JPH07228047A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material reduced in stickness at the time of recording and excellent in water resistance. CONSTITUTION:In a thermal recording material wherein a thermal recording layer containing a colorless or light-colored leuco dye and a coupler and, if necessary, a protective layer are successively provided on a support, a self- crosslinkable acrylic emulsion and a zirconium compd. are used in the thermal recording layer and/or the protective layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is excellent in running performance during recording,
Moreover, the present invention relates to a heat-sensitive recording material having good water resistance.

[0002]

2. Description of the Related Art Conventionally, a thermosensitive recording medium has been well known in which a coloring image is obtained by contacting both color-forming substances by heat by utilizing a color-forming reaction between a colorless or light-colored leuco dye and a color-forming agent. There is. Such a thermal recording medium has advantages such as a compact recording apparatus, low cost, and easy maintenance, and is not only used as a recording medium for a facsimile, an automatic ticket vending machine, or a scientific measuring machine, POS label, CA
It is widely used as an output medium for various printers and plotters for D and CRT medical images.

As a result, the number of cases where it is used outdoors increases,
Water resistance that has not been conventionally required has been demanded. Therefore, conventionally, many proposals have been made to use a water-soluble adhesive in combination with various cross-linking agents or a combination with a water-soluble adhesive having high cross-linking property (JP-A-49-32646, JP-A-49-36343). Japanese Patent Laid-Open No. 50-30539, Japanese Patent Laid-Open No. 52-145228, Japanese Patent Laid-Open No. 55-1
59993, JP-A-57-189889). However, even if the water-soluble adhesive was cross-linked, it could not be made completely waterproof. On the other hand, it has been known that water resistance can be improved by using a hydrophobic resin emulsion such as vinyl acetate emulsion, acrylic emulsion or SBR latex as an adhesive for the heat-sensitive recording layer, but it is used because sticking occurs during recording. I couldn't.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a thermosensitive recording medium which is free from sticks and is excellent in water resistance.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have proposed a thermosensitive recording layer in which a colorless or light-colored leuco dye and a color former are provided on a support and, if necessary, a protective layer. It was found that the above object can be achieved by using a self-crosslinking acrylic emulsion and a zirconium compound in the heat-sensitive recording layer and / or the protective layer,
The present invention has been completed.

[0006]

The self-crosslinking acrylic emulsion in the present invention is an acrylic emulsion having a reactive functional group on the surface of polymer or copolymer particles, and the crosslink reaction of this functional group produces a network polymer structure. In particular, a self-crosslinking acrylic emulsion in which emulsion particles are crosslinked with melamine is preferable because it causes less sticking. Specific examples of the functional group that causes a crosslinking reaction include, for example, acrylic acid, methacrylic acid, itaconic acid and the like carboxyl group, hydroxyl group, amino group, epoxide group, amide group, N
Of these, a methylolamide group and the like, and among them, a carboxyl group is preferable because of its excellent reactivity with the zirconium compound.

Specific examples of self-crosslinking acrylic emulsions include vinyl acetate-alkyl acrylate copolymers, vinyl acetate-alkyl methacrylate copolymers, acrylonitrile-acrylic acid copolymers, acrylonitrile-alkyl acrylate copolymers. Polymer, acrylonitrile
Alkyl methacrylate copolymer, acrylonitrile-methacrylic acid-alkyl acrylate-alkyl methacrylate-styrene copolymer, acrylonitrile-dialkylaminoalkyl methacrylate-acrylamide copolymer, vinyl acetate-acrylic acid copolymer, vinyl acetate- Metal salts such as methacrylic acid copolymers, acrylic acid-methacrylic acid copolymers, acrylic acid-alkyl acrylate copolymers, acrylic acid-alkyl acrylate-acrylamide copolymers, acrylic acid-methacrylamide-styrene acid copolymers Polymers, methacrylic acid-alkyl acrylate-alkyl methacrylate copolymers, methacrylic acid metal salts-alkyl acrylate-alkyl methacrylate copolymers, methacrylic acid-alkyl acrylate-alkyl methacrylate-
Acrylamide copolymer, methacrylic acid-alkyl methacrylate copolymer, alkyl acrylate-acrylamide-styrene copolymer, alkyl methacrylate-acrylic acid acrylic-maleic anhydride copolymer, alkyl methacrylate-alkyl acrylate-anhydrous Maleic acid copolymerization, alkyl acrylate-styrene-maleic anhydride copolymer, alkyl methacrylate-fumaric acid copolymer, alkyl acrylate-itaconic acid copolymer or ammonium, Li, Na, K of these copolymers , Mg, Ca and the like. Alkyl in the above self-crosslinking acrylic emulsion is methyl, ethyl, propyl,
Butyl, 2-ethylhexyl and the like, which shows a saturated hydrocarbon having a carbon number of 10 or less, and as the metal salt, ammonium, L
The salts of i, Na, K and the like are shown.

