JP7635174B2 - Thermal recording materials - Google Patents

Description

The present invention relates to a heat-sensitive recording material having a heat-sensitive recording layer containing an electron-donating dye precursor and an electron-accepting developer.

A heat-sensitive recording material having a heat-sensitive recording layer on a support is known.
For example, a known heat-sensitive recording material has a heat-sensitive recording layer containing an electron-donating dye precursor and an electron-accepting color developer provided on a support, the heat-sensitive recording layer containing 4,4'-dihydroxydiphenylsulfone as the electron-accepting color developer, diphenylsulfone as a low-melting heat-soluble component that accelerates the color-developing reaction, and a polymer having a core-shell structure consisting of a core essentially made of acrylonitrile and a shell essentially made of methacrylamide as a binder, and has a Gurley air resistance of 170 seconds or more as specified in JIS-P-8117 (see, for example, Patent Document 1). The heat-sensitive recording material described in Patent Document 1 is excellent in color development sensitivity, color regeneration property, heat-resistant image storage property, and moist heat-resistant image storage property.

In addition, in one embodiment of the thermal recording material, a thermal recording medium is known in which a thermal recording layer and a protective layer containing an aqueous adhesive are sequentially provided on one side of a support, and a rewettable adhesive layer is provided on the opposite side of the support (see, for example, Patent Document 2). The rewettable adhesive layer exhibits adhesiveness by wetting. That is, the rewettable adhesive layer does not exhibit adhesiveness in a dry state, so no release paper is required to cover a normal adhesive layer. Therefore, a thermal recording medium having a rewettable adhesive layer on the opposite side of the support is excellent in terms of disposal of release paper, reduction of resources required for producing release paper, and ease of handling.
The thermosensitive recording medium having a rewettable adhesive layer on the opposite side of the support is preferably used for logistics label applications. In logistics labels made of a thermosensitive recording medium having a rewettable adhesive layer on the opposite side of the support, variable information is printed and recorded on the thermosensitive recording layer, and then moisture is applied to the rewettable adhesive layer, which then develops adhesiveness and is attached to a delivery item.

JP 2012-148525 A Japanese Patent Application Publication No. 09-226252

The logistics labels are usually stored in the form of rolls or loaded inside a recording device.
When a thermosensitive recording medium having a rewetting adhesive layer on the opposite side of the support is in the form of roll paper, the thermosensitive recording layer and the rewetting adhesive layer are in contact with each other. Generally, the adhesive agent for the rewetting adhesive layer is chloroprene rubber, polyvinyl alcohol, starch, vinyl acetate copolymer, dextrin, gum arabic, glue, polyacrylamide, etc.
A thermosensitive recording medium having a rewettable adhesive layer on the opposite side of the support may develop adhesion depending on the environment and circumstances, such as a high humidity environment and unexpected moisture absorption. As a result, a thermosensitive recording medium having a rewettable adhesive layer on the opposite side of the support may cause blocking. Therefore, a thermosensitive recording medium having a rewettable adhesive layer on the opposite side of the support needs a thermosensitive recording layer that is less likely to cause blocking against the rewettable adhesive layer.
In addition, the color development property (also referred to as "recoloring property" in this specification) of the thermal recording layer of the thermal recording material tends to decrease when it is used after being stored for a long period of time. In particular, the color development property of the thermal recording layer of a thermal recording material having a rewetting adhesive layer on the opposite side of the support decreases when it is used after being stored for a long period of time under a high temperature and high humidity environment, compared with a thermal recording material having no rewetting adhesive layer on the opposite side of the support.

In view of the above, the object of the present invention is to provide a thermal recording material that has excellent recoloring properties and blocking resistance.

As a result of extensive investigations, the present inventors have found that the object of the present invention can be achieved by the following heat-sensitive recording material.
A thermal recording material having a support and a thermal recording layer on the support, the thermal recording layer containing an electron-donating dye precursor and an electron-accepting developer, characterized in that the thermal recording layer contains a high molecular weight polymer having a core-shell structure consisting of a core containing acrylonitrile as an essential component and a shell containing methacrylamide as an essential component, and a maleic anhydride copolymer, and has a rewettable adhesive layer on the side of the support opposite the thermal recording layer.

The present invention provides a thermal recording material with excellent recoloring and blocking resistance.

The present invention will now be described in more detail.

The thermal recording material has a thermal recording layer on one side of the support and a rewettable adhesive layer on the remaining side of the support. In some embodiments, the thermal recording material has a protective layer that contains a resin or contains a resin and a pigment and is conventionally known in the field of thermal recording materials, on the outer side of the thermal recording layer relative to the support. The reason for this is that it is possible to improve the blocking resistance of the thermal recording material or to protect the thermal recording layer.

The heat-sensitive recording material has a heat-sensitive recording layer that contains a high molecular weight polymer having a core-shell structure consisting of a core containing acrylonitrile as an essential component and a shell containing methacrylamide as an essential component (also referred to in this specification as a "core-shell type acrylic emulsion").
A polymer having a core-shell structure consisting of a core containing acrylonitrile as an essential component and a shell containing methacrylamide as an essential component is generally prepared by a seed emulsion polymerization method in which an emulsion of acrylonitrile is used as a seed, and methacrylamide is added as an essential component as a monomer for forming a polymer having properties different from that of the seed, and polymerization is carried out.
Examples of monomers that can be used in combination with methacrylamide to form a shell include acrylonitrile, styrene, ethyl acrylate, butyl acrylate, diethylene glycol acrylate, acrylates such as 2-ethylhexyl acrylate, methacrylates such as allyl methacrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate, and methacrylic acid. Core-shell acrylic emulsions are commercially available from, for example, Mitsui Chemicals, Inc.

