JPH06179290A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material having good thermal response by providing a thermal recording layer containing a dye precursor, a specific salicylic acid derivative or a metal salt thereof and a specific aliphatic amide compd. on a support. CONSTITUTION:A dye dispersion is prepared by dispersing a colorless or light- colored dye precursor in an aqueous soln. of a binder such as polyvinyl alcohol under stirring. A salicylic acid derivative expressed by formula I (wherein X is a divalent connection group, Y is an alkyl group or a halogen atom and R is a 4-18C alkyl group) or a metal salt thereof and an aliphatic amide compd. with the number of molecule constituting carbon atoms of 18 or more are dispersed in an aqueous soln. binder such as polyvinyl alcohol under stirring to prepare an electron acceptive compd. dispersion. Two kinds of these dispersions are mixed to prepare a coating soln. for a thermal recording layer and this coating soln. is applied to a support such as paper or a plastic film and dried to form the thermal recording layer, thus obtaining thermal recording material.

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 mainly composed of an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting developer. By heating with a thermal head, a heating pen, a laser beam or the like, a dye precursor and a developer react instantaneously to obtain a recorded image. JP-B-43-4160 and 45-45
No. 14039 is disclosed. Such a heat-sensitive recording material has the advantages that recording can be obtained with a relatively simple device, that maintenance is easy, and that noise is not generated, and measurement recorders, facsimiles, printers, computer terminals, It is used in a wide range of fields such as labels and ticket vending machines. Conventional thermal recording materials using an electron-donating colorless dye precursor and an electron-accepting substance have characteristics such as high color density, but on the other hand, the recorded image area is in contact with plastic such as polyvinyl chloride. And then erased by permeation of plasticizers and additives contained in the plastic,
It has the drawback of poor storage characteristics of recorded images, such as being erased by contact with chemicals contained in foods and cosmetics, or the discoloration of writing marks when writing with a writing instrument on the background. However, the present situation is that the application is subject to certain restrictions, and its improvement has been strongly desired. As a means for improving the storage characteristics of the recorded image part and the background part, a heat-sensitive recording using a salicylic acid derivative or a metal salt thereof having a substituent such as an alkyl group, an aralkyl group, an alkyloxy group and an acyl group as an electron accepting compound. Materials have been proposed. (JP-A-62-169681, JP-A-63-22683, JP-A-63-95977)

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]

DISCLOSURE OF THE INVENTION The present invention relates to a heat-sensitive recording material, and particularly to obtain a heat-sensitive recording material excellent in heat response and storage stability of the background portion and the image portion.

[0006]

A heat-sensitive recording material containing an electron-accepting substance which normally reacts with a colorless or light-colored dye precursor upon heating to develop a color of the dye precursor is represented by the following formula: Containing at least one salicylic acid derivative represented by (general formula 1) or a metal salt thereof,
By containing an aliphatic amide compound having a molecular constitutional carbon number of 18 or more, a heat-sensitive recording material excellent in heat response and storage stability of the background portion and the image portion can be obtained. Furthermore, by using 2-benzyloxynaphthalene together, a heat-sensitive recording material having further excellent thermal response could be obtained.

[0007]

[Chemical 2]

(In the formula, X represents a divalent linking group, Y represents a hydrogen atom, an alkyl group or a halogen atom, and R represents an alkyl group having 4 to 18 carbon atoms.)

The divalent linking group represented by X is, for example, an oxygen atom,> C = O, -COO-, -CONH-,
A group such as —NH— and —SO ₂ — is shown.

Specific examples of the salicylic acid derivative represented by the general formula 1 of the present invention or a metal salt thereof include, for example, those shown below, but the present invention is not limited thereto.

(1) 3-n-butyloxysalicylic acid (2) 3-n-pentyloxysalicylic acid (3) 3-n-hexyloxysalicylic acid (4) 3-cyclohexyloxysalicylic acid (5) 3-n-octyloxy Salicylic acid (6) 3-n-decyloxysalicylic acid (7) 3-n-dodecyloxysalicylic acid (8) 3-n-tetradecyloxysalicylic acid (9) 3-n-hexadecyloxysalicylic acid (10) 3-n- Octadecyloxysalicylic acid (11) 4-n-butyloxysalicylic acid (12) 4-n-pentyloxysalicylic acid (13) 4-n-hexyloxysalicylic acid (14) 4-cyclohexyloxysalicylic acid (15) 4-n-octyloxy Salicylic acid (16) 4-n-decyloxysalicylic acid (17) 4-n -Dodecyloxysalicylic acid (18) 4-n-tetradecyloxysalicylic acid (19) 4-n-hexadecyloxysalicylic acid (20) 4-n-octadecyloxysalicylic acid

