Thermal recording materials

Abstract

To provide a heat-sensitive recording material comprising a developer and a sensitizer, the heat-sensitive recording material being excellent in coloring sensitivity and in heat resistant preservability of a print part and a white part.SOLUTION: A heat-sensitive recording material comprises a heat-sensitive recording layer comprising a developer represented by the formula (1) and a sensitizer, the sensitizer being saturated fatty acid bisamide or unsaturated fatty acid bisamide. (In the formula (1), a, A, and L are as follows: a is an integer selected from 1 to 5; A independently represent a fluoro group or a perfluoroalkyl group; and L is a functional group represented by the formula (2). In the formula (2), R is a C1 to 4 alkyl group. * is a binding site to a sulfur atom in the formula (1)).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a heat-sensitive recording material obtained by using a color developer and a sensitizer which can provide a heat-sensitive recording material excellent in color development sensitivity and heat-resistant storage stability of printed areas and white areas. [Background technology]

[0002] In general, thermal recording materials having a thermal recording layer mainly composed of a colorless or light-colored basic (electron-donating) leuco dye (hereinafter sometimes abbreviated as "dye") and an electron-accepting developer (hereinafter sometimes abbreviated as "developer") that reacts with the dye to develop color when heated, have been widely used.

[0003] Many of the compounds used as such developers are compounds that mainly have a phenol structure, such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), bis(4-hydroxyphenyl)sulfone (bisphenol S), etc. On the other hand, due to concerns about environmental impact, studies are also being conducted to use compounds that do not have a phenol structure as developers.

[0004] For example, Patent Document 1 discloses that a thermal recording medium using a compound having a specific sulfonylurea structure as a developer has good color development sensitivity and good storage stability of the printed area in various durability tests such as heat resistance, plasticizer resistance, moisture resistance, water resistance, alcohol resistance, oil resistance, and grease resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 107037 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the studies of the present inventors, no thermal recording material exhibiting good preservation properties of the white area in a heat resistance durability test was obtained when the specific compound having a sulfonylurea structure shown in the above Patent Document 1 was used as a developer. That is, an object of the present invention is to provide a thermal recording material having excellent color development sensitivity and heat resistance preservation properties of the printed area and the white area. [Means for solving the problem]

[0007] As a result of extensive investigations, the present inventors have found that the above problems can be solved by using a heat-sensitive recording material containing a specific color developer and a specific sensitizer.

[0008] [1] A heat-sensitive recording material having a heat-sensitive recording layer containing a developer represented by the following formula (1) and a sensitizer, the sensitizer being a saturated fatty acid bisamide or an unsaturated fatty acid bisamide: [ka] (In the above formula (1), a, A, and L are as follows. a is an integer selected from 1 to 5, and each A is independently a fluoro group or a perfluoro group. is an arylalkyl group, L is any functional group represented by the following formula (2). [ka] In the above formula (2), R is an alkyl group having 1 to 4 carbon atoms. * indicates the bonding site with the sulfur atom in formula (1). [2] The heat-sensitive recording material according to [1], wherein the saturated fatty acid bisamide or the unsaturated fatty acid bisamide is represented by the following formula (3) or formula (4): [ka] [ka] (In the above formulas (3) and (4), B, C, and X are as follows: B and C are independently a hydrogen atom, an alkyl group, or an alkenyl group, and the alkyl group or alkenyl group may have a hydroxyl group or an organic group; X is an alkylene group. [3] The heat-sensitive recording material according to [1] or [2], wherein in the formulas (3) and (4), B and C each have 9 to 22 carbon atoms. [4] The heat-sensitive recording material according to any one of [1] to [3], wherein in the formulas (3) and (4), X has 1 to 10 carbon atoms. [5] The heat-sensitive recording material according to any one of [1] to [4], wherein in formula (1), A is substituted at the m-position and is a trifluoromethyl group. Effect of the Invention

[0009] A heat-sensitive recording material is provided which is excellent in color development sensitivity and in heat resistance preservation of printed and white areas. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below, but the present invention is not limited to the following description, and can be modified as desired without departing from the gist of the present invention. In the present invention, when a numerical value or physical property value is enclosed before and after "~", the value before and after the "~" is included.

[0011] [Thermal recording material] The thermosensitive recording material of the present invention is a thermosensitive recording material having a thermosensitive recording layer, which contains a specific color developer and a sensitizer. The thermosensitive recording material may be in the form of paper, film, synthetic paper, card, etc. The thermosensitive recording layer of the thermosensitive recording material may be provided on a support, and may have a protective layer, an underlayer, a back layer, an intermediate layer, etc., as described below, if necessary. Here, "on the support" refers to at least one surface of the support, and is usually one surface. "Provided on the support" means that the layer is present on at least a part of the support.

[0012] [Thermal recording layer] The thermosensitive recording material according to an embodiment of the present invention has a thermosensitive recording layer, which contains a color developer and a sensitizer. In addition to the color developer and the sensitizer, the thermosensitive recording layer may contain a leuco dye, a sensitizer other than the above-mentioned sensitizers (hereinafter sometimes referred to as "other sensitizers"), a color developer other than the above-mentioned color developer (hereinafter sometimes referred to as "other color developers"), a stabilizer, a binder, a crosslinking agent, a pigment, a lubricant, other additives, and the like.

[0013] [Developer] The thermal recording material according to an embodiment of the present invention contains a developer containing a compound represented by the following formula (1). In this specification, the compound represented by formula (1) may be referred to as "compound (1)". [ka] (In the above formula (1), a, A, and L are as follows. a is an integer selected from 1 to 5, and each A is independently a fluoro group or a perfluoroalkyl group; L is any functional group represented by the following formula (2). [ka] In the above formula (2), R is an alkyl group having 1 to 4 carbon atoms. * indicates the bonding site with the sulfur atom in formula (1).

