JP6277906B2 - Thermal recording material - Google Patents

Description

  The present invention relates to a heat-sensitive recording material utilizing a color development reaction between a leuco dye and a colorant.

  Generally, a heat-sensitive recording material is usually a colorless to light leuco dye and a colorant dispersed in fine particles, and then mixed together to produce an auxiliary agent such as an adhesive, a pigment, a sensitizer, and other lubricants. The coating liquid obtained by adding is applied onto a sheet-like support such as paper, synthetic paper, or plastic film. The heat-sensitive recording material is colored by an instantaneous chemical reaction by heating with a thermal head, hot stamp, thermal pen, laser beam or the like, and a recorded image is obtained. Thermosensitive recording media are used in a wide range such as facsimiles, computer terminal printers, automatic ticket vending machines, and measurement recorders. In recent years, the use of thermal recording labels in which the back surface is subjected to adhesive processing is increasing. These POS labels and process control agent labels have a long period until they are used after being subjected to adhesive processing. For this reason, components such as plasticizers and emulsifiers contained in the adhesive applied to the back surface during storage pass through the support and reach the heat-sensitive recording surface, causing color reaction inhibition (glue desensitization) and recording color development. There are problems such as remarkably degrading recording performance such as image quality and recording, and white spots in printing.

  In order to solve the above problem, a barrier layer containing polyvinyl alcohol and a pigment having a high saponification degree and a pigment is provided between the support and the pressure-sensitive adhesive layer (see Patent Document 1), and a styrene-butadiene copolymer is provided on the back of the support. A back coat layer containing a polymer and a pigment is provided (see Patent Document 2), and a back layer containing a water-soluble acrylic resin as a main component is provided on the side of the support opposite to the thermosensitive recording layer (patent) Reference 3), and a back coat layer containing a styrene-acrylic resin having a glass transition point of 10 ° C. or less and a 0.01% by weight aqueous solution having a transmittance at 280 nm of 2.0% or less (see Patent Document 4) ) Etc. have been proposed, but at present, satisfactory results have not been obtained.

Japanese Patent Laid-Open No. 5-4450 JP-A-9-150576 JP 2004-284089 A JP 2009-255309 A

  The present invention is excellent in recording color development and recording image quality, and has no hindrance to coloring reaction (glue desensitization) by the adhesive component after being processed into a thermal recording label, and has excellent recording performance withstanding long-term storage. The main purpose is to provide a thermal recording medium.

  As a result of intensive studies, the present inventors have provided an anchor layer containing plastic hollow particles and a sizing agent containing a styrene-containing copolymer as a main component, and an undercoat layer containing plastic hollow particles. The present inventors have found that the above problem can be solved and have completed the present invention. That is, the present invention relates to the following thermal recording material.

  Item 1: An anchor layer containing at least a plastic hollow particle and a sizing agent containing a styrene-containing copolymer as a main component on a support made of a paper support, and an undercoat containing the plastic hollow particle on the anchor layer A heat-sensitive recording material comprising a heat-sensitive recording layer containing a leuco dye and a colorant on the undercoat layer.

  Item 2: The sizing agent comprising the styrene-containing copolymer as a main component is at least one selected from the group consisting of a styrene-acrylic sizing agent and a styrene-maleic acid sizing agent. Thermal recording material.

  Item 3: The content ratio of a sizing agent containing a styrene-containing copolymer contained in the anchor layer as a main component is 1 to 9% by mass in terms of solid content in the total solid amount of the anchor layer. Or a heat-sensitive recording material according to 2.

  Item 4: The mass ratio of the sizing agent mainly composed of a plastic hollow particle / styrene-containing copolymer contained in the anchor layer is 95/5 to 50/50 in terms of solid content, The heat-sensitive recording material according to any one of the above.

  Item 5: The heat-sensitive recording material according to any one of Items 1 to 4, wherein the sizing agent containing the styrene-containing copolymer as a main component is a styrene-acrylic sizing agent.

  Item 6: The heat-sensitive recording material according to any one of Items 1 to 5, wherein the sizing agent containing the styrene-containing copolymer as a main component is a styrene-acrylic emulsion type sizing agent.

  Item 7: The heat-sensitive recording material according to any one of Items 1 to 6, wherein the content ratio of the plastic hollow particles contained in the undercoat layer is 40 to 95% by mass in the total solid content of the undercoat layer.

  Item 8: The thermal recording material according to any one of Items 1 to 7, wherein the mass ratio of the hollow plastic particles in the anchor layer / the hollow plastic particles in the undercoat layer is 20/80 to 60/40.

Item 9: The heat-sensitive recording material according to any one of Items 1 to 8, wherein the surface roughness of the support surface under a pressure of 20 kg / cm ² by microtopography is 6 μm or more.

  Item 10: The heat-sensitive recording material according to any one of Items 1 to 9, wherein the support has a Steecht sizing degree of 15 seconds or less.

  Item 11: The heat-sensitive recording material according to any one of Items 1 to 10, wherein a pressure-sensitive adhesive layer is provided on a support opposite to the heat-sensitive recording layer.

  The thermal recording material of the present invention is excellent in recording color development and recording image quality, has no inhibition of color development reaction (adhesive desensitization) due to the adhesive component after being processed into a thermal recording label, and withstands long-term storage and improves recording performance. Excellent.

  The heat-sensitive recording material of the present invention comprises an anchor layer containing at least plastic hollow particles and a sizing agent-containing sizing agent as a main component on a support, and an undercoat containing plastic hollow particles on the anchor layer. With layers. Thereby, excellent recording color development and recording image quality can be obtained. Further, even after processing into a heat-sensitive recording label, penetration of the plasticizer, emulsifier and the like contained in the pressure-sensitive adhesive layer into the heat-sensitive recording layer is prevented, and the recording performance after long-term storage is excellent.

  The sizing agent has high water resistance of the coating itself, and once dried, it does not dissolve again even if it comes into contact with water. In the present invention, by providing an intermediate layer having a multilayer structure such as an anchor layer or an undercoat layer between the support and the thermosensitive recording layer, the sizing agent is uniformly distributed, while the plastic hollow particles are bleeded to provide a barrier property. It is thought that it is raising. As a result, the component that inhibits the color development reaction does not pass through the support, the penetration of the coating solution for the undercoat layer into the anchor layer is suppressed, and the penetration of the coating solution for the thermal recording layer into the undercoat layer is suppressed, Forms a uniform coating layer and excels in recording performance. Further, by providing a multilayer structure between the support and the heat-sensitive recording layer, it is possible to reduce uneven coloring due to coating unevenness and improve the halftone image quality in a single layer structure.

  In this invention, the anchor layer containing the sizing agent which has as a main component the copolymer containing styrene is provided on the support body. Such sizing agents are generally referred to as paper sizing agents, and include synthetic resin sizing agents such as styrene-acrylic sizing agents and styrene-maleic acid sizing agents. The form of the sizing agent may be a solution type or an emulsion type. These can be used alone or in combination of two or more. The styrene-maleic acid sizing agent includes a styrene-maleic anhydride sizing agent. The styrene-acrylic sizing agent includes a styrene-acrylic acid copolymer salt, and the salt includes a sodium salt, a potassium salt, an ammonium salt, or a mixture of these salts. In addition, the styrene-maleic anhydride sizing agent includes styrene-maleic anhydride copolymer salts, which include sodium salts, potassium salts, ammonium salts, or those in which these salts coexist. . Further, the styrene-maleic anhydride sizing agent includes esters of styrene-maleic anhydride copolymer, and butyl ester of styrene-maleic anhydride copolymer is particularly preferable.

  Although it does not restrict | limit especially as a sizing agent which has as a main component the copolymer containing styrene contained in an anchor layer, At least 1 chosen from the group which consists of a styrene-acrylic sizing agent and a styrene-maleic acid sizing agent. Species are preferred, styrene-acrylic sizing agents are more preferred, and styrene-acrylic emulsion sizing agents are even more preferred. By using the emulsion type, bleeding occurs during the drying process of the anchor layer, forming a film on the upper side, enhancing the coverage of the support with a rough surface, excellent recording color development and recording image quality, and desensitization. It is considered that the recording performance is excellent by suppressing the above.

  The content ratio of the sizing agent mainly containing a copolymer containing styrene contained in the anchor layer is preferably about 1 to 9% by mass in the total solid amount of the anchor layer in terms of solid content, and is preferably 2 to 8%. About mass% is more preferable, and about 2.5-5 mass% is still more preferable. By setting it to 1% by mass or more, it can sufficiently withstand long-term storage after being processed into a thermosensitive recording label, and can improve recording color quality and improve recording image quality. On the other hand, when the content is 9% by mass or less, it is possible to improve the recording colorability and improve the sensitivity of the thermosensitive recording layer.

  The anchor layer in the present invention may contain other aqueous resins, auxiliaries and the like as long as the effects of the present invention are not impaired. Examples of other aqueous resins include polyvinyl alcohol, modified polyvinyl alcohol, starch, modified starch, starch-vinyl acetate graft copolymer, casein, gelatin, polyacrylamide, polyamide, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and styrene-butadiene. System latex, polyurethane latex, acrylic latex and the like. These other aqueous resins may be used in combination, and the total content is not particularly limited, but is preferably about 5 to 30% by mass, and about 8 to 20% by mass in the total solid content of the anchor layer. More preferably, about 10-20 mass% is still more preferable. In the present invention, it is preferable not to contain starches from the viewpoint of pot life such that the viscosity of the coating liquid decreases with time.

  Examples of the auxiliary agent include, for example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salt and the like, glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, Dialdehyde starch, melamine resin, polyamide resin, polyamide polyamine-epichlorohydrin resin, ketone-aldehyde resin, borax, boric acid, ammonium zirconium carbonate, epoxy compound, hydrazide compound, oxazoline group-containing compound, sodium glyoxylate, di (glyoxylic acid) Water resistant agents such as calcium and glyoxylates such as ammonium glyoxylate, antifoaming agents and the like can be mentioned.

  The anchor layer in the present invention further contains plastic hollow particles. Examples of the plastic hollow particles contained in the anchor layer include conventionally known particles, for example, particles having a hollow ratio of about 50 to 99% in which the film material is made of an acrylic resin, a styrene resin, a vinylidene chloride resin, or the like. . Here, the hollowness is a value obtained by the following formula (d / D) × 100. In the formula, d represents the inner diameter of the plastic hollow particle, and D represents the outer diameter of the plastic hollow particle. The average particle size of the plastic hollow particles is preferably about 0.5 to 10 μm, more preferably about 1 to 3 μm. The content ratio of the plastic hollow particles is not particularly limited, but is preferably about 2 to 90% by mass, more preferably about 5 to 70% by mass, and further preferably about 10 to 50% by mass in the total solid content of the anchor layer. .

  In this invention, it is preferable that the mass ratio of the size agent which has as a main component the copolymer containing plastic hollow particle / styrene containing in an anchor layer is 95 / 5-50 / 50 in conversion of solid content. By setting the mass ratio of the plastic hollow particles to 95 or less, the desensitization can be suppressed and the recording performance can be improved. On the other hand, when it is 50 or more, the recording color development can be improved.

  The anchor layer is preferably a pigment coating layer containing a pigment. Such pigments can contain other pigments other than the plastic hollow particles. By containing other pigments, the unevenness of the support having a rough surface can be filled to improve the recording color development and recording image quality. Further, the penetration of the sizing agent contained in the anchor layer into the support can be suppressed to improve the covering property, and the desensitization can be suppressed to improve the recording performance.

  The pigment contained in the anchor layer is not particularly limited, but oil-absorbing pigments and / or thermally expandable particles having an oil absorption of 70 ml / 100 g or more, particularly about 80 to 150 ml / 100 g are preferable. Here, the oil absorption is a value determined according to the method of JIS K 5101.

  Various types of oil-absorbing pigments contained in the anchor layer can be used, and specific examples include inorganic pigments such as calcined kaolin, amorphous silica, light calcium carbonate, and talc. Of these, calcined kaolin is preferred from the viewpoint of improving recording performance. The average particle diameter of the primary particles of these oil-absorbing pigments is preferably about 0.01 to 5 μm, particularly preferably about 0.02 to 3 μm. The content of the oil-absorbing pigment is not particularly limited, but is preferably about 2 to 90% by mass, more preferably about 5 to 90% by mass, and still more preferably about 30 to 80% by mass in the total solid content of the anchor layer.

