JP2007203574A - Thermal recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal recording material with high-resolution recording characteristics. <P>SOLUTION: This thermal recording material, in which an undercoat layer and a thermal color-development layer are sequentially provided on a substrate, is characterized in that the substrate is paper which contains an inorganic filler by 10 mass% or more with respect to pulp; and a heat-insulating organic pigment is contained as a pigment for the undercoat layer by 20 mass% or more of the total amount of pigment. Otherwise, a protective layer, in which at least one kind of aluminum hydroxide, amorphous silica and colloidal silica, having a mean particle diameter of 3 μm or less, is contained as the pigment, is provided on the thermal color-development layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material excellent in recording high-definition characters or images.

  A heat-sensitive recording material is generally a material in which a support is provided with a heat-sensitive recording layer mainly composed of an electron-donating ordinary colorless to light-colored dye precursor and an electron-accepting developer, and is heated with a thermal head or the like. By doing so, the dye precursor and the developer react instantaneously to obtain a recorded image. A recording device for recording on such a heat-sensitive recording material is advantageous in that it is relatively inexpensive, compact, easy to maintain, and free from noise. It is used in a wide range of fields as a recording medium for facsimiles, printers, computer terminals, labels, ticket vending machines, and the like. In particular, when a thermal recording material is applied to uses such as tickets, voting tickets, securities, and receipt documents, it is necessary to input a large amount of information, and it is desired to have a higher definition print quality.

  In order to perform high-definition recording, it is important that the thermal head and the thermal recording material are sufficiently in close contact when performing thermal printing with a thermal head. In the past, techniques such as flattening the surface of a base paper as a support to improve adhesion (for example, see Patent Documents 1 and 2) have been used.

However, even if the surface of the base paper is flattened, the flatness of the base paper is lost during coating, and sufficient characteristics cannot be obtained, or a polyolefin resin film is required on the base paper.
JP 2005-052990 A Japanese Patent Laid-Open No. 2005-052991

  An object of the present invention is to provide a heat-sensitive recording material that has high-definition recording characteristics, can increase the amount of information, and can be widely applied to various applications.

  As a result of intensive studies, the present inventors have invented the information recording material of the present invention capable of solving the problems. That is, a heat-sensitive recording material in which an undercoat layer containing 20% by mass or more of a heat insulating organic pigment and a heat-sensitive color developing layer are sequentially provided on a base paper containing 10% by mass or more of an inorganic filler with respect to pulp. It is.

  Further, a protective layer containing at least one of aluminum hydroxide, amorphous silica, or colloidal silica having an average particle diameter of 3 μm or less as a pigment can be provided on the thermosensitive coloring layer.

  By providing an undercoat layer containing 20% by mass or more of a heat-insulating organic pigment with respect to the total pigment and a heat-sensitive color developing layer on a base paper containing 10% by mass or more of an inorganic filler with respect to the pulp, high-definition It was possible to have recording characteristics.

  The heat-sensitive recording material of the present invention is characterized in that an undercoat layer and a heat-sensitive color-developing layer that is colored by heat are sequentially provided on a base paper. Hereinafter, the content of the present invention will be described more specifically.

  In the present invention, a base paper containing 10% by mass or more, preferably 12 to 20% by mass, of an inorganic filler is used as a support with respect to the pulp. If the amount is less than 10% by mass, the cushioning property is low, so that the contact with the thermal head is insufficient, and high-definition printing quality cannot be obtained.

  In the present invention, as the pulp in the base paper, whether dry pulp or wet pulp is used, NBKP, LBKP, NBSP, LBSP, CGP, GP, waste paper pulp, various non-wood pulps, etc. may be used alone or in combination. I can do it.

  In the present invention, the filler in the base paper includes calcium carbonate, magnesium carbonate, kaolin, calcined kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, diatomaceous earth, aluminum silicate. Inorganic substances such as calcium silicate and magnesium silicate, and organic substances such as polystyrene resin particles and urea formalin resin particles can be used alone or in combination.

