JPH05318933A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material reduced in background fog, forming a recording image having excellent preservability against oils and fats, a solvent or a plasticizer, reduced in the yellowing of a background part due to light exposure and having excellent light fastness. CONSTITUTION:In a thermal recording material wherein a recording layer containing a colorless or light-colored basic dye and a developer and a protective layer are successively provided on a support, a composite zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid is at least used in the recording layer as a developer and a microcapsule (mean particle size; 0.1-3mum) including an ultraviolet absorber substantially having no color forming capacity is added to the protective layer.

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 having excellent storage stability of recorded images and light resistance of the background.

[0002]

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

For example, one of the fields of use thereof is a heat-sensitive recording label for a POS (point of sales) system of a retail store, etc. In addition to food labels, which have completed their missions, the number of uses for which they are attached to products for a long period of time is increasing. However, in such applications, they are often exposed to water, wraps, oil, etc., and are exposed to indoor light and sunlight for a long period of time, which causes the recorded image (printing) on the thermal recording label to fade. Or the background part turns yellow,
As a result, the product image will be significantly impaired. For this reason, it is strongly demanded that the heat-sensitive recording material has storage stability such as water resistance, plasticizer resistance, oil resistance, and light resistance.

However, since a phenol-based developer such as bisphenol A is used in an ordinary thermosensitive recording medium, for example, when human skin oil, a solvent, a plasticizer or the like comes into contact with the recording layer, the density of a recorded image is greatly increased. However, there is a drawback that the color develops undesirably or causes unnecessary color development called background fog.
For the purpose of improving such defects, various proposals have been made such as a method of providing a protective layer on the recording layer, a method of adding a preservative improving agent to the recording layer, or a method of using a new developer. However, the effect is not sufficient to satisfy the preservability of the recorded image.

Further, there has been proposed a method of adding finely pulverized ultraviolet absorber to the heat-sensitive recording layer or the protective layer for the purpose of preventing yellowing of the background portion of the heat-sensitive recording material due to light.
Finely pulverized UV absorbers may not provide sufficient effect due to poor UV absorption efficiency, but use of a large amount in the heat-sensitive recording layer may cause background fog or decrease recording density. And other new defects will occur. Further, when a finely pulverized ultraviolet absorber is added to the protective layer, the ultraviolet absorber is eluted by the influence of plasticizers and oils and fats to impair the function of the protective layer, and as a result the storage stability of the recorded image is deteriorated. Therefore, further improvement is strongly demanded.

[0006]

DISCLOSURE OF THE INVENTION The object of the present invention is to reduce the background fog, to have excellent preservability of recorded images against oils and fats, solvents, plasticizers, etc., and to prevent yellowing of the background area against light exposure. It is an object to provide a heat-sensitive recording material that is stable and has excellent light resistance.

[0007]

SUMMARY OF THE INVENTION The present invention comprises:
A thermosensitive recording medium provided with a recording layer containing a colorless or light basic dye and a color developer, wherein a complex zinc salt of terephthalaldehyde acid and another aromatic carboxylic acid is contained as a color developer, The heat-sensitive recording material is characterized in that a protective layer containing an ultraviolet absorber therein and containing microcapsules having substantially no color-forming ability is provided thereon.

[0008]

In the present invention, a complex zinc salt of terephthalaldehyde acid and another aromatic carboxylic acid is used as a color developer. However, in a heat sensitive recording material using only the zinc salt of terephthalaldehyde acid as a color developer, background fogging is caused. However, it does not always have sufficient recording sensitivity, and sufficient recording density was obtained only by a thermal printer capable of printing with high energy. However, it has been found that the color developer composed of a complex zinc salt of terephthalaldehyde acid and another aromatic carboxylic acid not only improves the recording sensitivity but also exhibits a better effect on the storability of the recorded image. Was issued.

Other aromatic carboxylic acids constituting the terephthalaldehyde acid and the complex zinc salt of the present invention include benzoic acid derivatives, naphthoic acid derivatives, phthalic acid derivatives, phthalamic acid derivatives, orthobenzoylbenzoic acid derivatives, salicylic acid derivatives and the like. The following compounds can be specifically exemplified. Of course, the present invention is not limited to these specific examples, and two or more kinds of aromatic carboxylic acids can be used in combination, if necessary.

Benzoic acid, o-toluic acid, p-toluic acid, m-toluic acid, o-chlorobenzoic acid, p-chlorobenzoic acid, o-bromobenzoic acid, p-bromobenzoic acid,
2,4-dichlorobenzoic acid, 3,4-dichlorobenzoic acid, 3,5-dichlorobenzoic acid, 2,6-dichlorobenzoic acid, o-nitrobenzoic acid, p-nitrobenzoic acid, 2,
4-dinitrobenzoic acid, 3,4-dinitrobenzoic acid,
3,5-dinitrobenzoic acid, 2,6-dinitrobenzoic acid, 2-chloro-4-nitrobenzoic acid, 2-chloro-5
-Nitrobenzoic acid, 4-chloro-2-nitrobenzoic acid,
4-chloro-3-nitrobenzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, gallic acid, p -Cyanobenzoic acid,
m-trifluoromethylbenzoic acid, 2,4-dimethylbenzoic acid, 3,4-dimethylbenzoic acid, 3,5-dimethylbenzoic acid, o-ethoxybenzoic acid, p-ethoxybenzoic acid, 3,5-dimethoxybenzoic acid Acid, pn-propoxybenzoic acid, 3,4,5-trimethoxybenzoic acid, p-phenoxybenzoic acid, o-phenylbenzoic acid, p-phenylbenzoic acid, o-cumylbenzoic acid, p-cumylbenzoic acid, 2,4-dicumylbenzoic acid, 4,6-dicumylbenzoic acid, p-acetylbenzoic acid, 2-cyclohexylbenzoic acid, 4- (2-phenoxyethoxy) benzoic acid, 2-
Benzoic acid derivatives such as ethoxymethyl-4- (p-chlorophenoxy) benzoic acid, 2-benzylbenzoic acid and 4- (p-methylbenzyloxy) benzoic acid.

