JP7633918B2 - Thermal recording composition - Google Patents

Description

The present invention relates to a heat-sensitive recording material that has excellent thermal response and storage stability.

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 a binder, a sensitizer, a filler, and a lubricant, and coating the resulting liquid onto paper, film, synthetic paper, etc. When the coating thus obtained is heated using a thermal printer or the like equipped with a 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, thermal recording 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 the fields of facsimile, computer output, printers such as calculators, recorders for medical measurement, automatic ticket vending machines, thermal recording labels, etc.

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 systemization of retail stores and supermarkets, and the automation systemization of transportation. In these applications, resistance of the recorded image (printing, image, pattern) to water, alcohol, etc. is an essential condition. In addition, the demand for high-speed recording to improve productivity is increasing, and there is a strong demand for the development of thermal recording materials with excellent thermal response that can fully handle high-speed recording. In order to improve thermal response, a color-developing compound with a low melting point and small heat of fusion is generally required. However, when such a color-developing compound is used, the unprinted parts (background) of the thermal recording material tend to darken during production, use, or storage, a phenomenon known as background fogging, and therefore improvement of the stability of the background is desired.

Generally, color-developing compounds with phenolic hydroxyl groups have high color-developing ability, and many reports have been published on bisphenol-based compounds due to their high color-developing density. 2,2-bis(4-hydroxyphenylpropane) (bisphenol A) (Patent Document 1) and 4,4'-dihydroxydiphenylsulfone (bisphenol S) (Patent Document 2) have been proposed. However, these compounds have a high melting point, which means that they have 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 the endocrine problem, and there is a demand for non-phenol-based color-developing compounds that do not contain a phenol structure.

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 area and a background that exhibits high stability against heat. However, the thermal response of this compound is not sufficient, and further improvement in thermal response is desired to accommodate high-speed recording.

Usually, a method of adding a sensitizer with a low melting point (a thermofusible compound) is adopted to improve the thermal response of thermal recording materials. A sensitizer with a relatively high melting point may be added to maintain heat-resistant storage stability in a high-temperature environment, but 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 an issue.

U.S. Pat. No. 3,539,375 Japanese Unexamined Patent Publication No. 57-11088 Patent No. 6529197

The present invention aims to solve the problems of the prior art described above, and more specifically, to provide a thermal recording material that has excellent thermal response and excellent heat resistance and preservation properties of the printed area and background in high-temperature environments.

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):

(In formula (1), ^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 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] The thermal recording composition according to the above [1], wherein R ¹ , R ² , R ⁴ and R ⁵ are hydrogen atoms.
[3] The thermal recording composition according to the above item [2], wherein R ³ is a methyl group.
[4] The compound represented by formula (1) is represented by the following formula (2):

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-N-n-dibutylamino-6-methyl-7-anilinofluoran, the thermal recording composition according to the preceding item [6], which contains a fluoran compound selected from the group consisting of fluoran, 3-diethylamino-6-methyl-7-(m-methylanilino)fluoran, 3-N-n-dibutylamino-7-(o-chloroanilino)fluoran, 3-(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 above items [1] to [7] on a support.
[9] The heat-sensitive recording material according to the above item [8], wherein the support is a wood-free paper, a synthetic paper or a plastic film; and [10] the heat-sensitive recording material according to the above item [8] or [9], wherein the coating amount of the heat-sensitive recording layer is 1 to 20 g/ ^m2 .
Regarding.

The present invention provides a thermal recording material that has excellent thermal response and heat-resistant storage stability in high-temperature environments for the printed area and the background.

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.

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 and fluorene compounds are preferred, and fluoran compounds are more preferred.These color-forming compounds can be used alone or in combination.

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, 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)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-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-(N-p-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[phthalido-3,9'-xanthene] (S-205), 2'-anilino-6'-(N,N-dipentan-1-ylamino)-3'-methyl-3H-spiro[isobenzofuran-1,9'-xanthene]-3-one (Black 305), 2'-anilino-6'-(dibutylamino)-3'-methylspiro[phthalido-3,9'-xanthene] (B LACK400), 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 (Black100), 1-ethyl-8-[N-ethyl-N-(4-methylphenyl)amino]-2,2,4-trimethyl- Examples of the fluoranol include 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), and 3-dibutylamino-6-methyl-7-anilinofluoran is preferred.

