JP2000015928A - Thermal recording body containing bisbenzotriazole compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the light fastness, chemical resistance, and record-traveling property of a recorded part and unrecorded part by containing at least one kind of specific bisbenzotriazole compounds in a thermal recording body in application with the coloring reaction of an electron donative compound and an electron acceptable compound. SOLUTION: The thermal recording body is formed on a base material with a thermal recording layer containing an electron donative compound, an electron acceptable compound, and a bonding agent, in which at least one kind of bisbenzotriazole compounds having a melting point of 280 deg.C or more is contained. In formula, R is a bivalent aromatic cycle, and there are given, e.g. 1,2-phenylene, 1,3-phenylene thereto. Also, X, Y show a hydrogen atom or 1-8C alkyl group, and a halogen atom. For such a bisbenzotriazole compound, there is given bis[4-(2H-benzotriazole-2-il)-3-hydroxyphenol]terephthalate in terms of light fastness and high temperature stability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording material utilizing a color development reaction between an electron donating compound and an electron accepting compound, and to a thermosensitive recording material containing a bisbenzotriazole compound.

[0002]

2. Description of the Related Art In a thermosensitive recording system, a thermosensitive recording layer mainly comprising an electron-donating usually colorless or pale-color dye precursor and an electron-accepting developer is provided on a support. By heating with a pen, a laser beam, or the like, the dye precursor and the developer are instantaneously reacted to obtain a recorded image. Japanese Patent Publication Nos. 43-4160 and 45-1
No. 4039, for example. Such thermosensitive recording paper has the advantages of being able to record with a relatively simple device, being easy to maintain, and having no noise.It has a measuring recorder, facsimile, printer, computer terminal, It is used in a wide range of fields such as labels and ticket vending machines. As one application of the heat-sensitive recording paper, in recent years, it has been frequently used for various heading labels, display media such as posters, and the like. In these applications, the thermal recording paper is often exposed to room light or sunlight for a long period of time, and as a result, the background of the thermal recording paper yellows or the stability of the recorded image is impaired. ,
As a result, the product image is significantly impaired.

[0003] In order to solve these problems, a method of adding a finely pulverized ultraviolet absorber to a heat-sensitive recording layer or a protective layer in a conventional heat-sensitive recording paper (Japanese Patent Laid-Open No. 50-1980).
04650, 55-55891, 55
-93492, 58-87093, etc.)
Has been proposed. However, if the heat-sensitive recording layer contains a finely pulverized ultraviolet absorber to obtain sufficient light resistance, it is necessary to add a large amount of these ultraviolet absorbers in terms of ultraviolet absorption efficiency and shielding efficiency. is there. Therefore, when such a heat-sensitive recording medium is placed in a high-temperature environment, it causes new flaws such as background fogging or a decrease in recording density, and it cannot provide a sufficiently satisfactory light resistance. There is a disadvantage that the performance as a heat-sensitive recording medium is impaired. In addition, even if the protective layer contains a finely pulverized ultraviolet absorber, if it is a conventionally proposed ultraviolet absorber, the ultraviolet absorber elutes due to the influence of a plasticizer, oils and the like, and the protective layer is removed. Function is lost, and as a result, the storability of the recorded image is reduced. In addition, because the UV absorber is easily melted by heating the thermal head during recording, probably because the compound has a relatively low melting point, scum and sticking occur, and the thermal head is stained by long-term marking. It is.

Recently, a heat-sensitive recording material using an ultraviolet absorbing agent in which an ultraviolet absorbing benzotriazole molecule or a benzophenone molecule is bonded with methylene or the like has been disclosed in Japanese Patent Laid-Open Publication No. Hei 7 (1994).
314894, JP-A-9-221487, JP-A-9-
268183, JP-A-9-314496, JP-A-10-
No. 71770, for example. However, although the compounds described in these documents have an effect of improving scum and sticking, the effects are not yet sufficient, and a problem is caused in that the thermal head is stained by long-time printing.

