JPH07314894A - Heat-sensitive recording material and heat-sensitive recording material for label - Google Patents

Abstract

PURPOSE:To improve the lightfastness of a texture section and an image section by forming a heat-sensitive recording layer composed of a blend of a leuco dye, a developer and a dimer ultraviolet ray absorbent to form a heat-sensitive recording material on one face of a substrate. CONSTITUTION:When a heat-sensitive recording material containing a leuco dye and a developer on one face of a substrate, a dimer ultraviolet absorbent represented by a general formula (R7 represents 1-18C alkyl and R8 represents hydrogen atom, halogen atom, alkyl, alkoxyl, aryloxy or aryl) is contained at least in one of a heat-sensitive recording layer and a protective layer formed on the heat-sensitive recording layer. The melting point of the above-said dimer ultraviolet absorbent is higher compared to that of a prior art monomer ultraviolet absorbent, and the absorbent forms no obstruction to the heat-resistant characteristics of the heat-sensitive material, and further improves the yellowing of a texture section and decoloration of an image section by the exposure to sun or the like, as the good ultraviolet absorption characteristics are provided by its molecular structure.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermal recording material,
In particular, the present invention relates to a heat-sensitive recording material having excellent light resistance in the background and image areas, and further relates to a heat-sensitive recording material having excellent heat resistance in the background and storage characteristics in the image area.

[0002]

2. Description of the Related Art A heat-sensitive recording material generally comprises a support and a heat-sensitive recording layer containing an electron-donating, usually colorless or pale-colored leuco dye and an electron-accepting developer as main components. By heating with a thermal head, a heating pen, a laser beam or the like, the leuco dye and the developer react instantaneously to obtain a recorded image. Such a heat-sensitive recording material has the advantages that recording can be obtained with a relatively simple device, that maintenance is easy, and that noise is not generated, and measurement recorders, facsimiles, printers, computer terminals, It is used in a wide range of fields such as labels and ticket vending machines. Conventional thermal recording materials using leuco dyes and color developers have characteristics such as high color density, but on the other hand,
There was a phenomenon that the white part and the recorded image part turned yellow due to exposure to sunlight and room light, and the recorded image part faded.
With the expansion of applications of the heat-sensitive recording material, a heat-sensitive recording material having excellent resistance to such light has been demanded. or,
Conventional thermal recording materials are erased by contact with plastics such as polyvinyl chloride and permeation of plasticizers and additives contained in the plastics, and contact with chemicals contained in foods and cosmetics. It has been pointed out that, for example, the storage characteristics of the recorded image are inferior, or that the handwriting discolors when writing on the background with a writing instrument, and the improvement of these drawbacks is Is desired.

Resistance to light in white area and image area (hereinafter,
It is known that a UV absorber such as a benzotriazole derivative or a benzophenone derivative is added to the heat-sensitive recording layer or a protective layer provided on the heat-sensitive recording layer as a means for improving the light resistance. Kaisho 50-1046
50, JP 61-242878 A, JP 62-160280 A). Specifically, 2- (5-
Methyl-2-hydroxyphenyl) benzotriazole, 2- (3,5-ditertiarybutyl-2-hydroxyphenyl) benzotriazole, 2- (2′-hydroxy-5′-tercaryoctylphenyl) benzotriazole, 2- Hydroxy-4-methoxybenzophenone and the like are mentioned. However, with these derivatives, sufficient light resistance may not be obtained, the color development characteristics of the thermal paper may be deteriorated, and the storage characteristics, particularly the fogging of the background in heat resistance tests, may be adversely affected, The reality was that the characteristics were not obtained.

[0004]

The present invention relates to a heat-sensitive recording material, and in particular to obtain a heat-sensitive recording material excellent in light resistance of the background portion and the image portion, and further, heat resistance of the background portion and preservation of the image portion. To obtain a heat-sensitive recording material having excellent characteristics.

[0005]

DISCLOSURE OF THE INVENTION As a result of intensive studies to improve these drawbacks, the present inventors have found that in a heat-sensitive recording material containing a leuco dye and a color developer on one surface of a support,
At least one of the heat-sensitive recording layer or the protective layer provided on the heat-sensitive recording layer contains a dimer UV absorber to improve yellowing of the background and fading of the image due to exposure to sunlight. Then, it was possible to obtain a heat-sensitive recording material having excellent storage characteristics in the background portion and the image portion.

