JPH11157210A - Thermal recording medium - Google Patents

Abstract

(57) [Problem] To provide a thermosensitive recording medium having excellent transparency in an unrecorded portion and also having excellent sticking resistance. A heat-sensitive recording layer containing an electron donating compound and an electron accepting compound, an intermediate layer mainly containing an adhesive, and a top layer mainly containing a pigment and an adhesive are formed on a transparent support. As one means for solving the above-mentioned problems in the sequentially provided thermal recording medium, the present invention provides a solid coating amount of the uppermost layer of 0.1 to 1.0 g / m ² , The pigment is contained in an amount of 55 to 90% by weight based on the total solid content of the ink, and the haze value of the heat-sensitive recording material is 45% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color-forming reaction between an electron-donating compound and an electron-accepting compound, and more particularly to a heat-sensitive recording material having excellent transparency in an unrecorded portion and excellent recording running properties. It is.

[0002]

2. Description of the Related Art A thermosensitive recording medium utilizing a color development reaction between an electron-donating compound and an electron-accepting compound is inexpensive itself, and a recording apparatus for recording thereon is compact and inexpensive. And easy to maintain,
It is widely used not only as a recording medium for facsimile machines, automatic ticket vending machines, and scientific measuring machines, but also as an output medium for various printers and plotters such as POS labels, CAD, and CRT medical images.

Recently, a multi-layered structure has been used as a support for a thermal image recording medium for a CRT plotter which requires uniformity of recorded images and high resolution and a dimensional stability and a CAD plotter which requires fine line recording. Synthetic paper, and a biaxially stretched thermoplastic resin film as necessary.

Japanese Patent Application Laid-Open No. 4-325287 discloses a heat-sensitive recording medium in which a heat-sensitive recording layer, an intermediate layer and an uppermost layer containing a pigment and an adhesive are provided on a transparent support.
There is a demand for one having more excellent recording running properties and transparency of unrecorded portions.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording medium which is excellent in transparency of an unrecorded portion and also has excellent sticking resistance.

[0006]

Means for Solving the Problems On a transparent support, a heat-sensitive recording layer containing an electron donating compound and an electron accepting compound, an intermediate layer containing an adhesive as a main component, and a pigment and an adhesive as a main component As one means for solving the above-mentioned problems, in the thermosensitive recording medium having the uppermost layer sequentially provided, the present invention provides a solid coating amount of the uppermost layer of 0.1 to 1.0 g / m ^2.
And the pigment in the uppermost layer is 55% of the total solid content of the uppermost layer.
-90% by weight and the haze value of the heat-sensitive recording medium is 4
5% or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a heat-sensitive recording layer containing an electron-donating compound and an electron-accepting compound, an intermediate layer mainly containing an adhesive, and a pigment and an adhesive on a transparent support. In a thermosensitive recording medium in which the uppermost layer as a main component is sequentially provided, the coating amount of the uppermost layer is 0.1 to 1.0 g / m ² ,
The pigment in the top layer is 55 to 90 based on the total solids of the top layer.
% By weight, and the haze value of the heat-sensitive recording medium is 45% or less, and the solid coating amount of the uppermost layer is 0.1 g.
/ M ² and the amount of pigment in the uppermost layer is less than 55% by weight, sticking may occur during recording.

If the solid coating amount of the uppermost layer exceeds 1.0 g / m ² , or if the amount of the pigment in the uppermost layer exceeds 90% by weight, the recorded image may be whitened, and the haze value of the heat-sensitive recording medium may decrease. If it exceeds 45%, the recorded image observed by Schaucusten may become unclear, and the amount of the pigment in the uppermost layer is more preferably about 70 to 80% by weight.

