JP2010046797A - Heat-sensitive recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-sensitive recording medium which shows excellent heat resistance, water resistance, light fastness and recording sensitivity. <P>SOLUTION: The heat-sensitive recording medium has a heat-sensitive recording layer, containing leuco dye and a coloring agent, formed on the support. The heat-sensitive recording layer uses two different kinds of special chemical compounds as the coloring agent, and a shelf stability improver contains a special diphenylsulfone crosslinking chemical compound. The above two different kinds of special chemical compounds are: 2-[(4-hydroxyphenyl)methyl]-6-[(2-hydroxyphenyl)methyl]-4-(sec-butyl)phenol and 2,6-bis[(4-hydroxyphenyl)methyl]-4-(sec-butyl)phenol. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material utilizing a color development reaction between a basic colorless dye and an organic developer.

In general, a heat-sensitive recording material having a heat-sensitive color developing layer mainly composed of a colorless or light-colored dye precursor and a color developer that reacts with the dye precursor when heated is widely put into practical use. A thermal printer with a built-in thermal head is used for recording on this thermal recording medium, but such a thermal recording method has no noise during recording as compared with other recording methods that have been put to practical use. With the development of the information industry, with the development of the information industry, development and fixing are not necessary, maintenance is free, the equipment is relatively inexpensive and compact, and the resulting color development is very clear. Widely used for various measuring instruments and labels.
With the diversification and high performance of these recording apparatuses, the required quality for thermal recording media has become higher. With respect to the color development sensitivity, it is required that a clear color image with a high density can be obtained even with a small amount of heat energy as the apparatus is miniaturized and the recording speed is increased. In order to satisfy this requirement, a method (see Patent Document 1) is described in which the color development sensitivity is increased by using a novel developer.

  On the other hand, the use of heat-sensitive recording media in various natural environments such as heat, water, and light has increased with the spread of usage. However, the heat-sensitive recording material using a leuco dye and a colorant has a drawback that depending on the material used, the background part may develop color or the printed part may fade, and there is a strong demand for improvement. .

In addition, by using 2,6-bis [(2-hydroxy-5-methylphenyl) methyl] -4-methylphenol as a colorant for the heat-sensitive recording material, it is excellent in oil resistance, fingerprint resistance and heat resistance. Method for obtaining a thermal recording material (Patent Document 2), 2,6-bis [(2-hydroxy-5-methylphenyl) methyl] -4-methylphenol and 2,6-bis [(2-hydroxy-5-methyl) A method of obtaining a thermosensitive recording material excellent in whiteness, water resistance and stability over time by using in combination with (phenyl) methyl] -4-tert-butylphenol has also been proposed (Patent Document 3).

JP 2002-301873 A JP-A-6-115255 (Examples 6 and 9) JP 2001-96926 A (Claim 2)

  An object of the present invention is to provide a heat-sensitive recording material excellent in heat resistance, water resistance, light resistance and recording sensitivity of the heat-sensitive recording material.

  The present invention relates to a heat-sensitive recording material in which a heat-sensitive recording layer containing a leuco dye and a colorant is provided on a support, and the heat-sensitive recording layer is represented by the following general formulas (1) and (2) as a colorant. In addition, it is possible to solve the above problems by using a diphenylsulfone cross-linked compound represented by the following general formula (3) as a preservability improver.

  That is, the present invention provides the following thermal recording material.

Item 1: In a heat-sensitive recording material in which a heat-sensitive recording layer containing a leuco dye and a colorant is provided on a support, the heat-sensitive recording layer is represented by the following general formulas (1) and (2) as a colorant. A thermosensitive recording material comprising a compound and a diphenylsulfone cross-linking compound represented by the following general formula (3) as a preservability improver.

（式中、Ｒ１、Ｒ２はそれぞれｎ−ブチル基、ｉｓｏ−ブチル基、ｓｅｃ−ブチル基またはｔｅｒｔ−ブチル基を表す。）

(In the formula, R1 and R2 each represent an n-butyl group, an iso-butyl group, a sec-butyl group, or a tert-butyl group.)

