JP2011037213A - Method for manufacturing thermal recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a thermal recording medium, which causes no streak-like defect in the flowing direction when applying and drying simultaneous multi-layer curtain coating on the support body with a coating liquid for a thermal recording layer containing a leuco dye and a color developer and with a coating liquid for at least one protective layer, thereby obtaining uniform printing quality, excellent productivity and a high quality thermal recording medium. <P>SOLUTION: The method for manufacturing a thermal recording medium forms the thermal recording layer and a protective layer using a coating device including curtain heads provided at certain intervals and a guide sheet which sequentially laminates the coating liquid injected downward sequentially from each curtain head onto the slating surface while moving the coating liquid on the slating surface, and then transfers the coating liquid as coating liquid curtain from the downward curtain guide at the bottom end of the slating surface to the web surface. When the liquid temperature of the coating liquid for thermal recording layers is 25°C, the shear viscosity is 60 to 150 mPa s at the shear speed of 5,000 s<SP>-1</SP>, and the viscosity measured by the B-type viscometer is 400 to 1,200 mPa s. <P>COPYRIGHT: (C)2011,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 thermal recording medium is relatively inexpensive, and the recording equipment is compact and easy to maintain. For example, it can be used in facsimiles, computer outputs, handy terminals, POS systems (store point-of-sale information management systems), and transportation systems. It is used in a wide range of fields such as passenger tickets and commuter passes. Recently, due to the diversification of application development and the enhancement of the functions of the system, the required quality of the thermal recording medium has become high.

  Conventionally, methods such as air knife coating, blade coating, rod coating, roll coating, and bar coating are commonly used as methods for applying a coating solution to a substrate such as paper or film. However, the heat-sensitive recording material produced by such a method has poor coating quality, and when the multilayer coating is applied, the upper layer is caused by penetration of the upper layer coating liquid into the lower layer, repelling during the upper layer coating, etc. In addition to problems such as pinholes and quality variations in continuous application over a long period of time, there are limits to high-speed application, and there are problems such as a decrease in productivity resulting from many applications.

  In contrast to these coating methods, the curtain coating method is a method in which a falling curtain of coating liquid is formed, and this is applied by colliding with a support, and the coating quality is good and it is suitable for high-speed coating. Are known. Moreover, by forming a coating film composed of a plurality of coating liquids using a slide hopper type curtain coating apparatus or a multilayer type extrusion hopper type curtain coating apparatus provided with a plurality of flow paths inside, and applying the curtain, It is also possible to apply a plurality of layers at the same time, and the productivity of multilayer application can be greatly improved.

  However, when multi-layer coating is performed using the slide hopper type curtain coating apparatus described in Patent Document 1 or the multilayer extrusion hopper type curtain coating apparatus described in Patent Document 2, coating to a head that is not used when coating is stopped. There is a problem that it is necessary to stop the supply of the liquid, and unless the supply of the coating liquid to the head that is not used is stopped, the coating liquids are mixed, and the individual coating liquids cannot be collected alone.

  On the other hand, when the supply of the coating liquid to the unused head is stopped, the coating liquids are not mixed with each other, but the coating liquid cannot be circulated, so that the coating liquid of the unused head portion dries and the coating liquid adheres to the head. For this reason, when coating is started again, there are problems such as streaks due to contamination of the coating liquid adhering to the head, clogging of the die slit, and inability to supply uniform coating liquid in the width direction. Arise.

  Therefore, when the coating liquid of any head is stopped, it is necessary to stop the coating once and clean the head. However, since cleaning water is mixed into the operating head during cleaning, the other head Must be stopped and cleaned at the same time. For this reason, when changing the type of product to be coated, it is necessary to stop coating and clean all the heads, and it takes a considerable time to resume coating.

  In this way, in the slide die type coating method capable of multilayer coating and multilayer extrusion hopper type curtain coating device, the coating liquid is mixed, so it is necessary to clean all heads when switching coating. There is a problem that it is not easy to start and stop coating.

  On the other hand, the curtain coating method capable of multilayer coating described in Patent Document 3 is provided with an arbitrary interval, and includes a plurality of curtain heads that spray the coating liquid downward, and a plurality of curtain heads. The coating liquid sprayed from the curtain head sequentially toward the slope is sequentially stacked as it moves on the slope to form a plurality of coating liquid layers, and is applied from the downward curtain guide section of the slope. A coating apparatus comprising a guide sheet for transferring a liquid layer onto a web surface as a coating liquid curtain, and a receiving container for receiving a coating liquid ejected from a curtain head that is not used for coating among a plurality of curtain heads; Since it is further equipped with a circulation means that circulates the coating liquid received in the receiving container to the curtain head again, the coating liquid of the head that is not in use can be circulated, and the coating liquid adhered to the head and dried That there is no occurrence of streaks, it is possible to prevent the nonuniformity in the width direction of the coating liquid supply caused by clogging of the coating liquid. Further, among the plurality of curtain heads, a supply means for supplying water to a curtain head that is not used for coating, a receiving container for receiving water etc. ejected from the curtain head, and water received by the receiving container are again curtained. Since there is a circulation means for circulating in the head, there is a feature that cleaning is easy and productivity is excellent. However, when a thermal recording material is produced using this coating method, the present situation is that a satisfactory result is not always obtained for the coating quality.

