Method for manufacturing a thermal recording material

Abstract

To provide a method capable of producing a thermal recording material that offers high print density, minimal unwanted reddish coloration in the background, and superior production stability.SOLUTION: A thermal recording layer comprises, as a dye precursor, at least one selected from 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran and, as dispersants for the dye precursor, a maleic acid-based copolymer with a degree of esterification of 15% or more and a nonionic surfactant with an HLB value of 10 or more. The dye precursor is subjected to wet grinding with the content of the nonionic surfactant set to be 0.15-4 mass% relative to the dye precursor.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a thermal recording material, which can provide a thermal recording material with high print density, little red cast on the background, and excellent production stability. [Background technology]

[0002] A thermal recording material generally comprises a support and a thermal recording layer containing an electron-donating dye precursor (hereinafter referred to as the dye precursor) and an electron-accepting developer (hereinafter referred to as the developer). When the thermal recording layer is heated with a thermal head, a thermal pen, laser light, or the like, the dye precursor and the developer react instantaneously to produce a recorded image. Such thermal recording materials have advantages such as the ability to produce recorded images with relatively simple equipment, ease of maintenance, and the absence of noise. They are therefore used in a wide range of applications, including measurement recorders, facsimiles, printers, computer terminals, label printers, and ticket vending machines. In particular, thermal recording materials have recently been used in financial recording paper, such as receipts for gas, water, and electricity bills, ATM statements from financial institutions, and various receipts, as well as thermal recording labels and tags for POS systems.

[0003] These applications demand a thermal recording material that exhibits high print density. To meet this demand, the dye precursor is used after being atomized by wet grinding using a grinder such as a sand grinder, a ball mill, an attritor, or a bead mill. The use of atomized dye precursor makes it easier for the dye precursor to melt when heated, and the molten dye precursor mixes with the developer at the molecular level, accelerating the color-developing reaction.

[0004] In addition, as for thermal recording materials, not only black color-developing thermal recording materials but also red color-developing thermal recording materials are sometimes used. Red color-developing thermal recording materials tend to have more noticeable red cast on the background than black color-developing thermal recording materials, and therefore thermal recording materials with less red cast on the background are required.

[0005] Known dye precursors that develop a red color include 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran. For example, Japanese Patent Application Laid-Open Publication No. 2006-281473 (Patent Document 1) describes a multicolor thermal recording material containing 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran, which exhibits good color separation between low-temperature and high-temperature printed areas, excellent lightfastness of image areas of each color tone, and suppressed deterioration of color-developing function even during long-term lightfastness tests. However, in recent years, the environments in which thermal recording materials are used have become more severe, and thermal recording materials containing 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide or 3-diethylamino-7-chlorofluoran in the thermal recording layer have not been fully satisfactory in terms of reducing red casts on the background.

[0006] It is known that background fogging can be improved by using a nonionic surfactant as a dispersant when wet-milling a dye precursor, as described, for example, in JP-A-6-206374 (Patent Document 2) and JP-A-2002-283727 (Patent Document 3). However, when this technology is used to disperse 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide or 3-diethylamino-7-chlorofluoran, problems with production stability have arisen, such as gelation of the dispersion containing the dye precursor, and precipitation and coagulation of the dispersoid. It is also known that background fogging can be improved by using a styrene-maleic acid copolymer as a dispersant when wet-milling a dye precursor, as described, for example, in JP-A-8-39931 (Patent Document 4). However, when this technique is used, there is a problem that the red cast of the background of a thermal recording material using 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide or 3-diethylamino-7-chlorofluoran becomes worse. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-281473 [Patent Document 2] Japanese Patent Application Publication No. 6-206374 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-283727 [Patent Document 4] Japanese Patent Application Publication No. 8-39931 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a method for producing a heat-sensitive recording material which can provide a heat-sensitive recording material with high print density, little red cast on the background, and excellent production stability. [Means for solving the problem]

[0009] A method for producing a thermosensitive recording material having a thermosensitive recording layer containing a dye precursor and a developer on a support, wherein the thermosensitive recording layer contains at least one dye precursor selected from 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran, and a maleic acid copolymer having an esterification degree of 15% or more and a nonionic surfactant with an HLB value of 10 or more as a dispersant for the dye precursor, and the dye precursor is wet-pulverized under conditions where the content of the nonionic surfactant relative to the dye precursor is 0.15 to 4% by mass. [Effects of the Invention]

[0010] The present invention provides a method for producing a thermal recording material that can provide a thermal recording material with high print density, little red fogging on the background, and excellent production stability. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will now be described in more detail.

[0012] In the present invention, the dye precursor contained in the thermal recording layer is at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran. The dye precursor is wet-pulverized using a maleic acid copolymer with an esterification degree of 15% or more and a nonionic surfactant with an HLB value of 10 or more as a dispersant, with the content of the nonionic surfactant being 0.15% by mass or more and 4% by mass or less relative to the dye precursor. If the HLB value of the nonionic surfactant is less than 10, gelation is likely to occur during preparation of the dye precursor dispersion, resulting in reduced manufacturing stability. Furthermore, if the content of the nonionic surfactant is less than 0.15% by mass, a reddish cast occurs on the background, while if the content of the surfactant is more than 4% by mass, sufficient print density cannot be obtained.

[0013] In the present invention, the nonionic surfactant has a hydrophilic group composed of a hydroxyl group or an ether bond that does not ionize in water, and examples thereof include polyoxyethylene octylphenyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, polyoxyethylene castor oil ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyalkylene alkyl ether, polyoxyethylene oleate, polyoxyethylene nonylphenyl ether, sorbitan laurate, sorbitan stearate, sorbitan oleate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan stearate, polyoxyethylene sorbitan oleate, polyoxyethylene sorbitan trioleate, polyoxyethylene polystyrene phenyl ether, polyethylene glycol, polyoxyethylene polyoxypropylene ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene fatty acid ester, etc. These surfactants may be used alone or in combination of two or more. Such nonionic surfactants can be commercially available, such as Emulgen® MS-110 (polyoxyethylene polyoxypropylene alkyl ether) and Rheodol® TW-L120 (polyoxyethylene sorbitan monolaurate) from Kao Corporation. Furthermore, in the present invention, a content of the nonionic surfactant relative to the total amount of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran contained in the thermosensitive recording layer is preferably in the range of 0.2% to 4% by mass, since this reduces background red cast, provides a thermosensitive recording material with high print density, and excellent manufacturing stability. Furthermore, a nonionic surfactant with an HLB value in the range of 10 to 18 is also preferred, since this reduces background red cast, provides a thermosensitive recording material with high print density, and excellent manufacturing stability.

[0014] The maleic acid copolymer used in the wet grinding of the dye precursor in the present invention is a copolymer containing maleic acid as a monomer unit, in which 15% or more of the maleic acid monomer units are esterified (i.e., the degree of esterification is 15% or more). If the degree of esterification is less than 15%, sufficient production stability cannot be achieved even when an appropriate amount of the above-mentioned nonionic surfactant is used in combination. Maleic acid copolymers can be obtained by radical copolymerization of maleic anhydride with various known monomers, followed by esterification and hydrolysis of the maleic anhydride units of the copolymer. Examples of such copolymers include copolymers of α-olefins and maleic acid, copolymers of alkyl vinyl ethers and maleic acid, and copolymers of styrene derivatives and maleic acid. In particular, the maleic acid copolymer in the present invention preferably has an esterification degree of 15% or more and a mass average molecular weight of 5,000 to 60,000, which allows for excellent production stability in dispersing 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide or 3-diethylamino-7-chlorofluoran without causing high viscosity or poor pulverization.

[0015] One or more of these maleic acid copolymers can be used as needed. Commercially available maleic acid copolymers can also be used, and suitable examples include Arakawa Chemical Industries, Ltd.'s Polymaron (registered trademark) 1318 (esterification degree 70%, average molecular weight 50,000 to 60,000) and KS-1333 (esterification degree 70%, average molecular weight 10,000 to 20,000).

[0016] In the present invention, 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran can be used in combination. The ratio of the two can be selected in consideration of the color tone of the image area and the light resistance of the image area, but a ratio of 3-diethylamino-7-chlorofluoran of 50% or more is preferred because the color tone of the image area becomes a vivid vermilion color.

