THERMAL RECORDING MATERIAL

Abstract

 <Object>
An object of the present invention is to provide a thermal recording material that is excellent in thermal responsiveness and in oil resistance of recorded images.
<Solution>
Provided is a thermal recording material having, on a support, a heat-sensitive recording layer containing an ordinarily colorless or light-colored electron-donating dye precursor and an electron-accepting compound which reacts with the dye precursor on heating and converts the dye precursor to its colored form,
the heat-sensitive recording layer containing a specific electron-accepting compound and an aromatic isocyanate compound.

Description

TECHNICAL FIELD

[0001] The present invention relates to a thermal recording material that is excellent in print quality and in oil resistance of recorded images.

BACKGROUND ART

[0002] Generally, thermal recording materials have, on a support, a heat-sensitive recording layer containing, as main components, an ordinarily colorless or light-colored electron-donating dye precursor and an electron-accepting compound. By application of heat to such thermal recording materials with a thermal print head, a thermal stylus, laser beam, etc., an instant reaction between the electron-donating dye precursor and the electron-accepting compound serving as a developer occurs and thereby a recorded image is produced thereon. Such thermal recording materials have several advantages, for example, that records can be made thereon with a relatively simple device ensuring easy maintenance and no noise generation, and therefore are widely used for measuring recorders, facsimiles, printers, computer terminals, label printers, ticket machines for passenger tickets or other tickets, and the like.

[0003] Along with the recent development of high-speed recording devices, thermal recording materials are required to excel not only in thermal responsiveness as a basic quality but also in image stability. The excellent image stability is required of thermal recording materials used for receipts of gas, water, electricity and other bill payments, account statements issued from ATMs at financial institutions, various receipts, public lotteries, thermal recording labels for point of sales (POS) system, etc. In addition, in the case where thermal recording materials are used as labels for food products typified by labels for microwavable processed food products, the oil resistance must be so high that records will not be erased by exposure to edible oils etc.

[0004] WO 2014/080615 (Patent Literature 1) describes a thermal recording material using a specific non-phenolic compound as an electron-accepting compound. The use of this electron-accepting compound can provide a thermal recording material that is excellent in color development and image stability, more particularly plasticizer resistance, heat resistance, water resistance and alcohol resistance of recorded images, but the thermal recording material is unsatisfactory in terms of the oil resistance of recorded images.

[0005] JP-A 2009-234068 (Patent Literature 2) and JP-A 2007-216512 (Patent Literature 3) describe that the combination of a specific electron-accepting compound and an aromatic isocyanate compound can provide a thermal recording material having improvements in plasticizer resistance, light resistance, etc. of recorded images, but the thermal recording material is still unsatisfactory in terms of the oil resistance of recorded images.

CITATION LIST

[0006] Patent Literature

Patent Literature 1: WO 2014/080615

Patent Literature 2: JP-A 2009-234068

Patent Literature 3: JP-A 2007-216512

SUMMARY OF INVENTION

TECHNICAL PROBLEM

[0007] An object of the present invention is to provide a thermal recording material that is excellent in thermal responsiveness and in oil resistance of recorded images.

SOLUTION TO PROBLEM

[0008] The above-mentioned object is solved by the following.

(1) A thermal recording material having, on a support, a heat-sensitive recording layer containing an ordinarily colorless or light-colored electron-donating dye precursor and an electron-accepting compound which reacts with the dye precursor on heating and converts the dye precursor to its colored form,
the heat-sensitive recording layer containing at least one kind of compound represented by the general formula (1):

(wherein X₁ and X₂ each represent a divalent hydrogen-bonding group) as the electron-accepting compound and an aromatic isocyanate compound.

(2) The thermal recording material according to the above (1), wherein the heat-sensitive recording layer further contains an imino compound.

ADVANTAGEOUS EFFECTS OF INVENTION

[0009] The present invention can provide a thermal recording material that is excellent in thermal responsiveness and in oil resistance of recorded images.

DESCRIPTION OF EMBODIMENTS

[0010] Hereinafter, the present invention will be described in detail.

[0011] The present invention is based on the findings that, in the course of the production of a thermal recording material having, on a support, a heat-sensitive recording layer containing a dye precursor and an electron-accepting compound as essential components, the use of a compound represented by the general formula (1) (hereinafter also referred to as the compound of the present invention) as the electron-accepting compound in the heat-sensitive recording layer, in combination with an aromatic isocyanate compound can provide the thermal recording material with excellent thermal responsiveness and excellent oil resistance of recorded images.

[0012] In the general formula (1), X₁ and X₂ each represent a divalent hydrogen-bonding group. Examples of the divalent hydrogen-bonding group include -NHCO, -CONH-, -NHCONH-, -CONHNHCO-, -NHCOCONH-, -SO₂NH- and -NHSO₂-. Particularly preferred is a compound of the general formula (1) in which X₁ is -NHCONH- and X₂ is -NHSO₂-. The use of this compound can provide a thermal recording material that is particularly excellent in thermal responsiveness and in oil resistance of recorded images.

[0013] The compound of the present invention has three benzene rings in the structure, as shown in the general formula (1). These benzene rings each may have a substituent, and examples of the substituent include an alkyl group, an aralkyl group, an aryl group, an alkoxy group, an acyl group, an acyloxy group, an alkoxycarbonyl group, a hydroxy group, a mercapto group, an amino group, a nitro group, a cyano group, a formyl group, a sulfo group, a sulfonyl group, a sulfinyl group and a halogen atom. Among them, an alkyl group is preferred, and an alkyl group having not more than four carbon atoms is particularly preferred. The compound of the present invention may be the one in which only one of the three benzene rings has a substituent, or the one in which two or all three of the benzene rings have a substituent as described above. In addition, it is possible that any one or two, or all of the three benzene rings have a plurality of substituents as described above.

[0014] Preferable examples of the compound represented by the general formula (1) in the present invention include, but are not limited to, N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide, N-(2-{[(4-methylphenyl)carbamoyl]amino}phenyl)benzenesulfon amide, 4-methyl-N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfona mide and 4-methyl-N-(2-{(4-methylphenyl)carbamoyl]amino}phenyl)benze nesulfonamide. The compound of the general formula (1) used in the present invention may be of one kind or any combination of two or more kinds.

[0015] For excellent oil resistance, particularly preferred as the compound represented by the general formula (1) is N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide.

[0016] The heat-sensitive recording layer which constitutes the thermal recording material of the present invention contains an aromatic isocyanate compound. The aromatic isocyanate compound is preferably a colorless or light-colored aromatic or heterocyclic isocyanate compound which has one or more isocyanate groups in one molecule and is solid at ordinary temperature.

[0017] Specific examples of the aromatic isocyanate compound include 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, diphenylether-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, 3,3'-dichlorobiphenyl-4'-diisocyanate, 2,2',5,5'-tetrachlorobiphenyl-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 triphenylamine, 4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine, p-N,N-dimethylaminophenyl isocyanate, 5,7-diisocyanate-1,1-dimethyl-6-n-propylindan, 5,7-diisocyanate-1,1,4,6-tetramethylindan and tris(4-isocyanatephenyl)thiophosphate.

