JP2008094092A - Thermosensitive recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensitive recording material excellent in the water resistance of an image printed in water color flexographic ink on the surface. <P>SOLUTION: This thermosensitive recording material comprises a support, a thermosensitive color-developing layer at least including a leuco dye and a developer on the support, and a protective layer provided on the thermosensitive color-developing layer, wherein the protective layer includes diacetone-modified polyvinyl alcohol resin and (meth)acrylic resin. The (meth)acrylic resin is preferably a styrene-acrylic acid copolymer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermal recording material suitably used in the field of computer output, the field of printers such as calculators, the field of recorders for medical measurement, the field of low-speed and high-speed facsimiles, the field of automatic ticket machines, the field of handy terminals, and the like.

  Conventionally, many proposals have been made on a thermal recording material having a thermosensitive coloring layer containing at least a leuco dye and a developer on a support and utilizing a coloring reaction between the leuco dye and the developer. Has been made. Such heat-sensitive recording materials (1) do not require complicated processing such as development and fixing, can be recorded in a short time with a relatively simple apparatus, (2) generate less noise, (3) In addition to being used for copying books, documents, etc., it is widely used as a recording material for electronic computers, facsimiles, ticketing machines, label printers, recorders, handy terminals and the like.

As the heat-sensitive recording material, there is a demand for a material that quickly develops a high density and has a high color fastness and a colored image. In recent years, it has been frequently used even in fields in which the reliability of recorded images such as labels is important, especially storage stability against plasticizers and oils contained in organic polymer materials used for packaging. Higher ones are demanded.
For this reason, a heat-sensitive recording material has been proposed in which a protective layer is provided on the heat-sensitive coloring layer. As the binder resin in such a protective layer, polyvinyl alcohol, modified polyvinyl alcohol, or a combination of these and a water-resistant agent is used. For example, it has been proposed to use diacetone-modified polyvinyl alcohol in combination with a hydrazine compound (see Patent Document 1). However, when this proposed material is used for the protective layer, there is a problem that the water-resistant reaction is promoted in the applied state and the protective layer coating solution is thickened over time.
Further, there has been proposed a heat-sensitive recording material using diacetone-modified polyvinyl alcohol as a binder resin for the protective layer and containing a hydrazine compound in the heat-sensitive color developing layer (see Patent Document 2). However, this proposal has problems that the water resistance of the protective layer is insufficient, the viscosity of the thermosensitive coloring layer coating solution is increased, and the coloring of the thermosensitive coloring layer is inhibited by the hydrazine-based compound.
In addition, a heat-sensitive recording material using a copolymerized polyvinyl alcohol containing diacetone acrylamide as a simple substance, a water-soluble hydrazine compound, and a water-soluble amine has been proposed (see Patent Document 3). However, when this proposed material is used for the protective layer, the water-soluble amine adversely affects the thermosensitive coloring layer, causing color development on the background, pH control is difficult, and liquid thickening is promoted depending on the amount of aqueous amine added. There's a problem.

As a method for improving these problems, Patent Document 4 proposes a heat-sensitive recording material in which polyvinyl alcohol having a reactive carbonyl group, a hydrazide compound, and a basic filler are combined (see Patent Document 4). . According to this proposal, the problem about thickening could be improved.
However, the heat-sensitive recording material using a polyvinyl alcohol having a reactive carbonyl group and a hydrazide compound as in Patent Document 4 is easily affected by an external force when an image printed with a water-based flexographic ink comes into contact with water for a long time. There is a problem that the image is peeled off, and the present situation is that the solution is desired.

Japanese Patent Application Laid-Open No. 8-151212 JP 11-314457 A Japanese Patent Laid-Open No. 10-87936 JP 2002-283717 A

  This invention is made | formed in view of this present condition, and makes it a subject to solve the said various problems in the past and to achieve the following objectives. That is, the present invention is excellent in water resistance of an image printed with a water-based flexographic ink on the surface, has good transportability under high-temperature and high-humidity environment conditions, and good sticking property under low-temperature and low-humidity environment conditions, and has high sensitivity. An object is to provide a heat-sensitive recording material.

  As a result of extensive studies by the present inventors to solve the above problems, in the thermosensitive recording material having a thermosensitive coloring layer on a support and a protective layer on the thermosensitive coloring layer, diacetone-modified in the protective layer. By including polyvinyl alcohol and (meth) acrylic resin, the image printed with water-based flexographic ink on the surface of the heat-sensitive recording material can effectively suppress peeling when contacted with water, and the water resistance of the printed image Has been found to improve.

The present invention is based on the above findings by the present inventors, and means for solving the above problems are as follows. That is,
<1> A support, a thermosensitive color-developing layer containing at least a leuco dye and a developer on the support, and a protective layer on the thermosensitive color-developing layer. A heat-sensitive recording material comprising an alcohol resin and a (meth) acrylic resin.
<2> A homopolymer obtained by polymerizing either (meth) acrylic acid or (meth) acrylic acid ester, (meth) acrylic acid, (meth) acrylic acid ester, and The heat-sensitive recording material according to <1>, wherein the heat-sensitive recording material is any one of copolymers obtained by copolymerizing a monomer copolymerizable with these.
<3> The thermosensitive recording material according to any one of <1> to <2>, wherein the (meth) acrylic resin is a styrene-acrylic acid copolymer.
<4> The thermosensitive recording according to any one of <1> to <3>, wherein the content of the (meth) acrylic resin in the protective layer is 1 to 50 parts by mass with respect to 100 parts by mass of the diacetone-modified polyvinyl alcohol resin. Material.
<5> The thermosensitive recording material according to any one of <1> to <4>, wherein the acid value of the (meth) acrylic resin is 100 mgKOH / g or more.
<6> The heat-sensitive recording material according to any one of <1> to <5>, wherein the protective layer contains a hydrazine compound, and the hydrazine compound is adipic acid dihydrazide.
<7> From the above <1> to <6>, which is a thermosensitive recording label having a pressure-sensitive adhesive layer and a release paper on the surface of the pressure-sensitive adhesive layer on the surface opposite to the surface having the heat-sensitive coloring layer of the support. The heat-sensitive recording material according to any one of the above.
<8> Any one of <1> to <6>, which is a thermosensitive recording label having a thermosensitive adhesive layer that exhibits adhesiveness by heating on the surface opposite to the surface having the thermosensitive coloring layer of the support. The heat-sensitive recording material described in 1.

