JPH05177929A - Multicolor thermosensitive recording material - Google Patents

Abstract

PURPOSE:To provide a multicolor thermosensitive recording material which has a long shelf life and can be prepared properly. CONSTITUTION:A thermosensitive recording material includes two or more thermosensitive recording layers containing a colorless or slightly colored coloring component that develops color by heating are formed on a substrate. An intermediate layer containing at least gelatin and/or a gelatin derivative and an acid polymer is formed between the thermosensitive recording layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor thermosensitive recording material, and more particularly to a multicolor thermosensitive recording material which is excellent in raw storage stability and manufacturability.

[0002]

2. Description of the Related Art A thermal recording method has been remarkably developed in recent years and has been applied to various purposes because it is highly reliable and requires no maintenance although the recording apparatus used is simple. Therefore, recently, it has been proposed to record a multicolor image or a full color image by thermal recording.

In general, when multicolor recording is performed by thermal recording, an electron-donating dye precursor (color former) and an electron-accepting property that develop different hues (called color fractions) by heating with different thermal energies. A combination of a compound (developing agent) or a combination of a diazo compound (color former) and a coupling component (developing agent) is used.

In general, a multicolor thermosensitive recording material is produced by laminating multiple layers of thermosensitive recording layers having different coloring hues on a support, so that the thermosensitive recording layers may be mixed when laminating. After the lamination, a color-forming component, a sensitizer, etc. may be diffused and mixed between the layers to cause a color mixing phenomenon or a decrease in thermal sensitivity. Therefore, in order to prevent this, and in order to improve the color-fractionation property of specifying the color-developing color layer depending on the magnitude of the heat energy applied, an intermediate layer containing a water-soluble polymer as a main component is conventionally provided between the thermal recording layers. Is being done. However, although the intermediate layer is excellent in the color-fractionation property and the diffusion prevention effect, it has a drawback that the production of the multicolor heat-sensitive recording material is complicated.

The inventors of the present invention include gelatin or a gelatin derivative as a binder in the heat-sensitive recording layer, and provide an intermediate layer containing gelatin or a gelatin derivative as a main component so that the color-developing component in the heat-sensitive recording layer can be prevented. It has been found that an upper multi-layer coating method that is excellent in preventing diffusion between layers can be used, and that a multicolor heat-sensitive recording material having excellent manufacturing suitability can be obtained, and that the above-mentioned drawbacks can be improved ( Japanese Patent Application No. 2-142637).

[0006]

However, even with such a multicolor heat-sensitive recording material, when it is stored for a long period of time (referred to as raw storability), the diffusion of the color-developing component between the recording layers is completely prevented. However, there is a drawback in that the color mixture phenomenon and the desensitization phenomenon due to diffusion cannot be avoided.

When a substance known to have an effect of preventing diffusion resistance is added to the intermediate layer containing gelatin as a main component, the effect of preventing diffusion is improved, but Since the substance interacts with gelatin or the like to cause the gelatin or the like to aggregate or gel, the stability of the coating liquid is poor, and the production suitability of the multicolor heat-sensitive recording material is deteriorated.

The inventors of the present invention have conducted extensive studies to solve the above-mentioned drawbacks, and as a result, not only the production suitability is good when a certain amount of polyanion binder is contained in the gelatin of the intermediate layer. The inventors have found that the raw storability of the heat-sensitive recording material is remarkably improved and have reached the present invention. Therefore, an object of the present invention is to provide a multicolor thermosensitive recording material which is excellent in raw storability and production suitability.

[0009]

The above objects of the present invention are as follows.
A heat-sensitive recording material in which two or more heat-sensitive recording layers containing at least a colorless or light-colored color-forming component which develops color upon heating and a binder are provided on a support, wherein at least gelatin and / or a gelatin derivative is provided between the heat-sensitive recording layers. ,
And a multicolor thermosensitive recording material characterized by the provision of an intermediate layer containing an acidic polymer.

Next, materials used in the multicolor heat-sensitive recording material of the present invention will be described. The color-developing component used in the multicolor thermosensitive recording material of the present invention is a substance that causes a color-developing reaction on contact with a substance by heating, and specifically, an electron-donating dye precursor (color-forming agent) and an electron-accepting compound ( Or a combination of a diazo compound (color former) and a coupler (color former).

Examples of the electron-donating dye precursor include triarylmethane compounds, diphenylmethane compounds, thiazine compounds, xanthene compounds, spiropyran compounds, and the like. Particularly, triarylmethane compounds and xanthene compounds are preferable. It is useful because the color density is high.

