JP3301640B2 - Thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium. More specifically, the present invention relates to a heat-sensitive recording material which is free from background fog and sensitivity, has excellent storage stability, has a high glossiness, and has a high quality feel.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive recording medium for obtaining a recorded image by reacting a colorless or light-colored basic dye with an organic or inorganic colorant by heat is relatively inexpensive, and the apparatus is compact and maintenance-free. Therefore, in the field of facsimile and printers in recent years, the demand for thermal recording media such as POS labels, overhead projectors (OHP), second original drawings such as design drawings, cards and the like has been expanding.

[0003] However, these heat-sensitive recording media have problems in storage stability (especially, fading of a color-developed image by a plasticizer, oil, and water), and also have disadvantages such as background fog. As a method to solve this problem, a method of providing a radiation-curable resin layer on the heat-sensitive layer (Japanese Patent Publication No. 58-35478) and a method of providing a radiation-curable resin layer on the heat-sensitive layer via an intermediate layer are proposed. (JP-A-59-26291).

[0004]

In the above-described method of providing a radiation-curable resin layer on a heat-sensitive layer, the radiation-curable resin or a commonly used diluting solvent is used for coating the heat-sensitive layer. , And it was not practical.
Also, the method of providing a radiation-curable resin layer on the heat-sensitive layer with an intermediate layer interposed therebetween has not been able to provide satisfactory background fogging and storage stability. Further, in order to increase the commercial value of the thermal recording medium, high glossiness is required in the market.However, in order to obtain a high glossy thermal recording body, the barrier property of the intermediate layer becomes a problem. It was not enough.

[0005] Radiation-curable resins are used in many fields because of their simple curing equipment and good productivity. However, radiation-curable resins are reactive diluents due to handling and coating problems. And an organic solvent must be used in many cases, and the composition has problems in workability and safety in terms of skin irritation, odor, and toxicity. As a means for solving the problem, there is an emulsion of a radiation-curable resin, and the present inventors disperse / emulsify a composition mainly composed of a UV or EB-curable resin in water to form an emulsion of a heat-sensitive layer. An application has been filed for a thermosensitive recording medium overcoated thereon. When an emulsion obtained by dispersing and emulsifying a composition containing such a radiation-curable resin as a main component in water is used as the overcoat layer, the penetration into the heat-sensitive layer and the intermediate layer is particularly large. There were problems with both fogging and storage stability. Further, the conventional method has not been practical for obtaining a high-gloss, high-grade thermal recording medium.

In recent years, with the diversification of thermal recording methods and higher performance, hardware such as thermal printers and facsimile machines have been remarkably advanced, and in the case of high-speed printing and printing with a video printer, the intermediate layer and overcoat layer are required. Even if it is provided, it has problems such as adhesion of debris to the thermal head and generation of sound during printing (sticking noise),
No good thermal recording medium has been obtained. In addition, there is also a problem that the sensitivity of the thermosensitive recording medium is lowered due to the penetration of the intermediate layer and the overcoat layer, and development of an intermediate layer having excellent barrier properties has been desired. In any case, the object of obtaining a heat-sensitive recording material which is free from background fogging and sensitivity reduction, has excellent storage stability, and has a high gloss and a high-grade feel has not yet been achieved.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, completed the present invention. That is, the present invention provides (1) a heat-sensitive recording layer containing a colorless or pale-colored basic dye and a colorant capable of causing the basic dye to develop color when heated on a support; An intermediate layer having a 60-degree specular gloss of 6 or more, which is formed by a paint containing a molecular compound emulsion and / or a mixture of a water-soluble polymer compound and a water-proofing agent as a resin component;
-A hydrophobic polymer compound emulsion which is a copolymer of ethylhexyl acrylate / methyl methacrylate,
It is formed by a paint mainly containing a mixture of an epoxy compound and a water-soluble polymer compound which is an ammonium salt of a copolymer of isobutylene / maleic anhydride / N-phenylmaleimide. An object of the present invention is to provide a heat-sensitive recording body, characterized by having an overcoat layer formed by an emulsion obtained by dispersing and emulsifying a composition mainly composed of a curable resin in water.

The heat-sensitive recording material of the present invention is characterized in that it has no background fogging or a decrease in sensitivity, has excellent storage stability, and has particularly high gloss and high-grade feel. The colorless or light-colored basic dye and colorant used in the heat-sensitive recording layer in the present invention are not particularly limited, and those known per se can be used, and on a support using a usual binder. Coated. or,
If necessary, a sensitizer and other additives can be mixed.

