JP2023163992A - Heat-sensitive recording material - Google Patents

Abstract

To provide a heat-sensitive recording material which exhibits omission resistance and defect resistance for suppressing the occurrence of omission and defects of a heat-sensitive recording layer and blocking resistance and adhesion worsening resistance for preventing blocking and adhesion worsening of the heat-sensitive recording material.SOLUTION: This heat-sensitive recording material contains a (meth)acrylamide copolymer and has at least a heat-sensitive recording layer, a support, and a re-wettable paste layer in this order. The heat-sensitive recording layer has a composition including mineral oil and hydrophobic silica and a core shell structure.SELECTED DRAWING: None

Description

The present invention relates to a heat-sensitive recording material having a heat-sensitive recording layer on the surface of the support and a rewettable glue layer on the back surface of the support.

Heat-sensitive recording materials having sequentially at least a rewettable glue layer containing a rewettable glue and a sulfone-modified polyvinyl alcohol, a support, and a heatsensitive recording layer containing a leuco dye and a coloring agent are already known ( For example, see Patent Document 1). The heat-sensitive recording material as described in Patent Document 1 has excellent adhesive strength when the rewettable glue layer is rewetted and adhesive strength of the rewettable glue layer to the adherend. On the other hand, regarding the heat-sensitive recording material as described in Patent Document 1, an antifoaming agent is only described as an example of an auxiliary agent in the coating liquid for the heat-sensitive recording layer.

Regarding the heat-sensitive recording material and antifoaming agent, for example, the main components are a leuco dye and a phenolic compound as a color developer, and a non-cellulose ether water-soluble polymer compound and hydroxyethyl methylcellulose are used as a binder. A heat-sensitive recording material characterized in that 0.005 parts by weight or more and 1.0 parts by weight or less of an antifoaming agent mainly composed of mineral oil and a nonionic activator are added to 100 parts by weight of the hydroxyethyl methylcellulose. It is publicly known (for example, see Patent Document 2).

Japanese Patent Application Publication No. 11-085030 Japanese Unexamined Patent Publication No. 58-142892

The heat-sensitive recording layer usually contains water containing an electron-donating dye, a dye precursor, a color-forming dye such as a basic dye and a leuco dye, a color developer also called an electron-accepting compound or a coloring agent, and a binder. It can be obtained by preparing a dispersion by dispersing it in a medium such as, and coating and drying the dispersion on a support such as paper. However, since color developers have poor dispersibility, a dispersant is used for dispersion. Dispersions tend to foam under the influence of dispersants and binders. Therefore, an antifoaming agent as described in Patent Document 2 is used.
In a dispersion containing an antifoaming agent, the adhesion to the support and undercoat layer decreases when the dispersion is coated and dried on the support and undercoat layer. As a result, a heat-sensitive recording layer obtained by applying a dispersion containing an antifoaming agent to a support, an undercoat layer, etc. and drying the same may cause chipping from the support, undercoat layer, etc. Furthermore, in a dispersion containing an antifoaming agent, the antifoaming agent deteriorates the compatibility with the color-forming dye, color developer, and binder. As a result, a heat-sensitive recording layer obtained by coating and drying a dispersion containing an antifoaming agent on a support, an undercoat layer, etc. may have defects on the surface of the heat-sensitive recording layer.

The thermosensitive recording material as described in Patent Document 1 is suitable for use in logistics labels, for example. Logistics labels are usually stored in the form of paper rolls or loaded inside recording equipment. A heat-sensitive recording material having a heat-sensitive recording layer on the surface of the support and a re-wettable glue layer on the back side of the support is in the form of a roll paper, in which the heat-sensitive recording layer and the re-wettable glue layer are in contact with each other. become. Generally, chloroprene rubbers, polyvinyl alcohols, starches, vinyl acetate copolymers, dextrin, gum arabic, glue, polyacrylamide, and the like are used as the glue for the rewettable glue layer.
A thermosensitive recording material having a thermosensitive recording layer on the front side of the support and a rewettable glue layer on the back side of the support is sensitive to environmental and situational conditions, such as high humidity environments and unexpected moisture absorption. The rewettable adhesive layer may become sticky. As a result, the thermosensitive recording material develops blocking. Therefore, it is necessary to reduce such blocking. Furthermore, when the heat-sensitive recording material is in the form of a roll paper, in the heat-sensitive recording layer obtained by coating and drying a dispersion containing an antifoaming agent, the antifoaming agent component migrates to the rewettable glue layer. As a result, the tackiness of the rewettable glue layer may deteriorate.

From the above, the objects of the present invention are chipping resistance and defect resistance that suppress the occurrence of chipping and defects in a heat-sensitive recording layer, and blocking resistance and adhesion deterioration resistance that prevent blocking and adhesion deterioration of a heat-sensitive recording material. An object of the present invention is to provide a heat-sensitive recording material having the following properties.