Naphthoic acid derivatives such as 1-naphthoic acid, 2-naphthoic acid, 1-hydroxy-2-naphthoic acid, 2-hydroxy-1-naphthoic acid and 2-hydroxy-3-naphthoic acid. Phthalic acid, isophthalic acid, terephthalic acid,
3-nitrophthalic acid, 4-nitrophthalic acid, 4-chlorophthalic acid, 4-bromophthalic acid, 4,5-dichlorophthalic acid, 3,6-dichlorophthalic acid, tetrachlorophthalic acid, tetrabromophthalic acid, 3,6- Dibromo-4,5
Phthalic acid derivatives such as dichlorophthalic acid, and monomethyl ester, monoethyl ester, monopropyl ester, monobutyl ester, monostearyl ester, monobenzyl ester, mono- of these phthalic acid derivatives
p-chlorobenzyl ester, mono-p-methylphenyl ester, mono-2,4-dimethylphenyl ester, mono-p-chlorophenyl ester, mono-m-methoxyphenyl ester, mono-p-methoxyphenyl ester, mono-m -Ethoxyphenyl ester, mono-p-ethoxyphenyl ester, mono-1-naphthyl ester, mono-2-naphthyl ester, monocyclohexyl ester, mono-2-methylcyclohexyl ester, mono-3-methylcyclohexyl ester, mono-2 -Hydroxyethyl ester, mono-2-hydroxybutyl ester, mono-2-hydroxy-1-methylpropyl ester, mono-4-hydroxybutyl ester, mono-2,3-dihydroxypropyl ester, mono-2- (2- Hide Kishietokishi) ethyl ester,
Phthalic acid derivatives such as mono-p-methylbenzyl ester.

Phthalamic acid, 3-chlorophthalamic acid, 4-chlorophthalamic acid, 4-bromophthalamic acid, 4,5-dichlorophthalamic acid, 3,6-dichlorophthalamic acid, tetrachlorophthalamic acid , Tetrabromophthalamic acid, 3,6-dibromo-4,5
-Phthalamic acid derivatives such as dichlorophthalamic acid,
Furthermore, N-methyl and N of these phthalamic acid derivatives
-Ethyl, N-butyl, N-cyclohexyl, N-benzyl, Np-chlorobenzyl, Np-methylbenzyl, N-phenyl, N-1-naphthyl, N-2-naphthyl, N, N-diethyl , N-methyl-N-benzyl,
Phthalamic acid derivatives such as N, N-pentamethylene.

2-benzoylbenzoic acid, 2- (4'-methylbenzoyl) benzoic acid, 2- (2'-hydroxy-)
5-methylbenzoyl) benzoic acid, 2- (4'-hydroxybenzoyl) benzoic acid, 2- (2'-hydroxybenzoyl) benzoic acid, 2- (3'-methyl-4'-hydroxybenzoyl) benzoic acid, 2- (2'-hydroxy-
5'-tert-butylbenzoyl) benzoic acid, 2- (2 '
-Hydroxy-5'-tert-octylbenzoyl) benzoic acid, 2- (2'-hydroxy-5'-cyclohexylbenzoyl) benzoic acid, 2- (2 ', 4'-dihydroxybenzoyl) benzoic acid, 2- (2 ′ -Hydroxy-
5'-phenylbenzoyl) benzoic acid, 2- (4'-chlorobenzoyl) benzoic acid, 2- (4'-cyclohexylbenzoyl) benzoic acid, 2- (4'-phenylbenzoyl) benzoic acid, 2- (4 ' -Chlorobenzoyl) benzoic acid, 2- (2 ', 4'-dichlorobenzoyl) benzoic acid, 2- (2'-hydroxy-5'-chlorobenzoyl) benzoic acid, 2- (3'-methyl-4'- Orthobenzoylbenzoic acid derivatives such as hydroxybenzone) benzoic acid and 2- (4'-bromobenzoyl) benzoic acid.

5-tert-octylsalicylic acid, 3,5-
Di-tert-butylsalicylic acid, 3-chloro-5-cumylsalicylic acid, 3-methyl-5-tert-octylsalicylic acid, 3-methyl-5-α-methylbenzylsalicylic acid,
3-methyl-5-cumylsalicylic acid, 3,5-di-tert
-Amylsalicylic acid, 3-phenyl-5-benzylsalicylic acid, 3-phenyl-5-tert-octylsalicylic acid, 3-phenyl-5-α-methylbenzylsalicylic acid, 3,5-di-tert-octylsalicylic acid, 3,5 −
Di (α-methylbenzyl) salicylic acid, 3,5-dicumylsalicylic acid, 4-methyl-5- (α-methylbenzyl) salicylic acid, 4-methyl-5-cumylsalicylic acid,
3- (α-methylbenzyl) -6-methylsalicylic acid,
3- (α-methylbenzyl) -6-phenylsalicylic acid, 3-triphenylmethylsalicylic acid, 3-diphenylmethylsalicylic acid, 4-n-dodecylsalicylic acid, 4
-Tert-dodecylsalicylic acid, 4-n-pentadecylsalicylic acid, 4-n-peptadecylsalicylic acid, 5-
(1,3-Diphenylbutyl) salicylic acid, 5-n-octadecylsalicylic acid, 5-dodecylsulfonylsalicylic acid, 5-dodecylsulfosalicylic acid, 3-methyl-5
-Salicylic acid derivatives such as dodecylsulfosalicylic acid.

