JP2000198271A - Thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording medium which shows outstanding resistance to a yellowing phenomenon and high recording density in a recording layer and also superior water resistance on the recording face side. SOLUTION: This thermal recording medium comprises a primer coat layer containing a water-soluble polymer, a recording layer formed by applying and drying a coating liquid for recording containing a leuco dye, a coloring agent and an additive and a protecting layer containing a water-soluble polymer, sequentially formed on one face of a support. In addition, a zirconium ammonium carbonate is added to a coating liquid for the recording layer and the pH value of the coating liquid for the recording layer is set to be 8-10.

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 utilizing a color-forming reaction between a leuco dye and a color former.

[0002]

2. Description of the Related Art A thermosensitive recording medium in which a recording portion is obtained by reacting both coloring materials with heat energy from a thermal head utilizing a color reaction between a leuco dye and a coloring agent is well known. Such a thermosensitive recording medium is relatively inexpensive, and since the recording equipment is compact and its maintenance is relatively easy, it is used not only as a recording medium for facsimile and various computers but also as a recording medium for a label printer. ing.

[0003] Recording media for label printers include:
For example, a thermal recording medium for a POS (point of sales) system may be used. For POS labels and merchandise labels affixed to household goods and foods sold at supermarkets and convenience stores, heat-sensitive recording media having a high recording density are required with the speeding up of label printers. Further, when such a heat-sensitive recording medium is stored under high-temperature and high-humidity conditions or used in a state of being immersed in water, a problem that an unrecorded portion (background portion) yellows occurs, Has occurred, and the displayed letters and numbers have become unreadable, which has degraded the value of the product.
Further improvements are required.

As a method for improving the water resistance of the recording layer side of the heat-sensitive recording material, for example, a heat-sensitive recording material having a protective layer containing a water-soluble polymer compound containing zirconium ammonium carbonate in the recording layer is disclosed in Although described in JP-A-61-110585, further improvement in water resistance is demanded.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording medium which is excellent in yellowing resistance and recording density of a recording layer and which has excellent water resistance on the recording surface side.

[0006]

Means for Solving the Problems A coating solution for a recording layer containing an undercoat layer containing a water-soluble polymer, a leuco dye, a coloring agent and an adhesive is formed on one surface of a support by drying and then dried. As one means for solving the above problems, the present invention provides a recording layer, and a thermosensitive recording medium having a protective layer containing a water-soluble polymer in order to solve the above-mentioned problem. And the pH of the recording layer coating liquid is adjusted to 8 to 10.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention comprises
An undercoat layer containing a water-soluble polymer, a recording layer formed by applying and drying a coating solution for a recording layer containing a leuco dye, a color former and an adhesive, and a protective layer containing a water-soluble polymer are sequentially formed. The recording medium having a thermosensitive recording medium, wherein the coating liquid for a recording layer contains ammonium zirconium carbonate, and the pH of the coating liquid for a recording layer is 8 to 10, and the pH of the coating liquid for a recording layer is 8 to 10 By doing so, the effect of excellent mechanical stability of the coating liquid and the background fog resistance of the recording layer, the effect of yellowing resistance of the recording layer and the excellent water resistance of the recording layer side can be obtained.

If the pH of the coating liquid for the recording layer is less than 8, the mechanical stability of the coating liquid is reduced, and the unrecorded portion (background portion) of the recording layer is apt to yellow. On the other hand, if the pH of the coating liquid exceeds 10, the coating liquid may thicken, making it difficult to form a uniform recording layer.

The means for adjusting the pH of the recording layer coating solution to 8 to 10 is not particularly limited. For example, a basic pigment such as calcium carbonate or magnesium carbonate is added to the total solid content of the recording layer in the recording layer coating solution. It can be obtained by adding about 1 to 20% by weight to the composition. By including such a pigment in the coating liquid for the recording layer, an effect having more excellent water resistance and yellowing resistance can be obtained.

The amount of zirconium ammonium carbonate contained in the recording layer coating liquid is not particularly limited, but is preferably 0.1 to 10% based on the total solid content of the recording layer.
%, More preferably about 0.1 to 5% by weight.

