JPH09156222A - Production of thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material high in surface gloss and recording density and excellent in sticking resistance. SOLUTION: A thermal recording material is produced by successively providing a thermal recording layer containing a leuco dye, a coupler and an adhesive and a protective layer on at least the single surface of a support. In this case, a solventless coating soln. for the protective layer with viscosity of 1.0-80 Pa.S containing an ultraviolet curable compd. and 5-30% by wt. of the ultraviolet curable compd. of aluminum hydroxide is applied to the thermal recording layer and subsequently irradiated with ultraviolet rays to cure the ultraviolet curable compd. to provide the protective layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermosensitive recording material utilizing a color-forming reaction between a leuco dye and a color former.
In particular, the present invention relates to a method for producing a thermosensitive recording medium having high surface gloss and high recording density and excellent in sticking resistance.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known in which a color image is obtained by contacting both color-forming substances by heat by utilizing a color-forming reaction between a colorless or light-colored leuco dye and a color-forming agent. Since such a thermal recording material is relatively inexpensive and the recording device is compact and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

One of the fields of use thereof is thermal recording paper for POS (point of sales) systems in retail stores and the like. With the expansion of the system, there is a strong demand for a thermal recording material having excellent surface gloss in order to enhance the commercial value. As a method of obtaining a thermal recording material having excellent surface gloss,
A heat-sensitive recording material having a heat-sensitive recording layer provided with a protective layer containing a resin cured by irradiating a UV-curable compound with ultraviolet rays is disclosed in JP-A-57-69091 and JP-A-59-26.
No. 291, JP-A-6-344664 and JP-A-7-40658, the phenomenon in which the thermal head adheres to the protective layer during recording, that is, sticking occurs, and a uniform recorded image is obtained. There is a risk that you will not be able to.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a thermosensitive recording medium which has a high surface gloss and a high recording density and is excellent in sticking resistance.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a heat-sensitive recording medium in which a heat-sensitive recording layer containing a leuco dye, a coloring agent and an adhesive and a protective layer are sequentially provided on at least one surface of a support. In the above, the thermosensitive recording layer contains 5 to 30% by weight of aluminum hydroxide with respect to the ultraviolet curable compound and the ultraviolet curable compound, and has a viscosity of 1.0 to 80.
By applying a solvent-free coating solution for a protective layer, which is Pa · s, and then providing a protective layer obtained by irradiating ultraviolet rays to cure an ultraviolet-curable compound, the above problems can be solved and completed. I arrived.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a method for producing a heat-sensitive recording medium, which comprises a support, a heat-sensitive recording layer containing a leuco dye, a coloring agent and an adhesive, and a protective layer, which are provided on at least one side of the support. On the heat-sensitive recording layer, 5% of aluminum hydroxide is added to the ultraviolet curable compound and the ultraviolet curable compound.
-30% by weight, and the viscosity when applied is 1.0-80.
After coating a solvent-free coating solution for a protective layer that is Pa · s, a protective layer is provided by irradiating ultraviolet rays to cure an ultraviolet-curable compound, and sticking-resistant when aluminum hydroxide is less than 5% by weight. 30% by weight
If it exceeds the range, the recording density and surface gloss may decrease, and the range of 10 to 20% by weight is more preferable. If the viscosity of the coating liquid is less than 1.0 Pa · s, the thermosensitive recording layer may be impregnated with the protective layer coating liquid, and the gloss of the protective layer surface may decrease.
On the other hand, if it exceeds 80 Pa · s, a uniform coating surface may not be formed and the recording image quality may deteriorate.
The range of s is more preferable. It is also possible to apply the protective layer coating liquid by heating.

The average particle diameter of aluminum hydroxide in the protective layer is not particularly limited, but it is more preferably 0.5 to 3 μm, and if it is less than 0.5 μm, the sticking resistance decreases and exceeds 3 μm. And the surface gloss may decrease.

