JPH0592664A - Thermal recording material - Google Patents

Abstract

(57) [Summary] [Object] To provide a heat-sensitive recording material excellent in image storability, which has improved sensitivity (heat response) while improving discoloration of the background due to light. A heat-sensitive recording material comprising an aromatic isocyanate compound, at least one imino compound having a> C = NH group which develops a color upon heating, a fluorane dye and a phenol compound, wherein the fluorane dye is used. Is represented by Chemical formula 1. [Chemical 1] However, R1 and R2 both represent an alkyl group or an alkoxyalkyl group, and at least one of them has 3 or more carbon atoms. R3 represents a lower alkyl group or a lower alkoxy group. R4 and R5 represent hydrogen, halogen, an alkyl group or an alkoxy group.

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 suppresses discoloration of the background (unprinted portion) due to light and has improved sensitivity (heat response) and excellent image storability.

[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 colorless dye precursor and an electron-accepting developer as main components. By heating with a pen, laser light, etc., the colorless dye precursor and the developer react instantaneously to obtain a recorded image. JP-B-43-4160 and JP-B-45-14039
It is disclosed in Japanese Patent Publication No.

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. A recording recorder for measurement, a facsimile, a printer, It is used in a wide range of fields such as computer terminals, labels, ticket vending machines, etc.

A heat-sensitive recording material using such an electron-donating colorless dye precursor and an electron-accepting color developer has a good appearance.
While it has excellent properties such as good feel, high color density, and various color hues, the thermosensitive color part (recorded image part) contacts plastic such as polyvinyl chloride The storability of records is such that it disappears due to plasticizers and additives contained in, or easily disappears by contact with chemicals contained in foods and cosmetics, or fading easily after exposure to sunlight for a short time. It has the drawback of being inferior, and due to this drawback, its application is subject to certain restrictions, and its improvement is strongly desired.

As a heat-sensitive recording material capable of reacting when two components are heated to obtain a recorded image with good storage stability, for example, JP-A-58-54085 and JP-A-58-104 are known.
959, JP-A-58-149388, JP-A-59-
No. 1,158,87, JP-A-59-115888, and US Pat. No. 4,521,793.
A heat-sensitive recording material whose components are an imino compound and an isocyanate compound is disclosed.

The heat-sensitive recording materials comprising these imino compounds and isocyanate compounds are very excellent in the storability of recorded images, but their sensitivity (thermoresponsiveness) is poor. To improve the sensitivity of this heat-sensitive recording material, JP-A-61-1 is used.
Japanese Patent No. 10586 discloses a heat-sensitive recording material comprising four components of an aromatic isocyanate, an imino compound, a specific fluorane dye and an alkylcarbonylaminophenol or an alkylaminocarbonylphenol compound, but the sensitivity is still insufficient. This is sufficient, and a recent high-speed facsimile or a printing device such as a printer cannot obtain a recorded image with sufficient density. In addition, JP-A-59-
Japanese Patent No. 135186 discloses a heat-sensitive recording material composed of an aromatic isocyanate, an imino compound, a leuco dye and an acidic substance that develops a color by reacting with the leuco dye. However, it is possible to broaden the selection range of hues for color development. It is intended, and the sensitivity is not sufficient. In addition, the fogging of the background is also bad, which is a practical problem. In addition to these, JP-A-60
-262686, Japanese Patent Application Laid-Open No. 2-103180 and Japanese Patent Application No. 4-4159898 disclose a heat-sensitive recording material comprising three components of an aromatic isocyanate, an imino compound and a specific fluorane compound. However, the sensitivity is not sufficient for practical use.

[0007]

The heat-sensitive recording material of the present invention solves these problems, improves the discoloration of the background due to light and improves the sensitivity (heat response), and is excellent in image storability. The present invention is intended to provide a heat-sensitive recording material.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that at least one> C═NH that develops a color when reacted with an aromatic isocyanate compound under heat. By using the fluorane-based dye represented by Chemical Formula 1 in the heat-sensitive recording material composed of the imino compound having a group, the fluorane-based dye and the phenol compound, the intended heat-sensitive recording material could be produced.

