JPH06305254A - Thermosensitive recording material - Google Patents

Abstract

PURPOSE:To provide a thermosensitive recording material with good light resistance which can be manufactured without difficulty. CONSTITUTION:An ultraviolet absorbing is encapsulated in a thermosensitive recording material in which a thermosensitive coloring layer and an ultraviolet absorbing layer containing the ultraviolet absorbing agent which is placed to reduce the ultraviolet incidence into the thermosensitive coloring layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material excellent in light resistance of recorded images and background.

[0002]

2. Description of the Related Art In recent years, heat-sensitive recording materials have been used in facsimiles, printers, etc., and have been used in various applications as the demand for them has increased, so that recorded images may be displayed outdoors or in the office for a long time. became. However, conventionally, the heat resistance of the heat-sensitive recording material is insufficient and there is a defect that the background is discolored and the image is discolored or discolored.

As a method for improving such drawbacks,
For example, there is known a method of providing a light-blocking layer in which an ultraviolet absorber is dispersed together with a protective colloid, but this method requires a large amount of the ultraviolet absorber because the ability to block ultraviolet rays is reduced by light scattering. Therefore, there is a disadvantage that not only the thermal sensitivity is lowered but also the light blocking layer becomes opaque, and the density of the recorded image is lowered (for example, Japanese Patent Publication No.
3-23205, JP-A-60-112487, JP-A-61-193883, and JP-A-61-24872.
No. 8, JP-A No. 54-18752, etc.).

Therefore, in order to solve the above-mentioned drawbacks, a method of emulsifying and dispersing an ultraviolet absorber to make the light blocking layer transparent has been proposed (for example, JP-A-4-197778), but in this case. However, since a flammable low-boiling solvent is used during emulsification, there are drawbacks such as background fog in the color-forming layer and the need for explosion-proof equipment during emulsification and coating.

[0005]

Therefore, as a result of diligent studies to solve the above-mentioned drawbacks, the present inventors have found that when an ultraviolet absorber is contained in a microcapsule,
Since the light scattering by the ultraviolet absorber can be prevented, the inventors have found that by doing so, the ultraviolet absorbing ability can be enhanced more than ever before and the present invention has been reached. Therefore, a first object of the present invention is to provide a heat-sensitive recording material having excellent light resistance. A second object of the present invention is to provide a thermal recording material excellent in coating suitability and light resistance without requiring explosion-proof coating equipment.

[0006]

The above objects of the present invention are to provide a thermosensitive coloring layer on a support, and an ultraviolet absorber provided so as to reduce the incidence of ultraviolet rays on the thermosensitive coloring layer. A heat-sensitive recording material having a UV-absorbing layer containing the above, wherein the UV-absorbing agent is contained in microcapsules.

In the present invention, an image is recorded by causing a color former and a developer, which are separated from each other at room temperature, to come into contact with each other by heating to develop a color. As a color former and a color developer, a combination of an electron-donating dye precursor (color former) and an electron accepting compound (color former), or a combination of a diazo compound (color former) and a coupling compound (color former) Is preferable, and it is particularly preferable to adopt the former combination from the viewpoint of image clarity.

The electron-donating dye precursor used in the present invention is not particularly limited, but it has a property of developing a color by donating an electron or accepting a proton such as an acid, and a lactone. Compounds having a partial skeleton such as lactam, sultone, spiropyran, ester, amide, etc., which are ring-opened or cleaved upon contact with a color developer, are generally colorless compounds. Examples of such electron-donating dye precursors include crystal violet lactone, benzoyl leuco methylene blue, malachite green lactone, rhodamine B lactam,
1,3,3-trimethyl-6'-ethyl-8'-butoxyindolinobenzospiropyran and the like.

As the electron-accepting compound (developing agent) for these color-forming agents, phenol compounds, organic acids or metal salts thereof, acidic substances such as oxybenzoic acid esters, etc. are used. 61-2911
No. 83. Examples of the heat-sensitive recording material in which the electron-donating dye precursor (color former) and the electron-accepting compound (developing agent) are combined are described in, for example, US Pat.
71,034, 4,839,332, JP-A-63.
No. 22682, No. 63-265682, No. 63
The details are described in JP-A-227375 and JP-A-1-105782.

The diazo compound that can be used in the present invention is a compound that reacts with a developer called a coupling component described below to develop a desired hue, and emits light of a specific wavelength before the reaction. It is a photodecomposable diazo compound that decomposes when received and no longer has the ability to develop color even when the coupling component acts. The hue in this coloring system is mainly determined by the diazo dye produced by the reaction of the diazo compound and the coupling component. Therefore, as is well known, the coloring hue can be easily changed by changing the chemical structure of the diazo compound or the chemical structure of the coupling component, and almost any coloring hue can be obtained depending on the combination. it can.

