JP2018134818A - Thermal recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording body excellent in light ground fogging property even when being exposed to light for a longer period, and in which there is no residue in composite fine particles.SOLUTION: There is provided a thermal recording body comprising on at least one surface of a support medium, a thermal recording layer having composite fine particles and coloring agent, in which the composite fine particles include a leuco dye, a hydrophobic resin, and ultraviolet absorber, and the composite fine particles include as the ultraviolet absorber, a reaction product of 2-(2'-hydroxy-5'-methylphenyl) benzotriazol and 1-dodecene by 15-150 mass parts with respect to 100 mass parts of the leuco dye, in the leuco dye, at least one kind leuco dye selected from a group formed of leuco dyes whose development color is red, vermilion, magenta, blue, cyan, yellow, and green respectively, is included by 50 mass% or more.SELECTED DRAWING: None

Description

  The present invention relates to a heat-sensitive recording material utilizing a color development reaction between a leuco dye and a colorant.

  Conventionally, a color reaction between a leuco dye and a colorant that is brought into contact with the leuco dye under heating to develop a color is used. Recording materials are widely known. Such a heat-sensitive recording material is relatively inexpensive, has a compact recording device, and is easy to maintain. Therefore, it is used in a wide range of fields as a recording medium for facsimiles, word processors, various computers, and other applications. ing.

  The quality required for thermal recording materials is diversifying with the expansion of their applications, and for example, there are demands for higher sensitivity, image stabilization, multi-color recording, and the like.

  The multi-color recording means has an advantage that characters and figures to be emphasized can be remarkably displayed in a color tone different from other parts. Among them, a multicolor thermosensitive recording material capable of recording two or more colors of red, blue, yellow and black is highly demanded for practical use because of its excellent versatility. As multicolor thermal recording systems, attempts have been made to utilize the difference in heating temperature or the difference in thermal energy, and various multicolor thermal recording materials have been proposed.

  Conventional thermal recording materials using leuco dyes and colorants are not sufficiently light-resistant, and when exposed to strong light including ultraviolet rays for a long time, the background portion gradually turns yellow or the image density decreases. As a result, a method for improving this phenomenon has been proposed.

  As a method for preventing yellowing of the white part due to light in a heat-sensitive recording medium using a black color developing dye precursor, it has been proposed to include a benzophenone compound in composite fine particles containing the dye precursor (Patent Document). 1).

  Further, as a method for preventing yellowing of the background and a decrease in image density without impairing gradation, 2-hydroxy-4-octyloxybenzophenone and a specific benzotriazole compound are added at a specific ratio in the heat-sensitive recording layer. It has been proposed to use them together (Patent Document 2). The example of Patent Document 2 is a heat-sensitive recording material that develops color in black, and colors other than black have not been studied.

  Thus, as described in Patent Documents 1 and 2, the thermal recording material that develops color in black has a problem that the white part turns yellow when exposed to light. As a means for achieving this, combinations of UV absorbers and usage ratios have been studied.

JP-A-10-166729 JP 2009-56443 A

  However, when a color other than black is used, various problems that do not occur in a heat-sensitive recording material that develops color in black may occur. For example, in a thermal recording medium that develops color in black, coloring of the background of the thermal recording medium (optical background fogging) that occurs when stored under light irradiation is rarely a major problem, but colors other than black (especially reddish) In the case of a heat-sensitive recording material that develops with a color of (a), optical background fog may be a problem. Actually, a thermal recording medium that develops color in a reddish color tone does not have sufficient light-resistant background fogging resistance (resistance to light background fogging), and when exposed to light for a long time, the background color develops red. It has been found that a problem that does not occur in the heat-sensitive recording medium that develops black color is generated.

  In addition, the light-resistant background fogging property is often evaluated by an accelerated test, but when exposed to light for a longer time, a difference in performance may appear. Furthermore, when a dye precursor that develops a color tone other than black and an ultraviolet absorber are contained in the composite fine particles, there is a problem that a large amount of residue is generated in the composite fine particle dispersion.

  An object of the present invention is to provide a heat-sensitive recording material that is excellent in light-resistant background fogging resistance even when exposed to light for a longer time and in which no residue is generated in the composite fine particles.

  As a result of intensive studies to solve the above-mentioned object, the present inventors can solve the above-mentioned problems by including a specific ultraviolet absorber in a specific ratio in the composite fine particles containing a leuco dye. As a result, the present invention has been completed. That is, the present invention relates to the following thermal recording material.

Item 1: A heat-sensitive recording material having a heat-sensitive recording layer containing composite fine particles and a colorant on at least one surface of a support, wherein the composite fine particles contain a leuco dye, a hydrophobic resin, and an ultraviolet absorber, The composite fine particle contains 15 to 150 parts by mass of a reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene as an ultraviolet absorber with respect to 100 parts by mass of the leuco dye, The dye contains 50% by mass or more of at least one leuco dye selected from the group consisting of red, vermilion, magenta, blue, cyan, yellow and green leuco dyes, or in the leuco dye 50% by weight or less of at least one leuco dye selected from the group consisting of red, vermilion, magenta, blue, cyan, yellow and green leuco dyes Thermosensitive recording medium, wherein the color tone or contains more than 50% by weight of leuco dye is black.
Item 2: The heat-sensitive recording material according to Item 1, wherein the composite fine particle contains an ultraviolet absorber in an amount of 25 to 150 parts by mass with respect to 100 parts by mass of the leuco dye.
Item 3: The reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene is 2- (3′-dodecyl-2′-hydroxy-5′-methylphenyl) benzo Item 3. The thermal recording material according to Item 1 or 2, which is thiazole.
Item 4: The leuco dye having a color tone of red, vermilion or magenta is 3-diethylamino-7-chlorofluorane, 3-diethylamino-6,8-dimethylfluorane, 3- (N-ethyl-N-isoamylamino) ) -7,8-benzofluorane, 2-methyl-6- (Np-tolyl-N-ethylamino) -fluorane, 3-di (n-butyl) amino-6-methyl-7-bromofluorane And thermal recording according to any one of items 1 to 3, which is at least one selected from the group consisting of 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide body.
Item 5: A leuco dye having a blue or cyan color tone is 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- ( 4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylamino-2-methylphenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3 -(2-n-hexyloxy-4-diethylaminophenyl) -4-azaphthalide, 3- [1,1-bis (p-diethylaminophenyl) ethylene-2-yl] In any one of Items 1-4, which is at least one selected from the group consisting of 6-dimethylaminophthalide and 3,3′-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide The heat-sensitive recording material described.
Item 6: The leuco dye having a yellow color tone is selected from the group consisting of 3,6-dimethoxyfluorane and 1- (4-n-dodecyloxy-3-methoxyphenyl) -2- (2-quinolyl) ethylene Item 6. The heat-sensitive recording material according to any one of Items 1 to 5, which is at least one kind.
Item 7: The leuco dye having a green color tone is at least one selected from the group consisting of 3-diethylamino-7-dibenzylaminofluorane and 3-pyrrolidino-7-dibenzylaminofluorane The heat-sensitive recording material according to any one of -6.
Item 8: Black leuco dye is 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-amyl) amino-6-methyl-7-ani Linofluorane, 3-diethylamino-6-methyl-7- (2,6-dimethylanilino) fluorane, 3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluorane, and 2,4 Item 8. The thermal recording material according to any one of items 1 to 7, which is at least one selected from the group consisting of dimethyl-6- (4-dimethylaminoanilino) fluorane.
Item 9: The heat-sensitive recording material according to any one of Items 1 to 8, wherein the heat-sensitive recording layer contains a second leuco dye that develops a color tone different from that of the leuco dye contained in the composite fine particles.
Item 10: The method according to any one of Items 1 to 9, further comprising a second heat-sensitive recording layer containing a second leuco dye that develops a color tone different from the leuco dye contained in the composite fine particles and a second colorant. Thermal recording material.

