oil available as KMC-113 (2,7 diisopropylnaphthalene) from Vents Gmbh) is used, and as the magenta dye, a leuco dye for magenta coloring, for example, Red-3 manufactured by Yamamoto Kasei Co. is used. . In FIG. 1, the magenta coloring material enclosed in the first pressure-sensitive microcapsule 16 is indicated by “MA” representing magenta.

The heat-sensitive and pressure-sensitive microcapsules 18 are filled with, for example, a black color material, and this black color material is also composed of a suitable vehicle in which a black dye is dissolved or dispersed. Similar to the case of the first pressure-sensitive magenta capsule 16, the vehicle is a suitable transparent oil or a low melting point wax (melting point 90 ° C or lower) which is liquid at room temperature.
May be used, and as the black dye, any black dye can be appropriately selected. In the present embodiment, the above-mentioned KMC-113 is used as the vehicle, and the black coloring leuco dye such as ODB manufactured by Yamamoto Kasei is used as the black dye. In addition, in FIG. 1, the black color material enclosed in the second pressure-sensitive microcapsule 18 is shown by “BK” representing black.

The pressure-sensitive microcapsules 16 can be manufactured by a well-known microcapsule manufacturing method such as an in situ polymerization method, and the average particle size thereof is about 5 μm. Pressure-sensitive microcapsule 16
The thickness of the wall film is such that the pressure-sensitive microcapsules 16 can be broken under a pressure of 0.2 MPa or more accompanied by shearing force. That is, the pressure-sensitive microcapsule 16 is provided with a pressure rupture characteristic which enables it to be ruptured under a pressure of 0.2 MPa or more accompanied by shearing force.

The pressure-sensitive microcapsules 16 which can be broken under a pressure of 0.2 MPa or more accompanied by shearing force are as follows.
An example for manufacturing (average particle size of about 5 μm) will be 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 aqueous solution Partial sodium salt of polyvinylbenzenesulfonic acid… 5g Purified water… 95g (C) Melamine- Formalin prepolymer aqueous solution Melamine… 11.2g Formalin… 28.8g Purified water… 40g (Formalin is 2% sodium hydroxide solution
37% formaldehyde prepared in H9 is used. (28.8 g of this formalin and 11.2 g of melamine were mixed and heated to 70 ° C., and after the melamine was dissolved, 40 g of purified water was added and stirred to obtain (C) melamine-formalin prepolymer aqueous solution)

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 4.5 μm.

3) Next, the (C) melamine-formalin prepolymer aqueous solution was added to and mixed with the above emulsified dispersion liquid, and the mixed liquid was slowly stirred while maintaining the temperature at 30 ° C. to 20%.
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 first pressure-sensitive microcapsules 16 having an average particle size of about 5 μm.

The thickness of the wall film of the pressure-sensitive microcapsule 16 thus obtained is such that it can be broken under a pressure of 0.2 MPa or more accompanied by shearing force. The thickness of the wall film of the pressure-sensitive microcapsule 16 mainly depends on the amount of melamine in the melamine-formalin prepolymer aqueous solution. The larger the amount, the thicker the film thickness becomes. The pressure resistance increases.

As shown in detail in FIG. 2, each heat-sensitive pressure-sensitive microcapsule 18 has a double-walled structure, its outer wall film 18 ₁ is made of a suitable wax material, and its outer wall film 18 ₂ is melamine. Formed from resin. Outer wall film 1
8 The _first wax material, is used Mitsui Hi-wax 405MP Mitsui Chemicals, Inc., the heat melting temperature is about 125 ° C..

In order to produce such a heat-sensitive microcapsule having a double-wall structure, first, a pressure-sensitive microcapsule 18 'as shown in FIG. 3 is manufactured, and the pressure-sensitive microcapsule 18' is heat-sensitive. It corresponds to the pressure-sensitive microcapsule 18 from which the outer wall film 18 ₁ is removed. The average particle size of the pressure-sensitive microcapsules 18 'is 5 μm as in the case of the pressure-sensitive microcapsules 16 described above, but the wall membrane of the pressure-sensitive microcapsules 18' is 2.8 MPa or more accompanied by shearing force. Shall be capable of being destroyed under the pressure of.

