JP2010005928A - Manufacturing process of heat sensitive recording body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing process of a heat sensitive recording body, which does not cause mixing of air bubbles and poor film forming when carrying out a curtain application of a coating liquid for protective layers, and which forms stable curtain film and excels in productivity and quality etc. <P>SOLUTION: In the manufacturing process of the heat sensitive recording body which, on a supporting body, has, in this order, a heat sensitive recording layer containing at least leuco dye and developer and a protective layer, the coating liquid for protective layers contains a water-soluble adhesive bond, and the consistency ratio at the time of the shear rate 1 s<SP>-1</SP>and 1,000 s<SP>-1</SP>at the liquid temperature of 25°C of the coating liquid for protective layers is 1:0.30 to 1:0.80, and the protective layer is formed by coating and drying at least the coating liquid for protective layers in the curtain application method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a thermal recording material.

  2. Description of the Related Art A heat-sensitive recording material is well known in which a recording image is obtained by making a color developing reaction between a colorless or light leuco dye and an organic or inorganic developer by bringing both coloring materials into contact with each other by heat. Such a thermal recording medium is relatively inexpensive, and the recording equipment is compact and easy to maintain. For example, it can be used in facsimiles, computer outputs, handy terminals, POS systems (store point-of-sale information management systems), and transportation systems. However, recently, due to the diversification of application development and the enhancement of the functions of the system, the required quality for the thermal recording medium has become high.

  That is, with the increase in recording speed, high density and clear recorded images are required even with a small amount of heat energy, and in applications such as POS system labels, tickets, commuter passes, water, vinegar, oil, plasticizer It is important that the vinyl chloride sheet for wrapping and the volatile solvent (ethanol, hair styling agent) having polarity, and the like are not subjected to adhesion, background fogging due to contact, decoloration and fading of recorded images. In order to improve the storability of the recording part, conventionally, there is a method of providing a protective layer on the heat-sensitive recording layer, and many overcoat agents have been proposed.

  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 liquid on a support such as paper or film. The heat-sensitive recording material produced in 1) has poor coating quality, soaking of the upper coating liquid into the lower layer, upper pinholes due to repelling during upper 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 disclosed in Japanese Patent Publication No. 49-24133 is a method in which a free-falling curtain film of a coating liquid is formed, and this is applied by colliding with a support. It is known that the coating quality is good and it is suitable for high-speed coating. Moreover, it is also possible to form a coating liquid film composed of a plurality of layers of coating liquid and apply the curtain, thereby greatly improving the productivity of multilayer coating. This curtain coating method is a method in which a coating liquid is dropped from a slit-shaped coater lip onto a support and applied in a film form. In order to prevent defects, fine adjustments are required for static surface tension, dynamic surface tension, viscosity, and the like (for example, JP-A-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 method of applying a curtain by blending a specific adhesive or a surfactant in the thermal recording layer has been proposed in order to stabilize and uniformly apply the curtain film during curtain coating. For example, a method of adding 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 has been proposed (see Patent Document 1). In addition, a method of adding dodecylbenzene sulfonate to the protective layer coating solution (see Patent Document 2) has been proposed. Furthermore, a method (see Patent Document 3) in which a specific sulfate ether type surfactant and a specific phosphate ester type surfactant are included in the thermal recording layer and / or protective layer coating solution has also been proposed. In addition, a method of adding a composition of an acetylene glycol derivative and an anionic surfactant to the coating solution for the protective layer (see Patent Document 4), adding ethylene oxide and other alkylene oxides to tetramethyldecine diol There has also been proposed a method (see Patent Document 5) in which the surfactant is added to the thermal recording layer coating solution.

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

  However, even if the surface tension is reduced by the addition of a surfactant, film sway, film breakage, etc. occur due to air bubbles or poor film formation, especially during high-speed coating or low-speed coating of a thin film. There is a problem that a curtain film cannot be obtained. In addition, at the moment when the coating liquid is applied onto the support on the curtain, the coating liquid is not uniformly stretched, causing coating unevenness, resulting in a coating defect and lowering productivity. Depending on the type and amount of surfactant used, quality problems such as reduced color density, decoloration of recorded areas, and background fogging may occur. Is the current situation.