When the self-crosslinking acrylic emulsion is used in the heat-sensitive recording layer, it is preferably added in an amount of 3 to 20% by weight, more preferably 5 to 15% by weight, based on the total solid amount of the heat-sensitive recording layer. If it is less than this range, the water resistance is insufficient, and if it is more than this range, the sensitivity is drastically reduced. When it is used for the protective layer, it is 5 to 95% by weight, preferably 20 to 80% by weight, based on the total solid content of the protective layer. However, it was found that this self-crosslinking acrylic emulsion alone had insufficient stick and water resistance, and stick and water resistance could be improved only in combination with the zirconia compound.

In the present invention, a protective layer is optionally provided on the heat-sensitive recording layer, and the most preferred use form is to contain a self-crosslinking acrylic emulsion and a zirconium compound in the uppermost protective layer.

Known zirconia compounds in the present invention
Although various ones can be used, the following are preferable ones.
Something like this. Na₂ZrSiO₃, ZrO
Cl₂・ 8H₂O, ZrOSO_Four・ NH₂O, ZrO (NO
₃)₂・ 4H₂O, ZrO (CO ₃)₂・ NH₂O, ZrO
(OH)₂・ NH₂O, ZrO (C₂H₃O₂)₂, (N
H_Four)₂ZrO (CO₃)₂・ 4H₂O, ZrO (C₁₈H₃₅
O₂)₂, ZrO (C₈H₁₅O₂)₂, ZrSiO_Four, ZrO
₂etc. Above all (NH_Four)₂ZrO (CO₃)₂・ 4H₂O is good
It showed good results. Zirconia compounds are self-crosslinking activators.
0.5 to 50 for 100% by weight of rill emulsion
Wt% is preferred, more preferably 3 to 30 wt%
is there. If the amount is less than this, the water resistance will be insufficient.
If it is more than this range, there is a problem with the stability of the paint over time.
Occurs.

As the leuco dye contained in the heat-sensitive recording layer of the present invention, a known colorless or light-colored leuco can be used. Specific examples thereof include 3,3-bis (p-dimethylaminophenyl) -6. -Dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl)
-3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluorane, 3- (N-ethyl-
N-p-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6-bis (diethylamino) fluorane -Γ
-Anilinolactam, 3-cyclohexylamino-6-
Chlorofluorane, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N
-Methyl-N-cyclohexyl) amino-6-methyl-
7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl)
Amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3- Di (n-butyl) amino-7- (o-chlorophenylamino) fluorane, 3-
Diethylamino-7- (o-fluorophenylamino)
Fluorane, 3-di (n-butyl) amino-7- (o-
Chlorophenylamino) fluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane,
3-di (n-butyl) amino-7- (o-fluorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3-
(N-ethyl-p-toluidino) -6-methyl-7-
(P-Toluidino) fluorane, 3- (N-ethyl-N)
-Furfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (N-methyl-Nn-propylamino) -6-methyl -7-Anilinofluorane, 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-dimethylaminoanilino) anilino-6-methyl-7-chlorofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl- N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3,6,11-tri (dimethylamino) fluorane and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

As the color former used in the present invention, various known color formers can be used. For example, activated clay,
Intapulgite, colloidal silica, inorganic acid substances such as aluminum silicate, 4,4'-isopropylidenediphenol, 2,2-bis (4-hydroxyphenyl)-
4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, 4
-Benzyl hydroxybenzoate, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4 -Hydroxy-4'-methyldiphenyl sulfone, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, bis (p-hydroxyphenyl) butyl acetate, bis Methyl (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di Phenolic compounds such as (4-hydroxy-3-methylphenyl) sulfin 4- [2-(p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3-
Aromatic carboxylic acids such as (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and zinc salts of these aromatic carboxylic acids, 4,4′- Screw (p
Examples include urea derivatives such as -toluenesulfonylaminocarbonylamino) diphenylmethane, and organic acid substances such as antipyrine complex of zinc thiocyanate.

The use ratio of the leuco dye and the color developing agent is appropriately selected according to the type of the color developing agent to be used and is not particularly limited, but generally 1% by weight of the leuco dye. 1 to 50% by weight, preferably 1
About 10% by weight of the coloring agent is used. The coating liquid for the heat-sensitive recording layer containing the substances as described above generally uses water as a dispersion medium, and disperses the dye and the colorant together or separately by an agitator / mill such as a ball mill, attritor, or sand mill. And then prepared.

In the present invention, the adhesive resin contained in the heat-sensitive recording layer and / or the protective layer is mainly a self-crosslinking acrylic emulsion, but it is generally used for the heat-sensitive recording layer or the protective layer in order to improve the fluidity of the paint. It is also possible to use a known adhesive resin in combination with. For example,
Polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, cation group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, silica-modified polyvinyl alcohol, starch and its derivatives, gum arabic, gelatin, casein, methyl cellulose, hydroxyethyl cellulose, Hydroxymethyl cellulose, polyvinylpyrrolidone, polyacrylic acid salt, polyacrylic amide,
Styrene-maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, and water-soluble resins such as isopropylene-maleic anhydride copolymer can be mentioned, but in order not to impair the water resistance of the coating film, the reaction It is preferable to use a water-soluble resin adhesive containing, for example, an acetoacetyl group, a carboxyl group, an amide group or the like as the functional group in combination. Particularly, the resin / pigment ratio of the protective layer is 80/20
The range of 20 to 80 is good, and the compounding ratio of the resin is 80.
If it exceeds%, there is a problem that sticking occurs during printing and the adhesiveness of printing ink decreases during label processing.

Various pigments can be added to the heat-sensitive recording layer or the protective layer, for example, aluminum hydroxide, calcium carbonate, magnesium carbonate, talc, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, Examples include inorganic fine powders such as aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica, and organic fine resin powders such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin. it can.

Further, various auxiliary agents can be added to the heat-sensitive recording layer or the protective layer, if necessary. For example, sodium dioctyl sulfonate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate, fatty acid metal salt. Dispersion such as zinc stearate, calcium stearate, polyethylene wax,
Waxes such as carnauba wax, paraffin wax, and ester wax, and auxiliary additive components conventionally used in thermal recording media, such as dispersants, surfactants, antioxidants, UV inhibitors, coloring dyes, and coloring pigments Can be mentioned.

If desired, a sensitizer may be used in combination with the heat-sensitive recording layer. Specific examples of the sensitizer include:
For example, stearic acid amide, methoxycarbonyl-N-
Stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebisstearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide, dibenzyl terephthalate, p-benzyloxybenzoic acid Benzyl, phenyl 1-hydroxy-2-naphthoate, 2
-Naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, di-p-methylbenzyl oxalate,
Oxalic acid-di-p-chlorobenzyl, 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,
1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-
Methylthiophenyl benzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxy) Examples include ethoxy) benzene and 1-isopropylphenyl-2-phenylethane. The addition amount of these sensitizers is not particularly limited, but in general, the coloring agent 1
It is desirable to adjust within the range of not more than 4% by weight with respect to the weight%.

If desired, a storability improver may be added to the heat-sensitive recording layer in order to enhance the storage stability of the recorded image. Specific examples of such storage improvers include, for example, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2, 2'-ethylidene bis (4,6-di-tert-butylphenol), 4,
4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert-
Butylphenol), 4,4'-thiobis (2-methylphenol), 4,4'-butylidenebis (6-tert-
Butyl-m-cresol, 1- [α-methyl-α-
(4'-Hydroxyphenyl) ethyl] -4- [α ',
α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, 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'-dihydroxy-3,
3 ', 5,5'-tetrabromodiphenyl sulfone,
4,4'-dihydroxy-3,3 ', 5,5'-tetramethyldiphenyl sulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-
Hindered phenol compounds such as bis (4-hydroxy-3,5-dichlorophenyl) propane and 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene, 4, 4'-
Diglycidyl oxydiphenyl sulfone, diglycidyl terephthalate, cresol novolac type epoxy resin,
Epoxy compounds such as phenol novolac type epoxy resin and bisphenol A type epoxy resin, N, N'-di-
2-naphthyl-p-phenylenediamine, sodium 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate, N, N′-di-2-naphthyl-p-phenylenediamine and the like can be mentioned. .

The method for forming the heat-sensitive recording layer and the protective layer is not particularly limited, and suitable examples include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating and die coating. Depending on the coating method, a thermosensitive recording layer coating solution and, if necessary, a protective layer coating solution are successively applied and dried on a support such as high-quality paper, coated paper, synthetic paper, or film. The coating amount of the heat-sensitive recording layer is 2 to dry weight.
12 g / m ² , preferably 3-10 g / m ² . The coating amount of the protective layer is preferably adjusted within the range of 0.5 to 10 g / m ² , and preferably 1.0 to 7 g / m ² .

The thermosensitive recording medium of the present invention is provided with a subbing layer on the support, or after the undercoat layer, the thermosensitive recording layer and the protective layer are coated, smoothing treatment such as super calendering is applied. Various known techniques in the manufacturing field can be added as necessary. Further, the heat-sensitive recording material of the present invention may be provided with a back surface layer on the surface opposite to the heat-sensitive recording layer, if necessary, to correct curl.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to these. Also, "part" and "%" in the example
Indicates "part by weight" and "% by weight", respectively.

[Example 1] Preparation of liquid A 40 parts of 3-dibutylamino-6-methyl-7-anilinofluorane, 20% aqueous solution of styrene ammonium ammonium maleate anhydride (trade name: Polymalon 1333, manufactured by Arakawa Chemical Co., Ltd. ) A composition comprising 20 parts and 40 parts of water was pulverized by an Ultra Viscomill (sand grinder manufactured by IMEX Co., Ltd.) so that the average particle size was about 1 μm, and a liquid A was obtained.

Preparation of Solution B 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane 20 parts, oxalic acid di-p
-A composition containing 25 parts of methylbenzyl ester, 10 parts of a 20% aqueous solution of styrene ammonium ammonium maleate anhydride (trade name: Polymalon 1333, manufactured by Arakawa Chemical Co., Ltd.), and 45 parts of water was added to Ultra Viscomil (sand grinder manufactured by IMEX Co., Ltd. ) Was pulverized to obtain an average particle diameter of about 1 μm to obtain a liquid B.

Preparation of liquid C 60 parts of aluminum hydroxide (trade name: Hydilite H42, manufactured by Showa Denko KK), 0.1 part of polycarboxylic acid type polymer activator (trade name: Caribbon L400, manufactured by Sanyo Kasei Co., Ltd.),
A composition consisting of 40 parts of water and water is dispersed with a stirrer, and C
A liquid was obtained.

Formation of Thermosensitive Recording Layer Liquid A 25 parts, liquid B 90 parts, liquid C 40 parts, zinc stearate 30% dispersion 8 parts, paraffin wax 30% dispersion 15 parts, solid concentration 25 as adhesive % Of self-crosslinking acrylic resin emulsion (trade name: FC60, manufactured by Nippon Pure Chemical Co., Ltd.) and 2 parts of zirconia ammonium monoxide (Baycoat 20, manufactured by Nippon Light Metal Co., Ltd.) with a solid concentration of 45% (50 g) / m on one surface of woodfree paper having ^2, applied as coating amount after drying of 6.0 g / m ^2, dried, Oken type smoothness of supercalendered (J.TAP
PI No. Smoothing treatment was carried out so that 5) was 2000 seconds to obtain a thermosensitive recording medium.

Example 2 Preparation of Liquid D 60 parts of a self-crosslinking acrylic resin emulsion having a solid concentration of 25% (trade name: FC60, manufactured by Nippon Pure Chemical Co., Ltd.), zirconia ammonium carbonate having a solid concentration of 45% (Baycoat 20, Japan) 5 parts (manufactured by Light Metal Co., Ltd.), 50 parts of a 10% aqueous solution of carboxy-modified polyvinyl alcohol, and 25 parts of solution C were mixed and stirred with a stirrer to obtain solution D.