The pressure-sensitive microcapsules 18 'can be manufactured by the same process as that of the pressure-sensitive microcapsules 16 described above. That is, instead of the above (A) magenta coloring material solution, a black coloring agent solution prepared by dissolving 4 g of ODB in 100 g of KMC-113 was used, and the amount of melamine in the melamine-formalin prepolymer aqueous solution was 11.2 g. Pressure-sensitive microcapsules 18 'by increasing to 21g
(FIG. 3) will be manufactured. In short, melamine
-The amount of melamine in the formalin prepolymer aqueous solution is 11.
Since it is increased from 2 g to 21 g, the film thickness of the second pressure-sensitive microcapsule 18 is formed to be thicker than that of the pressure-sensitive microcapsule 16, whereby the pressure-sensitive microcapsule 18 ′ is destroyed by a pressure of 2.8 MPa or more. That is, the pressure-sensitive characteristic is given. In addition, as the amount of melamine increased, melamine
-The amount of formalin and purified water of the formalin prepolymer aqueous solution is increased to 54 g and 75 g, respectively.

By appropriately coating the pressure-sensitive microcapsules 18 'with Mitsui High Wax 405MP to form the outer wall film 18 ₁ , the heat-sensitive pressure-sensitive microcapsules 18 as shown in FIG. 2 can be obtained. The puncture-resistant pressure of the heat-sensitive pressure-sensitive microcapsules 18 is greatly increased as compared with the rupture-resistant pressure of 2.8 MPa of the pressure-sensitive microcapsules 18 ′ due to the outer wall film 18 ₁ , but the heat-sensitive pressure-sensitive microcapsules 18 are melted by heat. When exposed to a temperature of 125 ° C. or higher, the outer wall film 18 ₁ is melted by heat, so that its puncture resistance pressure is
It will be 2.8 MPa. Thus, heat-sensitive pressure-sensitive microcapsules 1
8 is under the precondition that it is heated to a temperature of 125 ° C or higher.
It has a heat and pressure sensitive property that it is destroyed at a pressure of 2.8 MPa or more. In short, the heat-sensitive characteristics of the heat-sensitive pressure-sensitive microcapsules 18 are obtained from the outer wall film 18 ₁ formed of Mitsui High Wax 405MP, and the pressure-sensitive characteristics are obtained from the inner wall film 18 ₂ formed of melamine resin.

For forming the color forming layer 14, a composition liquid having the composition shown in the following table is prepared. Composition Weight part (1) 25W% microcapsule (16) aqueous dispersion 1.0 (2) 25W% microcapsule (18) aqueous dispersion 1.0 (3) 20W% K-5 aqueous dispersion 1.0 ( 4) 17W% acetoacetanilide aqueous dispersion ... 0.5 (5) 20W% silica aqueous dispersion ... 0.5 (6) 20W% PVA (polymerization degree 200) aqueous solution ... 0.5 where composition (1) is purified water Pressure-sensitive microcapsule 16
25% by weight is added to disperse (suspend). Composition (2) is heat-sensitive pressure-sensitive microcapsules 18 in purified water.
25% by weight is added to disperse (suspend). Composition (3) is prepared by adding 20% by weight of K-5 (developing agent) to purified water and dispersing (suspending) it. The composition (4) is prepared by adding 17% by weight of acetoacetanilide (sensitizer) to purified water and dispersing (suspending) it, and the sensitizer is a powder having an average particle diameter of 1 μm or less. Composition (5) is 20% by weight of silica (filler) in purified water and dispersed (suspended).
It was made. Composition (6) is prepared by adding 20% by weight of PVA (polyvinyl alcohol) to purified water and dissolving it.

