DE102016219091B4 - Thermal recording material - Google Patents

Abstract

A thermal recording material having a heat-sensitive recording layer on a support, the heat-sensitive recording layer containing at least one usually colorless or slightly colored electron-donating dye precursor and an electron-accepting compound which reacts with the dye precursor when heated and converts the dye precursor into its colored form, characterized in that the electron-accepting compound is a compound represented by the general formula (1) in which X1 and X2 independently represent a divalent group capable of forming hydrogen bonds, and that the heat-sensitive recording layer further contains a core-shell structured (meth) acrylamide copolymer.

Description

TECHNICAL AREA

The present invention relates to a thermal recording material which is excellent in thermal response and image stability and has improved printability in UV ink printing.

BACKGROUND

In general, thermal recording materials have, on a support, a heat-sensitive recording layer containing, as main components, an electron-donating dye precursor and an electron-accepting compound, usually colorless or lightly colored. When heat is applied to such thermal recording materials with a thermal head, a thermal pen, a laser beam, etc., an instant reaction occurs between the electron-donating dye precursor and the electron-accepting compound which serves as a color developer, thereby forming a recorded image thereon. Such thermal recording materials have some advantages, for example that recorded images can be formed thereon with a relatively simple device, which ensures easy maintenance and no noise generation. They are therefore widely used for measurement recording devices, fax machines, printers, computer terminals, label printers, ticket machines for tickets or other tickets, and the like.

In general, phenol compounds have often been used as color developers heretofore. However, the use of phenol compounds hardly produces satisfactory results in terms of the stability of image areas. For this reason, so-called non-phenolic color developers, i.e., color developers which are free of hydroxyl groups and capable of generating an acidic environment which allows a dye precursor to be converted into its colored form, have been developed to improve the stability of image areas. A known example of such a non-phenolic color developer is the electron accepting compound described in Patent Literature 1. By using this electron-accepting compound, a thermal recording material excellent in thermal responsiveness and image stability against moisture and heat can be obtained.

In recent years, the use of thermal recording materials has become more widespread, and thermal recording materials are used as financial data records such as receipts for gas, water, electricity and other bill payments, bills issued from ATMs of financial institutions, and various Receipts, thermal record labels or tags used for point-of-sales systems (POS systems), etc. With such diversification of the application of thermal recording materials, thermal recording materials which have previously been subjected to ordinary printing such as offset printing and flexographic printing are increasingly used. For this purpose, excellent printability of thermal recording materials is desired. However, UV ink printing on thermal recording materials containing the above-mentioned non-phenolic color developer may cause fogging in a non-image area (background area), and further improvement of such thermal recording materials has been required.

Patent Literature 2 discloses a thermal recording material having a thermosensitive recording layer containing a core-shell structured acrylic emulsion and colloidal silica. This thermal recording material is described as being less likely to have white spots in an image area after UV ink printing. Patent Literature 3 discloses a thermal recording material having a heat-sensitive recording layer containing a water-dispersible polymer composed of a core which contains acrylonitrile as an essential component and a shell which contains methacrylamide as an essential component. This thermal recording material is shown to be excellent in the quality of the coating surface, water resistance, plasticizer resistance, and so on. Patent Literature 4 discloses a thermal recording material containing 4,4'-dihydroxydiphenyl sulfone as an electron-accepting color developer, diphenyl sulfone as a heat-fusible substance with a low melting point, which promotes the color formation reaction, and a core-shell structured water-dispersible polymer as a binder, the polymer being composed of a core with acrylonitrile as an essential component and a shell with methacrylamide as an essential component, the thermal recording material being characterized in that the air resistance measured by the Gurley method specified in JIS-P-8117 is 170 seconds or more. This thermal recording material is described as excellent in color sensitivity, preservation of color developability, image stability against heat, image stability against moisture and heat, and so on.

CITATION LIST

• Patentliteratur 1: WO 2014/080615
• Patentliteratur 2: JP-A 2003-285556
• Patentliteratur 3: JP-A 2000-158815
• Patentliteratur 4: JP-A 2012-148525

Patent literature

• Patent Literature 1: WO 2014/080615
• Patent literature 2: JP-A 2003-285556
• Patent Literature 3: JP-A 2000-158815
• Patent Literature 4: JP-A 2012-148525

SUMMARY OF THE INVENTION

TECHNICAL TASK

An object of the present invention is to provide a thermal recording material which is excellent in thermal response and stability of image areas to moisture and heat and which has improved background fogging resistance in UV ink printing.

SOLUTION OF THE TASK

The above object is achieved by the following.
(1) A thermal recording material having a heat-sensitive recording layer on a support, the heat-sensitive recording layer containing at least one usually colorless or lightly colored electron-donating dye precursor and an electron-accepting compound which reacts with the dye precursor when heated and converts the dye precursor into its colored form,
characterized in that the electron accepting compound is a compound represented by the general formula (1) shown below,
and that the heat-sensitive recording layer further contains a core-shell structured (meth) acrylamide copolymer.
(2) The thermal recording material according to item (1) above, wherein the heat-sensitive recording layer further contains an aromatic isocyanate compound.

General formula (1)

In the general formula (1), X ₁ and X ₂ each represent a divalent group capable of forming hydrogen bonds.

ADVANTAGEOUS EFFECTS OF THE INVENTION

The present invention can provide a thermal recording material which is excellent in thermal response and stability of image areas to moisture and heat, and which has improved resistance to background fogging in UV ink printing.

DETAILED DESCRIPTION OF EMBODIMENTS

• Die Bereitstellung eines thermischen Aufzeichnungsmaterials, das ausgezeichnet bezüglich thermischem Ansprechverhalten und in der Stabilität von Bildbereichen gegen Feuchtigkeit und Wärme ist, und das eine verbesserte Beständigkeit gegenüber Hintergrundverschleierung bei UV-Tintendruck hat, wird erreicht durch die Herstellung eines thermischen Aufzeichnungsmaterials mit einer wärmeempfindlichen Aufzeichnungsschicht auf einem Träger. Die wärmeempfindliche Aufzeichnungsschicht enthält zumindest einen Farbstoffvorläufer und eine elektronenaufnehmende Verbindung, wobei die elektronenaufnehmende Verbindung in der wärmeempfindlichen Aufzeichnungsschicht eine Verbindung dargestellt durch die allgemeine Formel (1) ist (nachfolgend auch bezeichnet als die „Verbindung der vorliegenden Erfindung“), wobei die wärmeempfindliche Aufzeichnungsschicht weiterhin ein Kern-Schale-strukturiertes (Meth-)Acrylamid-Copolymer enthält.

