Thermal recording composition

Abstract

To provide a heat-sensitive recording composition which is excellent in thermal responsibility and has excellent heat-resistant storage stability of a printing part and a texture under a high temperature environment.SOLUTION: There is provided a heat-sensitive recording composition which comprises a coloring agent, a developer and a sensitizer, wherein the developer contains a compound represented by the following formula (1) (wherein, R1 to R5 each independently represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkyl sulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group or an arylamino group and the sensitizer contains 1,2-Bis(tosyloxy)ethane.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a heat-sensitive recording material having excellent thermal response and storage stability. [Background technology]

[0002] Thermal recording materials are generally prepared by dispersing a colorless or pale-colored leuco dye and a color-developing compound such as a phenolic compound into fine particles, mixing the two, adding additives such as binders, sensitizers, fillers, and lubricants, and applying the resulting coating liquid to paper, film, synthetic paper, etc. When the coating thus obtained is heated using a thermal printer or the like with a built-in thermal head, a colored record (print) is obtained by a chemical reaction that occurs when one or both of the leuco dye and the color-developing compound melt and come into contact with each other. Compared with other recording methods, the thermal recording method has the following advantages: (1) no noise is generated during recording; (2) no development or fixing is required; (3) it is maintenance-free; and (4) the machines are relatively inexpensive. Therefore, it is widely used in fields such as facsimile machines, computer output, printers such as calculators, recorders for medical measurements, automatic ticket vending machines, and thermal recording labels.

[0003] In recent years, the use of thermal recording materials has been increasing in the fields of labels, passenger tickets, and coupon tickets associated with the POS systems of retail stores and supermarkets and the automated systems of transportation. In these applications, resistance of the recorded image (print, image, pattern) to water, alcohol, etc. is an essential condition. In addition, the demand for high-speed recording to improve productivity is increasing, and the development of a thermal recording material with excellent thermal response that can fully accommodate high-speed recording is strongly desired. In order to improve thermal response, a color-developing compound with a low melting point and a small heat of fusion is generally required. However, when such a color-developing compound is used, the unprinted part (background) of the thermal recording material is likely to darken during production, use, or storage, a phenomenon known as background fogging, and therefore improvement of the stability of the background is desired.

[0004] Generally, color-developing compounds having a phenolic hydroxyl group have high color-developing ability, and among them, many reports have been made on bisphenol-based compounds due to their high color-developing density, and 2,2-bis(4-hydroxyphenylpropane) (bisphenol A) (Patent Document 1) and 4,4'-dihydroxydiphenyl sulfone (bisphenol S) (Patent Document 2) have been proposed. However, these compounds have a high melting point, which results in poor thermal response, and the printed area has a drawback of poor water resistance. Moreover, the use of phenol-based compounds such as bisphenol A has been pointed out as problematic due to endocrine problems, and there is a demand for non-phenol-based color-developing compounds that do not contain a phenol structure.

[0005] In response to such demands, Patent Document 3 discloses [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate as a non-phenolic color-developing compound that has excellent water resistance in the printed portion and high stability against heat in the background. However, the thermal response of this compound is not sufficient, and further improvement in the thermal response is desired to accommodate high-speed recording.

[0006] Typically, in order to improve the thermal response of thermal recording materials, a method of adding a sensitizer with a low melting point (thermofusible compound) is adopted. In order to maintain heat-resistant storage stability in high-temperature environments, a sensitizer with a relatively high melting point may also be added. However, in the low applied energy range, melting of the sensitizer becomes difficult, and the printing color reaction is not sufficiently induced, so further improvement of the thermal response is a challenge. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 3,539,375 [Patent Document 2] Japanese Patent Publication No. 57-11088 [Patent Document 3] Patent No. 6529197 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to solve the problems of the prior art described above, and more specifically, to provide a heat-sensitive recording material which has excellent thermal response and excellent heat-resistant preservation properties of the printed area and background even in a high-temperature environment. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have newly discovered that a thermal recording material containing a color-forming compound, a color-developing compound having a specific structure, and a sensitizer compound having a specific structure can solve the above-mentioned problems, and have thus completed the present invention. That is, the present invention is [1] A thermal recording composition comprising a color former, a color developer, and a sensitizer, wherein the color developer is represented by the following formula (1):

[0010] [ka]

[0011] (In formula (1), R 1 ~R 5 each independently represents a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group. and a sensitizer containing 1,2-bis(tosyloxy)ethane. [2] R 1 , R 2 , R 4 and R 5 The thermal recording composition according to the above item [1], wherein [3] R 3 The thermal recording composition according to the above item [2], wherein [4] The compound represented by formula (1) is represented by the following formula (2):

[0012] [ka]

[0013] The thermal recording composition according to the above item [3], [5] The thermal recording composition according to any one of the above items [1] to [4], wherein the content of the sensitizer is 10 to 250% by mass of the content of the color developer. [6] The thermal recording composition according to any one of the above items [1] to [5], wherein the color former contains a compound selected from the group consisting of triarylmethane compounds, fluoran compounds, azaphthalide compounds, and fluorene compounds. [7] The color former is 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(o,p-dimethylanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-(cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 3-Nn-dibutylamino-6-methyl-7-anilinofluoran, a thermal recording composition according to the preceding item [6], which contains a fluoran compound selected from the group consisting of N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran and 3-dipentylamino-6-methyl-7-anilinofluoran; [8] A heat-sensitive recording material having a heat-sensitive recording layer made of the heat-sensitive recording composition according to any one of the preceding items [1] to [7] on a support. [9] The thermal recording material according to the preceding paragraph [8], wherein the support is high-quality paper, synthetic paper or a plastic film; and

[10] The coating amount of the thermal recording layer is 1 to 20 g / m 2 The thermal recording material according to the above item [8] or [9], Regarding. Effect of the Invention

[0014] According to the present invention, it is possible to provide a heat-sensitive recording material having excellent thermal response and excellent heat-resistant storage stability in a high-temperature environment of the printed portion and the background. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described in detail below based on the embodiments, but the present invention is not limited to these embodiments. The thermal recording composition of the present invention contains a color former, a color developer containing the compound represented by the above general formula (1), and a sensitizer containing 1,2-bis(tosyloxy)ethane.

[0016] The color former used in the thermal recording composition of the present invention is not particularly limited as long as it is a color former that is generally used in pressure-sensitive recording paper or thermal recording paper. Specific examples of color formers (color-forming compounds) include fluoran compounds, triarylmethane compounds, spiro compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds and vinylphthalide compounds, among which triarylmethane compounds, fluoran compounds, azaphthalide compounds or fluorene compounds are preferred, and fluoran compounds are more preferred.These color-forming compounds can be used alone or in combination.

