JPH10278425A - Novel thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material having satisfactory color developability and preservability without skin fog by providing excellent adhesive properties of a print layer and protective layer made of ultraviolet curable resin. SOLUTION: In the thermal recording material comprising a thermal color developing layer provided on a support made of sheet, plastic sheet or synthetic sheet, and a print layer and/or protective layer formed on the thermal color developing layer made of ultraviolet curable resin via an intermediate layer, the intermediate layer contains styrene/acrylonitrile/(meth)acrylate ester copolymer or composite material of copolymer and colloidal silica.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat-sensitive recording material. More specifically, in a thermosensitive recording material in which a printing layer and / or a protective layer of an ultraviolet curable resin is provided on a thermosensitive coloring layer, the printing layer and the protecting layer are excellent in adhesion, have no background fog, and have colorability and storage. The present invention relates to a thermosensitive recording material having good properties.

[0002]

2. Description of the Related Art Heat-sensitive recording materials utilizing a colorless or pale-colored color-forming compound and a color-developing compound capable of forming the color-forming compound upon heating are disclosed in JP-B-43-4160 and JP-B-45-14.
No. 039, etc., and are widely used. Generally, a thermosensitive recording material is prepared by separately dispersing a developer such as a leuco dye and a phenolic substance into fine particles, and then mixing the two, and then adding additives such as a binder, a sensitizer, a filler, and a lubricant. Is added to form a coating liquid, coated on a support such as paper, film, synthetic paper, etc., and one or both of the leuco dye and the developer are melted by heating, and a color reaction record is formed by a chemical reaction caused by contact. The heat-sensitive recording material is usually prepared in the form of a sheet. A thermal printer with a built-in thermal head or the like is used for coloring the heat-sensitive recording sheet. This thermal recording method, compared to other recording methods,
Due to the features of (1) no noise during recording, (2) no need for development and fixing, (3) maintenance-free, and (4) relatively inexpensive machines, the facsimile field and computer It is widely used in the field of printers such as outputs and calculators, the field of recorders for medical measurements, the field of automatic ticket vending machines, and the field of thermosensitive recording labels.

In order to print on such a heat-sensitive recording sheet or to form a protective layer for imparting robustness, use of an ultraviolet curable resin is increasing. The main reason for using UV-curable resins is that they do not contain volatile solvents such as those found in conventional water-based or solvent-based paints or inks, and therefore do not require a large amount of heat for drying. .

[0004] However, ultraviolet curable resins have high shrinkage during curing and are hard, so that when a protective layer or print layer made of the same resin is formed on the thermosensitive coloring layer, they have poor adhesion. There is a disadvantage that it is easily peeled off by friction or adhesive tape.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the disadvantages of the prior art as described above. That is,
In a thermosensitive recording material in which a printing layer and / or a protective layer of an ultraviolet curable resin is provided on a thermosensitive coloring layer, the printing layer and the protecting layer have excellent adhesion, have no background fog, and have good coloring and preservability. It is to provide a heat-sensitive recording material.

[0006]

The present inventor has made various studies to solve the above-mentioned problems, and as a result, completed the present invention. That is, the present invention provides (1) a heat-sensitive color-forming layer comprising, as main components, a colorless or light-colored color-forming compound and a color-developing compound capable of causing the color-forming compound to develop color when heated on a support; In a thermosensitive recording material in which a print layer and / or a protective layer formed via an intermediate layer are made of an ultraviolet curable resin, the intermediate layer is a copolymer of styrene / acrylonitrile / (meth) acrylate or the polymer And a colloidal silica composite.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The copolymer of styrene / acrylonitrile / (meth) acrylate used for the intermediate layer in the present invention uses styrene, acrylonitrile and (meth) acrylate as monomer components. Specific examples of the (meth) acrylate include methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and acrylic acid. Hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, -tert-butyl methacrylate, and the like, and styrene / acrylonitrile / (meth) Component ratio of the acrylic acid ester,
Of the whole, acrylonitrile is 1 to 20% by weight, preferably 1 to 10% by weight, and styrene: (meth) acrylic acid ester may be in any ratio, but is preferably 1: 1 by weight.

