JP2002127601A - Heat-sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording body with excellent color developing properties, water resistance, plasticizer resistance and oil resistance and excellent yellowing resistance of unrecorded parts. SOLUTION: In the heat-sensitive recording body with a heat-sensitive recording layer containing an electron-donating compound, an electron-accepting compound and an aqueous adhesive on a substrate, as one of means for solving the above described problem, a diacetone-modified polyvinyl alcohol is used as an adhesive in the heat-sensitive recording layer and in addition, a polyamideamine-epichlorohydrin resin and a carboxylic acid dihydrazide compound are incorporated in the heat-sensitive recording layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material which utilizes a color-forming reaction between an electron-donating compound and an electron-accepting compound, and in particular, a recorded image can be obtained by a color-forming reaction using thermal energy.

[0002]

2. Description of the Related Art A thermosensitive recording medium in which an electron-donating compound and an electron-accepting compound are brought into contact by thermal energy to obtain a recorded image is well known. Such a thermosensitive recording medium is relatively inexpensive, has a compact recording device, and is easy to maintain. Therefore, it is used for a recording medium such as a facsimile or various computers.

[0003] In recent years, particularly with the development of recording systems, even under severer conditions in the use environment of thermal recording media, storage characteristics of recorded images are required in addition to recording suitability.

It has been found that the combined use of diacetone-modified polyvinyl alcohol and carboxylic acid dihydrazide as a crosslinking agent provides an excellent effect on water resistance, and that such a combined system can be used for a heat-sensitive recording layer.
JP-A-11-314456 describes a heat-sensitive recording material in which diacetone-modified polyvinyl alcohol is used as an adhesive for a protective layer, and a carboxylic acid dihydrazide is contained in a heat-sensitive recording layer as a crosslinking agent. However, further improvement in water resistance has been demanded.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which is excellent in coloring properties, water resistance, plasticizer resistance, oil resistance and yellowing resistance of an unrecorded portion. It is in.

[0006]

Means for Solving the Problems In a heat-sensitive recording medium having a heat-sensitive recording layer containing an electron-donating compound, an electron-accepting compound and an aqueous adhesive on a support, one of the above-mentioned objects can be attained. As a means, using diacetone-modified polyvinyl alcohol as an adhesive in the heat-sensitive recording layer,
Further, the thermosensitive recording layer contains a polyamidoamine / epichlorohydrin resin and a carboxylic acid dihydrazide compound.

Further, in a heat-sensitive recording medium having, in order, a heat-sensitive recording layer containing an electron-donating compound, an electron-accepting compound and an aqueous adhesive, and a protective layer containing an aqueous adhesive, Diacetone-modified polyvinyl alcohol is used as an aqueous adhesive, and a polyamidoamine / epichlorohydrin resin is contained in the protective layer.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Diacetone-modified polyvinyl alcohol used as an adhesive in a heat-sensitive recording layer or a protective layer is a partially or completely saponified copolymer of a monomer having a diacetone group and a vinyl ester. It is produced by saponifying a resin obtained by copolymerizing a monomer having a diacetone group and a vinyl ester. When the diacetone-modified polyvinyl alcohol is used in the heat-sensitive recording layer, the amount is 1 to the total solid content of the heat-sensitive recording layer.
About 50% by weight, preferably about 3 to 35% by weight. When diacetone-modified polyvinyl alcohol is used for the protective layer, the content is 10% by weight or more, preferably about 20 to 80% by weight, based on the total solid content of the protective layer.

The amount of the polyamidoamine / epichlorohydrin resin contained as a crosslinking agent in the heat-sensitive recording layer or the protective layer is not particularly limited, but is about 1 to 50% by weight, preferably about 5 to 30% by weight. It is.

The aqueous adhesive in the protective layer or the heat-sensitive recording layer is diacetone-modified polyvinyl alcohol, and a polyamidoamine / epichlorohydrin resin and a carboxylic acid dihydrazide compound are used as a crosslinking agent in the protective layer or the heat-sensitive recording layer. When contained, the amount of the carboxylic acid dihydrazide compound used is not particularly limited, but may be 0.1 to 0.1 based on the diacetone-modified polyvinyl alcohol in each layer.
It is about 20% by weight, preferably about 1 to 10% by weight. When a polyamidoamine / epichlorohydrin resin and a carboxylic acid dihydrazide compound are used in the same layer, the carboxylic acid dihydrazide compound is preferably about 1 to 20% by weight based on the polyamidoamine / epichlorohydrin resin.

