JP2011173309A - Thermosensitive recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensitive recording medium excelling in waterproof blocking characteristics especially to a polystyrene film base material. <P>SOLUTION: The thermosensitive recording medium includes a thermosensitive recording layer containing leuco dye, a coloring agent and an aqueous adhesive, on a support body, and a protective layer containing an aqueous adhesive, on the thermosensitive recording layer. The aqueous adhesive in the protective layer is at least one kind selected from acetoacetyl modified polyvinyl alcohol, diacetone modified polyvinyl alcohol and carboxy modified polyvinyl alcohol, and the protective layer contains at least one kind selected from glyoxylic acid sodium, di(glyoxylic acid calcium) and glyoxylic acid ammonium, and polyamideamine epichlorohydrin resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material that utilizes a color-forming reaction between an electron-donating compound and an electron-accepting compound and that can obtain a recorded image by a color-forming reaction by thermal energy.

  A heat-sensitive recording material in which a recorded image is obtained by bringing an electron-donating compound and an electron-accepting compound into contact with each other by thermal energy is well known. Such a heat-sensitive recording material is relatively inexpensive, has a compact recording device, and is easy to maintain, so it is used for recording media such as facsimiles and various computers.

  Recently, due to the development of a recording system, in addition to the recording suitability, the storage characteristics of the recorded image are required even under the severer conditions of use of the thermal recording medium.

Method of using acetoacetyl-modified PVA and water-soluble polyamide resin for protective layer (see Patent Document 1), water-based adhesive in protective layer is diacetone-modified PVA, and further contains polyamidoamine / epichlorohydrin resin in protective layer And a method in which the water-based adhesive in the heat-sensitive recording layer is diacetone-modified PVA, and further contains a polyamidoamine / epichlorohydrin resin and a carboxylic acid dihydrazide compound in the heat-sensitive recording layer (see Patent Document 2). A method of containing an acetoacetyl-modified resin and a polyamidoamine / epichlorohydrin resin, containing a polyvalent carboxylic acid hydrazide compound in the heat-sensitive recording layer (see Patent Document 3), diacetone acrylamide copolymer modification as a thermal paper coating agent Polyvinyl alcohol, water-soluble hydrazine compounds and A method using water-soluble organic amine or ammonia (see Patent Document 4), and a thermosensitive recording layer using diacetone-modified polyvinyl alcohol as an adhesive for the protective layer and containing a carboxylic acid dihydrazide compound as a crosslinking agent in the thermosensitive recording layer. A recording material (see Patent Document 5) and a heat-sensitive recording material (see Patent Document 6) containing glyoxylate and a glyoxylate derivative in acetoacetyl-modified PVA in the protective layer are described.
There are many uses for thermal recording media. For example, it is used for frozen foods that require exceptional water resistance, and is stored frozen with the thermal label attached, and then defrosted for sale. Is often attached to the surface of the recording medium, placed in close contact with the surrounding film substrate, and placed in close contact.
In such a state, when the surroundings are dried, a part of the protective layer and heat-sensitive recording layer components are melted, causing contact with the film substrate and blocking, and in the worst case, it is described on the label. Information cannot be read. This blocking property greatly depends on the type of substrate. In particular, when the film base material used is a polystyrene film base material, blocking is remarkably generated. Therefore, an improvement in water blocking resistance for the polystyrene film base material is desired.

JP 2002-019196 A JP 2002-127601 A JP 2002-301868 A Japanese Patent Laid-Open No. 10-087936 JP 11-314457 A WO2009 / 028646

  An object of the present invention is to provide a heat-sensitive recording material excellent in water-resistant blocking property particularly for a polystyrene film substrate.

  As a result of various studies on the above problems, the present inventor has provided a heat-sensitive recording layer containing a leuco dye, a colorant and a water-based adhesive on the support, and a protective layer containing a water-based adhesive on the heat-sensitive recording layer. In the heat-sensitive recording material, the protective layer further contains at least one kind selected from sodium glyoxylate, di (glyoxylic acid) calcium and ammonium glyoxylic acid, and a polyamidoamine / epichlorohydrin resin. The present inventors have found that the problem can be solved and have completed the present invention.

  That is, the present invention provides the following thermal recording material.