  An object of the present invention is to provide a method for producing a heat-sensitive recording material that is excellent in productivity and quality by forming a stable curtain film without causing bubbles and the like to cause poor film formation when the protective layer coating liquid is applied to the curtain. It is to provide.

The present inventors, as a result of various studies of the above problems, the ratio of the viscosity of the viscosity and at a shear rate 1000 s ^-1 of at shear rate of ^{1s -1} at a liquid temperature 25 ° C. of the protective layer coating solution 1: 0.30 It is ˜1: 0.80, and by forming a protective layer by applying and drying the protective layer coating liquid by a curtain coating method, it is possible to form a stable curtain film that is thin and free from film cracking, In addition, the present inventors have found that uniform recording image quality can be obtained without occurrence of coating unevenness, and the present invention has been completed. That is, the present invention relates to the following method for producing a thermal recording material.

Item 1: In a method for producing a heat-sensitive recording material comprising, on the support, a heat-sensitive recording layer containing at least a leuco dye and a developer, and a protective layer in this order, the protective layer coating solution contains a water-soluble adhesive. The ratio of the viscosity at a shear rate of 1 s ^{-1 to} the viscosity at a shear rate of 1000 s ^-1 at a liquid temperature of 25 ° C. of the coating liquid for the protective layer is 1: 0.30 to 1: 0.80, and at least the protection A method for producing a heat-sensitive recording material, wherein the protective layer is formed by applying and drying a layer coating solution by a curtain coating method.

  Item 2: The thermal recording material according to Item 1, wherein the protective layer coating liquid contains 15 to 50% by mass of polyvinyl alcohol having a polymerization degree of 1000 to 3000 as a water-soluble adhesive with respect to the total solid content of the protective layer. Manufacturing method.

  Item 3: The method for producing a thermosensitive recording material according to Item 2, wherein the polyvinyl alcohol is acetoacetyl-modified polyvinyl alcohol.

  Item 4: The protective layer coating solution contains 0.01 to 1.50% by mass of at least one compound represented by the following general formulas (1) and (2) with respect to the total solid content of the protective layer. Item 4. The method for producing a heat-sensitive recording material according to any one of Items 1 to 3.

（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、ｍは１〜５の整数を表し、ｎは２〜８の整数を表す。）

(In the formula, m represents an integer of 1 to 5, and n represents an integer of 2 to 8.)

  According to the present invention, when a protective layer coating solution is applied to a curtain, a method for producing a heat-sensitive recording material that forms a stable curtain film without causing bubbles and the like and does not cause poor film formation and is excellent in productivity and quality. Can be provided.

In the present invention, the protective layer coating solution containing a water-soluble adhesive, the liquid temperature 25 ° C. of the protective layer coating solution, the ratio of the viscosity of the viscosity and 1000s h ^-1 o'clock shear rate of 1s ^-1 1: By setting it to 0.30 to 1: 0.80, it is possible to form a stable curtain film that is thin and has no film cracking. The ratio of the viscosity at a shear rate of 1 s ^{-1 to} the viscosity at 1000 s ^-1 is more preferably 1: 0.35 to 0.70. When the ratio of the viscosity at 1000 s ^-1 is less than 0.30, the viscosity rapidly decreases in the high shear rate region, and therefore the viscosity of the portion where the shear is applied (both ends) and the portion where the curtain film is not applied (center portion). A difference occurs, the curtain film is not stabilized, and the curtain film is easily cut in the width direction during curtain coating. On the other hand, if it exceeds 0.80, the coating liquid is not stretched well due to the viscous resistance at the time of coating, resulting in coating unevenness, and recording image quality and barrier properties tend to be non-uniform.

