JP2011255554A - Manufacturing method of thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a thermal recording material excellent in recording sensitivity, printing image quality and printability.SOLUTION: In the manufacturing method of the thermal recording material the support of which sequentially has an anchor layer containing plastic hollow particles, an undercoat layer containing an oil absorbing pigment of an oil absorption (JIS K 5101) of 40-120 ml/100 g, and a thermal recording layer containing a leuco dye and a developer, the anchor layer and the undercoat layer are formed by applying a coating liquid for the anchor layer and a coating liquid for the undercoat layer by a simultaneous multilayer curtain coating method, and drying.

Description

  The present invention relates to a method for producing a heat-sensitive recording material.

  A heat-sensitive recording material is known which utilizes a color reaction between a colorless or light leuco dye and an organic or inorganic developer to bring a coloring image into contact with both coloring substances by heat. Such heat-sensitive recording materials are relatively inexpensive, and since the recording equipment is compact and relatively easy to maintain, they are used not only as recording media for facsimiles and various printers but also in a wide range of fields.

  As a method of applying the coating liquid to a support such as paper or film, 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. The heat-sensitive recording material produced in step 1 has poor coating quality, soaking the upper layer coating liquid into the lower layer, repellency during upper layer coating, etc. In addition to the above problems, there are problems such as a limitation in high-speed coating and a decrease in productivity caused by many coatings.

  In contrast to these coating methods, the curtain coating method is a method in which a free fall curtain of coating liquid is formed, and this is applied by colliding with a support, the coating quality is good, and it is suitable for high-speed coating. Is known (see Patent Document 1). Moreover, it is also possible to form a coating film composed of a plurality of coating liquid films and apply it on a curtain, and the productivity of multilayer coating can be greatly improved. This curtain coating method is a method in which the coating liquid is applied in a film form from a slit-shaped coater lip on a substrate, and the coating properties of the coating liquid and the wettability to the substrate are improved to prevent uneven coating and coating. In order to prevent defects, fine adjustment is required for static surface tension, dynamic surface tension, viscosity, and the like (see Patent Document 2). From such a viewpoint, the uniform stability of the coating itself is extremely important, and the performance and production efficiency of the heat-sensitive recording material obtained thereby are greatly affected.

  The simultaneous multilayer coating by the curtain coating method has the advantage that the productivity can be greatly improved since a plurality of layers can be coated simultaneously as described above, and has been studied in the production method of thermal recording paper.

  However, what has been mainly studied so far is simultaneous multilayer coating of a heat-sensitive recording layer and a protective layer (see Patent Document 3), and has hardly been studied in simultaneous multilayer coating including an undercoat layer. The reason for this is that, from the viewpoint of recording sensitivity and image quality, the undercoat layer coating liquid is more smoothly applied to the support by means of a rod coater, blade coater, roll coater, etc. than the curtain coating method, which is contour coating. This is because it was considered preferable.

  For example, as a method of curtain coating the undercoat layer coating solution, the undercoat layer coating solution containing a pigment having an oil absorption amount (JIS K 5101) of 75 ml / 100 g or more is dispersed and mixed in a binder. A method of simultaneously applying a multilayer coating for a heat-sensitive recording layer (Patent Document 4), and applying a coating solution for an undercoat layer containing a calcined kaolin concentration of 25 to 75% at a coating speed of 500 m / min or more. A method is also disclosed (Patent Document 5). Also disclosed is a heat-sensitive recording material formed by curtain-coating a paint film comprising a plurality of coating liquid films of an undercoat layer and a heat-sensitive recording layer (Patent Document 6). However, these conventionally disclosed techniques still have a problem in practical use because the recording sensitivity and image quality are still inferior compared with the case where the undercoat layer is applied smoothly by a blade coating method or the like.

  On the other hand, as a method for improving the recording sensitivity of heat-sensitive recording paper, an undercoat layer containing plastic hollow particles has been introduced between the support and the heat-sensitive recording layer. For example, a method of providing a first undercoat layer containing hollow fine particles and a second undercoat layer containing an organic filler and / or an inorganic filler between a substrate and a heat-sensitive recording layer (Patent Document 7), a support Organic micro hollow particles having a film thickness / particle diameter ratio of 0.15 or less are provided as an undercoat layer between the organic micro hollow particle layer and the heat sensitive recording layer. Is known as a second undercoat layer, and Mayer bar coating is described as a coating method (Patent Document 8). Also, the under layer containing hollow plastic particles is blade coating, and two or more layers including a thermosensitive coloring layer provided on the under layer are simultaneously applied by a curtain coating method (Patent Document 9). ), And a first intermediate layer mainly composed of an inorganic pigment and a binder between the support and the thermosensitive coloring layer, and a second intermediate layer formed on the first intermediate layer by a free-fall curtain method are provided. A heat-sensitive recording material (Patent Document 10) that is sequentially laminated is disclosed.

