JPH05124349A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having excellent preservation properties and high thermal responsiveness. CONSTITUTION:The subject thermal recording material consists of a thermal recording layer containing an aromatic isocyanate compound and an imino compound which becomes tinted through a chemical reaction with said isocyanate compound formed on a support. In addition, at least, one type of indole or its derivatives is added to the material as a sensitizer for improving the thermal responsiveness.

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 which has excellent image storability and good thermal response.

[0002]

2. Description of the Related Art In recent years, heat-sensitive recording materials for recording with heat energy have been used in a wide range of fields such as printers and recorders for various measuring instruments, printers for labels, printers for POS, and automatic ticket vending machines such as tickets. It started to come.

However, the conventional heat-sensitive recording material using the electron-donating colorless dye precursor and the electron-accepting developer has a good appearance, a good feel, a high color density, and various colored hues can be obtained. On the other hand, the recorded image part (thermosensitive color part) comes into contact with plastic such as polyvinyl chloride and disappears due to plasticizers and additives contained in the plastic, or There is a drawback in that the preservability of the record is poor, such that it easily disappears when it comes into contact with chemicals contained in foods and cosmetics, or it is easily faded by exposure to sunlight for a short time. In view of this point, as a heat-sensitive recording material capable of reacting when two components are heated to obtain a recorded image with good storability, JP-A-58-38733, JP-A-58-54085, and JP-A-58-54085 are disclosed. 58-10
Japanese Patent No. 4959 discloses a heat-sensitive recording material whose two components include an isocyanate compound and an imino compound.

However, the heat-sensitive recording material containing the imino compound and the isocyanate compound has a drawback that it is inferior in thermal response (sensitivity). Various sensitizers have been studied in order to improve the thermal response, but the thermal response is still insufficient.

[0005]

An object of the present invention is to improve the thermal responsiveness (sensitivity) of a thermal recording material containing an imino compound and an isocyanate compound which are excellent in image storability.

[0006]

A thermosensitive recording material comprising a support and a thermosensitive recording layer containing an aromatic isocyanate compound and an imino compound that develops a color upon reacting with the isocyanate compound is provided on a support. By incorporating at least one indole or its derivative as a sensitizer for improving the above-mentioned (1), a heat-sensitive recording material excellent in thermal response could be obtained.

The indole derivative referred to in the present invention means that the carbon atoms constituting the indole ring do not necessarily have to be unsaturated. Therefore, indole derivatives include compounds such as oxindole in which carbon atoms constituting the ring are partially saturated.

Preferred as the indole or its derivative in the present invention are the compounds represented by the formulas 1-2.

[0009]

[Chemical 1]

In the chemical formula 1, R ¹ and R ² are each an alkyl group, aralkyl group, aryl group, alkoxy group, aryloxy group, aralkyloxy group, halogen atom, hydrogen, hydroxy group, hydroxyalkyl group, formyl group, carbamoyl. Group, alkylcarbonyl group, aralkylcarbonyl group, arylcarbonyl group, alkylcarbonyloxy group, aralkylcarbonyloxy group, arylcarbonyloxy group, alkyloxycarbonyl group, aralkyloxycarbonyl group, aryloxycarbonyl group, which are different from each other. May be the same.

[0011]

[Chemical 2]

In Chemical formula 2, R ¹ and R ² are the same as those in Chemical formula 1. R
³ represents an oxygen atom or an alkylene group.

Specific examples of the indole or its derivative in the present invention include indole, 3-acetoxy-5-bromoindole, 3-acetylindole, 5-benzyloxyindole and indole-2.
-Ethyl carboxylate, 3-indolyl acetate, 3-
Carbamoyl-2-methylindole, 4-chloroindole, 5-chloroindole, 6-chloroindole, 1,2-dimethylindole, 2,5-dimethylindole, 2,3-dimethylindole, 1-ethyl-
2-phenylindole, 4-hydroxyindole,
5-hydroxyindole, indole-3-aldehyde, 2- (3-indole) ethanol, 5-methoxyindole, 5-methoxy-2-methylindole, N
-Methylindole, 2-methylindole, 3-methylindole, 5-methylindole, 1-methyl-2
-Phenylindole, 2-phenylindole, oxindole and the like can be mentioned, but the present invention is not limited thereto.

