JP2000238437A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a heat-sensitive recording material of high sensitivity, good heat resistance and superior storage stability of a ground section and an image section. SOLUTION: A heat-sensitive recording material contains at least one kind of a derivative of alicyclic acid represented by the formula or its metal salt and also contains 4,4'-thio bis(6-t-butyl-m-cresol). In the formula, X1 and X2 represent a hydrogen atom, an alkyl, an aralkyl, an aryl or a halogen atom, and R represents an alkyl, an alkenyl, an aralkyl or an aryl.

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 high sensitivity, good heat resistance, and excellent storage stability of a background portion and an image portion.

[0002]

2. Description of the Related Art A thermosensitive recording material generally comprises a support provided with a thermosensitive recording layer mainly composed of an electron-donating, usually colorless or pale-colored dye precursor and an electron-accepting developer. By heating with a thermal head, a hot pen, a laser beam or the like, the dye precursor and the developer react instantaneously to obtain a recorded image.
It is disclosed in, for example, Japanese Patent Publication No. 14039. Such a heat-sensitive recording material has the advantages that recording can be obtained with a relatively simple device, maintenance is easy, and there is no generation of noise.Measurement recorder, facsimile, printer, computer terminal, It is used in a wide range of fields, such as label and ticket vending machines. Conventional heat-sensitive recording materials using an electron-donating colorless dye precursor and an electron-accepting compound have properties such as high color density, but the recorded image area comes in contact with plastics such as polyvinyl chloride. It has the drawback that the storage properties of recorded images are poor, such as discoloration due to penetration of plasticizers and additives contained in plastics, and discoloration upon contact with chemicals contained in foods and cosmetics. ,
Alternatively, it has a drawback that a writing mark is discolored when writing is performed on a ground portion with a writing instrument. At present, certain restrictions are imposed on its use, and improvement thereof has been strongly desired.

In order to improve 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. (Japanese Patent Laid-Open No. 62-16968)
No. 1, No. 63-22683, No. 63-959
No. 77)

[0004] However, the salicylic acid derivative described in the publication has insufficient storage characteristics of a color image or storage stability of a background portion, and further has low color development sensitivity and practical high speed. It was hard to say a thermosensitive recording material compatible with recording.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material having high sensitivity, good heat resistance, and excellent storage stability of a background portion and an image portion.

[0006]

Means for Solving the Problems The present inventor has made intensive studies to improve these drawbacks. As a result, an electron which normally reacts with a colorless or pale color dye precursor upon heating to form a color is obtained. The heat-sensitive recording material contains a salicylic acid derivative represented by the general formula 1 or a metal salt thereof as an electron-accepting compound, and comprises 4,4′-thiobis (6-t-butyl-). m-cresol).

[0007]

Embedded image (In the formula, X ₁ and X ₂ each 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.)

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the heat-sensitive recording material of the present invention will be described in detail. The heat-sensitive recording material of the present invention contains at least one salicylic acid derivative represented by the general formula 1 or a metal salt thereof as an electron-accepting compound;
A heat-sensitive recording material characterized by containing 4'-thiobis (6-t-butyl-m-cresol), having high sensitivity, good heat resistance, and excellent image storability in the background and the image area. Could be obtained.

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,
There are the following, but the present invention is not limited to these.

(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 Leoxycarbonylaminosalicylic acid (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-hexadecylioic acid 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-butyloxycarbonyl 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 general formula 1 according to the present invention, the metal salt contains a monovalent or higher valent metal salt such as sodium, potassium, lithium and the like. Alternatively, it is a water-insoluble divalent, trivalent or tetravalent metal salt, and more preferably a divalent or trivalent metal salt.

Specific examples of divalent, trivalent or tetravalent metal salts include zinc, cadmium, mercury, magnesium, calcium, barium, nickel, tin, gallium, chromium, copper, molybdenum, tungsten, zirconium, strontium, and manganese. , Cobalt, titanium, aluminum and iron salts, preferably zinc, calcium, barium, nickel, manganese, cobalt and aluminum salts. Particularly, a zinc salt is preferable. The salicylic acid derivative represented by the general formula 1 or a metal salt thereof may form a solvate such as a hydrate depending on the production conditions, and the solvate also forms an electron acceptor used in the thermosensitive recording material of the present invention. Suitable as an active compound.

The salicylic acid derivative represented by the general formula 1 or a metal salt thereof according to the present invention can be prepared by a known method (for example, J. Am.
Pharm. Sci. , 52, 927 (1963), B
ull. de. Socie. Chim. France,
1189 (1955). That is, for example, the aminosalicylic acid derivative can be suitably synthesized by allowing an approximately equivalent amount of a chloroformate compound to act on the derivative.