  In the present invention, the anchor layer preferably contains an oil-absorbing pigment and plastic hollow particles. The oil-absorbing pigment and the plastic hollow particles are used within the above-mentioned content ratio, and the total content ratio of the oil-absorbing pigment and the plastic hollow particles is preferably about 5 to 93% by mass in the total solid amount of the anchor layer. 10 to 85% by mass is more preferable.

  In the present invention, the mass ratio of the oil-absorbing pigment / plastic hollow particles in the anchor layer is preferably in the range of 90/10 to 40/60, and more preferably in the range of 85/15 to 70/30. By setting the mass ratio of the oil-absorbing pigment to 90 or less, it is possible to improve the cushioning property of the anchor layer and improve the recording color development and recording image quality. On the other hand, by setting it to 40 or more, the oil absorption of the anchor layer can be sufficiently exerted, and the image quality due to the head wrinkles can be reduced and the recording image quality can be improved. Moreover, by setting it as this range, barrier property can be improved further and it can fully endure long-term storage after processing into a thermosensitive recording label.

The anchor layer is generally applied using an anchor layer coating liquid prepared by mixing water with a dispersion medium, plastic hollow particles and a specific sizing agent, if necessary, other pigments, aqueous resins, auxiliaries, and the like. Thereafter, it is dried and formed on a support. The application amount of the anchor layer is not particularly limited, but is preferably about 3 to ²⁰ g / m ² by dry weight, and more preferably about 5 to 15 g / m ² .

  In the present invention, an undercoat layer is provided on the anchor layer. The undercoat layer in the present invention contains plastic hollow particles. The plastic hollow particles contained in the undercoat layer are not particularly limited, and can be appropriately selected from those that can be used for the anchor layer, for example. The plastic hollow particles may be the same in both the anchor layer and the undercoat layer, or may be different.

  The content of the plastic hollow particles in the undercoat layer is preferably about 40 to 95% by mass, more preferably about 45 to 85% by mass, and still more preferably about 70 to 85% by mass in the total solid content of the undercoat layer. By setting it to 40% by mass or more, it is possible to improve heat insulation and improve recording color development and recording image quality. On the other hand, by setting it to 95% by mass or less, it is possible to prevent deterioration in image quality such that the thermal insulation becomes too high and the thermal printing becomes thicker to spread.

  In the present invention, an embodiment in which the mass ratio of the hollow plastic particles in the anchor layer / the hollow plastic particles in the undercoat layer is in the range of 20/80 to 60/40 is preferable. By making it within this range, the balance between barrier properties and coverage of the anchor layer and undercoat layer is excellent due to the synergistic effect with the sizing agent, enhancing the recording color development and recording image quality, and long-term storage after processing into a thermal recording label Recording performance sufficient to withstand the above can be provided.

  The undercoat layer in the present invention preferably contains a sizing agent. The sizing agent is not particularly limited and may be appropriately selected from those referred to as paper sizing agents. However, at least one selected from the group consisting of styrene-acrylic sizing agents and styrene-maleic acid sizing agents. Species are preferred, styrene-maleic anhydride sizing agents are more preferred, and butyl esters of styrene-maleic anhydride copolymers are even more preferred. As a result, the synergistic effect with the plastic hollow particles is enhanced, the desensitization is suppressed, and the recording performance is excellent. The sizing agent may be the same for both the anchor layer and the undercoat layer, or may be different.

  The content of the sizing agent contained in the undercoat layer is preferably about 0.5 to 7% by mass, more preferably about 2.5 to 6.5% by mass in the total solid content of the undercoat layer in terms of solid content. More preferably, it is about 2.5 to 4.5% by mass. By setting the content to 0.5% by mass or more, it is possible to sufficiently withstand long-term storage after being processed into a thermal recording label, and to improve recording color development and recording image quality. By setting the content to 7% by mass or less, the recording colorability can be improved and the sensitivity of the heat-sensitive recording layer can be improved.

  In the present invention, the multilayer structure of the anchor layer and the undercoat layer can be effectively formed by adjusting the coating amounts of all the sizing agents and all the plastic hollow particles contained in the anchor layer and the undercoat layer. This coating amount is preferably about 3 to 30 parts by mass of all sizing agents with respect to 100 parts by mass of all plastic hollow particles in terms of solid content. More preferably, it is about 5-25 mass parts, More preferably, it is about 6.0-17 mass parts. By setting it to 3 parts by mass or more, it is possible to sufficiently withstand long-term storage after being processed into a heat-sensitive recording label, and to improve recording color development and recording image quality. On the other hand, when the content is 30 parts by mass or less, the recording colorability can be improved and the sensitivity of the heat-sensitive recording layer can be improved.

  The undercoat layer in the present invention may contain other aqueous resins, other pigments other than the plastic hollow particles, auxiliary agents, and the like as long as the effects of the present invention are not impaired. Other aqueous resins and auxiliaries are not particularly limited, and can be appropriately selected from those that can be used for the anchor layer, for example. Examples of the pigment include organic pigments such as urea, phenol, epoxy, styrene, nylon, polyethylene, melamine, benzoguanamine resin, urea-formalin resin, or calcined kaolin, silicic acid, porous calcium carbonate, talc, kaolin, calcium carbonate. And inorganic pigments such as magnesium carbonate, zinc oxide, titanium oxide, aluminum silicate, calcium silicate, and aluminum hydroxide.

The undercoat layer is generally coated with an undercoat layer coating solution prepared by mixing water with a dispersion medium, plastic hollow particles, if necessary, a sizing agent, other pigments, an aqueous resin, an auxiliary agent, and the like. It is dried and formed on the anchor layer. The coating amount of the undercoat layer is not particularly limited, is preferably about 0.5 to 10 g / ^{m 2} by dry weight, about 1 to 5 g / ^{m 2} is more preferable.

  The heat-sensitive recording layer in the present invention can contain various known leuco dyes and colorants. In addition, you may contain a sensitizer, a preservability improving agent, a pigment, various adjuvants, etc. as needed. Such a heat-sensitive recording layer is provided on the undercoat layer.

