JP6581527B2 - Method for producing thermal recording material - Google Patents

Description

  The present invention relates to a method for producing a heat-sensitive recording material, in which a high-print density is obtained and a heat-sensitive recording material excellent in production stability, plasticizer resistance, heat-resistant background fog resistance, and moisture and heat-resistant background fog resistance is obtained. It is.

  A heat-sensitive recording material generally comprises an electron-donating dye precursor (hereinafter referred to as a dye precursor) and an electron-accepting developer (hereinafter referred to as a developer) as main components on a support. A heat-sensitive recording layer is provided, and by heating with a thermal head, a thermal pen, laser light or the like, the dye precursor and the developer react instantaneously to obtain a recorded image. Such heat-sensitive recording materials have advantages such as the ability to obtain recorded images with a relatively simple device, ease of maintenance, and the absence of noise. Measurement recorders, facsimiles, printers, computer terminals It is used in a wide range of fields, such as label printing machines, boarding tickets, and ticket issuing machines. In recent years, in particular, thermal recordings such as receipts for gas, water, and electricity bills, ATM usage statements for financial institutions, various receipts, etc., financial recording sheets, thermal recording labels or thermal recording tags for POS systems, etc. Materials are being used and their applications are expanding rapidly.

  Regarding the POS system application, since the information on the products sold based on the barcode information is instantly read, a heat-sensitive recording material showing a high print density is desired. In order to satisfy this requirement, the dye precursor is used after being atomized by a wet pulverization method using a pulverizer such as a sand grinder, ball mill, attritor or bead mill. By using the atomized dye precursor, the dye precursor is easily melted by heating, and the melted dye precursor is mixed with the developer at the molecular level to promote the color development reaction.

  For POS system applications, not only black color but also blue color thermal recording material may be used. Blue-colored thermal recording materials tend to have poor storage characteristics compared to black-colored thermal recording materials, and are included in plastic when the image area of the thermal recording material comes into contact with plastics such as polyvinyl chloride. Due to the penetration of additives such as plasticizers, there is a problem that the image density is lowered and it is difficult to read, and the storability of the image part with respect to the plasticizer (hereinafter referred to as “plasticizer resistance”). There is a need for excellent thermal recording materials.

  Crystal violet lactone (3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide) is known as a dye precursor that develops a blue color. When crystal violet lactone is used as the dye precursor in the heat-sensitive recording layer, a high printing density is obtained, and a heat-sensitive recording material excellent in image portion preservability and background portion preservability is obtained, for example, -58950 (Patent Document 1), JP-A-2002-283740 (Patent Document 2), and JP-A-2003-182244 (Patent Document 3). However, when crystal violet lactone is wet pulverized, there is a problem in production stability such that the crystal violet lactone dispersion becomes a gel or the dispersoid settles and solidifies. Also, in recent years, the use environment of heat-sensitive recording materials has become more severe, but heat-sensitive recording materials using crystal violet lactone are resistant to heat-resistant background fog when exposed to high-temperature environments, and high-temperature and high-humidity environments. It was not satisfactory in terms of moisture and heat-resistant surface fog when exposed underneath.

  On the other hand, by using a maleic anhydride copolymer and polyvinyl alcohol as a dispersant when wet-pulverizing a heat-fusible component (sensitizer) having an appropriate low melting point for promoting color development or color development, It is known that the production stability and the storage stability of the background portion can be improved, and are described in, for example, Japanese Patent Application Laid-Open No. 2011-189525 (Patent Document 4). However, even with this technique, the heat-resistant recording material using crystal violet lactone cannot be sufficiently satisfied with respect to the moisture and heat-resistant background fogging, and an improvement has been demanded.

JP-A-11-58950 JP 2002-283740 A JP 2003-182244 A JP 2011-189525 A

  An object of the present invention is a method for producing a heat-sensitive recording material, in which a high print density is obtained, and a heat-sensitive recording material excellent in production stability, plasticizer resistance, heat-resistant background fog resistance, and moisture-and-heat background fog resistance is obtained. Is to provide.

A supporting lifting member, a manufacturing method of the heat-sensitive recording material having a thermosensitive recording layer containing a wet-milled dye precursor and wet milled developer, dye precursor is crystal violet lactone, the proportion of crystal violet lactone occupied in organic dispersoid during wet grinding of crystal violet lactone is at least 95 wt%, polyvinyl alcohol and using maleic anhydride copolymer, the dispersant total solid content as a dispersant ratio of maleic anhydride copolymer accounted for is 1 is 5 wt%, the heat-sensitive recording a volume average particle diameter of the dispersoid containing the crystal violet lactone, characterized in that wet-ground to 1.5μm or less Material manufacturing method.

  According to the present invention, there is provided a method for producing a heat-sensitive recording material, in which a high-print density is obtained and a heat-sensitive recording material excellent in production stability, plasticizer resistance, heat-resistant background fog resistance, and moisture-and-heat background fog resistance is obtained. can do.

  Hereinafter, the content of the present invention will be described more specifically.

  As described above, crystal violet lactone is known as a blue dye precursor, and a thermosensitive recording material using crystal violet lactone wet-pulverized as a dye precursor in the thermosensitive recording layer is excellent in print density. However, when the crystal violet lactone is wet pulverized to a volume average particle size of 1.5 μm or less, the crystal violet lactone dispersion liquid has a problem in production stability such as gelation or dispersoid sedimentation and solidification. Furthermore, the heat-sensitive recording material containing crystal violet lactone as a dye precursor in the heat-sensitive recording layer is not sufficiently satisfactory in terms of plasticizer resistance, heat-resistant background fog resistance, and heat-and-humidity background fog resistance. As a result of intensive studies on this problem, the present inventor has found that when wet-grinding crystal violet lactone, the proportion of crystal violet lactone in the organic dispersoid is 95% by mass or more, and polyvinyl alcohol and anhydrous maleic are used as dispersants. An acid copolymer is used, the proportion of maleic anhydride copolymer in the total solid content of the dispersant is 1 to 15% by mass, and the volume average particle diameter of the dispersoid containing the crystal violet lactone is 1. It has been found that by wet-grinding to 5 μm or less, a high-printing density can be obtained, and a heat-sensitive recording material excellent in production stability, plasticizer resistance, heat-resistant background fog resistance, and moisture-and-heat background fog resistance can be obtained. The present invention has been reached.

