JPH0725162A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material forming an image excellent in light fastness by providing a thermal recording layer based on a diazo compd. and a barbituric acid derivative and containing a compd. represented by a specific general formula on a support. CONSTITUTION:A diazo compd., a barbituric acid derivative (coupler) and a compd. represented by formula I (wherein R and R' are an alkyl group or an alkenyl group, R0 is a substituent and n is an integer of 0-4) are separately dispersed in an aq. soln. of a water-soluble polymer such as polyvinyl alcohol and the respective dispersions are mixed to prepare a coating soln. which is, in turn, applied to a support such as paper, synthetic paper or a plastic film and dried to form a thermal recording layer to obtain a thermal recording material. The barbituric acid derivative being the coupler is represented by formula II and, as a concrete example of the diazo compd., 4-(N-(2-(2,4-di-tert- amylphenoxy)butylyl)piperadino)benzenediazonium is designated.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A heat-sensitive recording method has made remarkable progress in recent years and has been applied to various purposes because it is highly reliable and requires no maintenance despite the fact that the recording apparatus used is simple. It has been said that reproduction of multicolor images is difficult as compared with electrophotographic recording methods and inkjet methods. In this regard, a thermosensitive coloring layer containing an electron-donating dye precursor and an electron-accepting compound as a main component on a support, or a thermosensitive coloring layer containing a diazo compound and a coupler which develops a color upon thermal reaction with the diazo compound. It has been found that a multicolor thermosensitive recording material can be obtained by providing a color forming layer. However, since the light fastness of an image obtained by this method is significantly worse than that of an image obtained by another method, it has been required to improve the light fastness of the image. It has been attempted to improve the light fastness of an image, and as one of them, catechol diether and other anti-fading agents are described in JP-A-62-146678. It is a well known fact that the system using the coupler of (1) does not have the same effect, and that it is necessary to select an anti-fading agent according to the coloring dye.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording material using a thermosensitive recording layer containing a diazo compound and a coupler which reacts with the diazo compound to form a color, and which is excellent in light fastness of an image. It is to provide a heat-sensitive recording material in which the coupler is a barbituric acid derivative.

[0004]

The above objects of the present invention are as follows.
A heat-sensitive recording material provided with a thermosensitive recording layer containing a diazo compound and a coupler which develops a color when reacted with the diazo compound as a main component on a support, wherein the thermosensitive recording layer contains at least one compound represented by the following general formula 1. This has been achieved by a heat-sensitive recording material characterized by containing the above.

[0005]

[Chemical 3]

In the formula, R and R'may be the same or different and each represents an alkyl group or an alkenyl group, and R ₀ represents a substituent. n represents an integer of 0 to 4. R and R ', R and R _0, R' and R _0, may form a 5- or 6-membered ring together two R ₀ in the ortho position to each other.

The compound represented by formula 1 will be described in more detail. R and R ′ are alkyl groups (linear, branched or cyclic alkyl groups such as methyl, ethyl, propyl, iso-propyl, butyl, tert-butyl, hexyl, decyl, hexadecyl, cyclohexyl, benzyl) and alkenyl groups (eg, Vinyl, allyl, oleyl, cyclohexenyl). R ₀ represents a substituent, for example, an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, an alkoxy group, an alkenoxy group, an aryloxy group, a heterocyclic oxy group, an alkylthio group, an alkenylthio group, an arylthio group, a heterocyclic thio group. Group, amino group, acylamino group, sulfonamide group, alkylamino group, arylamino group, heterocyclic amino group, alkyloxycarbonyl group, aryloxycarbonyl group, halogen atom, acyl group, sulfonyl group, carbamoyl group, sulfamoyl group, Examples thereof include a cyano group, a nitro group, a sulfo group and a carboxyl group. n represents an integer of 0 to 4. R and R ', R and R _0, R' and R _0, 2 one of R ₀ are bonded to each other 5-6 membered ring (e.g. coumaran ring, chroman ring at the ortho position to each other, indane ring, methylenedioxy ring , Spirocoumaran ring, spirochroman ring, spiroindane ring) may be formed. When n is 2 or more, a plurality of R ₀ may be the same or different.

Among the compounds represented by the general formula 1, preferred compounds have a total carbon number of 14 or more, and more preferably 20 or more. Among the compounds represented by the general formula 1, preferred compounds are represented by the general formula 2.