The heat-sensitive recording material of the present invention comprises a heat-sensitive color-developing layer containing at least a leuco dye and a developer on a support, and a protective layer on the heat-sensitive color-developing layer. Contains alcohol resin and (meth) acrylic resin. In an image printed with water-based flexographic ink on the surface of the heat-sensitive recording material, the carboxyl group of the acrylic resin in the protective layer and the binder resin in the water-based flexographic ink are bonded at the interface between the protective layer and the water-based flexographic ink. Thus, the binding property with the water-based flexographic ink is strengthened. As a result, the image printed with the water-based flexographic ink is excellent in water resistance, transportability under high-temperature and high-humidity environment conditions, and good sticking property under low-temperature and low-humidity environment conditions.
Here, the flexographic ink is classified into an alcohol type and an aqueous type according to the type of solvent used. The alcohol-type flexographic ink is produced by using a low-boiling substance such as ethanol and a slow drying alcohol-based solvent such as glycol. On the other hand, the water-based flexographic ink is an ink type that uses water or a small amount of alcohol in combination, and does not contain a solvent. Therefore, the water-based flexographic ink is widely used because it can greatly contribute to resource saving and environmental hygiene. is there.

  According to the present invention, the conventional problems can be solved, the water-resistant flexographic image printed on the surface is excellent in water resistance, transportability under high-temperature and high-humidity environment conditions, and sticking property under low-temperature and low-humidity environment conditions. It is possible to provide a heat-sensitive recording material that is good and has high sensitivity.

  The heat-sensitive recording material of the present invention comprises a support, a heat-sensitive color developing layer on the support, and a protective layer on the heat-sensitive color developing layer, and if necessary, other layers such as a back layer and an intermediate layer. It has the layer of.

<Protective layer>
The protective layer contains a diacetone-modified polyvinyl alcohol resin and a (meth) acrylic resin, and contains a crosslinking agent and, if necessary, other components.

-Diacetone modified polyvinyl alcohol resin-
The diacetone-modified polyvinyl alcohol resin is polyvinyl alcohol having a hydroxyl group modified with diacetone, and an appropriately synthesized product or a commercially available product may be used.
In the former case, the diacetone-modified polyvinyl alcohol resin can be produced by a known method such as saponification of a copolymer obtained by copolymerizing a vinyl monomer having a diacetone group and a fatty acid vinyl ester.

Examples of the vinyl monomer having a diacetone group include diacetone acrylamide and diacetone methacrylamide.
Examples of the fatty acid vinyl ester include vinyl formate, vinyl acetate, and vinyl propionate. Among these, vinyl acetate is particularly preferable.
The diacetone-modified polyvinyl alcohol resin may be obtained by copolymerizing another copolymerizable vinyl monomer. Examples of these copolymerizable vinyl monomers include acrylic acid esters, butadiene, ethylene, propylene, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and itaconic acid.

The content of the reactive carbonyl group in the diacetone-modified polyvinyl alcohol resin is preferably 0.5 to 20 mol% and more preferably 2 to 10 mol% in the polymer. When the content is less than 0.5 mol%, water resistance may be insufficient in practical use. When the content exceeds 20 mol%, improvement in water resistance is not seen and the cost becomes expensive. There is.
There is no restriction | limiting in particular in the polymerization degree of the said diacetone modified polyvinyl alcohol resin, Although it can select suitably according to the objective, 300-3,000 are preferable and 500-2,000 are more preferable.

-(Meth) acrylic resin-
There is no restriction | limiting in particular as said (meth) acrylic resin, It can select from a well-known thing suitably, may be synthesize | combined suitably, and may be a commercial item.
In the former case, as the (meth) acrylic resin, a homopolymer obtained by polymerizing any of (meth) acrylic acid and (meth) acrylic acid ester, and (meth) acrylic acid, (meth) Any of acrylic acid esters and copolymers obtained by copolymerizing monomers copolymerizable therewith are suitable.

There is no restriction | limiting in particular as said (meth) acrylic acid ester, According to the objective, it can select suitably, Generally, the monomer thru | or oligomer etc. which are generally used for ultraviolet curing resin or electron beam curing resin etc. are mentioned suitably. It is done. Among these, those having a flexible structure are preferable, and aliphatic compounds are more preferable. In addition, what has a chain structure in an aromatic compound is preferable. Monofunctional monomers or bifunctional monomers are preferable to trifunctional or higher polyfunctional monomers.
Examples of the (meth) acrylic acid ester include (meth) acrylic acid alkyl ester having an alkyl group, amino (meth) acrylic acid ester having an alkyl group, glycol di (meth) acrylic acid ester, and allyl (meth) acrylic acid. Esters, trimethylolpropane tri (meth) acrylate, glycidyl (meth) acrylate, acrylamide, diacetone acrylamide, (meth) acrylonitrile, benzyl (meth) acrylate, dimethylaminoethyl (meth) acrylate methyl Examples include chloride salt, allyl (meth) acrylate, trimethylolpropane tri (meth) acrylate, and glycidyl (meth) acrylate. These may be used individually by 1 type and may use 2 or more types together.

There is no restriction | limiting in particular as (meth) acrylic-acid alkylester which has the said alkyl group, According to the objective, it can select suitably, For example, a C1-C18 thing is preferable, 3-15 are more preferable, Specifically, methyl (meth) acrylate ester, ethyl (meth) acrylate ester, n-butyl (meth) acrylate ester, i-butyl (meth) acrylate ester, cyclohexyl (meth) acrylate ester, Examples include 2-ethylhexyl (meth) acrylic acid ester, lauryl (meth) acrylic acid ester, stearyl (meth) acrylic acid ester, and the like.
If the carbon number of the alkyl group is too short, the flexibility of the (meth) acrylic resin may be lacking. If it is too long, the methylene chains of the side chains are regularly arranged, and the (meth) acrylic resin May lack flexibility.