[0017] In the present invention, at least one compound selected from 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran is preferably wet-milled using water as a dispersion medium. Examples of dispersion media other than water include water-compatible organic solvents, such as methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, and ethylene glycol. From the viewpoint of dispersion stability, the proportion of water in the entire dispersion medium is preferably 90% by mass or more. In the present invention, the term "use as a dispersant" means that the dispersion medium contains these compounds during wet milling.

[0018] In the present invention, 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran are ground using various wet grinders such as sand grinders, ball mills, attritors, and bead mills until the volume average particle size of the dispersoid containing at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran is preferably 0.1 to 1.5 μm, and then used to prepare the thermosensitive layer coating solution for the thermosensitive recording layer. When the thermosensitive recording layer contains at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran, it is preferable to wet-grind the 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran separately from the viewpoint of dispersion stability. If the volume average particle diameter of the dye precursor is larger than 1.5 μm, the print density may deteriorate. This is because, when a dye precursor with a large volume average particle diameter is used, the dye precursor is difficult to melt by heating, and the molten dye precursor is difficult to mix with the developer at the molecular level, suppressing the color-developing reaction.

[0019] Commercially available products can be used as the 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran, and an example of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide is Red-40, available from Yamamoto Chemical Industry Co., Ltd., and an example of 3-diethylamino-7-chlorofluoran is Red-8, also available from Yamamoto Chemical Industry Co., Ltd. The volume-average particle size in the present invention refers to the volume-average particle size calculated from a particle size distribution obtained by a laser diffraction / scattering method, and can be measured, for example, using the MICROTRAC® series manufactured by Microtrac-Bell, Inc., the LA series manufactured by Horiba, Ltd., the SALD® series manufactured by Shimadzu Corporation, or the LS series manufactured by Beckman Coulter, Inc.

[0020] In the present invention, when 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran are wet-milled, examples of dispersants that can be used in combination with the nonionic surfactants with an HLB value of 10 or more and the maleic acid copolymers with an esterification degree of 15% or more include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, and epoxy-modified polyvinyl alcohol are also listed. Examples of suitable surfactants include polyvinyl alcohols such as methyl alcohol, starch or derivatives thereof, cellulose derivatives, proteins such as gelatin and casein, acid-neutralized chitosan, sodium alginate, polyvinylpyrrolidone, water-soluble polymers such as ethylene / acrylic acid copolymer salts, styrene / acrylic acid copolymer salts, and polyacrylate salts, anionic low-molecular-weight surfactants such as dodecylbenzenesulfonates, dialkyl sulfosuccinates, alkylnaphthalenesulfonates, alkyldiphenyletherdisulfonates, and fatty acid metal salts, and nonionic surfactants with an HLB value of less than 10. However, these surfactants are not limited to these, and one or more surfactants may be used as needed. In the present invention, the total solids content of the maleic acid copolymer having an esterification degree of 15% or more, the nonionic surfactant with an HLB value of 10 or more, and other dispersants that can be used in combination is preferably in the range of 3 to 30% by mass relative to the total amount of dispersoids in the dispersion containing at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran.

[0021] In the present invention, when wet-milling at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran, the particle size of the media used can be appropriately selected depending on the desired particle size of the dispersoid to be obtained. However, to achieve a sharp particle size distribution and promote atomization, beads with a diameter in the range of 0.2 to 2.0 mm are preferred, and examples of materials include glass, zirconia, and alumina. The bead filling rate in the milling chamber is preferably 30 to 95% by volume. Furthermore, when milling 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran, the temperature of the dispersion is preferably 50°C or less. Processing at temperatures higher than 50°C may cause gelation.

[0022] In the present invention, when at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran is wet-milled, it is also possible to wet-mill it together with an inorganic dispersoid to reduce reddish background color. Examples of inorganic dispersoids include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, amorphous calcium silicate, calcium sulfate, calcium silicate, magnesium carbonate, magnesium silicate, magnesium phosphate, magnesium oxide, magnesium hydroxide, aluminum hydroxide, aluminum silicate, alumina, colloidal alumina, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, colloidal silica, barium sulfate, zinc sulfide, zinc carbonate, satin white, lithopone, zeolite, hydrotalcite, and hydrated halloysite. The proportion of inorganic dispersoids in the total dispersoids is preferably less than 20% by mass. This allows for the production of a thermal recording material with excellent stability. Furthermore, the dispersion liquid after grinding at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran may be heated to a temperature that does not impair the effects of the present invention, and a coating layer formed from an organic polymer may be provided on the surface of the ground particles.

[0023] The total content of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran contained in the thermal recording material of the present invention is preferably in the range of 1 to 30 mass % relative to the total solid content of the thermal recording layer, since this results in a thermal recording material with high print density and excellent manufacturing stability.

[0024] The heat-sensitive recording layer of the heat-sensitive recording material of the present invention can contain at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran as dye precursors, as well as an appropriate combination of dye precursors generally used in pressure-sensitive recording materials and heat-sensitive recording materials. Specific examples include, but are not limited to, those listed below.

[0025] Examples of black dye precursors include 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-di-n-pentylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7-(2-carbomethoxyphenylamino)fluoran, 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilinofluoran, and 3-(N-cyclopentyl-N-ethyl)amino-6-methyl-7 -anilinofluoran, 3-(N-isoamyl-N-ethyl)amino-6-methyl-7-anilinofluoran, 3-(N-ethyl-4-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-4-toluidino)-6-methyl-7-(4-toluidino)fluoran, 3-(N-methyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-(4-n-butylphenylamino)fluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-anilinofluoran,

[0026] Red dye precursors include 3,3-bis(1-n-butyl-2-methylindol-3-yl)tetrachlorophthalide, 3,3-bis(1-n-butylindol-3-yl)phthalide, 3,3-bis(1-n-pentyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-n-hexyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-n-octyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-methyl-2-methylindol-3-yl)phthalide, and 3,3-bis( 1-ethyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-propyl-2-methylindol-3-yl)phthalide, 3,3-bis(2-methylindol-3-yl)phthalide, rhodamine B-anilinolactam, rhodamine B-(o-chloroanilino)lactam, rhodamine B-(p-nitroanilino)lactam, 3-diethylamino-5-methyl-7-dibenzylaminofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-5-methyl-7-dibenzylaminofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-6-methylfluoran, 3-diethylamino-6-methyl-7-chloro-8-benzylfluoran, 3-diethylamino-6,7-dimethylfluoran, 3-diethylamino-6,8-dimethylfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-(N-acetyl-N-methyl)aminofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-n-propoxyfluoran, 3-diethylamino-7-p-methylphenylfluoran, 3-diethylamino No-7,8-benzofluoran, 3-diethylaminobenzo[a]fluoran, 3-diethylaminobenzo[c]fluoran, 3-dimethylamino-7-methoxyfluoran, 3-dimethylamino-6-methyl-7-chlorofluoran, 3-dimethylamino-7-methylfluoran, 3-dimethylamino-7-chlorofluoran, 3-(N-ethyl-p-toluidino)-7-methylfluoran, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-chlorofluoran, 3-(N-ethyl-N-isoamyl)amino-7,8-benzofluoran, 3-(N-ethyl-N-isoamyl)amino-7-methylfluoran, 3-(N-ethyl-Nn-octyl)amino-6-methyl-7-chlorofluoran, 3-(N-ethyl-Nn-octyl)amino-7,8-benzofluoran, 3-(N-ethyl-Nn-octyl)amino-7-methylfluoran, 3-(N-ethyl-Nn-octyl)amino-7-chlorofluoran, 3-(N-ethyl-N-4-methylphenyl)amino-7,8-benzofluoran, 3-(N-ethoxyethyl-N-ethyl)amino-7,8-benzofluoran, 3-(N-ethoxyethyl-N-ethyl)amino-7-chlorofluoran, 3-di-n-butylamino-6-methyl-7-chlorofluoran, 3-di-n-butylamino-7,8-benzofluoran, 3-di-n-butylamino-7-chlorofluoran, 3-di-n-butylamino-7-methylfluoran, 3-diallylamino-7,8-benzofluoran, 3-diallylamino-7-chlorofluoran, 3-di-n-butylamino-6-methyl-7-bromofluoran, 3-cyclohexylamino-6-chlorofluoran, 3-pyrrolidylamino-7-methylfluoran, 3-ethylamino-7-methylfluoran, 3-(N-ethyl-N-isoamyl)amino-benzo[a]fluoran, 3-di-n-butylamino-6-methyl-7-bromofluoran, 3,6-bis(diethylaminofluoran)-γ-(4′-nitro)anilinolactam,