  In the present invention, sizing agents such as rosin, petroleum resin, alkyl ketene dimer, alkenyl succinic anhydride and stearic anhydride, polyacrylamide polymer, polyethyleneimine and derivatives thereof, polyamine, polyamide / polyamine And its derivatives, polyethylene oxide, starch, polyvinyl alcohol, cationic latex, cationic urea formalin resin, melamine formalin resin, polyamide resin and other organic compounds, as well as pH adjusters, pitch control agents, antifoaming agents, etc. It can be added as appropriate.

  In the present invention, a water-soluble binder such as starch and polyvinyl alcohol, a styrene / butadiene copolymer, a water-dispersible resin such as a styrene / acrylic acid ester copolymer, and a styrene / maleic anhydride copolymer are used as necessary for the base paper. These can be surface-sized with a size press or the like alone or in combination.

  In the present invention, in order to improve the smoothness of the base paper surface, an on-machine calendar, a super calendar, or the like may be applied as necessary.

  As the pigment constituting the undercoat layer of the heat-sensitive recording material of the present invention, polyamide resin, polyester resin, polycarbonate resin, polyether resin, polyolefin resin, polysulfone resin, polystyrene resin, polyvinyl chloride resin, polyvinylidene chloride resin, A heat insulating organic pigment such as ethylene-vinyl acetate copolymer resin, polymethyl methacrylate, ionomer resin, polyphenylene sulfide resin, styrene copolymer resin is used. If necessary, calcium carbonate, magnesium carbonate, kaolin, calcined kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, diatomaceous earth, aluminum silicate, calcium silicate, It can be used in combination with inorganic pigments such as magnesium silicate, colloidal silica, alumina, alumina hydrate, pseudoboehmite, aluminum hydroxide, magnesium hydroxide, lithopone, zeolite, and hydrohalosite. The mass ratio of the heat insulating organic pigment to the total pigment is 20% or more, preferably 30% by mass or more. If it is less than 20% by mass, the adhesion with the thermal head becomes insufficient, and high-definition printing quality cannot be obtained.

  Examples of the binder used in the undercoat layer of the present invention include starches, unmodified polyvinyl alcohol having a saponification degree of 95% or more, silanol-modified polyvinyl alcohol, epoxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and acrylamide. / Acrylonitrile modified polyvinyl alcohol, hydroxymethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, gelatin, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide, acrylamide / acrylate ester copolymer, acrylamide / acrylate ester / methacrylic acid ternary copolymer Polymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, styrene / maleic anhydride Water-soluble resins such as alkali salts of acid copolymers, alkali salts of ethylene / maleic anhydride copolymers, alkali salts of isobutylene / maleic anhydride copolymers, and styrene / butadiene copolymers, acrylonitrile / butadiene copolymers Polymer, methyl acrylate / butadiene copolymer, acrylonitrile / butadiene / styrene terpolymer, polyvinyl acetate, vinyl acetate / acrylate copolymer, ethylene / vinyl acetate copolymer, polyacrylate, Examples thereof include water dispersible resins such as styrene / acrylic acid ester copolymers and polyurethane.

The undercoat layer of the present invention has, for example, an undercoat layer coating solution prepared by mixing and stirring together water, a pigment, a binder, and, if necessary, an auxiliary agent on a support, and the coating amount after drying is 1 to 30 g / ^{m 2,} more preferably formed by coating and drying so that 3 to 20 g / ^{m 2} approximately. Examples of the auxiliary agent contained in the coating solution for the undercoat layer include known surfactants, colored dyes, fluorescent dyes, lubricants, ultraviolet absorbers and the like.

  The thermosensitive coloring layer of the present invention can be obtained by mixing each aqueous dispersion obtained by finely pulverizing each coloring component and a binder, and coating and drying on the undercoat layer. The layer structure of the thermosensitive coloring layer may be single or multilayer.

