JP2010179592A - Method of manufacturing heat-sensitive recording body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a heat-sensitive recording body, capable of forming a stable and uniform curtain film, free from coating irregularity, and excellent in productivity and quality, when forming a heat-sensitive recording layer and a protection layer by applying and drying a coating liquid for the heat-sensitive recording layer and a coating liquid for the protection layer concurrently using a curtain applying method. <P>SOLUTION: In this method of manufacturing the heat-sensitive recording body including at least an undercoating layer, the heat-sensitive recording layer containing a Leuco dye, a color developer and a water-soluble adhesive, and the protection layer, on a support body, a viscosity is 40-150 mPa s at the time of 2,000 s<SP>-1</SP>of share rate at 25°C of liquid temperature in the coating liquid for the heat-sensitive recording layer, a ratio of a viscosity at the time of 1 s<SP>-1</SP>of share rate to the viscosity at the time of 2,000 s<SP>-1</SP>of share rate is 1:0.01 to 0.08, and the heat-sensitive recording layer and the protection layer are formed by applying and drying the coating liquid for the heat-sensitive recording layer and the coating liquid for the protection layer concurrently using the curtain applying method, in the method of manufacturing the heat-sensitive recording body. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a thermal recording material utilizing a color development reaction between a leuco dye and a developer.

  2. Description of the Related Art A heat-sensitive recording material is well known in which a recording image is obtained by contacting a coloring material with heat by utilizing a coloring reaction between a colorless or light leuco dye and an organic or inorganic developer. Such a heat-sensitive recording medium is relatively inexpensive, and the recording device is compact and easy to maintain. For example, in a facsimile, a computer output, a handy terminal, a POS system (store point-of-sale information management system), or a transportation system. However, recently, due to the diversification of application development and higher functionality of the system, the required quality for the thermal recording medium has become high.

  That is, with the increase in recording speed, a clear printed image with a high density is required even with a small amount of heat energy, and in applications such as labels for POS systems, tickets, commuter passes, water, vinegar, oil, plasticizer It is important that the vinyl chloride sheet for wrapping and the volatile solvent (ethanol, hairdressing agent) having polarity, adhesion of background fogging due to contact, decoloration of the printed image, and fading are not caused.

  On the other hand, methods such as an air knife coating method, a blade coating method, a rod coating method, a roll coating method, and a bar coating method are used as a method for coating a coating solution on a substrate such as paper or film. The thermal recording material produced by this method has poor coating quality, soaking of the upper coating liquid into the lower layer, upper layer pinholes due to repelling during upper layer coating, etc. In addition to problems such as variations, there are problems such as a limitation in high-speed coating and a decrease in productivity caused by multiple coatings.

  In contrast to these coating methods, a curtain coating method proposed in Japanese Patent Publication No. 49-24133 is a method in which a free fall curtain of coating liquid is formed, and this is applied by colliding with a support. It is known that the quality is good and it is suitable for high-speed coating. Moreover, it is also possible to form a coating film composed of a plurality of coating liquids and apply the curtain, and the productivity of multilayer coating can be greatly improved. In this curtain coating method, the coating liquid is applied in a film form from a slit-shaped coater lip onto a substrate. If the physical properties of the coating liquid are not appropriate, film cracking of the curtain film or the coater lip of the curtain coater A phenomenon (neck-in) in which the coating width becomes narrower than the width tends to occur. In addition to this, a phenomenon in which the coating liquid jumps without adhering to the support (drip), or a phenomenon in which minute air is caught between the curtain and the support when the coating speed is high, a so-called air entrainment phenomenon. Such problems in coating cause uneven coating and coating defects. From this point of view, when producing a thermal recording material by the curtain coating method, it is important to control the physical properties of the coating liquid for the uniform stability of the curtain film, and the performance and production efficiency of the resulting thermal recording material are affected. It is greatly influenced.

  In curtain coating on a thermal recording material, a method is disclosed in which a specific adhesive or surfactant is blended and applied in the thermal recording layer coating liquid in order to stabilize the curtain film. For example, it has been proposed to add a carboxymethyl cellulose sodium salt having a degree of etherification of 0.7 or more and a 1% viscosity of 300 cps or more to a coating solution for a heat-sensitive recording layer (see Patent Document 1). It has also been proposed to include a specific sulfate ether type surfactant and a specific phosphate ester type surfactant in the thermal recording layer and / or protective layer coating solution (see Patent Document 2). Furthermore, dodecylbenzenesulfone salt is added to the coating solution for the protective layer (see Patent Document 3), and a composition of an acetylene glycol derivative and an anionic surfactant is added to the coating solution for the protective layer (see Patent Document 4). ) Is also described. In addition, it has also been proposed to add a surfactant obtained by adding ethylene oxide and other alkylene oxides to tetramethyldecine diol to the thermal recording layer coating solution (see Patent Document 5).

  However, even if the surface tension is reduced by the addition of a surfactant, the coating liquid is not uniformly stretched at the moment when the coating liquid is applied onto the base material, resulting in uneven coating, resulting in a coating defect, resulting in reduced productivity. In some cases, the thickness of the coating film may be uneven and the print quality may be deteriorated. Further, depending on the type and addition amount of the surfactant, there is a problem that the quality as a heat-sensitive recording material is inferior, for example, the color density is lowered, the printing erasure, the background fogging, and the like are deteriorated. In addition, when the coating liquid is applied at a low flow rate and at a high speed, it is difficult to completely eliminate the air entrainment phenomenon, so that a coating defect cannot be prevented, and as a result, there is a problem that print quality is deteriorated.

Japanese Patent Laid-Open No. 3-21086 Japanese Patent Laid-Open No. 10-157299 JP-A-6-336083 JP 2004-314614 A JP 2005-238539 A

  An object of the present invention is to form a stable and uniform curtain film, particularly when a thermal recording layer and a protective layer are formed by simultaneously applying and drying a thermal recording layer coating liquid and a protective layer coating liquid by a curtain coating method. Another object of the present invention is to provide a method for producing a thermal recording material which is free from coating unevenness and is excellent in productivity and quality.

  As a result of intensive studies in view of the above-described conventional technology, the present inventors have solved the above problems. That is, the present invention relates to the following method for producing a thermal recording material.

