JPH05177937A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material wherein yellowing of a texture part is very little against exposure to light for a long time without impairing shelf life stability of a recording image and further is excellent in water resistance. CONSTITUTION:In a thermal recording material wherein a recording layer which contains a colorless or light colored basic dye and a developing agent and a protective layer are successively provided, an ultraviolet absorbent is contained in the protective layer, and a microcapsule having substantially no coloring fuculty wherein denatured polyvinyl alcohol is used as an emulsifier for preparation of the capsule contains the thermal recording material.

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 material having excellent storage stability, particularly light resistance and water resistance.

[0002]

2. Description of the Related Art A heat-sensitive recording material which utilizes a color reaction between a colorless or light-colored basic dye and an organic or inorganic color-forming agent to bring both color-forming substances into contact with each other by heat to obtain a recorded image is often used. Are known. Since such a thermal recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

One of the fields of use thereof is, for example, POS.
(Point of sales) Thermal recording labels for systems can be cited, but with the expansion of the system, it has been attached to products for a long period of time, apart from food labels that end their mission in a short period as before. The usage as tag paper used in the state or handy terminal paper for collection and delivery which is often handled outdoors is increasing. However, in such applications, it is often exposed to room light or sunlight for a long period of time, which causes the background portion of the thermosensitive recording material to turn yellow, resulting in a marked loss of the product image. For this reason, there is a demand for a thermosensitive recording medium in which the background portion does not turn yellow due to room light or sunlight.

Conventionally, there has been proposed a method in which a finely pulverized ultraviolet absorber is added to a heat-sensitive recording layer or a protective layer for the purpose of preventing yellowing of the background portion of a heat-sensitive recording material due to light. However, the finely pulverized UV absorber does not have sufficient effect due to poor UV absorption efficiency, and if the amount of use is increased, a new defect such as a background or fog, or a decrease in recording density may occur. At the same time, it is not possible to obtain sufficiently satisfactory light resistance as a result.

Also in the heat-sensitive recording material used as the tag paper or the handy terminal paper as described above, the resistance of the recorded image to chemicals such as plasticizer, edible oil and sebum, and water is required, so that the recording layer on the recording layer is required. Generally, a protective layer is provided on the protective layer, but if a finely pulverized UV absorber is contained in such a protective layer, the UV absorber elutes due to the influence of plasticizers and oils and fats, and the protective layer functions. Is damaged. Further, if the water resistance of the protective layer is weak, the protective layer is peeled off when the recording medium is wet with water, or the recorded image is whitened, and as a result, the storability of the recorded image is deteriorated.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material having a protective layer on the recording layer, which does not impair the storage stability of the recorded image, and causes the yellow portion of the background portion to be exposed to light for a long period of time. An object of the present invention is to provide a heat-sensitive recording material that has very little change and is excellent in water resistance.

[0007]

SUMMARY OF THE INVENTION The present invention comprises:
A heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent, and a heat-sensitive recording layer sequentially provided with a protective layer, in which a UV absorber is included in the protective layer and modified polyvinyl as an emulsifier for capsule preparation. By containing microcapsules that use alcohol and have practically no color-developing ability, there is very little yellowing of the background part due to long-term light exposure without lowering the recording density or impairing the storage stability of the recorded image. Moreover, they have found that a heat-sensitive recording material excellent in water resistance can be obtained, and completed the present invention.

[0008]