In the following, the present invention will be described in detail. The invention is based on the following results:

• The provision of a thermal recording material which is excellent in thermal response and in the stability of image areas to moisture and heat, and which has an improved resistance to background fogging in UV ink printing, is achieved by the preparation of a thermal recording material having a heat-sensitive recording layer on a Carrier. The heat-sensitive recording layer contains at least a dye precursor and an electron-accepting compound, wherein the electron-accepting compound in the heat-sensitive recording layer is a compound represented by the general formula (1) (hereinafter also referred to as the "compound of the present invention"), the heat-sensitive recording layer further contains a core-shell structured (meth) acrylamide copolymer.

In the general formula (1), X ₁ and X ₂ each represent a divalent group capable of forming hydrogen bonds. Examples of the divalent group capable of forming hydrogen bonds include -NHCO-, -CONH-, -NHCONH-, - CONHNHCO-, -NHCOCONH-, - SO ₂ NH- and -NHSO ₂ -. A compound of the general formula (1) in which X _{1 is} -NHCONH- and X _{2 is} -NHSO ₂ - is particularly preferred. With the use of this compound, a thermal recording material which is particularly excellent in the stability of image areas against moisture and heat can be obtained.

The compound of the present invention has three benzene rings in the structure as shown in the general formula (1). These benzene rings may each 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. Of these, an alkyl group is preferred, and an alkyl group having not more than four carbon atoms, that is, an alkyl group selected from methyl, ethyl, propyl, and butyl, 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 benzene rings have any of the above-described substituents. In addition, it is possible that any one or two or all three of the benzene rings have two or more of the substituents described above.

Preferred 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) benzenesulfonamide, 4-methyl-N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide, and 4-methyl-N- (2- { (4-methylphenyl) carbamoyl] amino} phenyl) benzenesulfonamide.
The compound of the general formula (1) used in the present invention may be only one specific compound, or it may be any combination of two or more specific compounds. According to the present invention, for sufficient thermal responsiveness and sufficient stability of image areas against moisture and heat, the total amount of the compounds represented by the above general formula (1) is preferably from 0.1 to 50% by weight, and more preferably from 1 to 30% by weight based on the total solids content of the heat-sensitive recording layer.

Among the compounds represented by the general formula (1), N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide is particularly preferred. A thermal recording material containing this compound in the heat-sensitive recording layer is particularly excellent in the background fogging resistance in UV ink printing and in the image stability against moisture and heat.

According to 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 in the heat-sensitive recording layer. The other electron-accepting compound which can be used in combination with the compound represented by the general formula (1) is actually not limited, and electron-accepting compounds commonly used in pressure-sensitive recording materials and thermal recording materials can be used therefor.

Examples of the electron accepting compound which can be used in combination with the compound represented by the general formula (1) include
4,4'-dihydroxydiphenylsulfone,
2,4 '-dihydroxydiphenylsulfone,
4-hydroxy-4'-propoxydiphenyl sulfone,
4-hydroxy-4'-isopropoxydiphenyl sulfone,
4-hydroxy-4'-allyloxydiphenylsulfone,
4-hydroxy-4'-octyloxydiphenyl sulfone,
4-hydroxy-4'-dodecyloxydiphenyl sulfone,
4-hydroxy-4'-benzyloxydiphenyl sulfone,
bis (3-allyl-4-hydroxyphenyl) sulfone,
3,4-dihydroxy-4'-methyldiphenyl sulfone,
4-hydroxy-4'-benzenesulfonyloxydiphenylsulfone,
2,4-bis (phenylsulfonyl) 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) -1-phenylethane,
1,3-bis [2- (p-hydroxyphenyl) -2-propyl] benzene,
1,3-bis [2- (3,4-dihydroxyphenyl) -2-propyl] benzene,
1,4-bis [2- (p-hydroxyphenyl) -2-propyl] benzene,
4,4'-dihydroxydiphenyl ether,
3,3'-dichloro-4,4'-dihydroxydiphenyl sulfide,
Methyl 2,2-bis (4-hydroxyphenyl) acetate,
Butyl-2,2-bis (4-hydroxyphenyl) acetate,
4,4'-thiobis (2-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 (α-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.

One of these electron accepting compounds which can be used in combination with the compound represented by the general formula (1) can be used alone, or two or more of them can be used in combination. 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 less than 100% by weight, more preferably less than 30% by weight, and even more preferably less than 10% by weight based on the amount of the compound represented by the general formula (1). For advantageous thermal response, the combined amount of the above compound represented by the general formula (1) and the other electron accepting compound (s) is preferably from 0.1 to 50% by weight, and more preferably from 1 to 30% by weight. based on the total solids content of the heat-sensitive recording layer.

According to the present invention, the heat-sensitive recording layer contains an electron-donating dye precursor usually colorless or lightly colored.

Exemplary dye precursors for black dyes 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-anilinofluoran,
3-pyrrolidino-6-methyl-7-anilinofluoran,
3-pyrrolidino-6-methyl-7- (4-n-butylphenylamino) fluoran, and
3-piperidino-6-methyl-7-anilinofluoran.