Thermal recording methods applied to a thermal recording layer containing an electron donating compound and an electron accepting compound include, for example, a combination of a leuco dye and a color former, a combination of a diazonium salt and a coupler, iron, cobalt, and the like. ,nickel,
A combination of a transition metal such as copper with a chelate compound, a combination of an aromatic isocyanate compound and an imino compound, and the like can be mentioned, but a combination of a leuco dye and a color former is preferably used because of its excellent color density. Hereinafter, the thermosensitive recording medium in which the thermosensitive recording layer is composed of a combination of a leuco dye and a color former will be described in more detail.

As the leuco dye and the color former contained in the heat-sensitive recording layer, various known ones can be used. Specific examples of koiko dyes include the following. 3,3-bis (p-dimethylaminophenyl) -6
Blue-coloring dyes such as -dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide; 3- (N-ethyl-N -P-tolyl) amino-7-
N-methylanilinofluoran, 3-diethylamino-
Green-coloring dyes such as 7-anilinofluoran; 3-diethylamino-7-methylfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-chlorofluoran, 3- ( N-ethyl-p-
Red-forming dyes such as toluidino) -7-methylfluoran; 3- (N-ethyl-N-isoamyl) amino-6
Methyl-7-anilinofluoran, 3- (N-methyl-
N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7-
Anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n
-Amyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (o-chloroanilino)
Fluoran, 3-di (n-butyl) amino-7- (o-
Chloroanilino) fluoran, 3-diethylamino-7
-(O-fluoroanilino) fluoran, 3-di (n-
(Butyl) amino-7- (o-fluoroanilino) fluoran, 3-diethylamino-7- (m-trifluoromethylanilino) fluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7- Anilino fluoran, 3
-(N-ethyl-p-toluidino) -6-methyl-7-
(P-toluidino) fluoran, 3-diethylamino-
6-chloro-7-anilinofluoran, 3-di (n-butyl) amino-6-methyl-7-m-toluidinofluoran, 3-piperidino-6-methyl-7-anilinofluoran and the like And the like. Of course, the present invention is not limited to these, and two or more of them can be used as needed. The amount of the leuco dye used is not particularly limited, but is about 5 to 40% by weight based on the heat-sensitive recording layer.

Specific examples of the coloring agent include, for example, hydroquinone monobenzyl ether, 4,4'-isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, and 4,4'-dihydroxydiphenyl-2. , 2-butane, 4,4'-dihydroxydiphenylmethane, 2,2-bis (4-hydroxyphenyl)-
4-methylpentane, 2,2-bis (hydroxyphenyl) heptane, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4 ′
-Hydroxyphenyl) ethyl] benzene, 4,4'-
Dihydroxydiphenyl sulfide, di (4-hydroxy-3-methylphenyl) sulfine, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy- 4'-isopropoxydiphenyl sulfone, 4-hydroxyphenyl-
4'-benzyloxydiphenylsulfone, 4-hydroxy-3 ', 4'-tetramethylenebiphenylsulfone, 3,4-dihydroxyphenyl-p-tolylsulfone, benzyl 4-hydroxy-benzoate, N, N-di-
m-chlorophenylthiourea, zinc 4- [2- (p-methoxyphenoxy) ethyloxy] salicylate,
[3- (p-Tolylsulfonyl) propyloxy] zinc salicylate, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] zinc salicylate, 4,4'-bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane , Np-tolylsulfonyl-N'-phenylurea and the like.

The proportion of the leuco dye to the color former is not particularly limited, but is 1 to 8 parts by weight, preferably about 2 to 5 parts by weight, per 1 part by weight of the leuco dye.

Further, the heat-sensitive recording layer may contain a sensitizer for increasing the recording sensitivity and a storability improving agent for further improving the aging stability of the recording portion. Specific examples of such a sensitizer include, for example, stearic acid amide,
Ethylene bisamide stearate, 2-naphthyl benzyl ether, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, dibenzyl terephthalate, dibenzyl terephthalate, 1- Hydroxynaphthoic acid phenyl ester, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, p-acetotoluizide, p-acetophenethene Zide, N-acetoacetyl-p-toluidine, p-benzylbiphenyl and the like.

