JP3094596B2 - Thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the storage stability of a recorded image,
Particularly, the present invention relates to a heat-sensitive recording medium having excellent light fastness.

[0002]

2. Description of the Related Art A thermosensitive recording material 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,
Further, since the recording apparatus is compact and easy to maintain, 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 of the application fields, PO
With the expansion of the S (point of sales) system, the use of thermosensitive recording materials as labels for displaying products and the like is increasing. The thermal recording medium for labels affixed to products is often exposed to room light or sunlight for a long period of time, which may cause the background to yellow and significantly impair the product image. is there. Therefore, there is a demand for a heat-sensitive recording medium in which the yellow color of the background portion is small when exposed to room light or sunlight.

Heretofore, there has been proposed a method in which a finely pulverized ultraviolet absorbent is contained in a heat-sensitive recording layer or a protective layer in order to prevent yellowing of the background portion of the heat-sensitive recording medium due to light. However, finely crushed UV absorbers are not effective enough due to the poor UV absorption efficiency, and additional drawbacks such as background fogging or reduced recording density when the amount used is increased. However, as a result, it has not yet been possible to obtain sufficiently satisfactory light resistance.

Further, a heat-sensitive recording material using a microcapsule containing a hydrophobic medium, a colorless or light-colored basic dye (leuco dye) and an ultraviolet absorber is disclosed in JP-A-61-2.
JP-A-83589, JP-A-61-283590,
JP-A-61-213591, JP-A-63-230
No. 387, because the leuco dye in the microcapsules is dissolved in the hydrophobic medium, it is more likely to be yellowed by light exposure than the solid state leuco dye. Therefore, even if the hydrophobic medium, the leuco dye and the ultraviolet absorber are encapsulated in the microcapsules, if the irradiation amount of light increases, a coloring phenomenon appears and the effect of the satisfactory ultraviolet absorber has not been obtained. .

Further, when a protective layer is provided for the purpose of improving the preservability of a recorded image with respect to chemicals such as plasticizers and oils, if the protective layer contains a finely pulverized ultraviolet absorber, the ultraviolet absorber is removed. It dissolves in a plasticizer and does not provide the desired preservability of a recorded image for chemicals.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording medium having a protective layer on a heat-sensitive recording layer without lowering the recording density or impairing the storage stability of the recorded image and for prolonged light exposure. An object of the present invention is to provide a heat-sensitive recording medium which is excellent in light fastness, in which yellowing of a background portion is extremely small.

[0008]

Means for Solving the Problems A heat-sensitive recording layer comprising a colorless or light-colored basic dye and a colorant capable of forming a color upon contact with the dye, and a protective layer are successively provided on a support. In the recording medium, at least in the protective layer, a benzotriazole derivative-based ultraviolet absorber liquid at room temperature is included,
Polyurethane / polyurea with virtually no coloring ability
A microcapsule having a wall film made of a resin is contained.

[0009]

The ultraviolet absorbent used in the present invention is a liquid at ordinary temperature, and therefore, when synthesizing oil-in-water microcapsules, it is not necessary to dissolve the ultraviolet absorbent in an organic solvent. It can be contained at a concentration, and the ultraviolet absorbing ability is also remarkably improved.

The ultraviolet absorber used in the present invention is not particularly limited as long as it is a liquid ultraviolet absorber at room temperature, but a benzotriazole derivative is particularly preferable, and specific examples thereof include the following. . 2- (2 '
-Hydroxy-3'-dodecyl-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-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
-[3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate and polyethylene glycol (molecular weight about 300)
And condensates. Of these, preferred are 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) -4-hydroxyphenyl] propionate and polyethylene glycol (molecular weight: about 300).

The amount of the ultraviolet absorber used is as follows.
It is preferably present in the protective layer in the range of 0.1 to 3.0 g / m ² , more preferably 0.2 to 2.0 g / m ^2.
Range. When the amount of the ultraviolet absorbent encapsulated in the microcapsules in the protective layer is less than 0.1 g / m ² , the effect of preventing the background portion of the thermal recording medium from yellowing is reduced. On the other hand, if it exceeds 3.0 g / m ² , the protective layer is inevitably thick, so that the recording sensitivity is lowered. Further, the content of the ultraviolet absorber is preferably 10% by weight or more based on the microcapsule core material composed of a mixed solution of the ultraviolet absorber and, if necessary, an organic solvent. That is, the organic solvent is preferably less than 90% by weight, more preferably 2% by weight, based on the microcapsule core material.
It is in the range of about 0 to 70% by weight.

