JP3023341B2 - Thermal recording paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Explanation of Terms] In the present invention, "sublimable dye" means
A dye that can be dissolved or dispersed in a volatile or nonvolatile organic solvent, and that sublimates when heated to a temperature of 50 ° C. or higher. Further, the “microcapsules” used here may be basically composed of a sublimable dye as a content and a wall material surrounding the dye.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-sensitivity heat-sensitive recording paper excellent in fastness of image recording and storage stability of the recording paper itself.

[0003]

2. Description of the Related Art Thermosensitive recording papers capable of forming an image record by heating are conventionally known (JP-B-43-4160 and JP-B-45-14039). For example, the above-mentioned
No. -4160 and Japanese Patent Publication No. 45-14039, a thermal recording paper is provided with a thermosensitive coloring layer comprising a colorless or pale leuco dye and an organic developer on a support, and a thermal head When the heat-sensitive coloring layer is heated by, for example, melting and coloring, an image is recorded. Such thermosensitive recording paper has been widely used as a printing recording paper for facsimile and word processors. However, in the above-described thermosensitive recording paper, the formed image recording lacks the fastness over time, and thus has a drawback that the image recording gradually becomes thin or yellowish, and forcibly disappears. Further, the heat-sensitive recording paper also has a drawback that the contact portion may develop color when a small pressure or friction is applied during storage and transport or during use, and as a result, the product value is reduced.

As means for overcoming the above disadvantages, for example,
JP-B-58-13359 and JP-B-1-46319 have a support 510 provided with a heat-sensitive recording layer 511 composed of a pigment, a heat-meltable wax, a thermoplastic resin, and the like. A heat-sensitive recording material 500 formed by combining another high-quality recording paper 520 (see FIG. 2). When the heat-sensitive recording material having such a structure is heated using a thermal head or the like, the heat-sensitive recording layer is transferred from the support side to the surface of the recording paper, and a heat-sensitive image recording portion 100 'is formed.
As another method described above, a support (also referred to as a donor film) provided with a layer containing a sublimable dye instead of a pigment, and a resin layer capable of dyeing the sublimable dye opposed to the layer are provided. And sublimation dye transfer thermosensitive recording materials composed of paper (for example, Japanese Patent Publication No. 3-8011)
No. 6 publication). When the heat-sensitive recording material is heated, the sublimable dye sublimates and moves to the opposite resin layer, and is dyed to form an image record. All of the image records thus obtained have good stability over time.

[0005] However, the heat-sensitive recording material has a drawback that the cost of the product is high because it is necessary to prepare a recording paper different from the heat-sensitive transfer support in view of its structure. In addition, the heat-sensitive recording material is preferable in terms of maintaining information confidentiality, since the heat-sensitive recording layer remains on the support in an inverted image mode corresponding to the image recorded on the high-quality paper after thermal transfer. Absent. Further, the latter heat-sensitive recording material has a problem that the operation of discarding the donor film coated with the sublimable dye after use is extremely complicated.

The present applicants have also developed a heat-sensitive recording material for obtaining a heat-sensitive image record in addition to the above-mentioned thermal transfer recorded image (Japanese Patent Application Laid-Open No. 9-248971). The heat-sensitive recording material,
A heat-sensitive layer containing a sublimable dye sublimated by the heat of a thermal head or the like on a support surface, and a fixing layer containing a white pigment such as a thermoplastic resin and titanium oxide dyeable with the sublimable dye are sequentially laminated. Become. The white pigment is added in order to improve the whiteness of the heat-sensitive recording material having the layer and maintain the same hue and appearance as high-quality paper. In such a heat-sensitive recording material, the sublimable dye in the sublimated heat-sensitive layer develops a clear color in the fixing layer by heating with a thermal head or the like, so that a recorded image having excellent fastness can be obtained. It is a desirable thermal recording paper that is free from damage during storage and transportation.