Item 1: A heat-sensitive recording layer having a heat-sensitive recording layer containing a leuco dye, a colorant and a water-based adhesive on a support, and further having a protective layer containing a water-based adhesive on the heat-sensitive recording layer. The aqueous adhesive is at least one selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and carboxy-modified polyvinyl alcohol, and further, sodium glyoxylate, di (glyoxylic acid) calcium, and ammonium glyoxylate in the protective layer. A heat-sensitive recording material comprising at least one selected from polyamidoamine and epichlorohydrin resin.
Item 2: The heat-sensitive recording material according to Item 1, comprising 1 to 20% by mass of amorphous silica as a pigment in the protective layer, based on the total pigment.
Item 3: The heat-sensitive recording material according to Item 1 or 2, wherein the support is a synthetic film.

  The heat-sensitive recording material of the present invention has an effect excellent in water blocking resistance against a polystyrene film substrate.

  The thermal recording material according to the present invention will be described in detail below. In the present invention, in the heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye, a colorant and a water-based adhesive on a support, and further a protective layer containing a water-based adhesive on the heat-sensitive recording layer, The aqueous adhesive in the layer is at least one selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol, and sodium glyoxylate, di (glyoxylic acid) calcium and glyoxylic acid in the protective layer It contains at least one selected from ammonium and a polyamidoamine / epichlorohydrin resin.

[Glyoxylate]
First, the glyoxylate contained in the protective layer of the present invention will be described.
Examples of the glyoxylate include various salts, including alkali metal and glyoxylic acid metal salts, alkaline earth metal and glyoxylic acid metal salts, amines and glyoxylic acid salts, and preferably It is at least one metal salt of glyoxylic acid selected from alkali metal and glyoxylic acid metal salts and alkaline earth metal and glyoxylic acid metal salts. As a metal salt of alkali metal and glyoxylic acid, for example, a metal salt of alkali metal such as sodium or potassium and glyoxylic acid, as a metal salt of alkaline earth metal and glyoxylic acid, as an alkaline earth metal such as magnesium or calcium, and glyoxylic acid Examples of metal salts and metal salts of amines and glyoxylic acid include salts of amines such as ammonia, monomethylamine, dimethylamine, and trimethylamine and glyoxylic acid.

  In particular, in the present invention, it is considered that the hydrophilicity of the carboxylate group introduced into the crosslinked structure is small compared to the carboxylic acid group, which contributes to the improvement of the water resistance of the crosslinked polymer. As the acid salt, a glyoxylate having a lower solubility in water is preferable. Specifically, the solubility in water at 23 ° C. is 0.01 to 100%, particularly 0.1 to 50%, and further 0.5. Those of ˜20% are preferably used. Specifically, examples of the glyoxylate having low water solubility include sodium glyoxylate (solubility: about 17%), calcium glyoxylate (solubility: about 0.7%), and ammonium glyoxylate (solubility: 14). %).

  As a method for producing glyoxylate, a known method can be used. For example, (1) a method based on a neutralization reaction of glyoxylic acid, (2) a salt of glyoxylic acid with an acid dissociation constant larger than glyoxylic acid, And (3) a method by alkaline hydrolysis of glyoxylic acid ester (see, for example, JP-A No. 2003-3000926). In particular, when the alkaline compound used for the neutralization reaction with glyoxylic acid is highly water-soluble, the method of (1) is a salt of an acid whose glyoxylate salt is low in water solubility and has an acid dissociation constant greater than glyoxylic acid. When the water solubility of is high, the method (2) is preferably used.

  The method (1) is usually carried out using water as a medium. Glyoxylic acid and an alkaline compound, for example, an alkali metal hydroxide or an alkaline earth metal hydroxide are reacted in water, and the precipitated glyoxylate salt is reacted with water. It can be produced by filtration and drying.

  The method (2) is also generally carried out in water, and glyoxylate can be obtained in the same manner as the method (1). Examples of the acid salt having a larger dissociation constant than glyoxylic acid used in the method (2) include alkali metal or alkaline earth metal salts of aliphatic carboxylic acids such as sodium acetate, calcium acetate, and calcium propionate. Can be mentioned.

