JP2001058469A - Heat-sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording body, in which recording sensitivity and preservation stability of a recording part are excellent and also texture fog is a little. SOLUTION: In the heat-sensitive recording body in which a heat-sensitive recording layer containing leuco dye, a coloring agent and a sensitizer is provided on a supporting body, 2,2'-bis[4-(4-hydroxyphenylsulfonyl) phenoxy] diethyl ether is contained in the heat-sensitive recording layer as the coloring agent. Furthermore, diphenyl sulfone and higher fatty acid amide are contained as a sensitizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material which utilizes a color-forming reaction between a leuco dye and a coloring agent, and in particular, a recorded image can be obtained by a color-forming reaction with heat energy.

[0002]

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.
As described above, the thermosensitive recording medium is relatively inexpensive, the recording apparatus is compact, and the maintenance thereof is easy. Therefore, the thermosensitive recording medium is used in recording media such as facsimile machines and various computers, and in a wide variety of fields.

[0003] However, as the field of use expands, the use environment of the thermal recording medium is becoming more severe.
Especially for industrial labels, sensitivity and image quality at high speed recording,
What satisfy | fills the storage stability of a recorded image simultaneously is calculated | required.

A heat-sensitive recording material using 2,2'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether as a coloring agent in order to enhance the plasticizer resistance and oil resistance of the recording portion is particularly important. JP-A-8-333329,
It is described in JP-A-10-29969 and the like, and JP-A-10-297089 contains 2,2'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether and a diphenylsulfone derivative. However, sufficient recording sensitivity has not been obtained, and there is a demand for a recording medium having a higher recording sensitivity.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which is excellent in recording sensitivity and storage stability of a recording portion and has less background fog.

[0006]

Means for Solving the Problems In a heat-sensitive recording medium having a heat-sensitive recording layer containing a leuco dye, a color former and a sensitizer on a support, as one means for solving the above problems, In the present invention, the heat-sensitive recording layer contains 2,2'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether as a colorant, and further contains diphenylsulfone and a higher fatty acid amide as a sensitizer. It is to let.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION 2,2'-Bis [4- (4-hydroxyphenylsulfonyl) phenoxydi] ethyl ether (hereinafter referred to as "color-forming agent") contained in a heat-sensitive recording layer
The amounts of diphenyl sulfone and higher fatty acid amide (referred to as a specific sensitizer) contained as a sensitizer and diphenyl sulfone contained as a sensitizer are not particularly limited, but are each 10 to 50 relative to the heat-sensitive recording layer. % By weight is preferred.

In the specific sensitizer, the ratio between diphenyl sulfone and higher fatty acid amide is not particularly limited.
About 10 to 50 parts by weight of higher fatty acid amide is preferably used for 100 parts by weight of diphenylsulfone, because it particularly enhances recording sensitivity and recording running property.

Specific examples of the higher fatty acid amide include, for example, myristic amide, stearic amide, oleic amide, behenic amide, methylenebisstearic amide, ethylenebisstearic amide and the like. Above all, stearic amide has excellent recording sensitivity,
In addition, it has an excellent effect on the background fog resistance, and is therefore preferable.

The heat-sensitive recording layer contains a specific colorant and a specific sensitizer, but may contain other colorants and sensitizers as long as the desired effects of the present invention are not impaired. It can also be done.

Examples of such color formers include, for example, 4,4 ′
-Isopropylidene diphenol, 4,4'-cyclohexylidene diphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, benzyl 4-hydroxybenzoate, 2,4'-dihydroxydiphenyl sulfone, , 4'-dihydroxydiphenyl sulfone,
4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenylsulfone 1,1-bis (4-hydroxyphenyl) -1-phenyl Phenolic compounds such as ethane, N- (p-tolylsulfonyl) carbamoyl-p-cumylphenyl ester, N- (p-tolylsulfonyl) carbamoyl-p-benzyloxyphenyl ester, N- (o-tolyl) -P-tolylsulfonamide, 4,4'-bis (N
Those having a -SO ₂ NH- bond in -p- tolyl sulfonylamino Cabo sulfonyl amino) intramolecular diphenylmethane, p- chlorobenzoic acid zinc, 4- [2-(p-methoxyphenoxy) ethyloxy] zinc salicylate, 4 −
Zinc salts of aromatic carboxylic acids such as [3- (p-tolylsulfonyl) propyloxy] zinc salicylate and 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid.