However, the heat-sensitive recording paper has a complicated manufacturing process because the heat-sensitive layer and the fixing layer must always be overlaid. Further, there is also a problem that the thermal sensitivity may be reduced because the coating layer is thicker than a conventional thermosensitive recording paper coated only with a thermosensitive layer. Further, since there is no colorless or light-colored sublimable dye contained in the heat-sensitive layer, when provided on a recording paper, even if the white pigment is used, it is extremely difficult to obtain a recording paper having a white background. It was difficult.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above problems, and in particular, improves the robustness and storage stability.
Another object of the present invention is to develop a heat-sensitive recording material having high heat sensitivity and reduced production cost.

[0009]

SUMMARY OF THE INVENTION The present invention provides a thermosensitive recording paper which has two functions of color development and fixing in the same thermosensitive recording layer, but has high sensitivity and a white appearance. Specifically, the present invention comprises (a) a microcapsule containing at least one sublimable dye on a support, (b) a thermoplastic resin dyeable with the sublimable dye, and (c) a white pigment. A heat-sensitive recording paper comprising at least one heat-sensitive recording layer is provided. Here, the microcapsules (a) are made of fine particles by using a resin as a wall material and enclosing a sublimable dye in the resin.
The heat-sensitive recording layer may further contain a color developer and / or a decolorant.

[0010]

The effect of incorporating microcapsules in the heat-sensitive layer of the heat-sensitive recording material is described in, for example, Japanese Patent Publication No. 04-0075147, Japanese Patent Publication No. 04-0044595, Japanese Patent Publication No. 05-0064118, and Japanese Patent Publication No. 79867, JP-A-5-305767, JP-A-4-290788 and JP-A-4-4960, etc., but there is no description about the microencapsulated sublimable dye, and it was used. The action of the heat-sensitive recording material itself is not known at all. The heat-sensitive recording material of the present invention has the following utility. 1) By microencapsulating the sublimable dye, it is possible to prevent color development and damage due to application of pressure or the like before use. 2) Whitening of the layer containing the sublimable dye can be realized by including the colored sublimable dye in the microcapsules of fine particles. That is, the white appearance of the obtained thermosensitive recording paper can be improved. 3) By including a sublimable dye, a thermoplastic resin dyeable with the dye, and a thermosensitive recording layer containing a color developer and / or a decolorant, color development and fixing within the same thermosensitive recording layer are possible. . That is, the production efficiency is increased by reducing the number of manufacturing steps. 4) By heating with a normal heating device such as a thermal head, image recording with high sensitivity can be obtained, and the image recording has excellent fastness over time.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The structure of the thermal recording paper of the present invention and the thermal recording process thereof will be described with reference to FIG. The thermosensitive recording paper 10 of the present invention comprises a support 1 and at least one thermosensitive recording layer 2 provided thereon. The heat-sensitive recording layer 2 contains a microcapsule 21 containing a sublimable dye and an organic white pigment, a thermoplastic resin 22 dyeable with the sublimable dye, and a white pigment 23. The thermal recording paper
When 10 is heated by the thermal head 30 or the like, the microcapsules 21 are broken or softened and deformed by heat in the heat-sensitive recording layer 2 at the heated portion, whereby the sublimable dye 210 in the microcapsules 21 is released. The released sublimable dye 210 sublimates, dyes and fixes the thermoplastic resin 22 contained in the same thermosensitive recording layer,
A color image record 100 is formed.

As examples of the support used in the thermal recording paper of the present invention, any material known in the art, such as a base paper or a polymer film, described in JP-A-9-248967 may be used. it can.

In the present invention, at least one support is provided on the support.
A thermosensitive recording layer is provided. Here, the thermosensitive recording layer comprises: (a) a microcapsule containing at least one sublimable dye and at least one organic white pigment; (b) a thermoplastic resin dyeable with the sublimable dye; and (c) ) Containing white pigments.

