JPH0890923A - Thermal recording paper - Google Patents

Abstract

PURPOSE: To provide thermal recording paper usable as the second original drawing and a design drawing, excellent in recording image quality and reduced in background fog. CONSTITUTION: Thermal recording paper is obtained by providing an intermadiate layer based on an aq. adhesive and a thermal recording layer containing a leuco dye and a coupler on at least one surface of a support obtained by applying an org. solvent coating soln. containing a resin to the single surface or both surfaces of glassine paper and drying the coated paper.

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 paper utilizing the coloring reaction between a leuco dye and a color-developing agent, which can be used especially for the second original drawing and the design drawing, and has excellent recording image quality, and more It relates to less thermal recording paper.

[0002]

2. Description of the Related Art A heat-sensitive recording paper, which utilizes a color reaction between a colorless or light-colored leuco dye and a color-developing agent to react both color-forming substances with thermal energy from a thermal head to obtain a recorded image, is often used. Are known. Since such thermal recording paper is relatively inexpensive and the recording device is compact and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computing devices but also in a wide range of fields. Among such applications, there is a demand for thermal paper that can be used for diazo secondary original drawings and design drawings, and thermal paper that uses transparent film or impregnated paper with thermoplastic resin impregnated into high-quality paper as a support. Recording paper (JP-A-56-5309)
4, JP-A-57-15013, and JP-A-57-15013.
-103892 and JP-A-61-108581) have been developed.

However, a thermal recording paper using a resin film such as polypropylene or polyester phthalate as a support is expensive because the support is more expensive than paper, and when a resin film is used as the support. Had a defect that the bent part was whitened. Also,
In the impregnated paper in which the thermoplastic acrylic resin is soaked in the base paper, it is necessary to increase the amount of resin in order to improve the transparency.
As a result, the storage stability of the recorded image is lowered, and the folding endurance is weakened so that it cannot be folded and stored. Also,
Efforts have also been made to increase the whiteness and transparency of the heat-sensitive recording layer, and the compatibility between the adhesive and the fluorescent dye in the coating solution has a great influence on the whiteness and opacity. Among them, there is a problem that the whiteness is high, but the opacity is high, and as a result, the suitability for diazo copy is deteriorated. Therefore, there is a strong demand for a thermal recording paper having high whiteness and high transparency.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording paper which can be used as a second original drawing and a design drawing, has excellent recording image quality, and has less background fog.

[0005]

Means for Solving the Problems The inventors of the present invention applied an organic solvent coating solution containing a dissolved resin to one or both surfaces of glassine paper and dried it, and then applied an aqueous adhesive on at least one surface. The present invention has been completed by discovering that the above problems can be effectively solved by sequentially providing an intermediate layer containing the main component and a heat-sensitive recording layer containing a leuco dye and a color developing agent, and completed the present invention.

[0006]

The semi-transparent glassine paper used in the present invention is a fine paper-like thin paper made of highly viscous beaten chemical pulp as a raw material and having its surface smoothed by a super calender. It is commonly called glossy paper, glass paper, etc. It is used as a protective packaging for various foods, tobacco chemicals, metal parts, etc., and as a base material for release paper of adhesive paper, and has an opacity of 75. % Or less, and the basis weight is 15 to 100 g / m ² , preferably 20 to 80 g / m ^2.
Used. As a method for beating the chemical pulp to a high degree, a pulp suspension having a pulp concentration of 0.2 to 5% is subjected to a freeness value (CS) by a beating machine or a sand mill.
It is preferable that the treatment is performed so that F) is 120 cc or less.

When a water-based heat-sensitive paint is directly applied to glassine paper, there are problems in production such as wrinkles and paper breaks. Also, when printed, the image quality deteriorates due to the wrinkles and line breaks occur. Occurs and affects the quality. Therefore, the coating amount after drying the organic solvent coating solution in which the resin is dissolved is 0.2 to 8 g / m ² , preferably 1 to 6 g / on one side or both sides of the glassine paper before forming the thermal recording layer. m ²
The transparency is increased by coating and drying so that However, in the support obtained by applying and drying the organic solvent coating liquid in which the resin is dissolved on the glassine paper, the background fog is generated in the heat-sensitive recording layer due to the organic solvent remaining in the support.
Therefore, since an intermediate layer containing a water-based adhesive as a main component is provided on a support obtained by applying and drying an organic solvent coating solution in which a resin is dissolved in glassine paper, a heat-sensitive recording layer is provided to reduce the background fog. Occurrence is suppressed.

