JPH1035109A - Heat-sensitive recording body and its method of use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of first coat fog even when being used or stored under the high temperature environment by containing 1-phenoxy-2-(2- naphthoxy)ethane and/or 1,3-bis(2-naphthoxy)propane in a recording layer. SOLUTION: 1-phenoxy-2-(2-naphthoxy)ethane and/or 1,3-bis(2-naphthoxy) propane is contained in a recording layer of a heat-sensitive recording body. A coloration agent is a diphenylsulfone derivative represented by the formula I. In the formula, R1 and R2 represent respectively C1 -C4 alkyl, C2 -C4 alkenyl, C1 -C4 alcoxyl, benzyl oxy or halogen atom. (m) represents 0-2 integers, (n) represents 1-3 integers, and (p) and (q) represent respectively 0-2 integers. The generation of first coat fog is reduced when being exposed under the high temperature condition by the arrangement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermosensitive recording medium,
In particular, the present invention relates to a thermosensitive recording medium which does not cause a decrease in whiteness in a high-temperature environment and has excellent storage stability of a recorded image, and a method for using the same.

[0002]

2. Description of the Related Art A thermosensitive recording material which utilizes a reaction between a colorless or pale-colored basic dye and a color former to form a recording image by contacting both coloring materials by heat is well known. . Such a thermosensitive recording medium is used in a wide range of fields because the recording apparatus is relatively inexpensive and the recording apparatus is compact and maintenance-free.

As one example, POS (point of sale)
s) The label system is used in various manufacturing processes. For example, there is a case where a thermal recording medium is used by installing a printer in a high temperature environment of 80 ° C. or more. Further, the thermosensitive recording medium after recording may be placed in an environment where the recording medium is heated to a temperature of 80 ° C. or more. Thermal recording media used in such an environment include:
Each of them is required to be free from background fog even when exposed to a high-temperature environment of 80 ° C. or higher and to have good preservability of recorded images. However, in the sensitizers generally used conventionally, even if the recording sensitivity is improved, there are drawbacks such as occurrence of background fog in such a high-temperature environment, and satisfactory results have not been obtained. is there.
For this reason, there is a strong demand for a thermosensitive recording medium that has excellent recording sensitivity, does not reduce the whiteness of the white paper portion of the recording layer even when used or stored in a high-temperature environment, and can stably maintain a recorded image.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material which is less likely to cause background fog even when used or stored in a high-temperature environment, and which has excellent storage stability of a recorded image, and a method of using the same. To provide.

[0005]

The present invention relates to a thermosensitive recording medium having a recording layer containing a colorless or light-colored basic dye and a color former on a support, wherein 1-phenoxy-2 is added to the recording layer. -(2-naphthoxy) ethane and / or 1,
The present invention relates to a heat-sensitive recording material characterized by containing 3-bis (2-naphthoxy) propane. The present invention also relates to a method for using a thermosensitive recording medium used or stored in a high temperature environment, wherein 1-phenoxy-2 is contained in the recording layer of the thermosensitive recording medium.
The present invention relates to a method for using a thermosensitive recording material, characterized by containing-(2-naphthoxy) ethane and / or 1,3-bis (2-naphthoxy) propane.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a thermosensitive recording medium having a recording layer containing a colorless or pale-colored basic dye and a color former, wherein the recording layer contains 1-phenoxy-2- (2-naphthoxy). ) By containing ethane and / or 1,3-bis (2-naphthoxy) propane, it is possible to obtain a heat-sensitive recording material having less occurrence of background fog even when exposed to high-temperature conditions and having excellent storage stability of recorded images. It is obtained.

1-phenoxy-2- used in the present invention
(2-Naphthoxy) ethane and 1,3-bis (2-naphthoxy) propane are used in, for example, a thermal recording medium described in Japanese Patent Publication No. 4-33630. However, the purpose here is to improve the recording sensitivity of the thermosensitive recording medium, and there is no description of the thermosensitive recording medium and the method of using the thermosensitive recording medium having no background fog even at high temperatures as described in the present invention and also having good preservability of the recorded image. There was no suggestion. The present invention provides for the selective use of such specific heat-fusible materials,
It is intended to obtain a thermosensitive recording medium which has less occurrence of background fogging even when used or stored in a high temperature environment of 80 ° C. or higher and has excellent storage stability of a recorded image. Note that the upper limit temperature at which such an effect is obtained cannot be unconditionally specified because it varies depending on the types and the use ratios of the basic dye, the color former, and the heat-fusible substance constituting the color-forming system.
The effect can be obtained up to about 20 ° C. The amount of 1-phenoxy-2- (2-naphthoxy) ethane and / or 1,3-bis (2-naphthoxy) propane used in the heat-sensitive recording medium of the present invention is not necessarily limited, but is not limited to a basic dye. 10-7 for 100 parts by weight
It is desirably adjusted to be 00 parts by weight, preferably 50 to 500 parts by weight.

