JP2713049B2 - Thermal recording medium - Google Patents

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 particularly, to a thermosensitive recording medium suitable for use in a thermographic printer for outputting a CRT image for medical measurement as a hard copy. Things.

[0002]

2. Description of the Related Art A thermosensitive recording medium is generally composed of a support made of paper, synthetic paper or a plastic film on at least one side thereof, a colorless or pale-colored coloring substance such as an electron-donating leuco dye, and an electron-accepting phenol. A thermosensitive coloring layer containing an organic acid developer such as a hydrophilic compound and an adhesive as main components is provided, and the color forming dye is reacted with the developer by thermal energy to record a color. Images can be obtained.

Such a thermosensitive recording medium has advantages such as a compact and inexpensive recording apparatus and easy maintenance, and is used only as a recording medium for facsimile machines, 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. Among them, an image printer for CRT medical measurement requiring uniformity of recorded images and high resolution, and a C printer requiring dimensional stability and fine line recording
For the AD plotter, a synthetic paper having a multilayer structure or a biaxially stretched thermoplastic resin film containing an inorganic pigment as necessary is used.

[0004] In particular, recording paper having high whiteness and high gloss is desired for image printer paper for CRT medical measurement. However, conventional recording paper has low gloss and insufficient contrast. . The glossiness of the heat-sensitive recording medium is adjusted, for example, according to JIS in order to make the contrast satisfactory.
The glossiness of the printed area measured according to P 8142 is 60%
It is necessary. For this purpose, it is necessary to provide an intermediate layer and a glossy layer on the thermosensitive coloring layer. However, since only a small amount of pigment of 10% or less can be blended in the glossy layer, the smoothness becomes high, and sticks and scratches occur. There was a problem to do.

[0005] In order to prevent sticks and scratches, it is necessary to lower the smoothness of the glossy layer. As a method of reducing the smoothness with a compounding amount of 10% or less, the average particle size is larger than the thickness of the glossy layer. It is conceivable to mix the pigment in the glossy layer, but in this case, the pigment falls off by the super calender or the slitter, which causes not only a problem in operation but also a problem in that the effect of improving the stick and the scratch is lost.

[0006]

DISCLOSURE OF THE INVENTION The present invention aims at increasing the glossiness of a heat-sensitive recording medium and improving sticks and scratches.
It is an object of the present invention to provide a thermosensitive recording medium in which a pigment having a particle size larger than the thickness of a gloss layer is mixed in a gloss layer in a small amount, and the pigment does not fall off in a super calendar or a slitter.

[0007]

Means for Solving the Problems The present inventors blended a pigment having an average particle size larger than the thickness of the gloss layer into the gloss layer to not only increase the gloss but also prevent sticking and scratching. As a result of intensive studies on a method for preventing the pigment from falling off in the super calender and the slitter in the heat-sensitive recording medium, the present invention was completed.

That is, according to the present invention, a heat-sensitive coloring layer containing, as a main component, a colorless or light-colored electron-donating leuco dye, an organic acid substance capable of developing the leuco dye by heating, and an adhesive is provided on at least one surface of the support. After providing an intermediate layer containing a water-soluble resin and / or a water-dispersible resin, a pigment and a crosslinking agent as main components on the thermosensitive coloring layer, a water-soluble resin and / or a water-dispersible resin is further provided on the intermediate layer. In a thermosensitive recording medium provided with a gloss layer containing a resin and a lubricant as main components, a pigment having an average particle diameter larger than the total thickness of the intermediate layer and the gloss layer and not more than 3 times is mixed in the intermediate layer. To prevent the pigment from falling off in the super calendar and the slitter.

When the average particle size of the pigment is larger than the thickness of the intermediate layer, the pigment easily falls off when a lateral force is applied to the surface of the coating film, but the adhesive strength is obtained by coating a glossy layer thereon. Is increased, and even if subjected to a super calendering treatment after coating the glossy layer or subjected to a strong force such as a slitting treatment, the falling off of the pigment is eliminated. In addition, since the smoothness of the glossy layer is reduced, the problem of sticks and scratches is also improved.
It is difficult to measure the thickness of the intermediate layer and the glossy layer accurately, but for convenience, the specific gravity of the coating film is set to 1.0, and the coating amount (g / m ² ) is directly changed to the film thickness (μm). May be calculated as equal to

The support used in the present invention is prepared by heating and kneading a polyolefin resin and a white inorganic pigment, extruding from a die, and stretching in the machine direction. ~ 2
Laminated layers, synthetic paper produced by stretching in the horizontal direction, and thermoplastic resins such as polyolefin resins and polyester resins alone or in a mixture extruded from a die and biaxially stretched. In addition to the one obtained by heating and kneading the pigment and extruding it from a die and biaxially stretching, those manufactured 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, it is desirable that the support made of pulp fibers be provided with a coating layer in advance and then coated with a heat-sensitive layer.