  In particular, when glyoxylic acid is used as a raw material, there is a possibility that glyoxal, which is a by-product when producing the glyoxylate, may be contained in the crosslinking agent, and the content of such glyoxal is 0% by mass. Most preferably, it is 5% by mass or less, particularly 2% by mass or less, and further preferably 1% by mass or less. When the content of glyoxal is high, the stability of the aqueous solution mixed with acetoacetyl-modified polyvinyl alcohol is lowered, and the pot life is shortened. It may be colored with.

  The protective layer contains at least one kind selected from sodium glyoxylate, di (glyoxylic acid) calcium and ammonium glyoxylate as a crosslinking agent, but the total amount is the amount of aqueous adhesive used in the protective layer It is 0.5-20 mass% with respect to it, Preferably it is about 1-10 mass%.

  With respect to the ratio of at least one selected from sodium glyoxylate, di (glyoxylic acid) calcium and ammonium glyoxylic acid to the polyamidoamine / epichlorohydrin resin, the polyamidoamine / epichlorohydride is based on 100 parts by mass of the compound. The phosphorus resin is preferably 10 to 1000 parts by mass, more preferably 30 to 500 parts by mass.

  As the aqueous adhesive in the protective layer, at least one selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol is preferably used.

  The acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and carboxy-modified polyvinyl alcohol used in the protective layer were obtained by copolymerizing a monomer having an acetoacetyl group, a diacetone group, and a carboxyl group and a vinyl ester, respectively. It is produced by saponifying the resin.

  The degree of saponification is preferably from about 85 mol% to about 100 mol% of complete saponification, more preferably from about 90 to 100 mol%. The average degree of polymerization is preferably about 300 to 3000, and more preferably about 400 to 2000. The degree of modification is preferably about 0.5 to 10 mol%, more preferably about 1 to 9 mol%. The higher the degree of polymerization and the degree of saponification, the better the water resistance, but it is necessary to select from the paint concentration, viscosity, coating property or drying property according to the situation.

  If the degree of modification is in the range of about 0.5 to 10 mol%, sufficient water resistance is obtained, and the solubility in water does not decrease, so that the solution concentration can be prevented from being lowered.

  The amount of at least one selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol used in the protective layer is 10 to 90% by mass, preferably based on the total solid content of the protective layer, About 15-50 mass% is more preferable.

  As the water-based adhesive used for the protective layer, other adhesives can be used in combination as long as the effects of the present invention are not impaired. Examples of the adhesive include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, silicon-modified polyvinyl alcohol, starch, oxidized starch, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, diisobutylene and maleic anhydride. Copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, urea resin, melamine resin, amide resin, acrylic resin latex, urethane resin Examples include latex.

  Examples of the pigment used in the protective layer include inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, amorphous silica, aluminum hydroxide, barium sulfate, talc, kaolin, clay, and calcined kaolin, and nylon resin. Examples thereof include organic pigments such as fillers, urea / formalin resin fillers, and raw starch particles. Among these, amorphous silica is preferably used because the surface of the resulting heat-sensitive recording material is roughened and has an effect of being excellent in water blocking resistance, which is an effect of the present invention. Further, kaolin and aluminum hydroxide are preferably used because they have little decrease in barrier properties against chemicals such as plasticizers and oils, and the decrease in recording density is also small. The average particle size of the pigment used in the protective layer is preferably 0.5 to 8 μm, and more preferably 1 to 6 μm. In addition, about an average particle diameter, it is the numerical value represented by the median diameter by the laser diffraction type particle size measuring device SALD2200 (made by Shimadzu Corporation).

  Content of the said amorphous silica is 1-20 mass% with respect to the pigment in a protective layer, and is about 0.5-15 mass% with respect to the total solid of a protective layer. Moreover, kaolin and aluminum hydroxide are 60-99 mass% with respect to the pigment in a protective layer, and are about 20-80 mass% with respect to the total solid of a protective layer.

  Moreover, the stability of the coating liquid for protective layers is further improved by containing a water-soluble acidic compound in the protective layer. The water-soluble acidic compound added to the protective layer coating solution is not particularly limited, but boric acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, Water-soluble organic acids having a carboxyl group such as adipic acid, pimelic acid, fumaric acid, maleic acid, tartaric acid, citric acid, lactic acid, benzoic acid, phthalic acid, benzenetricarboxylic acid and the like are preferable.