The amount of indole or its derivative used in the present invention is 5 with respect to the aromatic isocyanate compound.
˜400 wt%, preferably 10-300 wt%. If it is less than 5% by weight, good thermal response cannot be obtained,
When it is 0% by weight or more, a dilution effect occurs, and similarly good thermal response cannot be obtained.

The aromatic isocyanate compound used in the present invention refers to a colorless or light-colored aromatic isocyanate compound or heterocyclic isocyanate compound which is solid at room temperature, and for example, one or more of the following may be used.

2,6-dichlorophenyl isocyanate, p-chlorophenyl isocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1,3-dimethylbenzene-4,6-diisocyanate, 1,4-dimethylbenzene-2,5-diisocyanate, 1-methoxybenzene-2,4-diisocyanate, 1-methoxybenzene-2,5-diisocyanate, 1-ethoxybenzene-2,4- Diisocyanate, 2,5-dimethoxybenzene-1,4-diisocyanate, 2,5-diethoxybenzene-1,4-diisocyanate, 2,5-dibutoxybenzene-1,4
-Diisocyanate, azobenzene-4,4'-diisocyanate, diphenyl ether-4,4'-diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, naphthalene-
2,6-diisocyanate, naphthalene-2,7-diisocyanate, 3,3'-dimethyl-biphenyl-4,
4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenyldimethylmethane-4,4'-diisocyanate, benzophenone-
3,3'-diisocyanate, fluorene-2,7-diisocyanate, anthraquinone-2,6-diisocyanate, 9-ethylcarbazole-3,6-diisocyanate, pyrene-3,8-di Isocyanate, naphthalene-1,3,7-triisocyanate, biphenyl-
2,4,4'-triisocyanate, 4,4 ', 4 "-
Triisocyanate-2,5-dimethoxytriphenylamine, p-dimethylaminophenylisocyanate,
Examples include tris (4-phenylisocyanate) thiophosphate. These isocyanate compounds may be used in the form of so-called block isocyanate, which is an addition compound with phenols, lactams, oximes, etc., if necessary, and a diisocyanate dimer,
For example, it may be used in the form of isocyanurate, which is a dimer or trimer of 1-methylbenzene-2,4-diisocyanate, or used as a polyisocyanate adducted with various polyols. Is also possible.

The imino compound used in the present invention is a compound represented by the general formula 3 (φ is an aromatic compound residue capable of forming a conjugated system with an adjacent C═N), which is solid at room temperature. It is a colorless or pale compound.

[0018]

[Chemical 3]

(1) 1,3-Diiminoisoindolines: 1,3-Diiminoisoindoline, 1,3-Diimino-4,5,5
6,7-Tetrachloroisoindoline, 1,3-Diimino-6-methoxyisoindoline, 1,3-Diimino-
6-cyanoisoindoline, 1,3-diimino-4,7
-Dithia-5,5,6,6-tetrahydroisoindoline, 1-phenylimino-3-iminoisoindoline,
1- (3'-chlorophenylimino) -3-iminoisoindoline, 1- (2 ', 5'-dichlorophenylimino) -3-iminoisoindoline, 1- (2', 4 ',
5'trichlorophenylimino) -3-iminoisoindoline, 1- (2'-cyano-4'-nitrophenylimino) -3-iminoisoindoline, 1- (2'-chloro-5'-cyanophenylimino) -3-iminoisoindoline, 1- (2 ', 6'-dichloro-4'-nitrophenylimino) -3-iminoisoindoline, 1-
(2 ', 5'-Dimethoxyphenylimino) -3-iminoisoindoline, 1- (2', 5'-diethoxyphenylimino) -3-iminoisoindoline, 1- (2 '
-Methyl-4'-nitrophenylimino) -3-iminoisoindoline, 1- (5'-chloro-2'-phenoxyphenylimino) -3-iminoisoindoline, 1-
(4'-N, N-dimethylaminophenylimino) -3
-Iminoisoindoline, 1- (3'-N, N-dimethylamino-4'-methoxyphenylimino) -3-iminoisoindoline, 1- (2'-methoxy-5'-N-
Phenylcarbamoylphenylimino) -3-iminoisoindoline, 1- (2'-chloro-5'-trifluoromethylphenylimino) -3-iminoisoindoline, 1- (5 ', 6'-dichlorobenzothiazolyl −
2'-imino) -3-iminoisoindoline, 1-
(6'-methylbenzothiazolyl-2'-imino) -3
-Iminoisoindoline, 1- (4'-phenylaminophenylimino) -3-iminoisoindoline, 1-
(P-phenylazophenylimino) -3-iminoisoindoline, 1- (naphthyl-1′-imino) -3-iminoisoindoline, 1- (anthraquinone-1′-imino) -3-iminoisoindoline, 1- (5'-chloroanthraquinone-1'-imino) -3-iminoisoindoline, 1- (N-ethylcarbazolyl-3'-imino) -3-iminosoindoline, 1- (naphthoquinone-
1'-imino) -3-iminoisoindoline, 1- (pyridyl-4'-imino) -3-iminoisoindoline,
1- (benzimidazolone-6'-imino) -3-iminoisoindoline, 1- (1'-methylbenzimidazolone-6'-imino) -3-iminoisoindoline, 1
-(7'-Chlorobenzimidazolone-5'-imino)
-3-iminoisoindoline, 1- (benzimidazolyl-2'-imino) -3-iminoisoindoline, 1-
(Benzimidazolyl-2'-imino) -3-imino-
4,5,6,7-tetrachloroisoindoline, 1-
(2 ', 4'-Dinitrophenylhydrazone) -3-iminoisoindoline, 1- (indazolyl-3'-imino) -3-iminoisoindoline, 1- (indazolyl-3'-imino) -3-imino- 4,5,6,7-Tetrabromoisoindoline, 1- (indazolyl-3'-
Imino) -3-imino-4,5,6,7-tetrafluoroisoindoline, 1- (benzimidazolyl-2'-
Imino) -3-imino-4,7-dithiatetrahydroisoindoline, 1- (4 ', 5'-dicyanoimidazolyl-2'-imino) -3-imino-5,6-dimethyl-
4,7-pyradiisoindoline, etc.