When the amount of the ultraviolet absorbent is less than 10% by weight based on the core material of the microcapsule, the amount of the microcapsule applied must be increased in order to exhibit the effect of preventing the background portion of the thermosensitive recording material from yellowing. Therefore, the protective layer is inevitably thickened and the recording sensitivity is reduced. Furthermore, it is also possible to use an ultraviolet absorber which is solid at ordinary temperature as long as the effects of the present invention are not impaired. The following are specific examples of the ultraviolet absorber which is solid at ordinary temperature. Phenyl salicylate, p-tert-butylphenyl salicylate, salicylic acid-based ultraviolet absorbers such as p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone and the like Benzophenone ultraviolet absorbers, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-tert-butylphenyl) benzotriazole, 2- (2'-hydro Shi-3 ', 5'-di -ter
t-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'-ter
t-octylphenyl) benzotriazole, 2-
Benzotriazole ultraviolet absorbers such as [2'-hydroxy-3 ', 5'-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2-ethylhexyl-2-cyano-3,3'- There are cyanoacrylate UV absorbers such as diphenyl acrylate and ethyl-2-cyano-3,3'-diphenyl acrylate, and hindered amine UV absorbers. Two or more of these ultraviolet absorbers can be used in combination, and a benzotriazole derivative is preferred in terms of effect.

The microcapsules containing the ultraviolet absorbent used in the present invention can be prepared by various known methods. Generally, a mixed solution of the ultraviolet absorbent and, if necessary, an organic solvent is used as a core substance. It is prepared by a method of emulsifying and dispersing in an aqueous medium and forming a polymeric material wall film therearound. As wall material, polyurethane, polyurea, polyurethane polyurea, polyester,
Polycarbonate, amino aldehyde resin, melamine resin, polystyrene, styrene-methacrylate copolymer, styrene-acrylate copolymer, gelatin, polyvinyl alcohol and the like can be mentioned.

In the present invention, since microcapsules are added to the protective layer, the use of a polyurethane / polyurea resin having excellent heat resistance as a wall film material also has the effect of preventing sticking with a thermal head during recording. Can be In addition, when the inorganic pigment added to the protective layer for the purpose of improving printability and sticking is high in the addition ratio, the recorded image is whitened and the recording density is reduced, but the micro pigment of the polyurethane / polyurea resin wall film is reduced. The capsule has a lower refractive index than the inorganic pigment, and has a spherical shape, so that the whitening of the recorded image due to irregular reflection of light in the protective layer is small.

The polyurethane / polyurea wall film is prepared by mixing a polyol reacting with a polyvalent isocyanate or an adduct of a polyvalent isocyanate with a polyol in a core material to be encapsulated, and dissolving a protective colloid material such as polyvinyl alcohol. It is manufactured by emulsifying and dispersing in an aqueous medium, raising the liquid temperature, and causing a polymer formation reaction at the 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 an adduct of tolylene diisocyanate and hexane triol.

Examples of the polyol compound include 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-propanediol, 2,4-pentanediol, 2,5-
Hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, 1,2,2
6-trihydroxyhexane, phenylethylene glycol, 1,1,1-trimethylolpropane, hexanetriol, aliphatic polyols such as pentaerythritol, glycerin, 1,4-di (2-hydroxyethoxy) benzene, resorcinol dihydroxyethyl ether And condensation products of aromatic polyhydric alcohols and alkylene oxides, such as p-xylylene glycol, m-xylylene glycol, α, α′-dihydroxy-p-diisopropylbenzene, and 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 A polyol compound such as an oxide adduct can be used, and various auxiliaries such as a reaction accelerator can be used in combination.
Of course, the polyvalent isocyanate compound and the polyol compound are not limited to those described above, and two or more kinds can be used in combination.