The present inventors have intensively studied the combination of a binder and a composition having antifoaming properties, and have discovered the following invention. The above problem is solved by the following invention.
[1] It has at least a heat-sensitive recording layer, a support, and a rewetting adhesive layer in this order, and the heat-sensitive recording layer has a composition containing mineral oil and hydrophobic silica and a core-shell structure (Meta) A heat-sensitive recording material containing an acrylamide copolymer.

According to the present invention, a heat-sensitive recording material has chipping resistance and defect resistance that suppress the occurrence of chipping and defects in the heat-sensitive recording layer, and blocking resistance and adhesion deterioration resistance that prevent blocking and adhesion deterioration of the heat-sensitive recording material. can be provided.

Hereinafter, the content of the present invention will be specifically explained.

The heat-sensitive recording material has at least a heat-sensitive recording layer, a support, and a rewettable glue layer in this order. That is, the heat-sensitive recording material has a support, a heat-sensitive recording layer on the surface of the support, and a rewetting adhesive layer on the back surface of the support. Here, the front and back surfaces of the support are convenient descriptions to distinguish between the surfaces of the support, and do not refer to the front and back surfaces that depend on physical or chemical differences between the supports. .

In some embodiments, the heat-sensitive recording material has a subbing layer between the support and the heat-sensitive recording layer and/or between the support and the rewettable glue layer. This is because the support can be protected from heat and moisture, or the adhesion of the heat-sensitive recording layer can be improved. The undercoat layer is conventionally known in the field of heat-sensitive recording materials and includes a pigment and a binder.

The pigments contained in the undercoat layer are conventionally known in the coated paper field. Pigments include, for example, diatomaceous earth, talc, clay, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, titanium dioxide, zinc oxide, silicon oxide, amorphous calcium silicate, silica, colloidal silica. , colloidal alumina, calcium sulfate, barium sulfate, zinc sulfide, zinc carbonate, satin white, aluminum silicate, calcium silicate, magnesium silicate, alumina, aluminum hydroxide, magnesium hydroxide, lithopone, zeolite, and hydrated halloysite. .

The binder is a water-soluble or water-dispersible resin conventionally known in the coated paper field. Binders include, for example, polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol and modified polyvinyl alcohol, cellulose derivatives such as polyvinyl acetal, polyvinylpyrrolidone, hydroxymethylcellulose, hydroxypropylcellulose, methylcellulose, ethylcellulose and carboxymethylcellulose. , proteins such as gelatin and casein, starches such as sodium alginate, starch and its modified products, poly(meth)acrylic acid and its salts, poly(meth)acrylic ester, (meth)acrylic acid amide acrylic ester copolymer Various copolymers of poly(meth)acrylic acid esters such as polymers, polyacrylamides, polymaleic acids and their salts, styrene (anhydrous) maleic acid copolymers, isobutylene (anhydrous) maleic acid copolymers, and their salts, etc. Various (anhydrous) maleic acid copolymers, acrylamide acrylic ester copolymers, acrylamide acrylic ester (meth)acrylic acid copolymers, ethylene maleic anhydride copolymers and their salts, styrene maleic anhydride copolymers, and Water-soluble resins such as salts thereof, isobutylene maleic anhydride copolymers and salts thereof, styrene isobutylene maleic anhydride copolymers and salts thereof, polyvinyl acetate, polyurethane, styrene butadiene copolymers, vinyl chloride vinyl acetate copolymers , ethylene-vinyl acetate copolymer, styrene-butadiene (meth)acrylic ester copolymer, as well as styrene-butadiene (meth)acrylonitrile, acrylonitrile-butadiene-styrene copolymer, vinyl acetate/(meth)acrylic ester copolymer, etc. Dispersible resins can be mentioned.

Furthermore, the undercoat layer can contain various conventionally known additives, if necessary. Examples of additives include dispersants, surfactants, colored dyes, fluorescent dyes, lubricants, waxes, antifoaming agents, ultraviolet absorbers, curing agents, and crosslinking agents.

In some embodiments, the heat-sensitive recording material has a protective layer on the outside of the heat-sensitive recording layer with respect to the support. The reason for this is that the blocking resistance of the heat-sensitive recording material can be improved or the heat-sensitive recording layer can be protected. The protective layer is conventionally known in the field of heat-sensitive recording materials, and contains a binder, and if necessary, a pigment and various additives. Examples of additives include surfactants, colored dyes, fluorescent dyes, lubricants, antifoaming agents, ultraviolet absorbers, curing agents, and crosslinking agents. The binder and pigment are the same as those exemplified for the undercoat layer, and will not be described here. In some embodiments, the protective layer also includes waxes and/or fatty acid metal salts. The reason for this is that blocking resistance can be further improved.

The undercoat layer and the protective layer can be obtained by coating a coating solution containing each material using a conventionally known coating device and drying using a conventionally known drying device.

The support is conventionally known in the field of heat-sensitive recording materials. Supports include, for example, paper such as coated paper and uncoated paper, synthetic resin laminated paper, synthetic paper, various nonwoven fabrics, woven fabrics, synthetic resin films, metal foils, ceramic paper, glass plates, and combinations thereof. Composites or laminates may be mentioned.
In some embodiments, the support is paper, such as coated and uncoated paper, containing cellulose derived from wood and/or non-wood sources. The reason for this is that it has less burden on the environment than other supports.

