JP2001096917A - Heat-sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording body wherein light-resistance is especially favorable. SOLUTION: For this heat-sensitive recording body, on a supporting body, a heat-sensitive recording layer containing a colorless or light-colored basic colorless dye, and an organic developer as the major components, is provided. In such a heat-sensitive recording body, at least one kind of a water-base emulsion type polymer ultraviolet absorber comprising an emulcifying copolymer of an ultraviolet absorbing monomer (a), a vinyl compound monomer (b) which can be copolymerized with the monomer (a), a hydrophilic monomer (c), and a reactive emulsifier (d), and an ultraviolet ray shielding agent are contained. By this constitution, the light-resistance (the yellowing of the base and the reduction of the image density) can be improved for the heat-sensitive recording body.

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 particularly excellent light fastness.

[0002]

2. Description of the Related Art In general, a thermosensitive recording medium is usually prepared by grinding and dispersing a colorless or light-colored basic colorless dye and an organic developer such as a phenolic substance into fine particles, and then mixing and mixing the two. A coating solution obtained by adding an agent, a sensitivity improver, a lubricant and other auxiliaries to a support such as paper, synthetic paper, film, plastic, etc. The color recording is obtained by an instantaneous chemical reaction caused by heating such as described above. These heat-sensitive recording materials are applied to a wide range of fields such as measurement recorders, computer terminal printers, facsimile machines, automatic ticket vending machines, and barcode labels.

[0003] As one application of the heat-sensitive recording material, in recent years, it has been frequently used for various display media such as heading labels and posters, and tickets. However, this type of thermosensitive recording medium has low stability to light and heat, and if the thermosensitive recording medium is exposed to room light or sunlight for a long period of time or is exposed to high humidity, the background will turn yellow. As a result, the appearance deteriorates or the stability of the recorded image is impaired, and as a result, the product image of the thermosensitive recording medium is significantly impaired.

In order to improve the light fastness of a thermosensitive recording medium,
A method in which an inorganic filler having an ultraviolet blocking effect is contained in a heat-sensitive recording layer or a protective layer covering the same (Japanese Patent Laid-Open No. Sho 62-62).
18626, JP-A-6-64324, etc.),
A method in which a pulverized ultraviolet absorber is added to a heat-sensitive recording layer and / or a protective layer covering the same (Japanese Patent Application Laid-Open No. Sho 50/1985).
JP-A-104650, JP-A-55-55891, JP-A-58-87093, etc.) and a method using a water-soluble ultraviolet absorber (JP-A-55-93492, JP-A-7-17131). Publication), a method of adding a microencapsulated ultraviolet absorber to a protective layer (Japanese Patent Application Laid-Open No. 5-155134, etc.), and a method of using an ultraviolet absorber having a polymerized benzotriazole molecule or benzophenone molecule capable of absorbing ultraviolet light. (JP-A-7-31489
4, Japanese Patent Application Laid-Open No. 9-221487, Japanese Patent Application Laid-Open
268183, JP-A-9-314496,
JP-A-10-71770, JP-A-10-3637
No. 1, JP-A-6-73368), a method in which an ultraviolet absorbent composed of an emulsion copolymer of an ultraviolet absorbing monomer, a vinyl compound monomer copolymerizable with the monomer, and a crosslinkable monomer is used for a heat-sensitive recording layer (Japanese Patent Application Laid-Open No. 6-73368). And the like are disclosed. Also, a method of using an ultraviolet ray blocking agent and an ultraviolet ray absorber in combination (Japanese Patent Application Laid-Open Nos. 9-156227 and
JP-A-278428) and a method of using a plurality of ultraviolet absorbers in combination (JP-A-7-137453). As described above, although the provision of light resistance to a heat-sensitive recording medium using an ultraviolet ray blocking agent or an ultraviolet absorber has been performed for a long time, the required quality level relating to the light resistance of the heat-sensitive recording medium has recently increased. As a result, at present, satisfactory light fastness cannot be obtained with the above-mentioned conventional method.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermosensitive recording medium having particularly excellent light fastness.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have obtained a heat-sensitive recording material of the present invention. That is, the invention according to claim 1 of the present invention relates to a heat-sensitive recording medium having a heat-sensitive recording layer having a colorless or pale-colored basic colorless dye and an organic color developer as main components on a support. Aqueous emulsion type UV absorber comprising an emulsion copolymer of a reactive monomer (a), a vinyl compound monomer (b) copolymerizable with the monomer, a hydrophilic monomer (c), and a reactive emulsifier (d) Characterized in that it contains at least one of the foregoing and an ultraviolet ray blocking agent. Further, the invention according to claim 2 has a three-layer structure in which the ultraviolet ray blocking agent has a flaky pigment surface having a refractive index of about 1.5 to 1.6 coated with an insoluble cerium compound and amorphous silica. It is characterized by comprising a fired product of particles. The invention according to claim 3 is characterized in that the ultraviolet ray blocking agent is made of an inorganic powder obtained by drying or firing particles having a two-layer structure in which an insoluble cerium compound is coated with amorphous silica. It is.

[0007] Even when the aqueous emulsion type polymer ultraviolet absorber of the present invention is used alone, good light fastness can be obtained to some extent, but it does not reach sufficient light fastness intended for the present invention. However, in the present invention, by combining this ultraviolet absorber with an ultraviolet ray blocking agent, particularly the light resistance is extremely improved. In the present invention, the reason why good light fastness is obtained is not clearly elucidated, but due to the synergistic effect of the combination of the ultraviolet absorber and the ultraviolet ray blocking agent of the present invention, yellowing of the background portion and fading of the image portion are caused. It is considered that ultraviolet rays having a contributing wavelength are effectively blocked and absorbed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As the UV-absorbing monomer (a) constituting the aqueous emulsion type polymer UV-absorbing agent contained in the heat-sensitive recording medium of the present invention, any monomer can be used as long as it is a UV-absorbing monomer. But preferably, a 2-hydroxybenzophenone group which may be substituted by an alkyl group or an alkoxyl group having 1 to 6 carbon atoms, or a 2-hydroxy group which may be substituted by a hydrocarbon group having 1 to 6 carbon atoms. A polymerizable vinyl compound having a benzotriazole group bonded thereto, and specific examples thereof include the following (1) or (2). Further, (1) and (2) can be used in combination. Of course, the present invention is not limited to these, and two or more of these UV-absorbing monomers can be used in combination. In particular, (2) is preferably used. (1) A 2-hydroxybenzophenone derivative represented by the general formula (I).