[0009]

[Chemical 4]

Wherein R, R ', R "and R"' are general formulas
1 represents a group defined by R or R ′ of 1₀And R
₀'Is R in general formula 1₀Represents a group defined in. l and m
May be the same or different and each represents an integer of 0 to 2.
Forget R₁, R₂, R₃, R ₁', R₂'And R₃'Is the same
Or they may be different, and each is a hydrogen atom or an alkyl group.
Or represents an aryl group.

Of the compounds represented by the general formula 2, R,
It is preferred that R ′, R ″ and R ″ ′ are the same group. R ₀ and R ₀ 'are an alkyl group, an alkenyl group,
It is preferably a group selected from a halogen atom, an alkoxy group and an alkylthio group. 1 and m are preferably 0 to 1, and more preferably 1 and m are 0.

Typical examples of these compounds are shown below.
This does not limit the compounds used in the present invention.

[0013]

[Chemical 5]

[0014]

[Chemical 6]

[0015]

[Chemical 7]

[0016]

[Chemical 8]

[0017]

[Chemical 9]

[0018]

[Chemical 10]

[0019]

[Chemical 11]

[0020]

[Chemical 12]

The compounds of the present invention are described, for example, in US Pat.
It can be easily synthesized by the method described in No. 60,589 or a method analogous thereto. The compound of the present invention is particularly preferably added to the heat-sensitive recording layer containing as a main component a diazo compound and a coupler which reacts with the diazo compound to form a color. When carrying out the present invention, they may be used alone or in combination of two or more kinds, and it is more preferable to use them together with other compounds having an action of improving light fastness, particularly bisphenols. The addition amount of these is 10 to 1000 mol%, preferably 40 to 400 mol%, based on the coupler used. Further, these are preferably dissolved in a high boiling organic compound and used as an emulsion together with a suitable protective colloid. More preferably, it is used by coemulsifying with a coupler.

The barbituric acid derivative which is the coupler used in the present invention is preferably selected from the compounds represented by the following general formula 3.

[0023]

[Chemical 13]

In the formula, R ₁ and R ₂ represent a hydrogen atom, a substituted or unsubstituted alkyl group, an aralkyl group or an aryl group. As the substituent further bonded to R ₁ and R ₂ , an alkyl group, an alkoxy group, an aryl group, a cyano group, a halogen atom, a halogenated alkyl group, an alkoxycarbonyl group, an alkylcarbonyl group, an arylcarbonyl group,
Examples thereof include an amino group, a carbamoyl group, an acylamino group and a sulfonyl group. R ₁ and R ₂ have 1 to 25 carbon atoms
Are more preferable, the aryl group of 6 to 30 and the aralkyl group of 7 to 30 are more preferable. It is preferable that the total carbon number of R ₁ and R ₂ is 14 or more for the purpose of lowering water solubility and improving oil solubility.

Specific examples are shown below, but the present invention is not limited to these compounds.

[0026]

[Chemical 14]

[0027]

[Chemical 15]

[0028]

[Chemical 16]

These couplers may be used alone or in combination of two or more. These couplers are usually used in the range of 0.05 to 5 g / m ² .

The other components used in the present invention will be described below. The compound used in the heat-sensitive color forming layer containing a diazo compound and a coupler that reacts with the diazo compound to form a color when heated is a known photodegradable diazo compound, a coupler capable of reacting with the diazo compound to form a dye, It is a basic substance or the like that promotes the reaction between the diazo compound and the coupler. The photodecomposable diazo compound in the present invention mainly refers to an aromatic diazo compound, and more specifically, an aromatic diazonium salt, a diazosulfonate compound, a diazoamino compound and the like. Among these, in terms of thermal sensitivity,
It is particularly preferable to use a diazonium salt.

[0031] Generally the diazonium salt type Ar-N ₂ ⁺ X ^- (wherein Ar represents an aromatic moiety, X ^- represents an acid anion) is a compound represented by the. These have various maximum absorption and 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-ethoxybenzodiazonium, 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 can be mentioned. In the present invention, these hexafluorophosphate salts, tetrafluoroborate salts, and 1,5-naphthalenesulfonate salts are particularly useful because they have low water solubility and are soluble in organic solvents.

