JP2011201178A - Thermal recording material - Google Patents

Abstract

In a thermal recording material in which a thermal recording layer and a protective layer are substantially simultaneously curtain-coated after providing an undercoat layer containing a pigment and a binder on a support, interlayer mixing is suppressed and good color development is achieved. A heat-sensitive recording material having sensitivity, solvent barrier properties, and sticking suitability is provided.
An undercoat layer containing a pigment, a binder, boric acid or borax is provided on a support, and then a plurality of coating liquids constituting a heat-sensitive recording layer and a protective layer are substantially simultaneously curtain-coated. A heat-sensitive recording material, comprising a polyvinyl alcohol as a binder in the heat-sensitive recording layer.
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Description

  The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having good color development sensitivity, solvent barrier properties, and sticking suitability.

  A heat-sensitive recording material generally comprises a heat-sensitive recording layer mainly comprising an electron-donating usually colorless or light-colored dye precursor and an electron-accepting developer on a support. By heating with a thermal pen, laser light, etc., the dye precursor and the developer react instantaneously to obtain a recorded image. Such a heat-sensitive recording material can record a recorded image with a relatively simple device. It has advantages such as ease of maintenance, no generation of noise, etc., and it is used in a wide range of fields such as facsimiles, measurement recorders, printers, label printers, tickets, ticket issuing machines, etc. .

  As the uses and demands of thermal recording materials are expanding, a recorded image that can be read even at low applied energy can be obtained. The recorded image does not disappear even when it comes into contact with various chemicals. There is a demand for heat-sensitive recording materials that have high color development sensitivity, such as no sticking to the recording material and poor running), and excellent solvent barrier properties and sticking suitability. In order to obtain a heat-sensitive recording material with high color development sensitivity, a method of increasing the efficiency of applied energy by coating an undercoat layer containing heat-absorbing inorganic pigment or organic pigment on the support mainly for heat insulation. Generally done. In addition, for example, in order to obtain a solvent barrier property for cosmetics such as water-based ink, oil-based ink, fluorescent pen, adhesive, hand cream, hair tonic, and emulsion, and to improve sticking suitability, etc., on the thermal recording layer In addition, a method of coating a protective layer containing a lubricant, an ultraviolet absorber, an antioxidant, a water-soluble polymer, a water-dispersible resin, or the like is generally performed. Furthermore, as a method for improving sticking suitability, a method is generally employed in which an oil-absorbing inorganic pigment is added to the heat-sensitive recording layer, and a molten component such as a developer or a dye in the heat-sensitive recording layer is adsorbed. As described above, the heat-sensitive recording material comprises a plurality of undercoat layers mainly for heat insulation on the support, a heat-sensitive recording layer that develops color with applied energy, and a protective layer mainly intended to provide improved solvent barrier properties and sticking suitability. This layer is formed by coating.

  Conventionally, in a heat-sensitive recording material in which a plurality of layers are coated on a support, each layer is coated and dried for each layer by air knife coating, blade coating, rod coating, reverse roll coating, etc. The heat-sensitive recording material coated and dried for each layer as described above has problems such as poor coating quality and reduced productivity caused by multiple coatings.

  In response to the problem of reduced productivity caused by multiple times of application, the curtain application methods disclosed in Patent Documents 1 and 2 apply the application liquids constituting multiple layers simultaneously using a slide curtain coater or the like, Multi-layer simultaneous application is also possible. This simultaneous application of multiple layers can greatly improve the productivity when a plurality of layers are applied.

  However, when a coating solution that forms a plurality of layers is coated on a support in such a multilayer simultaneous coating, the coating solution that forms each layer is mixed, and the layer configuration is disturbed. appear.

  Conventionally, in the field of photographic photosensitive materials and the like in which multi-layer simultaneous coating is performed, gelatin is usually contained as a binder in the coating liquid, and cooling is performed immediately after the coating liquid is transferred onto the support. Gelatin in the coating solution gels and the coating solution is immobilized, so that the layer structure is not disturbed and interlayer mixing is difficult to occur. On the other hand, in the heat-sensitive recording material, if gelatin that only suppresses interlayer mixing is added, there are problems that characteristics such as color development sensitivity and solvent barrier property are greatly deteriorated. It cannot be prevented.

  In Patent Documents 3 and 4, when a protective layer is applied, after applying a coating liquid that constitutes an adjacent lower layer, a coating liquid that constitutes the protective layer is applied without interposing a drying step. Although a method of suppressing the interlayer mixing due to the penetration of the coating solution constituting the protective layer into the adjacent lower layer by performing on-wet coating and sufficiently exerting the function of each layer is described, This method alone is insufficient to prevent interlayer mixing, and it has been difficult to obtain a heat-sensitive recording material having good color development sensitivity, solvent barrier properties, sticking suitability, and the like.

  Further, in Patent Document 5, in the multilayer simultaneous coating in which a plurality of layers are simultaneously coated, the viscosity of the coating liquid constituting the plurality of layers is all 100 mPa · s or more, thereby reducing interlayer mixing. However, it is difficult to prevent interlayer mixing, and it is difficult to obtain a heat-sensitive recording material having good color development sensitivity and solvent barrier properties.

  Patent Document 6 discloses a multilayer coating sheet and a method for producing the multilayer coating sheet, in which each layer is divided using an intermediate layer containing a water-soluble resin or a water-dispersible resin in order to prevent interlayer mixing, and simultaneous multilayer coating is performed. However, although it is possible to suppress interlayer mixing, there is a problem that the amount of coating solution increases, so that the load during drying increases and productivity decreases.

  As described above, it has been difficult to obtain a heat-sensitive recording material having good color development sensitivity, solvent barrier property, and sticking suitability by simultaneous multilayer coating without interlayer mixing.

Japanese Patent Publication No.49-24133 Japanese Patent Publication No.49-35447 JP 2007-326221 A JP 2007-326220 A JP 2001-18526 A JP 2008-238503 A

  In view of the above-mentioned problems of the prior art, the present invention is a heat-sensitive recording material formed by applying a primer layer containing a pigment and a binder on a support, and then simultaneously curtain-coating a heat-sensitive recording layer and a protective layer. It is an object of the present invention to provide a heat-sensitive recording material having good color development sensitivity, solvent barrier properties, and sticking suitability.

  As a result of intensive studies to solve the above problems, the present inventors have determined that a plurality of coating liquids constituting a heat-sensitive recording layer and a protective layer after providing an undercoat layer containing a pigment, a binder, boric acid or borax on a support. It has been found that the above-mentioned problems can be solved by a heat-sensitive recording material formed by applying curtains at substantially the same time and characterized in that the heat-sensitive recording layer contains polyvinyl alcohols as a binder.

  According to the present invention, in a heat-sensitive recording material formed by applying a coating liquid constituting a heat-sensitive recording layer and a protective layer substantially simultaneously with a curtain after providing an undercoat layer on a support, good color development sensitivity is obtained. It is possible to provide a heat-sensitive recording material having solvent barrier properties and sticking suitability.