In some embodiments, the content of the core-shell type acrylic emulsion in the thermosensitive recording layer is 5% by mass or more and 40% by mass or less based on the total dry solid content forming the thermosensitive recording layer, because this improves recoloring property and blocking resistance.
The heat-sensitive recording layer may contain one or more of conventionally known binders, binding agents and polymeric polymers that act as binders, in addition to the core-shell type acrylic emulsion. Examples of polymeric polymers other than the core-shell type acrylic emulsion include acrylic polymers other than the core-shell type acrylic emulsion, starches such as starch and modified starch, celluloses such as cellulose and modified cellulose, proteins such as gelatin and casein, polyvinyl alcohols such as polyvinyl alcohol and modified polyvinyl alcohol, sodium alginate, polyvinylpyrrolidone, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylonitrile-butadiene-styrene copolymers, polyvinyl acetate resins, ethylene-vinyl acetate copolymers, polyurethane resins, etc.

In some embodiments, the content of the core-shell acrylic emulsion in the thermal recording layer of the thermal recording material is 30% by mass or more relative to the total content of the core-shell acrylic emulsion and the content of the polymer other than the core-shell acrylic emulsion. In at least one embodiment, the content of the core-shell acrylic emulsion in the thermal recording layer of the thermal recording material is 10% by mass or more and 40% by mass or less relative to the total dry solid content forming the thermal recording layer. The reason for this is that the recoloring property and blocking resistance of the thermal recording material are improved.

The thermosensitive recording material contains a maleic anhydride copolymer in the thermosensitive recording layer, which contains at least maleic anhydride as a monomer. In some embodiments, the content of the maleic anhydride copolymer in the thermosensitive recording layer is 0.1% by mass or more and 10% by mass or less based on the total dry solid content forming the thermosensitive recording layer. This is because the recoloring property and blocking resistance of the thermosensitive recording material are improved.
The maleic anhydride copolymer refers to a copolymer containing maleic anhydride as a monomer. Examples of comonomers copolymerizable with maleic anhydride include styrene, α-alkylstyrene, benzyl methacrylate, isobutylene, ethylene, vinyl acetate, vinyl toluene, maleic acid, and methyl vinyl ether. The maleic anhydride copolymer also includes those that are partially esterified and/or form salts. In some embodiments, the maleic anhydride copolymer is a styrene-maleic anhydride copolymer. In at least one embodiment, the maleic anhydride copolymer is a styrene-maleic anhydride ammonium salt. The reason for this is that the recoloring property and blocking resistance of the thermal recording material are improved.
Maleic anhydride copolymers are commercially available from, for example, Arakawa Chemical Industries, Tomoe Kogyo, Vertellus, Mitsubishi Chemical, and Dow Chemical Japan.

The thermosensitive recording layer of the thermosensitive recording material contains an electron-donating dye precursor. The electron-donating dye precursor is a conventionally known dye precursor used in thermosensitive recording materials, and is not particularly limited. Examples of the electron-donating dye precursor are as follows. The electron-donating dye precursor is one or more types selected from the group consisting of these.

Examples of black electron donating dye precursors include 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-di-n-pentylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7-(2-carbomethoxyphenylamino)fluoran, 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilinofluoran, 3-(N-cyclopentyl-N-ethyl)amino-6-methyl-7-anilinofluoran, Examples of such fluoran include 3-(N-isoamyl-N-ethyl)amino-6-methyl-7-anilinofluoran, 3-(N-ethyl-4-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-4-toluidino)-6-methyl-7-(4-toluidino)fluoran, 3-(N-methyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-(4-n-butylphenylamino)fluoran, 3-piperidino-6-methyl-7-anilinofluoran, and 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-anilinofluoran.

Examples of red electron donating dye precursors include 3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-n-butyl-2-methylindol-3-yl)tetrachlorophthalide, 3,3-bis(1-n-butylindol-3-yl)phthalide, 3,3-bis(1-n-pentyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-n-hex ... bis(1-n-octyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-methyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-propyl-2-methylindol-3-yl)phthalide, 3,3-bis(2-methylindol-3-yl)phthalide, rhodamine B-anilinolactam, rhodamine B-(o-chloroanilino)lactam, rhodamine B -(p-nitroanilino)lactam, 3-diethylamino-5-methyl-7-dibenzylaminofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-6-methylfluoran, 3-diethylamino-6-methyl-7-chloro-8-benzylfluoran, 3-diethylamino-6,7-dimethylfluoran, 3-diethylamino-6,8-dimethylfluoran, 3-diethylamino Amino-7-chlorofluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-(N-acetyl-N-methyl)aminofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-n-propoxyfluoran, 3-diethylamino-7-p-methylphenylfluoran, 3-diethylamino-7,8-benzofluoran, 3-diethylaminobenzo[a]fluoran, 3-diethylaminobenzo[c]fluoran fluoran, 3-dimethylamino-7-methoxyfluoran, 3-dimethylamino-6-methyl-7-chlorofluoran, 3-dimethylamino-7-methylfluoran, 3-dimethylamino-7-chlorofluoran, 3-(N-ethyl-p-toluidino)-7-methylfluoran, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-chlorofluoran, 3-(N-ethyl-N-isoamyl)amino-7,8-benzo ... amyl)amino-7-methylfluoran, 3-(N-ethyl-N-n-octyl)amino-6-methyl-7-chlorofluoran, 3-(N-ethyl-N-n-octyl)amino-7,8-benzofluoran, 3-(N-ethyl-N-n-octyl)amino-7-methylfluoran, 3-(N-ethyl-N-n-octyl)amino-7-chlorofluoran, 3-(N-ethyl-N-n-octyl)amino-7-methylfluoran, 3-(N-ethyl-N-n-octyl)amino-7-chlorofluoran, 3-(N-ethyl-N-4-methylphenyl)amino-7,8-benzofluoran, 3-(N-ethoxyethyl n-Dibutylamino-7,8-benzofluoran, 3-n-dibutylamino-7-chlorofluoran, 3-n-dibutylamino-6-methyl-7-chlorofluoran, 3-n-dibutylamino-7,8-benzofluoran, 3-n-dibutylamino-7-chlorofluoran, 3-n-dibutylamino-7-methylfluoran, 3-diallylamino-7,8-benzofluoran, 3-diallylamino-7-chlorofluoran, 3-di- Examples include n-butylamino-6-methyl-7-bromofluoran, 3-cyclohexylamino-6-chlorofluoran, 3-pyrrolidylamino-7-methylfluoran, 3-ethylamino-7-methylfluoran, 3-(N-ethyl-N-isoamyl)amino-benzo[a]fluoran, 3-n-dibutylamino-6-methyl-7-bromofluoran, and 3,6-bis(diethylaminofluoran)-γ-(4'-nitro)anilinolactam.