As well known, as the raw materials used in the heat-sensitive recording layer containing the electron-donating dye precursor and the electron-accepting compound as the main components, the electron-donating dye precursor and the electron-accepting compound, and these are heated. Sometimes there are low-melting organic compounds and the like that help react. As the electron-donating dye precursor, a triarylmethane compound, a diphenylmethane compound, a thiazine compound, a xanthene compound,
Examples include spiropyran-based compounds, but triarylmethane-based compounds and xanthene-based compounds are particularly useful because of their high color density.

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-
Yl) 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-benzylspirodinaphthopyran, 3-propyl-spiro-
There are 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, 2-ethylhexyl p-hydroxybenzoate, p-phenylphenol, p- Examples include cumylphenol.

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.

A basic compound is added to the heat-sensitive recording layer composed of a diazonium salt and a coupler in order to accelerate the reaction thereof. The basic substance includes not only an inorganic or organic basic compound but also a compound that decomposes upon heating to release an alkaline substance.

Representative examples include organic ammonium salts,
Organic amines, amides, urea and thiourea, their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines,
Examples thereof include nitrogen-containing compounds such as 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, Two
3-tricyclohexylguanidine, guanidine trichloroacetate, N, N'-dibenzylpiperazine, 4,
There are 4'-dithiomorpholine, morpholinium trichloroacetate, 2-aminobenzothiazole, 2-benzoylhydrazinobenzothiazole and the like. These may be used in combination of two or more.

In order to dissolve the coloring component or additive,
A high-boiling point organic solvent used as a dispersion solvent for a color material (coupler, dye-donor compound, etc.) of an ordinary color light-sensitive material can be used. For example, alkyl phthalate (eg, dibutyl phthalate, dioctyl phthalate, etc.), phosphoric acid ester (eg, diphenyl phosphate, triphenyl phosphate, etc.), citric acid ester (eg, tributyl acetyl citrate), benzoic acid ester (eg, octyl benzoate) ), Alkylamides (eg diethyllaurylamide), aliphatic esters (eg dibutoxyethylsuccinate), trimesic acid esters (eg tributyl trimesate), JP-A-63
-85633 carboxylic acids, JP-A-59-83
No. 154, Nos. 59-178451 to 178455,
And the compounds described in JP-A-59-178457.

In the present invention, a protective layer may be provided on the thermosensitive coloring layer in order to further improve light fastness. Further, in the multicolor thermosensitive material, an intermediate layer may be provided between the thermosensitive recording layers in order to further improve the heat fractionation property. The material of the layer used for these is preferably an emulsion or latex of a water-soluble polymer or a hydrophobic polymer.

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, polystyrene sulfonic acid, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer, oxidized starch, phosphorylated starch, gelatin, carboxymethyl cellulose , Methyl cellulose, sodium alginate, sulfated cellulose, hydroxyethyl cellulose and the like. Examples of the emulsion or latex of the hydrophobic polymer include styrene-butadiene copolymer, carboxy-modified styrene-butadiene copolymer, acrylonitrile-butadiene copolymer and the like.

Next, a method for producing the heat-sensitive recording material will be described.
In the thermal recording material of the present invention, all the thermal recording layers are
The color-forming components, that is, the electron-donating dye precursor and the electron-accepting compound, or the diazo compound and the coupler, are uniformly dispersed in the binder and held in the recording layer so as not to come into contact with each other before heating. There is a need.

As a specific method, each material is separately dispersed in a water-soluble polymer (for example, polyvinyl alcohol) aqueous solution, and the water-soluble polymer is sufficiently adsorbed on the surface of each material and then mixed. There are a method of microencapsulating at least one of the components, a method of separating the reaction components layer by layer, and the like, and a method of microencapsulating one of the color-forming components is particularly preferable.

The electron-donating dye precursor and the electron-accepting compound will be described below as examples, but the same applies to the case of the diazo compound and the coupler. In the above method, an electron-donating dye precursor (for example, crystal violet lactone) is put into an aqueous solution of a water-soluble polymer (for example, polyvinyl alcohol) and dispersed by means of a ball mill or the like. In this operation, the crystal of the electron-donating dye precursor is pulverized into fine particles, and at the same time, the water-soluble polymer is adsorbed on the surface of the crystal, and the electron-donating dye precursor is protected by the water-soluble polymer adsorption layer. A fine particle dispersion of is obtained. Similarly, a fine particle dispersion of an electron accepting compound (for example, bisphenol A) can be obtained. Even when both dispersions thus obtained are mixed, no color-forming reaction occurs because each color-forming component is protected by the water-soluble polymer adsorption layer. Therefore, a recording material can be obtained by applying this mixed liquid onto a support. However, when heated for recording, at least one of the color-forming components melts, breaks the adsorption layer and diffuses, and as a result, both color-forming components come into contact with each other, so that a color-forming reaction occurs and a colored image is obtained.

