JPH06328839A - Heat-sensitive recording body - Google Patents

Abstract

PURPOSE:To obtain a heat sensitive recording body whose recorded information should not be known by a third party, by a method wherein a heat-sensitive recording layer, a consealing layer which is strippable and has an opaqueness of at least 90%, an achromatic layer, and a heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloration agent are provided in order on a substrate in a coating process. CONSTITUTION:In a heat-sensitive recording body, a heat-sensitive recording layer, a consealing layer which is strippable and has an opaqueness of at least 90% based on JIS-P-8138, an achromatic layer and the heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloration agent are provided in order on a substrate in a coating process. In the case where the heat-sensitive recording body is used as a slip or a receipt, a letter or a sign are put in the substrate by a watermark processing or embossing processing or after a coating process of base paper or any of the layers, a form or a forgery preventive letter or sign or advertisement or explanatory note can be print-processed also. Then, a sealing effect also can be improved by performing printing processing on the rear of the substrate or the consesling layer by a thick color.

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 material in which information recorded by a heat-sensitive recording method is not known to a third party.

[0002]

2. Description of the Related Art Utilizing a color reaction between a color former and a color former,
A heat-sensitive recording material in which a recording image is obtained by reacting both color-developing substances with heat energy from a thermal head is well known. Generally, thermal recording materials are relatively inexpensive, and the recording equipment is compact and easy to maintain.
It is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields. However,
In general, the thermosensitive recording medium that is commercially available is recorded in a state where the output information can be seen by anyone,
It is not suitable for communicating confidential information. Therefore, in order to conceal the information output to the thermosensitive recording medium, a method of laminating a base material having a concealing property on the thermosensitive recording layer is disclosed in Japanese Unexamined Patent Publication No. Sho 6-62.
As described in JP-A-1-248785 and JP-A-2-286391, the preservability of a recorded image may be reduced or fog may be caused on a background portion depending on the type of an adhesive used for bonding substrates. Occurs. In addition, the adhesion between the heat-sensitive recording material and the concealing substrate is incomplete, or after bonding,
Curling that is difficult to correct may occur. Furthermore,
The production of these thermosensitive recording bodies requires a step of laminating them using equipment such as a laminator, resulting in a high cost.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium in which information recorded by the thermosensitive recording system is not known to a third party.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that a thermosensitive recording layer A, which is peelable and has an opacity (JIS
(Based on P 8138) 90% or more of a concealing layer, a decoloring layer, and a heat-sensitive recording layer B containing a colorless or light-colored basic dye and a coloring agent are sequentially provided in the coating step, whereby the above problems are solved. I found it resolved. Further, by forming an erasing layer and a thermosensitive recording layer B that develops color with low applied energy on the concealing layer in sequence, when writing the address or address of the destination, the applied thermal energy is the lowest with the applied energy. When recording only the recording layer to develop color and writing confidential information, high applied energy is used to melt the decolorizing agent in the decoloring layer and the dye in the top thermosensitive recording layer, The present invention has been completed by opening up a new application in which the color development of the uppermost heat-sensitive recording layer can be suppressed by contacting with it and recording can be performed in the heat-sensitive recording layer below the concealing layer.

[0005]

The heat-sensitive recording material of the present invention comprises a support, a heat-sensitive recording layer A, a peelable and opaque material (JIS P 813).
(Based on 8) of 90% or more of a concealing layer, a decoloring layer, and a heat-sensitive recording layer B are sequentially provided by a coating process, and the heat-sensitive recording layer A or the heat-sensitive recording layer A and a peeling layer are provided. By incorporating at least one of a metal salt of a higher fatty acid, a wax, and a silicone-based compound in the intermediate layer provided between the layers as a peelability improving agent, the hiding layer can be easily peeled off. When the layer adjacent to the concealing layer is the heat-sensitive recording layer A, 5 parts of the above-mentioned peeling improver is added to the total solid amount of the heat-sensitive recording layer.
It is desirable to adjust the content in the range of 50 to 50% by weight, preferably 10 to 30% by weight. When the layer adjacent to the concealing layer is the intermediate layer, the peeling improving agent is added in an amount of 5 relative to the total solid amount of the intermediate layer.
It is desirable to add more than 10% by weight, preferably more than 10% by weight.

