JPH05208553A - Two-color thermal recording material - Google Patents

Abstract

PURPOSE:To enhance sharpness and preservability, in a two-color thermal recording material having a high temp. color forming layer, an intermediate layer containing a color erasing agent and a low temp. color forming layer and containing a leuco dye and a developer in its color forming layers, by using a phthalide derivative expressed by a specific formula in one of the color forming layers. CONSTITUTION:In a two-color thermal recording material wherein at least high temp. color forming layer, an intermediate layer containing a color erasing agent and a low temp. color forming layer are successively formed on a support and the color forming layers contain a leuco dye and a developer, at least one kind of a phthalide derivative expressed by general formula (wherein R1-R6 are a hydrogen atom, an alkyl group, an unsaturated alkyl group, an alicyclic group, an aryl group, an aralkyl group, a tetrahydroxyfurfuryl group or a group substituted with a halogen atom, an alkyl group or an alkoxy group and X and Y are a halogena atom or an alkyl group) is pref. used in the high temp. color forming layer in order to satisfy a demand such as the enhancement of sensitivity, the stabilization of an image or multicolor recording.

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 two color-developing layers which develop different color tones.

[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, the image becomes unclear due to color mixture and blurring occurs, so that the second method is generally suitable as a method for obtaining an image of two colors. Only two-color thermosensitive recording papers that develop black and red have been put into practical use for proofreading or plotters.

However, recently, for the purpose of emphasizing safety indications, for example, a two-color thermosensitive recording paper that develops black and blue has been demanded, but it is usually used as a leuco dye for blue coloring thermosensitive recording. , 3-Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide provides clear recording even when the intermediate layer containing the decoloring agent is adjacent, but the decoloring It was found that the storage stability of the recorded image was insufficient, probably because of the influence. In addition, in other blue-coloring leuco dyes, a two-color heat-sensitive recording material which is not necessarily satisfactory in practical use has not been obtained because the vividness of the color tone is poor.

[0006]

In view of the above situation, the present inventors extensively studied the field of blue-coloring leuco dyes in order to solve the above-mentioned problems in the two-color thermosensitive recording medium. It was found that the selective use of a specific triallylmethanephthalide derivative can provide an excellent two-color heat-sensitive recording material satisfying both the sharpness and storability of the recorded image, and completed the present invention. It was

[0007]

According to the present invention, at least a high temperature color forming layer, an intermediate layer containing a decoloring agent, and a low temperature color forming layer are sequentially laminated on a support, and the color forming layer comprises a leuco dye. In a two-color thermosensitive recording medium containing a color former, at least one phthalide derivative represented by the following general formula [Chemical Formula 1] is used in either one of the coloring layers.
It is a color thermosensitive recording medium.

[0008]

[Chemical 1]

[Wherein R _{1 to} R ₆ are each a hydrogen atom; an alkyl group; an unsaturated alkyl group; an alicyclic group; an aryl group; an aralkyl group; a tetrahydrofurfuryl group or a halogen atom, an alkyl group, It indicates substituted groups alkoxyl group, and R ₁ and R _2, R ₃ and R _4, R ₅ and R
₆ can also form a ring with each other. X and Y each represent a hydrogen atom; a halogen atom; an alkyl group; an alkoxyl group or an acyloxy group. However, X and Y do not represent hydrogen atoms at the same time. ]

[0010]

In the two-color thermosensitive recording medium of the present invention, a phthalide derivative represented by the above general formula [Chemical Formula 1] is used as a leuco dye in either one of the low temperature coloring layer and the high temperature coloring layer. It has a significant feature in. Although the reason is not clear, the phthalide derivative used in the present invention is considered to be extremely unlikely to be affected by the decoloring agent used in the intermediate layer, and the white paper portion is changed even when exposed to high temperature and high humidity conditions for a long time. It is presumed that a clear and stable blue recorded image is maintained.

