JP2946811B2 - Two-color thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-color heat-sensitive recording material having a plurality of color-forming layers each having a different color tone.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive recording material has been obtained in which a color-forming image is obtained by contacting both color-forming substances by heat utilizing a color reaction between a leuco dye and a color-forming agent which forms a color upon contact with the dye. Is well known. Such a thermosensitive recording medium is relatively inexpensive, and its recording equipment is compact and its maintenance is relatively easy. Therefore, it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

[0003] However, the required performance and quality have been diversified with the expansion of applications, and for example, high sensitivity, image stabilization, multicolor recording, and the like have been demanded. In particular, since multicolor recording has a wide range of applications, many recording materials have been researched and proposed to date. 2 as an example of a multicolor thermal recording material
Although there is a color thermosensitive recording medium, a conventional two-color thermosensitive recording medium is roughly classified into the following two types. The first is a method in which a low-temperature coloring layer is colored at the time of low-temperature heating, and both a low-temperature coloring layer and a high-temperature coloring layer are colored at the time of high-temperature heating to obtain a mixed color (addition method).
The second method is to obtain a color tone of only the high-temperature coloring layer at the time of high-temperature heating by using a decoloring agent having a decoloring effect on a low-temperature coloring system at the time of high-temperature heating. ).

Recently, there has been a demand for the development of a two-color heat-sensitive recording material which emits red when heated at a low temperature and blue or black when heated at a high temperature. In such a two-color thermosensitive recording medium, when a coloring agent such as bisphenol A is used as a coloring agent for the high-temperature coloring layer, a part of the high-temperature coloring layer also develops color at the time of low-temperature heating, and the low-temperature coloring image becomes turbid. There is a defect that will occur. Such a phenomenon occurs in both the color addition method and the color erasing method.

Further, the two-color thermosensitive recording medium utilizing the decoloring method does not necessarily have sufficient storage stability of the recorded image because of the use of the decoloring agent. There is also a demand for a two-color heat-sensitive recording medium.
However, such a two-color heat-sensitive recording medium needs to use a low-temperature coloring layer as a red coloring layer because the color addition method is used, and in this case, color turbidity occurs in the low-temperature coloring layer as described above. I will.

[0006]

In view of this situation, the present inventors have solved the above-mentioned problems in the two-color heat-sensitive recording medium, and have succeeded in reducing the coloring property of the high-temperature coloring layer during low-temperature heating. As a result of extensively examining the field of colorants in order to obtain a two-color heat-sensitive recording material with extremely low color turbidity, if a specific diphenylsulfone-based colorant is selectively used as a colorant for a high-temperature coloring layer, such a purpose is obtained. Have been found to be able to be achieved efficiently, and the present invention has been completed.

[0007]

According to the present invention, at least a high-temperature coloring layer and a low-temperature coloring layer are sequentially laminated on a support,
In a two-color thermosensitive recording medium in which both coloring layers contain a leuco dye and a coloring agent, 2,4'-
A two-color heat-sensitive recording material using dihydroxydiphenylsulfone and / or 3,4-dihydroxy-4'-methyldiphenylsulfone.

[0008]

The two-color heat-sensitive recording material of the present invention has an important feature in that the above-mentioned specific dihydroxydiphenylsulfone compound is used as a coloring agent for the high-temperature coloring layer. In order to minimize the coloring of the high-temperature coloring layer at the time of low-temperature heating, it is considered advantageous to increase the melting point of the coloring agent used in the high-temperature coloring layer, but if a compound having a high melting point was simply selected, At the time of heating at a low temperature, the sensitizer in the low-temperature color-forming layer is affected, which also causes color turbidity. However, the above-mentioned specific dihydroxydiphenylsulfone compound is hardly affected by such influence, and remarkably exerts the desired effects of the present invention.

