JP2006062189A - Thermal recording material and use thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize compatibility of a head matching function with a barrier function by making a protective layer contain a disk-like stearic acid metal salt as a slip additive, in a thermal recording material constituted by sequentially providing on a substrate an undercoat layer, a thermal development layer developing color with heat and the protective layer constituted mainly of a resin and a pigment. <P>SOLUTION: In the thermal recording material constituted by sequentially providing on the substrate the undercoat layer, the thermal development layer developing color with heat and the protective layer constituted mainly of the resin and the pigment, the protective layer contains the disk-like stearic acid metal salt as the slip additive. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-sensitive recording material, including an undercoat layer containing organic polymer hollow particles between a support and a heat-sensitive color-developing layer, and a protective layer on the heat-sensitive color-developing layer so that printer printing can be performed. The present invention relates to a heat-sensitive recording material with improved properties and an invention of its use.

In recent years, various recording materials have been researched, developed and put into practical use in the field of information recording in accordance with social demands such as diversification and increase of information, resource saving, and pollution-free. Among them, the recording method using the thermal recording material is
An image is obtained simply by heating, and there is no need to perform complicated processing such as development and fixing.
Recording can be performed in a short time with a relatively simple device.
Cost is low.
In addition to being used for copying books and documents, it is widely used as a recording material for electronic computers, facsimiles, ticket issuing machines, label printers, recorders, handy terminals, and the like.

  Due to the spread of the thermal recording system, the quality required for the thermal recording material has been diversified. For example, miniaturization of printers that are printing devices. Due to energy savings, transportability at the time of printing with low torque is required, and thus the demand for a head matching function is increasing.

  On the other hand, the durability of the color image and the durability of the background portion (non-printing portion) are also required due to the usage environment of the issued label and the like. In particular, there is a demand for barrier properties of the protective layer for the purpose of protecting the color image from oil, plasticizer, and the like and preventing color development due to a solvent in the background portion.

  However, the protective layer generally comprises a resin and a pigment as main components, and other components (for example, a lubricant component) are added as necessary. Among them, the barrier function is realized by a resin component, and the head matching function is expressed not only by the resin but also by an additive component such as a pigment and a lubricant. However, the pigment component and the lubricant component mentioned here basically lower the film formability by the resin, and as a result, lower the barrier function of the protective layer. Therefore, it is highly difficult to achieve both barrier properties while improving the head matching function, but it has a great merit when realized.

  Under such circumstances, various studies have been made so far for the purpose of improving the head matching property. In particular, many proposals have been made on additives such as lubricants, which are effective in improving the head matching function by adding a small amount.

  Among them, fatty acid metal salts such as zinc stearate, which have been put into practical use, are materials having both slippery and releasability functions, and are inexpensive. Therefore, many techniques relating to their use have recently been proposed. Yes.

  Conventionally, a barrier protective layer using a combination of a viscosity mineral potassium / montmorillonite and a higher fatty acid and utilizing a solation phenomenon due to the swelling property of potassium / montmorillonite has been proposed (for example, see Patent Document 1).

  Further, a combination of a protective layer using an emulsified and dispersed zinc stearate and a heat insulating under layer (see, for example, Patent Document 2), and a technique using a pigment surface-treated with a higher fatty acid metal salt as a pigment in the protective layer (for example, a patent) Reference 3), ratio adjustment of pigment (aluminum hydroxide) in protective layer and resin component of lubricant (zinc stearate) (see, for example, Patent Document 4), particle diameter limitation of zinc stearate (0.6-2) 0.5 μm) (for example, see Patent Document 5), higher fatty acid metal salt particle size limitation (0.5 μm or less) (for example, Patent Document 6), zinc stearate particle size limitation (2 to 10 μm) (for example, Patent Document 7) Improvement of the head matching property and the like has been proposed.

  Among the known techniques, Patent Document 1 utilizes a sol-formation phenomenon of a pigment component, and expresses a barrier function by utilizing a film forming property after coating and drying of the pigment itself. Yes, it is combined with the head matching function by the fatty acid metal salt as a lubricant, but the barrier function due to the presence of the fatty acid metal salt particle itself cannot be compensated for, but rather it is close to an inorganic film Therefore, it does not exceed the barrier function when a water-soluble resin is used.

