JP2936556B2 - 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 which has excellent light resistance and prevents adhesion of dregs, sticking and head wear.

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording material having a heat-sensitive recording layer mainly composed of a colorless or light-colored dye precursor and a color developer which reacts with the dye precursor by heating to form a color is disclosed in JP-B-45-14.
No. 035 and widely used. In order to perform recording on this thermal recording medium, a thermal printer or the like having a built-in thermal head is used, but such a thermal recording method is compared with other recording methods that have been practically used in the past.
With features such as no noise at the time of recording, no need for development and fixing, maintenance-free, relatively inexpensive and compact equipment, and very clear color development, with the development of the information industry, Widely used in facsimile and computer fields, various measuring instruments, labels, etc.

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 area is reduced and the color of the background area is discolored.

In order to improve the light resistance, a method of incorporating an inorganic filler having an ultraviolet shielding effect into a heat-sensitive layer or a protective layer has been disclosed in JP-A-62-18626 and JP-A-6-64.
No. 324. However, in the case of an inorganic filler having an ultraviolet shielding effect, there is a problem that the effect is small due to poor ultraviolet absorption efficiency, and when the amount of use is increased, the coloring portion is concealed by the inorganic filler, thereby lowering the print density.

Japanese Patent Application Laid-Open No. Sho 61-193883 discloses a method in which a benzotriazole-based hydrophobic ultraviolet absorbent is contained in a protective layer. However, when a hydrophobic ultraviolet absorber is used, scum sticking or sticking occurs during printing, and a heat-sensitive recording medium of sufficient quality cannot be obtained. On the other hand, in the case where a water-soluble ultraviolet absorber is used, the thermal head is made electrochemically because the water-soluble ultraviolet absorber forms ions such as sodium salts upon solubilization in JP-A-7-17131. It is described that abrasion occurs.

Japanese Patent Application Laid-Open No. Sho 62-184880 discloses a method in which a fluorescent whitening agent is contained in a protective layer. The improvement effect of the fluorescent whitening agent alone mainly depends on the appearance of white paper. It has not been improved to improve the light resistance.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which is excellent in light fastness, prevents adhesion of scum and sticking, and has high head abrasion resistance.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a heat-sensitive recording material which has achieved the above object can be obtained by including a water-soluble ultraviolet absorber, a fluorescent dye and aluminum hydroxide in a protective layer. Was obtained, and the present invention was completed.

That is, the present invention provides a heat-sensitive recording layer comprising, as a main component, at least a colorless or light-colored dye precursor, and a color developing agent which causes the dye precursor to develop color when heated. The present invention also relates to a thermosensitive recording medium provided with a protective layer, wherein the protective layer contains a binder, a water-soluble ultraviolet absorber, a fluorescent dye, and aluminum hydroxide.

In the heat-sensitive recording medium of the present invention, various known water-soluble ultraviolet absorbers can be used in the protective layer. 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. The present invention is not limited to these, but among them, a benzophenone-based ultraviolet absorber having a sulfone group is preferable because it is excellent in preventing adhesion of dregs and sticking, and in particular, 2-hydroxy-4- having a sulfonic acid group is preferable. Methoxybenzophenone-
5-Sulphonic acid is most preferred because of its high head wear resistance.
Further, in the present invention, two or more kinds can be used in combination as needed.

[0011] It is also possible to use a hydrophobic ultraviolet absorber in combination as long as the effects of the present invention are not impaired. Examples of the hydrophobic ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, and 2,2 ′. -Dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-
Benzophenone ultraviolet absorbents such as 5-sulfo benzophenone, 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-te
rt-butylphenyl) -5-tert-butylbenzotriazole, 2- (2'-hydroxy-3'-dodecyl-
5′-methylphenyl) benzotriazole, 2-
[2′-hydroxy-4 ′-(2 ″ -ethylhexyl) oxyphenyl] benzotriazole, methyl-3
Condensation product with-[3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate-polyethylene glycol (molecular weight: about 300), 5-tert-butyl-3- (5-chloro-2H-
Benzotriazol-2-yl) -4-hydroxybenzene-octyl propionate, 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6
-(2H-benzotriazol-2-yl) phenol, 2- (2'-hydroxy-3'-sec-butyl-
Benzotriazole UV absorbers such as 5'-tert-butylphenyl) -5-tert-butylbenzotriazole, and salicylic acid UV absorbers such as phenyl salicylate, p-tert-butylphenyl salicylate and p-octylphenyl salicylate Agent, 2-ethylhexyl-2
A cyanoacrylate-based ultraviolet absorber such as -cyano-3,3'-diphenylacrylate, ethyl-2-cyano-3,3'-diphenylacrylate;
6,6, -tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) succinate, 2- (3,5-di-tert-ester)
Hindered amine-based ultraviolet absorbers such as -butyl) malonic acid-bis (1,2,2,6,6-pentamethyl-4-piperidyl) ester and the like.