The opacity of the concealing layer is determined according to JIS P after coating and drying a desired amount of a coating liquid for forming the concealing layer on a transparent film.
8138. When the opacity of the hiding layer is less than 90%, it is easy to read the recorded image formed on the heat-sensitive recording layer from above the hiding layer, so 95% or more is preferable. The hiding layer of the present invention is mainly composed of a pigment or a dye and an adhesive, and as the pigment, an inorganic, organic white or colored pigment, and a dye can be used, for example, calcium carbonate, zinc oxide, aluminum oxide, Inorganic pigments such as titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, talc, kaolin, clay, calcined kaolin, bronze powder, carbon black, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, phthalocyanine, Examples thereof include organic pigments such as metal salts of phthalocyanine and dyes such as methyl violet. Further, in order to obtain a high hiding effect with a small amount of use, it is desirable to use bronze powder, carbon black, and a pigment or dye having a similar color to the recorded image of the thermosensitive coloring layer, which have excellent hiding properties.

In the hiding layer coating liquid, usually as a binder,
Starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group 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 emulsion, urea resin, At least one of melamine resin, amide resin, polyurethane resin and the like is blended in the range of about 20 to 80% by weight based on the total solid content of the hiding layer. Further, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound may be added to further improve the film forming property.

Further, various auxiliary agents can be added to the coating liquid, if desired, and examples thereof include dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. , An antifoaming agent, a fluorescent dye, a coloring dye, etc. are appropriately added. The hiding layer coating liquid generally uses water as a dispersion medium and is formed on the heat-sensitive recording layer or the intermediate layer. The coating amount of the masking layer coating liquid is 3 to 80 g / m as a dry weight.
² , preferably in the range of 5 to 40 g / m ² .

In the present invention, the concealment is provided by providing an intermediate layer containing at least one of a metal salt of a higher fatty acid, a wax and a silicone compound as a peelability improving agent between the heat-sensitive recording layer A and the concealing layer. The peeling of the layers becomes easier. In the intermediate layer, as a binder together with a release modifier, for example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group 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 emulsion, urea Resin, melamine resin, amide resin, polyurethane ionomer and the like are used in combination.

It is also possible to use various pigments in combination, for example, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcination. Examples thereof include inorganic pigments such as kaolin and colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, raw starch particles, and organic pigments such as polyurethane / polyurea microcapsules. Further, in the coating liquid, various surfactants such as sodium dioctylsulfosuccinate (dispersant, wetting agent), antifoaming agent, potassium alum, water-soluble polyvalent salt such as aluminum acetate, etc. may be added as necessary. It can also be added as appropriate. The intermediate layer coating liquid is generally formed on the thermosensitive recording layer using water as a dispersion medium. The coating amount of the coating liquid for the intermediate layer is adjusted to a dry weight of 0.1 to 15 g / m ² , preferably about 0.5 to 6 g / m ² .

In the heat-sensitive recording material of the present invention, the recording mechanism used in the heat-sensitive recording layer A may be one that develops or discolors by heat, for example, a combination of a colorless or light basic dye and a coloring agent. , A combination of a diazonium salt and a coupler, a combination of a transition metal such as iron and a chelate compound,
Examples thereof include a combination of an aromatic isocyanate compound and an imino compound, but a combination of a colorless or light-colored basic dye and a colorant is preferably used because it is excellent in recording density, background and preservability of a recorded image. . The recording mechanism used in the heat-sensitive recording layer B is a combination of a colorless or pale basic dye having high reactivity with a decoloring agent and a color developing agent. Hereinafter, the heat-sensitive recording layer formed by combining a colorless or light-colored basic dye and a coloring agent will be specifically described.

As the colorless or light-colored basic dye, various known compounds can be used, and the following are exemplified. 3,3-bis (p-dimethylaminophenyl) -6
-Dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] Fluoran, 3- (N-ethyl-N-p-tolyl) amino-7-
N-methylanilinofluorane, 3-diethylamino-
7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino- 6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl) -N-cyclohexyl)
Amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane,
3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-
7- (o-chlorophenylamino) fluorane, 3-di (n-butyl) amino-7- (o-chlorophenylamino) fluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-di (n -Butyl) amino-7- (o-fluorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p)
-Toluidino) -6-methyl-7- (p-toluidino)
Fluoran, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3
-(N-methyl-Nn-propylamino) -6-methyl-7-anilinofluorane, 3,3-bis [1- (4
-Methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1 -(4-Pyrrolidinophenyl) ethylene-
2-yl] -4,5,6,7-tetrachlorophthalide,
3,3-Bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3-p- (p-anilinoanilino) anilino-6 -Methyl-7-chlorofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] ] Phenyl} propane,
3,6, -bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Various known colorants are known for use in combination with the above basic dye,
For example, the following are exemplified. Inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate, 4-cumylphenol, hydroquinone monobenzyl ether, 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenol,
1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4'-dihydroxydiphenyl-2,2-butane, 4,4'-dihydroxydiphenylmethane, 2,2
-Bis (4-hydroxyphenyl) -4-methylpentane, 2,2-bis (4-hydroxyphenyl) heptane, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-
Oxapentane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α -Methyl-α- (4'-hydroxyphenyl) ethyl] benzene, 4,4'-dihydroxydiphenyl sulfide, bis (4-hydroxy-3-)
Methylphenyl) sulfine, benzyl 4-hydroxybenzoate, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, (4
-Hydroxyphenylthio) acetic acid-2- (4-hydroxyphenylthio) ethyl ester, di (p-hydroxyphenylthioethyl) ether, N, N'-di-m-chlorophenylthiourea, N- (phenoxyethyl)- Four
-Phenolic compounds such as hydroxyphenylsulfonamide, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 5- [p- (2- p
-Methoxyphenoxyethoxy) cumyl] salicylic acid,
Aromatic carboxylic acids such as p-chlorobenzoic acid, salts of these aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, and antipyrine of zinc thiocyanate. Examples include organic acidic substances such as complexes. In the heat-sensitive recording material of the present invention, the use ratio of the basic dye contained in the recording layer and the color developing agent is not particularly limited, but is generally 10 to 5 relative to 100 parts by weight of the basic dye.
It is desirable to use about 100 parts by weight, and preferably about 50 to 300 parts by weight, of the color developing agent.

In the heat-sensitive recording material of the present invention, a sensitizer can be added to the heat-sensitive recording layer according to the purpose. Specific examples of the sensitizer include stearic acid amide and methoxycarbonyl-N-stearic acid. Benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide, dibenzyl terephthalate, dimethyl terephthalate,
Dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate,
Dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p-chlorobenzyl, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxy). Ethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (phenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,
2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2
-Methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetizide,
N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, p- (4-tolyloxy) biphenyl, 5
-Bis (4-methoxyphenoxy) -3-oxa-hentane and the like are exemplified. Among these sensitizers, 1,
2-di (3-methylphenoxy) ethane, 1,2-di (phenoxy) ethane, 2-naphthylbenzyl ether, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p-chlorobenzyl , 2-naphthylbenzyl ether, p- (4-tolyloxy) biphenyl, 5-bis (4-methoxyphenoxy) -3-
Oxa-hentane is more preferable because it shows a particularly excellent sensitizing effect. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

Further, a preservative improving agent may be used in combination depending on the purpose so as to further enhance the preservability of the recorded image as long as the effect is not impaired. Specific examples of such a storability improver include, for example, 1,4-diglycidyloxybenzene,
4,4'-diglycidyloxydiphenyl sulfone, 4
-Benzyloxy-4 '-(2-methylglycidyloxy) diphenyl sulfone, diglucidyl terephthalate,
Epoxy compounds such as bisphenol A type epoxy resin,
2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-) tert-butylphenol), 4,
4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert-
Butylphenol), 4,4'-butylidene bis (6-
tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4)
-Hydroxy-5-tert-butylphenyl) butane,
4,4'-thiobis (3-methylphenol), 4,
4'-dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,
3 ', 5,5'-tetramethyldiphenyl sulfone,
2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,
5-dichlorophenyl) propane, 2,2-bis (4-
Hindered phenol compounds such as hydroxy-3,5-dimethylphenyl) propane, 1- [α-methyl-α-
(4'-Hydroxyphenyl) ethyl] -4- [α ',
α'-bis (4 "-hydroxyphenyl) ethyl] benzene, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-
Butylphenyl) sodium phosphate and the like.

In order to prepare a coating liquid for a recording layer containing these substances, water is generally used as a dispersion medium, and a basic dye, a coloring agent, and further a basic dye, a coloring agent, and further are required by a stirring / grinding machine such as a ball mill, attritor, or sand mill. A sensitizer or the like added according to the above is dispersed together or separately to prepare a coating liquid.
In the coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, arabic gum as an adhesive,
Carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, fully saponified and partially saponified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid Copolymer salts, styrene / acrylic acid copolymer salts, styrene / butadiene copolymer emulsions, etc. are used in an amount of 10 to 40% by weight, preferably about 15 to 30% by weight, based on the total solid content.

It is also possible to use various pigments in combination in the coating liquid. For example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles can be used. Furthermore, various auxiliaries can be added to the coating liquid, for example, disodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, lauryl alcohol sulfate / sodium salt, alginate, fatty acid metal salt, and other dispersants. , Benzophenone-based, triazole-based UV absorbers,
Other examples include antifoaming agents, fluorescent dyes, and coloring dyes.
The coating liquid for the thermosensitive recording layer A is generally formed on a support by using water as a dispersion medium. The coating amount of the coating liquid for the thermosensitive recording layer A is 0.1 to 15 g / m ^{2 on} a dry weight basis, and preferably 0.1.
It is adjusted within the range of about 5 to 6 g / m ² .

The decoloring layer of the present invention contains a decoloring agent as a main component, but in addition, various kinds of adhesives, pigments, heat-fusible substances, auxiliaries and the like as in the above-mentioned thermosensitive recording layer A are appropriately used. Be compounded.
Further, the layer structure of the decoloring layer is not limited to a single layer, and a decoloring layer containing a decoloring agent as a main component and a layer containing another material as a main component are used
It may be laminated in more than two layers. In particular, a decolorizing layer having a two-layer structure in which a barrier layer containing a pigment and / or a heat-fusible substance as a main component is laminated on a layer containing a decolorizing component as a main component is It is excellent in desired effects of the invention.

The decolorizing agent used in the decoloring layer of the thermosensitive recording medium of the present invention is not particularly limited, but aliphatic amines, piperidines, piperazines, pyridines,
Imidazoles, imidazolines, morpholines, guanidines, amidines, polyethers, glycols, aromatic amides and the like are preferably used. The amount of the decoloring agent used is 0.1 to 20 parts by weight, preferably 0.5 to 6 parts by weight, based on 1 part by weight of the total amount of the basic leuco dye and the color former used in the thermal recording layer B. It is desirable to adjust within the range of parts. Further, it is of course possible to use two or more kinds of decolorizing agents together. The decoloring layer is generally formed on the concealing layer using water as a dispersion medium, and the coating amount of the decoloring layer is not particularly limited, but it is preferable to adjust it in the range of 1 to 10 g / m ² .

Materials used in the heat-sensitive recording layer B are appropriately selected from the basic dyes, colorants, sensitizers, adhesives, pigments and auxiliaries exemplified in the description of the heat-sensitive recording layer A. It is possible to use a preservability improving agent within a range that is selected and used and does not impair the decoloring effect. Further, when the thermal recording layer B is brought into direct contact with a recording device or a recording head, various lubricants may be added so as not to cause sticking. For example, stellaric acid, polyethylene, carnauba wax, paraffin wax, stearin. Examples thereof include zinc acid, calcium stearate and ester wax. The coating amount of the heat-sensitive recording layer B is not particularly limited, but can be 0.
It is desirable to adjust the amount between 5 and 10 g / m ² , preferably between 1 and 6 g / m ² .

In the present invention, the heat-sensitive recording layer A, the hiding layer,
The method for forming the decolorizing layer and the heat-sensitive recording layer B is not particularly limited, and it can be formed according to a conventionally well-known and common technique, for example, air knife coating, varibar blade coating, pure blade coating, short coating It can be formed by a method of applying a coating liquid on a support by dwell coating, curtain coating, or the like, followed by drying. As the support, paper, synthetic paper, plastic film or the like is appropriately selected and used.

In the present invention, if necessary, a resin layer may be provided on the back side of the recording medium, a protective layer may be provided on the thermal recording layer B, or an undercoat may be provided between the support and the thermal recording layer. Add various publicly known technologies in the field of thermal recording media, such as providing a layer to improve image quality and sensitivity, processing the back surface of the recording material with an adhesive to process it into an adhesive label, and providing a magnetic layer on the back surface of the recording material. It is possible. Further, the image quality and the image density can be improved by performing a super calendering process after forming each layer. Further, it is conceivable that a processing treatment is applied after coating the hiding layer so that the hiding layer can be peeled off without using a special peeling tool or the like. Examples of such a processing treatment include, for example, a perforation processing, a cutting processing or a punching processing by a method that does not penetrate the hiding layer into an end portion or a part of the support of the recording material, or vice versa. A process of cutting or punching,
Alternatively, a process of adhesively adding a pull tab on the concealing layer may be used.

When the thermosensitive recording medium of the present invention is used as a slip or receipt, characters or symbols are put on the support by watermarking or embossing, or the base paper or any of the layers is coated with a foam. It is also possible to print the anti-counterfeiting characters and symbols, advertisements, and explanatory notes.
Further, it is possible to enhance the hiding effect by performing a dark color printing process on the back surface of the support or on the hiding layer.

[0024]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, "part" and "%" in an example show "weight part" and "weight%", respectively, unless there is particular notice.

Example 1 (1) Formation of Undercoat Layer Fired clay (trade name: Ansilex, manufactured by EMC) 1
00 parts, styrene-butadiene copolymer latex (solid content: 50%) 15 parts, polyvinyl alcohol 10
% Aqueous solution 30 parts and water 200 parts were mixed and stirred to prepare an undercoat layer coating liquid. The coating liquid obtained was applied to one side of 160 g / m ² of high-quality paper (paper thickness 180 μm), and the coating amount after drying was 10 g.
/ M ² and by coating and drying so as to form an undercoat layer.

(2) Preparation of solution A 10 parts of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane, 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of methylcellulose % Aqueous solution 5 parts and water 40 parts were pulverized with a sand mill until the average particle size became 0.5 μm.

(3) Preparation of solution B A composition consisting of 30 parts of 4,4'-isopropylidenediphenol, 5 parts of a 5% aqueous solution of methylcellulose and 80 parts of water was pulverized with a sand mill until the average particle size became 0.8 μm. did.

(4) Preparation of liquid C Tetrakis (1,2,2,6,6-pentamethyl-4-)
Piperidyl) -1,2,3,4-butanetetracarboxylate 50 parts, 25% 5% aqueous solution of styrene / maleic anhydride copolymer salt (trade name: POLYSTAR A-1060, NOF Corporation), water 110 The composition consisting of 1 part was pulverized with a sand mill until the average particle size became 3 μm.

(5) Preparation of Solution D A composition consisting of 30 parts of 4,4'-cyclohexylidenediphenol, 5 parts of a 5% aqueous solution of methylcellulose and 80 parts of water was ground by a sand mill until the average particle size became 3 μm.

(6) Preparation of solution E 3- (n-ethyl-n-isoamylamino) -6-methyl-7-phenylaminofluorane 10 parts, dibenzyl terephthalate 20 parts, 5% aqueous solution of methylcellulose 15 parts and water A composition consisting of 80 parts was ground with a sand mill until the average particle size became 3 μm.