Resins that can be applied to glassine paper with an organic solvent and dried include methyl acrylate resin, ethyl acrylate resin, 2-ethylhexyl acrylate resin, decyl acrylate resin, isobutyl methacrylate resin, and 2-ethylhexyl methacrylate resin. Acrylic ester resin such as, vinyl acetate resin, unsaturated polyester resin, epoxy resin, urethane resin, polyethylene terephthalate, ethylene-vinyl acetate copolymer, butyral resin,
Polyester resin, nitrocellulose, polystyrene,
Styrene-methyl methacrylate-based copolymer, styrene-ethyl methacrylate-based copolymer, styrene-methyl acrylate-based copolymer, terephthalic acid and ethylene glycol A copolymer as a component, a copolymer of vinyl chloride and vinyl acetate,
Examples thereof include phenolic resins. Among them, a copolymer containing styrene and methyl tacrylate as the main component, a copolymer containing terephthalic acid and ethylene glycol as the main component (polyethylene terephthalate), or a copolymer of vinyl chloride and vinyl acetate is mixed with the pigment. It is preferable because it is easy and has excellent adhesion to the heat-sensitive recording layer. Of course, it is also possible to use two or more of these resins in combination.

Such resins include toluene, ethanol,
A coating solution can be obtained by dissolving in a suitable organic solvent such as methanol, methyl ethyl ketone, xylene and the like. Further, it is also possible to add a pigment to the resin coating liquid, for example, clay, deckite, nacrite, kaolin, aluminum hydroxide, magnesium hydroxide, calcium carbonate, calcined clay, amorphous silica, alumina, calcined kaolin, Examples thereof include barium sulfate, titanium oxide, pigments obtained by treating the surface of these pigments with beef tallow, and plastic pigments.
Such a coating liquid is applied and dried by a suitable coating device such as a bar coater, a contra coater, a gravure coater, a curtain coater, a chanplex coater, a roll coater and a blade coater.

In the present invention, the intermediate layer is preferably provided on the resin-coated surface, but it goes without saying that the intermediate layer can be provided on the uncoated surface. As the water-based adhesive used in the intermediate layer, for example, polyvinyl alcohol,
Carboxy group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, cation group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, silica-modified polyvinyl alcohol, starch and its derivatives, casein, methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, polyacrylic amide, styrene A water-soluble adhesive such as a maleic anhydride copolymer,

Natural latex such as natural rubber, styrene
Butadiene-based copolymer, acrylonitrile-butadiene-based copolymer, acrylate-butadiene-based copolymer, acrylic resin, styrene-acrylic acid ester-based copolymer, polyurethane-based resin, polyvinyl chloride-based resin, polyvinylidene chloride A synthetic latex such as a resin, a methacrylic acid ester copolymer emulsion, and an acrylic acid ester copolymer can be used. Of these, a natural or synthetic latex is preferable to a water-soluble adhesive because it has excellent adhesiveness to a support coated with an organic solvent coating solution in which a resin is dissolved and dried, and is therefore preferable. In particular, natural or synthetic latex having a diene polymer such as natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylate-butadiene copolymer, etc. forms a film rich in elasticity. Alternatively, it is preferable because a thermosensitive recording material having excellent recording image quality can be obtained. Of course, it is also possible to use a water-based adhesive in combination with a latex, and further a pigment is used in an amount of 3 to 30% by weight, preferably 5 to 20% by weight based on the total solid amount of the intermediate layer.
It is also possible to add by weight%.

Examples of pigments include clay, calcium carbonate, magnesium carbonate, talc silica, diatomaceous earth,
Synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated inorganic fine powder such as calcium carbonate and silica, and urea-
Organic resin fine powder such as formalin resin, styrene-methacrylic acid copolymer and polystyrene resin can be used.