  Next, the form for implementing this invention is demonstrated.

  In the heat-sensitive recording material of the present invention, an undercoat layer containing a pigment, a binder, boric acid or borax is provided on a support, and then a plurality of coating liquids constituting the heat-sensitive recording layer and the protective layer are substantially curtain-coated. The heat-sensitive recording material is characterized in that the heat-sensitive recording layer contains polyvinyl alcohol as a binder.

  In the present invention, on an undercoat layer containing a pigment, a binder, boric acid or borax, a coating liquid constituting a thermal recording layer (hereinafter referred to as a thermal recording layer coating liquid) and a coating liquid constituting a protective layer (hereinafter referred to as a protective layer). (The coating solution) is applied substantially simultaneously, and the polyvinyl alcohol contained in the heat-sensitive recording layer gels instantaneously when it comes into contact with boric acid or borax in the undercoat layer, thereby suppressing interlayer mixing between the heat-sensitive recording layer and the protective layer. It is considered that a heat-sensitive recording material having good color development sensitivity, solvent barrier properties, and sticking suitability can be obtained because the functions of each layer can be sufficiently exhibited.

  Next, the undercoat layer according to the present invention will be described in detail.

  In the heat-sensitive recording material of the present invention, an undercoat layer containing a pigment, a binder, boric acid or borax is coated on the support. The amount of boric acid or borax added to the undercoat layer is the total solid content of the undercoat layer. On the other hand, it is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 5% by mass or less. If the amount added to the total solid content of the boric acid or borax undercoat layer is less than 0.1% by mass, the polyvinyl alcohol in the thermal recording layer coating solution will instantly gel when it comes into contact with the boric acid or borax in the undercoat layer. Therefore, interlayer mixing of the thermal recording layer coating solution and the protective layer coating solution is induced, and the functions that each layer should originally perform cannot be sufficiently exhibited, and it becomes difficult to obtain good color development sensitivity, solvent barrier properties, and sticking suitability. . On the other hand, if it exceeds 10% by mass, it is difficult to obtain good color development sensitivity.

  The pigments added to the undercoat layer according to the present invention can be broadly classified into organic or inorganic pigments. Examples of the organic pigment according to the present invention include polyamide resin, polyester resin, polycarbonate resin, polyether resin, polyolefin resin, polysulfone resin, polystyrene resin, polyvinyl chloride resin, polyvinylidene chloride resin, and ethylene-vinyl acetate copolymer. Organic pigments using generally known resins such as resins, polymethyl methacrylate, ionomer resins, polyphenylene sulfide resins, styrene copolymer resins, and the like can be used. In addition, in order to increase the printing density in the low energy region, an organic pigment with high heat insulation is used.

Examples of the organic pigment having high heat insulation include a method of forming a layer containing a foaming agent that generates a gas such as CO ₂ , N ₂ , NH ₃ , and O ₂ and a thermoplastic polymer. However, this method requires a step of foaming the foam and has production problems such as difficulty in controlling to obtain a stable quality, and therefore has a non-foaming organic pigment, particularly a hollow structure. Organic hollow pigments are widely used.

  As an example of the non-foaming organic hollow pigment, JP-A-4-220393, JP-A-4-241987, JP-A-5-318927, which contains a thermoplastic polymer substance as a shell and contains air or other gas inside. Such as a non-foaming organic hollow pigment described in JP-A-10-264536, or a spherical hollow polymer particle made of a thermoplastic polymer substance described in JP-A-10-264536. And organic pigments that are bowl-shaped with openings, and organic pigments with through holes.

  As the non-foaming organic hollow pigment, particles having a hollow ratio (volume ratio of the space portion to the total volume of the resin portion and the space portion of the particle) of 20 to 90%, more preferably 40 to 90% are used. For example, it is commercially available as the SX series from Rohm and Haas Japan Co., Ltd., and from the Ropeke series and JSR Co., Ltd., and can be obtained. Specific examples include Raw Pake HP-91, Low Pake OP-62, Low Pake OP-84J, SX8782, SX8782 (D), SX866, and the like.

  In addition, the organic pigment having a through-hole is a (meth) crosslinkable monomer mixture having two or more polymerizable unsaturated bonds in one molecule such as trimethylolpropane trimethacrylate, divinylbenzene, and ethylene glycol diacrylate. It can be obtained by emulsion polymerization with an aromatic vinyl compound vinyl monomer such as acrylic acid esters, vinyl acetate, vinyl esters, vinyl cyanide compounds, halogenated vinyl compounds, styrene, α-methylstyrene, vinyltoluene, etc. They are commercially available from Mitsui Chemicals, Inc. under the product names such as Grosdale 2001TX and Grosdale 2000TX.

  Further, an organic pigment having a bowl-like shape having an opening as obtained by cutting a part of a spherical hollow polymer particle made of a thermoplastic polymer material described in JP-A-10-264536 on a plane. However, when it is present in the undercoat layer, it has high heat insulating properties. This is commercially available, for example, under the product name MH-8055 from Nippon Zeon Co., Ltd.

  An organic hollow pigment having a thermoplastic polymer as a shell, an organic pigment having a bowl-like shape, or an organic pigment having a through-hole having an average particle outer diameter of 0.3 to 20 μm can be used. Are preferred. When the average particle outer diameter is smaller than 0.3 μm, there are problems in production such as difficulty in making the hollow ratio arbitrary, or in cost, and conversely, those larger than 20 μm are the surface after coating and drying. Therefore, the adhesion with the thermal head is lowered, the dot reproducibility is deteriorated, and the effect of improving the color development sensitivity is lowered. Accordingly, it is desirable that such particle size distribution has an average particle outer diameter in the above range, and at the same time, has a small distribution and a uniform distribution peak.

  Examples of inorganic pigments added to the undercoat layer include diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, Examples thereof include inorganic pigments such as barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate, and colloidal silica.

  An example of the inorganic pigment added to the undercoat layer is calcined kaolin having high heat insulation and oil absorption, and is commercially available, for example, under the product name Ansilex from Engelhard. The calcined kaolin can be obtained by various production methods. For example, a partially calcined kaolin produced by calcining kaolinite at a temperature of about 650 to 700 ° C. and a completely calcined kaolin calcined at about 1000 to 1050 ° C. There is. The oil absorption of the calcined kaolin obtained by these methods is 80 to 120 ml / 100 g, which is highly effective in improving the color development sensitivity and sticking suitability. Here, the method for measuring the oil absorption is a method based on JIS-K5101.

