JP3136734B2 - Thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording medium having excellent storage stability, especially light fastness, and having little background fog.

[0002]

2. Description of the Related Art A thermosensitive recording medium which uses a color reaction between a colorless or light-colored basic dye and an organic or inorganic colorant to contact both coloring materials by heat to obtain a recorded image is often used. Are known. Such a thermosensitive recording medium is relatively inexpensive, and its recording equipment is compact and easy to maintain, so that it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

Conventionally, in order to increase the recording sensitivity of a thermosensitive recording medium, a sensitizer which causes a melting point drop with a basic dye or a colorant is added to the recording layer, or a basic dye or a colorant is added to the recording layer. Although methods such as miniaturization have been proposed, there is a disadvantage that background fogging occurs with the improvement in recording sensitivity. Further, a method of adding a finely pulverized ultraviolet absorber to a recording layer or a protective layer has been proposed for the purpose of preventing yellowing due to light on a background portion of a thermal recording medium. If it is increased, there arises a disadvantage that the recording sensitivity is lowered and the background fog is caused. Also,
If the protective layer contains a finely ground UV absorber,
UV absorbers elute under the influence of plasticizers and fats and oils, impairing the function of the protective layer, deteriorating the storage stability of recorded images, causing new flaws such as background fog, and as a result, At present, satisfactory light fastness has not yet been obtained.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermosensitive recording medium having a protective layer on a recording layer, in which the discoloration of the recorded image and the yellowing of the background portion due to exposure to light are extremely small. An object of the present invention is to provide a thermosensitive recording medium with less fog.

[0005]

Means for Solving the Problems The present inventors have proposed a thermosensitive recording medium in which a recording layer containing a colorless or pale-colored basic dye and a color former and a protective layer are sequentially provided on a support. The layer contains at least one compound represented by the following general formula (1) or (2) as an ultraviolet absorber and a basic dye as a basic dye, and is contained in the protective layer at room temperature.
Benzotriazole-based UV absorbers , and have virtually no color-forming ability , including polyurethane and polyurea resins.
Others by causing contain microphone <br/> Rokapuseru having a wall film made of aminoaldehyde resin, discoloration of the recorded image to light exposure, and yellowing is extremely small in the background section, yet that background fogging is less The present invention has been completed.

[0006]

Embedded image

[In the formula, R ₁ and R ₂ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms which may be substituted by an alkoxyl group having 1 to 4 carbon atoms. However, R ₁ and R ₂ do not bond to each other. ]

[0008]

Embedded image

[In the formula, R ₃ and R ₄ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms which may be substituted by an alkoxyl group having 1 to 4 carbon atoms. However, R ₃ and R ₄ do not bond to each other. X ₁ is a fluorine atom,
Indicates a chlorine atom. ]

[0010]

The specific examples of the basic dye represented by the general formula (1) used in the recording layer in the present invention include the following. 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3
-Diethylamino-6-methyl-7-anilinofluoran, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6
-Methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-furfurylamino) -6 Methyl-7-anilinofluoran, 3-
(N-methyl-NN-propylamino) -6-methyl-7-anilinofluoran, 3-di (n-propyl) amino-6-methyl-7-anilinofluoran and the like

Further, specific examples of the basic dye represented by the general formula (2) include the following.
3-diethylamino-7-o-chloroanilinofluoran, 3-di (n-butyl) amino-7-o-chloroanilinofluoran, 3-diethylamino-7-o-fluoroanilinofluoran, 3- Di (n-butyl) amino-
7-o-fluoroanilinofluoran, 3- (N-ethyl-N-isoamyl) amino-7-o-chloroanilino) fluoran, 3- (N-ethyl-Nn-hexyl) amino-7-o- Chloroanilinofluoran, 3-
(N-ethyl-N-isoamyl) amino-7-o-fluoroanilinofluoran, 3-di (n-pentyl) amino-7-o-chloroanilinofluoran, 3- (N-methyl-N- n-propylamino) -7-o-chloroanilinofluoran and the like. Of course, the invention is not limited to these, and two or more of them can be used in combination.

In the present invention, various known colorless or light-colored basic dyes can be used in combination depending on the purpose. Various materials are also known as colorants used in combination with the specific basic dyes and various known basic dyes as described above, for example, activated clay, attapulgite, colloidal silica, and inorganic acidic substances such as aluminum silicate. 4,4'-isopropylidene diphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyl Diphenyl sulfone, bis (4-hydr (Xyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl)-
1-phenylethane, 1,4-bis [α-methyl-α-
(4'-hydroxyphenyl) ethyl] benzene, 1,
3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfine, 4,4′-dihydroxydiphenyl-2,2-butane, 4'-dihydroxydiphenylmethane, 4-cumylphenol, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone,
2,2-bis (4-hydroxyphenyl) heptane,
1,1-bis (4-hydroxyphenyl) cyclohexane, 3,4-dihydroxyphenyl-p-tolylsulfone, di (p-hydroxyphenylthioethyl) ether, N, N'-di-m-chlorophenylthiourea, −
Hydroxy-3 ', 4'-tetramethylenebiphenylsulfone, (4-hydroxyphenylthio) acetic acid-2-
(4-hydroxyphenylthio) ethyl ester, N-
Phenolic compounds such as (phenoxyethyl) -4-hydroxyphenylsulfonamide, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid,
Aromatic carboxylic acids such as {3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, zinc p-chlorobenzoate, and aromatics thereof Salts of carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel,
Further, organic acidic substances such as an antipyrine complex of zinc thiocyanate and the like are exemplified.