Exemplary dye precursors for red dyes 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-chlorofluorane,
3-diethylamino-6-methoxyfluorane,
3-diethylamino-6-methylfluorane,
3-diethylamino-6-methyl-7-chloro-8-benzylfluorane,
3-diethylamino-6,7-dimethylfluorane,
3-diethylamino-6,8-dimethylfluorane,
3-diethylamino-7-chlorofluorane,
3-diethylamino-7-methoxyfluorane,
3-Diethylamino-7- (N-acetyl-N-methyl) aminofluoran,
3-diethylamino-7-methylfluorane,
3-diethylamino-7-n-propoxyfluorane,
3-diethylamino-7-p-methylphenylfluorane,
3-diethylamino-7,8-benzofluoran,
3-diethylaminobenzo [a] fluorane,
3-diethylaminobenzo [c] fluorane,
3-dimethylamino-7-methoxyfluorane,
3-dimethylamino-6-methyl-7-chlorofluorane,
3-dimethylamino-7-methylfluorane,
3-dimethylamino-7-chlorofluorane,
3- (N-ethyl-p-toluidino) -7-methylfluorane,
3- (N-Ethyl-N-isoamyl) amino-6-methyl-7-chlorofluorane,
3- (N-ethyl-N-isoamyl) amino-7,8-benzofluoran,
3- (N-ethyl-N-isoamyl) amino-7-methylfluorane,
3- (N-ethyl-Nn-octyl) amino-6-methyl-7-chlorofluorane,
3- (N-ethyl-Nn-octyl) amino-7,8-benzofluoran,
3- (N-ethyl-Nn-octyl) amino-7-methylfluorane,
3- (N-ethyl-Nn-octyl) amino-7-chlorofluorane,
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-chlorofluorane,
3-n-dibutylamino-6-methyl-7-chlorofluorane,
3-n-dibutylamino-7,8-benzofluoran,
3-n-dibutylamino-7-chlorofluorane,
3-n-dibutylamino-7-methylfluorane,
3-diallylamino-7,8-benzofluoran,
3-diallylamino-7-chlorofluorane,
3-di-n-butylamino-6-methyl-7-bromofluorane,
3-cyclohexylamino-6-chlorofluorane,
3-pyrrolidylamino-7-methylfluorane,
3-ethylamino-7-methylfluorane,
3- (N-Ethyl-N-isoamyl) amino-benzo [a] fluorane,
3-n-dibutylamino-6-methyl-7-bromofluorane, and
3,6-bis (diethylaminofluoran) -γ- (4'-nitro) anilinolactam.

Exemplary dye precursors for green dyes include
3- (N-ethyl-Nn-hexyl) amino-7-anilinofluoran,
3- (N-Ethyl-Np-tolyl) amino-7- (N-phenyl-N-methyl) aminofluoran,
3- (N-ethyl-Nn-propyl) amino-7-dibenzylaminofluoran,
3- (N-ethyl-Nn-propyl) amino-6-chloro-7-dibenzylaminofluoran,
3- (N-Ethyl-N-4-methylphenyl) amino-7- (N-methyl-N-phenyl) aminofluoran,
3- (N-ethyl-4-methylphenyl) amino-7-dibenzylaminofluoran,
3- (N-ethyl-4-methylphenyl) amino-6-methyl-7-dibenzylaminofluoran,
3- (N-Ethyl-4-methylphenyl) amino-6-methyl-7- (N-methyl-N-benzyl) aminofluoran,
3- (N-methyl-Nn-hexyl) amino-7-anilinofluoran,
3- (N-propyl-Nn-hexyl) amino-7-anilinofluoran,
3- (N-ethoxy-Nn-hexyl) amino-7-anilinofluoran,
3- (Nn-pentyl-N-allyl) amino-6-methyl-7-anilinofluoran,
3- (Nn-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) aminofluoran,
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) fluoroan.

Exemplary dye precursors for blue dyes include
3- (1-Ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) phthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -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-methylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-ethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-dimethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-di-n-propylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-di-n-butylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-di-n-pentylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-di-n-hexylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-dihydroxyaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-dichloroaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-dibromaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diallylaminophenyl) -4-azaphthalide, 3- (1 -Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-dimethoxyaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethoxyaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-dicyclohexylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-di-n-propoxyaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-di-n-butoxyaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-di-n-hexyloxyaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-dimethylcyclohexylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-dimethoxycyclohexylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-pyrrolidylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (3-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2,3-diethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-chloro-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (3-chloro-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-bromo-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (3-bromo-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethyl-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-n-propyl-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (3-methyl-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-nitro-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-hydroxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-cyano-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-cyclohexylethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-methylethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-cyclohexylethyl-4-diethylaminophenyl) -4-azaphthalide,
3- (2-Ethylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-chlorindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-bromindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-ethylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-propylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methoxyindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-ethoxyindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-phenylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,
3- (1-Ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4,7-diazaphthalide,
3- (1-Ethyl-4,5,6,7-tetrachlor-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-4-nitro-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Ethyl-4-methoxy-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -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-diethylaminophenyl) -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-diethylaminophenyl) -4-azaphthalide, 3- (1-bromo-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-methyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1 -Methyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, 3- (1-n-propyl-2-methylindol-3-yl) -3- (2 -ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-n-Butyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -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-diethylaminophenyl) -4-azaphthalide,
3- (1-n-Hexyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-n-Hexyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,

3- (1-n-Octyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-n-Octyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,
3- (1-n-octyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4,7-diazaphthalide,
3- (1-n-Nonyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Methoxy-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethoxy-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-Phenyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-n-Pentyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,
3- (1-n-heptyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,
3- (1-n-Nonyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -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-hexyloxyphenyl) -4-azaphthalide.

One of these dye precursors for black, red, green or blue dyes can be used alone, or two or more of them can be used as a mixture.

Other types of dye precursors include dye precursors for near infrared absorbing dyes, which are dye precursors for functional dyes. When a dye precursor is used for a near infrared absorbing dye for color development at a high temperature, alone or in combination with another dye precursor, one has a color development at a high temperature The resulting image has near-infrared absorption and can be used as a machine-readable image under near-infrared light. The use of a dye precursor for a near-infrared absorbing dye in the present invention enables a combined use of an image with absorption only in the visible light region with an image or the like with absorption in the near-infrared region, resulting in the production of a Recording material leads with a high degree of security.