  On the other hand, in Patent Document 3, a pigment surface-treated with a higher fatty acid metal salt is used as a pigment for the protective layer, thereby improving the slipperiness of the pigment itself and improving the head matching function. However, even in this case, the barrier function is not improved.

In addition, the above-described known techniques other than these are techniques using higher fatty acid metal salts such as zinc stearate as a lubricant component, and are mainly techniques in which the particle diameter is varied. Its content is to prevent adhesion with the thermal head by increasing the particle size, and conversely, by increasing the establishment of presence on the surface of the thermal recording material by reducing the particle size, the head matching technology is improved. Is. These are also considered as directions for improving the head matching property, but are not considered to improve the barrier function. Even if the particle diameter of the higher fatty acid metal salt such as zinc stearate is reduced, the number of existing points is increased, so that the barrier function is not necessarily improved.
JP 2003-63137 A JP 2003-291527 A Japanese Patent No. 3182254 JP-A-10-35103 JP-A-9-39405 JP-A-6-135148 JP-A-8-156406

  The present invention has been made in consideration of the above-mentioned circumstances. An undercoat layer is provided on a support, and a heat-sensitive color developing layer that develops color by heat thereon and a protective layer mainly composed of a resin and a pigment are sequentially provided. The present invention relates to a heat-sensitive recording material provided, and it is an object of the present invention to realize both a head matching function and a barrier function by including a disc-shaped metal stearate as a lubricant in the protective layer. In particular, an object of the present invention is to realize extremely excellent head matching even when the undercoat layer contains plastic spherical hollow particles and exhibits excellent color development characteristics.

  In order to solve the above-mentioned problems, the invention described in claim 1 includes an undercoat layer on a support, a thermosensitive coloring layer that develops color by heat, and a protective layer containing a resin and a pigment (resin and pigment as main components) The protective layer contains a disc-shaped metal stearate as a lubricant.

  The invention described in claim 2 is characterized in that the undercoat layer provided on the support contains hollow particles made of organic polymer.

  The invention according to claim 3 is characterized by the heat-sensitive recording material according to claim 1, wherein the metal stearate is zinc stearate.

  The invention according to claim 4 is characterized in that the protective layer contains a scaly inorganic pigment as the pigment.

  The invention according to claim 5 is characterized in that the scaly inorganic pigment is kaolin, according to claim 4.

  The invention according to claim 6 is characterized in that the resin is composed of polyvinyl alcohol and a cross-linking agent.

  The invention according to claim 7 is the heat-sensitive recording material according to claim 6, wherein the polyvinyl alcohol and the crosslinking agent are diacetone-modified polyvinyl alcohol and a hydrazine derivative.

  The invention according to claim 8 is characterized by the heat-sensitive recording material according to claim 2, wherein the hollow ratio of the plastic spherical hollow particles is 80% or more.

  A ninth aspect of the invention is characterized by a thermal recording label obtained by printing on one or both sides of the thermal recording material of the first to eighth aspects.

  The invention described in claim 10 is characterized in that an adhesive layer is provided on the back surface of the heat-sensitive recording paper described in claims 1-8.

  The invention described in claim 11 is characterized in that a heat-sensitive adhesive layer that exhibits adhesiveness by heat is provided on the back surface of the heat-sensitive recording paper described in claims 1-8.

  According to a twelfth aspect of the present invention, a magnetic recording layer is provided on the back surface of the thermal recording paper of the first to eighth aspects.

  According to the present invention, in the thermosensitive recording material in which an undercoat layer is provided on a support and a heat-sensitive color-developing layer that develops color by heat and a protective layer mainly composed of a resin and a pigment are sequentially provided thereon, the protective layer Has excellent disc releasability from the thermal head under printing conditions (during heating), and excellent head matching and barrier properties. A heat-sensitive recording material can be obtained.

  Furthermore, the heat-sensitive recording material of the present invention can have good head matching properties regardless of the structure of the undercoat layer.

  Hereinafter, embodiments of the present invention will be described in detail. According to the present invention, in the heat-sensitive recording material in which the undercoat layer is provided on the support, and the heat-sensitive color-developing layer on which color is developed by heat and the protective layer mainly composed of a resin and a pigment are sequentially provided, By using a disk-shaped metal stearate as the lubricant, a head matching function and a barrier function can be achieved at the same time.