A dimer ultraviolet absorber is disclosed in Japanese Examined Patent Publication Sho 55-3.
No. 9180, Japanese Patent Publication No. 57-35220, and Japanese Examined Patent Publication No. 4-58469.
2'-methylenebis (3-benzyloxy-6-benzoylphenol), 2,2'-isopropylidenebis (3-methoxy-6-benzoylphenol), 2,
2'-methylenebis (3-methoxy-6-benzoylphenol), 2,2'-cyclohexylidenebis (3-
Methoxy-6-benzoylphenol), 2,2'-methylenebis [4-methyl-6-benzotriazolyl) phenol], 2,2'-methylenebis [4-methyl-6]
-(5'-methylbenzotriazolyl) phenol],
2,2'-methylenebis [4-methyl-6- (5'-chlorobenzotriazolyl) phenol], 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6 -Benzotriazolyl) phenol], 2,
2'-methylenebis [(4-tert-butyl-6-benzotriazolyl) phenol], 2,2'-propylidene bis [4-methyl-6-benzotriazolyl) phenol], 2,2'-isopropylidene Bis [4-methyl-
6-benzotriazolyl) phenol], 2,2'-isopropylidenebis [4- (1,1,3,3-tetramethylbutyl) -6-benzotriazolyl) phenol], 2,2'- Octylidene bis [4-methyl-6-
Examples thereof include (5′-methylbenzotriazolyl) phenol, and among these compounds, the compound represented by Chemical formula 7 (general formula 3) and 2,2′-methylenebis (3-methoxy-6-benzoylphenol) Is preferable from the viewpoint of light resistance, and particularly 2,2′-methylenebis [4- (1,1,3,
3-tetramethylbutyl) -6-benzotriazolyl-
Phenol] is preferred.

[0007]

[Chemical 7] (In the formula, R7 represents an alkyl group having 1 to 18 carbon atoms, and R8 represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryloxy group, or an aryl group.)

The dimer UV absorber has a higher melting point than conventional monomer UV absorbers and does not hinder the storage characteristics such as heat resistance of the heat-sensitive recording material. Due to the good ultraviolet absorption characteristics that are thought to be caused,
Excellent light resistance.

The dimer UV absorber of the present invention is suitably used in an amount of 10 to 500% by weight, more preferably 50 to 500% by weight, based on the leuco dye. If the addition amount is too small, a sufficient effect for improving the light resistance cannot be obtained, and if the addition amount is too large, the color developing property may be deteriorated.

As the color developer used in the present invention, a phenol derivative, an aromatic carboxylic acid derivative, an N, N'-diarylthiourea derivative, which has been conventionally generally used,
A polyvalent metal salt such as a zinc salt of an organic compound can be used.

Specifically, p-phenylphenol, p
-Hydroxyacetophenone, 4-hydroxy-4'-
Methyldiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-
4'-benzenesulfonyloxydiphenyl sulfone,
1,1-bis (p-hydroxyphenyl) propane,
1,1-bis (p-hydroxyphenyl) pentane,
1,1-bis (p-hydroxyphenyl) hexane,
1,1-bis (p-hydroxyphenyl) cyclohexane, 2,2-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) 2-ethylhexane, 2,2-bis (3-chloro-4-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl) -1-phenylethane, 1,3-di- [2
-(P-Hydroxyphenyl) -2-propyl] benzene, 1,3-di- [2- (3,4-dihydroxyphenyl) -2-propyl] benzene, 1,4-di- [2-
(P-Hydroxyphenyl) -2-propyl] benzene, 4,4'-dihydroxydiphenyl ether, 4,
4'-dihydroxydiphenyl sulfone, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfone,
3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfide, methyl 2,2-bis (4-hydroxyphenyl) acetate, 2,2- Butyl bis (4-hydroxyphenyl) acetate, 4,4'-thiobis (2-
t-butyl-5-methylphenol), benzyl p-hydroxybenzoate, chlorobenzyl p-hydroxybenzoate, dimethyl 4-hydroxyphthalate, benzyl gallate, stearyl gallate and the like.

As a developer which is preferable for the storage property of the image area, a salicylic acid derivative or a metal salt thereof and 2,4'-dihydroxydiphenyl sulfone are used. Among the salicylic acid derivatives, the salicylic acid derivative represented by the following chemical formula 8 (general formula 2) or a metal salt thereof is particularly preferable. Most preferably, 4-n-octyloxycarbonylaminosalicylic acid or its metal salt can be used. The compound represented by the general formula 2 is synthesized by the method shown in EP0534257.

[0013]

[Chemical 8] (In the formula, R4 and R5 represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a halogen atom, and R6 represents an alkyl group, an alkenyl group, an aralkyl group or an aryl group.)

As the salicylic acid derivative, 4-n-octyloxysalicylic acid, 4-benzyloxysalicylic acid, 4- (4-methoxyphenoxyethoxy) salicylic acid, 4- (p-tolylethoxy) salicylic acid, 4- (p
-Tolylsulfonylpropyloxy) salicylic acid and the like. Furthermore, as the salicylic acid derivative represented by the general formula 2, 3-methyloxycarbonylaminosalicylic acid, 3-ethyloxycarbonylaminosalicylic acid, 3
-N-propyloxycarbonylamino salicylic acid, 3
-Isopropyloxycarbonylaminosalicylic acid, 3
-N-butyloxycarbonylaminosalicylic acid, 3-
Isobutyloxycarbonylamino salicylic acid, 3-se
c-Butyloxycarbonylaminosalicylic acid, 3-n
-Pentyloxycarbonylaminosalicylic acid, 3-isopentyloxycarbonylaminosalicylic acid, 3-n
-Hexyloxycarbonylaminosalicylic acid, 3-n
-Heptyloxycarbonylaminosalicylic acid, 3-n
-Octyloxycarbonylaminosalicylic acid,