There is no restriction | limiting in particular as amino (meth) acrylic acid ester which has the said alkyl group, According to the objective, it can select suitably, For example, a C1-C5 thing is preferable, Specifically, dimethylamino Examples include ethyl (meth) acrylate ester dimethylaminoethyl, (meth) acrylate ester, and the like.
There is no restriction | limiting in particular as said glycol di (meth) acrylic acid ester, According to the objective, it can select suitably, For example, ethylene glycol di (meth) acrylic acid ester, butylene glycol di (meth) acrylic acid ester, etc. Is mentioned.

  Examples of the copolymerizable monomer include vinyl arenes such as styrene, α-methyl styrene, monochlorostyrene and dichlorostyrene; vinylcyans such as acrylonitrile and methacrylonitrile; vinyl chloride, vinyl bromide and chloroprene. Vinyl halides; vinyl acetate; alkenes such as ethylene, propylene, butylene, butadiene, isobutylene; halogenated alkenes; allyl methacrylate, diallyl phthalate, triallyl cyanurate, monoethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, Examples include polyfunctional monomers such as tetraethylene glycol dimethacrylate, divinylbenzene, and glycidyl methacrylate.

These (meth) acrylic resins may be used alone or in combination of two or more. Among these, an acrylic resin containing ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate as a copolymer component, or a copolymer component such as methacrylic acid ester, styrene, acrylonitrile, and vinyl acetate as a copolymer component is preferable. A styrene-acrylic acid copolymer is particularly preferred from the viewpoint of binding properties with the resin contained in the water-based flexographic ink.
The acrylic resin can provide the same water-resistant effect of printed images for both water-soluble type and emulsion type, but when the emulsion type is used, the barrier properties such as plasticizer resistance and oil resistance deteriorate. Therefore, the water-soluble type is preferable.

The content of the (meth) acrylic resin in the protective layer is preferably 1 to 50 parts by mass and more preferably 5 to 30 parts by mass with respect to 100 parts by mass of the diacetone-modified polyvinyl alcohol resin. When the content is less than 1 part by mass, a water-resistant effect may not be seen on the printed image of the water-based flexo ink. When the content exceeds 50 parts by mass, the sticking property in a low-temperature and low-humidity environment is inferior. There is.
The acid value of the (meth) acrylic resin is preferably 100 mgKOH / g or more, and more preferably 150 to 250 mgKOH / g. When the acid value is less than 100 mgKOH / g, a sufficient effect may not be obtained for the water resistance of the printed image of the water-based flexographic ink.
Here, the acid value of the (meth) acrylic resin can be measured, for example, by a test method defined in JIS K0070.
There is no restriction | limiting in particular as a mass mean molecular weight of the said (meth) acrylic resin, Although it can select suitably according to the objective, 1,000-300,000 are preferable.

-Crosslinking agent-
There is no restriction | limiting in particular as said crosslinking agent, Although it can select suitably according to the objective, A hydrazide compound is suitable.
The hydrazine compound is not particularly limited as long as it has a hydrazide group, and can be appropriately selected according to the purpose. Acid dihydrazide, adipic acid dihydrazide, azelaic acid hydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, benzoic acid hydrazide, glutaric acid dihydrazide dihydric acid dihydroxide diglycolic acid dihydride diglycolic acid dihydric acid Examples include dihydrazide, isophthalic acid hydrazide, terephthalic acid dihydrazide, 2,7-naphthoic acid dihydrazide, polyacrylic acid hydrazide, and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, adipic acid dihydrazide is particularly preferable from the viewpoint of water resistance and safety.

  The addition amount of the crosslinking agent varies depending on the modification amount and type of the functional group of the crosslinking agent, but is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the diacetone-modified polyvinyl alcohol resin. Is more preferable.

  The crosslinking agent of the present invention may be used in combination with known crosslinking agents such as glyoxal, melamine, aziridine compound, polyamide epichlorohydrin resin, zirconium ammonium carbonate, ethylenediamine and the like, as long as the function is not impaired. .

  The protective layer may further contain a filler as necessary. Examples of the filler include inorganic fine powders such as aluminum hydroxide, calcium carbonate, silica, zinc oxide, titanium oxide, zinc hydroxide, barium sulfate, clay, talc, surface-treated calcium, and surface-treated silica; urea Examples thereof include organic fine powders such as formalin resin, styrene-methacrylic acid copolymer, and polystyrene resin. Among these, aluminum hydroxide and calcium carbonate are particularly preferable because they have good wear resistance to the thermal head when printing is performed for a long period of time.

The method for forming the protective layer is not particularly limited and may be appropriately selected depending on the intended purpose. However, a method for forming the protective layer by applying a protective layer coating solution on the thermosensitive coloring layer is preferable. .
There is no restriction | limiting in particular as said application | coating method, According to the objective, it can select suitably, For example, a spin coat method, a dip coat method, a kneader coat method, a curtain coat method, a blade coat method etc. are mentioned. Among these, the spin coating method and the dip coating method are particularly preferable from the viewpoint of coating efficiency and the like.
After the application, it may be dried as necessary. The drying temperature is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 100 to 250 ° C.
Dry coating amount of the protective layer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably ^{0.5~5.0g / m 2, 1.5~3.5g / m} 2 is More preferred. When the dry coating amount is less than 0.5 g / m ² , a sufficient function as a protective layer cannot be obtained, and the printed image is faded by an external chemical such as oil, plasticizer, water, or the like. If it exceeds 5.0 g / m ² , the function of the protective layer is not further improved, and the color development sensitivity may be lowered.

<Thermosensitive coloring layer>
The thermosensitive coloring layer contains at least a leuco dye, a developer, and a binder resin, and further contains other components as necessary.