The polyurethane / polyurea wall film material used in the present invention is preferably a material having three or more isocyanate groups in the molecule of a polyvalent isocyanate compound or an adduct of a polyvalent isocyanate compound and a polyol.
In general, the high-boiling point hydrophobic medium can be included in the microcapsules used in the present invention with an ultraviolet absorbent.
Specific examples of the high boiling point hydrophobic medium preferably used in the present invention include, for example, phosphate esters such as tricresyl phosphate and octyl diphenyl phosphate, phthalate esters such as dibutyl phthalate and dioctyl phthalate, and butyl oleate. Carboxylic acid esters, various fatty acid amides, alkylated naphthalenes such as diethylene glycol dibenzoate, diisopropyl naphthalene and diisopropyl naphthalene, alkylated biphenyls such as isopropyl biphenyl, xenoxy alkanes such as o-phenylphenol glycidyl ether, and trimethylolpropane triacrylate Acrylate ester, ester of polyhydric alcohol and unsaturated carboxylic acid, chlorinated paraffin, 1-
Phenyl-1-methyl-1-xylermethane and the like can be mentioned. Of course, two or more of these may be used in combination. In emulsification, the lower the viscosity of the hydrophobic medium, the smaller the emulsified particle size tends to be and the narrower the particle size distribution is. Therefore, a low-boiling solvent can be added as necessary. Specific examples of the low-boiling solvent include ethyl acetate, butyl acetate, and methylene chloride. Of course, the present invention is not limited to these, and two or more kinds may be used in combination.

When a wrap film is wound around the protective layer surface of the thermal recording medium of the present invention, if the wall film material is small, the core substance in the microcapsules is extracted by the action of the plasticizer added to the wrap film, and the background fog is reduced. And so on, the microcapsule wall material may be 3% smaller than the microcapsule core material and the microcapsule wall material.
It is preferably in the range of 5 to 95% by weight, more preferably 40% by weight.
~ 80% by weight. The wall film material of the microcapsule is 80
If the content is more than 10% by weight, fine particle emulsification becomes difficult.

The emulsifier used for producing microcapsules includes various anions, nonions, cations or amphoteric water-soluble polymers and surfactants. The amount of the emulsifier used is not particularly limited, but generally the wall film is
In the case of a polyurethane / polyurea resin, it may be adjusted within a range of 1 to 50% by weight, more preferably about 3 to 30% by weight, based on the microcapsule wall film agent and the core substance.

The average particle size of the microcapsules used in the present invention is desirably adjusted in the range of 0.1 to 3 μm in consideration of ultraviolet absorption efficiency, image quality of a recorded image, and the like. The microcapsule dispersion is contained at least in the protective layer, but can be added to the heat-sensitive recording layer. The content of the microcapsules in the protective layer is from 5 to 80% by weight of the total solids of the protective layer, more preferably from 20 to 80% by weight.
It is desirable to adjust it in the range of about 70% by weight.

In the present invention, examples of the basic dye contained in the heat-sensitive recording layer include various known colorless or light-colored basic dyes, for example, 3,3-bis (p-dimethylaminophenyl) -6. -Dimethylaminophthalide, 3-
(4-diethylamino-2-methylaminophenyl)-
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-dibenzylaminofluoran, 3,6-bis (diethylamino) fluoran-γ-
Anilinolactam, 3-cyclohexylamino-6-chlorofluoran, 3-diethylamino-6-methyl-7
-Chlorofluorane, 3-diethylamino-7-chlorofluoran, 3-N-ethyl-N-isopentylamino-6-methyl-7-anilinofluoran, 3-N-methyl-N-cyclohexylamino-6 -Methyl-7-anilinofluoran, 3-diethylamino-6-methyl-
7-anilinofluoran, 3-di-n-butylamino-
6-methyl-7-anilinofluoran, 3-di-n-pentylamino-6-methyl-7-anilinofluoran,
3-diethylamino-7- (o-chlorophenylamino) fluoran, 3-di-n-butylamino-7- (o
-Chlorophenylamino) fluoran, 3-diethylamino-7- (o-fluorophenylamino) fluoran, 3-di-n-butylamino-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) fluorene and the like. Of course, the present invention is not limited to these, and two or more of these basic dyes can be used in combination as needed.