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-halophenyl leuco 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-cyclohexylmethylaminofluorane, 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,
3-benzyl-spiro-dinaphthopyran, 3-propyl-spiro-dibenzopyran and the like.

Examples of the electron accepting compound include phenol derivatives, salicylic acid derivatives, hydroxybenzoic acid esters and the like. Among these, bisphenols and hydroxybenzoic acid esters are particularly preferable. Examples of some of these include 2,2-bis (p-hydroxyphenyl) propane (ie, bisphenol A), 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 (tert-butyl) salicylic acid and its polyvalent Metal salts, 3-α, α-dimethylbenzyl salicylic acid and polyvalent metal salts thereof, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p
Examples include 2-ethylhexyl hydroxybenzoate, p-phenylphenol, p-cumylphenol and the like.

A sensitizer for promoting the reaction is preferably added to the heat-sensitive recording layer 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-butane Diol-p-methylphenyl ether, 1,4-butanediol-p-ethylphenyl ether, 1,4-butanediol-m-methylphenyl ether, 1-phenoxy-2- (p-tolyloxy)
Examples thereof include ethane, 1-phenoxy-2- (p-ethylphenoxy) ethane, 1-phenoxy-2- (p-chlorophenoxy) ethane and p-benzylbiphenyl.

On the other hand, the compound used in the heat-sensitive recording layer containing a diazo compound and a coupler which reacts with the diazo compound when heated to produce a color is a known photodegradable diazo compound, and a dye is reacted with the diazo compound to form a dye. It is a basic substance which is optionally used to accelerate the reaction between the coupler and the diazo compound that can be formed with the coupler.

The photodecomposable diazo compound referred to 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.

[0019] Generally the diazonium salt type Ar-N ₂ ⁺ X ^- (wherein Ar represents an aromatic moiety, N ₂ + diazonium salt, X ^- represents an acid anion) is a compound represented by the. These have various maximum absorption wavelengths depending on the position and type of the substituent of the Ar portion.

Specific examples of the diazo compound used in the present invention include 4- (N- (2- (2,4-di-tert-
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-tert-
Amylphenoxy) butyryl) piperazino) benzenediazonium, 2,5-dibutoxy-4-tolylthiobenzenediazonium, 3- (2-octyloxyethoxy) -4-morpholinobenzenediazonium, and the like. In the present invention, in particular, these hexafluorophosphate salts, tetrafluoroborate salts, 1,
The 5-naphthalene sulfonate salt is useful because it has low solubility in water and is soluble in organic solvents.

The couplers which react with the diazo compound used in the present invention to produce a color when heated are 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 diazonium salt and the coupler includes an inorganic or organic basic compound as well as a compound that decomposes when heated to release an alkaline substance. Representative examples are organic ammonium salts, organic amines, amides, urea and thiourea, their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles. And nitrogen-containing compounds such as morpholines, piperidines, amidines, formazines and pyridines.

Specific examples of these include tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine; allylurea, thiourea, methylthiourea, allylthiourea, ethylenethiourea; 2
-Benzyl imidazole, 4-phenyl imidazole,
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 trichloroacetic acid salt; N, N'-dibenzylpiperazine;4,4'-dithiomorpholine, morpholinium Trichloroacetic acid salt; 2-aminobenzothiazole, 2-benzoylhydrazinobenzothiazole and the like. These may be used in combination of two or more.

The color-forming agent used in the present invention is a raw-storing property of the heat-sensitive recording layer (preventing fog), such as preventing contact between the color-developing agent and the color-developing agent at room temperature, and coloring with desired heat energy. From the viewpoint of controlling the color forming sensitivity, it is preferable to encapsulate the color forming agent before use.

Any of an interfacial polymerization method, an internal polymerization method and an external polymerization method can be adopted for producing the microcapsules which can be used in the present invention. In particular, the color former is used as a non-aqueous solvent. It is preferable to employ an interfacial polymerization method in which the core substance dissolved or dispersed is emulsified in an aqueous solution in which a water-soluble polymer is dissolved, and then a wall of the polymer substance is formed around the oil droplets. 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 the capsule wall material, polyisocyanates such as diisocyanate, triisocyanate, tetraisocyanate and polyisocyanate prepolymer, and polyamines such as diamine, triamine and tetraamine, and amino groups. The microcapsule wall can be easily formed by reacting a prepolymer containing two or more of the above, piperazine or a derivative thereof, a polyol and the like by an interfacial polymerization method in an aqueous solvent.