The heat-sensitive recording layer of the heat-sensitive recording material is a color-forming layer containing a color-forming dye, and is conventionally known in the field of heat-sensitive recording materials. In some embodiments, the heat-sensitive recording layer contains a dye precursor that is a color-forming dye, a color developer, a pigment, and a binder. Further, in some embodiments, the heat-sensitive recording layer contains a sensitizer and various additives as necessary.

The dye precursor is conventionally known in the field of heat-sensitive recording materials, and includes, for example, triaryl, diphenylmethane, triphenylmethane, thiazine, phenothiazine, spiro, spiropyran, lactam, fluoran, and auramine dye precursors. and leuco derivatives such as indolinophthalide series. Each dye precursor has a unique color tone, and examples of the color tone include black, red, magenta, orange, blue, green, and yellow. In some embodiments, the dye precursor is one or more selected from the group consisting of these.

Examples of dye precursors that provide black coloring include 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, and 3-(N-isoamyl). -N-ethylamino)-7-(o-chloroanilino)fluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-2- Tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-anilinofluoran Oran, 3-di-n-amylamino-6-methyl-7-anilinofluorane, 3-(N-isoamyl-N-ethyl)amino-6-methyl-7-anilinofluorane, 3-(N- n-hexyl-N-ethyl)amino-6-methyl-7-anilinofluorane, 3-[N-(3-ethoxypropyl)-N-ethylamino)-6-methyl-7-anilinofluorane, 3-[N-(3-ethoxypropyl)-N-methyl]amino-6-methyl-7-anilinofluorane, 3-diethylamino-7-(2-chloroanilino)fluorane, 3-di-n-butylamino -7-(2-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(2,6-dimethylanilino)fluoran, 3-diethylamino- 6-Methyl-7-(2,4-dimethylanilino)fluorane, 2,4-dimethyl-6-(4-dimethylaminoanilino)fluorane, and 3-(N-cyclohexyl-N-methyl)amino-6 -methyl-7-anilinofluorane and the like.
Examples of dye precursors that develop a red color include 3,6-bis(diethylamino)fluoran-γ-anilinolactam, 3,6-bis(diethylamino)fluoran-γ-(p-nitro)anilinolactam, 3,6-bis(diethylamino)fluorane-γ-(o-chloro)anilinolactam, 3-dimethylamino-7-bromofluorane, 3-diethylaminofluorane, 3-diethylamino-6-methylfluorane, 3- Diethylamino-7-methylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-bromofluorane, 3-diethylamino-7,8-benzofluorane, 3-diethylamino-6,8-dimethylfluoran oran, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-tert-butylfluorane, 3-(N-ethyl-N-tolyl)amino-7-methylfluorane, 3-( N-ethyl-N-tolyl)amino-7-ethylfluorane, 3-(N-ethyl-N-isobutyl)amino-6-methyl-7-chlorofluorane, and 3-(N-ethyl-N-isoamyl) )Amino-7,8-benzofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-di-n-butylamino-6-methyl-7-bromofluorane, 3-di-n-butylamino- 7,8-benzofluorane, 3-tolylamino-7-methylfluorane, 3-tolylamino-7-ethylfluorane, 2-(N-acetylanilino)-3-methyl-6-di-n-butylamino Fluoran, 2-(N-propionylanilino)-3-methyl-6-di-n-butylaminofluoran, 2-(N-benzoylanilino)-3-methyl-6-di-n-butylamino Fluoran, 2-(N-carbobutoxyanilino)-3-methyl-6-di-n-butylaminofluorane, 2-(N-formylanilino)-3-methyl-6-di-n-butylaminofluoran oran, 2-(N-benzylanilino)-3-methyl-6-di-n-butylaminofluorane, 2-(N-allylanilino)-3-methyl-6-di-n-butylaminofluorane, and 2-(N-methylanilino)-3-methyl-6-di-n-butylaminofluorane, 3-diethylamino-7-phenoxyfluorane, 3-(N-ethyl-N-isoamyl)amino-7-phenoxy Fluoran, 3,3'-bis(1-n-butyl-2-methylindol-3-yl)phthalide, 3,3'-bis(1-ethyl-2-methylindol-3-yl)phthalide, 3 ,3'-bis(1-n-octyl-2-methylindol-3-yl)phthalide, 7-(N-ethyl-N-isoamylamino)-3-methyl-1-phenylspiro[(1,4- dihydrochromeno[2,3-c]pyrazole)-4,3'-phthalide], 7-(N-ethyl-N-isoamylamino)-3-methyl-1-p-methylphenylspiro[(1,4 -dihydrochromeno[2,3-c]pyrazole)-4,3'-phthalide], and 7-(N-ethyl-Nn-hexylamino)-3-methyl-1-phenylspiro[(1, Examples include 4-dihydrochromeno[2,3-c]pyrazole)-4,3'-phthalide.
Examples of dye precursors that give blue coloring include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-methylphenyl)-3-(4- dimethylaminophenyl)-6-dimethylaminophthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)phthalide, 3-(1-ethyl-2-methylindole) -3-yl)-3-(2-methyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-n-hexyloxy-4-diethylaminophenyl)-4-azaphthalide, and 3,6-bis Examples include (diphenylamino)fluoran.
Examples of dye precursors that give green coloring include 3-(N-ethyl-Nn-hexyl)amino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,3- Bis(4-diethylamino-2-ethoxyphenyl)-4-azaphthalide, 3-(N-ethyl-N-p-tolyl)amino-7-(N-phenyl-N-methylamino)fluoran, 3-[p- Examples include (p-anilinoanilino)anilino]-6-methyl-7-chlorofluorane and 3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide. can.
Examples of dye precursors that give a yellowish color include 3,6-dimethoxyfluorane and 1-(4-n-dodecyloxy-3-methoxyphenyl)-2-(2-quinolyl)ethylene. be able to.

