JPH058542A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide an overcoat type thermal recording material having excellent printability and excellent in preservability such as solvent resistance, oil resistance or plasticizer resistance and recording running properties. CONSTITUTION:In a thermal recording material wherein a recording layer containing at least a color former and a developer is provided on a support and an overcoat layer is further provided on the recording layer, at least a polyurethane ionomer and polyvinyl alcohol with a saponification value of 85% or more are added to the overcoat 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, and more particularly to a heat-sensitive recording material having excellent storability of recorded images and recording runnability and good printability.

[0002]

2. Description of the Related Art Utilizing a color reaction between a color former and a color former,
A heat-sensitive recording material in which both substances are reacted by heat to obtain a recorded image is well known. Since such a thermosensitive recording medium is relatively inexpensive and the recording device is compact and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

For example, as one of the fields of use thereof, cases of being used for POS (point of sales) labels in retail stores are increasing. However, a thermal recording material using a combination of a colorless or light-colored basic dye and an acidic substance in the coloring system has a problem in fingerprint resistance, solvent resistance, etc., and human skin oil or solvent may contact the recording layer. Then, there are drawbacks that the recording density is lowered and unnecessary coloration called background fog occurs. In addition, when a thermal label composed of such a coloring system is applied to a POS system such as a supermarket, the label often comes into contact with water, wraps, oil, etc., and as a result, the thermal label is recorded. Defects in which the image (print) fades are observed. Therefore, the thermal recording material is required to have storage stability such as water resistance, plasticizer resistance, and oil resistance.

Recently, it has become popular to print on a thermosensitive recording medium by a method such as letterpress, gravure, offset or the like, and a performance excellent in printability is required. Conventionally, in order to improve the storability of a recorded image, a method of coating an aqueous emulsion of a resin having film forming ability and chemical resistance on a thermosensitive recording layer (JP-A-55-128).
No. 347) and a method of applying a water-soluble polymer compound such as polyvinyl alcohol (Japanese Utility Model Publication No. 56-125354). However, the conventionally proposed methods are accompanied by new defects such as a decrease in recording runnability accompanying the improvement, the effect of improving the storage stability is not always sufficient, and the printability is insufficient. Met.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and provides a heat-sensitive recording material having excellent recording runnability and storability and excellent printability. .

[0006]

SUMMARY OF THE INVENTION The present invention comprises:
A heat-sensitive recording material comprising a recording layer containing at least a color-forming agent and a color-forming agent, and further comprising an overcoat layer on the recording layer, wherein the saponification degree of at least the polyurethane ionomer and the saponification degree is 85% or more in the overcoat layer. A heat-sensitive recording material characterized by containing polyvinyl alcohol.

[0007]

In the present invention, the color-forming system constituting the heat-sensitive recording layer is not particularly limited, and any combination that causes a color reaction by heat energy from the heat-sensitive head can be used. Combination of light-colored basic dye and inorganic or organic acidic substance, combination of higher fatty acid metal salt such as ferric stearate and phenols such as gallic acid, diazonium compound, coupler compound and base at the time of heat melting Examples include combinations of compounds exhibiting a sexual atmosphere. But,
The overcoat layer of the present invention is particularly preferable when it is applied to a color-developing system in which a basic dye and an acidic substance are combined, because the characteristics of the overcoat layer are fully exhibited and a heat-sensitive recording material having extremely excellent recording suitability is obtained. Various types of such colorless to light-colored basic dyes are known,
For example, the following is exemplified.