  The heat-sensitive recording material of the present invention is excellent in light fogging resistance even when exposed to light for a longer time, and no residue is generated in the composite fine particles.

  In this specification, the expression “comprising” includes the concepts of “comprising”, “consisting essentially of”, and “consisting solely”.

  The present invention is a thermal recording body having a thermal recording layer containing composite fine particles and a colorant on at least one surface of a support, wherein the composite fine particles include a leuco dye, a hydrophobic resin, and an ultraviolet absorber. The leuco dye contains 50% by mass or more of at least one leuco dye selected from the group consisting of red, vermilion, magenta, blue, cyan, yellow and green leuco dyes, or the leuco dye A leuco dye containing 50% by mass or less of at least one leuco dye selected from the group consisting of red, vermilion, magenta, blue, cyan, yellow, and green having a color tone of 50% by mass or less. And the composite fine particle is a reaction product of 2- (2-hydroxy-5-methylphenyl) benzotriazole and 1-dodecene as an ultraviolet absorber. Hereinafter, containing also referred) and a specific ultraviolet absorbent in the present invention, is characterized in that it contains 15 to 150 parts by weight per 100 parts by weight leuco dye the ultraviolet absorber.

[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, In addition to resin-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. The thickness of the support is not particularly limited, and is usually about 20 to 200 μm.

[Undercoat layer]
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. In addition, the inclusion of a plastic pigment, hollow particles, foam or the like 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.

[Thermosensitive recording layer]
The heat-sensitive recording layer in the heat-sensitive recording material of the present invention can contain various known leuco dyes of colorless or light color. Specific examples of such leuco dyes are given below.

  Examples of leuco dyes that develop red or vermilion colors include 3,6-bis (diethylamino) fluorane-γ-anilinolactam and 3,6-bis (diethylamino) fluorane-γ- (p-nitro) anilinolactam. 3,6-bis (diethylamino) fluorane-γ- (o-chloro) anilinolactam, 3-dimethylamino-7-bromofluorane, 3-diethylaminofluorane, 3-diethylamino-6-methylfluorane, 3 -Diethylamino-7-methylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-bromofluorane, 3-diethylamino-7,8-benzofluorane, 3-diethylamino-6,8-dimethyl Fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethy Amino-7-tert-butylfluorane, 3- (N-ethyl-N-tolylamino) -7-ethylfluorane, 3- (N-ethyl-N-isobutylamino) -6-methyl-7-chlorofluorane Etc.

  Further, as leuco dyes that develop a red or vermilion color tone, 3-cyclohexylamino-6-chlorofluorane, 3-di (n-butyl) amino-6-methyl-7-bromofluorane, 3-di ( n-butyl) amino-7,8-benzofluorane, 3-tolylamino-7-methylfluorane, 3-tolylamino-7-ethylfluorane, 2- (N-acetylanilino) -3-methyl-6- Di (n-butyl) aminofluorane, 2- (N-propionylanilino) -3-methyl-6-di (n-butyl) aminofluorane, 2- (N-benzoylanilino) -3-methyl- 6-di (n-butyl) aminofluorane, 2- (N-carbobutoxyanilino) -3-methyl-6-di (n-butyl) aminofluorane, 2- (N-formylanilino) -3- Til-6-di (n-butyl) aminofluorane, 2- (N-benzylanilino) -3-methyl-6-di (n-butyl) aminofluorane, 2- (N-allylanilino) -3- Methyl-6-di (n-butyl) aminofluorane, 2- (N-methylanilino) -3-methyl-6-di (n-butyl) aminofluorane, 3-diethylamino-7-phenoxyfluorane, 2- And methyl-6- (Np-tolyl-N-ethylamino) -fluorane.

  Furthermore, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3,3-bis (1-n-octyl-2-methylindol-3-yl) phthalide, 7- ( N-ethyl-N-isoamylamino) -3-methyl-1-phenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) -4,3′-phthalide], 7- (N— Ethyl-N-isoamylamino) -3-methyl-1-p-methylphenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) -4,3′-phthalide], 7- (N -Ethyl-Nn-hexylamino) -3-methyl-1-phenylspiro [(1,4-dihydrochromeno [2,3-c] pyrazole) -4,3′-phthalide] etc. in magenta color system Listed as leuco dyes that develop colors Door can be.

  Examples of leuco dyes that develop a magenta color tone include 3- (N-ethyl-N-isoamylamino) -7,8-benzofluorane, 3,3-bis (1-n-butyl-2-methylindole) -3-yl) phthalide, 3- (N-ethyl-N-isoamylamino) -7-phenoxyfluorane and the like can also be mentioned.