The composite of the copolymer and colloidal silica can be obtained, for example, by the same method as described in Japanese Patent Publication No. 1-196389. In the case of the present invention, the ratio of the colloidal silica in the composite is It is 70% by weight, preferably 30% by weight or less. In the present invention, the amount of the copolymer or composite contained in the intermediate layer is 40 to 100% by weight.
It is. The intermediate layer may contain, in addition to the copolymer or the composite, other components as described below in a range of 60% by weight or less.

In the intermediate layer of the present invention, a binder, a filler and other various additives used for preparing the thermosensitive coloring layer of the present invention described below can be used in combination, if necessary.

The heat-sensitive coloring layer of the present invention contains a coloring compound, a coloring compound, a binder and, if necessary, a filler, a heat-fusible compound, a surfactant and the like.

Examples of the color-forming compound used in the heat-sensitive coloring layer are not particularly limited as long as they are generally used for pressure-sensitive recording paper or heat-sensitive recording paper, and include, for example, fluoran compounds, triarylmethane compounds, and spirochromic compounds. Compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds and the like.

Among these, fluoran compounds include, for example, 3-diethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl- N-cyclohexylamino) -6-methyl-7-anilinofluoran, 3
-(N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluoran, 3-isobutylethylamino-6-methyl-7-anilinofluoran, 3- [N
-Ethyl-N- (3-ethoxypropyl) amino] -6
-Methyl-7-anilinofluoran, 3- (N-ethyl-N-hexylamino) -6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluoran, 3-
(N-ethyl-N-tetrahydrofurylamino) -6
Methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (p-chloroanilino) fluoran, 3-diethylamino-6-methyl-7- (p-fluoroanilino) fluoran, 3- (p- Toluidinoethylamino) -6-methyl-7-anilinofluoran, 3
-Diethylamino-6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamino-7-
(O-chloroanilino) fluoran, 3-diethylamino-7- (o-fluoroanilino) fluoran, 3-dibutylamino-7- (o-fluoroanilino) fluoran, 3-diethylamino-7- (3,4-dichloro Anilino) fluorane, 3-pyrrolidino-6-methyl-7-
Anilinofluoran, 3-diethylamino-6-chloro-7-ethoxyethylaminofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino- 6-chloro-7-methylfluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-phenylfluoran, 3- (p-toluidinoethyl Amino) -6-methyl-7-phenethylfluoran and the like.

The triarylmethane compounds include:
For example, 3,3-bis (p-dimethylaminophenyl)-
6-dimethylaminophthalide (alias: crystal violet lactone or CVL), 3,3-bis (p-dimethylaminophenyl) phthalide 3- (p-dimethylaminophenyl) -3- (1,2-dimethylaminoindole- 3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3-
(2-phenylindol-3-yl) phthalide, 3,
3-bis (1,2-dimethylindol-3-yl)-
5-dimethylaminophthalide, 3,3-bis (1,2-
Dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazole-3)
-Yl) -5-dimethylaminophthalide, 3,3- (2
-Phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-
(1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like.

Further, as a spiro compound, for example, 3-
Methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3′-dichlorospirodinaphthopyran,
3-benzylspirodinaphthopyran, 3-propylspirobenzopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 1,3,3-trimethyl-6-nitro-8'-methoxyspiro (indoline-2,2 '-
Benzopyran) and the like, as diphenylmethane compounds, for example, N-halophenyl-leuco auramine,
4-bis-dimethylaminophenylbenzhydrylbenzyl ether, N-2,4,5-trichlorophenylleucouramine and the like; thiazine compounds such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue; Examples of the fluorene-based compound include rhodamine B anilinolactam and rhodamine B-p-chloroanilinolactam, and examples of the fluorene-based compound include 3,6-bis (dimethylamino) fluorenespiro (9,3 ′)-6. '-Dimethylaminophthalide, 3,6-bis (dimethylamino) fluorenespiro (9,3')-6'-pyrrolidinophthalide,
3-dimethylamino-6-diethylaminofluorenespiro (9,3 ')-6'-pyrrolidinophthalide and the like. These color forming compounds are used alone or in combination.

