JPH06305242A - Thermal recording material - Google Patents

Abstract

PURPOSE:To make concealing and presentation of recorded contents easy by a method wherein a thermal recording layer, a peelable intermediate layer which contains an aqueous high polymer, and a concealing layer of which opacity is specific value or higher are successively laminated on a base material. CONSTITUTION:A color developing agent or the like such as colorless or light- colored basic dye, activated clay, etc., are added into aqueous solution of a binder such as polyvinyl alcohol or the like, and mixed to prepare coating liquid for thermal recording layer. Aqueous high polymers of hydroxyethyl cellulose, casein, etc., are dissolved in water to prepare coating liquid for intermediate layer. A specific amount of an inorganic or organic and white or colored pigment is added into the aqueous solution of the binder such as polyvinyl alcohol or the like, and mixed to prepare coating liquid for concealing layer. The coating liquid for thermal recording layer is applied onto base materials of synthetic resin, non-woven fabric, etc., and dried to form a thermal recording layer. Thereafter, the coating liquid for intermediate layer is applied thereon, and dried to laminate an intermediate layer. The liquid for concealing layer is applied on the intermediate layer, and dried to laminate a concealing layer which is 90% or higher in opacity measured by JIS P-8138.

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.

[0004]

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.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have found that a thermosensitive recording layer, an aqueous polymer-containing and peelable intermediate layer, and an opacity (based on JIS P 8138) of 90 are formed on a support. % Or more of the hiding layer is sequentially applied to achieve the above-mentioned object, and at the same time, a thermosensitive recording medium having information hiding property at low cost can be obtained without using special processing equipment and process such as a laminator. They have found that they can be provided and have completed the present invention.

[0006]

In the heat-sensitive recording material of the present invention, the heat-sensitive recording layer is coated with an aqueous polymer-containing and peelable intermediate layer and a hiding layer having an opacity (according to JIS P 8138) of 90% or more. 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. preferable. Incidentally, the opacity of the hiding layer is a desired amount of the coating liquid for forming the hiding layer on a transparent film,
After coating and drying, it is measured according to JIS P 8138.

The pigment used in the hiding layer is an inorganic pigment,
All kinds of organic white or colored pigments can be tried, for example calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin. , Inorganic pigments such as bronze powder and colloidal silica, carbon black, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, raw starch particles, and organic pigments such as polyurethane / polyurea microcapsules. In order to obtain a high hiding effect with a small amount of use, it is desirable to use bronze powder, carbon black, or a pigment having the same or similar color as the color of the heat-sensitive color-developing layer after coloring, which has 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 5 to 40% by weight based on the total solid content of the hiding layer.

If desired, various auxiliary agents can be added to the coating solution. For example, 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 coating liquid for the hiding layer is generally prepared by using water as a dispersion medium, and the dry weight is 1 to 30 on the intermediate layer.
g / m ^2, it is applied preferably 3 to 20 g / m ² range of about.

When the heat-sensitive recording layer contains at least one of a metal salt of a higher fatty acid, a wax and a silicone compound as a peelability improving agent, the peeling of the intermediate layer becomes easy. It is desirable to adjust the above-mentioned release modifier in the range of 5 to 50% by weight, preferably 10 to 30% by weight, based on the total solid content of the heat-sensitive recording layer. If the peelability improving agent in the heat-sensitive recording layer is less than 5%, the peeling of the intermediate layer becomes difficult, and if it exceeds 50%, the recording density decreases.

Specific examples of the peelability improving agent are shown below, but the invention is not necessarily limited to these. Examples of metal salts of higher fatty acids include aluminum stearate; calcium stearate; zinc stearate; zinc oleate; waxes such as beeswax; animal waxes such as shellac wax; vegetable waxes such as carnauba wax;
Paraffin wax; petroleum waxes such as microcrystalline wax; polyethylene wax; higher alcohols; higher ketones; higher amines; condensates of higher fatty acids and amines; synthetic paraffins; chlorinated paraffins; silicone compounds such as silicone resins; Methyl-modified silicone resin; alkyl-modified silicone; higher oil-and-fat-modified silicone; epoxy-modified silicone; methylphenylsilicone and the like.

As the recording mechanism used in the heat-sensitive recording layer of the present invention, any recording mechanism can be used as long as it develops or changes color by heat, for example, a combination of a basic dye and a color former, a diazonium salt. And a coupler, a combination of a chelate compound of a transition element such as iron and a colorant, a combination of an aromatic isocyanate compound and an imino compound, and a hydrophobic polymer emulsion that becomes transparent by heat. The combination of the functional dye and the color former is preferably used because it is excellent in the color density, the background portion and the storability of the recorded image. As such a basic dye, various known colorless or light-colored basic dyes can be used, and specifically, for example, 3,3-bis (p-dimethylaminiphenyl) -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-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-ani Rinofluoran, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) fluorane, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (N-methyl) -N-n-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-dimethylaminoanilino) anilino-6-methyl-7-chlorofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl- N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3,6,11-tri (dimethylamino) fluorane 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 materials are known as a colorant used in combination with the basic dye as described above, for example, activated clay, attapulgite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4,4'- Isopropylidene diphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4 '
-Dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-
4-hydroxyphenyl) sulfone, 4-hydroxy-
4'-methyldiphenyl sulfone, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, bis (p-hydroxyphenyl) butyl acetate, bis (p- Hydroxyphenyl) methyl acetate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4- Phenolic compounds such as hydroxy-3-methylphenyl) sulfine, 4- [2-
Aromatic carboxylic acids such as (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, And salts of these aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel, and organic acid substances such as antipyrine complexes of zinc thiocyanate.

The use ratio of the basic dye and the color developing agent is appropriately selected according to the type of the basic dye or the color developing agent to be used and is not particularly limited, but in general, the basic dye 1 is used. 1 to 50 parts by weight, preferably 2 to parts by weight
About 10 parts by weight of coloring agent is used. A heat-sensitive recording layer coating liquid containing these substances is generally prepared by dispersing water and a dye and a coloring agent together or separately with a stirring / milling machine such as a ball mill, attritor, or sand mill, using water as a dispersion medium. To be done.

In the coating liquid for the heat-sensitive recording layer, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, etc. are usually used as a binder.
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,
At least one kind of styrene / butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin, etc. is contained in an amount of 5 to 30 relative to the total solid content of the recording layer.
It is blended in the range of about wt%.

If desired, various auxiliary agents can be added to the coating solution. For example, 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. 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, fine anhydrous silica, inorganic clay such as activated clay and styrene. Examples thereof include microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles.

Further, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include, for example, stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-
Eicosanoic acid amide, ethylenebisstearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, 1
-Phenyl hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-
Di-p-chlorobenzyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) 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- (3-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 and the like are exemplified. 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 added to enhance the preservability of the recorded image depending on the purpose. Specific examples of the preservability improving agent include, for example, 2,2'-methylenebis (4-methyl-6-tert-butylphenol) and 2,2'-methylenebis (4-ethyl-6-t).
ert-butylphenol), 2,2'-ethylidenebis (4,6-di-tert-butylphenol), 4,
4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-t
ert-butylphenol), 4,4′-thiobis (2
-Methylphenol), 4,4'-thiobis (2,6-
Dimethylphenol), 4,4'-thiobis (2,6-
Di-tert-butylphenol), 2,2'-thiobis (4-tert-octylphenol), 2,2'-
Thiobis (3-tert-octylphenol), 4,
4'-butylidene bis (6-tert-butyl-m-cresol, 1- [α-methyl-α- (4'-hydroxyphenyl) ethyl] -4- [α ', α'-bis (4 "-
Hydroxyphenyl) ethyl] benzene, 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'-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-
Hindered phenol compounds such as bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenyl sulfone, diglycidyl terephthalate,
Epoxy compounds such as cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, N, N'-di-2-naphthyl-
p-phenylenediamine, sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, N, N'-di-2-naphthyl-p-phenylenediamine, 4,4'-bis ( Examples thereof include ethyleneiminecarbonylamino) diphenylmethane.

In the present invention, a film-forming intermediate layer is provided on the heat-sensitive recording layer to facilitate peeling. Examples of the aqueous polymer used for the intermediate layer include starches and hydroxy. Ethyl 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 /
Examples thereof include butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane ionomer and the like.