Specific examples of the phthalide derivative represented by the above general formula [Chemical Formula 1] used in the present invention include the following compounds. 3- (4-Dimethylaminophenyl) -3- (4-dimethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-
Methylphenyl) -6-dimethylaminophthalide, 3-
(4-Dimethylaminophenyl) -3- (4-dibutylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3-
(4-Diallylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (4-allylamino-2-methylphenyl) -6-dimethylaminophthalide, 3 -(4-Dimethylaminophenyl) -3- (4-N-methyl-N-allylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3-
(4-dipropargylamino-2-methylphenyl) -6
-Dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (4-propargylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-
Dimethylaminophenyl) -3- (4-N-methyl-N
-Propagylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (4-N-methyl-N-cyclohexylamino-2-methylphenyl) -6- Dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (4-
N-ethyl-p-toluidino-2-methylphenyl)-
6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (4-N-methyl-N-benzylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethyl Aminophenyl) -3- (4
-N-ethyl-N-tetrahydrofurfurylamino-2
-Methylphenyl) -6-dimethylaminophthalide, 3
-(4-Dimethylaminophenyl) -3- (4-N-methyl-N-ethoxymethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- ( 4-dimethylamino-2-
Ethylphenyl) -6-dimethylaminophthalide, 3-
(4-Dimethylaminophenyl) -3- (4-diethylamino-2-ethylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3-
(4-diethylamino-2-isobutylphenyl) -6
-Dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methoxyphenyl) -6-dimethylaminophthalide, 3- (4-
Dimethylaminophenyl) -3- (4-diethylamino-2-ethoxyphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (4-
Diethylamino-2-acetoxyphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-chlorophenyl) -6-dimethylaminophthalide, 3- (4-dimethyl) Aminophenyl) -3- (4-dimethylamino-2-
Methylphenyl) -6-diethylaminophthalide, 3-
(4-Dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-diethylaminophthalide, 3- (4-dimethylaminophenyl) -3-
(4-Diethylamino-2-methylphenyl) -6-pyrrolidinophthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-piperidinophthalide, 3- (4-Diethylaminophenyl) -3- (4-dimethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4
-Diethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-diethylaminophenyl) -3- (4-
Diethylamino-2-methylphenyl) -6-diethylaminophthalide, 3- (4-dibutylaminophenyl)
-3- (4-diethylamino-2-methylphenyl)-
6-Dimethylaminophthalide, 3- (4-dibutylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dibutylaminophthalide, 3- (4-
Dibutylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dibutylaminophthalide, 3- (4-N-methyl-N-cyclohexylaminophenyl) -3- (4-diethylamino-2- Methylphenyl) -6-dimethylaminophthalide, 3- (4-N
-Ethyl-N-isopentylaminophenyl) -3-
(4-Diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-N-ethyl-N-cyclopentylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethyl Aminophthalide, 3- (4-piperidinophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-pyrrolidinophenyl) -3-
(4-Diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3,3-bis (4-dimethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3,3-bis (4- Diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3,3-bis (4-diethylamino-2-ethylphenyl) -6-
Dimethylaminophthalide etc.

Among the various blue-colored phthalide derivatives as described above, the compound represented by the following general formula [Chemical Formula 2] is particularly easy to produce, and the heat-sensitive recording material prepared using them is a recorded image. Is particularly preferable because it has excellent storage stability.

[0013]

[Chemical 2]

[In the formula, R _{7 to} R ₁₂ each represent a C _{1 to} C ₆ alkyl group or a C _{3 to} C ₆ unsaturated alkyl group, and R ₇ and R ₈ , R ₉ and R ₁₀ , R ₁₁ and R ₁₂ can also form a ring with each other. Z represents an alkyl group of C ₁ -C _4. ]

The present invention uses the above-mentioned specific phthalide derivative in one of the low-temperature color developing layer and the high-temperature color developing layer. The leuco dyes used in the other color developing layer include, for example, the following various types. The colorless to pale basic dyes are known, and it is possible to appropriately select and use from these. 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole-3-)
Yl) -6-Dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6 -Triallylmethane dyes such as dimethylaminophthalide, lactam dyes such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-cyclohexylamino-6-chloro Fluorane, 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-tetrahydrofurfurylamino) -6-
Fluoran dyes such as methyl-7-anilinofluorane. Of course, the leuco dyes are not limited to these leuco dyes, and if necessary, two or more kinds may be used in combination.