3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p
-Dimethylaminophenyl) phthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2)
-Methylphenyl) -6-dimethylaminophthalide, 3
-(P-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3 , 3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole-3-)
Yl) -6-Dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6 -Dimethylaminophthalide, 3-
(P-Dimethylaminophenyl) -3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 3
-(P-dibenzylaminophenyl) -3- (1,2-
Dimethylindol-3-yl) -7-azaphthalide,
3- (4-diethylamino-2-ethoxyphenyl)-
3- (1-ethyl-2-methylindol-3-yl)
-7-azaphthalide, 3,3-bis (1-ethyl-2-
Methylindol-3-yl) phthalide, N-butyl-
Triarylmethane dyes such as 3- {bis [4- (N-methylanilino) phenyl] methyl} carbazole,
4,4'-bis (dimethylamino) benzhydryl benzyl ether, N-halophenyl-leuco auramine,
Diphenylmethane dyes such as N-2,4,5-trichlorophenyl leuco auramine and 4,4'-bis (dimethylamino) benzhydryl-p-toluenesulfinic acid ester, 3,3-bis [1,1-bis ( 4-Pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7
-Tetrabromophthalide, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2
-Yl] -divinylphthalide dye such as 4,5,6,7-tetrachlorophthalide, 3,7-bis (diethylamino) -10-benzoylphenoxazine, benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue, etc. Thiazine dyes, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-
Phenylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho (6′-methoxybenzo) spiropyran, 3-propylspirodibenzopyran, di-β-naphthospiropyran, 3-methyl-di-β
-Spiro dyes such as naphthospiropyran, rhodamine-
Lactam dyes such as B-anilinolactam, rhodamine (p-nitroanilino) lactam and rhodamine (o-chloroanilino) lactam, 3-diethylamino-6-methylfluorane, 3-dimethylamino-7-methoxyfluorane, 3- Diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3
-Diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N
-Ethyl-p-toluidino) -7-methylfluorane,
3-diethylamino-7- (N-acetyl-N-methylamino) fluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-
(N-methyl-N-benzylamino) fluorane, 3-
Diethylamino-7- (N-β-chloroethyl-N-methylamino) fluorane, 3-diethylamino-7-diethylaminofluorane, 4-benzylamino-8-diethylaminobenzo [a] fluorane, 3- [4- (4
-Dimethylaminoanilino) anilino] -7-chloro-
6-methylfluorane, 8- [4- (4-dimethylaminoanilino) anilino] benzo [a] fluorane, 3-
(N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3-dimethylamino -6-Methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-
7-phenylaminofluorane, 3-dibutylamino-
6-methyl-7-phenylaminofluorane, 3-dipentylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7- (2-carbomethoxy-phenylamino) fluorane, 3- (N-ethyl) -N
-Isoamylamino) -6-methyl-7-phenylaminofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7- Phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7
-(O-chlorophenylamino) fluorane, 3-dibutylamino-7- (o-chlorophenylamino) fluorane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-phenylaminofluorane, 3- (N-methyl-N-propylamino) -6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3- (N-ethyl-N) -Isobutylamino) -6-
Methyl-7-phenylaminofluorane, 3- (N-methyl-Nn-hexylamino) -6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-)
Hexylamino) -6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-cyclopentylamino) -6-methyl-7-phenylaminofluorane, 3
-[N- (3-Ethoxypropyl) -N-methylamino] -6-methyl-7-phenylaminofluorane, 3
-[N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7-phenylaminofluorane, 3
-Diethylamino-7- [m- (trifluoromethyl)
Phenylamino] fluorane, 3-diethylamino-7
-(O-Fluorophenylamino) fluorane, 3-dibutylamino-7- (o-fluorophenylamino) fluorane, 3-diethylamino-6-chloro-7-phenylaminofluorane, 3- (N-ethyl-N-) p-tolylamino) -7-methylfluorane, 3- (N-cyclopentyl-N-ethylamino) -6-methyl-7-anilinofluorane, 2,2-bis {4- [6 '-(N-
Fluorane dyes such as cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2'-ylamino] phenyl} propane;
3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, 3-diethylamino-6- (N-allyl-N-methylaminofluorene-9-spiro-3'-(6'-Dimethylamino) phthalide, 3,6-bis (dimethylamino) -spiro [fluorene-9,6'-6'H-chromeno (4,3
-B) indole], 3,6-bis (dimethylamino)
-3'-methyl-spiro [fluorene-9,6'-6 '
H-chromeno (4,3-b) indole], 3,6-bis (diethylamino) -3'-methyl-spiro [fluorene-9,6'-6'H-chromeno (4,3-b) indole] Fluorene dyes, etc. Of course, the dyes are not limited to these dyes, and two or more kinds of dyes may be used in combination if necessary.

