JPH05169826A - Two-color thermal recording material - Google Patents

Abstract

PURPOSE:To provide a two-color thermal recording material of a black.green color developing system forming a sharp black color image at low temp. and a sharp green color image at high temp. and extremely excellent in the contrast between both hues. CONSTITUTION:In a two-color thermal recording material wherein at least a high temp. color forming layer, an intermediate layer containing a color erasing agent and a low temp. color forming layer are successively laminated to a support and both color forming layers contain leuco dyes and developers and the low temp. color forming layer is a black color forming system, a leuco dye of a green color developing system whose reflectivity after the development of a color is 35% or more at 460-480nm and 20% or less at 600nm is used in the high temp. color forming layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-color thermosensitive recording medium which has two color-developing layers each of which develops a different color tone and which develops black at a low temperature and green at a high temperature.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive recording material which utilizes a coloring reaction between a leuco dye and a coloring agent which develops a color by contacting with the dye, and by contacting both color-forming substances with heat to obtain a color-developed image. Is well known. Since such a thermal recording medium is relatively inexpensive and the recording device is compact and its maintenance is relatively easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

However, the performances and qualities required have been diversified with the expansion of applications, and for example, high sensitivity, image stabilization, multicolor recording, etc. have been demanded. In particular, because of its wide range of application for multicolor recording, many recording bodies have been proposed to date. A two-color heat-sensitive recording material is an example of the multi-color heat-sensitive recording material, and the conventional two-color heat-sensitive recording material is roughly classified into the following two. The first is a method (coloring method) in which the low temperature coloring layer is colored during low temperature heating, and both the low temperature coloring layer and the high temperature coloring layer are colored during high temperature heating (coloring method), and the second method is high temperature heating. A method to obtain the color tone of only the high temperature color layer at high temperature heating by using together with a color erasing agent that has an erasing effect on the color development system of low temperature color development (erasing method)
Is.

In the first method, a relatively pale color is usually developed at a low temperature, and a dark color tone is obtained at a high temperature.
However, in the second method, a dark color is produced at low temperature,
It is possible to obtain a light color tone at high temperature, and black recording with high coloring sensitivity is generally preferred from the viewpoint of recording frequency. Therefore, a two-color thermosensitive recording medium using a black coloring system on the low temperature coloring layer side is most suitable. It is common. In the past, only a two-color thermosensitive recording material that develops black and red has been put into practical use for scoring, proofing, plotting, etc. However, recently, for the purpose of emphasizing safety indications, the development of a two-color thermal recording material that develops green on the high temperature side has been demanded. When a green-coloring leuco dye is used, a slight amount of black color remains and edging affects, so the actual situation is that a recorded image with a sharp contrast that is satisfactory in actual use has not been obtained. ..

[0005]

In view of the above situation, the present inventors have investigated the characteristics of green-coloring leuco dyes in order to solve the above-mentioned problems in a black / green color two-color thermosensitive recording medium. As a result of extensive studies, it has been found that such a purpose can be efficiently achieved by selectively using a dye having a specific reflectance as the green-coloring dye of the high-temperature color-developing layer, and has completed the present invention.

[0006]

According to the present invention, at least a high-temperature color-developing layer, an intermediate layer containing a decoloring agent, and a low-temperature color-developing layer are sequentially laminated on a support, and both color-developing layers are colored with a leuco dye. In a two-color thermosensitive recording medium containing an agent and having a low-temperature color-developing layer of a black color-developing system, the high-temperature color-developing layer has a reflectance of 46 after coloring.
35% or more at 0 to 480 nm and 20 at 600 nm
A two-color heat-sensitive recording material characterized by using a green-coloring leuco dye whose content is less than or equal to%.

[0007]

The two-color heat-sensitive recording material of the present invention has an important feature in that the green color-forming dye having the above-mentioned specific reflectance is used as the leuco dye in the high temperature color-developing layer.
That is, according to the results of studies by the present inventors, the reflection spectrum of the leuco black dye after color development has broad absorption peaks around 440 to 480 nm and around 540 to 600 nm. Also, the reflection spectrum after color development has the same absorption peaks in the vicinity of 440 to 480 nm and 580 to 600 nm, so that it is clear that the contrast with black is low and the sharpness is insufficient. In particular, it was revealed that the reflection spectrum of a normal green leuco dye after color development has a strong absorption in the vicinity of 440 to 480 nm, so that the sharpness is greatly reduced.

