JP2000168232A - Thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording medium having excellent recording sensitivity, chemical resistance, water resistance and impressionability and little skin fog. SOLUTION: In the thermal recording medium sequentially comprising a thermal recording layer containing a leuco dye, a colorant and an aqueous adhesive as main components and a protective layer containing a pigment and an aqueous adhesive as main components on a support, 1 to 30 wt.% of paraffin wax is contained in the recording layer, and a crosslinker is contained in the recording layer or the protective layer.

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.

2. Description of the Related Art A thermosensitive recording medium in which a recording image is obtained by contacting a plurality of coloring substances with heat is well known.
Such a thermosensitive recording medium is relatively inexpensive, has a compact recording apparatus, and is easy to maintain. Therefore, it is used in recording media such as facsimile machines and various computers, and in a wide range of fields other than the above. Examples of the recording medium other than the facsimile and the various computers include a thermal recording ticket for a POS (point of sales) system device and various thermal recording cards.

Conventionally, in these applications, a thermal transfer recording system has been adopted. Therefore, when a thermal recording system is adopted, not only recording suitability but also storage stability of an unrecorded portion and a recorded portion are improved.
In addition, writing properties and stamping properties such as vermilion and stamps are also required.

In order to improve the printability of the heat-sensitive recording medium on the side of the heat-sensitive recording layer, a protective layer containing an aqueous adhesive and aluminum hydroxide or talc as a pigment is provided on the heat-sensitive recording layer. No. 57384, Japanese Unexamined Patent Publication No.
Although it is described in Japanese Patent Application Laid-Open No. 227294 and Japanese Patent Application Laid-Open No. Hei 8-337059, there is a problem that the recording portion disappears due to the printing ink when the printing performance is improved.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which is excellent in recording sensitivity, chemical resistance, water resistance and printing property and has little background fog.

[0005]

Means for Solving the Problems A thermosensitive recording layer having a leuco dye, a coloring agent and a water-based adhesive as main components and a protective layer mainly containing a pigment and a water-based adhesive are sequentially formed on a support. In a recording medium, as one means for solving the above-mentioned problems, the present invention relates to a heat-sensitive recording layer comprising 1 to 30% by weight of paraffin wax based on the heat-sensitive recording layer, A crosslinking agent is contained therein.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS If the pigment ratio in the protective layer is increased in order to improve the printability of the protective layer surface of the thermal recording medium, the chemical resistance of the recording portion due to alcohol, plasticizer, oil or the like is reduced.
However, by including a crosslinking agent for the water-based adhesive in the heat-sensitive recording layer or the protective layer, and further including paraffin wax in the heat-sensitive recording layer in an amount of 1 to 30% by weight based on the heat-sensitive recording layer, the chemical resistance of the recording part is improved The effect of achieving both the properties and the sealability of the protective layer can be obtained.

If the amount of paraffin wax in the heat-sensitive recording layer is less than 1% by weight with respect to the heat-sensitive recording layer, the coating liquid for the protection layer is impregnated into the heat-sensitive recording layer during the formation of the protection layer. If the chemical property is reduced, and if the content exceeds 30% by weight, the printability of the protective layer may be reduced, more preferably about 3 to 20% by weight. Although the melting point of paraffin wax is not particularly limited, it is 40 to 90.
C. is preferred because it can be emulsified and dispersed so that the average particle size is easily 3 μm or less.

The crosslinking agent contained in the heat-sensitive recording layer or the protective layer is not particularly limited as long as it has a crosslinking reaction with the aqueous adhesive. Specific examples of the crosslinking agent include, for example, compounds having an aldehyde group such as glyoxal and dialdehyde starch, compounds having a methylol group such as urea-formaldehyde resin, melamine-formaldehyde resin, methylolurea and ketone resin, polyamide epichlorohydrin, and glycerol poly. Compounds having an epoxy group such as glycidyl ether, boric acid, borax, dihydrazide adipate, zirconium ammonium carbonate and the like can be mentioned. Among them, compounds having an epoxy group such as polyamide epichlorohydrin and glycerol polyglycidyl ether are preferred.