[0005]

As described above, it has been practiced for a long time to impart light fastness to heat-sensitive recording paper using an ultraviolet absorber, but a satisfactory method has not yet been developed. is the current situation. Therefore, an object of the present invention is to provide excellent light resistance of a recorded portion and an unrecorded portion without impairing the basic performance of a heat-sensitive recording medium, and plasticizer resistance, oil resistance, chemical resistance such as solvent resistance, and the like. An object of the present invention is to provide a thermosensitive recording medium having excellent recording running properties.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, the base material contains an electron donating compound, an electron accepting compound, and a binder. By including at least one of the bisbenzotriazole compounds represented by the following general formula (1) in the thermosensitive recording medium having the thermosensitive coloring layer formed thereon, an excellent thermosensitive recording medium that has solved the above-mentioned problems can be obtained. This led to the completion of the present invention.

[0007]

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Wherein R represents a divalent aromatic ring, for example, 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 2,6-naphthylene, 1,5-naphthylene,
1,8-naphthylene is mentioned. Among them, 1,4-phenylene or naphthylene is preferable because the melting point is increased. X and Y each represent a hydrogen atom or an alkyl group of C1 to C8, or a halogen atom such as chloro, bromo, iodo, or fluoro.
An alkyl group of 4 is preferred.

The present inventors have obtained a heat-sensitive recording material having excellent light fastness of an image and a background portion by using a bisbenzotriazole compound represented by the above general formula (1) as an ultraviolet absorber in the heat-sensitive recording material. It has been found that the present invention has been achieved. In addition, the present inventors have found that when using such a specific bisbenzotriazole compound, there was a problem when using an existing ultraviolet absorber, the background fog when blended into the recording layer, or the protective layer. It has been found that the blending can prevent the deterioration of the recording runnability due to the generation of the plasticizer resistance and the oil resistance, scum, sticking and the like.

[0010] The reason is that the bisbenzotriazole compound of the present invention has a high melting point without impairing the ultraviolet absorption of the benzotriazole compound.
This is probably because even the heating of the thermal head does not easily melt. For example, among the conventional existing ultraviolet absorbers, 2,2'-methylenebis [6- (2H-benzotriazol-2-yl)-described in JP-A-7-314894 described above.
4- (1,1,3,3-tetramethylbutyl) phenol] is a compound having a relatively high melting point, but has a melting point of 195 ° C., and in a thermosensitive recording medium containing this compound in the protective layer, , And stick sticking occurs and cannot be put to practical use. Even with other bisbenzotriazole compounds, the melting point is at most about 240 ° C., and the effect is not sufficient.

On the other hand, the bisbenzotriazole compound represented by the general formula (1) used in the present invention is an aromatic dicarboxylic acid ester of the benzotriazole compound, and therefore, is much more expensive than known compounds. It is thought that it becomes possible to efficiently prevent the generation of scum sticking even when the protective layer is contained based on the melting point. In particular, in the present invention, the use of a bisbenzotriazole compound having a melting point of 280 ° C. or higher, preferably 300 ° C. or higher can completely prevent the generation of sticking. As described above, the melting point of the compound of the present invention is remarkably improved. Therefore, the thermosensitive recording medium containing this compound can completely suppress the occurrence of scum sticking.

Further, the present inventors have found that the bisbenzotriazole compound represented by the general formula (1) has very low solubility in general organic solvents in addition to the above characteristics. Therefore, even if the thermosensitive recording medium containing the present compound in the protective layer comes into contact with a plasticizer, a fat or the like, the present compound does not elute due to the influence thereof. The reason for this is not clear, but it is presumed that the solubility of aromatic dicarboxylic acid in various organic solvents is very low, and the property is also exhibited in the bisbenzotriazole compound of the present invention. From these characteristics, it is considered that the thermosensitive recording medium containing the bisbenzotriazole compound of the present invention can obtain an excellent effect of improving the stability of recorded images, light resistance, and recording running properties.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The general formula (1) used in the present invention
Was synthesized for the first time by Murayama et al. And reported in 1976 (JP-A-51-7128).
6). This compound has a structure in which a benzotriazole compound exhibiting ultraviolet absorbing properties is bonded with an aromatic dicarboxylic acid ester, and Murayama et al. Use this compound to prevent ultraviolet light degradation of synthetic polymer substances such as polyester. . Specifically, the synthesis method is described below. A benzotriazole compound represented by the general formula (2) and an aromatic dicarboxylic acid chloride represented by the general formula (3) are converted into a tertiary amine such as triethylamine in an organic solvent such as methyl ethyl ketone. By heating in the presence of an amine, a bisbenzotriazole compound of the general formula (1) is obtained. Since the compound can be synthesized by a one-step reaction of the benzotriazole compound of the general formula (2) with the aromatic dicarboxylic acid chloride of the general formula (3), the compound is very excellent also from the viewpoint of the synthesis method.

