JPH07276807A - Multicolor thermal recording material and thermal recording method using the same - Google Patents

Abstract

PURPOSE:To provide a multicolor thermal recording material capable of sharply reproducing two or more developed hues and excellent in production aptitude and a thermal recording method using the same. CONSTITUTION:In a multicolor thermal recording material wherein a thermal recording layer containing at least a microcapsule including a diazo compd., a microcapsule including a coupler reacting with the diazo compd. to form a color and a colorless or light-colored electron donating dye precursor and an electron acceptive compd. reacting with the electron donating dye precursor to develop a hue different from the developed hue due to the coupling reaction of the diazo compd. is provided on a support, the glass transition point of the wall material of the microcapsule including the diazo compd. is lower than that of the wall material of the microcapsule including the electron donating dye precursor.

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 an inexpensive multicolor heat-sensitive recording material which is excellent in manufacturing suitability and a heat recording method using the same.

[0002]

2. Description of the Related Art In a thermal recording method, (1) development is unnecessary, (2) when the support is paper, the paper quality is close to that of ordinary paper,
(3) Easy to handle, (4) High color density,
(5) The recording device is simple and inexpensive, and (6) there is no noise at the time of recording. Therefore, it has been rapidly popularized in the field of monochrome facsimiles and printers in recent years. These heat-sensitive recording materials are those in which a heat-sensitive recording layer containing a color former and a developer is provided on a support such as paper or synthetic paper, and based on an electric signal corresponding to the original using a thermal head. Recorded by the heating process. Even in such a recording field, with the rapid development of the information industry, there is an increasing demand for obtaining a color hard copy from a terminal of an information device such as a computer or a facsimile.

As a multicolor thermosensitive recording material which meets such a demand, a recording material has already been used in which two kinds of color forming components which form different color tones at different coloring temperatures are mixed and used in the same thermosensitive coloring layer (Japanese Patent Publication No. 49-69), a recording material in which a thermosensitive coloring layer having a high coloring temperature and a thermosensitive coloring layer having a low coloring temperature are sequentially laminated on a support (Japanese Patent Publication No. 51-19989).
No. 54-88135, 55-133991.
Nos. 55-133992 and 48-15540), a thermosensitive coloring layer having a high coloring temperature and a thermosensitive coloring layer having a low coloring temperature are sequentially laminated on a support, and a color is formed in the low temperature coloring layer. Recording materials containing an erasing agent having the effect of erasing the components (Japanese Patent Publication No. 17866/1975)
Nos. 1-5791, JP-A-55-161688 and the like) have been developed.

However, all of these recording materials have a drawback in that color mixing and color blurring occur in the image, and a clear and stable color image cannot be obtained.
The present applicant, as a recording material for solving the above problems,
We have already developed a heat-sensitive recording material in which a thermochromic element which is composed of a diazo compound and a coupling component and develops different colors is provided on a support, and generally good results have been obtained (JP-A-61-40193). Gazette). However, the above-mentioned heat-sensitive recording material has a drawback that the manufacturing cost of the recording material is increased because the color-forming component is contained in each recording layer for each different hue.

[0005]

The inventors of the present invention have made diligent studies to solve the above-mentioned drawbacks, and as a result, as a color-forming component, a diazo compound, a coupler and an electron-donating dye precursor capable of forming different hues have been developed. A diazo compound is encapsulated in a microcapsule composed of a wall material having a low glass transition point by using a combination of a compound and an electron-accepting compound, and an electron-donating dye precursor is added to the glass transition point having a glass transition point higher than the glass transition point of the microcapsule wall. It has been found that extremely good results can be obtained when the microcapsules made of a wall material having dots are included, and the present invention has been completed. Therefore, a first object of the present invention is to provide a multicolor heat-sensitive recording material which has a clear image, is inexpensive, and has excellent manufacturing suitability. A second object of the present invention is to provide a method for easily performing multicolor recording excellent in color separation.

[0006]

The above-mentioned various objects of the present invention include at least a microcapsule encapsulating a diazo compound and a coupler capable of developing a color by a coupling reaction with the diazo compound on the outside of the microcapsule, and a colorless Alternatively, a microcapsule containing a light-colored electron-donating dye precursor therein, and an electron which reacts with the electron-donating dye precursor outside the microcapsule and develops a hue different from the hue developed by the coupling reaction of the diazo compound. A multicolor thermosensitive recording material having a thermosensitive recording layer containing a receptive compound on a support, wherein the glass transition point of the capsule wall material of the microcapsules encapsulating the diazo compound is the electron-donating dye precursor. A multicolor thermosensitive recording material characterized by being lower than the glass transition point of the capsule wall material of the encapsulated microcapsules and It was achieved by thermal recording method using the record.

