JP6011466B2 - 2-color thermal recording medium - Google Patents

Description

  The present invention utilizes a reaction between a dye precursor and a developer, and a portion colored by thermal energy from a thermal head, a thermal stamp or the like shows a yellow color tone and a black color tone, The present invention relates to a two-color heat-sensitive recording material having a high color density in color tone and excellent color separation of a recording portion.

  A heat-sensitive recording material is known which uses a reaction between a dye precursor and a developer and causes both substances to react with each other by thermal energy to obtain a recorded image. Such a heat-sensitive recording material is relatively inexpensive, and since the recording device is compact and easy to maintain, it is used not only as a recording medium for facsimiles and printers but also in a wide range of fields.

  However, the performance and quality required with the expansion of applications are diversifying, and not only a single color tone, but also a plurality of color tone, the recording density is high in each color tone, and the recording portion There is a need for a multicolor thermal recording material excellent in color separation.

  In particular, a two-color thermosensitive recording medium having a yellow color tone is highly demanded for practical use because it can enhance characters and figures by making use of the vivid yellow color tone.

  As a multicolor thermosensitive recording medium having a yellow coloring color tone, only the low temperature coloring layer develops color by the low temperature coloring operation, and in the high temperature coloring operation, it has an erasing effect on the coloring system of the low temperature coloring layer. The colorant acts to obtain a color of only the high-temperature color-developing layer (see Patent Documents 1 to 3), and two heat-sensitive recording color-developing layers that develop colors of different colors are stacked and discriminated by applying different amounts of heat 2 Although it has been proposed to obtain a color (see Patent Document 4), the present situation is that a satisfactory result is not necessarily obtained.

JP-A-5-185715 Japanese Patent Laid-Open No. 5-193254 JP-A-5-270126 JP 2001-105744 A

  The main object of the present invention is to provide a two-color thermal recording material that exhibits a yellow color tone and a black color tone, has a high color density in each color tone, and is excellent in color separation of the recording portion. Objective.

  As a result of intensive studies, the present inventors have a first dye precursor having a pyridine skeleton in the molecular structure represented by the following general formula (1) as a dye precursor, and a melting point of 200 ° C. or higher. By including the second dye precursor that develops a black color tone, the above-mentioned problems have been solved. That is, the present invention relates to the following two-color thermal recording material.

  Item 1: A heat-sensitive recording material comprising a heat-sensitive recording layer containing a dye precursor and a developer on a support, wherein the dye precursor has a molecular structure represented by the following general formula (1) as pyridine. A two-color thermal recording comprising a first dye precursor having a skeleton and a second dye precursor that develops a black color tone, wherein the second dye precursor has a melting point of 200 ° C. or higher. body.

（式中、Ｒ^１及びＲ^２は水素原子もしくは炭素数１〜８のアルコキシ基を表し、Ｒ^３は炭素数１〜４のアルキル基を表す。Ｒ^１及びＲ^２は同一であっても、異なっていてもよい。）

(In the formula, R ¹ and R ² represent a hydrogen atom or an alkoxy group having 1 to 8 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms. Even if R ¹ and R ² are the same, May be different.)

  Item 2: The two-color heat-sensitive recording material according to Item 1, wherein the first dye precursor and the second dye precursor are both contained in the heat-sensitive recording layer in the form of solid dispersed fine particles.

  Item 3: The heat-sensitive recording layer has a multilayer structure composed of at least a first heat-sensitive recording layer and a second heat-sensitive recording layer, the first heat-sensitive recording layer contains a first dye precursor, and the second heat-sensitive recording layer Item 3. The two-color thermal recording material according to Item 1 or 2, wherein the recording layer contains a second dye precursor.

  Item 4: The total content of the dye precursor that develops a black color tone including the second dye precursor is more than 0.5 times and more than 2.5 times the content of the first dye precursor Item 2. The two-color thermosensitive recording material according to any one of Items 1 to 3, which is a small range.

  Item 5: The first dye precursor having the pyridine skeleton is 4- [2- (2-butoxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2- ( 2-pentyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2- (2-hexyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N- Dimethylbenzenamine, 4- [2- (2-octyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6-bis (2-butoxyphenyl) -4 -Pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6-bis (2-pentyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine, 4- [ , 6-Bis (2-hexyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine and 4- [2,6-bis (2-octyloxyphenyl) -4-pyridinyl] -N, N Item 5. The two-color thermal recording material according to any one of Items 1 to 4, which is at least one selected from the group consisting of dimethylbenzenamine.

  Item 6: The dynamic color density obtained by printing the two-color thermosensitive recording medium with an applied energy of 0.66 mJ / dot by a thermal head is 1.00 or more, and the applied thermal energy is 0.97 mJ / dot. Item 6. The two-color heat-sensitive recording material according to any one of Items 1 to 5, wherein the dynamic color density obtained by printing according to Item 1 is 1.00 or more.

  Item 7: The two-color thermosensitive recording material according to any one of Items 1 to 6, wherein the support has a metallic luster.

  The two-color thermosensitive recording material of the present invention exhibits a yellow color tone and a black color tone, has a high color density in each color tone, and is excellent in color separation of the recording portion. In addition, when a support body has metallic luster, a color image of a golden metal tone can be obtained.

  The present invention relates to a heat-sensitive recording material provided with a heat-sensitive recording layer containing a dye precursor and a developer on a support, and the dye precursor has a molecular structure represented by the following general formula (1) as pyridine. A first dye precursor having a skeleton and a second dye precursor that develops a black color tone are contained, and the melting point of the second dye precursor is 200 ° C. or higher. In the present invention, the second dye precursor is selected by selecting a specific first dye precursor which is limited to a yellow color as a color tone different from that of a black color and has a high color density and a bright yellow color tone. Thus, it is possible to obtain a heat-sensitive recording material exhibiting two colors of a yellow first color and a black second color which are excellent in color separation property and visibility.