The amount of the crosslinking agent used is not particularly limited, but is about 0.01 to 50% by weight, preferably 0.1 to 2% by weight based on the aqueous adhesive in the heat-sensitive recording layer or the protective layer.
It is about 0% by weight.

The leuco dye and color former contained in the heat-sensitive recording layer are not particularly limited, and for example, various known dyes can be used. Specific examples of such leuco dyes include the following. 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) 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, 33-di (n-butyl) amino-7- (o-chlorophenylamino) fluoran, 3
-Diethylamino-7- (o-fluorophenylamino) fluoran, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- Black-coloring dyes such as p-ethoxyanilinofluoran, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- ( 4-dimethylaminophenyl) -6
Blue-coloring dyes such as dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluoran, and 3,6-bis (diethylamino) fluoran-γ
-Anilinolactam, 3-cyclohexylamino-6-
Chlorofluorane, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7,8-benzofluoran, 3- (N-ethyl-p-toluidino) -7-
Red-coloring dyes such as methylfluoran and 3-diethylamino-6,8-dimethylfluoran; 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- [p- (p-dimethylaminoanilino) anilino] -6-methylfur Orane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 ′-(6′-dimethylamino) phthalide, 3,3′-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide,
3-di (n-butyl) amino-6,8,8-trimethyl-8,9-dihydro- (3,2, e) pyridfluoran, 3- [1,1-bis (p-diethylaminophenyl) ethylene-2 -Yl] -6-dimethylaminophthalide, 3- (pn-butylaminoanilino) -6-methyl-7-chlorofluoran, 2-mesidino-8-diethylamino-benz [C] fluoran and the like The amount of the leuco dye such as an infrared color forming dye is not particularly limited, but is preferably about 0.1 to 3 g / m ² .

[0011] Examples of the coloring agent include 4,4'-
Isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4
-Hydroxyphenyl) -4-methylpentane, 4,
4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4'-dihydroxybenzophenone, 2,
4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, -Hydroxy-4'-methyldiphenylsulfone, 4-hydroxyphenyl-
4′-benzyloxyphenyl sulfone, methyl bis (p-hydroxyphenyl) acetate, 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] phenolic compounds such as benzene, thiourea compounds such as N, N'-di-m-chlorophenylthiourea, N- (p-tolylsulfonyl) carbamoyl-p-cumylphenyl ester , N- (o-tolyl) -p-tolylsulfonamide, N
- (p-tolyl sulfonyl) -N '- (p-tolyl) having a -SO ₂ NH- bond in the molecule, such as urea, 4-
[2- (p-methoxyphenoxy) ethyloxy] zinc salicylate, zinc 4- [3- (p-tolylsulfonyl) propyloxy] salicylate, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] zinc salicylate, etc. And zinc salts of aromatic carboxylic acids.

The ratio of the leuco dye to the colorant is appropriately selected according to the type of the leuco dye and the colorant used, and is not particularly limited. 1 to 15 parts by weight, preferably 2 to
About 10 parts by weight of a color former is used.

The heat-sensitive recording layer may further contain a storability improving agent for improving the storability of the recording portion or a sensitizer for further improving the recording sensitivity. Examples of such a preservability improver include 2,2′-methylenebis (4-methyl-6-tert-butylphenol),
2′-ethylidenebis (4,6-di-tert-butylphenol), 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate), 4 4,4'-thiobis (2-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol),
-[Α-methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-
Hindered phenol compounds such as methyl-4-hydroxy-5-cyclohexylphenyl) butane and 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane; 1,4-diglycidyl Oxybenzene, 4,4'-diglycidyloxydiphenylsulfone, 4- (2-methylglycidyloxy) -4'-
Examples include epoxy compounds such as benzyloxydiphenyl sulfone, diglycidyl terephthalate, cresol novolak type epoxy resin, phenol novolak type epoxy resin, bisphenol A type epoxy resin, and bis (4-ethyleneiminocarbonylaminophenyl) methane.