Japanese Patent Publication No. 49-24133 JP-A-57-39985 Japanese Patent No. 3579392 Japanese Patent Publication No. 4-8238 International Publication WO2005 / 084958 JP 2001-18526 A Japanese Patent Laid-Open No. 62-117787 JP-A-1-285383 JP 2010-94981 A JP 2000-108518 A

  An object of the present invention is to provide a method for producing a heat-sensitive recording material excellent in recording sensitivity, print image quality, and printability.

  As a result of various studies on the above problems, the present inventors have found that an anchor layer containing plastic hollow particles on the support, an undercoat layer containing an oil-absorbing pigment having an oil absorption (JIS K 5101) of 40 to 120 ml / 100 g, A method for producing a heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye and a developer in sequence, wherein the anchor layer and the undercoat layer are formed by simultaneously coating the anchor layer coating solution and the undercoat layer coating solution. The present invention has been completed by finding that the above-mentioned problems can be solved by employing a method for producing a heat-sensitive recording material characterized in that it is formed by coating and drying.

  That is, the present invention provides the following method for producing a thermal recording material.

Item 1: An anchor layer containing hollow plastic particles on a support, an undercoat layer containing an oil-absorbing pigment having an oil absorption (JIS K 5101) of 40 to 120 ml / 100 g, a thermal recording containing a leuco dye and a developer. The anchor layer and the undercoat layer are formed by applying and drying the anchor layer coating solution and the undercoat layer coating solution by a simultaneous multilayer curtain coating method. A method for producing a heat-sensitive recording material.
Item 2: The method for producing a heat-sensitive recording material according to Item 1, wherein the plastic hollow particles are contained in an amount of 5 to 75% by mass based on the total solid content of the anchor layer.
Item 3: The method for producing a heat-sensitive recording material according to Item 1 or 2, wherein in the undercoat layer, the content of the plastic hollow particles is 7.5 g / m ² or less.
Item 4: The method for producing a heat-sensitive recording material according to any one of Items 1 to 3, wherein the hollow ratio of the plastic hollow particles is 50 to 90%.
Item 5: The method for producing a heat-sensitive recording material according to any one of Items 1 to 4, wherein the oil-absorbing pigment of the undercoat layer is calcined kaolin.
Item 6: The method for producing a heat-sensitive recording material according to any one of Items 1 to 5, wherein the total coating amount of the anchor layer and the undercoat layer is 5 to 15 g / m ² .
Item 7: Any one of Items 1 to 6, wherein the thermosensitive recording layer is formed by applying and drying the thermosensitive recording layer coating solution together with the anchor layer coating solution and the undercoat layer coating solution by a simultaneous multilayer curtain coating method. 2. A method for producing a heat-sensitive recording material according to item 1.

  According to the present invention, there is provided a method for producing a heat-sensitive recording material excellent in recording sensitivity, print image quality, and printability.

  Hereinafter, the method for producing the heat-sensitive recording material of the present invention will be described in detail. The present invention relates to an anchor layer containing plastic hollow particles on a support, an undercoat layer containing an oil-absorbing pigment having an oil absorption amount (JIS K 5101) of 40 to 120 ml / 100 g, a heat sensitive material containing a leuco dye and a developer. A method for producing a heat-sensitive recording material having recording layers sequentially, wherein the anchor layer and the undercoat layer are formed by applying and drying the anchor layer coating solution and the undercoat layer coating solution by a simultaneous multilayer curtain coating method. Is a method for producing a heat-sensitive recording material.

(Anchor layer)
In the present invention, an anchor layer containing plastic hollow particles is formed on a support.

Examples of the plastic hollow particles include conventionally known ones such as micro hollow particles having a thermoplastic polymer shell, and a copolymer resin mainly composed of an acrylic resin, a styrene resin, an acrylic-styrene resin, a vinylidene chloride tree, and acrylonitrile. And a copolymer resin mainly composed of isobornyl methacrylate and acrylonitrile. The hollowness is expressed by the following formula, and is preferably 50 to 90%, more preferably 60 to 80% from the viewpoint of elasticity and heat insulation. When the hollowness is less than 50%, the heat insulation and elasticity are insufficient, and the thermal energy from the thermal head is released to the outside of the thermal recording material, so that the recording sensitivity is lowered, or the thermal head and the thermal recording material. The image quality deteriorates due to poor adhesion. Moreover, it is technically difficult to manufacture a product having a hollowness ratio exceeding 90%.
Hollow ratio (%) = (inner diameter of hollow particle / outer diameter of hollow particle) × 100

  The plastic hollow particles in the anchor layer are preferably blended in an amount of 5 to 75% by mass, more preferably 7 to 60% by mass, and most preferably 10 to 50% by mass with respect to the total solid content of the anchor layer. If the amount is less than 5% by mass, the effect of the present invention is hardly observed. If the amount is more than 75% by mass, the surface strength may be lowered. Moreover, it is preferable that the average particle diameter of a plastic hollow particle is about 0.4-4.0 micrometers. When the average particle diameter is less than 0.4 μm, the elasticity becomes insufficient and the image quality deteriorates. When it is larger than 4.0 μm, the surface smoothness is lowered, or when the anchor layer coating solution and the undercoat layer coating solution are simultaneously curtain coated, the layer is disturbed during coating, and this undercoat layer When the heat-sensitive recording layer is formed thereon, the image quality is deteriorated.