[0008] Therefore, based on such knowledge, as a result of further diligent research, the absorption peak is below 440 nm.
It has been found that a vivid contrast with black can be obtained by selectively using a green-coloring dye having relatively small absorption around 40 to 480 nm. The reflectance of the green color image when the color was developed at 150 ° C. after the high temperature thermosensitive recording layer was formed was 4
35% or more at 60 to 480 nm, preferably 50 to 80
%, And it was found that a recorded image of black / green color development having an extremely sharp contrast can be obtained by selectively using a green color-forming leuco dye whose content is 20% or less at 600 nm. The color tone of green is not particularly limited, and an image having extremely excellent sharpness can be obtained as a black / green color heat-sensitive recording medium in practice even if the color tone is slightly bluish.

Specific examples of the green-coloring leuco dye having the above-mentioned properties, which are used in the high-temperature color-developing layer, are not particularly limited, but include, for example, 3,3-bis (4-diethylamino-2-). Ethoxyphenyl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (4-N-phenyl-N-ethylamino-2
-Ethoxyphenyl) -4-azaphthalide and other azaphthalides, 3,6-bis (dimethylamino) fluorene spiro (9,3 ')-6'-dimethylaminophthalide,
3,6-bis (dimethylamino) fluorene spiro (9,3 ')-6'-diethylaminophthalide, 3,6
-Bis (diethylamino) fluorene spiro (9,
3 ')-6'-Dimethylaminophthalide, 3,6-bis (diethylamino) fluorenspiro (9,3')-
Fluorene phthalides such as 6'-diethylaminophthalide and 3,6-bis (dimethylamino) fluorenspyro (9,3 ')-6'-dipropylaminophthalide can be mentioned. And among these, 3,3-bis (4-
Diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (4-N-phenyl-N-ethylamino-
2-ethoxyphenyl) -4-azaphthalide, 3,6-
Bis (dimethylamino) fluorene spiro (9,3 ')
The use of such dyes is one of the preferred embodiments of the present invention, since the desired effect of the present invention is achieved extremely significantly by using at least one selected from -6'-dimethylaminophthalide. ..

In the two-color thermosensitive recording medium of the present invention, specific examples of the coloring agent contained in the color forming layer include, for example, activated clay, acid clay, attapulgite, bentonite, colloidal silica, and 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'-sec-butyldendiphenol, 4-phenylphenol, 4,4'- Isopropylidene diphenol (bisphenol A), 2,2 '
-Methylenebis (4-chlorophenol), hydroquinone, 4,4'-cyclohexylidene diphenol, 4
-Benzyl 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, 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 and aromatic carboxylic acids, such as zinc, magnesium, aluminum, calcium and titanium. Examples thereof include organic acidic substances such as salts with polyvalent metals such as manganese, tin, and nickel. Of course, the substances are not limited to these substances, and if necessary, two or more kinds of coloring agents can be used in combination.

Examples of the leuco dye to be incorporated in the low temperature color forming layer include the following various dyes, which are appropriately selected from these and used alone or in combination to form a black color forming color forming layer. .. It is also possible to use these dyes in the high temperature color-developing layer in combination as long as the desired effects of the present invention are not impaired. 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-methylindole-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-phenylindole-
Triylmethane dyes such as 3-yl) -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoauramine, N-2,4,5-. Diphenylmethane dyes such as trichlorophenyl leuco auramine, benzoyl leuco methylene blue, thiazine dyes such as p-nitrobenzoyl leuco methylene blue, 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-dibenzopyran and other spiro dyes, rhodamine-B-anilinolactam, rhodamine (p- Nitroanilino) Lacta , Rhodamine (o-chloroanilino) lactam dyes such lactam, 3-cyclohexylamino-6-chloro fluoran, 3-dimethylamino -
7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7,8-benzofluorane, 3-diethylamino-5-methyl-7-dibenzylaminofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N-ethyl-p-toluidino) )
-7-Methylfluorane, 3- (N-ethyl-p-toluidino) -7- (N-phenyl-N-methylamino) fluorane, 3-diethylamino-7-N-acetyl-N
-Methylaminofluorane, 3-diethylamino-7-
N-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane, 3
-Diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-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-dibutylamino-6
-Methyl-7-phenylaminofluorane, 3-dipentylamino-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-N-) Fluorane dyes such as tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane. Of course, it is not limited to these leuco dyes, and if necessary, 2
It is also possible to use two or more kinds in combination.

In the two-color thermosensitive recording medium of the present invention, the black color-forming leuco dye as described above is used in the low-temperature color-developing layer.
The color tone is appropriately adjusted depending on the leuco dye used, but particularly 3-diethylamino-6-methyl-7-phenylaminofluorane and 3-dibutylamino-6-methyl-7-phenylaminofluorane. , 3-dipentylamino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-isoamylamino)-
6-methyl-7-phenylaminofluorane, 3- (N
-Cyclohexyl-N-methylamino) -6-methyl-
7-phenylaminofluorane, 3- (N-ethyl-N
-Tetrahydrofurfurylamino) -6-methyl-7-
When phenylaminofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluorane and 3-dibutylamino-7- (o-chlorophenylamino) fluorane are selectively used The use of these dyes is preferable in the present invention because a very clear black color image is obtained, and in the combination with the specific green color-forming leuco dye of the present invention, much better contrast is obtained. This is one of the embodiments.

The ratio of the leuco dye to the coloring agent in each color forming layer is not particularly limited, but generally 1 to 50 parts by weight of the coloring agent, preferably 1 part by weight of the leuco dye. It is desirable to use it in the range of about 1.5 to 8 parts by weight.

In the coating liquid for forming the color forming layer, as the adhesive component, 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-based 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. Inorganic pigments such as talc, clay, and calcined clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch granules can be added.

Further, various other auxiliaries may be added to the coating solution for forming the color forming layer, if necessary. For example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, and lauryl alcohol sulfate. Examples thereof include dispersants such as sodium salts, alginates and fatty acid metal salts, ultraviolet absorbers such as benzophenone and triazole, defoaming agents, fluorescent dyes and coloring dyes.

Lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide and coconut fatty acid amide. , 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) butane and other hindered phenols, dibenzyl terephthalate, 1,2-
Naphthol derivatives such as di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 4,4'-ethylenedioxy-bis-benzoic acid diphenylmethyl ester, 1-naphthylbenzyl ether and 2-naphthylbenzyl ether, A naphthoic acid derivative such as 1-hydroxy-2-naphthoic acid phenyl ester and 2-hydroxy-3-naphthoic acid benzyl ester, and various known heat-fusible substances can be used in combination.

In the coating liquid for the low temperature color forming layer, it is desirable to use a compound having a melting point of 70 to 120 ° C., preferably a melting point of 80 to 100 ° C., among the above-mentioned heat fusible substances. The coating amount of each color forming layer is not particularly limited, but is generally adjusted in the range of about 1.5 to 12 g / m ² in dry weight. In the heat-sensitive recording material of the present invention, the intermediate layer has a decolorizing layer as a main component, but various adhesives such as those described in the description of the coloring layer coating liquid are contained in the coating liquid forming the intermediate layer. Agents, dispersants, lubricants, heat-fusible substances, inorganic pigments,
In addition to organic pigments, various other auxiliaries such as defoaming agents, ultraviolet absorbers, fluorescent dyes, and coloring dyes can be appropriately added.

The coating amount of the intermediate layer is 1 to 10 g / m ^2.
It may be adjusted within a certain range. The layer structure of the intermediate layer is not limited to a single layer, and two or more layers containing a decoloring agent as a main component may be laminated. In particular, a pigment may be formed on the decoloring layer containing a decoloring agent as a main component. An intermediate layer having a two-layer structure in which a layer containing a heat-fusible substance as a main component is laminated is excellent in the desired effects of the present invention, and is therefore one of the preferred embodiments.

Examples of the decolorizing agent include aliphatic amines,
Piperidines, piperazines, pyridines, imidazoles, imidazolines, morpholines, guanidines,
Amidines, polyethers, glycols, aromatic amides and the like are used, but specifically, the substances described in various publicly known documents as described below can be appropriately used. Alkylene oxide adducts of bisphenols [JP-A-54-13
9741]; ethylene oxide adduct of terephthalic acid [JP-A-55-25306]; long-chain 1,2-glycol [JP-A-55-27217]; glycerin fatty acid ester [JP-A-55- No. 113593]; Urea derivative [JP-A-55-55]
139290]; alkylene oxide adduct of linear glycol [JP-A-55-152094]; morpholine derivative [JP-A-56-40588] solid alcohol [JP-B-50-17]
865]; polyether and polyethylene glycol derivatives [JP-B-50-17867, JP-B-50-1786]
No. 8]; nitrogen-containing crystalline organic compounds [Japanese Patent Publication No. 51-1999]
No. 1]; guanidine derivative [JP-B-51-29024]; amine or quaternary ammonium salt [JP-A-50-18
No. 048]; di-substituted amide compounds of aliphatic and aromatic carboxylic acids [JP-A-61-120792 and JP-A-61-1692]
77 gazette] etc.

