JP2003054137A - Heat-sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording medium which shows superb recording sensitivity and the high keeping quality of a recording part and is almost free from a texture fog. SOLUTION: In the heat-sensitive recording medium having a heat-sensitive recording layer containing a leuco dye and a coloring agent formed on a support, at least one kind selected from among an N-p-tolylsulfonyl-N'-3-(p- tolylsulfonyloxy)urea, a 4-(p-tolylsulfonylamino carbonylamino)butyl bensoate, a 4,4'-bis(p-tolylsulfonylamino carbonylamino)diphenylmethane and an N-p- tolylsulfonyl-N'-phenylurea and a 1,3,3-trimethyl-1-(p-hydroxyphenyl)-6- hydroxyindane are used together, as the coloring agent, as a means to solve the subject problem.

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 utilizing a color-forming reaction between a leuco dye and a color former, and more particularly to a heat-sensitive recording material having high sensitivity and excellent image storability.

[0002]

2. Description of the Related Art A heat-sensitive recording material is known in which a recording image is obtained by heat by utilizing a color-forming reaction between a leuco dye and a color-developing agent. Since such a thermal recording material is relatively inexpensive, and the recording device is compact and easy to maintain, it can be used not only as a recording medium such as an output of a facsimile or various computers, a printer of a scientific measuring instrument, etc., but also as a POS. It is widely used as a recording medium for various printers such as labels, ATM, CAD, handy terminals, and CRT medical images.

In such a thermosensitive recording medium, a thermosensitive coloring layer containing a coloring component capable of causing a coloring reaction by heating is usually coated on a support such as paper, synthetic paper or synthetic resin film.
It is manufactured by drying, and the obtained heat-sensitive recording material is heated with a hot pen or a thermal head to obtain a recorded image. Further, in recent years, there has been a demand for high-speed printing of a printer and high-density printing color development even with low energy, and a high-sensitivity thermal recording material has been required.

JP-A-57-41991, JP-A-6-61991
No. 0-260386 discloses 1,3,3 as a color developing agent.
-Trimethyl-1- (p-hydroxyphenyl) -6-
Although a heat-sensitive recording material using hydroxyindane is described, there is a problem with the storage stability of the recording portion over time.

Np-tolylsulfonyl-
A thermosensitive recording medium using N'-3- (p-tolylsulfonyloxy) urea is described in WO 00/35679, and 4,4'-bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane or Np Although heat-sensitive recording using -tolylsulfonyl-N'-phenylurea is well known, it has a drawback that the color tone becomes greenish black with respect to the black colorant, the coiro dye.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium which is excellent in recording sensitivity and storability of a recording portion and has less background fog.

[0007]

In a thermal recording medium having a thermosensitive recording layer containing a leuco dye and a color developing agent on a support, Np-tolylsulfonyl-N 'is used as the color developing agent.
-3- (p-tolylsulfonyloxy) urea, 4-
At least one selected from (p-tolylsulfonylaminocarbonylamino) benzoic acid butyl ester, 4,4′-bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane and Np-tolylsulfonyl-N′-phenylurea, It is used in combination with 1,3,3-trimethyl-1- (p-hydroxyphenyl) -6-hydroxyindane.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION N-p-tolylsulfonyl-N'-3- (p-tolylsulfonyloxy) is used as a coloring agent.
Urea, 4- (p-tolylsulfonylaminocarbonylamino) benzoic acid butyl ester, 4,4′-bis (p
-Tolylsulfonylaminocarbonylamino) diphenylmethane and N-p-tolylsulfonyl-N'-phenylurea (hereinafter, referred to as Coloring Agent A) and 1,3,3-trimethyl-1- (p −
The ratio of hydroxyphenyl) -6-hydroxyindane (hereinafter referred to as color developing agent B) is not particularly limited, but the color developing agent A and the color developing agent B are in a weight ratio of 10:90 to 7.
About 0:30 is particularly preferable.

The ratio of the color former A and the color former B is 10:90.
If it is smaller, the effect of improving the storability of the recording portion with time decreases, and if it is larger than 70:30, background fog may occur. In particular, the coloring color tone of the recording portion may be greenish black with respect to the black coloring leuco dye.

The total amount of the color former A and the color former B used is preferably about 10 to 70% by weight based on the thermosensitive recording layer.

N-p-tolylsulfonyl-containing colorant A
The combined use of N′-3- (p-tolylsulfonyloxy) urea and the coloring agent B produces an effect that the occurrence of background fog is extremely small and that the recording portion is excellent in storage stability over time.

Various known leuco dyes can be used as the leuco dye contained in the heat-sensitive recording layer. Specific examples of such leuco dyes include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl). ) -6-Dimethylaminophthalide and other blue-coloring leuco dyes; 3- (N-ethyl-N-p)
-Tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3
-Green-coloring leuco dyes such as diethylamino-7-dibenzylaminofluorane;

3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-di-n-butylamino-
6-methyl-7-bromofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-diethylbutylamino-7-chlorofluorane, 3-diethylamino-
Red-coloring leuco dyes such as 7,8-benzofluorane, 3- (N-ethyl-p-toluidino) -7-methylfluorane and 3-diethylamino-6,8-dimethylfluorane;

3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-
Methyl-N-cyclohexyl) amino-6-methyl-7
-Anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6
-Methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3
-Di (n-amyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-di (n-butyl) amino-7
-(O-chloroanilino) fluorane, 3-diethylamino-7- (o-fluoroanilino) fluorane, 3-
Di (n-butyl) amino-7- (o-fluoroanilino) fluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3- (N-ethyl-p-toluidino) -6- Methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3- (N-
Ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N)
-N-propyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (N-methyl-Nn-propyl) amino-6- Methyl-7-anilinofluorane, 3
-Di (n-butyl) amino-6-methyl-7-m-toluidinofluorane, 3- (N-n-hexyl-N-ethyl) amino-6-methyl-7-anilinofluorane, 3
-(N-ethyl-N-isobutyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-
Methyl-7-p-ethoxyanilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-
Piperidino-6-methyl-7-anilinofluorane,
2,2-bis {4- [6- (N-cyclohexyl-N-
Methyl) amino-3-methylspiro [phthalide-3,9
-Xanthene] -2-isoamyl] phenyl} propane and other black-coloring leuco dyes;

3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-
2-yl] -4,5,6,7-tetrachlorophthalide,
3,3-bis [1- (4-methoxyphenyl) -1-
(4-Pyrrolidinophenyl) ethylene-2-yl]-
4,5,6,7-Tetrachlorophthalide, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene-
2-yl] -4,5,6,7-tetrabromophthalide,
3-p- (p-dimethylaminoanilino) anilino-6
-Methyl-7-chlorofluorane, 3-p- (p-chloroanilino) anilino-6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9
Examples thereof include leuco dyes having an absorption wavelength in the near infrared region at the time of color development such as -spiro-3- (6-dimethylamino) phthalide. Of course, it is not limited to these, and if necessary, two or more kinds may be used in combination.

Among them, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane and 3- (N-methyl-N-) which are black color-producing leuco dyes.
Cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-
7-anilinofluorane, 3-di (n-amyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane , 3- (N-ethyl-p-toluidino) -6-
Methyl-7- (p-toluidino) fluorane, 3-di (n-butyl) amino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane and the like are good. It is preferable because recording sensitivity and storability can be obtained, and black with no tint can be obtained.

Further, the heat-sensitive recording layer may contain a sensitizer for increasing recording sensitivity. Specific examples of the sensitizer include, for example, stearic acid amide, stearic acid methylene bisamide, stearic acid ethylene bisamide, 4-benzyl biphenyl, p-tolyl biphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-diester. (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, 2-naphthylbenzyl ether, 1- (2-naphthyloxy) -2-phenoxy Ethane, 1,3-di (naphthyloxy) propane, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, dibutyl terephthalate, dibenzyl terephthalate, paraacetotoluidide, 1 -Phenyl hydroxynaphthoate and the like can be mentioned. Of course, it is not limited to these, and two or more kinds can be used in combination.

Among them, 4-benzylbiphenyl, 2-
Naphthylbenzyl ether, 1,2-diphenoxyethane, 1,2-di (3-methylphenoxy) ethane, di-p-methylbenzyl oxalate and di-p-chlorobenzyl oxalate, paraacetotoluidide, diphenyl Sulfone is preferable because it is excellent in the effect of increasing the recording sensitivity. The amount of sensitizer used is 0.1 parts by weight per 1 part by weight of leuco dye.
It is about 4 parts by weight.

In the present invention, the above-mentioned color formers A and B are used as the color formers, but other color formers may be used in combination as long as the desired effects of the present invention are not impaired. You can also

Other coloring agents include, for example, 2,2'-bis [4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4,4'-. Dihydroxydiphenyl sulfone, 2,4′-dihydroxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 2,4-bis (phenylsulfonyl)
Phenol, 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenol, 2,
Phenolic compounds such as 2-bis (4-hydroxyphenyl) -4-methylpentane, benzyl 4-hydroxybenzoate and 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 4- [2- ( Zinc p-methoxyphenoxy) ethyloxy] salicylate, 4- [3- (p
Known examples include zinc salts of aromatic carboxylic acids such as -tolylsulfonyl) propyloxy] zinc salicylate and 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid.

The heat-sensitive recording layer contains, for example, water as a dispersion medium, a leuco dye, a color former A, a color former B, and a sensitizer.
Alternatively, a thermosensitive recording layer coating solution prepared separately by finely pulverizing with a stirrer / pulverizer such as a ball mill or a sand mill so that the average particle diameter is at least 3 μm or less is prepared by adding an adhesive to paper (acidic paper, Neutral paper), plastic film, synthetic paper, non-woven fabric, metal deposition sheet, etc.
It is formed by coating and drying so that the coating amount after drying is about ² to 15 g / m ² .

Specific examples of the adhesive added to the coating liquid for the heat-sensitive recording layer include, for example, methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, cellulose, completely (partially) saponified polyvinyl alcohol, and acetoacetyl. Modified polyvinyl alcohol, silicon modified polyvinyl alcohol, carboxy modified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol,
Polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch and its derivatives, casein, gelatin, alkali salt of styrene-maleic anhydride copolymer,
Water-soluble adhesives such as alkali salts of iso (or diiso) butylene-maleic anhydride copolymer, and water dispersibility of ethylene-vinyl acetate copolymer, acrylic latex, polyurethane latex, styrene-butadiene latex, etc. An adhesive may be used. The amount of the adhesive used is about 5 to 50% by weight, preferably 5 to 30% by weight, based on the total solid amount of the coating liquid for the heat-sensitive recording layer.

Further, the heat-sensitive recording layer may contain a storability improving agent for further improving the storability of the recording portion. Specific examples of the storage stability improving agent include, for example, 2,2'-
Methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-
tert-butylphenol), 2,2′-ethylidenebis (4,6-di-tert-butylphenol),
4,4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6)
-Tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol),
2,5-di (tert-amyl) hydroquinone, 1,
1,3-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4-benzyloxy -4 '-(2-
Methylglycidyloxy) diphenyl sulfone, 4,
4'-diglycidyloxydiphenyl sulfone, 4,
4'-dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 2,2-bis (4-hydroxy3.5-dimethylphenyl) propane, N, N'-di-
2-naphthyl-p-phenylenediamine and the like can be mentioned.

If desired, various auxiliaries can be added to the heat-sensitive recording layer coating liquid. For example, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, lauryl alcohol sulfate ester
Surfactants such as sodium salts and fatty acid metal salts, waxes such as polyethylene wax, carnauba wax, paraffin wax and ester wax, kaolin, clay, talc, calcium carbonate, calcined kaolin, titanium oxide, amorphous silica, aluminum hydroxide, etc. Pigments, glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, dialdehyde starch, melamine resin, polyamide resin, polyamide-epichlorohydrin resin, ketone-aldehyde resin, borax, boric acid, ammonium zirconium carbonate. , Water resistant agents such as epoxy compounds, defoaming agents, fluorescent dyes, coloring dyes and the like.

By providing an undercoat layer containing a pigment and an adhesive as the main components between the support and the thermosensitive recording layer, the recording sensitivity and the recording running property can be further improved. The pigment is not particularly limited, but a specific oil-absorbing pigment having an oil absorption amount according to JIS K 5101 of 70 to 200 ml / 100 g or a hollow organic pigment is particularly preferable because of excellent recording sensitivity. The average particle size of the pigment is 0.5 to 20 μm.
The thickness is about m, preferably about 0.5 to 3 μm.

Specific oil-absorbing pigments include, for example, calcined kaolin, magnesium carbonate, amorphous silica, aluminum silicate, magnesium silicate, calcium silicate, calcium carbonate, urea-forlin resin filler and the like.

Examples of the organic hollow particles include vinyl chloride, vinylidene chloride, vinyl acetate, methyl acrylate,
Examples thereof include particles having a resin containing a monomer such as ethyl acrylate, methyl methacrylate, acrylonitrile, or styrene as a main component or a copolymer resin containing these monomers as a main component as a shell. The hollowness of the organic hollow particles (ratio of the volume of voids in particles to the total volume of particles) is 50 to
About 98% is preferable.

Examples of the adhesive used in the undercoat layer together with a specific oil-absorbing pigment or organic hollow particles include gelatin, casein, starch and its derivatives, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose and methoxy. Cellulose, completely (partially) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acrylamide-ethyl acrylate copolymer, styrene-maleic anhydride copolymer salt, isobutylene-maleic anhydride. Examples thereof include water-soluble polymers such as acid copolymer salts, and hydrophobic polymers such as styrene-butadiene resins, styrene-acrylic resins, vinyl acetate resins and acrylic resins. The hydrophobic polymer is preferably used in the form of latex.

The amount of the specific oil-absorbing pigment, the organic hollow particles and the adhesive used with respect to the total solid amount of the undercoat layer is as follows.
It is preferable that the specific oil absorbing pigment is about 60 to 95% by weight, the organic hollow particles are about 20 to 95% by weight, and the adhesive is about 5 to 35% by weight.

On the heat-sensitive recording layer, a coating liquid for a protective layer containing an adhesive having a film-forming property as a main component in order to enhance the resistance to discoloration against chemicals in the recording portion, the recording running property and the abrasion resistance to abrasion. A protective layer can be provided by coating and drying. Examples of the adhesive having film-forming properties include those contained in the coating liquid for the thermal recording layer. Further, an auxiliary agent used in the coating liquid for the heat-sensitive recording layer can be added to the coating liquid for the protective layer.

The method for forming the undercoat layer, the heat-sensitive recording layer and the protective layer is not particularly limited, and examples thereof include air knife coating, varibar blade coating, pure blade coating, rod blade coating,
It is formed by a known appropriate coating method such as short dwell coating, curtain coating, die coating, and gravure coating. The coating amount of the undercoat layer and the protective layer is 3 to 3 dry weight, respectively.
It is about 15 g / m ^{2 and} about 0.5 to 5.0 / m ² .

In the heat-sensitive recording material of the present invention, a protective layer (barrier) may be provided on the back side, if necessary.
Alternatively, smoothing treatment such as super calendering may be performed after coating each layer.

[0033]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. In the examples and comparative examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 Preparation of coating liquid for undercoat layer Baked kaolin [trade name: Ansilex 93, oil absorption 9
0 ml / 100 g, manufactured by EC] 80 parts, hollow organic pigment slurry (trade name: Ropaque HP-91, manufactured by Rohm & Haas Co.) 50 parts, partially saponified polyvinyl alcohol 1
A composition comprising 70 parts of a 0% aqueous solution, 15 parts of a styrene-butadiene-based latex having a solid content of 48%, 2 parts of a 20% aqueous solution of sodium polyacrylate and 200 parts of water was mixed and stirred to prepare a coating solution for the undercoat layer. Obtained.

Preparation of Solution A 40 parts of 3-di (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 20 parts of a 20% aqueous solution of polyvinyl alcohol modified with sulfonic acid and 5 parts of water.
A composition consisting of 5 parts was sand milled to give an average particle size of 1.0 μm.
Liquid A was obtained by pulverizing to m or less.

Preparation of Solution B A sand mill was used to prepare a composition comprising 40 parts of 1,3,3-trimethyl-1- (p-hydroxyphenyl) indan-6-ol, 20 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol and 55 parts of water. And pulverized until the average particle diameter becomes 1.5 μm or less to obtain a liquid B.

Preparation of Solution C A composition comprising 40 parts of Np-tolylsulfonyl-N'-3- (p-tolylsulfonyloxy) urea, 20 parts of a 20% aqueous solution of sulfonation-modified polyvinyl alcohol and 55 parts of water was sand-milled. C liquid was obtained by pulverizing until the average particle diameter became 1.5 μm or less.

Preparation of D liquid 40 parts of 2-naphthylbenzyl ether, 20 parts of 20% aqueous solution of sulfonic acid modified polyvinyl alcohol and 55 parts of water
The composition of 1 part was pulverized with a sand mill until the average particle size was 2 μm to obtain a liquid D.

Preparation of coating liquid for heat-sensitive recording layer 25 parts of solution A, 25 parts of solution B, 25 parts of solution C, 50 parts of solution D, vinyl acetate modified starch (trade name: Petrocoat C-8, Nichiden Chemical Co., Ltd. )) 20% aqueous solution 75 parts, aluminum hydroxide (trade name: Heidilite H-42, Showa Light Metal Industry
A composition consisting of 30 parts (manufactured by K.K.) and 10 parts of a 36% dispersion of zinc stearate was mixed and stirred to obtain a coating liquid for the heat-sensitive recording layer.

Preparation of coating liquid for protective layer Diacetone amide modified polyvinyl alcohol (trade name:
270 parts of a 10% aqueous solution of D-700, manufactured by Unitika Ltd.,
Polyamidoamine-epichlorohydrin resin (trade name:
40% of a 25% aqueous solution of WS-547 (manufactured by Japan PMC)
Department, Kaolin [Product name: UW-90, manufactured by EC] 60
Part, a composition comprising 5 parts of a spherical organic pigment made of an internally crosslinked polymethylmethacrylate having an average particle diameter of 2 μm, 10 parts of a 30% aqueous dispersion of zinc stearate and 150 parts of water, and stirred to form a protective layer. A coating liquid was obtained.

Preparation of thermosensitive recording medium Basis weight 53g / m^TwoCoating solution for undercoat layer on one side of high quality paper,
Coating amount after drying the thermal recording layer coating liquid and protective layer coating liquid
8g / m each^Two5 g / m^Two5 g / m ^TwoBecomes
As shown below to form an undercoat layer and a thermal recording layer.
A thermosensitive recording material was obtained. After forming each layer,
-Calendar treatment is applied to smooth the protective layer side (TAP
PI NO. 5-B) should be 700 ± 200 seconds
did.

Example 2 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, the solution B 25
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the B part and the C liquid 25 parts were changed to the B liquid 15 parts and the C liquid 35 parts.

Example 3 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, the solution B 25
Parts and 25 parts of C solution, 42.5 parts of B solution, 7.5 parts of C solution
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the parts were used.

Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 1,2-diphenoxyethane was used in place of 2-naphthylbenzyl ether in the preparation of the liquid D of Example 1.

Example 5 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, 30 parts of D solution and 20 parts of stearic acid amide were used instead of 50 parts of D solution.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 40% of the dispersion liquid was used.

