JP3311409B2 - Thermal recording sheet for label - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording sheet for labels, and more particularly to a water-resistant printed plastic image, a plasticizer, and an improved adhesiveness with an adhesive.

[0002]

2. Description of the Related Art Electron-donating dyes (hereinafter referred to as color formers)
And a thermosensitive recording sheet using an electron-accepting acidic substance having a thermochromic reaction with the color former (hereinafter, referred to as a color developer)
JP-B-43-4160, JP-B-45-14039, JP-A-59-19886 and the like are described in detail.
Widely used for computer output, facsimile, tickets, commuter passes, credit cards, etc. Furthermore, in recent years, it has been used as a label for a POS system (store point of sale information management system) in accordance with expansion.

[0003]

That is, for label applications, fresh foods are wrapped in a wrap film such as polyvinyl chloride, and a label is printed on the film with the product name, price, bar code, etc. printed and colored by a thermal head. If you use a normal heat-sensitive recording sheet for the display label, the displayed colored characters will be water or oil adhering or a wrap containing a plasticizer such as dioctyl phthalate or dioctyl adipate. It disappears easily due to the contact of the film.

Therefore, a protective layer (hereinafter, referred to as an overcoat layer) is provided on the thermosensitive coloring layer in order to prevent color erasure.
For example, a carboxy-modified polyvinyl alcohol aqueous solution is applied (Japanese Patent Application Laid-Open No. 56-126193), and a layer containing an NN′-ethylene urea resin, a filler and a water-soluble binder is provided (Japanese Patent Application Laid-Open No. 56-82291). And fine particles of a styrene-methacrylic acid copolymer having a thickness of 0.1 to 3 .mu.m (JP-A-58-25988), and a water-soluble resin containing a wetting agent having an HLB of 4 to 20 (JP-A-58-1983). 1228
No. 92), a layer containing boric acid in polyvinyl alcohol to form a layer (JP-A-58-188689), a block copolymer of polyvinyl alcohol and acrylamide is applied (JP-A-59-7090), terephthalic acid By applying dimethyl or phenyl benzoate and a pigment together with a binder (JP-A-59-33184), and applying carboxy-modified polyvinyl alcohol and a polyester resin or a polyurethane resin (JP-A-59-52693).
It is a measure of prevention.

However, since the display label is stuck on the wrap film, there is a phenomenon that the plasticizer having a decoloring effect from the wrap film becomes an atmosphere and penetrates from the back surface of the label to decolor the display. A thermal recording sheet for labels has been proposed in which an overcoat layer is provided on the surface of a thermal recording sheet and a back coating layer (hereinafter, referred to as a back coat) is also provided on the back surface to prevent the penetration of a plasticizer. Specifically, most of the overcoat layers are formed by mixing and applying a water-soluble polymer and a waterproofing agent or a filler,
For the back coat layer, a water-soluble polymer such as polyacrylamide (Japanese Patent Laid-Open No. 57-123088), an alkali salt of an isobutylene-maleic anhydride copolymer or a diisobutylene-maleic anhydride copolymer (Japanese Patent Laid-Open No. 909
No. 1), a mixed resin containing a polyvinyl alcohol / acrylamide or methacrylamide / acrylonitrile or methacrylonitrile copolymer resin in polyvinyl alcohol or carboxy-modified polyvinyl alcohol (JP-A-59-78887), a fluorine resin ( JP 5
No. 9-150791), a pigment having an oil absorption of 50 ml / 100 g or more, a water-soluble polymer and a water-proofing agent (JP-A-61-41).
594), polyurethane compounds (JP-A-61-472).
No. 92), an alkali salt of a styrene-maleic anhydride copolymer containing a white pigment (JP-A-61-57386), a zirconium compound (JP-A-61-95978), hydrophobicity such as atactic polypropylene and polyurethane. Polymer (JP-A-61-57386), colloidal silica (JP-A-62-32081), hot water-soluble polyester resin containing a sulfonate group (JP-A-62-16815)
), A water-soluble polymer and a water-proofing agent (JP-A-1-28848).
), Release agents and waxes (JP-A-2-165988)
No.), a water-soluble metal salt, a white pigment and a binder thereof (Japanese Patent Laid-Open No.
-135785), etc., and when the inventors of the present invention conduct confirmation experiments and evaluate them, there is a method in which the effect is certainly recognized. However, the curl that occurs due to the difference in the moisture absorption between the thermosensitive coloring layer and the back coat layer. And the adhesion between the back coat layer and the adhesive layer is poor, which is a practical step.

