JPH08156426A - Thermal recording material - Google Patents

Abstract

PURPOSE: To obtain a thermal recording material high in recording sensitivity and whiteness and excellent in the storage stability of a developed color image and a white paper part by adding a specific N-arylsulfonylurea derivative to a recording layer as a coupler and using a solid soln. obtained by melting of two kinds of specific esters as a sensitizer. CONSTITUTION: An N-arylsulfonylurea derivative represented by formula I (wherein R1 is a 1-4C alkyl group, a 1-4C alkoxy group, a benzyloxy group, a halogen atom or a hydroxy group) or formula II (wherein R2 and R3 are a 1-4C alkyl group, a 1-4C alkoxy group, a benzyloxy group, a halogen atom or a hydroxy group) is added to the recording layer provided on a support as a coupler. As a sensitizer, a solid soln. obtained by melting or dissolving di(p-chlorobenzyl) oxalate and di(p-methylbenzyl) oxalate is added. By this constitution, the recording material high in recording sensitivity and whiteness and excellent in the long-term preservability of a white paper part is obtained.

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-developing agent, and particularly to a heat-sensitive recording material having high recording sensitivity and whiteness and excellent storage stability of recorded images. It is about.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known in which a color image is obtained by contacting both color-forming substances with heat by utilizing a color reaction between a leuco dye and an organic or inorganic color developing agent. Since such a heat-sensitive recording material is relatively inexpensive and the recording device is compact and its repair is relatively easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

In recent years, the thermal facsimiles, thermal printers, etc. using such thermal recording media have been improved in their apparatus, and are capable of high-speed printing and high-speed image formation, which have been difficult in the past. With the speedup of equipment and hardware fields,
The thermal recording material used is also required to have higher recording sensitivity than ever before. Many proposals have been made to meet these demands, but most of them relate to the combination of a leuco dye and a colorant with a heat-fusible substance. These heat-fusible substances are called sensitizers and include, for example, phenyl 1-hydroxy-2-naphthoate (JP-A-57-19109), p-benzylbiphenyl (JP-A-60-2382), Benzylnaphthyl ether (JP-A-58-87094), dibenzyl terephthalate (JP-A-58-98285), p
-Benzyloxybenzoic acid benzyl (JP-A-57-20)
1691), m-terphenyl (JP-A-57-8).
9994), oxalic acid dibenzyl ester, oxalic acid di (p-chlorobenzyl) ester, oxalic acid di (p-methylbenzyl) ester, and the like.

When a heat-sensitive recording material containing these sensitizers is heated, the sensitizers are first melted, and the dyes and the colorants are melted into each other to mix the two at a molecular level.
A coloring reaction is induced. Therefore, these sensitizers must have an appropriate melting point (80 to 150 ° C.) and have excellent compatibility with dyes and color formers. Further, in order to improve the moisture resistance storage property, it is desirable that these sensitizers are hardly soluble in water and do not cause the thermosensitive coloring layer to develop a ground color. Further, it is required that the sublimation property is low due to the phenomenon of so-called whitening, in which the surface of the heat-colored portion of the heat-sensitive recording material becomes dusty with time. Further, the heat-sensitive recording material is often exposed to a relatively high temperature of 60 ° C. to 70 ° C. during use, and in order to improve heat-resistant storage stability, the recording layer may not develop a ground color at these temperatures. desirable. And when using this industrially,
It is also important to be relatively cheap. Although a large number of sensitizers have been proposed as described above, few sensitizers satisfy all the above conditions, and therefore new materials satisfying these requirements are required.