Further, in the case of a two-color thermosensitive recording material which develops black and blue, a black coloring system, which is usually recorded frequently, is used for the low temperature coloring layer side, and the blue coloring phthalide derivative used in the present invention is used for the high temperature coloring layer side. It is preferably used. The color tone of the low temperature coloring layer is adjusted by selecting the above leuco dye,
Among them, 3-diethylamino-6-methyl-7-phenylaminofluorane, 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-phenylaminofluorane, 3- (N-ethyl-p-toluidino)-
6-Methyl-7-phenylaminofluorane and 3-dibutylamino-7- (o-chlorophenylamino) fluorane give a very clear black color image, and therefore, they can be combined with the specific blue-colored phthalide derivative of the present invention. In combination, good contrast can be obtained, and image storability is also extremely excellent, which is particularly preferable.

In the present invention, various known compounds can be used as the color former contained in the color forming layer, and the following can be exemplified. Activated clay, acid clay, attapulgite, bentonite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4-tert-butylphenol, 4
-Hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenone, 4-tert-
Octyl catechol, 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, benzyl 4-hydroxybenzoate, 4-
Dimethyl hydroxyphthalate, hydroquinone monobenzyl ether, 4-hydroxyphenyl-4'-isopropyloxyphenyl sulfone, novolac type phenol 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- ( α, α-dimethylbenzyl) salicylic acid, 3, - di -α- aromatic carboxylic acids such as methylbenzyl salicylic acid, and phenolic compounds, aromatic carboxylic acid and, for example, zinc, magnesium, aluminum, calcium, titanium, manganese,
Organic acidic substances such as salts with polyvalent metals such as 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.

In the present invention, the use ratio of the leuco dye and the coloring agent in each color forming layer is not particularly limited, but generally 1 to 5 parts by weight of the coloring agent per 1 part by weight of the leuco dye.
It is desirable to use 0 part by weight, preferably 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, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch granules can be added to the coating liquid.

Further, various other auxiliaries may be added to the coating solution for forming the color-developing 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. Further, 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 methylenebisamide, 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-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 A naphthoic acid derivative 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. Incidentally, in the coating liquid of the low temperature color forming layer,
Among the above heat fusible substances, the melting point is 70 to 120.
It is desirable to use a compound having a melting point of 80 ° C, preferably 80 ° C 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 by dry weight.
It is adjusted within the range of about 2 g / m ² .

In the heat-sensitive recording material of the present invention, the intermediate layer has a decolorizing layer as a main component, and the other coating liquids for forming the intermediate layer are described in the description of the coloring layer coating liquid. Such as various adhesives, dispersants, lubricants, heat-fusible substances, inorganic pigments, organic pigments, etc., and other additives such as defoaming agents, ultraviolet absorbers, fluorescent dyes, coloring dyes, etc. can do. Further, the coating amount of the intermediate layer is 1 to 10 g / m.
^It should be adjusted in the range of about ² . 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 and / or Alternatively, an intermediate layer having a two-layer structure in which layers containing a heat-fusible substance as a main component are laminated is the most preferable embodiment because it is excellent in desired effects of the present invention.

As the decoloring agent, for example, aliphatic amines,
Piperidines, piperazines, pyridines, imidazoles, imidazolines, morpholines, guanidines,
Amidines, polyethers, glycols, aromatic amides and the like can be used, and specifically, the substances described in various publicly known documents such as the following 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- 113593); urea derivatives (JP-A-55-
139290); alkylene oxide adducts of linear glycols (JP-A-55-152094); morpholine derivatives (JP-A-56-40588); solid alcohols (JP-B-50-).
17865); polyether and polyethylene glycol derivatives (JP-B-50-17867 and JP-B-50-17)
868); nitrogen-containing crystalline organic compound (Japanese Patent Publication No. 51-19)
991); guanidine derivative (JP-B-51-29024); amine or quaternary ammonium salt (JP-A-50-
18048); di-substituted amide compounds of aliphatic and aromatic carboxylic acids (JP-A-61-120792 and JP-A-61-16)
9277 publication) and the like.

