JPH09125046A - Ultraviolet light absorber, its preparation and heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultraviolet light absorber resistant to heat and external pressure, excellent in ultraviolet light absorption and a low cost, capable of retaining a clear image for a long period of time when used as a heat-sensitive recording material, by making a host compound include an ultraviolet light absorbing compound. SOLUTION: This an ultraviolet light absorber is obtained by including (A) an ultraviolet light absorbing compound such as a benzotriazole-based, a hindered amine-based, a salicylic acid-based, a benzophenone-based or a cyanoacrylate-based ultraviolet light absorbing compound in (B) a host compound such as a cyclodextrin compound, an amylose, a dextran (gel) or cyclophan. The absorber, for example, is obtained by blending or stirring the component A with a medium having dissolved or dispersed the component B at a temperature equal to or below the boiling temperature of the medium and removing the medium under reduced pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet absorber, a method for producing an ultraviolet absorber and a heat-sensitive recording material, and more specifically, a stable ultraviolet absorber having a high ultraviolet absorption efficiency and a method for producing the ultraviolet absorber in a high yield. And a heat-sensitive recording material excellent in image storability.

[0002]

2. Description of the Related Art A heat-sensitive recording material for obtaining an image by applying heat to a heat-sensitive recording layer containing at least a light-colored or colorless dye and a developer of this dye to obtain an image by contacting the dye and the developer is It is used in printers for measuring instruments, printers for computers, and facsimiles. The heat-sensitive recording material is inexpensive, and since the recording equipment is simple and maintenance is easy, the usage and the demand amount are expanding.

As the applications and demands of heat-sensitive recording materials are expanding, it is necessary to leave images for a long time.
During that time, there is a problem that the image part, which is the coloring part, is discolored by being exposed to light such as room light and sunlight, and conversely, the non-image part that is not colored is colored or yellowed, and the image is damaged. There is.

As a method for improving the light resistance of a heat-sensitive recording material, an ultraviolet absorbing compound is used in a heat-sensitive recording layer, an overcoat layer provided on the heat-sensitive recording layer, an intermediate layer provided between the heat-sensitive recording layer and a support and the like. A method of adding is proposed. However, the overcoat layer and the undercoat layer often contain additives such as plasticizers and fats and oils, and these additives elute the ultraviolet absorbing compound, resulting in a decrease in light resistance. In addition, there is a problem in that the ultraviolet absorbing compound causes yellowing of the non-image area and fading of the image area.

As means for solving these problems, JP-A-5-155134, JP-A-5-162442, and JP-A-6-155134.
Japanese Patent Publication No. 92028 proposes a method of incorporating an ultraviolet absorbing compound into microcapsules. By using transparent microcapsules, there is a protective wall between the ultraviolet absorbing compound and the dye, developer, and additive, and the image is not deteriorated by the ultraviolet absorbing compound, and the image is not generated. It is possible to solve problems such as fading of parts and yellowing of non-image parts.

However, in order to increase the ultraviolet absorption efficiency, it is necessary to contain as many ultraviolet absorbing compounds as possible in the microcapsules. When a solid ultraviolet absorbing compound is used, it must be dissolved in an organic solvent or the like, and the ultraviolet absorbing compound concentration cannot be increased. Therefore, there is a drawback that the usable ultraviolet absorbing compound is limited to liquid.

Since the microcapsules containing the UV absorbing compound must be stable to heat and pressure,
The film thickness must be increased. This causes a cost increase. Also, in order to improve the absorption efficiency of ultraviolet rays, it is necessary to miniaturize the microcapsules, but the synthetic minimum value is limited. Therefore, in order to develop sufficient light resistance, the amount of the microcapsules containing the ultraviolet absorbing compound is increased, and there is a drawback that the cost of the thermal paper, which is inexpensive, is increased.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
An object of the present invention is to provide an ultraviolet absorber which is resistant to external pressure such as pressure, has excellent ultraviolet absorption efficiency, and is low in manufacturing cost, and an easy method for producing an ultraviolet absorber. Another object of the present invention is to provide a thermosensitive recording material capable of suppressing fading of the image area and yellowing of the non-image area.

[0009]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found an ultraviolet absorber characterized in that an ultraviolet absorbing compound is included in a host compound.

Further, the inventors have found a method for producing an ultraviolet absorber characterized in that a medium in which a host compound and an ultraviolet absorbing compound are dissolved or dispersed is mixed or stirred at a temperature not higher than the boiling point of the medium, and then the medium is removed under reduced pressure.

Further, a thermal recording material having a thermal recording layer on a support and at least one of an undercoat layer between the support and the thermal recording layer and an overcoat layer on the thermal recording layer, We have found a heat-sensitive recording material characterized in that at least one of the coat layer and the undercoat layer contains an ultraviolet absorber in which an ultraviolet absorber is included in a host compound.

Hereinafter, the present invention will be described in detail. The ultraviolet absorbent of the present invention is obtained by including an ultraviolet absorbing compound in a host compound. Examples of the ultraviolet absorbing compound relating to the ultraviolet absorbent of the present invention include the compounds described in 1) to 5) below.