In the present invention, various known compounds can be used as the coloring agent to be contained in the low-temperature coloring layer, and examples thereof include the following. Activated clay, acid clay, attapulgite, bentonite, colloidal silica, inorganic acid substances such as aluminum silicate, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol,
β-naphthol, 4-hydroxyacetophenone, 4-
tert-octylcatechol, 2,2'-dihydroxydiphenyl, 2,2'-methylenebis (4-methyl-6-
tert-butylphenol), 4,4'-isopropylidenebis (2-tert-butylphenol), 4,4'-se
c-butyldenediphenol, 4-phenylphenol, 4,4'-isopropylidenediphenol (bisphenol A), 2,2'-methylenebis (4-chlorophenol), hydroquinone, 4,4'-cyclohexylidenediphenol, Phenolic compounds such as benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolak phenolic resin, phenolic polymer, benzoic acid, p
-Tert-butylbenzoic acid, trichlorobenzoic 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- (α, α-dimethylbenzyl)
Aromatic carboxylic acids such as salicylic acid and 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and various compounds such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel. Organic acidic substances such as salts with valent metals. Of course, the present invention is not limited to these substances, and two or more colorants can be used in combination as needed.

As the leuco dye used in the present invention, for example, the following various colorless or light-colored basic dyes are known, and may be appropriately selected from these and used. 3,3-bis (p-dimethylaminophenyl) -6
-Dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindole-3
-Yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindole-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)-
Triallylmethane dyes such as 6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydryl benzyl ether, N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine Thiazine dyes such as diphenylmethane dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue; 3-methyl-spiro-dinaphthopyran; 3-ethyl-spiro-dinaphthopyran;
Phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-
Spiro dyes such as methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, and rhodamine-B-
Anilinolactam, rhodamine (p-nitroanilino)
Lactam dyes such as lactam and rhodamine (o-chloroanilino) lactam, 3-cyclohexylamino-6-
Chlorofluorane, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran,
3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-
Diethylamino-7,8-benzofluoran, 3-diethylamino-5-methyl-7-dibenzylaminofluoran, 3-diethylamino-6,7-dimethylfluoran, 3- (N-ethyl-p-toluidino)- 7-methylfluoran, 3-diethylamino-7-N-acetyl-
N-methylaminofluoran, 3-diethylamino-7
-N-dibenzylaminofluoran, 3-diethylamino-7-N-methyl-N-benzylaminofluoran,
3-diethylamino-7-N-chloroethyl-N-methylaminofluoran, 3-diethylamino-7-N-diethylaminofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluor Oran, 3- (N-cyclopentyl-N-ethylamino)-
6-methyl-7-anilinofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-methyl-
7-phenylaminofluoran, 3-dibutylamino-
6-methyl-7-phenylaminofluoran, 3-dipentylamino-6-methyl-7-phenylaminofluoran, 3-diethylamino-7- (2-carbomethoxy-phenylamino) fluoran, 3- (N-ethyl -N
-Isoamylamino) -6-methyl-7-phenylaminofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluoran, 3-pyrrolidino-6-methyl-7- Phenylaminofluoran, 3-piperidino-6-methyl-7-phenylaminofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7
-(O-chlorophenylamino) fluoran, 3-dibutylamino-7- (o-chlorophenylamino) fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, 3- (N-methyl-N Fluoran dyes such as -tetrahydrofurfurylamino) -6-methyl-7-anilinofluoran; Of course, it is not limited to these leuco dyes, and two or more of them can be used in combination as needed.

In the two-color thermosensitive recording medium of the present invention, the color tone of the color-forming layer is adjusted by selecting the above leuco dye.
For example, when using the additive method, the low-temperature coloring layer is yellow,
It is preferable to use a color developing system that develops a single color such as red and blue and the high-temperature coloring layer be composed of a color developing system that develops a multicolor system such as green, purple and black, since the effects of the present invention can be fully exhibited. In this case, a clear color tone can be easily obtained,
It is preferable to use a black-coloring leuco dye for the high-temperature color-forming layer, especially 3-diethylamino-6-methyl-7-.
Phenylaminofluoran, 3-dibutylamino-6
Methyl-7-phenylaminofluoran, 3-dipentylamino-6-methyl-7-phenylaminofluoran, 3- (N-ethyl-N-isoamylamino) -6
Methyl-7-phenylaminofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-
Phenylaminofluoran, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-phenylaminofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenyl Aminofluoran,
When 3-dibutylamino-7- (o-chlorophenylamino) fluoran is used in combination with a specific dihydroxydiphenylsulfone, there is no color fog at the time of low-temperature heating, and an extremely clear black color image can be obtained at the time of high-temperature heating. Therefore, it is particularly preferable. Further, among these, when 3-dibutylamino-6-methyl-7-phenylaminofluoran and 3-dipentylamino-6-methyl-7-phenylaminofluoran are used, the whiteness is maintained even when stored under high temperature conditions. This is most preferable because a two-color heat-sensitive recording material with a very small decrease in image quality can be obtained.