Examples of green electron donating dye precursors include 3-(N-ethyl-N-n-hexyl)amino-7-anilinofluoran, 3-(N-ethyl-N-p-tolyl)amino-7-(N-phenyl-N-methyl)aminofluoran, 3-(N-ethyl-N-n-propyl)amino-7-dibenzylaminofluoran, 3-(N-ethyl-N-n-propyl)amino-6-chloro-7-dibenzylaminofluoran, 3-(N-ethyl-N-4-methylphenyl)amino-7-(N-methyl-N-phenyl)aminofluoran, 3-(N-ethyl-4-methylphenyl)aminofluoran, amino-7-dibenzylaminofluoran, 3-(N-ethyl-4-methylphenyl)amino-6-methyl-7-dibenzylaminofluoran, 3-(N-ethyl-4-methylphenyl)amino-6-methyl-7-(N-methyl-N-benzyl)aminofluoran, 3-(N-methyl-N-hexyl)amino-7-anilinofluoran, 3-(N-propyl-N-n-hexyl)amino-7-anilinofluoran, 3-(N-ethoxy-N-n-hexyl)amino-7-anilinofluoran, 3-(N-pentyl-N-allyl)amino-6-methyl-7- Anilinofluoran, 3-(N-n-pentyl-N-allyl)amino-7-anilinofluoran, 3-di-n-butylamino-6-chloro-7-(2-chloroanilino)fluoran, 3-di-n-butylamino-6-methyl-7-(2-chloroanilino)fluoran, 3-di-n-butylamino-6-methyl-7-(2-fluoroanilino)fluoran, 3-n-dibutylamino-7-(2-chloroanilino)fluoran, 3-di-n-butylamino-7-(2-chlorobenzylanilino)fluoran, 3,3-bis(4-diethylamino-2-ethoxyphenyl) n-cyclohexyl)-4-azaphthalide, 3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide, 3-diethylamino-6-methyl-7-benzylaminofluoran, 3-diethylamino-6-methyl-7-dibenzylaminofluoran, 3-diethylamino-6-methyl-7-n-octylaminofluoran, 3-diethylamino-6-methyl-7-(N-cyclohexyl-N-benzyl)aminofluoran, 3-diethylamino-6-methyl-7-(2-chloroanilino)fluoran, 3-diethylamino-6-methyl-7- (2-trifluoromethylanilino)fluoran, 3-diethylamino-6-methyl-7-(3-trifluoromethylanilino)fluoran, 3-diethylamino-6-methyl-7-(2-ethoxyanilino)fluoran, 3-diethylamino-6-methyl-7-(4-ethoxyanilino)fluoran, 3-diethylamino-6-chloro-7-(2-chloroanilino)fluoran, 3-diethylamino-6-chloro-7-dibenzylaminofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-ethylethoxy-7 -anilinofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7-methylanilinofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-n-octylaminofluoran, 3-diethylamino-7-p-chloroanilinofluoran, 3-diethylamino-7-p-methylphenylanilinofluoran, 3-diethylamino-7-(N-cyclohexyl-N-benzyl)aminofluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-7-(3- trifluoromethylanilino)fluoran, 3-diethylamino-7-(2-trifluoromethylanilino)fluoran, 3-diethylamino-7-(2-ethoxyanilino)fluoran, 3-diethylamino-7-(4-ethoxyanilino)fluoran, 3-diethylamino-7-(2-chlorobenzylanilino)fluoran, 3-dimethylamino-6-chloro-7-dibenzylaminofluoran, 3-dimethylamino-6-methyl-7-n-octylaminofluoran, 3-dimethylamino-7-dibenzylaminofluoran, 3-dimethylamino-7-n -octylaminofluoran, 3-di-n-butylamino-7-(2-fluoroanilino)fluoran, 3-anilino-7-dibenzylaminofluoran, 3-anilino-6-methyl-7-dibenzylaminofluoran, 3-pyrrolidino-7-dibenzylaminofluoran, 3-pyrrolidino-7-(4-cyclohexylanilino)fluoran, 3-dibenzylamino-6-methyl-7-dibenzylaminofluoran, and 3,7-bis(dibenzylamino)fluoran, 3-dibenzylamino-7-(2-chloroanilino)fluoran, etc.