[0014] In the above formula (1), a is an integer selected from 1 to 5, and is preferably 3 or less, more preferably 2 or less, and particularly preferably 1. It is believed that if a is large, the hydrophobicity increases, decreasing dispersibility in water, the molecular weight increases, making it difficult for the molecules to move when melted, and the compatibility with the leuco dye and sensitizer decreases too much, decreasing the color developing performance. In the above formula (1), the number of carbon atoms of the perfluoroalkyl group in A is usually 1 to 12. The number of carbon atoms is preferably 6 or less, more preferably 4 or less, and particularly preferably 1 (trifluoromethyl group). It is considered that perfluoroalkyl groups with a large number of carbon atoms have too high hydrophobicity and thus reduce dispersibility in water, or have too high molecular weight, which makes it difficult for the molecules to move during melting, or have too low compatibility with leuco dyes and sensitizers, resulting in reduced color development performance. Each A is independently a fluoro group or a perfluoroalkyl group, and when a is 2 or more, all A may be the same or different substituents, and it is more preferable that all A are the same substituent. As A, a fluoro group or a trifluoromethyl group is preferable because it provides appropriate hydrophobicity and compatibility, and a trifluoromethyl group is particularly preferable because it is easy to realize high color development sensitivity due to its high compatibility.

[0015] In the above formula (1), the substitution position of the fluoro group or perfluoro group in A is not particularly limited, but is preferably the o-position or m-position, since it suppresses crystallinity and provides appropriate amorphous stability. On the other hand, it is preferably the m-position or p-position, since it is spatially separated from the adjacent NH moiety and does not inhibit reactivity with the leuco dye. The m-position is particularly preferred, since it is easy to achieve both appropriate amorphousness and reactivity. Note that when a is 2 or more, it is preferable that at least one A is the m-position.

[0016] L is any one selected from the functional groups represented by the above formula (2), that is, functional groups consisting of a phenyl group and a mono-substituted phenyl group. In the above formula (2), R is an alkyl group having 1 to 4 carbon atoms, and is preferably a methyl group or an ethyl group, with a methyl group being particularly preferred, since thermal motion is suppressed and storage stability is likely to be improved. The functional group represented by the above formula (2) is preferably a phenyl group, an o-tolyl group, an m-tolyl group, or a p-tolyl group. Among the compounds represented by the above formula (1), compounds represented by the following formula (5) are particularly preferred. [ka]

[0017] [Sensitizer] The thermal recording material according to the embodiment of the present invention contains a saturated fatty acid bisamide or an unsaturated fatty acid bisamide as a sensitizer. The saturated fatty acid bisamide or the unsaturated fatty acid bisamide is represented by the following formula (3) or formula (4). In this specification, the compound represented by formula (3) may be referred to as "compound (3)" and the compound represented by formula (4) may be referred to as "compound (4)". [ka] [ka] (In the above formulas (3) and (4), B, C, and X are as follows: B and C are independently a hydrogen atom, an alkyl group, or an alkenyl group, and the alkyl group or alkenyl group may have a hydroxyl group or an organic group; X is an alkylene group.

[0018] The heat-sensitive recording material according to the embodiment of the present invention has excellent color development sensitivity and heat resistance storage stability of the printed and white areas. The thermal recording material exhibits such a remarkable effect that it is excellent. It is presumed that the reason why the thermal recording material exhibits such an excellent effect is as follows. That is, by introducing a fluoro group or a perfluoroalkyl group as a substituent into the sulfonylurea compound of the color developer, the acidity and / or hydrogen bond donating ability of the NH site is improved, and the color development sensitivity is improved by making it easier to react with the leuco dye, and at the same time, the color development state is stabilized, thereby improving the storage stability of the printed part against various durability tests. In addition, by having a fluoro group or a perfluoroalkyl group as a substituent of the color developer, the association and / or crystallinity are appropriately suppressed, so that the amorphous stability can be effectively increased without excessively reducing the energy required for melting, and the storage stability of the metastable color development state is improved. On the other hand, the characteristic of this developer that is easy to color creates a problem that the white part is easily colored in a heat resistance test, but by making the sensitizer a specific bisamide structure, it is thought that the ease of mixing (compatibility) at the molecular level between the developer and the leuco dye is slightly reduced, and heat resistance that does not cause the white part to color can be exhibited. On the other hand, according to the study by the present inventor, when the sensitizer is a monoamide, heat resistance that does not cause the white part to color in a heat resistance test can be exhibited, but the heat resistance of the printed part is significantly deteriorated. Therefore, it is thought that this specific bisamide structure can appropriately adjust the compatibility between the developer and the leuco dye, while further increasing their association force and increasing amorphous stability, and thus the printed part can maintain heat resistance.

[0019] In the above formula (3) and formula (4), B and C are independently a hydrogen atom, an alkyl group, or an alkenyl group, and the alkyl group or alkenyl group may have a hydroxyl group or an organic group. An alkyl group or an alkenyl group is preferable. The number of carbon atoms in the alkyl group or alkenyl group is not particularly limited, but is usually 5 to 30, preferably 9 to 22, and more preferably 15 to 22. It may be either linear or branched, but is preferably linear. There is no particular limit to the position of the double bond in the alkenyl group.

[0020] Examples of the alkyl group include pentyl, 1-ethylpentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, and triacontyl groups. Preferred are nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl, and docosyl groups, and more preferred are pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl, and docosyl groups.

