JP2770258B2 - Thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording medium having excellent printability for water-based ink on its surface, and more particularly to paper sheets such as tickets and pass tickets, cards such as prepaid cards, and POS (Point of Sales). The present invention relates to a thermosensitive recording medium applicable to labels such as labels.

[0002]

2. Description of the Related Art In general, a heat-sensitive recording medium having a heat-sensitive recording layer mainly composed of a colorless or light-colored leuco dye and a color developer which reacts with the leuco dye when heated to form a color is disclosed in
It is published in, for example, Japanese Patent Publication No. 14035 and widely used.
In order to perform recording on the thermosensitive recording medium, a thermal printer or the like having a built-in thermal head is used. Compared with other conventional recording methods, such a heat-sensitive recording method has no noise at the time of recording, does not require development and fixing, is maintenance-free, is relatively inexpensive and compact, and is obtained. Because of its distinctive color development, it is widely used as computer output, facsimile, recorder paper for calculators and various measuring instruments, and ticket paper for automatic ticket vending machines. In the conventional thermal recording medium used for various applications as described above, if storage stability of an image such as chemical resistance and water resistance is required in addition to the recording characteristics, a method disclosed in JP-A-57-188392 is required.
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-207, etc., those having a configuration in which a protective layer is provided on a heat-sensitive recording layer are used. The composition of such a protective layer is generally a mixture of a water-soluble or water-dispersible polymer compound and various additives such as a pigment.

[0003] In recent years, there has been a strong demand for printing with a water-based ink on the surface of the protective layer in the label field such as POS labels and ticket paper such as tickets, and in particular, in water tickets, water-based ink was used in place of conventional scissors. A ticket inspection method using a stamp is employed. However, although the recording properties, chemical resistance, water resistance, etc. of the conventional heat-sensitive recording medium have been sufficiently studied as described above, printing suitability such as ink absorbency, drying property, fixing property, etc. for water-based inks is almost considered. Therefore, the printing characteristics were poor. That is, a water-soluble polymer such as polyvinyl alcohol, which has been conventionally used as a protective layer, does not provide sufficient printing characteristics for aqueous inks. Further, in order to improve blocking resistance under high humidity conditions, emulsion-based The use of the resin or the water-proofing agent to suppress water absorption and achieve water-proofing has an adverse effect on printability for water-based inks and has an adverse effect. Although the absorption of the water-based ink can be improved by increasing the amount of the pigment added, the transparency of the protective layer is reduced, and the problem is that the image clarity of the heat-sensitive recording layer is reduced. As described above, in the conventional thermosensitive recording medium, the printability of the water-based ink cannot be satisfied, and a heat-sensitive recording medium having excellent printability of the water-based ink at the same time as good recording characteristics and image storability has been desired. It is the present situation.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has excellent printability for aqueous inks without impairing the recording characteristics and storage stability required for a thermosensitive recording medium. The present invention provides a thermosensitive recording medium having on the surface thereof.

[0005]

The present invention relates to a heat-sensitive recording medium having a structure in which a heat-sensitive recording layer is laminated on at least one surface of a support, and has an acetalization degree of 0.1 to 0.1 on the heat-sensitive recording layer.
A thermosensitive recording medium comprising a layer containing 5 mol% of a polyvinyl acetal resin (hereinafter, referred to as a resin A) and a polyvinyl acetal resin having a degree of acetalization of 20 to 60 mol% (hereinafter, referred to as a resin B). In the heat-sensitive recording medium of the present invention, the protective layer on the heat-sensitive recording layer may contain the resin A and the resin B, and the ink absorption containing the resin A and the resin B on the protective layer. A layer may be provided.

The polyvinyl acetal resins A and B used in the present invention are those having a chemical structure represented by the following structural formula (1) in the molecule and examples of modified polyvinyl acetal:
An example is a carboxyl-modified polyvinyl acetal .

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In the structural formula (1), R is a lower alkyl group , and n is an acetalized compound contained in one molecule.
Represents the molar ratio of the portion represented by As described above, the polyvinyl acetal resin is obtained by treating polyvinyl alcohol with an aldehyde such as formaldehyde and acetaldehyde in the presence of an acid catalyst. The acid component as a catalyst is neutralized with sodium hydroxide or the like after completion of the reaction. The resin A used in the present invention corresponds to the polyvinyl acetal resin represented by the above structure in which n is 0.1 to 5, that is, the degree of acetalization is 0.1 to 5 mol%, and the resin B is Means that n is 20 to 60, that is, the degree of acetalization is 20 to 60 mol%. In order to control the degree of acetalization, the amount of the aldehyde used in the reaction may be adjusted. Further, in the present invention, the water-soluble polyvinyl acetal resin in which R is a methyl group in the above structural formula has excellent properties without impairing any of the properties in printing properties for aqueous inks, barrier properties as a protective layer, and blocking resistance. Is particularly preferred because

The protective layer or the ink absorbing layer constituting the heat-sensitive recording medium of the present invention has a composition based on a combination of these resins A and B. The preferred mixing ratio of the resin A and the resin B in the protective layer or the ink absorbing layer is from 95: 5 to 50:50, particularly preferably from 80:20 to 60:40. If the compounding ratio of the resin A is too small, sufficient printability with respect to the aqueous ink cannot be obtained, and if the compounding ratio of the resin A is too large, the flexibility of the protective layer becomes high and blocking becomes easy.

In the present invention, two kinds of polyvinyl acetal resins having the above structure and a modified polyvinyl acetal are used.
Tar such as carboxyl-modified polyvinyl acetal Ru is used. The tool body Examples of other optional monomer components that make up <br/> these polyvinyl acetal resins, ethylene, propylene, N- vinylpyrrolidone and derivatives thereof, vinyl chloride, vinyl acetate, styrene, vinyl toluene, divinyl benzene , Vinylidene chloride, vinyl group-containing monomers such as tetrafluoroethylene and vinylidene fluoride, and (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acrylate , Isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, benzyl (meth) acrylate, phenyl (Meth) acrylate, cyclohexyl (meth) acrylate, acrylamide, acrylonitrile, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, N
-(Meth) acrylic monomers such as alkylol (meth) acrylamide and glycidyl (meth) acrylate; and unsaturated acids such as fumaric acid, maleic acid and itaconic acid. These monomers may be used as a copolymer component when producing polyvinyl alcohol as a raw material, or may be copolymerized by a method such as graft polymerization before and after acetalization.

The protective layer or the ink absorbing layer in the present invention contains the above-mentioned two kinds of polyvinyl acetal resins. It is preferable that the acetal resin content be contained in the range of 5 to 90% by weight. 5% by weight of polyvinyl acetal resin
If it is less than 90%, sufficient printability cannot be obtained, and if it exceeds 90% by weight, sufficient chemical resistance may not be obtained.

The various water-soluble or water-dispersible polymer compounds used as necessary for the protective layer of the present invention include, for example, polyvinyl alcohol, polyvinylpyrrolidone, and the like.
Casein, gelatin, oxidized starch, isobutylene-maleic anhydride copolymer resin, diisobutylene-maleic anhydride copolymer resin, styrene-maleic anhydride copolymer resin, carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, polyvinyl acetate, Poly (meth) acrylic acid, poly (meth) acrylate, vinyl chloride-vinyl acetate copolymer, SBR, NB
Emulsions such as R, latex and the like can be used alone or in a suitable mixture.

In the protective layer or the ink absorbing layer of the thermal recording medium of the present invention, various pigments, for example, clay, may be used as needed in order to obtain matching properties with the thermal head.
Use talc, diatomaceous earth, alumina, calcium carbonate, calcium sulfate, zeolite, cellulose fine powder, polyethylene fine powder, silicone resin fine powder, phenol resin fine powder, benzoguanamine resin fine powder, etc., zinc stearate, calcium stearate, It is possible to use a lubricity improver such as a fluororesin, a release agent such as silicone grease, and a water-proofing agent such as glyoxal, chrome ban, melamine resin, melamine formaldehyde resin, polyamide resin, polyamide-epichlorohydrin resin, and the like. it can.