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 to be the reaction solution. It can be prepared by warming. Details of the method for producing a composite wall composed of these polyurea and polyamide are described in JP-A-58-6.
6948.

Further, 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 from 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 or the like is preferably used.

In the present invention, a color forming aid can be used. The color-forming aid 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.It has the effect of lowering the melting point of coupling components, basic substances, diazo compounds, etc., and lowering the softening point of the capsule wall. , A diazo compound, a basic substance, a coupling component, etc. are easily prepared.

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, 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 coloring layer can be provided to improve the image quality of a multicolor image. In this case, the developer for the electron-donating dye precursor or 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 surfactant. And / or mixed with an aqueous phase having a water-soluble polymer as a protective colloid and used in the form of an emulsified dispersion. From the viewpoint of facilitating emulsion dispersion, it is preferable to use a surfactant.

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. Among these, it is preferable to use the esters from the viewpoint of the 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 color developer is particularly good. Yes preferred. The above oils can be used together or with other oils.

In the present invention, an auxiliary solvent can 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 is 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 (for example, polyoxyethylene nonylphenyl ether), and the like.

The emulsified dispersion of the present invention comprises a means used for ordinary fine particle emulsification such as high speed stirring and ultrasonic dispersion of an oil phase containing the above components and an aqueous phase containing a protective colloid and a surfactant. It can be easily mixed and dispersed by using. 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 and the layer becomes thin, so that sufficient color developability cannot be obtained.
On the other hand, when it is 0.6 or more, the viscosity of the liquid becomes high, which causes inconvenience in handling and a decrease in coating liquid stability.

In the present invention, gelatin and / or gelatin suitable for multi-layer coating is used as a binder for fixing various materials such as color-developing materials on the support or on the already coated heat-sensitive recording layer or intermediate layer. It is preferable to use a gelatin derivative in the heat-sensitive recording layer. The gelatin that can be used in the present invention is not particularly limited, and alkali-treated gelatin, acid-treated gelatin, etc., and gelatin derivatives include modified gelatin obtained by modifying a part of the functional groups of gelatin (for example, phthalate). Gelatinized gelatin etc.) can be used. Examples of commercially available gelatin include, for example, # 680 gelatin and # 6 manufactured by Nitta Gelatin Co., Ltd.
81 gelatin, # 690 gelatin, # 700 gelatin,
Examples include # 701 gelatin, # 721 gelatin, # 750 gelatin, # 760 gelatin, # 810 gelatin, # 860 gelatin and # 950 gelatin.

From the viewpoint of preventing metal corrosion during thermal recording of the thermal head, it is preferable to use gelatin having a low content of monovalent metal ions or halogen ions. In the present invention, as the binder,
Other binders can be used together with gelatin. In this case, the amount of gelatin in the binder is preferably 50% by weight or more, and particularly preferably 65% by weight or more.

Other binders that can be used in the present invention include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, arabic rubber, polyvinyl pyrrolidone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate and poly. Examples thereof include various emulsions such as acrylic acid ester and ethylene-vinyl acetate copolymer.

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

In the present invention, it is preferable to provide a protective layer on the heat-sensitive recording layer. 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 thermal recording layer,
The mechanical strength of the surface of the thermosensitive recording layer can be improved.

Pigments, metal soaps, waxes, cross-linking agents and the like are added to the protective layer for the purpose of improving matching with a thermal head during thermal recording and improving water resistance of the protective layer. Details of these pigments, metal soaps, waxes, crosslinking agents, etc. 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, fluorine-containing surfactants, etc.
Examples thereof 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 transparency is not required for the protective layer, a publicly known protective layer may be appropriately provided. In the present invention, it is necessary to provide an intermediate layer between the recording layers from the viewpoint of improving storability and thermal fractionation.

The intermediate layer in the present invention is particularly an intermediate layer containing gelatin and / or a gelatin derivative and an acidic polymer from the viewpoint of improving raw storability and production suitability. The gelatin and the gelatin derivative are the same as the gelatin used as the binder in the heat-sensitive recording layer. The acidic polymer is a polymer having an acidic group such as a carboxyl group or a sulfone group, and specific examples thereof include poly (meth) acrylic acid and its copolymer, polystyrene sulfonic acid and its copolymer, and the like. Be done.

In order to add an acidic polymer to gelatin in the intermediate layer, a solution containing gelatin and a polyanion binder may be applied and dried. As the polyanion binder, in addition to H-type acidic polymers such as carboxylic acids and sulfonic acids, ammonium salts of acidic polymers, low molecular weight amine salts, etc., salts that become ammoniacal polymers by volatilization of ammonia and low molecular weight amine during coating and drying. Can be mentioned.

