JPH06143804A - Heat-sensitive recorder - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a thermosensitive recording medium having high whiteness, good recording uniformity, and no density unevenness. [Structure] In a thermosensitive recording medium having a structure in which a thermosensitive coloring layer, an intermediate layer and a gloss layer are sequentially provided on one side of a support, the intermediate layer and / or the gloss layer are coated by a microgravure coating method. [Effect] It is possible to obtain recording with high whiteness, good recording uniformity, and no density unevenness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium, and more specifically, CAD (Computer Aid)
The present invention relates to a thermal plotter that outputs a drawing created in an ed design system, and a thermal recording paper suitable for use in a thermal printer for images that outputs a CRT image for medical measurement as a hard copy.

[0002]

2. Description of the Related Art A thermosensitive recording medium is generally composed of paper, synthetic paper, plastic film or the like on one side of which a colorless or pale color-forming substance such as an electron-donating leuco dye and an electron-accepting phenol. A thermosensitive color-developing layer containing an organic acidic developer such as a photosensitive compound and an adhesive as main components, and a color-recorded image is formed by reacting these color-forming dyes and the developer with thermal energy. Obtainable.

Such a thermal recording medium has the advantages that the recording apparatus is compact and inexpensive, and that maintenance is easy, and is only used as a recording medium for facsimiles, automatic ticket vending machines, and scientific measuring machines. Not POS label, C
It is widely used as an output medium for various printers and plotters for AD and CRT medical images.

In particular, it is desired that the image printer paper for CRT medical measurement has high whiteness and glossiness, has a color density (γ characteristic) with respect to recording energy within a specific range, and has little variation. The conventional recording paper has a low glossiness and insufficient contrast, and the glossiness (measured according to JIS P8142) of the recording portion of the thermosensitive recording medium is set to 60% or more in order to obtain a satisfactory contrast. Had to do. For that purpose, it is necessary to provide an intermediate layer and a gloss layer on the thermosensitive coloring layer, and it is necessary to strictly control the coating amounts of the intermediate layer and the gloss layer in order to reduce variations in the γ characteristics.

The coating amount of the intermediate layer and the gloss layer is 1 to
3 g / m ^2, is about 0.5 to 2 g / m ^2, thus accurately reproduce small coating amount of such, in order to control has a problem in the conventional coating method. For example, in the Mayer bar method, it is necessary to use a thin wire bar, so streaks and scrapes are likely to occur, and the coating amount changes depending on the tension during coating, making stable coating difficult. Met. In addition, as the practically thinnest bar in bar coating, there is used a wire having a diameter of 6 mil (0.15 mm) which is in contact with each other around a stainless steel rod having a diameter of 6 to 15 mm and wound in a spiral shape. Since the paint is applied in a wet state of about 15 g / m ^2, it is necessary to make the solid content of the paint about 7% in order to obtain a coating amount of 1.0 g / m ² after drying. However, coating unevenness due to a decrease in viscosity is likely to occur, and it is necessary to heat to evaporate about 14 g / m ² of water excluding solids, which causes problems such as a decrease in whiteness. Further, as a problem of the bar coating method, there is a drawback that the coating amount fluctuates greatly if there is lumpiness or lumpiness in the winding before coating.

Further, in the blade system, the reverse roll system, the slit die system, etc., in order to obtain a small coating amount of 3.0 g / m ² or less, a paint having a solid content of 10% or less is used, and Since it is necessary to increase the coating amount, there was a problem of reduced whiteness as in the bar coating. These problems were found not only in water-based paints but also in solvent-based paints. The air knife method can use only water-based paints, and the paints are easily foamed, and there is a problem that bubbles remain on the coated surface. The direct gravure method is excellent in terms of coating amount control and has the advantage of being able to coat a small amount of paint with a relatively high solid content, but a pattern in which the paint splits occurs when the gravure roll and the substrate surface are separated. However, there is a problem that coating unevenness remains even if it is made uniform with a smoothing roll.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a thermosensitive recording medium having a structure in which a thermosensitive coloring layer, an intermediate layer and a gloss layer are sequentially provided on one side of a support, and a uniform coating surface with less variation in coating amount. The present invention aims to obtain a heat-sensitive recording material having the above-mentioned properties and having little decrease in whiteness due to coating and drying.