Examples of the fluorane dye represented by Chemical formula 1 are 3- (methyl-n-propylamino) -6-methyl-7-anilinofluorane and 3-methylcyclohexylamino-6-methyl-7-anilino. Fluoran, 3-ethylisopropylamino-6-methyl-7-anilinofluorane, 3-ethylisobutylamino-6-methyl-
7-anilinofluorane, 3-ethylisopentylamino-6-methyl-7-anilinofluorane, 3-di-n
-Butylamino-6-methyl-7-anilinofluorane, 3-di-isobutylamino-6-methyl-7-anilinofluorane, 3-di-n-pentylamino-6-methyl-7-anilino Fluoran, 3-n-decyl-cyclohexylamino-6-methyl-7-anilinofluorane, 3-n-dodecyl-cyclohexylamino-6-methyl-7-anilinofluorane, 3- (N-methyl- N
-3'-Ethoxypropylamino) -6-methyl-7-
Anilinofluorane, 3- (N-ethyl-N-3′-ethoxypropylamino) -6-methyl-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7
-(4'-methylanilino) fluorane, 3-di-n-
Butylamino-6-methyl-7- (4'-n-butylanilino) fluorane, 3-di-n-butylamino-6-
Methyl-7- (2 ', 6'-dimethylanilino) fluorane, 3-di-n-butylamino-6-methyl-7-
(4'-Ethoxyanilino) fluorane, 3-di-n-
Butylamino-6-methyl-7- (2'-chloroanilino) fluorane, 3-di-n-butylamino-6-methyl-7- (2'-fluoroanilino) fluorane, 3-
Examples thereof include di-n-butylamino-6-methoxy-7-anilinofluorane. One type of these fluoran dyes or a plurality of types are used depending on the purpose.

The fluoran dye according to the present invention is usually added in an amount of 1% by weight or more based on the imino compound. It is preferably 5 to 300% by weight, particularly 10 to 2
00 is preferable. If the addition amount is less than 1% by weight, sufficient sensitivity cannot be obtained, and if it is more than 300% by weight, the sensitivity and the background fogging are not significantly improved, which is economically disadvantageous.

Examples of the phenol compound include 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane and 2,2-bis (4).
-Hydroxyphenyl) pentane, 2,2-bis (4-
Hydroxyphenyl) heptane, 1,1-bis (4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) butyl acetate, bis (4-hydroxyphenyl) benzyl acetate, bis (4-hydroxyphenyl)
Sulfone, bis (3-methyl-4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-4'-methylphenyl sulfone, 3-chloro-4-hydroxyphenyl-4'-methylphenyl sulfone, 3,4-dihydroxyphenyl- 4'-methylphenyl sulfone, 4-isopropylphenyl-4'-hydroxyphenyl sulfone, 4-isopropyloxyphenyl-4'-hydroxyphenyl sulfone, bis (2-allyl-4-hydroxyphenyl) sulfone, 4-hydroxyphenyl- 4 '
-Benzyloxyphenyl sulfone, 4-isopropylphenyl-4'-hydroxyphenyl sulfone, bis (2-methyl-3-tert.-butyl-4-hydroxyphenyl) sulfide, ethyl 4-hydroxybenzoate,
Benzyl 4-hydroxybenzoate, 4-hydroxybenzoic acid (4'-chlorobenzyl), 1,2-bis (4'-
Ethyl hydroxybenzoate, 1,5-bis (4'-hydroxybenzoic acid) pentyl, 1,6-bis (4'-hydroxybenzoic acid) hexyl, dimethyl 3-hydroxyphthalate, stearyl gallate, lauryl gallate. And so on. The amount of phenolic compound added is
It is preferably 50% by weight or more and 250% by weight or less with respect to the fluoran dye. If it is less than 50% by weight, the fluoran compound cannot develop color completely, resulting in no sensitivity.
Even if it exceeds 5% by weight, no significant improvement effect on sensitivity and background fog is recognized, which is economically disadvantageous.

The aromatic isocyanate compound used in the present invention is a colorless or light-colored aromatic isocyanate compound or a heterocyclic isocyanate compound which is solid at room temperature. For example, one or more of the following isocyanate compounds are used. Be done.

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'-dimethylbiphenyl-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-diisocyanate , Naphthalene-
1,3,7-triisocyanate, biphenyl-2,
4,4′-triisocyanate, 4,4 ′, 4 ″ -triisocyanate-2,5-dimethoxytriphenylamine, p-dimethylaminophenylisocyanate, tris (4-phenylisocyanato) thiophosphate, etc. There is.

If desired, these isocyanate compounds may be used in the form of so-called block isocyanates, which are addition compounds with phenols, lactams, oximes, etc., and diisocyanate dimers. For example, it may be used in the form of isocyanurate which is a dimer and trimer of 1-methylbenzene-2,4-diisocyanate, or is used as a polyisocyanate adducted with various polyols. It is also possible.

The imino compound used in the present invention is a compound represented by Chemical formula 2, which is a colorless or light-colored compound which is solid at room temperature. A specific example is shown below. It is also possible to use two or more kinds of imino compounds in combination depending on the purpose.

[0016]

[Chemical 2] However, in Chemical formula 2, φ represents an aromatic compound residue capable of forming a conjugated system with the adjacent C = N.