  The maleic anhydride copolymer in the present invention refers to a copolymer containing maleic anhydride as a monomer unit, and the comonomer includes α-alkylstyrene, isobutylene, ethylene, vinyl acetate, styrene, styrene benzyl methacrylate, vinyl toluene, Examples include maleic acid and methyl vinyl ether. Further, it may be esterified or a salt. Moreover, the maleic anhydride copolymer like these can also use 1 type, or 2 or more types as needed. In the above maleic anhydride copolymer, when a crystal violet lactone is wet pulverized using a styrene maleic anhydride copolymer ammonium salt or a styrene isobutylene maleic anhydride copolymer ammonium salt, the thermal recording is particularly excellent in production stability. Since a material can be obtained, it is more preferable. Commercially available maleic anhydride copolymers such as these can be used, such as those sold under the product names such as Polymeron 1318 from Arakawa Chemical Co., Ltd. and Orotan 165A from Dow Chemical Japan Co., Ltd. It is also possible to obtain and use.

  The polyvinyl alcohol in this invention points out the polymer comprised from vinyl alcohol as a monomer unit. Further, a functional group may be introduced into the side chain of polyvinyl alcohol, such as sulfonic acid-modified polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicone. Examples thereof include modified polyvinyl alcohol, nitrile modified polyvinyl alcohol, pyrrolidone modified polyvinyl alcohol, and butyral modified polyvinyl alcohol. Moreover, the polyvinyl alcohol like these can also use 1 type, or 2 or more types as needed. In the above polyvinyl alcohol, it is more preferable that crystal violet lactone is pulverized using sulfonic acid-modified polyvinyl alcohol or carboxylic acid-modified polyvinyl alcohol because a heat-sensitive recording material having particularly excellent production stability can be obtained.

  In the present invention, crystal violet lactone is preferably wet milled using water as a dispersion medium. Examples of the dispersion medium other than water include water-compatible organic solvents 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. In the present invention, the use of polyvinyl alcohol and a maleic anhydride copolymer as a dispersant means that the dispersion medium described above contains these compounds during wet pulverization.

  In the present invention, the crystal violet lactone is a dispersoid containing the crystal violet lactone by using a wet grinder such as a sand grinder, a ball mill, an attritor, or a bead mill so that the ratio of the crystal violet lactone in the organic dispersoid is 95% by mass or more. After being pulverized until the volume average particle diameter of the heat-sensitive recording layer becomes 1.5 μm or less, it is used for preparing a heat-sensitive layer coating solution for the heat-sensitive recording layer. Examples of other organic dispersoids that can be pulverized with the crystal violet lactone of the present invention include dye precursors other than crystal violet lactone, sensitizers, and storage stability improvers. When the proportion of crystal violet lactone in the organic dispersoid is in the range of less than 95% by mass, the moisture and heat resistant ground fogging property deteriorates. This is presumably because the color-forming reaction in the case of a heat-sensitive recording material is promoted by the compatibility effect of crystal violet lactone and other organic dispersoids, and the moisture and heat-resistant background fogging property deteriorates. Moreover, when the volume average particle diameter of the dispersoid containing the crystal violet lactone is larger than 1.5 μm, the print density and the plasticizer resistance are deteriorated. This is because, when a dye precursor having a large volume average particle size is used, the dye precursor is difficult to melt by heating, and the melted dye precursor is mixed with the developer at the molecular level to suppress the color reaction. Because. In addition, crystal violet lactone can also use a commercial item, for example, it can also obtain and use what is marketed by Yamada Chemical Industry Co., Ltd. by the product name, such as CVL. In addition, the volume average particle diameter in the present invention is a volume average particle diameter calculated from the particle size distribution obtained by the laser diffraction / scattering method. Specifically, the volume average particle diameter is manufactured by Microtrack Bell Co., Ltd. It can be measured by the track series, the LA series manufactured by Horiba, Ltd., the SALD series manufactured by Shimadzu, and the LS series manufactured by Beckman Coulter, Inc.

  In the present invention, when the crystal violet lactone is wet pulverized, the ratio of the maleic anhydride copolymer to the total solid content of the dispersant is 1 to 15% by mass. A more preferable ratio of the maleic anhydride copolymer is 1 to 5% by mass with respect to the total solid content of the dispersant. By adjusting to such a range, it is possible to obtain a heat-sensitive recording material that is particularly excellent in moisture and heat resistant background fogging.

  When a thermal recording material is produced by wet pulverizing crystal violet lactone with maleic anhydride copolymer and polyvinyl alcohol in the above-mentioned range, production stability, print density, plasticizer resistance, heat-resistant background fogging property, and The reason why a heat-sensitive recording material excellent in all of the moisture and heat resistant surface fogging properties is presumed as follows.

  When wet pulverizing crystal violet lactone using maleic anhydride copolymer as a dispersant, the affinity between maleic anhydride copolymer and crystal violet lactone is high, so crystal violet lactone is a maleic anhydride copolymer. Therefore, it becomes difficult to gel during wet pulverization, and even in the state of the crystal violet lactone dispersion after pulverization, the dispersoid hardly settles and the precipitate is less likely to coagulate. However, when the ratio of the maleic anhydride copolymer is higher than 15% by mass with respect to the total solid content of the dispersant, the moisture and heat resistant ground fog is deteriorated. This is because the above-mentioned affinity becomes too high, and crystal violet lactone is excessively pulverized, so that an active surface is generated, and crystal violet lactone fine particles alone are not mixed with the developer. It is thought to change color to blue. On the other hand, as a dispersant, maleic anhydride copolymer and polyvinyl alcohol are used in combination, and the ratio of the maleic anhydride copolymer to the total solid content of the dispersant is 1 to 15% by mass. When pulverized, an excellent protective film is formed by the interaction of maleic anhydride copolymer and polyvinyl alcohol on the surface of crystal violet lactone, which prevents gelation and prevents excessive pulverization. It is presumed that the moisture and heat resistant surface fogging property is obtained.

