Heat-sensitive recording body

Abstract

Disclosed is a heat-sensitive recording body comprising, on a support: at least a heat-sensitive recording layer containing a leuco dye and a developer; and a protective layer containing an adhesive and a slipperiness-imparting agent in this order. The heat-sensitive recording body is characterized in that: the heat-sensitive recording layer contains, as the developer, at least one selected from the group consisting of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, and 1,3-diphenylurea; and the protective layer contains, as the slipperiness-imparting agent, at least one selected from the group consisting of microcrystalline wax and carnauba wax.

Description

Thermal recording device

[0001] This invention relates to a thermal recording material.

[0002] Thermal recording media that utilize the color reaction between leuco dyes and color developers are relatively inexpensive, the recording equipment is compact, and maintenance is easy. Therefore, they are widely used not only as recording media for facsimile machines, various computers, and CAD plotters, but also for food applications such as fresh food, bento boxes, and prepared foods, medical applications such as labels for drug management, and labels for process control.

[0003] In food applications, when used as labels, top seals, or bands for transparent containers holding salads, prepared foods, etc., a highly transparent medium is often required so that the contents can be clearly seen. In such cases, transparent thermal film with a transparent PET film base is commonly used.

[0004] Furthermore, color developers generally have drawbacks such as poor thermal responsiveness and poor water resistance of the printed area. In addition, phenolic compounds such as bisphenol A have endocrine problems. For these reasons, demand for thermal recording paper using non-phenolic color developers is increasing, particularly in Europe, and various new non-phenolic color developers are being developed.

[0005] Patent Document 1 reports that a thermal film comprising a substrate, a heat-sensitive layer partially provided on at least one surface of the substrate, and a protective layer, wherein the heat-sensitive layer is colored by a thermal head or has been colored, wherein the protective layer is provided on the surface of the substrate on the side where the heat-sensitive layer is provided, covering the entire surface of the heat-sensitive layer, in the contact area between the thermal film and the thermal head, and further comprising an intermediate layer between the heat-sensitive layer and the protective layer, the intermediate layer containing a core-shell structured resin, the substrate being a transparent synthetic resin film, and the protective layer containing colloidal silica with a particle size of 1.0 μm or less, can suppress wear of the thermal head.

[0006] Patent Document 2 reports that a transparent thermal recording medium for labels, comprising a transparent support, a thermal recording layer provided on the transparent support, and a protective layer provided on the thermal recording layer, wherein the protective layer contains an ultraviolet-curable resin and a pigment other than a silicone resin pigment, the maximum surface height Rz of the protective layer is 0.2 μm or more and 1.0 μm or less, and the haze degree measured in accordance with ASTM D1003 or ISO 14782 is 35% or less, exhibits excellent transparency, head matching properties, and printability.

[0007] Patent Document 3 reports that a thermal recording medium having a support and a thermal recording layer on the support, wherein the thermal recording layer contains a specific non-phenolic color developer and a styrene-acrylic resin, possesses resistance to hot water, water, ethanol, temperature and humidity, water abrasion, and heat, and can produce high-density images.

[0008] Patent Document 4 reports that a thermal recording body comprising a thermal recording layer on a support containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, and a protective layer on the thermal recording layer, wherein the thermal recording layer contains at least one urea compound and the protective layer contains a phosphate ester compound, exhibits good printability during long-run printing (particularly in terms of head residue adhesion resistance).

[0009] Japanese Patent Publication No. 7069446, Japanese Patent Publication No. 7073627, Japanese Unexamined Patent Publication No. 2022-146283, International Publication No. 2024 / 195412

[0010] The main objective of this invention is to provide a thermal recording material that is highly sensitive, has excellent heat resistance in the background and plasticizer resistance in the printed area, and exhibits good thermal head matching, particularly good head cussion suitability for long-distance printing.

[0011] In view of the above-mentioned prior art, the present inventors have conducted extensive research and have succeeded in solving the above-mentioned problems. That is, the present invention relates to the following thermal recording body.

[0012] Item 1: A thermal recording body having, in this order, a thermal recording layer containing a leuco dye and a color developer, an adhesive and a protective layer containing a lubricity agent on a support, wherein the thermal recording layer contains at least one selected from the group consisting of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea as a color developer, and the protective layer contains at least one selected from the group consisting of microcrystalline wax and carnauba wax as a lubricity agent. Item 2: The thermal recording body according to Item 1, wherein the content of at least one selected from the group consisting of microcrystalline wax and carnauba wax is 1 to 20% by mass of the total solid content of the protective layer. Item 3: The thermal recording body according to Item 1 or 2, wherein the content of at least one selected from the group consisting of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, and 1,3-diphenylurea is 1.0 to 70.0% by mass of the total solid content of the thermal recording body. Item 4: The thermal recording body according to any one of Items 1 to 3, wherein the protective layer contains polyvinyl acetal resin as an adhesive. Item 5: The thermal recording body according to any one of items 1 to 4, wherein the protective layer further contains silicone oil. Item 6: The thermal recording body according to any one of items 1 to 5, wherein the protective layer further contains light calcium carbonate with an average particle size of 2.0 μm or less. Item 7: The thermal recording body according to any one of items 1 to 6, wherein the support is a transparent film. Item 8: The thermal recording body according to any one of items 1 to 7, wherein the support is a translucent or transparent support made of glassine paper or resin laminate paper.Item 9: A thermal recording body according to any one of items 1 to 8, wherein the support has a heat-seal layer on at least a portion of one or both sides. Item 10: A thermal recording body according to any one of items 1 to 9, wherein the thermal recording layer contains a vinylpyrrolidone-vinyl acetate copolymer as an adhesive. Item 11: A thermal recording body according to any one of items 1 to 10, wherein the thermal recording layer further contains colloidal silica with an average particle size of 45 nm or less. Item 12: A thermal recording body according to any one of items 1 to 11, wherein the support has an undercoat layer between it and the thermal recording layer.

[0013] The thermal recording material of the present invention is highly sensitive, has excellent heat resistance in the background and plasticizer resistance in the printed area, and exhibits good head matching properties, particularly good head slag suitability for long-distance printing.

[0014] In this specification, the expression "includes" includes the concepts of "includes," "substantially consist of," and "consisting only of." In this specification, numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits. In the present invention, latex includes the state of a gel or dried film formed by drying a dispersion medium.

[0015] The present invention provides a thermal recording body having, in this order, a thermal recording layer containing a leuco dye and a color developer, an adhesive and a protective layer containing a lubricity agent on a support, wherein the thermal recording layer contains at least one selected from the group consisting of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea as a color developer, and the protective layer contains at least one selected from the group consisting of microcrystalline wax and carnauba wax as a lubricity agent.