  In the present invention, among the above leuco dyes that develop colors of red, vermilion or magenta, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6,8-dimethylfluorane, 3- (N- Ethyl-N-isoamylamino) -7,8-benzofluorane, 2-methyl-6- (Np-tolyl-N-ethylamino) -fluorane, 3-di (n-butyl) amino-6-methyl It is preferable to use at least one selected from the group consisting of -7-bromofluorane and 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide.

  Examples of leuco dyes that develop a blue color tone include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3- (4-diethylamino-2-methylphenyl) -3- (4- Dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (1 -Ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) phthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylamino) Phenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4- Zaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-n-hexyloxy-4-diethylaminophenyl) -4-azaphthalide, 3-diphenylamino-6-diphenylaminofluorane Etc.

  Examples of leuco dyes that develop a cyan color tone include 3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylamino-2-methylphenyl) -4-azaphthalide, 3- [ 1,1-bis (p-diethylaminophenyl) ethylene-2-yl] -6-dimethylaminophthalide, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3,3′- Bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide and the like can be mentioned.

  In the present invention, among the above leuco dyes that develop a blue or cyan color tone, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2- Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (1-ethyl-2-methylindole-3-yl) -3- (4-diethylamino-2-methylphenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindole) -3-yl) -3- (2-n-hexyloxy-4-diethylaminophenyl) -4-azaphthalide, 3- [1,1-bis (p-diethylaminophenyl) E) at least one selected from the group consisting of ethylene-2-yl] -6-dimethylaminophthalide and 3,3′-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide Is preferred.

  Examples of leuco dyes that develop a yellow color tone include 4- [2- [2- (butoxy) phenyl] -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2- [2 -(Octyloxy) phenyl] -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2- [2- (ethoxy) phenyl] -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6-bis (2-ethoxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine, 4- (2,6-diphenyl-4-pyridinyl) -N, N-dimethylbenzenamine, 4- [2,6-bis (2-butoxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6-bis (2-octyloxyphenyl) − -Pyridinyl] -N, N-dimethylbenzenamine, 4- [2- [2- (hexyloxy) phenyl] -6-phenyl-4-pyridinyl] -N, N-dimethylbenzenamine, 4- [2,6 -Bis (2-hexyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine, 3,6-dimethoxyfluorane, 1- (4-n-dodecyloxy-3-methoxyphenyl) -2- ( 2-quinolyl) ethylene and the like.

  In the present invention, among the leuco dyes that develop a yellow color tone, 3,6-dimethoxyfluorane and 1- (4-n-dodecyloxy-3-methoxyphenyl) -2- (2-quinolyl) It is preferable to use at least one selected from the group consisting of ethylene.

  Examples of leuco dyes that develop a green color tone include 3- (N-ethyl-Nn-hexylamino) -7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-pyrrolidino- 7-dibenzylaminofluorane, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3- (N-ethyl-Np-tolylamino) -7- (N-phenyl-N -Methylamino) fluorane, 3- [p- (p-anilinoanilino) anilino] -6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6' -Dimethylamino) phthalide and the like.

  In the present invention, at least one selected from the group consisting of 3-diethylamino-7-dibenzylaminofluorane and 3-pyrrolidino-7-dibenzylaminofluorane among the leuco dyes that develop a green color tone. It is preferred to use seeds.

  Examples of leuco dyes that develop a black color tone include 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6- Methyl-7- (m-methylanilino) fluorane, 3- (N-isoamyl-N-ethylamino) -7- (o-chloroanilino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7 -Anilinofluorane, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3 -Di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-amyl) amino-6-methyl-7-anilinofluorane, 3 (N-isoamyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- (Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3-Ethoxypropyl) -N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-methylamino) -6-methyl-7 -Anilinofluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-di (n-butyl) amino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilino Fluorane, 3-diethylamino-6-methyl-7- (2,6-dimethylanilino) fluorane, 3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluor Emissions, 2,4-dimethyl-6- (4-dimethylamino) -6-fluoran, 3- (N-cyclohexyl--N- methylamino) -6-methyl-7-anilino can be exemplified fluoran like.

  Among the leuco dyes that develop a black color tone, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane and 3-di (n-amyl) amino, which have relatively excellent light resistance -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2,6-dimethylanilino) fluorane, 3-diethylamino-6-methyl-7- (2,4-dimethylani It is preferable to use at least one selected from lino) fluorane and 2,4-dimethyl-6- (4-dimethylaminoanilino) fluorane.

  Further, as a leuco dye having absorption in the near infrared region, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromo Phthalide, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3 -Bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3- [p- (p-anilinoanilino) ) Anilino] -6-methyl-7-chlorofluorane, 3- [p- (p-dimethylaminoanilino) anilino] -6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene -9-spiro-3 '-(6' Dimethylamino) phthalide, bis (p-dimethylaminostyryl) -p-tolylsulfonylmethane, 3- [p- (p-dimethylaminoanilino) anilino] -6-methylfluorane, 3-di (n-pentyl) Amino-6,8,8-trimethyl-8,9-dihydro- (3,2, e) pyridfluorane, 3-di (n-butyl) amino-6,8,8-trimethyl-8,9-dihydro- ( 3,2, e) pyridofluorane, 3- (pn-butylaminoanilino) -6-methyl-7-chlorofluorane, 2-mesidino-8-diethylamino-benz [C] fluorane .

  In the present invention, in the leuco dye, at least one leuco dye selected from the group consisting of leuco dyes whose color tone is red, vermilion, magenta, blue, cyan, yellow and green is 50% by mass or more, preferably 70% by mass. % Or more, more preferably 80% by mass or more. By containing the leuco dye having such a composition, it is desirable that the heat-sensitive recording layer can be colored in red, vermilion, magenta, blue, cyan, yellow or green. When coloring in such a color tone, background fogging due to light can be remarkably suppressed.

  As a particularly preferred embodiment, at least one leuco dye selected from the group consisting of red, vermilion and magenta is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass in the leuco dye. As a result, it is desirable that the heat-sensitive recording layer can be colored in red, vermilion or magenta. When coloring in such a color tone, background fogging due to light can be particularly significantly suppressed.