In the present invention, the use ratio of the leuco dye to the color former in each color-forming layer is not particularly limited, but generally 1 to 5 parts by weight of the leuco dye per 1 part by weight of the leuco dye.
It is desirable to use 0 parts by weight, preferably in the range of about 1.5 to 8 parts by weight.

[0013] In the coating liquid for forming the color forming layer, for example, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
Gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride 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 / vinyl acetate emulsion, etc. It is added in the range of about 50% by weight.

As the pigment component, for example, diatomaceous earth, calcined diatomaceous earth, kaolin, calcined kaolin, white carbon, magnesium carbonate, calcium carbonate, zinc oxide, aluminum oxide, titanium oxide, silicon oxide, aluminum hydroxide, barium sulfate, zinc sulfate And inorganic pigments such as talc, clay and calcined clay; organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch granules.

Further, various other auxiliaries may be added to the coating solution for forming the color forming layer, if necessary, for example, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, lauryl alcohol sulfate. -Dispersants such as sodium salts, alginates and fatty acid metal salts, ultraviolet absorbers such as benzophenone type and triazole type, other antifoaming agents, fluorescent dyes and coloring dyes. Also, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., fatty acid amides such as stearic acid amide, methylene bisamide stearate, oleic acid amide, palmitic acid amide, coconut fatty acid amide, 2 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-3-methylphenol),
1,1,3-tris (2-methyl-4-hydroxy-5
-Tert-butylphenol) hindered phenols such as butane, dibenzyl terephthalate, 1,2-di (3
-Methylphenoxy) ethane, 1,2-diphenoxyethane, 4,4'-ethylenedioxy-bis-benzoic acid diphenylmethyl ester, naphthol derivatives such as 1-naphthylbenzyl ether and 2-naphthylbenzyl ether, 1-hydroxy Naphthoic acid derivatives, such as -2-naphthoic acid phenyl ester and 2-hydroxy-3-naphthoic acid benzyl ester, and various known heat-fusible substances can also be used in combination. In the coating liquid of the low-temperature coloring layer,
Among the above-mentioned heat-fusible substances, the melting point is 70 to 120.
° C, preferably a compound having a melting point of 80 to 100 ° C.

In the present invention, the coating amount of each color forming layer is not particularly limited, but is generally 1.5 to 1 in terms of dry weight.
It is adjusted within a range of about 2 g / m ² . Further, in the present invention, it is of course possible to provide an intermediate layer between the high-temperature coloring layer and the low-temperature coloring layer. Further, when the decoloring method is employed, the intermediate layer or a separately provided decoloring layer may be used. And various known color erasing agents.