Various leuco dyes are known as the leuco dye contained in the heat-sensitive recording layer, and the following are exemplified.
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3,3-bis (9-ethylcarbazol-3-yl)- 6-Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3- (1-methylpyrrole-3-
Yl) -6-dimethylaminophthalide, 3- (p-dibenzylaminophenyl) -3- (1,2-dimethylindol-3-yl) -7-azaphthalide and other triarylmethane dyes, 4,4 '-Bis (dimethylamino) benzhydrylbenzyl ether, benzhydryl-p-
Diphenylmethane dyes such as toluenesulfinic acid ester, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, etc. Divinylphthalide dye, 3,
Thiazine dyes such as 7-bis (diethylamino) -10-benzoylphenoxazine, benzoylleuco methylene blue, p-nitrobenzoyl leuco methylene blue, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-phenylspirodie. Spiro dyes such as naphthopyran, lactam dyes such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam,

3-diethylamino-6-methylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N-ethyl-p-toluidino) -7-Methylfluorane, 3- (N-ethyl-p-toluidino)-
6-methyl-7-phenylaminofluorane, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-dimethylamino-6-methyl-7-phenylaminofluorane, 3
-Dibutylamino-6-methyl-7-phenylaminofluorane, 3-dipentylamino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7- Phenylaminofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, 3
-(N-ethyl-N-isobutylamino) -6-methyl-7-phenylaminofluorane, 3- (N-methyl-)
N-n-hexylamino) -6-methyl-7-phenylaminofluorane, 3- [N- (3-ethoxypropyl) -N-methylamino] -6-methyl-7-phenylaminofluorane, 3- Dibutylamino-7- (o-fluorophenylamino) fluorane, 3-diethylamino-6-chloro-7-phenylaminofluorane, 3-
Fluorane dyes such as (N-ethyl-Np-tolylamino) -7-methylfluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, 3,6-bis (dimethylamino) -3'-methyl-spiro [fluorene-9,6'-
6'H-chromeno (4,3-b) indole] and the like. Of course, the dyes are not limited to these dyes, and two or more dyes may be used in combination.

Further, in the heat-sensitive recording paper of the present invention, various known colorants can be used in combination as the colorant for developing the leuco dye in the recording layer, and the following can be exemplified. 4-phenylphenol, 4,4'-dihydroxy-diphenylmethane, 4,4'-isopropylidene diphenol (bisphenol A), 4,4'-cyclohexylidenebisphenol, 4,4 '-[1,3-phenylenebis (1-Methylethylidene)] bisphenol, 4,4 ′-(1,3-dimethylbutylidene) bisphenol, 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-
Hydroxy-4′-methyldiphenyl sulfone, 4-hydroxy-4′-methoxydiphenyl sulfone, 4-hydroxy-4′-isopropoxydiphenyl sulfone,
4-hydroxy-3 ', 4'-trimethylene diphenyl sulfone, 4-hydroxy-3', 4'-tetramethylene diphenyl sulfone, 3,4-dihydroxy-4'-
Phenolic compounds such as methyldiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxybenzoic acid-p-methoxybenzyl, novolac type phenol resin, phenol polymer, 4,
A sulfonylurea derivative such as 4′-bis (p-toluenesulfonylaminocarbonylamine) diphenylmethane,
3,5-Dimethyl-4-hydroxybenzoic acid, 3-isopropylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-phenyl-5- ( Aroma such as α, α-dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4- (2-p-methoxyphenoxyethoxy) salicylic acid, 4- (3-p-tolylsulfonylpropyloxy) salicylic acid Group carboxylic acids,
And organic acid substances such as salts of these phenolic compounds and aromatic carboxylic acids with polyvalent metals such as zinc, magnesium and aluminum. Among these, 4,
4′-Bis (p-toluenesulfonylaminocarbonylamine) diphenylmethane is preferable because of excellent storage stability of recorded images. Of course, these colorants may be used in combination of two or more, if necessary.