The H-type acidic polymer is represented by the following chemical formula 1.
In addition to the compounds represented by Chemical formulas 4 to 4, a high molecular weight polymer containing at least 5% by weight of at least any one of the above Chemical formulas 1 to 4; Containing --COOH group or --SO ₃ H group, alginic acid or cellulose derivative --COOH group or --SO ₃ H group
The thing containing a group etc. can be mentioned.

[0050]

[Chemical 1] However, R _{1 to} R ₃ in the chemical formula 1 have a hydrogen atom or a carbon number of 1 to
3 is an alkyl group, and n is an integer of 3 or more.

[0051]

[Chemical 2] However, in the reduction 2 R ₁ to R ₃ and n are in one of R ₁ to R ₃
And n, respectively, and R ₄ is an alkylene group having 1 to 3 carbon atoms or a phenylene group.

[0052]

[Chemical 3] However, in the reduction 3 R ₁ to R ₃ and n in the reduction 1 R ₁ to R ₃
And n, respectively.

[0053]

[Chemical 4] However, in the reduction 4 R ₁ to R ₃ and n in the reduction 1 R ₁ to R ₃
And n, respectively, and R ₄ is an alkylene group having 1 to 3 carbon atoms or a phenylene group.

Specific examples of the H-type acidic polymer represented by the above chemical formula 1 include the polymers of the following chemical formulas 5 to 7.

[Chemical 5]

[Chemical 6]

[Chemical 7] These polymers are commercially available from Nippon Pure Chemical Co., Ltd., for example.

As the H-type acidic polymer represented by the above Chemical formula 2, the polymer of the following Chemical formula 8 is exemplified.

[Chemical 8]

Further, specific examples of the H-type acidic polymer represented by Chemical formula 3 include the polymers of Chemical formulas 9 to 11 below.

[Chemical 9]

[Chemical 10]

[Chemical 11]

Further, specific examples of the compounds represented by the chemical formula 4 include those represented by the following chemical formula 12 (for example, Chemistat SA-201 manufactured by Sanyo Kasei Co., Ltd .: trade name),
Specific examples of the high molecular weight copolymer containing 5% or more of the monomer unit of Chemical formula 4 are those represented by Chemical formula 13 (for example, Crustomer AP20 manufactured by Kuraray Co., Ltd .: trade name) and those of Chemical formulas 1 to 4 Specific examples of the polymer include those represented by Chemical formula 14. In addition, l and m in Chemical formula 14
Satisfies the condition of l + m ≧ 3.

[0058]

[Chemical 12]

[Chemical 13]

[Chemical 14]

Further, the surface of the polymer latex is --COO.
As those having an H group, there are those in which the surface of SBR latex is modified with a carboxyl group, which is, for example, N in the product SN-307 manufactured by Sumitomo Nogatak Co., Ltd.
It can be obtained by exchanging a ion for H by an ion exchange method.

The content of the acidic polymer in the intermediate layer is
Solid content 5% to 100% by weight of gelatin
It is preferable that If the amount is 5% by weight or less, the shelf life is not sufficient, and if the amount is 100% by weight or more, the multilayer multi-layer coating becomes difficult and the manufacturability becomes insufficient. By doing so, it is possible to more completely prevent the mass transfer between the recording layers and to reduce the curl of the product, as compared with the case of the intermediate layer containing only gelatin.
In the intermediate layer of the present invention, other binders may be used in combination with the above binders. As the other binder, an emulsion or latex of a water-soluble polymer or a hydrophobic polymer is preferable.

Examples of the water-soluble polymer include polyvinyl alcohol, silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, styrene-maleic anhydride copolymer and its ester, butadiene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer. Polymer, isobutylene-maleic anhydride copolymer, polyacrylamide, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer, oxidized starch, phosphorylated starch, carboxymethylcellulose, methylcellulose, sodium alginate, Examples include sulfated cellulose and hydroxyethyl cellulose. Examples of the hydrophobic polymer emulsion or latex include a styrene-butadiene copolymer, a carboxy-modified styrene-butadiene copolymer, and an acrylonitrile-butadiene copolymer.