The color developer is conventionally known in the field of heat-sensitive recording materials, and is a material that has the property of liquefying or dissolving with an increase in temperature and causing the dye precursor to develop color when it comes into contact with the dye precursor. . Examples of the color developer include organic acid compounds such as phenolic compounds, aromatic carboxylic acid compounds, and polyvalent metal salts of these compounds. The color developer can be present in composite microparticles or microcapsules. Further, the color developer can be present in the form of solid dispersed fine particles.

Examples of color developers include bis(3-allyl-4-hydroxyphenyl)sulfone, 3-(3-tosylureido)phenyl-p-toluenesulfonate, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxy Diphenylsulfone, 4-hydroxy-4'-propoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-allyloxydiphenylsulfone, 4-hydroxy-4'-octyloxydiphenylsulfone, 4-hydroxy-4'-dodecyloxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 3,4-dihydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-benzenesulfonyloxydiphenylsulfone, 2,4-bis(phenylsulfonyl)phenol, p-phenylphenol, p-hydroxyacetophenone, 1,1-bis(p-hydroxyphenyl)propane, 1,1-bis(p-hydroxyphenyl)pentane, 1,1 -bis(p-hydroxyphenyl)hexane, 1,1-bis(p-hydroxyphenyl)cyclohexane, 2,2-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)hexane, 1 , 1-bis(p-hydroxyphenyl)-2-ethylhexane, 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 1,1-bis(p-hydroxyphenyl)-1-phenylethane, 1,3-bis[2-(p-hydroxyphenyl)-2-propyl]benzene, 1,3-bis[2-(3,4-dihydroxyphenyl)-2-propyl]benzene, 1,4-bis[ 2-(p-hydroxyphenyl)-2-propyl]benzene, 4,4'-dihydroxydiphenyl ether, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfide, 2,2-bis(4-hydroxyphenyl) Methyl acetate, 2,2-bis(4-hydroxyphenyl)butyl acetate, 4-[4-(4-{4-[4-(isopropoxy)phenylsulfonyl]phenoxy}butoxy)phenylsulfonyl]phenol, 4,4 '-[oxybis(ethyleneoxy-p-phenylenesulfonyl)]diphenol, 4,4'-thiobis(2-tert-butyl-5-methylphenol), dimethyl 4-hydroxyphthalate, benzyl 4-hydroxybenzoate, Methyl 4-hydroxybenzoate, benzyl gallate, stearyl gallate, salicylanilide, 5-chlorosalicylanilide, salicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-bis(α-methylbenzyl)salicylic acid, 4-[2'-(4-methoxyphenoxy)ethyloxy]salicylic acid, 3-(octyloxycarbonylamino)salicylic acid or metal salts of these salicylic acid derivatives, N-(4-hydroxyphenyl)-p-toluenesulfonamide, N- (4-Hydroxyphenyl)benzenesulfonamide, N-(4-hydroxyphenyl)-1-naphthalenesulfonamide, N-(4-hydroxyphenyl)-2-naphthalenesulfonamide, N-(4-hydroxynaphthyl)-p -Toluenesulfonamide, N-(4-hydroxynaphthyl)benzenesulfonamide, N-(4-hydroxynaphthyl)-1-naphthalenesulfonamide, N-(4-hydroxynaphthyl)-2-naphthalenesulfonamide, N-( 3-hydroxyphenyl)-p-toluenesulfonamide, N-(3-hydroxyphenyl)benzenesulfonamide, N-(3-hydroxyphenyl)-1-naphthalenesulfonamide, N-(3-hydroxyphenyl)-2- Naphthalenesulfonamide, 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, N-(2- {[(4-methylphenyl)carbamoyl]amino}phenyl)benzenesulfonamide, 4-methyl-N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide, 4-methyl-N-(2-{ [(4-methylphenyl)carbamoyl]amino}phenyl)benzenesulfonamide, N-butylbutyl-4-[3-(p-toluenesulfonyl)ureido]benzoate, 3,3'-(4,4'-methylene diphenyl) Bis(ureido p-trisulfone), bis{3-[3'-(p-toluenesulfonyl)ureido]benzoate}, 1,5-(3-oxopentylene)bis{3'-[3'-(p -toluenesulfonyl)ureido]benzoate}, and derivatives of N-phenylsulfonyl-N'-phenylurea.
In some embodiments, the color developer is one or more selected from the group consisting of these.