Specific examples of the preservability improver include, for example, 2,2'-methylenebis (4-methyl-6-tert-
Butylphenol), 2,2′-ethylenebis (4-methyl-6-tert-butylphenol), 2,2′-ethylidenebis (4,6-di-tert-butylphenol),
2,2′-ethylidenebis (4-methyl-6-tert-butylphenol), 2,2′-ethylidenebis (4-ethyl-6-tert-butylphenol), 1- [α-methyl-α- (4 ′ -Hydroxyphenyl) ethyl] -4-
[Α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-methyl-4-
(Hydroxy-5-cyclohexylphenyl) butane,
1,1,3-tris (2-methyl-4-hydroxy-5
-Tert-butylphenyl) butane, N, N'-di-2-
Naphthyl-p-phenylenediamine, sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, 4-benzyloxy-4 '-(2-methyl-2,
3-epoxypropyloxy) diphenyl sulfone, novolak type resin and the like.

These sensitizers and storability improvers are usually used in an amount of about 0.1 to 4 parts by weight based on 1 part by weight of the leuco dye.

The heat-sensitive recording layer is formed by using water or an organic solvent as a dispersion medium, stirring with a ball mill, an attritor, a sand mill or the like, and using a pulverizer, a leuco dye, a colorant, and, if necessary, a sensitizer and a storage improver. And separately or together with a dispersing agent and finely dispersing them so that the average particle size becomes about 0.05 to 2 μm, and then adding an adhesive and mixing and stirring to prepare a coating solution for a heat-sensitive recording layer which is transparent. It is formed by coating and drying on a suitable support. The coating amount of the heat-sensitive recording layer coating liquid is 2 by dry weight.
-20 g / m ² , preferably about 4-15 g / m ² . In particular, the average particle size of the leuco dye is 0.05 to
About 0.5 μm is preferable because the recording sensitivity is excellent and the haze value of the thermosensitive recording medium is reduced.

As the adhesive used for the heat-sensitive recording layer,
For example, starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, completely (partially) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-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, styrene / butadiene resin, acrylic resin, urethane resin, vinyl acetate Resins. The amount of the adhesive used is about 10 to 45% by weight based on the total solid content of the heat-sensitive recording layer.

Further, pigments such as calcium carbonate, zinc oxide, aluminum oxide, amorphous silica, calcined kaolin, aluminum hydroxide, barium sulfate, talc, kaolin, and urea / formalin resin filler are contained in the coating solution for the heat-sensitive recording layer. Lubricants such as calcium stearate and zinc stearate, surfactants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate and sodium lauryl alcohol sulfate, and auxiliaries such as coloring dyes, fluorescent dyes, and waterproofing agents However, the amount of the pigment added may be 2 to the heat-sensitive recording layer.
0% by weight or less is desirable. If it exceeds 20% by weight, the desired haze value may be exceeded.

The transparent support on which the heat-sensitive recording layer is formed is not particularly limited as long as it has a haze value of 10 or less. For example, a polycarbonate film having a thickness of about 20 to 200 μm, a polystyrene film, a polypropylene film, Examples include a polyethylene terephthalate film. Of course, such a film may be subjected to coloring, anchor coating, corona discharge treatment, or the like.

Examples of the method for applying the coating solution for the heat-sensitive recording layer include gravure coating, pure blade coating, rod blade coating, curtain coating, and die coating.

The intermediate layer is made of water or a liquid electron beam or ultraviolet curable compound as a medium. For example, when water is used as a medium, an intermediate layer coating mainly containing an adhesive dissolved or dispersed in water is used. The coating amount of the liquid on the heat-sensitive recording layer after drying is about 0.5 to 7.0 g / m ² , preferably 1.0 to 5.0 g / m ² .
It is formed by coating and drying so as to have a weight of about 0 g / m ² .

When the medium is water, the adhesive contained in the coating solution for the intermediate layer includes, for example, starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, completely (partially) saponified polyvinyl Alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-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 salts, styrene / butadiene latex, acrylic latex, urethane latex, and vinyl acetate latex are exemplified.