-Leuco dye-
The leuco dye is not particularly limited and can be appropriately selected according to the purpose from those usually used in heat-sensitive recording materials. For example, triphenylmethane, fluoran, phenothiazine, auramine A leuco compound of a dye such as a spiropyran type or indinophthalide type is preferably used.
Specific examples of such leuco dyes include, for example, 2-anilino-3-methyl-6-dibutylaminofluorane, 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p -Dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chloro Fluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-ben Fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluorane, 2- {N- (3 ' -Trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6-bis (diethylamino) -9- (o-chloroanilino) xanthylbenzoate lactam}, 3-diethylamino-6-methyl-7- (M-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-7-o -Chloranilino) fluorane, 3-N-methyl-N, n-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N- Chlohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) -5-methyl-7- (N, N -Dibenzylamino) fluorane, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3- (2'-hydroxy) -4′-dimethylaminophenyl) -3- (2′-methoxy-5′chlorophenyl) phthalide, 3- (2′-hydroxy-4′-dimethylaminophenyl) -3- (2′-methoxy-5 ′) -Nitrophenyl) phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl) phthalide, 3 (2′-methoxy-4′-dimethylaminophenyl) -3- (2′-hydroxy-4′-chloro-5′-methylphenyl) phthalide, 3- (N-ethyl-N-tetrahydrofurfuryl) amino- 6-methyl-7-anilinofluorane, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3-N-methyl-N-isobutyl-6 Methyl-7-anilinofluorane, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro- 7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethy Ruamino-5-chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxy) Carbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7 -(Pn-butylanilino) fluorane, 3-di-n-butylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorene spiro (9,3 ')-6' -Dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4′-propyl Lomofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ′, 5′-benzofluorane, 3-N-methyl-N-isopropyl-6 -Methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ', 4'-dimethylani Lino) fluorane, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N- Benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-die Tylamino-5-chloro- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenyl) Amino) fluorane, 3-diethylamino-5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piberidinofluorane, 2-chloro-3- (N-methyltoluidino) -7- ( p-N-butylanilino) fluorane, 3,6-bis (dimethylamino) fluorene spiro (9,3 ′)-6′-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6 -Benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7-anilino Luolan, 3-N-ethyl-N-(-2-ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-ani Linofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ′, 5′-benzofluorane, 3-p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) Ethylene-2-yl} phthalide, 3- (p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} -6-dimethylaminophthalide, 3- ( p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-1-phenylethylene-2-yl) phthalide, 3- (p-dimethylaminophenyl) -3- ( -P-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl) -6-dimethylaminophthalide, 3- (4'-dimethylamino-2'-methoxy) -3- (1 "-p-dimethyl Aminophenyl-1 "-p-chlorophenyl-1", 3 "-butadiene-4" -yl) benzophthalide, 3- (4'-dimethylamino-2'-benzyloxy) -3- (1 "-p-dimethyl Aminophenyl-1 "-phenyl-1", 3 "-butadiene-4" -yl) benzophthalide, 3-dimethylamino-6-dimethylamino-fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide 3,3-bis (2- (p-dimethylaminophenyl) -2-p-methoxyphenyl) ethenyl) -4,5,6,7-tetrachlorophthalide, 3-bis {1,1-bi (4-Pyrrolidinophenyl) ethylene-2-yl} -5,6-dichloro-4,7-dipromophthalide, bis (p-dimethylaminostyryl) -1-naphthalenesulfonylmethane, bis (p-dimethylaminostyryl) Examples include -1-p-tolylsulfonylmethane. These may be used individually by 1 type and may use 2 or more types together.

-Developer-
As the developer, various electron-accepting compounds that cause the leuco dye to develop a color upon contact, or an oxidizing agent can be applied.
Specific examples of the developer are not particularly limited and may be appropriately selected from known ones according to the purpose. For example, 4,4′-isopropylidenebisphenol, 4,4′-isopropylidenebis (O-methylphenol), 4,4′-secondary butylidenebisphenol, 4,4′-isopropylidenebis (2-tertiarybutylphenol), zinc p-nitrobenzoate, 1,3,5-tris (4- Tertiary butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2- (3,4'-dihydroxydiphenyl) propane, bis (4-hydroxy-3-methylphenyl) sulfide, 4- {β -(P-methoxyphenoxy) ethoxy} salicylic acid, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxa Heptane, 1,5-bis (4-hydroxyphenthio) -5-oxapentane, phthalic acid monobenzyl ester monocalcium salt, 4,4′-cyclohexylidene diphenol, 4,4′-isopropylidenebis (2- Chlorophenol), 2,2'-methylenebis (4-methyl-6-tertiary-butylphenol), 4,4'-butylidenebis (6-tertiarybutyl-2-methyl) phenol, 1,1,3-tris (2 -Methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4'-thiobis (6-tertiary- Butyl-2-methyl) phenol, 4,4′-diphenolsulfone, 4-isopropoxy-4′-hydroxydiphe Rusulfone (4-hydroxy-4′-isopropoxydiphenylsulfone), 4-benzyloxy-4′-hydroxydiphenylsulfone, 4,4′-diphenol sulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, protocatechuyl Benzyl acid, stearyl gallate, lauryl gallate, octyl gallate, 1,3-bis (4-hydroxyphenylthio) -propane, N, N′-diphenylthiourea, N, N′-di (m-chlorophenyl) ) Thiourea, salicylanilide, bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis (4-hydroxycumyl) benzene, 1,4-bis (4-Hydroxycumyl) benzene, 2,4′-diphenol Sulfone, 2,2′-diallyl-4,4′-diphenolsulfone, 3,4-dihydroxyphenyl-4′-methyldiphenylsulfone, zinc 1-acetyloxy-2-naphthoate, 2-acetyloxy-1- Zinc naphthoate, zinc 2-acetyloxy-3-naphthoate, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, 4 4,4′-thiobis (2-methylphenol), 4,4′-thiobis (2-chlorophenol), and the like. These may be used individually by 1 type and may use 2 or more types together.

  The content of the developer is preferably 1 to 20 parts by mass and more preferably 2 to 10 parts by mass with respect to 1 part by mass of the leuco dye.

-Binder resin-
There is no restriction | limiting in particular as said binder resin, Although it can select suitably according to the objective from well-known things, For example, polyvinyl alcohol, starch or its derivative; methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose Cellulose derivatives such as: polyacrylic acid soda, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid terpolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-anhydrous Water-soluble polymers such as maleic acid copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, casein; polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester , Emulsions such as polymethacrylic acid ester, polybutyl methacrylate, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer; latexes such as styrene-butadiene copolymer, styrene-butadiene-acrylic copolymer Etc. These may be used individually by 1 type and may use 2 or more types together.

