JPH08156427A - Thermal recording material - Google Patents

Abstract

PURPOSE: To obtain a thermal recording material excellent in the storage stability of a background part and an image part by adding a specific salicylic acid derivative or a metal salt thereof as an electron acceptive compd. and adding one kind of a specific substance as a sensitizer. CONSTITUTION: A salicylic acid derivative represented by formula (wherein X1 and X2 are a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a halogen atom and R is an alkyl group, an alkenyl group, an aralkyl group or an aryl group) or a metal salt thereof is added as an electron acceptive compd. allowing a dye precursor to form a color in an amt. of 50-300% by wt. of the dye precursor. As a sensitizer, one kind of a compd. is selected from 1,4-dibenzyloxybenzene, methyl p-benzoyloxybenzoate and 4,4'- diallyloxydiphenylsulfone to be added in an amt. of 50-300% by wt. of the dye precursor. By this constitution, a thermal recording material excellent in thermal response, the storage stability of a background part and an image part and the heat resistance of the background part can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermal recording material,
Especially excellent in thermal responsiveness and storage stability of the background part and image part,
The present invention also relates to a heat-sensitive recording material having excellent heat resistance of the background part.

[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 light-colored dye precursor and an electron-accepting developer as main components. By heating with a thermal head, a heating pen, a laser beam, etc., a dye precursor and a developer react instantaneously to obtain a recorded image. JP-B-43-4160 and JP-A-45-45
-14039 gazette etc. are disclosed. Such a heat-sensitive recording material has advantages such that recording can be obtained by a relatively simple device, maintenance is easy, and noise is not generated.
It is used in a wide range of fields such as measurement recorders, facsimiles, printers, computer terminals, labels, and ticket vending machines. Conventional thermal recording materials using electron-donating colorless dye precursors and electron-accepting compounds have characteristics such as high color density, but on the other hand, the recorded image area contacts plastic such as polyvinyl chloride. It also has the drawback that the storage characteristics of recorded images are poor, such as discoloration due to penetration of plasticizers and additives contained in plastics, and discoloration by contact with chemicals contained in foods and cosmetics. ,
Alternatively, it has a drawback that the writing trace is discolored when writing on the background with a writing instrument, and the present situation is that the use thereof is subject to certain restrictions, and its improvement has been strongly desired. Further, the heat-sensitive recording material may be used in an automobile or used in a microwave oven or the like, and in this case, heat resistance of the background portion is required.

As means for improving the storage characteristics of the recorded image area and the background area, a salicylic acid derivative having a substituent such as an alkyl group, an aralkyl group, an alkyloxy group, an acyl group or a metal salt thereof is used as an electron-accepting compound. Thermal recording materials to be used have been proposed. (JP-A-62-16968
1 gazette, the same 63-22683 gazette, the same 63-959.
(Gazette No. 77)

However, the salicylic acid derivative described in this publication has insufficient storage characteristics for a colored image, insufficient storage stability of the background portion, and low coloration sensitivity, which is not practical. It was hard to say that it was a heat-sensitive recording material compatible with high-speed recording.

Further, Japanese Unexamined Patent Publication No. 6-72984 describes an electron-accepting compound described in the present application, and although the background part and the image part preservation property are good, the thermal response is insufficient, Even if the sensitizer described in the publication is used to improve the thermal response, the heat resistance of the background part is deteriorated.

[0006]

The present invention relates to a heat-sensitive recording material, and in particular, to obtain a heat-sensitive recording material which is excellent in heat response and storage stability of the background portion and image portion, and excellent in heat resistance of the background portion. Is.

[0007]

A heat-sensitive recording material containing a usually colorless to light-colored dye precursor and an electron-accepting compound which reacts with heating to develop the dye precursor,
At least one salicylic acid derivative represented by the following chemical formula 2 (general formula 1) or a metal salt thereof is contained as an electron-accepting compound, and 1,4-dibenzyloxybenzene and methyl p-benzoyloxybenzoate are used as a sensitizer. By containing at least one selected from ester and 4,4'-diallyloxydiphenyl sulfone, a heat-sensitive recording material having excellent storage stability in the background and image areas could be obtained.

