JPH07266702A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material excellent in recording image quality and recording sensitivity. CONSTITUTION:In a thermal recording material wherein a thermal recording layer containing a leuco dye and a coupler and a protective layer based on a water-soluble adhesive and pigment are successively provided on a support, dialkylsulfosuccinate having a 10-20C alkyl group is added to the thermal recording layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium utilizing the reaction between a leuco dye and a color former, and more particularly to a thermosensitive recording medium excellent in recording image quality and recording sensitivity.

[0002]

2. Description of the Related Art Heretofore, a heat-sensitive recording material has been well known in which a reaction between a colorless or light-colored leuco dye and a coloring agent is utilized to react both coloring substances by heat to obtain a recorded image. Since such a thermosensitive recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

One of the fields of application of the thermal recording material is, for example, a thermal recording label for a POS (point of sales) system. The label is used as a label for foods, side dishes, etc., but these are edible oil, water, solvent,
It often comes into contact with a plasticizer or the like, and in order to protect the thermosensitive recording layer, it is common to provide a protective layer on the thermosensitive recording layer.

Further, as the recording speed increases, the sensitivity of the thermal recording material is required to be increased. Various methods and means have been considered for increasing the sensitivity of thermal recording media. For example,
As a powerful method for increasing the sensitivity, there is atomization of leuco dyes and colorants. As the atomization method, it is common to mechanically pulverize using a sand mill or cobol mill,
Usually, a water-soluble polymer such as a cellulose derivative, a starch derivative, or polyvinyl alcohol is used as the protective colloid agent. Further, for the purpose of reducing the particle size to increase the recording sensitivity and shortening the crushing time, various kinds of dispersants are being used in combination. For example, Japanese Patent Publication No. 4-33631
The publication describes a heat-sensitive recording material using dioctyl sulfosuccinate as a dispersant in the heat-sensitive recording layer.
However, when the protective layer is smeared on the heat-sensitive recording layer, a phenomenon in which the protective layer locally becomes thicker or thinner (paint unevenness) may occur. If the protective layer is thin or thick, the recording density may vary, or if the thin part of the protective layer comes into contact with oil or plasticizer, the print may be erased. There will be new problems such as

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium having excellent recording image quality and recording sensitivity.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have successively provided on a support a heat-sensitive recording layer containing a leuco dye and a color former and a protective layer containing a water-soluble adhesive and a pigment as main components. In the heat-sensitive recording material, it was found that the above-mentioned problems can be achieved by including a dialkylsulfosuccinate having an alkyl group having 10 to 20 carbon atoms in the heat-sensitive recording layer, and completed the present invention. .

[0007]

In the present invention, the thermosensitive recording layer contains a dialkylsulfosuccinate having an alkyl group having 10 to 20 carbon atoms, preferably 12 to 16 carbon atoms, as a dispersant or a wetting agent. A uniform protective layer is formed on the layer, and the alkyl group has 9 or less carbon atoms or 2
When it is 1 or more, it adversely affects the uniform smearing of the protective layer,
We have found that it is the cause of uneven swimming in the protective layer. The reason for this is not clear, but it is presumed that there is a difference in water permeability on the surface of the thermosensitive recording layer.

Further, when a specific dialkyl sulfosuccinate is used for the atomization treatment of the leuco dye or the color developing agent, the effect of improving the pulverization efficiency is recognized and the recording sensitivity is increased. The atomization treatment is performed by using a sand mill or a cobol mill and a protective colloid agent and a dispersant.

As the alkyl group of the specific dialkylsulfosuccinate used in the heat-sensitive recording layer, a straight chain or side chain can be used, and the carbon number of the alkyl is within a range not impairing the effect of the present invention. It is also possible to use a dialkyl sulfosuccinate having a ratio of 9 or less or another surfactant as a dispersant for a leuco dye or a color developing agent. Specific dialkyl sulfosuccinate salts include sodium,
Monovalent salts such as potassium and ammonium are used. The amount added is not particularly limited, but is 0.01 to 5% by weight, preferably 0.1% to the total solid amount of the thermosensitive recording layer.
It is desirable to adjust in the range of 2 to 2% by weight. Further, a specific dialkyl sulfosuccinate and a dialkyl sulfosuccinate having 9 or less carbon atoms or another surfactant may be used in combination within a range that does not impair the effects of the present invention.