(2) 3-iminoisoindoline-1-ones: 3-iminoisoindoline-1-one, 3-imino-4,5,6,7-tetrachloroisoindoline-1
-One, 3-imino-4,5,6,7-tetrabromoisoindoline-1-one, 3-imino-4,5,6,7
-Tetrafluoroisoindoline-1-one, 3-imino-5,6-dichloroisoindoline-1-one, 3-
Imino-4,5,7-trichloro-6-methoxyisoindoline-1-one, 3-imino-4,5,7-trichloro-6-methoxyisoindoline-1-one, 3-imino-4,5,5 7-Trichloro-6-methylmercaptoisoindoline-1-one, 3-imino-6-nitroisoindoline-1-one, 1-iminonaphthalimide, 1-iminodiphenimide, 3-iminoisoindoline-1-spiro -Dioxolane, 1,1-dimethoxy-3-iminoisoindoline, 1,1-diethoxy-
3-imino-4,5,6,7-tetrachloroisoindoline, 1-ethoxy-3-iminoisoindoline, 3-
Imino-2-methyl-4,5,6,7-tetrachloroisoindoline-1-one, 1- (cyanocarbomethoxymethylene) -3-iminoisoindoline, 1- (cyanocarboethoxymethylene) -3-imino Isoindoline, 7-amino-2,3-dimethyl-5-oxopyrrolo [3,4b] pyrazine, 7-amino-2,3-diphenyl-5-oxopyrrolo [3,4b] pyrazine, and the like,