[0008]

Embedded image (In the formula, X ₁ and X ₂ represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a halogen atom, and R represents an alkyl group, an alkenyl group, an aralkyl group, or an aryl group.)

Specific examples of the salicylic acid derivative represented by the general formula 1 or the metal salt thereof according to the present invention include, for example,
Although the following are listed, the present invention is not limited thereto.

(1) 3-Methyloxycarbonylaminosalicylic acid (2) 3-Ethyloxycarbonylaminosalicylic acid (3) 3-n-Propyloxycarbonylaminosalicylic acid (4) 3-Isopropyloxycarbonylaminosalicylic acid (5) 3- n-Butyloxycarbonylaminosalicylic acid (6) 3-isobutyloxycarbonylaminosalicylic acid (7) 3-sec-butyloxycarbonylaminosalicylic acid (8) 3-n-pentyloxycarbonylaminosalicylic acid (9) 3-isopentyloxycarbonyl Aminosalicylic acid (10) 3-n-hexyloxycarbonylaminosalicylic acid (11) 3-n-heptyloxycarbonylaminosalicylic acid (12) 3-n-octyloxycarbonylaminosalicylic acid (13) 3 (2'-Ethylhexyl) oxycarbonylaminosalicylic acid (14) 3-n-nonyloxycarbonylaminosalicylic acid (15) 3-n-decyloxycarbonylaminosalicylic acid (16) 3-n-undecyloxycarbonylaminosalicylic acid (17) 3-n-dodecyloxycarbonylaminosalicylic acid (18) 3-n-tridecyloxycarbonylaminosalicylic acid (19) 3-n-tetradecyloxycarbonylaminosalicylic acid (20) 3-n-pentadecyloxycarbonylaminosalicylic acid (21) ) 3-n-hexadecyloxycarbonylaminosalicylic acid (22) 3-n-heptadecyloxycarbonylaminosalicylic acid (23) 3-n-octadecyloxycarbonylaminosalicylic acid (24) 3-cyclopen (25) 3-Cyclohexyloxycarbonylaminosalicylic acid (26) 3-Allyloxycarbonylaminosalicylic acid (27) 3-Benzyloxycarbonylaminosalicylic acid (28) 3-Phenyloxycarbonylaminosalicylic acid (29) 3- (4'-Methylphenyl) oxycarbonylaminosalicylic acid (30) 3- (4'-methoxyphenyl) oxycarbonylaminosalicylic acid

(31) 3- (4'-chlorophenyl) oxycarbonylaminosalicylic acid (32) 3- [2 '-(4-methoxyphenyl) oxyethyl] oxycarbonylaminosalicylic acid (33) 4-methyloxycarbonylaminosalicylic acid ( 34) 4-Ethyloxycarbonylaminosalicylic acid (35) 4-n-propyloxycarbonylaminosalicylic acid (36) 4-Isopropyloxycarbonylaminosalicylic acid (37) 4-n-butyloxycarbonylaminosalicylic acid (38) 4-isobutyloxy Carbonylaminosalicylic acid (39) 4-sec-butyloxycarbonylaminosalicylic acid (40) 4-n-pentyloxycarbonylaminosalicylic acid (41) 4-isopentyloxycarbonylaminosalicylic acid (42) ) 4-n-hexyloxycarbonylaminosalicylic acid (43) 4-n-heptyloxycarbonylaminosalicylic acid (44) 4-n-octyloxycarbonylaminosalicylic acid (45) 4- (2′-ethylhexyl) oxycarbonylaminosalicylic acid 46) 4-n-nonyloxycarbonylaminosalicylic acid (47) 4-n-decyloxycarbonylaminosalicylic acid (48) 4-n-undecyloxycarbonylaminosalicylic acid (49) 4-n-dodecyloxycarbonylaminosalicylic acid (50) ) 4-n-Tridecyloxycarbonylaminosalicylic acid (51) 4-n-tetradecyloxycarbonylaminosalicylic acid (52) 4-n-pentadecyloxycarbonylaminosalicylic acid (53) 4-n-hexadecylo Cycarbonylaminosalicylic acid (54) 4-n-heptadecyloxycarbonylaminosalicylic acid (55) 4-n-octadecyloxycarbonylaminosalicylic acid (56) 4-cyclopentyloxycarbonylaminosalicylic acid (57) 4-cyclohexyloxycarbonylaminosalicylic acid ( 58) 4-allyloxycarbonylaminosalicylic acid (59) 4-benzyloxycarbonylaminosalicylic acid (60) 4-phenyloxycarbonylaminosalicylic acid