Next, the heat-sensitive recording layer of the present invention will be described. The heat-sensitive recording layer contains a colorless or light-colored leuco dye and a color developer for developing the leuco dye as main components. Typical leuco dyes used include crystal violet lactone, 3-diethylamino-7-chlorofluoran, 3-diethylamino-
6-methyl-7-chlorofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-7-dibenzylaminofluoran, 3-pyrrolidino-
6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-ethylisoamylamino-6-methyl-7-anilinofluoran, 3-diethylamino-7- ( o-chloroanilino)
Fluorane, 3-dibutylamino-7- (o-chloroanilino) fluoran and the like are not particularly limited.

Further, as a color developer which reacts with the leuco dye to form a color, α-naphthol, β-naphthol,
4-t-butylphenol, 4-t-octylphenol, 4-phenylphenol, 2,2-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) butane, 4,4'-cyclohexyl Dendiphenol, 2,2-bis (2,5-dibromo-4-
(Hydroxyphenyl) propane, 4,4′-isopropylidenebis (2-t-butylphenol), 2,2′-
Methylenebis (4-chlorophenol), 4,4'-thiodiphenol, 4,4'-sulfonyldiphenol,
Derivatives of benzoic acid, salicylic acid, gallic acid and the like, but are not limited thereto.

As the binder used in the heat-sensitive recording layer, various water-soluble or water-dispersible polymer compounds are used. For example, polyvinyl alcohol, casein, oxidized starch, gelatin, isobutylene-maleic anhydride copolymer is used. Copolymer resin, diisobutylene-maleic anhydride copolymer resin, styrene-maleic anhydride copolymer resin, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, polyvinyl acetate, poly (meth) acrylate, vinyl chloride-vinyl acetate copolymer Styrene-butadiene copolymer and the like, but are not limited thereto.

Further, in order to improve the recording sensitivity, various heat-fusible substances can be added to the heat-sensitive recording layer as needed. Further, various fillers can be added to improve the image quality. Examples of these heat-fusible substances include organic compounds having a suitable melting point, for example, higher fatty acid amides such as stearamide, beeswax, animal waxes such as shellac wax, vegetable waxes such as carnauba wax, Mineral waxes such as montan wax, paraffin wax, microcrystalline wax, higher fatty acids, esters of higher fatty acids, aromatic carboxylic acid esters such as dimethyl terephthalate and diphenyl phthalate, alkyl naphthalene derivatives, alkyl diphenyl derivatives, alkyl ta-phenyl derivatives, etc. Is used. Furthermore, inorganic and organic pigments as fillers in the heat-sensitive recording layer, for example, clay, talc, diatomaceous earth, alumina, calcium carbonate, calcium sulfate, zeolite, cellulose fine powder, polyethylene fine powder, silicone resin fine powder, By adding a phenol resin fine powder, a benzoguanamine resin fine powder, or the like, the sharpness of a color image can be improved. In addition, various surfactants, defoamers, antioxidants, ultraviolet absorbers, and the like can be added as needed.

The heat-sensitive recording layer according to the present invention has the above-mentioned composition, and a coating comprising the leuco dye, a color developer and a binder, and other optional compounds is coated on a support. The coating is a coating liquid that is pulverized by a disperser such as a media-type wet disperser, and has a particle size of a leuco dye and a developer that are the object to be dispersed. Is preferably 5 μm or less, particularly preferably 3 μm or less, from the viewpoint of recording characteristics.

The protective layer constituting the heat-sensitive recording medium of the present invention may be formed by pressure coloring caused by rubbing, scratching, or the like, or unnecessary coloring or recording due to penetration of a plasticizer, oil, or other various chemicals into the heat-sensitive recording layer. A water-soluble or water-dispersible polymer compound as a binder for the heat-sensitive recording layer is used to prevent decoloration of an image. In addition,
If necessary, to improve the water resistance, a water-resistant agent such as glyoxal, chromium ban, melamine resin, melamine-formaldehyde resin, polyamide resin, polyamide-epichlorohydrin resin may be added to the binder and used. it can.