In the present invention, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include 1,2-di (3-methylphenoxy) ethane and 1,2-
Diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, parabenzyl biphenyl, naphthylbenzyl ether, benzyl-4-methylthiophenyl ether, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester , Oxalic acid-
Di-p-methylbenzyl ester, oxalic acid-di-p-
Chlorbenzyl ester, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester, 1-
Examples thereof include hydroxynaphthoic acid phenyl ester and various known heat-fusible substances. Among them, 1,2-di (3-
Methylphenoxy) ethane, 1,2-diphenoxyethane and 1-phenoxy-2- (4-methylphenoxy) ethane are particularly preferred. Although the amount of the sensitizer used is not particularly limited, it is generally desirable to adjust the amount within a range of about 400 parts by weight or less relative to 100 parts by weight of the color developing agent.

It is permissible to add a storability improver to further improve the storability of the recording layer. Examples of such a shelf life improver include 1,3,5-tris (4
-Tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3- Phenolic compounds such as tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane and 1,1-bis (2-methyl-4-hydroxy-5-tert-butylphenyl) butane

4- (2-methyl-1,2-epoxyethyl) diphenyl sulfone, 4- (2-ethyl-1,2)
-Epoxyethyl) diphenylsulfone, 4- (2-
Methyl-glycidyl) diphenyl sulfone, 4- (2
-Ethyl-glycidyl) diphenyl sulfone, 4-
(2-butyl-glycidyl) diphenyl sulfone, 4
-(3-Methyl-3,4-epoxybutyl) diphenylsulfone, 4- (2-methyl-3,4-epoxybutyl) diphenylsulfone, 4- (2-methyl-3,4)
-Epoxybutyl) diphenylsulfone, 4- (2-
Methyl-glycidyloxy) -2 ', 4'-dichlorodiphenyl sulfone, 4- (2-methyl-glycidyloxymethoxy) diphenyl sulfone, 4- (2-methyl-glycidyloxy-4'-(p-methoxybenzyloxy) Examples thereof include diphenylsulfone derivatives such as diphenylsulfone, etc. Of course, the present invention is not limited to these, and two or more kinds of compounds can be used in combination as required.

These color formers, newsprinting agents, storability improvers, etc. are used separately or together with leuco dyes, etc., using water as a dispersion medium, and polyacrylamide by various wet pulverizers such as a sand grinder, an attritor, a ball mill and a covol mill. , Water-soluble synthetic polymer compounds such as polyvinylpyrrolidone, polyvinyl alcohol, carboxymethyl cellulose, and styrene-maleic anhydride copolymer salts and their derivatives, as well as surfactants and the like to form a dispersion liquid, and then a recording layer coating Used for preparation.

In the present invention, other materials constituting the heat-sensitive recording layer include adhesives, inorganic or organic pigments, waxes, metal soaps, water-proofing agents and, if necessary, ultraviolet absorbers, fluorescent dyes, colorants, etc. Can be mentioned. Examples of the adhesive resin include polyvinyl alcohol, carboxy group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, cation group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, silica-modified polyvinyl alcohol, starch and derivatives thereof,
Casein, methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, polyacrylic amide, styrene-maleic anhydride copolymer, styrene-
Water-dispersible resins such as butadiene latex, vinyl acetate-acrylic acid ester copolymer emulsion, polyurethane emulsion, polyvinyl chloride emulsion, polyvinylidene chloride emulsion, methacrylic acid ester copolymer emulsion and acrylic acid ester copolymer emulsion can be used. . Further, in order to make the water resistance of the coating film strong, a reactive group such as an acetoacetyl group,
It is preferable to use a water-soluble and / or water-dispersible resin adhesive containing a carboxyl group or an amide group in combination with a crosslinking agent.

As the crosslinking agent, polyvalent aldehyde compounds such as glyoxal, glutaraldehyde, dialdehyde starch, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, diglycidyl compounds such as glycerin diglycidyl ether, A dimethylol urea compound, an inorganic compound such as ammonium persulfate, ferric chloride, and magnesium chloride, boric acid, or borax can be used.

Examples of pigments include clay, calcium carbonate, magnesium carbonate, talc silica, diatomaceous earth,
Synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated inorganic fine powder such as calcium carbonate and silica, and urea-
Organic resin fine powder such as formalin resin, styrene-methacrylic acid copolymer and polystyrene resin can be used. Examples of the wax include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax, higher fatty acid amides such as stearic acid amide and ethylenebisstearic acid amide, and higher fatty acid esters.