  The specific ultraviolet absorber in the present invention can remarkably suppress background fogging due to light even for a leuco dye that develops a black color tone. In this case, the leuco dye contains 50% by mass or less of at least one leuco dye selected from the group consisting of leuco dyes whose color tone is red, vermilion, magenta, blue, cyan, yellow and green, and the color tone is An embodiment containing 50% by mass or more of black leuco dye is particularly preferable. The content ratio of the leuco dye whose color tone is black in the leuco dye is preferably 60% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more. By using the specific ultraviolet absorber in the present invention, the composite fine particles can be made into only the leuco dye having a black color tone as the leuco dye.

  In the present invention, the leuco dye is contained in the heat-sensitive recording layer in the form of composite fine particles containing a leuco dye and a hydrophobic resin.

As the form of composite fine particles containing a leuco dye and a hydrophobic resin,
(1) A form in which one or more leuco dyes are microencapsulated using a hydrophobic resin as a wall film,
(2) A form in which one or more leuco dyes 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 leuco dye 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 hydrophobic resin forming the composite fine particles is not particularly limited, and examples thereof include urea resins, urethane resins, urea-urethane resins, styrene resins, acrylic resins, and the like. Among these, urea resins and urea-urethane resins are preferable because they are excellent in heat-resistant background fogging.

  The polyvalent isocyanate compound used for the production of the composite fine particles is a compound that forms polyurea or polyurea-polyurethane by reacting with water, and may be a polyvalent isocyanate compound alone or a polyvalent isocyanate. It may be a compound, a polyol that reacts with this, a mixture of polyamines, or an adduct of a polyvalent isocyanate compound and a polyol, a multimer such as a biuret or isocyanurate of a polyvalent isocyanate compound. A leuco dye is dissolved in these polyvalent isocyanate compounds, and this solution is dissolved in an aqueous medium containing a protective colloid substance such as polyvinyl alcohol, and the volume average particle diameter is preferably about 0.2 to 3.0 μm. More preferably, the polyisocyanate compound is polymerized by emulsifying and dispersing to a thickness of about 0.2 to 1.5 μm, and further mixing a reactive substance such as polyamine if necessary, and then heating the emulsified dispersion. Let As a result, the polyvalent isocyanate compound can be polymerized to form composite fine particles containing a leuco dye.

  The leuco dye contained in the composite fine particles is highly separable from the outside, and the color developing body has very good storage stability compared to the color developing body colored in the state of solid dispersed fine particles, particularly for oils and plasticizers. Excellent resistance. The reason for this is not necessarily clear, but it is considered that the color former and the polymer substance (matrix) have some interaction and are stabilized.

  The appearance of the composite fine particles used in the present invention is almost spherical when observed with an electron microscope, or is somewhat erythrocytic. In cross-sectional observation with an electron microscope, the shape is an internal body, a porous body, or a hollow body. The average particle size is desirably about 0.2 to 1.5 μm in order to obtain appropriate recording sensitivity. By setting the average particle diameter to 0.2 μm or more, it is desirable from the viewpoint of improving the storage stability of the color developing part with respect to oil, plasticizer and the like.

  The content ratio of the leuco dye is preferably about 5 to 30% by mass, more preferably about 7 to 30% by mass, and further preferably about 7 to 25% by mass in the total solid content of the heat-sensitive 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 30 mass% or less.

  The content of the leuco dye in the composite fine particles is preferably 15 to 40% by mass, more preferably 20 to 35% by mass.

The content of the leuco dye in the heat-sensitive recording layer is preferably about 0.2 to 2.0 g / m ² , more preferably about 0.4 to 1.5 g / m ² . This can be measured by high performance liquid chromatography.

  In one embodiment of the present invention, the heat-sensitive recording layer further contains a second leuco dye that develops a color different from the leuco dye contained in the composite fine particles (hereinafter sometimes referred to as “first leuco dye”). An embodiment is mentioned. In this case, it is desirable that the second leuco dye is contained in the form of solid dispersed fine particles.

  The leuco dye contained in the composite fine particles is highly separable from the outside. For example, the first leuco dye is colored at a high temperature, and the second leuco dye is colored at a low temperature, so that the color is excellent. Thermal recording is possible.

  As another aspect of the present invention, the thermosensitive recording layer has a multilayer structure comprising at least a first thermosensitive recording layer and a second thermosensitive recording layer, and the first thermosensitive recording layer comprises a first leuco dye and a hydrophobic resin. There is a mode in which the first leuco dye is contained in the form of composite fine particles containing, and the second thermal recording layer contains the second leuco dye in the form of solid dispersed fine particles. The first heat-sensitive recording layer and the second heat-sensitive recording layer further contain a color former (a first colorant and a second colorant, respectively). By using a multilayer structure, the color separation can be further enhanced. Either the first thermosensitive recording layer or the second thermosensitive recording layer may be on the side close to the support.

As a method for performing multicolor thermal recording in the present invention, for example, a thermal head can be used and recording can be performed by changing the applied energy by controlling the width of one pulse and the number of repetitions with a constant applied voltage. As a specific example, for example, an applied energy that is insufficient to reach the color development start temperature of the composite fine particles containing the first leuco dye and is sufficient to reach the color development start temperature of the solid dispersed fine particles of the second leuco dye. By giving the color tone, the color tone of the second leuco dye can be obtained. On the other hand, both the first leuco dye and the second leuco dye are provided by applying sufficient energy to reach the color development start temperature of both the composite fine particles containing the first leuco dye and the solid dispersed fine particles of the second leuco dye. A second color is obtained by coloring and mixing.
Since the color development start temperature depends on the polymer characteristics of the composite fine particles and the type of leuco dye, it is not limited by the type of leuco dye having a specific melting point. A dye can be selected and used in combination. The polymer characteristics of the composite fine particles can be controlled by the composition and production conditions of the composite fine particles such as the polyvalent isocyanate compound and reaction accelerator used.

  Furthermore, by further using a third leuco dye that develops a color tone different from that of the first leuco dye and the second leuco dye in the heat-sensitive recording material of the present invention in the above-described form, a multicolor having at least four types of color tone Thermal recording is possible.