In the composite zinc salt of the present invention, the ratio of terephthalaldehyde acid to other aromatic carboxylic acid is not particularly limited, but preferably 0.5 to 2 equivalents per 1 equivalent of terephthalaldehyde acid, Most preferably it is desirable to use one equivalent of aromatic carboxylic acid. Here, for example, “using 1 equivalent of an aromatic carboxylic acid to 1 equivalent of terephthalaldehyde acid” means that an aromatic compound having one carboxyl group in the molecule per 1 mol of terephthalaldehyde acid. This means that 1 mol of carboxylic acid is used, while 0.5 mol is used in the case of an aromatic carboxylic acid having two carboxyl groups.

Such a complex zinc salt of terephthalaldehyde acid and another aromatic carboxylic acid is, for example, an alkali metal salt of terephthalaldehyde acid and another aromatic carboxylic acid in water or a mixed medium of water and an organic solvent. It can be produced by a method of reacting an alkali metal salt with a zinc compound, a method of wet co-milling terephthalaldehyde acid, another aromatic carboxylic acid, and a zinc compound.

In the present invention, when the complex zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid is the main component, a zinc salt containing only a small amount of terephthalaldehyde acid or aromatic carboxylic acid as a by-product is used. Even if it is contained, the desired effect is sufficiently exhibited. In the present invention, various known colorless or light-colored basic dyes can be used as the basic dye constituting the heat-sensitive recording layer, and specifically, for example, 3,3-bis (p-dimethylaminophenyl) -6. -Dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-
Diethylamino-7-dibenzylamino-benzo [a]
Fluorane, 3- (N-ethyl-N-p-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3
-Cyclohexylamino-6-chlorofluorane, 3-
Diethylamino-6-methyl-7-chlorofluorane,
3-diethylamino-7-chlorofluorane, 3- (N
-Ethyl-N-isoamyl) amino-6-methyl-7-
Anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n- Butyl) amino-6-methyl-
7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3-di (n-butyl) Amino-7- (o-chlorophenylamino) fluorane, 3-diethylamino-7-
(O-Fluorophenylamino) fluorane, 3-di (n-butyl) amino-7- (o-fluorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilino Fluoran, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) fluorane, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (N-methyl) -N-n-propylamino) -6-methyl-7-anilinofluorane, 3,3-
Bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5
6,7-Tetrachlorophthalide, 3,3-bis [1-
(4-Methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1,1-bis (4- Pyrrolidinophenyl) ethylene-2-yl] -4,5,
6,7-Tetrabromophthalide, 3-p- (p-anilinoanilino) anilino-6-methyl-7-chlorofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methyl Amino) -3'-methylspirophthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3,6, -bis (methylamino) fluorene-9-spiro-3 '-(6'- Dimethylamino) phthalide and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

In the heat-sensitive recording material of the present invention, the ratio of the basic dye to be contained in the recording layer, the complex zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid, to the basic dye or complex zinc to be used. It should be appropriately selected according to the type of aromatic carboxylic acid constituting the salt and is not particularly limited, but generally 0.5 to 50 parts by weight, preferably 1 to 10 parts by weight with respect to 1 part by weight of the basic dye. It is desirable to use parts by weight of the composite zinc salt.

The present invention is characterized in that a complex zinc salt of terephthalaldehyde acid and another aromatic carboxylic acid is used as a color developer. It is also possible to use a known color developer such as 4-tert-butylphenol,
α-naphthol, β-naphthol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec
-Butylidene diphenol, 4-phenylphenol,
4,4'-dihydroxy-diphenylmethane, 4,4 '
-Isopropylidene diphenol (bisphenol A), hydroquinone, 4,4'-cyclohexylidene bisphenol, 4,4 '-[1,4-phenylene bis (1-methylethylidene)] bisphenol, 4,4'
-[1,3-Phenylenebis (1-methylethylidene)] bisphenol, 4,4 '-(1,3-dimethylbutylidene) bisphenol, 2,2-bis (4-hydroxyphenyl) -4-methyl-pentane , 4, 4'-
Dihydroxydiphenyl sulfide, 4,4'-thiobis (6-tert-butyl-3-methylphenol),
4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-
Hydroxy-3 ', 4'-trimethylene diphenyl sulfone, 4-hydroxy-3', 4'-tetramethylene diphenyl sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, bis (3-allyl-4-hydroxy) Phenyl) sulfone, 1,3-di [2- (4-hydroxyphenyl) -2-propyl] benzene, hydroquinone monobenzyl ether, bis (4-hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzophenone, 2,4- Dihydroxybenzophenone, 2,4
4'-trihydroxybenzophenone, 2,2 ', 4
4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate,
Ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, -sec-butyl 4-hydroxybenzoate,
Pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, 4-
Tolyl hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, -p-chlorobenzyl 4-hydroxybenzoate, -p-methoxybenzyl 4-hydroxybenzoate, bis (4-Hydroxyphenyl) acetic acid-2-phenoxyethyl ester, p-hydroxy-N- (2-phenoxyethyl) benzenesulfonamide, dimethyl 4-hydroxyphthalate, 1,5
-Bis (4-hydroxyphenylthio) -3-oxa-
Pentane, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxa-heptane, 1,8-bis (4
-Hydroxyphenylthio) -3,6-dioxa-octane, (4-hydroxyphenylthio) acetic acid-2- (4
-Hydroxyphenylthio) ethyl ester, novolac type phenolic resin, phenolic compound such as phenolic polymer and the like.

In the heat-sensitive recording material of the present invention, a sensitizer can be added to the recording layer according to the purpose. Specific examples of the sensitizer include stearic acid amide and methoxycarbonyl-N-stearic acid. Benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p-chlorobenzyl, 2-naphthylbenzyl ether, m- Terphenyl, p-benzylbiphenyl, tri Biphenyl ether, di (p- methoxyphenoxy) 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-diphenoxy Ethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane,
p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-
Examples include acetophenetide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within a range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

Further, a preservative improving agent may be used in combination so as to further enhance the preservability of the recorded image depending on the purpose as long as the effect is not impaired. Specific examples of such a storage stability 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'-ethylidene bis (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), 1,1,3-tris (2-methyl-4-hydroxy-) 5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4′-thiobis (3-methylphenol), 4,4′- Dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3', 5,5'-
Tetramethyldiphenyl sulfone, 2,2-bis (4-
Hydroxy-3,5-dibromophenyl) propane,
2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,
Hindered phenol compounds such as 5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene,
Epoxy compounds such as 4,4'-diglycidyloxydiphenyl sulfone, diglycidyl terephthalate, and bisphenol A type epoxy resin, 1- [α-methyl-α-
(4'-Hydroxyphenyl) ethyl] -4- [α ',
α'-bis (4 "-hydroxyphenyl) ethyl] benzene, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-
Butylphenyl) sodium phosphate and the like.