The microcapsule (a) used in the present invention basically comprises a sublimable dye and an organic white pigment as contents, and a wall material surrounding them.
Resins that can be used as the wall material of the microcapsules (a) include synthetic resins, in particular, polyurea, polyurea / urethane, polyurethane, polyester, polyamide, epoxy, urea-formalin, melamine-formalin resin, or a mixture thereof, Polyurea or polyurethane is most preferred from the viewpoint of the difficulty in the capsule production method and the strength resistance of the capsule, particularly the moisture resistance and heat resistance.

For example, when the wall material of the microcapsule (a) is polyurea or polyurethane, a polyvalent isocyanate and a polyhydric alcohol or a polyamine which reacts with the polyisocyanate are used as the wall forming material. However,
The above-mentioned polyvalent isocyanate, polyhydric alcohol and polyamine are described in U.S. Pat.
No. 5, JP-B-48-40347, JP-A-48-80191 and the like can all be used, and their contents are inserted here.

The microcapsules (a) enclosing the sublimable dye and the organic white pigment do not break down under pressure or heat generated during storage or transportation before use, and can sufficiently retain the contents. Any heating can be used as long as it can partially break or soften and release the sublimable dye contained therein. Such a microcapsule is, for example, Japanese Patent Publication No. 04-0075147,
JP-B04-0044595, JP-B05-0064118, JP-B6-79867, JP-A-5-305767, JP-A-4-2
It can be produced by a method similar or similar to the method described in Japanese Patent No. 90788 and Japanese Patent Application Laid-Open No. 4-4960. Here, the contents of the publication are inserted.

For example, when the wall material is made of polyurea or polyurethane, first, a polyvalent isocyanate and a sublimable dye as the first wall forming material are mixed with a water-insoluble or insoluble nonvolatile organic solvent (for example, phosphate ester, Dissolve or disperse in phthalic acid esters, fatty acid amides, alkylated biphenyls, alkylated naphthalenes, diarylethanes, etc.) and / or volatile organic solvents (eg, toluene, benzene, xylene, ketones, esters, etc.).
Thereafter, the obtained solution or dispersion was mixed by dissolving a second wall forming material such as polyhydric alcohol or polyamine and a water-soluble polymer (eg, gelatin, gum arabic, methylcellulose, polyvinyl alcohol, etc.). Emulsification / dispersion is carried out by adding to the aqueous solution by such means as to obtain finely dispersed particulate droplets having a particle size in the range of about 0.1 to about 5.0 μm.

The obtained emulsified / dispersed solution is heated at about 30 to about 80 ° C.
The first wall forming material and the second wall forming material are completely reacted by heating while stirring for about 1 to about 8 hours to obtain microcapsules (a) having an outer diameter of 0.5 to 5.0 μm. .

In the present invention, the sublimable dye contained in the microcapsule (a) is a dye that can be dissolved or dispersed in a volatile or nonvolatile organic solvent and heated to a temperature of 50 ° C. or more. Can be sublimated. Suitable sublimable dyes include sublimable dyes mainly used as disperse dyes or oil-soluble dyes in thermal transfer recording materials and thermal transfer printing, for example, JP-A-63-650.
No. 29, CI Disperse Yellow No. 1, 3,
8, 9, 16, 41, 54, 60, 77, 116, etc .; CI Disperred No. 1, 4, 6, 11, 15, 17, 55, 59, 60, 73, 83, etc .;
I. Disperse Blue No. 3, 14, 19, 26, 55, 60, 64, 7
2, 99, 108, etc .; Solvent Yellow No. 77 and 116
No.23, 25, 27 etc. of CI Solvent Red; and
CI Solvent Blue No. 36, 83, 105 and the like.

The above-mentioned sublimable dyes can be used alone or in combination with each other, and are used by dissolving them in the above-mentioned volatile or nonvolatile organic solvent at a concentration of about 5 to about 15%.