  When the leuco dye 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, polyvinyl pyrrolidone, polyvinyl alcohol, modified polyvinyl alcohols such as sulfone-modified polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer salts, derivatives thereof, etc. 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. Also, after dissolving the leuco dye 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 use the leuco dye as solid dispersed fine particles. You can also In any case, the volume average particle size of the solid dispersed fine particles of the leuco dye used in the form of the solid dispersed fine particles is preferably about 0.2 to 3.0 μm, more preferably in order to obtain appropriate recording sensitivity. It is about 0.3 to 1.0 μm.

  The composite fine particles contain an ultraviolet absorber in addition to the leuco dye. In addition to the antioxidant and the release agent, a sensitizer as known for heat-sensitive recording media may be added to the composite fine particles as necessary.

  The ultraviolet absorber contained in the composite fine particles is a reaction product of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole and 1-dodecene. Thereby, the outstanding light-resistant background fogging property can be exhibited. Also, if the content of leuco dye in the composite fine particles is increased to increase the light resistance, a large amount of residue is generated in the composite fine particle dispersion depending on the type of the UV absorber, and white spots etc. occur in the color image. Among the problems such as defects and abnormalities in the heat-sensitive recording layer coating that cannot be applied, the specific ultraviolet absorber in the present invention can improve the light resistance without producing a residue. Although this ultraviolet absorber is not specifically limited in this invention, It is preferable that it is 2- (3'-dodecyl-2'-hydroxy-5'-methylphenyl) benzothiazole.

  As content of the specific ultraviolet absorber in this invention, it is about 15-150 mass% with respect to the sum total of the leuco dye in composite fine particles, Preferably it is about 25-150 mass%, More preferably, it is 50-150 mass. %. By setting it as this range, it is excellent in light-resistant background fogging property even when exposed to light for a longer time, and it is possible to prevent poor preparation of composite fine particles.

  The total content of the leuco dye and the ultraviolet absorber in the composite fine particles is preferably 25.0 to 45.0 mass%, more preferably 30.0 to 45.0 mass%.

The content of the ultraviolet absorber of the composite fine particles in the heat-sensitive recording layer is preferably 0.05~0.50g / ^{m 2,} more preferably about 0.10 to 0.40 g / ^{m 2} approximately. This can be measured by high performance liquid chromatography.

  In the present invention, a specific ultraviolet absorber is used, but various known ultraviolet absorbers can be used in combination as long as there is no problem. In such a case, it can be contained in the heat-sensitive recording layer as composite fine particles or microcapsules enclosing an ultraviolet absorber, or as solid dispersed fine particles of the ultraviolet absorber.

  Specific examples of the ultraviolet absorber include salicylic acid-based ultraviolet absorbers such as phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate; 2′-ethylhexyl-2-cyano-3,3-diphenyl acrylate And cyanoacrylate-based ultraviolet absorbers such as ethyl-2-cyano-3,3-diphenylacrylate.

  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, and styrene-methacrylate copolymer resin. Styrene-acrylate resin, gelatin, polyvinyl alcohol and the like.

  The colorant 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 a leuco dye. Examples thereof include organic acidic substances such as phenol compounds, aromatic carboxylic acids, and polyvalent metal salts of these compounds.

  The color former may be usually present in the composite fine particles or the microcapsules, or may be present in the state of solid dispersed fine particles. The content of the colorant is preferably about 30 to 1500 parts by weight, more preferably about 50 to 1000 parts by weight, and still more preferably 100 to 600 parts by weight with respect to a total of 100 parts by weight of the leuco dye in each thermosensitive recording layer. About 150 parts by weight, particularly preferably about 120 to 500 parts by weight, and most preferably about 150 to 400 parts by weight. The composite fine particles can be prepared by a method similar to the method of preparing the composite fine particles containing a leuco dye.

  Typical colorants include, for example, 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec-butylidene diphenol, 4-phenylphenol, 4,4′-dihydroxy Diphenylmethane, 4,4′-isopropylidene diphenol, 4,4′-dihydroxydiphenyl ether, 4,4′-cyclohexylidene diphenol, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4 -Hydroxyphenyl) -1-phenylethane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-dihydroxydiphenylsulfone, 2,4 ' -Dihydroxydiphenylsulfone, 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 ( And compounds such as 3-tosylureido) diphenylmethane .

  Further, in the present invention, compounds that can be used as a colorant include 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoate-sec-butyl. Phenol compounds such as phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenyl ether; benzoic acid, p-tert-butylbenzoate 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-butylsalicylyl Aromatic carboxylic acids and the like; the phenolic compounds such as aromatic carboxylic acids, zinc, magnesium, aluminum, organic acidic substances of salts with polyvalent metals such as calcium and the like.

  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 and 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) )] Phenol compounds such as bisphenol, 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisphenol; 4-benzyloxyphenyl-4 ′-(2-methyl-2,3-epoxypropyloxy) ) Phenylsulfone, 4- (2-methyl-1,2-epoxyethyl) diphenylsulfone, 4- (2-ethyl-1,2-epoxyethyl) di Use at least one selected from epoxy compounds such as enylsulfone; and isocyanuric acid compounds such as 1,3,5-tris (2,6-dimethylbenzyl-3-hydroxy-4-tert-butyl) isocyanuric acid; Can do. 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.

  The heat-sensitive recording layer in the present invention may contain a sensitizer. Thereby, the recording sensitivity can be increased. Examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-stearic acid benzamylide, N-benzoyl stearic acid amide, N-eicosanoic acid amide, ethylene bis stearic acid amide, behenic acid amide, methylene bis stearic acid amide, N-methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, diphenylsulfone, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl P-benzylbiphenyl, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, oxalic acid dibenzyl ester, p-tolylbiphenyl ether, di (p-methoxypheno) (Ciethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4 -Chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetide, N-acetoacetyl-p-toluidine, 1,2-diphenoxymethylbenzene, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1- Isopropylphenyl-2-phenylethane, di-o-chlorobenzyl adipate, 1,2-bis (3,4-dimethyl) Phenyl) ethane, 1,3-bis (2-naphthoxy) propane, diphenyl, benzophenone and the like. These can be used in combination as long as there is no hindrance. The content of the sensitizer may be an amount effective for sensitization, but is usually preferably about 2 to 40% by mass, and about 5 to 25% by mass of the total solid content of the heat-sensitive recording layer. Is more preferable.