The ratio between the basic dye and the colorant is appropriately selected according to the type of the basic dye and the colorant used, and is not particularly limited. 1 to 50 parts by weight, preferably 2 to 5 parts by weight
About 10 parts by weight of a color former is used.

Further, specific examples of the solid ultraviolet absorber used in the recording layer of the present invention and the solid ultraviolet absorber contained in the microcapsules are as follows. Phenyl salicylate, p-tert-butylphenyl salicylate, salicylic acid ultraviolet absorbers such as p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone and the like Benzophenone ultraviolet absorbers, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-tert-butylphenyl) benzotriazole,
2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-
5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-
3 ', 5'-di-tert-amylphenyl) benzotriazole, 2- [2'-hydroxy-3'-(3 ",
4 ", 5", 6 "-tetrahydrophthalimido-methyl) -5'-methylphenyl] benzotriazole,
-(2'-hydroxy-5'-tert-octylphenyl) benzotriazole, 2- [2'-hydroxy-
Benzotriazole ultraviolet absorbers such as 3 ', 5'-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, Succinic acid-bis (2,2,6,6-tetramethyl-4-piperidyl) ester, 2- (3,5-di-tert-butyl) malonic acid-
Hindered amine UV absorbers such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) ester

Further, specific examples of the liquid ultraviolet absorber contained in the microcapsules of the present invention include the following. 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2
-(2'-hydroxy-3'-undecyl-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-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 "-propyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-(2" -propylheptyl) oxyphenyl ]
Benzotriazole, 2- [2'-hydroxy-4'-
(2 "-propylhexyl) 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 "-propyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-(1" -propylheptyl) oxyphenyl ]
Benzotriazole, 2- [2'-hydroxy-4'-
(1 "-propylhexyl) oxyphenyl] benzotriazole, methyl-3- [3-tert-butyl-5-
Benzotriazole ultraviolet absorbers such as condensates of (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate and polyethylene glycol (molecular weight: about 300), 2'-ethylhexyl-2-cyano-3,3 Cyanoacrylate-based ultraviolet absorbers such as -diphenylacrylate, ethyl-2-cyano-3,3-diphenylacrylate , etc.

Of course, the present invention is not limited to these, and two or more of them can be used in combination as needed. Among these ultraviolet absorbers, benzotriazole-based ultraviolet absorbers are particularly preferable as the ultraviolet absorber used in the recording layer, and 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5
-Chlorobenzotriazole is more preferably used because it exhibits a particularly remarkable light resistance improving effect. Also,
Benzotriazole-based ultraviolet absorbers are also preferred among the ultraviolet absorbers included in the microcapsules.
(2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy -3'-dodecyl-
5'-methylphenyl) benzotriazole, 2-
[2'-hydroxy-4 '-(2 "-ethylhexyl)
Oxyphenyl] benzotriazole, methyl-3-
A condensate of [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate and polyethylene glycol (molecular weight: about 300) exhibits a particularly remarkable effect of improving light resistance. More preferably used.

Conventionally, low-melting-point UV absorbers and UV absorbers that are liquid at room temperature, which have been difficult to use in terms of background fog and preservability, can be used by enclosing them in microcapsules. The width of the can be widely spread.

The amount of the ultraviolet absorber used is not particularly limited, but is preferably about 10 to 500% by weight based on the basic dye in the recording layer in the protective layer.
More preferably, it is desirable to adjust so as to be in the range of about 20 to 300% by weight. In the recording layer, the content is preferably about 10 to 300% by weight, more preferably about 20 to 200% by weight, based on the basic dye.

According to the present invention, the solid UV absorber and the specific basic dye are contained in the recording layer, the solid or liquid UV absorber is contained in the protective layer, and Microcapsules with virtually no coloring ability
It has a significant feature in the inclusion.
Various heat-sensitive recording materials and pressure-sensitive recording materials using microcapsules containing a colorless or light-colored basic dye and an ultraviolet absorber have been proposed, but these microcapsules also contain a basic dye. Therefore, not only does the coloring phenomenon occur with an increase in the light irradiation amount, but it is not possible to exert a sufficient light resistance improving effect over a long period of time.