Accordingly, an object of the present invention is to provide a thermal recording sheet for labels which has a high printing density with minute heat energy, which is the most important characteristic of the thermal recording sheet, and has good thermal head matching properties such as sticking and head residue. An object of the present invention is to provide a heat-sensitive recording sheet for labels which is excellent in water resistance and plasticizer resistance, has no curl, has improved adhesion to an adhesive layer, and is practically excellent.

[0007]

According to the present invention, there is provided a heat-sensitive coloring layer comprising, as a main component, an electron-donating dye and an electron-accepting acidic substance having a thermochromic reaction with the dye on the surface of the support. In a thermal recording sheet for a label comprising an adhesive layer and a release paper provided on the back surface of the support, the core is a copolymer of acrylonitrile and butyl acrylate, and the outer layer is methyl methacrylate between the support and the adhesive layer. Thermosensitive recording sheet provided with a back coating layer mainly composed of a two-layer acrylate copolymer which is a copolymer of butyl acrylate and acrylamide (here, the two-layer acrylate copolymer) The coalescence has an average particle size of 0.05 to
0.8 μm, wherein the molar ratio of the acrylonitrile to the methyl methacrylate is 10:90 to 5
0 to 50).

In the double-layer acrylate copolymer used in the present invention, the core is a copolymer of acrylonitrile and butyl acrylate, and the outer layer is a copolymer of methyl methacrylate, butyl acrylate and acrylamide. It is composed of a two-layer acrylate copolymer, has an average particle size of 0.05 to 0.8 μm, is an emulsion, and has a molar ratio of acrylonitrile and methyl methacrylate of 10:90 to 50:50. 50. The double-layer acrylate copolymer is obtained by a known polymerization method, and is preferably emulsified in a water-based medium by a radical polymerization method using a redox catalyst.

The two-layer acrylic ester copolymer emulsion used in the present invention is used in combination with a crosslinking agent. As the crosslinking agent used in the present invention, for example, glyoxal,
Formalin, borax, dialdehyde starch, melamine resin, polyamide resin, polyethyleneimine resin, polyamide-epichlorohydrin resin, ketone-aldehyde resin, glycine, glycidyl ester, glycidyl ether, ketene dimer, dimethylol urea, ammonium chloride, magnesium chloride, chloride Examples thereof include calcium, aluminum sulfate, magnesium sulfate, calcium hydroxide, and zirconium-ammonium carbonate, and a polyamide-epichlorohydrin resin is particularly preferred.
The two-layer acrylic ester copolymer emulsion used in the present invention is mixed with a crosslinking agent and a white pigment such as calcium carbonate, calcined kaolin, silica, etc., and also with a conductive agent, a lubricant and an antifoaming agent to form a coating solution for a back coat layer. The coating amount is 0.5 to 5 g / on a support such as paper by a coating method such as an air knife, a bar, a blade, a gravure, or a roll coater.
m ² (dry weight solids), preferably 1 to ² g / m ² , to form a back coat layer by applying and drying. The back coat layer of the present invention is adhered to a pressure-sensitive adhesive such as a styrene-butadiene-based, acrylic-based, or vinyl acetate-based adhesive which is an adhesive for label processing, and a release paper is provided to further prevent adhesion with others. Then, if necessary, the release paper is peeled off and attached to a wrap film.