  Specific examples of the leuco dye include 3-diethylamino-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-N-isoamylamino) -6-methyl-7-arininofluorane, 3- (N-ethyl-p-) Toluidino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3- (N -Isoamyl-N-ethylamino) -7- (o-chloroanilino) fluorane, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane 3-diethylamino-6-chloro-7-anilinofluorane, 3- (Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxy Propyl) -N-ethylamino] -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-methylamino] -6-methyl-7-anilinofluorane, 3 -Diethylamino-7- (2-chloroanilino) fluorane, 3-di (n-butylamino) -7- (2-chloroanilino) fluorane and the like. These leuco dyes can be used alone or in combination of two or more. The content ratio of the leuco dye is not particularly limited, and is preferably about 3 to 30% by mass in the total solid content of the heat-sensitive recording layer.

  Specific examples of the colorant include, for example, 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec-butylidene diphenol, 4-phenylphenol, 4,4′-dihydroxy Diphenylmethane, 4,4′-isopropylidene diphenol, 4,4′-cyclohexylidene diphenol, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 4,4′-dihydroxydiphenyl sulfide, 4, 4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy- 4'-n-propoxydiphenyl Lufone, 4-hydroxy-4′-allyloxydiphenylsulfone, 3,3′-diallyl-4,4′-dihydroxydiphenylsulfone, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, etc. Phenolic compounds, 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoate-sec-butyl, phenyl 4-hydroxybenzoate, 4- Phenolic compounds such as benzyl hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenyl ether, or benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalate Aromatic carboxylic acids such as acid, salicylic acid, 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, and the like Phenolic compounds, organic acidic substances such as salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, etc., Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) Phenylurea, Np-toluenesulfonyl-N′-p-butoxycarbonylphenylurea, Np-tolylsulfonyl-N′-phenylurea, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, 4,4′-bis [(4-methyl-3-phenoxycal Sulfonyl aminophenyl) ureido] urea compounds such as diphenyl sulfone. These colorants can be used alone or in combination of two or more. The content of the colorant is not particularly limited and may be adjusted according to the leuco dye to be used, and is generally preferably about 0.5 to 10 parts by mass with respect to 1 part by mass of the leuco dye, 0.8 About 10 mass parts is more preferable, About 1-10 mass parts is still more preferable, About 1.5-5 mass parts is especially preferable.

  Specific examples of the sensitizer include, for example, stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoyl stearic acid amide, N-eicosanoic acid amide, ethylene bistearic acid amide, behenic acid amide, methylene bis stearin. Acid amide, N-methylol stearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl , Dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p-chlorobenzyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di ( 3-me Ruphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxy Ethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetoluidide, p-acetophenetide, N -Acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, diphenylsulfone and the like. The content of such a sensitizer is not particularly limited, but it is generally desirable to adjust it in a range of about 4 parts by mass or less with respect to 1 part by mass of the colorant.

  Specific examples of the preservability improver include, for example, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-ethylenebis (4-methyl-6-tert-butylphenol), 2 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4,6-di-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-tert) -Butylphenol), 2,2'-ethylidenebis (4-methyl-6-tert-butylphenol), 2,2'-ethylidenebis (4-ethyl-6-tert-butylphenol), 2,2 '-(2, 2-propylidene) bis (4,6-di-tert-butylphenol), 2,2′-methylenebis (4-methoxy-6-tert-butyl) Enol), 2,2′-methylenebis (6-tert-butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-thiobis (2-methyl-6-tert- Butylphenol), 4,4′-thiobis (5-methyl-6-tert-butylphenol), 4,4′-thiobis (2-chloro-6-tert-butylphenol), 4,4′-thiobis (2-methoxy-) 6-tert-butylphenol), 4,4′-thiobis (2-ethyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 1- [α-methyl- α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, 1,1 , 3-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4′- Thiobis (3-methylphenol), 4,4′-dihydroxy-3,3 ′, 5,5′-tetrabromodiphenyl sulfone, 4,4′-dihydroxy-3,3 ′, 5,5′-tetramethyldiphenyl Sulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3) , 5-dimethylphenyl) propane, a hindered phenol compound, N, N′-di-2-naphthyl-p-phenylenediamine, 2,2′-methylenebis (4 6- di -tert- butylphenyl) phosphate sodium, and the like.

  Specific examples of pigments contained in the heat-sensitive recording layer include, for example, kaolin, calcium carbonate, magnesium carbonate, aluminum hydroxide, barium sulfate, talc, calcined kaolin, titanium oxide, zinc oxide, diatomaceous earth, particulate anhydrous silica, active Inorganic pigments such as clay, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea-formalin resin filler, styrene-methacrylic acid copolymer resin, polystyrene resin, and raw starch particles. The pigment content is preferably 50% by mass or less in an amount that does not lower the color density, that is, in the total solid content of the heat-sensitive recording layer.

The heat-sensitive recording layer is generally averaged by a stirrer / crusher such as a ball mill, an attritor, or a sand mill, with water as a dispersion medium, and a leuco dye and a colorant, and if necessary, a sensitizer and a preservative improver. Using a dispersion obtained by dispersing so that the particle diameter is 2 μm or less, and applying a coating solution for a thermal recording layer prepared by mixing pigments, adhesives, auxiliaries, etc., if necessary, drying To be formed on the undercoat layer. The coating amount of the heat-sensitive recording layer is not particularly limited, is preferably about 1~12g / ^{m 2} of the coating amount after drying, more preferably ^{2~10g / m 2, 2.5~5.5g / m} 2 is Particularly preferred. The thermosensitive recording layer can be formed by dividing into two or more layers as necessary, and the composition and application amount of each layer may be the same or different.