The thermosensitive coloring layer of the present invention contains a colorless or light-colored electron-donating leuco dye, an organic acid substance capable of coloring the leuco dye upon heating and an adhesive as main components. It may contain heat-fusible substances, auxiliary additives such as dispersants, defoamers, fluorescent dyes and the like.

The heat-sensitive coloring layer of the present invention is coated on at least one surface of the support by an air knife method, a Meyer bar method, a blade method, a reverse roll method, a slit die method, etc., which have been used by those skilled in the art. formed by coating amount after drying 2~12g / m ^2, desirably it applied so as to 4~10g / m ^2. Further, the surface of the heat-sensitive coloring layer is subjected to a smoothing treatment using a super calender, a gloss calender, a machine calender, or the like, so that the coatability of the intermediate layer can be improved and an intermediate layer having a uniform thickness can be formed.

The color-forming dye used in the present invention includes a colorless or pale-color electron-donating leuco dye capable of forming a color by reacting with a developer under heating. For example, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamido] phenyl} propane,
-Diethylamino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexylamino)
-6-methyl-7-anilinofluoran, 3-diethylamino-7-chloroanilinofluoran, 3- [N-ethyl-N- (p-methylphenyl) amino] -6-methyl-7-anilino Fluoran, 3-diethylamino-7
-(Metatrifluoromethyl) anilinofluoran, 3
-(N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isopentyl) amino-6-methyl-7-anilinofluoran, 3 -(N, N-dibutyl) amino-
It is composed of at least one member of a fluoran dye such as 6-methyl-7-anilinofluoran.

The developer used in the present invention comprises an electron-accepting organic acidic substance capable of reacting with a color-forming dye under heating to form a color. Such a developer liquefies or vaporizes at room temperature or higher, preferably 70 ° C. or higher, and reacts with the above-described coloring dye to form a color. Developers usually have the highest color density,
It is mixed and used at a ratio of 1 to 5 parts by weight, preferably 1.5 to 3 parts by weight with respect to 1 part by weight of the coloring dye.

Examples of the color developer include 4,4'-isopropylidene diphenol (bisphenol A) and 4,4'-
Isopropylidenebis (2-chlorophenol), 4,
4′-isopropylidenebis (2-methylphenol), 4,4′-isopropylidenebis (2,6-t-
Butylphenol), 4,4'-sec-butylidenediphenol, 4,4'-cyclohexylidenediphenol, 4-t-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 3,3'-dihydroxydiphenylsulfone, 3,3'-diamino-4,4'-dihydroxy-diphenylsulfone, 3,3'-diallyl-4,
4'-dihydroxydiphenylsulfone, 3,3'-dichloro-4,4'-dihydroxydiphenylsulfone,
4-hydroxydiphenylsulfone, 4-hydroxy-
4′-isopropyloxydiphenylsulfone, 4-hydroxy-4′-isopropyloxydiphenylsulfone, 4-hydroxy-4′-benzyloxydiphenylsulfone, 2,4-dihydroxydiphenylsulfone,
It is composed of at least one member selected from 2,4-dihydroxy-4'-methyldiphenylsulfone, 3,4-dihydroxyphenyl-p-trisulfone and the like.

In the present invention, the adhesive contained in the thermosensitive coloring layer may be any of a water-soluble resin and a water-dispersible resin. For example, polyvinyl alcohol, starch, modified starch, gum arabic, gelatin, casein, chitosan,
Methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, polyvinylpyrrolidone, polyacrylate, polyacrylamide, polyester resin, styrene-acrylate copolymer resin, styrene-maleic anhydride copolymer resin, methylvinyl ether-maleic anhydride copolymer resin Water-soluble resins such as isopropylene-maleic anhydride copolymer resin, vinyl acetate emulsion, acrylate copolymer emulsion, methacrylate copolymer emulsion, vinyl acetate- (meth) acrylate copolymer emulsion, polyurethane emulsion , Polyvinyl chloride emulsion, polyvinylidene chloride emulsion, SBR latex, MBR latex, etc. The good water-dispersible resin alone or in combination may be used.

