JPH08197845A - Manufacturing method of thermal recording paper - Google Patents

Abstract

(57) [Abstract] [Purpose] It is intended to provide a method for producing a thermal recording paper which does not deteriorate the recording image quality due to wrinkles. [Structure] An aqueous recording layer coating liquid containing a leuco dye, a coloring agent and an adhesive is applied on a base paper having a basis weight of 25 to 60 g / m ² and dried to contain the recording layer, and a pigment and an adhesive. In a method for producing a thermosensitive recording paper in which a water-based protective layer coating liquid is applied by roll blade coating and dried to sequentially provide a protective layer, when the protective layer coating liquid is applied, the surface temperature of the recording layer is 35 to 60 ° C. And the value (Y / T) of the ratio of the tensile strength (Y) in the transverse direction to the tensile strength (T) in the longitudinal direction is 0.6 to
A method for producing a thermal recording paper using a base paper of 0.9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording paper utilizing the color forming reaction between a leuco dye and a color former, and more particularly to a method for producing a thermosensitive recording paper having excellent recording image quality.

[0002]

2. Description of the Related Art Utilizing a color reaction between a color former and a color former,
A heat-sensitive recording paper in which both substances are reacted by heat to obtain a recorded image is well known. Such heat-sensitive recording paper is relatively inexpensive, and its recording equipment is compact and its maintenance is relatively easy. Therefore, it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields. For example, as one of the fields of use thereof, cases of being used for POS (point of sales) labels at retail stores are increasing. However, the heat-sensitive recording paper using a combination of colorless or light-colored leuco dye and an acidic substance in the coloring system has poor fingerprint resistance, solvent resistance, etc., and is recorded when human sebum or solvent contacts the recording layer. There is a defect that the density is lowered and unnecessary coloration called background fog occurs.
Moreover, when a thermal label composed of such a coloring system is applied to a POS system such as a supermarket, the label often comes into contact with water, wraps, oil, etc. As a result, the recorded image of the thermal label is affected. A defect that the (printing) fades is recognized. Therefore, the thermal recording paper is water resistant,
It is required to have storability such as plasticizer resistance and oil resistance. Further, in order to record more information at high speed, there is an increasing demand for improvement in recording sensitivity and image quality. To this end, an undercoat layer containing an inorganic pigment having a high oil absorption property (Japanese Patent Laid-Open No. 63-38318). Undercoat layer containing organic hollow particles (JP-A-62-
No. 5885) is provided between the support and the recording layer to improve heat insulation and smoothness.

A method of coating an aqueous emulsion of a resin having film forming ability and chemical resistance on the recording layer having improved smoothness so as to improve the storability of a recorded image (JP-A-55-128347). Method) and a method of applying a water-soluble polymer such as polyvinyl alcohol (Act.
No. 5354) has been tried. However, when a protective layer is provided by air knife coating or bar coating after a recording layer is provided on a thin base paper having a basis weight of 25 to 60 g / m ² using a conventional coating method, the concentration and viscosity of the coating solution are lowered. Therefore, it was difficult to satisfy the preservability because it was necessary to apply it by coating. Therefore, in order to solve this problem, a method of applying a protective layer by roll blade coating is disclosed in JP-A-1-113280, JP-A-6-48023, and JP-A-6-1351.
No. 37, the application of a water-based protective layer coating solution containing a pigment and an adhesive by roll blade coating after providing a recording layer and drying to provide a protective layer, when applied to the base paper. Alternatively, wrinkles occur during drying, and as a result, problems such as deterioration in recording image quality occur.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a heat-sensitive recording paper which does not deteriorate the recording image quality due to the generation of wrinkles.

[0005]

The present invention has a basis weight of 25 to 6
A water-based recording layer coating liquid containing a leuco dye, a colorant, and an adhesive is applied onto 0 g / m ² of base paper and dried to form a recording layer and a water-based protective layer coating liquid containing a pigment and an adhesive. In a method for producing a heat-sensitive recording paper in which a protective layer is applied by roll blade coating and dried to sequentially provide a protective layer, the surface temperature of the recording layer when applying the protective layer coating liquid is 35 to 60 ° C.
And tensile strength in the transverse direction (Y) and tensile strength in the longitudinal direction (T)
By using a base paper having a ratio value (Y / T) of 0.6 to 0.9, the above problems have been solved and completed.