Various materials are also known as inorganic or organic colorants which form a color upon contact with a basic dye as described above, for example, inorganic acid substances such as activated clay, apalgite, colloidal silica and aluminum silicate. 4,4'-isopropylidene diphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4 ′
-Dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropyloxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenylsulfone, Di (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-
(Hydroxyphenylthio) -3-oxapentane, 4-
[2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, bis (p -Hydroxyphenyl) butyl acetate, methyl bis (p-hydroxyphenyl) 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 Further, salts of these phenolic compounds and aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel, and organic acid such as antipyrine complex of zinc thiocyanate. Substances are exemplified.

The ratio of the basic dye and the colorant used is appropriately selected depending on the type of the basic dye and the colorant used, and is not particularly limited. 1 to 50 parts by weight, preferably 2-1
About 0 parts by weight of a color former is used. The heat-sensitive recording layer paint containing these substances is generally prepared by dispersing dyes and color formers together or separately with a stirring / pulverizer such as a ball mill, an attritor, and a sand mill using water as a dispersion medium. .

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
Butadiene copolymer emulsions, urea resins, melamine resins, amide resins, polyurethane ionomers and the like are used.

Various pigments can be used in combination, for example, kaolin, clay, calcium carbonate, calcined clay,
Inorganic pigments such as calcined kaolin, titanium oxide, diatomaceous earth, fine anhydrous silica, activated clay, styrene microballs,
Organic pigments such as nylon powder, polyethylene powder, urea / formalin resin filler, raw starch particles, and the like.

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, a sensitizer can be used in combination depending on the purpose. Specific examples of the sensitizer include, for example, stearic acid amide, p-methoxycarbonyl-stearic acid anilide, N-benzoylstearylamine, N-eicosanoic acid amide, N, N'-ethylenebisstearic acid amide, behenic acid amide, N , N'-methylenebisstearic acid amide, N-methylolstearic acid amide, acetanilide, benzanilide, N-acetyl-p-phenetidine, benzenesulfonic acid anilide, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, 2-phenyl Naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, p-benzylbiphenyl, tolylbiphenyl 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, p-methylthiophenylbenzyl ether, p-methoxy- o'-
Methyl-1,2-diphenoxyethane, p-acetotoluidide, p-acetophenethidide, benzyl p-benzyloxybenzoate, N-acetoacetyl-p-toluidine, di (p-methoxyphenoxyethyl) ether, di ( β-biphenylethoxy) benzene, 1,4-di (phenylthio) butane, p-di (vinyloxyethoxy)
Compounds such as benzene and 1-iso-propylphenyl-2-phenylethane are exemplified.

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. Further, according to the purpose, a preservability improving agent for a printed portion may be used in combination. Specific examples of the preservability improver include, for example, 2,2'-methylenebis (4-methyl-6-tert-butylphenol),
2,2'-ethylenebis (4-methyl-6-tert-
Butylphenol), 2,2'-methylenebis (4,6
-Di-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-tert-butylphenol), 2,2'-ethylidenebis (4-methyl-6-t
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-te
rt-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'-
Tetramethyldiphenyl sulfone, 2,2-bis (4-
(Hydroxy-3,5-dibromophenyl) propane,
2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,
5-dimethylphenyl) propane, N, N'-di-2-
Naphthyl-p-phenylenediamine, sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate and the like. Of course, it is not limited to these,
Two or more of them can be used in combination.

Examples of the water-soluble or water-dispersible polymer used in the protective layer of the present invention include various binders used in the heat-sensitive recording layer as described above. Among them, acetoacetyl-modified polyvinyl alcohol and carboxy-modified Polyvinyl alcohol is particularly preferably used for forming a strong film. In the protective layer, a pigment can be added as needed to further improve printability and sticking. Specific examples thereof include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, and silicon dioxide. , Aluminum hydroxide, barium sulfate,
Zinc sulfate, talc, kaolin, clay, calcined kaolin,
Inorganic pigments such as colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea
Organic pigments such as formalin resin fillers and raw starch particles are exemplified. It is generally desirable to adjust the amount of use in the range of about 5 to 500 parts by weight with respect to 100 parts by weight of the resin component.

