JPH07223375A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material excellent in recording sensitivity and the transparency of an unrecorded part. CONSTITUTION:In a thermal recording material wherein a thermal recording layer containing two or more kinds of leuco dyes and a coupler is provided on a transparent support, two or more kinds of the leuco dyes are simultaneously ground so as to have an average particle diameter of 0.8mum 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, and more particularly to a heat-sensitive recording material having excellent recording sensitivity and transparency of an unrecorded portion.

[0002]

2. Description of the Related Art Heretofore, a heat-sensitive recording material has been often used in which a color or color reaction between a colorless or light-colored leuco dye and an organic or inorganic coloring agent is used to obtain a recorded image by contacting both coloring substances with heat. Are known. Since such a thermosensitive recording medium 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 printers but also in a wide range of fields. Along with the recent diversification of needs, there is an increasing demand for development of a thermal recording material having a transparent unrecorded portion which can be used for OHP sheets and X-ray sheets. As a method for obtaining a heat-sensitive recording material in which the unrecorded area is transparent, for example, Japanese Patent Laid-Open No. 2-9938.
No. 5 discloses that an average particle size is 0.8 μm on a transparent support.
A heat-sensitive recording material provided with a recording layer containing a leuco dye having a size of m or less and a color developing agent is described, and JP-A-54-109454 discloses a heat-sensitive recording material obtained by simultaneously grinding two kinds of leuco dyes. Although described, the current situation is that sufficient recording sensitivity and transparency are not obtained.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium which has excellent recording sensitivity and transparency of unrecorded areas.

[0004]

Means for Solving the Problems The present inventors have proposed a thermosensitive recording medium comprising a transparent support and a thermosensitive recording layer containing two or more leuco dyes and a coloring agent. It has been found that the above objects can be achieved by using, as the leuco dye of one kind or more, two or more kinds of leuco dyes, which are pulverized at the same time so as to have an average particle diameter of 0.8 μm or less. The present invention has been completed.

[0005]

In the present invention, as the leuco dye, two or more kinds of leuco dyes, which are crushed at the same time and have an average particle diameter of 0.8 μm or less, are used. This is what the recording body found. This is more than two leuco dyes at the same time, 0.8μm
It is considered that the crushing causes the crystallinity of the leuco dye to remarkably decrease, which in turn lowers the refractive index and eliminates the difference from the refractive index of the adhesive or the like. When the average particle diameter exceeds 0.8 μm, the transparency and recording sensitivity are deteriorated, and the desired transparency cannot be obtained even if two or more leuco dyes individually ground are used.

Various types of colorless or light-colored leuco dyes used in the heat-sensitive recording layer are known, and examples thereof include the following. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-
Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (1,2-Dimethylindol-3-yl) -5-dimethylaminophthalide, 3,
3-bis (1,2-dimethylindol-3-yl)-
6-Dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylamino Triarylmethane dyes such as phthalide and 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydryl Diphenylmethane dyes such as benzyl ether, N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, thiazine dyes such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue, 3-methyl- Spiro-
Dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-
Spiro dyes such as (6′-methoxybenzo) spiropyran and 3-propyl-spiro-dibenzopyran, lactam dyes such as rhodamine-B anilinolactam, rhodamine (p-nitroanilino) lactam and rhodamine (o-chloroanilino) lactam , 3-dimethylamino-7-
Methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane,
3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7- (N-acetyl-N-methylamino) fluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7- (N-methyl-N- Benzylamino) fluorane, 3-diethylamino-7- (N-chloroethyl-
N-methylamino) fluorane, 3-diethylamino-
Yellow or red coloring fluorane dyes such as 7-diethylaminofluorane. 3- (N-ethyl-p-toluidino)-
6-methyl-7-phenylaminofluorane, 3- (N
-Cyclopentyl-N-ethylamino) -6-methyl-
7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-di (N-Butyl) amino-6-
Methyl-7-phenylaminofluorane, 3-di (n-
Pentyl) amino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7- (2-carbomethoxy-phenylamino) fluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7. -Phenylaminofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6 -Methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-
7- (o-chlorophenylamino) fluorane, 3-dibutylamino-7- (o-chlorophenylamino) fluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3- (N-methyl-) Black coloring fluoran such as N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane and 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane dye.

Among them, 3-di (n-butyl) amino-6
It is preferable to use -methyl-7-phenylaminofluorane in combination with another leuco dye of a black coloring system. The ratio is particularly preferably in the range of 10 to 100% by weight of another black-coloring leuco dye with respect to 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane.