Among them, 4- (2-methylglycidyloxy) -4'-benzyloxydiphenylsulfone not only improves the storage stability of recorded images with respect to plasticizers and oils, but also provides water resistance, light resistance, and heat treatment. This is preferable because the stability of the recorded image after the moisture resistance treatment is also improved.

Specific examples of the sensitizer include, for example, stearic acid amide, N-eicosanoic acid amide, ethylenebisstearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide,
Dibenzyl terephthalate, benzyl p-benzyloxybenzoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, di-p oxalate -Methylbenzyl, p-benzylbiphenyl, p
-Tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxy) Phenoxy) ethane,
1,2-di (4-chlorophenoxy) ethane, 1,2-
Diphenoxyethane, 1- (4-methoxyphenoxy)
-2- (3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1- (2-naphthyloxy) -2-phenoxyethane, 1,3-di (naphthyloxy) propane, p-acetotoluizide, p-acetotol Examples include phenetizide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, and the like.

The amounts of the storability improver and the sensitizer are not particularly limited, but are generally 0.1 to 1 part by weight of the color former.
About 4 parts by weight.

The heat-sensitive recording layer is formed by using water as a medium and, for example, using a stirring / pulverizer such as a ball mill, an attritor or a sand mill, a leuco dye, a color former, and a paraffin wax, and if necessary, a preservability improver, a sensitizer, etc. After pulverizing together or separately so that the average particle size is 3 μm or less,
The coating amount after drying the heat-sensitive recording layer coating liquid prepared by adding an aqueous adhesive and optionally a crosslinking agent is 2 to
It is formed by coating and drying so as to have a weight of about 15 g / m ² .

Examples of the aqueous adhesive used in the coating solution for the heat-sensitive recording layer include starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, diisobutylene / maleic anhydride copolymer salt, and styrene. -Maleic anhydride copolymer salt, ethylene-acrylic acid copolymer salt, styrene-acrylic acid copolymer salt, polyvinyl alcohol, modified polyvinyl alcohol, water-soluble adhesives such as polyvinylpyrrolidone, urethane latex, acrylic Water-dispersible adhesives such as latex and styrene-butadiene latex are exemplified. Above all, a water-soluble adhesive is preferable since it hardly reduces the printing property. In particular, polyvinyl alcohols are most preferably used because they have a high effect of increasing the cohesive strength of the heat-sensitive recording layer.

The amount of the aqueous adhesive used in the heat-sensitive recording layer is not particularly limited, but may be from 10% by weight to 30% by weight based on the heat-sensitive recording layer.
% By weight is preferred. When the amount of the adhesive is less than 10% by weight, the cohesive strength of the heat-sensitive recording layer becomes insufficient, and when the amount exceeds 30% by weight, the printability of the protective layer surface may be deteriorated.

Various auxiliaries can be further added to the coating solution for the heat-sensitive recording layer, if necessary. Examples of such auxiliaries include pigments such as kaolin, talc, calcium carbonate, aluminum hydroxide, calcined kaolin, titanium oxide, amorphous silica, urea-formalin resin filler, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, lauryl Examples include surfactants such as sodium alcohol sulfate, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax and ester wax, antifoaming agents, and coloring dyes. Further, the pH value of the coating solution can be adjusted with an organic or inorganic acid or base to promote the water resistance reaction.

The protective layer provided on the heat-sensitive recording layer is a protective layer prepared by mixing and stirring water, for example, a dispersed pigment, a dissolved or dispersed aqueous adhesive, and optionally a crosslinking agent. The coating amount after drying the application coating solution on the protective layer is about 1 to 10 g / m ² , preferably ² to 6 g / m ^2.
It is formed by coating and drying to a degree.