The photodecomposable diazo compound in the present invention mainly refers to an aromatic diazo compound, and more specifically, a compound such as an aromatic diazonium salt, a diazosulfonate compound or a diazoamino compound. The diazonium salt is
A compound represented by the general formula ArN ₂ ⁺ X ⁻ (wherein
Ar represents a substituted or unsubstituted aromatic moiety,
N ₂ ⁺ represents a diazonium group, and X ⁻ represents an acid anion). It is generally said that the photolysis wavelength of a diazonium salt is its absorption maximum wavelength. It is known that the absorption maximum wavelength of diazonium salt changes from about 200 nm to about 700 nm depending on its chemical structure ("Photolysis and chemical structure of photosensitive diazonium salt" written by Takahiro Tsunoda and Ao Yamaoka, Japan Photo Academic Journal 29 (4) pp. 197-205 (1965) That is, when a diazonium salt is used as a photodegradable compound, it is decomposed by light having a specific wavelength according to its chemical structure, and the chemical structure of the diazonium salt is If you change
Even when the coupling reaction with the same coupling component, the hue of the obtained dye changes.

Many diazosulfonates that can be used in the present invention are known, and they can be obtained by treating each diazonium salt with a sulfite. As the diazoamino compound which can be used in the present invention, the diazo group is coupled with dicyandiamide, sarcosine, methyltaurine, N-ethylanthranic acid-5-sulphonic acid, monoethanolamine, diethanolamine, guanidine and the like. It is a compound. Details of these diazo compounds are described in, for example, JP-A-2-136286.

The coupling component for forming a dye by coupling with the diazo compound (diazonium salt) used in the present invention includes, for example, 2-hydroxy-3-naphthoic acid anilide and resorcin as a starting point. -14
The thing described in 6678 can be mentioned. Further, by using two or more of these coupling components in combination, an image with any color tone can be obtained. Since the coupling reaction between these diazo compound and the coupling component easily occurs in a basic atmosphere, it is preferable to add a basic substance in the layer.

As the basic substance, a hardly water-soluble or water-insoluble basic substance or a substance which generates an alkali upon heating is used. Examples thereof are inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and their derivatives, thiazoles, pyrroles, pyrimidines,
Examples thereof include nitrogen-containing compounds such as piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines, formazines and pyridines. Specific examples of these are described, for example, in JP-A-61-291183. Two or more basic substances may be used in combination. Examples of the heat-sensitive recording material using a combination of the above-mentioned diazo compound (color former) and coupling compound (developing agent) include, for example, JP-B-2-28479 and 2-31.
No. 674 and No. 2-20434.

The color former used in the present invention can be usually used by dispersing it in a solid state, but from the viewpoint of raw storability of the heat-sensitive recording layer (prevention of fogging), such as preventing contact between the color former and the developer at room temperature. From the viewpoint of controlling the color developing sensitivity of causing color development with desired heat energy, etc., the color developing agent is used in the present invention by being encapsulated in microcapsules such as those used for the ultraviolet absorber described later.

The ultraviolet absorbent used in the ultraviolet absorbent layer in the present invention is not particularly limited and can be appropriately selected from known ultraviolet absorbents. Specific examples of the ultraviolet absorber include 2- (5-methyl-2'-hydroxyphenyl) benzotriazole and 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-. Benzotriazole, 2- (3,5-di-
t-butyl-2-hydroxyphenyl) benzotriazole, 2- (3-t-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2-
(3,5-di-t-butyl-2-hydroxyphenyl)
-5-chlorobenzotriazole, 2- (3,5-di-
t-amyl-2-hydroxyphenyl) benzotriazole, 5-t-butyl-3- (5-chloro-2H-benzotriazol-2-yl) -4-hydroxybenzenepropionic acid octyl ester, 2- (2'- Benzotriazole-based UV absorbers such as hydroxy-3′-n-dodecyl-5′-methyl) phenylbenzotriazole; 2-hydroxy-4-methoxybenzophenone, 2
Examples thereof include benzophenone-based ultraviolet absorbers such as -hydroxy-4-octoxybenzophenone.

As the benzotriazole type ultraviolet absorber, those which are solid at room temperature may be used, but those which are liquid at room temperature are preferably used from the viewpoint of production and the like. Specific examples of such a benzotriazole-based ultraviolet absorber that is liquid at room temperature are disclosed in JP-B-55-36984, JP-B-55-12587, and JP-A-58-2141.
This is described in detail in Japanese Patent Publication No. 52. Further, other preferable benzotriazole-based UV absorbers are disclosed in JP-A-58
-212844, 59-46646, 59-109055, Japanese Patent Publications 36-10466, 42-26187, 48-5496, 48-41572, and U.S. Patents. 3,75
4, 919 and 4,220,711.

Specific examples of the benzophenone type ultraviolet absorber include US Pat. No. 3,707,375 and JP-B-48-
30492, JP-A-47-10537 and 58-1.
11942, 59-945, 63-535.
Examples thereof include those described in each publication such as No. 44, or those synthesized according to the methods described therein. In addition to those described above, the ultraviolet absorber that can be used in the present invention is described in detail in JP-A-4-19778. In addition, the above-mentioned ultraviolet absorber,
You may use together hindered phenol, a hindered amine, a hydroquinone derivative, etc.