  In the present invention, when wet milling crystal violet lactone, other dispersants that can be used in addition to maleic anhydride copolymer and polyvinyl alcohol include starch or derivatives thereof, hydroxyethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose, carboxymethylcellulose. Cellulose derivatives such as gelatin, protein such as casein, acid neutralized product of chitosan, sodium alginate, polyvinylpyrrolidone, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, polyacrylic acid salt, polyacrylic acid Water-soluble polymer compounds such as sulfonate, dodecylbenzenesulfonate, dialkylsulfosuccinate, alkylnaphthalenesulfonate, alkyldiphenylether disulfonate Anionic low molecular surfactants such as fatty acid metal salts, nonionic surfactants such as acetylene glycol, and the like are exemplified, but the invention is not limited to these, and one or more kinds may be used as necessary. it can. In the present invention, the total solid content of the dispersant is preferably used in the range of 5 to 30% by mass with respect to the total amount of dispersoids including crystal violet lactone. A maleic anhydride copolymer and polyvinyl alcohol are preferable because they are particularly excellent in production stability when used in a range of 80% by mass or more based on the total solid content of the dispersant.

  In the present invention, when the crystal violet lactone is wet pulverized, the particle size of the medium to be used may be appropriately selected according to the desired particle size of the dispersoid to be obtained, but in order to promote sharp particle size distribution and atomization Are preferably beads having a diameter of 0.2 to 2.0 mm, and examples of the material include glass, zirconia, and alumina. The apparent filling rate of the bead particles in the grinding chamber is preferably 30 to 95% by volume, more preferably 40 to 90% by volume. Furthermore, it is desirable that the processing temperature when pulverizing crystal violet lactone is 50 ° C. or less. When processed at a temperature higher than 50 ° C., gelation may be caused.

As the dye precursor contained in the heat-sensitive recording layer constituting the heat-sensitive recording material of the present invention, in addition to the above-described crystal violet lactone, the dye precursor generally used for pressure-sensitive recording materials or heat-sensitive recording materials is contained. Can do. For example, 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, 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-dimethylaminopheny ) -4-Azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methyl) Indol-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-pentylamino) Phenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-di-n-hexylaminophenyl) -4-azaphthalide, 3- (1 -D Ru-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-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-hexyloxyaminophenol) ) -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-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-diethylamino) Phenyl) -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-methylindo) -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-diethyl) Minophenyl) -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-fe Nylindole-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-methyl) Indol-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-diethyla Nophenyl) -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-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-methylin) -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-die) Tilaminophenyl) -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-azaf Lido, 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-methylindo) -3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, 3- (4-dimethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethyl Aminophthalides, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylamino-2-n-hexyloxyphenyl) -4-azaphthalide, and the like, but are not limited thereto. It is not something. Moreover, these can be used individually or in mixture of 2 or more types. The proportion of crystal violet lactone is preferably 50% by mass or more, more preferably 75% by mass or more, based on the total solid content of the dye precursor used in the thermosensitive recording layer constituting the thermosensitive recording material of the present invention. . In order to obtain sufficient thermal response, the total amount of the dye precursor in the total solid content of the heat-sensitive recording layer preferably occupies 5 to 40% by mass.

  In the present invention, when the crystal violet lactone is wet pulverized, it can be wet pulverized with an inorganic dispersoid for the purpose of improving the heat-resistant background fogging resistance and the moist-and-heat-resistant fogging property. 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, water A halloy site etc. are illustrated. The proportion of the inorganic dispersoid in the total dispersoid is preferably less than 20% by mass. Thereby, a thermosensitive recording material excellent in production stability can be obtained. Furthermore, you may heat-process the dispersion liquid after grind | pulverizing crystal violet lactone in the range of 40-80 degreeC.

  As the developer used for the heat-sensitive recording layer constituting the heat-sensitive recording material of the present invention, various known ones can be used. 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, bis (3-allyl-4-hydroxy) Phenyl) sulfone, 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) 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, 2,2-bis (4-hydroxyphenyl) butyl acetate, 4,4′-thiobis (2-tert-butyl-5-methylphenol), dimethyl 4-hydroxyphthalate, benzyl 4-hydroxybenzoate, 4-hydroxy Methyl benzoate, 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) ) Benzenesulfone 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}, derivatives of N-phenylsulfonyl-N′-phenylurea, etc. Although it is mentioned, it is not limited to this. These may be used alone or in combination of two or more. Among them, dihydroxydiphenylsulfone derivatives such as 4,4′-dihydroxydiphenylsulfone and bis (3-allyl-4-hydroxyphenyl) sulfone, 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) Ureido] heat-sensitive recording material having excellent plasticizer resistance when a developer having a phenylureido structure in the molecule, such as diphenylsulfone and 3- (3-tosylureido) phenyl p-toluenesulfonate, is used. In particular, when 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone or 4,4′-dihydroxydiphenylsulfone is used, in addition to the above-described effects, In addition, it is particularly excellent for heat-resistant and moisture-resistant skin fog. It preferred for heat-sensitive recording material is obtained.

  The content ratio of the dye precursor and the developer is appropriately determined according to these types and combinations thereof, but the total amount of the developer may be 100 to 500% by mass with respect to the total amount of the dye precursor. Preferably, it is 150-350 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 the color development reaction in order to further improve the thermal response. In this case, the sensitizer is preferably a compound having a melting point of 60 to 180 ° C. Specific examples of the sensitizer 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, methylene bis stearic acid Amide, methylol stearamide, N-stearyl urea, 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, terephthalic acid Dimethyl, dibenzyl terephthalate, benzenesulfonic acid phenyl ester, bis (4-allyloxyphenyl) sulfone, 1,2-bis (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 4-acetylacetophenone, acetoacetic acid Examples include, but are not limited to, anilides and fatty acid anilides. Such sensitizers can be used alone or in combination of two or more. Moreover, in order to obtain sufficient thermal responsiveness, it is preferable that the total amount of the sensitizer occupies 5 to 50% by mass in the total solid content of the thermosensitive recording layer.