[0014]

Embedded image

X and Y are each a hydrogen atom or C1 to C
It represents any of up to 8 alkyl groups and halogen atoms.

[0016]

Embedded image

Wherein R is a divalent aromatic ring, phenylene,
Indicates naphthylene and the like.

Hereinafter, the thermosensitive recording medium of the present invention will be described in detail. The thermosensitive recording medium is usually obtained by providing a thermosensitive recording layer containing an electron donating compound and an electron accepting compound on a support. In the present invention, in addition to the thermosensitive coloring layer, a protective layer containing a water-soluble or water-dispersible binder as a main component on the thermosensitive coloring layer, an intermediate layer between the thermosensitive recording layer and the protective layer,
It is possible to adopt a laminated structure in which an under layer mainly containing a filler and a binder is provided between the support and the thermosensitive coloring layer. These layer configurations may be appropriately combined according to the required quality, and a known technique usually used in the field of thermal recording can be applied.

The thermosensitive recording medium of the present invention is characterized in that at least one of these contains at least one of the bisbenzotriazole compounds represented by the above formula (1) as an ultraviolet absorber. By using this bisbenzotriazole compound, the light resistance of the recorded part and the unrecorded part of the thermal paper is remarkably improved. In particular, from the viewpoint of ultraviolet absorption, a protective layer is provided on the thermal layer. It is desirable that it be contained in. Further, even when the bisbenzotriazole compound of the present invention is blended in the recording layer, background fog in a high-temperature environment is extremely small. Moreover, since it hardly dissolves in plasticizers, oils, organic solvents, etc.,
When used as a protective layer, even when the surface of the protective layer comes into contact with these organic solvents, the barrier function does not decrease due to the elution of the ultraviolet absorber, and an improvement effect with excellent chemical resistance is obtained. Can be In addition, the high-temperature stability of these compounds ensures that stable recording and traveling properties are obtained without sticking or head residue due to melting during recording with a thermal head.

Examples of the bisbenzotriazole compound represented by the general formula (1) include bis [4- (2H-benzotriazol-2-yl) -3-hydroxyphenyl] terephthalate and bis [4- (2H -Benzotriazol-2-yl) -5-hydroxy-2-methylphenyl] terephthalate, bis [4- (5-chloro-2H)
-Benzotriazol-2-yl) -3-hydroxyphenyl] terephthalate, bis [4- (2H-benzotriazol-2-yl) -3-hydroxyphenyl]
2,6-naphthalenedicarboxylate, bis [4-
(2H-benzotriazol-2-yl) -5-hydroxy-2-tert-butylphenyl] 2,6-naphthalenedicarboxylate, bis [4- (5-chloro-2H-
Benzotriazol-2-yl) -3-hydroxyphenyl] 2,6-naphthalenedicarboxylate. In particular, screws [4
-(2H-benzotriazol-2-yl) -3-hydroxyphenyl] terephthalate (melting point: 320 ° C) is preferred. When the bisbenzotriazole compound of the present invention is used for a thermosensitive recording medium, the average particle diameter is preferably 2 μm or less, particularly 0.5 μm, in order to obtain a desired effect.
m is more preferable. When the average particle size is 0.5 μm or less, not only the ultraviolet absorption efficiency is remarkably improved, but also when contained in the protective layer, the recorded image is hardly concealed, so that a clear recorded image can be obtained. As a method of reducing the average particle diameter of the bisbenzotriazole compound to 2 μm or less, generally, water is used as a dispersion medium, and additives such as a dispersant and an antifoaming agent are added as needed, and a ball mill, an attritor, a sand mill, or the like is used. And the like can be achieved by pulverization and atomization by such methods. Among them, a sand mill type pulverizer is desirable, and the average particle size of the dispersion medium is preferably 1 mm or less.