Specific examples of the aqueous adhesive contained in the coating liquid for the protective layer include completely saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, or carboxy-modified polyvinyl alcohol or acetoacetyl-modified polyvinyl based on them. Alcohol, silicon-modified polyvinyl alcohol, modified polyvinyl alcohol such as diacetone-modified polyvinyl alcohol, copolymers of these polyvinyl alcohol and other polymers, starches, hydroxyethyl cellulose, methyl cellulose,
Carboxymethyl cellulose, gelatin, casein, gum arabic, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene
Examples include water-soluble adhesives such as acrylic acid copolymer salts and styrene / acrylic acid copolymer salts, and styrene / butadiene latexes, acrylic latexes, and urethane latexes.

Among them, modified polyvinyl alcohols such as acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and carboxy-modified polyvinyl alcohol can be easily made water-resistant and improve the barrier against low-concentration alcohols. It is preferably used.

The amount of the water-based adhesive used is not particularly limited, but may be from 10% by weight to 50% by weight based on the protective layer.
The degree is preferred.

Examples of the pigment contained in the protective layer include kaolin, talc, calcium carbonate, aluminum hydroxide, calcined kaolin, titanium oxide, amorphous silica, and urea-formalin resin filler. Alternatively, aluminum hydroxide is preferable, and talc is particularly preferable. Of course, two or more pigments can be used in combination.

The amount of the pigment used in the protective layer is not particularly limited, but is about 30 to 80% by weight, more preferably about 45 to 70% by weight, based on the protective layer.

Further, the protective layer may contain an ultraviolet absorber, a fluorescent dye, a coloring dye, a release agent, an antioxidant and the like.

The method for forming the heat-sensitive recording layer and the protective layer is not particularly limited. For example, an appropriate method such as air knife coating, variver blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. The method is such that a coating solution for a heat-sensitive recording layer is applied and dried on a support by a coating method, and then a coating solution for a protective layer is applied and dried on the recording layer. The support is appropriately selected from paper (neutral paper, acidic paper), plastic film, synthetic paper, nonwoven fabric, metal deposit, and the like. The coating amount of the protective layer coating liquid for dry weight 0.1 to 10 g / m ² in, preferably 0.5 to 5 g / m ²
It is about.

If necessary, a protective layer may be provided on the back side of the heat-sensitive recording medium, a gloss layer containing an ionizing radiation-effect resin as a main component may be provided on the protective layer, or the recording sensitivity may be improved. An undercoat layer containing an oil-absorbing pigment having an oil absorption of 80 to 300 cc / 100 g as measured according to JIS K 5101 may be provided between the support and the heat-sensitive recording layer. Further, various known techniques in the field of heat-sensitive recording material production, such as performing a smoothing treatment such as super calendering after forming each layer, can be added as necessary.

[0030]

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.

Example 1 Preparation of coating liquid for undercoat layer 100 parts of calcined clay [oil absorption: 90 ml / 100 g]
A composition composed of 200 parts of a 10% aqueous solution of polyvinyl alcohol and 100 parts of water was mixed and stirred to obtain a coating liquid for an undercoat layer.

Preparation of solution A 3- (N-ethyl-p-toluidino) -6-methyl-7
-10 parts of anilinofluorane, 5% of methylcellulose
A composition comprising 5 parts of an aqueous solution and 25 parts of water was pulverized by a sand mill until the average particle diameter became 1.0 μm.

Preparation of Solution B 30 parts of bis (3-allyl-4-hydroxyphenyl) sulfone, 5 parts of a 5% aqueous solution of methylcellulose and 8 parts of water
The composition consisting of 5 parts was sand-milled to an average particle size of 1.0
Milled to a μm.

Preparation of Solution C A composition comprising 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose and 55 parts of water is pulverized by a sand mill until the average particle diameter becomes 1.0 μm. did.

Preparation of Coating Solution for Thermosensitive Recording Layer 40 parts of solution A, 120 parts of solution B, 80 parts of solution C, 160 parts of a 10% aqueous solution of partially saponified polyvinyl alcohol (trade name: PVA-210, manufactured by Kuraray Co., Ltd.) 30% aqueous dispersion 3 of talc (trade name: High Micron HE-5, manufactured by Takehara Chemical Co., Ltd.)
3 parts, paraffin wax [Product name: Hydrine P-
7, manufactured by Chukyo Yushi Co., Ltd.] and a composition comprising 33 parts of a 30% aqueous dispersion and 1 part of a 40% aqueous solution of glyoxal were mixed and stirred to obtain a coating solution for a heat-sensitive recording layer.