As the leuco dye used in the heat-sensitive recording layer, various known leuco dyes can be used, and specific examples thereof include
For example, the following are mentioned. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl)
-3- (4-Dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluoran, 3- (N-ethyl-
Np-tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3,6-bis (diethylamino) fluoran −γ
-Anilinolactam, 3-cyclohexylamino-6-
Chlorofluorane, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (m-tri Fluoromethylanilino)
Fluoran, 3- (N-methyl-N-cyclohexyl)
Amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane,
3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-
7- (o-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- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-furfurylamino)-
6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3- (N
-Methyl-N-n-propylamino) -6-methyl-7
-Anilinofluorane, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl)
Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-
Yl] -4,5,6,7-tetrachlorophthalide, 3,
6, -bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide and the like. Of course, it is not limited to these, and two or more kinds may be used in combination as required. The amount of leuco dye used is not particularly limited, but is preferably about 5 to 40 parts by weight with respect to the heat-sensitive recording layer.

As the coloring agent used in combination with the leuco dye, various known ones can be used, for example, hydroquinone monobenzyl ether, 4,4'-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl). )
Cyclohexane, 4,4'-dihydroxydiphenyl-
2,2-butane, 4,4'-dihydroxydiphenylmethane, 2,2-bis (4-hydroxyphenyl) -4-
Methylpentane, 2,2-bis (4-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′-benzyloxyphenyl sulfone, 4-hydroxy-3 ′, 4′-tetramethylenebiphenyl sulfone,
3,4-dihydroxyphenyl-p-tolylsulfone,
Benzyl 4-hydroxybenzoate, N, N'-di-m-
Chlorophenylthiourea, zinc 4- [2- (p-methoxyphenoxy) ethyloxy] salicylate, 4- [3-
(P-Tolylsulfonyl) propyloxy] salicylate zinc, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylate zinc, 4,4′-bis (p-tolylsulfonylcarbonylaminocarbonyl) diphenylmethane, N- p-tolyl sulfonyl-N'-phenyl urea etc. are mentioned.

The protective layer of the present invention comprises 4,4 'as a color former.
With respect to the heat-sensitive recording layer using -bis (p-tolylsulfonylcarbonylaminocarbonyl) diphenylmethane, the effect of causing less background fog and reducing the recording density is extremely small.

The ratio of the leuco dye to the coloring agent used is appropriately selected according to the type of leuco dye used and is not particularly limited, but generally leuco dye 1
1 to 10 parts by weight, preferably 2 to 5 parts by weight is desirable with respect to parts by weight.

The heat-sensitive recording layer containing a leuco dye and a color former is
Generally, water is used as a dispersion medium, and a ball mill, attritor,
After finely dispersing the leuco dye and the coloring agent together or separately with a dispersant so that the average particle diameter is about 0.5 to 3 μm, by a stirring and crushing machine such as a sand mill, an adhesive is added and mixed. The thermosensitive recording layer coating liquid prepared by stirring is applied on a support and dried.

The adhesive used for the heat-sensitive recording layer can be any of a water-soluble resin and a water-dispersible resin. For example, completely (partially) saponified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol. Silicon-modified polyvinyl alcohol, starch, oxidized starch, gum arabic, gelatin, casein, chitosan, methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, styrene-acrylic acid copolymer salt, styrene-maleic anhydride copolymer salt, methyl vinyl ether- Water-soluble resins such as salts of maleic anhydride copolymer, salts of isopropylene-maleic anhydride copolymer, and vinyl acetate latex, acrylic ester copolymer latex, methacrylic ester copolymer latex, vinyl acetate -(Meth) acrylic acid ester copolymer latex, polyurethane latex, polyvinyl chloride latex, polyvinylidene chloride latex, styrene-
Water-dispersible resins such as butadiene-based latex are exemplified. The amount of the adhesive used is 5 to 5
A range of 30% by weight is preferred.