Various inorganic or organic acidic substances that are colored by contact with the basic colorless dye as described above are also known, and examples thereof include activated clay, acid clay, attapulgite, bentonite, colloidal silica and silicic acid. Inorganic acidic substances such as aluminum, 4-tert-butylphenol,
4-hydroxydiphenoxide, α-naphthol, β-
Naphthol, 4-hydroxyacetophenol, 4-te
rt-octylcatechol, 2,2'-dihydroxydiphenol, 2,2'-methylenebis (4-methyl-6-)
tert-butylphenol), 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-se
c-butylidene diphenol, 4-phenylphenol, 4,4'-isopropylidenediphenol, 2,
2'-methylenebis (4-chlorophenol), hydroquinone, 4,4'-cyclohexylidene diphenol,
4-hydroxy-4′-isopropoxydiphenyl sulfone, benzyl 4-hydroxybenzoate, hydroquinone monobenzyl ether, novolac type phenol resin,
Phenolic compounds such as phenolic polymers, benzoic acid,
p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid,
3,5-Dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α- Aromatic carboxylic acids such as methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, and 3,5-di-α-methylbenzylsalicylic acid, Examples thereof include organic acidic substances such as salts of these phenolic compounds, aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel. Of course, it is not limited to these acidic substances, and if necessary, two or more types of acidic substances can be used together.

The amount of the acidic substance used is not necessarily limited, but generally 100 to 700 parts by weight, more preferably 150 parts by weight, relative to 100 parts by weight of the basic dye.
˜400 parts by weight of acidic substance is blended.

Further, in the heat-sensitive recording material of the present invention, various known sensitizers may be used in combination, if necessary, and examples thereof include the following compounds. Caproic acid amide,
Capric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, linolenic acid amide, N-methylstearic acid amide, stearic acid anilide, N-methyloleic acid amide, benzanilide, linoleic acid Anilid, N-
Fatty acid amides such as ethylcapric acid amide, N-butyllauric acid amide, N-octadecylacetamide, N-oleinacetamide, N-oleylbenzamide, N-stearylcyclohexylamide, stearic acid methylenebisamide, and coconut fatty acid amide, 2,2 ′-
Methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-
3-methylphenol), 2,2'-methylenebis (4
-Ethyl-6-tert-butylphenol), 2,4-di-tert-butyl-3-methylphenol, 1,1,3-
Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (5-cyclohexyl-4-hydroxy-2-methylphenyl) butane, 1,3,5-tris ( 4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid and other hindered phenols, 2- (2′-hydroxy-)
5'-methylphenyl) benzotriazole, 1,2-
Di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, 1- (2-methylphenoxy) -2-
(4-Methoxyphenoxy) ethane, parabenzylbiphenyl, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, benzyl-4-methylthiophenyl ether, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, shu Acid-di-
p-methylbenzyl ester, oxalic acid-di-p-chlorobenzyl ester, terephthalic acid dimethyl ester,
Terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester, and various known heat-fusible substances. Among these, 1,2-di (3
-Methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy)
Ethane, 1- (2-methylphenoxy) -2- (4-methoxyphenoxy) ethane, oxalic acid dibenzyl ester and oxalic acid-di-p-methylbenzyl ester are particularly preferable in terms of the sensitizing effect. The amount of the sensitizer used is not particularly limited, but is generally 4 per 100 parts by weight of the color developing agent.
It is desirable to adjust the amount within the range of about 100 parts by weight or less.