Regarding the amount of the water-soluble ultraviolet absorber used,
It is preferred to be present in an amount of 2 to 30% by weight based on the total solid content of the protective layer. More preferably, it is in the range of 8 to 20% by weight. When the amount of the ultraviolet absorber in the protective layer is 2% by weight or less, the effect on light resistance is reduced. When the amount is 30% by weight or more, the viscosity of the protective layer coating increases with time, and the coating suitability is poor. It will be.

As the fluorescent dye in the protective layer of the present invention, various known dyes can be used, and examples thereof include stilbene derivatives, coumarin derivatives, pyrazoline derivatives, bisstyryl biphenyl derivatives, naphthalimide derivatives and bisbenzooxazolyl derivatives. The diaminostilbene disulfonic acid derivative is particularly preferred, although not limited thereto, because of its high effect on light resistance.

The amount of the fluorescent dye used is preferably 0.01 to 3% by weight based on the total solid content of the protective layer. More preferably, it is in the range of 0.1 to 2% by weight.
When the amount of the ultraviolet absorber in the protective layer is 0.01% by weight or less, the effect on light resistance is reduced. Leads to.

In the present invention, the ratio of the water-soluble ultraviolet absorber and the fluorescent dye contained in the protective layer is from 4: 1 to 1: 1.
Desirably, it is in the range of 200: 1. If the amount of the fluorescent dye is too large, the coating of the protective layer is colored. If the amount is too small, the effect on light resistance is reduced.

The protective layer of the present invention contains aluminum hydroxide as a filler. In the present invention, since the protective layer contains the water-soluble ultraviolet absorber, head wear is easily caused by ions formed from the water-soluble ultraviolet absorber. On the other hand, the aluminum hydroxide used in the present invention is excellent in the adsorbability of these ions, and it is considered that the ions which adversely affect the thermal head are adsorbed and the wear of the head is reduced.

The average particle size of the aluminum hydroxide particles is preferably about 15 μm or less, more preferably from the viewpoints of good recorded images, smoothness of the protective layer, and barrier properties (hiding properties). 0.5 to 10 μm.
The amount of aluminum hydroxide used is not particularly limited, but it is generally desirable to adjust the amount in the range of about 5 to 500 parts by weight per 100 parts by weight of the binder component.

The binder in the protective layer of the present invention includes:
It is possible to use a binder composed of a polymer compound usually used in the field of thermal recording. 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,
Examples thereof include melamine resins, amide resins, and polyurethane resins, and are not particularly limited. Among them, styrene-acrylic acid copolymers, ethylene-acrylic acid copolymers, and hydrophobic polymers such as acrylic emulsions are the main components. It is more preferable to use as a thermosensitive recording medium having excellent barrier properties and a high print density.

Further, in the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax or the like, or a surfactant such as sodium dioctyl sulfosuccinate (dispersant, wetting agent). Agents), an antifoaming agent, and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate. 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 recording 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, 3-diethylamino-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, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran is preferably used in view of price, availability and the like.

The color developer used for coloring the dye precursor contained in the heat-sensitive recording 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 preferably used because of excellent storage stability of recorded images.

The ratio of the dye precursor to the developer used is appropriately selected according to 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.