The color former of the heat-sensitive color-forming layer which is applied to the surface of a support such as paper with the color former used in the present invention and a color developer having a thermal color-developing reaction as a main component is a phthalide compound, Examples include fluoran compounds, spiropyran compounds, diphenylmethane compounds, and thiazine compounds. Examples of the phthalide compound include 3,3-
Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (p-dibenzylaminophenyl)
-3- (1 ', 2'-dimethyl-3'-indolyl)-
7-azaphthalide, 3,3-bis (4'-dimethylaminophenyl) -phthalide, 3- (4-dimethylamino-
2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3-
(4-diethylamino-2-ethoxyphenyl) -3-
(1-ethyl-2-methylindol-3-yl) -7
-Azaphthalide, 3,3-bis [2- (p-dimethylaminophenyl) -2-phenylethenyl] phthalide,
3,3-bis [2- (p-pyrrolidiphenyl) -2-
(P-methylphenyl) ethenyl] phthalide, 3- (p
-Methoxyphenyl) -3- [1,1-bis (p-dimethylaminophenyl) ethylene-2-yl] -6-dimethylaminophthalide, 1-ethyl-8- (dibutylamino) -1,2-dihydro -2,2,4-trimethylspiro [11H- (1) benzopyrano (2,3-g) quinoline-11,3'-phthalide], 8- (diethylamino)
-12-methyl-1,2-dihydro-2,2,4-trimethylspiro [11H- (1) benzopyrano (2,3-
g) Quinoline-11,3'-phthalide], 3,3-bis [2- (p-dimethylaminophenyl) -2-phenylethenyl] -4,5,6,7-tetrachlorophthalide,
3,3-bis [2- (p-dimethylaminophenyl)-
2- (p-methylphenyl) ethenyl] -4,5,6
7-tetrachlorophthalide and the like.

The fluoran compounds include, for example, 3,
6-dimethoxyfluoran, 4-amino-8-diethylamino-benzo [a] fluoran, 2-amino-8-diethylamino-benzo [a] fluoran, 4-benzylamino-8-diethylamino-benzo [a] fluoran, 3 -Diethylamino-6-methylfluoran, 3-
Diethylamino-7-aminofluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-
6-methyl-7-chlorofluoran, 2-methyl-6
(Np-tolyl-N-ethylamino) fluoran, 1
0-diethylaminobenzo [c] fluoran, spiro (xanthen-9,1′-phthalane) -6-diethylamino-2-phenyl-3′-one, spiro (xanthen-9,1′-phthalane) -3-diethylamino- 2-methoxy-3'-one, spiro (xanthen-9,1'-
Phthalane) -3-diethylamino-6-methoxy-3 ′
-One, spiro (xanthene-9,1'-phthalane)-
6-diethylamino-2- (N-methyl-N-acetoamino) -3′-one, 3-cyclohexylamino-6
Chlorofluorane, 3-diethylaminobenzo [a] fluoran, 3-diethylamino-6,8-dimethylfluoran, 3-benzylamino-6-chlorofluoran,
3-cyclohexylamino-7-methylfluoran, 2
-Methoxy-8-diethylamino-benzo [c] fluoran, 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluoran, 3- (N, N-diethylamino) -7-bis (dimethylbenzyl ) Aminofluorane, 3-diethylamino-7-N-cyclohexyl-N-benzylaminofluoran, 3-pyridino-7-cyclohexylaminofluoran, 3-diethylamino-6-methyl-7-p-butylanilinofluoran 3-diethylamino-6-methyl-7-p-phenetidinofluoran, 3-diethylamino-6-methyl-
7-anilinofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7-chloroanilinofluoran, 3-diethylamino-7- (2-carbomethoxyanilino) fluoran, 2
-Anilino-3-methyl-6- (N-ethyl-p-toluidino) fluoran, 2-p-toluidino-3-methyl-6- (N-ethyl-p-toluidino) fluoran,
3- (N-cyclohexyl-N-methylamino) -6
Methyl-7-anilinofluoran, 3-pyridilino-6
-Methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3- (N-
Ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl- 7- (o, p-dimethylanilino) fluoran, 3-pyrrolidino-6-methyl-7-
Anilinofluoran, 3-pyrrolino-6-methyl-7
-Anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran,
3-diethylamino-7- (m-trifluoromethylanilino) fluoran, 3-Nn-dibutylamino-7
-(O-chloroanilino) fluoran, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluoran, 3-dibutylamino-6
-Methyl-7- (o, p-dimethylanilino) fluoran, 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-
6-Chloro-7-anilinofluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamino-7- (o-chloroanilino) fluoran and the like.