The pigment and binder contained in the heat-sensitive recording layer are the same as those exemplified for the undercoat layer, and their explanation will be omitted here.

The sensitizer is a compound that is conventionally known in the field of heat-sensitive recording materials, such as a heat-soluble component with a low melting point, and improves the color development of the heat-sensitive recording material. Sensitizers include, for example, diphenylsulfone, stearic acid monoamide, N-hydroxymethyl stearic acid amide, N-stearyl stearic acid amide, ethylene bis stearic acid amide, methylene bis stearic acid amide, methylol stearic acid amide, N-stearylurea. , benzyl-2-naphthyl ether, p-toluenesulfonamide, m-terphenyl, 4-benzylbiphenyl, 2,2'-bis(4-methoxyphenoxy) diethyl ether, α,α'-diphenoxy-o-xylene, Bis(4-methoxyphenyl) ether, diphenyl adipate, dibenzyl oxalate, bis(4-methylbenzyl) oxalate, bis(4-chlorobenzyl) oxalate, dimethyl terephthalate, dibenzyl terephthalate, benzenesulfonic acid phenyl ester, Examples include bis(4-allyloxyphenyl)sulfone, 1,2-bis(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 4-acetylacetophenone, acetoacetic anilides, and fatty acid anilides. can.
In some embodiments, the sensitizer is one or more selected from the group consisting of these.

The additives that the heat-sensitive recording layer contains as necessary are conventionally known additives, such as dispersants, surfactants, colored dyes, fluorescent dyes, lubricants, antifoaming agents, ultraviolet absorbers, curing agents, and Examples include crosslinking agents. Further, as the additive, for example, a core-shell structure copolymer can be mentioned as a resin used in combination with the binder.

The heat-sensitive recording layer contains a composition containing mineral oil and hydrophobic silica, and a (meth)acrylamide copolymer having a core-shell structure.

A composition containing mineral oil and hydrophobic silica is, for example, a type of oil-based antifoaming agent that uses mineral oil as a carrier component (solvent) to increase the diffusivity of the antifoaming component (hydrophobic silica). This antifoaming agent is a composition containing hydrophobic silica and mineral oil. Compositions containing mineral oil and hydrophobic silica are commercially available from, for example, Adeka, Sannopco, and Asahi Kasei Wacker Silicone.
Mineral oils are conventionally known in the field of oil agents, and include mineral oil, vaseline, paraffin, liquid paraffin, and the like. Mineral oil is liquid mineral oil or solid mineral oil (wax). In some embodiments, the mineral oil is one or more selected from the group consisting of these.
Hydrophobic silica is conventionally known in the paint field, and includes two methods: forming an ester by reacting the silanol groups on the silica surface in a silica sol with a higher alcohol, and preparing a silica hydrogel by hydrolyzing tetraethylsilicic acid. , a method of hydrothermally treating this at 100°C in water adjusted to pH 11 with sodium hydroxide, a method of reacting a silica hydrogel with a methoxysilane coupling agent, a method of reacting it with an alkylchlorosilane or an alkoxychlorosilane, a cationic interface Silica with a hydrophobic surface that can be obtained by a method of producing hydrophobic organocolloidal silica using a dehydration reaction from an activator and anionic colloidal silica, or a method of treating silica and various silicone oils at high temperatures. It is.

In some embodiments, the content of the composition containing mineral oil and hydrophobic silica in the heat-sensitive recording layer is 0.1% by mass or more and 0.4% by mass or less based on the total solid content forming the heat-sensitive recording layer. It is. The reason for this is that the blocking resistance and/or the resistance to deterioration of adhesion of the heat-sensitive recording material are improved.

A (meth)acrylamide copolymer having a core-shell structure is produced by copolymerizing (meth)acrylamide, or (meth)acrylamide and a monomer copolymerizable with (meth)acrylamide in the presence of a seed emulsion serving as a core particle. It is obtained by polymerization. A (meth)acrylamide copolymer having a core-shell structure is commercially available from, for example, Mitsui Chemicals.
The seed emulsion serving as the core particle is a conventionally known polymer, such as (meth)acrylic acid ester type, styrene butadiene type, styrene (meth)acrylic acid ester type, (meth)acrylic acid ester butadiene type, ( Examples include meth)acrylonitrile, (meth)acrylonitrile butadiene, vinyl chloride, and vinyl acetate.
Monomers copolymerizable with (meth)acrylamide include, for example, ethylene, propylene, (meth)acrylic acid, itaconic acid, maleic anhydride, fumaric acid, unsaturated carboxylic acids such as crotonic acid, styrene, α-methyl Aromatic vinyls such as styrene and divinylbenzene, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid esters such as 2-hydroxypropyl (meth)acrylate, 2-aminoethyl (meth)acrylate, 2-(N-methylamino)ethyl (meth)acrylate, and glycidyl (meth)acrylate; Examples include N-substituted unsaturated carboxylic acid amides such as N-methylol(meth)acrylic acid amide, vinyl acetate, vinyl esters, and nitrile group-containing monomers such as (meth)acrylonitrile.