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 4-(4-diethylamino-2-ethoxyphenyl)-7-(1-ethyl-2-methyl-1H-indol-3-yl)furo[3,4-b]pyridin-5(7H)-one (Blue 63), and the like.

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 the spiro compound 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).

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.

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.

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.

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.

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).

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), ^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 alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.

The alkyl group represented by ^R1 to ^R5 in formula (1) 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.
Specific examples of the alkyl group represented by R ¹ to R ⁵ in formula (1) include linear 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 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.

The alkoxy group represented by ^R1 to ^R5 in formula (1) 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.
Specific examples of the alkoxy group represented by R ¹ to R ⁵ in formula (1) 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.

The aryloxy group represented by R ¹ to R ⁵ in formula (1) 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.

The alkyl group in the alkylcarbonyloxy group represented by ^R1 to ^R5 in formula (1) 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.
Specific examples of the alkylcarbonyloxy group represented by R ¹ to R ⁵ in formula (1) include linear alkylcarbonyloxy groups such as methylcarbonyloxy group, ethylcarbonyloxy group, n-propylcarbonyloxy group, n-butylcarbonyloxy group, n-pentylcarbonyloxy group, n-hexylcarbonyloxy group, n-heptylcarbonyloxy group, n-octylcarbonyloxy group, n-nonylcarbonyloxy group, and n-decylcarbonyloxy group; isopropylcarbonyloxy group, isobutylcarbonyloxy group, sec-butylcarbonyloxy group, t-butylcarbonyloxy group, isoamylcarbonyloxy group, t-amylcarbonyloxy group, isohexylcarbonyloxy group, branched chain (preferably having 3 to 10 carbon atoms in the alkyl portion) alkylcarbonyloxy groups such as a t-hexylcarbonyloxy group, an isoheptylcarbonyloxy group, a t-heptylcarbonyloxy group, an isooctylcarbonyloxy group, a t-octylcarbonyloxy group, a 2-ethylhexylcarbonyloxy group, an isononylcarbonyloxy group, or an isodecylcarbonyloxy group; and cyclic (preferably having 3 to 7 carbon atoms in the alkyl portion) alkylcarbonyloxy groups such as a cyclopropylcarbonyloxy group, a cyclobutylcarbonyloxy group, a cyclopentylcarbonyloxy group, a cyclohexylcarbonyloxy group, or a cycloheptylcarbonyloxy group.

The alkyl group in the alkylcarbonylamino group represented by ^R1 to ^R5 in formula (1) 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.
Specific examples of the alkylcarbonylamino group represented by R ¹ to R ⁵ in formula (1) 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, and an isohexylcarbonylamino group. 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.

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

The alkyl group in the alkylsulfonylamino group represented by ^R1 to ^R5 in formula (1) is not limited to being linear, branched, or cyclic, but is preferably an alkylsulfonylamino group in which the alkyl group is linear or branched, more preferably a linear alkylsulfonylamino group. The number of carbon atoms in the alkylsulfonylamino group is preferably 1 to 10.
Specific examples of the alkylsulfonylamino group represented by R ¹ to R ⁵ in formula (1) 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, and an isohexylsulfonylamino group. branched chain (preferably having 3 to 10 carbon atoms in the alkyl moiety) alkylsulfonylamino groups such as t-hexylsulfonylamino, isoheptylsulfonylamino, t-heptylsulfonylamino, isooctylsulfonylamino, t-octylsulfonylamino, 2-ethylhexylsulfonylamino, isononylsulfonylamino, and isodecylsulfonylamino; and cyclic (preferably having 3 to 7 carbon atoms in the alkyl moiety) alkylsulfonylamino groups such as cyclopropylsulfonylamino, cyclobutylsulfonylamino, cyclopentylsulfonylamino, cyclohexylsulfonylamino, and cycloheptylsulfonylamino.

The arylsulfonylamino group represented by ^R1 to ^R5 in formula (1) is preferably an arylsulfonylamino group having an aryl group with 6 to 12 carbon atoms, and specific examples thereof include a phenylsulfonylamino group, a toluenesulfonylamino group, a naphthylsulfonylamino group, and a biphenylsulfonylamino group.