Preparation of Coating Liquid for Protective Layer 10 of acetoacetyl-modified polyvinyl alcohol [trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Co., Ltd.]
% Aqueous solution, talc [trade name: High Micron HE
-5, manufactured by Takehara Chemical Co., Ltd.] and a composition comprising 6 parts of a 36% aqueous dispersion of zinc stearate, 6 parts, were mixed and stirred to obtain a coating liquid for a protective layer.

Preparation of heat-sensitive recording medium On one side of a high-quality paper (neutral paper) of 85 g / m ² , the coating amounts of the undercoat layer coating solution, the heat-sensitive recording layer coating solution and the protective layer coating solution after drying were respectively determined. 9 g / m ² , 6 g / m ² , 4 g / m ²
Then, an undercoat layer, a heat-sensitive recording layer and a protective layer were sequentially formed to obtain a heat-sensitive recording material. After the formation of each layer, the surface was smoothed by a super calender.

Example 2 In the preparation of solution A of Example 1, 3- (N-ethyl-p
Example 1 except that 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane were used instead of 10 parts of -toluidino) -6-methyl-7-anilinofluoran. In the same manner as in the above, a thermosensitive recording medium was obtained.

Example 3 A 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol [trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Co., Ltd.] was prepared in the same manner as in Example 1.
Instead of 0 parts, 35% of a 10% aqueous solution of silicon-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 0 part was used.

Example 4 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, 1 part of adipic acid dihydrazide was used in place of 1 part of a 40% aqueous solution of glyoxal, and in the preparation of the coating solution for the protective layer, Acetyl-modified polyvinyl alcohol [trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Company]
A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 350 parts of a 10% aqueous solution of diacetone-modified polyvinyl alcohol (trade name: D-1480, manufactured by Unitika) was used instead of 350 parts of a 10% aqueous solution of Obtained.

Example 5 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, the 40% aqueous solution of glyoxal 1 was not used, and in the preparation of the coating solution for the protective layer, acetoacetyl-modified polyvinyl alcohol [trade name: Go 350 parts of a 10% aqueous solution of carboxy-modified polyvinyl alcohol [brand name: KL-318, manufactured by Kuraray Co., Ltd.] and a 20% aqueous solution of polyamide epichlorohydrin instead of 350 parts of a 10% aqueous solution of Cephimer Z-200, manufactured by Nippon Gohsei Kagaku A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 20 parts were used.

Example 6 In the preparation of the coating solution for the protective layer of Example 1, aluminum hydroxide [instead of 210 parts of a 30% aqueous dispersion of talc (trade name: Himicron HE-5, manufactured by Takehara Chemical Co.)] was used. Product name: Heidilite H-42M, manufactured by Showa Denko KK]
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 210 parts of the aqueous dispersion was used.

Example 7 In Example 5, talc in the coating liquid for the protective layer [trade name:
High Micron HE-5, manufactured by Takehara Chemical Co., Ltd.] except that 210 parts of a 30% aqueous dispersion of calcium carbonate (trade name: Brilliant-15, manufactured by Shiraishi Calcium Co.) was used instead of 210 parts of a 30% aqueous dispersion. In the same manner as in Example 5, a thermosensitive recording medium was obtained.

Example 8 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, instead of 33 parts of a 30% aqueous dispersion of paraffin wax (trade name: Hydrine P-7, manufactured by Chukyo Yushi Co., Ltd.), the same dispersion was used. A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 66 parts were used.

Example 9 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, a 33% aqueous dispersion of paraffin wax (trade name: Hydrine P-7, manufactured by Chukyo Yushi Co., Ltd.) was used instead of 33 parts of the same dispersion. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 4 parts were used.

