JP2009045759A - Thermosensitive recording body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensitive recording body with high transparency and excellent water resistance. <P>SOLUTION: The thermosensitive recording body constituted by arranging at least a thermosensitive recording layer containing a leuco dye and a coloring agent, an intermediate layer, and a protecting layer in series on one surface of a transparent supporting body is characterized in that the protecting layer contains a carboxyl group containing aqueous polymer and is formed by applying and drying a coating liquid for the intermediate layer containing an oxazoline group containing compound as a cross-linking agent. It is preferable that the consumption of the oxazoline group containing compound is 1 to 15 mass% relative to the carboxyl group containing aqueous polymer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  2. Description of the Related Art Conventionally, a heat-sensitive recording material using a color development reaction by heat between a leuco dye and a colorant is well known. Such a thermal recording medium is relatively inexpensive, and the recording device is compact and relatively easy to maintain, so that it can be used not only as a recording medium for facsimiles and various computers, but also for CRT medical diagnosis, X-ray image printers, It is also used as a recording medium such as a CAD plotter.

  In particular, the heat-sensitive recording material for Saucusten used for a recording medium of a medical device is required to have transparency and gradation of a transmission recording image.

  For this reason, a thermal recording material used as a recording medium for medical devices requires a high transmission density, and the thermal energy applied by the thermal head increases, which causes the surface of the recorded image portion to become rough and uneven, resulting in thermal recording. A problem arises in that white spots occur in the layer and the recorded image density decreases. From the viewpoint of improving such problems, a protective layer is provided on the thermosensitive recording layer.

  At this time, in order to prevent a decrease in transparency due to mixing of the heat-sensitive recording layer and the protective layer, it has been proposed to provide an intermediate layer mainly composed of a water-soluble resin on the heat-sensitive recording layer (Patent Documents 1 and 2). reference). However, with regard to the water resistance and transparency required particularly when used as an image recording medium for medical diagnostic equipment, satisfactory results are not always obtained.

JP 2003-094826 A JP 2005-31478 A

  An object of the present invention is to provide a heat-sensitive recording material having high transparency and excellent water resistance.

  As a result of intensive studies in view of the above-described conventional techniques, the present inventors applied and dried an intermediate layer coating solution containing a carboxyl group-containing aqueous polymer and containing an oxazoline group-containing compound as a crosslinking agent. By providing the intermediate layer formed in this way, the above-mentioned problems have been solved. That is, the present invention relates to the following thermal recording material.

  Item 1. A thermosensitive recording medium comprising at least a thermosensitive recording layer containing a leuco dye and a colorant, an intermediate layer and a protective layer on one side of a transparent support, comprising a carboxyl group-containing aqueous polymer and an oxazoline group as a crosslinking agent A heat-sensitive recording material comprising an intermediate layer formed by applying and drying an intermediate layer coating solution containing a compound.

  Item 2. Item 2. The thermal recording material according to item 1, wherein the amount of the oxazoline group-containing compound used is 1 to 15% by mass relative to the carboxyl group-containing aqueous polymer.

  Item 3. Item 3. The heat-sensitive recording material according to Item 1 or 2, wherein the leuco dye is contained in the heat-sensitive recording layer in the form of composite particles containing a leuco dye and a hydrophobic resin.

  Item 4. Item 4. The heat-sensitive recording material according to Item 3, wherein the hydrophobic resin forming the composite particles is a urea resin or a urea-urethane resin.

  Item 5. Item 5. The heat-sensitive recording material according to any one of Items 1 to 4, wherein the heat-sensitive recording layer, the intermediate layer, and the protective layer are layers formed by simultaneously applying and drying.

  Item 6. Item 6. The heat-sensitive recording material according to any one of Items 1 to 5, wherein the transparent support is a polyethylene terephthalate film.

  The heat-sensitive recording material of the present invention is highly transparent and has an effect of excellent water resistance.

  The present invention is characterized in that it is an intermediate layer formed by applying and drying an intermediate layer coating liquid containing a carboxyl group-containing aqueous polymer and containing an oxazoline group-containing compound as a crosslinking agent. As a result, a heat-sensitive recording material having high transparency and excellent water resistance can be obtained.