In the present invention, the light absorption of the ultraviolet absorber is prevented to enhance the ultraviolet absorbing ability to improve the light resistance of the recorded image and to absorb the ultraviolet light without using a flammable low boiling point solvent. From the viewpoint of providing a layer, the ultraviolet absorber is used after being microencapsulated. For the production of microcapsules that can be used in the present invention, any of the interfacial polymerization method, the internal polymerization method, and the external polymerization method can be adopted, but in particular, a core substance containing an ultraviolet absorber is used. , After emulsifying in an aqueous solution in which a water-soluble polymer is dissolved,
It is preferable to adopt an interfacial polymerization method of forming a wall of a polymer substance around the oil droplet.

The reactant forming the polymer substance is added inside the oil droplet and / or outside the oil droplet. Specific examples of the polymer substance include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer and the like. Preferred polymeric substances are polyurethanes, polyureas, polyamides, polyesters and polycarbonates, particularly preferably polyurethanes and polyureas. Two or more polymer substances can be used in combination. Specific examples of the water-soluble polymer include gelatin, polyvinylpyrrolidone, polyvinyl alcohol and the like.

For example, when polyurea is used as a capsule wall material, polyisocyanates such as diisocyanate, triisocyanate, tetraisocyanate and polyisocyanate prepolymer, and polyamines such as diamine, triamine and tetraamine, amino. The microcapsule wall can be easily formed by reacting a prepolymer containing two or more groups, piperazine or a derivative thereof, a polyol or the like with an interfacial polymerization method in an aqueous solvent. Further, for example, the composite wall made of polyurea and polyamide or the composite wall made of polyurethane and polyamide is prepared by using, for example, polyisocyanate and acid chloride or polyamine and polyol, and adjusting the pH of the emulsifying medium to be the reaction liquid, and then heating. Can be prepared by For details of the method for producing a composite wall composed of these polyurea and polyamide, see Japanese Patent Laid-Open No.
No. 8-66948.

In order to microencapsulate the ultraviolet absorbent, it is preferable to use the ultraviolet absorbent dissolved in an organic solvent. Examples of such an organic solvent include ethyl acetate, methyl acetate, carbon tetrachloride, chloroform, methanol, ethanol, n-butanol, low-boiling solvents such as dioxane, acetone and benzene, and carboxylic acid esters such as phosphoric acid ester and phthalic acid ester. , Fatty acid amides, alkylated biphenyls, alkylated terphenyls, chlorinated paraffins, alkylnaphthalenes, diarylethanes and the like. Such an organic solvent is described in detail in JP-A-4-197778.

The ultraviolet absorbing layer prepared by coating and drying the ultraviolet absorbing layer liquid prepared as described above by the method described below is used as a protective layer for the thermosensitive coloring layer (hereinafter, simply referred to as "thermosensitive layer") or as a thermosensitive layer. In the case of a multicolor thermosensitive recording material having two or more layers, it may be provided as an intermediate layer, but from the viewpoint of effectively preventing the light fading of a recorded image by absorbing ultraviolet rays before reaching the recording layer, It is preferable that it is provided on the upper side of the heat-sensitive color forming layer and adjacent to the heat-sensitive layer when viewed from the observation direction. The relationship between the ultraviolet absorbing layer and the thermosensitive coloring layer is described in detail in JP-A-4-19778. The amount of the ultraviolet absorber contained in the ultraviolet absorbing layer may be appropriately determined according to the characteristics of the ultraviolet absorber used, but it is usually preferably 0.01 to 2.00 g / m ² . If necessary, a pigment such as calcium carbonate or aluminum hydroxide, a release agent such as zinc stearate, or a binder or a surfactant to be used in the thermosensitive coloring layer, which will be described later, can be used in the ultraviolet absorbing layer. . When the ultraviolet absorbing layer is used as the protective layer, the additives to be used for the protective layer, which will be described later, can be appropriately used.

In the case of microcapsules containing a color-forming agent, a solid sensitizer may be added to swell the microcapsule wall when heated. As the solid sensitizer, those which are solid at room temperature and have a melting point of 50 ° C. or higher, preferably 120 ° C. or lower, can be selected and used from among the plasticizers of polymers used for the microcapsule wall. For example, when the wall material is made of polyurea or polyurethane, a hydroxy compound, a carbamic acid ester compound, an aromatic alkoxy compound, an organic sulfonamide compound, an aliphatic amide compound, an arylamide compound and the like are preferably used.

In the present invention, when a diazo compound is used as a color forming agent, a color forming auxiliary agent can be used. The coloring aid that can be used in the present invention is a substance that increases the coloring density during heating printing or lowers the minimum coloring temperature, lowers the melting point of the coupling component or the diazo compound, or capsule wall. This is to create a situation in which the diazo compound and the coupling component easily react with each other by the action of lowering the softening point of. Examples of the coloring aid include phenol compounds, alcoholic compounds, amide compounds, sulfonamide compounds, and the like, and specific examples thereof include p-tert-octylphenol, p-benzyloxyphenol, phenyl p-oxybenzoate, and benzyl carbanylate. , Phenethyl carbanylate, hydroquinone dihydroxyethyl ether, xylylenediol, N-hydroxyethyl-methanesulfonic acid amide,
Examples thereof include compounds such as N-phenyl-methanesulfonic acid amide. These may be contained in the core substance or may be added as a dispersion outside the microcapsules.