  The disc shape here is a metal stearate salt having a disc shape, which is clearly different from a usual irregular shape. When it is contained and applied in the protective layer coating solution, it exhibits a property of spreading thinly on the surface of the protective layer. Of course, there are some that are buried inside the protective layer, but at least the outermost layer spreads thinly, so that it is possible to express the smoothness and releasability on the surface more efficiently than the amorphous one. . Further, due to the shape, the barrier function by the resin in the protective layer can be maintained in a high state without deteriorating the barrier function. Moreover, since the surface spreads thinly, the function can be expressed by addition of a small amount.

  Various sizes can be used as the size of such a disk-shaped metal stearate, and it can be adjusted by dispersion or the like, but usually has a diameter of 0.2 to 5 μm and a thickness of 0.1 μm or less. Is preferred. At this time, when the size is increased, there is a possibility of causing a problem in an actual coating process, and when the thickness is increased, there is a relationship with the size, but it is considered that the surface cannot be spread thinly.

  Further, according to the present invention, since the shape of the pigment contained in the protective layer is in the form of flakes (thin structure), the disc-shaped metal stearate easily spreads thinly, and thus exhibits an excellent function. . Moreover, the resin in a protective layer can express the outstanding function because it is polyvinyl alcohol and a crosslinking agent. This is partly due to the barrier property of polyvinyl alcohol itself, but in addition to this, it seems to have a function of effectively extracting the function of the disc-shaped metal stearate itself. The reason is unknown, but in combination with the disc-shaped metal stearate, it is considered that the disc-like particles are acting as a protective colloid in such a state that the particles in the disc state tend to spread thinly on the surface.

  Further, according to the present invention, even when the undercoat layer contains hollow particles, the effect is surely exhibited. Usually, when the undercoat layer contains hollow particles, the higher the hollowness of the hollow particles, the better the adhesion between the thermal head and the outermost layer of the thermal recording material. Therefore, the transportability at the time of printing or the like tends to be poor, but in the technique described in this case, in order to be in contact with the surface of the metal stearate salt spread thinly on the surface, Can also demonstrate excellent performance.

  Specific examples of the disk-shaped metal stearate that can be used in the present invention include zinc stearate, calcium stearate, magnesium stearate, etc. Among them, zinc stearate is preferable. Specific examples of these include, for example, Nissan Electol MZ-2 (zinc stearate), Nissan Electol MC-2 (calcium stearate), Nissan Electol MM-2 (magnesium stearate) manufactured by Nippon Oil & Fats Co., Ltd. However, it is not limited to these.

  About these stearic acid metal salts, it is effective to use 0.01-0.5 part with respect to 1 part of resin components in a protective layer, Preferably it is a ratio of 0.05-0.3 part. . In addition, it is conceivable that the function of the metal salt of fatty acid other than stearic acid is improved as compared with an amorphous state by adopting the same shape.

  Specific examples of the pigment added in the protective layer in the present invention are given below. About these pigments, it can be used individually or in mixture of 2 or more types. Silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, kaolin (kaolinite), calcined kaolin, mica, talc, surface-treated silica and other inorganic fine powders, urea-formalin Examples thereof include organic fine powders such as resins, styrene / methacrylic acid copolymers, polystyrene resins, vinylidene chloride resins, styrene / acrylic copolymers, and plastic spherical hollow fine particles, but the present invention is not limited thereto. is not. Among these pigments, scaly (thin structure) pigments such as kaolin and mica are preferable.

  Specific examples of the resin used for the protective layer (overcoat layer) in the present invention include those shown below, but the present invention is not limited thereto.

  Polyvinyl alcohol, modified polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, polyacrylic acid soda, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid Ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer antkari salt, isobutylene / maleic anhydride copolymer antkari salt, polyacrylamide, modified polyacrylamide, methyl vinyl ether-maleic anhydride copolymer, Carboxy-modified polyethylene, polyvinyl alcohol / acrylamide block copolymer, melamine-formaldehyde resin, urea-formalde De resins, sodium alginate, gelatin, and the like water-soluble polymer such as casein.