3- (2'-ethylhexyl) oxycarbonylaminosalicylic acid, 3-n-nonyloxycarbonylaminosalicylic acid, 3-n-decyloxycarbonylaminosalicylic acid, 3-n-undecyloxycarbonylaminosalicylic acid, 3-n -Dodecyloxycarbonylaminosalicylic acid, 3-n-tridecyloxycarbonylaminosalicylic acid, 3-n-tetradecyloxycarbonylaminosalicylic acid, 3-n-pentadecyloxycarbonylaminosalicylic acid, 3-n-hexadecyloxycarbonylaminosalicylic acid , 3-n-heptadecyloxycarbonylaminosalicylic acid, 3-n-octadecyloxycarbonylaminosalicylic acid, 3-cyclopentyloxycarbonylaminosalicylic acid, 3-
Cyclohexyloxycarbonylaminosalicylic acid, 3
-Allyloxycarbonylaminosalicylic acid, 3-benzyloxycarbonylaminosalicylic acid, 3-phenyloxycarbonylaminosalicylic acid, 3- (4'-methylphenyl) oxycarbonylaminosalicylic acid, 3-
(4'-methoxyphenyl) oxycarbonylaminosalicylic acid, 3- (4'-chlorophenyl) oxycarbonylaminosalicylic acid,

3- [2 '-(4-methoxyphenyl) oxyethyl] oxycarbonylaminosalicylic acid, 4-
Methyloxycarbonylaminosalicylic acid, 4-ethyloxycarbonylaminosalicylic acid, 4-n-propyloxycarbonylaminosalicylic acid, 4-isopropyloxycarbonylaminosalicylic acid, 4-n-butyloxycarbonylaminosalicylic acid, 4-isobutyloxycarbonylaminosalicylic acid, 4-sec-butyloxycarbonylaminosalicylic acid, 4-n-pentyloxycarbonylaminosalicylic acid, 4-isopentyloxycarbonylaminosalicylic acid, 4-n-hexyloxycarbonylaminosalicylic acid, 4-n-heptyloxycarbonylaminosalicylic acid, 4 -N-octyloxycarbonylaminosalicylic acid, 4- (2'-ethylhexyl) oxycarbonylaminosalicylic acid, 4-n
-Nonyloxycarbonylamino salicylic acid, 4-n-
Decyloxycarbonylaminosalicylic acid, 4-n-undecyloxycarbonylaminosalicylic acid, 4-n-
Dodecyloxycarbonylamino salicylic acid, 4-n-
Tridecyloxycarbonylamino salicylic acid, 4-n
-Tetradecyloxycarbonylamino salicylic acid, 4
-N-pentadecyloxycarbonylaminosalicylic acid, 4-n-hexadecyloxycarbonylaminosalicylic acid, 4-n-heptadecyloxycarbonylaminosalicylic acid, 4-n-octadecyloxycarbonylaminosalicylic acid, 4-cyclopentyloxycarbonylaminosalicylic acid, 4-cyclohexyloxycarbonylaminosalicylic acid, 4-allyloxycarbonylaminosalicylic acid, 4-benzyloxycarbonylaminosalicylic acid,

4-Phenyloxycarbonylaminosalicylic acid, 4- (4'-methylphenyl) oxycarbonylaminosalicylic acid, 4- (4'-methoxyphenyl)
Oxycarbonylaminosalicylic acid, 4- (4'-chlorophenyl) oxycarbonylaminosalicylic acid, 4-
[2 ′-(4-methoxyphenyl) oxyethyl] oxycarbonylaminosalicylic acid, 5-methyloxycarbonylaminosalicylic acid,

5-ethyloxycarbonylaminosalicylic acid, 5-n-propyloxycarbonylaminosalicylic acid, 5-isopropyloxycarbonylaminosalicylic acid 5-n-butyloxycarbonylaminosalicylic acid, 5-isobutyloxycarbonylaminosalicylic acid, 5-sec- Butyloxycarbonylaminosalicylic acid, 5-n-pentyloxycarbonylaminosalicylic acid, 5-isopentyloxycarbonylaminosalicylic acid, 5-n-hexyloxycarbonylaminosalicylic acid, 5-n-heptyloxycarbonylaminosalicylic acid, 5-n-octyl Oxycarbonylaminosalicylic acid, 5- (2'-ethylhexyl) oxycarbonylaminosalicylic acid, 5-n-nonyloxycarbonylaminosalicylic acid, 5-n- Syloxycarbonylaminosalicylic acid, 5-n-undecyloxycarbonylaminosalicylic acid, 5-n-dodecyloxycarbonylaminosalicylic acid, 5-n-tridecyloxycarbonylaminosalicylic acid, 5-n-tetradecyloxycarbonylaminosalicylic acid, 5 -N-pentadecyloxycarbonylaminosalicylic acid, 5-n-hexadecyloxycarbonylaminosalicylic acid, 5-n-heptadecyloxycarbonylaminosalicylic acid, 5-n-octadecyloxycarbonylaminosalicylic acid, 5-cyclopentyloxycarbonylaminosalicylic acid, 5-cyclohexyloxycarbonylaminosalicylic acid,