  As the adhesive used for the heat-sensitive recording layer coating liquid, for example, any of a water-soluble adhesive and a water-dispersible adhesive can be used. Examples of the water-soluble adhesive include polyvinyl alcohol, modified polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, and ethylcellulose, polyacrylic acid soda, polyvinylpyrrolidone, and acrylic acid. Examples include amide-acrylic acid ester copolymers, acrylic acid amide-acrylic acid ester-methacrylic acid copolymers, polyacrylamide, sodium alginate, gelatin, and casein. Water dispersible adhesives include polyvinyl acetate, polyurethane, styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride-acetic acid Examples thereof include latex of water-insoluble polymers such as vinyl copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, silylated urethane, acrylic-silicon composite, and acrylic-silicon-urethane composite. These can be used alone or in combination of two or more.

  In the heat-sensitive recording layer coating liquid, auxiliary agents such as dispersants, water-proofing agents, waxes, metal soaps, colored dyes, colored pigments, fluorescent dyes, oil repellents, antifoaming agents, and viscosity modifiers as necessary. Can be contained.

  Examples of water-resistant agents include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, dimethylol urea compounds, aziridine compounds, blocked isocyanate compounds, and adipic acid dihydrazides. Examples thereof include acid dihydrazide compounds, glyoxylate salts, and inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, potassium tetraborate, and boric acid, boric acid triesters, boron polymers, and the like. These can be used alone or in combination of two or more. These waterproofing agents are preferably used in the range of 0.1 to 10% by mass in the total solid content of the heat-sensitive recording layer.

  In the present invention, a protective layer can be provided on the heat-sensitive recording layer as necessary. The protective layer preferably contains a pigment and an adhesive. Furthermore, the protective layer preferably contains a lubricant such as polyolefin wax or zinc stearate for the purpose of preventing sticking to the thermal head, and can also contain an ultraviolet absorber. In addition, the added value of the product can be increased by providing a glossy protective layer.

  The adhesive contained in the protective layer is not particularly limited, and any water-based adhesive such as a water-soluble adhesive and a water-dispersible adhesive can be used. The adhesive can be appropriately selected from those that can be used for the heat-sensitive recording layer. By containing 15 to 50% by mass of polyvinyl alcohol having a polymerization degree of 1000 to 3000 as a water-soluble adhesive in the total solid content of the protective layer, the effects of the present invention can be further enhanced. Examples of the polyvinyl alcohol having a polymerization degree of 1000 to 3000 include fully saponified or partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol. Among these, acetoacetyl-modified polyvinyl alcohol and diacetone-modified polyvinyl alcohol are preferable because they can improve the barrier property of the surface of the protective layer and improve the storage stability such as chemical resistance.

  The total content of the aqueous adhesive contained in the protective layer is preferably about 10 to 80% by mass and more preferably about 20 to 75% by mass in the total solid content of the protective layer. By setting it as 10 mass% or more, the outstanding barrier property can be obtained, and also generation | occurrence | production of paper dust can be prevented by improving surface strength. On the other hand, by setting it to 80% by mass or less, sticking that is a recording failure can be suppressed.

  Examples of the pigment in the protective layer include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, amorphous silica, synthetic mica, aluminum hydroxide, barium sulfate, talc, kaolin, calcined kaolin and other inorganic pigments, nylon resin filler And organic pigments such as urea-formalin resin filler and raw starch particles. Among these, kaolin and aluminum hydroxide are preferable because they have a small decrease in barrier properties against chemicals such as plasticizers and oils and a small decrease in recording density.

  The content ratio of the pigment in the protective layer is preferably about 5 to 80% by mass and more preferably about 10 to 70% by mass in the total solid content of the protective layer. By setting the content to 5% by mass or more, the sliding with the thermal head can be improved, and sticking and head wrinkles can be suppressed. On the other hand, by setting it to 80% by mass or less, the barrier property can be improved.

The protective layer is generally formed on the heat-sensitive recording layer after coating using a protective layer coating solution prepared by mixing water, a dispersion medium, and a pigment, an adhesive, and, if necessary, an auxiliary agent. Is done. The coating amount of the coating liquid for the protective layer is not particularly limited, and is preferably about 0.3 to 15 g / m ² , more preferably about 0.3 to 10 g / m ² by dry weight, and 0.5 to 8 g / m. ^{About 2} is more preferable, and about 1.0 to 8 g / m ² is particularly preferable. In addition, a protective layer can be divided and formed in two or more layers as needed, and the composition and coating amount of each layer may be the same or different.

  Auxiliaries used in the coating liquid for the protective layer include, for example, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, sodium alkylbenzene sulfonate, sodium dioctyl sulfosuccinate, sulfonic acid-modified polyvinyl. Surfactants such as alcohol, acetylene glycol-based, fluorine-based, silicon-based, phosphate-based, ether-type surfactants, or amphoteric surfactants such as betaine, aminocarboxylate, imidazoline derivatives, glyoxal, Water resistance agents such as boric acid, dialdehyde starch, methylol urea, glyoxylate, epoxy compounds, hydrazine compounds, hydrophobic polycarboxylic acid copolymers, UV absorbers, fluorescent dyes, coloring dyes, release agents, oxidation Inhibitor And the like. The usage-amount of auxiliary agent can be suitably set from a wide range.

  In the present invention, the method for forming the anchor layer, the undercoat layer, the heat-sensitive recording layer and the protective layer is not particularly limited, and the air knife method, blade method, gravure method, roll coater method, curtain method, spray method, dip method, Known coating methods such as a bar method and an extrusion method can be employed. In the present invention, a smoothing process using a super calendar can be performed in an arbitrary process after the formation of each layer or after the formation of a specific layer.

  The support in the present invention is a paper support. The paper support is not particularly limited, and examples thereof include high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, cast-coated paper, and the like. Moreover, as a fiber which comprises a support body, both hardwood pulp and conifer pulp can be used. Examples of such pulp include chemical pulp such as LBKP and NBKP, mechanical pulp such as GP and TMP, and waste paper pulp such as DIP. If necessary, glass fiber and various synthetic pulps can be used in combination.

In the present invention, a support having a surface roughness of 6 μm or more under a pressure of 20 kg / cm ² by microtopography on the surface of the support is preferable because the effect of improving the printing quality is further observed. By providing the anchor layer and the undercoat layer in the present invention, the coverage of the thermosensitive recording layer is improved, and the support has a rough surface with a surface roughness of 6 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more. However, it is possible to improve recording color development and recording image quality. On the other hand, when the surface roughness is about 15 μm or less, sufficient recording performance can be obtained. Here, the surface roughness is the maximum value from the measured values at five locations using a surface contactor “Microtopograph” manufactured by Toyo Seiki Seisakusho using a 5.5 cm diameter pressure contact with a contact time of 990 ms. And the average value of three locations excluding the minimum value.

