JP2024028081A - Method for manufacturing heat-sensitive recording material - Google Patents

Abstract

An object of the present invention is to provide a method for producing a heat-sensitive recording material capable of obtaining a heat-sensitive recording material that provides high print density, has little red cast on the background, and has excellent production stability. [Solution] The heat-sensitive recording layer contains at least one selected from 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran as a dye precursor; A maleic acid copolymer having an esterification degree of 15% or more and a nonionic surfactant having an HLB value of 10 or more are contained as a dispersant for the dye precursor, and the nonionic surfactant is The dye precursor is wet-pulverized under conditions where the content is 0.15% to 4% by mass. [Selection diagram] None

Description

The present invention relates to 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.

A thermosensitive recording material generally contains an electron-donating dye precursor (hereinafter referred to as a dye precursor) and an electron-accepting color developer (hereinafter referred to as a color developer) on a support. It is equipped with a heat-sensitive recording layer, and by heating the heat-sensitive recording layer with a thermal head, a thermal pen, a laser beam, etc., the dye precursor and color developer react instantly and a recorded image is obtained. be. Such heat-sensitive recording materials have the advantages of being able to obtain recorded images with relatively simple equipment, being easy to maintain, and producing no noise. It is used in a wide range of fields, including label printing machines, train tickets, and ticket issuing machines. In particular, in recent years, thermal recording has been applied to financial records such as gas, water, and electricity bill receipts, financial institution ATM usage statements, and various receipts, as well as thermal recording labels and thermal recording tags for POS systems. material is used.

For these uses, there is a demand for heat-sensitive recording materials that exhibit high print density. In order to meet this requirement, the dye precursor is used after being pulverized by wet pulverization using a pulverizer such as a sand grinder, ball mill, attritor, or bead mill. By using a finely divided dye precursor, the dye precursor is easily melted by heating, and the molten dye precursor mixes with the color developer at the molecular level to promote color development reaction.

In addition, as for the heat-sensitive recording material, not only a black-coloring heat-sensitive recording material but also a red-coloring heat-sensitive recording material may be used. Red-colored heat-sensitive recording materials tend to have a more noticeable red cast on the background than black-colored heat-sensitive recording materials, and there is a demand for heat-sensitive recording materials with less red cast on the background.

3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran are known as dye precursors that develop a red color. For example, Japanese Patent Laid-Open No. 2006-281473 (Patent Document 1) discloses that the color separation between the low-temperature print area and the high-temperature print area is good, the image area of each tone has excellent light resistance, and even in long-term light resistance tests. As a multicolor thermosensitive recording material with suppressed deterioration of coloring function, a multicolor thermosensitive recording material containing 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluoran is used. Color thermosensitive recording materials are described. However, in recent years, the environment in which heat-sensitive recording materials are used has become more severe, and 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7 -The heat-sensitive recording material containing chlorofluorane was not fully satisfactory in terms of red cast on the background.

It is known that background fogging can be improved by using a nonionic surfactant as a dispersant when wet-pulverizing a dye precursor. -283727 (Patent Document 3). However, when using this technique to disperse 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide or 3-diethylamino-7-chlorofluorane, the dye precursor containing There were problems with production stability, such as gelation of the dispersion liquid and sedimentation and coagulation of the dispersoid. Furthermore, it is known that background fogging can be improved by using a styrene-maleic acid copolymer as a dispersant when wet-pulverizing a dye precursor; It is described in However, when this technology is used, the background redness of heat-sensitive recording materials using 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane cannot be improved. This had the problem of worsening fogging.

JP2006-281473A Japanese Patent Application Publication No. 6-206374 Japanese Patent Application Publication No. 2002-283727 Japanese Patent Application Publication No. 8-39931

An object of the present invention is to provide a method for producing a heat-sensitive recording material that can provide a high print density, have little red cast on the background, and have excellent production stability.

A method for producing a heat-sensitive recording material having a heat-sensitive recording layer containing a dye precursor and a color developer on a support, the heat-sensitive recording layer containing 3,3-bis(1-n-butyl-) as a dye precursor. At least one selected from 2-methyl-3-indolyl) phthalide and 3-diethylamino-7-chlorofluoran, a maleic acid copolymer with an esterification degree of 15% or more as a dispersant for the dye precursor, and HLB. Wet-pulverize the dye precursor under conditions where the dye precursor contains a nonionic surfactant having a value of 10 or more, and the content of the nonionic surfactant relative to the dye precursor is 0.15% to 4% by mass. A method for producing a heat-sensitive recording material, characterized by:

ADVANTAGE OF THE INVENTION According to the present invention, it is possible to provide a method for producing a heat-sensitive recording material that can obtain a heat-sensitive recording material that provides high print density, has little red cast on the background, and has excellent production stability.

Hereinafter, the content of the present invention will be explained in more detail.

In the present invention, at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane contained as a dye precursor in the heat-sensitive recording layer is 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, the content of the nonionic surfactant relative to the dye precursor is adjusted to 0. Wet pulverization is carried out under conditions of 15% by mass or more and 4% by mass or less. If the HLB value of the nonionic surfactant is less than 10, gelation tends to occur when obtaining a dye precursor dispersion, resulting in decreased production stability. Further, if the content of the nonionic surfactant is less than 0.15% by mass, a reddish tint occurs on the background, and if the content of the surfactant exceeds 4% by mass, sufficient print density cannot be obtained.

In the present invention, the nonionic surfactant has a hydrophilic group composed of a hydroxyl group or an ether bond that does not ionically dissociate in water, such as polyoxyethylene octylphenyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene lauryl, etc. 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 Examples include polystyrene phenyl ether, polyethylene glycol, polyoxyethylene polyoxypropylene ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene fatty acid ester, and the like. These can be used alone or in combination of two or more. Such nonionic surfactants can be commercially available, such as Emulgen (registered trademark) MS-110 (polyoxyethylene polyoxypropylene alkyl ether) and Rheodol (registered trademark) TW- from Kao Corporation. L120 (polyoxyethylene sorbitan monolaurate) and the like can be suitably used. In addition, in the present invention, a nonionic surfactant is added to the total amount of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane contained in the heat-sensitive recording layer. A content in the range of 0.2% by mass to 4% by mass is preferable because a heat-sensitive recording material with less red cast on the background, high print density and excellent manufacturing stability can be obtained. Further, it is preferable that the HLB value of the nonionic surfactant is in the range of 10 or more and 18 or less because a heat-sensitive recording material with little red cast on the background, high print density and excellent manufacturing stability can be obtained.