  In the present invention, it is further preferable that the protective layer coating solution contains 15 to 50% by mass of polyvinyl alcohol having a polymerization degree of 1000 to 3000 as a water-soluble adhesive with respect to the total solid content of the protective layer. As a result, the viscosity of the coating liquid is suitably adjusted, and a further excellent curtain film breakage suppressing effect and recording image quality can be obtained. In addition, as for the polymerization degree of polyvinyl alcohol, 1000-2700 are more preferable. On the other hand, as for content of polyvinyl alcohol, 15-45 mass% is more preferable with respect to the total solid of a protective layer.

  As the polyvinyl alcohol used in the coating liquid for the protective layer, it is preferable to use acetoacetyl-modified polyvinyl alcohol from the viewpoint of excellent barrier properties and improving the recording image quality with a smaller coating amount. Other usable polyvinyl alcohols include, for example, complete (or partial) saponified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, butyralized polyvinyl alcohol, cation-modified polyvinyl alcohol, sulfone-modified polyvinyl alcohol, Examples include acetoacetyl-modified polyvinyl alcohol. These polyvinyl alcohols may be used in combination of two or more.

  The protective layer coating solution may contain an adhesive other than the polyvinyl alcohol as long as the effects of the present invention are not impaired. Specific examples of the adhesive 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, Cellulose derivatives such as methylcellulose, ethylcellulose, carboxymethylcellulose, methoxycellulose, hydroxyethylcellulose and hydroxypropylmethylcellulose, polyacrylic acid soda, polyacrylamide, polyvinylpyrrolidone, acrylic acid amide-acrylic acid ester copolymer, acrylic acid amide-acrylic acid ester -Water-soluble adhesives such as methacrylic acid copolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, sodium alginate, gelatin, casein Polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, polybutyl methacrylate, styrene-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene-acrylic Examples thereof include water dispersible adhesives such as copolymers.

In the present invention, the protective layer coating liquid contains at least one of a dialkylsulfosuccinate represented by the following general formula (1) and a peroxyalkyl group-containing polyoxyethylene ether represented by the following general formula (2). It is preferable to contain 0.01-1.50 mass% with respect to the total solid of a protective layer. Thereby, the ratio of the viscosity at the shear rate of 1 s ^{-1 to} the viscosity at 1000 s ^-1 at a liquid temperature of 25 ° C. of the coating liquid for the protective layer can be easily adjusted to a desired range.

（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、ｍは１〜５の整数を表し、ｎは２〜８の整数を表す。）

(In the formula, m represents an integer of 1 to 5, and n represents an integer of 2 to 8.)

  As the dialkylsulfosuccinate represented by the general formula (1), an alkali metal salt or ammonium salt of a dialkylsulfosuccinate is preferably used, and a sodium salt is particularly preferable. Further, the alkyl group of the dialkyl sulfosuccinate is preferably an alkyl group having 2 to 20 carbon atoms, and more preferably an alkyl group having 4 to 10 carbon atoms. Specific examples include an isobutyl group, a hexyl group, a cyclohexyl group, an octyl group, an isooctyl group, and a 2-ethylhexyl group. Among these, an octyl group or 2-ethylhexyl group having 8 carbon atoms is particularly preferable.

  The perfluoro group of the perfluoroalkyl group-containing polyoxyethylene ether represented by the general formula (2) is preferably a C 2-10 perfluoro group, and more preferably a C 4-8 perfluoro group. . Moreover, as an addition amount of polyoxyethylene ether, 2-8 mol is preferable and 3-7 mol is especially preferable.

  The content of at least one of the dialkyl sulfosuccinate and the perfluoroalkyl group-containing polyoxyethylene ether is preferably 0.01 to 1.50 mass% with respect to the total solid content of the protective layer. Thereby, preferable surface tension can be obtained, curtain film breakage hardly occurs, and at the same time, foaming of the coating liquid is small, and coating defects can be hardly caused. More preferably, it is 0.015-1.20 mass%.