In order to prepare a coating liquid for a recording layer containing these substances, water is generally used as a dispersion medium, and a basic dye, terephthalaldehyde acid and other aromas are mixed with a stirring / grinding machine such as a ball mill, attritor or sand mill. A composite zinc salt of a group carboxylic acid, and further, a sensitizer and the like added as necessary are dispersed together or separately to prepare a coating liquid.
In the coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, arabic gum as an adhesive,
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, etc. are 10 to 40% by weight of the total solid content, preferably 15
Used in an amount of about 30% by weight.

Further, various auxiliary agents can be added to the coating liquid, for example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate / sodium salt, alginate, fatty acid metal salt and the like. Dispersant, benzophenone-based,
Examples thereof include UV absorbers such as triazole type, other defoaming agents, fluorescent dyes, coloring dyes and the like. If necessary, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax,
Lubricants such as ester wax, and inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica and activated clay can also be added.

The present invention has a significant feature in that a protective layer containing microcapsules containing an ultraviolet absorber and having substantially no color forming ability is provided on the heat-sensitive recording layer thus formed. is there. Various thermal recording media and pressure-sensitive recording media using microcapsules containing a basic dye and an ultraviolet absorber have been proposed, but these microcapsules also contain a basic dye. Not only does the coloring phenomenon occur with an increase in the irradiation amount of light, but also the effect of sufficiently improving the light resistance cannot be exhibited for a long period of time.

In the present invention, the following are specific examples of the ultraviolet absorbent contained in the microcapsules. Salicylic acid-based UV absorbers such as phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-
Benzophenone-based UV absorbers such as dimethoxybenzophenone and 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 "-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, polyethylene glycol (molecular weight about 300) and methyl-3- [3-
tert-butyl-5- (2H-benzotriazole-2-
Benzotriazole-based UV absorbers such as condensates with yl) -4-hydroxyphenyl] propionate, 2'-
Cyanoacrylate-based UV 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) 6
-Pentamethyl-4-piperidyl) ester and other hindered amine UV absorbers and the like.

Of course, the present invention is not limited to these, and two or more kinds may be used in combination if necessary. In the heat-sensitive recording material of the present invention, since the ultraviolet absorbent is used by being encapsulated in microcapsules, it is a low-melting ultraviolet absorbent which has been difficult to use in terms of background fog and storability, and at room temperature. Liquid UV absorbers can also be used,
The range of choice is greatly expanded.

Among these ultraviolet absorbers, benzotriazole type ultraviolet absorbers are preferable, and especially 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, polyethylene glycol (molecular weight about 300) and methyl-3- [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-
A condensate with hydroxyphenyl] propionate exhibits a particularly remarkable effect of improving light resistance and is therefore more preferably used.

The amount of the ultraviolet absorber used is not particularly limited, but the basic dye 100 in the heat-sensitive recording layer is used.
It is desirable to adjust the amount to be in the range of preferably 10 to 500 parts by weight, more preferably 20 to 300 parts by weight with respect to parts by weight. The microcapsules used in the present invention can be prepared by various known methods. Generally, a core substance obtained by dissolving a solid or liquid UV absorber at room temperature as described above in an organic solvent as necessary is aqueous. It is prepared by a method of emulsifying and dispersing in a medium and forming a wall film made of a polymer material around oily droplets. Specific examples of the polymeric substance that becomes the wall film of the microcapsule include, for example, polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-acrylate copolymer resin, Examples thereof include styrene-methacrylate copolymer resin, gelatin, polyvinyl alcohol and the like. Among these, in particular, the microcapsules having a wall film made of polyurethane / polyurea resin or aminoaldehyde resin are excellent in heat resistance, and therefore inorganic pigments added to the protective layer for the purpose of preventing sticking to the thermal head. It also has an excellent collateral effect of also fulfilling the function of, and has a lower refractive index than other microcapsules consisting of wall films and ordinary pigments, and its shape is spherical, so a large amount is contained in the protective layer. Even if blended in, there is no risk of causing a reduction in the density of a recorded image (so-called whitening phenomenon) due to diffused reflection of light, and therefore it is preferably used.

The microcapsules having a wall film composed of polyurethane / polyurea resin are a core substance for encapsulating a capsule wall film material such as a polyvalent isocyanate and a polyol which reacts therewith, or an adduct of a polyvalent isocyanate and a polyol. It is manufactured by emulsifying and dispersing it in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved, and raising the liquid temperature to cause a polymer forming reaction at the oil droplet interface.

The microcapsules having a wall film made of an aminoaldehyde resin are manufactured by a formulation in which a wall film material is added after emulsification of the core substance, so that the thickness of the wall film can be controlled regardless of the particle size of the emulsion. The merit that can be done is also demonstrated.
Capsules having an aminoaldehyde resin wall film generally include at least one amine such as urea, thiourea, alkylurea, ethyleneurea, acetoguanamine, benzoguanamine, melamine, guanidine, biuret, and cyanamide, and formaldehyde, acetaldehyde, and paraformaldehyde. , Hexamethylenetetramine, glutaraldehyde, glyoxal, furfural, and the like, or an in-situ polymerization method using an initial condensate obtained by condensing them.