In providing the heat-sensitive coloring layer in the present invention, the color-developing compound used can be used without any particular limitation as long as it is generally used in pressure-sensitive recording paper or heat-sensitive recording paper. Specific examples of the color-developing compound include, for example, α-naphthol, β-naphthol, p-octylphenol, 4-t-octylphenol, p-t
-Butylphenol, p-phenylphenol, 1,1
-Bis (p-hydroxyphenyl) propane, 2,2-
Bis (p-hydroxyphenyl) propane (alias: bisphenol A or BPA), 2,2-bis (p-hydroxyphenyl) butane, 1,1-bis (p-hydroxyphenyl) cyclohexane, 4,4′-thiobisphenol 4,4′-cyclohexylidenediphenol,
2,2 ′-(2,5-dibromo-4-hydroxyphenyl) propane, 4,4-isopropylidenebis (2-t
-Butylphenol), 2,2'-methylenebis (4-
Chloroenol), 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 2,4-dihydroxyphenyl-p-tolylsulfone, 4-hydroxy -4'-methoxydiphenylsulfone, 4-hydroxy-4'-ethoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-butoxydiphenylsulfone, bis- (4-hydroxyphenyl) Methyl acetate, butyl bis- (4-hydroxyphenyl) acetate, benzyl bis- (4-hydroxyphenyl) acetate, 2,4
Phenolic compounds such as -dihydroxy-2'-methoxybenzanilide, benzyl p-hydroxybenzoate,
ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, 5-
Examples thereof include aromatic carboxylic acid derivatives such as ethyl hydroxyisophthalate, 3,5-di-t-butylsalicylic acid, and 3,5-di-α-methylbenzylsalicylic acid, aromatic carboxylic acids and metal salts thereof.

In the present invention, specific examples of the binder that can be used for forming the thermosensitive coloring layer include methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, cellulose, polyvinyl alcohol (PVA), and carboxyl group-modified polyvinyl. Alcohol, sulfonic acid group-modified polyvinyl alcohol, silyl group-modified polyvinyl alcohol, polyvinylpyrrolidone,
Polyacrylamide, polyacrylic acid, starch and derivatives thereof, casein, gelatin, water-soluble isoprene rubber, styrene / maleic anhydride copolymer alkali salt,
Water-soluble ones such as alkali salts of iso (or diiso) butylene / maleic anhydride copolymer, styrene / butadiene (SB) copolymer, carboxylated styrene / butadiene (SB) copolymer, styrene / butadiene / Acrylic acid copolymer, polyvinyl acetate, polyvinyl chloride,
Vinyl chloride / vinyl acetate copolymer, polystyrene, acrylic resin, acrylic / styrene resin, polyacrylate, polyester, polycarbonate, polyurethane, polybutyral, epoxy resin, furan resin, vinyltoluene resin, rosin ester resin, colloidal silica Examples include hydrophobic polymer compounds such as composite particles of an acrylic copolymer or emulsions thereof.

Specific examples of the filler which can be used in the same manner include:
For example, calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay,
Alumina, magnesium hydroxide, aluminum hydroxide,
Aluminum oxide, barium sulfate, polystyrene resin,
Urea-formalin resin and the like.

Specific examples of the heat-fusible compound that can be used include waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, acetylated aromatic amines, naphthalene derivatives, and aromatic compounds. Aromatic ethers, aromatic carboxylic acid derivatives, aromatic sulfonic acid ester derivatives, carbonic acid or oxalic acid diester derivatives, biphenyl derivatives, terphenyl derivatives, etc.
Those which are solid at room temperature and have a melting point of about 70 ° C. or higher are mentioned.