In the present invention, it is preferred that the support has a sizing degree of 15 seconds or less. More preferably, it is 10 seconds or less. By providing the anchor layer and the undercoat layer in the present invention, the penetration of the coating liquid into the support can be suppressed, and a uniform heat-sensitive recording layer can be formed. And recording quality can be improved. The lower limit of the Steecht sizing degree is not particularly limited, but is preferably 1 second or longer and more preferably 5 seconds or longer from the viewpoint of improving the coating suitability of the coating liquid when forming the anchor layer. Note that the degree of steechtite is measured according to JIS P 8122. As the basis weight of the support is not particularly limited, about 40~70g / ^{m 2} is preferred.

  In this invention, it can use suitably as a thermal recording body provided with the adhesive layer on the support body on the opposite side to a thermal recording layer. Examples of the pressure-sensitive adhesive used in the present invention include those mainly composed of rubber-based materials such as natural rubber, styrene-butadiene rubber, polyisobutylene rubber, and isoprene rubber, and those mainly composed of vinyl ether-based materials. -The thing which has acrylic materials, such as a copolymer polymer which has ethylhexyl acrylate as a main monomer, as a main component, and the thing which has rubbery siloxane and resinous siloxane as a main component are mentioned. These can be used as various adhesives of emulsion, solvent, or solventless type. A plasticizer and an emulsifier can be contained as an adhesive component.

  When using a release sheet, the adhesive may be applied directly on the support to provide an adhesive layer, or the adhesive is applied to the release sheet surface of the release sheet to provide an adhesive layer, and then supported. It may be attached to the opposite side of the body to the thermosensitive recording layer, and the adhesive layer may be transferred and provided. In either case, it is desirable that the pressure-sensitive adhesive layer is used by sticking a release sheet and peeling it off as desired in order to prevent unnecessary adhesion except during use. On the other hand, in the no-separate type that does not use a release sheet, the heat-sensitive recording layer and the pressure-sensitive adhesive layer are laminated with a release layer or the like sandwiched between them, and the support and the pressure-sensitive adhesive layer are wound in a wound state. The effect of the present invention can be exhibited without regret because the pressure-sensitive adhesive component is affected by contact.

The release sheet is a high-density base paper such as glassine paper, clay-coated paper, kraft paper, or release base paper such as polylaminate paper in which polyethylene is laminated on high-quality paper, etc., and fluorine resin or silicone resin as a release agent And the like having a peel surface attached in a range of about 0.05 to 3 g / m ² by dry weight. For example, a roll coater, a knife coater, a bar coater, a slot die coater or the like is used as a method for applying the pressure-sensitive adhesive, and the coating amount is adjusted in a range of about 5 to 50 g / m ² in terms of dry weight.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, “parts” and “%” indicate “parts by mass” and “% by mass” unless otherwise specified.
Example 8 is a reference example.

  The average particle diameter of the dispersions used in Examples and Comparative Examples was measured by a median diameter using a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation).

Example 1
-Preparation of coating solution for anchor layer 130 parts of 50% aqueous dispersion of calcined kaolin (trade name: Ansilex 93, manufactured by BASF), plastic hollow particle dispersion (trade name: Ropaque SN-1055, hollow ratio: 55% , 48 parts by average particle size, 1.0 μm, manufactured by Dow Coating Materials, solid content concentration 26.5%), styrene-butadiene latex (trade name: L-1571, manufactured by Asahi Kasei Chemicals, solid content concentration 48%) 29 parts, 12.8 parts of styrene-acrylic emulsion type sizing agent (trade name: POLYMALON E-100, manufactured by Arakawa Chemical Industry Co., Ltd., solid content concentration 30%), carboxymethyl cellulose (trade name: Serogen AG gum, Daiichi Kogyo) 2.3 parts of dioctyl sulfosuccinic acid sodium salt (trade name: SN wet OT-70, manufactured by San Nopco) 0.2 part of 0% aqueous solution, 1 part of 5% emulsion of natural oil and fat-based antifoaming agent (trade name: Nopco 1407H, manufactured by San Nopco), 45 parts of ammonium zirconium carbonate (trade name: Baycoat 20, manufactured by Nippon Light Metal Co., Ltd.) A composition comprising 4 parts of a% aqueous solution and 73 parts of water was mixed and stirred to obtain an anchor layer coating solution.

-Preparation of coating solution for undercoat layer: 293 parts of plastic hollow particle dispersion (trade name: Ropaque SN-1055, supra), 22 parts of styrene-butadiene latex (trade name: L-1571, supra), styrene-anhydrous 26 parts of butyl ester of maleic acid copolymer (trade name: POLYMALON HAM-15, manufactured by Arakawa Chemical Industry Co., Ltd., solid content concentration 15%), 2.4 parts of carboxymethyl cellulose (trade name: Serogen AG gum, supra), Dioctyl sulfosuccinic acid sodium salt (trade name: SN wet OT-70, supra) 0.2 part of 10% aqueous solution, natural fat-based antifoaming agent (trade name: Nopco 1407H, supra) 1 part of 5% emulsion, And a composition comprising 4 parts of a 45% aqueous solution of zirconium carbonate ammonium salt (trade name: Baycoat 20, supra) and mixed with stirring to obtain a coating solution for undercoat layer Got.

-Solution A preparation (preparation of leuco dye dispersion)
100 parts of 3-di (n-butyl) -6-methyl-7-anilinofluorane, 50 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.), natural fats and oils A composition comprising 10 parts of a 5% emulsion of a series antifoaming agent (trade name: Nopco 1407H, supra) and 90 parts of water is pulverized with a sand mill until the average particle size becomes 0.5 μm to obtain liquid A It was.

・ B liquid preparation (preparation of colorant dispersion)
100 parts of 4,4′-dihydroxydiphenylsulfone, 50 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, supra), natural fat-based antifoaming agent (trade name: Nopco 1407H, supra) A composition comprising 10 parts of a 5% emulsion and 90 parts of water was pulverized with a sand mill until the average particle size became 1.0 μm to obtain a liquid B.