  The addition amount of the water-soluble acidic compound is not particularly limited, but is preferably added so that the pH of the protective layer coating solution is 2 to 7, and more preferably 4 to 7. If pH is the range of 2-7, it will be suppressed that the viscosity of a coating liquid becomes high.

  Examples of auxiliary agents that can be added to the coating solution for the protective layer include lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, sodium alkylbenzene sulfonate, sodium dioctyl sulfosuccinate, and sulfone-modified polyvinyl. Surfactants such as alcohol and sodium polyacrylate, water-resistant agents such as dialdehyde starch, methylol urea, epoxy compounds, hydrazine compounds, and UV absorbers, fluorescent dyes, coloring dyes, mold release agents, antioxidants Auxiliaries such as these can also be added.

  The protective layer coating solution is selected from an aqueous solution in which at least one selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol is dissolved, sodium glyoxylate, di (glyoxylate) calcium and ammonium glyoxylate. Prepared by mixing and stirring at least one selected from the group consisting of a polyamidoamine / epichlorohydrin resin and, if necessary, the above-mentioned pigment, a water-soluble acidic compound and various auxiliary agents.

  Next, the thermal recording layer will be described.

  Examples of the thermal recording system having an electron donating compound and an electron accepting compound include a combination of a leuco dye and a colorant, a combination of a diazonium salt and a coupler, and a combination of a transition element such as iron, cobalt and copper and a chelate compound. And a combination of an aromatic isocyanate compound and an imino compound, and the combination of a leuco dye and a colorant is preferably used because of its excellent color density. Hereinafter, the thermosensitive recording layer comprising a combination of a leuco dye and a colorant will be described in detail.

  Various known leuco dyes and colorants can be used. Specific examples of the leuco dye include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl). ) -6-dimethylaminophthalide, 3- (N-ethyl-Np-tolyl) amino-7-N-methylanilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6 -Methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3-di (n-butyl) ) Amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-p) Toluidino) -6-methyl-7-anilinofluorane, 3-di (nbutyl) amino-6-chloro-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3 Piperidino-6-methyl-7-anilinofluorane, 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-chlorofluorane, 3-p- (p-chloroanilino) anilino-6-methyl-7-chloro Fluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 ′-(6′-dimethylamino) phthalide and the like can be mentioned.

  Of course, it is not limited to these, Moreover, 2 or more types can also be used together. The amount of the leuco dye used is not limited because it varies depending on the colorant used, but is preferably about 3 to 50% by mass, particularly about 5 to 40% by mass, based on the total solid content of the heat-sensitive recording layer.

  Examples of the colorant include 4,4′-isopropylidenediphenol, 4,4′-cyclohexylidenediphenyl, 1,1-bis (4-hydroxyphenyl) -ethane, 1,1-bis (4-hydroxy). Phenyl) -1-phenylethane, 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 3,3′-diallyl-4,4′- Dihydroxydiphenylsulfone, 2,2′-bis [4- (4-hydroxyphenyl) phenoxy] diethyl ether, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea, 4-hydroxybenzoic acid Acid benzyl ester, N, N′-di-m-chlorophenylthiourea, Np-to Rusulfonyl-N′-phenylurea, 4,4′-bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane, zinc 4- [2- (p-methoxyphenoxy) ethyloxy] salicylate, 4- {3- (p- And zinc [trilylsulfonyl) propyloxy] salicylate, zinc 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylate, and the like.

  The amount of the colorant used is not limited because it varies depending on the dye used, but it is preferably about 10 to 70% by mass, particularly about 12 to 50% by mass, based on the total solid content of the heat-sensitive recording layer.