The method for preparing a coating liquid for a heat-sensitive recording layer containing these substances is generally a method in which water is used as a dispersion medium and wet pulverization is performed by using an attritor, a ball mill, a sand mill or the like, and each compound is treated by, for example, heat treatment. After dissolving with a solvent etc.,
Examples thereof include a method of dispersing in water to form an emulsion. Various kinds of dispersants can be used for wet pulverization, and examples thereof include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, vinyl acetate resins containing sulfonic acid groups, starches, sodium polyacrylate, sodium polysulfonate, dioctylsulfone. Examples of the dispersant include sodium succinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate / sodium salt, and metal salt of fatty acid.

Further, binders are usually blended in the heat-sensitive recording layer. Examples of binders include starches, hydroxyethyl cellulose, methyl cellulose,
Carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene /
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene /
Examples thereof include butadiene copolymer emulsion, urea resin, melamine resin, amide resin and the like. The binders are preferably blended in an amount of 5 to 40% by weight, more preferably 10 to 30% by weight, based on the total solid content of the recording layer.

Further, various known pigments can be added to the heat-sensitive recording layer within a range that does not impair the desired effects of the present invention. For example, magnesium carbonate, calcite-based light calcium carbonate, aragonite-based light calcium carbonate, and heavy carbonic acid. Calcium, calcium sulphoaluminate, aluminum hydroxide, alkali-modified silica, kaolin, clay, talc, calcined kaolin, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, inorganic pigments such as activated clay, styrene microballs, nylon powder, Examples thereof include polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles.

If necessary, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, dioctyl sulfosuccinic acid sodium salt,
A dispersant such as sodium dodecylbenzenesulfonic acid salt, sodium lauryl alcohol sulfate / sodium salt, a fatty acid metal salt, an ultraviolet absorber such as a benzophenone type, an antifoaming agent, a fluorescent dye, a coloring dye and the like may be appropriately added.

The method for forming the recording layer is not particularly limited, and suitable coating such as air knife coating, varibar blade coating, rod blade coating, pure blade coating, short dwell coating, curtain coating, die coating, etc. It is formed by applying a coating liquid for the heat-sensitive recording layer onto a support and drying it according to the method. The coating amount of the coating liquid is not particularly limited, usually dry weight 2~12g / m ^2, is preferably adjusted in the range of about 3 to 10 g / m ^2. As the support, paper, plastic film, synthetic paper or the like is used as appropriate.

In the heat-sensitive recording material of the present invention, an overcoat layer in which a polyurethane ionomer as a resin component and polyvinyl alcohol having a saponification degree of 85% or more are selectively combined is provided on the heat-sensitive recording layer thus obtained. It has important characteristics. The polyurethane ionomer used in the present invention is different from the emulsion type in which a polyurethane resin is dispersed in water by a conventional emulsifier, etc., and an urethane resin having ionicity, that is, an ionic group contained in the polyurethane ionomer is used, and an emulsifier or an organic solvent is used. It is a so-called colloidal dispersion type aqueous urethane resin which is dissolved in water or dispersed in extremely fine particles without being processed.

When such a polyurethane ionomer is used as a resin component of the overcoat layer, it forms a film having excellent adhesion to a printing ink, and a thermal recording material having excellent printability can be obtained, but in terms of storage stability. Not always enough. However, when such a polyurethane ionomer is used in combination with polyvinyl alcohol having a saponification degree of 85% or more, the preservability is remarkably improved and, as a result, a thermal recording material excellent in printability, preservability and recording runnability. Is obtained. In addition, such an improvement effect is
It does not work with polyvinyl alcohol having a saponification degree of less than 85%.

Specific examples of the polyurethane ionomer include Hydran HW series and Hydran AP series manufactured by Dainippon Ink and Chemicals, and Superflex series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.
Further, in the present invention, a modified polyvinyl alcohol having a substituent introduced may be used as long as the saponification degree is 85% or more. For example, acetoacetyl group modified polyvinyl alcohol, carboxyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, sulfonic acid modified. Examples thereof include polyvinyl alcohol, olefin modified polyvinyl alcohol, nitrile modified polyvinyl alcohol, amide modified polyvinyl alcohol, and pyrrolidone modified polyvinyl alcohol.