When diacetone-modified polyvinyl alcohol is used in the protective layer, the protective layer contains a polyamidoamine / epichlorohydrin resin, and further contains a carboxylic acid dihydrazide compound in the heat-sensitive recording layer or the protective layer. By doing so, an effect that is much more excellent in water resistance can be obtained. In consideration of the pot life of the protective layer coating solution for forming the protective layer, it is preferable to include a carboxylic acid dihydrazide compound in the heat-sensitive recording layer.

The content of the monomer having a diacetone group in the diacetone-modified polyvinyl alcohol is not particularly limited, but is preferably about 0.5 to 10 mol% with respect to all the monomers in the diacetone-modified polyvinyl alcohol. Is about 1 to 7 mol%. When the content of the monomer having a diacetone group is less than 0.5 mol%, the water resistance of the protective layer may be reduced. When the content exceeds 10 mol%, not only the solubility in water is reduced, Water resistance as a protective layer may also be reduced due to a reduction in film forming properties.

[0013] The degree of polymerization and the degree of saponification of the diacetone-modified polyvinyl alcohol are not particularly limited.
The degree of polymerization is about 300 to 3000, preferably 4
It is adjusted at about 00 to 2000. The degree of saponification is preferably adjusted to 90% or more.

The vinyl ester used in the above copolymerization is not particularly limited, and vinyl acetate is industrially preferred. Further, the monomer having a diacetone group is not particularly limited, and examples thereof include diacetone acrylamide, diacetone acrylate, and diacetone methacrylate. Of these, diacetone acrylamide is preferred.

When the protective layer has a hydrazine compound as a water-proofing agent in the heat-sensitive recording layer, the protective layer contains a water-soluble acidic compound to increase the water resistance of the protective layer. More enhanced. The amount of the water-soluble acidic compound to be added is not particularly limited, but is preferably added so that the pH of the protective layer coating solution is 2 to 7. If the pH is less than 2, the coating liquid may abnormally thicken or fog may occur on the heat-sensitive recording layer. If the pH exceeds 7, the water resistance of the protective layer may be reduced, and the pH is more preferably 3 to 5.

The water-soluble acidic compound added to the protective layer is not particularly limited, but may be formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, oxalic acid, malonic acid,
Water-soluble organic acids having a carboxyl group such as succinic acid, glutaric acid, adipic acid, pimelic acid, fumaric acid, maleic acid, tartaric acid, citric acid, lactic acid, benzoic acid, phthalic acid and benzenetricarboxylic acid are preferred.

Specific examples of the carboxylic acid dihydrazide compound include, for example, adipic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, oxalic acid dihydrazide, malonic dihydrazide, succinic dihydrazide, glutaric dihydrazide, sebacide Maleic dihydrazide, fumaric dihydrazide, itaconic dihydrazide,
And polyacrylic hydrazide. They are,
It can be used alone or in combination. Of these, adipic dihydrazide is most preferred.

In the present invention, diacetone-modified polyvinyl alcohol is contained as an adhesive for the heat-sensitive recording layer or the protective layer. However, other adhesives may be used in combination as long as the effects of the present invention are not impaired. Examples of such adhesives include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, starch, oxidized starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, Casein, gum arabic, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, urea resin, melamine resin, An amide resin, an acrylic resin-based latex, a urethane resin-based latex, and the like can be given.

Examples of the thermal recording system having an electron donating compound and an electron accepting compound include, for example, a combination of a leuco dye and a color former, a combination of a diazonium salt and a coupler,
Examples include a combination of a chelating compound with a transition element such as iron, cobalt, and copper, and a combination of an aromatic isocyanate compound and an imino compound. A combination of a leuco dye and a color former is preferably used because of its excellent color density. . Hereinafter, the thermosensitive recording medium comprising a combination of a leuco dye and a color former will be described in detail.

Various known dyes can be used as the leuco dye and the color former. Specific examples of leuco dyes include:
For example, 3,3-bis (p-dimethylaminophenyl)-
6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (N-
Ethyl-Np-tolyl) amino-7-N-methylanilinofluoran, 3-cyclohexylamino-6-chlorofluoran, 3-diethylamino-6-methyl-7-
Chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3-di (n-
Butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-
Anilinofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3-di (nbutyl) amino-6-chloro-7-anilinofluoran, 3- Pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylamino Phenyl) ethylene-
2-yl] -4,5,6,7-tetrachlorophthalide,
3-p- (p-dimethylaminoanilino) anilino-6
-Methyl-7-chlorofluorane, 3-p- (p-chloroanilino) anilino-6-methyl-7-chlorofluoran, 3,6-bis (dimethylamino) fluorene-9
-Spiro-3 '-(6'-dimethylamino) phthalide and the like.