In the two-color heat-sensitive recording material of the present invention, it is particularly preferable to use amidines or piperidines as a decoloring agent. Specific examples of amidines include N,
N'-diphenylformamidine, N, N'-di-o-
Trilformamidine, N, N′-diphenylbenzamidine, N, N′-di-p-tolyl-N′-phenylbenzamidine, N, N ′, N ″, N ″ ′-tetraphenyl-heptadiamidine, N, N ′, N ″, N ′ ″-tetraphenyl-p-xylylene diamidine and the like can be mentioned. In addition, specific examples of piperidines include (2, 2,
6,6-Tetramethyl-4-piperidyl / tridecyl)
-1,2-ethanedicarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, tetrakis (1-methyl-4-) Piperidyl) -1,
2,3,4-butane tetracarboxylate, {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-butane tetracarboxylate,
{1,2,2,6,6-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 these decoloring agents to be used is 0.1 to 20% by weight, more preferably 0.5 to 6% by weight, based on the total weight of the leuco dye and the coloring agent compounded in the low temperature color forming layer. %
It is preferable to adjust the range.

In the two-color thermosensitive recording medium 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 stirrer / pulverizer such as a ball mill, attritor or sand mill. It The method for forming each color forming layer and the intermediate layer is not particularly limited, and it is formed by a method of coating and drying the coating solution on the support by, for example, air knife coating, blade coating, or the like according to a conventionally known and commonly used technique. ..

The support is also not particularly limited, and high-quality paper, base paper made by Yankee machine, single-sided gloss base paper,
Papers such as double-sided glossy base paper, cast coated paper, art paper, coated paper, medium coated paper, synthetic fiber paper, synthetic resin film, etc. are appropriately used. In addition, apply a coloring layer or intermediate layer
After drying, a smoothing treatment such as super calendering can be applied if necessary.

Various variations are possible within the scope of the present invention. For example, an overcoat layer may be provided on the color forming layer for the purpose of protecting the color forming layer, or an undercoat layer may be previously formed on the support. Various known techniques in the field of heat-sensitive recording materials can be added, such as coating or providing a conductive layer or an adhesive layer on the back surface. Further, various kinds of variations can be applied to color-forming materials and color tones constituting each color-forming layer, and they 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 is an excellent two-color heat-sensitive recording material capable of forming an image having a clear color tone for both black and green colors and an extremely good contrast between both colors.

[0027]

EXAMPLES 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, "part" and "%" in the examples mean "part by weight" and "% by weight", respectively.

Example 1 Preparation of Liquid A 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide 10 parts Methylcellulose 5% aqueous solution 5 parts Water 25 parts This composition was sand milled to give an average particle size of It was pulverized to a size of 1.5 μm. Preparation of Solution B 4,4′-Cyclohexylidenediphenol 30 parts Methylcellulose 5% aqueous solution 30 parts Water 70 parts This composition was ground with a sand mill until the average particle size became 1.5 μm.

Preparation of Solution C Tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate 50 parts Methylcellulose 5% aqueous solution 25 parts Water 110 parts The product was ground with a sand mill until the average particle size became 1.5 μm. Preparation of liquid D 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane 10 parts 1,2-di (3-methylphenoxy) ethane 20 parts Methylcellulose 5% aqueous solution 15 parts water 80 parts The composition was ground with a sand mill until the average particle size became 1.5 μm.

[Preparation of Coating Liquid for High Temperature Thermosensitive Recording Layer] Liquid A 20
Part, B solution 65 parts, kaolin (trade name: UW-90, EM
C) 60 parts, 100 parts 20% aqueous solution of oxidized starch, water 1
55 parts were mixed and stirred to obtain a coating liquid. [Preparation of Coating Solution for Decoloring Intermediate Layer] 185 parts of C liquid, 50 parts of 20% aqueous solution of oxidized starch and 65 parts of water were mixed and stirred to prepare a coating solution. [Preparation of coating liquid for low temperature thermosensitive recording layer] 125 parts of solution D, solution B 1
30 parts, silicon oxide pigment (trade name: Mizukasil P-52
7, manufactured by Mizusawa Chemical Co., Ltd.) 20 parts, 20% aqueous solution of oxidized starch 10
0 part and 125 parts of water were mixed and stirred to obtain a coating liquid. [Formation of recording layer] A high-quality paper having a basis weight of 50 g / m ² is coated with a coating solution for a high-temperature heat-sensitive recording layer, a coating solution for a decoloring intermediate layer and a coating solution for a low-temperature heat-sensitive recording layer in this order after drying 7g / each
A two-color heat-sensitive recording material was obtained by applying and drying the coating solution so as to have m ² , 3 g / m ² , and 4 g / m ^2, and applying it on a super calender.