In some embodiments, the (meth)acrylamide copolymers having a core-shell structure include acrylonitrile [core]/(meth)acrylamide [shell] copolymers and acrylonitrile [core]/styrene (meth)acrylamide copolymers [ It is a (meth)acrylamide copolymer having a core-shell structure such as [shell]. The reason for this is that chipping resistance, defect resistance, and/or blocking resistance of the heat-sensitive recording material are improved.

In some embodiments, the content of the (meth)acrylamide copolymer having a core-shell structure in the thermosensitive recording layer is 5% by mass or more and 35% by mass or less based on the total solid content forming the thermosensitive recording layer. The reason for this is that the chipping resistance and/or defect resistance of the heat-sensitive recording material is improved.

Since the heat-sensitive recording layer contains a composition containing mineral oil and hydrophobic silica and a (meth)acrylamide copolymer having a core-shell structure, the coating liquid for forming the heat-sensitive recording layer contains mineral oil and hydrophobic silica. Since it contains a composition containing silica and a (meth)acrylamide copolymer having a core-shell structure, the coating liquid for forming the heat-sensitive recording layer is effectively defoamed, suppressing the occurrence of defects in the heat-sensitive recording layer. . Furthermore, the combination of a composition containing mineral oil and hydrophobic silica and a (meth)acrylamide copolymer having a core-shell structure does not inhibit adhesion to the support, thereby suppressing the occurrence of chipping of the heat-sensitive recording layer.
Furthermore, even in a heat-sensitive recording material having a rewettable adhesive layer on the back side, the combination of a composition containing mineral oil and hydrophobic silica and a (meth)acrylamide copolymer having a core-shell structure can improve blocking resistance and It can provide resistance to deterioration of adhesion.

In the heat-sensitive recording material, the heat-sensitive recording layer can be provided on the support or on the undercoat layer by a conventionally known method. For example, the heat-sensitive recording layer is coated with a dispersion for forming the heat-sensitive recording layer containing a dye precursor, a color developer, a pigment, a binder, and if necessary a sensitizer and various additives. It can be obtained by coating a support or an undercoat layer using a drying device and drying device and drying.
Examples of the coating device include air knife coaters, various blade coaters, various bar coaters, various curtain coaters, and various roll coaters. Coating devices include methods using various printing methods such as planography, letterpress, intaglio, flexo, gravure, and screen.
Examples of the drying device include hot air dryers such as a straight tunnel dryer, an arch dryer, an air loop dryer, and a sine curve air float dryer, an infrared heating dryer, and a dryer using microwaves.

The rewetting adhesive layer contains as a main component a sizing agent that exhibits adhesive properties when wetted. The sizing agent used in the rewettable sizing layer is conventionally known in the sizing field. Sizing agents include, for example, chloroprene rubbers, polyvinyl alcohols, starches, vinyl acetate copolymers such as vinyl acetate acrylate copolymers and vinyl acetate methacrylate copolymers, dextrin, gum arabic, glue, and polyacrylamide. The sizing agent is one or more types selected from the group consisting of these.
In some embodiments, the sizing agent is one or more selected from the group consisting of polyvinyl alcohols and starches. The reason for this is that blocking resistance is improved due to the relationship between the rewetting adhesive layer and the heat-sensitive recording layer in contact with it.

The rewettable adhesive layer can contain various auxiliary agents in addition to the adhesive, as long as the properties of the adhesive are not impaired. Examples of the auxiliary agents include pigments, antioxidants, ultraviolet absorbers, dyes, antibacterial agents, fungicides, fragrances, and flame retardants.

In the heat-sensitive recording material, the rewettable adhesive layer can be provided on the support by a conventionally known method. For example, the rewettable adhesive layer is prepared by supporting a coating solution for forming the rewetting adhesive layer containing a sizing agent and various auxiliary agents as necessary using a conventionally known coating device and drying device. It can be obtained by applying it to the body and drying it. The coating device and drying device are the same as those for the heat-sensitive recording layer, and their explanation will be omitted here.

The undercoat layer, heat-sensitive recording layer, protective layer and/or rewettable glue layer can be calendered. Calendering can be accomplished using calendering equipment conventionally known in the papermaking art. Examples of calendering include machine calenders, soft nip calenders, super calenders, multi-stage calenders, multi-nip calenders, and the like.

The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way. In addition, in the examples, mass % and mass parts represent the dry solid content or the substantial component amount. The coating amount represents the dry solid content.

<Example 1>
(Support)
As a support, high-quality paper containing pulp, filler, sizing agent, and paper strength agent and having a basis weight of 60 g/m ² was used. The high-quality paper used as the support had a Beck smoothness of 60 seconds on both the front and back surfaces and an ash content of 10% by mass.