  Various thermofusible substances can be used as a sensitivity improver in the thermosensitive coloring layer. Examples of the heat-fusible substance include fatty acids such as stearic acid and behenic acid; fatty acid amides such as stearic acid amide and palmitic acid amide; zinc stearate, aluminum stearate, calcium stearate, zinc palmitate, behen Fatty acid metal salts such as zinc acid; p-benzylbiphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, β-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid phenyl Esters, 1-hydroxy-2-naphthoic acid methyl ester, diphenyl carbonate, terephthalic acid dibenzyl ester, terephthalic acid dimethyl ester, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibenzyloxynaphth Talene, 1,2-bis (phenoxy) ethane, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-bis (phenoxy) butane, 1, 4-bis (phenoxy) -2-butene, 1,2-bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1,4-bis (phenylthio) butane, 1,4-bis (phenylthio) -2- Butene, 1,2-bis (4-methoxyphenylthio) ethane, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2-vinyl Oxyethoxy) biphenyl, p-aryloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, 1,3-dibenzoyloxypropane, Benzyl disulfide, 1,1-diphenylethanol, 1,1-diphenylpropanol, p- (benzyloxy) benzyl alcohol, 1,3-diphenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecyl Carbamoylbenzene, succinic acid dibenzyl ester, 1,5-bis (p-methoxyphenyloxy) -3-oxapentane and the like can be mentioned. These may be used individually by 1 type and may use 2 or more types together.

If necessary, the thermosensitive coloring layer can be used in combination with various auxiliary additives such as surfactants, lubricants, fillers and the like. Examples of the lubricant include higher fatty acids or metal salts thereof, higher fatty acid amides, higher fatty acid esters, animal waxes, vegetable waxes, mineral waxes, petroleum waxes, and the like.
Examples of the filler include inorganic systems such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, kaolin, talc, surface-treated calcium, and surface-treated silica. Fine powders: Urea-formalin resins, styrene / methacrylic acid copolymers, polystyrene resins, organic fine powders such as vinylidene chloride resins, and the like.

The thermosensitive coloring layer is not particularly limited and can be formed by a generally known method. For example, a leuco dye, a developer separately from a binder resin, other components, a ball mill, an attritor, a sand mill, etc. The dispersion particle size of the mixture is pulverized and dispersed until the dispersed particle diameter becomes 0.1 to 3 μm, and mixed with a filler, a lubricant, etc. as necessary to prepare a thermosensitive coloring layer coating solution on the support. The thermosensitive coloring layer can be formed by applying to the coating.
Deposition amount after drying of the heat-sensitive coloring layer, said depend application of the composition and the heat-sensitive adhesive material of the heat-sensitive coloring layer to unequivocally can not be determined, preferably ^{1~20g / m 2, 3~10g / m} 2 Is more preferable.

<Support>
The support is not particularly limited in shape, structure, size, material, and the like, and can be appropriately selected according to the purpose. Examples of the shape include a sheet shape, a roll shape, and a flat plate shape. Etc. The structure may be a single layer structure or a laminated structure, and the size may be appropriately selected according to the size of the heat-sensitive recording material. Examples of the material include plastic film, synthetic paper film, fine paper, waste paper pulp, recycled paper, glossy paper, oil-resistant paper, coated paper, art paper, cast coated paper, finely coated paper, and resin-laminated paper. Can be mentioned.

There is no restriction | limiting in particular as said support body, According to the objective, it can select suitably, For example, paper, a film, a synthetic paper, a release paper etc. can be used suitably. As the paper, either acid paper or neutral paper can be used. Further, regarding the release paper made of the neutral paper support and the neutral paper, one having a small amount of calcium is preferable. Thus, the release paper which consists of neutral paper and neutral paper with little calcium content is obtained by reducing the ratio of the used paper for papermaking. In addition, calcium carbonate is usually used as an internal additive and alkyl ketene dimer or alkenyl succinic anhydride is used as a sizing agent, whereas talc is used as an internal additive for papermaking of neutral paper with a small amount of calcium. It can be obtained by combining with a neutral rosin sizing agent instead of or clay.
There is no restriction | limiting in particular as thickness of the said support body, It can select suitably according to the objective, 30-2,000 micrometers is preferable and 50-1,000 micrometers is more preferable.

  The layer structure of the heat-sensitive recording material of the present invention includes a support, a heat-sensitive color forming layer provided on the support, a protective layer on the heat-sensitive color developing layer, and no heat-sensitive color forming layer as a support. An intermediate layer (heat insulation layer) may be formed on the side surface (back surface), or between the support and the thermosensitive coloring layer, between the thermosensitive coloring layer and the protective layer, and between the support and the back layer. Among these, it is particularly preferable to form a heat insulating layer between the support and the thermosensitive coloring layer, and this heat insulating layer preferably uses hollow resin particles having a hollow ratio of 80% or more as a filler. Each of these layers may be a single layer or a plurality of layers.

  Since the heat-sensitive recording material of the present invention is remarkably improved in adhesion to the thermal head by the calendering process, it is particularly preferable to carry out the calendering process on the heat-sensitive coloring layer or the protective layer. That is, by controlling the smoothness of the surface by the pressure of the calendering treatment to the thermosensitive coloring layer or the protective layer, it is possible to obtain a thermosensitive recording material having no background fog and having a higher definition than before. .

<Thermal recording label>
In the first embodiment, the thermosensitive recording label as the thermosensitive recording material has a pressure-sensitive adhesive layer on the back surface opposite to the surface having the heat-sensitive coloring layer of the support, and a release paper on the surface of the pressure-sensitive adhesive layer. And other configurations as necessary. Note that the back layer surface is also included on the back surface.
The material for the pressure-sensitive adhesive layer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include urea resin, melamine resin, phenol resin, epoxy resin, vinyl acetate resin, and vinyl acetate-acrylic copolymer. Polymer, ethylene-vinyl acetate copolymer, acrylic resin, polyvinyl ether resin, vinyl chloride-vinyl acetate copolymer, polystyrene resin, polyester resin, polyurethane resin, polyamide resin, chlorinated polyolefin Examples thereof include resins, polyvinyl butyral resins, acrylic ester copolymers, methacrylic ester copolymers, natural rubber, cyanoacrylate resins, and silicone resins. These may be used individually by 1 type and may use 2 or more types together.