  In the present invention, the coloring component contained in the thermosensitive coloring layer is not particularly limited, and any combination capable of causing a color reaction with the energy applied by the thermal head can be used. For example, coloring systems such as a combination of a colorless or light-colored electron-donating dye precursor and an electron-accepting compound, a combination of an aromatic isocyanate compound and an imino compound are included.

The colorless or light-colored electron-donating dye precursor used in the present invention is not particularly limited as long as it is a known substance used for general pressure-sensitive recording paper, heat-sensitive recording paper and the like. Specific examples will be given below, but the invention is not limited thereto.
(1) Triarylmethane compounds 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- ( p-dimethylaminophenyl) -3- (1,2-dimethylindol-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-ethylcarbazol-3-yl ) -5-dimethylaminophthalide, 3,3-bis- (2-phenylindol-3-yl) -5-dimethylaminotalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrole-2) -Yl) -6-dimethyl-aminophthalide and the like.

(2) Diphenylmethane compounds 4,4′-bisdimethylaminobenzhydrin benzyl ether, N-halophenyl leucooramine, N-2,4,5-trichlorophenyl leucooramine and the like.

(3) Xanthene compounds Rhodamine B-anilinolactam, rhodamine Bp-nitroanilinolactam, rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7 -Octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino-7- (3,4-dichloro) anilinofluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino -7- (4-nitroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (3-trifluoromethylanilino) fluorane, 3-piperidino-6-methyl- 7-anilinofluorane, 3- (N-methyl-N- Propyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-4-) Tolyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-4-tolyl) amino-6-methyl-7-phenethylfluorane, 3-dibutylamino-6-methyl- 7-anilinofluorane, 3-dibutylamino-7- (2-chloroanilino) fluorane, 3-dipentylamino-6-methyl-7-anilinofluorane and the like.

(4) Thiazine compounds benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, and the like.

(5) Spiro compounds 3-methyl-spiro-dinaphthopyrans, 3-ethyl-spiro-dinaphthopyrans, 3,3'-dichloro-spiro-dinaphthopyrans, 3-benzylspiro-dinaphthopyrans, 3-methylnaphtho- (3-methoxy-benzo ) -Spiropyran, 3-propyl-spiro-dibenzopyran and the like.
Or said various mixtures can be mentioned. These are determined by the application and desired properties.

  Examples of the electron-accepting compound include clay substances, phenol derivatives, aromatic carboxylic acid derivatives, urea derivatives such as N, N′-diallylthiourea derivatives, N-sulfonylurea, and metal salts thereof. Specifically, clay materials such as activated clay, zeolite, bentonite, 4-phenylphenol, 4-t-butylphenol, 4-hydroxyacetophenone, 2,2′-dihydroxydiphenyl, 2,2′-methylenebis (4-methyl) -6-tert-butylphenol), 4,4'-ethylenebis (2-methylphenol), 1,1-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) pentane, 1-bis (4-hydroxyphenyl) hexane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) hexane, 2,2-bis (4-hydroxyphenyl) -2-ethylhexane, 2,2-bis (3-chloro-4 Hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) -1-phenylpropane, 4,4′-hydroxydiphenyl ether, 4,4′-cyclohexylidenebis (2-isopropylphenol), 4,4 ′ -Dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 4-hydroxy-4′-benzyloxydiphenylsulfone, 4-hydroxy-4′-benzenesulfonyloxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (3-chloro-4-hydroxyphenyl) sulfone 2,4-di Phenylsulfonyl) phenol, bis (3-chloro-4-hydroxyphenyl) sulfide, 4,4′-thiobis (2-tert-butyl-5-methylphenol), 2,2′-bis (4-hydroxyphenylthio) Diethyl ether, 1,7-di (4-hydroxyphenylthio) -3,5-dioxaheptane, dimethyl 4-hydroxyphthalate, 2,2-bis (4-hydroxyphenyl) acetic acid esters, gallic acid alkyl esters Phenolic compounds such as salicylanilide, 5-chlorosalicylanilide, novolac-type phenolic resin, modified terpenephenolic resin, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, 4-hydroxy Benzyl benzoate, chloro 4-hydroxybenzoate Hydroxybenzoic acid esters such as benzyl, benzoic acid, salicylic acid, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 5-cyclohexylsalicylic acid, 3,5- Di-t-butylsalicylic acid, 3,5-di-t-nonylsalicylic acid, 3,5-didodecylsalicylic acid, 3-methyl-5-t-dodecylsalicylic acid, 3,5-bis (α, α-dimethylbenzyl) Known organic acids such as salicylic acid, 3-methyl-5- (α-methylbenzyl) salicylic acid, tartaric acid, oxalic acid, boric acid, citric acid, and atearic acid, or metal salts thereof such as zinc, nickel, aluminum, calcium, etc. The electron-accepting compound according to the present invention is not limited to these substances. Without also be used alone or as a mixture of two or more thereof, if desired.