In the present invention, the thermal responsiveness of the formed microcapsules, that is, the susceptibility of the microcapsules to destruction or softening deformation by heating with a thermal head or the like is determined by the outer diameter of the microcapsules, the type or thickness of the wall material, or the like. (That is, the difference between the particle diameter of the sublimable dye contained therein and the outer diameter of the formed microcapsules).

Alternatively, the thermal responsiveness can be increased by adding a heat-fusible substance such as p-benzyloxyphenol to the microcapsules. Such a heat-meltable substance has, in particular, a melting point.
Hydroxy compounds at 50 ° C to 171 ° C (eg, Pt-butylphenol, p-benzylphenol, propyl p-hydroxybenzoate, p-benzyloxyphenol, etc.), carbamates (eg, benzyl N-phenylcarbamate) , An aromatic methoxy compound (for example,
It is effective to use 2-methoxybenzoic acid). The heat-fusible substance is preferably added in an amount of about 0.5 to 5 parts by weight based on 1 part by weight of the whole microcapsules.

The sublimable dye released from the microcapsule (a) by heating is captured by the thermoplastic resin (b) contained in the same thermosensitive recording layer, and is dyed and fixed. As the thermoplastic resin (b) suitable for use in the heat-sensitive recording layer, for example, any commonly available resin such as an amide resin, a vinyl resin, an acrylic resin, an acrylate resin, and a polyester resin can be used. However, among them, it is particularly preferable to use a polyester resin from the viewpoint of dyeing properties. In the heat-sensitive recording layer, the thermoplastic resin is in the form of a film or in the form of finely dispersed fine particles.

In the present invention, it is particularly advantageous that the thermoplastic resin has a large surface area from the viewpoint of capturing and fixing the released sublimable dye. Therefore, the thermoplastic resin is preferably used in the form of a polyester resin dispersion dispersed in fine particles. Further, in order to improve the dyeability of the thermoplastic resin by the sublimable dye, it is preferable that the thermoplastic resin be easily softened by heat from a thermal head or the like, for example, a polyester resin having a relatively low molecular weight. May be.

Therefore, in the present invention, a resin dispersion having a dispersed particle size of 10 μm or less in which a polyester resin having a glass transition temperature or a melting point of 100 ° C. or less is dispersed in water is preferably used. The polyester resin dispersion is commercially available. For example, the product name of Polyester (a polyester resin with a glass transition point of 57 ° C
Dispersion containing 20%: dispersed particle diameter is about 5 μm).

In the present invention, the white pigment (c) is used for the purpose of obtaining a thermosensitive recording material having a white appearance by concealing the color of the sublimable dye contained in the microcapsules. As such a white pigment (c), any conventionally known one can be used. The present inventors have found that it is particularly preferable to use titanium oxide as the white pigment (c) since a heat-sensitive recording material having excellent whiteness can be obtained. As the titanium oxide, any of commercially available anatase and rutile types can be used. Titanium oxide is typically from about 0.2 to about 0.5μ
Although it has a particle size of m, it is desirable in the present invention to have a particle size smaller than the above value.

For the purpose of concealing the coloring of the sublimable dye and further increasing the whiteness as thermal recording paper, if necessary, an inorganic pigment such as zinc oxide or calcium carbonate may be combined with the titanium oxide. Can also be used.

In the present invention, the white pigment (c) is
By distributing them around the microcapsules (a) and enclosing them in the microcapsules (a), the color of the sublimable dye can be hidden and the whiteness of the heat-sensitive recording layer can be remarkably improved. In order to achieve the above object, among the white pigments (c), an organic white pigment which can be dispersed in a nonvolatile or volatile organic solvent can be included in the microcapsule (a) together with the sublimable dye. Such organic white pigments include, in particular, N, N'-bis
(4,6-Diamino-1,3,5-triamine-2-yl) ethylenediamine fine powder (trade name: Shigenox-OWP, manufactured by Hako Chemical Co., Ltd.) is effective. The organic white pigment is used in an amount ranging from about 5 to about 25% based on the sublimation dye solution in the microcapsule.

