JP3094623B2 - Thermal recording medium - 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 material, and more particularly to a heat-sensitive recording material excellent in storage stability of a recorded image and light resistance of a background portion.

[0002]

2. Description of the Related Art A thermosensitive recording medium which uses a color reaction between a colorless or light-colored basic dye and an organic or inorganic colorant to contact both coloring materials by heat to obtain a recorded image is often used. Are known. Such a thermosensitive recording medium is relatively inexpensive, and its recording equipment is compact and easy to maintain, so that it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

[0003] For example, as one field of use of that, heat-sensitive recording label of POS (point of sales) for the system of a retail store and the like, along with the expansion of the system of,
Apart from food labels whose mission is completed in a short period of time as in the past, applications for attaching and using products for a long period of time are increasing. However, in such applications, they often come into contact with water, wraps, oil, etc., and they are often exposed to room light or sunlight for a long period of time, and as a result, the recorded image (print) on the thermal label fades. In addition, the background portion turns yellow, and as a result, the product image is significantly impaired. For this reason, it is strongly demanded that the heat-sensitive recording medium be provided with storability such as water resistance, plasticizer resistance, oil resistance and light resistance.

Conventionally, in order to improve the preservability of a recorded image, a method of applying an aqueous emulsion of a resin having a film forming ability and chemical resistance on a recording layer (Japanese Patent Laid-Open No. Sho 54-1).
No. 28347), a method of applying a water-soluble polymer compound such as polyvinyl alcohol (Japanese Utility Model Application Laid-Open No. 56-12535).
No. 4) has been proposed. Also, methods of adding various preservability improvers to the recording layer have been proposed, but in each case, the recording density decreases with the improvement, and new disadvantages such as a decrease in the whiteness of the recording layer have been introduced. Concomitantly, no satisfactory results have been obtained. Also, for the purpose of preventing yellowing of the background portion of the heat-sensitive recording material due to light, a method has been proposed in which a finely pulverized ultraviolet absorbent is added to the heat-sensitive recording layer or the protective layer. In the case where is contained in the heat-sensitive recording layer, a sufficient effect cannot be obtained due to poor absorption efficiency of ultraviolet rays, and when the amount used is increased, background fogging is caused or the recording density is lowered. If a finely pulverized ultraviolet absorber is contained in the protective layer, the ultraviolet absorber elutes under the influence of a plasticizer or fats and oils, impairs the function of the protective layer, and as a result, the storage stability of the recorded image is reduced. . For this reason, at present, it is not possible to obtain a sufficiently satisfactory light resistance.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium having a protective layer on a recording layer, in which the storage stability of a recorded image, particularly the resistance to plasticizer and oil, is remarkably improved.
In addition, it is an object of the present invention to provide a thermosensitive recording medium which has very little yellowing of a background portion upon exposure to light.

[0006]

SUMMARY OF THE INVENTION The present inventors have developed a novolak type epoxy in a recording layer of a thermosensitive recording material utilizing a color reaction between a colorless or light-colored basic dye and a colorant capable of forming a color. resins, glycidyl ether or glycidyl ester compound benzene ring as a core, a sulfone is at least one selected from the nucleus to the glycidyl ether or glycidyl ester compound and a bisphenol a type epoxy resin, is in the protective layer, at room temperature It contains a liquid benzotriazole-based UV absorber and has virtually no color-forming ability .
Has a wall film made of rare resin or aminoaldehyde resin
By causing containing microcapsules, the storage stability of recorded images, particularly the plasticizer resistance, oil resistance is remarkably improved, yet to Heading that very little yellowing of the background portion to light exposure, the The invention has been completed.

[0007]

