JPH07101156A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material excellent in thermal response and also excellent in the storage stability of both 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. allowing a dye precursor to develop a color and further adding l, l-bis(4-hydroxyphenyl)cyclohexane. CONSTITUTION:In a thermal recording material containing a usually colorless or light-colored dye presursor and an electron acceptive compd. reacting with the dye precursor at the time of heating to allow the dye presursor to develop a color, as the electron acceptive compd., at least one kind of a salicylic acid presursor represented by formula wherein X1 and X2 are H, 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 and, further 1,1-bis(4-hydroxyphenyl)cyclohexane is added. As a result, the thermal recording material excellent in heat response and also excellent in the storage stability of a background part and an image part can be obtained.

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 which is excellent in heat responsiveness and storage stability of a background portion and an image portion.

[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, ticket vending machines, etc. Conventional thermal recording materials using an electron-donating colorless dye precursor and an electron-accepting compound have characteristics such as high color density, but on the other hand, the recorded image area is different from plastic such as polyvinyl chloride. It has the disadvantage that the storage characteristics of the recorded image are poor, such as the contact image is erased by permeation of plasticizers and additives contained in the plastic, and the product is erased by contact with chemicals contained in foods and cosmetics. Or, it has the drawback that the writing traces become discolored when writing with a writing instrument on the background part, and it is the current situation that there are certain restrictions on its use, and its improvement is strongly desired. It was

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, more particularly, to obtaining a heat-sensitive recording material excellent in thermal response and storage stability of the background portion and the image portion.

[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 2 (general formula 1) or a metal salt thereof as an electron-accepting compound, and by incorporating 1,1-bis (4-hydroxyphenyl) cyclohexane, thermal responsiveness can be improved. Also, a heat-sensitive recording material having excellent storage stability in the background and image areas could be obtained. Further, as a sensitizer, a melting point of 80 to 150
Even better thermal response can be obtained by adding an organic compound at ℃, but among them, 2-benzyloxynaphthalene was found to be particularly good.

[0007]

[Chemical 2] (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:
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. Alternatively, it is a 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, 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.

Further, the 1,1-bis (4-hydroxyphenyl) cyclohexane of the present invention is excellent in the storage stability of the background portion as compared with other phenol compounds, and is excellent when used together with the above salicylic acid derivative. It is possible to obtain a heat-sensitive recording material which is excellent in heat responsiveness and has excellent storage characteristics in the background portion and the image portion.

Further, by adding an organic compound having a melting point of 80 ° C. to 150 ° C., a better thermal response can be obtained. Some specific examples of these compounds include stearic acid amide, N-hydroxymethylstearic acid amide, behenic acid amide, N-hydroxymethylbehenic acid amide, N-stearyl stearic acid amide, and ethylenebisstearic acid amide. Aliphatic amides, 2-benzyloxynaphthalene, 4-benzylbiphenyl, diphenyl adipate, dimethyl terephthalate, 1,2-
Examples thereof include bis (3,4-dimethylphenyl) ethane, m-terphenyl, dibenzyl oxalate, di (4-methylbenzyl) oxalate, di (4-chlorobenzyl) oxalate, dibenzyl terephthalate, and dimethyl phthalate. However, 2-benzyloxynaphthalene exhibits the most excellent properties in terms of heat response and heat resistance of the background. These compounds may be used alone or in combination of two or more kinds.

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, 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.

Specific examples are 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 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, Further, a dispersant such as sodium dioctylsulfosuccinate, an ultraviolet absorber such as a benzophenone-based or a benzotriazole-based, 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,
A synthetic paper, a metal foil, or a composite sheet in which these are combined can be arbitrarily used. Further, in order to protect the heat-sensitive recording layer, an overcoat layer is provided, or an undercoat layer composed of a single layer or a plurality of layers of pigments or resins is provided between the heat-sensitive recording layer and the support. Various known techniques in manufacturing 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. 0.1
When the amount is less than g / m ² , sufficient color forming properties cannot be obtained, and when the amount is more than 1.0 g / m ² , the color developing sensitivity is not improved, which is economically disadvantageous. is there. The amount of the salicylic acid derivative represented by the general formula 1 is based on the dye precursor.
It is added in an amount of 5 to 400% by weight, and a particularly preferable amount is 20 to 300% by weight. The addition amount of 1,1-bis (4-hydroxyphenyl) cyclohexane is preferably 20 to 400% by weight based on the dye precursor.