Diazo compound (color former) used in the present invention
Is a compound which causes a color reaction upon contact with a coupler (developing agent) by heating, and a compound which develops a color different from that of the electron-donating dye precursor (coloring agent) described later is selected. The coupler which develops a color by reacting with the diazo compound and the diazo compound by heating is a known photodegradable diazo compound and a coupler capable of reacting with the diazo compound to form a dye. If necessary, a basic substance or the like is used to accelerate the reaction between the diazo compound and the coupler.

The photodecomposable diazo compound in the present invention mainly means an aromatic diazo compound, and more specifically, an aromatic diazonium salt, a diazosulfonate compound, a diazoamino compound and the like. Among these, it is particularly preferable to use a diazonium salt from the viewpoint of thermal sensitivity. The diazonium salt of the general formula _{^{Ar-N 2 + X - (}} Ar wherein represents an aromatic moiety, N ₂ ⁺ diazonium salt,
X ⁻ represents an acid anion). These diazonium salts have various maximum absorption wavelengths depending on the positions and types of substituents on the Ar moiety. Specific examples of the acid forming the diazonium salt include HP
F ₆ , HBF ₄ , HB (Ph) ₄ C _n F _{2n + 1} COOH
(N is 3-9 _{integer), C m F 2m + 1} SO 3 H (m is 2
8 is an integer). However, Ph represents a phenyl group.

The diazo compound used in the present invention is
It is preferable that the hue that develops by heating becomes red. As a diazo compound that develops red (hereinafter, referred to as a red-colored diazo compound), not only a diazo compound that independently develops red, but a diazo compound that develops yellow (hereinafter referred to as a yellow-colored diazo compound) and magenta are developed. It is also possible to use a diazo compound (hereinafter referred to as a magenta coloring diazo compound) to mix colors to develop a red color.

Examples of red-colored diazo compounds include diazonium salts having a photolytic wavelength of 340 to 370 mμ. Specific examples of the red-colored diazonium salt having a photolytic wavelength of 340 to 370 mμ include 1-diazo-4.
-(N, N-dioctylcarbamoyl) benzene, 1-
Diazo-2-octadecyloxybenzene, 1-diazo-4- (4-tertiary-octylphenoxy) benzene, 1-diazo-4- (2,4-ditertiary-amylphenoxy) benzene, 1-diazo-2- (4 -Tertiary-octylphenoxy) benzene, 1-diazo-5
-Chloro-2- (4-tert-octylphenoxy) benzene, 1-diazo-2,5-bis-octadecyloxybenzene, 11-diazo-4- (N-octyltheuroylamino) benzene and the like can be mentioned. .

Specific examples of the yellow or magenta coloring diazo compound include 4- (N- (2- (2,4-di-te
rt-Amylphenoxy) butyryl) piperazino) benzenediazonium, 4-dioctylaminobenzenediazonium, 4- (N- (2-ethylhexanoyl) piperazino) benzenediazonium, 4-dihexylamino-2-hexyloxybenzenediazonium, 4- N-
Ethyl-N-hexadecylamino-2-ethoxybenzenediazonium, 3-chloro-4-dioctylamino-
2-octyloxybenzenediazonium, 2,5-dibutoxy-4-morpholinobenzenediazonium, 2,
5-octoxy-4-morpholinobenzenediazonium, 2,5-dibutoxy-4- (N- (2-ethylhexanoyl) piperazino) benzenediazonium, 2,5
-Diethoxy-4- (N- (2- (2,4-di-ter
Examples thereof include t-amylphenoxy) butyryl) piperazino) benzenediazonium, 2,5-dibutoxy-4-tolylthiobenzenediazonium, and 3- (2-octyloxyethoxy) -4-morpholinobenzenediazonium.