[0018] As needed, these aromatic isocyanate compounds may be used in the form of, what is called, a block isocyanate, which is an adduct with phenols, lactams, oximes or the like; in the form of a dimer of diisocyanate, for example, 1-methylbenzene-2,4-diisocyanate; or in the form of an isocyanurate, which is a trimer of diisocyanate. Another usable form is a polyisocyanate which is formed by a reaction with polyols or the like, for example, by a reaction of tolylene diisocyanate with trimethylolpropane. The isocyanate compound used in the present invention may be of one kind or a mixture of two or more kinds of isocyanate compounds including the forms of block isocyanates, diisocyanate dimers, diisocyanate trimers and polyisocyanates.

[0019] In the present invention, the amount of the aromatic isocyanate compound contained in the heat-sensitive recording layer is preferably 1 to 1000% by mass, and particularly preferably 10 to 200% by mass as a mass ratio to the dye precursor. When the amount of the aromatic isocyanate compound relative to the dye precursor is within this range, the oil resistance of recorded images will be significantly improved.

[0020] Preferably, the heat-sensitive recording layer in the present invention further contains an imino compound in addition to the electron-accepting compound represented by the general formula (1) and the aromatic isocyanate. In this case, a thermal recording material that is particularly excellent in oil resistance of recorded images can be obtained. The imino compound in the present invention is, more specifically, a compound having one or more imino groups in one molecule, and specific examples of the imino compound include the following compounds:

3-iminoisoindolin-1-one,

3-imino-4,5,6,7-tetrachloroisoindolin-1-one,

3-imino-4,5,6,7-tetrabromoisoindolin-1-one,

3-imino-4,5,6,7-tetrafluoroisoindolin-1-one,

3-imino-5,6-dichloroisoindolin-1-one,

3-imino-4,5,7-trichloro-6-methoxyisoindolin-1-one,

3-imino-4,5,7-trichloro-6-methylmercaptoisoindolin-1-one,

3-imino-6-nitroisoindolin-1-one,

3-iminoisoindoline-1-spiro-dioxolane,

1,1-dimethoxy-3-iminoisoindoline,

1,1-diethoxy-3-imino-4,5,6,7-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,

1-iminonaphthalimide, 1-iminodiphenimide,

1-phenylimino-3-iminoisoindoline,

7-amino-2,3-dimethyl-5-oxopyrrolo[3,4-b]pyrazine,

7-amino-2,3-diphenyl-5-oxopyrrolo[3,4-b]pyrazine,

1-(2'-cyano-4'-nitrophenylimino)-3-iminoisoindoline,

1-(2'-chloro-5'-cyanophenylimino)-3-iminoisoindoline,

1-(2',6'-dichloro-4'-nitrophenylimino)-3-iminoisoindoline,

1-(3'-chlorophenylimino)-3-iminoisoindoline,

1-(2',5'-dichlorophenylimino)-3-iminoisoindoline,

1-(2',4',5'-trichlorophenylimino)-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-(2'-methoxy-5'-N-phenylcarbamoylphenylimino)-3-iminoisoin doline,

1-(6'-methylbenzothiazolyl-2'-imino)-3-iminoisoindoline,

1-(3'-dimethylamino-4'-methoxyphenylimino)-3-iminoisoindoli ne,

1-(2'-chloro-5'-trifluoromethylphenylimino)-3-iminoisoindol ine,

1-(5',6'-dichlorobenzothiazolyl-2'-imino)-3-iminoisoindolin

e, 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-imino-4,7-dithiatetrahydroiso indolline,

1-(benzimidazolyl-2'-imino)-3-iminoisoindoline,

1-(benzimidazolyl-2'-imino)-3-imino-4,5,6,7-tetrachloroisoi ndoline,

1-(2',4'-dinitrophenylhydrazone)-3-iminoisoindoline,

1-(indazolyl-3'-imino)-3-iminoisoindoline,

1-(indazolyl-3'-imino)-3-imino-4,5,6,7-tetrabromoisoindolin e,

1-(indazolyl-3'-imino)-3-imino-4,5,6,7-tetrafluoroisoindoli ne,

1-(4',5'-dicyanoimidazolyl-2'-imino)-3-imino-5,6-dimethyl-4 ,7-pyraziisoindoline,

1-(cyanobenzoylmethylene)-3-iminoisoindoline,

1-(cyanocarbonamidemethylene)-3-iminoisoindoline,

1-(cyanocarbomethoxymethylene)-3-iminoisoindoline,

1-(cyanocarboethoxymethylene)-3-iminoisoindoline,

1-(cyano-N-phenylcarbamoylmethylene)-3-iminoisoindoline,

1-[cyano-N-(3'-methylphenyl)carbamoylmethylene]-3-iminoisoi ndoline,

1-[cyano-N-(4'-chlorophenyl)carbamoylmethylene-3-iminoisoin doline,

1-[cyano-N-(4'-methoxyphenyl)-carbamoylmethylene]-3-iminois oindoline,

1-(cyano-p-nitrophenylmethylene)-3-iminoisoindoline,

1-[cyano-N-(3'-chloro-4'-methylphenyl)carbamoylmethylene]-3

-iminoisoindoline, 1-(dicyanomethylene)-3-iminoisoindoline,

1-(cyano-1',2',4'-triazolyl-(3')-carbamoylmethylene)-3-imin oisoindoline,

1-(cyanothiazoyl-2'-carbamoylmethylene)-3-iminoisoindoline,

1-(cyanobenzimidazolyl-2'-carbamoylmethylene)-3-iminoisoind oline,

1-(cyanobenzothiazolyl-2'-carbamoylmethylene)-3-iminoisoind oline,

1-[cyanobenzimidazolyl-2'-methylene]-3-iminoisoindoline,

1-[cyanobenzimidazolyl-2'-methylene]-3-imino-4,5,6,7-tetrac hloroisoindoline,

1-[cyanobenzimidazolyl-2'-methylene]-3-imino-5-methoxyisoin doline,

1-[cyanobenzimidazolyl-2'-methylene]-3-imino-6-chloroisoind oline,

1-[cyanobenzimidazolyl-2'-methylene]-3-imino-4,7-dithiatetr ahydroisoindolline,

1-[(1'-phenyl-3'-methyl-5-oxo)-pyrazolidene-4']-3-iminoisoi ndoline,

1-[cyanobenzimidazolyl-2'-methylene]-3-imino-5,6-dimethyl-4 ,7-pyraziisoindoline, 1-[(1'-methyl-3'-n-butyl)-barbituric acid-5']-3-iminoisoindoline, 3-imino-1-sulfobenzimide,

3-imino-1-sulfo-6-chlorobenzimide,

3-imino-1-sulfo-5,6-dichlorobenzimide,

3-imino-1-sulfo-6-nitrobenzimide,

3-imino-1-sulfo-6-methoxybenzimide,

3-imino-1-sulfo-4,5,7-trichloro-6-methylmercaptobenzimide,

3-imino-1-sulfonaphthimide,

3-imino-1-sulfo-5-bromonaphthimide and

3-imino-2-methyl-4,5,6,7-tetrachloroisoindolin-1-one.