  The carboxyl group-containing aqueous polymer is not limited, and various known polymers can be used. Examples thereof include carboxyl group-modified polyvinyl alcohol, carboxyl group-containing acrylic emulsion, and carboxyl group-containing styrene-butadiene latex. These carboxyl group-containing aqueous polymers may be used individually by 1 type, and may use 2 or more types together.

  The oxazoline group-containing compound of the present invention is obtained by polymerizing an addition-polymerizable oxazoline and at least one other monomer as required. By using the oxazoline group-containing compound, the compatibility with the carboxyl group-containing aqueous polymer is improved in the intermediate layer coating solution, and the intermediate layer formed by applying and drying the intermediate layer coating solution is uniformly formed. Therefore, the transparency can be improved, and a heat-sensitive recording material excellent in water resistance can be obtained.

  In the present invention, the addition-polymerizable oxazoline is represented by the following general formula (1).

［式中、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４はそれぞれ独立に水素原子、ハロゲン原子、アルキル基、アラルキル基、フェニル基、または置換フェニル基を表わし、Ｒ^５は付加重合性不飽和結合を持つ非環状有機基を表わす。]

[Wherein R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, a phenyl group or a substituted phenyl group, and R ⁵ represents an addition-polymerizable unsaturated bond. Represents an acyclic organic group having ]

  Specific examples of the addition polymerizable oxazoline include, for example, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2. -Oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like. One or a mixture of two or more selected from these groups can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially.

  The amount of addition polymerizable oxazoline used is not limited and is preferably 5% by mass or more in the oxazoline group-containing compound. If it is less than 5% by mass, the degree of curing is insufficient and the water resistance tends to be impaired.

  In the present invention, the other monomer is not particularly limited as long as it is a monomer that can be copolymerized with an addition-polymerizable oxazoline and does not react with the oxazoline group. For example, methyl (meth) acrylate, (meth) (Meth) acrylic acid esters such as butyl acrylate, 2-ethylhexyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, sodium (meth) acrylate, potassium (meth) acrylate, (meth) acrylic acid (Meth) acrylates such as ammonium, unsaturated nitriles such as (meth) acrylic nitrile, unsaturated amides such as (meth) acrylamide, N-methylol (meth) acrylamide, vinyl acetate, vinyl propionate, etc. Vinyl ethers, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, Α-olefins such as tylene and propion, halogen-containing α and β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride, α and β-unsaturated aromatics such as styrene and α-methylstyrene And monomers. These monomers can be used alone or in combination of two or more.

  The oxazoline group-containing compound can be produced by subjecting an addition-polymerizable oxazoline and, if necessary, at least one other monomer to solution polymerization or emulsion polymerization in an aqueous medium by a conventionally known polymerization method. The aqueous medium that can be used is not particularly limited as long as it is miscible with water. , Diethylene glycol, acetone, methyl ethyl ketone and the like.

  The amount of the oxazoline group-containing compound used is preferably 1 to 15% by mass, more preferably about 2 to 10% by mass, based on the carboxyl group-containing aqueous polymer. By setting it as 1 mass% or more, transparency is high and water resistance can be improved. On the other hand, if the amount exceeds 15% by mass, the water resistance is saturated. Therefore, by setting the amount to 15% by mass or less, the cost can be suppressed, and there is a non-uniform coating of a pear skin pattern on the protective layer formed on the intermediate layer. An effect of suppressing the generation is obtained, and a uniform coated surface is formed, so that further excellent transparency can be obtained. And the effect that the pot life of the coating liquid for intermediate | middle layers improves can also be acquired.