  Further, as long as the effect of the present invention is not impaired, all of the general inorganic and organic pigments can be added as the pigment in the anchor layer, but an oil-absorbing pigment having an oil absorption (JIS K 5101) of 40 ml / 100 g or more is particularly preferable. . Specific examples of the oil-absorbing pigment include aluminum oxide, calcined diatomaceous earth, aluminum silicate, calcium carbonate, magnesium carbonate, barium sulfate, aluminum hydroxide, kaolin, calcined kaolin, amorphous silica, talc and the like. Moreover, organic pigments, such as urea- formalin resin other than a hollow particle, a styrene-methacrylic acid copolymer, a polystyrene resin, and an amino resin filler, can also be contained.

(Undercoat layer)
In the present invention, an undercoat layer containing an oil-absorbing pigment having an oil absorption (JIS K 5101) of 40 to 120 ml / 100 g is provided between the anchor layer and the heat-sensitive recording layer. The undercoat layer is formed by coating and drying by the simultaneous multilayer curtain coating method with the anchor layer.

  The oil-absorbing pigment for the undercoat layer preferably has an oil absorption (JIS K 5101) of 40 to 120 ml / 100 g, more preferably 60 to 120 ml / 100 g. When the oil absorption amount (JIS K 5101) exceeds 120 ml / 100 g, the binder component in the heat-sensitive recording layer penetrates and is absorbed, and the surface strength is significantly reduced. On the other hand, if it is less than 40 ml / 100 g, the heat insulating property is poor and the recording sensitivity is lowered.

  Specific examples of the oil-absorbing pigment include aluminum oxide, calcined diatomaceous earth, aluminum silicate, calcium carbonate, magnesium carbonate, barium sulfate, aluminum hydroxide, kaolin, calcined kaolin, amorphous silica, talc and the like. Of these, calcined kaolin is most preferred. In addition, organic pigments (including hollow particles) such as urea-formalin resin, styrene-methacrylic acid copolymer, polystyrene resin, and amino resin filler can also be contained.

The plastic hollow particles described in the anchor layer, the content in the undercoat layer is preferably 7.5 g / ^{m 2} or less, more preferably 6.0 g / ^{m 2} or less, 5.0 g / Most preferably m ² or less. If it exceeds 7.5 g / m ² , the effects of the present invention may not be obtained.

  In the present invention, as an adhesive for the anchor layer and the undercoat layer, for example, oxidized starch, acid-modified starch, phosphate esterified starch, enzyme-modified starch, cation-modified starch, esterified starch, etherified starch and vinyl acetate-modified graft Starch such as 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, sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone, acrylic acid Acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid copolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, sodium alginate, gelatin, Water-soluble polymers such as casein; polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, polybutyl methacrylate, styrene / butadiene copolymer, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer In addition, latex such as styrene / butadiene / acrylic copolymer can be used, but from the viewpoint of curtain coating suitability, at least one adhesive selected from polyvinyl alcohol and starch is added to the total solid content of each layer. It is preferable to contain 3-25 mass% with respect to it. Within this range, the curtain film becomes unstable, causing coating defects, the undercoat layer coating solution cannot completely cover the unevenness of the base paper, and whiteness is deteriorated, resulting in deterioration in image quality. There is no problem that the film strength is low, the printability is inferior, the heat insulation is impaired, and the recording sensitivity and image quality are not lowered.

  In the present invention, the anchor layer coating solution and the undercoat layer coating solution preferably have a viscosity of 60 rpm measured by a Brookfield type viscosity (B type viscosity) meter at 25 ° C. in the range of 200 to 1500 mPa · s. In particular, the pressure is preferably about 300 to 1200 mPa · s. If it is less than 200 mPa · s, interlayer mixing between the anchor layer coating solution and the undercoat layer coating solution is likely to occur, and the image quality and recording sensitivity are lowered. On the other hand, if it exceeds 1500 mPa · s, bubbles in the anchor layer coating solution and the undercoat layer coating solution are difficult to be removed, resulting in coating defects due to bubbles or streaky coating unevenness in the flow direction. Is likely to occur.

  Since the anchor layer and the undercoat layer in the present invention are formed by the simultaneous curtain coating method, a surfactant is used for the anchor layer coating solution and the undercoat layer coating solution in order to stabilize the curtain film by adjusting the surface tension. Is preferably added. As the range of the surface tension, the static surface tension measured by a platinum plate method at 25 ° C. is preferably adjusted to 25 to 36 mN / m, more preferably 26 to 34 mN / m. When the static surface tension is less than 25 mN / m, defects due to bubbles are likely to occur. On the other hand, when the static surface tension exceeds 36 mN / m, the curtain film stability is deteriorated.