The alkyl group in the monoalkylamino group represented by ^R1 to ^R5 in formula (1) 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.
Specific examples of the monoalkylamino group represented by R ¹ to R ⁵ in formula (1) 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- Examples of the monoalkylamino group include branched-chain (preferably having 3 to 10 carbon atoms) monoalkylamino groups, such as a hexylamino group, an isoheptylamino group, a t-heptylamino group, an isooctylamino group, a t-octylamino group, a 2-ethylhexylamino group, an isononylamino group, and an isodecylamino group; and cyclic (preferably having 3 to 7 carbon atoms) monoalkylamino groups, such as a cyclopropylamino group, a cyclobutylamino group, a cyclopentylamino group, a cyclohexylamino group, and a cycloheptylamino group.

The alkyl group in the dialkylamino group represented by ^R1 to ^R5 in formula (1) is not limited to being 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.
Specific examples of the dialkylamino group represented by R ¹ to R ⁵ in formula (1) include dialkylamino groups having a straight-chain alkyl group such as dimethylamino group, diethylamino group, di-n-propylamino group, di-n-butylamino group, di-n-pentylamino group, di-n-hexylamino group, di-n-heptylamino group, di-n-octylamino group, di-n-nonylamino group, and di-n-decylamino group; diisopropylamino group, diisobutylamino group, di-sec-butylamino group, di-t-butylamino group, diisoamylamino group, di-t-amylamino group, diisohexylamino group, di- Examples of such dialkylamino groups include dialkylamino groups having a branched alkyl group (preferably having 3 to 10 carbon atoms), such as t-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.

The arylamino group represented by R ¹ to R ⁵ in formula (1) 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.
Specific examples of the arylamino group represented by R ¹ to R ⁵ in formula (1) include a phenylamino (anilino) group, a naphthylamino group, a biphenylamino group, a diphenylamino group, a dinaphthylamino group, and a di(biphenyl)amino group.

According to a preferred embodiment of the present invention, R ¹ to R ⁵ in the above general formula (1) are 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.

According to a preferred embodiment of the present invention, R ¹ , R ² , R ⁴ , and R ⁵ in the above general formula (1) are hydrogen atoms, 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, with a hydrogen atom or an alkyl group being more preferred, a hydrogen atom or an alkyl group having 1 to 8 carbon atoms (preferably a linear alkyl group) being even more preferred, a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (preferably a linear alkyl group) being particularly preferred, and a methyl group being most preferred.

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 the ortho, meta, or para position relative to the aminocarbonyl group on the benzene ring, but is preferably the ortho or meta position, and more preferably the meta position.

According to a preferred embodiment of the present invention, the color-developing compound is a compound of the above general formula (1) in which R ¹ to R ⁵ are 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, more preferably a compound of the above general formula (1) in which R ¹ to R ⁵ are 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, even more preferably a compound of the above general formula (1) in which R ¹ to R ⁵ are 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 with respect to the aminocarbonyl group on the benzene ring, and particularly preferably a compound of the above general formula (1) in which R ¹ to R ⁵ are a methyl group 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.

According to another preferred embodiment of the present invention, the color-developing compound is a compound of the above general formula (1) in which R ¹ , R ² , R ⁴ and R ⁵ are hydrogen atoms, 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 the general formula (3) is an ortho-position, a meta-position or a para-position with respect to the aminocarbonyl group on the benzene ring, more preferably a compound of the above general formula (1) in which R ¹ , R ² , R ⁴ and R ⁵ are hydrogen atoms, R ³ is a hydrogen atom or an alkyl group, and the substitution position of the partial skeleton represented by the general formula (3) is an ortho-position or a meta-position with respect to the aminocarbonyl group on the benzene ring, more preferably a compound of the above general formula (1) in which R ¹ , R 2 , R ⁴ and R 5 are hydrogen atoms, R a compound of the above general formula (1) in which R 1 , R ² , R 4 , and R ⁵ are hydrogen atoms, 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 with respect to the aminocarbonyl group on the benzene ring, more preferably a compound of the above general formula (1) in which R ¹ , R ² , R ⁴ , and R ⁵ are hydrogen atoms, 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 with respect to the aminocarbonyl group on the benzene ring, and particularly preferably a compound of the above general formula (1) in which R ¹ , R ² , R ⁴ , and R ⁵ are hydrogen atoms, R ³ is a methyl group, 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.

In addition, as the compound represented by formula (1), combinations of preferred or more preferred embodiments of the above-mentioned R ¹ , R ² , R ⁴ and R ⁵ , R ³ and the 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).