[0008]

Means for Solving the Problems The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, the present invention is colorless on one side of the support,
Alternatively, a light-sensitive electron-donating leuco dye, a thermosensitive coloring layer containing an organic acidic substance that develops the leuco dye by heating and an adhesive as main components, and a water-soluble and / or water-dispersible resin on the thermosensitive coloring layer. A thermal recording material comprising an intermediate layer containing a pigment, a pigment, and a cross-linking agent, and further comprising a gloss layer on the intermediate layer, wherein the intermediate layer and / or the gloss layer are coated by a microgravure coating method. It exists in the body.

The micro gravure coating method used in the present invention is, as shown in Japanese Patent Laid-Open No. 2-119977, the running direction and the axial direction of the base material below the running continuous base material. A gravure roll, which is arranged so as to alternate with each other and has a diameter of about 20 mm to about 50 mm and in which a gravure pattern is engraved all around, is rotated at a peripheral speed having a relative speed with the base material, and The excess coating agent is wiped off from the surface by a doctor blade before the coating, and a fixed amount of the coating agent is applied to the lower surface of the base material at a position where the upper surface of the base material is in the free state, The coating method is characterized by applying a coating agent to a base material.

The coating amount of the coating agent can be controlled by the number of lines (mesh) per inch of the gravure pattern. For example, when a 100 mesh to 250 mesh diagonal gravure roll is used, the wet coating amount can be controlled to about 1 g / m ^{2 to} 15 g / m ^2, and thus the coating amount after drying is 1.0 g / m ^2. 1 if solid
It can be applied with a paint of 100%. Therefore, in the case of water-soluble paint, it is possible to apply paint with a high solid content as much as possible,
There is no coating unevenness due to low viscosity, and the decrease in whiteness can be minimized. Further, it is possible to uniformly apply a small amount of a paint having a solid content of 100% such as an ultraviolet curable paint and an electron beam curable paint.

The support used in the present invention is obtained by heat-kneading a polyolefin resin and a white inorganic pigment, extruding from a die, and stretching in the machine direction, and 1-2 films on both sides of the polyolefin resin and the white inorganic pigment. Layers stacked,
Heat-kneading synthetic paper produced by making it translucent or opaque by stretching in the transverse direction, and thermoplastic resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin, polyvinyl chloride, polystyrene, polyester, etc., alone or in a mixture. Then, the film obtained by extruding from the die and biaxially stretching, or a white inorganic pigment is mixed with these resins,
In addition to the axially stretched opaque film, those produced from pulp fibers such as high-quality paper, medium-quality paper, roll paper, recycled paper and coated paper can be used. In order to improve the uniformity of the image, the support made of pulp fibers is provided with a coating layer in advance,
It is desirable to apply a heat sensitive layer.

The thermosensitive coloring layer of the present invention contains, as main components, a colorless or light-colored electron-donating leuco dye, an organic acid substance that causes the leuco dye to develop a color by heating, and an adhesive, and, if necessary, a crosslinking agent. It can be provided by applying a thermosensitive coloring layer coating material containing a pigment and a heat-fusible substance. The coating amount of the heat-sensitive color forming layer is generally preferably 3 to 10 g / m ^{2 in} terms of color forming sensitivity and color forming density. As a coating method, an air knife method, a Meyer bar method, a blade method, a reverse roll method, a slit die method, or the like conventionally used by those skilled in the art can be used. Further, by smoothing the surface of the thermosensitive coloring layer with a super calender, a gloss calender, a machine calender, etc., the coatability of the intermediate layer can be enhanced and the recording density and sensitivity can be improved.

As the color-forming dye, a colorless or light-colored electron-donating leuco dye capable of reacting with a color developer under heating to form a color is used. The color forming dye used in the present invention is, for example, 2,2 bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-xanthene) -2. '-Ylamido] phenyl} propane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-piperidino-6-
Methyl-7-anilinofluorane, 3- (N-methyl-
N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7-chloroanilinofluorane, 3- [N-ethyl-N- (p-methylphenyl) amino] -6-methyl -7-anilinofluorane, 3-diethylamino-7- (metatrifluoromethyl) anilinofluorane, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluorane , 3- (N-ethyl-N-isopentyl)
Amino-6-methyl-7-anilinofluorane, 3-
It is composed of at least one member of a fluorane dye such as (N, N dibutyl) amino-6-methyl-7-anilinofluorane.