  In the protective layer coating solution, kaolin, calcined kaolin, clay, aluminum hydroxide, calcium carbonate, titanium oxide, colloidal silica, amorphous silica, magnesium carbonate, talc, zinc oxide, synthetic mica, barium sulfate, urea-formalin A pigment such as a resin filler can be contained. Moreover, you may contain water-proofing agents, such as a glyoxal, methylol melamine, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, boric acid, ammonium chloride, and ammonium zirconium carbonate as needed. Furthermore, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, antifoaming agents, water-soluble polyvalent metal salts such as potassium alum and aluminum acetate, benzophenone and triazole UV absorption Various auxiliary agents such as an agent, a fluorescent dye, and a coloring dye can also be contained as appropriate.

The protective layer generally contains water as a medium, for example, a water-soluble adhesive, if necessary, other adhesives, dialkyl sulfosuccinate and at least one perfluoroalkyl group-containing polyoxyethylene ether, a pigment, and an auxiliary agent. The protective layer coating liquid prepared by mixing is formed by coating and drying by a curtain coating method. The coating amount of the protective layer coating solution 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 the coating amount after drying.

  The curtain coating method is a method in which a free-falling curtain film of a coating liquid is formed, and the coating liquid is applied by colliding with a support that travels. Specifically, known methods such as a slide curtain coating method, a couple curtain coating method, a twin curtain coating method, and the like can be employed, and are not particularly limited. Further, 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 support by forming a curtain film.

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

  The coating apparatus used for the curtain coating method is not particularly limited, and examples thereof include an extrusion hopper type curtain coating apparatus, a slide hopper type curtain coating apparatus, and the method described in JP-A-2006-247611.

  If necessary, the protective layer can be formed in multiple layers. In this case, a plurality of protective layers may be simultaneously applied (wet-on-wet) and then dried, or the protective layers may be sequentially laminated by repeating application and drying.

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

  The leuco dye contained in the heat-sensitive recording layer is not limited to these, and two or more kinds can be used in combination. The content of the leuco dye is not particularly limited, and is about 3 to 30% by mass with respect to the total solid content of the heat-sensitive recording layer.

  In the present invention, when the leuco dye is used in a solid fine particle state, water is used as a dispersion medium, modified polyvinyl alcohol such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, sulfone-modified polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, styrene. -In addition to water-soluble polymers such as maleic anhydride copolymer salts and their derivatives, as well as surfactants and antifoaming agents as necessary, by various wet pulverizers such as sand mills, attritors, ball mills, cobo mills, etc. The dispersion liquid is pulverized and dispersed in a dispersion medium, 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 water-soluble polymer as a stabilizer, and then the solvent is evaporated from the emulsion to use the leuco dye as solid fine particles. . In any case, the average particle size of the dispersed particles of the leuco dye used in the solid fine particle state is preferably 0.2 to 3.0 μm, more preferably 0.3 to 1 in order to obtain an appropriate recording sensitivity. 0.0 μm.

  As a method of using the leuco dye in the present invention, in addition to using it in the above-mentioned solid fine particle state, it can also be used as a composite particle comprising an organic polymer and a leuco dye. 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 below. The composite particle is a water-insoluble organic solvent having a boiling point of 100 ° C. or lower, such as a leuco dye and a polymer-forming raw material such as a polyisocyanate compound capable of forming at least one of polyurea and polyurea-polyurethane by polymerization. The organic solvent solution 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 further, if necessary, a reactive substance such as polyamine is mixed. Thereafter, the emulsion dispersion is heated to volatilize and remove the organic solvent, and then the polymer-forming raw material is polymerized, or the leuco dye is dissolved in the polymer-forming raw material. The polymer-forming raw material is polymerized after this solution is emulsified and dispersed to an average particle size of about 0.5 to 3 μm by the above method. It is prepared by.