(3) 3-iminoisoindolines: 1-
(Cyanobenzoylmethylene) -3-iminoisoindoline, 1- (cyanocarbamidomethylene) -3-iminoisoindoline, 1- (cyano-N-phenylcarbamoylmethylene) -3-iminoisoindoline, 1- [cyano-N -(3'-Methylphenyl) carbamoylmethylene] -3-iminoisoindoline, 1- [cyano-N
-(4'-chlorophenyl) carbamoylmethylene]-
3-iminoisoindoline, 1- [cyano-N- (4 '
-Methoxyphenyl) -carbamoylmethylene] -3-
Iminoisoindoline, 1- [cyano-N- (3'-chloro-4'-methylphenyl) -carbamoylmethylene] -3-iminoisoindoline, 1- (cyano-p-
Nitrophenylmethylene) -3-iminoisoindoline, 1- (dicyanomethylene) -3-iminoisoindoline, 1- (cyano-1 ′, 2 ′, 4′-triazolyl- (3 ′)-carbamoylmethylene) -3 -Iminoisoindoline, 1- (cyanothiazoyl- (2 ')-carbamoylmethylene) -3-iminoisoindoline, 1-
(Cyanobenzimidazolyl- (2 ')-carbamoylmethylene-3-iminoisoindoline, 1- (cyanobenzothiazolyl- (2')-carbamoylmethylene)-
3-iminoisoindoline, 1-[(cyanobenzimidazolyl-2 ')-methylene] -3-iminoisoindoline, 1-[(cyanobenzimidazolyl-2') methylene] -3-imino-4,5,6 , 7-Tetrachloroisoindoline, 1-[(cyanobenzimidazolyl-
2 ')-methylene] -3-imino-5-methoxyisoindoline, 1-[(cyanobenzimidazolyl-2')
-Methylene] -3-imino-6-chloroisoindoline, 1-[(1'-phenyl-3'-methyl-5-oxo) -pyrazolidene-4 ']-3-iminoisoindoline, 1-[(cyano Benzimidazolyl-2 ')-methylene] -3-imino-4,7-dithiatetrahydroisoindoline, 1-[(cyanobenzimidazolyl-
2 ')-Methylene] -3-imino-5,6-dimethyl-
4,7-pyradiisoindoline, 1-[(1'-methyl-3'-n-butyl) -barbituric acid-5 ']-3-iminoisoindoline and the like,

(4) 3-imino-1-sulfobenzoic acid imides: 3-imino-1-sulfobenzoic acid imide, 3-
Imino-1-sulfo-6-chlorobenzoic acid imide, 3-
Imino-1-sulfo-5,6-dichlorobenzoic acid imide, 3-imino-1-sulfo-4,5,6,7-tetrachlorobenzoic acid imide, 3-imino-1-sulfo-4,
5,6,7-Tetrabromobenzoic acid imide, 3-imino-1-sulfo-4,5,6,7-tetrafluorobenzoic acid imide, 3-imino-1-sulfo-6-nitrobenzoic acid imide, 3- Imino-1-sulfo-6-methoxybenzoic acid imide, 3-imino-1-sulfo-4,5,7-trichloro-6-methylmercaptobenzoic acid imide, 3-
Imino-1-sulfonaphthoic acid imide, 3-imino-1
-Sulfo-5-bromonaphthoic acid imide, etc., and two or more kinds of imino compounds can be used in combination depending on the purpose.

The amount of the aromatic isocyanate compound used is not particularly limited as long as it reacts with the imino compound and a color image is obtained, but it is preferably contained in an amount of 1% by weight or more based on the imino compound. Preferably 5 to 1
It is 000% by weight.

Paper is mainly used as a support for the heat-sensitive recording material of the present invention. In addition to paper, various non-woven fabrics, woven fabrics, synthetic resin films, laminated papers, synthetic papers, metal foils and the like, or these A composite sheet obtained by combining the above can be arbitrarily used according to the purpose.

The layer structure of the heat-sensitive recording layer may be a single layer or a multilayer structure. In the case of multiple layers, an intermediate layer may be interposed between each layer, and the intermediate layer may be composed of a plurality of layers. A protective layer may be provided on the heat-sensitive recording layer, or an intermediate layer may be provided between the heat-sensitive recording layer and the support. In this case, each of the protective layer and the intermediate layer may be composed of a single layer or a plurality of layers of two layers or three layers or more. Further, a back coat layer may be provided on the surface of the support opposite to the surface on which the heat-sensitive recording layer is provided for the purpose of preventing curling and charging.

The heat-sensitive recording layer can be obtained by mixing the respective aqueous dispersions obtained by finely pulverizing the respective color-forming components with a binder and the like, coating on a support and drying. In this case, for example, each color-forming component may be contained in one layer to form a multilayer structure.

The sensitizer for improving the thermal response is usually contained in the heat-sensitive recording layer together with each color-forming component and the binder. When each color-forming component is contained one by one to form a multilayer structure, It does not necessarily have to be contained in all layers constituting the thermal recording layer. Also, a sensitizer layer may be provided separately.