Item 1: In a method for producing a heat-sensitive recording layer comprising at least an undercoat layer, a leuco dye, a developer and a water-soluble adhesive on a support, and a protective layer, a liquid temperature 25 viscosity at a shear rate of 2000s ^-1 at ℃ is 40~150mPa · s, and the ratio of the viscosity of the viscosity and 2000s h ^-1 o'clock shear rate ^{1s -1} is 1: 0.01 to 0.08 A method for producing a thermal recording material, wherein the thermal recording layer and the protective layer are formed by simultaneously applying and drying the thermal recording layer coating liquid and the protective layer coating liquid by a curtain coating method. .

  Item 2: The heat-sensitive recording layer coating solution contains 0.05 to 1.0% by mass of a dialkylsulfosuccinate represented by the following general formula (1) with respect to the total solid content of the heat-sensitive recording layer. 2. A method for producing a heat-sensitive recording material according to 1.

（式中、Ｒ^１、Ｒ^２は同一または異なる炭素数２〜２０の脂肪族または脂環式炭化水素基を表し、Ｍはアルカリ金属塩またはアンモニウム塩を表す。）

(Wherein R ¹ and R ² represent the same or different aliphatic or alicyclic hydrocarbon groups having 2 to 20 carbon atoms, and M represents an alkali metal salt or an ammonium salt.)

  Item 3: The heat-sensitive recording material according to Item 1 or 2, wherein the water-soluble adhesive contains 2 to 12% by mass of completely saponified polyvinyl alcohol having a polymerization degree of 800 to 3000 based on the total solid content of the heat-sensitive recording layer. Manufacturing method.

  Item 4: The method for producing a thermosensitive recording material according to any one of Items 1 to 3, wherein the protective layer coating solution contains a dialkylsulfosuccinate represented by the general formula (1).

  Item 5: As the developer, 2,2′-bis (4-hydroxyphenyl) propane, 4-hydroxy-4′-isopropoxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxy Diphenylsulfone, 3,3′-diallyl-4,4′-dihydroxydiphenylsulfone, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, N- (p-toluenesulfonyl) -N′-3- Item 5. The method for producing a thermal recording material according to any one of Items 1 to 4, comprising at least one selected from the group consisting of (p-toluenesulfonyloxy) phenylurea.

  Item 6: The undercoat layer contains plastic hollow particles and calcined kaolin, and an undercoat layer coating solution containing 10 to 100% by mass of plastic hollow particles with respect to 100 parts by mass of calcined kaolin is applied by a blade coating method. Item 6. The method for producing a thermal recording material according to any one of Items 1 to 5, wherein the undercoat layer is formed by drying.

  According to the present invention, in particular, when the thermal recording layer and the protective layer are formed by simultaneously applying and drying the thermal recording layer coating liquid and the protective layer coating liquid by the curtain coating method, mixing of bubbles and poor film formation are prevented. It is possible to provide a method for producing a heat-sensitive recording material which does not occur, forms a stable and uniform curtain film, has no coating unevenness, and is excellent in productivity and quality.

In the present invention, the ratio of the viscosity of the liquid temperature 25 ° C. of the heat-sensitive recording layer coating solution, viscosity 40~150mPa · s o'clock shear rate 2000s ^-1, and viscosity and 2000s h ^-1 o'clock shear rate ^{1s -1} By setting the ratio to 1: 0.01 to 0.08, it is possible to form a stable curtain film that is a thin film and has no film cracking, and to prevent coating defects caused by dripping or air entrainment. The viscosity at a shear rate of 2000 s ⁻¹ is more preferably about 70 to 120 mPa · s. When the viscosity at a shear rate of 2000 s ⁻¹ is less than 40 mPa · s, the viscosity of the curtain film when applied on the support is insufficient, and the coating liquid is not sufficiently stretched and coating unevenness tends to occur. On the other hand, the viscosity is greater than 150 mPa · s o'clock shear rate 2000s ^-1, poor leveling properties of the coating liquid, fine undulation of or coated surface coating becomes unstable (living) occurs, printing quality Cause trouble.

  The heat-sensitive recording layer in the present invention contains a water-soluble adhesive. As the water-soluble adhesive, fully saponified polyvinyl alcohol having a polymerization degree of 800 to 3000 is preferable, and a polymerization degree is preferably 1000 to 2700. The content of the completely saponified polyvinyl alcohol is preferably 2 to 10% by mass, more preferably 4 to 10% by mass, based on the total solid content of the heat-sensitive recording layer. By containing such a water-soluble adhesive, the viscosity of the thermal recording layer coating liquid can be suitably adjusted. The completely saponified polyvinyl alcohol in the present invention preferably has a saponification degree of 95% or more, more preferably 98% or more.

  Other water-soluble adhesives contained in the heat-sensitive recording layer include, for example, partially saponified polyvinyl alcohol and derivatives thereof, starch and derivatives thereof, casein, gelatin, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, Cellulose derivatives such as ethyl cellulose, polyvinylpyrrolidone, alkali salt of acrylic acid polymer, alkali salt of ethylene-acrylic acid copolymer, alkali salt of styrene-acrylic acid copolymer, alkali salt of styrene-maleic anhydride copolymer And an alkali salt of an isobutylene-maleic anhydride copolymer, an acrylamide copolymer, and the like.

  Moreover, a water dispersible adhesive agent can also be contained in the range which does not impair the effect of this invention. Examples of the water-dispersible adhesive include vinyl acetate latex, urethane latex, acrylic latex, and styrene-butadiene latex. These can be used individually by 1 type or in combination of 2 or more types.

  In the present invention, the coating solution for the heat-sensitive recording layer is preferably 0.01 to 1.0% by mass, more preferably 0.05 to 1.0% by mass of a dialkylsulfosuccinate represented by the following general formula (1). %, Particularly preferably 0.05 to 0.8% by mass. Thereby, the viscosity of the coating liquid for the heat-sensitive recording layer can be suitably adjusted, it is difficult to cause curtain film breakage, and the foaming of the coating liquid is reduced, thereby improving coating defects.

（式中、Ｒ^１、Ｒ^２は同一または異なる炭素数２〜２０の脂肪族または脂環式炭化水素基を表し、Ｍはアルカリ金属塩またはアンモニウム塩を表す。）

(Wherein R ¹ and R ² represent the same or different aliphatic or alicyclic hydrocarbon groups having 2 to 20 carbon atoms, and M represents an alkali metal salt or an ammonium salt.)

