JPH08175011A - Thermal recording paper - Google Patents

Abstract

PURPOSE: To provide a thermal recording material usable for a second original drawing or a design drawing and reduced in the generation of fog during preservation. CONSTITUTION: In thermal recording paper obtained by applying an org. solvent coating soln. of a resin to the single surface or both surfaces of raw paper to dry the coated paper and subsequently providing a recording layer containing a leuco dye and a coupler one at least one surface thereof, the residual amt. of the org. solvent in the thermal recording paper is 0.3g/m<2> or less.

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, and relates to a heat-sensitive recording paper usable as a second original drawing and a design drawing.

[0002]

2. Description of the Related Art A thermosensitive recording medium 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 2nd original drawings and design drawings. A thermal paper that uses transparent film or impregnated paper in which thermoplastic resin is impregnated into high-quality paper as a support is used. 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, the thermosensitive recording medium using a resin film such as polypropylene or polyethylene terephthalate as the support is expensive because the support is more expensive than paper, and when the resin film is used as the support. Had a defect that the bent part was whitened.
In addition, the impregnated paper in which the thermoplastic acrylic resin is soaked in the base paper has a large amount of resin in order to improve the transparency, so that the background fog may occur during storage.

[0004]

The problem to be solved by the present invention is the second object.
An object of the present invention is to provide a heat-sensitive recording paper which can be used for original drawings and design drawings, and which has less background fog during storage.

[0005]

Means for Solving the Problems The present inventor has applied a coating solution of an organic solvent in which a resin is dissolved to one or both sides of a base paper and drying it, and then, at least on one side thereof, a leuco dye and a coloring agent. In a thermal recording paper provided with a recording layer containing it, it was found that the organic solvent remaining on the thermal recording paper causes background fog during storage. Then, as a result of various experiments and studies, it was found that the above problems can be solved by setting the amount of the organic solvent remaining on the thermal recording paper to 0.3 g / m ² or less, and the present invention has been completed.

[0006]

For use as the second original drawing and the design drawing,
A base paper is used which is impregnated with an organic solvent coating solution in which a resin is dissolved to improve transparency. As base paper, basis weight 20-80g
/ M ² neutral or acidic wood free paper or glassine is used. In particular, since the glassine paper has excellent transparency even when the solid coating amount of the organic solvent coating liquid in which the resin is dissolved is small, the effect of particularly less background fog can be obtained. Such glassine papers are highly viscous beaten LBKP, NB
It is a thin paper with a fine paper quality, made from chemical pulp such as KP as a raw material and smoothed on a super calender. It is commonly called glossy paper or glass paper,
It is used as a protective packaging for various foods, tobacco chemicals, metal parts, etc. and a base material for release paper of adhesive paper,
The opacity is preferably 65% or less. As a method for highly beating the chemical pulp, it is preferable to treat a pulp suspension having a pulp concentration of 0.2 to 5% by a beating machine or a sand mill so that the freeness value (CSF) becomes 120 cc or less.

When water-based heat-sensitive paint is applied to high-quality paper, especially glassine paper, there are problems in production such as wrinkles and paper breaks, and when printed, the image quality is poor due to the effects of wrinkles. There are problems such as. Therefore, the coating amount of the organic solvent coating solution in which the resin is dissolved is 0.2 to 10 g / m ² , preferably 0.5 on one or both sides of the base paper.
The transparency is increased by coating and drying so as to be ~ 6 g / m ² . However, when a recording layer is formed on a support obtained by applying an organic solvent coating liquid in which a resin is dissolved on a base paper and drying the same, the amount of the organic solvent remaining in the thermal recording paper is 0.3 g / m ^2.
If it exceeds, the background fog will be strongly generated in the recording layer. The organic solvent remaining in the thermal recording paper is 0.1
It is more preferably g / m ² or less.

The amount of the organic solvent remaining in the support, which is obtained by coating and drying the organic solvent coating liquid in which the resin is dissolved on the base paper, is preferably 0.5 g / m ² or less. 0.5 g / m ²
If it exceeds, the fog may occur at the same time when the recording layer is formed. The drying temperature at that time is 80 to 15
The range of 0 ° C is preferred. If the temperature is 80 ° C or lower, the amount of residual solvent increases, and if the temperature is 150 ° C or higher, blisters may occur on the coated surface.