5-allyloxycarbonylaminosalicylic acid, 5-benzyloxycarbonylaminosalicylic acid, 5-phenyloxycarbonylaminosalicylic acid,
5- (4'-methylphenyl) oxycarbonylaminosalicylic acid, 5- (4'-methoxyphenyl) oxycarbonylaminosalicylic acid, 5- (4'-chlorophenyl) oxycarbonylaminosalicylic acid, 5- [2'-
(4-Methoxyphenyl) oxyethyl] oxycarbonylaminosalicylic acid, 6-methyloxycarbonylaminosalicylic acid, 6-ethyloxycarbonylaminosalicylic acid, 6-n-propyloxycarbonylaminosalicylic acid, 6-isopropyloxycarbonylaminosalicylic acid, 6-n -Butyloxycarbonylaminosalicylic acid, 6-isobutyloxycarbonylaminosalicylic acid, 6-sec-butyloxycarbonylaminosalicylic acid, 6-n-pentyloxycarbonylaminosalicylic acid, 6-isopentyloxycarbonylaminosalicylic acid, 6-n-hexyloxy Carbonylaminosalicylic acid, 6-n-heptyloxycarbonylaminosalicylic acid, 6-n-octyloxycarbonylaminosalicylic acid, 6- (2'- Cyclohexyl) oxycarbonylaminosalicylic acid, 6-n-nonyloxycarbonylaminosalicylic acid, 6-n-decyloxycarbonylaminosalicylic acid, 6-n-undecyloxycarbonylaminosalicylic acid, 6-n-dodecyloxycarbonylaminosalicylic acid, 6- n-tridecyloxycarbonylaminosalicylic acid,

6-n-tetradecyloxycarbonylaminosalicylic acid, 6-n-pentadecyloxycarbonylaminosalicylic acid, 6-n-hexadecyloxycarbonylaminosalicylic acid, 6-n-heptadecyloxycarbonylaminosalicylic acid, 6-n -Octadecyloxycarbonylaminosalicylic acid, 6-cyclopentyloxycarbonylaminosalicylic acid, 6-cyclohexyloxycarbonylaminosalicylic acid, 6-allyloxycarbonylaminosalicylic acid, 6-benzyloxycarbonylaminosalicylic acid, 6-phenyloxycarbonylaminosalicylic acid, 6- ( 4'-methylphenyl)
Oxycarbonylaminosalicylic acid 6- (4'-methoxyphenyl) oxycarbonylaminosalicylic acid, 6- (4'-chlorophenyl) oxycarbonylaminosalicylic acid, 6- [2 '-(4-methoxyphenyl) oxyethyl] oxycarbonylaminosalicylic acid, etc. Is mentioned.

In the metal salt of the salicylic acid derivative according to the present invention, there is a metal salt containing a monovalent metal salt such as sodium, potassium or lithium, but it is preferably a water-insoluble or water-insoluble divalent salt. It is a trivalent or tetravalent metal salt, more preferably a divalent or trivalent metal salt.

Specific examples of the divalent, trivalent or tetravalent metal salt include zinc, cadmium, mercury, magnesium, calcium, barium, nickel, tin, gallium, chromium,
Copper, molybdenum, tungsten, zirconium, strontium, manganese, cobalt, titanium, aluminum, iron salts can be mentioned, preferably zinc,
It is a salt of calcium, barium, nickel, manganese, cobalt and aluminum. A zinc salt is particularly preferable.
The metal salt of salicylic acid may form a solvate such as a hydrate depending on the production conditions, and the solvate is also suitable as the electron-accepting compound of the present invention.

The leuco dye used in the present invention is not particularly limited as long as it is generally used for pressure-sensitive recording paper or heat-sensitive recording paper.

Specifically, the following compounds can be used. (1) Triarylmethane compound: 3,3-bis (p
-Dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p
-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-3-
Yl) phthalide, 3- (p-dimethylaminophenyl)
-3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindole-3-
Yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide,
3,3-bis (2-phenylindol-3-yl)-
5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6
-Dimethylaminophthalide, etc.

(2) Diphenylmethane compound: 4,
4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, etc.,

(3) Xanthene compound: Rhodamine B
Anilinolactam, Rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino -7-Chlorofluorane, 3
-Diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-
Methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-dipentylamino-6-methyl-7-anilinofluorane, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Anilinofluorane, 3-piperidino-6-methyl-7
-Anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-phenethylfluorane,
3-diethylamino-7- (4-nitroanilino) fluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilino Fluoran, 3- (N-
Ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane,
3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluorane and the like,

(4) Thiazine-based compounds: benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue, etc.

(5) Spiro compound: 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran,
3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 3-propylspirobenzopyran, and the like, which may be used alone or in combination with 2 It can be used as a mixture of two or more.