The maleic acid-based copolymer used in the wet milling of the dye precursor in the present invention is a copolymer containing maleic acid as a monomer unit, and 15% or more of the maleic acid monomer units are esterified (i.e. degree of esterification is 15% or more). When the degree of esterification is less than 15%, sufficient production stability cannot be obtained even if the above-mentioned nonionic surfactant is used in an appropriate amount. Maleic acid copolymers can be obtained by radical copolymerization of maleic anhydride and various known monomers, and by esterifying and hydrolyzing the maleic anhydride units of the copolymer. Examples include copolymers of maleic acid, copolymers of alkyl vinyl ether and maleic acid, and copolymers of styrene derivatives and maleic acid. In particular, the maleic acid copolymer in the present invention preferably has a degree of esterification of 15% or more and a mass average molecular weight of 5,000 to 60,000. -Methyl-3-indolyl) phthalide and 3-diethylamino-7-chlorofluorane can be dispersed with excellent production stability without causing high viscosity or poor pulverization.

These maleic acid copolymers may be used alone or in combination of two or more, if necessary. Commercially available maleic acid copolymers such as these can be used, such as Polymalon (registered trademark) 1318 (degree of esterification 70%, average molecular weight 50,000 to 60,000) manufactured by Arakawa Chemical Co., Ltd., KS- 1333 (degree of esterification 70%, average molecular weight 10,000 to 20,000), etc. can be suitably used.

In the present invention, 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane can be used in combination. The ratio used in combination can be selected arbitrarily taking into account the color tone of the image area and the light resistance of the image area, but if the ratio of 3-diethylamino-7-chlorofluorane is 50% or more, the color tone of the image area will be vivid. It is preferable because it turns vermilion.

In the present invention, at least one selected from 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane preferably uses water as a dispersion medium. It is then wet-milled. Examples of the dispersion medium other than water include organic solvents that are compatible with water, such as methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, and ethylene glycol. The proportion of water in the entire dispersion medium is preferably 90% by mass or more from the viewpoint of stability of the dispersion liquid. In the present invention, the term "used as a dispersant" means that the above-mentioned dispersion medium contains these compounds during wet pulverization.

In the present invention, 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane are ground by various wet grinding methods such as a sand grinder, ball mill, attritor, and bead mill. Depending on the machine, the volume average particle diameter of the dispersoid containing at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane is preferably reduced to 0. After pulverizing it to a size of .1 to 1.5 μm, it is used to prepare a heat-sensitive layer coating solution for a heat-sensitive recording layer. When the heat-sensitive recording layer contains at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane, the above The wet milling of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane is preferably carried out separately. Note that if the volume average particle diameter of the dye precursor described above is made 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, it becomes difficult to melt the dye precursor by heating, and the molten dye precursor is difficult to mix with the color developer at the molecular level, suppressing the color reaction. This is to put it away.

Commercially available products can be used as the 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane; -n-butyl-2-methyl-3-indolyl) phthalide can be exemplified by Red-40, which is commercially available from Yamamoto Kasei Co., Ltd., and 3-diethylamino-7-chlorofluorane is also available from Yamamoto Kasei Co., Ltd. An example of this is Red-8, which is commercially available from Co., Ltd. In addition, the volume average particle diameter in the present invention refers to the volume average particle diameter calculated from the particle size distribution obtained by laser diffraction/scattering method, and specifically, the volume average particle diameter is calculated from the particle size distribution obtained by laser diffraction/scattering method. (registered trademark) series, the LA series manufactured by Horiba, Ltd., the SALD (registered trademark) series manufactured by Shimadzu Corporation, the LS Leeds manufactured by Beckman Coulter, and the like.

In the present invention, when wet-pulverizing 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane, a nonionic surfactant with an HLB value of 10 or more is used. Other dispersants that can be used in combination with the maleic acid copolymer with a degree of esterification of 15% or higher include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, and carboxylic acid-based copolymers. Polyvinyl alcohols such as 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 its derivatives, cellulose derivatives, gelatin, proteins such as casein, etc. , acid neutralized chitosan, sodium alginate, polyvinylpyrrolidone, ethylene/acrylic acid copolymer salt, styrene/acrylic acid copolymer salt, water-soluble polymer compounds such as polyacrylates, dodecylbenzenesulfonate, Examples include anionic low-molecular surfactants such as dialkyl sulfosuccinates, alkylnaphthalene sulfonates, alkyldiphenyl ether disulfonates, fatty acid metal salts, nonionic surfactants with an HLB value lower than 10, etc. There are no limitations, and one or more types can be used as necessary. In the present invention, the total solid content of the maleic acid copolymer with 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 3,3-bis(1 -n-butyl-2-methyl-3-indolyl) phthalide and 3-diethylamino-7-chlorofluorane, the amount may be in the range of 3 to 30% by mass based on the total amount of dispersoid of the dispersion containing at least one of 3-diethylamino-7-chlorofluoran. preferable.

In the present invention, the particle size of the media used is The beads can be selected as appropriate depending on the desired particle size of the dispersoid to be obtained, but beads with a diameter of 0.2 to 2.0 mm are preferable in order to achieve a sharp particle size distribution and atomization, and the material is glass. , zirconia, alumina, etc. Further, the bead filling rate in the crushing chamber is preferably 30 to 95% by volume. Furthermore, the temperature of the dispersion when pulverizing 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane should be 50°C or lower. desirable. When processed at temperatures higher than 50°C, gelation may occur.

In the present invention, when at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane is wet-pulverized, the red cast on the skin is improved. For this purpose, it is also possible to perform wet milling together with inorganic dispersoids. The 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, hydrated Examples include halloysite. The proportion of inorganic dispersoids in the total dispersoids is preferably less than 20% by mass. Thereby, a heat-sensitive recording material with excellent production stability can be obtained. Furthermore, a dispersion obtained by pulverizing at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane is used to inhibit the effects of the present invention. A heating treatment may be performed to the extent that the powder is not heated, and a coating layer formed from an organic polymer may be provided on the surface of the particles after pulverization.

The total content of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane contained in the heat-sensitive recording material of the present invention is When the amount is in the range of 1 to 30% by mass based on the total solid content, it is preferable because a heat-sensitive recording material with high print density and excellent manufacturing stability can be obtained.

The heat-sensitive recording layer of the heat-sensitive recording material of the present invention contains 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane as dye precursors. In addition to at least one of the above, dye precursors generally used in pressure-sensitive recording materials and heat-sensitive recording materials may be contained in appropriate combinations. Specific examples include those listed below, but are not limited to these.