Examples of dye precursors for near infrared absorbing dyes include
3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylen-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-tetrabroniphthalide, 3- [1,1-bis (p-diethylaminophenyl) ethylene-2- yl] -6-dimethylaminophthalide, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '- (6'-dimethylamino) phthalide, 3- [p- (p-dimethylaminoanilino) anilino] -6-methylfluorane,
3- [p- (p-Dimethylaminoanilino) anilino] -6-methyl-7-chlorofluorane, 3- (pn-butylaminoanilino) -6-methyl-7-chlorofluorane,
3- [p- (p-anilinoanilino) anilino] -6-methyl-7-chlorofluorane,
3- [p- (p-chloroanilino) anilino] -6-methyl-7-chlorofluorane,
3- (Np-Tolyl-N-ethylamino) -6,8,8-trimethyl-9-ethyl-8,9-dihydro- (3,2-e) pyridofluoran,
3-di (n-butyl) amino-6,8,8-trimethyl-8,9-dihydro- (3,2-e) pyridofluoran, 3'-phenyl-7-N-diethylamino-2,2'-spirodi (2H-1-benzopyran), bis (p-dimethylaminostyryl) -p-trisulfonylmethane, and
3,7-bis (dimethylamino) -10-benzoylphenothiazine.

One of these electron donating dye precursors can be used alone, or two or more of them can be used in combination, according to need.

The ratio of the compound represented by the general formula (1) of the present invention to the electron-donating dye precursor (ie, [compound represented by the general formula (1)]: [electron-donating dye precursor]) is preferably a weight ratio of 0.05: 1 to 10: 1. A weight ratio of 0.1: 1 to 5: 1 is even more preferred. When the amount of the compound represented by the general formula (1) in relation to the electron donating dye precursor is within this range, a thermal recording material excellent in thermal response can be obtained.

The heat-sensitive recording layer of the thermal recording material of the present invention further contains a core-shell structured (meth) acrylamide copolymer. With the use of this copolymer, the background fogging resistance of UV ink printing can be increased.

To form the core-shell structured (meth) acrylamide copolymer, a (meth) acrylamide and optionally an unsaturated monomer which can be copolymerized with (meth) acrylamide are polymerized as core particles in the presence of a seed emulsion.

The seed emulsion used as the core particle may be a known seed emulsion, or it may be prepared by a known polymerization method. Examples of the seed emulsion include a (meth) acrylate-based seed emulsion, a styrene-butadiene-based seed emulsion, a styrene (meth) acrylate-based seed emulsion, a (meth) acrylate-butadiene -based seed emulsion, a (meth) acrylonitrile-based seed emulsion, a (meth) acrylonitrile-butadiene-based seed emulsion, a vinyl chloride-based seed emulsion, and a vinyl acetate-based seed emulsion. Conventional polymer emulsions can be used without being limited to these emulsions. One of these emulsions can be used alone, or two or more of them can be used as a mixture, according to need.

Examples of the optionally used unsaturated monomer which can be copolymerized with the (meth) acrylamide include, but are not limited to, unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, maleic anhydride, fumaric acid, and crotonic acid; aromatic vinyl monomers such as styrene, α-methylstyrene, and divinylbenzene; (Meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2- Aminoethyl (meth) acrylate, 2- (N-methylamino) ethyl (meth) acrylate, and glycidyl (meth) acrylate; N-substituted unsaturated carboxamides such as N-methylol (meth) acrylic acid amide; Vinyl esters such as vinyl acetate and vinyl propionate; and nitrile-containing monomers such as (meth) acrylonitrile.

In the core-shell structured (meth) acrylamide copolymer used in the present invention, the combined amount of the (meth) acrylamide and the optionally used unsaturated monomer is which are copolymerized with the (meth) acrylamide may, preferably from 5 to 500% by weight, and more preferably from 10 to 200% by weight with respect to the amount of the seed emulsion. If the amount is less than 5% by weight, the improvement in background fogging resistance in UV ink printing may be insufficient. If the amount exceeds 500% by weight, the thermal response of the thermal recording material may be lowered. The core-shell structured (meth) acrylamide copolymer can be a common and commercially available product and, for example, the products commercially available from Mitsui Chemicals, Inc. under the trade names BARIASTAR BM-1000, BARIASTAR OM-1050, etc. can be used. be used.

According to the present invention, the heat-sensitive recording layer may contain various kinds of binder resins used for conventional coating in addition to the above-mentioned core-shell structured (meth) acrylamide copolymer.

Specific examples of the binder resin include, but are not limited to, water-soluble binders such as starch, hydroxymethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium alginate, polyvinyl pyrrolidone, polyacrylamide, an acrylamide / acrylic acid ester copolymer, an acrylamide / acrylic acid ester copolymer, 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.

According to the present invention, the proportion of the core-shell structured (meth) acrylamide copolymer in the heat-sensitive recording layer is preferably from 5 to 30% by weight based on the total solid content of the heat-sensitive recording layer. The proportion of the sum of the binder resin and the core-shell structured (meth) acrylamide copolymer in the heat-sensitive recording layer is preferably from 5 to 30% by weight based on the total solid content of the heat-sensitive recording layer. The core-shell structured (meth) acrylamide copolymer preferably makes up from 25 to 100% by weight of the combined amount of the binder resin and the core-shell structured (meth) acrylamide copolymer.

The heat-sensitive recording layer of the thermal recording material of the present invention preferably contains an aromatic isocyanate compound. When the non-phenolic color developer represented by the general formula (1) is contained in a thermal recording material, the hue (hue in the middle density range) of an image recorded thereon by the application of heat has a slight tendency to be in the blue to green range. For this reason, conventional thermal recording materials containing a non-phenolic color developer are not preferred for use in reproducing images such as representations and photographs. However, a thermal recording material having a heat-sensitive recording layer containing an aromatic isocyanate compound as an additional component can preferably be used even for reproducing images such as images and photographs. The aromatic isocyanate compound is preferably a colorless or slightly colored aromatic or heterocyclic isocyanate compound which has one or more isocyanate groups in the molecule and is solid at normal temperatures.

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,
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,
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,
pN, N-dimethylaminophenyl isocyanate,
5,7-diisocyanate-1,1-dimethyl-6-n-propylindane,
5,7-diisocyanate-1,1,4,6-tetramethylindane, and
tris (4-isocyanatophenyl) thiophosphate.

Depending on requirements, these aromatic isocyanate compounds can be used in the form of a so-called 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 form that can be used is a polyisocyanate which is formed by a reaction with polyols or the like, for example by a reaction of toluene diisocyanate with trimethylolpropane. The isocyanate compound used in the present invention may be one kind or a mixture of two or more kinds of isocyanate compounds including block isocyanates, diisocyanate dimers, diisocyanate trimers and polyisocyanates.

