JP3114171B2 - Thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording medium having excellent light fastness, good white paper appearance, and prevention of scum adhesion and sticking.

[0002]

2. Description of the Related Art In general, a heat-sensitive recording material having a heat-sensitive coloring layer mainly composed of a colorless or pale-colored dye precursor and a color developing agent which reacts with the dye precursor by heating to form a color is disclosed in Japanese Patent Publication No. 45-1.
No. 4035, which is widely used.
In order to perform recording on this thermosensitive recording medium, a thermal printer or the like having a built-in thermal head is used.However, such a thermosensitive recording method has less noise at the time of recording as compared with other recording methods that have been practically used conventionally. With no development and fixing, maintenance-free, relatively inexpensive and compact equipment, and very clear color development, the facsimile and computer fields Widely used for various measuring instruments and labels.

However, a heat-sensitive recording material using such a heat-sensitive recording material has a defect in light resistance of an image portion and a background portion. That is, when exposed to sunlight for a long period of time, the density of the image portion decreases and the color of the background portion discolors, causing image damage.

Japanese Patent Application Laid-Open No. 62-18626 describes a method for incorporating zinc oxide, which is an inorganic filler having an ultraviolet shielding effect, into a thermosensitive coloring layer in order to improve light resistance. However, in the case of an inorganic filler having an ultraviolet shielding effect, although the ultraviolet shielding effect is large, the transmittance in the visible light region is small, and the coloring portion is concealed and the printing density is lowered.
Therefore, if the amount used is reduced to such an extent that a sufficient print density can be maintained, there is a problem that the effect of blocking ultraviolet rays is deteriorated, which is not practical. Further, a method of incorporating cerium oxide fine particles into a protective layer is described in JP-A-6-64324. However, cerium oxide itself may be colored, which is not suitable as a material for a thermal recording medium.

Japanese Patent Application Laid-Open No. Hei 7-25147 discloses a three-layer ultraviolet shielding structure in which cerium oxide is coated on core particles made of an inorganic pigment, and the surface coated with cerium oxide is coated with an inorganic pigment identical or different from the inorganic pigment. A method for incorporating an agent into the protective layer is described. Although the coloring of the cerium oxide was somewhat inconspicuous, the effect of blocking the ultraviolet rays of the cerium oxide was blocked, and it could not be said that sufficient light resistance was obtained.

On the other hand, JP-A-61-193883 discloses a method of incorporating a benzotriazole-based hydrophobic ultraviolet absorber into a protective layer for the purpose of improving light resistance. However, when a hydrophobic ultraviolet absorber is contained in the protective layer, there is a drawback that scum sticking and sticking occur during printing. On the other hand, when a water-soluble ultraviolet absorber is used, ions such as sodium salts are formed upon solubilization of the water-soluble ultraviolet absorber as described in JP-A-7-17131. Therefore, there is a disadvantage that the thermal head is electrochemically worn. In Japanese Patent Application Laid-Open No. Sho 62-176879, a benzotriazole compound is contained in the undercoat layer and the protective layer to absorb ultraviolet rays from the back surface. This causes sticking and sticking at the time of printing, and a thermosensitive recording medium of sufficient quality could not be obtained.

Japanese Patent Application Laid-Open No. Sho 62-184880 describes a method of incorporating a fluorescent whitening agent into a protective layer. The effect of the fluorescent whitening agent alone is mainly based on the appearance of white paper. However, light resistance has not been improved.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording medium which overcomes the conventional problems, has excellent light fastness, has good white paper appearance, and prevents the generation of scum and sticking. Is to do.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a thermosensitive recording medium which has achieved the above object can be obtained by containing a specific ultraviolet ray blocking agent together with an ultraviolet ray absorbing agent. The present invention has been completed.

That is, the present invention provides an undercoat layer on a support,
In a thermosensitive recording medium in which a thermosensitive coloring layer and a protective layer are sequentially laminated, an ultraviolet absorber is contained in the undercoat layer and / or the thermosensitive coloring layer, and the refractive index in the thermosensitive coloring layer and / or the protective layer is 1.5 to 1.5. The present invention relates to a heat-sensitive recording material containing an ultraviolet ray blocking agent comprising a baked product of particles obtained by coating the surface of a flake pigment with an insoluble cerium compound and amorphous silica, and a fluorescent dye in a protective layer.

In the heat-sensitive recording material of the present invention, the UV absorber contained in the undercoat layer or the heat-sensitive coloring layer includes:
Various known hydrophobic or water-soluble substances can be used.