In the present invention, in particular, these hexafluorophosphate salts, tetrafluoroborate salts,
And 1,5-naphthalene sulfonate salts are useful because they have low solubility in water and are soluble in organic solvents. Examples of the coupler that reacts with the diazo compound used in the present invention to produce a color upon heating include resorcin, phloroglucin, sodium 2,3-dihydroxynaphthalene-6-sulfonate, 1-hydroxy-2-naphthoic acid morpholinopropylamide, 1, 5-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,3-dihydroxy-6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid anilide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-hydroxy-3- Naphthoic acid octylamide, 2-hydroxy-3-naphthoic acid-N-dodecyloxypropylamide, 2-hydroxy-3-naphthoic acid tetradecylamide;

Acetanilide, acetoacetanilide,
Benzoylacetanilide, 2-chloro-5-octylacetoacetanilide; 1- (2-tetradecanooxyphenyl) -2-carboxymethylcyclohexane-3,
5-dione, 1-phenyl-3-methyl-5-pyrazolone, 1- (2'-octylphenyl) -3-methyl-5
-Pyrazolone, 1- (2 ', 4', 6'-trichlorophenyl) -3-benzamido-5-pyrazolone, 1-
(2 ', 4', 6'-trichlorophenyl) -3-anilino-5-pyrazolone, 1-phenyl-3-phenylacetamido-5-pyrazolone and the like can be mentioned. Two or more of these couplers may be used in combination.

The basic substance that accelerates the reaction between the diazo compound and the coupler includes an inorganic or organic basic compound, as well as a compound that decomposes upon heating to release an alkaline substance. Typical examples include organic ammonium salts, organic amines, amides, urea and thiourea, 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 include tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine; allylurea, thiourea, methylthiourea, allylthiourea, ethylenethiourea; 2
-Benzylimidazole, 4-phenylimidazole,
2-phenyl-4-methylimidazole, 2-undecylimidazoline, 2,4,5-trifuryl-2-imidazoline, 1,2-diphenyl-4,4-dimethyl-2-
Imidazoline, 2-phenyl-2-imidazoline;

1,2,3-triphenylguanidine,
1,2-dicyclohexylguanidine, 1,2,3-tricyclohexylguanidine, guanidine trichloroacetate; N, N'-dibenzylpiperazine;4,4'-dithiomorpholine, morpholinium trichloroacetate; 2
-Aminobenzothiazole, 2-benzoylhydrazinobenzothiazole and the like. These may be used in combination of two or more.

The colorless or light-colored electron-donating dye precursor (color former) used in the present invention is substantially colorless before being heated, and when heated, it is brought into contact with an electron-accepting compound (developing agent). Is a compound which develops a color reaction based on the above, and develops a color different from that of the diazo compound (color former). Also,
A low melting point organic compound or the like that helps these react with each other when heated is used as a sensitizer.

The electron-donating dye precursor used in the present invention is particularly preferably an electron-donating dye precursor that exhibits a blue hue when heated (referred to as a blue-coloring dye precursor). As described above, by selecting a red-coloring compound as the diazo compound and a blue-coloring compound as the electron-donating dye precursor, it is possible to easily carry out black recording which is most needed. Examples of the electron-donating dye precursor include triarylmethane-based compounds, diphenylmethane-based compounds, thiazine-based compounds, xanthene-based compounds, spiropyran-based compounds, and the like, but particularly triarylmethane-based compounds and xanthene-based compounds have a coloring density. Is useful because it is expensive.

Specific examples thereof include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (that is, crystal violet lactone),
3,3-bis (p-dimethylamino) phthalide, 3-
(P-Dimethylaminophenyl) -3- (1,3-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-
3-yl) phthalide, 3- (o-methyl-p-dimethylaminophenyl) -3- (2-methylindole-3-
Il) phthalide;

4,4'-bis (dimethylamino) benzhydrin benzyl ether, N-halophenylleuco auramine, N-2,4,5-trichlorophenyl leuco auramine, rhodamine-B-anilinolactam, rhodamine. (P-nitroanilino) lactam, rhodamine-
B- (p-chloroanilino) lactam;

2-benzylamino-6-diethylaminofluorane, 2-anilino-6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-cyclohexylmethyl Aminofluorane, 2-anilino-3-methyl-6-isoamylethylaminofluorane, 2-
(O-chloroanilino) -6-diethylaminofluorane, 2-octylamino-6-diethylaminofluorane, 2-ethoxyethylamino-3-chloro-2-diethylaminofluorane, 2-anilino-3-chloro-6
-Diethylaminofluorane;

Benzoyl leuco methylene blue, p-nitrobenzyl leuco methylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran,
There are 3-benzylspirodinaphthopyran, 3-propyl-spiro-dibenzopyran and the like.

The electron-donating dye precursor that turns blue when colored can be used by appropriately selecting from the above-mentioned ones. Examples of the electron accepting compound include phenolic compounds, salicylic acid derivatives, hydroxybenzoic acid esters and the like. Among these, phenol compounds and hydroxybenzoic acid esters are particularly preferable, and phenol compounds are most preferable.