[0017] The fluoran compound used as a color former is not particularly limited as long as it is a compound having a fluoran skeleton that is generally used as a color former for thermal recording paper. Specific examples of fluoran compounds include 3-diethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran, and 3-[N-ethyl-N-(3-ethoxypropyl)amino]-6-methyl-7-anilinofluoran. , 3-(N-ethyl-N-hexylamino)-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-tetrahydrofurylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(p-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-(p-fluoroanilino)fluoran, 3-[N-ethyl-N-(p-tolyl)a amino]-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(p-toluidino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-diethylamino-7-(o-fluoroanilino)fluoran, 3-dibutylamino-7-(o-fluoroanilino)fluoran, 3-diethylamino-7-(3,4-dichloroanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-diethylamino No-6-chloro-7-ethoxyethylaminofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-octylfluoran, 3-[N-ethyl-N-(p-tolyl)amino]-6-methyl-7-phenethylfluoran, 2-methyl-6-(Np-tolyl-N-ethylamino)fluoran (RED520), 9-(N-ethyl-N-isopentylamino)spiro[benzo[a]xanthene-12,3'-phthalide] (RED500), 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[phthalide-3,9'-xanthene] (S-205), 2'-anilino-6'-(N,N-dipentan-1-ylamino)-3'-methyl-3H-spiro[isobenzofuran-1,9'-xanthene]-3-one (Black305), 2'-anilino-6'-(dibutylamino)-3'-methylspiro[phthalide-3,9'-xanthene] (Black400), 2'-anilino-6'-[N-ethyl-N-(4-tolyl)amino]-3'-methyl-3H-spiro[isobenzofuran-1,9'-xanthene]-3-one (ETAC), 6- (Diethylamino)-2-[(3-trifluoromethyl)anilino]xanthene-9-spiro-3'-phthalide (Black 100), 1-ethyl-8-[N-ethyl-N-(4-methylphenyl)amino]-2,2,4-trimethyl-1,2-dihydrospiro[11H-chromeno[2,3,-g]quinoline-11,3'-phthalide] (H-1046), 3-dibutylamino-6-methyl-7-bromofluoran and 3-[4-(diethylamino)phenyl]-3-(1-ethyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone (Blue 502) are included, and 3-dibutylamino-6-methyl-7-anilinofluoran is preferred.

[0018] The triarylmethane compound used as a color former is not particularly limited as long as it is a compound having a triarylmethane skeleton that is generally used as a color former for thermal recording paper. Specific examples of triarylmethane compounds include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone or CVL), 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylaminoindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-phenylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3-yl)-5-dimethylaminophthalide, 3,3-(2-phenylindol-3-yl)phthalide, 3-(4-diethylamino-2-methylphenyl)-3-(1-ethyl-2-methylindol-3-yl)-5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-2-yl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-methylphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (Blue 200), 3-[4-(diethylamino)-2-hexyloxyphenyl]-3-(1-ethyl-2-methylindol -3-yl)-4-azaphthalide (Blue 203), 3-(4-diethylamino-2-methylphenyl)-3-(1-ethyl-2-methyl-1H-indol-3-yl)-4-azaphthalide (Blue 220) and 7-(4-diethylamino-2-ethoxyphenyl)-7-(1-ethyl-2-methyl-1H-indol-3-yl)furo[3,4-b]pyridin-5(7H)-one (Blue 63).

[0019] The spiro compound used as the color former is not particularly limited as long as it is a compound having a spiro skeleton that is generally used as a color former for thermal recording paper. Specific examples of spiro compounds include 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-propylspirobenzopyran, 3-methylnaphtho-(3-methoxybenzo)spiropyran, and 1,3,3-trimethyl-6-nitro-8'-methoxyspiro(indoline-2,2'-benzopyran).

[0020] The diphenylmethane compound used as a color former is not particularly limited as long as it is a compound having a diphenylmethane skeleton that is generally used as a color former for thermal recording paper. Specific examples of diphenylmethane compounds include N-halophenyl-leucoauramine, 4,4-bis-dimethylaminophenyl benzhydryl benzyl ether, and N-2,4,5-trichlorophenyl leucoauramine.

[0021] The thiazine compound used as a color former is not particularly limited as long as it is a compound having a thiazine skeleton that is generally used as a color former for thermal recording paper. Specific examples of thiazine compounds include benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue, and the like.

[0022] The lactam compound used as a color former is not particularly limited as long as it is a compound having a lactam skeleton that is generally used as a color former for thermal recording paper. Specific examples of lactam compounds include rhodamine B anilinolactam and rhodamine B p-chloroanilinolactam.

[0023] The fluorene compound used as a color former is not particularly limited as long as it is a compound having a fluorene skeleton that is generally used as a color former for thermal recording paper. Specific examples of the fluorene compound include 3,6-bis(dimethylamino)fluorene spiro(9,3')-6'-dimethylaminophthalide, 3,6-bis(dimethylamino)fluorene spiro(9,3')-6'-pyrrolidinophthalide, and 3-dimethylamino-6-diethylaminofluorene spiro(9,3')-6'-pyrrolidinophthalide.

[0024] The vinylphthalide compound as the color former is not particularly limited as long as it is a compound having a vinylphthalide skeleton that is generally used as a color former for thermal recording paper. Specific examples of vinylphthalide compounds include 3-[2,2-bis(4-diethylaminophenyl)vinyl]-6-dimethylaminophthalide (H-3035) and 3,3-bis[2-(4-dimethylaminophenyl)-2-(4-methoxyphenyl)vinyl]-4,5,6,7-tetrachlorophthalide (NIR Black 78).

[0025] The thermal recording composition of the present invention contains a developer containing the compound represented by the above formula (1) as an essential component. In formula (1), R 1 ~R 5 each independently represents a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.

[0026] R in Equation (1) 1 ~R 5 The alkyl group represented by is not limited to being linear, branched, or cyclic, but is preferably linear or branched, more preferably linear, and usually has 1 to 12 carbon atoms, preferably 1 to 8, more preferably 1 to 6, and even more preferably 1 to 4. R in Equation (1) 1 ~R 5Specific examples of the alkyl group represented by include straight-chain alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, and an n-dodecyl group; branched-chain alkyl groups such as an isopropyl group, an isobutyl group, a sec-butyl group, a t-butyl group, an isopentyl group, an isohexyl group, and an isooctyl group; and cyclic alkyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.

[0027] R in Equation (1) 1 ~R 5 The alkoxy group represented by is not limited to being linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear. It usually has 1 to 12 carbon atoms, preferably 1 to 8, more preferably 1 to 6, and even more preferably 1 to 4. R in Equation (1) 1 ~R 5 Specific examples of the alkoxy group represented by the formula (I) include linear alkoxy groups such as a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentoxy group, an n-hexyloxy group, an n-heptoxy group, an n-octyloxy group, an n-nonyloxy group, and an n-decyloxy group; an isopropoxy group, an isobutoxy group, a sec-butoxy group, a t-butoxy group, an isoamyloxy group, a t-amyloxy group, an isohexyloxy group, a t-hexyloxy group, and the like. Examples of alkoxy groups include branched alkoxy groups (preferably having 3 to 10 carbon atoms), such as an alkoxy group, an isoheptoxy group, a t-heptoxy group, an isooctyloxy group, a t-octyloxy group, a 2-ethylhexyloxy group, an isononyloxy group, or an isodecyloxy group; and cyclic alkoxy groups (preferably having 3 to 7 carbon atoms), such as a cyclopropoxy group, a cyclobutoxy group, a cyclopentoxy group, a cyclohexyloxy group, or a cycloheptoxy group.

[0028] R in Equation (1) 1 ~R 5 The aryloxy group represented by is preferably an aryloxy group having 6 to 12 carbon atoms in the aryl group, and specific examples thereof include a phenoxy group, a naphthyloxy group, and a biphenyloxy group.

