JP5417929B2 - Thermal recording material - Google Patents

Description

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

  A heat-sensitive recording material is known which utilizes a color reaction between a colorless or light-colored basic dye and an organic or inorganic developer to bring a coloring image into contact with each other by heat to obtain a color image. Such a heat-sensitive recording material is relatively inexpensive, and the recording device is compact and relatively easy to maintain, so that it is used not only as a recording medium for facsimiles and various printers but also in a wide range of fields.

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

  In contrast to these coating methods, the curtain coating method disclosed in Japanese Patent Publication No. 49-24133 is a method in which a free fall curtain of coating liquid is formed and applied by colliding with a support. It is known that the quality is good and it has high-speed coating suitability. Moreover, it is also possible to form a coating film composed of a plurality of coating liquids and apply the curtain, and the productivity of multilayer coating can be greatly improved. This curtain coating method is a method in which a coating liquid is dropped on a substrate from a slit-shaped coater lip and applied to improve the film forming property of the coating solution and the wettability of the substrate. In order to prevent defects, fine adjustments are required for static surface tension, dynamic surface tension, viscosity, and the like (Japanese Patent Laid-Open No. 57-39985). From this point of view, the uniform stability of the coating itself is extremely important, and the performance and production efficiency of the resulting thermal recording material are greatly affected.

  In the thermal recording material, a specific adhesive or surfactant is blended in the thermal recording layer in order to stabilize and uniformly apply the curtain film without causing air bubbles or poor film formation during curtain coating. It has been proposed to apply curtains. For example, it has been proposed to add a carboxymethyl cellulose sodium salt having a degree of etherification of 0.7 or more and a 1% viscosity of 300 cps or more to a coating solution for a heat-sensitive recording layer (see Patent Document 1). It has also been proposed to include a specific sulfate ether type surfactant and a specific phosphate ester type surfactant in the thermal recording layer and / or protective layer coating solution (see Patent Document 2). Furthermore, dodecylbenzenesulfone salt is added to the coating solution for the protective layer (see Patent Document 3), and a composition of an acetylene glycol derivative and an anionic surfactant is added to the coating solution for the protective layer (see Patent Document 4). ) Has also been proposed. In addition, it has also been proposed to add a surfactant obtained by adding ethylene oxide and other alkylene oxides to tetramethyldecine diol to the thermal recording layer coating solution (see Patent Document 5).

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

  However, even if the surface tension is reduced by the addition of a surfactant, stable film wobble, film breakage, etc. due to air bubbles or poor film formation, especially in high-speed coating or thin film coating during low-speed coating. The curtain film may not be obtained, and the coating liquid is not uniformly stretched at the moment when the coating liquid is curtain coated on the base material, resulting in coating unevenness, resulting in a coating defect and lowering productivity. There's a problem. In addition, depending on the type and amount of the surfactant, there are problems such as a decrease in color density, printing erasing, and storage stability such as background fogging.

  An object of the present invention is to form a stable curtain film without causing bubbles and the like to form a defective film when the thermal recording layer coating liquid and the protective layer coating liquid are curtain-coated. An object of the present invention is to provide a thermal recording material excellent in quality, in particular, print storage stability.

  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 thermal recording material.

  Item 1: A heat-sensitive recording layer comprising, in this order, a heat-sensitive recording layer containing a leuco dye and a developer on a support, and a protective layer, wherein at least the heat-sensitive recording layer and the protective layer are a coating solution for a heat-sensitive recording layer. And a dialkylsulfosuccinic acid represented by the following general formula (1), wherein the heat-sensitive recording layer coating solution contains a water-soluble adhesive. A salt or a compound represented by the following general formula (2), and 2,2 ′-[4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether, 4,4′-bis [( 4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, and a complex zinc salt formed from an aromatic monocarboxylic acid and an aromatic dicarboxylic acid. Heat-sensitive recording material, characterized in that also contain one.

（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)

（式中、Ｒ^３〜Ｒ^６は水素原子、炭素数1〜８の分岐、直鎖または環状の無置換または置換アルキル基、炭素数６〜１０の無置換または置換アリール基を表し、Ｒ^７〜Ｒ^１０は水素原子またはメチル基を表し、ｍ及びｎはそれぞれ独立に０〜５０の整数を表す。）

(Wherein R ^{3 to} R ⁶ represent a hydrogen atom, a branched group having 1 to 8 carbon atoms, a linear or cyclic unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, and R ⁷ to R ¹⁰ represents a hydrogen atom or a methyl group, m and n each independently represents an integer of 0 to 50.)

  Item 2: Polyvinyl alcohol having a polymerization degree of 1000 to 3000 as the water-soluble adhesive is contained in an amount of 5 to 25% by mass with respect to the total solid content of the heat-sensitive recording layer, and the B-type viscosity at 25 ° C. of the heat-sensitive recording layer coating liquid is Item 2. The heat-sensitive recording material according to Item 1, which is 200 to 2000 mPa · s.

  Item 3: The content of the dialkylsulfosuccinate represented by the general formula (1) is 0.05 to 3% by mass with respect to the total solid content of the heat-sensitive recording layer, and the general formula (2) Item 3. The heat-sensitive recording material according to Item 1 or 2, wherein the content of the compound represented is from 0.1 to 5% by mass.

  Item 4: The aromatic dicarboxylic acid is terephthalic acid and / or isophthalic acid, and the molar ratio of the aromatic dicarboxylic acid to the aromatic monocarboxylic acid (aromatic dicarboxylic acid / aromatic monocarboxylic acid) is 0. The molar ratio of the zinc content to the total molar amount of the aromatic monocarboxylic acid and aromatic dicarboxylic acid (zinc / (aromatic monocarboxylic acid + aromatic dicarboxylic acid)) is 0 to 0.80. Item 4. The thermal recording material according to any one of Items 1 to 3, which is from 4 to 1.0.

