JP2015036237A - Thermosensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording medium excellent in workability with an auto-labeler without being affected by static electricity under a low humidity environment by obtaining an extremely uniform antistatic layer having coating film strength.SOLUTION: There is provided a thermosensitive recording medium which comprises: a thermosensitive recording layer containing a colorless or pale-colored basic dye and a coloring agent which reacts with a basic dye on one surface of a support; and an antistatic layer on the other surface, wherein the antistatic layer contains at least one selected from smectite clay and hectorite clay and at least one selected from a phosphate and a starch and a derivative thereof and further an adhesive agent layer and a release sheet are provided on the antistatic layer.

Description

  The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that can always perform stable recording without being affected by external conditions such as humidity conditions and recording conditions such as recording speed.

  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 colorant to bring a recording image into contact with both coloring materials by heat. Such a heat-sensitive recording material is relatively inexpensive and has a compact recording device and is relatively easy to maintain, so that it is used in a wide range of fields as a recording medium for facsimiles, printers, and various computers. However, for example, when recording is performed in a low humidity environment, the suitability of passing the recording paper decreases due to frictional charging between the recording device and the recording paper, paper jamming or sticking to the recording device occurs, a thermal head or other There is a problem that circuit breakage, abnormality, malfunction, etc. occur. For this reason, it has been proposed to treat the recording material with various conductive materials such as metal oxides, metal halides, polymer electrolytes, surfactants, hygroscopic materials (see Patent Documents 1 to 4).

  On the other hand, a heat-sensitive recording material excellent in resolution for medical use, a heat-sensitive recording material using a plastic film or a synthetic paper as a support has been proposed for the purpose of using multiple colors or an overhead projector (OHP). When a plastic film is used for the support, the problem due to static electricity is remarkable, and frictional charging is particularly remarkable under low humidity conditions, and the conductive material as described above does not provide a sufficient antistatic effect. When a large amount of a conductive material is used to improve the antistatic performance, the conductivity is increased to some extent, but there is a problem that a background coloring (so-called background fogging) phenomenon that is unnecessary for the heat-sensitive recording material occurs. In the case where the conductive material is a polymer electrolyte, problems such as aggregation occur during the production of the thermosensitive recording material, resulting in a decrease in yield and continuous operability. In order to improve conductivity, use of a metal-based conductive agent has been proposed. However, since the metal body is expensive, it is economically unfavorable, and the metal body has problems such as coloring the heat-sensitive recording medium, and the actual situation is that satisfactory quality is not obtained. In order to solve such problems, it has been proposed to provide an antistatic layer containing smectite clay or hectorite clay, which are clay minerals, in the antistatic layer (see Patent Documents 5 to 7). However, in such an antistatic layer, the coating film strength is inferior and sufficient adhesive label suitability is not obtained at present.

  The heat-sensitive recording material subjected to the pressure-sensitive adhesive label process is used as a heat-sensitive recording label by laminating an adhesive layer and a release mount on the back surface. Due to the recent automation, automatic labelers (automatic labeling machines) are used to automatically wrap trays containing sugar beets and then apply thermal recording labels. However, in winter, when humidity is low, There is a problem that the label is attached to the side of the arm of the auto labeler or the position to apply the label is shifted.

  Smectite clay and hectorite clay can be prepared as a uniform sol or gel-like coating solution up to a concentration of about 10% in water, and can form an antistatic layer having excellent conductivity when applied to a support and dried. Is possible. However, when smectite clay or hectorite clay is prepared as an aqueous dispersion coating solution and applied to a support by continuous operation, the viscosity partially increases due to fluctuations in the concentration of the coating solution resulting from continuous operation. Aggregates resulting from clay components are generated, and there is a problem that, for example, bar stripes and coating unevenness occur in a coating process such as bar coating. When such a problem occurs, the actual situation is that operations with poor production efficiency such as remaking the coating liquid and lowering the coating speed are being carried out.

JP-A-57-148687 JP 57-156292 A JP-A-57-170794 JP-A-57-199687 JP-A-2-139279 JP-A-2-214689 Japanese Patent No. 2815954

  The main object of the present invention is to provide a heat-sensitive recording material which is excellent in coating strength and is not affected by static electricity in a low-humidity environment by obtaining an extremely uniform antistatic layer and excellent in workability with an auto labeler. Objective.

  As a result of intensive studies in view of the above prior art, the present inventors have provided a thermosensitive recording layer on one side of the support, and the other side (hereinafter also referred to as the back side of the support or simply referred to as the back side). By providing a specific antistatic layer, the above-mentioned problems have been solved. That is, the present invention relates to the following thermal recording material.

  Item 1: A thermosensitive recording layer comprising a colorless or light-colored basic dye and a colorant that reacts with the basic dye on one side of the support, and an antistatic layer on the other side In the recording medium, the antistatic layer contains at least one selected from smectite clay and hectorite clay, phosphate, and at least one selected from starch and derivatives thereof, and further includes an adhesive on the antistatic layer. A heat-sensitive recording material comprising a layer and a release sheet.