Some examples of these are 2,2-bis (p-hydroxyphenyl) propane (that is, bisphenol A) and 2,2-bis (p-hydroxyphenyl).
Pentane, 2,2-bis (p-hydroxyphenyl) ethane, 2,2-bis (p-hydroxyphenyl) butane, 2,2-bis (4'-hydroxy-3 ', 5'-dichlorophenyl) propane, 1 , 1- (p-hydroxyphenyl) cyclohexane, 1,1- (p-hydroxyphenyl) propane, 1,1- (p-hydroxyphenyl) pentane, 1,1- (p-hydroxyphenyl)-
2-ethylhexane, 3,5-di (α-methylbenzyl) salicylic acid and its polyvalent metal salt, 3,5-di (te
rt-Butyl) salicylic acid and its polyvalent metal salts, 3-
α, α-dimethylbenzyl salicylic acid and its polyvalent metal salts, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, 2-ethylhexyl p-hydroxybenzoate, p-phenylphenol, p-cumylphenol, etc. Can be mentioned.

A sensitizer for accelerating the reaction is preferably added to the color forming system composed of the electron-donating dye precursor and the electron-accepting compound. As the sensitizer, a low melting point organic compound having an aromatic group and a polar group in the molecule is preferable, and specific examples thereof include benzyl p-benzyloxybenzoate, α-naphthylbenzyl ether,
β-naphthylbenzyl ether, β-naphthoic acid phenyl ester, α-hydroxy-β-naphthoic acid phenyl ester, β-naphthol- (p-chlorobenzyl) ether, 1,4-butanediol phenyl ether,
1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-ethylphenyl ether, 1,4-butanediol-m-methylphenyl ether, 1-phenoxy-2- (p-tolyloxy) Ethane, 1-phenoxy-2- (p-ethylphenoxy)
Examples thereof include ethane, 1-phenoxy-2- (p-chlorophenoxy) ethane, p-benzylbiphenyl and the like.

In the present invention, from the viewpoint of heat energy fractionation and color development, the glass transition point of the capsule wall material of the microcapsules containing the diazo compound is the capsule wall of the microcapsules containing the electron-donating dye precursor. It is necessary to make it lower than the glass transition point of the material. Here, the glass transition point is measured using a capsule or (capsule wall / glass transition point regulator outside the capsule) interacting substance using vibron (DD-III type: trade name manufactured by Toyo Baldwin Co., Ltd.). In this case, it means the peak temperature of Tan σ, which is the dynamic loss elastic modulus divided by the storage rate.

For the production of microcapsules, an interfacial polymerization method,
Either internal polymerization method or external polymerization method can be adopted. In particular, a core substance obtained by dissolving or dispersing a color former in a non-aqueous solvent is emulsified in an aqueous solution in which a water-soluble polymer is dissolved. After that, it is preferable to adopt an interfacial polymerization method in which a wall of a 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 using polyurea as a capsule wall material, diisocyanate, triisocyanate, tetraisocyanate, polyisocyanate such as polyisocyanate prepolymer, and polyamine such as diamine, triamine, tetraamine, and two amino groups The microcapsule wall can be easily formed by reacting the prepolymer containing the above, 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 added, for example, by using polyisocyanate and acid chloride or polyamine and polyol, after adjusting the pH of the emulsifying medium 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 the present invention, a mixture of 30% by weight of polyamide represented by the following chemical formula 1 and 70% by weight of polyurethane represented by the following chemical formula 2 is used, particularly when a microcapsule wall having a high glass transition point is used. It is preferable to use 100% by weight of the above polyamide in the case of forming a microcapsule wall having a glass transition point lower than that.

[Chemical 1]

[Chemical 2]

Further, in order to swell the microcapsule wall during heating, a sensitizer may be added in an emulsified dispersion or solid dispersion state. As the 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, a coloring aid can be used. The color-forming auxiliary that can be used in the present invention,
It is a substance that raises the coloring density during heating recording or lowers the minimum coloring temperature.By lowering the melting point of the coupling component, basic substance, diazo compound, etc., or lowering the softening point of the capsule wall. , A diazo compound, a basic substance, a coupling component and the like are prepared to easily react with each other.

Examples of the color-forming assistant include phenol compounds, alcoholic compounds, amide compounds, sulfonamide compounds and the like. Specific examples are p-tert-octylphenol, p-benzyloxyphenol, phenyl p-oxybenzoate, and Examples thereof include benzyl carbanylate, phenethyl carbanylate, hydroquinone dihydroxyethyl ether, xylylenediol, N-hydroxyethyl-methanesulfonic acid amide, N-phenyl-methanesulfonic acid amide. These may be contained in the core substance or may be added outside the microcapsules as an emulsified dispersion.