  Item 5: In any one of Items 1 to 4, wherein the coating liquid for a protective layer contains a dialkylsulfosuccinate represented by the general formula (1) or a compound represented by the general formula (2). The heat-sensitive recording material described.

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

  Item 7: The curtain coating method is a simultaneous multilayer curtain coating method of a thermal recording layer coating solution and a protective layer coating solution, or a thermal recording layer coating solution is applied by a curtain method, and the thermal recording layer is in a wet state. Item 7. The thermal recording material according to any one of Items 1 to 6, wherein the protective layer coating liquid is sometimes applied in a curtain manner.

  When the thermal recording material of the present invention is used for curtain coating of the thermal recording layer coating liquid and the protective layer coating liquid, it does not cause mixing of bubbles or film formation failure, and forms a stable curtain film, thereby improving productivity. In addition to being excellent, it is excellent in quality, especially in print storage stability.

  The thermal recording layer coating liquid in the invention contains a water-soluble adhesive. As a water-soluble adhesive, at least one kind of polyvinyl alcohol having a polymerization degree of 1000 to 3000 is contained, and a B-type viscosity at a liquid temperature of 25 ° C. of the coating liquid is set to 200 to 2000 mPa · s. It is preferable because it effectively suppresses the mixing of bubbles and film formation defects, and can stabilize and uniformly apply the curtain film.

  The content of the polyvinyl alcohol is preferably 5 to 25% by mass, more preferably 7 to 20% by mass with respect to the total solid content of the thermosensitive recording layer. By setting it as 5 mass% or more, a preferable viscosity range can be adjusted easily, the intensity | strength of a coating film can be improved, and omission of a coating film can be suppressed. On the other hand, by setting it to 25% by mass or less, an increase in viscosity can be suppressed and sensitivity can be improved.

  Specific examples of the polyvinyl alcohol include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and acetoacetyl-modified polyvinyl alcohol. These can be used alone or in combination of two or more.

  The thermal recording layer coating solution contains a dialkylsulfosuccinate represented by the general formula (1) or a compound represented by the general formula (2).

  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. Moreover, as an alkyl group of a dialkyl sulfosuccinate, an alkyl group having 2 to 20 carbon atoms is preferable, and an alkyl group having 4 to 10 carbon atoms is particularly preferable. Specific examples include an isobutyl group, a hexyl group, a cyclohexyl group, an octyl group, an isooctyl group, and a 2-ethylhexyl group, and an octyl group or a 2-ethylhexyl group having 8 carbon atoms is particularly preferable.

In the compound represented by the general formula (2), R ^{3 to} R ⁶ are a hydrogen atom, a branched group having 1 to 8 carbon atoms, a linear or cyclic unsubstituted or substituted alkyl group, and an unsubstituted group having 6 to 10 carbon atoms. or a substituted aryl ^group, R 7 ^{to R 10} represents a hydrogen atom or a methyl group, m and n each independently represents an integer of 0 to 50. The sum of m and n is preferably 5 or less, and more preferably m and n are both 0. The smaller the sum of m and n, the greater the effect of surface activity. When both m and n are 0, the surface activity is the largest and the stability of the curtain film is maximized. On the other hand, when the sum of m and n increases, the effect of the surface activity decreases and the coating liquid easily foams. In particular, in the curtain coating method of the present invention, foam defects are likely to occur, background fogging and print decoloring occur. There is concern that it will get worse.

  The content of the dialkyl sulfosuccinate represented by the general formula (1) is 0.05 to 3% by mass, more preferably 0.1 to 2% by mass, based on the total solid content of the thermosensitive recording layer. The content of the compound represented by the general formula (2) is 0.1 to 5% by mass, more preferably 0.2 to 3% by mass with respect to the total solid content of the thermosensitive recording layer. As a result, the static surface tension of the thermal recording layer coating liquid can be easily adjusted within a preferred range. The range of the static surface tension is preferably 20 to 45 mN / m, and more preferably 25 to 40 mN / m. By setting the static surface tension to 20 mN / m or more, foaming of the coating liquid can be suppressed, productivity and quality can be improved, and particularly sensitivity and print storage stability can be further improved. On the other hand, by setting it to 45 mN / m or less, the curtain film can be stabilized, film breakage is hardly caused, and productivity can be improved. The static surface tension can be measured using, for example, a surface tension meter (trade name: CBVP-Z, manufactured by Kyowa Interface Science Co., Ltd.).

  The heat-sensitive recording layer coating solution contains 2,2 ′-[4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether, 4,4′-bis [(4-methyl-3-phenoxycarbonylamino) as a developer. Phenyl) ureido] diphenylsulfone, and at least one selected from a complex zinc salt formed from an aromatic monocarboxylic acid and an aromatic dicarboxylic acid. The content of the developer is preferably 1 to 45% by mass and more preferably 3 to 40% by mass with respect to the total solid content of the heat-sensitive recording layer. By setting the content to 1% by mass or more, the print storability can be further improved. On the other hand, by setting it as 45 mass% or less, background fog can be suppressed and whiteness can be improved.

  A composite zinc salt formed from an aromatic monocarboxylic acid and an aromatic dicarboxylic acid (hereinafter sometimes simply referred to as “composite zinc salt”) is a compound that supplies an aromatic monocarboxylic acid ion and an aromatic dicarboxylic acid ion. A composite zinc salt obtained by reacting with a zinc-containing compound may be contained in the heat-sensitive recording layer, or for a heat-sensitive recording layer containing an aromatic monocarboxylic acid ion, an aromatic dicarboxylic acid ion and a zinc ion. A composite zinc salt may be contained in the heat-sensitive recording layer by preparing a coating solution, applying the solution on a support and drying it.