Examples of blue electron donor dye precursors include 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)phthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-methyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-aminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-methylaminophenyl)-4-azaphthalide, -azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-ethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dimethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-propylaminophenyl)-4-azaphthalide nophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-butylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-pentylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-hexylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-hexylaminophenyl)-4-azaphthalide (2-ethoxy-4-dihydroxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dichloroaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dibromoaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diallylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diarylaminophenyl)-4-azaphthalide, -yl)-3-(2-ethoxy-4-dihydroxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dimethoxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethoxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dicyclohexylaminophenyl)-4-azaphthalide, 3-(1-ethyl 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-propoxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-butoxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-hexyloxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-hexyloxyaminophenyl)-4-azaphthalide, xylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-methoxycyclohexylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-pyrrolidylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(3-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(3-ethoxy-4-diethylaminophenyl)-4-azaphthalide, )-3-(2,3-diethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-chloro-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(3-chloro-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(3-chloro-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)
-3-(2-bromo-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(3-bromo-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-n-propyl-4-diene 3-(1-ethyl-2-methylindol-3-yl)-3-(3-methyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-nitro-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-aryl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-hydroxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyano-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyclohexylethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyclohexylethoxy-4-diethylaminophenyl)-4-azaphthalide, Ethyl-2-methylindol-3-yl)-3-(2-methylethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyclohexylethyl-4-diethylaminophenyl)-4-azaphthalide, 3-(2-ethylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-chloroindol 3-(1-ethyl-2-bromoindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-ethylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-ethylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-propylindol-3-yl)-3-(2 -ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methoxyindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-ethoxyindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-phenylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, aminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4,7-diazaphthalide, 3-(1-ethyl-4,5,6,7-tetrachloro-2-methylindol-3-yl)-3-(2-ethoxy-4-di 3-(1-ethyl-4-nitro-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-4-methoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-4-methylamino-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-4-methyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-chloro-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide phenyl)-4-azaphthalide, 3-(1-bromo-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-methyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-methyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3 -(1-n-propyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-n-butyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-n-butyl-2-indol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-pentyl -2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-n-hexyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-n-hexyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-octyl-2-methyl indol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-n-octyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-octyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4,7-diazaphthalide, 3-(1-n-nonyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4,7-diazaphthalide 3-(1-methoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-methoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-phenyl-2-methylindol-3-yl)-3-( 2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-n-pentyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-heptyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-nonyl-2-methylindol-3-yl)-3-(2-ethoxy- 3-(4-dimethylaminophenyl)-7-azaphthalide, 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-dimethylamino-2-methylphenyl)-3-(4-dimethylaminophenyl)-6-dimethylaminophthalide, and 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylamino-2-n-hexyloxyphenyl)-4-azaphthalide.

In some embodiments, the content of the electron donating dye precursor in the thermosensitive recording layer of the thermosensitive recording material is 1% by mass or more and 30% by mass or less based on the total dry solid content forming the thermosensitive recording layer. This is because the thermosensitive recording material can obtain sufficient thermal responsiveness.

Thermal recording material has a thermal recording layer containing an electron-accepting color developer. The electron-accepting color developer is a conventionally known color developer used in thermal recording materials, and is not particularly limited. Examples of electron-accepting color developers are as follows. The electron-accepting color developer is one or more types selected from the group consisting of these.

Examples of electron-accepting color developers include 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-propoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, 4-hydroxy-4'-octyloxydiphenyl sulfone, 4-hydroxy-4'-dodecyloxydiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-benzenesulfonyloxydiphenyl sulfone, 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) 1,4-bis[2-(p-hydroxyphenyl)-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'-thiobis(2-tert-butyl-5-methylphenol), dimethyl 4-hydroxyphthalate, butyl 4-hydroxybenzoate benzyl, 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-hydroxy N-(3-hydroxyphenyl)benzenesulfonamide, N-(3-hydroxyphenyl)-1-naphthalenesulfonamide, N-(3-hydroxyphenyl)-2-naphthalenesulfonamide, 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, 3-(3-tosylureido)phenyl p-toluenesulfonate, N-[2-(3-phenylureido)phenyl]benzenesulfonamide sulfonamide, 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'-methylenediphenyl)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 can be mentioned.

In some embodiments, the electron-accepting developer has a solubility of 0.01 g/100 g water (25° C.) or less. This is because it is possible to prevent deterioration in color development due to elution of the rewettable adhesive layer components when the thermal recording material is stored in a high-temperature and high-humidity environment and/or deterioration in the blocking resistance of the thermal recording layer caused by the rewettable adhesive layer of the thermal recording material becoming wet and exhibiting adhesiveness. Examples of developers having a solubility of 0.01 g/100 g water (25° C.) or less include 4-hydroxy-4'-isopropoxydiphenylsulfone and bis(3-allyl-4-hydroxyphenyl) sulfone .

In some embodiments, the mass ratio of the electron donor dye precursor to the electron acceptor developer in the thermosensitive recording layer is 100% by mass or more and 500% by mass or less of the electron acceptor developer relative to the electron donor dye precursor. In at least one embodiment, the mass ratio of the electron donor dye precursor to the electron acceptor developer in the thermosensitive recording layer is 150% by mass or more and 350% by mass or less of the electron acceptor developer relative to the electron donor dye precursor. The reason for this is that the recoloring property is improved.

In some embodiments, the thermosensitive recording layer of the thermosensitive recording material contains a sensitizer. This is because the thermal response of the thermosensitive recording material is improved. The sensitizer is one that is conventionally known in the field of thermosensitive recording materials and is not particularly limited. Examples of sensitizers are as follows. The sensitizer is one or more selected from the group consisting of these. In some embodiments, the content of the sensitizer in the thermosensitive recording layer is 5% by mass or more and 50% by mass or less based on the total dry solid content that forms the thermosensitive recording layer.

Examples of sensitizers include diphenyl sulfone, stearic acid monoamide, N-hydroxymethyl stearic acid amide, N-stearyl stearic acid amide, ethylene bisstearic acid amide, methylene bisstearic acid amide, methylol stearic acid amide, N-stearyl urea, benzyl-2-naphthyl ether, p-toluenesulfonamide, m-terphenyl, 4-benzyl biphenyl, 2,2'-bis(4-methoxyphenoxy)diethyl ether, and 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, phenyl benzenesulfonate, bis(4-allyloxyphenyl)sulfone, 1,2-bis(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 4-acetylacetophenone, acetoacetic anilides, and fatty acid anilides can be mentioned.

In some embodiments, the thermal recording material has a thermal recording layer that contains one or more compounds selected from the group consisting of hindered phenol compounds, hindered amine compounds, phosphate derivatives, and benzotriazole derivatives. In at least one embodiment, the total content of the compounds selected from the group consisting of hindered phenol compounds, hindered amine compounds, phosphate derivatives, and benzotriazole derivatives in the thermal recording layer is 5% by mass or more and 300% by mass or less relative to the electron donating dye precursor. This is because the storage stability of the thermal recording layer is improved.