In the following general formula (1), R ¹ and R ² represent a hydrogen atom or an alkoxy group having 1 to 8 carbon atoms which may be branched, and R ³ represents an alkyl group having 1 to 4 carbon atoms which may be branched. R ¹ and R ² may be the same or different from each other, but at least R ¹ and R ² are preferable because a linear saturated hydrocarbon group can be easily introduced industrially. From the viewpoint of increasing the color density, it is preferable to exclude the case where R ¹ and R ² in the general formula (1) are hydrogen atoms at the same time.

（式中、Ｒ^１及びＲ^２は水素原子もしくは炭素数１〜８のアルコキシ基を表し、Ｒ^３は炭素数１〜４のアルキル基を表す。Ｒ^１及びＲ^２は同一であっても、異なっていてもよい。）

(In the formula, R ¹ and R ² represent a hydrogen atom or an alkoxy group having 1 to 8 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms. Even if R ¹ and R ² are the same, May be different.)

  The first dye precursor having the pyridine skeleton is 4- [2- (2-butoxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2- (2-pentyl). Oxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2- (2-hexyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine 4- [2- (2-octyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6-bis (2-butoxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6-bis (2-pentyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6 Bis (2-hexyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine and 4- [2,6-bis (2-octyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzene One type selected from the group consisting of amines is preferred.

In the present invention, from the viewpoint of increasing the color density and improving the storability and light resistance of the color image, ^one of R ¹ and R ^{2 in} the general formula (1) is an alkoxy having 4 to 8 carbon atoms. It is preferable to represent a group. Furthermore, from the viewpoint of further increasing the color density, it is preferable that either R ¹ or R ² represents a hydrogen atom.

  The second dye precursor is not particularly limited as long as it has a melting point of 200 ° C. or higher and develops a black color tone. Specific examples thereof include, for example, 3-pyrrolidino-6-methyl-7-anisate. Linofluorane (melting point 226 ° C.), 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane (melting point 207 ° C.), 3-diethylamino-7- (2-chloroanilino) fluorane ( Melting point 220 ° C.), 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane (melting point 228 ° C.), 3-diethylamino-7- (o-fluoroanilino) fluorane ( Mp 215 ° C.), 3- (N-cyclohexyl-N-methylamino) 6-methyl-7-anilinofluorane (mp 202 ° C.), 3-piperidino-6-methyl-7-anilinofur Run (mp 226 ° C.), 3- (4-dimethylamino) anilino-5,7-dimethyl fluoran (melting point 235 ° C.), and the like. Among these, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane is excellent in light resistance and is particularly preferable.

  In the present invention, it is preferable that both the first dye precursor and the second dye precursor are contained in the heat-sensitive recording layer in the form of solid dispersed fine particles. Since the color density of the first dye precursor is high and gives a vivid yellowish color tone, an effect excellent in color separation is obtained without forming the second dye precursor in the form of composite fine particles to be described later. be able to.

  When the dye precursor is used in the form of solid dispersed fine particles, for example, water is used as a dispersion medium and pulverized by various wet pulverizers such as a sand mill, an attritor, a ball mill, and a cobo mill to obtain a dispersion. In addition to water-soluble polymer compounds such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, modified polyvinyl alcohols such as sulfone-modified polyvinyl alcohol, methylcellulose, carboxymethylcellulose, styrene-maleic anhydride copolymer salts and derivatives thereof, are necessary. Depending on the above, it can be dispersed in a dispersion medium in the presence of a surfactant, an antifoaming agent or the like to form a dispersion. What is necessary is just to prepare the coating liquid for forming a thermosensitive recording layer using this dispersion liquid. In addition, after dissolving the dye precursor in an organic solvent, this solution is emulsified and dispersed in water using the above water-soluble polymer compound as a stabilizer, and then the organic solvent is evaporated from the emulsion to make the dye precursor into solid dispersed fine particles. Can also be used. In any case, the volume average particle diameter of the solid dispersion fine particles of the dye precursor used in the form of the solid dispersion fine particles is preferably about 0.2 to 3.0 μm, more preferably in order to obtain appropriate recording sensitivity. Is about 0.3 to 1.0 μm.

  The first dye precursor (yellow color) and the second dye precursor (black color) contained in the heat-sensitive recording layer may be contained in the same recording layer or in different recording layers. However, in the present invention, from the viewpoint of improving color separation, the heat-sensitive recording layer has a multilayer structure composed of at least a first heat-sensitive recording layer and a second heat-sensitive recording layer, and the first heat-sensitive recording layer is the first heat-sensitive recording layer. It is preferable that one dye precursor is contained and the second thermosensitive recording layer contains a second dye precursor.

  When the first dye precursor and the second dye precursor are contained in separate heat-sensitive recording layers, any heat-sensitive recording layer may be on the surface layer side. In the present invention, the heat-sensitive recording layer is a support. Having a multi-layer structure including a first thermosensitive recording layer formed on the side closer to the substrate and a second thermosensitive recording layer formed on the side far from the support, wherein the first thermosensitive recording layer contains the first dye precursor. It is preferable that the second thermosensitive recording layer contains a second dye precursor. As a result, the black color as the second color obtained by mixing the yellow color tone by the first dye precursor and the black color tone by the second dye precursor can be made clearer. .

  In the present invention, the total content of the dye precursor that develops a black color tone including the second dye precursor in the thermosensitive recording layer is more than 0.5 times the coating amount of the first dye precursor. A range less than 5 times is preferable. More preferably, it is the range of 1.0 times or more and 2.0 times or less. As a result, it is possible to further improve the color separation between the yellow-colored color tone that is the first color and the black color that is the mixed color that is the second color.