  When an organic pigment and an inorganic pigment are used in combination as the pigment for the undercoat layer, these ratios are not particularly limited. In general, inorganic pigments have poor heat insulation properties compared to organic pigments, but the color sensitivity of the resulting heat-sensitive recording material is low, but because they have higher oil absorption than organic pigments, they have sticking suitability and headcass suitability. Improve. The ratio of the organic pigment and the inorganic pigment is appropriately selected according to the target color development sensitivity, sticking suitability, and head residue suitability.

  A binder is added to the undercoat layer in order to obtain good surface strength and the like. The binder includes unmodified starch, oxidized starch, phosphate esterified starch, urea modified phosphate esterified starch, hydroxyethylated starch, cold water soluble starch, pyrodextrin, unmodified polyvinyl alcohol, diacetone modified polyvinyl alcohol, silanol modified polyvinyl. Alcohol, epoxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acrylic acid amide-acrylonitrile-modified polyvinyl alcohol, hydroxymethylcellulose, hydroxyethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, gelatin, casein, sodium alginate, polyvinylpyrrolidone, Water-soluble polymers such as polyacrylamide, acrylamide-acrylic acid Ter copolymer, acrylamide-acrylic acid ester-methacrylic acid terpolymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, alkali salt of styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer Water-soluble resin such as alkali salt of polymer, alkali salt of isobutylene-maleic anhydride copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene copolymer, acrylonitrile-butadiene -Water dispersibility of styrene terpolymer, polyvinyl acetate, vinyl acetate-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, polyacrylic acid ester, styrene-acrylic acid ester copolymer, polyurethane, etc. Resin, these may be used alone or in multiple sets It can be used in conjunction.

  The amount of binder added in the undercoat layer is not particularly limited, but usually 5 parts by mass or more and 50 parts by mass with respect to 100 parts by mass of the organic or inorganic pigment in the undercoat layer in order to obtain good color development sensitivity and coating layer strength. Hereinafter, it is more preferably added in an amount of 10 to 40 parts by mass.

  Examples of the auxiliary agent added to the undercoat layer coating solution include a viscosity modifier, an antifoaming agent, an antifoaming agent, a surfactant, a coloring dye, a fluorescent whitening agent, a preservative, and a lubricant.

  The coating solution constituting the undercoat layer is usually dried on a support by a known coater and then dried. Specific examples of the coater include a bar coater, a rod blade coater, an air knife coater, a blade coater, a roll coater, a film press coater, a curtain coater, a gravure coater, and a spray coater. In addition, the undercoat layer may be applied by various printing machines using a planographic, letterpress, flexographic, gravure, screen, hot melt, or the like.

Subbing layer according to the present invention, an undercoat layer coating solution, the coating amount after drying 1 to 30 g / m ^2, coating preferably on a support so as to 2 to 20 g / m ^2, dried Coating Is done. When the coating amount of the undercoat layer after drying is less than 1 g / m ² , the support cannot be sufficiently covered and the heat insulating property is insufficient, so that good color sensitivity cannot be obtained. Moreover, even if it coats exceeding 30 g / m < ² >, the improvement of color development sensitivity cannot be expected.

  After the undercoat layer is applied, a calendar process such as a machine calendar, a TG calendar, a soft calendar, a super calendar, and a shoe calendar can be performed for the purpose of further improving the smoothness.

  Next, the thermal recording layer and the protective layer according to the present invention which are applied by curtain coating substantially simultaneously will be described in detail.

  In the present invention, the thermal recording layer coating solution and the protective layer coating solution are applied onto the undercoat layer substantially simultaneously by curtain coating and then dried.

  As a method of applying the coating liquid constituting a plurality of layers substantially simultaneously, a method of simultaneously applying multiple layers by using a slide hopper type such as a slide bead coater or a slide curtain coater, or an extrusion type coater, or Examples include a so-called wet-on-wet coating method in which a plurality of slit die coaters are used and a heat-sensitive recording layer coating solution applied on an undercoat layer is wet while a protective layer coating solution is applied. .

  It is necessary to add polyvinyl alcohol as a binder to the heat-sensitive recording layer according to the present invention. By adding polyvinyl alcohols to the heat-sensitive recording layer, the heat-sensitive recording layer coating solution instantly gels with boric acid or borax in the undercoat layer, which can suppress inter-layer mixing with the protective layer coating solution, good solvent barrier properties, etc. Can be obtained. The addition amount of the polyvinyl alcohol is preferably 5% by mass or more and 30% by mass or less, more preferably 8% by mass or more and 18% by mass or less, with respect to the total solid content of the thermosensitive recording layer. When the amount of polyvinyl alcohol added is less than 5% by mass based on the total solid content of the heat-sensitive recording layer, even if the heat-sensitive recording layer coating solution comes into contact with boric acid or borax in the undercoat layer, it does not instantly gel and mixes between layers. Occurs, the color development sensitivity and the solvent barrier property are lowered, and it is not preferable, and when it exceeds 30% by mass, the color development sensitivity is remarkably lowered, which is not preferable.

  The degree of polymerization of the polyvinyl alcohol used in the heat-sensitive recording layer according to the present invention is not particularly limited, but is usually selected from the range of 100 to 3,000, and the degree of saponification is not particularly limited as long as it is a water-soluble range. Usually, it is selected from the range of 70 to 100 mol%.

  Polyvinyl alcohols include unmodified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, epoxy-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and acetoacetyl-modified. Polyvinyl alcohol and the like can be mentioned, and modified polyvinyl alcohol obtained by copolymerizing ethylene, vinyl ether having a long chain alkyl group, (meth) acrylamide or the like can be used, and these can be used alone or in combination.

  In the heat-sensitive recording layer according to the present invention, the above-mentioned polyvinyl alcohols and various binders used in usual coating can be used in combination as a binder. Specifically, starches, hydroxymethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, gelatin, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid ternary Copolymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, alkali salt of styrene-maleic anhydride copolymer, alkali salt of ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer Water-soluble binder such as alkali salt, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene copolymer, acrylonitrile-butadiene-styrene Copolymers, polyvinyl acetate, vinyl acetate-acrylic acid ester copolymers, ethylene-vinyl acetate copolymers, polyacrylic acid esters, styrene-acrylic acid ester copolymers, water-dispersible binders such as polyurethane, etc. However, it is not limited to these.

  An inorganic pigment can be added to the heat-sensitive recording layer according to the present invention for the purpose of improving sticking suitability.

  Examples of the inorganic pigment added to the heat-sensitive recording layer according to the present invention include diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, and hydroxide. Examples include inorganic pigments such as magnesium, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate, and colloidal silica, but are not limited thereto.

  The surface tension of the heat-sensitive recording layer coating solution according to the present invention is adjusted as necessary in order to form a uniform curtain during curtain coating. Further, by adjusting the surface tension of the thermal recording layer coating solution to be higher than the surface tension of the protective layer coating solution, problems such as repellency of the protective layer and pinholes due to the difference in surface energy can be suppressed.

  As a method for adjusting the surface tension of the coating solution, a method of adding various surfactants is common. The kind of surfactant to be added is not particularly limited, and any surfactant having an effect of reducing the surface tension can be used.