The color developer used in the present invention comprises an electron-accepting organic acidic substance capable of reacting with a color-forming dye under heating to develop a color. Such a color developer liquefies or vaporizes at room temperature or higher, preferably 70 ° C. or higher, and reacts with the color forming dye to develop a color. In order to maximize the color density, the color developer is usually used in a proportion of 1 to 5 parts by weight, preferably 1.5 to 3 parts by weight, based on 1 part by weight of the color forming dye.

The color developer is, for example, 4,4'-isopropylidene diphenol (bisphenol A), 4,4'-.
Isopropylidene bis (2-chlorophenol), 4,
4'-isopropylidene bis (2-methylphenol), 4,4'-isopropylidene bis (2,6-t-
Butylphenol), 4,4'-sec-butylidene diphenol, 4,4'-cyclohexylidene diphenol, 4-t-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenyl sulfone, 3,3'-dihydroxydiphenyl sulfone, 3,3'-diamino-4,4'-dihydroxydiphenyl sulfone, 3,3'-diallyl-4,4 '
-Dihydroxydiphenyl sulfone, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfone, 4-
Hydroxydiphenyl sulfone, 4-hydroxy-4 '
-Isopropyloxydiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, 2,
4-dihydroxydiphenyl sulfone, 2,4-dihydroxy-4′-methyldiphenyl sulfone, and 3,
It is composed of at least one member selected from 4-dihydroxyphenyl-p-trisulfone and the like.

In the present invention, the adhesive contained in the thermosensitive coloring layer may be either a water-soluble resin or a water-dispersible resin. For example, polyvinyl alcohol, starch, modified starch, gum arabic, gelatin, casein, chitosan,
Methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, polyvinylpyrrolidone, polyacrylic acid salt, polyacrylic amide, polyester resin, styrene-acrylic acid ester copolymer resin, styrene-maleic anhydride copolymer resin, methyl vinyl ether-maleic anhydride copolymer resin , Water-soluble resins such as isopropylene-maleic anhydride copolymer resin, and vinyl acetate emulsion, acrylic ester copolymer emulsion, methacrylic ester copolymer emulsion, polyurethane emulsion, polyvinyl chloride emulsion, polyvinylidene chloride emulsion, SBR Latex, M
A water-dispersible resin having a good film-forming property with a minimum film-forming temperature of 20 ° C. or lower, which is an emulsion such as BR latex, can be used alone or in combination.

However, it is necessary that the mixed liquid does not develop color, aggregate, or have a high viscosity when mixed with the respective dispersion liquids of the color forming dye and the color developing agent, and formed. The thermal recording layer film is tough,
It is necessary that there is no desensitizing effect. The content of the adhesive in the thermosensitive coloring layer is preferably 8 to 20% with respect to the solid content of the thermosensitive coloring layer.
If it exceeds 0%, there is a problem that the sensitivity decreases.

Further, in order to improve the water resistance of the thermosensitive coloring layer, a crosslinking agent for curing the resin can be used. For example, glyoxal, dialdehyde compounds such as polyaldehydes, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins,
Melamine resins, diglycidyl compounds such as glycerin diglycidyl ether, dimethylolurea compounds, aziridine compounds, blocked isocyanate compounds, and ammonium persulfate and ferric chloride, and magnesium chloride, sodium tetraborate, potassium tetraborate, etc. The compound or boric acid, boric acid triester, or boron-based polymer can be used in the range of 1% to 10% with respect to the solid content of the thermosensitive coloring layer.

The pigment has a high whiteness and an average particle size of 5 because it improves the whiteness of the thermosensitive coloring layer and reduces sticking and dust.
It is possible to use a fine particle pigment having a particle size of not more than μm. For example, inorganic materials such as calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica. Pigments and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, polystyrene resin and the like can be used. The blending amount of the pigment is preferably 40% or less with respect to the solid content of the thermosensitive coloring layer in order not to reduce the coloring density.