  The two-color heat-sensitive recording material of the present invention is sufficiently black as the first dye precursor develops color and exhibits a yellowish color tone when the temperature increases, and then the second dye precursor develops color and mixes. Second color can be exhibited. In the present invention, the two-color thermal recording can be performed by changing the applied energy by, for example, using a thermal head and controlling the width of one pulse and the number of repetitions with a constant applied voltage. . As a specific example, for example, by applying an applied energy that is sufficient to reach the color development start temperature of the first dye precursor and is insufficient to reach the color development start temperature of the second dye precursor, A first color is obtained by color development of one dye precursor. On the other hand, by applying sufficient energy to reach the color development start temperature of both the first dye precursor and the second dye precursor, both the first dye precursor and the second dye precursor are colored and mixed. The resulting second color is obtained.

  In the present invention, as the form of the dye precursor contained in the heat-sensitive recording layer, the first dye precursor and the second dye precursor are preferably contained in each heat-sensitive recording layer in the form of solid dispersed fine particles. However, when other dye precursors are used in combination, the other dye precursors include a dye precursor and a hydrophobic resin such as a urea resin, a urethane resin, a urea-urethane resin, a styrene resin, and an acrylic resin. You may contain in the form of the composite fine particle to contain.

As a form in which composite fine particles containing a dye precursor and a hydrophobic resin are formed,
(1) A form in which one or more dye precursors are microencapsulated using a hydrophobic resin as a wall film,
(2) A form in which one or more dye precursors are contained in a base material made of a hydrophobic resin obtained from a polyvalent isocyanate or the like,
(3) A form in which a compound having an unsaturated carbon bond is polymerized on the surface of one or more dye precursor fine particles,
Etc. For example, a method described in JP-A-60-244594 can be cited as a method for producing the particles having the form (1). Examples of the method for producing particles having the form (2) include the method described in JP-A-9-263057. Examples of the method for producing the particles having the form (3) include the method described in JP-A No. 2000-158822.

  The content ratio of the dye precursor is preferably about 5 to 35% by mass, more preferably about 7 to 30% by mass in the total solid content of the thermosensitive recording layer. By setting the content to 5% by mass or more, the color density can be improved. Heat resistance can be improved by setting it as 35 mass% or less.

  In addition to the dye precursor, the composite fine particles contain, as necessary, a sensitizer as known for heat-sensitive recording materials in addition to an ultraviolet absorber, an antioxidant, and a release agent, which will be described later. May be.

  In the present invention, a dynamic color density obtained by printing a two-color thermal recording medium with a thermal head with an applied energy of 0.66 mJ / dot is 1.00 or more, and a thermal head with an applied energy of 0.97 mJ / dot. It is preferable that the dynamic color density obtained by printing with the above is 1.00 or more. Thereby, it is possible to obtain a further excellent color separation property and a sufficient yellowish color tone. The difference in applied energy is preferable in order to improve color separation, and by setting the applied energy within this range, there is no fear of background fogging, and the load on the printer can be reduced. By setting the dynamic color density to 1.00, it reaches a level that can be evaluated to be sufficient by visual observation. More preferably, the dynamic color density obtained by printing with a thermal head with an applied energy of 0.66 mJ / dot is 1. 10 or more, more preferably 1.15 or more. More preferably, the dynamic color density obtained by printing with a thermal head with an applied energy of 0.97 mJ / dot is 1.40 or more, and more preferably 1.80 or more. Here, the color density indicates the Y (yellow) density.

  The developer contained in the heat-sensitive recording layer in the present invention is selected from those having the property of being liquefied or dissolved by an increase in temperature and having the property of causing color development upon contact with the dye precursor. Specific examples include organic acidic substances such as phenol compounds, aromatic carboxylic acids, and polyvalent metal salts of these compounds.

  The developer may be usually present in the composite fine particles or microcapsules, or may be present in the form of solid dispersed fine particles. The content of the developer is preferably about 30 to 1500 parts by mass, more preferably about 50 to 1000 parts by mass, and still more preferably about 100 to 600 parts by mass, with respect to the total 100 parts by mass of the dye precursor. Preferably it is about 140-600 mass parts, Most preferably, it is about 200-500 mass parts. The composite fine particles can be prepared by a method similar to the method of preparing the composite fine particles containing the dye precursor.

  Representative developers include 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec-butylidenediphenol, 4-phenylphenol, 4,4′-dihydroxydiphenylmethane, 4,4′-isopropylidene diphenol, 4,4′-dihydroxydiphenyl ether, 4,4′-cyclohexylidene diphenol, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxy) Phenyl) -1-phenylethane, 4,4′-dihydroxydiphenyl sulfide, 4,4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxy Diphenyl sulfone, 4-hydroxy-4 ' Isopropoxydiphenylsulfone, 4-hydroxy-4′-n-propoxydiphenylsulfone, 4-hydroxy-4′-allyloxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4,4′-bis [ (4-Methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4- [4 ′-(1′-methylethyloxy) phenyl] sulfonylphenol, N- (p-toluenesulfonyl) -N ′-(3 -P-toluenesulfonyloxyphenyl) urea, Np-tolylsulfonyl-p-butoxycarbonylphenylurea, N- (p-toluenesulfonyl) -N'-phenylurea, 4,4'-bis (3-tosylureido) Mention may be made of compounds such as diphenylmethane.

  Further, in the present invention, compounds that can be used as a developer include 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, and 4-hydroxybenzoic acid-sec-butyl. Phenyl compounds such as phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenyl ether, or benzoic acid, p-tert-butyl Benzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3,5- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsali Aromatic carboxylic acids such as Le acid, and the phenolic compounds, aromatic carboxylic acid and, for example, zinc, magnesium, aluminum, organic acidic substances of salts with polyvalent metals such as calcium and the like.

  Among these developers, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy-4′-n-propoxydiphenylsulfone, 4-hydroxy-4′-allyloxydiphenylsulfone, bis (3-allyl -4-hydroxyphenyl) sulfone, 4,4'-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, Np-tolylsulfonyl-N'-p-butoxycarbonylphenylurea, N -(P-toluenesulfonyl) -N '-(3-p-toluenesulfonyloxyphenyl) urea, N- (p-toluenesulfonyl) -N'-phenylurea, 4,4'-bis (3-tosylureido) diphenylmethane At least one selected from the group consisting of As a result, a brighter yellow color tone can be obtained, and the effects of the present invention can be exhibited without regret. Furthermore, 4-hydroxy-4′-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, N- (p-toluenesulfonyl) -N ′-(3-p-toluenesulfonyloxyphenyl) urea 4,4′-bis (3-tosylureido) diphenylmethane, N- (p-toluenesulfonyl) -N′-phenylurea, Np-tolylsulfonyl-N′-p-butoxycarbonylphenylurea Species are preferred.