[0021] In the present invention, the amount of the imino compound contained in the heat-sensitive recording layer is preferably 10 to 300% by mass, and more preferably 15 to 250% by mass as a mass ratio to the aromatic isocyanate compound. When the amount of the imino compound relative to the aromatic isocyanate compound is within this range, the oil resistance of recorded images will be significantly improved.

[0022] The heat-sensitive recording layer of the present invention is preferably produced by preparing aqueous dispersions of finely-ground components needed for color development, mixing these aqueous dispersions with a resin and the like, applying the mixture onto a support, and drying it.

[0023] In the present invention, the ordinarily colorless or light-colored electron-donating compound contained as a dye precursor in the heat-sensitive recording layer is typified by electron-donating compounds generally used in pressure-sensitive recording materials and thermal recording materials, and is of one kind or a combination of two or more kinds as needed. Specific examples of the electron-donating compound include the following, but are not limited thereto.

[0024] Exemplary black dye precursors include

3-di-n-butylamino-6-methyl-7-anilinofluoran,

3-di-n-pentylamino-6-methyl-7-anilinofluoran,

3-diethylamino-6-methyl-7-anilinofluoran,

3-di-n-butylamino-7-(2-chloroanilino)fluoran,

3-diethylamino-7-(2-chloroanilino)fluoran,

3-diethylamino-6-methyl-7-xylidinofluoran,

3-diethylamino-7-(2-carbomethoxyphenylamino)fluoran,

3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilinofluoran,

3-(N-cyclopentyl-N-ethyl)amino-6-methyl-7-anilinofluoran,

3-(N-isoamyl-N-ethyl)amino-6-methyl-7-anilinofluoran,

3-(N-ethyl-4-toluidino)-6-methyl-7-anilinofluoran,

3-(N-ethyl-4-toluidino)-6-methyl-7-(4-toluidino)fluoran,

3-(N-methyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofl

uoran, 3-pyrrolidino-6-methyl-7-anilinofluoran,

3-pyrrolidino-6-methyl-7-(4-n-butylphenylamino)fluoran and

3-piperidino-6-methyl-7-anilinofluoran.

[0025] Exemplary red dye precursors include

3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide,

3,3-bis(1-n-butyl-2-methylindol-3-yl)tetrachlorophthalide,

3,3-bis(1-n-butylindol-3-yl)phthalide,

3,3-bis(1-n-pentyl-2-methylindol-3-yl)phthalide,

3,3-bis(1-n-hexyl-2-methylindol-3-yl)phthalide,

3,3-bis(1-n-octyl-2-methylindol-3-yl)phthalide,

3,3-bis(1-methyl-2-methylindol-3-yl)phthalide,

3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide,

3,3-bis(1-propyl-2-methylindol-3-yl)phthalide,

3,3-bis(2-methylindol-3-yl)phthalide, rhodamine

B-anilinolactam, rhodamine B-(o-chloroanilino)lactam,

rhodamine B-(p-nitroanilino)lactam,

3-diethylamino-5-methyl-7-dibenzylaminofluoran,

3-diethylamino-6-methyl-7-chlorofluoran,

3-diethylamino-6-methoxyfluoran,

3-diethylamino-6-methylfluoran,

3-diethylamino-6-methyl-7-chloro-8-benzylfluoran,

3-diethylamino-6,7-dimethylfluoran,

3-diethylamino-6,8-dimethylfluoran,

3-diethylamino-7-chlorofluoran,

3-diethylamino-7-methoxyfluoran,

3-diethylamino-7-(N-acetyl-N-methyl)aminofluoran,

3-diethylamino-7-methylfluoran,

3-diethylamino-7-n-propoxyfluoran,

3-diethylamino-7-p-methylphenylfluoran,

3-diethylamino-7,8-benzofluoran,

3-diethylaminobenzo[a]fluoran,

3-diethylaminobenzo[c]fluoran,

3-dimethylamino-7-methoxyfluoran,

3-dimethylamino-6-methyl-7-chlorofluoran,

3-dimethylamino-7-methylfluoran,

3-dimethylamino-7-chlorofluoran,

3-(N-ethyl-p-toluidino)-7-methylfluoran,

3-(N-ethyl-N-isoamyl)amino-6-methyl-7-chlorofluoran,

3-(N-ethyl-N-isoamyl)amino-7,8-benzofluoran,

3-(N-ethyl-N-isoamyl)amino-7-methylfluoran,

3-(N-ethyl-N-n-octyl)amino-6-methyl-7-chlorofluoran,

3-(N-ethyl-N-n-octyl)amino-7,8-benzofluoran,

3-(N-ethyl-N-n-octyl)amino-7-methylfluoran,

3-(N-ethyl-N-n-octyl)amino-7-chlorofluoran,

3-(N-ethyl-N-4-methylphenyl)amino-7,8-benzofluoran,

3-(N-ethoxyethyl-N-ethyl)amino-7,8-benzofluoran,

3-(N-ethoxyethyl-N-ethyl)amino-7-chlorofluoran,

3-n-dibutylamino-6-methyl-7-chlorofluoran,

3-n-dibutylamino-7,8-benzofluoran,

3-n-dibutylamino-7-chlorofluoran,

3-n-dibutylamino-7-methylfluoran,

3-diallylamino-7,8-benzofluoran,

3-diallylamino-7-chlorofluoran,

3-di-n-butylamino-6-methyl-7-bromofluoran,

3-cyclohexylamino-6-chlorofluoran,

3-pyrrolidylamino-7-methylfluoran,

3-ethylamino-7-methylfluoran,

3-(N-ethyl-N-isoamyl)amino-benzo[a]fluoran,

3-n-dibutylamino-6-methyl-7-bromofluoran and

3,6-bis(diethylaminofluoran)-γ-(4'-nitro)anilinolactam.

[0026] Exemplary green dye precursors include

3-(N-ethyl-N-n-hexyl)amino-7-anilinofluoran,

3-(N-ethyl-N-p-tolyl)amino-7-(N-phenyl-N-methyl)aminofluora

n, 3-(N-ethyl-N-n-propyl)amino-7-dibenzylaminofluoran,

3-(N-ethyl-N-n-propyl)amino-6-chloro-7-dibenzylaminofluoran,

3-(N-ethyl-N-4-methylphenyl)amino-7-(N-methyl-N-phenyl)amin ofluoran,

3-(N-ethyl-4-methylphenyl)amino-7-dibenzylaminofluoran,

3-(N-ethyl-4-methylphenyl)amino-6-methyl-7-dibenzylaminoflu oran,

3-(N-ethyl-4-methylphenyl)amino-6-methyl-7-(N-methyl-N-benz yl)aminofluoran,

3-(N-methyl-N-n-hexyl)amino-7-anilinofluoran,

3-(N-propyl-N-n-hexyl)amino-7-anilinofluoran,

3-(N-ethoxy-N-n-hexyl)amino-7-anilinofluoran,

3-(N-n-pentyl-N-allyl)amino-6-methyl-7-anilinofluoran,

3-(N-n-pentyl-N-allyl)amino-7-anilinofluoran,

3-di-n-butylamino-6-chloro-7-(2-chloroanilino)fluoran,

3-di-n-butylamino-6-methyl-7-(2-chloroanilino)fluoran,

3-di-n-butylamino-6-methyl-7-(2-fluoroanilino)fluoran,

3-n-dibutylamino-7-(2-chloroanilino)fluoran,

3-di-n-butylamino-7-(2-chlorobenzylanilino)fluoran,

3,3-bis(4-diethylamino-2-ethoxyphenyl)-4-azaphthalide,

3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino

)phthalide, 3-diethylamino-6-methyl-7-benzylaminofluoran,

3-diethylamino-6-methyl-7-dibenzylaminofluoran,

3-diethylamino-6-methyl-7-n-octylaminofluoran,

3-diethylamino-6-methyl-7-(N-cyclohexyl-N-benzyl)aminofluor an, 3-diethylamino-6-methyl-7-(2-chloroanilino)fluoran,