As the hydrophobic ultraviolet absorber, for example,
2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-
Octyloxybenzophenone, 2-hydroxy-4-
Benzophenone ultraviolet absorbers such as dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone 2- (2′-hydroxyphenyl) benzotriazole, 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-aminophenyl) benzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-butylphenyl) -5-
tert-butylbenzotriazole, 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy-4'-
(2 ″ -ethylhexyl) oxyphenyl] benzotriazole, methyl-3- [3-tert-butyl-5-
(2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate-polyethyleneglycol-
Condensate with 5-tert-butyl-
Octyl 3- (5-chloro-2H-benzotriazol-2-yl) -4-hydroxybenzene-propionate, 2,2-methylenebis [4- (1,1,3,3,-
Tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2'-hydroxy-3'-sec-butyl-5'-tert-butylphenyl)
Benzotriazole-based ultraviolet absorbers such as -5-tert-butylbenzotriazole, phenyl salicylate, p
-Tert-butylphenyl salicylate, salicylic acid-based ultraviolet absorbers such as p-octylphenyl salicylate,
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-tetra Methyl-4-
Piperidyl) sebacate, bis-succinate-bis (2,2,
6,6, -tetramethyl-4-piperidyl) ester,
Hindered amine ultraviolet absorbers such as 2- (3,5-di-tert-butyl) malonic acid-bis (1,2,2,6,6-pentamethyl-4-piperidyl) ester and the like can be exemplified. .

As the water-soluble ultraviolet absorber, for example, 2
-Hydroxy-4-methoxybenzophenone-5-sulfonic acid, sodium 2-hydroxy-4-methoxybenzophenone-5-sulfonate, potassium 2-hydroxy-4-methoxybenzophenone-5-sulfonate, 2,
Sodium 2'-dihydroxy-4,4'-dimethoxybenzophenone-5-sulfonate, sodium 2,4-dihydroxybenzophenone-5-sulfonate,
Sodium 2'-dihydroxy-4,4'-dimethoxybenzophenone-5,5'-disulfonate, sodium 2,4-dihydroxybenzophenone-5'-sulfonate, 2,2 ', 4,4'-tetrahydroxybenzophenone- Benzophenone-based ultraviolet absorbers such as sodium 5,5'-disulfonate, 2- (2'-hydroxy-
4'-methoxy-5'-sulfophenyl) benzotriazole sodium salt, 2- (2'-hydroxy-4'-
Butoxy-5'-sulfophenyl) benzotriazole sodium salt and other benzotriazole ultraviolet absorbers.

In the present invention, the benzotriazole-based ultraviolet absorber having the highest effect on light resistance is preferably used. Also, two or more kinds can be used in combination as needed. In particular, when it is contained in the thermosensitive coloring layer, 2,2-methylenebis [4-
(1,1,3,3-tetramethylbutyl) -6- (2
H-benzotriazol-2-yl) phenol]
This is desirable because the coloring is less and the heat resistance of the thermosensitive recording medium is improved.

[0015] The amount of the ultraviolet absorber used is from 0.1% by weight to the dry weight of the undercoat layer or the thermosensitive coloring layer.
About 15% by weight is contained. More preferably, the content is 1% by weight to 10% by weight based on the dry weight of the undercoat layer, and 2% by weight to 10% by weight based on the dry weight of the thermosensitive coloring layer. When the amount of the ultraviolet absorber used in the undercoat layer or the thermosensitive coloring layer is 0.1% by weight or less, the effect on light resistance is low,
When the content is 15% by weight or more, the coloring sensitivity and image storability of the thermosensitive recording medium are reduced.

In the heat-sensitive recording medium of the present invention, the ultraviolet ray blocking agent contained in the heat-sensitive coloring layer or the protective layer is desirably one having high transparency and low hiding property from the viewpoint of color density. In the present invention, a flake-like pigment having a refractive index of 1.5 to 1.6 is coated with an insoluble cerium compound, and a baked product of particles having a three-layer structure coated with amorphous silica is used.

Such an ultraviolet ray blocking agent is disclosed in
No. 45645, which is publicly known. In order to produce this ultraviolet ray blocking agent, first, an aqueous cerium salt solution is added dropwise to an aqueous dispersion of a flake pigment under heating in an amount of 1 to 30% by weight as CeO ₂ with respect to the pigment, and the pH is adjusted to 7 to 9 to prepare the pigment. An insoluble cerium compound is deposited on the surface to form a cerium-coated pigment. Then, a silicate solution was added to the aqueous dispersion of the cerium-coated pigment under heating, the pH was adjusted to 6 to 8, and amorphous silica was deposited and coated on the surface of the pigment.
It is obtained by firing at a high temperature of 200 ° C. or higher.
Deposition of atypical silica is in the range of 2 to 40 wt% with respect to cerium-coated pigment as SiO _2.

The pigment serving as a nucleus is preferably in the form of a flake having a refractive index of about 1.5 to 1.6. Such pigments include mica, talc, sericite, aluminum hydroxide, calcium carbonate, kaolin, calcium hydroxide, aluminum silicate, polyethylene powder,
Examples include polystyrene and latex. Among them, mica, talc, and sericite are preferable because a thermosensitive recording medium having a good color density can be obtained. Further, as the cerium compound, cerium chloride, cerium nitrate, cerium sulfate and the like can be used, and as the silicate,
Organic silicates can be used in addition to inorganic salts such as sodium silicate.

