Compositions and methods for thermal media

Abstract

Heat-sensitive recording composition and recording material. The recording material comprises a substrate, and a heat-sensitive composition comprising a color former, a color developer, and a sensitizer comprising a combination of ortho-toluenesulfonamide and para-toluenesulfonamide (OPTSA) is deposited on a surface of the substrate.

Description

[Technical field]

[0001] Claiming priority This application claims the benefit of U.S. Provisional Application No. 63 / 154,685, filed February 27, 2021, and U.S. Non-Provisional Application No. 17 / 652,116, filed February 23, 2022, which are incorporated herein by reference.

[0002] Technical Field A heat-sensitive or heat-responsive recording material comprising a support or substrate having provided thereon, in substantially contiguous relationship, one or more layers of a heat-sensitive coating comprising a colour former, a colour developer and a sensitiser. [Background technology]

[0003] Heat sensitive or heat responsive recording materials, such as thermal paper, are well known and are used in many applications such as point-of-sale (POS) receipts, tickets, tags and labels.

[0004] The method of manufacturing a heat-sensitive recording material is well known in the art. For example, at least one color former, at least one developer, optionally at least one sensitizer, optionally at least one stabilizer, and optionally at least one pigment are ground separately or mixed in water or a compound having dispersibility using a grinder such as a bead mill or similar grinding device to form a fine particle dispersion having an average particle size of preferably 0.1 to 2.0 μm, more preferably 0.3 to 1.0 μm.

[0005] In the manufacture of thermally sensitive recording sheets, a composition or blend containing a color former, usually an electron donating leuco dye, and a color developer (an electron accepting compound) is applied to one or both surfaces of a base paper as a coating recording layer. When the coating is heated by a thermal print head or a laser, they melt, mix and react with each other to produce a developed recorded image.

[0006] For the purpose of improving recording speed and to obtain the desired optical density at a particular printing energy level, also called dynamic sensitivity, sensitizers having a lower melting point than the color developers and color formers are used, which reduces the amount of heat energy that needs to be applied to the thermal recording sheet to produce the desired image. Summary of the Invention [Problem to be solved by the invention]

[0007] For this purpose, a relatively low melting point, chemical affinity between the sensitizer, developer and colour former, and the viscosity of the molten material are the necessary parameters to dissolve the colour former or developer and produce the desired image.

[0008] There is a continuing need to discover non-toxic, non-phenolic, non-eco-toxic materials that can improve the dynamic sensitivity of the developer, and more particularly, Pergafast™ 425, without adversely affecting its other qualities.

[0009] Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background. [Means for solving the problem]

[0010] A heat-sensitive recording composition is provided that includes one or more color formers, one or more color developers, and at least one sensitizer that includes a mixture of ortho-toluenesulfonamide and para-toluenesulfonamide (OPTSA).

[0011] Also provided is a method for producing a heat-sensitive recording material. The method includes providing a support or substrate, which may optionally have one or more coating layers or undercoatings on one or both sides of the substrate. One or more layers of a heat-sensitive recording composition are deposited or applied onto the substrate or onto the one or more coating layers on the substrate to form a heat-sensitive layer. The heat-sensitive recording composition includes one or more color formers; one or more color developers; and at least one sensitizer including a mixture of ortho-toluenesulfonamide and para-toluenesulfonamide (OPTSA); thereby producing the recording material. Also, one or more topcoats or protective layers may be deposited or applied onto the heat-sensitive layer.

[0012] Finally, a recording sheet is provided, the recording sheet including a substrate or support and a recording composition disposed or applied on the substrate, the recording composition including one or more color formers, one or more color developers, and at least one sensitizer including a mixture of ortho-toluenesulfonamide and para-toluenesulfonamide (OPTSA). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or its application and uses. Moreover, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

[0014] The heat-sensitive recording compositions and embodiments herein can be used for any purpose, for example, as heat-sensitive recording materials, as long as the recording material contains the color former, developer, and sensitizer described herein.

[0015] In one embodiment, the heat-sensitive recording composition, also referred to simply as the recording composition or heat-sensitive composition, comprises one or more color formers; one or more color developers; and at least one sensitizer comprising a mixture of ortho-toluenesulfonamide and para-toluenesulfonamide (OPTSA).

[0016] In some embodiments of the recording composition, the at least one sensitizer has a ratio of ortho-toluenesulfonamide to para-toluenesulfonamide of about 0.5:99.5 to about 99.5:0.5, can be about 5:90 to about 90:5, can be 10:85 to about 85:10, can be about 20:80 to about 80:20, or can be about 40:60 to about 60:40, based on the dry weight of the OPTSA mixture.

[0017] In other embodiments of the recording composition, the at least one sensitizer is present in an amount of about 0.1 to about 6 parts by dry weight, can be present in an amount of 0.5 to 5.0 parts by dry weight, and may be present in an amount of 1.0 to 4.0 parts by dry weight per part of the color former or color formers.

[0018] In some embodiments of the recording composition, the one or more color developers may include phenolic color developers, non-phenolic color developers, and combinations thereof. For example, the one or more color developers may include 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, and [3-(p-tolylsulfonylcarbamoylamino)phenyl]4-methylbenzenesulfonate, 2,4'-dihydroxydiphenyl sulfone, 4.4'-dihydroxydiphenyl sulfone, bis-(3-allyl-4-hydroxyphenyl)sulfone, 4-[4'-[(1'-methylethyloxy)phenyl]sulfonyl]phenol, 4-hydroxyphenyl The aryl group may be selected from 4-isopropyloxyphenyl sulfone, N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide, phenol, 4-[[4-(2-propenyloxy)phenyl]sulfonyl, 4-hydroxy-4'benzyloxydiphenyl sulfone, and 4,4'bis(N-carbamoyl-4-methylbenzenesulfonamido)diphenylmethane, 1,1'-oxybis[2-chloroethane], phenols, 4,4'-sulfonyl bis-polymers including urea urethane compounds, and combinations thereof.

[0019] In yet another embodiment of the recording composition, the developer is selected from the group consisting of bisphenol A, 4,4'-sec-butylidene bisphenol, 4,4'-cyclohexylidene bisphenol, 2,2'-bis(4-hydroxyphenyl)-3,3'-dimethylbutane, 2,2'-dihydroxydiphenyl, pentamethylene-bis(4-hydroxybenzoate), 2,2'-dimethyl-3,3'-di(4-hydroxyphenyl)pentane, 2,2'-di(4-dihydroxyphenyl)hexane, 2,2-bis(4-hydroxyphenyl)propane, 2, 2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 4,4'-(1-phenylethylidene)bisphenol, 4,4'-ethylidenebisphenol, (hydroxyphenyl)methylphenol, 2.2'-bis(4-hydroxy-3-phenyl-phenyl)propane, 4.4'-(1.3-phenylenediisopropylidene)bisphenol, 4.4'-(1.4-phenylenediisopropylidene)bisphenol, and 2.2-bis(4-hydroxyphenyl)butyric acid. bisphenol compounds such as 4,4'-dihydroxydiphenyl thioether, 1,7-di(4-hydroxyphenylthio)-3,5-dioxaheptane, 2,2'-bis(4-hydroxyphenylthio)diethyl ether, and 4,4'-dihydroxy-3,3'-dimethyldiphenyl thioether; sulfur-containing bisphenol compounds such as 4,4'-dihydroxydiphenyl thioether, 1,7-di(4-hydroxyphenylthio)-3,5-dioxaheptane, 2,2'-bis(4-hydroxyphenylthio)diethyl ether, and 4,4'-dihydroxy-3,3'-dimethyldiphenyl thioether; benzyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, isopropyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, 4-hydroxybenzoic acid, ... 4-Hydroxybenzoic acid esters such as isobutyl dibenzoate, chlorobenzyl 4-hydroxybenzoate, methylbenzyl 4-hydroxybenzoate, and diphenylmethyl 4-hydroxybenzoate; metal salts of benzoic acid such as zinc benzoate and zinc 4-nitrobenzoate; salicylic acid such as 4-[2-(4-methoxyphenyloxy)ethyloxy]salicylic acid; metal salts of salicylic acid such as zinc salicylate and zinc bis[4-(octyloxycarbonylamino)-2-hydroxybenzoate]; 4.4'-dihydroxydiphenyl sulfone, 2.4'-Dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-butoxydiphenyl sulfone, 4.4'-dihydroxy-3.3'-diallyldiphenyl sulfone, 3.4-dihydroxy-4'-methyldiphenyl sulfone, 4.4'-dihydroxy-3.3'.5.5'-tetrabromodiphenyl sulfone, 4-allyloxy-4'-hydroxydiphenyl sulfone , 2-(4-hydroxyphenylsulfonyl)phenol, 4.4'-sulfonylbis[2-(2-propenyl)]phenol, 4-[[4-(propoxy)phenyl}sulfonyl]phenol, 4-[{4-(allyloxy)phenyl}sulfonyl]phenol, 4-[{4-(benzyloxy)phenyl}sulfonyl]phenol, and 2,4-bis(phenylsulfonyl)-5-methyl-phenol; 2.4'-dihydroxydiphenylsulfone (BPS 2.4'), bis-(4-hydroxyphenyl)sulfone (BPS 4.4'), bis(3-allyl-4-hydroxyphenyl)sulfone (TG-SA), B-TUM, SZ110, 4-phenylsulfonylphenoxy-zinc Polyvalent metal salts of hydroxysulfones such as magnesium, aluminum and titanium; 4-hydroxyphthalic acid diesters such as dimethyl 4-hydroxyphthalate, dicyclohexyl 4-hydroxyphthalate and diphenyl 4-hydroxyphthalate; hydroxynaphthoic acid esters such as 2-hydroxy-6-carboxynaphthalene; trihalomethylsulfones such as tribromomethylphenylsulfone; sulfonylureas such as 4.4'-bis(p-toluenesulfonylaminocarbonylamino)diphenylmethane and N-(4-methylphenylsulfonyl)-N'-(3-(4-methylphenylsulfonyloxy)phenyl)urea; hydroxyacetophenone, p-phenylphenol, 4-hydroxyphenyl benzyl acetate, p-benzylphenol, hydroquinone monobenzyl ether, 2.4-dihydroxy-2'-methoxybenzanilide, tetracyanoquinodimethane, N-(2-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, N-(4-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, 4-hydroxybenzenesulfonanilide, 4'-hydroxy-4-methylbenzenesulfonanilide, 4.4'-bis(4-methyl-3-phenoxycarbonyl)aminophenylureido)diphenylsulfone, 3-(3-phenylureido)benzenesulfonanilide, octadecylphosphoric acid, and dodecylphosphoric acid; and bridged diphenylsulfone compounds represented by the following formula or mixtures thereof. [ka]