[0009]

Embedded image

(R ₁ : hydrogen, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, R ₂ : an alkylene group or an oxyalkylene group having 1 to 10 carbon atoms, or absent (in this case, X is directly Bond), X: ester bond, amide bond, ether bond or urethane bond, R ₃ : hydrogen or lower alkyl group) The monomer represented by the general formula (I) is, for example, BP-R
_2- OH (BP: 2-hydroxybenzophenone skeleton)
And a UV absorbing compound having a functional group such as CH ₂ ＣC
Reacting with a polymerizable vinyl compound having a functional group such as R ₃ —COOH, and bonding an ultraviolet absorbing compound residue to the polymerizable vinyl compound by an ester bond X (—COO—);
It can be obtained by introducing. Specific examples of the monomer compound represented by the general formula (I) include 2-hydroxy-
4-acryloyloxybenzophenone, 2-hydroxy-4-methacryloyloxybenzophenone, 2-hydroxy-4- (2-acryloyloxy) ethoxybenzophenone, 2-hydroxy-4- (2-methacryloyloxy) ethoxybenzophenone, 2-hydroxy- 4- (2-methyl-2-acryloyloxy) ethoxybenzophenone and the like. (2) A 2-hydroxybenzotriazole derivative represented by the general formula (II).

[0011]

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(R ₄ : hydrogen, halogen or methyl group,
R _5: a hydrogen or a hydrocarbon group having 1 to 6 carbon atoms, R _6: an alkylene group having 1 to 10 carbon atoms or not oxyalkylene group or present, (in this case X is bonded directly to the benzene ring), X : An ester bond, an amide bond, an ether bond or a urethane bond, R ₇ : an alkylene group having 1 to 8 carbon atoms, an aminoalkylene group or an alkyl group having a hydroxyl group in a side chain, or absent (in this case,
X and C are directly bonded), R ₈ : hydrogen or a lower alkyl group) Specific examples of the monomer compound represented by the general formula (II) include 2- [2′-hydroxy-5 ′-(methacryloyloxy). ) Phenyl] benzotriazole, 2-
[2'-hydroxy-5 '-(acryloyloxy) phenyl] benzotriazole, 2- [2'-hydroxy-3'-t-butyl-5'-(methacryloyloxy)
Phenyl] benzotriazole, 2- [2'-hydroxy-3'-methyl-5 '-(acryloyloxy) phenyl] benzotriazole, 2- [2'-hydroxy-
5 '-(methacryloyloxypropyl) phenyl]-
5-chlorobenzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl]
Benzotriazole, 2- [2'-hydroxy-5'-
(Acryloyloxyethyl) phenyl] benzotriazole, 2- [2′-hydroxy-3′-t-butyl-
5 '-(methacryloyloxyethyl) phenyl] benzotriazole, 2- [2'-hydroxy-3'-methyl-5'-(acryloyloxyethyl) phenyl] benzotriazole, 2- [2'-hydroxy-5'-
(Methacryloyloxypropyl) phenyl] -5-chlorobenzotriazole, 2- [2′-hydroxy-
5 '-(acryloyloxybutyl) phenyl] -5-
Methylbenzotriazole, [2-hydroxy-3-t
-Butyl-5- (acryloyloxyethoxycarbonylethyl) phenyl] benzotriazole and the like.

Other vinyl compound monomers (b) copolymerizable with the above-mentioned ultraviolet absorbing monomer (hereinafter referred to as copolymerized monomers) include acrylonitrile, alkyl acrylate, alkyl methacrylate, alkyl vinyl ether , Alkyl vinyl ester, styrene and the like. In this case, the number of carbon atoms of the alkyl group is not particularly limited, but is preferably 1 to 18.
The following are specific examples of these compounds. (1) Alkyl acrylate and alkyl methacrylate. Methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate and the like. (2) Alkyl vinyl ether. Methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, stearyl vinyl ether and the like. (3) Alkyl vinyl esters. Vinyl acetate, ethyl vinyl, butyl vinyl, 2-ethylhexyl vinyl and the like. As the copolymerization ratio of the copolymerized monomer, 5 to 69% by weight of all the monomers is used.

Further, by using the hydrophilic monomer (c), the solvent resistance and the compatibility with the hydrophilic resin are improved, and a durable ultraviolet absorbing polymer film is formed. As the hydrophilic monomer, any monomer may be used as long as it has a hydrophilic reactive functional group.Preferably, a hydroxy group-containing monomer, a carboxylic acid-containing monomer, etc., and specific examples thereof include the following: No. (1) Hydroxy group-containing monomers. 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl methacrylate and the like. (2) Carboxylic acid group-containing monomers. Acrylic acid, methacrylic acid, etc. The copolymerization ratio of the hydrophilic monomer is preferably from 1 to 20% by weight of all the monomers. If it exceeds 20% by weight, it is difficult to polymerize due to the problem of copolymerizability with the ultraviolet absorbing monomer.

The aqueous emulsion type polymer ultraviolet absorber used in the present invention is obtained by mixing each monomer together with an emulsifier in an aqueous medium and subjecting the mixture to emulsion polymerization using a water-soluble polymerization initiator. The emulsion copolymer desirably has a somewhat higher glass transition temperature (Tg) from the viewpoint of heat resistance of the film and the like, and when the Tg is 50 ° C. or more, excellent heat resistance (stick resistance) of the film is obtained. Is obtained. It is preferably at least 70 ° C, more preferably at least 80 ° C. In the present invention, by adjusting the composition of the monomer to be emulsion-copolymerized, an aqueous emulsion type polymer ultraviolet absorber having a Tg of 50 ° C. or higher can be easily obtained.

As the reactive emulsifier, any radically polymerizable reactive emulsifier conventionally used in emulsion polymerization can be used, but a polymerizable vinyl compound is more preferable. The reactive emulsifier is not limited to a single type, and two or more types can be used as a mixture. These are taken into the copolymer obtained at the time of emulsion polymerization and can prevent adverse effects on the water resistance and transparency of the film after formation of the film, which are generally observed with non-reactive emulsifiers. Specifically, Latemul S-18
0, S-180A, S-120A (Kao Corporation), Aqualon HS-10, HS-20, RN series (Daiichi Kogyo Pharmaceutical Co., Ltd.), Eleminor JS-2 (Sanyo Chemical Industry Co., Ltd.), Adecaria Soap NE-30 (Asahi Denka Kogyo Co., Ltd.), and the like. An anionic reactive emulsifier is preferably used from the viewpoint of the coloring property of the thermosensitive recording medium.
The amount of the reactive emulsifier to be used is preferably 0.5 to 5 parts by weight based on 100 parts by weight of the total amount of the monomers. When used in an amount of more than 5 parts by weight, the effect on the basic colorless dye is large, which causes color development inhibition and the like, and the water resistance of the film tends to be poor.

In general, many emulsifiers used for emulsification exist in a state of being in contact with and surrounding the material to be emulsified. On the other hand, the reactive emulsifier used in the present invention reacts with the material to be emulsified and becomes a part of itself, so that the form does not remain as an emulsifier, and therefore, the aqueous emulsion type polymer ultraviolet absorption of the present invention. It is considered that the agent is in a soap-free state and has an advantage that it hardly affects the coloring material.

Examples of the water-soluble polymerization initiator include peroxides such as persulfates, percarbonates and perborates, and 2,2'-
Azobis [2- (2-imidazolin-2-yl) propane] hydrochloride, 2,2′-azobis (2-methylpropionamidine) hydrochloride, 2,2′-azobis [N- (2-
Hydroxyethyl) -2-methylpropionamidine]
Hydrochloride, 2,2′-azobis [2- (5-hydroxy-
Azo-based water-soluble polymerization initiators such as 3,4,5,6-tetrahydropyrimidin-2-yl) propane] hydrochloride can be used. The amount of the water-soluble polymerization initiator to be used is preferably 0.05 to 1% by weight per monomer.

The emulsion copolymer constituting the aqueous emulsion type polymer ultraviolet absorber used in the present invention is an internally crosslinked polymer particle having an average particle size of 500 nm to 8 nm.
Those having a thickness of about 0 nm can be preferably used. More preferably, it is larger than 100 nm. The aqueous emulsion type polymer ultraviolet absorber of the present invention can be obtained by carrying out emulsion polymerization using the above-mentioned components, and specific preparation examples are shown below.

(Example of preparation of ultraviolet absorber) Aqualon HS
-20 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1 g, 2- (2′hydroxy-5′-methacryloyloxyethylphenyl)
A monomer mixture 301 g composed of 50 g of -2H-benzotriazole, 10 g of 2-ethylhexyl methacrylate, 1 g of methacrylic acid, 39 g of methyl methacrylate, and 200 g of ion-exchanged water was prepared.
The mixture was added to a glass reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen introduction tube and a dropping funnel, and emulsified at 70 ° C. for 30 minutes. Then, as a water-soluble polymerization initiator,
2'-azobis [2- (2-imidazolin-2-yl)
Propane] An aqueous solution in which 0.5 g of hydrochloride was dissolved in 33 g of ion-exchanged water was added to the reaction vessel, and the remaining amount of the monomer mixture was immediately dropped continuously into the reaction vessel over 90 minutes, and polymerization was carried out at 70 ° C. Was. After completion of the dropping of the monomer mixture, the mixture was aged at 70 ° C. for 90 minutes to obtain an aqueous emulsion type polymer ultraviolet absorber (average particle size: 200 nm) of Preparation Example.

The aqueous emulsion type polymer UV absorber used in the present invention has a high UV absorbing ability due to a large amount of UV absorbing monomer contained in the molecule and exhibits good light resistance when used in a small amount. Avoids lowering of the color density of the body and background fogging.Since the reactivity of the emulsifier has a small effect on the color forming material, good color developability and white paper appearance can be obtained. Good solubility and plasticizer,
Low solubility in solvents such as oils and organic solvents,
When blended in the protective layer, the barrier function does not decrease due to the elution of the ultraviolet absorber and the chemical resistance is excellent, and when the glass transition point (Tg) is high, the heat resistance is good and the protective layer is improved. When the recording head is used for recording, there is no sticking or head residue caused by melting during recording with a thermal head, and an excellent effect of improving the recording running property can be obtained.

The amount of the ultraviolet absorbent used in the undercoat layer of the present invention is 0.1 to 8 with respect to the dry weight of the undercoat layer.
It is preferable to contain 0% by weight. More preferably 1
５０50% by weight. If the amount is less than 0.1% by weight, it is difficult to obtain sufficient light resistance. 80% by weight
If it exceeds, the binding property between the support and the undercoat layer is reduced, and as a result, the surface strength of the thermosensitive recording medium is reduced. Therefore, it is unsuitable for applications requiring therotropic strength, printability, and the like.

The amount of the ultraviolet absorbent of the present invention used in the heat-sensitive recording layer is 0.1 to the dry weight of the heat-sensitive recording layer.
It is preferable to contain ２５25% by weight. More preferably, it is 1 to 20% by weight. If the amount is less than 0.1%, it is difficult to obtain sufficient light resistance. 25% by weight
Exceeding the range has a large effect on lowering of color density and background fog.

The amount of the ultraviolet absorbent of the present invention used in the protective layer is 0.1 to 30 with respect to the dry weight of the protective layer.
It is preferred that the content is contained by weight. More preferably, 1
２５25% by weight. If the amount is less than 0.1% by weight, it is difficult to obtain sufficient light resistance. 30% by weight
If it exceeds, the barrier properties tend to be insufficient. When used in the heat-sensitive recording layer or the protective layer, it is desirable that the ultraviolet blocking agent used in the present invention has high transparency and low hiding property from the viewpoint of color density. As such an ultraviolet blocking agent, for example, the surface of a flake-like pigment having a refractive index of about 1.5 to 1.6 according to claim 2 of the present invention is coated with an insoluble cerium compound, and further coated with amorphous silica. Examples include a fired product of particles having a three-layer structure or an inorganic powder obtained by drying or firing particles having a two-layer structure in which the insoluble cerium compound according to claim 3 is coated with amorphous silica. These are preferably used in the present invention.

With respect to such an ultraviolet ray blocking agent, a fired product of particles having a three-layer structure is described in JP-A-6-145645, and an inorganic powder obtained by drying or firing particles having a two-layer structure is described in JP-A-6-145645. No. 9-202048, which is well known. In order to produce this ultraviolet ray blocking agent having a three-layer structure, first, an aqueous cerium salt solution is added to an aqueous dispersion of a flake pigment as CeO ₂ to the pigment under heating by heating.
0% by weight is added dropwise, the pH is adjusted to 7 to 9, and an insoluble cerium compound is deposited on the surface of the pigment to obtain a cerium-coated pigment. Then, a silicate solution was added to the aqueous dispersion of the cerium-coated pigment under heating to adjust the pH to 6 to 8, and the surface of the pigment was deposited and coated with amorphous silica.
It is obtained by firing at the above high temperature. 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 silica, mica, talc, sericite, aluminum hydroxide, calcium carbonate, kaolin,
Examples include calcium hydroxide, aluminum silicate, polyethylene powder, polystyrene, latex and the like. Among these, silica, mica, talc, and sericite are preferable because a heat-sensitive recording material having a good coloring density can be obtained. Further, as the cerium compound, cerium chloride, cerium nitrate, cerium sulfate or the like can be used. As the silicate, an inorganic silicate such as sodium silicate or the like can be used.

The ultraviolet blocking agent having a two-layer structure is prepared by adding a cerium salt solution and an alkaline solution to water maintained at a liquid temperature of 60 ° C. or lower and a pH of 5 or higher, and forming a slurry of cerium hydroxide in water of 80%. Amorphous silica is produced by adding a sodium silicate solution and a mineral acid solution while heating the mixture to a temperature of not lower than 9 ° C. and maintaining the pH at 9 or more, washing with water, filtering, and then drying or calcining. The ultraviolet ray blocking agent used in the present invention is composed of a pigment (filler) generally used in a thermosensitive recording medium, which has a characteristic layer structure and can maintain sufficient whiteness. Therefore, even when it is contained in the heat-sensitive recording layer, there is no adverse effect such as background fogging and desensitization, and when it is contained in the protective layer, the heat-sensitive recording medium can have a writing property.