When the medium is an electron beam or ultraviolet curable compound, the medium itself is polymerized by application of an electron beam or ultraviolet light after application of the intermediate layer, and becomes an adhesive. As such an electron beam or ultraviolet curable compound,
The following are used for the uppermost layer. The amount of the adhesive used in the intermediate layer is 50% by weight or more based on the intermediate layer.

The above-mentioned auxiliary agent which can be used in the heat-sensitive recording layer can be further added to the coating solution for the intermediate layer, but the amount of the pigment to be added is preferably 20% by weight or less based on the intermediate layer. . If it exceeds 20% by weight, the desired haze value may be exceeded.

After the formation of the heat-sensitive recording layer and the intermediate layer, a smoothing treatment using a super calender is particularly preferable because the recording sensitivity of the heat-sensitive recording material is increased and the haze value is reduced.

The uppermost layer is made of water, an organic solvent, or a liquid ultraviolet or electron beam curable compound as a medium. For example, when water is used as a medium, an adhesive and a pigment dissolved or dispersed in water are used. Are mixed and stirred, and the coating liquid for the uppermost layer obtained by drying is applied onto the intermediate layer and dried so that the coating amount after drying is 0.1 to 1.0 g / m ² .

As the adhesive, the medium of the coating liquid for the uppermost layer is
In the case of water or an organic solvent, the adhesive contained in the heat-sensitive recording layer is used. The content of the adhesive in the uppermost layer is about 5 to 45% by weight, preferably about 8 to 25% by weight based on the uppermost layer.

The liquid ultraviolet ray or electron beam curable compound serving as the medium of the coating liquid for the uppermost layer and the adhesive for the uppermost layer includes, for example, ethylenically unsaturated monocarboxylic acid or polycarboxylic acid. Carboxyl group-containing monomers and salts thereof, amide group-containing monomers such as ethylenically unsaturated (meth) acrylamide or alkyl-substituted (meth) acrylamide, sulfonic acid group-containing monomers such as aliphatic or aromatic vinylsulfonic acid and salts thereof, ethylene Hydroxyl-containing monomers such as unsaturated unsaturated ethers and (meth) acrylate esters of polyhydric alcohols; amino-containing monomers such as dimethylaminoethyl (meth) acrylate-2-vinylpyridine; and diesters of polybasic acids and unsaturated alcohols. Ester group-containing bifunctional monomer, divinylbenzene, divinyl ether Glycol, divinyl sulfone, divinyl ether, bifunctional monomers such as divinyl ketone, an ester group-containing polyfunctional monomers such as polyesters of polycarboxylic acid unsaturated alcohols, and aliphatic,
Poly (meth) acrylates of alicyclic and araliphatic dihydric to hexavalent alcohols and polyalkylene glycols, aliphatic, alicyclic, araliphatic, aromatic divalent to hexavalent polyhydric alcohols and alkylene oxides , Poly (meth) acrylate of polyhydric alcohol, poly (meth) acryloyloxyalkyl phosphate, polyester poly (meth) acrylate, epoxy (meth) acrylate, polyurethane urethane poly (meth) acrylate, polyamide poly (meth) acrylate, There are vinyl or diene oligomers having a (meth) acryloyloxy group at the side chain and / or terminal.

As the pigment used in the uppermost layer, for example, light calcium carbonate, aluminum hydroxide, zinc oxide,
Amorphous silica, benzoguanimine resin filler, urea
Formalin resin filler and the like can be mentioned. The average particle size of the primary particles of the pigment is preferably 1 μm or less, and the lower the refractive index of the pigment, the more preferable. Particularly, amorphous silica and kaolin are preferable.

In the uppermost layer, if necessary, additives such as an antifoaming agent, a lubricant, a surfactant, a plasticizer, and an ultraviolet absorber may be appropriately added.