The above-mentioned composition liquid is applied onto the sheet paper 12 in an amount of about 4 to 6 grams per square meter and dried to obtain the multicolor recording medium 10 having the color forming layer 14 as shown in FIG. To be Since such color forming layer 14 contains acetoacetanilide as a sensitizer, the thermal melting temperature of the color developer (K-5) is about 145 ° C to about 90 ° C due to the eutectic action with the sensitizer. Can be lowered to.

Incidentally, polyvinyl alcohol (PVA) functions as a binder, and has the function of fixing the compositions (1) to (5) to each other for integration and fixing the color forming layer 14 to the sheet paper 12. In other words, the developer layer composed of the compositions (3) to (6) functions as a binder layer for holding the pressure-sensitive microcapsules 16 and the heat-sensitive pressure-sensitive microcapsules 18 on the sheet paper 12.

Referring to FIG. 4, the color development characteristics of the multi-color recording medium 10 constructed as described above are shown in the form of a graph. In the graph, a curve PC1 shows the pressure rupture characteristic of the pressure-sensitive microcapsule 16, and a curve P
C2 represents the pressure rupture characteristic of the heat-sensitive pressure-sensitive microcapsule 18. As is apparent from FIG. 4, the magenta coloring area MA and the black coloring area BK are defined by the pressure breakdown characteristic curves PC1 and PC2 and the pressure and temperature to be applied to the coloring layer 14.

That is, the color forming layer 14 is heated to a heat melting temperature of about 90 ° C. or more of the developer component (K-5), and the color forming layer 14 is also heated.
When a breaking pressure of 0.2 MPa or more is applied to the pressure sensitive microcapsules 16, only the pressure sensitive microcapsules 16 are broken, and at this time, the magenta coloring material is released, and the magenta coloring leuco dye component reacts with the heat-melting developer to generate magenta. The color-developing layer 14 is heated to a temperature at which the outer wall film 18 ₁ of the pressure-sensitive microcapsule 18 has a heat melting temperature of 125 ° C. or higher.
When a pressure of 2.8 MPa or more is applied to 8, the heat-sensitive pressure-sensitive microcapsules 18 are destroyed, and at this time, the black coloring material is released, and the black coloring leuco dye component reacts with the heat-melting color developer to develop a color. Color black. When the heat-sensitive pressure-sensitive microcapsules 18 are destroyed, the pressure-sensitive microcapsules 16 are also destroyed and cyan is colored, but the cyan is absorbed by black.

Referring to FIG. 5, a recording device for recording an image on the multi-color recording medium 10 is schematically shown, and the recording device is configured as a thermal line printer.

As shown in FIG. 5, the recording apparatus includes a housing 20 having a substantially rectangular shape, and an inlet 22 for introducing the multi-color recording medium 10 is formed on the upper side wall of the housing 20. . A discharge port 24 for discharging the multi-color recording medium 10 is formed on one of the side walls of the housing 20. FIG. 3 shows a multi-color recording medium 10
The moving path of the multicolor recording medium 10 is introduced into the introduction port 22 during image recording, is moved along the moving path 26, and is then ejected from the ejection port 24.

A thermal head support 28 is provided at a predetermined position in the housing 20, and the thermal head support 28 defines a part of the moving path 26. A first thermal head 30 ₁ and a second thermal head 30 ₂ are sequentially mounted on the thermal head support 28 from the inlet 22 to the outlet 24, and each thermal head follows the movement path of the multi-color recording medium 10. A large number of electric resistance elements, that is, heating elements, are arranged in a straight line extending in the transverse direction and along the extending direction. In this embodiment,
The first thermal head 30 ₁ is used to obtain magenta dots, and the second thermal head 30 ₂ is used to obtain black dots. Each of the first and second thermal heads 30 ₁ and 30 ₂ includes the same number of heating elements (n).