In the coating liquid for forming the intermediate layer, various adhesives, dispersants, and the like as described in the description of the color-forming layer coating liquid are included.
Including lubricants, heat-fusible substances, inorganic pigments, organic pigments, etc.
In addition, various auxiliaries such as an antifoaming agent, an ultraviolet absorber, a fluorescent dye, and a coloring dye can be appropriately compounded. Further, the coating amount of the intermediate layer may be adjusted in a range of about 1 to 10 g / m ² . Examples of the decoloring agent include aliphatic amines, piperidines, piperazines, pyridines, imidazoles, imidazolines, morpholines, guanidines, amidines, polyethers, glycols, aromatic amides and the like. More specifically, it is described in various known documents such as the following. Alkylene oxide adducts of bisphenols (JP-A-54-139741); ethylene oxide adducts of terephthalic acid (JP-A-55-25306); long-chain 1,2-glycol [JP-A-55-27217] Glycerin fatty acid ester [JP-A-55-113593]; urea derivative [JP-A-55-139290]; alkylene oxide adduct of linear glycol [JP-A-55-152094]
JP-A-56-40588] Solid alcohol [JP-B-50-17865]; Polyether and polyethylene glycol derivatives [JP-B Sho.
No. 50-17867, Japanese Patent Publication No. Sho 50-17868]; Nitrogen-containing crystalline organic compound (Japanese Patent Publication No. Sho 51-19991); Guanidine derivative (Japanese Patent Publication No. Sho 51-29024); amine or quaternary ammonium salt [JP-A-5018048]; disubstituted amide compounds of aliphatic and aromatic carboxylic acids [
61-120792, JP-A-61-169277] and the like. Other examples include amidines and piperidines. Examples of the amidines include N, N'-diphenylformamidine, N, N'-di-o-tolylformamidine, and N, N'-diphenylformamidine.
N'-diphenylbenzamidine, N, N'-di-p-
Tolyl-N'-phenylbenzamidine, N, N'N "
N "-tetraphenyl-heptadiamidine, N, N '
N "N" -tetraphenyl-p-xylylenediamidine and the like. Examples of the piperidine include (2,
2,6,6-tetramethyl-4-piperidyl / tridecyl) -1,2-ethanedicarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,3 4-butanetetracarboxylate, tetrakis (1-methyl-4-piperidyl) -1,
2,3,4-butanetetracarboxylate, $ 2
2,6,6-tetramethyl-4-piperidyl / β, β,
β'β'-tetramethyl-3,9- [2,4,8,10-
Tetraoxaspiro (5,5) undecane] diethyl
-1,2,3,4-butanetetracarboxylate,
{1,2,2,6,1-pentamethyl-4-piperidyl / β, β, β′β′-tetramethyl-3,9- [2
[4,8,10-tetraoxaspiro (5,5) undecane] diethyl} -1,2,3,4-butanetetracarboxylate, (1,2,2,6,6-pentamethyl-4
-Piperidyl) -1-heptanecarboxylate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate and the like. The amount of the decoloring agent used is about 0.1 to 20% by weight, more preferably about 0.5 to 6% by weight, based on the total weight of the leuco dye and the color former mixed in the low-temperature coloring layer. Adjusted in range.

In the two-color heat-sensitive recording material of the present invention, the coating solution for each color-forming layer or intermediate layer is generally prepared by using water as a dispersion medium and appropriately using a ball mill, an attritor, a sand mill or the like, and a pulverizer. You. The method for forming each color-forming layer and the intermediate layer is not particularly limited, and is formed by a method of applying and drying a coating solution on a support by, for example, air knife coating, blade coating, or the like according to a conventionally known technique. .

The support is also not particularly limited, and high-quality paper, base paper made by a Yankee machine, single-side glossy base paper,
Paper such as double-sided glazed base paper, cast-coated paper, art paper, coated paper, medium-coated paper, synthetic fiber paper, synthetic resin film and the like are appropriately used. Further, after applying and drying the color-forming layer and the intermediate layer, if necessary, a smoothing treatment such as super calendaring can be performed.

Further, various variations are possible without departing from the gist of the present invention. For example, an overcoat layer is provided on the color-forming layer for the purpose of protecting the color-forming layer, or an undercoat layer is formed on the support in advance. Various known techniques in the field of thermal recording media can be added, such as coating or providing a conductive layer or an adhesive layer on the back surface. Also, the color-forming material and color tone constituting each color-forming layer can be variously varied, and can be appropriately selected according to the intended two-color thermosensitive recording medium.

The two-color heat-sensitive recording material of the present invention thus obtained has excellent color separation properties, does not cause color turbidity when heated at a low temperature, and is capable of forming a clear color image. It is a recording medium.