[0029] R in Equation (1) 1 ~R 5 The alkyl group in the alkylcarbonyloxy group represented by is not limited to being linear, branched, or cyclic, but is preferably a linear or branched alkylcarbonyloxy group, more preferably a linear alkylcarbonyloxy group. The number of carbon atoms in the alkylcarbonyloxy group is preferably 1 to 10. R in Equation (1) 1 ~R 5 Specific examples of the alkylcarbonyloxy group represented by the formula (I) include linear alkylcarbonyloxy groups such as a methylcarbonyloxy group, an ethylcarbonyloxy group, an n-propylcarbonyloxy group, an n-butylcarbonyloxy group, an n-pentylcarbonyloxy group, an n-hexylcarbonyloxy group, an n-heptylcarbonyloxy group, an n-octylcarbonyloxy group, an n-nonylcarbonyloxy group, and an n-decylcarbonyloxy group; an isopropylcarbonyloxy group, an isobutylcarbonyloxy group, a sec-butylcarbonyloxy group, a t-butylcarbonyloxy group, an isoamylcarbonyloxy group, a t-amylcarbonyloxy group, and an isohexylcarbonyloxy group. branched chain (preferably having 3 to 10 carbon atoms in the alkyl portion) alkylcarbonyloxy groups such as t-hexylcarbonyloxy group, isoheptylcarbonyloxy group, t-heptylcarbonyloxy group, isooctylcarbonyloxy group, t-octylcarbonyloxy group, 2-ethylhexylcarbonyloxy group, isononylcarbonyloxy group, and isodecylcarbonyloxy group; and cyclic (preferably having 3 to 7 carbon atoms in the alkyl portion) alkylcarbonyloxy groups such as cyclopropylcarbonyloxy group, cyclobutylcarbonyloxy group, cyclopentylcarbonyloxy group, cyclohexylcarbonyloxy group, and cycloheptylcarbonyloxy group.

[0030] R in Equation (1) 1 ~R 5The alkyl group in the alkylcarbonylamino group represented by is not limited to being linear, branched, or cyclic, but is preferably a linear or branched alkylcarbonylamino group, more preferably a linear alkylcarbonylamino group. The number of carbon atoms in the alkylcarbonylamino group is preferably 1 to 10. R in Equation (1) 1 ~R 5 Specific examples of the alkylcarbonylamino group represented by the formula (I) include linear alkylcarbonylamino groups such as a methylcarbonylamino group, an ethylcarbonylamino group, an n-propylcarbonylamino group, an n-butylcarbonylamino group, an n-pentylcarbonylamino group, an n-hexylcarbonylamino group, an n-heptylcarbonylamino group, an n-octylcarbonylamino group, an n-nonylcarbonylamino group, and an n-decylcarbonylamino group; an isopropylcarbonylamino group, an isobutylcarbonylamino group, a sec-butylcarbonylamino group, a t-butylcarbonylamino group, an isoamylcarbonylamino group, a t-amylcarbonylamino group, an isohexylcarbonylamino group, Examples of such alkylcarbonylamino groups include branched chain (preferably having 3 to 10 carbon atoms in the alkyl portion) alkylcarbonylamino groups such as t-hexylcarbonylamino group, isoheptylcarbonylamino group, t-heptylcarbonylamino group, isooctylcarbonylamino group, t-octylcarbonylamino group, 2-ethylhexylcarbonylamino group, isononylcarbonylamino group, and isodecylcarbonylamino group; and cyclic (preferably having 3 to 7 carbon atoms in the alkyl portion) alkylcarbonylamino groups such as cyclopropylcarbonylamino group, cyclobutylcarbonylamino group, cyclopentylcarbonylamino group, cyclohexylcarbonylamino group, and cycloheptylcarbonylamino group.

[0031] R in Equation (1) 1 ~R 5 The arylcarbonylamino group represented by the formula (I) is preferably an arylcarbonylamino group having 6 to 12 carbon atoms in the aryl group, and specific examples thereof include a phenylcarbonylamino group, a naphthylcarbonylamino group, and a biphenylcarbonylamino group.

[0032] R in Equation (1) 1 ~R 5 The alkyl group in the alkylsulfonylamino group represented by is not limited to being linear, branched, or cyclic, but is preferably an alkylsulfonylamino group in which the alkyl group is linear or branched, and more preferably an alkylsulfonylamino group in which the alkyl group is linear. The number of carbon atoms in the alkylsulfonylamino group is preferably 1 to 10. R in Equation (1) 1 ~R 5 Specific examples of the alkylsulfonylamino group represented by the formula (I) include linear alkylsulfonylamino groups such as a methylsulfonylamino group, an ethylsulfonylamino group, an n-propylsulfonylamino group, an n-butylsulfonylamino group, an n-pentylsulfonylamino group, an n-hexylsulfonylamino group, an n-heptylsulfonylamino group, an n-octylsulfonylamino group, an n-nonylsulfonylamino group, and an n-decylsulfonylamino group; an isopropylsulfonylamino group, an isobutylsulfonylamino group, a sec-butylsulfonylamino group, a t-butylsulfonylamino group, an isoamylsulfonylamino group, a t-amylsulfonylamino group, an isohexylsulfonylamino group, Examples of such alkylsulfonylamino groups include branched chain (preferably having 3 to 10 carbon atoms in the alkyl portion) alkylsulfonylamino groups, such as t-hexylsulfonylamino group, isoheptylsulfonylamino group, t-heptylsulfonylamino group, isooctylsulfonylamino group, t-octylsulfonylamino group, 2-ethylhexylsulfonylamino group, isononylsulfonylamino group, and isodecylsulfonylamino group; and cyclic (preferably having 3 to 7 carbon atoms in the alkyl portion) alkylsulfonylamino groups, such as cyclopropylsulfonylamino group, cyclobutylsulfonylamino group, cyclopentylsulfonylamino group, cyclohexylsulfonylamino group, and cycloheptylsulfonylamino group.

[0033] R in Equation (1) 1 ~R 5The arylsulfonylamino group represented by the formula (I) is preferably an arylsulfonylamino group having 6 to 12 carbon atoms in the aryl group, and specific examples thereof include a phenylsulfonylamino group, a toluenesulfonylamino group, a naphthylsulfonylamino group, and a biphenylsulfonylamino group.

[0034] R in Equation (1) 1 ~R 5 The alkyl group in the monoalkylamino group represented by is not limited to being linear, branched, or cyclic, but is preferably a monoalkylamino group in which the alkyl group is linear or branched, more preferably a linear monoalkylamino group. The number of carbon atoms in the monoalkylamino group is preferably 1 to 10. R in Equation (1) 1 ~R 5 Specific examples of the monoalkylamino group represented by the formula (I) include linear monoalkylamino groups such as a methylamino group, an ethylamino group, an n-propylamino group, an n-butylamino group, an n-pentylamino group, an n-hexylamino group, an n-heptylamino group, an n-octylamino group, an n-nonylamino group, and an n-decylamino group; an isopropylamino group, an isobutylamino group, a sec-butylamino group, a t-butylamino group, an isoamylamino group, a t-amylamino group, an isohexylamino group, a t-heptylamino group, and an isopropylamino group, branched-chain monoalkylamino groups (preferably having 3 to 10 carbon atoms), such as an xylamino group, an isoheptylamino group, a t-heptylamino group, an isooctylamino group, a t-octylamino group, a 2-ethylhexylamino group, an isononylamino group, or an isodecylamino group; and cyclic monoalkylamino groups (preferably having 3 to 7 carbon atoms), such as a cyclopropylamino group, a cyclobutylamino group, a cyclopentylamino group, a cyclohexylamino group, or a cycloheptylamino group.