3-diethylamino-6-methyl-7-(2-trifluoromethylanilino)fluoran,

3-diethylamino-6-methyl-7-(3-trifluoromethylanilino)fluoran,

3-diethylamino-6-methyl-7-(2-ethoxyanilino)fluoran,

3-diethylamino-6-methyl-7-(4-ethoxyanilino)fluoran,

3-diethylamino-6-chloro-7-(2-chloroanilino)fluoran,

3-diethylamino-6-chloro-7-dibenzylaminofluoran,

3-diethylamino-6-chloro-7-anilinofluoran,

3-diethylamino-6-ethylethoxy-7-anilinofluoran,

3-diethylamino-7-anilinofluoran,

3-diethylamino-7-methylanilinofluoran,

3-diethylamino-7-dibenzylaminofluoran,

3-diethylamino-7-n-octylaminofluoran,

3-diethylamino-7-p-chloroanilinofluoran,

3-diethylamino-7-p-methylphenylanilinofluoran,

3-diethylamino-7-(N-cyclohexyl-N-benzyl)aminofluoran,

3-diethylamino-7-(2-chloroanilino)fluoran,

3-diethylamino-7-(3-trifluoromethylanilino)fluoran,

3-diethylamino-7-(2-trifluoromethylanilino)fluoran,

3-diethylamino-7-(2-ethoxyanilino)fluoran,

3-diethylamino-7-(4-ethoxyanilino)fluoran,

3-diethylamino-7-(2-chlorobenzylanilino)fluoran,

3-dimethylamino-6-chloro-7-dibenzylaminofluoran,

3-dimethylamino-6-methyl-7-n-octylaminofluoran,

3-dimethylamino-7-dibenzylaminofluoran,

3-dimethylamino-7-n-octylaminofluoran,

3-di-n-butylamino-7-(2-fluoroanilino)fluoran,

3-anilino-7-dibenzylaminofluoran,

3-anilino-6-methyl-7-dibenzylaminofluoran,

3-pyrrolidino-7-dibenzylaminofluoran,

3-pyrrolidino-7-(4-cyclohexylanilino)fluoran,

3-dibenzylamino-6-methyl-7-dibenzylaminofluoran,

3,7-bis(dibenzylamino)fluoran and

3-dibenzylamino-7-(2-chloroanilino)fluoran.

[0027] Exemplary blue dye precursors include

3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)phth alide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-methyl-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-aminophenyl)-4 -azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-methylaminophe nyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-ethylaminophen yl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dimethylaminop henyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-propylami nophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-butylamin ophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-pentylami nophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-hexylamin ophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dihydroxyamino phenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dichloroaminop henyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dibromoaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diallylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dimethoxyamino phenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethoxyaminop henyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dicyclohexylam inophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-propoxyam inophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-butoxyami nophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-hexyloxya minophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-methylcyclo hexylaminophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-methoxycycl ohexylaminophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-pyrrolidylamin ophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(3-ethoxy-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2,3-diethoxy-4-diethylami nophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)-4-a zaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-chloro-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(3-chloro-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-bromo-4-diethylaminophe nyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(3-bromo-4-diethylaminophe nyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethyl-4-diethylaminophe nyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-n-propyl-4-diethylamino phenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(3-methyl-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-nitro-4-diethylaminophe nyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-allyl-4-diethylaminophe nyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-hydroxy-4-diethylaminop henyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyano-4-diethylaminophe nyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyclohexylethoxy-4-diet hylaminophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-methylethoxy-4-diethyla minophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyclohexylethyl-4-dieth ylaminophenyl)-4-azaphthalide,

3-(2-ethylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-a zaphthalide,

3-(1-ethyl-2-chloroindol-3-yl)-3-(2-ethoxy-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-bromoindol-3-yl)-3-(2-ethoxy-4-diethylaminophe nyl)-4-azaphthalide,

3-(1-ethyl-2-ethylindol-3-yl)-3-(2-ethoxy-4-diethylaminophe nyl)-4-azaphthalide,

3-(1-ethyl-2-propylindol-3-yl)-3-(2-ethoxy-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methoxyindol-3-yl)-3-(2-ethoxy-4-diethylaminop henyl)-4-azaphthalide,

3-(1-ethyl-2-ethoxyindol-3-yl)-3-(2-ethoxy-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-phenylindol-3-yl)-3-(2-ethoxy-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminoph enyl)-7-azaphthalide,

3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminoph enyl)-4,7-diazaphthalide,

3-(1-ethyl-4,5,6,7-tetrachloro-2-methylindol-3-yl)-3-(2-eth oxy-4-diethylaminophenyl)-4-azaphthalide,

3-(1-ethyl-4-nitro-2-methylindol-3-yl)-3-(2-ethoxy-4-diethy laminophenyl)-4-azaphthalide,

3-(1-ethyl-4-methoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diet hylaminophenyl)-4-azaphthalide,

3-(1-ethyl-4-methylamino-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide,

3-(1-ethyl-4-methyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dieth ylaminophenyl)-4-azaphthalide,

3-(2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide,

3-(1-chloro-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminop henyl)-4-azaphthalide,

3-(1-bromo-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminoph enyl)-4-azaphthalide,

3-(1-methyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminop henyl)-4-azaphthalide,

3-(1-methyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminop henyl)-7-azaphthalide,

3-(1-n-propyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamin ophenyl)-4-azaphthalide,

3-(1-n-butyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-4-azaphthalide,

3-(1-n-butyl-2-indol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl )-7-azaphthalide,

3-(1-n-pentyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamin ophenyl)-4-azaphthalide,

3-(1-n-hexyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-4-azaphthalide,

3-(1-n-hexyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-7-azaphthalide,

3-(1-n-octyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-4-azaphthalide,

3-(1-n-octyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-7-azaphthalide,

3-(1-n-octyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-4,7-diazaphthalide,

3-(1-n-nonyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-4-azaphthalide,

3-(1-methoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-4-azaphthalide,

3-(1-ethoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminop henyl)-4-azaphthalide,

3-(1-phenyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminop henyl)-4-azaphthalide,

3-(1-n-pentyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamin ophenyl)-7-azaphthalide,

3-(1-n-heptyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamin ophenyl)-7-azaphthalide,

3-(1-n-nonyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-7-azaphthalide,

3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide,

3-(4-dimethylamino-2-methylphenyl)-3-(4-dimethylaminophenyl )-6-dimethylaminophthalide and

3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylamino-2-n-hexylo xyphenyl)-4-azaphthalide. These dye precursors may be used alone or as a mixture of two or more kinds thereof.