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

The compounding ratio of the salicylic acid derivative represented by the general formula 1 or its metal salt and 4,4'-thiobis (6-t-butyl-m-cresol) used in the present invention is as follows:
The range of 1: 0.1 to 1: 2 is preferred, and especially 1: 0.3
A range of １1: 1 is preferred.

The heat-sensitive recording material of the present invention generally comprises, on a support, a main component comprising an electron-donating, usually colorless or pale-colored dye precursor and an electron-accepting compound, which are dispersed and coated together with a binder to form a heat-sensitive recording material. By providing a layer and heating with a thermal head, a hot pen, a laser beam, or the like, the dye precursor and the electron-accepting compound react instantaneously to obtain a recorded image. -1403
No. 9 and other publications. Pigment,
A sensitizer, an antioxidant, an anti-sticking agent and the like are added as needed.

The dye precursor used in the heat-sensitive recording material of the present invention is typically, but not particularly limited to, those used in 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-dimethylindol-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 and the like.

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

(3) Xanthene compound: rhodamine B
Anilinolactam, rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-phenylfluoran, 3-diethylamino -7-chlorofluoran, 3
-Diethylamino-6-chloro-7-methylfluoran, 3-diethylamino-7- (3,4-dichloroanilino) fluoran, 3-diethylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6
Methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Anilinofluoran, 3-piperidino-6-methyl-7
-Anilinofluoran, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-phenethylfluoran,
3-diethylamino-7- (4-nitroanilino) fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilino Fluoran, 3- (N-
Ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran,
3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluoran and the like,

(4) Thiazine compounds: benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene 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 can be used alone or 2 It can be used by mixing more than seeds.

The heat-sensitive recording material of the present invention is characterized by containing at least one salicylic acid derivative represented by the general formula 1 or a metal salt thereof as an electron-accepting compound. Other electron-accepting compounds can be used in combination as long as they do not impair. The electron accepting compound that can be used in combination is generally represented by an acidic substance used in thermal paper, but is not particularly limited.

For example, phenol derivatives, aromatic carboxylic acids and derivatives thereof, N, N'-diarylthioureas,
A urea derivative such as N-sulfonylurea or a polyvalent metal salt thereof can be used in combination.

Specifically, p-phenylphenol, p
-Hydroxyacetophenone, 4-hydroxy-4'-
Methyldiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-
4'-benzenesulfonyloxydiphenyl sulfone,
1,1-bis (4-hydroxyphenyl) propane,
1,1-bis (4-hydroxyphenyl) pentane,
1,1-bis (4-hydroxyphenyl) hexane,
1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) cyclododecane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) ) Hexane, 2,2-bis (4-hydroxyphenyl) octane, 1,1-bis (4-hydroxyphenyl) -2-ethylhexane, 2,2-bis (3-chloro-4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,3-di- [2
-(4-hydroxyphenyl) -2-propyl] benzene, 1,3-di- [2- (3,4-dihydroxyphenyl) -2-propyl] benzene, 1,4-di- [2-
(4-hydroxyphenyl) -2-propyl] benzene, 4,4'-dihydroxydiphenyl ether, 4,
4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 3,3'-dichloro-
4,4'-dihydroxydiphenyl sulfone, 3,3 '
-Diallyl-4,4'-dihydroxydiphenylsulfone, 3,3'-dichloro-4,4'-dihydroxydiphenylsulfide, methyl 2,2-bis (4-hydroxyphenyl) acetate, 2,2-bis (4- (Hydroxyphenyl) butyl acetate, 4,4′-thiobis (2-t-butyl-5-methylphenol), benzyl p-hydroxybenzoate, chlorobenzyl p-hydroxybenzoate,
-Dimethyl hydroxyphthalate, benzyl gallate, stearyl gallate, salicylanilide, 5-chlorosalicylanilide, novolak phenol resin, modified terpene phenol resin, N, N'-di-m-chlorophenylthiourea, N- (p-toluene Sulfonyl) -N'-
Phenylurea, 3,5-di-t-butylsalicylic acid,
3,5-di-t-nonylsalicylic acid, 3,5-didodecylsalicylic acid, 3-methyl-5-t-dodecylsalicylic acid, 5-cyclohexylsalicylic acid, 3,5-bis (α, α-dimethylbenzyl) salicylic acid, 3-methyl-5- (α-methylbenzyl) salicylic acid and the like, and metal salts of zinc, nickel, aluminum, calcium and the like.

The binder used in the heat-sensitive recording material of the present invention includes starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
Gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer,
Water-soluble adhesives such as alkali salts of styrene / maleic anhydride copolymer, alkali salts of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylate, styrene / butadiene copolymer, acrylonitrile / Latexes such as butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer and the like can be mentioned.

The pigment used in the heat-sensitive recording material of the present invention includes diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide,
Examples include zinc oxide, silicon oxide, aluminum hydroxide, and urea-formalin resin.