1) Benzotriazole type ultraviolet absorbing compound 2- (5'-methyl-2'-hydroxyphenyl) benzotriazole, 2- [2'-hydroxy-3 ', 5'
-Bis (α, α-dimethylbenzyl) phenyl] -2H
-Benzotriazole, 2- (2'-hydroxy-5 '
-Methylphenyl) benzotriazole, 2- (2'-
Hydroxy-5'-t-butylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t
-Butylphenyl) benzotriazole, 2- (2'-
Hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3
′ -T-Butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′,
5'-di-t-butylphenyl) -5-chlorobenzotriazole, 2- (3 ', 5'-di-t-amyl-2-
Hydroxyphenyl) benzotriazole, 2- (2 '
-Hydroxy-5'-t-octylphenyl) benzotriazole, methyl-3- [3-t-butyl-5- (2
H-benzotriazol-2-yl) -4-hydroxyphenyl] propinate-polyethylene glycol condensate, 2- (2'-hydroxy-3'-dodecyl-5'-
Methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-undecyl-5'-methylphenyl)
Benzotriazole, 2- (2'-hydroxy-3'-
Tridecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tetradecyl-5
′ -Methylphenyl) benzotriazole, 2- (2 ′)
-Hydroxy-3'-pentadecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-
3'-hexadecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy-3 '-(3 ",
4 ", 5", 6 "-tetrahydrophthalimido-methyl) -5'-methylphenyl] benzotriazole, 2
-[2'-hydroxy-3 ', 5'-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-4'-(2 "-ethylhexyl) oxyphenyl] Benzotriazole, 2-
[2'-hydroxy-4 '-(2 "-ethylheptyl)
Oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(2 "-ethyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-
4 '-(2 "-propylhexyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-
(2 "-propylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(2"-
Propyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(1 "-ethylhexyl) oxyphenyl] benzotriazole, 2-
[2'-hydroxy-4 '-(1 "-ethylheptyl)
Oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(1 "-ethyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-
4 '-(1 "-propylhexyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-
(1 "-propylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(1"-
Propyloctyl) oxyphenyl] benzotriazole and the like.

2) Hindered amine ultraviolet absorbing compounds bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 2 -(3,5-
Di-tert-butyl-4-hydroxybenzyl) -2-n-
Bis (1,2,2,6,6-pentamethyl-4-piperidyl) butylmalonate, 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate and the like.

3) Salicylic acid-based ultraviolet absorbing compound phenyl salicylate, pt-butylphenyl salicylate, p-octylphenyl salicylate and the like.

4) Benzophenone type ultraviolet absorbing compound 2,4-dihydroxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-
Dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone and the like.

5) Cyanoacrylate-based ultraviolet absorbing compound ethyl-2-cyano-3,3-diphenylacrylate, octyl-2-cyano-3,3-diphenylacrylate and the like.

The ultraviolet absorbing compound according to the present invention is not limited to the above examples. Further, two or more kinds may be used in combination, if necessary.

The host compound according to the present invention means the inside of a three-dimensional structure as described in "Host Guest Chemistry" (edited by Hiraoka, Yanagita, Ohara and Koga, published by Kodansha Scientific, published in 1984). It is a molecule or molecular assembly having pores in it. The host compound can incorporate other ions, atoms, molecules, etc. as guests, and forms adducts generally called inclusion compounds.
In the present invention, the ultraviolet absorbing compound serves as a guest.

Specific examples of the host compound according to the present invention include α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, 2,6-di-o-methyl-α-cyclodextrin and 2,6-di -O-methyl-
β-cyclodextrin, 2,6-di-o-methyl-γ
-Cyclodextrin, hydroxypropyl-α-cyclodextrin, hydroxypropyl-β-cyclodextrin, hydroxypropyl-γ-cyclodextrin, 6-o-maltosyl-α-cyclodextrin, 6
-O-maltosyl-β-cyclodextrin, 6-o-
Maltosyl-γ-cyclodextrin, 2,3,6-tri-o-methyl-β-cyclodextrin, poly-β-
Cyclodextrin compounds such as cyclodextrin, D
-Amylose, which is a linear polymer in which glucopyranose is polymerized by α-1,4 bond, dextran, dextran gel obtained by crosslinking dextran with epichlorohydrin, cyclophane, which is a macrocyclic compound having an aromatic ring, etc. Is mentioned. The host compound according to the present invention is not limited to the above examples, and two or more kinds can be used in combination.

The form in which the host compound according to the present invention includes the ultraviolet absorbing compound includes not only the form in which the ultraviolet absorbing compound is completely incorporated into the pores formed by the three-dimensional structure of the host compound, but also the ultraviolet absorbing compound. Various forms such as a partly incorporated state, a part or all of the ultraviolet absorbing compound and a host compound in addition or bonding other than pores.

Since the inclusion efficiency of the ultraviolet absorbent according to the present invention and the ultraviolet absorbent according to the present invention varies depending on the kind of the host compound, a combination is selected so that the inclusion can be carried out more reliably. For example, in the case of using a host compound such as a cyclodextrin compound or amylose, which is hydrophilic in appearance but has a hydrophobic pore in which an ultraviolet absorbing compound is included, an aliphatic alkyl group or an aromatic alkyl group is used. It is preferable to use an ultraviolet absorbing compound having a hydrophobic substituent such as

The ultraviolet absorbent of the present invention and the ultraviolet absorbent according to the present invention can be prepared by a method generally known as a method for preparing an inclusion compound. For example, a method in which the host compound and the ultraviolet absorbing compound are added to a medium that is a good solvent for at least one of the host compound and the ultraviolet absorbing compound and the mixture is stirred for several tens of minutes to several hours, and a suitable medium for the host compound and the ultraviolet absorbing compound is used. There are a method of adding and kneading, a method of emulsifying and dispersing using a homogenizer and the like. However, in order to include the UV absorbing compound in the host compound in a high yield, a method of adding and stirring the UV absorbing compound in a state where the host compound is completely dissolved in the medium is preferable. Further, in this case, if the ultraviolet absorbing compound is a liquid, the number of contact between the host compound and the ultraviolet absorbing compound is increased, and the ultraviolet absorbing agent can be obtained in a higher yield.