However, it is necessary that the mixture does not develop color, agglomerate, or become highly viscous when mixed with the dispersion of the color-forming dye and the developer.
In addition, it is necessary that the formed heat-sensitive recording layer film is tough and has no desensitizing effect. The amount of the adhesive in the thermosensitive coloring layer is preferably 8 to 20% based on the solid content of the thermosensitive coloring layer.
If it exceeds 0%, there is a problem that the sensitivity decreases.

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 polyaldehyde, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins,
Melamine resins, diglycidyl compounds such as glycerin diglycidyl ether, dimethylol urea compounds, aziridine compounds, blocked isocyanate compounds, and ammonium persulfate, ferric chloride, and magnesium chloride, sodium tetraborate, potassium tetraborate, and the like. Inorganic compounds or boric acid, boric acid triesters, and boron-based polymers can be used in the range of 1% to 10% based on the solid content of the thermosensitive coloring layer.

Examples of white pigments that can be used in the heat-sensitive layer of the present invention include calcium carbonate, magnesium carbonate, magnesium oxide, kaolin, clay, talc, calcined clay,
Silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate,
Surface-treated inorganic pigments such as calcium carbonate and silica, and organic pigments such as urea resin, styrene-methacrylic acid copolymer, and polystyrene resin with an average particle size of 5 μm
The following fine particle pigments can be used. Further, in order to improve the wetting of the heat-sensitive layer paint and eliminate repelling, a wetting property improver such as acetylene glycol or dialkyl sulfosuccinate may be added.

Examples of the heat-fusible substance include stearamide, stearic acid ethylenebisamide, oleamide, palmitamide, coconut fatty acid amide, and the like.
Fatty acid amides such as behenic acid amide, zinc stearate, calcium stearate, polyethylene wax,
Waxes such as carnauba wax, paraffin wax and ester wax, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, dimethyl terephthalate, dibutyl terephthalate, dibenzyl terephthalate, 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'-butylidenebis (6-t-butyl-3-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butyl) Phenyl) butane, 2,2′-methylenebis (4-ethyl-6-t-butylphenol),
2,4-di-t-butyl-3-methylphenol, 4,
Hindered phenols such as 4′-thiobis (3-methyl-6-t-butylphenol), 2- (2′-hydroxy-5′-methylphenyl) -benzotriazole,
And sensitizers such as 2-hydroxy-4-benzyloxybenzophenone, antioxidants, and ultraviolet absorbers.
In general, the heat-fusible substance is preferably contained in the thermosensitive coloring layer at a ratio of 4 parts by weight or less to 1 part by weight of the developer.

The intermediate layer provided on the thermosensitive coloring layer of the present invention comprises:
There is a problem that the required glossiness cannot be obtained even when the glossy layer is directly coated on the thermosensitive coloring layer, that the thermosensitive coloring layer is colored by the influence of the glossy layer chemical, and that the colored portion is erased. In order to prevent an increase in smoothness after coating the gloss layer, a pigment having an average particle size larger than the total thickness of the intermediate layer and the gloss layer and not more than 3 times is compounded. Is what you do.

The water-soluble and / or water-dispersible resin used for the intermediate layer has poor crystallinity, good film-forming properties, strong binding power, and, after drying, can form a colorless and transparent continuous film. desirable. Such a resin can be appropriately selected and used from resins used for the thermosensitive coloring layer. The amount of the resin is preferably 40 to 90% based on the solid content of the intermediate layer. The crosslinking agent used for the intermediate layer can be appropriately selected from the crosslinking agents used for the thermosensitive coloring layer and used. The amount of the crosslinking agent is preferably 1 to 20% based on the solid content of the intermediate layer.