According to the present invention, the amount (on a weight basis) of the aromatic isocyanate compound contained in the heat-sensitive recording layer is preferably from 1 to 1000% by weight, and particularly preferably from 10 to 200% by weight, based on the dye precursor . When the amount of the aromatic isocyanate compound with respect to the dye precursor is in this range, the improvement in the color tone of the image areas is achieved.

Preferably, the heat-sensitive recording layer in the present invention further contains an imino compound in addition to the aromatic isocyanate. In this case, a thermal recording material on which an image having a particularly favorable color tone can be produced can be obtained. The imino compound in the present invention is, more specifically, a compound having one or more imino groups in the molecule. 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-methoxyisoindofin-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-iminoisoindoline,
1- (6'-methylbenzothiazolyl-2'-imino) -3-iminoisoindoline,

1- (3'-Dimethylamino-4'-methoxyphenylimino) -3-iminoisoindoline,
1- (2'-chloro-5'-trifluoromethylphenylimino) -3-iminoisoindoline,
1- (5 ', 6'-dichlorobenzothiazolyl-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-imino-4,7-dithiatetrahydroisoindoline,

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- (4 ', 5'-Dicyanoimidazolyl-2'-imino) -3-imino-5,6-dimethyl-4,7-pyraziisoindoline,
1- (cyanobenzoylmethylene) -3-iminoisoindoline,
1- (Cyanocarbonamidmethylene) -3-iminoisoindoline,
1- (cyanocarbomethoxymethylene) -3-iminoisoindoline,
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-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-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- [cyanobenzimidazolyl-2'-methylene] -3-imino-4,7-dithiatetrahydroisoindoline,
1 - [(1'-Phenyl-3'-methyl-5-oxo) -pyrazoliden-4 '] - 3-iminoisoindoline,
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.

According to the present invention, taking the hue of recorded images into consideration, the amount (on a weight basis) of the imino compound contained in the heat-sensitive recording layer is preferably from 10 to 300% by weight, and more preferably from 15 to 250% by weight .-% based on the aromatic isocyanate compound.

According to the present invention, the heat-sensitive recording layer preferably contains a heat-fusible substance as a sensitizer for improving thermal responsiveness. For this purpose, the melting point of the heat-fusible substance to be used is preferably from 60 to 180 ° C, and particularly preferably from 80 to 140 ° C.

Specific examples of the heat-fusible substance include known heat-fusible substances such as stearic amide, palmitic amide, behenamide, N-hydroxymethyl stearic amide, N-stearyl stearic amide, ethylenebis (stearic amide), methylenebis (stearic amide), methylolstearic amide, N-stearylurea, 2-benzyl urea -Benzylbiphenyl, 2,2'bis (4-methoxyphenoxy) diethyl ether, α, α'-diphenoxy-o-xylene, bis (4-methoxyphenyl) ether, diphenyl adipate, dibenzyloxalate, bis (4-methylbenzyl) oxalate, bis (4- Chlorobenzyl) oxalate, dimethyl terephthalate, dibenzyl terephthalate, phenylbenzenesulfonate, diphenylsulfone, bis (4-allyloxyphenyl) sulfone, 1,2-bis (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 4-acetylacetophenone, acetoacetanilides, and.

One of these heat-fusible substances can be used alone, or two or more of them can be used in combination. For sufficient thermal response, the content of the sensitizer is preferably from 5 to 50% by weight based on the total solids content of the heat-sensitive recording layer.

According to the present invention, it is preferred that the heat-sensitive recording layer is obtained as follows: all of the above components such as an electron accepting compound represented by the general formula (1), another electron accepting compound, a dye precursor, a sensitizer, an aromatic isocyanate The compound and an imino compound are separately finely ground and dispersed in water, the resulting aqueous dispersions and a resin, etc. are mixed together, and the mixture is coated on a support and then dried. In a preferred embodiment of the present invention, the components are finely ground to fine particles, preferably fine particles with a volume average particle diameter of, in the presence of a dispersant in water as the dispersing medium using a wet mill such as a sand mill, a ball mill, an attritor and a bead mill 0.1 to 5.0 µm, and the resulting dispersions containing fine particles are used to prepare a coating liquid for the preparation of a heat-sensitive recording layer. In a preferred embodiment of the present invention, the dye precursor is separately from the electron accepting compound, which serves as a color developer, in the presence of a dispersant in water as a dispersing medium using a wet mill such as a sand mill, a ball mill, an attritor and a bead mill, milled to fine Particles, preferably fine particles having a volume average particle diameter of 0.1 to 5.0 µm, can be obtained, and the resulting fine particle-containing dispersion is used to prepare a coating liquid for the preparation of a heat-sensitive recording layer.

Examples of the dispersant used for dispersing the above compound components required for color formation include water-soluble high molecular compounds such as polyvinyl alcohols (e.g., fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, Diacetone-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, epoxy-modified polyvinyl alcohol, etc.), starch or derivatives thereof, cellulose derivatives (e.g. hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose (e.g., carboxy ethyl cellulose, proteins, etc.) Gelatin, casein, etc.), acid neutralizing agents such as chitosan, sodium alginate, polyvinylpyrrolidone, salts of a diisobutylene / maleic anhydride copolymer, salts of a Styrene / isobutylene / maleic anhydride copolymer, salts of styrene / maleic anhydride copolymer, salts of ethylene / acrylic acid copolymer, salts of styrene / acrylic acid copolymer, polyacrylates and polyacrylsulfonates; low molecular weight anionic surfactants such as dodecylbenzenesulfonates, dialkylsulfosuccinates, alkylnaphthalene sulfonates, alkyldiphenylether disulfonates and fatty acid metal salts; and nonionic surfactants such as acetylene glycol. The dispersant is not limited to these examples. One of these compounds or two or more of them can be used as needed.

The thermal recording material of the present invention ensures favorable stability of image areas against moisture and heat based on the use of the electron accepting compound represented by the general formula (1), however, for a higher degree of light resistance, etc., hindered phenol compounds, hindered amine compounds, phosphate esters -Derivatives and / or benzotriazole derivatives can be used as an additional component in the heat-sensitive recording layer as required.