  Auxiliaries such as colorants, preservatives, and sensitizers used in the heat-sensitive recording layer are dispersed in water in the same manner as when the leuco dye 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 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 leuco dye.

  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. The pigment content is preferably an amount that does not decrease the color density, that is, 50% by mass or less based on the total solid content of the thermosensitive coloring layer.

  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 hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, and ethyl cellulose, sodium polyacrylate, polyvinyl pyrrolidone, and acrylamide-acrylic acid ester copolymer. Water-soluble polymer materials such as polymer, acrylamide-acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and derivatives thereof, poly Vinyl acetate, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer Emulsions etc., styrene - butadiene copolymer, styrene - butadiene - can be given latex water-insoluble polymer such as an acrylic copolymer.

  A crosslinking agent for curing the binder of the heat sensitive layer or other layers can be contained in the heat sensitive recording layer. Thereby, the water resistance of the thermosensitive recording layer can be improved. Examples of the crosslinking agent include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, glyoxylate salts, dimethylol urea compounds, aziridine compounds, blocked isocyanate compounds; ammonium persulfate Inorganic compounds such as ferric chloride, magnesium chloride, sodium tetraborate and potassium tetraborate; boric acid, boric acid triester, boron-based polymer, hydrazide compound, glyoxylate and the like. 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; for example, 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. In the case where the thermosensitive recording material of the present invention is a two-color thermosensitive recording material, it is possible to contain a colored dye or colored pigment having a color tone complementary to the low-temperature color tone in the thermosensitive recording layer. It is preferably used to adjust the color tone of the multicolor thermal recording material before and after printing. 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.

The heat-sensitive recording layer in the present invention uses, for example, a dispersion in which water is used as a dispersion medium, and specific composite fine particles, a colorant, if necessary, a preservability improver, a sensitizer, and the like are dispersed together or separately. The coating amount is preferably about ² to 12 g / m ² by dry weight, more preferably about ² to 12 g / m ² , more preferably using a coating solution for a thermal recording layer prepared by mixing pigments, binders, crosslinking agents, and other auxiliaries as necessary. 2 to 8 g / ^{m 2} approximately, are formed further preferably such that the 2~7g / ^{m 2} approximately, coating and drying on a support.

[Middle layer]
In the present invention, for example, when a plurality of heat-sensitive recording layers are provided, an intermediate layer may be provided between them or between the heat-sensitive recording layer and the protective layer. For the intermediate layer, a water-soluble polymer material or a water-insoluble polymer used in conventionally known thermal recording materials can be used. Specific examples include those similar to the specific examples used as the binder mentioned in the heat-sensitive recording layer. Further, the intermediate layer may contain an organic compound such as a pigment having a high porosity such as silica or calcined kaolin, a plastic pigment, a hollow particle, a foam, or a polyethylene wax having a glass transition point or a melting point as an auxiliary agent.
The intermediate layer is generally applied using water as a dispersion medium, for example, a water-soluble polymer material and, if necessary, an intermediate layer coating solution prepared by mixing various additives such as an auxiliary agent and a surfactant. It is formed by coating and drying so that the amount is preferably about 3.0 to 40.0 g / m ² by dry weight, more preferably about 8.0 to 35.0 g / m ² .

[Protective layer]
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 thermal recording media on the thermal 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 possible to add a crosslinking agent to impart water resistance to the protective layer.

  In the present invention, the light resistance can be significantly improved by incorporating microcapsules encapsulating the ultraviolet absorber or 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 color density, that is, 60% by mass or less of the total solid content of the protective layer.

The protective layer is, for example, a coating solution for the protective layer prepared by mixing a binder, and if necessary, a crosslinking agent, a pigment, and other auxiliaries using water as a dispersion medium. 1 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.

[Resin 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 on the intermediate 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.

[Other layers]
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 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, the penetration of oil and plasticizer from the back surface of the heat-sensitive recording material can be suppressed, and a back layer can be provided for curling control and antistatic.

[Thermal recording material]
Examples of the method for forming each layer on the support include an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dip method, a bar method, a curtain method, a slot die method, a slide die method, and an extrusion method. Any of the known coating methods may be used. In addition, each coating solution may be applied and dried one layer at a time to form each layer, or the same coating solution may be applied in two or more layers. Furthermore, simultaneous multi-layer coating in which two or more layers are simultaneously coated may be performed.
In the present invention, from the viewpoint of improving the recording sensitivity and improving the image uniformity, after completing the formation of each layer or after completing the formation of all the layers, a super calendar, a soft calendar, etc. It is preferable to perform a smoothing process using a known method.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “parts” and “%” represent “parts by mass” and “mass%”, respectively.

Example 1
(1) Preparation of composite particle dispersion (liquid A) 15 parts of 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide as leuco dye and 2- (2 ′) as ultraviolet absorber 10 parts of 2- (3′-dodecyl-2′-hydroxy-5′-methylphenyl) benzothiazole, which is a reaction product of -hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene, at 150 ° C. As a heated polyvalent isocyanate compound, 5 parts of m-tetramethylxylylene diisocyanate and 13.8 parts of dicyclohexylmethane-4,4′-diisocyanate are dissolved. ] 1.5 parts surfactant (trade name: Olphin E1010, manufactured by Nissin Chemical Co., Ltd.) The mixture was gradually added to the obtained aqueous solution for dispersion, and emulsified and dispersed by stirring at a rotational speed of 8500 rpm using a homogenizer (trade name: TK ROBOMICS, manufactured by Primix). The emulsion dispersion was heated to 50 ° C., 10 parts of a 10% aqueous solution of polyethyleneimine [trade name: Epomin SP-006, manufactured by Nippon Shokubai Co., Ltd.] was added as a curing accelerator, heated to 80 ° C., and 6 hours. A dispersion liquid (liquid A) of leuco dye-containing composite fine particles having an average particle diameter of 0.7 μm was prepared. In addition, water was added so that the solid content concentration of the composite fine particle dispersion was 30%.