  Aromatic monocarboxylic acids include benzoic acid, salicylic acid, p-hydroxybenzoic acid, p-nitrobenzoic acid, acetylsalicylic acid, p-chlorobenzoic acid, p-formylbenzoic acid, and the like. Alkyl, acetyl, nitro, halogen, hydroxyl, aldehyde substituted or unsubstituted benzoic acid can be used. From the viewpoint of the stability of the composite zinc salt, it is preferable that an electron withdrawing group such as a halogen atom is substituted on the aromatic, but the handling property that there is no problem of generation of halogen gas at the time of production and incineration of the heat-sensitive recording material. Benzoic acid is most preferably used from the viewpoint of cost and price.

  As aromatic dicarboxylic acid ions, not only aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, and isophthalic acid, but also compounds that dissolve in water to form aromatic dicarboxylic acid ions, such as phthalic anhydride, can be used. . These aromatic dicarboxylate ions can be used singly or in combination of two or more, but terephthalic acid and isophthalic acid are preferably used because they have excellent oil resistance and plasticizer resistance in the recording area. .

  The content ratio of the aromatic monocarboxylic acid and the aromatic dicarboxylic acid in the heat-sensitive recording layer is preferably 0.02 to 0.80 as the molar ratio of aromatic dicarboxylic acid / aromatic monocarboxylic acid, more Preferably it is 0.05-0.50. When the molar ratio of the aromatic dicarboxylic acid to the aromatic monocarboxylic acid is less than 0.02, it is difficult to obtain a remarkable oil resistance and plasticizer resistance increasing effect. On the other hand, if the molar ratio of the aromatic dicarboxylic acid exceeds 0.80, the recording density tends to decrease, which is not preferable.

  The molar ratio (zinc / (aromatic monocarboxylic acid + aromatic dicarboxylic acid)) of zinc content to the total molar amount of aromatic monocarboxylic acid and aromatic dicarboxylic acid in the heat-sensitive recording layer is 0.4 to 1.0. Is preferred. More preferably, it is 0.4-0.9, Most preferably, it is 0.4-0.7.

  The zinc carboxyl group equivalent ratio (zinc / aromatic carboxylic acid-derived carboxyl group) in the colorant is preferably 0.80 to 1.50. When the molar ratio of the zinc content to the total molar amount of aromatic carboxylic acid is less than 0.4 or the carboxyl group equivalent ratio of zinc is less than 0.8, the content ratio of carboxyl ions that do not form a salt increases. This means that oil resistance and plasticizer resistance may be reduced, and a lot of background fogging may occur. On the other hand, when the molar ratio of the zinc content to the total molar content of the aromatic carboxylic acid exceeds 1.0, the recording density tends to decrease. Similarly, when the zinc carboxyl group equivalent ratio exceeds 1.50, even if the molar ratio of aromatic dicarboxylic acid / aromatic monocarboxylic acid is within the range of 0.02 to 0.80, the recording is performed. Oil resistance and plasticizer resistance tend to decrease, and recording density tends to decrease.

As the zinc ion supply compound used to form the composite zinc salt in the present invention, a zinc-containing compound such as zinc oxide, zinc sulfate, zinc nitrate, zinc chloride can be used, depending on the method for producing the composite zinc salt. Can be selected as appropriate.

  As a method for producing such a composite zinc salt, for example, an aromatic monocarboxylic acid, an aromatic dicarboxylic acid and zinc oxide are mixed at a predetermined molar ratio, dissolved in ammonia water, and then dried. Alternatively, it may be synthesized by a salt exchange method in which an aqueous solution of a salt of zinc and inorganic acid such as zinc sulfate is added to a sodium salt aqueous solution of aromatic monocarboxylic acid or aromatic dicarboxylic acid to precipitate a zinc salt. Good. Or you may synthesize | combine by wet-pulverizing the suspension which mixed aromatic monocarboxylic acid, aromatic dicarboxylic acid, and zinc oxide by the predetermined molar ratio. Adjustment of the molar ratio of aromatic monocarboxylic acid, aromatic dicarboxylic acid, and zinc can supply aromatic monocarboxylic acid ions and aromatic dicarboxylic acid ions in the zinc salt production process or thermal recording layer coating liquid. It can also carry out by adjusting content of the compound and the compound which can supply a zinc ion.

  The heat-sensitive recording layer can contain a developer other than those described above as long as the effects of the present invention are not impaired. 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 monocarboxylic acid zinc salts Colorants such as zinc 4- [2- (p-methoxyphenoxy) ethyloxy] salicylate, zinc 4- [3- (p-tolylsulfonyl) propyloxy] salicylate, 5- [p- (2-p-methoxy) Phenoxyethoxy) cumyl] zinc salicylate, 4,4′-bis (Np-tolylsulfonylaminocarbonylamino) diphenylmethane, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea, N- (p-toluenesulfonyl) -N ′-(p-butoxycarbonyl) phenylurea Urea compounds such as N-p-tolyl sulfonyl -N'- phenylurea and the like. Among these, 4,4′-isopropylidene diphenol, 4-hydroxy-4′-isopropoxydiphenyl sulfone, 2,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl sulfone, 4,4′-bis (Np-tolylsulfonylaminocarbonylamino) diphenylmethane and the like are preferable. The content of these other developers is preferably 20% by mass or less based on the total amount of the specific developer of the present invention.

  In the present invention, various known leuco dyes can be contained in the heat-sensitive recording layer. Examples of leuco dyes that give a black color include 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-anilinofluor Lan, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (Nn-hexyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- [N- (3 -Ethoxypropyl) -N-ethylamino] -6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-methylamino] -6-methyl-7-anilinofluorane 3-diethylamino-7- (2-chloroanilino) fluorane, 3-di (n-butylamino) -7- (2-chloroanilino) fluorane, and the like. If necessary, a leuco dye that develops a color tone different from that of black, such as red, magenta, orange, blue, green, etc., can also be used. These leuco dyes may be used alone or in combination of two or more.

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

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

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

  The content of the leuco dye is not particularly limited, but is preferably about 3 to 30% by mass with respect to the total solid content of the heat-sensitive recording layer. When the leuco dye is contained in the form of composite particles, the content of the leuco dye in the composite particles is preferably about 10 to 70% by mass, more preferably, based on the total solid content of the composite particles. It is about 30-60 mass%.

  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 developer used, and is not particularly limited, but generally 1 mass of leuco dye. About 1 to 7 parts by mass, preferably about 1 to 4 parts by mass of the developer is used.

  Furthermore, the heat-sensitive recording layer can contain a sensitizer for increasing the recording sensitivity. 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, oxalic acid-di-p-methylbenzyl, oxalic acid-di-p-chlorobenzyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3 -Mechi Phenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetoluidide, p-acetophenetide, N- Examples include acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, and the like. The amount of these sensitizers to be used is not particularly limited, but generally it is preferably adjusted within a range of about 4 parts by mass or less with respect to 1 part by mass of the developer.

  Further, the heat-sensitive recording layer may contain a storability improving agent for improving the storability of the recorded image. Specific examples of the storage stability improver include 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-ethylenebis (4-methyl-6-tert-butylphenol) 2,2 '-Methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4,6-di-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-tert-butylphenol) ), 2,2′-ethylidenebis (4-methyl-6-tert-butylphenol), 2,2′-ethylidenebis (4-ethyl-6-tert-butylphenol), 2,2 ′-(2,2- Propylidene) bis (4,6-di-tert-butylphenol), 2,2′-methylenebis (4-methoxy-6-tert-butylphenol) 2,2′-methylenebis (6-tert-butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-thiobis (2-methyl-6-tert) -Butylphenol), 4,4'-thiobis (5-methyl-6-tert-butylphenol), 4,4'-thiobis (2-chloro-6-tert-butylphenol), 4,4'-thiobis (2-methoxy) -6-tert-butylphenol), 4,4'-thiobis (2-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol), 1- [α-methyl -Α- (4'-hydroxyphenyl) ethyl] -4- [α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene, 1,1,3 -Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4'-thiobis ( 3-methylphenol), 4,4′-dihydroxy-3,3 ′, 5,5′-tetrabromodiphenylsulfone, 4,4′-dihydroxy-3,3 ′, 5,5′-tetramethyldiphenylsulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,5) Hindered phenol compounds such as -dimethylphenyl) propane, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6 Di -tert- butylphenyl) phosphate sodium, and the like.

  Further, in order to improve the whiteness and image uniformity, the heat-sensitive recording layer may contain a fine pigment having a high whiteness and an average particle diameter of 10 μm or less. Specific examples of the pigment include, for example, kaolin, clay, calcium carbonate, magnesium carbonate, aluminum hydroxide, barium sulfate, talc, calcined clay, calcined kaolin, titanium oxide, zinc oxide, diatomaceous earth, particulate anhydrous silica, activated clay, etc. Organic pigments such as inorganic pigments, styrene microballs, nylon powder, polyethylene powder, urea-formalin resin filler, styrene-methacrylic acid copolymer resin, polystyrene resin, raw starch particles and the like can be mentioned. The pigment content is preferably 50% by mass or less with respect to the total solid content of the heat-sensitive recording layer, in such an amount that does not decrease the color density.

  The coating solution for the thermal recording layer contains auxiliary agents such as the following cross-linking agents, waxes, metal soaps, colored dyes, colored pigments, fluorescent dyes, oil repellents, antifoaming agents and viscosity modifiers as necessary. Can be made.

  Examples of the crosslinking agent include aldehyde compounds such as glyoxal, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, dimethylol urea compounds, aziridine compounds, blocked isocyanate compounds, and adipic acid dihydrazides. A dihydrazide compound and an inorganic compound such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, potassium tetraborate, or at least one crosslinkable compound selected from boric acid, boric acid triester, boron-based polymer, etc. It is preferably used in the range of 0.1 to 10% by mass with respect to the total solid content of the heat-sensitive recording layer.

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

  Examples of the metal soap include higher fatty acid polyvalent metal salts such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

  The thermosensitive recording layer may contain an adhesive other than polyvinyl alcohol as long as the effects of the present invention are not impaired. Specific examples of such adhesives include, for example, starches such as oxidized starch, acid-modified starch, phosphate esterified starch, enzyme-modified starch, cation-modified starch, esterified starch, etherified starch and vinyl acetate-modified grafted starch. Polyvinyl alcohol having a polymerization degree of less than 500, cellulose derivatives such as methylcellulose, ethylcellulose, carboxymethylcellulose, methoxycellulose, hydroxyethylcellulose and hydroxypropylmethylcellulose, polyacrylic acid soda, polyacrylamide, polyvinylpyrrolidone, acrylic acid amide-acrylic acid ester copolymer Polymers, acrylic acid amide-acrylic acid ester-methacrylic acid copolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, algi Water-soluble adhesives such as acid soda, gelatin, and casein, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, polybutyl methacrylate, styrene-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, ethylene Latex such as vinyl acetate copolymer and styrene-butadiene-acrylic copolymer can be used in combination.

The heat-sensitive recording layer generally uses water as a dispersion medium.For example, a leuco dye and a developer, and a sensitizer and a storage stabilizer, if necessary, separately or separately by a pulverizer such as a ball mill, an attritor, or a sand mill. By applying and drying a thermal recording layer coating solution prepared by further mixing an adhesive, a surfactant, and, if necessary, an auxiliary agent using the dispersion obtained by the curtain coating method. It is formed. The coating amount of the heat-sensitive recording layer coating composition is not particularly limited, it is preferably about 1~12g / ^{m 2} in solid coating amount, more preferably ^{2~10g / m 2, 2.5~5.5g / m} 2 Is particularly preferred.

(Protective layer)
The protective layer in the present invention is formed by laminating at least one layer 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 can contain an adhesive and a pigment. In particular, the protective layer preferably contains a lubricant such as polyolefin wax or zinc stearate for the purpose of preventing sticking to the thermal head, and can also contain an ultraviolet absorber. In addition, the added value of the product can be increased by providing a glossy protective layer.

  As the adhesive used for the protective layer, any water-based adhesive such as a water-soluble adhesive and a water-dispersible adhesive can be used. Examples of the water-soluble adhesive include fully (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, and the like. Water-soluble resins such as cellulose resin, gelatin, casein, alkali salt of styrene-maleic anhydride copolymer, alkali salt of ethylene-acrylic acid copolymer, alkali salt of styrene-acrylic acid copolymer, etc. . Examples of the water-dispersible adhesive include hydrophobic resins obtained from latexes such as styrene-butadiene latex, acrylic latex, and urethane latex. Among these, acetoacetyl-modified polyvinyl alcohol and diacetone-modified polyvinyl alcohol are preferably used because they can improve the surface barrier properties and improve the storage stability such as chemical resistance. These can be used alone or in combination of two or more.

  10-80 mass% is preferable with respect to the total solid amount of a protective layer in total, and, as for the usage-amount of an adhesive agent, 20-75 mass% is more preferable. By setting it as 10 mass% or more, barrier property can be improved and surface strength can be improved and generation | occurrence | production of paper dust can be suppressed. On the other hand, by setting it to 80% by mass or less, the sticking resistance can be further improved. Such water-soluble adhesives and water-dispersible adhesives can be used in combination. Although the usage ratio is not particularly limited, it is preferable to use 5 to 100 parts by mass of a water-dispersible adhesive with respect to 100 parts by mass of the water-soluble adhesive in mass ratio.

  Examples of the pigment used for the protective layer include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, amorphous silica, synthetic mica, aluminum hydroxide, barium sulfate, talc, kaolin, clay, calcined kaolin and other inorganic pigments, nylon Organic pigments such as resin fillers, urea-formalin resin fillers, and raw starch particles are exemplified. Of these, kaolin and aluminum hydroxide are preferable because they have little decrease in barrier properties against plasticizers, oils, and the like, and the decrease in recording density is also small.

  5-80 mass% is preferable with respect to the total solid amount of a protective layer, and, as for the usage-amount of a pigment, 10-70 mass% is more preferable. By setting the content to 5% by mass or more, it is possible to improve the sliding with the thermal head, make sticking difficult to occur, and suppress the generation of 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.

  As auxiliary agents, for example, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and other lubricants, alkyl alkenyl sulfonate sodium, dioctyl sodium sulfosuccinate, 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 solution 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. And amphoteric surfactants such as betaines, aminocarboxylates, and imidazoline derivatives, and the like. In particular, dialkylsulfosuccinic acid represented by the above general formula (1) contained in the coating solution for the heat-sensitive recording layer A salt or a compound represented by the general formula (2) is preferred.

  In the present invention, the protective layer coating solution is preferably 0.03 to 2.00% by mass, more preferably the dialkylsulfosuccinate represented by the general formula (1) with respect to the total solid amount of the protective layer. It contains 0.05 to 1.50 mass%. Alternatively, the compound represented by the general formula (2) is preferably contained in an amount of 0.05 to 3.00 mass%, more preferably 0.10 to 2.50 mass%, based on the total solid content of the protective layer. . Thereby, the static surface tension of the coating liquid for protective layers can be adjusted to a preferable range.

The protective layer is generally formed by applying and drying a protective layer coating liquid prepared by mixing an adhesive, a pigment, a surfactant, and an auxiliary agent by a curtain coating method using water as a medium. . The coating amount of the coating liquid for the protective layer is not particularly limited, and is preferably about 0.5 to 7.0 g / m ² , more preferably 0.8 to 6.0 g / m ^{2 in} terms of solid content. ˜3.5 g / m ² is particularly preferred. In addition, a protective layer can be divided and formed in two or more layers as needed, and the composition and application amount of each layer can be changed. After forming the heat-sensitive recording layer and the protective layer, the surface of the protective layer may be subjected to a known smoothing process such as a calendar, if necessary.

(Curtain application method)
The heat-sensitive recording layer and the protective layer in the present invention are formed by a curtain coating method using a heat-sensitive recording layer coating solution and a protective layer coating solution. Thereby, the barrier property of the protective layer can be further enhanced to improve the chemical resistance, the production efficiency can be improved, and the energy consumption during production can be reduced.

  The curtain coating method is a method of flowing down the coating liquid and free-falling and applying it to the support in a non-contact manner, and a known method such as a slide curtain method, a couple curtain method, a twin curtain method, etc. can be employed. There is no particular limitation. Further, as described in JP-A-2006-247611, the coating liquid is ejected downward from the curtain head to form a coating liquid layer on the slope, and the coating liquid is applied from the downward curtain guide portion of the slope. It is also possible to transfer the coating liquid layer onto the web surface by forming a curtain. In the present invention, the simultaneous multilayer curtain coating method of the thermal recording layer coating liquid and the protective layer coating liquid, or the thermal recording layer coating liquid is applied by the curtain system, and further the protective layer coating liquid is applied when the thermal recording layer is wet. The liquid is preferably applied in a curtain manner.

(Undercoat layer)
In the present invention, an undercoat layer formed by applying and drying an undercoat layer coating solution containing hollow plastic particles and calcined kaolin by a blade coating method between a support and a heat-sensitive recording layer, the content ratio Is preferably 10 to 100 parts by mass of plastic hollow particles, more preferably 15 to 70 parts by mass with respect to 100 parts by mass of calcined kaolin. Thereby, excellent chemical resistance and sticking resistance can be obtained.

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

  By making the content of the hollow plastic particles 100 parts by mass or less, the hydrophobicity of the surface of the undercoat layer is prevented from increasing extremely, and the undercoat is applied until the thermal recording layer coating liquid is immobilized in the drying step. Since the heat-sensitive recording layer is uniformly formed without being disturbed on the layer, the barrier property of the protective layer is improved, and further excellent chemical resistance can be exhibited. Moreover, it is excellent in the ability to absorb the hot melt and can improve the effect of suppressing sticking to the thermal head, so-called sticking. On the other hand, when the content is 10 parts by mass or more, the recording sensitivity and the image quality can be improved, and the effect of suppressing intermixing between the heat-sensitive recording layer and the protective layer can be improved.

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

  The calcined kaolin preferably has an oil absorption specified by JIS-K5101 of 70 ml / 100 g or more from the viewpoint of improving the sticking resistance.

  In the present invention, a specific pigment is contained in the undercoat layer, but other pigments can be used as long as the desired effects of the present invention are not impaired. As other pigments, both inorganic and organic pigments can be used. In particular, an oil-absorbing pigment having an oil absorption of 40 ml / 100 g or more can be suitably used. Examples of the oil-absorbing pigment include aluminum oxide, magnesium carbonate, calcined diatomaceous earth, aluminum silicate, calcium carbonate, barium sulfate, aluminum hydroxide, kaolin, amorphous silica, talc and the like. In addition, solid plastic particles can be used as other pigments. The total amount of the pigment containing the plastic hollow particles and the calcined kaolin is preferably 40 to 90% by mass with respect to the total solid content of the undercoat layer.

  As the adhesive used for the coating solution for the undercoat layer, for example, any water-based adhesive such as a water-soluble adhesive and a water-dispersible adhesive can be used. Examples of the water-soluble adhesive include polyvinyl alcohol, modified polyvinyl alcohol, starch and oxidized starch, acid-modified starch, phosphate esterified starch, enzyme-modified starch, cation-modified starch, esterified starch, etherified starch and vinyl acetate-modified. Starch derivatives such as grafted starch, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide-acrylic acid ester copolymer, acrylic acid amide- Water-soluble polymers such as acrylic acid ester-methacrylic acid copolymer, styrene-maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and caseinWater dispersible adhesives include polyvinyl acetate, polyurethane, styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride-acetic acid Examples thereof include latex of a hydrophobic polymer such as vinyl copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, silylated urethane, acrylic-silicon composite, and acrylic-silicon-urethane composite. These can be used alone or in combination of two or more.

  The amount of the adhesive used is not particularly limited, and is determined in consideration of the coating strength and the recording sensitivity of the heat-sensitive recording layer, but is preferably 3 to 100 parts by mass with respect to 100 parts by mass of the pigment contained in the undercoat layer. 5 to 50 parts by mass is more preferable, and 7 to 40 parts by mass is particularly preferable. Moreover, in the coating liquid for undercoat layers, auxiliary agents, such as various well-known thickeners, wax, an antifoamer, and surfactant, can also be contained as needed.

  For the undercoat layer, a coating solution for an undercoat layer prepared by mixing plastic hollow particles and calcined kaolin with an adhesive and, if necessary, an auxiliary agent is generally applied onto a support by a blade coating method using water as a medium. And formed by drying. In the present invention, the unevenness of the surface of the undercoat layer can be reduced by selecting the blade coating method in particular, and the coating thickness of the heat-sensitive recording layer and the protective layer formed on the undercoat layer is made uniform, The barrier property can be improved.

  The blade coating method is not limited to the coating method using blades represented by the bevel type and vent type, 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. After forming the undercoat layer, a known smoothing treatment such as a calendar may be applied to the surface of the undercoat layer as necessary.

The coating amount of the undercoat layer is not particularly limited, may be suitably selected according to the characteristics of the heat-sensitive recording material but is preferably 2 g / ^{m 2} or more, 3 g / ^{m 2} or more preferably, 4~10g / ^{m 2} is Further preferred is 5.5 to 8.5 g / m ² .

(Support)
The support in the present invention is not particularly limited. For example, high-quality paper such as acidic high-quality paper, neutral high-quality paper, old paper-containing high-quality paper, art paper, synthetic paper, PET film, non-woven high-quality paper, coated paper, In addition to cast-coated paper, glassine paper, resin-laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, nonwoven fabric, synthetic resin film, and the like, various transparent supports can be appropriately selected and used.

(Thermal recording material)
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 on 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.

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

  The 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 coating solution for undercoat layer 60 parts of calcined kaolin with oil absorption of 110 ml / 100 g, plastic hollow particle emulsion (trade name: AE852, styrene-acrylic copolymer hollow particles, solid content concentration 26%, hollow rate 80%, average 80 parts of particle diameter 1.0 μm, manufactured by JSR), 20 parts of styrene-butadiene copolymer latex (trade name: L-1571, manufactured by Asahi Kasei Chemicals) having a solid content concentration of 48% as an adhesive, carboxymethylcellulose (trade name) : Serogen 7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 20 parts of 5% aqueous solution, oxidized starch (trade name: Oji Ace A, manufactured by Oji Cornstarch Co., Ltd.), 25 parts of aqueous solution, and 60 parts of water are mixed to form an undercoat layer. A coating solution was obtained.

Preparation of leuco dye dispersion (liquid A) A composition comprising 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 5 parts of a 5% aqueous solution of methylcellulose and 15 parts of water. Then, the liquid A was obtained by pulverizing with a sand mill until the median diameter (trade name: SALD2200, 50% value by Shimadzu Corporation) by a laser diffraction particle size distribution measuring device was 0.5 μm.

・ Preparation of developer dispersion (B-1 solution) A composition comprising 10 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water was subjected to laser diffraction using a sand mill. The B-1 solution was obtained by pulverizing until the median diameter (trade name: SALD2200, 50% value manufactured by Shimadzu Corporation) by the particle size distribution analyzer became 1.0 μm.

-Preparation of developer dispersion (Liquid B-2) 10 parts of 2,2 '-[4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water The composition was pulverized with a sand mill until the median diameter (trade name: SALD2200, 50% value manufactured by Shimadzu Corporation) with a laser diffraction particle size distribution measuring device was 1.0 μm to obtain a liquid B-2.

Preparation of sensitizer dispersion (liquid C) A composition comprising 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was laser-diffracted from a sand mill. C liquid was obtained by pulverizing until the median diameter (trade name: SALD2200, 50% value manufactured by Shimadzu Corporation) by a particle size distribution measuring device was 1.0 μm.

-Preparation of coating solution for thermosensitive recording layer A part 25 parts, B-1 part 40 parts, B-2 part 15 parts, C part 55 parts, aluminum hydroxide (trade name: Heidilite H-42M, manufactured by Showa Denko KK ) 20 parts, fully saponified PVA (trade name: PVA110, polymerization degree 1000, saponification degree 98.5 mol%, manufactured by Kuraray Co., Ltd.) 15 parts aqueous solution 50 parts, partially saponified PVA (trade name: PVA205, polymerization degree 500, saponification degree 88) 0.0 mol%, manufactured by Kuraray Co., Ltd.) 20 parts 20% aqueous solution, 5 parts 35% aqueous dispersion of adipic acid dihydrazide, dioctyl sulfosuccinate sodium salt (trade name: Sanmorin OT-70, manufactured by San Nopco) 10 parts A composition for thermal recording layer was obtained by mixing the composition.

-Preparation of coating liquid for protective layer A dispersion obtained by dispersing 50 parts of kaolin (trade name: UW-90, manufactured by Engelhard) in 50 parts of water, and acetoacetyl-modified polyvinyl alcohol (trade name: Gocepha) 400 parts of 10% aqueous solution of Immer Z-200 (manufactured by Nippon Synthetic Chemical Co., Ltd.), zinc stearate (trade name: Hydrin Z-8-36, solid content concentration 36%, manufactured by Chukyo Yushi Co., Ltd.), and dioctylsulfosuccinic acid A coating solution for a protective layer was obtained by mixing 10 parts of a 5% aqueous solution of a sodium salt (trade name: Sanmorin OT-70, manufactured by San Nopco).

- on one surface of woodfree paper having produced a basis weight of 60 g / m ² of the heat-sensitive recording material, a subbing layer by coating and drying the undercoat layer coating liquid was a blade coater so coated amount after drying of 7 g / m ² A coated base paper was obtained. Furthermore, on the base paper coated with the undercoat layer, the thermal recording layer coating solution and the protective layer coating solution are applied from the undercoat layer side to the thermal recording layer coating solution and the protective layer coating solution using a slide hopper type curtain coating device. to form a coating liquid film formed in this order, so that the solid content coating amount of each layer is a heat-sensitive recording layer 4g / ^{m 2,} the protective layer 2.5 g / ^{m 2,} a curtain coating method at a coating speed of 600 meters / min After forming a heat-sensitive recording layer and a protective layer by simultaneous multi-layer coating and drying, the surface of the protective layer is treated with a super calender, and the surface has a smoothness of 1000 to 4000 seconds with a Wangken-type smoothness meter. Got the body.

Example 2
In the preparation of the thermal recording layer coating liquid of Example 1, 2,4,7,9-tetramethyl-5-decyne-4,7-diol was used instead of 10 parts of 5% aqueous solution of dioctyl sulfosuccinic acid sodium salt. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 10 parts of a 5% aqueous solution having an addition mole number of ethoxylated compound and ethylene oxide of 10 (trade name: Orphine E1010, manufactured by Nissin Chemical Co., Ltd.) was used.

Example 3
-Preparation of developer dispersion (liquid B-3) 4,4'-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl sulfone 10 parts, magnesium silicate 0.5 parts, methylcellulose A composition comprising 5 parts of 5% aqueous solution and 15 parts of water is pulverized with a sand mill until the median diameter (trade name: SALD2200, 50% value by Shimadzu Corporation) is 1.0 μm by a laser diffraction particle size distribution analyzer. did. Further, this dispersion was subjected to a heat treatment at 70 ° C. for 4 hours to obtain a liquid B-3.

  In the preparation of the heat-sensitive recording layer coating liquid of Example 1, a heat-sensitive recording material was obtained in the same manner as in Example 1 except that 15 parts of the B-3 liquid was used instead of 15 parts of the B-2 liquid. It was.

Example 4
-Preparation of developer dispersion (liquid B-4) 122.1 parts of benzoic acid, 16.6 parts of terephthalic acid, 48.8 parts of zinc oxide, 88% by mole of saponification, 20% of polyvinyl alcohol having a polymerization degree of 300 A composition (suspension) consisting of 93.8 parts of an aqueous solution, 40 parts of a 5% emulsion of a natural fat and oil-based antifoaming agent, and 199 parts of water has a median diameter of 1.5 μm as measured by a laser diffraction particle size distribution measuring apparatus using a sand mill It processed so that it might become, and B-4 liquid was obtained.

  In the preparation of the heat-sensitive recording layer coating liquid of Example 1, Example 1 was used except that 60 parts of the B-4 liquid was used instead of 40 parts of the B-1 liquid and 15 parts of the B-2 liquid. A heat-sensitive recording material was obtained in the same manner.

Example 5
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 5% aqueous solution of dioctylsulfosuccinic acid sodium salt was changed to 60 parts instead of 10 parts. .

Comparative Example 1
Curtain coating was carried out in the same manner as in Example 1 except that dioctyl sulfosuccinate sodium salt was not used in the preparation of the heat-sensitive recording layer coating liquid and the protective layer coating liquid of Example 1, Since the film was not stable and the film was frequently cut, the application was stopped.

Comparative Example 2
In the preparation of the thermal recording layer coating liquid of Example 1, Example 1 was used except that instead of 40 parts of the B-1 liquid and 15 parts of the B-2 liquid, 55 parts of the B-1 liquid was used. A heat-sensitive recording material was obtained in the same manner.

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

(Curtain film cut)
Regarding the curtain film breakage, the stability of the coating liquid film (the film falling freely) was visually evaluated.
A: No film breakage is observed.
○: Almost no film breakage is observed.
X: Curtain film breakage occurs, which is an operational problem.

(Recording sensitivity)
Using a thermal recording simulator (TH-PMD, manufactured by Okura Electric Co., Ltd.), recording is performed at an applied energy of 0.24 mJ / dot, and the recording density of the recording unit is a Macbeth densitometer (RD-914, manufactured by Macbeth). Measured with

(Plasticizer resistance)
The printed part of the heat-sensitive recording material 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 by a vinyl chloride wrap film (Hi-Ssoft TM350, manufactured by Nippon Carbide Industries Co., Ltd.). After being left for 24 hours in an environment of ° C., the density of the printed portion was measured in a visual mode of a Macbeth densitometer (trade name: RD-914, manufactured by Macbeth). The closer to the density before being left (recording sensitivity density), the better the print storability.

  The thermal recording material of the present invention does not cause defective curtain film formation during curtain coating, and forms a stable curtain film. Productivity is achieved by simultaneously applying multilayer coating of the thermal recording layer and the protective layer coating liquid by the curtain coating method. In addition, it is possible to provide a thermosensitive recording material excellent in recording sensitivity and print storage stability.

Claims (7)

A heat-sensitive recording layer comprising a leuco dye and a developer on a support, and a heat-sensitive recording material having a protective layer in this order, wherein at least the heat-sensitive recording layer and the protective layer comprise the heat-sensitive recording layer coating liquid and the protective layer. A dialkylsulfosuccinate represented by the following general formula (1) or the following general formula (1), wherein the heat-sensitive recording layer coating liquid contains a water-soluble adhesive: Contains a compound represented by the general formula (2) (however, a dialkylsulfosuccinate represented by the following general formula (1) including dioctylsulfosuccinate and a compound represented by the following general formula (2)) And 2,2 ′-[4- (4-hydroxyphenylsulfonyl) phenoxy] diethyl ether, 4,4′-bis [(4-methyl-3-phenoxy) as a developer. A dialkylsulfosuccinic acid represented by the above general formula (1), which contains at least one selected from (rubonylaminophenyl) ureido] diphenylsulfone and a complex zinc salt formed from an aromatic monocarboxylic acid and an aromatic dicarboxylic acid. A heat-sensitive recording material, wherein the salt is dioctylsulfosuccinate, and the curtain coating method is applied by a simultaneous multilayer curtain coating method of a heat-sensitive recording layer coating liquid and a protective layer coating liquid.

(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).

(Wherein R ^{3 to} R ⁶ represent a hydrogen atom, a branched group having 1 to 8 carbon atoms, a linear or cyclic unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, and R ⁷ to R ¹⁰ represents a hydrogen atom or a methyl group, m and n each independently represents an integer of 0 to 50.)   Polyvinyl alcohol having a polymerization degree of 1000 to 3000 is contained as the water-soluble adhesive in an amount of 5 to 25% by mass with respect to the total solid content of the heat-sensitive recording layer, and the B-type viscosity at 25 ° C. of the heat-sensitive recording layer coating liquid is 200 to 2000 mPa. The heat-sensitive recording material according to claim 1, which is s. Wherein based on the total solids content of the heat-sensitive recording layer, the content of the previous SL dioctyl sulfosuccinate is from 0.05 to 3 wt%, the heat-sensitive recording material according to claim 1 or 2.   The heat-sensitive recording material according to claim 1 or 2, wherein the content of the compound represented by the general formula (2) is 0.1 to 5% by mass with respect to the total solid content of the heat-sensitive recording layer.   The aromatic dicarboxylic acid is terephthalic acid and / or isophthalic acid, and the molar ratio of the aromatic dicarboxylic acid to the aromatic monocarboxylic acid (aromatic dicarboxylic acid / aromatic monocarboxylic acid) is 0.02 to 0 .80, and the molar ratio of the zinc content to the total molar amount of the aromatic monocarboxylic acid and aromatic dicarboxylic acid (zinc / (aromatic monocarboxylic acid + aromatic dicarboxylic acid)) is 0.4 to The heat-sensitive recording material according to claim 1, which is 1.0. Any of the Claims 1-5 in which the coating liquid for said protective layers contains the compound represented by the dialkyl sulfosuccinate represented by the said General formula (1) containing the dioctyl sulfosuccinate or the said General formula (2). 2. The heat-sensitive recording material according to item 1.   Between the support and the heat-sensitive recording layer, there is an undercoat layer formed by applying and drying an undercoat layer coating solution containing plastic hollow particles and fired kaolin by a blade coating method, and the content ratio thereof is the fired kaolin. The thermosensitive recording material according to any one of claims 1 to 6, wherein the amount of the plastic hollow particles is 10 to 100 parts by mass with respect to 100 parts by mass.