The pigment used in the intermediate layer has an average particle size larger than the total film thickness of the intermediate layer and the glossy layer and is three times or less. An extender pigment having high oil absorbency and an average particle diameter smaller than the thickness of the intermediate layer can be used. The average particle size of the pigment of the present invention needs to be larger than the total film thickness of the intermediate layer and the glossy layer, but if it exceeds three times, the smoothness of the glossy layer is greatly reduced and the uniformity of the image is reduced. There is. Usually, the total film thickness of the intermediate layer and the glossy layer is 1 to 6 μm, so the average particle size of the pigment of the present invention incorporated in the intermediate layer needs to be larger than 1 μm and 18 μm or less.

Such a pigment is an inorganic pigment or an organic pigment, and can be appropriately selected from pigments used in the heat-sensitive coloring layer. Examples of the pigment include calcium carbonate, magnesium carbonate, magnesium oxide, kaolin, clay, and talc. ,
Of inorganic pigments such as calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica, only primary particles with a large particle size Instead, a secondary particle having a larger particle diameter can be used. Further, organic pigments such as urea resin powder, styrene-methacrylic acid copolymer powder, polystyrene resin powder, benzoguanamine resin powder, and silicon resin powder, which have a mean particle size of more than 1 μm and 18 μm or less can be used.

The extender pigment having a large oil absorbing property is used in the heat-sensitive coloring layer, and fine particles having an average particle diameter of 1 μm or less can be used.

The intermediate layer has a coating amount after drying on the thermosensitive coloring layer of 0.5 to 5.5 g / m ² , preferably 1.0 to 5.0 g / m ² .
g / m ² . The coating method can be appropriately selected and used from the methods used for the heat-sensitive coloring layer. If the coating amount of the intermediate layer is less than 0.5 g / m ² , the coating film is not formed uniformly, so that the coating material of the gloss layer to be applied thereon penetrates and the gloss developability is reduced. When the coating amount exceeds 5.5 g / m ² , the glossiness is improved, but the sensitivity is lowered and the recording density is disadvantageously lowered.

Among the pigments to be mixed in the intermediate layer, the mixing ratio of the pigment having an average particle diameter of more than 1 times and not more than 3 times the thickness of the intermediate layer and the glossy layer is 0.1 to 10 with respect to the solid content of the intermediate layer. % Is good. If it is less than 0.1%, it is difficult to control the smoothness, and if it exceeds 10%, there is a problem that the gloss is reduced. The pigment of the intermediate layer including the extender pigment is preferably 0.1 to 50% with respect to the solid content of the intermediate layer, and if it exceeds 50%, there is a disadvantage that the gloss developing property is reduced and the recording density is reduced.

The gloss layer provided on the intermediate layer contains a water-soluble resin and / or a water-dispersible resin and a lubricant as main components and, if necessary, a crosslinking agent, and enhances gloss after recording. At the same time, the running property of sticks, scum, etc. is improved. Water-soluble resin used for the gloss layer and / or
Or in addition to the water-dispersible resin used for the thermosensitive coloring layer,
It is possible to select and use a resin having good slipperiness such as a silicone-acrylic copolymer resin or a silicone resin, which increases the glossiness after recording. The amount of the resin is preferably 50 to 90% based on the solid content of the glossy layer.

[0029] Lubricants used in the glossy layer include arylalkyl phosphates such as lauryl phosphate, oleyl phosphate and stearyl phosphate and alkali metal salts thereof, lauryl sulfonate, oleyl sulfonate and stearyl sulfonate. Glyceryl fatty acid esters such as alkyl sulfonates and alkali metal salts thereof, glyceryl monomyristate, glyceryl monostearate, glyceryl monooleate, glyceryl distearate, glyceryl dioleate, diglyceryl monolaurate, diglyceryl dilaurate , Tetraglyceryl monolaurate,
Examples include polyglycerin fatty acid esters such as hexaglyceryl monolaurate and decaglyceryl monolaurate.

The amount of the lubricant used in the gloss layer is preferably 5 to 40% with respect to the solid content of the gloss layer. If it is less than 5%, the stick is not effective, and if it exceeds 40%, the strength of the gloss layer decreases, It is a problem. The crosslinking agent used in the glossy layer, if necessary, can be selected from those used in the thermosensitive coloring layer. The amount of the crosslinking agent is preferably 1 to 40% based on the solid content of the glossy layer.

When the coating amount of the glossy layer is less than 0.5 g / m ² , the coating film is not formed uniformly, so that the glossiness does not increase and the stick deteriorates. Coating amount is 5.0 g / m
^{When the} ratio exceeds ² , glossiness and stick are improved, but sensitivity and recording density are disadvantageously reduced. The method for coating the gloss layer can be selected from those used for coating the thermosensitive coloring layer and used.