As black dye precursors, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-di-n-pentylamino-6-methyl-7-anilinofluoran, 3 -diethylamino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-7-(2-chloroanilino)fluorane, 3-diethylamino-7-(2-chloroanilino)fluorane, 3-diethylamino-6 -Methyl-7-xylidinofluorane, 3-diethylamino-7-(2-carbomethoxyphenylamino)fluoran, 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilinofluorane, 3-(N-cyclopentyl-N-ethyl)amino-6-methyl-7-anilinofluorane, 3-(N-isoamyl-N-ethyl)amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-4-toluidino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-4-toluidino)-6-methyl-7-(4-toluidino)fluorane, 3-(N -Methyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-(4- n-butylphenylamino)fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-anilinofluorane,

Examples of red dye precursors include 3,3-bis(1-n-butyl-2-methylindol-3-yl)tetrachlorophthalide and 3,3-bis(1-n-butylindole-3-yl). 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, 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-dibenzylaminofluorane, 3-diethylamino- 6-Methyl-7-chlorofluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-6-methylfluorane, 3-diethylamino-6-methyl-7-chloro-8-benzylfluorane, 3-diethylamino-6-methylfluorane Diethylamino-6,7-dimethylfluorane, 3-diethylamino-6,8-dimethylfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-(N-acetyl-N-methyl)aminofluorane , 3-diethylamino-7-methylfluorane, 3-diethylamino-7-n-propoxyfluorane, 3-diethylamino-7-p-methylphenylfluorane, 3-diethylamino-7,8-benzofluorane, 3- Diethylaminobenzo[a]fluorane, 3-diethylaminobenzo[c]fluorane, 3-dimethylamino-7-methoxyfluorane, 3-dimethylamino-6-methyl-7-chlorofluorane, 3-dimethylamino-7-methyl Fluoran, 3-dimethylamino-7-chlorofluoran, 3-(N-ethyl-p-toluidino)-7-methylfluoran, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7 -chlorofluorane, 3-(N-ethyl-N-isoamyl)amino-7,8-benzofluorane, 3-(N-ethyl-N-isoamyl)amino-7-methylfluorane, 3-(N- Ethyl-Nn-octyl)amino-6-methyl-7-chlorofluorane, 3-(N-ethyl-Nn-octyl)amino-7,8-benzofluorane, 3-(N-ethyl- N-n-octyl)amino-7-methylfluorane, 3-(N-ethyl-Nn-octyl)amino-7-chlorofluorane, 3-(N-ethyl-N-4-methylphenyl)amino -7,8-benzofluorane, 3-(N-ethoxyethyl-N-ethyl)amino-7,8-benzofluorane, 3-(N-ethoxyethyl-N-ethyl)amino-7-chlorofluoran , 3-di-n-butylamino-6-methyl-7-chlorofluorane, 3-di-n-butylamino-7,8-benzofluorane, 3-di-n-butylamino-7-chlorofluoran Orane, 3-di-n-butylamino-7-methylfluorane, 3-diallylamino-7,8-benzofluorane, 3-diallylamino-7-chlorofluorane, 3-di-n-butylamino- 6-Methyl-7-bromofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-pyrrolidylamino-7-methylfluorane, 3-ethylamino-7-methylfluorane, 3-(N-ethyl -N-isoamyl)amino-benzo[a]fluorane, 3-di-n-butylamino-6-methyl-7-bromofluorane, 3,6-bis(diethylaminofluorane)-γ-(4'-nitro ) Anilinolactam,

Green dye precursors include 3-(N-ethyl-Nn-hexyl)amino-7-anilinofluorane, 3-(N-ethyl-Np-tolyl)amino-7-(N -phenyl-N-methyl)aminofluorane, 3-(N-ethyl-Nn-propyl)amino-7-dibenzylaminofluorane, 3-(N-ethyl-Nn-propyl)amino-6 -Chloro-7-dibenzylaminofluorane, 3-(N-ethyl-N-4-methylphenyl)amino-7-(N-methyl-N-phenyl)aminofluorane, 3-(N-ethyl-4 -methylphenyl)amino-7-dibenzylaminofluorane, 3-(N-ethyl-4-methylphenyl)amino-6-methyl-7-dibenzylaminofluorane, 3-(N-ethyl-4-methyl phenyl)amino-6-methyl-7-(N-methyl-N-benzyl)aminofluorane, 3-(N-methyl-Nn-hexyl)amino-7-anilinofluorane, 3-(N- Propyl-Nn-hexyl)amino-7-anilinofluorane, 3-(N-ethoxy-Nn-hexyl)amino-7-anilinofluorane, 3-(Nn-pentyl-N- Allyl)amino-6-methyl-7-anilinofluorane, 3-(Nn-pentyl-N-allyl)amino-7-anilinofluorane, 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-fluoro anilino)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 -benzylaminofluorane, 3-diethylamino-6-methyl-7-dibenzylaminofluorane, 3-diethylamino-6-methyl-7-n-octylaminofluorane, 3-diethylamino-6-methyl-7-( N-cyclohexyl-N-benzyl)aminofluorane, 3-diethylamino-6-methyl-7-(2-chloroanilino)fluorane, 3-diethylamino-6-methyl-7-(2-trifluoromethylanilino)fluorane, 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-anilinofluorane, 3-diethylamino-6-ethoxyethyl-7-anilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-methylanilinofluorane, 3-diethylamino- 7-dibenzylaminofluorane, 3-diethylamino-7-n-octylaminofluorane, 3-diethylamino-7-p-chloroanilinofluorane, 3-diethylamino-7-p-methylphenylanilinofluorane, 3-diethylamino-7-(N-cyclohexyl-N-benzyl)aminofluorane, 3-diethylamino-7-(2-chloroanilino)fluorane, 3-diethylamino-7-(3-trifluoromethylanilino)fluorane, 3 -Diethylamino-7-(2-trifluoromethylanilino)fluoran, 3-diethylamino-7-(2-ethoxyanilino)fluoran, 3-diethylamino-7-(4-ethoxyanilino)fluoran, 3-diethylamino- 7-(2-chlorobenzylanilino)fluorane, 3-dimethylamino-6-chloro-7-dibenzylaminofluorane, 3-dimethylamino-6-methyl-7-n-octylaminofluorane, 3-dimethyl Amino-7-dibenzylaminofluorane, 3-dimethylamino-7-n-octylaminofluorane, 3-di-n-butylamino-7-(2-fluoroanilino)fluorane, 3-anilino-7- Dibenzylaminofluorane, 3-anilino-6-methyl-7-dibenzylaminofluorane, 3-pyrrolidino-7-dibenzylaminofluorane, 3-pyrrolidino-7-(4-cyclohexylanilino)fluorane, 3 -dibenzylamino-6-methyl-7-dibenzylaminofluoran, 3,7-bis(dibenzylamino)fluoran, 3-dibenzylamino-7-(2-chloroanilino)fluoran,

Examples of blue dye precursors include 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylaminophenyl)phthalide, 3-(1-ethyl-2-methylindol-3-yl) 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, 3-(1-ethyl-2-methylindole) -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, 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-methylindole) -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-butoxy aminophenyl)-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-methylindole-3- yl)-3-(2-ethoxy-4-di-methoxycyclohexylaminophenyl)-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)-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-methylindole-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-ethylindole-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-ethylindole) -3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-ethyl-2-propylindol-3-yl)-3-(2-ethoxy-4-diethylamino phenyl)-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-azapthalide, 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-methyl indol-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-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-diethylamino phenyl)-4-azaphthalide, 3-(1-chloro-2-methylindol-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(1-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-methylindole- 3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 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)-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-methylindole- 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, 3-(4-dimethylamino-2-methylphenyl)-3- (4-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(1-ethyl-2-methylindol-3-yl)-3-(4-diethylamino-2-n-hexyloxyphenyl)-4- Examples include azaphthalide. These can be used alone or in combination of two or more.