Thermal recording materials are generally used under high temperature and high humidity or exposed to light, and are used for stationery such as water-based ink pens, oil-based paint pens, fluorescent pens, vermilion and glue, office supplies, hand creams, hair tonics, emulsions and the like. There is a strong demand for improvement of cosmetics, and further, when they touch a wrap film containing salad oil or a plasticizer, the recording portion is discolored or the blank paper portion is colored.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to have high recording sensitivity and whiteness, and to be excellent in preservability of a recorded image against oil and the like and long-term preservability of a blank sheet portion. Another object of the present invention is to provide a heat-sensitive recording material having less residue on the thermal head during recording.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have found that a thermosensitive recording medium comprising a support and a recording layer containing a leuco dye and a coloring agent is used as a coloring agent in the recording layer. At least one N-arylsulfonylurea derivative represented by formula (1) or general formula (2) is contained, and oxalic acid di (p-chlorobenzyl) ester and oxalic acid di (p-methylbenzyl) ester are melted. Further, it was found that a thermosensitive recording material having high recording sensitivity and whiteness, and excellent storage stability of a color image and a white paper portion can be obtained by containing a solid solution obtained by dissolution treatment, and completed the present invention. Came to do.

[0008]

Embedded image

[In the general formula (1), R ₁ is C _{1 to} C
_{4 represents} an alkyl group, a C ₁ -C ₄ alkoxyl group, a benzyloxy group, a halogen atom or a hydroxyl group, and A is 2
A group having a valence of at least one, n is an integer of 2 or more, and m is 0 to 5
Indicates an integer. ]

[0010]

[Chemical 4]

[In the general formula (2), R₂, R₃Haso
C each₁~ C_FourAlkyl group of C ₁~ C_FourArco
Xyl group, benzyloxy group, halogen atom or hydroxy
Represents a group, and p and q each represent an integer of 0 to 5. ]

[0012]

In general, in a heat-sensitive recording material provided with a recording layer containing a leuco dye and a color-developing agent, when two kinds of sensitizers are used in combination in the recording layer, the melting point is lowered, so that the temperature at which background fogging occurs However, there is a drawback that they are lower than those using the sensitizer alone. However, oxalic acid di (p-chlorobenzyl) ester and oxalic acid di (p-
The solid solution obtained by melting or dissolving the methylbenzyl) ester has a characteristic that the temperature at which the background fog is generated is higher without lowering the recording sensitivity as compared with the solid solutions. The reason why the specific solid solution of the present invention improves the performance of the thermosensitive recording medium is not sufficiently clear, but the solubility in water is reduced, the compatibility with dyes and colorants is improved, and new properties such as a change in melting point are obtained. Is considered to be the effect.

The formation of a solid solution by melting or dissolving oxalic acid di (p-chlorobenzyl) ester and oxalic acid di (p-methylbenzyl) ester was found from the phase diagram (phase diagram). The ratio when the di (p-chlorobenzyl) ester and the oxalic acid di (p-methylbenzyl) ester are treated together is not particularly limited, but is 100 parts by weight with respect to 100 parts by weight of the oxalic acid di (p-methylbenzyl) ester. , Oxalic acid di (p-chlorobenzyl) ester is preferably 25 to 400 parts, and particularly preferably 50 to 200 parts. Particularly, those treated with a mixing ratio of 100 parts of oxalic acid di (p-chlorobenzyl) ester and 100 parts of oxalic acid di (p-methylbenzyl) ester have good recording sensitivity, high whiteness, heat resistance and moisture resistance. Excellent in high speed recording. As these melt-processed products, those produced from a specific mixing ratio may be used alone, or two or more kinds having different mixing ratios may be used. Further, conventionally known sensitizers may be used together within a range that does not impair the desired effect.

Examples of the method for melt-treating oxalic acid di (p-chlorobenzyl) ester and oxalic acid di (p-methylbenzyl) ester include, for example, oxalic acid di (p-chlorobenzyl) ester and oxalic acid di (p-chlorobenzyl) ester. -Methylbenzyl) ester is melted at 150 ° C and then cooled, and as a method for dissolution treatment, a mixture of oxalic acid di (p-chlorobenzyl) ester and oxalic acid di (p-methylbenzyl) ester is used. Is dissolved in an organic solvent such as acetone, methanol, ethanol or acetonitrile, and then the solvent is removed.

The above-mentioned specific solid solution is particularly excellent in recording sensitivity with respect to the N-arylsulfonylurea derivative, exhibits little adhesion of lees to the thermal head at the time of recording, and exhibits an effect of suppressing the occurrence of background fog.