The resin used in the organic solvent coating solution in which the resin is dissolved is, for example, methyl acrylate resin, ethyl acrylate resin, 2-ethylhexyl acrylate resin, decyl acrylate resin, isobutyl methacrylate resin, methacrylic resin. Acrylic ester resin such as acid-2-ethylhexyl resin, vinyl acetate resin, unsaturated polyester resin, epoxy resin, urethane resin, polyethylene terephthalate, ethylene-vinyl acetate copolymer, butyral resin, polyester resin, nitrocellulose, polystyrene , A copolymer containing styrene-methyl methacrylate as a main component, a copolymer containing styrene-ethyl methacrylate as a main component, a copolymer containing styrene-methyl methacrylate as a main component, vinyl chloride and vinyl acetate Copolymer of phenol resin And the like. Among them, a copolymer of vinyl chloride and vinyl acetate in which vinyl acetate is copolymerized in the range of 80 to 120% by weight with respect to vinyl chloride is preferable because of excellent storage stability of recorded images. Of course, it is also possible to use two or more of these resins in combination.

The organic solvent for dissolving such a resin is not particularly limited, but ethyl alcohol (79
℃), hexyl alcohol (156 ℃), ethyl acetate (77 ℃), butyl acetate (124 ℃) methyl ethyl ketone (80 ℃), xylene (ortho 144 ℃, meta 139)
℃, para 138 ℃), toluene (111 ℃), hexane (69 ℃), heptane (98 ℃), octane (126
C.), decane (174.degree. C.) and the like (the numbers in parentheses indicate boiling points). Among them, ethyl acetate and toluene are preferable because they are easy to handle. These organic solvents may be used alone or as a mixture. When an organic solvent having a boiling point of 110 ° C. or higher is used, the amount of the residual solvent can be reduced without being dried at a high temperature by using together with an organic solvent having a boiling point of 80 ° C. or lower. It is particularly preferable because it can be easily reduced.

It is also possible to add a pigment to the organic solvent coating liquid, and the addition amount thereof is not particularly limited, but 5 to 40% by weight, preferably 10 to 30% by weight based on the total solid amount of the resin. Used by weight% If it is less than 5% by weight, blisters are generated when the organic solvent resin coating liquid is applied to the base paper, which deteriorates the recording image quality, and if it exceeds 40% by weight, the transparency is lowered and the blister is used for the second original drawing. The suitability may be reduced.

Specific examples of such pigments include clay, deckite, nacrite, kaolin, aluminum hydroxide, magnesium hydroxide, calcium carbonate, calcined clay, amorphous silica, alumina, calcined kaolin, and plastic pigments. . Among them, kaolin having an average particle size of 1 μm or less, amorphous silica, and calcium carbonate are preferable because of their excellent transparency.

The organic solvent coating liquid has a coating amount of 1 to 1 after drying.
It is preferably applied in the range of 0 g / m ² . As a coater for applying the coating liquid, for example, a bar coater, a contra coater, a gravure coater, a curtain coater, a chanplex coater, a roll coater, a blade coater or the like is used.

Various types of leuco dyes, which are colorless or light-colored, to be contained in the recording layer in the invention are known, and examples thereof include the following. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide,
3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,
2-Dimethylindol-3-yl) phthalide, 3,3
-Bis (1,2-dimethylindol-3-yl) -5
-Dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3- (1-methylpyrrol-3-yl)-
6-Dimethylaminophthalide, N-halophenyl-leuco auramine, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5, 6,7-tetrachlorophthalide, 3,7-bis (diethylamino) -10-benzoylphenoxazine, rhodamine (o-chloroanilino) lactam,