The following are specific examples of the compound having an epoxy group contained in the recording layer in the present invention. Phenol novolak epoxy resin, ortho-cresol novolak epoxy resin, halogen-substituted phenol novolak epoxy resin, 1,4-di (1,2-
Epoxyethyl) benzene, 1,4-diglycidylbenzene, 1,4-di (glycidyloxy) benzene,
4-di (glycidyloxy) -3,6-dibromobenzene, 1,4-di (glycidyloxy) -3,6-dichlorobenzene, 1,4-di (glycidyloxy) -3-methylbenzene, 1,4 -Di (glycidyloxy) -3-
Methoxybenzene, 1,4-di (2-glycidyloxyethoxy) benzene, 1,4-di (4-glycidyloxybutoxy) benzene, 1,4-di (2-glycidyloxyethoxy) -3,6-dibromobenzene , 1,4-
Di (2-glycidyloxyethoxy) -3,6-dichlorobenzene, 1,4-di (2-glycidyloxyethoxy) -3-methylbenzene, 1,4-diglycidyl phthalate, 1,4-diglycidyl-3- Methyl phthalate, 1,4-diglycidyl-3-methoxyphthalate,
1,4-diglycidyl-3-ethoxyphthalate, 1,
4-di (2-glycidyloxyethyl) phthalate, glycidyloxybenzene, monoglycidyl phthalate,
Monoglycidyl terephthalate, 1-phenoxy-1,
4-glycidyloxy-3,6,9,12-tetraoxatetradecane, bisphenol A type epoxy resin obtained by condensing bisphenol A with epichlorohydrin or tetrabromobisphenol A and epichlorohydrin, 4- (1,2-epoxyethyl ) Diphenylsulfone, 4-glycidyldiphenylsulfone, 4-
(3,4-epoxybutyl) diphenyl sulfone, 4-
(2,3-epoxybutyl) diphenyl sulfone, 4-
(1,2-epoxyethyloxy) diphenyl sulfone,
4-glycidyloxydiphenyl sulfone, 4- (3,
4-epoxybutyloxy) diphenyl sulfone, 4-
(2,3-epoxybutyloxy) diphenylsulfone, 4-glycidyloxy-4'-bromodiphenylsulfone, 4-glycidyloxy-4'-methyldiphenylsulfone, 4-glycidyloxy-4'-ethyldiphenylsulfone, 4- Glycidyloxy-2 ', 4'-
Dimethyldiphenylsulfone, 4-glycidyloxy-
2 ', 4'-dichlorodiphenylsulfone, 4-glycidyloxy-4'-(n-propyl) diphenylsulfone, 4-glycidyloxy-4'-isopropyldiphenylsulfone, 4-glycidyloxy-4 '-(tert-
Butyl) diphenylsulfone, 4-glycidyloxy-
4'-isoamyldiphenylsulfone, 4-glycidyloxy-4'-methoxydiphenylsulfone, 4-glycidyloxy-4'-ethoxydiphenylsulfone, 4
-Glycidyloxy-4'-isopropyloxydiphenylsulfone, 4-glycidyloxy-4'-n-pentyloxydiphenylsulfone, 4-glycidyloxy-2 ', 4'-dimethoxydiphenylsulfone, 4,
4'-diglycidyloxydiphenyl sulfone, 4,
4'-diglycidyloxy-3,3'-dichlorodiphenylsulfone, 4,4'-diglycidyloxy-2,
2'-dibromodiphenylsulfone, 4,4'-diglycidyloxy-3,3 ', 5,5'-tetrabromodiphenylsulfone, 4,4'-bis (2-glycidyloxyethoxy) diphenylsulfone, 4,4 '-Bis (2
-Glycidyloxyethoxy) -3,3 ', 5,5'-
Tetrabromodiphenyl sulfone, 4,4'-bis (2
-Glycidyloxyethoxy) -3,3 ', 5,5'-
Tetramethyldiphenylsulfone, 4,4'-bis (3,4-epoxybutyloxy) diphenylsulfone, 4-[(2,3-epoxy-2-methyl) propyloxy] phenyl-4 '-(benzyloxy) phenyl Sulfone and the like. Of course, the invention is not limited to these, and two or more of them can be used in combination as needed. Among these epoxy compounds, the softening point is 65 to 100 ° C.
Orthocresol novolak type epoxy resin, phenol novolak type resin, halogen-substituted phenol novolak type resin, and 4,4'-diglycidyloxydiphenyl sulfone are particularly excellent in plasticizer resistance and are preferably used.

The use amount of these epoxy resins is not particularly limited, but is about 1 to 500% by weight, preferably about 5 to 200% by weight, based on the colorant. still,
These epoxy resins may be used by being encapsulated in microcapsules.

Specific examples of the ultraviolet absorbent included in the microcapsules of the present invention include the following. Phenyl salicylate, p-tert-butylphenyl salicylate, salicylic acid ultraviolet absorbers such as p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy Benzophenone-based ultraviolet absorbers such as -4-methoxy-5-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-3'-(3 ",
4 ", 5", 6 "-tetrahydrophthalimidomethyl)
-5'-methylphenyl] benzotriazole, 2-
(2'-hydroxy-5'-tert-octylphenyl)
Benzotriazole, 2- [2'-hydroxy-3 ',
5'-bis (α, α-dimethylbenzyl) phenyl]-
2H-benzotriazole, 2- (2'-hydroxy-
3'-dodecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-undecyl-
5'-methylphenyl) benzotriazole, 2-
(2'-hydroxy-3'-undecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tridecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy- 3'-tetradecyl-5'-methylphenyl) benzotriazole,
2- (2'-hydroxy-3'-pentadecyl-5'-
Methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-hexadecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy-
4 '-(2 "-ethylhexyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-
(2 "-ethylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(2" -ethyloctyl) oxyphenyl] benzotriazole,
2- [2'-hydroxy-4 '-(2 "-propyloctyl) oxyphenyl] benzotriazole, 2-
[2'-hydroxy-4 '-(2 "-propylheptyl) oxyphenyl] benzotriazole, 2- [2'
-Hydroxy-4 '-(2 "-propylhexyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-(1" -ethylhexyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-
4 '-(1 "-ethylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-
(1 "-ethyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(1" -propyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-(1 "-Propylheptyl) oxyphenyl] benzotriazole, 2-
[2'-hydroxy-4 '-(1 "-propylhexyl) oxyphenyl] benzotriazole, methyl-3
A benzotriazole-based ultraviolet absorber such as a condensate of [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate and polyethylene glycol (molecular weight: about 300), 2 ' −
Cyanoacrylate-based ultraviolet absorbers such as ethylhexyl-2-cyano-3,3-diphenylacrylate and ethyl-2-cyano-3,3-diphenylacrylate; bis (2,2,6,6-tetramethyl-4-piperidyl) )
Sebacate, succinic acid-bis (2,2,6,6-tetramethyl-4-piperidyl) ester, 2- (3,5-di-tert-butyl) malonic acid-bis (1,2,2,6, 6
Hindered amine-based ultraviolet absorbers such as -pentamethyl-4-piperidyl) ester; Of course, the invention is not limited to these, and two or more of them can be used in combination as needed. Among these ultraviolet absorbers, benzotriazole-based ultraviolet absorbers are preferable, and particularly, 2- (2 ′).
-Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-
5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-dodecyl-5'-
Methylphenyl) benzotriazole, 2- [2'-hydroxy-4 '-(2 "-ethylhexyl) oxyphenyl] benzotriazole, methyl-3- [3-tert-
Butyl-5- (2H-benzotriazol-2-yl)
A condensate of [-4-hydroxyphenyl] propionate and polyethylene glycol (molecular weight: about 300) is more preferably used because it exhibits a particularly remarkable effect of improving light resistance.