3-iminoisoindoline-1-one, 3
-Imino-4,5,6,7-tetrachloroisoindoline-1-one, 3-imino-4,5,6,7-tetrabromoisoindoline-1-one, 3-imino-4,5,5
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-methylmercapto-isoindoline-1-one, 3-imino-6-nitroisoindoline-
1-one, 3-imino-isoindoline-1-spiro-
Dioxolane, 1,1-dimethoxy-3-iminoisoindoline, 1,1-diethoxy-3-imino-4,5,5
6,7-Tetrachloroisoindoline, 1-ethoxy-
3-iminoisoindoline, 1,3-diiminoisoindoline, 1,3-diimino-4,5,6,7-tetrachloroisoindoline, 1,3-diimino-6-methoxyisoindoline, 1,3- Diimino-6-cyanoisoindoline, 1,3-Diimino-4,7-dithia-5,
5,6,6-tetrahydroisoindoline, 7-amino-2,3-dimethyl-5-oxopyrrolo [3,4b] pyrazine, 7-amino-2,3-diphenyl-5-oxopyrrolo [3,4b] pyrazine, 1-iminonaphthalimide, 1-iminodiphenimide, 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-iminoisoindoline, 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, 1- (cyanobenzoylmethylene) -3-iminoisoindoline, 1- (cyanocarbonamidomethylene) -3-iminoisoindoline, 1- (cyanocarbomethoxymethylene) -3-imino Isoindoline, 1- (cyanocarboethoxymethylene) -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-[(cyanobenzimidazolyl-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, 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-4,5,5
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, 3-imino-2-methyl-4,5,
6,7-tetrachloroisoindoline-1-one and the like.

The heat-sensitive recording material according to the present invention may contain a heat-fusible substance in order to improve its thermal response. In this case, 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. Specific examples of the heat-fusible substance (sensitizer) for improving such thermal response include N-hydroxymethylstearic acid amide, stearic acid amide, palmitic acid amide, oleic acid amide, and ethylene.・ Bismearic acid amide, ricinoleic acid amide, paraffin wax, microcrystalline wax, polyethylene wax, rice wax,
Waxes such as carnauba wax, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2-bis (3-methylphenoxy) ethane,
Polyether compounds such as 2,2′-bis (4-methoxyphenoxy) diethyl ether and bis (4-methoxyphenyl) ether; carbonic acid such as diphenyl carbonate, dibenzyl oxalate and di (p-chlorobenzyl) oxalate; Examples thereof include oxalic acid diester derivatives. These sensitizers can be used alone or in combination of two or more. Further, in order to obtain a sufficient thermal response, it is necessary to add 10 to 30 to the aromatic isocyanate compound.
It is preferable to use 0% by weight, and more preferably 20 to 250% by weight.

Further, the heat-sensitive recording material according to the present invention may contain an aniline derivative having at least one amino group, which is shown in the international application WO87 / 06885 by the present inventors. These aniline derivatives are also effective in preventing background fogging.

In addition, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin and the like are used as pigments in the heat-sensitive recording layer. It Further, 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, stearamide, and castor wax, and dioctyl are also used. Dispersants such as sodium sulfosuccinate, UV absorbers such as benzophenone-based and benzotriazole-based,
Furthermore, a surfactant, a fluorescent dye, etc. are added as needed.

As the binder used in the heat-sensitive recording layer, various binders that are commonly used can be used. For example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
Gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylic acid ester copolymer, acrylamide /
Acrylic ester / methacrylic acid terpolymer, water-soluble binder such as alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, and styrene / butadiene copolymer, Examples include latex-based water-insoluble binders such as acrylonitrile / butadiene copolymer and methyl acrylate / butadiene copolymer.

The heat-sensitive recording material according to the present invention comprises a support having thereon a heat-sensitive recording layer for color development. Paper is mainly used as the support, but in addition to paper, various woven fabrics, non-woven fabrics, synthetic resin films, laminated paper, synthetic paper, metal foils, or composite sheets in which these are combined are arbitrarily used according to the purpose. be able to. The thermal recording layer may have a single layer structure or a multi-layer structure. For example, each color-forming component is contained in one layer,
It may have a multilayer structure. Further, a protective layer may be provided on the heat-sensitive recording layer. This heat-sensitive recording layer can be obtained by mixing each aqueous dispersion obtained by finely pulverizing each color forming component or other components with a binder, coating the mixture on a support, and drying.

[0023]

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
It was dispersed in a ball mill together with 0 g for 24 hours. on the other hand,
10 g of 4,4 ′, 4 ″ -triisocyanate-2,5, -dimethoxytriphenylamine was dispersed in a ball mill for 24 hours together with 40 g of a 1% polyvinyl alcohol aqueous solution. Further, 10 g of 3-di-n-butylamino-6-methyl-7-anilinofluorane was dispersed in a ball mill for 24 hours together with 40 g of a 1% polyvinyl alcohol aqueous solution. Further, 15 g of 2,2-bis (4-hydroxyphenyl) propane was dispersed in a ball mill for 24 hours together with 60 g of a 1% polyvinyl alcohol aqueous solution.