Referring to FIG. 6, some of the n heating elements included in the first thermal head 30 ₁ are designated by reference numerals R ₁₁ , R ₁₂ and R ₁₃ , and the second thermal head 3 is shown.
A part of the n heating elements included in 0 ₂ is a reference numeral R ₂₁ ,
It is represented by R ₂₂ and R ₂₃ . As is clear from FIG. 6, n
The heat generating elements R ₁₁ , R ₁₂ , R ₁₃ , ... R _1n and the n heat generating elements R ₂₁ , R ₂₂ , R ₂₃ , ... R _2n are arranged in a matrix of 2 × n, and both n elements are arranged. Heating elements (R ₁₁ , R ₁₂ , R
_{13, ... R 1n: R 21} , R 22, R 23, ... R 2n) is aligned with one another along the moving direction of the multi-color recording medium 10, respectively.

The first of the n heating elements R ₁₁ of the thermal head _{30 1, R 12, R 13} , ... R 1n is connected to the first thermal head drive circuit 32 _1, the first thermal head drive circuit 32 ₁ , n heating elements R ₁₁ , R ₁₂ , R
_13, ... R _1n is made to generate heat allowed to selectively energized in accordance with n pieces of pixel data for one line. That is, the heating elements (R ₁₁ , R ₁₂ , R ₁₃ , ... R _1n ) corresponding to the magenta pixel data of the n pixel data have the temperature T _{1 of} 90 ° C. or more of the melting temperature of the developer component “×”. Heat is generated up to (for example, 100 ° C).

Similarly, the n of the second thermal head 30 ₂ is
The heating elements R ₂₁ , R ₂₂ , R ₂₃ , ... R _2n are connected to the _second thermal head drive circuit 32 _2, and the second thermal head drive circuit 32 ₂ causes n heating elements R ₂₁ ,
_{R 22, R 23, ... R} 2n is exothermic and allowed to selectively energized in accordance with n pieces of pixel data for one line. That is, the heating elements (R ₂₁ , R ₂₂ , R ₂₃ , ... R _2n ) corresponding to the black pixel data among the n pixel data are the heat melting temperature 125 of the outer wall film 18 ₁ of the pressure-sensitive microcapsule 18. Heat is generated up to a temperature T ₂ (for example, 150 ° C.) which is equal to or higher than ° C.

Referring again to FIG. 5, the first roller platen 34 ₁ is applied to the first thermal head 30 ₁ .
A first pressure applying spring means 36 ₁ is combined with the first roller platen 34 ₁ . The first pressure applying spring means 36 ₁ is configured to exert a pressure P ₁ (for example, 0.3 MPa) sufficiently exceeding the critical breaking pressure 0.2 MPa of the pressure-sensitive microcapsules 16 on the _first roller platen 34 ₁ . As a result, the first roller platen 34 ₁ is pressed against the first thermal head 30 ₂ with a pressure of 0.3 MPa.

Similarly, a second roller platen 34 ₂ is applied to the second thermal head 30 _2, and a second pressure applying spring means 36 ₂ is combined with the second roller platen 34 ₂ . The second pressure applying spring means 36 ₂ is the second
The roller platen 34 _{2 is} subjected to a pressure P ₂ (for example, 3.0 MPa) sufficiently exceeding the critical breaking pressure of 2.8 MPa when the outer wall film 18 ₁ is removed from the heat-sensitive pressure-sensitive microcapsules 18. As a result, the second roller platen 34 ₂ is pressed against the second thermal head 30 ₂ with a pressure of 3.0 MPa.

When a color image is recorded on the color forming layer 14 of the multi-color recording medium 10, each of the heating elements described above has a size and shape corresponding to a pixel unit (that is, a dot) of the color image. That is, as will be described later, a dot as a pixel unit is generated on the coloring layer 14 by the heat generation of each heating element, but in the present embodiment, the dot size is about 50 μm to 100 μm. It is given to each heating element.

In FIG. 3, reference numeral 37 indicates the first.
And a control circuit board for controlling the operation of the first and second drive circuits 32 ₁ and 32 ₂ for driving the second thermal heads 30 ₁ and 30 ₂ , respectively, and reference numeral 3
Reference numeral 8 denotes a power supply device, and the power supply device 38 supplies power to the respective heating elements of the first and second thermal heads 30 ₁ and 30 ₂ and the control circuit board 37.