The bisbenzotriazole compound of the present invention can be used in combination with other known ultraviolet absorbers as long as the desired effect is not impaired. Also, nickel bis (octylphenyl) sulfide, [2, 2 ′
-Thiobis (4-tert-octylphenolate)]
UV stabilizers such as -n-butylamine nickel, nickel complex-3,5'-di-tert-butyl-4-hydroxybenzyl-phosphate monoethylate, nickel dibutyl dithiocarbamate, benzoate type quencher, and bis (2 It is also preferable to use a hindered amine light stabilizer such as (2,6,6-tetramethyl-4-piperidyl) sebacate.

In the present invention, examples of a thermal recording system utilizing a color development reaction between an electron donating compound and an electron accepting compound include, for example, a combination of a basic dye and a developer, a combination of a diazonium salt and a coupler, iron, and the like. Combination of a transition element and a chelate compound, a combination of an aromatic isocyanate compound and an imino compound, and the like.The combination of a basic dye and a developer is also excellent in color density and recording sensitivity. A heat-sensitive recording material utilizing a color development reaction between a basic dye and a developer will be described in detail.

As the dye used in the present invention, various known basic dyes can be used. These may be used alone or in combination of two or more, and are selected depending on the application and required characteristics. Specific examples include, but are not limited to, the following compounds. (1) Triarylmethane compound 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis-
(9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis- (2-phenylindol-3-yl) -5-dimethylaminophthalide and the like. (2) Diphenylmethane compounds 4,4-bis (dimethylamino) benzhydrin benzyl ether, N-halophenyl-leuco auramine, N
-2,4,5-trichlorophenylleuco auramine and the like.

(3) Xanthene compounds Rhodamine B-anilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-butylaminofluoran, 3-diethylamino-7- (2-chloroanilino) Fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-
Piperidino-6-methyl-7-anilinofluoran, 3
-Ethyltolylamino-6-methyl-7-anilinofluoran, 3-cyclohexylmethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6
Chloro-7- (β-ethoxyethylamino) fluoran, 3-diethylamino-6-chloro-7- (γ-chloropropylamino) fluoran, 3-diethylamino-
6-chloro-7-anilinofluoran, 3-N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluoran, 3-diethylamino-7-phenylfluoran, 3- (N-isoamyl- N-ethylamino)-
6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran and the like. (4) Thiazine-based compounds Benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue and the like can be mentioned. (5) Spiro compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3
-Methylnaphtho- (3-methoxybenzo) spiropyran;

Next, as a developer, benzyl parahydroxybenzoate, dimethyl hydroxyphthalate, 2,4-dihydroxybenzophenone, N-stearyl-p-aminophenol, 3,4-bisphenol A, 4-hydroxy Salicylanilide, 4,4'-dihydroxydiphenyl ether, 4,4'-ethylidenebisphenol, 4,4'-isopropylidenediphenol (bisphenol A), 4,4 '-(1-methylpentylidene) bisphenol, tetramethylbisphenol A, 4,4 ′-(α-methylbenzylidene) bisphenol, 4,4 ′-(p-phenylenediisopropylidene) bisphenol, 4,4 ′-[(1,3-phenylenebis- (1-methylethylidene) ] Bisphenol, 4,4'-cyclohexylide Bisphenol,
2,2′-bis- (4-hydroxy-3-isopropylphenyl) propane, α, α′-bis- (3-methyl-
4-hydroxyphenyl) -m-diisopropylbenzophenone, n-butylbis (hydroxyphenyl) acetate, α, α ′, α ″ -tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene, 4,
4 '-[1- [4- [1- (4-hydroxyphenyl)
-1-methylethyl] phenyl] ethylidene] bisphenol, stearyl gallate, 2,3,4,4'-tetrahydroxybenzophenone, 4-hydroxy-4'-
Isopropoxydiphenyl sulfone, 2,2-bis (4,4′-hydroxyphenyl) sulfone, 4,4 ′
-Thiobis (6-t-butyl-m-cresol), 2,
2-bis (3-allyl-4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfide,
Bis (4-hydroxy-3-methylphenyl) sulfide, tetramethylbisphenol S and the like can be mentioned.