Of course, it is not limited to these,
Also, two or more kinds can be used in combination. Further, the amount of the leuco dye to be used cannot be limited because it differs depending on the coloring agent used, but it is about 5 to 35% by weight based on the heat-sensitive recording layer.

Examples of the coloring agent include 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenyl, 1,1-bis (4-hydroxyphenyl) -ethane, and 1,1-bis ( 4-hydroxyphenyl) -1-phenylethane, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 3,3'-diallyl-4, 4'-dihydroxydiphenyl sulfone, 2,2'-bis [4-
(4-hydroxyphenyl) phenoxy] diethyl ether, Np-toluenesulfonyl-N′-3- (p-
Toluenesulfonyloxy) phenylurea, benzyl 4-hydroxybenzoate, N, N'-di-m-
Chlorophenylthiourea, Np-tolylsulfonyl-
N′-phenylurea, 4,4′-bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane,
4- [2- (p-methoxyphenoxy) ethyloxy]
Zinc salicylate, 4- {3- (p-tolylsulfonyl)
Propyloxy] zinc salicylate, 5- [p- (2-p
-Methoxyphenoxyethoxy) cumyl] zinc salicylate;

The ratio of the leuco dye to the colorant is appropriately selected according to the type of the leuco dye and the colorant used, and is not particularly limited. 1 to 10 parts by weight, preferably 1 to
About 5 parts by weight of a coloring agent is used.

The heat-sensitive recording layer may contain a storability improving agent for improving the storage stability of the recording portion, and a sensitizer for improving the recording sensitivity. Specific examples of such a preservability improver include, for example, 2,2′-ethylidenebis (4,6-di-tert-butylphenol), 4,4′-
Thiobis (2-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-
Hindered phenol compounds such as tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, and 4,4′-diglycidyloxy Epoxy compounds such as diphenylsulfone, 4-benzyloxy-4 '-(2-methylglycidyloxy) diphenylsulfone, diglycidyl terephthalate, cresol novolak type epoxy resin, phenol novolak type epoxy resin, bisphenol A type epoxy resin, N, N '-
Di-2-naphthyl-p-phenylenediamine, bis (4
-Ethyleneiminocarbonylaminophenyl) methane and the like.

Specific examples of the sensitizer include, for example, stearic acid amide, methylenebisstearic acid amide, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl , P-tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,
2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-
Chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p −
Acetotoluidide, p-acetophenethidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, di-p-chlorobenzyl oxalate, di-p-methylbenzyl oxalate, di-oxalate Benzyl esters and the like are exemplified. The amounts of these preservatives and sensitizers are not particularly limited,
Generally, it is desirable to adjust the amount to 4 parts by weight or less with respect to 1 part by weight of the coloring agent.

The heat-sensitive recording layer is formed by using water as a dispersing medium, a leuco dye, a coloring agent, and if necessary, a sensitizer and a preservative improving agent together or separately, using a stirring / pulverizing machine such as a ball mill, an attritor or a sand mill. And then finely dispersed so as to have an average particle diameter of 2 μm or less, for example, a heat-sensitive recording layer coating prepared by adding diacetone-modified polyvinyl alcohol, a polyamidoamine / epichlorohydrin resin and a carboxylic acid dihydrazide compound as an adhesive. The solution is formed by applying and drying the liquid on one surface of the support.

Further, various auxiliaries can be added to the heat-sensitive recording layer coating liquid as needed, for example, kaolin,
Light (heavy) calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, amorphous silica, pigments such as urea / formalin resin filler, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate , Dispersants such as fatty acid metal salts, zinc stearate, calcium stearate, polyethylene wax,
Carnauba wax, paraffin wax, waxes such as ester wax, hydrazine-based compounds, glyoxal, boric acid, dialdehyde starch, methylol urea, water-proofing agents such as epoxy-based compounds, defoamers, coloring dyes and fluorescent dyes No.