The support used in the thermal recording medium of the present invention includes paper, thermoplastic resin sheet, metal foil, metal plate,
There are no particular limitations on metal-deposited sheets, ceramic sheets, woven fabrics, non-woven fabrics, and composites thereof. In the present invention, in order to form the heat-sensitive recording layer, the protective layer and the ink absorbing layer on the support, a coating solution obtained by dispersing or dissolving the above-mentioned materials for forming each layer is subjected to a roll coating method or a blade coating method. It is performed by applying and drying by a method such as a spray coating method, an air knife coating method, and a rod bar coating method. The preferable coating amount of the heat-sensitive recording layer and the protective layer is 2 to 1 for the heat-sensitive recording layer.
0 g / m ^2, more preferably 5~8g / m ^2. Similarly, about ² to 10 g / m ² is appropriate for the protective layer, but more preferably 3 to 8 g / m ² .
The preferred coating amount of the ink absorbing layer is 1 to 10 g / m ² ,
Particularly preferably, it is ² to 4 g / m ² .

In the heat-sensitive recording medium of the present invention, an under layer may be provided between the support and the heat-sensitive recording layer, if necessary, to improve the smoothness of the support surface and improve the sharpness of the image. Can be. In addition, by providing a back layer on the surface of the support opposite to the surface on which the heat-sensitive recording layer is provided, it is possible to prevent various chemicals from penetrating from the back surface of the heat-sensitive recording medium, thereby making the heat-sensitive recording layer unnecessary. Color and decoloring of recorded images can be prevented. The under layer and the back layer are mainly composed of various water-soluble or water-dispersible polymer compounds which are binders used for the heat-sensitive recording layer, and are added with pigments and various additives as necessary. Can be formed. The coating amount of both the under layer and the back layer is 0.5 to 10 g.
/ M ² is preferred. The surface smoothness can be further improved by performing a calendering treatment after the under layer is applied.

Further, the heat-sensitive recording medium of the present invention is excellent in water-based ink by providing a magnetic recording layer between the support and the heat-sensitive recording layer or on the surface of the support on which the heat-sensitive recording layer is not provided. As a heat-sensitive magnetic recording medium having printability, it can be used for a wide range of uses, for example, as tickets such as a ticket, a pass, and a parking ticket. The magnetic recording layer is made of, for example, γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co.
Kneading and dispersing a magnetic substance such as -γ-Fe ₂ O ₃ or BaO · 6Fe ₂ O ₃ with an appropriate binder resin, for example, a polymer compound such as a polyester resin or a polyurethane resin, various additives, and a solvent; The paint prepared in this manner may be applied on a support, dried and placed. In this case,
As with the case where the heat-sensitive recording layer and the protective layer are provided, various coating methods can be applied. Further, a magnetic recording layer having excellent wear resistance and heat resistance can be provided by using an ultraviolet curable binder or an electron beam curable binder for the magnetic recording layer. When a heat-sensitive recording layer is provided on the magnetic recording layer, it is preferable to provide a concealing layer between the magnetic recording layer and the heat-sensitive recording layer for concealing coloring of the magnetic recording layer.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. In addition, the number of parts indicating the combination is all parts by weight. Examples 1 to 7
Are examples in which the protective layer contains polyvinyl acetal resins A and B, and Examples 8 to 14 are examples in which the ink absorbing layer contains polyvinyl acetal resins A and B. Example 1 In order to produce a coating for a heat-sensitive recording layer, the following [A]
A dispersion composed of [B] and [C] was prepared. [A] solution ・ 30 parts of 3-butylamino-6-methyl-7-anilinofluoran ・ 50 parts of methylcellulose aqueous solution (solid content concentration: 5%) ・ 20 parts of water [B] solution ・ 4-isopropoxy-4 ′ -Hydroxydiphenyl sulfone 30 parts ・ Polyvinyl alcohol aqueous solution (solid content concentration 5%) 50 parts ・ Water 20 parts [C] solution ・ Kaolin 40 parts ・ Polyvinyl alcohol aqueous solution (solid content concentration 5%) 40 parts ・ Water 20 parts or more [A] solution 30 parts, [B] solution 9 thus obtained
0 parts of [C] was 100 parts, and polyvinyl alcohol (solid content of 10%) the coating for heat-sensitive recording layer composed of 150 parts to prepare a basis weight of 60 g / m ² fine paper dry coating amount of 7 g /
m ² to provide a heat-sensitive recording layer.