In the second form, the thermosensitive recording label further comprises a thermosensitive adhesive layer that exhibits adhesiveness by heating on the back surface opposite to the surface having the thermosensitive coloring layer of the support. Accordingly, other configurations are provided. Note that the back layer surface is also included on the back surface.
The heat-sensitive adhesive layer contains a thermoplastic resin and a heat-meltable substance, and further contains a tackifier as necessary.
The thermoplastic resin imparts adhesive strength and adhesive strength. The heat-meltable substance is solid at room temperature, so it does not give plasticity to the resin, but melts by heating to swell or soften the resin and develop adhesiveness. The tackifier has a function of improving tackiness.

<Thermal recording magnetic paper>
The heat-sensitive recording magnetic paper as the heat-sensitive recording material has a magnetic recording layer on the back surface of the support opposite to the surface having the heat-sensitive color-developing layer. Have. Note that the back layer surface is also included on the back surface.
As the magnetic recording layer, for example, iron oxide, barium ferrite, etc., and vinyl chloride resin, urethane resin, nylon resin, etc. are used to coat or form on a support, or vapor deposition, sputtering, etc. It is formed without using resin by a method.
The magnetic recording layer is preferably provided on the surface of the support opposite to the thermochromic layer, but may be provided between the support and the thermochromic layer and part of the thermochromic layer.

  There is no restriction | limiting in particular as a shape of the heat-sensitive recording material of this invention, According to the objective, it can select suitably, A label form, a sheet form, a roll form etc. are mentioned suitably.

The recording method using the heat-sensitive recording material of the present invention is not particularly limited, and is performed by a thermal pen, a thermal head, laser heating or the like depending on the purpose of use.
The heat-sensitive recording material of the present invention is used in the POS field such as for fresh foods, lunch boxes and prepared foods; in the field of copying books and documents; in the field of communication such as facsimile; in the field of ticketing such as ticket machines, receipts and receipts; It is suitably used in various fields such as baggage tags, and heat sensitive recording materials are exposed to water in an environment where they come into contact with water (for example, in refrigerators, supermarket shelves, around water, etc.). Since the image printed with the aqueous flexo ink on the surface of the recording material is not easily peeled off, it can be particularly suitably used in such applications.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Example 1)
<Preparation of thermal recording material>
(1) Preparation of dye dispersion (Part A)
The following composition was dispersed with a sand mill until the average particle size became 0.5 μm to prepare solution A.
-2-anilino-3-methyl-6-dibutylaminofluorane ... 20 parts by mass-10% by weight aqueous solution of polyvinyl alcohol ... 20 parts by mass-water ... 60 parts by mass

(2) Preparation of Liquid B The following composition was dispersed with a ball mill until the average particle size became 1.5 μm to prepare Liquid B.
Aluminum hydroxide: 20 parts by mass 4-hydroxy-4'-isopropoxydiphenylsulfone: 20 parts by mass 10% by weight aqueous polyvinyl alcohol solution: 20 parts by mass Water: 40 parts by mass

(3) Preparation of liquid C The following composition was dispersed with a ball mill until the average particle size became 1.5 μm to prepare liquid C.
Aluminum hydroxide: 100 parts by weight Polyvinyl alcohol 10% by weight aqueous solution: 20 parts by weight Water: 40 parts by weight

(4) Preparation of thermosensitive coloring layer coating solution The following composition was mixed to prepare a thermosensitive coloring layer coating solution.
-A part-20 parts by mass-B part-60 parts by mass-Resin aqueous solution (diacetone-modified polyvinyl alcohol, solid content = 10% by mass) ... 30 parts by mass-Dioctyl sulfosuccinic acid aqueous solution (solid content = 5% by mass) ... 1 part by mass

(5) Preparation of protective layer coating solution The following composition was mixed to prepare a protective layer coating solution.
-C liquid ... 60 parts by mass-Diacetone-modified polyvinyl alcohol aqueous solution (solid content = 10% by mass) ... 100 parts by mass-Acrylic resin aqueous solution (acid value = 600 mg KOH / g, sodium polyacrylate, Julimer AC103, Nippon Pure Chemical Industries, Ltd., solid content = 10% by mass) 20 parts by mass Adipic acid dihydrazide aqueous solution (solid content = 10% by mass) 10 parts by mass Dioctylsulfosuccinic acid aqueous solution (solid content = 5 mass) %) ... 1 part by mass

(6) Preparation of thermosensitive recording paper On the support (high-quality paper with a basis weight of 60 g / m ² ), the above thermosensitive coloring coating solution was applied so that the dye adhesion amount was 0.50 g / m ² and dried. A thermosensitive coloring layer was formed. The protective layer coating solution was applied onto the thermosensitive coloring layer so that the dry adhesion amount was 3.0 g / m ² and dried to form a protective layer. Then, it processed with the super calendar. Thus, a thermal recording paper as a thermal recording material of Example 1 was produced.

(Example 2)
-Production of thermal recording material-
Styrene-acrylic acid copolymer resin aqueous solution (acid value = 195 mgKOH / g, John Crill 61J, manufactured by Johnson Polymer Co., Ltd., solid content = 10% by mass) instead of the acrylic resin aqueous solution used in the protective layer coating solution of Example 1 ) Was used in the same manner as in Example 1 except that 20 parts by mass was used.

(Example 3)
-Production of thermal recording material-
Styrene-acrylic acid copolymer resin aqueous solution (acid value = 195 mgKOH / g, John Crill 61J, manufactured by Johnson Polymer Co., Ltd., solid content = 10% by mass) instead of the acrylic resin aqueous solution used in the protective layer coating solution of Example 1 The heat-sensitive recording material of Example 3 was produced in the same manner as in Example 1 except that 2 parts by mass of) was added.

Example 4
-Production of thermal recording material-
Styrene-acrylic acid copolymer resin aqueous solution (acid value = 195 mgKOH / g, John Crill 61J, manufactured by Johnson Polymer Co., Ltd., solid content = 10% by mass) instead of the acrylic resin aqueous solution used in the protective layer coating solution of Example 1 ) Was added in the same manner as in Example 1 except that 0.5 part by mass was added.