  The dialkylsulfosuccinate represented by the general formula (1) is preferably an alkali metal salt or ammonium salt of a dialkylsulfosuccinate, and more preferably a sodium salt. Moreover, as an alkyl group of dialkyl sulfosuccinate, a C2-C20 alkyl group is preferable and a C4-C10 alkyl group is more preferable. Specific examples include an isobutyl group, a hexyl group, a cyclohexyl group, an octyl group, an isooctyl group, and a 2-ethylhexyl group, and an octyl group or a 2-ethylhexyl group having 8 carbon atoms is particularly preferable.

  The heat-sensitive recording layer in the present invention can contain a known leuco dye and a developer. For example, as leuco dyes that give black color, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (N-pentyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-arininofluorane, 3- (N-ethyl-p -Toluidino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3- ( N-isoamyl-N-ethylamino) -7- (o-chloroanilino) fluorane, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl-7-anilinofur Oran, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3 -Ethoxypropyl) -N-ethylamino] -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-methylamino] -6-methyl-7-anilinofluorane 3-diethylamino-7- (2-chloroanilino) fluorane, 3-di (n-butylamino) -7- (2-chloroanilino) fluorane, and the like. If necessary, a leuco dye that develops a color tone different from that of black, such as red, magenta, orange, blue, green, etc., can also be used. These leuco dyes may be used alone or in combination of two or more.

  In the present invention, when the leuco dye is used as a solid fine particle state, the leuco dye is pulverized by various wet pulverizers such as a sand grinder, an attritor, a ball mill, a cobo mill, etc., using water as a dispersion medium. In addition to water-soluble synthetic polymer compounds such as pyrrolidone, polyvinyl alcohol, modified polyvinyl alcohols such as sulfone-modified polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, styrene-maleic anhydride copolymer salts and derivatives thereof Accordingly, it can be dispersed in a dispersion medium together with a surfactant, an antifoaming agent and the like to obtain a dispersion liquid, and this dispersion liquid can be used for the preparation of a thermal recording layer coating liquid.

  Alternatively, after dissolving the leuco dye in a solvent, the solution is emulsified and dispersed in water using the above water-soluble polymer as a stabilizer, and then the solvent is evaporated from the emulsion to use the dye precursor as solid fine particles. it can. In any case, the average particle diameter of the dispersed particles of the dye precursor used in the solid fine particle state is preferably 0.2 to 3.0 μm, more preferably 0.3 to 3.0 in order to obtain appropriate color development sensitivity. 1.0 μm.

  In the present invention, as a method of using the leuco dye, it can be used as a composite particle composed of an organic polymer and a leuco dye, in addition to the above-mentioned solid fine particle state. The composite particles can be produced by a known method. For example, as a method for producing composite particles in which the organic polymer is at least one of polyurea and polyurea-polyurethane, a leuco dye and a polyvalent isocyanate that forms at least one of polyurea and polyurea-polyurethane by polymerization are used. A molecule-forming raw material is dissolved and mixed in a water-insoluble organic solvent having a boiling point of 100 ° C. or lower, and this organic solvent solution is mixed with a hydrophilic protective colloid solution such as polyvinyl alcohol so that the average particle size is about 0.5 to 3 μm. After emulsifying and dispersing, and further mixing a reactive substance such as polyamine if necessary, this emulsified dispersion is heated to volatilize and remove the organic solvent, and then the polymer-forming raw material is polymerized to form composite particles. Or a leuco dye is dissolved in a polymer-forming raw material, and this solution is added to the average particle by the above-mentioned method. After size emulsified and dispersed in about 0.5 to 3 [mu] m, and a method of a polymer-forming material is prepared by polymerization.

  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, based on the total solid content of the composite particles. It is about 30-60 mass%.

  As the developer, a known compound can be used. Specific examples of the developer include 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec-butylidenediphenol, 4-phenylphenol, 4,4′- Dihydroxydiphenylmethane, 2,2′-bis (4-hydroxyphenyl) propane, 4,4′-cyclohexylidenediphenol, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 4,4′-dihydroxy Diphenyl sulfide, 4,4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone 4-hydroxy-4'-allyl Xylodiphenylsulfone, phenolic compounds such as 3,3′-diallyl-4,4′-dihydroxydiphenylsulfone, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, 4-hydroxybenzophenone Dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoate-sec-butyl, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, 4-hydroxybenzoate Phenolic compounds such as tolyl acid, chlorophenyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenyl ether, or benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butyl Aromatic carboxylic acids such as salicylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and For example, organic acidic substances such as salts with polyvalent metals such as zinc, magnesium, aluminum and calcium, N- (p-toluenesulfonyl) -N′-3- (p-toluenesulfonyloxy) phenylurea, 4,4 ′ -Urea compounds such as bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, N- (p-toluenesulfonyl) -N ′-(p-butoxycarbonylphenyl) urea, Np-tolylsulfonyl-N′-phenylurea Is mentioned. Among these, 2,2′-bis (4-hydroxyphenyl) propane, 4-hydroxy-4′-isopropoxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, 3, 3′-diallyl-4,4′-dihydroxydiphenylsulfone, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, N- (p-toluenesulfonyl) -N′-3- (p-toluenesulfonyl) By containing at least one selected from the group consisting of (oxy) phenylurea, a high-quality image can be recorded, which is preferable.

  In the present invention, the use ratio of the leuco dye and the developer in the heat-sensitive recording layer should be appropriately selected according to the type of leuco dye and developer used, and is not particularly limited. About 1 to 7 parts by mass, preferably about 1 to 4 parts by mass of the developer is used with respect to 1 part by mass.

  The heat-sensitive recording layer may contain a sensitizer as necessary. Thereby, the recording sensitivity can be increased. Examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoyl stearic acid amide, N-eicosanoic acid amide, ethylene bistearic acid amide, behenic acid amide, methylene bis stearic acid amide, N -Methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate Oxalic acid-di-p-methylbenzyl, oxalic acid-di-p-chlorobenzyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylpheno) B) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetoluidide, p-acetophenetide, N- Examples include acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, and the like. The amount of these sensitizers to be used is not particularly limited, but it is generally desirable to adjust in a range of about 4 parts by mass or less with respect to 1 part by mass of the developer.