  Specific examples of the developer contained in the heat-sensitive recording layer include, for example, 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec-butylidenediphenol, and 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'-isopropoxy Diphenyl sulfone, 4-hydroxy-4'- Ryloxydiphenyl sulfone, phenolic compounds such as bis (3-allyl-4-hydroxyphenyl) sulfone, bis (p-hydroxyphenyl) butyl acetate, methyl bis (p-hydroxyphenyl) acetate, 4-hydroxybenzophenone, 4 -Dimethyl hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoate-sec-butyl, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate Phenolic compounds such as 4-hydroxybenzoic acid chlorophenyl and 4,4′-dihydroxydiphenyl ether, or benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-butyl Aromatic carboxylic acids such as lithylic acid, 3-isopropylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids And organic acidic substances such as salts with polyvalent metals such as zinc, magnesium, aluminum and calcium, N- (p-toluenesulfonyl) -N′-3- (p-toluenesulfonyloxyphenyl) urea, N- ( p-toluenesulfonyl) -N ′-(p-butoxycarbonyl) urea, N- (p-toluenesulfonyl) -N′-phenylurea, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, etc. Examples include urea compounds. Among these, 4,4′-isopropylidene diphenol, 4-hydroxy-4′-isopropoxydiphenyl sulfone, 2,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl sulfone, 4,4′-bis It is preferable to use at least one selected from (p-toluenesulfonylaminocarbonylamino) diphenylmethane from the viewpoint of recording a high-quality image.

  In the present invention, the content ratio of the leuco dye and the developer in the heat-sensitive recording layer should be appropriately selected according to the type 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 1 part by mass.

  In the heat-sensitive recording layer coating liquid, auxiliary agents such as surfactants, cross-linking agents, waxes, metal soaps, colored dyes, colored pigments, fluorescent dyes, oil repellents, antifoaming agents and viscosity modifiers are included as necessary. Can be contained.

  Examples of the surfactant include alkylbenzene sulfonates, acetylene glycol compounds, fluorine surfactants, silicon surfactants, phosphate ester surfactants, ether surfactants or betaines, aminocarboxylates And amphoteric surfactants such as imidazoline derivatives.

  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. Examples thereof include acid dihydrazide compounds and inorganic compounds such as ammonium persulfate, ferric chloride, magnesium chloride, sodium tetraborate, potassium tetraborate, boric acid, boric acid triester, boron polymers, and the like. The amount of the crosslinking agent used is preferably in the range of 0.1 to 10% by mass relative to the total solid content of the thermosensitive recording layer.

  Examples of the wax include waxes such as paraffin wax, carnauba wax, microcrystalline wax, polyolefin wax, and polyethylene wax, 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.

  In the present invention, in order to improve the whiteness of the heat-sensitive recording layer and improve the uniformity of the image, a pigment having a high whiteness and an average particle diameter of 10 μm or less can be contained in the heat-sensitive recording layer. For example, inorganic pigments such as 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, styrene microballs, Examples of the organic pigment include nylon powder, polyethylene powder, urea-formalin resin filler, styrene-methacrylic acid copolymer resin, polystyrene resin, and raw starch particles. The pigment content is preferably an amount that does not decrease the color density, that is, 50% by mass or less based on the total solid content of the heat-sensitive recording layer.

  Further, 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 it is generally desirable to adjust in a range of about 4 parts by mass or less with respect to 1 part by mass of the developer.

  In addition, 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.

The heat-sensitive recording layer generally uses water as a medium, and, for example, a leuco dye and a developer, and if necessary, a sensitizer and a storage stabilizer are dispersed together or separately by a pulverizer such as a ball mill, an attritor, or a sand mill. It is formed by coating and drying a coating solution for a heat sensitive recording layer prepared by further mixing an adhesive, a surfactant, and if necessary, an auxiliary agent and a pigment, using the obtained dispersion. The The coating amount of the heat-sensitive recording layer coating composition is not particularly limited, is preferably about 1.0 to 10.0 g / ^{m 2} of the coating amount after drying, more preferably 2.0~7.0g / ^{m 2, 2} .5~6.0g / ^{m 2} is particularly preferred. As an adhesive, it can select from the thing used for the coating liquid for protective layers, for example, and can use it suitably.