As the water-soluble polymer used in the above method, the water-soluble polymer used in the above-mentioned intermediate layer can be used, but in particular, polyvinyl alcohol and its derivative, polyacrylamide and its copolymer,
Hydroxyethyl cellulose, starch derivatives and the like are preferable.

In the method of microencapsulating at least one of the components, the electron-donating colorless dye and / or the electron-accepting compound may be encapsulated by a conventional method.

The microcapsules used in the present invention are
It is a thermo-responsive microcapsule that has the property of strictly isolating the substance inside the capsule from the substance outside the capsule at room temperature, and at the same time can accelerate the reaction of the coloring component by increasing the permeability of the wall when heated. Need to be

As the wall material of the capsule, gelatin, polyurea, polyurethane, polyimide, polyester, polycarbonate, melamine and the like can be used, but polyurea or polyurethane is preferably used from the viewpoint of obtaining thermoresponsive microcapsules. Further, in order to impart thermal responsiveness to the capsule wall, the glass transition point of the capsule wall may be room temperature to 200 ° C., particularly 70 ° C.
It is preferably in the range of 150 ° C.

The glass transition temperature of the capsule wall can be controlled by selecting the polymer species of the capsule wall or adding an appropriate plasticizer. Examples of such a plasticizer include a phenol compound, an alcohol compound, an amide compound, a sulfonamide compound, and the like, which may be contained in the core material of the capsule or added as a dispersion outside the microcapsule. .

Specific examples of the microencapsulation technique, materials and compounds to be used are described in, for example, US Pat. No. 37.
No. 26804 and No. 3796696. The method of microencapsulating the electron-donating dye precursor will be described below, but the same applies to the case of microencapsulating other materials.

For example, when polyurethane or polyurea is used as the capsule wall material, the polyvalent isocyanate and the second substance (eg, polyol or polyamine) which reacts with the polyisocyanate to form the capsule wall are used as an aqueous phase or an oily substance to be encapsulated. After mixing in a liquid to form a core composition, the core composition is emulsified and dispersed in water, and then the temperature is raised to cause a polymer forming reaction at the oil drop interface to form a microcapsule wall. In this case, the glass transition point of the capsule wall can be significantly changed by appropriately selecting the polyvalent isocyanate as the first wall film forming substance and the polyol or polyamine as the second wall film forming substance.

Further, a low-boiling auxiliary solvent can be added to assist the dissolution of the electron-donating dye precursor. Specific examples of the auxiliary solvent include ethyl acetate, isopropyl acetate, butyl acetate, methylene chloride, cyclohexanone and the like. Further, a protective colloid or a surfactant can be added to the aqueous phase in order to stably produce emulsified oil droplets.

As the protective colloid, water-soluble polymers can generally be used, and specific examples thereof include polyvinyl alcohol, modified polyvinyl alcohol, methyl cellulose, sodium polystyrene sulfonate, ethylene / maleic acid copolymer and the like. Can be mentioned.

The size of the microcapsules is 0.2 μm in volume average, especially from the viewpoint of improving the image resolution and handling.
m to 20 μm is preferable, and more preferably 0.4 μm to
It is 4 μm.

Since the separating action of the material by the microcapsule wall is generally more complete than the separating action of the material by the adsorption layer of the water-soluble polymer, by microcapsulating one of the reaction components, the reaction components can be sufficiently separated from each other. Can be suppressed. Therefore, for example, when the electron-donating dye precursor is microencapsulated, the electron-accepting compound can be mixed with the capsule liquid as a dispersion in which the electron-accepting compound is simply dispersed in fine particles. However, it is also possible to dissolve the electron-accepting compound in a high boiling point solvent, emulsify it in an aqueous solution of a water-soluble polymer, and then mix with the capsule liquid.

In the latter case, there is an advantage that a transparent thermosensitive recording layer can be obtained by applying a coating solution on a support and drying it. Therefore, in this case, a transparent thermosensitive recording material can be obtained by using a transparent support such as a plastic base as the support.