At the time of image recording, the multi-color recording medium 10 is introduced into the introduction port 22. At this time, regarding the orientation of the multi-color recording medium 10, the color forming layer 14 side is the first and second thermal heads 30 ₁ and 30. _{The two} heating elements (R ₁₁ , ... R _1n ; R ₂₁ , ... R _2n ) are brought into contact with each other.

Next, a color forming process for recording a color image on the color forming layer 14 of the multi-color recording medium 10 using the above-described recording apparatus will be described.

When the multi-color recording medium 10 is passed between the first thermal head 30 ₁ and the first roller platen 34 ₁ , the coloring layer 14 of the multi-color recording medium 10 has the first pressure applying spring means. The heating elements R ₁₁ , R ₁₂ , R ₁₃ , ... R of the first thermal head 30 ₁ for 36 ₁ .
_Although it will receive a pressure of 0.3 MPa with shearing force from _1n ,
When each heating element is not energized, that is, when each heating element is at room temperature, the pressure is 0.3 MPa because the developer component “x” in the color forming layer 14 has a solid phase. And the second pressure-sensitive microcapsules 16 and 18 are not directly affected.

However, any _one of the heating elements R ₁₁ , R ₁₂ , R ₁₃ , ... R _1n of the first thermal head 30 ₁ is energized based on the magenta pixel data of the n pixel data for one line. Then, the energization heating element (R ₁₁ , ...
R _1n ) is heated to at least 100 ° C. When a temperature of 100 ° C. is applied to the coloring layer 14 by the heating elements (R ₁₁ , ... R _1n ), the developer component “x” is melted due to the eutectic action with the sensitizer (acetoacetanilide). Therefore, the heating elements (R ₁₁ , ... R _1n ) penetrate into the coloring layer 14 as shown in FIG. 7, and the pressure-sensitive microcapsules 16 and the heat-sensitive pressure-sensitive microcapsules 18 are destroyed by a shear force of 0.3 MPa. It will exert pressure. At this time, the pressure-sensitive microcapsules 16 are destroyed, but the heat-sensitive pressure-sensitive microcapsules 18 endure a breaking pressure of 0.3 MPa. Thus, only the pressure-sensitive microcapsules 16 are destroyed, the magenta coloring material is released from the destroyed microcapsules, and the magenta coloring leuco dye component (Red-3) reacts with the developer component “x” to develop the coloring reaction. Then, magenta dots are colored on the coloring layer 14.

Next, when the multicolor recording medium 10 is passed between the second thermal head 30 ₂ and the second roller platen 34 ₂ , the color forming layer 14 of the multicolor recording medium 10 is exposed to the second pressure. The heating elements R ₂₁ , R ₂₂ , of the second thermal head 30 ₂ for the application spring means 36 ₂ .
A pressure of 3.0 MPa is received from R ₂₃ , ... R _2n .

The heating element R of the _second thermal head 30 _2.
When any one of ₂₁ , R ₂₂ , R ₂₃ , ... R _2n is energized based on the black pixel data among the n pixel data for one line, the energization heating element (R ₂₁ , ... R _2n ) Is heated to at least 150 ° C. Heating element (R ₂₁ , ...
When a temperature of 150 ° C. is applied to the color forming layer 14 by R _2n ), the developer component “x” is melted due to the eutectic action with the sensitizer (acetoacetanilide), and therefore the heating element (R ₂₁ , ... R _2n ) penetrates into the coloring layer 14 as in the case described above (FIG. 7), and the pressure-sensitive microcapsules 1
6 and the heat-sensitive pressure-sensitive microcapsules 18 are accompanied by shearing force 3.
A breaking pressure of 0 MPa will be exerted. At this time, since the outer wall film 18 ₁ of the heat-sensitive pressure-sensitive microcapsule 18 is melted by heat, both the pressure-sensitive microcapsule 16 and the heat-sensitive pressure-sensitive microcapsule 18 are destroyed and the magenta is destroyed from both of the destroyed microcapsules. The coloring material and the black coloring material are released, and the leuco dye component (Re
d-3) and the black color forming leuco dye component (ODB) each cause a color forming reaction with the developer component "x", and magenta dots and black dots are colored on the color forming layer 14. However, since the magenta dots are absorbed by the black dots, black dots are formed on the coloring layer 14.