After coating the glossy layer, a backing layer is coated as necessary from the viewpoint of curling prevention and antistatic, and further, a smoothing process is performed by a super calender, gloss calender, machine calender, etc. Can be improved, and the glossiness can be increased.

[0033]

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, “parts” indicates “parts by weight”. Example 1 On one surface of synthetic paper YUPO FPG-80, a thermosensitive coloring layer paint shown below was applied so that the coated amount after drying was 6.5 g / m ^2, and further an intermediate layer paint and The coating amount after drying the glossy layer paint is 1.0 g / m ² and 1.0 g / m ² , respectively.
Coating was performed in order to obtain ² .

Preparation of paint for heat-sensitive coloring layer A liquid (thermosensitive dye dispersion) 3- (N, N-dibutyl) amino-6-methyl-7-anilinofluoran 20 parts 10% aqueous polyvinyl alcohol solution 20 Part water 10 parts liquid B (developer dispersion liquid) 4-hydroxy-4'-isopropyloxydiphenylsulfone 50 parts 10% aqueous polyvinyl alcohol solution 50 parts water 25 parts liquid A and liquid B are separately dispersed with an Ultraviscomil. And pulverized to adjust the average particle diameter to 1 μm or less. Solution A 38 parts, Solution B 75 parts, 60% calcium carbonate slurry 50 parts, 10% polyvinyl alcohol (Gohsenol NM-11, manufactured by Nippon Synthetic Chemical Co., Ltd.) aqueous solution 60
Parts, SBR latex (PT-1004, solid content 43
%, Manufactured by ZEON CORPORATION), 17 parts of a 30% zinc stearate dispersion, and 60 parts of water were mixed to prepare a thermosensitive coloring layer paint.

Intermediate layer paint 60% kaolinite clay (average particle size 0.6 μm) dispersion liquid 33 parts Carboxy-modified polyvinyl alcohol (Gosenal T-330, manufactured by Nippon Synthetic Chemical Co., Ltd.) aqueous solution (solid content 10%) 310 Part Acrylic emulsion (SC-1225, solid content 40%, manufactured by Nippon Shokubai Co., Ltd.) 88 parts Dimethylol urea solution (solid content 30%) 33 parts 30% benzoguanamine resin powder dispersion (Eposter M-30, average particle size 3) 0.03 μm, manufactured by Nippon Shokubai Co., Ltd.) 13 parts of water and 523 parts of water were mixed to prepare an intermediate layer paint.

Gloss layer paint Polysiloxane graft acrylic emulsion (GF-256, manufactured by Nippon Shokubai Co., Ltd., solid content: 20%) 375 parts Alkyl phosphate potassium salt (TRL-20, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) 40 parts of water and 245 parts of water were mixed to obtain a glossy layer paint. Further, a coating material for the back layer was applied on the opposite surface such that the coating amount after drying was 1.5 g / m ² . A smoothing treatment was performed with a super calender to obtain a heat-sensitive recording material having a gloss layer of Oken type smoothness (J. TAPPI No. 6) of 7,000 seconds.

Back layer paint Polystyrene sodium sulfonate (Chemistat SA-9, manufactured by Sanyo Chemical Co., Ltd., solid content: 33%) 30 parts SBR latex (0528, manufactured by Nippon Synthetic Rubber Co., solid content: 50%) 70 Part 10% oxidized starch aqueous solution (Ace A, manufactured by Oji Cornstarch Co., Ltd.) 150 parts 60% Kaolinite clay slurry (Hydrogross 90, manufactured by Huber) 67 parts Water 83 parts were mixed to prepare a back layer paint.

Examples 2 to 4 In the same manner as in Example 1 except that the following intermediate layer was used instead of the intermediate layer used in Example 1, a thermosensitive recording medium was obtained.