The support used in the present invention may be transparent or opaque. Examples of the opaque support include paper, synthetic paper, an aluminum vapor-deposited base, and a transparent support described below coated with a white pigment.
The paper used for the support is a heat-extracted pH sized with a neutral sizing agent such as alkyl ketene dimer.
Is 6 to 9 neutral paper (for example, JP-A-55-14281).
No.) is advantageous in terms of storage stability over time.

On the other hand, 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, and the like. Examples thereof include a polyvinyl chloride film, a polyvinylidene chloride film, a polyacrylic acid copolymer film, and a polycarbonate film. These can be used alone or by laminating them, but especially polyester film is subjected to heat treatment and antistatic treatment. Those obtained are preferred. The thickness of the transparent support is 20 to 200 μm,
Particularly, those having a thickness of 50 to 100 μm are preferable.

In the present invention, when a polymer film support is used, it is preferable to provide an undercoat layer between the support and the thermosensitive recording layer in order to enhance the adhesiveness between them. As a 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} , preferably in the range particularly ^{0.2g / m 2 ~1.0g / m 2} .

When the heat-sensitive recording layer is coated on the undercoat layer, it may swell due to water contained in the heat-sensitive recording layer to deteriorate the image quality of the heat-sensitive recording layer. It is desirable to cure by curing. Examples of the hardener include those described in JP-A-2-141279.

The addition amount of these hardeners is in the range of 0.20% by weight to 3.0% by weight based on the weight of the undercoat material, and the addition amount is appropriate according to the coating method and the desired degree of curing. You can choose. Depending on the hardening agent used, if necessary, caustic soda may be further 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. Also, in order to eliminate the bubbles generated during application,
It is possible to add an antifoaming agent, or it is possible to add an activator in order 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, corona treatment, glow discharge treatment, or the like is used, but from the viewpoint of cost or simplicity, US Pat. Nos. 2,715,075 and 2
The corona discharge treatments described in No. 846,727, No. 3,549,406, No. 3,590,107 and the like are most preferably used.

The heat-sensitive recording material of the present invention is prepared as a coating liquid containing microcapsules containing an electron-donating dye precursor or a diazo compound and a dispersion in which at least a color developer is emulsified and dispersed, a binder, and other additives. It is coated and dried by bar coating, blade coating, air knife coating, gravure coating, roll coating coating, spray coating, dip coating or the like on a support such as high-quality paper or the above-mentioned film to obtain a solid content of 2.5. It is manufactured by providing a thermosensitive recording layer of ˜25 g / m ² .

The coating amount of the color-forming component is 0.5 to 3.0 g / m as the color-forming component (the sum of the electron-donating dye precursor and the developer or the sum of the diazo compound and the coupler) in each thermosensitive recording layer.
² is preferable, and especially 0.8 to 2.0 g / m ²
It is preferable that US Patent No. 2, as required
761,791, 3,508,947, 2,941,898, and 3,526,528, Yuji Harazaki, "Coating Engineering," page 253 (1
2 issued by Asakura Shoten in 973)
It is also possible to divide into more than one layer and apply at the same time, and an appropriate method can be selected depending on the application amount, the application speed and the like.

If necessary, a pigment dispersant, a thickener, a flow modifier, an antifoaming agent, a foam suppressor, a release agent, a colorant and the like may be appropriately added to the coating liquid used in the present invention. As long as it does not hurt. 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. When a diazo compound is used as a color former and is subjected to photofixation, an exposure zone for photodecomposition is provided.

The arrangement of the recording head and the exposure zone is roughly classified into two types. One is that after recording once, light irradiation for photolysis is performed, and before and after this light irradiation, the recording material is in the recording waiting state so that it can be recorded again at the place where it was once recorded by the recording material feeding mechanism. Then, the recording material is radiated again, the recording material is irradiated again, and the recording material is returned to its original shape. This is a so-called 1-head multi-scan method. It is a so-called multi-head one-scan method that has a light irradiation zone between them, and both methods may be combined if necessary, and the thermal energy applied to the head can be changed as necessary. May be.

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. In some cases, a multicolor sample can be obtained by placing the recording material, which has been once recorded, in sunlight, a fluorescent lamp or the like, fixing mainly with light in the visible light region and then recording again.

Next, a method for obtaining a good multicolor image by using the multicolor heat-sensitive recording material of the present invention will be described. In the present invention, for example, a full-color multicolor heat-sensitive recording material is provided by providing each layer in multiple layers on one surface of the support so that the cyan color forming layer, the magenta color forming layer and the yellow color forming layer are formed in order from the support side. Can be obtained.