  In the present invention, a preservability improving agent can be further contained in the heat-sensitive recording layer mainly in order to further improve the preservability of the color image. Examples of such preservability improvers include 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-). 5-tert-butylphenyl) butane, 1,1-bis (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4 ′-[1,4-phenylenebis (1-methylethylidene) ] Phenols such as bisphenol and 4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenol, 4-benzyloxyphenyl-4'-(2-methyl-2,3-epoxypropyloxy) ) Phenylsulfone, 4- (2-methyl-1,2-epoxyethyl) diphenylsulfone, and 4- (2-ethyl-1,2-epoxyethyl) ) At least one selected from epoxy compounds such as diphenylsulfone and isocyanuric acid compounds such as 1,3,5-tris (2,6-dimethylbenzyl-3-hydroxy-4-tert-butyl) isocyanuric acid is used. be able to. Of course, the storage stability improving agent is not limited to these, and two or more kinds of compounds may be used in combination as required.

  In the present invention, a sensitizer can be further contained in the heat-sensitive recording layer in order to improve the recording sensitivity. As the sensitizer, a compound conventionally known as a sensitizer for a thermal recording material can be used. For example, parabenzylbiphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dioxalate Benzyl ester, di-o-chlorobenzyl adipate, 1,2-diphenoxyethane, 1,2-di (3-methylphenoxy) ethane, di-p-methylbenzyl oxalate, di-p-chlorooxalate Benzyl ester, 2-naphthylbenzyl ether, diphenylsulfone, 1,2-diphenoxymethylbenzene, 1,2-bis (3,4-dimethylphenyl) ethane, 1,3-bis (2-naphthoxy) propane, metater Phenyl, diphenyl, benzophenone and the like can be mentioned.

  Auxiliaries such as developers, storability improvers and sensitizers used in the heat-sensitive recording layer are dispersed in water in the same manner as when the dye precursor is used in the form of solid dispersed fine particles. What is necessary is just to mix with this in the case of preparation of a coating liquid. Moreover, these adjuvants can be dissolved in a solvent and emulsified in water using a water-soluble polymer compound as an emulsifier. Further, the preservability improver and the sensitizer may be contained in the composite fine particles containing the dye precursor.

  In order to improve the whiteness of the heat-sensitive recording layer and improve the uniformity of the image, a fine pigment having a high whiteness and an average particle diameter of 10 μm or less can be contained in the heat-sensitive recording layer. For example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface treated inorganic pigments such as calcium carbonate and silica In addition, organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, and polystyrene resin can be used.

  As other component materials constituting the heat-sensitive recording layer, a binder is used, and if necessary, a crosslinking agent, waxes, metal soaps, colored dyes, colored pigments, fluorescent dyes and the like can be used. Examples of the binder include polyvinyl alcohol and derivatives thereof, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, polyacrylic acid soda, polyvinylpyrrolidone, and acrylamide-acrylic acid ester copolymer. Water-soluble polymer materials such as acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and derivatives thereof, and Polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate Butadiene copolymer, styrene - - emulsion and styrene polymers such as butadiene - can be given latex water-insoluble polymer such as an acrylic copolymer.

  Examples of the cross-linking agent include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxylate, dimethylol urea compounds, aziridine compounds, blocked isocyanate compounds, and peroxides. Inorganic compounds such as ammonium sulfate, ferric chloride, magnesium chloride, sodium tetraborate, and potassium tetraborate, or boric acid, boric acid triester, boron-based polymer, hydrazide compound, glyoxylate, and the like can be given. These may be used individually by 1 type and may be used in combination of 2 or more type. The amount of the crosslinking agent used is preferably in the range of about 1 to 10 parts by mass with respect to 100 parts by mass of the total solid content of the thermosensitive recording layer. Thereby, the water resistance of the thermosensitive recording layer can be improved.

  Examples of the wax include waxes such as paraffin wax, carnauba wax, microcrystalline wax, polyolefin wax, and polyethylene wax, and higher fatty acid amides such as stearic acid amide and ethylenebisstearic acid amide, higher fatty acid esters, and derivatives thereof. Can be mentioned.

  Examples of the metal soap include higher fatty acid polyvalent metal salts such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate. Further, if necessary, various auxiliary agents such as an oil repellent, an antifoaming agent and a viscosity modifier can be further added to the heat-sensitive recording layer as long as the effects of the present invention are not impaired.

  Furthermore, the light resistance can be greatly improved by incorporating microcapsules enclosing an ultraviolet absorber or solid dispersed fine particles of the ultraviolet absorber in the heat-sensitive recording layer.

  Specific examples of the ultraviolet absorber include salicylic acid-based ultraviolet absorbers such as phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-octyloxy Benzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2- Examples thereof include benzophenone-based ultraviolet absorbers such as hydroxy-4-methoxy-5sulfobenzophenone.

  Furthermore, 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-amylphenyl) benzotriazole, 2- [2'-hydroxy -3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimido-methyl) -5′-methylphenyl] benzotriazole, 2- (2 ′ Hydroxy-5′-tert-octylphenyl) benzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′- Hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy-4 '-(2 "-ethylhexyl) oxyphenyl] benzotriazole, polyethylene glycol (molecular weight about 300) and methyl-3 -[3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] benzoic acid UV absorbers such as condensates with propionate, 2'-ethylhexyl-2-cyano- 3,3-diphenyl acrylate, ethyl-2-cyano-3,3-diphenyl acrylate It may be mentioned ultraviolet absorbent cyanoacrylate such bets, and the like. Of course, not limited thereto, may be used in combination of two or more depending also required.