・ C liquid preparation (preparation of sensitizer dispersion)
100 parts of diphenylsulfone, 50 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, supra), 10 parts of a 5% emulsion of a natural fat-based antifoaming agent (trade name: Nopco 1407H, supra) And the composition which consists of 90 parts of water was grind | pulverized until the average particle diameter was set to 1.0 micrometer with the sand mill, and C liquid was obtained.

・ D liquid preparation (preparation of preservative improver dispersion)
4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone 100 parts, magnesium silicate 5 parts, sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, supra) A composition comprising 50 parts of an aqueous solution, 10 parts of a 5% emulsion of a natural fat / oil defoaming agent (trade name: Nopco 1407H, supra) and 90 parts of water is pulverized with a sand mill until the average particle size becomes 1.0 μm. As a result, liquid D was obtained.

-Preparation of coating solution for heat-sensitive recording layer A part 38 parts, B part 106 parts, C part 30 parts, D part 11 parts, kaolin (trade name: HG90, manufactured by KaMin LLC) 11 parts, 6 parts of 60% aqueous dispersion of light calcium carbonate (trade name: Brilliant S-15, manufactured by Shiraishi Kogyo Co., Ltd.), 42 parts of 8% aqueous solution of polyvinyl alcohol (PVA-124, manufactured by Kuraray Co., Ltd., degree of polymerization 2400), styrene Butadiene latex (trade name: L-1571, supra) 3.9 parts, adipic acid dihydrazide 35% aqueous dispersion 7.5 parts, dioctylsulfosuccinate sodium salt (trade name: SN wet OT-70, supra) ), A composition consisting of 2.6 parts of a 10% aqueous solution of oil, 1.4 parts of a 5% emulsion of a natural oil and fat antifoaming agent (trade name: Nopco 1407H, supra), and 70 parts of water. To obtain a layer coating solution.

-Preparation of coating solution for protective layer 108 parts of kaolin (trade name: HG90, supra) 50% aqueous dispersion, 7.4 parts of aluminum hydroxide (trade name: Heidilite H-42, Showa Denko) 270 parts of a 10% aqueous solution of diacetone-modified polyvinyl alcohol (trade name: DF-20, manufactured by Nihon Acetate / Poval, degree of polymerization 2000), polyvinyl alcohol (trade name: JC-40, manufactured by Nihon Acetate / Poval, polymerized) 112 parts of a 6% aqueous solution having a degree of 4000), an aqueous dispersion of zinc stearate (trade name: Hydrin Z-8-36, solid content concentration 36%, manufactured by Chukyo Yushi Co., Ltd.), polyethylene dispersion (trade name) : Chemipearl W400, manufactured by Mitsui Chemicals, solid concentration 40%) 2.6 parts, ammonium salt of hydrophobic polycarboxylic acid copolymer (trade name: Orotan 165A, Dow Cotin Gmaterials, solid concentration 21.8%), dioctylsulfosuccinate sodium salt (trade name: SN Wet OT-70, supra) 1.1 parts of 10% aqueous solution, and natural fat and oil defoamer ( 20 parts of a 5% emulsion (trade name: Nopco 1407H, supra) was mixed and stirred to obtain a coating solution for a protective layer.

-Preparation of thermosensitive recording material On a paper support having a basis weight of 50 g / m ² and a surface roughness of 8 μm under pressure of 20 kg / cm ² by microtopography, the coating amount after drying becomes 6.0 g / m ^2. Thus, the anchor layer coating solution was applied and dried to form an anchor layer. An undercoat layer was formed by applying and drying an undercoat layer coating solution on the resulting anchor layer so that the coating amount after drying was 3.0 g / m ² . A thermosensitive recording layer was formed by applying and drying the thermosensitive recording layer coating solution on the resulting undercoat layer so that the coating amount after drying was 3.0 g / m ² . Further, a protective layer was formed by applying and drying a protective layer coating solution on the heat-sensitive recording layer so that the coating amount after drying was 2.5 g / m ² . Thereafter, smoothing was performed with a super calender under a pressure condition of linear pressure of 78 N / m to obtain a heat-sensitive recording material. In addition, the steadiness sizing degree of the support was 10 seconds.

Example 2
Example 1 except that the amount of calcined kaolin was 62 parts instead of 130 parts and the amount of plastic hollow particle dispersion was 176 parts instead of 48 parts in the preparation of the anchor layer coating liquid of Example 1. In the same manner, a heat-sensitive recording material was obtained.

Example 3
In the preparation of the anchor layer coating liquid of Example 1, the heat-sensitive recording material was the same as Example 1 except that the amount of the styrene-acrylic emulsion type sizing agent was changed to 3.3 parts instead of 12.8 parts. Got.

Example 4
A thermosensitive recording material was obtained in the same manner as in Example 1 except that in the preparation of the anchor layer coating liquid of Example 1, the amount of the styrene-acrylic emulsion type sizing agent was changed to 30 parts instead of 12.8 parts. It was.

Example 5
A thermosensitive recording medium was prepared in the same manner as in Example 1 except that in the preparation of the coating solution for the undercoat layer of Example 1, the amount of butyl ester of the styrene-maleic anhydride copolymer was changed to 40 parts instead of 26 parts. Obtained.

Example 6
In the preparation of the coating liquid for the undercoat layer of Example 1, the amount of the plastic hollow particle dispersion was changed to 176 parts instead of 293 parts, and a 50% aqueous dispersion 62 of calcined kaolin (trade name: Ansilex 93, supra) was used. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the part was added.

Example 7
In the production of the heat-sensitive recording material of Example 1, the basis weight was 50 g / m ² , the surface roughness under pressure of 20 kg / cm ² by microtopography was 8 μm, and the basis weight was 50 g / m ² . A heat-sensitive recording material was obtained in the same manner as in Example 1 except that a paper support having a surface roughness of 15 μm under a pressure of 20 kg / cm ² by a topograph was used. In addition, the steadiness sizing degree of the support was 7 seconds.