[0020] In some embodiments of the recording composition, the one or more color formers can be fluorans, phthalides, lactams, triphenylmethanes, phenothiazines, spiropyran leuco dyes, and combinations thereof. For example, the one or more color formers can be 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-dibutylaminofluoran, 2-anilino-3-methyl-6-(methyl-N-isoamylamino)fluorine, 2-anilino-3-methyl-6-(N-ethyl-N-propylamino)fluoran, 2-anilino-3-methyl-6-di-n-amylaminofluoran, 2-anilino-3-methyl-6-(N-ethyl-N-butrylamino)fluoran, 2-anilino-3-methyl-6-N-ethyl-N-sec-butylaminofluoran, 3-di-(n-pentylamino) ... amino)-6-methyl-7-anilinofluoran, 3-(N-isoamyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-(Nn-hexyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-[N-(3-ethoxypropyl)-N-ethylamino]-6-methyl-7-anilinofluoran, 3-di-(n-butylamino)-7-2-chloroanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran and combinations thereof.

[0021] In yet another embodiment of the recording composition, the one or more colour formers are selected from the group consisting of 3-diethylamino-6-methylfluoran, 3-dimethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(2.4-dimethylanilino)fluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6-methyl-7-(3-trifluoromethylanilino)fluoran, 3-diethylamino-6-methyl-7-(2-chloroanilino)fluoran, fluoran, 3-diethylamino-6-methyl-7-(4-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-(2-fluoroanilino)fluoran, 3-diethylamino-6-methyl-7-(4-n-octylanilino)fluoran, 3-diethylamino-7-(4-n-octylamino)fluoran, 3-diethylamino-7-(n-octylamino)fluoran, 3-diethylamino-7-(dibenzylamino)fluoran, 3-diethylamino-6-methyl-7-(dibenzylamino)fluoran, 3-diethylamino-6-chloro ... Fluoro-7-methylfluoran, 3-diethylamino-7-t-butylfluoran, 3-diethylamino-7-carboxyethylfluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-(3-methylanilino)fluoran, 3-diethylamino-6-methyl-7-(4-methylanilino)fluoran, 3-diethylamino-6-ethoxyethyl-7-anilinofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7 -(3-trifluoromethylanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-7-(2-fluoroanilino)fluoran, 3-diethylamino-benzo[a]fluoran, 3-diethylamino-benzo[c]fluoran, 3-dibutylamino-7-dibenzylaminofluoran, 3-dibutylamino-7-anilinofluoran, 3-diethylamino-7-anilinofluoran, 3-dibutylamino-6-methylfluoran, 3-dibutylamino-6-methyl-7-anilinofluoran,3-dibutylamino-6-methyl-7-(2.4-dimethylanilino)fluoran, 3-dibutylamino-6-methyl-7-(2-chloroanilino)fluoran, 3-dibutylamino-6-methyl-7-(4-chloroanilino)fluoran, 3-dibutylamino-6-methyl-7-(2-fluoroanilino)fluoran, 3-dibutylamino-6-methyl-7-(3-trifluoromethylanilino)fluoran, 3-dibutylamino-6-ethoxyethyl-7-anilinofluoran, 3-dibutylamino-6-chloro-anilinofluoran, 3-di Butylamino-6-methyl-7-(4-methylanilino)fluoran, 3-dibutylamino-7-(2-chloroanilino)fluoran, 3-dibutylamino-7-(2-fluoroanilino)fluoran, 3-dibutylamino-7-(N-methyl-N-formylamino)fluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-(4-2-chloroanilino)fluoran, 3-dipentylamino-7-(3-trifluoromethylanilino)fluoran, 3-dipentylamino-6-chloro-7 -Anilinofluoran, 3-dipentylamino-7-(4-chloroanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran Fluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-chloro-7-anilinofluoran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran, 3-(N-butyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-(N-isopropyl-N-3-pentylamino)-6-methyl-7-anilinofluoran,3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluoran, 3-cyclohexylamino-6-chlorofluoran, 2-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 2-methoxy-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 2-chloro-3-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran, 2-diethylamino-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 2-phenyl-6-methyl Fluoran, 2-benzyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran, 3-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 3-diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluoran, 3-diethylamino-6-p-(p-dibutylaminophenyl)aminoanilinofluoran, 2.4-dimethyl-6-[(4-dimethylamino)anilino]fluoran, 3-[(4-dimethylamino)anilino]fluoran, 4-dimethyl-6-[(4-dimethylamino)anilino]fluoran, 5-[(4-dimethylamino)anilino]fluoran, 6-[(4-dimethylamino)anilino]fluoran, 1-[(4-dimethylamino)anilino]fluoran, 2-[(4-dimethylamino)anilino]fluoran, 1-[(4-dimethylamino)anilino]fluoran, 2-[(4-dimethylamino)anilino]fluoran, 3-[(4-dimethylamino)anilino]fluoran, 1-[(4-dimethylamino)anilino]fluoran, 2-[(4-dimethylamino)anilino]fluoran, 2-[(4-dimethylamino)anilino]fluoran, 3 ... 3.6.6'-tris(dimethylamino)spiro[fluorene-9.3'-phthalide], 3.6.6'-tris(diethylamino)spiro[fluorene-9.3'-phthalide], 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3.3-bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl-4.5.6.7-tetrabromophthalide, 3.3-bis- [2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl-4.5.6.7-tetrachlorophthalide, 3.3-bis[1.1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4.5.6.7-tetrabromophthalide, 3.3-bis-(1-(4-methoxyphenyl)-1-(4-pyridinophenyl)ethylene-2-yl]-4.5.6.7-tetrachlorophthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide,3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindol-3-yl)-4-azaphthalide, 3-(4-cyclohexylethylamino-2-methoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3.3-bis(1-ethyl-2-methylindol-3-yl)phthalide, 3.3-bis(1-octyl-2-methylindol-3-yl)phthalide, 2-phenyl-4-(4-diethylaminophenyl)-4-(4-methoxyphenyl )-6-methyl-7-dimethylamino-3.1-benzoxazine and 2-phenyl-4-(4-diethylaminophenyl)-4-(4-methoxyphenyl)-8-methyl-7-dimethylamino-3.1-benzoxazine, 4.4'-[1-methylethylidene)-bis(4.1-phenyleneoxy-4.2-quinazolinediyl)]bis[N,N-diethylbenzenamine], bis(N-methyldiphenylamine)-4-yl-(N-butylcarbazolyl)-3-ylmethane, and combinations thereof.

[0022] In yet another embodiment of the recording composition, the color former is 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(3-methylanilino)fluoran, 3-diethylamino-6-methyl-7-(2.4-dimethylanilino)fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3- It may be dibutylamino-7-(2-chloroanilino)fluoran, 3-N-ethyl-p-toluidino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran, 3-N-ethyl-N-ethoxypropylamino-6-methyl-7-anilinofluoran, 2,4-dimethyl-6-[(4-dimethylamino)anilino]fluoran, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindol-3yl)-4-azaphthalide, 3.3-bis(p-dimethylamino-phenyl)-6-dimethylaminophthalide and mixtures thereof. It is also possible to use a solid solution containing at least two color formers or color-forming compounds.

[0023] In some embodiments of the recording composition, the color former can be used alone or in mixtures with other color formers, or may be used with additional black color formers or color forming compounds.

[0024] In yet another embodiment of the recording composition, the composition may further comprise image stabilizers, sensitizers, fillers, binders, dispersants, antioxidants, antiblocking agents, desensitizers, defoamers, light stabilizers, optical brighteners, and combinations thereof.