Formation of Protective Layer Liquid D was applied onto the thermosensitive recording layer of the thermosensitive recording medium obtained in Example 1 so that the coating amount after drying was 6.0 g / m ² .
After drying, a super calendar was used to obtain Oken smoothness (J.
TAPPI No. Smoothing treatment was carried out so that 5) was 2000 seconds to obtain a thermosensitive recording medium.

[Example 3] In the formation of the heat-sensitive recording layer of Example 1, zirconia ammonium carbonate (bay coat 20,
A thermal recording material was obtained in the same manner as in Example 2 except that (Japan Light Metal Co., Ltd.) was omitted.

Example 4 In the formation of the heat-sensitive recording layer of Example 1, 20 parts of self-crosslinking acrylic resin emulsion (trade name: FC60, manufactured by Nippon Pure Chemical Co., Ltd.) was used, and self-crosslinking with a solid concentration of 25% was carried out. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 20 parts of a type acrylic resin emulsion (trade name: Kogum RT-110, manufactured by Showa High Polymer Co., Ltd.) was used.

Example 5 In the formation of the heat-sensitive recording layer of Example 1, 20 parts of the self-crosslinking acrylic resin emulsion (trade name: FC60, manufactured by Nippon Pure Chemical Co., Ltd.) was used, and self-crosslinking with a solid concentration of 60% was performed. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of a type acrylic resin emulsion (trade name: Primal NW-E358, manufactured by Rohm & Haas) was used.

Comparative Example 1 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that zirconia ammonium carbonate (trade name: Baycoat 20, manufactured by Nippon Light Metal Co., Ltd.) was omitted from the formation of the thermosensitive recording layer of Example 1. Got

Comparative Example 2 In the formation of the heat-sensitive recording layer of Example 1, instead of 20 parts of self-crosslinking acrylic resin emulsion (trade name: FC60, manufactured by Nippon Pure Chemical Co., Ltd.), a thermoplastic resin having a solid concentration of 45% was used. Type acrylic resin emulsion (Product name: Primal AC22358, manufactured by Rohm & Haas)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts were used.

[Comparative Example 3] In the formation of the heat-sensitive recording layer of Example 1, instead of 20 parts of the self-crosslinking acrylic resin emulsion (trade name: FC60, manufactured by Nippon Pure Chemical Co., Ltd.), a 40% 15% aqueous solution of polyvinyl alcohol was used. Except for part used,
A thermal recording material was obtained in the same manner as in Example 1.

[Comparative Example 4] A thermosensitive recording medium was obtained in the same manner as in Example 2 except that zirconia ammonium carbonate (Baycoat 20, manufactured by Nippon Light Metal Co., Ltd.) was omitted from the preparation of the liquid D.

The thermal recording material thus obtained was evaluated as follows, and the results are shown in Table 1. The recording sensitivity was printed with NEC High Speed Facsimile: Nefax 23 using the standard chart N0.2 of the Institute of Image Electronics, and the stick was sensory evaluated, and the color density at that time was measured with the Macbeth densitometer RD-914. However, a value representative of the recording sensitivity of the thermosensitive recording medium was used. As for water resistance, one drop of water was dropped on the surface of the heat-sensitive recording layer, and the degree of peeling of the recording surface was visually evaluated by rubbing with a finger 50 times.

[Stick Evaluation Criteria] ◯: No sticking was generated Δ: Sticking sound was recognized ×: Large sticking sound was generated and line spacing was disturbed in the image

[Water resistance evaluation] ◯: Almost no peeling of the recording surface Δ: Some peeling of the recording surface X: Many peeling of the recording surface

[0038]

[Table 1]

[0039]

As is apparent from Table 1, the heat-sensitive recording material of the present invention has no stick and has good water resistance.

Claims (1)

[Claims] 1. A heat-sensitive recording medium comprising a support, on which a colorless or light-colored leuco dye and a coloring agent are contained, and a protective layer if necessary.
Alternatively, a thermosensitive recording medium characterized in that a self-crosslinking acrylic emulsion and a zirconium compound are used in the protective layer.