As an emulsifier (protective colloidal agent) used for microencapsulation, various anions, nonions, cations or amphoteric water-soluble polymer compounds are used. The amount of the emulsifier used is not particularly limited, but in general, when the polyurethane / polyurea resin is used as the wall film material, the total amount of the wall film material, the ultraviolet absorber and the organic solvent is three. It may be adjusted in the range of 1 to 50% by weight, preferably 3 to 30% by weight. When the aminoaldehyde resin is used as the wall film material, the amount of the emulsifier used is adjusted to 1 to 20 parts by weight, preferably 3 to 10 parts by weight, based on 100 parts by weight of the hydrophobic core substance. It

The organic solvent is not particularly limited and may be appropriately selected and used from various high-boiling point hydrophobic media used in the field of pressure-sensitive copying paper, and specifically, for example, phosphoric acid. Phosphates such as tricresyl, octyldiphenyl 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 isopropyl biphenyl, xenoxyalkanes such as o-phenylphenol glycidyl ether, Examples thereof include acrylic acid esters such as trimethylolpropane triacrylate, esters of polyhydric alcohols and unsaturated carboxylic acids, chlorinated paraffins, and kerosene. Of course, these may be used in combination of two or more. Among the above high boiling point hydrophobic media, it is preferable because it exhibits excellent solubility in relation to the alkylated naphthalene and alkylated benzene, and the ultraviolet absorber used in the present invention. In addition, 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. Therefore, if necessary, the viscosity of the mixture is decreased. A low boiling point solvent may be used together for the purpose. Specific examples of such a low boiling point solvent include:
Examples thereof include ethyl acetate, butyl acetate, methylene chloride and the like.

The amount of the organic solvent used is not particularly limited and should be appropriately adjusted according to the type and amount of the ultraviolet absorber used, the type of the organic solvent and the like. However, since it is preferable that the ultraviolet absorbent is sufficiently dissolved in the microcapsules, in the case of polyurethane / polyurea resin, the total amount of the organic solvent, the ultraviolet absorbent, and the microcapsule wall film material is Therefore, it is desirable to adjust the ratio of the organic solvent to be in the range of generally 10 to 60% by weight, preferably 20 to 60% by weight. In the case of amino aldehyde resin,
It is desirable to adjust the content of the ultraviolet absorber in the range of 50 to 2000% by weight, preferably 100 to 1000% by weight. When the ultraviolet absorber that is liquid at room temperature is used, the organic solvent is not always essential, and may be appropriately adjusted within the above range if necessary. Further, the amount of the capsule wall film material is not particularly limited, but the organic solvent in the microcapsules may seep out due to long-term storage and reduce the storage stability of the thermosensitive recording medium. It is preferable to use a large amount of wall film material compared to the above. In the case of polyurethane / polyurea resin, the ratio of the wall film material to the total of the organic solvent, the ultraviolet absorber and the microcapsule wall film material Is 3
It is desirable to select it in the range of 5 to 70% by weight, preferably 35 to 60% by weight. In the case of aminoaldehyde resin, the total amount of the ultraviolet absorber and the organic solvent used as necessary is , The wall film material is 30 to 300% by weight,
It is desirable to select it so that it is preferably in the range of 35 to 200% by weight.

Further, the amount of the ultraviolet absorber used in the microencapsulation should be appropriately selected according to the kind of the ultraviolet absorber and the organic solvent used, and is not particularly limited, but a remarkable effect is obtained. Therefore, in the case of polyurethane / polyurea resin, the amount of the ultraviolet absorber is about 3 to 50% by weight, preferably about 3 to 20% by weight, based on the total of the three of the organic solvent, the ultraviolet absorber and the microcapsule wall membrane material. It is desirable to mix so that
In the case of an aminoaldehyde resin, it is 3 to 75% by weight, preferably 3 to 75% by weight based on the total of the three components of the ultraviolet absorber, the microcapsule wall film material and the organic solvent used as necessary.
It is desirable to mix the ultraviolet absorber in an amount of about 50% by weight.

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. Further, at the time of microencapsulation, a tin compound, a polyamide compound, an epoxy compound, a polyamine compound or the like can be used together as a reaction accelerator. When a polyamine compound is used, it is desirable to use an aliphatic polyamine compound in terms 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 it so that it is within the range. Also,
The content of the microcapsules in the protective layer should be appropriately selected depending on the type of the ultraviolet absorber, the concentration in the capsules, and the desired quality, etc., but generally with respect to the total solid content of the protective layer. 5 to 80% by weight, preferably 20 to 70% by weight.

As described above, the thermosensitive recording medium of the present invention has a protective layer containing microcapsules containing an ultraviolet absorber. The protective layer is water-soluble or water-dispersible with the microcapsules. It is composed mainly of a binder made of a polymer compound. Specific examples of the binder include 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, Examples thereof include amide resins and polyurethane resins. Among them, acetoacetyl group-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol can form a strong film. Preferably used for.

A pigment may be added to the protective layer as needed in order to further improve printability and sticking. Specific examples thereof include calcium carbonate,
Inorganic pigments such as zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea. Examples thereof include formalin resin fillers and organic pigments such as raw starch particles. It is generally desirable to adjust the amount used in the range of about 5 to 300 parts by weight with respect to 100 parts by weight of the binder component.

The method for preparing the coating liquid for forming the protective layer is not particularly limited, and generally, water is used as the dispersion medium, and the specific microcapsules (dispersion liquid), the binder, the pigment added as necessary, and the like are used. It is prepared by mixing.
Further, in the coating liquid for the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, a surfactant such as sodium dioctylsulfosuccinate (dispersant, wetting agent). Agents), antifoaming agents, and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate can be appropriately added. Further, in order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, and an epoxy compound can be used in combination.