Further, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., and a surfactant such as sodium dioctyl sulfosuccinate may be contained in the coating liquid for forming the protective layer, if necessary. Various assistants such as water-soluble polyvalent salts such as dispersants, wetting agents, defoamers, potassium alum, and aluminum acetate can also be added as appropriate. In order to further improve the water resistance, glyoxal, boric acid,
A curing agent such as dialdehyde starch can also be added.

The method of forming the heat-sensitive recording layer and the protective layer is not particularly limited. For example, an appropriate 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 the recording layer is applied to the support by a coating method and dried, the coating liquid for the protective layer is further applied and dried on the recording layer. Note that paper, plastic film, synthetic paper, or the like is used as the support. The coating amount of the coating liquid for the recording layer is 2 wt.
1212 g / m ² , preferably about 3-10 g / m ² , and the coating amount of the protective layer coating solution is 0.1-20 g / m ² , preferably 0.5-
It is adjusted in the range of about 10 g / m ² .

If necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storability. In addition, it is also possible to provide an undercoat layer on the support, apply super calendar after coating each layer, apply an adhesive treatment to the back of the recording body, process it into an adhesive label, etc. Various known techniques can be added as needed.

[0034]

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 [PVA-217, manufactured by Kuraray Co., Ltd.] was added. Medium. Separately, 3 parts of ethyl acetate, 12 parts of 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, a (3: 1) adduct of xylylene diisocyanate and trimethylolpropane [trade name: Takenate D-110N, manufactured by Takeda Pharmaceutical Co., Ltd., containing 25% by weight of ethyl acetate] as a core material and a wall film material for the capsule in the above aqueous medium for producing a capsule.
Using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), the mixture was emulsified and dispersed while cooling until the average particle size became 2 μm. 50 parts of water was added to this emulsified dispersion, and the mixture was reacted at 60 ° C. for 3 hours with stirring to prepare a microcapsule of a polyurethane / polyurea wall film containing an ultraviolet absorbent.

Solution B Preparation A composition comprising 10 parts of 3-di-n-butylamino-6-methyl-7-phenylaminofluoran, 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. Crushed to 3 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 was subjected to sand milling to give an average particle diameter of 3 parts.
Milled to a μm. Preparation of Solution D 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 with 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 a 10% aqueous solution of polyvinyl alcohol and calcium carbonate 3
The coating liquid obtained by mixing and stirring 5 parts was dry-coated on one surface of a high-quality paper of 60 g / m ² so that the coating amount after drying was 6 g / m ² to obtain a thermosensitive recording medium. Formation of protective layer 220 parts of solution A, 150 parts of a 10% aqueous solution of acetoacetyl group- modified polyvinyl alcohol, kaolin [trade name: UW
-90, manufactured by EMC] 15 parts, zinc stearate 30
% Of a protective layer coating liquid obtained by mixing and stirring a composition consisting of 6 parts of a 30% dispersion and 30 parts of water on a recording layer to give a coating amount of 6 g.
/ M ^2, and dried by calendering to obtain a thermosensitive recording medium.

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

Example 3 In the preparation of solution A, 3 parts of 1-phenyl-1-methyl-1-xylylmethane and 2- (2'-hydroxy-3'-dodecyl-5'-methyl were used instead of 3 parts of ethyl acetate. Instead of 12 parts of phenyl) benzotriazole, 2- (2'-hydroxy-3'-dodecyl-
6 parts of 5'-methylphenyl) benzotriazole and methyl-3- [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate-polyethylene glycol (molecular weight: about 300) A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 6 parts of the condensate 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. The mixture was stirred to obtain a coating liquid for an undercoat layer. 60g
/ M ² of high-quality paper on one side is 7 g /
m ^2, and the coating for the recording layer and the coating for the protective layer used in Example 1 were applied and dried so that the coating amount after drying was 6 g / m ² , respectively. Obtained.

Example 5 In the preparation of solution C, bis (4-hydroxyphenylthioethoxy) was used instead of 30 parts of 4-hydroxy-4'-isopropoxyphenylsulfone.
Using 30 parts of methane, the 1,2-di (3
Bis (4) instead of 20 parts of -methylphenoxy) ethane
-Hydroxyphenylthioethoxy) A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 20 parts of methane was used.