Japanese Patent Publication No.49-24133 Japanese Patent Laid-Open No. 3-123672 Japanese Patent Laid-Open No. 2006-247611

  An object of the present invention is to provide a plurality of curtain heads which are arranged at an arbitrary interval and each sprays a coating liquid downward, and a coating liquid which is sequentially ejected from the plurality of curtain heads toward a slope. Are stacked in order as they move on the inclined surface to form a plurality of coating liquid layers, and the coating liquid layer is applied on the web surface as a coating liquid curtain from a downward curtain guide portion at the lower end of the inclined surface. Using a coating apparatus having a guide sheet to be transferred, a thermal recording layer coating liquid containing a leuco dye and a developer, and at least one protective layer coating liquid are simultaneously multilayered on a support. When forming a thermal recording layer and a protective layer by applying curtain and drying, there is no generation of streak-like defects in the flow direction, a uniform print image quality is obtained, and a method for producing a thermal recording body excellent in productivity and quality is provided. Is to do

  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: A plurality of curtain heads arranged at arbitrary intervals and spraying the coating liquid downward, respectively, and the coating liquid sequentially ejected from the plurality of curtain heads toward the slope, A guide for forming a plurality of coating liquid layers by sequentially laminating on the slope, and transferring the coating liquid layer as a coating curtain from the downward curtain guide portion at the lower end of the slope to the web surface And a coating device for a heat-sensitive recording layer containing a leuco dye and a developer, and at least one protective layer coating solution simultaneously on a support using a coating apparatus comprising a sheet, A method for producing a heat-sensitive recording material comprising drying and forming a heat-sensitive recording layer and a protective layer, wherein the heat-sensitive recording layer coating solution has a shear viscosity of 60 to 150 mPa · s at a shear rate of 5000 s ⁻¹ at a liquid temperature of 25 ° C. And And the viscosity measured by a B-type viscometer is 400-1200 mPa * s, The manufacturing method of the thermal recording body characterized by the above-mentioned.

  Item 2: The method for producing a heat-sensitive recording material according to Item 1, wherein a static surface tension of the coating liquid for the heat-sensitive recording layer is 25 mN / m to 40 mN / m.

  Item 3: The heat-sensitive recording layer coating solution contains at least one kind of completely saponified polyvinyl alcohol having a polymerization degree of 800 to 3000, and the polyvinyl alcohol is 2 to 12 based on the total solid amount of the heat-sensitive recording layer coating solution. Item 3. The method for producing a heat-sensitive recording material according to Item 1 or 2, wherein the heat-sensitive recording material is contained by mass%.

  Item 4: At least one selected from the group consisting of poly (meth) acrylic acid alkali salts and (meth) acrylic acid-maleic acid copolymer alkali salts as the heat-sensitive recording layer coating liquid, Item 4. The method for producing a heat-sensitive recording material according to any one of Items 1 to 3, which is contained in an amount of 0.1 to 1.2% by mass.

  Item 5: The heat-sensitive recording layer coating solution contains 0.05 to 1.0% by mass of the dialkylsulfosuccinate represented by the following general formula (1) with respect to the total solid content of the heat-sensitive recording layer coating solution. Item 5. The method for producing a heat-sensitive recording material according to any one of Items 1 to 4.

（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 6: An undercoat layer coating solution containing calcined kaolin and plastic hollow particles at a ratio of 10 to 100% by mass of plastic hollow particles with respect to 100 parts by mass of calcined kaolin between the support and the heat-sensitive recording layer by a blade coating method Item 6. The method for producing a heat-sensitive recording material according to any one of Items 1 to 5, wherein an undercoat layer is formed by coating and drying.

  It is an object of the present invention to provide a method for producing a thermal recording material that is free from the occurrence of streak-like defects in the flow direction, provides uniform print image quality, and is excellent in productivity and quality.