  Item 2: The thermal recording according to Item 1, wherein a mass ratio of at least one selected from the smectite clay and hectorite clay to at least one selected from starch and derivatives thereof is 90:10 to 70:30. body.

  Item 3: The thermal recording material according to Item 1 or 2, wherein a mass ratio between the phosphate and at least one selected from starch and derivatives thereof is 1:99 to 55:45.

  Item 4: The thermal recording material according to any one of Items 1 to 3, which is used for an auto labeler.

  The heat-sensitive recording material of the present invention is excellent in coating film strength and provides a very uniform antistatic layer. For this reason, it is excellent in adhesive label suitability, is not affected by static electricity in a low humidity environment, and has excellent workability with an auto labeler.

  The antistatic layer in the present invention contains at least one selected from smectite clay and hectorite clay, phosphate, and at least one selected from starch and derivatives thereof.

  The smectite clay and hectorite clay used in the antistatic layer of the present invention are crystalline clay minerals, belonging to an unlimited expansion group having a three-layer structure, and there are natural products and synthetic products, both of which are in the present invention. It can be preferably applied.

Smectite clays, for example, the following equation, _{[(Si 8-a Al a)} (Mg 6-b Al b) · O 20 (OH) 4 ] ^- · ^M _{+ a-b} (Remark; ^{M +} is almost all Na ⁺ And ab> 0).

Hectorite clay is, for example, the following formula: [(Si ₈ (Mg _5.34 Li _0.66 ) O ₂₀ (OH, F) ₄ )] M ⁺ _0.66 (Remarks; M ⁺ is almost all Na ⁺ . )), And commercially available products such as Laponite B and Laponite S manufactured by Rockwood are known.

In addition, the following formula in which the central layer is all hydroxyl groups, [(Si ₈ (Mg _5.34 Li _0.66 ) O ₂₀ (OH) ₄ )] M ⁺ _0.66 (Remarks; M ⁺ is always Na ⁺ Examples of the hectorite clay displayed in the above are Laponite RD, Laponite RDS, Laponite XLG, Laponite XLS, etc. manufactured by Rockwood.

  Laponite as described above is a white powder, and when added to water, Laponite B, RD, and XLG easily form a gel, and Laponite S, RDS, and XLS easily form a sol. For example, in the case of laponite, the thickness of each layer of the crystal structure is about 1 nm and extends in two dimensions to form a platelet. The magnesium atom present in this platelet unit is isomorphously substituted with the lithium atom of the lower valence cation, and the platelet unit is negatively charged, but in the dry state, this negative charge is the lattice of the plate surface. It is balanced with a replaceable cation (usually a sodium ion) outside the structure. When this laponite is dispersed in deionized water at a concentration of 1.5 to 2.0 mass%, the replaceable cation outside the lattice structure is ionized and diffuses from the platelet surface, and the platelet surface is negative. The charge is repelled and repels each other to form a platelet unit or a dispersed colloidal dispersion, ie, a sol. The dispersed platelet has a negative charge inherent to the whole, and the edge of the platelet has a small local charge due to ion adsorption from the surrounding medium. This depends on the type and concentration of ions in the solution and the pH of the medium, but usually only cations are adsorbed and the edges are positively charged. As a result, end-to-face bonds occur to form a typical “card house” structure and form a gel. The strength of this gel depends on the concentration of laponite. When the concentration is low, a relatively loose particle chain network is formed and the gel strength is low, but as the concentration increases, the particle chain network is filled. Increase rapidly.

  When laponite having such properties is used for the coating solution of the antistatic layer, it has an appropriate viscosity even at a low concentration in the coating process, has little surface disturbance on the support, and can easily control the coating surface. And adhesion is relatively good. Moreover, since it has a replaceable ion, it is considered that it has excellent conductivity not only in a normal humidity environment but also in a low humidity environment.

  The smectite clay and hectorite clay can be prepared as a uniform sol or gel coating solution up to a concentration of about 10% in water, and exhibit excellent conductivity when applied to a support and dried. However, when smectite clay or hectorite clay is simply prepared as an aqueous dispersion coating solution on the support and applied, the dispersion stability in water is low, and precipitates due to aggregation tend to occur. There is a problem of causing application defects such as bar streaks and uneven coating in the application process.

  In the present invention, by adding a phosphate as a dispersant in the aqueous dispersion of the smectite clay or hectorite clay, the dispersion state of the smectite clay or hectorite clay in water is stabilized, and the precipitates due to aggregation are dispersed. Generation | occurrence | production can be suppressed and the stable dispersion liquid can be prepared.

  Examples of the phosphate used in the present invention include monobasic sodium phosphate, dibasic sodium phosphate, tribasic sodium phosphate, sodium pyrophosphate, acidic sodium pyrophosphate, sodium tripolyphosphate, sodium tetrapolyphosphate, sodium hexametaphosphate , Acidic sodium hexametaphosphate, or potassium, calcium and magnesium salts thereof. In particular, a sodium salt can be preferably used as a phosphate in the present invention because it is inexpensive and easy to produce.