  The heat-sensitive recording layer may contain a storability improving agent. Thereby, the preservability of a recording part can be improved. Examples of the storage stability improver include 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-ethylenebis (4-methyl-6-tert-butylphenol) 2,2'-methylenebis. (4-ethyl-6-tert-butylphenol), 2,2′-methylenebis (4,6-di-tert-butylphenol), 2,2′-ethylidenebis (4,6-di-tert-butylphenol), 2 , 2′-ethylidenebis (4-methyl-6-tert-butylphenol), 2,2′-ethylidenebis (4-ethyl-6-tert-butylphenol), 2,2 ′-(2,2-propylidene) bis (4,6-di-tert-butylphenol), 2,2′-methylenebis (4-methoxy-6-tert-butylphenol) 2,2′-methylenebis (6-tert-butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-thiobis (2-methyl-6-tert-butylphenol), 4,4′-thiobis (5-methyl-6-tert-butylphenol), 4,4′-thiobis (2-chloro-6-tert-butylphenol), 4,4′-thiobis (2-methoxy-6-tert) -Butylphenol), 4,4′-thiobis (2-ethyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 1- [α-methyl-α- ( 4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-Methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4′-thiobis (3- Methylphenol), 4,4′-dihydroxy-3,3 ′, 5,5′-tetrabromodiphenylsulfone, 4,4′-dihydroxy-3,3 ′, 5,5′-tetramethyldiphenylsulfone, 2, 2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethyl) Hindered phenol compounds such as phenyl) propane, N, N′-di-2-naphthyl-p-phenylenediamine, 2,2′-methylenebis (4,6-di-t) rt- butylphenyl) phosphate sodium, and the like.

  In the present invention, in order to improve the whiteness of the heat-sensitive recording layer and improve the uniformity of the image, a fine particle pigment having a high whiteness and an average particle size of 10 μm or less can be contained in the heat-sensitive recording layer. For example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface treated calcium carbonate, silica, etc. Inorganic pigments and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, and polystyrene resin can be used. The pigment content is preferably an amount that does not decrease the color density, that is, 50% by mass or less based on the total solid content of the heat-sensitive recording layer.

  The heat-sensitive recording layer generally contains water as a dispersion medium, and mixes a leuco dye dispersion, a developer dispersion and a water-soluble adhesive, and, if necessary, a storage stability improver, a sensitizer, a pigment, and an auxiliary agent. To be prepared.

  Examples of the auxiliary agent include cross-linking agents, waxes, metal soaps, colored dyes, colored pigments, fluorescent dyes, oil repellents, antifoaming agents, and viscosity modifiers.

  Examples of the cross-linking agent include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, dimethylol urea compounds, aziridine compounds, blocked isocyanate compounds, carboxylic acid dihydrazide compounds, and the like. Inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, potassium tetraborate, boric acid, boric acid triester, boron-based polymer, and the like can be given. The content of the crosslinking agent is preferably 1 to 10% by mass based on the total solid content of the heat-sensitive recording layer from the viewpoint of improving the water resistance of the heat-sensitive recording layer and three-dimensionally curing the adhesive. .

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

  Examples of the metal soap include higher fatty acid polyvalent metal salts such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate. In addition, a colored dye and / or a colored pigment may be included for adjusting the color tone of the white paper portion.

  In the present invention, in order to further increase the added value of the product, a multicolor thermosensitive recording material can be obtained. In general, multicolor thermal recording materials are an attempt to utilize the difference in heating temperature or thermal energy, and are generally constructed by sequentially laminating a high-temperature coloring layer and a low-temperature coloring layer that develop colors in different colors on a support. If these are roughly classified, a multicolor thermosensitive recording material is produced using two types, a decoloring type and a coloring type, a method using a microcapsule, and composite particles composed of an organic polymer and a dye precursor. There is a way to do it.

The coating amount of the thermal recording layer coating liquid is not particularly limited, and a desired quality can be achieved if the dry weight is about 1 to 12 g / m ² , particularly about ² to 10 g / m ² .

  On the heat-sensitive recording layer in the present invention, at least one protective layer is provided. As the protective layer, a protective layer that has been used in conventionally known thermal recording media can be used. The protective layer is mainly composed of an adhesive and a pigment. In particular, a lubricant such as polyolefin wax or zinc stearate is preferably added to the protective layer for the purpose of preventing sticking to the thermal head, and an ultraviolet absorber can also be included. In addition, the added value of the product can be increased by providing a glossy protective layer.

  As the adhesive, any one of a water-soluble adhesive and a water-dispersible adhesive can be used. Examples of water-soluble adhesives include fully saponified or partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol, starch and derivatives thereof, casein, and gelatin. , Carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, ethylcellulose and other cellulose derivatives, polyvinylpyrrolidone, acrylic acid polymer alkali salt, ethylene-acrylic acid copolymer alkali salt, styrene-acrylic acid copolymer Alkali salt of coalescence, alkali salt of styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer Alkali salts of acrylamide copolymers. Examples of the water-dispersible adhesive include resins obtained from vinyl acetate latex, urethane latex, acrylic latex, styrene-butadiene latex, and the like. Among these, acetoacetyl-modified polyvinyl alcohol and diacetone-modified polyvinyl alcohol are preferable because they can improve surface barrier properties and improve storage stability such as chemical resistance.

  The total amount of adhesive used is preferably about 10 to 80% by mass, and more preferably about 20 to 75% by mass, based on the total solid content of the protective layer. By setting it as 10 mass% or more, barrier property can fully be exhibited, and surface strength can be improved and the fall of paper dust can be prevented. On the other hand, by setting it to 80% by mass or less, sticking can be effectively prevented.

  When the water-soluble adhesive and the water-dispersible adhesive are used in combination, the mass ratio is preferably about 5 to 100 parts by mass with respect to 100 parts by mass of the water-soluble adhesive.