In the heat-sensitive recording material of the present invention, the water-soluble binder used for each layer includes starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, styrene-maleic anhydride. Water dispersibility of latexes such as acid copolymers, water-soluble binders such as ethylene-maleic anhydride copolymers, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, and methyl acrylate-butadiene copolymers Binders and the like. At least one of these water-soluble binders is used in a range of 15 to 80% by weight based on the total solid content of the heat-sensitive recording layer or the protective layer. Various crosslinking agents can be used to increase the water resistance of the film.

As the pigment, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin and the like are used. In addition, for the purpose of preventing head abrasion and preventing sticking, sensitized with higher fatty acid metal salts such as zinc stearate and calcium stearate, and waxes such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearic amide and caster wax. As the agent, various oxalic esters such as parabenzyl bisphenyl, esters of hydroxynaphthoic acid, stearic acid amide, tribenzylamine, naphthalene derivatives, dibenzyl terephthalate, and bis (paramethylbenzyl) oxalate can be used. Further, a dispersant such as sodium dioctylsulfosuccinate, a surfactant, a fluorescent dye and the like are used as required. Paper is mainly used as the substrate in the thermal recording medium of the present invention, and various nonwoven fabrics, plastic films, synthetic papers, metal foils and the like, or composite sheets obtained by combining these are arbitrarily used.

Using the various materials described above, the thermosensitive recording medium of the present invention can be manufactured by a conventionally known method. The method for preparing the coating solution for each layer of the thermosensitive recording medium is not particularly limited. In general, water is used as a dispersion medium, and in addition to the bisbenzotriazole of the present invention, a binder, a pigment to be added as necessary, a lubricant, and the like. It is prepared by mixing and stirring. In the case of a heat-sensitive recording layer, the adjustment is performed by adding a basic dye and a color developer. The basic dye and the developer are separately pulverized and dispersed in an aqueous system using a sand grinder, an attritor, a ball mill, or the like, and then mixed to obtain an aqueous paint, or any of the basic dyes and the developer. A method of obtaining a water-based paint after microencapsulation is known. The use ratio of the basic dye and the developer is appropriately selected depending on the type of the basic dye and the developer to be used and is not particularly limited, but is generally 1 to 50 parts by weight based on 1 part by weight of the basic dye. Parts by weight, preferably 2 to
A developer of about 10 parts by weight is used.

The bisbenzotriazole compound of the present invention is used in an amount of 1% based on the total solid content of each layer such as a heat-sensitive recording layer and a protective layer.
Preferably, it is present in the range of from 50 to 50% by weight, especially from 10 to 40% by weight. When the amount of such a compound is less than 1% by weight based on the total solid content, the light resistance of a recorded image and a white paper portion is remarkably reduced. Inferior. When it is contained in the protective layer, if it exceeds 50% by weight, the film-forming property of the protective layer is reduced and the chemical resistance of the recorded image is significantly reduced.

The method for forming each layer of the thermosensitive recording medium is not particularly limited, and air knife coating, buriba blade coating, pure blade coating,
Rod blade coating, short dwell coating, curtain coating, die coating and the like can be appropriately selected.For example, after coating a coating solution for a heat-sensitive coloring layer on a support and drying, a coating solution for a protective layer is further coated with a coating solution for a heat-sensitive coloring layer. It is formed by a method such as coating and drying. Further, the coating amount of the heat-sensitive recording layer coating liquid is 2 to 12 g by dry weight.
/ M ² , preferably about 3 to 10 g / m ² , and the coating amount of the coating solution for the intermediate layer or the protective layer is 0.1 to 15 g by dry weight.
/ M ² , preferably in the range of about 0.5 to 7 g / m ² . The thermosensitive recording medium of the present invention can be provided with a back coat layer on the back side of the support, if necessary, to further improve the storability. Furthermore, after each layer is formed, it is subjected to a smoothing treatment such as super calendaring, or a pressure-sensitive adhesive is applied to the rear surface of the heat-sensitive recording material to process the pressure-sensitive adhesive label. Various known techniques in the field of heat-sensitive recording material production, such as providing a recording layer, can be added according to the application.
Hereinafter, the present invention will be described in detail with reference to specific examples. However, the present invention is not limited to this embodiment. In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively, unless otherwise specified.

[0031]

EXAMPLES Example 1 Liquid A (Developer Dispersion) 4-Hydroxy-4'-isopropoxydiphenylsulfone 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts The mixture was ground with a sand grinder to an average particle size of 1 micron. Liquid B (dye dispersion liquid) 2,4-dimethyl-6-[(4-dimethylamino) anilino] fluorane 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts Water 2.6 parts Mixed solution of the above composition Was ground to an average particle size of 1 micron with a sand grinder. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. Solution A 36.0 parts Solution B 9.2 parts Kaolin clay 50% dispersion 12.0 parts Amount of each of the above coating solutions applied to one surface of a 50 g / m ² support 6.
The coating was dried at 0 g / m ² to form a heat-sensitive recording layer. Formation of protective layer (containing UV absorber) Liquid C (UV absorber dispersion) Bis [4- (2H-benzotriazol-2-yl) -3-hydroxyphenyl] terephthalate (melting point: 320 ° C) 12.0 parts 10 % Aqueous polyvinyl alcohol solution 6.7 parts Water 21.3 parts A mixture of the above compositions was ground with a sand grinder to an average particle size of 1 micron. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. 10% aqueous polyvinyl alcohol solution 60.0 parts Aluminum hydroxide (50% dispersion) 50.0 parts Zinc stearate 10.0 parts C solution 20.0 parts Dilution water 50.0 parts Fluorescent dye 25% aqueous solution 0.5 parts The coating solution was applied on the heat-sensitive recording layer so as to have a coating amount of 3.0 g / m ² and dried, and then subjected to a super calender treatment to obtain a heat-sensitive recording material.

Example 2 Formation of Thermal Recording Layer (Containing UV Absorber) Solution A (Developer Dispersion) 4-Hydroxy-4′-isopropoxydiphenyl sulfone 6.0 parts 10% aqueous solution of polyvinyl alcohol 18.8 parts Water 11.2 parts A mixture of the above composition was ground with a sand grinder to an average particle size of 1 micron. Liquid B (dye dispersion liquid) 2,4-dimethyl-6-[(4-dimethylamino) anilino] fluorane 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts Water 2.6 parts Mixed solution of the above composition Was ground to an average particle size of 1 micron with a sand grinder. Liquid C (ultraviolet absorbent dispersion) bis [4- (2H-benzotriazol-2-yl) -3-hydroxyphenyl] terephthalate 12.0 parts 10% aqueous polyvinyl alcohol solution 6.7 parts water 21.3 parts The mixture of the composition was ground with a sand grinder to an average particle size of 1 micron. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. Liquid A 36.0 parts Liquid B 9.2 parts Liquid C 20.0 parts Kaolin clay 50% dispersion liquid 12.0 parts Amount of each of the above coating liquids applied to one surface of a 50 g / m ² support 6.
The coating was dried at 0 g / m ² to form a heat-sensitive recording layer. Formation of protective layer A dispersion was mixed at the following ratio to obtain a coating liquid. 10% aqueous polyvinyl alcohol solution 60.0 parts Aluminum hydroxide (50% dispersion) 50.0 parts Zinc stearate 10.0 parts Dilution water 50.0 parts Fluorescent dye 25% aqueous solution 0.5 parts Heat-sensitive each coating solution After coating and drying on the recording layer to a coating amount of 4.0 g / m ² , a super calender treatment was performed to obtain a heat-sensitive recording material.