Other sensitizers include, for example, dibenzyl terephthalate, benzyl p-benzyloxybenzoate,
-Naphthylbenzyl ether, m-terphenyl, p-
Benzyl biphenyl, p-tolyl biphenyl ether,
Di (4-methoxyphenoxyethyl) ether, 1,2
-Di (3-methylphenoxy) ethane, 1,2-di (4
-Methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4
-Methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, di (β-biphenylethoxy) benzene, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester And oxalic acid dibenzyl ester.

Various known leuco dyes can be used in the heat-sensitive recording layer. Specific examples of such leuco dyes include the following. 3,
3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl)
-6-dimethylaminophthalide, 3-diethylamino-
Blue-coloring dyes such as 7-dibenzylamino-benzo [a] fluoran, 3- (N-ethyl-Np-tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-aniline Green chromogenic dyes such as linofluoran and 3-diethylamino-7-dibenzylaminofluoran;
3-cyclohexylamino-6-chlorofluoran, 3
Red-coloring dyes such as -diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-chlorofluoran, rhodamine (o-chloroanilino) lactam, 3-diethylamino-6,8-dimethylfluoran, -(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-butyl) amino-7- (o-fluorophenylamino) fluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-ani Linofluoran, 3- (N-ethyl-N
-Tetrahydrofurfurylamino) -6-methyl-7-
Anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran and the like Black coloring dye of 3,
3-bis [1- (4-methoxyphenyl) -1- (4-
Dimethylaminophenyl) ethylene-2-yl] -4,
5,6,7-tetrachlorophthalide, 3-p- (p-dimethylaminoanilino) anilino-6-methyl-7-chlorofluoran, 3-p- (p-chloroanilino) anilino-6-methyl- 7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3'-
Dyes having an absorption wavelength in the near infrared region, such as (6'-dimethylamino) phthalide, etc. Of course, the dyes are not limited to these, and two or more kinds may be used in combination. The use ratio of the leuco dye is about 5 to 35% by weight based on the heat-sensitive recording layer.

The ratio of the leuco dye to the specific colorant is not particularly limited, but the specific colorant is 1 to 10 parts by weight, preferably 1 to 5 parts by weight, per 1 part by weight of the leuco dye. Used to a degree.

The heat-sensitive recording layer may further contain a storage stability improving agent for further improving the storage stability of the recording portion. Specific examples of such a preservability improver include, for example, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6
-Tert-butylphenol), 4-4'-butylidenebis (6-tert-butyl-m-cresol), 1,
1,3-tris (2-methyl-4-hydroxy-5-te
rt-butylphenyl) butane, 1,1,3-tris (2
-Methyl-4-hydroxy-5-cyclohexylphenyl) butane, 2,2-bis (4-hydroxy-3,5-
Hindered phenol compounds such as dibromophenyl) propane and 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 4,4′-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4′-
(2-methylglycidyloxy) diphenyl sulfone,
Examples include epoxy compounds such as diglycidyl terephthalate, cresol novolak type epoxy resin, phenol novolak type epoxy resin, and bisphenol A type epoxy resin. The amount of these preservatives to be used is not particularly limited, but it is generally desirable to adjust the amount to 4 parts by weight or less based on 1 part by weight of the leuco dye.

The heat-sensitive recording layer generally uses water as a dispersion medium,
A leuco dye, a specific colorant, a specific sensitizer, and if necessary, a preservability improver or the like, or separately, using a ball mill, an attritor, a sand mill, or other agitator / pulverizer so that the average particle size becomes 2 μm or less. After finely dispersing, a coating solution for the heat-sensitive recording layer prepared by adding an adhesive is applied to a support such as high-quality paper (neutral or acidic paper), synthetic paper, transparent film, etc., and dried to form a coating. You.