The method for applying the coating solution for the heat-sensitive recording layer, the coating solution for the intermediate layer and the coating solution for the uppermost layer includes, for example, coating such as gravure coating, bar coating, pure blade coating, rod blade coating, curtain coating and die coating. Method.

When the coating liquid for the uppermost layer contains a liquid ultraviolet ray or an electron beam curable compound, the electron dose to be irradiated after application of the coating liquid for the uppermost layer on the intermediate layer is zero. .5-
A range of 10 Mrad is desirable. If it is less than 0.5 Mrad, the curing is insufficient, and if it exceeds 10 Mrad, there is a risk that the thermosensitive recording medium will develop color or the electron beam curable resin will be discolored. The irradiation acceleration voltage is preferably about 100 to 300 kV. As an electron beam irradiation method, a curtain beam method, a scanning method, a broad beam method, or the like can be used.

When irradiating ultraviolet rays, it is necessary to add a polymerization initiator to the coating liquid for the uppermost layer, and it is added in an amount of about 0.2 to 10% by weight based on the ultraviolet curable compound. Also,
As a light source for ultraviolet curing, 1 to 50 ultraviolet lamps, cekinone lamps, tungsten lamps and the like are used, and ultraviolet rays having an intensity of about 40 to 200 W / cm are irradiated.

Examples of the polymerization initiator include thioxanthone, benzoin, benzoin alkyl ether xanthone, dimethylxanthone, benzophenone, anthracene, 2,2-diethoxyacetophenone, anthraquinone, 1-chloroanthraquinone, 2-ethylanthraquinone, and 2-tert-thraquinone. Butyl anthraquinone and the like.

A back layer may be provided on the back side of the transparent support, if necessary, in order to prevent curling and charging.
A known technique such as providing an adhesive layer may be added.

[0036]

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 Preparation of solution A (thermosensitive coloring dye dispersion) 20 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 10% aqueous solution of sulfone-modified polyvinyl alcohol A composition consisting of 20 parts and 10 parts of water was prepared by using Ultra Viscomil to have an average particle diameter of 0.3 μm.
It grind | pulverized until it became m, and obtained liquid A.

Preparation of Liquid B (Developer Dispersion) 50 parts of 4-hydroxy-4′-isopropoxydiphenylsulfone, 1 part of sulfone-modified polyvinyl alcohol
A composition comprising 50 parts of a 0% aqueous solution and 25 parts of water was pulverized using an Ultra Visco mill until the average particle diameter became 0.3 μm, to obtain a liquid B.

Preparation of Coating Solution for Thermosensitive Recording Layer 40 parts of solution A, 60 parts of solution B, polyvinyl alcohol (PV
A117, 60 parts of a 10% aqueous solution of Kuraray Co., Ltd., styrene-butadiene latex (L-1537, solid content
48 parts of 50%, manufactured by Asahi Kasei Corporation, stearic acid amide dispersion (Himicron G-270, melting point 100 ° C., solid content 2)
A composition composed of 30 parts (1%, manufactured by Chukyo Yushi Co., Ltd.) and 58 parts of water was mixed and stirred to obtain a coating liquid for a heat-sensitive recording layer.

Preparation of Coating Solution for Intermediate Layer Carboxy-modified polyvinyl alcohol (Gohsenal T
-330, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
0 parts, zinc stearate dispersion (hydrin Z-7-3)
0, 11.5 parts of solid content, 1 part of Chukyo Yushi Co., Ltd., 1 part of glyoxal (40% of solid content, manufactured by Nippon Synthetic Chemical Company), and 60 parts of water. A liquid was obtained.

Preparation of Coating Liquid for Top Layer 120 parts of a 60% dispersion of kaolin (UW-90, average particle size 0.5 μm, manufactured by EC Company), an acrylic resin (OLY-
1493, 45 parts of a 51% aqueous solution of Showa Polymer Co., Ltd., and a 32% dispersion of zinc stearate (Hydrin Z-7-3)
(0, manufactured by Chukyo Yushi Co., Ltd.), 10 parts of a 30% dispersion of epoxy-modified silicone oil, and 230 parts of water were mixed and stirred to obtain a coating solution for the uppermost layer.

