JPH11148069A - New ultraviolet light absorbent, its production, and heat-sensitive recording unit with the same compounded therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat-sensitive recording material having high coloring sensitivity, and excellent light resistance and heat resistance at its base part. SOLUTION: This new ultraviolet light absorbent obtained by coating inorganic particles with a polymer containing an ultraviolet absorber is produced by carrying out a suspension polymerization of a polymerizable monomer with the ultraviolet absorber dissolved therein in the presence of the inorganic particles. The ultraviolet light absorbent is allowed to be included in at least one layer of a heat-sensitive coloring layer, an intermediate layer or a protecting layer composing a heat-sensitive recording unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel ultraviolet absorbing material, and more particularly to a heat-sensitive recording material using the ultraviolet absorbent to improve the light fastness of an image and the yellowing resistance of a white paper portion. It is.

[0002]

2. Description of the Related Art In a thermosensitive recording system, a thermosensitive recording layer mainly comprising an electron-donating, usually colorless or pale-colored dye precursor and an electron-accepting developer is provided on a support, and this is provided with a thermal head,
By heating with a hot pen, laser light, or the like, the dye precursor and the hanging color agent react instantaneously to obtain a recorded image.
It is disclosed in, for example, JP-A-14039. Such thermosensitive recording paper has the advantages of being able to record with a relatively simple device, being easy to maintain, and having no noise.It has a measuring recorder, facsimile, printer, computer terminal, It is used in a wide range of fields such as labels and ticket vending machines.

[0003] As one application of the heat-sensitive recording paper, in recent years, it has been often used for various heading labels, display media such as posters, and the like. In these applications, the thermal recording paper is often exposed to room light or sunlight for a long period of time, and as a result, the background of the thermal recording paper yellows or the stability of the recorded image is impaired. As a result, the product image is significantly impaired. In order to solve these problems, conventionally, in a heat-sensitive recording paper, a method of adding a finely pulverized ultraviolet absorber to a heat-sensitive recording layer or a protective layer (JP-A-50-104650, JP-A-55-104650).
55891, 55-93492, 58
No. 87093). But,
Finely pulverized UV absorbers have poor absorption efficiency of UV rays, failing to provide a sufficient effect.Additionally, increasing the amount used results in new flaws, such as fogging of the background or lowering of the recording density. At present, it has not been possible to obtain a sufficiently satisfactory light resistance. Also, if the protective layer contains a finely pulverized ultraviolet absorber, the ultraviolet absorber elutes due to the influence of plasticizers and oils and the like, losing the function of the protective layer, and as a result, the storability of the recorded image is reduced. Will drop.

Further, a compound made water-soluble by introducing a sodium sulfonate group into an ultraviolet absorber is used as a heat-sensitive layer and / or
A method of adding it to the protective layer is proposed in Japanese Patent Publication No. 61-57198. However, in this method, the introduction of a sodium sulfonate group has an adverse effect on the pH and liquidity of the prescription system, and also has a problem such as coloring of the background and an adverse effect on a heat-sensitive head. Is hard to say. In addition, Japanese Patent Application Laid-Open No. 5-155134 discloses that a microencapsulated ultraviolet absorber is added to a protective layer to obtain a heat-sensitive recording material having excellent storage stability and light resistance. However, this method requires microencapsulation of an ultraviolet absorber, and although it is superior to a finely pulverized product, the dispersibility of the ultraviolet absorber is lower than the dispersion at the molecular level, and the ultraviolet absorption efficiency becomes poor. The amount added has to be large.

Further, it has been disclosed in JP-A-7-13 to obtain a heat-sensitive recording medium having excellent storage stability and light resistance by adding a polymer containing an ultraviolet absorber to a heat-sensitive layer and / or a protective layer.
7453, 7-156548, 7-17
9046. However, if the polymer is hydrophobic, it must be pulverized into fine particles for addition to the thermosensitive layer and / or the protective layer. on the other hand,
When the polymer is water-soluble, a large amount of hydrophilic groups must be introduced to make the hydrophobic ultraviolet absorber water-soluble, and as a result, the ultraviolet absorption effect is reduced. Also,
JP-A-7-179045 discloses that a heat-sensitive recording medium having excellent storage stability and light resistance can be obtained by adding an inorganic filler having an ultraviolet absorbent adsorbed to the heat-sensitive layer and / or the protective layer.
No. 1993. In this method, a special method must be used to adsorb the ultraviolet absorber on the inorganic filler, and when making a paint for thermal paper by mechanically dispersing the material, the ultraviolet Absorbents can desorb, which is not a very effective method.