Example 10 In the preparation of the coating solution for the heat-sensitive recording layer in Example 1, 10 parts of a 40% aqueous glyoxal solution was used instead of 1 part of the aqueous solution, and the preparation of the coating solution for the protective layer in Example 1 was repeated. 10% of acetoacetyl-modified polyvinyl alcohol [trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Co., Ltd.]
10% of completely saponified polyvinyl alcohol [trade name: PVA-110, manufactured by Kuraray Co., Ltd.] instead of 350 parts of the aqueous solution
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 350 parts of the aqueous solution was used.

Comparative Example 1 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, talc (trade name) was used instead of 33 parts of a 30% aqueous dispersion of paraffin wax (trade name: Hydrin P-7, manufactured by Chukyo Yushi Co., Ltd.). Name: High Micron HE-5, manufactured by Takehara Chemical Co., Ltd.] was used in the same manner as in Example 1 except for using 33 parts of a 30% aqueous dispersion.

Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that 1 part of a 40% aqueous solution of glyoxal was not used in the preparation of the coating solution for the heat-sensitive recording layer of Example 1.

Comparative Example 3 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, the same dispersion was used in place of 33 parts of a 30% aqueous dispersion of paraffin wax (trade name: Hydrine P-7, manufactured by Chukyo Yushi Co., Ltd.). 200
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that parts were used.

Comparative Example 4 A heat-sensitive recording material was obtained in the same manner as in Example 5, except that 20 parts of a 20% aqueous solution of polyamide epichlorohydrin was not used in the coating liquid for the protective layer.

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

[Evaluation] [Coloring property] Applied energy: 0.4 mJ / d using a thermosensitive recording evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.)
Each thermosensitive recording medium was recorded at ot, and the optical density (recording density) and the background portion (unrecorded portion) of the recording portion were measured in a visual mode using a Macbeth densitometer (Model RD-914, manufactured by Macbeth).

[Chemical resistance] The protective layer surface of each thermosensitive recording medium recorded in the above evaluation of the coloring property was rubbed five times with a cotton swab impregnated with a 50% ethanol aqueous solution, and then naturally dried.
Using a Macbeth densitometer [RD-
914, manufactured by Macbeth Co.] in a visual mode to evaluate the chemical resistance.

[Imprintability] The surface of each heat-sensitive recording medium was imprinted with vermilion and Shachihata X-stamper. One hour later, the imprinted portion was rubbed with tissue paper to evaluate the imprintability as follows. A: The stamped character was not scraped off at all. ：: The stamped character is slightly scraped off. Δ: The stamped character is scraped off, but a trace remains and is legible. X: The stamped character is scraped off and cannot be read.

[0055]

[Table 1]

[0056]

As is clear from Table 1, the heat-sensitive recording material of the present invention has good coloring properties and chemical resistance, and also has excellent printing properties.

Claims (7)

[Claims] 1. A thermosensitive recording medium having a thermosensitive recording layer mainly comprising a leuco dye, a coloring agent and an aqueous adhesive and a protective layer mainly comprising a pigment and an aqueous adhesive on a support, A heat-sensitive recording material, characterized in that the heat-sensitive recording layer contains 1 to 30% by weight of paraffin wax based on the heat-sensitive recording layer, and the heat-sensitive recording layer or the protective layer contains a crosslinking agent. 2. The heat-sensitive recording material according to claim 1, wherein the pigment in the protective layer is talc or aluminum hydroxide. 3. The method according to claim 2, wherein the pigment in the protective layer is talc.
The thermosensitive recording medium as described. 4. The method according to claim 1, wherein the pigment in the protective layer is 30 to
The heat-sensitive recording material according to any one of claims 1 to 3, which is 80% by weight. 5. The heat-sensitive recording medium according to claim 1, wherein the crosslinking agent is a compound having an epoxy group. 6. The thermosensitive recording medium according to claim 1, wherein the aqueous adhesive in the protective layer is a polyvinyl alcohol-based adhesive. 7. The heat-sensitive recording material according to claim 6, wherein the polyvinyl alcohol-based adhesive is at least one selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and carboxy-modified polyvinyl alcohol.