Example 2 Intermediate layer paint 20% colloidal silica dispersion (Snowtex C, average particle size 0.01 μm, manufactured by Nissan Chemical Industries, Ltd.) 150 parts Carboxy-modified polyvinyl alcohol aqueous solution (Gothenal T-350, solid) 10%, manufactured by Nippon Synthetic Chemical Co., Ltd.) 190 parts Urethane-modified acrylic emulsion (Boncoat 3986, solid content: 40%, manufactured by Dainippon Ink and Chemicals, Inc.) 100 parts Dimethylol urea solution (solid content: 30%) 27 parts 30 % Of magnesium oxide powder dispersion (HP-10, average particle size 5.0 μm, manufactured by Kamishima Chemical Industry Co., Ltd.) 10 parts and water 524 parts were mixed to prepare an intermediate layer paint.

Example 3 Intermediate layer paint 20% colloidal silica dispersion (Snowtex C, average particle size 0.01 μm, manufactured by Nissan Chemical Industries, Ltd.) 150 parts acetoacetylated polyvinyl alcohol aqueous solution (Z-100, solid 10%, manufactured by Nippon Synthetic Chemical Co., Ltd.) 200 parts SBR latex (solid content 50%) 54 parts Glyoxal solution (solid content 40%) 50 parts 30% silicone resin powder dispersion (Tospearl 145, average particle size 4. 5 μm, manufactured by Toshiba Silicone Co., Ltd. (10 parts), water (536 parts) were mixed to prepare an intermediate layer paint.

Example 4 Intermediate layer paint 20% colloidal silica dispersion (Snowtex C, average particle size 0.01 μm, manufactured by Nissan Chemical Co., Ltd.) 150 parts Polyvinyl alcohol (Gohsenol NM-11, Nippon Synthetic Chemical Co., Ltd.) )) Aqueous solution (solid content 10%) 120 parts Urethane emulsion (AP-30, solid content 20%, manufactured by Dainippon Ink & Chemicals, Inc.) 200 parts Boron polymer (Hiboron DDGB-90, solid content 90%, boron international) 11 parts 50% marimo-like calcium carbonate dispersion (Callite SA, average particle size 3.5 μm, manufactured by Shiraishi Calcium Co., Ltd.) 16 parts Water 503 parts were mixed to prepare an intermediate layer paint.

Example 5 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following coating materials were applied as the intermediate layer and the glossy layer, respectively, at 2.5 g / m ² and 1.5 g / m ^2. It was created.・ Intermediate layer paint 60% Kaolinite clay (average particle size: 0.6 μm) Dispersion: 33 parts Polyvinyl alcohol aqueous solution (PVA-117, solid content: 10%, manufactured by Kuraray Co., Ltd.) 300 parts Acrylic emulsion (HONRON S-480, Solid content 47%, manufactured by Mitsui Toatsu Chemical Co., Ltd. 95 parts Dimethylol urea solution (solid content 30%) 33 parts 20% amorphous silica powder dispersion (Syloid 74, average particle diameter 7 μm, Fuji Devison Chemical Co., Ltd.) 10 parts of water and 529 parts of water were mixed to obtain an intermediate layer paint.

Glossy layer paint Acrylic silicon modified resin emulsion (Siren ARJ-2A, solid content 44%, manufactured by Nippon Pure Chemical Co., Ltd.) 191 parts Nonionic surfactant (Fcol 214, solid content 40% Matsumoto Yushi Pharmaceutical Co., Ltd.) Co., Ltd.) 40 parts Aziridine compound (crosslinking agent) 3 parts Water 766 parts were mixed to obtain a gloss layer paint.

Examples 6 and 7 A thermosensitive recording medium was prepared in the same manner as in Example 5, except that the following coating material was applied as the intermediate layer coating material. Example 6 Intermediate layer paint 70% calcium carbonate (average particle size 0.8 μm) dispersion 14 parts Polyvinyl alcohol (Gohsenol NL-05, manufactured by Nippon Synthetic Chemical Co., Ltd.) aqueous solution (solid content 10%) 300 parts Silica composite Styrene-acryl emulsion (LX-612, solid content 40%, manufactured by Hoechst Synthesis Co., Ltd.) 95 parts Boron polymer (Hiboron DDGB-90, solid content 90%, manufactured by Boron International Co., Ltd.) 33 parts Urea resin powder (Eupal) C-120, an average particle diameter of 10 μm, a solid content of 20%, and 10 parts of water (manufactured by Mitsui Toatsu Chemicals, Inc.) and 529 parts of water were mixed to prepare an intermediate layer paint.