When the content is less than 0.1% by weight, when the thermosensitive recording medium is immersed in water, the protective layer surface is easily peeled off from the recording layer surface, probably because the pressure-sensitive adhesive layer is provided on the other surface of the support.
There is a possibility that the desired water resistance effect cannot be obtained.
Exceeding the recording density may lower the recording density.

The leuco dye and colorant contained in the recording layer are not particularly limited, and for example, various known leuco dyes and colorants can be used. Examples of such leuco dyes include the following. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluoran, 3- (N-ethyl-Np-tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilinofur Oran, 3-diethylamino-7-dibenzylaminofluoran, 3,6-bis (diethylamino) fluoran-γ-anilinolactam, 3-cyclohexylamino-
6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-
Chlorofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluoran, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N- Methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3
-Diethylamino-6-methyl-7-anilinofluoran, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6
-Methyl-7-anilinofluoran, 3-diethylamino-7- (o-chlorophenylamino) fluoran, 3
-Di (n-butyl) amino-7- (o-chlorophenylamino) fluoran, 3-diethylamino-7- (o-
Fluorophenylamino) fluoran, 3-di (n-butyl) amino-7- (o-fluorophenylamino) fluoran, 3- (N-ethyl-p-toluidino) -6
Methyl-7-anilinofluoran, 3- (N-ethyl-
p-Toluidino) -6-methyl-7- (p-toluidino) fluoran, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro -7-anilinofluoran,
3- (N-methyl-NN-propylamino) -6-methyl-7-anilinofluoran, 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] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene- 2-yl] -4,5,6,7-tetrabromophthalide, 3-p- (p-anilinoanilino) anilino-6-methyl-7-chlorofluoran, 2,2-
Bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-
Xanthen-2'-ylamino] phenyl} propane,
3,6, -bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, etc. Of course, the invention is not limited to these, and two or more kinds may be used in combination as necessary. You can also.

Examples of colorants include 4-cumylphenol, hydroquinone monobenzyl ether, 4,4'-
Isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4'-dihydroxydiphenyl-2,2-butane, 4,4'-dihydroxydiphenylmethane, 2,2-bis (4-hydroxyphenyl ) -4-Methylpentane, 2,2-bis (4
-Hydroxyphenyl) heptane, 1,1-bis (4-
(Hydroxyphenyl) -1-phenylethane, 1,4-
Bis [α-methyl-α- (4′-hydroxyphenyl)
Ethyl] benzene, 1,3-bis [α-methyl-α-
(4'-hydroxyphenyl) ethyl] benzene, 2,
4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4 '
-Methyldiphenylsulfone, 4-hydroxy-4'-
Isopropoxydiphenylsulfone, 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone, 4-
Hydroxy-4'-benzyloxydiphenyl sulfone,
Benzyl 4-hydroxybenzoate, butyl bis (p-hydroxyphenyl) acetate, di (p-hydroxyphenylthioethyl) ether, N, N'-di-m-chlorophenylthiourea, N- (phenoxyethyl) -4- Phenolic compounds such as hydroxyphenylsulfonamide,
4- [3- (p-tolylsulfonyl) propyloxy]
Zinc salicylate, 4- [2- (p-methoxyphenoxy) ethyloxy] zinc salicylate, 5- [p- (2-
p-methoxyphenoxyethoxy) cumyl] and zinc salts of aromatic carboxylic acids such as zinc salicylate and zinc p-chlorobenzoate. The amount of the colorant is not particularly limited, but may be 0.1 to 1 part by weight of the carp dye.
It is about 5 to 5 parts by weight.

Further, the recording layer may contain a sensitizer for increasing the recording sensitivity and a storability improving agent for improving the storability of the recording portion. Examples of the sensitizer include stearic acid amide, ethylene bistearic acid amide, behenic acid amide, methylene bisstearic acid amide, N-methylol stearic acid amide, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, and dibenzyl oxalate. Di-p-methylbenzyl oxalate,
Di-p-chlorobenzyl oxalate, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, 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,
2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluizide, p-acetophene Tidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like.