As the spiropyran compound, for example, 2,
2'-spiro (benzo [f] chromene), spiro (3-
Methylchromene-2,2′-7′-diethylaminochromene), spiro (3-methyl-benzo [5,6-a] chromene-2,2′-7′-diethylaminochromene),
Spiro (3-methylchromene-2,2'-7'-dibenzylaminochromene), 3-methyl-di-β-naphthospiropyran, and the like. Examples of the diphenylmethane-based compound include 4,4'-bis (4,4'-tetramethyldiaminodiphenylmethylamino) diphenylmethane, bis [4,4'-bis (dimethylamino-benzhydryl)] ether, N, N'- Bis [bis (4′-dimethylaminophenyl) methyl] -1,6-hexamethylenediamine, N-bis (4-dimethylaminophenyl) methyl-glycine ethyl ether, 4,4′-bis-dimethylaminobenzhydryl Benzyl ether and the like.

Examples of the thiazine compounds include 3,7
-Bis (dimethylamino) -10-benzoylphenothiazine, 10- (3 ', 4', 5'-trimethoxy-benzoyl) -3,7-bis (dimethylamino) phenothiazine, 3-diethramino-7- (N-methylanilino ) -10-Benzoylphenoxazine, 4H-7-diethylamino-4,4′-bis- (9′-ethyl-3 ′)
-6'-carbazolyl) -2-t-butyroylamino-
3,1-benzothiazine, 4H-7-diethylamino-
4- (p-diethylaminophenyl) -4- (9'-ethyl-3'-methyl-6'-carbazolyl) -2-pivaloylamino-3,1-benzothiazine, 4H-6-methyl-4,4-bis ( p-dimethylaminophenyl)-
2-pivaloylamino-3,1-benzothiazine, 4H
-7-Dibenzylamino-4,4-bis (p-dimethylaminophenyl) -2-phenyl-3,1-benzothiazine, 4H-7-dibenzylamino-4,4-bis (p
-Dimethylaminophenyl) -2-pivaloylamino-
3,1-benzothiazine, 4H-7-dibenzylamino-2-isoptoxycarbonylamino-4,4-bis (p-dimethylaminophenyl) -3,1-benzothiazine, 4H-7-diethylamino-4,4- Screw [p-
[N-ethyl-N- (p-tolyl)] aminophenyl]
-2-pivaloylamino-3,1-benzothiazine and the like.

Examples of the developer used in the present invention include phenol compounds, aromatic carboxylic acid compounds and metal salts thereof. As phenol compounds, for example, 3,
5-xylenol, p-tert-butylphenol,
4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-naphthol, catechol, resorcinol,
Hydroquinone, 4-tert-octylcatechol,
4,4'-sec-butylidenephenol, 2,2'-
Dihydroxydiphenyl, 2,2′-methylenebis (4
-Methyl-6-tert-butylphenol), 2,
2′-bis (4-hydroxyphenyl) propane, 4,
4'-isopropylidene-bis (2-tert-butylphenol), 4,4'-sec-butylidenediphenol, pyrogallol, phloroglysin, phloroglysin carboxylic acid, 4-tert-octylphenol, 4-
Phenylphenol, 2,2′-bis (p-hydroxyphenyl) butane, 4,4′-cyclohexylidenediphenol, 2,2′-bis (2,5-dibromo-4-hydroxyphenyl) propane, 4,4 '-Isopropylidene diphenol, and the like. Examples of the phenolsulfonic acid-based compound include 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, and 4-hydroxy-4'-methoxy. Diphenylsulfone, 4-hydroxy-4′-isopropyloxydiphenylsulfone, 4-hydroxy-3 ′,
4′-trimethylene diphenyl sulfone, 4-hydroxy-3 ′, 4′-tetramethylene diphenyl sulfone,
3,4-dihydroxy-4′-methyldiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, and the like.