[0035] R in Equation (1) 1 ~R 5The alkyl group in the dialkylamino group represented by is not limited to be linear, branched or cyclic, but is preferably a dialkylamino group in which the alkyl group is linear or branched, and more preferably a linear dialkylamino group. The number of carbon atoms in the alkyl group in the monoalkylamino group is preferably 1 to 10. The number of carbon atoms in the two alkyl groups in the dialkylamino group may be the same or different, but is preferably the same. R in Equation (1) 1 ~R 5 Specific examples of the dialkylamino group represented by the formula (I) include dialkylamino groups having a straight-chain alkyl group such as a dimethylamino group, a diethylamino group, a di-n-propylamino group, a di-n-butylamino group, a di-n-pentylamino group, a di-n-hexylamino group, a di-n-heptylamino group, a di-n-octylamino group, a di-n-nonylamino group, and a di-n-decylamino group; a diisopropylamino group, a diisobutylamino group, a di-sec-butylamino group, a di-t-butylamino group, a diisoamylamino group, a di-t-amylamino group, a diisohexylamino group, a di-t dialkylamino groups having a branched alkyl group (preferably having 3 to 10 carbon atoms), such as di-hexylamino group, diisoheptylamino group, di-t-heptylamino group, diisooctylamino group, di-t-octylamino group, di-(2-ethylhexyl)amino group, diisononylamino group, and diisodecylamino group; and dialkylamino groups having a cyclic alkyl group (preferably having 3 to 7 carbon atoms), such as dicyclopropylamino group, dicyclobutylamino group, dicyclopentylamino group, dicyclohexylamino group, and dicycloheptylamino group.

[0036] R in Equation (1) 1 ~R 5 The arylamino group represented by is not limited to either a monoarylamino group or a diarylamino group, but is preferably a monoarylamino group, and the aryl group in the arylamino group preferably has 6 to 12 carbon atoms. R in Equation (1) 1 ~R 5Specific examples of the arylamino group represented by the formula (I) include a phenylamino (anilino) group, a naphthylamino group, a biphenylamino group, a diphenylamino group, a dinaphthylamino group, and a di(biphenyl)amino group.

[0037] According to a preferred embodiment of the present invention, R 1 ~R 5 is an alkyl group or a hydrogen atom, more preferably a linear alkyl group having 1 to 4 carbon atoms or a hydrogen atom, and particularly preferably a methyl group or a hydrogen atom.

[0038] According to a preferred embodiment of the present invention, R 1 , R 2 , R 4 , and R 5 is a hydrogen atom, and R 3 represents a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group, more preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms (preferably a linear alkyl group), still more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (preferably a linear alkyl group), particularly preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (preferably a linear alkyl group), and most preferably a methyl group.

[0039] The substitution position of the partial skeleton represented by the following general formula (3), which is bonded to one of the benzene rings of the diphenylurea structure in formula (1), is not limited to any of the ortho-position, meta-position, or para-position with respect to the aminocarbonyl group on the benzene ring, but is preferably the ortho-position or meta-position, and more preferably the meta-position.

[0040] [ka]

[0041] According to a preferred embodiment of the present invention, the colour developing compound is R 1 ~R 5 is an alkyl group or a hydrogen atom, and the substitution position of the partial skeleton represented by general formula (3) is an ortho-position or a meta-position with respect to the aminocarbonyl group on the benzene ring, and more preferably, R 1 ~R 5 is a linear alkyl group having 1 to 8 carbon atoms or a hydrogen atom, and the substitution position of the partial skeleton represented by general formula (3) is a meta position with respect to the aminocarbonyl group on the benzene ring, and more preferably, R 1 ~R 5 is a linear alkyl group having 1 to 4 carbon atoms or a hydrogen atom, and the substitution position of the partial skeleton represented by general formula (3) is a meta position relative to the aminocarbonyl group on the benzene ring. 1 ~R 5 is a methyl group or a hydrogen atom, and the substitution position of the partial skeleton represented by general formula (3) is the meta position relative to the aminocarbonyl group on the benzene ring.

[0042] According to another preferred embodiment of the present invention, the color-developing compound is R 1 , R 2 , R 4 , and R 5 is a hydrogen atom, and R 3 is a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group, and the substitution position of the partial skeleton represented by general formula (3) is the ortho position, meta position, or para position relative to the aminocarbonyl group on the benzene ring, and more preferably, R 1 , R 2 , R 4 , and R 5 is a hydrogen atom, and R3 is a hydrogen atom or an alkyl group, and the substitution position of the partial skeleton represented by general formula (3) is the ortho-position or meta-position relative to the aminocarbonyl group on the benzene ring, and more preferably, R 1 , R 2 , R 4 , and R 5 is a hydrogen atom, and R 3 is a linear alkyl group having 1 to 8 carbon atoms or a hydrogen atom, and the substitution position of the partial skeleton represented by general formula (3) is a meta position relative to the aminocarbonyl group on the benzene ring, and more preferably, R 1 , R 2 , R 4 , and R 5 is a hydrogen atom, and R 3 is a linear alkyl group having 1 to 4 carbon atoms or a hydrogen atom, and the substitution position of the partial skeleton represented by general formula (3) is a meta position relative to the aminocarbonyl group on the benzene ring, and is particularly preferably a compound of general formula (1) above. 1 , R 2 , R 4 , and R 5 is a hydrogen atom, and R 3 is a methyl group, and the substitution position of the partial skeleton represented by general formula (3) is the meta position relative to the aminocarbonyl group on the benzene ring, which is the compound of general formula (1).

[0043] The compound represented by formula (1) may be any of the above-mentioned R 1 , R 2 , R 4 And R 5 , R 3 and combinations of preferred or more preferred aspects of the respective substitution positions of the partial skeleton represented by formula (3) are preferred. That is, an example of a preferred embodiment of the compound represented by formula (1) is the compound represented by the above general formula (2).

[0044] Specific examples of the compound represented by formula (1) are given below, but the compound represented by formula (1) contained in the color developer as an essential component is not limited to these.

[0045] [Table 1]

[0046] [Table 2]

[0047] [Table 3]

[0048] [Table 4]

[0049] [Table 5]

[0050] [Table 6]

[0051] [Table 7]

[0052] The color developer contained in the thermal recording composition of the present invention may be used in combination with a color developer other than the compound represented by formula (1) within a range that does not impair the effects of the present invention. The color developer that can be used in combination is not particularly limited, and examples thereof include benzotriazole derivatives (compounds having a benzotriazole skeleton, hereinafter "derivatives" have the same meaning), saccharin derivatives, sulfonamide derivatives, malonamide derivatives, thiourea derivatives, sulfonylurea derivatives, and aromatic carboxylic acid derivatives.

[0053] Specific examples of the benzotriazole derivative include benzotriazole, 5-methyl-1H-benzotriazole, 4-methyl-1H-benzotriazole, phenyl-6-benzotriazole, phenyl-5-benzotriazole, chloro-5-benzotriazole, chloro-5-methylbenzotriazole, chloro-5-isopropyl-7-methyl-4-benzotriazole, and bromo-5-benzotriazole.

[0054] Specific examples of saccharin derivatives include saccharin, 1-bromosaccharin, 1-nitrosaccharin, and 1-aminosaccharin.

[0055] Specific examples of sulfonamide derivatives include methanilanilide, N-phenyl-4-aminobenzenesulfonamide, neourilone, N-phenyl-3-nitrobenzenesulfonamide, N-(4-methyl-2-nitrophenyl)benzenesulfonamide, N-(2-methoxyphenyl)-p-toluenesulfonamide, N-(4-methoxyphenyl)-p-toluenesulfonamide, N-(2-chlorophenyl)-p-toluenesulfonamide, N-(4-methylphenyl)-4-methylbenzenesulfonamide, N-(2-methylphenyl)-p-toluenesulfonamide, N-phenylbenzenesulfonamide, 4-bromo-4'-methylbenzenesulfonanilide, N-(4-bromophenyl)benzenesulfonamide, N-(3-nitrophenyl)benzenesulfonamide, N-(4-nitrophenyl)-4-methylbenzenesulfonamide, N-(4-methylphenyl)benzenesulfonamide, N-phenyl-p-toluenesulfonamide, and N-phenylbenzenesulfonamide.

[0056] Specific examples of malonamide derivatives include N,N'-bis(2-hydroxy-5-phenyl)phenyl-malonamide, N,N'-diphenylmalonamide, N,N'-bis(2,4,6-tribromophenyl)malonamide, N,N'-bis(2-aminophenyl)malonamide, N,N'-bis(m-trifluoromethylphenyl)malonamide, N,N'-bis(m-trifluoromethylphenyl)α,α-dichloromalonamide, and diethylmalondianilide.

[0057] Specific examples of the thiourea derivatives include 1,3-bis(4-methylphenyl)thiourea, 1,3-bisphenylthiourea, 1,3-bis(4-chlorophenyl)thiourea, 1,3-bis(4-methoxyphenyl)thiourea, N,N'-bis(3-chlorophenyl)thiourea, 1,3-bis(3-methoxyphenyl)thiourea, 1,3-bis(3-methylphenyl)thiourea, 1,3-bis(4-benzylphenyl)thiourea, 1,3-bis(4-bromophenyl)thiourea, 1-phenyl-3-butylthiourea, and 1-phenyl-3-ethylthiourea.

[0058] Specific examples of sulfonylurea derivatives include N-(p-toluenesulfonyl)-N'-(3-n-butylaminosulfonylphenyl)urea, N-(p-toluenesulfonyl)-N'-(4-trimethylacetophenyl)urea, N-(benzenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)urea, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonylphenyl)urea, N-(p-toluenesulfonyl)-N'-(3-phenylsulfonyloxyphenyl)urea, tolbutamide, and chlorpropamide.

[0059] Specific examples of aromatic carboxylic acid derivatives include benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5-di-t-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and aromatic carboxylic acids or polyvalent metal salts thereof.

[0060] The sensitizer contained in the thermal recording composition of the present invention may be used in combination with a sensitizer other than 1,2-bis(tosyloxy)ethane. Specific examples of the sensitizer that can be used in combination include waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, naphthalene derivatives, aromatic ethers, aromatic carboxylic acid derivatives, aromatic sulfonic acid ester derivatives, carbonic acid or oxalic acid diester derivatives, biphenyl derivatives, terphenyl derivatives, sulfone derivatives, aromatic ketone derivatives, and aromatic hydrocarbon compounds.

[0061] Specific examples of waxes include Japan wax, carnauba wax, shellac, paraffin, montan wax, paraffin oxide, polyethylene wax, and polyethylene oxide, while specific examples of higher fatty acids include stearic acid and behenic acid, etc. Specific examples of higher fatty acid amides include stearic acid amide, oleic acid amide, N-methylstearic acid amide, erucic acid amide, methylolbehenic acid amide, methylenebisstearic acid amide, and ethylenebisstearic acid amide, while specific examples of higher fatty acid anilides include stearic acid anilide and linoleic acid anilide, and specific examples of naphthalene derivatives include 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, and 2,6-diisopropylnaphthalene, etc. Specific examples of aromatic ethers include 1,2-diphenoxyethane, 1,4-diphenoxybutane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,2-bis(4-methoxyphenoxy)ethane, 1,2-bis(3,4-dimethylphenyl)ethane, 1-phenoxy-2-(4-chlorophenoxy)ethane, 1-phenoxy-2-(4-methoxyphenoxy)ethane, 1,2-diphenoxymethylbenzene, and diphenyl glycol. Specific examples of aromatic carboxylic acid derivatives include p-hydroxybenzoic acid benzyl ester, p-benzyloxybenzoic acid benzyl ester, and terephthalic acid dibenzyl ester. Specific examples of aromatic sulfonate derivatives include p-toluenesulfonic acid phenyl ester, phenyl mesitylene sulfonate, 4-methylphenyl mesitylene sulfonate, and 4-tolylmesitylene sulfonate. Specific examples of carbonic acid or oxalic acid diester derivatives include diphenyl carbonate, dibenzyl oxalate, di(4-chlorobenzyl) oxalate, and di(4-methylbenzyl) oxalate. Specific examples of biphenyl derivatives include p-benzylbiphenyl and p-allyloxybiphenyl.Specific examples of terphenyl derivatives include m-terphenyl, etc., specific examples of sulfone derivatives include p-toluenesulfonamide, benzenesulfonanilide, p-toluenesulfonanilide, and diphenylsulfone, etc., specific examples of aromatic ketone derivatives include 4,4'-dimethylbenzophenone and dibenzoylmethane, etc., and specific examples of aromatic hydrocarbon compounds include p-acetotoluidine, etc.

[0062] The heat-sensitive recording composition of the present invention may contain optional components such as a storage stability improver, a binder, a filler, and other additives, if necessary. These optional components may be contained in the heat-sensitive recording layer, but when the composition has a multi-layer structure or when an undercoat layer or a protective layer (overcoat layer) is provided on the upper and / or lower side of the heat-sensitive recording layer, they may be contained in each of these layers.

[0063] Specific examples of the storage stability improver that can be used in combination with the thermal recording composition of the present invention include 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2,2'-ethylidenebis(4,6-di-t-butylphenol), 4,4'-thiobis(2-methyl-6-t-butylphenol), 4,4'-butylidenebis(6-t-butyl-m-cresol), 1-[α-methyl-α-(4'-hydroxyphenyl)ethyl]-4-[α',α'-bis(4' -hydroxyphenyl)ethyl]benzene, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, tris(2,6-dimethyl-4-tert-butyl-3-hydroxybenzyl)isocyanurate, 4,4'-thiobis(3-methylphenol), 4,4'-dihydroxy-3,3',5,5'-tetrabromodiphenylsulfone, 4,4'-dihydroxy-3,3',5,5'-tetrabromodiphenylsulfone, Hindered phenol compounds such as methyldiphenyl sulfone, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4'-(2-methylglycidyloxy)diphenyl sulfone, diglycidyl terephthalate, cresol novolac type esters, Examples of the epoxy resin include epoxy compounds such as epoxy resin, phenol novolac type epoxy resin, and bisphenol A type epoxy resin, N,N'-di-2-naphthyl-p-phenylenediamine, sodium or polyvalent metal salt of 2,2'-methylenebis(4,6-di-t-butylphenyl)phosphate, bis(4-ethyleneiminocarbonylaminophenyl)methane, urea urethane compounds (such as color developing compound UU manufactured by Chemipro Chemical Co., Ltd.), and diphenylsulfone crosslinked compounds represented by the following formula (4) or mixtures thereof. In formula (4), a is an integer of 0 to 6.

[0064] [ka]

[0065] Specific examples of binders that can be used in combination with the thermal recording composition of the present invention include cellulose derivatives such as methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, and cellulose; polyvinyl alcohols having various degrees of saponification and polymerization such as polyvinyl alcohol (PVA), carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, silyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and acetoacetyl-modified polyvinyl alcohol; polyvinyl pyrrolidone, polyacrylamide, sodium polyacrylate, starch and its derivatives; sulfosuccinic acid esters such as dioctyl sodium sulfosuccinate; sodium dodecylbenzenesulfonate; sodium lauryl alcohol sulfate; fatty acid salts; casein; gelatin; and water-soluble isocyanates. Examples of the water-soluble polymers include isoprene rubber, alkali salts of styrene / maleic anhydride copolymers, and alkali salts of iso(or diiso)butylene / maleic anhydride copolymers; and hydrophobic polymer emulsions such as (meth)acrylic acid ester copolymers, styrene / (meth)acrylic acid ester copolymers, polyurethane, polyester polyurethanes, polyether polyurethanes, polyvinyl acetate, ethylene / vinyl acetate copolymers, polyvinyl chloride, vinyl chloride / vinyl acetate copolymers, polyvinylidene chloride, polystyrene, styrene / butadiene (SB) copolymers, carboxylated styrene / butadiene (SB) copolymers, styrene / butadiene / acrylic acid copolymers, acrylonitrile / butadiene (NB) copolymers, carboxylated acrylonitrile / butadiene (NB) copolymers, and composite particles of colloidal silica and (meth)acrylic resin.

[0066] Specific examples of fillers that can be used in combination with the thermal recording composition of the present invention include inorganic pigments such as calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, kaolin, calcined kaolin, lithopone, talc, clay, magnesium hydroxide, aluminum hydroxide, titanium oxide, zinc oxide, aluminum oxide, barium sulfate, diatomaceous earth, white earth oxide, bentonite, synthetic aluminum silicate, surface-treated calcium carbonate and silica, and organic pigments such as urea-formaldehyde resin, styrene-methacrylic acid copolymer resin, polystyrene resin, and raw starch particles.

[0067] Other additives that can be used in combination with the thermal recording composition of the present invention include, for example, higher fatty acid metal salts such as zinc stearate and calcium stearate, which are used in combination for the purposes of preventing abrasion and sticking of the thermal head, ultraviolet absorbers such as phenol derivatives, benzophenone compounds, and benzotriazole compounds, which are used in combination for the purposes of providing an antioxidant or anti-aging effect, various crosslinking agents, surfactants, antifoaming agents, etc. These antioxidants or ultraviolet absorbers may be microencapsulated as necessary.

[0068] The composition ratio of each component in the thermal recording composition of the present invention is not particularly limited as long as it does not impair the effects of the present invention, but the color former is usually 1 to 50 mass %, preferably 5 to 30 mass %, the color developer containing the compound represented by the above general formula (1) is usually 1 to 70 mass %, preferably 10 to 50 mass %, the sensitizer containing 1,2-bis(tosyloxy)ethane is usually 1 to 80 mass %, and the optional components of the storage stability improver are 30 mass % or less, the binder is 90 mass % or less, the filler is 80 mass % or less, and other additives such as lubricants, surfactants, antifoaming agents and ultraviolet absorbers are, for example, 30 mass % or less (mass % is the mass ratio of each component in the thermal recording material converted into the solid content).

[0069] In addition, the content of the developer containing the compound represented by formula (1) is usually 10 to 2000 mass%, preferably 50 to 1000 mass%, and more preferably 100 to 500 mass% of the content of the color former, and the content of the sensitizer containing 1,2-bis(tosyloxy)ethane is usually 10 to 250 mass% of the content of the developer containing the compound represented by formula (1) (parts by mass are calculated as solids content).

[0070] The heat-sensitive recording material of the present invention essentially comprises a support and a heat-sensitive recording layer formed on the support and comprising the heat-sensitive recording composition of the present invention. The material and shape of the support are not particularly limited, but examples include paper (plain paper, high-quality paper, coated paper, etc. can be used), synthetic paper, laminated paper, recycled paper such as waste paper pulp, film, films made of synthetic resins such as plastics and foamed plastics, and nonwoven fabrics. The method for providing a heat-sensitive recording layer on a support is not particularly limited. For example, a dispersion of the heat-sensitive recording composition of the present invention obtained by pulverizing and dispersing the composition using water as a dispersion medium with a dispersing machine such as a ball mill, an attritor, a sand mill, or a high-pressure jet mill is applied onto a support and dried to give a dry mass of preferably 1 to 20 g / m. 2 The thermal recording layer can be prepared as follows.

[0071] If necessary, an undercoat layer may be provided between the support and the thermosensitive recording layer, and a protective layer (overcoat layer) may be provided on the thermosensitive recording layer. The undercoat layer and the protective layer may be prepared, for example, by the same method as the above-mentioned method for preparing the thermosensitive recording layer, using a dispersion of a binder and other additives. The dry mass of the undercoat layer and the protective layer is preferably 0.1 to 10 g / m. 2 It is.

[0072] The undercoat layer preferably contains at least one pigment selected from organic pigments and inorganic pigments in order to further enhance recording sensitivity and recording runnability.

[0073] The inorganic pigment used in the undercoat layer is an oil-absorbing inorganic pigment having an oil absorption of preferably 70 ml / 100 g or more, more preferably 80 to 150 ml / 100 g, from the viewpoint of suppressing adhesion of scum and sticking to the thermal head. The oil absorption can be determined according to the method of JIS K 5101. Various oil-absorbing inorganic pigments can be used, including calcined kaolin, aluminum oxide, magnesium carbonate, amorphous silica, light calcium carbonate, talc, etc. The average particle size of the primary particles of these oil-absorbing inorganic pigments is preferably 0.01 to 5 μm, more preferably 0.02 to 3 μm. The proportion of the oil-absorbing inorganic pigment used can be selected from a wide range, but is generally preferably 2 to 95% by mass, more preferably 5 to 90% by mass, of the total solid content of the undercoat layer.

[0074] As the organic pigment used in the undercoat layer, for example, it is preferable to use non-foamable organic hollow particles (plastic hollow particles) that have a thermoplastic resin shell and contain gas inside to be already hollow, or thermally expandable particles that contain a low-boiling point solvent foaming agent inside and become foamed when heated. This can improve the recording sensitivity. In addition, the organic hollow particles (plastic hollow particles) remain on the support and form a uniform undercoat layer, improving the barrier properties, and thus preventing the color former from coming into contact with the plasticizer or the alkaline filler contained in the neutral paper, thereby suppressing the decrease in color development ability. Examples of organic hollow particles include conventionally known particles, such as particles whose film material is an acrylic resin, a styrene resin, a vinylidene chloride resin, or the like, and whose hollow ratio is 50 to 99%. Here, the hollow ratio is a value calculated by (d / D)×100. In the formula, d indicates the inner diameter of the organic hollow particles, and D indicates the outer diameter of the organic hollow particles. The average particle diameter of the organic hollow particles is preferably 0.5 to 10 μm, more preferably 1 to 4 μm, and even more preferably 1 to 3 μm. By making the average particle diameter 10 μm or less, when the coating liquid for the undercoat layer is applied by a blade coating method, problems such as streaks and scratches do not occur, and good coating suitability can be obtained. The proportion of the organic hollow particles used can be selected from a wide range, but generally, it is preferably 2 to 90 mass % of the total solid content of the undercoat layer, and more preferably 5 to 70 mass %.

[0075] When an oil-absorbing inorganic pigment is used in combination with organic hollow particles, the oil-absorbing inorganic pigment and the organic hollow particles are used in the above-mentioned ratio range, and the total amount of the oil-absorbing inorganic pigment and the organic hollow particles is preferably 5 to 90 mass %, more preferably 10 to 90 mass %, and even more preferably 10 to 80 mass %, of the total solid content of the undercoat layer.

[0076] The content of the organic hollow particles can be selected from a wide range, but is generally preferably 2 to 90% by mass of the total solid content of the undercoat layer. From the viewpoint of improving color development and enhancing barrier properties, the lower limit is more preferably 5% by mass or more, and even more preferably 10% by mass or more. On the other hand, from the viewpoint of suppressing adhesion of scum to the thermal head, the upper limit is more preferably 80% by mass or less, even more preferably 70% by mass or less, particularly preferably 60% by mass or less, and most preferably 50% by mass or less.

[0077] The undercoat layer is generally formed by applying a coating liquid for the undercoat layer, which is prepared by mixing organic hollow particles, pigments such as oil-absorbing pigments, adhesives, auxiliaries, etc., with water as a medium, onto a support and drying the coating liquid. The amount of the coating liquid for the undercoat layer to be applied is not particularly limited, but is preferably 3 to 20 g / m2 in terms of dry weight. 2 is preferred, and 5 to 12 g / m 2 is more preferred.

[0078] The adhesive used in the undercoat layer can be appropriately selected from those usable in the thermosensitive recording layer and the protective layer. In particular, from the viewpoint of improving the coating strength, oxidized starch, starch-vinyl acetate graft copolymer, polyvinyl alcohol, styrene-butadiene latex, etc. are preferred. The content of the adhesive can be selected from a wide range, but generally, it is preferably 5 to 30 mass % of the total solid content of the undercoat layer, more preferably 10 to 20 mass %.

[0079] The thermal recording material of the present invention may have a back layer mainly composed of a pigment and an adhesive on the side of the support opposite to the thermal recording layer, if necessary. This can further improve storage stability, curling resistance, and printer running performance. In addition, various known techniques in the field of thermal recording material production may be added as necessary, such as processing the back surface into an adhesive label by treating it with an adhesive, providing a magnetic recording layer, a printing coating layer, or even a thermal transfer recording layer or an inkjet recording layer.

[0080] The method for applying various dispersions or coating liquids onto a support is not particularly limited, and examples thereof include known coating methods such as bar coating, air knife coating, barber blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, and die coating. Each coating liquid may be applied and dried one layer at a time to form each layer, or the same coating liquid may be applied in two or more layers. Furthermore, simultaneous multi-layer coating may be performed in which two or more layers are applied simultaneously.

[0081] The coating method of the coating liquid for the undercoat layer is preferably a blade coating method from the viewpoint of improving the surface properties of the undercoat layer. This can eliminate unevenness of the support to form a thermosensitive recording layer of uniform thickness, thereby improving the recording sensitivity. In terms of quality, the surface smoothness of the undercoat layer is further improved, so that the coating uniformity of the coating liquid for the thermosensitive recording layer can be improved and curtain coating can be performed, and the barrier properties of the protective layer that is provided as necessary can be improved. The blade coating method is not limited to coating methods using blades such as bevel type and bent type, but also includes pure blade coating, rod blade method, bill blade method, etc.

[0082] The thermosensitive recording layer and the protective layer are preferably formed by simultaneous multi-layer coating by curtain coating or the like. This can form a uniform coating layer, improve the barrier properties of the protective layer, and increase productivity. Curtain coating is a method in which a coating liquid is allowed to flow down and fall freely to coat the support without contact, and known methods such as a slide curtain method, a couple curtain method, and a twin curtain method can be adopted, and there is no particular limitation. In addition, as described in JP-A-2006-247611 (Patent Document 4), the coating liquid is ejected downward from a curtain head to form a coating layer on a slope, and a curtain of the coating liquid is formed from a downward curtain guide part at the end of the slope to transfer the coating layer onto the web surface. In simultaneous multi-layer coating, each coating liquid may be laminated, coated, and then dried to form each layer, or the coating liquid forming the lower layer may be applied, and then the coating liquid forming the upper layer may be applied on the lower layer coating surface while the lower layer coating surface is wet without drying, and then dried to form each layer.

[0083] From the viewpoint of increasing the recording sensitivity and improving the image uniformity, a smoothing treatment may be carried out using a known method such as a super calendar or a soft calendar at any stage after the completion of the formation of each layer or after the completion of the formation of all layers.

[0084] The method for recording information on the heat-sensitive recording material of the present invention may be appropriately selected depending on the purpose, and examples thereof include a thermal head printer, a CO2 laser, a semiconductor laser, and the like. EXAMPLES

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the examples, "parts" means parts by mass and "%" means % by mass. The median particle size of the dispersion in the examples was measured using a laser diffraction / scattering type particle size distribution measuring device Microtrac MT3300EXII (manufactured by Microtrac Bell).

[0086] Example 1 (Preparation of the heat-sensitive recording material of the present invention) (Step 1) Preparation of developer dispersion [A] A mixture of the following composition was pulverized and dispersed using an Ashizawa Finetech bead mill (Labostar Mini LMZ015) to prepare a developer dispersion [A] with a median particle size of 0.7 μm. [A]Liquid Compound represented by formula (2) (see Patent Document 3) 30.0 parts 15.0 parts of 20% aqueous solution of sulfonic acid-modified polyvinyl alcohol (Gosenex L-3266, Mitsubishi Chemical Corporation) Water 55.0 parts

[0087] (Step 2) Preparation of color former dispersion [B] A mixture of the following composition was pulverized and dispersed using an Ashizawa Finetech bead mill (Labostar Mini LMZ015) to prepare a color former dispersion [B] with a median particle size of 1.0 μm. [B]Liquid 3-Dibutylamino-6-methyl-7-anilinofluoran (BLACK 400, Fukui Yamada Chemical Industry Co., Ltd.) 30.0 parts 15.0 parts of 20% aqueous solution of sulfonic acid-modified polyvinyl alcohol (Gosenex L-3266, Mitsubishi Chemical Corporation) Water 55.0 parts

[0088] (Step 3) Preparation of sensitizer dispersion [C] A mixture of the following composition was pulverized and dispersed to prepare a dispersion liquid [C] of a sensitizer having a median particle size of 1.0 μm. [C]Liquid 1,2-bis(tosyloxy)ethane (Tokyo Chemical Industry Co., Ltd.) 30.0 parts 15.0 parts of 20% aqueous solution of sulfonic acid-modified polyvinyl alcohol (Gosenex L-3266, Mitsubishi Chemical Corporation) Water 55.0 parts