In the present invention, various types of colorless or light-colored basic dyes constituting the recording layer of the thermosensitive recording medium are known, and examples thereof include the following. 3- (N
-Ethyl-N-isoamylamino) -6-methyl-7-
Anilinofluoran, 3-diethylamino-7- (m-
Trifluoromethylanilino) fluoran, 3- (N-
Ethyl-N-isoamylamino) -7- (o-chloroanilino) fluoran, 3-di-n-pentylamino-6
-Methyl-7-anilinofluoran, 3- [N- (3-
Ethoxypropyl) -N-ethylamino] -6-methyl-7-anilinofluoran, 3- [N- (3-ethoxypropyl) -N-methylamino] -6-methyl-7-anilinofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) fluorane, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- ( 2,4-xyridino)
Fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-di-n-butylamino-7-
(O-chloroanilino) fluoran, 3-di-n-butylamino-7- (o-fluoroanilino) fluoran,
3- (N-ethyl-N-cyclopentylamino) -6
Methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-
Anilinofluoran, 3-pyrrolidino-6-methyl-7
-Anilinofluoran, 3-diethylamino-6-methyl-7- (2,6-xyridino) fluoran, 3- (N
-Methyl-N-n-propylamino) -6-methyl-7
-Anilinofluoran, 2,2-bis {4- [6 '-(N
-Cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} propane, 3-diethylamino-6
-Methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6,7
-Dimethylfluorane, 3,3'-bis (1-ethyl-2
-Methylindol-3-yl) phthalide, 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylamino Phenyl) -6
Dimethylaminophthalide, 3,7-bis (dimethylamino) -10-benzoylphenothiazine, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7
-Tetrachlorophthalide, 3,3'-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide,
3-di-n-pentylamino-6,8,8-trimethyl-
9-ethyl-8,9-dihydro- (3,2, e) pyridfluoran, 3-di-n-butylamino-6,8,8-trimethyl-9-ethyl-8,9-dihydro- (3,2 , e)
Pyridofluorane, 3- [1,1-bis (4-diethylaminophenyl) ethylene-2-yl] -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl)
Amino-5,7-dimethylfluoran, 3- (4-dibutylaminophenyl) amino-6-methyl-7-chlorofluoran, 3- (1-methyl-2-phenylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-methyl-2-phenylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -4,7-diazaphthalide etc. Of course, it is not limited to these dyes, and two or more dyes can be used in combination.

Among these dyes, 3-di-
n-butylamino-6-methyl-7-anilinofluoran, 3-di-n-pentylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-7-
(O-Chloroanilino) fluoran and 3-diethylamino-7- (m-trifluoromethylanilino) fluoran are excellent in color development and background fog, and are particularly preferably used.

Various known compounds can be used as the colorant constituting the heat-sensitive recording layer, and specific examples thereof are as follows. 2,2-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl)
-4-methylpentane, bis (4-hydroxyphenylthioethoxy) methane, 1,4-bis [α-methyl-α
-(4'-hydroxyphenyl) ethyl] benzene,
3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone , Bis (3-allyl-4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1- [α-methyl-α-
(4-hydroxyphenyl) ethyl] -4- [α ′, α ′
-Bis (4-hydroxyphenyl) ethyl] benzene,
4-hydroxybenzoic acid benzyl ester, bis (4-
(Hydroxyphenyl) butyl acetate, bis (4-hydroxyphenylthioethyl) ether, N- (p-tolylsulfonyl) -N′-phenylurea, 4,4′-bis (p
-Toluenesulfonylaminocarbonylamino) diphenylmethane, zinc salt of 4- [2- (p-methoxyphenoxy) ethoxy] salicylic acid, zinc salt of 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5
-[P- (2-p-methoxyphenoxyethoxy) cumyl] zinc salt of salicylic acid, zinc salt of 4-octyloxyacetylaminosalicylic acid, antipyrine complex of zinc thiocyanate and the like. In addition, two or more kinds can be used in combination as needed.