[0021] Examples of the alkenyl group include pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, icosenyl, henicosenyl, docosenyl, tricosenyl, tetracosenyl, pentacosenyl, hexacosenyl, heptacosenyl, octacosenyl, nonacosenyl, and triacontenyl groups. Preferred are nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, icosenyl, henicosenyl, and docosenyl groups, and more preferred are pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, icosenyl, henicosenyl, and docosenyl groups. The position of the double bond in the alkenyl group is not particularly limited. Among the above alkenyl groups, pentadecenyl and hexadecenyl groups are particularly preferred. , heptadecenyl group, octadecenyl group, nonadecenyl group, icosenyl group, or henicosenyl group.

[0022] B and C may be the same or different, and are preferably the same. In the above formulas (3) and (4), X usually has 1 to 10 carbon atoms, preferably 1 to 6, particularly preferably 1 to 2, and is particularly preferably an ethylene group. The alkyl group or alkenyl group in B and C may have a substituent, but it is preferable that they have no substituent. If they have a substituent, it is preferably a hydroxyl group or an organic group. The organic group is not particularly limited, but may be an alkoxy group. The substituent is particularly preferably a hydroxyl group.

[0023] As the above formula (3) and formula (4), the following is preferably mentioned. [ka] [ka] [ka] [ka] [ka]

[0024] The sensitizers of formula (3) and formula (4) may be used alone or in combination of two or more. When a sensitizer is used, the amount thereof is preferably 25 to 250 parts by weight, more preferably 50 to 150 parts by weight, based on 100 parts by weight of the color developer of formula (1). The sensitizers of the above formulae (3) and (4) can be produced and used based on known methods. The sensitizers of the above formulae (3) and (4) may be commercially available products. Commercially available products include, but are not limited to, Mitsubishi Chemical's Bisamide LA (methylene bisstearic acid amide), Thripax C10 (ethylene biscapric acid amide), Thripax L (ethylene bislauric acid amide), Thripax E (ethylene bisstearic acid amide), Thripax H (ethylene bishydroxystearic acid amide), Thripax B (ethylene bisbehenic acid amide), Thripax ZHS (hexamethylene bisstearic acid amide), Thripax ZHB (ethylene bisbehenic acid amide), Thripax H (ethylene bishydroxystearic acid amide), Thripax H (ethylene bisbehen ... Examples of such compounds include hexamethylene bisbehenic acid amide), Thripax ZHH (hexamethylene bishydroxystearic acid amide), Thripax ZSA (N,N'-distearyl adipic acid amide), Thripax O (ethylene bisoleic acid amide), Thripax R (ethylene biserucic acid amide), Thripax ZHO (hexamethylene bisoleic acid amide), Thripax ZOA (N,N'-dioleyl adipic acid amide), and Thripax ZOS (N,N'-dioleyl sebacate amide).

[0025] [Other sensitizers] The thermosensitive recording layer may contain a sensitizer other than the sensitizer of formula (3) or formula (4) within a range that does not impair the effects of the present invention. As the other sensitizer, any sensitizer known in the field of conventional pressure-sensitive or thermosensitive recording paper can be used, and there is no particular limitation. The other sensitizer may be used alone or in combination of two or more kinds. When the other sensitizer is used, the amount thereof is preferably 1 to 5000 parts by weight, more preferably 5 to 1000 parts by weight, and even more preferably 10 to 500 parts by weight, based on 100 parts by weight of the developer of formula (1).

[0026] As the other sensitizer, any of those known in the field of conventional pressure-sensitive or thermal recording paper can be used, and there is no particular limitation. Examples of the other sensitizer include 1,2-di-(3-methylphenoxy)ethane, 2-benzyloxynaphthalene, fatty acid amides having 10 to 21 carbon atoms (e.g., stearic acid amide, palmitic acid amide, etc.), montanic acid wax, polyethylene wax, p-benzylbiphenyl, diphenyl sulfone, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di(p-chlorobenzyl) oxalate, di(p-methylbenzyl) oxalate, dibenzyl terephthalate, and p-benzyloxybenzoic acid benzoate. Examples of suitable amines that can be used include phenyl, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, o-xylene-bis-(phenyl ether), 4-(m-methylphenoxymethyl)biphenyl, 4,4'-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di(3-methylphenoxy)ethylene, bis[2-(4-methoxy-phenoxy)ethyl]ether, methyl p-nitrobenzoate, and phenyl p-toluenesulfonate.

[0027] [Leuco dyes] In this embodiment, the thermosensitive recording layer preferably contains a leuco dye. The leuco dye is usually basic, and any leuco dye known in the art of pressure-sensitive or thermosensitive recording paper can be used. Specific examples of the leuco dye include triphenylmethane-based leuco dyes, fluoran-based leuco dyes, fluorene-based leuco dyes, and divinyl-based leuco dyes. Specific examples of representative colorless or light-colored dyes (dye precursors) are shown below. These leuco dyes (leuco dye precursors) may be used alone or in combination of two or more. The leuco dye is preferably used in an amount of 10 to 200 parts by weight, more preferably 15 to 150 parts by weight, and even more preferably 20 to 100 parts by weight, per 100 parts by weight of the developer of formula (1).

[0028] Examples of triphenylmethane leuco dyes include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone); 3,3-bis(p-dimethylaminophenyl)phthalide (also known as malachite green lactone); and the like.