  Among these ultraviolet absorbers, benzotriazole-based ultraviolet absorbers are preferable, and in particular, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 2- (2′-hydroxy-3′-tert-butyl-5). -Methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy-4 '-(2 "-ethylhexyl) A condensate of oxyphenyl] benzotriazole, polyethylene glycol (molecular weight about 300) and methyl-3- [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate is In particular, it is more preferable because it exhibits a remarkable light resistance improvement effect.

  The content ratio of the microcapsules encapsulating the ultraviolet absorber or the solid dispersed fine particles of the ultraviolet absorber is not particularly limited, but is preferably about 5 to 70% by mass in the total solid content of the heat-sensitive recording layer. Especially preferably, it adjusts to the range of about 15-50 mass%. If the amount is less than 5% by mass, the effect of improving the light resistance is poor. Even if the content is more than 70% by mass, not only the effect of improving the light resistance is poor, but also the recording sensitivity of the thermosensitive recording layer may be lowered. It should be noted that the light resistance can be improved more effectively when the microcapsules encapsulating the ultraviolet absorber or the solid dispersed fine particles of the ultraviolet absorber are contained in the protective layer, which will be described later, rather than in the thermal recording layer. it can.

  The microcapsules encapsulating the ultraviolet absorber can be prepared by various known methods. In general, the core substance obtained by dissolving the above-described solid or liquid ultraviolet absorber in an organic solvent as required at room temperature ( Oily liquid) is prepared by a method of emulsifying and dispersing an oily liquid in an aqueous medium to form a wall film made of a polymer substance around oily droplets. Specific examples of the polymer substance that becomes the wall film of the microcapsule include, for example, polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-methacrylate copolymer resin, Examples thereof include styrene-acrylate resin, gelatin, polyvinyl alcohol and the like.

The heat-sensitive recording layer in the present invention uses, for example, water as a dispersion medium, a specific dye precursor, a developer, if necessary, a preservability improver, a sensitizer and the like, or a dispersion in which they are separately dispersed, The coating amount for the heat-sensitive recording layer prepared by mixing a pigment, a binder, a cross-linking agent, and other auxiliaries, if necessary, is preferably about ² to 12 g / m ² , more preferably 2 to 2 by dry weight. 8 g / ^{m 2} approximately, are formed further preferably such that the 2~7g / ^{m 2} approximately, coating and drying on a support.

  The support in the present invention is not particularly limited in type, shape, dimensions, etc., for example, high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, cast-coated paper, glassine paper, resin In addition to laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, non-woven fabric, synthetic resin film, etc., various transparent supports can be appropriately selected and used.

  In the present invention, an embodiment in which the support has a metallic luster is also preferable. Among the dye precursors that develop a yellow color tone, the first dye precursor having a pyridine skeleton in the present invention develops a bright yellow color tone and has a metallic luster that the support has, thereby providing a recording surface. As a color tone of the first color when viewed from the side, a color image of gold metal tone is obtained. In the present invention, variable information such as characters or figures can be obtained by combining the first color and the second color obtained by coloring and mixing the first dye precursor and the second dye precursor. Can be displayed by selecting negative / positive in golden metal tone.

  In the case of displaying a golden metal tone, it is sufficient that the support has a metallic luster on at least one side, and there is no particular limitation on the type, shape, dimensions, and the like. For example, a metal plate, a metal foil, a metal film or the like itself having a metallic luster, fine paper (acid paper, neutral paper), medium paper, coated paper, art paper, cast coated paper, glassine paper, A support provided with a metallic luster on a substrate having no metallic luster, such as paperboard, cardboard, resin-laminated paper, polyolefin synthetic paper, synthetic fiber paper, non-woven fabric, and synthetic resin film, can be appropriately selected and used. The substrate may be transparent, translucent, or opaque. Among these, since a specular gloss can be obtained visually, a support provided with a metallic gloss on a film or synthetic paper is preferable.

  As a method for imparting a metallic luster to the surface of the substrate, there are a method of plating, a method of bonding a metal foil such as an aluminum foil, and a method of bonding a paper or film having a metal vapor-deposited layer. Furthermore, there is a method in which a metal vapor deposition film such as aluminum or silver is directly provided on the substrate. In this case, a smooth resin layer is preliminarily provided on the surface of the substrate, and a direct vapor deposition method in which a metal vapor is deposited thereon to form a metal layer, or a metal vapor deposition layer previously provided on the film is bonded via an adhesive. There is a method in which the film is peeled off and transferred to a substrate. There is also a method of providing a metallic luster layer by printing or coating on a substrate. In this case, it is possible to obtain a metallic glossy surface using a metal ink obtained by mixing a metal powder such as aluminum powder or an aluminum paste in which aluminum powder is dispersed in a solvent with a vehicle. It is also possible to use not mica powder, but mica or ink using inorganic pearl pigment such as pigment obtained by coating mica with titanium oxide.

  In the above aspect, the thermosensitive recording layer covers part or all of the metallic luster of the support as viewed from the recording surface side. The heat-sensitive recording layer may be formed on the side having the metallic luster of the support, and for example, if it is a support having a metallic luster that can be visually confirmed through the substrate like a transparent substrate, You may form in the other side of the surface which has a metallic luster of a support body. Although an undercoat layer described later can be provided between the support and the heat-sensitive recording layer, it is preferable that the undercoat layer does not conceal the metallic luster of the support.

  When the support has a metallic luster, the first dye precursor present in a fine particle state in the heat-sensitive recording layer and a developer that reacts under heating to develop the first dye precursor are applied to a thermal head or the like. It is considered that once the material is melted and solidified again, irregular reflection in the heat-sensitive recording layer is reduced, and a golden metal tone can be obtained through the heat-sensitive recording layer. In the present invention, the heat-sensitive recording layer covers the metallic luster of the support, but since the color image exhibits a golden metal tone, the degree to which the thermo-sensitive recording layer conceals the metallic luster of the support is limited. There is no particular limitation. For example, when the recording surface is viewed as a mat-like plain paper-like recording with a margin left, it is possible to display three colors: a golden metal tone, black as a mixed color, and a white background. Further, if the metallic luster can be visually confirmed through the heat-sensitive recording layer, the recording can be performed with leaving a blank space, so that it is possible to display three colors of gold metal tone, black as a mixed color, and silver on the background. .