[0016] [Support] The support in this invention is not particularly limited in terms of type, shape, dimensions, etc., and can be appropriately selected and used from among, for example, high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, cast-coated paper, glassine paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, nonwoven fabric, cellophane, synthetic resin film, and various transparent supports. Preferably, it is a translucent or transparent support made of glassine paper or resin-laminated paper, or a transparent film (for example, a transparent film made of cellophane or synthetic resin film). These can be used to increase the transparency of the non-printed parts of the thermal recording material. Examples of resins in resin-laminated paper and synthetic resin films include polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polypropylene (PP) and polyethylene (PE). When using glassine paper as a support, an anchor coat layer containing polyethyleneimine can be provided on the glassine paper, and a first resin layer mainly containing polypropylene with a small amount of polyethylene can be provided on the anchor coat layer by melt extrusion lamination, thereby increasing the interlayer strength between the glassine paper and the first resin layer. Alternatively, a second resin layer containing polyethylene can be provided between the anchor coat layer and the first resin layer by melt extrusion lamination. The thickness of the support is not particularly limited, and is usually around 5 to 200 μm. The density of the support is also not particularly limited, and is 0.60 to 2.00 g / cm³. ３ A certain degree is desirable.

[0017] [Thermal Recording Layer] The thermal recording layer can be formed on a support by coating or printing using a thermal color-developing coating solution (which includes a water-based thermal color-developing coating solution used for coating and a thermal color-developing printing ink used for printing). The amount of thermal recording layer coated (formed) is not particularly limited, and is 1 to 12 g / m² by dry mass. ２ A suitable degree is 1 to 10 g / m ２ More preferably, 1.5 to 8 g / m ２ More preferably, 1.5 to 5.5 g / m ２This is particularly preferable. The thermal recording layer can be formed in two or more layers as needed, and the composition and coating amount of each layer may be the same or different.

[0018] [Thermochromic Coloring Coating] (Leuco Dyes) The thermochromic coloring coating can contain various known colorless or light-colored leuco dyes. Specific examples of such leuco dyes are listed below.

[0019] Specific examples of leuco dyes include, for example, blue-colored dyes such as 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-methylphenyl)-3-(4-dimethylaminophenyl)-6-dimethylaminophthalide, fluorane, 3-(N-ethyl-N-p-tolyl)amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, and rhodamine B-anilinolactam. Green coloring dyes such as 3,6-bis(diethylamino)fluoran-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-chlorofluoran, red coloring dyes such as 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexyl)amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3 -di(n-butyl)amino-6-methyl-7-anilinofluorane, 3-di(n-pentyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamylamino)-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-( N-n-hexyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-[N-(3-ethoxypropyl)-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, 4,4'-bis-dimethylaminobenzhydrinbenzylether, N-2,4,5-Trichlorophenylleucoauramine, 3-Diethylamino-7-butylaminofluorane, 3-Ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-Cyclohexyl-methylamino-6-methyl-7-anilinofluorane, 3-Diethylamino-6-chloro-7-(β-ethoxyethyl)aminofluorane, 3-Diethylamino-6-chloro-7-(γ-chloropropyl)aminofluorane, 3-Diethylamino-6-methyl-7-anilinofluorane, 3-(N-I Soamyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-dibutylamino-7-chloroanilinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-(p-toluidino)fluorane, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-diethylamino -6-chloro-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 2,2-bis{4-[6'-(N-cyclohexyl-N-methylamino)-3'-methylspiro[phthalide-3,9'-xanthene]-2'-ylamino]phenyl}propane, 3-diethylamino-7-(3'-trifluoromethylphenyl)aminofluorane, etc. Chromochemical dyes, 3,3-bis[1-(4-methoxyphenyl)-1-(4-dimethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3-p-(p-dimethylaminoanilino)anilino-6-methyl-7-chlorofluoran, 3-p-(p-chloroanilino)anilino-6-methyl-7-chlorofluoran, 3,Examples include dyes with absorption wavelengths in the near-infrared region, such as 6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide. Of course, the examples are not limited to these, and two or more compounds can be used in combination as needed.

[0020] For water-based heat-sensitive color-developing coatings, the content of such leuco dyes is not particularly limited, but is preferably about 3 to 30% by mass, more preferably about 5 to 25% by mass, and even more preferably about 7 to 20% by mass, based on the total solid content of the thermal recording layer. By setting it to 3% by mass or more, the color development ability can be enhanced and the recording density can be improved. By setting it to 30% by mass or less, the heat resistance can be improved. Furthermore, for heat-sensitive color-developing printing inks, the content of such leuco dyes is not particularly limited, but is preferably about 15 to 40% by mass, more preferably about 18 to 38% by mass, and even more preferably about 20 to 35% by mass, based on the total solid content of the thermal recording layer. By setting it to 15% by mass or more, the color development ability can be enhanced, the print density can be improved without using sensitizers that are easily soluble in organic solvents, and the print retention can be improved. By setting it to 40% by mass or less, the heat resistance can be improved.

[0021] (Color Developer) In the present invention, the thermal recording layer contains at least one color developer selected from the group consisting of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, and 1,3-diphenylurea. This improves head matching performance, especially head occlusion performance during long-distance printing, and also provides excellent heat resistance to the background. The preferred color developer is N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea.

[0022] For water-based heat-sensitive color-developing coatings, the content of such developer is not particularly limited, but is preferably about 0.1 to 40% by mass, more preferably about 10 to 35% by mass, and even more preferably about 15 to 30% by mass, of the total solid content of the heat-sensitive recording layer. By setting it to 0.1% by mass or more, the color development ability can be enhanced and the recording density can be improved. By setting it to 40% by mass or less, the heat resistance can be improved. Furthermore, for heat-sensitive color-developing printing inks, the content of such developer is not particularly limited, but is preferably about 0.1 to 70% by mass, more preferably about 20 to 60% by mass, and even more preferably about 35 to 50% by mass, of the total solid content of the heat-sensitive recording layer. By setting it to 0.1% by mass or more, recording performance can be enhanced and print retention can be improved without using sensitizers that are easily soluble in organic solvents. By setting it to 70% by mass or less, background clouding can be suppressed.

[0023] Furthermore, the content ratio of the color developer is generally preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1 part by mass or more, even more preferably 1.2 parts by mass or more, and particularly preferably 1.4 parts by mass or more, per 1 part by mass of leuco dye. In addition, the content of the color developer is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferably 3.5 parts by mass or less, per 1 part by mass of leuco dye. Recording performance can be improved by using 0.5 parts by mass or more. On the other hand, background clouding in high-temperature environments can be effectively suppressed by using 10 parts by mass or less.