The following are specific examples of the ultraviolet absorber used in the present invention. Salicylic acid-based UV absorbers such as phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-
Benzophenone-based UV absorbers such as sulfobenzophenone, 2- (2'-hydroxy-5'-methylphenyl)
Benzotriazole, 2- (2'-hydroxy-5'-
tert-butylphenyl) benzotriazole, 2-
(2'-Hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-
Chlorobenzotriazole, 2- (2'-hydroxy-
3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3',
5'-di-tert-amylphenyl) benzotriazole, 2- (2'-hydroxy-4'-octyloxyphenyl) benzotriazole, 2- [2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -Tetrahydrophthalimido-methyl) -5'-methylphenyl] -benzotriazole, 2- (2'-hydroxy-5'-tert-
Octylphenyl) -benzotriazole, 2- [2-
Hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, methyl-
Condensate of 3- [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate and polyethylene glycol (molecular weight about 300), 2- (5-methyl-3- A benzotriazole-based UV absorber such as dodecyl-2-hydroxyphenyl) benzotriazole, 2- [2'-hydroxy-4 '-(2 "-ethylhexyl) oxyphenyl] benzotriazole, 2-ethylhexyl-2-cyano-
Cyanoacrylate UV absorbers such as 3,3′-diphenyl acrylate and ethyl-2-cyano-3,3′-diphenyl acrylate, and hindered amine UV absorbers. Of course, it is not limited to these, and two or more kinds may be used in combination as required. Among these UV absorbers, UV absorbers having a light absorption peak in the range of 300 to 400 nm are preferable, and particularly, benzotriazole-based UV absorbers, 2- (2-hydroxy-5-methylphenyl) benzotriazole,
2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, methyl-3- [3-
tert-butyl-5- (2H-benzotriazole-2-
Yl) -4-hydroxyphenyl] propionate with polyethylene glycol (molecular weight about 300),
2- (5-methyl-3-dodecyl-2-hydroxyphenyl) benzotriazole, 2- [2'-hydroxy-
4 ′-(2 ″ -ethylhexyl) oxyphenyl] benzotriazole is more preferably used because it exhibits a particularly remarkable effect of improving light resistance.

The amount of the ultraviolet absorber used is not particularly limited, but is 0.1 to 3.0 in the protective layer.
g / m ^2, more preferably it is desirable to adjust the range of 0.2 to 2.0 g / m ^2. The microcapsules used in the present invention can be prepared by various known methods,
A core substance (oil-based liquid) composed of a solution of the above-mentioned ultraviolet absorber and, if necessary, an organic solvent, is emulsified and dispersed in an aqueous solution in which modified polyvinyl alcohol is dissolved as an emulsifier, and a polymer substance wall film is formed around it. Prepared by the method of forming.

As the modified polyvinyl alcohol used as an emulsifier in the present invention, an acetoacetyl group-modified polyvinyl alcohol, an acetoacetyl group-modified partially saponified polyvinyl alcohol, a carboxy-modified polyvinyl alcohol, and a silicon-modified polyvinyl can be obtained which have a water resistance effect at low temperature curing. Alcohols are preferable, and particularly, acetoacetyl group-modified polyvinyl alcohol (including acetoacetyl group-modified partially saponified polyvinyl alcohol) is more preferably used because an excellent water resistance effect can be obtained by the reaction with the aldebit compound.

Further, non-modified polyvinyl alcohol and a surfactant may be used in combination within the range that does not impair the effects of the present invention. The amount of the modified polyvinyl alcohol used as an emulsifier is not particularly limited, but it is 1 with respect to the microcapsule core substance and the wall film material.
It is desirable to adjust the content to be in the range of about 50% by weight, more preferably about 3 to 30% by weight.

[0012] Specific examples of the polymer substance which forms the wall film of the microcapsule include, for example, polyurethane resin, polyurea resin, polyamide resin, polyester resin,
Polycarbonate resin, amino aldehyde resin, melamine resin, polystyrene resin, styrene-methacrylate copolymer, styrene-acrylate copolymer,
Examples thereof include gelatin and polyvinyl alcohol. Among these, in particular, the microcapsules having a wall film made of polyurethane / polyurea resin are excellent in heat resistance, and therefore, they have an excellent function as an inorganic pigment added for the purpose of preventing sticking to the thermal head. It is effective, and has a lower refractive index than microcapsules composed of other wall films and ordinary pigments, and its spherical shape causes diffuse reflection of light even if added in large amounts in the protective layer. It is preferably used because there is no fear of causing a decrease in the density of the recorded image (so-called whitening phenomenon).