As the support used in the heat-sensitive recording material of the present invention, known materials such as paper, laminated paper obtained by laminating polyethylene on paper, synthetic paper, polyethylene terephthalate, polyimide, plastic film such as triacetyl cellulose are used. To be done. Further, these supports may be undercoated to improve the adhesion with the coating layer.

As a method for coating the support, an air knife coating method, a curtain coating method, a slide coating method,
Examples of the method include, but are not limited to, a roller coating method, a dip coating method, a wire bar coating method, a blade coating method, a gravure coating method, a spin coating method and an extrusion coating method. By these methods, the thermosensitive recording material of the present invention can be obtained by successively coating each thermosensitive recording layer on the support. If necessary, a protective layer may be provided on the heat sensitive layer as described above.

When recording on this recording material, first, heat is applied so that the heat-sensitive recording layer develops color, and after the color is developed, the entire surface of the recording material is irradiated with light to decompose the diazonium salt contained in the heat-sensitive layer. To do. Next, a recording method of the multicolor thermosensitive recording material will be described. First, the outermost heat-sensitive layer (first heat-sensitive recording layer) containing the diazo compound is colored by heat recording with low heat energy, and then light in the absorption wavelength range of the diazo compound contained in the heat-sensitive layer is emitted. The entire surface is irradiated with light using a light source to photolyze the diazo compound remaining in the uppermost heat-sensitive layer.

Then, the second heat-sensitive layer (second layer) containing a diazo compound having a higher energy than the previous time and having a light absorption wavelength range different from that of the diazo compound contained in the first layer.
After the color of the thermosensitive recording layer) is developed, the whole surface is irradiated again with a light source that emits light in the absorption wavelength range of the diazo compound, whereby the diazo compound remaining in the second heating layer is photodecomposed. To do. Finally, with higher energy, the innermost layer (third heat-sensitive recording layer) of the layer containing the electron-donating dye precursor is colored to complete the image recording. In the above case,
It is preferable that the outermost layer and the second layer are transparent heat-sensitive layers because each color becomes vivid.

In the present invention, a multicolor image can be obtained by using a transparent support as the support and coating any one of the above three layers on the back surface of the transparent support. In this case, the uppermost heat-sensitive layer on the side opposite to the image viewing side does not need to be transparent.

An ultraviolet lamp is usually used as a light source used for the photolysis of the diazo compound. An ultraviolet lamp is a fluorescent tube in which mercury vapor is filled in the tube, and fluorescent tubes having various emission wavelengths can be obtained depending on the type of fluorescent material applied to the inner wall of the tube.

[0063]

The heat-sensitive recording material of the present invention contains at least one compound represented by the following general formula 1 in the heat-sensitive recording layer containing a diazo compound and a coupler which reacts with the diazo compound to form a color.
Since it contains more than one species, it has excellent light fastness of the image.

[0064]

[Chemical 17]

In the formula, R and R ′ may be the same or different and each represents an alkyl group or an alkenyl group,
R ₀ represents a substituent. n represents an integer of 0 to 4. R and R ', R and R ₀ , R'and R ₀ , ortho to each other 2
One R ₀ may combine with each other to form a 5- or 6-membered ring.

[0066]

EXAMPLES Examples will be shown below, but the present invention is not limited thereto. All "parts" in the examples indicate parts by weight.

Example 1 (1) Preparation of coating liquid (KB-1) for heat-sensitive recording layer [Preparation of capsule liquid (CB-1) of diazo compound] (C-1) 2.8 in 19 parts of ethyl acetate Part, (C-2) 0.5
After dissolving 6 parts, tricresyl phosphate 5.9
And 2.5 parts of (C-3) were added and mixed uniformly. Next, 7.6 parts of (C-4) as a wall agent was added to this mixed solution and mixed uniformly to obtain a solution I. Next, 46.1 parts of an 8 wt% aqueous solution of phthalated gelatin, 17.5 parts of water, and 2 parts of a 10% aqueous solution of sodium dodecylbenzene sulfonate at 40 ° C.
The solution I was added to the mixture which had been uniformly mixed with, and was emulsified and dispersed for 10 minutes at 40 ° C. and 10,000 rpm using a homogenizer. After adding 20 parts of water to the obtained emulsion and homogenizing,
While stirring, the encapsulation reaction was performed at 40 ° C. for 3 hours to obtain a capsule liquid (CB-1). The particle size of the capsule is 0.
It was 35 μm.