Particularly preferable leuco dyes having a light-preserving property include compounds represented by the following chemical formula 9 (general formula 1). Specifically, 3-diethylamino-7- (2-chloroanilino) fluorane, 3- Dibutylamino-7-
(2-chloroanilino) fluorane, 3-diethylamino-7- (2-fluoroanilino) fluorane, 3-
(N-ethyl-N-isoamylamino) -7- (2-chloroanilino) fluorane, 2- (m-trifluoromethylphenyl) amino-6-diethylaminofluorane and the like can be mentioned, and more preferably 3-diethylamino-. 7- (m-trifluoromethylphenyl) aminofluorane may be mentioned.

[0030]

[Chemical 9] (In the formula, R1 and R2 represent an alkyl group, and R3 represents a halogen atom or a methyl group substituted with a halogen atom.)

The heat-sensitive recording material of the present invention can be used for facsimile paper, word processor paper, printer paper, label paper, and tag paper. Particularly, as label paper, that is, heat-sensitive recording material for labels, the other surface of the support is used. Usually, it is often used in the form of a release paper provided via a pressure-sensitive adhesive layer, but it is also possible to further provide a permeation preventive layer or the like between the support and the pressure-sensitive adhesive layer.

The components in the heat-sensitive recording layer generally include leuco dyes, color developers, pigments, binders and the like, and by further adding an organic compound having a melting point of 80 to 150 ° C., Good thermal response can be obtained. To give some specific examples, stearic acid amide, N-hydroxymethylstearic acid amide, behenic acid amide, N-hydroxymethylbehenic acid amide, N-
Aliphatic amides such as stearyl stearic acid amide and ethylene bis stearic acid amide, 2-benzyloxynaphthalene, 4-benzyl biphenyl, diphenyl adipate, dibenzyl terephthalate, 1,2-bis (3,4)
-Dimethylphenyl) ethane, m-terphenyl, dibenzyl oxalate, di (4-methylbenzyl) oxalate, di (4-chlorobenzyl) oxalate, 1,2-bis (3-methylphenoxy) ethane and the like can be mentioned. .

As the binder used in the heat-sensitive recording material, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylic acid soda, acrylic acid amide / acrylic acid ester copolymer. , Acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, ethylene /
Water-soluble adhesive such as alkali salt of maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic acid ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, Examples include latex such as ethylene / vinyl acetate copolymer.

Examples of the pigment include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide and urea-formalin resin.

In addition, for the purpose of preventing head wear and sticking, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearamide, caster wax and the like. Further, a dispersant such as sodium dioctylsulfosuccinate, a surfactant, a fluorescent dye and the like are added as necessary.

As the support used in the present invention, paper is mainly used, but non-woven fabric, plastic film, synthetic paper, metal foil, or a composite sheet in which these are combined can be optionally used. Further, various known techniques in the production of heat-sensitive recording materials can be used, such as providing an undercoat layer consisting of a single layer or a plurality of layers of pigments or resins between the heat-sensitive recording layer and the support.

In the present invention, a protective layer may be further provided on the heat-sensitive recording layer in order to further improve the solvent resistance.
A water-soluble resin such as polyvinyl alcohol or an aqueous emulsion can be smeared, and if necessary, a pigment, a wax, a water-proofing agent, etc. can be added.

The coating amount of the heat-sensitive recording layer is usually 0.1 to 1.0 g / m ^{2 in} terms of the coating amount of the leuco dye.

[0039]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The parts and% shown below are based on weight.

Example 1 Preparation of heat-sensitive recording material (A) Preparation of heat-sensitive coating liquid 3-dibutylamino-6-methyl-7 which is a leuco dye
-30 parts of anilinofluorane was pulverized with 70 parts of 2.5% aqueous solution of polyvinyl alcohol in a Dyno mill (sand mill manufactured by WEB) to obtain a leuco dye dispersion having a volume average particle diameter of 2 µm or less. Then, 40 parts of 2,2-bis (4-hydroxyphenyl) propane and 50 parts of 2-benzyloxynaphthalene as a color developer are pulverized together with 210 parts of 2.5% polyvinyl alcohol aqueous solution in a Dynomill (sand mill manufactured by WEB), A color developer dispersion having a volume average particle size of 2 μm or less was obtained. Furthermore, the ultraviolet absorber 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl)
-6-benzotriazolyl) phenol] 50 parts 2.
It was pulverized with 117 parts of a 5% polyvinyl alcohol aqueous solution in a Dynomill (sand mill manufactured by WEB) to obtain an ultraviolet absorbent dispersion having a volume average particle diameter of 2 μm or less.

After mixing the above-mentioned three kinds of dispersions, the following were added with stirring and mixed well to prepare a heat-sensitive coating liquid. 50% calcium carbonate aqueous dispersion 100 parts 40% zinc stearate aqueous dispersion 25 parts 10% polyvinyl alcohol aqueous solution 200 parts water 280 parts

(B) Preparation of heat-sensitive coated paper A base paper having a basis weight of 40 g / m ² is coated with a coating solution having the following composition so that the solid content is 9 g / m ² , dried, and heat-sensitive coated. Craft paper was prepared. Calcined Kaolin 100 parts 50% Styrene-butadiene latex aqueous dispersion 24 parts Water 200 parts

(C) Preparation of heat-sensitive recording material The heat-sensitive coating liquid prepared in (A) was smeared onto the surface of the heat-sensitive coated paper prepared in (B) so that the solid content was 4 g / m ^2. ,
After drying, the Beck's smoothness is 600 to 80 on the calendar.
The heat-sensitive recording material was prepared by processing for 0 second.