In the heat-sensitive recording material of the present invention, a sensitizer can be added for the purpose of improving the thermal response. As the sensitizer, an organic compound having a melting point of 80C to 150C can be used. Specific examples include stearic acid amide,
Aliphatic amides such as N-hydroxymethylstearic acid amide, behenic acid amide, N-hydroxymethylbehenic acid amide, N-stearylstearic acid amide, ethylenebisstearic acid amide, 2-benzyloxynaphthalene, 4-benzylbiphenyl, Diphenyl adipate, dimethyl terephthalate, 1,2-bis (3,4-dimethylphenyl) ethane, m-tert-phenyl, dibenzyl oxalate, di (4-methylbenzyl) oxalate, di (4-methyl oxalate)
Chlorobenzyl), dibenzyl terephthalate, dimethyl phthalate and the like. The use amount of these sensitizers is not particularly limited, but is generally preferably adjusted in the range of about 50 to 500% by weight based on the electron-accepting compound.

In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearic acid amide, caster wax and the like for the purpose of preventing head wear and sticking. Further, a dispersant such as sodium dioctyl sulfosuccinate, an ultraviolet absorber such as a benzophenone type or a benzotriazole type, a surfactant, a fluorescent dye and the like are added as required.

As the support used in the present invention, paper is mainly used, but woven fabric, nonwoven fabric, plastic film, synthetic paper, metal foil and the like or a composite sheet combining these can be used arbitrarily. Further, in the production of heat-sensitive recording materials, for example, a protective layer is provided to protect the heat-sensitive recording layer, or a single layer or a plurality of intermediate layers made of pigment or resin are provided between the heat-sensitive recording layer and the support. Various known techniques can be used.

The coating amount of the heat-sensitive recording layer is usually suitably from 0.1 to 1.0 g / m ^{2 as the} coating amount of the dye precursor. 0.1
When the amount is less than g / m ² , sufficient coloring properties cannot be obtained, and when the amount is more than 1.0 g / m ^2, no improvement in coloring sensitivity is observed, and this is economically disadvantageous. is there.

[0036]

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

Example 1 1. Preparation of Intermediate Layer Calcined Kaolin (Ansilex, manufactured by EMC) 100 parts 50% Styrene butadiene-based latex aqueous dispersion 24 parts Water 200 parts is stirred and dispersed to prepare an intermediate layer coating liquid, and a solid content is applied to 40 g / m ² base paper. The composition was smeared to an amount of 9 g / m ² and dried to form an intermediate layer.

[0038] 2. Preparation of thermosensitive coloring layer [Preparation of solution A] 3-dibutylamino-6-methyl-7-anilinofluoran 30 parts 2.5% aqueous solution of polyvinyl alcohol 70 parts Solution A was prepared using Dynomill (manufactured by Shinmaru Enterprises). To a volume average particle size of 0.7 μm.

[Preparation of solution B] zinc 4-n-octyloxycarbonylaminosalicylate 40 parts 2-benzyloxynaphthalene 50 parts 4,4'-thiobis (6-t-butyl-m-cresol) 20 parts 2.5 Liquid B was crushed to a volume average particle size of 1.1 μm using a Dynomill (manufactured by Shinmaru Enterprises).

[Formation of thermosensitive coloring layer] 100 parts of solution A, 440 parts of solution B, 40% zinc stearate emulsion 25
, 100 parts of a 50% aqueous calcium carbonate dispersion, 200 parts of a 10% aqueous polyvinyl alcohol solution, and 280 parts of water were mixed and stirred to obtain a thermosensitive coloring layer coating liquid. The heat-sensitive coloring layer coating solution was smear-dried on the intermediate layer so as to have a solid content of 4 g / m ² , and then subjected to a super calender treatment to obtain a heat-sensitive recording material.

Example 2 Example 1 was repeated except that the amount of zinc 4-n-octyloxycarbonylaminosalicylate was changed to 50 parts and the amount of 4,4′-thiobis (6-tert-butyl-m-cresol) was changed to 10 parts. In the same manner as in Example 1, a thermosensitive recording material was produced.

Example 3 Example 3 was repeated except that zinc 4-n-octyloxycarbonylaminosalicylate was changed to 30 parts and 4,4′-thiobis (6-t-butyl-m-cresol) was changed to 30 parts. In the same manner as in Example 1, a thermosensitive recording material was produced.

Example 4 A heat-sensitive recording material was prepared in the same manner as in Example 1, except that zinc 4-n-octyloxycarbonylaminosalicylate was changed to zinc 4-phenyloxycarbonylaminosalicylate.

Example 5 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that zinc 4-n-octyloxycarbonylaminosalicylate was changed to zinc 4-n-decyloxycarbonylaminosalicylate. .