Next, a coating material for a protective layer having the following composition was prepared and coated on the above-mentioned heat-sensitive recording layer so as to have a dry coating amount of 4 g / m ² , thereby producing a heat-sensitive recording medium of the present invention.・ Carboxyl-modified polyvinyl acetal aqueous solution 50 parts (solid content concentration 10%, acetalization degree 26 mol%) ・ Carboxyl modified polyvinyl acetal aqueous solution 50 parts (solid content concentration 10%, acetalization degree 1 mol%) ・ [C] solution 20 parts 5 parts of aqueous dispersion of zinc stearate (solid content 10%) 15 parts of polyamide epichlorohydrin (solid content 30%, manufactured by Toho Chemical Co., Sparamine A301)

Example 2 A heat-sensitive recording medium of the present invention was produced in exactly the same manner as in Example 1 except that the protective coating having the following composition was used.・ 5 parts of carboxyl-modified polyvinyl acetal aqueous solution (solid content concentration 10%, acetalization degree 49 mol%) ・ 95 parts of carboxyl-modified polyvinyl acetal aqueous solution (solid content concentration 10%, acetalization degree 1 mol%) ・ 20 parts of [C] solution 5 parts of aqueous dispersion of zinc stearate (solid content 10%) 15 parts of polyamide epichlorohydrin (solid content 30%, manufactured by Toho Chemical Co., Sparamine A301)

Example 3 Except that the following composition was used as the coating for the protective layer,
A thermosensitive recording medium of the present invention was produced in exactly the same manner as in Example 1. -30 parts of aqueous solution of carboxyl-modified polyvinyl acetal (solid content concentration 10%, degree of acetalization 49 mol%)-70 parts of aqueous solution of carboxyl-modified polyvinyl acetal (solid content concentration 10%, degree of acetalization 4 mol%)-[C] solution 20 parts 5 parts of aqueous dispersion of zinc stearate (solid content 10%) 15 parts of polyamide epichlorohydrin (solid content 30%, manufactured by Toho Chemical Co., Sparamine A301)

Example 4 Except that the following composition was used as the coating for the protective layer,
A thermosensitive recording medium of the present invention was produced in exactly the same manner as in Example 1.・ Aqueous solution of carboxyl-modified polyvinyl alcohol 10 parts (solid content 10%, T-330, manufactured by Nippon Synthetic Chemical Co.) ・ Aqueous solution of carboxyl-modified polyvinyl acetal 10 parts (solid content 10%, degree of acetalization 28 mol%) ・ Carboxyl-modified polyvinyl Acetal aqueous solution 80 parts (solid content concentration 10%, acetalization degree 1 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (solid content concentration) 30%, Sparamine A301, manufactured by Toho Chemical Co., Ltd.)

Example 5 Except for using the following composition as a protective layer paint,
A thermosensitive recording medium of the present invention was produced in exactly the same manner as in Example 1.・ Aqueous solution of carboxyl-modified polyvinyl alcohol 10 parts (solid content 10%, manufactured by Nippon Synthetic Chemical Co., T-330) ・ Aqueous solution of carboxyl-modified polyvinyl acetal 25 parts (solid content 10%, degree of acetalization 28 mol%) ・ Carboxyl-modified polyvinyl Acetal aqueous solution 65 parts (solid content concentration 10%, acetalization degree 1 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (solid content concentration) 30%, Sparamine A301, manufactured by Toho Chemical Co., Ltd.)

Example 6 137 g / m ² high-quality paper was used as a support, and the surface opposite to the surface on which the heat-sensitive recording layer was provided was previously coated with a magnetic recording layer paint having the following composition to a thickness of 13 μm. Except that the magnetic recording layer was provided, a thermosensitive recording medium of the present invention having a magnetic recording layer was produced in exactly the same manner as in Example 1. Barium ferrite 100 parts (coercive force 3000 Oersted, average particle diameter 0.6 μm) Polyester resin 40 parts (Byron 200, manufactured by Toyobo Co., Ltd.) Carbon black 5 parts (Mitsubishi Carbon No. 40, manufactured by Mitsubishi Kasei Corporation) Lecithin 2 parts ・ Methyl ethyl ketone 150 parts ・ Toluene 180 parts Example 7 The heat-sensitive recording medium of the present invention having a magnetic recording layer in exactly the same manner as in Example 6 except that the same coating as that of Example 5 was used as the coating for the protective layer. Was prepared.

COMPARATIVE EXAMPLE 1 Except for using the following composition as the coating for the protective layer,
A comparative thermosensitive recording medium was produced in exactly the same manner as in Example 1. 100 parts of a carboxyl-modified polyvinyl alcohol aqueous solution (solid content 10%, T-330 manufactured by Nippon Synthetic Chemical Co., Ltd.) 20 parts of [C] solution 5 parts of an aqueous dispersion of zinc stearate (solid content 10%) 5 parts 15 parts of polyamide epichlorohydrin (solid content: 30%, manufactured by Toho Chemical Co., Sparamine A301)

Comparative Example 2 A coating composition for a protective layer having the following composition was used,
A comparative thermosensitive recording medium was produced in exactly the same manner as in Example 1.・ Carboxyl-modified polyvinyl acetal aqueous solution 100 parts (solid content concentration 10%, acetalization degree 49 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (Solid content concentration 30%, manufactured by Toho Chemical Co., Sparamine A301)

Comparative Example 3 Except that the following composition was used as the coating for the protective layer,
A comparative thermosensitive recording medium was produced in exactly the same manner as in Example 1.・ Carboxyl-modified polyvinyl acetal aqueous solution 100 parts (solid content concentration 10%, acetalization degree 1 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (Solid content concentration 30%, manufactured by Toho Chemical Co., Sparamine A301)

Comparative Example 4 Except that the following composition was used as the coating for the protective layer,
A comparative thermosensitive recording medium was produced in exactly the same manner as in Example 1.・ Carboxyl-modified polyvinyl acetal aqueous solution 100 parts (solid content concentration 10%, acetalization degree 10 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (Solid content concentration 30%, manufactured by Toho Chemical Co., Sparamine A301)

Example 8 In the same manner as in Example 1, a thermosensitive recording layer was coated on a support to form a thermosensitive recording layer. Next, a coating for a protective layer having the following composition was prepared, and was applied onto the above-mentioned heat-sensitive recording layer so as to have a dry coating amount of 4 g / m ² , thereby providing a protective layer.・ 100 parts of carboxyl-modified polyvinyl alcohol aqueous solution (solid content 10%, Gohsenol T-330, manufactured by Nippon Synthetic Chemical Co., Ltd.) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content 10%) 5 parts・ 15 parts of polyamide epichlorohydrin (solid concentration 30%, Sparamine A301, manufactured by Toho Chemical Co., Ltd.)

Further, a paint for an ink absorbing layer having the following composition was prepared, and a thermosensitive recording medium of the present invention was prepared.・ Carboxyl-modified polyvinyl acetal aqueous solution 50 parts (solid content concentration 10%, acetalization degree 26 mol%) ・ Carboxyl modified polyvinyl acetal aqueous solution 50 parts (solid content concentration 10%, acetalization degree 1 mol%) ・ [C] solution 20 parts 5 parts of aqueous dispersion of zinc stearate (solid content 10%) 15 parts of polyamide epichlorohydrin (solid content 30%, manufactured by Toho Chemical Co., Sparamine A301)

Example 9 A heat-sensitive recording medium of the present invention was produced in exactly the same manner as in Example 8, except that the following composition was used as the paint for the ink absorbing layer.・ 5 parts of carboxyl-modified polyvinyl acetal aqueous solution (solid content concentration 10%, acetalization degree 49 mol%) ・ 95 parts of carboxyl-modified polyvinyl acetal aqueous solution (solid content concentration 10%, acetalization degree 1 mol%) ・ 20 parts of [C] solution 5 parts of aqueous dispersion of zinc stearate (solid content 10%) 15 parts of polyamide epichlorohydrin (solid content 30%, manufactured by Toho Chemical Co., Sparamine A301)

Example 10 A heat-sensitive recording medium of the present invention was produced in exactly the same manner as in Example 8, except that the following composition was used as the paint for the ink absorbing layer. -30 parts of aqueous solution of carboxyl-modified polyvinyl acetal (solid content concentration 10%, degree of acetalization 49 mol%)-70 parts of aqueous solution of carboxyl-modified polyvinyl acetal (solid content concentration 10%, degree of acetalization 4 mol%)-[C] solution 20 parts 5 parts of aqueous dispersion of zinc stearate (solid content 10%) 15 parts of polyamide epichlorohydrin (solid content 30%, manufactured by Toho Chemical Co., Sparamine A301)

Example 11 A heat-sensitive recording medium of the present invention was produced in exactly the same manner as in Example 8, except that the following composition was used as the paint for the ink absorbing layer.・ Aqueous solution of carboxyl-modified polyvinyl alcohol 10 parts (solid content 10%, T-330, manufactured by Nippon Synthetic Chemical Co.) ・ Aqueous solution of carboxyl-modified polyvinyl acetal 10 parts (solid content 10%, degree of acetalization 28 mol%) ・ Carboxyl-modified polyvinyl Acetal aqueous solution 80 parts (solid content concentration 10%, acetalization degree 1 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (solid content concentration) 30%, Sparamine A301, manufactured by Toho Chemical Co., Ltd.)

Example 12 A heat-sensitive recording medium of the present invention was produced in exactly the same manner as in Example 8, except that the following composition was used as the paint for the ink absorbing layer.・ Aqueous solution of carboxyl-modified polyvinyl alcohol 10 parts (solid content 10%, manufactured by Nippon Synthetic Chemical Co., T-330) ・ Aqueous solution of carboxyl-modified polyvinyl acetal 25 parts (solid content 10%, degree of acetalization 28 mol%) ・ Carboxyl-modified polyvinyl Acetal aqueous solution 65 parts (solid content concentration 10%, acetalization degree 1 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (solid content concentration) 30%, Sparamine A301, manufactured by Toho Chemical Co., Ltd.)

Example 13 A high-quality paper of 137 g / m ² was used as a support, and the surface opposite to the surface on which the heat-sensitive recording layer was provided was previously coated with a magnetic recording layer paint having the following composition to a thickness of 13 μm. A thermosensitive recording medium of the present invention having a magnetic recording layer was produced in exactly the same manner as in Example 8, except that the magnetic recording layer was provided. Barium ferrite 100 parts (coercive force 3000 Oersted, average particle diameter 0.6 μm) Polyester resin 40 parts (Byron 200, manufactured by Toyobo Co., Ltd.) Carbon black 5 parts (Mitsubishi Carbon No. 40, manufactured by Mitsubishi Kasei Corporation) Lecithin 2 parts ・ Methyl ethyl ketone 150 parts ・ Toluene 180 parts Example 14 The heat-sensitive recording of the present invention having a magnetic recording layer in the same manner as in Example 13 except that the same paint as in Example 8 was used as the paint for the ink absorbing layer. A medium was prepared.

Comparative Example 5 A comparative thermosensitive recording medium was prepared in exactly the same manner as in Example 8, except that the following composition was used as the coating material for the ink absorbing layer. 100 parts of a carboxyl-modified polyvinyl alcohol aqueous solution (solid content 10%, T-330 manufactured by Nippon Synthetic Chemical Co., Ltd.) 20 parts of [C] solution 5 parts of an aqueous dispersion of zinc stearate (solid content 10%) 5 parts 15 parts of polyamide epichlorohydrin (solid content: 30%, manufactured by Toho Chemical Co., Sparamine A301)

Comparative Example 6 A comparative thermosensitive recording medium was prepared in exactly the same manner as in Example 8, except that the coating composition for the ink absorbing layer used was of the following composition.・ Carboxyl-modified polyvinyl acetal aqueous solution 100 parts (solid content concentration 10%, acetalization degree 49 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (Solid content concentration 30%, manufactured by Toho Chemical Co., Sparamine A301)

Comparative Example 7 A comparative heat-sensitive recording medium was prepared in exactly the same manner as in Example 8, except that the paint having the following composition was used as the paint for the ink absorbing layer.・ Carboxyl-modified polyvinyl acetal aqueous solution 100 parts (solid content concentration 10%, acetalization degree 1 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (Solid content concentration 30%, manufactured by Toho Chemical Co., Sparamine A301)