Example 2 UV absorber 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- in Example 1
Benzotriazolyl) phenol], 2,
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that 2'-octylidenebis [4-methyl-6- (5'-methylbenzotriazolyl) phenol] was used.

Example 3 The leuco dye 3-dibutylamino-6 in Example 1
A thermosensitive recording material was prepared in the same manner as in Example 1 except that 3-diethylamino-7- (2-chloroanilino) fluorane was used instead of -methyl-7-anilinofluorane.

Example 4 The leuco dye 3-dibutylamino-6 in Example 1
A thermosensitive recording material was prepared in the same manner as in Example 1 except that 3-diethylamino-7- (m-trifluoromethylanilino) fluorane was used instead of -methyl-7-anilinofluorane.

Example 5 Ultraviolet absorber 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- in Example 4
Benzotriazolyl) phenol], 2,
A heat-sensitive recording material was produced in the same manner as in Example 4 except that 2'-methylenebis (3-methoxy-6-benzoylphenol) was used.

Example 6 Example 6 was repeated except that the color developer 2,2-bis (4-hydroxyphenyl) propane in Example 4 was replaced with zinc 4- (4-methoxyphenoxyethoxy) salicylate. A thermal recording material was prepared in the same manner as in 4.

Example 7 In the same manner as in Example 4, except that the zinc 2,4-bis (4-hydroxyphenyl) propane in Example 4 was replaced with zinc 4-n-octyloxycarbonylaminosalicylate. A recording material was prepared.

Example 8 A thermosensitive recording material was prepared in the same manner as in Example 7 except that zinc 4-n-hexyloxycarbonylaminosalicylate was used instead of zinc 4-n-octyloxycarbonylaminosalicylate in Example 7. It was made.

Example 9 A thermosensitive recording material was prepared in the same manner as in Example 7 except that zinc 4-phenyloxycarbonylaminosalicylate was used instead of zinc 4-n-octyloxycarbonylaminosalicylate in Example 7. .

Example 10 A thermosensitive recording material was prepared in the same manner as in Example 7 except that 2,4'-dihydroxydiphenyl sulfone was used instead of zinc 4-n-octyloxycarbonylaminosalicylate in Example 7. .

Example 11 Ultraviolet absorber 2,7'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- in Example 7
Benzotriazolyl) phenol], 2,
A thermal recording material was prepared in the same manner as in Example 7 except that 2'-methylenebis (3-methoxy-6-benzoylphenol) was used.

Example 12 A coating solution having the following composition was applied as a protective layer on the thermosensitive recording material of Example 7 so that the dry application amount was 3 g / m ^2, and after drying, the Beck smoothness was measured by a calendar. The heat-sensitive recording material was prepared by treating the material for 600 to 800 seconds.

1) Preparation of coating liquid for protective layer 8% polyvinyl alcohol aqueous solution 100 parts 40% zinc stearate dispersion liquid 5 parts 20% silicic acid dispersion liquid 50 parts The above aqueous solution and water dispersion liquid were mixed to prepare a protective layer coating liquid. did.

Example 13 A heat-sensitive recording layer was provided in the same manner as in Example 4, and a coating solution for protective layer having the following composition was smeared on the heat-sensitive layer so that the dry smear was 3 g / m ² and dried. After that, it was processed with a calendar so that the Beck's smoothness was 600 to 800 seconds to prepare a heat-sensitive recording material.

1) Preparation of coating liquid for protective layer 6 parts of 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6-benzotriazolylphenol] and 5% aqueous polyvinyl alcohol solution The volume average particle size of the liquid obtained by mixing 10 parts was 2.0 μm using Dynomill.
The mixture was pulverized to the following size, and 100 parts of an 8% polyvinyl alcohol aqueous solution and 40% zinc stearate dispersion liquid 5 were added.
Parts, and 50 parts of 20% silicic acid dispersion liquid were added to obtain a protective layer coating liquid.

Example 14 UV absorber 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6-benzotriazolylphenol used in the heat-sensitive coating liquid of Example 13 A thermosensitive recording material was prepared in the same manner as in Example 13 except that

Example 15 Example 15 was repeated except that zinc 2,4-bis (4-methoxyphenoxyethoxy) salicylate was used instead of 2,2-bis (4-hydroxyphenyl) propane used in the heat-sensitive recording layer of Example 14. A thermal recording material was prepared in the same manner as in Example 14.

Example 16 Example 16 was repeated except that zinc 2,4-bis (4-hydroxyphenyl) propane was used instead of 2,2-bis (4-hydroxyphenyl) propane used in the heat-sensitive recording layer of Example 14. A thermal recording material was prepared in the same manner as 14.