Examples of hindered phenol compounds include 1,1,2,2-tetrakis(5-cyclohexyl-4-hydroxy-2-methylphenyl)ethane, 1,1,2,2-tetrakis(3-phenyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-tert-butyl-4-hydroxyphenyl)ethane, 1,1,3-tris(3-cyclohexyl-4-hydroxyphenyl)butane, 1,1,3-tris(5-cyclohexyl-4-hydroxy-2-methylphenyl)butane, 1,1,3-tris(3-cyclohexyl-4-hydroxy-5-methylphenyl)butane, 1,1,3-tris(3-phenyl-4-hydroxyphenyl)butane, 1,1,3-tris(5-phenyl-4-hydroxyphenyl)butane, 1,1,3-Tris(3-tert-butyl-4-hydroxyphenyl)butane, 1,1,3-Tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, 1,1,3,3-Trikis(5-cyclohexyl-4-hydroxy-2-methylphenyl)propane, 1,1,3,3-Tetrakis(3-cyclohexyl-4-hydroxyphenyl)propane, 1,1,5,5-Tetrakis(5-cyclohexyl-4-hydroxy-2-methylphenyl)pentane, 1,1,3,3-Tetrakis(3-cyclohexyl-4-hydroxyphenyl)pentane, 1,1,3,3-Tetrakis(3-phenyl-4-hydroxyphenyl)pentane nyl)propane, 1,1,3,3-tetrakis(5-phenyl-4-hydroxy-2-methylphenyl)propane, 1,1,3,3-tetrakis(3-tert-butyl-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(5-tert-butyl-4-hydroxy-2-methylphenyl)propane, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis(4,6-di-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol) , 4,4'-thiobis(2-methylphenol), 4,4'-thiobis(2,6-dimethylphenol), 4,4'-thiobis(2,6-di-tert-butylphenol), 2,2'-thiobis(4-tert-octylphenol), 2,2'-thiobis(3-tert-octylphenol), 4,4'-butylidenebis(6-tert-butyl-m-cresol), 1-[α-methyl-α-(4'-hydroxyphenyl)ethyl]4-[α',α'-bis(4''-hydroxyphenyl)ethyl]benzene, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, and 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane can be mentioned. Hindered phenol compounds are not limited to these.

Examples of hindered amine compounds include bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, succinic acid bis(2,2,6,6-tetramethyl-4-piperidyl)ester, butane-1,2,3,4-tetracarboxylic acid tetrakis[1,2,2,6,6-pentamethyl(4-piperidyl)]ester, and butane-1,2,3,4-tetracarboxylic acid tetrakis[2,2,6,6-tetramethyl(4-piperidyl)]ester. Hindered amine compounds are not limited to these.

Examples of the phosphate ester derivatives include triphenyl phosphate, diphenyl phosphate, bis(4-tert-butylphenyl)phosphate, bis(4,6-di-tert-butylphenyl)phosphate, bis(4-chlorophenyl)phosphate, bis(benzyloxyphenyl)phosphate, 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, dimethyloxyphosphate, diethyloxyphosphate, bis(3,5-di-tert-butyl-4-hydroxyphenyl)phosphate, 3,5-di-tert-butyl Examples of the phosphate ester derivatives include diethyl diphenyl phosphate, diethyl (3,5-di-tert-butyl-4-hydroxyphenyl) phosphate, sodium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, calcium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, zinc salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, and ammonium and potassium salts of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate. The phosphate ester derivatives are not limited to these.

Benzotriazole derivatives include, for example, 2-(2-hydroxyphenyl)benzotriazole, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole, and 2-(2-hydroxy-3,5-di-tert-aminophenyl) Benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-tert-butylbenzotriazole, 2-(2-hydroxy-3-dodecyl-5-methylphenyl)benzotriazole, 2-[2-hydroxy-4-(2-ethylhexyl)oxyphenyl]benzotriazole, methyl-3-(3-tert-butyl-5-benzotriazolyl-4-hydroxyphenyl)propionate-polyethylene glycol (molecular weight about 300) condensate, 5-tert-butyl-3-(5-chloro-benzotriazolyl)-4-hydroxybenzene-octyl propionate, 2-(2 -hydroxy-3-sec-butyl-5-tert-butylphenyl)-5-tert-butylbenzotriazole, 2-(2-hydroxy-4-methoxy-5-sulfophenyl)benzotriazole sodium salt, 2-(2-hydroxy-4-butoxy-5-sulfophenyl)benzotriazole sodium salt, 2,2'-methylenebis(4-methyl-6-benzotriazolylphenol), 2,2'-methylenebis[4-methyl-6-(5-methylbenzotriazolyl)phenol], 2,2'-methylenebis[4-methyl-6-(5-chlorobenzotriazolyl)phenol], 2,2'-methylenebis Examples of the benzotriazole derivatives include 4-(1,1,3,3-tetramethylbutyl)-6-benzotriazolylphenol, 2,2'-methylenebis(4-tert-butyl-6-benzotriazolylphenol), 2,2'-propylidenebis(4-methyl-6-benzotriazolylphenol), 2,2'-isopropylidenebis(4-methyl-6-benzotriazolylphenol), 2,2'-isopropylidenebis[4-(1,1,3,3-tetramethylbutyl)-6-benzotriazolylphenol], and 2,2'-octylidenebis[4-methyl-6-(5-methylbenzotriazolyl)phenol]. Benzotriazole derivatives are not limited to these.