After mixing these four kinds of dispersions, 200 g of 40% dispersion of calcium carbonate was added, 25 g of 40% dispersion of zinc stearate, 100 g of 20% dispersion of 2-benzyloxynaphthalene, 160 g of a 10% polyvinyl alcohol aqueous solution and 65 g of water were added and sufficiently stirred to obtain a coating liquid. This coating solution was applied onto a base paper having a basis weight of 55 g / m @ 2 so that the solid content was 5.0 g / m @ 2, dried and processed with a super calendar to obtain a heat-sensitive recording material.

Examples 2 to 6 Instead of 3-di-n-butylamino-6-methyl-7-anilinofluorane used in Example 1, 3-di-n-
Pentylamino-6-methyl-7-anilinofluorane (Example 2), 3- (methyl-n-propylamino)-
6-Methyl-7-anilinofluorane (Example 3), 3
-Ethylisobutylamino-6-methyl-7-anilinofluorane (Example 4), 3- (N-ethyl-N-3 ')
-Ethoxypropylamino) -6-methyl-7-anilinofluorane (Example 5), 3-di-n-butylamino-6-methyl-7- (2 ', 6'-dimethylanilino).
A thermal recording material was obtained in the same manner as in Example 1 except that fluoran (Example 6) was used.

Comparative Examples 1-5 Instead of 3-di-n-butylamino-6-methyl-7-anilinofluorane used in Example 1, 3-diethylamino-6-methyl-7-anilinoflu Oran (Comparative Example 1), 3-pyrrolidino-6-methyl-7-anilinofluorane (Comparative Example 2), 3-piperidino-6-methyl-7.
-Anilinofluorane (Comparative Example 3), 3-di-n-butylamino-7- (2'-chloroanilino) fluorane (Comparative Example 4), 3-di-n-butylamino-7- (2 '
A thermosensitive recording material was obtained in the same manner as in Example 1 except that -fluoroanilino) fluorane (Comparative Example 5) was used.

Test 1 The heat-sensitive recording materials obtained in Examples 1 to 6 and Comparative Examples 1 to 5 were printed using a heat-sensitive facsimile printing tester under the condition of applied energy of 0.52 mJ, and the color images obtained were obtained. Optical density was measured using a Macbeth RD918. The results are shown in Table 1.

Test 2 The optical density of the background after leaving the background (unprinted portion) of the thermal recording materials obtained in Examples 1 to 6 and Comparative Examples 1 to 5 under fluorescent light of 10,000 lux for 2 days. It was measured using a Macbeth RD918. The results of discoloration of the background due to light are shown in Table 1.

[0030]

[Table 1]

Results As shown in Table 1, in Examples 1 to 6 using the fluorane dye represented by Chemical Formula 1, the sensitivity was good, the discoloration of the background due to light was small, and the image storability was excellent. A thermosensitive recording material could be obtained. On the other hand, Comparative Example 1 using 3-di-ethylamino-6-methyl-7-anilinofluorane having an ethyl group in which R1 and R2 in Chemical Formula 1 are both alkyl groups having 2 carbon atoms, and R1 and In Comparative Examples 2 and 3 using 3-pyrrolidino-6-methyl-7-anilinofluorane or 3-piperidino-6-methyl-7-anilinofluorane, which are cyclic polymethylene groups instead of R2. , The sensitivity is good, but the discoloration of the background due to light is extremely poor. Also, 3-di-n-butylamino-7- (2'-chloroanilino) fluorane or 3-di-n-butylamino-7- (2'-fluoroanilino) having no substituent at the 6-position.
In Comparative Examples 4 and 5 using fluoran, the discoloration of the background due to light is small, but the sensitivity is low and there is a practical problem.

[0032]

As clearly shown by the above results,
A thermal recording material comprising at least one imino compound having a> C = NH group which develops a color upon reaction with an aromatic isocyanate compound, a fluoran dye and a phenol compound, and a fluoran dye represented by Chemical Formula 1 By using, it was possible to provide a heat-sensitive recording material having improved image storability, which has improved sensitivity (heat response) while improving discoloration of the background due to light.

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising an aromatic isocyanate compound, an imino compound having at least-> C═NH groups which develops a color upon reaction with heating, a fluorane dye and a phenol compound. A heat-sensitive recording material characterized in that a fluoran dye is represented by Chemical Formula 1. [Chemical 1] However, in Chemical formula 1, R1 and R2 both represent an alkyl group or an alkoxyalkyl group, and at least one of them has 3 or more carbon atoms. R3 represents a lower alkyl group or a lower alkoxy group. R4 and R5 represent hydrogen, halogen, an alkyl group or an alkoxy group.