Example 2 In preparation of solution D, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane was replaced by 3-dibutylamino-6-methyl-7-phenyl. A two-color thermosensitive recording medium was obtained in the same manner as in Example 1 except that aminofluoran was used.

Example 3 In preparation of solution A, 3- (4-diethylamino-2-ethoxyphenyl) -3- (was used instead of 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide. 4-N-phenyl-N-ethylamino-2
A two-color thermosensitive recording medium was obtained in the same manner as in Example 1 except that -ethoxyphenyl) -4-azaphthalide was used.

Example 4 In the preparation of solution A, 3,6-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide was replaced with 3,6-bis (dimethylamino) fluorene spiro (9,3 '). ) -6'-Dimethylaminophthalide was used, and a two-color thermosensitive recording medium was obtained in the same manner as in Example 1.

Comparative Example 1 In preparation of solution A, 3-diethylamino-7- (N, N-dibenzylamino) fluorane was used in place of 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide. A two-color thermosensitive recording medium was obtained in the same manner as in Example 1 except that was used.

Comparative Example 2 In the preparation of solution A, 3- (N-ethyl-p-toluidino) -7- (N was used instead of 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide. −
A two-color thermosensitive recording medium was obtained in the same manner as in Example 1 except that phenyl-N-methylamino) fluorane was used.

The six kinds of two-color thermosensitive recording materials thus obtained were evaluated by the following methods. [Recording conditions] Thermal printer (PS-8600, manufactured by ROHM)
Thermal head: 8 dots / mm, heating resistance:
Approximately 1300 ohm / dot, main scanning recording speed: 20 msec /
line, sub-scan: 32 line / mm, head input: 0.44
Recording was carried out under the conditions of W / dot, low temperature color development energy: 0.26 mJ, high temperature color development energy: 1.06 mJ, and the density of the recording part was measured with a Macbeth densitometer (Macbeth RD914 type), and the results are shown in Table 1. Described in. The densities of the black and green recorded images were measured by using black filters and blue filters, respectively.

[Measurement of reflectance of high-temperature color-developing layer] The reflectance of the high-temperature color-developing layer was measured at 150 ° C. after formation of the high-temperature thermosensitive recording layer.
Color is developed for 10 seconds, and a spectrophotometer (UVIDEC-
505, manufactured by JASCO Corporation) was used to measure the reflectance at each wavelength, and the results are also shown in Table 1. [Clearness of Black / Green Colored Image] It was visually determined according to the following criteria. ⊚: The green color tone is very clear and the contrast with the black color is extremely good. ◯: The green color tone is clear and the contrast with the black color is good. X: The color tone of the green color is turbid and unclear, and the contrast with the black color is insufficient.

[0038]

[Table 1]

[0039]

EFFECT OF THE INVENTION In the color image obtained by the two-color thermosensitive recording medium of the present invention, both the black color image at low temperature and the green color image at high temperature are clear, and the contrast of the color tone of both images is extremely excellent. ..

Claims (2)

[Claims] 1. A high-temperature color-developing layer, an intermediate layer containing a decoloring agent, and a low-temperature color-developing layer are sequentially laminated on a support, both color-developing layers containing a leuco dye and a color-developing agent, and low-temperature color-developing. In a two-color heat-sensitive recording material having a black coloring layer, a green coloring leuco dye having a reflectance after coloring of 35% or more at 460 to 480 nm and 20% or less at 600 nm was used for the high temperature coloring layer. A two-color thermosensitive recording medium characterized by the above. 2. A green-coloring leuco dye in the high-temperature color-developing layer,
3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (4-N-phenyl-
A compound selected from the group consisting of N-ethylamino-2-ethoxyphenyl) -4-azaphthalide and 3,6-bis (dimethylamino) fluorenspiro (9,3 ')-6'-dimethylaminophthalide. The two-color thermosensitive recording medium according to 1.