  The aromatic isocyanate compound is a colorless or light-colored aromatic isocyanate compound or heterocyclic isocyanate compound that is solid at room temperature, specifically 2,6-dichlorophenyl isocyanate, p-chlorophenyl isocyanate, 1 , 3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1,3-dimethylbenzene-4,6-diisocyanate, 1,4-dimethylbenzene-2,5-diisocyanate, 1-ethoxy Benzene-2,4-diisocyanate, 2,5-dimethoxybenzene-1,4-diisocyanate, 2,5-diethoxybenzene-1,4-diisocyanate, 2,5-dibutoxybenzene-1 , 4-diisocyanate, azobenzene-4,4′-diisocyanate, diphenyl ether-4,4 ′ Diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7-diisocyanate, 3,3′-dimethyl Biphenyl-4,4′-diisocyanate, 3,3′-dimethoxy-4,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate, diphenyldimethylmethane-4,4′-diisocyanate Benzophenone-3,3′-diisocyanate, fluorene-2,7-diisocyanate, anthraquinone-2,6-diisocyanate, 9-ethylcarbazole-3,6-diisocyanate, pyrene-3, 8-diisocyanate, naphthalene-1,3,7-triisocyanate, biphenyl-2,4,4′-triisocyanate, , 4 ′, 4 ″ -triisocyanate-2,5-dimethoxytriphenylamine, p-dimethylaminophenyl isocyanate, tris (4-phenylisocyanato) thiophosphate, and the like. Such aromatic isocyanate compounds are not limited to these, and may be used alone or in admixture of two or more as required.

  These aromatic isocyanate compounds may be used in the form of so-called block isocyanate, which is an addition compound with phenols, lactams, oximes and the like, if necessary, dimer of diisocyanate, For example, it may be used in the form of 1-methylbenzene-2,4-diisocyanate dimer and trimer isocyanurate, or used as a polyisocyanate added with various polyols. Is also possible.