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, various kinds of surfactants (dispersing agents, wetting agents) such as sodium dioctyl sulfosuccinate, antifoaming agents, water-soluble polyvalent salts such as potassium alum, aluminum acetate, etc. may be contained in the coating liquid, if necessary. Auxiliary agents can be added as appropriate. The coating liquid for the intermediate layer is generally prepared using water as a dispersion medium, and has a dry weight of 1 to 30 g / m ² on the thermosensitive recording layer,
It is preferably applied in the range of about 5 to ²⁰ g / m ² .
The ratio of the aqueous polymer to the pigment used in the intermediate layer is 10 to 200% by weight of the pigment based on the water-soluble polymer, preferably 2
It is desirable to adjust in the range of 0 to 100% by weight. 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, 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 heat-sensitive recording layer, the intermediate layer and the concealing layer are conventionally well-known and commonly used coating techniques such as air knife coating, bar coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating and roll coating. Paper by an appropriate coating method such as
It is formed by a method such as coating and drying a coating liquid on a support such as synthetic paper or non-woven fabric. 90% as the opacity of the support
The above is preferable because the recorded image does not appear on the back surface.

If necessary, a recording layer may be provided on the back surface of the support, a protective layer may be provided on the back surface of the support to further enhance the storage stability of the recorded image, or an undercoat layer may be provided on the support, or thermal recording may be performed. Various known techniques in the field of thermal recording medium production can be added as necessary, such as providing a protective layer between the layer and the intermediate layer, and applying a smoothing treatment after coating each layer.

The heat-sensitive recording material of the present invention is preferably one in which the intermediate layer can be easily peeled off due to the characteristics of its usage. The adhesive force between the heat-sensitive recording layer and the intermediate layer can be adjusted depending on the type of the release agent and the amount of the above-mentioned material, but since each layer is formed by coating, the adhesion between the layers is good and the peeling trigger does not occur as it is. It is difficult to make. Therefore, it is conceivable to perform a processing treatment 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 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 a form or forgery prevention is applied after applying the base paper or any layer. It is also possible to print characters, symbols, advertisements, and explanations. 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.

[0025]

EXAMPLES Examples will be described below, 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 Fired clay (trade name: Ansilex, manufactured by EMC) 1
00 parts, styrene-butadiene copolymer latex (solid content: 50%) 15 parts, polyvinyl alcohol 10 parts
% 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.

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% aqueous solution of methylcellulose 5 Parts and 40 parts of water were 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 0.8 μm.

Formation of Thermosensitive Recording Layer 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 part and 50 parts of a 30% zinc stearate dispersion liquid was coated and dried on the above-mentioned undercoat layer so that the coating amount after drying was 6 g / m ^2, and heat-sensitive recording. Layers were formed. Next, super calendar processing was performed.

Formation of Intermediate Layer 80 parts of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) and 4 parts of a 50% aqueous dispersion of light calcium carbonate were mixed and stirred to obtain a coating solution. Then, the intermediate layer was formed by coating and drying on the thermosensitive recording layer so that the coating amount after drying was 5 g / m ² .

Formation of Concealment Layer 80 parts of bronze powder, polyvinyl alcohol (commodity
Name: PVA-117, manufactured by Kuraray Co., Ltd.) 10% aqueous solution 20
0 parts and styrene-butadiene copolymer latex
(Solid content: 50%) 20 parts and 100 parts of water are mixed and stirred.
The coating liquid thus obtained was coated on the above film-forming layer in an amount of 6 g after drying.
/ M²Was coated and dried to form a hiding layer. Next
Then, a super calender treatment was performed to obtain a thermosensitive recording medium.
(For forming a hiding layer on a transparent PET film with a thickness of 50 μm
The coating amount after drying the coating liquid of is 6 g / m ²The hiding layer provided
The transparency was 100%. )

Example 2 Formation of Thermosensitive Recording Layer 75 parts of solution A, 115 parts of solution B, polyvinyl alcohol (trade name)
Product name: PVA-117, manufactured by Kuraray Co., Ltd.) 10% aqueous solution 8
Obtained by mixing and stirring 0 part and 50 parts of a 30% dispersion of kaolin.
The obtained coating liquid was applied onto the undercoat layer obtained in Example 1 after drying.
The amount of cloth is 6g / m ²Coating and drying so that
Was formed. Next, super calendar processing was performed.