(Example 5)
-Production of thermal recording material-
Styrene-acrylic acid copolymer resin aqueous solution (acid value = 195 mgKOH / g, John Crill 61J, manufactured by Johnson Polymer Co., Ltd., solid content = 10% by mass) instead of the acrylic resin aqueous solution used in the protective layer coating solution of Example 1 The heat-sensitive recording material of Example 5 was produced in the same manner as in Example 1 except that 45 parts by mass of) was added.

(Example 6)
-Production of thermal recording material-
Styrene-acrylic acid copolymer resin aqueous solution (acid value = 195 mgKOH / g, John Crill 61J, manufactured by Johnson Polymer Co., Ltd., solid content = 10% by mass) instead of the acrylic resin aqueous solution used in the protective layer coating solution of Example 1 ) Was added in the same manner as in Example 1 except that 55 parts by mass was added.

(Example 7)
-Production of thermal recording material-
In place of the acrylic resin aqueous solution used in the protective layer coating solution of Example 1, a styrene-acrylic copolymer resin aqueous solution (acid value 100 mgKOH / g, John Crill 450, manufactured by Johnson Polymer Co., Ltd., solid content = 10% by mass). A heat-sensitive recording material of Example 7 was produced in the same manner as Example 1 except that 20 parts by mass was added.

(Example 8)
-Production of thermal recording material-
In place of the acrylic resin aqueous solution used in the protective layer coating solution of Example 1, a styrene-acrylic copolymer resin aqueous solution (acid value = 55 mg KOH / g, John Crill 775, manufactured by Johnson Polymer Co., Ltd., solid content = 10% by mass) A heat-sensitive recording material of Example 8 was produced in the same manner as Example 1 except that 20 parts by mass of was added.

(Comparative Example 1)
-Production of thermal recording material-
A thermosensitive recording material of Comparative Example 1 was prepared in the same manner as in Example 1 except that the acrylic resin aqueous solution was not added to the protective layer coating solution of Example 1.

(Comparative Example 2)
-Production of thermal recording material-
A carboxy-modified polyvinyl alcohol aqueous solution (solid content = 10% by mass) was used instead of the diacetone-modified polyvinyl alcohol aqueous solution used in the protective layer coating solution of Example 1, and a polyamide epichlorohydrin resin aqueous solution (solid content) instead of the adipic acid dihydrazide aqueous solution. = 10% by mass), and the heat-sensitive recording material of Comparative Example 2 was produced in the same manner as in Example 1 except that the aqueous acrylic resin solution (solid content = 10% by mass) was not added.

(Comparative Example 3)
-Production of thermal recording material-
A carboxy-modified polyvinyl alcohol aqueous solution (solid content = 10% by mass) was used instead of the diacetone-modified polyvinyl alcohol aqueous solution used in the protective layer coating solution of Example 1, and a polyamide epichlorohydrin resin aqueous solution (solid) instead of the adipic acid dihydrazide aqueous solution. A heat-sensitive recording material of Comparative Example 3 was produced in the same manner as in Example 1 except that min = 10% by mass).

(Comparative Example 4)
-Production of thermal recording material-
Comparative Example 4 was performed in the same manner as in Example 1 except that a carboxy-modified polyvinyl alcohol aqueous solution (solid content = 10% by mass) was used instead of the diacetone-modified polyvinyl alcohol aqueous solution used in the protective layer coating solution of Example 1. A heat-sensitive recording material was prepared.

Here, Table 1 summarizes the structures of the protective layers of the respective heat-sensitive recording materials of Examples 1 to 8 and Comparative Examples 1 to 4.

The symbols in Table 1 represent the following contents.
-Polyvinyl alcohol resin-
A-1: diacetone modified polyvinyl alcohol resin (reactive carbonyl group content = 4.0 mol%)
A-2: Carboxy-modified polyvinyl alcohol resin-acrylic resin-
B-1: sodium polyacrylate (acid value = 600 mg KOH / g, Jurimer AC-103, manufactured by Nippon Pure Chemical Co., Ltd.)
B-2: Styrene-acrylic copolymer resin (acid value = 195 mgKOH / g, Joncrill 61J, manufactured by Johnson Polymer Co., Ltd.)
B-3: Styrene-acrylic copolymer resin (acid value = 100 mg KOH / g, Jonkrill 450, manufactured by Johnson Polymer Co., Ltd.)
B-4: Styrene-acrylic copolymer resin (acid value = 55 mg KOH / g, John Crill 775, manufactured by Johnson Polymer Co., Ltd.)
-Crosslinking agent-
C-1: Adipic acid dihydrazide C-2: Polyamide epichlorohydrin resin

  Next, various characteristics were evaluated as follows about each produced thermal recording material of Examples 1-8 and Comparative Examples 1-4. The results are shown in Table 2.

<Water resistance evaluation of water-based flexographic printing>
For each heat-sensitive recording material, an aqueous flexo ink diluted to 25% by mass (manufactured by AKZO Nobel, MTQ 30302-404) was applied with a wire bar having a wire diameter of 0.10 mm, and the environment was 22 ° C. and 65% RH. After being allowed to stand for drying, a drop of water was dropped on the printed image, and after 5 minutes, it was rubbed once with a finger, and the water resistance was evaluated from the following criteria according to how the printed image peeled off.
[Water peeling test rank for water-based flexographic printing (4 levels)]
◎: No peeling at the printing part ○: Peeling of less than 1 to 25% occurred at the printing part Δ: Peeling at less than 25 to 50% occurred at the printing part ×: Peeling of 50% or more occurred at the printing part did

<Sensitivity magnification>
For each heat-sensitive recording material that has been calendared, a thermal printing experiment apparatus (manufactured by Matsushita Electric Parts Co., Ltd.) having a thin film head is used, a head power of 0.45 W / dot, a recording time of 20 msec / L, and a scanning density of 8 × 385. Printing was performed at a pulse width of 0.0 to 0.7 mmsec every 1 msec under dot / mm conditions, the print density was measured with a Macbeth densitometer RD-914, and the pulse width at which the density was 1.0 was calculated.
On the basis of Comparative Example 1, calculation is performed as (pulse width of Comparative Example 1) / (pulse width of measured sample) = sensitivity magnification. The larger the value, the better the sensitivity (thermal response).