Specific examples of the amidines and piperidines include the following. Examples of the amidines include N, N′-diphenylformamidine,
N, N'-di-o-tolylformamidine, N, N'-
Diphenyl benzamidine, N, N'-di -p- tolyl -N'- phenyl ^{benzamidine, N, N,, N ,,} , N,
^,, - tetraphenyl - ^{Heputajiamijin,} N, N,, N
^,,, N ^,,, -tetraphenyl-p-xylylene diamidine and the like, and 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.

Among these decoloring agents, N, N'-isophthaloyl-di (N-cyclohexyl-N-methylamide)
And N, N'-terephthaloyl-di (N-phenyl-N-
Disubstituted amides of aromatic divalent carboxylic acids such as ethylamide) and the above-mentioned piperidines show an excellent decoloring effect on the low-temperature color-developing layer at the time of high-temperature recording, and are suitable for color-developed images using the specific phthalide derivative. On the other hand, it is particularly preferably used because it has a very low influence upon storage. The amount of these decoloring agents used is 0.1 to 20 times by weight, and more preferably 0.5 to 6 times by weight, based on the total weight of the leuco dye and the color developing agent blended in the low temperature color forming layer. Adjusted in range.

In the two-color thermosensitive recording medium of the present invention, the coating liquid for each color forming layer or intermediate layer is generally prepared by using water as a dispersion medium and appropriately using a stirring or crushing machine 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. Further, after applying and drying the color-developing layer and the intermediate layer, 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, an adhesive layer, a magnetic recording layer, etc. 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 extremely excellent two-color heat-sensitive recording material capable of forming an image in which the color tone of the blue color image portion is clear and the storage stability is good.

[0031]

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 10 parts of 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 5% aqueous solution of methylcellulose 5
Parts and 25 parts of water were pulverized with a sand mill until the average particle diameter became 1.5 μm.

Preparation of Solution B 4,4′-Cyclohexylidenediphenol 30 parts,
A composition comprising 30 parts of a 5% aqueous solution of methyl cellulose and 70 parts of water was sand milled to have an average particle size of 1.5 μm
It was crushed until it became.

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 and 110 parts of water were pulverized with a sand mill until the average particle size became 1.5 μm.

Preparation of Solution D 3- (N-Ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane 10 parts, 1,2-
A composition consisting of 20 parts of di (3-methylphenoxy) ethane, 15 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water was pulverized with a sand mill until the average particle diameter 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 was dried in this order with a high-temperature heat-sensitive recording layer coating liquid, a decoloring intermediate layer coating liquid, and a low-temperature heat-sensitive recording layer coating liquid. the amount of coating is applied and dried so that each becomes ^{7g / m 2, 3g / m} 2, 4g / m 2, to obtain a 2-color heat-sensitive recording material was subjected super calender.

Example 2 The same procedure as in Example 1 was repeated except that 4-hydroxy-4'-isopropoxydiphenyl sulfone was used in place of 4,4'-cyclohexylidenediphenol in the preparation of solution B. A thermosensitive recording medium was obtained.

Example 3 In the preparation of solution B, 4,4'-isopropylidenediphenol was used in place of 4,4'-cyclohexylidenediphenol, and tetrakis (1,2,2,2) was prepared in preparation of solution C.
2,6,6-pentamethyl-4-piperidyl) -1,
A two-color thermosensitive recording medium was prepared in the same manner as in Example 1 except that N, N'-isophthaloyl-di (N-cyclohexyl-N-methylamide) was used instead of 2,3,4-butanetetracarboxylate. Obtained.

Example 4 In the preparation of solution A, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide was replaced with 3-
A two-color thermosensitive recording medium was obtained in the same manner as in Example 1 except that (4-dimethylaminophenyl) -3- (4-dimethylamino-2-methylphenyl) -6-dimethylaminophthalide was used.

Example 5 In the preparation of solution A, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide was replaced with 3-
A two-color thermosensitive recording medium was obtained in the same manner as in Example 1 except that (4-dimethylaminophenyl) -3- (4-diethylamino-2-ethylphenyl) -6-dimethylaminophthalide was used.