The polyurethane / polyurea wall film is prepared by mixing a polyol, which reacts with a polyvalent isocyanate to form a wall film, with a core substance to be encapsulated, and emulsifying and dispersing it in an aqueous medium in which a modified polyvinyl alcohol is dissolved. It is produced by raising the liquid temperature and causing a polymer formation reaction at the oil drop interface. Examples of the polyvalent isocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-
4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-
Diisocyanates such as 1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, Triisocyanates such as toluene-2,4,6-triisocyanate, 4,4 '
-Tetraisocyanates such as dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate, an adduct of hexamethylene diisocyanate and trimethylolpropane, an adduct of 2,4-tolylene diisocyanate and trimethylolpropane, Isocyanate prepolymers such as an adduct of xylylene diisocyanate and trimethylolpropane and an adduct of triresin isocyanate and hexanetriol can be used.

As the polyol compound, for example, ethylene glycol, 1,3-propanediol, 1,4
-Butanediol, 1,5-pentanediol, 1,6
-Hexanediol, 1,7-heptanediol, 1,
8-octanediol, propylene glycol, 2,3
-Dihydroxybutane, 1,2-dihydroxybutane,
1,3-dihydroxybutane, 2,2-dimethyl-1,
3-propanone diol, 2,4-pentane diol,
2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol,
Dihydroxycyclohexane, diethylene glycol,
1,2,6-trihydroxyhexane, phenylethylene glycol, 1,1,1-trimethylolpropane,
Hexanetriol, pentaerythritol, aliphatic polyols such as glycerin, aromatic polyhydric alcohols such as 1,4-di (2-hydroxyethoxy) benzene and 1,3-di (2-hydroxyethoxy) benzene, and alkylene oxides Condensation product, p-xylylene glycol, m-xylylene glycol, α, α′-dihydroxy-p-diisopropylbenzene, 4,4′-dihydroxydiphenylmethane, 2- (p, p′-dihydroxydiphenylmethyl) benzyl alcohol 4,4'-isopropylidenediphenol, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide and ethylene oxide adduct of 4,4'-isopropylidenediphenol, 4,4'-isopropylidene Redenediphenol And the propylene oxide adduct thereof.

Of course, the polyisocyanate compound and the polyol compound are not limited to the above compounds, and two or more kinds may be used in combination. The polyurethane / polyurea wall film material used in the present invention is preferably one having three or more isocyanate groups in the molecule of a polyvalent isocyanate compound or an adduct of a polyvalent isocyanate compound and a polyol compound.

The organic solvent added as a core substance, if necessary, is not particularly limited, and various high-boiling point hydrophobic media used in the field of pressure-sensitive paper can be appropriately selected and used. Specifically, for example, phosphates such as tricresyl phosphate and octyl diphenyl phosphate, phthalates such as dibutyl phthalate and dioctyl phthalate, carboxylic esters such as butyl oleate, various fatty acid amides, diethylene glycol dibenzoate, 1 -Methyl-1-phenyl-1-tolylmethane, 1-methyl-1-phenyl-1-xylylmethane, alkylated benzenes such as 1-phenyl-1-tolylmethane, alkylated naphthalene such as monoisopropylnaphthalene and diisopropylnaphthalene, isopropylbiphenyl Archi etc. Biphenyl, xenon Bruno alkoxy alkane such as o- phenylphenol glycidyl ether, acrylic acid esters such as trimethylolpropane triacrylate, esters of polyhydric alcohols and unsaturated carboxylic acids, chlorinated paraffin and kerosene and the like. Of course,
These may be used in combination of two or more. Among the above high-boiling point hydrophobic media, tricresyl phosphate and 1-phenyl-1-tolylmethane are preferable because they exhibit excellent solubility in relation to the ultraviolet absorber used in the present invention. Further, generally, the lower the viscosity of the mixture of the capsule wall film agent, the ultraviolet absorber and the organic solvent, the smaller the particle size after emulsification and the sharper the particle size distribution, and therefore the purpose of lowering the viscosity of the mixture as necessary. Thus, a low boiling point solvent can be added. Specific examples of the low boiling point solvent include ethyl acetate, butyl acetate and methylene chloride.