  Examples of the surfactant added to the anchor layer coating solution and the undercoat layer coating solution include sulfosuccinic acid-based alkali metal salts, alkylbenzene sulfonates, acetylene glycol-based compounds, fluorine-based surfactants, and silicon-based interfaces. Activators, phosphate surfactants, ether surfactants, or amphoteric surfactants such as betaines, aminocarboxylates, and imidazoline derivatives, etc. are particularly preferable from the viewpoint of curtain film stability. Is preferably a dialkylsulfosuccinate represented by the following general formula (1). Further, the salt is preferably an alkali metal salt or an ammonium salt, and the alkyl group is preferably 2 to 20 carbon atoms, more preferably 4 to 10 carbon atoms. Specifically, an isobutyl group, a hexyl group, a cyclohexyl group, an octyl group, an isooctyl group, and a 2-ethylhexyl group are preferable. Further, the addition amount of the surfactant is preferably about 0.01 to 2.0% by mass with respect to the total solid content of the anchor layer and the undercoat layer. If it is less than 0.01% by mass, the effect of addition is small, the surface tension is not sufficiently lowered, and the curtain film is easily cut off. If it exceeds 2.0% by mass, the anchor layer coating solution and the undercoat layer coating solution tend to foam and cause coating defects. From the balance between the effect and the physical properties of the paint, the more preferable addition amount of the surfactant is about 0.02 to 1.0% by mass.

（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は水素原子またはカチオン、ｘは１または２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, M represents a hydrogen atom or a cation, and x represents 1 or 2)

  Moreover, you may add a thickener, a wax, etc. in the coating liquid for anchor layers, and the coating liquid for undercoat layers as needed.

  In the present invention, the anchor layer coating solution and the undercoat layer coating solution are simultaneously applied by a coating method using a curtain coater. By coating with a curtain coater, the coating layer is formed porous, so that the image quality is improved. Further, by laminating an undercoat layer containing an oil-absorbing pigment on an anchor layer containing plastic hollow particles, the penetration of the thermal recording layer coating liquid into the anchor layer is suppressed, and the recording sensitivity is improved.

The coating amount of the anchor layer and the undercoat layer is not particularly limited, but the total coating amount is preferably 5 to 15 g / m ² by dry weight, more preferably 6 to 15 g / m ² , and 7 to 15 g / m ^2. m ² is particularly preferred.

(Thermosensitive recording layer)
In the present invention, as the adhesive of the heat-sensitive recording layer, for example, oxidized starch, acid-modified starch, phosphate esterified starch, enzyme-modified starch, cation-modified starch, esterified starch, etherified starch, vinyl acetate-modified grafted starch and the like Starch, methylcellulose, ethylcellulose, carboxymethylcellulose, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose and hydroxypropylmethylcellulose, fully (or partially) saponified polyvinyl alcohol, silicon modified polyvinyl alcohol, diacetone modified polyvinyl alcohol, carboxy modified polyvinyl alcohol, aceto Polyvinyl alcohols such as acetyl-modified polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyvinyl pyrrolidone, acrylamide acrylate Acid ester copolymer, 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. Water-soluble polymers: Polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic ester, polybutyl methacrylate, styrene / butadiene copolymer, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, styrene / Latex such as butadiene / acrylic copolymer can be used, but considering the curtain coating suitability, at least one adhesive selected from polyvinyl alcohol and starch is added to the total solid content of the thermosensitive recording layer. It is preferable to contain 3-25 mass% with respect to it. Within this range, there are no problems that the curtain film becomes unstable and coating defects occur, the coating film strength is low, the printability is poor, the recording sensitivity and the image quality are not lowered.

  In the present invention, in consideration of suitability for curtain coating, the heat-sensitive recording layer coating liquid has a viscosity of 60 rpm measured at 25 ° C. with a Brookfield viscosity (B-type viscosity) meter in the range of 200 to 1500 mPa · s. It is preferable that it is about 300-1200 mPa * s especially. If it is less than 200 mPa · s, interlayer mixing between the thermal recording layer coating liquid and the undercoat layer coating liquid tends to occur, and the image quality and recording sensitivity are lowered. On the other hand, if it exceeds 1500 mPa · s, bubbles in the heat-sensitive recording layer coating liquid are difficult to escape, so that coating defects due to bubbles occur or streaky coating unevenness tends to occur in the flow direction.

  As the pigment contained in the heat-sensitive recording layer in the present invention, various known pigments are used. For example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, Inorganic pigments such as silica, talc, and mica, and organic pigments such as plastic solid particles, plastic hollow particles, and raw starch can be used as appropriate, and are used alone or in combination.

  The heat-sensitive recording layer of the present invention contains various known leuco dyes and developers. In addition, you may contain a sensitizer, various adjuvants, etc. as needed.

  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-anilinov 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-butyl) amino-7- (2-chloroanilino) fluorane, and the like can be used. Further, if necessary, a leuco dye that develops a color tone different from black, for example, a color tone such as red, magenta, orange, blue, green, etc., 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 thermosensitive recording layer.