Conventionally, UV absorbers having a low melting point and UV absorbers which are liquid at room temperature, which have been difficult to use in terms of background fog and preservability, can be used, so that the range of choices can be greatly expanded. .

The amount of the ultraviolet absorber used is not particularly limited, but is preferably 10 to 500% by weight, more preferably 2 to 500% by weight based on the basic dye in the recording layer.
It is desirable to adjust so as to be in the range of about 0 to 300% by weight. The present invention has an important feature in that the specific epoxy compound as described above is contained in the recording layer, and the protective layer contains microcapsules having an ultraviolet absorber and having substantially no coloring ability. Have still,
Various heat-sensitive recording media and pressure-sensitive recording media using microcapsules in which an ultraviolet absorber is encapsulated together with a colorless or pale basic dye have been proposed, but these microcapsules also include a basic dye. Therefore, not only does the coloring phenomenon occur with an increase in the light irradiation amount, but it is not possible to exhibit a sufficient light resistance improving effect over a long period of time.

The microcapsules used in the present invention can be prepared by various known methods. Generally, a core substance (oil-based liquid) obtained by dissolving an ultraviolet absorbent as described above in an organic solvent is placed in an aqueous medium. It is prepared by a method of emulsifying and dispersing to form a wall film made of a polymer substance around oily droplets. Specific examples of the polymer substance serving as the wall film of the microcapsule include, for example, polyurethane resin, polyurea resin,
Examples include polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-acrylate copolymer resin, styrene-methacrylate copolymer resin, gelatin, and polyvinyl alcohol. Among these, especially microcapsules having a wall film made of polyurethane / polyurea resin or aminoaldehyde resin have excellent heat resistance, so they function as inorganic pigments and have an excellent accompanying effect of preventing sticking to a thermal head. Demonstrate. Moreover, since the refractive index is lower than that of microcapsules made of other wall films or ordinary pigments and the shape is spherical, even if a large amount is incorporated in the protective layer, the recorded image due to irregular reflection of light is generated. It is preferably used because there is no fear of causing a decrease in density (so-called whitening phenomenon).

The microcapsules having a polyurethane / polyurea resin wall film are made of a core material for encapsulating a capsule wall material such as a polyvalent isocyanate and a polyol which reacts with the polyisocyanate, or an adduct of a polyvalent isocyanate and a polyol. , And emulsified and dispersed in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved, and the polymer temperature is raised to cause a polymer formation reaction at an oil droplet 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-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1, Diisocyanates such as 4-diisocyanate; triisocyanates such as 4,4 ', 4 "-triphenylmethane triisocyanate and toluene-2,4,6-triisocyanate; 4,4'-dimethyldiphenylmethane-2,2' Tetraisocyanates such as 5,5,5'-tetraisocyanate, adducts of hexamethylene diisocyanate with trimethylolpropane, addition of 2,4-tolylenediisocyanate with trimethylolpropane , An adduct of xylylene diisocyanate and trimethylolpropane, an isocyanate prepolymer of adduct of trimethylolpropane resin isocyanate and hexane triol.

[0015] Also, as the port polyol compounds, such as 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-propanonediol, 2,4-pentanediol, 2,5-hexanediol, -Methyl-1,5
-Pentanediol, 1,4-cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, 1,2,6-trihydroxyhexane, phenylethylene glycol, 1,1,1-trimethylolpropane, hexanetriol, pentaerythritol, glycerin, etc. Aliphatic polyols, condensation products of aromatic polyhydric alcohols such as 1,4-di (2-hydroxyethoxy) benzene, 1,3-di (2-hydroxyethoxy) benzene and alkylene oxides, p-xylylene glycol , M-xylylene glycol, α, α'-dihydroxy-p-diisopropylbenzene, 4,4'-dihydroxydiphenylmethane, 2- (p, p'-dihydroxydiphenylmethyl) benzyl alcohol, 4,4 '
-Isopropylidene diphenol, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, ethylene oxide adduct of 4,4'-isopropylidene diphenol, propylene of 4,4'-isopropylidene diphenol Oxide adducts and the like can be mentioned.

Of course, the polyvalent isocyanate compound and the polyol compound are not limited to the above compounds, and two or more kinds can be used in combination as needed. Among the polyisocyanate compounds used in the present invention or the adduct of a polyvalent isocyanate compound and a polyol compound, those having three or more isocyanate groups in the molecule are particularly preferable.

