JP2599951B2 - Two-color thermal recording medium - Google Patents

Description

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

"Prior art" Conventionally, a thermosensitive recording in which a color-forming image is obtained by contacting both color-forming substances by heat using a color-forming reaction between a color-forming agent and a color-forming agent that forms a color in contact with the color-forming agent. The body 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.

However, the required performance and quality are diversified with the expansion of applications, and for example, high sensitivity, image stabilization, multicolor recording, and the like are mentioned. In particular, since multicolor recording has a wide range of applications, many recording materials have been researched and proposed to date.

Conventional two-color recording materials are roughly classified into the following two types. The first is to form a low-temperature heating coloring layer at the time of low-temperature heating,
During heating at a high temperature, both the low-temperature heat-sensitive coloring layer and the high-temperature heat-sensitive coloring layer are colored to obtain a mixed color. The other is a method of obtaining a color tone of only the high-temperature heat-sensitive 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 in the first method. .

In the first method, an image becomes unclear due to color mixing and blurring occurs. Therefore, the second method is generally suitable as a method for obtaining an image of two colors. In the second method, various decoloring agents having a decoloring effect on a color forming system composed of a basic leuco dye and an organic acidic substance have been proposed. However, when these color erasing agents are used directly adjacent to the high-temperature color-forming layer, the color erasing agent affects the high-temperature color-forming layer during the manufacturing process or during storage, particularly at the time of recording, and a sufficient color density at the time of high-temperature heating is obtained. Not only cannot it be obtained, but also has the disadvantage that the decoloring effect on the low-temperature coloring layer becomes insufficient. For this reason, a method of providing a barrier layer between the high-temperature coloring layer and the decoloring layer has been proposed. However, not only does the manufacturing process become complicated, but the recorded image of the high-temperature coloring layer may become unclear.

[Problems to be Solved by the Invention] The present invention improves the above-mentioned problems associated with the use of a decoloring agent, and provides two colors capable of forming a clear color tone image having good recording sensitivity and little color mixing or bleeding. It is intended to provide a thermosensitive recording medium.

"Means for Solving the Problems" The object as described above of the present invention is that at least a high-temperature coloring layer, an intermediate layer containing a decoloring agent, and a low-temperature coloring layer are sequentially laminated on a support, and the coloring layer is In a two-color thermosensitive recording medium which is a leuco-based coloring layer containing a leuco dye and a coloring agent, kaolin and / or aluminum hydroxide is contained in the high-temperature coloring layer in an amount of 40% by weight or more of the total solid content of the high-temperature coloring layer. And at least 10% by weight of an adhesive component.

"Action" The heat-sensitive recording material of the present invention contains kaolin and / or aluminum hydroxide as a pigment component in the high-temperature coloring layer in an amount of 40% by weight or more of the total solid content of the high-temperature coloring layer as described above, and an adhesive component. It has a significant feature in that it is contained at 10% by weight or more.

Since the high-temperature coloring layer of the two-color thermosensitive recording medium is provided on the lowermost layer, the recording sensitivity is reduced due to the effect of the intermediate layer containing the decoloring agent formed thereon, and the coloring image becomes unclear. Cheap. Although a method of increasing the sensitivity by reducing the coating amount of the intermediate layer is also conceivable, the decolorizing effect of the low-temperature coloring layer is reduced because the amount of the decoloring agent is also reduced with a reduction in the coating amount, and it is not necessarily satisfactory. No results were obtained.

However, the pigment component and the adhesive component were added to the high-temperature coloring layer in 50 parts.
% Or more, more preferably 60% by weight or more, because the penetration of the decoloring agent into the high-temperature coloring layer is hindered, or the intermediate layer containing the decoloring agent is formed directly on the high-temperature coloring layer. It was also found that the effect of the decoloring agent on the high-temperature coloring layer was extremely effectively prevented. As a result, even when the coating amount of the intermediate layer containing the decoloring agent is 7.0 g / m ² or less, particularly 4.5 g / m ² or less, a sufficient decoloring effect on the low-temperature coloring layer is obtained, It has been found that the effect of making the recorded image of the high-temperature coloring layer extremely sharp can be obtained by reducing the coating amount.