In the present invention, an undercoat layer can be provided between the support and the heat-sensitive recording layer as necessary. Thereby, the recording sensitivity can be further increased. The undercoat layer supports an undercoat layer coating liquid containing an oil-absorbing pigment having an oil absorption of 70 ml / 100 g or more, particularly about 80 to 150 ml / 100 g, at least one of organic hollow particles and thermally expandable particles, and a binder. It is formed by applying and drying on top. Here, the oil absorption is a value determined according to the method described in JIS K 5101. By using a pigment having a high porosity such as silica or calcined kaolin for the undercoat layer, the recording sensitivity of the thermosensitive recording layer can be increased. Further, the inclusion of a plastic pigment, hollow particles, foam, etc. in the undercoat layer is effective in improving the recording sensitivity of the thermosensitive recording layer formed thereon. The coating amount of the undercoat layer coating solution is preferably about 3 to ²⁰ g / m ² by dry weight, and more preferably about 4 to 12 g / m ² .

  The binder in the undercoat layer can be appropriately selected from those that can be used for the heat-sensitive recording layer. Among these binders, starch-vinyl acetate graft copolymer, polyvinyl alcohol, styrene-butadiene latex and the like are preferable from the viewpoint of improving barrier properties.

  In the present invention, it is desirable to provide a protective layer containing a water-soluble polymer material and a pigment as used in conventionally known heat-sensitive recording materials on the heat-sensitive recording layer. As the water-soluble polymer material and the pigment, materials exemplified in the above-mentioned heat-sensitive recording layer can be used. At this time, it is more desirable to add a crosslinking agent to impart water resistance to the protective layer.

  In the present invention, the light resistance can be greatly improved by incorporating the microcapsules encapsulating the ultraviolet absorber or the solid dispersed fine particles of the ultraviolet absorber in the protective layer. In particular, microcapsules having a wall film made of polyurethane-polyurea resin or aminoaldehyde resin are excellent in heat resistance, and are therefore added to the thermal recording layer or protective layer for the purpose of preventing sticking to the thermal head. In addition to the excellent accompanying effect of fulfilling the function of an inorganic pigment, the refractive index is lower than that of other wall membrane microcapsules and ordinary pigments, and the shape is spherical. Even if it is contained in a large amount, it is preferably used because it does not cause a decrease in density due to irregular reflection of light.

  Further, by including a pigment, it is possible to prevent the adhesion of the residue to the thermal head and the sticking. As the oil absorption amount of the pigment, it is preferable to use a pigment of 50 ml / 100 g or more. The pigment content is preferably an amount that does not decrease the recording density, that is, 50% by mass or less of the total solid content of the protective layer.

The protective layer is a protective layer coating solution prepared by mixing, for example, water as a dispersion medium and mixing a binder, and if necessary, a crosslinking agent, a pigment, and other auxiliaries. to 15 g / ^{m 2,} more preferably about so that 0.5 to 8 g / ^{m 2} approximately, is formed by applying and drying a heat-sensitive recording layer.

  In the present invention, a resin layer cured with an electron beam or ultraviolet light can be provided on the heat-sensitive recording layer or the protective layer. Examples of resins that can be cured with an electron beam are described in JP-A Nos. 58-177392 and 58-177392. In such a resin, auxiliary agents such as a non-electron beam curable resin, a pigment, an antifoaming agent, a leveling agent, a lubricant, a surfactant, and a plasticizer can be appropriately added. In particular, it is preferable to add pigments such as calcium carbonate and aluminum hydroxide, and lubricants such as waxes and silicon because this helps prevent sticking to the thermal head.

  In the present invention, in order to increase the added value of the heat-sensitive recording material, it can be further processed to obtain a heat-sensitive recording material having a higher function. For example, a pressure-sensitive adhesive paper, a re-humidified adhesive paper, or a delayed tack paper can be obtained by applying coating processing on the back surface with a pressure-sensitive adhesive, a re-humidified adhesive, a delayed tack type pressure-sensitive adhesive, or the like. In particular, the anti-counterfeit recording material of the present invention that has been subjected to adhesive processing is useful as a heat-sensitive label. In addition, by using the back surface, a function as a thermal transfer paper, an ink jet recording paper, a carbonless paper, an electrostatic recording paper, and a zeography paper can be added to form a recording paper capable of double-sided recording. Of course, a double-sided thermal recording material can also be used. Further, a back layer can be provided for suppressing permeation of oil and plasticizer from the back surface of the heat-sensitive recording material, and for curling control and antistatic.

  Examples of methods for forming each layer on the support include air knife method, blade method, gravure method, roll coater method, spray method, dipping method, bar method, curtain method, slot die method, slide die method, and extrusion method. Any of the known coating methods may be used.

  In the present invention, it is preferable that at least one layer formed on the support is a layer formed by a curtain coating method. Thereby, a layer having a uniform thickness can be formed, and the recording sensitivity can be increased, and the barrier property against oil, plasticizer, alcohol, etc. can be increased. The curtain coating method is a method in which the coating liquid is allowed to flow and fall freely, and is applied to the support in a non-contact manner, and known methods such as a slide curtain method, a couple curtain method, and a twin curtain method can be employed. There is no particular limitation. In the curtain coating method, a layer having a more uniform thickness can be formed by simultaneous multilayer coating. In simultaneous multi-layer coating, each coating solution is laminated and then applied, and then dried to form each layer. After applying a coating solution that forms the lower layer, the lower surface coating surface is wet without drying. In a state, you may apply | coat the coating liquid which forms an upper layer on a lower layer coating surface, and it may be made to dry after that, and may form each layer. In the present invention, an embodiment in which a heat-sensitive recording layer and a protective layer are simultaneously applied in multiple layers is preferable from the viewpoint of improving barrier properties.