  Examples of the pigment include inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, amorphous silica, synthetic mica, aluminum hydroxide, barium sulfate, talc, kaolin, clay, calcined kaolin, nylon resin filler, urea -Organic pigments such as formalin resin filler and raw starch particles. Among these, kaolin and aluminum hydroxide are preferable because they have a small decrease in barrier properties against chemicals such as plasticizers and oils and a small decrease in recording density.

  The usage-amount of a pigment is about 5-80 mass% with respect to the total solid of a protective layer, and the range of about 10-70 mass% is especially preferable. By setting the content to 5% by mass or more, it is possible to improve the sliding with the thermal head and to prevent the occurrence of sticking and head wrinkles. On the other hand, by setting it as 80 mass% or less, barrier property can be improved and the function as a protective layer can be improved significantly.

  The protective layer coating liquid is prepared, for example, by using water as a medium and mixing an adhesive, a pigment, and, if necessary, other auxiliaries.

  As auxiliary agents, for example, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and other lubricants, glyoxal, boric acid, dialdehyde starch, methylol urea, epoxy compounds, hydrazine compounds, etc. (Crosslinking agent), hydrophobic polycarboxylic acid copolymer, ultraviolet absorber, fluorescent dye, colored dye, mold release agent, antioxidant and the like. The usage-amount of auxiliary agent can be suitably set from a wide range.

  In the present invention, in order to stabilize the curtain film by adjusting the surface tension of the coating solution, a surfactant may be contained in the protective layer coating solution. Surfactants include, for example, sulfosuccinic acid alkali metal salts, alkylbenzene sulfonates, acetylene glycol compounds, fluorine surfactants, silicon surfactants, phosphate ester surfactants, and ether type surfactants. And amphoteric surfactants such as betaines, aminocarboxylates, and imidazoline derivatives, and the like, and dialkylsulfosuccinates represented by the following general formula (1) are particularly preferable. As the salt, an alkali metal salt or ammonium salt of a dialkylsulfosuccinate is preferably used, and a sodium salt is particularly preferable. Moreover, as an alkyl group of dialkyl sulfosuccinate, C2-C20 is preferable, and C4-C10 is especially preferable. Specific examples include an isobutyl group, a hexyl group, a cyclohexyl group, an octyl group, an isooctyl group, and a 2-ethylhexyl group, and an octyl group or a 2-ethylhexyl group having 8 carbon atoms is particularly preferable.

  As the usage-amount of this surfactant, about 0.05-3.0 mass% is preferable with respect to the total solid of a protective layer, and about 0.05-2.0 mass% is more preferable. By setting it as 0.05 mass% or more, surface tension can fully be reduced and it can be made hard to produce curtain film | membrane cut | disconnection. By setting it as 3.0 mass% or less, foaming of a coating liquid can be suppressed and a coating defect can be reduced.

（式中、Ｒ^１、Ｒ^２は同一または異なる炭素数２〜２０の脂肪族または脂環式炭化水素基を表し、Ｍはアルカリ金属塩またはアンモニウム塩を表す。）

(Wherein R ¹ and R ² represent the same or different aliphatic or alicyclic hydrocarbon groups having 2 to 20 carbon atoms, and M represents an alkali metal salt or an ammonium salt.)

The coating amount of the protective layer coating liquid, 0.5~7.0g / ^{m 2} approximately by dry weight, preferably 0.8~6.0g / ^{m 2} approximately. The protective layer can be divided into two or more layers as required, and the composition and application amount of each layer can be changed.

  In the present invention, the thermal recording layer coating liquid and the protective layer coating liquid are simultaneously applied and dried by the curtain coating method to form the thermal recording layer and at least one protective layer. Thereby, interlayer mixing can be prevented and the barrier property of the protective layer can be remarkably improved, production efficiency can be increased, and energy consumption during production can be further reduced. Here, simultaneous application is a method of applying the upper and lower layers simultaneously when applying two or more layers, and includes a method of applying the upper layer without drying after applying the lower layer.

  The curtain coating method is a method in which a free-falling curtain film of a coating liquid is formed, and the coating liquid is applied by colliding with a support that travels. Specifically, known methods such as a slide curtain coating method, a couple curtain coating method, a twin curtain coating method, and the like can be employed, and are not particularly limited. Further, for example, the coating liquid is ejected downward from the curtain head to form a coating liquid layer on the slope, and a coating liquid curtain is formed from the downward curtain guide portion at the end of the slope to form the coating liquid on the support. A method using a multi-stage curtain coater for transferring the layers can also be adopted. Examples of the method using a multistage curtain coater include the method described in JP-A-2006-247611.

  It should be noted that various conditions such as coating solution concentration, coating speed, curtain film width, and drop angle are desirably adjusted as appropriate in accordance with each curtain coating method and coating apparatus. Since these curtain coating methods are non-contact contour coating, a layer having a uniform thickness can be obtained. On the other hand, a contact coating method such as a blade coating method, a bar coating method, or an air knife coating method is affected by the surface properties (unevenness) of the support, and therefore the film thickness is non-uniform. For this reason, with the same coating amount, the thermal recording layer formed by the curtain coating method can improve the recording sensitivity, obtain a good image quality, and improve the storability of the recorded image with a smaller coating amount. You can also.

  The coating apparatus used in the curtain coating method is not particularly limited, and examples thereof include an extrusion hopper type curtain coating apparatus, a slide hopper type curtain coating apparatus, or the multistage curtain coater described in Japanese Patent Application Laid-Open No. 2006-247611. It is done.

  After forming the heat-sensitive recording layer and the protective layer, the surface of the protective layer may be subjected to a known smoothing process such as a calendar, if necessary. The surface of the protective layer may be applied to either the metal roll or the elastic roll of the calendar.

  The undercoat layer in the present invention is mainly composed of a pigment and an adhesive. As the pigment, it is preferable to use plastic hollow particles and calcined kaolin in combination from the viewpoint of improving chemical resistance and sticking resistance.