[0025] In some embodiments of the recording composition, the composition may include one or more sensitizers in addition to OPTSA. For example, additional sensitizers include higher fatty acid amides such as stearamide, stearic acid anilide, and palmitic acid amide; amides such as benzamide, acetoacetanilide, thioacetanilide acrylic acid amide, ethylene bisamide, ortho-toluenesulfonamide, and para-toluenesulfonamide; phthalic acid diesters such as dimethyl phthalate, dibenzyl isophthalate, dimethyl isophthalate, dimethyl terephthalate, diethyl isophthalate, diphenyl isophthalate, and dibenzyl terephthalate; dibenzyl oxalate; diesters of oxalic acid such as dibenzyl, di(4-methylbenzyl) oxalate, di(4-chlorobenzyl) oxalate, an equal mixture of dibenzyl oxalate and di(4-chlorobenzyl) oxalate, and an equal mixture of di(4-chlorobenzyl) oxalate and di(4-methylbenzyl) oxalate; bis(t-butylphenols) such as 2.2'-methylenebis(4-methyl-6-t-butylphenol) and 4.4'-methylenebis-2.6-di-t-butylphenol; 4.4'-dimethoxydiphenyl sulfone, 4.4'-diethoxydiphenyl 4.4'-dihydroxydiphenyl sulfone diethers such as 4.4'-dipropoxydiphenyl sulfone, 4.4'-diisopropoxydiphenyl sulfone, 4.4'-dibutoxydiphenyl sulfone, 4.4'-diisobutoxydiphenyl sulfone, 4.4'-dipentyloxydiphenyl sulfone, 4.4'-dihexyloxydiphenyl sulfone, and 4.4'-diallyloxydiphenyl sulfone; 2.4'-dimethoxydiphenyl sulfone, 2.4'-diethoxydiphenyl sulfone, 2.4'-dipropoxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone diethers such as 2,4'-oxydiphenyl sulfone, 2.4'-diisopropoxydiphenyl sulfone, 2.4'-dibutoxydiphenyl sulfone, 2.4'-diisobutoxydiphenyl sulfone, 2.4'-dipentyloxydiphenyl sulfone, 2.4'-dihexyloxydiphenyl sulfone, and 2.4'-diallyloxydiphenyl sulfone; 1,2-bis(phenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,2-bis(5-methylphenoxy)ethane, 1,2-bis(6-methylphenoxy)ethane, 1,2-bis(7-methylphenoxy)ethane, 1,2-bis(8-methylphenoxy)ethane, 1,2-bis(9-methylphenoxy)ethane, 1,2-bis(10-methylphenoxy)ethane, 1,2-bis(11-methylphenoxy)ethane, 1,2-bis(12-methylphenoxy)ethane, 1,2-bis(13-methylphenoxy)ethane, 1,2-bis(14-methylphenoxy)ethane, 1,2-bis(15-methylphenoxy)ethane, 1,2-bis(16-methylphenoxy)ethane, 1,2-bis(17-methylphenoxy)ethane, 1,2-bis(18-methylphenoxy)ethane, 1,2-bis(19-methylphenoxy)ethane, 1,2-bis(21-methylphenoxy)ethane, 1,2-bis(18-methylphenoxy)ethane, 1,2-bis(19-methylphenoxy)ethane, 1,2-bis(19-methylphenoxy)ethane, 1,2-bis(18-methylphenoxy)ethane, 1,2-bis(19-methylphenoxy)ethane, 1,22-bis(phenoxymethyl)benzene, 1.2-bis(4-methoxyphenylthio)ethane, 1.2-bis(4-methoxyphenoxy)propane, 1.3-phenoxy-2-propanol, 1.4-diphenylthio-2-butene, 1.4-diphenylthiobutane, 1.4-diphenoxy-2-butene, 1.5-bis(4-methoxyphenoxy)-3-oxapentane, 1.3-dibenzoyloxypropane, dibenzoyloxymethane, 4.4'-ethylenedioxy-bis-benzoic acid dibenzyl ester, bis[2-(4-methoxyphenoxy)ethyl]ether, 2-naphthylbenzyl ether, 1.3-bis(2-vinyloxyethoxy)benzene, 1.4-diethoxynaphthalene 1,4-dibenzyloxynaphthalene, 1,4-dimethoxynaphthalene, 1,4-bis(2-vinyloxyethoxy)benzene, p-(2-vinyloxyethoxy)biphenyl, p-aryloxybiphenyl, p-propargyloxybiphenyl, p-benzyloxybenzyl alcohol, 4-(m-methylphenoxymethyl)biphenyl, 4-methylphenyl-biphenyl ether, di-β-naphthylphenylenediamine, diphenylamine, carbazole, 2,3-di-m-tolylbutane, 4-benzylbiphenyl, 4.4'-dimethylbiphenyl, m-terphenyl and p-terphenyl and other terphenyls; 1,2-bis(3.4-dimethylphenyl)ethane, 2.3.5.6-tetramethyl-4'-methyldiphenylmethane, 4-acetylbiphenyl, dibenzoylmethane, triphenylmethane, phenyl 1-hydroxy-naphthoate, methyl 1-hydroxy-2-naphthoate, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, benzyl p-benzyloxybenzoate, phenyl β-naphthoate, methyl p-nitrobenzoate, diphenyl sulfone, diphenyl carbonate, guaiacol carbonate, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, etc. carbonic acid derivatives; 1,1-diphenylpropanol, 1,1-diphenylethanol, N-octadecylcarbamoylbenzene, dibenzyl disulfide, stearic acid, Amide AP-1 (a 7:3 mixture of stearamide and palmitamide), stearates such as aluminum stearate, calcium stearate, and zinc stearate; and zinc palmitate, behenic acid, zinc behenate, montanic acid wax, polyethylene wax, and combinations thereof.

[0026] The recording composition thus obtained can be applied to a suitable support or substrate, such as paper, plastic sheets, and resin-coated paper, and used as a heat-sensitive recording material. The embodiments herein can be used in other end uses that use color former materials, such as temperature indicating materials. As used herein, the terms substrate and support are used interchangeably.

[0027] Also provided is a method of producing a heat-sensitive recording material. The method comprises the steps of providing a substrate or support; applying or depositing one or more layers or coatings of a heat-sensitive recording composition, depositing or applying one or more layers of the heat-sensitive recording composition to the substrate, thereby forming a heat-sensitive layer; and thereby producing a heat-sensitive recording material. The heat-sensitive recording composition comprises one or more color formers; one or more color developers; and at least one sensitizer comprising a mixture of ortho-toluenesulfonamide and para-toluenesulfonamide (OPTSA).

[0028] In some embodiments of the method, at least one sensitizer of the recording composition has a ratio of ortho-toluenesulfonamide to para-toluenesulfonamide of about 0.5:99.5 to about 99.5:0.5, can be about 5:90 to about 90:5, can be 10:85 to about 85:10, can be about 20:80 to about 80:20, or can be about 40:60 to about 60:40, based on the dry weight of the OPTSA mixture.

[0029] In other embodiments of the method, the at least one sensitizer is present in an amount of about 0.1 to about 6 parts by dry weight, can be present in an amount of 0.5 to 5.0 parts by dry weight, and may be present in an amount of 1.0 to 4.0 parts by dry weight per part of the color former or color formers.

[0030] In some embodiments of the method, an undercoat layer may be deposited or applied on the substrate before depositing the heat-sensitive recording composition. The undercoat generally comprises a binder resin and a filler as its main components. For example, the binder resin in the undercoat layer may be polyvinyl alcohol; starch and starch derivatives; cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose; sodium polyacrylate; polyvinylpyrrolidone; polyacrylamide / acrylic acid ester copolymers; acrylamide / acrylic acid ester / methacrylic acid copolymers; alkali metal salts of styrene / maleic anhydride copolymers; alkali metal salts of isobutylene / maleic anhydride copolymers; polyacrylamide; sodium alginate; gelatin; casein; water-soluble polymers such as water-soluble polyesters and carboxyl-modified polyvinyl alcohols; polyvinyl acetate; polyurethane; styrene / butadiene copolymers; polyacrylic acid; polyacrylic acid esters; vinyl chloride / vinyl acetate copolymers; polybutyl methacrylate; ethylene / vinyl acetate copolymers and styrene / butadiene acrylic derivative copolymers.

[0031] In another embodiment of the method, the undercoat layer can be finely divided inorganic powders such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface treated calcium, silica or calcined clay (e.g., Ansilex, Engelhard Corp.), and finely divided organic powders such as urea-formaldehyde resins, styrene / methacrylic acid copolymers, polystyrene, and combinations thereof. The undercoat layer may also include a water resistant agent.