  In the present invention, the addition amount of these phosphates is not particularly limited, but is preferably 0.1 to 20 parts by mass with respect to at least one total of 100 parts by mass selected from smectite clay and hectorite clay. More preferably, 1 to 15 parts by mass, and still more preferably about 5 to 15 parts by mass are used.

  In addition, other dispersants can be used in combination as long as the effects of the present invention are not impaired.

  In the present invention, by using at least one selected from starch and derivatives thereof as a water-soluble resin in the antistatic layer, it is possible to develop an appropriate water retention in the coating liquid and form a uniform coated surface at the time of coating. And a highly uniform antistatic layer with little coating unevenness can be obtained. Moreover, it is excellent in the effect which prevents the cohesive failure of an antistatic layer as a binder of a smectite clay or hectorite clay, can improve the adhesiveness with the support body of an antistatic layer, and can raise coating-film intensity | strength.

  Specific examples of starch and its starch derivatives include, for example, untreated starch, oxidized starch, starch acetate, phosphate esterified starch, acetylated starch, etherified starch, cationized starch, carbamate esterified starch, and carboxymethylated. Examples include starch, carboxyethylated starch, hydroxyethylated starch, hydroxypropylated starch, dextrin, grafted starch, and cross-linked starch.

  Among these, oxidized starch is excellent in the binder effect and has an appropriate water retention property, so that the applicator roll can be used during continuous operation of thin film coating by a roll coater having countless fine cracks on the applicator roll surface described later. There is no problem due to the occurrence of clogging of fine cracks, and the adhesive strength after drying is sufficient, so that it is preferably used.

In addition, the antistatic layer in the present invention includes cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, polyacrylic acid soda, polyvinyl alcohol, polyvinylpyrrolidone, and acrylic acid amide as long as the effects of the present invention are not impaired. -Highly water-soluble such as acrylic acid ester copolymer, acrylic acid amide-acrylic acid ester-methacrylic acid ternary copolymer, styrene-maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein Molecular materials, polyvinyl acetate, polyurethane, styrene-butadiene copolymer, polyacrylic acid, polyacrylate ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer Body, and styrene - butadiene - may be used in combination with latexes such hydrophobic polymer such as an acrylic copolymer.

The antistatic layer in the present invention, for example, using water as a dispersion medium, at least one selected from the above smectite clay and hectorite clay, at least one selected from phosphate, starch, and derivatives thereof, if necessary. The coating solution for an antistatic layer prepared by mixing various auxiliaries is preferably about 0.1 to 10 g / m ² , more preferably 0.1 to 5 g / m ^{2 by} weight after drying on the back surface of the support. m ² approximately, is further preferably applied and dried such that 0.2-5 g / ^{m 2} approximately formed. As the auxiliary agent, known substances such as pigments, antifoaming agents, wetting agents, preservatives, thickeners and the like can be used.

  In the antistatic layer in the present invention, the mass ratio of at least one selected from smectite clay and hectorite clay to at least one selected from starch and derivatives thereof is preferably 90:10 to 70:30. 85:15 to 75:25 is more preferable. Moreover, it is preferable that the mass ratio of a phosphate and at least 1 sort (s) chosen from starch and its derivative (s) is 1: 99-55: 45, and it is more preferable that it is 10: 90-50: 50. Accordingly, at least one selected from smectite clay and hectorite clay is preferably 40 to 90% by mass, more preferably 50 to 90% by mass, and still more preferably 65 to 85% by mass in the total solid content of the antistatic layer. It can be blended with a high degree, and sufficient conductivity can be exhibited with a low coating amount. Moreover, even if it is highly blended, the stability of the dispersion liquid is not impaired, and a coated surface free from foreign matter and streak-like coating defects can be obtained effectively. Although it is not clear about this reason, it is considered that water retention can be effectively improved by the interaction between phosphate and at least one selected from starch and derivatives thereof.

  In the present invention, the antistatic layer coating solution is applied by a coating method such as a slot die, a slide bead, a curtain, an air knife, a blade, a gravure, a bar, a rod, or a roll coater. Among these, a roll coater in which a coating liquid is applied to a rotating roll and the coating liquid applied to the roll is applied to a support is preferably used because the coating liquid loss and the amount of defects generated during application are small. In particular, a reverse roll coater is preferable from the viewpoint of uniformly applying a thin film in high-speed coating. Furthermore, a roll coater provided with an applicator roll having innumerable cracks having a width of 1 to 10 μm on the surface is preferable as a coating method of the present invention from the viewpoint of more uniformly coating a thin film. The crack width is a value obtained by measuring the average value of the crack width from ten photographs taken at a magnification of 1000 times on the surface.

  In the present invention, an antistatic layer can be formed on the other surface in an arbitrary process of forming each layer including the thermosensitive recording layer on one surface of the support. In the method of manufacturing a heat-sensitive recording material in a wound state, an antistatic layer is formed from the viewpoint of suppressing peeling electrification on the support side and preventing scumming stains due to dust and the like adhering to the recording surface and white spots of printing. After that, it is preferable to form a heat-sensitive recording layer.

  The support in the present invention is, for example, a paper support such as high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, glassine paper, and resin-laminated paper, polyolefin-based synthetic paper, synthetic paper, etc. Supports such as fiber paper, nonwoven fabric, and synthetic resin film can be used. Among these, in the present invention, it is preferable to use a paper support from the viewpoint of excellent adhesion to starch and derivatives thereof contained in the antistatic layer.

  The support preferably has an air permeability of 50 seconds or less. In the present invention, the lower the air permeability (the smaller the numerical value), the higher the absorbability of the coating liquid and the sufficient penetration of the coating liquid into the support. By reducing coating defects such as unevenness, a more uniform antistatic layer can be obtained. For this reason, it is also possible to apply a coating liquid containing smectite clay or hectorite clay at high speed, and a sufficient application amount can be obtained even at high speed application, further increasing the application speed. be able to. In addition, as described above, the antistatic layer coating liquid is excellent in water retention, and therefore, the speed at which water in the coating liquid permeates into the paper can be suppressed, and the occurrence of paper breakage due to wet tension breakage can be effectively suppressed. In general, when a paper support is used as the support, the air permeability can be adjusted, for example, by changing the freeness of pulp constituting the base paper, the addition rate of ash such as filler, and the like. To adjust the air permeability to 50 seconds or less, the pulp C.I. S. The F freeness is preferably 400 ml or more. Here, the air permeability is the Oken air permeability measured according to JIS P 8117: 2009.

The heat-sensitive recording layer of the present invention contains a basic dye, a colorant, a binder and the like. Examples of the basic dye include various known colorless or light-colored basic dyes. For example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1 , 2-Dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindole-3) -Yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) ) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1) Triarylmethane dyes such as methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4′-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucooramine, N-2,4 Diphenylmethane dyes such as 1,5-trichlorophenyl leucooramine, thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl- Spiro dyes such as spiro-dinaphthopyrans, 3-benzyl-spiro-dinaphthopyrans, 3-methyl-naphtho- (6′-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B anilinolactam, rhodamine ( p-Nitroani Lino) lactam, lactam dyes such as rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3- Diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N-ethyl-p-toluidino) -7-methylfluor Oran, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7- N-methyl-N-benzylaminofluorane, 3-diethylamino- -N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- ( N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (2-carbomethoxy-anilino ) Fluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl- 7-anilinofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7- (o-chloroani C) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-pyrrolidino-6-methyl-7-p-butylanilinofluorane, 3-diethylamino-7- (o-fluoroanilino) fluorane 3-dibutylamino-7- (o-fluoroanilino) fluorane, 3- (N-methyl-Nn-amyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl- N-n-amyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-iso-amyl) amino-6-methyl-7-anilinofluorane, 3- (N- Methyl-Nn-hexyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-Nn-hexyl) amino-6-methyl-7-anilinofluorane, 3- ( N-e And fluorane dyes such as til-N-β-ethylhexyl) amino-6-methyl-7-anilinofluorane. In addition, these basic dyes can use 2 or more types together as needed.

Examples of the colorant include inorganic or organic acidic substances that are colored by contact with the basic dye when heated. For example, 4-tert-butylphenol, α-naphthol, β-naphthol, 4-acetylphenol, 4-phenylphenol, hydroquinone, 4,4′-isopropylidenediphenol (bisphenol A), 2,2′-methylenebis (4 -Chlorophenol), 4,4'-cyclohexylidene diphenol, 1,3-di [2- (4-hydroxyphenyl) -2-propyl] benzene, 4,4'-dihydroxydiphenyl sulfide, bis (3-allyl) -4-hydroxyphenyl) sulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, hydroxynon monobenzyl ether, 4-hydroxybenzophenone, 2 , 4-Dihydroxy Benzophenone, 2,4,4′-trihydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea, 4 , 4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, dimethyl 4-hydroxyphthalate, 4-hydroxy Methyl benzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoate-sec-butyl, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, 4 -Tolyl hydroxybenzoate, 4-H Chlorophenyl droxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-p-chlorobenzyl, 4-hydroxybenzoic acid-p-methoxybenzyl, novolak type phenolic resin, phenol polymer Phenolic compounds such as benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5- Dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid 3,5-di-t aromatic carboxylic acids such as rt-butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and Examples thereof include organic acidic substances such as salts with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel. Of course, these colorants can also be used in combination of two or more as required.

  The use ratio of the basic dye and the colorant is appropriately selected according to the type of the basic dye and the colorant used, and is not particularly limited, but is generally 1 part by mass of the basic dye. 1 to 20 parts by weight, preferably about 2 to 10 parts by weight of the colorant is used.

  The heat-sensitive recording layer coating solution containing a basic dye and a colorant generally uses water as a dispersion medium, agitation such as a ball mill, an attritor or a sand mill, and a basic dye and a colorant together with a pulverizer, or It is prepared using a dispersion obtained by dispersing separately.