The amount of the organic solvent used is not particularly limited and should be appropriately adjusted according to the type and amount of the ultraviolet absorber, the type of the organic solvent, etc., but the organic solvent and the capsule wall film are not particularly limited. It is desirable to adjust the ratio of the organic solvent to the total amount of the agent and the ultraviolet absorber in the range of generally 10 to 60% by weight, preferably 20 to 60% by weight.

The amount of the capsule wall film material to be used is also not particularly limited, but the organic solvent in the microcapsules may seep out due to long-term storage and the storage stability of the thermosensitive recording medium may be deteriorated. It is preferable to use a large amount of the wall film material as compared with a normal microcapsule, and the ratio of the wall film material to the total amount of the organic solvent, the ultraviolet absorber and the microcapsule wall film material is 20 to 70% by weight, It is desirable to select it in the range of preferably 30 to 60% by weight.

Further, the proportion of the ultraviolet absorber in the microcapsules is not particularly limited and should be appropriately selected according to the kind of the ultraviolet absorber and the organic solvent used, but in order to obtain a remarkable effect. 3 to 50% by weight, preferably 3 to 20% by weight, based on the total amount of the organic solvent, the ultraviolet absorber and the microcapsule wall film material.
It is desirable to select it so that the amount of the ultraviolet absorber is about the same.

The average particle size of the capsules used in the present invention is preferably adjusted in the range of about 0.1 to 3 μm in terms of the average particle size in consideration of ultraviolet absorption efficiency, image quality of recorded image and the like. The dispersion liquid is generally contained in the layer by a method of adding it to the protective layer coating material. The content of the capsule in the protective layer is 5 to 80% by weight of the total solid content of the protective layer,
More preferably, it is desirable to adjust in the range of 20 to 70% by weight.

In the present invention, various known colorless or light-colored basic dyes can be used as the basic dye constituting the heat-sensitive recording layer, and specifically, for example, 3,3-bis (p-dimethylaminophenyl). ) -6-Dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [A] Fluoran, 3- (N-ethyl-N-p-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylamino Fluoran, 3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3-cyclohexylamino-
6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-
Chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3
-(N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-
6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane,
3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3-di (n-butyl)
Amino-7- (o-chlorophenylamino) fluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-di (n-butyl) amino-7
-(O-Fluorophenylamino) fluorane, 3-
(N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3- (N -Ethyl-N-furfurylamino) -6-
Methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (N-methyl-Nn-propylamino) -6-methyl-7-anilinofluorane, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [ 1- (4-methoxyphenyl)-
1- (4-pyrrolidinophenyl) ethylene-2-yl]
-4,5,6,7-Tetrachlorophthalide, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthali 3-p- (p-dimethylaminoanilino) anilino-6-methyl-7-chlorofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3 '-Methylspiro [phthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3,
6,11-tri (dimethylamino) fluorane and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Various materials are known as a colorant used in combination with the basic dye as described above, for example, activated clay, attapulgite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4,4'- Isopropylidene diphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4 '
-Dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-
4-hydroxyphenyl) sulfone, 4-hydroxy-
4'-methyldiphenyl sulfone, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, bis (p-hydroxyphenyl) butyl acetate, bis (p- Hydroxyphenyl) methyl acetate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3- Bis [α-methyl-α-
Phenolic compounds such as (4'-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfin, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- {3- ( p-
Tolylsulfonyl) propyloxy] salicylic acid, 5-
Aromatic carboxylic acids such as [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and zinc, magnesium, aluminum of these aromatic carboxylic acids,
Examples thereof include salts with polyvalent metals such as calcium, titanium, manganese, tin and nickel, and organic acid substances such as antipyrine complex of zinc thiocyanate.