（式中、ｎは１〜７の整数を表す。）
項２：上記一般式（１）及び（２）で表される化合物が２−［（４−ヒドロキシフェニル）メチル］−６−［（２−ヒドロキシフェニル）メチル］−４−（ｓｅｃ−ブチル）フェノール及び２，６−ビス［（４−ヒドロキシフェニル）メチル］−４−（ｓｅｃ−ブチル）フェノールである、項１に記載の感熱記録体。
項３：上記一般式（１）及び（２）の併用比率が７０：３０〜３０：７０である、項１または２に記載の感熱記録体。
項４：感熱記録層中に増感剤として、１，２−ジ（３−メチルフェノキシ）エタン、シュウ酸ジ−ｐ−メチルベンジルエステル及び、シュウ酸ジ−ｐ−クロロベンジルエステルから選ばれる少なくとも１種を、感熱記録層の全固形分に対して３〜２３質量％含有する、項1〜３のいずれか一項に記載の感熱記録体。

(In the formula, n represents an integer of 1 to 7.)
Item 2: The compound represented by the general formulas (1) and (2) is 2-[(4-hydroxyphenyl) methyl] -6-[(2-hydroxyphenyl) methyl] -4- (sec-butyl) Item 2. The heat-sensitive recording material according to Item 1, which is phenol and 2,6-bis [(4-hydroxyphenyl) methyl] -4- (sec-butyl) phenol.
Item 3: The thermal recording material according to Item 1 or 2, wherein the combined ratio of the general formulas (1) and (2) is 70:30 to 30:70.
Item 4: At least selected from 1,2-di (3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, and di-p-chlorobenzyl oxalate as a sensitizer in the heat-sensitive recording layer Item 4. The heat-sensitive recording material according to any one of Items 1 to 3, wherein 1 type is contained in an amount of 3 to 23% by mass relative to the total solid content of the heat-sensitive recording layer.

  The heat-sensitive recording material of the present invention has excellent effects on the heat resistance of the background portion, the water resistance of the recording portion, the light resistance, and the recording sensitivity.

  In the present invention, a compound represented by the following general formulas (1) and (2) (hereinafter referred to as a specific colorant) is used as a colorant in the heat-sensitive recording layer, and a storage stability improver. It contains a diphenylsulfone cross-linking compound represented by the following general formula (3).

（式中、Ｒ１、Ｒ２はそれぞれｎ−ブチル基、ｉｓｏ−ブチル基、ｓｅｃ−ブチル基またはｔｅｒｔ−ブチル基を表す。）

(In the formula, R1 and R2 each represent an n-butyl group, an iso-butyl group, a sec-butyl group, or a tert-butyl group.)

（式中、ｎは１〜７の整数を表す。）

(In the formula, n represents an integer of 1 to 7.)

  The present invention includes, among various colorants, a specific colorant and a storage stability improver, thereby providing excellent effects in heat resistance of the background portion, water resistance of the recording portion, light resistance, and recording sensitivity. It was made by finding

  The compound represented by the general formulas (1) and (2) is particularly 2-[(4-hydroxyphenyl) methyl] -6-[(2-hydroxyphenyl) methyl] -4- (sec-butyl) phenol. And 2,6-bis [(4-hydroxyphenyl) methyl] -4- (sec-butyl) phenol are more preferably used in combination.

  The combined ratio of the general formulas (1) and (2) is not particularly limited, but a mass ratio of about 70:30 to 30:70 is preferable.

  In addition to the specific trinuclear compound, the colorant of the present invention may contain a mixture of polynuclear bodies produced as a by-product during synthesis.

In the present invention, a specific colorant and a preservability improver are selectively used as the colorant, but other colorants may be used depending on the purpose within a range not inhibiting the desired effect of the present invention. It can also be used together. Examples of such other colorants include 4,4′-isopropylidenediphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4′-cyclohexylidenediphenol, 4-hydroxy. Benzyl benzoate, 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy-4′-allyloxydiphenylsulfone, bis (3- Allyl-4-hydroxyphenyl) sulfone, 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4-hydroxy-4′-methyldiphenylsulfone, 3,4-dihydroxyphenyl -4′-methylphenylsulfone, bis (4-hydroxy Phenolic compounds such as phenylthioethoxy) methane and bis (p-hydroxyphenyl) butyl acetate, N- (p-toluenesulfonyl) carbamoyl acid-p-cumylphenyl ester, 4,4′-bis [(4-methyl- 3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4′-bis (Np-tolylsulfonylaminocarbonylamino) diphenylmethane, N- (o-tolyl) -p-tolylsulfoamide, N- (p- Compounds having a —SO ₂ NHCO— bond in the molecule such as tolylsulfonyl) -N′-phenylurea, zinc p-chlorobenzoate, zinc 4- [2- (p-methoxyphenoxy) ethyloxy] salicylate, 4- [ 3- (p-tolylsulfonyl) propyloxy] salicylate zinc, 5- [p- (2-p- Methoxyphenoxyethoxy) cumyl] zinc salts of aromatic carboxylic acids such as zinc salicylate.