[0017] Microcapsules having a wall film made of aminoaldehyde resin, by a formulation to add a wall film material after the core material emulsification, Ru can control the KabemakuAtsu without being influenced by the particle size of the emulsion. Capsules having an aminoaldehyde resin wall film used in the present invention are generally urea, thiourea, alkyl urea, ethylene urea, acetoguanamine, benzoguanamine, melamine, guanidine,
Biuret, at least one amine such as cyanamide, and at least one aldehyde such as formaldehyde, acetaldehyde, paraformaldehyde, hexamethylenetetramine, glutaraldehyde, glyoxal, and furfural, or an initial condensate obtained by condensing them. It is produced by the in-situ polymerization method used.

As an emulsifier (protective colloid agent) used for microencapsulation, various anions, nonions, cations or amphoteric water-soluble polymer compounds are used. Examples of the anionic polymer compound include -C
_{OO -, - SO 3 -,} - gum arabic having a OPO ₃ ^2-group, carrageenan, sodium alginate, pectic acid, gum tragacanth, almond gum, natural polymer compounds such as agar, carboxymethyl cellulose, cellulose sulfate, sulfated Semi-synthetic polymer compounds such as methylcellulose, carboxymethylated starch, phosphorylated starch, ligninsulfonic acid, and maleic anhydride (including those hydrolyzed).
), Acrylic acid, methacrylic acid, crotonic acid, vinyl
Benzenesulfonic acid or 2-acrylamide-2-
Synthesis of polymers and copolymers of methylpropanesulfonic acid, and partial amide derivatives or partially esterified products of these polymers or copolymers, carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl alcohol, etc. Molecular compounds and the like. Maleic acid (including those hydrolyzed)
Specific examples of the copolymer include methyl vinyl ether-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, α-methylstyrene-maleic anhydride copolymer, acetic acid Vinyl-maleic anhydride copolymer, methacrylamide-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, etc., and acrylic acid, methacrylic acid or
Specific examples of the copolymer of the acid include methyl acrylate-
Acrylic acid copolymer (hereinafter abbreviated as "copolymer"), ethyl acrylate-acrylic acid, methyl acrylate-methacrylic acid, methyl methacrylate-acrylic acid, methyl methacrylate-methacrylic acid, methyl acrylate-acrylamide- Acrylic acid, acrylonitrile-acrylic acid,
Acrylonitrile-methacrylic acid, hydroxyethyl acrylate-acrylic acid, hydroxyethyl methacrylate-methacrylic acid, vinyl acetate-acrylic acid, vinyl acetate-methacrylic acid, acrylamide-acrylic acid, acrylamide-methacrylic acid, methacrylamide-acrylic acid, methacrylamide- Copolymers such as methacrylic acid and vinyl acetate-crotonic acid are exemplified, and vinylbenzenesulfonic acid or 2-acrylamido-2-methyl-
Examples of the propanesulfonic acid copolymer include methyl acrylate-vinylbenzenesulfonic acid (or a salt thereof) copolymer, vinyl acetate-vinylbenzenesulfonic acid copolymer,
Acrylamide-vinylbenzenesulfonic acid copolymer,
Acryloyl morpholine - vinylbenzene sulfonic acid copolymers, vinylpyrrolidone - vinyl sulfonic acid copolymer, vinylpyrrolidone-2-methyl - copolymers such as propane sulfonic acid like et be.

Examples of the nonionic polymer compound include semi-synthetic polymer compounds such as hydroxyethylcellulose, methylcellulose, pullulan, soluble starch and oxidized starch having an -OH group, and synthetic polymer compounds such as polyvinyl alcohol. Examples of the cationic polymer compound include cation-modified polyvinyl alcohol. Examples of the amphoteric polymer compound include gelatin.

The amount of the emulsifier used is not particularly limited, but generally, in the case of a polyurethane / polyurea resin, it is 1 to 50% by weight based on the total of the wall film agent, ultraviolet absorber and organic solvent. %, Preferably 3 to 3
It may be adjusted within a range of about 0% by weight. In the case of an aminoaldehyde resin, the amount of the emulsifier used is generally 1 to 20% by weight, more preferably 3 to 10% by weight based on the hydrophobic core substance.
It is prepared in the range of about% by weight.

If necessary, the organic solvent used as the core material of the capsule is not particularly limited, and can be appropriately selected from various high-boiling hydrophobic media used in the field of pressure-sensitive copying paper. 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, and various fatty acid amides Alkylated naphthalenes such as diethylene glycol dibenzoate, monoisopropyl naphthalene, diisopropyl naphthalene, 1-methyl-1-phenyl-1-tolylmethane, 1-methyl-1-phenyl-1-xylylmethane,
Alkylated benzenes such as 1-phenyl-1-tolylmethane; alkylated biphenyls such as isopropyl biphenyl; xenoxyalkanes such as o-phenylphenol glycidyl ether; acrylic esters such as trimethylolpropane triacrylate; Esters of alcohols with unsaturated carboxylic acids, chlorinated paraffins,
And kerosene. Needless to say, two or more of these can be used in combination. Among the high boiling point hydrophobic media as described above, tricresyl phosphate, 1-methyl-1-phenyl-1-xylylmethane, and 1-phenyl-1
-Tolylmethane is preferred because it exhibits excellent solubility in relation to the ultraviolet absorber used in the present invention. Also, generally, the lower the viscosity of the mixture of the capsule wall film material, the ultraviolet absorber and the organic solvent, the smaller the particle size after emulsification and the sharper the particle size distribution, so if necessary, lower the viscosity of the mixture. A low-boiling solvent may be used in combination for the purpose. Specific examples of such low-boiling solvents include ethyl acetate, butyl acetate, methylene chloride and the like.