[0027] Green dye precursors include 3-(N-ethyl-Nn-hexyl)amino-7-anilinofluoran, 3-(N-ethyl-Np-tolyl)amino-7-(N-phenyl-N-methyl)aminofluoran, 3-(N-ethyl-Nn-propyl)amino-7-dibenzylaminofluoran, 3-(N-ethyl-Nn-propyl)amino-6-chloro-7-dibenzylaminofluoran, 3-(N-ethyl-N-4-methylphenyl)amino-7-(N-methyl-N-phenyl)aminofluoran, and 3-(N-ethyl-4-methylphenyl)amino- 7-Dibenzylaminofluoran, 3-(N-ethyl-4-methylphenyl)amino-6-methyl-7-dibenzylaminofluoran, 3-(N-ethyl-4-methylphenyl)amino-6-methyl-7-(N-methyl-N-benzyl)aminofluoran, 3-(N-methyl-Nn-hexyl)amino-7-anilinofluoran, 3-(N-propyl-Nn-hexyl)amino-7-anilinofluoran, 3-(N-ethoxy-Nn-hexyl)amino-7-anilinofluoran, 3-(Nn-pentyl-N-allyl)amino-6-methyl-7 -anilinofluoran, 3-(Nn-pentyl-N-allyl)amino-7-anilinofluoran, 3-di-n-butylamino-6-chloro-7-(2-chloroanilino)fluoran, 3-di-n-butylamino-6-methyl-7-(2-chloroanilino)fluoran, 3-di-n-butylamino-6-methyl-7-(2-fluoroanilino)fluoran, 3-di-n-butylamino-7-(2-chloroanilino)fluoran, 3-di-n-butylamino-7-(2-chlorobenzylanilino)fluoran, 3,3-bis(4-diethylamino- 2-ethoxyphenyl)-4-azaphthalide, 3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide, 3-diethylamino-6-methyl-7-benzylaminofluoran, 3-diethylamino-6-methyl-7-dibenzylaminofluoran, 3-diethylamino-6-methyl-7-n-octylaminofluoran, 3-diethylamino-6-methyl-7-(N-cyclohexyl-N-benzyl)aminofluoran, 3-diethylamino-6-methyl-7-(2-chloroanilino)fluoran,3-Diethylamino-6-methyl-7-(2-trifluoromethylanilino)fluoran, 3-Diethylamino-6-methyl-7-(3-trifluoromethylanilino)fluoran, 3-Diethylamino-6-methyl-7-(2-ethoxyanilino)fluoran, 3-Diethylamino-6-methyl-7-(4-ethoxyanilino)fluoran, 3-Diethylamino-6-chloro-7-(2-chloroanilino)fluoran, 3-Diethylamino-6-chloro-7-dibenzylaminofluoran, 3-Diethylamino-6-chloro-7-anilinofluoran oran, 3-diethylamino-6-ethoxyethyl-7-anilinofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7-methylanilinofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-n-octylaminofluoran, 3-diethylamino-7-p-chloroanilinofluoran, 3-diethylamino-7-p-methylphenylanilinofluoran, 3-diethylamino-7-(N-cyclohexyl-N-benzyl)aminofluoran, 3-diethylamino-7-( 2-chloroanilino)fluoran, 3-diethylamino-7-(3-trifluoromethylanilino)fluoran, 3-diethylamino-7-(2-trifluoromethylanilino)fluoran, 3-diethylamino-7-(2-ethoxyanilino)fluoran, 3-diethylamino-7-(4-ethoxyanilino)fluoran, 3-diethylamino-7-(2-chlorobenzylanilino)fluoran, 3-dimethylamino-6-chloro-7-dibenzylaminofluoran, 3-dimethylamino-6-methyl-7-n-octylaminofluoran, 3- Dimethylamino-7-dibenzylaminofluoran, 3-dimethylamino-7-n-octylaminofluoran, 3-di-n-butylamino-7-(2-fluoroanilino)fluoran, 3-anilino-7-dibenzylaminofluoran, 3-anilino-6-methyl-7-dibenzylaminofluoran, 3-pyrrolidino-7-dibenzylaminofluoran, 3-pyrrolidino-7-(4-cyclohexylanilino)fluoran, 3-dibenzylamino-6-methyl-7-dibenzylaminofluoran, 3,7-bis(dibenzylamino)fluoran,3-dibenzylamino-7-(2-chloroanilino)fluoran,

[0028] Examples of blue dye precursors include 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)phthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-methyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-aminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-methylaminophenyl)-4-azaphthalide, and 3-(1-ethyl -2-methylindol-3-yl)-3-(2-ethoxy-4-ethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dimethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-propylaminophenyl)-4-azaphthalide, 3-(1-ethyl -2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-butylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-pentylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-hexylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dihydroxyaminophenyl)-4-azaphthalide amide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dichloroaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dibromoaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diallylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dihydroxyaminophenyl)-4-azaphthalide,3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dimethoxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethoxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-dicyclohexylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-propoxyaminophenyl)-4-azaphthalide 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-butoxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-hexyloxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-n-hexyloxyaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-methylcyclohexylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-di-methylcyclohexylaminophenyl)-4-azaphthalide 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-pyrrolidylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(3-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2,3-diethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)-4-azaphthalide 3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-chloro-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(3-chloro-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-bromo-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(3-bromo-4-diethylaminophenyl)-4-azaphthalide,3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-n-propyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(3-methyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-nitro-4-diethylaminophenyl)-4-azaphthalide, 3-( 1-ethyl-2-methylindol-3-yl)-3-(2-allyl-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-hydroxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyano-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyclohexylethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-methylethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-cyclohexylethyl-4-diethylaminophenyl)-4-azaphthalide, 3-(2-ethylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-chloroindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide , 3-(1-ethyl-2-bromoindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-ethylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-propylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methoxyindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide,3-(1-ethyl-2-ethoxyindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-phenylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4,7 -diazaphthalide, 3-(1-ethyl-4,5,6,7-tetrachloro-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-4-nitro-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-4-methoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-4-methylamino-2 3-(1-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-4-methyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-chloro-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-chloro-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, bromo-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-methyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-methyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-propyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide,3-(1-n-butyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-n-butyl-2-indol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-pentyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-n-hexyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-aza phthalide, 3-(1-n-hexyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-octyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-n-octyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-octyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide phenyl)-4,7-diazaphthalide, 3-(1-n-nonyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-methoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethoxy-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-phenyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide 3-(1-n-pentyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-heptyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3-(1-n-nonyl-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide, 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide,Examples include 3-(4-dimethylamino-2-methylphenyl)-3-(4-dimethylaminophenyl)-6-dimethylaminophthalide and 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylamino-2-n-hexyloxyphenyl)-4-azaphthalide. These can be used alone or in combination of two or more.

[0029] Among functional dye precursors, there are those that have absorption in the near-infrared region. When this dye precursor is used alone or in combination with other dye precursors as a dye precursor for high-temperature color development, the high-temperature color development image can be an image that has absorption in the near-infrared region and can be automatically read using near-infrared light. When this dye precursor is used in the present invention, it becomes possible to use an image that has absorption only in the visible region and an image that has absorption in the near-infrared region in combination, thereby obtaining a recording material with high security.

[0030] Examples of such dye precursors having absorption in the near infrared region include 3,3-bis[1-(4-methoxyphenyl)-1-(4-dimethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[1-(4-methoxyphenyl)-1-(4-pyrrolidino ... and 3,3-bis[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide. 3-[1,1-bis(p-diethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrabromophthalide, 3-[1,1-bis(p-diethylaminophenyl)ethylene-2-yl]-6-dimethylaminophthalide, 3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide, 3-[p-(p-dimethylaminoanilino)anilino]-6-methylfluoran, 3-[p-(p-dimethylaminoanilino)anilino]-6-methylfluoran 3-[p-(p-anilinoanilino)anilino]-6-methyl-7-chlorofluoran, 3-(p-n-butylaminoanilino)-6-methyl-7-chlorofluoran, 3-[p-(p-anilinoanilino)anilino]-6-methyl-7-chlorofluoran, 3-[p-(p-chloroanilino)anilino]-6-methyl-7-chlorofluoran, 3-[p-(p-chloroanilino)anilino]-6-methyl-7-chlorofluoran, 3-(Np-tolyl-N-ethylamino)-6,8,8-trimethyl-9-ethyl-8,9-di Examples of dye precursors include hydro-(3,2,e)pyridofluoran, 3-di(n-butyl)amino-6,8,8-trimethyl-8,9-dihydro-(3,2,e)pyridofluoran, 3'-phenyl-7-N-diethylamino-2,2'-spirodi(2H-1-benzopyran), bis(p-dimethylaminostyryl)-p-trisulfonylmethane, and 3,7-bis(dimethylamino)-10-benzoylphenothiazine. These dye precursors can be used alone or in combination as needed. These dye precursors can also be wet dispersed with 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran.