  Polyvinyl acetate, polyurethane, styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, polyacrylic acid, polyacrylic ester, polymethacrylic ester, vinyl chloride / vinyl acetate copolymer, polybutyl Examples thereof include emulsions such as methacrylate, polyvinyl butyral, polyvinyl acetal, and ethylene / vinyl acetate copolymer. Among these, polyvinyl alcohol is excellent, and among them, diacetone-modified polyvinyl alcohol is excellent.

  Next, although the specific example of the crosslinking agent which can react with the water-soluble resin in the said resin is shown, it is not limited to these also about a crosslinking agent. The crosslinking agent (curing agent) in this case may be any one that can reduce the solubility of the water-soluble resin in water by reacting with the water-soluble resin. For example, a glyoxal derivative, a methylol derivative , Epichlorohydrin derivatives, epoxy compounds, aziridine compounds, hydrazine and hydrazide derivatives.

  In addition, the thermosensitive coloring layer in the present invention has a function of developing color by heat. As an example of the coloring system, a coloring reaction between a basic dye precursor (leuco dye) and an acidic substance (developer) is performed. Can be mentioned. In this case, the basic dye precursors (leuco dyes) used can be used alone or in combination of two or more. As such leuco dyes, those applied to heat-sensitive materials are arbitrarily used. For example, the following can be mentioned.

  3,3-bis (P-dimethylaminophenyl) phthalide, 3,3-bis (P-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-6-methyl-7-anilinofluorane, 3 -Dibutylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-butylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-propylamino-6 Methyl-7-anilinofluorane, 3-N-ethyl-N-propylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-amylamino-6-methyl-7-anilinofur Oran, 3-N-ethyl-N-amylamino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-isoamylamino-6-methyl-7-anilinofluorane, 3 N-hexyl-N-isoamylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-N-ethyl-N- Furanylmethylamino-6-methyl-7-anilinofluorane, 3-diethyl-N-butylamino-7- (2′-fluoroanilino) fluorane, 3-pyrrolidyl-7-dibenzylaminofluorane, 3 -Bis (diphenylamino) fluorane, 3-diethylamino-7- (2'-chloroanilino) fluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-dibutylamino-7- (2'-chloroanilino) Fluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-N Methyl-N-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-7- (2 ′, 4′-dimethylanilino) fluorane, 3-diethylamino-7-dibenzylaminofluorane, 3- Examples thereof include butylamino-7- (2′-chloroanilino) fluorane and 3-diethylamino-6-ethoxyethyl-7-anilinofluorane.

  Moreover, the following can be mentioned as a developer compound which colors the said leuco dye.

  4,4'-isopropylidenebisphenol, 4,4'-isopropylidenebis (o-methylphenol), 4,4'-VHF-butylidenebisphenol, 4,4'-isopropylidenebis (2-WHU-butylphenol) , Zinc p-nitrobenzoate, 1,3,5-tris (4-WHU-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2- (3,4-dihydroxyphenylpropane), Bis (4-hydroxy-3-methylphenyl sulfide), 4- (β- (p-methoxyphenoxy) ethoxy) salicylic acid, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, phthalate Acid monobenzyl ester monocarboxylic acid, 4,4′-cyclohexylidenebisphenol, 4,4′-isopropylidenebis (2-c Rophenol), 2,2′-methylenebis (4-methyl-6-WHU-butylphenol), 4,4′-butylidenebis (6-WHU-butyl-2-methyl) phenol, 1,1,3-tris (2 -Methyl-4-hydroxy-5-cyclohexyl) butane, 4,4'-thiobis (6-WHU-butyl 2-methylphenol) 4,4'-dihydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone 4-isopropyloxy-4′-hydroxydiphenyl sulfone, 4,4′-diphenol sulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechuate, stearyl gallate, 1,3-bis ( 4-hydroxyphenylthio) -propane, 1,3-bis (4-hydroxypheny) Thio) -2-hydroxypropane, N, N-diphenylthiourea, N, N-di (m-chlorophenylthiourea), salicylanilide, 5-chlorosalicylanilide, bis (4-hydroxyphenyl) acetic acid methyl ester, bis (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis (4-hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4′-dihydroxydiphenylsulfone, 2,2 '-Diallyl-4,4'-diphenolsulfone, 3,4-dihydroxy-4'-methyldiphenylsulfone, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, 4,4'-thiobis ( 2-methylphenol), 4,4′-thiobis (2-chlorophenol) and the like.