The protective layer is a protective layer coating solution prepared by mixing and stirring an aqueous solution in which diacetone-modified polyvinyl alcohol is dissolved, a polyamidoamine / epichlorohydrin resin, and, if necessary, the following pigments and various auxiliaries. On the heat-sensitive recording layer and dried.

Examples of pigments include inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, amorphous silica, aluminum hydroxide, barium sulfate, talc, kaolin, clay, calcined kaolin, nylon resin filler, urea. Examples include organic pigments such as formalin resin fillers and raw starch particles. Among them, kaolin or aluminum hydroxide is preferably used because the barrier property against chemicals such as a plasticizer and an oil is hardly reduced and the recording density is hardly reduced. The amount of the pigment used is about 5 to 80% by weight based on the total solid content of the protective layer.

Auxiliaries that can be added to the coating liquid for the protective layer include, for example, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, sodium alkylbenzenesulfonate, sodium dioctylsulfosuccinate, Surfactants such as sulfone-modified polyvinyl alcohol and sodium polyacrylate, glyoxal,
Water-proofing agents such as boric acid, dialdehyde starch, methylol urea, epoxy compounds, and hydrazine compounds, and auxiliary agents such as ultraviolet absorbers, fluorescent dyes, coloring dyes, mold release agents, and antioxidants may also be added. it can.

The method of forming the protective layer and the heat-sensitive recording layer is not particularly limited, and may be, for example, an air knife coating, a variver blade coating, a pure blade coating, a rod blade coating, a short dwell coating, a curtain coating, a die coating or the like. After applying and drying the coating solution for the heat-sensitive recording layer on a support such as paper (acid paper, neutral paper), plastic film, synthetic paper, or non-woven fabric by a suitable coating method, the coating solution for the protective layer is further coated with the heat-sensitive recording layer. It is formed by a method such as coating and drying.

The coating amount of the heat-sensitive recording layer coating solution is 2% by dry weight.
１２12 g / m ² , preferably about 3 to 10 g / m ² , and the coating amount of the protective layer coating solution is 0.1 to 10 g / m ^{2 in} terms of dry weight.
Preferably it is about 0.5 to 6 g / m ² .

If necessary, a protective layer, a printed layer, a magnetic recording layer, or an ink jet recording layer may be provided on the back side of the support of the thermosensitive recording medium, or an organic or inorganic recording medium may be provided between the support and the thermosensitive recording layer. It is also possible to provide an undercoat layer containing an oil-absorbing pigment as a main component, or to apply a smoothing treatment such as super calendering after coating each layer. Further, various known techniques in the field of heat-sensitive recording material production, such as providing an adhesive layer on the back side of the support of the heat-sensitive recording material, can be added as necessary.

[0034]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted to such specific Examples. In the examples, "parts" and "%" indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Embodiment 1

Preparation of Coating Liquid for Undercoat Layer Composition comprising 100 parts of calcined clay (oil absorption: 110 ml / 100 g), 200 parts of a 10% aqueous solution of polyvinyl alcohol (degree of saponification 88%, degree of polymerization 1000) and 100 parts of water. Was mixed and stirred to obtain a coating liquid for an undercoat layer.

Preparation of Solution A A composition comprising 10 parts of 3-di- (n-butyl) amino-6-methyl-7-anilinofluoran, 5 parts of a 5% aqueous solution of methylcellulose and 15 parts of water was subjected to average particle size milling using a sand mill. The solution A was obtained by crushing until the diameter became 1.0 μm.

Preparation of Solution B A composition comprising 10 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose and 15 parts of water is pulverized by a sand mill until the average particle diameter becomes 1.0 μm. Liquid B was obtained.

Solution C Preparation A composition comprising 10 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose and 15 parts of water is pulverized by a sand mill until the average particle diameter becomes 1.0 μm. Thus, solution C was obtained.

Preparation of coating solution for heat-sensitive recording layer 25 parts of solution A, 50 parts of solution B, 50 parts of solution C, 150 parts of a 10% aqueous solution of polyvinyl alcohol (degree of saponification 99%, degree of polymerization 1000), solid concentration 50% 20 parts of styrene-butadiene latex and 20 parts of light calcium carbonate,
100 parts of a 5% aqueous solution of adipic dihydrazide was mixed and stirred to obtain a coating solution for a heat-sensitive recording layer.