The use ratio of the polyurethane ionomer and the specific polyvinyl alcohol is not particularly limited, but is 20 to 500 parts by weight, particularly 100 to 500 parts by weight based on 100 parts by weight of the polyurethane ionomer.
It is desirable to use parts by weight of polyvinyl alcohol. Further, in the overcoat layer, in order to further improve the writability, printability, etc., for example, heavy calcium carbonate, light calcium carbonate, talc, clay, natural silicic acids, synthetic silicic acids, titanium oxide, aluminum hydroxide, Inorganic or organic pigments such as zinc oxide and urea formaldehyde resin powder may be added. If these pigments are added excessively, the printing density may be lowered. Therefore, the amount used is 20 to 70% by weight of the total solid content of the overcoat layer.
It is preferable to adjust the range.

Further, in the overcoat layer, if necessary, zinc stearate, calcium stearate, stearic acid amide, polyethylene wax, carnauba wax, paraffin wax, ester wax, lubricant such as silicone oil, sodium dioctyl sulfosuccinate, Sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate / sodium salt, alginic acid, surfactant such as fatty acid metal salt, UV absorber such as benzophenone-based or triazole-based, antifoaming agent, fluorescent dye, coloring dye, and further glyoxal, Methylol melamine, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, boric acid, alum, ammonium chloride, aminoplast resin, epoxy resin, aziridine It may be added in various aids such as a curing agent as appropriate.

The coating liquid for forming the overcoat layer is generally prepared as an aqueous coating liquid, and if necessary, sufficiently mixed and dispersed by a mixing / stirring machine such as a mixer, an attritor, a ball mill, a roll mill, and the like. The heat-sensitive recording layer is coated with a known coating device. The coating amount of the coating liquid for the overcoat layer is not particularly limited, but if it is less than 0.1 g / m ^2, it is difficult to obtain the desired effects of the present invention, and if it exceeds 20 g / m ² , the recording density is increased. Generally, the dry weight is 0.1 because it may significantly decrease.
It is desirable to adjust in the range of about 20 to ²⁰ g / m ² , preferably about 0.5 to 10 g / m ² .

In the present invention, the image quality and the recording density can be further improved by applying a super calendering treatment after coating the heat-sensitive recording layer or after coating the overcoat layer, if necessary. When the base paper is used as the support, an undercoat layer composed of an adhesive and a white pigment is provided so that the recording density, sensitivity,
The shelf life can also be improved. Further, a back barrier layer composed of an adhesive and a white pigment may be provided on the back surface of the recording medium to eliminate the influence of oil, plasticizer and the like from the back surface to further improve the storage stability. Further, various known techniques in the field of manufacturing a heat-sensitive recording material, such as a pressure-sensitive adhesive treatment on the back surface of the recording material and processing into an adhesive label, can be appropriately added.

[0024]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight" respectively.

Example 1 Solution A Preparation 3- (N-cyclohexyl-N-methylamino) -6-
Methyl-7-phenylaminofluorane 10 parts, 1,3
A composition consisting of 25 parts of di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose, and 50 parts of water was pulverized with a sand mill until the average particle diameter became 3 μm. Solution B Preparation A composition consisting of 10 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 25 parts of water was sand milled to obtain an average particle size of
It was pulverized to 3 μm.

Formation of Recording Layer 90 parts of solution A, 40 parts of solution B, 20% aqueous solution of oxidized starch 50
And 10 parts of water were mixed and stirred to prepare a coating liquid. The obtained coating liquid was applied to a base paper of 58 g / m ² and the coating amount after drying was 6 g / m ²
Was coated and dried to obtain a thermosensitive recording medium. Formation of overcoat layer Polyurethane ionomer (trade name: on the thermosensitive recording layer)
Hydran AP-30, Dainippon Ink and Chemicals, density 2
0%) 75 parts, polyvinyl alcohol (trade name: PVA
117, Kuraray Co., saponification degree 98%), 10% aqueous solution 2
Aqueous dispersion of 00 parts, kaolin 60 parts, zinc stearate (trade name: Hydrin Z-7, manufactured by Chukyo Yushi, concentration 30
%) 16.7 parts of water and 300 parts of water are mixed to obtain a coating solution having a coating amount of 3 g / m ² after drying, followed by drying and smoothing treatment with a super calender. A thermosensitive recording medium having a coat layer was obtained.