The hollow plastic particles are conventionally known, for example, fine hollow particles having a thermoplastic polymer as a shell, and a copolymer mainly composed of acrylic resin, styrene resin, acrylic-styrene resin, vinylidene chloride resin and acrylonitrile. Examples thereof include particles having a hollow ratio of about 50 to 99% made of a resin, a copolymer resin mainly composed of isobornyl methacrylate and acrylonitrile, and the like. Here, the hollow ratio is a ratio of the inner diameter to the outer diameter, and is expressed by the following formula.
Hollow ratio (%) = (inner diameter of hollow particle / outer diameter of hollow particle) × 100

  The content of the plastic hollow particles is preferably 10 to 100 parts by mass, more preferably 15 to 70 parts by mass, and particularly preferably 20 to 60 parts by mass with respect to 100 parts by mass of the calcined kaolin. By controlling the coating amount to 100 parts by mass or less, interlayer coating can be effectively suppressed and the coating uniformity can be improved when the thermal recording layer coating solution and the protective layer coating solution are simultaneously applied by the curtain coating method. It can improve the barrier property and can exhibit even better chemical resistance. Moreover, it is excellent in the ability to absorb the hot melt and can improve the effect of suppressing sticking to the thermal head, so-called sticking. On the other hand, when the content is 10 parts by mass or more, the recording sensitivity and the image quality can be improved, and the effect of suppressing intermixing between the heat-sensitive recording layer and the protective layer can be improved.

  The average particle diameter of the plastic hollow particles is preferably about 0.4 to 2.0 μm. By setting the average particle size to 2.0 μm or less, when the undercoat layer coating solution is applied by a blade coating method, troubles such as streaks and scratches are not caused, and good coating suitability can be obtained. Also, in terms of quality, the surface smoothness of the undercoat layer can be further enhanced. Therefore, when the multi-layer coating of the thermal recording layer coating liquid and the protective layer coating liquid is simultaneously performed by the curtain coating method, the coating uniformity is improved and the protective layer is improved. The barrier property can be improved.

  As the calcined kaolin, from the viewpoint of further improving the sticking resistance, the oil absorption specified by JIS-K5101 is preferably 70 ml / 100 g or more.

  Other pigments can also be contained in the undercoat layer. As other pigments, both inorganic and organic pigments can be used. In particular, an oil-absorbing pigment having an oil absorption of 40 ml / 100 g or more can be suitably used. Examples of the oil-absorbing pigment include aluminum oxide, magnesium carbonate, calcined diatomaceous earth, aluminum silicate, calcium carbonate, barium sulfate, aluminum hydroxide, kaolin, amorphous silica, talc and the like. In addition, solid plastic particles can be used as other pigments. 40-95 mass% is preferable with respect to the total solid of an undercoat layer, and, as for the total amount of the pigment containing said plastic hollow particle and baking kaolin, 50-90 mass% is more preferable.

  As the adhesive, for example, any of a water-soluble adhesive and a water-dispersible adhesive can be used. Examples of the water-soluble adhesive include polyvinyl alcohol, modified polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, and ethylcellulose, polyacrylic acid soda, polyvinylpyrrolidone, and acrylic acid. Examples include amide-acrylic acid ester copolymers, acrylic acid amide-acrylic acid ester-methacrylic acid copolymers, styrene-maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein. Water dispersible adhesives include polyvinyl acetate, polyurethane, styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride-acetic acid Examples thereof include latex of a hydrophobic polymer such as vinyl copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, silylated urethane, acrylic-silicon composite, and acrylic-silicon-urethane composite. These can be used alone or in combination of two or more.

  The amount of the adhesive used is not particularly limited, and is determined in consideration of the coating strength and the recording sensitivity of the heat-sensitive recording layer, but is preferably 3 to 100 parts by mass with respect to 100 parts by mass of the pigment contained in the undercoat layer. 5 to 50 parts by mass is more preferable, and 7 to 40 parts by mass is particularly preferable.

  For the undercoat layer, a coating solution for an undercoat layer prepared by mixing plastic hollow particles, calcined kaolin, adhesive, and, if necessary, an auxiliary agent is generally applied onto a support by a blade coating method using water as a medium. And formed by drying. In the present invention, from the viewpoint of improving the barrier properties of the protective layer by reducing the unevenness of the surface of the undercoat layer, making the coating thickness of the thermal recording layer and the protective layer formed on the undercoat layer uniform, and improving the barrier properties of the protective layer, It is preferable to form an undercoat layer.

  The blade coating method in the present invention is not limited to a coating method using a blade represented by a bevel type or a vent type, but includes a bill blade method and the like, and is not limited to an off-machine coater, and is installed in a paper machine. You may apply with an on-machine coater. After forming the undercoat layer, a known smoothing treatment such as a calendar may be applied to the surface of the undercoat layer as necessary.

The coating amount of the undercoat layer coating solution is not particularly limited and may be appropriately selected according to the characteristics of the heat-sensitive recording material. However, the dry weight is preferably ² to 10 g / m ^{2 and} more preferably 3 to 10 g / m ^2. 4 to 10 g / m ² is more preferable, and 5.5 to 8.5 g / m ² is particularly preferable.

  In general, when a coating liquid film consisting of a plurality of coating liquids of the thermal recording layer and the protective layer is applied simultaneously on the undercoat layer, it is used for the thermal recording layer that constitutes the coating liquid film between application and drying. The moisture in the coating liquid moves into the undercoat layer, and the moisture in the upper protective layer coating liquid moves toward the heat-sensitive recording layer. At this time, components other than water contained in the protective layer also move to the heat-sensitive recording layer side due to the movement of moisture, and mixing between layers occurs. Quality degradation such as property becomes a problem. The reason why excellent chemical resistance is obtained in the present invention is that plastic hollow particles having a specific gravity smaller than that of inorganic pigments and plastic dense particles are migrated upward from the application of the coating liquid for the undercoat layer to the end of drying. To increase the hydrophobicity of the surface of the undercoat layer and suppress the infiltration of moisture in the coating liquid for the thermal recording layer. As a result, the coating liquid for the thermal recording layer and the coating liquid for the protective layer It is considered that interlayer mixing is suppressed and the barrier property of the protective layer is improved. In the present invention, from the viewpoint of improving the sticking resistance and the barrier property, the content of the plastic hollow particles is preferably suppressed to be equal to or less than the content of the calcined kaolin.