[0029] Fluoran leuco dyes include 3-diethylamino-6-methylfluoran; 3-diethylamino-6-methyl-7-anilinofluoran; 3-diethylamino-6-methyl-7-(o,p-dimethylanilino)fluoran; 3-diethylamino-6-methyl-7-chlorofluoran; 3-diethylamino-6-methyl-7-(m-trifluoromethylanilino)fluoran; 3-diethylamino-6-methyl-7-(o-chloroanilino)fluoran; 3-diethylamino-6-methyl-7-(p-chloroanilino)fluoran. 3-Diethylamino-6-methyl-7-(o-fluoroanilino)fluoran;3-Diethylamino-6-methyl-7-(m-methylanilino)fluoran;3-Diethylamino-6-methyl-7-octylanilinofluoran;3-Diethylamino-6-methyl-7-octylaminofluoran;3-Diethylamino-6-methyl-7-benzylaminofluoran;3-Diethylamino-6-methyl-7-dibenzylaminofluoran;3-Diethylamino-6-chloro-7-methylfluoran;3-Diethylamino-6-chloro -7-Anilinofluoran;3-Diethylamino-6-chloro-7-p-methylanilinofluoran;3-Diethylamino-6-ethoxyethyl-7-anilinofluoran;3-Diethylamino-7-methylfluoran;3-Diethylamino-7-chlorofluoran;3-Diethylamino-7-(m-trifluoromethylanilino)fluoran;3-Diethylamino-7-(o-chloroanilino)fluoran;3-Diethylamino-7-(p-chloroanilino)fluoran;3-Diethylamino-7-(o-fluoroanilino)fluoran Fluoran;3-Diethylamino-benzo[a]fluoran;3-Diethylamino-benzo[c]fluoran;3-Dibutylamino-6-methyl-fluoran;3-Dibutylamino-6-methyl-7-anilinofluoran;3-Dibutylamino-6-methyl-7-(o,p-dimethylanilino)fluoran;3-Dibutylamino-6-methyl-7-(o-chloroanilino)fluoran;3-Dibutylamino-6-methyl-7-(p-chloroanilino)fluoran;3-Dibutylamino-6-methyl-7-(o-fluoroanilino)fluoran;3-Dibutylamino-6-methyl-7-(m-trifluoromethylanilino)fluoran;3-Dibutylamino-6-methyl-chlorofluoran;3-Dibutylamino-6-ethoxyethyl-7-anilinofluoran;3-Dibutylamino-6-chloro-7-anilinofluoran;3-Dibutylamino-6-methyl-7-p-methylanilinofluoran;3-Dibutylamino-7-(o-chloroanilino)fluoran;3-Dibutylamino-7-(o-fluoroanilino)fluoran;3-Dipentylamino-6-methyl-7-anilinofluoran 3-Di-pentylamino-6-methyl-7-(p-chloroanilino)fluoran;3-Di-pentylamino-7-(m-trifluoromethylanilino)fluoran;3-Di-pentylamino-6-chloro-7-anilinofluoran;3-Di-pentylamino-7-(p-chloroanilino)fluoran;3-Pyrrolidino-6-methyl-7-anilinofluoran;3-Piperidino-6-methyl-7-anilinofluoran;3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran;3-(N-methyl-N-cyclohexylamino) -6-Methyl-7-anilinofluoran;3-(N-ethyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran;3-(N-ethyl-N-xylamino)-6-methyl-7-(p-chloroanilino)fluoran;3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran;3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran;3-(N-ethyl-N-isoamylamino)-6-chloro-7-anilinofluoran;3-(N-ethyl-N-tetrahydrofurfurylamino)-6- Methyl-7-anilinofluoran;3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran;3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluoran;3-Cyclohexylamino-6-chlorofluoran;2-(4-oxahexyl)-3-dimethylamino-6-methyl-7-anilinofluoran;2-(4-oxahexyl)-3-diethylamino-6-methyl-7-anilinofluoran;2-(4-oxahexyl)-3-dipropylamino-6-methyl-7-anilinofluoran;2-METHYL-6-P-(P-DIMETHYLAMINOPHENYL) AMINOANILINOFLUORAN;2-METHOXY-6-P-(P-DIMETHYLAMINOPHENYL) AMINOANILINOFLUORAN;2-CHLORO-3-METHYL-6-P-(P-PHENYLAMINOPHENYL) AMINOANILINOFLUORAN;2-CHLORO-6-P-(P-DIMETHYLAMINOPHENYL) AMINOANILINOFLUORAN;2-NITRO-6-P-(P-DIETHYLAMINOPHENYL) AMINOANILINOFLUORAN;2-AMINO-6-P-(P-DIETHYLAMINOPHENYL) AMINOANILINOFLUORAN;2-DIETHYLAMINO-6-P-(P-DIETHYLAMINOPHENYL) AMINOANILINOFLUORAN;2-PHENYL 2-benzyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran; 2-hydroxy-6-p-(p-phenylaminophenyl)aminoanilinofluoran; 3-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran; 3-diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluoran; 3-diethylamino-6-p-(p-dibutylaminophenyl)aminoanilinofluoran; 2,4-dimethyl-6-[(4-dimethylamino)anilino]fluoran, and the like.

[0030] Examples of fluorene-based leuco dyes include 3,6,6'-tris(dimethylamino)spiro[fluorene-9,3'-phthalide]; 3,6,6'-tris(diethylamino)spiro[fluorene-9,3'-phthalide]; and the like.

[0031] Examples of divinyl leuco dyes include 3,3-bis[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl]-4,5,6,7-tetrabromophthalide; 3,3-bis[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl]-4,5,6,7-tetrachlorophthalide; 3,3-bis[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrabromophthalide; and 3,3-bis[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide.

[0032] Other leuco dyes include 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide; 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindol-3-yl)-4-azaphthalide; 3-(4-cyclohexylethylamino-2-methoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide; 3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide; 3,6-bis(diethylamino)fluoran-γ-(3'-nitro)anilinolactam; 3, 6-bis(diethylamino)fluoran-γ-(4'-nitro)anilinolactam; 1,1-bis[2',2',2",2"-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2,2-dinitrileethane; 1,1-bis[2',2',2",2"-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2-β-naphthoylethane; 1,1-bis[2',2',2",2"-tetrakis(p-dimethylaminophenyl)ethenyl]-2,2-diacetylethane; bis[2,2,2',2'-tetrakis(p-dimethylaminophenyl)ethenyl]-methylmalonic acid dimethyl ester, and the like.