(2) Preparation of Coloring Agent Dispersion (Liquid B) 40 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 40 parts of a 10% aqueous solution of polyvinyl alcohol (polymerization degree 500, saponification degree 88%), and water 20 The composition consisting of parts was pulverized using an ultra visco mill until the volume average particle diameter became 1.5 μm, and a colorant dispersion liquid B was obtained.

(3) Preparation of thermal recording layer coating liquid (I) A part 70 parts, B part 95 parts, styrene-butadiene latex (trade name: L1571, manufactured by Asahi Kasei, solid content concentration 48%) 25 parts, 10% polyvinyl Alcohol aqueous solution (trade name: Kuraray Poval PVA-110, manufactured by Kuraray Co., Ltd.) 80 parts, calcium carbonate (trade name: Brilliant 15, Shiraishi Kogyo Co., Ltd.) 17 parts, adipic acid dihydrazide (manufactured by Otsuka Chemical Co., Ltd.) 1 part, 5% A composition comprising 10 parts of an aqueous surfactant solution (trade name: SN Wet OT-70, manufactured by San Nopco) and 92 parts of water was mixed and stirred to obtain a coating solution (I) for a thermosensitive coloring layer.

(4) Preparation of Kaolin Dispersion (Liquid C) Kaolin (trade name: HYDRAGLOSS 90, manufactured by KaMin LLC) 59.5 parts, dispersant (trade name: Aron T-50, manufactured by Toa Gosei Co., Ltd., solid concentration 40%) A composition comprising 0.5 part and 40 parts of water was dispersed for 1 hour in a coreless to obtain a pigment dispersion for protective layer.

(5) Preparation of coating solution for protective layer Acetoacetyl-modified polyvinyl alcohol (trade name: Gohsephimer Z-200, degree of saponification: 99.4 mol%, average degree of polymerization: 1000, degree of modification: 5 mol%, Nippon Gosei Co., Ltd. 210 parts of 10% aqueous solution of Chemical Industries, Ltd., also acetoacetyl-modified polyvinyl alcohol (trade name: Goosefimer Z-100, degree of saponification: 99.4 mol%, average degree of polymerization: 500, degree of modification: 5 mol%) 80 parts of 20% aqueous solution, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., 100 parts of C solution, aqueous dispersion of zinc stearate (trade name: Hydrin Z-8-36, manufactured by Chukyo Yushi Co., Ltd., solid content concentration 36%) 5 6 parts and 2.5 parts of polyethylene wax emulsion (trade name: Chemipearl W-400, solid concentration 40%, manufactured by Mitsui Chemicals) are mixed and stirred to obtain a protective layer coating solution. It was.

(6) Production of thermosensitive recording material On one side of a synthetic paper (trade name: FPG-80, manufactured by YUPO Corporation, thickness: 80 μm), a thermosensitive recording layer coating liquid (I) and a protective layer coating liquid are prepared. the coating amount after drying each coated and dried so that 5.0 g / m ^2, and 2.5 g / m ^2, the heat-sensitive recording layer, and after sequentially forming a protective layer, the surface supercalendered smooth To obtain a heat-sensitive recording material.

Example 2
In the preparation of the composite particle dispersion (liquid A) of Example 1, 2- (3′-dodecyl-), which is a reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 10 parts of 2′-hydroxy-5′-methylphenyl) benzothiazole was changed to 5 parts.

Example 3
In the preparation of the composite particle dispersion (liquid A) of Example 1, 2- (3′-dodecyl-), which is a reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 10 parts of 2'-hydroxy-5'-methylphenyl) benzothiazole was 2.5 parts.

Example 4
In the preparation of the composite particle dispersion (liquid A) of Example 1, 2- (3′-), which is 10 parts of the reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene. A thermosensitive recording material was obtained in the same manner as in Example 1 except that 15 parts of dodecyl-2′-hydroxy-5′-methylphenyl) benzothiazole was used.

Example 5
In the preparation of the composite particle dispersion (liquid A) of Example 1, 2- (3′-dodecyl-), which is a reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 10 parts of 2'-hydroxy-5'-methylphenyl) benzothiazole was changed to 22 parts.

Example 6
(6) Preparation of Dye Dispersion (Liquid D) 4-[(2-Octyloxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine 40 parts, polyvinyl alcohol (polymerization degree 500, saponification degree 88%) 40 parts of a 10% aqueous solution and 20 parts of water are mixed and pulverized and dispersed to a mean particle size of 0.7 μm using a vertical sand mill (made by IMEX, sand grinder). A dye dispersion liquid D was obtained.

(7) Preparation of thermal recording layer coating solution (II) A solution 46.7 parts, D solution 17.5 parts, B solution 95 parts, styrene-butadiene latex (trade name; L1571, manufactured by Asahi Kasei Corporation, solid content Concentration 48%) 25 parts, 10% polyvinyl alcohol aqueous solution (trade name: Kuraray Poval PVA-110, Kuraray Co., Ltd.) 80 parts, calcium carbonate (trade name: Brilliant 15, Shiraishi Kogyo Co., Ltd.) 17 parts, adipic acid dihydrazide ( Otsuka Chemical Co., Ltd.) 1 part, 5% surfactant aqueous solution (trade name: SN Wet OT-70, San Nopco Co., Ltd.) 10 parts, and a composition comprising 98 parts of water and mixing and stirring, a coating solution for thermosensitive coloring layer (II) was obtained.

  A thermosensitive recording material was obtained in the same manner as in Example 1 except that the thermosensitive recording layer coating solution (I) was used instead of the thermosensitive recording layer coating solution (I) in the production of the thermosensitive recording material of Example 1. .

Comparative Example 1
In the preparation of the composite particle dispersion (liquid A) of Example 1, 15 parts of 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide was 19 parts, and 2- (2 ′ In place of 5 parts of 2- (3′-dodecyl-2′-hydroxy-5′-methylphenyl) benzothiazole, which is a reaction product of -hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene, 2- A thermosensitive recording material was obtained in the same manner as in Example 1 except that 5 parts of (3′-tert-butyl-5′-methyl-2′-hydroxyphenyl) -5-chlorobenzotriazole was used.