  Further, the heat-sensitive recording layer can further contain a preservability improver such as a hindered phenol compound, a hindered amine compound, a phosphate ester derivative, or a benzotriazole derivative, as necessary.

  Specific examples of hindered phenol compounds used in the heat-sensitive recording layer in the present invention as needed 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-2-methylphenyl) butane, 1,1,3-tris (3-cyclohexyl-4 -Hydroxy-5-methylphenyl) butane, 1,1,3-tris (3-phenyl-4-hydroxyphenyl) butane, 1,1,3-to (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-di-) Methylphenol), 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 and the like. However, it is not limited thereto, and these compounds may be used alone or in combination of two or more as required.

  Specific examples of the hindered amine compound used in the heat-sensitive recording layer in the present invention as needed include bis (2,2,6,6, -tetramethyl-4-piperidyl) sebacate and 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, and the like. These compounds may be used alone or in combination of two or more as required.

  Specific examples of the phosphate ester derivative used as necessary for the heat-sensitive recording layer in 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, 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 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate sodium salt, 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate calcium salt, 2,2 Mention of zinc salt of '-methylenebis (4,6-di-tert-butylphenyl) phosphate, ammonium salt of 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, potassium salt, etc. However, it is not limited to this, and these compounds can be used alone or in combination of two or more as required.

  Specific examples of the benzotriazole derivatives used as necessary for the heat-sensitive recording layer in 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-ter -Butylphenyl) -5-tert-butylbenzotriazole, 2- (2-hydroxy-3-dodecyl-5-methylphenyl) benzotriazole, 2- [2-hydroxy-4- (2-ethylhexyl) oxyphenyl] benzo Triazole, condensate with methyl-3- (3-tert-butyl-5-benzotriazolyl-4-hydroxyphenyl) propionate-polyethylene glycol (molecular weight about 300), 5-tert-butyl-3- (5- Chloro-benzotriazolyl) -4-hydroxybenzene-octylpropionate, 2- (2-hydroxy-3-sec-butyl-5-tert-butylphenyl) -5-tert-butylbenzotriazole, 2- (2 -Hydroxy-4-methoxy-5-sulfophenyl) benzotriazo 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), 2,2'-isopropylidenebis (4-methyl-6-benzoto) Reazolylphenol), 2,2'-isopropylidenebis [4- (1,1,3,3-tetramethylbutyl) -6-benzotriazolylphenol], 2,2'-octylidenebis [4-methyl -6- (5-methylbenzotriazolyl) phenol] and the like, but is not limited thereto, and these compounds may be used alone or in combination of two or more as required. can do.

  The amount of hindered phenol compound, hindered amine compound, phosphate ester derivative, or benzotriazole derivative used as necessary for the heat-sensitive recording layer in the present invention is a total amount of 5 to 5% of the dye precursor. 100% by mass is a preferable range, and a more preferable range is 10 to 80% by mass.

  In the present invention, various pigments can be used in the heat-sensitive recording layer depending on the purpose such as improvement of sticking resistance and whiteness. 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, hydrous halloysite, etc. However, it is not limited to these, and one type or two or more types can be used as necessary. The pigment is preferably used in the range of 10 to 50% by mass in the total solid content of the heat-sensitive recording layer.

  In the present invention, various water-soluble polymer compounds or water-dispersible polymer compounds used in ordinary coating can be used as the binder of the heat-sensitive recording layer. Specifically, starch or derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxypropylcellulose, methylcellulose, ethylcellulose, 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, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, styrene / maleic anhydride Alkali salt of acid copolymer, alkali salt of ethylene / maleic anhydride copolymer, alkali salt of isobutylene / maleic anhydride copolymer Water-soluble polymer compound, and styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, acrylonitrile / butadiene / styrene terpolymer, polyvinyl acetate, vinyl acetate / acrylic Examples include acid ester copolymers, ethylene / vinyl acetate copolymers, polyacrylic acid esters, styrene / acrylic acid ester copolymers, and water-dispersible polymer compounds such as polyurethane, but are not limited thereto. None, or one or more can be used as necessary. The binder is preferably used in the range of 5 to 20% by mass in the total solid content of the thermosensitive recording layer.

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

  Various components other than crystal violet lactone contained in the heat-sensitive recording layer constituting the heat-sensitive recording material of the present invention, such as dye precursors other than the above-described crystal violet lactone, developer, sensitizer, preservability improver, pigment The lubricant, wax and the like are preferably used for adjusting the heat-sensitive recording layer coating solution after being made into a dispersion. The dispersion is obtained by a method of dry pulverizing the compound constituting the color forming component and dispersing it in the dispersion medium, or a method of mixing the compound constituting the color forming component in the dispersion medium and wet pulverizing. In the present invention, each of the developer and the sensitizer is used alone or together, water is used as a dispersion medium, and the volume average particle diameter is adjusted together with the dispersant by various wet pulverizers such as a sand grinder, a ball mill, an attritor, and a bead mill. Preferably, it is preferably used for the preparation of a heat-sensitive recording layer coating liquid after pulverizing to 0.1 to 5.0 μm to form fine particles. Dye precursors other than crystal violet lactone use water as a dispersion medium separately from the developer, and use a wet grinder such as a sand grinder, ball mill, attritor, or bead mill together with the dispersant to obtain a volume average particle size. Is preferably pulverized to 0.1 to 5.0 μm to form fine particles and then used for the preparation of a heat-sensitive recording layer coating solution.

  In the present invention, as a dispersant used when dispersing various components other than crystal violet lactone contained in the heat-sensitive recording layer, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol , Carboxyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, epoxy-modified polyvinyl alcohol, etc., starch or derivatives thereof, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl Cellulose derivatives such as cellulose, ethyl cellulose, carboxymethyl cellulose, and zera Proteins such as ethanol and casein, acid neutralized products of chitosan, sodium alginate, polyvinylpyrrolidone, diisobutylene / maleic anhydride copolymer salt, styrene / isobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer Compound salts, ethylene / acrylic acid copolymer salts, styrene / acrylic acid copolymer salts, water-soluble polymer compounds such as polyacrylates and polyacrylsulfonates, dodecylbenzenesulfonate, dialkylsulfosuccinates, Anionic low molecular surfactants such as alkyl naphthalene sulfonates, alkyl diphenyl ether disulfonates, fatty acid metal salts, and the like, and nonionic surfactants such as acetylene glycol, are not limited to these. Use one or more if necessary It is possible. It is preferable that a dispersing agent is 0.5-30 mass% with respect to various components.