  Furthermore, various oligomer type compounds can also be mentioned. Further, the ratio of the leuco dye to the developer in the thermosensitive coloring layer is preferably 0.5 to 10 parts, preferably 1 to 5 parts (all parts are by weight).

  In the thermosensitive coloring layer, a sensitivity improver and various thermofusible substances can be used alone or in combination of two or more. Specific examples thereof include the following.

  Fatty acids such as stearic acid and behenic acid, stearic acid amide, erucic acid amide, palmitic acid amide, behenic acid amide, fatty acid amides such as palmitic acid amide, N-lauryl lauric acid amide, N-stearyl stearic acid amide, N -N-substituted amides such as oleyl stearamide, methylene bis stearamide, ethylene bis stearamide, ethylene bis laurate amide, ethylene biscapric amide, bis fatty acid amides such as ethylene bisbehenamide, hydroxy Hydroxy fatty acid amides such as stearamide, methylenebishydroxystearic acid, ethylenebishydroxystearic acid amide, hexamethylenebishydroxystearic acid amide, zinc stearate, aluminum stearate Fatty acid metal salts such as calcium stearate, zinc palmitate, zinc behenate, p-benzylbiphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, phenyl β-naphthoate, -Phenyl hydroxy-2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl carbonate, benzyl terephthalate, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibenzyloxynaphthalene, 1,2-diphenoxyethane, 1,2-bis (4-methylphenoxyethane), 1,4-diphenoxy-2-butene, 1,2-bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1 , 4-Diphenylthiobutane, 1,4-diphenylthio O-2-butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2-vinyloxyethoxy) biphenyl, p-aryloxybiphenyl , Dibenzoyloxymethane, dibenzoyloxypropane, dibenzyl disulfide, 1,1-diphenylethanol, 1,1-diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N-octadecylcarbamoyl -P-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2-bis (4-methoxyphenoxy) propane, 1,5-bis (4-methoxyphenoxy) -3-oxapentane, dibenzyl oxalate, bis (oxalate) ( 4-methylbenzyl) Oxalic acid bis (4-chlorobenzyl) or the like.

  These compounds can be used in combination with the disc-shaped metal stearate used in the protective layer.

  In preparing the heat-sensitive recording material of the present invention, various materials conventionally used for constituting a heat-sensitive recording material are appropriately used in addition to the developer, leuco dye, and heat fusible substance. Can do. Examples thereof include, for example, binders for binding various materials on a support or the like in a heat-sensitive recording layer, and these can be used alone or in combination of two or more. For the above, those mentioned as specific examples of the resin used for the protective layer (overcoat layer) can be used. Similarly, those mentioned as the crosslinking agent can be used as necessary.

  Furthermore, in the protective layer of the heat-sensitive recording material of the present invention, pigments other than the resin and crosslinking agent, and lubricants (thermofusible substances) can be used, and for these, the pigments, binders and crosslinking agents described above are used. The lubricant (heat fusible substance) can be used alone or in combination of two or more.

  In addition, an intermediate layer is provided between the support and the thermosensitive coloring layer. In this case, as the pigment and binder constituting the intermediate layer, each of the above pigments and binders is used alone or in combination of two or more. Can be used. The thermoplastic hollow resin particles which are an example of the pigment in this case are, for example, spherical hollow fine particles which are made of a thermoplastic polymer as a shell and contain air or other gas inside and are already in a foamed state. .

The hollow ratio of the thermoplastic hollow resin particles is a ratio of the outer diameter to the inner diameter of the hollow particles and is represented by the following formula.
Formula: Hollow ratio (hollowness) (%) = (inner diameter of hollow particles / outer diameter of hollow particles) × 100

  Plastic spherical hollow fine particles are acrylic resins such as acrylate and acrylonitrile, styrene resins such as styrene or copolymer resins thereof, acrylonitrile and / or methacrylonitrile and / or acrylate and / or methacrylate. It can be made from a polymer, a copolymer comprising a vinyl monomer having two or more vinyl groups per molecule and / or a monomer containing divinylbenzene.