Examples of the basic dye include fluoran compounds, triarylmethane compounds, spiropyran compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds and the like. Examples thereof include the following compounds.

Fluoran compounds; 2-anilino-3-
Methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6- (N-methyl-N-cyclohexylamino) -fluoran, 2-anilino-3-methyl-6
-(N-ethyl-N-isopentylamino) fluoran, 2-anilino-3-methyl-6-dibutylaminofluoran, 2- (p-chloroanilino) -3-methyl-
6-diethylaminofluoran, 2- (p-fluoroanilino) -3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6- (p-toluidinoethylamino) fluoran, 2- ( p-toluidino)-
3-methyl-6-diethylaminofluoran, 2- (o
-Chloroanilino) -6-dibutylaminofluoran,
2- (o-fluoroanilino-6-diethylaminofluoran, 2- (o-fluoroanilino) -6-dibutylaminofluoran, 2-anilino-3-methyl-6-piperidinofluoran, 2- Anilino-3-methyl-6
Pyrrolidinofluoran, 2-ethoxyethylamino-3
-Chloro-6-diethylaminofluoran, 2-anilino-3-chloro-6-diethylfluoran, 2-chloro-6-diethylaminofluoran, 2-methyl-6-diethylaminofluoran, 2-anilino-3-methyl −
6-dipentylaminofluoran, 2-anilino-3-
Triarylmethane compounds such as methyl-6- (N-ethyl-N-ethoxypropylamino) fluoran; 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (alias: crystal violet lactone) , 3,3-
Bis (p-dimethylaminophenyl) phthalide, 3-
(P-dimethylaminophenyl) -3- (1,2-dimethylaminoindole-3-isophthalide and the like,

Spiropyran compound; 3-methyl-3-
Spiro-dinaphthopyran, 1,3,3-trimethyl-6
-Nitro-8'-methoxyspiro (indoline-2,
2'-benzopyran); diphenylmethane compounds; N-halophenyl-leuco auramine; thiazine compounds; benzoyl leucomethylene blue; lactam compounds; rhodamine-B-anilinolactam; Bis (dimethylamino)
Fluorene spiro (9,3 ')-6'-dimethylaminophthalide, [3,6-bis (dimethylamino) fluorene spiro (9,3')-6'-pyrrolidinophthalide],
[3-dimethylamino-6-diethylaminofluorenespiro (9,3 ')-6'-pyrrolidinophthalide] and the like. These basic dyes can be used alone or in combination.

Examples of colorants include p-octylphenol, p-tert-butylphenol, 2,2-bis (p-hydroxyphenyl) propane, 1,1-bis-
(P-hydroxyphenyl) cyclohexane, 4,4'-
Thiobisphenol, 4,4′-sulfonyldiphenol, bis- (3-allyl-4-hydroxyphenyl) sulfone, novolak-type phenol resin, benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate,
Dimethyl-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 1,
7-di (hydroxyphenylthio) -3,5-dioxaheptane, 4-isopropoxy-4′-hydroxydiphenylsulfone, methyl bis (4-hydroxyphenyl) acetate, butyl bis (4-hydroxyphenyl) acetate,
Benzyl (bis (4-hydroxyphenyl) acetate) and aromatic carboxylic acids include polyvalent metal salts thereof. These colorants can be used alone or in combination.

The binder as a component forming the heat-sensitive recording layer includes methyl cellulose, methoxy cellulose,
Hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, silica-modified polyvinyl alcohol, alkali salts of styrene acrylate copolymer, polyvinyl pyrrolidone,
Water-soluble materials such as polyacrylamide, polyacrylic acid, starch and derivatives thereof, casein, gelatin, alkali salts of styrene / maleic anhydride copolymer, and alkali salts of iso (or diiso) butylene / maleic anhydride copolymer Or a water-insoluble emulsion such as polyvinyl acetate, a vinyl chloride-vinyl acetate copolymer, polystyrene, a styrene-butadiene-acrylic acid copolymer, or the like.

Examples of the filler include calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay, alumina, magnesium hydroxide, aluminum oxide, barium sulfate, polystyrene resin and urea-formalin resin. . Examples of sensitizers include waxes such as animal and vegetable waxes, polyethylene waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid metal salts, acetyl compounds of aromatic amines, aromatic ether compounds, and biphenyl derivatives. Those which are solid at ordinary temperature and have a melting point of about 80 ° C. or more are exemplified. Other additives include lubricants such as zinc stearate, calcium stearate, and aluminum stearate, and various other surfactants, defoamers, and the like can be added as necessary.