To carry out the above method, a medium that dissolves the host compound is used, and the ultraviolet absorbing compound is one that dissolves in the medium or, if it is insoluble, a temperature not higher than the boiling point of the medium. It is preferable to use a material having a melting point of. In this case, it is preferable that the temperature is not higher than the boiling point of the medium and that the host compound and the ultraviolet absorbing compound are not decomposed.

For example, when β-cyclodextrin is used as the host compound, water, dimethylformamide, dimethylsulfoxide or the like can be used as the medium. When dimethylformamide or dimethylsulfoxide is used, most of the above-mentioned ultraviolet absorbing compounds are soluble. If water is used as the medium,
A temperature of 50 ° C. or higher is required to dissolve β-cyclodextrin. In addition, since many of the ultraviolet absorbing compounds are water-insoluble, 2- (2'-hydroxy-5'-
Octylphenyl) benzotriazole, methyl-3-
[3-tert-butyl-5- (2H-benzotriazole-
2-yl) -4-hydroxyphenyl] propinate-
Polyethylene glycol condensate, 2- (2'-hydroxy-3'-dodecyl-5-methylphenyl) benzotriazole, bis (2,2,6,6-tetramethyl-4-)
Piperidyl) sebacate, bis (1, 2, 2, 6, 6-
Pentamethyl-4-piperidinyl) sebacate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octylbenzophenone, ethyl-2-cyano-3,3-diphenylacrylate, octyl-2.
It is preferable to use one having a melting point of 100 ° C. or lower, such as -cyano-3,3-diphenyl acrylate.

In the method for producing an ultraviolet absorbent of the present invention, a surfactant and an auxiliary solvent may be added in order to more surely include the host compound and the ultraviolet absorbent compound. Of these, it is highly possible that the surfactant cannot be finally removed from the ultraviolet absorber. Therefore, when this ultraviolet absorber is used for a heat-sensitive recording material, a surfactant that does not adversely affect the heat-sensitive recording is used. . It is necessary to consider that point also regarding the addition amount.

As the method for separating the ultraviolet absorbent of the present invention and the ultraviolet absorbent according to the present invention from the medium, the easiest method is to filter if the ultraviolet absorbent is insoluble in the medium. When the reaction system is concentrated under reduced pressure to remove the medium, the inclusion compound can be obtained in a higher yield. At this time, it is desirable to heat the medium for the purpose of quickly removing the medium and continuing the inclusion reaction. It is necessary that this temperature also does not exceed the decomposition temperature of the host compound and the ultraviolet absorbing compound. Further, the temperature at which the host compound is completely dissolved and the ultraviolet absorbing compound is liquid is desirable.

The thermosensitive recording material of the present invention has a structure in which a thermosensitive recording layer is provided on a support, and a protective layer is provided on the thermosensitive recording layer and at least one of the thermosensitive recording layer and the support. The protective layer provided on the thermosensitive recording layer is called an overcoat layer, and the protective layer provided between the thermosensitive recording layer and the support is called an undercoat layer. In the present invention, at least one of the overcoat layer and the undercoat layer contains an ultraviolet absorber. The sunlight or the ultraviolet rays contained in the fluorescent lamp cause the fading of the image area and the yellowing of the non-image area due to the decomposition reaction and the color reaction of the compound contained in the thermosensitive recording layer. By absorbing this ultraviolet ray in the overcoat layer and absorbing the ultraviolet ray transmitted through the heat-sensitive recording layer and reflected on the support by the undercoat layer, it is possible to solve such a problem.

The overcoat layer relating to the heat-sensitive recording material of the present invention contains a water-soluble or water-dispersible binder resin in addition to the UV absorber in which the UV absorbing compound is included in the host compound. Specific examples of the binder resin include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylic ester /
Water-soluble binder resin such as methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, and styrene / butadiene copolymer, acrylonitrile Examples thereof include latex-based water-dispersible binder resins such as / butadiene copolymer, methyl acrylate / butadiene copolymer, urea resin, melamine resin, amide resin and polyurethane resin.

For the purpose of crosslinking these binder resins, for example, ammonium zirconium carbonate,
Basic zirconium carbonate, melamine-formalin resin,
Epoxy polyamide polyamine, aziridine derivative,
A crosslinking agent such as an oxazoline-based reactive polymer, a diglycidyl ether of glycol, a polyglycidyl ether of polyol, or a reaction product of urea and formalin may be added.

The overcoat layer relating to the heat-sensitive recording material of the present invention has, for the purpose of improving the writability, for example, diatomaceous earth, talc, kaolin, calcined kaolin, clay, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide. , Silicon oxide, aluminum oxide, aluminum hydroxide, barium sulfate, zinc sulfate, colloidal silica, urea / formalin resin, styrene resin, nylon, pigment such as raw starch, resin and the like can be added.

The heat-sensitive recording material is generally printed by a heat-sensitive head of a heat-sensitive recording device. In order to improve running property, zinc stearate, calcium stearate, stearic acid amide, polyethylene wax, carnauba wax, paraffin wax, ester wax. Lubricants such as can be added.

The dry coating amount of the overcoat layer relating to the heat-sensitive recording material of the present invention is preferably 0.5 to 10 g / m ² . If the dry coating amount is less than 0.1 g / m ² , sufficient light resistance cannot be obtained. On the contrary, if it exceeds 20 g / m ² , the sensitivity is lowered.

The undercoat layer relating to the heat-sensitive recording material of the present invention comprises at least an ultraviolet absorber and a binder resin. As the binder resin that can be used for the undercoat layer, the same binder resin as that for the overcoat layer can be used. Also, for the undercoat layer,
The same cross-linking agent, pigment, resin, etc. as those of the overcoat layer can be added. The coating amount of the undercoat layer also conforms to that of the overcoat layer.