[0006]

According to the present invention, in the base paper for thermal recording paper having a basis weight of 25 to 60 g / m ² , the value of the ratio of the tensile strength (Y) in the transverse direction to the tensile strength (T) in the longitudinal direction (Y / T ) Is 0.6 to 0.9, and the surface temperature of the recording layer is 35 to 35 when the protective layer coating liquid is applied by roll blade coating.
When the Y / T ratio of the base paper is less than 0.6, wrinkles occur when the protective layer coating liquid is applied or when the Y / T ratio of the base paper is less than 0.6, and the Y / T ratio of 0. If it exceeds 9 or the basis weight of the base paper is less than 25 g / m ² , the tensile strength in the machine direction is lowered and paper breakage easily occurs during coating. Also,
When the basis weight of the base paper exceeds 60 g / m ² , almost no wrinkles are observed when the protective layer coating liquid is applied or dried.
The tensile strength of the base paper is measured according to JIS P8113.

When the protective layer coating liquid is applied by roll blade coating, if the surface temperature of the recording layer is lower than 35 ° C., the coating liquid is impregnated into the recording layer and the base paper unevenly, and wrinkles are likely to occur. When the temperature exceeds 60 ° C., the background fog is generated in the recording layer, or the barrier property of the protective layer is deteriorated and the protection property against chemicals such as a plasticizer is deteriorated.

The tensile strength (Y) in the transverse direction and the tensile strength (T) in the longitudinal direction of the base paper produced by the paper machine are, for example, the J / W ratio of the paper machine operation (slurry jet at the inlet outlet of various paper machines. It can be changed at appropriate times by adjusting the ratio of speed to wire speed), papermaking speed, and dehydration conditions of the wire part.

Various known leuco dyes can be used as the leuco dye contained in the recording layer of the present invention. Examples thereof include the following.

3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylamino Phthalide, 3-
Diethylamino-7-dibenzylamino-benzo [a]
Fluorane, 3- (N-ethyl-Np-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 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-diethylamino-7- (M-Trifluoromethylanilino) fluorane, 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)
Fluoran, 3- (N-ethyl-p-toluidino) -6
-Methyl-7-anilinofluorane, 3-diethylamino-6-chloro-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-p- (p-anilinoanilino) anilino-6-methyl -7-Chlorofluorane, 2,2-
Bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-
Xanthene-2′-ylamino] phenyl} propane,
3,6, -bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide and the like. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Various compounds are known as colorants used in combination with leuco dyes, such as 4-cumylphenol, hydroquinone monobenzyl ether and 4,4 '.
-Isopropylidenediphenol, 1,1-bis (4-
Hydroxyphenyl) cyclohexane, 4,4'-dihydroxydiphenyl-2,2-butane, 4,4'-dihydroxydiphenylsulfide, bis (4-hydroxy-3-methylphenyl) sulfide, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-
4'-benzyloxyphenyl sulfone, 4-hydroxy-3 ', 4'-tetramethylene biphenyl sulfone,
3,4-dihydroxyphenyl-p-tolyl sulfone,
4-Hydroxybenzoic acid benzyl ester, N, N'-
Di-m-chlorophenylthiourea, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4-
Examples include {3- (p-tolylsulfonyl) propyloxy] zinc salicylate, and 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] zinc salicylate.
In addition, if necessary, two or more kinds of these color-developing agents can be used in combination.

In the present invention, the use ratio of the colorless or light-colored leuco dye and the coloring agent in the recording layer is appropriately selected according to the kind of the colorless or light-colored leuco dye and the coloring agent used, and particularly, Although not limited, generally 1 to 1 part by weight of a colorless or light-colored leuco dye is used.
10 parts by weight, preferably 1 to 5 parts by weight of acidic substance are used.

To prepare a coating liquid containing these substances, generally, water is used as a dispersion medium, and a coloring agent and a coloring agent are averaged together or separately by stirring with a ball mill, attritor, sand mill or the like and a pulverizer. A particle diameter of 2 μm or less, preferably 1 μm or less is dispersed to prepare a coating liquid.

In such a coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, alkali salt of styrene / maleic anhydride copolymer, ethylene / acrylic acid are usually used as binders. Alkali salt of copolymer, alkali salt of styrene / acrylic acid copolymer, natural rubber emulsion, styrene / butadiene copolymer emulsion, acrylonitrile / butadiene copolymer emulsion, methyl methacrylate / butadiene copolymer emulsion, polychloroprene Emulsion, vinyl acetate emulsion, ethylene / vinyl acetate emulsion and the like are added in an amount of about 5 to 20% by weight of the total solid content of the recording layer.