[0068]

[Chemical 18]

[Preparation of Coupler Emulsion (CN-1)] 3 parts of the compound (B-5) of the present invention in 10.6 parts of ethyl acetate,
Triphenylguanidine 3 parts, (D-1) 3 parts, (D-
3) 6 parts, (D-4) 6 parts, (D-1) 3 parts, compound (A-9) 3 parts of the present invention, tricresyl phosphate 0.48 parts, maleic acid diethyl 0.24 parts Then, 0.53 part of a 70% methanol solution of calcium dodecylbenzenesulfonate was dissolved to obtain a liquid II. Next, 41.7 parts of a 15% by weight aqueous solution of lime-processed gelatin and 33.9 parts of water were added to 4 parts.
The liquid II was added to the mixture evenly mixed at 0 ° C., and the mixture was emulsified and dispersed at 40 ° C. at 10,000 rpm for 10 minutes using a homogenizer. The obtained emulsion was stirred at 40 ° C. for 2 hours to remove ethyl acetate, and then the weight of volatilized ethyl acetate and water was supplemented with water to obtain a coupler emulsion (CN-1).

[0070]

[Chemical 19]

[Preparation of coating liquid] 3.6 parts of (CB-1),
2.8 parts of water, 15% by weight aqueous solution of lime-processed gelatin.
After uniformly mixing 5 parts and 1.4 parts of a 48% aqueous solution of styrene-butadiene latex at 40 ° C., (CN-1)
7.9 parts was added and uniformly mixed to obtain a heat-sensitive recording layer coating solution (KB-1).

(2) Preparation of coating solution for protective layer (PB-1) Polyvinyl alcohol (polymerization degree: 1700, saponification degree: 88)
%) 10% aqueous solution 32 parts water 36 parts, (W-1) 2% aqueous solution 8.4 parts are uniformly mixed to form a protective layer coating solution (PB-1).
Got

[0073]

[Chemical 20]

(3) Coating On a printing paper support prepared by laminating polyethylene on high-quality paper, coating is sequentially carried out in the order of (KB-1) and (PB-1) with a wire bar and drying at 50 ° C. is carried out. A desired thermosensitive recording material was obtained. The coating amount as solid content is 6.1 g /
It was m ² and 1.05 g / m ² .

(4) Thermal recording Using a thermal head (KST type) manufactured by Kyocera Corporation,
Recording energy per unit area is 0-40 mJ / mm ²
The power applied to the thermal head and the pulse width are determined so that the thermal printing is performed on the thermosensitive recording layer to obtain a magenta image, and then the entire surface is irradiated for 15 seconds using an ultraviolet lamp with an emission center wavelength of 365 nm and an output of 40 W. did.

(5) Fading test The above sample was subjected to 3 times with a 12000 Lux fluorescent lamp fading tester.
Light irradiation was continuously performed for a day, and an image discoloration test was performed. For the density measurement, an X-Rite 310TR was used to examine the density change in the portion where the initial reflection density of magenta was about 1.1.

Example 2 Instead of 3 parts of (A-9) used in Example 1, (A-
2) A thermosensitive recording material was obtained in the same manner as in Example 1 except that 2.7 parts was used, and a fading test was conducted in the same manner as in Example 1.

Example 3 Instead of 3 parts of (A-9) used in Example 1, (A-
6) A thermosensitive recording material was obtained in exactly the same manner as in Example 1 except that 3.4 parts were used, and a fading test was conducted in the same manner as in Example 1.

Example 4 Instead of 3 parts of (A-9) used in Example 1, (A-1
1) A thermosensitive recording material was obtained in exactly the same manner as in Example 1 except that 3.7 parts was used, and a fading test was conducted in the same manner as in Example 1.

Example 5 Instead of 3 parts of (A-9) used in Example 1, (A-1
7) A thermosensitive recording material was obtained in exactly the same manner as in Example 1 except that 3.4 parts were used, and a fading test was conducted in the same manner as in Example 1.

Comparative Example 1 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that (A-9) used in Example 1 was excluded, and a fading test was conducted in the same manner as in Example 1.