As a method for forming a heat-sensitive recording layer using the above-mentioned materials, a basic dye and a colorant are separately added to a binder, water or other additives as necessary, and a protective colloid such as polyvinyl alcohol. After pulverizing and dispersing with a dispersing machine such as a ball mill, an attritor, or a sand mill together with the substance and the surfactant (usually, the basic dye or colorant is 5 to 70% of the system to be dispersed, and the binder is 5 to 5%). ５０50%, water is 30９０90%, pulverization and dispersion are carried out), and each is mixed to prepare a coating solution for the heat-sensitive recording layer (the ratio of the basic dye to the colorant is usually dry weight). In a ratio of 1: 1 to 1:10), a coating liquid on a support such as paper, plastic sheet, or synthetic paper in an amount of 5 to 40 g / m ^2.
Thus, a heat-sensitive recording layer can be obtained by coating with a bar coater, an air knife coater, a gravure coater, a roll coater or the like and drying.

On the heat-sensitive recording layer, there is provided an intermediate layer formed of a hydrophobic polymer compound emulsion, a mixture of a water-soluble polymer compound and a water-proofing agent alone or in combination. Examples of the water-soluble polymer compound include methylcellulose, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, silica-modified polyvinyl alcohol, and alkali of acrylic acid / styrene copolymer. Salt, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch and derivatives thereof, casein, gelatin, styrene-
Examples thereof include an alkali salt or an ammonium salt of a maleic anhydride copolymer, and an alkali salt or an ammonium salt of an iso (or diiso) butylene-maleic anhydride copolymer.
It also includes a semi-water-soluble self-emulsifying emulsion obtained by providing a large number of hydrophilic groups such as a hydroxyl group and a carboxyl group in a molecule with a hydrophobic polymer compound. Examples of the hydrophobic polymer compound emulsion include polystyrene, polyester, polyacrylate, polyurethane, styrene / butadiene copolymer, styrene / acrylate copolymer, styrene / butadiene / acrylate copolymer, and styrene. Emulsions such as acrylonitrile / butadiene copolymer and ethylene / acrylic acid copolymer. Further, those described in the above (2) are particularly preferable.

When these water-soluble polymer compounds and self-emulsifying emulsions are used for the coating for the intermediate layer, they are used to prevent background fogging at the time of coating the overcoat layer and to improve the preservability of the obtained heat-sensitive recording material. For example, glyoxal, methylolmelamine, water-soluble epoxy compounds and the like are required. Specific examples of the water-soluble epoxy compound include ethylene polyethylene glycol diglycidyl ether, propylene polypropylene glycol diglycidyl ether, glycerol polyglycidyl ether, lauryl alcohol glycidyl ether, and the like. The amount of the water-proofing agent is usually 0.5 to 50% by weight, more preferably 1 to 30% by weight, based on the amount of the water-soluble polymer compound.

In the intermediate layer paint, a benzophenone-based or triazole-based ultraviolet absorber, an antifoaming agent, a fluorescent dye,
Coloring dyes can be added as needed. Hydrophobic polymer compound emulsion, an intermediate layer paint alone or in combination of a mixture of a water-soluble polymer compound and a waterproofing agent,
After adding water and the like as needed, and thoroughly mixing with a general mixing and stirring machine such as a mixer, attritor, sand mill, etc., heat-sensitive recording is performed with various known coating devices such as a bar coater, a roll coater, a gravure coater, and an air knife coater. Coated on the layer and dried. If the coating amount of the intermediate layer is less than 0.1 g / m ² , the resulting heat-sensitive recording medium has insufficient storage stability, and if it exceeds 20 g / m ² , the sensitivity may be significantly reduced. 0.1 ~
20 g / m ^2, more preferably from 0.5 to 10 g / m ^2. In the thermosensitive recording medium of the present invention, the gloss of the intermediate layer thus obtained is extremely important. According to the method described in JIS Z8741, when the specular gloss at 60 ° (60 ° specular gloss) is less than 6, the barrier property of the intermediate layer is not sufficient, so that the background fog easily occurs. No heat-sensitive recording medium having high gloss can be obtained after it is provided. In addition, it may cause a decrease in storage stability. Therefore, the solid content of the coating for the intermediate layer is adjusted so that the 60-degree specular gloss of the intermediate layer is 6 or more. Further, if necessary, a calendering process is performed after the formation of the intermediate layer. In the thermosensitive recording medium of the present invention, an overcoat layer mainly composed of a radiation-curable resin is provided on the thus formed intermediate layer having a gloss of 6 or more.

The radiation-curable resin used in the overcoat layer includes the following prepolymers and monomers. Epoxy (meta) as the prepolymer
Acrylate, urethane (meth) acrylate, saturated polyester / styrene, polyethylene (meth) acrylate, polyether (meth) acrylate, silicon (meth) acrylate, polybutadiene (meth) acrylate, polyene / thiol, polystyrylethyl (meth) acrylate, Polyamide (meth) acrylate and the like can be mentioned. As monomers, styrene, vinyl acetate, vinyl monomers such as N-vinylpyrrolidone, butyl acrylate, 2-ethylhexyl acrylate,
monofunctional monomers such as n-hexyl acrylate, cyclohexyl acrylate, n-decyl acrylate isobornyl acrylate, dicyclopentenyloxyethyl acrylate, and phenoxyethyl acrylate;
4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol 400 diacrylate, tripropylene glycol diacrylate, bisphenol A diethoxy diacrylate, tetraethylene glycol diacrylate , Neopentyl glycol dihydroxypivalate diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate,
Examples include polyfunctional monomers such as pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate.

In addition, acetophenone, a photoinitiator usually required when an ultraviolet curing method is used,
Benzophenone, benzoin ether, chloroacetophenone, diethoxyacetophenone, hydroxyacetophenone, α-aminoacetophenone, benzylmethylketal, thioxanthone, α-acyloxime ester, acylphosphine oxide, glyoxyester, 3-ketocoumarin, 2-ethylanthraquinone, Examples thereof include camphorquinone, benzyl, and Michler's ketone, and these photoinitiators can be used in the present invention.

The overcoat paint of the present invention is an emulsion obtained by dispersing and emulsifying a composition mainly containing a radiation-curable resin in water. Examples of the dispersing / emulsifying agent that can be used in the present invention include polyoxyethylene alkyl ether, polyoxyethylene alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene derivative, oxyethylene / oxypropylene block copolymer, polyoxyethylene sorbitan fatty acid ester,
Nonionic surfactants such as polyethylene glycol fatty acid esters, fatty acid salts, alkyl sulfate salts, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, alkyl phosphates, polyoxyethylene General dispersing and emulsifying agents for anionic surfactants such as alkyl sulfate salts, naphthalenesulfonic acid formalin condensates, special polycarboxylic acid type polymer surfactants, and polyoxyethylene alkyl phosphates, and ethylene in the molecule Examples include reactive emulsifiers having a functional unsaturated group, etc., and select one or several types depending on the type of radiation-curable resin to be used, and if necessary, mix and use with an emulsifying dispersant other than the above. Can also. The amount of the dispersant / emulsifier used is usually in the range of 0.5 to 30% by weight, more preferably 1 to 20% by weight, based on the total solid content of the overcoat liquid.

Before dispersion and emulsification of a composition containing a radiation-curable resin as a main component, particularly in order to prevent sticking to the head and sticking during high-speed printing, a filler is added to the radiation-curable resin beforehand. Can be dispersed. Examples of the filler include inorganic fillers such as aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, aluminum oxide, silicon dioxide, titanium dioxide, talc, clay, kaolin, colloidal silica, metal powder and the like. Filler surface-treated filler, styrene microballs, polyethylene powder, tetrabromobisphenol A, decabromodiphenyl oxide, tricresyl phosphate, triethyl phosphate, tetrafluoride resin, aromatic polyester, aspartate derivative, zinc stearate, Organic fillers such as stearic acid amide and polyethylene wax are exemplified. These can be dispersed using a known dispersing machine such as a ball mill, a roll mill, and a sand mill.

In addition to these fillers, lubricants such as phosphate ester compounds and polyethylene wax, and reactive silicone compounds such as radical-reactive silicone macromers and siloxane modified with a hydroxyl-terminated polyester can also be added. Further, these overcoat paints may contain, if necessary, reactive silicone compounds, lubricants, polymers, leveling agents, defoamers, ultraviolet absorbers,
Additives such as a fluorescent dye, a fluorescent pigment, a coloring dye, and a coloring pigment can be appropriately used.

The method of dispersing and emulsifying the composition containing a radiation-curable resin as a main component is performed by a generally known method such as a high-speed stirrer such as a homomixer or a sand mill, or a microfluidizer.