[0031] The total content of the dye precursors contained in the thermosensitive recording material of the present invention is preferably 1 to 30% by mass based on the total solid content of the thermosensitive recording layer, which allows for sufficient thermal response.

[0032] As the color developer contained in the heat-sensitive recording layer of the heat-sensitive recording material of the present invention, various known color developers can be used, for example, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-propoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, 4-hydroxy-4'-octyloxydiphenyl sulfone, 4-hydroxy-4'-dodecyloxydiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, 2,2'-diallyl-4,4'-sulfonyldiphenyl sulfone, , 3,4-dihydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-benzenesulfonyloxydiphenyl sulfone, 2,4-bis(phenylsulfonyl)phenol, p-phenylphenol, p-hydroxyacetophenone, 1,1-bis(p-hydroxyphenyl)propane, 1,1-bis(p-hydroxyphenyl)pentane, 1,1-bis(p-hydroxyphenyl)hexane, 1,1-bis(p-hydroxyphenyl)cyclohexane, 2,2-bis(p-hydroxyphenyl)propane, 2, 2-bis(p-hydroxyphenyl)hexane, 1,1-bis(p-hydroxyphenyl)-2-ethylhexane, 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 1,1-bis(p-hydroxyphenyl)-1-phenylethane, 1,3-bis[2-(p-hydroxyphenyl)-2-propyl]benzene, 1,3-bis[2-(3,4-dihydroxyphenyl)-2-propyl]benzene, 1,4-bis[2-(p-hydroxyphenyl)-2-propyl]benzene, 4,4′-dihydroxydiphenyl Ether, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfide, methyl 2,2-bis(4-hydroxyphenyl)acetate, butyl 2,2-bis(4-hydroxyphenyl)acetate, 4,4'-thiobis(2-tert-butyl-5-methylphenol), dimethyl 4-hydroxyphthalate, benzyl 4-hydroxybenzoate, methyl 4-hydroxybenzoate, benzyl gallate, stearyl gallate, salicylanilide, 5-chlorosalicylanilide, salicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-Bis(α-methylbenzyl)salicylic acid, 4-[2'-(4-methoxyphenoxy)ethyloxy]salicylic acid, 3-(octyloxycarbonylamino)salicylic acid or metal salts of these salicylic acid derivatives, N-(4-hydroxyphenyl)-p-toluenesulfonamide, N-(4-hydroxyphenyl)benzenesulfonamide, N-(4-hydroxyphenyl)-1-naphthalenesulfonamide, N-(4-hydroxyphenyl)-2-naphthalenesulfonamide, N-(4-hydroxynaphthyl) -p-toluenesulfonamide, N-(4-hydroxynaphthyl)benzenesulfonamide, N-(4-hydroxynaphthyl)-1-naphthalenesulfonamide, N-(4-hydroxynaphthyl)-2-naphthalenesulfonamide, N-(3-hydroxyphenyl)-p-toluenesulfonamide, N-(3-hydroxyphenyl)benzenesulfonamide, N-(3-hydroxyphenyl)-1-naphthalenesulfonamide, N-(3-hydroxyphenyl)-2-naphthalenesulfonamide, 4,4′-bis[( 4-Methyl-3-phenoxycarbonylaminophenyl)ureido]diphenyl sulfone, 3-(3-tosylureido)phenyl p-toluenesulfonate, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, N-(2-{[(4-methylphenyl)carbamoyl]amino}phenyl)benzenesulfonamide, 4-methyl-N-{2-[(phenylcarbamoyl)amino]phenyl}benzenesulfonamide, 4-methyl-N-(2-{[(4-methylphenyl)carbamoyl]amino} Examples of the diphenyl benzenesulfonamide include N-butylbutyl-4-[3-(p-toluenesulfonyl)ureido]benzoate, 3,3'-(4,4'methylenediphenyl)bis(ureido p-trisulfone), bis{3-[3'-(p-toluenesulfonyl)ureido]benzoate}, 1,5-(3-oxopentylene)bis{3'-[3'-(p-toluenesulfonyl)ureido]benzoate}, and derivatives of N-phenylsulfonyl-N'-phenylurea, but are not limited to these. These can be used alone or in combination of two or more.

[0033] The content ratio of the dye precursors and the color developer is determined appropriately depending on the types and combinations thereof, but it is preferable that the total amount of the color developer is 100 to 500% by mass, more preferably 150 to 350% by mass, relative to the total amount of the dye precursors.

[0034] In the present invention, the thermosensitive recording layer may contain a low-melting thermosoluble component (hereinafter referred to as a sensitizer) that accelerates the color-developing reaction in order to further improve its thermal responsiveness. In this case, the sensitizer is preferably a compound having a melting point of 60 to 180°C. Specific examples of sensitizers include fatty acid monoamides such as palmitic acid monoamide and stearic acid monoamide, diphenyl sulfone, N-hydroxymethylstearic acid amide, N-stearylstearic acid amide, ethylene bisstearic acid amide, methylene bisstearic acid amide, methylolstearic acid amide, N-stearyl urea, benzyl-2-naphthyl ether, p-toluenesulfonamide, m-terphenyl, 4-benzylbiphenyl, 2,2'-bis(4-methoxyphenoxy)diethyl ether, α,α'-diphenoxy Examples of sensitizers include, but are not limited to, o-xylene, bis(4-methoxyphenyl)ether, diphenyl adipate, dibenzyl oxalate, bis(4-methylbenzyl)oxalate, bis(4-chlorobenzyl)oxalate, dimethyl terephthalate, dibenzyl terephthalate, phenyl benzenesulfonate, bis(4-allyloxyphenyl)sulfone, 1,2-bis(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 4-acetylacetophenone, acetoacetic anilides, and fatty acid anilides. These sensitizers can be used alone or in combination of two or more. To achieve sufficient thermal response, the total amount of sensitizers preferably accounts for 5 to 50% by mass of the total solid content of the thermal recording layer.

[0035] Furthermore, the heat-sensitive recording layer may further contain a storage stability improver such as a hindered phenol compound, a hindered amine compound, a phosphoric acid ester derivative, or a benzotriazole derivative, if necessary.

[0036] Specific examples of the hindered phenol compound that can be used as needed in the heat-sensitive recording layer of the present invention include 1,1,2,2-tetrakis(5-cyclohexyl-4-hydroxy-2-methylphenyl)ethane, 1,1,2,2-tetrakis(3-phenyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-tert-butyl-4-hydroxyphenyl)ethane, 1,1,3-tris(3-cyclohexyl-4-hydroxyphenyl)butane, 1,1,3-tris(5-cyclohexyl-4-hydroxy-o-tolyl)butane, 1,1,3-tris(5-cyclohexyl-4-hydroxy-o-tolyl)butane, 1,1,2,2-tetrakis(3-tert-butyl-4-hydroxyphenyl)ethane ... ,1,3-Tris(3-cyclohexyl-4-hydroxy-5-methylphenyl)butane, 1,1,3-tris(3-phenyl-4-hydroxyphenyl)butane, 1,1,3-tris(5-phenyl-4-hydroxy-2-methylphenyl)butane, 1,1,3-tris(3-tert-butyl-4-hydroxyphenyl)butane, 1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, 1,1,3,3-tetrakis(5-cyclohexyl-4-hydroxy-2-methylphenyl)propane, 1,1,3,3- Tetrakis(3-cyclohexyl-4-hydroxyphenyl)propane, 1,1,5,5-tetrakis(5-cyclohexyl-4-hydroxy-2-methylphenyl)pentane, 1,1,3,3-tetrakis(3-cyclohexyl-4-hydroxyphenyl)pentane, 1,1,3,3-tetrakis(3-phenyl-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(5-phenyl-4-hydroxy-2-methylphenyl)propane, 1,1,3,3-tetrakis(3-tert-butyl-4-hydroxyphenyl)propane, 1,1 ,3,3-tetrakis(5-tert-butyl-4-hydroxy-2-methylphenyl)propane, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis(4,6-di-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), 4,4'-thiobis(2-methylphenol), 4,4'-thiobis(2,Examples of the hydroxybenzoates include, but are not limited to, 4,4'-thiobis(2,6-di-tert-butylphenol), 4,4'-thiobis(2,6-di-tert-butylphenol), 2,2'-thiobis(4-tert-octylphenol), 2,2'-thiobis(3-tert-octylphenol), 4,4'-butylidenebis(6-tert-butyl-m-cresol), 1-[α-methyl-α-(4'-hydroxyphenyl)ethyl]4-[α',α'-bis(4'-hydroxyphenyl)ethyl]benzene, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, and 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane. These compounds can be used singly or in combination as needed.