In the present invention, a substantially transparent thermosensitive recording layer may be provided to improve the quality of multicolor images. In this case, the coupler for the diazo compound, which is a color former, is not solid-dispersed, but is dissolved in an organic solvent that is sparingly soluble or insoluble in water, and then this is used as a protective colloid with a water-soluble polymer and if necessary. And further mixed with an aqueous phase containing a surfactant and used in the form of an emulsified dispersion.

The organic solvent used in this case can be appropriately selected, for example, from the high boiling point oils described in JP-A-2-141279. It is preferable to use esters among these high-boiling oils from the viewpoint of emulsion stability of the emulsified dispersion, and above all, when tricresyl phosphate is used alone or as a mixture, the emulsion dispersion stability of the coupler is Especially good. The above oils can be used together or 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. In some cases, it is possible to use only the low boiling auxiliary solvent without the high boiling oil. The water-soluble polymer to be contained as a protective colloid in the aqueous phase mixed with the oil phase containing these components can be appropriately selected from known anionic polymers, nonionic polymers and amphoteric polymers. However, polyvinyl alcohol, gelatin, cellulose derivatives and the like are preferable.

The surface active agent contained in the aqueous phase is
Among the anionic or nonionic surfactants, those which do not cause precipitation or aggregation by acting on the protective colloid can be appropriately selected and used. Preferred surfactants include sodium alkylbenzene sulfonate, sodium alkylsulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether), and the like.

In the emulsified dispersion of the present invention, an oil phase containing the components and an aqueous phase containing the protective colloid and the surfactant are used by means such as high speed stirring and ultrasonic dispersion, which are commonly used for fine particle emulsification. It can be easily obtained by mixing and dispersing. In addition, the ratio of the oil phase to the water phase (oil phase weight /
The 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.

In the present invention, polyvinyl alcohol, gelatin and / or gelatin derivatives (for example, as a binder for fixing the coloring material or the like on the support).
Phthalated gelatin, etc.) can be used. Other binders may be used in combination as the binder. Other binders include methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, arabic gum, polyvinylpyrrolidone, casein,
Styrene-butadiene latex, acrylonitrile-
Examples thereof include various emulsions of butadiene latex, polyvinyl acetate, polyacrylic acid ester, ethylene-vinyl acetate copolymer and the like.

The amount of binder used is preferably 0.5 to 5 g / m ² in terms of solid content. In addition to the above materials, citric acid, tartaric acid, oxalic acid, boric acid, phosphoric acid, pyrophosphoric acid and the like can be added as an acid stabilizer.
When it is not necessary to make the thermosensitive recording layer transparent, a coupler or the like may be used by solid-dispersing it with a sand mill or the like.

In the present invention, a protective layer may be provided on the heat-sensitive recording layer. In particular, when transparency is required for the protective layer, it is preferable that the protective layer comprises 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. Details of these pigments, metal soaps, waxes, cross-linking agents and the like are described in, for example, JP-A-2-141279.

A surfactant is added to the coating solution for forming the protective layer in order to form the protective layer uniformly 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 may be added for preventing the heat-sensitive recording material from being charged. 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 . When the protective layer is not required to have transparency like a recording material in which the support is transparent and a recorded image is observed from the side of the support, a publicly known protective layer may be appropriately provided.

The support used in the present invention may be transparent or opaque. Examples of the opaque support include paper, synthetic paper, a paper laminated with a polymer film, an aluminum vapor deposition base, and a polymer film coated with a white pigment. As the paper used for the support, neutral paper having a heat extraction pH of 6 to 9 which is sized with a neutral sizing agent such as alkyl ketene dimer (for example, JP-A-55-14281) can be stored with time. Is advantageous in that.

Examples of the transparent support include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate films, polystyrene films, polypropylene films, polyolefin films such as polyethylene films, polyimide films and polychlorinated films. Vinyl film, polyvinylidene chloride film, polyacrylic acid copolymer film, polycarbonate film and the like can be mentioned, and these can be used alone or by laminating, but especially polyester film which has been subjected to heat treatment and antistatic treatment. Is preferred.

The support has a thickness of 20 to 200 μm, and preferably 50 to 100 μm. In the present invention, when a polymer film or a paper laminated with this is used as a support, or when a transparent support is used, in order to enhance the adhesiveness between the support and the heat-sensitive recording layer It is preferable to provide an undercoat layer.