In some embodiments, the heat-sensitive recording material contains a conventionally known white pigment in the heat-sensitive recording layer. This is because the sticking resistance and whiteness of the heat-sensitive recording material are improved. Examples of the white pigment include white inorganic pigments such as diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, amorphous calcium silicate, calcium sulfate, calcium silicate, magnesium carbonate, magnesium silicate, magnesium phosphate, magnesium oxide, magnesium hydroxide, aluminum hydroxide, aluminum silicate, alumina, colloidal alumina, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, colloidal silica, barium sulfate, zinc sulfide, zinc carbonate, satin white, lithopone, zeolite, hydrotalcite and hydrated halloysite, and white organic pigments such as hollow particles and solid particles made of various resins.
In some embodiments, the white pigment is one or more selected from the group consisting of: In at least one embodiment, the content of the white pigment in the thermosensitive recording layer is 5% by mass or more and 50% by mass or less based on the total dry solid content forming the thermosensitive recording layer.

Thermal recording materials may contain various additives in the thermal recording layer that are conventionally known in the field of thermal recording materials, as necessary. Examples of additives include higher fatty acid metal salts such as zinc stearate and calcium stearate to improve sticking resistance, waxes such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, and castor wax, hardeners and crosslinkers to improve water resistance, dispersants such as sodium dioctyl sulfosuccinate, surfactants, fluorescent dyes, coloring dyes, and bluing agents.

The thermal recording layer can be obtained, for example, by coating a thermal recording layer dispersion on a support and drying the support, the support being prepared by mixing and dispersing an electron-accepting developer, a sensitizer if necessary, one or more selected from the group consisting of hindered phenol compounds, hindered amine compounds, phosphoric acid ester derivatives and benzotriazole derivatives, a white pigment and various additives in a preliminary dispersion in which an electron-donating dye precursor is dispersed in a dispersion medium. The thermal recording layer can contain a high molecular weight polymer having a core-shell structure consisting of a core containing acrylonitrile as an essential component and a shell containing methacrylamide as an essential component, and a maleic anhydride copolymer, by mixing the dispersion for the thermal recording layer.
The preliminary dispersion in which the electron-donating dye precursor is dispersed in a dispersion medium can be obtained by a method of dry-grinding the electron-donating dye precursor and dispersing it in the dispersion medium, or by a method of adding the electron-donating dye precursor to a dispersion medium and wet-grinding it. In some embodiments, the electron-donating dye precursor is ground to a volume average particle size of 0.1 μm or more and 5.0 μm or less by various wet grinders such as a sand grinder, a ball mill, an attritor, and a bead mill using water as a dispersion medium to obtain a preliminary dispersion. The reason for this is that a thermal recording material with high color development sensitivity can be obtained.
In some embodiments, the electron accepting developer and the sensitizer are ground to a volume average particle size of 0.1 μm or more and 5.0 μm or less by various wet grinding machines such as a sand grinder, a ball mill, an attritor, and a bead mill using water as a dispersion medium, and then mixed and dispersed in the preliminary dispersion, because a thermal recording material with high color development sensitivity can be obtained.

When obtaining the above preliminary dispersion, dispersion, or dispersion for the thermal recording layer, pigments such as magnesium silicate, calcium silicate, magnesium carbonate, calcium carbonate, calcium sulfate, magnesium phosphate, magnesium oxide, aluminum oxide, titanium oxide, magnesium hydroxide, aluminum hydroxide, kaolin, talc, and hydrotalcite can be blended. In addition, the preliminary dispersion or dispersion can be heated to a temperature range of 40°C to 80°C. In addition, the electron-donating dye precursor can be provided with a coating layer formed of an organic polymer on the surface of the electron-donating dye precursor.

In some embodiments, a dispersant is blended in the dispersion medium of each of the preliminary dispersion, the dispersion, and the dispersion for the thermosensitive recording layer, because the dispersion of the preliminary dispersion, the dispersion, and the dispersion for the thermosensitive recording layer becomes stable.
Examples of the dispersant include polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, silanol modified polyvinyl alcohol, carboxyl modified polyvinyl alcohol, diacetone modified polyvinyl alcohol, acetoacetyl modified polyvinyl alcohol, phosphoric acid modified polyvinyl alcohol, butyral modified polyvinyl alcohol and epoxy modified polyvinyl alcohol, water-soluble polymers such as ethylene acrylate copolymer, styrene acrylate copolymer, polyacrylate and acrylic acid vinyl sulfonate copolymer , anionic low molecular surfactants such as dodecylbenzene sulfonate, dialkyl sulfosuccinate, alkylnaphthalene sulfonate, alkyldiphenyl ether disulfonate and fatty acid metal salt, and nonionic surfactants such as acetylene glycol. In some embodiments, the dispersant is one or more selected from the group consisting of these. The dispersant is not limited to these.

In some embodiments, the coating amount of the thermosensitive recording layer is from 2 g/ ^m2 to 15 g/ ^m2 in terms of dry solid content, because this is advantageous in terms of improving the color development sensitivity of the thermosensitive recording material and reducing the production cost of the thermosensitive recording material.

In some embodiments, the thermal recording material has an undercoat layer between the support and the thermal recording layer. This is because the smoothness of the thermal recording layer and the heat insulation against the support can be improved. The undercoat layer is conventionally known in the field of thermal recording materials. The undercoat layer contains, for example, a pigment and a binder conventionally known in the field of thermal recording media, and various additives selected from lubricants, defoamers, surfactants, preservatives, fluorescent brighteners, dispersants, thickeners, colorants, antistatic agents, and crosslinking agents as necessary. The undercoat layer can be provided, for example, by applying and drying a coating liquid for the undercoat layer to the support using a conventional coating device and drying device. In some embodiments, the coating amount of the undercoat layer is 1 g/m ² or more and 30 g/m ² or less in terms of dry solids. In at least one embodiment, the coating amount of the undercoat layer is 4 g/m ² or more and 20 g/m ² or less in terms of dry solids.