Formation of protective layer 70 parts of 10% aqueous solution of polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) and 30% dispersion of zinc stearate (trade name: Hydrin Z-7, manufactured by Chukyo Yushi Co., Ltd.) A coating solution obtained by mixing and stirring 10 parts was applied and dried on the thermosensitive recording layer so that the coating amount after drying was 3 g / m ² , to form a protective layer. Then, an intermediate layer and a hiding layer were formed on the protective layer in the same manner as in Example 1 and subjected to a super calendar treatment to obtain a thermosensitive recording medium.

Example 3 In the formation of the protective layer of Example 2, 10 parts of a 30% aqueous dispersion of zinc stearate (trade name: Hydrin Z-7, manufactured by Chukyo Yushi Co., Ltd.) was used instead of 35 parts of an epoxy-modified silicone oil. % Aqueous dispersion (trade name: Polon MF-11B,
A thermal recording material was obtained in the same manner as in Example 1 except that 9 parts by Shin-Etsu Chemical Co., Ltd.) was used.

Example 4 In the formation of the hiding layer of Example 2, bronze powder 80
80 parts of carbon black is used instead of 200 parts, and instead of 200 parts of a 10% aqueous solution of polyvinyl alcohol, silanol-modified polyvinyl alcohol (trade name: R-113
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 200 parts of a 10% aqueous solution (Kuraray Co., Ltd.) was used. (Thickness 50
The opacity of the concealing layer was 9 when the coating liquid for forming the concealing layer on the transparent PET film having a thickness of 6 μm was 6 g / m ² after drying.
It was 6%. )

Example 5 Bronze powder 80 was used in the formation of the hiding layer of Example 2.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 80 parts of titanium oxide was used instead of the parts and the coating amount after drying was adjusted to 20 g / m ² . (Coating amount after drying the coating liquid for forming the masking layer on a transparent PET film having a thickness of 50 μm was 6 g / m 2.
^{2 The} hiding layer provided had an opacity of 92%. )

Example 6 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 thermosensitive recording layer of Example 1. A thermal recording material was obtained in the same manner.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the protective layer and the intermediate layer were not formed.

Comparative Example 2 In the formation of the hiding layer of Example 1, bronze powder 8
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 80 parts of kaolin was used instead of 0 part. (The opacity of the concealing layer, which was formed by coating the coating liquid for forming the concealing layer on a transparent PET film having a thickness of 50 μm after drying by 6 g / m ² , was 23%.)

With respect to the eight kinds of thermal recording media thus obtained, a thermal recording simulator (PH-TMD type, manufactured by Okura Electric Co., applied voltage 18V, pulse width 2.5 msec).
The results obtained were recorded in Table 1 below.
It was shown to.

Hiding power After recording with a simulator, the hiding layer 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

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

Recording Density The density of the recorded image was measured with a Macbeth densitometer (RD-914 type, manufactured by Macbeth Co.) for those that could be peeled in the peelability test.

[0044]

[Table 1]

[0045]

As is clear from the results of [Table 1], each of the thermosensitive recording media obtained in the respective examples of the present invention has a concealing property of recorded contents, and when the contents are disclosed. Was a thermosensitive recording medium from which the intermediate layer could be easily peeled off.

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[Procedure amendment]

[Submission date] May 14, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

[0028] Solution B Preparation 4, 4'-isopropylidene Fe no le 30 parts, an average particle size of a 5% aqueous solution of 5 parts of a composition consisting of 80 parts of water with sand mill methylcellulose was pulverized to a 0.8μm .

Claims (2)

[Claims] 1. A heat-sensitive recording layer, an intermediate layer containing a water-soluble polymer and capable of peeling, and an opacity (JIS) on a support.
A heat-sensitive recording material, characterized in that a concealing layer having a content of 90% or more (based on P.8138) is sequentially provided by a coating process. 2. The heat-sensitive recording layer contains at least one kind of metal salts of higher fatty acids, waxes and silicone compounds in an amount of 5 to 50% by weight based on the total solid content of the heat-sensitive recording layer.
The heat-sensitive recording material described.