JPH07186527A - Thermal recording - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a thermosensitive recording medium having excellent transparency and having high reflection density and transmission density at the time of color development. In a heat-sensitive recording material in which a heat-sensitive recording layer containing a leuco dye and a color former and a protective layer are sequentially provided on a transparent support, the heat-sensitive recording layer has an average particle diameter of 0.1 to 0. 8
μm leuco dye and coloring agent, with an average particle size of 5 to 1
A thermal recording material containing 20 nm of colloidal silica.

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 transparency and high reflection and transmission densities during color development.

[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. With the recent diversification of needs, various properties are required for the thermal recording material.
Among them, by increasing the transparency of the thermal recording material,
It can also be used for P sheets and X-ray sheets. Furthermore, when the support is a metallic sheet, it can be used for metallic tone heat sensitivity and the like. Various methods are conceivable for this purpose, but the conventional ones have drawbacks such as low density in the color-developing portion even if it is transparent, and conversely, poor transparency when the color-developing density is high.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium which is excellent in transparency and has high reflection density and transmission density at the time of color development.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have found that in a thermal recording medium in which a transparent recording medium containing a leuco dye and a color former, and a protective layer are sequentially provided on a transparent support, In addition, by containing a leuco dye and a coloring agent having an average particle diameter of 0.1 to 0.8 μm and colloidal silica having an average particle diameter of 5 to 120 nm, excellent transparency is obtained,
Moreover, they have found that a thermosensitive recording medium having a high reflection density and a high transmission density at the time of color development can be obtained, and completed the present invention.

[0005]

As described above, the heat-sensitive recording material of the present invention comprises a leuco dye and a coloring agent having an average particle diameter of 0.1 to 0.8 μm and a colloidal particle having an average particle diameter of 5 to 120 nm in the heat-sensitive recording layer. Silica is contained, but when the average particle size of the leuco dye and the color former is less than 0.1 μm, the transparency of the heat-sensitive recording material obtained by aggregating the pulverized dispersion is remarkably lowered, and further Background fog is strongly generated. Further, if the average particle diameter exceeds 0.8 μm, the transparency is lowered. The average particle size is 5 to 120 nm, preferably 1
By using a colloidal silica of 0 to 50 nm in combination with the leuco dye and the color former, the transparency of the heat-sensitive recording material is improved, but when the average particle diameter is less than 5 nm, the transmission recording density decreases. , 120 nm, transparency is not improved. The content of the colloidal silica is 5 to 30 with respect to the total solid amount of the thermosensitive recording layer.
It is desirable to contain it in the range of wt%, more preferably in the range of 8 to 25 wt%.

Various 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)-
Triarylmethane dyes such as 3- (2-methylindol-3-yl) phthalide, 4,4′-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leuco auramine, N-2,4 , 5-trichlorophenyl leuco auramine and other diphenylmethane dyes, benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and other thiazine dyes, 3-
Methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) spiropyran, 3-propyl-spiro -Spiro dyes such as dibenzopyran, lactam dyes such as rhodamine-B anilinolactam, rhodamine (p-nitroanilino) lactam, 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-7-diethylaminofluorane,
3- (N-ethyl-p-toluidino) -6-methyl-7
-Phenylaminofluorane, 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-7
-(O-chlorophenylamino) fluorane, 3-dibutylamino-7- (o-chlorophenylamino) fluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3- (N-methyl-N) Fluorane dyes such as tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane and 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane.

Various compounds are known as colorants used in combination with leuco dyes, and the following are exemplified. 4-hydroxydiphenoxide, 4-hydroxyacetophenone, 4-tert-butylphenol, 4-tert
-Octylcatechol, 4,4'-isopropylidene diphenol (bisphenol A), 4,4'-cyclohexylidene diphenol, 2,2'-dihydroxydiphenol, 2,2'-methylenebis (4-methyl-6-
tert-butylphenol), 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-se
c-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 Phenolic compounds such as propoxydiphenyl sulfone, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenol resin, phenol polymer, N- (p-toluenesulfonyl) -N'-
Urea derivatives such as (p-tolyl) urea, p-tert-butylbenzoic acid, trichlorobenzoic acid, 3-sec-butyl-
4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-
Methylbenzyl) salicylic acid, 3-chloro-5- (α-
Aromatic carboxylic acids such as methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, And these phenolic compounds, aromatic carboxylic acids, and organic acidic substances such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel polyvalent metal salts.

In the present invention, the use ratio of the leuco dye and the color-developing agent in the recording layer should be appropriately selected according to the types of the leuco dye and the color-developing agent used and is not particularly limited. When using a coloring agent, generally 1 to 7 parts by weight, preferably 1 to 4 parts by weight of an acidic substance is used per 1 part by weight of the leuco dye. The coating liquid containing these substances is generally prepared by using water as a dispersion medium and stirring with a ball mill, an attritor, a sand mill, or the like.
A leuco dye and a coloring agent are dispersed together or separately by a pulverizer to prepare a coating liquid.

In such 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 auxiliary agents 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.

In addition, 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, 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 so as to further enhance the preservability of the recorded image depending on the purpose 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.

The protective layer of the present invention comprises a water-soluble resin as a main component, and specific examples of the water-soluble resin include, for example, oxidized starch, enzyme-modified starch, cation-modified starch, esterified starch and etherified starch. Starch such as starch, cellulose derivative such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, methoxy cellulose, hydroxyethyl cellulose, completely (or incompletely) saponified polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, silicon modified polyvinyl alcohol, etc. Polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid copolymer Styrene-maleic anhydride copolymer alkali salts, isobutylene-maleic anhydride copolymer alkali salts, sodium alginate, gelatin, water-soluble polymer such as casein, polyvinyl acetate, polyurethane,
Latex such as polyacrylic acid, polyacrylic acid ester, polybutylmethacrylate, styrene / butadiene copolymer, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, styrene / butadiene / acrylic copolymer Can be mentioned. 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 of atomizing the leuco dye, color former, sensitizer and the like is not particularly limited, and for example, a method of finely pulverizing an aqueous dispersion with a horizontal mill or a vertical mill,
Emulsified and dispersed dyes, colorants, and sensitizers may be used. Among them, leuco dyes and colorants which are finely divided by emulsification and dispersion have less round diffused particles so that transparency is further improved.

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 applying a coating solution on a support and drying the coating solution by an appropriate application method such as short dwell coating, curtain coating, or die coating.

The support may be a polyester type,
Although a transparent plastic film such as a polyolefin is used, the heat-sensitive recording layer of the present invention has excellent transparency, so a colored transparent or opaque support can be used. Thus, a recorded image with excellent contrast can be obtained. The coating amount of the coating liquid for the heat-sensitive recording layer is 1 to 30 g / m ^{2 on a} dry weight basis, preferably ² to 15 g / m ^2.
Adjusted in the range of. The coating amount of the coating liquid for the protective layer is 1 to 10 g / m ² , preferably 2 to 6 g / m ² in terms of dry weight.
^{Adjusted in} the range of ² .

[0019]

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 Liquid A 10 parts of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane, 20 parts of 1,2-di (3-methylphenoxy) ethane, methylcellulose A composition consisting of 30 parts of a 5% aqueous solution of 60 parts of water and 60 parts of water was pulverized with a sand mill until the average particle size became 0.5 μm.

Preparation of Solution B 20 parts of 4-hydroxy-4′-isopropoxydiphenylsulfone, 20 parts of 5% aqueous solution of methylcellulose,
A composition comprising 40 parts of water and water was pulverized with a sand mill until the average particle size became 0.5 μm.

Preparation of coating liquid for recording layer: 120 parts of solution A, 80 parts of solution B, 70 parts of colloidal silica having a solid concentration of 30% (average particle diameter 20 nm), solid concentration of 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 Coating Liquid for Protective Layer 150 parts of 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, 10 parts of sodium dioctylsulfosuccinate
% Aqueous solution and 8 parts of epoxy modified silicone emulsion having a solid concentration of 30% were mixed and stirred to obtain a coating liquid for protective layer.

Formation of Recording Layer and Protective Layer Transparent PET film [trade name: A-7300, thickness 10]
0 μm, manufactured by Toyobo Co., Ltd., and the coating amount after drying the above coating liquid for recording layer and coating liquid for protective layer was 3 g / m ² and 4, respectively.
It was applied and dried so as to obtain g / m ^2, and subjected to a super calender treatment to obtain a heat-sensitive recording material.

Example 2 The same procedure as in Example 1 was carried out except that colloidal silica having an average particle diameter of 8 nm was used in place of colloidal silica having an average particle diameter of 20 nm in the preparation of the recording layer coating liquid of Example 1. A thermosensitive recording material was obtained.

Example 3 The same procedure as in Example 1 was carried out except that colloidal silica having an average particle diameter of 100 nm was used instead of colloidal silica having an average particle diameter of 20 nm in the preparation of the recording layer coating liquid of Example 1. A thermosensitive recording material was obtained.

[Example 4] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the dispersion liquids were pulverized to have an average particle size of 0.7 µm in the preparation of the liquids A and B.

Example 5 In the preparation of the coating liquid for protective layer of Example 1, kaolin having a solid concentration of 30% was used instead of 8 parts of the epoxy-modified silicone emulsion having a solid concentration of 30% [trade name: UW-90, EMC. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 20 parts of the dispersion liquid manufactured by the company was used.

Example 6 In the preparation of solution A, 10 parts of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane and 20 parts of 1,2-di (3-methylphenoxy) ethane were used. Instead of 10 parts of 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-phenylaminofluorane and 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane 20 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that parts were used.

[Comparative Example 1] The same procedure as in Example 1 was carried out except that colloidal silica having an average particle diameter of 3 nm was used in place of colloidal silica having an average particle diameter of 20 nm in the preparation of the recording layer coating liquid of Example 1. A thermosensitive recording material was obtained.

[Comparative Example 2] The same procedure as in Example 1 was carried out except that colloidal silica having an average particle diameter of 200 nm was used in place of colloidal silica having an average particle diameter of 20 nm in the preparation of the recording layer coating liquid of Example 1. A thermosensitive recording material was obtained.

[Comparative Example 3] A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the liquid A and the liquid B of Example 1 were prepared until the average particle size of the dispersion liquid was 1.2 μm. Got

Comparative Example 4 In the preparation of the coating liquid for the recording layer of Example 1, 70 parts of colloidal silica having a solid concentration of 30% (average particle diameter 20 nm) was replaced by amorphous silica [trade name: Mizuka Seal P-527]. A thermal recording material was obtained in the same manner as in Example 1 except that 21 parts were used.

The 10 types of heat-sensitive recording materials thus obtained were subjected to the following evaluation tests, and the results are shown in Table 1. (1). Recording density 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 by using a Macbeth densitometer [trade name: RD914 Macbeth Company. And the transmission density was measured with a transmission densitometer [trade name: Color transmission densitometer DM-500, manufactured by SCREEN]. (2). Transparency of thermosensitive recording medium Haze meter [trade name: TC-H]
IV, manufactured by Tokyo Denshoku Co., Ltd.).

[0035]

[Table 1]

[0036]

As is apparent from the results shown in Table 1, according to the present invention, a thermosensitive recording medium having excellent transparency and having high reflection density and transmission density at the time of color development was obtained.

Claims (2)

[Claims] 1. A heat-sensitive recording material comprising a transparent support, a heat-sensitive recording layer containing a leuco dye and a color former, and a protective layer, which are successively provided, and the average particle diameter of the heat-sensitive recording layer is 0.1 to 0.1.
A heat-sensitive recording material comprising a leuco dye and a coloring agent having a thickness of 0.8 μm and colloidal silica having an average particle diameter of 5 to 120 nm. 2. Colloidal silica having an average particle size of 10 to 5
The thermal recording material according to claim 1, which has a thickness of 0 nm.