As the material for the undercoat layer, gelatin, synthetic polymer latex, nitrocellulose or the like is used. The coating amount of the undercoat layer is preferably in the range of ^{0.1g / m 2 ~2.0g / m 2} , in particular 0.2 g / m ² to 1.0 g
The range of / m ² is preferable. The undercoat layer may be swelled by water contained in the heat-sensitive recording layer when the heat-sensitive recording layer is applied thereon to deteriorate the image quality of the heat-sensitive recording layer. Therefore, the undercoat layer is cured using a hardener. Is desirable.

Examples of the hardener include, for example, JP-A-2-141.
The thing described in the 279 publication can be mentioned. The amount of these hardeners added is in the range of 0.20% to 3.0% by weight based on the weight of the undercoat layer, and an appropriate amount is selected according to the coating method and desired degree of curing. be able to.

Depending on the hardener used, if necessary, caustic soda may be added to bring the pH of the solution to the alkaline side, or the pH of the solution may be brought to the acidic side with citric acid or the like. It is also possible to add an antifoaming agent to eliminate bubbles generated during coating, or to add an activator to improve the leveling of the liquid and prevent the generation of coating streaks.

Further, it is desirable to activate the surface of the support by a known method before applying the undercoat layer.
As a method of activation treatment, etching treatment with acid,
Flame treatment with a gas burner or corona discharge treatment,
Glow discharge treatment or the like is used, but from the viewpoint of cost or simplicity, US Pat. Nos. 2,715,075, 2,846,727, 3,549,406 and 3 , 590,107, etc. are most preferably used.

The multicolor heat-sensitive recording material of the present invention is a comparison of microcapsules (referred to as low-temperature microcapsules) having a low glass transition point encapsulating a diazo compound and glass transition points encapsulating an electron-donating dye precursor. A high-quality paper or the above-mentioned film is prepared by preparing a coating solution containing a microcapsule (high temperature microcapsule) having a relatively high capsule wall material, a dispersion in which a coupler and an electron-accepting compound are solid-dispersed or emulsified, a binder, and other additives And the like on a support such as bar coating, blade coating, air knife coating, gravure coating, roll coating coating, spray coating, dip coating and the like, and dried to obtain a solid content of 2.5 to 25 g / m ^2. It is manufactured by providing the heat-sensitive recording layer.

The coating amount of the color-forming component is 0.5 to 3.0 g / as the color-forming component (sum of diazo compound and coupler or electron-donating dye precursor and electron-accepting compound) in the thermosensitive recording layer.
m ² is preferable, and 0.8 to 2.0 g / m is particularly preferable.
It is preferably ² . Proper blending of a pigment dispersant, a thickener, a flow modifier, a defoaming agent, a foam suppressant, a release agent, a colorant, etc., in the coating liquid used in the present invention as necessary does not impair the characteristics. As long as it doesn't matter.

The multicolor heat-sensitive recording material of the present invention can be used as a multicolor heat-sensitive recording material for a printer of a facsimile or an electronic computer which requires high speed recording. Since the multicolor heat-sensitive recording material of the present invention uses a diazo compound as a part of the color former, it has an exposure zone for photodecomposition in order to perform photofixation.

The arrangement of the recording head and the exposure zone is roughly classified into two types. First, after recording once, light irradiation for photolysis is performed, and before and after this light irradiation, the recording material feed mechanism puts the recording material in a recording standby state so that it can be recorded again at the place where it was once recorded. This is a so-called 1-head multi-scan method in which the recording material is returned, then recorded and irradiated with light, and the recording material returns to its original position. This is the so-called 1-head multi-scan method. This is a so-called multi-head, one-scan system in which a light irradiation zone is provided between them. In the present invention, both types may be combined if necessary, and the thermal energy applied to the head may be changed as necessary.

As the light source for photolysis, various light sources which emit light of a desired wavelength can be used. For example, various fluorescent lamps, xenon lamps, xenon flash lamps, mercury lamps of various pressures, photographic flashes, Various light sources such as a strobe can be used. Further, in order to make the light fixing zone compact, the light source section and the exposure section may be separated by using an optical fiber.

Next, a method for obtaining a good multicolor image by using the multicolor heat-sensitive recording material of the present invention will be described. For example, regarding a multicolor thermosensitive recording material using a low temperature microcapsule (called a red coloring capsule) containing a red coloring diazo compound and a high temperature microcapsule (called a blue coloring capsule) containing a blue coloring dye precursor, Thermal recording is carried out as follows.

First, the red color-forming capsule is given heat energy capable of heat-coloring to make it color, and after the first heat recording, the diazo compound is decomposed by irradiating with light having a wavelength that decomposes the diazo compound. Then, the second thermal recording is performed in which the heat energy that enables color development by the blue color microcapsules is applied to develop the color. That is, first, the red coloring capsules are independently colored with low heat energy. Then, the diazo compound in the capsule is photofixed by using a light source having a specific wavelength that photolyzes. Next, the blue coloring capsule is colored with higher heat energy than the previous time. In the above case, two colors of red and blue are realized with good color separation. The overlapping portion of the red and blue images becomes black.

Before photodecomposing the red-coloring diazo compound, heat energy necessary for the second thermal recording is applied to form a mixed color (black (red + blue)) image, and then red color is generated with low heat energy. After the color-forming capsules are independently colored, the diazo compound in the capsules may be photofixed using a light source of a specific wavelength, and then the blue-coloring capsules may be colored with higher heat energy than the previous time. In this case, black (red + blue),
Three colors of red and blue are realized with good color separation. It should be understood that the intermediate color can be reproduced appropriately by controlling the applied color energy to control the color density.

[0060]

INDUSTRIAL APPLICABILITY The multicolor heat-sensitive recording material of the present invention contains a diazo compound in a microcapsule composed of a wall material having a low glass transition point, and at the same time, an electron-donating dye precursor is added to the glass transition point of the microcapsule wall. Since it is encapsulated in a microcapsule made of a wall material having a higher glass transition point, there is no need to overlay the thermosensitive coloring layer,
Excellent manufacturing suitability. Further, since a compound capable of being optically fixed is also used as a color former, each hue can be vividly developed.

[0061]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.
In addition, "part" indicating the addition amount indicates "part by weight". Example 1. (1) Preparation of red coloring capsule solution (preparation of capsule solution containing diazo compound) 4-N-
3.4 parts of (2- (2,4-di-tert-amylphenoxy) butyryl) piperazinobenzenediazonium hexafluorophosphate (diazo compound: decomposed with light having a wavelength of 365 mμ), 15 parts of alkylnaphthalene and chloride After being dissolved in a mixed solution with 12 parts of methylene, the compound represented by the chemical formula 2 (capsule wall agent having a low glass transition point) 1
5 parts was added and uniformly mixed to obtain a solution of diazo compound.

The solution of the obtained diazo compound was added to a solution prepared by mixing 63 parts of an aqueous solution of 8% by weight of polyvinyl alcohol (having a degree of polymerization of 1700 and a breaking degree of 88%) with 100 parts of water, and using a homogenizer. It was emulsified and dispersed.
The obtained emulsified dispersion was heated to 40 ° C. with stirring, and the encapsulation reaction was carried out for 3 hours so that the average particle size of the capsules became 2 μm, then cooled to 20 ° C. and Amberlite IR-120B ( 100 ml of the ion exchange resin (trade name, manufactured by Rohm and Haas Co.) was added, and the mixture was stirred for 1 hour and then filtered to obtain a red coloring capsule solution.

(2) Dispersion of coupler and electron-accepting compound
Preparation of Liquid 14 parts of a compound (coupler) represented by the following chemical formula 3 and 15 parts of bisphenol A and 3 parts of 1,2,3-triphenylguanidine were added to an aqueous solution of 4% by weight of polyvinyl alcohol 13
After being charged into 8 parts, it was dispersed using a Dynomill (manufactured by Willie Ava Cohen AG) so that the average particle size was 3 μm to obtain a dispersion liquid.

[Chemical 3]

(3) Preparation of Blue Color Capsule Liquid (Preparation of Capsule Liquid Containing Electron Donating Dye Precursor)
After 3.0 parts of crystal violet lactone (electron-donating dye precursor) was dissolved in 20 parts of ethyl acetate, 20 parts of alkylnaphthalene, which is a high boiling point solvent, was added and heated to uniformly mix. Next, 20 parts of a mixture (capsule wall material having a high glass transition point) in which the weight ratio of the compound represented by the formula 1 / the compound represented by the formula 2 is 3/7 is added to this mixed liquid as a capsule wall agent. And stirred uniformly.

Next, the above-mentioned electron-donating dye precursor solution was added to 54 parts of a separately prepared 6 wt% aqueous solution of polyvinyl alcohol (polymerization degree 1700, saponification degree 88%), and the mixture was emulsified and dispersed using a homogenizer. did. 68 parts of water was added to the obtained emulsion for homogenization, the temperature was raised to 50 ° C. with stirring, and the encapsulation reaction was carried out for 3 hours to obtain a blue-colored capsule solution. The average particle size of the capsule was 1.6 μm.

(4) Preparation of coating liquid 1.2 parts of red coloring capsule liquid, 1.6 parts of blue coloring capsule liquid
Parts, 0.2 parts of an aqueous solution of 5% by weight of hydroquinone, 8.0 parts of a coupler / electron-accepting compound dispersion, and 3.7 parts of a color-forming auxiliary dispersion were mixed to obtain a coating solution. (5) Preparation of protective layer liquid Itaconic acid-modified polyvinyl alcohol (KL-318:
Product name of Kuraray Co., Ltd.) 100 g of 6% by weight aqueous solution
And a mixture of epoxy-modified polyamide (FL-71: trade name of Toho Kagaku Co., Ltd.) 30% by weight dispersion 10 g, and zinc stearate 40% by weight dispersion (Hydrin Z: Chukyo Yushi Co., Ltd.). 15 g of the product name) was added to obtain a protective layer liquid.

(6) Preparation of heat-sensitive recording material As a support, one surface of smooth high-quality paper (basis weight: 50 g / m ² ) was coated and dried so that the coating liquid was 25 ml / m ^2, and then the same. The same amount of the liquid was applied and dried, and then the protective layer liquid was applied and dried to obtain a multicolor heat-sensitive recording material. (7) Thermal recording Using the obtained recording material, thermal recording was performed as follows.

On the recording surface of the recording material, 70 ° C., 80 ° C., 9
When each plate heated to 0 ° C., 100 ° C. and 110 ° C. was pressed for 1 second, red color was developed at 80 ° C. and black color (red + blue) was developed at 90 ° C. or higher. Next, using Ricopy Super Dry 100 type, after irradiating with light of 340 to 370 mμ, a plate at 90 ° C. or higher was pressed for 1 second, and a blue color was developed.

As described above, the three color images of black, blue and red could be clearly recorded. Also, instead of contacting the hot plate, a Kyocera thermal head KST
When heat energy of 0 mJ / mm ² was applied, it developed a red color, and at 70 mJ / mm ² , it developed a black color (red + blue). Next, using Ricopy Super Dry 100 type, 3
After irradiating with light of 40 to 370 μm, 70
When heat of mJ / mm ² was applied, a blue color was formed.

Example 2. Instead of 3.4 parts of the diazo compound used in the red color-encapsulating liquid in Example 1, 4- (N-
(2- (2,4-di-tert-amylphenoxy) butyryl) piperazinobenzenediazonium hexafluorophosphate 2.0 parts and 2,5-dibutoxy-
A recording material was prepared in the same manner as in Example 1 except that 2.0 parts of 4-tolylthiobenzenediazonium hexafluorophosphate was used, and an image was recorded in the same manner as in Example 1. Images of three colors, blue, and red could be clearly recorded.

Comparative Example 1. A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the capsule wall material used in the red-coloring capsule solution in Example 1 was changed to the capsule wall agent having a high glass transition point used in the blue-coloring capsule solution. Prepared, Example 1
When heat recording was carried out in exactly the same manner as above, red color was not developed, only black color (mixed color of blue + red) and blue color were developed.

Claims (4)

[Claims] 1. A microcapsule containing at least a diazo compound, and a microcapsule containing, outside the microcapsule, a coupler that develops a color by a coupling reaction with the diazo compound, and a colorless or light-colored electron-donating dye precursor. On a support, a thermosensitive recording layer containing a capsule and an electron-accepting compound that develops a color different from a color developed by the coupling reaction of the diazo compound by reacting with the electron-donating dye precursor is provided on the support. In the multicolor heat-sensitive recording material having, the glass transition point of the capsule wall material of the microcapsule encapsulating the diazo compound is from the glass transition point of the capsule wall material of the microcapsule encapsulating the electron-donating dye precursor. A multicolor thermosensitive recording material characterized by a low value. 2. The multicolor heat-sensitive recording material according to claim 1, wherein the two hues to be colored are red and blue. 3. After the first thermal recording in which a color-forming reaction between the diazo compound and the coupler is performed, the remaining diazo compound is decomposed by irradiation with light, and then a higher heat than that during the first thermal recording is applied. A second thermal recording method, which comprises applying energy to carry out a second thermal recording in which a color-forming reaction is caused by the electron-donating dye precursor and the electron-accepting compound. 4. The thermal recording method according to claim 3, wherein the thermal energy required for the second thermal recording is applied before the diazo compound is decomposed to obtain a mixed color thermal recording.