The amount of the ultraviolet ray blocking agent used in the undercoat layer is preferably 5 to 80% by weight based on the dry weight of the undercoat layer. If the amount is less than 5% by weight, it is difficult to obtain sufficient light resistance. If the amount used exceeds 80% by weight, the strength of the undercoat layer is reduced, and as a result, the surface strength of the thermosensitive recording medium is reduced. Therefore, it is unsuitable for applications requiring celotropic strength, printability and the like.

The amount of the ultraviolet blocking agent used in the heat-sensitive recording layer is preferably 10 to 40% by weight based on the dry weight of the heat-sensitive recording layer. If the amount is less than 10% by weight, it is difficult to obtain sufficient light resistance. If the amount used exceeds 40% by weight, the color-forming sensitivity decreases.

The UV blocking agent is preferably used in the protective layer in an amount of 5 to 40% by weight based on the dry weight of the protective layer. If the amount is less than 5% by weight, it is difficult to obtain sufficient light resistance. If the amount is more than 40% by weight, it is difficult to obtain a sufficient barrier property of the protective layer, and the color sensitivity tends to be reduced due to the hiding property.

The present invention relates to a heat-sensitive recording layer containing a basic colorless dye and an organic developer on a support, and if necessary, an undercoat layer between the heat-sensitive recording layer and the support, In the heat-sensitive recording medium having a protective layer, an intermediate layer provided between the heat-sensitive recording layer and the protective layer, at least one of the above-mentioned aqueous emulsion type polymer ultraviolet absorber is contained in at least one layer, and at least one By including an ultraviolet ray blocking agent in the first layer, performance such as light resistance is remarkably improved as compared with a conventionally proposed technique. These ultraviolet absorbers and ultraviolet ray blocking agents can be contained in two or more layers, and the combination of the layers to be contained is not particularly limited. The number of the heat-sensitive recording layer, the undercoat layer, the intermediate layer, and the protective layer is not limited to one, and a plurality of layers can be provided.

The amount of these ultraviolet absorbers and ultraviolet blocking agents used in the heat-sensitive recording medium and the locations (layers) to be contained in the heat-sensitive recording medium depend on the performance quality required for the heat-sensitive recording medium. In terms of the efficiency of absorbing and blocking ultraviolet rays, it is better to mix an ultraviolet absorber and an ultraviolet ray blocking agent in the outer layer such as a heat-sensitive recording layer rather than an undercoat layer and a protective layer rather than the heat-sensitive recording layer. The aqueous emulsion type polymer UV absorber has a good barrier property against solvents, plasticizers, etc., and when Tg is high, it has excellent properties such as dregs and sticks. It is desirable to use it for the protective layer. Further, since the ultraviolet ray blocking agent is often a relatively hard substance, a thermal recording medium having better head abrasion can be obtained by using the ultraviolet ray shielding agent in a layer inside the outermost layer. In the present invention, when a protective layer is provided, the protective layer contains the ultraviolet absorbent of the present invention and the heat-sensitive recording layer or the undercoat layer contains an ultraviolet ray blocking agent, or when the protective layer is not provided, the heat-sensitive recording layer It is desirable that the undercoat layer contains the ultraviolet absorber of the present invention and the undercoat layer contains an ultraviolet absorber.

In the present invention, the basic colorless dye used in the heat-sensitive recording layer is not particularly limited, but is preferably a leuco dye such as triphenylmethane type, fluoran type, azaphthalide type or fluorene type. The specific examples are shown in FIG. These basic colorless dyes can be used alone or in combination of two or more.

<Triphenylmethane leuco dye> 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide [also known as crystal violet lactone] 3,3-bis (p-dimethylaminophenyl) phthalide [ Aka malachite green lactone)

<Fluoran Leuco Dye> 3-Diethylamino-6-methylfluoran 3-Diethylamino-6-methyl-7-anilinofluoran 3-Diethylamino-6-methyl-7- (o, p-dimethylanilino ) Fluoran 3-diethylamino-6-methyl-7-chlorofluoran 3-diethylamino-6-methyl-7- (m-trifluoromethylanilino) fluoran 3-diethylamino-6-methyl-7- (o-chloroanilino) Fluoran 3-diethylamino-6-methyl-7- (p-chloroanilino) fluoran 3-diethylamino-6-methyl-7- (o-fluoroanilino) fluoran 3-diethylamino-6-methyl-7- (m-methylanilino) Fluoran 3-diethylamino-6-methyl-7-n-octyl Anilino fluoran

3-Diethylamino-6-methyl-7-n
-Octylaminofluoran 3-diethylamino-6-methyl-7-benzylanilinofluoran 3-diethylamino-6-methyl-7-dibenzylanilinofluoran 3-diethylamino-6-chloro-7-methylfluoran 3 -Diethylamino-6-chloro-7-anilinofluoran 3-diethylamino-6-chloro-7-p-methylanilinofluoran 3-diethylamino-6-ethoxyethyl-7-anilinofluoran 3-diethylamino-7 -Methylfluorane 3-diethylamino-7-chlorofluorane 3-diethylamino-7- (m-trifluoromethylanilino) fluoran

3-diethylamino-7- (o-chloroanilino) fluoran 3-diethylamino-7- (p-chloroanilino) fluoran 3-diethylamino-7- (o-fluoroanilino) fluoran 3-diethylamino-benzo [a] fluoran 3-diethylamino-benzo [c] fluoran 3-dibutylamino-6-methyl-fluoran 3-dibutylamino-6-methyl-7-anilinofluoran 3-dibutylamino-6-methyl-7- (o, p- Dimethylanilino) fluorane 3-dibutylamino-6-methyl-7- (o-chloroanilino) fluoran 3-Dibutylamino-6-methyl-7- (p-chloroanilino) fluoran

3-dibutylamino-6-methyl-7-
(O-fluoroanilino) fluoran 3-dibutylamino-6-methyl-7- (m-trifluoromethylanilino) fluoran 3-dibutylamino-6-methyl-chlorofluoran 3-dibutylamino-6-ethoxyethyl -7-anilinofluoran 3-dibutylamino-6-chloro-7-anilinofluoran 3-dibutylamino-6-methyl-7-p-methylanilinofluoran 3-dibutylamino-7- (o- Chloroanilino) fluorane 3-dibutylamino-7- (o-fluoroanilino) fluoran 3-di-n-pentylamino-6-methyl-7-anilinofluoran 3-di-n-pentylamino-6-methyl- 7- (p-
Chloroanilino) fluoran 3-di-n-pentylamino-7- (m-trifluoromethylanilino) fluoran

3-di-n-pentylamino-6-chloro-7-anilinofluoran 3-di-n-pentylamino-7- (p-chloroanilino) fluoran 3-pyrrolidino-6-methyl-7-ani Linofluoran 3-piperidino-6-methyl-7-anilinofluoran 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluoran 3- (N-methyl-N-cyclohexyl Amino) -6-
Methyl-7-anilinofluoran 3- (N-ethyl-N-cyclohexylamino) -6
Methyl-7-anilinofluoran 3- (N-ethyl-N-xylamino) -6-methyl-
7- (p-chloroanilino) fluoran 3- (N-ethyl-Np-toluidino) -6-methyl-7-anilinofluoran 3- (N-ethyl-N-isoamylamino) -6-methyl-7 -Anilino fluoran

3- (N-ethyl-N-isoamylamino) -6-chloro-7-anilinofluoran 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofuran Oran 3- (N-ethyl-N-isobutylamino) -6-methyl-7-anilinofluoran 3- (N-ethyl-N-ethoxypropylamino) -6
-Methyl-7-anilinofluoran 3-cyclohexylamino-6-chlorofluoran 2- (4-oxahexyl) -3-dimethylamino-6
-Methyl-7-anilinofluoran 2- (4-oxahexyl) -3-diethylamino-6
-Methyl-7-anilinofluoran 2- (4-oxahexyl) -3-dipropylamino-
6-methyl-7-anilinofluoran 2-methyl-6-p- (p-dimethylaminophenyl)
Aminoanilinofluoran 2-methoxy-6-p- (p-dimethylaminophenyl) aminoanilinofluoran

2-chloro-3-methyl-6-p- (p-
Phenylaminophenyl) aminoanilinofluoran 2-chloro-6-p- (p-dimethylaminophenyl)
Aminoanilinofluoran 2-nitro-6-p- (p-diethylaminophenyl)
Aminoanilinofluoran 2-amino-6-p- (p-diethylaminophenyl)
Aminoanilinofluoran 2-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluoran 2-benzyl-6-p- (p-phenylaminophenyl) aminoanilinofluoran 2-hydroxy-6 p- (p-phenylaminophenyl) aminoanilinofluoran 3-methyl-6-p- (p-dimethylaminophenyl)
Aminoanilinofluoran 3-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluoran 3-diethylamino-6-p- (p-dibutylaminophenyl) aminoanilinofluoran 2,4-dimethyl- 6-[(4-dimethylamino) anilino] -fluoran

<Fluorene Leuco Dye>3,6,6'-Tris (dimethylamino) spiro [fluorene-9,3'-phthalide] 3,6,6'-Tris (diethylamino) spiro [fluorene-9,3 '-Phthalide] <Divinyl leuco dye> 3,3-bis- [2- (p-dimethylaminophenyl)
-2- (p-methoxyphenyl) ethenyl] -4,5
6,7-tetrabromophthalide 3,3-bis- [2- (p-dimethylaminophenyl)
-2- (p-methoxyphenyl) ethenyl] -4,5
6,7-tetrachlorophthalide 3,3-bis- [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide 3,3- Bis- [1- (4-methoxyphenyl) -1-
(4-pyrrolidinophenyl) ethylene-2-yl]-
4,5,6,7-tetrachlorophthalide

<Others> 3- (4-diethylamino-2-ethoxyphenyl)-
3- (1-ethyl-2-methylindol-3-yl)
-4-azaphthalide 3- (4-diethylamino-2-ethoxyphenyl)-
3- (1-octyl-2-methylindol-3-yl) -4-azaphthalide 3- (4-cyclohexylethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) ) -4-Azaphthalide 3,3-bis (1-ethyl-2-methylindole-3
-Yl) phthalide 3,6-bis (diethylamino) fluoran-γ- (3
'-Nitro) anilinolactam 3,6-bis (diethylamino) fluoran-γ- (4
'-Nitro) anilinolactam 1,1-bis- [2', 2 ', 2 ", 2" -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,
2-dinitrileethane 1,1-bis- [2 ', 2', 2 ", 2" -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2-
β-naphthoylethane 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,
2-Diacetylethane bis- [2,2,2 ', 2'-tetrakis- (p-dimethylaminophenyl) -ethenyl] -methylmalonic acid dimethyl ester

The organic color developer used in the heat-sensitive recording layer of the present invention is not particularly limited, and examples thereof include 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, 4-
Benzyl 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'-methyldiphenyl sulfone, 4-hydroxyphenyl-
4'-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, aminobenzenesulfonamide derivatives described in JP-A-8-59603,

Bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, butyl bis (p-hydroxyphenyl) acetate, bis (p-hydroxyphenyl) acetic acid Methyl, 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-
tert-octylphenol), International Publication WO97 / 16
No. 420 phenolic compounds such as diphenylsulfone cross-linked compound,

Thiourea compounds such as N, N'-di-m-chlorophenylthiourea, p-chlorobenzoic acid, stearyl gallate, zinc bis [4- (n-octyloxycarbonylamino) salicylate] dihydrate; 4- [2-
(P-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid aromatic carboxylic acid, and Of these aromatic carboxylic acids zinc, magnesium, aluminum, calcium, titanium, manganese,
Examples thereof include salts with polyvalent metal salts such as tin and nickel, and antipyrine complexes of zinc thiocyanate and composite zinc salts of terephthalaldehyde acid and other aromatic carboxylic acids. These organic developers may be used alone or in combination of two or more. In addition, JP-A-10-258
No. 577, metal chelate-type coloring components such as higher fatty acid metal double salts and polyvalent hydroxy aromatic compounds can also be used.

In the present invention, a sensitivity improver can be contained in the heat-sensitive recording layer in order to improve the heat-sensitive recording color development sensitivity. As the sensitivity improver, any compound can be used as long as it is a compound conventionally used in a thermosensitive recording medium. For example, stearic acid amide, fatty acid amide such as palmitic acid amide, ethylenebisamide, montan wax,
Polyethylene wax, dibenzyl terephthalate, p-
Benzyl benzyloxybenzoate, di-p-tolyl carbonate, p-benzylbiphenyl, phenyl α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1
-Hydroxy-2-naphthoic acid phenyl ester, 1,
2-di- (3-methylphenoxy) ethane, di (p-methylbenzyl) oxalate, β-benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, O-xylene-bis- (phenyl ether), 4- (M-Methylphenoxymethyl) biphenyl, p-toluenesulfonamide, o-toluenesulfonamide and the like can be added, but not particularly limited thereto. These sensitivity improvers may be used alone or in combination of two or more.

In the present invention, an image stabilizer may be contained in the heat-sensitive recording layer mainly for improving the preservability of the color recording image. Examples of such an image stabilizer include 1,1,3-tris (2-methyl-4-hydroxy-5).
-Cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1-bis (2-methyl-4-hydroxy-5-tert-butyl) Phenyl) butane, 4,4 '
-[1,4-phenylenebis (1-methylethylidene)] bisphenol and 4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenol, 4,4'-butylidene (6-t- Butyl-3-methylphenol), 2,2'-di-t-butyl-5,5 '
Phenolic compounds such as -dimethyl-4,4'-sulfonyldiphenol, 4-benzyloxyphenyl-
4 '-(2-methyl-2,3-epoxypropyloxy) phenylsulfone, 4- (2-methyl-1,2-epoxyethyl) diphenylsulfone, and 4- (2-
Epoxy compounds such as ethyl-1,2-epoxyethyl) diphenylsulfone, and 1,3,5-tris (2,
A compound containing one or more selected from isocyanuric acid compounds such as 6-dimethylbenzyl-3-hydroxy-4-tert-butyl) isocyanuric acid can be used. These image stabilizers can be used alone or in combination of two or more.

When a basic colorless dye and an organic developer are bonded and supported on a support for producing the thermosensitive recording medium of the present invention, a conventionally known binder can be appropriately used. Specific examples thereof include fully saponified polyvinyl alcohol having a degree of polymerization of 200 to 1900, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol,
Amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and ethyl cellulose, cellulose derivatives such as acetyl cellulose, styrene-maleic anhydride copolymer, Styrene-butadiene copolymer, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyvinyl butyral polystyrene and their copolymers, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, coumarone Resins. These polymer substances are used by dissolving them in solvents such as water, alcohols, ketones, esters, and hydrocarbons.Also, they are used in the form of emulsified or dispersed in water or other media in the form of a paste. They can be used together.

The filler used in the thermal recording medium of the present invention includes silica, calcium carbonate, clay, kaolin, calcined kaolin, diatomaceous earth, synthetic aluminum silicate, talc, zinc oxide, titanium oxide, aluminum hydroxide, water Inorganic fillers such as zinc oxide, barium sulfate, magnesium carbonate, surface-treated calcium carbonate and silica, and organic fillers such as urea-formalin resin, styrene-methacrylic acid copolymer resin, polystyrene resin, and vinylidene chloride. No. In addition, release agents such as fatty acid metal salts, lubricants such as waxes, waterproofing agents such as glyoxal, dispersants, defoamers, antioxidants,
Conventionally known materials commonly used for thermosensitive recording media, such as fluorescent dyes, can be used as appropriate.

The method for preparing the coating solution for the heat-sensitive recording layer of the present invention is not particularly limited, but generally the amounts of the basic colorless dye and the organic developer used for the recording medium, the types of other various components and The amount is determined according to the required performance and recording suitability. Usually, 1 to 8 parts of an organic color developer and 1 to 20 parts of a filler are used for 1 part of a basic colorless dye, and a binder is contained in the total solid content. 5-25% is appropriate. These basic colorless dyes, organic developers and materials to be added as necessary are pulverized into a particle size of several microns or less by a pulverizer such as a ball mill, an attritor, a sand glider or an appropriate emulsifying device, and a binder. And, if necessary, various additives such as the ultraviolet absorbent and the ultraviolet blocking agent of the present invention are added to form a coating liquid. The method for forming the heat-sensitive recording layer is not particularly limited. For example, a coating solution having the above composition is coated on a support by a blade coater, an air knife coater, a bar coater, a reverse roll coater, or the like, and dried to obtain the desired heat-sensitive recording. The body is obtained.

When an undercoat layer is provided between the heat-sensitive recording layer and the support in the heat-sensitive recording medium of the present invention, such an undercoat layer usually contains a binder and a filler. As the binder, the filler and the various auxiliaries, the materials exemplified as the components of the heat-sensitive recording layer can be appropriately used according to the required quality. In addition, Japanese Patent Publication 3-54
Known hollow particles conventionally used for an undercoat layer of a heat-sensitive recording medium, such as fine hollow sphere particles having a shell described in JP-A-0774, and bowl-shaped hollow polymer particles described in JP-A-10-258577, and calcined kaolin Has a high heat insulating effect and is more preferable as a filler for the undercoat layer. In the present invention, if necessary, the ultraviolet absorbent and the ultraviolet blocking agent of the present invention can be appropriately blended in the undercoat layer. The method for preparing the coating liquid for the undercoat layer is not particularly limited, and generally, water is used as a dispersion medium, and in addition to the binder and the filler, the ultraviolet absorber of the present invention, which is added as necessary, It is prepared by mixing an agent, an antifoaming agent and the like. The method for forming the undercoat layer is not particularly limited. For example, the undercoat layer is formed by applying and drying a coating solution for an undercoat layer on a support by various coating methods such as the method for forming a heat-sensitive recording layer.

In the case of providing a protective layer on the heat-sensitive recording layer in the heat-sensitive recording material of the present invention, such a protective layer is usually used.
It contains a water-soluble or water-dispersible binder and a filler. As the binder, the filler and the various auxiliaries, the materials exemplified as the components of the heat-sensitive recording layer can be appropriately used according to the required quality. At this time, it is more preferable to add a crosslinking agent to impart water resistance to the protective layer. In the present invention, if necessary, the ultraviolet absorbent and the ultraviolet blocking agent of the present invention can be appropriately blended in the protective layer. The method for preparing the coating liquid for the protective layer is not particularly limited, and generally, water is used as a dispersion medium, and in addition to the aqueous binder, the ultraviolet absorber, the ultraviolet ray blocking agent, and the filler of the present invention which are added as necessary. It is prepared by mixing an agent and a lubricant. The method for forming the protective layer is not particularly limited. For example, the protective layer is formed on the heat-sensitive recording layer by applying the coating liquid for the protective layer on the heat-sensitive recording layer by any of the various coating methods described above. In the case where an intermediate layer is provided between the heat-sensitive recording layer and the protective layer in the thermosensitive recording medium of the present invention, such an intermediate layer usually contains a binder and a filler. As the binder, the filler and the various auxiliaries, the materials exemplified as the components of the heat-sensitive recording layer can be appropriately used according to the required quality. At this time, a crosslinking agent may be added to impart water resistance to the intermediate layer. In the present invention, if necessary, the ultraviolet absorbent and the ultraviolet blocking agent of the present invention can be appropriately blended in the intermediate layer. The method for preparing the coating solution for the intermediate layer is not particularly limited, and generally, water is used as a dispersion medium, and in addition to the aqueous binder, the ultraviolet absorber, the ultraviolet ray blocking agent, and the filling agent of the present invention which are added as necessary. It is prepared by mixing an agent and a lubricant. The method for forming the intermediate layer is not particularly limited. For example, the intermediate layer is formed on the heat-sensitive recording layer by applying a coating liquid for the intermediate layer on the heat-sensitive recording layer by any of the various coating methods described above.

The support used in the heat-sensitive recording medium of the present invention includes heat-sensitive recording layers such as paper (acidic paper, neutral paper), recycled paper, plastic film, synthetic paper, nonwoven fabric, metal-deposited sheet, etc. Any layer can be used as long as it can hold the other layers provided.

[0055]

The present invention will be described below with reference to examples.
In addition, in description, unless otherwise indicated, a part shows a weight part.

<Production Example 1 of Ultraviolet Ray Blocking Agent> Flaky silica 5 serving as a core substance of the ultraviolet ray blocking agent used in the present invention
After dispersing 00 g in 10 liters of water, the mixture was dispersed for 1 hour using a despamill (manufactured by Hosokawa Micron). 80 ° C
264 g of a cerium nitrate aqueous solution (CeO ₂ content: 19% by weight, insoluble cerium compound deposition amount: 10% by weight as CeO ₂ ) was added dropwise to the mixture while heating and stirring. Subsequently, the mixture is neutralized to pH 7 to 9 with a sodium hydroxide solution, and cerium hydroxide is deposited on the silica surface to form a coating layer, which is then filtered, washed with water, dried and pulverized to obtain a flake-form cerium-coated silica. A pigment was obtained. Next, the cerium-coated silica pigment was dispersed in 10 liters of water, and then dispersed for 1 hour using a despamill. The dispersion is heated and stirred at 80 ° C. or higher while stirring No. 3 sodium silicate (SiO ₂ content: 28.5% by weight, amorphous silica deposition amount: 18% by weight as SiO ₂ ) 348
g was added. At this time, diluted sulfuric acid was also added to adjust the pH of the solution to 9 to
11 and continued stirring for another 1 hour,
Adjusted to ~ 8. This was filtered, washed with water, dried and pulverized to obtain a flake-form cerium-silica-coated silica pigment. Further, this is fired at 500 ° C. for 2 hours, and an ultraviolet ray blocking agent having a three-layer structure (CeO ₂ 10% by weight-SiO ₂ 18% by weight)
I got

<Production Example 2 of Ultraviolet Ray Blocking Agent> 488 g of cerium chloride CeCl ₃ was dissolved in water to prepare 3.3 liter of cerium chloride solution. Also, sodium hydroxide N
237 g of aOH was dissolved in water to prepare 3.3 liter of sodium hydroxide solution. A cerium chloride solution and a sodium hydroxide solution were simultaneously added dropwise to 8.5 liters of water heated to 30 to 40 ° C. with stirring so that the pH after the reaction was 9 to 11 and the temperature was kept at 50 ° C. or lower. After the dropping of both solutions was completed, stirring was continued for 30 minutes, and the pH of the reaction solution was adjusted to 5 or more. The resulting cerium hydroxide slurry was decanted and washed with water 4 to 5 times to prepare a cerium hydroxide slurry. Sodium silicate solution 5
62 g (SiO ₂ content: 28.5% by weight) was dissolved in water to prepare 2 liter of sodium silicate solution. 75.8 g of 95% by weight sulfuric acid was diluted with water to prepare 2 liter of dilute sulfuric acid solution. While heating and stirring the cerium hydroxide slurry at 80 ° C. or higher, a sodium silicate solution and a dilute sulfuric acid solution were simultaneously added dropwise so that the pH of the reaction solution could be maintained at 9 or higher. After stirring for 30 minutes after the dripping of both liquids was completed,
The pH of the reaction solution was adjusted to 7 to 8 with diluted sulfuric acid.
This was filtered, washed with water, dried and pulverized to obtain cerium oxide / amorphous silica composite particles containing 32% by weight of SiO ₂ .

<Manufacture of Thermosensitive Recording Material> [Example 1] In Example 1, the aqueous emulsion type polymer ultraviolet absorber of the preparation example was used for the protective layer, and the ultraviolet ray blocking agent of Production Example 1 was used for the thermosensitive recording layer. This is an example used. (1) Formation of undercoat layer 150 parts of 10% aqueous polyvinyl alcohol solution 250 parts of calcined kaolin (40% dispersion) 250 parts The materials were mixed and stirred at the above ratio to obtain a coating liquid for undercoat layer. This coating solution was applied and dried on one surface of a 50 g / m ² support at a coating amount of 5.0 g / m ² to form an undercoat layer. (2) Formation of heat-sensitive recording layer Each liquid of the following composition was applied to a sand glider with an average particle size of 1
Milled to a micron. Liquid A (developer liquid dispersion) 2,4'-dihydroxydiphenylsulfone 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts Liquid B (basic colorless dye dispersion) 3-di-butyl Amino-6-methyl-7-anilinofluoran (ODB-2) 2.0 parts 10% aqueous solution of polyvinyl alcohol 4.6 parts Water 2.6 parts Liquid C (sensitivity improver dispersion) parabenzylbiphenyl 4.0 Part 10% aqueous solution of polyvinyl alcohol 5.0 parts water 3.0 parts Liquid D (UV blocking agent dispersion liquid 1) 4.5 parts of UV blocking agent of Production Example 1 9.0 parts 10% aqueous solution of polyvinyl alcohol 9.0 parts water 9.0 parts Next, the dispersion liquid was mixed and stirred at the following ratio to obtain a coating liquid for a heat-sensitive recording layer. Liquid A 36.0 parts Liquid B 9.2 parts Liquid C 12.0 parts Liquid D 22.5 parts Kaolin clay (50% dispersion) 12.0 parts The above coating liquid was applied on the undercoat layer in an amount of 6.0 g / to obtain a heat-sensitive recording layer by coating and drying so as to m ^2. (3) Formation of protective layer A dispersion was mixed and stirred at the following ratio to obtain a coating liquid for a protective layer. 10% aqueous solution of polyvinyl alcohol 60.0 parts Aluminum hydroxide (50% dispersion) 30.0 parts Zinc stearate 10.0 parts Water 50.0 parts Aqueous emulsion type polymer ultraviolet absorber (30%) of preparation example 20 0.0 part of the above coating solution was applied onto the heat-sensitive recording layer so as to have a coating amount of 4.0 g / m ² and dried to obtain a protective layer. This sheet was treated with a super calender so that the Bekk smoothness was 200 to 600 seconds to obtain a heat-sensitive recording material.

Example 2 Example 2 is an example in which the aqueous emulsion type polymer ultraviolet absorber of the preparation example was used for the protective layer, and the ultraviolet blocking agent of Production Example 2 was used for the heat-sensitive recording layer. A heat-sensitive recording material was obtained in the same manner as in Example 1, except that in forming the heat-sensitive recording layer of Example 1, the solution E was mixed in place of the solution D in the coating solution for the heat-sensitive recording layer. E liquid (ultraviolet ray blocking agent dispersion liquid 2) 4.5 parts of ultraviolet ray blocking agent of Production Example 2 9.0 parts of 10% aqueous solution of polyvinyl alcohol 9.0 parts of water The liquid of the above composition was averaged with a sand glider to an average particle diameter of 1 micron. Grinded until

Example 3 Example 3 is an example in which the aqueous emulsion type polymer UV absorber of the Preparation Example was used for the protective layer, and the UV blocking agent of Production Example 1 was used for the undercoat layer.
Example 1 In the formation of the undercoat layer, in the same manner as in Example 1 except that the F solution was blended into the undercoat layer coating solution and the D solution was removed from the thermosensitive recording layer coating solution in forming the thermosensitive recording layer. A thermosensitive recording medium was obtained. Liquid F (UV blocking agent dispersion 3) UV blocking agent of Production Example 1 15.0 parts 10% aqueous solution of polyvinyl alcohol 30.0 parts Water 30.0 parts A solution of the above composition was averaged with a sand glider to an average particle diameter of 1 micron. Grinded until

Example 4 Example 4 is an example in which the aqueous emulsion type polymer ultraviolet absorber of the Preparation Example was used for the protective layer, and the ultraviolet blocking agent of Production Example 2 was used for the undercoat layer.
A thermosensitive recording medium was obtained in the same manner as in Example 3, except that the undercoat layer was formed with the solution G instead of the solution F in forming the undercoat layer. Liquid G (ultraviolet ray blocking agent dispersion liquid 4) 15.0 parts of the ultraviolet ray blocking agent of Production Example 2 30.0 parts of a 10% aqueous solution of polyvinyl alcohol 30.0 parts of water 30.0 parts of a liquid of the above composition was averaged with a sand glider to an average particle diameter of 1 micron. Grinded until

Example 5 In Example 5, the aqueous emulsion-type polymer ultraviolet absorber described in the above (Preparation example of ultraviolet absorber) was used for the heat-sensitive recording layer, and the ultraviolet ray shielding of Production Example 1 was used for the undercoat layer. It is an example of a heat-sensitive recording material without a protective layer using an agent. In the formation of the heat-sensitive recording layer in Example 3, the aqueous emulsion-type polymer UV absorber (30%) described in the above (Preparation Example of UV absorber) was added to the heat-sensitive recording layer coating solution in an amount of 1%.
A thermosensitive recording medium was obtained in the same manner as in Example 3, except that 5.0 parts were blended and the protective layer was not provided.

Example 6 In Example 6, the aqueous emulsion type polymer ultraviolet absorber of the preparation example was used for the heat-sensitive recording layer, and the ultraviolet blocking agent of Production Example 2 was used for the undercoat layer, and there was no protective layer. It is an example of a thermal recording medium. A thermosensitive recording medium was obtained in the same manner as in Example 5, except that in the formation of the undercoat layer of Example 5, the G solution was mixed in place of the F solution in the coating solution for the undercoat layer. The liquid of the above composition was ground with a sand glider to an average particle size of 1 micron.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 5 except that the undercoat layer was formed in the same manner as in Example 5 except that the solution F was removed from the undercoat layer coating liquid. [Comparative Example 2] Except that 50.0 parts of the aqueous emulsion type polymer ultraviolet absorber (30%) of the preparation example was blended in the undercoat layer coating liquid instead of the solution F in the formation of the undercoat layer in Example 5. In the same manner as in Example 5, a thermosensitive recording medium was obtained. [Comparative Example 3] In forming the heat-sensitive recording layer of Example 5, a solution prepared by removing the aqueous emulsion-type polymer UV absorber described in the above (Preparation example of UV absorber) from the coating solution for the heat-sensitive recording layer was used. Except for the above, a thermosensitive recording medium was obtained in the same manner as in Example 5. Comparative Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 5, except that the H liquid was used instead of the aqueous emulsion type polymer ultraviolet absorber used in the formation of the thermosensitive recording layer of Example 5. Liquid H (ultraviolet absorber dispersion liquid 1) 2,4-di-t-butylphenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate 4.5 parts 10% aqueous solution of polyvinyl alcohol 9.0 Part water 9.0 parts The liquid of the above composition was ground with a sand glider to an average particle size of 1 micron.

[Evaluation of light fastness] (1) The obtained thermal recording medium was manufactured by Okura Electric Co., Ltd.
Using an H-PMD (thermal recording paper printing tester, equipped with a Kyocera thermal head), applied energy 0.42 mJ
/ Dot. The density of the recording portion was measured with a Macbeth densitometer (RD-914, using an amber filter) (density: Da). (2) The thermosensitive recording medium printed under the above conditions was processed for 18 hours by a carbon arc fade meter (Toyo Seiki BH), and the density of the recording portion was measured under the above conditions (density: Db).
At the same time, the density of the white paper portion was measured by changing the filter used to blue (density: Dc). (3) Evaluation was performed by the following equation. Recording part light resistance (residual rate): Db / Da × 100 = Rd
(%) Blank part light resistance: The larger the value of Dc Rd, the better the light resistance of the recording part. Practically, 80% or more is desirable, and 85% or more is more desirable. Also, the smaller the value of Dc, the better the light resistance of the blank portion. Practically, 0.15 or less is desirable. The results are shown in Tables 1 and 2. In addition, A to E in Table 1 are respectively: A: aqueous emulsion type polymer ultraviolet absorber of the preparation example,
B: UV blocking agent of Production Example 1, C: UV blocking agent of Production Example 2, D: 2,4-di-t-butylphenyl-3 ′,
Represents 5'-di-t-butyl-4'-hydroxybenzoate.

[0066]

[Table 1]

[0067]

[Table 2]

As is clear from Table 2 above, when the aqueous emulsion type polymer UV absorber of the present invention is used in combination with an ultraviolet ray blocking agent, good light fastness is exhibited in both the background portion and the image portion. When these ultraviolet absorbers and ultraviolet blockers are used alone or in combination other than the present invention as in Comparative Examples 1 to 4, the light resistance is extremely poor as compared with the examples. Thus, it can be seen that a heat-sensitive recording medium excellent in light resistance can be obtained by using the aqueous emulsion type polymer ultraviolet absorber of the present invention and the ultraviolet ray blocking agent in combination.

[0069]

According to the present invention, a heat-sensitive recording medium having particularly good light fastness is provided.

Continued on the front page (72) Inventor Kaoru Hamada 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Japan Paper Manufacturing Co., Ltd. (72) Inventor Yoshihide Kimura 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Japan Paper Machinery F-term in Product Development Laboratory Co., Ltd. (reference) 2H026 AA07 BB02 BB24 DD15 DD32 DD46 DD53 DD55

Claims (3)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a colorless or light-colored basic colorless dye and an organic developer as main components. A vinyl compound monomer (b) copolymerizable with a monomer, a hydrophilic monomer (c), and at least one aqueous emulsion type polymer ultraviolet absorber comprising an emulsion copolymer with a reactive emulsifier (d), And a heat-sensitive recording material containing an ultraviolet ray blocking agent. 2. The ultraviolet blocking agent has a refractive index of 1.5 to 1.6.
2. The heat-sensitive recording material according to claim 1, comprising a baked product of particles having a three-layer structure in which the surface of the flaky pigment is coated with an insoluble cerium compound and amorphous silica. 3. The heat-sensitive material according to claim 1, wherein the ultraviolet ray blocking agent comprises an inorganic powder obtained by drying or firing particles having a two-layer structure in which an insoluble cerium compound is coated with amorphous silica. Record body.