The color-forming layer constituting the recording medium of the present invention is a leuco-based color-forming layer containing a leuco dye and a color former, and various useful colorless to light-colored basic dyes are known. , 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-dimethylindol-3-yl)
-5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6 -Dimethylaminophthalide, 3,3-bis (2-
Phenylindol-3-yl) -6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1
-Methylpyrrole-3-yl) -6-dimethylaminophthalide and other triallylmethane dyes, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucouramine, N-2, Diphenylmethane dyes such as 4,5-trichlorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue;
Methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) spiropyran, 3-propyl-spiro -Spiro dyes such as dibenzopyran, rhodamine-B anilinolactam, lactam dyes such as rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran, 3- Diethylamino-6-methoxyfluoran, 3-diethylamino-
7-methoxyfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7
-Chlorolan, 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-methylaminofluoran, 3-
Diethylamino-7-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-phenylaminofluoran, 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-diethylamino-7- (2-carbomethoxy-phenylamino) fluoran, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluor Oran,
3- (N-cyclohexyl-N-methylamino) -6
Methyl-7-phenylaminofluorane, 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-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-N
And fluoran dyes such as -ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran.

Various inorganic or organic acidic substances that are colored upon contact with a basic dye are also known, for example, activated clay, acidic clay, attapulgite, bentonite, colloidal silica, inorganic acid substances such as aluminum silicate, and 4-tert. −
Butylphenol, 4-hydroxydiphenoxide, α
Naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2,2′-
Dihydroxydiphenol, 2,2'-methylenebis (4
-Methyl-6-tert-isobutylphenol), 4,4 '
-Isopropylidenebis (2-tert-butylphenol), 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-isopropylidenediphenol (bisphenol A), 2,2'-methylenebis (4 −
Chlorophenol), hydroquinone, 4,4'-cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, 4-hydroxyphenyl-
Phenolic compounds such as 4'-isopropyloxyphenyl sulfone, novolak type 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
Aromatic carboxylic acids such as -butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids Examples thereof include organic acidic substances such as salts with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel.

In the heat-sensitive recording material of the present invention, the ratio of the basic colorless dye to the acidic substance in the color-forming layer is generally 1 basic colorless dye.
The acidic substance is used in an amount of 1 to 50 parts by weight, preferably about 1 to 10 parts by weight based on parts by weight.

In the coating liquid for forming the color-forming layer, as an adhesive component, for example, starches, 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 Emulsions, styrene / butadiene copolymer emulsions, acrylonitrile / butadiene copolymer emulsions, methyl methacrylate / butadiene copolymer emulsions, polychloroprene emulsions, vinyl acetate emulsions, ethylene / vinyl acetate emulsions and the like are added. In the coating liquid for forming the low-temperature coloring layer, as a 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,
Inorganic pigments such as zinc sulfate, talc, clay, calcined clay,
Organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, raw starch granules, etc. are added. Of course, the present invention is not limited to these exemplified substances. The above may be used in combination.

As described above, the heat-sensitive recording material of the present invention contains the pigment component and the adhesive component in the high-temperature coloring layer in an amount of 50% by weight or more, more preferably 60% by weight or more.
However, when the total content of the pigment component and the adhesive component in the high-temperature coloring layer is less than 50% by weight, the decolorizing agent in the intermediate layer is Due to the influence, the coloring density of the high-temperature coloring layer is reduced, and a clear recorded image cannot be obtained. In addition, it is desirable that the high-temperature coloring layer contains 40% by weight or more, more preferably 50% by weight or more of a pigment component in view of easiness of preparation of a coating solution and excellent coating applicability. The effect of the present invention becomes more remarkable by using a pigment having a plate-like structure or a pigment having excellent transparency.

Various other auxiliaries can be added to the coloring layer coating solution, for example, sodium dioctyl sulfosuccinate,
Sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, alginate,
Examples thereof include dispersants such as fatty acid metal salts, benzophenone-based and triazole-based ultraviolet absorbers, other defoamers, fluorescent dyes, and coloring dyes.

Further, 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'-methylenebis (4-methyl-6-t
ert-butylphenol), 4,4'-butylidenebis (6
-Tert-butyl-3-methylphenol), hindered phenols such as 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenol) butane, dibenzyl terephthalate, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 4,4'-ethylenedioxy-bis-benzoic acid diphenylmethyl ester, and various known heat-fusible substances can also be used in combination.