Various types of leuco dyes which are colorless or light-colored contained in the heat-sensitive recording layer of the present invention are known.
For example, the following is exemplified. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,
3-bis (p-dimethylaminophenyl) phthalide, 3
-(P-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3- (P-dimethylaminophenyl)
Phthalide dyes such as -3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3-diethylamino -6-Methylfluorane, 3-
Diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N-
Ethyl-p-toluidino) -7-methylfluorane, 3
-Diethylamino-7- (N-methyl-N-benzylamino) fluorane, 3-diethylamino-7-diethylaminofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-dimethylamino-
6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane,
3-dipentylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (2-carbomethoxy-anilino) fluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7. -Anilinofluorane, 3- (N-cyclohexyl-N-methylamino)-
6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7 -Xylidinofluorane, 3
-Diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3- (N-ethyl-N-cyclopentylamino) -6-methyl-7-anilinofluorane, Three
-[N- (3-ethoxypropyl) -N-methylamino] -6-methyl-7-anilinofluorane, 3- [N
-Ethyl-N- (3-ethoxypropyl) amino] -6
-Methyl-7-anilinofluorane, 3-diethylamino-7- [m- (trifluoromethyl) anilino] fluorane, 3-diethylamino-7- (o-fluoroanilino) fluorane, 3-dibutylamino-7- (O-Fluoroanilino) fluorane, 3-diethylamino-6
-Chloro-7-anilinofluorane, 3- (N-ethyl-Np-tolylamino) -7-methylfluorane, 3
-(N-ethyl-N-tetrahydrofurfurylamino)
-6-Methyl-7-anilinofluorane, 3- (N-cyclopentyl-N-ethylamino) -6-methyl-7-
Fluoran dyes such as anilinofluorane and 3- (N-ethyl-N-p-tolylamino) -6-methyl-7-anilinofluorane. Of course, the dyes are not limited to these dyes, and two or more dyes may be used in combination.

As the coloring agent used in combination with the above leuco dye, for example, the following known compounds are used. 4,4'-dihydroxy-diphenylmethane, 4,4'-isopropylidene diphenol (bisphenol A), hydroquinone, 4,4'-cyclohexylidene bisphenol, 4,4 '-[1,4-phenylenebis (1- Methylethylidene)] bisphenol, 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisphenol, 4,4 ′-(1,3-
Dimethylbutylidene) bisphenol, 2,2-bis (4-hydroxyphenyl) -4-methyl-pentane,
4,4'-dihydroxydiphenyl sulfide, 4,
4'-thiobis (6-tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenyl sulfone,
2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4) -Hydroxyphenyl) sulfone,
1,3-di [2- (4-hydroxyphenyl) -2-
Propyl] benzene, hydroquinone monobenzyl ether, methyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, 4
-Dimethyl hydroxyphthalate, 1,5-bis (4-hydroxyphenylthio) -3-oxa-pentane, (4
-Hydroxyphenylthio) acetic acid-2- (4-hydroxyphenylthio) ethyl ester, novolac type phenol resin, phenolic compound such as phenol polymer,
3-cyclohexyl-4-hydroxybenzoic acid, 3,5
-Dimethyl-4-hydroxybenzoic acid, 3,5-di-te
rt-Butylsalicylic acid, 3-benzylsalicylic acid, 3-
(Α-Methylbenzyl) salicylic acid, 3-chloro-5-
(Α-Methylbenzyl) salicylic acid, 3-phenyl-5
-(Α, α-Dimethylbenzyl) salicylic acid, 3,5-
Di-α-methylbenzyl salicylic acid, 4- (2-P-methoxyphenoxyethoxy) salicylic acid, 4- (3-P
An aromatic carboxylic acid such as -tolylsulfonylpropyloxy) salicylic acid, and a phenolic compound or aromatic carboxylic acid thereof and a polyvalent metal such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin or nickel. Organic acidic substances such as salt. Of course, these colorants may be used in combination of two or more, if necessary.

The ratio of the leuco dye and the color-developing agent to be used is appropriately selected depending on the type of the leuco dye or the color-developing agent to be used and is not particularly limited, but is generally 100 with respect to the leuco dye. ~ 800% by weight, preferably 150
About 400% by weight of the coloring agent is used.

A coating material for a heat-sensitive recording layer containing these substances is
Generally, water is used as a dispersion medium, and a ball mill, attritor,
It is prepared by dispersing the dye and the colorant together or separately by a stirrer / pulverizer such as a vertical or horizontal sand mill or colloid mill.

In such a coating liquid, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl are usually used as adhesives. Alcohol, diisobutylene / maleic anhydride copolymer salt, styrene /
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene /
At least one kind of butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin and the like is 2 to 40% by weight based on the total solid content of the heat-sensitive recording layer,
It is preferably mixed in the range of about 5 to 30% by weight.

If desired, various auxiliary agents can be added to the coating solution. For example, dispersants such as sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, zinc stearate,
Waxes such as calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, UV absorbers such as benzophenone-based, cyanoacrylate-based, and hydroxybenzoate-based waxes, other defoaming agents, and coloring dyes are appropriately added. When a dialkylsulfosuccinate having an alkyl carbon number of 9 or less is used, its content is 0.5% by weight based on the total solid content of the thermosensitive recording layer.
Must be:

It is also possible to use various pigments in combination in the coating liquid, for example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles can be used.

Further, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebisstearic acid amide, behenic acid amide, and methylenebisstearic acid amide. , N-
Methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate,
Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p- Chlorobenzyl, p-benzylbiphenyl, p-tolylbiphenyl ether, di (p-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, 1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetizide,
Examples include N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like. These sensitizers can be used in combination of two or more kinds as long as the effect of the present invention is not impaired. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

In the present invention, it is possible to add a storability improver in the heat-sensitive recording layer. Examples of such storability improvers include the following. 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 (2-
Methyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol),
1- [α-methyl-α- (4′-hydroxyphenyl)
Ethyl] -4- [α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2
-Methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,
4'-thiobis (3-methylphenol), 4,4'-
Dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3',
5,5'-tetramethyldiphenyl sulfone, 2,2-
Bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) Hindered phenol compounds such as propane, 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4 ′-(2-methylglycidyloxy) diphenyl sulfone, diglycidyl terephthalate, Epoxy compounds such as cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di) -Tert-Butylphenyl) phosphate sodium or polyvalent Shokushio, bis (4-ethylene iminocarbonyl aminophenyl) include methane and the like. Among them, 1,1,3-tris (2-methyl-4-)
Hydroxy-5-cyclohexylphenyl) butane is preferably used because it has an excellent effect on water resistance and is less likely to cause background fog. Of course, when these sensitizers and storability improvers are also used after being atomized,
It is desirable to use sodium dialkylsulfosuccinate having an alkyl carbon number of 10 or more.

The protective layer provided on the heat-sensitive recording layer is composed of an adhesive made of a water-soluble or water-dispersible polymer compound and a pigment. Specific examples of such an adhesive include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, and diisobutylene.・ Maleic anhydride copolymer salt, styrene ・
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene /
Examples thereof include butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin, etc. Among them, acetoacetyl group-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol must form a strong film. It is particularly preferably used because it can be produced.

Specific examples of the pigment include calcium carbonate,
Inorganic pigments such as zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea Examples include formalin resin fillers and organic pigments such as raw starch particles.

The method for preparing the coating liquid for forming the protective layer is not particularly limited, and it is generally prepared by using water as a dispersion medium and mixing and stirring an adhesive, a pigment and the like. Furthermore, in the coating liquid for the protective layer, if necessary, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, lubricants such as silicone oil, surfactants such as sodium dioctyl sulfosuccinate (dispersion) Agents, wetting agents), antifoaming agents, coloring dyes, fluorescent dyes, and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate can be appropriately added. Further, in order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, and an epoxy compound can be used in combination, and if necessary, an ultraviolet absorber or a microencapsulated ultraviolet absorber may be used. It can also be used together. Further, the protective layer may contain a dialkyl sulfosuccinate having an alkyl group having 10 to 20 carbon atoms.

The method for forming the heat-sensitive recording layer and the protective layer is not particularly limited, and suitable examples include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating and die coating. The coating liquid for heat-sensitive recording layer is applied and dried on the support by the coating method, and then the coating liquid for protective layer is further applied and dried on the heat-sensitive recording layer. The support may be appropriately selected from paper, plastic film, synthetic paper, non-woven fabric, metal deposit, etc., and used. The coating amount of the heat-sensitive recording layer coating composition is 2~12g / m ² in dry weight, preferably 3 to 10 g / m ² approximately,
The coating amount of the protective layer coating liquid is 0.1 to 20 g / m on a dry basis
² , preferably in the range of about 0.5 to 10 g / m ² .

If necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storage stability. Furthermore, an undercoat layer may be provided between the support and the thermosensitive recording layer, smoothing treatment such as super calendering may be applied after coating each layer, or adhesive treatment may be applied to the back surface of the recording material to form an adhesive label. Alternatively, various known techniques in the field of producing a thermosensitive recording medium, such as a magnetic thermosensitive recording layer, a coating layer for printing, and a thermal transfer thermosensitive recording layer, may be added as necessary.

[0024]

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. In addition, unless otherwise indicated, the part and% in an example show a weight part and weight%, respectively.

[Example 1] Formation of undercoat layer Fired clay (trade name: Ansilex, manufactured by EMC) 1
Undercoat layer coating liquid obtained by mixing and stirring a composition consisting of 00 parts, styrene / butadiene copolymer latex (solid content: 50%) 15 parts, 10% polyvinyl alcohol aqueous solution 30 parts and water 200 parts Was coated on one surface of a high-quality paper of 60 g / m ^{2 by} a pure blade coating method so that the coating amount after drying was 7 g / m ² to form an undercoat layer.

Preparation of Solution A 50 parts of bis (3-allyl-4-hydroxyphenyl) sulfone, 50 parts of 5% aqueous solution of methylcellulose, 8.3% aqueous solution of sodium ditridecylsulfosuccinate (trade name: Perex TRB Kao) 5 parts and water 30
The composition consisting of 1 part was pulverized with a sand mill for 3 hours to obtain a colorant dispersion.

Preparation of Solution B 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 5% aqueous solution of methylcellulose 1
0 parts, sodium ditridecyl sulfosuccinate 8.3
% Aqueous solution 2 parts and water 10 parts were pulverized with a sand mill for 3 hours to obtain a leuco dye dispersion.

Formation of Thermal Recording Layer A coating solution obtained by mixing 100 parts of A solution, 50 parts of B solution, 160 parts of 10% polyvinyl alcohol aqueous solution, 50 parts of aluminum hydroxide and 150 parts of water with stirring is prepared as the above-mentioned undercoat. A thermosensitive recording layer was formed by coating and drying the layer by a bar coating method so that the coating amount after drying was 6 g / m ² .

(8) Formation of protective layer 100 parts of a 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, kaolin having a solid concentration of 30% [trade name: U
W-90, manufactured by EMC Co., Ltd.] A coating solution for a protective layer obtained by mixing and stirring a composition consisting of 60 parts and 60 parts of water has a coating amount of 5 g / m ² after drying on a heat-sensitive recording layer. After coating and drying by the bar coating method as described above, a super calendering treatment was performed to obtain a heat-sensitive recording material.

Example 2 Example 1 was repeated except that polyvinyl alcohol was used in place of methyl cellulose in the preparation of solutions A and B of example 1.
A thermosensitive recording medium was obtained in the same manner as described above.

Comparative Example 1 In the preparation of solutions A and B of Example 1, an 8.3% aqueous solution of sodium dioctylsulfosuccinate was used instead of the sodium ditridecylsulfosuccinate aqueous solution (trade name: Rapisol B-07 manufactured by NOF Corporation). Example 1 except that
A thermosensitive recording medium was obtained in the same manner as described above.

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that sodium dioctylsulfosuccinate was used instead of sodium ditridecylsulfosuccinate in the preparation of solution A.

Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that sodium dioctylsulfosuccinate was used instead of sodium ditridecylsulfosuccinate in the preparation of solution B.

The following evaluation tests were conducted on the thus obtained thermosensitive recording medium and the three kinds of color formers or leuco dye dispersions obtained in Examples 1 and 2 and Comparative Example 1 and the results are shown in Table 1. And [Table 2].

[Evaluation] [Average particle size] 3 obtained in Examples 1 and 2 and Comparative Example 1
The average particle size of various types of coloring agents or leuco dye dispersions can be calculated by Coulter Counter (Coulter Electronics In
c.) and the results are shown in [Table 1].

[Recording Density] and [Recording Image Quality] Each thermosensitive recording medium was color-developed using a thermosensitive evaluation machine [trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.] at an applied energy of 0.4 mJ / dot. The color density of the recorded image was measured in a visual mode with a Macbeth densitometer [RD-914 type, manufactured by Macbeth Co.], and the applied energy was 0.2 mJ / d.
Each thermosensitive recording medium was allowed to develop color at ot, and the recorded image quality of the obtained recorded image was visually judged, and the results are shown in [Table 2]. (Recording image quality judgment criteria) There is almost no unevenness in the recording image quality. × The recording image quality is uneven.

[Applicability of protective layer smearing] In the formation of the protective layer of Examples and Comparative Examples, the protective layer coating liquid was colored with a small amount of a water-soluble dye, and then smeared on the heat-sensitive recording layer, and the smear unevenness was visually evaluated. The results are shown in [Table 2]. (Evaluation of suitability for smearing of protective layer) ○ ・ ・ ・ Uniform smearing and no unevenness × ・ ・ ・ Swimming unevenness on protective layer

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

As is clear from the results of [Table 1] and [Table 2], the thermosensitive recording medium of the present invention was a thermal recording medium excellent in smearing suitability and recording sensitivity.

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a support, on which a thermosensitive recording layer containing a leuco dye and a coloring agent and a protective layer containing an aqueous adhesive and a pigment as main components are sequentially provided. A heat-sensitive recording material comprising a dialkyl sulfosuccinate having an alkyl group having 10 to 20 carbon atoms.