[0006]

As described above, it has been practiced for a long time to impart light fastness to heat-sensitive recording paper using an ultraviolet absorber, but a satisfactory method has not yet been developed. is the current situation. Accordingly, an object of the present invention is to provide a UV-absorbing material which can be used for a heat-sensitive recording material having excellent light fastness of an image and excellent yellowing resistance of a white paper portion, and a heat-sensitive recording material using this UV-absorbing material. Is what you do.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, a commonly used ultraviolet absorbent has been dissolved in a polymerizable monomer in advance, and the polymerizable monomer is dissolved in inorganic particles. By polymerizing in the presence of a polymer, a composite material containing an ultraviolet absorber in a polymer and coating the inorganic particles with the polymer was successfully synthesized. Further, the present inventors have found that by using the novel ultraviolet absorbing material thus obtained, a heat-sensitive recording medium having excellent light fastness of an image and excellent yellowing resistance of a white paper portion can be obtained, and reached the present invention. .

The ultraviolet absorbing material of the present invention solves the problems of existing ultraviolet absorbing agents such as background fogging and poor plasticizer resistance by being contained in a polymer. In addition, since the inorganic particles are coated on the inorganic particles, the inorganic particles themselves have both the property of blocking ultraviolet rays and the property of an ultraviolet absorber, so that light resistance can be obtained efficiently. Conventional UV absorbers have a problem in whiteness in fields requiring high whiteness due to their coloring, but the UV absorbing material of the present invention has higher whiteness and is more useful than existing UV absorbers. . This is presumably because this color appears when a white inorganic filler is used in the center. Furthermore, the ultraviolet absorbing material of the present invention can be produced by suspension polymerization, and it is industrially advantageous because there is no need to use a special production technique such as encapsulation. As described above, the ultraviolet absorbing material of the present invention overcomes the drawbacks of the existing ultraviolet absorbing agents and provides new advantages.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the ultraviolet absorbing material of the present invention will be described in detail. The inorganic particles used in the present invention include, for example, heavy calcium carbonate, light calcium carbonate, natural silica, synthetic silica, kaolin, clay, titanium oxide, barium sulfate, zinc oxide (zinc white), aluminum hydroxide, alumina, water Magnesium oxide, talc,
Any water-insoluble substance such as mica and potassium titanate can be used.

As the ultraviolet absorber used in the present invention, any conventionally known compounds exhibiting ultraviolet absorption can be used. Hereinafter, specific examples of the ultraviolet absorber will be described. Specific examples of the 2-hydroxybenzophenone derivative include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-
4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone,
4-dihydroxybenzophenone, 2-hydroxy-4
-Methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane and the like.

Specific examples of the 2- (2-hydroxyphenyl) benzotriazole derivative include 2- (2-hydroxy-5-methylphenyl) benzotriazole,
(2-hydroxy-5-tert-butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole,
-(2-hydroxy-3-tert-butyl-5-methylphenyl) benzotriazole, 5-chloro-2-
(3-tert-butyl-2-hydroxy-5-methylphenyl) benzotriazole, 5-chloro-2-
(3,5-di-tert-butyl-2-hydroxyphenyl) benzotriazole, 2- (2-hydroxy-
3,5-di-tert-amylphenyl) benzotriazole, 2- (2-hydroxy-3- (3,4,5,6
-Tetraphthalimidomethyl) -5-methylphenyl)
Benzotriazole, 2,2'-methylenebis (4-
(1,1,3,3-tetramethylbutyl) -6- (2H
-Benzotriazol-2-yl) phenol) and the like. Examples of cyanoacrylate-based UV absorbers include 2-ethylhexyl-2-cyano-3,3'-
Diphenyl acrylate, ethyl-2-cyano-3,
3'-diphenyl acrylate and the like.

Examples of the salicylic acid type ultraviolet absorber include:
Examples include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate and the like. Examples of the dibenzoylmethane-based ultraviolet absorber include 1,3-diphenyl-1,3-propanedione, 2- (2-benzoylacetyl) benzoic acid, 4-tert-butyl-4′-methoxydibenzoylmethane, and the like. Is raised. In addition to the above, any ultraviolet absorber can be used, for example, a triazine compound, a cinnamate compound, and the like. Further, it may contain an ultraviolet stabilizer and an antioxidant. In the present invention, 2- (2
-Hydroxyphenyl) benzotriazole derivatives, especially 5-chloro-2- (3,5-di-tert-butyl-)
It is preferred to use (2-hydroxyphenyl) benzotriazole.