Example 8
In the preparation of the anchor layer coating liquid of Example 1, instead of the styrene-acrylic emulsion type sizing agent, a styrene-maleic acid copolymer ammonium salt (trade name: Polymeron 385, manufactured by Arakawa Chemical Industries, Ltd., solid content concentration) A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 25%) was used.

Example 9
In the preparation of the coating solution for the undercoat layer of Example 1, instead of 26 parts of the butyl ester of styrene-maleic anhydride copolymer, an olefin-maleic acid copolymer salt (Polymalon 1329, manufactured by Arakawa Chemical Industries, Ltd., solid A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 16 parts having a partial concentration of 25% were used.

Example 10
Example 1 except that the amount of calcined kaolin was 110 parts instead of 130 parts and the amount of the plastic hollow particle dispersion was 90 parts instead of 48 parts in the preparation of the anchor layer coating liquid of Example 1. In the same manner, a heat-sensitive recording material was obtained.

Example 11
A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the amount of the butyl ester of the styrene-maleic anhydride copolymer was changed to 16 parts instead of 26 parts in the preparation of the undercoat layer coating solution of Example 1. Obtained.

Comparative Example 1
A thermosensitive recording material was obtained in the same manner as in Example 1 except that the styrene-acrylic emulsion type sizing agent was not used in the preparation of the anchor layer coating solution of Example 1.

Comparative Example 2
In the preparation of the coating liquid for the undercoat layer of Example 1, in place of 293 parts of the plastic hollow particle dispersion, 155 parts of a 50% aqueous dispersion of calcined kaolin (trade name: Ancilex 93, supra) was used. Obtained a heat-sensitive recording material in the same manner as in Example 1.

  The thermosensitive recording material thus obtained was evaluated as follows. The results were as shown in Table 1.

(Recording performance 1: color development)
A checkered pattern is recorded using a label printer (trade name: L-2000, manufactured by Ishida Co., Ltd.), and the reflection density (recording density) of the recording portion is measured by a spectrophotometric optical densitometer (trade name: X-rite 939 type). , Manufactured by X-rite). It is preferable that the numerical value is large, indicating that the print density is high, and the recording portion is preferably 1.20 or more in practical use.

(Recording performance 1: Image quality 1)
A bar code was recorded using a label printer (trade name: L-2000, manufactured by Ishida Co., Ltd.), the recorded image quality was visually observed, and evaluated according to the following criteria.
○: There are no white spots in the image quality and no thickening of the barcode, and there is no problem at all.
(Triangle | delta): There is almost no whiteness of image quality and the thickness of a barcode, and there is no problem practically.
X: There are white spots in the image and the barcode is thick, which is a practical problem.

(Recording performance 1: Image quality 2)
Using a thermal recording evaluation machine (trade name: TH-PMH, manufactured by Okura Electric Co., Ltd.), continuous gradation from the reflection density level of the background part (unrecorded part) to the saturated density (recorded part) is recorded in one screen. The recording image quality in the halftone was visually observed and evaluated according to the following criteria.
A: There is no color unevenness and the image quality is uniform.
○: There is almost no color unevenness and there is no practical problem.
Δ: Streaky color unevenness is conspicuous and has practical problems.
X: Coloring unevenness is remarkable and image quality is non-uniform.

  (Recording performance 2: color development)

An acrylic resin-based adhesive is applied at 20 g / m ² on the support on the opposite side (back side) of the thermal recording layer of each thermal recording body to provide an adhesive layer, and a high-quality release sheet is provided on the adhesive layer. The heat-sensitive recording label processing (glue processing) was performed by bonding. Further, as an accelerated test for evaluating the desensitization, the film was stored in an environment of 40 ° C. and 90% RH for 7 days, and then the recording density was measured by the same method as in the recording performance 1. Further, the print reproducibility was obtained by the following formula, and the recording performance was evaluated according to the following criteria. Here, “recording density before label processing” is a value obtained by the above “recording performance 1: color development”.
Print reproducibility (%) = (recording density after storage after label processing / recording density before label processing) × 100
A: No problem at all if the print reproduction rate is 85% or more.
(Triangle | delta): If a printing reproduction rate is 70% or more and less than 85%, there is no problem practically.
X: If the print reproducibility is less than 70%, there is a practical problem.

(Recording performance 2: Image quality)
After the label processing by the method similar to the “recording performance 2: color developability”, the image was stored and then evaluated by the method similar to the “recording performance 1: image quality 1”.

Claims (8)

An anchor layer containing at least a plastic hollow particle and a sizing-containing sizing agent as a main component on a support made of a paper support, an undercoat layer containing a plastic hollow particle on the anchor layer, and an undercoat A heat-sensitive recording layer containing a leuco dye and a colorant is provided on the layer, a pressure-sensitive adhesive layer is provided on the support opposite to the heat-sensitive recording layer, and the copolymer containing styrene is a main component. heat-sensitive recording material, characterized in that it is an acrylic sizing agent - sizing agents styrene. Of the total solid amount of the content is the anchor layer of sizing agent composed mainly of copolymer containing styrene which is contained in the anchor layer, a 1-9 wt% in terms of solid content, according to claim 1 Thermal recording material. Weight ratio of sizing agent composed mainly of copolymer containing plastic hollow particles / styrene contained in the anchor layer is 95 / 5-50 / 50 in terms of solid content, according to claim 1 or 2 Thermal recording material. The heat-sensitive recording material according to any one of claims 1 to 3 , wherein the sizing agent containing the styrene-containing copolymer as a main component is a styrene-acrylic emulsion type sizing agent. The thermosensitive recording material according to any one of claims 1 to 4 , wherein a content ratio of the plastic hollow particles contained in the undercoat layer is 40 to 95% by mass in a total solid amount of the undercoat layer. Plastic mass ratio of the plastic hollow particles of the hollow particles / subbing layer is 20/80 to 60/40, the heat-sensitive recording material according to any one of claims 1 to 5, wherein the anchor layer. The Microtopographies surface roughness at 20 kg / cm ² pressure by the graph of the support surface is 6μm or more heat-sensitive recording material according to any one of claims 1-6. The heat-sensitive recording material according to any one of claims 1 to 7 , wherein the support has a Steecht sizing degree of 15 seconds or less.