  In the present invention, other aqueous resins can be used as long as the desired effects are not impaired. For example, polyvinyl alcohol and derivatives thereof, starch and derivatives thereof, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, polyvinyl pyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic Examples thereof include water-soluble resins such as acid ester copolymers, styrene-maleic anhydride copolymers, isobutylene-maleic anhydride copolymers, casein, and gelatin. Moreover, what is necessary is just to use in the form of latex, when using hydrophobic resin as aqueous resin. Examples of the hydrophobic resin latex include vinyl acetate latex, urethane latex, acrylic latex, and styrene-butadiene latex. In addition, as the usage-amount of a carboxyl group-containing aqueous polymer, 40-95 mass% is preferable with respect to the total solid amount of an intermediate | middle layer.

  In the present invention, other crosslinking agents can be used as long as the desired effects are not impaired. Other crosslinking agents include glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, dialdehyde starch, melamine resin, polyamide resin, polyamide-epichlorohydrin resin, ketone-aldehyde resin, borax, boric acid, carbonic acid Examples include zirconium ammonium and epoxy compounds.

  Furthermore, the intermediate layer may contain various additives as required. Examples of the additive include surfactants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate / sodium salt, fatty acid metal salt, waxes such as polyethylene wax, carnauba wax, paraffin wax, ester wax, and kaolin. And pigments such as clay, talc, calcium carbonate, calcined kaolin, titanium oxide, amorphous silica, and aluminum hydroxide, antifoaming agents, fluorescent whitening agents, and coloring dyes.

  The intermediate layer is prepared by, for example, applying and drying an intermediate layer coating solution prepared by mixing and stirring a carboxyl group-containing aqueous polymer, an oxazoline group-containing compound, and, if necessary, an additive, on a heat-sensitive recording layer. Formed.

  The heat-sensitive recording layer of the present invention contains various known leuco dyes and colorants.

  Examples of leuco dyes include 3- [2,2-bis (1-ethyl-2-methylindol-3-yl) vinyl] -3- (4-diethylaminophenyl) phthalide, 3,3-bis (p-dimethyl). Aminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-cyclohexylamino-6-chlorofur Oran, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,8-dimethylfluorane, 3-diethylamino-6,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3-di (n-butyl) Mino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl- 7-anilinofluorane, 3-di (n-butyl) amino-6-chloro-7-anilinofluorane, 3-diethylamino-6-methyl-7- (3-toluidino) fluorane, 3-pyrrolidino-6 -Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3,3-bis [1- (4-Methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3- [p- (p-dimethylaminoaniline) ) Anilino] -6-methyl-7-chlorofluorane, 3-p- (p-chloroanilino) anilino-6-methyl-7-chlorofluorane, 3- [1,1-bis (1-ethyl-2-) Methylindol-3-yl)]-3-p-diethylaminophenylphthalide, 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide, 3,6-bis (dimethylamino) And fluorene-9-spiro-3 ′-(6′-dimethylamino) phthalide. These can be used alone or in combination of two or more.

  The leuco dye may be contained in the heat-sensitive recording layer in the form of solid fine particles wet-dispersed by a sand mill or the like together with a protective colloid agent such as polyvinyl alcohol or methyl cellulose, or composite particles containing a leuco dye and a hydrophobic resin. It may be contained in the heat-sensitive recording layer in the formed form. Here, the leuco dye is “a form in which composite particles containing a leuco dye and a hydrophobic resin are formed”. For example, (1) one or more leuco dyes are described in JP-A-60-244594. A form in which a hydrophobic resin is microencapsulated by a wall method, and (2) a base material comprising one or more leuco dyes and a hydrophobic resin such as polyisocyanate by a method described in JP-A-9-263057 And (3) a form in which a compound having an unsaturated carbon bond is polymerized by the method described in JP-A No. 2000-158822 on the surface of fine particles of one or more leuco dyes. The leuco dyes in these composite particles are highly separable from the outside, less subject to background fogging due to heat and humidity, and decoloring of the recording area. Since it is dissolved in a solvent, the transparency of the heat-sensitive recording layer is preferable from the viewpoint that it is superior to the case where the leuco dye is used in the form of solid fine particles. The solid fine particles of the leuco dye preferably have a volume average particle size of about 0.2 to 1.0 μm. On the other hand, the leuco dye composite particles preferably have a volume average particle diameter of about 0.5 to 3.0 μm, more preferably about 0.5 to 1.5 μm.