Specific examples of the specific N-arylsulfonylurea derivative include the following. Bis (p-toluenesulfonylaminocarbonylamino) ketone, 1,2-bis (p-toluenesulfonylaminocarbonylamino) ethane, 1,5-bis (p-toluenesulfonylaminocarbonylamino) -3-oxapentane, 1, 3-bis (p-toluenesulfonylaminocarbonylamino) -2-propanone, 1,4-bis (p
-Toluenesulfonylaminocarbonylamino) benzene, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, 4,4'-bis (o-toluenesulfonylaminocarbonylamino) diphenylmethane, 2,2-bis [4 , 4 '-(p-toluenesulfonylaminocarbonylamino) phenyl] propane, 1,2-bis [4- (p-toluenesulfonylaminocarbonylamino) phenyloxy] ethane,
1,4-bis (p-toluenesulfonylaminocarbonylaminomethyl) benzene, 1,5-bis (p-toluenesulfonylaminocarbonylaminomethyl) naphthalene, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether 3,3′-bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfone, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfone,
4,4 '-(p-methoxyphenylsulfonylaminocarbonylamino) diphenylmethane, 4,4'-(p-
Isopropyloxyphenylsulfonylaminocarbonylamino) diphenylmethane, 4,4 ′-(p-benzyloxyphenylsulfonylaminocarbonylamino)
Diphenylmethane, 4,4 '-(p-chlorophenylsulfonylaminocarbonylamino) diphenylmethane,
N- (p-toluenesulfonyl) -N'-phenylurea, N- (p-toluenesulfonyl) -N '-(p-tolyl) urea, N- (p-toluenesulfonyl) -N'
-(O-tolyl) urea, N- (p-toluenesulfonyl) -N '-(pn-butylphenyl) urea, N-
(P-toluenesulfonyl) -N '-(o-methoxyphenyl) urea, N- (p-toluenesulfonyl)-
N '-(p-ethoxyphenyl) urea, N- (p-toluenesulfonyl) -N'-(p-chlorophenyl) urea, N- (p-toluenesulfonyl) -N '-(m-
Chlorophenyl) urea, N- (p-toluenesulfonyl) -N '-(2,4,6-trimethylphenyl) urea, N- (p-toluenesulfonyl) -N'-(p-hydroxyphenyl) urea, N- Benzenesulfonyl-
N'-phenylurea, N-benzenesulfonyl-N '
-(P-hydroxyphenyl) urea, N-benzenesulfonyl-N '-(o-hydroxyphenyl) urea,
N- (o-toluenesulfonyl) -N'-phenylurea, N- (p-ethoxyphenylsulfonyl) -N'-
Phenylurea, N- (p-isopropoxyphenylsulfonyl) -N'-phenylurea, N- (p-benzyloxyphenylsulfonyl) -N'-phenylurea, N- (2,4-dimethylphenylsulfonyl)-
N'-phenylurea, N- (2,3,4,5,6-pentachlorophenylsulfonyl) -N'-phenylurea and the like. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Among these N-arylsulfonylurea derivatives, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, N-
(P-toluenesulfonyl) -N'-phenylurea,
N- (p-toluenesulfonyl) -N '-(p-hydroxyphenyl) urea has a particularly high recording sensitivity and whiteness, and can provide a thermosensitive recording material excellent in color image and white paper storage stability. More preferably used.

The amount of the specific N-arylurea derivative used as a coloring agent is not particularly limited, but generally 50 to 700 parts by weight, preferably 100 to 500 parts by weight, relative to 100 parts by weight of the leuco dye. Adjusted in the range of. In addition, it is also possible to use other known color formers in combination as long as the desired effects of the present invention are not impaired.