In the thermosensitive recording medium of the present invention, the total content of the leuco dye, the coloring agent and the heat-fusible substance in the low-temperature coloring layer was 50%.
It is preferable to adjust the content to not less than 60% by weight, more preferably not less than 60% by weight, since the two color recording images are clearly distinguished. The coating amount of each color-forming layer is not particularly limited, but is generally adjusted in a range of about 1.5 to 12 g / m ² in dry weight.

In the heat-sensitive recording medium of the present invention, the intermediate layer contains a decoloring agent as a main component. In addition, various adhesives, pigments, heat-fusible substances, and the like as described above are appropriately compounded. Further, the layer configuration of the intermediate layer is not limited to a single layer, and a decoloring layer mainly composed of a decoloring agent and a layer mainly composed of other materials may be laminated in two or more layers. The intermediate layer having a two-layer structure in which a layer mainly composed of a pigment and / or a heat-fusible substance is laminated on a decoloring layer mainly composed of It is an aspect.

The decoloring agent contained in the decoloring layer in the present invention is not particularly limited, fatty acid amines, piperidines, piperazines, pyridines, imidazoles,
Imidazolines, morpholines, guanidines, amidines, polyethers, glycols, aromatic amides and the like are preferably used.

Specifically, for example, the following compounds are described in various known documents. Alkylene oxide adduct of bisphenols (JP-A-54-139741) 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 derivative (JP-A-55-139290) alkylene oxide adduct of linear glycol (JP-A-55-139290) JP-A-152094] Morpholine derivative [JP-A-56-40588] Solid alcohol [JP-B-50-17865] Polyether and polyethylene glycol derivatives [JP-B-50-17867, JP-B-50-17867]
No.-17868) nitrogen-containing crystalline organic compound (Japanese Patent Publication No. 51-1)
No. 9991] Guanidine derivative (JP-B-51-29024) amine or quaternary ammonium salt (JP-A-50-1804)
No. 8] disubstituted amide compounds of fatty acids and aromatic carboxylic acids [JP-A-60-120792] and the like.

Further, as specific examples of amidines, for example, N, N'-diphenylformamidine, N, N'-di-o-tolylformamidine, N, 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; specific examples of piperidines include (2,2,6,6-tetramethyl-4-piperidyl / tridecyl) -1,2- Ethanedicarboxylate, (1,2,2,6,6
-Pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, (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, 2,6,6-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, (2,2,6,6-tetramethyl-4 -Piperidyl) -1,2,3,4-butanetetracarboxylate and the like.

In addition, among these various decoloring agents, piperidines, amidines, and disubstituted amide compounds of aromatic carboxylic acids have a low degree of influence on the high-temperature coloring layer, and show an excellent decoloring effect on the low-temperature coloring layer. Therefore, it is particularly preferably used.

The above-described various decolorizing agents are generally contained in the decoloring layer in an amount of about 0.1 to 20 times by weight based on the total weight of the leuco dye and the color former in the low-temperature color-forming layer, but more preferably 0.5 to 6 times.
It is adjusted within the range of about weight times. It is of course possible to use two or more decoloring agents in combination.

In the coating liquid for forming the intermediate layer, various adhesives, dispersants, lubricants, heat-fusible substances, inorganic pigments, organic pigments, etc., as described in the description of the coloring layer coating liquid, and other defoaming Various auxiliaries such as an agent, an ultraviolet absorber, a fluorescent dye, and a coloring dye can be appropriately compounded. Further, as described above, the layer configuration of the intermediate layer is not limited to a single layer, and a decoloring layer containing a decoloring agent as a main component and a layer containing other materials as a main component may be laminated in two or more layers. A layer in which an adhesive, a heat-fusible substance, a pigment or the like is appropriately mixed may be formed between the high-temperature coloring layer and the decoloring layer according to the requirements.

In the heat-sensitive 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 ball mill, an attritor, a sand mill, or the like, and a pulverizer. 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 papers such as high-quality paper, base paper made by a Yankee machine, single-side polished base paper, double-side polished base paper, cast coated paper, art paper, coated paper, medium-coated paper, and synthetic fibers Paper, synthetic resin film and the like are used as appropriate. Further, after applying and drying the color-forming layer, a smoothing treatment such as super calendering can be performed as necessary.