The thus-obtained overcoat paint is diluted with a solvent or water as required, and is coated by a bar coater, an air knife coater, a gravure coater, offset printing, flexographic printing, screen printing, or the like. The overcoat layer can be formed by coating and drying the layer and irradiating ultraviolet rays or electron beams to cure the coating. The coating amount of the overcoat layer is not particularly limited, but the dry weight is 0.2 g / m2.
^If it is less than ² , it is difficult to achieve the object of the present invention, and if it is more than 20 g / m ² , the recording sensitivity of the thermosensitive recording medium may be reduced.
m ² , more preferably in the range of 0.5 to 10 g / m ² . In this case, when curing with an electron beam, an electron beam accelerator having an energy of 100 to 500 eV is preferable. On the other hand, when curing can be performed by ultraviolet rays, a xenon lamp, a high-pressure mercury lamp, or an ultraviolet irradiation device having a metal halide lamp is used as a light source, and the amount of light and the arrangement of the light source are determined as necessary. Transport speed of 20 to 60 m / min by a lamp having a light amount of up to 120 W / cm;
It is preferable to cure by irradiation four times.

[0026]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. still,
In the examples, parts mean parts by weight.

Example 1 Formation of heat-sensitive recording layer [A] solution: 2- (o-fluoroanilino) -6-diethylamino 25 parts fluoran 25% PVA aqueous solution 20 water 55〃 [B] solution: bis (3- Allyl-4-hydroxyphenyl) sulfone 25 parts 25% PVA aqueous solution 20〃 Calcium carbonate 15〃 Water 40 を Each of the above compositions is separately pulverized using a sand grinder so that the average particle diameter becomes 1 to 3 μm. Decentralized.

Next, 10 parts of the liquid [A], 20 parts of the liquid [B],
Hydrous carboxylated SB latex copolymer (solid content =
50%) 20 parts of water and 50 parts of water were mixed to prepare a coating solution for the heat-sensitive recording layer, and a dry coating amount of about 5 g / m.
² become as a coating and dried to obtain heat-sensitive recording sheet. Formation of intermediate layer Styrene / methyl methacrylate / 2-ethylhexyl acrylate copolymer emulsion (solid content 45%) 18 parts Ammonia salt aqueous solution of copolymer of isobutylene / maleic anhydride / N-phenylmaleimide (solid content 30%) 27） polyethylene Glycol diglycidyl ether 1 {water 54} The above composition was mixed to prepare a coating solution for the intermediate layer.
/ M ² and dried to obtain a thermosensitive recording sheet having an intermediate layer. The 60-degree specular gloss at this time was 38.

Formation of Overcoat Layer Dipentaerythritol hexaacrylate 25 parts Trimethylolpropane triacrylate 7 {Tripropylene glycol diacrylate 8} Photoinitiator (Irgacure 184; Ciba-Geigy) 5} Pluronic F-108 (Asahi Denka Kogyo) 5〃 Water 50〃 The above compounds are mixed, emulsified and dispersed to prepare a paint of an oil-in-water type radiation-curable resin emulsion composition, and on a heat-sensitive sheet having an intermediate layer obtained by After coating and drying with a bar coater so that the dry coating amount becomes 3 g / m ² , the conveyor speed is 40 m / min using an ultraviolet irradiation device (GS ASE-20; manufactured by Nippon Battery) having a high-pressure mercury lamp of 80 W / cm. And cured twice to obtain a thermosensitive recording medium of the present invention. 60 of this one
The degree of specular gloss was 88.

Reference Example 1 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the intermediate layer was prepared by mixing the following composition in the intermediate layer. Styrene / methyl methacrylate / 2-ethylhexyl acrylate copolymer emulsion (solid content 45%) 45 parts Water 55〃

Reference Example 2 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that an intermediate layer paint obtained by mixing the following composition in the intermediate layer was used. Ethylene / acrylic acid copolymer emulsion (solid content 30%) 70 parts Water 30cm

Reference Example 3 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that an intermediate layer paint obtained by mixing the following composition in the intermediate layer was used. Styrene / methyl methacrylate copolymer emulsion (solid content 40%) 15 parts Polyvinyl alcohol aqueous solution (solid content 30%) 80〃 Glyoxal 1〃 Water 4〃

Reference Example 4 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that an intermediate layer paint obtained by mixing the following composition in the intermediate layer was used. Ethyl acrylate / 2 ethylhexyl acrylate copolymer emulsion (solid content 40%) 25 parts Water 75