(61) 4- (4'-methylphenyl) oxycarbonylaminosalicylic acid (62) 4- (4'-methoxyphenyl) oxycarbonylaminosalicylic acid (63) 4- (4'-chlorophenyl) oxycarbonylaminosalicylic acid (64) 4- [2 '-(4-methoxyphenyl) oxyethyl] oxycarbonylaminosalicylic acid (65) 5-methyloxycarbonylaminosalicylic acid (66) 5-ethyloxycarbonylaminosalicylic acid (67) 5-n-propyloxy Carbonylaminosalicylic acid (68) 5-isopropyloxycarbonylaminosalicylic acid (69) 5-n-butyloxycarbonylaminosalicylic acid (70) 5-isobutyloxycarbonylaminosalicylic acid (71) 5-sec-butyloxycarbonic acid Aminosalicylic acid (72) 5-n-pentyloxycarbonylaminosalicylic acid (73) 5-Isopentyloxycarbonylaminosalicylic acid (74) 5-n-hexyloxycarbonylaminosalicylic acid (75) 5-n-heptyloxycarbonylaminosalicylic acid ( 76) 5-n-octyloxycarbonylaminosalicylic acid (77) 5- (2′-ethylhexyl) oxycarbonylaminosalicylic acid (78) 5-n-nonyloxycarbonylaminosalicylic acid (79) 5-n-decyloxycarbonylaminosalicylic acid (80) 5-n-undecyloxycarbonylaminosalicylic acid (81) 5-n-dodecyloxycarbonylaminosalicylic acid (82) 5-n-tridecyloxycarbonylaminosalicylic acid (83) 5-n Tetradecyloxycarbonylaminosalicylic acid (84) 5-n-pentadecyloxycarbonylaminosalicylic acid (85) 5-n-hexadecyloxycarbonylaminosalicylic acid (86) 5-n-heptadecyloxycarbonylaminosalicylic acid (87) 5- n-octadecyloxycarbonylaminosalicylic acid (88) 5-cyclopentyloxycarbonylaminosalicylic acid (89) 5-cyclohexyloxycarbonylaminosalicylic acid (90) 5-allyloxycarbonylaminosalicylic acid

(91) 5-benzyloxycarbonylaminosalicylic acid (92) 5-phenyloxycarbonylaminosalicylic acid (93) 5- (4'-methylphenyl) oxycarbonylaminosalicylic acid (94) 5- (4'-methoxyphenyl) ) Oxycarbonylaminosalicylic acid (95) 5- (4'-chlorophenyl) oxycarbonylaminosalicylic acid (96) 5- [2 '-(4-methoxyphenyl) oxyethyl] oxycarbonylaminosalicylic acid (97) 6-methyloxycarbonylamino Salicylic acid (98) 6-ethyloxycarbonylaminosalicylic acid (99) 6-n-propyloxycarbonylaminosalicylic acid (100) 6-isopropyloxycarbonylaminosalicylic acid (101) 6-n-butyloxycarbonyl Aminosalicylic acid (102) 6-isobutyloxycarbonylaminosalicylic acid (103) 6-sec-Butyloxycarbonylaminosalicylic acid (104) 6-n-pentyloxycarbonylaminosalicylic acid (105) 6-isopentyloxycarbonylaminosalicylic acid (106) 6-n-hexyloxycarbonylaminosalicylic acid (107) 6-n-heptyloxycarbonylaminosalicylic acid (108) 6-n-octyloxycarbonylaminosalicylic acid (109) 6- (2'-ethylhexyl) oxycarbonylaminosalicylic acid (110) ) 6-n-nonyloxycarbonylaminosalicylic acid (111) 6-n-decyloxycarbonylaminosalicylic acid (112) 6-n-undecyloxycarbonylaminosalicylic acid (113) 6-n-dodecyloxycarbonylaminosalicylic acid (114) 6-n-tridecyloxycarbonylaminosalicylic acid (115) 6-n-tetradecyloxycarbonylaminosalicylic acid (116) 6-n-pentadecyloxycarbonylamino Salicylic acid (117) 6-n-hexadecyloxycarbonylaminosalicylic acid (118) 6-n-heptadecyloxycarbonylaminosalicylic acid (119) 6-n-octadecyloxycarbonylaminosalicylic acid (120) 6-cyclopentyloxycarbonylaminosalicylic acid