The microcapsules used in the present invention can be prepared by various known methods. In general, a core substance (oil-based liquid) obtained by dissolving an ultraviolet absorbent as described above in an organic solvent is placed in an aqueous medium. It is prepared by a method of emulsifying and dispersing to form a wall film made of a polymer substance around oily droplets. Specific examples of the polymer substance serving as the wall film of the microcapsule include, for example, polyurethane resin, polyurea resin,
Examples include polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-acrylate copolymer resin, styrene-methacrylate copolymer resin, gelatin, polyvinyl alcohol, and the like. Among these, microcapsules having a wall film made of polyurethane / polyurea resin or aminoaldehyde resin are particularly excellent in heat resistance, and thus inorganic pigments added to the protective layer for the purpose of preventing sticking to the thermal head. In addition, it has an excellent ancillary effect that it also fulfills the function of, and has a lower refractive index and a spherical shape compared to microcapsules made of other wall films and ordinary pigments. Is preferably used because there is no possibility of causing a decrease in the density of a recorded image (a so-called whitening phenomenon) due to irregular reflection of light.

The microcapsules having a wall film made of a polyurethane / polyurea resin are used in a core material for encapsulating a capsule wall film material such as a polyvalent isocyanate and a polyol which reacts with the polyisocyanate, or an adduct of a polyvalent isocyanate and a polyol. , And emulsified and dispersed in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved, and the polymer temperature is raised to cause a polymer formation reaction at an oil droplet interface.

Examples of the polyvalent isocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate,
2,4-tolylene diisocyanate, naphthalene-1,
4-diisocyanate, diphenylmethane-4,4'-
Diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4
-Diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1, Diisocyanates such as 4-diisocyanate; triisocyanates such as 4,4 ', 4 "-triphenylmethane triisocyanate and toluene-2,4,6-triisocyanate; 4,4'-dimethyldiphenylmethane-2,2' Tetraisocyanates such as 5,5,5'-tetraisocyanate, adducts of hexamethylene diisocyanate with trimethylolpropane, addition of 2,4-tolylenediisocyanate with trimethylolpropane , An adduct of xylylene diisocyanate and trimethylolpropane, an isocyanate prepolymer of adduct of trimethylolpropane resin isocyanate and hexane triol.

[0023] Also, as the port polyol compounds, such as ethylene glycol, 1,3-propanediol, 1,
4-butanediol, 1,5-pentanediol, 1,
6-hexanediol, 1,7-heptanediol,
1,8-octanediol, propylene glycol,
2,3-dihydroxybutane, 1,2-dihydroxybutane, 1,3-dihydroxybutane, 2,2-dimethyl-1,3-propanonediol, 2,4-pentanediol, 2,5-hexanediol, -Methyl-1,5
-Pentanediol, 1,4-cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, 1,2,6-trihydroxyhexane, phenylethylene glycol, 1,1,1-trimethylolpropane, hexanetriol, pentaerythritol, glycerin, etc. Aliphatic polyols, condensation products of aromatic polyhydric alcohols such as 1,4-di (2-hydroxyethoxy) benzene, 1,3-di (2-hydroxyethoxy) benzene and alkylene oxides, p-xylylene glycol , M-xylylene glycol, α, α'-dihydroxy-p-diisopropylbenzene, 4,4'-dihydroxydiphenylmethane, 2- (p, p'-dihydroxydiphenylmethyl) benzyl alcohol, 4,4 '
-Isopropylidene diphenol, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, ethylene oxide adduct of 4,4'-isopropylidene diphenol, propylene of 4,4'-isopropylidene diphenol Oxide adducts and the like can be mentioned.

Of course, the polyvalent isocyanate compound and the polyol compound are not limited to the above compounds, and two or more kinds can be used in combination as needed. Among the polyisocyanate compounds used in the present invention or the adduct of a polyvalent isocyanate compound and a polyol compound, those having three or more isocyanate groups in the molecule are particularly preferable.

In the microcapsules having a wall film made of an aminoaldehyde resin, the wall thickness can be controlled irrespective of the particle size of the emulsified product by adding the wall film material after emulsifying the core substance. Capsules having an aminoaldehyde resin wall film used in the present invention are generally urea, thiourea, alkyl urea, ethylene urea, acetoguanamine, benzoguanamine, melamine, guanidine,
Biuret, at least one amine such as cyanamide, and at least one aldehyde such as formaldehyde, acetaldehyde, paraformaldehyde, hexamethylenetetramine, glutaraldehyde, glyoxal, and furfural, or an initial condensate obtained by condensing them. It is produced by the in-situ polymerization method used.

As an emulsifier (protective colloid agent) used for microencapsulation, various anions, nonions, cations or amphoteric water-soluble polymer compounds are used. Examples of the anionic polymer compound include -C
OO-, -SO ₃ ^-, gum arabic with -OPO ₃ ^2-group, carrageenan, sodium alginate, pectic acid, gum tragacanth, almond gum, natural polymer compounds such as agar, carboxymethyl cellulose, cellulose sulfate, sulfated Semi-synthetic polymer compounds such as methylcellulose, carboxymethylated starch, phosphorylated starch, ligninsulfonic acid, and maleic anhydride (including those hydrolyzed).
Free), acrylic acid, methacrylic acid, crotonic acid, polymers arrangement copolymers such as vinyl benzenesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid, and partial amide derivatives of these polymers or copolymers Or synthetic polymer compounds such as partially esterified products, carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, and phosphoric acid-modified polyvinyl alcohol.