The present invention is provided with a plurality of curtain heads arranged at an arbitrary interval and ejecting the coating liquid downward, respectively, and the coating liquid sequentially ejected from the plurality of curtain heads toward the slope, A plurality of coating liquid layers are formed in order as it moves on the slope, and the coating liquid layer is transferred onto the web surface as a coating curtain from the downward curtain guide portion of the lower end of the slope. Using a coating apparatus having a guide sheet, a multilayer curtain coating is applied simultaneously on the support with a thermal recording layer coating liquid containing a leuco dye and a developer, and at least one protective layer coating liquid. And a method for producing a heat-sensitive recording layer by drying to form a heat-sensitive recording layer and a protective layer, wherein the heat-sensitive recording layer coating liquid has a shear viscosity of 60 to 150 mPa · s at a shear rate of 5000 s ⁻¹ at a liquid temperature of 25 ° C. ,and By setting the viscosity measured by the B-type viscometer to 400 to 1200 mPa · s, streak defects in the flow direction can be prevented. The viscosity at a shear rate of 5000 s ⁻¹ is more preferably 70 to 150 mPa · s, and the viscosity measured by a B-type viscometer is more preferably 400 to 1000 mPa · s.

When the shear viscosity of the thermal recording layer coating liquid is less than 60 mPa · s at a shear rate of 5000 s ⁻¹ , the shear force when the protective layer coating liquid lands on the thermal recording layer coating liquid flowing down on the slope. This is difficult to withstand and causes streak-like defects. On the other hand, if the shear viscosity at a shear rate of 5000 s ⁻¹ is greater than 180 mPa · s, the leveling property of the coating liquid is inferior, so that the coating film becomes unstable or a uniform coating film cannot be obtained and the print quality is hindered. give.

  When the viscosity of the coating solution for the heat-sensitive recording layer measured by a B-type viscometer is 400 mPa · s or less, it is difficult to make it within the shear viscosity range of the present invention. On the other hand, when it is larger than 1200 mPa · s, problems such as reduction in leveling property and defoaming efficiency occur.

In the present invention, in order to set the shear viscosity at a shear rate of 5000 s ⁻¹ at a liquid temperature of 25 ° C. of the thermal recording layer coating liquid to 60 to 150 mPa · s, the thermal recording layer coating liquid serves as an adhesive with a polymerization degree of 800. The shear viscosity of the coating liquid is adjusted by containing at least one kind of completely saponified polyvinyl alcohol of ˜3000 and 2 to 10% by mass of completely saponified polyvinyl alcohol with respect to the total solid content of the heat-sensitive recording layer. Is preferred. The completely saponified polyvinyl alcohol in the present invention means a polyvinyl alcohol having a saponification degree of 95% or more, preferably 98% or more, and the polymerization degree of the completely saponified polyvinyl alcohol is more preferably 800 to 2700. . The content is more preferably 4 to 10% by mass with respect to the total solid content of the thermosensitive recording layer.

Furthermore, in the present invention, at least one selected from the group consisting of poly (meth) acrylic acid alkali salts and (meth) acrylic acid-maleic acid copolymer alkali salts as the heat-sensitive recording layer coating liquid, By containing 0.1 to 1.2% by mass with respect to the total solid content, the viscosity at a shear rate of 5000 s ⁻¹ at a liquid temperature of 25 ° C. of the coating solution for the thermosensitive recording layer is in the range of 60 to 150 mPa · s. Can be easily adjusted. (Meth) acrylic acid means acrylic acid and / or methacrylic acid. The polymerization ratio of the (meth) acrylic acid-maleic acid copolymer is preferably such that the weight ratio of (meth) acrylic acid to maleic acid is in the range of 99: 1 to 70:30.

  In the present invention, it is preferable that the static surface tension of the thermal recording layer coating liquid measured by the Wilhelmy plate method or the like is 25 mN / m to 40 mN / m. By setting the static surface tension to 40 mN / m or less, the leveling property on the slope can be improved. On the other hand, when a surfactant is used within a practical range, the static surface tension of the coating liquid is 25 mN / m or more.

  Furthermore, in the present invention, the heat-sensitive recording layer coating liquid contains 0.01 to 1.0% by mass of the dialkyl sulfosuccinate represented by the following general formula (1) with respect to the total solid content of the heat-sensitive recording layer coating liquid. By containing, the static surface tension of the thermal recording layer coating liquid can be easily adjusted to a range of 25 mN / m to 40 mN / m. More preferably, it is 0.05-1.0 mass%. By setting it within this range, a coating defect is unlikely to occur, and there is little foaming of the coating liquid. As a result, a heat-sensitive recording material excellent in coating quality can be obtained.

（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.)

  As the dialkylsulfosuccinate represented by the general formula (1), an alkali metal salt or ammonium salt of a dialkylsulfosuccinate is preferably used, and a sodium salt is particularly preferable. Further, the alkyl group of the dialkyl sulfosuccinate is preferably an alkyl group having 2 to 20 carbon atoms, and more preferably an alkyl group having 4 to 10 carbon atoms. 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 is formed using a heat-sensitive recording layer coating solution containing a leuco dye and a developer. Various known leuco dyes can be used. Examples of leuco dyes that give black color are 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-ali Ninofluorane, 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-tetrahydrofluoride) Ruamino) -6-methyl-7-anilinofluorane, 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, as the leuco dye, a leuco dye that develops a color tone different from that of black, for example, a color tone such as red, magenta, orange, blue, and green may be used.