In this case, in order to color each layer independently and bring a recorded multicolor image close to a natural color, at least the upper two color developing layers are disclosed in JP-A-6140192. It is preferable to employ a system of a coupling coloring reaction of a diazo compound and a photofixing reaction.

That is, first, the uppermost yellow coloring layer 1 on one surface is independently colored with low heat energy. After that, light fixation is performed using a light source having a specific wavelength that selectively photolyzes only the diazo compound in the layer. Next, a light source of a specific wavelength that thermally records the inner magenta color-developing layer with relatively higher heat energy than the previous time to independently develop the color of the magenta color-developing layer, and then selectively photodecomposes only the diazo compound of the layer is used. Use to fix light. Further, the cyan color-forming layer inside the magenta layer is thermally recorded with higher heat energy than the previous time, and color is independently developed. In this case, the cyan color forming layer at the bottom of the three layers does not necessarily need optical fixing.

In the above case, since cyan, magenta and yellow can be independently formed on one surface of the support, cyan, magenta, yellow, cyan + magenta (blue), magenta + yellow (red), A total of 7 colors of cyan + yellow (green) and cyan + magenta + yellow (black) are realized with good color separation.

Generally, in the case of a multi-layered multi-color recording material, it is preferable that the layers other than the layer farthest from the image observing side be transparent heat-sensitive recording layers because each color becomes vivid. In the present invention, a transparent support may be used as the support, and any one of the above three layers may be coated on the back surface of the transparent support to obtain a multicolor image similar to the above. In this case, the uppermost thermal recording layer on the side opposite to the image viewing side does not need to be transparent. Any one of the cyan color forming layer, the magenta color forming layer and the yellow color forming layer is used.
It goes without saying that two or three color multicolor images can be thermally recorded by appropriately selecting layers and sequentially providing them on the support.

Those skilled in the art can easily understand that an intermediate color can be appropriately reproduced by appropriately controlling the applied heat energy to control the color development of each unit. The intermediate layer in the present invention is
It is also effective as an intermediate layer of a recording material such as a photograph having a multi-layer structure using gelatin as a main binder.

[0079]

As described in detail above, since the multicolor heat-sensitive recording material of the present invention contains gelatin and / or gelatin derivative and acidic polymer in the intermediate layer, even after the recording material is stored for a long period of time. It does not show any color mixing phenomenon or desensitization phenomenon, and has excellent manufacturing suitability. Further, the curl of the product is reduced as compared with the case where only gelatin is used.

[0080]

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" which shows an addition amount shows a "weight part."

Example 1. An example of producing a full-color heat-sensitive recording material capable of independently heat-recording the three colors of yellow, magenta and cyan will be shown below.

(1) Preparation of cyan thermosensitive recording layer liquid (preparation of capsule liquid containing an electron-donating dye precursor) Solution A 3- (o-methyl-p-dimethylaminophenyl) -3
-(1'-Ethyl-2'-methylindol-3-yl) phthalide (electron donating dye precursor) was added to ethyl acetate 2
After dissolving in 0 part, 20 parts of alkylnaphthalene (high boiling point solvent) was added thereto, and heated to uniformly mix. A solution A was prepared by adding 20 parts of a 1/3 adduct of xylylene diisocyanate / trimethylolpropane to the obtained solution and stirring the mixture uniformly.

2. Solution B Solution B was prepared by adding 2 parts of a 2% by weight sodium dodecylsulfonate aqueous solution to 54 parts of an aqueous 6% by weight phthalated gelatin solution. Solution A was added to solution B, and the mixture was emulsified and dispersed using a homogenizer to obtain an emulsion dispersion. To the obtained emulsified dispersion liquid, 68 parts of water was added, mixed and homogenized, and the mixed liquid was heated to 50 ° C. with stirring to encapsulate the microcapsules so that the average particle diameter was 1.2 μm. The reaction was carried out for 3 hours to obtain a capsule liquid.

(Preparation of color developer emulsion dispersion) 1,1- (p
5 parts of -hydroxyphenyl) -2-ethylhexane (developing agent), 0.3 parts of tricresyl phosphate and 0.1 part of diethyl maleate were dissolved in 10 parts of ethyl acetate. The obtained solution is a 50% aqueous solution of 6% gelatin.
g and 2 g of a 2 wt% sodium dodecylsulfonate aqueous solution were added to a mixed solution, and the mixture was emulsified for 10 minutes using a homogenizer to obtain an emulsion dispersion.

(Preparation of coating liquid) The weight ratio of the capsule liquid containing the electron-donating dye precursor / the color developer emulsion dispersion is 1 /
A coating solution was obtained by mixing so as to obtain 4.

