JP2002240430A - Thermal recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording body excellent in shelf stability, running properties in recording, and printability. SOLUTION: In the thermal recording body having a thermal recording layer containing a leuco dye, a color developer and an adhesive and a protective layer constituted mainly of the adhesive and a pigment, on a substrate sequentially, a graft copolymer of a polymer containing an ethylene unsaturated carboxylic acid and of a silicone, and a polyvinyl alcohol, are used as the adhesive in the protective layer, and at least one kind of a kaolin and an aluminum hydroxide and an amorphous silica are used as the pigment.

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 a color-forming reaction between a leuco dye and a color former.

[0002]

2. Description of the Related Art Thermal recording media utilizing a color development reaction between a leuco dye and a color former by heat are well known. Such a thermosensitive recording medium is relatively inexpensive, the recording device is compact,
Because it is easy to maintain, it is used in recording media such as facsimile machines and various computers, and in a wide variety of other fields.

[0003] As one of the fields of use, for example, POS
(Point of sales) The use of thermal recording labels for systems is increasing. In recent years, applications for tags and tickets have been increasing, and in addition to the conventional water resistance and chemical resistance, various printing aptitudes (especially offset printing properties), recording traveling properties, and thermal printing heads by continuous printing have been developed. It is also required to prevent the adhesion of cakes.

A thermosensitive recording medium having a protective layer containing polyvinyl alcohol and a graft copolymer of silicone and a polymer containing an ethylenically unsaturated carboxylic acid has excellent effects on chemical resistance and printability. JP-A-6-7
Japanese Patent Application Laid-Open No. 2000-118138 discloses that the colloidal silica in the protective layer imparts an excellent effect on recording running property and adhesion resistance to foreign matter in a thermal recording head. Japanese Patent Laid-Open Publication No. 2000-238432 discloses a further improvement.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material having excellent storage stability, recording running property, and printability.

[0006]

According to the present invention, there is provided a thermosensitive recording medium having a thermosensitive recording layer containing a leuco dye, a colorant and an adhesive, and a protective layer mainly containing an adhesive and a pigment on a support. As one means for solving the above-mentioned problems, the present invention uses a graft copolymer of a polymer containing an ethylenically unsaturated carboxylic acid and a silicone as an adhesive in a protective layer, and polyvinyl alcohol. And at least one of kaolin and aluminum hydroxide as the pigment and amorphous silica.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The adhesive in the protective layer is a graft copolymer of a polymer containing an ethylenically unsaturated carboxylic acid and silicone (hereinafter referred to as a specific adhesive), and polyvinyl alcohol. The pigment is at least one of kaolin and aluminum hydroxide and amorphous silica, and the total ratio of the specific pigment is not particularly limited, but is 3 to the total solid content of the protective layer.
About 0 to 70% by weight is preferable.

If the total ratio of the pigment comprising at least one of kaolin and aluminum hydroxide in the protective layer and the amorphous silica is less than 30% by weight, the suitability for offset printing is lowered, and if it exceeds 70% by weight, the recording is effected. There is a possibility that the storage stability of a part of the composition against chemicals such as plasticizers, oils and fats and oils may be reduced. The average particle diameter of kaolin and aluminum hydroxide is preferably about 0.5 to 2.0 μm.

The ratio of the amorphous silica in the protective layer is preferably about 5 to 30% by weight based on the total solid content of the protective layer. As the amorphous silica, the primary particle diameter is 5 to 100 n.
m is preferable, and those obtained from colosidal silica are particularly preferable because they have less secondary aggregates. When the amount of the amorphous silica is less than 5% by weight, the fixability of the printed portion is reduced, and
If it exceeds 0, the preservability of the recording portion against chemicals such as plasticizers, oils, fats and oils may be reduced.

The total ratio of the specific adhesive and polyvinyl alcohol in the protective layer is not particularly limited, but is preferably about 20 to 60% by weight based on the total solid content of the protective layer. The amount of the specific adhesive used is preferably about 0.5 to 10% by weight based on the total solid content of the protective layer. If the specific adhesive is less than 0.5% by weight, the printing density may decrease. If it exceeds 10% by weight, the chemical resistance of the recording portion may decrease. preferable.

The polymer containing an ethylenically unsaturated carboxylic acid constituting the specific adhesive is, for example, an ethylenically unsaturated carboxylic acid, such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, and arylyl acid. Copolymers of a carboxylic acid monomer and an ethylenically unsaturated monomer such as methyl (meth) acrylate, ethyl acrylate, trimethylolpropane triacrylate, styrene, acrylonitrile, butadiene, acrylamide and the like can be mentioned.