3-diethylamino-6-methylfluorane, 3-dimethylamino-7-methoxyfluorane, 3
-Diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 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-di (n-butyl)
Amino-6-methyl-7-phenylaminofluorane,
3-di (n-pentyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-cyclohexyl-N
-Methylamino) -6-methyl-7-phenylaminofluorane, 3-diethylamino-7- (o-chlorophenyl) aminofluorane, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl- 7-phenylaminofluorane, 3- (N-methyl-N-propylamino) -6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-isobutyl) amino-6-
Methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-cyclopentylamino) -6- Methyl-7-phenylaminofluorane, 3- [N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7-phenylaminofluorane, 3-diethylamino-7- [m- (trifluoro Methyl) phenylamino] fluorane, 3-diethylamino-7- (o-fluorophenyl) aminofluorane, 3-diethylamino-6-chloro-7-phenylaminofluorane, 3- (N-ethyl-Np-tolylamino) ) -7-Methylfluorane, 3- (N-ethyl-)
N-tetrahydrofurfuryl) amino-6-methyl-7
-Anilinofluorane, 3- (N-cyclopentyl-N
-Ethyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-Np-tolylamino) -6-
Methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-
Dimethylamino) phthalide, 3-diethylamino-6-
(N-allyl-N-methylaminofluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, etc. Of course, the dyes are not limited to these dyes, and two or more dyes may be used in combination. Is.

In the heat-sensitive recording paper of the present invention, various known developers can be used in combination as the developers for developing the leuco dye in the recording layer. For example, the following can be exemplified. 4-tert-butylphenol, 4,4'-sec
-Butylidene diphenol, 4-phenylphenol,
4,4'-dihydroxy-diphenylmethane, 4,4 '
-Isopropylidene diphenol, 4,4'-cyclohexylidene bisphenol, 4,4 '-[1,4-phenylene bis (1-methylethylidene)] bisphenol, 2,2-bis (4-hydroxyphenyl) -4 -Methyl-pentane, 4,4'-thiobis (6-tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyl Diphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-3 ', 4'-trimethylene diphenyl sulfone, 3,4-dihydroxy-
4'-methyldiphenyl sulfone, bis (3-allyl-
4-hydroxyphenyl) sulfone, hydroquinone monobenzyl ether, methyl 4-hydroxybenzoate, 4
-Phenolic compounds such as propyl hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate and p-methoxybenzyl 4-hydroxybenzoate, p-tert-butylbenzoic acid, trichlorobenzoic acid, 3, 5-dimethyl-4-hydroxybenzoic acid,
Salicylic acid, 3-isopropylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-benzylsalicylic acid,
3- (α-methylbenzyl) salicylic acid, 3-chloro-
5- (α-methylbenzyl) salicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,
5-di-α-methylbenzyl salicylic acid, 4- (2-P
-Methoxyphenoxyethoxy) salicylic acid, 4- (3
Organic acid substances such as zinc salt of aromatic carvone such as -P-tolylsulfonylpropyloxy) salicylic acid. In addition,
Two or more kinds of these color developers can be used in combination, if necessary.

In the present invention, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include stearic acid amide, stearic acid methylenebisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide and other fatty acid amides, 1,2-di (3-methylphenoxy) ethane, 1 , 2-diphenoxyethane, 1
-Phenoxy-2- (4-methylphenoxy) ethane,
Parabenzyl biphenyl, naphthyl benzyl 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-chlorobenzyl ester, terephthalic acid dimethyl ester Examples thereof include esters, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester, 1-hydroxynaphthoic acid phenyl ester, and various known heat-fusible substances. Of these, 1,2-di (3-methylphenoxy) ethane is particularly preferable because it has excellent recording sensitivity. 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 recorded image. Examples of such a shelf life improver include 2,2′-methylenebis (4-methyl-6-tert-butylphenol),
4,4′-butylidene bis (6-tert-butyl-3-methylphenol), 1,1,3-tris (2-methyl-)
4-hydroxy-5-tert-butylphenyl) butane,
1,1,3-Tris (5-cyclohexyl-4-hydroxy-2-methylphenyl) butane, 1,3,5-Tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid Such as hindered phenols, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2-hydroxy-4-benzyloxybenzophenone, and other UV absorbers, and other phenolic compounds.