Specific examples of compounds represented by formula (1) are listed below, but the compounds represented by formula (1) contained in the color developer as essential components are not limited to these.

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) as long as the effect of the present invention is not impaired. There are no particular limitations on the color developer that can be used in combination, and examples 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.

Specific examples of benzotriazole derivatives 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.

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

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.

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.

Specific examples of 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.

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.

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.

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 sensitizers that may 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.

Specific examples of waxes include Japan wax, carnauba wax, shellac, paraffin, montan wax, paraffin oxide, polyethylene wax, and polyethylene oxide. Specific examples of higher fatty acids include stearic acid and behenic acid. 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. Specific examples of higher fatty acid anilides include stearic acid anilide and linoleic acid anilide. Specific examples of naphthalene derivatives include 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, and 2,6-diisopropylnaphthalene. 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-tolyl mesitylene 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. Specific examples of sulfone derivatives include p-toluenesulfonamide, benzenesulfonanilide, p-toluenesulfonanilide, and diphenylsulfone. Specific examples of aromatic ketone derivatives include 4,4'-dimethylbenzophenone and dibenzoylmethane. Specific examples of aromatic hydrocarbon compounds include p-acetotoluidine.

The thermal 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 thermal recording layer, but in the case of a multi-layer structure or when an undercoat layer or a protective layer (overcoat layer) is provided on the upper and/or lower part of the thermal recording layer, they may also be contained in each of these layers.

Specific examples of storage stability improvers 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'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3',5,5'-tetrabromodiphenyl sulfone, hindered phenol compounds such as methyldiphenylsulfone, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, and 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane; 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenylsulfone, 4-benzyloxy-4'-(2-methylglycidyloxy)diphenylsulfone, diglycidyl terephthalate, and cresol novolac type ethylene glycol. 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 developer 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 from 0 to 6.

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 with 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 isocyanate. 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, as well as 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.

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.

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, and defoamers. These antioxidants or ultraviolet absorbers may be microencapsulated as necessary.

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 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 storage stability improver is 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. (The mass% is the solid content converted mass ratio of each component in the thermal recording material).

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

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, film made of synthetic resin such as plastic or foamed plastic, and nonwoven fabric.
The method for providing a heat-sensitive recording layer on a support is not particularly limited, but for example, a dispersion of the heat-sensitive recording composition of the present invention obtained by crushing and dispersing 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 can be applied to a support and dried to prepare a heat-sensitive recording layer having a dry mass of preferably 1 to 20 g/ ^m2 .

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/ ^m2 .

It is preferable that the undercoat layer contains at least one pigment selected from organic pigments or inorganic pigments to further improve recording sensitivity and recording runnability.

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.

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 by heating. 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 property, and 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.
The organic hollow particles may be any of those known in the art, such as particles whose film material is an acrylic resin, a styrene resin, or a vinylidene chloride resin, and whose hollow ratio is 50 to 99%. Here, the hollow ratio is a value calculated by (d/D)×100. In this 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% by mass, more preferably 5 to 70% by mass, based on the total solid content of the undercoat layer.

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% by mass, more preferably 10 to 90% by mass, and even more preferably 10 to 80% by mass of the total solid content of the undercoat layer.

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 the color development and enhancing the 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.

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., to a support and drying the coating liquid. The amount of the coating liquid for the undercoat layer is not particularly limited, but is preferably 3 to 20 g/ ^m2 , more preferably 5 to 12 g/ ^m2 , in terms of dry weight.

The adhesive used in the undercoat layer can be appropriately selected from those usable in the thermal recording layer and 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% by mass, more preferably 10 to 20% by mass, of the total solid content of the undercoat layer.

If necessary, the thermal recording material of the present invention can be provided with a back layer mainly composed of a pigment and an adhesive on the side of the support opposite to the thermal recording layer. This can further improve storage stability, curling properties, and printer runnability. In addition, various known techniques in the field of thermal recording material manufacturing can be added as necessary, such as processing the back side into an adhesive label by applying an adhesive treatment, providing a magnetic recording layer, a printing coating layer, or even a thermal transfer recording layer or an inkjet recording layer.

The method for applying various dispersions or coating liquids onto a support is not particularly limited, but examples 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 at the same time.