The silicone constituting the specific adhesive is a silyl such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxy-ethoxysilane) and γ-methacryloxypropyltrimethoxysilanedimethylpolysiloxane. Examples of the polymer include a polymer having a group-containing monomer as a main component.

The mixing ratio of the silicone to the polymer containing the ethylenically unsaturated carboxylic acid is 5 to 5% based on the solid content.
It is in the range of 50% by weight, preferably 10 to 30% by weight. By the way, when the compounding ratio of silicone is less than 5% by weight, the effect of improving the printability cannot be sufficiently obtained, while when it exceeds 50% by weight, the storage stability of the printed portion decreases.

The water-soluble graft copolymer of a polymer containing an ethylenically unsaturated carboxylic acid and silicone is specifically used in the form of a salt such as sodium, potassium and ammonium.

The protective layer is formed by mixing and stirring an aqueous solution of polyvinyl alcohol, an aqueous solution of a specific adhesive and, if necessary, the following auxiliaries in, for example, amorphous silica, and slurry of kaolin and / or aluminum hydroxide using water as a medium. The coating liquid for a protective layer prepared as described above is formed on the heat-sensitive recording layer by applying and drying such that the applied amount after drying is about 0.5 to 6 g / m ² .

Auxiliaries which can be added to the coating solution for the protective layer include surfactants such as sodium alkylbenzenesulfonate, sodium dioctylsulfosuccinate, sulfone-modified polyvinyl alcohol, sodium polyacrylate, polyamidoamine / epichlorohydrin resin, glyoxal , Boric acid, dialdehyde starch, methylol urea, epoxy compounds, hydrazine compounds and other water-resistant agents, zinc stearate, calcium stearate,
Lubricants such as polyethylene wax and paraffin wax,
In addition, auxiliary agents such as an ultraviolet absorber, a fluorescent dye, a coloring dye, a release agent, and an antioxidant can also be added. Above all,
Zinc stearate having an average particle diameter of 1 μm or less further enhances recording runnability and is preferred.

Specific examples of the polyvinyl alcohol for the protective layer include, for example, completely saponified polyvinyl alcohol having a degree of polymerization of about 300 to 3000, partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, Examples include diacetone-modified polyvinyl alcohol.

Further, the protective layer may contain various other known adhesives as long as the desired effects of the present invention are not impaired. Such other adhesives include:
Examples include oxidized starch, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, urethane resin latex, and the like.

The heat-sensitive recording layer is made of a leuco dye, a colorant, an adhesive and, if necessary, the following sensitizer, storability, The coating liquid for the heat-sensitive recording layer prepared by mixing and stirring each slurry such as an improving agent and the following auxiliaries on a support so that the coated amount after drying is about ² to 10 g / m ^2. It is formed by coating and drying.

As the leuco dye and the color former, for example, the following various known ones can be used. Specific examples of such leuco dyes include, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide,
(4-diethylamino-2-methylphenyl) -3-
(4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (N-ethyl-Np-tolyl) amino-7-N-methylanilinofluoran, 3-cyclohexylamino-6-chlorofluoran , 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluoran, 3- (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-pentyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-p-toluidino ) -6-Methyl-7-anilinofluoran, 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,
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-chlorofluoran,
3,6-bis (dimethylamino) fluorene-9-spiro-3 ′-(6′-dimethylamino) phthalide and the like.

Specific examples of the coloring agent include, for example, 4,4 ′
Isopropylidene diphenol, 4,4′-cyclohexylidene diphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate,
2,4'-dihydroxydiphenyl sulfone, 4,4 '
-Dihydroxydiphenylsulfone, 4-hydroxy-
4'-isopropoxydiphenyl sulfone, bis (3-
Allyl-4-hydroxyphenyl) sulfone, 2,4-
Bis (phenylsulfonyl) phenol, 4-hydroxy-4'-methyldiphenylsulfone, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl)- 1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene Phenolic compounds such as N- (p-toluenesulfonyl) carbamoyl acid-
p-cumylphenyl ester, N- (p-toluenesulfonyl) carbamoyl acid-p-benzyloxyphenyl ester, N- (o-toluoyl) -p-toluenesulfonamide, 4,4'-bis (Np- those having a -SO ₂ NH- bond in the molecule such as toluene sulfonylamino Cabo sulfonyl) diphenylmethane, p- chlorobenzoic acid zinc, 4- [2-(p-methoxyphenoxy) ethyloxy] zinc salicylate, 4- [3 -(P-tolylsulfonyl) propyloxy] zinc salicylate, 5- [p-
(2-p-methoxyphenoxyethoxy) cumyl] and zinc salts of aromatic carboxylic acids such as salicylic acid.