  The leuco dye used in the present invention is not limited to these, and two or more kinds may be used in combination. The amount of the leuco dye used is about 3 to 30% by mass with respect to the total solid content of the thermal recording layer coating liquid.

  The leuco dye may be used as a protective colloid agent in the form of solid fine particles wet-dispersed with a sand mill or the like together with a water-soluble polymer such as polyvinyl alcohol or methylcellulose, or forms a composite particle containing a leuco dye and a hydrophobic resin. It may be used in the form.

  Forms in which composite particles containing a leuco dye and a hydrophobic resin are formed include (1) a form in which one or more leuco dyes are microencapsulated using a hydrophobic resin as a wall film, and (2) one or more kinds of leuco dyes. And (3) a form in which a compound having an unsaturated carbon bond is polymerized on the surface of one or more leuco dye fine particles. It is done. Examples of the method for producing the particles having the form (1) include the method described in JP-A-60-244594. Examples of the method for producing particles having the form (2) include the method described in JP-A-9-263057. Examples of the method for producing the particles having the form (3) include the method described in JP-A No. 2000-158822.

  Alternatively, after dissolving the leuco dye in a solvent, this 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 leuco dye as solid fine particles. it can. In any case, the average particle diameter of the dispersed particles of the leuco dye is preferably 0.2 to 3.0 μm, more preferably 0.3 to 1.0 μm in order to obtain an appropriate color development sensitivity.

  In the present invention, a known compound can be used as the developer used in the heat-sensitive recording layer. Specific examples of the developer include 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec-butylidenediphenol, 4-phenylphenol, 4,4′- Dihydroxydiphenylmethane, 4,4′-isopropylidene diphenol, 4,4′-cyclohexylidene diphenol, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 4,4′-dihydroxydiphenyl sulfide, 4 , 4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy -4'-allyloxydiph Nyl sulfone, phenolic compounds such as bis (3-allyl-4-hydroxyphenyl) sulfone, bis (p-hydroxyphenyl) butyl acetate, methyl bis (p-hydroxyphenyl) acetate, 4-hydroxybenzophenone, 4-hydroxyphthal Dimethyl acid, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoate-sec-butyl, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, 4- Phenolic compounds such as chlorophenyl hydroxybenzoate and 4,4′-dihydroxydiphenyl ether, or benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butylsalicylic acid, 3- Aromatic carboxylic acids such as sopropylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and eg zinc, Organic acidic substances such as salts with polyvalent metals such as magnesium, aluminum and calcium, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea, N- (p-toluenesulfonyl)- Examples include urea compounds such as N ′-(p-butoxycarboyl) urea and Np-toluenesulfonyl-N′-phenylurea, among which 2,2′-bis (4-hydroxyphenyl) propane, 4 -Hydroxy-4'-isopropoxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfur Emissions, 4,4'-dihydroxydiphenyl sulfone, 4,4'-bis (N-p-toluenesulfonyl-aminocarbonyl) diphenylmethane and the like.

  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 (Np-toluenesulfonylaminocarbonylamino) diphenylmethane, Np-toluenesulfonyl-N'-3- (p-toluenesulfonyloxy) It is particularly preferable to use at least one selected from phenylurea for recording a high-quality image.

  In the present invention, the use ratio of the leuco dye and the developer should be appropriately selected according to the kind of the leuco dye and the developer to be used, and is not particularly limited, but is generally based on 1 part by mass of the leuco dye. A developer of about 1 to 7 parts by mass, preferably about 1 to 4 parts by mass is used.

  Furthermore, a sensitizer can be used in combination according to the purpose. Specific examples of the sensitizer include, for example, 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 stearin. Acid amide, N-methylol stearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl Oxalic acid dibenzyl, oxalic acid-di-p-methylbenzyl ester, oxalic acid-di-p-chlorobenzyl ester, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1 2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenyl benzyl ether, 1,4-di (phenylthio) butane, p-acetoluidide, p- Examples include acetophenetide, N-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.

  Moreover, unless the desired effect is impaired, a preservability improver can be used in combination according to the purpose. Specific examples of such preservability improvers include, for example, 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- Tilphenol), 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'-tetrabromodiphenyl sulfone, 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- Hindered phenol compounds such as hydroxy-3,5-dimethylphenyl) propane, N, N′-di-2-naphthyl-p-phenylenediamine, 2,2′-methylenebi (4,6-di -tert- 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 inorganic pigments such as calcium carbonate and silica In addition, organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, and polystyrene resin can be used. The amount of the pigment blended 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.

  In the present invention, as other auxiliary agents constituting the heat-sensitive recording layer, a crosslinking agent, waxes, metal soaps, colored dyes, colored pigments, fluorescent dyes and the like can be used as necessary.