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

  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 size of the dispersed particles of the leuco dye used in the solid fine particle state is preferably about 0.2 to 3.0 μm, more preferably 0.3 to 3.0 in order to obtain appropriate recording sensitivity. It is about 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, a method for producing composite particles in which the organic polymer is at least one of polyurea and polyurea-polyurethane will be described. The composite particles are prepared by dissolving and mixing a leuco dye and a polymer-forming raw material that forms at least one of polyurea and polyurea-polyurethane by polymerization in a water-insoluble organic solvent having a boiling point of 100 ° C. or less. Is emulsified and dispersed in a hydrophilic protective colloid solution such as polyvinyl alcohol so that the average particle size is about 0.5 to 3 μm, and if necessary, a reactive substance such as polyamine is further mixed, and then this emulsified dispersion is heated. The organic solvent is volatilized and removed, and then the polymer-forming raw material is polymerized, or the leuco dye is dissolved in the polymer-forming raw material, and this solution is used as described above. And after the emulsion is dispersed to an average particle size of about 0.5 to 3 μm, the polymer-forming raw material is polymerized.

  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)- And urea compounds such as N ′-(p-butoxycarbonyl) urea and Np-toluenesulfonyl-N′-phenylurea.

  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 kind of the leuco dye and the developer used, and is not particularly limited. About 1 to 7 parts by mass, preferably about 1 to 6 parts by mass of the developer is used with respect to parts by mass. Preparation of coating solution for heat-sensitive recording layer containing these substances is generally carried out using water as a dispersion medium, and stirring or ball mill, attritor, sand mill, etc., and dispersing leuco dye and developer together or separately. By doing so, it is prepared as a coating solution.

  Furthermore, a sensitizer can be used in combination according to the purpose. Specific 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, and methylenebisstearic 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 ester, 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-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetoluidide , P-acetophenetide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, etc. . The amount of these sensitizers to be used is not particularly limited, but it is generally desirable to adjust in a range of 4 parts by mass or less with respect to 1 part by mass of the developer.

  Further, as long as the desired effect is not impaired, a storability improving agent may be used in combination in order to further improve the storability of the recorded image 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 2,2'-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-butyl) Ruphenol), 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 1,1,3-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'-tetra Methyldiphenylsulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy) -Hindered phenol compounds such as 3,5-dimethylphenyl) propane, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis 4,6-di -tert- butylphenyl) phosphate sodium, and more diphenylsulfone crosslinked type compound and the like.

  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 thermosensitive recording materials are an attempt to utilize the difference in heating temperature or the difference in heat energy, and are generally configured by sequentially laminating a high-temperature color-developing layer and a low-temperature color-developing layer that develop colors in different colors on a support. These are roughly divided into two types, a decoloring type and an additive type, a method using a microcapsule and a multicolor thermosensitive recording material using composite particles composed of an organic polymer and a dye precursor. There is a manufacturing method.

  In the present invention, when the heat-sensitive recording layer is formed by a curtain coating method, it is preferable to add a surfactant to stabilize the curtain film by adjusting the surface tension. As the range of the surface tension, the static surface tension measured by a platinum plate method at 25 ° C. is preferably adjusted to 25 to 31 mN / m, more preferably 27 to 30 mN / m. If the static surface tension is less than 25 mN / m, defects due to bubbles are likely to occur. On the other hand, if it exceeds 31 mN / m, the stability of the curtain film deteriorates or repellency occurs and uncoated parts occur. To do. Examples of the surfactant to be added include sulfosuccinic acid-based alkali metal salts, alkylbenzene sulfonates, acetylene glycol-based compounds, fluorine-based surfactants, silicon-based surfactants, phosphate ester-based surfactants, and ethers. Type surfactants or amphoteric surfactants such as betaines, aminocarboxylates and imidazoline derivatives, etc., and dialkylsulfosuccinates are preferred from the viewpoint of curtain film stability. Further, the salt is preferably an alkali metal salt or an ammonium salt, and the alkyl group is preferably 2 to 20 carbon atoms, more preferably 4 to 10 carbon atoms. Specifically, an isobutyl group, a hexyl group, a cyclohexyl group, an octyl group, an isooctyl group, and a 2-ethylhexyl group are preferable. The addition amount of the surfactant is preferably about 0.05 to 3.0% by mass with respect to the total solid content of the thermosensitive recording layer. If it is less than 0.05% by mass, the effect of addition is small, the surface tension is not sufficiently lowered, and the curtain film is easily cut off. If it exceeds 3% by mass, the coating liquid tends to foam and causes coating defects. In view of the balance between the effect and the physical properties of the paint, the more preferable addition amount of the surfactant is about 0.10 to 3.0% by mass.

  Various auxiliary agents can be added to the heat-sensitive recording layer as necessary. For example, antifoaming agents, waxes, metal soaps, fluorescent dyes, colored dyes, crosslinking agents, viscosity modifiers, and the like are appropriately added.