Of course, it is not limited to these,
Also, two or more kinds can be used in combination. Further, the amount of the leuco dye to be used cannot be limited because it differs depending on the coloring agent used, but it is about 5 to 35% by weight based on the heat-sensitive recording layer.

The ratio of the leuco dye to the colorant is appropriately selected according to the type of the leuco dye and the colorant used, and is not particularly limited. On the other hand, about 1 to 5 parts by weight of a coloring agent is used.

The heat-sensitive recording layer may contain a storability improving agent for improving the storage stability of the recording portion, and a sensitizer for improving the recording sensitivity. Specific examples of such a preservability improver include, for example, 2,2′-ethylidenebis (4,6-di-tert-butylphenol), 4,4′-
Thiobis (2-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-
Hindered phenol compounds such as tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene , 4,4'-diglycidyloxydiphenylsulfone, 4-benzyloxy-4 '-(2-methylglycidyloxy) diphenylsulfone, diglycidyl terephthalate, cresol novolak epoxy resin, phenol novolak epoxy resin, bisphenol A epoxy Epoxy compounds such as resins, N, N'-di-2-naphthyl-p-phenylenediamine, sodium or polyvalent metal salts of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, bis (4-ethyleneiminocarbonylaminofe Le) methane, and the like.

Specific examples of the sensitizer include, for example, stearic acid amide, methylenebisstearic acid amide, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, 2-naphthylbenzyl ether, m-terphenyl, 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-acetophenethidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, di-p-chlorobenzyl oxalate, di-p-methylbenzyl oxalate, di-oxalate Benzyl esters and the like are exemplified. The amounts of these preservatives and sensitizers are not particularly limited,
Generally, the amount is about 0.5 to 4 parts by weight per 1 part by weight of the coloring agent.

Specific examples of the adhesive used for the heat-sensitive recording layer include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and the like.
Gelatin, casein, gum arabic, polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, silicon polyvinyl alcohol, diacetone-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride Acid copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, urea resin, melamine resin, amide resin, urethane resin latex, acrylic resin latex, styrene / butadiene resin latex, etc. Is mentioned. The amount of the adhesive used is about 5 to 30% by weight based on the total solid content of the heat-sensitive recording layer.

Further, examples of the auxiliary agent contained in the coating solution for the heat-sensitive recording layer include kaolin, light (heavy) calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, amorphous silica, Pigments such as urea / formalin resin fillers, surfactants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin Lubricants such as wax and ester wax, the above-mentioned hydrazine-based compounds, glyoxal, boric acid, dialdehyde starch, methylol urea, epoxy-based compounds, water-resistant agents such as hydrazine-based compounds, defoamers, coloring dyes and fluorescent dyes Etc. The.

The method for forming the protective layer and the heat-sensitive recording layer is not particularly limited. For example, an appropriate method such as air knife coating, variver blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. After applying and drying the coating solution for the heat-sensitive recording layer on a support such as paper (acid paper, neutral paper), plastic film, synthetic paper, or non-woven fabric by the coating method, further apply the coating solution for the protective layer on the heat-sensitive recording layer. It is formed by a method such as coating and drying.

If necessary, a protective layer may be provided on the back side of the support of the thermosensitive recording medium, or a pigment or an organic hollow particle having an oil absorption of 70 ml / 100 g or more may be provided between the support and the thermosensitive recording layer. It is also possible to provide an undercoat layer as a component, or to apply a smoothing process such as super calendaring after forming each layer. In addition, various known techniques in the field of thermosensitive recording medium production, such as providing an adhesive layer and a magnetic recording layer on the back side (front side) of the support of the thermosensitive recording medium, can be added as necessary. It is.

[0030]

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. In the examples, "parts" and "%" indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 Preparation of coating liquid for undercoat layer Calcined clay [oil absorption: 110 ml / 100 g] 100
Parts, 40% aqueous solution of sodium polyacrylate 1 part, solid concentration 48% styrene-butadiene latex 14
Of a 10% aqueous solution of 100 parts of water and 100 parts of water were mixed and stirred to obtain a coating solution for an undercoat layer.

Solution A Preparation A composition consisting of 40 parts of 3-di- (n-butyl) amino-6-methyl-7-anilinofluoran, 20 parts of a 5% aqueous solution of methylcellulose and 40 parts of water is subjected to average particle size milling using a sand mill. It was pulverized until the diameter became 1.0 μm.