  The use ratio of the colorant is not particularly limited, but is preferably about 10 to 60% by mass with respect to the total solid content of the heat-sensitive recording layer. If the use ratio of the color former is less than 10% by mass, the recording sensitivity may be lowered, and if it exceeds 60% by mass, the ratio of the leuco dye may be lowered to lower the maximum recording density.

  The content of the diphenylsulfone crosslinking compound represented by the following general formula (3) used in the present invention is preferably 0.5 to 25% by mass, and 1 to 20% by mass with respect to the total solid content of the heat-sensitive recording layer. Is more preferable, and 3 to 18% by mass is most preferable. If it is less than 0.5% by mass, the water resistance of the recording part may be inferior, and if it exceeds 25% by mass, the heat resistance of the background part may be inferior.

（式中、ｎは１〜７の整数を表す。）

(In the formula, n represents an integer of 1 to 7.)

  Moreover, as another preservability improvement agent, it can use in the range which does not inhibit the desired effect of this invention. For example, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, , 1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2′-ethylidenebis (4,6-di-tert-butylphenol), 1,4-bis [α-methyl-α- (4 ′ -Hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 4,4′-thiobis (2-methyl-6-tert-butylphenol), 1 , 3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid and the like.

  In the present invention, a sensitizer can be used. Examples of the sensitizer include at least one of 1,2-di (3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, and di-p-chlorobenzyl oxalate. Is preferably used because the balance between the heat resistance of the background portion and the recording sensitivity is particularly excellent with respect to the compounds represented by the following general formulas (1), (2) and (3) used in the present invention. The content is 3 to 23% by mass based on the total solid content of the heat-sensitive recording layer. If it is less than 3% by mass, the recording sensitivity may be inferior, and if it exceeds 23% by mass, the heat resistance of the background portion may be inferior.

（式中、Ｒ１、Ｒ２はそれぞれｎ−ブチル基、ｉｓｏ−ブチル基、ｓｅｃ−ブチル基またはｔｅｒｔ−ブチル基を表す。）

(In the formula, R1 and R2 each represent an n-butyl group, an iso-butyl group, a sec-butyl group, or a tert-butyl group.)

（式中、ｎは１〜７の整数を表す。）

(In the formula, n represents an integer of 1 to 7.)

  Further, other sensitizers can be used in combination as long as the effects of the present invention are not impaired. Specific examples of the sensitizer include, for example, 1,2-diphenoxyethane, 1,2-di (4-methylphenoxy) ethane, 2-naphthylbenzyl ether, benzyl p-benzyloxybenzoate, dimethyl terephthalate, terephthalate Acid dibenzyl ester, m-terphenyl, diphenylsulfone, 1,2-diphenoxymethylbenzene, p-benzylbiphenyl, p-acetylbiphenyl, p-acetoluidide, 1,2-di (4-methoxyphenoxy) ethane, 1 , 2-di (4-chlorophenoxy) ethane, 1- (4-methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p- Trilbiphenyl ether, di (p-methoxyphenoxyethyl) A , Benzyl-4-methylthiophenyl ether, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, terephthalic acid dibutyl ester, isophthalic acid dibutyl ester, p-acetophenetide, N-acetoacetyl-p -Toluidine, di (β-biphenylethoxy) benzene and the like.

  An amide derivative can also be contained in the heat-sensitive recording layer. Specific examples of the amide derivatives include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, erucic acid amide, N-palmityl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl-12-hydroxy. Stearic acid amide, N-oleyl-12-hydroxystearic acid amide, N-methylol stearic acid amide, N-methylol behenic acid amide, methylene bis stearic acid amide, methylene bis lauric acid amide, methylene bis (12-hydroxy stearic acid amide) , Ethylene biscapric amide, ethylene bis lauric acid amide, ethylene bis stearic acid amide, ethylene bisisostearic acid amide, ethylene bis (12-hydroxystearic acid amide), ethylene bisbehen Amide, hexamethylene bis stearic acid amide, hexamethylene bis behenic acid amide, hexamethylene bis (12-hydroxystearic acid amide), butylene bis stearic acid amide, methylene bis oleic acid amide, ethylene bis oleic acid amide, ethylene bis erucic acid Amides, hexamethylenebisoleic acid amides, 1,3-xylylenebisstearic acid amides, N-butyl-N′-stearyl urea, N-phenyl-N′-stearyl urea, N, N′-distearyl urea, etc. Can be mentioned.