Furthermore, various variations are possible within a range not exceeding 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 or a backcoat layer is provided on the support. Various known techniques in the heat-sensitive recording medium field, such as the provision thereof, can be added. 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 heat-sensitive recording material of the present invention thus obtained is a very excellent two-color heat-sensitive recording material having good recording sensitivity and capable of forming a clear color tone image with little color mixing or bleeding.

"Examples" Examples are shown below to explain the present invention more specifically, but of course the present invention is not limited thereto. Unless otherwise specified, “parts” and “%” in the examples indicate “parts by weight” and “% by weight”, respectively.

Example 1 Preparation of solution A 3- (N-cyclohexyl-N-methylamino) -6
Methyl-7-phenylaminofluoran 10 parts Dibenzyl terephthalate 30 parts Methyl cellulose 5% aqueous solution 20 parts Water 100 parts This composition was pulverized with a sand mill until the average particle diameter became 3 μm.

Solution B Preparation 4,4'-isopropylidene diphenol 30 parts Methyl cellulose 5% aqueous solution 30 parts Water 70 parts This composition was pulverized by a sand mill until the average particle diameter became 3 μm.

Solution C preparation (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4
-Butanetetracarboxylate 50 parts Methylcellulose 5% aqueous solution 25 parts Water 110 parts This composition was pulverized with a sand mill until the average particle diameter became 3 µm.

Solution D Preparation 3-Diethylamino-7,8-benzofluoran 10 parts Methylcellulose 5% aqueous solution 5 parts Water 25 parts This composition was pulverized with a sand mill until the average particle diameter became 3 μm.

(Preparation of coating liquid for high-temperature heat-sensitive recording layer)

30 parts of liquid D, 100 parts of liquid B, kaolin (Product name: UW-90, EMC
Co., Ltd.), 50 parts of a 20% oxidized starch aqueous solution, and 100 parts of water were mixed and stirred to obtain a coating solution.

(Preparation of decolorizing layer coating liquid)

100 parts of C liquid, 125 parts of 10% aqueous solution of polyvinyl alcohol,
75 parts of water was mixed and stirred to obtain a coating liquid.

(Preparation of coating liquid for intermediate layer)

80 parts of a silicon oxide pigment (trade name: Mizukasil P-527, manufactured by Mizusawa Chemical Co., Ltd.), 200 parts of a 10% aqueous solution of polyvinyl alcohol,
220 parts of water were mixed and stirred to obtain a coating liquid.

(Preparation of coating liquid for low-temperature heat-sensitive recording layer)

160 parts of liquid A, 90 parts of liquid B, 200 parts of a silicon oxide pigment (trade name: Mizukasil P-527, manufactured by Mizusawa Chemical Co., Ltd.), 100 parts of a 20% oxidized starch aqueous solution, and 130 parts of water were mixed and stirred to form a coating liquid. .

(Formation of recording layer)

The high-quality paper having a basis weight 50 g / m ^2, the high-temperature heat sensitive recording layer coating solution, decolorizing layer coating solution, intermediate layer coating solution, a low-temperature heat-sensitive recording layer coating solution, the coating amount after drying in this order 6g / m ² , 2g / m ² , 2g /
m ² , 3 g / m ² were applied and dried, and subjected to a super calender to obtain a two-colored heat-sensitive recording paper.

Example 2 In the preparation of solution C, (2,2,6,6-tetramethyl-4-
Instead of (piperidyl) -1,2,3,4-butanetetracarboxylate, (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate is used. A two-colored heat-sensitive recording paper was obtained in the same manner as in Example 1 except that the recording paper was used.

Example 3 In the preparation of solution C, (2,2,6,6-tetramethyl-4-
Two-color development in the same manner as in Example 1 except that N, N'-dicyclohexyl-N, N'-dimethylisophthalamide was used instead of (piperidyl) -1,2,3,4-butanetetracarboxylate. A thermosensitive recording paper was obtained.

Example 4 As a coating solution for a high-temperature heat-sensitive recording layer, 40 parts of D solution, 130 parts of B solution
Part, 50 parts of kaolin, 50 parts of a 20% oxidized starch aqueous solution and 130 parts of water. Mix and stir.
A two-color heat-sensitive recording paper was obtained in the same manner as in Example 2 except that the amount was 4.5 g / m ² .