[0033] [Other color developers] The thermosensitive recording layer may contain a color developer other than that represented by formula (1) within a range that does not impair the effects of the present invention. As the other color developer, any color developer known in the field of conventional pressure-sensitive or thermosensitive recording paper can be used, and although there is no particular limitation, an electron-accepting color developer is preferable. The other color developer may be used alone or in combination of two or more kinds. When the other color developer is used, the amount of the other color developer is preferably 1 to 5000 parts by weight, more preferably 5 to 1000 parts by weight, and even more preferably 10 to 500 parts by weight, based on 100 parts by weight of the color developer represented by formula (1). By using other color developers, high color sensitivity is maintained while heat resistance and moisture resistance are improved. Thus, it is possible to obtain an excellent heat-sensitive recording material having improved image preservation properties such as colorfastness and water resistance. As the other color developer, any of those known in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used, and there is no particular limitation. As the other color developer, bisphenol-based compounds, urea-based compounds, and novolak-type phenol-based compounds are preferable.

[0034] Bisphenol compounds include 4,4'-isopropylidenediphenol, 2,2'-bis(4-hydroxy-3-methylphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, di(4-hydroxy-3-methylphenyl) sulfide, 2,2'-thiobis(3-tert-octylphenol), 2,2'-thiobis(4-tert-octylphenol), 4,4'-dihydroxydiphenyl sulfone, and 2,4'-dihydroxydiphenyl. Examples of such bisphenol sulfone include sulfone, 4-hydroxy-4'-propoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 3,4-dihydroxyphenyl-4'-methylphenyl sulfone, 2,4-bis(phenylsulfonyl)phenol, the bisphenol sulfone crosslinked compounds described in Japanese Patent No. 3913820, and the bisphenol sulfone derivatives described in Japanese Patent No. 4004289.

[0035] Examples of urea compounds include 4,4'-bis(3-(phenoxycarbonylamino)methylphenylureido)diphenylsulfone, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)urea described in Japanese Patent No. 4601174, 4,4'-bis(3-tosylureido)diphenylmethane described in Japanese Patent Publication No. 2011-105638, and N-[2 -(3-phenylureido)phenyl]benzenesulfonamide, N-[2-(acetoxy)phenyl]-N'-phenylurea, N-[3-(acetoxy)phenyl]-N'-phenylurea, N-[2-(benzoyloxy)phenyl]-N'-phenylurea, N-[3-(benzoyloxy)phenyl]-N'-phenylurea described in JP2017-165091A, Examples of amino acid derivatives include the above-mentioned N-(m-tolylaminocarbonyl)-phenylalanine, N-(p-toluenesulfonyl)-phenylalanine, N-(benzyloxycarbonyl)-valine, N-(m-tolylaminocarbonyl)-methionine, N-(m-tolylaminocarbonyl)-tyrosine, N-(m-tolylaminocarbonyl)-phenylglycine, N-(m-tolylaminocarbonyl)-valine, N-(m-tolylaminocarbonyl)-cysteine-S-benzyl, N-(m-tolylaminocarbonyl)-β-alanine, N-phenylaminothiocarbonyl-glycylglycine, N-(p-toluenesulfonylaminocarbonyl)-phenylalanine-methyl ester, N-(p-toluenesulfonyl)-β-alanine, N-(p-tolylaminocarbonyl)-methionine, and N-(phenylaminocarbonyl)-methionine.

[0036] Examples of the novolak-type phenolic compound include the phenol-formalin condensates described in WO 02 / 098674.

[0037] In addition to the compounds listed above, inorganic acidic substances such as activated clay, attapulgite, colloidal silica, and aluminum silicate, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, the aminobenzenesulfonamide derivatives described in JP-A-8-59603, bis(4-hydroxyphenylthioethoxy)methane, 1,5-di(4-hydroxyphenylthio)-3-oxapentane, bis(p-hydroxyphenyl)butyl acetate, bis(p-hydroxyphenyl)methyl acetate, 1,1-bis(4-hydroxyphenyl)- 1-Phenylethane, 1,4-bis[α-methyl-α-(4'-hydroxyphenyl)ethyl]benzene, 1,3-bis[α-methyl-α-(4'-hydroxyphenyl)ethyl]benzene, compounds described in International Publication No. 02 / 081229 and JP-A No. 2002-301873, thiourea compounds such as N,N'-di-m-chlorophenylthiourea, p-chlorobenzoic acid, stearyl gallate, bis[zinc 4-(octyloxycarbonylamino)salicylate] dihydrate, 4-[2-(p- Examples of the aromatic carboxylic acids include aromatic carboxylic acids such as 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, and salts of these aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, as well as antipyrine complexes of zinc thiocyanate and composite zinc salts of terephthalaldehydic acid and other aromatic carboxylic acids. Examples of the aromatic carboxylic acids include metal double salts of higher fatty acids and metal chelate complexes of polyvalent hydroxy aromatic compounds, as described in JP-A-10-258577.