If desired, various additives may be used in combination, for example, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax; calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide. , Silicon dioxide, aluminum hydroxide, barium sulfate, talc,
Inorganic pigments such as kaolin, clay, calcined clay and colloidal silica; organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin fillers; stearic acid amide, N-methylstearic acid amide, benzalinide, methylene stearate. Fatty acid amides such as bisamide;

4,4'-butylidene bis (6-tert-butyl-3-methylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,
4-di-tert-butyl-3-methylphenol, 1,
1,3-tris (2-methyl-4-hydroxy-5-te
rt-Butylphenyl) butane, 1,1,3-tris (5
-Cyclohexyl-4-hydroxy-2-methylphenyl) butane, 1,3,5-tris (5-tert-butyl-
Hindered phenols such as 3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid; 4- (2-methyl-1,2-epoxyethyl) diphenylsulfone, 4
Diphenylsulfone derivatives such as-(2-ethyl-1,2-epoxyethyl) diphenylsulfone and 4-benzyloxy-4 '-(2,3-glycidyloxy) diphenylsulfone; 2- (2'-hydroxy-5' -Methylphenyl) benzotriazole, 2-hydroxy-
UV absorbers such as 4-benzyloxybenzophenone;
1,2-di (3-methylphenoxy) ethane, 1,2-
Diphenoxyethane, 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 Examples thereof include heat sensitivity improvers (sensitizers) such as di-p-chlorobenzyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, and isophthalic acid dibutyl ester.

The average particle size of the above additives contained in the recording layer is preferably 2 μm or less. The amount of the additive used is not particularly limited, but for example, the amount of the sensitizer used is preferably adjusted within the range of about 4 parts by weight or less per 1 part by weight of the color developing agent.

The coating liquid for the recording layer containing these substances is generally prepared by wet grinding using a ball mill, an attritor, a sand mill or the like with water as a dispersion medium, or each compound is treated with heat, a solvent or the like. A method of dissolving and then dispersing in water to form an emulsion can be mentioned. Various kinds of dispersants can be used for wet pulverization, and examples thereof include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, vinyl acetate resins containing sulfonic acid groups, starches, sodium polyacrylate, sodium polysulfonate, dioctylsulfone. Examples of the dispersant include sodium succinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate / sodium salt, and metal salt of fatty acid.

Examples of the adhesive used in the recording layer include starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, carboxyl 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, natural rubber emulsion, styrene -Butadiene copolymer emulsion, acrylonitrile-butadiene copolymer emulsion, methyl methacrylate-butadiene copolymer emulsion, polychloroprene emulsion, vinyl acetate emulsion Emissions, ethylene-vinyl acetate emulsion, urea resins, melamine resins, amide resins. The adhesive is preferably 5 with respect to the total solid of the recording layer.
-40 wt%, more preferably about 10-30 wt% is added.

Further, various known pigments can be added to the recording layer within a range that does not impair the desired effects of the present invention. For example, magnesium carbonate, calcite-based light calcium carbonate, aragonite-based light calcium carbonate, and heavy calcium carbonate. , Inorganic pigments such as calcium sulfoaluminate, aluminum hydroxide, titanium dioxide, silicon dioxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, alkali-modified silica, particulate anhydrous silica, colloidal silica and styrene micro Examples include organic pigments such as balls, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch. If necessary, zinc stearate, calcium stearate,
Waxes such as polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., sodium dioctylsulfosuccinate, sodium dodecylbenzene sulfonate, dispersants such as sodium lauryl alcohol sulfate / sodium salt, alginate, fatty acid metal salt, benzophenone type Further, an ultraviolet absorber such as a triazole type, an antifoaming agent, a fluorescent dye, a coloring dye, or the like can be added.

The method for forming the recording layer is not particularly limited, and suitable coating methods such as air knife coating, varibar blade coating, rod blade coating, pure blade coating, short dwell coating, curtain coating, die coating and the like. Thus, the recording layer coating liquid is applied onto the support and dried, and the like. There is no particular limitation on the coating amount of the coating liquid, usually dry weight 1 to 10 g / m ^2, is preferably adjusted in the range of about 2~7g / m ^2.