  Although it does not specifically limit as hydrophobic resin which forms a composite particle, For example, urea type resin, urethane type resin, urea-urethane type resin, styrene type resin, acrylic resin etc. are mentioned. Of these, urea resins and urea-urethane resins are preferred because they are excellent in heat-resistant background fogging properties and can provide a heat-sensitive recording layer having high adhesion strength.

  The content of the leuco dye is not particularly limited, but is preferably about 5 to 30% by mass with respect to the total solid content of the heat-sensitive recording layer. When the leuco dye is contained in the form of composite particles, the content of the leuco dye in the composite particles is preferably about 10 to 70% by mass, more preferably 35%, based on the total solid content of the composite particles. About 60 mass%.

  Further, in the composite particles, an aromatic organic compound (sensitizer) having a melting point of about 40 to 150 ° C. for enhancing recording sensitivity as described later, and 2-hydroxy-4-octyloxybenzophenone for enhancing light resistance. And a preservability improving agent such as hindered phenol and hindered amine for enhancing the preservability of the recording part.

  Examples of the colorant include 4,4′-isopropylidenediphenol, 4,4′-cyclohexylidenephenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, and benzyl 4-hydroxybenzoate. 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy-4′-allyloxydiphenylsulfone, bis (3-allyl-4 -Hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, bis (4-hydroxyphenylthioethoxy) methane, bis (p-hydroxyphenyl) acetic acid Phenolic compounds such as butyl, 4, 4 -Bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4'-bis (Np-tolylsulfonylaminocarbonylamino) diphenylmethane, Np-tolylsulfonyl-N'-phenyl Sulfonyl and ureido groups in molecules such as urea, Np-tolylsulfonyl-N′-p-butoxycarbonylphenylurea, Np-tolylsulfonyl-N′-3- (p-tolylsulfonyloxy) phenylurea , Zinc p-chlorobenzoate, zinc 4- [2- (p-methoxyphenoxy) ethyloxy] salicylate, zinc 4- [3- (p-tolylsulfonyl) propyloxy] salicylate, 5- [p- ( 2-p-methoxyphenoxyethoxy) cumyl] aromatic carbon such as zinc salicylate Zinc salts of phosphate and the like. These can be used alone or in combination of two or more.

  The content of the colorant is not particularly limited, and may be appropriately selected according to the type of the leuco dye and the colorant to be used. The colorant is usually 1 to 10 parts by mass with respect to 1 part by mass of the leuco dye. Preferably, it is about 1-5 mass parts more preferably.

  If necessary, the heat-sensitive recording layer may contain a sensitizer. Thereby, the recording sensitivity can be increased. Examples of the sensitizer include stearamide, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, p-benzylbiphenyl, naphthylbenzyl ether, benzyl-4-methylthiophenyl ether, 1 -Hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid-di-p-chlorobenzyl ester, oxalic acid-di-p-methylbenzyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid Examples include acid dibutyl ester.

  If necessary, the thermosensitive recording layer may contain a storage stability improving agent. Thereby, the preservability of a recording part can be improved. Examples of the storage stability improver 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 (4-hydroxyphenyl) -1-phenylethane, 2,2'-ethylidenebis (4,6-di-tert-butylphenol), 1,4-bis [α- Methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 4,4′-thiobis (2-methyl-6) -Tert-butylphenol), 1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 4- (2-methyl-1,2) Epoxyethyl) diphenylsulfone, 4- (2-ethyl-1,2-epoxyethyl) diphenylsulfone, 4-benzyloxyphenyl-4 ′-(2-methyl-2,3-epoxypropyloxy) phenylsulfone, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-octyloxybenzophenone and the like.

The heat-sensitive recording layer is prepared by mixing and stirring a leuco dye, a colorant, a sensitizer, if necessary a dispersion of a storability improver, an adhesive, and an additive, for example, using water as a medium. The coating solution is applied and dried on the transparent support so that the coating amount after drying is about 3 to 30 g / m ² .