  Moreover, in order to improve the water resistance of the heat-sensitive recording layer, a crosslinking agent for three-dimensionally curing the adhesive can be contained in the heat-sensitive recording layer coating liquid. For example, 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, ammonium persulfate and Total solids of the thermal recording layer coating solution containing at least one cross-linking compound selected from diiron, inorganic compounds such as magnesium chloride, sodium tetraborate and potassium tetraborate or boric acid, boric acid triesters, boron-based polymers, etc. It is preferable to use in the range of 1 to 10% by mass with respect to the amount.

  Examples of the wax used in the heat-sensitive recording layer include waxes such as paraffin wax, carnauba wax, microcrystalline wax, polyolefin wax, and polyethylene wax, and higher fatty acid amides such as stearamide, ethylenebisstearic amide, and the like. Examples thereof include fatty acid esters and derivatives thereof.

  Examples of the metal soap used in the heat-sensitive recording layer 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 can be contained in the heat-sensitive recording layer in order to adjust the color tone of the white paper portion. If necessary, various additives such as an oil repellent, an antifoaming agent, and a viscosity modifier can be further added to the heat-sensitive recording layer as long as the effects of the present invention are not impaired.

  Specific examples of the adhesive used in the heat-sensitive recording layer coating liquid include, for example, oxidized starch, acid-modified starch, phosphate esterified starch, enzyme-modified starch, cation-modified starch, esterified starch, etherified starch and Starches such as vinyl acetate modified grafted starch, cellulose derivatives such as methylcellulose, ethylcellulose, carboxymethylcellulose, methoxycellulose, hydroxyethylcellulose and hydroxypropylmethylcellulose, fully (or partially) saponified polyvinyl alcohol, silicon modified polyvinyl alcohol, diacetone modified polyvinyl alcohol , Carboxy-modified polyvinyl alcohol, polyvinyl alcohols such as acetoacetyl-modified polyvinyl alcohol, polyacrylamide, polyvinyl pyrrolidone, acrylic acid amide-acrylic acid Water-soluble terpolymer, acrylic acid amide-acrylic acid ester-methacrylic acid copolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, sodium alginate, gelatin, casein, etc. Adhesive, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic ester, polybutyl methacrylate, styrene-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene -Water dispersible adhesives, such as an acrylic copolymer, are mentioned.

  In the present invention, in order to further increase the added value of the product, a multicolor thermosensitive recording material can be used. 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. When these are roughly classified, a multicolor thermosensitive recording material is produced using two types, a decoloring type and a color adding type, a method using a microcapsule, and composite particles comprising an organic polymer and a leuco dye. There is a way.

The heat-sensitive recording layer is generally prepared by mixing a leuco dye dispersion, a developer dispersion, an adhesive, and, if necessary, a coating solution for a heat-sensitive recording layer with a dry weight. It is applied and dried on a support or an undercoat layer provided as necessary so as to be about 1 to 12 g / m ² , particularly about ² to 10 g / m ² .

  In the present invention, at least one protective layer is provided on the heat-sensitive recording layer by simultaneous application with the heat-sensitive recording layer by a specific curtain coating method. 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 a pigment and an adhesive. In particular, a lubricant such as polyolefin wax or zinc stearate is preferably used for 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.

  The protective layer preferably contains a water-soluble adhesive and / or a water-dispersible adhesive as a main component. Examples of the water-soluble adhesive include fully saponified or partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and the like, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, etc. Cellulose-based resin, gelatin, casein, alkali salt of styrene-maleic anhydride copolymer, alkali salt of ethylene-acrylic acid copolymer, alkali salt of styrene-acrylic acid copolymer, and the like. Examples of the water-dispersible adhesive include latexes such as styrene-butadiene latex, styrene-butadiene-acrylonitrile latex, acrylic latex, and urethane latex. 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 content of the water-soluble polymer and / or the water-dispersible adhesive is preferably about 10 to 80% by mass, 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 be improved, surface strength can be improved, and generation | occurrence | production of paper dust can be suppressed. On the other hand, sticking can be suppressed by setting it as 80 mass% or less.

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

  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 slippage with the thermal head, suppress sticking, and reduce 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.

  Other auxiliary agents other than those described above can be used for the protective layer. As an auxiliary agent, for example, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and other lubricants, alkylbenzene sulfonate sodium, dioctyl sulfosuccinate sodium, sulfone-modified polyvinyl alcohol, polyacrylic acid sodium and the like surface activity Agent, glyoxal, boric acid, dialdehyde starch, methylol urea, epoxy compound, hydrazine compound, etc., waterproofing agent (crosslinking agent), hydrophobic polycarboxylic acid copolymer, UV absorber, fluorescent dye, coloring dye, release agent Examples thereof include a mold agent and an antioxidant. The usage-amount of auxiliary agent can be suitably set from a wide range.