In the heat-sensitive recording medium of the present invention, a sensitizer can be added to the heat-sensitive recording layer according to the purpose. Specific examples of the sensitizer include stearamide, methoxycarbonyl-N-stearic acid. Benzamide, N-benzoylstearic 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-
Benzyl benzyloxybenzoate, 1-hydroxy-2
Phenyl naphthoate, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, tolylbiphenyl ether Di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,
2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-
Chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p −
Examples include acetotoluidide, p-acetophenethidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, and the like. You.

In the heat-sensitive recording layer, various pigments can be used in combination. 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.

In the heat-sensitive recording layer, various auxiliaries can be added, 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.

In the present invention, it is possible to add a preservability improving agent to the heat-sensitive recording 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

The method of forming the heat-sensitive recording layer and the protective layer is not particularly limited. For example, an appropriate method such as air knife coating, variver blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. After the coating liquid for the recording layer is applied and dried on the support by a coating method, the coating liquid for the protective layer is further applied and dried on the recording layer. The support is appropriately selected from paper, plastic film, synthetic paper, nonwoven fabric, metal deposit, and the like.
The coating amount of the recording layer coating liquid is 2 to 12 g / dry weight.
m ^2, is preferably adjusted 3 to 10 g / m ² approximately, the coating amount of the protective layer coating composition is 0.1 to 20 g / m ² by dry weight, preferably 0.5 to 10 g / m ² range of about You.

[0028]

According to the present invention, a heat-sensitive recording medium having excellent light resistance can be obtained by including a water-soluble ultraviolet absorber and a fluorescent dye in a protective layer provided on the heat-sensitive recording layer. Although the reason is not clear, since the wavelength range of light absorption is different between the ultraviolet absorber and the fluorescent dye, by using both at the same time, it is possible to absorb in a wider range than when used alone, and the light resistance is dramatically improved. It is estimated that

On the other hand, in the present invention, by using a water-soluble ultraviolet absorber, water-soluble ultraviolet absorber is provided, although it has the effect of preventing scum adhesion and sticking which cannot be obtained when a hydrophobic ultraviolet absorber is contained. Ions are easily formed from the absorbent, which is considered to be one of the causes of head wear.

Therefore, in the present invention, by using aluminum hydroxide as a filler, it has succeeded in improving the adhesion of residue and preventing sticking and imparting abrasion resistance to the head. Although the reason for this is not clearly understood, it is thought that aluminum hydroxide is more excellent in adsorbing ions formed from a water-soluble ultraviolet absorber than other fillers, and thus can suppress the adverse effects of ions.

[0031]

The present invention will be described below with reference to examples.
In addition, in description, a part shows a weight part. [Example 1] Formation of heat-sensitive recording layer Liquid A (developer dispersion liquid) 4-hydroxy-4'-isopropoxydiphenylsulfone 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts Each liquid of the composition was ground with a sand grinder to an average particle size of 1 micron. Solution B (dye dispersion) 3-di (n-butyl) amino-6-methyl-7-anilinofluoran 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 A 36.0 parts Liquid B 9.2 parts Kaolin clay (50% dispersion) 12.0 parts Each of the above coating liquids is coated on one surface of a 50 g / m ² support.
The coating was dried at 0 g / m ² to form a heat-sensitive recording layer. Formation of Protective Layer Liquid C (Water-soluble UV absorber) 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid 5.0 parts Water 21.0 parts Prepare the above aqueous solution, and then mix the dispersion at the following ratio. To obtain a coating solution. 10% aqueous solution of polyvinyl alcohol 60.0 parts Aluminum hydroxide (50% dispersion) 50.0 parts Zinc stearate 10.0 parts C solution 26.0 parts Water 50.0 parts Fluorescent dye (diaminoaminobenzenesulfonic acid derivative; chirpy key) 0.5 part of each coating solution was coated on the 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 2] In the formation of the protective layer in Example 1, solution C (water-soluble ultraviolet absorber) 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid 7.0 parts Water 29.4 parts An aqueous solution was prepared, and then a dispersion was mixed at the following ratio to obtain a coating liquid. 10% aqueous solution of polyvinyl alcohol 60.0 parts Aluminum hydroxide (50% dispersion) 50.0 parts Zinc stearate 10.0 parts C solution 36.4 parts Water 50.0 parts Fluorescent dye (diaminoaminophensulfonic acid sulfonic acid derivative; chirpy key) A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 0.7 part of Chinoval ABPliq.