Example 6 In addition to the thermosensitive recording layer coating liquid and the protective layer liquid of Example 1, two types of thermosensitive recording layer coating liquids and one intermediate layer coating liquid were newly prepared. (1) Preparation of third heat-sensitive recording layer liquid [Preparation of capsule liquid of electron-donating dye precursor] 3.0 parts of crystal violet lactone, which is an electron-donating dye precursor, was dissolved in 20 parts of ethyl acetate and then increased. 20 parts of alkylnaphthalene which is a boiling solvent was added, and heated to uniformly mix. Then, as a capsule wall agent in this mixed solution,
20 parts of xylylene diisocyanate / trimethylolpropane adduct was added and stirred uniformly.

Next, a 6 wt% aqueous solution of separately prepared polyvinyl alcohol (polymerization degree 1700, saponification degree 88%) 5
The above electron-donating dye precursor solution was added to 4 parts, and the mixture was emulsified and dispersed using a homogenizer. 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 target capsule solution. The average particle size of the capsule was 1.6 μm.

[Preparation of Dispersion Liquid of Electron-Accepting Compound] 30 parts of bisphenol A, which is an electron-accepting compound, was added to 150 parts of a 4% by weight aqueous solution of polyvinyl alcohol and dispersed for 24 hours using a ball mill to prepare a dispersion liquid. . The average particle size of the electron-accepting compound in the dispersion was 1.2 μm.

[Preparation of Coating Solution] The above electron-donating dye precursor capsule liquid and the electron-accepting compound dispersion liquid were mixed so that the ratio of the electron-donating dye precursor / electron-accepting compound was 1/2. To prepare a coating solution.

(2) Preparation of first heat-sensitive recording layer liquid [Preparation of capsule liquid of diazo compound] 2,5-dibutoxy-4-tolylthiobenzenediazonium hexafluorophosphate: 3.0 parts of ethyl acetate 20 After being dissolved in 20 parts, 20 parts of a high boiling point alkylnaphthalene was added and heated to uniformly mix. Next, 15 parts of xylylene diisocyanate / trimethylolpropane adduct as a capsule wall agent was added to the obtained mixed liquid, and the mixture was stirred uniformly.

Next, a 6 wt% aqueous solution of separately prepared polyvinyl alcohol (polymerization degree 1700, saponification degree 88%) 5
The above solution of the diazo compound was added to 4 parts and emulsified and dispersed using a homogenizer. After 68 parts of water was added to the obtained emulsion to homogenize it, the temperature was raised to 40 ° C with stirring and 3
The encapsulation reaction was performed for a time to obtain a capsule liquid. The average particle size of the capsule was 1.0 μm.

[Preparation of Coupler Dispersion] 2-Chloro-5
-Octylacetoacetanilide as coupler 10
Parts, 5 parts of 1,2,3-triphenylguanidine which is an organic base and 20 parts of dodecyl parahydroxybenzoate were added to 200 parts of a 4% by weight polyvinyl alcohol aqueous solution,
A ball mill was used for dispersion for 24 hours to prepare a dispersion liquid. The average particle size of the dispersion was 1.2 μm.

[Preparation of Coating Liquid] The above-mentioned diazo compound capsule liquid and coupler dispersion liquid were mixed at a diazo compound / coupler ratio of 4/5 to prepare a coating liquid.

(2) Preparation of intermediate layer liquid (MC-1) 50 parts of a 15% by weight aqueous solution of lime-processed gelatin, water 11
Parts and 2 parts of a 2% aqueous solution of (E-1) were uniformly mixed at 42 ° C. to obtain an intermediate layer liquid (MC-1).

[0091]

[Chemical 21]

(3) Coating On a support for printing paper, which is made by laminating polyethylene on high-quality paper, apply a third heat-sensitive layer coating solution (MC-
1), the heat-sensitive layer (second heat-sensitive layer) coating liquid of Example 1, (MC
-1), the first thermosensitive layer coating liquid and the protective layer liquid were sequentially coated and dried at 50 ° C. to obtain a target multicolor thermosensitive recording material. The coating amount as solid content was 5.2 g / m ² , respectively.
0 g / m ² , 6.4 g / m ² , 3.0 g / m ² , 7.9 g /
It was m ² and 1.05 g / m ² . (5) Thermal recording Using a Kyocera thermal head (KST type),
Recording energy per unit area is 0 to 25 mJ / mm ²
The power applied to the thermal head and the pulse width are determined so that the first image is printed on the first thermal recording layer to obtain a yellow image, and then the entire surface is irradiated for 10 seconds using an ultraviolet lamp with a central emission wavelength of 420 nm and an output of 40 W. It was irradiated with light.