4- (2-methyl-1,2-epoxyethyl) diphenyl sulfone, 4- (2-ethyl-1,2)
-Epoxyethyl) diphenylsulfone, 4- (3-
Methyl-3,4-epoxybutyl) diphenylsulfone, 4- (2-methyl-1,2-epoxyethyloxy) diphenylsulfone, 4- (2-methyl-2,3
-Epoxybutyloxy) diphenylsulfone, 4-
(2-Methyl-1,2-glycidyloxy) diphenylsulfone, 4- (2-methyl-glycidyloxy)-
4'-chlorodiphenyl sulfone 4- (2-methyl-
Glycidyloxy) -2 ', 4'-dimethyldiphenylsulfone, 4- (2-methyl-glycidyloxymethoxy) diphenylsulfone, 4-benzyloxy-
Diphenyl sulfone derivatives such as 4 ′-(2,3-glycidyloxy) diphenyl sulfone can be mentioned. Of course, it is not limited to these, and two or more kinds of compounds can be used in combination as required.

These color formers, sensitizers, storability improvers and the like may be used separately or together with leuco dyes or the like using water as a dispersion medium, a sand grinder, an attritor,
In addition to water-soluble synthetic polymer compounds such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, carboxymethylcellulose, and styrene-maleic anhydride copolymer salts and their derivatives by various wet pulverizers such as ball mills and cobomills, interfaces The dispersion is dispersed with an activator or the like in an amount of 2 μm or less, preferably 1 μm or less, and then used for preparing a coating material for the recording layer.

In the present invention, other materials constituting the recording layer include adhesives, inorganic or organic pigments, waxes,
Metal soap, waterproofing agent, and if necessary UV absorber,
Examples of the storage stability improver, fluorescent dye, colorant and the like can be mentioned.

Specific examples of the adhesive include polyvinyl alcohol, carboxy group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, cation group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol,
Starch and its derivatives, casein, methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, polyvinylpyrrolidone, polyacrylic acid salt, polyacrylic amide, styrene-maleic anhydride copolymer,
Methyl vinyl ether-maleic anhydride copolymer, water-soluble resin such as isopropylene-maleic anhydride copolymer,
Examples thereof include water-dispersible resins such as styrene-butadiene latex, vinyl acetate-acrylic acid ester copolymer emulsion, polyurethane emulsion, polyvinyl chloride emulsion, polyvinylidene chloride emulsion, and methacrylic acid ester copolymer emulsion.

In order to strengthen the water resistance of the coating film, a water-soluble and / or water-dispersible resin adhesive containing a reactive group such as an acetoacetyl group, a carboxyl group, or an amide group. And a cross-linking agent are preferably used in combination.

Examples of the pigment 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-
Examples thereof include fine powders of organic resins such as formalin resin and styrene-methacrylic acid copolymer polystyrene resin. 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.

According to the present invention, by providing a protective layer containing a water-soluble resin as a main component on the recording layer, the effect of improving transparency and recording runnability can be obtained in addition to the improvement of the storability of recorded images against chemicals. To be Specific examples of the water-soluble resin used in such a 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, 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,
Examples thereof include amide resins and polyurethane resins. Among them, acetoacetyl group-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol are particularly preferably used because they form a strong film and are excellent in recording running property and transparency.

A pigment may be added to the protective layer, if necessary, in order to further improve printability and sticking. Specific examples thereof include calcium carbonate,
Zinc oxide, aluminum oxide, silicon dioxide, aluminum hydroxide, barium sulfate, talc, kaolin, clay,
Examples include inorganic pigments such as calcined kaolin and colloidal silica, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea-formalin resin filler, and raw starch particles. In general, it is desirable that the amount used is in the range of about 20 to 300 parts by weight with respect to 100 parts by weight of the binder component.

Furthermore, in the coating liquid for the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and a surfactant such as sodium dioctyl sulfosuccinate. , Various anti-foaming agents, and various auxiliary agents such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate can be added as appropriate. Further, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound may be used in combination for further improving the water resistance.

The method of forming the recording layer and the protective layer is not particularly limited, and the recording layer and the protective layer can be formed according to a conventionally known and commonly used technique, for example, air knife coating, varibar blade coating, pure blade coating, rod. Blade coating,
The dry amount of the coating liquid for the recording layer is ² to 12 g / m ² , preferably 3 to 10 by a suitable coating method such as short dwell coating, curtain coating, or die coating.
10 g / m ² , and the protective layer coating liquid has a dry weight of 0.5 to
7.0 g / m ^2, preferably it is desirable to adjust the range of 1.0~4.0g / m ^2.