[0024] Other color developers may be included as long as they do not impair the effects of the present invention. Specific examples of other color developers include, for example, 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxydiphenylmethane, 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenyl, 4,4'-cyclohexylidenediphenol, 1,1-bis(4-hydroxyphenyl)-ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, and 4,4'-bis (p-tolylsulfonylaminocarbonylamino)diphenylmethane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2'-bis[4-(4-hydroxyphenyl)phenoxy]diethyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,4'-dihydroxydiphenyl Lufon, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-propoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, bis(p-hydroxyphenyl)acetate butyl, bis(p-hydroxyphenyl)acetate methyl, hydroquinone monobenzyl ether, bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxy-4' -Methyldiphenylsulfone, 4-allyloxy-4'-hydroxydiphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, 4-hydroxybenzophenone, 4-dimethyl hydroxyphthalate, 4-methyl hydroxybenzoate, 4-propyl hydroxybenzoate, 4-sec-butyl hydroxybenzoate, 4-phenyl hydroxybenzoate, 4-benzyl hydroxybenzoate, 4-benzyl ester hydroxybenzoate, 4-tolyl hydroxybenzoate, 4-chlorophenyl hydroxybenzoate, 4,Phenolic compounds such as 4'-dihydroxydiphenyl ether, or benzoic acid, p-chlorobenzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3,5-di-tert-butylsalicylic acid, 4-[2-(p-methoxyphenoxy)ethyloxy]salicylic acid Acids, aromatic carboxylic acids such as 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, and 4-[3-(p-tolylsulfonyl)propyloxy]zinc salicylate, and their phenolic compounds, salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, and further, thiocyanates. Organic acidic substances such as lead antipyrine complexes, complex zinc salts of terephthalaldehyde acid and other aromatic carboxylic acids, urea compounds such as N-p-toluenesulfonyl-N'-3-(p-toluenesulfonyloxy)phenylurea, N-p-toluenesulfonyl-N'-p-butoxycarbonylphenylurea, N-p-tolylsulfonyl-N'-phenylurea, 4,4'-bis(p-toluenesulfonylaminocarbonylamino)diphenylmethane, 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, thiourea compounds such as N,N'-di-m-chlorophenylthiourea, N-(p-toluenesulfonyl)carbamoyl acid p-cumylphenyl ester, N-(p-toluenesulfonyl)carbamoyl acid p-benzyloxyphenyl ester, N-(o-toluyl)-p-toluenesulfamide, etc., with -SO in the molecule. ２ Examples include organic compounds containing NH- bonds, activated clay, attapulgite, colloidal silica, and inorganic acidic substances such as aluminum silicate.

[0025] Furthermore, examples include urea urethane derivatives such as 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, 4,4'-bis[(2-methyl-5-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, 4-(2-methyl-3-phenoxycarbonylaminophenyl)ureido-4'-(4-methyl-5-phenoxycarbonylaminophenyl)ureidodiphenylsulfone, diphenylsulfone derivatives represented by the general formula (2), and N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea. Of course, the examples are not limited to these, and two or more compounds can be used in combination as needed.

[0026]

[0027] (In the formula, n represents an integer from 1 to 6.)

[0028] (Adhesive) The heat-sensitive color-developing coating liquid of the present invention may contain an adhesive. As the adhesive, for example, either a water-soluble adhesive or a water-dispersible adhesive can be used. Examples of water-soluble adhesives include modified polyvinyl alcohol such as polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol; starch and its derivatives; cellulose derivatives such as methoxycellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, methylcellulose, and ethylcellulose; sodium polyacrylate; polyvinylpyrrolidone; polyamide; diisobutylene-maleic anhydride copolymer salt; styrene-acrylic acid copolymer salt; styrene-maleic anhydride copolymer salt; ethylene-maleic anhydride copolymer salt; acrylamide-acrylic acid ester copolymer; acrylamide-acrylic acid ester-methacrylic acid copolymer; polyacrylamide; sodium alginate; gelatin; casein; and gum arabic. Examples of water-dispersible adhesives include emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid esters, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or latexes of water-insoluble polymers such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. Alternatively, an organic solvent-soluble adhesive can be used. Examples of organic solvent-soluble adhesives include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, polyurethane, saturated polyester, polyester polyurethane, epoxy resin, phenoxy resin, nitrocellulose, melamine resin, vinylpyrrolidone-vinyl acetate copolymer, chlorinated polyethylene, and chlorinated polypropylene. Vinylpyrrolidone-vinyl acetate copolymer is particularly preferred. The molar ratio of vinylpyrrolidone to vinyl acetate in such vinylpyrrolidone-vinyl acetate copolymer is not particularly limited, but 50 / 50 to 30 / 70 is preferred, and 40 / 60 to 30 / 70 is more preferred. By setting the ratio to 50 / 50 to 30 / 70, the print density can be improved.The adhesive can be used alone or in combination of two or more. The content ratio of the adhesive can be selected from a wide range, but generally, about 5 to 35% by mass, more preferably about 9 to 33% by mass, in the total solid content of the heat-sensitive recording layer is preferable.

[0029] (Colloidal silica) In the present invention, colloidal silica having an average particle diameter of 45 nm or less can be further contained in the heat-sensitive coloring coating liquid. Thereby, the coloring ability can be enhanced and the printing density can be improved without impairing the transparency. The average particle diameter of the colloidal silica is preferably 60 nm or less, more preferably 45 nm or less. On the other hand, from the viewpoint of heat resistance, 5 nm or more is preferable. Here, the average particle diameter refers to the volume-based median diameter measured by any one of the BET method, the Shear's method, and the laser diffraction method. More simply, an electron microscope can be used, and the particle diameters can be measured from the particle images (SEM images) respectively, and the average value of 10 can be shown.

[0030] The content ratio of such colloidal silica having an average particle diameter of 45 nm or less is not particularly limited, and is preferably about 5 to 30% by mass, more preferably about 7 to 28% by mass, still more preferably about 10 to 25% by mass, in the total solid content of the heat-sensitive recording layer. By setting it to 5% by mass or more, the coating film strength can be improved. By setting it to 30% by mass or less, the transparency can be maintained.

[0031] (Solvent) The heat-sensitive coloring coating liquid can contain a solvent. Examples of such a solvent include water, alcohol, toluene, cyclohexane, methylcyclohexane, etc., and a solvent containing water and alcohol is preferable. As the alcohol, an alcohol having 5 or less carbon atoms is desirable, and examples of such an alcohol having 5 or less carbon atoms include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-pentyl alcohol, etc. By using alcohol as the solvent, it becomes possible to use the heat-sensitive coloring printing ink for gravure printing.