(21) 5-n-butyloxysalicylic acid (22) 5-n-pentyloxysalicylic acid (23) 5-n-hexyloxysalicylic acid (24) 5-cyclohexyloxysalicylic acid (25) 5-n-octyloxy Salicylic acid (26) 5-n-decyloxysalicylic acid (27) 5-n-dodecyloxysalicylic acid (28) 5-n-tetradecyloxysalicylic acid (29) 5-n-hexadecyloxysalicylic acid (30) 5-n- Octadecyloxysalicylic acid (31) 6-n-butyloxysalicylic acid (32) 6-n-pentyloxysalicylic acid (33) 6-n-hexyloxysalicylic acid (34) 6-cyclohexyloxysalicylic acid (35) 6-n-octyloxy Salicylic acid (36) 6-n-decyloxysalicytic acid Acid (37) 6-n- dodecyloxy salicylic acid (38) 6-n- tetradecyloxy salicylic acid (39) 6-n- hexadecyloxy salicylic acid (40) 6-n- octadecyl-oxy salicylic acid

(41) 5-n-hexanoylsalicylic acid (42) 5-n-octanoylsalicylic acid (43) 3-n-hexanoyloxysalicylic acid (44) 3-n-octanoyloxysalicylic acid (45) 3- n-Decanoyloxysalicylic acid (46) 4-n-hexanoyloxysalicylic acid (47) 4-n-octanoyloxysalicylic acid (48) 4-n-decanoyloxysalicylic acid (49) 5-n-hexanoyloxysalicylic acid (50) 5-n-octanoyloxysalicylic acid (51) 5-n-decanoyloxysalicylic acid (52) 6-n-hexanoyloxysalicylic acid (53) 6-n-octanoyloxysalicylic acid (54) 6-n -Decanoyloxysalicylic acid (55) 5-n-octanesulfonylsalicylic acid (5 ) 3-n-hexylaminosalicylic acid (57) 3-n-octylaminosalicylic acid (58) 3-n-decylaminosalicylic acid (59) 3-n-octadecylaminosalicylic acid (60) 4-n-hexylaminosalicylic acid (61) ) 4-n-octylaminosalicylic acid (62) 4-n-decylaminosalicylic acid (63) 4-n-dodecylaminosalicylic acid (64) 3-n-octanoylaminosalicylic acid (65) 3-n-decanoylaminosalicylic acid (66) 4-n-octanoylaminosalicylic acid (67) 3-n-decanoylaminosalicylic acid

In the metal salt of the salicylic acid derivative represented by the general formula 1 of the present invention, the metal salt is sodium,
It contains a monovalent metal salt such as potassium or lithium, but is preferably a sparingly water-soluble or water-insoluble divalent, trivalent or tetravalent metal salt, more preferably a divalent or trivalent metal salt. Is a metal salt of.

Specific examples of the divalent, trivalent or tetravalent metal salt include zinc, cadmium, mercury, magnesium, calcium, barium, nickel, tin, gallium, chromium,
Copper, molybdenum, tungsten, zirconium, strontium, manganese, cobalt, titanium, aluminum, iron salts can be mentioned, preferably zinc,
It is a salt of calcium, barium, nickel, manganese, cobalt and aluminum. A zinc salt is particularly preferable.

The number of carbon atoms constituting the molecule according to the present invention is 18
As the above aliphatic amide compound,
Those represented by 5 and 6 are preferable.

[0017]

[Chemical Formula 3] R ₁ CONH ₂

[0018]

[Chemical Formula 4] R ₂ CONHR ₃

[0019]

[Chemical Formula 5] R ₄ CONHR ₅ NHOCR ₄

[0020]

Embedded image R ₆ NHOCR ₇ CONHR ₆

In the above Chemical Formulas 3 to 6, R ₁ , R ₂ , R ₄ , R
₆ represents an alkyl group or an alkenyl group. R ₃ represents an alkyl group, an alkenyl group or a hydroxymethyl group. R ₅ and R ₇ represent a divalent linking group.