In the present invention, the method for forming the heat-sensitive recording layer and the protective layer is not particularly limited, and examples thereof include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating and die coating. The coating liquid for recording layer is applied and dried on the support by a suitable coating method such as the above, and then the coating liquid for protective layer is applied and dried on the recording layer. The support is appropriately selected from paper, plastic film, synthetic paper, non-woven fabric, metal vapor deposition and the like. The coating amount of the recording layer coating liquid for dry weight 2~12g / m ^2, 0.1~20g preferably 3 to 10 g / m ² approximately, the coating amount of the protective layer coating composition in a dry weight
/ M ² , preferably in the range of about 0.5 to 10 g / m ² .

If necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storage stability. Furthermore, an undercoat layer may be provided on the support, or smoothing treatment such as super calendering may be performed after coating each layer,
Alternatively, various well-known techniques in the field of heat-sensitive recording material production may be added as necessary, such as processing the back surface of the recording material with an adhesive to form an adhesive label.

[0042]

[Example 1]

Preparation of solution A 3- (N-cyclohexyl-N-methylamino) -6-
A composition consisting of 35 parts of methyl-7-phenylaminofluorane, 5 parts of a 5% aqueous solution of methyl cellulose, and 60 parts of water was pulverized by a sand mill until the average particle diameter became 2 μm to obtain a liquid A.

Preparation of Solution B 15 parts of terephthalaldehyde acid, 8.3 parts of isophthalic acid and 4 parts of sodium hydroxide were added to 200 parts of water,
It heated at 70 degreeC and stirred and melt | dissolved. Then in this solution,
A solution of 28.8 parts of zinc sulfate heptahydrate dissolved in 500 parts of water was added dropwise over 20 minutes. After completion of dropping, the mixture was stirred for 1 hour and then cooled to 50 ° C., 300 parts of ethyl acetate was added to dissolve the precipitate, and then the ethyl acetate phase was separated. Ethyl acetate was distilled off from the separated ethyl acetate solution under reduced pressure to obtain a mixed zinc salt whose main component was a complex zinc salt of terephthalaldehyde acid and isophthalic acid. It was

35 parts of a mixed zinc salt containing the above-mentioned composite zinc salt of terephthalaldehyde acid and isophthalic acid as a main component, 45 parts of a 10% aqueous solution of a dispersant (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), A composition comprising 20 parts of water and water was pulverized by a sand mill until the average particle size became 2 μm to obtain a liquid B. Preparation of liquid C 60 parts of an 8% aqueous solution of polyvinyl alcohol (trade name: PVA-217, manufactured by Kuraray Co., Ltd.) was added to a stirring and mixing container equipped with a heating device to prepare an aqueous medium for producing microcapsules. Separately, to 12 parts of diisopropyl naphthalene, 2-
(2'-Hydroxy-5'-methylphenyl) benzotriazole 2 parts, (3: 1) adduct of xylylene diisocyanate and trimethylolpropane [trade name: Takenate D-110N, Takeda Yakuhin Kogyo, 25% A solution obtained by dissolving 18 parts of [containing ethyl acetate] was added to the TK homomixer [model HV-
M, manufactured by Tokushu Kika Kogyo Co., Ltd.], and the average particle size is 2 μm.
It was emulsified and dispersed while cooling so that Next, 50 parts of water is added to this emulsified dispersion, and the mixture is stirred at 60 ° C. for 3 times.
Polyurethane containing UV absorber after reaction for a long time
A microcapsule dispersion having a wall film made of polyurea resin was prepared.

Formation of heat-sensitive recording layer 100 parts of solution A, 100 parts of solution B, 100 parts of 10% aqueous solution of polyvinyl alcohol (trade name: PVA110, manufactured by Kuraray Co., Ltd.), 10 parts of fine particle silica, 30% water of zinc stearate. parts dispersion 33, and the recording layer coating solution obtained by mixing and stirring 57 parts of water, the coating amount after drying on one surface of woodfree paper having 50 g / m ² is applied and dried such that the 5 g / m ² To form a recording layer.

Formation of protective layer 220 parts of C liquid, 150 parts of 10% aqueous solution of acetoacetyl group-modified polyvinyl alcohol [trade name: Gocefimer Z-200, manufactured by Nippon Gosei Kagaku], kaolin [trade name: UW-90] , Manufactured by EMC Inc.] 15 parts, 6 parts of a 30% zinc stearate aqueous dispersion, and 30 parts of a composition are mixed and stirred to obtain a coating solution for a protective layer, which is applied onto a recording layer after drying. After coating and drying so that the amount becomes 5 g / m ² ,
Super calendering was performed to obtain a heat sensitive recording material. [Example 2] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 13.6 parts of p-toluic acid was used in place of 8.3 parts of isophthalic acid in the production of the composite zinc salt prepared in solution B. .. [Example 3] The same as Example 1 except that 26.1 parts of 2- (4'-chlorobenzoyl) benzoic acid was used in place of 8.3 parts of isophthalic acid in the production of the composite zinc salt prepared in solution B. A thermal recording material was obtained in the same manner. [Example 4] Preparation of liquid D 15 parts terephthalaldehyde acid, 8.3 isophthalic acid
Parts, 8.1 parts of zinc oxide, dispersant (trade name: Gocelan L
3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10% aqueous solution 45
Parts of water and 25 parts of water with a sand mill have an average particle size of 2
The mixture was pulverized to a size of μm to obtain a liquid D containing a complex zinc salt of terephthalaldehyde acid and isophthalic acid as a main component.

