JPH0776165A - Thermal record body - Google Patents

Abstract

PURPOSE:To obtain a thermal record body whose thermally recorded information does not become known to a third person by arranging, in sequence on the top face of a support body, a thermal recording layer and a peelable masking layer formed by coating process so as to make recorded information unreadable, and making the face of the masking layer rough. CONSTITUTION:A thermal record body is constituted by arranging in sequence a thermal recording layer and a specified masking layer on the top face of a support body. That is, the masking layer is formed by coating process in a peelable way, so as to make recorded information unreadable. The face of the masking layer is roughed, or a roughed overcoat layer may be arranged on the top face of the masking layer in the thermal record body. In roughing the face, for example, the face is roughed by an embossing roll or a roughing roll after the masking layer is formed. Thus, a thermal record medium whose thermally recorded information does not become known to a third person is obtained.

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, since the thermosensitive recording medium which is generally commercially available is recorded in such a state that the output information can be seen by anyone, it is not suitable for the communication of confidential contents. 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 JP-A-61-248785.
As described in JP-A-2-286391, the preservability of a recorded image may be reduced or fog may be generated on the background portion depending on the type of the adhesive used when the substrates are bonded together. Further, the adhesion between the thermal recording material and the concealing substrate may be incomplete, or curling which is difficult to correct may occur after bonding. Further, the production of these thermal recording bodies requires a step of laminating them using equipment such as a laminator, resulting in high cost.

As a result of earnest studies to solve such a problem, the inventors of the present invention have proposed a heat-sensitive recording material in which a peelable concealing layer is provided on the heat-sensitive recording layer in a coating process (Japanese Patent Application No. 5-957).
41). However, as a result of repeated research, it was found that print marks remain on the surface of the concealing layer depending on recording conditions, and the print marks leak to a third party.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for recording information recorded by a heat-sensitive recording method on a heat-sensitive recording medium which is unknown to a third party.

[0006]

SUMMARY OF THE INVENTION The present invention comprises:
A heat-sensitive recording material comprising a heat-sensitive recording layer and a masking layer which is formed by a coating process and which is peelable and makes the recorded information unreadable. The heat-sensitive recording material is characterized in that the masking layer is roughened. It is a thermosensitive recording medium. Further, the present invention is a thermosensitive recording medium in which a thermosensitive recording layer and a concealing layer which is formed by a coating process and which can be peeled off and which makes recorded information unreadable are sequentially provided on a support. A heat-sensitive recording material having a surfaced overcoat layer.

[0007]

The heat-sensitive recording material of the present invention relates to a heat-sensitive recording material which is provided on the heat-sensitive recording layer or the intermediate layer by a coating process and which has a peelable concealing layer. Then, it is characterized in that the hiding layer or the overcoat layer provided on the hiding layer is roughened.

As a roughening method, after forming a layer, the surface is roughened by an embossing roll or a roughening roll.
Alternatively, to form a roughened layer by coating with a roll or the like having a concave-convex mold, or to press a film having irregularities after applying the coating liquid and take a mold to form a roughened layer, etc. There is a method.

By incorporating at least one of a metal salt of a higher fatty acid, a wax, and a silicone compound as a peelability improving agent in the layer adjacent to the masking layer, the masking layer can be easily peeled. When the layer adjacent to the concealing layer is a heat-sensitive recording layer, 5 to 50% by weight, preferably 10 to 30% by weight, of the above-mentioned peeling improver relative to the total solid amount of the heat-sensitive recording layer.
It is desirable to adjust within the range. When the layer adjacent to the concealing layer is an intermediate layer, it is desirable to add the peeling improver in an amount of 20% by weight or more, preferably 30% by weight, based on the total solid amount of the intermediate layer.

The higher the opacity of the hiding layer, the better. Apply the desired amount of coating liquid for forming the hiding layer on a transparent film.
After drying, if the value (opacity) measured according to JIS P 8138 is less than 90%, it is easy to read the recorded image formed on the heat-sensitive recording layer from above the hiding layer.
It is preferably 0% or more, and particularly preferably 95% or more.

The hiding layer is mainly composed of a pigment or a dye and an adhesive. As the pigment, an inorganic or organic white or colored pigment and a dye can be used. For example, calcium carbonate, zinc oxide, aluminum oxide, Titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, talc,
Inorganic pigments such as kaolin, clay, calcined kaolin, bronze powder, carbon black, styrene microballs, nylon powder, polyethylene powder, urea
Examples include formalin resin fillers, phthalocyanines, organic pigments such as metal salts of phthalocyanines, 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, various auxiliaries can be added to the coating liquid as required. For example, curing agents such as glyoxal, boric acid, dialdehyde starch, epoxy compounds, sodium dioctylsulfosuccinate, and dodecylbenzene. A dispersant such as sodium sulfonate, sodium lauryl alcohol sulfate, a fatty acid metal salt, a defoaming agent, a fluorescent dye, a coloring dye, a metal salt of a higher fatty acid, a wax and the like 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 by dry weight.
g / m ^2, it is preferably adjusted in the range of about 5 to 40 g / m ^2.