[0038] Among the other color developers mentioned above, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-propoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 4,4'-isopropylidenediphenol, 2,2'-bis(4-hydroxy-3-methylphenyl)propane, diphenyl sulfone crosslinked type compounds described in Patent No. 3913820, compounds described in Japanese Patent No. 4004289, diphenyl sulfone derivatives described in WO 02 / 098674, phenol-formalin condensates described in WO 02 / 098674, 4,4'-bis(3-(phenoxycarbonylamino)methylphenylureido)diphenyl sulfone, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)urea described in Japanese Patent No. 4601174, 4,4'-bis(3-tosylureido)diphenylmethane described in JP 2011-105638 A, N-[2 Preferred are N-(m-tolylaminocarbonyl)-phenylalanine and N-(m-tolylaminocarbonyl)-methionine described in WO 2017 / 047572, and more preferred are 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-propoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, bis(3-allyl-4-hydro More preferred are N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)sulfone, bisphenolsulfone bridged compounds described in Japanese Patent No. 3913820, bisphenolsulfone derivatives described in Japanese Patent No. 4004289, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)urea described in Japanese Patent No. 4601174, 4,4'-bis(3-tosylureido)diphenylmethane described in JP-A-2011-105638, and N-[2-(3-phenylureido)phenyl]benzenesulfonamide described in JP-A-2016-165835.By using these, it is possible to improve image storage stability (heat resistance, plasticizer resistance, moisture resistance, water resistance, grease resistance) while maintaining the color development sensitivity of the heat-sensitive recording material.

[0039] [Stabilizer] In order to improve the image preservation property of the heat-sensitive recording material, a stabilizer may be used in the heat-sensitive recording layer. The stabilizer is an agent that has the effect of improving the image preservation property. Examples of the stabilizer include hindered phenol compounds, ultraviolet absorbers (e.g., benzophenone compounds, triazole compounds), and antioxidants. Among these, hindered phenol compounds are preferred in terms of improving the image preservation property (heat resistance, moisture resistance, water resistance, plasticizer resistance, etc.) of the recording part. The hindered phenol compound usually has 1 or more and 15 or less in one molecule, preferably is a compound having 2 to 6 hydroxyphenyl groups. The molecular weight of the hindered phenol compound is usually 200 to 2000, preferably 250 to 1800, more preferably 300 to 1500. The melting point of the hindered phenol compound is preferably 100°C to 300°C. Furthermore, in at least one of the hydroxyphenyl groups contained in the hindered phenol compound, when the position of the phenolic hydroxyl group is taken as the 1st position, it is preferable that the carbon atom at either the 2nd or 6th position is bonded to a hydrogen atom (i.e., there is no substituent at the 2nd or 6th position).

[0040] Specific examples of the hindered phenol compound include tris(hydroxyphenyl)alkanes and 1,1,3-tris-substituted butane compounds described in JP-B-39-4469 and JP-A-56-40629, etc. These may be used in combination of two or more kinds. The hindered phenol compound may be used alone or in combination of two or more. When the hindered phenol compound is used in the thermal recording material, the content is preferably 1 to 100 parts by weight, more preferably 1 to 70 parts by weight, and even more preferably 1 to 50 parts by weight, based on 100 parts by weight of the color developer of formula (1). If the content of the hindered phenol compound is less than this range, the moisture resistance, water resistance, and heat resistance of the recorded part may decrease, and color development of the blank part due to heating may not be suppressed. If the content is more than this range, the color development sensitivity may decrease, and the plasticizer resistance of the recorded part may decrease.

[0041] 〔binder〕 It is preferable to use a binder to form the thermal recording layer. Examples of the binder include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, polystyrene, styrene copolymers such as styrene-maleic anhydride copolymers and styrene-butadiene copolymers, cellulose derivatives such as ethyl cellulose and acetyl cellulose, casein, gum arabic, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid esters, polyvinyl butyral, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, and coumarone resins. The amount of binder used is suitably about 5 to 25% by weight based on the solid content of the heat-sensitive recording layer. The binder is generally used as a solution, emulsion, dispersion, paste, or a combination thereof. Solvents for the solution, emulsion, or dispersion, or media for the paste, include, for example, water, alcohols, ketones, esters, hydrocarbons, and the like.

[0042] [Crosslinking Agent] Examples of the crosslinking agent include glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, ammonium chloride, etc. When a crosslinking agent is used, the amount thereof is preferably 0.5 to 500 parts by weight based on 100 parts by weight of the developer of formula (1).

[0043] [Pigments] Examples of pigments include inorganic or organic pigments such as silica (excluding colloidal silica), calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, aluminum hydroxide, etc. When a pigment is used, the amount thereof is preferably 25 to 1000 parts by weight based on 100 parts by weight of the color developer of formula (1).

[0044] [Lubricant] Examples of the lubricant include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, silicone resins, etc. When a lubricant is used, the amount thereof is preferably 0.5 to 500 parts by weight based on 100 parts by weight of the color developer of formula (1).

[0045] [Other additives] Examples of other additives include dispersants, antifoaming agents, fluorescent dyes, etc. When other additives are used, the amount of the additives is preferably 0.5 to 500 parts by weight based on 100 parts by weight of the color developer of formula (1).

[0046] [Support] The shape, structure, size, material, etc. of the support used in the thermal recording material are not particularly limited and can be appropriately selected according to the purpose. Examples of the shape of the support include sheet, roll, and flat plate. The support may have a single-layer structure or a laminated structure. The size of the support can be appropriately selected according to the intended use of the thermal recording material. Examples of the material of the support include plastic film, synthetic paper, wood-free paper, waste paper pulp, recycled paper, one-sided gloss paper, greaseproof paper, coated paper, art paper, cast-coated paper, lightly coated paper, resin-laminated paper, and release paper. A composite sheet combining these may also be used as the support. The thickness of the support is not particularly limited and can be appropriately selected depending on the purpose, and is preferably from 30 to 2,000 μm, more preferably from 50 to 1,000 μm.

