JPH0725150A - Alteration preventing recording method and thermal recording material therefor - Google Patents

Abstract

PURPOSE:To provide a hardly altered thermal recording method and a thermal recording material hardly altered in recorded content. CONSTITUTION:In a thermal recording material containing a combination of at least one kind of an electron donating dye precursor and a coupler and a combination of at least one kind of a diazo compd. and a coupler, thermal recording is performed by heat energy capable of developing the color forming components of both combinations and, subsequently, the entire surface of the recording material is irradiated with light having a wavelength capable of decomposing the diazo compd. to optically fix a recording image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prevention of falsification of thermal recording information, and more particularly to a falsification preventing recording method for a thermal recording material, and a thermal recording material suitable therefor.

[0002]

2. Description of the Related Art Thermosensitive recording materials have been used in various fields such as facsimiles and printers in recent years because they are highly reliable and require no maintenance, although the recording apparatus used is simple. . In recent years, its use has expanded to fields where there is a risk of being tampered with, such as payment slips of airlines, airline tickets, boarding tickets, and commuter passes, and methods to prevent tampering have been developed, but in the future, Further, it may be used for prepaid cards, credit cards, gift cards, lottery tickets, etc., and tampering prevention for such use has become more important.

As a method for preventing falsification of the thermal recording material,
A method in which an infrared absorption coloring layer and an opaque concealing layer are already combined to make visual reading difficult and information is read by infrared light (JP-A-4-129794 and JP-A-4-182188), and Thermal transfer sheet using a fluorescent substance (Japanese Patent Laid-Open Nos. 59-54598 and 6-59).
No. 1-222894), or a heat-sensitive recording material having an undercoat layer containing an inorganic fluorescent pigment between a substrate and the heat-sensitive recording layer (JP-A-4-135892).

However, if the visual reading is not possible, the application is inevitably limited. Further, in the case of Japanese Patent Application Laid-Open No. 4-135892, there is a drawback that when the falsification is performed by thermal recording, an image is formed by the fluorescent substance corresponding to the falsification, so that the falsification preventing function does not work.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made diligent studies to solve the above-mentioned drawbacks, and as a result, at least one electron-donating dye precursor and a color-developing agent were respectively developed as a thermochromic component. When the diazo compound is photolyzed after recording a mixed-color image on a heat-sensitive recording material containing a combination of agents and a combination of a diazo compound and a coupler, the initial recording is attempted even if thermal recording is attempted for falsification. The inventor has found that it is difficult to tamper with the image because the color mixture in (1) cannot be reproduced, and the present invention has been achieved. Therefore, a first object of the present invention is to provide a thermosensitive recording method that is not easily tampered with. A second object of the present invention is to provide a thermosensitive recording material in which recorded contents are not easily tampered with.

[0006]

The above objects of the present invention are to provide, as a thermochromic component, a combination of at least one electron-donating dye precursor and a developer, and at least one diazo compound and a coupler. Thermal recording on a heat-sensitive recording material containing a combination of the above-described combinations with heat energy capable of developing the color-forming components of both the combinations, and then irradiating the entire surface of the recording material with light having a wavelength capable of decomposing the diazo compound to perform optical fixing. This has been achieved by a tamper-proof recording method characterized by the above, and a heat-sensitive recording material used in the method.

In a heat-sensitive recording material, an image is recorded by heating a color-developing agent and a color-developing agent which are separated from each other at room temperature to bring them into contact with each other to develop a color. In the tamper-proof recording method of the present invention, in order to prevent tampering by making it difficult to reproduce the color mixture in the initial recording, an electron-donating dye precursor (color former) and a developer are contained in the heat-sensitive layer. And a combination of a diazo compound (color former) and a coupler (developing agent).

The above-mentioned electron-donating dye precursor is not particularly limited, but it has a property of developing a color by donating an electron or by accepting a proton such as an acid, and includes a lactone, a lactam and a sultone. , Spiropyran,
A generally colorless compound having a partial skeleton such as ester or amide, which is opened or cleaved by contact with a color developer, is usually used.

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 an electron-accepting compound (developing agent) for these color formers, acidic compounds such as phenol compounds, organic acids or metal salts thereof, and oxybenzoic acid esters are used. Specific examples thereof are, for example, JP-A-61- 29
1183.

The diazo compound is a compound which reacts with a color developer called a coupler to be described later to develop a desired hue, and is decomposed when light of a specific wavelength is received before the reaction, and the coupler no longer acts. It is a photodegradable diazo compound that loses its ability to develop color even if it is used. The hue in this coloring system is mainly determined by the diazo dye produced by the reaction of the diazo compound and the coupler. 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).

The photolysis wavelength of a diazonium salt is usually said to be 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.

As a light source for photolysis of diazo compounds,
Various light sources which emit light of a desired wavelength can be used, for example, various light sources such as various fluorescent lamps, xenon lamps, xenon flash lamps, mercury lamps of various pressures, photographic flashes and strobes. or,
In order to make the light fixing zone compact, the light source unit and the exposure unit may be separated by using an optical fiber. Many diazosulfonates are known and can be obtained by treating each diazonium salt with sulfite.

The diazoamino compound is a compound obtained by coupling a diazo group with dicyandiamide, sarcosine, methyltaurine, N-ethylanthranic acid-5-sulphonic acid, monoethanolamine, diethanolamine, guanidine and the like. . Details of these diazo compounds are described in, for example, JP-A-2-
No. 136286.

Examples of couplers for forming a dye by coupling with a diazo compound (diazonium salt) used in the present invention include, for example, 2-hydroxy-3-naphthoic acid anilide and resorcin as well as JP-A-62-14667.
The thing described in No. 8 can be mentioned. Further, by using two or more of these couplers in combination, an image with any color tone can be obtained. Since the coupling reaction between these diazo compound and the coupler 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 when heated 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.

The color former or developer used in the heat-sensitive recording material used in the tamper-proof recording method of the present invention can be used as a solid dispersion, but it prevents contact between the color former and the developer at room temperature. From the viewpoint of raw storage stability of the heat-sensitive recording layer (prevention of fog) and the control of color development sensitivity such as color development with desired heat energy, either one of a color former and a color developer is encapsulated in microcapsules. It is preferable.

Any of an interfacial polymerization method, an internal polymerization method, and an external polymerization method can be adopted for producing the above-mentioned microcapsules. In particular, the core substance is used in an aqueous solution in which a water-soluble polymer is dissolved. It is preferable to employ an interfacial polymerization method in which after emulsifying with, the wall of the polymer substance is formed 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,
Examples thereof include styrene-acrylate copolymer. 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, a polyisocyanate such as diisocyanate, triisocyanate, tetraisocyanate or polyisocyanate prepolymer, and a polyamine such as diamine, triamine or tetraamine, and an amino group are The microcapsule wall can be easily formed by reacting a prepolymer containing one or more of them, piperazine or a derivative thereof, a polyol or the like with an interfacial polymerization method in an aqueous solvent.

For example, the composite wall composed of polyurea and polyamide or the composite wall composed of polyurethane and polyamide is added, for example, by using polyisocyanate and acid chloride or polyamine and polyol after adjusting the pH of the emulsifying medium serving as the reaction liquid. It can be prepared by warming. For details of the method for producing a composite wall composed of these polyurea and polyamide, see JP-A-58-6.
6948.

In order to microencapsulate the color former, it is preferable to dissolve the color former in an organic solvent before use. 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-4-19778.

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.

When the developer is not microencapsulated, from the viewpoint of improving the transparency of the heat-sensitive recording layer, it is dissolved in an organic solvent that is sparingly soluble or insoluble in water, and then this is mixed with a surfactant. It is also possible to mix it with an aqueous phase having a water-soluble polymer as a protective colloid, and to use it in the form of an emulsified dispersion. The organic solvent used in this case can be appropriately selected from high boiling point oils.

Among the preferred oils, dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, diisobutylbiphenyl, 1-methyl-1-dimethylphenyl-1 are preferred as the oil.
-Phenylmethane, 1-ethyl-1-dimethylphenyl-1-phenylmethane, 1-propyl-1-dimethylphenyl-1-phenylmethane, triallylmethane (for example, tritoluylmethane, toluyldiphenylmethane), terphenyl compound ( For example, terphenyl),
Examples thereof include 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 emulsion 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. it can. Preferred surfactants include sodium alkylbenzene sulfonate, sodium alkylsulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether), and the like.

The emulsified dispersion is used for ordinary fine particle emulsification such as high speed stirring and ultrasonic dispersion of an oil phase containing the above components, a protective colloid, and an aqueous phase further containing a surfactant if necessary. It can be easily obtained by mixing and dispersing using a means. 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. 0.0
If it is 2 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 deterioration in coating liquid stability.

If necessary, a sensitizer, a pigment, a wax, a hardener, etc. may be added to the heat-sensitive layer. When applying the heat-sensitive layer liquid prepared as described above on the support, blade coating method, air knife coating method, gravure coating method, roll coating coating method, spray coating method, dip coating method, bar coating method, etc. A known coating means using a water-based or organic solvent-based coating liquid is used.

In this case, in order to apply the heat-sensitive layer liquid safely and uniformly and to maintain the strength of the coating film, in the present invention, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, polyvinyl alcohol, as a binder, Carboxy-modified polyvinyl alcohol, polyacrylamide, polystyrene and copolymers thereof, polyester and copolymers thereof, polyethylene and copolymers thereof, epoxy resin,
Acrylate and methacrylate resins and their copolymers, polyurethane resins, polyamide resins and the like can be used in combination for coating. The heat-sensitive layer is preferably applied such that the total amount of the color-developing agent and the color-developing agent is 1 to 20 g / m ² , and that the thickness of the layer is 1 to 20 μm.

The support used in the heat-sensitive recording material used in the present invention may be transparent or opaque. Examples of the transparent support include polyester films such as polyethylene terephthalate and polybutylene terephthalate,
Cellulose derivative film such as cellulose triacetate film, polystyrene film, polypropylene film,
Examples thereof include a polyolefin film such as a polyethylene film, a polyimide film, a polyvinyl chloride film, a polyvinylidene chloride film, a polyacrylic film, a polycarbonate film, and the like, and these can be used alone or in combination. On the other hand, examples of the opaque support of the recording material include paper, synthetic paper, an aluminum vapor deposition base, and the above transparent support coated with a pigment or the like.

When a polymer film is used as the support, an undercoat is applied on the support before the application of the heat-sensitive layer liquid containing microcapsules or the like for the purpose of preventing the whole heat-sensitive layer from peeling off from the support. It is desirable to provide layers. As the undercoat layer, an acrylic ester copolymer,
Polyvinylidene chloride, SBR, aqueous polyester and the like can be used, and the film thickness is preferably 0.1 to 0.5 μm. The undercoat layer composed of these compositions is applied by the same application method as that for applying the heat-sensitive layer liquid. The coating amount is preferably set to 0.1 to 10 g / m ^2, particularly preferably a 0.2 to 2 g / m ^2.

The uppermost layer of the heat-sensitive recording material used in the present invention is provided with a protective layer containing at least a fluorescent agent and a water-soluble resin in order to effectively prevent tampering with water-based ink, oil-based ink or pencil. Is preferred. The fluorescent agent is not particularly limited, and can be appropriately selected and used from known organic fluorescent agents and inorganic fluorescent agents.

As the organic fluorescent agent, for example, the following chemical formula 1
And the like.

[Chemical 1] Examples of the inorganic fluorescent agent include, for example, JP-A-4-1358.
Those described in Japanese Patent Publication No. 92 can be mentioned.

The above-mentioned water-soluble resin is not particularly limited and can be appropriately selected and used from known water-soluble resins. As the water-soluble resin, for example, polyvinyl alcohol, silicon-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch and its induction resistance, casein,
Examples thereof include sodium alginate, polyvinylpyrrolidone, sodium polyacrylate, polyacrylamide, styrene / maleic acid copolymer salt, polyurethane resin, urea resin and melamine resin.

The protective layer composed of these compositions is applied by the same application method as that for applying the heat-sensitive layer liquid.
The solid coating amount of the protective layer is preferably usually 0.2-5 g / m ^2, particularly preferably in 1 to 3 g / m ^2. The content of the fluorescent agent in the protective layer is preferably 0.5 to 30% by weight from the viewpoint of facilitating visual confirmation of tampering.

The tamper-proof recording method of the present invention is carried out as follows using the heat-sensitive recording material prepared as described above. That is, thermal recording is performed with heat energy capable of producing a color by both the color-forming components of the combination of the electron-donating dye precursor and the color developer (called leuco type) and the combination of the diazo compound and coupler (called diazo type), and then Light having a wavelength capable of decomposing the diazo compound is irradiated onto the entire surface of the recording material to be optically fixed.

As a result, the hue of the heat-recorded portion becomes a mixture of the leuco-based hue and the diazo-based hue, while the recording material is already photo-fixed even if heat recording is performed for tampering. Since the color components of the diazo color are no longer colored, only the color components of the leuco color are colored, so the hue of the recorded image will be different from the original when tampered with, and tampering can be easily detected. As a result, tampering can be substantially prevented.

Furthermore, when the heat-sensitive recording material of the present invention provided with a protective layer containing the above-mentioned fluorescent agent is tampered with by using an aqueous ink, the water-soluble resin is dissolved to cause bleeding in the recording portion, or When tampering with oil-based ink or pencil, fluorescence is blocked. Therefore, it is possible to easily prevent not only falsification due to thermal recording but also falsification due to these.

[0041]

According to the tamper-proof recording method of the present invention, it is difficult to tamper because the same hue as the original hue cannot be reproduced even after heat recording and optical fixing and then heat recording for tampering. Excellent tamper resistance. Further, when the heat-sensitive recording material of the present invention provided with a protective layer is used, not only tampering by thermal recording but also tampering with water-based ink, oil-based ink or pencil makes it easy to find tampering. Therefore, it has excellent tamper resistance.

[0042]

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 electron-donating dye precursor capsule liquid 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane (electron-donating dye precursor) 14
g, 75% by weight ethyl acetate solution of xylylene diisocyanate and trimethylolpropane (3: 1) adduct (Takenate D-110N: trade name of capsule wall material manufactured by Takeda Pharmaceutical Co., Ltd.) 60 g, and ultraviolet absorber (Sumithorpe) 200: Trade name of Sumitomo Chemical Co., Ltd.) 2 g, 1-
It was added and dissolved in a mixed solvent of 55 g of phenyl-1-xylylethane and 55 g of methylene chloride.

100 g of an aqueous solution of 8% by weight of polyvinyl alcohol, 40 g of water, and 1.4 g of a sodium salt of dioctyl sulfosuccinate (dispersing agent) of 2% by weight were obtained.
After being mixed with the aqueous solution of 1., the mixture was emulsified and dispersed at 10,000 rpm for 5 minutes using an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.). The resulting emulsified dispersion is further treated with water 150
After adding g, the encapsulation reaction was carried out at 40 ° C. for 3 hours to prepare an electron donating dye precursor capsule liquid having an average particle size of microcapsules of 0.7 μm.

Preparation of developer liquid 20 g of bisphenol A (developer), 20 g of 4-ethoxyphenyl-4'-chlorobenzyl ether (sensitizer)
Were dispersed with 100 g of a 5% by weight aqueous solution of polyvinyl alcohol (Kuraray PVA-105) on a pole mill for 24 hours to obtain dispersions having an average particle diameter of dispersoid of 1.5 μm.

Preparation of Pigment Liquid 80 g of calcium carbonate and 0.5 g of sodium hexametaphosphate
A 160% by weight solution was dispersed with a homogenizer to obtain a pigment dispersion. Preparation of diazo compound capsule liquid 4-N-hexyl-N- (4-methoxyphenoxyisopropoxy) amino-2-hexyloxybenzenediazonium-hexafluorophosphate (diazo compound) 2.0 parts, 2,2-dimethoxy- 2-Phenylacetophenone (0.4 parts) was dissolved in 20 parts of ethyl acetate, and then isopropyldiphenylethane (a high-boiling solvent) was added to the solution.
0 part was added, heated and uniformly mixed, and 15 parts of a xylylene diisocyanate and 1: 3 adduct of trimethylolpropane as a capsule wall agent was added to prepare a diazo compound liquid.

Separately, polyvinyl alcohol (polymerization degree: 17
00 parts, 54 parts of 6 wt% aqueous solution of saponification degree 88%) were prepared, the above diazonium compound solution was added, and the mixture was emulsified and dispersed at 5000 rpm for 1 minute using a homogenizer. After 68 parts of water was added to the obtained emulsified dispersion to make it uniform, the temperature was raised to 40 ° C. with stirring and the encapsulation reaction was carried out for 3 hours to obtain a target diazo compound capsule solution. The average particle size of the capsule was 1.0 μm.

Preparation of coupler emulsion dispersion N-phenyl-N '-(2,5-dioctoxyphenyl) barbituric acid 2.0 parts, 1,2,3-triphenylguanidine 2.0 parts, trichl. Dil phosphate 0.
3 parts and 0.1 part of diethyl maleate were dissolved in 10 parts of ethyl acetate. The resulting solution was treated with 10 parts of 1- (2′-octylphenyl) -3-methyl-5-pyrazolone and 20 parts of dodecyl parahydroxybenzoate, 50 parts of a 6% by weight polyvinyl alcohol aqueous solution and 2% by weight of sodium dodecyl sulfonate. An aqueous solution was added to the mixed solution, and the mixture was emulsified and dispersed using a homogenizer to prepare a coupler emulsion dispersion.

Preparation of coating liquid for heat-sensitive recording Obtained electron-donating dye precursor microcapsule liquid 5
g, a developer dispersion 10 g, a sensitizer dispersion 10 g, a pigment dispersion 15 g, a diazo compound capsule liquid 5 g and a coupler emulsion dispersion 15 g, and further, 21 wt% zinc stearate emulsion 3 g, melting point 68 ° C. 2 g of the paraffin wax dispersion (Hidrin D-337; trade name of Chukyo Yushi Co., Ltd.) was added to obtain a coating liquid for heat-sensitive recording.

Preparation of heat-sensitive recording material The obtained heat-sensitive recording coating liquid was applied to a wood free paper having a basis weight of 64 g / m ² using a coating bar so that the dry weight of the heat-sensitive layer was 5 g.
/ M ² and coated at 50 ° C. for 3 minutes to obtain a thermosensitive recording paper.

Formation of protective layer 7.4% by weight of polyvinyl alcohol (PVA-11
7; trade name of Kuraray Co., Ltd .; tear strength at 20 ° C. 60% RH is 4.0 kg / mm) Aqueous solution 409.5
g, 30% by weight zinc stearate emulsion 13.
3 g, 15 g of an inorganic fluorescent pigment made of Y ₂ O ₂ S and 100 g of water were added and mixed well to prepare a protective layer stock solution. Further, 27 g of amorphous silica (Nipseal E-150; trade name of Nippon Silica Co., Ltd.) and 0.27 g of sodium hexametaphosphate were dispersed with 73 g of water by a homogenizer to obtain a silica dispersion.

Similarly, 27 g of light calcium carbonate (light calcium carbonate PC; trade name of Shiraishi Industry Co., Ltd.),
0.27 g of sodium hexametaphosphate and 63 g of water were dispersed with a homogenizer to obtain a light calcium carbonate solution.
Next, 400 g of the protective layer stock solution, 6.45 g of the light calcium carbonate dispersion and 10.0 g of the amorphous silica dispersion were mixed to obtain a coating solution for the protective layer. The resulting coating liquid was applied onto the heat-sensitive layer previously formed so that the dry weight was 2.0 g / m ² , to obtain the desired heat-sensitive recording paper.

Evaluation test A bar code was recorded on the obtained heat-sensitive recording paper with an energy of 20 mJ / mm ² using a line head thermal head, and then an ultraviolet lamp with an emission center wavelength of 365 nm and an output of 40 W was used for 6 seconds. All surface light irradiation, thermal recording and optical fixing, then recording (tampering) with a heated soldering iron, recording with an aqueous pen,
Those recorded (altered) using an oil-based pen and those recorded using a pencil were visually evaluated under white light and UV irradiation. The results are as shown in Table 1.

Example 2. A thermal recording paper was prepared in the same manner as in Example 1 except that the protective layer in Example 1 was not provided, and evaluated in the same manner as in Example 1. The results are as shown in Table 1.

Example 3. A thermal recording paper was prepared in the same manner as in Example 1 except that the fluorescent agent used in the protective layer in Example 1 was not used, and evaluated in the same manner as in Example 1. The results are as shown in Table 1.

Comparative Example 1. A thermal recording paper was prepared in the same manner as in Example 1 except that the diazo compound capsule liquid and the coupler emulsion dispersion were not used, and evaluated in the same manner. The results are as shown in Table 1.

[0057]

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

Claims (2)

[Claims] 1. A thermosensitive recording material containing a combination of at least one electron-donating dye precursor and a developer as a thermochromic component, and at least one diazo compound in combination with a coupler. A tamper-proof recording method, which comprises thermally recording with a thermal energy capable of developing a color-forming component together, and then irradiating light having a wavelength capable of decomposing the diazo compound onto the entire surface of the recording material to perform optical fixing. 2. A heat-sensitive recording material containing a combination of an electron-donating dye precursor and a color developer, and a combination of a diazo compound and a coupler, as a heat-coloring component.
A heat-sensitive recording material, characterized in that a protective layer containing at least a fluorescent agent and a water-soluble resin is provided on the uppermost layer of the heat-sensitive recording material.