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 ethylenebisstearin. Acid amide, hexamethylenebisoleic acid amide, butylenebisstearic acid amide, hexamethylenebisstearic acid amide, N, N '
-Dioleyl sebacic acid amide, N, N'-dioleyl adipic acid amide, N, N'-distearyl sebacic acid amide, N, N'-distearyl adipic acid amide, etc. are mentioned. These may be used alone or as a mixture.

The amide compound according to the present invention has the general formula 1
It is preferable to use 10 to 300% by weight, and more preferably 20 to 200% by weight, of the salicylic acid derivative shown in (4).

The 2-benzyloxynaphthalene of the present invention can be used in combination with the amide compound of the present invention to further enhance the thermal response, and is used in an amount of 10 to 400% by weight based on the salicylic acid derivative represented by the general formula 1. It is preferable to use 20 to 200% by weight, and further preferable to use. The heat-sensitive recording material according to 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 in a binder.
By coating and providing a heat-sensitive recording layer and heating with a thermal head, a heating pen, a laser beam or the like, a dye precursor and an electron-accepting compound are instantly reacted to obtain a recorded image. JP-B-43-4160 JP-A-45-14039 and the like. Further, the heat-sensitive recording layer contains a pigment, a sensitizer,
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.

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-tetrahydrofuryl) amino-
6-methyl-7-anilinofluorane, etc.,

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

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

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 for 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 of ethylene / vinyl acetate copolymer and the like.

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, polyethylene oxide and castor wax, and dioctylsulfosuccinic acid. A dispersant such as sodium, a benzophenone-based or benzotriazole-based ultraviolet absorber, a surfactant, a fluorescent dye, and the like are added as necessary.

As the support used in the present invention, paper is mainly used, but non-woven fabric, plastic film,
Synthetic paper, metal foil, or a composite sheet in which these are combined can be arbitrarily used. In addition, 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, and the like. Various known techniques in manufacturing can be used.

The coating amount of the heat-sensitive recording layer is determined by the amounts of the dye precursor, which is a color-forming component, and the electron-accepting compound, and a dye coating amount of 0.1 to 1.0 g / m ² is usually suitable.

The amount of the electron-accepting compound is 5 to 400% by weight based on the dye precursor.
A preferable addition amount is 00% by weight. The compound of the present invention is added to the electron-accepting compound in an amount of 5 to 400% by weight, preferably 20 to 300% by weight.

[0039]

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

Example 1 Preparation of heat-sensitive recording material (A) Preparation of heat-sensitive coating liquid Dye precursor 3-dibutylamino-6-methyl-7
35 parts of anilinofluorane were crushed with 80 parts of a 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-octyloxysalicylate and 60 parts of stearic acid amide were pulverized together with 300 parts of a 2.5% aqueous solution of polyvinyl alcohol in a Dynomill (sand mill manufactured by WEB) to obtain an electron accepting property of a volume average particle diameter of 2 μm or less. A compound dispersion was obtained. After mixing the above two kinds of dispersions, the following components were added with stirring and mixed well to prepare a heat-sensitive coating liquid. 30% Dye dispersion 115 parts 25% Electron-accepting compound dispersion 400 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 smeared on a base paper having a basis weight of 40 g / m ² to a solid content of 9 g / m ² , dried, and heat-sensitive coated. I made engineering paper. 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 . 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-n-octyloxysalicylate was replaced with zinc 4-n-butyloxysalicylate.

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

Example 4 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that zinc 4-n-octanoylsalicylate was replaced with zinc 4-octyloxysalicylate of Example 1.

Example 5 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that zinc 4-n-octyloxysalicylate was replaced with zinc 4-n-octanoyloxysalicylate.

Example 6 A thermosensitive recording material was prepared in the same manner as in Example 1 except that zinc 4-n-octylaminosalicylate was used instead of zinc 4-n-octyloxysalicylate of Example 1.

Example 7 A thermosensitive recording material was prepared in the same manner as in Example 1 except that behenic acid amide was used instead of stearic acid amide in Example 1.

Example 8 Instead of the stearic acid amide in Example 1, N-
A thermosensitive recording material was prepared in the same manner as in Example 1 except that hydroxymethylstearic acid amide was used.

Example 9 Instead of the stearic acid amide in Example 1, N-
A thermosensitive recording material was prepared in the same manner as in Example 1 except that hydroxymethylbehenamide was used.

Example 10 Example 1 was repeated except that ethylenebisstearic acid amide was used instead of the stearic acid amide in Example 1.
A thermal recording material was prepared in the same manner as in.

Example 11 Instead of the stearic acid amide in Example 1, N-
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that stearyl stearic acid amide was used.