  In the present invention, a surfactant is added to the protective layer coating liquid in order to stabilize the curtain film by adjusting the surface tension. 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. Agents, amphoteric surfactants such as betaines, aminocarboxylates, and imidazoline derivatives.

The protective layer generally uses water as a medium. For example, a coating solution for the protective layer prepared by mixing a water-soluble adhesive, a pigment, and an auxiliary agent, if necessary, has a coating amount of 0.5 to 7.0 g after drying. / M ² , preferably applied and dried on the thermal recording layer so as to be about 0.8 to 6.0 g / m ² . 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 and at least one protective layer are simultaneously applied in a multilayer by a specific curtain coating method. Thereby, production efficiency can be improved and the energy consumption at the time of manufacture can be reduced more.

  The heat-sensitive recording material is produced by simultaneously applying a heat-sensitive recording layer and at least one protective layer on the undercoat layer provided on the support, if necessary, by the curtain coating method and then drying. As a coating apparatus used for curtain coating, a plurality of curtain heads described in Patent Document 3 are arranged with an arbitrary interval and each sprays a coating liquid downward, and a plurality of curtain heads are sequentially provided. The coating liquid sprayed toward the slope is laminated in order as it moves on the slope to form a plurality of coating liquid layers, and the coating liquid layer is applied from the downward curtain guide part of the slope. It is preferable to use a coating apparatus having a guide sheet that is transferred onto the web surface as a curtain. After application of the coating liquid, it is dried, and after that, it is preferably smoothed by a calendar or the like.

  In the present invention, an undercoat layer coating solution containing calcined kaolin and plastic hollow particles in a ratio of 10 to 100% by mass of plastic hollow particles with respect to 100 parts by mass of calcined kaolin is applied by blade coating between the support and the heat-sensitive recording layer. The undercoat layer is preferably formed by coating and drying by a method. By setting the content of the plastic hollow particles to 100% by mass or less, the penetration of the coating solution for the heat-sensitive recording layer is not excessively suppressed, so it is applied while swimming until the coating solution is immobilized during the drying process. The surface is not disturbed, the coating uniformity is increased, and the barrier property can be improved. Further, the ability to absorb the hot melt is improved, and sticking to the thermal head, so-called sticking can be suppressed. On the other hand, when the content is 10% by mass or more, the hydrophobicity of the surface of the undercoat layer can be increased, the penetration of the thermal recording layer coating liquid can be suppressed, and the barrier property of the protective layer can be improved.

The hollow plastic particles are conventionally known, for example, fine hollow particles made of a thermoplastic polymer as a shell, and a copolymer mainly composed of acrylic resin, styrene resin, acrylic-styrene resin, vinylidene chloride tree and acrylonitrile. Examples of the particles having a hollow ratio of about 50 to 99% made of a resin, a copolymer resin mainly composed of isobornyl methacrylate and acrylonitrile, etc., where the hollow ratio is a ratio of an inner diameter to an outer diameter, It is what is displayed.
Hollow ratio (%) = (inner diameter of hollow particles / outer diameter of hollow particles) × 100%

  Furthermore, it is preferable that the average particle diameter of a plastic hollow particle is 0.4-2.0 micrometers from the point of the smoothness of the surface of undercoat. By setting the average particle size to 2 μm or less, troubles such as streaks and scratches do not occur when applying the blade, and the surface smoothness can be improved to improve the image quality. Further, when the coating uniformity is improved and the thermal recording layer and the protective layer are simultaneously curtain coated, the layer is not disturbed, and the barrier property can be improved by suppressing interlayer mixing.

  The calcined kaolin preferably has an oil absorption specified by JIS-K5101 of 70 ml / 100 g or more. In addition, other inorganic and organic pigments can be used as the pigment in the undercoat layer as long as the effects of the present invention are not impaired, but an oil-absorbing pigment having an oil absorption of 40 ml / 100 g or more is particularly preferable. Specific 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. Moreover, a solid plastic particle can also be contained in the range which does not impair the effect of this invention. The total amount of the pigment including the plastic hollow particles and the calcined kaolin is preferably 40 to 85% by mass with respect to the total solid content of the undercoat layer.

  The adhesive used for the undercoat layer can be appropriately selected from those used for the protective layer. These may be used alone or in combination of two or more. The content of the adhesive is determined in view of the strength of the coating film and the color development sensitivity of the heat-sensitive recording layer, but is preferably 3 to 100% by mass, and preferably 5 to 50% by mass with respect to the pigment contained in the undercoat layer. Is more preferable, and 7 to 40% by mass is particularly preferable. Moreover, you may use auxiliary agents, such as a thickener, a wax, an antifoamer, and surfactant, in an undercoat layer as needed.

  In the present invention, a coating method using a blade coater is used for coating the coating solution for the undercoat layer. Thereby, since a uniform coated surface is obtained and the unevenness of the surface of the undercoat layer is reduced, the coating thickness of each layer becomes uniform, and the barrier property can be improved. After coating and drying, a smoothing process such as a calendar may be further performed as necessary.

  The method using the blade coater is not limited to the application method using bevel type or vent type blades, but also includes the rod blade method and the bill blade method, and is not limited to the off-machine coater. It may be applied with an on-machine coater.

The undercoat layer generally uses water as a medium. For example, the coating amount for the undercoat layer prepared by mixing calcined kaolin, plastic hollow particles, an adhesive, and, if necessary, an auxiliary agent is preferably 2 after coating. to 10 g / ^{m 2,} more preferably about 3 to 10 g / ^{m 2,} more preferably such that 4~10g / ^{m 2,} is provided by coating and drying on a support.

  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, in order to increase the added value of the heat-sensitive recording material, it can be further processed to provide a heat-sensitive recording material having a higher function. For example, it can be used as a pressure-sensitive adhesive paper, a re-humidified adhesive paper, or a delayed tack paper by applying a coating process such as a pressure-sensitive adhesive, a re-humidifying adhesive, or a delayed tack type pressure-sensitive adhesive to the back surface. Or it can also be set as the thermosensitive recording body which has a layer which can be magnetic-recorded in a back surface by giving magnetic processing. In particular, those subjected to adhesive processing and magnetic processing are useful for applications such as heat-sensitive labels and heat-sensitive magnetic tickets. In addition, by using the back surface, a function of thermal transfer paper, ink jet paper, carbonless paper, electrostatic recording paper, and xerographic paper can be added to the recording material to enable double-sided recording. Of course, a double-sided thermal recording material can also be used.

  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 size 1 0.0 μm, manufactured by JSR) 80 parts, styrene-butadiene-acrylonitrile copolymer latex (solid content 50%) 20 parts, carboxymethylcellulose (trade name: Cellogen 7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 20 parts A composition comprising 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 was mixed to obtain a coating solution for an undercoat layer.

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 with a sand grinder until the average particle size became 0.5 μm to obtain a leuco dye dispersion.

-Preparation of developer dispersion (liquid B) A composition consisting of 95 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 100 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was mixed with a sand grinder to obtain an average particle size. The developer dispersion was obtained by pulverizing to 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 mixed with a sand grinder and the average particle size was 0.5 μm. A sensitizer dispersion was obtained by grinding until

-Preparation of coating solution for heat-sensitive recording layer A part 40 parts, B part 80 parts, C part 40 parts, aluminum hydroxide (trade name: Hygielite H-42M, Showa Denko), complete polymerization degree 1000 70 parts of 10% aqueous solution of saponified PVA (trade name: PVA110, degree of saponification 98-99 mol%, manufactured by Kuraray Co., Ltd.), 5 parts of 10% aqueous solution of sodium polyacrylate, dioctylsulfosuccinate sodium salt (trade name: SN wet OT70, A composition comprising 10 parts of a 5% aqueous solution (manufactured by San Nopco) was mixed to obtain a coating solution for a thermosensitive recording layer.

・ 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: Goosefimmer Z-200, Nippon Synthetic Chemical Industry) 300 parts of an aqueous solution of 10% of zinc, 20 parts of zinc stearate (trade name: Hydrin Z-8-36, solid content 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 material On one side of a high-quality paper having a basis weight of 60 g / m ² , an undercoat layer coating solution is applied and dried with a blade coater so that the coating amount after drying is 7 g / m ^2. A finished support was obtained. Further, the thermal recording layer coating liquid and the protective layer coating liquid are coated on the support coated with the undercoat layer from the side close to the undercoat layer using the coating apparatus described in the present invention. , the coating liquid film is formed consisting of the order of protective layer coating solution, so that the solid coating amount of each layer is a heat-sensitive recording layer 3.5 g / m ^2, the protective layer 2.5 g / m ^2, coating After simultaneous multi-layer curtain coating and drying at a work speed of 600 m / min, supercalender treatment was performed, and a thermal recording material having a surface smoothness of 1000 to 4000 seconds was obtained with a Oken type smoothness meter.

Example 2
In the preparation of the thermal recording layer coating liquid of Example 1, instead of 5 parts of 10% aqueous solution of sodium polyacrylate, sodium salt of acrylic acid-maleic acid copolymer (weight ratio of acrylic acid to maleic acid = 90 : A thermal recording material was obtained in the same manner as in Example 1 except that 5 parts of 10% aqueous solution 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 the amount was 10 parts.

Comparative Example 1
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 70 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 70 parts of the aqueous solution was used.

Comparative Example 2
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, instead of 70 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, saponification). A thermosensitive recording material was obtained in the same manner as in Example 1 except that 70 parts of a 10% aqueous solution having a degree of 98 to 99 mol%, manufactured by Kuraray Co., Ltd. was used.