[0032] (Preservation Improvement Agent) In the present invention, the heat-sensitive color-developing coating liquid may further contain a preservation improvement agent, mainly to further enhance the preservation of the color image. Examples of such preservation improvement agents include 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1-bis(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisphenol, and 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisphenol At least one compound selected from phenolic compounds such as 4-benzyloxyphenyl-4'-(2-methyl-2,3-epoxypropyloxy)phenylsulfone, 4-(2-methyl-1,2-epoxyethyl)diphenylsulfone, 4-(2-ethyl-1,2-epoxyethyl)diphenylsulfone, and isocyanuric acid compounds such as 1,3,5-tris(2,6-dimethylbenzyl-3-hydroxy-4-tert-butyl)isocyanuric acid can be used. Of course, it is not limited to these, and two or more compounds can be used in combination as needed.

[0033] When using a preservation improver, the amount used should be sufficient to improve preservation, and is usually preferably about 1 to 30% by mass, and more preferably about 5 to 20% by mass, of the total solid content of the thermal recording layer.

[0034] (Sensitizer) A sensitizer can also be contained in the heat-sensitive recording layer in the present invention. By this, the recording sensitivity can be enhanced. Examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-benzamide stearate, N-benzoyl stearic acid amide, N-eicosanoic acid amide, ethylene bis stearic acid amide, behenic acid amide, methylene bis stearic acid amide, N-methylol stearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, diphenyl sulfone, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthyl benzyl ether, m-terphenyl, p-benzyl biphenyl, di-p-chlorobenzyl oxalate, di-p-methylbenzyl oxalate, dibenzyl oxalate, p-tolyl biphenyl 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-methylthiophenyl benzyl ether, 1,4-di(phenylthio)butane, p-acetotoluidide, p-acetophenetidide, N-acetylacetyl-p-toluidide, 1,2-diphenoxymethylbenzene, di(β-biphenylethoxy)benzene, p-di(vinyloxyethoxy)benzene, 1-isopropylphenyl-2-phenylethane, di-o-chlorobenzyl adipate, 1,2-bis(3,4-dimethylphenyl)ethane, 1,3-bis(2-naphthoxy)propane, diphenyl, benzophenone, and the like. These can be used in combination within a non-obstructive range. The content ratio of the sensitizer may be an amount effective for sensitization. Usually, about 2 to 40% by mass, preferably about 5 to 25% by mass, in the total solid content of the heat-sensitive recording layer is preferable.

[0035] As other component materials constituting the heat-sensitive color-developing coating liquid, a crosslinking agent, waxes, metal soaps, water resistance agents, pigments, dispersants, colored dyes, fluorescent dyes, etc. can be used as necessary.

[0036] (Crosslinking agent) A crosslinking agent for curing the adhesive of the thermal recording layer or other layers can be included in the thermal coloring coating liquid. This can improve the water resistance of the thermal recording layer. Examples of crosslinking agents include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxylates, dimethylolurea compounds, aziridine compounds, blocked isocyanate compounds; inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, potassium tetraborate; boric acid, trysterol borate, boron-based polymers, hydrazide compounds, glyoxylates, etc. These may be used individually or in combination of two or more. The amount of crosslinking agent used is preferably in the range of 0.1 to 10 parts by mass, and more preferably in the range of 1 to 10 parts by mass, per 100 parts by mass of the total solid content of the thermal coloring coating liquid. This can improve the water resistance of the thermal recording layer.

[0037] (Waxes) Examples of waxes include paraffin wax, carnauba wax, microcrystalline wax, polyolefin wax, polyethylene wax, and other waxes; for example, higher fatty acid amides such as stearic acid amide and ethylenebisstearic acid amide, higher fatty acid esters, and their derivatives.

[0038] (Metallic soaps) Examples of metallic soaps include polyvalent metal salts of higher fatty acids, such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate. Furthermore, if necessary, various auxiliary agents such as oil repellents, defoamers, and viscosity modifiers can be added to the heat-sensitive coloring coating liquid, as long as they do not impair the effects of the present invention.

[0039] Thermosensitive color-developing printing ink generally uses water and alcohol as solvents, and a leuco dye, a developer, and if necessary, an adhesive, a sensitizer, and a preservative improver are dispersed together or separately by various stirring and wet grinding machines such as a ball mill, a coball mill, an attritor, a vertical and a horizontal sand mill to obtain a dispersion liquid, and then a dispersion liquid obtained by dispersing so that the average particle size becomes 2 μm or less is used, and if necessary, an adhesive, an auxiliary agent, etc. are mixed to prepare it.

[0040] Using the thermosensitive color-developing coating liquid, a thermosensitive recording layer of a thermosensitive recording body can be formed on at least a part of one side or both sides of a support. The method for forming the thermosensitive recording layer is not particularly limited, and a printing method such as gravure printing is preferable.

[0041] [Protective layer] The protective layer can be formed on the thermosensitive recording layer by applying or printing using a coating liquid for the protective layer (including an aqueous coating liquid for the protective layer used for coating and a protective layer printing ink for the thermosensitive recording body used for printing or simply a protective layer printing ink). The coating amount (formation amount) of the protective layer is not particularly limited, and it is preferably about 0.3 to 15 g / m ２ and more preferably about 0.3 to 10 g / m ２ even more preferably about 0.3 to 8 g / m ２ and particularly preferably about 0.5 to 8 g / m ２ and very particularly preferably about 0.5 to 5 g / m ２ and even more preferably about this amount. In addition, the protective layer can be formed in two or more layers as necessary, and the composition and coating amount of each layer may be the same or different.

[0042] [Coating Liquid for Protective Layer] (Adhesive) The coating liquid for the protective layer in the present invention contains an adhesive. The adhesive contained in the protective layer is not particularly limited, and water-soluble or water-dispersible aqueous adhesives and solvent-based adhesives can be used. The adhesive can also be appropriately selected from those that can be used for thermal recording layers. Among these adhesives, various modified polyvinyl alcohols such as acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol, and polyvinyl acetal resins are more preferably used. The content of the adhesive is preferably 65% ​​by mass or more, and more preferably about 75 to 99% by mass, of the total solid content of the protective layer.

[0043] Polyvinyl acetal resin is particularly preferred as an adhesive. Polyvinyl acetal resin is a resin that can be produced by methods such as reacting polyvinyl alcohol with an aldehyde to form an acetal. The above aldehyde is not particularly limited and includes, for example, formaldehyde (including paraformaldehyde), acetaldehyde (including paraacetaldehyde), propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, glyoxal, glutaraldehyde, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, β-phenylpropionaldehyde, and the like.

[0044] Examples of polyvinyl acetal resins include polyvinyl butyral resins in which the acetal groups are butyral groups, and polyvinyl acetal acetal resins in which the acetal groups are acetal groups. The number average molecular weight of such polyvinyl acetal resins is preferably 15,000 to 140,000, more preferably 17,000 to 32,000, and even more preferably 17,000 to 27,000. In this invention, the number average molecular weight is the number average molecular weight analyzed by GPC (gel permeation chromatography).