The heat-sensitive recording paper surface, that is, the heat-sensitive layer, comes into direct contact with the thermal head during the heating process. Therefore, on these contact surfaces, an instantaneous bonding phenomenon accompanying melt cooling may occur. This phenomenon is called "sticking" and is generally known to occur in general-purpose thermal paper using a leuco dye. In order to prevent this phenomenon, various inorganic pigments are usually contained in the heat-sensitive layer of the heat-sensitive recording paper. In the present invention, in order to prevent the above phenomenon, the titanium oxide and the inorganic pigment other than the white pigment can be used together in the heat-sensitive recording layer, if necessary. Inorganic pigments suitable for the above purpose are those usually used in the field of paper processing, for example, clay, talc, magnesium carbonate, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, kaolin, zinc oxide, carbonate Examples include calcium and aluminum oxide. Furthermore, so-called release agents such as zinc stearate can be used in combination with the titanium oxide and the inorganic pigment.

Further, in the present invention, when the thermosensitive recording layer is heated using a thermal head or the like, the heated portion of the thermosensitive recording layer may be made transparent from the viewpoint that a color image having high saturation is obtained. Particularly preferred. For this purpose, it is preferable that crystalline fine powder silica (for example, trade name “Aerosil” manufactured by Nippon Aersil Co., Ltd.) is contained in the heat-sensitive recording layer. Generally, crystalline fine powder silica is used in a ratio of about 2 to 15% based on the total coating weight of the heat-sensitive recording layer.

In the thermosensitive recording layer of the present invention, microcapsules (a) containing a sublimable dye and an organic white pigment, a polyester resin as a thermoplastic resin (b) dyeable with the sublimable dye, and a white pigment ( The amount of each component c) can be appropriately selected depending on the purpose of use, and can be easily determined by those skilled in the art. In general, it is preferable to contain about 3 to 15% of a sublimable dye in the microcapsule (a), and (a) / (b) / (c) = about 10 to about 40 / About 3 to about
20 / about 15 to about 40 parts by weight.

The following is an example of a method for producing the thermosensitive recording paper of the present invention. First, a white pigment and, if desired, an inorganic pigment and crystalline fine powdered silica are added to an aqueous solution in which a water-soluble binder is dissolved, and the mixture is finely dispersed by a ball mill, an attritor, or the like. Thereafter, to the dispersion, a microcapsule dispersion containing a sublimable dye, and a dispersion of thermoplastic resin fine particles dyed with the sublimable dye are added and mixed to prepare a coating solution for a thermosensitive recording layer. I do. Here, as the water-soluble binder,
For example, any of water-soluble resins such as starch, gelatin, methylcellulose, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylamide can be used, and among them, polyvinyl alcohol is preferably used.

If necessary, a latex dispersion may be used alone or as a mixture in order to increase the adhesion strength of the coating liquid to the base paper.

Then, the above-mentioned coating solution for a heat-sensitive recording layer is uniformly coated on a desired support using a usual coating equipment such as a wire bar, an air knife, a roll, a gravure screen and the like, and dried to obtain heat-sensitive recording. A layer is formed. The coated amount of the heat-sensitive recording layer after drying is in the range of about 0.5 to 10 g / m ² , particularly preferably in the range of about ^{2 to 5} g / m ² .

In another embodiment of the present invention, two or more heat-sensitive recording layers are laminated on a support, and each heat-sensitive recording layer contains a separate microcapsule (a) containing a sublimable dye having a different hue. The present invention provides a heat-sensitive recording paper comprising: a heat-sensitive recording paper, which is capable of developing two or more colors by heating. Such a thermosensitive recording paper is provided, for example, as a first thermosensitive recording layer on a support, a thermosensitive recording layer containing microcapsules containing a red sublimable dye, and further thereon, a blue sublimable dye. It is manufactured by providing a second heat-sensitive recording layer containing microcapsules containing The heat-sensitive recording paper develops a blue color when heated at a low temperature, or a purple to black-violet color when heated at a high temperature. The resulting image record is extremely stable and has excellent fastness over time.