Some functional dye precursors have absorption in the near-infrared region. When this dye precursor is used as a dye precursor for high-temperature coloring, either alone or in combination with other dye precursors, high-temperature coloring images can be automatically read in near-infrared light with absorption in the near-infrared region. It can be an image that is possible. When this dye precursor is used in the present invention, it is possible to use a combination of images that absorb only in the visible region, images that absorb in the near-infrared region, etc., and it is possible to obtain recording materials with high security.

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-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7 -tetrachlorophthalide, 3,3-bis[1,1-bis(4-pyrrolidinophenyl)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-methylfluorane, 3-[p-(p-dimethylaminoanilino)anilino]-6-methyl-7-chlorofluorane, 3-( p-n-butylaminoanilino)-6-methyl-7-chlorofluorane, 3-[p-(p-anilinoanilino)anilino]-6-methyl-7-chlorofluorane, 3-[p-(p -chloroanilino)anilino]-6-methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ethylamino)-6,8,8-trimethyl-9-ethyl-8,9-dihydro-( 3,2,e) Pyridofluorane, 3-di(n-butyl)amino-6,8,8-trimethyl-8,9-dihydro-(3,2,e)pyridofluorane, 3'-phenyl-7-N- Examples include 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 of two or more, if necessary. These dye precursors can also be wet-dispersed together with 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane.

The total content of dye precursors contained in the heat-sensitive recording material of the present invention is preferably 1 to 30% by mass based on the total solid content of the heat-sensitive recording layer. This makes it possible to obtain sufficient thermal responsiveness.

Various known color developers can be used as the color developer contained in the heat-sensitive recording layer of the heat-sensitive recording material of the present invention. For example, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-propoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'- Allyloxydiphenylsulfone, 4-hydroxy-4'-octyloxydiphenylsulfone, 4-hydroxy-4'-dodecyloxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 2,2'-diallyl-4, 4'-sulfonyldiphenol, 3,4-dihydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-benzenesulfonyloxydiphenylsulfone, 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) -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, 2,2-bis(4-hydroxyphenyl)methyl acetate, 2,2-bis(4-hydroxyphenyl)butyl 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]diphenylsulfone, 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}phenyl)benzenesulfonamide, N-butylbutyl-4-[3-(p-toluenesulfonyl)ureido]benzoate, 3,3'-(4,4'methylenediphenyl)bis(ureido p -trissulfone), bis{3-[3'-(p-toluenesulfonyl)ureido]benzoate}, 1,5-(3-oxopentylene)bis{3'-[3'-(p-toluenesulfonyl) ureido]benzoate}, N-phenylsulfonyl-N'-phenylurea derivatives, etc., but are not limited thereto. These can be used alone or in combination of two or more.

The content ratio of the dye precursor and color developer is determined appropriately depending on the types and combination thereof, but it is preferable that the total amount of the color developer is 100 to 500% by mass with respect to the total amount of the dye precursor. Preferably, it is more preferably 150 to 350% by mass.

In the present invention, the heat-sensitive recording layer can contain a low-melting-point heat-soluble component (hereinafter referred to as a sensitizer) that promotes color reaction in order to further improve its heat 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-hydroxymethyl stearic acid amide, N-stearyl stearic acid amide, ethylene bis stearic acid amide, and methylene bis stearic acid. amide, methylol stearic acid amide, N-stearylurea, benzyl-2-naphthyl ether, p-toluenesulfonamide, m-terphenyl, 4-benzylbiphenyl, 2,2'-bis(4-methoxyphenoxy) diethyl ether, α,α′-diphenoxy-o-xylene, bis(4-methoxyphenyl) ether, diphenyl adipate, dibenzyl oxalate, bis(4-methylbenzyl) oxalate, bis(4-chlorobenzyl) oxalate, dimethyl terephthalate , dibenzyl terephthalate, benzenesulfonic acid phenyl ester, bis(4-allyloxyphenyl)sulfone, 1,2-bis(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 4-acetylacetophenone, acetoacetanilide and fatty acid anilides, but are not limited thereto. Such sensitizers can be used alone or in combination of two or more. Further, in order to obtain sufficient thermal responsiveness, it is preferable that the total amount of the sensitizer accounts for 5 to 50% by mass in the total solid content of the thermosensitive recording layer.

Further, the heat-sensitive recording layer may further contain a storage improving agent such as a hindered phenol compound, a hindered amine compound, a phosphoric acid ester derivative, or a benzotriazole derivative, if necessary.

A specific example of the hindered phenol compound used as necessary in the heat-sensitive recording layer of the present invention is 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-ο-tolyl)butane, 1,1,3-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(2,6-dimethylphenol), 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, 2 , 2-bis(4-hydroxy-3,5-dimethylphenyl)propane, etc., but are not limited thereto, and these compounds may be used alone or in combination as necessary. More than one species can be used.

Specific examples of hindered amine compounds that can be used as necessary in the heat-sensitive recording layer of the present invention include 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, butane-1,2,3,4-tetracarboxylic acid-tetrakis[2,2,6,6-tetramethyl(4-piperidyl)] ester, but are not limited thereto. Moreover, these compounds can be used alone or in combination of two or more, if necessary.

Specific examples of the phosphoric acid ester derivatives used as necessary in the heat-sensitive recording layer of the present invention include triphenyl phosphate, diphenyl phosphate, bis(4-tert-butylphenyl) phosphate, and bis(4,6-diphenyl phosphate). -tert-butylphenyl) phosphate, bis(4-chlorophenyl) phosphate, bis(benzyloxyphenyl) phosphate, 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, dimethyloxyphosphate, diethyloxy Phosphate, bis(3,5-di-tert-butyl-4-hydroxyphenyl) phosphate, 3,5-di-tert-butyldiphenyl phosphate, diethyl (3,5-di-tert-butyl-4-hydroxyphenyl) phosphate, and sodium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, calcium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, 2 , the zinc salt of 2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, the ammonium salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, and the potassium salt. However, the present invention is not limited thereto, and one or more of these compounds can be used as necessary.