[0045] (Slip-imparting agent) The protective coating liquid in the present invention contains at least one selected from the group consisting of microcrystalline wax and carnauba wax as a slip-imparting agent. This improves thermal head matching performance (stick resistance and head clogging suitability), particularly head clogging suitability during long-distance printing.

[0046] The content of at least one selected from the group consisting of microcrystalline wax and carnauba wax is not particularly limited, but is preferably about 1 to 20% by mass, more preferably about 1.0 to 10% by mass, and even more preferably about 3.0 to 7.0% by mass, of the total solid content of the protective layer. By setting it to 1% by mass or more, thermal head matching performance (stick resistance and head clump suitability) can be improved. By setting it to 20% by mass or less, head clump suitability during long-distance printing can be improved.

[0047] Other lubrication agents may be included as long as they do not impair the effects of the present invention. Examples of other lubrication agents include higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, paraffin oxide, polyethylene, polyethylene oxide, and waxes such as caster wax. The lubrication agents can be used individually or in combination of two or more.

[0048] (Pigments) The pigments contained in the protective layer are not particularly limited and include, for example, inorganic pigments such as amorphous silica, kaolin, clay, light calcium carbonate, heavy calcium carbonate, titanium dioxide, magnesium carbonate, aluminum hydroxide, colloidal silica, and synthetic layered mica, as well as plastic pigments such as urea-formaldehyde resin fillers.

[0049] As a pigment, light calcium carbonate with an average particle diameter of 2.0 μm or less is preferably used. The average particle diameter of the light calcium carbonate is preferably 1.5 μm or less, more preferably 1.2 μm or less. On the other hand, 0.05 μm or more is preferred. Here, the average particle diameter refers to the volume-based median diameter measured by one of the BET method, Sears method, or laser diffraction method. More simply, one may use an electron microscope to measure the particle diameter from the particle image (SEM image) and indicate the average value of 10 values.

[0050] The content of such light calcium carbonate with an average particle size of 2.0 μm or less is not particularly limited, but is preferably about 0.5 to 30% by mass, more preferably about 1.0 to 20% by mass, and even more preferably about 3.0 to 10% by mass, of the total solid content of the protective layer.

[0051] (Solvent) The protective coating liquid in the present invention may contain a solvent. Examples of such solvents include water, alcohol, cycloalkane, toluene, and methylcyclohexane, with solvents containing alcohol and cycloalkane being preferred. As for alcohols, alcohols with 5 or fewer carbon atoms are preferred, and examples of such alcohols with 5 or fewer carbon atoms include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and n-pentyl alcohol. Examples of cycloalkanes include cyclopentane, cyclohexane, cycloheptane, cyclocyclooctane, cyclononane, cyclodecane, methylcyclohexane, methylcyclooctane, dimethylcyclohexane, and ethylcyclohexane. By using alcohol as a solvent, the ink can be used for gravure printing.

[0052] Other components of the protective coating liquid may include, if necessary, silicone oil, crosslinking agents, and the like.

[0053] (Silicone oil) The protective coating liquid in the present invention may also contain silicone oil. This can improve the lubricity to the thermal head. The content of silicone oil is not particularly limited, but it is preferably about 0.1 to 10% by mass of the total solid content of the protective layer.

[0054] (Crosslinking agent) A crosslinking agent for curing the adhesive of the protective layer or other layers can be included in the protective layer coating liquid. This can improve the water resistance of the protective layer. Examples of crosslinking agents include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxylates, methylolurea compounds, aziridine compounds, blocked isocyanate compounds; inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, potassium tetraborate; boric acid, boric acid triester, boron-based polymers, hydrazide compounds, glyoxylates, etc. These may be used individually or in combination of two or more. The amount of crosslinking agent used is preferably in the range of 0.1 to 10 parts by mass, and more preferably in the range of 1 to 10 parts by mass, per 100 parts by mass of the total solid content of the protective layer coating liquid. This can improve the water resistance of the protective layer.

[0055] The protective layer printing ink of the present invention is generally prepared by mixing an alcohol and a cycloalkane as solvents with an adhesive, a lubrication agent, and optionally an auxiliary agent.

[0056] A protective layer can be formed on at least a portion of the thermal recording layer using a protective coating solution. The method for forming the protective layer is not particularly limited, but a printing method such as gravure printing is preferred.

[0057] [Undercoat layer] The thermal recording material of the present invention may optionally include an undercoat layer between the support and the thermal recording layer. The undercoat layer preferably contains an adhesive.

[0058] (Adhesives) Examples of adhesives include water-soluble polymer materials such as polyvinyl alcohol and its derivatives, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and their derivatives, as well as emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, and ethylene-vinyl acetate copolymer, or water-insoluble polymer latex such as styrene-butadiene copolymer and styrene-butadiene-acrylic copolymer. These can be preferably used on polyester films such as PET film and polyester resin laminated paper. Among these, it is preferable to use an adhesive containing latex. Examples of aqueous adhesives or solvent-based adhesives include chlorinated polyolefin resins. Chlorinated polyolefin resins can be preferably used with polyolefin films such as PP films, polyolefin synthetic paper, polyolefin resin laminated paper, paper such as glassine paper, and supports such as cellophane. The adhesive content can be selected from a wide range, but generally it is preferably about 10 to 70% by mass, and more preferably about 15 to 60% by mass, of the total solid content of the undercoat layer.

[0059] The adhesive preferably contains a binder resin with a glass transition temperature (Tg) of -10°C or lower. A glass transition temperature of -10°C or lower allows for improved image quality even in the low-energy range. A glass transition temperature of -30°C or lower is more preferable, as it further improves image quality in the low-energy range. On the other hand, a temperature of -40°C or higher is preferable because stickiness occurs below -50°C, which is undesirable.

[0060] The undercoat layer may contain at least one of the following as pigments: an oil-absorbing pigment with an oil absorption capacity of 70 ml / 100 g or more, particularly 80 to 150 ml / 100 g; organic hollow particles; and thermally expandable particles. Here, the above oil absorption capacity is determined according to the method of JIS K 5101.

[0061] Various oil-absorbing pigments can be used, but specific examples include inorganic pigments such as calcined kaolin, amorphous silica, light calcium carbonate, and talc. The average particle size of the primary particles of these oil-absorbing pigments is preferably about 0.01 to 5 μm, and particularly preferably about 0.02 to 3 μm. The amount of oil-absorbing pigment used can be selected from a wide range, but generally it is preferably about 20 to 80% by mass, and more preferably about 25 to 75% by mass, of the total solid content of the undercoat layer.