In order to improve the water resistance of the heat-sensitive recording layer, a crosslinking agent for curing the resin is used within the range of 1 to 10% by weight based on the solid amount of the adhesive in the heat-sensitive recording layer. You can Specific examples of such a cross-linking agent, for example, glyoxal, dialdehyde compounds such as dialdehyde starch, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, diglycidyl compounds such as glycerin diglycidyl ether, Examples thereof include dimethylolurea compound, aziridine compound, blocked isocyanate compound, ammonium persulfate, boric acid, borax, ferric chloride and magnesium chloride.

In the heat-sensitive recording layer, as pigments for improving coating suitability, for example, calcium carbonate, magnesium carbonate, magnesium oxide, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide. Heat sensitive inorganic pigments such as titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica, and organic pigments such as three-dimensionally cross-linked urea resin, styrene-methacrylic acid copolymer and polystyrene resin. It can also be used in the range of 5 to 40% by weight with respect to the recording layer.

Further, the heat-sensitive recording layer may contain a sensitizer for increasing the recording sensitivity and a storability improving agent for improving the storability of the recorded image. Specific examples of such sensitizers include fatty acid amides such as stearic acid amide, stearic acid ethylenebisamide, oleic acid amide, palmitic acid amide, and behenic acid amide, dibenzyl oxalate, and di-p-methylbenzyl oxalate. , Oxalic acid di-p-chlorobenzyl ester, terephthalic acid dimethyl ester, terephthalic acid dibenzyl ester, 1-hydroxynaphthoic acid phenyl ester,
1,2-di (3-methylphenoxy) ethane, 1,2-
Examples include diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, p-benzylbiphenyl and the like.

As the preservability improver, for example, 2,2'-
Methylene bis (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, 2,2′-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate,
4,4'-bis (ethyleneiminecarbonylamino) diphenylmethane, 4-benzyloxy-4 '-(2,3
-Glycidyloxy) diphenyl sulfone, novolak type resin and the like. The sensitizer or storability improver is preferably contained in the heat-sensitive recording layer in an amount of 0.1 to 4 parts by weight per 1 part by weight of the leuco dye.

In the coating liquid for the heat-sensitive recording layer, surfactants such as acetylene glycol and dialkylsulfosuccinate, fatty acid metal salts such as zinc stearate and calcium stearate, polyethylene wax, carnauba wax,
Lubricants such as paraffin wax and ester wax, coloring dyes, fluorescent dyes and the like can also be added.

The heat-sensitive recording layer of the present invention is provided on at least one surface of a support such as high-quality paper, synthetic paper, film, coated paper, etc., which is conventionally used by those skilled in the art, such as an air knife method, a Mayer bar method and a pure blade method. The coating amount after drying the thermosensitive recording layer coating solution is 1 to 1 by a coating method such as a rod blade method, a reverse roll method, or a slit die method.
It is formed by coating and drying so as to be 10 g / m ² , preferably 2 to 7 g / m ² .

The protective layer of the present invention is at least UV curable
Insoluble containing compound and specific amount of aluminum hydroxide
After applying the coating liquid for protective layer of the agent on the heat-sensitive recording layer, irradiate it with ultraviolet rays.
UV curable compound is cured by irradiation
Is done. The coating amount of the protective layer is the coating amount after curing.
Is 0.5 to 5 g / m^Two, More preferably 1 to 3 g / m ^Two
It is desirable to adjust within the range. The coating liquid for the protective layer
The coating method is the same as the above-mentioned coating method for the thermosensitive recording layer.
used.