The use ratio of the basic dye and the color developing agent is appropriately selected according to the type of the basic dye or the color developing agent to be used and is not particularly limited, but in general, the basic dye 1 is used. 1 to 50 parts by weight, preferably 2 to parts by weight
About 10 parts by weight of coloring agent is used. A heat-sensitive recording layer coating material containing these substances is generally prepared by using water as a dispersion medium and dispersing a dye and a coloring agent together or separately by a stirring / grinding machine such as a ball mill, attritor, or sand mill. ..

In the coating solution, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, etc. are used as usual binders in the coating liquid. Diisobutylene / maleic anhydride copolymer salt, styrene /
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene /
Examples thereof include butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin and the like.

If desired, various auxiliaries can be added to the coating liquid. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. , Zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and other waxes,
A curing agent such as glutaraldehyde or glyoxal, an antifoaming agent, a fluorescent dye, a coloring dye and the like are appropriately added.

It is also possible to use various pigments in combination, for example, inorganic pigments such as kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, activated clay and styrene microballs. , Nylon powder, polyethylene powder, urea / formalin resin filler, organic pigments such as raw starch particles, and the like.

Further, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, and methylenebisstearic acid. Amide, N-
Methylol stearic acid amide, 1-hydroxy-2-
Phenyl naphthoate, 2-naphthyl benzyl ether,
Dibenzyl terephthalate, p-benzyloxybenzoate benzyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p-chlorobenzyl, p
-Benzyl biphenyl, tolyl biphenyl ether, m
-Terphenyl, 1,2-di (3-methylphenoxy)
Ethane, 1,2-di (4-methylphenoxy) ethane,
1,2-di (4-methoxyphenoxy) ethane, 1,2
-Di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, p-methylthiophenylbenzyl ether, p-acetotoluidide, p-acetophenetizide,
N-acetoacetyl-p-toluidine, di (p-methoxyphenoxyethyl) ether, di (β-biphenylethoxy) benzene, 1,4-di (phenylthio) butane, p-di (vinyloxyethoxy) benzene, 1- Examples include compounds such as isopropylphenyl-2-phenylethane.

The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within a range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent. Further, depending on the purpose, a preservative improving agent may be added in order to enhance the preservability of the recording area. Specific examples of such a shelf life improver include:
For example, 2,2'-methylenebis (4-methyl-6-tert
Butylphenol), 2,2'-ethylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4,6-di-tert-butylphenol),
2,2'-ethylidene bis (4,6-di-tert-butylphenol), 2,2'-ethylidene bis (4-methyl-6-tert-butylphenol), 2,2'-ethylidene bis (4-ethyl-) 6-tert-butylphenol),
2,2 '-(2,2-propylidene) bis (4,6-di-tert-butylphenol), 2,2'-methylenebis (4-methoxy-6-tert-butylphenol), 2,
2'-methylenebis (6-tert-butylphenol),
4,4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-te
rt-butylphenol), 4,4'-thiobis (5-methyl-6-tert-butylphenol), 4,4'-thiobis (2-chloro-6-tert-butylphenol),
4,4'-thiobis (2-methoxy-6-tert-butylphenol), 4,4'-thiobis (2-ethyl-6-
tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol, 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl] -4-
[Α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-methyl-4-)
Hydroxy-5-cyclohexylphenyl) butane,
1,1,3-tris (2-methyl-4-hydroxy-5)
-Tert-butylphenyl) butane, 4,4'-thiobis (3-methylphenol), 4,4'-dihydroxy-
3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3', 5,5'-tetramethyldiphenyl sulfone, 2,2-bis (4-hydroxy-3,5 -Dibromophenyl) propane, 2,
2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,5)
-Dimethylphenyl) propane, N, N'-di-2-naphthyl-p-phenylenediamine, hydroquinone diglycidyl ether, 4,4'-diglycidyloxydiphenyl sulfone, monomer or prepolymer of epoxy compound, cresol novolac type epoxy Resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, 2,2'-methylenebis (4,6-di-tert.
-Butylphenyl) sodium phosphate and the like. Of course, it is not limited to these, and two or more kinds can be used in combination.