[0032] In another embodiment of the method, one or more topcoats or protective layers can be deposited or applied on one or more of the heat-sensitive recording composition layers. The topcoat or protective layer is dispersed on or applied to the heat-sensitive composition layer, whereas the undercoat layer is interposed between the substrate and the heat-sensitive composition. The topcoat can include a water-soluble resin to protect the heat-sensitive composition layer. If desired, the topcoat layer can include a water-soluble resin in combination with a water-insoluble resin, for example, polyvinyl alcohol; starch and starch derivatives; cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose; sodium polyacrylate; polyvinylpyrrolidone; polyacrylamide / acrylic acid ester copolymers; acrylamide / acrylic acid ester / methacrylic acid copolymers; alkali metal salts of styrene / maleic anhydride copolymers; alkali metal salts of isobutylene / maleic anhydride copolymers; polyacrylamide; sodium alginate; gelatin; casein; water-soluble polyesters and carboxyl-modified polyvinyl alcohols, and combinations thereof.

[0033] In other aspects of the method, the topcoat layer may include a water resistant agent such as polyamide resin, melamine resin, formaldehyde, glyoxal, or chrome alum. The topcoat layer may include a filler, for example, finely divided inorganic powders such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface treated calcium or silica, or finely divided organic powders such as urea-formaldehyde resin, styrene / methacrylic acid copolymer, or polystyrene, as well as combinations thereof.

[0034] In some embodiments of the method, the one or more developers of the recording composition may include phenolic developers, non-phenolic developers, and combinations thereof. For example, the one or more developers may include 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and [3-(p-tolylsulfonylcarbamoylamino)phenyl]4-methylbenzenesulfonate, 2,4'-dihydroxydiphenyl sulfone, 4.4'-dihydroxydiphenyl sulfone, bis-(3-allyl-4-hydroxyphenyl)sulfone, 4-[4'-[(1'-methylethyloxy)phenyl]sulfonyl]phenol, 4-hydroxyphenyl The aryl group may be selected from 4-isopropyloxyphenyl sulfone, N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide, phenol, 4-[[4-(2-propenyloxy)phenyl]sulfonyl, 4-hydroxy-4'benzyloxydiphenyl sulfone, and 4,4'bis(N-carbamoyl-4-methylbenzenesulfonamido)diphenylmethane, 1,1'-oxybis[2-chloroethane], phenols, 4,4'-sulfonyl bis-polymers with urea urethane compounds, and combinations thereof.

[0035] In yet another embodiment of the method, the developer of the heat-sensitive composition is a bisphenol compound, such as bisphenol A, 4.4'-sec-butylidene bisphenol, 4.4'-cyclohexylidene bisphenol, 2.2'-bis(4-hydroxyphenyl)-3.3'-dimethylbutane, 2.2'-dihydroxydiphenyl, pentamethylene-bis(4-hydroxybenzoic acid), 2.2-dimethyl-3.3-di(4-hydroxyphenyl)pentane, 2.2-di(4-hydroxyphenyl)hexane, 2.2-bis(4-hydroxyphenyl) Propane, 2.2-bis(4-hydroxyphenyl)butane, 2.2-bis(4-hydroxy-3-methylphenyl)propane, 4.4'-(1-phenylethylidene)bisphenol, 4.4'-ethylidenebisphenol, (hydroxyphenyl)methylphenol, 2.2'-bis(4-hydroxy-3-phenyl-phenyl)propane, 4.4'-(1.3-phenylenediisopropylidene)bisphenol, 4.4'-(1.4-phenylenediisopropylidene)bisphenol, and 2.2-bis(4-hydroxyphenyl)acetic acid. butyl; sulfur-containing bisphenol compounds such as 4.4'-dihydroxydiphenylthioether, 1.7-di(4-hydroxyphenylthio)-3.5-dioxaheptane, 2.2'-bis(4-hydroxyphenylthio)diethyl ether, and 4.4'-dihydroxy-3.3'-dimethyldiphenylthioether; 4-hydroxybenzoic acid esters such as benzyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, isopropyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, isobutyl 4-hydroxybenzoate, chlorobenzyl 4-hydroxybenzoate, methylbenzyl 4-hydroxybenzoate, and diphenylmethyl 4-hydroxybenzoate; metal salts of benzoic acid, such as zinc benzoate, zinc 4-nitrobenzoate; salicylic acid, such as 4-[2-(4-methoxyphenyloxy)ethyloxy]salicylic acid; metal salts of salicylic acid, such as zinc salicylate, zinc bis[4-(octyloxycarbonylamino)-2-hydroxybenzoate]; hydroxysulfones, such as 4.4'-dihydroxydiphenylsulfone, 2.4'-Dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-butoxydiphenyl sulfone, 4.4'-dihydroxy-3.3'-diallyldiphenyl sulfone, 3.4-dihydroxy-4'-methyldiphenyl sulfone, 4.4'-dihydroxy-3.3'.5.5'-tetrabromodiphenyl sulfone, 4-allyloxy-4'-hydroxydiphenyl sulfone Nylsulfone, 2-(4-hydroxyphenylsulfonyl)phenol, 4.4'-sulfonylbis[2-(2-propenyl)]phenol, 4-[[4-(propoxy)phenyl}sulfonyl]phenol, 4-[{4-(allyloxy)phenyl}sulfonyl]phenol, 4-[{4-(benzyloxy)phenyl}sulfonyl]phenol, and 2,4-bis(phenylsulfonyl)-5-methyl-phenol; 2.4'-dihydroxydiphenylsulfone (BPS 2.4'), bis-(4-hydroxyphenyl)sulfone (BPS 4.4'), bis(3-allyl-4-hydroxyphenyl)sulfone (TG-SA), B-TUM, SZ110, 4-phenylsulfonylphenoxy-zinc Polyvalent metal salts of hydroxysulfones such as magnesium, aluminum and titanium; 4-hydroxyphthalic acid diesters such as dimethyl 4-hydroxyphthalate, dicyclohexyl 4-hydroxyphthalate and diphenyl 4-hydroxyphthalate; hydroxynaphthoic acid esters such as 2-hydroxy-6-carboxynaphthalene; trihalomethylsulfones such as tribromomethylphenylsulfone; sulfonylureas such as 4.4'-bis(p-toluenesulfonylaminocarbonylamino)diphenylmethane and N-(4-methylphenylsulfonyl)-N'-(3-(4-methylphenylsulfonyloxy)phenyl)urea; hydroxyacetophenone, p-phenylphenol, 4-hydroxyphenyl benzyl acetate, p-benzylphenol, hydroquinone monobenzyl ether, 2.4-dihydroxy-2'-methoxybenzanilide, tetracyanoquinodimethane, N-(2-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, N-(4-hydroxyphenyl)-2-[(4-hydroxyphenyl)thio]acetamide, 4-hydroxybenzenesulfonanilide, 4'-hydroxy-4-methylbenzenesulfonanilide, 4.4'-bis(4-methyl-3-phenoxycarbonyl)aminophenylureido)diphenylsulfone, 3-(3-phenylureido)benzenesulfonanilide, octadecylphosphoric acid, and dodecylphosphoric acid; and bridged diphenylsulfone compounds represented by the following formula or mixtures thereof. [ka]

[0036] In some embodiments of the method, the one or more color formers of the heat-sensitive composition can be fluorans, phthalides, lactams, triphenylmethanes, phenothiazines, spiropyran leuco dyes, and combinations thereof. For example, the one or more color formers can be 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-dibutylaminofluoran, 2-anilino-3-methyl-6-(methyl-N-isoamylamino)fluorine, 2-anilino-3-methyl-6-(N-ethyl-N-propylamino)fluoran, 2-anilino-3-methyl-6-di-n-amylaminofluoran, 2-anilino-3-methyl-6-(N-ethyl-N-butrylamino)fluoran, 2-anilino-3-methyl-6-N-ethyl-N-sec-butylaminofluoran, 3-di-(n-pentylamino) ... and the like. The fluoranol may be selected from the group consisting of 3-(N-isoamyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-(N-hexyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-[N-(3-ethoxypropyl)-N-ethylamino]-6-methyl-7-anilinofluoran, 3-di-(n-butylamino)-7-2-chloroanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, and combinations thereof.