Preparation of Coating Solution for Protective Layer A 10% aqueous solution of diacetone-modified polyvinyl alcohol [trade name: D-Polymer, D700, manufactured by Unitika Ltd.] 25
0 parts, kaolin (trade name: UW-90, manufactured by EC) 67
Part, polyamidoamine / epichlorohydrin [trade name:
WS-547, manufactured by Nippon PMC Co., Ltd.]
Of a 30% aqueous dispersion of zinc stearate and 150 parts of water were mixed and stirred, and adjusted to pH 4.8 with a 10% aqueous acetic acid solution to obtain a coating liquid for a protective layer.

Preparation of Thermosensitive Recording Material On a 60 g / m ² acidic high quality paper, the undercoat layer coating solution was applied and dried so that the coating amount after drying was 9 g / m ² to form an undercoat layer. The surface was smoothed with a super calender. The smoothing processing has been primed layer, the heat-sensitive recording layer by coating and drying as the coating amount after drying a thermal recording layer coating solution and protective layer coating solution is respectively ^{6g / m 2, 4g / m} 2 After sequentially forming a protective layer and the protective layer, the surface was smoothed with a super calender to obtain a thermosensitive recording medium.

Example 2 In the preparation of the coating solution for the protective layer in Example 1, the same aqueous solution of polyamidoamine / epichlorohydrin (trade name: WS-547, manufactured by Nippon PMC) was used instead of 20 parts of a 25% aqueous solution. 24 parts and a 5% aqueous solution of adipic dihydrazide 4
Parts, and in the preparation of the coating solution for the heat-sensitive recording layer, polyamidoamine / epichlorohydrin (trade name: WS-) was used instead of 100 parts of a 5% aqueous solution of adipic dihydrazide.
547, manufactured by Nippon PMC Co., Ltd.], except that 20 parts of a 25% aqueous solution was used.

Example 3 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, 1 part of polyvinyl alcohol (degree of saponification: 99%, degree of polymerization: 1000) was used.
Instead of 150 parts of a 0% aqueous solution, 150 parts of a 10% aqueous solution of diacetone-modified polyvinyl alcohol (trade name: D-Polymer, D700, manufactured by Unitika Ltd.) is used, and polyamidoamine is used instead of 100 parts of a 5% aqueous solution of adipic dihydrazide.・ Epichlorohydrin [Product name: WS-5
47, manufactured by Nippon PMC Co., Ltd.], except that 20 parts of a 25% aqueous solution was used.

Embodiment 4

Preparation of Coating Solution for Thermosensitive Recording Layer 25 parts of solution A, 50 parts of solution B, 50 parts of solution C, diacetone-modified polyvinyl alcohol [trade name: D-polymer, D70]
0, manufactured by Unitika Ltd.], 200 parts of a 10% aqueous solution, amorphous Rishika [trade name: Mizukasil P-527, manufactured by Mizusawa Chemical Industry Co., Ltd.] 15 parts, light calcium carbonate 10 parts, polyamidoamine epichlorohydrin [trade name] : WS-547, manufactured by Nippon PMC Co., Ltd.] and 4 parts of a 5% aqueous solution of adipic dihydrazide were mixed and stirred to obtain a coating solution for a heat-sensitive recording layer.

Preparation of thermosensitive recording medium The coating amount of the undercoat layer after drying was 9 g / m ² on a high-quality paper containing only 60 g / m ² neutral non-chlorine bleached pulp (ECF) as a main component. After coating and drying to form an undercoat layer, the surface was smoothed by a super calender. On the smoothing-treated undercoat layer, a heat-sensitive recording layer coating solution is applied and dried so that the coating amount after drying is 6 g / m ² to form a heat-sensitive recording layer, and then the surface is smoothed with a super calender. Thus, a thermosensitive recording medium was obtained.

Comparative Example 1 In the preparation of the coating solution for the protective layer in Example 1, completely saponified polyvinyl alcohol [trade name: PVA] was used instead of 250 parts of a 10% aqueous solution of diacetone-modified polyvinyl alcohol.
-117, manufactured by Kuraray Co., Ltd.] was used in the same manner as in Example 1 except for using 250 parts of a 10% aqueous solution.

Comparative Example 2 In the preparation of the coating solution for the protective layer in Example 1, a polyamide resin [polyamideamine epichlorohydrin (trade name: WS-547, manufactured by Nippon PMC) was used instead of 20 parts of a 25% aqueous solution. Product name: PA-801, manufactured by PMC Japan)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 25 parts of a 0% aqueous solution was used.