The waxes include, for example, wood wax, carnauba wax, shellac, paraffin, montan wax, oxidized paraffin, polyethylene wax, polyethylene oxide, and the like, and the higher fatty acids include, for example, stearic acid and behenic acid. Examples of the fatty acid amide include, for example, stearic acid amide, oleic acid amide, N-methylstearic acid amide, erucic acid amide, methylolbehenic acid amide, methylolstearic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide, and the like. As the fatty acid anilide, for example, stearic acid anilide, linoleic acid anilide and the like, as the acetylated aromatic amine, for example, acetotoluidide and the like, and as the naphthalene derivative, for example, 1-benzyloxynaphthalene, - benzyloxy naphthalene, 1
-Hydroxynaphthoic acid phenyl ester and the like as aromatic ethers include, for example, 1,2-diphenoxyethane, 1,4-diphenoxyethane, 1,2-bis (3-
Methylphenoxy) ethane, 1,2-bis (4-methoxyphenoxy) ethane, 1,2-bis (3,4-dimethylphenyl) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1-phenoxy -2- (4-methoxyphenoxy) ethane and the like.

Examples of the aromatic carboxylic acid derivatives include benzyl p-hydroxybenzoate, benzyl p-benzyloxybenzoate, dibenzyl terephthalate, and the like. -Toluenesulfonic acid phenyl ester, phenylmesitylenesulfonate, 4-methylphenylmesitylenesulfonate and the like, and as carbonic acid or oxalic acid diester derivatives, for example, diphenyl carbonate, dibenzyl oxalate, di (4-methylbenzyl) oxalate Esters, di (4-chlorobenzyl) oxalate, etc., as biphenyl derivatives, for example, p-benzylbiphenyl, p-allyloxybiphenyl, etc., and as terphenyl derivatives, for example, m-terphenyl, etc., respectively. It is shown.

Further, various other lubricants, surfactants, defoamers, ultraviolet absorbers and the like are added as required.

In the present invention, the printing ink used for forming the printing layer contains, as a main component, an ultraviolet-curable resin used for forming the following protective layer, and may be a colored pigment or an extender, and other optional pigments. And a composition prepared from waxes and stabilizers. Examples of commercially available UV-curable inks include Daicure Ink (manufactured by Dainippon Ink and Chemicals, Inc.), Best Cure Ink (manufactured by T & K, TOKA), and UV REX Ink (manufactured by Dainippon Chemical Industries, Ltd.). And flash dry ink (manufactured by Toyo Ink Mfg. Co., Ltd.), and these inks are used for printing by a printing machine equipped with a usual ultraviolet curing device.

As the UV-curable resin used for the protective layer, a resin component such as a photopolymerizable monomer or a prepolymer is used, and a photopolymerization initiator is usually used in combination. Examples of the monomer include a bifunctional monomer composed of an alkyl ester of an ethylenically unsaturated carboxylic acid, a diester of an alkylene oxide addition polymer of a compound containing active hydrogen with mono (meth) acrylic acid, and N-vinylpyrrolidone. And amide group-containing monomers represented by vinyl lactams, and polyfunctional monomers comprising an ester of an alkylene oxide addition polymer of a compound having active hydrogen and (meth) acrylic acid. Examples of the prepolymer include aliphatic, alicyclic and aromatic-substituted aliphatic compounds of 2 to 6
And poly (meth) acrylates such as monovalent polyhydric alcohols. Examples of such poly (meth) acrylates include poly (meth) acrylate of polyalkylene glycol, poly (meth) acryloyloxyalkyl phosphate, polyester poly (meth) acrylate, epoxy (meth) acrylate, polyurethane Prepolymers such as poly (meth) acrylate, polyamide poly (meth) acrylate, polysiloxane poly (meth) acrylate, and vinyl- or diene-based low polymers having a meth (acryloyloxy group) in a side chain and / or a terminal are exemplified. Can be Examples of the photopolymerization initiator include benzophenone, 2-hydroxy-2-methyl-propiophenone,
2-hydroxy-cyclohexylphenyl ketone, 2,
Examples thereof include 2-diethylthioxanthone, which is used in a ratio of 0.5 to 10% by weight based on the prepolymer and the monomer. If necessary, the above-mentioned fillers, lubricants, surfactants and the like are used in combination. The thickness of the protective layer is preferably 1 to 6 g / m ² in solid weight.