[0037] In yet another embodiment of the method, the one or more color formers include, but are not limited to, 3-diethylamino-6-methylfluoran, 3-dimethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(2.4-dimethylanilino)fluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6-methyl-7-(3-trifluoromethylanilino)fluoran, 3-diethylamino-6-methyl-7-(2-chloroa ... 3-Diethylamino-6-methyl-7-(4-n-octylanilino)fluoran, 3-Diethylamino-6-methyl-7-(4-n-octylamino)fluoran, 3-Diethylamino-7-(4-n-octylamino)fluoran, 3-Diethylamino-7-(dibenzylamino)fluoran, 3-Diethylamino-6-methyl-7-(dibenz ... No-6-chloro-7-methylfluoran, 3-diethylamino-7-t-butylfluoran, 3-diethylamino-7-carboxyethylfluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-(3-methylanilino)fluoran, 3-diethylamino-6-methyl-7-(4-methylanilino)fluoran, 3-diethylamino-6-ethoxyethyl-7-anilinofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino No-7-(3-trifluoromethylanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-7-(2-fluoroanilino)fluoran, 3-diethylamino-benzo[a]fluoran, 3-diethylamino-benzo[c]fluoran, 3-dibutylamino-7-dibenzylaminofluoran, 3-dibutylamino-7-anilinofluoran, 3-diethylamino-7-anilinofluoran, 3-dibutylamino-6-methylfluoran, 3-dibutylamino-6-methyl-7-anilinofluoran,3-dibutylamino-6-methyl-7-(2.4-dimethylanilino)fluoran, 3-dibutylamino-6-methyl-7-(2-chloroanilino)fluoran, 3-dibutylamino-6-methyl-7-(4-chloroanilino)fluoran, 3-dibutylamino-6-methyl-7-(2-fluoroanilino)fluoran, 3-dibutylamino-6-methyl-7-(3-trifluoromethylanilino)fluoran, 3-dibutylamino-6-ethoxyethyl-7-anilinofluoran, 3-dibutylamino-6-chloro-anilinofluoran, 3-di Butylamino-6-methyl-7-(4-methylanilino)fluoran, 3-dibutylamino-7-(2-chloroanilino)fluoran, 3-dibutylamino-7-(2-fluoroanilino)fluoran, 3-dibutylamino-7-(N-methyl-N-formylamino)fluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-(4-2-chloroanilino)fluoran, 3-dipentylamino-7-(3-trifluoromethylanilino)fluoran, 3-dipentylamino-6-chloro-7 -Anilinofluoran, 3-dipentylamino-7-(4-chloroanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran Fluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-chloro-7-anilinofluoran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran, 3-(N-butyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-(N-isopropyl-N-3-pentylamino)-6-methyl-7-anilinofluoran,3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluoran, 3-cyclohexylamino-6-chlorofluoran, 2-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 2-methoxy-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 2-chloro-3-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran, 2-diethylamino-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 2-phenyl-6-methyl Fluoran, 2-benzyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran, 3-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran, 3-diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluoran, 3-diethylamino-6-p-(p-dibutylaminophenyl)aminoanilinofluoran, 2.4-dimethyl-6-[(4-dimethylamino)anilino]fluoran, 3-[(4-dimethylamino)anilino]fluoran, 4-dimethyl-6-[(4-dimethylamino)anilino]fluoran, 5-[(4-dimethylamino)anilino]fluoran, 6-[(4-dimethylamino)anilino]fluoran, 1-[(4-dimethylamino)anilino]fluoran, 2-[(4-dimethylamino)anilino]fluoran, 1-[(4-dimethylamino)anilino]fluoran, 2-[(4-dimethylamino)anilino]fluoran, 3-[(4-dimethylamino)anilino]fluoran, 1-[(4-dimethylamino)anilino]fluoran, 2-[(4-dimethylamino)anilino]fluoran, 2-[(4-dimethylamino)anilino]fluoran, 3 ... 3.6.6'-tris(dimethylamino)spiro[fluorene-9.3'-phthalide], 3.6.6'-tris(diethylamino)spiro[fluorene-9.3'-phthalide], 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3.3-bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl-4.5.6.7-tetrabromophthalide, 3.3-bis- [2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl-4.5.6.7-tetrachlorophthalide, 3.3-bis[1.1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4.5.6.7-tetrabromophthalide, 3.3-bis-(1-(4-methoxyphenyl)-1-(4-pyridinophenyl)ethylene-2-yl]-4.5.6.7-tetrachlorophthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide,3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindol-3-yl)-4-azaphthalide, 3-(4-cyclohexylethylamino-2-methoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3.3-bis(1-ethyl-2-methylindol-3-yl)phthalide, 3.3-bis(1-octyl-2-methylindol-3-yl)phthalide, 2-phenyl-4-(4-diethylaminophenyl)-4-(4-methoxyphenyl )-6-methyl-7-dimethylamino-3.1-benzoxazine and 2-phenyl-4-(4-diethylaminophenyl)-4-(4-methoxyphenyl)-8-methyl-7-dimethylamino-3.1-benzoxazine mixture, 4.4'-[1-methylethylidene)-bis(4.1-phenyleneoxy-4.2-quinazolinediyl)]bis[N,N-diethylbenzenamine], bis(N-methyldiphenylamine)-4-yl-(N-butylcarbazol)-3-ylmethane and combinations thereof.

[0038] In yet another embodiment of the method, the color former is 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(3-methylanilino)fluoran, 3-diethylamino-6-methyl-7-(2.4-dimethylanilino)fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, furfurylamino-7-(2-chloroanilino)fluoran, 3-N-ethyl-p-toluidino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran, 3-N-ethyl-N-ethoxypropylamino-6-methyl-7-anilinofluoran, 2,4-dimethyl-6-[(4-dimethylamino)anilino]fluoran, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindol-3yl)-4-azaphthalide, 3.3-bis(p-dimethylamino-phenyl)-6-dimethylaminophthalide and combinations thereof.

[0039] All of the above color formers can be used alone or in mixtures with other color formers, or may be used together with further black color formers or chromogenic compounds. It is also possible to use solid solutions comprising at least two color formers or chromogenic compounds.

[0040] In yet another aspect of the method, the recording composition may include image stabilizers, other sensitizers, fillers, binders, dispersants, antioxidants, antiblocking agents, defoamers, desensitizers, light stabilizers, optical brighteners, and combinations thereof.

[0041] These additional agents may be included in the heat-sensitive layer, or in any layer, such as a protective layer or topcoat layer, if the method is configured with a multi-layer structure. For example, if a topcoat layer or an undercoat layer is provided on the upper and / or lower side of the heat-sensitive layer, these layers may contain antioxidants, light stabilizers, etc. Furthermore, these antioxidants or light stabilizers may be included in these layers in the form of being encapsulated in microcapsules, if necessary.

[0042] In some embodiments of the method, the heat sensitive recording material is printed on a recording medium using a thermal printing process or a laser marking / printing process, such as CO 2 , Nd:YAG or FLDA-LED processes.

[0043] Also provided is a recording sheet comprising a substrate; and a recording composition deposited or applied onto the substrate, the recording composition comprising one or more color formers, one or more color developers, and at least one sensitizer comprising a mixture of ortho-toluenesulfonamide and para-toluenesulfonamide (OPTSA).

[0044] In some embodiments of the recording sheet, at least one sensitizer of the recording composition has a ratio of ortho-toluenesulfonamide to para-toluenesulfonamide of about 0.5:99.5 to about 99.5:0.5, can be about 5:90 to about 90:5, can be 10:85 to about 85:10, can be about 20:80 to about 80:20, or can be about 40:60 to about 60:40, based on the dry weight of the OPTSA mixture.

[0045] In other embodiments of the recording sheet, the at least one sensitizer of the recording composition is present in an amount of from about 0.1 to about 6 parts by dry weight per part of the color former or color formers, can be present in an amount of from 0.5 to 5.0 parts by dry weight, and may be present in an amount of from 1.0 to 4.0 parts by dry weight of the recording composition.

[0046] In some embodiments of the recording sheet, the developer or developers of the recording composition can be a phenolic developer, a non-phenolic developer, or a combination thereof. For example, the developer or developers of the recording composition can be 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and [3-(p-tolylsulfonylcarbamoylamino)phenyl]4-methylbenzenesulfonate, 2,4'-dihydroxydiphenyl sulfone, 4.4'-dihydroxydiphenyl sulfone, bis-(3-allyl-4-hydroxyphenyl)sulfone, 4-[4'-[(1'-methylethyloxy)phenyl]sulfonyl]phenol, 4-hydroxyphenyl 4-isopropyloxyphenyl sulfone, N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide, phenol, 4-[[4-(2-propenyloxy)phenyl]sulfonyl, 4-hydroxy-4'benzyloxydiphenyl sulfone, and 4,4'bis(N-carbamoyl-4-methylbenzenesulfonamido)diphenylmethane, 1,1'-oxybis[2-chloroethane], phenols, 4,4'-sulfonyl bis-polymers with urea urethane compounds, and combinations thereof.

[0047] In yet another embodiment of the recording sheet, the one or more color formers of the recording composition can be fluorans, phthalides, lactams, triphenylmethanes, phenothiazines, spiropyran leuco dyes, and combinations thereof. For example, the one or more color formers can be 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-dibutylaminofluoran, 2-anilino-3-methyl-6-(methyl-N-isoamylamino)fluorine, 2-anilino-3-methyl-6-(N-ethyl-N-propylamino)fluoran, 2-anilino-3-methyl-6-di-n-amylaminofluoran, 2-anilino-3-methyl-6-(N-ethyl-N-butrylamino)fluoran, 2-anilino-3-methyl-6-N-ethyl-N-sec-butylaminofluoran, 3-di-(n-pentylamino) ... amino)-6-methyl-7-anilinofluoran, 3-(N-isoamyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-(Nn-hexyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-[N-(3-ethoxypropyl)-N-ethylamino]-6-methyl-7-anilinofluoran, 3-di-(n-butylamino)-7-2-chloroanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, and combinations thereof.

[0048] Recording Sheets In yet another embodiment, the recording composition may further comprise image stabilizers, sensitizers, fillers, binders, dispersants, antioxidants, antiblocking agents, defoamers, light stabilizers, optical brighteners, and combinations thereof.