  An imino compound is a colorless or light-colored compound that is solid at room temperature. Specifically, 3-imino-4,5,6,7-tetrachloroisoindoline-1-one, 1,3-diimino-4 , 5,6,7-tetrachloroisoindoline, 1,3-diiminoisoindoline, 1,3-diiminobenz (f) isoindoline, 1,3-diiminonaphtho (2,3-f) isoindoline, 1,3 -Diimino-5-nitroisoindoline, 1,3-diimino-5-phenylisoindoline, 1,3-diimino-5-methoxyisoindoline, 1,3-diimino-5-chloroisoindoline, 5-cyano-1 , 3-Diiminoisoindoline, 5-acetamido-1,3-diiminoisoindoline, 1,3-diimino-5- (1H-1,2,3-triazol-1-yl -Isoindoline, 5- (pt-butylphenoxy) -1,3-diiminoisoindoline, 5- (p-cumylphenoxy) -1,3-diiminoisoindoline, 5-isobutoxy-1,3 -Diiminoisoindoline, 1,3-diimino-4,7-dimethoxyisoindoline, 4,7-diethoxy-1,3-diiminoisoindoline, 4,5,6,7-tetrabromo-1,3-di Iminoisoindoline, 4,5,6,7-tetrafluoro-1,3-diiminoisoindoline, 4,5,7-trichloro-1,3-diimino-6-methylmercaptoisoindoline, 1-iminodiphenic acid imide 1- (cyano-p-nitrophenylmethylene) -3-iminoisoindoline, 1- (cyanobenzothiazolyl- (2 ′)-carbamoylmethylene)- -Iminoisoindoline, 1-[(cyanobenzimidazolyl-2 ') methylene] -3-iminoisoindoline, 1-[(cyanobenzimidazolyl-2')-methylene] -3-imino-4,5,6 7-tetrachloroisoindoline, 1-[(cyanobenzimidazolyl-2 ′)-methylene] -3-imino-5-methoxyisoindoline, 1-[(1′-phenyl-3′-methyl-5-oxo) -Pyrazolidene-4 ']-3-iminoisoindoline, 3-imino-1-sulfobenzoimide, 3-imino-1-sulfo-4,5,6,7-tetrachlorobenzoimide, 3-imino- 1-sulfo-4,5,7-trichloro-6-methylmercaptobenzoic acid imide, 3-imino-2-methyl-4,5,6,7-tetrachloroisoindoline-1-one Which materials including but imino compound according to the present invention is not limited to, also may be used alone or as a mixture of two or more thereof, if desired.

  The thermosensitive coloring layer can contain a thermofusible substance in order to improve its thermal response. In this case, those having a melting point of 60 ° C. to 180 ° C. are preferred, and those having a melting point of 80 ° C. to 140 ° C. are particularly preferred. Specifically, stearic acid amide, N-hydroxymethyl stearic acid amide, N-stearyl stearic acid amide, ethylene bis stearic acid amide, oleic acid amide, palmitic acid amide, methylene bis hydrogenated tallow fatty acid amide, ricinoleic acid amide, etc. Synthesis and natural waxes such as fatty acid amides, paraffin wax, microcrystalline wax, polyethylene wax, carnauba wax, aliphatic urea compounds such as N-stearyl urea, benzyl-2-naphthyl ether, α, α'-diphenoxyxylene Bis (4-methoxyphenyl) ether, 2,2′-bis (4-methoxyphenoxy) diethyl ether, 1,2-bis (3-methylphenoxy) ethane, naphthyl ether derivative, anthryl ether derivative, Ether compounds such as aliphatic ethers, diphenyl adipate, di (4-methylbenzyl) oxalate, dibenzyl oxalate, di (4-chlorobenzyl) ester, diphenyl carbonate, dimethyl terephthalate, dibenzyl terephthalate, phenyl benzenesulfonate Known compounds such as esters, ester compounds such as 4-acetylacetophenone, biphenyl derivatives such as m-terphenyl, 4-benzylbiphenyl, 4-allyloxybiphenyl, bis (4-allyloxyphenyl) sulfonacetoacetic acid anilides, fatty acid anilides, etc. These compounds can be used, and these compounds can be used alone or in combination. Moreover, in order to obtain sufficient thermal responsiveness, it is preferable that a thermofusible substance is 20-400 mass% with respect to a leuco dye in a thermosensitive coloring layer, and 50-200 mass% is especially preferable.

  Examples of the binder for the thermosensitive coloring layer include unmodified polyvinyl alcohol having a saponification degree of 95% or more, silanol-modified polyvinyl alcohol, epoxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acrylic acid amide / acrylonitrile-modified polyvinyl alcohol, Hydroxymethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, gelatin, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, polyacrylic acid Alkali salt, alkali salt of polymaleic acid, alkali of styrene / maleic anhydride copolymer Water-soluble resins such as alkali salts of ethylene / maleic anhydride copolymers, alkali salts of isobutylene / maleic anhydride copolymers, and styrene / butadiene copolymers, acrylonitrile / butadiene copolymers, methyl acrylate / butadiene Copolymer, acrylonitrile / butadiene / styrene terpolymer, polyvinyl acetate, vinyl acetate / acrylic acid ester copolymer, ethylene / vinyl acetate copolymer, polyacrylic acid ester, styrene / acrylic acid ester copolymer And water dispersible resins such as polyurethane, and these can be used alone or in combination.

