JPH07117360A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve thermal response and the storage stability of a background part and an image part by adding a specific salicylic acid derivative or a metal salt thereof and d specific compd. as an electron acceptive compd. reacting with a dye precursor at the time of heating to develop a color. CONSTITUTION:A thermal recording material contains a usually colorless or light-colored dye precursor and an electron acceptive compd. reacting with the dye precursor at the time of heating to develop a color. In this case, as the electron acceptive compd., a salicylic acid derivative represented by general formula I (X1 and X2 are each a hydrogen atom, an alkyl group, an aralkyl group or the like and R is an alkyl group, an alkenyl group or the like) or a metal salt thereof and a compd. represented by formula II (R1 is a hydrogen atom, an alkyloxy group or the like, R2 is a hydrogen atom or an acetyl group and R3 is a hydrogen atom or an alkyl group) are added.

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 thermal responsiveness and excellent storage stability in the background and image areas.

[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.

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.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material having excellent thermal responsiveness and excellent storage stability in the background and image areas.

[0006]

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,
By containing at least one salicylic acid derivative represented by Chemical formula 3 (general formula 1) or a metal salt thereof as an electron-accepting compound and at least one compound selected from chemical formula 4 (general formula 2) It was possible to obtain a heat-sensitive recording material having excellent storage stability in the background and image areas.

[0007]

[Chemical 3] (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.)

[Chemical 4] (In the formula, R ₁ represents a hydrogen atom, an alkyl group, an alkyloxy group or a halogen atom, R ₂ represents a hydrogen atom or an acetyl group, and R ₃ represents a hydrogen atom or an alkyl 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:
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-butyloxycarboni 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 general formula 1 according to the present invention, the metal salt contains a monovalent metal salt such as sodium, potassium or lithium, but is preferably sparingly soluble in water or Water insoluble 2
It is a valent, 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 and manganese. , Cobalt, titanium, aluminum and iron salts can be mentioned, but zinc, calcium, barium, nickel, manganese, cobalt and aluminum salts 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 the metal salt thereof according to the present invention can be prepared by a known method {for example, J.
Pharm. Sci. , 52, 927 (1963), B
all. de. Socie. Chim. France,
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 represented by the general formula 1 or a metal salt thereof according to the present invention is 20 to 20% based on the dye precursor.
Addition of 500% by weight is preferable, and addition of 50 to 300% by weight is particularly preferable.

Further, as the compound represented by the general formula 2 of the present invention, acetanilide, acetoacetanilide, o
-Acetotoluidine, p-acetotoluidine, o-acetanisidine, p-acetanisidine, N-methylacetanilide, o-chloroacetoacetanilide, p-chloroacetoacetanilide and the like can be mentioned.

The compound represented by the general formula 2 is preferably added in an amount of 10 to 500% by weight of the dye precursor, and more preferably 20 to 30%.
Addition of 0% by weight is preferred. Further, an organic compound having a melting point of 80 ° C. to 150 ° C. can be used together for the purpose of further improving the thermal response. Some specific examples are aliphatic amides such as stearic acid amide, N-hydroxymethylstearic acid amide, behenic acid amide, N-hydroxymethylbehenic acid amide, N-stearyl stearic acid amide, and ethylene bisstearic acid amide. , 2-benzyloxynaphthalene, 4-benzylbiphenyl, diphenyl adipate, dibenzyl terephthalate, 1,2-bis (3,4-dimethylphenyl) ethane, m-terphenyl, dibenzyl oxalate, di (4-methyl oxalate) Benzyl), di (4-chlorobenzyl) oxalate, 1,2-bis (3-methylphenoxy) ethane and the like.

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, which are dispersed and coated in a binder to obtain a heat-sensitive recording. By providing a layer and heating with a thermal head, a thermal pen, a laser beam, etc., the dye precursor and the electron-accepting compound react instantaneously to obtain a recorded image,
It is disclosed in Japanese Examined Patent Publication Nos. 43-4160 and 45-14039. Further, a pigment, a sensitizer, an antioxidant, an anti-sticking agent, etc. are added to the heat-sensitive recording layer as needed.