Example 2 As an overcoat layer, 68 parts of polyurethane ionomer (trade name: Hydran AP-40, manufactured by Dainippon Ink and Chemicals, concentration: 22%), 200 parts of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA117) Example 1 except that 60 parts of kaolin, 16.7 parts of an aqueous dispersion of zinc stearate (trade name: Hydrin Z-7), and 300 parts of water were mixed and dried. Similarly, a thermal recording material having an overcoat layer was obtained.

Example 3 As an overcoat layer, 50 parts of a polyurethane ionomer (trade name: Superflex 100, manufactured by Dai-ichi Kogyo Seiyaku Co., concentration 30%), 200 parts of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA117), Same as Example 1 except that 60 parts of kaolin, 16.7 parts of zinc stearate aqueous dispersion (trade name: Hydrin Z-7), and 320 parts of water were applied and dried. A thermosensitive recording medium having an overcoat layer was obtained.

Example 4 As an overcoat layer, 75 parts of polyurethane ionomer (trade name: Hydran AP-30), 200 parts of 10% aqueous solution of polyvinyl alcohol (trade name: PVA217, manufactured by Kuraray Co., Ltd., saponification degree 88%), kaolin 60 copies,
Aqueous dispersion of zinc stearate (trade name: Hydrin Z-
7) A thermosensitive recording medium having an overcoat layer was obtained in the same manner as in Example 1 except that the coating liquid obtained by mixing 16.7 parts of water and 300 parts of water was applied and dried.

Example 5 As an overcoat layer, 75 parts of polyurethane ionomer (trade name: Hydran AP-30), 10% aqueous solution of polyvinyl alcohol (trade name: PVA117) 20
0 part, aluminum hydroxide (trade name: HAL-42, Showa Light Metal Co., Ltd.) 60 parts, aqueous dispersion of zinc stearate (trade name: Hydrin Z-7) 16.7 parts, and water 30
A thermosensitive recording medium having an overcoat layer was obtained in the same manner as in Example 1 except that the coating liquid obtained by mixing 0 parts was applied and dried.

Example 6 As an overcoat layer, 75 parts of a polyurethane ionomer (trade name: Hydran AP-30) and a 10% aqueous solution of silicon-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd., saponification degree 98%). 200 parts, aluminum hydroxide (trade name: HAL-42) 60 parts, aqueous dispersion of zinc stearate (trade name: Hydrin Z-7) 1
6.7 parts, and apply a coating solution obtained by mixing 300 parts of water,
A thermosensitive recording medium having an overcoat layer was obtained in the same manner as in Example 1 except that it was dried.

Example 7 100 parts of calcined clay (trade name: Ansilex, manufactured by Engel Hard Co., Ltd.), styrene-butadiene copolymer latex (trade name: L-1571, manufactured by Asahi Kasei Corporation, concentration 4)
8%) 25 parts, polyvinyl alcohol (trade name: PVA
110, Kuraray Co., saponification degree 98%) 10% aqueous solution 1
5 parts of water and 180 parts of water were mixed to obtain 46
The coating amount after drying base paper g / m ² was applied and dried such that the 6 g / m ^2. A heat-sensitive recording layer and an overcoat layer were provided on the undercoat base paper in the same manner as in Example 1 to obtain a heat-sensitive recording material.