  Furthermore, in the heat-sensitive recording material of the present invention, it is also possible to provide a back layer mainly composed of a pigment, a resin, a crosslinking agent and the like on the back surface of the support. In this case, the pigment, binder, and lubricant (heat fusible substance) are used as the pigment, binder, and lubricant.

  In addition to normal paper (acidic paper, neutral paper), any material that can be applied and processed can be arbitrarily used as the support, and examples thereof include synthetic paper and polymer films. In obtaining the heat-sensitive recording material of the present invention, in addition to the above, additive components commonly used in this type of heat-sensitive recording material, for example, a surfactant, a pressure coloring inhibitor, and the like can be used in combination.

Next, the present invention will be described in more detail with reference to examples. The following parts and percentages are based on weight.
<Preparation of Samples for Examples and Comparative Examples>
Preparation of coating solution for each layer (thermosensitive coloring layer, undercoat layer, protective layer) A mixture having the following composition is dispersed with a magnetic ball mill to prepare [A solution] to [E solution].

[Liquid A] = leuco dye dispersion 3-N, N dibutylamino-6-methyl-7-anilinofluorane 10 parts 10% aqueous polyvinyl alcohol solution 10 parts water 30 parts

[Liquid B] = developer dispersion 4-hydroxy-4′-isopropoxydiphenylsulfone 10 parts 10% aqueous polyvinyl alcohol solution 10 parts water 30 parts

[C liquid] = pigment dispersion silicon dioxide powder 10 parts 10% polyvinyl alcohol aqueous solution 10 parts water 30 parts

Thermosensitive coloring layer coating solution A mixture: B solution: C solution = 1: 3: 3 mixture.

Next, a mixture having the following composition was mixed and stirred to prepare an undercoat layer coating solution [U solution].
[U-1 solution]
Firing kaolin: 20 parts Styrene / butadiene copolymer latex (solid content concentration: 47.5%): 20 parts Water: 60 parts

[U-2 solution]
Plastic spherical hollow particles (solid content 40%): 25 parts Styrene / butadiene copolymer latex (solid content concentration 47.5%): 15 parts Water: 60 parts

  In addition, about the hollow ratio in the plastic spherical hollow particle in the said U-2 liquid, it is possible to use the thing of various hollow ratios suitably. Moreover, when solid content changes with the types, it converts according to the value.

Next, a protective layer coating solution [O solution] was prepared by mixing and dispersing a mixture having the following composition.
[O liquid]
Pigment dispersion (solid content: 20%) 50 parts Metal stearate (10% dispersion) 20 parts Resin (10% aqueous solution) 100 parts Crosslinker (10% aqueous solution) 20 parts Water 50 parts

  The pigment dispersion was prepared using the protective layer-containing pigment species shown in Table 1 in place of the silicon dioxide in [C solution]. The stearic acid metal salt dispersion was prepared by ball mill dispersion of a mixture having the following composition [D liquid].

[Liquid D] = Stearic acid metal salt dispersion metal stearate 10 parts 10% polyvinyl alcohol aqueous solution 10 parts Water 80 parts

  Using the coating solution prepared as described above, the undercoat layer forming solution is applied and dried on the surface of commercially available high-quality paper (basis weight 60 g / m 2) so that the dry weight is 3 g / m 2. A finished paper was obtained. Next, the thermochromic layer forming solution was applied and dried so that the dry weight of the leuco dye was 0.5 g / m 2 to obtain a paper coated with the thermochromic layer. Further, the protective layer coating solution is applied and dried so that the dry weight becomes 3.0 g / m 2, stored in a 40 ° C. environment for 15 hours, and then subjected to a calendar treatment at a pressure of 20 Kg / cm 2. A heat-sensitive recording material of the invention was obtained.