[0062] The undercoat layer is formed on the support by applying an undercoat coating solution, prepared by mixing an adhesive, pigment, and auxiliary agents with water as a medium, and then drying it. Alternatively, it can be formed by a printing method such as gravure printing, similar to the protective layer. The amount of undercoat coating solution applied is not particularly limited, but is 2 to 20 g / m² by dry mass. ２ A suitable degree is 2-12 g / m ２ A more moderate degree is preferable.

[0063] Examples of additives contained in the primer coating liquid include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts; waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester waxes; water-resistant agents such as hydrazide compounds, boric acid, dialdehyde starch, glyoxylates, and epoxy compounds; defoamers; coloring dyes; and fluorescent dyes.

[0064] [Heat seal layer and adhesive layer] The thermal recording body of the present invention may optionally include a heat seal layer and / or an adhesive layer on at least a portion of one or both sides of the support. Preferably, the heat seal layer and the adhesive layer are on the side of the support opposite to the thermal recording layer.

[0065] Examples of the heat seal layer in the present invention include a single-layer film composed of a single resin, and a single-layer or laminated film using multiple resins. Preferred examples of resins constituting the heat seal layer include polyolefin resins (especially polyethylene, polypropylene, etc.), polystyrene resins, polyester resins (especially polyethylene terephthalate resins), polyamide resins (especially nylon), and biodegradable resins.

[0066] Furthermore, polyethylene may be low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), or high-density polyethylene (HDPE).

[0067] Furthermore, the heat seal layer may be unstretched, or it may be uniaxially or biaxially stretched.

[0068] The thickness of the heat seal layer is not particularly limited, but is preferably about 10 to 70 μm, more preferably about 20 to 60 μm, and even more preferably about 30 to 50 μm.

[0069] The heat seal layer may contain additives such as fillers, antiblocking agents, antistatic agents, plasticizers, and oxidizing agents. These additives may be used individually or in combination of two or more.

[0070] The heat-seal layer may be formed by extruding and laminating a resin onto the support, or the support and the heat-seal layer may be bonded together using an adhesive. That is, there may be an adhesive layer containing an adhesive between the support and the heat-seal layer. Alternatively, there may be no heat-seal layer, and only an adhesive layer containing an adhesive may be present.

[0071] The adhesive used is not particularly limited and may be solvent-free, organic solvent-based, or water-based.

[0072] Examples of the main components of adhesives include (meth)acrylic acid ester copolymers, α-olefin copolymers, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyurethane, styrene-butadiene copolymers, polyvinyl chloride, epoxy resins, melamine resins, silicone resins, natural rubber, casein, and starch.

[0073] Furthermore, the heat seal layer and the support may be laminated after the adhesive is applied to the heat seal layer, or the support and the heat seal layer may be laminated after the adhesive is applied to the support, or the heat seal layer and the support may be laminated after the adhesive is applied to both the heat seal layer and the support, and there are no particular limitations.

[0074] The method for applying the adhesive can be appropriately selected from conventionally known methods and is not particularly limited, but examples include roll coaters, die coaters, and spray coaters.

[0075] The amount of adhesive to be applied is not particularly limited, but the amount applied after drying (coating amount) is preferably 0.5 g / m². ２ More preferably, 1.0 g / m ２ More preferably 1.5 g / m ２ The above applies, and preferably 10.0 g / m². ２ More preferably, 7.0 g / m ２ More preferably, 5.0 g / m ２ The following applies:

[0076] [Printed Layer] In this invention, a printed layer can be provided on the protective layer, between the thermal recording layer and the protective layer, between the support and the heat seal layer, and on at least one of the surfaces of the support opposite to the thermal recording layer. Printing inks used to form the printed layer include inks for relief printing, planographic printing, intaglio printing, stencil printing, etc., classified by printing plate. In addition, inks can be classified by drying method, such as penetration drying, evaporation drying, oxidative polymerization drying, and photopolymerization drying (ultraviolet curing type) inks. Printing methods such as flexographic printing, offset printing, gravure printing, and screen printing can be used to form the printed layer. Digital printing methods such as plateless on-demand printing and direct printing can also be used. The color tone of the printing ink is not particularly limited, but especially when thermal recording is performed on the printed layer, it is preferable that the optical density of the printed layer be lower than the optical density of the recording portion of the thermal recording layer. The printing pattern may be partial printing or full-surface solid printing, and it is preferable to have a background pattern with an optical density of about 0.1 to 0.6, or a fixed information pattern that does not overlap with the thermal recording. For example, when used as a top-seal lid material on which variable information such as product name, expiration date, and barcode is recorded using thermal imaging, it is preferable to partially print with white ink on the side opposite to the thermal recording layer of the support, which is the area behind the thermal recording. This can improve the readability of barcodes and the like.

[0077] [Thermal Recording Material] A thermal recording material can be manufactured by forming the above layers on a support. Any known coating method such as gravure printing, air knife method, blade method, gravure method, roll coater method, spray method, dip method, bar method, curtain method, slot die method, slide die method, or extrusion method may be used to form the above layers on the support. Gravure printing is preferred, and gravure printing is more preferred. In addition, each coating may be applied or printed one layer at a time and dried as necessary to form each layer, or the same coating may be applied or printed in two or more layers. Furthermore, simultaneous multilayer coating may be performed in which two or more layers are applied at the same time. In addition, after each layer has been formed, or at any stage after all layers have been formed, a smoothing treatment may be performed using a known method such as a supercalender or softcalender.

[0078] The method for recording an image on the thermal recording medium of the present invention is not particularly limited and can be appropriately selected depending on the purpose. Examples of image recording methods include a thermal head printer and laser light (e.g., carbon dioxide laser, UV laser, semiconductor laser light, YAG laser light, fiber laser light, solid-state laser light, dye laser light, etc.). The wavelength of the laser light used is not particularly limited and can be appropriately selected depending on the purpose.

[0079] The thermal recording material of the present invention can be used as a packaging material for food, pharmaceuticals, medical products, electronic components, etc. (for example, as packaging paper for pharmaceuticals). Furthermore, the thermal recording material of the present invention is suitably used in food applications, for example, as a label or lid material for transparent containers used for salads, prepared foods, etc., allowing for the confirmation of information such as raw materials related to the contents while observing the contents through the lid material. In addition, by using it as a lid material for top sealing, the application of thermal labels is unnecessary, improving the efficiency of packaging work and reducing the amount of plastic used.

[0080] The present invention will be described in more detail by reference to examples, but the present invention is not limited thereto. Unless otherwise specified, "parts" and "%" refer to "parts by mass" and "mass%", respectively. Particle sizes such as the average particle diameter were measured using a laser diffraction particle size distribution analyzer LB500 (manufactured by Horiba, Ltd.). Here, the average particle diameter is the median diameter (D50).