  In the present invention, it is preferable that the maximum surface temperature in the constant rate drying process of the undercoat layer is less than 100 ° C., and it is more preferable that the undercoat layer is dried at less than 85 ° C. By making the temperature lower than 100 ° C., under normal pressure, the plastic hollow particles can be aligned on the surface of the undercoat layer without causing water expansion and evaporation due to a rapid temperature increase in the constant rate drying process. Interlayer mixing of the layer and the protective layer can be effectively suppressed. Further, from the viewpoint of effectively promoting the migration of the hollow plastic particles and improving the drying efficiency, the lower limit of the maximum surface temperature in the constant rate drying process is preferably 45 ° C. or more, and 50 ° C. or more. Is more preferable. This can be achieved by appropriately controlling the drying air temperature and the drying air wet bulb temperature during the drying process. Here, the constant rate drying process in this invention means the period which shows the phenomenon in which the moisture content in a coating layer reduces in proportion to time.

  In the present invention, as the support, for example, high-quality paper, art paper, synthetic paper, PET film, non-woven fabric medium paper, coated paper, cast coated paper, glassine paper, resin laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, In addition to non-woven fabrics and synthetic resin films, various transparent supports and the like can be appropriately selected and used.

  In the present invention, a back layer may be provided on the support opposite to the thermosensitive recording layer from the viewpoint of improving the storage stability by suppressing the permeation of oil and plasticizer from the back surface of the thermosensitive recording body and controlling curl. it can. In addition, in order to increase the added value of the thermal recording medium, for example, adhesive paper, rewet adhesive paper, delayed tack paper can be applied by applying an adhesive, rewet adhesive, delayed tack type adhesive, etc. on the back side. Can be used as Alternatively, a thermal recording body having a magnetic recordable layer can be obtained by applying magnetic processing to the back surface. In particular, those subjected to adhesive processing and magnetic processing are useful for applications such as heat-sensitive labels and heat-sensitive magnetic tickets. Furthermore, using the back surface, it can be given a function as a thermal transfer paper, inkjet paper, carbonless paper, electrostatic recording paper, xerographic paper, and a recording body capable of double-sided recording can be obtained. Moreover, it can also be set as a double-sided thermal recording body.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Further, “parts” and “%” in the examples indicate “parts by mass” and “% by mass”, respectively, unless otherwise specified.

Example 1
Preparation of coating solution for undercoat layer 60 parts of calcined kaolin (trade name: Ancilex 90, manufactured by Engelhard), plastic hollow particle emulsion (trade name: AE852, solid content concentration 26%, hollow rate 80%, average particle diameter 1.0 part, 80 parts by styrene-butadiene copolymer latex (trade name: L-1571, solid content concentration 48%, manufactured by Asahi Kasei Kogyo Co., Ltd.), carboxymethylcellulose (trade name: Cellogen 7A, No. 1) A composition comprising 20 parts of a 5% aqueous solution (made by Ichi Kogyo Seiyaku Co., Ltd.), 25 parts of a 20% aqueous solution of oxidized starch (trade name: Oji Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 90 parts of water are mixed. A liquid was obtained.

Preparation of leuco dye dispersion (liquid A) Composition comprising 95 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 100 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water. Was pulverized using a sand mill until the average particle size became 0.5 μm to obtain a leuco dye dispersion.

-Preparation of developer dispersion (liquid B) An average particle size of a composition comprising 95 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 100 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was obtained using a sand mill. The developer dispersion was obtained by pulverizing until the diameter became 0.5 μm.

-Preparation of sensitizer dispersion (liquid C) A composition comprising 10 parts of di-p-methylbenzyl oxalate, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water was prepared using a sand mill. A sensitizer dispersion was obtained by pulverizing to 0.5 μm.

Preparation of coating solution for heat-sensitive recording layer A part 30 parts, B part 60 parts, C part 30 parts, aluminum hydroxide (trade name: Hydylite H-42M, Showa Denko), complete polymerization degree 1000 From 50 parts of 10% aqueous solution of saponified PVA (trade name: PVA110, degree of saponification 98-99 mol%, manufactured by Kuraray Co., Ltd.), 10 parts of 5% aqueous solution of sodium dioctylsulfosuccinate (trade name: SN wet OT70, manufactured by San Nopco) The resulting composition was mixed to obtain a thermal recording layer coating solution.

-Preparation of coating solution for protective layer 120 parts of 50% dispersion of kaolin (trade name: UW-90, manufactured by Engelhard), acetoacetyl-modified polyvinyl alcohol (trade name: Z-200, manufactured by Nippon Synthetic Chemical Industry) 300 parts of a 10% aqueous solution, 20 parts of zinc stearate (trade name: Hydrin Z-8-36, solid content concentration 36%, manufactured by Chukyo Yushi Co., Ltd.), sodium dioctylsulfosuccinate (trade name: SN wet OT70, A composition comprising 10 parts of a 5% aqueous solution (manufactured by San Nopco) was mixed to obtain a protective layer coating solution.

-Preparation of thermosensitive recording medium A blade coating method using a blade coater so that the coating amount after drying the coating liquid for the undercoat layer is 7 g / m ^{2 on} one surface of a high-quality paper having a basis weight of 60 g / m ² as a support. Then, the undercoat layer is formed by coating and drying, and the thermal recording layer coating solution and the protective layer coating solution are further applied onto the undercoat layer from the side close to the support using a slide hopper type curtain coating device. A coating film composed of a coating liquid for a protective layer and a coating liquid for a protective layer is formed in order, and the coating speed is 600 m so that the thermal recording layer is 3.5 g / m ² and the protective layer is 2.5 g / m ² by dry weight. After applying and drying at the same time by the curtain coating method at / min to form a heat-sensitive recording layer and a protective layer, the surface of the protective layer is supercalendered, and the surface smoothness is 1000 to 4000 seconds with a Oken type smoothness meter. A heat-sensitive recording material was obtained.

Example 2
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, instead of 50 parts of a 10% aqueous solution of fully saponified polyvinyl alcohol having a polymerization degree of 1000, completely saponified polyvinyl alcohol having a polymerization degree of 2400 (trade name: trade name: PVA124, saponification) A thermosensitive recording material was obtained in the same manner as in Example 1 except that 50 parts of a 10% aqueous solution having a degree of 98 to 99 mol%, manufactured by Kuraray Co., Ltd. was used.

Example 3
5% aqueous solution of ditridecyl sulfosuccinic acid sodium salt (trade name: Perex TRB, manufactured by Kao Corporation) instead of 10 parts of 5% aqueous solution of dioctyl sulfosuccinic acid sodium salt in the preparation of the thermal recording layer coating liquid of Example 1. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that was used.

Example 4
In the preparation of the leuco dye dispersion of Example 1, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea was used instead of 4-hydroxy-4′-isopropoxydiphenylsulfone. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that.

Comparative Example 1
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, instead of 50 parts of a 10% aqueous solution of fully saponified polyvinyl alcohol having a polymerization degree of 1000, a completely saponified polyvinyl alcohol having a polymerization degree of 500 (trade name: trade name: PVA105, saponified A thermosensitive recording material was obtained in the same manner as in Example 1 except that 50 parts of a 10% aqueous solution having a degree of 98 to 99 mol%, manufactured by Kuraray Co., Ltd. was used.

Comparative Example 2
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, 10% of oxidized starch (trade name: Oji Ace A, manufactured by Oji Cornstarch) was used instead of 50 parts of a 10% aqueous solution of fully saponified polyvinyl alcohol having a polymerization degree of 1000. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 50 parts of the aqueous solution was used.

Comparative Example 3
In the preparation of the thermal recording layer coating solution of Example 1, the thermal recording material was prepared in the same manner as in Example 1 except that the amount of 5% aqueous solution of dioctyl sulfosuccinic acid sodium salt was changed to 10 parts instead of 10 parts. Obtained.

Comparative Example 4
In the preparation of the heat-sensitive recording layer coating solution and the protective layer coating solution of Example 1, polyoxyalkylene lauryl ether (trade name: Neugen LP-100, No. 1) was used instead of 10 parts of a 5% aqueous solution of sodium dioctylsulfosuccinate. 10 parts of a 5% aqueous solution manufactured by Ichi Kogyo Co., Ltd. was used, but the curtain film stability deteriorated and film breakage occurred frequently. Therefore, the thermosensitive recording medium was prepared in the same manner as in Example 1 except that the amount was 40 parts. Obtained.

  The viscosity at a specific shear rate of the thermal recording layer coating solution was measured using DAR-100 (manufactured by Relogica Instruments).

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

(Coating uniformity)
The whole surface was colored by leaving it in an oven at 105 ° C. for 10 minutes, and the color unevenness was visually evaluated according to the following criteria.
A: Coloring unevenness is not seen at all.
○: Some color unevenness is observed, but there is no practical problem.
X: Coloring unevenness is observed, which is a practical problem.

(Recording sensitivity)
Using a thermal recording simulator (TH-PMD, manufactured by Okura Electric Co., Ltd.), recording was performed at an applied energy of 0.24 mJ / dot, and the recording density of the recording part was measured with a Macbeth densitometer (RD914, using visual mode).

(Plasticizer resistance)
The recording part recorded in the evaluation of the recording sensitivity is wound around an acrylic cylinder having a diameter of about 5 cm so as to be sandwiched from above and below by a vinyl chloride wrap film (Hiessoft TM350, manufactured by Nippon Carbide Industries Co., Ltd.), and in an environment of 40 ° C. for 24 hours. After being allowed to stand, the density of the recording part was measured in a visual mode of a Macbeth densitometer (trade name: RD-914, manufactured by Macbeth).

(Water resistance of paint film)
A drop of tap water was dropped on the surface of the protective layer of the heat-sensitive recording material, and immediately after rubbing with a finger, the state of the coating film falling off was sensory evaluated.
A: The coating film is not peeled off at all.
○: The surface is slightly swollen, but peeling of the coating film is not observed.
Δ: A small amount of the coating layer is melted, and the finger is slightly whitened.
X: Detachment of clear coating film is observed.

  According to the present invention, when the thermal recording layer and the protective layer are formed by simultaneously applying and drying the thermal recording layer coating liquid and the protective layer coating liquid by the curtain coating method, a stable and uniform curtain film is formed, In addition, it is possible to provide a method for producing a thermal recording material that is free from coating unevenness and is excellent in productivity and quality.

Claims (6)

In a method for producing a heat-sensitive recording body comprising at least an undercoat layer, a leuco dye, a developer and a water-soluble adhesive on a support, and a protective layer, the liquid temperature of the coating liquid for the heat-sensitive recording layer is 25. ℃ a viscosity of at a shear rate of 2000s ^-1 40~150mPa · s in, and the ratio of the viscosity of the viscosity and 2000s h ^-1 o'clock shear rate ^{1s -1} is 1: 0.01 to 0.08, A method for producing a thermal recording material, wherein the thermal recording layer and the protective layer are formed by simultaneously applying and drying the thermal recording layer coating liquid and the protective layer coating liquid by a curtain coating method. The heat-sensitive recording layer coating solution contains 0.05 to 1.0 mass% of a dialkylsulfosuccinate represented by the following general formula (1) with respect to the total solid content of the heat-sensitive recording layer. The manufacturing method of the heat-sensitive recording material as described.

(Wherein R ¹ and R ² represent the same or different aliphatic or alicyclic hydrocarbon groups having 2 to 20 carbon atoms, and M represents an alkali metal salt or an ammonium salt.)   The thermosensitive recording material according to claim 1 or 2, wherein the water-soluble adhesive contains 2 to 12% by mass of a completely saponified polyvinyl alcohol having a polymerization degree of 800 to 3000 based on the total solid content of the thermosensitive recording layer. Method.   The method for producing a heat-sensitive recording material according to any one of claims 1 to 3, wherein the protective layer coating solution contains a dialkylsulfosuccinate represented by the general formula (1).   As the developer, 2,2′-bis (4-hydroxyphenyl) propane, 4-hydroxy-4′-isopropoxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, 3,3′-diallyl-4,4′-dihydroxydiphenylsulfone, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, N- (p-toluenesulfonyl) -N′-3- (p- The method for producing a heat-sensitive recording material according to any one of claims 1 to 4, comprising at least one selected from the group consisting of (toluenesulfonyloxy) phenylurea.   The undercoat layer contains plastic hollow particles and calcined kaolin, and an undercoat layer coating solution containing 10 to 100% by mass of plastic hollow particles with respect to 100 parts by mass of calcined kaolin is applied and dried by a blade coating method. The method for producing a heat-sensitive recording material according to claim 1, wherein an undercoat layer is formed.