Example 17 The same as Example 14 except that 2,2-bis (4-hydroxyphenyl) propane used in the thermosensitive recording layer of Example 14 was replaced with 2,4′-dihydroxydiphenylsulfone. Then, a thermal recording material was prepared.

Example 18 The leuco dye of Example 14, 3-dibutylamino-
Instead of 6-methyl-7-anilinofluorane, 3-
A heat-sensitive recording material was produced in the same manner as in Example 14 except that diethylamino-7- (2-chloroanilino) fluorane was used.

Example 19 The leuco dye 3-diethylamino-in Example 14
A thermosensitive recording material was prepared in the same manner as in Example 14 except that 3-dibutylamino-6-methyl-7-anilinofluorane was used instead of 7- (m-trifluoromethylanilino) fluorane. .

Example 20 Ultraviolet absorber 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6 in Example 14
-Benzotriazolylphenol], 2,
A heat-sensitive recording material was produced in the same manner as in Example 14 except that 2'-methylenebis (3-methoxy-6-benzoylphenol) was used.

Comparative Example 1 2,2′-methylenebis [4- (1,1,
A thermal recording material was prepared in the same manner as in Example 4 except that [3,3-tetramethylbutyl) -6-benzotriazolylphenol] was omitted.

Comparative Example 2 2,2'-methylenebis [4- (1,1,
A thermosensitive recording material was prepared in the same manner as in Example 1 except that [3,3-tetramethylbutyl) -6-benzotriazolylphenol] was removed.

Comparative Example 3 2,2′-methylenebis [4- (1,1,
A thermosensitive recording material was obtained in the same manner as in Example 4, except that 3,3-tetramethylbutyl) -6-benzotriazolylphenol] was changed to 2- (5-methyl-2-hydroxyphenyl) benzotriazole. .

Comparative Example 4 2,2′-methylenebis [4- (1,1,
A heat-sensitive recording material was obtained in the same manner as in Example 4 except that 3,3-tetramethylbutyl) -6-benzotriazolylphenol] was changed to 2-hydroxy-4-methoxybenzophenone.

Comparative Example 5 2,2'-methylenebis [4- in the protective layer of Example 14
Example 1, except that (1,1,3,3-tetramethylbutyl) -6-benzotriazolylphenol] was omitted.
A thermal recording material was prepared in the same manner as in.

Comparative Example 6 2,2'-methylenebis [4- in the protective layer of Example 14
Instead of (1,1,3,3-tetramethylbutyl) -6-benzotriazolylphenol], 2- (5-methyl-2-hydroxyphenyl) benzotriazole was used, and Example 14 was used. A thermal recording material was prepared in the same manner.

Comparative Example 7 2,2'-methylenebis [4- in the protective layer of Example 14
(1,1,3,3-Tetramethylbutyl) -6-benzotriazolylphenol], and instead of 2-hydroxy-4-methoxybenzophenone, a thermosensitive recording material was prepared in the same manner as in Example 14. Was produced.

The thermal recording materials prepared in the above Examples and Comparative Examples were subjected to the following evaluations. Evaluation; [Formation of image part] Okura Electric Facsimile Testing Machine TH-
A printing test was conducted using PMD. A thermal head having a dot density of 8 dots / mm and a head resistance of 1290 Ω was used, and printing was performed by energizing at a head voltage of 21 V and a pulse width of 1.0 ms to form a colored image.

[Light resistance test of background portion and image portion] The light resistance test was conducted by using a xenon arc weatherometer Ci35W.
Irradiance 0.39W / m2 (340nm), ambient temperature 4
It was treated for 12 hours under conditions of 0 ° C. and 25% humidity, and the color difference change (ΔE ^* ab) of the background part and the image part at that time was measured by CR200 manufactured by Minolta Camera Co., Ltd. CIE-1976L ^* a ^*.
b ^* Measured with a color system. If ΔE ^* ab is 6 or less, it is a good level, and if it is 2.5 or less, it is a very good level with almost no deterioration.

[Heat resistance test on the background part] In the heat resistance test, the color development density of the background part was measured by a Macbeth densitometer at 60 ° C. for 24 hours. If the color density is 0.20 or less, it is at a good level.

[Moisture and heat resistance test of image part] The humidity and heat resistance test is 40
After processing for 24 hours under the condition of 90 ° C. and 90% relative humidity, the color density of the image area at that time was measured by a Macbeth densitometer. If the color density is 0.8 or more, it is legible as an image and 1.0
If it is above, more excellent reading can be performed.

[0076]

[Table 1]

[0077]

As is clear from Table 1 above, by using the dimer UV absorber of the present invention, good properties are exhibited with little discoloration in the background part and the image part in the light resistance test and test. In addition, the color development in the heat resistance test of the background such as when a monomer ultraviolet absorber is added is also suppressed. Further, by using the leuco dye represented by the general formula 1, the light resistance is further improved, and particularly 3-diethylamino-7-
The effect of using (m-trifluoromethylanilino) fluorane is great. Also in the color developer, by using a salicylic acid derivative or 2,4′-dihydroxydiphenyl sulfone, excellent storage characteristics were obtained in the wet heat test of the image area.

