JPH10100534A - Thermosensitive recording medium and its using method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of texture fogging due to use or storage in a high-temperature environment by incorporating 1-(4-methylphenoxy)-2-(2- naphthoxy)ethane and/or 1,4-bis(2-naphthoxy)butane as sensitizer in a recording layer of a thermosensitive recording medium. SOLUTION: In the thermosensitive recording medium formed to obtain a recording image by bringing both color developing substances into contact with one another by heat by utilizing reaction of basic dye with colorant, 1-(4- methylphenoxy)-2-(2-naphthoxy)ethane and/or 1,4-bis(2-naphthoxy)butane is contained in a recording layer. As the colorant, diphenylsulfone derivative represented by a general formula as shown is used. In the formula, R, R are 1-4C alkyl group, halogen atom, (m) is integer of 1 to 2, (n) is integer of 1 to 3, and (p), (q) are integers of 0 to 2. Further, as the dye, 3-(N-ethyl-p- toluidino)-6-methyl-7-anilinofluoran, etc., is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermosensitive recording medium,
In particular, the present invention relates to a heat-sensitive recording medium which has a small 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, a printer may be installed in a high-temperature environment of 100 ° C. or more to use a thermal recording medium. Further, the thermosensitive recording medium after recording may be placed in an environment where the thermosensitive recording medium is heated to a temperature of 100 ° C. or more. The heat-sensitive recording medium used in such an environment is required to be free from background fog even when exposed to a high-temperature environment of 100 ° C. or higher and to have good preservability of a recorded image. You. However, with sensitizers that have been conventionally used generally, even if the recording sensitivity is improved,
Under the high temperature environment, there is a drawback such as occurrence of background fogging, and satisfactory results have not been obtained. 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]

SUMMARY OF THE INVENTION The present invention relates to a thermosensitive recording medium having a recording layer containing a colorless or light-colored basic dye and a colorant on a support, wherein 1- (4- The present invention relates to a thermosensitive recording material containing methylphenoxy) -2- (2-naphthoxy) ethane and / or 1,4-bis (2-naphthoxy) butane. The present invention also relates to a method for using a thermosensitive recording medium used or stored in a high-temperature environment, wherein the recording layer of the thermosensitive recording medium contains 1-
The present invention relates to a method for using a thermosensitive recording material, characterized by containing (4-methylphenoxy) -2- (2-naphthoxy) ethane and / or 1,4-bis (2-naphthoxy) butane.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, 1- (4
By using -methylphenoxy) -2- (2-naphthoxy) ethane and / or 1,4-bis (2-naphthoxy) butane, there is little occurrence of background fog even when exposed to a high-temperature environment, and recording is performed. A heat-sensitive recording medium having excellent storage stability of an image is obtained.

The 1- (4-methylphenoxy) -2- (2-naphthoxy) ethane and 1,4 used in the present invention
-Bis (2-naphthoxy) butane is, for example,
It is used for a heat-sensitive recording medium described in Japanese Patent No. 3630. However, here, the purpose is to improve the recording sensitivity of the thermosensitive recording medium, and there is no description of a thermosensitive recording medium which has no background fogging even under a high-temperature environment as in the present invention and has good storage stability of a recorded image, and a method for using the same. There was no suggestion.
According to the present invention, by selectively using such a specific heat-fusible substance, the occurrence of background fogging is reduced even when used or stored in a high-temperature environment of 100 ° C. or higher, and the storage stability of a recorded image is improved. This also provides an excellent thermal recording medium.
In addition, about the upper limit temperature at which such an effect is obtained,
It cannot be unconditionally specified because it varies depending on the type and the use ratio of the basic dye, the color former and the heat-fusible substance constituting the color-forming system, but the effect can be obtained up to about 120 ° C. In the thermal recording medium of the present invention, the amount of 1- (4-methylphenoxy) -2- (2-naphthoxy) ethane and / or 1,4-bis (2-naphthoxy) butane is not necessarily limited. However, it is desirable to adjust the amount within a range from 10 to 700 parts by weight, preferably from 50 to 500 parts by weight, based on 100 parts by weight of the basic dye.

In the present invention, as the colorless or light-colored basic dye constituting the recording layer of the heat-sensitive recording material, various known dyes can be used. 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) fluoran, 3-diethylamino-
6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3
-Diethylamino-6-methyl-7- (2,4-xylidino) 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-NN-propylamino) -6-methyl-7-anilinofluoran, 2,2-bis {4-
[6 ′-(N-cyclohexyl-N-methylamino)-
3'-Methylspiro (phthalide-3,9'-xanthene)
-2'-ylamino] phenyl} propane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluoran, 3,3 ' -Screw (1
-Ethyl-2-methylindol-3-yl) phthalide, 3,3-bis (4-dimethylaminophenyl) -6
-Dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -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) pyridfluoran, 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 and the like. Of course, it is not limited to these dyes, and two or more dyes can be used in combination.

[0009] Among these dyes, 3- (N
-Ethyl-p-toluidino) -6-methyl-7-anilinofluoran and 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluoran are color formers and have lower fog. In that it is particularly preferred.

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, 1,1-bis (4-hydroxyphenyl)
-1-phenylethane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, bis (4-hydroxyphenylthioethoxy) methane, 1,4-bis [α-
Methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 4,4′-dihydroxydiphenylsulfone, 2,4 '-Dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, benzyl 4-hydroxybenzoate, butyl bis (4-hydroxyphenyl) acetate, bis (4-hydroxyphenylthioethyl) ether, N- (p-tolylsulfonyl) -N'-phenylurea, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, 4- [2- (p-
Methoxyphenoxy) ethoxy] zinc salt of salicylic acid,
4- [3- (p-tolylsulfonyl) propyloxy]
Zinc salt of salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] zinc salt of salicylic acid, 4-
Zinc salt of 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 medium having excellent preservability of a blank portion and a printed portion under a high-temperature environment 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 above general formula (1), bis (3-allyl-4-hydroxyphenyl) sulfone or 2,4'-dihydroxydiphenylsulfone is particularly useful in a blank area under a high temperature environment. Is more preferably used because of its excellent storage stability.