[0028] In addition, the dye precursor encompasses functional dye precursors, for example, near-infrared absorbing dye precursors. In the case where this kind of dye precursor is used as a dye precursor for color development under high temperature, alone or in combination with another dye precursor, an image having near-infrared absorption can be obtained by color development under high temperature and used as an image automatically readable under near infrared light. With the use of this kind of dye precursor in the present invention, a combination use of an image having absorption only in the visible light region and an image having absorption in the near-infrared region is feasible, thus enabling the production of a recording material of a high security level.

[0029] Examples of such a near-infrared absorbing dye include

3,3-bis[1-(4-methoxyphenyl)-1-(4-dimethylaminophenyl)ethyle n-2-yl]-4,5,6,7-tetrachlorophthalide,

3,3-bis[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethylen-2-yl]-4,5,6,7-tetrachlorophthalide,

3,3-bis[1,1-bis(4-pyrrolidinophenyl)ethylen-2-yl]-4,5,6,7-t etrabromophthalide,

3-[1,1-bis(p-diethylaminophenyl)ethylen-2-yl]-6-dimethylami nophthalide,

3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino )phthalide,

3-[p-(p-dimethylaminoanilino)anilino]-6-methylfluoran,

3-[p-(p-dimethylaminoanilino)anilino]-6-methyl-7-chlorofluo

ran, 3-(p-n-butylaminoanilino)-6-methyl-7-chlorofluoran,

3-[p-(p-anilinoanilino)anilino]-6-methyl-7-chlorofluoran,

3-[p-(p-chloroanilino)anilino]-6-methyl-7-chlorofluoran,

3-(N-p-tolyl-N-ethylamino)-6,8,8-trimethyl-9-ethyl-8,9-dihy dro-(3,2-e)pyridofluoran,

3-di(n-butyl)amino-6,8,8-trimethyl-8,9-dihydro-(3,2-e)pyrid ofluoran,

3'-phenyl-7-N-diethylamino-2,2'-spirodi(2H-1-benzopyran),

bis(p-dimethylaminostyryl)-p-trisulfonylmethane and

3,7-bis(dimethylamino)-10-benzoylphenothiazine. These electron-donating dye precursors may be used alone or in a combination of two or more kinds thereof as needed.

[0030] The ratio of the compound represented by the general formula (1) of the present invention and the electron-donating dye precursor (i. e. the compound represented by the general formula (1) : the electron-donating dye precursor) is preferably 0.05:1 to 10:1 as a mass ratio. More preferred is 0.1:1 to 5:1. When the amount of the compound represented by the general formula (1) relative to the dye precursor is within this range, the oil resistance of recorded images will be significantly improved.

[0031] In the heat-sensitive recording layer of the present invention, the compound represented by the general formula (1) can be used in combination with one or more kinds of other electron-accepting compounds. The electron-accepting compound that can be used in combination with the compound represented by the general formula (1) is not particularly limited, and electron-accepting compounds generally used in pressure-sensitive recording materials and thermal recording materials can be used.

[0032] Examples of the electron-accepting compound that can be used in combination with the compound represented by the general formula (1) include 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-propoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-allyloxydiphenylsulfone, 4-hydroxy-4'-octyloxydiphenylsulfone, 4-hydroxy-4'-dodecyloxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 3,4-dihydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-benzenesulfonyloxydiphenylsulfone, 2,4-bis(phenylslufonyl)phenol, p-phenylphenol, p-hydroxyacetophenone, 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)-l-phenylethane, 1,3-bis[2-(p-hydroxyphenyl)-2-propyl]benzene, 1,3-bis[2-(3,4-dihydroxyphenyl)-2-propyllbenzene, 1,4-bis[2-(p-hydroxyphenyl)-2-propyl]benzene, 4,4'-dihydroxydiphenylether, 3,3'-dichloro-4,4'-dihydroxydiphenylsulfide, methyl 2,2-bis(4-hydroxyphenyl)acetate, butyl 2,2-bis(4-hydroxyphenyl)acetate, 4,4'-thiobis(2-tert-butyl-5-methylphenol), dimethyl 4-hydroxyphthalate, benzyl 4-hydroxybenzoate, methyl 4-hydroxybenzoate, benzyl gallate, stearyl gallate, N,N'-diphenylthiourea, 4,4'-bis[3-(4-methylphenylsulfonyl)ureido]diphenylmethane, N-(4-methylphenylsulfonyl)-N'-phenylurea, salicylanilide, 5-chlorosalicylanilide, salicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-bis(a-methylbenzyl)salicylic acid, 4-[2'-(4-methoxyphenoxy)ethyloxy]salicylic acid, 3-(octyloxycarbonylamino)salicylic acid or metal salts of these salicylic acid derivatives, N-(4-hydroxyphenyl)-p-toluenesulfonamide, N-(4-hydroxyphenyl)benzenesulfonamide, N-(4-hydroxyphenyl)-1-naphthalenesulfonamide, N-(4-hydroxyphenyl)-2-naphthalenesulfonamide, N-(4-hydroxynaphthyl)-p-toluenesulfonamide, N-(4-hydroxynaphthyl)benzenesulfonamide, N-(4-hydroxynaphthyl)-1-naphthalenesulfonamide, N-(4-hydroxynaphthyl)-2-naphthalenesulfonamide, N-(3-hydroxyphenyl)-p-toluenesulfonamide, N-(3-hydroxyphenyl)benzenesulfonamide, N-(3-hydroxyphenyl)-1-naphthalenesulfonamide, N-(3-hydroxyphenyl)-2-naphthalenesulfonamide, N-(4-methylphenylsulfonyl)-N'-[3-(4-methylphenylsulfonyloxy )phenyl]urea, bis(4-tosylaminocarboxyaminophenyl)methane, urea-urethane compounds and sulfonyl urea compounds. These electron-accepting compounds usable in combination with the compound represented by the general formula (1) may be used alone or in a combination of two or more kinds thereof as needed. The amount of the electron-accepting compound(s) that can be used in combination with the compound represented by the general formula (1) is preferably 100% by mass or less, more preferably 30% by mass or less, and further preferably 10% by mass or less relative to the compound represented by the general formula (1).

[0033] The heat-sensitive recording layer can contain a heat-fusible substance as a sensitizer for improvement of thermal responsiveness. For this purpose, the melting point of the heat-fusible substance to be used is preferably 60 to 180°C, and particularly preferably 80 to 140°C

[0034] The specific examples include known heat-fusible substances such as stearamide, palmitamide, behenamide, N-hydroxymethyl stearamide, N-stearyl stearamide, ethylenebis(stearamide), methylenebis(stearamide), methylol stearamide, N-stearyl urea, 2-benzyloxynaphthalene, m-terphenyl, 4-benzylbiphenyl, 2,2'-bis(4-methoxyphenoxy)diethyl ether, α,α'-diphenoxy-o-xylene, bis(4-methoxyphenyl)ether, diphenyl adipate, dibenzyl oxalate, bis(4-methylbenzyl) oxalate, bis(4-chlorobenzyl) oxalate, dimethyl terephthalate, dibenzyl terephthalate, phenyl benzenesulfonate, bis(4-allyloxyphenyl)sulfone, 1,2-bis(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 4-acetylacetophenone, acetoacetanilides and fatty acid anilides. More preferred are higher fatty acid amides because they can also serve as a lubricant.

[0035] These heat-fusible substances may be used alone or in a combination of two or more kinds thereof. For sufficient thermal responsiveness, the sensitizer content is preferably 5 to 50% by mass relative to the total solid content of the heat-sensitive recording layer.

[0036] In the thermal recording material of the present invention, the above compound represented by the general formula (1) as an electron-accepting compound and the above aromatic isocyanate compound are used to achieve excellent thermal responsiveness and excellent oil resistance. If needed, the thermal recording material may further contain a hindered phenol compound or a hindered amine compound, a phosphoric acid ester derivative and/or a benzotriazole derivative for enhancement of light resistance etc.

[0037] Specific examples of the hindered phenol compound that can be used if needed in the heat-sensitive recording layer of the present invention include, but are not limited to,

1,1,2,2-tetrakis(5-cyclohexyl-4-hydroxy-2-methylphenyl)etha

ne, 1,1,2,2-tetrakis(3-phenyl-4-hydroxyphenyl)ethane,

1,1,2,2-tetrakis(3-tert-butyl-4-hydroxyphenyl)ethane,

1,1,3-tris(3-cyclohexyl-4-hydroxyphenyl)butane,

1,1,3-tris(5-cyclohexyl-4-hydroxy-2-methylphenyl)butane,

1,1,3-tris(3-cyclohexyl-4-hydroxy-5-methylphenyl)butane,

1,1,3-tris(3-phenyl-4-hydroxyphenyl)butane,

1,1,3-tris(5-phenyl-4-hydroxy-2-methylphenyl)butane,

1,1,3-tris(3-tert-butyl-4-hydroxyphenyl)butane,

1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane,

1,1,3,3-tetrakis(5-cyclohexyl-4-hydroxy-2-methylphenyl)prop

ane, 1,1,3,3-tetrakis(3-cyclohexyl-4-hydroxyphenyl)propane,

1,1,5,5-tetrakis(5-cyclohexyl-4-hydroxy-2-methylphenyl)pent

ane, 1,1,3,3-tetrakis(3-cyclohexyl-4-hydroxyphenyl)pentane,

1,1,3,3-tetrakis(3-phenyl-4-hydroxyphenyl)propane,

1,1,3,3-tetrakis(5-phenyl-4-hydroxy-2-methylphenyl)propane,

1,1,3,3-tetrakis(3-tert-butyl-4-hydroxyphenyl)propane,

1,1,3,3-tetrakis(5-tert-butyl-4-hydroxy-2-methylphenyl)prop

ane, 2,2'-methylenebis(4-methyl-6-tert-butylphenol),

2,2'-methylenebis(4-ethyl-6-tert-butylphenol),

2,2'-ethylidenebis(4,6-di-tert-butylphenol),

4,4'-thiobis(3-methyl-6-tert-butylphenol),

4,4'-thiobis(2-methyl-6-tert-butylphenol),

4,4'-thiobis(2-methylphenol),

4,4'-thiobis(2,6-dimethylphenol),

4,4'-thiobis(2,6-di-tert-butylphenol),

2,2'-thiobis(4-tert-octylphenol),

2,2'-thiobis(3-tert-octylphenol),

4,4'-butylidenebis(6-tert-butyl-m-cresol),

1-[α-methyl-α-(4'-hydroxyphenyl)ethyl]

4-[α',α'-bis(4"-hydroxyphenyl)ethyl]benzene,

2,2-bis(4-hydroxy-3,5-dibromophenyl)propane and

2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane. These compounds may be used alone or in a combination of two or more kinds thereof as needed.

[0038] Specific examples of the hindered amine compound that can be used if needed in the heat-sensitive recording layer of the present invention include, but are not limited to, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(2,2,6,6-tetramethyl-4-4-piperidyl) succinate, tetrakis[1,2,2,6,6-pentamethyl(4-piperidyl)] butane-1,2,3,4-tetracarboxylate and tetrakis[2,2,6,6-tetramethyl(4-piperidyl)] butane-1,2,3,4-tetracarboxylate. These compounds may be used alone or in a combination of two or more kinds thereof as needed.

[0039] Specific examples of the phosphoric acid ester derivative that can be used if needed in the heat-sensitive recording layer of the present invention include, but are not limited to, triphenyl phosphate, diphenyl phosphate, bis(4-tert-butylphenyl) phosphate, bis(4,6-di-tert-butylphenyl) phosphate, bis(4-chlorophenyl) phosphate, bis(benzyloxyphenyl) phosphate, 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, dimethyloxy phosphate, diethyloxy phosphate, bis(3,5-di-tert-butyl-4-hydroxyphenyl) phosphate, 3,5-di-tert-butyldiphenyl phosphate, diethyl (3,5-di-tert-butyl-4-hydroxyphenyl) phosphate, a sodium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, a calcium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, a zinc salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, an ammonium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate and a potassium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate.
These compounds may be used alone or in a combination of two or more kinds thereof as needed.

[0040] Specific examples of the benzotriazole derivative that can be used if needed in the heat-sensitive recording layer of the present invention include, but are not limited to, 2-(2-hydroxyphenyl)benzotriazole, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotria zole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-tert-aminophenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-tert-butylbenzotria zole, 2-(2-hydroxy-3-dodecyl-5-methylphenyl)benzotriazole, 2-[2-hydroxy-4-(2-ethylhexyl)oxyphenyl]benzotriazole, a condensate of methyl-3-(3-tert-butyl-5-benzotriazolyl-4-hydroxyphenyl)pro pionate and polyethylene glycol (molecular weight: about 300), octyl 5-tert-butyl-3-(5-chloro-benzotriazolyl)-4-hydroxybenzene-p ropionate, 2-(2-hydroxy-3-sec-butyl-5-tert-butylphenyl)-5-tert-butylbe nzotriazole, a sodium salt of 2-(2-hydroxy-4-methoxy-5-sulfophenyl)benzotriazole, a sodium salt of 2-(2-hydroxy-4-butoxy-5-sulfophenyl)benzotriazole, 2,2'-methylenebis(4-methyl-6-benzotriazolylphenol), 2,2'-methylenebis[4-methyl-6-(5-methylbenzotriazolyl)phenol ], 2,2'-methylenebis[4-methyl-6-(5-chlorobenzotriazolyl)phenol ], 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-benzotriaz olylphenol], 2,2'-methylenebis(4-tert-butyl-6-benzotriazolylphenol), 2,2'-propylidenebis(4-methyl-6-benzotriazolylphenol), 2,2'-isopropylidenebis(4-methyl-6-benzotriazolylphenol), 2,2'-isopropylidenebis[4-(1,1,3,3-tetramethylbutyl)-6-benzo triazolylphenol] and 2,2'-octylidenebis[4-methyl-6-(5-methylbenzotriazolyl)pheno l]. These compounds may be used alone or in a combination of two or more kinds thereof as needed.

[0041] The total amount of the hindered phenol compound or the hindered amine compound, the phosphoric acid ester derivative and the benzotriazole derivative that can be used if needed in the heat-sensitive recording layer of the present invention is preferably 5 to 100% by mass, and more preferably 10 to 80% by mass relative to the dye precursor.

[0042] The heat-sensitive recording layer which constitutes the thermal recording material of the present invention may be in the form of a monolayer or a multilayer.

[0043] In the heat-sensitive recording layer, various binders used for conventional coating can be used.

[0044] Specific examples of the binder include, but are not limited to, water-soluble binders such as starch, hydroxymethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, a modified polyvinyl alcohol, sodium alginate, polyvinyl pyrrolidone, polyacrylamide, an acrylamide/acrylic acid ester copolymer, an acrylamide/acrylic acid ester/methacrylic acid terpolymer, an alkali salt of polyacrylic acid, an alkali salt of polymaleic acid, an alkali salt of a styrene/maleic anhydride copolymer, an alkali salt of an ethylene/maleic anhydride copolymer and an alkali salt of an isobutylene/maleic anhydride copolymer; and water-dispersible binders such as a styrene/butadiene copolymer, an acrylonitrile/butadiene copolymer, a methyl acrylate/butadiene copolymer, an acrylonitrile/butadiene/styrene terpolymer, polyvinyl acetate, a vinyl acetate/acrylic acid ester copolymer, an ethylene/vinyl acetate copolymer, polyacrylic acid ester, a styrene/acrylic acid ester copolymer and polyurethane.

[0045] In the heat-sensitive recording layer, pigments can also be used. Examples of the pigment include inorganic pigments such as diatomite, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate and colloidal silica; and organic pigments such as a melamine resin filler, a urea-formalin resin filler, polyethylene powder and nylon powder.

[0046] If needed, the heat-sensitive recording layer may contain a lubricant (s) including higher fatty acid metal salts such as zinc stearate and calcium stearate, higher fatty acid amides such as stearamide, and waxes such as paraffin wax, polyethylene wax, oxidized polyethylene wax and castor wax for prevention of thermal print head wear or sticking; a surfactant(s) such as high-molecular-weight anionic or nonionic surfactants as a dispersing and wetting agent; and in addition, a fluorescent dye(s), a defoamant(s), etc.

[0047] The heat-sensitive recording layer can be formed by known techniques without any particular limitation. Specifically, a coating liquid is applied onto a support by a technique selected from various printing processes such as letterpress, lithographic, flexographic or gravure printing, air knife coating, rod blade coating, bar coating, blade coating, gravure coating, curtain coating, extrusion bar coating and the like, and then dried to form a heat-sensitive recording layer.

[0048] The suitable coating weight of the heat-sensitive recording layer is usually 0.1 to 2.0 g/m² on a solid basis in terms of the dye precursor. When the coating weight is within this range, a thermal recording material that is excellent in recorded image quality and thermal responsiveness and is cost advantageous can be produced.

[0049] In the thermal recording material of the present invention, if needed, one or more intermediate layers containing a pigment and/or a resin can be provided between the support and the heat-sensitive recording layer. In the case where the thermal recording material of the present invention has an intermediate layer, the coating weight of the intermediate layer is preferably 1 to 30 g/m², and more preferably 3 to 20 g/m² on a solid basis.

[0050] As the pigment in the intermediate layer, calcined kaolin is commonly used, but other pigments can also be used. Examples of the usable pigments include inorganic pigments such as diatomite, talc, kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate and colloidal silica; organic pigments such as a melamine resin filler, a urea-formalin resin filler, polyethylene powder, nylon powder, an acrylic resin filler and a styrene-acrylic-resin filler; and hollow pigments.

[0051] As the resin in the intermediate layer, various water-soluble resins and various water-dispersible resins (latices) used for conventional coating can be used. Specific examples of the usable resins include water-soluble resins such as starch, hydroxymethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, a modified polyvinyl alcohol, sodium alginate, polyvinyl pyrrolidone, polyacrylamide, an acrylamide/acrylic acid ester copolymer, an acrylamide/acrylic acid ester/methacrylic acid terpolymer, an alkali salt of polyacrylic acid, an alkali salt of polymaleic acid, an alkali salt of a styrene/maleic anhydride copolymer, an alkali salt of an ethylene/maleic anhydride copolymer and an alkali salt of an isobutylene/maleic anhydride copolymer; and water-dispersible resins such as a styrene/butadiene copolymer, an acrylonitrile/butadiene copolymer, a methyl acrylate/butadiene copolymer, an acrylonitrile/butadiene/styrene terpolymer, polyvinyl acetate, a vinyl acetate/acrylic acid ester copolymer, an ethylene/vinyl acetate copolymer, polyacrylic acid ester, a styrene/acrylic acid ester copolymer and polyurethane.

[0052] In the thermal recording material of the present invention, if needed, a protective layer can be provided on the heat-sensitive recording layer in order to enhance the chemical resistance of recorded images or to enhance runnability and printability. Such a protective layer can be formed as follows. As the main component, a membrane-forming water-soluble or water-dispersible resin is added to an adhesive solution or dispersion, and if needed, a known ultraviolet absorber, an auxiliary agent selected from those that can be contained in the heat-sensitive recording layer, and the like are further added to prepare a coating liquid for protective layer formation. The coating liquid is applied onto the heat-sensitive recording layer so that the coating weight after drying will be about 0.2 to 10 g/m², more preferably about 0.5 to 5 g/m², and then dried to form a protective layer.

[0053] The water-soluble resin or the water-dispersible resin in the protective layer can be selected as appropriate from conventionally known water-soluble polymers and water-dispersible resins. Examples of the water-soluble resin include polyvinyl alcohol, a modified polyvinyl alcohol, starch or its derivatives, cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, ethyl cellulose and carboxymethyl cellulose, polyvinyl pyrrolidone, polyacrylamide, an acrylamide/acrylic acid ester copolymer, an acrylamide/acrylic acid ester/methacrylic acid terpolymer, an alkali salt of polyacrylic acid, an alkali salt of polymaleic acid, an alkali salt of a styrene/maleic anhydride copolymer, an alkali salt of an ethylene/maleic anhydride copolymer, an alkali salt of an isobutylene/maleic anhydride copolymer, sodium alginate, gelatin, casein and an acid neutralizer for chitosan.

[0054] Examples of the water-dispersible resin include a styrene/butadiene copolymer, an acrylonitrile/butadiene copolymer, a methyl acrylate/butadiene copolymer, an acrylonitrile/butadiene/styrene terpolymer, polyvinyl acetate, a vinyl acetate/acrylic acid ester copolymer, an ethylene/vinyl acetate copolymer, polyacrylic acid ester, a styrene/acrylic acid ester copolymer, an acrylonitrile/acrylic acid ester copolymer, an acrylonitrile/acrylic acid ester/acrylic acid copolymer and polyurethane.

[0055] Among them, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, epoxy-modified polyvinyl alcohol and diacetone-modified polyvinyl alcohol are preferably used as the resin in the protective layer because they can form a strong membrane.

[0056] The protective layer can contain a pigment for enhancement of runnability, printability, writability, etc. Specific examples of the pigment include inorganic pigments such as diatomite, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate and colloidal silica; and organic pigments such as a melamine resin filler, a urea-formalin resin filler, polyethylene powder and nylon powder.