In the present invention, the solid content coating amount of the heat-sensitive recording layer is preferably ² to 15 g / m ² . If it is less than 2 g / m ² , the print density in the low thermal energy region may be low, and if it is more than 15 g / m ^{2, the} various performance improvements of the thermal recording layer will reach saturation, and production at the time of coating the thermal recording layer. Efficiency may be reduced.

  In the present invention, between the support and the heat-sensitive recording layer, for the purpose of improving the smoothness and heat insulation of the support, or suppressing various components contained in the support from adversely affecting the heat-sensitive recording layer. For the purpose, it is preferable to have an undercoat layer. The undercoat layer contains a binder and various inorganic and organic pigments, and can contain hollow particles and the like. Other auxiliary agents contained in the undercoat layer include lubricants, antifoaming agents, surfactants, preservatives, fluorescent brighteners, dispersants, thickeners, colorants, antistatic agents, crosslinking agents, etc. A well-known thing is mentioned.

  Examples of the pigment contained in the undercoat layer of the present invention include talc, kaolin, calcined kaolin, clay, calcined clay, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, magnesium silicate, zinc oxide, aluminum oxide, and hydroxide. Inorganic pigments such as aluminum, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, calcium silicate, diatomaceous earth, colloidal silica, melamine resin, urea-formaldehyde resin, polyethylene, polystyrene, ethylene-vinyl acetate, styrene Organic pigments such as microballs, nylon powder, polyethylene powder, urea-formalin resin filler, styrene-methacrylic acid copolymer resin, polystyrene resin, raw starch particles, etc., can be used alone or in combination of two or more. It can be, but not limited to, also one optionally or may be used two or more. Silicate minerals such as talc, kaolin and calcined kaolin are particularly preferred. The pigment content in the undercoat layer is preferably 60 to 90% by mass relative to the total solid content of the undercoat layer.

  In the undercoat layer, various water-soluble polymer compounds or water-dispersible polymer compounds used in ordinary coating can be used as a binder. Specific examples thereof include, for example, starch or derivatives thereof, 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, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, alkali salt of styrene / maleic anhydride copolymer, ethylene / Water-soluble polymer compounds such as alkali salt of maleic / maleic anhydride copolymer, alkali salt of isobutylene / maleic anhydride copolymer, and styrene / butadiene copolymer Polymer, Acrylonitrile / butadiene copolymer, Methyl acrylate / Butadiene copolymer, Acrylonitrile / butadiene / styrene terpolymer, Polyvinyl acetate, Vinyl acetate / Acrylate ester copolymer, Ethylene / vinyl acetate copolymer , Water dispersible polymer compounds such as polyacrylic acid esters, styrene / acrylic acid ester copolymers, and polyurethanes, but are not limited thereto. One or two or more binders can be used. It is preferable that the usage-amount of a binder shall be 10-30 mass% with respect to the total solid amount of an undercoat layer.

  In the present invention, when various components contained in the undercoat layer are mixed and stirred using water or the like as a medium, a dispersant can be used to improve dispersibility. Dispersants used include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, polyvinyl alcohols such as modified polyvinyl alcohol, starch or derivatives thereof, and cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose, carboxymethyl cellulose, etc. Proteins such as gelatin and casein, acid neutralized products of chitosan, sodium alginate, polyvinylpyrrolidone, diisobutylene / maleic anhydride copolymer salt, styrene / isobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer Polymer salts, ethylene / acrylic acid copolymer salts, styrene / acrylic acid copolymer salts, water-soluble polymer compounds such as polyacrylates and polyacrylsulfonates, Benzene sulfonate, dialkyl sulfosuccinate, alkyl naphthalene sulfonate, alkyl diphenyl ether disulfonate, anionic low molecular surfactants such as fatty acid metal salts, nonionic surfactants such as acetylene glycol, sodium hexametaphosphate, etc. Although it is mentioned, it is not limited to these, Moreover, 1 type, or 2 or more types can be used as needed. It is preferable that a dispersing agent is 0.1-30 mass% with respect to various components.

In the present invention, the undercoat layer is prepared by mixing and stirring a pigment, a binder and an auxiliary agent together with water or the like as a medium. The solid coating amount is preferably 1 to 30 g. / M ² , more preferably 4 to 20 g / m ² , by coating and drying on the support.

  In the present invention, the support may be any of transparent, translucent, and opaque. Paper, various nonwoven fabrics, woven fabric, synthetic resin film, synthetic resin laminated paper, synthetic paper, metal foil, ceramic paper, A glass plate or the like, or a composite sheet combining them can be arbitrarily used depending on the purpose.

  In the present invention, when a paper support is used as the support, the pulp used when producing the paper support is as follows: softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp ( NBSP), hardwood bleached sulfite pulp (LBSP), TMP, CTMP, BCTMP, GP, RGP, CGP, cotton pulp, etc., various waste paper pulps such as DIP, and non-wood fibers such as kenaf. It is not limited and 1 type, or 2 or more types can be used as needed.

  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 calcium carbonate, talc, kaolin, calcined kaolin, amorphous silica, illite, clay, calcined clay, inorganic fillers such as titanium dioxide, and organic fillers such as plastic pigments. However, it is not limited to these, and 1 type, or 2 or more types can be used as needed.