Specific examples of benzotriazole derivatives used as necessary in the heat-sensitive recording layer of the present invention include 2-(2-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, Triazole, 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 approx. 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-methyl benzotriazolyl)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), 2,2'-isopropylidene bis(4-methyl-6-benzotriazolylphenol), 2,2'-isopropylidene bis[4-(1,1,3,3-tetra Examples include, but are not limited to, Moreover, one type or two or more types of these compounds can be used as necessary.

The total amount of the hindered phenol compound, hindered amine compound, phosphoric acid ester derivative, or benzotriazole derivative used as necessary in the heat-sensitive recording layer of the present invention is 5 to 50% relative to the dye precursor. 500% by mass is preferred.

In the present invention, the heat-sensitive recording layer can contain various pigments depending on the purpose of improving sticking resistance, whiteness, etc. For example, 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, hydrated halloysite, and other white inorganic pigments. , organic pigments, hollow particles, and other known pigments, but are not limited to these, and one type or two or more types can be used as necessary. The pigment is preferably used in an amount of 5 to 50% by mass based on the total solid content of the heat-sensitive recording layer.

In the present invention, the heat-sensitive recording layer can contain, as a binder, various water-soluble polymer compounds or water-dispersible polymer compounds used in ordinary coating. Specifically, starch or its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxypropylcellulose, methylcellulose, ethylcellulose, and carboxymethylcellulose, proteins such as gelatin and casein, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and 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 , water-soluble polymer compounds such as ethylene/maleic acid copolymer salts, isobutylene/maleic acid copolymer salts, and styrene/butadiene copolymers, acrylonitrile/butadiene copolymers, methyl acrylate/butadiene copolymers, Acrylonitrile/butadiene/styrene terpolymer, polyvinyl acetate, vinyl acetate/acrylic ester copolymer, ethylene/vinyl acetate copolymer, polyacrylic ester, styrene/acrylic ester copolymer, polyurethane, etc. Examples include water-dispersible polymer compounds, but the present invention is not limited to these, and one type or two or more types can be used as necessary. The binder is preferably used in an amount of 5 to 30% by mass based on the total solid content of the heat-sensitive recording layer.

Further, the heat-sensitive recording layer may contain higher fatty acid metal salts such as zinc stearate and calcium stearate, and waxes such as paraffin, oxidized paraffin, polyethylene, polyethylene oxide, and castor wax to improve sticking resistance. Furthermore, the heat-sensitive recording layer uses various hardening agents, crosslinking agents, dispersants, surfactants, fluorescent dyes, colored dyes, antifoaming agents, preservatives, thickeners, antistatic agents, etc. in order to provide water resistance. can contain.

In the present invention, the heat-sensitive recording layer of the heat-sensitive recording material contains at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane. Various components, such as dye precursors other than the above-mentioned 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane, color developer, and sensitizer. It is preferable that the agent, storage improver, pigment, lubricant, wax, etc. be used in preparing the heat-sensitive recording layer coating solution after being made into a dispersion liquid. The dispersion liquid is obtained by dry-pulverizing and dispersing various components other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane. It can be obtained by a method of dispersing it in a medium, or a method of mixing the various components in a dispersion medium and wet-pulverizing the mixture. In the present invention, the color developer, sensitizer, etc. are used alone or together, and water is used as a dispersion medium, and the volume average particle size is It is preferable that the fine particles be pulverized to preferably 0.1 to 5.0 μm and then used for preparing the heat-sensitive recording layer coating solution. In addition, dye precursors other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane may be used separately from the color developer. Using water as a dispersion medium, grind together with a dispersant into fine particles with a volume average particle diameter of preferably 0.1 to 1.5 μm using various wet grinders such as a sand grinder, ball mill, attritor, bead mill, etc. It is preferably used for preparing a heat-sensitive recording layer coating solution.

In the present invention, the heat-sensitive recording layer contains various components other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane. Dispersants used during dispersion 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, and phosphoric acid. Polyvinyl alcohols such as modified polyvinyl alcohol, butyral modified polyvinyl alcohol, epoxy modified polyvinyl alcohol, starch or its derivatives, cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose, carboxymethyl cellulose, gelatin, protein such as casein, chitosan acid neutralized product, sodium alginate, polyvinylpyrrolidone, diisobutylene/maleic acid copolymer salt, styrene/isobutylene/maleic acid copolymer salt, styrene/maleic acid copolymer salt, ethylene/acrylic acid copolymer salt , water-soluble polymer compounds such as styrene/acrylic acid copolymer salts, polyacrylates, dodecylbenzenesulfonates, dialkylsulfosuccinates, alkylnaphthalenesulfonates, alkyldiphenyl ether disulfonates, fatty acid metal salts, etc. Examples include anionic low-molecular surfactants, nonionic surfactants such as acetylene glycol, etc., but are not limited to these, and one type or two or more types can be used as necessary. . The total amount of dispersants is preferably 0.5 to 30% by mass based on the total amount of dispersoids contained in the dispersion liquid.

Pulverize various components other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane contained in the above heat-sensitive recording layer. 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. You can also crush it. In addition, a dispersion of various components other than at least one of 3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide and 3-diethylamino-7-chlorofluorane was pulverized at 40% The particles may be heated in the range of ~80°C, and a coating layer made of an organic polymer may be provided on the surface of the particles after pulverization.

In the present invention, the solid coating amount of the heat-sensitive recording layer is preferably 2 to 15 g/m ² . If it is less than 2 g/ ^m2 , the printing density in the low thermal energy region may become low, and if it is more than 15 g/ ^m2 , the improvements in various performances of the heat-sensitive recording layer will reach saturation, and the production during coating of the heat-sensitive recording layer will be reduced. Efficiency may be reduced.

In the present invention, there is a space between the support and the heat-sensitive recording layer for the purpose of improving the smoothness, heat insulation, etc. of the support, or for suppressing the adverse effects of various components contained in the support on the heat-sensitive recording layer. For this purpose, an undercoat layer may be provided. The undercoat layer contains a binder and various inorganic or organic pigments, and may also contain hollow particles. In addition, other auxiliary agents that can be contained in the undercoat layer include lubricants, antifoaming agents, surfactants, preservatives, optical brighteners, dispersants, thickeners, colorants, antistatic agents, Known crosslinking agents may be used.

In the present invention, when an undercoat layer is used, a coating liquid for the undercoat layer prepared by mixing and stirring together a pigment, a binder, and an auxiliary agent in water or the like is preferably used in a solid coating amount. It is formed by coating it on a support and drying it to a weight of 1 to 30 g/m ² , more preferably 4 to 20 g/m ² .

Pigments that can be contained in the undercoat layer of the present invention include, for example, talc, kaolin, calcined kaolin, clay, calcined clay, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, magnesium silicate, zinc oxide, aluminum oxide. , inorganic pigments such as aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, calcium silicate, diatomaceous earth, colloidal silica, melamine resin, urea-formaldehyde resin, polyethylene, polystyrene, ethylene-acetic acid Vinyl, styrene microballs, nylon powder, polyethylene powder, urea-formalin resin filler, styrene-methacrylic acid copolymer resin, polystyrene resin, raw starch particles, etc. may be used alone or in combination of two or more. However, it is not limited to these, and one type or two or more types can be used as necessary.

Further, the undercoat layer can contain, as a binder, various water-soluble polymer compounds or water-dispersible polymer compounds used in normal coating. Specific examples include 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 , water-soluble polymer compounds such as isobutylene/maleic acid copolymer salts, styrene/butadiene copolymers, acrylonitrile/butadiene copolymers, methyl acrylate/butadiene copolymers, acrylonitrile/butadiene/styrene ternary copolymers Examples include water-dispersible polymer compounds such as polyvinyl acetate, vinyl acetate/acrylic ester copolymer, ethylene/vinyl acetate copolymer, polyacrylic ester, styrene/acrylic ester copolymer, and polyurethane. However, it is not limited to these. One kind or two or more kinds of binders can be used. The amount of binder used is preferably 10 to 30% by mass based on the total solid amount of the undercoat layer.

In the present invention, when mixing and stirring various components that can be contained in the undercoat layer using water as a medium, a dispersant can be used to improve dispersibility. Dispersants used include polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and modified polyvinyl alcohol, starch or its derivatives, and 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, diisobutylene/maleic acid copolymer salt, styrene/isobutylene/maleic acid copolymer salt, styrene/maleic acid copolymer salt , ethylene/acrylic acid copolymer salts, styrene/acrylic acid copolymer salts, water-soluble polymer compounds such as polyacrylates, dodecylbenzene sulfonates, dialkyl sulfosuccinates, alkylnaphthalene sulfonates, alkyldiphenyl ethers Examples include, but are not limited to, anionic low-molecular surfactants such as disulfonates and fatty acid metal salts, nonionic surfactants such as acetylene glycol, and sodium hexametaphosphate. One type or two or more types can be used. The total amount of dispersants is preferably 0.1 to 30% by mass based on the total amount of dispersoids contained in the dispersion liquid.

In the present invention, the support of the heat-sensitive recording material may be transparent, translucent, or opaque, and may include paper, various nonwoven fabrics, woven fabrics, synthetic resin films, synthetic resin laminated papers, synthetic papers, and metals. Foil, ceramic paper, glass plate, etc., or a composite sheet of a combination of these can be used as desired depending on the purpose.

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

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. Examples of such fillers include 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. However, it is not limited to these, and one type, or two or more types can be used as necessary.

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 texture and smoothness. If it exceeds 25% by mass, the smoothness will be saturated, but the size and surface strength of the base paper will decrease, and paper breakage will likely occur when applying an undercoat layer or a heat-sensitive recording layer. Further, the basis weight of the paper support is preferably about 20 to 300 g/m ² .

In the present invention, when a paper support is used as a support, a sizing agent for internal addition (internal addition sizing agent) may be added to the paper support, such as a reinforced rosin sizing agent or an emulsion sizing agent in the case of acidic papermaking. In the case of neutral papermaking, synthetic sizing agents, etc. may contain alkyl ketene dimer-based, alkenyl succinic anhydride-based, higher fatty acid-based, neutral rosin sizing agents, etc., but are limited to these. Alternatively, one type, or two or more types can be used as necessary. Sizing agents for external addition (external addition sizing agents) include styrene maleic acid copolymers, styrene acrylic acid copolymers, styrene polymers, isocyanate polymers, rosin, tall oil, and phthalic acid copolymers. Examples include saponified alkyd resins such as acids, polymers such as saponified petroleum resins and rosin, α-olefin-maleic acid copolymers, acrylic ester-acrylic acid copolymers, and alkyl ketene dimers. , and are not limited to these, and one type or two or more types can be used as necessary. Furthermore, in addition to the above-mentioned sizing agents, pulp, and various fillers, the paper support may also contain various types of nonionic, cationic, anionic, or amphoteric retention aids, freeness improvers, paper strength enhancers, etc. An internal additive for papermaking can be added as necessary. Specific examples of retention improvers, drainage improvers, and paper strength agents 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, polyamines, polyvinyl alcohol, polyethylene oxide, and the like.

In the present invention, the heat-sensitive recording layer has improved sticking resistance, prevention of scratches, improved water resistance, improved printability, improved imprintability, improved inkjet suitability, and plasticizer resistance of thermosensitive color images. A protective layer can be provided for the purpose of improving chemical resistance or the like. The protective layer may contain various adhesives, inorganic pigments, various curing agents, various crosslinking agents, ultraviolet absorbers, etc., and may be a single layer or a laminate of two or more layers. Furthermore, printing with UV ink or the like may be performed on the surface of the heat-sensitive recording layer or the protective layer.

In the present invention, the solid coating amount of the protective layer is preferably 0.5 to 5 g/m ² . If it is less than 0.5 g/ ^m2 , the various properties of the protective layer will not be exhibited, and if it is more than 5 g/ ^m2 , there will be a large loss of thermal energy reaching the heat-sensitive recording layer from the thermal head, leading to a decrease in color development. There are cases.

In the present invention, the surface of the support opposite to the surface on which the heat-sensitive recording layer is provided may have a back coat layer for the purpose of preventing curling, antistatic, etc., and may also be subjected to an adhesive treatment. Further, the support may have a layer containing a material capable of recording information electrically, magnetically, or optically, an inkjet recording layer, etc. on the surface having the heat-sensitive recording layer or the opposite surface. Further, in order to perform printing by laser light, a photothermal conversion material can be contained in any layer and support in the heat-sensitive recording material.

The method of forming each layer in the present invention is not particularly limited, and can be formed using well-known techniques, such as coating apparatuses such as air knife coaters, various blade coaters, various bar coaters, and various curtain coaters. Various printing methods such as lithography, letterpress, intaglio, flexography, gravure, and screen printing can be used. Furthermore, various known techniques in the production of heat-sensitive recording materials can be used to improve the surface smoothness, such as the use of machines such as machine calenders, supercalenders, gloss calenders, brushing and the like.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way. In the examples, unless otherwise noted, all percentages and parts are based on mass. Moreover, the coating amount is the solid content coating amount.