In the heat-sensitive recording material of the present invention, other heat-fusible substances can be used alone or in combination.
Those having a melting point of 60 ° C. to 180 ° C. are preferable, and those having a melting point of 80 ° C. to 140 ° C. are particularly preferable. For example, benzyl p-benzyloxybenzoate, stearic acid amide, palmitic acid amide, N-methylol stearic acid amide, β-naphthylbenzyl ether, N-stearyl urea, N, N′-distearyl urea, β-
Naphthoic acid phenyl ester, β-naphthol (p-methylbenzyl) ether, 1,4-dimethoxynaphthalene, 1-methoxy-4-benzyloxynaphthalene, N
-Stearoyl urea, 4-benzyl biphenyl, 1,
2-di (m-methylphenoxy) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1,4-butanediol phenyl ether, dimethyl terephthalate and the like can be mentioned.

Further, the heat-sensitive recording material of the present invention may contain an aniline derivative having at least one amino group, which is shown in the international application PCT / JP81 / 00300 by the applicant of the present invention. More effective.

Specific examples include (1) monoanilines: methyl p-aminobenzoate, p
-Ethyl aminobenzoate, -n-propyl p-aminobenzoate, -iso-propyl p-aminobenzoate, butyl p-aminobenzoate, dodecyl p-aminobenzoate, p
-Benzyl aminobenzoate, o-aminobenzophenone, m-aminoacetophenone, p-aminoacetophenone, m-aminobenzamide, o-aminobenzamide, p-aminobenzamide, p-amino-N-methylbenzamide, 3-amino-4 -Methylbenzamide,
3-amino-4-methoxybenzamide, 3-amino-
4-chlorobenzamide, p- (N-phenylcarbamoyl) aniline, p- [N- (4-chlorophenyl) carbamoyl] aniline, p- [N- (4-aminophenyl) carlvamoyl] aniline, 2-methoxy-5
(N-phenylcarbamoyl) aniline, 2-methoxy-5- [N- (2'-methyl-3'-chlorophenyl)
Carbamoyl] aniline, 2-methoxy-5- [N-
(2'-Chlorophenyl) carbamoyl] aniline, 5
-Acetylamino-2-methoxyaniline, 4-acetylaminoaniline, 4- (N-methyl-N-acetylamino) aniline, 2,5-diethoxy-4- (N-benzoylamino) aniline, 2,5-dimethoxy -4-
(N-benzoylamino) aniline, 2-methoxy-4
-(N-benzoylamino) -5-methylaniline, 4
-Sulfamoylaniline, 3-sulfamoylaniline, 2- (N-ethyl-N-phenylaminosulfonyl) aniline, 4-dimethylaminosulfonylaniline, 4-diethylaminosulfonylaniline, sulfathiazole, 4-aminodiphenylsulfone , 2-chloro-5-N-phenylsulfamoylaniline, 2-methoxy-5-N, N-diethylsulfamoylaniline, 2,5-dimethoxy-4-N-phenylsulfamoylaniline, 2-methoxy -5-benzylsulfonylaniline, 2-phenoxysulfonylaniline, 2-
(2'-chlorophenoxy) sulfonylaniline, 3-
Anilinosulfonyl-4-methylaniline and the like,

(2) Bisanilines: Bis [4- (m-
Aminophenoxy) phenyl] sulfone, bis [4-
(P-Aminophenoxy) phenyl] sulfone, bis [3-methyl-4- (p-aminophenoxy) phenyl] sulfone, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dimethyl- 4,4'-diaminobiphenyl, 2,2'-dichloro-4,4'-diamino-5,5'-dimethoxybiphenyl, 2,2 ',
5,5'-Tetrachloro-4,4'-diaminobiphenyl, ortho-sortidine sulfone, 2,4'-diaminobiphenyl, 2,2'-diaminobiphenyl, 4,4'-
Diaminobiphenyl, 2,2'-dichloro-4,4'-
Diaminobiphenyl, 3,3'-dichloro-4,4'-
Diaminobiphenyl, 2,2'-dimethyl-4,4'-
Diaminobiphenyl, 4,4'-thiodianiline, 2,
2'-dithiodianiline, 4,4'-dithiodianiline, 3,4'-diaminodiphenyl ether, 4,4 '
-Diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, bis (3-
Amino-4-chlorophenyl) sulfone, bis (4-aminophenyl) sulfone, bis (3-aminophenyl)
Sulfone, 3,4'-diaminodiphenyl sulfone,
3,3′-diaminodiphenylmethane, 4,4′-ethylenedianiline, 4,4′-diamino-2,2′-dimethyldibenzyl, 4,4′-diamino-3,3′-dichlorodiphenylmethane, 3, 3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3
-Aminophenoxy) benzene, 9,9-bis (4-aminophenyl) fluorene, 2,2-bis (4-aminophenoxyphenyl) propane, 4,4'-bis (4-
Aminophenoxy) diphenyl, etc.