  In the heat-sensitive recording layer coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, Silicon-modified polyvinyl alcohol, diisobutylene-maleic anhydride copolymer salt, styrene-maleic anhydride copolymer salt, ethylene-acrylic acid copolymer salt, styrene-acrylic acid copolymer salt, styrene-butadiene copolymer Emulsions, urea resins, melamine resins, amide resins and the like are used in an amount of about 2 to 40% by mass, preferably about 5 to 25% by mass, based on the total solid content of the thermosensitive recording layer.

  Furthermore, various auxiliary agents can be added to the coating solution for the heat-sensitive recording layer as necessary. For example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, lauryl alcohol sulfate-sodium salt, fatty acid metal salt, etc. A dispersing agent, a benzophenone-based ultraviolet absorber, other antifoaming agents, fluorescent dyes, colored dyes and the like are appropriately added.

  In addition, if necessary, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, stearic acid amide, stearic acid methylenebisamide, palmitic acid amide, coconut fatty acid amide and other fatty acid amides, Hindered phenols such as 2,2′-methylenebis (4-methyl-6-tert-butylphenol) and 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane; UV absorbers such as-(2'-hydroxy-5'-methylphenyl) benzotriazole and 2-hydroxy-4-benzyloxybenzophenone, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxy Ethane, 1-phenoxy-2- (4- Tilphenoxy) ethane, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, p-benzylbiphenyl, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, etc. Esters may be added to various known heat-fusible substances and inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, activated clay and the like. Moreover, a normal electroconductive substance can also be added in the range which does not impair the desired effect of this invention.

In the thermosensitive recording material of the present invention, the method for forming the thermosensitive recording layer is not particularly limited. For example, the coating solution for the thermosensitive recording layer is applied to one surface of the support by bar coating, air knife coating, blade coating or the like. It is formed by a method of applying and drying. The coating amount is not particularly limited, and is usually adjusted in the range of about 1 to ²⁰ g / m ² , more preferably about ² to 10 g / m ² in terms of dry weight.

  In the present invention, a protective layer may be provided on the thermosensitive recording layer. As a result, it is possible to improve the recording running property, the anti-friction fog property, the chemical resistance and the like.

The protective layer is, for example, a coating amount for the protective layer prepared by mixing water, a binder, and optionally a pigment, a crosslinking agent, a wax, a lubricant, etc. to 10 g / ^{m 2,} more preferably about formed by applying and drying a heat-sensitive recording layer so that 1 to 5 g / ^{m 2.} The binder can be appropriately selected from those that can be used for the thermal recording layer coating liquid.

In the present invention, an undercoat layer can be provided between the support and the heat-sensitive recording layer as necessary. Thereby, the recording sensitivity can be further increased. The undercoat layer is an undercoat layer coating solution containing an oil-absorbing pigment having an oil absorption of 70 ml / 100 g or more, particularly about 80 to 150 ml / 100 g, and / or organic hollow particles, and / or thermally expandable particles, and a binder. It is formed by coating and drying on a support. Here, the oil absorption is a value determined according to the method described in JIS K 5101. The coating amount of the undercoat layer coating solution is preferably about 3 to ²⁰ g / m ² by dry weight, and more preferably about 4 to 12 g / m ² .

  The binder in the undercoat layer can be appropriately selected from those that can be used for the heat-sensitive recording layer. Among these binders, starch-vinyl acetate graft copolymer, polyvinyl alcohol, styrene-butadiene latex and the like are preferable.

  Furthermore, in the present invention, after forming any one of the heat-sensitive recording layer, the antistatic layer, the undercoat layer provided if necessary, and the protective layer, or after completing the formation of all the layers, the super calender is used. Smoothing processing can also be performed.

  The heat-sensitive recording material of the present invention comprises a heat-sensitive recording layer on one surface and an antistatic layer on the other surface, and is further subjected to pressure-sensitive adhesive label processing so that an adhesive layer and a release sheet are provided on the antistatic layer. I have. The pressure-sensitive adhesive used in the present invention is not particularly limited. For example, the main component is a rubber-based material such as natural rubber, styrene-butadiene rubber, polyisobutylene rubber, or isoprene rubber, and the main component is a vinyl ether-based material. And those mainly composed of an acrylic material such as a copolymer having 2-ethylhexyl acrylate as the main monomer, and those mainly composed of rubbery siloxane and resinous siloxane. These can be used as emulsions, various solvents or solventless adhesives.

  The pressure-sensitive adhesive may be applied directly on the antistatic layer to provide a pressure-sensitive adhesive layer, or after the pressure-sensitive adhesive is applied to the release agent surface of the release sheet to provide a pressure-sensitive adhesive layer, the pressure-sensitive adhesive is applied on the antistatic layer. The adhesive layer may be transferred and provided. In either case, a release sheet is bonded to the pressure-sensitive adhesive layer in order to prevent unnecessary adhesion except when it is used, and it is peeled off if desired.