The thermal recording paper of the present invention comprises a recording layer thus obtained, which is coated with a water-based protective layer coating solution containing a pigment and an adhesive by roll blade coating and dried to form a protective layer. If the diameter of the roll used when applying the protective layer coating liquid is larger than 30 mm, the amount of the protective layer coated is likely to occur, but a roll pattern is likely to occur.
If it is less than mm, it is difficult to coat the protective layer, so 8
-30 mm is preferable. If the viscosity of the coating material for forming the protective layer is less than 100 cps, the coating material is impregnated into the recording layer by the pressure of the roll blade tube for controlling the coating amount, and the barrier property of the protective layer is lowered, and the recording sensitivity is lowered. It may decrease. Also, the viscosity of the paint is 5000c
If it exceeds ps, it is necessary to increase the pressure of the roll blade tube, which may cause breakage of the roll blade tube.

Adhesives used for such a protective layer include starch, casein, methyl cellulose, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, complete saponification. And partially saponified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol and the like. Among these, acetoacetyl group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are particularly preferable because they have excellent film-forming properties. Such adhesives include glyoxal, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, ammonium chloride, methylolmelamine, boric acid, alum, aminoplast resin, epoxy resin, aziridine and other curing agents. A protective layer having excellent water resistance and barrier properties is formed.

In order to further improve coating suitability, writability, printability, etc. in the protective layer coating liquid, for example, heavy calcium carbonate, light calcium carbonate, talc, clay, natural silicic acid, synthetic silicic acid, titanium oxide. 50-300 for inorganic or organic pigments such as kaolin, aluminum hydroxide, zinc oxide, urea formaldehyde resin powder, etc.
It is desirable to adjust the content in the range of 100% by weight, preferably 100 to 250% by weight. If the amount of the pigment added is less than 50% by weight, the printability cannot be obtained, and if it exceeds 300% by weight, the preservability for the plasticizer and the like deteriorates.

Further, in the protective layer, if necessary, zinc stearate, calcium stearate, stearic acid amide, polyethylene wax, carnauba wax, paraffin wax, ester wax, lubricant such as silicone oil, sodium dioctyl sulfosuccinate, dodecyl. Surfactants such as sodium benzene sulfonate, sodium lauryl alcohol sulfate / sodium salt, alginic acid, fatty acid metal salt, etc., UV absorbers such as benzophenone-based or triazole-based, antifoaming agents, fluorescent dyes, various dyes and other auxiliary agents. It can also be added. The coating amount of the protective layer coating liquid is not particularly limited, but is 0.5 g / m ²
If it is less than 10, it is difficult to obtain the desired effect of the present invention,
^If it exceeds ² , the recording density may be remarkably lowered, so that it is generally desirable to adjust the dry weight within the range of about 1 to 8 g / m ² .

In the present invention, the image quality and the recording density can be further improved by applying a recording layer coating liquid, drying the protective layer coating liquid or applying a supercalendering treatment after drying, if necessary. When base paper is used as the support, an undercoat layer composed of an adhesive and a white pigment may be provided to enhance recording density, sensitivity and storability. Further, a back barrier layer composed of an adhesive and a white pigment may be provided on the back surface of the recording medium to eliminate the influence of oil, plasticizer, etc. from the back surface to further improve the storage stability. Further, various well-known techniques in the field of heat-sensitive recording paper production, such as a pressure-sensitive adhesive treatment on the back surface of the heat-sensitive recording paper to process an adhesive label, can be added.

[0027]

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, oxalic acid di-p-chlorobenzidyl ester 10 parts, oxalic acid di-p -A composition comprising 10 parts of methylbenzyl ester, 5 parts of a 10% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, manufactured by Nippon Gohsei Kagaku Co., Ltd.), and 50 parts of water having an average particle diameter of 1 µm in a sand mill Crushed until

Preparation of Solution B 2,4′-Dihydroxy-diphenylsulfone 10
Parts, 5 parts of a 5% aqueous solution of methyl cellulose, and 70 parts of water
The composition of 1 part was pulverized with a sand mill until the average particle diameter became 2 μm.

Formation of Recording Layer 100 parts of solution A, 130 parts of solution B, 10% aqueous solution of polyvinyl alcohol (polymerization degree 1100, saponification degree 98%) 17
A coating liquid obtained by mixing and stirring a composition comprising 0 part, 3 parts of a 40% aqueous solution of glyoxal, and 4 parts of aluminum hydroxide (average particle size 1 μm) has a basis weight of 42 g / m ² , and Y / T.
A recording layer was formed by coating one surface of a neutral base paper having a ratio value of 0.65 by a roll blade coating method so that the coating amount after drying was 5 g / m ^2, and drying.