Using the above materials, the heat-sensitive recording material of the present invention is prepared, for example, by the following method. That is, first, the color-forming compound and the color-developing compound are separately pulverized and dispersed in a dispersing machine such as a ball mill, an attritor, and a sand mill together with a binder, a solvent or other additives as necessary, according to a conventional method. (When water is used for pulverization and dispersion, water is usually used as a medium.) The mixture is mixed to prepare a thermosensitive coloring layer coating solution, and is usually placed on a support such as paper, a plastic sheet, or a synthetic paper by a dry weight. It is applied by a bar coater, a blade coater or the like so that the concentration becomes ¹ to 20 g / m ² (the ratio of the color-forming compound to the color-developing compound is usually 1: 1 to 1:10 in terms of weight-drying ratio), and dried. A thermosensitive coloring layer is formed.

Next, a copolymer of styrene / acrylonitrile / (meth) acrylate or a composite of the copolymer and colloidal silica may be used alone or, if necessary, with a binder, a filler and other additives. Used together to form an intermediate layer forming coating liquid, and the solid content weight is 0.5 to 5 g on the thermosensitive coloring layer.
/ M ² and dried to form an intermediate layer.

Next, an ultraviolet-curable printing ink and / or a protective layer is printed on the intermediate layer provided on the thermosensitive coloring layer by using a screen printing machine, an offset printing machine, a gravure printing machine, or the like. Apply and irradiate UV light to cure the printing ink and / or protective layer,
The heat-sensitive recording material of the present invention is obtained. UV irradiation is, for example, 80
Under a high-pressure mercury lamp of W, a line speed of 5 cm at a distance of 10 cm
A method of passing several times under the condition of 20 m / min is adopted.
Incidentally, the thickness of the thermosensitive coloring layer is optionally selected as desired. Styrene / acrylonitrile /
The heat-sensitive recording material of the present invention provided with a printing layer and / or a protective layer of an ultraviolet curable resin via an intermediate layer containing a copolymer of a (meth) acrylate or a composite of the copolymer and colloidal silica. Has excellent adhesion between the printing layer and the protective layer, and between these layers and the intermediate layer or the heat-sensitive coloring layer, and at the same time, has no background fog, and has good coloring properties and storage stability.

[0027]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
In the examples, "parts" indicates parts by weight.

Example 1 (Formation of thermosensitive coloring layer) A mixture having the following composition was pulverized and dispersed using a sand grinder so that the average particle size became 2 μm or less, and [A] solution, [B] solution, Is prepared. [A] solution: 3-diethylamino-7- (o-fluoroanilino) fluoran 40 parts toluene 60 parts [B] solution: bis (3-allyl-4-hydroxyphenyl) sulfone 40 parts toluene 60 parts

Next, the respective preparations were mixed at the following ratio to prepare a coating solution for the thermosensitive coloring layer, and a white polyester film (trade name: Lumirror E24, thickness = 188 μm, Co., Ltd.)
It is applied to a dry weight of 6 g / m ² and dried to form a thermosensitive coloring layer. [A] solution 12.5 parts [B] solution 37.5 parts 20% methyl methacrylate / styrene copolymer (molecular weight = 100,000) toluene solution 40 parts

(Formation of Intermediate Layer) Next, a 45% styrene / acrylonitrile / 2-ethylhexyl acrylate copolymer (monomer weight ratio = 47.%) was used as a coating solution for the intermediate layer.
5: 5: 47.5) is applied on the thermosensitive coloring layer so that the weight at the time of drying becomes ² g / m ^2, and dried to form an intermediate layer.