The amount of the organic solvent to be used should be appropriately adjusted according to the type and amount of the ultraviolet absorber used, and furthermore, the type of the organic solvent, and is not particularly limited. Since it is preferable that the ultraviolet absorber is in a sufficiently dissolved state, in the case of polyurethane / polyurea resin, the ratio of the organic solvent to the total of the organic solvent, the ultraviolet absorber and the microcapsule wall film material is generally 10 to 60% by weight, preferably 20 to 6%
It is desirable to adjust so as to be in a range of about 0% by weight. In addition, in the case of an aminoaldehyde resin, if the ultraviolet absorber used is solid at room temperature, 5
It is desirable to adjust so as to be in the range of 0 to 2000% by weight, preferably 100 to 1000% by weight. When the ultraviolet absorbent used is a liquid at room temperature, it is appropriately used.

The amount of the capsule wall film material to be used is not particularly limited. However, since the organic solvent in the microcapsules may ooze out during long-term storage and the preservability of the thermosensitive recording medium may be reduced, it is usually used. It is preferable to use a large amount of wall film material as compared with the microcapsules. In the case of polyurethane / polyurea resin, the wall film material is used for the total of the organic solvent, the ultraviolet absorber and the microcapsule wall material. 35-70% by weight, preferably 3%
It is desirable to select so as to be in the range of 5 to 60% by weight. In addition, in the case of an aminoaldehyde resin, the ultraviolet absorber, if necessary, the total amount of the organic solvent used,
30 to 300% by weight, preferably 35 to 200% by weight of the wall film material
Desirably, it is selected to be in the range of weight percent.

The amount of the ultraviolet absorber used in the microencapsulation should be appropriately selected according to the type of the ultraviolet absorber and the organic solvent to be used, and is not particularly limited. Therefore, in the case of the polyurethane / polyurea resin, the amount of the ultraviolet absorber is 3 to 50% by weight, preferably about 3 to 20% by weight based on the total of the organic solvent, the ultraviolet absorber and the microcapsule wall material. It is desirable to mix them so that
In the case of an amino aldehyde resin, an ultraviolet absorber,
The amount of the ultraviolet absorbent is preferably about 3 to 75% by weight, preferably about 3 to 50% by weight, based on the total of the microcapsule wall material and the organic solvent used as required. desirable.

In the microcapsules used in the present invention, an antioxidant, an oil-soluble fluorescent dye, a release agent, and the like can be added, if necessary, in addition to the ultraviolet absorber. In addition, at the time of microencapsulation, a tin compound, a polyamide compound, an epoxy compound, a polyamine compound, or the like can be used in combination as a reaction accelerator. When a polyamine compound is used, it is desirable to use an aliphatic polyamine compound from the viewpoint of light resistance.

The average particle diameter of the microcapsules used in the present invention is 0.1 to 3 μm, preferably 0.3 to 2.5 μm in consideration of the absorption efficiency of ultraviolet rays and the quality of recorded images.
It is desirable to adjust so as to be within the range. Also,
The amount of the microcapsules to be incorporated into the protective layer is to be appropriately selected depending on the type of the ultraviolet absorber and the concentration in the capsule, and furthermore, the intended quality, etc., and is generally based on the total solid content of the protective layer. It is desirably adjusted in the range of about 5 to 80% by weight, preferably about 20 to 70% by weight.

In the present invention, as the basic dye constituting the recording layer, various known colorless or light-colored basic dyes can be used. 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-
Np-tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3,6-bis (diethylamino) fluoran −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-anilinofluoran, 3- (N
-Methyl-N-cyclohexyl) amino-6-methyl-
7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di (n-butyl)
Amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (o-chlorophenylamino) fluoran, 3- Di (n-butyl) amino-7- (o-chlorophenylamino) fluoran, 3-
Diethylamino-7- (o-fluorophenylamino)
Fluoran, 3-di (n-butyl) amino-7- (o-
Fluorophenylamino) fluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p- Toluzino) Fluoran, 3- (N-
Ethyl-N-furfurylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-
7-anilinofluoran, 3- (N-methyl-Nn-
Propylamino) -6-methyl-7-anilinofluoran, 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-tetrabromophthalide, 3-p
-(P-dimethylaminoanilino) anilino-6-methyl-7-chlorofluoran, 2,2-bis {4- [6 '
-(N-cyclohexyl-N-methylamino) -3'-
Methyl spiro [phthalide-3,9'-xanthen-2 '
-Ylamino] phenyl} propane, 3,6,11-tri (dimethylamino) fluoran and the like. Of course, the present invention is not limited to these, and two or more of them can be used as needed.

Various materials are also known for the coloring agents used in combination with the basic dyes as described above, for example, inorganic acid substances such as activated clay, attapulgite, colloidal silica and aluminum silicate, and 4,4'- Isopropylidene diphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4 '
-Dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-
4-hydroxyphenyl) sulfone, 4-hydroxy-
4'-methyldiphenylsulfone, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, butyl bis (p-hydroxyphenyl) 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-
(4'-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfine,
4,4'-dihydroxydiphenyl-2,2-butane,
4,4'-dihydroxydiphenylmethane, 4-cumylphenol, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 2,2-bis (4-hydroxyphenyl) heptane, 1,1-bis (4-hydroxyphenyl ) Cyclohexane, 3,4-dihydroxyphenyl-p-tolylsulfone, di (p-hydroxyphenylthioethyl) ether, N, N'-di-m-chlorophenylthiourea, 4-hydroxy-3 ', 4'-tetra Phenolic compounds such as methylenebiphenylsulfone, (4-hydroxyphenylthio) acetic acid-2- (4-hydroxyphenylthio) ethyl ester, N- (phenoxyethyl) -4-hydroxyphenylsulfonamide,
zinc p-chlorobenzoate, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- {3-
(P-tolylsulfonyl) propyloxy] salicylic acid, aromatic carboxylic acids such as 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and zinc, magnesium, aluminum, calcium of these aromatic carboxylic acids; Examples thereof include salts with polyvalent metals such as titanium, manganese, tin, and nickel, and organic acid substances such as an antipyrine complex of zinc thiocyanate.

The ratio between the basic dye and the colorant is appropriately selected according to the type of the basic dye and the colorant used, and is not particularly limited. 1 to 10 parts by weight, preferably 1 to 10 parts by weight
About 5 parts by weight of a coloring agent is used. The coating material for a heat-sensitive recording layer containing a basic dye, a coloring agent, and an epoxy resin in the present invention is generally dispersed together with water or a stirring medium such as a ball mill, an attritor, or a sand mill using water as a dispersion medium. It is prepared, for example.

In the coating solution, starch, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, Diisobutylene / maleic anhydride copolymer salt, styrene /
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene
At least one of a butadiene copolymer emulsion, a urea resin, a melamine resin, an amide resin, and a polyurethane resin is blended in an amount of about 5 to 40% by weight, preferably about 15 to 30% by weight based on the total solid content of the recording layer. Is done.

Various auxiliaries can be added to the coating solution, if necessary. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. Waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc.
An antifoaming agent, a fluorescent dye, a coloring dye and the like are appropriately added. Furthermore, a microcapsule containing the ultraviolet absorber of the present invention and a solid ultraviolet absorber are also incorporated in the recording layer coating liquid,
Light resistance can be further enhanced.

Further, various pigments can be used in the coating liquid, for example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth,
Examples include inorganic pigments such as finely divided anhydrous silica and activated clay, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles.

Further, a sensitizer can be used in combination depending on the purpose. Specific examples of the sensitizer include, for example, stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, methylenebisstearic acid amide , N-methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate,
Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthyl benzyl ether, m-terphenyl, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-oxalate Chlorobenzyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 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, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p
-Acetotoluidide, p-acetophenethidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like. Is done. The use amount of these sensitizers is not particularly limited, but it is generally desirable to adjust the sensitizer within a range of about 4 parts by weight or less based on 1 part by weight of the color former.

In order to further enhance the storability of the recorded image according to the purpose as long as the effect is not impaired, a storability improving agent can be used in combination. Specific examples of such a preservability improver include, for example, 2,2'-methylenebis (4-methyl-6
-Tert-butylphenol), 2,2'-ethylenebis (4-methyl-6-tert-butylphenol) 2,2 '
-Methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4,6-di-tert-
Butylphenol), 2,2'-ethylidenebis (4,
6-di-tert-butylphenol), 2,2'-ethylidenebis (4-methyl-6-tert-butylphenol), 2,2'-ethylidenebis (4-ethyl-6-te
rt-butylphenol), 2,2 '-(2,2-propylidene) bis (4,6-di-tert-butylphenol), 2,2'-methylenebis (4-methoxy-6-te
rt-butylphenol), 2,2'-methylenebis (6
-Tert-butylphenol), 4,4'-thiobis (3
-Methyl-6-tert-butylphenol), 4,4'-
Thiobis (2-methyl-6-tert-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'-tetrabromodiphenylsulfone, 4,4'-dihydroxy-3,3 ', 5,5'-tetramethyldiphenylsulfone, 2,2-bis (4-hydroxy-3,5
-Dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,
Hindered phenol compounds such as 2-bis (4-hydroxy-3,5-dimethylphenyl) propane;
N'-di-2-naphthyl-p-phenylenediamine,
Sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate and the like.

As described above, the thermosensitive recording medium of the present invention has a protective layer containing a microcapsule containing an ultraviolet absorbent, and the protective layer is formed of a water-soluble or water-dispersible microcapsule. The binder is composed of a polymer compound as a main component. Specific examples of such binders include, for example, 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, diisobutylene. Maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, urea resin, melamine resin, Amide resins, polyurethane resins and the like can be exemplified. Among them, acetoacetyl group-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol can form a strong film. Preferably used for.

In the protective layer, a pigment can be added as needed 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 Organic pigments such as formalin resin fillers and raw starch particles are exemplified. The amount used is generally 5 to 3 with respect to the binder component.
It is desirable to adjust it in the range of about 00% by weight.

The method for preparing the coating liquid for forming the protective layer is not particularly limited. Generally, water is used as a dispersion medium, and the above-mentioned specific microcapsules (dispersion liquid), a binder, and a pigment to be added as necessary are used. It is prepared by mixing. Further, in the coating liquid for the protective layer, if necessary, zinc stearate, calcium stearate, polyethylene wax,
Lubricants such as carnauba wax, paraffin wax and ester wax; surfactants (dispersants and wetting agents) such as dioctyl sodium sulfosuccinate; antifoaming agents; and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate. Can also be added as appropriate. In order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound can be used in combination.

The method for forming the recording layer and the protective layer is not particularly limited. For example, an appropriate coating such as air knife coating, variver blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating and the like. After the coating liquid for a recording layer is applied to a support by a method and dried, the coating liquid for a protective layer is further applied and dried on the recording layer. The support is appropriately selected from paper, plastic film, synthetic paper, nonwoven fabric, metal deposit, and the like. Also,
The coating amount of the coating liquid for the recording layer is ² to 12 g / m ² by dry weight,
It is preferably about 3 to 10 g / m ² , and the coating amount of the coating liquid for the protective layer is 0.1 to 20 g / m ² , preferably 0.1 to 20 g / m ² in dry weight.
It is adjusted in the range of about 5 to 10 g / m ² .

If necessary, a protective layer may be provided on the back side of the heat-sensitive recording medium to further improve the storability. Furthermore, an undercoat layer is provided on the support, or a smoothing treatment such as super calendaring is performed after each layer is coated,
Alternatively, various known techniques in the field of heat-sensitive recording material production can be added as necessary, such as applying a pressure-sensitive adhesive treatment to the back surface of the recording material to process it into an adhesive label.

[0040]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted to such specific Examples. In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 Preparation of Solution A In a stirring and mixing vessel equipped with a heating device, 60 parts of an 8% aqueous solution of polyvinyl alcohol (trade name: PVA-217, manufactured by Kuraray Co., Ltd.) was added, and an aqueous medium for producing microcapsules was added. did. Separately, 2- (2'-hydroxy-3'-dodecyl
-5'-methylphenyl) benzotriazole 12 parts ,
(3: 1) adduct of xylylene diisocyanate and trimethylolpropane [trade name: Takenate D-110]
N, manufactured by Takeda Pharmaceutical Company, containing 25% ethyl acetate] 1
The solution obtained by dissolving 8 parts was cooled in the above aqueous medium for producing capsules using a TK homomixer (model HV-M, manufactured by Tokushu Kika Kogyo Co., Ltd.) so that the average particle diameter became 2 μm. While emulsifying and dispersing. Next, 50 parts of water was added to the emulsified dispersion, and the mixture was reacted at 60 ° C. for 3 hours with stirring to prepare a microcapsule dispersion having a wall film made of a polyurethane / polyurea resin containing an ultraviolet absorbent.

Solution B Preparation 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 5% aqueous solution of methylcellulose 5
Parts and 40 parts of water were pulverized with a sand mill until the average particle size became 1.5 μm.

Solution C Preparation A composition comprising 30 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water is pulverized by a sand mill until the average particle diameter becomes 1.5 μm. did.

Solution D Preparation of 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 by a sand mill until the average particle diameter becomes 1.5 μm. Crushed.

Preparation of Solution E Orthocresol novolak type epoxy resin [manufactured by Asahi Kasei Corporation, trade name: ECN-299, softening point 97 ° C.] 20
Parts, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water
Part by weight of a composition comprising
m.

Formation of Recording Layer 55 parts of liquid B, 115 parts of liquid C, 80 parts of liquid D, 24 parts of liquid E,
A recording liquid coating liquid obtained by mixing and stirring 80 parts of a 10% aqueous solution of polyvinyl alcohol and 35 parts of calcium carbonate was used.
60 g / m ² of high-quality paper with a coating amount of 6 g /
The recording layer was formed by coating and drying so as to obtain m ² .

Formation of protective layer 220 parts of solution A, 150 parts of a 10% aqueous solution of acetoacetyl group-modified polyvinyl alcohol [trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Company], kaolin [trade name: UW-90] Co., Ltd., EMC) 15 parts, a 30% aqueous dispersion of zinc stearate, 6 parts, and 30 parts of water were mixed and stirred to obtain a coating liquid for a protective layer, which was dried and applied onto the recording layer. After coating and drying so that the amount becomes 6 g / m ² ,
A super calender treatment was performed to obtain a thermosensitive recording medium.

Example 2 In the preparation of solution A, 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole 1
Instead of 2 parts, 2- [2'-hydroxy-4 '-(2
[Ethylhexyl) oxyphenyl] benzotriazole was used in the same manner as in Example 1 except for using 12 parts to obtain a thermosensitive recording medium.

Example 3 In the preparation of solution A, 3 parts of 1-phenyl-1-methyl-1-xylylmethane and 2-
Instead of 12 parts of (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2-
6 parts of (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole and methyl-3- [3
-Tert-butyl-5- (2H-benzotriazole-2
-Yl) -4-hydroxyphenyl] propionate-
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 6 parts of a condensate with polyethylene glycol (molecular weight: about 300) was used.

Example 4 In the preparation of solution B, 3-di (n-butyl) amino-6
Instead of 10 parts of methyl-7-anilinofluoran, 3
Example except that 10 parts of-(N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran was used.
In the same manner as in Example 1 , a thermosensitive recording medium was obtained.