  Examples of methods for applying the thermal recording layer coating solution include air knife coating method, blade coating method, gravure coating method, curtain coating method, roll coater coating method, spray coating method, dip coating method, bar coating method, and extrusion coating. Any known coating method such as a method may be used. Among these, the curtain coating method is preferable from the viewpoint of improving the barrier property. Further, when the protective layer is formed on the heat-sensitive recording layer, the heat-sensitive recording layer coating liquid and the protective layer coating liquid can be simultaneously applied in multiple layers by the curtain coating method. As a result, the barrier property of the protective layer can be further enhanced, the production efficiency can be improved, and the energy consumption during production can be reduced. Here, the simultaneous multilayer coating is a method in which two or more layers are coated simultaneously, and includes a method in which the upper layer is coated without drying after the lower layer is coated.

  In the present invention, from the viewpoint of increasing the added value of the product, a multicolor thermosensitive recording material can be obtained. In general, multicolor thermal recording materials are an attempt to utilize the difference in heating temperature or thermal energy, and are generally constructed by sequentially laminating a high-temperature coloring layer and a low-temperature coloring layer that develop colors in different colors on a support. These are roughly classified into two types: decoloring type and additive type, multicolor using a method using microcapsules and composite particles composed of organic polymers and dye precursors such as leuco dyes. There is a method for producing a thermal recording material.

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

  In the present invention, an undercoat layer may be provided between the support and the thermosensitive recording layer. The undercoat layer is formed by applying and drying an undercoat layer coating solution mainly containing a pigment and an adhesive. Such pigments and adhesives can be appropriately selected from those used for the coating liquid for the protective layer. As a method for applying the coating solution for the undercoat layer on the support, an air knife coating method, a blade coating method, a gravure coating method, a roll coater coating method, a curtain coating method, a spray coating method, a dip coating method, a bar coating method, and Any known coating method such as an extrusion coating method may be used.

The undercoat layer in the invention is preferably applied using a blade coating method from the viewpoint of improving the recording image quality. The blade coating method is not limited to a coating method using a blade represented by a bevel type or a vent type, but includes a rod blade coating method, a bill blade coating method, and the like. The coating amount of the undercoat layer coating solution is not particularly limited, and is adjusted in the range of 1 to ²⁰ g / m ² , preferably 3 to 12 g / m ^{2 in} terms of the coating amount after drying.

  Further, from the viewpoint of improving the storage stability by suppressing the permeation of oil and plasticizer from the back surface of the heat-sensitive recording material, and from the viewpoint of curling control, a back surface layer can be provided on the support opposite to the heat-sensitive recording layer.

  Further, after the formation of each layer, smoothing using a known smoothing method such as a super calendar or a soft calendar further improves the recording image quality, and further increases the recording sensitivity of the thermal recording medium. From the viewpoint of obtaining In that case, the heat-sensitive recording layer side may be applied to either a metal roll or an elastic roll of the calendar. For example, a smoothing process can be additionally performed in an arbitrary process such as after the undercoat layer is formed.

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

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Further, “parts” and “%” in the examples indicate “parts by mass” and “% by mass”, respectively, unless otherwise specified. The average particle size was measured using a laser diffraction particle size distribution analyzer SALD2100 (manufactured by Shimadzu Corporation).

Example 1
(Preparation of coating solution for undercoat layer)
Baked kaolin (trade name: Ansilex 90, manufactured by Engelhard) 100 parts, styrene-butadiene copolymer latex (solid content 50%) 40 parts, oxidized starch (trade name: Oji Ace A, manufactured by Oji Cornstarch) A composition comprising 50 parts of a 10% aqueous solution and 150 parts of water was mixed to obtain an undercoat layer coating solution.

(Preparation of leuco dye dispersion (liquid A))
Using a sand mill, a composition comprising 10 parts of 3-dibutylamino-6-methyl-7-anilinofluorane, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water is used until the average particle size becomes 0.4 μm. A leuco dye dispersion was obtained by pulverization.

(Preparation of developer dispersion (liquid B))
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 pulverized using a sand mill until the average particle size became 0.4 μm. A colorant dispersion was obtained.