  Examples of the surfactant include sodium n-dodecylbenzenesulfonate, ammonium n-dodecylbenzenesulfonate, potassium n-dodecylbenzenesulfonate, triethanolamine n-dodecylbenzenesulfonate, sodium n-decylbenzenesulfonate, sulfonates such as sodium n-undecylbenzenesulfonate and sodium pentadecylbenzenesulfonate, anionic surfactants such as carboxylic acid ester, sulfate ester salt and phosphate ester salt, oxyethylene chain surfactant, acetylene Diol derivatives, sorbitan esters, glycerides, polyglycerin alkyl fatty acid esters, sucrose fatty acid esters, alkyl glyceryl ethers, alkyl polyglucosides, lecithin, polyoxyethylene octyl ester Nonionic surface activity such as tellurium, polyoxyethylene decyl ether, polyoxyethylene dodecyl ether, polyoxyethylene (2-ethylhexyl) ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonylphenyl ether Amphoteric surfactants such as adhesives, betaines, aminocarboxylates, imidazoline derivatives, etc., in amounts that do not impair the properties as heat-sensitive recording materials or cause aggregation in the coating solution, alone or in combination Used.

  A commercially available product can also be used as the surfactant. For example, from Kao Corporation, Emulgen 109P, Emulgen 903P, Neoperex G-15, Daiichi Industry Co., Ltd., Neugen EA-160, Neogen T, Nissin Chemical Industry Co., Ltd., Surfinol 104E, Surfinol SE-F Surfynol 465, Nopco Wet 50, etc. are commercially available from San Nopco Co., Ltd., and can be obtained.

  The heat-sensitive recording layer contains at least a binder, usually a colorless or light-colored electron-donating dye precursor, and an electron-accepting color developer.

The normally colorless or light-colored electron-donating dye precursor used in the present invention is typified by dye precursors used for general pressure-sensitive recording materials, heat-sensitive recording materials and the like, but is not particularly limited. As a specific example,
(1) Triarylmethane compounds: 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (P-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (P-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3 -Bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl)- -Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3- (1-methylpyrrol-2-yl) ) -6-dimethylaminophthalide, 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide, 3,3-bis (1-ethyl-2-methylindol-3-yl) ) Phthalide, 3,3-bis (1-n-hexyl-2-methylindol-3-yl) phthalide, etc.

  (2) Diphenylmethane compounds: 4,4'-bis (p-dimethylaminophenyl) benzhydrylbenzyl ether, N-chlorophenylleucooramine, N-2,4,5-trichlorophenylleucooramine, etc.

  (3) Xanthene compounds: Rhodamine B anilinolactam, rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino- 7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3- ( Di-n-butyl) amino-7- (2-chloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (di- n-butyl) amino-6-methyl-7-anilinofluorane, 3- (di-n- Nethyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-ani Linofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-phenethylfluorane, 3-diethylamino-7- (4-nitroanilino) fluorane, 3- (N-methyl-N-propyl) ) Amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl Ru-7- (3-trifluoromethylanilino) fluorane, 3-diethylamino-7-ethylcarboxylfluorane, 3-diethylamino-6,8-diethylfluorane, 3- (N-ethyl-N-isopropyl) aminobenzo [A] Fluorane, 3-dibutylamino-benzo [a] fluorane, 3-cyclohexylamino-6-chlorofluorane, 3-anilino-6-chlorofluorane, 3- (di-n-butyl) amino-6- Methyl-7-bromofluorane, 3- (N-ethyl-Np-tolyl) amino-7-methylfluorane, 3- (N-ethyl-N-isoamyl) amino-7-phenoxyfluorane, 3- Dimethylamino-7-methylfluorane, etc.

  (4) Thiazine compounds: benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.

  (5) Spiro compounds: 3-methylspirodinaphthopyrans, 3-ethylspirodinaphthopyrans, 3,3'-dichlorospirodinaphthopyrans, 3-benzylspirodinaphthopyrans, 3-methylnaphtholopyrans (3-methoxy) Benzo) spiropyran, 3-propyl spirobenzopyran and the like. These dye precursors can be used alone or in admixture of two or more as required.

  Electron-accepting developers are generally represented by acidic substances, and in particular, phenol derivatives, aromatic carboxylic acid derivatives, N, N′-diarylthiourea derivatives, polyvalent metal salts such as zinc salts of organic compounds, and the like. used.

  Specifically, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4- Hydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-ethoxydiphenylsulfone, 4-hydroxy-4'-n-butoxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (3,5-dibromo-4-hydroxyphenyl) sulfone, bis (3,5-dichloro-4- Hydroxyphenyl) sulfone 3,4-dihydroxydiphenylsulfone, 3,4-dihydroxy-4'-methyldiphenylsulfone, 3,4,4'-trihydroxydiphenylsulfone, 3,4,3 ', 4'-tetrahydroxydiphenylsulfone, 2, Diphenylsulfone derivatives such as 3,4-trihydroxydiphenylsulfone, 3-phenylsulfonyl-4-hydroxydiphenylsulfone, 2,4-bis (phenylsulfonyl) phenol,

  4-t-butylphenol, 2,2'-dihydroxybiphenyl, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-ethylenebis (2-methylphenol), 4,4 ' -Cyclohexylidenebis (2-isopropylphenol), p-phenylphenol, p-hydroxyacetophenone, 1,1-bis (p-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl) pentane, 1, 1-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) cyclohexane, 2,2-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) -2-ethylhexane, 2,2-bis (3 Chloro-4-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl) -1-phenylethane, 1,3-bis [2- (p-hydroxyphenyl) -2-propyl] benzene, 1,3 -Bis [2- (3,4-dihydroxyphenyl) -2-propyl] benzene, 1,4-bis [2- (p-hydroxyphenyl) -2-propyl] benzene, 4,4'-hydroxydiphenyl ether, 3 , 3'-dichloro-4,4'-hydroxydiphenyl sulfide,

  Bis (4-hydroxyphenyl) acetic acid esters such as methyl 2,2-bis (4-hydroxyphenyl) acetate and butyl 2,2-bis (4-hydroxyphenyl) acetate, 4,4′-thiobis (2-tert -Butyl-5-methylphenol), dimethyl 4-hydroxyphthalate, benzoic acid, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate and the like. Acid esters, benzyl gallate, stearyl gallate, N, N'-diphenylthiourea, 4,4'-bis [3- (4-methylphenylsulfonyl) ureido] diphenylmethane, N- (4-methylphenylsulfonyl) -N'-phenylurea, salicylanilide, 5-chlorosalicylanilide, sa Tyric acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4- [2 ′-(4-methoxyphenoxy) ethyloxy] Salicylic acid, 3- (octyloxycarbonylamino) salicylic acid or metal salts of these salicylic acid derivatives,