By providing a protective layer containing a water-soluble adhesive and a pigment as the main components on the heat-sensitive recording layer, the transparency and recording suitability of the heat-sensitive recording paper are further improved. Examples of the adhesive used for the protective layer include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, and silicon modified polyvinyl alcohol. , Diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, urea resin, melamine resin, amide resin, polyurethane Examples thereof include resins, but among them, acetoacetyl group-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol form a strong film,
Furthermore, since it is excellent in transparency, it is particularly preferably used.

Specific examples of pigments added to the protective layer for further improving printability and sticking include:
Inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, colloidal silica, styrene microballs, nylon powder, polyethylene powder , Urea / formalin resin fillers, organic pigments such as raw starch particles, and the like. Generally, it is desirable to prepare the use amount in the range of about 5 to 300 parts by weight with respect to 100 parts by weight of the binder component.

Furthermore, in the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., and a surfactant such as sodium dioctyl succinate (dispersant, wetting agent). Agents), antifoaming agents, and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate may be appropriately added. Further, in order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, and an epoxy compound can be used in combination.

It is possible to add a crosslinking agent and a lubricant to the protective layer in addition to the adhesive and the pigment. The resin / pigment ratio of the protective layer is preferably in the range of 80/20 to 40/60, and if the compounding ratio of the resin exceeds 80%, sticking may occur during printing or the adhesiveness of the printing ink during label processing may increase. There is a problem of decline.

The method for forming the intermediate layer, the heat-sensitive recording layer and the protective layer is not particularly limited, and examples thereof include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating,
By a suitable coating method such as die coating, the coating liquid for the intermediate layer has a dry weight of 1 to 6 g / m ² , preferably ² to 4 g / m ² .
m ^2, a recording layer coating solution 2~12g / m ² in dry weight, preferably 3 to 10 g / m ^2, also the protective layer coating composition by dry weight from 0.5 to 7. g / m ² , preferably 1 to 4 g / m ²
It is desirable to adjust within the range.

The heat-sensitive recording paper of the present invention may be provided with a back surface layer on the surface opposite to the heat-sensitive recording layer to correct the curl. The back surface layer (back coat layer) may have the same paint and coating method as the protective layer, and the coating amount and the resin / pigment ratio may be changed as necessary. Further, various modifications such as providing an undercoat layer under the heat-sensitive recording layer may be carried out if necessary. If necessary, various known techniques in the field of heat-sensitive recording paper production can be added such as smoothing treatment such as super calendering after coating each layer of the heat-sensitive recording layer and the protective 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. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively.

Example 1 Preparation of solution A 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 10 parts, 1,2-di (3-methylphenoxy) ethane 15 parts, methylcellulose 5% aqueous solution 5
Parts and 60 parts of water were pulverized with a sand mill until the average particle size became 1 μm.

Preparation of Solution B A composition consisting of 35 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 60 parts of water was pulverized with a sand mill until the average particle diameter became 2 μm.

Preparation of liquid C 20 parts of polyester resin was dissolved in 80 parts of toluene with a stirrer.

Preparation of Coating Liquid for Intermediate Layer Styrene-butadiene copolymer latex (65% by weight of styrene monomer, 30% by weight of butadiene monomer, 5% by weight of acrylic acid monomer, solid concentration 48%) 87 Part, 5 parts of fine particle silica, 3 parts of a 5% aqueous solution of sodium di (2-ethylhexyl) sulfosuccinate, and 20 parts of water were mixed and stirred to obtain a coating liquid.

Preparation of Coating Solution for Thermal Recording Layer 10 parts of A solution 100 parts, B solution 30 parts, silicon-containing modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.)
% Aqueous solution 150 parts, light calcium carbonate 10 parts, and water 30 parts in a composition, 2 parts of a 50% aqueous solution of a fluorescent dye (trade name: Kayahall Pass Liquid, manufactured by Nippon Kayaku Co., Ltd.) are mixed and stirred.