Example 1
(1) Preparation of dye precursor dispersion A The following formulation was mixed, and the bead filling rate in the crushing chamber was 80% by volume ( Dye precursor dispersion A was obtained by wet-pulverizing the dispersoid at a liquid temperature of 20° C. until the volume average particle diameter of the dispersoid became 0.8 μm.
3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Kasei Co., Ltd., Red-40)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex (registered trademark) L-3266 dissolved in water)
10% styrene maleic acid copolymer ammonium salt aqueous solution (butyl esterification, degree of esterification 70%) 5 parts (manufactured by Arakawa Chemical Co., Ltd., Polymalon 1318 diluted with water)
2 parts of polyoxyethylene polyoxypropylene alkyl ether (nonionic surfactant manufactured by Kao Corporation, Emulgen MS-110, HLB value 12.7)
Acetylene dialcohol composition 0.5 part (Nissin Chemical Industry Co., Ltd., Surfynol (registered trademark) 104E)
Water 170 parts

(2) Preparation of color developer dispersion The following formulation was mixed, and the bead filling rate in the crushing chamber was 80% by volume (diameter 0.6 mm (using glass beads) was wet-pulverized at a liquid temperature of 20° C. until the volume average particle diameter of the dispersoid became 0.8 μm to obtain 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 -ο-tolyl)butane
40 parts 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 440 parts (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
2 parts of acetylene dialcohol composition (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 738 parts

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

(4) Preparation of heat-sensitive recording layer coating solution The following formulations were mixed and sufficiently stirred to obtain a heat-sensitive recording layer coating solution.
Dye precursor dispersion A 377.5 parts Color developer dispersion 1620 parts Pigment dispersion 505 parts 10% fully saponified polyvinyl alcohol aqueous solution 1300 parts (manufactured by Nippon Ace Vine & Poval Co., Ltd., VC-13 dissolved in water) )
40% zinc stearate aqueous dispersion 175 parts (manufactured by Chukyo Yushi Co., Ltd., Hydrin L-536)
Water 775 parts

(5) Formation of heat-sensitive recording layer The heat-sensitive recording layer coating solution prepared in ( ⁴ ) above was applied to a high-quality paper (ash content 0.3 %), coated with an air knife coater to a solid content coating amount of 5 g/ ^m2 , dried to a moisture content of 6.5%, and further calendered using a super calender. A thermosensitive recording material was produced. The Bekk smoothness of the surface of the heat-sensitive recording layer after calendering was 250 seconds. (Measured using HL Beck smoothness tester manufactured by Kumagai Riki Kogyo Co., Ltd.)

Example 2
A heat-sensitive recording material of Example 2 was prepared in the same manner as in Example 1 except that the formulation of (1) dye precursor dispersion A in Example 1 was changed as follows. The Bekk smoothness of the surface of the heat-sensitive recording layer after calendering was 250 seconds.
3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Kasei Co., Ltd., Red-40)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
5 parts of 10% styrene-maleic acid copolymer ammonium salt aqueous solution (manufactured by Arakawa Chemical Co., Ltd., Polymalon 1318 diluted with water)
2 parts of polyoxyethylene sorbitan monolaurate (nonionic surfactant manufactured by Kao Corporation, Rheodol TW-L120, HLB value 16.7)
Acetylene dialcohol composition 0.5 part (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 170 parts

Example 3
A heat-sensitive recording material of Example 3 was prepared in the same manner as in Example 1 except that the formulation of (1) dye precursor dispersion A in Example 1 was changed as follows. The Bekk smoothness of the surface of the heat-sensitive recording layer after calendering was 250 seconds.
3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Kasei Co., Ltd., Red-40)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
5 parts of 10% styrene-maleic acid copolymer ammonium salt aqueous solution (manufactured by Arakawa Chemical Co., Ltd., Polymalon 1318 diluted with water)
Polyoxyethylene polyoxypropylene alkyl ether 0.3 parts (nonionic surfactant manufactured by Kao Corporation, Emulgen MS-110, HLB value 12.7)
Acetylene dialcohol composition 0.5 part (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 171.7 parts

Example 4
A heat-sensitive recording material of Example 4 was prepared in the same manner as in Example 1 except that the formulation of (1) dye precursor dispersion A in Example 1 was changed as follows. The Bekk smoothness of the surface of the heat-sensitive recording layer after calendering was 250 seconds.
3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Kasei Co., Ltd., Red-40)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
5 parts of 10% styrene-maleic acid copolymer ammonium salt aqueous solution (manufactured by Arakawa Chemical Co., Ltd., Polymalon 1318 diluted with water)
3 parts of polyoxyethylene polyoxypropylene alkyl ether (nonionic surfactant manufactured by Kao Corporation, Emulgen MS-110, HLB value 12.7)
Acetylene dialcohol composition 0.5 part (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 169 parts

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

A heat-sensitive 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 Bekk smoothness of the surface of the heat-sensitive recording layer after calendering was 250 seconds.
3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Kasei Co., Ltd., Red-40)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
10% styrene maleic acid copolymer A salt aqueous solution (butyl esterification, degree of esterification 30%) 5 parts polyoxyethylene polyoxypropylene alkyl ether 2 parts (nonionic surfactant manufactured by Kao Corporation, Emulgen MS-110) , HLB value 12.7)
Acetylene dialcohol composition 0.5 part (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 170 parts

Example 6
(7) Preparation of Dye Precursor Dispersion B Mix the following formulation and use DYNO-MILL MULTI-LAB (manufactured by Willy & Bacchofen) to obtain a bead filling rate of 80% by volume (diameter 0.6 mm) in the crushing chamber. Dye precursor dispersion B was obtained by wet-pulverizing the dispersoid at a liquid temperature of 20° C. until the volume average particle diameter of the dispersoid became 0.8 μm.
100 parts of 3-diethylamino-7-chlorofluorane (manufactured by Yamamoto Kasei Co., Ltd., Red-8)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
10% styrene maleic acid copolymer ammonium salt aqueous solution (butyl esterification, degree of esterification 70%) 5 parts (manufactured by Arakawa Chemical Co., Ltd., Polymalon 1318 diluted with water)
2 parts of polyoxyethylene polyoxypropylene alkyl ether (nonionic surfactant manufactured by Kao Corporation, Emulgen MS-110, HLB value 12.7)
Acetylene dialcohol composition 0.5 part (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 170 parts

A heat-sensitive recording material of Example 6 was prepared in the same manner as in Example 1, except that dye precursor dispersion A was changed to dye precursor dispersion B in (4) preparation of heat-sensitive recording layer coating solution. The Bekk smoothness of the surface of the heat-sensitive recording layer after calendering was 250 seconds.