  As the adhesive, either a water-soluble resin or a hydrophobic resin can be used. Examples of the water-soluble resin include polyvinyl alcohol and derivatives thereof, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and ethylcellulose, polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide -Acrylic acid ester-methacrylic acid ester copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and the like. The hydrophobic resin may be used in the form of latex, and examples thereof include vinyl acetate latex, urethane latex, acrylic latex, and styrene-butadiene latex. Although it does not specifically limit as content of an adhesive agent, About 5-40 mass% is preferable with respect to the total solid of a thermosensitive recording layer.

  Further, the heat-sensitive recording layer may contain other commonly used additives other than those described above. Examples of other additives include surfactants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate-sodium salt, and fatty acid metal salts, and waxes such as polyethylene wax, carnauba wax, paraffin wax, and ester wax. , Kaolin, clay, talc, calcium carbonate, calcined kaolin, titanium oxide, amorphous silica, pigments such as aluminum hydroxide, glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, dialdehyde starch, melamine Resin, polyamide resin, polyamide-epichlorohydrin resin, ketone-aldehyde resin, borax, boric acid, ammonium zirconium carbonate, epoxy compound, hydrazine Waterproofing agents such as compounds, antifoaming agents, fluorescent whitening agents, coloring dyes, and the like.

  In the present invention, the recording runnability and chemical resistance can be improved by having a protective layer. As the pigment constituting the protective layer, kaolin, aluminum hydroxide, calcined kaolin, colloidal silica, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, amorphous silica, barium sulfate, talc, styrene resin filler, nylon resin filler, Examples include urea / formalin resin filler. In particular, it is preferable to contain calcined kaolin together with at least one of kaolin and aluminum hydroxide from the viewpoint of suppressing residue adhesion to the thermal head. The content of the calcined kaolin is preferably about 0.3 to 5% by mass with respect to the total solid content of the protective layer. Further, the total pigment amount relative to the total solid amount of the protective layer is preferably about 15 to 35% by mass.

  As the adhesive constituting the protective layer, both water-soluble resins and hydrophobic resins can be used. Examples of the water-soluble resin include completely saponified or partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, and styrene. -Alkali salts of maleic anhydride copolymers, alkali salts of ethylene-acrylic acid copolymers, alkali salts of styrene-acrylic acid copolymers, and the like. The hydrophobic resin may be used in the form of a latex, and examples thereof include latex such as styrene-butadiene latex, acrylic latex, and urethane latex. In addition, 30-95 mass% is preferable with respect to the total solid of a protective layer, and, as for content of an adhesive agent, 50-85 mass% is more preferable.

  Among the adhesives, a specific polyvinyl alcohol composed of at least one selected from acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol and silicon-modified polyvinyl alcohol is preferable, and acetoacetyl-modified polyvinyl alcohol is more preferable. . Moreover, it is particularly preferable to use a hydrophobic resin obtained from such specific polyvinyl alcohol and urethane latex, since a protective layer having excellent film forming properties can be obtained.

  Examples of the resin obtained from such urethane latex include a polyester polyurethane resin having a softening point of 80 ° C. or higher, a polyether polyurethane resin, and an aliphatic polyurethane resin. In addition, although it does not specifically limit about the usage rate of resin obtained from specific polyvinyl alcohol and urethane type latex, 10-100 mass parts with respect to 100 mass parts of specific polyvinyl alcohol, Preferably it is 20-70. It is preferable to use a resin obtained from parts by mass of urethane latex.

  Further, the protective layer includes additives such as lubricants such as alkyl phosphates, stearamide, zinc stearate, calcium stearate, glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, boron Cross-linking agents (waterproofing agents) such as acid, borax, dialdehyde starch, melamine resin, polyamide resin, polyamide-epichlorohydrin resin, ketone-aldehyde resin, hydrazide compound such as adipic acid dihydrazide, zirconium carbonate ammonium and epoxy compound , Surfactants such as dialkylsulfosuccinates, alkylsulfonates, alkylcarboxylates, and alkylethylene oxides, fluorosurfactants, and the like.