Examples of the heat-fusible substance include stearic acid amide, stearic acid ethylenebisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide,
Fatty acid amides such as behenic acid amide, zinc stearate, calcium stearate, polyethylene wax,
Waxes (or lubricants) such as carnauba wax, paraffin wax, ester wax, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester, 1-hydroxynaphthoic acid phenyl ester, 1,
2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, diphenyl carbonate, p-benzylbiphenyl, 2,2'-methylenebis (4- Methyl-6-t
-Butylphenol), 4,4'-butylidene bis (6
-T-butyl-3-methylphenol), 1,1,3-
Tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 2,4-di-t-butyl-3-methyl Phenol, 4,4'-thiobis (3
-Methyl-6-t-butylphenol) and other hindered phenols, 2- (2'-hydroxy-5'-methylphenyl) -benzotriazole, and 2-hydroxy-4-benzyloxybenzophenone and other sensitizers, Antioxidants, UV absorbers, etc.

It is preferable that the heat-fusible substance is generally contained in the thermosensitive coloring layer in a ratio of 4 parts by weight or less relative to 1 part by weight of the color developer. Furthermore, in order to improve the wetting of the heat-sensitive color developing layer coating and eliminate cissing, acetylene glycol, a dispersant for pigments such as dialkyl sulfosuccinate, and a dispersant for the pigment,
An antifoaming agent, a fluorescent dye, etc. can also be added.

The intermediate layer of the present invention has a coating amount after drying of a coating material containing a water-soluble and / or water-dispersible resin, a pigment, a lubricant and a cross-linking agent as main components on the thermosensitive coloring layer in a range from 1.0 to 3.
It can be obtained by coating so as to be 0 g / m ² . If the coating amount is less than 1.0 g / m ² , the coating film will not be formed uniformly, so there will be pinholes and coating defects, and oil and plasticizer will penetrate from there, resulting in oil resistance and plasticizer resistance. Cause to decrease. If the coating amount exceeds 3.0 g / m ² , the sensitivity is lowered and the printing density is reduced. Since the fluctuation of the coating amount greatly affects the sensitivity, it is important to keep it as small as possible. To control the coating amount to 1.0 to 3.0 g / m ² and obtain a uniform coated surface, The microgravure coating method is desirable as the coating method.

The surface of the intermediate layer is a super calendar,
By performing a smoothing treatment with a gloss calender, a machine calender, etc., the coating property of the glossy layer can be enhanced and the recording density, sensitivity and glossiness can be improved. The resin of the intermediate layer is 40 to 80% with respect to the solid content of the intermediate layer, and the pigment is 20%.
The range of -40% is good, and if the compounding ratio of the resin exceeds 80%, sticking may occur during recording. Further, when the compounding ratio of the resin is less than 40%, the barrier property of the coating film is low and the oil resistance and the plasticizer resistance are lowered.

The lubricant may be added to the solid content of the intermediate layer, if necessary.
It is desirable to mix in the range of 30% or less. A crosslinking agent can be similarly compounded in the range of 5 to 30%. The resin, pigment and crosslinking agent used in the intermediate layer can be appropriately selected from those used in the heat-sensitive color forming layer.

Lubricants used in the intermediate layer include waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, and alkylyl phosphorus such as lauryl phosphate ester, oleyl phosphate ester and stearyl phosphate ester. Alkyl sulfonates such as acid esters and their alkali metal salts or amine salts, lauryl sulfonates, oleyl sulfonates, stearyl sulfonates and their alkali metal salts, or amine salts, glyceryl monomyristate, monostearic acid Glyceryl, glyceryl monooleate, glyceryl distearate, glyceryl fatty acid esters such as glyceryl dioleate, diglyceryl monolaurate,
There are polyglycerin fatty acid esters such as diglyceryl dilaurate, tetraglyceryl monolaurate, hexaglyceryl monolaurate, decaglyceryl monolaurate, etc., among which there is no desensitizing action, decolorizing action, or ground coloring action. You have to choose.

The gloss layer of the present invention has a coating amount of 0.5 to 2 after drying a coating material containing a water-soluble and / or water-dispersible resin, a pigment, a lubricant and a crosslinking agent as main components on the intermediate layer. 0.0 g
It can be obtained by coating so as to be / m ² . When the coating amount exceeds 2.0 g / m ² , there is a drawback that the sensitivity is lowered, the print density is reduced, and the glossiness after recording is lowered. If the coating amount is less than 0.5 g / m ² , there is a problem that the stick deteriorates. Further, the variation of the coating amount has a great influence on the sensitivity as in the case of the intermediate layer, so it is important to keep it as small as possible, and in order to obtain a uniform coating surface, the microgravure coating method is desirable as the coating method.