(7) Preparation of solution F 3- (n-diethylamino-2-methylphenyl) -7
-(4-Dimethylaminophenyl) -6-dimethylaminophthalide 10 parts, dibenzyl terephthalate 20
Parts, 15 parts of a 5% aqueous solution of methylcellulose and 80 parts of water
The composition consisting of 1 part was pulverized with a sand mill until the average particle size became 3 μm.

(8) Formation of Thermosensitive Recording Layer A 75 parts of solution A, 115 parts of solution B, 10% aqueous solution of polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) 8
A coating solution obtained by mixing and stirring 0 parts of the above was applied and dried on the above-mentioned undercoat layer so that the coating amount after drying was 6 g / m ^2, and then supercalendering treatment was carried out to form a thermosensitive recording layer A. .

(9) Formation of Intermediate Layer 80 parts of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) and a 30% aqueous dispersion of zinc stearate (trade name: Hydrin Z-7, Chukyo) A coating solution obtained by mixing and stirring 100 parts of Oils and Fats Co., Ltd. was coated and dried on the thermosensitive recording layer A so that the coating amount after drying was 5 g / m ² to form an intermediate layer.

(10) Formation of Concealing Layer 60 parts of bronze powder, 40% 10% aqueous solution of polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.)
A coating solution obtained by mixing and stirring 0 parts, 40 parts of styrene-butadiene copolymer latex (solid content: 50%), and 100 parts of water with a coating amount of 10 after drying on the intermediate layer.
After coating and drying so as to be g / m ² , super calendering treatment was performed to form a hiding layer. (The opacity of the hiding layer, which was provided on the transparent PET film having a thickness of 50 μm so that the coating amount after drying the hiding layer was 10 g / m ² , was 100%.)

(11) Formation of decolorizing layer 185 parts of C liquid, polyvinyl alcohol (trade name: PVA
-117, manufactured by Kuraray Co., Ltd.) and mixed with 100 parts of a 10% aqueous solution to obtain a coating liquid, which is coated and dried on the above-mentioned concealing layer so that the coating amount after drying is 3 g / m ^2. Was formed.

(12) Formation of Thermosensitive Recording Layer B 185 parts of D liquid, 95 parts of E liquid, 30 parts of F liquid, silicon oxide pigment (trade name: Mizukasil P-603, manufactured by Mizusawa Chemical Co., Ltd.) 20
Part, polyvinyl alcohol (trade name: PVA-117,
A coating solution obtained by mixing 100 parts of a 10% aqueous solution of Kuraray Co., Ltd.) and 50 parts of water with stirring is applied on the above decolorizable layer so that the coating amount after drying is 3 g / m ^2, and then dried. Then, a super calender treatment was performed to obtain a heat sensitive recording material.

Example 2 In the formation of the intermediate layer of Example 1, 30% of paraffin wax was used instead of 100 parts of a 30% aqueous dispersion of zinc stearate (trade name: Hydrin Z-7, Chukyo Yushi Co., Ltd.). A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 100 parts of an aqueous dispersion (Hydrin P-7, manufactured by Chukyo Yushi Co., Ltd.) was used.

Example 3 In the formation of the intermediate layer of Example 1, 100 parts of a 30% aqueous dispersion of zinc stearate (trade name: Hydrin Z-7, manufactured by Chukyo Yushi Co., Ltd.) was replaced with an epoxy-modified silicone oil. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 100 parts of 35% aqueous dispersion (product name: Polon MF-11B, manufactured by Shin-Etsu Chemical Co., Ltd.) of was used.

Example 4 In the formation of the thermosensitive recording layer of Example 1, 30% of zinc stearate was added to the coating liquid for the thermosensitive recording layer.
Water dispersion (trade name: Hydrin Z-7, Chukyo Yushi Co., Ltd.)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 40 parts were added and no intermediate layer was formed.

Example 5 In the formation of the hiding layer of Example 1, 60 parts of carbon black was used instead of 60 parts of bronze powder, and 400 parts of a 10% aqueous solution of polyvinyl alcohol was used instead of silanol-modified polyvinyl alcohol (trade name). A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 400 parts of a 10% aqueous solution of R-1130, manufactured by Kuraray Co., Ltd.) was used. (On a transparent PET film having a thickness of 50 μm, the coating amount after drying the coating liquid for forming the hiding layer was 10 g / m 2.
The opacity of the hiding layer provided so as to be ² was 100%. )

Example 6 In the formation of the concealing layer of Example 1, titanium oxide 6 was used instead of 60 parts of bronze powder.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 0 part was used and the coating amount after drying was 30 g / m ² . (Thickness 50
The opacity of the concealing layer, which was provided on the transparent PET film having a thickness of μm so that the coating amount for drying the concealing layer was 30 g / m ² , was 91%. )

Example 7 Example 1 was repeated except that a 30% aqueous dispersion of zinc stearate (trade name: Hydrin Z-7, manufactured by Chukyo Yushi Co., Ltd.) was not used in the formation of the intermediate layer of Example 1. A thermosensitive recording medium was obtained in the same manner as described above.

Comparative Example 1 In the formation of the hiding layer of Example 1, kaolin 60 was used instead of 60 parts of bronze powder.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the coating amount was 20 g / m ² after drying. (Thickness 50μ
The opacity of the hiding layer, which was provided on the transparent PET film of m so that the coating amount for drying the hiding layer was 20 g / m ² , was 28%. )

Comparative Example 2 Example 1 was repeated except that 60 parts of light calcium carbonate was used instead of 60 parts of bronze powder in the formation of the hiding layer of Example 1 and the coating amount after drying was 20 g / m ^2. A thermosensitive recording medium was obtained in the same manner as described above.
(The opacity of the hiding layer provided on the transparent PET film having a thickness of 50 μm so that the coating amount after drying the hiding layer-forming coating solution was 20 g / m ² was 35%.)

The 9 types of thermal recording materials obtained as described above were evaluated as follows, and the obtained results are shown in [Table 1]. Recording Density Recording was performed under the following conditions using a thermosensitive recording simulator (PH-TMD type, manufactured by Okura Electric Co., Ltd., applied voltage: 18 V), peeled from the peeling layer, and recorded on the thermosensitive recording layer A and the thermosensitive recording layer B. The density of the image is measured with a Macbeth densitometer (RD-914
Type, manufactured by Macbeth). (A) Applied energy: 0.2 mJ / dot (b) Applied energy: 0.5 mJ / dot

Concealment Property After recording with an applied energy of 0.5 mJ / dot, the concealment layer was visually observed to check whether or not the recorded image was visible. Evaluation criteria ⊚: The recorded image cannot be seen at all ∘: The recorded image is blurred and unreadable. ×: The recorded image can be seen through

Peelability After recording with a simulator, a cut was made from the back surface of the base paper at the end of the thermosensitive recording medium, and it was examined whether or not the concealing layer could be easily peeled with a finger by using that portion as a trigger. Evaluation criteria ◎: Very easily peelable ○: Easy peeling ×: Not peelable

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[Table 1]

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As is clear from the results of [Table 1], all of the thermosensitive recording materials of the present invention have the ability to conceal recorded contents, and the concealing layer is easily peeled off when disclosing the contents. It was a heat-sensitive recording material.

Claims (4)

[Claims] 1. A thermosensitive recording layer A on a support, which can be peeled off,
And 90% opacity (based on JISP 8138)
A heat-sensitive recording material comprising the above-mentioned concealing layer, decoloring layer, and heat-sensitive recording layer B containing a colorless or light-colored basic dye and a coloring agent, which are sequentially provided by a coating process. 2. The heat-sensitive recording material according to claim 1, wherein an intermediate layer is provided between the heat-sensitive recording layer A and the concealing layer. 3. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer A contains at least one selected from the group consisting of metal salts of higher fatty acids, waxes and silicone compounds. 4. The heat-sensitive recording material according to claim 2, wherein the intermediate layer contains at least one kind of metal salt of higher fatty acid, waxes and silicone compounds.