The UV-curable compound used in the protective layer of the present invention has a double bond 1 which can undergo a curing reaction upon irradiation with UV rays.
A liquid monomer or oligomer having at least one,
For example, (a) aliphatic, alicyclic, araliphatic poly (meth) acrylates of dihydric to polyhydric alcohols and polyalkylene glycols; (b) aliphatic, alicyclic, araliphatic, or aromatic A poly (meth) acrylate of a polyhydric alcohol obtained by adding an alkylene oxide to a divalent to hexavalent polyhydric alcohol; (c) a poly (meth) acryloyloxyalkyl phosphate ester; (d) a polyester poly (meth) acrylate; (e) Epoxy poly (meth) acrylate; (f) Polyurethane poly (meth) acrylate;
(g) polyamide poly (meth) acrylate; (h) polysiloxane poly (meth) acrylate; (i) side chains and / or
Or a vinyl-based or diene-based low polymer having a (meth) acryloyloxy group or at the terminal; (j) the (a)
Examples include prepolymers such as oligoester (meth) acrylate modified products described in (i) to (i). Of these, epoxy poly (meth) acrylate oligomers are particularly preferable because they have excellent sticking resistance.

As the monomer, (a) a carboxyl group-containing monomer represented by ethylenically unsaturated mono- or polycarboxylic acid, etc .; (b) ethylenically unsaturated (meth) acrylamide or alkyl-substituted (meth) ) Amide group-containing monomers represented by vinyl lactams such as acrylamide and N-vinylpyrrolidone; (c) Sulfonic acid group-containing monomers represented by aliphatic or aromatic vinyl sulfonic acids; (d) Hydroxyl group-containing monomer typified by ethylenically unsaturated ether; (e) Amino group-containing monomer such as dimethylaminoethyl (meth) acrylate-2-vinylpyridine; (f) Quaternary ammonium salt group-containing monomer (G) Alkyl ester of ethylenically unsaturated carboxylic acid; (h) Nitrile group-containing monomer such as (meth) acrylonitrile; (i)
Styrene; (j) Esters of ethylenically unsaturated alcohols such as vinyl acetate and (meth) allyl acetate;

(K) Mono (meth) acrylates of alkylene oxide addition polymers containing active hydrogen; (l) Ester group-containing bifunctional monomers represented by diesters of polybasic acids and unsaturated alcohols; (m) Bifunctional monomer consisting of diester of alkylene oxide addition polymer of active hydrogen-containing compound and (meth) acrylic acid; (n) N, N
-Bisacrylamide such as methylenebisacrylamide; (o) Bifunctional monomers such as divinylbenzene, divinylethylene glycol, divinylsulfone, divinyl ether, divinyl ketone; (p) Polyester of polycarboxylic acid and unsaturated alcohol Ester group-containing polyfunctional monomer; (q) polyfunctional monomer composed of polyester of (meth) acrylic acid and alkylene oxide addition polymer of compound containing active hydrogen; (r) trivinylbenzene Such polyfunctional unsaturated monomers and the like can be mentioned. In addition,
Two or more kinds of the above UV-curable compounds may be used in combination.

It is necessary to add a sensitizer capable of generating radicals when irradiated with ultraviolet rays to the protective layer coating liquid for forming the protective layer, and the sensitizer is added to the ultraviolet-curable compound in an amount of 0.2. It is added in the range of 10% by weight. Further, as the light source for ultraviolet curing, 1 to 50 ultraviolet lamps, xenon lamps, halogen lamps, etc. are used,
Ultraviolet rays having an intensity of about 40 to 200 W / cm are irradiated.

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

In the present invention, an intermediate layer containing an aqueous adhesive or an aqueous adhesive and a pigment as a main component can be provided between the heat-sensitive recording layer and the protective layer. By providing the intermediate layer, A protective layer having more excellent surface gloss is formed.
For example, in an intermediate layer containing an aqueous adhesive and a pigment as main components, the pigment used in the intermediate layer can be appropriately selected and used from the pigments used in the heat-sensitive recording layer. The blending amount of the pigment is 20 to 80% by weight based on the solid content of the intermediate layer.
Is desirable. If it is less than 20% by weight, the adhesiveness between the intermediate layer and the protective layer will be lowered, and if it exceeds 80% by weight, the surface gloss of the protective layer will be lowered.