Examples of the water-soluble or water-dispersible polymer used in the protective layer of the present invention include various binders used in the heat-sensitive recording layer as described above. Among them, acetoacetyl group-modified polyvinyl alcohol and carboxy-modified Polyvinyl alcohol is particularly preferably used because it forms a strong film and has a water resistance effect when cured at a low temperature.

A pigment may be added to the protective layer as needed in order to further improve printability and sticking. Specific examples thereof include calcium carbonate,
Inorganic pigments such as zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea Examples thereof include formalin resin fillers and organic pigments such as raw starch particles. It is generally desirable to adjust the amount used in the range of about 5 to 500 parts by weight with respect to 100 parts by weight of the resin component.

Further, in the coating solution for forming the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and a surfactant such as sodium dioctylsulfosuccinate ( It is also possible to appropriately add various auxiliaries such as a dispersant, a wetting agent), a defoaming agent, potassium alum, and a water-soluble polyvalent salt such as aluminum acetate. Also, to further improve water resistance, glyoxal, boric acid,
Hardeners such as dialdehyde starch and epoxy compounds can also be added.

The method for forming the heat-sensitive recording layer or the protective layer is not particularly limited, and suitable examples include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating and die coating. Depending on the coating method, apply the recording layer coating liquid to paper,
The thermosensitive recording layer and the protective layer are formed on the support such as a plastic film, a synthetic paper, a non-woven fabric, and a metal deposit by further coating and drying the coating solution for the protective layer on the thermosensitive recording layer. The coating amount of the coating liquid is not particularly limited, and in the case of the heat-sensitive recording layer,
Dry weight is ² to 12 g / m ² , preferably 3 to 10 g / m ² .
m ² . 0.1-20 g / dry weight for protective layer
m ² , preferably adjusted in the range of about 0.5 to 10 g / m ² .

If necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storability. Furthermore, it is possible to provide an undercoat layer on the support or to apply a super calender after coating each layer, and to apply a pressure-sensitive adhesive treatment to the back surface of the recording material to process it into an adhesive label. The publicly known technology can be added as required.

[0034]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, "part" and "%" in an example show "weight part" and "weight%", respectively, unless there is particular notice. [Example 1] Preparation of solution A 60 parts of 12% aqueous solution of acetoacetyl group-modified partially saponified polyvinyl alcohol [trade name: Gocefimer Z-210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] was placed in a stirring and mixing container equipped with a heating device. Was added to obtain an aqueous medium for producing microcapsules.

Separately, to 12 parts of tricresyl phosphate, 2-
2 parts of (2'-hydroxy-5'-methylphenyl) benzotriazole, (3: 1) adduct of xylylenediisocyanate and trimethylolpropane (trade name: Takenate D-110N, Takeda Pharmaceutical Co., Ltd., 25% by weight) A solution obtained by dissolving 18 parts (containing ethyl acetate) was used as a capsule core substance in the above-mentioned aqueous medium for capsule production using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain an average particle diameter of 2 μm.
It was emulsified and dispersed while cooling to m.