[Example 3] In the formation of the protective layer in Example 1, solution C (water-soluble ultraviolet absorber) 17.3 parts of 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid 72.7 parts of water An aqueous solution was prepared, and then a dispersion was mixed at the following ratio to obtain a coating liquid. 10% aqueous solution of polyvinyl alcohol 60.0 parts Aluminum hydroxide (50% dispersion) 50.0 parts Zinc stearate 10.0 parts C solution 90.0 parts Water 50.0 parts Fluorescent dye (diaminoaminobenzene sulfonate derivative; chidicakey) A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 1.5 parts of Chinoval ABPliq.

Example 4 In the preparation of solution C of Example 1, 2-hydroxy-4-methoxybenzophenone-5 was used.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that sulfonic acid was changed to sodium 2-hydroxy-4-methoxybenzophenone-5-sulfonate.

Example 5 In the preparation of solution C of Example 1, 2-hydroxy-4-methoxybenzophenone-5 was used.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that -sulfonic acid was changed to potassium 2-hydroxy-4-methoxybenzophenone-5-sulfonate.

Example 6 In the preparation of solution C of Example 1, 2-hydroxy-4-methoxybenzophenone-5 was used.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that -sulfonic acid was changed to sodium 2,2'-dihydroxy-4,4'-dimethoxybenzophenone-5-sulfonic acid.

Example 7 In the preparation of solution C of Example 1, 2-hydroxy-4-methoxybenzophenone-5 was used.
-Sulfonic acid is 2,4-dihydroxybenzophenone-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that sodium 5-sulfonate was used.

Example 8 In the preparation of solution C of Example 1, 2-hydroxy-4-methoxybenzophenone-5 was used.
-A thermosensitive recording medium was obtained in the same manner as in Example 1, except that sodium sulfonic acid was changed to sodium 2,2'-dihydroxy-4,4'-dimethoxybenzophenone-5,5'-disulfonic acid.

[Example 9] In the preparation of solution C of Example 1, 2-hydroxy-4-methoxybenzophenone-5 was used.
-Sulfonic acid is 2,4-dihydroxybenzophenone-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that sodium 5'-sulfonate was used.

Example 10 In the preparation of solution C of Example 1, 2-hydroxy-4-methoxybenzophenone-5 was used.
-A thermosensitive recording material was obtained in the same manner as in Example 1 except that sulfonic acid was changed to sodium 2,2'4,4'-tetrahydroxybenzophenone-5,5'-disulfonic acid.

[Example 11] In the preparation of solution C of Example 1, 2-hydroxy-4-methoxybenzophenone-5 was used.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that -sulfonic acid was changed to sodium 2- (2'-hydroxy-4'-methoxy-5'-sulfophenyl) benzotriazole.

Example 12 In the preparation of solution C of Example 1, 2-hydroxy-4-methoxybenzophenone-5 was used.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that -sulfonic acid was changed to 2- (2'-hydroxy-4'-butoxy-5'-sulfophenyl) benzotriazole sodium salt.

Example 13 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that the 10% aqueous polyvinyl alcohol solution was replaced with a 20% acrylic emulsion in the formation of the protective layer in Example 1.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that the liquid D was prepared and blended in place of the liquid C in forming the protective layer in Example 1. Liquid D (hydrophobic ultraviolet absorber) 2- (2'-hydroxy-5'-methylphenyl) benzotriazole 5.0 parts 3% PVA aqueous solution 1.0 part Water 20.0 parts The above composition is subjected to sand grinder. It was used by grinding to an average particle size of 1 micron.

[Comparative Example 2] In the formation of the protective layer of Example 1, the liquid C was not mixed, and the number of parts of the fluorescent dye was changed to 1.0.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the number of parts was changed.

[Comparative Example 3] In the formation of the protective layer of Example 1, no fluorescent dye was added, and 2-hydroxy-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the amount of 4-methoxybenzophenone-5-sulfonic acid was changed to 10.0 parts.

Comparative Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that the aluminum hydroxide in Example 1 was replaced with kaolin.