(121) 6-Cyclohexyloxycarbonylaminosalicylic acid (122) 6-allyloxycarbonylaminosalicylic acid (123) 6-benzyloxycarbonylaminosalicylic acid (124) 6-phenyloxycarbonylaminosalicylic acid (125) 6- (4 '-Methylphenyl) oxycarbonylaminosalicylic acid (126) 6- (4'-methoxyphenyl) oxycarbonylaminosalicylic acid (127) 6- (4'-chlorophenyl) oxycarbonylaminosalicylic acid (128) 6- [2'-( 4-Methoxyphenyl) oxyethyl] oxycarbonylaminosalicylic acid

In the metal salt of the salicylic acid derivative represented by the above general formula 1 according to the present invention, the metal salt contains a monovalent metal salt such as sodium, potassium and lithium, but is preferably water-resistant. It is a soluble or water-insoluble divalent, 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 and strontium. The salts of manganese, cobalt, titanium, aluminum and iron can be mentioned, but the salts of zinc, calcium, barium, nickel, manganese, cobalt and aluminum are preferable. A zinc salt is particularly preferable. The metal salt of salicylic acid represented by the general formula 1 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 salicylic acid derivative represented by the general formula 1 or its metal salt according to the present invention can be prepared by a known method {for example,
J. Pharm. Sci. , 52, 927 (196
3), Bull. de. Socie. Chim. Fra
nce, 1189 (1955)}. That is, for example, the aminosalicylic acid derivative can be suitably synthesized by reacting a chloroformate compound in an approximately equivalent amount.

The salicylic acid derivative or metal salt represented by the above general formula 1 according to the present invention is used in an amount of 20 relative to the dye precursor.
The addition of ˜500% by weight is preferable, and the addition of 50˜300% by weight is particularly preferable.

The sensitizer of the present invention, 1,4-dibenzyloxybenzene, p-benzoyloxybenzoic acid methyl ester, and 4,4'-diallyloxydiphenyl sulfone are contained in an amount of 10 to 500% by weight of the dye precursor. Is preferable, and addition of 50 to 300% by weight is particularly preferable.

The heat-sensitive recording material of the present invention generally comprises, on a support, an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting compound as main components, and these are dispersed and coated in a binder to obtain a heat-sensitive recording material. A recording layer is provided, and a thermal head, a thermal pen,
By heating with a laser beam or the like, a dye precursor and an electron-accepting compound react instantaneously to obtain a recorded image. JP-B-43-4160 and 45-14039.
It is disclosed in Japanese Patent Publication No. Further, the heat-sensitive recording layer contains a pigment,
Sensitizers, antioxidants, anti-sticking agents, etc. are added as necessary.

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

A specific example is as follows. (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 compounds: 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.

As the electron-accepting compound, at least one salicylic acid derivative represented by the general formula 1 or a metal salt thereof is used.
Although it is characterized by containing a seed, an electron-accepting compound can be used in combination within a range that does not impair the desired effects of the present invention. The electron-accepting compound that can be used in combination is not particularly limited as long as it is an acidic substance generally used in thermal paper.