  Gallic acid alkyl esters, phenolic compounds such as novolak type phenolic resins, naphthoic acid derivatives such as 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid and their metal salts, tartaric acid, succinic acid, citric acid Organic acids such as atearic acid or their metal salts, N- (p-toluenesulfonyl) -N ′-(3-p-toluenesulfonyloxyphenyl) urea, N- (4-hydroxyphenyl) -p-toluenesulfone Amide, N- (4-hydroxyphenyl) benzenesulfonamide, N- (4-hydroxyphenyl) -1-naphthalenesulfonamide, N- (4-hydroxyphenyl) -2-naphthalenesulfonamide, N- (4-hydroxy Naphthyl) -p-toluenesulfonamide, N- (4-hydroxynaphthyl) be Zensulfonamide, N- (4-hydroxynaphthyl) -1-naphthalenesulfonamide, N- (4-hydroxynaphthyl) -2-naphthalenesulfonamide, N- (3-hydroxyphenyl) -p-toluenesulfonamide, N Examples include known substances such as-(3-hydroxyphenyl) benzenesulfonamide, N- (3-hydroxyphenyl) -1-naphthalenesulfonamide, N- (3-hydroxyphenyl) -2-naphthalenesulfonamide, and the like. These can be used alone or in combination.

  The aromatic isocyanate compound is a colorless or light-colored aromatic isocyanate compound that is solid at room temperature, specifically, 2,6-dichlorophenyl isocyanate, p-chlorophenyl isocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene. Diisocyanate, 1,3-dimethylbenzene-4,6-diisocyanate, 1,4-dimethylbenzene-2,5-diisocyanate, 1-ethoxybenzene-2,4-diisocyanate, 2,5-dimethoxybenzene-1,4- Diisocyanate, 2,5-diethoxybenzene-1,4-diisocyanate, 2,5-dibutoxybenzene-1,4-diisocyanate, azobenzene-4,4'-diisocyanate, diphenyl ether-4,4'-diisocyanate, naphthalene- , 4-diisocyanate, naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7-diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxy Biphenyl-4,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenyldimethylmethane-4,4'-diisocyanate, benzophenone-3,3'-diisocyanate, fluorene-2,7-diisocyanate, anthraquinone-2 , 6-diisocyanate, 9-ethylcarbazole-3,6-diisocyanate, pyrene-3,8-diisocyanate, naphthalene-1,3,7-triisocyanate, biphenyl-2,4,4'-triisocyanate, 4,4 ′, "- triisocyanate-2,5-dimethoxyphenyl triphenylamine, p- dimethylaminophenyl isocyanate, tris (4-phenylisocyanate) thiophosphate, etc., one or more may be used.

  These aromatic isocyanate compounds may be used in the form of so-called blocked isocyanate, which is an addition compound with phenols, lactams, oximes, etc., if necessary, and diisocyanates of diisocyanates such as 1-methyl It may be used in the form of benzene-2,4-diisocyanate dimer and trimer isocyanurate, or it can be used as a polyisocyanate added with various polyols.

  An imino compound is a colorless or light-colored compound that is solid at room temperature. Specifically, 3-imino-4,5,6,7-tetrachloroisoindoline-1-one, 1,3-diimino-4 , 5,6,7-tetrachloroisoindoline, 1,3-diiminoisoindoline, 1,3-diiminobenz (f) isoindoline, 1,3-diiminonaphtho (2,3-f) isoindoline, 1,3 -Diimino-5-nitroisoindoline, 1,3-diimino-5-phenylisoindoline, 1,3-diimino-5-methoxyisoindoline, 1,3-diimino-5-chloroisoindoline, 5-cyano-1 , 3-Diiminoisoindoline, 5-acetamido-1,3-diiminoisoindoline, 1,3-diimino-5- (1H-1,2,3-triazol-1-yl -Isoindoline, 5- (p-tert-butylphenoxy) -1,3-diiminoisoindoline, 5- (p-cumylphenoxy) -1,3-diiminoisoindoline, 5-isobutoxy-1,3 -Diiminoisoindoline, 1,3-diimino-4,7-dimethoxyisoindoline, 4,7-diethoxy-1,3-diiminoisoindoline, 4,5,6,7-tetrabromo-1,3-di Iminoisoindoline, 4,5,6,7-tetrafluoro-1,3-diiminoisoindoline, 4,5,7-trichloro-1,3-diimino-6-methylmercaptoisoindoline, 1-iminodiphenic acid imide 1- (cyano-p-nitrophenylmethylene) -3-iminoisoindoline, 1- (cyanobenzothiazolyl-2′-carbamoylmethylene -3-Iminoisoindoline, 1- (cyanobenzimidazolyl-2'-methylene) -3-iminoisoindoline, 1- (cyanobenzimidazolyl-2'-methylene) -3-imino-4,5,6,7 -Tetrachloroisoindoline, 1- (cyanobenzimidazolyl-2'-methylene) -3-imino-5-methoxyisoindoline, 1-[(1'-phenyl-3'-methyl-5-oxo) -pyrazolidene- 4 ']-3-iminoisoindoline, 3-imino-1-sulfobenzoimide, 3-imino-1-sulfo-4,5,6,7-tetrachlorobenzoimide, 3-imino-1-sulfo -4,5,7-trichloro-6-methylmercaptobenzoimide, 3-imino-2-methyl-4,5,6,7-tetrachloroisoindoline-1-one Etc.

  It is also possible to form a multicolor thermosensitive recording layer in which a plurality of electron-donating dye precursors that develop colors different from each other depending on heating conditions such as a color development temperature and an electron-accepting developer are combined. Here, in a multicolor thermosensitive recording material that develops different color tones on the low-temperature side and the high-temperature side, as an electron-donating dye precursor that develops a color on the high-temperature side, see (1) vinyl. Use resin-coated dye precursors coated with a color control layer obtained by polymerizing monomers, or (2) composite particles comprising at least one polymer selected from polyurea and polyurethane and a dye precursor. You can also.

  In the heat-sensitive recording layer according to the present invention, a heat-fusible substance can be contained in the heat-sensitive recording layer in order to improve its thermal response. In this case, those having a melting point of 60 to 180 ° C. are preferred, and those having a melting point of 80 to 140 ° C. are particularly preferred. Specifically, stearic acid amide, N-hydroxymethyl stearic acid amide, N-stearyl stearic acid amide, ethylene bis stearic acid amide, N-stearyl urea, β-naphthyl benzyl ether, m-terphenyl, 4-benzylbiphenyl 2,2′-bis (4-methoxyphenoxy) diethyl ether, α, α′-diphenoxyxylene, bis (4-methoxyphenyl) ether, 1,2-bis (3-methylphenoxy) ethane, 1,2 -Succinic acid diester derivatives such as diphenoxyethane, diphenyl adipate, dibenzyl oxalate, bis (4-chlorobenzyl) oxalate, bis (4-methylbenzyl) oxalate, diphenyl sulfone, dimethyl terephthalate, dibenzyl terephthalate, Benzenesulfonic acid fe Well-known thermofusible substances such as ester, bis (4-allyloxyphenyl) sulfone, 4-acetylacetophenone, acetoacetate anilides, fatty acid anilides, and the like may be used alone or in combination of two or more. Can be used. Further, in order to obtain sufficient thermal responsiveness, it is preferable that the heat fusible substance occupies 5 to 50% by mass in the total solid content of the thermosensitive recording layer.