[0081] (Example 1) (1) Preparation of dye dispersion (Solution A) 30 parts of 3-di(n-butyl)amino-6-methyl-7-anilinofluorane, 13 parts of a 50% isopropyl alcohol solution of a vinylpyrrolidone-vinyl acetate copolymer with a vinylpyrrolidone / vinyl acetate ratio of 30 / 70, 44.5 parts of water, and 12.5 parts of isopropyl alcohol were mixed and ground using a sand mill (manufactured by AIMEX, sand grinder) until the average particle size was 0.15 μm to obtain dye dispersion (Solution A).

[0082] (2) Preparation of developer dispersion (Solution B) 30 parts of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, 13 parts of a 50% isopropyl alcohol solution of a vinylpyrrolidone-vinyl acetate copolymer with a vinylpyrrolidone / vinyl acetate ratio of 30 / 70, 44.5 parts of water, and 12.5 parts of isopropyl alcohol were mixed and ground using a sand mill (manufactured by AIMEX, sand grinder) until the average particle size was 0.15 μm to obtain the developer dispersion (Solution B).

[0083] (3) Preparation of heat-sensitive color-developing coating solution Ten parts of solution A, twenty parts of solution B, eight parts of a 20% aqueous dispersion of colloidal silica with an average particle size of 12 nm, 1.9 parts of water, and 1.9 parts of isopropyl alcohol were mixed and stirred to obtain a heat-sensitive color-developing coating solution.

[0084] (4) Preparation of protective coating solution 95.5 parts of polyvinyl acetal resin (product name: S-Lec KS-1, number average molecular weight: 27,000, manufactured by Sekisui Chemical Co., Ltd.), 4.5 parts of microcrystalline wax, 450 parts of isopropyl alcohol, and 450 parts of methylcyclohexane were mixed and stirred to obtain a protective coating solution.

[0085] (5) Preparation of thermal recording material Using a five-color gravure printing press, a thermal color coating solution was applied to one side of a 12 μm thick transparent PET film, with a dry coating amount of 4.0 g / m². ２ After printing, a coating amount of 1.0 g / m² is applied to the thermal recording layer after drying. ２ A protective coating was printed and rolled up to create the protective layer. Furthermore, 3 g / m of ester-based adhesive was applied to the other side opposite to the side printed with the heat-sensitive color coating using a dry lamination method. ２ A thermal recording material with a heat-seal layer was obtained by coating it and laminating it with a 30 μm thick low-density polyethylene film. The obtained thermal recording material was rolled into small windings using a slitter, and then cut into predetermined shapes to be used as a top-seal lid material, which allowed for sealing and airtight sealing of food packaging containers.

[0086] (Example 2) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of microcrystalline wax was changed from 4.5 parts to 1.5 parts in the preparation of the protective coating solution in Example 1.

[0087] (Example 3) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of microcrystalline wax was changed from 4.5 parts to 9.0 parts in the preparation of the protective coating solution in Example 1.

[0088] (Example 4) A thermal recording body was obtained in the same manner as in Example 1, except that the amount of microcrystalline wax was changed from 4.5 parts to 15.0 parts in the preparation of the protective coating solution in Example 1.

[0089] (Example 5) A thermal recording material was obtained in the same manner as in Example 1, except that N-[2-(3-phenylureido)phenyl]benzenesulfonamide (manufactured by Nippon Soda Co., Ltd.) was used instead of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in the preparation of the developer dispersion (Solution B) of Example 1.

[0090] (Example 6) A thermal recording material was obtained in the same manner as in Example 1, except that in the preparation of the developer dispersion (Solution B) of Example 1, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate (manufactured by Nippon Kayaku Co., Ltd.) was used instead of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea.

[0091] (Example 7) A thermal recording material was obtained in the same manner as in Example 1, except that in the preparation of the developer dispersion (Solution B) of Example 1, 5-(N-3-methylphenyl-sulfonamide)-(N',N''-bis-(3-methylphenyl)-isophthalic acid diamide (manufactured by Solenis) was used instead of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea.

[0092] (Example 8) A thermal recording material was obtained in the same manner as in Example 1, except that in the preparation of the developer dispersion (Solution B) of Example 1, 20 parts of 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate and 10 parts of 1,3-diphenylurea (manufactured by Xi'an Lanhao Adjuvants Factory) were used instead of 30 parts of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea.

[0093] (Example 9) A thermal recording body was obtained in the same manner as in Example 1, except that carnauba wax was used instead of microcrystalline wax in the preparation of the protective coating solution in Example 1.

[0094] (Example 10) A thermal recording body was obtained in the same manner as in Example 1, except that the protective coating liquid (6) described below was used in the protective coating liquid (4) of Example 1.

[0095] (6) Preparation of protective coating solution 92.5 parts of polyvinyl acetal resin (product name: S-Lec KS-1, number average molecular weight: 27,000, manufactured by Sekisui Chemical Co., Ltd.), 4.5 parts of microcrystalline wax, 6 parts of a 50% isopropyl alcohol solution of silicone oil, 450 parts of isopropyl alcohol, and 450 parts of methylcyclohexane were mixed and stirred to obtain a protective coating solution.

[0096] (Example 11) A thermal recording body was obtained in the same manner as in Example 1, except that the protective layer coating liquid (7) described below was used in Example 1 (4).

[0097] (7) Preparation of protective coating solution 82.5 parts of polyvinyl acetal resin (product name: S-Lec KS-1, number average molecular weight: 27,000, manufactured by Sekisui Chemical Co., Ltd.), 4.5 parts of microcrystalline wax, 6 parts of a 50% isopropyl alcohol solution of silicone oil, 50 parts of a 20% isopropyl alcohol dispersion of light calcium carbonate with an average particle size of 0.2 μm, 450 parts of isopropyl alcohol, and 450 parts of methylcyclohexane were mixed and stirred to obtain a protective coating solution.

[0098] (Example 12) In the preparation of the thermal recording material of Example 1, a thermal recording material was obtained in the same manner as in Example 1, except that a 25 μm thick OPP film was used instead of a 12 μm thick transparent PET film, and a 15 μm thick polyethylene film was laminated to the other side on which the thermal coloring coating liquid was printed by an extrusion lamination method.

[0099] (Example 13) In the preparation of the thermal recording material of Example 1, a thermal recording material was obtained in the same manner as in Example 1, except that the following support was used instead of a 12 μm thick transparent PET, and a thermal color-developing coating was printed on the first resin layer.

[0100] Support material (for preparing laminate 1): Glassine paper (product name: Graphan, manufactured by Oji F-Tex Co., Ltd., basis weight 35 g / m²) ２ Using a 31 μm thick, 72% haze, 1500 seconds of surface smoothing, and 250 mL of irregular freeness of disintegrated pulp, the single-sided coating amount (solid content) was 0.02 g / m² during the size press used in papermaking. ２ A polyethyleneimine solution (product name: Epomin P-1000, manufactured by Nippon Shokubai Co., Ltd.) was applied to obtain a base paper coated with an anchor coat layer.