Various compounds are known as the acidic substance used in combination with the leuco dye, and the following are exemplified. 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenone,
4-tert-butylphenol, hydroquinone, 4-te
rt-octylcatechol, 4,4'-isopropylidene diphenol (bisphenol A), 4,4'-cyclohexylidene diphenol, 2,2'-dihydroxydiphenol, 2,2'-methylenebis (4-methyl-6)
-Tert-butylphenol), 4,4'-isopropylidenebis (2-tert-butylphenol), 4,4'-
sec-butylidene diphenol, 4-phenylphenol, 2,2'-methylenebis (4-chlorophenol), 4,4'-dihydroxydiphenyl sulfone,
2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-chlorodiphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-iso Propoxydiphenyl sulfone, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenolic resin, phenolic compounds such as phenolic polymers, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid Acid, terephthalic acid, 3-sec-butyl-
4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid,
3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3,5-
Di-tert-butylsalicylic acid, 3-phenyl-5-
Aromatic carboxylic acids such as (α, α-dimethylbenzyl) salicylic acid and 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, titanium, Organic acidic substances such as polyvalent metal salts of manganese, tin, nickel, etc.

In the present invention, the use ratio of the leuco dye and the color-developing agent in the heat-sensitive recording layer should be appropriately selected according to the types of the leuco dye and the color-developing agent used, and it is not particularly limited. When a dye and an acidic substance are used, generally 1 to 7 parts by weight to 1 part by weight of a leuco dye,
Preferably, about 1 to 4 parts by weight of an acidic substance is used.

The coating liquid containing these substances is generally prepared by pulverizing or emulsifying and dispersing two or more leuco dyes and a coloring agent separately by using a water dispersion medium and a fine pulverizer such as a high speed jet mill and a sand mill. After that, they are mixed and stirred to prepare a coating liquid. Above all, it is preferable that two or more leuco dyes are simultaneously emulsified and dispersed to 0.8 μm or less. Further, the transparency of the thermosensitive recording medium is further improved by setting the average particle size of the color former to 0.8 μm or less.

In such a coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride are usually used as binders. Copolymer salt, ethylene / acrylic acid copolymer salt,
Styrene / acrylic acid copolymer salt, natural rubber emulsion, styrene / butadiene copolymer emulsion, acrylonitrile / butadiene copolymer emulsion, methyl methacrylate / butadiene copolymer emulsion, polychloroprene emulsion, vinyl acetate emulsion, ethylene At least one kind such as vinyl acetate emulsion is added in an amount of 10 to 40% by weight, preferably 15 to 35% by weight, based on the total solid content of the recording layer.

If desired, various auxiliaries can be added to the coating liquid. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. , Zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and other waxes,
An antifoaming agent, a fluorescent dye, a coloring dye, etc. are appropriately added.

Further, various pigments can be used in combination in the coating liquid as long as the characteristics of the present invention are not impaired. For example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, diatomaceous earth and fine anhydrous silica. , Inorganic pigments such as activated clay, styrene microballs, nylon powder,
Examples of the organic pigment include polyethylene powder, urea / formalin resin filler, and raw starch particles.

Further, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include, for example, stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, and methylenebisstearic acid. Amide, N-
Methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate,
Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p- Chlorobenzyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane,
1,2-di (4-methylphenoxy) ethane, 1,2-
Di (4-methoxyphenoxy) ethane, 1,2-di (4
-Chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p
-Acetotoluidide, p-acetophenetidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like are exemplified. To be done. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of 4 parts by weight or less relative to 1 part by weight of the color developing agent.

Further, a preservative improving agent may be used in combination depending on the purpose so as to further enhance the preservability of the recorded image as long as the effect is not impaired. Specific examples of such a storage stability improver include, for example, 2,2'-methylenebis (4-methyl-6).
-Tert-butylphenol), 2,2'-ethylenebis (4-methyl-6-tert-butylphenol) 2,2 '
-Methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4,6-di-tert-
Butylphenol), 2,2'-ethylidene bis (4,
6-di-tert-butylphenol), 2,2'-ethylidenebis (4-methyl-6-tert-butylphenol), 2,2'-ethylidenebis (4-ethyl-6-te)
rt-Butylphenol), 2,2 '-(2,2-propylidene) bis (4,6-di-tert-butylphenol), 2,2'-methylenebis (4-methoxy-6-te)
rt-butylphenol), 2,2'-methylenebis (6
-Tert-butylphenol), 4,4'-thiobis (3
-Methyl-6-tert-butylphenol), 4,4'-
Thiobis (2-methyl-6-tert-butylphenol), 4,4'-thiobis (5-methyl-6-tert-butylphenol), 4,4'-thiobis (2-chloro-)
6-tert-butylphenol), 4,4'-thiobis (2-methoxy-6-tert-butylphenol), 4,
4'-thiobis (2-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol), 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, 4,4'-thiobis (3-methylphenol), 4,4'-dihydroxy -3, 3 ', 5,
5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3 ', 5,5'-tetramethyldiphenyl sulfone, 2,2-bis (4-hydroxy-3,5
-Dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,
Hindered phenol compounds such as 2-bis (4-hydroxy-3,5-dimethylphenyl) propane, N,
N'-di-2-naphthyl-p-phenylenediamine,
2,2'-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate and the like can be mentioned.