In the present invention, a diphenylsulfone derivative represented by the following general formula (1) is preferably used because a heat-sensitive recording material having excellent preservability of a blank portion and a printed portion particularly at a high temperature can be obtained.

[0012]

Embedded image (Wherein R ₁ and R ₂ are each a C ₁ -C ₄ alkyl group, C ₂
Represents a C ₄ to alkenyl group, a C _{1 to} C ₄ alkoxyl group, a benzyloxy group, or a halogen atom. m is 0
An integer of 2, n is an integer of 1 to 3, p and q are each 0 to 2
Indicates an integer. )

Among the diphenylsulfone derivatives represented by the general formula (1), bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone or 2,4'- Dihydroxydiphenyl sulfone is more preferably used because of its excellent preservability of a recorded image and a blank portion particularly at a high temperature.

The ratio of the basic dye to the color former in the heat-sensitive recording layer is not particularly limited, but is generally 100 to 700 parts by weight, preferably 150 to 400 parts by weight, per 100 parts by weight of the basic dye. A degree of colorant is used.

In the heat-sensitive recording material of the present invention, various known heat-fusible substances can be used in combination in the recording layer as a recording sensitivity improver as long as the desired effect of the present invention is not impaired. Such heat-fusible substances include, for example, stearic acid amide, ethylene bis stearic acid amide, methylene bis stearic acid amide, N-methylol stearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, benzyl p-benzyloxybenzoate, -Hydroxy-2-naphthoic acid phenyl ester, oxalic acid di (p-chlorobenzyl) ester, oxalic acid di (p-methylbenzyl) ester, 2-naphthylbenzyl ether, p-benzylbiphenyl, biphenyl-p-tolyl ether, Bis (4-methoxyphenoxyethyl) ether, 1,4-bis (vinyloxyethoxy) benzene, etc. can be exemplified.

The recording layer may contain various known storage improvers for further improving the storage stability. Specific examples of the storage stability improver include the following compounds. 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4'-thiobis (3-methyl-6-tert-butylphenol), 1,3,5-trimethyl-2,4,6-tris (3,
5-di-tert-butyl-4-hydroxybenzyl)
Benzene, 2- (2-hydroxy-5-methylphenyl) benzotriazole, tetrakis (1,2,2,6,6
-Pentamethyl-4-piperidinyl) -1,2,3,4-
Butanetetracarboxylate, 4-benzyloxyphenyl-4 '-(2-methyl-2,3-epoxypropyloxy) phenylsulfone, 1,3,5-tris (4-t
tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 4,4′-butylidenebis (6
-Tert-butyl-m-cresol), bis [2-hydroxy-3- (2'H-benzotriazol-2'-yl) -5-octylphenyl] methane, 2,2'-methylenebis (4,6- Sodium salt or magnesium salt of di-tert-butylphenyl) phosphoric acid;

The coating liquid containing these is generally mixed with water, using a dispersing medium such as a ball mill, an attritor, a sand mill, a colloid mill, or the like, together with a dye, a colorant, a heat-fusible substance, or the like. It is prepared by mixing and stirring separately dispersed ones.

In such a coating solution, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, acetoacetyl group-modified are usually used as binders. Polyvinyl alcohol, various modified polyvinyl alcohols such as silicon-modified polyvinyl alcohol, styrene / maleic anhydride copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, etc., have a total solid content of 2 to 40. % By weight, preferably about 5 to 25% by weight. Of course, two or more of these binders can be used in combination.

Further, various auxiliaries can be added to the coating liquid, for example, a dispersion of sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate, sodium salt of fatty acid metal salt and the like. Agents, UV absorbers such as triazoles,
Other examples include an antifoaming agent, a fluorescent dye, a coloring dye, and an antioxidant. Also, a dispersion or emulsion of stearic acid, polyethylene wax, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, etc. in the paint so that the thermal recording medium does not stick due to contact with the recording device or recording head. Can also be added.

In addition, kaolin, clay, talc, calcium carbonate,
Inorganic pigments such as calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica and activated clay, or organic pigments such as urea-formaldehyde resin filler can also be added.