In the formation of the thermosensitive recording layer of Example 1, B
Except that 100 parts of D liquid was used instead of 100 parts of liquid,
A thermal recording material was obtained in the same manner as in Example 1. Example 5 A thermosensitive recording medium was obtained in the same manner as in Example 4 except that 13.6 parts of p-toluic acid was used in place of 8.3 parts of isophthalic acid in the preparation of solution D. [Example 6] In the preparation of solution D, 2- (4'-chlorobenzoyl) benzoic acid 2 was used instead of 8.3 parts of isophthalic acid.
A thermosensitive recording medium was obtained in the same manner as in Example 4 except that 6.1 parts were used. Example 7 In the preparation of solution C, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole was replaced by 2- (2'-hydroxy-3 ', 5'-di- instead of 2 parts.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 2 parts of tert-butylphenyl) -5-chlorobenzotriazole was used. [Example 8] 2- (2'-hydroxy-3 ', 5'-di-, instead of 2 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole in the preparation of solution C
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 2 parts of tert-amylphenyl) benzotriazole was used. [Example 9] In the preparation of solution C, 3 parts of ethyl acetate and 2- (2'-) were used instead of 12 parts of diisopropylnaphthalene.
2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole 1 instead of 2 parts of hydroxy-5'-methylphenyl) benzotriazole
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 2 parts were used. [Example 10] In the preparation of solution C, 2- [2'-hydroxy-4 '-(2 was used instead of 12 parts of 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole. A thermosensitive recording medium was obtained in the same manner as in Example 9 except that 12 parts of -ethylhexyl) oxyphenyl] benzotriazole was used. [Example 11] In the preparation of solution C, 1-phenyl-1-methyl-1 was used instead of 12 parts of diisopropylnaphthalene.
-Xylylmethane 3 parts, 2- (2'-hydroxy-3 '
Instead of 12 parts of -dodecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-
6 parts of dodecyl-5'-methylphenyl) benzotriazole and polyethylene glycol (molecular weight about 300) and methyl-3- [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl]
Example 9 except 6 parts of the condensate with propionate were used.
A thermosensitive recording medium was obtained in the same manner as described above. [Example 12] Preparation of solution E In a stirring and mixing vessel equipped with a heating device, 150 parts of a 5% aqueous solution of polyacrylic acid was added to adjust the pH of the system to 4.5 to obtain an aqueous medium for capsule production. Separately, 2- (2'-hydroxy-5'- is added to 100 parts of diisopropylnaphthalene.
A solution obtained by dissolving 16 parts of methylphenyl) benzotriazole was used as a capsule core substance, and this was added to the TK homomixer [Model HV-M,
It was emulsified and dispersed for 15 minutes at 10,000 rpm while cooling using a special machine made by Tokushu Kika Kogyo. 30% of a commercially available melamine-formaldehyde precondensate as a wall film material in this emulsion dispersion
After adding 190 parts of an aqueous solution and reacting the mixture at 90 ° C. for 3 hours while continuing stirring, the temperature was lowered to room temperature and an ultraviolet absorber was included to obtain an E liquid consisting of a melamine-formaldehyde resin wall film having an average particle diameter of 2 μm. It was

55 parts of E liquid, acetoacetyl group-modified polyvinyl alcohol [trade name: Gocefimer Z-20
0, manufactured by Nihon Gosei Co., Ltd.], 10 parts aqueous solution 150 parts, kaolin (trade name: UW-90 EMC Co., Ltd.) 15 parts, 30% zinc stearate dispersion 6 parts and water 30 parts protected by mixing and stirring. The layer coating liquid was applied and dried on the thermosensitive recording layer formed in the same manner as in Example 1 so that the coating amount after drying was 5 g / m ^2, and then supercalendering was performed to obtain a thermosensitive recording material. [Example 13] In the preparation of solution E, after the reaction was carried out at 90 ° C for 3 hours, the pH of the system was lowered to 3.5, and the mixture was stirred and kept at 80 ° C for 3 hours and then cooled to have an average particle diameter of 2.5 µm. A dispersion of microcapsules having a melamine-formaldehyde resin wall film was obtained. A thermosensitive recording medium was prepared in the same manner as in Example 12 except that 55 parts of the capsule dispersion liquid obtained above was used in the preparation of the thermosensitive recording medium of Example 12. [Example 14] In preparation of solution E, 1-methyl-1-phenyl- was used instead of 100 parts of diisopropylnaphthalene.
58 parts of 1-xylylmethane was used, and further 2- (2 '
-Hydroxy-5'-methylphenyl) benzotriazole 16 parts instead of 2- (2'-hydroxy-3'-
A thermosensitive recording medium was obtained in the same manner as in Example 12 except that 58 parts of dodecyl-5'-methylphenyl) benzotriazole was used. [Example 15] Preparation of liquid F 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 are mixed. By stirring, a coating liquid F for the undercoat layer was obtained.

Preparation of thermosensitive recording medium Liquid F was applied to one side of a high-quality paper of 50 g / m ² so that the coating amount after drying was 7 g / m ^2, and the recording was prepared in the same manner as in Example 1. The layer coating material and the protective layer coating liquid were each applied and dried so that the applied amount after drying was 5 g / m ^2, and then supercalendering was performed to obtain a heat-sensitive recording material. [Example 16] In the formation of the protective layer of Example 1, 150 parts of a 10% aqueous solution of carboxy-modified polyvinyl alcohol was used in place of 150 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol, and 15 parts of kaolin was used instead of 15 parts of kaolin. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 15 parts of calcium carbonate was used. [Comparative Example 1] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that isophthalic acid was not used and the amount of zinc sulfate heptahydrate used was 14.4 parts in the preparation of solution B. .. [Comparative Example 2] A thermosensitive recording medium was obtained in the same manner as in Example 4 except that isophthalic acid was not used and the amount of zinc oxide used was 4.1 parts in the preparation of liquid D. [Comparative Example 3] Preparation of liquid G: Zinc terephthalaldehyde acid salt 3 obtained by reacting sodium terephthalaldehyde acid with an equivalent amount of zinc sulfate
5 parts, 25 parts of a 10% aqueous solution of a dispersant (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and 40 parts of water were pulverized with a sand mill until the average particle size became 2 μm, and G liquid. Got

Preparation of solution H 35 parts of zinc salt of isophthalic acid obtained by reaction of sodium salt of isophthalic acid with an equivalent amount of zinc sulfate, 1 part of a dispersant (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.)
A composition consisting of 25 parts of a 0% aqueous solution and 40 parts of water was pulverized by a sand mill until the average particle size became 2 μm, to obtain H liquid.