In the present invention, a protective layer may be provided depending on the purpose. The protective layer is composed mainly of a water-soluble resin. Specific examples of the water-soluble resin include starches such as oxidized starch, enzyme-modified starch, cation-modified starch, esterified starch and etherified starch. , Methyl cellulose, ethyl cellulose, carboxymethyl cellulose,
Cellulose derivatives such as methoxycellulose and hydroxyethyl cellulose, completely (or incompletely) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, polyvinyl alcohol such as silicon-modified polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyvinyl Pyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid copolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, alginic acid Water-soluble polymers such as soda, gelatin, casein, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, polybutyl methacrylate, styrene Diene copolymers, vinyl acetate-vinyl chloride copolymer, ethylene-vinyl acetate copolymer include latexes such as styrene-butadiene-acrylic copolymer. Among these, polyvinyl alcohols such as completely (or incompletely) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, and silicon-modified polyvinyl alcohol, which exhibit an excellent effect of preserving recorded images, are particularly preferable. .

The coating liquid for the protective layer is prepared by using water as a dispersion medium and mixing and stirring a water-soluble resin. In the coating liquid, if necessary, a dispersant, a defoaming agent, a coloring dye, a fluorescent dye, a curing agent, an auxiliary agent such as an ultraviolet absorber, zinc stearate, calcium stearate, carnauba wax, paraffin wax, ester wax, Lubricants such as silicone oil, etc., and calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined clay, unless they impair the characteristics of the present invention. It is also possible to use an inorganic pigment such as colloidal silica. In particular, when colloidal silica and silicone oil are used together in the protective layer, the running property during recording is significantly improved without lowering the transparency.

The method for forming the heat-sensitive recording layer and the protective layer is not particularly limited, and examples thereof include air knife coating, varibar blade coating, pure blade coating, rod blade coating,
It is formed by a method such as coating the coating liquid for the recording layer on the support and drying the coating liquid by an appropriate coating method such as short dwell coating, curtain coating, or die coating. The support is appropriately selected from transparent plastic films such as polypropylene, styrene and polyethylene terephthalate. The surface of this transparent plastic film is preferably corona-treated or anchor-coated. The coating amount of the coating liquid for the recording layer is 1 to 40 g / m ² by dry weight, is preferably adjusted in the range of 2 to 20 g / m ^2. Protection coating amount of the coating liquid for layer 1 to 10 g / m ² by dry weight, is preferably adjusted in the range of 2 to 6 g / m ^2.

The thermosensitive recording medium of the present invention may be provided with a conductive layer on the back surface or may be subjected to an adhesive treatment. Further, by utilizing transparency, it is also possible to apply it on a printed film or the like to make the printing stand out, or apply it on metallic glossy paper to obtain a heat sensitive recording material having metallic gloss.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, “parts” and “%” in the examples mean “parts by weight” and “% by weight”, respectively.

Example 1 Preparation of Solution A 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane 15 parts, 3- (N-ethyl-N-isoamylamino) -6-methyl 5 parts of -7-phenylaminofluorane, 30 parts of a 5% aqueous solution of methylcellulose,
A composition comprising 60 parts of water and water was pulverized with a sand mill until the average particle size became 0.6 μm.

Preparation of Solution B 20 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 20 parts of 5% aqueous solution of methylcellulose,
A composition comprising 40 parts of water and 40 parts of water was pulverized with a sand mill until the average particle size became 0.6 μm.

Liquid C Preparation A composition consisting of 20 parts of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane, 30 parts of a 5% aqueous solution of methylcellulose, and 60 parts of water was averaged by a sand mill. It was pulverized until the diameter became 0.6 μm.

Solution D Preparation A composition comprising 20 parts of 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane, 30 parts of a 5% aqueous solution of methylcellulose, and 60 parts of water was sand milled. And pulverized until the average particle size was 0.6 μm.