Examples of the aromatic carboxylic acid compound include dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate,
-Sec-butyl hydroxybenzoate, benzyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate,
4-Hydroxybenzoic acid tolyl, 4-hydroxybenzoic acid chlorophenyl, 4-hydroxybenzoic acid phenylpropyl, 4-hydroxybenzoic acid phenethyl, 4-hydroxybenzoic acid-p-chlorobenzyl, 4-hydroxybenzoic acid-p-methoxybenzyl , Benzoic acid, p-te
rt-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid,
3-cyclohexyl-4-hydroxybenzoic acid, 3,5
-Dimethyl-4-hydroxybenzoic acid, 3-tert-
Butylsalicylic acid, 3-benzylsalicylic acid, 3- (α
-Methylbenzyl) salicylic acid, 3-chloro-5- (α
-Methylbenzyl) salicylic acid, 3,5-di-tert
-Butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and the like, and as metal salts thereof, zinc, magnesium, aluminum, calcium,
It is a polyvalent metal salt such as titanium, manganese, tin and nickel.

The ratio of the color former and the color developer used in the present invention varies depending on the types of the color former and the color developer, and is not particularly limited. In general, it is based on 100 parts by weight of the color developer. The developer is 100 to 1000 parts by weight, preferably 150 to 500 parts by weight.

The thermosensitive coloring layer of the present invention comprises a mixture of a binder, a sensitizer, a filler and the like. Examples of the binder include water-soluble polymers such as starch, hydroxyethylcellulose and polyvinyl alcohol; Examples thereof include hydrophobic polymers such as butadiene copolymer, styrene-acrylic acid copolymer, and vinyl acetate-acrylic acid copolymer. Examples of the sensitizer include stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, N-methyl oleic acid amide, linoleic acid amide, N-ethylcapric acid amide, N-butyl lauric acid amide, -Octadecylacetamide, N-oleic acid acetamide, N-oleic acid benzamide, N-
Cyclohexyl stearic acid, 2-benzyloxynaphthalene, P-benzylbiphenyl, di-oxalate
P-chlorobenzyl ester, oxalic acid di-P-methylbenzyl ester and the like can be mentioned. Examples of the filler include clay, talc, kaolin, titanium oxide, zinc oxide, calcium carbonate, magnesium carbonate, silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, aluminum oxide, zinc stearate, calcium stearate, and urea. -Formalin resin, polystyrene and the like, and one kind or a mixture of two or more kinds is used.

Further, in the present invention, if desired, waxes such as polyethylene wax, carnauba wax and paraffin wax; water-resistant agents such as formaldehyde, glyoxal, epoxy resin, melamine and melamine-formaldehyde resin; ultraviolet absorbers such as benzophenone; dioctyl Wetting agents such as sodium sulfosuccinate, dispersants such as sodium polyacrylate; forming a coating solution for a thermosensitive coloring layer by using a defoaming agent as an auxiliary agent and optionally adding a coloring pigment as necessary, to form an air-knife, curtain, A coating amount of 2 is applied to a support such as paper by a coating method such as a bar, a gravure, a roll coater, or the like.
１５15 g / m ² (dry weight solids), preferably 2-8
g / m ² and then dried by applying and drying.

An overcoat layer is provided on the heat-sensitive coloring layer of the present invention, and the main component of the overcoat layer is a film-forming polymer. The polymer is, for example, starch and its derivatives, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, gelatin, gum arabic, casein, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyvinyl alcohol, colloidal silica Water-soluble polymers such as modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide derivatives, polyethylene oxide, polyvinyl pyrrolidone, polystyrene sodium sulfonate, sodium alginate; styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, styrene- It is a hydrophobic polymer such as a vinyl acetate copolymer and used alone or in combination of two or more.
Further, in the present invention, if desired, a filler, a crosslinking agent, a wax, a surfactant, an ultraviolet absorber and the like are mixed to form a coating solution for overcoating, and an air knife, a curtain, a bar,
It is coated and dried by a coating method such as a gravure or a roll coater so that the coating amount is 0.5 to 5 g / m ² (dry weight solid content), preferably 0.8 to 3 g / m ² on the thermosensitive coloring layer. To provide an overcoat layer.