Production of Thermosensitive Recording Material As a support, polyethylene terephthalate (HMW-1) was used.
00, a haze value of 1 or less, the heat-sensitive recording layer coating solution of the following and on one side of the intermediate layer coating solution coating amount after drying respectively 8.0 g / m ² manufactured by Teijin Ltd.), 2.5 g / m ² After coating and drying so as to form a heat-sensitive recording layer and an intermediate layer sequentially,
Supercalendering was performed to obtain an intermediate layer having an Oken-type smoothness (J. TAPPI No. 6) of 1600 seconds on the surface of the intermediate layer. Next, after applying and drying the coating liquid for the uppermost layer on the intermediate layer so that the coating amount after drying was 0.8 g / m ² , a super calender treatment was performed to obtain a thermosensitive recording medium having the uppermost layer. .

Example 2 The following coating liquid for the uppermost layer was used in place of the coating liquid for the uppermost layer used in the production of the thermal recording medium of Example 1, and the coating amount after drying was 0.4 g / m ² . After coating and drying, a 4 Mrad electron beam was irradiated to obtain a thermosensitive recording medium having an uppermost layer. Preparation of Top Layer Coating Solution Acrylate Oligomer (trade name: KAYARAD®)
-551, manufactured by Nippon Kayaku Co., Ltd.) 23 parts, toluene 300 parts,
A composition comprising 72 parts of amorphous silica (average particle diameter: 0.3 μm), 5 parts of epoxy-modified silicone oil and 0.5 part of silicon-based leveling agent was dispersed by a three-roll mill to obtain a coating liquid for the uppermost layer.

Example 3 The coating solution for the uppermost layer of Example 1 was applied to a polyester film (thickness 2
0 μm) and dried so that the coating amount after drying is 0.6 g / m ² to form an uppermost layer film. Next, Example 1
2 g / m ^{2 of a} coating liquid for an adhesive layer composed of 100 parts of pentaerythritol triacrylate (trade name: Aronix M-305, manufactured by Toagosei Co., Ltd.) on the intermediate layer of the heat-sensitive recording medium after the formation of the intermediate layer of Then, the adhesive layer is applied to the upper surface of the adhesive layer, and the adhesive layer is cured by irradiating a 4 Mrad electron beam from the polyester film side. I got a body.

Example 4 In the preparation of the coating solution for the uppermost layer in Example 1, kaolin (UW-90, average particle size 0.5 μm) was used.
m, 120 parts of a 60% dispersion of EC and 35 parts of a 51% aqueous solution of an acrylic resin (OLY-1493, manufactured by Showa Polymer Co., Ltd.) instead of kaolin (UW-90, average particle size 0.5 μm). A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 140 parts of a 60% dispersion liquid (manufactured by EC Company) and 110 parts of a 10% aqueous solution of polyvinyl alcohol were used.

Example 5 In the preparation of the coating solution for the uppermost layer in Example 1, kaolin (UW-90, average particle size 0.5 μm) was used.
m, 120 parts of a 60% dispersion of EC and 35 parts of a 51% aqueous solution of an acrylic resin (OLY-1493, manufactured by Showa Polymer Co., Ltd.) instead of kaolin (UW-90, average particle size 0.5 μm). A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 100 parts of a 60% dispersion of EC Corporation and 350 parts of a 10% aqueous solution of polyvinyl alcohol were used. Example 6 In the preparation of the coating solution for the uppermost layer in Example 1,
Instead of amorphous silica, light calcium carbonate (trade name:
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that brilliant 15 (average particle diameter: 0.15 μm, manufactured by Shiraishi Industry Co., Ltd.) was used. Example 7 In the production of the thermosensitive recording medium of Example 1, a polyethylene terephthalate film (HMW-100,
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that a polystyrene film having a thickness of 80 μm (haze value: 1 or less) was used instead of Teijin Limited.