If necessary, a backside layer containing a water-soluble adhesive or a water-based adhesive and a pigment as a main component may be provided on the backside of the thermosensitive recording medium to further improve the storage stability or to support and the thermosensitive recording medium. An undercoat layer may be provided between the layers, or after each layer is applied, smoothing treatment such as super calendering may be applied to improve image quality and image density, or an adhesive treatment may be applied to the back side of the thermosensitive recording material to form an adhesive label. Various known techniques in the field of heat-sensitive recording material manufacturing such as processing and providing a magnetic layer can be added as necessary.

[0028]

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 of Examples and Comparative Examples, "part" and "%" indicate "part by weight" and "% by weight", respectively.

Example 1 Preparation of Liquid A 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 10 parts, 1,2-di (3-methylphenoxy) ethane 20 parts, sulfone A composition consisting of 10 parts of a 10% aqueous solution of modified polyvinyl alcohol and 60 of water was pulverized with an Ultraviscomyl until the average particle diameter was 0.9 μm, to obtain a liquid A.

Solution B Preparation A composition consisting of 20 parts of 4,4′-bis (p-tolylsulfonylcarbonylaminocarbonyl) diphenylmethane, 10 parts of a 10% aqueous solution of sulfone-modified polyvinyl alcohol, and 30 parts of water was prepared using Ultrabiscomyl. And pulverized until the average particle diameter was 1.3 μm, to obtain a liquid B.

Preparation of Coating Liquid for Undercoat Layer 100 parts of calcined kaolin having an oil absorption of 110 ml, 2 parts of a 40% aqueous solution of sodium polyacurate, 200 parts of water, polyvinyl alcohol (100 parts of a 10% aqueous solution of PVA110, and styrene- A composition consisting of 10 parts of butadiene-based latex (trade name: L-1537, solid concentration 48%, manufactured by Asahi Kasei Co., Ltd.) was mixed and stirred to obtain a coating liquid for undercoat layer Preparation of coating liquid for heat-sensitive recording layer Liquid A 100 parts, B solution 75 parts, light calcium carbonate 60
% Dispersion 2 parts, aluminum hydroxide 60% dispersion 38
Parts, polyvinyl alcohol (trade name: PVA117, manufactured by Kuraray Co., Ltd.) 150% 10% aqueous solution, 20 parts of 30% zinc stearate dispersion, and 50 parts of water are mixed and stirred to prepare a coating liquid for heat-sensitive recording layer. Got

Preparation of Coating Liquid for Protective Layer Epoxy poly (meth) acrylate oligomer (viscosity at 25 ° C., 3 Pa · s) 10 as an ultraviolet curable compound
A composition consisting of 0 part, 2 parts of 2-tert-butylanthraquinone and 15 parts of aluminum hydroxide having an average particle size of 1 μm was dispersed in a three-roll mill to give a viscosity of 40 at 25 ° C.
A coating liquid for protective layer of Pa · s was obtained.

Preparation of Thermosensitive Recording Material The coating liquid for the undercoat layer and the coating liquid for the thermal recording layer were dried on one side of an acid paper having a basis weight of 56 g / m ² of 8 g / m ² and 5 g, respectively. The coating solution for the protective layer at 25 ° C. is applied to the thermosensitive recording layer obtained by super calendering after coating and drying with a rod blade coater so that it becomes / m ² by a gravure printing machine having an ultraviolet irradiation device. After coating so as to have a coating amount of 1 g / m ² , ultraviolet rays were irradiated to obtain a thermosensitive recording material having a protective layer in which the ultraviolet curable compound was cured.

Example 2 In the preparation of solution B of Example 1, 4,4′-bis (p-tolylsulfonylcarbonylaminocarbonyl) diphenylmethane was used instead of 4,4′-bis (p-tolylsulfonylcarbonylaminocarbonyl) diphenylmethane.
Other than using 4'-isopropylidenediphenol,
A thermosensitive recording medium was obtained in the same manner as in Example 1.