The leuco dye used in the recording layer in the present invention includes triphenylmethane type compounds, fluorane type compounds, diphenylmethane type compounds and the like, which can be selected from conventionally known ones. For example, 3- (N-ethyl-N-isoamyl) amino-7- (o-chloroanilino) fluorane,
3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-
6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-di-n-
Butylamino-6-methyl-7-anilinofluorane,
3- (N-cyclohexyl-N-methyl) amino-6-
Methyl-7-anilinofluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6-methyl-7-chloro Fluoran, 3- (N-methyl-N-ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3
-(N-ethyl-p-toluidino) -6-methyl-7-
(P-Toluidino) fluorane, 3-di-n-butylamino-7- (o-chloroanilino) fluorane, 3-di-n-butylamino-6-methyl-7-m-toluidinofluorane, 3- Di-n-butylamino-7- (o-fluoroanilino) fluorane, 3-diethylamino-6
-Chloro-7-anilinofluorane, 3- (N-ethyl-N-cyclopentyl) -6-methyl-7-anilinofluorane, 3- (N-methyl-Nn-propyl) amino-6- Methyl-7-anilinofluorane, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) ) -6-
Dimethylaminophthalide, 3-di-n-pentylamino-6,8,8-trimethyl-8,9-dihydro- (3,3
2, e) pyridofluorane, 3-di-n-butylamino-6,8,8-trimethyl-8,9-dihydro- (3,
2, e) pyridofluorane, 3,3-bis [1- (4-
Methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 2,2-bis {4- [6 '-(N-cyclohexyl- N-methyl) amino-3′-methylspiro [phthalide-3,9′-xanthene] -2′-ylamino] phenyl} propane, 3,3-bis {4-diethylamino-2-ethoxyphenyl) -4-azaphthalide,
3-p- (p-anilinoanilino) anilino-6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, 3- One or more selected from [1,1-bis (p-diethylaminophenyl) ethylene-2-yl] -6-dimethylaminophthalide and the like can be used.

The heat-sensitive recording material of the present invention generally comprises a salicylic acid represented by the above general formula (1) or general formula (2) as a leuco dye or a coloring agent in a medium in which an adhesive is dissolved or dispersed. Derived zinc salt and oxalic acid di (p-chlorobenzyl) ester and oxalic acid di (p-methylbenzyl)
It is produced by coating a support with a coating liquid obtained by dispersing fine particles such as a solid solution obtained by dissolving or melting an ester, and drying.

The content of the leuco dye in the recording layer in the recording layer is generally 5 to 20% by weight based on the dry weight of the recording layer.
It is preferable that the content of the color developing agent is generally 10
It is preferably 50% by weight. Content is 10% by weight
When the amount is less than 50%, the coloring ability becomes insufficient, and even when the amount exceeds 50% by weight, the coloring ability is saturated and no particular improvement is observed, which may be economically disadvantageous. When waxes and white pigments are contained in the recording layer, their content ratios are 5 to 20 respectively.
%, Preferably 10 to 50% by weight, and the content of the adhesive is generally 5 to 20% by weight.

The coating liquid containing them is generally prepared by dispersing water with a dispersing medium and a dye and a color developing agent with a stirring / grinding machine such as a ball mill, attritor or sand mill. To be done.

In the coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene, etc. are usually used as an adhesive.
Maleic anhydride copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion and the like are 10 to 40% by weight of the total solid content, preferably 15 to 35%.
It is used in an amount of about wt%.

Further, various auxiliary agents can be added to the coating liquid, for example, dispersant such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate / sodium salt and fatty acid metal salt. UV absorbers such as triazoles, antifoaming agents, fluorescent dyes, coloring dyes, and antioxidants. In order to prevent sticking of the thermosensitive recording medium due to contact with recording equipment or recording head, use a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, etc. in the paint. It can also be added.

The recording layer may further contain, for example, the following compounds in order to further improve the storage stability.
1,1,3-tris (3'-cyclohexyl-4'-hydroxyphenyl) butane, 1,1,3-tris (2-
Methyl 4-hydroxy-5-tert-butylphenyl) butane, 4,4′-thiobis (3-methyl-6-t
ert-butylphenol), 1,3,5-trimethyl-2,4,6-tris (3,5-ditert-butyl-4-hydroxybenzyl) benzene, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone , P-
Octylphenyl salicylate, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, ethyl-2-cyano-3,3'-diphenylacrylate,
Tetra (2,2,6,6, -tetramethyl-4-piperidyl) 1,2,3,4-butane tetracarboate,
2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphoric acid sodium salt or magnesium salt.