Alternatively, a heat-sensitive recording layer containing a microcapsule containing a sublimable dye and a Japanese Patent Publication No. 5-71395, Japanese Patent Publication No. 5-77519, Japanese Patent Publication No. Sho 54-36863, and Japanese Patent Publication No. Sho 54-43383.
JP-A-5-201127, etc., a conventionally known heat-sensitive layer for a single-color or multi-color heat-sensitive paper (that is, a heat-sensitive layer containing a leuco dye, a color developer, and if necessary, a decolorant), The present invention also encompasses multicolor thermal paper produced by layering in combination with the thermal recording layer of the present invention.
Here, materials suitable for the leuco dye and the color developer include the above-mentioned JP-B 5-71395, JP-B 5-77519, and JP-B-54.
-36863, JP-B-54-43383, JP-A-5-201127, etc., can be used, and their contents are inserted here.

In the multicolor thermal paper, the thermal recording layer of the present invention may be provided at any position of the uppermost layer, the intermediate layer, or the lowermost layer of the thermal layer for the thermal paper.

A multicolor heat-sensitive recording material described in our earlier application (Japanese Patent Application Laid-Open No. 9-248967), wherein a sublimable dye layer and its sublimable dye are fixed on a support. Multicolor including a sublimable dye coloring layer composed of two layers of a coloring dye fixing layer, a leuco dye coloring layer containing a leuco dye and a developer, and a microcapsule containing a decoloring agent adjacent to the leuco dye coloring layer. It is clear that, in the heat-sensitive recording material, a multicolor heat-sensitive recording material in which the heat-sensitive recording layer of the present invention is layered as described above, instead of the sublimable dye coloring layer, also falls within the scope of the present invention.

[0039]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. Example 1: Thermal recording paper for yellow coloring a) Microcapsule dispersion: Yellow sublimable dye [Kayaseto
10 g of Yellow-AG (Nippon Kayaku)] and 60 g of a polyvalent isocyanate [Sumidur N-75 (Sumitomo Bayer)] were dissolved in 80 g of diisopropylnaphthalene [KMCoil (Kureha Chemical)].
An organic white pigment [Shigenox-OWP (manufactured by Hako Chemical Co., Ltd.); N, N'-bis (4,6-diamino) 1,3,5-triamine-2
-Yl) ethylenediamine] was added and dispersed to prepare a liquid containing microcapsules. Then
400 g of 10% PVA aqueous solution
The emulsion was emulsified and dispersed therein using a homogenizer at a rotation speed of about 1,000 rotations so that the particle diameter became 0.5 to 5 μm. Into a stirring emulsified dispersion, prepare a pre-prepared polyvalent amine (15 g of epicure U (shell oil) and hexamethylenediamine)
A solution in which 6 g was dissolved in 40 g of water was added, and heated at 40 to 50 ° C. for 6 hours to obtain a microcapsule dispersion. b) Polyester resin dispersion: 90 g of polyester resin aqueous dispersion (Polyester XWR-901 (Nihon Gosei)), 70 g of titanium oxide and 2.5 g of fine powdered silica (Aerosil # 200 (Nippon Aerosil)) are mixed, and ball mill or sand mill is used. C): A thermosensitive recording layer for yellow coloring was prepared by mixing 20 g of the microcapsule dispersion obtained in a) and 50 g of the polyester resin dispersion of b) above. A coating solution was used. This was coated on a high-quality paper of 55 g / m ² using a wire bar coating machine so that the coating amount was 6 g / m 2, and dried to obtain a yellow color thermosensitive recording paper.

Example 2 Thermal recording paper for black color formation In the above a), a black sublimation dye (Kaya
set black-922 (Nippon Kayaku)) except that in 7), and in b), a p-benzyloxyphenol dispersion was further added as a sensitizer to prepare a coating solution for a black color thermosensitive recording layer. In the same manner as in Example 1, a thermosensitive recording paper for coloring black was obtained.