Example 3 Preparation of Coating Liquid for Protective Layer 30 parts of trimethylolpropane triacrylate, 70 parts of epoxy poly (meth) acrylate oligomer (viscosity at 25 ° C., 3 Pa · s), 70 parts of 2-tert-butylanthraquinone A composition consisting of 2 parts and 5 parts of aluminum hydroxide having an average particle diameter of 1 μm was dispersed in a three-roll mill, and the temperature was 25 ° C.
To obtain a protective layer coating solution having a viscosity of 3.0 Pa · s.

Preparation of thermal recording material Thermal recording was carried out in the same manner as in Example 1 except that the above-mentioned protective layer coating liquid was used in place of the protective layer coating liquid used in the preparation of the thermal recording medium of Example 1. Got the body

Example 4 Preparation of Coating Liquid for Protective Layer 10 parts of trimethylolpropane triacrylate, 90 parts of epoxy poly (meth) acrylate oligomer (viscosity at 25 ° C., 3 Pa · s), 2-tert-butylanthraquinone A composition consisting of 2 parts and 25 parts of aluminum hydroxide having an average particle diameter of 2 μm was dispersed with a three-roll mill to give 25
A protective layer coating liquid having a viscosity at 30 ° C. of 30 Pa · s was obtained.

Preparation of Thermal Recording Material Thermal recording was carried out in the same manner as in Example 1 except that the above-mentioned coating liquid for protective layer was used instead of the coating liquid for protective layer used in the preparation of the thermal recording material of Example 1. Got the body

Example 5 Preparation of Coating Liquid for Protective Layer Epoxy poly (meth) acrylate oligomer (25 ° C.)
Viscosity of 3 Pa · s) 100 parts, 2-tert-butylanthraquinone 2 parts, and aluminum hydroxide 15 parts having an average particle diameter of 5 μm are dispersed in a three-roll mill to give a viscosity of 30 Pa · s at 25 ° C. A coating liquid for protective layer of s was obtained.

Preparation of Thermal Recording Material Thermal recording was carried out in the same manner as in Example 1 except that the above-mentioned protective layer coating liquid was used in place of the protective layer coating liquid used in the preparation of the thermal recording medium of Example 1. Got the body

Example 6 Preparation of Coating Liquid for Protective Layer Polyester poly (meth) acrylate oligomer (2
Viscosity at 5 ° C., 2 Pa · s) 100 parts, 2-tert-butylanthraquinone 2 parts, 15 parts of aluminum hydroxide having an average particle diameter of 5 μm are dispersed in a three-roll mill to obtain a viscosity at 25 ° C. A coating liquid for protective layer of 25 Pa · s was obtained.

Preparation of Thermal Recording Material Thermal recording was carried out in the same manner as in Example 1 except that the above-mentioned coating liquid for protective layer was used in place of the coating liquid for protective layer used in the preparation of the thermal recording material of Example 1. Got the body

Comparative Example 1 Preparation of Coating Liquid for Protective Layer 100 parts of trimethylolpropane triacrylate, 2
-Tert-Butylanthraquinone 2 parts, average particle size 2μ
A composition consisting of 40 parts of aluminum hydroxide of 3 m was dispersed with a three-roll mill to have a viscosity of 15 Pa · s at 25 ° C.
To obtain a coating liquid for protective layer.

Preparation of Thermosensitive Recording Material Thermal recording was carried out in the same manner as in Example 1 except that the above-mentioned protective layer coating solution was used instead of the protective layer coating solution used in the preparation of the thermal recording material of Example 1. Got the body

Comparative Example 2 Preparation of Coating Liquid for Protective Layer 100 parts of trimethylolpropane triacrylate, 2
-Tert-Butylanthraquinone 2 parts, average particle size 2μ
A composition consisting of 3 parts of aluminum hydroxide of m was dispersed in a three-roll mill, and the viscosity at 25 ° C. was 0.1 Pa · s.
To obtain a coating liquid for protective layer.