Example 6 3-diethylamino-7-chlorofluorane was used in place of 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane in the preparation of solution D. A two-color thermosensitive recording medium was obtained in the same manner as in Example 1 except for the above.

Example 7 In preparation of solution A, 3-diethylamino-7- was used instead of 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide. 3- (N-ethyl-N-isoamylamino) was used in the preparation of solution D using chlorofluorane.
Instead of -6-methyl-7-phenylaminofluorane, 3- (4-dimethylaminophenyl) -3- (4-
A two-color heat-sensitive recording material was obtained in the same manner as in Example 1 except that diethylamino-2-methylphenyl) -6-dimethylaminophthalide was used.

Example 8 In the preparation of solution A, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide was replaced with 3-
(N-ethyl-N-isoamylamino) -6-methyl-
A two-color thermosensitive recording medium was obtained in the same manner as in Example 7 except that 7-phenylaminofluorane was used.

Comparative Example 1 In preparation of solution A, 3,3 instead of 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide was used.
A two-color thermosensitive recording medium was obtained in the same manner as in Example 1 except that -bis (p-dimethylaminophenyl) -6-dimethylaminophthalide was used.

Comparative Example 2 In preparation of solution A, 3,3 instead of 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide was used.
A two-color thermosensitive recording medium was obtained in the same manner as in Example 2 except that -bis (p-dimethylaminophenyl) -6-dimethylaminophthalide was used.

Comparative Example 3 In the preparation of solution D, 3,3 instead of 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide was used.
A two-color heat-sensitive recording material was obtained in the same manner as in Example 7 except that -bis (p-dimethylaminophenyl) -6-dimethylaminophthalide was used.

Comparative Example 4 In the preparation of solution D, 3,3 was used instead of 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide.
A two-color thermosensitive recording medium was obtained in the same manner as in Example 8 except that -bis (p-dimethylaminophenyl) -6-dimethylaminophthalide was used.

The 12 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:
About 1300Ω / dot, main scanning recording speed: 20m sec / lin
e, sub-scan: 32 line / mm, head input: 0.44W
/ Dot, low temperature color development energy: 0.26 mJ, high temperature color development energy: 1.06 mJ. Macbeth densitometer (Macbeth, RD914
Type) and the results are shown in Table 1. The densities of red, blue, and black recorded images are for red,
It measured using each filter for blue and black.

[Preservation of Colored Image] The two-color thermosensitive recording material recorded by the above method was allowed to stand at 60 ° C. for 24 hours, and the image density of the recorded portion was measured. The results are shown in Table 1. did.

[0051]

[Table 1]

[0052]

EFFECTS OF THE INVENTION In the color image obtained by the two-color thermosensitive recording medium of the present invention, one blue color image is clear, the contrast of the two-color image is excellent, and the storability of the image is also very good.

Claims (3)

[Claims] 1. A two-color structure in which 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 the color-developing layer contains a leuco dye and a color-developing agent. A two-color heat-sensitive recording material, characterized in that at least one phthalide derivative represented by the following general formula [Chemical Formula 1] is used for either one of the color-developing layers in the heat-sensitive recording material. [Chemical 1] [Wherein, R _{1 to} R ₆ are each a hydrogen atom; an alkyl group; an unsaturated alkyl group; an alicyclic group; an aryl group; an aralkyl group;
A tetrahydrofurfuryl group or a group in which these are further substituted with a halogen atom, an alkyl group or an alkoxyl group is shown, and R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ may form a ring with each other. .. X and Y each represent a hydrogen atom; a halogen atom; an alkyl group; an alkoxyl group or an acyloxy group. However, X and Y do not represent hydrogen atoms at the same time. ] 2. A two-color thermosensitive recording medium according to claim 1, wherein at least one phthalide derivative represented by the general formula [Chemical Formula 1] is used in the high temperature color forming layer. 3. The two-color thermosensitive recording medium according to claim 1, wherein the decoloring agent is a piperidine or a disubstituted amide of an aromatic carboxylic acid.