In addition, kaolin, clay, talc, calcium carbonate,
It is also possible to add an inorganic pigment such as calcined clay, titanium oxide, diatomaceous earth, particulate anhydrous silica, activated clay.

The support may be paper, plastic film, synthetic paper, or a plastic film or synthetic paper laminated with coated paper or high-quality paper via an adhesive, or a paper laminated with plastic. used. Examples of such 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 of 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 the coating liquid by the above method. When a plastic film is used as the support, the coating efficiency can be increased by subjecting the surface to treatments such as corona discharge and electron beam irradiation. The coating amount of the coating liquid is also not particularly limited, but it is usually ^{2 to} 10 g / m ² , preferably 3 to 7 g in dry weight.
It is adjusted in the range of about / m ² .

Further, by providing a protective layer composed of an adhesive, a lubricant, a pigment or the like on the recording layer, a thermosensitive recording material having excellent chemical resistance against plasticizer, oil and the like can be obtained. Specific examples of the adhesive used in the protective layer include polyvinyl alcohols having various degrees of saponification, acetoacetyl group-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acrylic resin, and polyurethane resin. Further, it is desirable that these adhesives are adjusted in the range of 10 to 95% by weight, preferably 30 to 90% by weight, based on the total solid content.
The coating amount of the protective layer is 0.5 to 10 g / dry weight.
m ² , preferably adjusted in the range of about 1 to 7 g / m ² .

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, etc. It is of course possible to provide a protective layer on the back surface of the recording medium or to provide an undercoat layer on the support, and various known techniques in the field of producing a thermosensitive recording medium can be added.

[0031]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively.

Solid solution formation example 1 10 g each of oxalic acid di (p-chlorobenzyl) ester and oxalic acid di (p-methylbenzyl) ester were added to 500 m.
When placed in a heat-resistant container (1), heated on a hot plate at 150 ° C., completely melted and then cooled, uniform crystals were obtained. The melting point was 140 ° C.

Solid solution production example 2 10 g each of oxalic acid di (p-chlorobenzyl) ester and oxalic acid di (p-methylbenzyl) ester were added to 500 m.
The solution was placed in a 1-liter flask, dissolved by heating in 300 ml of acetone, and then acetone was removed by an evaporator to obtain uniform white crystals. The melting point was 140 ° C.

Example 1 [Formation of undercoat layer] A styrene-butadiene copolymer emulsion (solid content: 50) was prepared by dispersing 85 parts of calcined clay (trade name: Ansilex) in 320 parts of water.
%) 40 parts, the blade 10% oxidized starch aqueous solution as the coating amount after drying became 7.0 g / m ² an undercoat layer coating solution obtained by mixing 50 parts on a 48 g / m ² neutral paper It was applied to provide an undercoat layer.

[Preparation of solution A] 3-di-n-butylamino-
A composition consisting of 20 parts of 6-methyl-7-anilinofluorane, 10 parts of a 10% aqueous solution of methylcellulose, and 70 parts of water was pulverized by a sand mill until the average particle size became 0.8 μm, to obtain a liquid A.

[Preparation of solution B] A composition consisting of 20 parts of 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, 10 parts of a 10% aqueous solution of methylcellulose, and 70 parts of water was sand milled to give an average particle size of 1 It was pulverized to have a particle size of 0.0 μm to obtain a liquid B.

[Preparation of Solution C] 20 parts of the crystals produced in Solid Solution Production Example 1, 10% aqueous solution of polyvinyl alcohol 10
Parts and 70 parts of water were pulverized with a sand mill until the average particle size became 1.0 μm, and a liquid C was obtained.

[Formation of Recording Layer] Liquid A 60 parts, liquid B 120
Parts, liquid C 120 parts, light calcium carbonate 26 parts, zinc stearate 25% dispersion 12 parts, 30% paraffin dispersion 10 parts, and polyvinyl alcohol 10% aqueous solution 80 parts by mixing and stirring. The coating solution was applied onto the above-mentioned undercoat layer so that the dry weight was 5 g / m ² , dried, and subjected to a super calender treatment to obtain a thermosensitive recording medium.

Examples 2 to 3 Thermal recording was carried out in the same manner as in Example 1 except that the following compounds were used in place of 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane in the preparation of solution B. Got the body Example 2: N- (p-toluenesulfonyl) -N'-
Phenylurea Example 3: N- (p-toluenesulfonyl) -N'-
(P-hydroxyphenyl) urea

Example 4 A thermosensitive recording couple was obtained in the same manner as in Example 1 except that the crystals produced in the solid solution production example 2 were used in place of the crystals produced in the solid solution production example 1 in the preparation of the liquid C. .

Comparative Example 1 In preparation of solution B, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) was used in place of 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane. A thermal recording material was obtained in the same manner as in Example 1.

Comparative Example 2 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that oxalic acid di (p-chlorobenzyl) ester was used in place of the crystals produced in the solid solution producing example 1 in the preparation of solution C. Obtained.

Comparative Example 3 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that oxalic acid di (p-methylbenzyl) ester was used in place of the crystals produced in the solid solution producing example 1 in the preparation of the liquid C. Obtained.

Comparative Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that p-benzylbiphenyl was used in place of the crystals produced in the solid solution producing example 1 in the preparation of solution C.

The thermal recording material thus obtained was evaluated as follows, and the results are shown in Table 1. [Recording density] 0.39 mj / dot using a dynamic color tester which is a modification of Hitachi's commercial thermal facsimile machine.
The heat-sensitive recording material was caused to develop color by the applied energy of, and the density of the recording portion was measured with a Macbeth reflection densitometer RD-914.

[Head cas] Using a dynamic color tester obtained by modifying a commercially available thermal facsimile machine manufactured by Hitachi, 0.3
Thermal recording medium 25c with applied energy of 9mj / dot
After the m color was developed, the state of the lees attached to the thermal head was visually judged. Judgment Criteria ⊚: The thermal head has almost no adhesion of lees. ◯: There is some residue on the thermal head. X: A large amount of residue adhered to the thermal head.

[Whiteness] The whiteness of the thermosensitive recording medium was measured with a Hunter whiteness meter.

[Moisture resistance] After recording, after leaving for 72 hours under the condition of 50 ° C. and 75% RH, the densities of the blank part and the recording part were measured again by a Macbeth reflection densitometer.

[Oil resistance] After recording, apply salad oil,
After leaving at room temperature for 30 minutes, wipe off excess oil and
The densities of the blank area and the recorded area were measured with a Macbeth reflection densitometer.

[0050]

[Table 1]

[0051]

As is clear from the results of [Table 1], the thermosensitive recording medium of the present invention has high recording sensitivity and whiteness, has excellent storage stability in terms of humidity resistance and oil resistance, and has a head. It was a recording material with little adherence of lees.

Claims (1)

[Claims] 1. A leuco dye and a coloring agent are contained on a support.
In a thermosensitive recording medium provided with a recording layer that
A colorant represented by the following general formula (1) or general formula (2)
At least an N-arylsulfonylurea derivative
Contains one and di (p-chlorobenzyl oxalate)
Ester and oxalic acid di (p-methylbenzyl) ester
Containing a solid solution obtained by melting or dissolving
A thermosensitive recording medium characterized by. [Chemical 1][In the general formula (1), R₁Is C₁~ C_FourThe alkyl
Group, C₁~ C_FourAlkoxyl group, benzyloxy group,
Indicates a halogen atom or hydroxyl group, A is a valence of 2 or more
Group, n is an integer of 2 or more, m is an integer of 0-5
You. ] [Chemical 2][In the general formula (2), R₂, R₃Are C₁
~ C_FourAlkyl group of C ₁~ C_FourThe alkoxyl group of
Represents a benzyloxy group, a halogen atom or a hydroxyl group,
p and q each represent an integer of 0 to 5. ]