(Coating liquid for forming a heat-sensitive recording layer)
A dye precursor dispersion, a color developer and sensitizer dispersion, and a pigment dispersion were each prepared using water as a medium, and these were mixed. Finally, a coating liquid was prepared by dispersing or dissolving the following materials using water as a medium. The concentration of the coating liquid was 26% by mass.
Dye precursor 100 parts by mass Dispersant (sulfonic acid-modified polyvinyl alcohol) 20 parts by mass Developer 200 parts by mass Sensitizer 200 parts by mass Maleic anhydride copolymer 40 parts by mass Acetylene diol nonionic surfactant 2.5 Parts by mass Composition containing mineral oil and hydrophobic silica 1.7 parts by mass Aluminum hydroxide 125 parts by mass Amorphous silica 125 parts by mass Dispersant (ammonium polyacrylate) 2.5 parts by mass Having a core-shell structure (meth) Acrylamide copolymer 115 parts by mass Silanol-modified polyvinyl alcohol 115 parts by mass Zinc stearate 80 parts by mass

3-di-n-butylamino-6-methyl-7-anilinofluorane was used as a dye precursor. 4-hydroxy-4'-isopropoxydiphenyl sulfone was used as a color developer. 1,2-bis(3-methylphenoxy)ethane was used as a sensitizer. As the maleic anhydride copolymer, Polymalon (registered trademark) 1318 manufactured by Arakawa Chemical Industries, Ltd., which is a styrene-maleic anhydride copolymer, was used. Nopco (registered trademark) 8034 from San Nopco was used as the composition containing mineral oil and hydrophobic silica. Varistar (registered trademark) BM1000 manufactured by Mitsui Chemicals, Inc. was used as the (meth)acrylamide copolymer having a core-shell structure.

(thermal recording layer)
A coating solution for forming a heat-sensitive recording layer was applied to the surface of the support at a coating amount of 3.5 g/m ² and dried, followed by calendering using a supercalender. A heat-sensitive recording layer was formed.

(thermal recording material)
Polyvinyl alcohol (Kuraray Poval (registered trademark) 5-88, manufactured by Kuraray Co., Ltd.) was applied to the back side of the support with a heat-sensitive recording layer provided thereon at a coating amount of 17 g/m ² . and dried to form a re-wettable adhesive layer to produce a heat-sensitive recording material.

<Example 2>
In Example 1, except for changing the composition containing mineral oil and hydrophobic silica (Nopco 8034 of San Nopco Co., Ltd.) of Example 1 to a composition containing mineral oil and hydrophobic silica (SN Deformer 154 of San Nopco Co., Ltd.) Example 2 was prepared in the same manner as in Example 1.

<Example 3>
In Example 1, the composition containing mineral oil and hydrophobic silica (Nopco (registered trademark) 8034 from San Nopco) of Example 1 was replaced with the composition containing mineral oil and hydrophobic silica (Adekanate (registered trademark) from Adeka). Example 3 was prepared in the same manner as in Example 1 except for changing to B-940).

<Example 4>
In Example 1, except for changing the (meth)acrylamide copolymer having a core-shell structure (Mitsui Chemicals, Varistar BM1000) to a (meth)acrylamide copolymer having a core-shell structure (Mitsui Chemicals, Varistar OM1050) Example 4 was carried out in the same manner as in Example 1.

<Example 5>
Example 5 was prepared in the same manner as in Example 1, except that the partially saponified polyvinyl alcohol in Example 1 was changed to gum arabic as the adhesive for the rewettable adhesive layer.

<Example 6>
Example 5 was prepared in the same manner as in Example 1 except that starch paste was used instead of partially saponified polyvinyl alcohol as the glue for the rewettable glue layer.

<Comparative example 1>
Example 1 except that the composition containing mineral oil and hydrophobic silica (Nopco 8034, manufactured by San Nopco Co., Ltd.) in Example 1 was changed to a metal soap-based composition (Nopco DF-122, manufactured by San Nopco Company). Comparative Example 1 was prepared in the same manner as in .

<Comparative example 2>
Example 1 except that the (meth)acrylamide copolymer having a core-shell structure (Mitsui Chemicals, Varistar BM1000) was changed to an acrylonitrile/acrylamide/acrylic acid ternary copolymer having no core-shell structure. Comparative Example 2 was prepared in the same manner as above.

<Comparative example 3>
In Example 1, Comparative Example 3 was prepared in the same manner as in Example 1, except that the composition containing mineral oil and hydrophobic silica (Nopco 8034 from San Nopco Co., Ltd.) of Example 1 was changed to no formulation.

<Comparative example 4>
Comparative Example 4 was prepared in the same manner as in Example 1, except that the (meth)acrylamide copolymer having a core-shell structure (Mitsui Chemicals, Varistar BM1000) was not added.

The following items were evaluated for the heat-sensitive recording materials of each Example and Comparative Example. The results are shown in Table 1.