  In addition, for the thermosensitive coloring layer, diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, Inorganic pigments such as barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate, colloidal silica, and organic pigments such as melamine resin filler, urea-formalin resin filler, polyethylene powder, and nylon powder can be used. .

  For heat-sensitive coloring layer, higher fatty acid metal salts such as zinc stearate and calcium stearate, higher fatty acid amides such as stearamide, paraffin, polyethylene wax, polyethylene oxide, caster wax and other lubricants, benzophenone, benzotriazole, etc. Surfactants including ultraviolet absorbers, anionic and nonionic high molecular weight substances, fluorescent dyes, antifoaming agents, and the like are added as necessary.

The coating amount of the thermosensitive coloring layer is usually 0.1 to 2.0 g / m ^{2 in} terms of the coating amount of the dye precursor. When it is less than 0.1 g / m ² , a sufficient recording density cannot be obtained, and even if it exceeds 2.0 g / m ² , no improvement in coloration thermal response is observed, which is economical. It is disadvantageous.

In the heat-sensitive recording material of the present invention, a protective layer can be formed on the heat-sensitive color developing layer in order to further improve the chemical resistance of the recording part or to improve the recording running property. Such a protective layer comprises a resin component as a main component, and after drying a protective layer coating solution prepared by adding an ultraviolet absorber and an auxiliary agent that can be added to the thermosensitive coloring layer on the thermosensitive coloring layer, if necessary. the coating amount of 0.2 to 10 g / ^{m 2,} is preferably formed by coating and drying so that 0.5 to 5 g / ^{m 2} approximately. The protective layer may have a single layer structure or a multilayer structure.

  The protective layer contains a pigment in order to improve the recording running property. The pigment contains at least one kind of aluminum hydroxide, amorphous silica, or colloidal silica, and if necessary, diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, Inorganic pigments such as zinc oxide, aluminum oxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous calcium silicate, organic pigments such as melamine resin filler, urea-formalin resin filler, polyethylene powder, nylon powder, etc. Can be used as a mixture. The average particle diameter of the pigment is preferably 3 μm or less. If it is larger than 3 μm, the smoothness of the surface of the heat-sensitive recording material is impaired, so that high-definition printing quality cannot be obtained.

  The binder for the protective layer is appropriately selected from conventionally known water-soluble resins or water-dispersible resins. For example, unmodified polyvinyl alcohol having a saponification degree of 95% or more, silanol-modified polyvinyl alcohol, epoxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acrylamide / acrylonitrile-modified polyvinyl alcohol, hydroxymethyl cellulose, methyl cellulose, ethyl cellulose, carboxy Methylcellulose, gelatin, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid , Alkali salt of styrene / maleic anhydride copolymer, ethylene / maleic anhydride copolymer Water-soluble resin such as alkali salt of isobutylene / maleic anhydride copolymer, and styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, acrylonitrile / butadiene / Water-dispersible resins such as styrene terpolymers, polyvinyl acetate, vinyl acetate / acrylic acid ester copolymers, ethylene / vinyl acetate copolymers, polyacrylic acid esters, styrene / acrylic acid ester copolymers, and polyurethanes These can be used singly or in combination.

  In addition, the protective layer can contain various hardeners, cross-linking agents, UV absorbers, and the like for imparting water resistance, if necessary.