Comparative Example 5 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the aluminum hydroxide in Example 1 was replaced with kaolin, and the liquid C was not blended.

Table 1 shows the results of quality performance tests performed on the thermosensitive recording media 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) Light fastness: 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, then the density of the printed area was measured with a Macbeth densitometer, and the residual ratio was calculated by the following formula. did.

(Equation 1) Note (3) Scrap adhesion; Panasonic Panafax UF
Using -60, the printing mode was evaluated visually after printing 20 B4 vertical stripe originals in the copy mode. …: Very small △: small ×: large Note (4) Sticking: Using a Panasonic Panafax UF-22, printing was performed in a transmission mode and visually evaluated. …: Quiet sound △: Loud sound…: Stick pattern appears in image Note (5) Head wear: After printing 1 million lines with head friction evaluation pattern using thermal printer DPU-411 manufactured by Seiko Denshi Kogyo And the abrasion of the head was measured. ◎: Head wear is hardly observed ○: Head wear is slightly observed △: Head wear is considerably observed ×: Head breakage occurs in less than 1 million lines Note (6) Heat resistant ground color: Blank paper sample is dried at 80 ° C dry After standing for 24 hours, the measurement was performed with a Macbeth densitometer (amber filter).

[0050]

[Table 1]

As is clear from Table 1, in Examples 1 to 13 satisfying the requirements of the present invention, a good-quality heat-sensitive recording material having excellent light resistance and preventing adhesion of scum, sticking and head abrasion can be obtained. Have been. In particular, Examples 1 to 3 using 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid as the water-soluble ultraviolet absorber also have high head wear resistance.

On the other hand, in Comparative Example 1 using the hydrophobic ultraviolet absorbent, scum sticking and sticking were seriously generated, and in Comparative Examples 2 and 3 using only the fluorescent dye or the water-soluble ultraviolet absorbent, respectively. , Sufficient light fastness could not be obtained. In Comparative Examples 4 and 5 using kaolin instead of aluminum hydroxide, remarkable head wear was observed in addition to sticking and sticking.

[0053]

As described above, the heat-sensitive recording material of the present invention has improved light fastness by containing a water-soluble ultraviolet absorber and a fluorescent dye in the protective layer, and has a fading due to light and a yellow background. No change occurs, and the recording density does not decrease and the appearance does not deteriorate even when stored for a long time. Further, in the present invention, by using a water-soluble ultraviolet absorber or aluminum hydroxide, it is possible to prevent scum adhesion, sticking, and head abrasion, and it is possible to perform recording with a thermal head smoothly. The body is obtained.

──────────────────────────────────────────────────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 Nippon Paper Industries Co., Ltd. Product Development Laboratory (56) References JP-A-60-125694 (JP, A) JP-A-7-276801 (JP, A) JP-A-62-59081 (JP, A) JP-A-8-282114 (JP, A) JP-A-6-155923 (JP, A) JP-A-8-230331 (JP, A) JP-A-7-179048 (JP, A) (58) Fields investigated ( Int.Cl. ⁶ , DB name) B41M 5/28-5/34

Claims (5)

(57) [Claims] 1. A heat-sensitive recording layer comprising, as a main component, at least a colorless or light-colored dye precursor and a color developing agent which causes the dye precursor to develop color when heated, and a protective layer on the heat-sensitive recording layer. A heat-sensitive recording material, wherein the protective layer contains a binder, a water-soluble ultraviolet absorber, a fluorescent dye, and aluminum hydroxide. 2. The heat-sensitive recording material according to claim 1, wherein the water-soluble ultraviolet absorber is a benzophenone derivative having a sulfone group. 3. The heat-sensitive recording material according to claim 1, wherein the water-soluble ultraviolet absorber is a benzophenone derivative having a sulfonic acid group. 4. The method according to claim 1, wherein the content of the water-soluble ultraviolet absorber is 2 to 30% by weight based on the total solid content of the protective layer. 4. The thermosensitive recording medium according to claim 1, wherein the content of the fluorescent dye is 0.01 to 3% by weight based on the total solid content of the protective layer. 5. The thermosensitive recording material according to claim 1, wherein the binder in the protective layer contains a hydrophobic polymer as a main component.