The polymerizable monomer used in the present invention may be any one which is insoluble in water, can dissolve the above-mentioned ultraviolet absorbent at room temperature or when heated, and causes radical polymerization. Examples thereof include styrene and vinyl chloride. , Vinylidene chloride, vinyl acetate, chloroprene, methyl cyanoacrylate, N-vinylcarbazole, N-vinylpyrrolidone,
Monomers such as acrolein, nitroethylene, alkyl methacrylates such as methyl methacrylate, and alkyl acrylates such as methyl acrylate can be mentioned. In this case, the number of carbon atoms of the alkyl group is not particularly limited, but is preferably 1 to 18. Of these, alkyl methacrylate or styrene is particularly preferred from the viewpoint of polymerizability.

The radical polymerization initiator used in the present invention includes 2,2'-azobis (2-methylpropionamidine) dihydrochloride and 2,2'-azobis [2- (1-hydroxyethyl) -2- Imidazolidinone-2-yl) propane] dihydrochloride, 2,
A water-soluble azo-based polymerization initiator such as 2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] can be used. In addition, water-soluble inorganic peroxides such as potassium persulfate, ammonium persulfate, sodium hydrogen sulfite, and hydrogen peroxide can be used.

The surfactant used in the aqueous suspension polymerization includes, for example, oleic acid, resin acid, alkyl sulfate, lauryl sulfate, sulfated fatty acid monoglyceride, alkylbenzenesulfonic acid, decylbenzenesulfonic acid, dodecylbenzene. Sulfonic acid, naphthalenesulfonic acid formalin condensate, alkylnaphthalenesulfonic acid, isopropylnaphthalenesulfonic acid, monobutylphenylphenolmonosulfonic acid, monobutylbiphenylsulfonic acid, dibutylphenylphenoldisulfonic acid, diisobutylsulfonated succinic acid, diamylsulfonated Succinic acid, dihexylsulfonated succinic acid, dioctylsulfonated succinic acid, sulfonated petroleum or their sodium or potassium salts, amylphenol decaethylene glycol Lumpur, p- isooctylphenol decamethylene glycol, polyethylene 400 monolaurate, polyethylene glycol oleate, polyethylene glycol tall oil esters, polyethylene glycol sorbitan monolaurate, fatty acid amide condensates,
Examples thereof include alkyl polyethylene glycol thioether and oleyl polyethylene glycol ether.
Of these, sodium dodecyl sulfate is particularly preferred.

Next, a method for synthesizing the ultraviolet absorbing material of the present invention will be described. Several composite materials in which inorganic particles are coated with a polymer have already been reported (for example,
Hasegawa et al., Journal of Polymer
Science, Part A, Polymer C
hemistry, vol. 25, 3117 (19
87) et al., Tanaka et al., Coloring Materials, vol. 65 (8),
484 (1992) et al.), And the ultraviolet absorbing material of the present invention can be synthesized in the same manner. Specifically, first, the above-mentioned inorganic particles are put into a reactor, and the inside thereof is replaced with an inert gas such as argon. Distilled water is put therein, and a surfactant is further added therein to suspend the suspension. This surfactant is adsorbed on the surface of the inorganic particles,
It is added to provide a place for polymerization. The concentration of the inorganic particles used in the polymerization is added to the system so as to be 1 to 50% by weight of the whole during the polymerization.
0% by weight is preferred. Beyond this range, it is difficult to uniformly coat the polymer. The amount of the surfactant to be used is 0.01 to 10% by weight based on the polymerizable monomer, and is particularly preferably in the range of 0.1 to 2% by weight.

Subsequently, the surfactant is adsorbed on the inorganic particles by stirring for 2 hours while the system is suspended. Thereafter, the inside of the system is heated to 40 to 100 ° C.
0 ° C. is preferred. Next, a polymerizable monomer in which an ultraviolet absorber is dissolved is added to the suspension, and immediately thereafter, a reaction initiator is added. At that time, the concentration of the monomer used for the polymerization is added to the system so as to be 1 to 20% by weight of the whole at the time of the polymerization, and particularly preferably 2 to 10% by weight. Further, the amount of the ultraviolet absorber is such that the molar ratio of the ultraviolet absorber / polymerizable monomer is 1/9 to 1/1 with respect to the polymerizable monomer. Below this, the effect of the UV absorber does not appear, and above that, the UV absorber is not well incorporated into the polymer. The initiator is used in an amount of 0.01 to 10% by weight based on the polymerizable monomer.
It is preferably within the range of weight%.

Subsequently, the mixture is stirred for 0.5 to 3 hours while being heated, preferably about 1 hour. At this time, if the stirring is less than 0.5 hour, the polymerization does not proceed very much, which is not preferable. Even when the time is longer than 3 hours, the degree of polymerization of the polymer hardly changes. The degree of polymerization of the polymer is preferably in the range of 10 4 to 10 7 as the weight average molecular weight, and it is preferable to set the above-described conditions. afterwards,
Hydroquinone or the like is added as a terminator in an amount corresponding to the initiator, and the mixture is cooled to room temperature to terminate the polymerization. Further, the suspension is filtered, and the obtained particles are washed with water, washed with methanol to remove impurities, and dried, whereby inorganic particles coated with the target ultraviolet absorbent-containing polymer can be produced.

The inorganic particles coated with the ultraviolet absorbent-containing polymer thus obtained can be confirmed by electron microscopy that the inorganic particles are coated with the polymer (shown in FIG. 2). NMR of chloroform extract of the particles,
GPC, thermal weight loss, and UV absorption spectrum confirm that the particles contained a polymer and an ultraviolet absorber (shown in FIGS. 5, 6, 1, and 3). It can be confirmed from the infrared absorption spectrum and the thermogravimetric decrease that the ultraviolet absorber is contained in the polymer (FIGS. 4 and 1).

Next, a thermosensitive recording medium using the ultraviolet absorbing material of the present invention will be described. The thermosensitive recording medium is usually obtained by providing a thermosensitive recording layer containing an electron donating compound and an electron accepting compound on a support. In the present invention, in addition to the thermosensitive coloring layer, a protective layer containing a water-soluble or water-dispersible binder as a main component, an intermediate layer between the thermosensitive recording layer and the protective layer, a support and the thermosensitive coloring layer on the thermosensitive coloring layer. It is possible to adopt a laminated structure in which an under layer mainly containing a filler and a binder is provided between the color forming layer and the like. These layer configurations may be appropriately combined according to the required quality performance, and a known technique usually used in the thermal recording field can be applied. The thermosensitive recording medium of the present invention contains the above-mentioned ultraviolet absorbing material of the present invention as an ultraviolet absorbing agent in at least one of these layers. Particularly, from the viewpoint of ultraviolet absorption, it is desirable to provide a protective layer and to include the protective layer in the protective layer.

When the ultraviolet absorbing material of the present invention is used for a heat-sensitive recording medium, the average particle size is 2 μm in order to obtain a desired effect.
m, particularly preferably 0.5 μm or less. When the average particle size is 0.5 μm or less, not only the ultraviolet absorption efficiency is remarkably improved, but also when the protective layer is contained in the protective layer, the recorded image is hardly concealed and a clear recorded image can be obtained. In order to keep the average particle size of the ultraviolet absorbing material at 2 μm or less, the smaller the average particle size of the above-mentioned inorganic particles is, the better it is. It is preferable to use inorganic particles having an average particle size of 1 μm or less. More preferred. As a method of making finer, generally, water is used as a dispersion medium,
Additives such as a dispersant and an antifoaming agent may be added as needed, and a method using a stirring / pulverizer such as a ball mill, an attritor, a sand mill, or the like may be used. Among them, a sand mill type pulverizer is desirable, and the average particle size of the dispersion medium is preferably 1 mm or less.

The ultraviolet absorbing material of the present invention can be used in combination with other known ultraviolet absorbing agents as long as the desired effect is not impaired. Further, nickel bis (octylphenyl) sulfide, [2,2′-thiobis (4-
tert-octylphenolate)]-n-butylamine nickel, nickel complex-3,5'-di-
tert-butyl-4-hydroxybenzyl-phosphate monoethylate, nickel dibutyldithiocarbamate,
An ultraviolet stabilizer such as a benzoate-type quencher and a hindered amine-based light stabilizer such as bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate can be used in combination.

In the present invention, examples of the thermal recording system utilizing a color development reaction between an electron donating compound and an electron accepting compound include a combination of a leuco dye and a developer, a combination of a diazonium salt and a coupler, and a combination of iron and the like. Examples include a combination of a transition element and a chelate compound, and a combination of an aromatic isocyanate compound and an imino compound. A combination of a leuco dye and a developer is preferable because of its excellent color density and recording sensitivity. Hereinafter, a thermosensitive recording medium utilizing a color development reaction between a leuco dye and a color developer will be described in detail. Various known basic dyes can be used as the dye used in the present invention. These may be used alone or in combination of two or more, and are selected according to the use and required characteristics. Specific examples include, but are not limited to, the following compounds.

(1) Triarylmethane compound 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis-
(P-ethylcarbazol-3-yl) -3-dimethylaminophthalide, 3,3-bis- (2-phenylindol-3-yl) -6-dimethylaminophthalide and the like.

(2) Diphenylmethane compounds 4,4-bis-dimethylaminobenzhydryl benzyl ether, N-halophenyl-leuco auramine, N-
2,4,5-trichlorophenyl leuco auramine and the like.

(3) Xanthene compounds Rhodamine B-anilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-butylaminofluoran, 3-diethylamino-7- (2-chloroanilino) Fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-
Piperidino-6-methyl-7-anilinofluoran, 3
-Ethyltolylamino-6-methyl-7-anilinofluoran, 3-cyclohexylmethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6
Chloro-7- (β-ethoxyethyl) aminofluoran, 3-diethylamino-6-chloro-7- (γ-chloropropyl) aminofluoran, 3-diethylamino-
6-chloro-7-anilinofluoran, 3-N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluoran, 3-diethylamino-7-phenylfluoran, 3- (N-isoamyl- N-ethylamino)-
6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran and the like.

(4) Thiazine compounds Benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue and the like can be mentioned. (5) Spiro-based compounds 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methylnaphtho- (6'-methoxybenzo) -spiropyran and the like.

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

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

As the pigment, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin and the like are used. In addition, for the purpose of preventing head abrasion and sticking, zinc stearate, higher fatty acid metal salts such as calcium stearate, wax such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearic acid amide, caster wax, Examples of the sensitizer include parabenzyl bisphenyl, esters of hydroxynaphthoic acid, various oxalates such as stearamide, tribenzylamine, naphthalene derivatives, dibenzyl terephthalate, and bis (paramethylbenzyl) oxalate. Further, a dispersant such as sodium dioctyl sulfosuccinate, a surfactant,
A fluorescent dye or the like is added as desired.

Paper is mainly used as the base material in the heat-sensitive recording material of the present invention, and various nonwoven fabrics, plastic films, synthetic papers, metal foils and the like, or composite sheets obtained by combining these are arbitrarily used. Using the various materials described above, the thermal recording medium of the present invention can be manufactured by a conventionally known method. The method for preparing the coating liquid for each layer of the heat-sensitive recording medium is not particularly limited. In general, water is used as a dispersion medium, and in addition to the ultraviolet absorbing material of the present invention, a binder, a pigment, and a lubricant that are added as needed. It is prepared by mixing and stirring. In the case of a thermosensitive coloring layer, adjustment is made by adding a basic dye and a color developer. The basic dye and the developer are separately pulverized and dispersed in an aqueous system using a sand grinder, an attritor, a ball mill, or the like, and then a method of obtaining a paint by mixing, or any of the basic dye and the developer is used. A method of obtaining a water-based paint after microencapsulation is known. The use ratio of the basic dye and the developer is appropriately selected depending on the type of the basic dye and the developer to be used and is not particularly limited, but is generally 1 to 50 parts by weight based on 1 part by weight of the basic dye. The developer is used in an amount of 2 parts by weight, preferably about 2 to 10 parts by weight.

The ultraviolet absorbing material of the present invention comprises a heat-sensitive recording layer,
It is preferably present in an amount of 1 to 50% by weight, particularly 10 to 40% by weight, based on the total solid content of each layer such as a protective layer.
When the amount of the ultraviolet absorbing material is less than 1% by weight with respect to the total solid content, the light resistance of the recorded image and the white paper portion is remarkably reduced, and when the amount exceeds 50% by weight, the viscosity of the coating over time becomes severe and the coating suitability is increased. Inferior. When it is contained in the protective layer, if it exceeds 50% by weight, the film-forming property of the protective layer is reduced and the chemical resistance of the recorded image is significantly reduced. The method of forming each layer of the thermosensitive recording medium is not particularly limited, and air knife coating, buriba blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, and the like can be appropriately selected. For example, it is formed by a method in which a coating solution for a heat-sensitive coloring layer is applied on a support, dried, and then a coating solution for a protective layer is applied on the heat-sensitive coloring layer and dried. The coating amount of the coating solution for the thermosensitive recording layer is 2 to 2 by dry weight.
12 g / m ^2, preferably about 3 to 10 g / m ² approximately, the coating amount of the protective layer coating liquid for dry weight 0.1 to 20 g / m ²
Level, preferably in the range of about 0.5 to 10 g / m ² .

The heat-sensitive recording material of the present invention can be provided with a back coat layer on the back side of the support, if necessary, to further improve the storability. Furthermore, after each layer is formed, a smoothing treatment such as super calendaring is performed, or an adhesive treatment is performed on the back surface of the thermosensitive recording material to form an adhesive label, a magnetic thermosensitive recording layer, a printing coating layer, and a thermal transfer thermosensitive layer. Various known techniques in the heat-sensitive recording field, such as providing a recording layer, can be added according to the application.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to specific embodiments. Note that the present invention is not limited to this embodiment. <Production of Ultraviolet Absorbing Material of the Present Invention> Example 1
3 (Brilliant-15, average particle size 0.15μ)
m) 30 g, 300 ml of distilled water, and 88.1 mg (0.3 mmol) of sodium dodecyl sulfate (SDS) were added. This was stirred at room temperature and 300 rpm for 2 hours. The temperature was raised to 60-62 ° C. and the agitation was at 400 rpm. 8.56 g (0.085 mol) of methyl methacrylate and 5-chloro-
1.62 g of 2- (3 ', 5'-di-tert-butyl-2'-hydroxyphenyl) benzotriazole (0.
005 mol) of the mixture. Immediately after the addition of the monomer mixture, the initiator K ₂ S ₂ O ₈ 86.7 m
g (0.3 mmol) was added. Stirring was continued for 1 hour under these conditions. After 1 hour, the reaction was cooled to room temperature, and the reaction was stopped by adding 50.0 mg (0.4 mmol) of hydroquinone. Next, the reaction mixture was filtered. The residue obtained by filtration is twice with 500 ml of distilled water, 500 ml of MeOH.
, And water contained therein was distilled off with a vacuum dryer to obtain 37.52 g of a white solid.

The analysis results are shown below. Thermogravimetric reduction TG / DTA 320 The thermogravimetric differential thermogravimetry was measured using a simultaneous thermogravimetric analyzer (manufactured by Seiko Instruments Inc.). The results are shown in FIG. The weight loss of the ultraviolet absorber was about 4%, and the weight loss of polymethyl methacrylate was about 20%. Also,
Since no endothermic peak at the melting point of the ultraviolet absorber was observed, it was confirmed that the ultraviolet absorber was contained in the polymer. Scanning electron micrograph of the particles The results are shown in FIG. It was confirmed that the particles were coated. Ultraviolet absorption spectrum (diffuse reflection method) It measured using UV-3100 Spectrometer (made by Shimadzu Corporation). The results are shown in FIG. Ultraviolet absorption was also confirmed. The maximum absorption wavelength was 348 nm and 310 nm. Infrared absorption spectrum (relative reflection method) Magna 850 IR Spectrometer
(Nicolet). Fig. 4 shows the results.
Shown in From this spectrum, the absorption of polymethyl methacrylate was confirmed. NMR spectrum of chloroform extract from particles QE300 FT-NMR Spectrometer
(Manufactured by General Electric). FIG. 5 shows the results. From this spectrum, peaks of polymethyl methacrylate and an ultraviolet absorber were confirmed. Using a column of GPC Shodex KF802 + KF803 (manufactured by Showa Denko KK) for a chloroform extract of the particles, THF was used as a solvent, and the measurement was carried out using Shodex RI SE-61 (manufactured by Showa Denko KK). This was done by measuring the ratio. FIG. 6 shows the results. Polymethyl methacrylate and an ultraviolet absorber were confirmed.

Example 2 Inorganic particles coated with an ultraviolet absorbent-containing polymer were produced in the same manner as in Example 1, except that titanium oxide was used as the inorganic particles.

Example 3 Except that the inorganic particles used were aluminum hydroxide,
In the same manner as in Example 1, inorganic particles coated with the ultraviolet absorbent-containing polymer were produced.

Example 4 The UV absorber used was 5-chloro-2- (3'-tert
-Butyl-5'-methyl-2'-hydroxyphenyl)
Except for using benzotriazole, inorganic particles coated with an ultraviolet absorbent-containing polymer were produced in the same manner as in Example 1.

Example 5 Inorganic particles coated with a polymer containing an ultraviolet absorber were produced in the same manner as in Example 1 except that the ultraviolet absorber used was 2-hydroxy-4-methoxybenzophenone.

<Manufacture of Thermal Recording Medium> Example 6 Formation of Thermal Recording Layer Liquid A (Developer Dispersion) 4-Hydroxy-4′-isopropoxydiphenyl sulfone 6.0 parts 10% aqueous solution of polyvinyl alcohol 18.8 Part water 11.2 parts A mixture of the above composition was ground with a sand grinder to an average particle size of 1 micron. Liquid B (dye dispersion liquid) 2,4-dimethyl-6-[(4-dimethylamino) anilino] fluoran 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts Water 2.6 parts Mixture of the above compositions Was ground to an average particle size of 1 micron with a sand grinder. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. Solution A 36.0 parts Solution B 9.2 parts Kaolin clay 50% dispersion 12.0 parts Amount of each of the above coating solutions applied to one side of a 50 g / m 2 support 6.
The coating was dried at 0 g / m ² to form a heat-sensitive recording layer. Formation of protective layer (containing UV absorber) Liquid C (UV absorber dispersion) UV absorber synthesized in Example 1 12.0 parts 10% aqueous polyvinyl alcohol solution 6.7 parts Water 21.3 parts The above composition Was mixed with a sand grinder to an average particle size of 1 micron. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. 10% aqueous polyvinyl alcohol solution 60.0 parts Aluminum hydroxide (50% dispersion) 50.0 parts Zinc stearate 10.0 parts C solution 20.0 parts Dilution water 50.0 parts Fluorescent dye 25% aqueous solution 0.5 parts Each of the above coating liquids was coated on the heat-sensitive recording layer so as to have a coating amount of 4.0 g / m ² and dried, and then subjected to a super calender treatment to obtain a heat-sensitive recording material.

Example 7 Formation of Thermal Recording Layer Solution A (Developer Dispersion) 4-Hydroxy-4′-isopropoxydiphenylsulfone 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts Of the composition was ground to an average particle diameter of 1 micron with a sand grinder. Liquid B (dye dispersion liquid) 2,4-dimethyl-6-[(4-dimethylamino) anilino] fluoran 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts Water 2.6 parts Mixture of the above compositions Was ground to an average particle size of 1 micron with a sand grinder. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. Solution A 36.0 parts Solution B 9.2 parts Kaolin clay 50% dispersion 12.0 parts Amount of each of the above coating solutions applied to one side of a 50 g / m 2 support 6.
The coating was dried at 0 g / m ² to form a heat-sensitive recording layer. Formation of intermediate layer (containing UV absorber) Liquid C (UV absorber dispersion) UV absorber synthesized in Example 1 12.0 parts 10% aqueous polyvinyl alcohol solution 6.7 parts Water 21.3 parts The above composition Was mixed with a sand grinder to a mean particle size of 1 micron to obtain a coating solution. 50 g of this coating liquid
/ M ² was coated on one side of the support at a coating amount of 2.0 g / m ² and dried to form an intermediate layer. Formation of protective layer 10% polyvinyl alcohol aqueous solution 60.0 parts Aluminum hydroxide (50% dispersion) 50.0 parts Zinc stearate 10.0 parts Dilution water 50.0 parts Fluorescent dye 25% aqueous solution 0.5 parts The coating liquid was applied onto the heat-sensitive recording layer so as to have a coating amount of 4.0 g / m ² and dried, and then subjected to a super calender treatment to obtain a heat-sensitive recording material.

Example 8 Formation of Thermal Recording Layer (Containing UV Absorber) Solution A (Developer Dispersion) 4-Hydroxy-4′-isopropoxydiphenylsulfone 6.0 parts 10% aqueous solution of polyvinyl alcohol 18.8 parts Water 11.2 parts A mixture of the above composition was ground with a sand grinder to an average particle size of 1 micron. Liquid B (dye dispersion liquid) 2,4-dimethyl-6-[(4-dimethylamino) anilino] fluoran 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts Water 2.6 parts Mixture of the above compositions Was ground to an average particle size of 1 micron with a sand grinder. Liquid C (UV absorber dispersion) UV absorber synthesized in Example 1 12.0 parts 10% aqueous solution of polyvinyl alcohol 6.7 parts Water 21.3 parts Average particle diameter of a mixture of the above compositions with a sand grinder Milled to 1 micron. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. Liquid A 36.0 parts Liquid B 9.2 parts Liquid C 20.0 parts Kaolin clay 50% dispersion liquid 12.0 parts Amount of each of the above coating liquids applied to one surface of a 50 g / m ² support 6.
The coating was dried at 0 g / m ² to form a heat-sensitive recording layer. Formation of protective layer A dispersion was mixed at the following ratio to obtain a coating liquid. 10% aqueous polyvinyl alcohol solution 60.0 parts Aluminum hydroxide (50% dispersion) 50.0 parts Zinc stearate 10.0 parts Dilution water 50.0 parts Fluorescent dye 25% aqueous solution 0.5 parts Heat-sensitive each coating solution After coating and drying on the recording layer to a coating amount of 4.0 g / m ² , a super calender treatment was performed to obtain a heat-sensitive recording material.

Example 9 A heat-sensitive recording material was produced in the same manner as in Example 6, except that the inorganic particles coated with the ultraviolet absorbent-containing polymer produced in Example 2 were used. Example 10 A thermosensitive recording medium was produced in the same manner as in Example 6, except that the inorganic particles coated with the ultraviolet absorbent-containing polymer produced in Example 3 were used.

Example 11 A heat-sensitive recording material was produced in the same manner as in Example 6, except that the inorganic particles coated with the ultraviolet absorbent-containing polymer produced in Example 4 were used.

Example 12 A thermosensitive recording medium was produced in the same manner as in Example 6, except that the inorganic particles coated with the ultraviolet absorbent-containing polymer produced in Example 5 were used.

Comparative Example 1 A heat-sensitive recording medium was produced in the same manner as in Example 6, except that the inorganic particles coated with the ultraviolet absorbent-containing polymer were not used. Comparative Example 2 A copolymer of a reactive ultraviolet absorber and methyl methacrylate (PUVA-30M manufactured by Otsuka Chemical Co., Ltd.) was used instead of the inorganic particles coated with the ultraviolet absorber-containing polymer. Produced a thermosensitive recording medium in the same manner as in Example 6.

Table 1 shows the results of quality performance tests performed on the thermal recording media obtained in the above Examples and Comparative Examples.

[0048]

[Table 1]

Color development: UBI EasyCoder
The image density recorded at IIE (manufactured by UBI) at 450 mj / mm ² was measured with a Macbeth densitometer. Light fastness: The heat-sensitive recording medium printed under the above conditions was treated with a xenon lamp weather meter for 24 hours, and the density of the background was measured with a Macbeth densitometer. (Irradiance 67W /
m ² , integrated irradiance 5348 kj / m ² ) Head residue: UBI Eas
yCoder IIE (manufactured by UBI) 450 mj / mm
^The degree of dirt (head residue) of the thermal head after recording in ² was visually evaluated as follows. The evaluation criteria are as follows. ：: No head residue. ：: There is slight head residue, but there is no practical problem. ×: Many head residue.

[0050]

As described above, the heat-sensitive recording material using the ultraviolet absorbing material of the present invention is excellent in the stability of the recording portion and the light resistance of the background portion, and can be used for a long time under sunlight or high temperature. An excellent heat-sensitive recording material which does not change its color even when stored for a long time and does not impair the appearance can be obtained. In particular, from Example 6-8, as an ultraviolet absorber, 5-chloro-2- (3,5-di-ter) was used.
Those using (t-butyl-2-hydroxyphenyl) benztriazole and using calcium carbonate as the inorganic particles were excellent in color development and light resistance. In addition, since the expensive ultraviolet absorber is present on the particle surface and the central portion is made of an inexpensive inorganic filler, it is possible to solve the problem of high cost when a conventional ultraviolet absorber is used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a thermogravimetric reduction of an ultraviolet absorbing material of the present invention.

FIG. 2 is an electron micrograph of the ultraviolet absorbing material of the present invention.

FIG. 3 is an ultraviolet absorption spectrum of the ultraviolet absorbing material of the present invention.

FIG. 4 is an infrared absorption spectrum of the ultraviolet absorbing material of the present invention.

FIG. 5 is an NMR spectrum of a chloroform extract from the ultraviolet absorbing material of the present invention.

FIG. 6 is a GPC of a chloroform extract from the ultraviolet absorbing material of the present invention.

Claims (5)

[Claims] 1. An ultraviolet absorbing material obtained by polymerizing a polymerizable monomer in which an ultraviolet absorbing agent is dissolved in the presence of inorganic particles. 2. The ultraviolet absorbing material according to claim 1, wherein the polymerization is carried out under aqueous suspension conditions. 3. An ultraviolet absorber, 5-chloro-2-
The ultraviolet absorbing material according to claim 1 or 2, wherein (3,5-di-tert-butyl-2-hydroxyphenyl) benzotriazole is used, and calcium carbonate is used as the inorganic particles. 4. A method for producing an ultraviolet absorbing material, wherein a polymerizable monomer in which an ultraviolet absorbent is dissolved is subjected to suspension polymerization in an aqueous system in the presence of inorganic particles. 5. A thermosensitive recording medium utilizing a reaction between an electron donating compound and an electron accepting compound, wherein the ultraviolet absorbing material according to claim 1 is used as an ultraviolet absorbing agent. Thermosensitive recording medium.