  The method for applying the undercoat layer, heat-sensitive color developing layer, protective layer, and ink receiving layer of the present invention is not particularly limited. For example, an air knife coater, various blade coaters, various bar coaters, various curtain coaters, etc. Various printing methods such as an apparatus, a planographic plate, a relief plate, an intaglio plate, a flexo, a gravure, and a screen can be used.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In Examples,% and parts are all based on mass.

(1) Preparation of base paper 100 parts of LBKP (freeness: 300 ml, csf), 12 parts as a content of calcined kaolin, 0.3 part of alkyl ketene dimer (Harcon AS-236 manufactured by Japan PMC), positive starch (day) A base paper having a basis weight of 100 g / m ² was manufactured by a long net paper machine using a pulp slurry containing 0.7 part of Excel No. 4) manufactured by Starch Chemical Co., Ltd. In this paper machine, three stages of presses are installed in front of the dryer. After drying with a multi-cylinder dryer, the thickness was adjusted with a machine calendar so that the density was 0.70 g / cm ³ .

This base paper is sized with 5 parts of oxidized starch (MS-3800 manufactured by Nippon Shokuhin Kako Co., Ltd.), 0.2 parts of styrene / acrylic copolymer (Harsize KN-500 manufactured by Harima Kasei Co., Ltd.) and 94.8 parts of water. A press solution was prepared and subjected to size press treatment so that the solid adhesion amount was 1.2 g / m ^2, and a base paper used in the present invention was produced.

(2) Preparation of undercoat layer coated paper 333 parts of a heat insulating organic pigment dispersion (V1005 manufactured by Nippon Zeon Co., Ltd.) and 24 parts of a 50% styrene butadiene latex aqueous dispersion are mixed to form a coating solution concentration of 20% aqueous solution. The added water was added and the mixture was sufficiently stirred to prepare an undercoat layer coating solution. Subsequently, the paper produced in (1) was applied and dried so that the solid content application amount was 7 g / m ² , and an undercoat layer-coated paper was produced.

(3) Preparation of heat-sensitive color-developing layer-coated paper Dispersions A to D were prepared by the following method, and a heat-sensitive color-developing layer coating solution was prepared.

<Dispersion A>
200 g of 3-dibutylamino-6-methyl-7-anilinofluorane was dispersed in a mixture of 200 g of a 10% aqueous polyvinyl alcohol solution and 600 g of water, and pulverized with a bead mill until the average particle size became 1 μm.

<Dispersion B>
200 g of 2,4′-dihydroxydiphenylsulfone was dispersed in a mixture of 200 g of a 10% polyvinyl alcohol aqueous solution and 600 g of water, and pulverized with a bead mill until the average particle size became 0.7 μm.

<Dispersion C>
200 g of benzyl-2-naphthyl ether was dispersed in a mixture of 200 g of a 10% polyvinyl alcohol aqueous solution and 600 g of water, and pulverized with a bead mill until the average particle size became 0.7 μm.

<Dispersion D>
200 g of aluminum hydroxide was mixed with 800 g of a 0.5% sodium polyacrylate aqueous solution and dispersed with a homomixer for 10 minutes.

30 parts of Dispersion A, 70 parts of Dispersion B, 70 parts of Dispersion C, 40 parts of Dispersion D, and 100 parts of a 10% silanol-modified polyvinyl alcohol (Kuraray R1130) aqueous solution were mixed and stirred to prepare a coating solution for a thermosensitive coloring layer. Subsequently, after coating and drying on the undercoat layer-coated paper prepared in (2) so as to be 0.5 g / m ² in terms of the coating amount of the dye precursor, the Beck smoothness of the heat-sensitive surface becomes 200 to 300 seconds. The heat-sensitive recording material of Example 1 was produced by calendaring as described above.

  In Example 1, 167 parts of a 30% dispersion of an insulating organic pigment (V1005 made by Nippon Zeon Co., Ltd.), 50 parts of calcined kaolin, and 24 parts of a 50% styrene butadiene latex aqueous dispersion were mixed and applied as an undercoat layer coating liquid. A thermosensitive recording material of Example 2 was produced in the same manner as in Example 1 except that added water was added and the mixture was sufficiently stirred to adjust the liquid concentration to a 20% aqueous solution.