Solution B Preparation A composition comprising 40 parts of 4-hydroxy-4′-isopropoxydiphenylsulfone, 20 parts of a 5% aqueous solution of methylcellulose and 40 parts of water was pulverized by a sand mill until the average particle diameter became 1.0 μm. .

Solution C Preparation A composition comprising 40 parts of 1,2-di (3-methylphenoxy) ethane, 20 parts of a 5% aqueous solution of methylcellulose and 40 parts of water is pulverized by a sand mill until the average particle diameter becomes 1.0 μm. did.

Preparation of Coating Solution for Thermosensitive Recording Layer 25 parts of solution A, 75 parts of solution B, 50 parts of solution C, 100 parts of 10% aqueous solution of carboxy-modified polyvinyl alcohol, 25% aqueous solution of polyamidoamine / epichlorohydrin resin 1
0 parts, 20 parts of a styrene / butadiene latex having a solid concentration of 50%, 15 parts of light calcium carbonate, and 10 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: 300 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol [trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.], kaolin [trade name: UW-9]
0, manufactured by EC Corporation], a 50% aqueous dispersion of zinc stearate having an average particle diameter of 0.5 μm, and 110 parts of a 50% aqueous dispersion 10
Part, colloidal silica [trade name: Snowtex N, solid concentration 20%, manufactured by Nissan Chemical Co., Ltd.] 50 parts, graft copolymer of a polymer containing an ethylenically unsaturated carboxylic acid and silicone [trade name: Cymac US450] 10% aqueous solution and 50 parts of water were mixed and stirred to obtain a coating liquid for a protective layer.

Preparation of heat-sensitive recording medium ^On a high-quality paper (neutral paper) of 90 g / m ² , the coating amount of the undercoat layer coating liquid, the heat-sensitive layer coating liquid and the protective layer coating liquid was 8 g / m 2 after drying. ^{2, 6g / m 2, 3g} / m 2 and so as coated dried undercoat layer to obtain a heat-sensitive recording material was sequentially formed thermosensitive recording layer and the protective layer. After the formation of each layer, the surface was smoothed by a super calender.

Example 2 In the preparation of the protective layer coating solution of Example 1, 110 parts of a 50% aqueous dispersion of kaolin (trade name: UW-90, manufactured by EC Company) was added to 80 parts, and colloidal silica [trade name: Snowtex N, solid concentration 20%, manufactured by Nissan Chemical Co.]
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the composition was changed to parts.

Example 3 In the preparation of the coating solution for the protective layer in Example 1, 110 parts of a 50% aqueous dispersion of kaolin (trade name: UW-90, manufactured by EC Company) was added to 124 parts of colloidal silica [trade name: Snowtex N, solid concentration 20%, manufactured by Nissan Chemical Co.]
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the composition was changed to parts.

Example 4 In the preparation of the protective layer coating liquid of Example 1, 110 parts of a 50% aqueous dispersion of kaolin (trade name: UW-90, manufactured by EC Company) was added to 60 parts of colloidal silica [trade name: Snowtex N, solid concentration 20%, manufactured by Nissan Chemical Co.]
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the composition was changed to parts.

Example 5 In the preparation of the coating solution for the protective layer in Example 1, 300 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol was added to 7 parts.
00 kaolin [Kaolin [Product name: UW-90, EC]
Thermo-recording medium was obtained in the same manner as in Example 1 except that 110 parts of the 50% aqueous dispersion (produced by Sharp Corporation) was changed to 30 parts.

Example 6 In the preparation of the coating solution for the protective layer of Example 1, 300 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol was added to 3 parts.
Thermosensitive recording medium was prepared in the same manner as in Example 1 except that the amount was changed to 30 parts, and 10 parts of a 30% aqueous solution of a graft copolymer of a polymer containing an ethylenically unsaturated carboxylic acid and silicone was changed to 1 part. I got

Example 7 In the preparation of the coating solution for the protective layer in Example 1, 300 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol was added to 2 parts.
The heat-sensitive recording material was the same as in Example 1 except that the amount was changed to 10 parts, and 10 parts of a 30% aqueous solution of a graft copolymer of a polymer containing an ethylenically unsaturated carboxylic acid and silicone was changed to 40 parts. I got

Example 8 In the preparation of the protective layer coating solution of Example 1, 50
5 parts of aluminum hydroxide (trade name: Heidilite H42, manufactured by Showa Light Metal Industry Co., Ltd.)
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that a 0% aqueous dispersion was used.