[0049] In another embodiment of the recording sheet, one or more undercoats are applied between the substrate and the heat-sensitive or heat-responsive (used interchangeably herein) layer to improve the resolution of the image by increasing the surface smoothness of the substrate and to improve the sensitivity of the image by increasing the thermal insulation. The undercoat or layer mainly comprises an inorganic filler such as calcined kaolin and / or an organic filler such as hollow spheres, and a binder. To prevent the penetration, migration, and diffusion of external agents that may cause deterioration of the printed image and / or background, a topcoat layer having a barrier effect can be deposited or applied on the recording sheet, which layer can be composed of, for example, a water-resistance imparting agent, a pigment, an auxiliary, a binder, and one or more various auxiliary agents without the use of a pigment or a combination of a binder and a pigment. The protective layer coating composition may further comprise various auxiliary agents such as waxes, silicone derivatives, etc., if necessary. The undercoat layer is deposited directly on the support or substrate, followed by the deposition of the heat-sensitive composition layer, followed by the deposition of the topcoat layer or protective layer. The heat-sensitive recording material according to the first embodiment of the present invention may optionally include a back layer, which mainly contains a pigment and a binder and is formed on the support on the side opposite to the heat-sensitive recording layer. This may enhance storage stability, curl stability, and printing performance. Furthermore, various techniques known in the field of manufacturing heat-sensitive recording materials may be applied as necessary. For example, the back side of the heat-sensitive recording material may be treated with an adhesive to form an adhesive label, or a magnetic recording layer, a printing coating layer, a thermal transfer recording layer, an inkjet recording layer, etc. may be provided.

[0050] In yet another embodiment of the recording sheet, the recording sheet is printed using a thermal printing process or a laser marking / printing process, such as CO 2 , Nd:YAG or FLDA-LED processes. EXAMPLES

[0051] I. Preparation of Developer Dispersion A (Solution A) A mixture of 13.6 g of 5-(N-3-methylphenylsulfonylamido)-(N',N''-bis-(3-methylphenyl)-isophthalic diamide (Pergafast™ 425 from Solenis), 0.3 g of surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, 13.6 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as dispersant and binder and 22.5 g of demineralized water was milled in a bead mill to a median particle size diameter of 1.0 μm to obtain developer dispersion A.

[0052] II. Preparation of Developer Dispersion B (Solution B) A mixture of 13.6 g of [3-(p-tolylsulfonylcarbamoylamino)phenyl]4-methylbenzenesulfonate (Pergafast™ 201 from Solenis), 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, 13.6 g of an aqueous solution (as 10%) of Poval™ 6-77 KL (modified polyvinyl alcohol, Kuraray) as dispersant and binder and 22.5 g of demineralized water was ground in a bead mill to a median particle size diameter of 1.0 μm to obtain developer dispersion B.

[0053] III. Preparation of color former dispersion C (solution C) A mixture of 16.6 g of 3-di-n-butylamino-6-methyl-7-phenylaminofluoran (WinCon-2, Connect Chemicals), 22.2 g of a 15 wt % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 10.9 g of water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion C.

[0054] IV. Preparation of Sensitizer Dispersion D (Solution D) A mixture of 4.5 g o-toluenesulfonamide (Sigmaaldrich), 6.8 g p-toluenesulfonamide (Sigmaaldrich), 3.8 g of a 15 wt. % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion D.

[0055] V. Preparation of Sensitizer Dispersion E (Solution E) A mixture of 11.3 g of p-toluenesulfonamide (Sigmaaldrich), 3.8 g of a 15 wt. % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g of water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion E.

[0056] VI. Preparation of Sensitizer Dispersion F (Solution F) A mixture of 11.3 g of o-toluenesulfonamide (Sigmaaldrich), 3.8 g of a 15 wt. % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g of water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion F.

[0057] VII. Preparation of sensitizer dispersion G (solution G) A mixture of 11.3 g of 1,2-diphenoxyethane (DPE, Connect Chemicals), 3.8 g of a 15 wt. % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g of water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion G.

[0058] VIII. Preparation of sensitizer dispersion H (solution H) A mixture of 11.3 g of 1,2-bis(3-methylphenoxy)ethane (Connect Chemicals), 3.8 g of a 15 wt. % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as a dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g of water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion H.

[0059] XI. Preparation of Sensitizer Dispersion I (Solution I) A mixture of 11.3 g diphenylsulfone (Sigmaaldrich), 3.8 g of a 15 wt. % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion I.

[0060] X. Preparation of sensitizer dispersion J (solution J) A mixture of 11.3 g of benzyl-2-naphthyl ether (Pergaspeed™ 305, BASF SE), 3.8 g of a 15 wt. % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g of water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion J.

[0061] XI. Preparation of sensitizer dispersion K (solution K) A mixture of 11.3 g of di-(p-methylbenzyl) oxalate (DIC Corporation), 3.8 g of a 15 wt. % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as a dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g of water was ground in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion K.

[0062] XII. Preparation of sensitizer dispersion L (solution L) A mixture of 11.3 g dimethyl terephthalate (DMT) (Connect Chemicals), 3.8 g of a 15 wt % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as a dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain dispersion L.

[0063] XIII. Preparation of sensitizer dispersion M (solution M) A mixture of 11.3 g dimethyl terephthalate (DMT) (Connect Chemicals), 3.8 g of a 15 wt % solution of partially hydrolyzed polyvinyl alcohol (Poval™ 3-88, Kuraray), 5.7 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as a dispersant and binder, 0.3 g of the surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, and 29.0 g water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion M.

[0064] XIV. Preparation of filler dispersion N (solution N) A mixture of 19.8 g of calcined kaolin (Ansilex® 93, BASF SE), 0.5 g of an aqueous solution of dispersant (sodium polyacrylate (DISPEX® AA A4140, BASF SE), pH 7.5, active content 40% by weight), and 29.7 g of water was milled in a bead mill to an average particle diameter of 1.0 μm to obtain Dispersion N.

[0065] XV. Preparation of Filler Dispersion O (Solution O) A mixture of 9.1 g of silica with medium particle size and medium oil absorption capacity (Sipernat® 120, Evonik), 0.2 g of surfactant 2.4.7.9-tetramethyl-5-decyne-4.7-diol (Surfynol® 104 from Evonik) as a 20% solution in isopropanol, 9.1 g of an aqueous solution (as 10%) of Gohsenx™ L-3266 (sulfonated polyvinyl alcohol, Nippon Synthetic) as dispersant and binder, and 31.7 g of demineralized water was ground in a bead mill to an average particle diameter of 1.0 μm to obtain dispersion O.

[0066] Example 1 - Heat sensitive colours and coatings (see Table 1)

[0067] Sample A0 A heat-sensitive recording layer coating composition was obtained by mixing and stirring 125 parts of solution A, 50 parts of solution C, 15 parts of a stearic acid amide dispersion with a non-volatile content of 25% (Hymicron L-271, Chukyo Yushi Co., Ltd.), 40 parts of a zinc stearate dispersion with a dry content of 17% (Hidorin F115, Chuko Europe), 200 parts of an aqueous solution of 10% by weight polyvinyl alcohol (Poval® 28-99, polyvinyl alcohol, Kuraray Europe GmbH), 150 parts of solution N, and 580 parts of distilled water.

[0068] Base paper pre-coated with calcined kaolin (Ansilex® 93, BASF SE based, coating weight 7 g / m 2 ) was applied at 0.35 g / m using a suitable wire bar (#3-K bar, manufactured by RK Printcoat instruments Ltd). 2 The heat-sensitive recording layer coating composition was coated on the sheet to a dry color former coating weight of 100 g / m2 and dried with a hot air blower. The coated heat-sensitive sheet was stored at 40° C. for 24 hours. The heat-sensitive recording layer coating composition was calendered at 25 kN, 2 passes to obtain a smooth surface.

[0069] Sample A1 A heat-sensitive recording layer coating composition was obtained by mixing and stirring 125 parts of solution A, 50 parts of solution C, 75 parts of solution D, 15 parts of a stearic acid amide dispersion with a non-volatile content of 25% (Hymicron L-271, Chukyo Yushi Co., Ltd.), 40 parts of a zinc stearate dispersion with a dry content of 17% (Hidorin F115, Chuko Europe), 200 parts of an aqueous solution of 10% by weight polyvinyl alcohol (Poval® 28-99, polyvinyl alcohol, Kuraray Europe GmbH), 150 parts of solution N, and 510 parts of distilled water.

[0070] Base paper pre-coated with calcined kaolin (Ansilex® 93, BASF SE based, coating weight 7 g / m 2 ) was applied at 0.35 g / m using a suitable wire bar (#3-K bar, manufactured by RK Printcoat instruments Ltd). 2 The heat-sensitive recording layer coating composition was coated on the sheet to a dry color former coating weight of 100 g / m2 and dried with a hot air blower. The coated heat-sensitive sheet was stored at 40° C. for 24 hours. The heat-sensitive recording layer coating composition was calendered at 25 kN, 2 passes to obtain a smooth surface.