The heat-sensitive recording paper of the present invention may be provided with a back surface layer on the surface opposite to the recording layer to correct the curl. The coating material for the back surface layer (back coat layer) and the coating method may be the same as those for the protective layer, and the coating amount and the resin / pigment ratio may be changed as necessary. In the present invention, if necessary, a super calender may be applied after coating the recording layer to improve the image quality and the image density.

[0030]

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 represent parts by weight and% by weight, respectively.

Example 1 Preparation of solution A 10 parts of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane, 15 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of methylcellulose % Aqueous solution 5 parts and water 60 parts 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′-isopropoxydiphenylsulfone, 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 70 parts of vinyl chloride-vinyl acetate copolymer (trade name: Kanevirac L-CN, containing 100% by weight of vinyl acetate based on vinyl chloride, solid concentration 37%, manufactured by Kanebuchi Chemical Co., Ltd.) A coating liquid dissolved in 50 parts of toluene and 30 parts of ethyl acetate with a stirrer.

[0034] C solution coating Liquid C opacity 55% of the coating amount after drying glassine paper of 63 g / m ² was applied and dried so as to 4g / m ^2. The amount of residual solvent after coating and drying the C liquid was 0.15 g.
/ M ² .

Preparation of coating liquid for recording layer 100 parts of solution A, 30 parts of solution B, 10% aqueous solution of polyvinyl alcohol (trade name: PVA-235, manufactured by Kuraray Co., Ltd.) 1
A coating liquid obtained by mixing and stirring a composition consisting of 50 parts, 10 parts of kaolin (average particle size 0.8 μm) and 30 parts of water.

Formation of Recording Layer A recording layer coating liquid having the following composition was prepared, and the coating amount after drying was 5 g / m on the coating surface of the C liquid of the glassine paper coated with the C liquid.
^A recording layer was provided by coating and drying so as to be ² . The amount of residual solvent after forming the recording layer was 0.12 g / m ² .

Preparation of coating liquid for protective layer 60 parts of kaolin, acetoacetyl group-modified fully saponified polyvinyl chloride
Nyl alcohol (Brand name: Gocefimer Z-20
0, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 300 parts of 10% aqueous solution,
20 parts of 40% aqueous zinc arsenate dispersion and 120 parts water
A coating liquid obtained by mixing and stirring a composition consisting of parts. Forming a protective layer Prepare a protective layer paint with the following composition and apply it on the recording layer after drying.
The amount of cloth is 3g / m²Was applied and dried. In addition,
The amount of residual solvent after formation of the protective layer is 0.10 g / m ²So
Was. Thermal recording after smoothing with a super calender
Got the paper.

Examples 2 to 3 Thermal recording was carried out in the same manner as in Example 1 except that the amount of residual solvent was as shown in Table 1 below, and the C liquid, the thermal recording coating liquid and the protective layer coating liquid were applied and dried. Got the paper.

Example 4 In the coating of the liquid C, the high-quality paper of 40 g / m ² was used in place of the glassine paper of 63 g / m ² , and the residual solvent amount was as shown in Table 1 below. A heat-sensitive recording paper was obtained in the same manner as in Example 1 except that the heat-sensitive recording coating liquid and the protective layer coating liquid were applied and dried.

Example 5 Example 1 was repeated except that the following solution C was used and the amount of residual solvent was as shown in Table 1 below, and the solution C, the heat-sensitive recording coating solution and the protective layer coating solution were applied and dried. Thermal recording paper was obtained in the same manner.

Preparation of Solution C After stirring and dispersing 3 parts of fine particle silicon oxide [trade name: Mizuka Seal P527, manufactured by Mizusawa Chemical Co., Ltd.] in a solvent consisting of 50 parts of toluene and 30 parts of ethyl acetate, a vinyl chloride-vinyl acetate copolymer is prepared. (Brand name: Kanevirac L-CN, containing 100% by weight of vinyl acetate with respect to vinyl chloride, solid concentration 3
A coating solution in which 50 parts of 7% (Kanefuchi Chemical Co., Ltd.) was added with stirring.