For example, a polyvalent metal salt such as a phenol derivative, an aromatic carboxylic acid derivative, an N, N'-diarylthiourea derivative, or a zinc salt of an organic compound can be used.

Particularly preferred are phenol derivatives, 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, butyl 2,2-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, salicylanilide, 5-chlorosalicylanilide, salicylic acid, 3,5-di Examples include -tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4- [2 ′-(4-methoxyphenoxy) ethyloxy] salicylic acid, and metal salts of these salicylic acid derivatives.

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, an ultraviolet absorber such as a benzophenone-based or a benzotriazole-based, an antioxidant such as a hindered phenol compound, a surfactant, and a fluorescent dye 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, an overcoat layer is provided to protect the thermosensitive recording layer, or an undercoat layer composed of a single layer or a plurality of layers of pigments or resins is provided between the thermosensitive recording layer and the support. Various known techniques in can be used.

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

[0035]

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 Dye precursor 3-dibutylamino-6-methyl-7
30 parts of anilinofluorane were crushed with 70 parts of 2.5% aqueous solution of polyvinyl alcohol in a ball mill for 24 hours to obtain a dye dispersion liquid. Next, 40 parts of zinc 4-n-octyloxycarbonylaminosalicylate and 50 parts of 1,4-dibenzyloxybenzene were pulverized together with 210 parts of a 2.5% aqueous solution of polyvinyl alcohol in a Dynomill (sand mill manufactured by WEB) to obtain a volume average particle size. An electron-accepting compound dispersion liquid having a diameter of 2 μm or less was obtained. After mixing the above two kinds of dispersion liquids, the following components were added with stirring and mixed well to prepare a heat-sensitive coating liquid. 30% dye dispersion, 100 parts 30% electron-accepting compound dispersion, 300 parts 30% isocyanate compound dispersion, 100 parts 50% calcium carbonate aqueous dispersion, 100 parts 40% zinc stearate aqueous dispersion, 25 parts 10% polyvinyl alcohol aqueous solution, 200 parts water, 325 parts

(B) Preparation of heat-sensitive coated paper A coating solution having the following composition was smeared on a base paper having a basis weight of 40 g / m ^{2 so} as to have a solid content of 9 g / m ² , dried, and heat-sensitive coated. Craft paper was prepared. Calcined kaolin, 100 parts 50% styrene-butadiene latex aqueous dispersion, 24
Part 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. ,
A thermosensitive recording material was prepared by drying.

Example 2 A thermosensitive recording material was prepared in the same manner as in Example 1 except that zinc 4-phenyloxycarbonylaminosalicylate was used instead of zinc 4-n-octyloxycarbonylaminosalicylate in Example 1. .

Example 3 A thermosensitive recording material was prepared in the same manner as in Example 1 except that zinc 4-n-decyloxycarbonylaminosalicylate was used instead of zinc 4-n-octyloxycarbonylaminosalicylate in Example 1. It was made.

Example 4 A thermosensitive recording material was prepared in the same manner as in Example 1 except that p-benzoyloxybenzoic acid methyl ester was used instead of 1,4-dibenzyloxybenzene in Example 1.

Example 5 A thermosensitive recording material was prepared in the same manner as in Example 1 except that 4,4'-diallyloxydiphenyl sulfone was used instead of 1,4-dibenzyloxybenzene in Example 1.

Comparative Example 1 A thermosensitive recording material was prepared in the same manner as in Example 1 except that 1,4-dibenzyloxybenzene of Example 1 was omitted.

Comparative Example 2 A thermosensitive recording material was prepared in the same manner as in Example 1, except that the zinc 4-n-octyloxycarbonylaminosalicylate in Example 1 was changed to 2,2-bis (4-hydroxyphenyl) propane. It was made.

Comparative Example 3 A thermosensitive recording material was prepared in the same manner as in Example 1 except that the zinc 4-n-octyloxycarbonylaminosalicylate of Example 1 was changed to zinc 3,5-bis (α-methylbenzyl) salicylate. Was produced.