[0101] Using the above-mentioned anchor coat layer coated paper, a resin mixture is applied as the first resin layer on the anchor coat layer coated surface. This mixture consists of polypropylene resin PH800C (manufactured by Sun Allomer Co., Ltd.) and low-density polyethylene LC607K (manufactured by Nippon Polyethylene Co., Ltd.) in a mass ratio of 80:20, with a basis weight of 10 g / m².２ The laminate 1 was obtained by extruding and laminating it to a thickness of 11 μm.

[0102] (Example 14) A thermal recording material was obtained in the same manner as in Example 1, except that a transparent PET material with a thickness of 45 μm was used instead of a transparent PET material with a thickness of 12 μm in the preparation of the thermal recording material of Example 1.

[0103] (Comparative Example 1) A thermal recording material was obtained in the same manner as in Example 1, except that 4,4'-bis(N-p-tolylsulfonylaminocarbonylamino)diphenylmethane (manufactured by Nagase ChemteX Corporation) was used instead of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea in the preparation of the developer dispersion (Solution B) of Example 1.

[0104] (Comparative Example 2) A thermal recording body was obtained in the same manner as in Example 1, except that 4.5 parts of zinc stearate (average particle size 1.2 μm) were used instead of 4.5 parts of microcrystalline wax in the preparation of the protective coating solution in Example 1.

[0105] (Comparative Example 3) A thermal recording body was obtained in the same manner as in Example 1, except that 1.5 parts of zinc stearate (average particle size 1.2 μm) was used instead of 4.5 parts of microcrystalline wax in the preparation of the protective coating solution of Example 1.

[0106] (Comparative Example 4) A thermal recording body was obtained in the same manner as in Example 1, except that 9 parts of zinc stearate (average particle size 1.2 μm) were used instead of 4.5 parts of microcrystalline wax in the preparation of the protective coating solution for Example 1.

[0107] The above examples and comparative examples were evaluated using the following method. The results are shown in Table 1.

[0108] [Recording Density] <Thermal Printer Printing> Using a thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording material was recorded with an applied energy of 0.225 mJ / dot. The resulting printed area was placed on PPC paper with a whiteness of 85% (JIS P 8148) and measured with a spectrophotometer (X-Rite 504, manufactured by X-Rite Co., Ltd.). (Evaluation) 1.40 or higher: Very good 1.25 or higher and less than 1.40: Good 1.10 or higher and less than 1.25: No practical problems Less than 1.10: Unusable

[0109] [Heat resistance of the surface] A thermal gradient tester (HG-100, manufactured by Toyo Seiki Co., Ltd.) was used, with a temperature of 110°C and a pressure of 1.5 kgf / cm². ２ The thermal recording material was pressed onto a hot plate for 5 seconds, and after pressing, each thermal recording material was placed on PPC paper with a whiteness of 85% (JIS P 8148). The color density of the pressed area was measured using a spectrophotometer (X-Rite 504, manufactured by X-Rite Co., Ltd.). (Evaluation) Less than 0.20: Excellent 0.20 or more and less than 0.30: No practical problems 0.30 or more: Unusable

[0110] [Plasticizer Resistance of Printed Materials] Using a thermal recording evaluation machine (product name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording material was recorded with an applied energy of 0.225 mJ / dot. The resulting printed materials were then triple-layered with plasticizer-containing wrap (product name: Hi-S Soft TMH, manufactured by Nippon Carbide Industries Co., Ltd.) on both sides of the printed material and left in a laboratory chamber at 40°C dry for 24 hours. The print density before and after the test was measured using a spectrophotometer (X-Rite 504, manufactured by X-Rite Co., Ltd.), and the retention rate of the print density was calculated using the following formula: Retention rate (%) = Print density after test / Print density before test × 100 (Evaluation) 90% or more: Excellent 70% to less than 90%: No practical problems Less than 70%: Unusable

[0111] [Stick Resistance] Using a label printer (Lesprit V-ex, manufactured by Sato Corporation), the degree of sticking and printing noise were subjectively evaluated when printing with 4ips-1A, 75% black coverage, and under conditions of 23°C and 50% RH. (Evaluation) A: No sticking occurred, and there was almost no printing noise. B: A small amount of sticking occurred, but there was no printing noise. C: Sticking occurred frequently, and the printing noise was also high.

[0112] [Head Dust Suitability] Using a label printer (Lesprit V-ex, manufactured by Sato Corporation), the heating element of the thermal head was observed using a stereomicroscope (VH-Z100UR, manufactured by Keyence Corporation) after printing 5m to 1,000m at a print density of 4ips-1A and 100% solid black, and was evaluated by sensory evaluation. (Evaluation) AA: No head dust adhesion A: Slight head dust adhesion (no practical problem) B: Some head dust adhesion (no practical problem) C: Heavy head dust adhesion

[0113]

Claims

1. A thermal recording body having, in this order, a thermal recording layer containing a leuco dye and a color developer, an adhesive and a protective layer containing a lubricity agent on a support, wherein the thermal recording layer contains at least one selected from the group consisting of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea as a color developer, and the protective layer contains at least one selected from the group consisting of microcrystalline wax and carnauba wax as a lubricity agent.

2. The thermal recording body according to claim 1, wherein the content of at least one selected from the group consisting of microcrystalline wax and carnauba wax is 1 to 20% by mass of the total solid content of the protective layer.

3. The thermal recording material according to claim 1 or 2, wherein the content of at least one selected from the group consisting of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, and 1,3-diphenylurea is 1.0 to 70.0% by mass of the total solid content of the thermal recording layer.

4. The thermal recording body according to claim 1 or 2, wherein the protective layer contains polyvinyl acetal resin as an adhesive.

5. The thermal recording body according to claim 1 or 2, wherein the protective layer further contains silicone oil.

6. The thermal recording body according to claim 1 or 2, wherein the protective layer further contains light calcium carbonate with an average particle size of 2.0 μm or less.

7. The thermal recording body according to claim 1 or 2, wherein the support is a transparent film.

8. The thermal recording body according to claim 1 or 2, wherein the support is a translucent or transparent support made of glassine paper or resin laminate paper.

9. The thermal recording body according to claim 1 or 2, having a heat-seal layer on at least a portion of one or both sides of the support.

10. The thermal recording body according to claim 1 or 2, wherein the thermal recording layer contains a vinylpyrrolidone-vinyl acetate copolymer as an adhesive.

11. The thermal recording body according to claim 1 or 2, wherein the thermal recording layer further contains colloidal silica with an average particle size of 45 nm or less.

12. The thermal recording body according to claim 1 or 2, further comprising an undercoat layer between the support and the thermal recording layer.

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