Preparation of Thermal Recording Material Thermal recording was carried out in the same manner as in Example 1 except that the above-mentioned protective layer coating liquid was used in place of the protective layer coating liquid used in the preparation of the thermal recording medium of Example 1. Got the body

Comparative Example 3 Preparation of Coating Liquid for Protective Layer Epoxy poly (meth) acrylate oligomer (25 ° C.)
Viscosity at 3 Pa · s) of 100 parts, 2-tert-butylanthraquinone of 2 parts, and aluminum hydroxide having an average particle diameter of 1 μm of 40 parts are dispersed in a three-roll mill, and the viscosity at 25 ° C. is 90 Pa · s. A coating liquid for protective layer of s was obtained.

Preparation of thermal recording material Thermal recording was carried out in the same manner as in Example 1 except that the above-mentioned coating liquid for protective layer was used instead of the coating liquid for protective layer used in the preparation of the thermal recording medium of Example 1. Got the body

Comparative Example 4 Preparation of Coating Liquid for Protective Layer Epoxy poly (meth) acrylate oligomer (25 ° C.)
Viscosity of 3 Pa · s) 100 parts, 2-tert-butylanthraquinone 2 parts, and aluminum hydroxide having an average particle diameter of 1 μm 3 parts are dispersed in a three-roll mill,
A protective layer coating liquid having a viscosity at 25 ° C. of 4 Pa · s was obtained.

Preparation of thermal recording material Thermal recording was carried out in the same manner as in Example 1 except that the above-mentioned protective layer coating liquid was used in place of the protective layer coating liquid used in the preparation of the thermal recording medium of Example 1. Got the body

The thermal recording material thus obtained was evaluated as follows, and the obtained results are shown in Table 1.

[Recording Density] Thermal recording evaluation machine (trade name: T
Using an H-PMD (manufactured by Okura Electric Co., Ltd.), each thermosensitive recording medium was recorded at an applied energy of 0.3 mJ / dot, and the recorded density and unrecorded portion of the obtained recorded image were measured using a Macbeth densitometer (trade name: RD). -914 type, manufactured by Macbeth Corporation) in the visual mode.

[Sticking resistance] A facsimile machine UF-22 (copy mode) manufactured by Matsushita Electric Transmission Co., Ltd. was used to determine the sticking sound generated during recording and the obtained recording image quality as follows. Evaluation criteria ⊚: The sticking sound is low, and the recorded image quality is not impaired. ◯: The sticking sound is slightly high, but there is no problem in the recorded image quality. X: Sticking sound is high, and there are many obstacles to the recorded image quality.

[Surface gloss] An incident angle of 75 on the surface of the protective layer was measured using a gloss meter GM-26D manufactured by Murakami Color Research Laboratory.
The glossiness at ° was measured.

[0055]

[Table 1]

[0056]

As shown in Table 1, the method for producing a heat-sensitive recording material of the present invention has a high surface gloss and a high recording density and is excellent in sticking resistance.

Claims (3)

[Claims] 1. A method for producing a thermosensitive recording medium, which comprises sequentially providing a thermosensitive recording layer containing a leuco dye, a coloring agent and an adhesive on at least one surface of a support, and a protective layer.
A solvent-free coating liquid for a protective layer, which contains 5-30% by weight of aluminum hydroxide with respect to the ultraviolet-curable compound and the ultraviolet-curable compound, and has a viscosity of 1.0-80 Pa · s on the heat-sensitive recording layer. A method for producing a heat-sensitive recording material, characterized in that after the application, a protective layer obtained by irradiating ultraviolet rays to cure the ultraviolet-curable compound is provided. 2. The average particle size of aluminum hydroxide is 0.5.
The method for producing a thermosensitive recording medium according to claim 1, wherein the thermal recording medium has a thickness of 3 μm. 3. The method for producing a thermosensitive recording medium according to claim 1, wherein the color developing agent is 4,4′-bis (p-tolylsulfonylcarbonylaminocarbonyl) diphenylmethane.