The protective layer has a coating amount of 0.5 to 10 g after drying, for example, a protective layer coating liquid prepared by mixing and stirring an adhesive, a pigment, and, if necessary, an additive, with water as a medium on the intermediate layer. / M ² , preferably by coating and drying so as to be in the range of about 1 to 5 g / m ² .

  The method for forming the heat-sensitive recording layer, intermediate layer and protective layer is not particularly limited. It is formed by a known appropriate application method such as coating. Further, the above coating liquid may be applied and dried one by one, or the same coating liquid may be applied in two or more layers. Furthermore, two or more layers can be applied simultaneously. In the present invention, it is preferable to form by simultaneously applying and drying at least three layers of the heat-sensitive recording layer and the protective layer adjacent to the intermediate layer, since the effects of the present invention can be sufficiently exhibited.

  The transparent support is not limited. For example, a resin film having a thickness of about 40 to 250 μm is used, and specific examples of such a transparent film include, for example, a non-stretched or biaxially stretched polyethylene terephthalate film (PET film), Examples thereof include a polystyrene film, a polypropylene film, and a polycarbonate film. Among these, a PET film having a thickness of 100 to 200 μm and colored in blue and having a haze value of 10% or less is preferable because it has excellent suitability for Saucusten.

  In the present invention, an anchor coat layer may be provided on the surface of the transparent support in order to improve the adhesion to the heat-sensitive recording layer, or a corona discharge treatment may be performed prior to the application of the heat-sensitive recording layer coating liquid. Further, a conductive treatment with a conductive agent may be performed. Further, a back layer containing a pigment such as resin particles and an adhesive can be formed on the back surface of the support in order to improve the running property of the thermosensitive recording material. Furthermore, the heat-sensitive recording layer can be a multicolor heat-sensitive recording layer, a glossy layer cured by irradiating ultraviolet rays or electron beams on the protective layer, or a super calender in any process after forming each layer Various known techniques in the field of manufacturing a thermal recording material, such as a smoothing treatment, can be added as necessary.

The present invention will be described in more detail with reference to examples, but of course, the present invention is not limited thereto. Unless otherwise specified, “parts” and “%” represent “parts by mass” and “mass%”, respectively.
The average particle size of the composite particles and pigment used in Examples and Comparative Examples was measured using a laser diffraction particle size distribution analyzer SALD2000 (manufactured by Shimadzu Corporation), and the average particle size of the colorant was a dynamic light scattering type. It measured using the particle size distribution measuring apparatus LB-500 (made by Horiba Seisakusho).

Example 1
(Preparation of intermediate layer coating solution)
650 parts of 15% aqueous solution of carboxyl group-modified polyvinyl alcohol (trade name: KL-118, manufactured by Kuraray Co., Ltd.), oxazoline group-containing compound [trade name: Epocross (registered trademark) WS-700, solid content concentration: 25%, Nippon Shokubai Co., Ltd. Product] A composition comprising 30 parts and 130 parts of water was mixed and stirred to obtain a coating solution for an intermediate layer.

・ Preparation of liquid A (preparation of composite particle dispersion)
11 parts of 3-diethylamino-6-methyl-7- (3-toluidino) fluorane, 6 parts of 3-diethylamino-6,8-dimethylfluorane and 3,3-bis (4-diethylamino-2-ethoxy) as leuco dyes Phenyl) -4-azaphthalide 5 parts and 2-hydroxy-4-octyloxybenzophenone 10 parts, dicyclohexylmethane-4,4′-diisocyanate (trade name: Desmodur W, manufactured by Sumitomo Bayer Urethane Co., Ltd.), m -Tetramethylxylylene diisocyanate (trade name: TMXDI, manufactured by Mitsui Takeda Chemical Co., Ltd.) is heated and dissolved (150 ° C) in a mixed solvent consisting of 12 parts, and this solution is polyvinyl alcohol (trade name: Poval PVA-217EE, manufactured by Kuraray Co., Ltd.). ) 8.5 parts and acetylene glycol as ethylene surfactant The mixture was gradually added to 100 parts of a 10% aqueous solution containing 1.5 parts of a xide adduct (trade name: Orphine E1010, manufactured by Nissin Chemical Co., Ltd.), and emulsified and dispersed by stirring at a rotational speed of 10,000 rpm using a homogenizer. To this emulsified dispersion, an aqueous solution in which 30 parts of water and 2.5 parts of a polyvalent amine compound (trade name: Epicure T, manufactured by Shell International Petroleum) were dissolved in 22.5 parts of water was added and homogenized. This emulsified dispersion was heated to 75 ° C. and subjected to a polymerization reaction for 7 hours to prepare a leuco dye-containing composite particle dispersion having an average particle size of 0.8 μm. In addition, it diluted with water so that the leuco dye containing composite particle dispersion liquid might be 25%.