In the present invention, when a paper support is used as the support, the ash content of the paper support is preferably 5 to 25% by mass, more preferably 7 to 20% by mass. If it is less than 5% by mass, it is difficult to obtain good formation and smoothness. When the amount exceeds 25% by mass, the smoothness is saturated, while the size and surface strength of the base paper are lowered, and the paper breakage is likely to occur when the undercoat layer or the heat-sensitive recording layer is applied. 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 the support, the sizing agent for internal addition (internal sizing agent) in the paper support is used in the case of acidic papermaking, a reinforced rosin sizing agent, an emulsion. When the sizing agent, synthetic sizing agent, etc. are neutral papermaking, alkyl ketene dimer, alkenyl succinic anhydride, higher fatty acid, neutral rosin sizing agent, etc. can be included, but are not limited thereto. It is not a thing and 1 type, or 2 or more types can be used as needed. As sizing agents for external addition (external sizing agents), cationic polymers such as styrene maleic acid copolymer resins and styrene acrylic acid copolymer resins, anionic polymers, styrene polymers, and isocyanates are used. Anionic low molecular weight compounds such as saponified alkyd resins such as rosin, tall oil and phthalic acid, saponified petroleum resin and rosin, α-olefin-maleic acid copolymer resin, acrylic Examples include acid ester-acrylic acid copolymer resins and alkyl ketene dimers, but are not limited thereto, and one or more kinds can be used as necessary. In addition to the sizing agent, pulp and various fillers described above, the paper support is a nonionic, cationic, anionic or amphoteric yield improver, drainage improver, paper strength enhancer and the like. An internal additive for papermaking can be added as necessary. Specific examples of yield improvers, drainage improvers, and paper strength enhancers include, for example, polyvalent metal compounds such as aluminum (specifically, aluminum sulfate, aluminum chloride, sodium aluminate, basic aluminum compounds, etc.) Amorphous silica, various starches, urea resin, polyamide / polyamine resin, polyethyleneimine, polyacrylamide, polyamine, polyvinyl alcohol, polyethylene oxide and the like can be exemplified.

  In the present invention, a protective layer is provided on the heat-sensitive recording layer for the purpose of improving the sticking resistance, preventing scratches, improving the water resistance, and improving the plasticizer resistance and chemical resistance of the heat-sensitive color image. Can do. In the protective layer, various adhesives, inorganic pigments, various curing agents, various crosslinking agents, ultraviolet absorbers and the like can be contained, and a single layer or two or more layers can be laminated. Further, 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 coating amount of the protective layer is preferably 0.5 to 5 g / m ² . When the amount is less than 0.5 g / m ² , various performances of the protective layer are not exhibited, and when the amount is more than 5 g / m ² , the loss of thermal energy reaching the thermal recording layer from the thermal head increases, resulting in a decrease in color developability. There is a case.

  In the present invention, a backcoat layer may be provided on the surface opposite to the surface on which the heat-sensitive recording layer is provided for the purpose of preventing curling, preventing charging, etc., and further, adhesive processing or the like may be performed. Further, a layer containing a material capable of recording information electrically, magnetically, or optically, an ink jet recording layer, or the like may be provided on the surface on which the thermosensitive recording layer is provided or on the opposite surface. In addition, in order to perform printing with laser light, a photothermal conversion material can be contained in an arbitrary layer and support in the thermosensitive recording material.

  The formation method of each layer in the present invention is not particularly limited, and can be formed by using a well-known technique. For example, a coating apparatus such as an air knife coater, various blade coaters, various bar coaters, and various curtain coaters. In addition, various printing methods such as a planographic plate, a relief plate, an intaglio plate, a flexo, a gravure, and a screen can be used. Furthermore, in order to improve the surface smoothness, various known techniques in the production of heat-sensitive recording materials can be used, such as the use of machines such as a machine calendar, super calendar, gloss calendar, and brushing.

  EXAMPLES 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 noted,% and parts are all based on mass. The coating amount is an absolutely dry coating amount.

Example 1
(1) Preparation of undercoat layer coating solution The following composition was mixed and sufficiently stirred to obtain an undercoat layer coating solution.
20% styrene-butadiene latex 75 parts 20% urea-modified phosphate esterified starch aqueous solution 25 parts calcined kaolin 100 parts 10% ammonium polyacrylate aqueous solution 5 parts sodium hexametaphosphate 0.5 parts water 199.5 parts

(2) Formation of undercoat layer The undercoat layer coating solution prepared in (1) above was coated on a fine paper having a basis weight of 50 g / m ² and a hue b * value based on JIS P8150 of 1.8. The undercoat layer was formed on the paper support by coating and drying so that the work amount was 10 g / m ² . In addition, the hue b * value based on JIS P8150 of the produced undercoat paper was 1.8.

(3) Preparation of Dye Precursor Dispersion Mix the following ingredients and use SYNOL ENTERPRISES DYNO-MILL MULTI LAB and 0.6 mm diameter glass beads at a bead particle filling rate of 70% by volume in the grinding chamber. The dispersion was wet pulverized until the volume average particle diameter of the dispersoid became 0.8 μm under the condition of the liquid temperature of 20 ° C. to obtain a dye precursor dispersion.
100 parts of crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
99 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsenx L-3266)
1 part aqueous solution of ammonium salt of 10% styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industry Co., Ltd., diluted with polymeron 1318 with water)
160 parts of water

(4) Preparation of developer dispersion The following composition was mixed, and DYNO-MILL MULTI LAB made by Shinmaru Enterprises Co., Ltd. and 0.6 mm diameter glass beads were used at a bead particle filling rate of 80% by volume in the grinding chamber. Then, the dispersion liquid was wet pulverized until the volume average particle diameter of the developer reached 0.8 μm under the condition of a liquid temperature of 20 ° C. to obtain a developer dispersion.
4,4'-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl sulfone (Kemipro Kasei Co., Ltd., UU) 200 parts 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 200 parts water 330 parts

(5) Preparation of pigment dispersion The following composition was mixed and stirred to obtain a pigment dispersion.
Aluminum hydroxide 160 parts Amorphous silica 160 parts 10% ammonium polyacrylate aqueous solution 32 parts Water 720 parts

(6) Preparation of thermal recording layer coating solution The following ingredients were mixed and sufficiently stirred to obtain a thermal recording layer coating solution.
Dye precursor dispersion 360 parts Developer dispersion 730 parts Pigment dispersion 1072 parts 10% fully saponified polyvinyl alcohol aqueous solution 1200 parts 50% zinc stearate aqueous dispersion 160 parts

(7) Production of thermosensitive recording material On the undercoat layer formed on the paper support in (2) above, the thermosensitive recording layer coating solution prepared in (6) above was applied in a solid content amount of 3 g / m. After coating and drying so as to be ² , calendering was performed to produce the thermosensitive recording material of Example 1. The Beck smoothness of the heat-sensitive recording material after the calendar process was 350 seconds.