<Evaluation of transportability under high temperature and high humidity conditions>
Each thermal recording material and printer (SM-90, manufactured by Teraoka Seiko Co., Ltd.) was left in a high-temperature, high-humidity environment of 40 ° C and 90% RH for 1 hour to print the humidity, and printing was evaluated from the print length. did. The print length is the length from the print start portion to the print last portion when a specific print pattern is printed by the printer. When the transportability is excellent, the print pattern is printed accurately, and the print length of the print pattern is the same as the print length of the actually printed sample. On the other hand, when the transportability is inferior, the heat-sensitive recording material and the thermal head are poorly transported, and the printing portion is shortened to be printed, and further, the heat-sensitive recording material is meandered during the transport. For example, the print length of the print pattern becomes shorter. In this test, a printing pattern having a printing length of 100 mm was used.

<Evaluation of sticking property under low temperature and low humidity conditions>
Each thermal recording material and printer (L'esprit R-12, manufactured by Sato Co., Ltd.) was left in a low-temperature and low-humidity environment at 5 ° C and 30% RH for 1 hour to adjust the humidity, and then printed and evaluated sticking properties. did.
If the sticking property is excellent, the print pattern is printed accurately. On the other hand, when the sticking property is inferior, since the same portion of the heat-sensitive recording material is printed, the print pattern is not printed accurately. The printed image was visually confirmed, and the sticking property was evaluated according to the following criteria.
[Sticking visual inspection rank (5 levels)]
◎: Sticking does not occur ○: Sticking occurs, but there is no problem in quality △: Sticking occurs, and there is some problem in quality ×: Not transported completely and sticking occurs × ×: Not transported at all

<Evaluation of water resistance>
A test piece printed with an energy of 1.00 ms using a thermal recording material printing simulator manufactured by Okura Electric Co., Ltd. was immersed in 100 ml of water in an environment of 20 ° C. for 24 hours, and the density of the image area after the test was measured using a Macbeth densitometer RD. -914. In addition, water resistance is so favorable that a value is large.

表２の結果から、実施例１〜８の本発明の感熱記録材料は、比較例１〜４に比べて、高温高湿環境条件下での搬送性及び低温低湿環境条件下でのスティッキング性が良好であり、高感度を保持したまま、水性フレキソインクによる印刷画像の耐水性が向上していることが認められた。
これに対し、比較例１では、保護層にジアセトン変性ポリビニルアルコール樹脂を用いているが、アクリル樹脂を含んでいないため、水性フレキソインクによる印刷画像の耐水性が劣るものであった。
また、比較例２及び３では、保護層にカルボキシ変性ポリビニルアルコールを使用しているので、水性フレキソインクによる印刷画像の耐水性は良好であるが、スティッキング性が劣るものであった。
また、比較例４では、カルボキシ変性ポリビニルアルコールとアジピン酸ジヒドラジドは架橋反応を起こさないため、保護層としての機能を有しておらず、そのため、搬送性、スティッキング性、及び耐水性が劣るものであった。

From the results of Table 2, the heat-sensitive recording materials of the present invention of Examples 1 to 8 are more transportable under high-temperature and high-humidity environment conditions and sticking properties under low-temperature and low-humidity environment conditions than Comparative Examples 1 to 4. It was confirmed that the water resistance of the printed image with the aqueous flexo ink was improved while maintaining good and high sensitivity.
In contrast, in Comparative Example 1, a diacetone-modified polyvinyl alcohol resin was used for the protective layer, but since it did not contain an acrylic resin, the water resistance of the printed image with the aqueous flexo ink was inferior.
In Comparative Examples 2 and 3, since carboxy-modified polyvinyl alcohol was used for the protective layer, the water resistance of the printed image with the aqueous flexo ink was good, but the sticking property was inferior.
Further, in Comparative Example 4, carboxy-modified polyvinyl alcohol and adipic acid dihydrazide do not cause a crosslinking reaction, and thus do not have a function as a protective layer, and therefore have poor transportability, sticking property, and water resistance. there were.

  The heat-sensitive recording material of the present invention is printed with water-based flexographic ink on the surface of the heat-sensitive recording material by contact with water for a long time in an environment in contact with water (for example, in a refrigerator, a supermarket shelf, around water). Therefore, it is suitable for thermal recording paper, thermal recording label, thermal magnetic recording paper, thermal recording film, etc., for example, copying of books and documents, electronic computers, facsimiles, Widely used for recording materials for ticket issuing machines, label printers, recorders, handy terminals, etc., display labels for clothing, labels for parts management, logistics labels, etc.

Claims (8)

  A support, a thermosensitive color developing layer containing at least a leuco dye and a developer on the support, and a protective layer on the thermosensitive color developing layer, wherein the protective layer is at least a diacetone modified polyvinyl alcohol resin. And a (meth) acrylic resin.   A (meth) acrylic resin is a homopolymer obtained by polymerizing either (meth) acrylic acid or (meth) acrylic acid ester, and (meth) acrylic acid, (meth) acrylic acid ester, and these. The heat-sensitive recording material according to claim 1, which is any copolymer obtained by copolymerizing a polymerizable monomer.   The heat-sensitive recording material according to claim 1, wherein the (meth) acrylic resin is a styrene-acrylic acid copolymer.   The thermosensitive recording material according to any one of claims 1 to 3, wherein the content of the (meth) acrylic resin in the protective layer is 1 to 50 parts by mass with respect to 100 parts by mass of the diacetone-modified polyvinyl alcohol resin.   The heat-sensitive recording material according to any one of claims 1 to 4, wherein the acid value of the (meth) acrylic resin is 100 mgKOH / g or more.   6. The heat-sensitive recording material according to claim 1, wherein the protective layer contains a hydrazine compound, and the hydrazine compound is adipic acid dihydrazide.   The heat-sensitive recording label according to any one of claims 1 to 6, which is a heat-sensitive recording label having a pressure-sensitive adhesive layer and a release paper on the surface of the pressure-sensitive adhesive layer on a surface opposite to the surface having the heat-sensitive color developing layer. Thermal recording material.   The thermosensitive recording material according to any one of claims 1 to 6, which is a thermosensitive recording label having a thermosensitive adhesive layer that develops adhesiveness by heating on the surface opposite to the surface having the thermosensitive coloring layer of the support. .