Front page continuation (31) Priority claim number Japanese Patent Application No. 5-289233 (32) Priority Day 5 (1993) November 18 (33) Country of priority Japan (JP) (72) Inventor Naoya Sakata Tokyo 3-4 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Paper Mills, Ltd.

Claims (23)

[Claims] 1. A heat-sensitive recording material containing a leuco dye and a color developer on one surface of a support, wherein the heat-sensitive recording layer contains a UV absorber, wherein the UV absorber is a dimer. A heat-sensitive recording material characterized by being an ultraviolet absorber. 2. The heat-sensitive recording material according to claim 1, wherein the leuco dye is a compound represented by the following chemical formula 1 (general formula 1). [Chemical 1] (In the formula, R ₁ and R ₂ represent an alkyl group, and R ₃ represents a halogen atom or a methyl group substituted with a halogen atom.) 3. The leuco dye is 3-diethylamino-7.
The heat-sensitive recording material according to claim 1, which is-(m-trifluoromethylphenyl) aminofluorane. 4. The heat-sensitive recording material according to claim 1, wherein the developer is a salicylic acid derivative or a metal salt thereof. 5. The heat-sensitive recording material according to claim 4, wherein the developer is a salicylic acid derivative represented by the following chemical formula 2 (general formula 2) or a metal salt thereof. [Chemical 2] (In the formula, R ₄ and R ₅ represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a halogen atom, and R ₆ represents an alkyl group, an alkenyl group, an aralkyl group, or an aryl group.) 6. The heat-sensitive recording material according to claim 5, wherein the developer is 4-n-octyloxycarbonylaminosalicylic acid or a metal salt thereof. 7. The heat-sensitive recording material according to claim 1, wherein the developer is 2,4′-dihydroxydiphenyl sulfone. 8. The heat-sensitive recording material according to claim 1, wherein the dimer ultraviolet absorber is a compound represented by the following chemical formula 3 (general formula 3). [Chemical 3] (In the formula, R ₇ represents an alkyl group having 1 to 18 carbon atoms, and R ₈ represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryloxy group or an aryl group.) 9. The dimer UV absorber is 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6-benzotriazolyl) phenol]. 9. The heat-sensitive recording material according to claim 8. 10. The dimer UV absorber is 2,2′-
The heat-sensitive recording material according to claim 1, which is methylenebis (3-methoxy-6-benzoylphenol). 11. The thermosensitive recording material according to claim 1, wherein a protective layer is provided on the thermosensitive recording layer. 12. A heat-sensitive recording material comprising a support, on one surface of which a heat-sensitive recording layer containing a leuco dye and a color developer is provided, and a protective layer containing an ultraviolet absorber is provided on the heat-sensitive recording layer. A heat-sensitive recording material, wherein the agent is a dimer UV absorber. 13. The heat-sensitive recording material according to claim 12, wherein the heat-sensitive recording layer contains a dimer UV absorber. 14. The heat-sensitive recording material according to claim 12, wherein the leuco dye is the chemical formula 4 (general formula 1). [Chemical 4] (In the formula, R ₁ and R ₂ represent an alkyl group, and R ₃ represents a halogen atom or a methyl group substituted with a halogen atom.) 15. The leuco dye is 3-diethylamino-
The heat-sensitive recording material according to claim 14, which is 7- (m-trifluoromethylphenyl) aminofluorane. 16. The heat-sensitive recording material according to claim 12, wherein the developer is a salicylic acid derivative or a metal salt thereof. 17. The heat-sensitive recording material according to claim 16, wherein the developer is a salicylic acid derivative represented by Chemical formula 5 (general formula 2) or a metal salt thereof. [Chemical 5] (In the formula, R ₄ and R ₅ represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a halogen atom, and R ₆ represents an alkyl group, an alkenyl group, an aralkyl group or an aryl group.) 18. The heat-sensitive recording material according to claim 17, wherein the developer is 4-n-octyloxycarbonylaminosalicylic acid or a metal salt thereof. 19. The heat-sensitive recording material according to claim 12, wherein the developer is 2,4′-dihydroxydiphenyl sulfone. 20. The heat-sensitive recording material according to claim 12, wherein the dimer ultraviolet absorber is a compound represented by Chemical formula 6 (general formula 3). [Chemical 6] (In the formula, R ₇ represents an alkyl group having 1 to 18 carbon atoms, and R ₈ represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryloxy group, or an aryl group.) 21. The dimer ultraviolet absorber is 2,2′-
The heat-sensitive recording material according to claim 20, which is methylenebis [4- (1,1,3,3-tetramethylbutyl) -6-benzotriazolylphenol]. 22. The dimer UV absorber is 2,2′-
The heat-sensitive recording material according to claim 12, which is methylenebis (3-methoxy-6-benzoylphenol). 23. A heat-sensitive recording material for labels, characterized in that a release paper is provided on the other surface of the support of the heat-sensitive recording material according to claim 1 or 12 via a pressure-sensitive adhesive layer.