[0037] Specific examples of hindered amine compounds that may be used as needed in the thermosensitive recording layer of the present invention include, but are not limited to, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, succinic acid bis(2,2,6,6-tetramethyl-4-piperidyl)ester, butane-1,2,3,4-tetracarboxylic acid tetrakis[1,2,2,6,6-pentamethyl(4-piperidyl)]ester, and butane-1,2,3,4-tetracarboxylic acid tetrakis[2,2,6,6-tetramethyl(4-piperidyl)]ester, and the like. These compounds may be used singly or in combination of two or more as needed.

[0038] Specific examples of the phosphoric acid ester derivatives used as needed in the thermosensitive recording layer of the present invention include triphenyl phosphate, diphenyl phosphate, bis(4-tert-butylphenyl)phosphate, bis(4,6-di-tert-butylphenyl)phosphate, bis(4-chlorophenyl)phosphate, bis(benzyloxyphenyl)phosphate, 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, dimethyloxyphosphate, diethyloxyphosphate, bis(3,5-di-tert-butyl-4-hydroxyphenyl)phosphate, 3,5-di-tert-butyldiphenyl phosphate, Examples of suitable phosphate compounds include, but are not limited to, diethyl(3,5-di-tert-butyl-4-hydroxyphenyl)phosphate, sodium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, calcium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, zinc salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, ammonium salt and potassium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, and these compounds can be used singly or in combination as needed.

[0039] Specific examples of the benzotriazole derivatives used as needed in the heat-sensitive recording layer of the present invention include 2-(2-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5- Di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-tert-aminophenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-tert-butylbenzotriazole, 2-(2-hydroxy-3-dodecyl-5-methylphenyl)benzotriazole, 2-[2-hydroxy-4-(2-ethylhexyl)oxyphenyl]benzotriazole, methyl-3-(3-tert-butyl-5-benzotriazolyl-4-hydroxyphenyl) Condensate of propionate with polyethylene glycol (molecular weight about 300), 5-tert-butyl-3-(5-chloro-benzotriazolyl)-4-hydroxybenzene-octyl propionate, 2-(2-hydroxy-3-sec-butyl-5-tert-butylphenyl)-5-tert-butylbenzotriazole, 2-(2-hydroxy-4-methoxy-5-sulfophenyl)benzotriazole sodium salt, 2-(2-hydroxy-4-butoxy-5-sulfophenyl)benzotriazole sodium salt, 2,2′-methylenebis (4-methyl-6-benzotriazolylphenol), 2,2′-methylenebis[4-methyl-6-(5-methylbenzotriazolyl)phenol], 2,2′-methylenebis[4-methyl-6-(5-chlorobenzotriazolyl)phenol], 2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-benzotriazolylphenol], 2,2′-methylenebis(4-tert-butyl-6-benzotriazolylphenol), 2,2′-propylidenebis(4-methyl-6-benzotriazolylphenol), 2,Examples of suitable phenols include 2'-isopropylidenebis(4-methyl-6-benzotriazolylphenol), 2,2'-isopropylidenebis[4-(1,1,3,3-tetramethylbutyl)-6-benzotriazolylphenol], and 2,2'-octylidenebis[4-methyl-6-(5-methylbenzotriazolyl)phenol], but are not limited to these. These compounds can be used singly or in combination as needed.

[0040] The total amount of the hindered phenol compound, hindered amine compound, phosphate derivative, or benzotriazole derivative optionally added to the heat-sensitive recording layer of the present invention is preferably 5 to 500% by mass based on the dye precursor.

[0041] In the present invention, the thermosensitive recording layer can contain various pigments depending on the purpose, such as improving sticking resistance and whiteness. Examples of pigments include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, amorphous calcium silicate, calcium sulfate, calcium silicate, magnesium carbonate, magnesium silicate, magnesium phosphate, magnesium oxide, magnesium hydroxide, aluminum hydroxide, aluminum silicate, alumina, colloidal alumina, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, colloidal silica, barium sulfate, zinc sulfide, zinc carbonate, satin white, lithopone, zeolite, hydrotalcite, and hydrated halloysite. These pigments include known white inorganic pigments, organic pigments, and hollow particles. However, the pigments are not limited to these. One or more pigments can be used as needed. The pigment content is preferably 5 to 50% by mass of the total solids content of the thermosensitive recording layer.

[0042] In the present invention, the thermosensitive recording layer may contain, as a binder, various water-soluble or water-dispersible polymer compounds that are used in ordinary coating. Specific examples include starch or derivatives thereof, cellulose derivatives such as hydroxymethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, and carboxymethyl cellulose, proteins such as gelatin and casein, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, modified polyvinyl alcohol, sodium alginate, polyvinylpyrrolidone, polyacrylamide, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, polyacrylate, polymaleate, styrene / maleic acid copolymer salt, ethylene / maleic acid copolymer salt, and isobutylene / maleic acid copolymer salt, as well as water-soluble polymer compounds such as styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, acrylonitrile / butadiene / styrene terpolymer, polyvinyl acetate, vinyl acetate / acrylic acid ester copolymer, ethylene / vinyl acetate copolymer, polyacrylate, styrene / acrylic acid ester copolymer, and polyurethane, but are not limited to these. One or more types may be used as needed. The binder is preferably used in an amount of 5 to 30% by mass based on the total solid content of the thermosensitive recording layer.

[0043] In order to improve sticking resistance, the heat-sensitive recording layer may contain higher fatty acid metal salts such as zinc stearate and calcium stearate, and waxes such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, castor wax, etc. Furthermore, in order to impart water resistance, the heat-sensitive recording layer may contain various hardeners, crosslinking agents, dispersants, surfactants, fluorescent dyes, coloring dyes, antifoaming agents, preservatives, thickeners, antistatic agents, etc.

[0044] In the present invention, various components other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran contained in the thermosensitive recording layer of the thermosensitive recording material, such as dye precursors other than 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran, color developers, sensitizers, shelf-life improvers, pigments, lubricants, waxes, etc., are preferably prepared as a dispersion and then used to prepare a thermosensitive recording layer coating solution. The dispersion can be obtained by dry-milling the various components other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran and dispersing them in a dispersion medium, or by mixing the various components in a dispersion medium and wet-milling them. In the present invention, the color developer, sensitizer, etc., either alone or together with a dispersant, are preferably ground using water as a dispersion medium in a variety of wet grinders such as a sand grinder, ball mill, attritor, or bead mill to a volume average particle size of preferably 0.1 to 5.0 μm to form fine particles, which are then used in the preparation of a thermosensitive recording layer coating solution. Furthermore, dye precursors other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran are preferably ground using water as a dispersion medium in a variety of wet grinders such as a sand grinder, ball mill, attritor, or bead mill to a volume average particle size of preferably 0.1 to 1.5 μm, separately from the color developer, to form fine particles, which are then used in the preparation of a thermosensitive recording layer coating solution.

[0045] In the present invention, examples of dispersants used when dispersing various components other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran contained in the thermal recording layer include polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, and epoxy-modified polyvinyl alcohol; starch or derivatives thereof; hydroxyethyl cellulose; methyl cellulose; hydroxypropyl cellulose; ethyl cellulose; Examples of dispersants include, but are not limited to, water-soluble polymers such as cellulose, carboxymethylcellulose, gelatin, casein, and other proteins, neutralized chitosan, sodium alginate, polyvinylpyrrolidone, diisobutylene / maleic acid copolymer salt, styrene / isobutylene / maleic acid copolymer salt, styrene / maleic acid copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, and polyacrylate salts, anionic low-molecular surfactants such as dodecylbenzenesulfonate, dialkyl sulfosuccinate, alkylnaphthalenesulfonate, alkyldiphenyletherdisulfonate, and fatty acid metal salts, and nonionic surfactants such as acetylene glycol. The total amount of dispersants is preferably 0.5 to 30% by mass based on the total amount of dispersoids contained in the dispersion.