To this emulsified dispersion, 50 parts of water was added and reacted at 60 ° C. for 3 hours while stirring to prepare microcapsules of polyurethane / polyurea wall film containing an ultraviolet absorber. Preparation of Solution B A composition consisting of 10 parts of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane, 5 parts of a 5% aqueous solution of methylcellulose and 40 parts of water was sand milled to an average particle size of 2 μm. Crushed until Preparation of Solution C A composition consisting of 30 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose and 80 parts of water was sand milled to give an average particle size of 2
It was pulverized to a size of μm. Preparation of Liquid D A composition consisting of 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose and 55 parts of water was pulverized with a sand mill until the average particle size became 2 μm. Formation of recording layer 55 parts of liquid B, 115 parts of liquid C, 80 parts of liquid D, 80 parts of 10% aqueous solution of polyvinyl alcohol, 40 of glyoxal
% Aqueous solution (3 parts) and calcium carbonate (35 parts) are mixed and stirred, and the resulting coating solution is dried and coated on one side of a high-quality paper of 60 g / m ² so that the coating amount after drying is 6 g / m ² I got a record. Formation of protective layer 220 parts of solution A, acetoacetyl group-modified completely saponified polyvinyl alcohol [trade name: Gocefimer Z-200,
A composition comprising 150 parts of a 10% aqueous solution of Nippon Synthetic Chemical Industry Co., Ltd., 15 parts of kaolin [trade name: UW-90, manufactured by EMC], 6 parts of a 30% dispersion of zinc stearate and 30 parts of water is mixed and stirred. The protective layer coating liquid thus obtained was applied and dried on the recording layer so that the coating amount after drying was 6 g / m ^2, and calendering was performed to obtain a thermosensitive recording medium. [Example 2] In the preparation of solution A, a 12% aqueous solution of acetoacetyl group-modified partially saponified polyvinyl alcohol [trade name: Gocefimer Z-210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] 6
Acetoacetyl group-modified completely saponified polyvinyl alcohol instead of 0 part [trade name: Gocefimer Z-200,
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 60 parts of a 12% aqueous solution of Nippon Synthetic Chemical Industry Co., Ltd. was used. [Example 3] In the preparation of solution A, a 12% aqueous solution of acetoacetyl group-modified partially saponified polyvinyl alcohol [trade name: Gocefimer Z-210, manufactured by Nihon Gosei Kagaku] 6
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 60 parts of a 10% aqueous solution of carboxy-modified polyvinyl alcohol [trade name: KL-318, manufactured by Kuraray Co., Ltd.] was used instead of 0 part. [Example 4] A 12% aqueous solution of acetoacetyl group-modified partially saponified polyvinyl alcohol [trade name: Gocefimer Z-210, manufactured by Nippon Synthetic Chemical Industry] in the preparation of solution A 6
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 60 parts of a 10% aqueous solution of silicon-modified polyvinyl alcohol [trade name: R-1130, manufactured by Kuraray Co., Ltd.] was used instead of 0 part. [Example 5] In formation of the protective layer of Example 1, acetoacetyl group-modified completely saponified polyvinyl alcohol [trade name: Gocefimer Z-200, manufactured by Nippon Synthetic Chemical Industry]
In place of 150 parts of 10% aqueous solution of carboxy modified polyvinyl alcohol [trade name: KL-318, manufactured by Kuraray Co., Ltd.] 150 parts of 10% aqueous solution, kaolin [trade name: UW
-90, manufactured by EMC Co.] A thermal recording material was obtained in the same manner as in Example 3 except that 15 parts of calcium carbonate was used instead of 15 parts. Example 6 In the formation of the protective layer of Example 1, acetoacetyl group-modified completely saponified polyvinyl alcohol [trade name: Gocefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.]
1% of silicon-modified polyvinyl alcohol [trade name: R-1130, manufactured by Kuraray Co.] instead of 150 parts of 10% aqueous solution of
A thermosensitive recording medium was obtained in the same manner as in Example 4 except that 150 parts of 0% aqueous solution was used. Example 7 In preparation of solution A, tricresyl phosphate 1 was used.
Instead of 2 parts, 3 parts of ethyl acetate and 2- (2'-hydroxy-5'-methylphenyl) benzotriazole instead of 2 parts of 2- (2'-hydroxy-3'-dodecyl-
A thermal recording material was obtained in the same manner as in Example 1 except that 12 parts of 5'-methylphenyl) benzotriazole was used. [Example 8] Preparation of liquid E 100 parts of calcined clay [trade name: Ansilex, manufactured by EMC, oil absorption amount 110 ml / 100 g], 100 parts of a 10% aqueous solution of polyvinyl alcohol and 200 parts of water were mixed and stirred. To obtain a coating liquid for the undercoat layer.