The water-soluble and / or water-dispersible resin, pigment and cross-linking agent used in the gloss layer can be appropriately selected from those used in the heat-sensitive color forming layer, but they have water resistance and glossiness. In order to improve the film forming property, a film forming property is preferable. The lubricant can be appropriately selected and used from those used for the intermediate layer. In order to enhance the glossiness of the glossy layer, the amount of the pigment blended must be 20% or less based on the solid content of the glossy layer.
Lubricant and cross-linking agent are 20 to 20% of the solid content of the gloss layer, respectively.
It is desirable to add 40% or 5 to 30%. Instead of the water-soluble and / or water-dispersible resin, it is possible to use a solvent-based resin, an ultraviolet curable resin, or an electron beam curable resin as the gloss layer resin.

As the solvent type resin, for example, vinyl acetate resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, acrylic ester resin, butyral resin, polyester resin, nitrocellulose resin, styrene resin,
Styrene-acrylic copolymer resin or the like can be used. Furthermore, a crosslinking agent having an isocyanate group, an epoxy group, an ethyleneimine group, an alkoxymethyl group, a hydrazine group, an aziridine group, and the like, and if necessary, the above pigment,
A gloss layer coating material can be prepared by adding a lubricant or the like.

The UV-curable resin, as a photopolymerizable monomer such as an ethylene derivative, produces a radical by irradiation with UV light together with a monomer or oligomer such as polyol acrylate, polyester acrylate, urethane acrylate, epoxy acrylate, polyacetal acrylate, or silicon acrylate. A photopolymerization initiator such as benzoin alkyl ether, benzophenone, benzyl, Michler's ketone and the like can be used together. Furthermore, if necessary, the above-mentioned pigment, lubricant, etc. may be added to prepare a gloss layer coating material.

The electron beam curable resin is a poly (meth) acrylate of an aliphatic, alicyclic, araliphatic polyhydric alcohol having 2 to 6 valences and polyalkylene glycol or alkylene oxide. , Poly (meth) acryloyloxyalkyl phosphate ester, polyester poly (meth) acrylate, epoxy poly (meth) acrylate, polyurethane poly (meth) acrylate, polyamide poly (meth) acrylate, polysiloxane poly (meth) acrylate, side chain And / or vinyl-based or diene-based prepolymers having a (meth) acryloyloxy group at the end, carboxyl group-containing monomers represented by ethylenically unsaturated mono- or polycarboxylic acids, and alkali metal salts and ammonium salts thereof Carvone such as amine salt There is a base-containing monomers. Furthermore, if necessary, the above-mentioned pigment, lubricant, etc. may be added to prepare a gloss layer coating material.

Further, the recording density, sensitivity and glossiness can be improved by smoothing the surface of the gloss layer with a super calender, gloss calender, machine calender or the like.

[0032]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. In each example, “part” means “part by weight”. Example 1 A commercially available synthetic paper (Yupo FPG-80, manufactured by Oji Yuka Synthetic Paper Co., Ltd.) was coated on one side with a thermosensitive color developing layer coating composition shown below, which had a coating amount of 5.5 g / m ² . Bar coating method so that the coating amount after drying the intermediate layer coating and the gloss layer coating is 1.5 g / m ² (using 110 mesh roll) and 1.0 g / m, respectively. ² (using 200 mesh roll) was applied by the microgravure coating method.

Preparation of paint for thermosensitive coloring layer Liquid A (thermosensitive coloring dye dispersion liquid) 3- (N, N-dibutyl) amino-6-methyl-7-anilinofluorane 20 parts 10% polyvinyl alcohol aqueous solution 20 Part Water 10 parts Liquid B (developer developer dispersion) 4-Hydroxy-4'-isopropyloxydiphenyl sulfone 50 parts 10% polyvinyl alcohol aqueous solution 50 parts Water 25 parts Liquid A and liquid B are separately dispersed with Ultraviscomyl. The powder was pulverized and adjusted so that the average particle diameter was 1.0 ± 0.3 μm. Liquid A 30 parts, liquid B 90 parts, 60% calcium carbonate slurry 52 parts, 10% polyvinyl alcohol aqueous solution 40 parts, SBR latex (L-1537,
Solid content 50%, Asahi Kasei product 28 parts, stearic acid amide (Cerosol A-877, solid content 26.5%, Chukyo Yushi Co., Ltd. product) 11 parts, water 82 parts are mixed to obtain a thermosensitive coloring layer. It was paint.