  In Example 1, the undercoat layer coating solution was mixed with 100 parts of a 30% dispersion of a heat-insulating organic pigment (V1005 manufactured by Nippon Zeon), 70 parts of calcined kaolin, and 24 parts of a 50% styrene butadiene latex aqueous dispersion. A heat-sensitive recording material of Example 3 was produced in the same manner as in Example 1 except that added water was added and the mixture was sufficiently stirred to adjust the liquid concentration to a 20% aqueous solution.

  In Example 1, the undercoat layer coating solution was mixed with 67 parts of a 30% dispersion of a heat insulating organic pigment (V1005 manufactured by Nippon Zeon Co., Ltd.), 80 parts of calcined kaolin, and 24 parts of a 50% styrene butadiene latex aqueous dispersion. A heat-sensitive recording material of Example 4 was produced in the same manner as in Example 1 except that added water was added and sufficiently stirred so that the liquid concentration became a 20% aqueous solution.

On the thermosensitive coloring layer of Example 1, dispersion D 40 parts, 10% silanol-modified polyvinyl alcohol (Kuraray R1130) aqueous solution 80 parts, 30% zinc stearate dispersion 10 parts, 10% chitosan aqueous solution 20 parts, 10% glyoxal After coating and drying a protective layer coating solution prepared by mixing and stirring 10 parts of an aqueous solution and 60 parts of water so that the solid content coating amount is 2 g / m ² , the Beck smoothness of the heat-sensitive surface is 1000 to 1000. The heat-sensitive recording material of Example 5 was produced by calendaring to 1500 seconds.

(Comparative Example 1)
In Example 1, a heat-sensitive recording material of Comparative Example 1 was produced in the same manner as in Example 1 except that the content of the calcined kaolin was changed to 8 parts by blending the base paper.

(Comparative Example 2)
In Example 1, except that the undercoat layer coating solution was adjusted by mixing 100 parts of calcined kaolin and 24 parts of 50% styrene butadiene latex aqueous dispersion and adding added water so that the coating solution concentration became 20% aqueous solution. Produced a heat-sensitive recording material of Comparative Example 2 in the same manner as in Example 1.

(1) Evaluation of thermal response Printing was performed using a facsimile testing machine TH-PMD manufactured by Okura Electric. A thermal head having a dot density of 8 dots / mm and a head resistance of 1510Ω was used, and an image was obtained by energizing with a head voltage of 21 V and a pulse width of 1.2 msec. The density of the image area and the density of the unprinted background area were measured with a Macbeth RD-918 type reflection densitometer (visual filter).

(2) Evaluation of heat-resistant background preservation stability The density of the background part when an unprinted heat-sensitive recording material was stored at 75 ° C. for 24 hours was measured with a Macbeth RD-918 reflection densitometer (visual filter). The lower the density of the background, the less the background fog and the better the heat-resistant background preservation.

(3) Evaluation of printing quality Using a barcode printer B-433 manufactured by Toshiba Tec Corporation, barcodes and characters were printed, and the printing quality was visually evaluated according to the following criteria.
○: The printed part is not missing.
Δ: There is a portion lacking in the print portion, but it is not noticeable.
X: The part lacking in the printing part is conspicuous.

Claims (2)

  In a heat-sensitive recording material in which an undercoat layer and a thermosensitive coloring layer are sequentially provided on a support, the support is a paper containing 10% by mass or more of an inorganic filler with respect to pulp, and heat insulation as a pigment of the undercoat layer A heat-sensitive recording material comprising an organic pigment in an amount of 20% by mass or more based on the total amount of the pigment.   2. The thermal recording according to claim 1, wherein a protective layer containing at least one of aluminum hydroxide, amorphous silica or colloidal silica having an average particle size of 3 μm or less as a pigment is provided on the thermosensitive coloring layer. material.