The method of preparing the label heat-sensitive recording sheet of the present invention by applying it is not particularly limited. For example, after providing a back coat layer on the back surface of a support such as paper, heat-sensitive coloring is performed on the surface. A method of providing a layer, performing a super calendar finish, and providing an overcoat layer. Or after providing a heat-sensitive coloring layer on the surface of a support such as paper, performing a super calender finish, and then providing an overcoat layer,
There is a method of providing a back coat layer on the back surface. The support such as paper in the present invention is paper, film, non-woven fabric,
Synthetic paper and synthetic resin coated paper coated with polyethylene-based resin, etc., and laminated paper further laminated with aluminum foil etc.
Refers to what is usually used as a support for labels.
If desired, an intermediate layer can be provided by coating a porous white pigment between a support such as paper and a thermosensitive coloring layer, or two overcoat layers can be provided. Further, since the back coat layer of the present invention is particularly excellent in adhesion to a pressure-sensitive adhesive, it is used by applying it to a support such as a synthetic resin-coated paper or film in which both sides of the paper are coated with a polyethylene resin or the like. Even so, the object of the present invention is well achieved.

[0021]

The preferred embodiments and excellent effects of the present invention will be specifically described below with reference to the most typical examples. In addition, the following parts are all parts by weight, and all% represent weight%.

Example 1 [Thermosensitive Coloring Layer] A 10% aqueous polyvinyl alcohol solution (Gosenol G, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added to 125 parts of water.
L-05) 25 parts and 2-anilino-3-methyl-6-N
-Cyclohexyl-N-methylaminofluoran 100
The parts were mixed and pulverized by a ball mill until the average particle diameter became 1 μm to prepare a liquid A. 10% polyvinyl alcohol aqueous solution (Gohsenol GL-05) in 275 parts of water
25 parts, 100 parts of 4-hydroxy-4'-isopropyloxydiphenylsulfone, and 100 parts of methylene bisamide stearate were mixed and pulverized by a ball mill until the average particle diameter became 1 μm to prepare a liquid B. Water 100
Part is 1.5 parts of 40% aqueous solution of sodium polyacrylate (Toa Gosei Chemical Co., Ltd., Aron T-40) and 100 parts of calcium carbonate (Shiraishi Industry Co., Ltd., Brilliant-15) 100
After dispersion, 600 parts of a 10% aqueous solution of polyvinyl alcohol (Gohsenol NM-11) was mixed to prepare a liquid C. Solution A: Solution B: Solution C was mixed with dilution water at a dry weight solids ratio of 1: 2.5: 8, and mixed.
% Thermosensitive coloring layer coating solution. This coating solution was weighed 50 g /
After the application and drying in air knife coater so applied amount of fine paper surface of m ² is 5 g / m ² (dry weight solids), the supercalendered, provided a heat-sensitive coloring layer. [Overcoat layer] 10 parts of a 10% aqueous solution of sodium polyacrylate (Aron T-40) in 0.3 parts of water, silica fine powder (Fine Seal SP-, manufactured by Tokuyama Soda Co., Ltd.)
10) After dispersing 3 parts, 60 parts of a 25% zinc stearate dispersion, 1000 parts of a 10% aqueous polyvinyl alcohol solution (GOHSENOL NL-05), and 50 parts of a 10% aqueous dialdehyde starch solution are sequentially mixed to form an overcoat layer. Coating solution. This coating solution was applied and dried with an air knife coater on the thermosensitive coloring layer so as to have an application amount of 2 g / m ² (dry weight solid content), followed by super calendering to provide an overcoat layer. [Backcoat layer] Aqueous 50% two-layer acrylate copolymer emulsion in water (800 parts) (core is acrylonitrile / butyl acrylate copolymer, outer layer is methyl methacrylate / butyl acrylate / acrylamide copolymer, acrylonitrile : Emulsion having a molar ratio of methyl methacrylate of 15:85 and an average particle size of 0.2 µm) was mixed to prepare a coating solution for back coating. This coating solution is applied and dried with an air knife coater on the back surface of the high quality paper provided with the thermosensitive coloring layer and the overcoat layer so as to have an application amount of 2 g / m ² (dry weight solid content), followed by super calendering. Then, a heat-sensitive recording sheet for labels was prepared.