Example 2
A thermosensitive recording material of Example 2 was produced in the same manner as in Example 1 except that the formulation was changed as follows in the preparation of (3) the dye precursor dispersion of Example 1.
100 parts of crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
95 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsenx L-3266)
5 parts aqueous solution of ammonium salt of 10% styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industry Co., Ltd., diluted with polymeron 1318 with water)
160 parts of water

Reference example 1
A thermosensitive recording material of Reference Example 1 was prepared in the same manner as in Example 1 except that the formulation was changed as follows in the preparation of (3) the dye precursor dispersion of Example 1 .
100 parts of crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
90 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsenx L-3266)
10 parts of 10% aqueous solution of ammonium salt of styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industries, diluted with water of polymeron 1318)
160 parts of water

Reference example 2
A thermosensitive recording material of Reference Example 2 was prepared in the same manner as in Example 1 except that the formulation was changed as follows in the preparation of (3) the dye precursor dispersion of Example 1.
100 parts of crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
85 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsenx L-3266)
15 parts of 10% aqueous solution of ammonium salt of styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industries, Polymeron 1318 diluted with water)
160 parts of water

Example 5
In the preparation of the dye precursor dispersion liquid of Example 2 (3), instead of 5 parts of an aqueous 10% styrene maleic anhydride copolymer ammonium salt solution (produced by Arakawa Chemical Co., Ltd., polymeron 1318 diluted with water), Thermal recording of Example 5 in the same manner as in Example 2 except that 5 parts of 10% aqueous styrene isobutylene maleic anhydride copolymer ammonium salt solution (manufactured by Dow Chemical Japan Co., Ltd., orotan 165A diluted with water) was used. The material was made.

Example 6
A thermosensitive recording material of Example 6 was produced in the same manner as in Example 2 except that the formulation was changed as follows in the preparation of (3) the dye precursor dispersion of Example 2.
100 parts of crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
95 parts of 10% carboxylic acid-modified polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., 3-86SD)
5 parts aqueous solution of ammonium salt of 10% styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industry Co., Ltd., diluted with polymeron 1318 with water)
160 parts of water

Example 7
In Example 2 (3) Preparation of dye precursor dispersion and (6) Preparation of heat-sensitive recording layer coating liquid, Example 7 was used in the same manner as Example 2 except that the formulation was changed as follows. A heat-sensitive recording material was prepared.
(3) 100 parts of dye precursor dispersion crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
Diphenylsulfone 5 parts 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 95 parts (Nippon Gosei Chemical Co., Ltd., Gohsenx L-3266)
5 parts aqueous solution of ammonium salt of 10% styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industry Co., Ltd., diluted with polymeron 1318 with water)
170 parts of water (6) Thermosensitive recording layer coating solution The following ingredients were mixed and sufficiently stirred to obtain a thermosensitive recording layer coating solution.
Dye precursor dispersion 375 parts Developer dispersion 730 parts Pigment dispersion 1072 parts 10% fully saponified polyvinyl alcohol aqueous solution 1200 parts 50% zinc stearate aqueous dispersion 160 parts

Example 8
In the preparation of the developer dispersion of (4) in Example 2, 200 parts of 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl sulfone (Kemipro Kasei Co., Ltd., UU) Instead, a heat-sensitive recording material of Example 8 was obtained in the same manner as in Example 2 except that 200 parts of 4,4′-dihydroxydiphenylsulfone was used.

Example 9
In Example 2 (3) Preparation of dye precursor dispersion and (6) Preparation of thermosensitive recording layer coating liquid, Example 9 was used in the same manner as Example 2 except that the formulation was changed as follows. A heat-sensitive recording material was prepared.
(3) 100 parts of dye precursor dispersion crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
20 parts of magnesium silicate (Tomita Pharmaceutical Co., Ltd., Tomita-AD600)
95 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsenx L-3266)
5 parts aqueous solution of ammonium salt of 10% styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industry Co., Ltd., diluted with polymeron 1318 with water)
Water 205 parts (6) Thermosensitive recording layer coating solution The following ingredients were mixed and sufficiently stirred to obtain a thermosensitive recording layer coating solution.
Dye precursor dispersion 425 parts Developer dispersion 730 parts Pigment dispersion 1072 parts 10% fully saponified polyvinyl alcohol aqueous solution 1200 parts 50% zinc stearate aqueous dispersion 160 parts

Comparative Example 1
In the preparation of the dye precursor dispersion liquid of Example 1 (3), the composition was changed as follows and wet pulverization was attempted. However, the dye precursor dispersion liquid was gelled and a heat-sensitive recording material could not be obtained. It was.
100 parts of crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
100 parts of 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsenx L-3266)
160 parts of water

Comparative Example 2
A thermosensitive recording material of Comparative Example 2 was produced in the same manner as in Example 1 except that the formulation was changed as follows in the preparation of (3) the dye precursor dispersion of Example 1.
100 parts of crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
80 parts of a 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsenx L-3266)
20 parts aqueous solution of ammonium salt of 10% styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industry Co., Ltd., diluted with polymeron 1318 with water)
160 parts of water

Comparative Example 3
A thermosensitive recording material of Comparative Example 3 was produced in the same manner as in Example 1 except that the formulation was changed as follows in the preparation of (3) the dye precursor dispersion of Example 1.
100 parts of crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
100 parts of 10% aqueous solution of ammonium salt of styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industries, Polymeron 1318 diluted with water)
160 parts of water

Comparative Example 4
In the preparation of the dye precursor dispersion liquid of Example 2 (3), instead of 5 parts of an aqueous 10% styrene maleic anhydride copolymer ammonium salt solution (produced by Arakawa Chemical Co., Ltd., polymeron 1318 diluted with water), An attempt was made to wet pulverize using 5 parts of 10% aqueous solution of ammonium polyacrylate (manufactured by BASF, Dispex A40 diluted with water), but the dye precursor dispersion became a gel and a thermosensitive recording material could be obtained. There wasn't.