  Smoothing the heat-sensitive recording surface using a known smoothing method such as a super calender or soft calender has the effect of increasing the color development sensitivity. The heat-sensitive recording surface may be applied to either a metal roll or an elastic roll of the calendar.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “part” and “%” indicate “part by mass” and “% by mass”, respectively. Moreover, the volume average particle diameter of the pigment mix | blended with a color developer, a dye precursor, and a protective layer was measured using laser diffraction type particle size distribution analyzer SALD-2200 (made by Shimadzu Corporation).

Example 1
-Preparation of first dye precursor dispersion (liquid A) As a dye precursor that develops a yellowish color tone, 4- [2- (2-octyloxyphenyl) -6-phenyl-4-pyridinyl] -N , N-dimethylbenzenamine 40 parts, polyvinyl alcohol (polymerization degree 500, saponification degree 88%) 10% aqueous solution 40 parts, and water 20 parts were mixed, and average particle size was measured using a vertical sand mill (manufactured by IMEX). The particles were pulverized so as to have a diameter of 0.7 μm to obtain solid dispersed fine particles of the first dye precursor. Hereinafter, the obtained dispersion is also referred to as A liquid.

-Preparation of second dye precursor dispersion (liquid B) 3- (N-ethyl-p-toluidino) -6-methyl-7 as a dye precursor that develops a black color having a melting point of 200 ° C or higher -40 parts of anilinofluorane, 40 parts of a 10% aqueous solution of polyvinyl alcohol (polymerization degree 500, saponification degree 88%), and 20 parts of water were mixed, and the average particle size was measured using a vertical sand mill (manufactured by Imex). Was pulverized to a solid dispersion fine particle of the second dye precursor. Hereinafter, the obtained dispersion is also referred to as “Liquid B”.

-Preparation of developer dispersion (liquid C) From 40 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone, 40 parts of a 10% aqueous solution of polyvinyl alcohol (polymerization degree 500, saponification degree 88%), and water 20 parts The resulting composition was pulverized using a vertical sand mill (manufactured by Imex Co., Ltd.) until the volume average particle size became 1.5 μm to obtain a developer dispersion (hereinafter also referred to as “C solution”).

Preparation of sensitizer dispersion (liquid D) 40 parts of 1,2-di (3-methylphenoxy) ethane, 40 parts of a 10% aqueous solution of polyvinyl alcohol (polymerization degree 500, saponification degree 88%), and water 20 parts Were mixed using a vertical sand mill (manufactured by Imex Co., Ltd.) so as to have an average particle size of 1.0 μm to obtain a sensitizer dispersion (hereinafter also referred to as “liquid D”).

-Preparation of thermal recording layer coating liquid (I) 20 parts of liquid A, 5 parts of styrene-butadiene latex (trade name: L1571, manufactured by Asahi Kasei Co., Ltd., solid content concentration 48%), 10% aqueous polyvinyl alcohol solution (trade name: 25 parts of Poval (registered trademark) PVA-110 (manufactured by Kuraray Co., Ltd.), 23 parts of C solution, 11 parts of D solution, 2 parts of 5% surfactant aqueous solution (trade name: SN wet OT-70, produced by San Nopco), and A composition comprising 17 parts of water was mixed to obtain a thermal recording layer coating liquid (I).

-Preparation of thermal recording layer coating liquid (II) 20 parts of B solution, 5 parts of styrene-butadiene latex (trade name: L1571, manufactured by Asahi Kasei Co., Ltd., solid content concentration 48%), 10% aqueous polyvinyl alcohol solution (trade name: 25 parts of Poval (registered trademark) PVA-110 (manufactured by Kuraray Co., Ltd.), 23 parts of C solution, 11 parts of D solution, 2 parts of 5% surfactant aqueous solution (trade name: SN wet OT-70, produced by San Nopco), and A composition comprising 17 parts of water was mixed to obtain a thermal recording layer coating liquid (II).

-Preparation of kaolin dispersion (solution E) Kaolin (trade name: UW-90 (registered trademark), manufactured by BASF) 80 parts, 40% aqueous solution of sodium polyacrylate (trade name: Aron T-50, Toagosei Co., Ltd.) 1 part) and 53 parts of water were mixed and pulverized using a sand mill until the volume average particle diameter became 1.6 μm to obtain a kaolin dispersion (hereinafter also referred to as “E liquid”).

-Preparation of coating solution for protective layer E part 25 parts, acetoacetyl-modified polyvinyl alcohol (trade name: Gohsephimer (registered trademark) Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., degree of polymerization: about 1000, degree of saponification: about 98 mol%) 15% aqueous solution, paraffin wax (trade name: Hydrin P-7, manufactured by Chukyo Yushi Co., Ltd., solid content concentration 30%) 7.5 parts, 5% surfactant aqueous solution (trade name: SN wet) OT-70 (manufactured by San Nopco) 5 parts, Glyoxal (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., solid content concentration 40%) 0.3 part, and a composition comprising 12.5 parts of water and a coating solution for protective layer Got.

-Preparation of thermosensitive recording material After drying the coating solution (I) for thermosensitive recording layer on one side of a synthetic paper (trade name: FPG-80, manufactured by YUPO Corporation, thickness 80 μm) from the side close to the support. The coating amount is 2.5 g / m ² , the coating amount after drying the thermal recording layer coating liquid (II) is 4.0 g / m ² , and the coating amount after drying the protective layer coating liquid is 3.0 g / m. After coating and drying sequentially with a Mayer bar so as to be ² , supercalendering was performed to obtain a thermal recording material.

Example 2
In the production of the thermal recording material of Example 1, instead of coating the thermal recording layer coating liquid (II) so that the coating amount after drying was 4.0 g / m ² , the thermal recording layer coating liquid (II ) Was applied in the same manner as in Example 1 except that the coating amount after drying was 2.5 g / m ² .