Example 6 Example 1 was repeated except that the following solution C was used and the amount of residual solvent was as shown in Table 1 below, and the solution C, the heat-sensitive recording coating solution and the protective layer coating solution were applied and dried. Thermal recording paper was obtained in the same manner. Preparation of liquid C In a solvent consisting of 40 parts of toluene and 40 parts of methyl ethyl ketone, fine particle silicon oxide [trade name: Mizuka Seal P52
7, manufactured by Mizusawa Chemical Co., Ltd.] 3 parts by stirring were dispersed, and then polymethylmetharylylate (weight average molecular weight, about 120,000)
0) A coating liquid added with 20 parts while stirring.

Comparative Example 1 In Example 1 except that the amount of residual solvent in the coating of the liquid C was as shown in Table 1 below, the liquid C, the heat-sensitive recording coating liquid and the protective layer coating liquid were applied and dried. Thermal recording paper was obtained in the same manner.

Comparative Example 2 As in Example 5, except that the amount of residual solvent in the coating of the C liquid was as shown in Table 1 below, the C liquid, the heat-sensitive recording coating liquid and the protective layer coating liquid were applied and dried. Thermal recording paper was obtained in the same manner.

Comparative Example 3 The procedure of Example 1 was repeated except that the liquid C was not applied.
A thermal recording paper was obtained in the same manner as in Example 1.

The thermal recording paper thus obtained was subjected to the following quality evaluation test, and the results are shown in Table 1. "Recording density" Using a thermal recording simulator (TH-PMD type, manufactured by Okura Electric Co., Ltd.), recording was carried out under the condition of applied head energy of 0.4 mj / dot, and the density of the obtained recorded image was measured by a Macbeth densitometer (Macbeth (Manufactured by RD-914)
It was measured at.

"Opacity" Measured according to JIS-P8138.

"Background fog" The thermosensitive recording paper was allowed to stand for 7 days at 40 ° C., five sheets were piled up, and the whiteness was measured with a Hunter whiteness meter to examine the background fog.

"Recording image quality" Using a thermal recording simulator (TH-PMD type manufactured by Okura Electric Co., Ltd.), the image quality of a recorded image obtained by recording under the condition of an applied head energy of 0.4 mj / dot is visually judged. Judgment criteria ◎: The recording quality is excellent. ◯: Recording quality is slightly inferior

"Diazo Copy Suitability of Thermal Recording Paper" TERM
Using a thermosensitive recording paper recorded with AL PLOTTER [LTX-120 Roland Co.] as the original drawing (master), a diazo copy machine [Recopy SUP]
ER DRY 100 type, manufactured by Ricoh Co., Ltd.], and the obtained copy image and the density of the background portion were measured with a Macbeth densitometer.

"Amount of residual solvent" After coating and drying the liquid C, coating and drying the heat-sensitive recording layer coating liquid, and coating and drying the protective layer coating liquid, each sample of 10 cm x 10 cm was placed in a pressure-resistant airtight container, and 130 After the treatment at 15 ° C. for 15 minutes, the gasified organic solvent was quantified by a gas chromatography method.

[0052]

[Table 1]

(1) in the residual solvent amount in Table 1 represents the residual solvent amount (g / m ² ) after the coating of the C liquid. (2) represents the amount of residual solvent (g / m ² ) after formation of the thermosensitive recording layer. (3) represents the amount of residual solvent (g / m ² ) after formation of the protective layer.

[0054]

As is clear from the results shown in Table 1, the thermal recording paper of the present invention was a thermal recording paper for the second original image which had less background fog and was excellent in storage stability of recorded images.

Claims (3)

[Claims] 1. A heat-sensitive recording in which a recording layer containing a leuco dye and a coloring agent is provided on at least one surface after coating and drying an organic solvent coating liquid in which a resin is dissolved on one or both surfaces of a base paper. The thermal recording paper is characterized in that the amount of organic solvent remaining on the thermal recording paper is 0.3 g / m ² or less. 2. The thermosensitive recording paper according to claim 1, wherein the pigment is contained in the organic solvent coating liquid in which the resin is dissolved in an amount of 5 to 40% by weight based on the total solid amount of the resin. 3. The base paper is glassine paper as claimed in claim 1 or 2.
The thermal recording paper described.