Example 6 In the preparation of solution D, 2-part 2- (3-methylphenoxy) ethane was used instead of 20 parts of 1,2-di (3-methylphenoxy) ethane.
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 20 parts of naphthylbenzyl ether was used.

[0043] Example 7 acetoacetyl group in the coating solution preparation protective layer modified poly <br/> 10% aqueous solution of carboxy-modified polyvinyl alcohol in place of 10% aqueous solution 150 parts of a vinyl alcohol 15
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 0 part was used and 15 parts of calcium carbonate was used instead of 15 parts of kaolin.

Example 8 In the preparation of the solution A, xylylene diisocyanate and trimethylolpropane (3:
1) A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 8 parts were used instead of 18 parts of the adduct (containing 25% by weight of ethyl acetate).

Example 9 In the preparation of solution A, 2- (2 '
-Hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole was reduced to 3 parts, and a thermosensitive recording material was prepared in the same manner as in Example 1 except that 12 parts of diisopropylnaphthalene was used instead of 3 parts of ethyl acetate. Obtained.

[Comparative Example 1] In the preparation of solution A, 2- (2 '
(Hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole In place of 12 parts of diisopropylnaphthalene, a thermosensitive recording material was obtained in the same manner as in Example 1.

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. Grinding was performed until the diameter became 3 μm. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 45 parts of the F solution was used instead of 220 parts of the A solution in forming the protective layer of Example 1.

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

The following evaluations were performed on the 12 types of heat-sensitive recording media thus obtained, and the results are shown in Table 1. [Evaluation] [Coloring property] Thermal evaluation machine [Product name: TH-PMD, manufactured by Okura Electric Co., Ltd.] 2
The color density of a recorded image obtained by color development at 4V-2ms was measured with a Macbeth densitometer [RD-914, manufactured by Macbeth] (visual mode). [Light Resistance] After exposing the obtained heat-sensitive recording medium to direct sunlight for 7 days, the background density was measured with a Macbeth densitometer (blue filter). [Plasticizer resistance] A wrap film (trade name: KMA-W, manufactured by Mitsui Toatsu Chemicals Co., Ltd.) was placed on a polycarbonate pipe (40 mmφ pipe).
And heat-sensitive evaluation machine [Product name: TH-PM
D, manufactured by Okura Electric Co., Ltd.] A recording paper obtained by coloring at 24 V-2 ms is placed, and the wrap film is further wound on the recording paper three times, and the coloring density is measured after standing at 20 ° C. for 24 hours. Then, the plasticizer resistance was evaluated. [High-temperature and high-humidity resistance] Thermal evaluation machine [Product name: TH-PMD, manufactured by Okura Electric Co., Ltd.] 2
The recording paper obtained by coloring at 4V-2ms was heated at 50 ° C, 7
The color density and the background density after standing in 5% RH for 24 hours were measured, and the high temperature and high humidity resistance was evaluated. [Solvent resistance] The surface of the recording paper was wiped with gauze impregnated with ethanol, and the concentration of fog was measured to evaluate the solvent resistance.

[0050]

[Table 1]

[0051]

As is evident from the results of Table 1, all the heat-sensitive recording media of the present invention efficiently absorb ultraviolet rays, have very little discoloration in the background, and have excellent heat-generating properties and preservability. It was a record.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-267087 (JP, A) JP-A-58-214152 (JP, A) JP-A-4-189179 (JP, A) Patent 2780554 (JP, A B2) Japanese Patent Publication No. 55-36984 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41M 5/26-5/34 B01J 13/02

Claims (2)

(57) [Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a colorless or light-colored basic dye and a colorant capable of forming a color in contact with the dye, and a protective layer, which are sequentially provided. At least in the protective layer, benzotria liquid at room temperature
A wall made of polyurethane / polyurea resin that contains a sol derivative type UV absorber and has substantially no color-forming ability
A heat-sensitive recording material comprising microcapsules having a film . 2. A benzotriazole derivative which is liquid at normal temperature.
The system-based ultraviolet absorber 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-benzotriazol-2-yl) -4-hydroxy Phenyl] propionate and polyethylene glycol (molecular weight about 300)
And at least one selected from condensates with
The thermosensitive recording medium as described.