[0071] Sample A2 A heat-sensitive recording layer coating composition was obtained by mixing and stirring 125 parts of solution A, 50 parts of solution C, 150 parts of solution D, 15 parts of a stearic acid amide dispersion with a non-volatile content of 25% (Hymicron L-271, Chukyo Yushi Co., Ltd.), 40 parts of a zinc stearate dispersion with a dry content of 17% (Hidorin F115, Chuko Europe), 200 parts of an aqueous solution of 10% by weight of polyvinyl alcohol (Poval® 28-99, polyvinyl alcohol, Kuraray Europe GmbH), 150 parts of solution N, and 430 parts of distilled water.

[0072] Base paper pre-coated with calcined kaolin (Ansilex® 93, BASF SE based, coating weight 7 g / m 2 ) was applied at 0.35 g / m using a suitable wire bar (#3-K bar, manufactured by RK Printcoat instruments Ltd). 2 The heat-sensitive recording layer coating composition was coated on the sheet to a dry color former coating weight of 100 g / m2 and dried with a hot air blower. The coated heat-sensitive sheet was stored at 40° C. for 24 hours. The heat-sensitive recording layer coating composition was calendered at 25 kN, 2 passes to obtain a smooth surface.

[0073] Sample A3 A heat-sensitive recording material was produced in the same manner as in Sample A2, except that in the preparation of the heat-sensitive recording layer, 225 parts of solution D were used instead of 150 parts, and 360 parts of distilled water were used instead of 430 parts.

[0074] Sample A4 A heat-sensitive recording material was produced in the same manner as in Sample A3, except that in the preparation of the heat-sensitive recording layer, 300 parts of solution D were used instead of 225 parts, and 280 parts of distilled water were used instead of 360 parts.

[0075] Samples A5 and A6 Heat-sensitive recording materials were produced in the same manner as sample A2, except that solution E was used for sample A5 and solution F was used for sample A6 instead of solution D in the preparation of the heat-sensitive recording layer.

[0076] Sample A1-1 A heat-sensitive recording material was produced in the same manner as Sample A1, except that in the preparation of the heat-sensitive recording layer, an additional 75 parts of Solution G was added and 430 parts of distilled water was used instead of 510 parts.

[0077] Samples B1-1 and C1-1 Heat-sensitive recording materials were produced in the same manner as sample A1-1, except that solution H was used for sample B1-1 and solution I was used for sample C1-1 instead of solution G in preparing the heat-sensitive recording layer.

[0078] Sample A1-2 A heat-sensitive recording material was produced in the same manner as in Sample A1-1, except that in the preparation of the heat-sensitive recording layer, 150 parts of solution G was added instead of 75 parts, and 360 parts of distilled water was used instead of 430 parts.

[0079] Samples B1-2 and C1-2 Heat-sensitive recording materials were produced in the same manner as sample A1-2, except that solution H was used for sample B1-2 and solution I was used for sample C1-2 instead of solution G in preparing the heat-sensitive recording layer.

[0080] Sample A2-1 A heat-sensitive recording material was produced in the same manner as in sample A1-2, except that in the preparation of the heat-sensitive recording layer, 75 parts of solution G were added instead of 150 parts, and 150 parts of solution D were added instead of 75 parts.

[0081] Samples B2-1, C2-1, D2-1, E2-1 and F2-1 Heat-sensitive recording materials were produced in the same manner as sample A2-1, except that in the preparation of the heat-sensitive recording layer, solution H was used for sample B2-1, solution I for sample C2-1, solution J for sample D2-1, solution K for sample E2-1, and solution L for sample F2-1, instead of solution G.

[0082] Sample G1-1 A heat-sensitive recording material was produced in the same manner as sample A1, except that in preparing the heat-sensitive recording layer, 90 parts of a stearic acid amide dispersion with a non-volatile content of 25% (Hymicron L-271, Chukyo Yushi Co., Ltd.) was added instead of 15 parts, and 430 parts of distilled water was used instead of 510 parts.

[0083] Sample G1-2 A heat-sensitive recording material was produced in the same manner as sample G1-1, except that in the preparation of the heat-sensitive recording layer, 165 parts of a stearic acid amide dispersion with a non-volatile content of 25% (Hymicron L-271, Chukyo Yushi Co., Ltd.) was added instead of 90 parts, and 280 parts of distilled water was used instead of 430 parts.

[0084] Sample G2-1 A heat-sensitive recording material was produced in the same manner as sample A2, except that in preparing the heat-sensitive recording layer, 90 parts of a stearic acid amide dispersion with a non-volatile content of 25% (Hymicron L-271, Chukyo Yushi Co., Ltd.) was added instead of 15 parts, and 360 parts of distilled water was used instead of 430 parts.

[0085] Sample H-1 A heat-sensitive recording material was produced in the same manner as sample A1, except that in the preparation of the heat-sensitive recording layer, 37.5 parts of solution G were added, 52.5 parts of a stearic acid amide dispersion with a non-volatile content of 25% (Hymicron L-271, Chukyo Yushi Co., Ltd.) were added instead of 15 parts, and 430 parts of distilled water were used instead of 510 parts.

[0086] [Table 1]

[0087] Example 2 - Heat sensitive colouring and coatings (see Table 2)

[0088] Sample R1 A heat-sensitive recording layer coating composition was obtained by mixing and stirring 125 parts of solution B, 50 parts of solution C, 15 parts of a stearic acid amide dispersion with a non-volatile content of 25% (Hymicron L-271, Chukyo Yushi Co., Ltd.), 40 parts of a zinc stearate dispersion with a dry content of 17% (Hidorin F115, Chuko Europe), 200 parts of an aqueous solution of 10% by weight polyvinyl alcohol (Poval® 28-99, polyvinyl alcohol, Kuraray Europe GmbH), 150 parts of solution N, and 580 parts of distilled water.

[0089] Base paper precoated with calcined kaolin (Ansilex® 93, BASF SE based, coating weight 7 g / m 2 ) was applied at 0.35 g / m using a suitable wire bar (#3-K bar, manufactured by RK Printcoat instruments Ltd). 2 The heat-sensitive recording layer coating composition was coated on the sheet to a dry color former coating weight of 100 g / m2 and dried with a hot air blower. The coated heat-sensitive sheet was stored at 40° C. for 24 hours. The heat-sensitive recording layer coating composition was calendered at 25 kN, 2 passes to obtain a smooth surface.

[0090] Sample R2 A heat-sensitive recording layer coating composition was obtained by mixing and stirring 125 parts of solution B, 50 parts of solution C, 150 parts of solution D, 15 parts of a stearic acid amide dispersion with a non-volatile content of 25% (Hymicron L-271, Chukyo Yushi Co., Ltd.), 40 parts of a zinc stearate dispersion with a dry content of 17% (Hidorin F115, Chuko Europe), 200 parts of an aqueous solution of 10% by weight of polyvinyl alcohol (Poval® 28-99, polyvinyl alcohol, Kuraray Europe GmbH), 150 parts of solution N, and 430 parts of distilled water.

[0091] Base paper precoated with calcined kaolin (Ansilex® 93, BASF SE based, coating weight 7 g / m 2) was applied at 0.35 g / m using a suitable wire bar (#3-K bar, manufactured by RK Printcoat instruments Ltd). 2 The heat-sensitive recording layer coating composition was coated on the sheet to a dry color former coating weight of 100 g / m2 and dried with a hot air blower. The coated heat-sensitive sheet was stored at 40° C. for 24 hours. The heat-sensitive recording layer coating composition was calendered at 25 kN, 2 passes to obtain a smooth surface.

[0092] Sample R3 A heat-sensitive recording material was produced in the same manner as in Sample R1, except that Solution A was used instead of Solution B in the preparation of the heat-sensitive recording layer.

[0093] Sample R4 A heat-sensitive recording material was produced in the same manner as sample R2, except that solution A was used instead of solution B in the preparation of the heat-sensitive recording layer.

[0094] Sample R5 A heat-sensitive recording material was produced in the same manner as sample R4, except that in the preparation of the heat-sensitive recording layer, 250 parts of solution O were used instead of solution N, and 335 parts of distilled water were used instead of 430 parts.

[0095] [Table 2]

[0096] Evaluation of heat-sensitive recording compositions and materials (Tables 3 and 4)

[0097] Dynamic Sensitivity The heat-sensitive recording materials prepared according to the embodiments herein were evaluated as described below, and the results of the evaluation are summarized in Table 3.

[0098] The evaluation consisted of printing thermal image patterns at constant printing speed, at graded energy conditions per surface unit, and under dynamic conditions.

[0099] In this study, a ZEBRA™ ZT610 direct thermal printer (ZEBRA Technologies, Inc.) equipped with a 201 dpi flat thermal printhead was used. Each thermal recording material was printed at a speed of 200 mm / s with stepwise printing energy for the following patterns: 2-4-6-9-12-15-18-21-24-27-30.

[0100] The resulting printed patterns were evaluated by measuring the optical density (black filter) [OD] using an X-Rite / Densieye™ 700 (X-Rite Europe GmbH) optical densitometer. A higher OD under constant energy and speed conditions means a higher sensitivity of the dynamic image.