(Preparation of sensitizer dispersion (liquid C))
A composition comprising 10 parts of di-p-methylbenzyl oxalate, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water is pulverized using a sand mill until the average particle size is 0.4 μm. A dispersion was obtained.

(Preparation of thermal recording layer coating solution)
From 50 parts of 10% aqueous solution of 30 parts of A liquid, 60 parts of B liquid, 30 parts of C liquid, partially saponified polyvinyl alcohol (trade name: PVA-205, polymerization degree 500, saponification degree 88 mol%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) The resulting composition was mixed to obtain a thermal recording layer coating solution.

(Preparation of coating solution for protective layer)
120 parts of kaolin (trade name: UW-90, manufactured by Engelhard) 120% dispersion, 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Z-320, degree of polymerization 1700, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 300 parts of acidic solution, 20 parts of zinc stearate (trade name: Hydrin Z-8-36, solid content concentration 36%, manufactured by Chukyo Yushi Co., Ltd.), 5 parts of 10% aqueous solution of sodium bis (2-ethylhexyl) sulfosuccinate The composition was mixed to obtain a protective layer coating solution.

(Preparation of thermal recording material)
On one side of a high-quality paper having a basis weight of 78 g / m ^2, the undercoat layer coating solution is applied and dried by a blade coating method using a blade coater so that the coating amount after drying is 7 g / m ^2. the layers provided, the heat-sensitive recording layer coating solution on as the coating amount after drying of 5 g / m ² that is provided with a heat-sensitive recording layer was applied and dried by a curtain coating method using a curtain coater, Furthermore, a protective layer is provided by applying and drying at a coating speed of 700 m / min by a curtain coating method using a curtain coater so that the coating amount after drying the coating liquid for the protective layer becomes 3 g / m ^2. After that, a super calendar process was performed to obtain a heat-sensitive recording material.

Example 2
In the preparation of the protective layer coating liquid of Example 1, acetoacetyl-modified polyvinyl alcohol (trade name: Z-320, polymerization degree 1700, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10% aqueous solution instead of 300 parts was used. A thermosensitive recording material was obtained in the same manner as in Example 1 except that 300 parts of a 10% aqueous solution of alcohol (trade name: Z-200, polymerization degree 1100, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used.

Example 3
In the preparation of the coating solution for the protective layer of Example 1, acetoacetyl-modified polyvinyl alcohol (trade name: Z-320, polymerization degree 1700, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10% aqueous solution instead of 300 parts completely saponified polyvinyl alcohol (Product name: PVA117, polymerization degree 1700, manufactured by Kuraray Co., Ltd.) A thermosensitive recording material was obtained in the same manner as in Example 1 except that 300 parts of a 10% aqueous solution was used.

Example 4
In the preparation of the protective layer coating liquid of Example 1, the perfluoroalkyl group-containing polyoxyethylene ether represented by the general formula (2) was used instead of 5 parts of a 10% aqueous solution of sodium bis (2-ethylhexyl) sulfosuccinate. (M = 3, n = 5) A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 5 parts of a 10% aqueous solution was used.

Example 5
In the preparation of heat-sensitive recording material of Example 1, after providing an undercoat layer, a thermal recording layer coating solution and protective layer coating solution, the coating amount after each drying with ^{5g / m 2, 3g / m} 2 Thus, a thermal recording material was obtained in the same manner as in Example 1 except that a thermal recording layer and a protective layer were provided by simultaneous multilayer coating and drying by a curtain coating method using a curtain coater at a coating speed of 600 m / min. It was.

Comparative Example 1
In the preparation of the coating solution for the protective layer of Example 1, instead of 300 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Z-320, polymerization degree 1700, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), completely saponified polyvinyl A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 300 parts of a 10% aqueous solution of alcohol (trade name: PVA105, polymerization degree 500, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used.

Comparative Example 2
In the preparation of the protective layer coating liquid of Example 1, in place of 300 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Z-320, polymerization degree 1700, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), oxidized starch ( A thermosensitive recording material was obtained in the same manner as in Example 1 except that 300 parts of a 10% aqueous solution (trade name: Oji Ace A, manufactured by Oji Cornstarch Co., Ltd.) was used.