Example 12 Instead of the stearamide in Example 1, N,
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that N'-dioleyl sebacic acid amide was used.

Comparative Example 1 A thermosensitive recording material was prepared in the same manner as in Example 1 except that the stearic acid amide in Example 1 was not added.

Comparative Example 2 Instead of the stearic acid amide in Example 1, 2-
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that benzyloxynaphthalene was used.

Comparative Example 3 A thermosensitive recording material was prepared in the same manner as in Example 1 except that palmitic acid amide was used instead of stearic acid amide in Example 1.

Comparative Example 4 A thermosensitive recording material was prepared in the same manner as in Example 1 except that lauric acid amide was used instead of stearic acid amide in Example 1.

Comparative Example 5 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that 2,4-bis (4-hydroxyphenyl) propane was used instead of zinc 4-octyloxysalicylate in Example 1. Created.

Example 13 The thermosensitive recording material was prepared in the same manner as in Example 1 except that 50 parts of stearic acid amide and 10 parts of 2-benzyloxynaphthalene were used instead of 60 parts of stearic acid amide in Example 1. It was created.

Example 14 A thermosensitive recording material was prepared in the same manner as in Example 1 except that 10 parts of stearic acid amide and 50 parts of 2-benzyloxynaphthalene were used instead of 60 parts of stearic acid amide in Example 1. It was created.

Example 15 The same as Example 1 except that 60 parts of stearic acid amide in Example 1 was replaced with 10 parts of N-hydroxymethylstearic acid amide and 50 parts of 2-benzyloxynaphthalene. A thermosensitive recording material was prepared.

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 with a dot density of 8 dots / mm and a head resistance of 185Ω is used to print by energizing with a head voltage of 12 V, a pulse width of 0.7 and 1.0 millisecond, and a coloring density of Macbeth RD-918 type reflection densitometer. It was measured at. The results are shown in Tables 1 and 2.

For the storage characteristics of the background, a heat resistance test and a writing instrument test were conducted.

[Heat resistance test of the 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 larger the value is, the larger the color of the background is and the more dirty it is.

[Burning resistance test on the background part] In the writing resistance test, after writing the non-image area with a highlighter pen, the stain on the non-image area was visually determined after standing for 72 hours at room temperature. ◯ indicates almost no stain, x indicates that color development has occurred, and Δ indicates an intermediate between ◯ and x. The results are shown in Tables 1 and 2.

For the storage characteristics of the image area, a lap resistance test and a writing tool test were performed.

[Wrap resistance test of image part] In the lap resistance test, a commercially available wrap was put on the printed part of each thermal recording material printed with the pulse of 1.0 msec used in the evaluation of the color development property, and 2 g / sq. The state of decolorization of the printed part after the load was applied and the sample was stored in an environment of 40 ° C. for 24 hours was visually judged. ○ indicates that the printed portion remains almost without being erased, × indicates that the printed portion is almost erased and it is difficult to read the print information, and Δ indicates ○ and ×.
Shows the middle of.

[Writing resistance test for image area] The writing resistance test was performed after writing with a highlighter pen on the printing portion of each thermal recording material printed with the pulse of 1.0 msec used in the evaluation of the color development test.
The decolored state of the printed part after standing for 72 hours at room temperature was visually evaluated. ○ indicates that the printed area remains almost without being erased, × indicates that the printed area is almost erased, and it is difficult to read the print information. △ indicates the middle of ○ and ×. Is shown. The results are shown in Tables 1 and 2.

[0070]

[Table 1]

[0071]

[Table 2]

As is apparent from the examples, the electron-accepting compound represented by the general formula 1 of the present invention and the number of carbon atoms constituting the molecule are 18
By containing the above aliphatic amide compound, a heat-sensitive recording material having excellent thermal responsiveness and the storage stability of the background portion and the image portion can be obtained, and by further using 2-benzyloxynaphthalene together, A heat-sensitive recording material excellent in heat response was obtained.

Claims (2)

[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. A heat-sensitive recording material comprising at least one salicylic acid derivative represented by 1) or a metal salt thereof, and an aliphatic amide compound having a molecular number of carbon atoms of 18 or more. [Chemical 1] (In the formula, X represents a divalent linking group, Y represents a hydrogen atom, an alkyl group or a halogen atom, and R represents a carbon number of 4 to 18
Represents an alkyl group. ) 2. The heat-sensitive recording material according to claim 1, which contains 2-benzyloxynaphthalene.