[0031]

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 pulverized with 70 parts of 2.5% aqueous solution of polyvinyl alcohol in a ball mill for 24 hours to obtain a dye dispersion. Next, 40 parts of zinc 4-n-octyloxycarbonylaminosalicylate and 30 parts of 1,1-bis (4-hydroxyphenyl) cyclohexane were pulverized together with 210 parts of 2.5% aqueous polyvinyl alcohol solution in a Dynomill (sand mill manufactured by WEB), An electron-accepting compound dispersion liquid having a volume average particle 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 25% electron acceptor compound dispersion 280 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 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 solution prepared in (A) was smeared on the surface of the heat-sensitive coated paper prepared in (B) so that the solid content was 4 g / m ^2. Then, it was 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 133 parts of a 30% aqueous dispersion of 2-benzyloxynaphthalene was further added in the preparation of the thermosensitive coating liquid in Example 1. .

Example 3 A thermosensitive recording material was prepared in the same manner as in Example 1 except that zinc 4-n-octyloxycarbonylaminosalicylate in Example 2 was replaced with zinc 4-n-decyloxycarbonylaminosalicylate. Was produced.

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 2. did.

Example 5 Example 2 was repeated except that stearamide was used instead of 2-benzyloxynaphthalene in Example 2.
A thermal recording material was prepared in the same manner as in.

Example 6 A thermosensitive recording material was prepared in the same manner as in Example 2 except that oxalic acid dibenzyl ester was used instead of 2-benzyloxynaphthalene in Example 2.

Comparative Example 1 Thermal recording was carried out in the same manner as in Example 1 except that 1,1-bis (4-hydroxyphenyl) cyclohexane in Example 1 was changed to 2,2-bis (4-hydroxyphenyl) propane. The material was made.

Comparative Example 2 Thermal recording was conducted in the same manner as in Example 2 except that 1,1-bis (4-hydroxyphenyl) cyclohexane in Example 2 was changed to 2,2-bis (4-hydroxyphenyl) propane. The material was made.

Comparative Example 3 A thermosensitive recording material was prepared in the same manner as in Example 2 except that 1,1-bis (4-hydroxyphenyl) cyclohexane of Example 2 was omitted.

Comparative Example 4 A thermosensitive recording material was prepared in the same manner as in Example 2 except that the zinc 4-n-octyloxycarbonylaminosalicylate of Example 2 was omitted.

Comparative Example 5 A thermosensitive recording material was prepared in the same manner as in Example 2 except that the zinc 4-n-octyloxycarbonylaminosalicylate of Example 2 was changed to zinc 3,5-di (α-methylbenzyl) salicylate. Was produced.

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 heat resistance test and a writing tool test were conducted.

[Heat resistance test of background part] In the heat resistance test, the whiteness of each heat-sensitive recording material after being stored at 60 ° C. for 24 hours was measured by a Macbeth RD-918 type reflection densitometer. The results are shown in Table 1. The larger the value, the greater the color development of the background part, and the more dirty it is.

[Underwriting Writing Instrument Test on the Background] In the writing instrument test, after writing the non-image area with a highlighter pen, the stain on the non-image area 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 portion were subjected to a lap resistance test. [Wrap resistance test of image part] In the lap resistance test, a commercially available wrap was put on the printed part of each heat-sensitive recording material printed with a pulse of 1.0 millisecond used for evaluation of color development property, and 2 g / cm from the top.
A load of ² was applied, and the state of decoloration of the printed portion after storage for 24 hours in an environment of 40 ° C. was visually determined. A circle indicates that the printed portion remains almost without being decolored, and a cross indicates that the printed portion is almost decolored, making it difficult to read the print information.

[0051]

[Table 1]

[0052]

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 1,1-bis (4-hydroxyphenyl) cyclohexane is used. By using it, a heat-sensitive recording material excellent in heat response and storage stability of the background portion and the image portion could be obtained. Furthermore, by using 2-benzyloxynaphthalene as a sensitizer, it was possible to improve the color forming characteristics without increasing the heat fog on the background.

Claims (2)

[Claims] 1. A heat-sensitive recording material containing an usually colorless to light-colored dye precursor and an electron-accepting compound that reacts when heated to develop the color of the dye precursor. Contains at least one salicylic acid derivative represented by the formula 1) or a metal salt thereof, and
A heat-sensitive recording material containing 1-bis (4-hydroxyphenyl) cyclohexane. [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
It represents an alkyl group, an alkenyl group, an aralkyl group, or an aryl group. ) 2. The heat-sensitive recording material according to claim 1, which contains 2-benzyloxynaphthalene as a sensitizer.