Preparation of Coating Liquid for Protective Layer 80 parts of kaolin, acetoacetyl group-modified completely saponified polyvinyl alcohol (trade name: Gocefimer-Z-20
0, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 400 parts of 10% aqueous solution, 30 parts of 30% aqueous dispersion of zinc stearate, and 140 parts of water.
A coating liquid obtained by mixing and stirring a composition of parts.

Preparation of Thermosensitive Recording Paper Liquid C was applied and dried on glassine paper having a basis weight of 63 g / m ² and an opacity of 55% so that the applied amount after drying was 4 g / m ^2, and then used for the intermediate layer. The coating liquid, the thermal recording layer coating liquid and the protective layer coating liquid each had a coating amount of 4 g / m ² , 5 after drying.
g / m ^2, after sequentially applied and dried such that the way a 3 g / m ^2, to obtain a heat-sensitive recording paper was smoothed by super calender.

Example 2 In the preparation of the coating liquid for the intermediate layer of Example 1, instead of 87 parts of the styrene-butadiene copolymer latex, methylmethacrylate-butadiene latex (40% by weight of methylmethacrylate monomer, Butadiene monomer 6
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 75 parts of 0% by weight and a solid concentration of 48%) and 60 parts of a 10% aqueous solution of polyvinyl alcohol were used.

Example 3 In the preparation of the coating liquid for the intermediate layer of Example 1, a styrene-butyl acrylate copolymer (styrene monomer 50 was used instead of 87 parts of the styrene-butadiene copolymer latex).
%, Butyl acrylate monomer 45% by weight, acrylic acid 5%, solid concentration 50%)
A thermosensitive recording paper was obtained in the same manner as in (1).

Example 4 In the preparation of the coating liquid for the intermediate layer of Example 1, 75 parts of natural rubber latex (solid concentration 30%) and 10% aqueous solution of polyvinyl alcohol were used instead of 87 parts of styrene-butadiene copolymer latex. Example 1 except that 60 was used
A thermosensitive recording paper was obtained in the same manner as in (1).

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the intermediate layer was not provided in the preparation of the thermosensitive recording paper of Example 1.

Comparative Example 2 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the liquid C was not applied in the preparation of the thermosensitive recording paper of Example 1.

The heat-sensitive recording paper thus obtained was subjected to the following quality evaluation tests, and the results are shown in Table 1. [Recording Density] Using a thermal recording simulator (TH-PMD type, manufactured by Okura Electric Co., Ltd.), the density of the recorded image obtained by recording under the condition of an applied head energy of 0.4 mj / dot is Macbeth densitometer (Macbeth Co. Ltd.). Manufactured by RD-914).

[Opacity] The opacity was measured according to JIS P-8138. [Background fog] After leaving the thermosensitive recording medium at 40 ° C. for 24 hours, five sheets were stacked and the whiteness was measured by a Hunter whiteness meter to examine the background fog.

[Applicability of thermosensitive recording paper to diazo copying] THER
Using a thermosensitive recording paper recorded by MAL PLOTTER [LTX-120 Roland] as a master, a diazo copying machine [Ricoh Co., Ricopy SU
PER DRY 100 type], and the obtained copy image and the density of the background portion were measured with a Macbeth densitometer.

[Recording quality] THERMAL PLOTT
The image quality recorded by ER [LTX-120 Roland] was visually judged. Evaluation Criteria A: The image quality is extremely excellent. ○: The image quality is excellent. X: The image quality is inferior.

[0046]

[Table 1]

[0047]

As is clear from the results of Table 1, the thermal recording paper of the present invention was a thermal recording paper for the second original image which had excellent recording image quality and had little background fog.

Claims (3)

[Claims] 1. An intermediate layer containing an aqueous adhesive as a main component is provided on at least one surface of a support coated with an organic solvent coating liquid containing a dissolved resin and dried on one or both surfaces of glassine paper. A heat-sensitive recording paper having a heat-sensitive recording layer containing a leuco dye and a color former on the intermediate layer. 2. The thermal recording paper according to claim 1, wherein the water-based adhesive in the intermediate layer is a natural or synthetic latex. 3. The thermal recording paper according to claim 2, wherein the natural or synthetic latex is a natural or synthetic latex having a diene polymer.