(Formation of Protective Layer) Next, an ultraviolet curing ink (trade name: Kayarad DPHA, manufactured by Nippon Kayaku Co., Ltd. (97 parts), trade name: Irgacure 18) is formed on the intermediate layer.
4, made of Ciba-Geigy (3 parts)), applied at ² g / m ² , cured with an ultraviolet irradiation device manufactured by Nippon Battery (10 cm under a 80 W high-pressure mercury lamp, 3 passes at a line speed of 20 m / min.) The thermosensitive recording material of the invention is obtained.

Example 2 Example 1 was repeated using an emulsion of a copolymer having a monomer weight ratio of styrene: acrylonitrile: 2-ethylhexyl acrylate = 45: 10: 45 instead of the intermediate layer coating solution of Example 1. Similarly, the heat-sensitive recording material of the present invention is obtained.

Example 3 In place of the intermediate layer coating solution of Example 1, an emulsion of 45% styrene / acrylonitrile / ethyl acrylate copolymer (monomer weight ratio = 47.5: 5: 47.5) was used. The heat-sensitive recording material of the present invention is obtained in the same manner as in Example 1.

Example 4 In the same manner as in Example 1 except that an emulsion of 45% styrene / acrylonitrile / butyl acrylate copolymer (monomer ratio = 45: 10: 45) was used instead of the intermediate layer coating solution of Example 1. To obtain the heat-sensitive recording material of the present invention.

Example 5 A 45% styrene / acrylonitrile / methyl methacrylate / butyl acrylate copolymer (monomer ratio = 45: 10: 10: 3) was used in place of the intermediate layer coating solution of Example 1.
The heat-sensitive recording material of the present invention is obtained in the same manner as in Example 1 using the emulsion 5).

Example 6 (Formation of a thermosensitive coloring layer) A mixture having the following composition was pulverized and dispersed using a sand grinder so that the average particle diameter became 2 μm or less. Prepare. [C] Liquid: 3-dibutylamino-6-methyl-7-anilinofluoran 25 parts 25% PVA aqueous solution 20 parts Water 55 parts [D] Liquid: bisphenol A 25 parts 25% PVA aqueous solution 20 parts Water 55 parts

Next, each of the prepared solutions was mixed at the following ratio to prepare a coating solution for the thermosensitive coloring layer, and applied onto the white polyester film so that the weight when dried was 7 g / m ² .
Dry to form a thermosensitive coloring layer. [C] solution 16 parts [D] solution 32 parts 50% carboxylated SB copolymer latex 20 parts 20% methylol stearic acid amide aqueous dispersion 45 parts

(Formation of Intermediate Layer) Next, a 45% styrene / acrylonitrile / 2 of Example 1 was used as a coating solution for the intermediate layer.
- applying an emulsion of ethylhexyl acrylate copolymer as the weight when dry in the thermosensitive color developing layer is 2 g / m ^2, to form an intermediate layer and dried.

(Formation of Printing Layer) Next, an ultraviolet-curable ink (trade name: Best Cure No. 2U) was formed on the intermediate layer.
V thermal 118 red GX, manufactured by T & K, TOKA)
Is printed using an offset printing machine (manufactured by Hamada Printing Machines, Hamada 611XL) so that the thickness of the ink layer becomes 0.5 μm, and then cured by the ultraviolet irradiation device to obtain a printing layer.

(Formation of Protective Layer) Next, an ultraviolet curable ink (trade name: Kayarad DPHA, manufactured by Nippon Kayaku Co., Ltd. (97 parts), trade name: Irgacure 18) is formed on the printing layer.
4, Ciba-Geigy (3 parts)) and toluene were mixed at a weight ratio of 1: 1 to prepare a coating solution for the protective layer. The coating solution was dried so as to have a weight of 2 g / m ² and dried. Immediately, Nippon Battery's UV irradiation device (10 W
(3 passes at a line speed of 20 m / min.) to obtain the heat-sensitive recording material of the present invention.