Example 3: Two-color heat-sensitive recording paper The heat-sensitive recording layer coating solution for yellow color development described in Example 1 was coated on the heat-sensitive recording layer coating solution for black color development described in Example 2 and then applied. By layering two color thermosensitive recording layers,
A two-color heat-sensitive recording paper was obtained which developed yellow at low temperatures and black at high temperatures.

Example 4: 10-color thermal recording paper for two-color development 3,3-bis (4-diethylaminophenyl) -6-diethylaminophthalide 10 g, dibenzyl terephthalate 20 g, calcium carbonate 15 g, polyvinyl alcohol 5% aqueous solution 15 g
And 80 g of water were finely dispersed in a sand mill to an average particle size of 3 μm or less to obtain 10 g of a color former dispersion. Also,
4-hydroxy-4-isopropoxydiphenyl sulfone 20
g, 15 g of a 5% aqueous solution of polyvinyl alcohol, 15 g of calcium carbonate, and 80 g of water were similarly finely dispersed in a sand mill to an average particle diameter of 3 μm or less to obtain 20 g of a thermosensitive recording layer dispersion. 10 g of the color former dispersion and 20 g of the heat-sensitive recording layer dispersion were mixed with 50 g of the yellow color heat-sensitive recording layer coating liquid prepared in Example 1 to prepare a two-color heat-sensitive recording layer liquid. Here, 2-color development for heat-sensitive recording layer solution, the coating amount after drying, the range of 1.0 to 10.0 g / m ^2, in particular 2.0~5.0g / m ²
Was applied in such a manner as to fall within the range. The thermosensitive recording layer liquid for two-color development is uniformly coated on a desired support using a usual coating equipment such as a wire bar, an air knife, a roll, and a gravure screen, and dried to obtain a blue color at a low temperature. A two-color heat-sensitive recording paper which develops grass color at high temperature was obtained.

Example 5 a ') Decolorizing agent containing guanidine microcapsules: 8 g of diisopropylnaphthalene and di-o-tolylguanidine 1.
After adding 5 g and stirring and mixing, 4.6 g of 2,4-tolylene diisocyanate was added and dissolved to obtain a guanidine solution.
This guanidine solution is stirred at about 12,000 rpm
Gradually add to 40g of 10% polyvinyl alcohol aqueous solution,
The guanidine solution was emulsified into microdroplets 0.5-5 μm in diameter. After adding 0.5 g of a 20% aqueous solution of hexamethylenediamine to the obtained emulsion, the system was heated to 60 ° C. and stirred for 1 to 3 hours. Thereafter, 50 g of water was added to obtain a guanidine-containing decoloring agent microcapsule dispersion.

The above-mentioned decolorizing agent microcapsules were coated on the yellow color heat-sensitive recording paper of Example 1 using a wire bar coating machine so that the coating amount was 4 g / m ² . Then, a mixture of 10 g of the color dispersion and 20 g of the heat-sensitive recording layer dispersion prepared in Example 4 was used as a blue heat-sensitive recording layer with a wire bar coating machine so that the coating amount was 4 g / m ^2. By coating, a two-color heat-sensitive recording paper that develops blue at low temperatures and yellow at high temperatures was obtained.

COMPARATIVE EXAMPLE 1 In this comparative example, the inventors filed an earlier application (JP-A-9-248971).
According to Example 1 of Japanese Patent Application Laid-Open No. H10-264, a thermosensitive recording paper comprising two layers of a color developing layer and a fixing layer was produced. The contents are shown below.
(A) a sublimable dye layer coating solution comprising the following composition, and (b)
A coating solution for a sublimable dye fixing layer was prepared. On the base paper of 40g / m ²
Using a 0.15 mm wire bar, the solution (a) was applied as the first layer, and dried by applying hot air. Next, after sufficiently drying, the liquid (b) was layered thereon as a second layer, and the liquid was similarly applied using a 0.25 mm wire bar, and dried to obtain a thermosensitive recording paper which developed yellow. (a) Sublimation dye layer coating liquid weight part toluene 400 methyl ethyl ketone 400 denka vinyl # 1000AKT (Note 1) 100 Kaya set Yellow-AG (Note 2) 40 Aerosil # 200 (Note 3) 30