[0046] When grinding the various components other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran contained in the heat-sensitive recording layer, they may be ground together with inorganic pigments such as magnesium silicate, calcium silicate, magnesium carbonate, calcium carbonate, calcium sulfate, magnesium phosphate, magnesium oxide, aluminum oxide, titanium oxide, magnesium hydroxide, aluminum hydroxide, kaolin, talc, hydrotalcite, etc. Furthermore, the dispersion obtained after grinding the various components other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran may be heated in the range of 40 to 80°C, and a coating layer formed of an organic polymer may be provided on the surfaces of the ground particles.

[0047] In the present invention, the solid coating amount of the thermosensitive recording layer is 2 to 15 g / m 2 2g / m 2 If it is less than 15 g / m, the print density in the low heat energy area may be low. 2 If the content is greater than this, the improvement in various properties of the thermosensitive recording layer may reach saturation, and the production efficiency during coating of the thermosensitive recording layer may decrease.

[0048] In the present invention, an undercoat layer may be provided between the support and the thermosensitive recording layer for the purpose of improving the smoothness and heat insulation of the support or for the purpose of preventing various components contained in the support from adversely affecting the thermosensitive recording layer. The undercoat layer contains a binder and various inorganic or organic pigments, and may also contain hollow particles. Other auxiliary agents that may be contained in the undercoat layer include known agents such as lubricants, antifoaming agents, surfactants, preservatives, fluorescent brighteners, dispersants, thickeners, colorants, antistatic agents, and crosslinking agents.

[0049] In the present invention, when an undercoat layer is used, the coating liquid for the undercoat layer is prepared by mixing and stirring a pigment, a binder and an auxiliary agent in a medium such as water, and the solid coating amount is preferably 1 to 30 g / m. 2, more preferably 4 to 20 g / m 2 The coating is applied to the support and dried to form the coating.

[0050] Examples of pigments that can be contained in the undercoat layer of the present invention include inorganic pigments such as talc, kaolin, calcined kaolin, clay, calcined clay, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, magnesium silicate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, calcium silicate, diatomaceous earth, and colloidal silica; melamine resin, urea-formaldehyde resin, polyethylene, polystyrene, ethylene-vinyl acetate, styrene microballs, nylon powder, polyethylene powder, urea-formalin resin filler, styrene-methacrylic acid copolymer resin, polystyrene resin, and raw starch particles. These can be used alone or in combination of two or more types, but are not limited to these. One or more types can be used as needed.

[0051] The undercoat layer may contain various water-soluble or water-dispersible polymeric compounds as binders, which are commonly used in coating. Specific examples include, but are not limited to, water-soluble polymeric compounds such as starch or its derivatives, hydroxymethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, gelatin, casein, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, modified polyvinyl alcohol, sodium alginate, polyvinylpyrrolidone, polyacrylamide, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, polyacrylate, polymaleate, styrene / maleic acid copolymer salt, ethylene / maleic acid copolymer salt, and isobutylene / maleic acid copolymer salt, and water-dispersible polymeric compounds such as styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, acrylonitrile / butadiene / styrene terpolymer, polyvinyl acetate, vinyl acetate / acrylic acid ester copolymer, ethylene / vinyl acetate copolymer, polyacrylate, styrene / acrylic acid ester copolymer, and polyurethane. One or more binders can be used. The amount of binder used is preferably 10 to 30% by mass based on the total solid content of the undercoat layer.

[0052] In the present invention, when various components that can be contained in the undercoat layer are mixed and stirred in water as a medium, a dispersant can be used to improve dispersibility. Examples of dispersants that can be used include polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and modified polyvinyl alcohol; starch or derivatives thereof; cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose, and carboxymethyl cellulose; proteins such as gelatin and casein; acid-neutralized chitosan; sodium alginate; polyvinylpyrrolidone; water-soluble polymer compounds such as diisobutylene / maleic acid copolymer salt, styrene / isobutylene / maleic acid copolymer salt, styrene / maleic acid copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, and polyacrylate salt; anionic low-molecular surfactants such as dodecylbenzenesulfonate, dialkyl sulfosuccinate, alkylnaphthalenesulfonate, alkyldiphenyletherdisulfonate, and fatty acid metal salt; nonionic surfactants such as acetylene glycol; and sodium hexametaphosphate. Examples of dispersants that can be used include, but are not limited to, polyvinyl alcohols, and one or more of these may be used as needed. The total amount of the dispersant is preferably 0.1 to 30% by mass relative to the total amount of dispersoids contained in the dispersion.

[0053] In the present invention, the support of the thermal recording material may be transparent, translucent, or opaque, and any of paper, various nonwoven fabrics, woven fabrics, synthetic resin films, synthetic resin-laminated paper, synthetic paper, metal foil, ceramic paper, glass plates, and the like, or composite sheets combining these, can be used depending on the purpose.

[0054] In the present invention, when a paper support is used as the support, examples of the pulp contained in the paper support include various pulps such as softwood bleached kraft pulp (NBKP), hardwood bleached sulfite pulp (LBKP), softwood bleached sulfite pulp (NBSP), hardwood bleached sulfite pulp (LBSP), TMP, CTMP, BCTMP, GP, RGP, CGP, and cotton pulp, various recycled paper pulps such as DIP, and non-wood fibers such as kenaf, but are not limited to these. Furthermore, one or more types can be used as needed.

[0055] In the present invention, when a paper support is used as the support, the filler contained in the paper support can be appropriately selected from known fillers and used. Examples of such fillers include, but are not limited to, inorganic fillers such as calcium carbonate, talc, kaolin, calcined kaolin, amorphous silica, illite, clay, calcined clay, and titanium dioxide, and organic fillers such as plastic pigments. One or more types of fillers can be used as needed.

[0056] In the present invention, when a paper support is used as the support, the ash content of the paper support is preferably 0.1 to 25% by mass. If it is less than 0.1% by mass, it is difficult to obtain good formation and smoothness. If it exceeds 25% by mass, smoothness saturates, while the sizing ability and surface strength of the base paper decrease, making it more likely that the paper will break when the undercoat layer or thermosensitive recording layer is coated. In addition, the basis weight of the paper support is 20 to 300 g / m 2 The degree is preferable.

[0057] In the present invention, when a paper support is used as the support, the paper support may contain, as an internal sizing agent (internal sizing agent), for example, a reinforced rosin sizing agent, an emulsion sizing agent, or a synthetic sizing agent in the case of acidic papermaking, or an alkyl ketene dimer, alkenyl succinic anhydride, higher fatty acid, or neutral rosin sizing agent in the case of neutral papermaking, but the internal sizing agent is not limited to these, and one or more types may be used as needed. Furthermore, as an external sizing agent (external sizing agent), examples include, but are not limited to, styrene-maleic acid copolymers, styrene-acrylic acid copolymers, styrene polymers, isocyanate polymers, rosin, alkyd resin saponification products such as tall oil and phthalic acid, polymers such as saponification products of petroleum resin and rosin, α-olefin-maleic acid copolymers, acrylic ester-acrylic acid copolymers, and alkyl ketene dimers, and the external sizing agent may be, but is not limited to these, and one or more types may be used as needed. Furthermore, in addition to the above-mentioned sizing agents, pulp, and various fillers, various internal papermaking aids, such as nonionic, cationic, anionic, or amphoteric retention aids, drainage aids, and paper strength enhancers, may be added to the paper support as needed. Specific examples of retention aids, drainage aids, and paper strength enhancers include polyvalent metal compounds such as aluminum (specifically, aluminum sulfate, aluminum chloride, sodium aluminate, basic aluminum compounds, etc.), amorphous silica, various starches, urea resins, polyamide / polyamine resins, polyethyleneimine, polyacrylamide, polyamine, polyvinyl alcohol, and polyethylene oxide.

[0058] In the present invention, a protective layer can be provided on the thermosensitive recording layer for the purposes of improving sticking resistance, preventing scratches, improving water resistance, printability, stamping ability, inkjet suitability, and improving the plasticizer resistance and chemical resistance of the thermosensitive color-developed image. The protective layer can contain various adhesives, inorganic pigments, various curing agents, various crosslinking agents, ultraviolet absorbers, etc., and can be a single layer or two or more layers laminated. In addition, printing with UV ink or the like can be performed on the surface of the thermosensitive recording layer or protective layer.