Then, the applied power to the thermal head and the pulse width were determined so that the recording energy per unit area was 0 to 40 mJ / mm ^2, and the second thermal recording layer was thermally printed to obtain a magenta image. , Emission center wavelength is 36
The whole surface was irradiated with light for 15 seconds using an ultraviolet lamp of 5 nm and an output of 40 W.

Finally, the power applied to the thermal head and the pulse width were determined so that the recording energy per unit area was 0 to 60 mJ / mm ^2, and the third thermal recording layer was thermally printed to obtain a cyan image. . By this, magenta, yellow, cyan, cyan + magenta (blue),
Magenta + yellow (red), cyan + yellow (green) and cyan + magenta + yellow (black)
An image record of was obtained.

(5) Fading test The above sample was subjected to 12000 Lux fluorescent lamp fading test
Light irradiation was continuously performed for a week, and an image discoloration test was performed. For the density measurement, an X-Rite 310TR was used to examine the density change in the portion where the initial reflection density of magenta was about 1.1.

Example 7 A thermosensitive recording material was prepared in the same manner as in Example 6 except that the thermosensitive recording layer coating liquid of Example 2 was used in place of the thermosensitive recording layer coating liquid of Example 1 used in Example 6. Then, a fading test was performed in the same manner as in Example 6.

Example 8 A heat-sensitive recording material was prepared in the same manner as in Example 6 except that the heat-sensitive recording layer coating solution of Example 3 was used in place of the heat-sensitive recording layer coating solution of Example 1 used in Example 6. Then, a fading test was performed in the same manner as in Example 6.

Example 9 A thermosensitive recording material was prepared in the same manner as in Example 6 except that the thermosensitive recording layer coating solution of Example 4 was used in place of the thermosensitive recording layer coating solution of Example 1 used in Example 6. Then, a fading test was performed in the same manner as in Example 6.

Example 10 A thermosensitive recording material was prepared in the same manner as in Example 6 except that the thermosensitive recording layer coating solution of Example 5 was used in place of the thermosensitive recording layer coating solution of Example 1 used in Example 6. Then, a fading test was performed in the same manner as in Example 6.

Comparative Example 2 A thermosensitive recording material was prepared in the same manner as in Example 6 except that the thermosensitive recording layer coating solution of Comparative Example 1 was used in place of the thermosensitive recording layer coating solution of Example 1 used in Example 6. Then, a fading test was performed in the same manner as in Example 6.

Tables 1 and 2 show the density ratios before and after the fading test of magenta in each example and comparative example. These results show that the light fastness is improved by incorporating the compound of the following general formula 1 into the heat-sensitive recording layer.

[0102]

[Chemical formula 22]

In the formula, R and R ′ may be the same or different and each represents an alkyl group or an alkenyl group,
R ₀ represents a substituent. n represents an integer of 0 to 4. R and R ', R and R ₀ , R'and R ₀ , ortho to each other 2
One R ₀ may combine with each other to form a 5- or 6-membered ring.

[0104]

[Table 1]

[0105]

[Table 2]

Claims (3)

[Claims] 1. A heat-sensitive recording material provided with a heat-sensitive recording layer containing, as a main component, a diazo compound and a coupler which reacts with the diazo compound to form a color on a support, wherein the coupler is a barbituric acid derivative, and A heat-sensitive recording material comprising the heat-sensitive recording layer containing at least one compound represented by the following general formula 1. [Chemical 1] In the formula, R and R ′ may be the same or different and each represents an alkyl group or an alkenyl group, and R ₀ represents a substituent. n represents an integer of 0 to 4. R and R ', R and R _0, R' and R _0, may form a 5- or 6-membered ring together two R ₀ in the ortho position to each other. 2. The heat-sensitive recording material according to claim 1, wherein at least one of the color-forming components is encapsulated in microcapsules. 3. A coupler represented by the following general formula 1 among color-forming components:
The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording material is in the same emulsion as the compound of. [Chemical 2] In the formula, R and R ′ may be the same or different and each represents an alkyl group or an alkenyl group, and R ₀ represents a substituent. n represents an integer of 0 to 4. R and R ', R and R _0, R' and R _0, may form a 5- or 6-membered ring together two R ₀ in the ortho position to each other.