The average particle size of the higher fatty acid amide in the specific sensitizer is particularly preferably about 0.1 to 0.5 μm. When the thickness is less than 0.1 μm, background fog may easily occur in the heat-sensitive recording layer with time, and when it exceeds 0.5 μm, the effect of increasing the recording sensitivity may decrease.

As a method for reducing the average particle size of the higher fatty acid amide to 1 μm or less, the higher fatty acid amide in a heated and melted state is emulsified and dispersed together with warm water or hot water to which an emulsifier is added by an emulsifier such as a homomixer. can get.

Specific examples of the adhesive used in the coating solution for the heat-sensitive recording layer include, for example, oxidized starch, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol,
Acetoacetyl group-modified polyvinyl alcohol, silicon polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, Examples include urea resins, melamine resins, amide resins, polyurethane latex, styrene / butadiene latex, and acrylic latex. The amount of the adhesive used is 5 to 5% based on the total solid content of the heat-sensitive recording layer.
It is about 35% by weight.

Further, various auxiliaries can be added to the heat-sensitive recording layer coating liquid as needed, for example, kaolin,
Light (heavy) calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, amorphous silica, pigments such as urea / formalin resin filler, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, lauryl alcohol sulfate Sodium, surfactants such as fatty acid metal salts, zinc stearate, calcium stearate, waxes such as polyethylene wax, carnauba wax, paraffin wax, ester wax, glyoxal, urea formalin resin, polyamide epoxy resin, polyamide epichlorohydrin, adipic dihydrazide , Boric acid, borax, ammonium zirconium carbonate and the like, as well as UV absorbers, defoamers, fluorescent dyes, coloring dyes and the like.

A protective layer can be provided on the heat-sensitive recording layer in order to increase the chemical resistance and water resistance of the recording portion or to improve the recording running property. Such a protective layer is formed, for example, by applying a coating liquid for a protective layer containing a film-forming adhesive and, if necessary, a pigment as a main component on the heat-sensitive recording layer and drying.

The adhesive contained in the coating liquid for the protective layer includes completely saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol. Polyvinyl alcohols, starches, etc.
Hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, diisobutylene / maleic anhydride copolymer salt,
Styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt,
Styrene / butadiene latex, acrylic latex, urethane latex, and the like can be given. Further, in the coating solution for the protective layer, an auxiliary agent which can be added to the coating solution for the heat-sensitive recording layer may be added.

The coating amount of the heat-sensitive recording layer coating solution is 2% by dry weight.
To 12 g / m ^2, preferably from 3 to 7 g / m ² approximately, protective layer coating solution of the coating amount 0.5 to 10 g / m ² by dry weight, preferably 1 to 5 g / m ² approximately.

In order to improve recording sensitivity and recording image quality, an undercoat layer containing an oil-absorbing pigment or hollow particles as a main component is provided between the support and the heat-sensitive recording layer. It is also possible to apply a chemical treatment. Various other known techniques in the field of heat-sensitive recording medium production can be added as needed.

[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 to such specific Examples. Parts and% in Examples are parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 Preparation of coating liquid for undercoat layer 100 parts of calcined clay (trade name: Ansilex, manufactured by EC, oil absorption 110 ml / 100 g), 1 part of 40% aqueous solution of sodium polyacrylate, solid concentration 48% Of styrene-butadiene copolymer latex, 10 parts of polyvinyl alcohol (saponification degree 88%, polymerization degree 1000)
% Aqueous solution and 100 parts of water were mixed and stirred to obtain a coating liquid for an undercoat layer.

Solution A Preparation 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 5% aqueous solution of methylcellulose 5
Parts and 25 parts of water were pulverized with a sand mill until the average particle diameter became 1.0 μm.

Preparation of Solution B Coloring agent containing about 55% by weight of 2,2'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether (trade name: D-90, manufactured by Nippon Soda Co., Ltd.) 20
Part, 2,4'-dihydroxydiphenyl sulfone 10
Parts, 15 parts of a 5% aqueous solution of methylcellulose and 75 parts of water
The composition consisting of
m.

Preparation of Solution C A composition comprising 20 parts of diphenylsulfone, 10 parts of a 5% aqueous solution of methylcellulose and 50 parts of water was pulverized by a sand mill until the average particle diameter became 1.0 μm.