Thus, by using the recording apparatus as shown in FIGS. 5 and 6, it is possible to record a multicolor image composed of magenta dots and black colored dots on the multicolor recording medium 10. Here, it should be noted that the magenta coloring leuco dye and the black coloring leuco dye contained in the magenta coloring material and the black coloring material, which are encapsulated in the pressure-sensitive microcapsule 16 and the heat-sensitive microcapsule 18, respectively, are mutually restricted. It means that you can use any one without receiving it. That is,
This means that it is possible to freely select and use a magenta coloring leuco dye and a black coloring leuco dye having a hue according to a user's request.

In the above embodiment, the combination of the magenta color material and the black color material has been described, but the combination with other color materials is also possible. For example, instead of the black color material, a cyan color material obtained by mixing a vehicle (KMC-113) with an appropriate leuco dye for cyan color development may be used. In this case, the heat generated by the _second thermal head 30 ₂ is generated. Element R ₂₁ , R _2
2 , R ₂₃ , ..., R _2n cause blue dots, which is a mixed color of magenta and cyan, to develop color.

Further, in the above-mentioned embodiment, the pressure-sensitive microcapsules 16 and the heat-sensitive pressure-sensitive microcapsules 18 are used.
As the coloring material to be enclosed in each of the above, a coloring material based on a leuco dye is used, but based on a normal dye other than the leuco dye (that is, a dye which itself exhibits a predetermined color) It is also possible to use coloring materials. However, in that case, the wall films of the pressure-sensitive microcapsules 16 and the heat-sensitive pressure-sensitive microcapsules 18 need to be colored in the same color as the sheet paper 12 (usually white). For example, in order to color the wall films of the pressure-sensitive microcapsules 16 and the heat-sensitive pressure-sensitive microcapsules 18 white, the microcapsule dispersion liquid obtained by the above-mentioned microcapsule manufacturing method has an average particle size of about 0.1 μm It is possible to whiten the microcapsules by appropriately adding the titanium oxide fine powder of (3) and electrically adsorbing it to the surface of the microcapsules.

When a coloring material based on an ordinary dye other than a leuco dye is used as the coloring material to be enclosed in each of the pressure-sensitive microcapsules 16 and the heat-sensitive pressure-sensitive microcapsules 18, at least the coloring layer 14 is at least used. The pressure-sensitive microcapsules 16 and the heat-sensitive pressure-sensitive microcapsules 18 may be uniformly distributed in a binder layer made of a suitable binder material that melts at 90 ° C. or higher, for example, a low-melting wax material. it can.

In the above embodiment, both the pressure-sensitive microcapsules 16 and the pressure-sensitive heat-sensitive microcapsules 18 have the same average particle size (5 μm). In such cases,
When the black dots are colored, the magenta dots may not be completely covered by the black dots, so that magenta tends to be slightly colored on the outer peripheral edge of the black dots. In order to eliminate such a tendency, the average particle size of the heat-sensitive microcapsules 18 is smaller than the average particle size of the pressure-sensitive microcapsules 16, for example, 3
It can be μm. More specifically, even if the average particle size of the heat-sensitive pressure-sensitive microcapsules 18 is changed from 5 μm to 3 μm, the weight part of the composition (1) in the above-mentioned composition liquid remains 1.0, so that Second in the composition liquid of
The number of the pressure-sensitive microcapsules 18 in FIG. 3 increases, so that when the composition liquid is applied onto the sheet paper 12, the pressure-sensitive microcapsules 16 are surrounded by the heat-sensitive pressure-sensitive microcapsules 18 and thus black. When the dots are colored, the probability that the magenta dots will be completely obscured by the black dots is greatly increased, and the tendency of the magenta to develop slightly on the outer edges of the black dots can be almost eliminated.