As the support, paper (acid paper, neutral paper),
A plastic film, a synthetic paper, a plastic film or a synthetic paper bonded to a coated paper, a high-quality paper, or the like via an adhesive, or a plastic laminated on paper is used. Examples of such a plastic film include films of polyethylene, polyester, polypropylene, polyvinyl chloride, polystyrene, nylon and the like. As the synthetic paper, for example, a synthetic paper manufactured by a film method or a fiber method is used. In the film method, a synthetic resin, a filler and additives are melt-kneaded and then extruded to form a film. There are a system, a surface coating system in which a pigment coating layer is provided, a surface treatment system, and the like. Examples of the fiber synthetic paper include synthetic pulp paper and spunbond paper.

The method for applying the recording layer is not particularly limited, and the recording layer can be formed according to a conventionally known and commonly used technique, for example, bar coating, air knife coating, rod blade coating, pure blade coating, short dwell coating. It is formed by a method of applying and drying a coating liquid by curtain coating or the like. When a plastic film is used as the support, the coating efficiency can be increased by subjecting the surface to a treatment such as corona discharge or electron beam irradiation. The amount of the coating solution is not particularly limited, but is usually 2 to 10 g / m2 in dry weight.
² , preferably in the range of about 3 to 7 g / m ² .

Further, by providing a protective layer comprising an adhesive, a lubricant, a pigment, and the like on the heat-sensitive recording layer, a heat-sensitive recording material excellent in printability, redness suitability, writing suitability, and the like can be obtained. Specific examples of the adhesive used for the protective layer include, for example, polyvinyl alcohol having various degrees of saponification, acetoacetyl group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acrylic resin, and polyurethane resin. .
These adhesives are used in an amount of 10 to 95 with respect to the total solid amount.
%, Preferably in the range of 30 to 90% by weight. The coating amount of the protective layer, 0.5 to 10 g / m ² by dry weight, is adjusted preferably, 1 to 7 g / m ² range of about.

In addition, a layer containing a water-soluble, water-dispersible, electron beam-curable, or ultraviolet-curable resin may be provided on the protective layer for the purpose of imparting high gloss. Of course, it is also possible to provide a protective layer on the back surface or to provide an undercoat layer on the support, and it is possible to add various known techniques in the field of thermal recording medium production.

[0025]

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 thereto. Unless otherwise specified, parts and% in examples are parts by weight and% by weight, respectively.

Example 1 [Formation of undercoat layer] 100 parts of calcined clay (trade name: Ansilex, manufactured by Engelhardt Co.), 15 parts of styrene / butadiene copolymer latex (solid content: 50%), 1 part
30 parts of 0% aqueous polyvinyl alcohol solution and water 1
The composition consisting of 00 parts was mixed and stirred to obtain a coating liquid for an undercoat layer. The obtained coating liquid was applied to 50 g / m ² high-quality paper so that the coating amount after drying was 10 g / m ² , and dried to form an undercoat layer.

[Preparation of Solution A] 3-Di-n-butylamino-
A composition comprising 10 parts of 6-methyl-7-anilinofluorane, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water was pulverized by a sand mill until the average particle size became 1.0 μm.

[Preparation of solution B] 1-phenoxy-2- (2-
Naphthoxy) ethane 15 parts, methylcellulose 5%
A composition comprising 7 parts of an aqueous solution and 28 parts of water was pulverized by a sand mill until the average particle size became 1.5 μm.

[Preparation of Solution C] A composition comprising 20 parts of bis (3-allyl-4-hydroxyphenyl) sulfone, 10 parts of a 5% aqueous solution of methylcellulose, and 30 parts of water was subjected to sand milling until the average particle size became 1.4 μm. Crushed.

[Formation of Recording Layer] 30 parts of solution A, 50 parts of solution B
Part, C liquid 60 parts, 10% polyvinyl alcohol aqueous solution
150 parts and 10 parts of calcium carbonate were mixed and stirred to obtain a coating solution for a heat-sensitive recording layer. The obtained coating liquid was applied on the undercoat layer so as to have a dry weight of 4 g / m ² and dried to obtain a thermosensitive recording medium.

Example 2 The procedure of Example 1 was repeated except that 1,3-bis (2-naphthoxy) propane was used in place of 1-phenoxy-2- (2-naphthoxy) ethane in the preparation of solution B. A recording was obtained.