The release sheet is a high-density base paper such as glassine paper, clay-coated paper, kraft paper, or release base paper such as polylaminate paper in which polyethylene is laminated on high-quality paper, etc., and fluorine resin or silicone resin as a release agent And the like having a peel surface attached in a range of about 0.05 to 3 g / m ² by dry weight. For example, a roll coater, a knife coater, a bar coater, a slot die coater or the like is used as a method for applying the pressure-sensitive adhesive, and the coating amount is adjusted in a range of about 5 to 50 g / m ² by dry weight.

  The heat-sensitive recording material having a specific antistatic layer in the present invention has a high antistatic layer coating strength, and therefore there is no risk that the antistatic layer peels off together with the release sheet even with a pressure sensitive adhesive. No adhesive residue after peeling and excellent adhesive label suitability regardless of adhesive. In addition, when using an auto labeler, there is no problem that the label sticks to the side of the arm of the auto labeler due to the influence of static electricity in a low humidity environment in winter, or the position where the label is stuck is shifted. In particular, it is preferably used in an auto labeler having a label feeding speed of 3 m / min or more, which easily causes peeling charging and picking of the antistatic layer when the peeling speed is increased, because the effects of the present invention can be exhibited without regret.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “part” and “%” indicate “part by mass” and “% by mass”, respectively.

  The average particle size of the dispersions used in Examples and Comparative Examples was measured using a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation).

Example 1
・ Preparation of paper support In a pulp slurry containing 25 parts of NBKP (C.S.F. 550 ml) and 75 parts of LBKP (C.S.F. 560 ml), kaolin as a filler is reduced to 5.0%. Furthermore, the rosin size as a sizing agent was added to 1.5% and 2.0% of aluminum sulfate with respect to the absolutely dry pulp to obtain a paper stock. This stock was made with a long mesh multi-cylinder cylinder dryer and processed with a 4-stage super calender to obtain a paper support of 58 g / m ² . This paper support had a Oken air permeability of 10 seconds.

-Preparation of undercoat layer coating solution Fine hollow particles (trade name: Ropaque SN-1055) were dispersed in a dispersion obtained by dispersing 60 parts of calcined kaolin (trade name: Ansilex 93, manufactured by BASF) in 80 parts of water. , 75 parts by Rohm & Haas, solid content 26.5%), 31 parts styrene / butadiene latex (trade name: L-1571, solid content 48% by Asahi Kasei Chemicals) and carboxymethylcellulose (product) Name: Serogen 7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2.5 parts, similarly, a composition comprising 1 part of carboxymethyl cellulose (trade name: Serogen AG gum, Daiichi Kogyo Seiyaku Co., Ltd.) and 15.5 parts of water are mixed. By stirring, a coating solution for undercoat layer was obtained.

Preparation of liquid A (leuco dye dispersion) 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane 10 parts, 5 parts of 5% aqueous solution of methylcellulose, and 40 parts of water The composition was pulverized with a sand mill until the average particle size became 1 μm to obtain Liquid A.

-Preparation of liquid B (coloring agent dispersion) A composition consisting of 30 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water was mixed with an average particle diameter of 1 [mu] m using a sand mill. The liquid B was obtained by pulverizing.

-Preparation of liquid C (sensitizer dispersion) 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 averaged in a sand mill. C liquid was obtained by pulverizing to 1.5 μm.

-Preparation of coating solution for heat-sensitive recording layer A composition comprising 55 parts of liquid A, 115 parts of liquid B, 80 parts of liquid C, 80 parts of a 10% aqueous solution of polyvinyl alcohol, and 35 parts of calcium carbonate was mixed and stirred to produce a heat-sensitive recording layer. A coating solution was obtained.

-Preparation of coating liquid for protective layer 200 parts of 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol, 100 parts of kaolin (trade name: UW-90, manufactured by BASF), 30 parts of 30% aqueous dispersion of zinc stearate, and water A composition comprising 100 parts was mixed and stirred to obtain a protective layer coating solution.

-Preparation of coating solution (I) for antistatic layer 8 parts aqueous solution of oxidized starch (trade name: Ace C, manufactured by Oji Cornstarch Co., Ltd.), sodium pyrophosphate (trade name: Nankaline S1, manufactured by Phosphor Chemical Industries Co., Ltd.) 6 A composition comprising 45 parts of synthetic hectorite clay (trade name: Laponite B, manufactured by Rockwood) and 650 parts of water was mixed and stirred to obtain an antistatic layer coating liquid (I).

-Preparation of thermosensitive recording material Using a rolled paper support made of fine paper, the coating amount after drying the antistatic layer coating liquid (I) on the back surface of the paper support is 0.5 g / m ^2. In order to form an antistatic layer by applying and drying at a coating speed of 500 m / min by a reverse roll coater in which an infinite number of cracks having a crack width of 3 μm exist on the surface of the applicator roll, the film was once wound around a winder. . Further, by using the roll-shaped paper support on which the antistatic layer is formed, the surface of the paper support (the surface opposite to the antistatic layer of the paper support) is undercoated from the side close to the support. The coating amounts after drying in the order of the layer coating solution, the thermal recording layer coating solution, and the protective layer coating solution were 6.0 g / m ² , 4.5 g / m ² , and 2.0 g / m ² , respectively. It was applied and dried to form an undercoat layer, a heat-sensitive recording layer, and a protective layer, and the surface of the protective layer was smoothed with a super calender to obtain a rolled-up heat-sensitive recording material before processing an adhesive label. .