Preparation of coating solution for heat-sensitive recording layer. 40 parts of liquid A, 120 parts of liquid B, 80 parts of liquid C, a dispersion of stearic acid amide dispersed by an emulsification dispersion method [trade name:
High Micron G-270, average particle diameter 0.4 μm, solid concentration 21.5%, manufactured by Chukyo Yushi Co., Ltd.] 28 parts, 10% of polyvinyl alcohol (degree of saponification 88%, degree of polymerization 1000)
160 parts of an aqueous solution, 20 parts of a styrene / butadiene latex having a solid concentration of 50%, 17 parts of light calcium carbonate, and 12.5 parts 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 Solution for Protective Layer Acetoacetyl-modified polyvinyl alcohol [trade name:
Gosefimer Z200, manufactured by Nippon Synthetic Chemical Company]
% Aqueous solution, kaolin [trade name: UW-90, E
80 parts of a 50% aqueous dispersion (manufactured by Company C) was mixed and stirred to obtain a coating liquid for a protective layer.

Preparation of thermosensitive recording medium 64 g / m^TwoUndercoat layer on one side of high quality paper (neutral paper)
Liquid, heat-sensitive recording layer coating liquid and protective layer coating liquid.
Application amount after drying is 9 g / m^Two, 6g / m^Two, 3g / m ^TwoTona
So that the undercoat layer, thermal recording layer and protection
Layers were sequentially formed to obtain a thermosensitive recording medium. After each layer is formed
Was subjected to a surface smoothing treatment by a super calender treatment.

Example 2 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1,
Parts and 28 parts of the stearamide dispersion instead of 92 parts of the liquid C and the stearamide dispersion.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that parts were used.

Example 3 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1,
Parts and 28 parts of the stearamide dispersion, instead of 72 parts of the liquid C and the stearamide dispersion 37
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that parts were used.

Example 4 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1,
A thermosensitive recording material was obtained in the same manner as in Example 1, except that 96 parts of the same C liquid and 9 parts of the same stearamide dispersion were used instead of 28 parts of the emulsified dispersion of the stearamide.

Example 5 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1,
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 67 parts of the same C liquid and 43 parts of the same stearamide dispersion were used instead of 28 parts of the emulsified dispersion of stearamide and 28 parts of the emulsified dispersion of stearamide.

Example 6 The procedure of Example 1 was repeated except that 24 parts of the following solution D was used in place of 28 parts of the stearamide dispersion dispersed by the emulsifying dispersion method in the preparation of the coating solution for the heat-sensitive recording layer. A thermosensitive recording medium was obtained in the same manner as in Example 1. Preparation of Liquid D 10 parts of stearic acid amide, 1 part of a 10% aqueous solution of sodium di-2-ethylhexylsulfosuccinate, partially saponified polyvinyl alcohol (degree of saponification: 60 mol%) Of a 20% aqueous solution having a degree of polymerization of 100) and 25 parts of water were pulverized with a sand mill until the average particle size became 1.0 μm.

Example 7 In the preparation of the solution D of Example 6, a mixture of
A thermosensitive recording material was obtained in the same manner as in Example 6, except that 10 parts of methylenebisstearic acid amide was used instead of 10 parts.

Example 8 In the preparation of the solution D in Example 5, stearamide 10
Except that 10 parts of oleamide were used instead of 10 parts
A thermosensitive recording medium was obtained in the same manner as in Example 5.

Example 9 In the preparation of Solution B of Example 1, 2,2'-bis [4-
(4-Hydroxyphenylsulfonyl) phenoxy] 20 parts of a coloring agent containing about 55% by weight of diethyl ether (trade name: D-90, manufactured by Nippon Soda Co., Ltd.) and 2,4′-
Instead of 10 parts of dihydroxydiphenyl sulfone,
Except for using 30 parts of a color former (trade name: D-77, manufactured by Nippon Soda Co., Ltd.) containing about 75% by weight of 2'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] sidiethyl ether, A thermosensitive recording medium was obtained in the same manner as in Example 1.