Comparative Example 3 As a coating liquid for a high-temperature heat-sensitive recording layer, 40 parts of D liquid and 130 parts of B liquid
Parts, 30 parts of kaolin, 200 parts of a 20% oxidized starch aqueous solution, and 40 parts of water were mixed and stirred to obtain a two-color heat-sensitive recording paper in the same manner as in Example 2 except that a coating liquid obtained by stirring was used.

Except that coating amount after drying of the intermediate layer coating liquid between the Example 5 the hot heat-sensitive recording layer and the decoloring layer was coated to a 2 g / m ² Example 2
In the same manner as in the above, a two-color heat-sensitive recording paper was obtained.

Example 6 Example ² was repeated except that the coating solution for the intermediate layer was applied between the high-temperature heat-sensitive recording layer and the decoloring layer so that the coating amount after drying was 7 g / m 2.
In the same manner as in the above, a two-color heat-sensitive recording paper was obtained.

Example 7 In the preparation of solution A, the amount of dibenzyl terephthalate was changed from 30 parts to 10 parts, and 140 parts of solution A, 90 parts of solution B, 40 parts of silicon oxide pigment, 20% A two-colored thermosensitive recording paper was obtained in the same manner as in Example 2 except that a coating liquid obtained by mixing and stirring 100 parts of an oxidized starch aqueous solution and 130 parts of water was used.

Comparative Example 1 As a coating liquid for a high-temperature heat-sensitive recording layer, 40 parts of D liquid and 130 parts of B liquid were used.
Parts, 5 parts of kaolin and 50 parts of a 20% oxidized starch aqueous solution were mixed and stirred, and the coating amount after drying of the coating liquid for the high-temperature heat-sensitive recording layer was changed to 3.0 g / m ^2. In the same manner as in Example 2, a two-color heat-sensitive recording paper was obtained.

Comparative Example 2 As a coating solution for a high-temperature thermosensitive recording layer, 30 parts of D solution and 100 parts of B solution
Parts, kaolin 10 parts, 20% oxidized starch aqueous solution 100 parts and water 120 parts were mixed and used, and the coating amount after drying of the coating liquid for the high-temperature heat-sensitive recording layer was 3.0 g / m ^2. Example 2 except that
In the same manner as in the above, a two-color heat-sensitive recording paper was obtained.

The dynamic coloring characteristics of the thus obtained 11 kinds of two-color coloring thermal recording papers were tested by the following method.

[Recording conditions]

6 dot / mm thermal head (Matsushita Electronic Components,
Main scanning recording speed: 130msec / line, sub-scanning: 7.7line / mm, head input: 0.90W
/ Dot, low-temperature coloring energy: 1.3 mJ, high-temperature coloring energy: 3.0 mJ, and the density of the recording portion was measured with a Macbeth densitometer (manufactured by Macbeth, model RD-100R).

With low-temperature coloring energy, clear black coloring was obtained on all the heat-sensitive recording papers, and the image density was 1.0 to 1.1. The density of red coloring at high-temperature coloring energy was measured using a green filter, and the results are shown in the table below.

The color images of the two-color heat-sensitive recording paper of each example were extremely clear without color mixing or bleeding, but the recording paper of the comparative example was extremely poor in sharpness due to color mixing, and the image density was extremely low.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-42881 (JP, A) JP-A-55-21274 (JP, A) JP-A-62-33672 (JP, A) JP-A 57-428 181890 (JP, A) JP-A-59-55790 (JP, A) JP-A-62-284781 (JP, A) JP-A-62-33671 (JP, A)

Claims (1)

(57) [Claims] 1. A leuco-based color former comprising a high-temperature color-developing layer, an intermediate layer containing a decoloring agent and a low-temperature color-developing layer sequentially laminated on a support, wherein said color-developing layer contains a leuco dye and a color former. In the two-color thermosensitive recording layer, the high-temperature coloring layer contains kaolin and / or aluminum hydroxide in an amount of 40% by weight or more of the total solid content of the high-temperature coloring layer and the adhesive component in an amount of 10% by weight or more. A two-color heat-sensitive recording material characterized by the following: