JP3094609B2 - 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 medium having excellent storage stability, especially light fastness.

[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] As one of the fields of use, for example, POS
(Point of sales) Thermal recording labels for systems can be cited, but with the expansion of the system, apart from food labels, whose mission is to be completed in a short time as in the past, they have been attached to products for a long time and used. The use of the tag paper as a tag paper or a handy terminal paper for collection and delivery, which is often handled outdoors, is increasing. However, in such applications, the heat-sensitive recording medium is often exposed to room light or sunlight for a long period of time, and as a result, the background portion of the heat-sensitive recording material turns yellow, and as a result, the product image is significantly impaired.
For this reason, there is a strong demand for a thermosensitive recording medium that does not cause yellowing of the background even when exposed to room light or sunlight for a long time.

Conventionally, there has been proposed a method of adding a finely pulverized ultraviolet absorber to a heat-sensitive recording layer or a protective layer in order to prevent yellowing of a background portion of a heat-sensitive recording medium due to light. However, a finely pulverized ultraviolet absorber has a poor absorption efficiency of ultraviolet light, so that it cannot provide a sufficient effect. Further, when the amount of use is increased, a new disadvantage such as a background fog or a decrease in recording density is accompanied. As a result, it has not been possible to obtain sufficiently satisfactory light fastness as a result. Further, in the thermal recording medium used as the tag paper or the handy terminal paper as described above, a plasticizer, a solvent,
Since the resistance of the recorded image to oils and fats or sebum is required, a protective layer is generally provided on the recording layer. However, if the protective layer contains a finely pulverized ultraviolet absorber, In addition, the ultraviolet absorber elutes under the influence of the plasticizer, oils and fats, and impairs the function of the protective layer. As a result, the storage stability of the recorded image is reduced.

[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 without reducing the recording density or impairing the storage stability of a recorded image for a very long time. An object of the present invention is to provide a thermosensitive recording medium which does not cause yellowing of a background portion and has excellent light fastness.

[0006]

SUMMARY OF THE INVENTION The present invention provides a method for manufacturing a semiconductor device comprising the steps of:
In a thermosensitive recording medium provided with a recording layer containing a colorless or pale-colored basic dye and a coloring agent, and a protective layer in order , 2- (2'-hydroxy) is added as an ultraviolet absorber in the protective layer.
-5'-methylphenyl) benzotriazole, 2-
(2'-hydroxy-3 ', 5'-di-tert-butyl butyl
Enyl) benzotriazole and 2- (2'-hydro
Xy-3'-tert-butyl-5'-methylphenyl)-
At least one selected from 5-chlorobenzotriazole
Contains 20 to 70% by weight of a microcapsule containing one kind and having substantially no coloring ability based on the total solid content of the protective layer
It is to let .

[0007]

The following are specific examples of the ultraviolet absorber used in the present invention. Phenyl salicylate,
salicylic acid ultraviolet absorbers such as p-tert-butylphenyl salicylate and p-octylphenyl salicylate;
2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-
Octyloxybenzophenone, 2-hydroxy-4-
Benzophenone ultraviolet absorbers such as dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-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" -tetrahydrophthalimide- Methyl) -5'-methylphenyl] benzotriazole, 2- (2'-hydroxy-5'-tert-
Octylphenyl) benzotriazole, 2- [2'-
Benzotriazole-based ultraviolet absorbers such as hydroxy-3 ', 5'-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2-ethylhexyl-
A cyanoacrylate-based ultraviolet absorber such as 2-cyano-3,3'-diphenylacrylate, ethyl-2-cyano-3,3'-diphenylacrylate;
6,6-tetramethyl-4-piperidyl) sebacate,
Bis-succinate- (2,2,6,6-tetramethyl-4-
Hindered amine ultraviolet absorbers such as piperidyl) ester and 2- (3,5-di-tert-butyl) malonic acid-bis (1,2,2,6,6-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 preferred, and particularly, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole,
-(2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5
-Chlorobenzotriazole is more preferably used because it exhibits a particularly remarkable light resistance improving effect.

The amount of the ultraviolet absorbent used is not particularly limited, but the basic dye 10 in the recording layer may be used.
It is desirable to adjust the amount to preferably 10 to 500 parts by weight, more preferably about 20 to 250 parts by weight, based on 0 parts by weight. The present invention has an important feature in that microcapsules containing the above-mentioned ultraviolet absorber and having substantially no coloring ability are contained in a protective layer formed on the recording layer . Various thermal recording media using microcapsules containing a colorless or light-colored basic dye and an ultraviolet absorber have been proposed.However, since these microcapsules also contain a basic dye, light- Not only causes a coloring phenomenon with an increase in the amount of irradiation, but also cannot exert a sufficient effect of improving light resistance 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 a solid ultraviolet absorber in an organic solvent at ordinary temperature as described above is used. It is prepared by a method of emulsifying and dispersing in an aqueous medium 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 microcapsules include, for example, polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin,
Polystyrene resin, styrene-acrylate copolymer resin, styrene-methacrylate copolymer resin, gelatin, polyvinyl alcohol and the like can be mentioned. Among these, microcapsules having a wall film made of polyurethane / polyurea resin are particularly excellent in heat resistance.
In addition to the effect of an inorganic pigment added to the protective layer to prevent sticking to the thermal head, it has an excellent collateral effect, and compared to microcapsules consisting of other wall films and ordinary pigments It is preferably used because it has a low refractive index and a spherical shape, so that even if it is incorporated in a large amount in the protective layer, there is no danger of causing a decrease in the density of a recorded image (so-called whitening phenomenon) due to irregular reflection of light. Can be

The microcapsules having a wall film made of polyurethane / polyurea resin are used in a core material to encapsulate a capsule wall film 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.

[0012] As the polyol compound, 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.

The organic solvent is not particularly limited, and may be appropriately selected from various high-boiling-point hydrophobic media used in the field of pressure-sensitive copying paper. Phosphates such as tricresyl, octyl diphenyl phosphate, dibutyl phthalate,
Phthalates such as dioctyl phthalate; carboxylic esters such as butyl oleate; various fatty acid amides; alkylated naphthalenes such as diethylene glycol dibenzoate, monoisopropyl naphthalene and diisopropyl naphthalene; 1-methyl-1-phenyl- 1-
Alkylated benzenes such as tolylmethane, 1-methyl-1-phenyl-1-xylylmethane, 1-phenyl-1-tolylmethane, alkylated biphenyls such as isopropylbiphenyl, xenoxyalkanes such as o-phenylphenol glycidyl ether; Examples include acrylates such as trimethylolpropane triacrylate, esters of polyhydric alcohol and unsaturated carboxylic acid, chlorinated paraffin, and kerosene. Needless to say, two or more of these can be used in combination. In addition, tricresyl phosphate and 1-
Phenyl-1-tolylmethane is preferable 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 the ultraviolet absorber is preferably in a sufficiently dissolved state, 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 Is desirably adjusted to be in the range of about 20 to 60% by weight.

The amount of the capsule wall film material used is not particularly limited. However, the organic solvent in the microcapsules may ooze out over a long period of storage, thereby deteriorating the preservability of the thermosensitive recording medium. It is preferable to use a larger amount of the wall film material than the microcapsules, and the ratio of the wall film material to the total of the organic solvent, the ultraviolet absorber and the microcapsule wall film material is 35 to 70% by weight. %,
It is desirable to select the amount so as to be preferably in the range of 35 to 60% by weight.

Further, 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, but a remarkable effect is obtained. Therefore, 3 to 50% by weight, preferably 3 to 2% by weight based on the total of the organic solvent, the ultraviolet absorber and the microcapsule wall film material.
It is desirable to blend the ultraviolet absorbent in an amount of about 0% by weight.

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, carrageenan, sodium alginate, pectic acid with -OPO ₃ ^2-group,
Natural polymer compounds such as tragacanth gum, almond gum and agar, semi-synthetic polymer compounds such as carboxymethylcellulose, sulfated cellulose, sulfated methylcellulose, carboxymethylated starch, phosphorylated starch and ligninsulfonic acid, maleic anhydride (hydrolysis Including
), Acrylic acid, methacrylic acid, crotonic acid, vinyl
Benzenesulfonic acid and 2-acrylamide-2-me
Polymer sequence copolymer Chirupuropansu sulfonic acid, and partial amide derivatives or partial esters of these polymers or copolymers, carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, synthetic polymers such as phosphoric acid-modified polyvinyl alcohol And the like. Specific examples of the maleic anhydride copolymer include methyl vinyl ether-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, α-methylstyrene-maleic anhydride copolymer. polymers, vinyl acetate - maleic anhydride copolymer, methacrylamide - maleic anhydride copolymer, an isobutylene - maleic anhydride copolymer and the like, acrylic acid, methacrylic
As a specific example of a copolymer of cric acid and crotonic acid
It is methyl acrylate - acrylic acid copolymer (hereinafter "copolymer" is abbreviated), 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, acetic acid Vinyl-methacrylic acid, acrylamide-acrylic acid, acrylamide-methacrylic acid,
Copolymers such as methacrylamide-acrylic acid, methacrylamide-methacrylic acid, vinyl acetate-crotonic acid, and the like. Examples of vinylbenzenesulfonic acid and 2-acrylamido-2-methyl-propanesulfonic acid- based copolymer include acrylic. Acid methyl-vinylbenzenesulfonic acid (or salt thereof) copolymer, vinyl acetate-vinylbenzenesulfonic acid copolymer, acrylamide-vinylbenzenesulfonic acid copolymer, acryloylmorpholine-vinylbenzenesulfonic acid copolymer, vinylpyrrolidone -Vinylbenzenesulfonic acid copolymer, vinylpyrrolidone-2
- methyl - Ru Re et al mentioned propanesulfonic acid copolymers <br/>.

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 is generally 1 to 50% by weight, preferably 3 to 30% by weight based on the total of the wall film agent, the ultraviolet absorber and the organic solvent. It may be adjusted in the range of about weight%.
In the microcapsules used in the present invention, in addition to the ultraviolet absorber, if necessary, an antioxidant, an oil-soluble fluorescent dye,
A release agent or the like can be added. 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 size 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 heat-sensitive 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-N-p-tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7-dibenzylamino Fluoran, 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-toluidino) 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 '-Methylspiro [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 as colorants used in combination with the above basic dyes, for example, inorganic clays 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-
Phenolic compounds such as (4'-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfine, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- {3- ( p-
Tolylsulfonyl) propyloxy] salicylic acid, 5-
[P- (2-p-methoxyphenoxyethoxy) cumyl] aromatic carboxylic acids such as 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 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 50 parts by weight, preferably 2 to 5 parts by weight
About 10 parts by weight of a color former is used. The coating liquid for a recording layer containing these substances is generally prepared by dispersing a dye and a colorant together or separately with a stirring / pulverizer such as a ball mill, an attritor, and a sand mill using water as a dispersion medium. You.

In the coating solution, starch, 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
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 30% by weight based on the total solid content of the recording layer.

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. Further, microcapsules containing the ultraviolet absorbent of the present invention can be incorporated into the coating liquid for the recording layer to further enhance the light resistance.

It is also possible to use various pigments together 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, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, di- p-oxalate -Methylbenzyl , di -p-chlorobenzyl oxalate, 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- (3-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 enhance the preservability of the recorded image, a preservability improver can be added according to the purpose. Specific examples of such a preservability improver include, for example, 2,2'-methylenebis (4-methyl-6-tert-butylphenol) and 2,2'-ethylenebis (4-methyl-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-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-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, 2,2-bis (4-hydroxy-3,5
Hindered phenol compounds such as -dimethylphenyl) propane, 1,4-diglycidyloxybenzene,
Epoxy compounds such as 4'-diglycidyloxydiphenyl sulfone, diglycidyl terephthalate, cresol novolak type epoxy resin, phenol novolak type epoxy resin, bisphenol A type epoxy resin, N, N '
-Di-2-naphthyl-p-phenylenediamine, 2,
Sodium 2'-methylenebis (4,6-di-tert-butylphenyl) phosphate and the like.

As described above, the heat-sensitive recording material of the present invention has a protective layer containing a microcapsule containing an ultraviolet absorbent. 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, and 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 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 Organic pigments such as formalin resin fillers and raw starch particles are exemplified. Generally, it is desirable to adjust the amount of use in the range of about 5 to 300 parts by weight with respect to 100 parts by weight of the binder component.

The method of 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. Further , 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 method such as air knife coating, variver blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. 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.

[0035]

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) was added, and an aqueous medium for producing microcapsules was added. did. Separately, 2- (2 ′) is added to 12 parts of tricresyl phosphate.
-Hydroxy-5'-methylphenyl) benzotriazole (2 parts), a (3: 1) adduct of xylylene diisocyanate and trimethylolpropane [trade name: Takenate D
-110N, manufactured by Takeda Pharmaceutical Co., Ltd., containing 25% of ethyl acetate], and TK homomixer [Model HV-M, Tokushu Kika Kogyo Co., Ltd.] And emulsified and dispersed while cooling so that the average particle diameter becomes 2 μm. 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 of a composition comprising 10 parts of 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 5 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water was carried out using a sand mill. And pulverized until the average particle diameter becomes 3 μm.

Solution C Preparation A composition comprising 30 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water was pulverized by a sand mill until the average particle diameter became 3 μm.

Solution D Preparation A composition comprising 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 by a sand mill until the average particle diameter became 3 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, and calcium carbonate 35
The coating liquid for recording layer obtained by mixing and stirring the parts was coated and dried on one side of a high-quality paper of 60 g / m ² so that the coating amount after drying was 6 g / m ² to form a recording layer.

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 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole was used instead of 2 parts.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 2 parts of-(2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole was used.

Example 3 In the preparation of Solution A, 2 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole was used instead of 2 parts.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 2 parts of-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole was used.

Example 4 Preparation of Solution E A composition comprising 100 parts of calcined clay (trade name: Ansilex, manufactured by EMC, oil absorption: 110 ml / 100 g), 100 parts of a 10% aqueous solution of polyvinyl alcohol, and 200 parts of water was prepared. The mixture was stirred to obtain a coating liquid for an undercoat layer.

[0045] on one surface of woodfree paper produced 60 g / m ² of the heat-sensitive recording material, after the E liquid coating amount after drying was coated and dried so that 7 g / m ^2, a recording layer used in Example 1 The coating liquid and the coating liquid for the protective layer were each coated and dried so that the coating amount after drying was 6 g / m ² , to obtain a thermosensitive recording medium.

Example 5 In the preparation of solution C, 30 parts of bis (4-hydroxyphenylthioethoxy) methane was used instead of 30 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone.
Further, in the preparation of the liquid D, a thermosensitive recording medium was prepared 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. I got

Example 6 Thermal recording was conducted 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. I got a body.

[0048] In the formation of Example 7 protective layer, using a 10% aqueous solution of 150 parts of carboxy-modified polyvinyl alcohol in place of 10% aqueous solution 150 parts of acetoacetyl group-modified polyvinyl <br/> alcohol, instead of 15 parts of kaolin Calcium carbonate 15
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that parts were used.

Example 8 In the preparation of solution A, the amount of the (3: 1) adduct of xylylene diisocyanate and trimethylolpropane (containing 25% of ethyl acetate) was changed to 8 parts, and 2- (2'-hydroxy A heat-sensitive recording material was obtained in the same manner as in Example 1, except that the amount of (-5'-methylphenyl) benzotriazole was changed to 1.4 parts.