-Interlayer paint (solid content 15%) 60% Kaolinite clay (average particle size 0.6 μm) dispersion 42 parts Carboxy modified polyvinyl alcohol aqueous solution (solid content 10%) (Gothenal T-330, Nippon Synthetic Chemistry) 200 parts Acrylic emulsion (SC-2250, solid content 40%, Nippon Shokubai Co., Ltd. product) 100 parts Dimethylol urea solution (J-001, solid content 30%, Showa Denko KK product) 33 parts 40% zinc stearate dispersion (Himicron F-930, average particle size 0.9 μm, product of Chukyo Yushi Co., Ltd.) 13 parts Water 279 parts were mixed to prepare an intermediate layer paint.

-Gloss layer coating (solid content 20%) Polysiloxane graft acrylic emulsion 360 parts (GF-256 Nippon Shokubai Co., Ltd. product solid content 20%) 50% calcium carbonate slurry (Callite SA, average particle size 3.3 μm) Shiraishi Industry Co., Ltd. product 6 parts Alkyl phosphoric acid ester potassium salt (TRL-20 Matsumoto Yushi-Seiyaku Co., Ltd. product solid content 50%) 50 parts Water 84 parts was mixed to obtain a gloss layer paint. Furthermore, after coating the back layer coating on the opposite surface with a bar coating method so that the coating amount after drying will be 1.5 g / m ² , smoothing treatment is performed with a super calender, and the gloss layer is Oken type smoothing. Degree (J. TAPPI N
o. In 6), a thermosensitive recording medium having 7,000 seconds was obtained.

Back layer paint Sodium polystyrene sulfonate (Chemist SA-9, Sanyo Chemical Co., Ltd. product, solid content 33%) 30 parts SBR latex (0528, Nippon Synthetic Rubber Co., Ltd. product, solid content 50%) 70 parts 10% aqueous solution of oxidized starch (Ace A Oji Corn Starch Co., Ltd. product) 150 parts 60% kaolinite clay slurry 67 parts water 83 parts were mixed to prepare a back layer paint.

Example 2 The following intermediate layer paint was applied onto the thermosensitive color developing layer of Example 1 by a bar coating method (bar # 8) so that the coating amount after drying was 2.5 g / m ^2. And further on it, a polyester acrylate (FS-3062, which is an electron beam curable resin,
Mitsubishi Rayon Co., Ltd.) is applied by a micro gravure coating method so as to have a weight of 2.0 g / m ² (250 mesh roll is used), and a dose of 3 Mrad is irradiated by an electron curtain type electron beam irradiation device. A thermal recording material was obtained in the same manner as in Example 1.

-Interlayer paint (solid content 15%) Colloidal silica (Snowtex C, solid content 20%, Nissan Chemical Industries, Ltd.) 150 parts Carboxy modified polyvinyl alcohol aqueous solution (solid content 10%) (Gothenal T- 330, Nippon Synthetic Chemical Co., Ltd. product 200 parts Acrylic emulsion (SC-1225, solid content 20%, Nippon Shokubai Co., Ltd. product) 200 parts Glyoxal (solid content 40%, Nippon Synthetic Chemical Co., Ltd. product) 25 parts 92 parts of water was mixed to form an intermediate layer paint.

Example 3 A commercially available synthetic paper (Yupo FPG-80, manufactured by Oji Okaka Synthetic Paper Co., Ltd.) was coated on one side with the following thermosensitive color developing layer coating material at a coating amount of 5.5 g / m after drying. ² by bar coating method, and the coating amount after drying intermediate layer paint and gloss layer paint is 1.5 g / m ² (using 110 mesh roll), 1.0 g / M ² (using 150 mesh roll) was applied by the microgravure coating method.