By the way, as described above, the pressure-sensitive microcapsules 18 'shown in FIG. 3 are manufactured to withstand a pressure of 2.8 MPa or less. Only a small amount of weak strengths that can be broken under a pressure of MPa can be included.
Therefore, if the pressure-sensitive microcapsules 18 ′ are used instead of the heat-sensitive pressure-sensitive microcapsules 18, black may be erroneously colored due to the destruction of the microcapsules having weak strength when the magenta dots are colored. . However, in the above-described embodiment, the puncture resistance strength of the heat-sensitive pressure-sensitive microcapsules 18 depends on the outer wall film 18 thereof.
_Since it is greatly increased due to ₁ , it is possible to almost completely avoid accidentally destroying the heat-sensitive pressure-sensitive microcapsules 18 when the magenta dots are colored by the first thermal head. Fog can be completely prevented.

[0054]

As is apparent from the above description, according to the multi-color recording medium of the present invention, the color materials encapsulated in the pressure-sensitive microcapsules and the heat-sensitive pressure-sensitive microcapsules are substantially limited. It is possible to select an arbitrary color tone, and it is possible to realize a combination of hues that could never be obtained by the conventional additive multicolor thermal paper. Further, in the multi-color recording medium according to the present invention, since the coloring material for coloring on the low temperature side can be microencapsulated, even if the multi-color recording medium is exposed to a temperature of around 100 ° C. under ordinary conditions. Not only is erroneous color development such as background stain prevented, but it can also contribute to a reduction in the overall required printing energy.

[Brief description of drawings]

FIG. 1 is a schematic sectional view schematically showing a part of an embodiment of a multi-color recording medium according to the present invention.

FIG. 2 is an enlarged sectional view of a heat-sensitive pressure-sensitive microcapsule used in the multi-color recording medium shown in FIG.

FIG. 3 is an enlarged cross-sectional view similar to FIG. 2, showing the heat-sensitive pressure-sensitive microcapsules shown in FIG. 2 with the outer wall membrane removed.

FIG. 4 is a graph showing color development characteristics of the multi-color recording medium shown in FIG.

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

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

7 is a schematic cross-sectional view showing a state in which a heating element of the thermal head of the image recording apparatus shown in FIG. 5 causes a color-developing dot of a predetermined color to be colored on the color-developing layer of the multi-color recording medium of FIG.

[Explanation of symbols]

10 Multi-color recording medium 12 Support (sheet paper) 14 Coloring layer 16 Pressure-sensitive microcapsules 18 Heat-sensitive pressure-sensitive microcapsules

Claims (5)

[Claims] 1. A multi-color recording medium comprising a support and a color-developing layer coated on the surface of the support, wherein the color-developing layer comprises a binder layer comprising a number of pressure-sensitive microcapsules and a number of heat-sensitive pressure-sensitive microcapsules. The binder layer is provided with a temperature characteristic of being heat-melted at a first temperature, and the pressure-sensitive microcapsule contains a first coloring material and a first coloring material. Given the pressure rupture characteristics, which became to rupture under the pressure of 1,
A second color material is encapsulated in the heat-sensitive pressure-sensitive microcapsules and is destroyed at a second temperature higher than the first temperature and under a second pressure higher than the first pressure. A multi-color recording medium characterized by being provided with a temperature and pressure breakdown characteristic. 2. The multi-color recording medium according to claim 1, wherein each of the first and second color materials is prepared as a color material based on a leuco dye, and the binder layer is a developer of the leuco dye. A multicolor recording medium formed as a color material layer. 3. The multi-color recording medium according to claim 2, wherein the heat melting temperature of the developer layer is adjusted by the sensitizer component contained therein. 4. The multi-color recording medium according to claim 1, wherein the first temperature is set to 100 ° C. at the highest. 5. The multi-color recording medium according to claim 1, wherein the heat-sensitive pressure-sensitive microcapsules are coated with a wax material which is adapted to be melted by heat at the second temperature. A multi-color recording medium characterized by being provided.