Example 8 The coating solution for the uppermost layer of Example 1 was applied to a polyester film (thickness 2
0 μm) and dried so that the coating amount after drying is 0.6 g / m ² to form an uppermost layer film. Next, Example 1
The following intermediate layer coating solution was applied to the heat-sensitive recording layer of the heat-sensitive recording medium after the formation of the heat-sensitive recording layer up to 3 g / m ^2, and the intermediate layer surface and the uppermost layer surface were press-bonded to form a 4 Mrad electron. After the line was irradiated from the polyester film side to cure the intermediate layer, the polyester film and the uppermost layer were peeled off to obtain a thermosensitive recording medium. Preparation of Coating Solution for Intermediate Layer 91 parts of pentaerythritol triacrylate (trade name: Aronix M-305, manufactured by Toagosei Co., Ltd.), 6 parts of amorphous silica (trade name: Mizuka Seal P-527, manufactured by Mizusawa Chemical Industry Co., Ltd.), silicon A composition comprising 1.5 parts of a system leveling agent and 1.5 parts of an ester wax was dispersed by a three-roll mill to obtain a coating liquid for an intermediate layer.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that the uppermost layer was not provided in the production of the thermosensitive recording medium of Example 1.

Comparative Example 2 In the preparation of the coating solution for the uppermost layer in Example 1, kaolin (UW-90, average particle size 0.5 μm) was used.
m, 120 parts of a 60% dispersion of EC) and 35 parts of a 51% aqueous solution of an acrylic resin (OLY-1493, manufactured by Showa Polymer Co., Ltd.) instead of kaolin (UW-90, average particle size 0.5 μm, A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 80 parts of a 60% dispersion of EC Company and 92 parts of a 51% aqueous solution of an acrylic resin (OLY-1493, manufactured by Showa Polymer Co., Ltd.) were used. .

Comparative Example 3 In the preparation of the thermosensitive recording medium of Example 1, the coating amount of the uppermost layer coating liquid was 0.8 g / m ² .
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the amount was changed to ² g / m ² .

Comparative Example 4 In the preparation of the thermosensitive recording medium of Example 1, the coating amount of the uppermost layer coating liquid was 0.8 g / m ² .
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the amount was changed to 07 g / m ² .

The following evaluation was performed on the thus obtained heat-sensitive recording material, and the results are shown in Table 1. [Transparency] The haze value of the unprinted portion is measured by HAZMETER (TC-H III, manufactured by Tokyo Denshoku Co., Ltd.).

[Thermal Recording and Background Fogging] A 17-step gradation recording was performed by a thermal recording printer (UP-860, manufactured by Sony Corporation), and the 17th step and the unrecorded portion were recorded with a Macbeth TD-904 densitometer (transmission type). ).

[Stig resistance] 17 for recording density measurement
When recording the step, the loudness of the sticking sound generated at the time of recording I was heard by ear and judged as follows. Evaluation criteria A: There is almost no sound. ：: There is slight sound but no recording unevenness. Δ: Slight noise, slightly horizontal stripe-like recording unevenness occurs. ×: A loud sound is generated, and horizontal stripe-shaped recording unevenness occurs.

[0055]

[Table 1]

[0056]

As shown in Table 1, the thermosensitive recording medium of the present invention is excellent in transparency and recording running property.

Claims (2)

[Claims] 1. A heat-sensitive recording layer containing an electron donating compound and an electron accepting compound, an intermediate layer mainly containing an adhesive, and a top layer mainly containing a pigment and an adhesive on a transparent support. Are sequentially provided, the coating amount of the uppermost layer is 0.1 to 1.0 g / m ² , and the pigment in the uppermost layer is 55 to 90% by weight based on the total solid content of the uppermost layer. And a haze value of the heat-sensitive recording material is 45% or less. 2. The heat-sensitive recording material according to claim 1, wherein the pigment in the uppermost layer is amorphous silica or kaolin.