Example 7 Intermediate layer paint 60% Kaolinite clay (average particle size: 0.6 μm) 33 parts dispersion liquid Modified polyvinyl alcohol (Gosenal T-330, manufactured by Nippon Synthetic Chemical Co., Ltd.) aqueous solution (solid content: 10%) ) 370 parts Acrylic emulsion (Aron NS-1200, solid content 40%, manufactured by Toa Gosei Chemical Industry Co., Ltd.) 75 parts Glyoxal solution (solid content 40%) 25 parts 30% magnesium oxide powder dispersion (HP-10, average) A particle size of 5.0 μm, 10 parts of water and 487 parts of water (manufactured by Kamishima Chemical Industry Co., Ltd.) were mixed to prepare an intermediate layer paint.

Comparative Example 1 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that an intermediate layer paint containing no pigment having an average particle diameter larger than the thickness of the intermediate layer was used.・ Intermediate layer paint 60% Kaolinite clay (average particle size 0.6 μm) Dispersion liquid 33 parts Carboxy-modified polyvinyl alcohol (Gosenal T-330, manufactured by Nippon Synthetic Chemical Co., Ltd.) aqueous solution (solid content 10%) 350 parts Acrylic emulsion (SC-1225, solid content 40%, manufactured by Nippon Shokubai) 88 parts Dimethylol urea solution (solid content 30%) 33 parts Water 496 parts were mixed to prepare an intermediate layer paint.

Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Comparative Example 1, except that a glossy layer paint containing a pigment having an average particle diameter larger than the thickness of the glossy layer was applied. Gloss layer paint Polysiloxane graft acrylic emulsion (GF-256, Nippon Shokubai Co., Ltd., solid content 20%) 380 parts Alkyl phosphate potassium salt (TRL-20, Matsumoto Yushi Pharmaceutical Co., Ltd., solid content 50%) 40 parts 30% benzoguanamine resin powder dispersion (Eposter M-30, average particle size 3.0 μm, manufactured by Nippon Shokubai Co., Ltd.) 13 parts Water 567 parts were mixed to obtain a gloss layer paint.

When the heat-sensitive recording materials obtained in Examples 1 to 7 and Comparative Examples 1 and 2 were slit, the pigments fell off when slitting, and gradation recording was performed using a commercially available heat-sensitive printer (UP-850, manufactured by Sony). Then, the reflection density of the highest density portion, the stick sound at the time of recording, and the scratch on the surface were evaluated. The results are as shown in Table 1. In Examples 1 to 7, there was no loss of pigment in the slitter, no stick sound, high recording density, and high-contrast recording were obtained. In Example 1, a stick sound was heard during recording, and not only the recording length was short, but also many scratches occurred. In Comparative Example 2, the pigment was dropped off by the slitter, and the stick was insufficient.

[0049]

[Table 1]

Gloss: Measured according to JIS P8142. Pigment detachment: Evaluation of dirt on the paper roll of the slitter ：: No dirt. X: There is dirt. Recording density: Measured with a Mcbeth RD-914 densitometer. Stick: The loudness of the sound during recording was evaluated. ：: There is almost no sound. Δ: There is a small sound. Scratch: Visual evaluation of solid recording area ○: No scratch X: There are many scratches.

[0051]

According to the present invention, when producing a heat-sensitive recording material, there is no dropout of pigment by a super calender or a slitter, and when recording by a heat-sensitive printer, sticks and scratches are not generated, the image density is high, and the contrast is high. High recording can be obtained.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Murai 1-10-6 Shinonome, Koto-ku, Tokyo Oji Paper Co., Ltd. Product Research Institute (56) References JP-A-1-178486 (JP, A) Hei 4-5079 (JP, A)

Claims (1)

(57) [Claims] 1. A thermosensitive coloring layer comprising at least one surface of a support as a main component containing a colorless or pale-colored electron-donating leuco dye, an organic acid substance capable of developing the leuco dye by heating and an adhesive. After providing an intermediate layer containing a water-soluble resin and / or a water-dispersible resin, a pigment and a cross-linking agent as main components on the color-forming layer, a water-soluble resin and / or a water-dispersible resin, and a lubricant are further provided on the intermediate layer. In a thermosensitive recording medium provided with a gloss layer containing as a main component, a pigment having an average particle diameter larger than the total thickness of the intermediate layer and the gloss layer and not more than 3 times is blended in the intermediate layer. Thermosensitive recording medium.