Example 9 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the amount of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole was changed to 0.5 part in the preparation of solution A. Obtained.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 2- (2'-hydroxy-5'-methylphenyl) benzotriazole was not used in the preparation of solution A.

Comparative Example 2 Preparation of Solution F 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 3 μm.

In the formation of the protective layer for the production of the heat-sensitive recording medium, the above F
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 40 parts of the liquid was used.

Comparative Example 3 In the preparation of solution F, 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.

Comparative Example 4 In the preparation of Solution A, 2 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole was used instead of 2 parts.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 2 parts of-[2'-hydroxy-3 ', 5'-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole was used.

Comparative Example 5 In the preparation of Solution A, 2 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole was used instead of 2 parts.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 2 parts of-(2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole was used.

The following evaluation tests were performed on the 14 types of heat-sensitive recording media thus obtained, and the results are shown in Table 1.

[Coloring Property] 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.], and a recorded image was obtained. Was measured in visual mode using a Macbeth densitometer [RD-914, manufactured by Macbeth Co.].

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

[Plasticizer Resistance] A wrap film [trade name: KMA-W, manufactured by Mitsui Toatsu Chemicals, Inc.] was placed on a polycarbonate pipe (40 mmφ).
The thermosensitive recording medium recorded by the above method is placed on the thermosensitive recording medium, and a wrap film is further wound on the thermosensitive recording medium three times, and left at 20 ° C. for 24 hours. Was measured with a Macbeth densitometer (visual mode) to evaluate the plasticizer resistance.

[High-Temperature High-Humidity Resistance] The thermosensitive recording medium after the above recording was allowed to stand in an atmosphere of 50 ° C. and 95% RH for 24 hours, and then the color density of the recorded image and the density of the background portion were measured with a Macbeth densitometer. (Visual mode) to evaluate the high temperature and high humidity resistance.

[Solvent Resistance] The surface of the heat-sensitive recording medium before recording was wiped with a gauze containing ethanol, and the fog density was measured with a Macbeth densitometer (visual mode) to evaluate the solvent resistance.

[0063]

[Table 1]

UV in Table 1 is an ultraviolet absorber.

[0065]

As is clear from the results shown in Table 1, the heat-sensitive recording materials of the present invention are all excellent in light fastness, have almost no yellowing of the background portion, and have coloring and storage properties. It was an excellent recording medium.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-176880 (JP, A) JP-A-2-84376 (JP, A) JP-A-60-112487 (JP, A) JP-A-62 176879 (JP, A) JP-A-4-189179 (JP, A) Patent 2780554 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34 B41J 13 / 02

Claims (4)

(57) [Claims] To 1. A on a support, a recording layer containing a colorless or light-colored basic dye and color acceptor, and in a sequential provided a heat-sensitive recording material a protective layer, in the protective layer, an ultraviolet absorber
To give 2- (2'-hydroxy-5'-methylphenyl)
Benzotriazole, 2- (2'-hydroxy-3 ',
5'-di-tert-butylphenyl) benzotriazole
And 2- (2'-hydroxy-3'-tert-butyl-
5'-methylphenyl) -5-chlorobenzotriazoe
Enclosing at least one selected from the Le, and pair substantially free of coloring ability microcapsules on total solids of the protective layer
A heat-sensitive recording material characterized by containing 20 to 70% by weight . 2. The microcapsules having an average particle size of 0.1
2. The heat-sensitive recording medium according to claim 1, wherein the thickness is from 3 to 3 [mu] m. 3. The thermosensitive recording medium according to claim 1, wherein the microcapsules have a wall film made of polyurethane / polyurea resin. 4. The microcapsule is 3% of the total of the organic solvent, the ultraviolet absorber and the microcapsule wall material.
The heat-sensitive recording material according to claim 3, which is a microcapsule prepared using 5 to 70% by weight of a wall film material.