Example 6 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that di-p-methylbenzyl oxalate was used in place of 2-naphthylbenzyl ether in the preparation of solution D in Example 1. .

Example 7 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that di-p-chlorobenzyl oxalate was used in place of 2-naphthylbenzyl ether in the preparation of the liquid D of Example 1.

Example 8 In the preparation of solution C of Example 1, 4,4'-bis (p-tolylsulfonylamino) was used instead of Np-tolylsulfonyl-N'-3- (p-tolylsulfonyloxy) urea. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that carbonylamino) diphenylmethane was used.

Example 9 In the preparation of the liquid C of Example 1, N-p-tolylsulfonyl-N'-phenylurea was used instead of N-p-tolylsulfonyl-N'-3- (p-tolylsulfonyloxy) urea. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that was used.

Example 10 In the preparation of the liquid C of Example 1, 4- (p-tolylsulfonylaminocarbonylamino) benzoate was used instead of Np-tolylsulfonyl-N'-3- (p-tolylsulfonyloxy) urea. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the acid butyl ester was used.

Comparative Example 1 In the preparation of the coating liquid for the thermal recording layer of Example 1, C liquid 25
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 25 parts of the liquid B was used instead of the parts.

Comparative Example 2 In preparation of the coating liquid for the heat-sensitive recording layer of Example 1, B solution 25
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 25 parts of C liquid was used instead of parts.

[Evaluation] The thermal recording material thus obtained was evaluated as follows, and the results are shown in [Table 1].

Color development and color tone thermosensitive evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.)
Each thermosensitive recording material at 0.3 mJ / dot using
Macbeth densitometer [R
D-914, manufactured by Macbeth Co.]. In addition, the color tone of the recording portion was visually determined.

Each of the thermosensitive recording materials colored under the heat-resistant color development evaluation conditions was measured in a visual mode of a recorded and unrecorded Macbeth densitometer, which was allowed to stand at 60 ° C. for 24 hours.

Each heat-sensitive recording material colored under the conditions of evaluation of moisture resistance and color-forming property was heated at 40 ° C.
The recorded and unrecorded areas left at 90% RH for 24 hours were measured with a Macbeth densitometer in visual mode.

Each thermosensitive recording material colored under the plasticizer-resistant color development evaluation condition was sandwiched between a vinyl chloride film (Krehalon FAS-3: manufactured by Kureha Chemical Co., Ltd.) at 40 ° C. for 24 hours, and then the recording portion was measured by a Macbeth densitometer. Measured in visual mode.

[0058]

[Table 1]

[0059]

As shown in Table 1, the thermosensitive recording medium of the present invention has excellent effects in recording sensitivity and storage stability of the recording area.

Claims (3)

[Claims] 1. A thermosensitive recording medium having a thermosensitive recording layer containing a leuco dye and a color developing agent on a support, wherein the color developing agent is Np-tolylsulfonyl-N'-3- (p-tolylsulfonyl). Oxy) urea, 4- (p-tolylsulfonylaminocarbonylamino) benzoic acid butyl ester,
At least one selected from 4,4′-bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane and Np-tolylsulfonyl-N′-phenylurea, and 1,3,3-trimethyl-1- (p-hydroxy) A heat-sensitive recording material, which is phenyl) -6-hydroxyindane. 2. Np-tolylsulfonyl-N'-3-
(P-Tolylsulfonyloxy) urea, 4- (p-tolylsulfonylaminocarbonylamino) benzoic acid butyl ester, 4,4′-bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane and Np
At least one selected from -tolylsulfonyl-N'-phenylurea and 1,3,3-trimethyl-1-
The thermosensitive recording medium according to claim 1, wherein the weight ratio to (p-hydroxyphenyl) -6-hydroxyindane is 10:90 to 70:30. 3. The heat-sensitive recording material according to claim 1, wherein the leuco dye is a fluoran compound having a black coloring property.