In the present invention, the above-mentioned color developer can be used by being dispersed in solid form, but it is used for OHP by improving the transparency of the thermosensitive recording layer and improving the light transmittance of the thermosensitive recording material. From the viewpoint of making a heat-sensitive recording material or a multi-color heat-sensitive recording material by laminating a plurality of heat-sensitive layers, it is dissolved in a poorly water-soluble or insoluble organic solvent, and then it is mixed with a surfactant and water-soluble. It can also be used in the form of a dispersion obtained by mixing with an aqueous phase having a polymer as a protective colloid and emulsifying and dispersing.

The organic solvent used in this case can be appropriately selected from high boiling point oils. Among them, preferable oils include dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, diisobutylbiphenyl, 1-methyl-1-dimethylphenyl-1-phenylmethane, and 1 in addition to esters.
-Ethyl-1-dimethylphenyl-1-phenylmethane, 1-propyl-1-dimethylphenyl-1-phenylmethane, triallylmethane (eg, tritoluylmethane, toluyldiphenylmethane), terphenyl compound (eg, terphenyl) , Alkyl compounds, alkylated diphenyl ethers (eg propyl diphenyl ether), hydrogenated terphenyls (eg hexahydroterphenyl), diphenyl ethers and the like.
Among these, it is particularly preferable to use esters from the viewpoint of emulsion stability of the emulsified dispersion.

Examples of the esters include phosphoric acid esters (eg, triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate, cresyl diphenyl phosphate), phthalic acid esters (dibutyl phthalate, 2-ethylhexyl phthalate, phthalic acid). Ethyl, octyl phthalate, butylbenzyl phthalate), tetrahydrophthalate dioctyl, benzoic acid ester (ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate, benzyl benzoate), abietic acid ester (ethyl abietic acid, Benzyl abietic acid), dioctyl adipate, isodecyl succinate, dioctyl azelate, oxalate ester (dibutyl oxalate, dipentyl oxalate), diethyl malonate, maleate ester (dimethyl maleate, maleic acid) Diethyl acid, dibutyl maleate), tributyl citrate, sorbate (methyl sorbate, ethyl sorbate, butyl sorbate), sebacate (dibutyl sebacate, dioctyl sebacate), ethylene glycol esters (formic acid monoester) And diesters, butyric acid monoesters and diesters, lauric acid monoesters and diesters, palmitic acid monoesters and diesters, stearic acid monoesters and diesters, oleic acid monoesters and diesters), triacetin, diethyl carbonate, diphenyl carbonate, ethylene carbonate, carbonic acid propylene,
Examples thereof include boric acid esters (tributyl borate, tripentyl borate) and the like. Among these, the use of tricresyl phosphate alone or in combination is preferable because the emulsion dispersion stability of the developer is particularly good. It is also possible to use the above oils in combination, or to use in combination with other oils.

In the present invention, an auxiliary solvent may be added to the above organic solvent as a dissolution aid having a low boiling point. As such an auxiliary solvent, for example, ethyl acetate, isopropyl acetate, butyl acetate, methylene chloride and the like can be mentioned as particularly preferable ones. The water-soluble polymer to be contained as a protective colloid in the aqueous phase mixed with the oil phase containing these components may be appropriately selected from known anionic polymers, nonionic polymers and amphoteric polymers. However, polyvinyl alcohol, gelatin, cellulose derivatives and the like are preferable. The surfactant contained in the aqueous phase may be appropriately selected from anionic or nonionic surfactants that do not cause precipitation or aggregation by acting on the protective colloid. Preferred surfactants include sodium alkylbenzene sulfonate, sodium alkylsulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether), and the like.

The emulsified dispersion of the present invention comprises an oil phase containing the above components, a protective colloid, and an aqueous phase optionally containing a surfactant, which are subjected to high speed stirring, ultrasonic dispersion, etc.
It can be easily obtained by mixing and dispersing by using a means usually used for fine particle emulsification. Further, the ratio of the oil phase to the water phase (oil phase weight / water phase weight) is preferably 0.02 to 0.6, and particularly preferably 0.1 to 0.4. If it is 0.02 or less, the amount of the aqueous phase is too large to be diluted and sufficient color developability cannot be obtained, and if it is 0.6 or more, the viscosity of the liquid is increased, which causes inconvenience in handling and a decrease in coating liquid stability.

When the ultraviolet absorbing layer solution or heat-sensitive layer solution (hereinafter referred to as heat-sensitive layer solution) prepared as described above is coated on a support, a known water-based or organic solvent-based coating solution is used for coating. Means are used. In this case, in order to safely and uniformly apply the heat-sensitive layer liquid and maintain the strength of the coating film, in the present invention, as the polymer binder, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, polyvinyl alcohol, Carboxy-modified polyvinyl alcohol,
Polyacrylamide, polystyrene and copolymers thereof,
Polyester and its copolymer, polyethylene and its copolymer, epoxy resin, acrylate and methacrylate resin and its copolymer, polyurethane resin, polyamide resin and the like can be used together with the microcapsules. Further, pigments, waxes, hardeners and the like may be added to the heat-sensitive recording layer, if necessary. The heat-sensitive recording layer should be coated such that the total amount of the color-developing agent and the color-developing agent is 0.1 to 10 g / m ² , and the thickness of the layer is 1 to 10 g.
It is desirable that the coating be performed so that the thickness becomes μm.

In the present invention, when the ultraviolet absorbing layer is not used as a protective layer, it is preferable to provide a separate protective layer on the heat-sensitive layer from the viewpoint of protection of the heat-sensitive layer and runnability in an actual machine. In particular, when the protective layer is required to have transparency, it is preferably made of at least silicon-modified polyvinyl alcohol and colloidal silica. When the protective layer is provided on the uppermost layer of the thermosensitive recording layer, the mechanical strength of the surface of the thermosensitive recording layer can be improved. A pigment, a metal soap, a wax, a cross-linking agent and the like are added to the protective layer for the purpose of improving matching property with a thermal head during thermal recording and improving water resistance of the protective layer. These pigments,
Details of the metallic soap, wax, cross-linking agent and the like are described in, for example, JP-A-2-141279.

Further, a surfactant is added to the coating solution for forming the protective layer in order to uniformly form the protective layer on the heat-sensitive recording layer. Surfactants include sulfosuccinic acid-based alkali metal salts and fluorine-containing surfactants.
Examples include sodium salts or ammonium salts of (2-ethylhexyl) sulfosuccinic acid, di- (n-hexyl) sulfosuccinic acid, and the like. Further, in the protective layer, a surfactant, a polymer electrolyte or the like for preventing the heat-sensitive recording material from being charged may be added. The solid coating amount of the protective layer is usually 0.2 to 5
g / m ² is preferable, and more preferably 1 g to 3 g / m ^2.
Is. When transparency is not required for the protective layer, a publicly known protective layer may be appropriately provided.

Since the ultraviolet absorbing layer according to the present invention absorbs incident ultraviolet rays to enhance the light resistance of the recorded image, when an opaque support is used, a heat sensitive layer is provided on the support. It is preferable to provide an ultraviolet absorbing layer on it. When a transparent support is used, it is preferable to provide two ultraviolet absorbing layers above and below the heat sensitive layer. In this case, one ultraviolet absorbing layer may be provided on the back surface of the support. Examples of the opaque support include paper, coated paper, synthetic paper, a paper laminated with a polymer film, an aluminum vapor deposition base, and a polymer film coated with a white pigment.

The paper used for the support is neutral paper having a heat extraction pH of 6 to 9 and sized with a neutral sizing agent such as alkyl ketene dimer (for example, JP-A-55).
No. 14281) is advantageous in terms of storage stability over time. Examples of the transparent support include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate film, polystyrene films, polypropylene films, polyolefin films such as polyethylene films, polyimide films, polyvinyl chloride films, and the like. Examples thereof include a polyvinylidene chloride film, a polyacrylic acid copolymer film, a polycarbonate film and the like, and these can be used alone or by laminating them, and a polyester film subjected to heat treatment and antistatic treatment is particularly preferable. The thickness of the support is 2
0 to 200 μm is used, and particularly 50 to 100 μm.
m is preferable.

In the present invention, when a plastic film or the like is used as the support, the support is applied before coating the heat-sensitive layer containing microcapsules in order to prevent the heat-sensitive recording layer from peeling from the support. It is desirable to provide an undercoat layer on the body. An acrylic ester copolymer, polyvinylidene chloride, SBR, aqueous polyester, etc. can be used as the undercoat layer, and the film thickness is
It is desirable that the thickness is 0.1 to 0.5 μm.

The undercoat layer may deteriorate the image recorded on the heat-sensitive layer if the undercoat layer swells due to the water contained in the heat-sensitive layer when the heat-sensitive layer is coated thereon. Glutaraldehyde, 2,3-dihydroxy-
It is desirable to cure using a dialdehyde such as 1,4-dioxane and a hardener such as boric acid. The amount of these hardeners added is in the range of 0.20% by weight to 3.0% by weight based on the weight of the undercoat material, and an appropriate amount can be selected according to the desired degree of curing.

The heat sensitive layer, the ultraviolet absorbing layer, the protective layer, the undercoat layer and the like are known in the art such as blade coating method, air knife coating method, gravure coating method, roll coating coating method, spray coating method, dip coating method and bar coating method. It is applied by the coating method of. The coating amount is preferably from 1 to 20 g / m ^2, particularly preferably a 3 to 10 g / m ^2.

[0039]

Since the heat-sensitive recording material of the present invention is provided with the ultraviolet absorbing layer containing the ultraviolet absorbent encapsulated in the microcapsules, the ultraviolet absorbing efficiency is good and the image light resistance is excellent. Further, since the flammable low-boiling point solvent is encapsulated in the microcapsules, not only the background fog does not occur, but also explosion-proof coating equipment is not required, which is extremely useful.

[0040]

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto.

Example 1. Preparation of coating solution for heat-sensitive layer As an electron-donating dye precursor, 2-anilino-3-methyl-6-N-dibutyl-aminofluorane (ODB-
2: 20 parts by weight of Yamamoto Kasei Co., Ltd.) and 20 parts by weight of bisphenol A as an electron-accepting compound were added to 100 parts by weight of a 5% by weight aqueous solution of polyvinyl alcohol (Kuraray PVA-105) to obtain an average particle diameter. 1.5μ
The particles were dispersed using a ball mill for 24 hours to obtain an electron-donating dye precursor dispersion liquid and an electron-accepting compound dispersion liquid, respectively. On the other hand, 80 parts by weight of calcium carbonate was added to 160 parts by weight of a 0.5% by weight sodium hexametaphosphate solution and dispersed using a homogenizer to obtain a pigment dispersion liquid. 5 parts by weight of the electron-donating dye precursor dispersion prepared as described above, 10 parts by weight of the electron-accepting compound dispersion, and 5 parts by weight of the pigment dispersion were mixed, and then an emulsion containing 21% by weight of zinc stearate. Add 3 parts by weight
By mixing, a heat-sensitive layer coating solution was obtained.

Preparation of coating liquid for UV absorbing layer Preparation of capsule liquid As a UV absorber, 2- (2'-hydroxy-3'-
16 parts by weight of n-dodecyl-5'-methyl) phenylbenzotriazole (TINUVIN-171: trade name of Ciba-Geigy Co., Ltd.) was added to 10 parts by weight of ethyl acetate and dissolved, and then as a capsule wall material, xylylenediene 10 parts by weight of a 3: 1 adduct of isocyanate and trimethylolpropane (Takenate D-110N: trade name of Takeda Pharmaceutical Co., Ltd.) was added and dissolved. The obtained solution was mixed with 5% by weight of polyvinyl alcohol (PVA217
E: 57 parts by weight of an aqueous solution (trade name of Kuraray Co., Ltd.) was mixed and emulsified and dispersed using an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.) so that the average particle diameter was 1.0 μm. After further adding 60 parts by weight of water to the obtained emulsified dispersion liquid, an encapsulation reaction was performed at 60 ° C. for 2 hours to prepare a capsule liquid.

Preparation of coating liquid 50 parts by weight of a 5% by weight aqueous solution of polyvinyl alcohol (PVA217E: trade name of Kuraray Co., Ltd.) and sodium dodecylbenzenesulfonate 1 were added to the obtained capsule liquid.
A UV absorbing layer coating solution was prepared by adding and mixing 3 parts by weight of a 0% by weight aqueous solution. Preparation of protective layer coating liquid To 14 parts by weight of an aqueous 8% by weight polyvinyl alcohol solution,
1% by weight of an aqueous solution of 2% by weight of sodium salt of di- (2-ethyl-hexyl) sulfosuccinic acid, 1.8% by weight of an emulsion of 20% by weight of zinc stearate, and 50% by weight of a kaolin dispersion (Kawo Bright: Schiele Kaolin) Co., Ltd. (The Thiele Kaolin Company)
13 parts by weight of a product name) was added and mixed to prepare a protective layer coating solution. Preparation of heat-sensitive recording material ^On a high-quality paper having a basis weight of 50 g / m ² , from the support side, the heat-sensitive layer had a solid content of 5.0 g / m ² , the ultraviolet absorbing layer had a solid content of 2.0 g / m ² , and a protective layer was provided. The coating solutions were simultaneously multilayer-coated so that the solid content was 2 g / m ^2, and then dried to obtain the heat-sensitive recording material of the present invention.

Example 2. The heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the heat-sensitive layer coating solution was changed to the following heat-sensitive layer coating solution and the coating amount of the heat-sensitive layer was changed to 10 g / m ² in terms of solid content. . Preparation of coating liquid for heat-sensitive layer Preparation of capsule liquid 2 parts by weight of 2-methyl-3-anilino-7-cyclohexyl-N-methylaminofluorane as an electron-donating dye precursor, and xylylene diisocyanate and tri-capsule as a capsule wall material. 18 parts by weight of a 3: 1 adduct of methylolpropane (Takenate D-110N: trade name of Takeda Pharmaceutical Co., Ltd.) was added to a liquid mixture of 24 parts by weight of diisopropylnaphthalene and 5 parts by weight of ethyl acetate, and then heated. . The obtained solution was added to a mixed solution of 3.5 parts by weight of an aqueous solution of 5% by weight of polyvinyl alcohol (PVA217E: trade name of Kuraray Co., Ltd.) and 58 parts by weight of water,
While stirring, the mixture was heated to 50 ° C. and the encapsulation reaction was carried out for 2 hours to prepare a capsule liquid.

Preparation of color developer dispersion 20 parts by weight of bisphenol A was added to 100 parts by weight of a 5% by weight aqueous solution of polyvinyl alcohol, and dispersed using a sand mill for 3 hours so that the average particle size was 1 μm. A dispersion was obtained. Preparation of Pigment Dispersion Liquid 40 parts by weight of calcium carbonate (Brilliant-15: a product of Shiraishi Kogyo Co., Ltd.) was added to 60 parts by weight of water, and dispersed so that the average particle diameter was 0.8 μm to obtain a pigment dispersion liquid. Obtained. Preparation of coating liquid 40 parts by weight of the capsule liquid prepared as described above, 20 parts by weight of the developer dispersion liquid, 15 parts by weight of the pigment dispersion liquid, and 2% by weight.
3 parts by weight of an aqueous solution of sodium dodecylbenzene sulfonate was mixed to obtain a heat-sensitive layer coating solution.

Example 3. Preparation of coating liquid for heat-sensitive layer Preparation of capsule liquid 12 parts by weight of 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluorane as an electron-donating dye precursor, and xylylene diisocyanate as a capsule wall material And 20 parts by weight of a 3: 1 adduct of trimethylolpropane (Takenate D-110N: trade name of Takeda Pharmaceutical Co., Ltd.), 12 parts by weight of 1-phenyl-1-xylylethane and 20 parts by weight of ethyl acetate were mixed. It was added to the liquid and heated. The obtained solution was added to a solution prepared by mixing 60 parts by weight of an aqueous solution of 8% by weight of polyvinyl alcohol (PVA217E: trade name of Kuraray Co., Ltd.) and 20 parts by weight of water, and using a homogenizer, the average particle diameter was 0.8.
The mixture was emulsified and dispersed to have a particle size of 100 μm, then 100 parts by weight of water was added, and then an encapsulation reaction was performed at 50 ° C. for 2 hours to prepare a capsule liquid.

Preparation of Developer Emulsion Dispersion Liquid 5 parts by weight of the developer represented by the following formula 1, 2 parts by weight of the developer represented by the following formula 2 and developer 8 represented by the following formula 3. 1 part by weight of 1-phenyl-1-xylylethane and 7 parts by weight of ethyl acetate were added to 1 part by weight, and the mixture was heated and dissolved. The resulting solution was added to a solution prepared by mixing 37 parts by weight of an 8% by weight polyvinyl alcohol aqueous solution, 35 parts by weight of water, and 0.2 parts by weight of sodium dodecylbenzenesulfonate so that the average particle diameter was 1.5 μm. , Ace Homogenizer (manufactured by Nippon Seiki Co., Ltd.) for emulsification and dispersion to obtain a color developer emulsion dispersion.

[Chemical 1]

[Chemical 2]

[Chemical 3] Preparation of coating liquid The thermosensitive layer coating liquid was prepared by stirring and mixing 5 parts by weight of the obtained capsule liquid, 10 parts by weight of the color developer emulsion dispersion, and 5 parts by weight of water.

Preparation of coating liquid for UV absorbing layer Preparation of capsule liquid As a UV absorber, 2- (2'-hydroxy-5'-
39 parts by weight of t-octylphenyl) benzotriazole, 20 parts by weight of 2- (3-t-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 20 parts by weight of 2-hydroxy-phenylsalicylate and 2 -Hydroxy-4-methoxybenzophenone 11
After adding 77 parts by weight of diisopropyl naphthalene and 15 parts by weight of ethyl acetate to a liquid, 3: 1 adduct of xylylene diisocyanate and trimethylolpropane (Takenate D-110N:
2 parts by weight of Takeda Pharmaceutical Co., Ltd.
It was heated and dissolved. The obtained solution was added to a polyvinyl alcohol aqueous solution containing sodium triisopropylnaphthalenesulfonate, and the mixture was emulsified and dispersed using a colloid mill so that the average particle diameter was 0.4 μm.
0 part by weight was added and the encapsulation reaction was carried out at 50 ° C. for 3 hours to obtain a capsule liquid. Preparation of coating liquid 50 parts by weight of a 5% by weight aqueous solution of polyvinyl alcohol (PVA217E: trade name of Kuraray Co., Ltd.) and sodium dodecylbenzenesulfonate 10 were added to the obtained capsule liquid.
A coating solution for the ultraviolet absorbing layer was prepared by adding and mixing 3 parts by weight of a wt% aqueous solution.

Preparation of coating solution for protective layer To 2 parts by weight of 8% by weight aqueous polyvinyl alcohol solution was added 4 parts by weight.
0.1 parts by weight of 0% by weight boric acid aqueous solution, 0.2 parts by weight of 20% by weight zinc stearate dispersion and 0.05 parts by weight of ammonium laurate were added and dispersed using a homogenizer to form a protective layer coating solution. Was prepared.

Preparation of heat-sensitive recording material On the polyethylene terephthalate, from the support side, the ultraviolet absorption layer had a solid content of 2.0 g / m ² , the heat-sensitive layer had a solid content of 7.0 g / m ² , and the ultraviolet absorption layer had a solid content. 2.0 g / m
^2. Simultaneous multi-layer coating of each coating solution so that the solid content of the protective layer was 2 g / m ² , followed by drying to obtain the heat-sensitive recording material of the present invention.

Example 4. A heat-sensitive recording material of the present invention was obtained in exactly the same manner as in Example 1 except that the heat-sensitive layer coating liquid was changed to the following heat-sensitive layer coating liquid. Preparation of coating solution for heat-sensitive layer As an electron-donating dye precursor, 2-anilino-3-methyl-6-N-dibutyl-aminofluorane (ODB-
2: Product name of Yamamoto Kasei Co., Ltd.) 20 parts by weight, and
20 parts by weight of 4-hydroxy-4′-isopropoxy-diphenyl sulfone as an electron-accepting compound was added to 100 parts by weight of an aqueous solution of 5% by weight of polyvinyl alcohol (Kuraray PVA-105), and the average particle diameter was 1.5 μm. As described below, the mixture was dispersed all day and night using a ball mill to obtain an electron-donating dye precursor dispersion liquid and an electron-accepting compound dispersion liquid, respectively. On the other hand, 80 parts by weight of calcium carbonate was added to 160 parts by weight of a solution containing 0.5% by weight of sodium hexametaphosphate and dispersed using a homogenizer to obtain a pigment dispersion liquid. 5 g of the electron-donating dye precursor dispersion prepared as described above, 10 g of the electron-accepting compound dispersion, 10 g of the sensitizer dispersion and 5 g of the pigment dispersion were mixed, and then a 21 wt% zinc stearate emulsion 3 g of the solution was added and mixed to obtain a heat-sensitive layer coating solution.

Comparative Examples 1-4. Thermal recording materials of Comparative Examples 1 to 4 were obtained in exactly the same manner as in Examples 1 to 4 except that the ultraviolet absorbing layer was not provided.

Comparative Examples 5-7. As described below, the heat-sensitive recording materials of Comparative Examples 5 to 7 were prepared in exactly the same manner as in Examples 1 to 3 except that the ultraviolet absorbent was not encapsulated into microcapsules but was emulsion-dispersed to prepare an ultraviolet absorbing layer coating solution. Obtained. Comparative Examples 5 and 6 (corresponding to Examples 1 and 2 ) 2- (2'-hydroxy-3'-n-dodecyl-5'-
Methyl) phenylbenzotriazole (TINUVIN
-171: 16 parts by weight of Ciba Geigy Co., Ltd.) was added to 10 parts by weight of ethyl acetate and dissolved, and then mixed with 66 parts by weight of a 5% by weight aqueous solution of polyvinyl alcohol (PVA217E: trade name of Kuraray Co., Ltd.). Emulsion dispersion was performed at 10,000 rpm using an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.) so that the average particle diameter was 1.0 μm. The obtained emulsified dispersion liquid further contains 5% by weight.
31 parts by weight of a polyvinyl alcohol (PVA217E: trade name of Kuraray Co., Ltd.) aqueous solution and 1.8 parts by weight of a 10% by weight sodium dodecylbenzenesulfonate aqueous solution were added and mixed to prepare a coating solution for the ultraviolet absorbing layer.

Comparative Example 7 (corresponding to Example 3) Example 3 except that a 3: 1 adduct of xylylene diisocyanate and trimethylolpropane (Takenate D-110N: trade name of Takeda Pharmaceutical Co., Ltd.) was not used. The composition is exactly the same as that of the ultraviolet absorbing layer coating liquid used in Example 3,
In the same manner as in the above, the coating liquid for ultraviolet absorbing layer was prepared by emulsifying and dispersing.

Image Recording and Light Resistance Test Each of the heat-sensitive recording materials of Examples and Comparative Examples prepared as described above was attached to a heat-sensitive printer (thermal imager FT).
Model I-210: trade name of Fuji Photo Film Co., Ltd.)
The image was recorded using. The recorded image was irradiated with light of 32,000 lux at 25 ° C. for 3 days using a fluorescent lamp, and the density of the image part and the background part before and after the light irradiation was measured by a densitometer (RD-918 type: Macbeth It was measured using a trade name manufactured by the company. In addition, the density of the background portion was measured as a yellow value, and the density of the image portion was measured as a visual value. The above results are summarized in Table 1.

[0056]

[Table 1] The results in Table 1 demonstrate the effectiveness of the present invention.

Claims (1)

[Claims] 1. A heat-sensitive recording material having a thermosensitive coloring layer on a support and an ultraviolet absorbing layer containing an ultraviolet absorber provided so as to reduce the incidence of ultraviolet rays on the thermosensitive coloring layer. A heat-sensitive recording material, wherein the ultraviolet absorber is encapsulated in microcapsules.