[0047] [Protective layer] In the thermal recording material, a protective layer may be provided on the thermal recording layer. In general, when a protective layer is provided on the thermal recording layer to improve the image storage stability of the thermal recording material, the color development sensitivity decreases. However, since the color developer used in the thermal recording material has good color development sensitivity, the color development sensitivity required for thermal paper can be maintained even if a protective layer is provided on the thermal recording layer. The types and amounts of various components used in the protective layer are determined according to the required performance and recording suitability, and are not particularly limited.

[0048] [Underlayer, back layer, middle layer] In the thermal recording material, an underlayer mainly composed of a pigment and a binder may be provided between the support and the thermal recording layer in order to further increase the color development sensitivity. Also, in order to correct curling of the thermal recording material, a back layer may be provided on the surface of the support opposite to the surface on which the thermal recording layer is present. One embodiment of the layers in the thermal recording material of the present invention includes, but is not limited to, a layered embodiment in the order of protective layer / thermal recording layer / under layer / support / back layer. Furthermore, an intermediate layer may be formed between the support and the under layer, between the under layer and the thermosensitive recording layer, between the thermosensitive recording layer and the protective layer, and / or between the support and the back layer.

[0049] [Method of manufacturing thermal recording material] The heat-sensitive recording material can be produced by applying a coating liquid containing a basic leuco dye, a developer, and a sensitizer, and optionally other sensitizers, other developers, stabilizers, etc., to at least a portion of at least one side of a support and drying the coating liquid to form a heat-sensitive recording layer. The coating liquid can be applied according to a well-known conventional technique. The coating means is not particularly limited, and for example, an off-machine coater or an on-machine coater equipped with various coaters such as an air knife coater, a rod blade coater, a bent blade coater, a bevel blade coater, a roll coater, or a curtain coater can be used.

[0050] The coating liquid for forming the thermosensitive recording layer can be formed by, for example, mixing a color developer and a sensitizer, and if necessary, a leuco dye, other sensitizers, other color developers, stabilizers, etc., and then pulverizing the mixture to a particle size of several microns or less using a grinder such as a ball mill, an attritor, or a sand grinder, or an appropriate emulsifying device, and then adding a binder, etc. to the mixture. The solvent used for this coating liquid can be water, alcohol, etc. The solid content of the coating liquid is usually 20 to 40% by weight. The coating amount of the thermal recording layer can be appropriately selected depending on the composition and the application of the thermal recording material, but is usually 1 to 20 g / m2 in terms of dry weight. 2 , preferably 2 to 12 g / m 2 The range is.

[0051] Similarly to the above-mentioned thermosensitive recording layer, the protective layer, underlayer, back layer and intermediate layer can also be formed by applying and drying a coating liquid containing the constituent components thereof. Furthermore, the thermosensitive recording material on which each layer has been formed may be subjected to a treatment known in the art (for example, a smoothing treatment using a supercalender or the like).

[0052] [Use of the heat-sensitive recording material] The heat-sensitive recording material of this embodiment can be suitably used for applications such as paper, film, IC cards, and friction ball pens.

Examples

[0053] In the following Examples and Comparative Examples, paper with an underlayer provided on one side of the support was used, and a heat-sensitive recording layer (heat-sensitive coloring layer) was formed on the underlayer. In the following Examples and Comparative Examples, "parts" and "%", unless otherwise specified, indicate "parts by weight" and "weight%", respectively.

[0054] [Coating liquid for the heat-sensitive recording layer] The following Liquid A to Liquid F were each prepared. In Liquid A, Liquid B, and Liquid C, wet grinding was performed with a Ready Mill (RMB-02) manufactured by Imex until the average particle diameter of each component reached 0.5 μm. Here, the average particle diameter is the average diameter based on the volume-based distribution and was measured with a laser diffraction / scattering type particle size distribution measuring device (Microtrac MT3000II) manufactured by Nikkiso Co., Ltd.

[0055] [Example 1] [Liquid A] · 4-Methyl-N-[[[3-(trifluoromethyl)phenyl]amino]carbonyl]benzenesulfonamide (Synthesized by the same operation with reference to Synthesis Example 2 of Patent Document 1 (International Publication No. 2021 / 107037)): 40.0 parts · Polyvinyl alcohol (10% aqueous solution): 50.0 parts · Water: 10.0 parts [Liquid B] · 3-Dibutylamino-6-methyl-7-anilinofluoran (manufactured by Yamamoto Chemical Co., Ltd., trade name "ODB-2"): 36.5 parts · Polyvinyl alcohol (10% aqueous solution): 60.0 parts · Water: 3.5 parts [Liquid C] · Ethylene bisstearamide (manufactured by Mitsubishi Chemical Corporation, trade name "Slipax E fine powder"): 40.0 parts · Polyvinyl alcohol (10% aqueous solution): 50.0 parts · Water: 10.0 parts <Solution D> · 60% calcium carbonate dispersion (manufactured by Okutama Kogyo Co., Ltd., trade name "Tamapal TP - 123CS") <Solution E> · 36% zinc stearate dispersion (manufactured by Chukyo Yushi Co., Ltd., trade name "Hydrin Z - 8 - 36") <Solution F> · 10% polyvinyl alcohol aqueous solution (10% aqueous solution of "Gosenol NH - 18" manufactured by Nippon Gosei Co., Ltd.)

[0056] Each solution was mixed in the following ratios to prepare a coating solution for the thermal recording layer. Solution A: 18.89 parts Solution B: 10.00 parts Solution C: 9.44 parts Solution D: 17.87 parts Solution E: 6.00 parts Solution F: 19.62 parts Next, an underlayer was provided on one side of high - quality paper as the support, and on the underlayer, the coating solution of the thermal recording layer was applied and dried (using a hot - air dryer at 60 °C for 2 minutes) so that the dry weight of the thermal recording layer became 3 g / m 2 . Then, the support on which the underlayer and the thermal recording layer were formed was processed with a super calender so that the smoothness became 500 - 1000 seconds to obtain a thermal recording material. This was further smoothed by applying a pressure of 1 kgf / cm 2 with a super calender to obtain a thermal recording material.