*) Stearic acid metal salt species MZ-2 (disc-shaped zinc stearate / Nissan Electol MZ-2 manufactured by Nippon Oil & Fats Co., Ltd.)
MC-2 (Disc-shaped calcium stearate / Nissan Electol MC-2 manufactured by Nippon Oil & Fats Co., Ltd.)
MM-2 (Disk-shaped magnesium stearate / Nissan Electol MM-2 manufactured by Nippon Oil & Fats Co., Ltd.)
Ste-Zn (Amorphous zinc stearate / Nippon Yushi Co., Ltd.)
*) Thermoplastic hollow resin particles>
A1: Hollow resin particles made of styrene acrylic copolymer (hollow rate = 50%)
A2: Hollow resin particles made of vinylidene chloride, acrylonitrile, methacrylate copolymer (hollow rate = 90%)

  The heat-sensitive recording material prepared as described above was subjected to the following tests, and the results are shown in Table 2.

<Releasability evaluation>
A sample for evaluation (heat-sensitive recording material) is cut to a width of 2 cm, and the printed surface side is combined with a slide glass. Next, the sample and the glass surface are pressure-bonded under overheating conditions by heating from the back side (opposite side of the printing surface) of the heat-sensitive recording material with a thermal gradient tester (200 ° C., 1 kg / cm ² , 1.5 seconds). Form a state. The force required to peel the sample from the glass surface in this state was measured with a digital gauge.
Moreover, the state at the time of peeling was visually observed.

Visual evaluation of sticking property: Not sticking: Sticking but peeling off △: Some tearing occurs but peeling ×: Does not peel (breaking)

<Matching (sticking) evaluation>
Each thermal recording material and handy printer (type FHT205B, manufactured by Fujitsu Ltd.) was left in a low-temperature, low-humidity environment of 22 ° C and 65% RH for 1 hour to adjust the humidity, and then printed (printing conditions were printed as mode 6). . The print length is the length of the print from the print start part to the print last part when a specific print pattern is printed by the printer. When the sticking property is excellent, the print pattern is printed accurately. When the sticking property is inferior, the same part of the heat-sensitive recording material is printed twice, and the heat-sensitive recording material meanders. This is shorter than the print length when
In addition, visual print quality confirmation was also performed, and sticking was evaluated according to the following criteria.

Visual evaluation of sticking ◎ …… No sticking.
○ …… There is little sticking.
Δ: Slightly more sticking.
× …… There is a lot of sticking.

In addition, the density of the printed image portion was measured with a Macbeth reflection densitometer.
<Barrier property evaluation>
The surface of the heat-sensitive recording material was wiped with an absorbent cotton soaked with alcohol (ethanol), and the density of the background after natural drying was measured with a Macbeth reflection densitometer.

Claims (12)

  A heat-sensitive recording material comprising an undercoat layer, a heat-sensitive color-developing layer that develops color by heat, and a protective layer containing a resin and a pigment in this order on a support, wherein the protective layer serves as a lubricant and serves as a disc-shaped stearic acid A heat-sensitive recording material comprising a metal salt.   2. The heat-sensitive recording material according to claim 1, wherein the undercoat layer provided on the support contains hollow particles made of an organic polymer.   2. The heat-sensitive recording material according to claim 1, wherein the metal stearate is zinc stearate.   2. The heat-sensitive recording material according to claim 1, wherein the protective layer contains a flaky inorganic pigment as a pigment.   The heat-sensitive recording material according to claim 4, wherein the scaly inorganic pigment is kaolin.   2. The heat-sensitive recording material according to claim 1, wherein the resin comprises polyvinyl alcohol and a crosslinking agent.   The heat-sensitive recording material according to claim 6, wherein the polyvinyl alcohol and the crosslinking agent are diacetone-modified polyvinyl alcohol and a hydrazine derivative.   The heat-sensitive recording material according to claim 2, wherein the hollow ratio of the organic polymer hollow particles is 80% or more.   A thermosensitive recording label obtained by printing on one or both sides of the thermosensitive recording material according to claim 1.   A thermosensitive recording label comprising an adhesive layer provided on the back surface of the thermosensitive recording paper according to claim 1.   A heat-sensitive recording label that does not require a release paper, wherein a heat-sensitive adhesive layer that exhibits adhesiveness by heat is provided on the back surface of the heat-sensitive recording paper according to claim 1.   A heat-sensitive recording voucher comprising a magnetic recording layer provided on the back surface of the heat-sensitive recording paper according to claim 1.