The support of the thermal recording material is one that is conventionally known in the field of thermal recording materials. Examples of the support include paper, such as coated paper and uncoated paper, various nonwoven fabrics, woven fabrics, synthetic resin films, synthetic resin laminated paper, synthetic paper, metal foils, ceramic paper, and glass plates, as well as composites and laminates that combine these.

The rewettable adhesive layer contains as its main component a glue that exhibits adhesive properties when wetted. The glue used in the rewettable adhesive layer is one that is conventionally known in the field of glues. Examples of the glue include chloroprene rubbers, polyvinyl alcohols such as fully saponified polyvinyl alcohol and partially saponified polyvinyl alcohol, starches, vinyl acetate copolymers such as vinyl acetate acrylate copolymer and vinyl acetate methacrylate copolymer, dextrin, gum arabic, glue, and polyacrylamide. The glue is one or more types selected from the group consisting of these.

The rewettable adhesive layer may contain various auxiliary agents in addition to the adhesive, provided that the properties of the adhesive are not impaired. Examples of auxiliary agents include pigments, antioxidants, ultraviolet absorbers, dyes, antibacterial agents, antifungal agents, fragrances, and flame retardants.

In some embodiments, the coating amount of the rewettable paste layer is 5 g/m ² or more and 50 g/m ² or less in terms of dry solid content. The reason for this is that the development of adhesiveness and the manufacturing cost can be well balanced.

In some embodiments, the thermal recording material has an intermediate layer between the support and the rewetting paste layer. This is because the smoothness of the rewetting paste layer and its adhesion to the support can be improved. The intermediate layer is conventionally known in the field of coated paper. The intermediate layer contains, for example, a pigment and a binder conventionally known in the field of coated paper, and various additives selected from lubricants, defoamers, surfactants, preservatives, fluorescent brighteners, dispersants, thickeners, colorants, antistatic agents, and crosslinking agents as necessary. The intermediate layer can be provided, for example, by applying and drying an intermediate layer coating liquid to the support using a conventional coating device and drying device. In some embodiments, the coating amount of the intermediate layer is 0.5 g/m ² or more and 10 g/m ² or less in terms of dry solid content.

The undercoat layer, the thermal recording layer, the intermediate layer and/or the rewettable adhesive layer may be subjected to a calendaring treatment. The calendaring treatment may be achieved using a calendaring treatment device conventionally known in the papermaking field. Examples of calendaring treatment include a machine calendar, a soft nip calendar, a super calendar, a multi-stage calendar, and a multi-nip calendar.

Thermal recording material has a thermal recording layer containing an electron-donating dye precursor and an electron-accepting color developer, which contains a core-shell type acrylic emulsion and a maleic anhydride copolymer, and can obtain recoloring properties. Furthermore, by combining a thermal recording layer containing a core-shell type acrylic emulsion and a maleic anhydride copolymer with a rewetting adhesive layer, it can obtain blocking resistance, for example, in the case of roll paper. In particular, the thermal recording layer is suitable when the adhesive agent of the rewetting adhesive layer is a polyvinyl alcohol.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples, mass% and mass parts represent the amount of dry solids or the amount of actual components. The amount of coating represents the amount of dry solids.

Example 1
(Support)
As the support, a wood-free paper containing pulp, a filler, a sizing agent, and a paper strength agent and having a basis weight of 60 g/ ^m2 was used. The wood-free paper used as the support had a Beck smoothness of 60 seconds on both sides and an ash content of 10% by mass.

(Coating solution for undercoat layer)
The following materials were mixed with water to prepare a coating liquid for the undercoat layer.
Pigment (calcined kaolin) 1000 parts by weight Dispersant (ammonium polyacrylate) 1 part by weight Dispersant (sodium hexametaphosphate) 1 part by weight Binder (styrene butadiene copolymer) 120 parts by weight Binder (urea modified starch phosphate) 60 parts by weight

(Undercoat Layer)
The coating solution for the undercoat layer was applied to the support so as to give a coating amount of 10 g/m ² , and then dried to obtain an undercoat layer.

Dispersion of Electron Acceptor Developer and Sensitizer
A dispersion of the electron-accepting developer and sensitizer in the following composition was prepared in water using a Shinmaru Enterprises bead mill "DYNO-MILL MULTI LAB" and 0.6 mm diameter glass beads. The bead particle filling rate in the grinding chamber was 80 volume %. The dispersion was ground at a liquid temperature of 20°C until the volume average particle size was 0.8 μm.
Electron-accepting developer (4-hydroxy-4'-isopropoxydiphenylsulfone)
200 parts by weight Sensitizer (1,2-bis(3-methylphenoxy)ethane) 200 parts by weight Maleic anhydride copolymer 40 parts by weight Defoamer (acetylene dialcohol) 2 parts by weight

Here, the maleic anhydride copolymer used was Arakawa Chemical Industries Co., Ltd.'s Polymaron (registered trademark) 1318, a styrene-maleic anhydride copolymer.

(Pre-dispersion of Electron Donor Dye Precursor)
A preliminary dispersion of the electron donor dye precursor was prepared in water with the following composition using a Shinmaru Enterprises bead mill "DYNO-MILL MULTI LAB" and glass beads with a diameter of 0.6 mm. The bead particle filling rate in the grinding chamber was 80 volume %. The preliminary dispersion was ground at a liquid temperature of 20°C until the volume average particle diameter became 0.8 μm. The preliminary dispersion was then heated at 70°C for 30 minutes to obtain a preliminary dispersion.
Electron donating dye precursor (3-di-n-butylamino-6-methyl-7-anilinofluoran) 100 parts by weight Dispersant (sulfonic acid modified polyvinyl alcohol) 20 parts by weight Defoamer (acetylene-based dialcohol) 0.5 parts by weight

(Pigment Dispersion)
A pigment dispersion was prepared in water according to the following formula:
Aluminum hydroxide 125 parts by weight Amorphous silica 125 parts by weight Dispersant (ammonium polyacrylate) 2.5 parts by weight

(Dispersion for the Heat-Sensitive Recording Layer)
The above preliminary dispersion, dispersion and dispersion were mixed with water in the following proportions and stirred to obtain a dispersion for a heat-sensitive recording layer.
Dispersion of electron-accepting developer and sensitizer 442 parts by weight Pre-dispersion of electron-donating dye precursor 120.5 parts by weight Pigment dispersion 252.5 parts by weight Core-shell type acrylic emulsion 115 parts by weight Dispersant (silanol-modified polyvinyl alcohol) 115 parts by weight Additive (zinc stearate) 80 parts by weight

Here, the core-shell type acrylic emulsion used was Bariastar (registered trademark) BM1000 manufactured by Mitsui Chemicals.