Examples of the preservative improver include 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenylsulfone, diglucidyl terephthalate,
Epoxy compounds such as bisphenol A type epoxy resin,
2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis (4,6-di- tert-butylphenol), 4,
4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert-
Butylphenol), 4,4'-butylidenebis (6-
tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4)
-Hydroxy-5-tert-butylphenyl) butane;
4,4'-thiobis (3-methylphenol), 4,
4'-dihydroxy-3,3 ', 5,5'-tetrabromodiphenylsulfone, 4,4'-dihydroxy-3,
3 ', 5,5'-tetramethyldiphenyl sulfone,
2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,
5-dichlorophenyl) propane, 2,2-bis (4-
Hindered phenol compounds such as hydroxy-3,5-dimethylphenyl) propane, 1- [α-methyl-α-
(4'-hydroxyphenyl) ethyl] -4- [α ',
α'-bis (4 "-hydroxyphenyl) ethyl] benzene, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-
(Butylphenyl) sodium phosphate and the like. The use amount of the sensitizer and the preservability improver is about 0.1 to 4 parts by weight based on 1 part by weight of the leuco dye.

The recording layer is generally formed by using water as a dispersing medium, together with a leuco dye, a color former, and, if necessary, a sensitizer, a preservability improver, etc., by means of a stirring / pulverizer such as a ball mill, an attritor or a sand mill. After separately dispersing, a coating liquid for a recording layer prepared by adding an adhesive, an ammonium zirconium carbonate, an auxiliary agent, etc. is applied onto an undercoat layer provided on a support, and the coated amount after drying is 1 to 10 g / m2. It is formed by coating and drying so as to be about ² and preferably about ² to 7 g / m ² .

Examples of the adhesive contained in the recording layer coating liquid include starch oxide, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and the like.
Gelatin, casein, arabic gum, completely (partially) saponified polyvinyl alcohol, silicon-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer Water-soluble polymers such as alkali salts of ethylene, alkali salts of ethylene-acrylic acid copolymer, alkali salts of styrene-acrylic acid copolymer, and aqueous dispersion of styrene-butadiene latex, acrylic latex, urethane latex, etc. Functional polymers. The amount of the adhesive used is about 5 to 35% by weight based on the total solid content of the recording layer.

Examples of the auxiliary agent that may be contained in the coating liquid for the recording layer include pigments such as kaolin, clay, calcium carbonate, calcined kaolin, titanium oxide, amorphous silica, aluminum hydroxide, and urea / formalin resin filler; Surfactants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate and sodium lauryl alcohol sulfate; lubricants such as calcium stearate and zinc stearate; waxes such as paraffin wax, polyethylene wax and carnauba wax; Examples include a fluorescent dye and a colored dye.

An undercoat layer is provided between the support and the recording layer in order to enhance the preservability of the recording portion against chemicals such as an adhesive, a plasticizer and oil from the other surface of the support or the recording sensitivity. In addition, a protective layer is formed on the recording layer in order to improve the recording running property or the preservability of the recording portion for chemicals.

Examples of the water-soluble polymer contained in the undercoat layer and the protective layer provided on the recording layer include the above-mentioned water-soluble polymer contained as an adhesive in the recording layer coating solution. The amount of the water-soluble polymer used is preferably 10% by weight or more based on the total solids of the protective layer or the undercoat layer.
The undercoat layer and the protective layer may further contain an auxiliary contained in the above-mentioned coating solution for recording layer.

The undercoat layer and the protective layer are formed by using water as a medium,
For example, a coating amount for an undercoat layer prepared by mixing and stirring an aqueous solution in which a water-soluble polymer is dissolved and, if necessary, an auxiliary agent is dried on a support to have a coating amount of about 1 to 10 g / m ^2. It is formed by applying and drying the coating solution for the protective layer on the recording layer so that the coating amount after drying is about 1 to 6 g / m ² .

The method of applying each coating liquid for the recording layer, the protective layer and the undercoat layer is not particularly limited, and examples thereof include an air knife coating method, a variver blade coating method, a clavia coating method, and a bar coating method. , Pure blade coating method,
Curtain coating method and the like can be mentioned.

As the support, high quality paper, waste paper, synthetic paper,
A plastic film or the like is appropriately selected and used.