-Adhesive label processing Acrylic resin-based adhesive latex for low-temperature adhesion having a solid content concentration of 25% on a 65 g / m ² release sheet (glassine paper) coated with 1.0 g / m ^{2 of} silicone release agent and dried (trade name) : Acryset PS-5108 (manufactured by Nippon Shokubai Co., Ltd.) was applied and dried so that the coating amount after drying was 20 g / m ² to form a pressure-sensitive adhesive layer. This release sheet was bonded so that the antistatic layer and the pressure-sensitive adhesive layer were in contact with each other, and a heat-sensitive recording material after pressure-sensitive adhesive label processing further provided with the pressure-sensitive adhesive layer and the release sheet was obtained.

Example 2
In the preparation of the coating solution (I) for the antistatic layer of Example 1, instead of 45 parts of synthetic hectorite clay, 45 parts of synthetic smectite clay (trade name: Smecton SA-1, manufactured by Kunimine Kogyo Co., Ltd.) was used. Obtained the heat-sensitive recording material after pressure-sensitive adhesive label processing in the same manner as in Example 1.

Example 3
-Preparation of coating solution (II) for antistatic layer: 8 parts aqueous solution of oxidized starch (trade name: Ace C, manufactured by Oji Cornstarch Co., Ltd.), sodium pyrophosphate (trade name: Nankaline S1, manufactured by Phosphor Chemical Industries Co., Ltd.) 3 The composition consisting of 60 parts of synthetic hectorite clay (trade name: Laponite B, manufactured by Rockwood) and 800 parts of water was mixed and stirred to obtain an antistatic layer coating liquid (II).

-Preparation of thermosensitive recording material Example 1 except that the above antistatic layer coating solution (II) was used in place of the antistatic layer coating solution (I) in the preparation of the thermosensitive recording material of Example 1. In the same manner as above, a heat-sensitive recording material after processing of the adhesive label was obtained.

Example 4
-Preparation of coating solution (III) for antistatic layer 8 parts aqueous solution of oxidized starch (trade name: Ace C, manufactured by Oji Cornstarch Co., Ltd.) 110 parts, sodium pyrophosphate (trade name: Nankaline S1, manufactured by Phosphorus Chemical Industries) 5 A composition comprising 35 parts of synthetic hectorite clay (trade name: Laponite B, manufactured by Rockwood) and 500 parts of water was mixed and stirred to obtain an antistatic layer coating liquid (III).

-Preparation of thermosensitive recording material Example 1 except that the above antistatic layer coating solution (III) was used in place of the antistatic layer coating solution (I) in the preparation of the thermosensitive recording material of Example 1. In the same manner as above, a heat-sensitive recording material after processing of the adhesive label was obtained.

Example 5
In the production of the paper support of Example 1, the pulp freeness was changed, except that 75 parts of LBKP (C.S.F. 410 ml) was used instead of 75 parts of LBKP (C.S.F. 560 ml). In the same manner as in Example 1, a heat-sensitive recording material after processing of the adhesive label was obtained. The paper support was Oken type air permeability of 50 seconds.

Example 6
-Preparation of coating solution (IV) for antistatic layer 8 parts aqueous solution of oxidized starch (trade name: Ace C, manufactured by Oji Cornstarch Co., Ltd.), sodium pyrophosphate (trade name: Nankaline S1, manufactured by Phosphorus Chemical Industries) 9 A composition comprising 92 parts of synthetic hectorite clay (trade name: Laponite B, manufactured by Rockwood) and 1162 parts of water was mixed and stirred to obtain a coating solution (IV) for an antistatic layer.

-Preparation of thermosensitive recording material Example 1 except that the antistatic layer coating solution (IV) was used in place of the antistatic layer coating solution (I) in the preparation of the thermosensitive recording material of Example 1. In the same manner as above, a heat-sensitive recording material after processing of the adhesive label was obtained.

Example 7
-Preparation of coating solution (V) for antistatic layer 8% aqueous solution of oxidized starch (trade name: Ace C, manufactured by Oji Cornstarch), sodium pyrophosphate (trade name: Nankaline S1, manufactured by Rin Chemical Industry Co., Ltd.) 7 A composition comprising 65 parts of synthetic hectorite clay (trade name: Laponite B, manufactured by Rockwood) and 828 parts of water was mixed and stirred to obtain an antistatic layer coating liquid (V).

Production of thermosensitive recording material Example 1 except that the above antistatic layer coating solution (V) was used in place of the antistatic layer coating solution (I) in the production of the thermosensitive recording material of Example 1. In the same manner as above, a heat-sensitive recording material after processing of the adhesive label was obtained.