Example 2 A 50% double-layer acrylic ester having a 50:50 molar ratio of acrylonitrile: methyl methacrylate was used as the 50% double-layer acrylic ester copolymer emulsion for the back coat layer in Example 1. A thermosensitive recording sheet for a label was prepared by providing a thermosensitive coloring layer, an overcoat layer, and a backcoat layer in the same manner except that the same amount of the copolymer emulsion was used to prepare the coating solution for the backcoat layer.

[0024]

Example 3 A thermosensitive coloring layer and an overcoat were prepared in the same manner as in Example 1 except that 100 parts of a 10% aqueous solution of a polyamide-epichlorohydrin resin was mixed with the coating solution for the backcoat layer to prepare a coating solution for the backcoat layer. A thermosensitive recording sheet for a label was prepared by providing a layer and a back coat layer.

Example 4 100 parts of a 10% aqueous solution of a polyamide-epichlorohydrin resin and 80 parts of a 10% silica fine powder dispersion (Fine Seal SP-10) were successively mixed with the coating solution for the back coat layer of Example 1 and backed. A thermosensitive recording sheet for labels was prepared by providing a thermosensitive coloring layer, an overcoat layer, and a backcoat layer in the same manner except that the coating solution for the coating layer was used.

Comparative Example 1 The sheet provided with the thermosensitive coloring layer and the overcoat layer in Example 1 was used as a thermosensitive recording sheet for labels.

Comparative Example 2 800 parts of water, which is the coating solution for the back coat layer of Example 1, and 200 parts of a 50% two-layer acrylate copolymer emulsion were used in 1000 parts of a 5% aqueous polyvinyl alcohol solution (Gohsenol NM-11). A thermosensitive recording sheet for labels was prepared by providing a thermosensitive coloring layer, an overcoat layer, and a backcoat layer in the same manner except that the coating solution for the backcoat layer was used instead of the above.

COMPARATIVE EXAMPLE 3 800 parts of water and 200 parts of a 50% double-layered acrylate copolymer emulsion of the coating solution for the back coat layer of Example 1 were used in 1000 parts of a 5% aqueous polyvinyl alcohol solution (GOHSENOL NM-11). And a 50% aqueous solution of 10% glyoxal in place of the coating solution for the back coat layer, except that the thermosensitive coloring layer, the overcoat layer,
Then, a heat-sensitive recording sheet for a label was prepared by providing a back coat layer.

Comparative Example 4 The 50% two-layer acrylate copolymer emulsion for the back coat layer of Example 1 was replaced with a 50% carboxy-modified styrene-butadiene copolymer emulsion (Nipol LX407C, manufactured by Zeon Corporation). A thermosensitive recording sheet for a label was prepared by providing a thermosensitive coloring layer, an overcoat layer, and a backcoat layer in the same manner except that the amount was changed to a coating solution for a backcoat layer.

Comparative Example 5 A 50% two-layer acrylate copolymer emulsion for the back coat layer of Example 1 was replaced with a 50% vinyl acetate-acrylate copolymer emulsion (manufactured by Kanebo NSC, Inc. Sink 125-289
A thermosensitive recording sheet for a label was prepared by providing a thermosensitive coloring layer, an overcoat layer, and a backcoat layer in the same manner as in 9) except that the same amount was replaced with the coating solution for the backcoat layer.

Comparative Example 6 200 parts of the 50% double-layer acrylate copolymer emulsion for the back coat layer in Example 1 was replaced with a 46% acrylate copolymer emulsion (Zeon Corporation)
Nipol LX814) was replaced with 220 parts of a coating solution for a back coat layer, and a thermosensitive coloring layer, an overcoat layer, and a back coat layer were provided in the same manner to prepare a thermosensitive recording sheet for a label.