  In the heat-sensitive recording layer according to the present invention, generally known antioxidants and UV absorbers can be added for the purpose of improving light resistance or weather resistance.

  For the purpose of improving the water resistance, a crosslinking agent capable of crosslinking the binder of the thermal recording layer or a crosslinking agent capable of crosslinking the binder contained in the undercoat layer and the protective layer is added to the thermosensitive recording layer according to the present invention. You can also. The crosslinking agent that can be added is not particularly limited, but aldehyde compounds such as formaldehyde, glyoxal, and glutaraldehyde, methylol melamine, melamine resin, phenol resin, melamine formaldehyde resin, urea resin, melamine urea resin, epichlorohydrin system Resins, polyethylenimine resins, polyamine-amide resins, isocyanate compounds, compounds containing epichlorohydrin groups represented by polyamide-polyamine-epichlorohydrin resins, persulfates such as ammonium persulfate, peroxides, etc. Oxidants, oxazolines, aziridine compounds, polyvalent carboxylic acid hydrazide compounds, ferric chloride, magnesium chloride, polyvalent metal salts such as Al, Ti, Zr, Mg, etc. Single or multiple sets Together it can be used.

The coating amount of the heat-sensitive recording layer according to the present invention is generally 0.1 to 10 g / ^{m 2} by dry mass, preferably from 2 to 8 g / ^{m 2.}

  The protective layer according to the present invention may have a film-forming resin as a main component in order to obtain solvent barrier properties. Examples of the film-forming resin usually include water-soluble polymers and water-dispersible resins. Usually, it can be used alone or in combination.

  Water-soluble polymers used in the protective layer include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, and butyral-modified. Water-soluble celluloses such as polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, Acrylamide-acrylate copolymer, acrylic Mid-acrylic acid ester-methacrylic acid terpolymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, alkali salt of styrene-maleic anhydride copolymer, alkali salt of ethylene-maleic anhydride copolymer Examples thereof include alkali salts of isobutylene-maleic anhydride copolymer, and these can be used alone or in combination.

  Examples of the water-dispersible resin used in the protective layer include styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene copolymer, acrylonitrile-butadiene-styrene terpolymer, Examples thereof include vinyl acetate, vinyl acetate-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, polyacrylic acid ester, styrene-acrylic acid ester copolymer, polyurethane, and the like. These may be used alone or in combination. be able to.

  In the protective layer according to the present invention, a crosslinking agent can be added for the purpose of crosslinking the water-soluble polymer or water-dispersible resin of the protective layer and improving the surface strength or water resistance. The crosslinking agent is not particularly limited, but aldehyde compounds such as formaldehyde, glyoxal, glutaraldehyde, methylol melamine, melamine resin, phenol resin, melamine formaldehyde resin, urea resin, melamine urea resin, epichlorohydrin resin, Polyethyleneimine resins, polyamine-amide resins, ammonium persulfate, isocyanate compounds, compounds containing epichlorohydrin groups represented by polyamide-polyamine-epichlorohydrin resins, persulfates such as ammonium persulfate, peroxides Compounds generally used as crosslinking agents, such as oxidants such as oxazoline, aziridine compounds, polyvalent carboxylic acid hydrazide compounds, ferric chloride, magnesium chloride, polyvalent metal salts such as Al, Ti, Zr, and Mg Can be used

  An inorganic pigment can also be added to the protective layer according to the present invention mainly for the purpose of improving the head matching property.

  Examples of inorganic pigments added to the protective layer include diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, Examples thereof include barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate, colloidal silica and the like, and these can be used alone or in combination.

  Various additives may be added to the protective layer according to the present invention depending on other purposes. Additives include viscosity modifiers, inorganic antistatic agents, organic antistatic agents, hardeners, colored pigments, colored dyes, UV absorbers, antioxidants, dispersants, antifoaming agents, pH adjusting agents, preservatives Examples thereof include, but are not limited to, lubricants and waxes.

  The surface tension of the protective layer coating solution according to the present invention is adjusted as necessary to form a uniform curtain during curtain coating, as described above for the surface tension of the thermal recording layer coating solution. . Further, by making the surface tension of the protective layer coating solution lower than the surface tension of the thermosensitive recording layer coating solution, problems such as repellency of the protective layer and pinholes can be suppressed.

  As a method for adjusting the surface tension, a surfactant is generally added, and the same type of surfactant as that added to the above-mentioned thermal recording layer coating solution can be used.

  Further, in the present invention, a layer may be further coated on the protective layer for the purpose of imparting gloss or improving the solvent barrier property, and the curtain is substantially simultaneously with the thermal recording layer coating solution and the protective layer coating solution. It is also possible to apply by coating.

  In the heat-sensitive recording material of the present invention, a calendar process such as a machine calendar, a TG calendar, a soft calendar, a super calendar, and a shoe calendar can be performed for the purpose of improving the smoothness after coating. Further, a glossy surface can be formed by using a known cast coating method.

  As the support used in the heat-sensitive recording material of the present invention, a gas permeable or non-air permeable support can be used. As the non-permeable support in the present invention, synthetic paper, plastic film, resin-coated paper and the like can be used. The non-permeable support can be subjected to a treatment such as a corona treatment in order to improve wettability. The air-permeable paper support mainly comprises chemical pulp such as LBKP and NBKP, mechanical pulp such as GP, PGW, RMP, TMP, CTMP, CMP and CGP, wood pulp such as used paper pulp such as DIP, and conventionally known fillers. As a component, a binder and a sizing agent, a fixing agent, a yield improver, a cationizing agent, a paper strength enhancer, an antifoaming agent, a pitch control agent and the like are mixed using one or more kinds, and a long net paper machine, A base paper manufactured by various devices such as a circular paper machine and a twin wire paper machine, and further, a paper provided with a size press or an anchor coat layer of starch, polyvinyl alcohol, etc. on the base paper, and a coat layer thereon Coated paper such as art paper, coated paper, cast coated paper, etc., is also included. Such a paper and coated paper may be provided with the undercoat layer and the overcoat layer in the present invention as they are, or after using a calendar device such as a machine calendar, a TG calendar, or a soft calendar for the purpose of controlling flattening. An undercoat layer may be provided.