Comparative Example 1
In the production of the heat-sensitive recording material of Example 1, a heat-sensitive recording material after processing of the pressure-sensitive adhesive label was obtained in the same manner as in Example 1 except that the back surface of the paper support was processed without providing an antistatic layer. It was.

Comparative Example 2
In the preparation of the coating solution (I) for the antistatic layer of Example 1, an 8% aqueous solution of polyvinyl alcohol (trade name) was used instead of 100 parts of an 8% aqueous solution of oxidized starch (trade name: Ace C, manufactured by Oji Cornstarch). : PVA117, manufactured by Kuraray Co., Ltd.) Except for using 100 parts, a heat-sensitive recording material after pressure-sensitive adhesive label processing was obtained in the same manner as in Example 1.

Comparative Example 3
In the preparation of the coating solution (I) for the antistatic layer of Example 1, the same procedure as in Example 1 was conducted except that 5 parts of polyoxyethylene distearate was used as a dispersant instead of 5 parts of sodium pyrophosphate. A heat-sensitive recording material after processing of the adhesive label was obtained.

  The following evaluation was performed about the heat-sensitive recording body before and after processing of the pressure-sensitive adhesive label thus obtained. The results were as shown in Table 1.

(Reverse coating defect)
In the production of the above thermal recording material, the antistatic coating liquid was applied to the back surface of a paper support having a width of 500 mm at a coating speed of 500 m / min and dried at a length of 10,000 m, and then generated on the back surface. Foreign matters and streak defects were visually observed and evaluated according to the following criteria.
(Double-circle): There is no generation | occurrence | production of a foreign material and a streak defect, and it is satisfactory.
○: Almost no foreign matter or streak defects are generated.
(Triangle | delta): Although a foreign material and a streak defect are scattered, it is satisfactory practically.
X: The occurrence of foreign matter and streak defects is significant, which is a problem.

(Roll clogging)
In the preparation of the above-mentioned thermal recording material, an antistatic coating liquid was applied to the back surface of a paper support having a width of 500 mm at a coating speed of 500 m / min and a length of 10,000 m, and then an antistatic layer coating liquid. The condition of wettability to the applicator roll due to clogging of the applicator roll surface of the reverse roll coater was visually observed and evaluated according to the following criteria.
A: The wettability of the applicator roll is in a very good state and there is no problem.
○: The wettability of the applicator roll is slightly reduced, but there is no problem.
Δ: The wettability of the applicator roll is reduced over the entire width of the paper, but at a level that does not cause a problem.
X: The wettability of the applicator roll is remarkably lowered and clogging occurs on the entire surface, which is a problem.

(Reverse electrical resistance)
The above-mentioned heat-sensitive recording material before processing the pressure-sensitive adhesive label was cut into a sheet shape, and the electrical resistance value of the back surface (the surface of the antistatic layer) was measured under the following conditions and evaluated according to the following criteria.
Measuring equipment: HP4339B HIGHRESISTANCE METER made by HP
Measurement method: 100 V, 30 sec, 5 kg load Measurement environment: 10 ° C., 10% RH
○: The electrical resistance value on the back surface is less than 10 ¹⁴ Ω, and there is no problem.
X: The electrical resistance value on the back surface is 10 ¹⁴ Ω or more, which is a problem.

(Auto labeler suitability)
About the thermosensitive recording material after the above-mentioned adhesive label processing, the label feeding speed is 3 m / min on the automatically lapped tray using an auto labeler (AL-EMZ: manufactured by Ishida Co., Ltd.) in an environment of 23 ° C. and 10% RH. 10 sheets were continuously labeled at 4 m / min and 5 m / min.
○: All the labels are labeled at a predetermined position, and there is no problem.
Δ: Although there was a slight misalignment, almost all labels were labeled at a predetermined position, and there was no practical problem.
X: Large positional deviation or labeling may not be possible, which is a practical problem.

  The heat-sensitive recording material of the present invention is excellent in coating film strength and has an extremely uniform antistatic layer. For this reason, it is excellent in adhesive label suitability, is not affected by static electricity in a low humidity environment, and has excellent workability with an auto labeler in high-speed recording. It can be used in various fields as various thermal recording labels.

Claims (4)

  In a thermosensitive recording medium comprising a thermosensitive recording layer containing a colorless or light-colored basic dye and a colorant that reacts with the basic dye on one side of the support, and an antistatic layer on the other side. The antistatic layer contains at least one selected from smectite clay and hectorite clay, phosphate, and at least one selected from starch and derivatives thereof, and further peels from the adhesive layer on the antistatic layer. A heat-sensitive recording material comprising a sheet.   The thermosensitive recording material according to claim 1, wherein a mass ratio of at least one selected from smectite clay and hectorite clay to at least one selected from starch and derivatives thereof is 90:10 to 70:30.   The heat-sensitive recording material according to claim 1 or 2, wherein a mass ratio of the phosphate to at least one selected from starch and derivatives thereof is 1:99 to 55:45.   The heat-sensitive recording material according to any one of claims 1 to 3, which is used for an auto-traveller.