Example 8 As an overcoat layer, 10 parts of polyurethane ionomer (trade name: Hydran AP-30), acetoacetyl group-modified polyvinyl alcohol (trade name: Gocefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) were used. % Aqueous solution 200 parts, kaolin 60 parts, aqueous dispersion of zinc stearate (trade name: Hydrin Z-7) 16.7 parts, and water 3
A thermosensitive recording medium having an overcoat layer was obtained in the same manner as in Example 1 except that the coating liquid obtained by mixing 00 parts was applied and dried.

Comparative Example 1 As an overcoat layer, 300 parts of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA117), 60 parts of kaolin, 16.7 parts of an aqueous dispersion of zinc stearate (trade name: Hydrin Z-7). A thermosensitive recording medium having an overcoat layer was obtained in the same manner as in Example 1 except that a coating liquid obtained by mixing 300 parts of water and water was applied and dried.

Comparative Example 2 As an overcoat layer, 175 parts of a polyurethane ionomer (trade name: Hydran AP-30), 60 parts of kaolin, 16.7 parts of an aqueous dispersion of zinc stearate (trade name: Hydrin Z-7), A heat-sensitive recording material having an overcoat layer was obtained in the same manner as in Example 1 except that a coating liquid obtained by mixing and 300 parts of water was applied and dried.

Comparative Example 3 As an overcoat layer, 31 parts of a styrene / butadiene copolymer latex (trade name: L-1571), 200 parts of polyvinyl alcohol (trade name: PVA117), 60 parts of kaolin, and an aqueous dispersion of zinc stearate. A thermal recording material having an overcoat layer was prepared in the same manner as in Example 1 except that 16.7 parts of (trade name: Hydrin Z-7) and 300 parts of water were mixed and applied, and dried. Obtained.

Comparative Example 4 As the overcoat layer, 75 parts of a polyurethane ionomer (trade name: Hydran AP-30) and a 10% aqueous solution of polyvinyl alcohol (trade name: SMR-20M, manufactured by Shin-Etsu Chemical Co., Ltd., saponification degree 60%). Example except that 200 parts, 60 parts of kaolin, 16.7 parts of an aqueous dispersion of zinc stearate (trade name: Hydrin Z-7), and 300 parts of water were mixed and applied, and dried. A thermal recording material having an overcoat layer was obtained in the same manner as in 1.

The 12 kinds of heat-sensitive recording materials thus obtained were recorded by a heat-sensitive facsimile (PANAFAX UF150), and the following evaluations were carried out. The results are shown in Table 1. [Evaluation] (1) Running property (sticking property) The running property when recording with PANAFAX UF150 and the noise during recording were evaluated. (2) Recording Density The density of the obtained recorded image was measured with a Macbeth densitometer (Macbeth RD-100 type). (3) Solvent resistance A drop of ethanol was dropped on the recording surface and the state of fog was visually evaluated. (4) Salad oil was dripped on the oil resistance recorded image and allowed to stand in the room for one day, and the degree of fading was visually evaluated. (5) A vinylidene chloride film containing a plasticizer was overlaid on the heat-sensitive recording material after recording the plasticizer resistance, and left for 3 days in the room, and then the degree of fading was visually evaluated. (6) Printability The operability and the fixability of ink when printed by an off-line printing machine were evaluated.

The evaluation criteria for running property, solvent resistance, oil resistance, plasticizer resistance and printability were as follows. [Evaluation Criteria] ○: No practical problems △: Some practical problems ×: Practical problems

[0040]

[Table 1]

[0041]

As is clear from the results of Table 1, the thermal recording material of the present invention was a thermal recording material excellent in all of recording runnability, storability and printability.

Claims (2)

[Claims] 1. A thermosensitive recording medium comprising a support, a recording layer containing at least a color former and a color former, and an overcoat layer formed on the recording layer. A heat-sensitive recording material comprising a polyurethane ionomer and polyvinyl alcohol having a saponification degree of 85% or more. 2. The thermosensitive recording medium according to claim 1, wherein polyvinyl alcohol is used in a proportion of 100 to 500 parts by weight based on 100 parts by weight of the polyurethane ionomer.