・ B liquid preparation (preparation of colorant dispersion)
A composition comprising 42 parts of 4,4′-cyclohexylidenephenol, 60 parts of a 10% aqueous solution of sulfone-modified polyvinyl alcohol, and 18 parts of water was pulverized using Ultraviscomil until the average particle size became 0.3 μm. Thus, a colorant dispersion was obtained.

(Preparation of thermal recording layer coating solution)
100 parts of A liquid, 70 parts of B liquid, 70 parts of a 30% dispersion of stearamide, 46 parts of a styrene-butadiene latex having a solid content concentration of 48% (trade name: Smartex PA-9280, manufactured by Japan A & L), And the composition which consists of 30 parts of water was mixed and stirred, and the coating liquid for thermosensitive recording layers was obtained.

(Preparation of coating solution for protective layer)
Ionomer-type urethane resin latex [trade name: Hydran (registered trademark) AP-30F, manufactured by Dainippon Ink & Chemicals, Inc., solid content concentration 20%], 100 parts, acetoacetyl-modified polyvinyl alcohol [trade name: Goseifamer (registered) Trademark) Z-410, polymerization degree: about 2300, saponification degree: about 98 mol%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] 8 parts aqueous solution 500 parts, kaolin (trade name: UW-90, manufactured by Engelhard) 50 parts of 60% slurry atomized to a particle size of 1.6 μm, 2 parts of 40% slurry of calcined kaolin (trade name: Ansilex 93, manufactured by Engelhard) with an average particle size of 2.5 μm, stearic acid Amide (trade name: Hymicron L-271, solid concentration 25%, manufactured by Chukyo Yushi Co., Ltd.) 26 parts, stearyl phosphate potassium salt (product Name: Wopol 1800, solid content 35%, Matsumoto Yushi Seiyaku Co., Ltd.) 4 parts, perfluoroalkylethylene oxide adduct [trade name: Surflon (registered trademark) S-145, Seimi Chemical Co., Ltd.] 10% aqueous solution 15 parts And the composition which consists of 300 parts of water was mixed and stirred, and the coating liquid for protective layers was obtained.

(Preparation of thermal recording material)
On one side of a blue transparent polyethylene terephthalate film (trade name: Melinex 912, thickness 175 μm, manufactured by Teijin DuPont) as a support, from the support side, a coating solution for a thermal recording layer, a coating solution for an intermediate layer, and a protective layer coating amount of ^{20 g} / ^{m 2} after drying, respectively in the order of the coating liquid, 2.0g / m 2, by coating and drying for each layer using a slot die coater so that 1.5 g / ^{m 2} heat-sensitive recording material Got.

Example 2
In the preparation of the intermediate layer coating liquid of Example 1, 350 parts of a 15% aqueous solution of carboxyl group-modified polyvinyl alcohol (trade name: KL-118, manufactured by Kuraray Co., Ltd.), an aqueous medium containing a polyurethane ionomer, Latex polymerized with butadiene monomer (trade name: Pateracol H2020A, solid concentration 41%, manufactured by Dainippon Ink & Chemicals, Inc.) 120 parts, oxazoline group-containing compound [trade name: Epocross (registered trademark) WS-700, solid content A thermosensitive recording material was obtained in the same manner as in Example 1 except that 30 parts of a concentration of 25%, manufactured by Nippon Shokubai Co., Ltd., and 300 parts of water were used.