Comparative Example 5
In the preparation of the dye precursor dispersion liquid of Example 2 (3), instead of 5 parts of an aqueous 10% styrene maleic anhydride copolymer ammonium salt solution (produced by Arakawa Chemical Co., Ltd., polymeron 1318 diluted with water), An attempt was made to wet pulverize with 5 parts of a 10% aqueous solution of styrene acrylic solution (manufactured by Nippon Synthetic Chemical Co., Ltd., MoDM DM60 diluted with water), but the dye precursor dispersion may gel and obtain a thermosensitive recording material. could not.

Comparative Example 6
In the preparation of the dye precursor dispersion liquid of Example 2 (3), instead of 95 parts of a 10% sulfonic acid-modified polyvinyl alcohol aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., GOHSEX L-3266), 10% ammonium polyacrylate An attempt was made to wet pulverize using 95 parts of an aqueous solution (manufactured by BASF, Dispex A40 diluted with water), but the dye precursor dispersion gelled and a thermosensitive recording material could not be obtained.

Comparative Example 7
In the preparation of Example 3 (3) dye precursor dispersion and (6) thermosensitive recording layer coating liquid, the same as in Example 2 except that the formulation was changed as follows. A heat-sensitive recording material was prepared.
(3) 100 parts of dye precursor dispersion crystal violet lactone (manufactured by Yamada Chemical Co., Ltd., CVL)
Diphenylsulfone 10 parts 10% sulfonic acid-modified polyvinyl alcohol aqueous solution 95 parts (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Gohsenx L-3266)
5 parts aqueous solution of ammonium salt of 10% styrene maleic anhydride copolymer (manufactured by Arakawa Chemical Industry Co., Ltd., diluted with polymeron 1318 with water)
180 parts of water (6) Thermosensitive recording layer coating solution The following ingredients were mixed and sufficiently stirred to obtain a thermosensitive recording layer coating solution.
Dye precursor dispersion 390 parts Developer dispersion 730 parts Pigment dispersion 1072 parts 10% fully saponified polyvinyl alcohol aqueous solution 1200 parts 50% zinc stearate aqueous dispersion 160 parts

The heat-sensitive recording materials produced in Examples 1 and 2, 5 to 9, Reference Examples 1 and 2 and Comparative Examples 1 to 7 were subjected to the following evaluation. The results are shown in Table 1. In Table 1, the hatched portion means that the heat-sensitive recording material could not be produced along with the gelation of the dye precursor dispersion, and this item could not be evaluated.

[Manufacturing stability]
The state when the dye precursor dispersion was prepared was observed and evaluated according to the following criteria.
○: Gelation does not occur during and after pulverization of the dye precursor dispersion.
Δ: Gelation does not occur during and after pulverization of the dye precursor dispersion, but the discoloration of the dye precursor dispersion after pulverization is strong.
X: Gelled during or after pulverization of the dye precursor dispersion.

[Print density]
For each of the produced heat-sensitive recording materials, a blue solid was printed with an applied energy of 0.74 mJ / dot using a facsimile testing machine 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 with a densitometer (manufactured by GretagMacbeth, RD19) (cyan mode) in an environment of 23 ° C. and 50% RH, and evaluated according to the following criteria.
A: The color density of the printed part is 1.0 or more. B: The color density of the printed part is 0.7 or more and less than 1.0. X: The color density of the printed part is less than 0.7.

[Plasticizer resistance]
For each of the produced heat-sensitive recording materials, a blue solid was printed with an applied energy of 0.74 mJ / dot using a facsimile testing machine TH-PMD manufactured by Okura Electric Co., Ltd. in an environment of 23 ° C. and 50% RH. The printed surface of each heat-sensitive recording material obtained by printing is brought into close contact with a dialup NEW GSW manufactured by Mitsubishi Plastics, and placed in an environment of 23 ° C. and 50% RH for 24 hours, and then the dialup NEW GSW is removed. The optical density of the image area was measured with a densitometer (manufactured by GretagMacbeth, RD19) (cyan mode) in an environment of 23 ° C. and 50% RH, and evaluated according to the following criteria.
(Residual rate,%) = (Optical density after plasticizer treatment) / (Untreated optical density) × 100
A: Image portion remaining rate is 80% or more. B: Image portion remaining rate is 60% or more and less than 80%. X: Image portion remaining rate is less than 60%.

[Heat resistant skin fogging]
For each of the produced thermal recording materials, after being placed in an environment of 60 ° C. and 5% RH for 24 hours, the hue b * value of the background portion is measured based on JIS P8150 in an environment of 23 ° C. and 50% RH. And evaluated according to the following criteria.
A: The b * value of the background portion is larger than -1.6 .
○: The b * value of the background portion is greater than −2.0 and −1.6 or less.
×: b * value of the background portion is −2.0 or less.

[Moisture and heat resistant skin fogging]
For each of the produced thermal recording materials, after being placed in an environment of 50 ° C. and 95% RH for 24 hours, the hue b * value of the background portion is measured based on JIS P8150 in an environment of 23 ° C. and 50% RH. And evaluated according to the following criteria.
A: The b * value of the background portion is larger than -1.6 .
○: The b * value of the background portion is greater than −2.0 and −1.6 or less.
×: b * value of the background portion is −2.0 or less.

  As is clear from the description in Table 1, the production method of the present invention provides a high printing density, and thermal recording excellent in production stability, plasticizer resistance, heat-resistant background fog resistance, and moisture-and-heat background fog resistance. A material is obtained.

Claims (1)

On a support, a manufacturing method of the heat-sensitive recording material having a thermosensitive recording layer containing a wet-milled dye precursor and wet milled developer, dye precursor is Crystal Violet Lactone, Crystal The proportion of crystal violet lactone in the organic dispersoid during the wet pulverization of violet lactone is 95% by mass or more, and polyvinyl alcohol and maleic anhydride copolymer are used as a dispersant. The heat-sensitive recording material is characterized in that the proportion of maleic anhydride copolymer is 1 to 5 % by mass, and wet pulverization is performed until the volume average particle size of the dispersoid containing the crystal violet lactone is 1.5 μm or less. Manufacturing method.