Comparative Example 1 A thermosensitive recording medium was produced in the same manner as in Example 1 except that the above-mentioned ultraviolet absorbent was not used. Comparative Example 2 Instead of the above-mentioned ultraviolet absorbent, an existing ultraviolet absorbent, 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetra) Methyl butyl) phenol] (melting point 195 ° C.)
Otherwise, a thermosensitive recording medium was manufactured in the same manner as in Example 1. Comparative Example 3 Instead of the above ultraviolet absorber, 3-hydroxy-4-
Using (2H-benzotriazol-2-yl) phenylbenzoate (melting point: 174 ° C.), a thermosensitive recording medium was produced in the same manner as in Example 1 except for the above.

Table 1 shows the results of quality performance tests performed on the thermal recording media obtained in the above Examples and Comparative Examples. Color development: The image density recorded at 0.26 mj / dot of UBI EasyCoder IIE (manufactured by UBI) was measured with a Macbeth densitometer. Light fastness: The heat-sensitive recording medium printed under the above conditions was treated with a xenon lamp weather meter for 24 hours, and then the image density,
The density of the background was measured with a Macbeth densitometer. (Irradiance
67W / m ² , integrated irradiance 5348kj / m ² ) Head residue: UBI EasyCoder
After recording four times consecutively at IIE (manufactured by UBI) at 0.41 mj / dot (running distance: 400 mm), the degree of contamination (head residue) of the thermal head was visually evaluated as follows. Evaluation criteria ◎: No head residue. ：: There is slight head residue, but there is no practical problem. ×: Many head residue. Plasticizer resistance test: A heat-sensitive recording medium printed under the above conditions was applied to a vinyl chloride film (Mitsubishi Resin Co., Ltd.
0G), allowed to stand at 40 ° C. for 24 hours, and measured the density of the recorded portion with a Macbeth densitometer. Oil resistance test: The thermosensitive recording medium printed under the above conditions was immersed in salad oil for 1 hour, the oil was extracted and left at room temperature for 24 hours.
The density of the recording part was measured with a Macbeth densitometer.

[0035]

[Table 1]

[0036]

As described above, the heat-sensitive recording material of the present invention containing the bisbenzotriazole compound represented by the general formula (1) as an ultraviolet absorber is excellent in light resistance of a recording portion and a background portion. Even when stored for a long time in sunlight or at high temperature, the color does not change and the appearance is not impaired. Further, adhesion of head scum during recording is suppressed, and the recording traveling property is also good.
Furthermore, it can be said that it has a new advantage that has not been obtained in the past, such as high storage stability against plasticizers and fats and oils. Further, the compound represented by the general formula (1) used in the present invention can be synthesized and purified very easily and is industrially useful.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidetoshi Yoshioka 5-2-1-1, Oji, Kita-ku, Tokyo Nippon Paper Industries Central Research Laboratory F-term (reference) 2H026 AA07 BB02 BB21 DD46 DD53 DD55

Claims (3)

[Claims] 1. A heat-sensitive recording medium having a thermosensitive coloring layer containing an electron-donating compound, an electron-accepting compound, and a binder formed on a substrate, wherein a bisbenzo compound represented by the following general formula (1) is provided. A heat-sensitive recording material comprising at least one triazole compound. Embedded image Here, R represents a divalent aromatic ring, and X and Y each represent a hydrogen atom, an alkyl group of C1 to C8, or a halogen atom. 2. The heat-sensitive recording material according to claim 1, wherein the bisbenzotriazole compound represented by the general formula (1) has a melting point of 280 ° C. or higher. 3. The bisbenzotriazole compound represented by the general formula (1) is bis [4- (2H-benzotriazol-2-yl) -3-hydroxyphenyl] terephthalate. The thermosensitive recording medium as described.