Examples of the maleic anhydride copolymer, methyl vinyl ether - maleic anhydride copolymer, ethylene - maleic anhydride copolymer, styrene - maleic anhydride copolymer, alpha-methylstyrene - maleic anhydride Copolymers, vinyl acetate-maleic anhydride copolymer, methacrylamide-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer and the like, acrylic acid, methacrylic acid and crotonic acid- based copolymer Are methyl acrylate-acrylic acid copolymer (hereinafter abbreviated as “copolymer”), ethyl acrylate-acrylic acid, methyl acrylate-methacrylic acid, methyl methacrylate-acrylic acid, methyl methacrylate-methacrylic acid, Methyl acrylate-acrylamide-acrylic acid, acrylonitrile-acrylic acid, Ronitoriru - methacrylic acid, hydroxyethyl acrylate - acrylic acid, hydroxyethyl methacrylate - methacrylic acid, vinyl acetate - acrylic acid, vinyl acetate - methacrylic acid, acrylamide -
Acrylic acid, acrylamide-methacrylic acid, methacrylamide-acrylic acid, methacrylamide-methacrylic acid, copolymers such as vinyl acetate-crotonic acid,
Vinylbenzenesulfonic acid and 2-acrylamide-
As 2-methyl-propanesulfonic acid- based copolymer,
Methyl acrylate-vinylbenzenesulfonic acid (or salt thereof) copolymer, vinyl acetate-vinylbenzenesulfonic acid copolymer, acrylamide-vinylbenzenesulfonic acid copolymer, acryloylmorpholine-vinylbenzenesulfonic acid copolymer, vinyl Examples thereof include a pyrrolidone-vinylbenzenesulfonic acid copolymer and a vinylpyrrolidone-2-methyl-propanesulfonic acid copolymer.

Examples of the nonionic polymer compound include semi-synthetic polymer compounds such as hydroxyethyl cellulose, methyl cellulose, pullulan, soluble starch, and oxidized starch having an -OH group, and synthetic polymer compounds such as polyvinyl alcohol. Examples of the cationic polymer compound include cation-modified polyvinyl alcohol. Examples of the amphoteric polymer compound include gelatin.

The amount of the emulsifier used is not particularly limited, but generally, in the case of polyurethane / polyurea resin, it is 1 to 50% by weight based on the total of the wall film agent, ultraviolet absorber and organic solvent. %, Preferably 3 to 3
It may be adjusted within a range of about 0% by weight. In the case of an aminoaldehyde resin, the amount of the emulsifier used is generally 1 to 20% by weight, more preferably 3 to 10% by weight, based on the hydrophobic core substance.
It is prepared in the range of about% by weight.

If necessary, the organic solvent used as the core material of the capsule is not particularly limited, and may be appropriately selected from various high-boiling-point hydrophobic media used in the field of pressure-sensitive copying paper. Specifically, for example, phosphates such as tricresyl phosphate and octyl diphenyl phosphate; phthalates such as dibutyl phthalate and dioctyl phthalate; carboxylic esters such as butyl oleate; and various fatty acid amides , Alkylated naphthalenes such as diethylene glycol dibenzoate, monoisopropyl naphthalene, diisopropyl naphthalene, 1-methyl-1-phenyl-1-tolylmethane, 1-methyl-1-phenyl-1-xylylmethane, 1-phenyl-1-tolylmethane Alkylated benzenes such as isopro Alkylated biphenyls such as rubiphenyl, xenoxyalkanes such as o-phenylphenol glycidyl ether, acrylates such as trimethylolpropane triacrylate, esters of polyhydric alcohol and unsaturated carboxylic acid, chlorinated paraffin, And kerosene. Needless to say, two or more of these can be used in combination. In addition, among the high-boiling-point hydrophobic media as described above, tricresyl phosphate and 1-methyl-1
-Phenyl-1-xylylmethane and 1-phenyl-1-tolylmethane are preferable because they exhibit excellent solubility in relation to the ultraviolet absorbent used in the present invention. Also, generally, the lower the viscosity of the mixture of the capsule wall film material, the ultraviolet absorber and the organic solvent, the smaller the particle size after emulsification and the sharper the particle size distribution, so if necessary, lower the viscosity of the mixture. A low-boiling solvent may be used in combination for the purpose. As a specific example of such a low boiling point solvent,
Ethyl acetate, butyl acetate, methylene chloride and the like can be mentioned.

The amount of the organic solvent to be used should be appropriately adjusted according to the type and amount of the ultraviolet absorber used, and furthermore, the type of the organic solvent, and is not particularly limited. Since it is preferable that the ultraviolet absorber is in a sufficiently dissolved state, in the case of polyurethane / polyurea resin, the ratio of the organic solvent to the total of the organic solvent, the ultraviolet absorber and the microcapsule wall film material is generally 10 to 60% by weight, preferably 20 to 6%
It is desirable to adjust so as to be in a range of about 0% by weight. In addition, in the case of an aminoaldehyde resin, if the ultraviolet absorber used is solid at room temperature, 5
It is desirable to adjust so as to be in the range of 0 to 2000% by weight, preferably 100 to 1000% by weight. When the ultraviolet absorbent used is a liquid at room temperature, it is appropriately used.

Although there is no particular limitation on the amount of the capsule wall film material to be used, the organic solvent in the microcapsules may ooze out over a long period of storage and deteriorate the preservability of the thermosensitive recording medium. It is preferable to use a large amount of wall film material as compared with the microcapsules. In the case of polyurethane / polyurea resin, the wall film material is used for the total of the organic solvent, the ultraviolet absorber and the microcapsule wall material. 35-70% by weight, preferably 3%
It is desirable to select the amount so as to be in the range of 5 to 60% by weight. In the case of the aminoaldehyde resin, the wall film material is 30 to 300% based on the total amount of the ultraviolet absorber and the organic solvent used as needed. % By weight, preferably 35 to 200% by weight
It is desirable to select so as to fall within the range.

Further, the amount of the ultraviolet absorber used in the microencapsulation should be appropriately selected according to the type of the ultraviolet absorber and the organic solvent to be used, and is not particularly limited, but a remarkable effect is obtained. Therefore, in the case of the polyurethane / polyurea resin, the amount of the ultraviolet absorber is 3 to 50% by weight, preferably about 3 to 20% by weight based on the total of the organic solvent, the ultraviolet absorber and the microcapsule wall material. It is desirable to blend so that
In the case of an aminoaldehyde resin, it is 3 to 75% by weight, preferably 3 to 75% by weight based on the total of the ultraviolet absorber, the microcapsule wall film material and the organic solvent used as required.
It is desirable that the amount of the ultraviolet absorber is about 50% by weight.

The microcapsules used in the present invention may contain, if necessary, an antioxidant, an oil-soluble fluorescent dye, a release agent, etc. in addition to the ultraviolet absorber. In addition, at the time of microencapsulation, a tin compound, a polyamide compound, an epoxy compound, a polyamine compound, or the like can be used in combination as a reaction accelerator. When a polyamine compound is used, it is desirable to use an aliphatic polyamine compound from the viewpoint of light resistance.

The average particle diameter of the microcapsules used in the present invention is 0.1 to 3 μm, preferably 0.3 to 2.5 μm in consideration of the absorption efficiency of ultraviolet rays and the quality of recorded images.
It is desirable to adjust so as to be within the range. Also,
The amount of the microcapsules to be incorporated into the protective layer is to be appropriately selected depending on the type of the ultraviolet absorber and the concentration in the capsule, and furthermore, the intended quality, etc., and is generally based on the total solid content of the protective layer. It is desirably adjusted in the range of about 5 to 80% by weight, preferably about 20 to 70% by weight.
The heat-sensitive recording layer paint containing a basic dye, a color former, and an ultraviolet absorber in the present invention is generally used with water as a dispersion medium, and together or separately with a stirring / pulverizing machine such as a ball mill, an attritor, and a sand mill. It is prepared by dispersing.

In the coating solution, starch, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, Diisobutylene / maleic anhydride copolymer salt, styrene /
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene
At least one of a butadiene copolymer emulsion, a urea resin, a melamine resin, an amide resin, and a polyurethane resin is blended in an amount of about 5 to 40% by weight, preferably about 15 to 30% by weight based on the total solid content of the recording layer. Is done.

Various auxiliaries can be added to the coating solution, if necessary. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. Waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc.
An antifoaming agent, a fluorescent dye, a coloring dye and the like are appropriately added. Further, microcapsules containing the ultraviolet absorbent of the present invention can be incorporated into the coating liquid for the recording layer to further enhance the light resistance.

Further, various pigments can be used in the coating liquid, for example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth,
Examples include inorganic pigments such as finely divided anhydrous silica and activated clay, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles.

Further, a sensitizer can be used in combination depending on the purpose. Specific examples of the sensitizer include, for example, stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, methylenebisstearic acid Amide, N-
Methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate,
Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthyl benzyl ether, m-terphenyl, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-oxalate Chlorobenzyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane,
1,2-di (4-methylphenoxy) ethane, 1,2-
Di (4-methoxyphenoxy) ethane, 1,2-di (4
-Chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p
-Acetotoluidide, p-acetophenethidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like. Is done. The use amount of these sensitizers is not particularly limited, but it is generally desirable to adjust the sensitizer within a range of about 4 parts by weight or less based on 1 part by weight of the color former.

As long as the effect is not impaired, a preservability improver can be used in combination to further enhance the preservability of the recorded image according to the purpose. Specific examples of such a preservability improver include, for example, 2,2'-methylenebis (4-methyl-6
-Tert-butylphenol), 2,2'-ethylenebis (4-methyl-6-tert-butylphenol) 2,2 '
-Methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4,6-di-tert-
Butylphenol), 2,2'-ethylidenebis (4,
6-di-tert-butylphenol), 2,2'-ethylidenebis (4-methyl-6-tert-butylphenol), 2,2'-ethylidenebis (4-ethyl-6-te
rt-butylphenol), 2,2 '-(2,2-propylidene) bis (4,6-di-tert-butylphenol), 2,2'-methylenebis (4-methoxy-6-te
rt-butylphenol), 2,2'-methylenebis (6
-Tert-butylphenol), 4,4'-thiobis (3
-Methyl-6-tert-butylphenol), 4,4'-
Thiobis (2-methyl-6-tert-butylphenol), 4,4'-thiobis (5-methyl-6-tert-butylphenol), 4,4'-thiobis (2-chloro-
6-tert-butylphenol), 4,4'-thiobis (2-methoxy-6-tert-butylphenol), 4,
4′-thiobis (2-ethyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 1- [α-methyl-α- (4′-
Hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene,
1,1,3-tris (2-methyl-4-hydroxy-5
-Cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4'-thiobis (3-methylphenol), 4,4'-dihydroxy -3,3 ', 5
5'-tetrabromodiphenylsulfone, 4,4'-dihydroxy-3,3 ', 5,5'-tetramethyldiphenylsulfone, 2,2-bis (4-hydroxy-3,5
-Dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,
Hindered phenol compounds such as 2-bis (4-hydroxy-3,5-dimethylphenyl) propane;
Epoxy compounds such as diglycidyloxybenzene, 4,4'-diglycidyloxydiphenylsulfone, diglycidyl terephthalate, cresol novolak type epoxy resin, phenol novolak type epoxy resin, and bisphenol A type epoxy resin; N, N'-di- 2-naphthyl-p-phenylenediamine, sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate and the like.

As described above, the thermosensitive recording medium of the present invention has a protective layer containing a microcapsule containing an ultraviolet absorbent, and the protective layer is formed of a water-soluble or water-dispersible microcapsule. The binder is composed of a polymer compound as a main component. Specific examples of such binders include, for example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diisobutylene. Maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, urea resin, melamine resin, Amide resins, polyurethane resins and the like can be exemplified. Among them, acetoacetyl group-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol can form a strong film. Preferably used for.

In the protective layer, a pigment can be added as needed to further improve printability and sticking. Specific examples thereof include calcium carbonate,
Inorganic pigments such as zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea Organic pigments such as formalin resin fillers and raw starch particles are exemplified. Generally, it is desirable to adjust the amount of use in the range of about 5 to 300 parts by weight with respect to 100 parts by weight of the binder component.

The method for preparing the coating liquid for forming the protective layer is not particularly limited. Generally, water is used as a dispersion medium, and the above-mentioned specific microcapsules (dispersion liquid), a binder, and a pigment to be added as necessary are used. It is prepared by mixing.
Further, in the coating liquid for the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and the like, and a surfactant such as sodium dioctyl sulfosuccinate (dispersant, wetting agent) Agents), an antifoaming agent, and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate. In order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound can be used in combination.

The method for forming the recording layer and the protective layer is not particularly limited. For example, an appropriate coating such as air knife coating, variver blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. After the coating liquid for a recording layer is applied to a support by a method and dried, the coating liquid for a protective layer is further applied and dried on the recording layer. The support is appropriately selected from paper, plastic film, synthetic paper, nonwoven fabric, metal deposit, and the like. Also,
The coating amount of the coating liquid for the recording layer is ² to 12 g / m ² by dry weight,
It is preferably about 3 to 10 g / m ² , and the coating amount of the coating liquid for the protective layer is 0.1 to 20 g / m ² , preferably 0.1 to 20 g / m ² in dry weight.
It is adjusted in the range of about 5 to 10 g / m ² .

If necessary, a protective layer may be provided on the back side of the heat-sensitive recording medium to further improve the storability. Furthermore, an undercoat layer is provided on the support, or a smoothing treatment such as super calendaring is performed after each layer is coated,
Alternatively, various known techniques in the field of heat-sensitive recording material production can be added as necessary, such as applying a pressure-sensitive adhesive treatment to the back surface of the recording material to process it into an adhesive label.

[0046]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted to such specific Examples. In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively, unless otherwise specified.

[0047]Example 1  Solution A Preparation of polyvinyl alcohol in a stirring and mixing vessel equipped with a heating device
8% water in water (trade name: PVA-217, manufactured by Kuraray Co., Ltd.)
60 parts of the solution were added, and an aqueous medium for producing microcapsules was added.
did. Separately, ethyl acetate 3 parts, 2- (2'-hydroxy
-3'-dodecyl-5'-methylphenyl) benzotri
Azole 12 parts, xylylene diisocyanate and trime
(3: 1) adduct of tyrolpropane [trade name: Takene
D-110N, manufactured by Takeda Pharmaceutical Company, 25% acetate
The solution obtained by dissolving 18 parts
TK homomixer [model HV-
M, manufactured by Tokushu Kika Kogyo Co., Ltd.]
And emulsified and dispersed while cooling. Then this
Add 50 parts of water to the emulsified dispersion and stir at 60 ° C. for 3 hours.
Polyurethane containing UV absorber after reacting for hours
Microcapsules having wall films made of polyurea resin
A dispersion was prepared.

Solution B Preparation 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 5% aqueous solution of methylcellulose 5
Parts and 40 parts of water were pulverized with a sand mill until the average particle size became 1.5 μm.

Solution C Preparation A composition comprising 30 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water is pulverized by a sand mill until the average particle diameter becomes 1.5 μm. did.

Solution D Preparation of a composition comprising 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water by a sand mill until the average particle diameter becomes 1.5 μm. Crushed.

Preparation of Solution E A composition comprising 10 parts of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 5 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water was subjected to sand milling to give an average particle size of 1. It was pulverized to 5 μm.

Formation of Recording Layer 55 parts of B solution, 115 parts of C solution, 50 parts of D solution, 80 parts of E solution,
A recording layer coating liquid obtained by mixing and stirring 80 parts of a 10% aqueous polyvinyl alcohol solution and 35 parts of calcium carbonate was mixed with 6 parts of
0 g / m ² of high-quality paper with a coating amount of 6 g / m ² after drying on one side
Was applied and dried to form a recording layer.

Formation of protective layer 220 parts of solution A, 150 parts of a 10% aqueous solution of acetoacetyl group- modified polyvinyl alcohol [trade name: Gosefimer Z-200, manufactured by Nippon Synthetic Chemical Company], kaolin [trade name: UW-90] Co., Ltd., EMC) 15 parts, a 30% aqueous dispersion of zinc stearate, 6 parts, and 30 parts of water were mixed and stirred to obtain a coating liquid for a protective layer, which was dried and applied onto the recording layer. After coating and drying so that the amount becomes 6 g / m ² ,
A super calender treatment was performed to obtain a thermosensitive recording medium.

[0054]Example 2  In preparing solution A, 2- (2'-hydroxy-3'-d
Decyl-5'-methylphenyl) benzotriazole 1
Instead of 2 parts, 2- [2'-hydroxy-4 '-(2
-Ethylhexyl) oxyphenyl] benzotriazole
Except that 12 parts were used.Example 1Thermal recording in the same way as
I got a body.

[0055]Example 3  In the preparation of solution A, 1-f
3-part of nyl-1-methyl-1-xylylmethane, 2-
(2'-hydroxy-3'-dodecyl-5'-methylf
Enyl) instead of 12 parts of benzotriazole,
(2'-hydroxy-3'-dodecyl-5'-methylf
Enyl) benzotriazole (6 parts) and methyl-3- [3
-Tert-butyl-5- (2H-benzotriazole-2
-Yl) -4-hydroxyphenyl] propionate;
Condensate with polyethylene glycol (molecular weight about 300)
Except for using 6 partsExample 1In the same manner as
Obtained.

[0056]Example 4  In preparing solution B, 3-di (n-butyl) amino-6-
Instead of 10 parts of methyl-7-anilinofluoran, 3
-(N-ethyl-N-isoamyl) amino-6-methyl
Except for using 10 parts of -7-anilinofluoranExample
1In the same manner as in the above, a thermosensitive recording medium was obtained.

[0057]Example 5  In preparing solution B, 3-di (n-butyl) amino-6-
Instead of 10 parts of methyl-7-anilinofluoran, 3
-Di (n-butyl) amino-7-o-chloroanilinov
Using 10 parts of Luolan, in the preparation of solution E, 2,2'-
Methylene bis (4-methyl-6-tert-butylphenol
), Instead of 10 parts, 4,4'-thiobis (3-methyl
L-6-tert-butylphenol) except that 10 parts were used.
IsExample 1In the same manner as in the above, a thermosensitive recording medium was obtained.

[0058]Example 6  Solution F Preparation of polyacrylic acid in a stirring and mixing vessel equipped with a heating device
Add 150 parts of a 5% aqueous solution and adjust the pH of the system to 4.5.
This was used as an aqueous medium for producing capsules. Separately, diisopropyl
58 parts of lunaphthalene and 2- (2'-hydroxy-3'-
Dodecyl-5'-methylphenyl) benzotriazole
58 parts and mix it as a capsule core substance.
TK Homomixer [Model H
VM, manufactured by Tokushu Kika Kogyo Co., Ltd.)
It was emulsified and dispersed at 00 rpm for 15 minutes.

A 30% aqueous solution of a commercially available melamine-formaldehyde precondensate was used as a wall film material in this emulsified dispersion.
After adding 0 parts and reacting at 90 ° C. for 3 hours while stirring, the temperature was lowered to room temperature and an ultraviolet absorber was included.
A melamine-formaldehyde resin wall membrane capsule (solution F) having an average particle diameter of 2 μm was prepared.

[0060]Preparation of thermal recording medium  55 parts of solution F, acetoacetyl group-modified polyvinyl alcohol
[Product name: Gosefimer Z-200, Nippon Gosei
Of 10% aqueous solution of kaolin (trade name: UW
-90 EMC) 15 parts, 30% zinc stearate
Protective layer obtained by mixing and stirring 6 parts of dispersion and 30 parts of water
The coating amount after drying the coating liquid on the recording layer used in Example 1 was
6g / m^TwoApply and dry so that it becomes
To obtain a heat-sensitive recording medium.

[0061]Example 7  In the preparation of solution C, 4-hydroxy-4'-isopropo
Di (4-hydr) instead of 30 parts of xydiphenyl sulfone
Roxy-3-methylphenyl) sulfine using 30 parts
Other thanExample 5In the same manner as in the above, a thermosensitive recording medium was obtained.

[0062]Comparative Example 1  In the preparation of solution E, 2- (2'-hydroxy-5'-me
Do not use 10 parts of tylphenyl) benzotriazole)
A heat-sensitive recording material was obtained in the same manner as in Example 1 except for the above.

[0063]Comparative Example 2  In the preparation of solution E, 2- (2'-hydroxy-5'-me
Instead of 10 parts of tylphenyl) benzotriazole)
In addition, 4,4'-butylidenebis (6-tert-butyl-m
-Cresol) Same as Example 1 except that 10 parts were used
To obtain a thermosensitive recording medium.

[0064]Comparative Example 3  In preparing solution B, 3-di (n-butyl) amino-6-
Instead of 10 parts of methyl-7-anilinofluoran, 3
-(N-ethyl-p-toluidino) -6-methyl-7-
Example 1 with the exception that 10 parts of anilinofluoran were used.
A thermosensitive recording medium was obtained in the same manner.

Comparative Example 4 Preparation of Solution H A composition comprising 10 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 5 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water was subjected to sand milling to obtain an average particle size. Was reduced to 1.5 μm.

The heat-sensitive recording mediumProduction  In the formation of the protective layer, the above H
Except that 40 parts of the liquid was used, the thermal recording was performed in the same manner as in Example 1.
I got a copy.

[0067]Comparative Example 5  In preparing solution B, 3-di (n-butyl) amino-6-
Instead of 10 parts of methyl-7-anilinofluoran, 3
Using 10 parts of diethylamino-7-anilinofluoran
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the heat-sensitive recording medium was used.

The following evaluation tests were performed on the thus obtained heat-sensitive recording medium, and the results are shown in Table 1. [Coloring property and background fog] Each thermosensitive recording medium was colored with an applied voltage of 24 V and a pulse time of 2 ms using a thermosensitive recording medium evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.) to obtain a recorded image. Was measured in a visual mode using a Macbeth densitometer (Model RD-914, manufactured by Macbeth).

[Light Resistance] After exposing the heat-sensitive recording medium after recording in 1 to direct sunlight for 2 days, the densities of the recording portion and the background portion were measured with a Macbeth densitometer (using a blue filter).

[0070]

[Table 1]

[0071]

As is evident from the results of Table 1, all of the heat-sensitive recording materials of the present invention have extremely little discoloration of the recorded image and yellowing of the background portion upon exposure to light, The thermosensitive recording medium was less fogged.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-176880 (JP, A) JP-A-3-23986 (JP, A) JP-A-63-307981 (JP, A) JP-A 64-64 51997 (JP, A) JP-A 1-267087 (JP, A) JP-A 2-84376 (JP, A) JP-A 4-189180 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34

Claims (2)

(57) [Claims] 1. A thermosensitive recording medium comprising a support, on which a recording layer containing a colorless or pale-colored basic dye and a colorant, and a protective layer are provided in that order, an ultraviolet absorber, The following general formula (1) or general formula
Contain at least one compound represented by formula (2), it is in the protective layer, and containing a benzotriazole ultraviolet absorber liquid at room temperature, and substantially no color development ability, polyurethane
From tan polyurea resin or amino aldehyde resin
Thermosensitive recording material characterized by containing microcapsules having made the wall film. Embedded image [In the formula, R ₁ and R ₂ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms which may be substituted with an alkoxyl group having 1 to 4 carbon atoms. However, R ₁ , R ₂
Do not combine with each other. [Chemical formula 2] [In the formula, R ₃ and R ₄ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms which may be substituted with an alkoxyl group having 1 to 4 carbon atoms. However, R ₃ , R ₄
Do not combine with each other. X ₁ represents a fluorine atom or a chlorine atom. ] 2. A benzotriazole ultraviolet liquid which is liquid at normal temperature.
The line absorber is 2- (2'-hydroxy-3'-dodecyl-
5'-methylphenyl) benzotriazole, 2-
[2'-hydroxy-4 '-(2 "-ethylhexyl)
Oxyphenyl] benzotriazole, methyl-3-
[3-tert-butyl-5- (2H-benzotriazole
-2-yl) -4-hydroxyphenyl] propione
Of polyethylene glycol with a molecular weight of about 300
The thermosensitive recording medium according to claim 1, wherein the thermosensitive recording medium is at least one selected from the group consisting of compounds .