Specific examples of the hindered phenol compound which can be used according to need in the heat-sensitive recording layer of the present invention include
1,1,2,2-tetrakis (5-cyclohexyl-4-hydroxy-2-methylphenyl) ethane,
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) propane,
1,1,3,3-tetrakis (3-cyclohexyl-4-hydroxyphenyl) propane,
1,1,5,5-tetrakis (5-cyclohexyl-4-hydroxy-2-methylphenyl) pentane,
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) propane,
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. The hindered phenol compound is not limited to these examples. One of these compounds can be used alone, or two or more of them can be used in combination, according to need.

Specific examples of the hindered amine compound which can be used according to need in the heat-sensitive recording layer of the present invention include
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. The hindered amine compound is not limited to these examples. One of these compounds can be used alone, or two or more of them can be used in combination, according to need.

Specific examples of the phosphate ester derivative which can be used according to need in the heat-sensitive recording layer of the present invention include
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,
Dimethyl oxyphosphate,
Diethyloxyphosphate,
bis (3,5-di-tert-butyl-4-hydroxyphenyl) phosphate,
3,5-di-tert-butyl diphenyl 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. The phosphate ester derivative is not limited to these examples. One of these compounds can be used alone, or two or more of them can be used in combination, according to need.

Specific examples of the benzotriazole derivative which can be used according to need in the heat-sensitive recording layer of the present invention include
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-chlorobenzotriazole,
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-butylbenzotriazole,
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) propionate and polyethylene glycol (molecular weight: about 300), octyl-5-tert-butyl-3- (5-chlorobenzotriazolyl) - 4-hydroxybenzene propionate, 2- (2-hydroxy-3-sec-butyl-5-tert-butylphenyl) -5-tert-butylbenzotriazole,
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-benzotriazolylphenol],
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-benzotriazolylphenol], and
2,2'-Octylidenebis [4-methyl-6- (5-methylbenzotriazolyl) phenol]. The benzotriazole derivative is not limited to these examples. One of these compounds can be used alone, or two or more of them can be used in combination, according to need.

The combined amount of the hindered phenol compound, the hindered amine compound, the phosphate ester derivative and the benzotriazole derivative which can be used in the heat-sensitive recording layer of the present invention as needed is preferably from 5 to 100% by weight, and more preferably from 10 to 80% by weight based on the dye precursor.

The heat-sensitive recording layer may further contain a pigment. 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 silicon dioxide, amorphous calcium silicate, and colloidal silicon dioxide; and organic pigments such as a melamine filler resin, a urea-formaldehyde filler resin, polyethylene powder and nylon powder.

Depending on requirements, the heat-sensitive recording layer can further contain a lubricant comprising metal salts of higher fatty acids such as zinc stearate and calcium stearate, higher fatty acid amides such as stearic amide, and waxes such as paraffin wax, polyethylene wax, oxidized polyethylene wax and castor wax to prevent wear or jamming of the thermal Printhead; a surfactant such as high molecular weight anionic or nonionic surfactants as dispersing and wetting agents; and additionally a fluorescent dye, a defoamer, etc.

For forming the thermosensitive recording layer, known techniques can be used without any substantial limitation. Specifically, a coating liquid is applied onto a support by a technique selected from various printing processes such as letterpress printing, lithographic printing, flexographic printing or gravure printing, air brush coating, rod coating, rod coating, gravure coating, curtain coating, extrusion rod coating and the like, and then dried to form a heat-sensitive recording layer .

The suitable coating weight of the heat-sensitive recording layer is usually from 0.1 to 2.0 g / m ² on a solid basis in terms of the dye precursor. When the coating weight is within this range, a thermal recording material which is excellent in recorded image quality and thermal response, and which is inexpensive can be obtained. The heat-sensitive recording layer constituting the thermal recording material of the present invention may be in the form of a single layer or multiple layers.

In the thermal recording material of the present invention, one or more intermediate layers containing a pigment and / or a resin may be provided between the support and the heat-sensitive recording layer as required. When the thermal recording material of the present invention comprises one or more intermediate layers, the coating weight of the intermediate layer is preferably from 1 to 30 g / m ² , and more preferably from 3 to 20 g / m ² on a solid basis.

As the pigment contained in the intermediate layer, calcined kaolin is conventionally used, but other pigments can also be used. Examples of the pigments which can be used 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 silicon dioxide, amorphous calcium silicate, and colloidal silicon dioxide; organic pigments such as a melamine filler resin, a urea-formaldehyde filler resin, polyethylene powder, nylon powder, an acrylic filler resin, and a styrene-acrylic filler resin; and hollow pigments.

As the resin contained in the intermediate layer, there can be used various water-soluble resins and various water-dispersible resins (latexes) which are used for conventional ones Coating can be used. Specific examples of the resins which can be used include water-soluble resins such as starch, hydroxymethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium alginate, polyvinyl pyrrolidone, polyacrylamide, an acrylamide / acrylic acid ester copolymer, an acrylamide / acrylic acid ester / methacrylic acid ester / methacrylic acid ester , 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.

According to the present invention, a protective layer may be provided on the thermosensitive recording layer for purposes including improving the anti-stick property, preventing scratching, improving water resistance, and improving plasticizer and chemical resistance of thermally developed images. The protective layer can contain various types of adhesives, inorganic pigments, various types of hardeners, various types of crosslinking agents, UV absorbers, and so on. The protective layer can be a single layer or can be composed of two or more layers.

The thermal recording material of the present invention can have a back coating layer with an anti-curl, anti-static and / or other function on the side of the paper support opposite to the heat-sensitive recording layer. The surface of the back coat layer may have been subjected to an adhesive process and so on.

As the support of the thermal recording material of the present invention, depending on the purpose, any material selected from paper, various woven fabrics, non-woven fabric, a synthetic resin film, a synthetic resin laminated paper, a synthetic paper, a metal foil, a vapor deposition sheet, and a composite sheet made of the foregoing materials bonded by gluing, etc. can be used. Of these, paper such as acid-free paper and acid-containing paper is preferably used because the water content is easy to control.

Calendering may be carried out after coating to form the intermediate layer, the heat-sensitive recording layer, the protective layer or the back coat layer, as required, in order to improve the surface smoothness and printing quality of the thermal recording material of the present invention.

EXAMPLES

In the following, the present invention will be illustrated in more detail by way of examples, but the present invention is not limited to the examples. Various changes and modifications can be made without departing from the technical teachings of the present invention. In the following examples, all percentages (%) and proportions are based on weight. The coating weight indicates the weight of the fully dried coating.

example 1

Preparation of a coating liquid for forming the intermediate layer A mixture of 100 parts of calcined kaolin (manufactured by BASF, trade name: Ansilex), 40 parts of 50% styrene-butadiene latex, 50 parts of 10% aqueous solution of oxidized starch and 100 parts Water was stirred to obtain a coating liquid for interlayer formation.

Preparation of dispersion A

Thirty parts of N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide was dispersed in a mixture of 69 parts of a 2.5% aqueous sulfone-modified polyvinyl alcohol solution and 1 part of a 1% aqueous solution of an acetylene glycol-based one Surfactants. The mixture was ground in a bead mill until the average particle diameter was 0.8 µm, and Dispersion A was obtained.

Preparation of dispersion B

Thirty parts of 1,2-bis (3-methylphenoxy) ethane were dispersed in a mixture of 69 parts of a 2.5% aqueous sulfone-modified polyvinyl alcohol solution and 1 part of a 1% aqueous solution of an acetylene glycol-based surfactant. The mixture was ground in a bead mill until the average particle diameter was 0.8 µm, and Dispersion B was obtained.

Preparation of dispersion C

Thirty parts of 3-di-n-butylamino-6-methyl-7-anilinofluoran were dispersed in a mixture of 69 parts of a 2.5% aqueous sulfone-modified polyvinyl alcohol solution and 1 part of a 1% aqueous solution of an acetylene glycol based surfactant. The mixture was ground in a bead mill until the average particle diameter was 0.8 µm, and Dispersion C was obtained.

Preparation of a coating liquid for forming the thermosensitive recording layer

Next, dispersions (A), (B) and (C) and the other components listed below were mixed with stirring to obtain a coating liquid for preparing the heat-sensitive recording layer. Dispersion A 200 parts Dispersion B 200 parts Dispersion C 100 parts 40% aqueous aluminum hydroxide dispersion 150 parts 30% aqueous zinc stearate dispersion 30 parts 20% aqueous paraffin wax dispersion 50 parts 20% core-shell structured acrylic emulsion (manufactured by Mitsui Chemicals, Inc., trade name: BARIASTAR BM-1000) 200 parts 10% aqueous solution of a completely saponified 200 parts Polyvinyl alcohol (manufactured by The Nippon Synthetic Chemical Industry Co., Ltd., trade name: NM-11) water 100 parts

Production of a thermal recording material On an acid-free high-quality paper with a basis weight of 53 g / m ² , the coating liquids prepared as above were applied with an air brush applicator in such amounts that the coating weight ^{would be 10 g / m 2} on a solids basis for the intermediate layer, and 0 , 4 g / m ² on a solid basis in terms of the dye precursor for the heat-sensitive recording layer. This was followed by drying and calendering with a flotation dryer, and the thermal recording material from Example 1 was obtained in this way.

Example 2

Preparation of dispersion D

Thirty parts of 4-methyl-N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide were dispersed in a mixture of 69 parts of a 2.5% aqueous sulfone-modified polyvinyl alcohol solution and 1 part of a 1% aqueous solution an acetylene glycol based surfactant. The mixture was ground in a bead mill until the average particle diameter was 0.8 µm, and Dispersion D was obtained.

The thermal recording material of Example 2 was obtained in the same manner as in Example 1, except that 200 parts of Dispersion D was used instead of 200 parts of Dispersion A in “Preparation of a coating liquid for forming the thermosensitive recording layer”.

Example 3

The thermal recording material of Example 3 was obtained in the same manner as in Example 1, except that 200 parts of another 20% core-shell structured acrylic emulsion (manufactured by Mitsui Chemicals, Inc., trade name: BARIASTAR OM-1050) instead of 200 parts Parts of the 20% core-shell structured acrylic emulsion (manufactured by Mitsui Chemicals, Inc., trade name: BARIASTAR BM-1000) were used in "Preparation of a Coating Liquid for Forming the Heat-Sensitive Recording Layer".

Comparative example 1

Preparation of dispersion E

Thirty parts of 4,4'-dihydroxydiphenyl sulfone were dispersed in a mixture of 69 parts of a 2.5% aqueous sulfone-modified polyvinyl alcohol solution and 1 part of a 1% aqueous solution of an acetylene glycol-based surfactant. The mixture was ground in a bead mill until the average particle diameter was 0.8 µm, and Dispersion E was obtained.

The thermal recording material of Comparative Example 1 was obtained in the same manner as in Example 1, except that 200 parts of Dispersion E was used instead of 200 parts of Dispersion A in “Preparation of a coating liquid for forming the thermosensitive recording layer”.

Comparative example 2

Preparation of dispersion F

Thirty parts of 4,4'-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl sulfone were dispersed in a mixture of 69 parts of a 2.5% aqueous sulfone-modified polyvinyl alcohol solution and 1 part of a 1% aqueous solution Solution of an acetylene glycol-based surfactant. The mixture was ground in a bead mill until the average particle diameter was 0.8 µm, and Dispersion F was obtained.

The thermal recording material of Comparative Example 2 was obtained in the same manner as in Example 1, except that 200 parts of Dispersion F was used instead of 200 parts of Dispersion A in “Preparation of a coating liquid for forming the thermosensitive recording layer”.

Comparative example 3

The thermal recording material of Comparative Example 3 was obtained in the same manner as in Example 1, except that 400 parts of a 10% aqueous solution of a completely saponified polyvinyl alcohol instead of 200 parts of the 20% core-shell structured acrylic emulsion in the preparation of a coating liquid to form the heat-sensitive recording layer ”.

Comparative example 4

The thermal recording material of Comparative Example 4 was obtained in the same manner as in Example 1 except that 80 parts of a 50% acrylic emulsion (manufactured by The Nippon Synthetic Chemical Industry Co., Ltd., trade name: Mowinyl 718A, acrylic emulsion without a core-shell Structure) were used instead of 200 parts of the 20% core-shell structured acrylic emulsion in the "preparation of a coating liquid for forming the heat-sensitive recording layer".

The thermal recording materials from Examples 1 to 3 and Comparative Examples 1 to 4 were subjected to the tests shown below. The results are listed in Table 1.

Thermal response

On each of the thermal recording materials, solid black printing with an energy input of 0.30 mJ / dot was carried out using the fax tester TH-PMD (manufactured by Okura Engineering Co., Ltd.). The densities of the recorded part and the background part were measured with a Macbeth reflection densitometer model RD-918 (optical filter). The value of the density of the recorded part is preferably 1.0 or more for practical use. More preferable is 1.2 or more. The results are listed in Table 1.

UV ink printability

Each of the thermal recording materials produced was subjected to printing with the UV flexographic ink SICURA FLEX 39-8 YELLOW (manufactured by SIEGWERK) and then stored for 48 hours in an environment of 23 ° C. and 50% relative humidity. Optical density was measured with a Macbeth reflection densitometer model RD-918 (blue filter). The results are listed in Table 1. A lower value of the density indicates a higher UV printability.

Image stability against moisture and heat

Each of the thermal recording materials produced, which were printed in the thermal response test, was stored for 24 hours in an environment of 50 ° C. and 95% relative humidity. The optical density of the recorded portion was measured with a Macbeth Reflection Densitometer Model RD-918 (optical filter). This optical density was divided by the optical density of the same recorded portion measured in the thermal response test. The resulting value is listed in Table 1 as an index of image stability in the test for moisture and heat resistance. A larger value of the index for image stability indicates a higher image stability against moisture and heat. Table 1 Thermal response UV ink printability Image stability against moisture and heat example 1 1.35 0.12 89% Example 2 1.35 0.13 88% Example 3 1.33 0.12 89% Comparative example 1 1.34 0.30 66% Comparative example 2 1.21 0.27 91% Comparative example 3 1.33 0.20 89% Comparative example 4 1.32 0.19 88%

As clearly shown in Table 1, according to the present invention, there were obtained thermal recording materials which were excellent in thermal responsiveness and stability of image areas against moisture and heat, and which had improved resistance to background fogging by UV ink printing. The thermal recording materials of Comparative Examples 1 and 2 did not contain the compound represented by the general formula (1) and therefore were inferior in UV ink printability. In addition, the thermal recording material from Comparative Example 1 was also inferior in image stability to moisture and heat. The thermal recording materials from Comparative Examples 3 and 4 did not contain any core-shell structured (meth) acrylamide copolymer and were therefore poorer in terms of UV ink printability.

Example 4

Preparation of dispersion G

Thirty parts of 4,4 ', 4 "-triisocyanate-2,5-dimethoxytriphenylamine in 70 parts of a 2.5% polyvinyl alcohol aqueous solution were ground in a bead mill until the volume average particle diameter was 1 µm or less and dispersion G became obtain.

Preparation of dispersion H

Thirty parts of 1,3-diimino-4,5,6,7-tetrachloroisoindoline in 70 parts of a 2.5% polyvinyl alcohol aqueous solution was ground in a bead mill until the volume average particle diameter was 1 µm or less and dispersion H became obtain.

The thermal recording material from Example 4 was obtained in the same manner as in Example 1, except that 100 parts of each of the above-mentioned dispersions G and H were additionally used in “preparation of a coating liquid for forming the heat-sensitive recording layer”.

The thermal recording material thus obtained from Example 4 was tested for thermal response, UV ink printability and image stability to moisture and heat in the same way as the above-mentioned thermal recording materials from Examples 1 to 3 and from Comparative Examples 1 to 4. In addition, evaluation of the hue of a recorded image was made as described below. The results are listed in Table 2.

Hue of a recorded image

The hue of a recorded image in which the density was about 0.6 (mean density) as measured by a Macbeth reflection densitometer was evaluated using a gray scale (JIS L 0804). The assessment of the hue of the recorded image on the thermal recording material from Example 1 (containing no aromatic isocyanate compound) was used as a reference. The criterion used for the assessment ranges from “5”, which means no difference in hue, to “1”, which means a considerable difference in hue, graduated from 5 to 1 in intervals of 0.5. The preferred level for practical use is 3.5 or more. The result of the assessment of the thermal recording material from Example 1 for the color tone of a recorded image was “2”. Table 2 Thermal response UV ink printability Image stability against moisture and heat hue Example 4 1.34 0.13 91% 4th

As clearly shown in Table 2, with the thermosensitive recording material additionally containing an aromatic isocyanate compound, an image having excellent color tone was formed.

Claims (7)

A thermal recording material having a heat-sensitive recording layer on a support, the heat-sensitive recording layer containing at least one usually colorless or slightly colored electron-donating dye precursor and an electron-accepting compound which reacts with the dye precursor when heated and converts the dye precursor into its colored form, characterized in that the electron accepting compound is a compound represented by the general formula (1)

wherein X ₁ and X _2, independently of one another, each represent a divalent group capable of forming hydrogen bonds, and that the heat-sensitive recording layer furthermore contains a core-shell-structured (meth) acrylamide copolymer. The thermal recording material according to Claim 1 , characterized in that the heat-sensitive recording layer further contains an aromatic isocyanate compound. The thermal recording material according to Claim 1 or 2 , characterized in that the divalent group capable of forming hydrogen bonds is selected from the group consisting of -NHCO-, -CONH-, -NHCONH-, -CONHNHCO-, -NHCOCONH-, - SO ₂ NH- and -NHSO ₂ -. The thermal recording material according to Claim 3 , characterized in that X _{1 is} -NHCONH- and X _{2 is} -NHSO ₂ -. The thermal recording material according to any one of Claims 1 until 4th , characterized in that the compound represented by the general formula (1) is selected from the group consisting of N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide, N- (2 - {[(4-methylphenyl) carbamoyl) ] amino} phenyl) benzenesulfonamide, 4-methyl-N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide, and 4-methyl-N- (2 - {(4-methylphenyl) carbamoyl] amino} phenyl) benzenesulfonamide. The thermal recording material according to Claim 5 characterized in that the compound represented by the general formula (1) is N- {2 - [(phenylcarbamoyl) amino] phenyl} benzenesulfonamide. The thermal recording material according to any one of Claims 1 until 6th , characterized in that the compound of the general formula (1) is either only a specific compound or is any combination of two or more specific compounds.