  The heat-sensitive recording layer may contain a storability improving agent for increasing the storage stability of the recording portion and a sensitizer for increasing the recording sensitivity. Specific examples of such preservability improvers include, for example, 2,2′-ethylidenebis (4,6-di-tert-butylphenol), 4,4′-thiobis (2-methyl-6-tert-butylphenol), 1 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 2,2 Hindered phenol compounds such as bis (4-hydroxy-3,5-dimethylphenyl) propane, 4,4′-diglycidyloxydiphenylsulfone, 4-benzyloxy-4 ′-(2-methylglycidyloxy) diphenylsulfone , Diglycidyl terephthalate, cresol novolac epoxy resin, phenol novolac epoxy resin, vinyl Epoxy compounds such as bisphenol A type epoxy resin, N, N'-di-2-naphthyl -p- phenylenediamine, bis (4-ethylene iminocarbonyl aminophenyl) include methane and the like.

  When a preservability improver is used, the amount used may be an effective amount for improving the preservability, but it is usually about 1 to 30% by mass with respect to the total solid content of the thermosensitive recording layer. It is preferable to mix | blend in the range of about 5-20 mass%.

  Specific examples of the sensitizer include, for example, stearamide, methylenebisstearate, 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-acetoluidide, p-acetophene Examples include zido, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, and oxalic acid dibenzyl ester. .

  When a sensitizer is used, the amount used may be an effective amount for sensitization, but is usually about 2 to 40% by mass, particularly 5 to 5% by mass based on the total solid content of the heat-sensitive recording layer. It is preferable to mix in the range of about 25% by mass.

  The heat-sensitive recording layer uses water as a dispersion medium, leuco dye, colorant, if necessary, sensitizer, preservability improver, etc., or separately with an agitator / pulverizer such as a ball mill, attritor, sand mill, etc. After finely dispersing so that the diameter is 2 μm or less, a heat-sensitive recording layer coating solution prepared by adding an aqueous adhesive or the like is applied to one surface of the support and dried. The aqueous adhesive in the heat-sensitive recording layer preferably contains at least one selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and carboxy-modified polyvinyl alcohol.

  Furthermore, various auxiliary agents can be added to the thermal recording layer coating liquid as necessary. For example, kaolin, light (heavy) calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, Amorphous silica, pigments such as urea / formalin resin filler, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salt, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, Examples thereof include waxes such as paraffin wax and ester wax, the above-mentioned hydrazine compounds, glyoxal, boric acid, dialdehyde starch, methylolurea, epoxy compounds, and other water-resistant agents, antifoaming agents, coloring dyes and fluorescent dyes.

The support used in the heat-sensitive recording material of the present invention is not particularly limited, and examples thereof include neutral or acidic high-quality paper, synthetic paper, transparent or translucent plastic film, and white plastic film.
In applications that require water-resistant booking, the support is also required to have water resistance, so synthetic paper, transparent or translucent plastic films, white plastic films, and the like are more used as the support. In addition, although the thickness of a support body is not specifically limited, Usually, it is about 20-200 micrometers.

  In the present invention, if necessary, an undercoat layer can be provided between the support and the thermosensitive recording layer in order to further improve the recording sensitivity and the recording runnability. The undercoat layer has an oil absorption of 70 ml / 100 g or more, in particular, about 80 to 150 ml / 100 g of an oil-absorbing pigment and / or organic hollow particles and / or thermally expandable particles, and an undercoat layer coating solution mainly composed of an adhesive. Is formed by coating and drying on a support. Here, the oil absorption is a value determined according to the method of JIS K5101.

  As the oil-absorbing pigment, various pigments can be used. Specific examples include inorganic pigments such as calcined kaolin, amorphous silica, light calcium carbonate, and talc. The average particle diameter of the primary particles of these oil-absorbing pigments is preferably about 0.01 to 5 μm, particularly about 0.02 to 3 μm. The amount of the oil-absorbing pigment can be selected from a wide range, but generally it is preferably about 2 to 95% by mass, particularly preferably about 5 to 90% by mass with respect to the total solid content of the undercoat layer.

  If necessary, a protective layer, a printing layer, a magnetic recording layer, or an ink jet recording layer may be provided on the back side of the support of the heat-sensitive recording material, or an organic or inorganic oil absorbing property may be provided between the support and the heat-sensitive recording layer. It is also possible to provide an undercoat layer mainly composed of a pigment, or to apply a smoothing process such as supercalendering after smearing each layer or forming all layers. Further, various known techniques in the heat-sensitive recording body production field such as providing a pressure-sensitive adhesive layer on the back side of the support of the heat-sensitive recording body can be added as necessary.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” respectively represent “parts by mass” and “% by mass” unless otherwise specified.