[0057] [Comparative Example 1] Each solution was mixed in the following ratios to prepare a coating solution for the thermal recording layer. Solution A: 18.89 parts Solution B: 10.00 parts Solution D: 17.87 parts Solution E: 6.00 parts Solution F: 19.62 parts Next, an underlayer is provided on one side of the support of high-quality paper, and a thermal recording layer having a dry weight of 3 g / m2 is formed on the underlayer. 2 The coating solution for the thermosensitive recording layer was applied and dried (air blower, 60°C, 2 minutes) to form a thermosensitive recording layer. The support on which the underlayer and thermosensitive recording layer were formed was then treated with a supercalender to a smoothness of 500 to 1000 seconds to obtain a thermosensitive recording material. This was then treated with a supercalender to a smoothness of 1 kgf / cm 2 The film was smoothed by applying a pressure of 100 .mu.m to obtain a heat-sensitive recording material.

[0058] [Comparative Example 2] A thermal recording material was produced in the same manner as in Example 1, except that the ethylene bisstearic acid amide in the C liquid was changed to stearic acid amide (manufactured by Mitsubishi Chemical Corporation, product name "AP-1").

[0059] [Comparative Example 3] A thermal recording material was produced in the same manner as in Example 1, except that ethylene bisstearic acid amide in solution C was replaced with 2-(phenylmethoxy)naphthalene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). did.

[0060] [Comparative Example 4] A heat-sensitive recording material was produced in the same manner as in Example 1, except that the ethylene bisstearic acid amide in Solution C was changed to bis(4-methylbenzyl)oxalate (synthesized by the method described in JP-A-3-275650).

[0061] [Comparative Example 5] A heat-sensitive recording material was produced in the same manner as in Example 1, except that ethylene bisstearic acid amide in Liquid C was changed to diphenyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0062] [Comparative Example 6] A thermal recording material was produced in the same manner as in Example 1, except that the ethylene bisstearic acid amide in the C liquid was changed to 1,2-di-(3-methylphenoxy)ethane (manufactured by Sankosha, product name "KS-232").

[0063] [Comparative Example 7] A thermal recording material was produced in the same manner as in Example 1, except that the ethylene bisstearic acid amide in the C liquid was changed to 1,2-diphenoxyethane (manufactured by Sankosha, product name "KS-235").

[0064] <Color development sensitivity test> A gradation pattern was printed using an Okura Electric thermal printer (TH-M2 / PS), and the image density at an applied energy of 0.31 mJ / dot was measured using an X-Rite spectrodensitometer (eXact). The results are shown in Table 1. Note that the higher the image density in this test, the better the color development sensitivity.

[0065] <Heat resistance> A checkered pattern was printed on the thermal recording material using an Okura Electric thermal printer (TH-M2 / PS) with an applied energy of 0.36 mJ / dot. The material was then left in an environment at 80°C for 24 hours, after which the image density was measured using an X-Rite spectrodensitometer (eXact). Table 1 shows the image density after the test. Note that the higher the value of the printed area and the lower the value of the background area (white area), the better the image density in this test. The melting points (mp, °C) of each sensitizer are also shown.

[0066] [Table 1]

[0067] As is clear from the results in Table 1, the bisamide described in Example 1 exhibited improved color development sensitivity compared to Comparative Example 1, which did not contain a sensitizer, and therefore can be effective as a sensitizer. It is also found that when the bisamide described in Example 1 is used as a sensitizer, color development in the white area is suppressed in a heat resistance test, compared to the general-purpose sensitizers described in Comparative Examples 3 to 7. Furthermore, it is found that the durability of the printed area is also improved, compared to the case where the monoamide described in Comparative Example 2 is used as a sensitizer. From the above, it is found that the use of the developer described in the present application and a specific bisamide as a sensitizer provides excellent color development sensitivity, durability of the printed area in a heat resistance test, and storage stability of the white area.

[0068] As described above, the present invention provides a heat-sensitive recording material excellent in color development sensitivity and heat-resistant storage stability of printed and white areas.

Claims

1. A heat-sensitive recording material having a heat-sensitive recording layer containing a developer represented by the following formula (1) and a sensitizer, the sensitizer being a saturated fatty acid bisamide or an unsaturated fatty acid bisamide: 【Chemistry 1】 (In the above formula (1), a, A, and L are as follows: a is an integer selected from 1 to 5, and each A is independently a fluoro group or a perfluoroalkyl group; L is any functional group represented by the following formula (2). 【Chemistry 2】 In the above formula (2), R is an alkyl group having 1 to 4 carbon atoms. ＊ indicates the bonding site with the sulfur atom in formula (1).

2. 2. The heat-sensitive recording material according to claim 1, wherein the saturated fatty acid bisamide or the unsaturated fatty acid bisamide is represented by the following formula (3) or (4): 【Chemistry 3】 【Chemistry 4】 (In the above formulas (3) and (4), B, C, and X are as follows: B and C are each independently a hydrogen atom, an alkyl group, or an alkenyl group, and the alkyl group or alkenyl group may have a hydroxyl group or an organic group; X is an alkylene group.

3. 3. The heat-sensitive recording material according to claim 1, wherein in the formulas (3) and (4), B and C each have 9 to 22 carbon atoms.

4. 4. The heat-sensitive recording material according to claim 1, wherein in the formulas (3) and (4), X has 1 to 10 carbon atoms.

5. 5. The heat-sensitive recording material according to claim 1, wherein in formula (1), A is substituted at the m-position and is a trifluoromethyl group.

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