(B) Part by weight of sublimation dye fixing layer coating liquid aqueous polyester resin (Note 4) 700 Titanium oxide 300 Aerosil # 200 20

Comparative Example 2 In this comparative example, Japanese Patent Publication No. 43-4160 and Japanese Patent Publication No. 45-14
According to the description in JP-A-039, a comparative thermal paper using a conventionally known leuco dye and a developer was prepared.

Evaluation The heat-sensitive recording papers of Examples 1 to 5 and the heat-sensitive recording papers of Comparative Examples 1 and 2 were tested for visual appearance evaluation, image stability evaluation, paper storability and thermal sensitivity in the following manner. . Visual Appearance Evaluation The surface whiteness and planar smoothness were evaluated visually by comparing with high-quality paper having a specific gravity of 55 g / m ² as a reference material. Evaluation of Image Stability An image produced by using a thermal printer PW-PR01-02 manufactured by NEC Corporation was subjected to a standing treatment under an environment of 40 ° C. and 90% RH for 100 hours, and its discoloration / fading property was evaluated.

Paper preservability After the paper was left standing at 40 ° C. and 90% RH for 100 hours, a thermal printer PW-PR01-02 manufactured by NEC Corporation was used.
The image was produced by the following. As a control, an image was similarly prepared on untreated standard paper. The color development was evaluated by visual observation. Thermal Sensitivity An image was prepared using a thermal printer PW-PR01-02 manufactured by NEC Corporation, and the color density was evaluated by visual observation.

Table 1 summarizes the results.

[Table 1] From the results shown in Table 1, it can be seen that all of the heat-sensitive recording papers of Examples 1 to 3 of the present invention show excellent sensitivity and image recording fastness and good storage stability.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view in an image recording step of a thermosensitive recording paper of the present invention.

FIG. 2 is a schematic cross-sectional view of a conventional thermosensitive recording paper in an image recording process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Support, 2 ... Thermal recording layer, 10 ... Thermal recording paper, 21
... microcapsules, 22 ... thermoplastic resin particles, 23 ...
White pigment, 30 ... thermal head, 100, 100 '...
Colored image recording section, 210: sublimable dye released from microcapsule, 500: conventional thermal recording material, 510
... Support, 511 ... Thermal recording layer, 520 ... Quality paper for recording.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41M 5/28-5/36

Claims (7)

(57) [Claims] 1. A microcapsule enclosing (a) at least one sublimable dye and at least one organic white pigment on a support; (b) a thermoplastic resin dyeable with the sublimable dye; and c) Thermal recording paper comprising at least one thermal recording layer containing a white pigment. 2. The thermosensitive recording paper according to claim 1, wherein the thermoplastic resin (b) contains polyester resin particles. 3. The heat-sensitive recording paper according to claim 1, wherein the white pigment (c) contains titanium oxide particles. 4. The method according to claim 1, wherein the organic white pigment is N, N′-bis (4,6-
The heat-sensitive recording paper according to claim 1, which is diamino) 1,3,5-triamine-2-yl) ethylenediamine. 5. The heat-sensitive recording paper according to claim 1, wherein the heat-sensitive recording layer contains a leuco dye and a color developer. 6. The thermosensitive recording paper according to claim 1, wherein the thermosensitive recording layer further contains a decoloring agent. 7. The heat-sensitive recording layer is laminated two or more layers,
2. A heat-sensitive recording paper containing separate microcapsules (a) containing sublimable dyes having different hues in each heat-sensitive recording layer, wherein two or more hues can be developed. 7. The heat-sensitive recording paper according to any one of items 1 to 6,