[0022]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto. Unless otherwise specified, “parts” and “%” in the examples indicate “parts by weight” and “% by weight”, respectively.

Example 1 Preparation of Solution A 3-Dibutylamino-6-methyl-7-phenylaminofluoran 10 parts Methylcellulose 5% aqueous solution 5 parts Water 25 parts This composition was sand-milled to have an average particle diameter of 1.5 μm. Until ground. Preparation of Solution B 2,4'-dihydroxydiphenylsulfone 30 parts Methylcellulose 5% aqueous solution 30 parts Water 70 parts This composition was pulverized by a sand mill until the average particle diameter became 1.5 μm.

Solution C Preparation 3-Diethylamino-7-chlorofluorane 10 parts 1,2-di (3-methylphenoxy) ethane 20 parts Methylcellulose 5% aqueous solution 15 parts Water 80 parts It was pulverized to 1.5 μm. Solution D preparation 4,4'-isopropylidene diphenol 30 parts Methyl cellulose 5% aqueous solution 30 parts Water 70 parts This composition was pulverized with a sand mill until the average particle diameter became 1.5 μm.

[Preparation of Coating Solution for High Temperature Thermosensitive Recording Layer] Solution A 40
Parts, 130 parts of liquid B, 6 parts of a silicon oxide pigment (trade name: Mizukasil P-527, manufactured by Mizusawa Chemical Co., Ltd.), 30 parts of a 20% aqueous starch oxide solution, and 54 parts of water were mixed and stirred to obtain a coating liquid. [Preparation of Coating Solution for Low Temperature Thermosensitive Recording Layer] Solution C 125 parts, Solution D 1
30 parts, silicon oxide pigment (trade name: Mizukasil P-52)
7, Mizusawa Chemical Co., Ltd.) 10 parts, 20% oxidized starch aqueous solution 50
And 85 parts of water were mixed and stirred to obtain a coating liquid. The high-quality paper having a basis weight 50 g / m ² [Formation of recording layer], the high-temperature heat sensitive recording layer coating solution, a low-temperature heat-sensitive recording layer coating solution, the order of the coating amount after drying each 4g / m ^2, 3 g / M ² and dried by super calendering to obtain a two-color heat-sensitive recording material.

Example 2 In the preparation of Solution C, except that 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide was used instead of 3-diethylamino-7-chlorofluoran. A two-color heat-sensitive recording material was obtained in the same manner as in Example 1.

Example 3 In the preparation of solution A, 3-dibutylamino-6-methyl-
A two-color heat-sensitive recording material was obtained in the same manner as in Example 1 except that 3-dipentylamino-6-methyl-7-phenylaminofluoran was used instead of 7-phenylaminofluoran.

Example 4 In the preparation of solution A, 3-dibutylamino-6-methyl-
Instead of 7-phenylaminofluoran, 3- (N-
Except that ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-phenylaminofluoran was used.
A two-color thermosensitive recording medium was obtained in the same manner as in Example 1.

Example 5 In the preparation of solution A, 3-dibutylamino-6-methyl-
Instead of 7-phenylaminofluoran, 3-dibutylamino-7- (o-chlorophenylamino) fluoran was used, and in the preparation of solution B, 3,4-dihydroxy- A two-color heat-sensitive recording material was obtained in the same manner as in Example 1 except that 4'-methyldiphenylsulfone was used.

Comparative Examples 1 to 3 In the preparation of solution B, instead of 2,4'-dihydroxydiphenylsulfone, 4,4'-isopropylidenediphenol (Comparative Example 1), 4-hydroxy-4'-isopropylidenediphenyl were used. Three kinds of two-color thermosensitive recording materials were obtained in the same manner as in Example 1 except that sulfone (Comparative Example 2) and 4,4'-cyclohexylidenediphenol (Comparative Example 3) were used.