Comparative Example 2
In the preparation of the composite particle dispersion (liquid A) of Example 1, 2- (3′-dodecyl-), which is a reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene. 2'-hydroxy-5'-methylphenyl) benzothiazole instead of 10 parts 2-hydroxy-4-octyloxybenzophenone and 2- (3'-tert-butyl-5'-methyl-2'- A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 5 parts of hydroxyphenyl) -5-chlorobenzotriazole was used.

Comparative Example 3
In the preparation of the composite particle dispersion of Example 1, 15 parts of 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide was 19 parts, and 2- (2′-hydroxy-5) Instead of 10 parts of 2- (3′-dodecyl-2′-hydroxy-5′-methylphenyl) benzothiazole, which is a reaction product of “-methylphenyl) benzotriazole and 1-dodecene, 2-hydroxy-4- Example 1 except that 2.5 parts of octyloxybenzophenone and 2.5 parts of 2- (3′-tert-butyl-5′-methyl-2′-hydroxyphenyl) -5-chlorobenzotriazole were used. In the same manner, a heat-sensitive recording material was obtained.

Comparative Example 4
In the preparation of the composite particle dispersion of Example 1, 15 parts of 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide was 19 parts, and 2- (2′-hydroxy-5) Instead of 10 parts of 2- (3′-dodecyl-2′-hydroxy-5′-methylphenyl) benzothiazole, which is a reaction product of “-methylphenyl) benzotriazole and 1-dodecene, 2- (3′- tert-Butyl-5′-methyl-2′-hydroxyphenyl) -5-chlorobenzotriazole resulted in a large amount of residue in the composite fine particle dispersion, resulting in abnormalities in the thermal recording layer coating and heat sensitivity. A record was not obtained.

Comparative Example 5
In the preparation of the composite particle dispersion of Example 1, 2- (3′-dodecyl-2′-hydroxy), which is a reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene. As a result of using 10 parts of 2- (3′-tert-butyl-5′-methyl-2′-hydroxyphenyl) -5-chlorobenzotriazole instead of 10 parts of −5′-methylphenyl) benzothiazole, composite fine particles Since a large amount of residue was generated in the dispersion, an abnormality occurred in the thermal recording layer coating material, and no thermal recording material was obtained.

  The following evaluation was performed about the thermosensitive recording material produced in the above Examples 1-6 and Comparative Examples 1-5. The results were as shown in Table 1.

Light-resistant background fogging test An x-rite spectrodensitometer (trade name: x-rite 528) before and after the heat-sensitive recording material was exposed to fluorescent light (5000 Lux) and exposed to light for a longer time on the 7th and 9th. , Density measurement used), and the M (magenta) density of the background was measured.

  The background density after 7-day treatment is excellent in light resistance of 0.20 or less, and more preferably 0.10 or less. The background density after 9-day treatment, which is a more severe condition, is particularly excellent in light resistance when 0.20 or less.

Claims (10)

  A heat-sensitive recording material having a heat-sensitive recording layer containing composite fine particles and a colorant on at least one side of a support, wherein the composite fine particles contain a leuco dye, a hydrophobic resin and an ultraviolet absorber, A reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene is contained as an ultraviolet absorber in an amount of 15 to 150 parts by mass with respect to 100 parts by mass of the leuco dye. Contains 50% by mass or more of at least one leuco dye selected from the group consisting of red, vermilion, magenta, blue, cyan, yellow and green, or has a color tone in the leuco dye 50% by weight or less of at least one leuco dye selected from the group consisting of leuco dyes of red, vermilion, magenta, blue, cyan, yellow and green, and a coloring color Thermally sensitive recording medium but which is characterized in that either contains a leuco dye which is black at least 50 mass%.   The heat-sensitive recording material according to claim 1, wherein the composite fine particles contain 25 to 150 parts by mass of an ultraviolet absorber with respect to 100 parts by mass of the leuco dye.   The reaction product of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 1-dodecene is 2- (3′-dodecyl-2′-hydroxy-5′-methylphenyl) benzothiazole. The heat-sensitive recording material according to claim 1 or 2.   The leuco dye whose color tone is red, vermilion or magenta is 3-diethylamino-7-chlorofluorane, 3-diethylamino-6,8-dimethylfluorane, 3- (N-ethyl-N-isoamylamino) -7. , 8-benzofluorane, 2-methyl-6- (Np-tolyl-N-ethylamino) -fluorane, 3-di (n-butyl) amino-6-methyl-7-bromofluorane, and 3 The thermosensitive recording material according to claim 1, which is at least one selected from the group consisting of 1,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide.   The leuco dye whose color tone is blue or cyan is 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethyl) Aminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (1- Ethyl-2-methylindol-3-yl) -3- (4-diethylamino-2-methylphenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2 -N-hexyloxy-4-diethylaminophenyl) -4-azaphthalide, 3- [1,1-bis (p-diethylaminophenyl) ethylene-2-yl] -6- 5. The method according to claim 1, which is at least one selected from the group consisting of methylaminophthalide and 3,3′-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide. Thermal recording material.   The leuco dye whose color tone is yellow is at least one selected from the group consisting of 3,6-dimethoxyfluorane and 1- (4-n-dodecyloxy-3-methoxyphenyl) -2- (2-quinolyl) ethylene. The heat-sensitive recording material according to claim 1, which is a seed.   The leuco dye whose color tone is green is at least one selected from the group consisting of 3-diethylamino-7-dibenzylaminofluorane and 3-pyrrolidino-7-dibenzylaminofluorane. The heat-sensitive recording material according to any one of the above.   The leuco dye with black color tone is 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-amyl) amino-6-methyl-7-anilinofluorane 3-diethylamino-6-methyl-7- (2,6-dimethylanilino) fluorane, 3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluorane, and 2,4-dimethyl- The heat-sensitive recording material according to claim 1, which is at least one selected from the group consisting of 6- (4-dimethylaminoanilino) fluorane.   The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer contains a second leuco dye that develops a color tone different from that of the leuco dye contained in the composite fine particles.   The thermal sensor according to any one of claims 1 to 9, further comprising a second thermosensitive recording layer containing a second leuco dye that develops a color tone different from that of the leuco dye contained in the composite fine particles and a second colorant. Recorded body.