[0057] If needed, the protective layer may contain a lubricant (s) including higher fatty acid metal salts such as zinc stearate and calcium stearate, higher fatty acid amides such as stearamide, and waxes such as paraffin wax, polyethylene wax, oxidized polyethylene wax and castor wax for enhancement of runnability and printability by prevention of thermal print head wear and sticking.

[0058] The formation of the intermediate layer and the protective layer can also be achieved by known techniques without any particular limitation. Specifically, a coating liquid is applied by a technique selected from various printing methods, air knife coating, rod blade coating, bar coating, blade coating, gravure coating, curtain coating, extrusion bar coating and the like, and then dried to form a desired layer.

[0059] In the thermal recording material of the present invention, if needed, another protective layer (barrier), an adhesive layer and/or an information storage layer such as a magnetic recording layer and an inkjet recording layer may be provided on the back side of the support, i.e. the opposite side of the support from the heat-sensitive recording layer. If needed, smoothing such as supercalendering may also be performed after coating for formation of any layer.

EXAMPLES

[0060] Hereinafter, the present invention will be illustrated by Examples, but the present invention is not limited thereto. In Examples, percentages (%) and parts are all on a mass basis. The coating weight denotes a bone-dry coating weight.

<Example 1>

(A) Preparation of coating liquid for heat-sensitive recording layer formation

[0061] Thirty parts of 3-(N,N-dibutylamino)-6-methyl-7-anilinofluoran as a black color-forming dye precursor in 69 parts of a 2.5% aqueous polyvinyl alcohol solution as a dispersant was ground in a bead mill until the volume-average particle diameter became 1 µm or less, and a dye precursor dispersion was obtained. Next, 70 parts of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide as an electron-accepting compound and 70 parts of 2-benzyloxynaphthalene as a sensitizer in 310 parts of a 2.5% aqueous polyvinyl alcohol solution were ground in a bead mill until the volume-average particle diameter became 1 µm or less, and an electron-accepting compound-containing dispersion was obtained. Further, 30 parts of 4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine in 70 parts of a 2.5% aqueous polyvinyl alcohol solution was ground in a bead mill until the volume-average particle diameter became 1 µm or less, and an aromatic isocyanate dispersion was obtained. After the above three dispersions were mixed, the additives shown below were added with stirring and the whole was mixed well to prepare a coating liquid for heat-sensitive recording layer formation.

50% Aqueous dispersion of light calcium carbonate	180 parts
40% Aqueous zinc stearate dispersion	25 parts
10% Aqueous polyvinyl alcohol solution	272 parts
Water	300 parts

(B) Preparation of paper for heat-sensitive coating

[0062] A coating liquid of which the composition is shown below was applied onto a high-quality paper with a basis weight of 40 g/m² so that the coating weight would be 9 g/m² on a solid basis, and then dried to give a paper for heat-sensitive coating.

Calcined kaolin	100 parts
50% Aqueous dispersion of styrene-butadiene latex	24 parts
Water	200 parts

(C) Production of thermal recording material

[0063] The coating liquid for heat-sensitive recording layer formation prepared in (A) was applied onto the paper for heat-sensitive coating prepared in (B) so that the coating weight would be 0.3 g/m² in terms of the dye precursor, and then dried. Subsequently, calendering was performed so that the BEKK smoothness defined in JIS P8119: 1998 would be 400 seconds, and a thermal recording material was obtained.

<Example 2>

[0064] A thermal recording material was produced in the same manner as described in Example 1, except for the following procedures: 30 parts of 1,3-diimino-4,5,6,7-tetrachloroisoindoline in 70 parts of a 2.5% aqueous polyvinyl alcohol solution was ground in a bead mill until the volume-average particle diameter became 1 µm or less, the resulting imino compound dispersion was added to the coating liquid for heat-sensitive recording layer formation, and the whole was mixed with stirring.

<Example 3>

[0065] A thermal recording material was produced in the same manner as described in Example 1, except that 70 parts of 4-methyl-N-{2-[(phenylcarbamoyl)amino]phenyl]benzenesulfona mide was used instead of 70 parts of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide.

<Comparative Example 1>

[0066] A thermal recording material was produced in the same manner as described in Example 1, except that the aromatic isocyanate dispersion was not used.

<Comparative Example 2>

[0067] A thermal recording material was produced in the same manner as described in Example 1, except that 70 parts of N-(4-methylphenylsulfonyl)-N'-[3-(4-methylphenylsulfonyloxy )phenyl]urea was used instead of 70 parts of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide.

<Comparative Example 3>

[0068] A thermal recording material was produced in the same manner as described in Example 1, except that 70 parts of 4,4'-dihydroxydiphenylsulfone was used instead of 70 parts of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide.

<Comparative Example 4>

[0069] A thermal recording material was produced in the same manner as described in Example 1, except that 70 parts of 2,4'-dihydroxydiphenylsulfone was used instead of 70 parts of N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide.

<Thermal responsiveness test>

[0070] A printing test was performed using a facsimile tester TH-PMD (manufactured by Okura Engineering Co., LTD.). The tester was equipped with a thermal head featuring a dot density of 8 dots/mm and a head resistance of 818 Ω. Printing was performed with an electric current at a head voltage of 15 V and at a pulse-width of 1.2 msec. The optical density was measured with Macbeth reflection densitometer model RD-918. The evaluation results are shown in Table 1. The optical density is practically required to be 1.15 or more.

<Oil resistance test>

[0071] Onto the surface of the printed area of each thermal recording material which had been subjected to printing with an electric current at a pulse-width of 1.2 msec in the thermal responsiveness test, vegetable oil was applied, and each sample was stored for 24 hours. After this, the optical density of the printed area was measured with Macbeth reflection densitometer model RD-918. The optical density measured after 24-hour storage of each sample exposed to vegetable oil was divided by the optical density measured in the above thermal responsiveness test, and the resulting value is shown in Table 1 as a retention percentage in the oil resistance test. A larger value of the retention percentage indicates a higher oil resistance.

Table 1

	Thermal responsiveness (optical density)	Oil resistance
Example 1	1.35	84%
Example 2	1.35	93%
Example 3	1.36	82%
Comparative Example 1	1.34	67%
Comparative Example 2	1.36	74%
Comparative Example 3	1.15	39%
Comparative Example 4	1.38	36%

[0072] As clearly shown in Table 1, a thermal recording material that is excellent in thermal responsiveness and in oil resistance of recorded images can be obtained according to the present invention.

INDUSTRIAL APPLICABILITY

[0073] The present invention can provide a thermal recording material that is excellent in thermal responsiveness and in oil resistance of recorded images.

Claims

1. A thermal recording material having, on a support, a heat-sensitive recording layer containing an ordinarily colorless or light-colored electron-donating dye precursor and an electron-accepting compound which reacts with the dye precursor on heating and converts the dye precursor to its colored form,
the heat-sensitive recording layer containing at least one kind of compound represented by the general formula (1):

(wherein X₁ and X₂ each represent a divalent hydrogen-bonding group) as the electron-accepting compound and an aromatic isocyanate compound.

2. The thermal recording material according to claim 1, wherein the heat-sensitive recording layer further contains an imino compound.