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, 1- [α-methyl-α- (4
-Hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4-hydroxyphenyl) ethyl] benzene,
4'-butylidenebis (6-tert-butyl-m-cresol), bis [2-hydroxy-3- (2'H-benzotriazol-2'-yl) -5-octylphenyl] methane, 2,2'- Methylene bis (4,6-di-te
rt-butylphenyl) phosphoric acid sodium salt or magnesium salt and the like.

The coating liquid containing these is generally mixed with water as a dispersion medium, and is stirred by a ball mill, an attritor, a sand mill, a colloid mill or the like to obtain a basic dye, a colorant,
It is prepared by mixing and stirring those in which a heat-fusible substance or the like is dispersed together or separately.

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, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium salt of lauryl alcohol sulfate, fatty acid metal salt, etc. Examples thereof include triazole-based ultraviolet absorbers, other defoamers, fluorescent dyes, coloring dyes, antioxidants, and the like. Also, a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax or the like is contained in the coating so that the heat-sensitive recording medium does not stick due to contact with a recording device or a recording head. It 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 formalin 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 particular, microcapsules containing a liquid ultraviolet absorber such as 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole in a protective layer or bis [2- Hydroxy-3- (2'H-
By adding a finely divided ultraviolet absorber such as benzotriazol-2'-yl) -5-tert-butylphenyl] methane, the yellowing of the background and the fading of the recorded image with respect to light are remarkably improved. Is done.

In addition, it is also possible to provide a layer containing a water-soluble, water-dispersible, electron beam-curable or ultraviolet-curable resin 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.

[0026]

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 Engelhard 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- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran 10
Parts, 5 parts of a 5% aqueous solution of methylcellulose, and water 1
The composition comprising 5 parts was sand-milled to an average particle size of 1.0 μm.
And crushed until

[Preparation of Solution B] A composition comprising 15 parts of 1- (4-methylphenoxy) -2- (2-naphthoxy) ethane, 7 parts of a 5% aqueous solution of methylcellulose, and 28 parts of water was subjected to an average particle diameter by a sand mill. Was reduced to 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 adjusted to an average particle size of 1.4 μm by a sand mill. Crushed until it became.

[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.

Examples 2 to 3 A heat-sensitive recording material was 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 2: 4-hydroxy-4'-isopropoxydiphenyl sulfone Example 3: 2,4'-dihydroxydiphenyl sulfone

Example 4 In the preparation of solution B, 1- (4-methylphenoxy) -2
A heat-sensitive recording material was obtained in the same manner as in Example 1, except that 1,4-bis (2-naphthoxy) butane was used instead of-(2-naphthoxy) ethane.

Examples 5 to 7 Example 1 was repeated except that the following compound was used in place of 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran in the preparation of solution A. In the same manner as in the above, a thermosensitive recording medium was obtained. Example 5: 3- (N-ethyl-p-toluidino) -6
Methyl-7- (p-toluidino) fluoran Example 6: 3-di-n-butylamino-7- (o-chloroanilino) fluoran Example 7: 3-diethylamino-7- (m-trifluoromethylanilino) Fluoran

Examples 8 to 9 Example 4 was repeated except that the following compound was used instead of 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran in the preparation of solution A. In the same manner as in the above, a thermosensitive recording medium was obtained. Example 8: 3- (N-ethyl-p-toluidino) -6
Methyl-7- (p-toluidino) fluoran Example 9: 3-di-n-butylamino-6-methyl-7
-Anilino fluoran

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

Comparative Example 3 Example 1 was repeated except that the solution B was not used.
In the same manner as in the above, a thermosensitive recording medium was obtained.

The thus-obtained thermal recording medium was subjected to a thermal evaluation machine [TH-PMD type, manufactured by Okura Electric Co., Ltd., applied voltage of 18 V,
With a pulse cycle of 3.0 ms and an applied pulse width of 2.5 ms], and the density of the recorded portion and the blank portion were measured in a visual mode using a Macbeth densitometer (RD-914, manufactured by Macbeth Co.), and the result was recorded. The results are shown in Table 1. After the recording, the thermosensitive recording medium was kept in a hot air drier at 100 ° C. for 3 hours, the densities of the recording portion and the blank portion were measured, and the results are shown in Table 1 as after processing.

[0039]

[Table 1]

[0040]

As is clear from the results shown 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 has excellent preservability of the recorded image. The recording medium was extremely suitable for use or storage in such a high temperature environment.

Claims (4)

[Claims] 1. A thermosensitive recording medium having a recording layer containing a colorless or light-colored basic dye and a colorant on a support, wherein the recording layer contains 1- (4-methylphenoxy) -2-.
A heat-sensitive recording material comprising (2-naphthoxy) ethane and / or 1,4-bis (2-naphthoxy) butane. 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 method according to claim 1, wherein the basic dye is 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran and / or 3- (N-ethyl-p-toluidino) -6.
3. The thermosensitive recording medium according to claim 1, wherein the thermosensitive recording medium is methyl-7- (p-toluidino) fluoran. 4. A method for using a thermosensitive recording medium used or stored in a high-temperature environment, wherein 1- (4-methylphenoxy) -2- (2-naphthoxy) is contained in a recording layer of the thermosensitive recording medium. Use of a heat-sensitive recording material, characterized by containing ethane and / or 1,4-bis (2-naphthoxy) butane.