  In the present invention, for the purpose of preventing curling on the back surface of the support, a backcoat layer may be provided, or an undercoat layer, a heat-sensitive recording layer, and a protective layer according to the present invention may be laminated.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. Further, “parts” and “%” shown in the examples represent parts by mass and mass% unless otherwise specified.

<Support 1>
100 parts of pulp consisting of 70 parts of LBKP with a freeness of 450 ml CSF and 30 parts of NBKP with a freeness of 450 ml CSF, 5 parts of pigment with a ratio of light calcium carbonate / heavy calcium carbonate / talc of 30/35/35, alkylketene dimer 1 part, 0.03 part of cationic acrylamide, 1.0 part of cationized starch, and 0.5 part of sulfuric acid band were prepared, and papermaking was performed at a basis weight of 66 g / m ² using a long net paper machine. Obtained.

<Undercoat layer coating solution 1>
Baked kaolin [trade name: Ansilex, manufactured by Engelhard, Inc.] 160 parts, organic hollow pigment dispersion liquid having a solid content concentration of 27.5% [trade name: Ropeke HP91, manufactured by Rohm and Haas Japan Co., Ltd.] 145.5 parts 40 parts of styrene-butadiene latex with a solid content of 50%, 22.9 parts of urea-modified phosphate esterified starch solution dissolved in a solid content of 35%, 37 parts of a boric acid aqueous solution with a solid content of 5%, and a viscosity modifier A composition comprising 5.3 parts of Yodozol KA20 (manufactured by NSC Japan) having a solid content concentration of 30% and 140.8 parts of water was mixed and stirred, and the amount of boric acid added to the total solid content of the undercoat layer was 0.00. An undercoat layer coating solution 1 of 80% was prepared.

<Electron-donating dye precursor dispersion>
600 parts of polyvinyl alcohol dissolved in a solid content concentration of 10%, 600 parts of a dye precursor [trade name: ODB-2, manufactured by Yamada Chemical Co., Ltd.] and 830.8 parts of water are added, and an average particle diameter of 0.5 μm is obtained with a sand grinder. And an electron donating dye precursor dispersion having a solid content concentration of 32.5% was prepared.

<Electron-accepting developer dispersion>
350 parts of polyvinyl alcohol dissolved in a solid content concentration of 10%, 2,4′-dihydroxydiphenylsulfone [trade name: BPS-24C, manufactured by Nikka Chemical Co., Ltd.] 437.5 parts, 350 parts of benzyloxynaphthalene, water 844 quality Was added, and the mixture was ground to a mean particle size of 0.5 μm with a sand grinder to prepare an electron-accepting developer dispersion having a solid concentration of 41.5%.

<Thermosensitive recording layer inorganic pigment dispersion>
Precipitated calcium carbonate [trade name: Tama Pearl 123, manufactured by Okutama Kogyo Co., Ltd.] 525 parts, polycarboxylic acid type dispersant having a solid content concentration of 40% [trade name: Microsol KE-511, manufactured by Kyoyo Chemical Co., Ltd.] 9 parts Then, 788 parts of water was added and dispersed with a homogenizer to prepare a thermal recording layer inorganic pigment dispersion having a solid content of 40%.

<Thermosensitive recording layer polyvinyl alcohol aqueous solution>
36 parts of fully saponified unmodified polyvinyl alcohol having a polymerization degree of 1,700 [trade name: PVA117, manufactured by Kuraray Co., Ltd.] was added to 324 parts of cold water, heated to 90 ° C. and dissolved, and then a solid content concentration of 10%. A thermosensitive recording layer aqueous polyvinyl alcohol solution was prepared.

<Thermosensitive recording layer coating solution 1>
16.4 parts of a thermal recording layer inorganic pigment dispersion liquid having a solid content concentration of 40%, 118.9 parts of an electron-accepting developer dispersion liquid having a solid content concentration of 41.5%, and heat sensitivity having a solid content concentration of 10%. 120 parts of recording layer polyvinyl alcohol aqueous solution, 30% solid content concentration methylolamide dispersion [trade name: Hydrin K808, manufactured by Chukyo Yushi Co., Ltd.] 12.0 parts, solid content concentration 32.5% electron donating dye precursor 26.4 parts of body dispersion, 0.1 part of polymin 790A (manufactured by BASF Corp.) with a solid content concentration of 33% as a viscosity modifier, and Surfynol SE-F with a solid content concentration of 80% as a surfactant [Nisshin Chemical Co., Ltd.] Manufactured by Kogyo Co., Ltd.] 1.0 part of water and 109.6 parts of water were mixed and stirred to prepare a thermal recording layer coating solution 1 in which the amount of polyvinyl alcohol added to the total solid content of the thermal recording layer was 14.8%.

<Protective layer coating solution 1>
40 parts of aluminum hydroxide [trade name: Heidilite H42, Showa Denko Co., Ltd.], 0.8 part of Olfine EXP-4001 (Nisshin Chemical Co., Ltd.) as a dispersant, and 250.6 parts of water were added. 1503 parts of a polyvinyl alcohol aqueous solution previously dissolved at a solid content concentration of 10% in a pigment dispersion dispersed at a solid content concentration of 14%, Surfynol SE-F having a solid content concentration of 80% as a surfactant [Nisshin Chemical Industry Co., Ltd. Product] 4.6 parts, SN929S [manufactured by San Nopco Co., Ltd.] 71.7 parts and water 671.8 parts as a viscosity modifier were mixed and stirred to prepare protective layer coating solution 1.

Example 1
The undercoat layer coating solution 1 is coated on the support 1 with a blade coater so that the dry coating amount is 9 g / m ² and dried, and then the thermal recording layer coating solution 1 and the protective layer are coated with a slide curtain coater. after applied simultaneously to each dry coating amount of the coating solution 1 is ^{3g / m 2, 2g / m} 2, dried and subjected to smoothing treatment by a super calender to obtain a heat-sensitive recording material comprising as example 1 .

<Undercoat layer coating solution 2>
Undercoat layer coating solution 2 was prepared in the same manner as undercoat layer coating solution 1, except that 37 parts of borax aqueous solution with a solid content concentration of 5% was used instead of 37 parts of boric acid aqueous solution with a solid content concentration of 5%.

(Example 2)
A thermosensitive recording material of Example 2 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 2 was used instead of the undercoat layer coating solution 1.

<Undercoat layer coating solution 3>
An organic hollow pigment was not added to the undercoat layer coating solution, except that the calcined kaolin (trade name: Ansilex, manufactured by Engelhard) was changed from 160 parts to 200 parts, and the amount of water added was changed from 140.8 parts to 246.2 parts. Undercoat layer coating solution 3 was prepared in the same manner as undercoat layer coating solution 1.

(Example 3)
A heat-sensitive recording material of Example 3 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 3 was used instead of the undercoat layer coating solution 1.