[0089] (Step 4) Preparation of composition for thermal recording layer The above obtained solutions and the following chemicals were mixed in the following compositions to prepare coating solutions for the thermal recording layer. [A]Liquid 16.7 parts [B]Liquid 10.0 parts [C]Liquid 23.3 parts 67% calcium carbonate aqueous dispersion 12.0 parts 48% modified styrene-butadiene copolymer latex 10.7 parts 2.6 parts of 37% zinc stearate aqueous dispersion Water 34.5 parts

[0090] (Step 5) Preparation of the heat-sensitive recording material of the present invention Basis weight 50g / m 2 On a piece of wood-free paper, the mass of the color-forming compound when dried is 0.5 g / m 2 The composition for the heat-sensitive recording layer obtained in step 4 was applied in an amount that would result in a coating, dried, and then calendered to prepare the heat-sensitive recording material of the present invention.

[0091] Comparative Example 1 (Preparation of Comparative Thermal Recording Material) The above obtained solutions and the following chemicals were mixed in the following compositions to prepare coating solutions for the thermosensitive recording layer. Using the above obtained coating solutions for the thermosensitive recording layer, a comparative thermosensitive recording material was prepared in the same manner as in step 5. [A]Liquid 16.7 parts [B]Liquid 10.0 parts 67% calcium carbonate aqueous dispersion 6.8 parts 48% modified styrene-butadiene copolymer latex 6.0 parts 2.6 parts of 37% zinc stearate aqueous dispersion Water 54.0 parts

[0092] Comparative Example 2 (Preparation of Comparative Thermal Recording Material) A comparative heat-sensitive recording material was prepared in the same manner as in Example 1, except that in step 3, 1,2-bis(3-methylphenoxy)ethane was used instead of 1,2-bis(tosyloxy)ethane.

[0093] Comparative Example 3 (Preparation of Comparative Thermal Recording Material) A comparative heat-sensitive recording material was prepared in the same manner as in Example 1, except that in step 3, diphenylsulfone was used instead of 1,2-bis(tosyloxy)ethane.

[0094] [Dynamic color development sensitivity test] Each of the thermal recording materials prepared in Example 1 and Comparative Examples 1 to 3 was printed using a thermal printer (TH-M2 / PP) manufactured by Okura Engineering Co., Ltd. with an applied energy of 0.28 mJ / dot, and the optical density (OD value) of the printed area was measured using a reflection densitometer (product name: FD-7, manufactured by Konica Minolta, Inc.) under the following conditions. A higher value of the print density means better thermal response. The results are shown in Table 8. Measurement conditions Measurement method: Reflection measurement Lighting condition:C Observation field of view: 2° Density white standard: Absolute value

[0095] [Heat resistance test of the printed part] Each of the thermal recording materials prepared in Example 1 and Comparative Examples 1 to 3 was printed with an applied energy of 0.39 mJ / dot using a thermal printer (TH-M2 / PP) manufactured by Okura Engineering Co., Ltd., and then held at 90°C for 1 hour using a constant temperature incubator (product name: DKM-600) manufactured by Yamato Scientific Co., Ltd. The optical density (OD value) of the printed area before and after the test was measured using a reflection densitometer (product name: FD-7, manufactured by Konica Minolta, Inc.), and the remaining rate of the printed area after the test was calculated using the following formula. The optical density was measured under the same conditions as the optical density in the above-mentioned "Dynamic Color Development Sensitivity Test". The higher the remaining rate, the better the heat resistance of the printed area. The results are shown in Table 8. Residual rate (%) = (Optical density of printed area after test) / (Optical density of printed area before test) x 100

[0096] [Heat resistance test for skin] Each of the thermal recording materials prepared in Example 1 and Comparative Examples 1 to 3 was kept at 90°C for 1 hour using a constant temperature incubator with air blower (product name: DKM-600) manufactured by Yamato Scientific Co., Ltd. The whiteness of the background before and after the test was measured using a reflection densitometer (product name: FD-7, manufactured by Konica Minolta, Inc.). The optical density was measured under the same conditions as the optical density in the above-mentioned "Dynamic Color Development Sensitivity Test". The higher the value after the test, the better the heat resistance of the background. The results are shown in Table 8.

[0097] [Table 8]

[0098] From the results in Table 8, it is seen that the heat-sensitive recording material having a heat-sensitive recording layer made of the heat-sensitive recording composition of the present invention exhibits the same thermal response (print density) as the heat-sensitive recording material of Comparative Example 2 using 1,2-bis(3-methylphenoxy)ethane, which is a conventionally known sensitizer, and Comparative Example 3 using diphenyl sulfone, and is also superior in thermal response to the heat-sensitive recording material of Comparative Example 1 not containing a sensitizer. Furthermore, even in a high-temperature environment of 90°C, the remaining rate of the printed area and the background fog are superior to those of Comparative Examples 1 to 3, and it is seen that the heat-resistant storage stability is excellent. From the above results, it is clear that the heat-sensitive recording material made of the heat-sensitive recording composition of the present invention has excellent thermal response and also has excellent heat-resistant storage stability of the printed area and the background in a high-temperature environment. [Industrial Applicability]

[0099] By using the thermal recording composition of the present invention, it is possible to provide a thermal recording material having excellent thermal response and excellent heat-resistant storage stability in a high-temperature environment for the printed portion and the background.

Claims

1. A thermal recording composition comprising a color former, a color developer and a sensitizer, the color developer being represented by the following formula (1): 【Chemistry 1】 (In formula (1), R １ ~R ５ each independently represents a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group. and a sensitizer containing 1,2-bis(tosyloxy)ethane.

2. R １ , R ２ , R ４ and R ５ 2. The heat-sensitive recording composition according to claim 1, wherein is a hydrogen atom.

3. R ３ 3. The heat-sensitive recording composition according to claim 2, wherein is a methyl group.

4. The compound represented by formula (1) is represented by the following formula (2): 【Chemistry 2】 4. The thermal recording composition according to claim 3, wherein the compound is represented by the formula:

5. 5. The heat-sensitive recording composition according to claim 1, wherein the content of the sensitizer is from 10 to 250% by mass of the content of the developer.

6. 6. The heat-sensitive recording composition according to claim 1, wherein the color former comprises a compound selected from the group consisting of triarylmethane compounds, fluoran compounds, azaphthalide compounds and fluorene compounds.

7. The color former is 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(o,p-dimethylanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-(cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 3-N-n-dibutylamino-6-methyl-7-anilinofluoran, 7. The thermal recording composition according to claim 6, which contains a fluoran compound selected from the group consisting of 3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran and 3-dipentylamino-6-methyl-7-anilinofluoran.

8. A heat-sensitive recording material having a heat-sensitive recording layer comprising the heat-sensitive recording composition according to any one of claims 1 to 7 on a support.

9. 9. The heat-sensitive recording material according to claim 8, wherein the support is wood-free paper, synthetic paper or a plastic film.

10. The coating amount of the thermal recording layer is 1 to 20 g / m ２ 10. The heat-sensitive recording material according to claim 8, wherein

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