Test Method The heat-sensitive recording sheets for labels prepared in Examples 1 to 5 and Comparative Examples 1 to 6 were measured by the following test methods, and the results are shown in Table 1. Printing color density Thermal printing device (Ishida Hoki Seisakusho (manufactured by) Label Printing Machine I
SHIDA DEGITAL SCALE 805P,
Voltage 22.9V, resistance value 320Ω, conduction time 2.2m
s) The color density printed by the densitometer (Macbeth Co., Ltd.,
RD-100R, using an Ambar filter). The higher the value, the higher the print density. Water resistance of printing (%) Printed sheet is exposed to high temperature and humidity of 60 ° C and 95% RH for 24 hours.
After standing for a time, the residual concentration was measured with a densitometer, and the residual ratio (%) was determined by the following equation. Residual rate (%) = print density after processing / fresh print density × 100

Printed plasticizer resistance (%) Dioctyl phthalate 30
% -Containing vinyl chloride sheets were stacked and left in a dryer at 65 ° C. for 24 hours, and the residual concentration was measured with a densitometer, and the residual ratio (%) was determined by the following equation. Residual rate (%) = print density after processing / fresh print density × 100

Sheet curl The sheet cut into a square of 20 cm was cut at 20 ° C. and 65% RH for 3 hours, then at 30 ° C. and 90% RH for 3 hours, and further cut for 20 hours.
After standing at 65 ° C. and a relative humidity of 65% for 3 hours, the height (curl degree) of the four sides of the sheet was measured to obtain an average value, which was indicated by the following symbol. (+) Curl: Curled on the thermosensitive coloring layer side (0) Curl: Hardly curled (-) Curl: Curled on the backcoat layer side

Adhesion with Adhesive Layer A vinyl acetate emulsion pressure-sensitive adhesive was applied onto the back coat layer so as to have a coating amount of 15 g / m ² (dry solid content), and then dried. It was immersed in water for 30 minutes to observe the adhesiveness of the adhesive, and evaluated by ○ marks, Δ marks, and × marks. ○: Excellent adhesion between the backcoat layer and the adhesive layer △: Partially peeled off ×: Almost peeled off

[0037]

[Table 1]

[0038]

According to the present invention, a thermosensitive coloring layer mainly composed of an electron-donating dye and an electron-accepting acidic substance having a thermochromic reaction with the dye is provided on the surface of the support, and the adhesive layer is peeled off from the back of the support. In a thermosensitive recording sheet for labels provided with paper, a core is a copolymer of acrylonitrile and butyl acrylate, and an outer layer is a copolymer of methyl methacrylate, butyl acrylate and acrylamide between the support and the adhesive layer. A heat-sensitive recording sheet provided with a back coating layer mainly composed of a two-layered acrylate copolymer as a polymer (where the two-layered acrylate copolymer is
An emulsion having an average particle size of 0.05 to 0.8 μm, and the molar ratio of the acrylonitrile to the methyl methacrylate is 10:90 to 50:50). A thermosensitive recording sheet for a label was provided which was good, had a high print color density, was excellent in water resistance and plasticizer resistance, had no curl, and had excellent adhesion to a pressure-sensitive adhesive.

Claims (2)

(57) [Claims] 1. A heat-sensitive color-developing layer mainly comprising an electron-donating dye and an electron-accepting acidic substance having a thermochromic reaction with the dye on a surface of a support, and an adhesive layer is peeled off from the back of the support. In a thermosensitive recording sheet for labels provided with paper, a core is a copolymer of acrylonitrile and butyl acrylate, and an outer layer is a copolymer of methyl methacrylate, butyl acrylate and acrylamide between the support and the adhesive layer. A heat-sensitive recording sheet for labels, provided with a back coating layer mainly comprising a double-layered acrylate copolymer as a polymer. Here, the two-layer acrylate copolymer is an emulsion having an average particle size of 0.05 to 0.8 μm, and the molar ratio between the acrylonitrile and the methyl methacrylate is 10:90 to 50:50. It is 50 pairs. 2. The heat-sensitive recording sheet for labels according to claim 1, wherein the back coating layer contains a polyamide-epichlorohydrin resin.