Example 7
A heat-sensitive recording material of Example 7 was prepared in the same manner as in Example 1 except that the formulation (4) of Example 1 was changed as follows. The Bekk smoothness of the surface of the heat-sensitive recording layer after calendering was 250 seconds.
(4) Preparation of heat-sensitive recording layer coating solution The following formulations were mixed and sufficiently stirred to obtain a heat-sensitive recording layer coating solution.
Dye precursor dispersion A: 19 parts Dye precursor dispersion B: 358.5 parts Color developer dispersion: 1,620 parts Pigment dispersion: 505 parts 10% fully saponified polyvinyl alcohol aqueous solution: 1,300 parts (manufactured by Nippon Ace Vine & Poval Co., Ltd.) , VC-13 dissolved in water)
40% zinc stearate aqueous dispersion 175 parts (manufactured by Chukyo Yushi Co., Ltd., Hydrin L-536)
Water 775 parts

Comparative example 1
A heat-sensitive recording material of Comparative Example 1 was prepared in the same manner as in Example 1 except that the formulation of (1) dye precursor dispersion A in Example 1 was changed as follows. The precursor dispersion liquid 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 Kasei Co., Ltd., Red-40)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
5 parts of 10% styrene-maleic acid copolymer ammonium salt aqueous solution (manufactured by Arakawa Chemical Co., Ltd., Polymalon 1318 diluted with water)
2 parts of polyoxyethylene fatty acid monoester (nonionic surfactant manufactured by Sanyo Chemical Co., Ltd., Ionet (registered trademark) MO-200, HLB value 8.4)
Acetylene dialcohol composition 0.5 part (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 170 parts

Comparative example 2
A heat-sensitive recording material of Comparative Example 2 was prepared in the same manner as in Example 1 except that the formulation of (1) Dye Precursor Dispersion A in Example 1 was changed as follows. The Bekk smoothness of the surface of the heat-sensitive recording layer after calendering was 250 seconds.
3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Kasei Co., Ltd., Red-40)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
5 parts of 10% styrene-maleic acid copolymer ammonium salt aqueous solution (manufactured by Arakawa Chemical Co., Ltd., Polymalon 1318 diluted with water)
Acetylene dialcohol composition 0.5 part (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 172 parts

Comparative example 3
A heat-sensitive recording material of Comparative Example 3 was prepared in the same manner as in Example 1 except that the formulation of (1) dye precursor dispersion A in Example 1 was changed as follows. The Bekk smoothness of the surface of the heat-sensitive recording layer after calendering was 250 seconds.
3,3-bis(1-n-butyl-2-methyl-3-indolyl)phthalide 100 parts (Yamamoto Kasei Co., Ltd., Red-40)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
5 parts of 10% styrene-maleic acid copolymer ammonium salt aqueous solution (manufactured by Arakawa Chemical Co., Ltd., Polymalon 1318 diluted with water)
Polyoxyethylene polyoxypropylene alkyl ether 5 parts (nonionic surfactant manufactured by Kao Corporation, Emulgen MS-110, HLB value 12.7)
Acetylene dialcohol composition 0.5 part (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 167 parts

Comparative example 4
(8) Synthesis of styrene-maleic acid copolymer B salt In a four-neck flask equipped with a stirrer, a thermometer, and a reflux condenser, 45 parts of styrene, 43 parts of maleic anhydride, 300 parts of toluene, and Niper-BW (Japan (manufactured by Yushi Co., Ltd.) was added, heated in an oil bath, and reacted under reflux for 6 hours. This reaction solution was poured into 1500 ml of n-hexane to precipitate the resin, which was then filtered and dried. 350 parts of water and 20 parts of a 25% ammonia aqueous solution were added to the dried styrene-maleic anhydride copolymer and hydrolyzed at 60° C. for 5 hours, and water was added to adjust the solid content concentration to 10%. The degree of esterification of the obtained styrene-maleic acid copolymer B salt was 0%, and the weight average molecular weight was 50,000.

A heat-sensitive recording material of Comparative Example 4 was prepared in the same manner as in Example 1 except that the formulation of (1) dye precursor dispersion A in Example 1 was changed as follows. The precursor dispersion liquid 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 Kasei Co., Ltd., Red-40)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Mitsubishi Chemical Corporation, Gosenex L-3266 dissolved in water)
10% styrene maleic acid copolymer B salt aqueous solution (degree of esterification 0%) 5 parts polyoxyethylene polyoxypropylene alkyl ether 2 parts (nonionic surfactant manufactured by Kao Corporation, Emulgen MS-110, HLB value 12) .7)
Acetylene dialcohol composition 0.5 part (Surfynol 104E, manufactured by Nissin Chemical Industry Co., Ltd.)
Water 170 parts

The heat-sensitive recording materials produced in Examples 1 to 7 and Comparative Examples 1 to 4 above were subjected to the following evaluation. Table 1 shows each result. Note that in Table 1, the locations marked with "-" mean that the heat-sensitive recording material could not be produced due to gelation of the dye precursor dispersion, and therefore evaluation of such items could not be performed.

[Manufacturing stability]
The state of the dye precursor dispersion liquid when it was prepared was observed and evaluated according to the following criteria.
○: The dye precursor dispersion did not gel during or after pulverization.
×: The dye precursor dispersion liquid was gelatinized during or after pulverization.

[Red tint on the skin]
For each of the produced heat-sensitive recording materials, the hue a* value of the background portion was measured in an environment of 23° C. and 50% RH based on JIS P8150:2004, and evaluated according to the following criteria.
◎: The a* value of the skin part is less than 1.0 ○: The a* value of the skin part is 1.0 or more and less than 4.0 ×: The a* value of the skin part is 4.0 or more

[Print density]
For each of the produced heat-sensitive recording materials, a red solid was printed with an applied energy of 0.29 mJ/dot using a facsimile tester TH-PMD manufactured by Okura Electric Co., Ltd. in an environment of 23° C. and 50% RH. The optical density of the image area was measured using a densitometer (manufactured by Gretag Macbeth, RD19) (magenta mode) in an environment of 23° C. and 50% RH, and evaluated according to the following criteria.
◎: The color density of the printed part exceeds 1.2 ○: The color density of the printed part exceeds 0.9 and is 1.2 or less ×: The color density of the printed part is 0.9 or less

As is clear from the description in Table 1, by the method for producing a heat-sensitive recording material of the present invention, it is possible to obtain a heat-sensitive recording material that provides high printing density, has little red cast on the background, and has excellent production stability.

Claims (1)

A method for producing a heat-sensitive recording material having a heat-sensitive recording layer containing a dye precursor and a color developer on a support, the heat-sensitive recording layer containing 3,3-bis(1-n-butyl-) as a dye precursor. At least one selected from 2-methyl-3-indolyl) phthalide and 3-diethylamino-7-chlorofluoran, a maleic acid copolymer with an esterification degree of 15% or more as a dispersant for the dye precursor, and HLB. Wet-pulverize the dye precursor under conditions where the dye precursor contains a nonionic surfactant having a value of 10 or more, and the content of the nonionic surfactant relative to the dye precursor is 0.15% to 4% by mass. A method for producing a heat-sensitive recording material, characterized by: