JPH06234271A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having a superior recording image shelf stability and an enough light resistance to prevent the yellowing of a background for a very long term even under exposure to light, such as sunlight. CONSTITUTION:In a thermal recording material provided with a thermal recording layer formed by incorporating a colorless or light-colored basic dye and a color developer producing a color in contact with the dye on one surface of a substrate, a back coat layer formed by incorporating microcapsules including an ultraviolet light absorber and having substantially no color forming power is provided on a rear surface of the substrate.

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 material, and in particular, it has excellent storage stability of recorded images and excellent light resistance that does not cause yellowing of the background for a very long time even when exposed to light such as sunlight. The present invention relates to a thermosensitive recording medium.

[0002]

2. Description of the Related Art A heat-sensitive recording material which utilizes a color reaction between a colorless or light-colored basic dye and an organic or inorganic color-forming agent to bring both color-forming substances into contact with each other by heat to obtain a recorded image is often used. Are known. Since such a thermosensitive recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

For example, one of the fields of use thereof is a heat-sensitive recording label for a POS (point of sales) system of a retail store, etc. In addition to food labels that have completed their missions, the number of uses that are attached to products and used for a long period of time is increasing. Therefore, the thermal recording material is generally required to have stability of a recorded image. For this reason, a recording material obtained by coating an aqueous emulsion of a resin having film forming ability and chemical resistance on the thermal recording layer Kaisho 54-128347
(Japanese Patent Laid-Open No. 56-125354), and a recording material coated with an aqueous polymer compound such as polyvinyl alcohol have been proposed.

In recent years, due to the development of a wide variety of printers, advertisements such as bargains are output to thermal recording media in supermarkets, department stores, etc., and are used as banners or banners, or pasted on window glass in stores. It can be seen that it is used. In such a case, the back surface of the support may be exposed to sunlight. In particular, when paper, plastic film, or the like is used as the support, the light blocking property is not always sufficient, so that it is easily affected. For example, it is possible to block the light to the recording layer by taking measures such as thickening the support or providing a sheet or the like for blocking the light. However, there is a problem that it cannot be applied to the above, it becomes expensive, etc., and it has not been solved. Therefore, in some cases, the dye in the heat-sensitive recording layer may be colored under the influence of light from the back side of the support, impairing the product image and making the atmosphere in the store shabby.

For the purpose of preventing yellowing of the background portion of such a thermosensitive recording medium due to light, a method has been proposed in which a finely pulverized ultraviolet absorber is added to the thermosensitive recording layer or the backcoat layer. When a finely pulverized ultraviolet absorber is used in the heat-sensitive recording layer, the effect of absorbing ultraviolet rays is poor, so a sufficient effect cannot be obtained even when used in a small amount, and when used in a large amount in the recording layer, background fog may occur, Alternatively, a new defect such as a decrease in recording density occurs. In addition, even if a finely pulverized UV absorber is added to the back coat layer, not only the efficiency of absorbing UV rays is poor, but also the barrier property of the back surface, which is the original purpose of the back coat layer, is remarkably reduced. Labeled as the body, when the adhesive layer is provided on the back side, the background part is colored or the fading of the print occurs due to the effect of the emulsifier contained in the adhesive, and when it is attached to the wrapping film, The recorded image tends to be discolored due to the influence of the plasticizer contained in the wrapping film.

[0006]

SUMMARY OF THE INVENTION The above-mentioned problems of the thermal recording material are solved, and the storability of the recorded image and the light resistance of the printed portion and the background portion are excellent even when exposed to light from the back surface of the support, Moreover, the present invention provides a thermosensitive recording medium that can be labeled.

[0007]

Means for Solving the Problems The inventors of the present invention have earnestly studied to provide a heat-sensitive recording material having light resistance from the back side while ensuring the original function of the back coat layer. They have found that the problem can be solved by including microcapsules containing an absorbent.

That is, the present invention provides a heat-sensitive recording material having a heat-sensitive recording layer on one side of which a colorless or light basic dye and a developer which develops color by contacting with the dye are formed. The heat-sensitive recording material is characterized in that a back coat layer containing an ultraviolet absorber and containing microcapsules having substantially no color-forming ability is provided.

[0009]

The microcapsules used in the present invention are basically prepared by using an ultraviolet absorber, a film agent and an emulsifier. Specific examples of the ultraviolet absorber include the followings. Salicylic acid-based UV absorbers such as phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy -4-methoxy-5
-Benzophenone-based UV absorbers such as sulfobenzophenone, 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 "-tetrahydrophthalimidomethyl)
-5'-methylphenyl] benzotriazole, 2-
(2'-hydroxy-5'-tert-octylphenyl)
Benzotriazole, 2- [2'-hydroxy-3 ',
5'-bis (α, α-dimethylbenzyl) phenyl]-
2H-benzotriazole, 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, polyethylene glycol (molecular weight about 300) and methyl-3- [3-
tert-butyl-5- (2H-benzotriazole-
2-yl) -4-hydroxyphenyl] propionate and other benzotriazole-based UV absorbers,
Cyanoacrylate-based ultraviolet absorbers such as 2'-ethylhexyl-2-cyano-3,3-diphenylacrylate and ethyl-2-cyano-3,3-diphenylacrylate, 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-4-hydroxybenzyl-2-
N-butyl) malonic acid-bis (1,2,2,6,6-pentamethyl-4-piperidyl) ester and other hindered amine UV absorbers.

Of course, the present invention is not limited to these, and two or more kinds can be used in combination as required. In the heat-sensitive recording material of the present invention, since the ultraviolet absorbent is used by being encapsulated in microcapsules, it is conventionally difficult to use the ultraviolet absorbent having a low melting point in terms of preservability, and the ultraviolet light which is liquid at room temperature. Absorbents and the like can also be used, and the range of choice is greatly expanded.

Among these UV absorbers, the benzotriazole-based UV absorbers are preferable, and especially 2- (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, polyethylene glycol (molecular weight about 300) and methyl-3- [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-
Condensation products with hydroxyphenyl] propionate and the like exhibit a remarkable effect of improving light resistance and are therefore more preferably used.

Particularly, 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy-4'-, which is liquid at room temperature.
(2 ″ -Ethylhexyl) oxyphenyl] benzotriazole, polyethylene glycol (molecular weight about 300)
A condensate of methyl-3- [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate with a very remarkable light resistance improving effect is desirable.

The amount of the ultraviolet absorber used is not particularly limited, but it is preferably present in the back coat layer of the thermosensitive recording medium in an amount of 0.1 to 3.0 g / m ² , and more preferably 0.2. Is in the range of up to 2.0 g / m ² . If the amount of the ultraviolet absorber is less than 0.1 g / m ^{2, the} ultraviolet absorbing effect cannot be obtained sufficiently, and if it exceeds 3.0 g / m ² , the thickness of the coating layer itself becomes too thick. The operability is lowered, and blocking with the recording layer surface is likely to occur in the wound state.

The microcapsules used in the present invention can be prepared by various known methods. In general, cores obtained by dissolving a solid or liquid ultraviolet absorber at room temperature as described above in an organic solvent as needed. It is prepared by a method in which a substance is emulsified and dispersed in an aqueous medium to form a wall film made of a polymer substance around oily droplets.

Specific examples of the polymeric substance that forms the wall film of the microcapsule include, for example, polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin,
Examples thereof include polystyrene resin, styrene-acrylate copolymer resin, styrene-methacrylate copolymer resin, gelatin and polyvinyl alcohol. Among these, in particular, microcapsules having a wall film made of a polyurethane / polyurea resin or an aminoaldehyde resin are excellent in stability after capsule formation, and therefore, for the purpose of preventing blocking during storage in a wound state. It has an excellent accompanying effect that it also functions as an inorganic pigment added to the backcoat layer, and has a lower refractive index and a smaller shape than microcapsules composed of other wall films and ordinary pigments. Since it has a spherical shape, the barrier property is not deteriorated even if it is mixed in a large amount in the back coat layer, and there is no fear of impairing the original purpose of the back coat layer.

Microcapsules having a wall film made of polyurethane / polyurea resin are a core substance for encapsulating a capsule wall film material such as a polyvalent isocyanate and a polyol which reacts therewith, or an adduct of a polyvalent isocyanate and a polyol. It is produced by emulsifying and dispersing it in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved and raising the liquid temperature to cause a polymer forming reaction at the oil drop 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, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, triisocyanates such as toluene-2,4,6-triisocyanate, 4,4′-dimethyldiphenylmethane-2,2 ′ , 5,5'-Tetraisocyanate and other tetraisocyanates, addition product of hexamethylene diisocyanate and trimethylolpropane, addition of 2,4-tolylene diisocyanate and trimethylolpropane , An adduct of xylylene diisocyanate and trimethylolpropane, an isocyanate prepolymer of adduct of trimethylolpropane resin isocyanate and hexane triol.

Examples of the polyol compound include 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-propanone diol, 2,4-pentane diol,
2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol,
Dihydroxycyclohexane, diethylene glycol,
1,2,6-trihydroxyhexane, phenylethylene glycol, 1,1,1-trimethylolpropane,
Aromatic polyols such as hexanetriol, pentaerythritol and glycerin, aromatic polyhydric alcohols such as 1,4-di (2-hydroxyethoxy) benzene and 1,3-di (2-hydroxyethoxy) benzene, and alkylene oxides Condensation product, p-xylylene glycol, m-xylylene glycol, α, α′-dihydroxy-p-diisopropylbenzene, 4,4′-dihydroxydiphenylmethane, 2- (p, p′-dihydroxydiphenylmethyl) benzyl alcohol 4,4'-isopropylidenediphenol, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, ethylene oxide adduct of 4,4'-isopropylidenediphenol, 4,4'-isopropylidene Of ridenediphenol Examples include propylene oxide adducts.

Of course, the polyisocyanate compound and the polyol compound are not limited to the above compounds, and two or more kinds may be used in combination, if necessary.

Among the polyvalent isocyanate compounds used in the present invention or the adducts of polyvalent isocyanate compounds and polyol compounds, those having three or more isocyanate groups in the molecule are particularly preferable. From the viewpoint of coloring with light, a xylylene diisocyanate derivative and a hexamethylene diisocyanate derivative are preferably used. Furthermore, the value of the B-type viscometer at 25 ° C is 1000.
The hexamethylene diisocyanate derivative having a cps or less has good compatibility with other core substances, and therefore, it is easy to obtain microcapsules having strong strength and, in addition, since the viscosity of the core substance is low, it is easy to obtain microcapsules having a fine and uniform particle size. Therefore, it is preferable. In particular, the isocyanurate-type hexamethylene diisocyanate derivative is particularly preferably used because it has excellent compatibility with the ultraviolet absorber.

The microcapsules having a wall film made of an aminoaldehyde resin are manufactured by a formulation in which the wall film material is added after emulsifying the core substance, so that the thickness of the wall film can be controlled without being affected by the particle size of the emulsion. The merit that can be done is also demonstrated.
Capsules having an aminoaldehyde resin wall film generally include at least one amine such as urea, thiourea, alkylurea, ethyleneurea, acetoguanamine, benzoguanamine, melamine, guanidine, biuret, and cyanamide, and formaldehyde, acetaldehyde, and paraformaldehyde. , Hexamethylenetetramine, glutaraldehyde, glyoxal, furfural and the like, or an in-situ polymerization method using an initial condensate obtained by condensing them.

Milk used for microencapsulation
As an agent (protective colloid agent), various anions and
Nion, cation or amphoteric water-soluble polymer compound etc. are used
To be done. Examples of the anionic polymer compound include-
COO^-, -SO^3-, -OPO ₃ ^2-Arabi with groups etc.
Agum, carrageenan, sodium alginate, pectin
Natural such as acid, tragacanth gum, almond gum, agar
Polymer compounds, carboxymethyl cellulose, sulfated cellulose
Lulose, sulfated methyl cellulose, carboxymethyl
Semi-synthesis of modified starch, phosphorylated starch, lignin sulfonic acid, etc.
Polymer compounds, maleic anhydride (including hydrolyzed ones)
Mu) Copolymer, acrylic acid, methacrylic acid or
Polymers and copolymers of tonic acid, vinylbenzene sulfone
Acid or 2-acrylamido-2-methylpropane
Polymers and copolymers of rufonic acid, and these polymers
Or partial esterification of copolymers or copolymers
Products, carboxy-modified polyvinyl alcohol, sulfonic acid
Modified polyvinyl alcohol, phosphoric acid modified polyvinyl alcohol
Coal, acetoacetyl group-modified polyvinyl alcohol
(Acetoacetyl group-modified partially saponified polyvinyl alcohol
, Etc.) and the like.

More specifically, maleic anhydride (including hydrolyzed) copolymers include methyl vinyl ether-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, and styrene-maleic anhydride. Copolymer,
Examples include α-methylstyrene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, methacrylamide-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, and acrylic acid copolymer. As the methacrylic acid copolymer or the crotonic acid copolymer, methyl acrylate-acrylic acid copolymer, ethyl acrylate-acrylic acid copolymer, methyl acrylate-methacrylic acid copolymer, methyl methacrylate-acrylic Acid copolymer, methyl methacrylate-methacrylic acid copolymer, methyl acrylate-acrylamide-acrylic acid copolymer,
Acrylonitrile-acrylic acid copolymer, acrylonitrile-methacrylic acid copolymer, hydroxyethyl acrylate-acrylic acid copolymer, hydroxyethyl methacrylate-methacrylic acid copolymer, vinyl acetate-acrylic acid copolymer, vinyl acetate-methacrylic acid Copolymer, acrylamide-acrylic acid copolymer, acrylamide-
Methacrylic acid copolymer, methacrylamide-acrylic acid copolymer, methacrylamide-methacrylic acid copolymer,
Examples thereof include vinyl acetate-crotonic acid copolymer, vinylbenzenesulfonic acid or 2-acrylamido-2-
As the methyl-propanesulfonic acid copolymer, methyl acrylate-vinylbenzenesulfonic acid (or a salt thereof)
Copolymer, vinyl acetate-vinylbenzene sulfonic acid copolymer, acrylamide-vinylbenzene sulfonic acid copolymer, acryloylmorpholine-vinylbenzene sulfonic acid copolymer, vinylpyrrolidone-vinylbenzenesulfonic acid copolymer, vinylpyrrolidone- 2-methyl-propane sulfonic acid copolymer etc. can be illustrated.

Examples of the nonionic polymer compound are semi-synthetic polymer compounds having hydroxy groups such as hydroxyethyl cellulose, methyl cellulose, pullulan, soluble starch and oxidized starch, and synthetic polymer compounds such as polyvinyl alcohol and silicon-modified polyvinyl alcohol. And the like. Examples of the cationic polymer compound include cation-modified polyvinyl alcohol. Examples of the amphoteric polymer compound include gelatin and the like.

In the present invention, when the microcapsule wall film is a polyurethane / polyurea resin, a acetoacetyl group-modified polyvinyl alcohol (acetoacetyl group-modified partially saponified polyvinyl alcohol) which has a water resistance effect at low temperature curing and has a good effect on the storage stability is obtained. ), Carboxy-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are preferable, and particularly acetoacetyl group-modified polyvinyl alcohol (including acetoacetyl group-modified partially saponified polyvinyl alcohol) has an excellent effect of improving storage stability by reaction with an aldehyde compound. Therefore, it is more preferably used.

Although the amount of the emulsifier used is not particularly limited, in general, when the polyurethane / polyurea resin is used as the wall film material, the total of the wall film material, the ultraviolet absorber and the organic solvent is used. However, it may be adjusted in the range of 1 to 50% by weight, preferably 3 to 30% by weight. When the aminoaldehyde resin is used as the wall film material, the amount of the emulsifier used is the hydrophobic core substance 100.
It is prepared in an amount of 1 to 20 parts by weight, preferably 3 to 10 parts by weight, based on parts by weight.

The organic solvent is not particularly limited and may be appropriately selected and used from various high boiling point hydrophobic media used in the field of pressure-sensitive copying paper. Specifically, for example, phosphoric acid may be used. Phosphates such as tricresyl, octyldiphenyl phosphate, dibutyl phthalate,
Phthalates such as dioctyl phthalate, carboxylic esters such as butyl oleate, various fatty acid amides, alkylated naphthalenes such as diethylene glycol dibenzoate, monoisopropyl naphthalene and diisopropyl naphthalene, 1-methyl-1-phenyl- 1-
Alkylated benzenes such as tolylmethane, 1-methyl-1-phenyl-1-xylylmethane, 1-phenyl-1-tolylmethane, alkylated biphenyls such as isopropyl biphenyl, xenoxyalkanes such as o-phenylphenol glycidyl ether, Examples thereof include acrylic acid esters such as trimethylolpropane triacrylate, esters of polyhydric alcohols and unsaturated carboxylic acids, chlorinated paraffins, and kerosene. Of course, these may be used in combination of two or more kinds.

Among the above high boiling point hydrophobic media, tricresyl phosphate and 1-phenyl-1-tolylmethane are preferable because they exhibit excellent solubility in relation to the ultraviolet absorber used in the present invention. . Further, 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. Therefore, if necessary, the viscosity of the mixture is decreased. A low boiling point solvent may be used together for the purpose. Specific examples of such a low boiling point solvent include ethyl acetate,
Butyl acetate, methylene chloride and the like can be mentioned.

The amount of the organic solvent used is not particularly limited, and it should be appropriately adjusted according to the type and amount of the ultraviolet absorber used, the type of the organic solvent and the like. However, since it is preferable that the ultraviolet absorbent is sufficiently dissolved in the microcapsules, in the case of polyurethane / polyurea resin, the total amount of the organic solvent, the ultraviolet absorbent and the microcapsule wall film material is Therefore, it is desirable to adjust the ratio of the organic solvent so that it is generally 60% by weight or less. Further, in the case of an aminoaldehyde resin, it is desirable to adjust it so that it is in the range of 2000% by weight or less, preferably 1000% by weight or less with respect to the ultraviolet absorber. In addition, when the ultraviolet absorber which is liquid at room temperature is used, the organic solvent is not always essential, and may be appropriately adjusted within the above range as necessary.

Although the amount of the capsule wall film material used is not particularly limited, the organic solvent in the microcapsules may seep out due to long-term storage and the storage stability of the thermosensitive recording medium may be deteriorated. It is preferable to use a larger amount of wall film material than the microcapsules, and in the case of polyurethane / polyurea resin, the wall film is used for the total of the organic solvent, the ultraviolet absorber and the microcapsule wall film material. 20% to 70% by weight, preferably 2
It is desirable to select it so as to be in the range of 0 to 60% by weight. In the case of an aminoaldehyde resin, the wall film material is 30 to 300 with respect to the total of the ultraviolet absorber and the organic solvent used as necessary. % By weight, preferably 35-200% by weight
It is desirable to select the range so that

Further, the amount of the ultraviolet absorber used in the microencapsulation should be appropriately selected according to the kind of the ultraviolet absorber and the organic solvent used and is not particularly limited, but a remarkable effect is obtained. Therefore, in the case of polyurethane / polyurea resin, the amount of the ultraviolet absorber is about 3 to 80% by weight, preferably about 10 to 80% by weight, based on the total of the organic solvent, the ultraviolet absorber and the microcapsule wall membrane material. In the case of aminoaldehyde resin, 3 to 75% by weight based on the total of the ultraviolet absorber, the microcapsule wall film material, and the organic solvent used if necessary, It is desirable that the amount of the ultraviolet absorber is preferably about 3 to 50% by weight.

In the microcapsule used in the present invention, an antioxidant, an oil-soluble fluorescent dye, a release agent, etc. may be added, if necessary, in addition to the ultraviolet absorber. Further, at the time of microencapsulation, a tin compound, a polyamide compound, an epoxy compound, a polyamine compound or the like can be used together 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 size of the microcapsules used in the present invention is 0.1 to 3 μm, preferably 0.3, considering the absorption efficiency of ultraviolet rays and the suitability for smearing of the back coat layer.
It is desirable to adjust the thickness to be in the range of about 2.5 μm. By the way, if it is less than 0.1 μm, the film thickness becomes thin, which may adversely affect the storability, and if it exceeds 3 μm, the ultraviolet absorption efficiency deteriorates. The amount of the microcapsules to be incorporated in the back coat layer should be appropriately selected depending on the type of the ultraviolet absorber, the concentration in the capsules, the desired quality, etc. 5 to 90% by weight, preferably 20 to 8% based on the solid content
It is desirable to adjust within the range of about 0% by weight.

As described above, the thermal recording material of the present invention has a back coat layer containing microcapsules containing an ultraviolet absorber. The back coat layer is water-soluble or water-dispersible with the microcapsules. And a binder composed of a high-molecular compound.
Specific examples of the binder include 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 Examples include ethylene / acrylic acid copolymer salts, styrene / acrylic acid copolymer salts, styrene / butadiene copolymer emulsions, urea resins, melamine resins, amide resins, polyurethane resins, and the like.
Of these, acetoacetyl group-modified polyvinyl alcohol and carboxy-modified polyvinyl alcohol are particularly preferably used because they can form a strong film.

A pigment may be added to the back coat layer, if necessary, in order to further improve printability for printing performed as needed and blocking in a wound state. 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 Examples include formalin resin fillers and organic pigments such as raw starch particles. It is generally desirable to adjust the amount used 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 backcoat layer is not particularly limited, and generally water is used as the dispersion medium, the specific microcapsules (dispersion liquid), the binder, the pigment added as necessary, and the like. Are prepared by mixing. Furthermore, in the coating liquid for the back coat layer, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, if necessary,
Add appropriate additives such as ester wax and other lubricants, surfactants such as sodium dioctyl sulfosuccinate (dispersants, wetting agents), defoamers, and water-soluble polyvalent metal salts such as potassium alum and aluminum acetate. You can also Further, in order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, and an epoxy compound can be used in combination.

The method for forming the back coat layer is not particularly limited, and may be any suitable coating method such as air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating and the like. The coating solution is applied to one side or both sides of the support, if necessary, and dried to form a coating solution. The coating amount of the coating liquid for the back coat layer is 0.1 to 20 g / dry weight.
m ² , preferably adjusted in the range of about 0.5 to 10 g / m ² .

The support may be appropriately selected from paper, plastic film, synthetic paper, non-woven fabric, metal vapor deposition and the like.

Next, a heat-sensitive recording layer is formed on the surface of a support having a back coat layer on the back surface thus obtained and, if necessary, a coat layer of the same kind on the front surface. In the present invention, the basic dye contained in the heat-sensitive recording layer includes various known colorless or light-colored basic dyes,
Specifically, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-
Diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluorane, 3- (N-ethyl-N- p-tolyl) amino-7-N-methylanilinofluorane, 3-
Diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6-
Bis (diethylamino) fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane,
3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-
Cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane , 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3
-Diethylamino-7- (o-chlorophenylamino)
Fluorane, 3-di (n-butyl) amino-7- (o-
Chlorophenylamino) fluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane,
3-di (n-butyl) amino-7- (o-fluorophenylamino) fluorane, 3- (N-ethyl-N-isobutyl) amino-7- (p-trifluoromethylanilino) fluorane, 3-diethylamino -7- (m-trifluoromethylanilino) fluorane, 3- (N-ethyl-N-isobutyl) amino-7- (o-trifluoromethylanilino) fluorane, 3- (N-ethyl-N-
Isoamyl) amino-7- (p-trifluoromethylanilino) fluorane, 3-di (n-butyl) amino-7
-(M-trifluoromethylanilino) fluorane, 3
-(N-methyl-N-cyclohexyl) amino-7-
(O-trifluoromethylanilino) fluorane, 3-
(N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3- (N -Ethyl-N-furfurylamino) -6-
Methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (N-methyl-Nn-propylamino) -6-methyl-7-anilinofluorane, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [ 1- (4-methoxyphenyl)-
1- (4-pyrrolidinophenyl) ethylene-2-yl]
-4,5,6,7-Tetrachlorophthalide, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthali De, 3-p- (p-anilinoanilino) anilino-6-
Methyl-7-chlorofluorane, 2,2-bis {4-
[6 '-(N-cyclohexyl-N-methylamino)-
3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3,6,-
Bis (dimethylamino) fluorene-9-spiro-3 '
-(6'-dimethylamino) phthalide and the like can be mentioned.
Of course, it is not limited to these, and if necessary, two or more kinds may be used together.

Of these, the basic dyes represented by the following general formula (I) are preferably used because they are less likely to be colored by light and are excellent in the preservability of printing.

[0041]

[Chemical 2]

[0042] (wherein R _1, R ₂ represents an alkyl group having 1 to 7 carbon atoms, an isobutyl group, isoamyl group, a cyclohexyl group, .gamma. ethoxypropyl, a tetrahydrofurfuryl group. Further, R _1, R ₂ May be the same or different.)

Specifically, 3- (N-ethyl-N-isobutyl) amino-7- (p-trifluoromethylanilino) fluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane , 3- (N-ethyl-N-isobutyl) amino-7- (o-trifluoromethylanilino) fluorane, 3- (N-ethyl-N-
Isoamyl) amino-7- (p-trifluoromethylanilino) fluorane, 3-di (n-butyl) amino-7
-(M-trifluoromethylanilino) fluorane, 3
-(N-methyl-N-cyclohexyl) amino-7-
Examples thereof include compounds such as (o-trifluoromethylanilino) fluorane.

Various materials are known for the color former used in combination with the basic dye as described above, and the following are exemplified. Inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate,
4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2,2′-dihydroxydiphenol, 4,4′-
Isopropylidene bis (2-tert-butylphenol), 4,4'-sec-butylidene diphenol, 4-
Phenylphenol, 4,4'-isopropylidenediphenol (bisphenol A), 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,2'-
Methylenebis (4-chlorophenol), hydroquinone, 4,4'-cyclohexylidenediphenol, 4,
4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4
4'-trihydroxybenzophenone, 2,2 ', 4
4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate,
Propyl 4-hydroxybenzoate, sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, 4
-Chlorophenyl hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, -p-chlorobenzyl 4-hydroxybenzoate, -p-methoxybenzyl 4-hydroxybenzoate,
Phenolic compounds such as novolac type phenol resin and phenol polymer, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-
Aromatic carboxylic acids such as 4-hydroxybenzoic acid and 3,5-dimethyl-4-hydroxybenzoic acid, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-
Isopropyloxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 3,4-dihydroxydiphenyl sulfone, 3,4- 4-hydroxydiphenylsulfone derivative such as dihydroxy-4'-methyldiphenylsulfone, bis (3-tert-butyl-4-hydroxy-6-methylphenyl) sulfide, bis (2-methyl-4-hydroxy-6-tert-) Butylphenyl) sulfide, bis (4-hydroxy-3-methylphenyl) sulfide, and other sulfide derivatives, and further these phenolic compounds, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3 -(P-Tolylsulfonyl) pro Yloxy] salicylic acid, 5-
Aromatic carboxylic acids such as [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and polyvalent aromatic carboxylic acids such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel. Examples thereof include salts with metals, and organic acid substances such as antipyrine complexes of zinc thiocyanate.

The use ratio of the basic dye and the color developing agent is appropriately selected according to the types of the basic dye and the color developing agent to be used and is not particularly limited, but in general, the basic dye 1 is used. 1 to 50 parts by weight, preferably 2 to parts by weight
About 10 parts by weight of coloring agent is used.

The coating material for the heat-sensitive recording layer containing the basic dye and the color developing agent in the present invention generally uses water as a dispersion medium and is dispersed together or separately by a stirring / grinding machine such as a ball mill, attritor or sand mill. And then prepared.

In the coating liquid, 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 are usually used as binders in the coating liquid. 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 butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin and the like is blended in an amount of 5 to 40% by weight, preferably 15 to 30% by weight, based on the total solid content of the recording layer. To be done.

If desired, various auxiliary agents can be added to the coating liquid. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. , Zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and other waxes,
An antifoaming agent, a fluorescent dye, a coloring dye, etc. are appropriately added. Further, microcapsules containing an ultraviolet absorber may be blended in the recording layer coating liquid to further enhance light resistance.

It is also possible to use various pigments in combination in the coating liquid. For example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles can be used.

Further, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, and methylenebisstearic acid amide. , N-methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate,
Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p- 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-acetophenetidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like are exemplified. To be done. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

Further, a preservative improving agent may be used in combination depending on the purpose in order to further enhance the preservability of the recorded image as long as the effect is not impaired. Specific examples of such a storage stability 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'-ethylidene bis (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), 1,1,3-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'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3', 5,5'-
Tetramethyldiphenyl sulfone, 2,2-bis (4-
Hydroxy-3,5-dibromophenyl) propane,
2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,
Hindered phenol compounds such as 5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene,
Epoxy compounds such as 4,4′-diglycidyloxydiphenyl sulfone, diglycidyl terephthalate, and bisphenol A type epoxy resin, 1- [α-methyl-α-
(4'-Hydroxyphenyl) ethyl] -4- [α ',
α'-bis (4 "-hydroxyphenyl) ethyl] benzene, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-
Butylphenyl) sodium phosphate and the like.

The coating method of the recording layer is not particularly limited, and it can be formed on a support according to a conventionally known and commonly used technique, for example, bar coating, air knife coating, rod blade coating, pure blade coating, It is formed by a method of applying and drying a coating liquid by short dwell coating, varibar blade coating, curtain coating, die coating, or the like. Further, the coating amount of the coating liquid is not particularly limited, but usually 2 by dry weight.
˜12 g / m ² , preferably about 3 to 10 g / m ² .

It is preferable to provide a protective layer on the heat-sensitive recording layer because the storage stability of recording is further improved. Examples of the water-soluble or water-dispersible polymer used for forming the protective layer include polyvinyl alcohol, carboxy group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, and carboxy. Methyl cellulose, starch and its derivatives, casein,
Sodium alginate, polyvinylpyrrolidone, polyacrylamide, styrene-maleic acid copolymer salt, polyurethane resin, urea resin, melamine resin, polyamide resin,
Examples thereof include synthetic polymer emulsions such as epichlorohydrinized polyamide resin, styrene / butadiene emulsion, styrene / acrylic acid ester emulsion, and acrylic acid ester emulsion. Of course, two or more kinds of these polymer compounds may be mixed.

Among these polymer compounds, acetoacetyl group-modified polyvinyl alcohol and silicon-modified polyvinyl alcohol are preferably used because they form a strong resin film.

Various pigments may be added to the protective layer, and specific examples thereof include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate and talc. ,
Examples thereof include inorganic pigments such as kaolin, clay, calcined kaolin, calcined clay and colloidal silica, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles. It is generally desirable to adjust the amount used in the range of 20 to 500 parts by weight with respect to 100 parts by weight of the polymer compound.

Further, the coating liquid for forming the protective layer may contain microcapsules containing an ultraviolet absorber to further enhance the light resistance. Further, in the coating liquid, if necessary, used in the back coat layer, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, a surfactant such as sodium dioctylsulfosuccinate, Various auxiliaries such as defoaming agents can be added as appropriate.
Further, in order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde dampone, or an epoxy compound can be added.

The coating solution thus prepared is coated on the heat-sensitive recording layer by a suitable coating device. However, if the coating amount is less than 1 g / m ^{2 in} dry weight, the effect of improving the storage stability of printing is insufficient. However, sticking of the thermal head is likely to occur, and conversely, if it exceeds 20 g / m ² , the recording sensitivity of the thermal recording material may be remarkably reduced. Therefore, it is generally 1 to 20 g / m ² , preferably ^{2 to} 10 g / m ² . It is desirable to adjust in the range of about m ² . Incidentally, various known techniques in the field of producing a heat-sensitive recording material, such as providing an undercoat layer between the heat-sensitive recording layer and the support, can be added as necessary. Regarding the order of smearing, it is not always necessary to smear from the back coat layer, and the back coat layer may be formed after formation of the heat-sensitive recording layer.

It is also possible to provide an adhesive layer and usually a release sheet on the back surface of the heat-sensitive recording material thus obtained to obtain a heat-sensitive recording material which has been subjected to an adhesive treatment. The release sheet is not particularly limited, for example, a high-density base paper such as glassine paper, clay-coated paper, a laminated base material such as kraft paper or high-quality paper laminated with polyethylene, etc. A material coated with a release agent such as a fluorine compound is used. As the pressure-sensitive adhesive, various types of rubber-based, acrylic-based, vinyl ether-based emulsion or solvent or solventless pressure-sensitive adhesives are used. The surface of the support means the surface of the support on the side where the thermosensitive recording layer is provided, and the back surface of the support means the opposite surface. The support itself does not have a distinction between front and back.

[0059]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively.

[Example 1] Preparation of solution A 12% of saponified polyvinyl alcohol (trade name: Gocefimer Z-210, manufactured by Nippon Synthetic Chemical Co., Ltd.) in the acetoacetyl group-modified portion was placed in a stirring and mixing container equipped with a heating device. 220 parts of an aqueous solution was added to obtain an aqueous medium for capsule production. Separately, 2- (2'-hydroxy-3'-dodecyl-5'-
Methylphenyl) benzotriazole [trade name: Tinuvin 171, manufactured by Ciba Geigy] 77 parts, main component isocyanurate type hexamethylene diisocyanate [trade name: Takenate D-170HN, manufactured by Takeda Pharmaceutical Co., Ltd.] 3
A solution obtained by heating and mixing 3 parts to 40 ° C. and stirring was added to the above-mentioned aqueous medium for capsule production using a TK homomixer [Model HV-M, manufactured by Tokushu Kika Kogyo] to have an average particle size of 2
It was emulsified and dispersed while being cooled so as to have a thickness of μm. Then
To this emulsified dispersion was added 175 parts of water, and the mixture was stirred while stirring.
The reaction was carried out at 0 ° C. for 5 hours to prepare a microcapsule dispersion having a wall film made of a polyurethane polyurea resin containing an ultraviolet absorber.

Preparation of Solution B (Coating Solution for Backcoat Layer Formation) Solution A 220 parts Kaolin (trade name: UW-90, manufactured by Engelhard) 50 parts 20% acetoacetyl group-modified polyvinyl alcohol aqueous solution ( Product name: Gosfeimer Z-100, manufactured by Nippon Synthetic Chemistry) 100 parts This composition was mixed and stirred to obtain a coating liquid for forming a back coat layer. Formation of Backcoat Layer The backcoat layer was formed by coating and drying the solution B on one surface of a high-quality paper of 50 g / m ² as a support so that the coating amount after drying was 3 g / m ² .

Preparation of Solution C 3-diethylamino-7- (m-trifluoromethylanilino) fluorane 10 parts 5% aqueous solution of methylcellulose 5 parts water 40 parts This composition was sand milled to an average particle size of 2 μm. Crushed until. Preparation of Liquid D 4-hydroxy-4'-isopropoxydiphenyl sulfone 30 parts 5% aqueous solution of methylcellulose 5 parts water 80 parts This composition was ground with a sand mill until the average particle size became 2 μm. Preparation of solution E: 1,2-di (3-methylphenoxy) ethane 20 parts 5% aqueous solution of methylcellulose 5 parts water 55 parts This composition was ground by a sand mill until the average particle size became 2 μm.

55 parts of C liquid, 115 parts of D liquid, 80 parts of E liquid, and 200 parts of 10% aqueous solution of polyvinyl alcohol were formed on the surface of the support obtained in the formation of the recording layer on the side opposite to the surface on which the back coat layer was formed. And 35 parts of calcium carbonate were mixed and stirred to form a thermosensitive recording layer by coating and drying the coating liquid so that the coating amount after drying was 6 g / m ² .

Preparation of solution F (coating solution for forming a protective layer) -Acetoacetyl group-modified polyvinyl alcohol 10% aqueous solution 200 parts-Kaolin (trade name: UW-90, EMC Co.) 100 parts-30% zinc stearate dispersion 30 parts water 100 parts This composition was mixed and stirred to obtain a liquid F (coating liquid for forming a protective layer). Formation of Protective Layer Liquid F was applied and dried on the thermosensitive recording layer so that the coating amount after drying was 5 g / m ^2, and then supercalendering was performed to obtain a thermosensitive recording material.

Example 2 In the preparation of solution A of Example 1, xylylene diisocyanate and trimethylolpropane were used instead of 33 parts of isocyanurate type hexamethylene diisocyanate (trade name: Takenate D-170HN, Takeda Pharmaceutical Co., Ltd.). (3: 1) Addition product (Brand name: Takenate D-110N, Takeda Yakuhin Kogyo KK, containing 25% ethyl acetate) 44 parts, and change reaction condition 90 ° C 5 hours to 60 ° C 3 hours. A thermal recording material was obtained in the same manner as in Example 1 except for the above.

Example 3 In the preparation of solution A of Example 1, 2- (2'-hydroxy-3'-dodecyl-5'-
Thermal recording in the same manner as in Example 1 except that 66 parts of tricresyl phosphate and 11 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole were replaced with 77 parts of methylphenyl) benzotriazole. Got the body

Example 4 Preparation of Liquid G In a stirring and mixing vessel equipped with a heating device, 150 parts of a 5% aqueous solution of polyacrylic acid was added and the pH of the system was adjusted to 4.5 to give an aqueous medium for capsule production. . Separately, a solution obtained by dissolving 16 parts of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole in 100 parts of tricresyl phosphate was used as a capsule core substance, and this was used as TK in the above-mentioned aqueous medium for capsule production. The mixture was emulsified and dispersed at 10,000 rpm for 15 minutes while cooling using a homomixer [Model HV-M, manufactured by Tokushu Kika Kogyo Co., Ltd.]. To this emulsion dispersion, 190 parts of a 30% aqueous solution of a commercially available melamine-formaldehyde initial condensate was added as a wall film material, and the mixture was reacted at 90 ° C. for 3 hours while continuing stirring, and then the temperature was lowered to room temperature to obtain an ultraviolet absorber. A melamine-formaldehyde resin wall membrane capsule having an average particle diameter of 2 μm was prepared.

Formation of Backcoat Layer In the same manner as in Example 1, except that in the preparation of solution B in Example 1, 150 parts of solution G was used instead of 220 parts of solution A to prepare the coating solution for the backcoat layer. The formation of the backcoat layer was formed. Thereafter, a thermal recording material was obtained in the same manner as in Example 1.

Example 5 Preparation of Solution H 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 10 parts 5% aqueous solution of methylcellulose 5 parts water 40 parts This composition Was pulverized with a sand mill until the average particle size became 2 μm. Formation of Thermosensitive Recording Layer A thermosensitive recording layer was formed in the same manner as in Example 1 except that 55 parts of H liquid was used in place of 55 parts of C liquid in the formation of the recording layer of Example 1. A thermal recording material was obtained in the same manner as in 1.

Example 6 Before forming the thermosensitive recording layer,
For the purpose of obtaining a thermosensitive recording material having a high dynamic color density, a thermosensitive recording material having an undercoat layer formed on a support was formed as described below. Preparation of liquid I • Calcined clay (trade name: Ansilex, manufactured by EMC) 100 parts • 10% polyvinyl alcohol aqueous solution (trade name: PVA-210, manufactured by Kuraray Co., Ltd.) 100 parts • Water 200 parts Mixing and stirring these compositions Thus, a dispersion liquid of liquid I was obtained. Formation of Recording Body The amount of the liquid I applied between the support and the thermosensitive recording layer was 7 after drying.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the undercoat layer was formed by coating and drying so as to have g / m ² .

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the back coat layer was not formed.

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 220 parts of solution A was not added in the preparation of solution B (coating solution for forming a backcoat layer) of example 1. It was

[Comparative Example 3] In the preparation of solution A of Example 1, 2- (2'-hydroxy-3'-dodecyl-5'-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that methylphenyl) benzotriazole was not added.

Comparative Example 4 Preparation of Liquid J 2- (2'-hydroxy-5'-methylphenyl) benzotriazole 10 parts 5% aqueous solution of methyl cellulose 5 parts water 40 parts These compositions were sand milled. And the average particle size is 1.5 μm
It was crushed until it became. Preparation of Backcoat Layer-Forming Coating Liquid A backcoat layer-forming coating liquid was prepared in the same manner as in Example 1 except that 100 parts of Solution J was used instead of 220 parts of Solution A. A thermosensitive recording material was obtained.

[Comparative Example 5] As in Comparative Example 1, 55 parts of C liquid was added to one surface of the support on which the back coat layer was not formed,
The coating liquid obtained by mixing and stirring 115 parts of D liquid, 80 parts of E liquid, 90 parts of J liquid, 200 parts of 10% aqueous solution of polyvinyl alcohol, and 35 parts of calcium carbonate had a coating amount of 6 g / m ² after drying. Was coated and dried to form a thermosensitive recording layer.

Thereafter, a thermal recording material was obtained in the same manner as in Example 1. The 11 kinds of thermal recording materials thus obtained were subjected to the following quality evaluation tests, and the results are shown in Table 1.

[Evaluation Items] [Initial Color Density] The color density of the recorded image obtained by printing with a thermal printer (Okura Simulator, applied energy 0.4 mJ / dot) was measured by a Macbeth densitometer (Macbeth RD-914R).
Type) in visual mode.

[Light resistance] After measuring the initial density of the background portion of the obtained recording medium with a Macbeth densitometer (using a blue filter), the recording surface was made to be the indoor side and the inside of the window glass facing south was covered with cellophane tape. Macbeth densitometer (using a blue filter) in the same way as the density of the background after pasting and exposing to direct sunlight for 20 days
It was measured at.

Further, the recording body after the evaluation of the above [initial color density] was similarly attached to a window glass, and the density of the recorded image after being exposed to direct sunlight for 20 days was measured by a Macbeth densitometer (using a visual filter). ).

[Plastic resistance] After the evaluation of the above [initial color density], a rubber adhesive (ECOMELT manufactured by West Germany that does not cause discoloration or the like on the back surface of the recording paper of the thermal recording material, that is, on the back coat layer surface. AGOME Corp. ECOMELT L-302) was applied so that the coating amount after drying was 20 g / m ² to form a pressure-sensitive adhesive layer.

Next, polypropylene pipe (40 mm
φ) vinylidene chloride wrap film [Product name: KM
AW, manufactured by Mitsui Toatsu Kagaku Co., Ltd.] was wound in three layers, and the pressure-sensitive adhesive layer formed as described above was attached to the surface thereof to attach the thermosensitive recording medium. Furthermore, a polyethylene film containing no plasticizer was wound on it in three layers, and the color density after standing at 40 ° C. for 24 hours was measured by the Macbeth densitometer.

[Solvent resistance (property of spray paste)] Adhesion using a spray paste (Spray paste 55: synthetic rubber adhesive from Sumitomo 3M, containing 65% of organic solvent) on the back coat layer of the thermosensitive recording medium Processed. In Comparative Example 1 in which the back coat layer was not provided, the surface of the support, which was not provided with the heat-sensitive recording layer, was subjected to an adhesive treatment.

This test was carried out to confirm whether or not the back coat layer could sufficiently protect the heat-sensitive recording layer from the organic solvent such as 1,1,1 trichloroethane contained in the spray paste or the like. When the surface of the heat-sensitive recording layer was colored, it was marked with x, and when it was not colored, it was marked with o.

[0084]

[Table 1]

[0085]

As is clear from the results shown in Table 1, the thermosensitive recording medium of the present invention has a backcoat layer having excellent plasticizer resistance and solvent resistance, and also has a thermosensitive recording even when the back side is exposed to light. A heat-sensitive recording material having excellent light resistance, in which the layer surface did not discolor or the printing did not fade, was obtained.

Claims (4)

[Claims] 1. A heat-sensitive recording material having a thermosensitive recording layer comprising, on one surface of a support, a colorless or light-colored basic dye and a color developer which develops color by contacting with the dye. A heat-sensitive recording material comprising a back coat layer containing an agent and containing microcapsules having substantially no coloring ability. 2. The heat-sensitive recording material according to claim 1, wherein a compound represented by the following general formula (I) is used as the basic dye in the heat-sensitive recording layer. [Chemical 1] (In the formula, R ₁ and R ₂ represent an alkyl group having 1 to 7 carbon atoms, an isobutyl group, an isoamyl group, a cyclohexyl group, γ-ethoxypropyl, and a tetrahydrofurfuryl group. R ₁ and R ₂ are the same. But it may be different.) 3. The heat-sensitive recording material according to claim 1, wherein the microcapsules are microcapsules having a wall film made of polyurethane-polyurea resin. 4. The heat-sensitive recording material according to claim 1, wherein the ultraviolet absorber is a benzotriazole derivative which is liquid at room temperature.