Example 3
In the production of the thermal recording material of Example 1, instead of coating the thermal recording layer coating liquid (I) so that the coating amount after drying was 2.5 g / m ² , the thermal recording layer coating liquid (II ) Is applied so that the coating amount after drying is 4.0 g / m ^2, and the coating solution (II) for the thermal recording layer is applied so that the coating amount after drying is 4.0 g / m ^2. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the coating solution (I) for heat-sensitive recording layer was applied so that the coating amount after drying was 2.5 g / m ² .

Example 4
In the preparation of the liquid A of Example 1, instead of 4- [2- (2-octyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine as the first dye precursor, 4- A heat-sensitive recording material was obtained in the same manner as in Example 1 except that [2- (2-butoxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine was used.

Example 5
In the production of the thermal recording material of Example 1, instead of coating the thermal recording layer coating liquid (II) so that the coating amount after drying was 4.0 g / m ² , the thermal recording layer coating liquid (II ) Was applied in the same manner as in Example 1 except that the coating amount after drying was 5.0 g / m ² .

Example 6
In the production of the thermal recording material of Example 1, instead of coating the thermal recording layer coating liquid (I) so that the coating amount after drying was 2.5 g / m ² , the thermal recording layer coating liquid (I ) Is applied so that the coating amount after drying is 4.0 g / m ^2, and the coating solution (II) for the thermal recording layer is applied so that the coating amount after drying is 4.0 g / m ^2. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the coating solution (II) for heat-sensitive recording layer was applied so that the coating amount after drying was 2.5 g / m ² .

Example 7
Instead of one side of synthetic paper (trade name: FPG-80, manufactured by YUPO Corporation, thickness 80 μm) as the support of Example 1, an aluminum vapor-deposited film (trade name: VM-PET, manufactured by Toray Industries, Inc., thickness) A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the surface provided with the 50 μm) aluminum vapor-deposited layer was used.

Comparative Example 1
In the preparation of the liquid A of Example 1, instead of 4- [2- (2-octyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine as the first dye precursor, 1- A heat-sensitive recording material was obtained in the same manner as in Example 1 except that (4-n-dodecyloxy-3-methoxyphenyl) -2- (2-quinolyl) ethylene was used.

Comparative Example 2
Instead of 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane as the second dye precursor in the preparation of solution B of Example 1, a red color tone having a melting point of 215 ° C. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 3-diethylamino-7,8-benzofluorane, which is a dye precursor that develops color, was used.

Comparative Example 3
Instead of 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane as the second dye precursor in the preparation of solution B of Example 1, 3-di ( A heat-sensitive recording material was obtained in the same manner as in Example 1 except that n-butyl) amino-6-methyl-7-anilinofluorane was used.

  The thermosensitive recording material thus obtained was evaluated as follows. The results were as shown in Table 1.

(Color tone and color density)
Using a thermal recording simulator (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.), recording was performed under conditions of applied energy of 0.660 mJ / dot and 0.968 mJ / dot, and x-rite spectroscopy was used as the color density of the recording portion. Y (Yellow) and V (Visual) concentrations were measured with a densitometer (trade name: x-rite 528, manufactured by X-Rite, color measurement mode). In Comparative Example 2 only, Y (Yellow) and M (Magenta) concentrations were measured. Moreover, the color tone was evaluated visually.

(Color separation)
The image developed under the above application conditions was visually observed, and the color separation was evaluated according to the following criteria.
○: Recognized clearly as each color tone.
○-: Recognized as each color tone.
X: Cannot be recognized as each color tone.

  The two-color heat-sensitive recording material of the present invention has a high color density, develops a bright yellow color tone with a specific dye precursor, and is excellent in yellow and black color separation properties. It is suitable for applications such as gold vouchers, tickets, tickets, bags, labels, coupons, etc. that take advantage of the appearance of golden metal.

Claims (6)

A thermosensitive recording medium comprising a thermosensitive recording layer containing a dye precursor and a developer on a support , wherein the support has a metallic luster, and the dye precursor is represented by the following general formula (1): A first dye precursor having a pyridine skeleton in the molecular structure represented, and a second dye precursor that develops a black color tone, and the melting point of the second dye precursor is 200 ° C. or higher. A characteristic two-color thermal recording material.

(In the formula, R ¹ and R ² represent a hydrogen atom or an alkoxy group having 1 to 8 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms. Even if R ¹ and R ² are the same, May be different.)   The two-color thermal recording material according to claim 1, wherein both the first dye precursor and the second dye precursor are contained in the thermal recording layer in the form of solid dispersed fine particles.   The thermosensitive recording layer has a multilayer structure comprising at least a first thermosensitive recording layer and a second thermosensitive recording layer, the first thermosensitive recording layer contains a first dye precursor, and the second thermosensitive recording layer is The two-color heat-sensitive recording material according to claim 1 or 2, comprising a second dye precursor.   The total content of the dye precursor that develops a black color tone including the second dye precursor is more than 0.5 times and less than 2.5 times the content of the first dye precursor. The two-color thermosensitive recording material according to any one of claims 1 to 3.   The first dye precursor having the pyridine skeleton is 4- [2- (2-butoxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2- (2-pentyl). Oxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2- (2-hexyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine 4- [2- (2-octyloxyphenyl) -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6-bis (2-butoxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6-bis (2-pentyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6 Bis (2-hexyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine and 4- [2,6-bis (2-octyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzene The two-color heat-sensitive recording material according to any one of claims 1 to 4, which is at least one selected from the group consisting of amines.   The dynamic color density obtained by printing the two-color thermal recording material with a thermal head at an applied energy of 0.66 mJ / dot is 1.00 or more, and printing is performed with a thermal head at an applied energy of 0.97 mJ / dot. The two-color thermal recording material according to claim 1, wherein the dynamic color density obtained is 1.00 or more.