Example 5 Preparation of solution F Into a stirring and mixing vessel equipped with a heating device, 150 parts of a 5% aqueous solution of polyacrylic acid was added, and the pH of the system was adjusted to 4.5 to prepare an aqueous medium for capsule production. Separately, 2- (2'-hydroxy-3'-dode was added to 58 parts of diisopropylnaphthalene.
Decyl-5'-methylphenyl) benzotriazole 5
8 parts were dissolved and used as a capsule core substance in the above aqueous medium for producing capsules using a TK homomixer [model HV-
M, manufactured by Tokushu Kika Kogyo Co., Ltd.)
m for 15 minutes.

This emulsified dispersion was used as a wall film material in a 30% aqueous solution of a commercially available melamine-formaldehyde precondensate 19
After adding 0 parts and reacting at 90 ° C. for 3 hours while stirring, the temperature was lowered to room temperature and an ultraviolet absorber was included.
A melamine-formaldehyde resin wall membrane capsule having an average particle diameter of 2 μm was prepared.

55 parts of solution F, acetoacetyl group-modified polyvinyl alcohol [trade name: Gosefimer Z-20]
0, manufactured by Nihon Gosei Co., Ltd.], 150 parts of a 10% aqueous solution, 15 parts of kaolin (trade name: manufactured by UW-90 EMC), 6 parts of a 30% zinc stearate dispersion, and water 30 were mixed and stirred to obtain a protective layer. The coating solution was applied and dried on the recording layer used in Example 1 so that the applied amount after drying was 6 g / m ^2, and calendered to obtain a thermosensitive recording material.

[0054] except for not adding the E liquid in the formation of the recording layer of Comparative Example 1 Example 1 to obtain a heat-sensitive recording layer in Example 1.

Comparative Example 2 Preparation of Solution H A composition comprising 10 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 5 parts of a 5% aqueous solution of methylcellulose and 40 parts of water was subjected to sand milling to obtain an average particle size. Was reduced to 1.5 μm.

Preparation of Thermosensitive Recording Material In the formation of the protective layer, the H
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 45 parts of the liquid was used.

Comparative Example 3 In the preparation of solution H, 10 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole was used instead of 10 parts.
A heat-sensitive recording material was obtained in the same manner as in Comparative Example 2 , except that 10 parts of 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole was used.

The following evaluation tests were performed on the thus obtained heat-sensitive recording medium , and the results are shown in Table 1.

1. [Coloring Density] Each thermosensitive recording medium was colored with an applied voltage of 24 V and a pulse time of 2 ms using a thermosensitive recording medium evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.). The color density of the recorded image was measured in a visual mode using a Macbeth densitometer (RD-914, manufactured by Macbeth).

2. [Plasticizer resistance] A vinyl chloride wrap film (manufactured by Mitsui Toatsu Chemicals, Inc.) was wound three times on a polypropylene pipe (40 mmφ pipe).
A thermosensitive recording material, which is printed and colored by the above-described evaluation device, is sandwiched thereon so that the printed color surface is outside, and a vinyl chloride wrap film is further wound three times from above and printed after being left at 30 ° C. for 24 hours. The plasticizer resistance was evaluated from the concentration.

3. [Light Resistance] After exposing each heat-sensitive recording medium to direct sunlight for 2 days, the background was measured with a Macbeth densitometer (using a blue filter).

4. [Oil resistance] Cottonseed oil was dropped on the heat-sensitive recording material that had been printed and colored by the above-described evaluation machine, and the state of the recorded image after standing at room temperature for 24 hours was visually evaluated.

[0063]

[0064]

[Table 1]

[0065]

As is clear from the results shown in Table 1, all of the heat-sensitive recording materials of the present invention are extremely excellent in the preservability of the recorded image with respect to the plasticizer, and the yellowing of the background portion due to light exposure. The number of recordings was also small.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-267087 (JP, A) JP-A-2-289378 (JP, A) JP-A-3-190788 (JP, A) JP-A-2- 178083 (JP, A) JP-A-2-215589 (JP, A) JP-A-3-189188 (JP, A) JP-A-3-26590 (JP, A) JP-A-2-84376 (JP, A) JP-A-5-162442 (JP, A) Patent 2780554 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34 B41J 13/02

Claims (2)

(57) [Claims] 1. A thermosensitive recording medium comprising a support and a recording layer containing a colorless or light-colored basic dye and a colorant, and a protective layer sequentially provided on a support, wherein a novolak epoxy resin, a benzene ring glycidyl ether or glycidyl ester compound as the core, the diphenyl sulfone contains at least one selected from the nucleus to the glycidyl ether or glycidyl ester compound and a bisphenol a type epoxy resin, is in the protective layer, a liquid at room temperature benzotriazole enclosing the system ultraviolet absorbers, and virtually no coloration ability, polyurethane polyurea resin or
Or a microcapsule having a wall film made of an aminoaldehyde resin . 2. A benzotriazole ultraviolet liquid which is liquid at normal temperature.
The radiation absorbing agent is 2- (2'-hydroxy-3'-dodecyl);
-5'-methylphenyl) benzotriazole, 2-
[2'-hydroxy-4 '-(2 "-ethylhexyl)
[Oxyphenyl] benzotriazole and methyl-3
-[3-tert-butyl-5- (2H-benzotriazo-
Ru-2-yl) -4-hydroxyphenyl] propione
Of polyethylene glycol with a molecular weight of about 300
2. The composition according to claim 1, which is at least one selected from condensates.
Thermal recording medium.