Formation of thermosensitive recording medium 10 parts of liquid A 100 parts, liquid G 67 parts, liquid H 33 parts, polyvinyl alcohol (trade name: PVA110, manufactured by Kuraray Co., Ltd.)
% Aqueous solution, 10 parts of finely divided silica, 33 parts of a 30% aqueous dispersion of zinc stearate, and 57 parts of water were mixed and stirred to obtain a recording layer coating liquid, and 50 g / m ² of one side of high-quality paper A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the recording layer was formed by coating and drying so that the coating amount after drying was 5 g / m ² . [Comparative Example 4] Preparation of liquid I From 30 parts of terephthalaldehyde acid, 8.1 parts of zinc oxide, 25 parts of a 10% aqueous solution of a dispersant (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and 40 parts of water. The resulting composition was pulverized with a sand mill until the average particle size became 2 μm, to obtain a dispersion I liquid of zinc terephthalaldehyde acid salt.

Preparation of Solution J A composition consisting of 25 parts of isophthalic acid, 12.3 parts of zinc oxide, 25 parts of a 10% aqueous solution of a dispersant (trade name: Gocelan L-3266, manufactured by Nippon Gosei Kagaku Co., Ltd.), and 40 parts of water. Was pulverized with a sand mill until the average particle diameter became 2 μm, to obtain a dispersion liquid J of isophthalic acid zinc salt.

Formation of thermosensitive recording medium 100 parts of A solution, 66 parts of I solution, 33 parts of J solution, 10 parts of polyvinyl alcohol (trade name: PVA110, manufactured by Kuraray Co., Ltd.)
% Aqueous solution, 10 parts of finely divided silica, 33 parts of a 30% aqueous dispersion of zinc stearate, and 57 parts of water were mixed and stirred to obtain a recording layer coating liquid, and 50 g / m ² of one side of high-quality paper A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the recording layer was formed by coating and drying so that the coating amount after drying was 5 g / m ² . [Comparative Example 5] Preparation of K liquid A composition consisting of 30 parts of bisphenol A, 5 parts of a 5% aqueous solution of methyl cellulose, and 65 parts of water was pulverized with a sand mill until the average particle size became 2 µm to obtain a K liquid.

Formation of Thermosensitive Recording Medium Example 1 was repeated except that 100 parts of the above-mentioned liquid K was used in place of 100 parts of the liquid B in the formation of the thermal recording layer of the first embodiment.
A thermosensitive recording medium was obtained in the same manner as above. [Comparative Example 6] 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 the liquid C. [Comparative Example 7] Preparation of L liquid 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 used in a sand mill to give an average particle diameter of It was pulverized to a size of 1.5 μm to obtain L liquid.

Formation of Thermal Recording Material A thermal recording material was obtained in the same manner as in Example 1 except that in the formation of the protective layer in Example 1, 40 parts of the L liquid was used in place of 220 parts of the C liquid. [Comparative Example 8] In the preparation of solution L, 2- (2'-hydroxy-3 ', 5'-di-tert- was used instead of 10 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole. A thermosensitive recording medium was obtained in the same manner as in Comparative Example 7 except that 10 parts of butylphenyl) -5-chlorobenzotriazole was used.

The 24 types of thermal recording materials thus obtained were subjected to the following quality evaluation tests, and the results are shown in [Table 1]. [Color density] The color density of the recorded image obtained by printing with a thermal printer (Okura Simulator, applied energy 0.4 mJ / dot) was measured by a Macbeth densitometer (Macbeth RD-
100R type). [Plastic resistance] A vinylidene chloride wrap film (manufactured by Mitsui Toatsu Kagaku Co., Ltd.) was wound around a polypropylene pipe (40 mmφ) in three layers, and sandwiched so that the color-developed surface of the heat-sensitive recording body on which print color was formed was the outer side. , And then wrap the vinylidene chloride wrap film in three layers, and
After leaving for one day, the color density of the recorded image was measured again with a Macbeth densitometer to evaluate the plasticizer resistance. [Light resistance] The thermal recording material after recording in 2 above is exposed to direct sunlight 2
After exposure for a day, the density of the background part was measured with a Macbeth densitometer (using a blue filter). [Oil resistance] The edible oil was dropped on the heat-sensitive recording material on which the color was printed, and the state of printing after standing for 24 hours was visually evaluated. [Solvent resistance] A yellow oil-based magic ink was used for writing on a heat-sensitive recording material on which printing was performed, and the state of subsequent printing was visually evaluated. [Evaluation Criteria] The evaluation criteria for oil resistance and solvent resistance were as follows.

◎ −−−−− ○ −−−− Δ −−−− × Excellent Excellent Inferior

[0058]

[Table 1]

[0059]

As is apparent from the results of [Table 1], the heat-sensitive recording materials of the present invention are excellent in storage stability of recorded images.
Moreover, it was a recording material with little yellowing of the background portion to light exposure.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 6956-2H B41M 5/18 112

Claims (3)

[Claims] 1. A thermosensitive recording medium comprising a support, on which a recording layer containing a colorless or light-colored basic dye and a developing agent and a protective layer are sequentially provided, and at least terephthalate is used as the developing agent in the recording layer. A heat-sensitive recording material comprising a composite zinc salt of an aldehyde acid and another aromatic carboxylic acid, and a protective layer containing microcapsules containing an ultraviolet absorber having substantially no color-forming ability. 2. The average particle size of the microcapsules is 0.1 to 10.
The thermal recording medium according to claim 1, which has a thickness of 3 μm. 3. The thermosensitive recording medium according to claim 1, wherein the microcapsules are microcapsules having a wall film made of polyurethane polyurea resin or aminoaldehyde resin.