The UV blocking agent is preferably used in an amount of 5% by weight to 40% by weight based on the dry weight of the protective layer. When the content is 5% by weight or less, the effect on light resistance is small, and when the content is 40% by weight or more, the barrier properties (hiding properties) and color sensitivity of the protective layer are reduced. In the thermosensitive coloring layer, the content is preferably 10% by weight to 40% by weight based on the dry weight. When the content is 10% by weight or less, the effect on light resistance is small, and when the content is 40% by weight or more, the coloring sensitivity is reduced.

Further, in the thermal recording medium of the present invention,
The fluorescent dye contained in the protective layer also contributes to the improvement of light resistance. As the fluorescent dye, various known dyes can be used, and examples thereof include, but are not limited to, stilbene derivatives, coumarin derivatives, pyrazoline derivatives, bisstyryl biphenyl derivatives, naphthalimide derivatives, and bisbenzooxazolyl derivatives. However, diaminostilbene disulfonic acid derivatives are particularly preferred because of their high effect on light resistance.

The amount of the fluorescent dye used is preferably 0.01 to 3% by weight based on the dry weight of the protective layer. More preferably, it is in the range of 0.1 to 2% by weight.
When the amount of the fluorescent dye in the protective layer is 0.01% by weight or less, the effect on light resistance is reduced, and when the amount is 3% by weight or more, coloring of the protective layer paint becomes intense, and the ground color of the recording medium is reduced. Connect.

The ultraviolet ray blocking agent used in the present invention has a characteristic three-layer structure and can maintain a sufficient whiteness. Further, since it is composed of a pigment generally used in a thermosensitive recording medium, even when it is contained in the thermosensitive coloring layer, there is no adverse effect such as background fog and desensitization. Further, when it is contained in the protective layer, the thermosensitive recording medium can be provided with writability. Further, the ultraviolet ray blocking agent may be contained in the undercoat layer.

However, the light fastness required by the present invention cannot be obtained even when the heat-sensitive recording medium contains only the ultraviolet ray blocking agent. This is probably because the cerium compound is covered with amorphous silica, and the ultraviolet blocking effect of the cerium compound is blocked. The present invention is characterized in that it contains an ultraviolet absorber together with the ultraviolet ray blocking agent and a fluorescent dye, and a thermal recording medium having excellent light fastness is obtained by the interaction of these. In particular, when the undercoat layer contains an ultraviolet absorber and the thermosensitive coloring layer contains an ultraviolet absorber and an ultraviolet blocker, high light resistance is obtained and effective. When the heat-sensitive coloring layer contains an ultraviolet absorber and an ultraviolet ray blocking agent, the ultraviolet absorbing agent and the ultraviolet ray blocking agent may be blended in a ratio of 1: 4 to 4: 1.

In the present invention, the undercoat layer or the thermosensitive coloring layer may contain an ultraviolet absorbent to contain
It is considered that not only the ultraviolet ray from the rear surface of the thermosensitive recording medium is absorbed, but also the ultraviolet ray absorbing ability is increased by a synergistic effect with the ultraviolet ray blocking agent and the fluorescent dye in the thermosensitive coloring layer or the protective layer. When the ultraviolet absorbent is contained not in the undercoat layer but in the protective layer, for example, the benzotriazole-based ultraviolet absorbent has a low melting point of about 120 to 150 ° C., and is melted when heated by the thermal head and causes scum and the like. Become. Therefore, when the undercoat layer or the thermosensitive coloring layer contains an ultraviolet absorber and the thermosensitive coloring layer or the protective layer contains an ultraviolet ray blocking agent as in the present invention, the light resistance is improved, and scum adhesion and sticking are caused. This is an effective means for preventing

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to obtain a thermosensitive recording medium of the present invention,
For example, an undercoat layer coating solution is prepared by dispersing an ultraviolet absorber composed of a benzotriazole compound together with a binder and a filler, and then coated on a support and dried to form an undercoat layer. Next, a dispersion in which a dye and a developer are respectively dispersed together with a binder is mixed, a filler and other necessary additives are added to prepare a thermosensitive coloring layer coating solution, and the thermosensitive coloring layer is coated on the undercoat layer and dried to form a thermosensitive layer. A coloring layer is formed. Furthermore, a refractive index of 1.5 to
1.6 necessary additives such as an ultraviolet ray blocking agent, a fluorescent dye, a water-soluble polymer, and a filler, which are formed by firing a specific particle having a three-layer structure in which the surface of the flake-like pigment of 1.6 is coated with an insoluble cerium compound and amorphous silica. The thermosensitive recording medium of the present invention can be manufactured by preparing a protective layer coating solution containing the above, and coating and drying the thermosensitive coloring layer to form a protective layer.

In the undercoat layer of the present invention, as a binder, a commonly used emulsion of a water-soluble polymer or a hydrophobic polymer or the like can be appropriately used.
Specific examples include polyvinyl alcohol, polyvinyl acetal, hydroxyethylcellulose, methylcellulose, cellulose derivatives such as carboxymethylcellulose, starch and its derivatives, sodium polyacrylate,
Polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid copolymer, styrene / maleic anhydride copolymer alkaline salt, isobutylene / maleic anhydride copolymer alkaline salt, Water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, casein, polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate And an emulsion of a hydrophobic polymer such as an ethylene / vinyl acetate copolymer or a styrene / butadiene / acrylic copolymer.

As the filler in the undercoat layer, known fillers generally used in the past, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, calcined kaolin, In addition to inorganic fillers such as clay and talc, organic fillers such as styrene-methacrylic copolymer resin, urea-formalin resin, and polystyrene resin can be used.

In the protective layer of the present invention, various known fillers can be used. Specific examples of such fillers include kaolin, clay, calcium carbonate, calcined clay,
Inorganic pigments such as calcined kaolin, aluminum hydroxide, titanium oxide, diatomaceous earth, fine anhydrous silica, activated clay, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, raw starch particles, and the like. Can be

As the binder in the protective layer, a binder composed of a polymer compound usually used in the field of thermal recording can be used. Specific examples of such a binder include, for example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, polyvinyl acetate , Vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer, vinyl acetate-acrylic acid copolymer, ethylene-acrylic acid copolymer, styrene-acrylic acid copolymer Copolymer, acrylic ester resin, acrylic emulsion, diisobutylene / maleic anhydride copolymer, styrene / maleic anhydride copolymer, styrene / butadiene copolymer emulsion , Methyl methacrylate-butadiene copolymer, methyl methacrylate-styrene-butadiene copolymer, styrene polymer, isoprene polymer, butadiene polymer, vinyl chloride polymer, vinylidene chloride polymer, urea resin, melamine resin, amide Resin, polyurethane resin and the like can be exemplified.

The protective layer may further contain, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax or ester wax, or a surfactant such as sodium dioctylsulfosuccinate (dispersant, wetting agent). Agents), an antifoaming agent, and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate. Further, in order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound can be used in combination.

In the heat-sensitive recording material of the present invention, the colorless or light-colored dye precursor contained in the heat-sensitive coloring layer includes:
Various known materials can be used. Specifically, for example, 3,3
-Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl)-
6-dimethylaminophthalide, 3-diethylamino-7
Blue-coloring dyes such as -dibenzylamino-benzo [a] fluoran, 3- (N-ethyl-N-p-tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilino Fluoran, 3-diethylamino-
Green color-forming dyes such as 7-dibenzylaminofluoran,
3,6-bis (diethylamino) fluoran-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluoran , Rhodamine (o-chloroanilino) lactam,
Rhodamine (p-chloroanilino) lactam, 3-diethylamino-7,8-benzofluoran, 3- (N-ethyl-p-toluidino) -7-methylfluoran, 3-
Red-coloring dyes such as diethylamino-6,8-dimethylfluoran, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) ) Amino-6-methyl-7-
Anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n
-Pentyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (o-chlorophenylamino) fluoran, 3-di (n-butyl) amino-7
-(O-chlorophenylamino) fluoran, 3-diethylamino-7- (o-fluorophenylamino) fluoran, 3-di (n-butyl) amino-7- (o-fluorophenylamino) fluoran, 3- (N- Ethyl-
p-Toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-chloro-7 -Anilinofluoran, 3- (N
-Methyl-N-n-propylamino) -6-methyl-7
-Anilinofluoran, 3-dimethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6
-Methyl-7-m-toluidinofluoran, 3- (N-
n-hexyl-N-ethyl) amino-6-methyl-7-
Anilinofluoran, 3- (N-ethyl-N-isobutyl) amino-6-methyl-7-anilinofluoran, 3
-Diethylamino-6-methyl-7-p-ethoxyanilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-
Anilinofluoran, 2,2-bis {4- [6 '-(N
-Cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 2,4-dimethyl-6-
[(4-dimethylamino) anilino] -fluoran, 3
-Diethylamino-7- (3'-trifluoromethylphenyl) aminofluoran, 3-dipentylamino-7
Black-color-forming dyes such as-(3'-trifluoromethylphenyl) aminofluorane; 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-tetrabromophthalide, 3-p- (p-dimethylaminoanilino) anilino- 6-methyl-7-chlorofluoran, 3-p-
(P-chloroanilino) anilino-6-methyl-7-chlorofluoran, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-[6'-dimethylamino]
Dyes having an absorption wavelength in the near infrared region such as phthalide are exemplified. Of course, it is not limited to these,
If necessary, two or more kinds can be used in combination,
Among them, from economics such as price and availability, 3-
Di (n-butyl) amino-6-methyl-7-anilinofluoran is preferably used.

The color developer used for coloring the dye precursor contained in the heat-sensitive color developing layer of the present invention includes, for example, the following known color developers. Activated clay, attapulgite, colloidal silica, inorganic acid substances such as aluminum silicate, 4,4'-isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4'-
Dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy-4 ′
-N-propoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone,
3,4-dihydroxyphenyl-4'-methylphenylsulfone, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, bis (p-hydroxyphenyl) Butyl acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl)-
1-phenylethane, 1,4-bis [α-methyl-α-
(4′-hydroxyphenyl) ethyl] benzene, 1,
3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-te
rt-octylphenol), 2,2′-thiobis (4-
phenolic compounds such as tert-octylphenol),
Thiourea compounds such as N, N'-di-m-chlorophenylthiourea, p-chlorobenzoic acid, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4-
Aromatic carboxylic acids such as [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and zinc, magnesium and aluminum of these aromatic carboxylic acids , Salts with polyvalent metals such as calcium, titanium, manganese, tin, nickel, etc., and organic acid substances such as antipyrine complex of zinc thiocyanate, double zinc salt of terephthalaldehyde acid and other aromatic carboxylic acids, etc. Is exemplified. Among them, 4-hydroxy-4′-isopropoxydiphenylsulfone and bis (3-allyl-4-hydroxyphenyl) sulfone are preferred because they provide excellent general preservability of recorded images.

The use ratio of the dye precursor and the developer is appropriately selected depending on the type of the dye precursor and the developer used, and is not particularly limited. 1 to 50 parts by weight, preferably 2 to 5 parts by weight
A developer of about 10 parts by weight is used.

A sensitizer can be added to the heat-sensitive coloring layer according to the purpose. Specific examples of the sensitizer include stearamide, methoxycarbonyl-N-stearic acid benzamide, and N-benzoyl stearin. Acid amide,
N-eicosanoic acid amide, ethylenebisstearic acid amide, behenic acid amide, methylenebisstearic acid amide, methylolamide, N-methylolstearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, p-benzyloxybenzoate Benzyl acid, 1-hydroxy-2-phenyl naphthoate, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, 2-naphthylbenzyl ether, m-terphenyl, p- Benzyl biphenyl, tolyl biphenyl 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-diphenoxy Ethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane,
p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-
Examples include acetophenethidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, and the like.

Various pigments can be used in combination in the thermosensitive coloring layer, for example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, aluminum hydroxide, titanium oxide, diatomaceous earth, fine anhydrous silica, Examples include inorganic pigments such as activated clay, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles.

Various auxiliaries can be added to the heat-sensitive coloring layer, if necessary, such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate,
Dispersants such as fatty acid metal salts and the like, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and other waxes, defoamers, coloring dyes and the like are appropriately added.

It is also possible to add a preservability improver to the thermosensitive coloring layer. Examples of such a preservability improver include the following. 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,
2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,2′-ethylidenebis (4,6-di-
tert-butylphenol), 4,4′-thiobis (2-
Methyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol),
1- [α-methyl-α- (4′-hydroxyphenyl)
Ethyl] -4- [α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,3-tris (2-methyl-4
-Hydroxy-5-tert-butylphenyl) butane;
4,4′-thiobis (3-methylphenol), 4,
4'-dihydroxy-3,3 ', 5,5'-tetrabromodiphenylsulfone, 4,4'-dihydroxy-3,
3 ′, 5,5′-tetramethyldiphenyl sulfone,
2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,
5-dichlorophenyl) propane, 2,2-bis (4-
Hindered phenol compounds such as hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenylsulfone, 4-benzyloxy-4 ′-(2-methylglycidyl) Oxy) diphenyl sulfone, diglycidyl terephthalate, cresol novolak type epoxy resin,
Epoxy compounds such as phenol novolak type epoxy resin and bisphenol A type epoxy resin, N, N'-di-
2-naphthyl-p-phenylenediamine, sodium or polyvalent metal salts of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate, bis (4-ethyleneiminocarbonylaminophenyl) methane, and the like. Can be

In the heat-sensitive recording medium of the present invention, the method of forming the undercoat layer, the heat-sensitive color-forming layer and the protective layer is not particularly limited, and examples thereof include air knife coating, variver blade coating, pure blade coating, rod blade coating, and short-circuit. After applying and drying the coating liquid for the recording layer on the support by an appropriate coating method such as dwell coating, curtain coating, and die coating, the coating liquid for the protective layer is further applied and dried on the recording layer. It is formed. In addition, as a support, paper,
The material is appropriately selected from plastic films, synthetic papers, nonwoven fabrics, metal deposits and the like. The coating amount of the undercoat layer coating liquid for 2~12g / m ² in dry weight, preferably 3 to 10 g / m ² approximately, the coating amount of the recording layer coating liquid for dry weight 2~12g / m ² And preferably about 3 to 10 g / m ² , and the coating amount of the protective layer coating liquid is 0.1 to 20 g in terms of dry weight.
/ M ² , preferably in the range of about 0.5 to 10 g / m ² .

[0039]

The present invention will be described below with reference to examples.
In addition, in description, a part shows a weight part. <Production of ultraviolet ray blocking agent> After dispersing 500 g of a flake pigment serving as a core substance of the ultraviolet ray blocking agent used in the present invention in 10 liters of water,
264 g of an aqueous cerium nitrate solution is added dropwise while heating and stirring at 0 ° C. Subsequently, the solution was neutralized to pH 7 to 9 with a sodium hydroxide solution, cerium hydroxide was deposited on the surface of the pigment, and then dried and pulverized to obtain a cerium-coated pigment. Next, after dispersing the cerium-coated pigment in 10 liters of water, 348 g of No. 3 sodium silicate was added with heating and stirring at 80 ° C. or higher, and the pH was adjusted to 6 to 8 with sulfuric acid. A pigment was obtained. This was further calcined at 500 ° C. for 2 hours to obtain an ultraviolet ray blocking agent.

<Manufacture of Thermosensitive Recording Material> Example 1 (1) Formation of Undercoat Layer Solution A (UV absorber dispersion liquid 1) 2- (2′-hydroxyphenyl-5′-methylphenyl) benzotriazole 5 parts 3% aqueous solution of polyvinyl alcohol 1 part Water 20 parts Each liquid of the above composition was ground with a sand grinder to an average particle diameter of 1 micron. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. Liquid A 26 parts 10% polyvinyl alcohol aqueous solution 150 parts Calcined kaolin (40% dispersion) 250 parts The above-mentioned coating liquid was applied on one surface of a support of 50 g / m ² 5.0.
g / m ² and dried by application to form an undercoat layer. (2) Formation of thermosensitive coloring layer solution B (developer dispersion liquid) 4-hydroxy-4'-isopropoxydiphenyl sulfone 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts water 11.2 parts The above composition Were ground to an average particle size of 1 micron with a sand grinder. Liquid C (dye dispersion) 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts water 2.6 parts of the above composition Each liquid was ground with a sand grinder to an average particle diameter of 1 micron. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. Liquid B 36.0 parts Liquid C 9.2 parts Kaolin clay (50% dispersion) 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 thermosensitive coloring layer. (3) 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) 30.0 parts Zinc stearate 10.0 parts Ultraviolet ray blocking agent (core pigment is flaky sericite with refractive index of 1.556) 30% dispersion 30.0 parts Water 50.0 parts Fluorescent dye (Cyaminopropyl sulfonic acid derivative; Chinoval ABPliq., Manufactured by Chihwa Kayky Ltd.) 0.5 part Coating amount of each of the above coating solutions on the recording layer 4.0 g / m ² After coating and drying, a super calender treatment was performed to obtain a heat-sensitive recording material. (This is an example in which the undercoat layer contains an ultraviolet absorber and the protective layer contains an ultraviolet blocker and a fluorescent dye.)

Example 2 The procedure of Example 1 was repeated, except that the ultraviolet ray blocking agent was changed to a flake talc having a refractive index of 1.549 in the formation of the protective layer of Example 1. A thermosensitive recording medium was obtained.

Example 3 The procedure of Example 1 was repeated, except that the ultraviolet ray blocking agent was changed to a flake-like mica having a refractive index of 1.578 in the formation of the protective layer of Example 1. A thermosensitive recording medium was obtained.

Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that Liquid D was used instead of Liquid A in forming the undercoat layer of Example 1. Liquid D (UV absorber dispersion liquid 2) 2- (2'-hydroxyphenyl-5'-methylphenyl) benzotriazole 15 parts 3% aqueous polyvinyl alcohol solution 3 parts Water 60 parts Each liquid of the above composition is sand-grindered. Milled to an average particle size of 1 micron. Subsequently, the dispersion liquid was mixed at the following ratio to obtain a coating liquid. Liquid D 78 parts 10% polyvinyl alcohol aqueous solution 150 parts Calcined kaolin (40% dispersion) 250 parts

Example 5 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that the dispersion of the ultraviolet blocking agent was changed to 60 parts in the formation of the protective layer in Example 1.

Example 6 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that one part of the fluorescent dye was used in forming the protective layer in Example 1.

[Example 7] In the formation of the thermosensitive coloring layer of Example 1, a dispersion was mixed at the following ratio to prepare a coating liquid. Liquid B 36.0 parts Liquid C 9.2 parts UV blocking agent of Example 1 (30% dispersion) 13.3 parts Kaolin clay (50% dispersion) 12.0 parts A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the blocking agent dispersion was not blended. (An ultraviolet absorber is contained in the undercoat layer, an ultraviolet blocker is contained in the thermosensitive coloring layer, and a fluorescent dye is contained in the protective layer.)

Example 8 In the formation of the thermosensitive coloring layer of Example 7, the solution E (ultraviolet absorbent dispersion 3) was further added with 2,2-methylenebis [4- (1,1,3,3, -tetramethyl) Butyl) -6- (2H-benzotriazol-2-yl) phenol] 1.5 parts 10% aqueous solution of polyvinyl alcohol 3.0 parts 7.8 parts of water 6.0 parts were added to form a coating solution. In the same manner as in Example 7, a thermosensitive recording medium was obtained. (The undercoat layer contains an ultraviolet absorber, the heat-sensitive coloring layer contains an ultraviolet absorber and an ultraviolet blocker, and the protective layer contains a fluorescent dye.)

[Comparative Example 1] In the formation of the undercoat layer in Example 1, the liquid A (UV absorber dispersion liquid 1) was not blended, and in the formation of the protective layer, the UV-blocker dispersion liquid and the fluorescent dye were blended. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that no heat-sensitive recording medium was used. (Does not contain anything.)

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the ultraviolet ray blocking agent dispersion and the fluorescent dye were not used in forming the protective layer in Example 1. (Only contains an ultraviolet absorber in the undercoat layer.)

[Comparative Example 3] In the formation of the undercoat layer of Example 1, the liquid A (ultraviolet absorbent dispersion liquid 1) was not blended. A heat-sensitive recording material was obtained in the same manner as in Example 1, except that 7.8 parts of the absorbent dispersion 3) was blended, and the ultraviolet ray blocking agent dispersion and the fluorescent dye were not blended in forming the protective layer. (Only an ultraviolet absorber is contained in the thermosensitive coloring layer.)

Comparative Example 4 The procedure of Example 7 was repeated except that the liquid A (ultraviolet absorbent dispersion liquid 1) was not used in forming the undercoat layer, and the protective layer was not used in the formation of a fluorescent dye. In the same manner as in Example 7, a thermosensitive recording medium was obtained. (Only an ultraviolet ray blocking agent is contained in the thermosensitive coloring layer.)

Comparative Example 5 The procedure of Example 1 was repeated except that the liquid A (ultraviolet absorbent dispersion 1) was not used in forming the undercoat layer of Example 1 and the fluorescent dye was not used in forming the protective layer. In the same manner as in Example 1, a thermosensitive recording medium was obtained. (Only an ultraviolet ray blocking agent is contained in the protective layer.)

[Comparative Example 6] Except that no liquid A (UV absorber dispersion liquid 1) was blended in the formation of the undercoat layer in Example 1 and no ultraviolet ray blocking agent was blended in the formation of the protective layer.
A thermosensitive recording medium was obtained in the same manner as in Example 1. (Only contains a fluorescent dye in the protective layer.)

[Comparative Example 7] Thermal recording was performed in the same manner as in Example 1 except that the ultraviolet ray blocking agent dispersion was not used and the aluminum hydroxide dispersion was used in the formation of the protective layer in Example 1. I got a body. (The undercoat layer contains an ultraviolet absorber and the protective layer contains a fluorescent dye.)

Comparative Example 8 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that no fluorescent dye was used in forming the protective layer in Example 1. (An ultraviolet absorber is contained in the undercoat layer, and an ultraviolet blocker is contained in the protective layer.)

Comparative Example 9 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that Liquid A (UV absorber dispersion liquid 1) was not used in forming the undercoat layer of Example 1. (The protective layer contains an ultraviolet ray blocking agent and a fluorescent dye.)

Comparative Example 10 In the formation of the protective layer of Example 1, 26 parts of Solution A (UV absorber dispersion 1) was added instead of the UV-blocker dispersion, and 48 parts of aluminum hydroxide dispersion were used. A heat-sensitive recording material was obtained in the same manner as in Example 1 except for mixing. (The undercoat layer contains an ultraviolet absorber and the protective layer contains an ultraviolet absorber and a fluorescent dye.)

Comparative Example 11 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that a zinc oxide dispersion (30%) was used in place of the ultraviolet blocking agent dispersion in forming the protective layer of Example 1. I got (The undercoat layer contains an ultraviolet absorber, and the protective layer contains zinc oxide and a fluorescent dye.)

Table 1 shows the results of quality performance tests performed on the heat-sensitive recording materials obtained in the above Examples and Comparative Examples. Note (1) Color development: manufactured by Tokyo Shibaura Electric-Thermal facsimile K
Using B-4800, applied energy 18.03V,
The image density recorded with a pulse width of 3 or 2 milliseconds was measured with a Macbeth densitometer (RD-914, using an amber filter).

Note (2) Residual rate of light fastness: The thermal recording medium printed under the above conditions was treated with a fade meter (BH, manufactured by Toyo Seiki Co., Ltd.) for 12 hours, and the density of the printed area was measured with a Macbeth densitometer. Was calculated from the following equation.

## EQU1 ## Residual rate = (image density after light fastness test / unprocessed image density) × 100%

Note (3) Lightfast ground color: The heat-sensitive recording medium printed under the above conditions was treated with a fade meter (BH, manufactured by Toyo Seiki Co., Ltd.) for 12 hours, and the density of the white paper was measured with a Macbeth densitometer (blue filter). did.

Note (4) Adhesion of scum; Evaluated visually after printing 20 B4 vertical stripe originals in a copy mode using Panasonic UF-60 manufactured by Panasonic. ◎… very small ○… less ×… more

Note (5) Sticking: After printing in a transmission mode using a Panasonic Panafax UF-22, visual evaluation was performed. ◎… The sound is quiet ○… The sound is loud ×… Stick pattern appears in the image

Note (6) White paper appearance: The whiteness of the white paper part was visually evaluated. ◎: bluish white ○: white △: yellowish white ×: yellowish

[0065]

[Table 1] Table 1 Quality performance test results

As is evident from Table 1, Examples 1 to 8 satisfying the requirements of the present invention have high light resistance, prevent adhesion of scum and sticking, and have good quality of white paper. A thermal recording medium has been obtained. On the other hand, the light fastness of Comparative Examples 1 to 6, which do not contain any of the ultraviolet absorber, the ultraviolet ray blocking agent, and the fluorescent dye, or contain any of them alone, is low.

In Comparative Example 7, in which aluminum hydroxide was used instead of the ultraviolet ray blocking agent, the light resistance was very poor. Furthermore, Comparative Example 8 lacking the fluorescent dye in the protective layer was inferior to white paper in appearance and light resistance as compared with Example 1, and Comparative Example 9 lacking the ultraviolet absorber in the undercoat layer also had low light resistance. Was. On the other hand, in Comparative Example 10 in which an ultraviolet absorber was contained in the protective layer instead of the ultraviolet light blocking agent, scum sticking and sticking occurred remarkably, and the appearance of white paper was poor. In Comparative Example 11 in which zinc oxide was added instead of the ultraviolet blocking agent, the light resistance and the appearance of white paper were inferior, and scum adhesion and sticking occurred.

As described above, even if any of the requirements of the present invention are omitted, a thermosensitive recording medium having the required performance cannot be obtained.

[0069]

As described above, an ultraviolet absorber,
By simultaneously containing an ultraviolet ray blocking agent and a fluorescent dye, light resistance is improved, discoloration and background yellowing due to light do not occur, and the recording density does not decrease and the appearance does not deteriorate even after long storage. A heat-sensitive recording medium is obtained. Further, in the heat-sensitive recording medium of the present invention, since the occurrence of adhesion of scum and sticking can be suppressed, recording by a thermal head can be performed smoothly, which is extremely useful.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshimi Midorikawa 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Nihon Paper Industries Co., Ltd. (72) Inventor Yutaka Wakita 1-30-1 Kamiochiai, Shinjuku-ku, Tokyo No. 6 Inside the Product Development Laboratory of Nippon Paper Industries Co., Ltd. (56) References JP-A-7-25147 (JP, A) JP-A-6-145645 (JP, A) JP-A-7-172055 (JP, A) JP-A-6-48038 (JP, A) JP-A-62-176879 (JP, A) JP-A-61-242878 (JP, A) JP-A-6-219047 (JP, A) JP-A-9-202048 (JP, A) JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34 C09K 3/00

Claims (6)

(57) [Claims] 1. A thermosensitive recording material comprising a support, on which an undercoat layer, a thermosensitive coloring layer and a protective layer are sequentially laminated, wherein the undercoat layer and / or the protective layer are
Alternatively, the thermosensitive coloring layer contains an ultraviolet absorber, and the thermosensitive coloring layer and / or the protective layer have a refractive index of 1.5 to 1.
6. A thermosensitive recording material, comprising an ultraviolet ray blocking agent comprising a baked product of particles obtained by coating the surface of a flake-like pigment with an insoluble cerium compound and amorphous silica, and a fluorescent dye in the protective layer. . 2. A thermosensitive recording medium comprising a support, on which an undercoat layer, a thermosensitive coloring layer and a protective layer are sequentially laminated, wherein the undercoat layer and the thermosensitive coloring layer contain an ultraviolet absorber, and A UV-blocking agent comprising a baked product of particles in which the surface of a flake pigment having a refractive index of 1.5 to 1.6 is coated with an insoluble cerium compound and amorphous silica, and a fluorescent dye is contained in the protective layer. A heat-sensitive recording material comprising: 3. The thermosensitive recording medium according to claim 1, wherein the ultraviolet absorber contained in the undercoat layer and / or the thermosensitive coloring layer is a benzotriazole compound. 4. The content of the ultraviolet absorber contained in the undercoat layer and / or the thermosensitive coloring layer is 0.1% by weight to 15% by weight relative to the undercoating layer dry weight, and the thermosensitive coloring layer dry weight 4. The thermosensitive recording medium according to claim 1, wherein the content is 0.1% by weight to 15% by weight. 5. The content of the ultraviolet ray blocking agent contained in the thermosensitive coloring layer and / or the protective layer is 10% by weight to 40% by weight based on the dry weight of the thermosensitive coloring layer, and based on the dry weight of the protective layer. 5. The heat-sensitive recording medium according to claim 1, wherein the content is 5% by weight to 40% by weight. 6. The method according to claim 1, wherein the content of the fluorescent dye contained in the protective layer is 0.01 to 3% by weight based on the dry weight of the protective layer. Or a thermosensitive recording material according to 5.