Example 1
Solution A Preparation 3-Di- (n-butyl) amino-6-methyl-7-anilinofluorane 10 parts, 5 parts of a 5% aqueous solution of methylcellulose and 15 parts of water were mixed with a laser diffraction type particle in a sand mill. A liquid A was obtained by pulverizing until the median diameter was 1.0 μm using a diameter measuring device SALD2200 (manufactured by Shimadzu Corporation).

-Solution B preparation A composition comprising 10 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose and 15 parts of water was subjected to a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) with a sand mill. The liquid B was obtained by pulverizing until the median diameter by 1.0 became 1.0 μm.

-Solution C preparation A composition comprising 10 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose and 15 parts of water was subjected to a laser diffraction particle size analyzer SALD2200 (manufactured by Shimadzu Corporation) with a sand mill. C) was obtained by pulverizing until the median diameter by 1.0) became 1.0 μm.

-Preparation of coating solution for heat-sensitive recording layer A part 30 parts, B part 60 parts, C part 60 parts, polyvinyl alcohol (saponification degree 99%, average polymerization degree 1000) 10% aqueous solution 150 parts, solid concentration 50% 20 parts of styrene / butadiene latex and 20 parts of light calcium carbonate were mixed and stirred to obtain a thermal recording layer coating solution.

Preparation of coating liquid for protective layer Acetoacetyl-modified polyvinyl alcohol (trade name: Z-200, degree of saponification: 99.4 mol%, average degree of polymerization: 1000, degree of modification: 5 mol%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd. ), 300 parts of kaolin (trade name: UW-90, average particle size: 2 μm, manufactured by EC), amorphous silica (trade name: Mizukasil P-527, average particle size: 4.4 μm) 4 parts, manufactured by Mizusawa Chemical Co., Ltd., 10 parts of 10% aqueous solution of sodium glyoxylate (trade name: SPM-01, manufactured by Nippon Synthetic Chemical Industry), 25% aqueous solution of polyamidoamine / epichlorohydrin resin (trade name: WS) -4024 (manufactured by Seiko PMC), a composition comprising 2 parts of a 30% aqueous dispersion of zinc stearate and 150 parts of water was mixed and stirred, and adjusted to pH 6.5 with a 5% aqueous boric acid solution. To obtain a protective layer coating solution was.

-Preparation of thermosensitive recording body The coating amount after drying the coating solution for the thermal recording layer and the coating solution for the protective layer on a synthetic paper (trade name: YUPO FPH # 95, manufactured by YUPO Corporation) with a thickness of 95 μm is 6.5 g. / M ² and 2.5 g / m ² were applied and dried to sequentially form a heat-sensitive recording layer and a protective layer, and then the surface was smoothed with a super calendar to obtain a heat-sensitive recording material.

Example 2
In preparation of the coating liquid for protective layer of Example 1, instead of acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol (trade name: D-700, saponification degree: 99.8 mol%, average polymerization degree: 1700, A heat-sensitive recording material was obtained in the same manner as in Example 1 except that a 10% aqueous solution having a degree of modification: 5 mol%, manufactured by Unitika Ltd.) was used.

Example 3
In the preparation of the coating solution for the protective layer of Example 1, carboxy-modified polyvinyl alcohol (trade name: T-215, saponification degree: 97 mol%, average polymerization degree: 1100, modification degree instead of acetoacetyl-modified polyvinyl alcohol. : 4 mol%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), a thermosensitive recording material was obtained in the same manner as in Example 1 except that a 10% aqueous solution was used.

Example 4
In preparation of the coating liquid for protective layer of Example 1, di (glucoxylate) calcium (trade name: SPM-02, Nippon Synthetic Chemical) instead of 10% aqueous solution of sodium glyoxylate (trade name: SPM-01, supra) A thermosensitive recording material was obtained in the same manner as in Example 1 except that 1 part of Kogyo Kogyo) was used.

Example 5
In the preparation of the coating solution for the protective layer of Example 1, Example 1 was used except that 10 parts of 10% aqueous solution of ammonium glyoxylate was used instead of the 10% aqueous solution of sodium glyoxylate (trade name: SPM-01, supra). In the same manner, a heat-sensitive recording material was obtained.