In the present invention, simultaneous multi-layer application of the anchor layer, the undercoat layer and the heat-sensitive recording layer by the curtain coating method can improve the stability of the curtain film, further improve the production efficiency, and further reduce the energy consumption during production. It is more preferable at the point which can do. In the present invention, the curtain coating method used in the application of the anchor layer, the undercoat layer, and the heat-sensitive recording layer is a method in which the coating liquid is allowed to flow down and fall freely to be applied to the support in a non-contact manner. A known method such as a curtain method or a twin curtain method can be adopted and is not particularly limited. Also, as described in Japanese Patent Application Laid-Open No. 2006-247611, paint is ejected downward from the curtain head to form a paint layer on the slope, and a paint curtain film is formed from the downward curtain guide portion of the slope. The paint layer can also be transferred onto the web surface. 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 . The anchor layer, the undercoat layer, and the heat-sensitive recording layer can be changed in composition and coating amount of each layer as necessary. It should be noted that various conditions such as coating concentration, coating speed, curtain film width, drop angle, and the like are desirably adjusted appropriately according to each curtain coating method and coating apparatus. Since these curtain coating methods are non-contact contour coating, a coating layer having a uniform thickness can be obtained. On the other hand, in contact-type coating such as blade and bar coating, the film thickness is non-uniform because it is affected by the surface properties (unevenness) of the support. For this reason, with the same coating amount, a heat-sensitive recording layer formed by curtain coating can obtain better image quality and also improve image storability. In addition, each coating liquid can be defoamed before application | coating by various well-known methods as needed.

  In the present invention, at least one protective layer may be provided on the thermosensitive recording layer. 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 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.

  After the application of the coating liquid, it is dried, and after that, it is preferably smoothed by a calendar process 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 obtain 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 on the back surface. Or it can also be set as the thermosensitive recording material 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.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” in the examples represent “part by mass” and “% by mass”, respectively.

Example 1
(Preparation of anchor layer coating solution)
70 parts of calcined kaolin (trade name: Ancilex 93, manufactured by Engelhard, oil absorption 110 ml / 100 g), plastic hollow particle emulsion (trade name: AE852, solid content concentration 26%, hollow rate 80%, average particle size 1. 0 μm, 50 parts by JSR), 10 parts light calcium carbonate (trade name: Brilliant-15, manufactured by Shiroishi Chemical Co., Ltd.), styrene-butadiene copolymer latex (trade name: PT-1004A, solid content concentration 43%, Japan) 8 parts of Zeon), 60 parts of 15% aqueous solution of fully saponified polyvinyl alcohol (trade name: PVA124, polymerization degree 2400, saponification degree 98.5%, manufactured by Kuraray Co., Ltd.), and dioctylsulfosuccinate sodium salt (trade name: SN 1 part of 10% aqueous solution of wet OT-70 (manufactured by San Nopco), and 90 parts of water 25 ° C., to obtain an anchor layer coating liquid B type viscosity 600 mPa · s at 60 rpm. Moreover, the static surface tension of the coating liquid for anchor layers measured by a platinum plate method at 25 ° C. was 32.0 mN / m.

(Preparation of coating solution for undercoat layer)
Baked kaolin (trade name: Ancilex 93, manufactured by Engelhard, oil absorption 110 ml / 100 g) 90 parts, light calcium carbonate (trade name: Brilliant-15, manufactured by Shiroishi Chemical Co., Ltd.), 10 parts, styrene / butadiene copolymer latex (Trade name: PT-1004A, solid content concentration 43%, manufactured by Nippon Zeon Co., Ltd.) 8 parts, fully saponified polyvinyl alcohol (trade name: PVA124, polymerization degree 2400, saponification degree 98.5%, manufactured by Kuraray Co., Ltd.) 60 parts of an aqueous solution, further 1 part of a 10% aqueous solution of dioctylsulfosuccinic acid sodium salt (trade name: SN Wet OT-70, manufactured by San Nopco) and 90 parts of water were uniformly mixed and stirred, and B at 25 ° C. and 60 rpm. An undercoat layer coating solution having a mold viscosity of 600 mPa · s was obtained. Moreover, the static surface tension of the coating liquid for undercoat layers measured by a platinum plate method at 25 ° C. was 32.0 mN / m.

(Leuco dye / sensitizer dispersion (liquid A) preparation)
25 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 20 parts of 1,2-di (3-methylphenoxy) ethane, 25 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol, and A composition comprising 30 parts of water was pulverized with a sand mill until the average particle size became 0.9 μm to obtain a leuco dye / sensitizer dispersion (liquid A).

(Preparation of developer dispersion (liquid B))
A composition comprising 45 parts of 2,2′-bis (4-hydroxyphenyl) propane, 25 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol, and 30 parts of water is pulverized with a sand mill until the average particle size becomes 1.5 μm. Thus, a developer dispersion (liquid B) was obtained.