(3) Phenylenediamines: bis (3,3
4-diaminophenyl) sulfone, 3,3 ′, 4,4 ′
-Tetraaminodiphenyl ether, 3,3 ', 4,
4'-tetraaminodiphenyl sulfone, 3,3 ',
4,4'-tetraaminobenzophenone and the like can be mentioned.

Further, in the heat-sensitive recording layer, pigments such as diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and others. For the purpose of preventing head abrasion, sticking, etc., higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearic acid amide and castor wax, and dioctylsulfosuccinic acid. A dispersant such as sodium acid salt, a benzophenone-based or benzotriazole-based ultraviolet absorber, a surfactant, a fluorescent dye, and the like may be contained.

[0034]

The present invention will be described in more detail with reference to the following examples.

Example 1 15 g of 1,3-diimino-4,5,6,7-tetrachloroisoindoline was added to a 1% aqueous solution of polyvinyl alcohol 6
Grind with 0g in a ball mill for 24 hours, and
10 g of 4 ', 4 "-triisocyanato-2,5-dimethoxytriphenylamine was pulverized with 40 g of a 1% aqueous solution of polyvinyl alcohol in a ball mill for 24 hours to obtain a dispersion. Further, 5-benzyloxyindole (melting point: 1
(00 ° C) 25 g of 1% aqueous solution of polyvinyl alcohol 12
Dispersion was carried out in the same manner with 5 g to obtain a dispersion liquid. After mixing these three types of dispersions, 40% aqueous dispersion of calcium carbonate 125
g, 30% aqueous dispersion of zinc stearate 50 g, 10%
A polyvinyl alcohol aqueous solution (135 g) and water (90 g) were added and sufficiently stirred to obtain a coating liquid. This coating solution was applied onto a base paper having a basis weight of 50 g / m ² so as to obtain a coating amount of 5.2 g / m ² in terms of solid content, dried and then treated with a super calendar to obtain a heat-sensitive recording material. Obtained.

Examples 2-5 Instead of 5-benzyloxyindole used in Example 1, ethyl indole-2-carboxylate (Example 2, melting point 122 ° C.) and 2,5-dimethylindole (Example) were used, respectively. A thermosensitive recording material was prepared in the same manner as in Example 1 except that Example 3, melting point 112 ° C), 3-indolyl acetate (Example 4, melting point 128 ° C), and oxindole (Example 5, melting point 125 ° C) were used. Obtained.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the 5-benzyloxyindole of Example 1 was not used.

Test 1 (coloring density = thermoresponsiveness) The thermal recording materials obtained in Examples 1 to 5 and Comparative Example 1 were applied with 0.9 msec and 1.2 applied pulses using a thermal facsimile printing tester, respectively. Printing was performed under the condition of an applied voltage of 12.0 V for milliseconds, and the density of the obtained color image was measured using a densitometer Macbeth RD918. The results are shown in Table 1.
It was shown to.

Test 2 (Plasticizer resistance = image storability) The heat-sensitive recording materials obtained in Examples 1 to 5 and Comparative Example 1 were each overlaid with a vinyl chloride sheet, and a load of 300 g / m ² was applied thereto at 40 ° C. After storing for 24 hours in the atmosphere described above, the density of the color-developed portion was measured in the same manner as in Test 1. The image residual rate was calculated according to the following formula 1. As a result, the image residual rates of the thermal recording materials obtained in Examples 1 to 5 and Comparative Example 1 were all 100%.

[0040]

[Equation 1] A = (B / C) × 100 A: Image residual ratio (%) B: Density of image area after test C: Density of image area before test

[0041]

[Table 1]

[0042]

By using the compound according to the present invention, a heat-sensitive recording material having excellent image storability and thermal responsiveness can be obtained.

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[Procedure amendment]

[Submission date] December 25, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

[0011]

[Chemical 2]

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing an aromatic isocyanate compound and an imino compound, wherein the heat-sensitive recording material contains at least one indole or a derivative thereof.