(Thermal Recording Layer)
The dispersion for the thermosensitive recording layer was applied to the undercoat layer of the support having the undercoat layer so as to give a coating amount of 3.1 g/m ² and then dried. Then, a supercalendering treatment was carried out to obtain a thermosensitive recording layer.

(Thermal recording material)
On the side of the support opposite the thermosensitive recording layer formed as described above, a partially saponified polyvinyl alcohol having an average polymerization degree of 500 and a saponification degree of 88 mol% was applied as a glue to a coating amount of 17 g/ ^m2 and dried to form a rewettable glue layer, thereby obtaining a thermosensitive recording material having a thermosensitive recording layer and a rewettable glue layer on the side of the support opposite the thermosensitive recording layer.

Example 2
Example 2 was prepared in the same manner as Example 1, except that the electron-accepting developer (4-hydroxy-4'-isopropoxydiphenyl sulfone) in Example 1 was changed to an electron-accepting developer (bis(3-allyl-4-hydroxyphenyl)sulfone).

Example 3
Example 3 was prepared in the same manner as in Example 1, except that the electron-accepting developer (4-hydroxy-4'-isopropoxydiphenylsulfone) in Example 1 was changed to an electron-accepting developer (2,4'-dihydroxydiphenylsulfone).

Example 4
Example 4 was prepared in the same manner as in Example 1, except that the core-shell type acrylic emulsion (Mitsui Chemicals, Inc., Barrier Star BM1000) in Example 1 was changed to a core-shell type acrylic emulsion (Mitsui Chemicals, Inc., Barrier Star OM1050).

Example 5
Example 5 was prepared in the same manner as in Example 1, except that the maleic anhydride copolymer (styrene maleic anhydride copolymer) in Example 1 was changed to a maleic anhydride copolymer (styrene isobutylene maleic anhydride copolymer, Dow Chemical Japan, Orotane (registered trademark) 165A).

Example 6
Example 6 was prepared in the same manner as in Example 1, except that the partially saponified polyvinyl alcohol in the rewettable paste layer was changed to gum arabic.

<Comparative Example 1>
Comparative Example 1 was prepared in the same manner as in Example 3, except that the core-shell type acrylic emulsion blended in the dispersion liquid for the thermal recording layer was changed to a styrene-butadiene copolymer.

<Comparative Example 2>
Comparative Example 2 was prepared in the same manner as in Example 3, except that the maleic anhydride copolymer blended in the dispersion of the electron-accepting developer and sensitizer was changed to sulfonic acid-modified polyvinyl alcohol.

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

<Recoloration>
The thermal recording material was left to stand for 168 hours in an environment of 40°C and 90% RH. After standing, the thermal recording material was left to stand for 3 hours in an environment of 23°C and 50% RH to relax the temperature and moisture of the thermal recording material. In an environment of 23°C and 50% RH, a black solid was printed with an applied energy of 0.60 mJ/dot using a facsimile tester TH-PMD manufactured by Okura Electric Co., Ltd. The print density of the printed portion was measured in an environment of 23°C and 50% RH using an RD19I optical densitometer (black mode) manufactured by X-Rite Co., Ltd. The measured values were evaluated according to the following criteria. In the present invention, a thermal recording material that is rated A or B is considered to have excellent recoloring properties.
A: The color density of the printed area is 1.1 or more.
B: The color density of the printed portion is 1.0 or more and less than 1.1.
C: The color density of the printed portion is less than 1.0.

<Blocking resistance>
Two copies of each thermal recording material were prepared, and the same type of thermal recording material was used to stack the thermal recording layer and the rewetting adhesive layer facing each other. The stacked materials were left to stand for 24 hours under a load of 0.5 kPa/A4 size, at 40°C and 90% RH. The stacked materials were then left to stand for 3 hours in an environment of 23°C and 50% RH to relax the temperature and moisture of the thermal recording materials. The stacked materials were then peeled off, and the surface conditions of the facing thermal recording layer and rewetting adhesive layer were evaluated according to the following criteria. In the present invention, a thermal recording material is considered to have excellent blocking resistance if it is rated A or B.
A: No damage was observed in the heat-sensitive recording layer and the rewettable adhesive layer.
B: Although inferior to A above, damage to the heat-sensitive recording layer and the rewettable adhesive layer is generally not observed.
C: Although inferior to B above, slight damage was observed in the heat-sensitive recording layer and the rewetting adhesive layer.
D: Damage was observed in the heat-sensitive recording layer and/or the rewetting adhesive layer.

From Table 1, it can be seen that Examples 1 to 6, which satisfy the configuration of the present invention, are thermal recording materials that are excellent in recoloring and blocking resistance. On the other hand, it can be seen that Comparative Examples 1 and 2, which do not satisfy the configuration of the present invention, are thermal recording materials that are unable to obtain at least either recoloring or blocking resistance.

Claims (1)

A thermal recording material having a support and a thermal recording layer on the support that contains an electron donating dye precursor and an electron accepting color developer, the thermal recording layer containing a high molecular weight polymer and a maleic anhydride copolymer having a core-shell structure with a core whose essential component is acrylonitrile and a shell whose essential component is methacrylamide, and a rewetting adhesive layer on the surface of the support opposite the thermal recording layer.