Comparative Example 1 A comparative thermosensitive recording medium was obtained in the same manner as in Example 1 except that an intermediate layer paint obtained by mixing the following composition in the intermediate layer was used. Polyvinyl alcohol aqueous solution (solid content 30%) 30 parts Water 70〃

Comparative Example 2 A heat-sensitive recording medium for comparison was obtained in the same manner as in Example 1 except that the intermediate layer was prepared by mixing the following composition in the intermediate layer. Ethyl acrylate / methyl methacrylate copolymer emulsion (solid content 40%) 85 parts Water 15〃

Comparative Example 3 A comparative thermosensitive recording medium was obtained in the same manner as in Example 1 except that the intermediate layer was prepared by mixing the following composition in the intermediate layer. Styrene / methyl methacrylate copolymer emulsion (solid content 40%) 40 parts Water 60〃

Table 1 shows the results of evaluation using each of the thus-obtained thermosensitive recording media. The color density, water resistance, and plasticizer resistance were evaluated by printing with a dot line type thermal printer (Matsushita test printer) having a resistance value of 325Ω. The following evaluation criteria were used.

[0038]

[Table 1] Table 1 Evaluation results Intermediate layer gloss Thermal recording medium gloss Background coloring density Water resistance Plasticizer resistance Example 1 3888 ○ ○ ○ ○ Reference Example 1 28 86 ○ ○ ○ ○ Reference Example 2 2786 ○ ○ ○ ○ Reference Example 3 784 ○ ○ ○ ○ Reference Example 4 1 282 ○ ○ ○ ○ Comparative Example 1 2047 × × × × 〃 2552 × × × × 〃 3218 × × × ×

(1) Gloss 60 degree specular gloss according to JIS Z8741. For the measurement, a gloss checker IG-320 (manufactured by Horiba, Ltd.) was used. Intermediate layer gloss: Gloss after forming intermediate layer Thermal recording medium gloss: Gloss after overcoating (2) Background ○: Good without background fog ×: Background fog (3) Color density ○: Printing Good color development of the part X: Insufficient color development of the printed part (4) Water resistance test ○: Almost no fading of the color-developed part even when the thermosensitive recording medium colored as described above is immersed in water at 20 ° C for 24 hours. Was. C: The color-developed part faded when the thermosensitive recording medium colored as described above was immersed in water at 20 ° C. for 24 hours. (5) Plasticizer resistance test ；: A plasticizer (D
Even when OP) was dropped, there was almost no fading of the color-developed portion. ×: A plasticizer (D) was placed on the heat-sensitive recording material colored as described above.
When OP) was dropped, discoloration of the color-developed portion was observed.

[0040]

According to the present invention, the intermediate layer is formed of a paint containing a hydrophobic polymer emulsion and / or a mixture of a water-soluble polymer compound and a water-proofing agent as a resin component, and has a 60-degree specular gloss of 6 or more. By providing an intermediate layer, even when using an overcoat paint of an emulsion obtained by dispersing and emulsifying a composition containing a radiation-curable resin as a main component in water, there is no background fogging or reduction in sensitivity, and excellent storage stability. A high-gloss, high-grade thermal recording medium was obtained.

Continuation of the front page (56) References JP-A-4-303677 (JP, A) JP-A-63-99984 (JP, A) JP-A-62-279980 (JP, A) JP-A-4-22677 (JP) JP-A-1-247192 (JP, A) JP-A-1-215578 (JP, A) JP-A-4-329180 (JP, A) JP-A-59-26291 (JP, A) 6-286321 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41M 5/28-5/34

Claims (1)

(57) [Claims] 1. A heat-sensitive recording layer containing a colorless or pale-colored basic dye and a colorant for causing the basic dye to develop color when heated is provided on a support, and a hydrophobic polymer compound emulsion is provided on the heat-sensitive recording layer. And / or an intermediate layer formed of a paint containing a mixture of a water-soluble polymer compound and a water-proofing agent as a resin component and having a 60-degree specular gloss of 6 or more, wherein the intermediate layer is styrene-2-ethylhexyl acrylate. The main component is a mixture of a hydrophobic polymer compound emulsion that is a copolymer of methyl methacrylate and a water-soluble polymer compound that is an ammonium salt of a copolymer of isobutylene, maleic anhydride, and N-phenylmaleimide, and an epoxy compound. An emulsion obtained by dispersing and emulsifying a composition containing a radiation-curable resin as a main component on water on the intermediate layer. Thermosensitive recording material characterized by providing an overcoat layer formed me.