[0101] [Table 3]

[0102] The dynamic sensitivity was evaluated by comparing the optical density (OD) in the print range of 9 to 21, with higher OD at the same print energy indicating higher sensitivity corresponding to better quality.

[0103] The maximum image density achievement can be evaluated in the print range of 27-30, with higher OD indicating higher maximum image density providing better image quality (darker image).

[0104] From sample A0 (no sensitizer) to sample A4, it can be seen that OPTSA improves the dynamic sensitivity, and the higher the OPTSA ratio, the higher the dynamic sensitivity, even at maximum image density, even when saturation begins to appear above an OPTSA to developer ratio of 3.0.

[0105] PTSA (A5) and OTSA (A6) also function as sensitizers with the developer Pergafast™ 425, but the mixture OPTSA (A2) shows better dynamic sensitivity levels. Results also show that combinations of OPTSA with other sensitizers or waxes improve dynamic sensitivity (e.g., Samples A1-1 to H1).

[0106] [Table 4]

[0107] In the present study, two different developers were evaluated without OPTSA sensitizer (R1 and R3) and with OPTSA as sensitizer (R2, R4 and R5). The results show that the use of OPTSA in combination with the two developers significantly increases the dynamic sensitivity and improves the maximum image density.

[0108] Example 3 – Image and background stability The optical density (OD) of the thermally printed image and the background whiteness of the non-thermally printed areas of the media were measured before and after exposure to the aging test.

[0109] The smaller the difference in optical density (OD) between the initial level and the level after aging, the greater the stability and durability of the thermal media. Table 5 below summarizes the results of this study.

[0110] Image quality assessment by optical density (OD) Each heat-sensitive recording material was printed at 200 mm / s with an applied energy of 30 using a ZEBRA™ ZT610 direct thermal printer (manufactured by ZEBRA Technologies) equipped with a 201 dpi flat thermal printhead, and the density of the resulting recorded image was measured with an X-Rite / Densieye™ 700 (manufactured by X-Rite Europe GmbH) optical densitometer. The quality of the background was evaluated by optical density (OD).

[0111] The optical density (OD) of the unrecorded surface of the coated substrate was measured with an X-Rite / Densieye™ 700 (X-Rite Europe GmbH) optical densitometer.

[0112] water resistance After thermal printing, the coated substrate was immersed in deionized water at 40° C. for 24 hours.

[0113] After this treatment, the samples were kept at room temperature for the time required for complete drying, after which the OD of the image and background were measured using an X-Rite / Densieye™ 700 (X-Rite Europe GmbH) optical densitometer.

[0114] The Remaining Image ratio is evaluated by the following calculation: Residual rate (%) = (OD after water resistance test) / (OD of untreated material) x 100

[0115] Plasticizer Face Resistance After thermal printing, the «face side» of the coated substrate, on which the printed image is recorded, is intimately adhered to a sheet of PVC wrapping film (containing a phthalate type plasticizer) from Jet Cut GmbH, under a pressure of 50 g / cm-2 for 15 hours at 40°C.

[0116] After this treatment, the PVC film is removed from the face surface and the sample is kept at room temperature for 1 hour.

[0117] The OD of the image and background was then measured within 8 hours after removal of the PVC film using an X-Rite / Densieye™ 700 (X-Rite Europe GmbH) optical densitometer.

[0118] The remaining image ratio was evaluated by the following calculation method: Residual rate (%) = (OD after plasticizer face resistance test) / (OD of untreated material) x 100

[0119] Oil resistance After thermal printing, 0.05 ml of virgin olive oil was applied evenly onto the face side of the coated substrate, and the sample was kept at 25° C. for 24 hours.

[0120] After this processing, the OD of the image and background was measured using an X-Rite / Densieye™ 700 (X-Rite Europe GmbH) optical densitometer.

[0121] The remaining image ratio was evaluated by the following calculation method: Residual rate (%) = (OD after oil resistance test) / (OD of untreated material) x 100

[0122] heat resistance After thermal printing, the coated substrate was placed in a dry oven at 80° C. / 90° C. / 100° C. for 1 hour.

[0123] After this treatment, the samples were kept at room temperature for 1 hour, after which the OD of the image and background were measured using an X-Rite / Densieye™ 700 (X-Rite Europe GmbH) optical densitometer.

[0124] The remaining image ratio was evaluated by the following calculation method: Residual rate (%) = (OD after heat resistance test) / (OD of untreated material) x 100

[0125] Example 4 - Image and Background Stability Results of Tested Thermal Papers

[0126] Light (xenon light) resistance After thermal printing, the heat sensitive recording material was stored in a xenon weather meter (Atlas Suntest CPS + WB 300-800 nm with window glass filter / 500 W-temperature kept below 40° C.) for 4 hours.

[0127] After this processing, the OD of the image and background was measured using an X-Rite / Densieye™ 700 (X-Rite Europe GmbH) optical densitometer.

[0128] The Remaining Image ratio is evaluated by the following calculation: Residual rate (%) = (OD after oil resistance test) / (OD of untreated material) x 100

[0129] [Table 5]

[0130] [Table 6]

[0131] It was found that when OPTSA was used as a sensitizer, the printed and unprinted (BG) areas of the recording sheet had excellent stability and resistance. When OPTSA was used as a sensitizer in the composition, the resistance of unprinted areas to thermal background fogging was improved. Usually, a high proportion of sensitizer adversely affects the thermal resistance of the background.

[0132] Also, when OPTSA was a component of a heat-sensitive formulation, resistance to plasticizers and oils was excellent. Finally, high levels of preservability of colour developers, such as Pergafast™ 425, were maintained when used in combination with OPTSA.

[0133] While the above detailed description presents at least one exemplary embodiment, it should be understood that a vast number of variations exist. It should also be understood that the exemplary embodiment is merely an example, and is not intended to limit the scope, applicability, or configuration of the present disclosure in any manner. Rather, the above detailed description provides those skilled in the art with a convenient road map for implementing the exemplary embodiments of the present disclosure. It should be understood that various changes may be made in the function and arrangement of elements described in the exemplary embodiments without departing from the scope of the present disclosure as set forth in the appended claims.

Claims

1. a) 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-dibutylaminofluoran, 2-anilino-3-methyl-6-(methyl-N-isoamylamino)fluoran, 2-anilino-3-methyl-6-(N-ethyl-N-propylamino)fluoran, 2-anilino-3-methyl-6-di-n-amylaminofluoran, 2-anilino-3-methyl-6-(N-ethyl-N-butylamino)fluoran, 2-anilino-3-methyl-6-N-ethyl-N-sec-butylaminofluoran, 3-di-(n-pentylamino)-6-methyl-7-amylaminofluoran, one or more color formers selected from nilinofluoran, 3-(N-isoamyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-(N-n-hexyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-[N-(3-ethoxypropyl)-N-ethylamino]-6-methyl-7-anilinofluoran, 3-di-(n-butylamino)-7-2-chloroanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, and combinations thereof; b) 5-(N-3-methylphenyl-sulfonylamido)-(N',N''-bis-(3-methylphenyl)-isophthalic acid diamide, [3-(p-tolylsulfonylcarbamoylamino)phenyl]4-methylbenzenesulfonate, 2,4'-dihydroxydiphenyl sulfone, 4.4'-dihydroxydiphenyl sulfone, bis-(3-allyl-4-hydroxyphenyl)sulfone, 4-[4'-[(1'-methylethyloxy)phenyl]sulfonyl]phenol, 4-hydroxyphenyl 4-isopropyloxyphenyl sulfone one or more colour developers selected from 4,4'-sulfonyl bis-polymers having 1,1'-oxybis[2-chloroethane], phenols, 4-[[4-(2-propenyloxy)phenyl]sulfonyl, 4-hydroxy-4'benzyloxydiphenylsulfone, and 4,4'-bis(N-carbamoyl-4-methylbenzenesulfonamido)diphenylmethane, 1,1'-oxybis[2-chloroethane], phenols, urea urethane compounds, and combinations thereof; and c) at least one sensitizer comprising a mixture of ortho-toluenesulfonamide and para-toluenesulfonamide (OPTSA); A heat-sensitive recording composition comprising:

2. 2. The recording composition of claim 1, wherein the at least one sensitizer has a ratio of ortho-toluenesulfonamide to para-toluenesulfonamide of from 0.5:99.5 to 99.5:0.5, based on the dry weight of the OPTSA mixture.

3. 3. The recording composition of claim 1, wherein the at least one sensitizer is present in an amount of from 0.1 to 6 parts by dry weight per part of the color former or color formers.

4. 1. A method for producing a heat-sensitive recording material, the method comprising the steps of: providing a substrate; A process for producing said heat-sensitive recording material by applying or depositing one or more layers of the heat-sensitive recording composition according to claim 1 onto said substrate forming a heat-sensitive layer. A method comprising:

5. The method of claim 4 , wherein the substrate has one or more coatings on a surface thereof and the thermal recording composition is deposited on the one or more coatings.

6. substrate; The recording composition of claim 1 disposed on the substrate. Including, a recording sheet.