Comparative Example 3 Thermal recording was performed in the same manner as in Example 1 except that 3 parts of water was used instead of 3 parts of a 5% aqueous solution of adipic dihydrazide in the preparation of the coating solution for the thermal recording layer of Example 4. I got a body.

Comparative Example 4 In the preparation of the coating liquid for the protective layer of Example 1, acetoacetyl-modified polyvinyl alcohol [trade name: Gosefimer Z-200, Nippon Gohsei] was used instead of 250 parts of a 10% aqueous solution of diacetone-modified polyvinyl alcohol. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 250 parts of a 10% aqueous solution of Chemical Industry Co., Ltd. was used.

The following evaluation test was performed on the thus obtained heat-sensitive recording material, and the results are shown in Table 1.

[Coloring property] Thermal recording evaluation machine [Product name: TH]
-PMD, manufactured by Okura Electric Co., Ltd.] and applied energy:
Each thermosensitive recording medium was recorded at 0.35 mJ / dot, and the optical density (recording density) of the recording section was measured using a Macbeth densitometer [RD-9].
14 type, manufactured by Macbeth Co.] in the visual mode. The unrecorded portion was measured in the Macbeth densitometer in a blue filter mode.

[Water resistance] One drop (approximately 30 μl) of water was dropped on the protective layer surface of a 5 cm × 5 cm heat-sensitive recording material, and another heat-sensitive recording material was overlaid thereon so that the protective layer surfaces were in contact with each other, and allowed to dry naturally. Thereafter, when the heat-sensitive recording material was peeled off from the heat-sensitive recording material by hand, the surface water resistance was evaluated as follows, based on the degree of sticking between the protective layers. (Evaluation criteria) ：: The protective layer surfaces naturally separate from each other. ：: The protective layer surfaces adhere to each other, but the thermal recording media easily peeled off from each other, and there was no peeling of the protective layer surface. Δ: The protective layer surfaces adhere to each other, the heat-sensitive recording media are hardly peeled off, and the protective layer surface is peeled. ×: The protective layer surfaces adhere to each other, the thermal recording media do not peel off, and the thermal recording media are broken.

[Plasticizer Resistance] The heat-sensitive recording materials of Examples 1 to 3 and Comparative Examples 1 to 3 were wrapped on a polycarbonate pipe (40 mm in diameter) on a wrap film (trade name: High Wrap SAS, manufactured by Mitsui Chemicals, Inc.). Is wound three times, the thermal recording medium after recording in the measurement of recording density is placed thereon, and a wrap film is further wound three times thereon,
After standing at 0 ° C. for 24 hours, the optical density of the recording portion was measured with the above-mentioned Macbeth densitometer to evaluate the plasticizer resistance.

[Yellowing Resistance] A thermosensitive recording medium was heated at 50 ° C. and 95%
After standing for 24 hours under the condition of RH, the degree of yellowing of the unrecorded portion was measured by the Macbeth densitometer in the blue filter mode. The smaller the value, the better the yellowing resistance.

[0057]

[Table 1]

[0058]

As shown in [Table 1], the heat-sensitive recording material of the present invention has excellent coloring properties, water resistance, plasticizer resistance, and oil resistance, as well as yellowing resistance in unrecorded areas. Also have excellent effects.

Claims (4)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer containing an electron-donating compound, an electron-accepting compound and an aqueous adhesive on a support, wherein the aqueous adhesive in the heat-sensitive recording layer is diacetone-modified polyvinyl alcohol. And a thermosensitive recording medium characterized in that the thermosensitive recording layer contains a polyamidoamine / epichlorohydrin resin and a carboxylic acid dihydrazide compound. 2. A thermosensitive recording medium having a thermosensitive recording layer containing an electron-donating compound, an electron-accepting compound and an aqueous adhesive, and a protective layer containing an aqueous adhesive sequentially on a support. Wherein the aqueous adhesive is diacetone-modified polyvinyl alcohol, and the protective layer contains a polyamidoamine / epichlorohydrin resin. 3. The heat-sensitive recording material according to claim 2, wherein a carboxylic acid dihydrazide compound is contained in at least one of the heat-sensitive recording layer and the protective layer. 4. The thermosensitive recording medium according to claim 2, wherein the aqueous adhesive in the thermosensitive recording layer is diacetone-modified polyvinyl alcohol.