Example 7 A composite of 45% styrene / acrylonitrile / 2-ethylhexyl acrylate copolymer and colloidal silica (monomer weight ratio = 4) was used in place of the intermediate layer coating solution of Example 6.
7.5: 5: 47.5, weight ratio of copolymer: colloidal silica = 80: 20) The heat-sensitive recording material of the present invention is obtained in the same manner as in Example 6 using the emulsion.

Comparative Example 1 A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that a 45% aqueous solution of PVA was used instead of the 45% styrene / acrylonitrile / 2-ethylhexyl acrylate copolymer emulsion of Example 1. .

Comparative Example 2 A heat-sensitive recording material for comparison was prepared in the same manner as in Example 6 except that the 45% styrene / acrylonitrile / 2-ethylhexyl acrylate copolymer emulsion (intermediate layer coating solution) of Example 6 was used. Get. Table 1 shows the quality performance of the present invention and the comparative thermosensitive recording material obtained as described above.

[0044]

Table 1 Quality Performance Test Table Background 1) Color density 2) Adhesion 3) Water resistance 4) Plasticizer resistance 5) Example 1 0.07 1.55 ○ 1.54 Example 20 0.07 1.55 ○ ○ 1.55 Example 3 0.07 1.57 ○ ○ 1.57 Example 4 0.07 1.56 ○ ○ 1.55 Example 5 0.07 1.57 ○ ○ 1 .56 Example 6 0.05 1.86 ○ 1.88 Example 7 0.05 1.85 ○ 1.86 Comparative Example 1 0.07 1.60 Δ × 1.12 Comparative Example 20 34 1.89 ○ ○ 0.45

1) Background The density of an uncolored recording surface is measured using a Macbeth reflection densitometer (RD-91).
Measured according to 4). 2) Color density The density of the color area printed by a thermal printer (D-805P) manufactured by Ishida Co., Ltd. was measured by a Macbeth reflection densitometer. 3) Adhesion After pressing the adhesive tape against the recording surface, the adhesive tape is peeled off and the peeling state of the protective layer or the printed layer is observed. ○ --No peeling. Δ ---- There was slight peeling. × --- There was peeling. XX --- peeling is remarkable. 4) Water resistance After immersing the uncolored sample in tap water for 7 hours, rub the surface with a finger and observe peeling. ○--No peeling. △---There is little peeling. × --- There is peeling. XX --- peeling is remarkable. 5) Plasticizer resistance A sample colored with the above printer was superimposed on a commercially available plastic eraser, and was subjected to 48 g at room temperature under a load of 200 g / cm ^2.
The density of the colored surface after standing for a time was measured with a Macbeth reflection densitometer.

As is clear from the table, the heat-sensitive recording material of the present invention has better adhesion between the protective layer and the print layer, has no background fog, has better color developability and storability than the heat-sensitive recording material for comparison. is there.

[0047]

According to the present invention, there is provided a heat-sensitive recording material comprising a heat-sensitive coloring layer provided with a printing layer and / or a protective layer of an ultraviolet-curable resin, and a styrene / acrylonitrile / (meth) acrylate copolymer or a copolymer thereof. By providing an intermediate layer containing a composite with colloidal silica, a heat-sensitive recording material having excellent adhesion between a printing layer and a protective layer, between these layers and the intermediate layer or the printing layer, free from background fog, and having good color developability and storage stability. was gotten.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B41M 5/18 101D

Claims (1)

[Claims] 1. A heat-sensitive color-forming layer comprising a colorless or light-colored color-forming compound and a color-developing compound capable of coloring the color-forming compound upon heating as a main component is provided on a support, and an intermediate layer is interposed therebetween. In a heat-sensitive recording material in which the printing layer and / or the protective layer formed by UV-curable resin are formed, the intermediate layer is a copolymer of styrene / acrylonitrile / (meth) acrylate or a mixture of the polymer and colloidal silica. A heat-sensitive recording material comprising a composite.