Example 3
In the production of the heat-sensitive recording material of Example 1, a coating solution for a heat-sensitive recording layer was formed on one side of a blue transparent polyethylene terephthalate film (trade name: Melinex 912, thickness 175 μm, manufactured by Teijin DuPont) as a support. , the intermediate layer coating solution, the coating amount after drying each in the order of protective layer coating solution is ^{20g / m 2, 2.0g / m} 2, using a slide bead coater such that the 1.5 g / ^{m 2} 3 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the layers were simultaneously applied and dried.

Comparative Example 1
In the preparation of the intermediate layer coating liquid of Example 1, instead of 30 parts of an oxazoline group-containing compound [trade name: Epocross (registered trademark) WS-700, solid concentration 25%, manufactured by Nippon Shokubai Co., Ltd.], adipic acid dihydrazide A thermal recording material was obtained in the same manner as in Example 1 except that 50 parts (trade name: O-Link S05, solid content concentration 5%, manufactured by Otsuka Chemical Co., Ltd.) were used.

Comparative Example 2
In the preparation of the intermediate layer coating liquid of Example 1, 650 parts of a 15% aqueous solution of completely saponified polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.), an oxazoline group-containing compound [trade name: Epocross (registered trademark) WS -700, manufactured by Nippon Shokubai Co., Ltd., solid content concentration 25%], and 25 parts of water and 100 parts of water were used in the same manner as in Example 1 to obtain a heat-sensitive recording material.

Comparative Example 3
Except that the oxazoline group-containing compound [trade name: Epocross (registered trademark) WS-700, solid content concentration: 25%, manufactured by Nippon Shokubai Co., Ltd.] was not used in the preparation of the intermediate layer coating liquid of Example 2. A heat-sensitive recording material was obtained in the same manner as in Example 2.

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

(Recording sensitivity)
The thermal recording medium is recorded in the gradation mode using the thermal printing printer UP-DF500 (manufactured by Sony Corporation), and the recording sections of the 9th and 16th gradations of all 16 gradations in an environment of 23 ° C.-50% RH. The concentration of was measured. The density of the unrecorded part and the recorded part was measured in a visual mode of a Macbeth densitometer (trade name: TR-927J type, manufactured by Macbeth).

(Water resistance evaluation)
5 cc of water droplets were dropped on an unrecorded portion of the heat-sensitive recording surface of the heat-sensitive recording material, and after 10 seconds, the water droplets were wiped off using a nonwoven fabric, and the dropping surface was visually evaluated.
○: No change.
○ △: Almost no whitening is observed.
Δ: Whitening is observed.
X: Peeling of the heat-sensitive recording layer occurs.

(Haze value)
The haze value of the heat-sensitive recording material was measured with a haze meter (trade name: TC-H, manufactured by Tokyo Denshoku Co., Ltd.) to evaluate the transparency. The smaller the value, the better the transparency.

Claims (6)

  A thermosensitive recording medium comprising at least a thermosensitive recording layer containing a leuco dye and a colorant, an intermediate layer and a protective layer on one side of a transparent support, comprising a carboxyl group-containing aqueous polymer and an oxazoline group as a crosslinking agent A heat-sensitive recording material comprising an intermediate layer formed by applying and drying an intermediate layer coating solution containing a compound.   The heat-sensitive recording material according to claim 1, wherein the amount of the oxazoline group-containing compound used is 1 to 15% by mass relative to the carboxyl group-containing aqueous polymer.   The heat-sensitive recording material according to claim 1, wherein the leuco dye is contained in the heat-sensitive recording layer in the form of composite particles containing a leuco dye and a hydrophobic resin.   The heat-sensitive recording material according to claim 3, wherein the hydrophobic resin forming the composite particles is a urea resin or a urea-urethane resin.   The heat-sensitive recording material according to any one of claims 1 to 4, wherein the heat-sensitive recording layer, the intermediate layer, and the protective layer are layers formed by simultaneously applying and drying.   The heat-sensitive recording material according to claim 1, wherein the transparent support is a polyethylene terephthalate film.