COMPARATIVE EXAMPLE 1 In the preparation of the coating solution for the protective layer in Example 1, instead of 10 parts of a 30% aqueous solution of a graft copolymer of a polymer containing an ethylenically unsaturated carboxylic acid and silicone, silicon-modified polyvinyl alcohol was used. Example 1 except that 30 parts of a 10% aqueous solution of alcohol (trade name: R1130, manufactured by Kuraray Co., Ltd.) was used.
In the same manner as in the above, a thermosensitive recording medium was obtained.

Comparative Example 2 In the preparation of the coating solution for the protective layer in Example 1, kaolin [trade name: UW-] was used instead of 50 parts of colloidal silica (trade name: Snowtex N, solid concentration: 20%, manufactured by Nissan Chemical Industries, Ltd.).
90, manufactured by EC Company], except that 20 parts of a 50% aqueous dispersion was used in the same manner as in Example 1 to obtain a thermosensitive recording medium.

Comparative Example 3 In the preparation of the coating solution for the protective layer of Example 1, light calcium carbonate [trade name: Brilliant] was used instead of 110 parts of a 50% aqueous dispersion of kaolin (trade name: UW-90, manufactured by EC Company). -15, manufactured by Shiraishi Calcium Co.] 50% aqueous dispersion 110
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that parts were used.

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

[Recording density] Thermal recording evaluation machine [Product name: T
H-PMD, manufactured by Okura Electric Co., Ltd.], and applied energy:
Each thermosensitive recording medium was recorded at 0.50 mJ / dot, and the optical density (recording density) of the recording portion and the unrecorded portion were measured with a Macbeth densitometer (Model RD-914, manufactured by Macbeth) in visual mode.

[Plasticizer resistance] A wrap film (trade name: High Wrap KMA-W, manufactured by Mitsui Chemicals, Inc.) was triple wound on a polycarbonate pipe (40 mm diameter).
Place the thermosensitive recording medium after recording in the measurement of recording density on top of it, and further wrap a wrap film on it three times,
After standing at 40 ° C. for 24 hours, the optical density of the recording portion was measured with the above Macbeth densitometer to evaluate the plasticizer resistance.

[Offset Printing Density] (Adhesion) An ultraviolet-curable offset printing ink (black ink) was used on an offset rotary printing press provided with an ultraviolet irradiation device on the protective layer surface of the roll-shaped thermal recording medium. : Best cure
Vector HD Process, manufactured by Toka Pigment Co., Ltd.], and a pattern (5 mm square) was printed by patterning, and the density of the printed portion was measured by the Macbeth densitometer described above.

[Adhesion resistance to residue] Applied energy: 0.35 mJ / dot, printing speed 4 inc using a thermal recording printer (trade name: DT-310-2, manufactured by SATO)
Each thermosensitive recording medium was printed at 10 m at h / sec, and the adhesion of the residue to the thermal head was evaluated. A: There is no adhesion of residue on the thermal head. ：: Almost no residue adhered to the thermal head. : Slight adhesion of residue to thermal head. X: There is much residue adhesion to the thermal head.

[0053]

[Table 1]

[0054]

As shown in Table 1, the heat-sensitive recording material of the present invention is excellent in storage stability, printability, prevention of adhesion of debris to the heat-sensitive recording head, and excellent recording running property. It has excellent effects.

Claims (5)

[Claims] 1. A thermosensitive recording medium having a thermosensitive recording layer containing a leuco dye, a coloring agent and an adhesive, and a protective layer containing an adhesive and a pigment as main components in order on a support. The adhesive is a graft copolymer of a polymer containing an ethylenically unsaturated carboxylic acid and a silicone, and polyvinyl alcohol, and the pigment is at least one of kaolin and aluminum hydroxide, and amorphous silica. Thermosensitive recording medium. 2. The heat-sensitive device according to claim 1, wherein the total ratio of at least one of kaolin and aluminum hydroxide in the protective layer and amorphous silica is 30 to 70% by weight based on the total solid content of the protective layer. Record body. 3. The heat-sensitive recording material according to claim 1, wherein the amorphous silica is 5 to 30% by weight based on the total solid content of the protective layer. 4. The total ratio of a polyvinyl alcohol and a graft copolymer of a polymer containing an ethylenically unsaturated carboxylic acid and a silicone in a protective layer to a total solid content of the protective layer is 20 to 60. 4. The heat-sensitive recording medium according to claim 1, wherein the weight is% by weight. 5. The thermosensitive recording medium according to claim 1, wherein the graft copolymer is 0.5 to 10% by weight based on the total solid content of the protective layer.