Preparation of Solution E 3- (N-cyclohexyl-N-methylamino) -6-
A composition comprising 20 parts of methyl-7-phenylaminofluorane, 30 parts of a 5% aqueous solution of methyl cellulose, and 60 parts of water was pulverized by a sand mill until the average particle size became 0.6 μm.

Preparation of coating liquid for heat-sensitive recording layer Liquid A 120 parts, liquid B 80 parts, solid content 30% colloidal silica (average particle diameter 20 nm) 70 parts, solid concentration 50
% Styrene-butadiene 58 parts, 1 part of a 10% aqueous solution of sodium dioctylsulfosuccinate, and 71 parts of water were mixed and stirred to obtain a recording layer coating liquid.

Preparation of Protective Layer Coating Liquid 100 parts of a 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group and 10 parts of sodium dioctylsulfosuccinate.
% Aqueous solution 1 part, solid concentration 30% kaolin [trade name: U
W-90, manufactured by EMC] 40 parts were mixed and stirred to obtain a coating liquid for protective layer.

Formation of recording layer and protective layer PET film [trade name: A-7300, thickness 100 μ
m, manufactured by Toyobo Co., Ltd., and the coating amounts after drying the above-mentioned recording layer coating liquid and protective layer coating liquid were 5 g / m ² and 2 g / m ² , respectively.
It was sequentially coated so as to be m ² and dried to obtain a thermosensitive recording medium.

Example 2 The procedure of Example 1 was repeated, except that 4,4′-isopropylidenediphenol was used instead of 4-hydroxy-4′-isopropoxydiphenylsulfone. A thermal recording material was obtained in the same manner as in 1.

Example 3 In the preparation of the liquid A of Example 1, 15 parts of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane was added to 10 parts to prepare 3- (N
-Cyclohexyl-N-methylamino) -6-methyl-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 5 parts of 7-phenylaminofluorane was added.

[Example 4] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that in the preparation of the liquids A and B of Example 1, the average particle size of the dispersions was both 0.4 µm. It was

Comparative Example 1 In the same manner as in Example 1, except that 90 parts of C liquid and 30 parts of D liquid were used in place of 120 parts of A liquid in the preparation of the recording layer coating liquid of Example 1. A thermosensitive recording medium was obtained.

Comparative Example 2 In the preparation of the recording layer coating liquid of Comparative Example 1, 4-hydroxy-
A thermosensitive recording medium was obtained in the same manner as in Comparative Example 1 except that 4,4'-isopropylidenediphenol was used instead of 4'-isopropoxydiphenylsulfone.

Comparative Example 3 A comparative example except that 60 parts of C liquid, 30 parts of D liquid and 30 parts of E liquid were used in place of 120 parts of A liquid in the preparation of the recording layer coating liquid of Example 1. A thermal recording material was obtained in the same manner as in 1.

[Comparative Example 4] A thermosensitive recording medium was obtained in the same manner as in Comparative Example 1 except that in the preparation of the liquids C and D of Comparative Example 1, the average particle size of the dispersion was 0.4 μm. It was

[Comparative Example 5] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the average particle size of the dispersion was 1.2 μm in the preparation of the solutions A and B of Example 1. It was

[Comparative Example 6] In the preparation of C liquid, D liquid and E liquid of Comparative Example 1, the average particle diameter of the dispersion liquid was 1.2.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the thickness was changed to μm.

The following 10 types of thermal recording papers thus obtained were subjected to the following evaluation tests, and the results are shown in Table 1. (1). Recording sensitivity Recording was performed with a thermal printer [trade name: Mitsubishi SCTP-65, manufactured by Mitsubishi Electric Corporation], and the density of the obtained recorded image was measured with a Macbeth densitometer [trade name: RD914 Macbeth company]. did.

(2). Transparency The transparency of the thermosensitive recording medium is measured by the Haze meter [trade name: MO
DEL TC-H3, manufactured by Tokyo Denso Co., Ltd.].

[0040]

[Table 1]

[0041]

As is clear from the results shown in Table 1, the thermosensitive recording medium of the present invention has excellent recording sensitivity and transparency.

Claims (2)

[Claims] 1. A thermosensitive recording medium comprising a transparent support and a thermosensitive recording layer containing two or more leuco dyes and a coloring agent, wherein the two or more leuco dyes are simultaneously and A heat-sensitive recording material, characterized in that it is pulverized to have an average particle diameter of 0.8 μm or less. 2. The heat-sensitive recording according to claim 1, wherein the two or more kinds of leuco dyes are 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane and other black coloring leuco dyes. body.