Examples 3 to 5 Thermosensitive recording materials were obtained in the same manner as in Example 1 except that the following compound was used in place of bis (3-allyl-4-hydroxyphenyl) sulfone in the preparation of solution C. . Example 3: 4-hydroxy-4'-isopropoxydiphenyl sulfone Example 4: 2,4'-dihydroxydiphenyl sulfone Example 5: 1,1-bis (4-hydroxyphenyl)-
1-phenylethane

Examples 6 to 7 A heat-sensitive recording material was obtained in the same manner as in Example 2 except that the following compound was used instead of bis (3-allyl-4-hydroxyphenyl) sulfone in the preparation of solution C. . Example 6: 4-hydroxy-4'-isopropoxydiphenyl sulfone Example 7: 2,4'-dihydroxydiphenyl sulfone

Examples 8 to 10 The procedure of Example 1 was repeated, except that the following compound was used instead of 3-di-n-butylamino-6-methyl-7-anilinofluoran in the preparation of solution A. A thermosensitive recording medium was obtained. Example 8: 3-di-n-pentylamino-6-methyl-
7-anilinofluorane Example 9: 3-di-n-butylamino-7- (o-chloroanilino) fluoran Example 10: 3-diethylamino-7- (m-trifluoromethylanilino) fluoran

Examples 11 to 13 The procedure of Example 2 was repeated, except that the following compound was used instead of 3-di-n-butylamino-6-methyl-7-anilinofluoran in the preparation of solution A. A thermosensitive recording medium was obtained. Example 11: 3-di-n-pentylamino-6-methyl-7-anilinofluoran Example 12: 3-di-n-butylamino-7- (o-chloroanilino) fluoran Example 13: 3- Diethylamino-7- (m-trifluoromethylanilino) fluoran

Comparative Examples 1 to 4 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the following compound was used instead of 1-phenoxy-2- (2-naphthoxy) ethane in the preparation of Solution B. Comparative Example 1: 1,2-diphenoxyethane Comparative Example 2: 1-phenoxy-2- (1-naphthoxy) ethane Comparative Example 3: 1,2-bis (3-methylphenoxy) ethane Comparative Example 4: 2-naphthyl Benzyl ether

The 17 types of heat-sensitive recording media thus obtained were recorded by a heat-sensitivity evaluation machine (manufactured by Okura Electric Co., Ltd., TH-PMD type, applied voltage 18 V, pulse cycle 3.0 ms, applied pulse width 2.0 ms). The densities of the recording portion and the blank portion were measured in a visual mode using a Macbeth densitometer (RD-914, manufactured by Macbeth), and the results are shown in Table 1.
After the recording, the heat-sensitive recording medium was placed in a 90 ° C.
After holding for a period of time, the densities of the recording portion and the blank portion were measured, and the results are also shown in Table 1 as “after processing”.

[0038]

[Table 1]

[0039]

As is clear from the results in Table 1, the heat-sensitive recording material of the present invention has a small decrease in the whiteness of the white paper portion under a high-temperature environment, and is excellent in the preservability of the recorded image. It was extremely suitable for use or storage in such a high temperature environment.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tetsuo Tsuchida 4-3-1 Jokoji Temple, Amagasaki-shi, Hyogo Oji Paper Co., Ltd. Amagasaki Research Center (72) Inventor Toranosuke Saito 1-chome 24-10 Itokaichi, Ibaraki-shi, Osaka No. Sanko Development Science Laboratory Co., Ltd. (72) Inventor Takashi Ishibashi 1-10-24 Itukaichi, Ibaraki-shi, Osaka

Claims (4)

[Claims] 1. A heat-sensitive recording medium having a recording layer containing a colorless or light-colored basic dye and a color former on a support, wherein 1-phenoxy-2- (2-naphthoxy) ethane is contained in the recording layer. And / or 1,3-bis (2-naphthoxy) propane. 2. The heat-sensitive recording material according to claim 1, wherein the color former is at least one of diphenylsulfone derivatives represented by the following general formula (1). Embedded image (Wherein R ₁ and R ₂ are each a C ₁ -C ₄ alkyl group, C ₂
Represents a C ₄ to alkenyl group, a C _{1 to} C ₄ alkoxyl group, a benzyloxy group, or a halogen atom. m is 0
An integer of 2, n is an integer of 1 to 3, p and q are each 0 to 2
Indicates an integer. ) 3. The heat-sensitive composition according to claim 1, wherein the coloring agent is bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone or 2,4′-dihydroxydiphenylsulfone. Record body. 4. A method for using a thermosensitive recording medium used or stored in a high temperature environment, wherein 1-phenoxy-2- (2-naphthoxy) ethane and / or 1-phenoxy-2- (2-naphthoxy) ethane is contained in a recording layer of the thermosensitive recording medium. , 3-bis (2-naphthoxy) propane.