Comparative Example 4 A thermosensitive recording material was prepared in the same manner as in Example 1, except that 1,4-dibenzyloxybenzene in Example 1 was changed to 2-benzyloxynaphthalene.

The heat-sensitive recording materials prepared in Examples 1 to 5 and Comparative Examples 1 to 4 had a Beck smoothness of 40 on the heat-sensitive coated surface.
It was subjected to a calendar treatment for 0 to 500 seconds and then subjected to the following evaluations.

Evaluation: [Formation of image part] Facsimile testing machine TH- manufactured by Okura Electric Co., Ltd.
A printing test was conducted using PMD. A thermal head with a dot density of 8 dots / mm and a head resistance of 1290 Ω is used to print by energizing with a head voltage of 21 V and a pulse width of 1.0 ms, and the density of the color image is determined by a Macbeth densitometer RD918.
It was measured at. When the color density is 1.0 or more, the heat-sensitive recording material has sufficient thermal response.

[Heat resistance test of the background part] In the heat resistance test of the background part, the non-image area was left in a dryer at 80 ° C. for 30 minutes, and the optical density of the background part after standing was measured with a Macbeth densitometer RD918. It was measured. If the background density after the test is 0.2 or less, it can be said that the image recording can be sufficiently read and the heat-sensitive recording material has excellent heat resistance.

The storage characteristics of the image area were subjected to a lap resistance test and a moisture and heat resistance test. [Wrap resistance test of image part] In the lap resistance test, a commercially available lap is put on the printed part of each heat-sensitive recording material printed with a pulse of 1.0 millisecond, and a load of 2 g / cm <2> is applied from the top. The state of decoloring of the printed part after storage for 24 hours in an environment of ° C was visually judged. The results are shown in Table 1. ○ indicates that the printed portion remains almost without being erased, Δ indicates that the printed information is erasable but the print information can be read, and × indicates that it is printed. Most of the parts are decolored, indicating that it is difficult to read the print information.

[Moisture and heat resistance test of image part]
The printed part of each thermosensitive recording material printed with a pulse of 1.0 millisecond was treated for 24 hours in a thermo-hygrostat at 40 ° C. and a relative humidity of 90%, and the fading rate of the density of the printed part was measured. The fading rate was calculated by the following equation 1, and the results are shown in Table 1. If the fading rate is 80% or more, the storage characteristics are good.

[0052]

[Equation 1] Fading rate (%) = (printed portion density after test / printed portion density before test) × 100

[0053]

[Table 1]

As is clear from Table 1 above, the heat-sensitive recording materials of Examples 1 to 5 exhibit good thermal responsiveness and good image area storage characteristics. On the other hand, the thermal recording material of Comparative Example 1 has a poor thermal response, and Comparative Example 2 has a deterioration in image storability. Further, it is understood that Comparative Examples 3 and 4 have poor heat resistance in the background part.

[0055]

As is apparent from the examples, the salicylic acid derivative represented by the general formula 1 of the present invention or a metal salt thereof is used as an electron-accepting compound, and 1,4-dibenzyloxybenzene is used as a sensitizer. By containing at least one selected from p-benzoyloxybenzoic acid methyl ester and 4,4′-diallyloxydiphenyl sulfone, it is possible to obtain excellent thermal responsiveness and storage stability of the background and image areas, and A heat-sensitive recording material excellent in heat resistance could be obtained.

Claims (1)

[Claims] 1. A heat-sensitive recording material containing a normally colorless to light-colored dye precursor and an electron-accepting compound that reacts when heated to develop the color of the dye precursor. It contains at least one salicylic acid derivative represented by the general formula 1) or a metal salt thereof, and as a sensitizer, 1,4-dibenzyloxybenzene, p-
Benzoyloxybenzoic acid methyl ester, 4,4'-
A heat-sensitive recording material comprising at least one selected from diallyloxydiphenyl sulfone. Embedded image (In the formula, X ₁ and X ₂ represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a halogen atom, and R represents
It represents an alkyl group, an alkenyl group, an aralkyl group, or an aryl group. )