Comparative Example 4 A two-color heat-sensitive recording material was prepared in the same manner as in Example 2 except that 4,4'-isopropylidenediphenol was used instead of 2,4'-dihydroxydiphenylsulfone in the preparation of solution B. I got

Example 6 Preparation of Solution E 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide 10 parts Methylcellulose 5% aqueous solution 5 parts Water 25 parts This composition was sand-milled to have an average particle diameter of 1 It was pulverized to 0.5 μm. Preparation of solution F Tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate 10 parts Methylcellulose 5% aqueous solution 5 parts Water 25 parts This composition was sand-milled. And pulverized until the average particle diameter becomes 1.5 μm.

[Preparation of Coating Solution for High Temperature Thermosensitive Recording Layer] Solution E 40
Part, B part 130 parts, kaolin (trade name: UW-90, E
MC Co., Ltd.) (40 parts), 100 parts of a 20% oxidized starch aqueous solution, and 90 parts of water were mixed and stirred to obtain a coating liquid. [Preparation of Coating Solution for Decoloring Intermediate Layer] 40 parts of solution F and 40 parts of a 10% aqueous solution of polyvinyl alcohol were mixed and stirred to obtain a coating solution.

[Preparation of Coating Solution for Low Temperature Thermosensitive Recording Layer] Solution C 12
5 parts, 130 parts of solution D, 10 parts of a silicon oxide pigment (trade name: Mizukasil P-527, manufactured by Mizusawa Chemical Co., Ltd.), 50 parts of a 20% starch oxide aqueous solution, and 85 parts of water were mixed and stirred to obtain a coating liquid. [Formation of Recording Layer] Coating solution for high-temperature heat-sensitive recording layer, coating solution for decoloring intermediate layer, and coating solution for low-temperature heat-sensitive recording layer were coated on high-quality paper having a basis weight of 50 g / m ² in this order after drying. Is 7g /
m ² , 3 g / m ² , 3 g / m ² , coating and drying, and supercalendering to obtain a two-color heat-sensitive recording material.

Comparative Example 5 A two-color heat-sensitive recording material was prepared in the same manner as in Example 6, except that 4,4'-isopropylidenediphenol was used in place of 2,4'-dihydroxydiphenylsulfone in the preparation of solution B. Obtained.

The eleven kinds of two-color heat-sensitive recording media thus obtained were evaluated by the following methods. [Recording conditions] Thermal printer (PS-8600, manufactured by ROHM)
Using a thermal head: 8 dots / mm, heating resistance:
Approximately 1300 ohm / dot, main scanning recording speed: 20msec /
line, sub-scan: 32 line / mm, head input: 0.44
The recording was performed under the conditions of W / dot, low-temperature coloring energy: 0.26 mJ, and high-temperature coloring energy: 1.06 mJ, and the density of the recording portion was measured by a Macbeth densitometer (RD914, manufactured by Macbeth). It described in. In addition, red,
The densities of the blue and black recorded images were measured using red, blue and black filters, respectively. The density of black (or blue) fog based on the high-temperature coloring layer during low-temperature coloring is measured using a blue filter when the low-temperature coloring layer is red, and using a yellow filter when blue. did. When the density of black (or blue) fog exceeds 0.2, the sharpness of both red and blue colors is significantly reduced.

[0037]

[Table 1]

[0038]

The color image obtained by the two-color heat-sensitive recording material of the present invention has almost no color mixing in the low-temperature color image, and has good recording sensitivity for the high-temperature color image.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A 1-275185 (JP, A) JP-A 63-252785 (JP, A) JP-A 63-209992 (JP, A) JP-A 63-252 3991 (JP, A) JP-A-62-35882 (JP, A) JP-A-56-127486 (JP, A) JP-A-1-288484 (JP, A) JP-A-63-1589 (JP, A) JP-A-62-299382 (JP, A) JP-A-62-270380 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/28-5/34

Claims (1)

(57) [Claims] 1. A two-color thermosensitive recording medium comprising a support and at least a high-temperature color-forming layer and a low-temperature color-forming layer sequentially laminated, and both color-forming layers contain a leuco dye and a coloring agent. A two-color heat-sensitive recording material characterized by using 2,4'-dihydroxydiphenylsulfone and / or 3,4-dihydroxy-4'-methyldiphenylsulfone as a coloring agent.