  Among the above amide derivatives, palmitic acid amide, stearic acid amide, behenic acid amide, N-methylol stearic acid amide, and ethylenebisstearic acid amide are preferably used because of their excellent thermal response.

  Specific examples of the leuco dye include 3- [2,2-bis (1-ethyl-2-methylindol-3-yl) vinyl] -3- (4-diethylaminophenyl) phthalide, 3,3-bis ( p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-cyclohexylamino-6 -Chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,8-dimethylfluorane, 3-diethylamino-6,7-dimethylfluorane, 3-diethylamino-7-chloro Fluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3-di (n- Til) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6 Methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-chloro-7-anilinofluorane, 3-diethylamino-6-methyl-7- (3-toluidino) fluorane, 3-pyrrolidino -6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3,3 -Bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3-p- (p-dimethylamino) Nilino) anilino-6-methyl-7-chlorofluorane, 3-p- (p-chloroanilino) anilino-6-methyl-7-chlorofluorane, 3- [1,1-bis (1-ethyl-2-yl) Methylindol-3-yl)]-3-p-diethylaminophenylphthalide, 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide, 3,6-bis (dimethylamino) And fluorene-9-spiro-3 ′-(6′-dimethylamino) phthalide.

The heat-sensitive recording layer is generally used for a heat-sensitive recording layer prepared by mixing and stirring a dye, a specific colorant, a specific preservability improver, a sensitizer, an adhesive, and an auxiliary agent using water as a medium. coating amount after drying a coating liquid on the support is formed by coating and drying so that 3 to 10 g / m ² approximately.

  The heat-sensitive recording layer may have a structure of a multilayer color forming layer in which a plurality of leuco dyes are arranged in different layers, or a structure of a single layer color forming layer in which a plurality of leuco dyes are contained in the same layer. .

  The method for forming the heat-sensitive recording layer is not particularly limited. For example, known appropriate application methods such as air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, gravure coating, etc. It is formed by.

  Examples of the adhesive compounded in the thermal recording layer coating liquid include polyvinyl alcohols such as partially saponified or fully saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol. Starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, ethylcellulose, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene -Water-soluble adhesives such as maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin, Vinyl acetate-based latex in beauty, urethane latex, acrylic latex, styrene - butadiene latex, and the like.

  Examples of the auxiliary agent include surfactants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate / sodium salt, fatty acid metal salt, and waxes such as polyethylene wax, carnauba wax, paraffin wax, ester wax, and the like. , Kaolin, clay, talc, calcium carbonate, calcined kaolin, titanium oxide, amorphous silica, pigments such as aluminum hydroxide, glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, dialdehyde starch, melamine Resin, polyamide resin, polyamide-epichlorohydrin resin, ketone-aldehyde resin, adipic acid dihydrazide, borax, boric acid, ammonium zirconium carbonate, epoxy Waterproofing agents shea based compounds, and other defoaming agents, fluorescent dyes, coloring dyes and the like.

  The support on which the heat-sensitive recording layer is provided is not particularly limited, and examples thereof include paper, synthetic paper, and film base materials such as polyethylene terephthalate, polypropylene, and polyethylene. The thickness of the support is about 20 to 200 μm, and in the case of synthetic paper or film, an anchor coat layer may be provided on the surface or a corona discharge treatment may be performed to improve the adhesion to the heat-sensitive recording layer. it can. Further, a conductive treatment with a conductive agent may be performed.

  In the heat-sensitive recording material of the present invention, in order to further increase the recording sensitivity, a pigment having an oil absorption of 70 ml / 100 g or more, or organic hollow particles and an adhesive are mainly contained between the support and the heat-sensitive recording layer. An undercoat layer, a protective layer mainly composed of an adhesive having a film-forming property in order to improve the recording runnability and chemical resistance, or on the back side of the support, or Various known heat-sensitive recording body manufacturing techniques such as applying a smoothing process such as supercalendering after coating each layer, or providing a magnetic recording layer or an adhesive layer on the back side of the support may be added. it can.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “parts” and “%” represent “parts by mass” and “mass%”, respectively.

Example 1
-Preparation of leuco dye dispersion (liquid A) consisting of 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 5 parts of 5% aqueous solution of methylcellulose, and 7.8 parts of water. The composition was pulverized with a sand mill until the average particle size became 0.7 μm to obtain a leuco dye dispersion (liquid A).