As the overcoat layer, an organic or inorganic pigment, a curing agent, a dispersant, an antifoaming agent, a fluorescent dye, a coloring dye, a metal salt of a higher fatty acid, an auxiliary agent such as waxes, and the like can be used as the overcoat layer. Is added appropriately. Of course,
Bronze powder, carbon black, or a pigment or dye having a color similar to that of the recorded image of the thermosensitive coloring layer can be added to further enhance the hiding property. The coating amount of the overcoat layer is adjusted in the range of about 3 to 80 g / m ^{2 in} dry weight.

In the present invention, a metal salt of a higher fatty acid, a wax, or the like is used as a peelability improving agent between the heat-sensitive recording layer and the hiding layer.
By providing the intermediate layer containing at least one of the silicone compounds, the masking layer can be peeled off more easily. In the intermediate layer, as a binder together with a peelability improving agent, 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, if necessary, various kinds of surfactants (dispersing agents, wetting agents) such as sodium dioctylsulfosuccinate, antifoaming agents, water-soluble polyvalent salts such as potassium alum, aluminum acetate, etc. in the coating liquid. Auxiliary agents can be added as appropriate. The intermediate layer coating liquid generally uses water as a dispersion medium,
The heat-sensitive recording layer is formed on the heat-sensitive recording layer by the forming method exemplified above. The coating amount of the coating liquid for the intermediate layer is 0.1% by dry weight.
It is adjusted in the range of ¹ to 15 g / m ² , preferably 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 may be one that develops or changes color by heat, for example, a combination of a colorless or light-colored basic dye and a color former, Examples include a combination of a diazonium salt and a coupler, a combination of a transition metal such as iron and a chelate compound, a combination of an aromatic isocyanate compound and an imino compound, and a combination of a colorless or light-colored basic dye and a colorant. Is preferably used because it is excellent in the recording density, the background portion and the storability of the recorded image. Various known compounds can be used as the colorless or light-colored basic dye, 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] fluorane, 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) fluorane, 3- (N-ethyl-N-flu) Furylamino) -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'- Xanthene-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.

Further, various known colorants are known as colorants used in combination with the above basic dyes,
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 former is
Although it is not particularly limited, a basic dye 100 is generally used.
10-500 parts by weight, preferably 50-
It is desirable to use about 300 parts by weight of the coloring agent.

In the heat-sensitive recording material of the present invention, a sensitizer can be added to the 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,
Oxalic acid-di-p-chlorobenzyl, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) 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-acetophenetidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, p- Examples include (4-tolyloxy) biphenyl and 5-bis (4-methoxyphenoxy) -3-oxa-hentane. Among these sensitizers, 1,2-di (3-methylphenoxy) ethane, 1,2-di (phenoxy) ethane, 2-naphthylbenzyl ether, dibenzyl oxalate, and oxalic acid-di-p-methyl. Benzyl, oxalic acid-di-p-chlorobenzyl, 2-naphthylbenzyl ether, p- (4-tolyloxy) biphenyl,
5-bis (4-methoxyphenoxy) -3-oxa-hentane is more preferable because it exhibits 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 for the purpose of further enhancing 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,
Epoxy compounds such as 4,4'-diglycidyloxydiphenyl sulfone, diglycidyl terephthalate, and 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-
Hindered phenol compounds such as bis (4-hydroxy-3,5-dichlorophenyl) propane and 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1- [α-methyl-α- (4 '-Hydroxyphenyl) ethyl] -4- [α', α'-bis (4 "-hydroxyphenyl) ethyl] benzene, N, N'-di-2-
Examples thereof include naphthyl-p-phenylenediamine and 2,2'-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate.

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 the like are required by a stirring / milling 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.

Further, various auxiliaries can be added to the coating liquid, for example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, lauryl alcohol sulfate / sodium salt, alginate, fatty acid metal salt and the like. Dispersant, benzophenone type,
Examples thereof include UV absorbers such as triazole type, defoaming agents, fluorescent dyes, and coloring dyes.

In the present invention, the method for forming the heat-sensitive recording layer, the intermediate layer and the hiding layer is not particularly limited,
It can be formed according to well-known and conventional techniques,
For example, it can be formed by a method of coating and drying the coating liquid on a support by air knife coating, varibar blade coating, pure blade coating, short dwell coating, curtain coating, or the like. 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, or an undercoat layer may be provided between the support and the thermosensitive recording layer to improve image quality and sensitivity, and It is possible to add various known techniques in the field of heat-sensitive recording material production, such as processing an adhesive label on the back surface to form an adhesive label, or providing a magnetic layer on the back surface of the recording material. 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. Examples of the process include a process of cutting and punching, and a process of adhering a pull tab to the concealing layer.

When the heat-sensitive recording material of the present invention is used as a slip or receipt, characters or symbols are put on the support by watermarking, or a form or forgery is prevented after coating the base paper or any layer. It is also possible to print the characters, symbols, advertisements, explanations, and the like. 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.