[0059] In the present invention, the solid coating amount of the protective layer is 0.5 to 5 g / m 2 0.5g / m 2 If it is less than 5g / m, the protective layer will not exhibit its various functions. 2 If the amount is larger than this, the loss of thermal energy reaching the thermal recording layer from the thermal head increases, which may result in a decrease in color development.

[0060] In the present invention, the surface of the support opposite to the surface having the thermosensitive recording layer may have a backcoat layer for purposes such as preventing curling and static electricity, and may further be subjected to adhesive processing, etc. Furthermore, the surface of the support having the thermosensitive recording layer or the surface opposite to the surface may have a layer containing a material capable of recording information electrically, magnetically, or optically, an inkjet recording layer, etc. Furthermore, in order to perform printing with laser light, a photothermal conversion material may be incorporated into any layer in the thermosensitive recording material and into the support.

[0061] The method for forming each layer in the present invention is not particularly limited and can be formed using well-known techniques, such as coating devices such as air knife coaters, various blade coaters, various bar coaters, and various curtain coaters, and various printing methods such as planographic, relief, intaglio, flexographic, gravure, and screen printing. Furthermore, in order to improve surface smoothness, various well-known techniques for producing thermal recording materials can be used, such as using devices such as machine calenders, super calenders, gloss calenders, and brushing. [Example]

[0062] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified, all percentages and parts are by mass. The coating amount is the solid coating amount.

[0063] Example 1 (1) Preparation of dye precursor dispersion A The following ingredients were mixed and wet-milled in a DYNO (registered trademark)-MILL MULTI-LAB (Willi & Bachofen) under conditions of a bead filling rate of 80 volume % (glass beads with a diameter of 0.6 mm) in the milling chamber and a dispersion temperature of 20°C until the volume average particle size of the dispersed substance reached 0.8 μm, thereby obtaining a dye precursor dispersion A. 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Chemical Co., Ltd., Red-40) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex (registered trademark) L-3266 dissolved in water) 10% styrene-maleic acid copolymer ammonium salt aqueous solution (butyl esterified, esterification degree 70%) 5 parts (Arakawa Chemical Industries, Ltd., Polymaron 1318 diluted with water) Polyoxyethylene polyoxypropylene alkyl ether 2 parts (Kao Corporation nonionic surfactant, Emulgen MS-110, HLB value 12.7) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol (registered trademark) 104E) Water 170 parts

[0064] (2) Preparation of developer dispersion The following formulation was mixed and wet-milled in a DYNO-MILL MULTI-LAB (Willi & Bachofen) under conditions of a bead filling rate in the milling chamber of 80 volume % (using glass beads with a diameter of 0.6 mm) and a dispersion temperature of 20°C until the volume average particle size of the dispersed substance reached 0.8 μm, thereby obtaining a color developer dispersion. 2,2'-diallyl-4,4'-sulfonyldiphenol 200 parts 2-(2'-hydroxy-5'-methylphenyl)benzotriazole 200 parts 1,1,3-Tris(5-cyclohexyl-4-hydroxy-o-tolyl)butane 40 copies 440 parts of 10% aqueous solution of sulfonic acid-modified polyvinyl alcohol (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) Acetylenic dialcohol composition 2 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Water 738 parts

[0065] (3) Preparation of pigment dispersion The following ingredients were mixed and stirred to obtain a pigment dispersion. Light calcium carbonate 150 parts (Tama Pearl (registered trademark) TP-123, manufactured by Okutama Kogyo Co., Ltd.) 15 parts of 10% aqueous solution of ammonium polyacrylate (Microsol KE-511, manufactured by Goo Chemical Industry Co., Ltd., diluted with water) Water 340 parts

[0066] (4) Preparation of the thermosensitive recording layer coating solution The following ingredients were mixed and thoroughly stirred to obtain a coating liquid for a thermosensitive recording layer. Dye precursor dispersion A 377.5 parts Developer dispersion 1620 parts Pigment dispersion 505 parts 10% fully saponified polyvinyl alcohol aqueous solution 1300 parts (Japan Vinyl Acetate & Poval Co., Ltd., VC-13 dissolved in water) 40% zinc stearate aqueous dispersion 175 parts (Hydrin L-536, manufactured by Chukyo Yushi Co., Ltd.) Water 775 parts

[0067] (5) Formation of the thermosensitive recording layer The thermosensitive recording layer coating solution prepared in (4) above was applied to a film having a basis weight of 200 g / m 2 , based on JIS P8150, a color a* value of 1.6 on fine paper (ash content 0.3%), with a solid coating weight of 5 g / m 2The mixture was coated with an air knife coater so that the moisture content was 6.5%, and then dried to a moisture content of 6.5%. The resultant was then subjected to a calendering treatment using a supercalender to prepare a thermal recording material. The Beck smoothness of the thermal recording layer surface after the calendering treatment was 250 seconds (measured using an HL Beck smoothness tester manufactured by Kumagai Riki Kogyo Co., Ltd.).

[0068] Example 2 A thermosensitive recording material of Example 2 was prepared in the same manner as in Example 1, except that in the preparation of (1) dye precursor dispersion A of Example 1, the formulation was changed as follows: The Beck smoothness of the thermosensitive recording layer surface after calendering was 250 seconds. 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Chemical Co., Ltd., Red-40) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) 10% styrene-maleic acid copolymer ammonium salt aqueous solution 5 parts (Arakawa Chemical Industries, Ltd., Polymaron 1318 diluted with water) Polyoxyethylene sorbitan monolaurate 2 parts (Kao Corporation nonionic surfactant, Rheodol TW-L120, HLB value 16.7) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Water 170 parts

[0069] Example 3 A thermosensitive recording material of Example 3 was prepared in the same manner as in Example 1, except that in the preparation of (1) dye precursor dispersion A of Example 1, the formulation was changed as follows: The Beck smoothness of the thermosensitive recording layer surface after calendaring was 250 seconds. 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Chemical Co., Ltd., Red-40) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) 10% styrene-maleic acid copolymer ammonium salt aqueous solution 5 parts (Arakawa Chemical Industries, Ltd., Polymaron 1318 diluted with water) Polyoxyethylene polyoxypropylene alkyl ether 0.3 parts (Kao Corporation nonionic surfactant, Emulgen MS-110, HLB value 12.7) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Wednesday 171.7 parts

[0070] Example 4 A thermosensitive recording material of Example 4 was prepared in the same manner as in Example 1, except that in the preparation of (1) dye precursor dispersion A of Example 1, the formulation was changed as follows: The Beck smoothness of the thermosensitive recording layer surface after calendaring was 250 seconds. 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Chemical Co., Ltd., Red-40) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) 10% styrene-maleic acid copolymer ammonium salt aqueous solution 5 parts (Arakawa Chemical Industries, Ltd., Polymaron 1318 diluted with water) Polyoxyethylene polyoxypropylene alkyl ether 3 parts (Kao Corporation nonionic surfactant, Emulgen MS-110, HLB value 12.7) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Wednesday 169 parts

[0071] Example 5 (6) Synthesis of styrene-maleic acid copolymer A salt A four-neck flask equipped with a stirrer, thermometer, and reflux condenser was charged with 45 parts of styrene, 43 parts of maleic anhydride, 300 parts of toluene, and 1 part of Nyper® BW (manufactured by Nippon Oil & Fats Co., Ltd.), and the mixture was heated in an oil bath under reflux and reacted for 6 hours. 16 parts of butanol and 0.5 parts of hydroquinone were then added to the reaction mixture, and the mixture was heated in an oil bath under reflux and reacted for 12 hours. The esterified solution was then cooled and poured into 1500 ml of n-hexane to precipitate a resin, which was then filtered and dried. 350 parts of water and 20 parts of a 25% aqueous ammonia solution were added to the dried resin, and the mixture was hydrolyzed at 60°C for 5 hours. Water was then added to adjust the solids concentration to 10%. The resulting styrene-maleic acid copolymer A salt had a degree of esterification of 30% and a weight-average molecular weight of 50,000.

[0072] A thermosensitive recording material of Example 5 was prepared in the same manner as in Example 1, except that in the preparation of (1) dye precursor dispersion A of Example 1, the formulation was changed as follows: The Beck smoothness of the thermosensitive recording layer surface after calendaring was 250 seconds. 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Chemical Co., Ltd., Red-40) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) 10% styrene-maleic acid copolymer A salt aqueous solution (butyl esterified, degree of esterification 30%) 5 parts Polyoxyethylene polyoxypropylene alkyl ether 2 parts (Kao Corporation nonionic surfactant, Emulgen MS-110, HLB value 12.7) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Water 170 parts

[0073] Example 6 (7) Preparation of dye precursor dispersion B The following ingredients were mixed and wet-milled in a DYNO-MILL MULTI-LAB (Willi & Bachofen) under conditions of a bead filling rate of 80 volume % (using glass beads with a diameter of 0.6 mm) in the milling chamber and a dispersion temperature of 20°C until the volume average particle size of the dispersed substance reached 0.8 μm, thereby obtaining dye precursor dispersion B. 3-Diethylamino-7-chlorofluoran 100 parts (Yamamoto Chemical Co., Ltd., Red-8) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) 10% styrene-maleic acid copolymer ammonium salt aqueous solution (butyl esterified, esterification degree 70%) 5 parts (Arakawa Chemical Industries, Ltd., Polymaron 1318 diluted with water) Polyoxyethylene polyoxypropylene alkyl ether 2 parts (Kao Corporation nonionic surfactant, Emulgen MS-110, HLB value 12.7) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Water 170 parts

[0074] A thermosensitive recording material of Example 6 was prepared in the same manner as in Example 1 (4) Preparation of thermosensitive recording layer coating liquid, except that dye precursor dispersion A was changed to dye precursor dispersion B. The Beck smoothness of the thermosensitive recording layer surface after calendaring was 250 seconds.

[0075] Example 7 A thermosensitive recording material of Example 7 was prepared in the same manner as in Example 1, except that in (4) Preparation of thermosensitive recording layer coating liquid of Example 1, the formulation was changed as follows: The Beck smoothness of the thermosensitive recording layer surface after calendaring was 250 seconds. (4) Preparation of the thermosensitive recording layer coating solution The following ingredients were mixed and thoroughly stirred to obtain a coating liquid for a thermosensitive recording layer. Dye precursor dispersion A 19 parts Dye precursor dispersion B 358.5 parts Developer dispersion liquid 1620 parts Pigment dispersion 505 parts 10% fully saponified polyvinyl alcohol aqueous solution 1300 parts (Japan Vinyl Acetate & Poval Co., Ltd., VC-13 dissolved in water) 40% zinc stearate aqueous dispersion 175 parts (Hydrin L-536, manufactured by Chukyo Yushi Co., Ltd.) Water 775 parts

[0076] Comparative Example 1 An attempt was made to prepare a heat-sensitive recording material of Comparative Example 1 in the same manner as in Example 1, except that in the preparation of (1) dye precursor dispersion A in Example 1, the formulation was changed as follows, but the dye precursor dispersion gelled and a heat-sensitive recording material could not be obtained. 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Chemical Co., Ltd., Red-40) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) 10% styrene-maleic acid copolymer ammonium salt aqueous solution 5 parts (Arakawa Chemical Industries, Ltd., Polymaron 1318 diluted with water) Polyoxyethylene fatty acid monoester 2 parts (Ionet (registered trademark) MO-200, nonionic surfactant manufactured by Sanyo Chemical Industries, Ltd., HLB value 8.4) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Water 170 parts

[0077] Comparative Example 2 A thermosensitive recording material of Comparative Example 2 was prepared in the same manner as in Example 1, except that in the preparation of (1) dye precursor dispersion A in Example 1, the formulation was changed as follows: The Beck smoothness of the thermosensitive recording layer surface after calendering was 250 seconds. 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Chemical Co., Ltd., Red-40) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) 10% styrene-maleic acid copolymer ammonium salt aqueous solution 5 parts (Arakawa Chemical Industries, Ltd., Polymaron 1318 diluted with water) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Water 172 parts

[0078] Comparative Example 3 A thermosensitive recording material of Comparative Example 3 was prepared in the same manner as in Example 1, except that in the preparation of (1) dye precursor dispersion A in Example 1, the formulation was changed as follows: The Beck smoothness of the thermosensitive recording layer surface after calendaring was 250 seconds. 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Chemical Co., Ltd., Red-40) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) 10% styrene-maleic acid copolymer ammonium salt aqueous solution 5 parts (Arakawa Chemical Industries, Ltd., Polymaron 1318 diluted with water) Polyoxyethylene polyoxypropylene alkyl ether 5 parts (Kao Corporation nonionic surfactant, Emulgen MS-110, HLB value 12.7) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Wednesday 167 parts

[0079] Comparative Example 4 (8) Synthesis of styrene-maleic acid copolymer B salt A four-neck flask equipped with a stirrer, thermometer, and reflux condenser was charged with 45 parts of styrene, 43 parts of maleic anhydride, 300 parts of toluene, and 1 part of Nyper-BW (manufactured by Nippon Oil & Fats Co., Ltd.), and the mixture was heated in an oil bath under reflux and reacted for 6 hours. The reaction solution was poured into 1500 ml of n-hexane, and a resin was precipitated, filtered, and dried. 350 parts of water and 20 parts of a 25% aqueous ammonia solution were added to the dried styrene-maleic anhydride copolymer, and the mixture was hydrolyzed at 60°C for 5 hours. Water was then added to adjust the solids concentration to 10%. The resulting styrene-maleic acid copolymer B salt had a degree of esterification of 0% and a weight-average molecular weight of 50,000.

[0080] An attempt was made to prepare the heat-sensitive recording material of Comparative Example 4 in the same manner as in Example 1, except that in the preparation of (1) dye precursor dispersion A in Example 1, the formulation was changed as follows, but the dye precursor dispersion gelled and the heat-sensitive recording material could not be obtained. 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Chemical Co., Ltd., Red-40) 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 100 parts (Mitsubishi Chemical Corporation's Gohsenex L-3266 dissolved in water) 10% styrene-maleic acid copolymer B salt aqueous solution (esterification degree 0%) 5 parts Polyoxyethylene polyoxypropylene alkyl ether 2 Department (Kao Corporation nonionic surfactant, Emulgen MS-110, HLB value 12.7) Acetylenic dialcohol composition 0.5 parts (Nissin Chemical Industry Co., Ltd., Surfynol 104E) Water 170 parts

[0081] The thermosensitive recording materials prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were subjected to the following evaluations. The results are shown in Table 1. In Table 1, a "-" indicates that the thermosensitive recording material could not be prepared due to gelation of the dye precursor dispersion, and therefore evaluation of that item was not possible.

[0082] [Manufacturing stability] The state of the dye precursor dispersion during preparation was observed and evaluated according to the following criteria. ◯: No gelation occurs during or after pulverization of the dye precursor dispersion. ×: The dye precursor dispersion gelled during or after pulverization.

[0083] [Red cast on scalp] For each of the prepared thermal recording materials, the hue a* value of the background was measured in an environment of 23°C and 50% RH according to JIS P8150:2004, and evaluated according to the following criteria. ◎: a* value of the skin area is less than 1.0 ○: a* value of the skin part is 1.0 or more and less than 4.0 ×: a* value of the skin part is 4.0 or more

[0084] [Print density] For each of the prepared thermal recording materials, a solid red image was printed at an applied energy of 0.29 mJ / dot using a facsimile tester TH-PMD manufactured by Ohkura Electric Co., Ltd., under an environment of 23°C and 50% RH. The optical density of the image area was measured using a densitometer (RD19 manufactured by GretagMacbeth) (magenta mode) under an environment of 23°C and 50% RH, and evaluated according to the following criteria. ◎: The color density of the printed area exceeds 1.2 ○: The color density of the printed area is greater than 0.9 and less than 1.2 ×: Color density of printed area is 0.9 or less

[0085] [Table 1]

[0086] As is clear from Table 1, the method for producing a thermal recording material of the present invention can provide a thermal recording material with high print density, little reddish background, and excellent production stability.

Claims

[Claim 1] A method for producing a thermosensitive recording material having a thermosensitive recording layer on a support, the thermosensitive recording layer containing a dye precursor and a color developer, the method comprising wet-pulverizing the dye precursor under conditions in which the dye precursor contains at least one dye precursor selected from the group consisting of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran, and a maleic acid copolymer having an esterification degree of 15% or more and a nonionic surfactant with an HLB value of 10 or more as a dispersant for the dye precursor, the nonionic surfactant being present in an amount of 0.15 to 4% by mass relative to the dye precursor.

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