The method of applying 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 makes it possible to form a thermal recording layer of uniform thickness without unevenness on the support, thereby increasing recording sensitivity. In terms of quality, the surface smoothness of the undercoat layer is further improved, so that the coating liquid for the thermal recording layer can be curtain coated with improved coating uniformity, improving the barrier properties of the protective layer that is provided if necessary. Blade coating methods are not limited to coating methods using blades such as bevel type and bent type, but also include pure blade coating, rod blade method, bill blade method, etc.

It is preferable to form the thermal recording layer and the protective layer by simultaneous multi-layer coating such as curtain coating. 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 the coating liquid is allowed to flow down and fall freely to be applied to the support without contact, and known methods such as the slide curtain method, couple curtain method, and twin curtain method can be adopted, and there is no particular limitation. Also, as described in JP-A-2006-247611 (Patent Document 4), the coating liquid can be ejected downward from a curtain head to form a coating layer on a slope, and a curtain of the coating liquid can be 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.

From the viewpoint of increasing the recording sensitivity and improving the image uniformity, a smoothing process may be performed using a known method such as a super calendar or soft calendar at any stage after each layer has been formed or after all layers have been formed.

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.

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 by a laser diffraction/scattering type particle size distribution measuring device, Microtrac MT3300EXII (manufactured by Microtrac Bell).

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

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

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

(Step 4) Preparation of composition for heat-sensitive recording layer The above-obtained solutions and the following chemicals were mixed in the following compositions to prepare coating solutions for heat-sensitive 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 37% zinc stearate aqueous dispersion 2.6 parts Water 34.5 parts

(Step 5) Preparation of the heat-sensitive recording material of the present invention The composition for the heat-sensitive recording layer obtained in step 4 was applied onto a piece of high-quality paper having a basis weight of 50 g/ ^m2 in an amount such that the mass of the color-forming compound when dried would be 0.5 g/ ^m2 , and then the paper was dried and calendared to prepare the heat-sensitive recording material of the present invention.

Comparative Example 1 (Preparation of Comparative Heat-Sensitive 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] solution 16.7 parts [B] solution 10.0 parts 67% calcium carbonate aqueous dispersion 6.8 parts 48% modified styrene-butadiene copolymer latex 6.0 parts 37% zinc stearate aqueous dispersion 2.6 parts Water 54.0 parts

Comparative Example 2 (Preparation of Comparative Heat-Sensitive 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(tosyloxy)ethane was replaced with 1,2-bis(3-methylphenoxy)ethane.

Comparative Example 3 (Preparation of Comparative Heat-Sensitive 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.

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

[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

[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". A larger value after the test means that the heat resistance of the background is more excellent. The results are shown in Table 8.

From the results in Table 8, it can be seen that the thermal recording material having a thermal recording layer made of the thermal recording composition of the present invention exhibits thermal response (print density) equivalent to that of the thermal recording material of Comparative Example 2 using 1,2-bis(3-methylphenoxy)ethane, a conventionally known sensitizer, and Comparative Example 3 using diphenyl sulfone, and is also superior in thermal response to the thermal recording material of Comparative Example 1, which does not contain 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 can be seen that the thermal storage stability is excellent. From the above results, it is clear that the thermal recording material made of the thermal recording composition of the present invention has excellent thermal response and excellent heat-resistant storage stability of the printed area and background in a high-temperature environment.

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

Claims (10)

A thermal recording composition comprising a color former, a color developer and a sensitizer, the color developer being represented by the following formula (1):

(In formula (1), ^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 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. The heat-sensitive recording composition according to claim 1, wherein ^R1 , ^R2 , ^R4 and ^R5 are hydrogen atoms. 3. The heat-sensitive recording composition according to claim 2, wherein ^R3 is a methyl group. The compound represented by formula (1) is represented by the following formula (2):

4. The thermal recording composition according to claim 3, wherein the compound is represented by the formula: The thermal recording composition according to any one of claims 1 to 4, wherein the content of the sensitizer is 10 to 250% by mass of the content of the developer. The thermal recording composition according to any one of claims 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. 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 The thermal recording composition according to claim 6, which contains a fluoran compound selected from the group consisting of 3-(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. A thermal recording material having a thermal recording layer made of the thermal recording composition according to any one of claims 1 to 7 on a support. The thermal recording material according to claim 8, wherein the support is high-quality paper, synthetic paper or a plastic film. 10. The heat-sensitive recording material according to claim 8, wherein the coating amount of the heat-sensitive recording layer is from 1 to 20 g/m ^<2> .