<Defect resistance>
The obtained heat-sensitive recording material was cut into A4 size sheets, and the presence or absence of defects observed in the heat-sensitive recording layer was observed for 100 sheets of the A4-size heat-sensitive recording material. The defect resistance was evaluated based on the observation results using the following criteria. In the present invention, the heat-sensitive recording material is considered to have defect resistance if it is evaluated as A or B.
A: No defects observed in 100 sheets, good quality.
B: Good, with defects observed only in 1 out of 100 sheets.
C: Defects are observed in 2 to 3 out of 100 sheets, which is the lower limit of actual production.
D: Defects are observed in 4 or more out of 100 sheets.

<Crack resistance>
Ten sheets of A4-sized heat-sensitive recording materials were stacked with the heat-sensitive recording layer and rewettable adhesive layer in contact with each other, and an A4-sized metal plate (1 kg) was placed on top of the stack, and the heat-sensitive recording materials were stacked in an environment of 23° C. and 50% RH. It was left undisturbed for 3 hours. After standing still, the lamination was unraveled and defects in the heat-sensitive recording layer were visually observed. The chipping resistance was evaluated based on the observation results using the following criteria. In the present invention, the heat-sensitive recording material is considered to have chipping resistance if it is evaluated as A or B.
A: Good with no defects observed.
B: No defects were observed, and although there was some slight fluffing on the surface, it was generally good.
C: Lower limit of usability, although no defects were observed and the surface was partially fluffy.
D: Defects are observed.

<Blocking resistance>
Ten sheets of A4-sized heat-sensitive recording materials were stacked with the heat-sensitive recording layer and rewetting adhesive layer in contact with each other, and an A4-sized metal plate (1 kg) was placed on top of the stack in an environment of 40°C and 90% RH. It was left undisturbed for 24 hours. Thereafter, the stacked state was left standing in an environment of 23° C. and 50% RH for 3 hours to moderate the temperature and moisture of the heat-sensitive recording material. Next, the lamination was unraveled and the thermosensitive recording layer facing the rewettable adhesive layer was observed. Blocking resistance was evaluated based on the observation results using the following criteria. In the present invention, if the heat-sensitive recording material is evaluated as A or B, it is assumed that the heat-sensitive recording material has blocking resistance.
A: No damage was observed in the heat-sensitive recording layer due to blocking.
B: Although inferior to the above A, almost no damage was observed in the heat-sensitive recording layer due to blocking.
C: Slight damage is observed in the heat-sensitive recording layer due to blocking.
D: Damage is observed in the heat-sensitive recording layer due to blocking.

<Adhesion resistance>
Ten sheets of A4-sized heat-sensitive recording materials were stacked with the heat-sensitive recording layer and rewetting adhesive layer in contact with each other, and an A4-sized metal plate (1 kg) was placed on top of the stack in an environment of 40°C and 90% RH. It was left undisturbed for 24 hours. Thereafter, the stacked state was left standing in an environment of 23° C. and 50% RH for 3 hours to moderate the temperature and moisture of the heat-sensitive recording material. Next, the lamination was unraveled, and the A4-sized heat-sensitive recording material was cut into smaller paper pieces of 2.5 cm x 10 cm.
The rewettable glue layer of the paper strip was impregnated with water. The water application to the rewettable glue layer was 20 g/m ² . After the rewetting adhesive layer was sufficiently soaked with water, the heat-sensitive recording material was placed on the surface of the Styrofoam so that the surface of the rewetting adhesive layer was in contact with the surface. Next, the heat-sensitive recording material was adhered to the surface of the foamed polystyrene by pressing the heat-sensitive recording material against the surface of the foamed polystyrene. When pressing the heat-sensitive recording material, a 2 kg hand roller was used to make one reciprocation over the entire length of the heat-sensitive recording material at a moving speed of 10 m/min. The heat-sensitive recording material was adhered to the surface of the Styrofoam and left for 24 hours in an environment of 23° C. and 50% RH. Thereafter, the heat-sensitive recording material was peeled from the surface of the styrofoam to measure the peel strength by a method based on ISO 29862:2007 "Self adhesive tapes - Determination of peel adhesion properties." The resistance to deterioration of adhesion was evaluated based on the measurement results based on the following criteria. In the present invention, if the heat-sensitive recording material is evaluated as A or B, it is assumed that the heat-sensitive recording material has adhesive deterioration resistance.
A: 0.32N/25mm or more.
B: 0.27N/25mm or more and less than 0.32N/25mm.
C: 0.22N/25mm or more and less than 0.27N/25mm.
D: Less than 0.22N/25mm.

From Table 1, it can be seen that Examples 1 to 6 that satisfy the constitution of the present invention are heat-sensitive recording materials having chipping resistance, defect resistance, blocking resistance, and adhesion deterioration resistance. On the other hand, it can be seen that Comparative Examples 1 to 4, which do not satisfy the constitution of the present invention, are heat-sensitive recording materials that cannot obtain any of chipping resistance, defect resistance, blocking resistance, and resistance to deterioration of adhesion.

Claims (1)

The thermosensitive recording layer has at least a heat-sensitive recording layer, a support, and a rewetting adhesive layer in this order, and the heat-sensitive recording layer includes a composition containing mineral oil and hydrophobic silica, and a (meth)acrylamide copolymer having a core-shell structure. Heat-sensitive recording material containing coalescence.