Example 10 In the preparation of the coating solution for the thermosensitive recording layer of Example 1, 25 parts of a 20% aqueous solution of adipic dihydrazide was used instead of 12.5 parts of a 40% aqueous solution of glyoxal, and acetoacetyl was used in forming the protective layer. Instead of 500 parts of a 10% aqueous solution of a modified polyvinyl alcohol [trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.], diacetone modified polyvinyl alcohol [trade name: D polymer D-
3480, manufactured by Unitika Ltd.], except that 500 parts of a 10% aqueous solution was obtained in the same manner as in Example 1.

Comparative Example 1 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, except that 24 parts of the liquid C was used in place of 28 parts of the stearamide dispersion dispersed by the emulsification dispersion method. In the same manner as in Example 1, a thermosensitive recording medium was obtained.

Comparative Example 2 In the preparation of the coating solution for the heat-sensitive recording layer of Example 1,
70 parts of a stearamide dispersion (trade name: High Micron G-270, average particle diameter 0.4 μm, solid concentration 21.5%, manufactured by Chukyo Yushi Co., Ltd.) dispersed by an emulsification dispersion method is used instead of parts. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that

Comparative Example 3 In the preparation of Solution C of Example 1, diphenyl sulfone 20
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 20 parts of oxalic acid di-p-methylbenzyl ester was used instead of parts.

Comparative Example 4 In the preparation of solution C in Example 1, diphenyl sulfone 20
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 20 parts of 1,2-di (3-methylphenoxy) ethane was used instead of parts.

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

[Recording Sensitivity] Thermal Sensitivity Evaluation Machine [Product Name: TH-
PMD, manufactured by Okura Electric Co., Ltd.
Record each thermosensitive recording adhesive sheet at 0 mJ / dot,
The density of the recorded area and the unrecorded area were measured using a Macbeth densitometer [RD-
Model 914, manufactured by Macbeth Co.] in the visual mode.

[Plasticizer resistance] Polypropylene pipe (4
A wrap film (trade name: High Wrap KMA-W, manufactured by Mitsui Chemicals, Inc.) is wound three times on a 0 mm φ tube, the thermosensitive recording medium after recording in the measurement of the recording density is placed thereon, and the wrap film is further placed thereon. , And allowed to stand at 40 ° C. for 24 hours. Then, the optical density of the recording portion was measured with the above-mentioned Macbeth densitometer to evaluate the plasticizer resistance.

[Water-resistant plasticizer] A wrap film (trade name: High Wrap KMA-W, manufactured by Mitsui Chemicals, Inc.) is wound three times on a polypropylene pipe (40 mm diameter pipe), and the thermal recording after recording in the measurement of the recording density thereon Place the body, drop a drop of water on the top layer, further wrap the wrap film in triplicate, leave it at room temperature for 72 hours, measure the optical density of the recording part with the above Macbeth densitometer, The agent properties were evaluated.

[Oil resistance] After recording in the measurement of recording density, the heat-sensitive recording medium was immersed in edible oil, left at room temperature for 24 hours to wipe off the oil, and the optical density of the recording portion was measured with the above-mentioned Macbeth densitometer. Then, the oil resistance was evaluated.

[0051]

[Table 1]

[0052]

As is clear from Table 1, the heat-sensitive recording material of the present invention is excellent in recording sensitivity and storage stability of a recording portion, and has an effect of reducing background fog.

Claims (4)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye, a color former and a sensitizer on a support, wherein 2,2'-bis [4] is used as a color former in the heat-sensitive recording layer.
-(4-hydroxyphenylsulfonyl) phenoxy]
A heat-sensitive recording material comprising diethyl ether and diphenyl sulfone and a higher fatty acid amide as sensitizers. 2. The fatty acid amide is 10 to 50 parts by weight based on 100 parts by weight of diphenyl sulfone.
The thermosensitive recording medium as described. 3. The heat-sensitive recording material according to claim 1, wherein the higher fatty acid amide is stearic acid amide. 4. The higher fatty acid amide having an average particle size of 0.1
The thermal recording medium according to any one of claims 1 to 3, wherein the thermal recording medium has a thickness of from 0.5 m to 0.5 m.