Preparation of paint for thermosensitive coloring layer Liquid A (dispersion liquid of thermosensitive coloring dye) 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane 20 parts 10% polyvinyl alcohol Aqueous solution 20 parts Water 10 parts Liquid B (developing agent dispersion) 4,4'-isopropylidenediphenol 50 parts 10% polyvinyl alcohol aqueous solution 50 parts Water 25 parts Liquids A and B are separately dispersed in Ultraviscomill. The powder was pulverized and adjusted so that the average particle diameter was 1.0 ± 0.3 μm. Solution A 25 parts, solution B 90 parts, 60% calcium carbonate slurry 55 parts, 10% polyvinyl alcohol aqueous solution 40 parts, SBR latex (L-1537,
Solid content 50%, Asahi Kasei product 28 parts, stearic acid amide (SA-21, solid content 20%, Kyosho Chemical Co., Ltd.)
15 parts of water) and 80 parts of water were mixed to obtain a thermosensitive coloring layer coating material.

-Interlayer paint (solid content 15%) 20% synthetic aluminum silicate dispersion (Persilex P-820, product of Degussa) 125 parts Carboxy modified polyvinyl alcohol aqueous solution (solid content 10%) (Gothenal T-330, Nippon Synthetic Chemical Co., Ltd. product 200 parts Acrylic emulsion (SC-2251, solid content 40%, Nippon Shokubai Co., Ltd. product) 113 parts Dimethylol urea solution (J-001, solid content 30%, Showa Denko product) ) 33 parts water 196 parts were mixed to form an intermediate layer paint.

-Gloss layer coating (solid content 15%) Self-crosslinking acrylic emulsion (SC-2000, Nippon Shokubai Co., Ltd. product, solid content 20%) 310 parts 30% benzoguanamine resin powder dispersion (Eposter M-30, average) Particle size 3.0 μm, Nippon Shokubai Co., Ltd. product 10 parts Monolauric acid decaglyceride (Nikko Chemical Co., Ltd. product) 25 parts Glyoxal (solid content 40%, Nippon Synthetic Chemical Co., Ltd. product) 25 parts Water 297 parts The mixture was mixed to obtain a gloss layer paint. Further, a back layer coating material was applied to the opposite surface in the same manner as in Example 1 and then smoothed with a super calendar to obtain a thermal recording material having a gloss layer having an Oken type smoothness of 9,000 seconds.

Examples 4 and 5 When an intermediate layer and a gloss layer were provided on the thermosensitive coloring layer of Example 3 as in Example 1 (Example 4) and as in Example 2, the intermediate layer and gloss were provided. A layer is provided (Example 5), and further Example 1
After the back layer was provided in the same manner as above, a super calender treatment was carried out to obtain a thermosensitive recording medium.

Comparative Examples 1 to 3 On the thermosensitive color developing layers of Examples 1, 3 and 4, the respective intermediate layer paints and gloss layer paints were all coated by the bar coating method as shown in Table 1. Example 1 except that coating was performed under the working conditions
A thermal recording material was obtained in the same manner as in (Comparative Example 1), Example 3 (Comparative Example 2) and Example 4 (Comparative Example 3). Whiteness (measured according to JIS P8123) of the 110 mm wide thermal recording media obtained in Examples 1 to 5 and Comparative Examples 1 to 3 and a commercially available thermal printer (UP-860, Sony Corporation). The recording unevenness when halftone recording was performed was evaluated.

The results are shown in Table 1.
In Example 5, the whiteness was high, the recording uniformity was good, and halftone recording without density unevenness was obtained, whereas in Comparative Examples 1 to 5, the whiteness was low and uneven density was observed. I only got a strong record.

[0046]

[Table 1]

[0047]

The thermosensitive recording medium produced according to the present invention has high whiteness, good recording uniformity, and good recording without uneven density.

Claims (1)

[Claims] 1. A thermosensitive coloring layer containing a colorless or light-colored electron-donating leuco dye, an organic acidic substance that develops the color of the leuco dye by heating, and an adhesive as main components on one surface of the support, and the thermosensitive coloring layer is provided. In a heat-sensitive recording material comprising an intermediate layer containing a water-soluble and / or water-dispersible resin, a pigment, and a crosslinking agent on the color forming layer, and a gloss layer on the intermediate layer. A thermosensitive recording medium, characterized in that the layer is coated by a microgravure coating method.