<Undercoat layer coating solution 4>
The addition amount of boric acid aqueous solution with a solid content concentration of 5% is 37 parts to 4.6 parts, the addition amount of water is 246.2 parts to 274.5 parts, and the addition amount of boric acid to the total solid content of the undercoat layer is 0.80. Undercoat layer coating solution 4 was prepared in the same manner as undercoat layer coating solution 3 except that the content was changed from% to 0.10%.

Example 4
A heat-sensitive recording material of Example 4 was obtained in the same manner as in Example 1 except that the undercoat layer coating liquid 4 was used instead of the undercoat layer coating liquid 1.

<Thermosensitive recording layer coating solution 2>
120 to 37.5 parts of a thermosensitive recording layer polyvinyl alcohol aqueous solution having a solid content concentration of 10% contained in the thermal recording layer coating solution 1 and an addition amount of water of 109.6 to 150.9 parts. Heat-sensitive recording layer coating solution 2 was prepared in the same manner as heat-sensitive recording layer coating solution 1, except that the amount of polyvinyl alcohol added relative to the content was changed from 14.8% to 5.2%.

(Example 5)
A thermal recording material of Example 5 was obtained in the same manner as in Example 1 except that the undercoat layer coating liquid 4 and the thermal recording layer coating liquid 2 were used instead of the undercoat layer coating liquid 1 and the thermal recording layer coating liquid 1. It was.

<Undercoat layer coating solution 5>
The addition amount of boric acid aqueous solution having a solid content concentration of 5% is 37 to 240.0 parts, the addition amount of water is 246.2 parts to 67.0 parts, and the addition amount of boric acid to the total solid content of the undercoat layer is 0.80. Undercoat layer coating solution 5 was prepared in the same manner as undercoat layer coating solution 3, except that the content was changed from% to 5.0%.

<Thermosensitive recording layer coating solution 3>
120 to 270 parts of a heat-sensitive recording layer polyvinyl alcohol aqueous solution having a solid content concentration of 10% contained in the heat-sensitive recording layer coating solution 1, and 109.6 to 34.7 parts of water is added to the total solid content of the heat-sensitive recording layer. A thermal recording layer coating solution 3 was prepared in the same manner as the thermal recording layer coating solution 1 except that the amount of polyvinyl alcohol added was changed from 14.8% to 28.2%.

(Example 6)
The thermosensitive recording material of Example 6 was prepared in the same manner as in Example 1 except that the undercoat layer coating solution 5 and the thermosensitive recording layer coating solution 3 were used instead of the undercoat layer coating solution 1 and the thermosensitive recording layer coating solution 1. Obtained.

<Undercoat layer coating solution 6>
The same as undercoat layer coating solution 1, except that no boric acid aqueous solution with a solid content concentration of 5% was added, the amount of water added was 278.0 parts, and the amount of boric acid added to the total solid content of the undercoat layer was 0%. Undercoat layer coating solution 6 was prepared.

<Thermosensitive recording layer coating solution 4>
120 to 30.0 parts of a heat-sensitive recording layer polyvinyl alcohol aqueous solution having a solid content concentration of 10% contained in the heat-sensitive recording layer coating liquid 1, 154.7 parts of water, and the amount of polyvinyl alcohol added to the total solid content of the heat-sensitive recording layer is 4. A thermal recording layer coating solution 4 was prepared in the same manner as the thermal recording layer coating solution 1 except that the content was 2%.

(Comparative Example 1)
The thermosensitive recording material of Comparative Example 1 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 6 and the thermosensitive recording layer coating solution 4 were used instead of the undercoat layer coating solution 1 and the thermosensitive recording layer coating solution 1. It was.

<Thermosensitive recording layer coating solution 5>
Heat-sensitive recording layer 10% solid content polyvinyl alcohol aqueous solution contained in the heat-sensitive recording layer coating solution 1 is not added, 24 parts of 50% solid content styrene-butadiene latex, 205.7 parts of water, total heat-sensitive recording layer solids A heat-sensitive recording layer coating solution 5 was prepared in the same manner as the heat-sensitive recording layer coating solution 1 except that the amount of polyvinyl alcohol added to the content was 0.0%.

(Comparative Example 2)
A thermosensitive recording material of Comparative Example 2 was obtained in the same manner as in Example 1 except that the thermosensitive recording layer coating solution 5 was used in place of the thermosensitive recording layer coating solution 1.

<Coloring sensitivity evaluation method>
The thermal recording materials of Examples 1 to 6 and Comparative Examples 1 and 2 produced as described above were printed with a thermal printer [device name: TH-PMD, manufactured by Okura Electric Co., Ltd.], and the color density at 0.192 mJ / dot was obtained. , And a densitometer [device name: RD19, manufactured by GretagMacbeth]. The results are shown in Table 1. 0.65 or more is an allowable range.

<Solvent barrier evaluation method>
Acetone was applied with absorbent cotton on the protective layers of the heat-sensitive recording materials of Examples 1 to 6 and Comparative Examples 1 and 2 prepared as described above, and the solvent barrier property of the blank paper portion was visually evaluated. The results are shown in Table 1. ○ The above is the allowable range.
A: No fogging due to the solvent is observed, and the solvent barrier property is very high.
○: Some fogging due to the solvent is observed, but the solvent barrier property is in an acceptable range.
(Triangle | delta): The fogging by a solvent is observed and a solvent barrier property is an unacceptable range.
X: Fog due to the solvent is remarkably observed, and the solvent barrier property is in an unacceptable range.

<Sticking aptitude evaluation method>
The thermal recording materials of Examples 1 to 6 and Comparative Examples 1 and 2 prepared as described above were printed with a thermal printer HT-180 manufactured by Canon, and the presence or absence of sticking was visually evaluated as follows. ○ The above is an acceptable range.
A: Sticking is not observed. It is an acceptable range.
○: Some sticking is observed, but it is in an acceptable range.
Δ: Sticking is observed and is in an unacceptable range.
X: Sticking is observed remarkably and is in an unacceptable range.

  As is apparent from Table 1, a plurality of coating liquids constituting the heat-sensitive recording layer and the protective layer are substantially simultaneously formed after providing an undercoat layer containing a pigment, binder, boric acid or borax on the support of the present invention. The heat-sensitive recording material of Examples 1 to 6, which is a heat-sensitive recording material formed by applying a curtain and contains a polyvinyl alcohol as a binder in the heat-sensitive recording layer, has good color development sensitivity and solvent barrier properties. It is clear that it has.

  On the other hand, in Comparative Examples 1 and 2 that did not satisfy the specific requirements of the present invention, good color development sensitivity and solvent barrier properties could not be obtained.

Claims (1)

  A heat-sensitive recording material formed by applying a plurality of coating liquids constituting a heat-sensitive recording layer and a protective layer substantially simultaneously with a curtain after providing an undercoat layer containing a pigment, binder, boric acid or borax on a support. A thermosensitive recording material comprising polyvinyl alcohols as a binder in the thermosensitive recording layer.