(2) Preparation of magenta thermosensitive recording layer liquid (preparation of capsule liquid containing diazo compound) 4-N-
2.0 parts of (2- (2,4-di-tert-amylphenoxy) butyryl) piperazinobenzenediazonium hexafluorophosphate (diazo compound: decomposed by light having a wavelength of 365 nm) 2.0 parts were dissolved in 20 parts of ethyl acetate. After that, 20 parts of alkylnaphthalene was further added, and heated to uniformly mix. To the resulting solution, 15 parts of an adduct of 1/3 of xylylisocyanate / trimethylolpropane (capsule wall agent) was added and uniformly mixed to obtain a solution of a diazo compound.

The resulting solution of the diazo compound was added to a mixed solution of 54 parts of a 6% by weight aqueous solution of phthalated gelatin and 2 parts of a 2% by weight aqueous solution of sodium dodecylsulfonate, and the mixture was emulsified and dispersed using a homogenizer. .. To the obtained emulsified dispersion liquid, 68 parts of water was added and mixed uniformly, and the mixture was heated to 40 ° C. with stirring, and the average particle size of the capsule was 1.2 μm.
The encapsulation reaction was performed for 3 hours to obtain a capsule solution.

(Preparation of Coupler Emulsion Dispersion) 1- (2 '
-Octylphenyl) -3-methyl-5-pyrazolone (coupler) 2 parts, 1,2,3-triphenylguanidine 2 parts, tricresyl phosphate 0.3 parts and diethyl maleate 0.1 part and ethyl acetate 10. Dissolved in parts. 50 g of a 6% by weight aqueous solution of gelatin was obtained.
And 2 g of an aqueous solution containing 2% by weight of sodium dodecyl sulfonate
After being added to the mixed aqueous solution, the mixture was emulsified for 10 minutes using a homogenizer to obtain an emulsified dispersion.

(Preparation of coating liquid) A capsule liquid containing a diazo compound / a coupler emulsion was mixed at a weight ratio of 2/3 to obtain a coating liquid.

(3) Preparation of Yellow Thermosensitive Recording Layer Liquid (Preparation of Capsule Liquid Containing Diazo Compound) 2,5-
After dissolving 3.0 parts of dibutoxy-4-tolylthiobenzenediazonium hexafluorophosphate (diazo compound: decomposed by light having a wavelength of 420 nm) in 20 parts of ethyl acetate, 20 parts of alkylnaphthalene as a high-boiling solvent was added to the solution.
Parts were added and heated to mix evenly. Xylylene diisocyanate /
15 parts of 1/3 adduct of trimethylolpropane were added and mixed uniformly to obtain a solution of diazo compound.

The solution of the obtained diazo compound was added to a solution prepared by mixing 54 parts of a 6% by weight aqueous solution of phthalated gelatin and 2 parts of an aqueous solution of sodium dodecylsulfonate, and emulsified and dispersed using a homogenizer. 68 parts of water was added to the obtained emulsified dispersion, and the homogeneously mixed solution was heated to 40 ° C. with further stirring, and the average particle size of the capsule was 1.3 μm.
The encapsulation reaction was performed for 3 hours to obtain a capsule solution.

(Preparation of coupler emulsion dispersion) 2-chloro-5- (3- (2,4-di-tert-pentyl) phenoxypropylamino) acetoacetanilide 2 parts,
1,2,3-triphenylguanidine 1 part, tricresyl phosphate 0.3 part and diethyl maleate 0.1
Parts in 10 parts ethyl acetate to give 6% by weight of gelatin
50 g of the aqueous solution and 2 g of a 2% by weight aqueous solution of sodium dodecyl sulfonate were added to the mixed solution and emulsified using a homogenizer for 10 minutes to obtain an emulsified dispersion.

(Preparation of Coating Liquid) A capsule liquid containing a diazo compound / a coupler emulsion dispersion was mixed at a weight ratio of 2/3 to obtain a coating liquid.

(4) Preparation of Intermediate Layer Liquid Gelatin (# 750: trade name of Nitta Gelatin Co., Ltd.) Polyacrylic acid (trade name of JULIMER AC-10L: manufactured by Nippon Pure Chemical Co., Ltd.) was added to 10 parts of 15% by weight aqueous solution. ) Of 15
3 parts by weight of a wt% aqueous solution was added and mixed uniformly to obtain an intermediate layer liquid.

(5) Preparation of protective layer liquid Itaconic acid-modified polyvinyl alcohol (KL-318:
100 g of 6 wt% aqueous solution of Kuraray Co., Ltd.)
A mixture of 10 g of a 30 wt% dispersion of epoxy-modified polyamide (FL-71: trade name of Toho Kagaku Co., Ltd.) and 40 wt% zinc stearate dispersion (Hydrin Z: manufactured by Chukyo Yushi Co., Ltd. (Trade name) 15 g was added to obtain a protective layer liquid.

(6) Preparation of Thermosensitive Recording Material On one side of polyethylene terephthalate having a thickness of 75 μm, using a slide type hopper type bead coating device, a cyan thermosensitive recording layer solution, an intermediate layer solution, and a cyan thermal recording layer solution were sequentially formed on a slide from a support. A multi-layer heat sensitive recording material was obtained by applying multi-layered multilayer coating so as to form a magenta heat sensitive recording layer solution, an intermediate layer solution, a yellow heat sensitive recording layer solution and a protective layer solution.

The coating amount, calculated as the solid content after drying, is 6.1 g / m ^{2 for} the cyan thermosensitive recording layer, 1.0 g / m ^{2 for} the intermediate layer and 7.8 g / m for the magenta thermosensitive recording layer in order from the support side. m
² , the intermediate layer was 1.0 g / m ² , the yellow heat-sensitive recording layer was 7.2 g / m ^2, and the protective layer was 2.0 g / m ² , respectively. When the cross section of the coating layer of the obtained coating material was observed with a scanning electron microscope, it was confirmed that the layers were separated extremely well. The obtained thermosensitive recording material was substantially transparent and light transmissive.

(7) Thermal recording The obtained recording material was stored at 40 ° C. and 90% relative humidity for 3 days and then recorded as follows. As a result, the color mixing phenomenon was caused due to the diffusion of the coloring component between the recording layers. Etc. were not seen at all. Using a thermal head KST type (trade name, manufactured by Kyocera Corporation), the applied power and the pulse width were adjusted so that the recording energy per unit area was 34 mJ / mm ^2, and the obtained recording material was colored yellow. The image was recorded.

Then, the yellow heat-sensitive recording layer was optically fixed by exposing it to an ultraviolet lamp having an emission center wavelength of 420 nm and an output of 40 W for 10 seconds, and then applied power and pulse width so that the recording energy of the thermal head became 68 mJ / mm ^2. Was adjusted to record a magenta image. Furthermore, after exposing it to a magenta thermosensitive recording layer for 15 seconds by exposing it to a UV lamp having an emission center wavelength of 365 nm and an output of 40 W,
A cyan image was recorded by adjusting the applied power and the pulse width so that the recording energy of the thermal head was 102 mJ / mm ² .

In this way, in addition to the yellow, magenta, and cyan color-developed images, the image portion where the yellow and magenta recordings overlap is red, the image portion where the magenta and cyan recordings overlap is blue, and the yellow The portion where the recordings of cyan and cyan are overlapped is green, and the portion of the image where the recordings of yellow, magenta and cyan are overlapped is colored black.
The obtained recorded image had no white turbidity and was a clear image having high light transmittance.

Example 2. In the intermediate layer liquid, completely the same as in Example 1 except that an ammonia neutralized product (pH 6) of polystyrene sulfonic acid (Chemist SA-20: Sanyo Kasei Co., Ltd.) was used in place of polyacrylic acid. When a heat-sensitive recording material was prepared in the above manner and heat recording was carried out in the same manner, the same good result as in Example 1 was obtained.

Comparative Example 1. A thermosensitive recording material was prepared in the same manner as in Example 1 except that a 6% by weight aqueous gelatin solution was used as the intermediate layer liquid instead of the intermediate layer liquid used in Example 1, and the temperature was 40 ° C. and the relative humidity was 90%. When the heat recording was performed in exactly the same manner after storage for 3 days, the color mixing phenomenon of yellow and magenta, and the desensitization phenomenon that the thermal sensitivities of cyan, magenta, and yellow markedly decreased were observed.

Claims (2)

[Claims] 1. A heat-sensitive recording material comprising two or more heat-sensitive recording layers containing at least a colorless or light-colored color-forming component which develops color upon heating and a binder on a support,
A multicolor thermosensitive recording material comprising an intermediate layer containing at least gelatin and / or a gelatin derivative and an acidic polymer between the thermosensitive recording layers. 2. The multicolor thermosensitive recording material according to claim 1, wherein the binder is gelatin and / or a gelatin derivative.