Comparative Example 1 Example 1 was repeated except that 4,4′-thiobis (6-tert-butyl-m-cresol) was changed to water.
In the same manner as in the above, a heat-sensitive recording material was produced.

Comparative Example 2 Example 4 was repeated except that 4,4′-thiobis (6-tert-butyl-m-cresol) was changed to zinc 4-n-octyloxycarbonylaminosalicylate (total amount: 60 parts). A thermosensitive recording material was produced in the same manner as in Example 1.

Comparative Example 3 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that zinc 4-n-octyloxycarbonylaminosalicylate was changed to 2,2-bis (4-hydroxyphenyl) propane. Was prepared.

Comparative Example 4 Thermal recording was performed in the same manner as in Example 1 except that zinc 4-n-octyloxycarbonylaminosalicylate was changed to zinc 3,5-di (α-methylbenzyl) salicylate. Materials were made.

Comparative Example 5 In Example 1, zinc 4-n-octyloxycarbonylaminosalicylate was converted to 4,4'-thiobis (6-t-
A heat-sensitive recording material was produced in the same manner as in Example 1 except that butyl-m-cresol) was changed to a total amount of 60 parts.

The heat-sensitive recording materials prepared in Examples 1 to 5 and Comparative Examples 1 to 5 were applied to the heat-sensitive coated surface having a Beck smoothness of 40.
After calendering for 0 to 500 seconds, the following evaluation was performed, and the results are shown in Table 1 below. In addition, each evaluation method is as follows.

[Coloring Density] A printing test was performed using a facsimile testing machine TH-PMD manufactured by Okura Electric. Using a thermal head with a dot density of 8 dots / mm and a head resistance of 1290 Ω, printing was performed by energizing with a head voltage of 21 V and a pulse width of 1.0 ms, and the color density was measured using a Macbeth densitometer RD
918.

[Heat-resistant ground color] The uncolored portion was left in an atmosphere of 60 ° C. for 24 hours and then measured with a Macbeth densitometer RD-918.

For the storage characteristics of the background, a writing instrument test was conducted. [Writing resistance test of background portion] In the writing resistance test, the uncolored portion was written with a fluorescent pen, and then the degree of discoloration of the uncolored portion after standing at room temperature for 72 hours was visually determined. The symbol “ほ と ん ど” shows little discoloration, and the symbol “X” shows that discoloration has occurred and it is dirty.

As for the storage characteristics of the image portion, a lap resistance test and a moist heat resistance test were performed. [Lap resistance test of image part] The lap resistance test is performed by placing a commercially available wrap on the image part of each thermosensitive recording material printed with a pulse of 1.0 millisecond, applying a load of 2 g / cm 2 from the top, and applying an environment of 40 ° C. The residual ratio of the image area after storage for 24 hours was measured. The larger the number, the better the image preservability,
Practically, 80% or more is desirable.

[Moisture and heat resistance test of image area]
The image area of each thermosensitive recording material printed with a pulse of 1.0 millisecond was processed in a thermo-hygrostat at 40 ° C. and 90% relative humidity for 24 hours, and the residual ratio of the image area was measured.

[0056]

[Table 1]

As shown in Table 1, the heat-sensitive recording materials of Examples 1 to 5 contain at least one salicylic acid derivative represented by the general formula 1 or a metal salt thereof as an electron-accepting compound. '-Thiobis (6-t-butyl-m
-Cresol) is particularly excellent in color density, heat resistance, and storability of the background portion and the image portion.

The heat-sensitive recording materials of Comparative Examples 1 and 2 were 4,
Since 4'-thiobis (6-t-butyl-m-cresol) is omitted, the color density is low. Since the heat-sensitive recording materials of Comparative Examples 3 and 4 use an electron-accepting compound other than the salicylic acid derivative or the metal salt thereof shown in the general paper 1 of the present invention, the storability of the background portion and the image portion is poor. In the heat-sensitive recording material of Comparative Example 5, since the salicylic acid derivative represented by the general formula 1 of the present invention or the metal salt thereof was omitted, the preservability of the background portion and the image portion was poor.

[0059]

As is clear from the heat-sensitive recording materials of the above Examples and Comparative Examples, the heat-sensitive recording material of the present invention has high sensitivity, good heat resistance, and excellent storage stability of the background portion and the image portion. Was something.

Claims (1)

[Claims] 1. A thermosensitive recording material containing a colorless or pale-colored dye precursor and an electron-accepting compound capable of reacting upon heating to form the dye precursor, wherein the electron-accepting compound is represented by the general formula 1. A heat-sensitive recording material comprising at least one salicylic acid derivative or a metal salt thereof, and 4,4'-thiobis (6-t-butyl-m-cresol). Embedded image (In the formula, X ₁ and X ₂ each 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.)