-Preparation of colorant dispersion (Liquid B) 2-[(4-hydroxyphenyl) methyl] -6-[(2-hydroxyphenyl) methyl] -4- (sec-butyl) phenol 10 parts, 2,6 -A composition comprising 10 parts of bis [(4-hydroxyphenyl) methyl] -4- (sec-butyl) phenol, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water in a sand mill with an average particle size of 0.7 μm The resulting colorant dispersion (liquid B) was obtained by grinding.

・ Preparation of preservative improver dispersion (liquid C)

前記一般式（３）で示されたジフェニルスルホン架橋型化合物（商品名：Ｄ−９０、nが１〜７の合計含有比率が８７質量％、日本曹達社製）１０部、メチルセルロースの５％水溶液５部、及び水７．８部からなる組成物をサンドミルで平均粒子径が１．０μｍとなるまで粉砕して保存性向上剤分散液（Ｃ液）を得た。

10 parts of diphenylsulfone crosslinking compound represented by the general formula (3) (trade name: D-90, n is 1 to 7 in total content of 87% by mass, manufactured by Nippon Soda Co., Ltd.), 5% aqueous solution of methylcellulose A composition comprising 5 parts and 7.8 parts of water was pulverized with a sand mill until the average particle size became 1.0 μm to obtain a preservative improver dispersion (liquid C).

Preparation of sensitizer dispersion liquid (liquid D) A composition comprising 10 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose, and 7.8 parts of water was averaged by a sand mill. A sensitizer dispersion (D liquid) was obtained by pulverizing until the diameter became 1.0 μm.

-Preparation of sensitizer dispersion liquid (E liquid) A composition comprising 10 parts of di-p-methylbenzyl oxalate, 5 parts of a 5% aqueous solution of methyl cellulose, and 7.8 parts of water was mixed with a sand mill to obtain an average particle size of 1 A sensitizer dispersion liquid (E liquid) was obtained by pulverizing to 0.0 μm.

Preparation of sensitizer dispersion (liquid F) A composition comprising 10 parts of di-p-chlorobenzyl oxalate, 5 parts of a 5% aqueous solution of methylcellulose, and 7.8 parts of water was mixed with a sand mill to obtain an average particle size of 1 A sensitizer dispersion (F liquid) was obtained by pulverizing to 0.0 μm.

・ Preparation of colorant dispersion (liquid G)
A composition comprising 10 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 7.8 parts of water is pulverized with a sand mill until the average particle size is 0.7 μm, and colored. An agent dispersion (liquid G) was obtained.

Preparation of preservative improver dispersion (liquid H) 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane 10 parts, methylcellulose 5% aqueous solution 5 parts, and water The composition consisting of 7.8 parts was pulverized with a sand mill until the average particle size became 1.0 μm to obtain a preservability improving agent dispersion (liquid H).

-Preparation of coating solution for undercoat layer To a dispersion obtained by dispersing 85 parts of calcined kaolin (trade name: Ancilex, Engelhard) in 320 parts of water, a styrene-butadiene copolymer emulsion (solid content) 40 parts of (concentration 50%) and 50 parts of 10% aqueous solution of oxidized starch were mixed and stirred to obtain an undercoat layer coating solution.

・ Preparation of coating solution for heat-sensitive recording layer A part 25 parts, B part 50 parts, C part 25 parts, D part 25 parts, light calcium carbonate 10 parts, amorphous silica 15 parts, polyvinyl alcohol (acrylamide / acrylic acid derivative) -Acrylonitrile) graft copolymer (trade name: Polymeron-1560, solid content concentration 15%, manufactured by Arakawa Chemical Co., Ltd.) 67 parts, polyvinyl alcohol (trade name: Poval PVA-235, manufactured by Kuraray Co., Ltd.) A composition comprising 50 parts of a 10% aqueous solution, 8 parts of an aqueous dispersion of zinc stearate (trade name: Hydrin Z-8-36, solid concentration 36%, manufactured by Chukyo Yushi Co., Ltd.), and 110 parts of water is mixed and stirred. Thus, a thermal recording layer coating solution was obtained.

-Preparation of coating solution for protective layer 100 parts of 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Gohsephimer Z-200, polymerization degree 1000, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), acrylic resin (trade name: Barrier Star OT-1035-1, solid content concentration 25%, manufactured by Mitsui Chemicals, Inc.) 40 parts, 40% aluminum hydroxide dispersion 40 parts, composition comprising 2 parts of 30% zinc stearate dispersion mixed and stirred to protect A layer coating solution was obtained.