The coating solution for the overcoat layer and undercoat layer relating to the heat-sensitive recording material of the present invention is generally prepared by mixing the above-mentioned ultraviolet absorber, binder resin, pigment and other additives with water as a dispersion medium. It is prepared by dispersion. At the time of preparation, various surfactants may be added to enhance dispersibility. Further, a defoaming agent, an auxiliary agent or the like may be added. mixture,
A crusher such as a ball mill, an attritor, a paint conditioner or a sand grinder can be used for dispersion.

The color-forming component of the heat-sensitive recording layer relating to the heat-sensitive recording material of the present invention is not particularly limited. It should be one that exhibits a color reaction due to heat. Examples thereof include a combination of a colorless or light-colored electron-donating dye and an electron-accepting developer, and a combination of an aromatic isocyanate compound and an imino compound. These color-forming components can be used not only in a single combination but also in a plurality of combinations.

Examples of colorless to light-colored electron-donating dyes that can be used in the present invention include the following 1) to 5).
The ones mentioned are mentioned.

1) Triarylmethane compounds and indolylphthalide compounds 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-) Dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-diethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-3)
-Yl) phthalide, 3- (2-methyl-4-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl)-
3- (2-phenylindol-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) -5-dimethylaminophthalide,
3,3-bis (2-phenylindol-3-yl)-
5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6
-Dimethylaminophthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-dimethylamino-2-ethoxyphenyl) -4-azaphthalide, 3-
(1-ethyl-2-methylindol-3-yl) -3
-(4-Dimethylamino-2-ethoxyphenyl) -7
-Azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-dimethylamino-2-ethoxyphenyl) -4,7-diazaphthalide, 3,3-
Bis (4-diethylamino-2-ethoxyphenyl)-
4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (4-N-phenyl-N-ethylamino-2-ethoxyphenyl) -4-azaphthalide and the like.

2) Diphenylmethane compounds 4,4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like.

3) 2-anilinofluorane (or 7-anilinofluorane) type compounds 3-diethylamino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluor Oran, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (4
-Methylanilino) fluorane, 3-diethylamino-
6-methyl-7- (4-n-butylanilino) fluorane, 3-diethylamino-6-methyl-7- (4-ethoxyanilino) fluorane, 3-pyrrolidino-6-methyl-7- (4-methylanilino) fluorane , 3-pyrrolidino-6-methyl-7- (4-n-butylanilino)
Fluoran, 3-pyrrolidino-6-methyl-7- (4-
Ethoxyanilino) fluoran, 3-di-n-propylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-di- n-pentylamino-6-methyl-7-
Anilinofluoran, 3- (N-methyl-NNn-propyl) amino-6-methyl-7-anilinofluoran,
3- (N-ethyl-Nn-propyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N)
-Isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isobutyl) amino-
6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-tetrahydrofuran-2-ylmethyl) Amino-6-methyl-7-
Anilinofluoran, 3- (N-ethyl-N-tetrahydrofurylmethyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-tetrahydrofuran-2-yl) amino-6 Methyl-7-anilinofluoran, 3- (N-ethyl-N-tetrahydrofuryl)
Amino-6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7-anilinofluoran,
3- (N-methyl-N-ethyl) amino-6-methyl-
7-anilinofluoran, 3-isopentylamino-6
-Methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7- (2-fluoroanilino)
Fluoran, 3-dibutylamino-6-methoxy-7-
Anilinofluoran, 3-di-n-butylamino-6-
Methyl-7- (2,6-dimethylanilino) fluoran, 3- (N-ethyl-N-3-ethoxypropyl) amino-6-methyl-7-anilinofluoran, 3- (N
-Methyl-N-3-ethoxypropyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-
6-methyl-7- (3-trifluoromethylanilino)
Fluorane, 3-diethylamino-7- (3-trifluoromethylanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-7- (3-chloroanilino) fluorane, 3
-Di-n-butylamino-7- (3-chloroanilino)
Fluoran, 3-diethylamino-7- (2-fluoroanilino) fluoran, 3-diethylamino-7- (2
-Methoxyanilino) fluoran, 3-pyrrolidino-7
-(2-chloroanilino) fluoran, 3-pyrrolidino-7- (3-chloroanilino) fluoran, 3-pyrrolidino-7- (2-methoxyanilino) fluoran, 3-
Diethylamino-7- (2-isopentyloxycarbonylanilino) fluorane, 3- (N-ethyl-N-p
-Tolyl) amino-6-methyl-7-anilinofluorane and the like.

4) Fluoran compounds and xanthene compounds 3-pyrrolidino-7-cyclohexylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-n-octylaminofluorane, 3- Diethylamino-7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-
Diethylamino-6-chloro-7-methylfluoran,
3-diethylamino-6-methyl-7-chlorofluorane, 3-di-n-butylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3-ethylamino-6-
Chlorofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-di-n-butylamino-7-
(2-chlorobenzylamino) fluorane, rhodamine B anilinolactam, rhodamine B-p-chloroanilinolactam and the like.

5) Spiro compounds such as vinylogous triarylmethane compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphtho Spiropyran compounds such as pyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, and 3-propylspirobenzopyran,
3 ', 6'-bisdiethylamino-5-diethylaminospiro (isobenzofuran-1,9'-fluorene)-
A compound having a fluorene skeleton such as 3-one, 3 ', 6'-bisdimethylamino-5-dimethylaminospiro (isobenzofuran-1,9'-fluorene) -3-one,
3,3-bis- [2- (4-methoxyphenyl) -2-
(4-Dimethylaminophenyl) ethenyl] -4,5,
6,7-Tetrachlorophthalide and the like.

Examples of the electron-accepting color developer include those described in 1) to 4) below. 1) Phenol derivative p-phenylphenol, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) propane, 1,1 -Bis (p-hydroxyphenyl) -1-phenylethane, 1,4-di [2
-(P-hydroxyphenyl) -2-propyl] benzene, 4,4'-dihydroxydiphenyl ether, 2,
Methyl 2-bis (4-hydroxyphenyl) acetate and the like.

2) Aromatic carboxylic acids and their esters Benzoic acid, pt-butylbenzoic acid, trichlorobenzoic acid, 3-s-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3 , 5-Dimethyl-4-hydroxybenzoic acid, benzyl p-hydroxybenzoate, propyl p-hydroxybenzoate, salicylic acid, 3-isopropylsalicylic acid, 3-t-butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methyl) Benzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3,5-di-t-butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,5-di -Α-methylbenzyl salicylic acid, dimethyl p-hydroxyphthalate, terephthalic acid, benzyl gallate, sa Chiruanirido like.

3) A polyvalent metal salt of the above phenol derivative or aromatic carboxylic acid and zinc, magnesium, calcium, titanium, manganese, tin, nickel or the like.

4) Inorganic compounds such as activated clay, acid clay, attapulgite, bentonite and aluminum silicate.

The aromatic isocyanate compound which can be used in the heat-sensitive recording material of the present invention is a colorless or light-colored aromatic isocyanate compound or a heterocyclic isocyanate compound which is solid at room temperature. For example, 2,6-dichlorophenyl isocyanate, 1,4-phenylene diisocyanate, 1-methoxybenzene-2,5-diisocyanate, 2,5-diethoxybenzene-1,4-
Diisocyanate, azobenzene-4,4'-diisocyanate, diphenyl ether-4,4'-diisocyanate, naphthalene-1,4-diisocyanate, 3,
3'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, diphenyldimethylmethane-4,4'-
Diisocyanate, fluorene-2,7-diisocyanate, 9-ethylcarbazole-3,6-diisocyanate, pyrene-3,8-diisocyanate, biphenyl-2,4,4'-triisocyanate, 4,4 ', 4 "
-Triisocyanate-2,5-dimethoxytriphenylamine, p-dimethylaminophenylisocyanate and the like can be mentioned.

The imino compound that can be used in the heat-sensitive recording material of the present invention is a colorless or light-colored compound that is solid at room temperature. For example, 3-imino-4,5,6,7-
Tetrachloroisoindoline-1-one, 1,3-diimino-4,5,6,7-tetrachloroisoindoline,
1-iminodiphenimide, 1- (cyano-p-nitrophenylmethylene) -3-iminoisoindoline, 1
-(Cyanobenzothiazolyl- (2 ')-carbamoylmethylene) -3-iminoisoindoline, 1-[(cyanobenzimidazolyl-2')-methylene] -3-iminoisoindoline, 1-[(cyanobenz Imidazolyl-2 ')-methylene] -3-imino-4,5,6,7-
Tetrachloroisoindoline, 1-[(cyanobenzimidazolyl-2 ')-methylene] -3-imino-5-methoxyisoindoline, 1-[(1'-phenyl-3'
-Methyl-5-oxo-) pyrazolidene-4 ']-3-
Iminoisoindoline, 3-imino-1-sulfobenzoic acid imide, 3-imino-1-sulfo-4,5,6,7-
Tetrachlorobenzoic acid imide, 3-imino-1-sulfo-4,5,7-trichloro-6-methylmercaptobenzoic acid imide, 3-imino-2-methyl-4,5,6,7
-Tetrachloroisoindoline-1-one and the like.

The coating solution for the heat-sensitive recording layer relating to the heat-sensitive recording material of the present invention is prepared by mixing a dye and a developer separately with a ball mill, an attritor, a sand mill, a paint conditioner, or a crusher, or together. Do it dispersedly.

In the heat-sensitive recording layer relating to the heat-sensitive recording material of the present invention, as a pigment, diatomaceous earth, talc, kaolin, calcined kaolin, clay, calcined clay, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, water. Inorganic pigments such as aluminum oxide, anhydrous silica, activated clay,
Resins such as styrene, nylon, polyethylene, starch, urea-formalin resin and the like can be used.

Further, a lubricant such as stearic acid, a metal salt of stearic acid, paraffin wax, carnauba wax, polyethylene wax, and ester wax, an interface of sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, a fatty acid metal salt, etc. Activator, antifoaming agent, fluorescent dye,
A coloring dye or the like can be added as appropriate.

The heat-sensitive recording layer of the heat-sensitive recording material of the present invention comprises
Binder resin is added. Examples of the binder resin include starch, hydroxycellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylate, acrylamide / acrylic acid ester / methacrylic acid terpolymer, diester Water-soluble binder resin such as isobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, natural rubber emulsion, Use of latex-based water-insoluble binder resin such as styrene / butadiene copolymer emulsion, acrylonitrile / butadiene copolymer emulsion, polychloroprene emulsion, vinyl acetate emulsion, ethylene / vinyl acetate emulsion, etc. Can.

The general dry coating amount of the heat-sensitive recording layer relating to the heat-sensitive recording material of the present invention is 3 to 10 g / m ² .

The method for forming the overcoat layer, the heat-sensitive recording layer and the undercoat layer relating to the heat-sensitive recording material of the present invention is as follows:
It can be formed by an appropriate coating method such as an air knife coating method, a short dwell coating method, a curtain coating method, a rod blade coating method, a varibar blade coating method, a pure blade coating method, or a die coating method. The heat-sensitive recording material according to the present invention is prepared by applying an undercoat layer on a support, followed by drying, then applying the heat-sensitive recording layer, drying and then applying an overcoat layer. Further, if necessary, it is possible to improve the smoothness by performing a super calendar treatment after forming each layer.

As the support for the heat-sensitive recording material of the present invention, paper, synthetic resin film, synthetic paper, woven cloth, non-woven cloth,
A metal vapor deposition sheet, laminated paper, etc. can be used.

[0056]

The present invention relates to an ultraviolet absorber, a method for producing the ultraviolet absorber and a heat-sensitive recording material containing the ultraviolet absorber. Since the ultraviolet absorbent of the present invention and the ultraviolet absorbent according to the present invention have the ultraviolet absorbing compound clathrated by the host compound, they have resistance to external pressure such as pressure and temperature. When using an ultraviolet absorber, working conditions such as kneading and dispersion are not limited. Also,
The production cost can be reduced by using an inexpensive host compound.

Unlike the microencapsulated ultraviolet absorbent, the ultraviolet absorbent of the present invention has a molecular level in size, and therefore has an ultraviolet absorption efficiency equivalent to that of the guest ultraviolet absorbing compound. Therefore, in the heat-sensitive recording material of the present invention in which the ultraviolet absorber of the present invention is contained in the overcoat layer or the undercoat layer of the heat-sensitive recording material, it is possible to efficiently absorb ultraviolet rays with a minimum amount of the ultraviolet absorbing compound used. . In addition, since it is stable against external pressure when stored for a long period of time, there is no problem that the clathrated ultraviolet absorbing compound leaks to the outside and deteriorates the image.

Further, according to the method for producing an ultraviolet absorber of the present invention, it is possible to produce an ultraviolet absorber in a high yield by a very simple method, and it is possible to keep the production cost low.

[0059]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples unless it is contrary to the gist thereof.

Preparation Example 1 Preparation of Ultraviolet Absorber A After dissolving 20 parts by weight of β-cyclodextrin in 200 parts by weight of ion-exchanged water heated to 90 ° C., 2- (3,5-di-) which is an ultraviolet absorbing compound. t-amyl-2-hydroxyphenyl) benzotriazole (melting point 90 ° C.) 5.8
7 parts by weight was added and stirred for 4 hours. Then increase the temperature to 9
The ion-exchanged water was removed under reduced pressure while maintaining the temperature at 0 ° C. It was dried under reduced pressure in the presence of phosphorus pentoxide at room temperature to obtain 19.3 parts by weight of ultraviolet absorber A which was a β-cyclodextrin clathrate compound.

Preparation Example 2 Preparation of Ultraviolet Absorber B After dissolving 20 parts by weight of amylose (average molecular weight of 30,000) in ion-exchanged water heated to 90 ° C., 2- (2′-hydroxy-3) which is an ultraviolet absorbing compound. ′ -Dodecyl-5′-methylphenyl) benzotriazole (melting point 20 ° C. or lower)
1.57 parts by weight and 0.002 parts by weight of polyoxyethylene sorbitan monooleate, which is a surfactant, were added and dispersed using a homogenizer for 3 hours. Then increase the temperature to 9
The ion-exchanged water was removed under reduced pressure while maintaining the temperature at 0 ° C. It was dried at room temperature under reduced pressure in the presence of phosphorus pentoxide to obtain 18.7 parts by weight of ultraviolet absorber B which is an amylose inclusion compound.

Preparation Example 3 Preparation of Ultraviolet Absorber C After dissolving 20 parts by weight of maltosyl cyclodextrin in 100 parts by weight of deionized water at 40 ° C., 2-hydroxy-4-methoxybenzophenone (melting point: 60) as an ultraviolet absorbing compound. (° C.) 3.8 parts by weight was added and stirred for 3 hours.
Then, after the temperature was raised to 50 ° C., the medium, ion-exchanged water was removed under reduced pressure. It was dried at room temperature under reduced pressure in the presence of phosphorus pentoxide to obtain 15.3 parts by weight of ultraviolet absorber C which was a clathrate compound of maltosyl cyclodextrin.

Preparation Example 4 Preparation of Ultraviolet Absorber D After dissolving 20 parts by weight of β-cyclodextrin in 200 parts by weight of ion-exchanged water heated to 90 ° C., 2- (2′-hydroxy-5) which is an ultraviolet absorbing compound. ′ -T-octylphenyl) benzotriazole (melting point 103 ° C.) 5.4
Part by weight was added and stirred for 6 hours. Then the temperature was lowered to room temperature and the precipitate was collected by filtration. This precipitate was dried at room temperature under reduced pressure in the presence of phosphorus pentoxide to obtain 10.6 parts by weight of the clathrate compound UV absorber D.

In Preparation Examples 1 to 4, the ultraviolet absorber A to
Although it was possible to obtain D, in Preparation Examples 1 to 3, which is the method for preparing an ultraviolet absorbent of the present invention, the ultraviolet absorbent could be obtained in a high yield. Further, in Preparation Examples 1 and 2 in which the melting point of the ultraviolet absorbing compound was lower than the temperature of the inclusion reaction and was a liquid, the ultraviolet absorbing agent could be obtained in a higher yield.

Example 1 Preparation of coating liquid for thermosensitive recording layer 30 parts by weight of electron donating dye 3-diethylamino-6-methyl-7-anilinofluorane was added to 50 parts by weight of 10% polyvinyl alcohol solution and ion-exchanged water. It was pulverized with 20 parts by weight of a paint conditioner to obtain an electron donating dye dispersion liquid p. Next, 30 parts by weight of the electron-accepting developer bisphenol A, 40 parts by weight of a 10% polyvinyl alcohol aqueous solution, and 30 parts by weight of ion-exchanged water were dispersed by a paint conditioner to obtain an electron-accepting developer dispersion liquid q.

Next, 30 parts by weight of the electron-donating dye dispersion p and 150 parts by weight of the electron-accepting developer dispersion q are mixed, and then the following components are added and mixed with stirring to prepare a heat-sensitive recording layer coating solution r. Was produced. 40% zinc stearate aqueous dispersion 25 parts by weight 10% polyvinyl alcohol aqueous solution 220 parts by weight calcium carbonate 50 parts by weight ion-exchanged water 410 parts by weight

Overcoat layer and undercoat layer
Preparation of dual-purpose coating liquid 50 parts by weight of ultraviolet absorber A, 50 parts by weight of ion-exchanged water,
0.5 parts by weight of polyvinyl alcohol was dispersed with a paint conditioner to obtain an ultraviolet absorbent A dispersion. The following components were mixed with 50 parts by weight of this ultraviolet absorbent A dispersion liquid to obtain a coating liquid a for both overcoat layer and undercoat layer. 30% aluminum hydroxide dispersion liquid 80 parts by weight 10% polyvinyl alcohol aqueous solution 500 parts by weight Ion exchange water 370 parts by weight

Preparation of Thermosensitive Recording Material The undercoat layer coating liquid a was coated on a base paper having a basis weight of 40 g / m ² to a dry coating amount of 6.0 g / m ² , dried, and calendered. On top of that, the thermosensitive recording layer coating liquid r was coated so that the dry coating amount was 5.0 g / m ² .
It was dried and calendered. Further, the overcoat layer coating liquid a was applied so as to have a dry coating amount of 2.0 g / m ² , dried and calendered to obtain a thermal recording material I.
I got

Evaluation of Coloring Property A thermosensitive recording material I was used as a thermosensitive facsimile printing tester TH-PMD manufactured by Okura Electric Co., Ltd. with a print head LH4409 manufactured by TDK.
With a pulse width of 0.4 to 2.8 milliseconds and a voltage of 2
Gradation printing was performed under the condition of 0 volt. The applied energy per unit area in this printing test is 20 to 140 mJ / mm
It is in the range of ² . (Hereinafter, the applied energy per unit area is simply abbreviated as the applied energy.) The density of the printed portion and the like was measured using a densitometer Macbeth RD918. The filter used black.

Evaluation of Light Resistance After the thermal recording material I after printing was irradiated with direct sunlight for 14 days, the image area and the non-image area were measured with a Macbeth densitometer (filter; black and yellow). The results are shown in Table 1.

Examples 2 to 4 Coating solutions for both overcoat layer and undercoat layer
Preparation Using 50 parts by weight of each of the UV absorbers B to D, adding 50 parts by weight of ion-exchanged water and 0.5 part by weight of polyvinyl alcohol, and dispersing with a paint conditioner to obtain a dispersion liquid of the UV absorbers B to D. Got each. The following components were mixed with 50 parts by weight of each of the dispersion liquids of the ultraviolet absorbers B to D to obtain coating liquids b to d for both overcoat layer and undercoat layer. 30% aluminum hydroxide dispersion liquid 80 parts by weight 10% polyvinyl alcohol aqueous solution 500 parts by weight Ion exchange water 370 parts by weight

Preparation of thermal recording materials II to IV Undercoat layer coating liquids b to d were separately coated on a base paper having a basis weight of 40 g / m ^{2 to} a dry coating amount of 6.0 g / m ² and dried. , Calendered. The thermal recording layer coating liquid r was dried thereon to a dry coating amount of 5.0 g / m 2.
^It was applied, dried and calendered so that it would be ² .
Further, the overcoat layer coating liquids b to d are applied, dried and calendered correspondingly to the undercoat layer coating liquids b to d so that the dry coating amount becomes 2.0 g / m ² , respectively, to obtain a thermal recording material. II-IV were obtained.

Evaluation of Coloring Property and Evaluation of Light Resistance The thermal recording materials II to IV were gradation printed under the same conditions as in Example 1 and the density of the printed portion was measured. Thermal recording material after printing
After irradiating II to IV with direct sunlight in the same manner as in Example 1, the densities of the image area and the non-image area were measured with a Macbeth densitometer. The results are shown in Table 1.

[0074] coated with a heat-sensitive recording layer coating solution r to a dry coating weight 5.0 g / m ² on a base paper of Example 5-6 thermosensitive recording material V~VI Preparation basis weight of 40 g / m ^2, dried Then, calendering treatment was performed to form a heat-sensitive recording layer. Further, the overcoat layer coating liquids a to b were applied in a dry coating amount of 2.0 g / m ^2.
Coating, drying and calendering were performed to obtain heat-sensitive recording materials V to VI.

Evaluation of Coloring Property and Evaluation of Light Resistance The thermal recording materials V to VI were subjected to gradation printing under the same conditions as in Example 1 and the density of the printed portion was measured. The printed thermal recording materials V to VI were exposed to direct sunlight in the same manner as in Example 1, and then the densities of the image area and the non-image area were measured with a Macbeth densitometer. The results are shown in Table 1.

Examples 7 to 8 Preparation of thermal recording materials VII to VIII Coating solutions a to b for the undercoat layer were coated on a base paper having a basis weight of 40 g / m ² so that the dry coating amount was 6.0 g / m ^2. ,
It was dried and calendered. The heat-sensitive recording layer coating solution r was applied thereon, dried so as to have a dry coating amount of 5.0 g / m ² , and calendered to obtain a heat-sensitive recording material VII.
I got ~ VIII.

Evaluation of Coloring Property and Evaluation of Light Resistance The thermosensitive recording materials VII to VIII were gradation printed under the same conditions as in Example 1 and the density of the printed portion was measured. The printed thermal recording materials VII to VIII were exposed to direct sunlight in the same manner as in Example 1, and then the densities of the image area and the non-image area were measured with a Macbeth densitometer. The results are shown in Table 1.

[0078]

[Table 1]

Comparative Example 1 Overcoat layer and undercoat layer combined coating solution e
Preparation of Disperse the liquid of the following composition with a paint conditioner,
A coating liquid e that did not contain an ultraviolet absorber and was used as both an overcoat layer and an undercoat layer was obtained. 30% aluminum hydroxide dispersion 90 parts by weight 10% polyvinyl alcohol aqueous solution 500 parts by weight ion-exchanged water 370 parts by weight

Preparation of heat-sensitive recording material IX An undercoat layer coating solution e was applied on a base paper having a basis weight of 40 g / m ^{2 so} that the dry coating amount was 6.0 g / m ² , dried and calendered. . On top of that, the thermosensitive recording layer coating liquid r was coated so that the dry coating amount was 5.0 g / m ² .
It was dried and calendered. Further, the overcoat layer coating liquid e is applied so as to have a dry coating amount of 2.0 g / m ² , dried and calendered, and the overcoat layer and the undercoat layer do not contain an ultraviolet absorber. Got

Evaluation of Coloring Property and Evaluation of Light Resistance The thermosensitive recording material IX was gradation printed under the same conditions as in Example 1 and the density of the printed portion was measured. Thermal recording material after printing IX
Was irradiated with direct sunlight in the same manner as in Example 1, and the densities of the image area and the non-image area were measured with a Macbeth densitometer. The results are shown in Table 2.

Comparative Example 2 Overcoat layer and undercoat layer combined coating solution f
Preparation of 2- (2'-hydroxy-3 ', an ultraviolet absorbing compound
15 parts by weight of -dodecyl-5'-methylphenyl) benzotriazole (melting point 20 ° C or lower), 50 parts by weight of ion-exchanged water, and 0.15 parts by weight of polyvinyl alcohol were dispersed with a paint conditioner to obtain an ultraviolet absorbing compound dispersion liquid. . The following components were mixed with 50 parts by weight of this ultraviolet absorbing compound dispersion liquid to obtain a coating liquid f for both overcoat layer and undercoat layer. 30% aluminum hydroxide dispersion liquid 80 parts by weight 10% polyvinyl alcohol aqueous solution 500 parts by weight Ion exchange water 370 parts by weight

Preparation of Thermosensitive Recording Material X Coating solution f for undercoat layer was coated on a base paper having a basis weight of 40 g / m ^{2 so} that the dry coating amount was 6.0 g / m ² , dried, and calendered. . On top of that, the thermosensitive recording layer coating liquid r was coated so that the dry coating amount was 5.0 g / m ² .
It was dried and calendered. Further, the coating liquid f for the overcoat layer is applied so as to have a dry coating amount of 2.0 g / m ² , dried and calendered to absorb ultraviolet rays not included in the host compound in the overcoat layer and the undercoat layer. A thermal recording material X containing the compound was obtained.

Evaluation of Coloring Property and Evaluation of Light Resistance The thermal recording material X was subjected to gradation printing under the same conditions as in Example 1 and the density of the printed portion was measured. Thermal recording material X after printing
Was irradiated with direct sunlight in the same manner as in Example 1, and the densities of the image area and the non-image area were measured with a Macbeth densitometer. The results are shown in Table 2.

[0085]

[Table 2]

As shown in Table 1, when the ultraviolet absorber is contained in at least one selected from the overcoat layer and the undercoat layer, the ultraviolet absorber is contained in the overcoat layer and the undercoat layer. As compared with the case (Comparative Example 1), the yellowing of the non-image area and the fading of the image area were suppressed.

Further, as in Comparative Example 2, when an oily ultraviolet absorbing compound was added at room temperature, oil bleeding was formed when the overcoat layer was formed, and the light resistance such as color development at that portion was poor. It was However, in Example 2 in which the UV absorbing compound was included in the host compound, oil bleeding could occur when the heat-sensitive recording material was formed without impairing the inclusion in dispersion and preparation of the coating liquid. There was no. Therefore, a clear image could be stably retained.

[0088]

As described above, the ultraviolet absorbent of the present invention has resistance to external pressure such as heat and pressure, and can effectively absorb ultraviolet light. Therefore,
In the heat-sensitive recording material containing the ultraviolet absorbent of the present invention in at least one selected from the overcoat layer and the undercoat layer, deterioration of the image caused by ultraviolet rays is suppressed, and a clear image can be retained for a long time. It will be possible. Furthermore, the ultraviolet absorbent preparation method of the present invention can provide the ultraviolet absorbent easily and in high yield.

Claims (4)

[Claims] 1. An ultraviolet absorber characterized in that an ultraviolet absorbing compound is included in a host compound. 2. A method for producing an ultraviolet absorber, which comprises mixing or stirring a medium in which a host compound and an ultraviolet absorbing compound are dissolved or dispersed at a temperature not higher than the boiling point of the medium, and then removing the medium under reduced pressure. 3. A thermosensitive recording material comprising a thermosensitive recording layer on a support and at least one of an undercoat layer between the support and the thermosensitive recording layer and an overcoat layer on the thermosensitive recording layer. A heat-sensitive recording material, characterized in that at least one of a coat layer and an undercoat layer contains an ultraviolet absorber in which an ultraviolet absorber is included in a host compound. 4. The method for producing an ultraviolet absorbent according to claim 2, wherein the melting point of the ultraviolet absorbing compound is not higher than the boiling point of the medium.