Comparative Example 3
In the preparation of the coating solution for the protective layer of Example 3, Example 3 and Example 3 were performed except that 300 parts of a 10% aqueous solution of completely saponified polyvinyl alcohol (trade name: PVA117, polymerization degree 1700, manufactured by Kuraray Co., Ltd.) was replaced with 45 parts. A heat-sensitive recording material was obtained in the same manner.

Comparative Example 4
A thermosensitive recording material was obtained in the same manner as in Example 1 except that in the preparation of the coating solution for the protective layer of Example 1, 5 parts of a 10% aqueous solution of sodium bis (2-ethylhexyl) sulfosuccinate was replaced with 20 parts. .

Comparative Example 5
In the preparation of the coating solution for the protective layer of Example 1, instead of 5 parts of a 10% aqueous solution of sodium bis (2-ethylhexyl) sulfosuccinate, a perfluoroalkylbetaine represented by the following structural formula (1) (trade name: A thermosensitive recording material was obtained in the same manner as in Example 1 except that 5 parts of 10% aqueous solution of Surflon S-131 (manufactured by Seimi Chemical Co., Ltd.) was used.

The viscosity at a shear rate of 1 s ^{−1 and} a viscosity at 1000 s ⁻¹ at a liquid temperature of 25 ° C. of the protective layer coating solution were measured using DAR-100 (manufactured by Relogica Instruments).

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

(Curtain film cut)
The curtain film of the protective layer coating liquid (the film of the coating liquid falling freely) was observed and evaluated according to the following evaluation criteria.
A: No curtain film breakage is observed, and the productivity is remarkably excellent.
○: Curtain film breakage is hardly observed and the productivity is excellent.
X: Curtain film breakage occurs, productivity is inferior, and this is a manufacturing problem.

(Recording quality)
Using a thermal recording simulator (TH-PMD, manufactured by Okura Electric Co., Ltd.), a thermal recording body was recorded at an applied energy of 0.27 mJ / dot, and the image quality of the solid recording portion was visually evaluated according to the following evaluation criteria.
A: Striped unevenness is not observed at all, and the quality is remarkably excellent.
○: Striped unevenness is hardly seen and the quality is excellent.
X: Striped unevenness is observed, the quality is inferior, and this is a practical problem.

  According to the present invention, when a coating liquid for a protective layer is applied to a curtain, a method for producing a heat-sensitive recording material that forms a stable curtain film without causing bubbles and the like and does not cause poor film formation, and is excellent in productivity, quality, and the like. Can be provided.

Claims (4)

In the method for producing a heat-sensitive recording material comprising, in this order, a heat-sensitive recording layer containing at least a leuco dye and a developer on a support, and a protective layer, the coating liquid for the protective layer contains a water-soluble adhesive, The ratio of the viscosity at a shear rate of 1 s ^{−1 to} the viscosity at a shear rate of 1000 s ⁻¹ at a liquid temperature of 25 ° C. of the layer coating solution is 1: 0.30 to 1: 0.80, and at least the protective layer coating A method for producing a thermal recording material, wherein the protective layer is formed by applying and drying a liquid by a curtain coating method.   The thermosensitive recording material according to claim 1, wherein the protective layer coating liquid contains 15 to 50 mass% of polyvinyl alcohol having a polymerization degree of 1000 to 3000 as a water-soluble adhesive with respect to the total solid amount of the protective layer. Method.   The method for producing a heat-sensitive recording material according to claim 2, wherein the polyvinyl alcohol is acetoacetyl-modified polyvinyl alcohol. The protective layer coating solution contains 0.01 to 1.50% by mass of at least one compound represented by the following general formulas (1) and (2) with respect to the total solid content of the protective layer. The manufacturing method of the thermal recording body of any one of Claims 1-3.

(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).

(In the formula, m represents an integer of 1 to 5, and n represents an integer of 2 to 8.)