Formation of Protective Layer On the recording layer having a surface temperature of 40 ° C., 230 parts of a 13% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, 60 parts of kaolin having an average particle diameter of 0.8 μm, and 3 parts of zinc stearate.
A coating solution (viscosity 200 cps-25) obtained by mixing and stirring a composition consisting of 16 parts of 0% differential acid solution and 120 parts of water.
Applying ° C.) so that the coating amount after drying by a roll blade coating method is 4g / m ^2, and dried to form a protective layer, performs the smoothing process with super calender, a heat-sensitive recording paper having a protective layer Obtained.

Example 2 In the formation of the recording layer of Example 1, the basis weight is 42 g / m ² ,
Y / T ratio of 0.65 instead of neutral base paper 42
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that an acidic base paper having a g / m ² and a Y / T ratio of 0.85 was used.

Example 3 In the formation of the recording layer of Example 1, the basis weight is 42 g / m ² ,
Y / T ratio of 0.65 instead of neutral base paper, basis weight 3
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that an acidic base paper having a 0 g / m ² Y / T ratio value of 0.63 was used.

Example 4 In the formation of the recording layer of Example 1, the basis weight is 42 g / m ² ,
Y / T ratio of 0.65 instead of neutral base paper, basis weight 5
A thermal recording paper was obtained in the same manner as in Example 1 except that a neutral base paper having a value of 5 g / m ² Y / T ratio of 0.83 was used.

Example 5 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the protective layer was formed on the recording layer having a surface temperature of 50 ° C. in the formation of the protective layer of Example 1.

Comparative Example 1 In the formation of the recording layer of Example 1, the basis weight was 42 g / m ² ,
Y / T ratio of 0.65 instead of neutral base paper, basis weight 4
A thermal recording paper was obtained in the same manner as in Example 1 except that a neutral base paper having a value of ² g / m ² Y / T ratio of 0.52 was used.

Comparative Example 2 In the formation of the recording layer of Example 1, the basis weight is 42 g / m ² ,
Y / T ratio of 0.65 instead of neutral base paper, basis weight 4
A thermal recording paper was obtained in the same manner as in Example 1 except that a neutral base paper having a value of ² g / m ² Y / T ratio of 0.97 was used.

Comparative Example 3 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the air knife coating method was used instead of the roll blade coating method in forming the protective layer of Example 1.

Comparative Example 4 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the protective layer was formed on the recording layer having a surface temperature of 30 ° C. in the formation of the protective layer in Example 1.

Comparative Example 5 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the protective layer was formed on the recording layer having a surface temperature of 65 ° C. in the formation of the protective layer in Example 1.

The thermal recording paper thus obtained was evaluated as follows, and the results are shown in Table 1. [Evaluation] Recording Density and Recording Image Quality The density of the recorded image obtained by a thermal simulator (TH-PMD manufactured by Okura Electric Co., Ltd.) was measured with a Macbeth densitometer (RD-100 type manufactured by Macbeth Co.), and the recording quality was recorded. The image was visually judged. [Evaluation Criteria] A: The recording image quality is excellent. ○: The recording image quality is slightly inferior. X: The recording image quality is poor.

Plasticizer Resistance A vinylidene chloride film containing a plasticizer was overlaid on a heat-sensitive recording paper after recording, and left for 3 days in a room, and then its fading was visually evaluated. [Evaluation Criteria] ◎: No problem in practical use ○: Almost no problem in practical use ×: Problems in practical use

After providing the wrinkle protective layer, the wrinkles generated on the thermal recording paper were visually judged. ⊚: Wrinkles are not generated at all. ◯: There are some wrinkles. X: Many wrinkles occur.

Paper breakage The frequency of paper breakage that occurred when the protective layer was formed was evaluated. ⊚: There are few pieces of paper. X: There are many pieces of paper.

[0045]

[Table 1]

[0046]

As is clear from the results of Table 1, the thermal recording paper of the present invention was a wrinkle-free thermal recording paper excellent in recording image quality.

Claims (1)

[Claims] 1. A base paper having a basis weight of 25 to 60 g / m ² is coated with a water-based recording layer coating liquid containing a leuco dye, a coloring agent and an adhesive and dried to form the recording layer, and a pigment and an adhesive. In a method for producing a thermosensitive recording paper in which a water-based protective layer coating solution containing a protective layer coating solution is applied by roll blade coating and dried to sequentially provide a protective layer, the surface temperature of the recording layer when the protective layer coating solution is applied is 35 to 60. And the ratio value (Y / T) of the tensile strength (Y) in the transverse direction and the tensile strength (T) in the longitudinal direction of the base paper is 0.6 to 0.9. Method for manufacturing thermal recording paper.