[0029]

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] "Formation of undercoat layer" 100 parts of calcined clay (trade name: Ansilex, manufactured by EMC), 15 parts of styrene-butadiene copolymer latex (solid content: 50%), polyvinyl alcohol 10 % Aqueous solution 30 parts and water 200 parts were mixed and stirred to prepare an undercoat layer coating liquid. 16 of the obtained coating liquid
An undercoat layer was formed by coating and drying on one side of 0 g / m ² of high quality paper (paper thickness 180 μm) so that the coating amount after drying was 10 g / m ² .

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

"Preparation of solution B" A composition consisting of 30 parts of 4-4'-isopropylidenediphenyl, 5 parts of a 5% aqueous solution of methylcellulose and 80 parts of water was pulverized with a sand mill until the average particle diameter became 0.7 μm.

"Formation of thermosensitive recording layer" 75 parts of solution A, solution B 1
15 parts, polyvinyl alcohol (trade name: PVA-11
(7, manufactured by Kuraray Co., Ltd.) and mixed with 80 parts of a 10% aqueous solution to obtain a coating liquid, and the coating amount after drying is 6 on the undercoat layer.
A thermosensitive recording layer was obtained by coating and drying so as to obtain g / m ² .
Next, a super calender treatment was performed to form a heat-sensitive recording layer.

"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 Yushi) The coating liquid obtained by mixing and stirring 100 parts of the product) was applied and dried on the thermosensitive recording layer so that the coating amount after drying was 5 g / m ² , to form an intermediate layer.

[Formation of Concealment Layer] Bronze Powder 55
Part, polyvinyl alcohol (trade name: PVA-117,
Kuraray's 10% aqueous solution 400 parts and styrene.
Butadiene copolymer latex (solid content: 50%) 40
Parts of water and 100 parts of water were mixed and stirred, and the coating liquid obtained was coated and dried on the intermediate layer so that the coating amount after drying was 10 g / m ² to form a masking layer. Then, using an embossing machine, a satin pattern was applied to the hiding layer to obtain a heat-sensitive recording material of the present invention.

[Comparative Example 1] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the embossing machine was not used but a super calender was used to smooth the surface of the hiding layer.

[Example 2] 60 parts of titanium oxide was used instead of 55 parts of bronze powder, and the coating amount after drying was 3 parts.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the amount was 0 g / m ² .

[Comparative Example 2] A thermosensitive recording medium was obtained in the same manner as in Example 2 except that the embossing machine was not used but a super calender was used to smooth the surface of the hiding layer.

[Example 3] "Preparation of coating liquid for overcoat layer" Carbon black 6
0 parts, polyvinyl alcohol (trade name: PVA-11
7, Kuraray's) 10% aqueous solution 400 parts, styrene.
Butadiene copolymer latex (solid content: 50%) 40
Parts and 100 parts of water were mixed and stirred to obtain a coating liquid for the overcoat layer.

"Formation of overcoat layer" After the concealing layer of Example 1 was formed, the coating amount of this coating solution after drying was 8 g.
/ M ² was applied and dried to form an overcoat layer, and a satin pattern was applied to the overcoat layer using an embossing machine to obtain a thermal recording material of the present invention.

[Comparative Example 3] A thermosensitive recording medium was obtained in the same manner as in Example 3 except that the embossing machine was not used and the surface of the overcoat layer was smoothed using a super calendar.

Example 4 The coating liquid for overcoat layer obtained in Example 3 was applied and dried so that the coating amount after drying was 8 g / m ² after forming the masking layer of Example 2. An overcoat layer was formed. Next, using an embossing machine,
A matte pattern was applied to the overcoat layer to obtain the heat-sensitive recording material of the present invention.

[Comparative Example 4] In Example 4, a thermosensitive recording medium was obtained by smoothing the surface of the overcoat layer using a super calendar without using an embossing machine.

The eight kinds of thermal recording materials obtained as described above were recorded by using a commercially available thermal facsimile machine (Panafax UF-6, manufactured by Matsushita Electric Transport Co., Ltd.), and the following evaluations were carried out to obtain: The results are shown in [Table 1].

Concealment Property The recording medium after recording was visually observed to see if 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

Applicability of print traces The state of print traces was evaluated by irradiating light obliquely on the surface of the recording body after recording. ◯: The print mark was not readable at all x: The print mark was readable

Peelability 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 off with a finger, triggered by the cut. Evaluation Criteria ○: Can be easily peeled ×: Cannot be peeled

[0048]

[Table 1]

[0049]

As is clear from the results of [Table 1], all of the thermal recording materials of the present invention conceal the recorded contents, and the information cannot be read from the printed marks. Moreover, when disclosing the contents, the hiding layer was a heat-sensitive recording material from which the hiding layer could be easily peeled off. Further, since each layer constituting the thermosensitive recording medium is provided by coating, the recording medium can be provided at an extremely low cost.

Claims (2)

[Claims] 1. A heat-sensitive recording medium comprising a heat-sensitive recording layer and a concealing layer which is formed by a coating process and which is peelable and makes the recorded information unreadable. A thermosensitive recording material characterized by being surfaced. 2. A heat-sensitive recording medium comprising a heat-sensitive recording layer and a concealing layer which is formed by a coating process and which can be peeled off and which makes the recorded information unreadable. A heat-sensitive recording material comprising a planarized overcoat layer.