・ Production of thermal recording material
An undercoat layer coating solution is applied and dried on one side of a 48 g / m ² base paper so that the applied amount after drying is 9.0 g / m ^2, and the applied amount after drying is 4 on the undercoat layer. The coating solution for the heat sensitive recording layer was applied and dried so as to be 0.0 g / m ² . Further, the protective layer coating solution was applied and dried on the heat-sensitive recording layer so that the coating amount after drying was 2.0 g / m ² . Thereafter, the surface was smoothed by a super calender, and a thermal recording material having a surface smoothness of about 1000 to 4000 seconds was obtained with a Oken type smoothness meter.

Example 2
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 25 parts of E liquid was used instead of 25 parts of D liquid in the preparation of the thermal recording layer coating liquid of Example 1.

Example 3
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 25 parts of the F liquid was used instead of 25 parts of the D liquid in the preparation of the thermosensitive recording layer coating liquid of Example 1.

Example 4
A thermosensitive recording material was obtained in the same manner as in Example 1 except that in the preparation of the thermal recording layer coating liquid of Example 1, 15 parts of E liquid and 10 parts of F liquid were used instead of 25 parts of D liquid.

Comparative Example 1
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 50 parts of the G liquid was used instead of 50 parts of the B liquid in the preparation of the coating solution for the thermosensitive recording layer of Example 1.

Comparative Example 2
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 25 parts of the H liquid was used instead of 25 parts of the C liquid in the preparation of the thermal recording layer coating liquid of Example 1.

Comparative Example 3
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 25 parts of the liquid C was not used in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

  The following evaluations were performed on the seven types of heat-sensitive recording materials thus obtained, and the results are shown in Table 1.

Recording sensitivity Using a thermal evaluation machine (trade name: Barrabe 300, manufactured by SATO), each thermal recording medium at a printing speed of 4 inches, printing energy of 0.13 mj / dot, 0.15 mj / dot, and 0.20 mj / dot. The solid color was developed, and the density of the recorded portion was measured in a visual mode of a Macbeth densitometer (trade name: RD-914, manufactured by Macbeth).

・ Heat resistance (background)
Each thermal recording medium was allowed to stand in a dryer at 80 ° C. for 24 hours, and then the background density of the blank paper portion was measured in a visual mode of a Macbeth densitometer (trade name: RD-914, supra).

Water resistance The printed matter evaluated by the recording sensitivity was immersed in water for 24 hours, then taken out from water and air-dried, and then the recording portion of 0.20 mj / dot was placed on a Macbeth densitometer (trade name: RD-914, supra). ) In the visual mode.

-Light resistance A 0.20 mj / dot recorded portion evaluated by recording sensitivity was left in a light resistance tester (trade name: Xenon Weather Meter XL-75, manufactured by Suga Test Co., Ltd.) at 63 ° C and 40% for 24 hours. The density of the recording part was measured in the visual mode of a Macbeth densitometer (trade name: RD-914, supra).

Claims (4)

In a heat-sensitive recording material in which a heat-sensitive recording layer containing a leuco dye and a colorant is provided on a support, the heat-sensitive recording layer is used in combination with the compounds represented by the following general formulas (1) and (2) as a colorant And a diphenylsulfone cross-linking compound represented by the following general formula (3) as a preservability improver.

(In the formula, R1 and R2 each represent an n-butyl group, an iso-butyl group, a sec-butyl group, or a tert-butyl group.)

(In the formula, n represents an integer of 1 to 7.)   The compounds represented by the general formulas (1) and (2) are 2-[(4-hydroxyphenyl) methyl] -6-[(2-hydroxyphenyl) methyl] -4- (sec-butyl) phenol and 2 The heat-sensitive recording material according to claim 1, which is 1,6-bis [(4-hydroxyphenyl) methyl] -4- (sec-butyl) phenol.   The heat-sensitive recording material according to claim 1 or 2, wherein the combined ratio of the general formulas (1) and (2) is 70:30 to 30:70.   As a sensitizer in the heat-sensitive recording layer, at least one selected from 1,2-di (3-methylphenoxy) ethane, oxalic acid di-p-methylbenzyl ester, and oxalic acid di-p-chlorobenzyl ester is used. The heat-sensitive recording material according to any one of claims 1 to 3, which is contained in an amount of 3 to 23% by mass relative to the total solid content of the heat-sensitive recording layer.