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 can be mentioned, and these can be used alone or 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 phenol derivative, an aromatic carboxylic acid derivative, an N, N'-diarylthiourea derivative, a polyvalent metal salt such as 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, stearic acid amide and castor wax, A dispersant such as sodium dioctylsulfosuccinate, an ultraviolet absorber such as a benzophenone type or a benzotriazole type, 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, etc., or a composite sheet in which these are combined can be arbitrarily used. In addition, an overcoat layer may be provided to protect the heat-sensitive recording layer, or an undercoat layer composed of a single layer or a plurality of layers of pigments or resins may be provided between the heat-sensitive recording layer and the support. Various known techniques in the art can be used.

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 dye precursor.

[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 3-dibutylamino-6-methyl-7 which is a dye precursor
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, 50 parts and 50 parts of acetanilide were pulverized together with 270 parts of a 2.5% aqueous solution of polyvinyl alcohol in a Dynomill (sand mill manufactured by WEB) to obtain an electron acceptor having a volume average particle diameter of 2 μm or less. A dispersion of the organic compound 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 25% electron acceptor compound dispersion 360 parts 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 coating solution having the following composition was applied to a base paper having a basis weight of 40 g / m ^{2 so} that the solid coating amount was 9 g / m ² , and dried. A heat-sensitive coated 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 solution prepared in (A) was applied onto the surface of the heat-sensitive coated paper prepared in (B) so that the solid content coating amount was 4 g / m ^2. It was worked and dried to prepare a heat-sensitive recording material.

Example 2 A thermosensitive recording material was prepared in the same manner as in Example 1 except that o-acetotoluidine was used instead of acetanilide in Example 1.

Example 3 A thermosensitive recording material was prepared in the same manner as in Example 1 except that p-acetanisidine was used instead of acetanilide in Example 1.

Example 4 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 5 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.

Comparative Example 1 A thermosensitive recording material was prepared in the same manner as in Example 1 except that the acetanilide 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-di (α-methylbenzyl) salicylate. It was made.

The heat-sensitive recording materials prepared in the above Examples and Comparative Examples were calendered so that the Bekk smoothness of the heat-sensitive coated surface was 400 to 500 seconds, and then subjected to the following evaluations.

Evaluation: [Evaluation of color development characteristics] Okura Electric Facsimile Testing Machine TH
-Printing test was performed using PMD. A thermal head having a dot density of 8 dots / mm and a head resistance of 1290 Ω was used to conduct printing with a head voltage of 21 V and a pulse width of 1.0 ms, and the color density was measured with a Macbeth RD-918 type reflection densitometer. The results are shown in Table 1.

For the storage characteristics of the background, a writing resistance test was conducted. [Burning resistance test on the background part] In the writing resistance test, after writing the non-image part with a highlighter, the stain on the non-image part after standing for 72 hours at room temperature was visually determined. ◯ indicates that there is almost no stain, and x indicates that stain has occurred due to color development. The results are shown in Table 1.

The storage characteristics of the image area were subjected to a lap resistance test. [Wrap resistance test of image part] In the lap resistance test, the printed part of each thermal recording material printed with a pulse of 1.0 millisecond is covered with a commercially available wrap, and a load of 2 g / square centimeter is applied from above to an environment of 40 ° C. The state of decoloration of the printed portion after storage for 24 hours was visually determined. The results are shown in Table 1, in which ◯ indicates that the printed portion remained without being erased, and ×
Indicates that the printed portion is almost decolored and it is difficult to read the printed information.

[0050]

[Table 1]

As shown in Table 1, the heat-sensitive recording materials of Examples 1 to 5 have high color-developing characteristics and excellent storage characteristics in the background and image areas. On the other hand, it can be seen that Comparative Example 1 has poor color development characteristics, and Comparative Examples 2 and 3 have poor storage characteristics in the background and image areas.

[0052]

As is apparent from the examples, by using the salicylic acid derivative represented by the general formula 1 of the present invention or a metal salt thereof as an electron accepting compound and using the compound represented by the general formula 2, It was possible to obtain a heat-sensitive recording material having excellent responsiveness and excellent storage stability in the background and image areas.

Claims (1)

[Claims] 1. A heat-sensitive recording material containing an electron-accepting compound that normally reacts with a colorless or light-colored dye precursor when heated to cause the dye precursor to develop a color. Containing at least one salicylic acid derivative represented by 1) or a metal salt thereof, and
A heat-sensitive recording material comprising a compound represented by (general formula 2). [Chemical 1] (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.) (In the formula, R ₁ represents a hydrogen atom, an alkyl group, an alkyloxy group or a halogen atom, R ₂ represents a hydrogen atom or an acetyl group, and R ₃ represents a hydrogen atom or an alkyl group.)