An adhesive layer may be provided on the other surface (back surface) of the support, and various known strong adhesive or removable adhesives are used for the adhesive layer. For example, butyl (meth) acrylate,
Examples include an acrylic pressure-sensitive adhesive obtained by copolymerizing a monomer such as 2-ethylhexyl (meth) acrylate, and natural rubber. Examples of the removable adhesive include, for example, a two-part crosslinking agent obtained by reacting an acrylic adhesive with a crosslinking agent having an epoxy group, and an acrylic adhesive.
And isoprene / styrene block copolymer. Such a pressure-sensitive adhesive is used as a coating liquid for a pressure-sensitive adhesive layer in a state of being dissolved in an organic solvent or in the form of a latex using water as a dispersion.

The pressure-sensitive adhesive layer has a coating amount of 5 to 5 after drying the coating solution for the pressure-sensitive adhesive layer on the back side of the support or on the release layer of release paper.
After coating and drying so as to have a weight of about 30 g / m ² , the thermosensitive recording medium, the pressure-sensitive adhesive layer and the release layer are formed so as to sequentially overlap each other. Also, a delayed tack type which does not require a release paper as an adhesive can be used. In addition, as a coating system of the coating liquid for an adhesive layer, the above-mentioned system is mentioned.

Various known techniques in the field of heat-sensitive recording paper, such as applying a smoothing treatment such as super calendering after forming an undercoat layer, a recording layer, or a protective layer, can be added as necessary. .

[0027]

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.

Preparation of Coating Solution for Undercoat Layer 80 parts of calcined clay [oil absorption: 110 ml / 100 g]
10% aqueous solution of partially saponified polyvinyl alcohol 120
Part, styrene-butadiene latex (solids concentration 4
(8%) 14 parts, a composition comprising 2 parts of a 40% aqueous solution of sodium polyacrylate and 100 parts of water were mixed and stirred to obtain a coating liquid for an undercoat layer.

Preparation of Solution A 40 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 5% aqueous solution of methylcellulose 1
A composition consisting of 0 parts and 50 parts of water was pulverized by a sand mill until the average particle size became 1.0 μm.

Preparation of solution B 3- (N-ethyl-p-toluidino) -6-methyl-7
-40 parts of anilinofluorane, 5% of methylcellulose
A composition comprising 10 parts of an aqueous solution and 50 parts of water was pulverized by a sand mill until the average particle size became 1.0 μm.

Preparation of Solution C A composition comprising 30 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 25 parts of water is pulverized by a sand mill until the average particle diameter becomes 1.4 μm. did.

Preparation of Solution D A composition comprising 30 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose and 25 parts of water is subjected to sand milling until the average particle diameter becomes 1.2 μm. Crushed.

Preparation of Coating Solution for Recording Layer 25 parts of solution A, 25 parts of solution B, 60 parts of solution C, 60 parts of solution D, 15% aqueous solution of partially saponified polyvinyl alcohol 100
Parts, 10 parts of calcium carbonate, 10 parts of magnesium carbonate,
A composition comprising 10 parts of a 20% aqueous solution of zirconium ammonium carbonate and 100 parts of water was stirred and mixed to obtain a coating liquid for a recording layer.

Preparation of Coating Solution for Protective Layer 250 parts of 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol, 70 parts of kaolin, 30 parts of zinc stearate
% Aqueous dispersion and 150 parts of water were mixed and stirred to obtain a coating liquid for a protective layer having a pH of 9.4.

Preparation of heat-sensitive recording medium On one surface of a high-quality paper (acid paper) of 58 g / m ² , the coating amount of the undercoat layer coating solution, the recording layer coating solution and the protective layer coating after drying was 9 g / m 2. ^{2, 5g / m 2, 3g} / m 2 and so as to each coating dried undercoat layer was provided a recording layer and a protective layer (Incidentally, the smoothing process by a super calender after forming each layer) the heat-sensitive recording material I got Then, a coating liquid for an adhesive layer composed of an acrylic adhesive latex having a solid concentration of 40% is applied to the release layer surface of a commercially available release paper and dried so that the applied amount after drying is 20 g / m ^2, and the adhesive layer is dried. Was formed, and the pressure-sensitive adhesive layer was adhered to the other surface of the support of the thermal recording paper so that the thermal recording label was obtained.