Comparative Example 7 A comparative thermosensitive recording medium was prepared in exactly the same manner as in Example 8, except that the paint having the following composition was used as the paint for the ink absorbing layer.・ Carboxyl-modified polyvinyl acetal aqueous solution 100 parts (solid content concentration 10%, acetalization degree 10 mol%) ・ [C] solution 20 parts ・ Zinc stearate aqueous dispersion (solid content concentration 10%) 5 parts ・ Polyamide epichlorohydrin 15 parts (Solid content concentration 30%, manufactured by Toho Chemical Co., Sparamine A301)

Tables 1 and 2 show the results of evaluating the thermal recording media obtained in Examples 1 to 14 and Comparative Examples 1 to 8 for each item by the following methods. <Recording characteristics> Recording was performed with a thermal printing device manufactured by Matsushita Electronic Components Co., Ltd. at an applied power of 0.5 W / dot and a pulse width of 1.0 msec, and the density of the solid black portion was measured using a Macbeth reflection densitometer RD-914.
And the recording density was evaluated. <Printability> Using a stamp using water-based ink,
Five seconds after stamp printing on the protective layer, the printed portion was rubbed with a fingertip to evaluate dryness and fixability.印字 indicates that printing was hardly obtained due to friction, Δ indicates that printing was considerable, and X indicates that printing was hardly obtained and was not practical.

<Blocking Resistance> Under an environment of 30 ° C. and 80% RH, a stack of 20 thermosensitive recording media and a load of 60
After standing for 24 hours under the condition of kg / m ² , a blocking test was performed. A sample having almost no blocking and having no practical problem at all was marked as "A", a sample with some blocking occurred as "A", and a sample with completely blocked and unpractical was rated as "x". <Barrier Property of Protective Layer> Methyl alcohol was applied to the surface of the protective layer or the ink absorbing layer, and a test was conducted on the chemical barrier property of the protective layer. In the case of poor barrier properties, methyl alcohol penetrates and reaches the heat-sensitive recording layer to form color. Therefore, the barrier properties of the protective layer were visually evaluated.も の indicates no color development, 認 め indicates some color development, and × indicates that the front surface was completely colored and could not withstand practical use.

[0046]

[Table 1]

[0047]

[Table 2]

As shown in Tables 1 and 2, the heat-sensitive recording medium of the present invention is an excellent heat-sensitive recording medium having good printability for aqueous inks without impairing properties such as recording properties, blocking properties and barrier properties. Was confirmed. Further, the thermosensitive magnetic recording media obtained in Examples 6, 7, 13 and 14 are further applied to a vending machine for cash vouchers having a thermosensitive recording mechanism, and write and read of predetermined magnetic information, and the amount of money indicated by the remaining balance are detected by heat. When applied to the recording surface, it was confirmed that there was no problem at all.

[0049]

The heat-sensitive recording medium of the present invention has an excellent effect that the printing characteristics for aqueous inks are good without impairing the necessary characteristics such as recording characteristics, chemical resistance, water resistance and blocking resistance. Things. Further, by providing a magnetic recording layer on the heat-sensitive recording medium of the present invention, it can be widely used as a heat-sensitive magnetic recording medium having excellent printing characteristics for water-based ink, for example, as a ticket such as a ticket, a pass, a parking ticket, and the like. It can be used for.

Claims (2)

(57) [Claims] 1. A heat-sensitive recording medium comprising a support and a heat-sensitive recording layer laminated on at least one surface of the support, a polyvinyl acetal resin having an acetalization degree of 0.1 to 5 mol% and an acetalization degree of 20 to 5 mol% on the heat-sensitive recording layer. A thermosensitive recording medium comprising a layer containing 60 mol% of a polyvinyl acetal resin. 2. A polyvinyl acetal resin having a degree of acetalization of 0.1 to 5 mol% and a degree of acetalization of 20 to 60.
2. The heat-sensitive recording medium according to claim 1, wherein the compounding ratio of the polyvinyl acetal resin of mol% is 95: 5 to 50:50 by weight.