Example 6
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that amorphous silica was removed in the preparation of the protective layer coating solution of Example 1.

Example 7
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 25 parts of amorphous silica was used in the preparation of the protective layer coating solution of Example 1.

Example 8
In the preparation of the protective layer coating solution of Example 1, thermal recording was performed in the same manner as in Example 1 except that 2.5 parts of a 10% aqueous solution of sodium glyoxylate (trade name: SPM-01, supra) was used. Got the body.

Example 9
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that boric acid was not added in the preparation of the protective layer coating solution of Example 1. In addition, about the coating liquid for protective layers obtained in Example 9, the viscosity rose 3 days after preparation.

Comparative Example 1
A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 10 parts of a 10% aqueous solution of sodium glyoxylate (trade name: SPM-01, supra) was removed in the preparation of the coating solution for the protective layer of Example 1. Obtained.

Comparative Example 2
In the preparation of the coating solution for the protective layer of Example 1, the same procedure as in Example 1 was performed except that 2 parts of a 25% aqueous solution of polyamidoamine / epichlorohydrin resin (trade name: WS-4024, supra) was excluded. A heat-sensitive recording material was obtained.

Comparative Example 3
In the preparation of the coating solution for the protective layer of Example 1, completely saponified polyvir alcohol (trade name: PVA110, saponification degree: 99 mol%, average polymerization degree: 1000, manufactured by Kuraray Co., Ltd.) instead of acetoacetyl-modified polyvinyl alcohol A heat-sensitive recording material was obtained in the same manner as in Example 1 except that was used.

[Color development]
Using a thermal recording evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording body is recorded at an applied energy of 0.35 mJ / dot, and the optical density (recording density) of the recording part is set to Macbeth density. It was measured in a visual mode with a meter (RD-914 type, manufactured by Macbeth).

〔water resistant〕
One drop (about 30 μl) of water was dropped on the protective layer surface of a 10 cm × 5 cm thermosensitive recording medium, and the protective layer surface was rubbed with a finger thereon, and the evaluation was evaluated as follows according to the following evaluation criteria.
(Evaluation criteria)
A: The heat-sensitive recording layer does not dissolve at all even after 30 times.
○: The heat-sensitive recording layer melts slightly after 30 times, but there is no practical problem.
X: The thermosensitive recording layer melts after 20 times, which is practically problematic.

[Water blocking resistance-1]
Drop one drop (about 30 μl) of water on the polystyrene film, place the protective layer surface on it, place a 5 cm diameter cylindrical brass weight (9.8 N), remove the weight after 3 days, The protective layer surface was peeled off, and the evaluation was evaluated as follows according to the following evaluation criteria.
(Evaluation criteria)
A: Peel almost without resistance.
○: Although there is some resistance, there is no peeling of the thermosensitive recording layer, and there is no practical problem.
X: Some heat-sensitive recording layers peel off, which is a problem in practical use.

[Water blocking resistance-2]
Except for changing the material from polystyrene film to polyethylene terephthalate film, a water-resistant blocking test was conducted and evaluated according to the above evaluation criteria.

[Barrier properties]
The barrier property of the coated surface was evaluated using an oil-based magic pen (Mckee EXTRSBOLD: manufactured by Zebra).
(Evaluation criteria)
○: No pin pole.
Δ: Some pin poles are seen, but there is no practical problem.
X: A considerable number of pinholes are observed, which is a problem in practical use.

Claims (3)

  A heat-sensitive recording layer having a heat-sensitive recording layer containing a leuco dye, a colorant and a water-based adhesive on a support, and further having a protective layer containing a water-based adhesive on the heat-sensitive recording layer. The agent is at least one selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol, and at least selected from sodium glyoxylate, di (calcium glyoxylate) and ammonium glyoxylate in the protective layer. A heat-sensitive recording material comprising one kind and a polyamidoamine / epichlorohydrin resin.   The heat-sensitive recording material according to claim 1, comprising amorphous silica as a pigment in the protective layer in an amount of 1 to 20 mass% based on the total pigment.   The heat-sensitive recording material according to claim 1 or 2, wherein the support is a synthetic film.