(Preparation of thermal recording layer coating solution)
A part 60 parts, B part 70 parts, light calcium carbonate (trade name: Brilliant 15, manufactured by Shiraishi Chemical Co., Ltd.) 60% aqueous dispersion, aluminum hydroxide (trade name: Heidilite H42, Showa Denko Co., Ltd.) ) 60% aqueous dispersion, heavy calcium carbonate (trade name: Softon 2200, manufactured by Okutama Kogyo Co., Ltd.) 60% aqueous dispersion, fully saponified polyvinyl alcohol (trade name: PVA-124, polymerization degree 2400) 60 parts of a 15% aqueous solution of a saponification degree of 98.5 mol%, manufactured by Kuraray Co., Ltd., 30 parts of a 30% aqueous solution of zinc stearate, and sodium dioctylsulfosuccinate (trade name: SN wet OT-70, manufactured by San Nopco) 10 parts of a 10% aqueous solution and 90 parts of water were sequentially added, mixed and stirred to obtain a coating solution for a thermal recording layer having a B-type viscosity of 500 mPa · s at 25 ° C. and 60 rpm. It was. The static surface tension of the coating solution for heat-sensitive recording layer measured by a platinum plate method at 25 ° C. was 29.0 mN / m.

(Preparation of thermal recording material)
Using a slide hopper type curtain coating device, apply an anchor layer coating solution and an undercoat layer coating solution to one side of a high-quality paper having a basis weight of 60 g / m ² from the support side of the anchor layer coating solution and the undercoat layer coating solution. forming a coating film composed of sequentially solid coating amount of each layer anchor layer 1.0 g / ^{m 2,} so that the undercoat layer 7.0 g / ^{m 2,} simultaneous multilayer at coating speed 600 meters / min The curtain layer was applied and dried to form an anchor layer and an undercoat layer. Next, a heat sensitive recording layer coating solution is applied on the rod blade coater so that the solid content is 3.0 g / m ² and dried to form a heat sensitive recording layer, followed by supercalendering. A heat-sensitive recording material was obtained.

Example 2
In the preparation of the anchor layer coating solution of Example 1, 70 parts of calcined kaolin (trade name: Ancilex 93, supra) is 10 parts, and 50 parts of plastic hollow particle emulsion (trade name: AE852, supra) is 200 parts. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the parts were changed.

Example 3
In the preparation of the coating solution for the undercoat layer of Example 1, 90 parts of calcined kaolin (trade name: Ansilex 93, supra) was added to talc (trade name: Himicron HE-5, Takehara Chemical Co., Ltd., oil absorption 50 ml / 100 g). ) A thermosensitive recording material was obtained in the same manner as in Example 1 except that the coating solution for the undercoat layer was changed to 90 parts.

Example 4
In the preparation of the anchor layer coating liquid of Example 1, 50 parts of a plastic hollow particle emulsion (trade name: AE852, supra) was used as a plastic hollow particle emulsion (trade name: Ropeke HP-91, manufactured by Rohm & Haas, solid content). A thermosensitive recording material was obtained in the same manner as in Example 1 except that the concentration was changed to 25 parts (concentration: 27.5%, hollow ratio: 50%, average particle size: 1.0 μm).

Example 5
In the production of the heat-sensitive recording material of Example 1, the heat-sensitive recording layer coating liquid was applied with a rod blade coater so that the solid content was 3.0 g / m ² and dried to form no heat-sensitive recording layer. Using a slide hopper type curtain coating device, form a coating film composed of the coating solution for the anchor layer, the coating solution for the undercoat layer, and the coating solution for the thermal recording layer from the support side, and the solid content coating amount of each layer Except for simultaneous multilayer curtain coating and drying at a coating speed of 600 m / min so that the anchor layer is 1.0 g / m ² , the undercoat layer is 7.0 g / m ² , and the thermosensitive recording layer is 3.0 g / m ^2. In the same manner as in Example 1, a thermosensitive recording material was obtained.

Example 6
(Preparation of coating solution for protective layer)
To 50 parts of a 50% aqueous dispersion of kaolin (primary kaolin, trade name: UW-90, manufactured by Engelhard), acetoacetyl-modified polyvinyl alcohol (trade name: Goosefimmer Z-410, polymerization degree 2400, Nippon Synthetic Co., Ltd.) 600 parts of a 10% aqueous solution of Chemical Co., Ltd., zinc stearate (trade name: Hydrin Z-8-36, solid concentration 36%, manufactured by Chukyo Yushi Co., Ltd.), and dioctyl sulfosuccinate sodium salt (trade name: SN 20 parts of a 5% aqueous solution of wet OT-70, supra) was mixed and stirred to obtain a protective layer coating solution. In addition, the static surface tension of the coating liquid for protective layers measured by 25 degreeC and the platinum plate method was 32.0 mN / m.