Example 2 The procedure of Example 1 was repeated except that 10 parts of aluminum hydroxide was used instead of 10 parts of magnesium carbonate to obtain a coating liquid for a recording layer having a pH of 8.2. Example 1
In the same manner as in the above, a thermosensitive recording medium and a thermosensitive recording label were obtained.

Example 3 A heat-sensitive material was prepared in the same manner as in Example 1 except that 35 parts of a 20% aqueous solution of zirconium ammonium carbonate was used instead of 10 parts of an aqueous solution of zirconium carbonate in preparing the coating solution for the recording layer of Example 1. A recording medium and a thermosensitive recording label were obtained.

Comparative Example 1 Thermal recording was performed in the same manner as in Example 1 except that 10 parts of water was used instead of 10 parts of a 20% aqueous solution of zirconium ammonium carbonate in the preparation of the coating solution for the recording layer of Example 1. Body and thermal recording labels were obtained.

Comparative Example 2 In the preparation of the coating solution for the recording layer of Example 1, 80 parts of a 25% dispersion of calcium sulfoaluminate was used instead of 10 parts of calcium carbonate and 10 parts of magnesium carbonate.
A heat-sensitive recording material and a heat-sensitive recording label were obtained in the same manner as in Example 1 except that a coating liquid for a recording layer having a pH of 10.8 was obtained.

Comparative Example 3 The procedure of Example 1 was repeated except that, in place of 10 parts of calcium carbonate and 10 parts of magnesium carbonate, 20 parts of kaolin was used instead of 10 parts of calcium carbonate and 10 parts of magnesium carbonate to obtain a coating solution for a recording layer having a pH of 7.4. In the same manner as in Example 1, a thermosensitive recording medium and a thermosensitive recording label were obtained.

Comparative Example 4 The procedure of Example 1 was repeated except that 10 parts of a 20% aqueous solution of glyoxal was used in place of 10 parts of a 20% aqueous solution of ammonium zirconium carbonate in the preparation of the coating solution for the recording layer of Example 1. Thus, a thermosensitive recording medium and a thermosensitive recording label were obtained.

Comparative Example 5 The procedure of Example 1 was repeated except that 10 parts of a 20% aqueous solution of dimethylol urea was used instead of 10 parts of a 20% aqueous solution of ammonium zirconium carbonate.
In the same manner as in Example 1, a thermosensitive recording medium and a thermosensitive recording label were obtained.

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

[Method of Evaluating Color Density] The color density of a recording portion obtained by using a thermal recording simulator [TH-PMD, manufactured by Okura Electric Co., Ltd., applied energy 0.47 mj / dot] was measured using a Macbeth densitometer [RD-914]. Type, manufactured by Macbeth Corporation] in the visual mode.

[Yellowing Evaluation Method]
The color tone of the recording layer after standing for 72 hours at 0 ° C. and 90% RH was measured with a color difference meter (CR-200, manufactured by Minolta Co.), and evaluated by the b value. The larger the b value, the stronger the yellowing on the recording layer side.

[Method for Evaluating Water Resistance] The obtained heat-sensitive recording medium was immersed in tap water at 20 ° C. for 15 hours, and then the water resistance was evaluated based on whether or not water blemishes occurred on the recording layer surface side.

[0047]

[Table 1]

[0048]

As is evident from the results in Table 1, the heat-sensitive recording material of the present invention has excellent effects of yellowing resistance and recording density of the recording layer, and excellent water resistance on the recording surface side. It is.

Claims (3)

[Claims] 1. A recording formed by applying and drying a coating liquid for a recording layer containing an undercoat layer containing a water-soluble polymer, a leuco dye, a color former and an adhesive on one surface of a support. layer,
And a heat-sensitive recording material having a protective layer containing a water-soluble polymer sequentially, wherein the recording layer coating liquid contains ammonium zirconium carbonate and the recording layer coating liquid has a pH of 8 to 10.
10. A thermosensitive recording medium, which is 10. 2. The heat-sensitive recording material according to claim 1, wherein the coating liquid for a recording layer further contains calcium carbonate or magnesium carbonate. 3. The heat-sensitive recording material according to claim 1, wherein the amount of the ammonium zirconium carbonate is 0.1 to 5% by weight based on the total solid content of the coating solution for the recording layer.