Liquid E was dried and coated on one surface of a high-quality paper of 60 g / m ² so that the coating amount after drying was 7 g / m ^2, and the coating for the recording layer and the protective layer used in Example 1 were used. The coating material was applied and dried so that the coating amount after drying was 6 g / m ² , respectively, to obtain a thermosensitive recording medium. The coating material for recording layer used in Example 1 was dried and coated so that the coating amount after drying was 6 g / m ² , to obtain a thermosensitive recording medium. [Example 9] 4-hydroxy-4'- in the preparation of solution C
30 parts of bis (4-hydroxyphenylthioethoxy) methane instead of 30 parts of isopropoxydiphenyl sulfone
Was used in the same manner as in Example 1 except that 20 parts of bis (4-hydroxyphenylthioethoxy) methane was used instead of 20 parts of 1,2-di (3-methylphenoxy) ethane in the preparation of solution D. I got a record. [Example 10] A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 20 parts of 2-naphthylbenzyl ether was used instead of 20 parts of 1,2-di (3-methylphenoxy) ethane in the preparation of solution D. Obtained. [Comparative Example 1] A 12% aqueous solution 60 of acetoacetyl group-modified partially saponified polyvinyl alcohol [trade name: Gocefimer Z-210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.]
Partially saponified polyvinyl alcohol instead of parts [Product name:
A thermal recording material was obtained in the same manner as in Example 1 except that 60 parts of an 8% aqueous solution of PVA-217, manufactured by Kuraray Co., Ltd. was used. [Comparative Example 2] A 12% aqueous solution of acetoacetyl group-modified partially saponified polyvinyl alcohol [trade name: Gocefimer Z-210, manufactured by Nippon Synthetic Chemical Industry] in the preparation of solution A 60
Partially saponified polyvinyl alcohol instead of parts [Product name:
A thermal recording material was obtained in the same manner as in Example 1 except that 60 parts of an 8% aqueous solution of PVA-217EE, manufactured by Kuraray Co., Ltd. was used. [Comparative Example 3] Preparation of solution F A composition consisting of 10 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 5 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water was sand milled to give an average particle size of It was crushed to 3 μm. Formation of thermosensitive recording medium In the formation of the protective layer, the above F was used instead of 220 parts of A liquid.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 40 parts of the liquid was used.

The 13 types of thermal recording materials thus obtained were evaluated as follows, and the results are shown in [Table 1]. [Evaluation] [Color development] Thermosensitive evaluation machine [Product name: TH-PMD, manufactured by Okura Electric Co., Ltd.] 2
The color density of the recorded image obtained by color development at 4V-2ms was measured by a Macbeth densitometer [Macbeth RD-914 type] (visual mode). [Light resistance] Thermosensitive evaluation machine [Product name: TH-PMD, manufactured by Okura Electric Co., Ltd.] 2
The recording paper obtained by color development at 4V-2ms was exposed to direct sunlight for 2 days, and then the densities of the recording area and the background area were measured with a Macbeth densitometer (blue filter). [Water resistance] Thermosensitive evaluation machine [Product name: TH-PMD, Okura Electric Co., Ltd.] 2
The recording paper obtained by color development at 4 V-2 ms was immersed in tap water at 20 ° C. for 24 hours, and the color density was measured to evaluate the water resistance.

[0039]

[Table 1]

[0040]

As is clear from the results of [Table 1], all of the thermosensitive recording materials of the present invention efficiently absorb ultraviolet rays to cause very little discoloration of the background part, and also have excellent coloring properties and storage stability. It was a record.

Claims (4)

[Claims] 1. A thermal recording medium comprising a support and a recording layer containing a colorless or light-colored basic dye and a coloring agent and a protective layer, which are successively provided. The ultraviolet absorber is included in the protective layer. A heat-sensitive recording material comprising microcapsules containing modified polyvinyl alcohol as an emulsifier for preparing capsules and having substantially no color-developing ability. 2. The heat-sensitive recording material according to claim 1, wherein the modified polyvinyl alcohol is at least acetoacetyl group-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol. 3. The heat-sensitive recording material according to claim 1, wherein the modified polyvinyl alcohol is acetoacetyl group-modified polyvinyl alcohol. 4. The wall film of the microcapsule is made of polyurethane.
The heat-sensitive recording material according to claim 1, which is a polyurea resin.