Comparative Example 3
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that in the preparation of the heat-sensitive recording layer coating liquid of Example 1, the amount of 10% aqueous solution of sodium polyacrylate was changed to 20 parts instead of 5 parts. .

  The shear viscosity at the shear rate of the thermal recording layer coating solution was measured using Physica MCR301 (manufactured by Anton Paar). Moreover, the static surface tension of the coating liquid for heat-sensitive recording layers was measured using a Wilhelmy plate type surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., model: CBVP-Z).

  The heat-sensitive recording material thus obtained was evaluated as follows, and the results are shown in Table 1.

(Striped coating defect evaluation)
The heat-sensitive recording material was allowed to stand in an oven at 130 ° C. for 10 minutes to develop the entire surface, and the streaky coating defect was visually evaluated according to the following criteria.
A: No streak-like coating defect is observed at all.
○: Some streaky coating defects are observed, but there is no practical problem.
X: A streaky coating defect is seen, which is a practical problem.

(Recording sensitivity evaluation)
Using a thermal recording simulator (TH-PMD, manufactured by Okura Electric Co., Ltd.), a thermal recording body was recorded at an applied energy of 0.24 mJ / dot, and the reflection density of the recording portion was measured using a Macbeth densitometer (trade name: RD-914). (Manufactured by Macbeth).

(Plasticizer resistance)
The recording part of the heat-sensitive recording medium colored at 0.24 mJ / dot was wound around an acrylic cylinder having a diameter of about 5 cm so as to be sandwiched from above and below with a vinyl chloride wrap film (Hiessoft TM350, manufactured by Nippon Carbide Industries Co., Ltd.) After being left for 24 hours in an environment of 40 ° C., the reflection density of the recorded portion was measured in a visual mode of a Macbeth densitometer (trade name: RD-914, manufactured by Macbeth Co.).

(Water resistance of paint film)
One drop of tap water was dropped on the surface of the heat-sensitive recording surface side, 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.
X: Detachment of clear coating film is observed.

  According to the present invention, when a multi-layer curtain coating is simultaneously applied to a heat-sensitive recording layer coating solution and a protective layer coating solution, a stable curtain film is formed and there is no coating defect, which is excellent in productivity, recording sensitivity, image quality, and chemical resistance. It is possible to provide a method for producing a heat-sensitive recording material excellent in properties and the like.

Claims (6)

A plurality of curtain heads arranged at arbitrary intervals and spraying the coating liquid downward, respectively, and coating liquid sprayed sequentially from the plurality of curtain heads toward the slope, respectively, on the slope. A plurality of coating liquid layers are formed in order as they are moved, and a guide sheet for transferring the coating liquid layer as a coating liquid curtain from a downward curtain guide part on the lower end of the inclined surface onto the web surface Using the coating apparatus provided, a multi-layer curtain coating and drying of a heat-sensitive recording layer coating solution containing a leuco dye and a developer and at least one protective layer coating solution are simultaneously applied and dried on a support. A method for producing a heat-sensitive recording material for forming a heat-sensitive recording layer and a protective layer, wherein the heat-sensitive recording layer coating liquid has a shear viscosity of 60 to 150 mPa · s at a shear rate of 5000 s ⁻¹ at a liquid temperature of 25 ° C. and A method for producing a thermal recording material, wherein the viscosity measured by a B-type viscometer is 400 to 1200 mPa · s.   The method for producing a heat-sensitive recording material according to claim 1, wherein a static surface tension of the coating liquid for the heat-sensitive recording layer is 25 mN / m to 40 mN / m.   The thermal recording layer coating solution contains at least one kind of completely saponified polyvinyl alcohol having a polymerization degree of 800 to 3000, and the polyvinyl alcohol contains 2 to 12% by mass with respect to the total solid content of the thermal recording layer coating solution. The method for producing a heat-sensitive recording material according to claim 1 or 2.   The heat-sensitive recording layer coating liquid is at least one selected from poly (meth) acrylic acid alkali salts and (meth) acrylic acid-maleic acid copolymer alkali salts, based on the total solid content of the heat-sensitive recording layer coating liquid. The method for producing a heat-sensitive recording material according to any one of claims 1 to 3, wherein the content is 0.1 to 1.2% by mass. The said thermal recording layer coating liquid contains 0.05-1.0 mass% of dialkyl sulfosuccinate represented by following General formula (1) with respect to the total solid of the thermal recording layer coating liquid. The method for producing a heat-sensitive recording material according to any one of 1 to 4.

(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.)   An undercoat layer coating solution containing calcined kaolin and plastic hollow particles at a ratio of 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 between the support and the thermosensitive recording layer. The method for producing a heat-sensitive recording material according to any one of claims 1 to 5, wherein an undercoat layer is formed by drying.