(Preparation of thermal recording material)
A slide hopper type curtain coating apparatus is used to apply the anchor layer coating solution, the undercoat layer coating solution, the thermal recording layer coating solution and the protective layer coating solution of Example 1 on one surface of a high-quality paper having a basis weight of 60 g / m ^2. Is used to form a coating film composed of an anchor layer coating solution, an undercoat layer coating solution, a heat-sensitive recording layer coating solution, and a protective layer coating solution in this order. Simultaneously at a coating speed of 600 m / min so that the anchor layer is 1.0 g / m ² , the undercoat layer is 7.0 g / m ² , the thermosensitive recording layer is 3.0 g / m ² , and the protective layer is 2.5 g / m ^2. After the multi-layer curtain was applied and dried, a super calendar process was performed to obtain a heat-sensitive recording material.

Comparative Example 1
In the production of the heat-sensitive recording material of Example 1, instead of the multilayer curtain coater, the anchor layer coating solution was applied and dried after forming the anchor layer, and then the undercoat layer coating was applied. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that drying was performed after application of the liquid to form an undercoat layer.

Comparative Example 2
In the production of the thermosensitive recording material of Example 1, the undercoat layer coating solution was not used, and the thermosensitive recording layer coating solution was further applied with a rod blade coater so that the solid content application amount was 3.0 g / m ^2. , dried without forming the heat-sensitive recording layer, the anchor layer coating liquid, each solid coating amount of thermosensitive recording layer coating solution is the anchor layer 8.0 g / m ^2, a heat-sensitive recording layer 3.0 g / m ² Thus, a heat-sensitive recording material was obtained in the same manner as in Example 1 except that the simultaneous multilayer curtain was applied and dried at a coating speed of 600 m / min.

Comparative Example 3
In the preparation of the anchor layer coating liquid of Example 1, 70 parts of calcined kaolin (trade name: Ancilex 93, supra), 50 parts of plastic hollow particle emulsion (trade name: AE852, supra), light calcium carbonate (commodity) A heat-sensitive recording material was obtained in the same manner as in Comparative Example 2, except that 10 parts of name: Brilliant-15, supra) was changed to 360 parts of plastic hollow particle emulsion (trade name: AE852, supra).

Comparative Example 4
In the preparation of the anchor layer coating liquid of Example 1, the plastic hollow particle emulsion (trade name: AE852, supra) was not used, and the calcined kaolin (trade name: Ansilex 93, supra) was 70 to 85 parts. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the above was changed.

  The obtained thermal recording material was subjected to the following evaluation tests, and the results are shown in Table 1.

(Recording sensitivity)
Using a thermal recording simulator (TH-PMD, manufactured by Okura Electric Co., Ltd.), recording was performed at an applied energy of 0.27 mJ / dot, and the density of the solid recording portion was visualized by a Macbeth densitometer (trade name: RD914, manufactured by Macbeth). Measured in mode. The recording unit is required to be 1.20 or more practically.

(Print quality)
The print image quality of the solid recording part was visually evaluated.
A: There is no omission and the image quality is extremely excellent.
○: Some omissions are seen, but the image quality is good.
(Triangle | delta): Although omission is seen, it is a practical use level.
X: Remarkably many omissions are observed, image quality is poor and practically problematic.

(Printability)
Each of the obtained heat-sensitive recording materials was printed with an RI tester (manufactured by Meisei Seisakusho) using a pick strength evaluation ink [TOKA Printing in Super Deluxe T = 13], and the surface strength was evaluated.
A: There is no peeling of the printed surface.
○: Slight peeling of the printing surface is observed.
Δ: Peeling of the printed surface is seen at various places, but at a practical level.
X: The entire printed surface is peeled off, which is a practical problem.

Claims (7)

  On the support, an anchor layer containing plastic hollow particles, an undercoat layer containing an oil-absorbing pigment having an oil absorption (JIS K 5101) of 40 to 120 ml / 100 g, and a heat-sensitive recording layer containing a leuco dye and a developer are sequentially formed. A method for producing a heat-sensitive recording material, wherein the anchor layer and the undercoat layer are formed by applying and drying an anchor layer coating solution and an undercoat layer coating solution by a simultaneous multilayer curtain coating method. A method for producing a thermal recording material.   The method for producing a heat-sensitive recording material according to claim 1, wherein the plastic hollow particles are contained in an amount of 5 to 75% by mass with respect to the total solid content of the anchor layer. The method for producing a thermosensitive recording material according to claim 1 or 2, wherein in the undercoat layer, the content of the plastic hollow particles is 7.5 g / m ² or less.   The method for producing a heat-sensitive recording material according to any one of claims 1 to 3, wherein the hollow ratio of the plastic hollow particles is 50 to 90%.   The method for producing a heat-sensitive recording material according to claim 1, wherein the oil-absorbing pigment in the undercoat layer is calcined kaolin. The total coating amount of the anchor layer and the undercoat layer is 5 to 15 g / m ^2, the manufacturing method of the heat-sensitive recording material according to any one of claims 1 to 5.   The thermal recording layer is formed by applying and drying a thermal recording layer coating solution together with an anchor layer coating solution and an undercoat layer coating solution by a simultaneous multilayer curtain coating method. A method for producing a heat-sensitive recording material according to 1.